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- What Causes the Chronic Inflammation of Aging?
- Mitochondrial Peptides and the Still Unrealized Vision of Therapeutic Autophagy
- How Much of the Effect of Calorie Restriction is Due to Suppression of Senescent Cells?
- Results from a Preliminary Human Trial of Nicotinamide Riboside Supplementation
- An Interview on the Unknowns of the Epigenetic Clock
- A Short Report from the Undoing Aging Conference
- Vascular Degeneration in the Brain Correlates with Behavioral Change in Old Mice
- Ischemic Conditioning and Exercise as an Example of the Overlap Between Beneficial Stress Response Mechanisms
- An Early Test for Alzheimer's Disease, and Treatment with NSAIDs to Postpone Development of the Condition
- Comparative Biology and the Search for Longevity-Associated Genes
- An Interesting Programmed Aging View on Telomerase and the Epigenetic Clock
- The Rise of Oisin Biotechnologies
- Engineering Greater Radiation Resistance may well Lead to a Slowing of Aging
- An Interview on Mitochondrial Decline in Aging and Neurodegeneration
- ADP Sensitivity in Muscle Mitochondria Declines with Age Independently of Fitness
What Causes the Chronic Inflammation of Aging?
Many mechanisms of aging are two-way streets: A accelerates B, but B also makes A worse. Or A leads to B that causes C which aggravates A. Chronic inflammation, a persistent and damaging activation of the immune system, is a player in many of these sorts of circular relationships and feedback loops. The open access paper noted here briefly covers some of the known contributions to increased inflammation in aging. Inflammation is a vital part of the way in which the immune system coordinates with tissues in order to repel invaders and respond to injury; it is beneficial when temporary. When inflammation is constant, however, regeneration and tissue maintenance start to run awry, cancer rates rise, and many disease processes accelerate. Among the inflammatory conditions of aging are found osteoarthritis, the many forms of fibrosis, near all neurodegenerative diseases, atherosclerosis, and more.
What causes the raised level of chronic inflammation found in older people? Well, at root the forms of molecular damage outlined in the SENS view of rejuvenation biotechnology, but the line between root cause and age-related inflammation is only clear and direct in a couple of cases. Aging is a spreading, vastly complex network of many layers of cause and effect, branching out from the few fundamental forms of tissue damage, influencing one another along the way. So there are few simple answers when it comes to the proximate causes of chronic inflammation - they are very complicated in their details. It is easy enough to say that a part of it is the signaling of senescent cells, and a part of it is particular to the way in which the immune system runs down and malfunctions in later life. But those short sentences cover a ferociously complex biochemistry that is only partially understood.
There are a few simple ways forward towards effective control of some of the sources of inflammation in aging, however. Selectively destroying senescent cells removes their inflammatory influence without having to understand the details. Similarly, clearing out all immune cells while using cell therapy to speed their replacement is a viable approach to some of the issues in the aged immune system that result in higher levels of inflammation. Restoring the ability of the thymus to produce a larger supply of new immune cells is probably also useful. These and a few other plausible approaches don't require a great deal of new knowledge and largely bypass the state of ignorance regarding the biochemical details of inflammatory aging. Sometimes it doesn't matter why something takes place, given a comprehensive enough approach to removing it or otherwise dealing with it.
Source of Chronic Inflammation in Aging
At present, chronic inflammation is thought to be a risk factor for a broad range of age-related diseases such as hypertension, diabetes, atherosclerosis, and cancer. The burdens of unhealthy aging associated with lifestyle are increasing, both in developed and developing regions. Therefore, the elucidation of the sources and cellular pathways/processes of chronic inflammation is an urgent task.
There are several possible factors that initiate and maintain a low-grade inflammatory response. These include aging, unbalanced diet, low level of sex hormones, and smoking. In contrast to young individuals, aged individuals have consistently elevated levels of inflammatory cytokines, especially interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), which may induce muscle atrophy and cancer through DNA damage. Visceral fat tissue from obese individuals can also produce both IL-6 and TNF-α, affecting systemic metabolism. The accumulation of macrophages in visceral fat seems to be proportional to body mass index and appears to be a major source of low-grade persistent, systemic inflammation and insulin resistance in obese individuals. Chronic smoking increases production of several pro-inflammatory cytokines such as IL-6, TNF-α, and interleukin-1β (IL-1β), increases systemic inflammation and is an independent risk factor for several lifestyle-related diseases.
Acute inflammation is indispensable for immune responses to invading pathogens or acute traumatic injuries. This process enables repair and cell turnover in multiple tissues. In contrast, chronic inflammation normally causes low-grade and persistent inflammation, leading to tissue degeneration. Chronic, low-grade inflammation is a crucial contributor to various age-related pathologies and natural processes in aging tissue, including the nervous and the musculoskeletal system. Many tissues in the elderly are chronically inflamed, and inflammatory cytokines such as IL-6, IL-1β, and TNF-α are known to weaken the anabolic signaling cascade, including insulin and erythropoietin signaling, leading to the development of sarcopenia.
Debris and immunoglobulin accumulation due to inappropriate cell elimination systems in aging trigger the innate immune system activation leading to persist inflammation. Among the complex determinants of aging, mitochondrial dysfunction has attracted attention for some time. The consequences of age-related failing mitochondrial quality control include the release of mitochondria-derived damage-associated molecular patterns (DAMPs). Mitochondrial DAMPs, especially cell-free circulating mitochondrial DNA, have recently become the subject of intensive research because of their possible involvement in conditions associated with inflammation, such as aging and degenerative diseases. Through their bacterial ancestry, these molecules contribute to increasing an inflammatory response by interacting with receptors similar to those involved in pathogen-associated responses.
The barrier of the oral and gut mucosa against bacterial invasion deteriorates with age. Periodontal disease has also demonstrated to cause chronic low-grade inflammation. The gut microbiota of elderly people displays decreased diversity. The abundance of anti-inflammatory microbiota are diminished in aged individuals. Conversely, inflammatory and pathogenic microbiota are increased with age.
Cellular senescence is defined as irreversible cell cycle arrest driven by a variety of mechanisms. It is evident that the number of senescent cells in several organs increases with age; these cells secrete multiple inflammatory cytokines, generating low-grade inflammation. This phenotype of senescent cells is termed the senescence-associated secretory phenotype or SASP, which recently has been proposed as the main origin of inflammaging in both aging and age-related diseases such as atherosclerosis, cancer, and diabetes. Increasing evidence has suggested that the clearance of senescent cells in animal models attenuates the progression of age-related disorders, including atherosclerosis and osteoarthritis. These data strongly support the hypothesis that senescent cell clearance, reprogramming of senescent cells, and the modulation of pro-inflammatory pathways related to the acquisition of SASP might be pursued as potential anti-aging strategies for combating age-related diseases and expanding the health span of humans.
"Immunosenescence", which is the age-related dysregulation of an innate immune system, is characterized by persistent inflammatory responses. Immunosenescence increases the susceptibility to malignancy, autoimmunity, and infections; decreases the response to vaccinations; and impairs wound healing. Conversely, chronic inflammatory disease can accelerate the "immunosenescence" process. The mechanisms that underlie this persistent aging-associated inflammation remain incompletely understood but seem to involve changes in the numbers and functions of innate immune cells. Changes in the expression of pattern recognition receptors (PRRs), activation of PRRs by endogenous ligands associated with cellular damage, and unusual downstream signaling events of PRRs activation have been implicated to induce chronic cytokine secretion. Thus, together with cell senescence, dysregulation of immunological imprinting mediated by trained innate immunity might also contribute to persistent low-grade inflammation that occurs even after the initial stimulus has been removed.
Mitochondrial Peptides and the Still Unrealized Vision of Therapeutic Autophagy
Researchers have been talking about therapies based on enhanced levels of autophagy for about as long as I've been paying attention to the field of aging research. Autophagy is a collection of processes responsible for breaking down and recycling damaged structures and unwanted proteins in cells. More aggressively removing harmful or malfunctioning cellular systems and wastes reduces the amount of time they exist to cause problems, and results in better functioning of cells and tissues. Ultimately, more autophagy modestly slows aging and allows individuals to live longer. Many of the varied methods of manipulating metabolism to slow aging demonstrated over the past few decades appear to either depend on autophagy or include increased autophagy among their mechanisms of action.
