$54,000
$1,097

What Can be Achieved if the Epigenetic Clock is an Accurate Reflection of Aging?

The difference between having and not having an accurate, rapid, low-cost measure of biological age is night and day. If such a thing did exist, then it is immediately the case that a good few dozen interventions could be rapidly tested in humans, taking a month or two between before and after measurements. The cost is low enough that volunteer groups and philanthropy could manage it. Look at what Betterhumans is doing in trials of cheap senolytic compounds, for example, and then add a robust assessment to that in order to definitively say whether or not rejuvenation occurred. I expect that only a few of the obvious candidate interventions that people will put forward will in fact turn out to make a difference. This is still important: the absence of results for the rest should go some way towards shutting off useless work on supplements and dietary tinkering that absorbs a great deal of time and funding both within and without scientific community.

Is there such a thing as an accurate, low-cost test that measures biological age, however? The later variants of the epigenetic clock might fit the bill, though it is still impossible to say whether or not they broadly reflect the causes of aging, or are tied to just a few narrow causes of aging. Absent a way to effectively reverse one of those narrow causes on its own, the mystery will likely persist; as of today, only senolytic therapies are capable of that feat, and they are not yet widely tested in humans. That the clock is uncertain in its mechanism of action is actually all the more reason to be running these studies. Both the clock and interventions alleged to slow or reverse or compensate for the progression of degenerative aging can be validated against one another.

The posts noted here cover an outline of one possible direction for evaluation of interventions against the epigenetic clock. They are largely not the sort of thing I believe should be the primary focus of the research community. These approaches are for the most part calorie restriction mimetic and similar compounds that trigger or enhance stress responses. All such methods have been shown to scale down in the extension of healthy life span as species life span increases. Calorie restriction itself produces 40% gains in mouse life span, but is unlikely to change human lifespan by more than five years or so. That said, there is merit, I think, in being able to show, robustly, that these approaches have only small effects, and thus redirect research and development efforts elsewhere, hopefully towards the SENS damage repair approaches that can in principle produce rejuvenation rather than just a slight slowing of aging.

The Mother of All Clinical Trials, Part I

There are a great number of promising interventions that might have anti-aging benefits. There is a testing bottleneck, which means that we don't know what works. By way of contrast, there is a well-documented catalog of life extension interventions in lab worms, but for humans we're mostly in the dark. To complicate things further, lab worms are clonal populations, while every human is different, and there are growing indications that many if not most medications work for some people and not others. Horvath's methylation clock is a disruptive technology that could make human testing of longevity interventions ten times faster and 100 times cheaper than it has been in the past. No one is yet doing this kind of testing, but you and I should be advocating vigorously, and volunteering as subjects to help test whatever it is that we are already doing.

There are a great number of promising interventions that might have anti-aging benefits, singly and in combination. Some are already approved and safe for use in humans, yet we don't know what will be most effective. Because human longevity studies are prohibitively slow and expensive, none have ever been funded or conducted. (We know only accidentally that aspirin and metformin lower mortality rates in humans, because these drugs were prescribed to tens of millions of people beginning in the 1960s for cardiovascular disease and diabetes, respectively, with no premonition that they might extend lifespan.)

Testing of anti-aging interventions in humans has been so expensive and slow that we have been forced to make inferences from animal tests, supplemented by historic (human) data from drugs that happen to have a large user base going back decades. As it turns out, it is much easier to extend lifespan in worms than in mammals, and even the interventions that work in rodents don't always work in humans. Conversely, there are drugs that work in humans that don't work in mice - how are we to find them?

Just this year, a test is available that is accurate enough to measure anti-aging benefits on short time scales, without waiting for subjects to die. DNAm PhenoAge is a simple blood test developed at the lab of Steve Horvath. It determines risk of age-related mortality accurate to about 1 year of biological age. Averaging over just a hundred people pinpoints biological age with accuracy of one month. This implies that an anti-aging benefit can be detected with high reliability using a test population of just a few hundred people, followed for two years, tested at the beginning and end of this period. A study that might have required fifteen years and cost hundreds of millions of dollars can now be completed in two years at a cost of less than $1 million. When this new technology is embraced, we will have the means to separate the most effective treatment combinations from a large field of contenders.

The Mother of All Clinical Trials, Part II

Methylation isn't the only means by which gene expression is controlled - there are many others. But it is far the best-studied and, given present technology, it is the only epigenetic marker that can be routinely measured, for a few hundred dollars in a small sample of blood, urine, or nanogram-scale biopsy of other tissue. The clock was developed by Steve Horvath, and first published in 2013. He scanned the entire genome for sites that changed most with age, and varied least from one tissue type to another. In this way, he identified 353 sites, and optimized a set of 353 multipliers, such that multiplying levels of methylation at each site by each multiplier and adding the products produced a number that could be mapped onto chronological age.

Five years after Horvath's original publication, there are several other clocks based on methylation. Just this spring, Horvath has developed a new clock, not yet published, which, to my knowledge, is the best standard we have. This is the Levine/Horvath clock. It is based on 513 methylation sites and it is calibrated not to chronological age, but to a tighter measure of age-based health, derived from blood lipid profiles, inflammatory markers, insulin resistance, etc, which Horvath calls "phenotypic age". Consequently, it is less well correlated with chronological age than the original, but it is better able to predict mortality than either the classic Horvath clock or chronological age itself.

The original Horvath clock was developed by a statistical process that took into account only chronological age. But Horvath age turns out to be a better predictor than chronological age for risk of all the diseases of old age. This is powerful evidence that methylation is measuring something fundamental about the aging process. If an individual's methylation age is higher or lower than his chronologial age, the difference is a powerful predictor of his disease risk and how long he will live. This can only be true if methylation is associated with a fundamental cause of age-related decline.

Aubrey de Grey in Fine Form on the Ethical Imperative to Defeat Aging

Aubrey de Grey, cofounder of the Methuselah Foundation and SENS Research Foundation, has little patience for those people who persist in clinging to the idea that it is in any way acceptable to let the death and suffering caused by aging continue. If we lived in a world in which there was nothing we could do, then perhaps accepting aging would be the sensible thing to do. But we do not. We live in a world in which the first rejuvenation therapies capable of reversing a root cause of aging, the accumulation of senescent cells, are entering human trials. Numerous other classes of potential rejuvenation therapy are well described, well understood, and only lacking sufficient financial support to move forward at the same pace. Aging and all of its consequences can be brought under medical control: all that is needed is the will and the funding to move ahead and get the job done.

Having publicly declared that the first person to live for more than a millennium is likely alive today, de Grey has dedicated large amounts of energy and time to the pursuit of medical technology which may one day allow humans to live indefinitely. Having graduated with a degree in computer science in 1985, de Grey switched fields in his late twenties upon discovering "the horrifying fact that most people, and indeed most biologists, viewed ageing as not very important or interesting." He appears both astonished and disgusted that the world pays so little attention to ageing, the one malady which affects us all.

De Grey defines ageing as "the collection of types of damage that the body does to itself throughout life as consequences of its normal operation." His major breakthrough came through the realisation that rather than attempting to delay the damage inflicted by ageing, as was the established practice, gerontologists could do better by repairing this damage after it has occurred. This idea, though "counterintuitive" to many of his colleagues, has now become "totally mainstream" in the field, and forms the basis of the Strategies for Engineered Negligible Senescence (SENS) Research Foundation which de Grey co-founded in 2009.

Speaking of the work taking place at SENS, and around the world, de Grey proudly declares that there have been "huge advances" in implementing his theory of damage repair. "Among the most high-profile is the ability to remove senescent cells using certain drugs, but there's a lot more that is more esoteric, such as making backup copies of the mitochondrial DNA in the nucleus and introducing bacterial enzymes to eliminate otherwise indigestible waste products." Asked about the biggest barriers currently facing progress, de Grey replies: "Money, money and money." He blames the field's financial struggles on "the desperation that almost all people have to put ageing out of their minds and pretend that it is some kind of blessing in disguise, so that they can get on with their miserably short lives without being preoccupied by the terrible thing that awaits them." According to de Grey, this attitude is "psychologically understandable but morally inexcusable".

De Grey rejects criticism of his field as "unnatural", citing this challenge as another "great example of the desperation of so many people to switch off their brains when confronted with the need to discuss the defeat of ageing." Towards those who make the "unnatural" claim, de Grey is both indignant and dismissive: "It takes about ten IQ points and ten milliseconds to notice that the whole of technology is 'unnatural' - including, of course, the whole of medicine - endeavours that those who voice this objection do not tend to oppose."

Morally, de Grey does not have any doubts about the quest to extend life: "For something to be an ethical issue it has to be a meaningful dilemma and in order to make that case one must make the case either that people who were born a long time ago have less entitlement to health, as a human right, than younger people, or that health itself is a lesser human right than other things that might end up being mutually exclusive with it, like parenthood. Once one focuses on the fact that this is just medicine, that any longevity effects would be just side-effects of health, the 'ethics' of the matter rather rapidly vaporises."

Link: https://www.varsity.co.uk/science/15317

Leonard Hayflick is not in Favor of Greatly Extending Healthy Human Life Spans

This is very old news for anyone who participates in the aging research community, but a significant fraction of the leading researchers of recent generations are either not interested in or actively opposed to efforts to extend human life. Leonard Hayflick, for whom the Hayflick limit is named, is in this camp. This is one of the contributing factors in the story of how research and funding institutions spent decades working to suppress any inclination among their members to try to treat aging as a medical condition. It is arguably the case that we could be much further ahead than we are today on the road to human rejuvenation - even given the lesser technological capabilities twenty and thirty years ago, meaningful progress towards, for example, senolytic drugs might have been made in a world in which treating aging was considered seriously by those who steered research strategy.

The potential for undying tyrants or tyrannical bodies is one reason Leonard Hayflick, one of the world's preeminent experts on aging, is against slowing down or eliminating the aging process. He has other reasons, too. "To slow, or even arrest, the aging process in humans is fraught with serious problems in the relationships of humans to each other and to all of our institutions. By allowing antisocial people - tyrants, dictators, mass murderers, and people who cause wars - to have their longevity increased should be undesirable ... I would rather experience the aging process as it occurs, and death when it occurs, in order to avoid allowing the people who I just described to live longer."

Despite his reservations about radical life extension, Hayflick is a big proponent of studying aging at a more fundamental level. "Most studies are either descriptive, studies on longevity determinants, or studies on age-associated diseases. None of this research will reveal information about the fundamental biology of aging. Less than 3 percent of the budget of the National Institute on Aging in the past decade or more has been spent on research on the fundamental biology of aging." He's a bit annoyed, for instance, that about a half of the National Institute on Aging's budget goes toward researching Alzheimer's disease. "The resolution of Alzheimer's disease as a cause of death will add about 19 days onto human life expectancy. I have suggested that the name of the institute be changed to the National Institute on Alzheimer's Disease. Not that I support ending research on Alzheimer's disease, I do not, but the study of Alzheimer's Disease and even its resolution will tell us nothing about the fundamental biology of aging."

Hayflick also has some advice on what we should teach scientists and the public about aging. "That education must include an understanding that the massive amount of research funds spent on studying the leading causes of death will not advance our understanding of the basic biology of aging. It also must include an understanding that the study of longevity determinants (anabolic processes) will not reveal information about the basic biology of aging (catabolic processes). Finally, we need to educate scientists and the public, to support research on the differences between young cells and old cells that make the latter more vulnerable to age-associated diseases."

Link: http://nautil.us/blog/this-famous-aging-researcher-doesnt-want-us-to-live-forever

The Fable of the Dragon-Tyrant, and the Courage to Speak Out in Opposition to Aging

It has been thirteen years since Nick Bostrom published The Fable of the Dragon-Tyrant, a clear call to action regarding our relationship with aging and medical technology. The world has come to treat aging and the vast tide of death and suffering it causes as something set in stone, and so it was, for in past generations even the best of medicine could do little to influence the course of aging. Yet today we stand in the midst of revolutionary progress in biotechnology, and all of the old limits and incurable conditions might be addressed given sufficient funding and will. Unfortunately, a majority of people continue to hold that old belief that aging cannot be changed, even as we move into an era in which it is possible to create real, working rejuvenation therapies.

Our community is one of patient advocacy, philanthropic support of science, research into aging, and medical development, aimed squarely at the defeat of aging and the deployment of means of human rejuvenation in the clinic. Over the years, philanthropic funding and research programs have produced results, and the first rejuvenation therapies, those based on clearance of senescent cells, are entering clinical trials. Our numbers have grown considerably since the Fable of the Dragon-Tyrant was first written, and many of the newer faces might not even know of this important work. So is pleasant to see the sizable audience and effort put into this adaptation by the same YouTube creators who produced the excellent Why Age? Should We End Aging Forever? last year. Take a look and see what you think.

The Fable of the Dragon-Tyrant

Once upon a time, the planet was tyrannized by a giant dragon. The dragon stood taller than the largest cathedral, and it was covered with thick black scales. Its red eyes glowed with hate, and from its terrible jaws flowed an incessant stream of evil-smelling yellowish-green slime. It demanded from humankind a blood-curdling tribute: to satisfy its enormous appetite, ten thousand men and women had to be delivered every evening at the onset of dark to the foot of the mountain where the dragon-tyrant lived. Sometimes the dragon would devour these unfortunate souls upon arrival; sometimes again it would lock them up in the mountain where they would wither away for months or years before eventually being consumed...

Stories about aging have traditionally focused on the need for graceful accommodation. The recommended solution to diminishing vigor and impending death was resignation coupled with an effort to achieve closure in practical affairs and personal relationships. Given that nothing could be done to prevent or retard aging, this focus made sense. Rather than fretting about the inevitable, one could aim for peace of mind. Today we face a different situation. While we still lack effective and acceptable means for slowing the aging process, we can identify research directions that might lead to the development of such means in the foreseeable future. "Deathist" stories and ideologies, which counsel passive acceptance, are no longer harmless sources of consolation. They are fatal barriers to urgently needed action.

The quality and length of the rest of our lives depends on the degree to which the world at large - its research and development institutions, its public voices, its funding institutions - choose to bring an end to aging. It can be accomplished, but it will only be accomplished if a sufficiently large number of people first desire that goal, and then act on that desire. In an environment of widespread passive acceptance of a terrible status quo, persuasion is just as important as scientific progress.

Significant Improvements to Chimeric Antigen Receptor T Cell Therapies Lie Ahead

Chimeric antigen receptor T cell (CAR-T) therapies have proven to be a promising advance in the state of the art when it comes to cancer immunotherapy, though there are certainly challenges remaining to be overcome. The real promise is not only the improved effectiveness, however, but rather that this technology platform offers the ability to treat many different cancers with only an incremental cost in adaptation to each new target.

Over the long term, economics is the driver of success in cancer research. Given that there are hundreds of types of cancer and only so many scientists and only so much funding, the most important lines of research and development are those that can be cost-effectively turned to address many or all cancers. The defeat of cancer in our lifetimes requires universal therapies. CAR-T as a technology platform is now well enough known and proven to be attracting a great deal of interest in its evolution and improvement. This is now beginning to manifest in proof of principle results such as those noted here.

There have been few cancer treatments with such a promising future as using the patient's own immune system. Known as chimeric antigen receptor T-cell therapy, or CAR-T, this treatment uses re-engineered killer T-cells to attack cancer cells, but it also causes potentially deadly side effects. Now, research is opening doors to making such therapy safer and more effective. The researchers see the current CAR-T system as having three major flaws: target specificity; strength of response; and lack of adaptive capability, which is essentially the issue of relapse. "Our system has the ability to address those three problems."

Traditional CAR-T is a treatment engineered for one specific patient to treat one specific type of cancer cell. The new refined system - called split, universal and programmable (SUPRA) CAR-T - can be continuously altered to target different types of cancer cells, turned on and off, and overall offers a significantly more finely tuned treatment than the current therapies. "Instead of thinking about CAR-T as engineering cells that kill cancer, the way I think about it is as an antibody that drags a killer T-cell with it. What's amazing about it is that once the CAR T-cell binds and activates, it will recruit more T-cells and make copies of itself. Drugs don't do that."

This overwhelming immune response is also what causes the severe side effects. And there have been advances in drug therapy to mitigate these side effects by blocking unnecessary portions of the immune response while still allowing the CAR-T to attack the cancer cells. And the greater number of cancer cells means a stronger immune response. But the SUPRA CAR-T system would let doctors deactivate the entire treatment in case the side effects became too severe. The normal immune system requires T-cells to sense two targets coming from an invader cell before it attacks it and SUPRA CAR-T works in the same way. Before SUPRA CAR-T attacks cancer cells, it needs to sense that both targets are present on the cell. If only one is present, the system isn't activated.

SUPRA CAR-T also splits the T-cell from the target-sensing portion of the system. The target on cancer cells is called an antigen and whichever antigen is chosen is sought out by an antibody on the CAR T-cells. The new system breaks apart the T-cell from the antibody and allows for the ability to switch targets. The ability to switch targets is what can prevent relapse in patients. Cancer cells are smart and will mutate to no longer display the target when they sense the T-cells attacking after attaching to it. The SUPRA CAR-T system allows the T-cells to attack a new target by simply injecting the patient with a new batch of antibodies rather than having to re-engineer the T-cells, which is the most expensive portion of the treatment.

The third feature this split system produces is the ability to finely tune how active the T-cell response, which helps mitigate the dangerous side effects of previous CAR-T systems. By introducing a third component that can block the bonding of the T-cell and the antibody, the SUPRA CAR-T system can be deactivated. The level of deactivation can be tuned by choosing the strength to which this third component binds to the antibody.

Link: http://www.bu.edu/eng/2018/04/26/upgrading-the-immune-system/

Does Immune System Decline Determine the Contribution of Senescent Cells to Aging?

The self-experimentation rumor mill has it that presently available senolytic pharmaceuticals, repurposed chemotherapeutics that can selectively destroy some fraction of senescent cells, can show results for inflammatory conditions in elderly individuals. Equally, they don't appear to produce evident benefits in basically healthy 40-somethings. While senescent cells are indeed a source of chronic inflammation, one should never act on whispers: wait until data from the present or near future clinical studies is published and ratified. We can certainly debate and hypothesize, however, where anecdotes overlap with existing animal data and supporting evidence from other lines of research.

My thinking runs much as follows: the immune system is responsible for destroying cancerous cells and those senescent cells that fail to self-destruct. Immune cells are very efficient when it comes to this task, and thus the risk posed by both of these classes of harmful cell remains low for much of life. This is the case until immune function has declined significantly with age; one can look at the models that correlate cancer risk with atrophy of the thymus, and therefore reduction in T cell generation, for example. It fits well. Peak cancer risk lies between 60 and 80, which is also, more or less, where one starts to see incidence of inflammatory age-related conditions linked to cellular senescence increase greatly.

No-one has yet run the studies needed to build a decent picture of senescent cell burden by age. I will go out on a limb and wager that when this is accomplished, the numbers will closely mirror both cancer risk and loss of immune function. Some researchers have been thinking along these lines for a while now, and I noticed this commentary in the middle of a recent interview conducted by the Life Extension Advocacy Foundation volunteers:

Research suggests that "inflammaging" plays a key role in aging; many publications also suggest that of the various sources of this chronic age-related inflammation, senescent cell accumulation and the senescence-associated secretory phenotype it produces is the primary culprit. What might we expect to see if therapies to remove these problem cells are used in people?

I have a different view from the majority. I was one of the big fans of senescent cells, and I was 100% inspired by the idea of finding them, eradicating them, and using that for rejuvenation. However, after we spent several years very focused on an extensive study of senescent cells in vivo, we realized that for a major portion of the mouse lifespan, we simply cannot find these cells. This is not because they don't exist; I think they appear pretty frequently during our lives and mice's lives, but they are being very efficiently eradicated by the immune system.

Whether the changes in inflammation in vivo with age are due to the activity of senescent cells is a big question, because when we tried to find these cells in, for example, an irradiated organism, most of the cells that people thought were senescent before the existence of conventional biomarkers appeared to be just parts of the immune system, which is malfunctioning in aging and created the appearance of senescent cells. Macrophages frequently become positive for biomarkers of senescent cells, and people using these biomarkers without looking carefully call them senescent. You might say that does not matter because the whole concept did not change that much; who cares what you name these cells? If certain cells with certain properties accumulate with life and if they secrete something bad, the concept is still intact, and I agree with that.

However, knowing the nature of these cells, we can choose the right weapon against them, and as long as we try to kill the cells that we can make senescent in culture and think we are killing the same cells in vivo, I think that we are on the wrong path. This is my first problem; my second problem is that the accumulation of senescent cells means a malfunction of the immune system because the normal immune system gets rid of them very efficiently. If you kill a cell that cannot be removed by the immune system, you are not getting rid of this potential garbage; you turn it into a different type of garbage. Because to eradicate a senescent cell, something needs to find it and eat it, swallow it, such as a macrophage.

If this function is not working very well and you simply help the immune system by killing these cells, they still remain in the same place where they were; they're just dead. Maybe this is good or not; maybe this will indeed help another branch of the immune system to clean up. I think, in general, that this is not obvious; first, it's not obvious to me that senescent cells are unique in creating the "smell" of garbage that leads to inflammation or if it's only one of many types of cells that become damaged and accumulate with age. I'm not sure that killing them physically really helps to improve the situation, because you are creating a wave of remains that has to be taken care of, too.

I personally chose an approach to invest in the immune system and repair its function so that it can do its job better, instead of us thinking that we can substitute it. So far, in medicine, substitution of lost function has only worked well in orthopedics but not in other areas. Therefore, I think that we need to either invest in a mechanism that blocks the appearance of senescent cells or invest into the mechanism of natural eradication to make the immune system work better. For example, if the part of the immune system that is responsible for clearing senescent cells gets exhausted, you can always try to redirect adaptive immunity against them by vaccination; I would see that as a more appealing thing.

Link: https://www.leafscience.org/interventions-to-extend-healthspan-and-lifespan-2018-dr-andrei-gudkov/

Another Example of a Marginal Senolytic Drug Candidate

Today, let us consider what happens when a new area of medical development arises, attracts a great deal of research funding, and then one or more companies raise even larger amounts of venture funding to take the first therapies to the clinic. This is the case for senolytics, the development of therapies - mostly pharmaceuticals - that can selectively destroy senescent cells. Good evidence for these cells to be a root cause of aging has existed for decades, but it wasn't until 2011 that research and scientific funding institutions were presented with animal study data that they couldn't continue to ignore. The years since have been a steady avalanche of ever more funding, evidence to link senescent cells to specific age-related conditions, and demonstrations of reversal of aspects of aging in mice through clearance of senescent cells.

What happens is that people take notice. Any group able to write a credible grant proposal in the aging research community has probably by now written several on the topic of cellular senescence. Grant writing follows the state of funding, and all academic organizations tend to steer themselves towards the better funded areas of their field. Equally, anyone in a position to start a pharmaceutical company or spin off a new program in their existing company is certainly giving strong consideration to senolytic research given the $300 million or so that Unity Biotechnology has raised to date. The upshot of all this is that a great deal of discovery work is taking place, both inside and outside the scientific community; people are sifting drug databases and the compounds of the natural world in search of gold. Of course, the median result is much less valuable.

In any sort of drug discovery research, the outcome of the average well-informed project is usually many dead ends and a marginal lead or two if luck is with the researchers. Good results are rare. This means that the present few effective senolytics will soon be vastly outnumbered by marginal and alleged senolytics, the latter being those for which the research community struggles to replicate results. That in and of itself usually indicates that the effect size is small, or that reported positive effects are due to experimental error. Going forward, as the public at large gains a greater awareness of senescent cells and senolytics, supplement makers will seize upon any plant extracts claimed to have (likely tiny) effects on senescent cells, and start marketing to the gullible. The first thing you should look at for any newly claimed senolytic is the size of the effect. Most can be safely ignored on this basis alone, as is the case in the cell culture study noted here.

Blocking negative effects of senescence in human skin fibroblasts with a plant extract

Cellular senescence is involved in the development of age-related diseases and the loss of tissue functionality with age. Senescent cells accumulate in vivo and their selective elimination increases the healthspan of mice. While transiently present senescent cells have beneficial functions in wound healing, their chronic persistence and accumulation with age negatively affects the surrounding tissue by the senescence-associated secretory phenotype (SASP). This consists of pro-inflammatory cytokines and chemokines, extracellular matrix (ECM) remodelling proteases and growth factors and results in a vicious cycle of progressive functional loss in tissues and organs.

Negative effects of cellular senescence can be counteracted by: (i) delaying the loss of cell type specific functionality mediated by senescence-associated de- or trans-differentiation, (ii) interfering with the negative effects of SASP or by (iii) selectively eliminating senescent cells. Indeed, several clinically approved drugs including glucocorticoids, metformin, rapamycin, and JAK inhibitors attenuate the SASP. In addition, senolytic substances have been identified including quercetin, dasatinib, navitoclax, piperlongumine, fisetin, A1331852, A1155463 and FOXO4 inhibiting peptides.

Solidago virgaurea, also known as goldenrod, is traditionally used as an anti-inflammatory herbal medicine. A recent study identified 3,4,5-tri-O-caffeoylquinic acid as the constituent with the highest reduction of tumour necrosis factor-alpha and interleuin (IL)-1β concentrations. However, the effect of extracts from S. virgaurea on cellular senescence and fibroblast subpopulations have not been studied so far. Here we report an alcoholic extract of Solidago alpestris (1201) with the ability to block negative effects of senescence in human skin fibroblasts including the SASP in vitro. We screened seven different plant extracts. 1201 showed the clearest effects in terms of changing cell morphology and of reducing SA-β-galactosidase activity and was therefore selected for further studies.

The extract 1201 exhibited weak senolytic activity and delayed the acquisition of a senescent phenotype. When administered to stress-induced premature senescent fibroblasts, this extract changed their global mRNA expression profile and particularly reduced the expression of various SASP components, thereby ameliorating the negative influence on nearby cells. The caffeoylquinic acids with their anti-inflammatory property are likely to be candidates for the SASP-attenuating property of 1201, whereas the three derivatives of quercetin, one of the three naturally occurring senolytics reported so far, could be the driving force behind the slow selective elimination of senescent cells. Thus, the investigated plant extract represents a promising possibility to block age-related loss of tissue functionality.

More Supporting Evidence for the "Amyloid then Tau" View of Alzheimer's Disease

Alzheimer's disease is a complex condition because the brain is a complex environment. Neurodegeneration is caused by the accumulation of two forms of protein aggregate, amyloid-β and tau. There is evidence to suggest that each can spur the generation of the other, and that they act in synergy to cause worse harm to the brain than either would alone, but the present consensus is that amyloid-β precedes tau in the development of the condition. It may even turn out to be the case that tau causes the majority of the damage in the later stages of the condition, not amyloid-β.

Whether this means that amyloid-β causes tau aggregration is another question entirely, and one that is unlikely to be adequately answered without the development of reliable means to clear amyloid-β from the brain. That has so far proven to be more challenging than was originally hoped, and even those clinical efforts that did remove amyloid-β to some degree failed to show benefits in patients. Varied factions within the research community have their theories as to why this might be the case, and scientists here note one of them - that by the time clinical symptoms manifest, it is past the point at which removing amyloid-β would be helpful, as tau has become the major issue.

The rate at which the protein amyloid-β accumulates into the sticky plaques associated with Alzheimer's disease (AD) is already slowing by the time a patient would be considered to have preclinical AD, according to a longitudinal study of healthy adults. The research suggests that anti-amyloid therapies would be most effective before individuals reach the threshold for preclinical AD, long before the first signs of memory issues. Determining how early to intervene is a central challenge in slowing the progression of AD. Clinical trials of drugs for lowering amyloid levels typically involve individuals who do not yet have symptoms but are considered "amyloid positive" and at risk for developing AD. These trials have been largely unsuccessful, perhaps because they begin too late.

To untangle the relationship between amyloid-β, the AD-associated protein tau, and memory impairment over time, researchers studied healthy men and women between the ages of 61 and 88 over a five-year period. Brain scans revealed that even trace amounts of amyloid-β predicted future levels of tau, and both preceded memory decline. The researchers found that greater baseline levels of amyloid-β were associated with a faster rate of accumulation, but only to a point, after which higher amyloid-β levels were associated with slower accumulation. "It appears rates of amyloid accumulation already begin to slow in preclinical AD, suggesting it is a relatively late stage of AD progression. Thus, it is crucial to examine older adults early, before amyloid levels have saturated, to intervene to slow disease progression."

Link: https://www.eurekalert.org/pub_releases/2018-04/sfn-dad041718.php

Exercise Increases the Rate at Which New Heart Cells are Produced

To follow on from yesterday's set of exercise related research, here is an interesting note on what exercise does to the basis for heart tissue maintenance. The heart is one of the least regenerative organs in mammals, not capable of repairing itself to any significant degree following injury. Nonetheless, within those limited bounds, exercise makes a sizable difference. This is supported by the evidence showing that heart disease patients have a better prognosis when they maintain a program of exercise, even to the lesser degree that they are capable of sustaining.

In a new study performed in mice, researchers uncovered one explanation for why exercise might be beneficial: It stimulates the heart to make new muscle cells, both under normal conditions and after a heart attack. The human heart has a relatively low capacity to regenerate itself. Young adults can renew around 1 percent of their heart muscle cells every year, and that rate decreases with age. Losing those cells is linked to heart failure, so interventions that increase cell formation have the potential to help prevent it.

"We wanted to know whether there is a natural way to enhance the regenerative capacity of heart muscle cells. So we decided to test the one intervention we already know to be safe and inexpensive: exercise." To test its effects, the researchers gave one group of healthy mice voluntary access to a treadmill. When left to their own devices, the mice ran about 5 kilometers each day. The other healthy group had no such gym privileges, and remained sedentary.

To measure heart regeneration in the mouse groups, the researchers administered a labeled chemical that was incorporated into newly made DNA as cells prepared to divide. By following the labeled DNA in the heart muscle, the researchers could see where cells were being produced. They found that the exercising mice made more than 4.5 times the number of new heart muscle cells as did the mice without treadmill access. After experiencing heart attacks, mice with treadmill access still ran 5 kilometers a day, voluntarily. Compared with their sedentary counterparts, the exercising mice showed an increase in the area of heart tissue where new muscle cells are made. The researchers now plan to pinpoint which biological mechanisms link exercise with increased regenerative activity in the heart.

Link: https://news.harvard.edu/gazette/story/2018/04/exercise-may-help-make-heart-younger-harvard-affiliated-study-says/

Recent Research on the Benefits of Exercise in Later Life

A sizable body of work points to the ability of older individuals to continue to obtain benefits through regular physical activity, and particularly in the case of strength training. A perhaps surprisingly large fraction of what is commonly regarded as an inevitable decline in physical fitness and muscle quality with age is in fact the result of lifestyle choices - in particular the choice to exercise less, and the failure to work on maintenance of strength in muscles. We live in an age of comparative comfort, surrounded by low cost transportation machinery, calories, and tools to substitute for physical effort. The result is a growing number of people who are weak and overweight in comparison to their ancestors. Those ancestors still had a much worse time of it, of course, given the absence of modern medicine and sanitation, but we sabotage ourselves nonetheless.

