Fight Aging! provides a weekly digest of news and commentary for thousands of subscribers interested in the latest longevity science: progress towards the medical control of aging in order to prevent age-related frailty, suffering, and disease, as well as improvements in the present understanding of what works and what doesn't work when it comes to extending healthy life. Expect to see summaries of recent advances in medical research, news from the scientific community, advocacy and fundraising initiatives to help speed work on the repair and reversal of aging, links to online resources, and much more.
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- New Data on Progerin and Cellular Senescence in Normal Aging
- Envisaging For-Profit Alternatives to Fight Aging! and Similar Initiatives
- A Surprisingly Large Change in Metabolism in Mice Lacking a Sense of Smell
- Detailed Investigations of Autophagy to Better Understand why it Declines with Age
- Initial Coin Offerings as a Fundraising Strategy
- An Interview with Eric Verdin of the Buck Institute for Research on Aging
- Death is not what Gives Life Meaning
- Engineering New Bile Ducts to Treat Failing Liver Function
- Overexpression of the DNA Repair Gene PRP19 is Shown to Modestly Extend Life in Female Flies
- A Popular Science Overview of Recent Calorie Restriction Research
- Supporting Evidence for the Importance of Mitochondrial DNA Deletions in Aging
- Progress in Engineering Digestive System Tissue Structures
- Can Existing Mechanisms be Enhanced to Clear Age-Related Protein Aggregates?
- Progress in the Creation of a Neoantigen Cancer Vaccine
- Recent Research into the Effects of Increased FGF21 Levels
New Data on Progerin and Cellular Senescence in Normal Aging
One of the interesting items that has emerged from the discovery of the cause of progeria, a condition that strongly resembles accelerated aging, is that this single molecular cause is also present to a much smaller degree in normally old individuals. Progeria is caused by a mutation in the lamin A (LMNA) gene, important in the establishment of cell structure, and therefore also important to the correct function of just about every vital cellular process. The condition is very rare because this mutation must randomly occur in a germ cell or during very early embryonic development. It is an inherited condition in that sense, but patients don't live long enough to have children of their own. The mutated form of the lamin A protein is known as progerin, and over the past decade researchers have noted that small amounts of progerin can also be found in normal individuals.
Here, it is important to note that what are commonly referred to as accelerated aging conditions, progeria being one example, are not in fact accelerated aging. They look that way, superficially at least, but they are better thought of as runaway damage conditions. One type of cellular damage, in many cases a type of cellular damage that - so far as we know - has little to no relevance in normal aging, runs amok. The result is some combination of impaired regeneration, impaired DNA maintenance, cells that become broken and dysfunctional, tissues and organs with failing functionality. This sounds a lot like aging, true, but then so does poisoning or viral disease when it is expressed in those terms. The result is functional decline, dysfunction, and death, but the details are different, and the deeper you look into the biochemistry, the more different they become. Just as you can't learn much about aging from examining victims of slow poisoning, you also can't learn much about aging from any narrow form of molecular breakage that doesn't occur to a significant degree in normal aging.
What about progerin, however? Did I not just mention that it does appear in normally aged tissues? Well, this is true, it does. So do a great many other things, however. The trick lies in proving that there is a significant contribution to degenerative aging resulting from progerin. A number of research groups have been slowly chasing this down over the past fifteen years, with an increasing focus on cellular senescence, as the cells of progeria patients appear to have at least some aspects in common with senescent cells, even if there are marked differences between the two. Senescent cells, of course, are now well recognized to be a contributing cause of normal degenerative aging. Another area of interest is the possible impact of progerin on stem cell activity, required for tissue maintenance. This maintenance activity declines with aging, likely a response to rising levels of cellular damage that serves to reduce cancer risk, but the research community is a fair way from being able to pin down specific causes and the degree to which they contribute to this loss of function.
The open access paper noted here is representative of the state of the field, in which researchers are starting to be confident enough in their understanding of progerin in normal aging to advance possible mechanisms for its effects, and run animal studies to try to put some numbers to those claims. The authors link progerin with cellular senescence in fat tissue, in the sense they think a small number of progerin-loaded cells are accelerating the creation of lingering senescent cells, which go on to carry out their characteristic damage to health and tissue function. Unfortunately, I'd say the results published here are a little too tentative to provide good support for the authors' theory on what is taking place under the hood, for all that it sounds plausible. It is an interesting direction, however, and I would expect to see further similar work on this topic in the years ahead.
Rare progerin-expressing preadipocytes and adipocytes contribute to tissue depletion over time
One of the major physiological changes that arises with aging is the loss of subcutaneous white adipose tissue (sWAT). White adipose tissue is known to be involved in energy storage, in the form of lipids, but also in immunity, adipokine and inflammatory cytokine production. Different fat depots can be found in both humans and mice, which appear to have distinct functions. Subcutaneous fat works as an endocrine organ, secreting, in particular, the hormones leptin and resistin. Its role is to store triglycerides and free-fatty acids in order to prevent their ectopic deposition. In the case of lipoatrophy, sWAT's ability to store energy is impaired, which results in ectopic fat deposition either in visceral depots or in non-adipose sites.
The investigation of premature aging syndromes has had a considerable impact on the understanding of some of the bases of physiological aging. One of these syndromes is the Hutchinson-Gilford Progeria Syndrome (HGPS), commonly known as Progeria, a rare genetic disease characterized by clinical features resembling certain aspects of premature aging. Although several mutations have been reported to cause HGPS, this disease most often results from a de novo point mutation in the LMNA gene. Progerin accumulates at the inner nuclear membrane causing distortion of the membrane and disrupting nuclear functions. Accumulation of progerin is thought to be responsible for abnormal functional changes associated with HGPS including suppressed Nrf2 antioxidant pathway signalling and impaired adult stem cell function.
HGPS shares several features with normal aging, one of them being the loss of sWAT. Several studies have revealed the presence of low levels of progerin or rare progerin-expressing cells in normal fibroblasts (between 0.5% and 3%) and arteries (between 0.001% and 1.97%), with amounts sometimes increasing during aging. Low tissue levels of progerin can either be attributed to low expression in many cells, or to high expression in a small fraction of cells. However, it is still arguable that low levels of progerin significantly contribute to the reduced tissue function associated with aging.
In this study, we used a mouse model with sustained long-term expression of human progerin in a low frequency of cells of the adipose tissue to determine the contribution of progerin to progressive sWAT depletion. Our results provide evidence that adipose tissue is highly sensitive to progerin expression and further emphasize progerin's possible causal role in certain tissue alterations during aging. However, the frequency of progerin positive cells in the sWAT of our mouse model was higher than what was observed in healthy human sWAT, in which progerin could not be detected on protein level. Other researchers have suggested a hypothetical model whereby aging of adipose tissue results in cellular senescence and consequent tissue pathology. Our results provide evidence that a similar mechanism is to be found in subcutaneous fat, with progerin accumulation during aging triggering a cascade of events contributing to progressive tissue depletion.
We propose that with chronic exposure to low numbers of progerin expressing cells, sWAT pathology begins, initially with hyperproliferation. Hyperproliferation in turn contributes to abnormal cellular development and subsequent senescence. As paracrine activity is high in adipose tissue, senescence spreads to surrounding cells through activation of the senescence-associated secretory phenotype (SASP). Simultaneously, aging sWAT accumulates DNA double-strand breaks, which upon reaching a certain threshold lead to an increase in cell death, encouraging macrophage infiltration, as well as exacerbating the senescence phenotype. This pro-inflammatory environment of the adipose tissue ultimately activates the immune system machinery resulting in systemic inflammation.
Envisaging For-Profit Alternatives to Fight Aging! and Similar Initiatives
Useful activities in our community can be powered either by zealotry or by money. Zealotry has the advantage of being cheap, but the profound disadvantages of being rare, unreliable, and never quite optimally opinionated for the task at hand. Set a zealot to a challenge and you get the output the zealot decides upon, and only for so long as he or she is suitably motivated by whatever internal alchemy is at work in that particular case. Sustainable, reliable, long-term zealots only exist in stories. Money, on the other hand, has the disadvantage of being expensive, but for for so long as income is greater than expenditure, it can be used to produce reliable, sustainable, long-term outcomes. Changing the world always starts with the zealots, but the whole point of the subsequent bootstrapping process is to transition to money rather than zealotry as a power source just about as rapidly as possible. The future is defined by the few visionaries who care greatly enough to set aside their lives to work upon it, but it is enacted by the vastly greater number of people who take a paycheck and go home at the end of the work day.
