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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- Impressions from the January 2019 Juvenescence Gathering
- Nattokinase and Reversal of Atherosclerotic Lesions
- Accelerated Bone Regeneration via Transplant of Engineered Perivascular Stem Cells
- Ceramides in Extracellular Vesicles Increase with Age and Induce Cellular Senescence
- 771,393 Donated to the SENS Research Foundation at the End of 2018
- PUM2 and MFF in the Dysregulation of Mitochondrial Fission in Aging
- Tau Impairs Both Mitochondrial Function and Quality Control
- Versican May Increase Cellular Senescence and Calcification in the Blood Vessels of Hyperglycemic Patients
- The Second Ending Age-Related Diseases Conference will be Held in July 2019
- MANF Declines with Age and is Required for Parabiosis Benefits to the Liver
- Suppression of Neural Plasticity in the Visual Cortex Reversed in Adult Mice
- Blood-Brain Barrier Dysfunction as an Early Driver of Dementia
- Large Genome-Wide Study Finds Only a Few Genetic Influences on Human Longevity
- What is Known of the Behavior of Regulatory T Cells in Aging Fat Tissue
- One of the Ways Researchers Narrow the Search for Drugs to Slow Aging
Impressions from the January 2019 Juvenescence Gathering
The JP Morgan Healthcare conference took place in San Francisco this past week. The conference is less interesting in and of itself, but it is the spur for any number of other short gatherings of various biotech investment and business interest groups. So in the middle of last week, Jim Mellon and the other Juvenescence principals were in town to host their second annual showcase for startups working on aging, and the BioAge and Felicis Ventures folk hosted the overlapping Extending Human Lifespan event on the same day. I had to miss that second one, as I was presenting Repair Biotechnologies at the Juvenescence event to a small crowd of other entrepreneurs, angel investors, and venture capitalists of varied allegiances, and stayed for the whole event to see the other presentations.
Many of our fellow travelers associated with SENS rejuvenation research and Methuselah Foundation spheres were present to meet and greet: the SENS Research Foundation folk; much of the Oisin Biotechnologies team; Doug Ethell of Leucadia Therapeutics; Frank Schüler of Forever Healthy Foundation; a number of angel investors I’ve interacted with in the past while we were interested in the same companies; and many others arriving and leaving as they moved between events.
One thing that caught my eye is that the theme of diversity and new hypotheses in Alzheimer’s research (or outright rebellion against the past two decades of relentless focus on clearing amyloid via immunotherapies, present it as you will) has robustly made its way to the commercial development stage. Leucadia Therapeutics were presenting their latest work on ferrets as an animal model to illustrate that the development of Alzheimer’s occurs due to blocked drainage of cerebrospinal fluid though the cribriform plate. Related company Enclear Therapies was not present, but was a topic of discussion given that their founders have very similar thoughts on filtration of cerebrospinal fluid. Maxwell Biosciences principals presented their work on the LL-37 antimicrobial peptide as a test of the microbial theories of Alzheimer’s disease, in which infection is provoking greater aggregation of amyloid and inflammation to accelerate other aspects of the condition. An attempt at intervention is perhaps the best way to clear up questions of causality here: do we see microbial infections in the Alzheimer’s brain because they are an important cause, or because immune dysfunction in general tends to be more advanced in these patients?
A further contingent of startups at the Juvenescence event were similarly of interest for having a good shot at answering scientific questions very much faster than the academic community can, due to the influx of resources from the venture community. Elevian falls into this category, with their work on GDF11. Early work on parabiosis, joining the circulatory systems of an old and young mouse, pointed to GDF11 as a possible factor in conveying benefits to the old mouse. There is now some debate over why parabiosis works, however, casting doubt on the argument of beneficial factors in young blood. Similarly, there has been some back and forth in the research community regarding whether or not past work on GDF11 is as it appears to be, but the Elevian staff claim to have resolved the conflicts. In many cases, the best way to resolve a debate of this nature is to just forge ahead and try to build a therapy; that effort can pull in much greater funding more rapidly than the academic community can manage via the usual channels available to researchers.
Another item that caught my attention, and seems worthy of consideration, is that the infrastructure and drug discovery companies in our space of treating aging as a medical condition are the furthest ahead in terms of building out relationships with venture concerns, obtaining larger funding, and breaking ground on their larger and later projects. This may reflect the focus of groups like Juvenescence from the past couple of years, their approach to establish an initial presence in a field. Examples of this trend include In Silico Medicine and Ichor Therapeutics’ portfolio company Antoxerene, both of which offer faster, cheaper discovery of small molecule drugs for any sort of use, but both of which happen to have founders very interested in aging and longevity over and above any of the myriad other uses for their technologies. In Silico Medicine in particular is clearly advancing by leaps and bounds in Asia as they gather support from the high-end venture groups there.
(I’ll confess that I’ve never found the development of lower level biotechnological infrastructure all that interesting as a topic. Obviously it is vital, and acceleration of technological progress is achieved by making common tasks easier, faster, and cheaper. Someone has to do it, invest in it, and focus on it, but that someone will never be me. I am far more interested in specific implementations of rejuvenation therapies, the development groups who might end up using the infrastructure to build a given treatment).
San Francisco is ever a hub of connections for the venture and technology spaces. It is the base of operations and home for a sizable number of high net worth individuals, agents for other high net worth individuals, fund partners deploying sizable amounts of capital, successful founders turned angel investors, successful angel investors turned founders – all rubbing shoulders, bumping into one another at the supermarket, and two degrees of separation removed at most. It is through this very connected network that interest in the biotechnologies of rejuvenation has been spreading these past fifteen years, pushed along by the presence of the SENS Research Foundation in the Bay Area. This occurred slowly at first, given that the focus was initially philanthropic funding of research rather than startups, but much more rapidly these past few years now that the first rejuvenation biotechnology startups are arriving on the scene.
At a small gathering after the Juvenescence event, those attending included an older AI-focused entrepreneur-turned-investor who has a growing interest in biotechnology, and a recently successful young founder from the technology space who is now taking life science classes to get up to speed on what he considers to be his next area of interest. The next day I met with an angel investor who attended the Juvenescence event, and who is cheerfully incorporating biotech companies into his previously tech-company-heavy portfolio. This dynamic is similarly reflected in venture firms such as Y Combinator, Felicis Ventures, and (closer to our community) Kizoo Technology Ventures led by Michael Greve, among others. They are transitioning into biotechnology, and the interest in doing something about aging is a driving motivation for many involved. For others, it is the realization that successful rejuvenation therapies will lead to a market so enormous as to make a pittance of near everything that has come before. Self-interest is a machine to be harnessed in these matters: while fundamental research is very cheap, later commercialization and distribution of medical therapies to millions of patients is enormously expensive. We need the deep pockets to enter this space, and to pull in all of their allies and other interested parties, if we are to see a reasonable rate of progress in moving rejuvenation therapies from lab to clinic.