Today I'll point out a few recent papers on activity and strength (or lack thereof), and the benefits realized (or lost). They may for interesting reading, but I think it is important to bear in mind that this is only of interest because exercise is essentially free, and is a reliable source of the benefits it provides. These benefits are not large in the grand scheme of things: 75% of the fittest people fail to reach 90 years of age. It is impossible to add decades to human life spans through exercise. When looking ahead to the future, the quality and length of our lives will become ever more determined by the state of progress in rejuvenation therapies, treatments capable of repairing the cell and tissue damage that causes aging, and ever less by modestly effective approaches to good general health, a few of which can slightly slow the progression of that damage. Large gains can only arrive through the right sorts of progress in medical science.

Resistance training enhances recycling capacity in muscles

Autophagy is a major catabolic route in cells responsible for the clearance of proteins and organelles. Pathological levels of autophagy are associated with muscle wasting, but physiological levels are important for cellular recycling. In the present study, indicators of autophagy and unfolded protein response (UPR), which is another system for maintaining cellular homeostasis, were investigated from the muscle biopsies after a single bout of resistance exercise and after 21 weeks of resistance training in previously untrained young and older men.

Aging may blunt some of the positive effects of resistance training when it comes to improvement in muscle quality, but the researchers reported that UPR that is induced by the accumulation of misfolded proteins in endoplasmic reticulum (ER) was activated by a bout of unaccustomed resistance exercise regardless of age. Skeletal muscle appears to adapt to resistance exercise similarly in young and older people in many ways.

Exercise after a heart attack. It could save your life

Becoming more physically active after a heart attack reduces the risk of death. A study that followed more than 22,000 patients found that those who became more physically active after a heart attack halved the risk of death within four years. Levels of physical activity were reported 6-10 weeks and 12 months after the heart attack. The difference between answers was considered a change in physical activity over the year following the heart attack.

On both occasions, patients were asked how many times they had exercised for 30 minutes or longer during the previous seven days. Patients were categorised as constantly inactive, reduced activity, increased activity, or constantly active. A total of 1,087 patients died during an average follow-up of 4.2 years. The researchers analysed the association between the four categories of physical activity and death, after adjusting for age, sex, smoking, and clinical factors. Compared to patients who were constantly inactive, the risk of death was 37%, 51%, and 59% lower in patients in the categories of reduced activity, increased activity, or constantly active, respectively. "Our study shows that this advice applies to all heart attack patients. Exercise reduced the risk of death in patients with large and small myocardial infarctions, and for smokers and non-smokers, for example."

Sitting is bad for your brain - not just your metabolism or heart

Researchers recruited 35 people ages 45 to 75 and asked about their physical activity levels and the average number of hours per day they spent sitting over the previous week. Each person had a high-resolution MRI scan, which provides a detailed look at the medial temporal lobe, or MTL, a brain region involved in the formation of new memories. The researchers found that sedentary behavior is a significant predictor of thinning of the MTL and that physical activity, even at high levels, is insufficient to offset the harmful effects of sitting for extended periods.

This study does not prove that too much sitting causes thinner brain structures, but instead that more hours spent sitting are associated with thinner regions, researchers said. In addition, the researchers focused on the hours spent sitting, but did not ask participants if they took breaks during this time. The researchers next hope to follow a group of people for a longer duration to determine if sitting causes the thinning and what role gender, race, and weight might play in brain health related to sitting.

Study highlights need for strength training in older women to ward off effects of aging

"Frailty progresses with aging, but older women who engage in a high level of daily physical activity can reverse certain characteristics related to aging, such as slow walking and decreased function. But for women over the age of 75, muscle strength and endurance declines. Starting resistance exercise when they are young and continuing it is important so that when they reach a very advanced age they have already built up their strength and endurance reserves."

The study looked at 46 women across two different age ranges, 60-74 and 75-90, to learn how physical activity affects frailty differently in the two groups. Researchers found that there was a larger difference between the two groups in terms of muscle strength and endurance among those who were very physically active. With mobility - as measured by the length of a person's step - and basic functional ability, there was a gap between the two age groups among women who engaged in minimal physical activity. However, that gap disappeared if they did a high level of physical activities. "Their main physical activities consisted of light gardening, light housework and stretching. Is this because they are still working and don't have time for exercise, or do they think they are healthy and don't need to? It appears that committing to regular exercise is not yet a standard part of older women's lifestyles and is instead a reactive behavior to, for example, falls or illness."

Two Faces of Macrophages in Cancer Tissue

This popular science article looks at opposing views of the role of macrophages in the development of tumors. Some groups see macrophages as aiding the cancer, and want to suppress them, while others are engaged in turning macrophages into an effective weapon to destroy cancer cells. This two-faced nature echos a range of unrelated work on macrophage behavior. These cells can be classed by their activities into what are known as polarizations. The M1 polarization is aggressive and inflammatory, willing to attack cells and pathogens, while the M2 polarization aids tissue growth and regeneration. The balance between the two shifts according to circumstances. Both are necessary, but M1 is too prevalent throughout the body in older individuals, hindering tissue maintenance. In cancers, the problem is reversed: too many M2 macrophages are present to help the cancer, while too few M1 macrophages actively attempt to destroy its cells.

In the late 2000s, researchers found that leukemia cells highly expressed a gene encoding CD47, a surface molecule known for its role on normal, healthy cells as a "don't eat me" signal to phagocytosing macrophages. Researchers demonstrated in cell culture experiments that macrophages only engulfed leukemia cells that did not display CD47 on their surface, and since then have found CD47 on every type of cancer they've been able to get their hands on. "It was shocking. We knew that we were on the track of a potential therapeutic." At least three biomedical companies have raised and invested tens of millions of dollars to test drugs that block CD47.

But back in 2008, when the researchers first tried to publish work on how macrophages engulfed leukemia cells lacking CD47, reviewers didn't buy it. Since the 1980s, cancer researchers have linked macrophages and macrophage-stimulating genes to tumor growth and poor outcomes for cancer patients, and the cells had been pegged as nothing but bad news when it came to cancer. In 1996, for example, researchers reported that women whose breast cancer biopsies contained a high density of macrophages were much more likely to succumb to the disease over the subsequent five years than those with low densities. The same correlation was later confirmed in a dozen other types of cancer. These cells earned the name tumor-associated macrophages, or TAMs, and research focused on where they came from and how to block or deplete them. The data suggesting that macrophages could help defeat cancer just didn't fit.

TAMs, which can make up as much as 50 percent of a tumor's mass, had been found to repress other immune cell activity, encourage blood and lymph vessel development to support growing tumors, and help cancer cells metastasize to new sites in the body. But over the past decade, some research has surfaced to support the conclusion that TAMs may have an upside. "Several years ago, the idea was, 'Let's deplete these cells because they are bad.' I think now we are back to saying, 'Maybe it's just very complex.'"

Even as therapies that block TAM activity or prevent macrophage recruitment to tumors reach clinical trials, many researchers are not ready to give up on what macrophages may have to offer in the fight against cancer. There's no question that macrophages can participate in antitumor responses, "it's just that the tumors develop a way of polarizing or educating those macrophages to help the tumors rather than destroy them." Many researchers are now taking advantage of macrophages' plasticity to re-educate the cells to work for the patient. One way to switch TAMs from what's known as the M2 phenotype, which promotes cancer growth, to the immune-boosting M1 phenotype is to provide the cells with proinflammatory stimuli, such as interferons or ligands for Toll-like receptors. Alternatively, researchers can directly target molecular switch proteins responsible for driving M2 characteristics, such as PI3-kinase and the transcription factor STAT3. In animal models, drugs that inhibit these molecules have successfully skewed TAMs toward M1 phenotypes and shrunk tumors.

Link: https://www.the-scientist.com/?articles.view/articleNo/52134/title/Macrophages-Play-a-Double-Role-in-Cancer/

Extracellular Vesicles Used to Promote Heart Regeneration in Rats

First generation stem cell therapies largely achieve their results through brief signaling changes, not through any lasting work on the part of the transplanted cells. Those cells in fact die quite rapidly, but the signals they secrete while still alive change the behavior of native cells. This produces benefits such as reduced inflammation or improved regenerative capacity. Given this, why not deliver the signals instead of the cells? It could in principle be an easier, less complex task. Much of cell signaling involves the exchange of extracellular vesicles, tiny membrane-bound packages of molecules. Numerous groups are presently engaged in animal studies of vesicle-based approaches to regenerative therapy, and the one noted here is representative of the type.

The adult human heart cannot regenerate itself after injury, and the death of cardiac muscle cells, known as cardiomyocytes, irreversibly weakens the heart and limits its ability to pump blood. Researchers have turned their focus to stem cell transplantation for cardiomyocyte replacement and recovery of heart function, but studies have shown that implanted stem cells have difficulty surviving and differentiating into cardiomyocytes to repair the damaged muscle. When stem cells were differentiated into cardiomyocytes before implantation, heart function improved, but with a complication: the implanted cardiomyocytes did not contract synchronously with the heart, thus causing potentially lethal arrhythmias (abnormal heart rhythm).

A team of researchres has designed a creative new approach to help injured hearts regenerate by applying extracellular vesicles secreted by cardiomyocytes rather than implanting the cells. Cell-secreted microvesicles are easy to isolate and can be frozen and stored over long periods of time. Such an "off-the-shelf" product has several major advantages over cell therapy-1) it can be used immediately in an acute-care setting, unlike cells that can take months to isolate and grow; 2) it does not cause arrhythmia (which often occurs when cells are transplanted); and 3) the regulatory path towards clinical application is much simpler than for a cell-based therapy.

It is well known from numerous clinical studies that most of the implanted stem cells are washed away within hours of the treatment, but there still are beneficial effects. This has led to the informal "hit-and-run" hypothesis, meaning that the cells deliver their cargo of regulatory molecules before leaving the site of injury. "Consistent with this hypothesis, we postulated that the benefits of cell therapy of the heart could be coming from the secreted bioactive molecules (such as microRNAs), rather than the cells themselves. So we explored whether the benefits of cell therapy of the injured heart could be achieved without using the cells. This way, we would largely simplify the translation into the clinic, and avoid the burden of arrhythmia associated with implantation of contractile cells."

The team derived cardiomyocytes from adult human stem cells and cultured these cells to allow them to secrete extracellular vesicles. The vesicles secreted by undiffereniated stem cells were used for comparison. The researchers then used next-generation sequencing to read their messages and instructions. They found that the extracellular vesicles from cardiomyocytes - but not from stem cells - contained cardiogenic and vasculogenic microRNAs that are very powerful regulatory molecules. The team encapsulated the vesicles in a collagen-based patch that slowly released them over the course of four weeks when implanted onto the injured heart in rat models of myocardial infarction. "We were really excited to find that not only did the hearts treated with cardiomyocyte extracellular vesicles experienced much fewer arrhythmias, but they also recovered cardiac function most effectively and most completely. In fact, by four weeks after treatment, the hearts treated with extracellular vesicles had similar cardiac function as those that were never injured."

Link: http://engineering.columbia.edu/news/cell-therapy-heart-recovery

Dementia Risk Trends Downward and Later in Life, Due in Part to Cardiovascular Health

Research papers and popular science articles noting the ongoing decline in dementia risk have become a regular occurrence. Since dementia is driven in part by cardiovascular aging, it is tempting to suggest that this is a side-effect of the improvements in control over blood pressure and treatment of cardiovascular disease obtained in recent decades. From studies that have run the numbers, that incremental progress is as much due to reductions in smoking as it is to the deployment of successful medications such as statins. We do not yet live in an age in which medical technology has reliably outpaced lifestyle choice in the matter of aging and age-related disease. Interesting, those researchers who run the numbers on dementia suggest that improvements in cardiovascular health cannot explain all of the reduction in dementia risk.

Cardiovascular decline contributes to dementia in a number of ways. Firstly, capillary networks spread throughout tissues become less dense, and so less able to deliver sufficient nutrients and oxygen to cells. Declining fitness and heart failure achieve a similar outcome, in different ways. Blood vessels become less elastic with age, causing the increase in blood pressure known as hypertension. Blood vessel walls become compromised by the fatty plaques of atherosclerosis, initially seeded by an excessive inflammatory reaction to oxidized lipids in the bloodstream, but eventually growing to distort, narrow, and block blood vessels. The combination of increased blood pressure and weakened blood vessels is damaging to sensitive tissues, causing cell death and structural harm. In the brain, aging is accompanied by many tiny, silent strokes, each destroying a minuscule section of brain tissue - but it adds up over time.

Considering the damage done by the above processes, what might account for the missing benefits that do not arise from either slowing or compensating for cardiovascular degeneration in aging? Age-related dysfunction of the immune system might be a candidate. All neurodegenerative disease appears to have an inflammatory component, and the immune system of the central nervous system is arguably far more complex and far more involved in correct function of tissue than is the case elsewhere in the body. Further, better lifestyle choices and better control over infectious disease may well lead to, all other things being equal, a slower decline into immunosenescence. This is speculative thinking, however, and a thesis that would have to be proven from the data.

Dementia trend shows later onset with fewer years of the disease

A recently released study indicates that dementia's impact might be compressing a bit. That is, people might be developing dementia later and living with it for a shorter period of time. In data from four different time periods over a period of 30 years, the mean age at dementia onset increased, while the length of time living with dementia decreased. Is it because prevention and care of stroke today is superior compared to decades ago? Stroke is a major risk factor for dementia.

"Prevention of stroke and reduced impact of stroke are great advances, but neither completely explains the trend we are seeing. We are looking at other causes, such as lower burden of multiple infections because of vaccination, and possibly lower levels of lead or other pollutants in the atmosphere. Early education and nutrition might also play a role. Stroke risk has decreased because of greater control of blood pressure. In the past, if you had a stroke you were at 90 percent greater risk to develop dementia. Today, you have a 40 percent greater risk."

Are Trends in Dementia Incidence Associated With Compression in Morbidity?

A total of 5,205 participants from the Framingham Original and Offspring cohorts were studied. Four epochs were considered from 1977-1984 to 2004-2008. Gender and education adjusted 5-year mortality risks were estimated using delayed entry Cox models with the earliest epoch as reference category. Stratified analyses by sex, education, and age were undertaken. A nested case control study of 317 dementia cases and 317 controls matched on age, gender and epoch was initiated.

In the whole sample, 5-year mortality risk has decreased with time, it was 33% lower in the last epoch compared to the earliest. In the 317 persons who developed dementia, age at onset increased (1.5 years/epoch), and years alive with dementia decreased (1 year/epoch) over time. We observed however, a decreased adjusted relative mortality risk (by 18%) in persons with dementia in 1986-1991 compared to 1977-1983 and no significant change from then to the latest epoch. The nested case control study suggested in matched controls that 5-year mortality relative risk had increased by 60% in the last epoch compared to Epoch 1.

In conclusion, in the Framingham Heart Study population, in the last 30 years, disease duration in persons with dementia has decreased. However, age-adjusted mortality risk has slightly decreased after 1977-1983. Consequences of such trends on dementia prevalence should be investigated.

Towards a Better Epigenetic Clock

Researchers here report on an improved version of the epigenetic clock. A few carefully defined patterns of DNA methylation, including the original epigenetic clock, correlate quite closely with age. The current commercial implementation of the epigenetic clock, MyDNAge, has a margin of error of two years or so. While the consensus is that the clock reflects biological age, it is still the case that we might ask what exactly is being measured. The answer to that question remains to be established. It is plausible that DNA methylation changes with age are a reaction to all of the forms of cell and tissue damage that drive aging, but this is by no means certain - it could be more specific than that, tied to only some of the causes of aging.

One of the major goals of geroscience research is to define "biomarkers of aging", which can be thought of as individual-level measures of aging that capture inter-individual differences in the timing of disease onset, functional decline, and death over the life course. While chronological age is arguably the strongest risk factor for aging-related death and disease, it is important to distinguish chronological time from biological aging. Individuals of the same chronological age may exhibit greatly different susceptibilities to age-related diseases and death, which is likely reflective of differences in their underlying biological aging processes. Such biomarkers of aging will be crucial to enable evaluation of interventions aimed at promoting healthier aging, by providing a measurable outcome, which unlike incidence of death and/or disease, does not require extremely long follow-up observation.

One potential biomarker that has gained significant interest in recent years is DNA methylation (DNAm). Chronological time has been shown to elicit predictable hypo- and hyper-methylation changes at many regions across the genome, and as a result, the first generation of DNAm based biomarkers of aging were developed to predict chronological age. The blood-based algorithm by Hannum and the multi-tissue algorithm by Horvath produce age estimates (DNAm age) that correlate with chronological age for full age range samples. Nevertheless, while the current epigenetic age estimators exhibit statistically significant associations with many age-related diseases and conditions, the effect sizes are typically small to moderate. One explanation is that using chronological age as the reference, by definition, may exclude CpG sites whose methylation patterns don't display strong time-dependent changes, but instead signal the departure of biological age from chronological age. Thus, it is important to not only capture CpG sites that display changes with chronological time, but also those that account for differences in risk and physiological status among individuals of the same chronological age.

Previous work by us and others have shown that "phenotypic aging measures", derived from clinical biomarkers, strongly predict differences in the risk of all-cause mortality, cause-specific mortality, physical functioning, cognitive performance measures, and facial aging among same-aged individuals. What's more, in representative population data, some of these measures have been shown to be better indicators of remaining life expectancy than chronological age, suggesting that they may be approximating individual-level differences in biological aging rates. As a result, we hypothesize that a more powerful epigenetic biomarker of aging could be developed by replacing prediction of chronological age with prediction of a surrogate measure of "phenotypic age" that, in and of itself, differentiates morbidity and mortality risk among same-age individuals.

Using a novel two-step method, we were successful in developing a DNAm based biomarker of aging that is highly predictive of nearly every morbidity and mortality outcome we tested. Training an epigenetic predictor of phenotypic age instead of chronological age led to substantial improvement in mortality/healthspan predictions over the first generation of DNAm based biomarkers of chronological age. In doing so, this is the first study to conclusively demonstrate that DNAm biomarkers of aging are highly predictive of cardiovascular disease and coronary heart disease. The new measure, DNAm PhenoAge, also tracks chronological age and relates to disease risk in samples other than whole blood. Finally, we find that an individual's DNAm PhenoAge, relative to his/her chronological age, is moderately heritable and is associated with activation of pro-inflammatory, interferon, DNA damage repair, transcriptional/translational signaling, and various markers of immunosenescence: a decline of naïve T cells and shortened leukocyte telomere length.

Link: http://www.aging-us.com/article/101414/text

Glial Cell Behavior Critical to Proficient Central Nervous System Regeneration

Why can species such as salamanders regrow organs and limbs while mammals cannot? This proficiency even extends to portions of the central nervous system, such as the spinal cord. In recent years, researchers have made good progress in understanding exceptional regeneration, finding that, for example, differences in the behavior of immune cells called macrophages are essential to regrowth. In the central nervous system, glial cells are somewhat analogous to macrophages in other tissues, and in the research noted here, scientists report on evidence for an equivalent importance in mammalian versus salamander regenerative capacities.

Given the macrophage and glial cell connection, this area of comparative biology is moving of late from speculative to relevant to clinical development. Numerous research groups are investigating the alteration of macrophage and glial cell behavior in order to spur greater regeneration in mammals. These cells can be classified by their behavior, either aggressive and inflammatory while seeking out pathogens, or more focused on aiding regeneration. Both behaviors are needed, but in mammals, and in the old, there is too much of the first type and too little of the second type of behavior. In learning to adjust cell behavior to change this imbalance, the foundations may be laid for more profound enhancements of regeneration in the years ahead, building on what is learned from salamanders.

One of the most vexing problems with spinal cord injuries is that the human body does not rebuild nerves once they have been damaged. Other animals, on the other hand, seem to have no problem repairing broken neurons. Researchers have studied an amphibian known as the axolotl or Mexican salamander. Captive-bred axolotls are frequently used in biological research, both to learn from the animal's remarkable ability to regenerate body parts and to help inform conservation efforts.

When an axolotl suffers a spinal cord injury, nearby cells called glial cells kick into high gear, proliferating rapidly and repositioning themselves to rebuild the connections between nerves and reconnect the injured spinal cord. By contrast, when a human suffers a spinal cord injury, the glial cells form scar tissue, which blocks nerves from ever reconnecting with each other.

Researchers traced the molecular mechanisms at work in each case. They found a particular protein called c-Fos, which affects gene expression, is essential to the processes axolotls use to repair injured nerves. While humans also have c-Fos, in humans the protein functions in concert with other proteins, in the JUN family, that cause cells to undergo reactive gliosis, which leads to scar formation. In axolotls, this molecular circuitry is carefully regulated to direct axolotl glial cells toward a regenerative response instead.

"Our approach allows us to identify not just the mechanisms necessary to drive regeneration in salamanders but what is happening differently in humans in reposes to injury. In addition to spinal cord regeneration, our work also focuses on other forms of regeneration including scar-free wound healing and limb regeneration."

Link: https://www.eurekalert.org/pub_releases/2018-04/eb2-eso041218.php

Cornelis (Cees) Wortel, Ichor Therapeutics Chief Medical Officer, on Rejuvenation Research and Its Engagement with the Established Regulatory System

Ichor Therapeutics is the most mature of the US-based companies that have emerged from the SENS rejuvenation research community in recent years. You might recall a number of interviews back in the Fight Aging! Archives with founder and CEO Kelsey Moody. He has his own take on how our community should proceed from laboratory to clinic: he is very much in favor of demonstrating (a) that the formal regulatory path offered by the FDA can work for the treatment of aging, and (b) that - given the right strategic approach - rejuvenation therapies can attract the attention, collaboration, and backing of Big Pharma entities in the medical development marketplace. Indeed, he holds that this is a vital transition for the community to make.

As a step towards this goal, Ichor has recently gained the support of long-standing industry veteran Cornelis (Cees) Wortel, who is aiding the company in the role of Chief Medical Officer. He has advised on and guided near two hundred clinical trials in his career, and is now focused on helping Ichor's therapies to achieve success in the regulatory pipeline. Here, he writes on some of the subtleties inherent in the complex regulatory systems of the FDA in the US and EMA in Europe, and the priorities that companies must develop in order to be successful - particularly those that newcomers to the regulatory environment might find surprising or unexpected. I think you'll find it a most interesting and informative read, regardless of your position on the current regulatory system for medical research and development. You might look at some of my recent comments on nuanced opposition to the FDA as a companion piece to the article here.

Most products provided to people, which may impact their safety one way or another, undergo some form of regulatory review and approval before they are allowed on the market. Medications and devices undergo a very extensive development, review and approval process, as they can have a significant short term and very long term impact on a patient's safety and quality of life. The regulatory bodies, including the FDA and analogous regulatory authorities in other parts of the world, are not perfect. The premise of regulation in medical development however is good and very necessary: to ensure that people are safe and that therapies work. These regulatory agencies focus on consumer protection and aim to prevent serious harm such as that which came to patients when medical research was not done properly, such as the thalidomide disaster which caused countless women to give birth to babies with extremely deformed limbs and other birth defects. Treatments also have to have the effect they promise, as patients pay for them and tolerate the side effects that often come with the treatments. The overall risk-benefit balance needs to be known and acceptable.

The execution of the regulatory development path can be flawed in all the usual ways present in any structure built by fallible human beings, however. I would imagine everyone who has spent significant time working with regulators has a list of items they'd like to change or improve upon. That said, the regulatory systems available are the only viable way to put safe, new treatments into the clinic, and make them ultimately available to large numbers of people. Once we realize and embrace this, we can engage with the regulatory agencies in an informed and purposeful manner and work towards the best common path forward across different parts of the globe.

I have just recently engaged with the rejuvenation research community and it seems that it has been firmly focused, and rightly so, on the early stage research portion of progress, but it may have had comparatively little experience with later stage clinical development of agents for this new frontier. This is the natural progression of a new and exciting frontier in clinical development. I understand the existence of a certain amount of regulatory phobia, as the first view of the enormous cost and complexity of the path of clinical trials for a new therapy is very intimidating. Having been engaged in many clinical trials developing potential treatments for life-threatening diseases such as pediatric brain tumors, I also understand the enormous frustration and the need for access to new potential solutions. But as long as drug candidates are under clinical study, there is still a real inherent risk that one does more harm than good (which is exactly what the trials are intended to find out) and thus the regulations are designed to protect the trial participants first and foremost. In too many cases potential treatments have turned out ultimately harmful or have a much more modest effect impacting the risk-benefit balance negatively. Thus engaging the current regulatory systems is the road we have to travel in order to get treatment options in the hands of medical professionals and patients.

Not all study drugs in development make it; in fact most drugs turn out to be toxic or do not have an acceptable risk-benefit balance. I have been lucky enough to be part of a few innovative drug development projects which dramatically improved the medical outlook for some serious diseases (Remicade, the very first anti-TNF monoclonal antibody was the first successful drug development project I became deeply involved in). It is very gratifying to know that so many patients with Rheumatoid Arthritis, Crohn's Disease and other serious ailments are benefitting from treatment with biologicals, far beyond the reach of any single doctor's direct patient focused capabilities.

For drug development, there are ways to de-risk the complex development path. The development pathway is broken up in separate pieces, which makes the phases more manageable and the development risks (and safety risk for the trial participants) are decreased along the way. Doing this translational step from science to the clinic poorly however, often results in very promising technologies 'dying on the vine' and therefore deprives us all of potential worthwhile solutions. One of the reasons I joined Ichor Therapeutics is to help build this development bridge for the team across its varied projects, to build on and validate the scientific focus by constructing a robust infrastructure for the clinical development of innovative new options to treat aging and its conditions.

A Pharmaceutical Developer's Initial Considerations

As a company founder and pharmaceutical developer, with a specific implementation of new technology in mind, what should one be thinking about? An important initial step is to build a living model of the path ahead, and the first and most important consideration is which indication or indications to pursue. An indication is the reason to use the treatment under development, meaning the specific medical condition and class of patients that will be treated to produce the intended benefits. For example, a therapy that enhances muscle growth might be applied, depending on the technical details, to muscular dystrophy, frailty syndrome, sarcopenia, cancer cachexia, and so forth. Selecting the best initial indication can be based on different departing points: the indication with the best regulatory approval pathway versus an indication which reaches the most patients in a common disease, for instance. Choosing an indication also depends on the initial funding available and timeline constraints. There are almost always far more choices than can reasonably be tackled in the near future by any one company, and understanding the development ramifications of each top contender is key.

Interactions with regulators over the initial development years of any drug candidate will be focused on preparing for, building, and conducting a series of experiments - clinical trials - to rigorously prove that the therapy is safe and effective for the selected indication. This will involve a sizable amount of time and effort; the following costs are middle of the road estimates for indications with a high medical need and a modest sample size studying a chemical drug and might be halved or doubled for any specific company and therapy. Much will depend on the cost of manufacturing the therapeutic, implementing the pre-clinical programs, the regulatory filings, the type of disease and therapy, the medical assessments needed to prove safety and efficacy, the required length of follow up for patients, the geographical location of the trials and so forth.

a) Getting ready for the pre-trial engagement with regulators: design the overall development plan, rigorously develop the manufacturing process and implement the animal studies for initial safety assessment and other scientific building blocks such as mechanism of action and drug exposure. The doses in the animal models are much higher and exposure much larger than will be given to people and thus provide a safety margin. Costs depend on many factors, including whether the drug in development is a chemical or biological drug, the duration of intended treatment and number of patients dosed for instance. This initial work can easily cost $4-6 million, of which about half goes to the manufacturing.

b) Phase I trials: the purpose is to establish safety in a limited number of people (first in man and thus limited exposure of number of individuals) and obtain a baseline set of mainly safety data across escalating doses. Expect at least $2.5-4 million for the trial alone, and then an additional $2.5-3 million for ongoing support and all of the other work necessary to run the development team and activities in a company.

c) Phase II trials: the purpose of phase II is to 1) expand the safety database on recipients of the study drug and to start understanding how the trial endpoints are changed due to exposure to the study drug, meaning the specific measurements of the disease needed to prove safety and effectiveness, and 2) obtain information on the optimal dosage. It takes often at least 300 patients to obtain a rigorous set of data for these items. Much depends on the magnitude of the difference in an endpoint between treated and control participants. This builds the necessary data to design a Phase III. Often multiple Phase II studies are needed. This will cost $10-15 million for a single Phase II trial, and expect the average pharmaceutical company to spend another $10-15 million on ongoing operations and related costs.

d) Phase III trials: the purpose of Phase III is to determine the treatment benefit to a specific population. It also provides most of the safety data. Two such trials are typically needed, and these are the big, expensive, high-publicity projects. The cost will often run $25-50 million for the trial alone.

e) Often other specialized Phase II trials are needed to study the effects on the heart, metabolic breakdown of the study drug, and interactions with other drugs already on the market, for instance, adding to the cost. Also not included are the ongoing manufacturing costs for the study drug needed for the trials, which for each Phase grows in size of number of patients included in the trial, as well as all the regulatory costs (for instance safety reporting). Later stage trials also often require expanded pre-clinical safety work.

The overall development costs vary per study drug and indication and often run in the hundreds of millions of dollars or more. Once a drug is approved for one indication, one can build on the existing file to develop follow-on indications, saving significantly on additional development costs.

A full Gantt chart for the end to end process of all the development tasks might take 3 months to assemble and be 3 meters long when printed out. Given that, and the escalating costs during the development timeline, the more that can be done early on to consider and design the best path ahead, the better off one is. No-one wants to have to raise the funding to repeat a later stage trial which came up short, but this happens! In many cases, better planning and choices made far earlier could have avoided such costly outcomes.

An Initial Model of Indications

Many therapies will have multiple possible indications, which can be developed in interactions with regulators. Some will be better than others from the perspective of establishing a foothold in the clinic, and some will be better than others from the point of view of helping more patients (suffering from a disease which affects more people). It is usually the case that these two concerns are opposed as far as size of the required dataset for approval: the intent of the regulator is to protect the public, and applications for approval that lead to the most widespread use will generally require more evidence, time, and funding to reach a sufficient standard of proof of safety and efficacy.

Thus the preferred strategy (if possible) for clinical development professionals is to put forward an initial application for a narrow, critical usage that solves a focused, high medical need problem, one that can be evaluated and proven more easily. Then, once this is well underway, the company can expand their work with regulators to cover other, larger uses of the therapy. This sort of incremental approach to development also allows for applying what one has learned along the way, letting it be more readily incorporated into the ongoing development of the product. A second regulatory application will usually be able to build on the manufacturing and pre-clinical dataset developed for the first indication.