Despite all of the talking - and the many papers and years of work examining various controlling mechanisms associated with autophagy - there is as yet no real progress towards therapeutics that work via the deliberate, targeted upregulation of autophagy. That is if we don't count things like calorie restriction mimetics, which improve autophagy along the way of changing many other aspects of metabolism. Calorie restriction itself appears to stop producing benefits to health if autophagy is disabled. Calorie restriction mimetics are not really all that solidified yet as a class of therapeutic, however. The most compelling, such as mTOR inhibitors, have significant side-effects that are still being worked around. The rest are largely so marginal or the data for positive effects in animal studies so unreliable as to be unworthy of serious consideration in a world in which one can just eat less and definitely benefit from it.
The editorial here (still in PDF format only at the time of writing) presents a more recent example of research aimed at identifying targets for the therapeutic enhancement of autophagy. It is similar in tone and scope to a dozen others I've seen over the years, and little has come of them as of yet - even the important work from a decade ago, showing restoration of liver function in old mice. The research community, for reasons that remain unclear to me, seems challenged when it comes to moving beyond mapping and investigation in order to build something of practical use on the foundation provided by this part of the field.
Humanin enhances the cellular response to stress by activation of chaperone-mediated autophagy
Increased oxidative stress and loss of proteostasis are characteristics of aging. Failure to remove the oxidative stress-damaged components has been recognized to play critical roles in the pathophysiology of common age-related disorders including neurodegenerative disease and cardiovascular diseases such as myocardial infarction and heart failure. Strategies to diminish oxidative stress or effectively eliminate oxidative-damaged intracellular proteins may therefore provide novel therapeutic option for many age-related diseases.
Chaperone-mediated autophagy (CMA) allows for selective degradation of soluble proteins in lysosomes, contributing to the cellular quality control and maintenance of cellular energetic balance. CMA substrate proteins are targeted by the chaperone hsc70 to the lysosomal surface where, upon binding to the lysosome-associated membrane protein type 2A (LAMP2A), they are translocated into the lysosomal lumen for degradation. CMA is activated by oxidative stress to facilitate degradation of damaged proteins, thereby eliminating the insults of oxidative stress. Given the fact that CMA activity declines with age, and oxidative damage in cells increases during aging, CMA activators hold the potential for development as a new generation of treatment option for age-related diseases.
In our recent study, we identified that humanin (HN), an antiapoptotic, mitochondria-associated peptide is an endogenous CMA activator. We demonstrated that HN protects multiple cell types including cardiomyoblasts, primary cardiomyocytes and dopaminergic neuronal cells from oxidative stress-induced cell death in a CMA dependent manner. In fact, this protective effect is lost in CMA-incompetent cells (LAMP-2A knockdown). Both exogenously added HN as well as the endogenously generated HN cooperate in CMA activation. Thus, knockdown of endogenous HN decreases CMA activation in response to oxidative stress. Both endogenous and exogenous HN localize at the lysosomal membrane where they cooperate to enhance CMA efficiency. HN acts by stabilizing binding of the chaperone HSP90 to the upcoming substrates at the cytosolic side of lysosomal membrane.
Our study provided the first evidence that regulatory signals from mitochondria can control CMA. We propose that while generating reactive oxygen species (ROS) from metabolism, mitochondria simultaneously initiates signals such as HN to eliminate ROS by increasing antioxidant enzyme activities, and decrease oxidative insults by activating CMA, and that perturbations in this process could cause accumulation of oxidative damage leading to cell death and human diseases. It is interesting to note that HN and CMA both decline with age and that genetic correction of the CMA defect in livers from old mice was effective in improving hepatic homeostasis, conferring higher resistance to stress and improved organ function.
We propose that interventions aimed to enhance mitochondrial peptide HN levels could have a similar effect, and protect against oxidative stress by enhancing removal of oxidative-damage proteins through CMA. Whether this is a unique function of HN, or is shared by other mitochondria-encoded peptides such as small humanin like peptides (SHLPS) requires future investigation. Efforts should be directed to testing a possible protective effect of HN in age-related diseases with a primary defect on CMA such as Parkinson's disease.
How Much of the Effect of Calorie Restriction is Due to Suppression of Senescent Cells?
The paper I'll point out today reports on the effects of calorie restriction in mice and humans on markers of cellular senescence, one of the contributing cause of aging. Calorie restriction is well known to slow aging and extend life span in a near all species and lineages tested, with that effect being largest in short-lived species. Mice live up to 40% longer when calorie restricted, but in humans it would be surprising to find an effect larger than five years or so - once firm data is in hand, which is not presently the case. Nonetheless, the short term benefits to health and the changes to cellular metabolism produced by the practice of calorie restriction are quite similar across mammalian species of different life spans.
These are sweeping changes: near every measure of metabolic activity and progression of aging is altered by calorie restriction. Given that, it is challenging to identify the size of the contribution of any given mechanism, but it is certainly fair to ask. To what degree does calorie restriction act through a reduction of each of the forms of cell and tissue damage that cause aging? One of the forms of damage is an accumulation of senescent cells. Cellular senescence is a fascinating phenomenon with both positive and negative outcomes; it is beneficial when temporary, as cells briefly become senescent in order to aid in regeneration or reduce the risk of damaged cells becoming cancerous. When senescent cells fail to quickly self-destruct, however, they linger to cause harm to surrounding tissue. Their signals generate chronic inflammation, destroy important molecular structures, and change the behavior of other cells for the worse.
Removing all senescent cells increases mouse life span by 25%, calorie restriction increases mouse life span by 40%, and calorie restricted mice still have some number of senescent cells. From a first glance at the numbers and the existing evidence, reduced cellular senescence can only only account for a modest fraction of the benefits of calorie restriction. In line with that, the paper noted here shows that calorie restricted mice and humans appear to have fewer signs of senescent cell activity, consistent with reductions in all of the other measures of age-related damage under calorie restriction.
The interesting question is how exactly calorie restriction produces this outcome. Fewer cells become senescent? More senescent cells successfully self-destruct? Individual senescent cells are less actively harmful, and their signaling is reduced? One item to bear in mind while thinking about this is the evidence for the benefits of calorie restriction to be absolutely reliant upon autophagy - increased autophagy is a feature of calorie restriction, as well as many other methods of slowing aging, and in animals in which autophagy is disabled, calorie restriction does not improve life span or health. So it seems to me that any consideration of calorie restriction and cellular senescence must in some way involve autophagy.
The effects of graded caloric restriction: XII. Comparison of mouse to human impact on cellular senescence in the colon
While genetic manipulations of model organisms have set important milestones for the understanding of the aging process, calorie restriction (CR) is a well-established nongenetic approach able to improve health span and lifespan in different organisms. However, the precise mechanisms by which CR improves health are not fully understood. More than 50 years ago, cellular senescence was discovered. Subsequent studies demonstrated that senescent cells gradually accumulate with increasing age in various organisms. During aging, senescent cells impair cellular turnover and tissue regeneration due to their inability to proliferate, and stimulate a pro-disease environment by the chronic secretion of various pro-inflammatory and tissue-remodeling factors, a phenotype called Senescence-Associated Secretory Phenotype (SASP).
Genetic and pharmacological elimination of senescent cells is sufficient to improve health span. Interestingly, a previous report suggested that CR prevented accumulation of senescent cells in the mouse liver and intestine. To further explore the potential reduction in senescent cells upon short-term CR, and whether this phenomenon might potentially happen in humans, we analyze various classical transcriptomic markers for senescence and SASP in short-term CR interventions in the mouse and human colon mucosa specimens.