The only other alternative is some form of major, lasting revolution in the regulatory environment, as that is the dominant cause of cost and delay. Therapies could be brought to market just as safely as they are today at a fraction of the present cost; the majority of cost and time imposed by the FDA, EMA, and the like is entirely unnecessary, some of it the debris of regulatory capture used by larger pharmaceutical entities to suppress competition, some of it the consequences of bureaucrats going to any lengths to avoid negative press, even by the means of preventing most new technologies from ever being approved. I’m certainly in favor of great upheaval in the development of medical therapies, but tearing down the present edifice is a vast project, and arguably one that will be much less costly and difficult to undertake given the existence of the first rejuvenation therapies and the public demand for more.
A final thought on investors and the science of rejuvenation: most of the newcomers are still finding their way to an understanding of the science in this space. They cannot yet tell the difference between projects likely to produce significant gains in human life span, those based on repair of the damage that causes aging, and those that cannot in principle produce large gains, those based on, say, upregulation of stress responses, such as mTOR inhibitors. Investors are guided by potential for financial gains, but that metric is not in fact a great way to tell the difference between better and worse approaches to aging. The typical competently run medical biotechnology company is acquired or goes public before the final determination of effectiveness of their programs; perhaps somewhere just after the first human trial, or even prior to that when the market is hot. Companies can do this after showing marginal benefits, or even just potential for marginal benefits, with a therapy that will never produce large or reliable benefits in larger patient populations, and yet still realize large gains for the early investors. So this is a challenge, and an opportunity for patient advocates to make a difference – to help guide those people chasing gains into obtaining those gains by backing better rather than worse technologies.
Nattokinase and Reversal of Atherosclerotic Lesions
Atherosclerosis is one of the great killers. Fatty deposits form in blood vessels walls, narrowing and weakening the vessels. Eventually something ruptures, and the result is a stroke or heart attack, but even absent that the condition can narrow vessels sufficiently to cause fatal coronary artery disease. Even with modern medicine, the condition is inexorable: the toolkit doesn’t yet include a way to more than slightly reverse the buildup of these plaques, and medical professionals must focus on ways to incrementally slow the progression of atherosclerosis rather than delivering any true cure.
One of the side-effects of starting a company, Repair Biotechnologies, that is working on a way to reverse atherosclerotic plaque is that I’ve been doing a great deal more reading on the topic of atherosclerosis than I would otherwise have done in the course of writing Fight Aging! Thus I turn up interesting items from the past few years that I missed at the time because I lacked the context to understand why they were worthy of notice, or just didn’t have the sort of focus on atherosclerosis that I have at the moment. The papers I’ll share today fall into this category, providing evidence for nattokinase, a very simple and readily available supplement, to have a surprisingly large effect on atherosclerotic lesions in humans. After six months of treatment, a third of the lesions were removed.
A clinical study on the effect of nattokinase on carotid artery atherosclerosis and hyperlipidaemia
All enrolled patients were from the Out-Patient Clinic of the Department of TCM at the 3rd Affiliated Hospital of Sun Yat-sen University. Using randomised picking method, all patients were randomly assigned to one of two groups, nattokinase (NK) and statin (ST) group. NK Group-patients were given NK at a daily dose of 6000 FU and ST Group-patients were treated with statin (simvastatin 20 mg) daily. The treatment course was 26 weeks. Common carotid artery intima media thickness (CCA-IMT), carotid plaque size and blood lipid profile of the patients were measured before and after treatment.
A total of 82 patients were enrolled in the study and 76 patients completed the study. Following the treatments for 26 weeks, there was a significant reduction in CCA-IMT and carotid plaque size in both groups compared with the baseline before treatment. The carotid plaque size and CCA-IMT reduced from 0.25±0.12cm2 to 0.16±0.10cm2 and from 1.13±0.12mm to 1.01±0.11mm, repectively. The reduction in the NK group was significantly profound, a 36.6% reduction in plaque size in NK group versus 11.5% change in ST group. Both treatments reduced total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG).
Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases
Nattokinase (NK), the most active ingredient of natto, possesses a variety of favourable cardiovascular effects and the consumption of Natto has been linked to a reduction in cardiovascular disease mortality. Recent research has demonstrated that NK has potent fibrinolytic activity, antihypertensive, anti-atherosclerotic, and lipid-lowering, antiplatelet, and neuroprotective effects. This review covers the major pharmacologic effects of NK with a focus on its clinical relevance to cardiovascular disease.
This effect size on atherosclerotic lesions is big enough to be suspicious, given that nattokinase is a supplement in common use, and the dose used is not outrageously large. We seem to be seeing a lot of that sort of thing these days, however; sometimes significance goes unnoticed, but equally sometimes it is an issue with the study that will be corrected later. It is hard to tell which without meaningful further effort. Does bisphosphonate treatment actually extend life expectancy by five years, and did this really did go unnoticed despite its widespread use in older people? Is fisetin actually a significantly effective senolytic compound in humans despite being widely used; did the very high senolytic dose in comparison to the usual supplement dose successful hide this property? How did nearly twenty years of earnest development and use of the chemotherapeutic dasatinib go past without anyone noticing that it killed enough senescent cells to improve health and measures of aging in mice and people? And so forth.
Over the past few decades, hundreds of millions of in funding (at the very least) has been spent on clinical trials to try to reverse atherosclerosis – to give existing repair systems in the body sufficient breathing space or increased capacity, allowing them to break down the fatty deposits that form in blood vessels. The sponsors of any of those trials would have been ecstatic to find a reliable reversal of atherosclerotic plaque that was half the size of that noted in the nattokinase trial here. One might take a look at a 2012 review paper that surveys the degree to which treatments at the time could achieve the goal of reversing atherosclerosis. A reversal of 15-20% in an unreliable fraction of patients was about the best that could be done. Most approaches were considerably less effective than that. Not a lot has changed in this high level picture since then.
At present the dominant approach to treatment of atherosclerosis is reduction of blood cholesterol, the cholesterol attached to LDL particles, or LDL-C. Statins are the long-standing approach, and are now being joined by even more effective treatments such as PCSK9 inhibitors. This slows down atherosclerosis by (a) lowering overall cholesterol, and thus freeing up some fraction of the macrophage cells that would otherwise have had to shovel it out of blood vessel walls, but more importantly (b) lowering oxidized cholesterol, which is very damaging to macrophages. When considering atherosclerosis and its treatments it is important to consider macrophages: they are drawn to the fatty lesions, and their task once there is to mine cholesterol from the lesion, ingest it, and hand it off to HDL particles that carry it back to the liver for excretion. This is called reverse cholesterol transport.