When looking over possible indications, one should consider the following:

a) The medical need - the greater the better. Are patients suffering severe disease effects? Is there no existing therapy? This goes a long way towards determining the degree to which all involved (patients, professionals, doctors, and regulators) will work with you and proactively support your application through the process.

b) The patient population size. This is important in several ways. Firstly, a small population size can lead to an orphan designation, which can offer a number of advantages to development, though maybe now less so than used to be the case. On the other hand, a population that is too small will require more time to enroll the number of patients needed and will render the company unable to produce data that is rigorous enough to pass muster in a reasonable timeframe. A very large population is good as enrollment may be much easier and it supports the ultimate goal of a company to help more people, but as noted above it will lead to greater demands for stringent proof of safety from the regulators - it is often not the optimal first step, but better attempted as an expansion of an indication with a smaller patient population, once the study drug manufacturing is accepted and the drug is proven to be safe in at least one indication. Larger disease indications also may have more competing treatments under development and thus also compete for patient enrollment in these studies.

c) The disease severity. A more severe disease makes it easier to obtain strong data, because the size and speed of onset of the intended benefit resulting from a successful therapy is proportionally larger. It is much easier and less costly to prove effectiveness given large and relatively rapid changes in patient health than it is for more subtle effects which appear over time. Large and rapid beneficial changes are generally only possible to achieve in severe disease conditions.

d) Plausible endpoints that can be measured, and the cost of measuring them. Mortality is a definitive and good endpoint because it is less expensive to assess, but a hard to reach endpoint because patients will have to be followed for many years, unless the disease is rapidly fatal and amenable to intervention. Endpoints based on simple biomedical assays or measurements that can run soon after a therapy is administered, such as presence of a persistent virus, or blood pressure, or blood lipid levels, are much more cost effective where they have been well established in the field and are already accepted by regulators for an indication. Where they have not been established, be aware that the process of introducing a new surrogate endpoint is a long and expensive struggle. Further, some endpoints, such as imaging endpoints, can increase the cost of a trial significantly.

e) The duration of a trial. The cost of a trial is as much determined by its duration as by the number of patients enrolled. Diseases for which there is much competition to enroll patients can be also hard, as all companies and academic groups are looking for the same patients. Some indications will be ruled out for a company at earlier stages simply because there is no practical way to raise sufficient funding given a very long timeline for trials to lead to concrete results.

In most cases, the best approach will either stand out, or be the one left standing after others are eliminated. Here, eliminated can mean "put off for later" as all companies will try to expand their indications as they move forward with more successful data and proven confidence in their approach.

Orphan Indications

Orphan designation can be obtained for an indication that has a has a small population size and great medical need. The intent on the part of regulators is to incentivize companies to work on therapies for what would otherwise be financially impossible diseases. This is achieved through a combination of fast-tracking, vouchers to speed later development, and a greater willingness on the part of regulators to work with companies to smooth the passage of a therapy for an orphan indication. Success in an initial orphan indication has in the past been a more reliable road to initial approval for many companies, even though on the whole it doesn't make the process significantly less expensive. As a consequence, a complex structure and industry has sprung up around the orphan designation, which has arguably veered into attempts to game the system.

On this topic, it is important to realize that the system is not just the rules as written. It is the intent of the regulators, the interpretation of the regulations, and the relationship built with regulators. I have sat in numerous meetings over the years listening to people engage with the regulators to try to design short cuts, where in the end they would have been far better off trying to work within the regulations while building the relationship with regulators in different jurisdictions around the world. Regulators are people just like the rest of us, and being open, earnest, and intent on producing a good outcome for patients receiving the treatment goes a lot further than aggressively trying to cut corners and rules-lawyering. The degree to which the regulatory teams you interact with are engaged with you can be an important determinant of the pace of the regulatory progress. For instance, once I have been happily surprised to receive a phone call from an FDA doctor overseeing the complex important trial I was running, asking how the agency could help us to increase the difficult enrollment and help getting the trial finished.

On starting with an orphan indication, consider, for example, that most gene therapies will be applicable to some form of genetic disorder. If a gene or protein is being manipulated, then there is probably a population of patients who have loss of function mutations in that gene resulting in an inherited disorder. But what if there are only ten such patients ever recorded, all of whom die young, and none presently known? It simply isn't practical to try to address this super rare condition at the outset of development as an orphan indication. Even if a patient is found in the next few years, the results from one intervention are not rigorous enough to proceed with. I'm aware of a trial for a rare condition that lasted for more than 25 years in order to find 90 or so patients, for example, and that is far beyond any timeline a startup company should be considering.

Further, is a proposed orphan designation biologically defensible? For example, one could look at the very large HIV patient population and try to designate a small orphan population of individuals who show adverse reactions to the common antiretroviral drugs, and thus cannot find effective treatment without bothersome side effects. But is that designation of a biological population, and the measures or metrics used, widely accepted by the research community and by regulators, or does it look more like an entirely novel slicing and dicing of the patient population to enable the aforementioned gaming of the system to try to gain advantage? If the end goal is to treat all HIV patients, then the regulators will see that and treat the application accordingly.

At the end of the day, the final safety database resulting from the clinical trial work available for submission should provide sufficient protection to the population of patients who will receive the treatment in the real world. And if that population would be much larger than the one studied, side effects that are less common (and thus not likely observed in the smaller population) will impact the larger population and only be found after exposure of many more individuals. It is because of this that regulators are stringently doing their reviews. Consider work on an orphan indication, but don't take it as a mandatory step and plan to build a safety database commensurate with the intended patient exposure.

Off-Label Usage

Off-label usage interacts with orphan indications and other incremental approaches to providing a therapy to an ever-large patient population over time, and can be viewed through a similar set of lenses. In principal, any approved medical technology can be prescribed for off-label use - for use with another, different medical condition, unrelated to the approved indication. The manufacturer cannot advertise that use, but physicians and patients can follow their own judgment. In practice, consider that the intent of the regulator is firstly to minimize possible harm to patients, and secondly for all use to be tested and proven to accepted and sufficiently high standards. Small amounts of off-label use will typically fly under the radar, as regulators have limited resources. If off-label use expands greatly for any particular therapy, then regulators are bound to intervene and with good reason.

Thus it isn't wise to adopt a restricted or orphan indication and expect off-label use to take the therapy to the broader patient population. Ethically one should be going through the formal and full regulatory process to bring a therapy to that larger population in order to do no harm (primum non nocere, as the first principle). Doing things the right way in the end also works far more effectively than trying to find loopholes and does justice to the risk taken by the study participants and the recipients of the drug when on the market.

There is another factor to consider, as well. A common joke in the development community is that "it is easy to obtain approval, but hard to obtain reimbursement." It is of course not at all easy to obtain approval, which is where the humor lies. In recent years, the payer institutions, such as insurance companies and government medical entitlement programs, have become a gatekeeper and very important factor in the drug development planning of pharma/biotechnology companies. It used to be the case that one could largely put this off as a concern in the earlier stages of company development, but now it has become the case that one can have a therapy approved, but find that no insurance company or other payer will pay for it. Thus in addition to proving worthiness to regulators, when planning trials one must also take into account the evidence that payers will require in order to accept the treatment in their plans. This also serves to suppress any significant off-label use.

Aiming to be a Worldwide Company

It is a good strategy, and well established in practice, to work on application for approval of an indication with multiple regulatory bodies. The goal is to make a successful therapy available to patients globally and a larger eventual market also provides a more realistic scenario to recoup the significant developmental costs and eventually may provide profits for corporate growth, return of investment for early (high risk) investors and further development of additional drug and indications. For example, the US FDA and the European EMA and others, have a solid set of guidelines for harmonized submissions under the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). In the course of talking to both the US and EU, one can craft a plan for trials that will satisfy both agencies, at a similar cost to just one filing. The trials are designed to have the standard components and answer all specific questions for each party, are run once, and provide data for multiple applications, in order to gain approval to access two or more large markets.

My experience is largely with the FDA and EMA. I prefer Europe, as in my experience the Netherlands and Belgium are the best and the fastest locations for the initiation of the initial Phase I study. In general, studies can be conducted at a lower cost and the regulations are more accommodating in Europe. Currency exchange rates can influence these cost differences dramatically, of course.

If Europe is cheaper and faster, then why submit to the FDA early on? A counterpoint is that the US has deep clinical research experience for many diseases in its academic centers and hospitals, and a very sophisticated disease tracking system. This helps in designing clinical trial protocols and predicting enrollment. It also has an extremely large patient population. Compared to Europe, one does not have to deal with quite so many language barriers in the execution of clinical trials. So each continent has its own advantages and certainly the indication should be driven by the geography: certain diseases are not found in the highly developed countries for instance and others are predominantly found there due to lifestyle issues. Certain diseases can only be found in certain geographies or populations.

In summary, the regulators will accept clinical trial data that is developed under ICH guidelines from many parts of the world as long as the clinical trials are implemented appropriately and it is worthwhile to engage with multiple regulatory agencies once one enters later stage trials. As the regulations and local issues constantly change, it is important to keep up to speed or receive the latest information from professionals in the field.

Developing for Quality is Vital

As I mentioned, one of the important parts of the early work in a company that leads up to engagement with regulators is to develop a highly robust development plan and manufacturing and toxicity assessment process. This is the item that surprises many founders, both in terms of the stringency required by regulators, and in terms of the cost of achieving this goal.

It is comparatively easy to produce research grade products on an ad hoc basis, with a moderately wide variation in quality of the output. The core demonstration in cells or mice in any gene therapy paper can be recreated in a laboratory for $100,000 or less, and much of that cost lies in setting up the protocols, not actually running them or assessing the mice. That is far from good enough for a study drug entering the clinic, however. It does in fact cost a few million dollars to assemble a suitable infrastructure to narrow down the product quality to a level suitable for medicine. Appropriately manufactured drug product needs to be used in the definitive pre-clinical toxicity tests as well (non-GLP experiments can provide early stage guidance to select drug candidates and inform the toxicity models).

The focus on developing the overall development plan and required infrastructure and embracing its necessity from the start is one of the distinguishing marks between successful and likely-to-fail startup companies. Smaller startups are able to make enormous advances with relatively little initial funding nowadays, often stimulated with local seed investments. The next phase during the "valley of death" selects the ones which will continue to grow, as they are able to obtain follow-on funding for the more financially challenging phases of the development path. In order to obtain such follow-on funding, a solid and living development plan and meticulous execution of the steps (and if needed, adjustments to the plan!) are key. It pays to be data driven. So is making sure one always has a little extra financial buffer before the next round of funding is thought to be needed, as milestones are always harder to meet and may take a little bit longer. Having to go back for more money before a value inflection milestone is a hit will cost dearly.

Regulation is Complex, and Guidance is Necessary

I would not advocate start up founders attempting to navigate the drug development pathway and regulatory system by themselves. While founders as a category are obviously capable of rapid self-education, in the case in which they are not yet trained and have access to expertise, this isn't in the same category of difficulty as, say, raising the first round with a lead investor (and we all know how difficult that is). It is a much more complex, living, constantly dynamic system that changes in its nuances year to year, and is as much about actual practice (interpretation of regulations), good people, and knowledgeable resources, as it is about the regulations as written.

Find a guide who understands drug development and the regulatory systems you intend to work with very early in the life of the company, soon after founding, and preferably before even starting on the development work - as that work will be strongly shaped by the nature of the indications you choose. Talk to several such people to obtain different views of the development path and regulatory field, and engage one as a consultant and truly integral part of your team. Use smart outsourcing for those activities, which are much better done in specialized (large scale) vendors, and use their highly specialized expertise in a true team like fashion. Never lose oversight though, and manage for success with your associated expert partners as extended team members.

In summary, drug development is a challenging road - don't let anyone tell you differently. The reward at the end is building an extended team with highly specialized complex expertise, now successfully applied, and resulting in the ability to meaningfully improve the lives of patients. Once the core engine is built and running, many projects can be taken through the pipeline and new medical frontiers can be forever changed.

DNA Demethylase Activation via Klotho Reduces Arterial Stiffening in Mice

Age-related hypertension is largely a consequence of arterial stiffening, as the loss of elasticity causes the evolved feedback mechanisms that control blood pressure to run awry. For the causes of blood vessel stiffening, we can look at, for example, cross-linking in the extracellular matrix, and senescent cells and other sources of inflammation producing calcification in blood vessel walls. Other sources of dysfunction appear to involve more complex and poorly understood changes in cell behavior, however. This includes the failure of vascular smooth muscle tissue to contract and dilate appropriately, and alterations in the activities of cells responsible for maintaining the structure of the extracellular matrix that determines the physical properties of blood vessel walls.

Changes in cell behavior are more complicated than purely chemical processes such as cross-linking, but also more comfortable for researchers used to the present dominant approach in medical research, which is to deliver new instructions to cells, in an effort to partially override their reaction to damage and the aged environment. The open access paper here is an example of the type. Benefits can be achieved in this way, as the stem cell research community has demonstrated over the past few decades, even though it is not the most optimal path forward for the treatment of aging. Override one narrow reaction to underlying damage, and the damage is still there, still causing all of its other secondary and later problems.

DNA demethylation is an important process that maintains transcriptional activity of genes. An increase in methylation in the promoter region of a gene diminishes the promoter activity and gene transcription. Numerous studies showed that DNA methylation is increased with age. Coincidently, the prevalence of arterial stiffness and hypertension also increases with age. Arterial stiffening is an independent predictor of cardiovascular outcomes, such as hypertension, myocardial infarction, cognitive decline in aging, stroke, and kidney diseases. However, the relationship of DNA methylation and aging-related arterial stiffening is unclear. Whether increased methylation led to arterial stiffening has never been determined. Physiologically, an appropriate methylation level is maintained by the balanced methyltransferase and demethylase activity. In this study, we assessed if activation of the demethylase affects arterial stiffening and hypertension in aged mice.

The Klotho gene was originally identified as a putative aging-suppressor gene in mice that extended lifespan when overexpressed and caused multiple premature aging phenotypes when disrupted. The Klotho level decreases with age, while the prevalence of arterial stiffness and hypertension increases with age. At age 70 years, the serum level of Klotho is only about one half of what it was at age 40 years. Moreover, the serum Klotho level is significantly decreased in patients with arterial stiffness in chronic kidney diseases. Our recent study showed that haplodeficiency of Klotho gene caused arterial stiffness. We found, in cultured renal tubule cells, that a small compound (compound H) may be a potential inducer of Klotho gene expression. Whether compound H promotes Klotho expression and release in vivo has never been determined. In this study, we investigated whether compound H increases Klotho levels and attenuates aging-associated arterial stiffening and hypertension.

Our results demonstrated that aging-related arterial stiffening and hypertension are attributed, at least in part, to the increased DNA methylation. Compound H activates demethylases and attenuates arterial stiffening and hypertension in aged mice likely via increasing the Klotho levels. Aging-related arterial stiffness was associated with accumulation of stiffer collagen and degradation of elastin. These changes were effectively attenuated by compound H, suggesting rejuvenation of aged arteries.

Link: https://doi.org/10.1111/acel.12762

A Set of Marginal and Alleged Senolytics Show No Meaningful Benefits in a Cell Study

Senolytic compounds are those that selectively destroy senescent cells. As the accumulation of senescent cells is one of the root causes of aging, and senescent cells contribute directly to many specific age-related diseases, there is some interest in the development of effective senolytics. As is the case for any field of medical development, however, there are as many marginal and possible senolytic drugs as there are useful and proven senolytic drugs. The size of effect, the nature of the side-effects, and the quality of the evidence all matter greatly - indeed, this is the whole of the point when looking at whether a particular compound is viable or not.

The researchers here report on a few of the marginals and the possibles, compared against navitoclax, and observed no useful effect in a cell study. This is useful confirmatory work, even through the outcome is to be expected based on past evidence, particularly for quercetin. That said, it is important to note that different types of senescent cell have been shown to have quite different degrees of vulnerability to various classes of senolytic. It isn't quite as straightforward as failure in one cell type disqualifying a potential senolytic completely, but more a consideration of the balance of evidence from multiple studies.

Senolytic drugs hold the perspective to specifically target senescent cells and thereby to rejuvenate tissues or organisms. Several compounds have been suggested to possess senolytic effects, including navitoclax (ABT-263), quercetin, danazol, and nicotinamide riboside. ABT-263 inhibits BCL-2 protein family members, which are crucial regulators of the apoptosis pathway. ABT-263 was shown to deplete senescent cells of human umbilical vein epithelial cells (HUVECs), fibroblasts, but not human primary pre-adipocytes. Danazol is a synthetic androgen with telomere elongating capacity, which has been used to target accelerated telomere attrition - a hallmark of aging and senescence. Quercetin is a proteasome activator with anti-oxidant properties that triggers apoptosis via the BCL-2 pathway. Nicotinamide riboside increases levels of nicotinamide adenine dinucleotide (NAD+). Aged mice supplemented with nicotinamide riboside revealed increased lifespan and rejuvenated muscle stem cells.

Primary cells undergo a limited number of divisions before entering the state of replicative senescence. The process of senescence induces changes in morphology, metabolism, secretory phenotype, and differentiation potential of cells, thereby having a significant impact on experimental outcomes and affecting their therapeutic potential. This applies particularly to mesenchymal stromal cells (MSCs), which raise high hopes in tissue engineering and are concurrently tested in a multitude of clinical trials. MSCs comprise a multipotent subset of cells, capable of differentiation towards osteogenic, chondrogenic, and adipogenic lineages. The selective removal of senescent MSCs from cultures might improve standardization and effectiveness of cell preparations for cell therapeutics in regenerative medicine. We have therefore directly compared the senolytic capacity of ABT-263, quercetin, danazol, and nicotinamide riboside in human MSCs during long-term culture.

The effects of these compounds were analysed during long-term expansion of MSCs, until replicative senescence. Furthermore, we determined the effect on molecular markers for replicative senescence, such as senescence-associated beta-galactosidase staining (SA-β-gal), telomere attrition, and senescence-associated DNA methylation changes. Experiments revealed that ABT-263 had a significant but moderate senolytic effect. This was in line with reduced SA-β-gal staining in senescent MSCs upon treatment with ABT-263. However, none of the drugs had significant effects on the maximum number of population doublings, telomere length, or epigenetic senescence predictions. Of the four tested drugs, only ABT-263 revealed a senolytic effect in human MSCs - and even treatment with this compound did not rejuvenate MSCs with regard to telomere length or epigenetic senescence signature. It will be important to identify more potent senolytic drugs to meet the high hopes for regenerative medicine.

Link: https://doi.org/10.1186/s13287-018-0857-6

As Cicero Said, We Must Fight Against Aging as We Would Against a Disease

The firm distinction made between aging and age-related disease is a modern phenomenon, a product of the way in which the regulation of medical research and development has progressed. It wasn't so very long ago, considered in the grand scheme of things, that much of dementia and cardiovascular disease were thought parts of aging, prior to the ability to accurately map and categorize specific biological manifestations of aging. Present regulatory systems are set up to approve (a) the existence of clearly defined and bounded medical conditions based more on their biochemistry than their epidemiology, and (b) treatments narrowly applied to one approved condition. The result is a slow slicing of aging into a potentially endless series of named conditions, as each small piece of the enormously complex end state of decline is defined and given a name. This implicitly favors the poor strategy of trying to control narrow parts of the complicated end stage of disease, pretending they are isolated when in fact they are not, and makes it harder to pursue the much better strategies of either prevention or ways to repair and reverse the root causes of aging.

Aging and age-related disease are clearly not distinct from one another. Aging is just a collection of countless age-related diseases, the few defined and the many not yet defined. Age-related diseases are just arbitrary lines drawn around parts of aging. Looking at it a different way, an age-related disease is an aspect of aging that has progressed far enough to be unbearable. Aging and age-related disease are caused by the same underlying mechanisms - the cell and tissue damage outlined in the SENS research proposals.

Is aging as a whole a disease? Can we just draw a line around the whole thing? This question has been asked ever more frequently of late. It is trivial semantics - except that regulators will not let a treatment for aging progress to the clinic unless they agree that aging is a disease by their formal definitions. Which they currently do not. Absent a defined path to the clinic, research funding for efforts to treat aging as a medical condition is much harder to obtain than would otherwise be the case. The whole development pipeline suffers, all the way back to fundamental science in this part of the field. It has required philanthropy and advocacy and non-profit organizations dedicated to aging to make any meaningful progress since the turn of the century. Now that it is becoming plausible to effectively reverse some of the causes of aging, such as via senolytic therapies to destroy senescent cells, it becomes ever more important that this ridiculous situation is resolved in a way that allows funding to flow and therapies to reach the clinic.

The Continuum of Aging and Age-Related Diseases: Common Mechanisms but Different Rates

The longstanding question if old age is itself a disease has been addressed since ancient times, starting from the Roman playwright Terentius, who claimed "senectus ipsa est morbus" (old age itself is a disease), and Cicero who some decades later argued in De Senectute: "pugnandum, tamquam contra morbum sic contra senectutem" (we have to fight against aging, as we do against a disease). These quotations elegantly summarize a long-held view of aging and old age addressed by several scholars. Notwithstanding, with the birth of modern medicine in the nineteenth century, this old tenet has been somehow put apart, as the main interest at that time was to define precise medical entities (diseases and syndromes) and their causes (infections, genetics, degenerative processes, inflammation, etc.). This process ended up in considering aging and diseases as separate phenomena that could eventually interact but that are essentially different in nature.

In this review, we will reappraise and challenge the old tenet that aging and age-related diseases (ARDs) and geriatric syndromes (GSs) are separate entities, and we will suggest instead that both should be considered as parts of a continuum. To support this hypothesis, we will highlight that aging and ARDs/GSs share the same basic molecular and cellular mechanisms. Aging is the predominant risk factor for most diseases and conditions that limit healthspan. Accordingly, interventions in animal models that end up in an extension of lifespan prevent or delay many chronic diseases. Why? For many years the explanation was that aging per se is a physiological condition, which favors the onset of many diseases. However, their relationship is likely much more complex, and a major reason is because they share the basic mechanisms. Assuming that aging and ARDs/GSs share the same mechanisms, which are commonalities and differences?

We will argue that an integrated hypothesis, fitting most epidemiological and experimental data, is to consider ARDs/GSs as an acceleration of the aging process. The conceptualization of accelerated aging started from the observation of rare genetic disorders such as Hutchinson-Gilford progeria. Here, we extend the concept of acceleration of aging to those members of the general population undergoing ARDs and GSs, in comparison with a small minority of people, such as centenarians, who reach extreme age largely avoiding or postponing most ARDs/GSs. This consideration is reinforced by the observation that among centenarians there are few subjects who never suffered of any overt ARDs. These exceptional individuals can be taken as a proof of principle that "healthy" aging and diseases can occur separately, as phenotypes at the extreme of a continuum, which is fueled by a common set of molecular and cellular mechanisms.

Which are the basic mechanisms shared by aging and ARDs/GSs? A group of international experts identified "seven pillars" which actually include adaptation to stress, loss of proteostasis, stem cell exhaustion, metabolism derangement, macromolecular damage, epigenetic modifications, and inflammation. Following this idea, the very difference between aging and diseases would relay on the speed and intensity of aging cellular and molecular processes, combined with the genetic and lifestyle predisposition of specific organs and systems. Thus, on the long run, all the functional domains undergo a physiological decline that eventually can lead to overt clinical diseases, favored by system-specific genetic and environmental factors. This progressive path generates a continuum between the healthy juvenile status and the impaired unhealthy elderly one. Accordingly, all major ARDs/GSs are characterized by a long subclinical incubation period, where the diagnostic signs of diseases are largely unobservable due to the high operational redundancy of biological systems.

In conclusion, a debate exists on whether aging is a disease in itself. Some authors suggest that physiological aging (or senescence) is not really distinguishable from pathology, while others argue that aging is different from age-related diseases and other pathologies. It is interesting to stress that the answer to this question has important theoretical and practical consequences, taking into account that various strategies capable of setting back the aging clock are emerging. The most relevant consequence is that, if we agree that aging is equal to disease, all human beings have to be considered as patients to be treated, being an open question when this treatment should start. Many mechanisms proposed to cause aging are the same as those known to underlie ARDs/GSs, lending support to the hypothesis that the aging phenotype and ARDs/GSs are not separate entities but rather the visible consequences of the same processes which likely proceed at different rates.

A second conclusion is that medicine should combat aging to combat many ARDs at a time and not one by one. In this perspective, one could envisage following two possible strategies to attain this result: (A) Try to slow the aging rate through changes in life style, and possibly drugs or medical treatments that counteract the impairment of mechanisms such as those proposed in the "seven pillars." This strategy should help people to stay healthy and active as long as possible and pospone ARDs for decades, ideally until the apparently inevitable limit of human lifespan. (B) More radically, try to rejuvenate human tissues, organs, and whole body. In this case, also the limits of human lifespan could be likely overtaken.

We are relatively ready to the first strategy that appears more feasible and acceptable from an ethical and social point of view, as it would be very similar to what is already happening nowadays, i.e., an increase in life expectancy and in the number of people who attain 90 or 100 years of age and more in good health. We are not yet ready, in particular from a social and ethical point of view, for the second strategy, which opens uncanny scenarios of rejuvenating bodies and very long life for the bulk of the population, a topic addressed in utopian, dystopian, and science fiction novels. Taking into account the fantastic, unprecedented rate of scientific discoveries in the field of aging and rejuvenation, it is timely and urgent to open a large debate.

SPATA31 Gene Family Copy Numbers as a Human Example of Antagonistic Pleiotropy

Antagonistic pleiotropy is the name given to the phenomenon in which evolutionary processes select for a genetic variant that aids in evolutionary fitness when young, but then causes harm to the individual later in life. Many theorists consider aging as a whole to be antagonistic pleiotropy writ large, but one can pick out individual mechanisms in many species that are compelling candidates to be the result of such a process. In the open access paper noted here, the authors point out one plausibly pleiotropic set of genes in our species.

Expansion of gene families with the concomitant acquisition of new functions can be a driving force for the evolutionary differentiation of species. Compared to other mammals, primate and human genomes include many interspersed segmental duplications, which may have been of special relevance for the evolution of the primate lineage. About 430 blocks of the human genome have been identified as having been subject to multiple duplications during hominoid evolution. Clustering analysis of these segmentally duplicated regions in the human genome suggests that a part of the duplication blocks have formed around a "core" or "seed" duplicon.

The SPATA31 gene family belongs to the core duplicon gene families and it has been shown to be one of the fastest evolving gene families in the human lineage. It has expanded from a single copy in mouse to at least nine copies in humans, located at seven different sites on both arms of chromosome 9. Compared to the mouse gene, we found that the human SPATA31 genes are broadly expressed and have acquired new functional domains, among them a cryptochrome/photolyase domain, suggesting the acquisition of a function in UV damage repair.

Antibody staining showed that the protein is re-localized from the nucleolus to the whole nucleus upon UV irradiation, a pattern known for proteins involved in UV damage sensing and repair. Based on CRISPR/Cas mediated knockouts of members of the gene family in fibroblast cell cultures, we found that the reduction of copy number in cells leads to enhanced sensitivity towards UV-irradiation. Given that increased UV-light resistance of the skin may have played a major role in human evolution, we proposed that the acquisition of an involvement in UV damage sensing or repair has lead to the adaptive evolution of SPATA31.

An interesting side effect of the SPATA31 gene knockouts was that the respective cells survived somewhat longer than normal primary fibroblast cell lines, although this was difficult to quantify. We have therefore used here the alternative approach, namely to over-express a representative member of the SPATA31 gene family, SPATA31A1, and study its effect on cell survival. We find that this over-expression results indeed in premature senescence of the cells, through interference with known aging related pathways. Based on these results, we asked whether natural copy number variation in humans correlates with senescence, in the sense that fewer SPATA31 copies should correlate with longer life span. We can indeed show this effect in a cohort of long-lived individuals. Humans that have reached an age of 95 or higher have on average fewer SPATA31 gene copies than a younger control population.

It has generally been suggested that there is a complex interaction between cellular senescence, tumor incidence due to somatic mutations, and aging. Our data imply that SPATA31 genes are part of this process and that their variation in copy number contributes via this effect to longevity in humans. Having more copies may lead to more somatic mutations, including some that cause cancer, while having fewer copies reduces this effect, thus allowing longer life spans.

The SPATA31 copy number effect on aging can be seen as an example for antagonistic pleiotropy. Higher copy numbers provide a benefit early in life, due to better protection of the skin against sunlight, allowing to spend more time during the day for foraging, social life, mate seeking and child care, all factors that should increase reproductive fitness. Hence, there would be positive selection for higher copy numbers. But more copies would also lead to a higher expression of SPATA31 and our cell-culture results show that such a higher expression induces DNA repair pathways. This could lead to a higher incidence of repair-induced damage in the cells and thus to cancer. If this becomes a problem during reproductive age, one would have a potential negative selection against high copy number. Hence, a balance in copy number should be maintained in the population, but with a certain variance. This variance has the effect that total lifetime beyond reproductive age is affected, with individuals with fewer copies having a higher probability to live longer.

Link: https://doi.org/10.18632/aging.101421

Results from a Human Trial of Mitochondrially Targeted Antioxidant MitoQ

A range of mitochondrially targeted antioxidant compounds have been developed over the past decade or more: SkQ1, SS-31, and MitoQ, the subject of the trial here. The present consensus in the research community is that ordinary antioxidants are probably, on balance, somewhat harmful if used over the long term. They sabotage the oxidative signaling need for the beneficial response to exercise, for example. Mitochondrially targeted antioxidants, on the other hand, appear to modestly slow aging in a range of species, and have proven an effective treatment for some conditions characterized by inflammation and oxidative stress, meaning the excessive production of oxidative molecules and resultant damage to molecular machinery. It can be debated on a case by case basis as to the degree to which this is a compensatory treatment versus addressing a specific causative issue in any given condition.

Mitochondria in cells generate oxidative molecules in the course of producing chemical energy stores to power cellular processes. Moderately raised production can result in overall benefits, because cells react with increased housekeeping activities. Greatly increased production is harmful, however, and appears as aging progresses due to the accumulation of mitochondrial damage. It raises the level of oxidized lipids in the bloodstream, a contributing factor in atherosclerosis. It can cause cells to become dysfunctional, though the details are varied and tissue specific. It can spur chronic inflammation. In this trial, it is interesting to see confirmation of these various themes, with a focus on the vascular system in aging, though I think the pulse wave velocity data is mixed at best. The reduction in oxidized LDL cholesterol is more interesting, and more compelling when one considers that this outcome is the goal of statin drugs.

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality in developed societies. Advancing age is the primary risk factor for CVD, which is largely mediated by adverse changes to arteries. Two features of vascular aging that are key antecedents to CVD are the development of endothelial dysfunction, as assessed by reduced endothelium-dependent dilation (EDD), and stiffening of the large elastic arteries. Vascular dysfunction with age is a consequence of excessive superoxide-related oxidative stress, much of which is of mitochondrial origin. Given the projected increase in CVD prevalence in the coming decades, driven mainly by increases in the number of middle-aged and older (MA/O) adults, identifying novel strategies that reduce excess mitochondrial reactive oxygen species (mtROS) to improve vascular function and reduce CVD risk in this population is a biomedical priority.

MitoQ is a mitochondria-targeted antioxidant consisting of the naturally occurring antioxidant ubiquinol attached to a lipophilic cation; the lipophilicity and positive charge of this compound enable it to cross cell membranes and accumulate in the matrix facing the surface of the mitochondrial inner membrane where it is optimally positioned to reduce mtROS. MitoQ is now available as a dietary supplement and recently was administered chronically (3 weeks) to healthy young adults without adverse effects. However, presently, the efficacy of chronic MitoQ supplementation for improving vascular function in healthy MA/O adults is unknown. Accordingly, we sought to translate our preclinical findings to humans by conducting the first randomized, double-blind, placebo-controlled clinical trial with MitoQ in healthy late MA/O humans.