Male mice were aged 20 weeks when they entered four levels of CR for 12 weeks: 10%, 20%, 30%, and 40% restriction from baseline food intake. The colon of these mice was divided into three regions: proximal, medial, and distal. In the proximal colon, the expression levels of two classical markers of senescence-associated growth arrest, p16 and p21, did not change significantly among groups. Selected markers for the SASP also did not significantly change. In the medial colon, while there were no differences among the two controls and the lowest CR interventions (10%-20%), all markers of senescence were downregulated at higher CR regimens. A similar trend was present in the distal colon. These data suggest that short-term CR at higher levels can prevent or decrease the accumulation of senescent cells in the mouse colon, even in adult but relatively young animals on short-term restriction.
We then sought to determine whether CR modifies the expression levels of senescence and SASP markers in the human sigmoidal colon mucosa. To this end, we recruited and studied 12 middle-aged (61.7 ± 8.4 years), weight-stable very lean (BMI = 19.1 ± 1.3 kg/m2) members of the Calorie Restriction Society who have been practicing ~30% CR with adequate nutrition (at least 100% of RDI for each nutrient) for an average of 10.1 years. Levels of p16 were significantly lower in the CR group. Levels of p21 followed the trend observed in p16, but did not reach statistical significance. In accordance with a previous study, we observed significantly lower level of SASP factors, but only three reached statistical significance. These data suggest that CR could potentially prevent the accumulation of age-associated senescent cells in the colon mucosa of human beings, and the reduction in senescence might explain the much lower levels of inflammation observed in CR individuals.
Results from a Preliminary Human Trial of Nicotinamide Riboside Supplementation
What sort of evidence would it take to challenge my assessment of the data to date that methods of raising NAD+ levels with age, such as nicotinamide riboside supplementation, are not worth pursuing as a major area of focus in research and development? Given the history of work in this area of metabolism, mostly that relating directly to sirtuins and their manipulation, one has to be a little skeptical. Initially promising (and overhyped) results in mice went essentially nowhere, or turned out to make the condition of obesity a little less harmful, while showing little evidence of utility for healthy individuals.
To answer the question, human data showing meaningful benefits that could not be achieved via exercise or calorie restriction would be very interesting. Human data showing some reliable level of reproduction of the benefits of exercise or calorie restriction without side-effects would be good news for the present majority who don't put in the effort to stay in shape. Good news for supplement sellers as well - there is no shortage of people who would pay rather than exercise or eat less, even if the results were mixed or marginal.
In either case, the cost-benefit analysis runs along the lines of (a) as an individual, how much it is worth spending on a supplement that can capture a fraction of the benefits of exercise or calorie restriction, but also (b) is it worth making this a major focus of the research community, versus the rejuvenation biotechnology that can achieve far greater gains? I think (b) is always going to be answered in the negative, for me at least. No calorie restriction mimetic or exercise mimetic can possibly be as good as functional SENS repair biotechnologies. They cannot achieve the results produced by senolytics, or any of the other ways to remove the root causes of aging. If one looks at NAD+ research as the final stage of sirtuin-related calorie restriction research as a whole, it has taken as much funding to get here as it would to completely implement the SENS rejuvenation therapy package in mice. Yet we know that exercise and calorie restriction cannot add decades to healthy life, as is possible in principle for repair therapies.
The data here on human nicotinamide riboside supplementation seems promising in comparison to the results of past sirtuin research, but I'd like to see a larger study group. If that larger group shows similar results, then maybe this is worth it for individuals. Either way, it is appreciated that the authors avoided running a study in overweight individuals - in this part of the field, that just muddies the waters, given the very different effects of sirtuin manipulation on thin versus fat animals. Nonetheless, it still appears to be the case that this is essentially a way to gain some of the beneficial long-term effects of fitness without putting in the physical effort. I expect future NAD+ studies and exercise studies in older individuals to converge in some ways, showing overlapping effects on cellular biochemistry. It is arguable as to whether taking up exercise, eating less, or artificially increasing NAD+ levels should be termed rejuvenation. There is certainly a sizable grey area at the intersection of repair, compensation, and overriding regulatory signals that respond to aging.
A pill that staves off aging? It's on the horizon
Scientists have long known that restricting calories can fend off physiological signs of aging. A new study indicates that when people consume a natural dietary supplement called nicotinamide riboside (NR) daily, it mimics caloric restriction, aka CR, kick-starting the same key chemical pathways responsible for its health benefits. "This was the first ever study to give this novel compound to humans over a period of time. We found that it is well tolerated and appears to activate some of the same key biological pathways that calorie restriction does."
Researchers included 24 lean and healthy men and women ages 55 to 79. Half were given a placebo for six weeks, then took a 500 mg twice-daily dose of nicotinamide riboside (NR) chloride (NIAGEN). The other half took NR for the first six weeks, followed by placebo. The researchers took blood samples and other physiological measurements at the end of each treatment period. Participants reported no serious adverse effects. The researchers found that 1,000 mg daily of NR boosted levels of another compound called nicotinamide adenine dinucleotide (NAD+) by 60 percent. NAD+ is required for activation of enzymes called sirtuins, which are largely credited with the beneficial effects of calorie restriction. It's involved in a host of metabolic actions throughout the body, but it tends to decline with age.
Research suggests that as an evolutionary survival mechanism, the body conserves NAD+ when subjected to calorie restriction. But only recently have scientists begun to explore the idea of supplementing with so-called "NAD+-precursors" like NR to promote healthy aging. "The idea is that by supplementing older adults with NR, we are not only restoring something that is lost with aging (NAD+), but we could potentially be ramping up the activity of enzymes responsible for helping protect our bodies from stress."
The new study also found that in 13 participants with elevated blood pressure or stage 1 hypertension (120-139/80-89 mmHg), systolic blood pressure was about 10 points lower after supplementation. A drop of that magnitude could translate to a 25 percent reduction in heart attack risk. "If this magnitude of systolic blood pressure reduction with NR supplementation is confirmed in a larger clinical trial, such an effect could have broad biomedical implications."
Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults
Nicotinamide adenine dinucleotide (NAD+) has emerged as a critical co-substrate for enzymes involved in the beneficial effects of regular calorie restriction on healthspan. As such, the use of NAD+ precursors to augment NAD+ bioavailability has been proposed as a strategy for improving cardiovascular and other physiological functions with aging in humans. Here we provide the evidence in a 2 × 6-week randomized, double-blind, placebo-controlled, crossover clinical trial that chronic supplementation with the NAD+ precursor vitamin, nicotinamide riboside (NR), is well tolerated and effectively stimulates NAD+ metabolism in healthy middle-aged and older adults.
Our results also provide initial insight into the effects of chronic NR supplementation on physiological function in humans, and suggest that, in particular, future clinical trials should further assess the potential benefits of NR for reducing blood pressure and arterial stiffness in this group.
An Interview on the Unknowns of the Epigenetic Clock
The Life Extension Advocacy Foundation volunteers have a stack of interview materials piled up from the recent Undoing Aging conference, I'll wager. Today they published a lengthy interview with Steve Horvath, originator of one of the epigenetic clocks that assess age based on patterns of DNA methylation. I have to say that it is a pleasure to see so many researchers now willing to talk openly about therapies for aging and their hopes for the future of the field. For so very many years that just didn't happen; no researcher was willing to speak in public on the topic of treating aging as a medical condition and extending healthy life.
When I first become interested in this field, the research and funding institutions that dominated the study of aging were quite hostile towards anyone who wanted to intervene in the aging process and thereby produce longer lives in patients. Thankfully, times have certainly changed since then, and for that we can thank the hard-working community of advocates, scientists, and philanthropists who have since the turn of the century built funding and support for rejuvenation biotechnology, and for the transformation of medical science through the treatment of aging.