To the extent we agree that the advocacy, fundraising, and other matters accomplished via Fight Aging! are good things, we'd like to see more of this taking place. More of it, and not dependent on the fickle motivations of zealots. Ultimately that means finding ways to do what Fight Aging! does, but for profit, with money. In this I do not mean Fight Aging! itself, which will be powered by zealotry until such time as the alchemy fails, at which point it will vanish just like everything else does in time, but something like it, and preferably dozens of varied somethings. Experimentation and diversity drive progress, and we won't find out exactly what it is that Fight Aging! is doing suboptimally without the existence of many other attempts at the same types of initiative.
In the years that I have been running Fight Aging!, I've seen many longevity science interest and news sites come and go. Zealotry has a short half-life. When it comes to the money side of the house, things haven't been much better, however. The typical ad-supported sites roll over and die fairly quickly; there never was enough money in that to do it for a niche interest such as ours over the past fifteen years. Their business models fail, and they linger a little while on the fumes of zealotry until that also departs. The initiatives that try sponsorship from the "anti-aging" marketplace tend to last longer, but are so corrupted by that revenue that they quickly lose all possible usefulness and relevance. You can't take money from people pushing interventions that do not work and still speak with correctness and authority.
See the Life Extension Foundation's long-running magazine, for example; how is any layperson supposed to tell the difference between the bulk of self-serving nonsense and the occasional perspicacious and useful article? And these are people who are strong supporters of the use of medicine to end aging, and fund some quite sensible research with proceeds from their business, but is really isn't possible to discern this from their materials, where they are doing just as much damage to the future of the field of longevity science as any other random "anti-aging" supplement company. The point of the exercise is to identify and advocate lines of research and development with high expectation values when it comes to effects on healthy life span, and unfortunately all of the ready money willing to pay for eyeballs-slash-victims involves selling snake oil or convincing the world that snake oil is the way forward.
This might change. One could envisage a Fight Aging! clone comfortably sponsored by the rounding errors in Unity Biotechnology's annual budget, or by some near future responsible confederacy of clinics offering senolytic therapies. Here the challenge becomes the more subtle one of being beholden to the controllers of a particular approach or orthodoxy that happens to work. It is infinitely better than taking money from people selling resveratrol laced with outright lies about the state of the science, but still has its problems. A more desirable situation is represented by, say, ALZFORUM, in which the money comes from a large research funding source, and is thus more agnostic on what can and can't be said. Still, we're talking about degrees of editorial freedom, not its absence. Money always comes with at least some strings attached. Further, research funding sources with an interest in this sort of thing are not common, sad to say.
Another interesting model, somewhat similar to that for ALZFORUM, perhaps, is that represented by Geroscience, supported by Apollo Ventures. For a venture fund, running an online magazine is a small expense, and well justified given the uses it can be put to, even if comparatively editorially independent. A venture fund is an opinion crystallized into money, a wager on the future of an industry that will tend to do better the more that people agree with its core opinion. So why not have a magazine to talk up the market and raise awareness? I'm actually quite surprised that this approach doesn't have a wider adoption in venture capital circles. Geroscience has a likely life span of a decade or more because it is coupled to a fund, which is plenty of time to gather a sizable audience by producing a quality product, but I don't think that the owners are going about things in quite the right way to gain that broader visibility and higher traffic. This is possibly because they have no need to do that to satisfy their immediate goals. Daily or near-daily updates in addition to longer articles are necessary and powerful, and they are not doing this.
A further option for involving money in the process as a slow replacement for initial zealotry is that used by Longecity to some degree, and by the Life Extension Advocacy Foundation of late, which is sponsorship by members and patrons. I really can't point to many past examples of this in our space, and it unclear as to whether this is because ours is a small, comparatively young community measured in the grand scheme of things, or because this approach to introducing money is hard to carry out. I do think we have a challenge in the form of cheap research costs; this is of course a blessing for the pace of research and the ability to crowdfund useful work, but makes it hard to fund any of the many necessary areas of community infrastructure that are not research. When meaningful research projects and meaningful advocacy projects cost the same few tens of thousands, it is a tough choice to give to the latter. The rational actors in our community of supporters near always makes the short-term decision to donate to the SENS Research Foundation rather than to the organization helping to expand awareness of SENS and raise funds for the SENS Research Foundation. This isn't sustainable, however, because it means that necessary functions in our community wind up propped up by zealotry rather than money - and that always comes to its inevitable end sooner rather than later.
In any case, there is no particular conclusion to this line of thinking today, beyond a note that I'd like to see more Fight Aging! alternatives out there, ones running on some basis other than volunteer efforts, but which nonetheless are capable of unbiased advocacy and discussion of the best approaches to enhancing healthy human longevity.
A Surprisingly Large Change in Metabolism in Mice Lacking a Sense of Smell
One of the ongoing offshoots from the mainstream of calorie restriction research is the investigation of the impact of sensing food on the effects of dietary intake and the operation of metabolism. While there is no necessary reason for research into sensing of nutritional cues to be connected to research into reduced calorie intake, this is how things have worked out in practice. It all stems from calorie restriction research projects some years back in which the scientists involved noted that the flies in their studies seemed to undergo short-term changes in metabolism that were independent of the content of the food provided, and even occurred a little in advance of the flies actually undertaking the new, lower calorie diet.
Via further experimentation, this led to the conclusion that scent plays an important role in the regulation of metabolism in this and other lower species. For example it is possible to block the benefits of eating less in flies by providing an environment filled with the scent of greater amounts of food. The neural structures involved appear to listen as much to what is scented of food content as to what is actually consumed. In the past few years, this line of inquiry has moved from lower animals into mice. This is reasonable; the calorie restriction response of improved health and extended healthy life span came into being very early in the evolution of life, and appears to some degree or another in near all species and lineages tested to date, mammals included. So if the basic cellular processes are much the same between all of these species, widely dispersed across the tree of life, why not also the importance of olfactory mechanisms?
So we come to today's research results, which retain the investigation of scent in metabolic response to diet, but depart from calorie restriction for the other end of the spectrum: high calorie diets and obesity. Normally this isn't all that interesting as a topic for the audience here, but as a new set of data to take back to current investigations of sensory manipulation of calorie restriction responses, it is worth noting. If nothing else, the size of the effect in mice is certainly very surprising, even given somewhat analogous results in flies and worms. It certainly raises questions as to what similar examinations might find in human regulation of metabolism.
Smelling your food makes you fat
Our sense of smell is key to the enjoyment of food, so it may be no surprise that in experiments, obese mice who lost their sense of smell also lost weight. What's weird, however, is that these slimmed-down but smell-deficient mice ate the same amount of fatty food as mice that retained their sense of smell and ballooned to twice their normal weight. In addition, mice with a boosted sense of smell - super-smellers - got even fatter on a high-fat diet than did mice with normal smell. The findings suggest that the odor of what we eat may play an important role in how the body deals with calories. If you can't smell your food, you may burn it rather than store it.
These results point to a key connection between the olfactory or smell system and regions of the brain that regulate metabolism, in particular the hypothalamus, though the neural circuits are still unknown. Mice as well as humans are more sensitive to smells when they are hungry than after they've eaten, so perhaps the lack of smell tricks the body into thinking it has already eaten. While searching for food, the body stores calories in case it's unsuccessful. Once food is secured, the body feels free to burn it.
The smell-deficient mice rapidly burned calories by up-regulating their sympathetic nervous system, which is known to increase fat burning. The mice turned their beige fat cells - the subcutaneous fat storage cells that accumulate around our thighs and midriffs - into brown fat cells, which burn fatty acids to produce heat. Some turned almost all of their beige fat into brown fat, becoming lean, mean burning machines. In these mice, white fat cells - the storage cells that cluster around our internal organs and are associated with poor health outcomes - also shrank in size. The obese mice, which had also developed glucose intolerance - a condition that leads to diabetes - not only lost weight on a high-fat diet, but regained normal glucose tolerance.