MitoQ was well tolerated, and plasma MitoQ was higher after the treatment versus placebo period. Brachial artery flow-mediated dilation was 42% higher after MitoQ versus placebo; the improvement was associated with amelioration of mitochondrial reactive oxygen species-related suppression of endothelial function. Aortic stiffness (measured via carotid-femoral pulse wave velocity) was lower after MitoQ versus placebo in participants with elevated baseline levels. Plasma oxidized LDL (low-density lipoprotein), a marker of oxidative stress, also was lower after MitoQ versus placebo. These findings in humans extend earlier preclinical observations and suggest that MitoQ and other therapeutic strategies targeting mitochondrial reactive oxygen species may hold promise for treating age-related vascular dysfunction.

Link: https://doi.org/10.1161/HYPERTENSIONAHA.117.10787

Continuing the Debate Over the Heart of the Mitochondrial Theory of Aging

Every cell contains hundreds of mitochondria, the distant descendants of ancient symbiotic bacteria. They have evolved to become cellular components, tightly integrated into many vital functions, but still replicate like bacteria, and still contain a small remnant circular genome, known as mitochondrial DNA. Of the varied tasks undertaken by mitochondria, the most important is the generation of the chemical energy store molecule ATP, used to power cellular operations. This is a necessarily energetic operation and produces oxidative molecules as a byproduct, capable of reacting with and damaging the proteins that make up cellular machinery. This sort of reaction happens constantly and is repaired constantly, as a cell is a fluid bag of countless proteins and other molecules bumping into one another. Too much is harmful, however.

Mitochondrial DNA encodes a few vital proteins, necessary for the correct function of mitochondria, particularly when it comes to the mechanisms of ATP generation. Unfortunately mitochondrial DNA is right next door to the machinery that produces ATP and reactive molecules, it replicates far more frequently than the DNA of the cell nucleus, thus generating errors at a greater rate, and in addition has inferior protective and repair mechanisms in comparison to nuclear DNA. Mutations accumulate over time, in a random way.

The core of the mitochondrial theory of aging is that this mutational damage contributes to aging. The mechanism of production of ATP is disrupted, moves to much less efficient modes, and generates excessive reactive byproducts. Cells appear in which mutant mitochondrial have taken over, being more resistant to cellular quality control systems, or being able to replicate more efficiently. These cells cause harm to surrounding tissues, exporting large numbers of reactive oxidative molecules, resulting in oxidatively damaged lipids travelling far and wide in the body via the bloodstream, contributing to the progression of degenerative aging. As the open access paper here notes, however, there is an ongoing debate in the research community over which forms of mutation are more important, and how they occur. The evidence is contradictory, and each new attempt to produce mice in which certain forms of mitochondrial mutation are prevalent muddies the waters further. The paper is an example of the continued scholarly discussion on this topic.

The SENS rejuvenation research approach to mitochondrial DNA damage is to copy the thirteen vital mitochondrial genes into the cell nucleus, suitably altered so that the proteins will be shipped back to mitochondria. The advantage of this approach is that it doesn't matter how the mutations happen - the approach will fix the problem regardless of its source. No matter how ragged mitochondrial DNA might become, the proteins needed for correct function will still be available. It bypasses the need to fully understand the roots of the problem, a task that is proving to be challenging, slow, and expensive. To date, the SENS program - at the Methuselah Foundation and later the SENS Research Foundation - has funded the work that led to Gensight Biologics and their focus on copying the ND4 gene into the cell nucleus, and then demonstrated a similar proof of concept for ATP6 and ATP8.

Is There Still Any Role for Oxidative Stress in Mitochondrial DNA-Dependent Aging?

The central principles of the mitochondrial theory of aging are that (i) mitochondrially produced reactive oxygen species (ROS) can damage mitochondrial DNA (mtDNA), and (ii) ROS-induced lesions in mtDNA can lead to somatic mutations that accumulate, affect the integrity of respiratory chain, and cause mitochondria-dependent aging. More recent data seem to indicate that mtDNA might be more resistant to oxidative damage than previously thought. Instead, many have suggested that the origin of somatic mtDNA mutations is associated with the fidelity of the mtDNA polymerase γ (POLG). Additionally, there seems to be little experimental support for the vicious cycle theory, which attempts to explain the age-dependent accumulation of mutations by proposing a mutation-dependent increase of mitochondrial ROS production that, in turn, would result in elevated oxidative mtDNA damage.

Rather, the age-dependent increase in the somatic mutation load of mtDNA reported by many groups can be explained sufficiently by the replicative segregation of mitochondrial mutations. This theory has been supported by evidence that individual cells of aged persons accumulate high levels of only one specific mutation. Additionally, the effect of mtDNA mutations on mitochondrial ROS production has been reported to be strongly mutation dependent. Only certain mutations that affect the activity of Complex I and Complex V have been convincingly shown to increase mitochondrial ROS production, while random mtDNA point mutations do not seem to be associated with elevated oxidative stress.

One of the most important issues relating to the mitochondrial theory of aging is the very low frequency of somatic mutations detected in the mtDNA in tissue samples from older individuals. Obviously, the mitochondrial genome is present in multiple copies (approximately 10 copies per mitochondrium), and it is a well-established fact that intact mtDNA can complement for mutated genomes. Therefore, it is difficult to imagine how minor changes in the mitochondrial genome could lead to functional effects on the cellular level. Only a mosaic distribution of mutated genomes, resulting from preferential accumulation of mutants in certain cells, can explain the occurrence of such functional effects in these cells. To cause a functional effect within a cell, a pathogenic point mutation must typically exceed 85-90% heteroplasmy, while deletions appear to cause functional effects at heteroplasmy levels above only 60%.

This threshold concept has been validated in tissue samples from numerous patients with mitochondrial diseases harboring pathogenic point mutations or mtDNA deletions, which contain a mosaic of cells with defects in oxidative phosphorylation (OxPhos) that are usually detectable by testing for missing cytochrome c oxidase (COX). Similar mosaics of cells that do not have COX have been reported in postmitotic tissues, such as skeletal muscle, heart muscle, or the brain. However, the number of cells lacking COX in these cases is much lower than that reported in cases of mitochondrial diseases.

First attempts have been made to clarify the potential physiological impact of low amounts of cells lacking COX on intact tissues. In research studying such effects on mouse hearts, compelling evidence has been provided that if the frequency of deletions in a small number of individual heart cells exceeds the above-mentioned threshold, then arrhythmia - a typical symptom of age-related heart disease - may develop. Similarly, it is easy to imagine that individual neurons with impairment of OxPhos, which have been detected in many central nervous system disorders and in the aging brain, can affect the function of complex neuronal networks. However, this hypothesis remains to be investigated and further substantiated.

Cells in High Risk, Unstable Atherosclerotic Plaque Exhibit a Cancer-Like Metabolism

Atherosclerosis is the development of fatty plaques in blood vessel walls, formed of damaged lipids and the debris of dead cells. Once developed in earnest, these become localized areas of chronic inflammation. Inflammatory signaling continually calls in macrophages that attempt to clear up the damage, become overwhelmed, and add their remains to the growing mass. In the late stage of the condition, blood vessels are narrowed and weakened, and the plaques become unstable, prone to rupture. Here, researchers show that cells found in unstable fatty plaque are distinct from those in stable plaque. They look more like cancer cells or activated immune cells in the operation of their metabolism.

This is interesting in light of the recent discovery that growth and instability in atherosclerotic plaque is driven in part by the senescence of macrophages. The macrophages attempting to clean up the plaque become senescent as they are overwhelmed by damaged lipids that they cannot effectively break down. They become foam cells as they are loaded with lipids, and the foam cells become senescent in response to their own damaged state and the plaque environment. Senescent cells secrete signals that promote inflammation and disruptive remodeling of surrounding tissue structure, and are different from normal cells in other ways as well. Removing just senescent macrophages can stabilize plaque and slow or reverse the progression of atherosclerosis. This is something to think about while looking over the results here.

Atherosclerotic plaques form over a long time by a focal accumulation of lipids, immune cells, and smooth muscle cells in the arterial wall and plaques that rupture can cause acute cardiovascular events, such as myocardial infarction and stroke. Rupture-prone, high-risk plaques are associated with clinical symptoms and characterized by histological evidence of vulnerability and a high inflammatory burden. While this knowledge has advanced considerably over the past few years, our understanding of the metabolic processes within plaques in this inherently metabolic disorder has been lagging behind.

Emerging research has shown that cell metabolism and the inflammatory response are tightly intertwined. Macrophages, abundantly found in atherosclerotic plaques, and other leucocytes, change their metabolism according to their tasks in the immune response. Activated leucocytes change to a predominantly anabolic metabolism by upregulating pathways, such as glycolysis, the pentose-phosphate pathway (PPP), and glutaminolysis, to provide the necessary energy to enable their activation and proliferation. In contrast, catabolic pathways, such as fatty acid oxidation (FAO), are downregulated in these cells. Recently, it has been shown that overutilization of glucose is crucial for blood monocytes and in vitro differentiated macrophages from patients with coronary artery disease (CAD) to mount a destructive inflammatory response. Yet, it remains to be determined whether such an interconnection between cellular metabolism and the inflammatory response is present in human atherosclerotic plaques.

Recent studies have challenged the established concept of the vulnerable atherosclerotic plaque and call for improved methods for identification of the high-risk plaque. Plaque metabolomics might be able to provide a largely unexplored layer of functional characterization of high-risk lesions and thus add value to future risk stratification strategies and novel therapeutic approaches. Metabolic profiling of atherosclerotic tissues has so far focused on comparing lipid metabolite levels in different parts of the same plaque or to plaque adjacent intimal thickenings without being able to produce clear biological insights of clinical significance.

A more clinically relevant approach is to distinguish high- from low-risk plaques according to their metabolic profile. Therefore, we assessed metabolite profiles of 159 highly stenotic carotid atherosclerotic plaques isolated from patients with or without symptoms. We show that high-risk plaques, characterized as being symptomatic, vulnerable by histology, and inflamed with elevated inflammatory mediators, had a specific metabolite signature, distinct from the metabolite profile of low-risk plaques. These data highlight a previously unappreciated role of cellular metabolism in the high-risk plaque and as a discriminating feature from low-risk plaques, indicating that metabolic pathways could be targeted to treat and identify high-risk atherosclerotic plaques.

Link: https://doi.org/10.1093/eurheartj/ehy124

CXCR4 as an Indicator of Microglial Involvement in Neurodegenerative Diseases

The open access paper noted here reports on the use of a genetic analysis to shed further light on the relative importance of shared mechanisms across a range of neurodegenerative conditions in which tau aggregation is thought to be important. The researchers find associations in gene expression between these conditions that suggesting microglial dysfunction is an important common determinant of disease progression.

If one looks over all of the most common neurodegenerative diseases, patients exhibit a number of overlapping mechanisms that appear plausible as proximate causes of brain cell dysfunction and death. Some conditions share the aggregation of damaged proteins such as amyloid-β and tau. Most share harmful alterations in the behavior of immune cells such as microglia, either causing or responding to a state of raised chronic inflammation. The progression of vascular aging, leading to inadequate delivery of oxygen and nutrients, and mitochondrial dysfunction are also common in neurodegenerative conditions. All of these observations, sadly, tell us far less than we'd like about cause and effect in the aging brain. All of the signs progress over time, and absent technologies that can carefully block one of those signs, in order to see what happens next, it is very challenging to determine causality by observation alone.

Uncovering the shared genetic architecture across neurodegenerative diseases may elucidate underlying common disease mechanisms and promote early disease detection and intervention strategies. Progressive supranuclear palsy (PSP), frontotemporal dementia (FTD), Parkinson's disease (PD), and Alzheimer's disease (AD) are age-associated neurodegenerative disorders placing a large emotional and financial impact on patients and society. Despite variable clinical presentation, PSP, AD, and FTD are characterized by abnormal deposition of tau protein in neurons and/or glia. While PD is classically characterized by alpha-synuclein deposits, recent studies support the role of tau and neurofibrillary tangles in modifying PD clinical symptoms and disease risk.

Genome-wide association studies (GWAS) and candidate gene studies have identified single nucleotide polymorphisms (SNPs) in MAPT (which encodes tau) that increase risk for PSP, FTD, AD, and PD. However, beyond MAPT, the extent of genetic overlap across these diseases and its relationship with common pathogenic processes observed in PSP, FTD, AD, and PD remain poorly understood. Here, using previously validated methods, we assessed shared genetic risk across PSP, PD, FTD, and AD. We then applied molecular and bioinformatic tools to elucidate the role of these shared risk genes in neurodegenerative diseases.

We identified CXCR4 as a novel locus associated with increased risk for both PSP and PD. We found that CXCR4 and functionally associated genes exhibit altered expression across a number of neurodegenerative diseases. In a mouse model of tauopathy, CXCR4 and functionally associated genes were altered in the presence of tau pathology. Together, our findings suggest that alterations in expression of CXCR4 and associated microglial genes may contribute to age-associated neurodegeneration. Despite the lack of strong genetic association across these three neurodegenerative diseases, we found that CXCR4 expression was altered in brains that are pathologically confirmed for PSP, PD, and FTD. Thus, these findings support our hypothesis that these three neurodegenerative disorders share common pathobiological pathways.

CXCR4 is a chemokine receptor protein with broad regulatory functions in the immune system and neurodevelopment. CXCR4 has been shown to regulate neuronal guidance and apoptosis through astroglial signaling and microglial activation. Furthermore, it has been shown that CXCR4 is involved in cell cycle regulation through p53 and Rb. Our results provide additional evidence that immune and microglial dysfunction contribute to the pathophysiology in PSP, PD, and FTD. These findings have important implications for future work focused on monitoring microglial activation as a marker of disease progression and on developing anti-inflammatory therapies to modify disease outcomes in patients with neurodegenerative diseases.

Link: https://doi.org/10.1038/s41398-017-0049-7

Genetic Manipulation to Increase the Proportion of Brown Fat Tissue is Shown to Modestly Extend Mouse Life Span

The operation of metabolism determines species longevity, and in short-lived species this link tends to be highly variable in response to circumstances: exercise, diet, and consequences such as amounts and types of muscle and fat tissue. Longer lived species such as our own are, if anything, remarkable for the comparative lack of variation in life span across large differences in diet and the configuration of muscle and fat in our bodies. As researchers continue to map the interaction of metabolism and aging in laboratory mice, one interesting theme that has emerged is the importance of brown adipose tissue. In the open access paper noted here, the authors report that increasing the proportion of fat tissue that is brown rather than white can produce a 10-15% increase in mouse life span. They suggest this is mediated by SIRT3 activity and downstream effects on mitochondrial function.

The results here might be compared with a very intriguing study published last year in which researchers described what happens to metabolism and fat tissue in mice if their sense of smell is disabled. That resulted in healthier, metabolically superior mice characterized by a greater proportion of brown fat tissue. It built upon a range of past research suggesting that sense of smell plays a sizable role in the metabolic reaction to food. Unfortunately, for these and all other similar metabolic manipulations, we can't expect sizable results to transfer to humans and other long-lived mammals. For those interventions wherein researchers can directly compare mice and humans, the outcome on human life spans is much smaller, and supporting evidence strongly suggests that this holds up across the spectrum of everything involving diet, fat, and metabolism. The health benefits - distinct from effects on the pace of aging - may still be worth pursuing, if the costs are reasonable, however. Consider calorie restriction, for example.

There is also the point that a 10% life span effect in short-lived species is somewhere in the margin of error, and may well be hard to replicate. Looking back at the past few decades, 10% effects come and go in mice. One of the challenges is that an intervention may make mice choose to eat less for any number of reasons. The effects of calorie restriction are so large that they can swamp whatever else is going on in the study. The researchers here report carefully on the details of their many measures of metabolism, but one always has to read those details in order to understand whether they rule out a calorie restriction effect. That may not be the case here, for all that various aspects of the biochemistry under study match up well with what is presently known.

Enhanced longevity and metabolism by brown adipose tissue with disruption of the regulator of G protein signaling 14

There are two distinctly different types of fat found in mammals: white adipose tissue (WAT), which is an essential site for triglyceride storage, and brown adipose tissue (BAT). The BAT is a protective mechanism of recent interest. BAT enhances energy metabolism and protects against cold exposure and obesity. A novel model to investigate the role of BAT in healthful aging and lifespan is the mouse model of the gene knockout (KO) of the regulator for G protein signaling 14 (RGS14), which has increased BAT.

Most prior work on RGS14 focused on its effects on embryonic development and on the visual cortex and central nervous system. The role of BAT in RGS14 KO and its ability to enhance lifespan and improve metabolism, the focus of the present investigation, have never been explored. To confirm the essential role of BAT in mediating the protection in the RGS14 KO, we transplanted BAT from RGS14 KO to wild type (WT) mice, a technique that is equivalent to a BAT KO, as it disrupts the salutary phenotype in the RGS14 KO and transplants these features to their WT, receiving the BAT.

Lifespan was monitored in the mice, and we observed significantly longer lifespan of RGS14 KO vs. WT mice. Median lifespan was increased by 4 months from 24 to 28 months. Median lifespan and maximum lifespan were increased to a similar extent in females and males. The older RGS14 KO mice were also protected from aging-induced atrophy of the thymus. It is also important that BAT protects against the aging phenotype, for example, graying and loss of hair, dermatitis, and hunched back, all of which were observed in old WT mice, but not observed in old RGS14 KO mice or in old WT mice, which received BAT transplants.

RGS14 KO mice had improved body composition compared to WT mice. RGS14 KO mice had lower body weight and WAT index (% of white fat to total body weight). The BAT index (% of brown fat to total body weight) was increased in RGS14 KO by 77% compared to their WT littermates. From RT-qPCR analysis to profile changes in BAT transcript levels, we found that BAT-specific markers were significantly upregulated. As healthful longevity and BAT are known to improve metabolic function, we assessed metabolism through indirect calorimetry and demonstrated greater oxygen consumption in RGS14 KO than WT mice.

In the RGS14 KO, SIRT1 was downregulated, while SIRT3 was upregulated. To confirm the role of the SIRT3 mechanism, a double KO (RGS14 KO X SIRT3 KO) was studied. The RGS14 X SIRT3 double KO mice lost their improved metabolism, pointing to SIRT3 as a mediator of the beneficial effects on metabolic regulation in the RGS14 KO animals. Therefore, RGS14 deficiency promotes increased SIRT3 activity, not only by increasing its expression levels, but also by increasing the availability of NAD+, an important cofactor required for sirtuin function. SIRT3 activation, in turn, leads to improved mitochondrial biogenesis, providing the molecular basis for healthful aging in the RGS14 KO animals.

An Interview with a Programmed Aging Theorist

Josh Mittledorf holds an interesting somewhat group selection based view on the evolution of programmed aging, and here is interviewed by the Life Extension Advocacy Foundation volunteers. I have long said that the important divide in the research community is between (a) those who think that aging is programmed, in the sense that evolution selects for epigenetic changes in later life that are a primary cause of damage and dysfunction, and (b) those who see aging as a stochastic process of damage accumulation, that occurs in later life because there is little to no selection pressure for ways to prevent it, and this damage causes epigenetic changes and dysfunction.

This is an important divide because the two views lead to very different strategies for the development of therapies to treat aging. The programmed aging theorist wants to force reversion of epigenetic changes to a youthful pattern, and expects damage and dsyfunction to be reversed as a result. In the damage accumulation view, exemplified by the SENS research programs, repair of damage is the right path, with the expectation that dysfunction and epigenetic changes will revert themselves once the damage is gone. In either case, if the other side is right, the chosen strategy will produce poor results. Now that the research community is earnestly engaged with the idea of treating aging, whether researchers and institutions invest in good or bad strategies is of great importance to the near future of medicine and our own lives.

It seems like the field of aging science has grown remarkably. Are you optimistic that we're on the verge of real breakthroughs in longevity improvements?

I'm not as optimistic as I was a few years ago. The Next Big Thing in the field is likely to be senolytic drugs. These are able to selectively remove the body's worn-out cells that have become toxic, without poisoning our healthy cells. I think they'll add a decade or more to the human lifespan. Calorie restriction mimetic and exercise mimetic drugs will be another boost if they can be made safe. After that, I think the big challenge will require taking control of our epigenetics (heritable changes that don't require changes to the genome itself). Epigenetics, I believe, is in control of aging at a deep level. Epigenetics is so complicated that 20 years into the age of epigenetics, we're still just beginning to understand how it works.

Why are you less optimistic about the potential for major breakthroughs in aging science now in 2018 than you were previously?

Originally, my thinking went like this: The conventional view has been that aging exists despite evolution's best efforts over hundreds of millions of years to eradicate it. Evolution is already trying to make us live as long as possible, and for humans to extend our lifespan, we'll have to do some pretty fancy thinking to come up with something that evolution hasn't already tried. However, this conventional view is wrong. In fact, evolution has preferred defined lifespans to indefinite lifespans. So, we might hope that we can eliminate aging entirely by understanding the mechanisms of self-destruction that evolution has built into our life history and biochemically disabling them. I had thought that this could probably be done by blocking the signals, jamming the works. Pharmaceutical companies are generally quite good at turning off a hormone or a whole biochemical pathway once it's been identified.

The reason I'm less optimistic now is that I believe that the evolved mechanism of self-destruction involves gene expression, which is to say epigenetics. Different genes are turned on at different stages of life (this is a big part of what epigenetics is), and the genes turned on late in life turn the body against itself. Mechanisms like apoptosis (cell death), autoimmunity, and inflammation are all dialed up. The reason my expectations are scaled back now is that epigenetics has turned out to be enormously complicated. We once thought that a few transcription factors controlled a large number of genes, turning them on and off en masse. We now know that there are thousands of different transcription factors, almost as many as there are genes. And there is wide overlap between genes that have transcriptional functions and genes that have metabolic functions.

Could you flesh out a little your contributions to aging science, in terms of the evolutionary theory of programmed death in humans and most other species?

In the modern understanding of evolutionary fitness, evolution is highly motivated to make you live as long as possible, so long as you are still churning out babies. So, where does aging come from? The standard answer is that there are genes that tie fertility directly to deterioration late in life, and evolution has not found a way around this; it has not found a way to have lots of fertility early in life without incurring damage later on, despite hundreds of millions of years of trying to overcome this limitation.

I have described a great mass of evidence against this picture. Much of it is common sense, but there is a lot of technical, genomic evidence as well. The evidence strongly points to the inference that natural selection has preferred shorter lifespans to indefinite (or very long) lifespans. Why might this be? My theory is that it is about ecosystem stability. It's not possible to construct a stable ecosystem out of selfish individuals that are each trying to live as long as possible and produce as many offspring as possible. In order to have stable ecosystems, nature has had to accept limits to fertility and to lifespan.

The reason that the evolutionary community is so resistant to this idea is that it requires natural selection to occur within entire ecosystems. In other words, this ecosystem persisted because it was stable, while that one collapsed because it was way out of balance. For largely historical reasons, evolutionary theory grew up in a way that was committed to the selfish gene. Most evolutionary biologists today believe that the selfish gene is the only mode by which evolution operates, though they could not articulate a reason why, if challenged.

Link: https://www.leafscience.org/dr-josh-mitteldorf-are-we-on-the-verge-of-major-breakthroughs-in-anti-aging-science/

Inflammatory Signaling Reduces Pancreatic Islet Cell Replication in Aging

Aging is marked by rising chronic inflammation and a decline in many aspects of tissue maintenance, such as stem cell activity, and willingness of somatic cells to replicate. Chronic inflammation appears to disrupt regenerative processes, but there are many distinct mechanisms involved, varying by tissue type, and present understanding is far from complete. Researchers here investigate one narrow slice of the problem in the pancreas in zebrafish, finding that beta cells, important to metabolic function due to their control of insulin, reproduce less readily in old individuals due to greater inflammation.

A hallmark of aging is the reduction in cellular renewal and proliferation across different tissues and organs. The insulin producing beta cells, which reside in the islets of Langerhans, provide a good model to study regulators of cellular aging. Whereas young beta-cell are highly proliferative and increase rapidly in number from the prenatal phase until early stages of development in mammals, beta-cell proliferation becomes dramatically reduced in adults.

Previous studies have indicated that both extrinsic factors, such as the vasculature, and intrinsic factors, such as chromatin modifications, may influence the age-related changes in beta-cells. For example, rejuvenating the beta-cell environment by implanting old islets in younger animals is sufficient to restore the proliferative potential of the aged beta-cells. In addition, transcriptome and methylome studies revealed age-dependent DNA methylation changes at cell-cycle regulators, which may contribute to the quiescence of aging beta-cell.

To identify signals that change in beta-cells during organismal aging, we used the zebrafish as a model. We first characterized the rate of beta-cell proliferation in juvenile, younger, and older adults, and found that proliferation declines with advancing age. We performed transcriptomics of beta-cells from younger and older animals, which identified an upregulation of genes involved in inflammation, including NF-kB signaling. The analysis of inflammatory signaling with single-cell resolution confirmed that NF-kB signaling was activated in a heterogeneous manner at the level of individual beta-cells. Notably, beta-cells with higher levels of NF-kB signaling exhibit a more pronounced proliferative decline compared to their neighbors with lower activity.

Link: https://doi.org/10.7554/eLife.32965

Fibrosis is Harmful, and Varied Approaches to Suppress it are Under Development

Fibrosis is one of the major age-related failures of mammalian regenerative processes. Instead of reconstructing or maintaining the correct form of tissue, scar-like structures are deposited, disrupting organ function. Enough of this is fatal in organs such as the heart, liver, kidney, or lungs. Rising levels of fibrosis, and particularly following trauma such as infection or structural failure of aged blood vessels, are a significant component of loss of organ function and mortality in the old. Worse, the medical community has little in the way of therapies that can treat fibrosis; those that do exist are marginal in their benefits.

The causes of fibrosis are thought to be complex and tissue specific because regeneration is complex and tissue specific. Considered at the high level, it is a coordinated dance carried out between stem and progenitor cells of various types, the somatic cells already present in the tissue to be worked on, and immune cells, with many and varied signals passing back and forth between all of these types. The lower level details vary considerably by tissue type and structure.

In recent years, however, investigation of senescent cells - and the ability to slow aging by targeted removal of those cells - has revealed that a fair amount of fibrosis appears secondary to cellular senescence. Senescent cells generate chronic inflammation, as well as signals related to construction and destruction of the extracellular matrix, so it seems almost obvious in hindsight that they would be involved. A range of supporting evidence makes it seem plausible that inflammation causes disarray in the role of immune cells in regeneration and tissue maintenance, and comparisons between highly regenerative and less regenerative species suggest that immune cells strongly determine the quality of regeneration. Fibrosis in the lungs and other organs can be reversed through the use of senolytic treatments that destroy some fraction of senescent cells, a result so far demonstrated in animal studies only.

The research noted here is an example of bypassing all of these consideration in favor of outright sabotage of a crucial mechanism in tissue maintenance that is needed for fibrosis to occur. Unfortunately, this will also sabotage other important forms of normal regeneration, which may well limit its application to the treatment of critical cases after the fact, rather than as a form of prevention to keep the damage of fibrosis to a low level. Other forms of medicine with similar downsides have done well - think of the biologics for autoimmune disease that work through blanket suppression of parts of the immune system, for example - but I would hope that the research community can do better than this class of approach in the years ahead.

Blocking Matrix-Forming Protein Might Prevent Heart Failure

Researchers tested a manufactured peptide called pUR4 to block the fibronectin protein in human heart cells donated by heart failure patients. The treatment prevented the human heart cells from failing and restored their function. The treatment also reduced fibrosis and improved heart function after a simulated heart attack in mice.

Fibronectin is normally a good actor in the body. It helps form a cell-supporting matrix for the body's connective tissues, aiding tissue repair after injury. But after a heart attack, fibronectin overreacts, it polymerizes and helps produce too much connective matrix. It also causes hyperactive production of clogged and dysfunctional cardiac myofibroblast cells that damage the heart. The pUR4 compound is designed so it will attach to surface points on fibronectin, effectively inhibiting its effects in injured heart cells.

The pUR4 molecular treatment used in the current study is one of several compounds that show promise in preliminary preclinical research data. A key question in the current study was verifying the results of pUR4 targeted molecular therapy in both the mouse models and human heart failure cells. In mice with simulated heart attack that as a control experiment received a placebo therapy, the animals developed significant fibrosis and heart failure. When researchers treated mice with pUR4 for just the first seven days after heart attack, or genetically deleted fibronectin activity from the heart cells of mice, these reduced fibrosis and improved cardiac function. Treatment of human failing heart cells with pUR4 also reduced their fibrotic behavior.

The researchers emphasize it's too early to know whether the experimental therapy in this study can one day be used to treat human heart patients clinically. Extensive additional research is needed first, including proving pUR4's safety in larger animal models and then moving on to establish proof-of-principal effectiveness treating heart failure in those models.

Inhibiting Fibronectin Attenuates Fibrosis and Improves Cardiac Function in a Model of Heart Failure

Fibronectin (FN) polymerization is necessary for collagen matrix deposition and is a key contributor to increased abundance of cardiac myofibroblasts (MF) following cardiac injury. We hypothesized that interfering with FN polymerization or its genetic ablation in fibroblasts would attenuate MF, fibrosis, and improve cardiac function following ischemia/reperfusion (I/R)-injury.

Mouse and human MF were utilized to assess the impact of the FN polymerization inhibitor (pUR4) in attenuating pathologic cellular features such as proliferation, migration, extracellular matrix (ECM) deposition, and associated mechanisms. To evaluate the therapeutic potential of inhibiting FN polymerization in vivo, wild-type (WT) mice received daily intraperitoneal injections of either pUR4 or control peptide immediately after cardiac surgery, for seven consecutive days.

pUR4 administration on activated MF reduced FN and collagen deposition into the ECM and attenuated cell proliferation, likely mediated through decreased c-myc signaling. pUR4 also ameliorated fibroblast migration. In vivo, daily administration of pUR4 for seven days post-I/R significantly reduced MF markers and neutrophil infiltration. This treatment regimen also significantly attenuated myocardial dysfunction, pathologic cardiac remodeling, and fibrosis up to 4 weeks post-I/R. Finally, inducible ablation of FN in fibroblasts post-I/R resulted in significant functional cardioprotection with reduced hypertrophy and fibrosis.

Regenerative Medicine as an Approach to Treat Alzheimer's Disease

The authors of this open access paper consider the potential for regenerative medicine to treat Alzheimer's disease, such as by increasing production of new neurons, or delivering neurons via transplantation. While there has been something of an exodus from the amyloid hypothesis of late, given the litany of failure in clinical trials aiming to reduce amyloid in the brain, it still seems clear that protein aggregates (amyloid and tau) occupy a central position in the progression of neurodegeneration. Spurring greater brain tissue maintenance via generation of neurons is a beneficial goal in and of itself, but as a compensatory treatment, it can't be enough on its own to turn back neurodegeneration primarily caused by factors such as metabolic waste and chronic inflammation.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive cognitive decline. Tremendous efforts have been made to develop novel therapeutics to potentially reverse disease progression. Substantial neuronal loss is observed even in mild AD patients. Intuitively, increasing the number of neurons or replacing lost neurons are potential therapeutic strategies for AD. Stem cells are capable of renewing themselves continuously and differentiating into specialized cells, including neurons.