Atherosclerosis exists because macrophages become overwhelmed, mostly by oxidized cholesterol, but also by sheer volume of cholesterol, or by an overly inflammatory environment. They become agitated, call for help, become foam cells (some of which become senescent, causing further issues) or die. Most of a plaque is made up of the debris of dead macrophages, and the plaque itself is a self-expanding disaster area that calls ever more macrophages to their doom. Reducing the LDL-C slows down this feedback loop, but it cannot do much for existing plaques. There is some regression (the aforementioned 15-20% at best) because macrophages are given some breathing room, but plaques continue to grow at the new slower pace, and people continue to die.
There has been a considerable amount of work undertaken over the years on alternatives to lowering LDL-C. Researchers have tried all sorts of ways to improve the ability of macrophages to mine cholesterol and send it back to the liver. They have tried increased numbers of HDL particles (which are formed from APOA1 protein). They have tried altered forms of APOA1 found in some human populations that are associated with lower levels of atherosclerosis. They have tried the introduction of artificial HDL particles to swell the numbers. They have tried upregulation of the ABCA1 and ABCG1 proteins that perform the actual handoff of cholesterol molecules to APOA1. There is more in the same vein.
All of these things work pretty well in mice; the current best approaches produce 50% reversion of atherosclerotic lesions in animal studies. Yet all of those tried in humans, meaning the HDL and APOA1 approaches, have failed miserably in clinical trials. What this means is that there is something that the research community doesn’t yet understand in the low-level detailed differences between human and mouse reverse cholesterol transport. That is a big roadblock for anyone turning up to propose some form of enhanced cholesterol transport as a therapy, even if intending to try one of the varied effective-in-mice approaches that hasn’t yet been trialed in humans.
In this context, one can see that evidence for a common supplement to manage 36% reversion of lesions in humans is both welcome and jarring. It will certainly have to be replicated before many researchers in the LDL-C-focused side of the scientific community are likely to take it all that seriously. Any simple, easily obtained improvement should be welcome. Nonetheless, it is still only reversion by a third. The disease will still progress, and will still kill people. The research community has to do better than this.
Accelerated Bone Regeneration via Transplant of Engineered Perivascular Stem Cells
Reprogramming stem or progenitor cells to adjust their behavior is growing in popularity as an approach to regenerative medicine. The large reductions in the cost of exploring cellular mechanisms achieved over the past twenty years mean that there is now a much greater understanding of relevant mechanisms, as well as a greater capacity to discover novel targets of interest for specific goals in altered cell behavior. The more straightforward outcome in this part of the field is simply to increase stem cell activity, to reduce the amount of time these cells spend quiescent rather than actively supplying tissue with new daughter somatic cells to assist in repair. As today’s open access paper illustrates, there are certainly other options on the table, however.
Many stem cell populations are multipotent, meaning that they are capable of generating several different types of somatic cell. If only one type is desired for regeneration, then steering the stem cells into creating only that type for a while is effectively the same thing as speeding up their activity in general. Researchers here do this for cells that create both fat and bone tissue, identifying a regulatory protein, WISP1, that determines which is produced. These cells can then be harvested, engineered to express a higher level of WISP1, and used as a cell therapy to accelerate bone regrowth. That, at least, is the hope, given the initial evidence here from an animal study.
Stem Cell Signal Drives New Bone Building
Stem cells have the potential to develop into a variety of cell types including those that make up living tissues, such as bones. Scientists have long sought ways to manipulate the growth and developmental path of these cells, to repair or replace tissue lost to disease or injury. Previous studies showed that a particular type of stem cell – perivascular stem cells – had the ability to become either bone or fat, and that the protein WISP-1 plays a key role in directing these stem cells.
In a new study, researchers engineered stem cells collected from patients to block the production of the WISP-1 protein. Looking at gene activity in the cells without WISP-1, they found that four genes that cause fat formation were turned on 50-200 percent higher than control cells that contained normal levels of the WISP-1 protein. The team then engineered human fat tissue stem cells to make more WISP-1 protein than normal, and found that three genes controlling bone formation became twice as active as in the control cells, and fat driving genes such as peroxisome proliferator-activated receptor gamma (PPARγ) decreased in activity in favor of “bone genes” by 42 percent.
The researchers next designed an experiment to test whether the WISP-1 protein could be used to improve bone healing in rats that underwent a type of spinal fusion. The researchers mimicked the human surgical procedure in rats, but in addition, they injected – between the fused spinal bones – human stem cells with WISP-1 turned on. After four weeks, the researchers studied the rats’ spinal tissue and observed continued high levels of the WISP-1 protein. They also observed new bone forming, successfully fusing the vertebrae together, whereas the rats not treated with stem cells making WISP-1 did not show any successful bone fusion during the time the researchers were observing.
WISP-1 drives bone formation at the expense of fat formation in human perivascular stem cells
The vascular wall within adipose tissue is a source of mesenchymal progenitors, referred to as perivascular stem/stromal cells (PSC). Those factors that promote the differentiation of PSC into bone or fat cell types are not well understood. Here, we observed high expression of WISP-1 among human PSC in vivo, after purification, and upon transplantation in a bone defect. Next, modulation of WISP-1 expression was performed, using WISP-1 overexpression, WISP-1 protein, or WISP-1 siRNA. Results demonstrated that WISP-1 is expressed in the perivascular niche, and high expression is maintained after purification of PSC, and upon transplantation in a bone microenvironment.
In vitro studies demonstrate that WISP-1 has pro-osteogenic/anti-adipocytic effects in human PSC, and that regulation of BMP signaling activity may underlie these effects. In summary, our results demonstrate the importance of the matricellular protein WISP-1 in regulation of the differentiation of human stem cell types within the perivascular niche. WISP-1 signaling upregulation may be of future benefit in cell therapy mediated bone tissue engineering, for the healing of bone defects or other orthopedic applications.
Ceramides in Extracellular Vesicles Increase with Age and Induce Cellular Senescence
Much of the signaling that passes between cells travels via varieties of extracellular vesicle, tiny membrane-bound packages that contain a wide variety of presently poorly cataloged molecules. The varieties of vesicle are also poorly catalogued, and are at present given a loose taxonomy based on size. No doubt there are many subtypes within any given size category, depending on circumstance and mechanism, with the contents varying characteristically by subtype. Nothing is simple in cellular biology.
Vesicles are currently a subject of growing interest in many fields of medical research. In regenerative medicine, for example, it is hoped that harvesting vesicles from stem cells in culture and delivering them to patients can replicate much of the beneficial effects of stem cell therapies, but at a lower cost and with fewer complicating factors. Vesicles should not provoke immune reactions, for example, and thus do not require patient-matched or otherwise carefully chosen and engineered cells. In most cell therapies used to date, the transplanted cells die out quite rapidly. Beneficial outcomes result from the signals that they secrete, inducing changes in the native cell behavior. Thus why not just stop using the cells for this class of treatment?