The Sense of Smell Impacts Metabolic Health and Obesity
The regulation of whole-body energy homeostasis relies on an intricate balance between food intake and energy expenditure. This balance requires the coordinated response of peripheral and central neuronal inputs including hormones, multiple peptides, and neurotransmitters. In the hypothalamus, the melanocortin system in the arcuate nucleus (ARC) controls feeding in response to circulating insulin and leptin levels. Among the many sensory stimuli that influence behavioral decisions about food choice, olfactory inputs are likely to contribute to the regulation of energy homeostasis. Remarkably, the sensory perception of a hidden food cue, without its ingestion, at least transiently switches the activation state of AgRP and POMC neurons. In mice and other rodents, the hypothalamus receives indirect inputs from olfactory sensory neurons (OSNs) through signals entering from the main olfactory bulb (MOB) and transmitted to the centers of the olfactory cortex. Therefore, olfactory signals may prime the activity of key homeostatic neurons in the hypothalamus to adapt systemic metabolism under conditions of anticipated food intake.
We investigated the role of OSNs in the control of energy balance. To this end, we examined the consequence of genetically ablating the ability of animals to smell, by disrupting OSNs, on whole-body energy homeostasis in lean and obese animals. We find that mice with reduced olfaction, i.e., hyposmia, are leaner upon diet-induced obesity (DIO) either before or after the onset of obesity. These animals exhibit increased energy expenditure and enhanced fat burning capacity as a consequence of enhanced sympathetic nerve activity in brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT). Conversely, we describe that conditional ablation of the IGF1 receptor in OSNs results in enhanced olfactory perception. Complementing the results observed in the hyposmic animals, these hyperosmic mice have increased adiposity and insulin resistance. Collectively, the results reveal a critical role for olfactory sensory perception in coordinately regulating peripheral metabolism via control of autonomic innervation.
The finding that OSNs can control peripheral metabolism is intriguing, and multiple mechanisms could be engaged in this circuitry. It is mainly thought that the hypothalamus receives indirect inputs from OSNs through the MOB and transmitted to the centers of the olfactory cortex. Interestingly, direct connections between discrete subpopulations of OSNs and several nuclei from the hypothalamus have been observed, reinforcing the idea that an active circuitry initiated in OSNs might influence metabolic homeostasis. Our data strongly indicate a circuit that relays information to autonomic neurons and may require central neurons. In line with this hypothesis, fiber photometry recording of AgRP and POMC neurons activity in the hypothalamus of awake, behaving animals shows that the perception of food rapidly switches the activation state of these neurons upon hunger and can be immediately reversed by removing the food cues. Additionally, olfactory inputs may be integrated by a complex interplay of different hypothalamic and brainstem nuclei expressing appetite-modulatory neuropeptides. Regardless, the potential of modulating olfactory signals in the context of metabolic syndrome or diabetes is attractive. The data presented here show that even relatively short-term loss of smell improves metabolic health and weight loss, despite the negative consequences of being on a high-fat diet.
Detailed Investigations of Autophagy to Better Understand why it Declines with Age
Autophagy is the name given to a collection of recycling mechanisms involved in cellular maintenance. These processes clear out metabolic waste and break down damaged cellular components so that the parts, proteins and their constituents, can be used elsewhere. The better documented forms of autophagy involve the coordination of (a) systems that flag structures and molecules for recycling, (b) systems that engulf the flagged materials in membranes for delivery to cellular recycling centers, and (c) the recycling structures called lysosomes, packed with enzymes capable of dismantling up most of what they will encounter.
Autophagy fails with age, and this failure is thought to contribute to degenerative aging to some degree; certainly many of the methods of modestly slowing aging in laboratory species appear to at least involve - and in some cases rely upon - increased autophagy. Exactly why does autophagy falter with age, however? There are a lot of answers to that question, of varying degrees of incompleteness, speculation, and supporting evidence. The challenge here, as for everything that goes on inside a cell, is that autophagy is a highly dynamic, enormously complex chain of mechanisms. Failures could be subtle and hard to detect in any one component part, or they could be distributed throughout the system, and there are a lot of pieces to examine. It has taken decades for the modern research community to gather today's comparatively sophisticated, partial picture of what is going on under the hood, and the tools of biotechnology are only now gaining the capacity to do better than this given a reasonable amount of time and funding.
A further consideration is that autophagy is a large enough research space to develop specializations: teams will tend to have more experience in just one aspect of this set of processes. It is, like much of the life sciences, a case of the blind men and the elephant, and intensive, ongoing collaboration is required in order to gain any sort of holistic picture. Many autophagic mechanisms no doubt all become dysfunctional in their own particular ways across the course of aging, and each such chain of cause and effect reaches from the beginning of some form of fundamental molecular damage through numerous stages to reach whatever layer of the onion that any given scientist happens to be investigating. When people publish papers on the age-related decline of autophagy, it is always worth bearing this in mind: it is rare that anyone is working with more than a slice of the whole at one time.
That said, the research here is an example of the sort of approach needed to improve the present understanding of how autophagy works in detail, and thus build a better map of where it runs off the rails over the course of aging. You might compare the report here with, say, the standard SENS view of dysfunctional autophagy resulting from hardy metabolic waste accumulated in lysosomes, or the discovery that loss of autophagy can be restored at least partially through genetic engineering to add more receptors to lysosomes, increasing their ability to receive flagged materials for recycling. The lysosome is just one part of a much larger set of autophagic systems, however, and problems can certainly exist elsewhere - though it has to be said that the findings noted below are consistent with theories placing the whole of the problem in the lysosome, and thus supportive of the SENS approach to therapies.
Scientists Take a Deeper Dive Into Cellular Trash
"Autophagy," which means "self-eating" based on its Greek roots, is the normal physiological process the body's cells use to remove viruses, bacteria, and damaged material from the cell. Autophagy also helps cells "clean house" by recycling building blocks - similar to the way we recycle glass, plastic and metal. In recent years, defective autophagy has been linked to age-related diseases such as cancer, neurodegeneration and heart disease. "Increasingly, researchers are asking whether there is an age-related decline in autophagy and if it's connected to diseases that occur more frequently in older individuals. Exposing how autophagy becomes faulty with age may reveal opportunities for us to therapeutically intervene and correct the process to promote health aging."
Autophagy is a dynamic, multi-step process that starts with the formation of a double-membrane sac in the cell cytoplasm called the isolation membrane (IM). These structures engulf cellular material and debris, expanding in size to form vesicles called autophagosomes (APs). Finally, APs fuse with lysosomes to form autolysosomes (ALs) that digest and release the breakdown products for re-use, much like a recycling plant would repurpose incoming trash. "A major challenge with understanding how aging impacts autophagy is that researchers have been capturing a dynamic process with static measurements. Autophagy is most commonly monitored by counting the number of APs, which really only provides a snapshot of the process - similar to how counting the number of garbage trucks on the street doesn't tell you how much garbage is actually being recycled at the plant. And typically older organisms have an increased number of APs, but we don't know exactly why."
"We wanted to ask how age impacts autophagy - is it at the beginning of the process by increasing the rate at which APs are formed, or, by analogy, how many garbage trucks are rolling out on the street - or is it at the end of the process by blocking the conversion of APs to ALs, i.e., how much recycling is taking place at the recycling plant. Either one of these scenarios would cause an increased number of APs, but knowing which one would help pinpoint where interventions may be helpful. We found that there is indeed an age-dependent decline in autophagy over time in all tissues examined. We further provide evidence that the increase in APs results from an impairment at a step after APs are made. So basically the autophagy recycling process becomes incomplete with age by stopping somewhere after APs are formed. This research is important because it helps provide time- and site-of-action information for potential future interventions directed at sustaining autophagy to extend lifespan. Our next step will be to perform biochemical research to further pinpoint exactly how autophagy fails to complete its cycle, possibly providing targets to develop specific interventions."
Spatiotemporal regulation of autophagy during Caenorhabditis elegans aging
Macroautophagy (hereafter referred to as autophagy) is a multistep cellular recycling process in which cytosolic components are encapsulated in membrane vesicles and ultimately degraded in the lysosome. As interest in this pathway and its pathophysiological roles has increased, it has become clear that measurement of autophagic vesicle levels at steady state, without monitoring the overall pathway flux, can lead to controversial results. Autophagy is commonly monitored by enumerating APs under steady-state conditions, also referred to as the AP pool size, using a GFP-tagged Atg8 marker. During AP formation, Atg8 is cleaved, conjugated to phosphatidylethanolamine, and inserted into the vesicle membrane, thus serving as a marker for IMs and APs. However, GFP-Atg8 only reports on the size of the IM and AP pools, not the rate by which IMs and APs are formed, or converted to ALs. For example, an increase in GFP-Atg8 could result from increased formation of APs or blockade of the downstream steps.