The Horvath epigenetic clock has a commercial implementation, myDNAage, produced by Zymo Research. The folk there claim it to be quite stable over time and circumstances in its assessment, with a margin of error of 1.7 years. As noted in the interview, it is one thing to have a metric that maps to age quite well, and shows some signs of reflecting biological age versus chronological age, but it is quite another to know what it is actually measuring. These changes in DNA methylation are some reflection of the growing damage and dysfunction of aging, but are they a very selective reflection? What if it is found that when a human undergoes a senolytic therapy to remove senescent cells, one of the root causes of aging, that before and after measures of epigenetic age are the same? That would be an interesting outcome, and we're about to find out, but what could we learn from it? This result seems unlikely given that cellular senescence appears to contribute to many aspects of age-related decline, but it isn't impossible. Researchers really don't know whether the epigenetic clock reflects one or many of the underlying aspects of aging.
Science and medicine are often a process of starting at the ends and meeting in the middle. A list of the root causes of aging exist, and measures of the state of aging exist, but there is not good map to link those two. Aging progresses in a very complex way, even though it is caused by comparatively simple and easily understood processes, because our biology is very complex. The fastest way to build rejuvenation therapies and metrics to measure the results of rejuvenation therapies is to start on both lines of research and development at the same time, and compare the results against one another. Iteration on this theme will find the path ahead, and allow unhelpful approaches to be discarded earlier rather than later.
Steve Horvath - Aging and the Epigenetic Clocks
Why is the epigenetic clock more accurate than measuring telomere length?
Yes, it is far more accurate, there is no comparison. Why is a good question. In my opinion, it shows that epigenetic changes are far more important for aging than telomere maintenance. People have studied telomeres for many years, including me, but telomere shortening alone does not explain aging. You may know that mice have perfect telomeres, but they only live three years.
It's known that cells in our body are renewed at different speeds; why does your clock measure the age of the tissue or whole organ and not the age of specific cells?
Actually, it does measure the age of specific cells. You can have liver cells, and the epigenetic clock works beautifully. It also works very well for neurons and glial cells. Even in blood, you can have sorted blood, for example T cells or B cells, and the clock works on those cells.
Does your clock represent aging?
This is a good question with two answers. One way to ask this question is to ask if methylation changes cause aging. And we honestly don't know; there is no data. The other question to ask is if the epigenetic clock is the indicator of a biochemical process that plays a role in aging. Which I think it is; it is a biomarker of a process. There is no question that this process that underlies the clock, that if you target this process, you slow aging; this, we know.
What is going to happen if we influence this methylation process?
With the methylation process, we don't know. Imagine that you have a clock; there is the clock face with the dials, and then there is the clockwork. The discussion with the epigenetic clock is whether methylation is part of the dial or is it part of the clockwork. There is no doubt that it is part of the dial, and if you interfere with the clockwork, there is no question you that rejuvenate people. But it could be that the clockwork might not be the same as methylation; we are not sure. With a clock face, you can just take the hands and move them, but it may do nothing to actual time. Behind the clock, there is the clockwork, and we don't completely understand the clockwork. A lot of people are asking about it, but we just don't know yet.
Can we slow down aging now?
I want to tell you that I am very optimistic and that we will have treatments against aging in a few years. I could be wrong, and I want to be cautious, but I want to tell you that I am very optimistic because we already have encouraging results. We already have treatments that have a huge effect, like the Yamanaka factors in mice, but also in human cells. If you use Yamanaka factors on human cells, it completely reverses their age. The problem is how to make them safe.
My hope is that maybe even our generation will benefit from it; certainly, my daughter should benefit from it. I would be absolutely shocked if the next generation does not live twenty years longer. On that level, I am very optimistic. If you ask me right now what you should do, I can only tell you boring things; immediately stop smoking, avoid obesity, avoid diabetes; if you are a diabetic, manage it; avoid high blood pressure, and if you have it, take action. It is boring, but all my studies show that this is the best thing we can do now.
What are the main challenges in your research in aging?
Scientific challenges, honestly I don't have them. Because there is so much work to do and I have a good plan, it is not a problem. Financially, there is a challenge; research is expensive, especially human trials. I have a very exciting collaboration with a company which has an anti-aging treatment, and to test it will cost three million in funding. So, as you can imagine, money is the challenge.
A Short Report from the Undoing Aging Conference
The LongLongLife team here reports briefly on their time at the recent Undoing Aging conference. This was the first in a series of conferences, hosted jointly by the SENS Research Foundation and Forever Healthy Foundation, that will mix the scientific and academic focus of the SENS rejuvenation research conferences with the biotechnology industry focus of the Rejuvenation Biotechnology conferences. By all accounts the initial Undoing Aging event was well received.
The very first Undoing Aging Congress was held in March 2018 in Berlin, and was attended by 350 people from a total of 36 countries. Initiated by Aubrey de Grey, co-founder of the SENS Research Foundation, and Michael Greve, founder and CEO of the Forever Healthy Foundation, the conference focused on the most promising advances in anti-aging research. The congress, which lasted for three days, was divided into different sessions, each of which dealt with a specific theme of anti-aging research. Among the major issues were regenerative medicine, the elimination of senescent cells, cancer therapies, and biomarkers of aging.
Dr. Doug Ethell, founder and director of Leucadia Therapeutics, linked the site of the development of Alzheimer's disease in the brain to the presence of a porous bone plate at the same site that drains the cerebrospinal fluid (fluid that cleanses the intercellular space of the brain). With age, this bone plate becomes blocked, no longer allowing the toxic metabolites carried by the cerebrospinal fluid to pass. The accumulation of these wastes would lead to the formation of plaques, at the origin of the development of the disease. Leucadia Therapeutics has developed a therapeutic device which restores the flow of cerebrospinal fluid and the elimination of toxic metabolites. Dr. Ethell hopes clinical trials can begin in 2019.
Transthyrethin amyloidosis is a rare disease in two forms (cardiomyopathy and polyneuropathy) and develops with age. It is caused by the accumulation of transthyretin protein (TTR) incorrectly folded into amyloid plaques. There is currently no FDA approved treatment for this disease. Dr. Isabella Graef, co-founder of Eidos Therapeutics, explained how her laboratory discovered a drug candidate that could work on both forms of the disease. It is a small molecule that can bind and stabilize TTR, preventing the formation of amyloid plaque, and which could stop the progression of the disease. This molecule has been in phase 1 clinical trials (trials on healthy subjects) since 2017.
Regenerative medicine aims to create new tissues or organs to replace defective ones. This medicine is booming and the technological processes that allow its development are constantly progressing. Dr. Eric Lagasse of the University of Pittsburgh presented at the congress the work of his LyGenesis laboratory, which has developed a technology to generate the liver from lymph nodes. The goal of the method is to transplant healthy hepatocyte cells into the lymph nodes, resulting in the generation functional liver tissue. This technology has already shown its effectiveness in mice and pigs.
Dr. Steve Horvath, a professor at the University of California at Los Angeles, has a long history of working on biomarkers of aging. He is behind Horvath's epigenetic clock, which predicts biological age as a function of genome methylation. Predicting biological age using methylation is now the most accurate way, says Dr. Horvath. He proposes that DNA methylation should be measured in clinical trials as part of the fight against aging. Finally, his goal by 2021 is to develop an epigenetic clock that applies to all mammals.
Vascular Degeneration in the Brain Correlates with Behavioral Change in Old Mice
The research here is an interesting view on the relevance of vascular aging in cognitive decline and later dementia. The researchers find similar changes in blood vessels in both old mice and mice engineered to undergo the amyloid and tau aggregation characteristic of human Alzheimer's disease. In humans, a sizable proportion of people suffering Alzheimer's disease also have vascular dementia - one of the many challenges facing any group trying to prove success in a therapy intended to narrowly address aspects of Alzheimer's biochemistry. That success, if it takes place at all, could well be masked in many patients by the loss of function that results from vascular aging.
With age, blood vessels stiffen and are weakened by corrosive fatty deposits. Blood pressure rises, causing an increase in the breakage of small blood vessels and consequent damage to surrounding tissue. The heart weakens. Capillary growth into tissues declines for reasons that are still comparatively poorly understood. Further, the amyloid associated with Alzheimer's can also emerge in blood vessels and cause dysfunctional behavior there. The brain is an energy-hungry organ, and all of these problems combine to reduce the supply of needed oxygen and nutrients. Dementia is the end result. That so many of these processes of harm are accelerated by chronic inflammation, such as that produced by excess fat tissue, is why a number of forms of dementia appear to have a strong lifestyle component - Alzheimer's included.