Another area of interest is the way in which senescent cells manage to wreak havoc in tissues even when they are present in small numbers. They generate a potent mix of signals that creates chronic inflammation, destructively remodels the surrounding extracellular matrix, and alters the behavior of other cells for the worse, directly or indirectly. Moreover, senescent cells encourage other cells to become senescent. Therefore we should expect to see intracellular signals in the aged environment that can induce senescence. Those are starting to be discovered: versican is one example, to go along with the very long chain ceramides noted in today’s paper.
The vesicles containing these molecules may be secreted by senescent cells. Or they may be generated in other ways, implying that the state of senescence is more readily achieved in older, damaged tissues independently of existing senescent cells. Or both. Knowing more about these mechanisms will inform the appropriate use of senolytic drugs to remove senescent cells in the years to come: if senescence occurs more often in old tissues, then senolytic drugs should be used more often rather than less often by older people. If, on the other hand, new senescence is largely driven by existing senescence, then much more infrequent use is all that is needed.
Very Long-Chain C24:1 Ceramide Is Increased in Serum Extracellular Vesicles with Aging and Can Induce Senescence in Bone-Derived Mesenchymal Stem Cells
Emerging patterns of disease progression suggest that degenerative changes in one organ or system are likely to contribute to degenerative changes in other organs and systems. For example, reductions in lean mass and bone loss have both been observed to precede the age-related development of cognitive impairment and Alzheimer’s disease. Thus, cross-talk among various cells, tissues and organs may underlie non-autonomous aging in different cell and tissue populations. This concept is supported by studies in which young cells exposed to aged serum exhibited changes characteristic of older cells.
A barrier to progress in correcting the problem of age-related tissue dysfunction is the poor understanding of the molecular and cellular mechanisms underlying these non-autonomous cellular communication pathways. Exosomes are small (40-150 nm) and microvesicles are larger (more than 100 nm) membrane-derived structures that are released into the extracellular space by a variety of cell types. These membrane-bound extracellular vesicles (EVs) can transport proteins, lipids, and mRNAs between cells, delivering these molecules to target cells. EVs are highly enriched in the sphingolipid ceramide, which is known to promote cell senescence and apoptosis. In addition, EVs play a key role in a number of pathologies in vivo such as cancer metastasis and neurodegenerative disease. Thus, EV-derived ceramide is one potential aging factor that may promote degeneration in multiple organs and tissues.
We investigated the ceramide profile of serum exosomes from young (24-40 years) and older (75-90 years) women and young (6-10 years) and older (25-30 years) rhesus macaques to define the role of circulating ceramides in the aging process. EVs were isolated using size-exclusion chromatography and specific ceramide species were identified with lipidomic analysis. Results show a significant increase in the average amount of C24:1 ceramide in EVs from older women (15.4 pmol/sample) compared to those from younger women (3.8 pmol/sample). Results were similar in non-human primate serum samples with increased amounts of C24:1 ceramide (9.3 pmol/sample) in older monkeys compared to the younger monkeys (1.8 pmol/sample).
In vitro studies showed that primary bone-derived mesenchymal stem cells (BMSCs) readily endocytose serum EVs, and serum EVs loaded with C24:1 ceramide can induce BMSC senescence. Elevated ceramide levels have been associated with poor cardiovascular health and memory impairment in older adults. Our data suggest that circulating EVs carrying C24:1 ceramide may contribute directly to cell non-autonomous aging.
771,393 Donated to the SENS Research Foundation at the End of 2018
The philanthropists of our community, of greater and lesser means, stepped up to provide more than three quarters of a million in donations to the SENS Research Foundation in the last months of 2018. The work of the SENS Research Foundation depends on our support: building the foundations for rejuvenation therapies that would not otherwise be constructed, unblocking important research that is stuck, cultivating vital but neglected fields of science. Look at the yearly reports for much more detail. This non-profit is entirely dependent on philanthropic donations to power the vital work undertaken by its staff and allies in the research community.
Thank you very much to everyone who contributed to 2018’s Reimagine Aging end-of-year fundraising campaign. The original General Fund goal of 500,000 was our most ambitious yet, and you enabled us to exceed this goal for an incredible 771,393 total! We are grateful beyond measure for your generosity and support to continue our mission of curing age-related disease. Every donation helps bring the future we all want to bring into existence.
A very special thanks to Vitalik Buterin for his incredible gift of 350,000 in Ethereum, as well to IAS, Josh Triplett, Reason, Christophe and Dominique Cornuejols, Didier Coeurnelle, and Olivier Roland for providing matching grants during this campaign.
Here at Fight Aging!, Josh Triplett, Christophe and Dominique Cornuejols, and I put up a challenge fund for SENS Patrons, the monthly donors that supply a steady stream of funding to the foundation. For several years now we’ve aimed to grow that community of grassroots donors. They are steady folk; 80% of all of those who sign up stick around for at least a year, and the more donations that arrive on a schedule, the easier it becomes for the SENS Research Foundation staff to plan ahead and organize longer-term projects. We didn’t do as well in 2018 as in 2017, only hitting 50% of our goal: 29,987 out of the 54,000 target – but it wasn’t very many years ago that this would have been a sizable set of funding for the small organization that the SENS Research Foundation was back then.
In general, 2018 was a more muted environment for charitable fundraising. It would have been hard to top the end of 2017, at the height of the cryptocurrency bubble, when a great deal of philanthropic funding was disbursed to many research organizations. Now we are back to the point of having to work hard once again to grow our community, to persuade people that, in the midst of enthusiasm over clearance of senescent cells as a rejuvenation therapy, there is a great deal more necessary work to accomplish. One success does not complete the job at hand – there are still forms of age-related damage for which the science continues to languish, and each of them is enough on its own to produce age-related disease and death.
The efforts of the SENS Research Foundation and allied groups such as the Methuselah Foundation are just as vital now that the first rejuvenation therapies have been achieved as they were when only the vision existed. The road is only partly traveled, the journey only just begun, and our help is still required.
PUM2 and MFF in the Dysregulation of Mitochondrial Fission in Aging
Mitochondria, the power plants of the cell, become dysfunctional over the course of aging. This is a general process in all mitochondria, and not the same thing as the severe mitochondrial DNA damage that occurs in only a few cells, but that has a widespread detrimental effect. In this more general mitochondrial malaise, there are changes in shape and important functions decline; energy-hungry tissues such as brain and muscle suffer as a consequence.