A tandem-tagged mCherry-GFP-Atg8 reporter, which separately monitors both IMs/APs and ALs can help distinguish between these possibilities.Specifically, when used in combination with chemical inhibitors of autophagy tandem-tagged reporters can assess autophagic activity in so called autophagic flux assays. Although tandem-tagged Atg8 markers have been used extensively to monitor autophagy in mammalian cells, as well as in adult Drosophila melanogaster and in Caenorhabditis elegans embryos, this reporter has not previously been used in adult C. elegans, and no comprehensive spatial or temporal analyses of autophagic activity have been reported in any animal thus far.
Autophagy plays important roles in numerous cellular processes and has been linked to normal physiological aging as well as the development of age-related diseases. Furthermore, accumulating evidence in long-lived species demonstrates that autophagy genes are required for extended longevity. In particular, autophagy is essential for lifespan extension by inhibition of the nutrient sensor mTOR. In C. elegans, autophagy genes are also required for the long lifespan induced by other conserved longevity paradigms, such as reduced insulin/IGF-1 signaling, germline ablation, and reduced mitochondrial respiration, and all these longevity mutants have increased transcript levels of several autophagy genes.
To better understand how aging affects autophagy in C. elegans, we employed a GFP-tagged and a novel tandem-tagged (mCherry/GFP) form of LGG-1 (a C. elegans ortholog of Atg8) to investigate the spatial and temporal autophagy landscape in wild-type (WT) and long-lived daf-2 mutants and germline-less glp-1 animals. Our data indicate that WT animals displayed an age-dependent increase in AP and AL numbers in all tissues, which flux assays suggest reflects a decrease in autophagic activity over time. In contrast, daf-2 and glp-1 mutants showed unique age- and tissue-specific differences consistent with select tissues displaying elevated, and in one case possibly reduced autophagic activity compared with WT animals. Moreover, tissue-specific inhibition of autophagy in the intestine significantly reduced the long lifespan of glp-1 mutants but not of daf-2 mutants, suggesting that autophagy in the intestine of daf-2 mutants may be dispensable for lifespan extension. Our study represents the first efforts to comprehensively analyze autophagic activity in a spatiotemporal manner of a live organism and provides evidence for an age-dependent decline in autophagic activity, and for a complex spatiotemporal regulation of autophagy in long-lived daf-2 and glp-1 mutants.
Initial Coin Offerings as a Fundraising Strategy
For those who haven't been keeping a close eye on the evolution of blockchain systems such as Bitcoin and Ethereum, and the ever-expanding collection of altcoins built atop or otherwise reliant upon the few core blockchains, the recent spate of large Initial Coin Offerings (ICOs) might seem as though they arrived from out of the blue. Startup companies have been raising tens of millions on the basis of the most flimsy and unrealistic of business proposals, simply by launching and then selling a new set of limited issue tokens based on the Ethereum system. The promise of these tokens being used in some future API or system of exchange is barely even visualized in many cases, let alone planned or under construction. Yet the tokens are eagerly purchased in exchange for bitcoins or ether cryptocurrency, and then go on to trade for multiples of that price. Those of us in fields like longevity science that struggle for funding might well look at this and ask how we can participate in this apparently magical money fountain.
So what is going on here? The answer to that comes in two parts. Firstly, the technical underpinnings. Blockchains considered in the abstract are a use of cryptography to solve an important problem in distributed collaboration. Within their bounds, they can be used to enable verification of identity, trust between anonymous parties, business ledgers that do not rely upon any one central party, escrow that doesn't require a trusted escrow holder, and so on. This clearly has value, and the fact that the various cryptographically assured tokens associated with blockchains trade at a price is due to the underlying value of what can be achieved with blockchain technologies. Bitcoin is a first generation, comparatively crude blockchain, while Ethereum opens up the technology to allow the operation of arbitrary logic in the way in which cryptographic tokens and the blockchain operate. In both cases there are open markets where the tokens associated with the blockchain can be traded, an operation that is carried out without the need for any market maker, using the power of the blockchain to enable trusted exchanges between arbitrary third parties, ensured by cryptographic exchanges. This is a very high level sketch indeed, and I'd encourage you to read some of the longer summaries for laypeople that can be found online.
That blockchains in the abstract have value - and potentially considerable value in the longer term - doesn't explain why ICOs exist in their present form, enriching startup owners on the basis of dubious business propositions and minimal effort, however. The current consensus view is that there is a lot of money bottled up in some combination of (a) the cryptographic tokens held by people who came into ownership early-on, and (b) the wealth of countries like China with strong currency controls. Mostly the latter option. The flood of money into ICOs is driven by these sources of wealth seeking a place to convert or move their assets, and since this tends to raise the market value of these tokens in the short term, this drags in every speculator in town. Many fairly sophisticated entities with deep pockets are now involved in cryptocurrency trading.
Thus when an ICO takes place, sells out quickly, and the tokens purchased are immediately sold for a profit on the open market, along the way money from currency-controlled regions moves to other jurisdictions via the blockchain as an intermediary, people with large unrealized gains in bitcoins and ether can diversify their holdings, and various other entities can achieve their own goals. So in the short term, it is likely that a great deal of the current market value of blockchains lies in their being a very accessible way to work around currency controls, and ICOs are just a particularly convenient manifestation of this point. Absent regulatory intervention - something that is anticipated by observers in the US, since ICOs look a lot like a way to circumvent SEC rules on startup fundraising - this will probably continue for some years, I'd imagine, if what I've said here is an accurate assessment of why the current situation exists.
So then, back to the question at hand: how could the funding-starved longevity science community drink from this money fountain, while at the same time offering a legitimate use of an ICO? The most obvious path forward seems to involve some form of Kickstarter-like model of funding development by preordering the product. This of course has a high rate of failure, but that seems to be accepted by both Kickstarter backers and by the SEC, tacitly or otherwise, as a way to bring in the necessary funding to a startup company to allow an attempt at development of the product. The further you are in advance of an actual product the more morally dubious it becomes to sell preorders; when you are researching whether or not your approach to building a produce is possible at all, one can argue that it is somewhat outrageous to be taking preorders. (Arguably many Kickstarter projects that are purely development work are also making outrageous claims of certainty in their ability to deliver, but the similarities between that situation and the uncertaintities of real scientific research are superficial at best).
Nonetheless, for research that is further along the pathway, this seems defensible. I'll paint a few scenarios of varying degrees of plausibility and risk of failure here. Let us look at senolytic rejuvenation therapies, for example. Imagine that Oisin Biotechnologies hires a programmer to create a simple Ethereum redemption token type. Oisin pledges to exchange a token for their senolytic treatment at a time at which the cost of that service is 10,000 or less, in any jurisdiction where the treatment is approved for clinical use. Perhaps there are some additional perks, such as token holders gaining priority when space is limited. Some fraction of those tokens are then put out in an ICO. The expected plan would be to sell several tens of millions in value of these tokens in exchange for 10,000 each in ether, in the full understanding that the entities initially buying these tokens have no great interest in what they are later to be used for. Then convert the ether into currency, and treat that as a form of fungible loan or obligation - one that can be obtained somewhat more easily and at much better terms than are available through any existing financial institution. Later funding rounds and deals with third parties to provide the services offered to token holders may be used to dilute the effective cost of this loan and of honoring the tokens.
Alternatively, consider a group of people with a suitable biotechnology firm on contract who make much the same ICO offer, but selling tokens at 2,000, and pledging a place in an open human trial of whichever package of senolytics they settle upon. Depending on the amount raised, they pledge to run mouse studies for the promising senolytic drug candidates with only cell studies, and initial human volunteer tests for senolytic drug candidates with only animal data. They offer no guarantee as to which senolytics will be used in the end, and the expected package for people who redeem the token is a kit sent in the mail, with instructions on how to coordinate with a local physician to obtain before and after measurements. You can adjust the per token cost and the type of support and logistics offered by the venture, ranging from the minimal product described above to travel to a location for a medical tourism-like package, to ensure better data collection.