Researchers have demonstrated for the first time that anxiety and problems with blood vessels present a close relationship with Alzheimer's disease, which particularly affects females. Vascular disease resulting from oxidative stress and inflammation is gaining clinical interest, given that subsequent cardiovascular insufficiency can alter the blood flow distribution to different organs and tissues, including the brain, which can worsen a pathology related to this type of dementia.
The research provides the first evidence that mice of advanced ages suffering from Alzheimer's disease present substantial alterations in small blood vessels, which are essential in nourishing different organs and tissues and in the regulation of blood pressure. "The study demonstrates that the sex of the mice is a determining factor. It is specifically the female mice which show more pronounced vascular alterations, which suggests that women of advanced ages suffering from Alzheimer's disease may suffer more from cardiovascular malfunctions."
The characteristics of small arteries were studied under different physiological conditions. Further research revealed that these vascular changes appear in both the vascular structure and function, which suggests an abnormal distribution in peripheral blood flow. Researchers also assessed animal behaviour. This allowed them to discover the existence of a strong relation between the vascular parameters analysed - structure, elasticity, function - and different patterns of anxiety in mice models of Alzheimer's, but also in mice ageing normally.
"Although we must be cautious with these results, the correlation of behaviours propose the existence of direct or indirect relations between conduct and the function of peripheral arteries. These interactions may be able to explain the anomalies of the neuro-immuno-endocrine system, which regulates the performance of different organs and tissues."
Ischemic Conditioning and Exercise as an Example of the Overlap Between Beneficial Stress Response Mechanisms
I point out this interesting open access paper not as a suggestion that anyone should consider trying remote ischemic conditioning - one should adopt some form of calorie restriction and greater levels of regular exercise before embarking upon fancier hobbies - but rather because it is illustrative of the degree to which common stress response mechanisms overlap. Heat, exercise, ischemia, and lack of nutrients all share some of the same channels of signal and response that lead to cells undertaking greater maintenance or building more robust tissue structures. That in turn means that we already have a fairly good idea of the plausible bounds on beneficial results when it comes to therapies that use pharmaceutical or other means to induce stress responses. They will be able to move people closer to the life trajectory of a very healthy, well maintained body, but more than that seems unlikely to be attained via this strategy.
Thirty years ago, researchers first discovered the phenomenon of ischemic pre-conditioning in an animal experiment. The seminal discovery that brief episodes of ischemia followed by reperfusion could significantly reduce myocardial infarct size gave rise to the area of myocardial protection firstly and then propagated to multi-organ protection. Ischemic preconditioning has evolved into remote ischemic conditioning (RIC). Although the underlying mechanisms of RIC are still unclear, it was found to be safe and well tolerated in both patients and healthy volunteers.
The use of long-term repeated RIC comes with the expectation that RIC can play its protective roles consistently; this RIC treatment protocol is now called chronic RIC. Clinical studies have demonstrated that chronic RIC could reduce adverse clinical events and improve neurological function, which was rare in previous studies using a once-only RIC treatment protocol. Intriguingly, some sports specialists, inspired by the favorable effects of RIC on skeletal muscles and endothelial function, applied RIC to exercise training, as intense exercise has been demonstrated to lead to a form of cardiac and skeletal muscles ischemic insult. To date, RIC has been shown to improve the maximal performance in highly trained swimmers, enhance 5-km time trial performance and attenuate the submaximal level of blood lactate during the incremental running test. Therefore, RIC could improve exercise performance as does regular interval exercise training.
Given the similar time window of early and late phase protection seen with both exercise and RIC, and their comparable effects on improving exercise performance, it is reasonable to speculate that the underlying mechanisms of RIC likely overlap with those of exercise. Heat shock protein (HSP) 70 family, especially HSP72, has been demonstrated to be associated with cardioprotection. Previous studies found significantly increased HSP72 levels after acute aerobic exercise. Similarly, increased HSP72 has been reported after RIC stimulus. Studies have demonstrated that exercise promoted endothelial NO synthase activity, increased the production of NO and improved endothelial cell function. Similarly, chronic RIC has been demonstrated to significantly improve flow-mediated dilation and enhance endothelial NO synthase expression in patients with coronary heart disease.
Autophagy is a process for eliminating dysfunctional organelles and protein aggregates, which is a kind of endogenous protection and required for cellular survival and homeostasis in response to stress. Studies have found that protective effects of RIC on cell survival were mediated by autophagy pathway, and autophagy participants in RIC-induced protection. Exercise induces the adaptational response from multiple organs (primarily in skeletal muscle), which will benefit human body. Recently, autophagy has been found to be an essential process involved in conserving and recycling the cellular resources, an important process of the adaptation response.
Exercise has direct beneficial effects on the cellular immune system, and it can mobilize NK and T cells to circulation during exercise. The immune cell activity may also be influenced by the exercise-induced release of immune regulatory cytokines. Similarly, RIC has also been demonstrated to influence inflammatory response and immune cells, and these are the essential underlying mechanisms of RIC-induced protection. RIC reduces inflammatory gene expression and dramatically changes the immune response, which induces protection.
From the data available so far, it appears that chronic RIC mimics regular exercise. Further studies are however urgently needed to validate this phenomenon. However, there are still several hurdles for popularizing chronic RIC. Currently, different chronic RIC protocols are used in various studies, the periods of using chronic RIC vary from 1 week to 1 year, and its frequencies vary from twice daily to once every two weeks. Although chronic RIC benefits health and protects organs from injury, its optimal protocol is still unclear.
An Early Test for Alzheimer's Disease, and Treatment with NSAIDs to Postpone Development of the Condition
Alzheimer's disease, like most neurodegenerative conditions, has a strong inflammatory component. The importance of inflammation is one possible way to explain why Alzheimer's risk appears to have a significant lifestyle component: Alzheimer's disease is associated with excess visceral fat tissue and all of the choices made along the way of gaining and retaining that fat tissue. Fat tissue is a notable source of chronic inflammation, acting to accelerate all of the common process and conditions of aging. There are numerous other paths to inflammation, of course.
If chronic inflammation is important in Alzheimer's disease, how useful is a chronic anti-inflammatory treatment? Various groups have considered this over the years, but the one noted here appears more optimistic than most - and the data is fairly compelling. As an aside, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen have been shown to modestly slow aging and extend life in a few laboratory species, though the exact mechanisms are up for debate. I normally point this out to dampen enthusiasm for any novel pharmaceutical shown to have similarly sized effects in short-lived species - one shouldn't expect anything more interesting than NSAIDs to result, and the data to date suggests that NSAIDs don't in fact do a great deal for human life span. Can simple, proven methods of suppressing inflammation help people who are declining into Alzheimer's disease, however? That is a separate question, and it will be interesting to see how this line of research progresses.
In 1990, we wrote a short report indicating a substantial sparing of Alzheimer's disease (AD) in patients with rheumatoid arthritis. We suggested that anti-inflammatory therapy might be the explanation. We chose rheumatoid arthritis for the study since it typically commences at an earlier age than AD, and is universally treated with anti-inflammatory agents. Our report of AD sparing in patients consuming anti-inflammatory agents was soon confirmed in 17 epidemiological studies of patients consuming nonsteroidal anti-inflammatory drugs (NSAIDs) compared with controls. There was one consistent caveat in these epidemiological studies. The NSAIDs needed to have been started at least 6 months, and preferably as long as 5 years, before the clinical diagnosis of AD.