Mitochondria are the descendants of ancient symbiotic bacteria, and thus act much like bacteria in carrying out fission and fusion, and passing component parts around between one another. In recent years, researchers have found that imbalances between fission and fusion appear in aging, this impairs the ability of autophagic processes to remove damaged mitochondria, and that provoking more fission or less fusion slows aging in short-lived species. Researchers continue to investigate the mechanisms underlying this imbalance; the results noted here are an illustrative example of the progress taking place in this part of the field.
Mechanisms based on mRNA transcription, a very important step in gene expression, are a part of the complex regulatory mechanisms in our cells. RNA-binding proteins (RBPs) bind mRNA molecules and regulate their fate after gene transcription. In this study, scientists screened cells from old animals to identify any RBPs that change upon aging. The screening showed that one particular protein, Pumilio2 (PUM2), was highly induced in old animals. PUM2 binds mRNA molecules containing specific recognition sites. Upon its binding, PUM2 represses the translation of the target mRNAs into proteins.
Using a systems genetics approach, the researchers then identified a new mRNA target that PUM2 binds. The mRNA encodes for a protein called Mitochondrial Fission Factor (MFF), and is a pivotal regulator of mitochondrial fission – a process by which mitochondria break up into smaller mitochondria. Having high levels of MFF also allows the clearance of broken up, dysfunctional mitochondria, a process called mitophagy.
The study found that this newly identified PUM2/MFF axis is dysregulated upon aging. Evidence for this came from examining muscle and brain tissues of old animals, which were found to have more PUM2, and, consequently, fewer MFF proteins. This leads to a reduction of mitochondrial fission and mitophagy, and without the ability to chop up and remove smaller mitochondria, the aged tissues start accumulating bigger and unhealthy organelles.
But removing PUM2 from the muscles of old mice can reverse this. “We used the CRISPR-Cas9 technology to specifically target and inactivate the gene encoding for Pum2 in the gastrocnemius muscles of old rodents. Reducing Pum2 levels, we obtained more MFF protein and increased mitochondrial fragmentation and mitophagy. Notably, the consequence was a significant improvement of the mitochondrial function of the old animals.”
Tau Impairs Both Mitochondrial Function and Quality Control
Researchers here show that tau protein, a feature of late stage Alzheimer’s disease, causes issues with mitochondrial quality control mechanisms responsible for removing damaged or dysfunctional mitochondria. Since tau also harms the function of mitochondria, this is particularly pernicious, and may be a significant component of the cell death that follows tau aggregation. Mitochondrial dysfunction is a feature of most neurodegenerative diseases, causing cellular processes in the brain to falter for lack of energy, but the question of where it sits in the web of cause and consequence in relation to other disease mechanisms remains to be resolved. Is the case that Alzheimer’s tends to occur more readily in people with worse age-related mitochondrial dysfunction, or does one or more of the other aspects of Alzheimer’s, such as tau aggregation, produce the observed greater level of mitochondrial dysfunction as a downstream effect? Or both? This sort of question is surprisingly hard to answer in conditions that have many contributing causes.
Accumulation of clumps of tau is a well-established hallmark of Alzheimer’s disease and other neurodegenerative disorders, as is the aggregation of damaged mitochondria, the powerhouse of a cell. However, the interaction between tau and mitochondria is still being explored, and new research has found an additional disruptive function of tau in terms of mitochondrial health. “It has long been known that there is an accumulation of abnormal mitochondria in neurodegenerative diseases, including Alzheimer’s disease. More specifically, tau has previously been shown to impair different aspects of mitochondrial function, and here, we find that tau also impairs the degradation of mitochondria. This causes a toxic cycle whereby tau both damages mitochondria and then also prevents their removal.”
One of the ways by which tau causes cell damage is by preventing the removal of damaged mitochondria, a process referred to as mitophagy. Normally, damaged mitochondria are trafficked to the lysosome (the waste remover of the cell) for destruction, by a molecule called Parkin, which moves from the intracellular fluid to the impacted mitochondria to start the trafficking process. However, researchers found tau impaired this process by interacting “aberrantly” with the Parkin protein in the intracellular fluid before it could reach the mitochondria, thereby preventing the removal process, and with damaging consequences for the cell.
Versican May Increase Cellular Senescence and Calcification in the Blood Vessels of Hyperglycemic Patients
I found this paper quite intriguing, as it links together a number of themes in vascular aging and the similar forms of vascular dysfunction seen in metabolic syndrome and diabetes. The molecular damage of aging in blood vessel walls causes stiffness of blood vessels, which in turn causes hypertension. This is one of the more important means by which low level biochemical damage is translated to high level structural damage to tissues, as raised blood pressure causes all sorts of harm. The damage that leads to vascular stiffness includes (a) cross-linking, in which sugary metabolic byproducts form links between molecules of the extracellular matrix, impeding its elasticity, (b) calcification, in which cells begin to inappropriately deposit calcium into the extracellular matrix, also degrading elasticity, and (c) failure of the vascular smooth muscle cells to perform appropriately when constricting or dilating blood vessels.
This last item has a number of poorly mapped underlying causes, but chronic inflammation appears to be a contributing issue. Chronic inflammation is also implicated in calcification. Chronic inflammation is one of the downstream consequences of cellular senescence, and there is evidence for the presence of senescent cells to be involved in calcification in blood vessel walls. So these items are already quite well connected together. The paper here closes the loop further by finding a form of intracellular signaling that is likely present in hyperglycemic individuals, who also exhibit raised levels of cross-linking, that spurs the formation of more senescent cells in blood vessel walls. Hyperglycemia is just the excessive case: everyone who consumes the usual modern amount of dietary sugar is probably in an incrementally worse position over the long term than people who consume less sugar, due to this and related mechanisms.
A major determinant of vascular aging is vascular calcification, characterized by vascular smooth muscle cells (VSMCs) calcification. Transdifferentiation of VSMCs into osteoblasts is considered to be the most critical pathophysiological of VSMCs calcification. There is accumulating evidence suggesting that VSMCs calcification/senescence have central roles in the development and progression of diabetes-related cardiovascular disorders.
The vascular response to hyperglycemia is a multifactorial process involving endothelial cells (ECs) and VSMCs, although the mechanism by which the information in circulating blood are transferred from ECs to VSMCs is yet to be understood. Signaling between ECs and VSMCs is crucial for the pathogenesis of diabetic vascular calcification/aging. However, how does circulating high glucose affect the calcification/senescence of VSMCs that are not directly contact with the blood? Exosomes, small vesicles with a diameter of 40-100 nm released from various cell types, have gained much attention for their role in intercellular communication. Exosomes can transfer active proteins, lipids, small molecules, and RNAs from their cell of origin to the target cell. ECs have been demonstrated to secrete exosomes, and the transfer of signaling molecules by exosomes may thus provide a way for communicating between ECs and VSMCs. Similarly, prior study has demonstrated that exosomes from senescent ECs promotes VSMCs calcification.