The point here is that none of these things could do very well when it comes to raising funds in the present environment of crowdfunding absent this unusual dynamic flowing through the blockchain system. They are legitimate products, analogous to many Kickstarter efforts, but our community of longevity science supporters simply isn't large enough and longevity science is not yet entrenched enough in popular culture to bring in tens of millions in this way. But near anything put in the path of the money flows and incentives currently operating in the major blockchains right now will, if properly executed, stand a good chance of raising significant funding in this way. Will that continue, or will it be diluted to nothing by the gold miners even now heading in that direction? Who knows. But you don't find out without giving it a try. It is of course the responsibility of those who do this to conduct themselves in an ethical way that reflects well upon our community, but I think this to be a practical possibility, and one we should look into.
An Interview with Eric Verdin of the Buck Institute for Research on Aging
Eric Verdin is the present CEO of the Buck Institute for Research on Aging. From my perspective most of the research programs carried out there, with the notable exception of matters involving cellular senescence, is fairly distant from the SENS rejuvenation research we'd like to see prosper. The Buck Institute as a whole reflects the broader research community focus on greater understanding of how aging progresses at the detail level, absent intervention, and on the development of ways to modestly slow the accumulation of damage, such as calorie restriction mimetic drugs.
Thus even among those researchers interested in treating aging as a medical condition, our community still needs to persuade many more of them to work on damage repair strategies capable in principle of producing rejuvenation in the old, rather than tinkering with metabolism to merely slow down the rate at which damage accrues. The hope is that as SENS approaches such as senescent cell clearance show themselves to be far more reliable, as well as cheaper and faster to bring to the clinic, this will happen. Meanwhile we have the existence of numerous research centers of a size comparable to the Buck Institute, with ten times the annual budget of the SENS Research Foundation, working on comparatively little that can possible produce meaningful outcomes in aging in the near future.
Biologist Eric Verdin considers aging a disease. His research group famously discovered several enzymes, including sirtuins, that play an important role in how our mitochondria - the powerhouses of our cells - age. His studies in mice have shown that the stress caused by calorie restriction activates sirtuins, increasing mitochondrial activity and slowing aging. In other words, in the lab, calorie restriction in mice allows them to live longer. His work has inspired many mitochondrial hacks - diets, supplements, and episodic fasting plans - but there is not yet evidence that these findings translate to humans.
Why is there so much energy and excitement surrounding aging research right now?
Something happened in the 1990s. There were three groups that did an experiment that was really unexplained. Those groups all identified unique mutations in laboratory species that could actually increase lifespan. At that time, it was a quite astute observation in the way they completely turned upside down our conception of what aging was. The whole idea of aging was sort of an entropy problem where everything falls apart like your car rusting, but what these papers showed is that you can make a single change in one whole organism like C. elegans with a 100 million base pair genome, and you can double its lifespan. That by itself was mindboggling for a lot of people and suggested there might be pathways to regulate aging, and if there are pathways that means there are proteins, and that means you can eventually develop drugs. Today we're at a point where people are considering starting clinical trials. This is why there is so much excitement and interest.
The Buck Institute focuses on research aimed at increasing healthspan. What do you mean by healthspan?
The whole mission of the Buck is not only to increase healthspan but also lifespan, but we don't want to increase lifespan at the expense of healthspan. Every decade over the last hundred years, lifespan has increased by two years. That's amazing because we've gone from an average life expectancy in the 1900s, which was around 47, to 77 today. That's an incredible achievement, but this extended lifespan is not all rosy. We also have an epidemic of what we call the chronic disease of aging.
Can those incredible increases in lifespan continue? Is there an upper limit?
There currently is an upper limit, and the upper limit is probably around 115, 120. You have a very large number - 100 billion people to choose the number of people that have ever lived - and you have only one who has made it through to 122, Jeanne Calment. The second oldest was 119. That's already a pretty good limit. If we could all live to 110 healthy and a disease in the last five years of life, I think most people would sign for this. But this does not anticipate future developments in biology. I've been in experimental biology for about 30 years. What we're doing today is just amazing in comparison to what we were doing when I started. You can't imagine what we will be able to do in biology in 30, 50, 100 years. That's why I don't like the idea that there's an absolute upper limit that man will never live above 120.
Why isn't there more interest in aging research in the larger biomedical community?
Aging research is a real paradigm shift in a way that really changes much of what we think about these chronic diseases. I think the biggest resistance is from medicine because medicine is organized in a way that is not so compatible with what we're doing. Medicine is organized based on organs. You have a heart attack, you go see a cardiologist, and he's going to take care of your heart by deferring the risk for heart attacks and controlling high blood pressure or high cholesterol. What our field is proposing is that aging is the major risk factor for all of these diseases. We should start targeting not cholesterol and blood pressure. I mean, you still have to do this, but if you start targeting the mechanism of aging, you will have a much more profound effect against all of these diseases. That really is the promise of what we're doing.
Death is not what Gives Life Meaning
Everyone who advocates for far longer and far healthier human lives, a goal to be achieved through progress in medicine, sooner or later runs into the "death is necessary to give life meaning" objection. It sounds deep, but turns out to be complete nonsense once you start to break it down into its component parts for examination. The meaning of your life is what you decide it to be, and that is determined while living, while being alive to think, plan, and achieve. Living is what is necessary to give a life meaning for the person who lives it, and it isn't as though other opinions really count in this matter. This strangely nonsensical argument for death is really just another facet of the naturalistic fallacy coupled with the lazy conservatism inherent in human nature. It is painting what happens to be the state of the world now as the best of all possibilities, because it is easier to do that than to set forth to change it. There is no state of the world so terrible that you would not find the majority talking themselves into accepting it as the status quo.
It is not uncommon for people to accept, rather uncritically, the stale cliché according to which life gets its meaning from death, and without the latter, it would not have meaning. If rejuvenation can stave off death and extend lives indefinitely, will these extended lives be utterly meaningless? No. Time and time again have I said this before, but I still fear that this misconception may be one of the worst enemies of rejuvenation; consequently, I spend much time thinking about its roots and how to debunk it. Whether life gets its meaning from death or not, people who think it does implicitly admit that life has no meaning per se. In a general sense, this is correct. Meaning is not an intrinsic property of anything. To paraphrase a common adage, meaning lies in the head of the beholder, and that's where you should expect to find the meaning - if any - of anything, life included. In other words, it is up to you to find meaning in your life, and you should neither expect it to have meaning by default, nor let others decide for you what the meaning of your life is.
It is obvious why a strong wish to live exists: if I fear death and try to avoid it by all possible means, I stand a better chance to live long enough to reproduce than somebody who isn't so afraid. Therefore, evolution has penalised creatures who did not have a strong survival instinct, and rewarded those who did. This is why we hold our lives so dear. Human intelligence made us extremely fit for survival; our curiosity and drive to answer questions that we ourselves ask are among the things that make us unique on this planet. Eventually, they made us wonder why we die. Evolution has made us fear death and wish to live indefinitely, but at the same time, it has not given us the means to fulfill that wish.
The first and most evident sign of our attempts to address this problem are religions. Yes, we fear death and don't want it, but we don't really die, only the body does, or so is the claim. Some of us have resorted to accepting it, which seems to boil down to convincing yourself there's nothing to fear in death and you're okay with it. The final way to circumvent the death paradox is the fabled 'meaning of life'. What better way can there be to rationalise death and escape our mortal fear of it than making it what gives life itself its meaning? Far from being something we should fear or avoid, death becomes thus essential, for without it, life would have no point.
What does it even mean, to give meaning to life? Most would probably agree that filling your life with activities, people, and things you love and enjoy is a valid candidate for the meaning of life; so is helping others, or doing something for the common good; something that we feel is appreciated by others, and are thus gratified by. Giving meaning to life might mean doing some of these things, and clearly, none of these potential meanings is given to life by death. However, these are viable options but aren't the answer, because there is no single answer. You decide what is the meaning of your life; not old legends, not old myths, not clichés, not other people; you do. Thus, the only way death could be the meaning of your life would be if you decided so, which I hope you won't do. Ultimately, there's nothing especially wise in accepting death. The natural length of our lifespans is the result of a meaningless, purposeless process that happened for no other reason than the fact it could.
Engineering New Bile Ducts to Treat Failing Liver Function
Researchers have recently demonstrated the ability to transplant seeded scaffolds in order to engineer the growth of new bile duct structures in mice. The engineered bile ducts became functional - not exactly the same as a natural bile duct, but close enough to perform the same tasks. This approach, once mature, has the potential to restore liver function in conditions involving bile duct failure.
