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

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

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

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

Dementia trend shows later onset with fewer years of the disease

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

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

Are Trends in Dementia Incidence Associated With Compression in Morbidity?

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

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

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

Towards a Better Epigenetic Clock

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

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

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

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

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


Glial Cell Behavior Critical to Proficient Central Nervous System Regeneration

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

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

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

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

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

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


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

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

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

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

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

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

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

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

A Pharmaceutical Developer's Initial Considerations

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

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

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

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

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

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

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

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

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

An Initial Model of Indications

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

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

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

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

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

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

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

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

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

Orphan Indications

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

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

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

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

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

Off-Label Usage

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

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

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

Aiming to be a Worldwide Company

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

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

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

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

Developing for Quality is Vital

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

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

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

Regulation is Complex, and Guidance is Necessary

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

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

DNA Demethylase Activation via Klotho Reduces Arterial Stiffening in Mice

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Results from a Human Trial of Mitochondrially Targeted Antioxidant MitoQ

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


CXCR4 as an Indicator of Microglial Involvement in Neurodegenerative Diseases

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

An Interview with a Programmed Aging Theorist

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

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

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

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

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

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

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

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

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

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

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


Inflammatory Signaling Reduces Pancreatic Islet Cell Replication in Aging

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

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

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

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