A new field of research had been opened up with these epidemiological studies. It required that some important questions be answered. Why was it necessary to commence taking NSAIDs so long before the clinical onset of AD? What was the appropriate NSAID dose? And was it necessary to take NSAIDs on a continuing basis? New techniques were required to provide answers to these questions. We emphasize here the two most important of these: positron emission tomography revealing that deposits of amyloid-β protein (Aβ) build up in the brain of AD cases; and cerebrospinal fluid (CSF) Aβ levels revealing their consequent reduction. These two techniques are complementary. Since the brain Aβ deposits accumulate over time, the effect is integral. Since CSF turns over every few hours, the effect is differential.
Disease development, as revealed by biomarker studies, follows this sequence of events. It commences with Aβ deposits developing in the brain of AD cases. These deposits can be detected by positron emission tomography (PET). The depositions result in a concomitant decrease of Aβ in the CSF. Years later, less definitive biomarkers become positive. These later biomarkers reveal loss of brain tissue. When they become positive, cognitive deficits have already appeared. Together, these studies indicate that AD onset commences more than a decade before clinical signs develop. The ability to identify the onset of AD a decade or more before clinical signs appear creates a window of opportunity to intervene in the process. Moreover, it explains the epidemiological data in which NSAIDs must be commenced years before clinical detection. The missing link is a simple, non-invasive method for identifying those at risk at an age well below the typical age of AD onset.
Analysis of saliva for Aβ42 may provide the missing link. We first developed a simple method for determining Aβ42 levels in tissues as well as saliva. The results showed that Aβ42 is produced in all tissues of the body, and not just in brain as many have believed. Aβ42 secretion in saliva is a reflection of its production by submandibular glands. The non-AD cases resolved into two distinct categories: those with low levels in the 19-25 pg/ml range, and those with high levels in the AD range of 41-60 pg/ml. Significantly, there were no overlapping cases. Analysis of Aβ42 levels in saliva demonstrates three remarkable facts. Firstly, controls, who are not at risk for AD, secrete levels close to 20 pg/ml, regardless of sex or age. Secondly, this production is constant, being invariant with time of day, and from day to day. Thirdly, those at risk for AD secrete levels comparable to AD cases. Widespread application of this test to detect high levels, followed by NSAID consumption, could substantially reduce the prevalence of AD.
Comparative Biology and the Search for Longevity-Associated Genes
One of the primary goals of the aging research community is to determine exactly how aging progresses from moment to moment at the detailed level of genes and cellular biochemistry. This is a sizable task, not particularly driven by any application in medicine, and will be only incrementally more advanced by the time that rejuvenation therapies based on the SENS model of damage repair are a going concern. The big advantage of the damage repair approach is that it bypasses the need to understand exactly how aging progresses: since the root cause damage is known, it is possible to make progress immediately and quantify the resulting benefits along the way.
If one was to go about searching for genetic contributions to longevity, however, then the method here is a decent way to go about it. The standard problem in this space is one of complexity and limited resources: there are a lot of genes, and only so many scientists with sufficient funding to look for the needles in the haystack. The researchers here reduce the size of the problem by comparing the genomes of closely related rodent species with varying life spans; the set of genetic differences, much smaller than an entire rodent genome, should include those genes most influential on life span.
As an adaption to different environments rodents have evolved a wide range of lifespans. While most rodents are short-lived, along several phylogenetic branches long-lived species evolved. This provided us a unique opportunity to search for genes that are associated with enhanced longevity in mammals. Towards this, we computationally compared gene sequences of exceptional long-lived rodent species (like the naked mole-rat and chinchilla) and short-lived rodents (like rat and mouse) and identified those which evolved exceptionally fast. As natural selection acts in parallel on a multitude of phenotypes, only a subset of the identified genes is probably associated with enhanced longevity.
A set of 250 identified positively selected genes (PSGs) in liver tissue exhibited a highly significant pattern of down-regulation in the long-lived naked mole-rat and up-regulation in the short-lived rat, fitting the antagonistic pleiotropy theory of aging. Moreover, we found the PSGs to be enriched for genes known to be related to aging. Among these enrichments were "cellular respiration" and "metal ion homeostasis", as well as functional terms associated with processes regulated by the mTOR pathway: translation, autophagy, and inflammation. Remarkably, among PSGs are RHEB, a regulator of mTOR, and IGF1, both central components of aging-relevant pathways, as well as genes yet unknown to be aging-associated but representing convincing functional candidates, e.g. RHEBL1, AMHR2, PSMG1 and AGER.
We conclude that lifespan extension in rodents can be attributed to changes in their defense against free radicals, iron homeostasis as well as cellular respiration and translation as central parts of the growth program. This confirms aging theories assuming a tradeoff between fast growth and long lifespan. Moreover, our study offers a meaningful resource of targets, i.e. genes and specific positions therein, for functional follow-up studies on their potential roles in the determination of lifespan-regardless whether they are currently known to be aging-related or not.
An Interesting Programmed Aging View on Telomerase and the Epigenetic Clock
The author noted here sees aging as programmed, in the sense that it is an epigenetic program selected for by evolution because shorter life spans prevent population-level ecological issues. His writing is usually a good illustration of how this concept of aging as a selected epigenetic program leads to very different conclusions on the nature of aging as a whole, as well as on any specific research result. In the case of this post, the topic is the role of telomere length and telomerase in aging, and their relationship to the established DNA methylation biomarkers of aging.
The mainstream view of epigenetic change with age is that it is a reaction to accumulated cell and tissue damage, one that evolved in the limited selection pressure thought to characterize post-reproductive life span. Both damage and epigenetic changes are components of a decline that is an accidental outcome of the aggressive selection for success in early life. Evolution produces biological systems that do well initially, then corrode and fail in a haphazard fashion, because there was no selection for long-term function. Thus systems that generate damage as a side-effect of normal operation, and systems that have limited capacity that fills up and causes issues in later life are found everywhere in our biology.
The debate over programmed versus non-programmed aging, and the ordering of cause and effect between cell and tissue damage versus epigenetic change, will be settled over the next decade or two. If one side produces therapies that revert epigenetic changes and the other side produces therapies that repair cell and tissue damage, then simple observation of the results will determine who is right. The greatest extension of life span and health will point the way to the correct interpretation of the process of aging.
Just a few weeks ago, I learned of a new study linking telomerase to the changes in DNA methylation that the epigenetic clock associates with aging. The implication is that telomerase accelerates aging. It began with an investigation asking what genetic variations are associated with people who age faster or slower than average, according to the epigenetic clock? Researchers performed a genome-wide search for statistical correlates and the standout association was telomerase. People who have small genetic variations that support greater telomerase expression tend to have longer telomeres, but they also tend to age faster, as measured by the epigenetic clock.
The association between telomerase and accelerated aging (measured by methylation) was found in the genetic statistics, and then confirmed in a cell culture. When telomerase was artificially activated in the cell culture, the methylation patterns changed in the cells consistent with older age according to the epigenetic clock. In fact (and remarkably in my opinion) they found no epigenetic aging at all in the cell cultures that lacked telomerase. Could it be that telomerase is the one and only driver of epigenetic aging at the cellular level?
So, what's going on? My inclination is always to think in evolutionary terms. Fixed lifespan, (especially when modified conditions of food stress) is helpful in preventing population overshoot that can lead to famines, epidemics, and extinction. But whenever a trait is good for the community and bad for the individual, there is a temptation for the individual to cheat. In this case, cheating would mean evolving a longer lifespan via selfish genes, such as those enabling greater telomerase expression, that spread rapidly through the population. Individual competition would erase aging if left unchecked. The results would be great for individual fitness, but soon would be disastrous for the population. Thus evolution places barriers in the way of individual selection for ever longer lifespan.
My guess is that the connection between telomerase and epigenetic aging is an example of antagonistic pleiotropy crafted by natural selection in its long-term mode. Limiting lifespan has been so important to the viability of the population that evolution has arranged to protect it from leaking away due to cheating, and antagonistic pleiotropy is one of the ways in which this is arranged. I believe that the preponderance of evidence still indicates that activating telomerase has a net benefit for lifespan, but that probably we can add at most a few years by this route. I think that epigenetics is much closer to the core, the origin of aging, and that interventions to modify epigenetic aging will eventually be our holy grail.