The process of generating new fate-specified, functional neurons from neural progenitor cells, which are functionally incorporated into a neural circuit, is defined as neurogenesis. Across different species, neural regeneration mainly takes place at the dentate gyrus of the hippocampus and the subventricular zone along the lateral ventricle. Notably, the dentate gyrus, which plays a crucial role in memory formation processes, is related to early memory loss in AD. Neurogenesis decline accompanies normal aging. For AD, accumulating evidence suggests that impaired neurogenesis plays a role in its pathogenesis. Multiple molecules involved in AD pathogenesis, such as ApoE, PS1, and APP were recognized to take part in neurogenesis modulation. Therefore, understanding the mechanism of neurogenesis dysfunction and intervening with neurogenesis represents an alternative AD therapeutic strategy.

Generally, neurogenesis can be modulated by multiple factors that are related to lifestyle, including learning, exercise, social interaction, caloric restriction, blood oxygen level, and even microbial colonization. In this regard, advocating a healthy lifestyle exerts at least a mild effect on preventing or controlling AD in the long run. Apart from lifestyle modification, which exerts mild effects, several pioneering studies identified key molecules or drugs that rescue or reverse NSC dysfunction in elderly animal models, such as via plasma exchange.

Transplanting stem cells to substitute for lost neurons is another intuitively feasible strategy. However, studies have confirmed that the main benefit of stem cell transplantation is a neurosecretory effect. Various neurotrophic factors involved in modulating multiple cellular functions that promote the amelioration of pathological features and cognition in animal models have been recognized. There has been increasing commercial interest to transform current advances in transplantation into clinical practice on human patients.

Link: https://doi.org/10.3389/fnagi.2018.00077

The Fight Against Aging and the Fight Against Ageism

If the old are thought to be inferior, used up, done, then would the rest of the population be less likely to support efforts to help older individuals? Ageism is certainly a real phenomenon, but it is an interesting question as to whether it is a major factor in the challenges we face in persuading the world to support work on rejuvenation therapies. Consider that those people with influence and wealth sufficient to steer the path of research and development in medicine are largely older, not younger. To the degree that ageism is a problem, I'd have to say that it seems likely to me to be a matter of the elderly accepting the mantle of this prejudice upon themselves. Or perhaps a matter of the old and declining leading implementations of discrimination against the elderly and declined. But this is just a viewpoint; the author here, a long-standing member of our community of patient advocates, argues that ageism is a core concern.

To me, efforts to counteract biological aging and fighting chronological ageism are two sides of the same coin. But for many this is probably not the case. For one, this is just not an issue at all people in general think about. And yet, all the people reaching adulthood and more are taking hits both from biological aging and from ageism during their lifetime. If you work on counteracting biological aging, you are working on fighting one form of ageism already. And am also hoping that if you think yourself as one who fights ageism you will recognize that understanding biological aging and support scientific efforts to extend healthy lifespan might be the most effective way to support the life of older people in the long term.

The World Health Organization defines ageism as the stereotyping, prejudice, and discrimination towards people on the basis of age. The claim I would like to make is there are two forms of discriminatory ageism, but only one of them has a connection to biological age. The first type is intergenerational ageism, and the main machinery involved here is chronological age. If you think that the deleterious effects of biological aging is the main or only cause for prejudice against older people then imagine a world where biological aging doesn't exist, yet kids are still born and new generations develop their own culture and references. It seems clear that in a world like that ageism and tensions between generations would still be an issue. Biological aging is not needed in order for ageism to happen.

For the second type: does the existence of biological aging and the visible signs of biological aging trigger ageism all by themselves? Yes, this is classical ageism, rooted in a positive bias for the young, and it has a long, long history in human culture. This type of biologically triggered ageism goes one way though, as it affects only older people by definition.

By now you might have guessed the argument I'm going to construct: people working on interventions to counteract processes of biological aging are at the same time working on removing the physiological, cognitive differences between the biologically old and biologically young. So they fight not just biological aging but biologically driven ageism too. Minimizing the differences between biological ages and maximizing the differences between chronological ages, they will make it hard for decision-makers to build ageism into the very fabric of companies and other institutions.

Link: https://pimm.wordpress.com/2018/04/15/fighting-aging-and-fighting-ageism-two-sides-of-the-same-coin/

A Nuanced Opposition to the FDA and Similar Regulatory Agencies

As regular readers will know, I am no great admirer of medical regulation as it presently exists in the wealthier parts of the world. It is a burdensome system, in which whatever power good intentions have to make the world a better place has long been eroded away by the short-term human incentives present in any large bureaucratic organization. What is left is a system in which it costs multiples of what it should cost to bring medicine into the clinic at an appropriate level of risk, a system that acts primarily to suppress rather than encourage development of new medical technology, and a system that tramples upon the rights of patients to make their own informed choices.

In the past my prescription for a better future has been one in which medical tourism flourishes: the use of regulatory arbitrage to bring medicine to the clinic in a responsible way in places outside the US. The eminently dysfunction US medical system, in which no party is incentivized to control costs, the most influential parties collude to prevent cost discovery, and quoted costs have little relation to actual costs, leads to a situation in which it is cheaper to fly halfway around the world to another country to receive even modest procedures. So let medical tourism grow as a form of pressure upon the existing regulatory system, because competition from outside is the only thing that has a hope of resulting in significant reform.

Any number of people work within the system on initiatives to make it better. There are non-profits and high net worth individuals and patient advocates all calling for reform of the FDA in one way or another. All are distinguished by having had very little positive effect over the years of their efforts. Indeed, over the last decade the cost of FDA approval has doubled, the time lengthened, and the rate at which new medical technologies are approved is stagnating. This has happened over the course of a period of enormous, staggering progress in biotechnology, in which costs of the underlying technologies have fallen dramatically. How can this be the case? Cynically, I would say this was also a period of great progress in connectivity and media exposure. Thus the tendency of bureaucrats to prioritize the minimization of bad press and accountability leads to ever greater demands, costs, and delays placed on regulatory applications, in search of a mythical, non-existent minimum level of risk that can only really be obtained by preventing new technologies from arriving at all.

Medical tourism, however, has challenges, primarily that it remains a highly disorganized market. Few of the people who might benefit significantly in fact do so. It requires a fair amount of research and determination; there is no easy on-ramp. I think that it will require universally desired enhancement therapies, such as follistatin or myostatin gene therapies for muscle growth, to obtain a large enough number of potential customers to generate sufficient organization in this marketplace to build that on-ramp. The number of people with severe illnesses is simply too small for the self-organization of entrepreneurship and venture funding to snowball in medical tourism - if it was going to happen, it would have happened already.

Here is another question: how do new therapies become available via medical tourism? Just as medical tourism is disorganized, so too there are large challenges facing company founders who want to responsibly develop and offer a therapy outside the established mainstream regulatory systems. A clear path forward to this goal has not been built; there is no roadmap. It is the jungle of uncertainty, and investors fear uncertainty. The founders of a company heading in this direction, such as BioViva Sciences and a few others, are faced with not just the challenging of building a therapy that is safe and reliable, but also building the entire infrastructure - the relationships, the legal understandings, the third party validation of safety and effectiveness - to bring that therapy into a clinic. Then they must also survive the bombardment of negative press from organizations invested in the status quo, hostile to the idea that proving safety and responsibility really doesn't require more than a fraction of the costs that the FDA imposes. Further, the founders must successfully woo investors who are very used to the present beaten path and nervous regarding anything new.

Taken together, this is a tall order. It is a task suited to a non-profit, or more accurately a dedicated organization, or a distributed bootstrapping process of cultural change driven by many such groups. The prize is well worth it, in terms of an acceleration of progress towards many new classes of therapy, a removal of the dead weight cost that slows and suppresses advances in medicine. As is so often the case, it is far easier to articulate the change we'd like to see than to make it happen, however.

So if I started a medical biotech company, I'd have to say that I would take it through the current regulatory system, while (a) being an honest player by the rules of that system, because that is the best way through the gauntlet, and (b) continuing to hold the view that the whole thing should be replaced with a far less self-serving, onerous, expensive, and terrible option. Unfortunately, the standard regulatory path is the only fairly reliable way to put a therapy in the hands of large numbers of patients. The other, ethically far better paths, such as that pursued by BioViva, have the unfortunate outcome of great uncertainty in whether patients will ever be able to use the treatment in large numbers. I'm sure I'm not alone in having come to this position.

The change the world needs here is clear: a far more organized industry of medical tourism, and an infrastructure for responsible medical development and validation of therapies, outside the established regulatory systems, that is generally accepted by investors. These challenges are easy to state, but resistant to any sort of easy solution that can do better than reaching a fraction of the patients who might benefit. At present any one company might succeed against the odds in obtaining enough funding and support to set up an offshore clinic - but how many patients can they reach? Small heroic battles, one company at a time, will not be enough. Until greater change is achieved, near everyone who starts the process of medical development will likely look at the landscape and make the rational short-term choice to pass through the existing regulatory gauntlet.

Calorie Restriction as the "Most Reasonable Anti-Aging Intervention"

The practice of calorie restriction slows aging in near all species and lineages tested to date. It produces significant health benefits in humans. Unfortunately the gain in life span scales down as species life span scales up. While calorie restriction extends maximum life span in mice and median life span in short-lived, small primates by 40% or more, it is not likely to have an effect size of more than five years when it comes to human life spans. That said, calorie restriction is by far the most robust and well tested of the few means available to adjust life span. Is it, however, as the authors of this paper would have it, the "most reasonable anti-aging intervention?"

Reliability is good, but size of effect is also important. Calorie restricted individuals still age and die on much the same schedule as the rest of us, just a fraction less rapidly. Good health practices can't add decades to life: three quarters of the healthiest people are dead by age 90, even given access to the best of medical technology over the course of the past half century. Calorie restriction, like exercise, is something that everyone should consider because it is essentially free, and has some benefit. But future life spans will be determined by new medical technology such as senolytic therapies, built on the SENS model of repairing the damage that causes aging, not by calorie restriction or recreation of some of its effects via pharmaceuticals.

Research on the biology of ageing has been conducted for centuries. Survival curves showing the surviving proportion of a population versus time are an intuitive means of illustrating the whole lifespan of a group of organisms and remain a key component of ageing research. Various anti-ageing interventions have been demonstrated to extend the lifespan of model organisms ranging from nematodes to fruit flies to rodents, with contradictory reports in rhesus monkeys. These interventions have mainly included calorie restriction (CR), genetic manipulations, and pharmaceutical administration.

However, whether these interventions extend the lifespan via universal or distinct patterns remains unclear. Traditionally, in ageing research, survival data from lifespan experiments are mainly analysed in the original study, and data are not collected and stored together. Meta-analyses are mainly limited to either sufficiently large subsets of survival data acquired under identical conditions or the application of methods accounting for varying additional factors. The published meta-analyses of survival data have mostly assessed CR. For example, reportedly, CR significantly extends lifespan, and the proportion of protein intake is more important for lifespan extension than the degree of CR. No study has demonstrated whether CR, genetic manipulation, or pharmaceutical administration is superior at extending lifespan and delaying ageing.

Here, we attempted to resolve this question by conducting a comprehensive and comparative meta-analysis of the effect patterns of these different interventions and their corresponding mechanisms via survival curves. We have focused our analyses on Caenorhabditis elegans and Drosophila, powerful model systems that are widely used in ageing research. We developed an algorithm that enabled us to combine multiple strains of these species from a large number of studies and to extract general trends from relevant results.

Our study indicated that CR and genetic manipulations are effective ways in delaying senescence. The effect pattern of CR is superior to that of genetic manipulation in Caenorhabditis elegans but similar to that of genetic manipulation in Drosophila. Genetic manipulation in mammals faces many problems and risks, and CR, including changes in diet composition, time-restricted feeding, or CR mimetics, could be a more feasible approach for humans. These considerations and our results support CR as a feasible and effective anti-ageing intervention.

Link: https://doi.org/10.1038/s41598-018-24146-z

Delivery of Exosomes Improves Recovery from Stroke in Pigs

The benefits of most first generation stem cell therapies, in which the overwhelming majority of transplanted cells die fairly rapidly, appear to be mediated by the signals briefly generated by those cells. A sizable portion of the signaling between cells is carried by extracellular vesicles such as exosomes, tiny membrane-wrapped packages of molecules. Given these two points, why not skip the cells in favor of delivering exosomes? This is an expanding area of activity in the regenerative medicine community. Some initiatives, such as the one noted here, have advanced to animal studies - human trials will not be so very many years away.

As regenerative research and development evolves away from the standard practice of the stem cell medicine of the past two decades, the future appears to involve a split of the community into two broad paths. The first path is as described above, to isolate the signals that are important in spurring regeneration, and thus gain control over the behavior of native cells. The second is to solve the problem of transplanted cells dying rather than thriving to undertake useful work. Progress is being made on this front in the form of tissue patches: rather than delivering cells haphazardly, researchers first build a structured pseudo-tissue patch of cells and scaffolding, closer in form to the native tissue. This makes the cells much more resilient and ready to integrate. The next decade in this field will see important advances in the ability to treat many degenerative conditions, I believe.

ArunA Biomedical today announced the publication of data demonstrating that neural stem cell-derived extracellular vesicles (NSC EVs) improved tissue and functional recovery in pigs following ischemic stroke. This is the first ever study to evaluate the therapeutic potential of human NSC EVs in a large animal model representative of the human brain. The neural-derived exosomes, a form of EVs, are a new class of cell-free biologics and cell-mediated drug delivery systems to treat central nervous system and neurodegenerative disorders.

"This study, coupled with our previously published studies focused on a mouse model, represents the first time that a company demonstrated proof-of-concept of the therapeutic potential of extracellular vesicles in two divergent animal species and two stroke types - embolic and ischemic." This is the third study recently completed by ArunA, the first two of which demonstrated improved outcomes in middle-aged and aged mice following embolic stroke.

Study results showed NSC EV treatment: was neuroprotective; eliminated intracranial hemorrhage in ischemic lesions; improved behavior and mobility; decreased cerebral infarct volume and brain swelling; and led to significant improvements at the tissue and functional levels.

Link: https://www.businesswire.com/news/home/20180412005439/en/ArunA-Biomedical-Announces-Publication-Study-Stroke-Reports

A Peptide Based on Amelogenin can Induce Regrowth of Lost Tooth Enamel

Teeth are subject to many problems, most of which are caused by bacteria. Unfortunately, the state of medical technology when it comes to control of harmful bacteria in the mouth lags far behind the policing of bacterial populations in other scenarios and locations. It is fairly well understood how bacteria cause gum disease and cavities, meaning which species are responsible and which mechanisms are important, but so far no lasting strategy for removing unwanted oral bacteria or blocking their activities has made it out of the laboratory and into the clinic. Getting rid of bacteria in the mouth is easy, but ensuring that only certain specific types are removed, and keeping them removed past a few hours or days, has turned out to be far more challenging.

Nonetheless, some promising avenues have emerged, even though they remain somewhere in the process of development. This is the case for methods of regrowth of tooth enamel; I recall discussing a few specific approaches more than a decade ago, and yet here we are, still reliant upon drills and fillings. Some groups have pursued cell and tissue engineering approaches to growing enamel. Back in 2010, a group demonstrated regeneration of cavities in mice by delivering a peptide known to encourage bone formation, and that worked on enamel as well. That attempt was conceptually similar to far more recent research noted here, in which a different peptide is used to spur enamel deposition.

Peptide-based biogenic dental product may cure cavities

Researchers have designed a product that uses proteins to rebuild tooth enamel and treat dental cavities. This can - in theory - rebuild teeth and cure cavities without today's costly and uncomfortable treatments. "Remineralization guided by peptides is a healthy alternative to current dental health care. Peptide-enabled formulations will be simple and would be implemented in over-the-counter or clinical products."

Bacteria metabolize sugar and other fermentable carbohydrates in oral environments and acid, as a by-product, will demineralize the dental enamel. Although tooth decay is relatively harmless in its earliest stages, once the cavity progresses through the tooth's enamel, serious health concerns arise. Good oral hygiene remains the best prevention. Taking inspiration from the body's own natural tooth-forming proteins, researchers came up with a way to repair the tooth enamel. They accomplished this by capturing the essence of amelogenin - a protein crucial to forming the hard crown enamel - to design amelogenin-derived peptides that biomineralize and are the key active ingredient in the new technology.

"These peptides are proven to bind onto tooth surfaces and recruit calcium and phosphate ions." The peptide-enabled technology allows the deposition of 10 to 50 micrometers of new enamel on the teeth after each use. Once fully developed, the technology can be used in toothpaste, gels, solutions and composites as a safe alternative to existing dental procedures and treatments. The technology would enable people to rebuild and strengthen tooth enamel on a daily basis as part of a preventive dental care routine.

Biomimetic Tooth Repair: Amelogenin-Derived Peptide Enables in Vitro Remineralization of Human Enamel

White spot lesions (WSL) and incipient caries on enamel surfaces are the earliest clinical outcomes for demineralization and caries. If left untreated, the caries can progress and may cause complex restorative procedures or even tooth extraction which destroys soft and hard tissue architecture as a consequence of connective tissue and bone loss. Current clinical practices are insufficient in treating dental caries.

A long-standing practical challenge associated with demineralization related to dental diseases is incorporating a functional mineral microlayer which is fully integrated into the molecular structure of the tooth in repairing damaged enamel. This study demonstrates that small peptide domains derived from native protein amelogenin can be utilized to construct a mineral layer on damaged human enamel in vitro. Six groups were prepared to carry out remineralization on artificially created lesions on enamel: (1) no treatment, (2) Ca2+ and PO43- only, (3) 1100 ppm fluoride (F), (4) 20 000 ppm F, (5) 1100 ppm F and peptide, and (6) peptide alone. While the 1100 ppm F sample (indicative of common F content of toothpaste for homecare) did not deliver F to the thinly deposited mineral layer, high F test sample (indicative of clinical varnish treatment) formed mainly CaF2 nanoparticles on the surface.

Fluoride, however, was deposited in the presence of the peptide, which also formed a thin mineral layer which was partially crystallized as fluorapatite. Among the test groups, only the peptide-alone sample resulted in remineralization of fairly thick (10 μm) dense mineralized layer containing HAp mineral, resembling the structure of the healthy enamel. The newly formed mineralized layer exhibited integration with the underlying enamel as evident by cross-sectional imaging. The peptide-guided remineralization approach sets the foundation for future development of biomimetic products and treatments for dental health care.

Precision Vaccination Against LDL Cholesterol Reduces Atherosclerotic Plaque in Mice

Vaccination technology has advanced to the point at which tiny fragments of a protein can be used to direct the adaptive immune system to attack very specific targets. In this case, the target is LDL cholesterol. Reducing the amount of LDL cholesterol in the bloodstream is a proven strategy to slow the onset and progression of atherosclerosis. In this condition, damaged lipids carried in the bloodstream irritate cells in the blood vessel wall, leading to a runaway process of inflammation and cell death that generates fatty plaques. These eventually lead to rupture or blockage of blood vessels that is severe enough to result in death. A global reduction in blood lipids - in cholesterol in the bloodstream - reduces the input of damaged lipids to this process.

In recent years the research community has broadened its efforts in this direction, moving beyond pharmaceuticals such as statins in order to find more efficient means of long-term reduction in blood lipids. Examples other than the vaccination approach noted here include PCSK9 gene therapies, or similar efforts that target other genes noted to significantly reduce cholesterol levels without side-effect in mammals. Diversity in research for any particular therapeutic goal is usually a good sign for future progress.

Researchers report successful vaccination of atherosclerotic mice with a small chunk of protein snipped out of "bad cholesterol." Vaccination reduced plaque levels in test mice, and other experiments with human blood samples identified the class of T cells likely responsible for positive outcomes. The results suggest that a comparable strategy could form the basis of a human vaccine. "We knew atherosclerosis had an inflammatory component but until recently didn't have a way to counteract that. We now find that our vaccination actually decreases plaque burden by expanding a class of protective T cells that curb inflammation."

So-called "bad cholesterol" is actually an amalgam of the lipid cholesterol carried on Low Density Lipoprotein, or "LDL". To create the new vaccine, the team engineered a short stretch (or peptide) of the core LDL protein. They then undertook a type of molecular fishing expedition, using a version of the peptide mounted on a scaffold called a tetramer as bait, to identify what immune cells became active in its presence. To do that, the researchers obtained human blood from two groups - women with plaque accumulation in their carotid arteries versus women without plaque formation - and screened those samples for immune cells that latched onto the peptide. In both groups, the peptide bound to subset of CD4+ T cells known as T regulatory cells (or "Tregs"). But the percentage of Tregs from atherosclerotic subjects was much smaller, and other types of T cells were much more common than in healthy donors, suggesting that the Tregs may undergo some kind of molecular switch that hampers their effectiveness once cardiovascular disease progresses.

Beyond addressing a major health concern, this paper exemplifies next-generation vaccinology. "We are now engineering vaccines to be more specific. Once we can manipulate the immune response with a single peptide or epitope, we will be able to create more highly targeted vaccines with fewer non-specific responses." These results is evidence that this goal is feasible against atherosclerosis, but more work is needed to create a vaccine appropriate for human use. A preventative, not just a treatment like statins, is needed to block plaque deposition, because atherosclerosis can go undiagnosed. "Men in their 50's with apparently normal cholesterol may be at risk, and seemingly healthy people occasionally suffer fatal heart attacks. Only then their docs realize they had atherosclerotic disease." A widely available vaccine that prevented plaque formation would make that scenario a thing of the past.

Link: http://www.lji.org/news-events/news/post/lji-researchers-are-one-step-closer-to-an-effective-anti-atherosclerosis-vaccine/

A Failure to Treat Alzheimer's by Interfering in RAGE-Induced Inflammation

Alzheimer's disease certainly has an inflammatory component to it, as do other neurodegenerative conditions. The immune system of the brain runs awry in characteristic ways. Evidence exists to suggest that short-lived advanced glycation end products (AGEs) of the sort found in individuals with metabolic syndrome and type 2 diabetes are a significant source of inflammation. They act via the receptor for AGEs, RAGE. This, I should note, is entirely unrelated to the detrimental effects of persistent, long-lived AGEs on tissue structure. Short-lived AGEs are more of a lifestyle issue, in that everyone has them to some degree, but they are strongly associated with diet, obesity, and the metabolic diseases of obesity.

In any case, some effort has gone into building ways to interfere in RAGE-induced inflammation, and one of them made it as far as clinical trials for Alzheimer's disease. Unfortunately it joins the sizable and growing pyre of failed trials for this condition - and by the look of it was running largely on hope for much of its lifetime, one of many things wrong with the present system of trials and its dominant focus on marginal effects. It is possible that reducing inflammation simply isn't enough on its own, given everything else that is going on in the Alzheimer's brain, or that RAGE is not an important source of inflammation in comparison to others in Alzheimer's patients, or the effects did not translate well from animal studies.

Yesterday, vTv Therapeutics announced the termination of both parts of its STEADFAST clinical study, which had been testing the small molecule azeliragon in patients with probable Alzheimer's. According to data from the Phase 3 clinical trial, patients who took the drug for 18 months performed no better than those on placebo in tests of cognition and function. Though only a fraction of patients in Part B, which is identical in design, have completed 12 months on the drug, the company has terminated that trial.

Azeliragon blocks the receptor for advanced glycation end products (RAGE), which can cause inflammation in the brain. Because microglia and astrocytes upregulate expression of RAGE in AD, and because evidence suggested RAGE binds and mediates toxicity, researchers reasoned that blocking the receptor would be beneficial. TransTech Pharma discovered azeliragon, a.k.a. TTP 488, and licensed it to Pfizer, which, together with the National Institute on Aging, sponsored an 18-month trial of the antagonist back in 2007. Run by the Alzheimer's Disease Cooperative Study, it tested daily doses of 5 mg and 20 mg given after six-day ramp-ups of 15 mg and 60 mg, respectively, in patients with mild to moderate AD. Trials of both dosing regimens were halted early for lack of efficacy.

Latching onto hints of a benefit in patients with mild AD, TransTech Pharma, which would become vTv, received fast-track approval from the Food and Drug Administration to test the drug in patients with probable AD and a brain MRI consistent with that diagnosis. No other markers were used for inclusion criteria. The STEADFAST study was slated to recruit 800 participants randomized to either 5 mg/day azeliragon or placebo.

Link: https://www.alzforum.org/news/research-news/fighting-rage-no-help-alzheimers-disease-patients

Mitochondria Touch on All of the Present Methods of Slowing Aging

Read on the topic aging research and one will soon enough arrive at a consideration of mitochondria, their function and dysfunction. They are everywhere in the literature. These organelles are responsible for processing nutrients into chemical energy stores, and also play a role in a variety of important mechanisms in cell growth and cell death. They mediate many beneficial cellular responses to stress via generation of reactive oxygen species in greater or less amounts. Further, they are a primary target for the cellular maintenance processes of autophagy, as when mitochondria malfunction they can cause serious harm to a cell and its surroundings. That portfolio of functions and concerns is connected to all of the present methods of metabolic alteration shown to modestly slow aging in laboratory animals.

Most of these methods utilize the induction of stress response mechanisms, particular those involved in calorie restriction, the reduction of nutrient intake, which overlap with responses to exercise, to heat, to toxins, and to lack of oxygen. Altered mitochondrial function appears frequently as a central mediating mechanism. Calorie restriction itself appears to depend on increased levels of autophagy - and as soon as autophagy is involved one has to consider the reduction in mitochondrial breakage and dysfunction that results from more active mitochondrial quality control. It is even possible to tie mitochondria to the more recent efforts that depart from metabolic manipulation in order to produce rejuvenation through targeted destruction of senescent cells. Since senescent cells are primed to self-destruct, and since that process of self-destruction is mediated by mitochondria, the various pharmaceutical senolytic drug candidates target mitochondrial molecular machinery in order to force the issue.

How much of degenerative aging is mediated by mitochondria? Mitochondrial composition correlates well with species life span, suggesting importance, but that doesn't necessarily bear any relationship to the degree of harm done in any given species by the age-related failure of mitochondrial function, by the damage that accumulates in mitochondrial DNA. The only sure way to find out is to repair the damage, restore mitochondrial function, and watch what happens in a mouse study. Unfortunately, the research community is not yet capable of achieving that goal, though inroads have been made on the SENS approach of allotopic expression - copying mitochondrial DNA into the cell nucleus to prevent damage to mitochondrial genes from depriving mitochondria of necessary proteins.

Targeting Mitochondria to Counteract Age-Related Cellular Dysfunction

In a rapidly aging society, new treatment options for age-related disorders and diseases will be increasingly important. Consequently, in recent decades, research has focused heavily on the processes of aging to reveal potential targets for prolonging health and lifespan. Consistent with this, interventions such as caloric restriction (CR) or exercise, as well as pharmacological strategies have been well established to improve health and to slow down aging.

As adenosine triphosphate (ATP)-producing power plants of the cell, mitochondria are in a unique position to influence an organism's aging process. Recent reports suggest that mitochondrial function is linked to age-associated biphasic alterations in metabolic activity, including an increase and afterwards progressive decrease in mitochondrial function. In addition, the byproducts of mitochondrial respiration, reactive oxygen species (ROS), are key determinants in the initiation of cellular senescence when present in high concentrations. Moreover, changes in mitochondrial dynamics in fusion and fission, as well as alterations in the mitochondrial membrane potential have been reported to cause cellular dysfunctions during senescence. Consequently, it seems reasonable that life-prolonging interventions, such as CR or exercise, as well as various drugs, target mitochondria.

Notably, impaired mitochondrial functions are reported to cause accelerated aging that affects primarily organs with high levels of energy demand, such as the brain, the heart, the skeletal muscle, as well as liver and kidney. The critical role of mitochondria in these organs becomes clinically visible in the case of mitochondrial diseases that frequently affect organs with high energy demand. The link between mitochondrial dysfunction and age-related diseases is well-established for Alzheimer's disease, myocardial infarction, and sarcopenia.

The process of aging evokes various alterations in mitochondrial Ca2+ handling, mitochondrial respiration, mitochondrial structure, as well as in the mitochondrial genome, which are mutually interrelated to each other. Results from cell culture and animal experiments suggest enhanced mitochondrial activity in middle age, but a decline in old age. Initially, increased activity of mitochondria might compensate for the decreased mitochondrial efficiency that occurs during aging. However, this enhanced mitochondrial activity might harm the cell long-term, for instance, by increased ROS production, and might even further promote age-related cellular dysfunction. It is of major importance to further investigate the molecular processes behind the role of mitochondria in aging, as well as their potential to serve as targets for therapeutic interventions.

Journalistic Views of Aging and Longevity Have Yet to Reach Maturity

While journalistic treatment of serious rejuvenation research has improved greatly over the past decade, the mainstream media remains decidedly childish at times. Much of the profession of journalism works hard at producing the appearance of educated folk paid to play the fool, writing for an imagined audience of inattentive, ignorant peers, while ensuring that their education slips through the mask just enough to be seen. It degrades the author and insults the world at large. Everyone in this picture is better than they are portrayed, capable of introspection and self-determination. I noted the article here because it veers from the histrionic to the sensible, covering in one outing a fair portion of the existing journalistic spectrum of quality and common sense regarding aging and age-related disease. It predictably asks whether or not we should work to make progress in medical science, thereby producing far longer healthy life spans - the manticore of journalistic balance in place of actual thought on the matter.

Advances in anti-aging medicine suggest that even serious life extension may be within reach. Millions of dollars have poured into longevity research ranging from the radical (head transplants, cancer-killing nanobots) to the slightly more recognizable (repurposing diabetes medications to kill off senescent cells, drugs to mimic genes that have quadrupled the lives of worms). The hotly debated question among longevity experts, in fact, is not whether we'll celebrate significantly more birthdays but how many more.

Saving a life and extending a life are part of the same continuum. When we save a life, with defibrillators or bypass surgery or by pulling someone who's drowning out of a lake, we move the time of death. "We all believe in postponing deaths. We all want our own deaths postponed and we invest vast amounts as individuals and societies in methodologies for achieving that. To withdraw from that is to say that postponing death is not a good thing."

For all but our most recent history, death was a common, ever-present possibility. Life expectancy has increased in the West mainly because fewer children are dying before that fifth birthday, mostly thanks to improved nutrition, sanitation, and vaccines. But modern medicine has also helped the "bottom to drop out later and later" - past 50, past 80, past 100. In Canada, for the first time in history, there are now more over-65s than under 15s, and the biggest boom is in the centenarians, whose numbers grew by 41 per cent from 2011 to 2016.