Researchers have grown 3D cellular structures which, once transplanted into mice, developed into normal, functioning bile ducts. Bile ducts are long, tube-like structures that carry bile, which is secreted by the liver and is essential for helping us digest food. If the ducts do not work correctly, for example in the childhood disease biliary atresia, this can lead to damaging build of bile in the liver. The study suggests that it will be feasible to generate and transplant artificial human bile ducts using a combination of cell transplantation and tissue engineering technology. This approach provides hope for the future treatment of diseases of the bile duct; at present, the only option is a liver transplant.
The researchers extracted healthy cells (cholangiocytes) from bile ducts and grew these into functioning 3D duct structures known as biliary organoids. When transplanted into mice, the biliary organoids assembled into intricate tubular structures, resembling bile ducts. The researchers then investigated whether the biliary organoids could be grown on a 'biodegradable collagen scaffold', which could be shaped into a tube and used to repair damaged bile ducts in the body. After four weeks, the cells had fully covered the miniature scaffolding resulting in artificial tubes which exhibited key features of a normal, functioning bile duct. These artificial ducts were then used to replace damaged bile ducts in mice. The artificial duct transplants were successful, with the animals surviving without further complications.
"Our work has the potential to transform the treatment of bile duct disorders. At the moment, our only option is liver transplantation, so we are limited by the availability of healthy organs for transplantation. In future, we believe it will be possible to generate large quantities of bioengineered tissue that could replace diseased bile ducts and provide a powerful new therapeutic option without this reliance on organ transplants. This demonstrates the power of tissue engineering and regenerative medicine. These artificial bile ducts will not only be useful for transplanting, but could also be used to model other diseases of the bile duct and potentially develop and test new drug treatments."
Overexpression of the DNA Repair Gene PRP19 is Shown to Modestly Extend Life in Female Flies
Genetic and other interventions that extend life span in only one gender of a laboratory species seem not to involve large effects, judging from those discovered to date. In this example, a gene known to be involved in DNA repair is found to decline with age in a more pronounced way in female flies. In turn, enhanced levels of the protein produced from this gene extend only female median life span in flies, by something like 10-25% according to the data presented in this paper. This isn't all that large an effect in the grand scheme of things; short-lived species have a far greater plasticity of life span in response to environment and genetic alterations, and researchers have produced far larger gains than this in flies using methods that are known to produce very little effect on life expectancy in humans.
This is the way things tend to work: members of longer lived species have life spans that are relatively unresponsive to environmental influences and single gene alterations that produce quite large changes in the life spans of flies, worms, and mice. These interventions are are all based on producing altered states of metabolism capable of slowing down the pace of aging in some way, however. They are a slowing of the accumulation of damage, without any attempt to repair that damage. There is as yet no data on how the other approach to the problem, actually repairing that cell and tissue damage in order to produce rejuvenation, will differ between short-lived and long-lived species. This will arrive in the years ahead; there is life span data now for senescent cell clearance in mice, and something like a five year study of efficient senolytic treatments in old humans should provide enough data to estimate the effects on human life span.
According to the disposability hypothesis of aging, functional decline results from the accumulation of stochastic damage, for example, due to somatic mutations, and is counteracted by investment into somatic maintenance and repair. Accumulation of DNA damage due to decreased repair can accelerate aging, as is observed in progeroid syndromes in humans and mouse models. Similarly, increased exposure to DNA damaging agents, for instance during chemotherapy, can lead to a phenotype of acquired premature progeroid syndrome. Accelerated accumulation of DNA damage and premature aging phenotypes are typically well correlated, but whether improved DNA damage repair (DDR) can extend organismal life span remains largely unclear.
In the fruit fly (Drosophila melanogaster), a well-studied model for dissecting the mechanisms of aging, spontaneous somatic mutations accumulate with age, and defective DNA repair is associated with reduced life span. However, overexpression of DNA repair factors in the fly seems to have highly variable, sometimes contradictory effects that depend on sex, developmental stage, and the tissue of intervention. For instance, PARP-1 modifies histones, transcription factors and repair enzymes in response to DNA breaks, and its endogenous activity is well correlated with life span in several mammalian species. In Drosophila, overexpression of PARP-1 prolongs life span in both sexes, yet only when restricted to the adult nervous system. Similarly, overexpression of Gadd45, a regulator of DNA repair and cellular stress responses, in the nervous system increases fly life span but ubiquitous expression is lethal. Thus DNA repair factors can affect Drosophila life span and stress resistance either positively or negatively, depending on the sex and on whether overexpression is ubiquitous or limited to the nervous system. Interestingly, all repair factors that were expressed throughout the adult fly body were found to shorten life span.
Here, we examine the role of adult-specific overexpression of the DNA repair factor Prp19 in affecting life span, stress resistance, and DNA damage in Drosophila. Biochemically, PRP19 interacts with multiple players in the DNA repair pathways. Apart from its role in the DNA damage response, an intriguing aspect of PRP19 function is its concomitant and essential involvement in co-transcriptional splicing, where the PRP19 complex regulates the rearrangement of the spliceosome.
In support of a role for PRP19 in the aging process, it has previously been shown that decreased levels of PRP19 accelerate the induction of cellular senescence in mouse embryonic fibroblasts, reduce self renewal of mouse hematopoietic stem cells, increase UV-A-induced skin aging in mice and decrease differentiation of human adipose-derived stromal cells. Conversely, increased levels of PRP19 extend the replicative potential and total life span of cultured human endothelial cells. However, the role of PRP19 in organismal life span is unknown. Here, we show that ubiquitous overexpression of the Drosophila ortholog of PRP19, dPrp19, reduces DNA damage and extends organismal life span of adult female flies. Our results suggest that PRP19 plays an evolutionarily conserved role in the DNA damage response, aging, and stress resistance.
A Popular Science Overview of Recent Calorie Restriction Research
This article covers some of the advances of recent years in understanding the effects of varied forms of calorie restriction in humans. Efforts to quantify the results and find a good 80/20 point, at which most of the effects of longer and more stringent reductions in calorie intake are still evident, have resulted in practical outcomes. A number of quite interesting discoveries have been made along the way, such as the ability of longer fasting periods to clear out and replace damaged immune cells to some degree.
The second phase of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE 2) trial demonstrated that it's feasible for humans to limit calories for an extended period. In addition, participants who cut back on calories lost weight and kept it off for the duration of the study. There were no adverse effects on quality of life and the participants netted improvements in blood pressure, cholesterol, and insulin resistance - all risk factors of age-related diseases. Significant changes in the study's primary end points -resting metabolic rate and core body temperature - didn't materialize, however. These two factors are believed to slow aging in animal models of caloric restriction.
Scientists have known since the 1930s that restricting calories by roughly 20% to 50% without malnutrition dramatically extends the healthspan and lifespan of some strains of rodents, and in the decades that followed, caloric restriction has been shown to increase the healthy lifespan of creatures ranging from yeast to guppies to monkeys. It's still an open-ended question whether dietary intervention - or any intervention at all - can dramatically extend humans' maximum lifespan. But epidemiological evidence and cross-sectional observations of centenarians and groups that voluntarily cut their calories strongly suggest that the practice could help people extend their average lifespan and live healthier, as well. While participants in the CALERIE 2 trial did benefit from the intervention, they likely would have had better results had they achieved a full 25% reduction in calories.
"You can prescribe whatever you want, but it's another story to have the people following that religiously." Having come to terms with this reality, scientists have been seeking more practical approaches. They've increasingly become interested in fasting-based analogues to daily caloric restriction, such as intermittent or alternate-day fasting. The results of a recent phase 2 trial published earlier this year suggest that less severe energy restriction could provide bigger improvements with fewer fasting days per month. In the trial, dieters only had to restrict their calories 60% for 5 consecutive days a month over 3 months to get the benefits of the so-called "fasting-mimicking diet."