The Rise of Oisin Biotechnologies
This recent interview with Gary Hudson of Oisin Biotechnologies covers a range of topics; there is a lot more to it than is quoted here. The company is working on the application of a programmable gene therapy to the targeted destruction of senescent and cancerous cells. Since the approach can be adjusted to kill cells that express significant amounts of any arbitrarily selected target protein, it can in principle be adapted to destroy other types of unwanted cell. The immune system in older individuals or patients with autoimmune diseases, for example, contains any number of problem cells that it would be beneficial to remove. As noted in the interview, destruction is only one possibility, however. Cells could be enhanced or have their behavior changed in other ways: destroying cells is the simple first exploration of a class of genetic technology that will over time grow to power a vast and diverse field of targeted cell reprogramming.
Feinerman: Your last interview was in July 2017, more than half a year ago. What has been accomplished?
Hudson: We have conducted many pre-clinical mouse experiments on both cancer and senescent cell removal. All have been successful and produce very remarkable results. We've also conducted a pilot toxicity and safety trial on non-human primates. The results of that trial were also successful and encourage us to proceed to human safety trials as soon as regulatory authorities approve them. We have also spun-out a cancer-focused company, Oisin Oncology, and raised a seed round for that venture.
Feinerman: Great to hear! However, when can we see some papers?
Hudson: Papers are being prepared now for submission to major journals, but that process takes time, especially the peer review. For the moment, most of our data is only available to investors and partners in pharma and the biotech industry.
Feinerman: You planned human clinical trials, have you carried them out?
Hudson: It takes quite some time to organize a human trial and to get it approved. Before one can be conducted, we have to set up so-called "GMP (Good Manufacturing Practice)" manufacture of our therapeutic, and then we have to conduct "GLP (Good Laboratory Practice)" toxicity studies in two different species. Once that is all completed later this year, then we can begin a human safety trial, or a "Phase 1" trial. All this takes time, but we hope that first safety trials in oncology indications might begin this year, or in early 2019.
Feinerman: When we can expect your therapy available in the clinic?
Hudson: It's very difficult to predict. I believe that our cancer treatment will make it to the clinic first, and that could happen in less than five years. Since the FDA doesn't regard ageing as an indication, it may take longer for our treatment to reach the public, since the regulatory environment will need to change.
Feinerman: Now you use only a suicide gene as an effector, do you plan to use other genes? For example to enhance the cells, give them ability to produce new enzymes, or temporarily shutdown telomerase to help anti-cancer therapy to be more effective.
Hudson: We believe we can express any gene under the control of any promoter we wish to use, so the possibilities are almost endless. If people wish to design their own constructs for particular applications they may contact us for collaboration, though we do have several collaborations active at the moment so we may already be working on similar ideas.
Feinerman: How much resources, finances and personnel, you need to move as quickly as possible? Have you open positions? Maybe, some of our readers have enough finances or experience.
Hudson: We could effectively spend tens of millions or more, very easily, but it isn't realistic to assume we could raise that amount - and if we did, we'd lose control of Oisin's ageing focus, since investors would most likely want us to aim at quick returns. We are always interested in talking with "mission minded" investors, however. As for hiring, we have to do that slowly and judiciously, since labour is one of the biggest costs to a start up company and over-hiring can sink a project quickly. We already have more potential hires than we can bring on-board.
Feinerman: One person has said, we get what we ask for. Can we now aim high and publicly claim that our main goal is not additional five years of life but LEV - Longevity Escape Velocity and finally unlimited healthy life?
Hudson: This is a difficult public relations problem. Most investors, the scientific community, and the public are not yet ready to embrace the notion of longevity escape velocity. Thus at Oisin we do pitch health span as a primary goal. But personally I don't believe that you can obtain health span improvements without making significant progress towards LEV. So in the end, I think we get LEV by targeting health span, and we reduce the controversy by doing so.
Engineering Greater Radiation Resistance may well Lead to a Slowing of Aging
While I suspect that improvements in energy management coupled with magnetic field technologies are the cost-effective way forward when it comes to engineering defenses against radiation for space travel, it is certainly possible to consider classes of biomedical solution that could in principle greatly improve resistance to radiation in mammals. Insofar as that would require an improved capacity for cells to manage and repair oxidative damage and DNA damage, it seems likely that success would lead to treatments and enhancement biotechnologies that also slow the progression of aging.
The degree of slowing, and how it breaks down into cancer resistance versus other aspect of aging, depends on the degree to which DNA damage and oxidative damage are important in normal aging, versus the contributions of other causes and processes. The evidence of recent decades doesn't provide sufficient support for a definitive view on this topic. That will continue to be the case, I suspect, until such time as effective ways to repair or remove individual contributions to aging in isolation from one another are developed and extensively tested. So far theory and inspection have proven poor approaches to the production of good numbers for the relative contribution of specific processes to the progression of aging. Our biology is too complex to make much headway towards these detailed answers via analysis without intervention at the present time.
While many efforts have been made to pave the way toward human space colonization, little consideration has been given to the methods of protecting spacefarers against harsh cosmic and local radioactive environments. The main components of space radiation are solar particle events (SPE), geomagnetically trapped radiation, and galactic cosmic radiation (GCR). The contribution of the first two to the total dose absorbed by astronauts would obviously be negligible on long-duration missions away from Earth and the Sun. Consequently, GCR consisting mainly of highly-energetic particles would be the primary type of radiation encountered by humans under this scenario. It has been estimated that a return trip to Mars could subject astronauts to radiation doses of 660 mSv. Although great uncertainties exist with respect to health (cancer) risk estimates from exposure to cosmic radiation, this dose alone represents more than half of the total NASA astronaut career limit.
In principle, ionizing radiation interacts along charged particle tracks with biological molecules such as DNA. The process is largely stochastic, and can damage DNA via direct interactions or via indirect interactions such as through the production of reactive oxygen species (ROS). Radioresistance denotes the capacity for organisms to protect against, repair and remove molecular, cellular, and tissue damage caused by ionizing radiation. It is a quality that varies greatly in terms of effectiveness between different organisms. For instance, it is well-known that certain organisms are remarkably resistant to the damaging effects of radiation. The bacterium Deinococcus radiodurans, for instance, possess error-free DNA repair mechanisms and can withstand doses as high as 7 kGy. Similarly, tardigrades can withstand doses as high as 5 kGy, though doses exceeding 1 kGy render them sterile.
All eukaryotic organisms have evolved against a backdrop of constant exposure to endogenous and exogenous mutagens, and as such have developed robust cellular mechanisms for DNA repair and protection against DNA damage. Substantial experimental evidence suggests that low-dose radiation may trigger a variety of protective responses within cells, tissues and organisms that serve to protect them from both exogenous (e.g high doses of radiation) and endogenous (e.g. age-related accumulation of DNA damage) genomic instabilities. Importantly, these responses, collectively termed radioadaptive responses or radiation hormesis, may protect against spontaneous or induced cancer.
Genome instability resulting from DNA damage and mutation in both nuclear DNA and mitochondrial DNA caused by replication errors and exposure to endogenous and exogenous mutagens has long been implicated as one of the main causes of aging. All strategies for enhancing radioresistance in humans, from the expression and overexpression of exogenous and endogenous DNA repair genes, antioxidants, and ROS scavengers, to the expression of exogenous radioprotective genes, would also serve as a means of attenuating DNA damage and mutation implicated in eukaryotic aging. As such, strategies for enhancing radioresistance in humans would also constitute a promising geroprotective strategy and a means of attenuating aging and promoting longevity and extension of both lifespan and healthspan in humans as well.
An Interview on Mitochondrial Decline in Aging and Neurodegeneration
In this interview, a researcher focused on mitochondrial biochemistry discusses the role of these important cellular structures in aging and neurodegeneration, particularly Parkinson's disease. There are really two ways of looking at mitochondria in aging. The first, the view incorporated into the SENS program, looks at damage to mitochondrial DNA and its consequences. A small but significant number of cells fall into a dysfunctional state because some forms of randomly occurring mitochondrial DNA damage can replicate rapidly within the cell, leading to cells that pollute their surroundings with reactive, harmful molecules. This might be addressed by providing backup copies of mitochondrial genes, a methodology known as allotopic expression.