Still, when we do die we tend to follow a predictable period of decline. By age 85, half of us will have three or more major chronic diseases. Our lungs start to give out, our reflexes slow, our vision dims. But Aubrey de Grey hopes to pull us out of that dive. Reach age 40, say, and then go in for a series of "rejuvenation" tune-ups that return us to the biological fitness (inside and out) of a a 20- or 30-year-old. Repeat a few decades later. And again, and again - until we achieve what de Grey calls "longevity escape velocity," renewal at a pace faster than aging. SENS-funded researchers, some of them leaders in their field, are working towards a panel of rejuvenation therapies to repair or eliminate seven different kinds of biological "junk" that accumulates as we age - cell loss, mutations in chromosomes, death-resistant cells, and so on - so that we are able to get seriously old without falling apart.

Link: http://nationalpost.com/feature/do-you-really-want-to-live-foreverish

The SENS Research Foundation on the Ongoing Development of Senolytic Therapies to Treat Neurodegenerative Conditions

Senescent cells are a significant cause of age-related disease. Now that the research community is earnestly developing ways to remove senescent cells, and trying them out in animal studies, every few months there is a new announcement of one or another definitive connection between the accumulation of senescent cells and a specific medical condition. The SENS vision for the development of rejuvenation therapies assembled the existing evidence and strongly advocated for senescent cell clearance around the turn of the century, ten long years prior to the point at which the rest of the research community finally got on board. In a better world, most of the impressive progress today towards the effective treatment of many age-related diseases by clearance of senescent cells would have happened certainly ten and perhaps twenty years ago. There is no compelling technical reason for it to have waited until now; the delay is near all cultural, a consequence of the attitudes of the research community during the decades in which its members actively discouraged work on slowing or reversing the aging process.

It was a bit of a mystery to the scientists investigating the phenomenon: a brain disease driven by the death of specialized neurons was strongly linked to exposure to a particular pesticide. Why, then, didn't exposing those same neurons directly to that same pesticide seem to affect them? Parkinson's disease (PD) is a neurodegenerative disease of aging, whose most obvious symptoms involve the loss of fine motion control. This is the result of the loss of specialized cells in an area of the brain called the substantia nigra pars compacta (SNc) that specialize in producing the chemical signal-molecule dopamine. Once a critical number of these dopaminergic SNc neurons are lost, the unbalanced firing of those neurons begins to manifest itself in the main motion-related symptoms of the disease.

In all but a few people with rare mutations, degenerative aging processes (such as the accumulation of mitochondrial mutations in SNc neurons) are primarily responsible for the disease. But lifestyle and environmental factors also damage these neurons. A striking example of this is MPP+, a well-established neurotoxin that specifically attacks the SNc dopaminergic neurons. For a long time, scientists have focused on paraquat, a neurotoxic pesticide subject to restricted use. Paraquat was originally restricted because it can cause lung damage when workers are exposed to high levels of it in the air, but scientists studying it also noted that it has a strong structural resemblance to MPP+. And sure enough, under some conditions it can cause a Parkinson's-like syndrome in laboratory animals, and a strong and consistent relationship has been found between on-farm exposure to paraquat in farm workers and risk of PD.

Yet, puzzlingly, paraquat doesn't seem to be particularly toxic to dopaminergic neurons when tested directly; much of the rodent data that seems to show such an effect is ambiguous or unlikely to reflect paraquat exposures actually present in the brain. So what might be going on? As it turned out, the scientists were looking in the wrong place. Paraquat, it turns out, doesn't directly kill dopaminergic neurons. Instead, it acts by deranging the cells that are supposed to support and nourish them. Meanwhile, the same thing goes wrong in the aging brain, culminating in Parkinson's and other degenerative syndromes. The lesson here isn't just "avoid exposure to dangerous pesticides." The same study that revealed this surprising indirect mechanism of paraquat's neurotoxicity also showed how much of the harm can be blocked, and in doing so revealed a new tool in our toolbox for taking the "normal" Parkinson's disease of aging out of our futures forever.

Astrocytes are a kind of support cell for the neurons in the brain. They provide a source of nutrients, maintain the equilibrium in the fluids that surround the neurons, participate in neural repair, and take up and release brain messenger-molecules. Scientists discovered several years ago, however, that rising numbers of astrocytes in the aging brain become senescent. Senescent cells lose their normal function in the tissue, cease dividing, and begin secreting a deadly mix of inflammatory and tissue-degrading factors collectively known as the senescence-associated secretory phenotype (SASP) that damages and deranges local tissues.

It was no surprise, then, when scientists found that the burden of astrocytes with tell-tale signs of senescence rises with age in the brain and even faster in those with Alzheimer's disease. Could it also be part of the explanation for the effect of paraquat? And what are the therapeutic implications of such findings in aging people not exposed to this neurotoxin? When the researchers examined the brains of PD patients, they found more cells exhibiting signs of senescence than in people without the disease - and especially astrocytes.

How might one prove that the newly-discovered induction of senescence in astrocytes was responsible for the damage, and not some other direct or indirect effect? The "damage-repair" heuristic of SENS suggested eliminating the senescent cells themselves, and seeing if that was enough to block the downstream mayhem. Research have in fact found that eliminating senescent astrocytes confers benefits to mice with a model of PD that mimics the fundamental processes that drive Parkinson's in aging people. In recent years, researchers have developed so-called "senolytic" drugs that wipe out senescent cells in aging mice and mouse models of age-related disease, exploiting the high dependence of these cells on specific biochemical survival pathways. The benefits of senescent cell clearance to the health and longevity of aging mice have turned out to be more dramatic and sweeping than anyone ever expected.

Link: http://www.sens.org/research/research-blog/save-your-brain-slay-zombie-senescent-cells

Three Recent Papers on the Use of Senolytic Therapies to Address Age-Related Disease

Today, a few papers on cellular senescence and the application of therapies to remove senescent cells. Senescent cells are one of the root causes of aging. Over the past five years, once the research community finally started to make progress on ways to selectively destroy senescent cells, the presence of these cells has been directly implicated in a wide range of age related diseases. They cause fibrosis. They produce calcification in blood vessels. They help to upset the balance of bone maintenance to generate osteoporosis. They are at the root of localized inflammatory conditions such as osteoarthritis. They harm lung function. And so on and so forth through a long list of issues. All of this progress in knowledge and methods of therapy could have happened ten or twenty years earlier, in a different world, in which the leadership of the aging research community didn't engage in decades of hostility towards anyone who wanted to treat aging as a medical condition. The evidence was there.

Countless cells become senescent in the body day in and day out. It is the end state of somatic cells that reach the Hayflick limit on replication, quickly followed by programmed cell death or destruction by the immune system. Cells also become senescent in response to injury, a toxic cellular environment, or DNA damage likely to lead to cancer. Again, a quick destruction is their fate. A very tiny fraction of senescent cells evade this fate to linger indefinitely, however. These lingering cells secrete a potent mix of molecules that triggers chronic inflammation, damages the surrounding tissue structures, and changes the behavior of nearby cells for the worse. The harm grows as the number of senescent cells grows.

Fortunately, work on senolytic therapies capable of selectively destroying senescent cells has moved out of the laboratory and into a number of startup companies. Numerous different pharmaceuticals trigger senescent cells to self-destruct by interfering in mechanisms that are only of great importance in the senescent state, and Unity Biotechnology is moving ahead with several of those. Oisin Biotechnologies is pioneering a programmable gene therapy that can destroy cells based on their internal biochemistry. SIWA Therapeutics is working on an immunotherapy approach to the problem of senescent cells. There will be others in the years ahead - there is plenty of room in a market in which every adult over the age of 40 is a potential customer. Effective senolytic therapies would likely be undertaken once every few years at most, to keep the number of senescent cells too low to cause serious issues, thus taming this contribution to degenerative aging. That advance in clinical medicine is just a few years away now.

Strategies targeting cellular senescence

Cellular senescence is a physiological phenomenon that has both beneficial and detrimental consequences. Senescence limits tumorigenesis and tissue damage throughout the lifetime. However, at the late stages of life, senescent cells increasingly accumulate in tissues and might also contribute to the development of various age-related pathologies. Recent studies have revealed the molecular pathways that preserve the viability of senescent cells and the ones regulating their immune surveillance. These studies provide essential initial insights for the development of novel therapeutic strategies for targeting senescent cells. At the same time they stress the need to understand the limitations of the existing strategies, their efficacy and safety, and the possible deleterious consequences of senescent cell elimination. Here we discuss the existing strategies for targeting senescent cells and upcoming challenges in translating these strategies into safe and efficient therapies. Successful translation of these strategies could have implications for treating a variety of diseases at old age and could potentially reshape our view of health management during aging.

Senescent cells: a therapeutic target for cardiovascular disease

Cellular senescence, a major tumor-suppressive cell fate, has emerged from humble beginnings as an in vitro phenomenon into recognition as a fundamental mechanism of aging. In the process, senescent cells have attracted attention as a therapeutic target for age-related diseases, including cardiovascular disease (CVD), the leading cause of morbidity and mortality in the elderly. Given the aging global population and the inadequacy of current medical management, attenuating the health care burden of CVD would be transformative to clinical practice. Here, we review the evidence that cellular senescence drives CVD in a bimodal fashion by both priming the aged cardiovascular system for disease and driving established disease forward. Hence, the growing field of senotherapy (neutralizing senescent cells for therapeutic benefit) is poised to contribute to both prevention and treatment of CVD.

Senescent cells and osteoarthritis: a painful connection

Senescent cells (SnCs) are associated with age-related pathologies. Osteoarthritis is a chronic disease characterized by pain, loss of cartilage, and joint inflammation, and its incidence increases with age. For years, the presence of SnCs in cartilage isolated from patients undergoing total knee artificial implants has been noted, but these cells' relevance to disease was unclear. In this review, we summarize current knowledge of SnCs in the multiple tissues that constitute the articular joint. New evidence for the causative role of SnCs in the development of posttraumatic and age-related arthritis is reviewed along with the therapeutic benefit of SnC clearance. As part of their senescence-associated secretory phenotype, SnCs secrete cytokines that impact the immune system and its response to joint tissue trauma. We present concepts of the immune response to tissue trauma as well as the interactions with SnCs and the local tissue environment. Finally, we discuss therapeutic implications of targeting SnCs in treating osteoarthritis.

All Current Assessment Methods for Frailty Correlate with Future Mortality

Researchers here report on the effectiveness of methods used by researchers and clinicians to assess degree of frailty in older patients. They find that all methods correlate with future mortality, but there are variances in the details of how they correlate to the risk of suffering specific age-related conditions. An optimist might take this to mean that any future rejuvenation therapy with sizable, reliable effects could be correctly categorized as a real rejuvenation therapy by applying the existing systems of testing and assessment. New biomarkers of aging would help, but they are not necessarily required. We'll find out whether or not this is the case over the next five to ten years as senolytic therapies work their way into widespread use, and the large assessment studies begin.

Frailty is common in elderly people with cardiovascular disease and goes along with elevated mortality. However, no consensus exists on the definition of frailty. Many scores have been developed to assess frailty and to make predictions on disease and mortality, but there is no gold standard. Researchers examined the predictive ability of 35 frailty scores for cardiovascular disease, cancer and all-cause mortality using data from the English Longitudinal Study of Ageing. The analysis reveals that all frailty scores are associated with future mortality, and that some are linked to cardiovascular disease but none to cancer. The study underscores that the comparative evaluation of strength of associations between health outcomes in elderly people provides a solid evidence base for researchers and health professionals.

In this study, the scientists analysed frailty scores identified by a systematic literature review on their ability to predict mortality, cardiovascular disease, and cancer. Data was used from 5,294 adults aged 60 years or more and followed up over a period of seven years within the English Longitudinal Study of Ageing. The researchers observed that all frailty scores were associated with all-cause mortality, some were also associated with the incidence of cardiovascular disease, but none were associated with cancer events. In models adjusted for demographic and clinical information, 33 out of 35 frailty scores showed significant added predictive performance for all-cause mortality. Certain scores outperform others with regard to all-cause mortality and cardiovascular health outcomes in later life. The authors specify that multidimensional frailty scores may have a more stable association with mortality and incidence of cardiovascular disorders.

Link: https://www.lih.lu/blog/our-news-1/post/associating-frailty-to-cardiovascular-disease-and-mortality-189

Correlating Hair Graying and Cardiovascular Disease

Whenever one looks at correlations discovered between manifestations of aging, it is worth bearing in mind that it is easy to find these correlations, but hard to show that they are in any way meaningful. Aging is caused by a few comparatively simple processes of damage accumulation that spread out into a vast, complicated, branching tree of interacting secondary and later consequences. Aging is complicated because our biology is very complicated, not because its causes are especially complicated. This spreading out from common roots means that many parts of aging proceed at fairly similar rates in any given individual. That can be true even if those correlated portions of aging have little connection to one another aside from that same root cause, all the way down beneath many layers of cause and effect.

Aging is a complex process that affects all of us. All organs undergo a series of age related changes, in which the vascular system is prominent. Hair graying is one of the natural aging processes. Although it is generally not a medical problem, it greatly concerns many people for aesthetic reasons. Because of the strong association between aging and hair graying, many researchers have been concerned that hair graying, especially when occurs prematurely, is a predictor of some severe systemic disease and several studies evaluated the association of premature hair graying (PHG) with osteopenia or coronary artery disease (CAD).

Atherosclerosis and graying of hair share a similar mechanism includes impaired DNA repair, oxidant stress, androgens, inflammatory processes, and senescence of functioning cells, and the incidence of both conditions increases with age. Accordingly, this study was conducted to determine the prevalence and degree of hair graying among a cohort of males with suspected CAD who underwent computed tomography coronary angiography (CTCA) and whether it is an independent marker for CAD.

This study recruited 545 adult male patients who underwent a CTCA for suspicion of CAD. Extent of grayness was assessed with two observers using hair whitening score (HWS), defined according to percentage of gray/white hairs. Patients were divided into different subgroups according to the percentage of gray/white hairs and to the absence or presence of CAD.

We found that patients who had atherosclerotic CAD were older in age and among all cardiovascular risk factors, hypertension, diabetes, and dyslipidemia were more prevalent, and that high HWS was associated with increased risk of CAD independent of chronological age and other established cardiovascular risk factors. The results of our study not only confirm an association between hypertension, diabetes, smoking, and hair graying but also shows that coronary calcification detected by CTCA was significantly higher in patient with high HWS.

Link: https://doi.org/10.1016/j.ehj.2017.07.001

A Mouse Model of Accelerated Mitochondrial Deletion Mutations that Doesn't Exhibit Signs of Accelerated Aging

Few roads in the life sciences are straight and broad, and the way forward to prove and quantify the contribution of mitochondrial DNA damage to aging is turning out to be particularly winding. The open access paper noted below is the latest in a series of attempts to engineer mice that generate specific forms of mitochondrial mutation at an accelerated rate. The hope here is that this sort of study will, even if carried out for other reasons, help to clarify contradictory results obtained from prior lineages of mitochondrial mutator mice, but I'm not sure that any such goal has been achieved in this case. When compared with the theory of what is expected to happen as the result of a greater number of mitochondrial mutations, the results here are more of an additional puzzle than an answer to outstanding questions.

There is a herd of mitochondria in every cell, replicating like bacteria, and each carrying their own small circular genome - mitochondrial DNA. One important view of mitochondrial DNA mutation in aging is summarized in the SENS research proposals. In short, deletion mutations eliminate important mitochondrial genes, and an affected mitochondrion malfunctions in a way that causes it to either replicate more efficiently or resist cellular quality control mechanisms more effectively than its undamaged peers. The cell is overtaken by the descendants of this broken mitochondria, and as a consequence enters a dysfunctional state that exports harmful reactive molecules into the environment, contributing to the aging process.

In this view, point mutations are not thought to be anywhere near as important - but they are much more common. Indeed, some thought has to go into explaining how deletion mutations can be significant in aging given their rarity. In the course of investigating these questions, mice have been engineered to have abnormally high levels of mitochondrial mutations. There are mice with enormous numbers of point mutations in mitochondria that exhibit no signs of accelerated aging, and there are the later mitochondrial mutator mice with both greatly increased point mutations and deletions that do exhibit accelerated aging. A reasonable conclusion on this basis is that the deletions are the important factor.

Now, however, we have this new lineage of mice exhibiting extra deletions and no point mutations, but that also show no signs of accelerated aging. At this point, I think we're forced to concede that the implementation details matter greatly, and every one of these studies and models is going to have to be picked over with a fine comb in order to figure out what to try next. It is perhaps time to give up on building a model of accelerated aging, and put time and effort into engineering a mouse with fewer mitochondrial mutations to see if more can be learned by trying to slow aging.

On this front, it isn't clear that the SENS program of allotopic expression has progressed far enough to make an attempt to gain data in mice. There are thirteen mitochondrial genes to protect, and only protecting the three that can so far be protected might not be enough of a difference to obtain reliable data for outcomes on aging. Mitochondrial damage is only one of seven classes of damage that cause aging, and what is the effect size of a quarter of a seventh? How comfortably would anyone feel trying to find an adjustment in aging rate of a few percentage points in mice? Smaller effects are very hard to reliably identify in animal studies, in which 10% effect sizes typically come and go at random and should really be treated as noise. Up to a certain point, it is more cost effective to put resources towards protecting more mitochondrial genes.

Mice lacking the mitochondrial exonuclease MGME1 accumulate mtDNA deletions without developing progeria

Mutations in nuclear genes can cause mitochondrial DNA (mtDNA) instability resulting in mtDNA depletion or accumulation of deletions and/or point mutations, ultimately leading to impaired oxidative phosphorylation (OXPHOS). The vast majority of mutations causing human mtDNA instability map to genes encoding proteins involved in mtDNA replication. Extensive in vitro work has led to significant progress in our understanding of the biochemical processes underlying mtDNA maintenance disorders, but animal models are nevertheless essential to understand the wide range of phenotypes and secondary metabolic consequences of mtDNA instability in different tissues.

To gain further insight into diseases of defective mtDNA replication, we created a knockout mouse model for the recently described disease gene encoding MGME1 (also known as Ddk1). Loss-of-function mutations in MGME1 were reported to cause a severe multisystem mitochondrial disorder in humans with depletion and rearrangements of mtDNA. Loss of MGME1 expression, either in siRNA treated cells or in patient fibroblasts, leads to an accumulation of 7S DNA, which is the single-stranded DNA species formed by premature replication termination at the end of the control region of mtDNA, thus suggesting a role for MGME1 in repressing formation or increasing turnover of these molecules.

We have studied the in vivo mtDNA replication phenotypes associated with MGME1 deficiency in various mouse tissues of knockout mice. Although MGME1 is not essential for embryonic development, its loss leads to accumulation of multiple deletions and depletion of mtDNA in a range of different mouse tissues.

A hallmark of MGME1 deficiency in patient fibroblasts and mice is an 11 kb linear mtDNA fragment spanning the entire major arc of the mtDNA, which has been previously described in mtDNA mutator mice and flies. Numerous studies suggest that mtDNA mutations and deletions contribute to the ageing phenotypes in experimental animals and in humans. Indeed, mtDNA mutator mice develop progressive premature ageing syndrome phenotypes. In addition to the presence of the above mentioned 11 kb subgenomic mtDNA species, the mtDNA mutator mice also accumulate an increased number of point mutations, that most likely drive the ageing phenotype. Consistent with this hypothesis, Mgme1-/- mice do not accumulate point mutations and do not display a progeroid phenotype. In line with this finding, mtDNA subgenomic fragments have not been detected in tissues from aging mammals further indicating that this lesion on its own does not induce ageing.

MicroRNA-150 is Important in the Contribution of Macrophages to Age-Related Disease

Researchers here provide evidence for microRNA-150 to be a part of the regulatory machinery that determines whether macrophage behavior is inflammatory and damaging, or regenerative and helpful. This is part of a most interesting line of research that examines the various polarizations of macrophages, a polarization being a class of behavior and activity, and their contribution to age-related disease. As aging progresses, an ever large fraction of the macrophage population in many tissues becomes inflammatory and aggressive, hindering regeneration, or promotes unhelpful functions in tissue, such as excessive growth of blood vessels. The exact chain of cause and effect that lies between the known root causes of aging and macrophage dysfunction is yet to be determined, but researchers are making progress in mapping mechanisms that might be used to force macrophages to be less damaging in older individuals.

Macrophages are critical effector cells of the innate immune system. Multiple groups, including our own, have reported that macrophages from aged mice demonstrate a functional drift compared with those isolated from young mice. For example, aged macrophages exhibit epigenomic changes, leading to reduced autophagic capacity, and are defective in their ability to fight viral infections due to reduced phagocytic activity. Moreover, aged macrophages are skewed toward a proangiogenic gene and cytokine expression profile, which leads to dysregulated inflammation and the inability to inhibit pathological angiogenesis. Aged macrophages also exhibit impaired cholesterol efflux due to decreased Abca1 expression, leading to intracellular cholesterol accumulation and pathologic vascular proliferation. Age-associated macrophage dysfunction has been proposed to contribute to the pathogenesis of numerous diseases of aging, including age-related macular degeneration (AMD) and atherosclerosis. In addition, age-associated changes in microglia, the major resident immune cell in the retina with similar phagocytic functions, may also promote AMD.

AMD is a leading cause of blindness in industrialized nations and displays a complex disease course characterized, initially, by accumulation of cholesterol-rich deposits known as drusen underneath the retina. Though drusen themselves do not typically cause vision loss, they are risk factors for progression to one of 2 forms of advanced AMD: advanced neovascular (wet) AMD, characterized by pathologic subretinal angiogenesis, or advanced dry AMD, characterized by geographic atrophy secondary to loss of retinal neurons and underlying cells. Both forms of advanced AMD can cause debilitating blindness, though wet AMD causes a significant portion of the vision loss associated with AMD.

There is support for the idea that impaired cholesterol homeostasis contributes to AMD pathogenesis. Impaired cholesterol homeostasis also contributes to the pathogenesis of atherosclerosis. Atherosclerotic plaque formation begins when circulating monocytes adhere to the vascular endothelium, migrate to the sub-endothelial space, and activate into macrophages that take up lipids and become foam cells. Past studies have demonstrated that the activation/polarization state of macrophages is important for predicting plaque phenotype and stability. For example, in patients with hypercholesterolemia, macrophages polarize to a more proinflammatory state, which could predispose to plaque formation. Remarkably, atherosclerotic plaques and drusen have similar lipid compositions, unifying the pathogenic pathways underlying these diseases. Based on these similarities, some have proposed that it may be possible to repurpose statins, lipid-lowering drugs used to treat atherosclerosis, for treating AMD.

Despite these advances in our understanding of the phenotype of aged macrophages and how such changes contribute to age-associated diseases, the molecular mechanisms by which macrophages drift toward the disease-promoting phenotype remain elusive. Given the immense spectrum of these changes in aged macrophages, we hypothesized that microRNAs (miRs) may regulate the transcriptome of macrophages and, thereby, the transition of macrophages to a disease-promoting phenotype. The ability of miRs to target multiple genes makes them strong candidates as molecular regulators.

In this study, we sought to identify one or more miRs that regulate the disease-promoting programmatic changes in macrophages that are associated with AMD. Our results demonstrate that miR-150 is highly upregulated both in disease-promoting murine macrophages and in human peripheral blood mononuclear cells (PBMCs) from AMD patients. Moreover, we show that miR-150 regulates macrophage-mediated inflammation and pathologic angiogenesis, suggesting that it regulates the transition of macrophages from a healthy profile to the AMD-promoting phenotype. Ultimately, these findings provide insight into the mechanisms underlying the pathological programmatic changes in aged macrophages and may lead to the identification of novel therapeutic targets and candidate biomarkers.

Link: https://doi.org/10.1172/jci.insight.120157

Mitochondrial Mutations and Stem Cell Aging

This open access review paper looks over current thinking on the role of mutations in mitochondrial DNA in the decline of stem cell activity in aging. Every cell contains a swarm of mitochondria, the evolved descendants of symbiotic bacteria now responsible for generating chemical energy store molecules. Each contains a small amount of mitochondrial DNA, the last remnant of the original bacterial genome that hasn't either been lost over time or moved to the cell nucleus. Mutational damage in this DNA can produce significant cellular dysfunction, and unfortunately it is a good deal less robust and protected than the DNA of the cell nucleus. It is also right next to energetic chemical processes that produce reactive molecules as a byproduct, and it replicates more frequently than nuclear DNA, all of which suggests a greater rate of damage and error. In long-lived and important stem cell populations, this process is probably important.

Ageing is a process where tissue gradually loses homeostasis and regeneration. This process is systemic and closely associated to age-related changes in somatic stem cells. These cells renew themselves and differentiate into tissue-specific daughter cells for tissue maintenance and regeneration. The age-related alterations in somatic stem cell properties include failure to generate functional progenies, depletion of the stem cell pool, and cancerous transformation. These changes largely affect mitotic tissue, such as blood, intestine, and skin, where the stem cells actively produce progenies to maintain the high turnover of the tissue. However, they also contribute to ageing post-mitotic tissue, such as brain and muscle, though stem cells in these tissues are considered quiescent under normal physiological conditions and activated in response to damage for repairing the tissue.

Mitochondria synthesize ATP via oxidative phosphorylation (OXPHOS) through five multi-subunit complexes. Mitochondria contain their own DNA (mtDNA), which encodes key subunits of these complexes. Replication of the mitochondrial genome is independent of the cell cycle. In addition, mtDNA is susceptible to damage due to lack of histone protection and proximity to oxidative stress. Due to these reasons, compared with the nuclear DNA, mtDNA is more prone to mutations. Multiple copies of mtDNA reside in a cell. Mutations of mtDNA usually occur as a proportion of the total copies and once they reach a threshold, mitochondria will display respiratory chain deficiency, a consequence of which is potentially excessive production of reactive oxygen species (ROS).

Ageing is accompanied by a reduction of mitochondrial function, resulting in respiratory chain defects which are thought to be associated with the accumulation of somatic mtDNA mutations. The age-related change in mitochondria may in turn accelerate the ageing process. Although the significance of mtDNA mutations in various parenchymal cells in normal ageing and age-related degenerative diseases has been broadly studied, the findings might not be able to be extrapolated to stem cells, as they are distinct from somatic cells in terms of biological and metabolic characteristics.

Somatic mtDNA mutations accumulating in stem cell populations in normal humans have a tissue-specific ability to expand clonally during ageing. The premature ageing mtDNA-mutator mouse model gives insight into how acquired mtDNA mutations affect the function of the stem cells and progenitors in both the mitotic and post-mitotic tissue, as well as the potential mechanisms by which age-related mtDNA mutagenesis affects stem cell homeostasis. Recently, studies have reported that stem cells might actively regulate their identity by manipulating the quality control of the mitochondria, for example, by removing the dysfunctional mitochondria or by unevenly segregating young and aged mitochondria. The quality control system might lose its function during ageing, leading to the absence of selective pressures on the somatic mtDNA mutations, which in turn accelerates ageing.

Link: https://doi.org/10.3390/genes9040182

Vast Funding is Available for the Later Stages of Development of any Credible Therapy that Addresses a Cause of Aging

Today I'll point out a couple of recent news items that illustrate there is no funding drought for any group that manages to bring a credible approach to addressing one of the causes of aging to the point of human clinical trials. This is the case even when it is generally understood by all involved that the therapies in question are first generation attempts at implementation, subject to all the normal challenges that brings, and in principle not as good as competing forms of technology that are still at an earlier stage in the process of development. The drought lies in the number of groups who can make it to this stage, because there are never enough entrepreneurs, and the issues with fundraising are all further back in the pipeline: it is hard to raise funds for research into most means of rejuvenation, and it is hard to raise funds at the early startup stage, though that second point is rapidly becoming easier with the growth in the number of incubators focused on biotechnology and aging. Look at YC Bio, for example, or Age 1.

(That it takes a ridiculous amount of funding to pass regulatory hurdles on the way to the clinic is an entire and separate topic for discussion. The task of proving that a treatment works and quantifying the risk of using it to a satisfactory level simply doesn't cost more than a small fraction of the amount that the FDA forces it to cost. Everything above that much lower amount is unnecessary waste, the standard corrosion of efficiency produced by the incentives of a large bureaucratic organization, one whose managers are more interested in practice in perpetuating their positions, expanding their powers, and minimizing bad press than in advancing the state of medicine).

The two groups I'll point out today are Unity Biotechnology, working on pharmaceutical means of senescent cell clearance, and Eidos Therapeutics, who are bringing a therapy for transthyretin amyloidosis to the clinic. In the case of Unity Biotechnology, the better technology and earlier stage competitor is represented by Oisin Biotechnologies, who field a programmable cell killing gene therapy that is in principle a considerable improvement over pharmaceuticals. For Eidos Therapeutics, who are putting forward a therapy that would have to be taken continuously to suppress the creation of harmful amyloid, the earlier, better competing approach is typified by the work of Covalent Bioscience, working on a class of therapy that would clear out the amyloid rather than suppressing its creation. Thus treatment would have to be undertaken less often, and would be more helpful for people further along in the process of accumulating amyloid. All this said, there is of course the point that the better therapy at this moment is the one you can take advantage of today, not the one you wish you could take advantage of today.

Unity Biotechnology has pulled in quite the sizable amount of funding in the past year; they start to look more like a finance operation with a sideline in rejuvenation research than a dedicated biotechnology company. That they are now filing for an IPO before announcing any human clinical trial results is, it has to be said, unusually rapid. But if they can raise the funds and put them to good use, good for them - they have declared ambitions to move beyond senolytics to address other mechanisms of aging, which is certainly a good reason to have a sizable pool of funding. Any successful biotechnology company in one of the fields relevant to the SENS view of aging, damage, and rejuvenation could do a great deal to advance all of the others as well, as the cost of early stage progress is small in comparison to the amounts being raised for later clinical development. We'll see how it turns out once the dust has settled.

Unity Biotechnology files for $85M IPO to take anti-aging drugs into phase 1

Unity Biotechnology has filed for an $85 million IPO. Hitting the target would bring the preclinical anti-aging startup's fundraising haul up toward $300 million and set it up to move two assets into the clinic. Unity last tapped private investors last month with a $55 million series C round. But it is already after its next financial hit. This time, Unity wants public investors to buy into its experimental ideas.

The $85 million IPO would secure Unity's financial future into 2020. Over that period, Unity plans to move two drugs into human testing. Lead program UBX0101, an inhibitor of the MDM2-p53 protein interaction, is due to begin testing in osteoarthritic patients in the next couple of months. UBX1967, an inhibitor of certain Bcl-2 apoptosis regulatory proteins, will arrive in the clinic next year. Unity's initial target indications for the drugs - osteoarthritis and an ophthalmologic disease - reflect its strategy for making the daunting task of tackling aging more manageable. The indications enable Unity to start out administering its drugs locally, before expanding into diseases that require systemic treatment if the early trials validate its approach. Systemic administration would open up indications related to the aging of the heart, kidney, and liver.

Whatever the route of administration, Unity will seek to slow or reverse aging by targeting cellular senescence. This process sees cells halt division, leading to the accumulation of senescent cells and secretion of inflammatory factors, proteases, and other proteins. Unity thinks the proteins disturb tissues and trigger senescence in other cells, leading to the emergence of aged or diseased tissues. A lot of questions remain unanswered, though. All biotechs face uncertainties going into the clinic for the first time, but few pocket more than $200 million and then swing for $85 million IPOs before generating human data. With the delivery of that data still on the horizon, the IPO is a test of investors' willingness to put their faith in a management team and founding investor that have delivered in the past - and the appeal of a big idea.