Researchers initially tested this diet in middle-aged mice, subjecting them to 4 consecutive days of the fast twice a month until their deaths. Mice on the diet lived an average of 11% longer than control mice and had fewer cancers, less inflammation, less visceral fat, slower loss of bone density, and improved cognitive performance. Autopsies revealed that fasting shrunk the rodents' kidneys, hearts, and livers, but the refeeding period appeared to kick start regeneration, increasing bone marrow-derived stem cells and progenitor cells and returning organs to normal weights. Researchers also tested the diet in a small pilot clinical trial. After 3 monthly cycles of a 5-day fasting-mimicking diet, the 19 generally healthy participants in the intervention group reported no major adverse effects and had decreased risk factors and biomarkers for aging, diabetes, cardiovascular disease, and cancer compared with the control group, which maintained its normal caloric intake. Those results were confirmed in a larger phase 2 trial reported this year, which enrolled 100 generally healthy participants.
Supporting Evidence for the Importance of Mitochondrial DNA Deletions in Aging
Mitochondrial DNA damage is thought to be important in aging, but not all such damage is similarly relevant to aging. For example, researchers have produced mice that generate excessive numbers of point mutations in mitochondrial DNA, and these mice appear to suffer little harm as a result (with the caveat that different groups have found different degrees of outcome in this sort of investigation). Deletion mutations, however, are a different story. Some deletions result in mitochondria that are both dysfunctional and privileged in some way, better able to replicate or evade quality control mechanisms than their peers, even while they fail to properly perform their assigned tasks. These broken mitochondria quickly take over the mitochondrial population of a cell, turning that cell into a malfunctioning exporter of damaging oxidative molecules.
Unfortunately comprehensive proof of this picture, as opposed to the existing strong indirect evidence, has yet to be assembled. That proof may or may not arrive before the development of some form of rejuvenation therapy based on prevention or repair or working around deletion mutations, such as the allotopic expression of mitochondrial genes. Such a therapy would in and of itself provide strong evidence for or against mitochondrial mutations as a cause of aging, based on whether or not it works in animal studies. For now, more indirect evidence is what we have, however, and here researchers here provide a new set of supporting evidence for the importance of mitochondrial DNA deletions in degenerative aging by comparing samples from people with and without Alzheimer's disease. On average, comparing people of the same chronological age, those suffering from later stages of age-related disease should have a higher load of the forms of cell and tissue damage that cause aging.
Research suggests that mitochondrial changes are a driving force, rather than a consequence, of the aging process and Alzheimer's disease pathogenesis. Although point mutations of mitochondrial DNA have been hypothesized as being a critical cause of aging, there is evidence that they may not be fully explanatory. Mitochondria are dynamic organelles with very short half-lives. Continuous replication of mitochondrial DNA (mtDNA) is required for assignment to new mitochondria, resulting in a significant error rate and accumulation of mutated in mtDNA genome over time and space. We hypothesized that, beyond point mutations, different types of mtDNA rearrangements should be extensively distributed in aging cells. As these rearrangements are often not detected by routine methods such as polymerase chain reaction, we applied the approach of directly sequencing mtDNA from isolated mitochondria derived from fresh frozen brain samples.
Our data show that different types of mitochondrial rearrangements are very common in both the aging brain and Alzheimer's disease (AD) brain. Three types of mitochondrial DNA (mtDNA) rearrangements have been seen in post mortem human brain tissue from patients with AD and age matched controls. These observed rearrangements include deletion, F-type rearrangement, and R-type rearrangement. F-type rearrangement is defined as fragments with two different sections of mtDNA joined together in the same direction. R-type rearrangement is defined as rearrangement of mtDNA originating from two different orientations of mtDNA fragments. We detected a high level of mtDNA rearrangement in brain tissue from cognitively normal subjects, as well as the patients with Alzheimer's disease (AD). The rate of rearrangements was calculated by dividing the number of positive rearrangements by the coverage depth. The rearrangement rate was significantly higher in AD brain tissue than in control brain tissue (17.9% versus 6.7%). Of specific types of rearrangement, deletions were markedly increased in AD (9.2% versus 2.3%).
Evidence indicates that mitochondrial dysfunction has an early and preponderant role in Alzheimer's disease. Our data supports this, as the AD brain samples had more than 2.7 times the recombinant rate of similarly-aged controls. Significantly, the rate for deletion in AD was 4 times that of the control samples. The position of deletion joining points was not evenly distributed across the entire genome and instead was concentrated between regions 6kb and 15kb of the mitochondrial genome, which happens to be the area containing the DNA sequences for synthesizing all three cytochrome oxidases necessary for correct electron transport chain function. This makes it is reasonable to advance the concept that increased deletions in this area may affect the ability of mtDNA to synthesize cytochrome oxidase. Our results are consistent with reports of decreased cytochrome oxidase activity in AD brain samples.
Progress in Engineering Digestive System Tissue Structures
Researchers here report on progress in engineering a few parts of the digestive system. The intestine and sphincter work here goes together with advances in the production of small sections of functional stomach tissue reported earlier this year. The field is doing well, considering that the challenge of generating the blood vessel networks necessary to support larger tissue masses has not yet been resolved. Researchers are finding a fair number of areas where they can proceed to potentially produce useful therapeutic outcomes even absent that capability.
Researchers have reached important milestones in their quest to engineer replacement tissue in the lab to treat digestive system conditions. They have verified the effectiveness of lab-grown anal sphincters to treat a large animal model for fecal incontinence, an important step before advancing to studies in humans, and also achieved success in implanting human-engineered intestines in rodents. The lab-engineered sphincters are designed to treat passive incontinence, the involuntary discharge of stool due to a weakened ring-like muscle known as the internal anal sphincter. The muscle can lose function due to age or can be damaged during child birth and certain types of surgery, such as cancer. Current options to repair the internal anal sphincter include grafts of skeletal muscle, injectable silicone material or implantation of mechanical devices, all of which have high complication rates and limited success.
The team has been working to engineer replacement sphincters for more than 10 years. In 2011, the team was the first to report functional, lab-grown anal sphincters bioengineered from human cells that were implanted in immune-suppressed rodents. The current study involved 20 rabbits with fecal incontinence. The sphincters were engineered using small biopsies from the animals' sphincter and intestinal tissue. From this tissue, smooth muscle and nerve cells were isolated and then multiplied in the lab. In a ring-shaped mold, the two types of cells were layered to build the sphincter. The entire process took about four to six weeks. In the animals receiving the sphincters, fecal continence was restored throughout a three month follow-up period, compared to the other groups, which did not improve. Measurements of sphincter pressure and tone showed that the sphincters were viable and functional and maintained both the muscle and nerve components. Currently, longer follow up of the implanted sphincters is close to completion with good results.
The intestine project is aimed at helping patients with intestinal failure, which is when the small intestine malfunctions or is too short to digest food and absorb nutrients essential to health. Intestinal transplant is an option, but donor tissue is in short supply and the procedure has high mortality rates. "A major challenge in building replacement intestine tissue in the lab is that it is the combination of smooth muscle and nerve cells in gut tissue that moves digested food material through the gastrointestinal tract." Through much trial and effort, the team has learned to use the two cell types to create "sheets" of muscle pre-wired with nerves. The sheets are then wrapped around tubular molds made of chitosan.
In the current study, the tubular structures were implanted in rats in two phases. In phase one, the tubes were implanted in the omentum, which is fatty tissue in the lower abdomen, for four weeks. Rich in oxygen, this tissue promoted the formation of blood vessels to the tubes. During this phase, the muscle cells began releasing materials that would eventually replace the scaffold as it degraded. For phase two, the bioengineered tubular intestines were connected to the animals' intestines, similar to an intestine transplant. During this six-week phase, the tubes developed a cellular lining as the body's epithelial cells migrated to the area. The rats gained weight and studies showed that the replacement intestine was healthy in color and contained digested food.
Can Existing Mechanisms be Enhanced to Clear Age-Related Protein Aggregates?
Human biochemistry does include systems capable of breaking down or otherwise removing the hyperphosphorylated tau protein deposits observed to be associated with the neurodegenerative conditions known as tauopathies, a class that includes Alzheimer's disease. Obviously, these mechanisms are far from adequate in the normal operation of aged metabolism, but could they be boosted to effectively clear out deposits of broken proteins? That is essentially what is taking place in the development of immunotherapies to clear out β-amyloid and tau in Alzheimer's patients, harnessing the immune system to the task. But are there other, more fundamental approaches that may just involve enhancing the amounts or activities of specific proteins? The research here suggests that this might be the case.