Exosomes from human umbilical vein endothelial cells (HUVEC-Exos) were isolated from normal glucose (NG) and high glucose (HG) stimulated HUVECs (NG/HG-HUVEC-Exos). Exosomes isolated from HG-HUVEC-Exos induced calcification/senescence in VSMCs. HG-HUVEC-Exos significantly increased lactate dehydrogenase (LDH) activity, as well as the product of lipid peroxidation, and decreased oxidative stress marker activity, as compared with NG-HUVEC-Exos. Moreover, mechanism studies showed that mitochondrial membrane potential and the expression levels of mitochondrial function related protein HADHA and Cox-4 were significantly decreased in HG-HUVEC-Exos compared to controls. Proteomic analysis showed that HG-HUVEC-Exos consisted of higher level of versican (VCAN), as compared with NG-HUVEC-Exos.
VCAN is mainly localized to the mitochondria of VSMCs. Knockdown of VCAN with siRNA in HUVECs, inhibited HG-HUVEC-Exos-induced mitochondrial dysfunction and calcification/senescence of VSMCs. Our data suggest a functional role for VCAN inside VSMCs. VCAN carried by HG-HUVEC-Exos promotes VSMCs calcification/senescence, probably by inducing mitochondrial dysfunction. Since VSMCs calcification/senescence could induce vascular dysfunction, blockage of the exosome-mediated transfer of VCAN between these two cells may serve as a potential therapeutic target against diabetic vascular complications. More work will be needed to explore this possibility and to better understand the intracellular roles of VCAN.
The Second Ending Age-Related Diseases Conference will be Held in July 2019
The second Ending Age-Related Diseases conference, hosted by the Life Extension Advocacy Foundation (LEAF) staff and volunteers, will be held in New York this coming July. It will bring together entrepreneurs, investors, and researchers to discuss progress towards bringing aging under medical control, and thus creating true cures for age-related conditions. I attended last year’s inaugural conference in the series, and recommend it. LEAF puts on a good conference, so consider registering.
After the incredible success of the conference Ending Age-Related Diseases 2018, the Life Extension Advocacy Foundation is happy to announce its second annual conference, Ending Age-Related Diseases 2019, which is to be held at Cooper Union in New York City on July 11-12th, 2019. The conference is aimed at focusing the NYC business community’s attention on the current state of aging and rejuvenation research that has the potential to prevent and cure age-related diseases. With multiple research projects targeting the underlying processes of aging in order to develop preventive medicines, promoting collaboration between academia, the rejuvenation industry, and investors becomes an increasingly important task.
The list of confirmed speakers already includes renowned researchers and visionaries, such as Dr. Aubrey de Grey (SENS Research Foundation), Michael Greve (KIZOO Technology Ventures, Forever Healthy Foundation), Dr. Vadim Gladyshev (Harvard Medical School), Dr. Vera Gorbunova (University of Rochester), Dr. Alex Zhavoronkov (Insilico Medicine), and Reason and Bill Cherman (Repair Biotechnologies), with more speakers from rejuvenation biotechnology companies and the investment sector to be confirmed soon.
“This year’s conference will focus on two main topics. The first topic will be progress in aging research, from fundamental studies to the interventions that are being tested in human clinical trials and the development of reliable biomarkers of aging. The second topic will be devoted to the hurdles of implementing these emerging rejuvenation biotechnologies into clinical practice, with a special focus on investment, the regulatory landscape, and the preparedness of the medical community. This way, we hope not only to attract the attention of investors to these very promising medical innovations but also to promote public dialogue on how to ensure their availability and accessibility to our aging society.”
MANF Declines with Age and is Required for Parabiosis Benefits to the Liver
Researchers have identified MANF as a factor responsible for at least some of the benefits provided to the older of two animals with linked circulatory systems. Joining two animals, usually mice, in this way is known as parabiosis. It has been used a tool to explore the role of the signaling environment of blood and tissues in aging. Stem cell function, for example, declines with age, and a sizable part of that decline appears to be a reaction to the changing, damaged environment rather than inherent damage in the stem cells themselves. Thus signals must exist to mediate the altered behavior of cells in response to what is going on around them.
If signals exist, then they can be overridden. Some research groups are searching for factors in young blood that might be used to boost stem cell function and tissue function in old mice. Other groups are convinced that the effect is due to dilution of harmful factors in old blood rather than the addition of helpful factors in young blood. The evidence on both sides is compelling, and the conflicts are yet to be resolved. While that debate is ongoing, it seems reasonable to expect further discoveries of signals and regulators that can increase stem cell activity in old tissues to some degree. That tends to help spur greater tissue maintenance and repair, but with some presently unknown additional cancer risk as damaged cells are forced back to work.
Older mice who are surgically joined with young mice in order to share a common bloodstream get stronger and healthier, making parabiosis one of the hottest topics in age research. Researchers report that MANF (mesencephalic astrocyte-derived neurotrophic factor) is one of the factors responsible for rejuvenating the transfused older mice. Researchers also show the naturally-occurring, evolutionarily-conserved repair mechanism protects against liver damage in aging mice and extends lifespan in flies.
While researchers have yet to understand why MANF levels decrease with age, MANF deficiency has obvious hallmarks. Flies genetically engineered to express less MANF suffered from increased inflammation and shorter lifespans. MANF-deficient mice had increased inflammation in many tissues as well as progressive liver damage and fatty liver disease. Older mice who shared blood with MANF-deficient younger mice did not benefit from the transfusion of young blood.
“MANF appears to regulate inflammatory pathways that are common to many age-related diseases. We are hoping its effects extend beyond the liver, we plan to explore this in other tissues. The search for systemic treatments that would broadly delay or prevent age-related diseases remains the holy grail of research in aging. Given that MANF appears to modulate the immune system, we are excited to explore the larger implications of its therapeutic use. We are also cautious. There are many tissues and organ systems to evaluate in terms of MANF and we have yet to determine its effects on lifespan in the mouse.”
Suppression of Neural Plasticity in the Visual Cortex Reversed in Adult Mice
Researchers here identify a mechanism that suppresses neural plasticity in the visual cortex of adult mice, a part of the developmental process that permits greater plasticity in childhood, but then restricts it in adults. This plasticity is the generation and integration of new neurons into neural circuits. Increased plasticity in adults may be beneficial, allowing for better maintenance and regeneration in the aging brain. That benefit must be balanced against whatever functional reason has led evolution to establish diminished plasticity with advancing age. If resistance to cancer is the answer, similar to the explanation for reduced stem cell function throughout the body in later life, then this can be addressed along the way. If there are other functional reasons for lower levels of plasticity in adults, and thus increased plasticity might damage the adult brain in some way, such as by causing disarray in established neural networks, then this will be more challenging to resolve.