Eidos Therapeutics completes $64M Series B financing

Eidos Therapeutics, Inc., a clinical stage biopharmaceutical company developing a novel oral therapy to treat transthyretin (TTR) amyloidosis (ATTR), today announced a $64.0 million Series B financing. Proceeds from the financing will be used to advance Eidos' small molecule product candidate, AG10, into Phase 2 clinical trials and to continue preparations for Phase 3 clinical trials. AG10 targets ATTR at its source by potently binding and stabilizing TTR tetramers, the destabilization of which underlies the development of ATTR. The Series B financing brings the total capital raised by Eidos to approximately $91.0 million.

"Our clinical data demonstrate that AG10 has a safe, well-tolerated profile and is able to stabilize 100% of plasma TTR at peak concentrations and provide average levels of stabilization greater than 95% at steady-state. Given that increasing levels of stabilization have yielded progressively better clinical results in past trials, our near-complete levels of stabilization suggest that AG10 could be a best-in-class solution. We are targeting ATTR at its source by stabilizing TTR, an approach that is validated by genetics and clinical data."

The Methuselah Foundation Return on Mission Report

The Methuselah Foundation has hard at work on the matter of aging for more than fifteen years. It is where SENS rejuvenation research first moved from idea to reality, prior to spinning off into the SENS Research Foundation. Over the years, the Methuselah Foundation principals and volunteers have been involved in many of the activities that have helped to transform the aging research community since the turn of the century, setting into motion the projects that will lead to clinical therapies that can turn back aging. In this Return on Mission report (PDF), written for all of us who have supported the Methuselah Foundation over the years, the progress achieved to date is reviewed.

Methuselah Foundation is a biomedical charity co-founded by David Gobel and Dr. Aubrey de Grey. Our mission is to make 90 the new 50 by 2030. We chose that mission because it's falsifiable - it keeps us committed to "return on mission." Having a falsifiable mission keeps us focused. It drives a mindset based in urgency and action. We never want to become the type of charity that exists for existing's sake! Our approach is to put the mission first and money second. We look for high-leverage interventions that spur concrete progress in the short term, and synergistic ripple effects over time. We have built a record of spotting and betting early on people and projects that, with our significant incubation and strategic services, go on to realize remarkable results.

When we began in 2001, it was widely considered both immoral and a fool's errand to work on extending healthy human life. For scientists, it was academically dangerous to even discuss the possibility. Seventeen years later, Methuselah Foundation, its partners and donors have played an unmistakable role in transforming the scientific and cultural outlook. We've had the honor to serve as the first charity to catalyze the movement to address aging. That is almost solely thanks to those of you who've stepped up as the bold few committed to extending healthy life, even in the face of that aim being derided by the press and scientific establishment over the last decade. Our Return on Mission report is an eye-opening look at how far our community has traveled - when progress was never inevitable. It doesn't seem unreasonable to think the last 15 years embody how even a small group can move society. If you've contributed to this progress, thank you!

It has always been the fervent desire of the Methuselah Foundation to find itself with nothing left to accomplish. Over the years, we have been focused on seeking the point of greatest leverage to prevent or reverse the damage associated with aging. We treat aging the way a Medieval diamond cutter would face the challenge of cleaving one of the most valuable and hardest substances known to man. In an era where tools were primitive, the gem cutter would carefully examine the internal crystalline structure, as well as the faults in the diamond. After careful and methodical analysis, the gem cutter would strike the diamond with a cleaver, which would result in the large diamond breaking into predictable and useful smaller pieces, ready for polishing and setting in jewelry.

Aging has been, not just an engineering problem, but a cultural one. One of our "first strikes at the diamond" was aimed not just at scientific progress, but also at publicly celebrating advances in the field. This was the Methuselah Mouse Prize, designed to reward scientific advances and simultaneously overcome the reluctance of the biogerontology community to deliberately explore extending healthy human lifespan. As a social engineering effort, the prize has been spectacularly successful. Efforts to engineer life extension have gone from practically zero dollars worth of investment when we began, to well over a billion dollars in investment.

When we started, the very idea of working on increasing the human lifespan would result in career suicide. Now, the worldwide community is publicly focused on extending lifespan and reversing aging. Due to these early successes, more and more investors are giving attention and funding to our space. In anticipation of this sea change, the Methuselah Foundation created the Methuselah Fund to help curate and direct investments into projects and startups that will move the needle in the near future as we prosecute our mission to extend healthy human lifespan. None of this would have happened without the incredible support of our donors over the years.

Link: https://mfoundation.org/files/pdf/methuselah-foundation-return-on-mission-report.pdf

Calorie Restriction Extends Life Span Significantly in Short-Lived Primates

The practice of calorie restriction slows aging to a degree that scales with species life span. Short lived species exhibit a sizable gain in maximum life span, while long-lived species do not. In this paper, researchers report on a study of calorie restriction in grey mouse lemurs, one of our more distant and short-lived primate cousins. The effects are about as dramatic as those observed in mice, and the study is interesting on that point: lab mice normally reach 50% mortality due to aging after 2-3 years while the lemurs used here reach that point at 6-7 years, so one might have expected the lemurs to exhibit much smaller gains in life span as a result of calorie restriction. Nonetheless, by the end of the study, the longest surviving non-calorie-restricted lemurs had been dead for a year, while more than a third of the calorie restricted animals were still alive. Calorie restriction extended the 50% mortality age from 6-7 years to 9-10 years in this species, quite similar to the relative size of results in mice.

Caloric restriction, i.e., reducing calorie availability by ~20-50%, is one of the rare known strategies that can extend lifespan. In short-lived species such as rodents, caloric restriction can increase maximal lifespan up to 50% while improving general health and decreasing aging-associated diseases. Beneficial effects of caloric restriction on age-related diseases have also been reported for long-lived species, including rhesus monkeys.

Here we examine the effects of caloric restriction on the health and lifespan of the grey mouse lemur Microcebus murinus, a small lemurid primate with a median survival in captivity of 5.7 years for males and maximum lifespan of 12 years. Mouse lemurs are widely used models for human ageing. They display age-related alterations of their sensorial system, motor functions, biological rhythms, and immune and endocrine systems. In this species, aging leads to increased prevalence of diseases such as neoplasia or sarcopenia and glucoregulatory function alterations that also increase with aging in humans. Finally, their cerebral aging profile is similar to that of humans.

Because of their reduced lifespan (as compared to rhesus macaque), cohorts of calorie-restricted lemurs can be easily created to evaluate mechanisms leading to caloric restriction-related changes. Here we provide the first complete set of caloric restriction-related survival data for a non-human primate in association with a longitudinal follow-up of age-associated alterations in cognition and brain volumes.

In 2006, 34 captive adult male mouse lemurs (age 3.2 ± 0.1 years) were randomly assigned to either a control diet or a chronic 30% caloric restriction diet. Compared to control animals, caloric restriction extended lifespan by 50% (from 6.4 to 9.6 years, median survival), reduced aging-associated diseases and preserved loss of brain white matter in several brain regions. However, caloric restriction accelerated loss of grey matter throughout much of the cerebrum. Cognitive and behavioural performances were, however, not modulated by caloric restriction. Thus chronic moderate caloric restriction can extend lifespan and enhance health of a primate, but it affects brain grey matter integrity without affecting cognitive performances.

Link: https://doi.org/10.1038/s42003-018-0024-8

Uncertainty Over Whether or Not Adult Neurogenesis Occurs to Any Significant Degree

Does the adult human brain normally produce a significant number of new neurons, integrating them into new networks? This process is called neurogenesis, and until the 1990s, the answer was thought to be no. Then studies in rodents found that animals of those species do produce new neurons at an appreciable pace, and that this was important to memory, learning, degree of recovery from damage such as stroke, as well as aging and neurodegeneration, as the pace of neurogenesis declines with age. Studies in humans followed to provide supporting evidence that looked convincing enough to believe that rodents were a good model for other mammalian species, including our own. Then, just recently, a well-conducted study in humans found no evidence of any significant level of neurogenesis in adult human brains. Given the degree to which the scientific community is enthusiastically in search of ways to enhance regeneration in the central nervous system, this has produced the expected level of debate.

For today, and as a further illustration of what a field in flux looks like, I'll point out another new study in which the researchers feel fairly confident in claiming that adult neurogenesis both occurs and proceeds at similar levels in both old and young humans. Science is never a matter of absolute confidence in any piece of knowledge; as a layperson, one has to weigh the studies and the discussions of experts, for and against. Here, however, the situation is disordered and uncertain: not enough time has passed for the research community to properly process the new discoveries. Expect that to require some years to reach a new consensus; it takes a year at minimum to complete a suitably weighty investigation, and another year to pass the peer review gauntlet and be published.

The overwhelming weight of evidence remains in favor of adult neurogenesis in rodents, while in humans the results and methodologies are in a sudden state of uncertainty. Yet a great deal of work has proceeded in recent years based on the assumed existence of adult neurogenesis, and various neurological phenomena shared by humans and rodents have been linked by theories that prominently feature adult neurogenesis. So it isn't just a matter of a battle of a few cell-level studies of the brain, but rather of the validity of a broad segment of scientific endeavor over the past few decades. That is not to mention the hopes of an easier road in the future towards ways to induce functional regeneration in the aging brain.

Older adults grow just as many new brain cells as young people

Researchers show for the first time that healthy older men and women can generate just as many new brain cells as younger people. There has been controversy over whether adult humans grow new neurons, and some research has previously suggested that the adult brain was hard-wired and that adults did not grow new neurons. This studycounters that notion, and the findings may suggest that many senior citizens remain more cognitively and emotionally intact than commonly believed.

"We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do. We also found equivalent volumes of the hippocampus (a brain structure used for emotion and cognition) across ages. Nevertheless, older individuals had less vascularization and maybe less ability of new neurons to make connections. It is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout life and that declines may be linked to compromised cognitive-emotional resilience.

Human Hippocampal Neurogenesis Persists throughout Aging

Healthy aging is crucial in a growing older population. The ability to separate similar memory patterns and recover from stress may depend on adult hippocampal neurogenesis (AHN), which is reported to decline with aging in nonhuman primates and mice. New neurons are generated in the dentate gyrus (DG) of the adult human hippocampus, even after middle age, but the extent to which neurogenesis occurs in humans is highly debated and quantitative studies are scarce.

Phylogenetic differences between humans and rodents mandate assessment of the different stages of neuronal maturation in the human DG. For example, striatal neurogenesis is found only in humans, while olfactory bulb neurogenesis is absent in humans but present in other mammals. Previous analyses of human AHN did not address the effects of aging, although studies have examined AHN in older populations. Using histological techniques that could not distinguish mature and immature neurons, several groups estimated that DG neurons did not decline in aging humans.

AHN and angiogenesis are co-regulated. Exercise enhances cerebral blood volume, which results in more AHN in mice and better cognitive performance in humans, but it may have a reduced impact in older people. Thus, we quantified AHN, angiogenesis, and DG volume and their relationship in people of different ages, hypothesizing that they would concurrently decrease with aging and correlate with each other. Given the different functions of the rostral and caudal DG, we assessed the anterior, mid, and posterior hippocampus postmortem from 28 women and men 14 to 79 years of age. In each region, we characterized and quantified angiogenesis, volume, and cells at different maturational stages in the DG neurogenic niche, using unbiased stereological methods. To avoid confounders, subjects studied had no neuropsychiatric disease or treatment.

In medication-free subjects with no brain disease and no reported cognitive impairment, good global functioning as per Global Assessment Scale, and low recent (last 3 months) life event-related stress, quantified by St. Paul-Ramsey Life Experience Scale, we found persistent AHN into the eighth decade of life, and stable DG volume over a 65-year age span. In contrast, we found declining neuroplasticity and angiogenesis with older age, and a possibly diminished multipotent quiescent radial-glia-like type I neural progenitor cells (QNPs) pool selectively in anterior-mid DG, while the QNP pool remained unchanged in posterior DG, possibly reflecting less cognitive and emotional resilience with aging.

Older nonhuman primates and rodents have more granule neurons (GNs) and less AHN than younger ones, contrary to our findings in humans. Since new GNs may assist in pattern separation and old GNs in pattern completion, steady AHN and concurrent elimination of older GNs likely supports human complex learning and memory and emotion-guided behavior throughout a long lifespan. Persistent AHN is vital for preserving cognitive flexibility and allowing memory-guided decision-making without the interference of irrelevant outdated information. Our findings of thousands of new intermediate neural progenitors (INPs) and immature neurons at the time of death, in anterior, mid, and posterior human subgranular zone, suggest that the number of newly generated neurons could be sufficient for them to have a relevant impact on the DG circuit.

How Great is the Dormant Potential for Regeneration in Tissues?

Over the years numerous research groups have claimed the existence of novel stem cell or stem cell like populations in various tissues. Stem cells spend much of their time dormant, but with the right signals or other form of control, it is plausible that they could be directed to greater activity, enhancing tissue regeneration. This is a slow process of discovery, however, usually accompanied by debates over whether or not cells of a claimed type actually exist, whether the research methodologies used in published studies are sound, and so forth. It is wise not to become too excited over any specific claim, but the prevalence of this sort of research suggests that there may be something there. The results noted here are an example of the type, in this case for the central nervous system. The potential to induce regeneration of nerve tissue and the brain is a topic of great interest in the research community.

A major goal of regenerative research is to repair the brain efficiently following injury, for example due to stroke, Alzheimer's disease or head trauma, disease or ageing. The brain is poor at repairing itself; however, it may become possible to improve repair without surgery by targeting stem cells residing in patients' brains. Stem cells have the unique capacity to produce all of the cells in the brain but are normally kept inactive in a form of cellular 'sleep' known as quiescence. Quiescent cells do not proliferate or generate new cells. Thus, any regenerative therapy targeting stem cells must first awaken them from quiescence.

Researchers now report the discovery in the brain of a new type of quiescent stem cell (known as 'G2 quiescent stem cell') with higher regenerative potential than quiescent stem cells identified previously. Importantly, G2 quiescent stem cells awaken to make the key types of cell in the brain - neurons and glia - much faster than known quiescent stem cells, making them attractive targets for therapeutic design. "The brain is not good at repairing itself, but these newly-discovered stem cells suggest there may be a way to improve its ability. These stem cells are in a dormant state, but once awake, they have the ability to generate key brain cells."

By studying the fruit fly (Drosophila), the authors identified a gene known as tribbles that selectively regulates G2 quiescent stem cells. The DNA of fruit flies has many similarities with that of humans, making them a useful model to understand human biology, and 60% of human genes associated with disease are also found in Drosophila. The tribbles gene has counterparts in the mammalian genome that are expressed in stem cells in the brain. The researchers believe that drugs that target tribbles might be one route to awakening G2 quiescent stem cells. "We've found the gene that directs these cells to become quiescent. The next step is to identify potential drug-like molecules that block this gene and awaken a person's stem cells."

Link: https://www.eurekalert.org/pub_releases/2018-04/uoc-sc040518.php

Better Understanding Why the Liver is a Highly Regenerative Organ

In adult mammals, the liver is the most regenerative organ, capable of significant regrowth following injury. Why is this the case? Researchers here point to a small subset of liver cells in mice that are distinguished by telomerase expression, and while mice and humans have quite different telomerase and telomere dynamics, indirect evidence suggests that a similar population may exist in our species. Significant telomerase expression is the characteristic of stem cells that allows for unlimited replication: telomerase acts lengthen telomeres, the caps at the ends of chromosomes that shorten with each cell division. When too short, cells enter senescence or destroy themselves. Lacking telomerase, the vast majority of cells can only divide a set number of times.

This segregation between a few privileged stem cells and the vast mass of restricted somatic cells is the primary strategy by which multicellular life keeps the incidence of cancer to a manageable level. Mutations occur constantly, and evolution requires mutation, even when harmful to individuals, but it is much harder for mutational damage to cause somatic cells to run amok, given their inherent limitations. Unsurprisingly then, researchers are interested in the source of the liver's regenerative capacity not just to improve on it, or to find ways to regenerate other organs, but also to gain insight into the origins and peculiarities of liver cancer.

A subset of liver cells with high levels of telomerase renews the organ during normal cell turnover and after injury, according to researchers. The cells are distributed throughout the liver's lobes, enabling it to quickly repair itself regardless of the location of the damage. Understanding the liver's remarkable capacity for repair and regeneration is a key step in understanding what happens when the organ ceases to function properly, such as in cases of cirrhosis or liver cancer. "It's critical to understand the cellular mechanism by which the liver renews itself. We've found that rare, proliferating cells are spread throughout the organ, and that they are necessary to enable the liver to replace damaged cells. We believe that it is also likely that these cells could give rise to liver cancers when their regulation goes awry."

The liver's cells, called hepatocytes, work to filter and remove toxins from the blood. The liver is unique among organs in its ability to fully regenerate from as little as 25 percent of its original mass. Stem cells and some cancer cells make enough telomerase to keep their telomeres from shortening. Mutations that block telomerase activity cause cirrhosis in mice and humans. Conversely, mutations that kick telomerase into high gear are frequently found in liver cancers. Telomerase is a protein complex that "tops off" the ends of chromosomes after DNA replication. Without its activity, protective chromosomal caps called telomeres would gradually shorten with each cell division. Most adult cells have little to no telomerase activity, and the progressive shortening of their telomeres serves as a kind of molecular clock that limits the cells' life span.

Researchers found that, in mice, about 3-5 percent of all liver cells express unusually high levels of telomerase. The cells, which also expressed lower levels of genes involved in normal cellular metabolism, were evenly distributed throughout the liver. During regular cell turnover or after the liver was damaged, these cells proliferate in place to make clumps of new liver cells. "These rare cells can be activated to divide and form clones throughout the liver. As mature hepatocytes die off, these clones replace the liver mass. But they are working in place; they are not being recruited away to other places in the liver. This may explain how the liver can quickly repair damage regardless of where it occurs in the organ. You could imagine developing drugs that protect these telomerase-expressing cells, or ways to use cell therapy approaches to renew livers. On the cancer side, I think that these cells are very strong candidates for cell of origin. We are finally beginning to understand how this organ works."

Link: http://med.stanford.edu/news/all-news/2018/04/telomerase-expressing-liver-cells-regenerate-the-organ.html

Results from Another Trial of a Tissue Engineered Retinal Pigment Epithelium Patch

Just a few weeks ago I noted the results from an early trial of a form of retinal patch, in which the patients involved showed striking signs of improved vision, considering their age and the degree to which their macular degeneration had advanced. Today another set of clinical trial results were published by a separate group using a similar approach - human embryonic stem cells are used to derive sufficient retinal pigment epithelium cells to create a structured patch, resembling retinal tissue in at least some aspects. The patch is then implanted into the retina, and sufficient cells survive and integrate to restore some function to areas damaged by the progression of age-related macular degeneration. That two teams are seeing positive outcomes from this type of approach is good news for the broader field.

The advance over prior efforts to produce a cell therapy for macular degeneration, present in both of these trials, lies in the methodologies that allow cells to form a more life-like retinal structure prior to implantation. Cells transplanted into the retina without that support largely die before they can do much good, and this is an issue across the entire spectrum of cell therapies. Many present cell therapies are only marginally beneficial precisely because the transplanted cells last a few days or a few weeks at most. They change the balance of local signaling for a while, and this can have quite useful effects, such as the suppression of inflammation achieved via mesenchymal stem cell therapies, but this doesn't realize the potential of cell therapies to achieve regeneration and replacement of tissue.

The tissue engineering community has, over the past few years, made meaningful progress towards the delivery of structured patches rather than cells on their own. For example, heart muscle patches have recently demonstrated much higher rates of cell survival and integration. Just like the retinal patches noted here, these are cells and scaffolds that are similar to the native tissue, more resilient and more effective. We should expect to see this type of approach spread widely throughout the field, now that it has been proven effective in multiple different tissues - though it will take some time, as each tissue type requires the establishment of its own recipes and methods.

Researchers test stem cell-based retinal implant for common cause of vision loss

The treatment, which consists of a layer of human embryonic stem cell-derived retinal pigment epithelium cells on an ultrathin supportive structure, was implanted in the retina of four patients. The patients were followed for up to one year to assess its safety. There were no severe adverse events related to the implant or the surgical procedure, indicating that the treatment was well-tolerated. There was also evidence that the implant integrated with the patients' retinal tissue, which is essential for the treatment to be able to improve visual function.

"This is the first human trial of this novel stem cell-based implant, which is designed to replace a single-cell layer that degenerates in patients with dry age-related macular degeneration. This implant has the potential to stop the progression of the disease or even improve patients' vision. Proving its safety in humans is the first step in accomplishing that goal." Dry age-related macular degeneration is the most common type of age-related macular degeneration. Over time, it can lead to loss of central vision, which can diminish people's ability to perform daily tasks like reading, writing, driving and seeing faces.

As part of the study, the research team also performed a preliminary assessment of the therapy's efficacy. One patient had improvement in visual acuity, which was measured by how many letters they could read on an eye chart, and two patients had gains in visual function, which was measured by how well they could use the area of the retina treated by the implant. None of the patients showed evidence of progression in vision loss.

A bioengineered retinal pigment epithelial monolayer for advanced, dry age-related macular degeneration

Retinal pigment epithelium (RPE) dysfunction and loss are a hallmark of photoreceptors ultimately degenerate, leading to severe, progressive vision loss. Clinical and histological studies suggest that RPE replacement strategies may delay disease progression or restore vision. A prospective, interventional, U.S. Food and Drug Administration-cleared, phase 1/2a study is being conducted to assess the safety and efficacy of a composite subretinal implant in subjects with advanced NNAMD. The composite implant, termed the California Project to Cure Blindness-Retinal Pigment Epithelium 1 (CPCB-RPE1), consists of a polarized monolayer of human embryonic stem cell-derived RPE (hESC-RPE) on an ultrathin, synthetic parylene substrate designed to mimic Bruch's membrane.

We report an interim analysis of the phase 1 cohort consisting of five subjects. Four of five subjects enrolled in the study successfully received the composite implant. In all implanted subjects, optical coherence tomography imaging showed changes consistent with hESC-RPE and host photoreceptor integration. None of the implanted eyes showed progression of vision loss, one eye improved by 17 letters and two eyes demonstrated improved fixation. The concurrent structural and functional findings suggest that CPCB-RPE1 may improve visual function, at least in the short term, in some patients with severe vision loss from advanced NNAMD.

Calorie Restriction Slows the Age-Related Accumulation of DNA Damage, Inflammation, and Cellular Senescence in Fat Tissue

The practice of calorie restriction slows near all measures of aging, slowing aging to a degree that appears to scale down with increased species life span. Calorie restricted mice live 40% longer, but calorie restricted humans are thought to at most gain five years or so - though a firm number has yet to be determined in our species. The short term changes to metabolism and benefits to health are nonetheless quite similar. As a companion piece to recent work on the effects of calorie restriction on cellular senescence, this open access paper makes for interesting reading. Senescent cells accumulate with age, and the damage they do to their environment via a potent mix of signal molecules is one of the root causes of aging and age-related disease. Unsurprisingly, calorie restriction slows this accumulation, just as it impacts all other processes of aging.

White adipose tissue (WAT) forms an endocrine organ with both positive and negative effects on metabolism. By secreting adipokines, adipocytes regulate metabolism, energy intake, and fat storage. Adipocytes are known to enlarge during obesity and the ageing process. In contrast, caloric restriction results in decreased body mass, and preferentially reduced the mass of different fat depots including up to 78% in visceral fat. Several studies demonstrated that increased fat cell size is a significant predictor of altered blood lipid profiles and glucose-insulin homeostasis. The contribution of visceral adiposity to these associations seems to be of particular importance.

Senescence and inflammation are two important mechanisms contributing to ageing and the metabolic consequences of obesity. Inflammation can result from accumulation of macrophages in adipose tissue via production of cytokines such as TNFα and IL-6. Increase in lipolysis has been shown to induce macrophage migration in vitro. Macrophage numbers in adipose tissue also increase with obesity and ageing where they scavenge dead or senescent adipocytes. However, inflammatory cytokines and chemokines are also characteristics of the senescence-associated secretory phenotype (SASP) in senescent cells. We have shown previously that reactive oxygen species (ROS), DNA damage, and mitochondrial dysfunction are instrumental to maintain cellular senescence.

Various treatments have been suggested to delay senescence in adipose tissues while obesity and short telomeres exacerbated senescence. A recent study showed that feeding a high-fat diet ad libitum induced senescence in mouse visceral adipose tissue which could be ameliorated by exercise. However, dietary restriction (DR) seems to regulate many more genes than exercise in subcutaneous fat in humans.

We have demonstrated previously that short-term dietary restriction in wild type mice decreased the amount of senescent cells in various tissues. We hypothesise that pro-inflammatory cytokines and senescence are also causally related in visceral WAT, increase together during ageing, and might be rescued during DR. We used visceral WAT from mice of different ages as well as mice on late-onset, short term DR to investigate the changes in adipocyte size, accumulation of DNA damage during ageing and DR, together with the expression of pro-inflammatory cytokines TNFα, IL-6, IL-1β, and senescence markers p16 and p21. We also analysed AMPK activity which is an important signal transduction pathway implicated in the regulation of physiological processes of DR. AMPK activation is thought to be able to inhibit inflammatory responses and plays a central role in the regulation of whole body energy homeostasis and functions as a key regulator of intracellular fatty acid metabolism.

Our results demonstrate increased senescence and inflammation during ageing in mouse visceral fat while DR was able to ameliorate several of these parameters. DR was able to significantly reduce adipocyte size and multiple markers of adipocyte senescence (significant for DNA damage, p21 and IL-6 expression). This indicates that DR acts as a senolytic treatment in visceral fat, similar to its effects in other tissues. This highlights the health benefits of a decreased nutritional intake over a relatively short period of time at middle age.

Link: https://doi.org/10.1007/s12603-017-0968-2

A Marker for Cancer Stem Cells that Might Also Lead to a Cell-Killing Treatment

At least some forms of cancers are generated and supported by a small population of cancer stem cells, a malfunctioning, rapidly growing mirror of the healthy tissue environment in which large number of somatic cells are supported by a small number of stem cells. It is the presence of these cancer stem cells that makes it challenging to permanently clear cancer from a patient - if only a few such cells survive, the cancer will return, and the present generation of cancer treatments cannot reliably remove 100% of the targeted cells. Looking on the bright side, if a method of selectively targeting and destroying cancer stem cells could be developed, then this could be a very useful approach to cancer therapeutics. While it is still up for debate as to what degree of useful, exploitable similarity exists between the cancer stem cells that have been identified in cancers of various different types, the research here makes for interesting reading in this context. It strongly suggests that these similarities exist and are broadly present in many tissue types.

"Cancer stem cells", also known as tumor-initiating cells (TIC), appear to cause relapses after radiation and chemotherapy because a single surviving TIC can cause a new tumor to grow. In addition, they appear to be the main cause of metastasis. Effective tumor treatment must therefore aim to kill off TICs as extensively as possible. To this end, a "probe" that marks these cancer stem cells would be useful so that they become visible. Although there are markers that also recognize TICs associated with some types of cancer, no universal, selective probe for cancer stem cells has been found.

Researchers have now succeeded in finding such a probe. They were able to show that their new probe, a fluorescent dye, selectively stains TICs from a broad variety of cancers, including tumors of the lung, central nervous system, breast, kidney, ovary, colon, and prostate, as well as melanomas. Healthy cells and "ordinary" tumor cells were not marked. At high concentrations, the dye also demonstrates considerable cytotoxicity toward TIC, while other cells are barely affected.

The researchers discovered that their probe, named TiY (for tumor-initiating cell probe yellow), recognizes vimentin, which is a molecule in the cytoskeleton. Vimentin is more concentrated in epithelial cells when they transform into mesenchymal cells. Epithelial cells form the tissue that covers the inner and outer surfaces of the body, forming a boundary with the environment. The cells are polar, meaning that the side facing toward the underlying tissue and the side directed outward toward the lumen are different. The cells are also firmly integrated into the cell wall. When they transform into mesenchymal cells, they lose their polarity, are freed from the cell structure, and may wander. This process plays an important role in the development of embryos and healing of wounds. It is also involved in the metastasis of tumors.

Link: https://www.eurekalert.org/pub_releases/2018-04/w-mfc040418.php

A Lengthy Discussion of Oxidative Stress in the Progression of Alzheimer's Disease

Alzheimer's disease is very complex and incompletely understood because the brain is very complex and incompletely understood. Efforts to make progress towards therapies for Alzheimer's disease have progressed in parallel with, and often driven and funded, efforts to map the works of the brain at the detail level of cellular biochemistry. Even though Alzheimer's will turn out to have easily stated causes, a set of comparatively simple biochemical processes, even simple origins expand - over time and through chains of cause and effect - to produce end state conditions that are as complex as their environment.

Researchers tend to specialize. There is too much biochemistry to hold it all in one mind, even for a single medical condition. So the research community tends to act in practice much like the blind men and the elephant, everyone focused on their particular facet of the larger condition. Focus is necessary to make progress on understanding that facet, but at the end of the day someone needs to occasionally review all of the facets together to see if the picture still makes sense. Synthesis is an increasingly important function in modern life science research, becoming ever more challenging as the facets grow in size, but sadly undervalued. Alzheimer's research and development still awaits a definitive synthesis, the theory and proof that will show us which of the facets of the condition are important, which are primary and which are secondary.

The open access paper here discusses the oxidative stress view of Alzheimer's disease, a basis for considering progression of the condition that doesn't get as much attention as work on aggregates of amyloid-β and tau. Oxidative stress refers to the rising level of oxidative molecules and signs of the damage they do to molecular machinery inside and outside cells. Oxidation is a fact of life in cells, a necessary part of the way in which biology works: damage happens constantly, and is repaired constantly. Ever more oxidative damage and oxidative molecules are present in the body and brain with the progression of aging, alongside a growth in chronic inflammation - oxidative stress and inflammation are usually found together, linked by a number of mechanisms. Alzheimer's and most other neurodegenerative conditions appear to have a strong inflammatory component, and thus there is oxidative stress to observe as well.

A Long Journey into Aging, Brain Aging, and Alzheimer's Disease Following the Oxidative Stress Tracks

Nowadays, Alzheimer's disease (AD) is the most diagnosed type of dementia. For a long time, amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs) have been considered unquestionably the main cause of AD pathogenesis, but many other theories have been proposed, including oxidative stress and neuroinflammation, to explain a still unknown disease.

For many years, the amyloid cascade hypothesis has dominated AD thinking, modeling, and therapeutic approach. Amyloid proteins are beta-sheet proteins that can easily aggregate. Aβ is a proteolytic degradation product of a larger molecule called amyloid-β protein precursor (AβPP). The amyloid cascade hypothesis postulates an overproduction of Aβ, which leads to neuronal dysfunction and apoptosis causing AD clinical manifestations. According to this hypothesis, amyloid accumulation represents the "upstream" event in AD pathogenesis. This point of view has been overcome by the possibility that soluble Aβ oligomers, more than mature amyloid plaques, are the key toxic moieties. In fact, it has been demonstrated that amyloid oligomers may access intracellular organelles, including mitochondria, and compromise their function. Amyloid deposition causes local inflammatory and immunologic alterations for a direct neurotoxicity with microglial recruitment and astrocyte activation. It is also associated with the release of cytokines, nitric oxide, and other radical species that can promote neuroinflammation and neurodegeneration.