Inside the cell, proteins need to be folded to be functional and active. Molecular chaperones are key enzymes that assist in folding proteins by stabilizing nascent polypeptide chains and by facilitating interactions that help stabilize a final structure. These chaperones also prevent the aggregation of newly formed proteins and can shunt misfolded proteins toward degradation pathways. In addition to interacting with newly synthesized proteins, chaperones also help to maintain cellular homeostasis by triaging toxic protein aggregates, which are responsible for causing neurodegenerative diseases.
Two proteins that can form these toxic aggregates are tau and α-synuclein, which form tangles in Alzheimer's disease and Lewy bodies in Parkinson's disease, respectively. These proteins aggregate to form small, soluble aggregates termed oligomers and long fibrils often termed amyloids, both of which are thought to be toxic. Here we show that a chaperone, cyclophilin 40 (CyP40), interacts with and dissolves tau and α-synuclein aggregates. CyP40 may accomplish this by interacting with proline residues in these proteins, which are known to play a key role in fibril stability. We show that CyP40 both lowers tau fibrils and oligomers in mice that overexpress tau protein and preserves cognition in these transgenic animals.
While being the first human PPIase to display disaggregation activity, CyP40 is not the first disaggregase to be identified. Certain chaperone complexes have been shown to facilitate the disaggregation of oligomers and fibrils. The existence of amyloid disaggregases presents a new avenue for therapeutic strategies. The procognitive effects of CyP40 overexpression in the tauopathic brain suggest that strategies to either induce or deliver disaggregases to the central nervous system could halt or even rescue cognitive deficits associated with neurotoxic amyloids.
Though CyP40 can directly interact with the chaperone heat shock protein Hsp90, the effects described here do not appear to be Hsp90 dependent. Further studies are required to determine if there are endogenous mechanisms to increase CyP40 activity either through the up-regulation of CyP40 expression, by increasing CyP40 stability, or by increasing the enzymatic activity of CyP40. Recent work suggests that upon cellular stress Hsp90 may dissociate from CyP40, leading to an increased pool of more catalytically active CyP40. This may hint at a possible mechanistic pathway by which CyP40 may be "turned on" in response to stress, including toxic amyloid build-up. In addition to CyP40, there are currently 41 known human PPIases within the cyclophilin, FKBP, and parvulin families. Therefore, future screening may reveal additional PPIases with activities similar to CyP40, including disaggregation. Additionally, CyP40 and other PPIases should be further characterized for disaggregation activity against proline-containing amyloids, especially those associated with disease.
Progress in the Creation of a Neoantigen Cancer Vaccine
Targeting therapies to some combination of neoantigens, distinctive markers on the surface of cancerous cells that the immune system learns to recognize, and which vary from patient to patient, represents an advance in the specificity of targeted cancer immunotherapy. It should, in principle, better rouse the immune system to attack cancerous cells, while producing fewer side-effects. Researchers here report on an early human trial of this sort of approach; the initial results look promising, certainly from the perspective of an absence of serious side-effects, though a more robust demonstration of the ability to reduce tumor burden is still needed.
A personal cancer treatment vaccine that targets distinctive "neoantigens" on tumor cells has been shown to stimulate a potent, safe, and highly specific immune anti-tumor response in melanoma patients. Antigens are molecules that are displayed on the surface of cells and stimulate the immune system. Neoantigens are molecules on cell's surfaces that are produced by DNA mutations that are present in cancer cells but not in normal cells, making neoantigens ideal targets for immune therapy against cancer. The vaccines used in the phase I trial contained up to 20 neoantigens, derived from an individual patient's tumor. The vaccines were administered to patients to train their immune system to recognize these neoantigens, with the goal of stimulating the immune system to destroy the cancer cells that display them.
While other immunotherapies, such as checkpoint inhibitor drugs, also trigger immune responses against cancer neoantigens, they are not designed to be specific. They can also induce responses against normal tissue antigens, leading the immune system to attack normal tissues and cause toxicity in a subset of patients. The researchers found that the personal vaccine induced a focused T cell response against several tumor neoantigens, beyond what is normally seen in response to existing immunotherapies.
The vaccine was administered to six patients with melanoma whose tumors had been removed by surgery and who were considered at high risk for recurrence. The vaccinations were started at a median of 18 weeks after surgery. At a median of 25 months after vaccination, four of the six patients showed no evidence of cancer recurrence. In the other two patients, whose cancer had spread to their lungs, the disease recurred after vaccination. At that point, they began treatment with the drug pembrolizumab, which inhibits the PD-1 immune checkpoint. Both patients had complete resolution of their tumors and remain free of disease according to imaging scans.
The study results suggest, that a personalized neoantigen vaccine can potentially overcome two major hurdles in cancer therapy. One is the heterogeneity of tumors - the fact that they are made up of cells with a variety of different traits, which often allows cancers to evade drugs targeted to malignant cells having a single genetic abnormality. The vaccine, because it contains many different neoantigens from the tumor, targets multiple genetic types of tumor cells. A second hurdle in cancer is to generate an immune response sharply focused on cancer cells while avoiding normal cells and tissues. This aim was achieved by the vaccine, which appeared to have few "off-target" effects, causing only flu-like symptoms, fatigue, rashes, and irritation at the site of the vaccine injection, according to the report.
Recent Research into the Effects of Increased FGF21 Levels
The protein FGF21 came to be an area of interest because its production is increased as a result of calorie restriction, an intervention that extends healthy life span in near all species tested to date. Further investigation found that genetic engineering to artificially boost FGF21 production extends life in mice, probably through effects on the well-known insulin signaling systems that appear involved in the way in which the operation of metabolism determines natural variations in life span. Like many such approaches to slowing aging in mice, it isn't expected to have as significant an effect in long-lived humans as it does in short-lived mice. Researchers are also interested in the positive impact of FGF21 on regeneration, however: it has been shown to slow thymus degeneration and enhance liver regeneration, for example. Here, researchers further investigate the impact of altered levels of FGF21 on metabolism:
Mildly stressing muscle metabolism boosts levels of a beneficial hormone that prevents obesity and diabetes in mice, according to a new study. The new findings show that triggering a certain type of metabolic stress in mouse muscle cells causes them to produce and secrete significant amounts of fibroblast growth factor-21 (FGF21), which then has widespread beneficial effects on whole-body metabolism. The mice in the experiments were completely protected from obesity and diabetes that normally develop due to aging or eating a high-fat diet. Moreover, triggering the FGF21 production after the mice had become obese and diabetic reversed these conditions and returned the mice to normal weight and blood sugar levels.
"There is a biological phenomenon known as hormesis where a little bit of stress a can be a good thing." Researchers used genetic engineering to reduce levels of a mitochondrial protein called OPA1 in the muscles of mice. Mitochondria are tiny organelles that produce a cell's energy. This OPA1 deficiency disrupted muscle metabolism and caused a small amount of muscle loss in the mice. Despite the mild muscle atrophy, which did decrease grip strength, the older mice with OPA1 deficiency had greater endurance on the treadmill than older control mice. In addition, activity levels and energy expenditure that normally decline in mice as they age were preserved in OPA1 deficient mice.
Interestingly, the altered mice also were completely protected from the weight gain and glucose intolerance that normally develop in mice as they age or when they eat a high-fat diet. Moreover, the research team showed that reducing OPA1 levels in muscle, after mice had become obese and diabetic, reversed these problems - normalizing body weight and reversing glucose intolerance even though the high fat diet continued. These metabolic improvements correlated with increased levels of circulating FGF21. The researchers were able to prove that muscle was the source of the FGF21 by creating a mouse that had the OPA1 deficiency and also was missing the FGF21 gene in muscle. These mice were no longer able to produce FGF21 in muscle in response to OPA1 deficiency, and, just like control mice, they became obese and developed diabetes. "These experiments prove that muscle is the source of circulating FGF21 in the OPA1 deficient mice, and that muscle-derived FGF21 prevents diet-induced obesity and insulin resistance in these mice."
Further investigation demonstrated that the small degree of mitochondrial stress induced in muscle by the reduction of OPA1 is sufficient to activate another cellular stress response pathway called endoplasmic reticulum (ER) stress, which then dramatically increases FGF21 levels. "The follow up work on this will be understanding how a little bit of mitochondrial stress can actually increase the ER stress response and if we can mimic that safely. There are agents that have been used to activate ER stress pathways. So, I think the opportunity here would be to find ways to turn on this pathway in a very controlled way to get enough of this subsequent FGF21 response in muscle to be of benefit."