The human brain is very plastic during childhood, and all young mammals have a critical period when different areas of their brains can remodel neural connections in response to external stimuli. Disruption of this precise developmental sequence results in serious damage; conditions such as autism potentially involve disrupted critical periods. “It’s been known for a while that maturation of inhibitory nerve cells in the brain controls the onset of critical period plasticity, but how this plasticity wanes as the brain matures is not understood. We’ve had some evidence that a set of molecules called SynCAMs may be involved in this process, so we decided to dig deeper into those specific molecules.”
The study focused on the visual cortex, the part of the brain responsible for processing visual scenes, in which plasticity has been examined in many species. The researchers were able to measure activity of neurons in awake mice freely responding to visual stimuli. They found that removal of the SynCAM 1 molecule from the brain increased plasticity in the visual cortex of both young and adult mice. Further research found that SynCAM 1 controls a very specific type of neuronal connection termed synapses: the long-distance synapses between the visual thalamus, located beneath the cerebral cortex, and inhibitory neurons in the cortex. SynCAM 1 was found to be necessary for the formation of synapses between thalamus and inhibitory neurons, which in turn helps inhibitory neurons to mature and actively restrict critical period plasticity.
The researchers liken inhibitory neurons to a dial controlling when brain plasticity can occur. Plasticity is needed during early development, as the function of different brain areas matures. Mature function is then cemented into place by molecules like SynCAM 1. “Therefore, the limited ability of the mature brain to change is not simply a consequence of age but is directly enforced by the SynCAM 1 mechanism. This allows us to target the mechanism to re-open plasticity in the mature brain, which could be relevant for treating disorders like autism. Combined with the latest approaches in genetic manipulation, this may prove to be a new path to tackle both childhood disorders and brain injury in adults.”
Blood-Brain Barrier Dysfunction as an Early Driver of Dementia
The blood-brain barrier surrounds blood vessels in the brain, enforcing restrictions on the passage of molecules and cells between brain and blood supply. Like all bodily systems, the blood-brain barrier breaks down with aging, yet another consequence of rising levels of cellular damage and disarray. The passage of inappropriate cells and molecules into the brain is thought to cause a range of issues, but, as is the case for all aspects of the biochemistry of the brain, this is a very complex environment and set of processes. Firm answers are ever elusive, and a great deal of the fine detail of the aging of the brain has yet to be robustly cataloged. The relative importance of different forms of damage and dysfunction are not well established in many cases. It is challenging to make that sort of determination given the many interacting forms of degeneration that combine to cause dementia in old age, but results such as those presented here are nonetheless intriguing.
Leaky capillaries in the brain portend early onset of Alzheimer’s disease as they signal cognitive impairment before hallmark toxic proteins appear. This finding could help with earlier diagnosis and suggest new targets for drugs that could slow or prevent the onset of the disease. A five-year study, which involved 161 older adults, showed that people with the worst memory problems also had the most leakage in their brain’s blood vessels – regardless of whether abnormal proteins amyloid and tau were present. In healthy brains, the cells that make up blood vessels fit together so tightly they form a barrier that keeps stray cells, pathogens, metals, and other unhealthy substances from reaching brain tissue. Scientists call this the blood-brain barrier. In some aging brains, the seams between cells loosen, and the blood vessels become permeable.
Participants in the study had their memory and thinking ability assessed through a series of tasks and tests, resulting in measures of cognitive function and a clinical dementia rating score. Individuals diagnosed with disorders that might account for cognitive impairment were excluded. The researchers used neuroimaging and cerebral spinal fluid analysis to measure the permeability, or leakiness, of capillaries serving the brain’s hippocampus, and found a strong correlation between impairment and leakage. “The results were really kind of eye-opening. It didn’t matter whether people had amyloid or tau pathology; they still had cognitive impairment.”
Large Genome-Wide Study Finds Only a Few Genetic Influences on Human Longevity
The influence of genetic variants on natural variations in human longevity is a very complex matter. The evidence to date supports a model in which thousands of genes have individually tiny, conditional effects. Near all associations identified in any given study population have failed to appear in any of the other study populations, and effect sizes for the very few longevity-associated genes that do appear in multiple studies are not large in the grand scheme of things. These variants provide a small increase in the odds of living to be very old, but the individuals bearing them are still diminished and damaged by aging. The genetics that determine how cellular metabolism gives rise to variations in aging are of great scientific interest, but there is nothing here that can act as the foundation for therapies that will help people to live significantly longer.
The extent of the role of genetic variation in human lifespan has been widely debated, with estimates of broad sense heritability ranging from around 25% based on twin studies to around 16.1% based on large-scale population data. One very recent study suggests it is much lower still (less than 7%), pointing to assortative mating as the source of resemblance amongst kin. Despite this modest heritability, extensive research has gone into genome-wide association studies (GWAS) finding genetic variants influencing human survival. Only two robustly replicated, genome-wide significant associations (near APOE and FOXO3) have been made to date, however.
An alternative approach is to study lifespan as a quantitative trait in the general population and use survival models to allow long-lived survivors to inform analysis. However, given the incidence of mortality in middle-aged subjects is low, studies have shifted to the use of parental lifespans with subject genotypes, circumventing the long wait associated with studying age at death in a prospective study. In addition, the recent increase in genotyped population cohorts around the world, and in particular the creation of UK Biobank, has raised GWAS sample sizes to hundreds of thousands of individuals, providing the statistical power necessary to detect genetic effects on mortality. A third approach is to gather previously published GWAS on risk factors thought to possibly affect lifespan, such as smoking behaviour and cardiovascular disease (CVD), and estimate their actual independent, causal effects on mortality.
Here, we blend these three approaches to studying lifespan and perform the largest GWAS on human lifespan to date. First, we leverage data from UK Biobank and 26 independent European-heritage population cohorts to carry out a GWAS of parental survival. We then supplement this with data from 58 GWAS on mortality risk factors. Finally, we use publicly available case-control longevity GWAS statistics to compare the genetics of lifespan and longevity and provide collective replication of our lifespan GWAS results.
We identified 11 novel genome-wide significant associations with lifespan and replicated six previously discovered loci. We also replicated long-standing longevity SNPs near APOE, FOXO3, and 5q33.3/EBF1 – albeit with smaller effect sizes in the latter two cases – but found evidence of no association (at effect sizes originally published) with lifespan for more recently published longevity SNPs near IL6, ANKRD20A9P, USP42, and TMTC2. Despite studying over 1 million lives, our standard GWAS only identified 12 variants influencing lifespan at genome-wide significance. This contrasts with height (another highly polygenic trait) where a study of around 250,000 individuals found 423 loci.