In addition to the amyloid cascade, intracellular neurofibrillary tangles (NFTs) are found in AD brain. They consist of hyperphosphorylated tau protein. Interestingly, NFTs correlate more closely with the severity of dementia than plaque counts. The association of tangles with a variety of brain damage supports the "tauopathy" concept of neurodegeneration, although tauopathy as a primary cause of neurodegenerative diseases is currently demonstrable only in a subgroup of familial frontotemporal dementia. However, the recent failures of drugs targeting amyloid pathways have raised questions not only about this approach but also on the validity of the amyloid cascade hypothesis itself.

Oxidative stress is a condition where reactive oxygen species (ROS) production exceeds the cellular antioxidant defense system. The brain is highly susceptible to an oxidative imbalance due to its high-energy demand, high oxygen consumption, an abundance of easily peroxidable polyunsaturated fatty acids, high level of potent ROS catalyst iron, and a relative paucity of antioxidant enzymes, this latter more evident in AD brain. Mitochondria are prone to oxidative damage. Mitochondrial DNA (mtDNA) is particularly susceptible to oxidative damage. The simultaneous increased oxidation of mtDNA and deficiency of DNA repair could enhance the lesion to mitochondrial genome, potentially causing neuronal damages. On this basis, it is reasonable that oxidatively mediated damage to biomolecules is extensively reported in AD, suggesting that oxidative stress plays a critical role in the disease pathogenesis. As the main source of ROS generation and a major target of oxidative damage, progressive impairment of mitochondria has been implicated in aging and AD.

It is generally accepted that mitochondrial function progressively declines along with age when compensation is no longer possible. In summary, the mitochondrial cascade hypothesis proposes that every single person has a genetically determined mitochondrial starting line, that together with environmental factors determine the age at which clinical disease may ensue. Thus, the "mitochondrial cascade hypothesis" places the mitochondrial dysfunction as the leading factor in the late-onset AD pathology cascade, underlying the individual genetic background able to regulate since birth its mitochondrial function and sustainability. For this reason, the rate at which age-related mitochondrial dysfunction proceeds differs among individuals. When the mitochondrial function declines and falls below a critical threshold, AD-typical dysfunction at the cellular level may ensue, including Aβ production, tau phosphorylation, synaptic degeneration, and oxidative stress.

Greater Aerobic Fitness Correlates with Better Memory Function in Later Life

This interesting open access paper reports on one of a number of efforts to map the details of the association between cardiovascular fitness and memory function over the course of aging. The brain is that the mercy of the vascular system in many ways. There is the age-related reduction in capillary formation cutting down the supply of nutrients and oxygen to the brain. Stiffening of blood vessels results in hypertension, and raised blood pressure pummels delicate tissue structures in the brain, kidney, and elsewhere. The structural decline of the vascular system, the weakening of blood vessels due to atherosclerotic lesions, combines with raised blood pressure to produce many ruptures of lesser blood vessels in the brain over the years, destroying small areas of functional tissue in silent, tiny strokes.

All of these processes are to some degree slowed by maintaining cardiovascular fitness - even capillary formation. Physical activity also adjusts many signaling processes related to tissue maintenance, such as the pace of neurogenesis in the brain, the production and integration of new neurons. To look at it the other way, in our modern age of comfort and indolence, most people fail to put in the necessary maintenance activity required to keep the declines of aging to the slowest possible rate. No-one can reliably add decades to life through exercise, but it is certainly possible to find oneself in one's sixties, unfit, overweight, encountering the first earnestly troubling signs of mental decline, and all the while regretting the path not taken.

Aging is associated with progressive changes in brain structure that gradually impair essential cognitive functions, including memory. Numerous mechanisms have been proposed to underlie memory decline, such as altered plasticity, connectivity, and excitability. One change of particular interest is the reduction of hippocampal neurogenesis and the observation that age-associated declines in neurogenesis and memory can be partly rescued in animals that engage in aerobic exercise. Aerobic exercise also increases hippocampal blood volume in humans. Critically, this suggests that physical activity in older humans may be associated with better memory performance. However, some aspects of memory processing may be more associated with aerobic fitness than others. The present study compared age-related differences for two critical memory processes: high-interference memory and general recognition memory.

High-interference memory represents the ability to discriminate between highly similar yet distinct items. In animal models, high-interference memory can be improved by stimulating neurogenesis and is impeded by interfering with neurogenesis. Younger adults (YA) have better high-interference memory than older adults (OA), therefore, the decline in hippocampal neurogenesis that occurs with aging may impact high-interference memory. General recognition is another aspect of memory that represents the ability to discriminate novel stimuli from those previously encountered. Unlike high-interference memory, general recognition memory may not be as dependent on hippocampal neurogenesis. The recruitment of a more distributed network for processing by general recognition may mean that this aspect of memory is less affected by the age-related decline. Indeed, YA and OA have been shown to have similar performance on general recognition memory tasks.

Individual differences influencing age-related decline of memory extend beyond biological aging to include lifestyle factors, such as physical activity. The present study investigated the effects of aging on high-interference memory and general recognition memory. Ninety-five YA and eighty-one OA performed the Mnemonic Similarity Task (MST). Age-related differences in high-interference memory were observed across the lifespan, with performance progressively worsening from young to old. In contrast, age-related differences in general recognition memory were not observed until after 60 years of age. Furthermore, OA with higher aerobic fitness had better high-interference memory, suggesting that exercise may be an important lifestyle factor influencing this aspect of memory. Overall, these findings suggest different trajectories of decline for high-interference and general recognition memory, with a selective role for physical activity in promoting high-interference memory.

Link: https://doi.org/10.3389/fnagi.2018.00063

No Sign of Benefits in a Study of Higher Protein Intake in Older Individuals

One of the many theories regarding the cause of sarcopenia, age-related loss of muscle mass and strength, is that impaired processing of the essential amino acid leucine is a significant cause. If this is the case, then leucine supplementation should help to some degree. Similar suggestions have been made for a few other aspects of aging - that we should assign a modest fraction of the blame to the typically lower protein intake observed in older people, as tissues find themselves lacking sufficient raw materials needed to maintain themselves. The study here suggests that this is not the case, or at least that the contribution of reduced protein intake is small in comparison to the other mechanisms of degenerative aging.

Regardless of whether an adult is young or old, male or female, their recommended dietary allowance (RDA) for protein is the same: 0.8g/kg/day. Many experts and national organizations recommend dietary protein intakes greater than the recommended allowance to maintain and promote muscle growth in older adults. However, few rigorous studies have evaluated whether higher protein intake among older adults provides meaningful benefit.

"It's amazing how little evidence there is around how much protein we need in our diet, especially the value of high-protein intake. Despite a lack of evidence, experts continue to recommend high-protein intake for older men. We wanted to test this rigorously and determine whether protein intake greater than the recommended dietary allowance is beneficial in increasing muscle mass, strength, and wellbeing."

The clinical trial, known as the Optimizing Protein Intake in Older Men (OPTIMen) Trial, was a randomized, placebo-controlled, double-blind, parallel group trial in which men aged 65 or older were randomized to receive a diet containing 0.8-g/kg/day protein and a placebo injection; 1.3-g/kg/day protein and a placebo injection; 0.8-g/kg/day protein and a weekly injection of testosterone; or 1.3-g/kg/day protein and a weekly injection of testosterone. All participants were given prepackaged meals with individualized protein and energy contents and supplements. Seventy-eight participants completed the six-month trial.

The team found that protein intake greater than the RDA had no significant effect on lean body mass, fat mass, muscle performance, physical function, fatigue or other well-being measures. "Our data highlight the need for re-evaluation of the protein recommended daily allowance in older adults, especially those with frailty and chronic disease."

Link: https://www.eurekalert.org/pub_releases/2018-04/bawh-emp040218.php

Methionine Restriction Should Slightly Slow Aging in Humans

The beneficial effects of calorie restriction on health and longevity are well researched in mammals, but while a sizable fraction of those benefits are thought to be mediated via sensing of amounts of specific proteins such as methionine and cysteine, there is comparatively little investigation of protein restriction strategies - usually meaning a reduced dietary intake of one or more proteins, while overall calorie intake remains at the same level. Work in this part of the field is taking place, and shows extension of life span to some degree in rodent studies, but it has a long way to go to catch up to the breadth of research into calorie restriction.

Calorie restriction is, of course, not yet decisively proven to slow aging extend life in humans, through the existing data makes a strong argument for this to be the case. It isn't expected to have much more than a five year effect on human life span, however. While the short term benefits of calorie restriction are similar in different mammalian species, the measured effects on longevity scale down with species life span. The reasons for this to be the case remain to be determined.

While specific aspects of the biochemistry of the calorie restriction response are quite well investigated, such as its effects on autophagy, there is enormous complexity in the way in which all of the changes fit together with the details of metabolism to determine the pace of aging. Meaningful progress towards a full map of the biochemistry and progression of aging still lies ahead - and will likely still be an ongoing project well after rejuvenation therapies based on the SENS model of damage repair are a going concern.

In this open access review, the authors argue that there is enough evidence at the present time to expect protein restriction strategies such as methionine restriction to produce benefits in our species. We should be looking at protein restriction in much the same way as we look at exercise and calorie restriction: a reliable, demonstrated way to slightly slow the aging process and obtain benefits to long term health, a method just one step short of the final decisive proof and calibration of the size of the effect.

Sulfur amino acid restriction could amount to new dietary approach to health

Amino acids are the building blocks of all proteins in the body. A subcategory called sulfur amino acids includes methionine (Met) and cysteine (Cys), which not only make up proteins but also play many roles in metabolism and health. Researchers have been interested in dietary sulfur amino acid restriction since the 1990s, when studies began to show health benefits in animals fed Met-restricted diets. In one early study involving rats, 80 percent Met restriction increased average and maximum lifespans by between 42 and 44 percent.

Scientists have long known that animals on calorie-restricted diets live longer and healthier, but they've been searching for ways bring about the improvements without asking people to eat less. In new review of studies, sulfur amino acid restriction consistently demonstrated a range of beneficial effects including enhanced lifespan - without calorie restriction. The analysis found that Met restriction has been associated with delayed aging and longer lifespans in human cells, yeast, and animals including fruit flies and rodents. Animals fed sulfur amino acid-restricted diets also had health improvements including reductions in body weight, fat and oxidative stress; fewer cancerous tumors; enhanced insulin sensitivity; and more efficient fuel-burning.

"This review describes a number of studies which provide some hints that sulfur amino acid restriction might achieve some of the benefits observed in animal models, including cancer inhibition and reducing risks for cardiovascular disease." Researchers are now overseeing the first tightly controlled feeding study of dietary sulfur amino acid restriction in human subjects, which may provide more direct evidence of health benefits.

Disease prevention and delayed aging by dietary sulfur amino acid restriction: translational implications

Sulfur amino acids (SAAs) play numerous critical roles in metabolism and overall health maintenance. Preclinical studies have demonstrated that SAA-restricted diets have many beneficial effects, including extending life span and preventing the development of a variety of diseases. Dietary sulfur amino acid restriction (SAAR) is characterized by chronic restrictions of methionine and cysteine but not calories and is associated with reductions in body weight, adiposity, and oxidative stress, and metabolic changes in adipose tissue and liver resulting in enhanced insulin sensitivity and energy expenditure. SAAR-induced changes in blood biomarkers include reductions in insulin, insulin-like growth factor-1, glucose, and leptin and increases in adiponectin and fibroblast growth factor 21.

On the basis of these preclinical data, SAAR may also have similar benefits in humans. While little is known of the translational significance of SAAR, its potential feasibility in humans is supported by findings of its effectiveness in rodents, even when initiated in adult animals. To date, there have been no controlled feeding studies of SAAR in humans; however, there have been numerous relevant epidemiologic and disease-based clinical investigations reported. Here, we summarize observations from these clinical investigations to provide insight into the potential effectiveness of SAAR for humans.

A Correlation Between More AGEs in the Skin and Worse Pulmonary Function

The researchers here show an association between greater presence of advanced glycation end-products (AGEs) in skin and worse pulmonary function - which sounds plausible if we think of AGEs as a cause of loss of elasticity in tissues. Cross-links are formed by AGEs, and by linking and restricting the dynamics of structural proteins, they degrade the important structural properties of tissues, particularly elasticity. The details always bear examining however. In this study, the level of AGEs in skin was assessed using fluorescence, and based on the research of recent years, the important AGE when it comes to aging, glucosepane, is not fluorescent. Glucosepane forms truly persistent cross-links that human biochemistry struggles to remove, while other AGEs are transient in their effects, and more amenable to removal.

In people who do not have an abnormal metabolism characterized by raised levels of various AGEs, as is observed in diabetic patients, it is entirely plausible that glucosepane levels are fairly well correlated to levels of other, fluorescent AGEs. But it still makes this paper one that is most likely observing a relationship based on inflammation rather than structural properties: short-lived (and fluorescent) AGEs can induce inflammation via their interaction with RAGE, and this is one of the ways in which the abnormal diabetic biochemistry causes further harm, for example. There is a fair amount of evidence to suggest that chronic inflammation negatively affects pulmonary function. Now that it is possible to reduce inflammation by removing senescent cells, there is even data in mice to show that this reverses loss of lung tissue elasticity to some degree. Every decline in aging has multiple contributing factors.

According to recent studies, the level of advanced glycation end products (AGEs) increases with age and is higher in smokers and chronic obstructive pulmonary disease (COPD) patients. AGEs are bioactive molecules formed by the nonenzymatic glycation or peroxidation of proteins, lipids, and nucleic acids. AGEs increase inflammation by binding to receptors for AGE (RAGE), which are present on cell surfaces in tissues. Therefore, AGE accumulation may play a role in the pathogenesis of COPD by increasing inflammation. Several AGEs, such as pentosidine and Nε-(Carboxymethyl)-L-lysine (CML), have been reported to emit a characteristic fluorescence in human skin. AGEs assessed by skin autofluorescence (SAF) could help in the rapid evaluation of AGE accumulation in clinical settings.

Investigating factors associated with deteriorations in pulmonary function could help develop strategies to prevent the development of COPD in people with normal spirometry results, particularly given the serious impact of COPD on the risk of chronic disabilities and mortality. Therefore, we focused on the relationship between AGEs and pulmonary function in a general population with normal spirometry results. Moreover, given that aging is accompanied by an increase in AGEs and a decrease in pulmonary function, it would be informative to compare relationships between AGEs and pulmonary function in younger and elderly individuals. To this end, the present study aimed to evaluate the relationship between SAF and pulmonary function in younger and elderly people with normal spirometry results.

Two hundred and seventy-two males and females were enrolled in this study. Subjects underwent hematological examinations and additional assessments, such as the accumulation of AGEs in skin and pulmonary function. Subjects with an obstructive, restrictive, or mixed disorder pattern on the pulmonary function test were excluded. In addition, subjects with diseases that could influence pulmonary function (e.g., COPD, interstitial pneumonia, or asthma) or who received medications that could influence pulmonary function were excluded. Those with diabetes or hemoglobin A1c (HbA1c) higher than 6.5% were also excluded since diabetes and glycemic levels are known to be associated with both pulmonary function and level of SAF. The final study population consisted of 201 subjects (116 males).

We found that SAF is an independent factor negatively associated with the FEV1/FVC measure of pulmonary in elderly people with normal spirometry results, but not in younger people. Pack-years of smoking was a significant independent factor associated with FEV1/FVC in the elderly group. This study demonstrated that SAF is an independent factor associated with FEV1/FVC in the elderly group. According to other studies, AGEs in the blood and AGE accumulation in skin were higher in smokers than in non-smokers. AGEs can bind to and activate RAGE, which are present on cell surfaces in tissues, especially in the lung. Activation of RAGE increases inflammation via NF-κB. Therefore, the decrease in FEV1/FVC was likely accelerated by AGE accumulation.

With respect to the younger group, SAF was not associated with decreased FEV1/FVC. There are several potential explanations for the differences observed between the younger and elderly groups regarding factors associated with FEV1/FVC. First, the value of SAF is strongly related to age. In the present study, the value of SAF was significantly lower in the younger group compared to the elderly group. Therefore, inflammation resulting from AGEs might have been lower in younger subjects, resulting in the maintenance of FEV1/FVC. Second, the amount and/or activity of endogenous antioxidant enzymes between the two groups may have differed. It is well known that reactive oxygen species (ROS) can be buffered by endogenous antioxidant enzymes such as superoxide dismutase and catalase, and previous studies have demonstrated that levels of these antioxidant enzymes decrease with age.

Link: https://doi.org/10.1589/jpts.30.413

A Demonstration that Smooth Muscle Cell Dysfunction Contributes Significantly to Age-Related Vascular Stiffening

A few different mechanisms plausibly contribute to the stiffening of blood vessels that takes place with aging. This is one of the most harmful aspects of aging, as it causes hypertension by upsetting the feedback mechanisms that control blood pressure. Hypertension in turn damages organ tissues, weakens the heart, and raises the risk of fatal rupture of a weakened blood vessel. The mechanisms of interest include (a) calcification, which may be secondary to inflammation and cellular senescence, (b) the formation of persistent cross-links in the extracellular matrix, degrading structural properties such as elasticity, and (c) dysfunction in the smooth muscle responsible for contraction and dilation of blood vessels.

We can hope that calcification will be improved by senolytic therapies to clear senescent cells, and that near future cross-link breakers based on programs funded by the SENS Research Foundation will make short work of that contribution of cross-links to degenerative aging. Dysfunctional smooth muscle cells are more of a problem, however, as it is far from clear as to what exactly is going wrong and how it might be effectively addressed. In this paper, the researchers mount what I think is a fairly convincing demonstration that this cellular dysfunction is significant and distinct from other factors related to vascular stiffening, and is inherent to the cells rather than being caused directly by the environment of the surrounding aged tissue. This calls for more attention to be directed towards this part of the problem.

Increased aortic stiffness, whatever the underlying cause, is also an independent predictor of outcomes of cardiovascular diseases in the elderly. It is well known that hypertension is a highly age-related human disease. Despite a widely held belief that increased aortic stiffness in hypertensive patients is largely a manifestation of long-standing hypertension-related damage, a recent statement from the American Heart Association (AHA) asserts that aortic stiffening is a cause rather than a consequence of hypertension in middle-aged and older individuals.

Our recent studies with atomic force microscopy (AFM) have demonstrated similar characteristics of aortic vascular smooth muscle cells (VSMCs) in both aging and hypertension, indicating that VSMC-mediated regulation is a fundamental basis of aortic stiffening in both conditions. However, the underlying mechanisms are not fully understood. It is conceivable that, in addition to intracellular effects, VSMCs are able to contribute to aortic stiffening via extracellular effects. However, it is difficult to discern the extracellular effects of VSMCs in intact aortic tissue in vivo.

In our previous study, integrin β1 was found to be significantly increased in VSMCs from stiffened aortas in aging monkeys, indicating that integrin β1 may contribute to aortic stiffening. Other recent studies emphasize the potential role of Lysyl oxidase (LOX) in vascular remodeling and the regulation of the biomechanical properties of the extracellular matrix (ECM). Different patterns of LOX expression/activity have been associated with distinct vascular pathological processes. For example, downregulation of LOX has been associated with destructive remodeling of arteries during aorta aneurysm (AA) development. Deletion of the mouse LOX gene promotes fragmentation of elastic fibers and VSMC discontinuity in the aortic wall. Loss-of-function mutations of LOX can cause AAs and aortic stiffening in humans. These studies indicate an essential role of LOX in maintaining the tensile and elastic features of blood vessels.

The present study tests our hypothesis that aortic VSMCs contribute to aortic wall stiffness via both increased intrinsic stiffness and extracellular dysregulation mediated through altered regulation of integrin and LOX signaling. Firstly, aortic stiffening was confirmed in spontaneously hypertensive rats (SHRs) versus Wistar-Kyoto (WKY) rats. Vascular smooth muscle cells were isolated from thoracic aorta and embedded into an in vitro 3D model to form reconstituted vessels. Reconstituted vessel segments made with SHR VSMCs were significantly stiffer than vessels made with WKY VSMCs. SHR VSMCs in the reconstituted vessels exhibited different morphologies and diminished adaptability to stretch compared to WKY VSMCs, implying dual effects on both static and dynamic stiffness. Mechanistically, compared to WKY VSMCs, SHR VSMCs exhibited an increase in the levels of active integrin β1- and bone morphogenetic protein 1 (BMP1)-mediated proteolytic cleavage of lysyl oxidase (LOX).

Link: https://doi.org/10.1111/acel.12748

Exosome Signaling Appears to Mediate Age-Related Changes in Bone Tissue Maintenance Leading to Osteoporosis

Bone might be more solid than other tissues, but it is just as dynamic: maintenance of bone is a constant, balanced process of creation by osteoblast cells and destruction by osteoclast cells. With age, this balance breaks down, however. Osteoblasts accomplish proportionally less work, and osteoclasts accomplish more. As a result, bone becomes weakened, porous, and fragile, leading to the clinical condition of osteoporosis. This is a significant component of frailty and mortality, as fractures and breaks of bone in elderly individuals can happen with little provocation, and when they do, that trauma often marks the beginning of the final spiral downwards.

In seeking to understand osteoporosis, researchers are largely working backwards from the disease state, looking for mechanisms that change the balance of osteoblast and osteoclast cell populations and activity. There are a sizable number of plausible candidates. Chronic inflammation, for example, is thought to be a part of the problem, and it certainly disrupts many other important systems of cellular coordination related to regeneration and tissue maintenance. Senescent cells are a significant source of inflammation in older individuals, and researchers have demonstrated that removing them can partially reverse osteoporosis in mice.

Without a deep examination of the causes, researchers are also mapping changes in the signaling mechanisms by which cells communicate. These communications steer cellular behavior, so in at least some cases it is though that benefits might be obtained by interfering in the signaling responses to the underlying damage of aging, rather than by fixing the damage itself. Much of this signaling is not in the form of molecules secreted unprotected into the intercellular spaces, but rather via vesicles of various types. These are membrane-wrapped packages of molecules, much smaller than cells, and classified by size into classes such as exosomes, microvesicles, and so forth. Research into vesicles is currently blossoming, with scientists hoping to be able to use them to beneficially influence cell behavior in any number of ways. First, however, a certain amount of mapping and experimentation must take place, as is illustrated in this open access paper.

It is worth considering, however, that is probably better to repair the underlying damage that causes signaling changes. That damage causes all sorts of issues, not just the ones that a research team is presently narrowly focused on. It isn't cost-effective, and may not even be possible to intercept and prevent every downstream change without actually repairing the root cause. Here it is hard to even make the argument that all of the important root causes are mysterious and unassailable at this time, given that cellular senescence appears to be significant, and dealing with that via senolytic therapies is almost certainly cheaper right now than working with exosomes.

Involvement of serum-derived exosomes of elderly patients with bone loss in failure of bone remodeling via alteration of exosomal bone-related proteins

Normal bone remodeling is activated by osteoclasts that are unique in their function of bone resorption, followed by a constructive process in which new bone is generated by osteoblasts. The coordinated regulation of these important cell types is critical for maintaining physiological bone remodeling, which is tightly controlled by physical cell-cell interactions, secretory signals, and the endocrine system. Osteoclast activation occurs after binding of receptor activator of nuclear factor κB (RANKL) to its receptor RANK, which is expressed in the membrane of osteoclast precursors.

Recent studies have revealed that various key factors involved in bone remodeling are packaged in spherical bilayered membrane vesicles called exosomes. These organelles function as cell-cell communicators by transferring biologically active molecules to adjacent or distant cell. Various cell types secrete exosomes. With an average diameter of 40-150 nm, exosomes are released into the circulation and transfer the biologically active molecules contained within to target cells.

Recent reports indicate the involvement of bone-associated exosomes in regulating bone remodeling, mainly via the transfer of critical molecules required for the regulation of osteoclasts and osteoblasts. However, the comprehensive changes among the proteins in serum-derived exosomes (SDEs) of aged patients with osteoporosis or osteopenia and their functions in bone remodeling remain largely unclear. Here, to determine the biological functions of SDEs in osteoporosis and osteopenia, we compared the proteomic profiles of exosomes purified from the serum of elderly patients with osteoporosis and low bone mass with those of aged and young normal volunteers.

In the present study, we discovered that the SDEs from osteoporosis patients inhibited osteoblastic bone matrix mineralization and promoted osteoclast differentiation. In contrast, SDEs from osteopenia patients enhanced both osteoblast function and osteoclast activation, leading to a compensatory increase in bone remodeling. The SDEs from aged normal volunteers might play a protective role in bone health through facilitating adhesion of bone cells and suppressing aging-associated oxidative stress. The differently expressed proteins identified were involved in different processes and functions intrinsic to bone, including mechanosensation, inflammation, and cell senescence, which are the apparent protagonists in bone remodeling.

Long Lived Species May Require Greater Accuracy in Protein Translation

This commentary on research results from last year is a good introduction to the topic of protein translation errors and their relationship with species longevity. Translation is one of the steps in the complex process of gene expression, in which genes are used as a blueprint to assemble proteins. Nothing is perfect and errors take place in translation, as everywhere else. Such errors are in effect a form of damage, causing issues for the cell until the broken protein is removed.

It is fairly well established that greater levels of the cellular maintenance processes of autophagy, responsible for removing damaged proteins, metabolic waste, and failing cellular structures, can result in slowed aging in a range of species. It sounds plausible that reducing the rate at which malformed proteins are produced would be beneficial for similar reasons, but this is harder to prove one way or another. The present laboratory is made up of the biochemistry of similar species with different life spans, translation machinery, and error rates. Unfortunately there are also many other differences: the study of aging is made very challenging by the inability to completely isolate mechanisms of interest, and dial them up or down without changing anything else.

When a protein is made by the cell, the genetic information is first decoded into mRNA, then this mRNA directs the protein synthesis. This is the flow of genetic information in cells from DNA to RNA to protein, the central dogma of molecular biology. The "error catastrophe" theory of aging, proposed in the 1960s, posits that translation errors decrease the fidelity of translation, setting in motion a vicious cycle of increasingly inaccurate protein synthesis, ultimately causing a failure of the gene expression machinery. However, in the 1980s, several approaches including enzymatic assays of protein synthesis errors, as well as analysis of proteins on 2D gels in aged animals and senescent cells, did not detect a significant increase in mistranslated proteins during aging and cellular senescence. These negative results were not consistent with the error catastrophe theory and errors in translation were largely discounted as being a contributing factor to aging.

Recent work brings the protein translation fidelity back into the spotlight of aging research. Importantly, the assays used to detect aberrant proteins in the 1980s had limited sensitivity to detect rare aberrant proteins, but in 2013 a new highly sensitive luciferase-based assay was developed to measure the rate of mistranslation in mammalian cells. This new assay showed that mouse fibroblasts make up to 10 times more errors in protein translation than fibroblast from the longest-lived rodent species, the naked mole rat. This was the first indication that a longer-lived species may evolve more accurate protein translation machinery. Later work compared the fidelity of protein translation in fibroblasts from 17 rodent species with diverse lifespans, and demonstrated that translation fidelity at the first and second codon positions correlates positively with species maximum lifespan, i.e. longer-lived species have more accurate translation.

The relationship between species maximum lifespan and translation fidelity shows that longer-lived species evolve more accurate protein synthesis. This, however, does not imply that protein translation errors lead to aging in individual organisms. This would be important to test using the new sensitive assays. In the future, a knock-in mouse model with luciferase reporters can be generated to examine the accumulation of mistranslated protein in different organs during aging. Mistranslated proteins may not impact cellular proteostasis significantly at young age, largely due to rapid protein turnover and efficient protein clearance. However, protein turnover rates, proteasome activity, and autophagy decline with age, making aged organisms more sensitive to errors in protein translation. Thus, even if protein translation fidelity does not change over the course of lifespan, long-lived species may require more accurate protein synthesis.

Link: https://doi.org/10.18632/aging.101398

Finding a Causal Relationship Between Exercise and Longevity in Human Data is More Challenging than One Might Imagine

It is straightforward enough to prove that exercise extends healthy (but not average or overall) life span in studies of mice. It is far less straightforward to demonstrate that same proof in human epidemiological data. We can't put humans into carefully controlled groups stratified by life-long differences in exercise and follow them from birth to death, as is the case for mice. As a consequence, near all studies of physical activity and longevity produce only correlations, as there is no practical way to derive causation given the data to hand. It is felt that these correlations likely reflect causation because of the extensive animal studies and the essential similarities of biochemistry between the mammalian species involved, but that isn't the same thing as a rigorous determination. The editorial here is a discussion of this point; the authors look at the limitations and challenges that face any attempt to generate better evidence in support of the generally accepted proposition that exercise causes extended healthy life span in humans.

While epidemiological findings show that increased physical activity (PA) lengthens the life span, it has been argued that intervention studies do not support PA causing a reduced risk of death, and that limitations in previous observational studies may have led to spurious conclusions. This coincides with the publication of findings from the large-scale Prospective Urban Rural Epidemiologic (PURE) study of 130,843 participants, which identified a graded lower rate of mortality among those individuals achieving moderate and high levels of PA compared with those with low PA. While this study is undeniably an impressive endeavour, collecting prospective data on participants from 17 countries, the findings are, as so often, unable to fully assert a causal (rather than correlational) role for PA levels in reducing mortality.

Epidemiological study designs are vulnerable to limitations that may skew or distort observational associations and impede the distinction between correlation and causation. Such distortions of observed relationships may arise due to confounding by measured/unmeasured lifestyle, behavioural, and biological factors (such as higher fitness, lower body mass index (BMI), genetic variation, and socioeconomic factors) correlated with both PA and longevity. If not appropriately accounted for, confounding factors make the ascertainment of underlying causal mechanisms and pathways exceptionally complex. Such was illustrated by the noted London busmen study, where confounding by baseline adiposity biased findings that bus conductors had lower risk of coronary heart disease than their less-active driver counterparts.

The possibility of reverse causation may also lead to misinterpretation of observed associations. For example, the notion that reducing PA increases the risk of becoming overweight/obese is as plausible as the reverse, where being overweight/obese renders PA difficult. Studies of older adults or those with many comorbidities are particularly vulnerable to reverse causation. For example, aged individuals who are healthy enough to participate in PA due to a lack of chronic illness will seemingly have a reduced risk of death compared with their less-fit peers. Furthermore, comparing estimates of risk for physically demanding versus sedentary occupations may suffer reverse causation, particularly when high fitness and good health are criteria for recruitment into such physically demanding occupations.

Related to this, in the setting of evaluating potential causes of mortality, both selection and survival biases, which influence participation rates in epidemiological studies, can also lead to distortion of associations among respondents. In these cases, the population under study (and therefore the observed associations) may differ from the population not selected or who were unable/unwilling to participate (due to morbidity or lack of interest in surveys relating to health).

Link: http://dx.doi.org/10.1136/bjsports-2017-098995