The second view looks at mitochondrial dynamics and morphology, both of which change considerably in response to differences in the environment between old cells and young cells, old tissues and young tissues. This is a much more complex problem to consider, as no-one has yet mapped the chains of cause and effect that stretch from the fundamental forms of damage at the root of aging to this downstream manifestation of aging. Nor is it entirely clear how to best go about reversing these changes - not to mention whether or not some are adaptive to the damaged environment, protective rather than the cause of even more harm.
How many mitochondria are there within each dopamine producing neuron and how frequently are they created?
The dopaminergic neurons in the pars compacta of the substantia nigra, the ones most related to Parkinson's disease, have enormous axons. If you add up all the branches, it is estimated that you would have several meters of axon coming from each cell. If you take the density of mitochondria in a segment of axon, you can then calculate what the total would be. The number is roughly two million mitochondria in each neuron. That's two million mitochondria frantically consuming oxygen and making ATP, all to keep that one cell alive.
On top of that, the proteins in the mitochondria are not going to stay stable for the 80 to 100 years that we live for. The proteins start to fall apart because of heat and the environment they are in. It turns out the mitochondria are a particularly dangerous place for a protein to be, because the mitochondria, in the process of its respiration, generate reactive oxygen species (ROS) which collide with proteins and chemically alter and damage them. Proteins everywhere in the cell have to be constantly degraded and replaced; in a mitochondrion that is even more true because the proteins get damaged even faster.
So we did a back of the napkin calculation, and asked how many mitochondria that cell would have to create every day in order to keep its two million mitochondria healthy and happy? The answer is something like thirty thousand mitochondria created every day. Most of the cells in our body don't have this problem, skin cells and liver cells are tiny and don't need nearly as many mitochondria. That could be part of the reason why, when something is wrong with our mitochondria, it is our neurons that suffer first, particularly the biggest neurons.
Does all that explain why, in Parkinson's disease, these neurons die and not other neurons?
Well, we don't know for sure yet what makes one cell more sensitive than another, but I think that is an excellent guess. The fact that those nerve cells fire at a very high rate, and that every time they fire it opens up a particular type of calcium channel that lets a lot of calcium in, means that you are going to need a lot of ATP to pump that calcium back out of the cell, as well as pumping sodium and other things. That puts a very strong demand on the cell. Then the fact that it has so many branches and so many synapses on the end of it also means that you are going to need a lot of energy to power those synapses. It is indeed a very energy hungry type of nerve cell, and nerve cells are the most energy hungry type of cell in the body. So it has this dual problem of supplying enough mitochondria and then putting strain on the mitochondria to travel through the axons and pump out enough ATP.
Which therapies that target mitochondrial health are you most hopeful for?
I think there are four ways to try to approach it. If you can figure out what is damaging the mitochondria and stop the damage that would be a great thing. In some cases antioxidants might do that. In cases where there are environmental toxins, like paraquat or rotenone, getting those out of the environment is definitely going to help. But in the case where there is a genetic mutation, you can increase the rate at which damaged mitochondria are removed and hope that the cell compensates by increasing the rate of production of healthy ones. There are also genes that control how mitochondria replicate and how they get new proteins added to them, if we can figure out how the cell controls the number of mitochondria and increase that number, that could improve the health of the cell.
Finally, the one that I am most interested in is the transportation problem. It is one thing to try and get proteins into the mitochondria in the cell body, but that cell body is just a tiny fraction of the volume of the neuron, way less that 1% of the cell. The cell has to somehow get mitochondria all the way out to the periphery of the cell and through all of its many axons. Improving the delivery of mitochondria into the remote regions of the cell should also improve the health of the cell.
ADP Sensitivity in Muscle Mitochondria Declines with Age Independently of Fitness
The research here notes an aspect of mitochondrial biochemistry that declines with age in a way that appears unaffected by fitness and exercise. One of the challenges inherent in investigating the mechanisms of aging in muscle tissue is determining the difference between decline due to disuse (secondary aging) versus decline due to intrinsic processes of damage accumulation (primary aging). We live in a world in which being older tends to mean being wealthier, with greater access to transportation and calories. Near all older adults fail to maintain a good program of exercise and diet, and the difference between those who make the effort to remain fit and slim and those who do not is sizable. That much is demonstrated by the significant gains in cardiovascular health and muscle strength that can be achieved in the elderly through structured exercise programs. So it is interesting to see research results in which the data makes it very clear that a specific measure of aging in muscle tissue is independent of exercise.
Aging is a complex process associated with skeletal muscle and strength loss as well as insulin resistance. The cellular mechanisms causing muscular and/or metabolic dysfunction with aging remain poorly understood. However, one proposed mechanism of action driving the aging process is an increase in mitochondrial-derived reactive oxygen species (ROS). Specifically, increased ROS emission has been associated with motor unit loss and abnormal morphology, muscle fiber atrophy, insulin resistance, inflammation, and apoptosis. Conversely, transgenic and pharmacological approaches that attenuate mitochondrial ROS have been shown to preserve insulin sensitivity, mitochondrial content, and muscle mass in diverse models while also prolonging lifespan. Altogether, these data implicate mitochondrial ROS as a fundamental mechanism of action influencing the aging phenotype.
Although these elegant rodent models provide compelling evidence to link mitochondrial ROS with age-associated pathologies, the data in humans remain ambiguous. Contradictory findings suggest that either mitochondria are not responsible for the increased oxidative stress with aging or, alternatively, contemporary in vitro assessment of mitochondrial ROS emission does not accurately reflect in vivo responses. ADP transport is a highly regulated process that is attenuated with rodent models of insulin resistance and improved following high-intensity exercise. Moreover, there is indirect evidence to suggest that the protein required for ADP transport into mitochondria, adenine nucleotide translocase (ANT), is impaired with aging in housefly and rat skeletal muscle. Therefore, previous assessments of mitochondrial ROS emission in the absence of ADP may not adequately reflect the in vivo environment, and as a result current data from human skeletal muscle may underestimate the importance of mitochondrial ROS in the aging process.
In the present study we re-evaluated mitochondrial bioenergetics by establishing a protocol in permeabilized muscle fibers to simultaneously examine mitochondrial respiration and hydrogen peroxide (H2O2) emission in the presence of various substrates and ADP concentrations. Using this in vitro protocol, we assessed age-related mitochondrial defects by comparing healthy young males to healthy older males. We also examined whether potential age-related defects in mitochondrial bioenergetics could be improved over 12 weeks of resistance exercise training. We provide compelling evidence that although the capacity for mitochondrial ROS emission is not increased with aging, mitochondrial ADP sensitivity is impaired, such that mitochondrial ROS, and the fraction of electron leak to ROS, are increased in the presence of virtually all ADP concentrations examined. In addition, although resistance-type exercise training improved several aspects of muscle health in older individuals, the fraction of electron leak to ROS, mitochondrial H2O2 emission rates in the presence of ADP, and muscle oxidative stress were unaltered, suggesting an increase in mitochondrial ROS accompanies the aging process.
Altogether, the assessment of mitochondrial bioenergetics in the presence of sub-saturating ADP concentrations has revealed that there are age-associated impairments in mitochondrial bioenergetics, which are not fully recovered with prolonged resistance-type exercise training. The mechanism for the attenuation in ADP sensitivity remains unknown, but oxidative damage has been proposed as a likely explanation. Regardless of this knowledge gap, the present data imply that an increase in mitochondrial ROS is associated with the primary aging process. Moreover, despite the inability of resistance training to rectify age-related mitochondrial ROS emission, older individuals experienced favorable changes in muscle mass, strength, and fat mass, reinforcing the importance of a physically active lifestyle throughout the lifespan.