This difference can partly be explained by the much lower heritability of lifespan (0.12 versus 0.8 for height), consistent with evolution having a stronger influence on the total heritability of traits more closely related to fitness and limiting effect sizes. In addition, the use of indirect genotypes reduces the effective sample size to 1/4 for the parent-offspring design. When considering these limitations, we calculate our study was equal in power to a height study of only around 23,224 individuals, were lifespan to have a similar genetic architecture to height. Under this assumption, we would require a sample size of around 10 million parents (or equivalently 445,000 nonagenarian cases, with even more controls) to detect a similar number of loci.
Individual genetic variants that increase dementia, cardiovascular disease, and lung cancer – but not other cancers – explain the most variance in lifespan. We hoped to narrow down the search and discover specific genes that directly influence how quickly people age, beyond diseases. If such genes exist, their effects were too small to be detected in this study. The next step will be to expand the study to include more participants, which will hopefully pinpoint further genomic regions and help disentangle the biology of ageing and disease.
What is Known of the Behavior of Regulatory T Cells in Aging Fat Tissue
Visceral fat tissue produces chronic inflammation through its interactions with the immune system. Numerous mechanisms are involved: generation of additional senescent cells and their inflammatory signaling; normal fat cells secreting signals similar to those of infected cells; DNA debris from dead fat cells; and others. In younger individuals, problematic inflammation arises through having too much fat tissue, being overweight or obese. In older individuals, however, many of the same problems of chronic inflammation arise even given lesser amounts of visceral fat tissue. This paper reviews some of the relevant mechanisms, comparing aging with obesity, looking for the differences under the hood in T cell behavior.
Basic aging mechanisms such as cellular senescence and diminished number or dysfunction of immune progenitor cells are causative factors of development of low-grade inflammation. Immunosenescence is a term to describe the decline of immune function associated with aging, which can lead to increased susceptibility to infections, cancer, and metabolic and autoimmune disorders. During the state of infection or tissue damage in healthy young individuals, the immune system moves quickly. After the effective removal of the invading pathogen, the host immune response must be deactivated and return to a quiescent state to prevent further tissue damage. A subset of T lymphocytes called regulatory T cells are responsible for suppressing the deleterious effects of immune response.
In general, both innate and adaptive immune systems are affected by aging, but adaptive immunity, especially T lymphocytes, are most susceptible to the detrimental effects of aging. Gradual deterioration of the immune system over the course of time leads to a mismatch between proinflammatory and anti-inflammatory signals that may disrupt inflammatory homeostasis causing inflammaging.
Inflammation in adipose tissue, mainly evidenced by increased accumulation and proinflammatory polarization of T cells and macrophages, has been well-documented in obesity and may contribute to the associated metabolic dysfunctions including insulin resistance. Studies show that increased inflammation, including inflammation in adipose tissue, also occurs in aging. Aging-associated inflammation in adipose tissue has some similarities but also differences compared to obesity-related inflammation. In particular, conventional T cells are elevated in adipose tissue in both obesity and aging and have been implicated in metabolic functions in obesity.
However, the changes and also possibly functions of regulatory T cells in adipose tissue are different in aging and obesity. In this review, we summarize recent advances in research on the changes of these immune cells in adipose tissue with aging and obesity and discuss their possible contributions to metabolism and the potential of these immune cells as novel therapeutic targets for prevention and treatment of metabolic diseases associated with aging or obesity.
One of the Ways Researchers Narrow the Search for Drugs to Slow Aging
Small molecule and drug candidate libraries are huge. Much of modern medical research is a process of screening subsets of those libraries in search of molecules that can produce benefits with minimal side-effects. Usually the output of a successful screen is taken as a starting point for further exploration and molecular tinkering, to improve the effect or minimize undesirable side-effects. The great hope for gene therapy is that it will render all of this largely obsolete by offering ways to directly influence a molecular mechanism to a configurable degree without meaningful side-effects. That remains a way off in the future, however, and meanwhile a very sizable slice of medical research is still all about finding which cataloged molecules might be interesting to work with.
Thus when it comes to aging, a majority of efforts are focused on adjusting the operation of metabolism via small molecules from the catalogs, interacting with one of the known aging-related mechanisms discovered via examination of the biology of calorie restriction, or autophagy, or other stress response mechanisms. This is somewhat depressing: none of this work offers either hope or possibility of doing more than slightly increasing human life span, yet it is where most the funding and effort is focused. An increasing fraction of those initiatives are concerned with ways to speed up this process, to make it more rational, to cut down the number of molecules to be assessed. These advances are interesting to the degree that they can be applied more generally, to any area of development. There are parts of the SENS rejuvenation research portfolio in which small molecule drug discovery might lead to useful therapies, for example.
Several bioinformatic methods have been developed to identify potential geroprotective drugs. For instance, caloric restriction (CR) mimetics have been identified, by comparing genes differentially expressed in rat cells exposed to serum from CR rats and rhesus monkeys with gene expression changes caused by drugs in cancer cell lines. Structural and sequence information on ageing-related proteins have been combined with experimental binding affinity and bioavailability data to rank chemicals by their likelihood of modulating ageing in the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Drug-protein interaction information has also been used to predict novel pro-longevity drugs for C. elegans, using a set of effective and ineffective lifespan-extending compounds and a list of ageing-related genes. A similar approach used chemical descriptors of ageing-related compounds from the DrugAge database together with gene ontology terms related to the drug targets. Enrichment of drug targets has been assessed for a set of human orthologs of genes modulating longevity in animal models to identify new anti-ageing candidates.
Despite the increasing interest in drug-repurposing for human ageing, research has tended to focus on predicting life-extending drugs for animal models. However, the translation from non-mammalian species to humans is still a challenge, and certain aspects of ageing may be human-specific. Only a few studies have focused on data from humans. For instance, researchers applied the GeroScope algorithm to identify drugs mimicking the signalome of young human subjects based on differential expression of genes in signalling pathways involved in the ageing process. Another study correlated a set of genes up- and down-regulated with age in the human brain with drug-mediated gene expression changes in cell lines from the Connectivity Map.
In the present study, we rank-ordered drugs according to their probability of affecting ageing, by measuring whether they targeted more genes related to human ageing than expected by chance, by calculating the statistical significance of the overlap between the targets of each drug and a list of human ageing-related genes. Additionally, to enhance the power of the approach, we mapped the drugs’ gene targets and ageing-related genes to pathways, gene ontology terms, and protein-protein interactions, and repeated the analysis. We found that, independently of the data source used, the analysis resulted in a list of drugs significantly enriched for compounds previously shown to extend lifespan in laboratory animals. We integrated the results of seven ranked lists of drugs, calculated using the different data sources, into a single list, and we experimentally validated the top compound, tanespimycin, an HSP-90 inhibitor, as a novel pro-longevity drug.