Fight Aging!

It is very hard to coax a damaged machine into continued operation without repairing the damage. It is expensive and time-consuming, the machine works poorly, and fails catastrophically only a little later than it would have done without all of that effort. Keeping damaged machines running is exactly the goal of near all work on treating age-related disease, however. Very few projects are focused on addressing the cell and tissue damage that causes aging. Anything other than repairing or otherwise reversing that damage will produce only marginal gains, at great expense.

This has been well demonstrated. With the best will in the world, an enormous amount of effort has been put towards helping older people by treating age-related diseases, but near all of that effort has gone towards therapies that cannot even in principle help all that much - because they do not address aging, the cause of age-related disease. So we have marginally longer lives, but increased disability, at great cost. This must change, and the focus must shift towards therapies that address the underlying mechanisms of aging, to repair the damage and make the machine work well once again. That is the only cost-effective way to extend healthy life spans.

Longevity leap: mind the healthspan gap

Notably, the societal triumph of longevity is plagued with debilitating morbidity, accentuated towards the end of life. The average life expectancy - a benchmark of population health - has risen from 47 to 73 years of age in these seven decades, a 26-year expansion. This remarkable trajectory in human longevity has generated a redistribution in demographic structure underpinned by a disproportionate surge in those over 70 years of age. Notably, the societal triumph of longevity is plagued with debilitating morbidity, accentuated towards the end of life.

Lifelong (also referred as "chronic" or "non-communicable") diseases are the leading cause of mortality and disability worldwide. Collectively, chronic diseases are responsible for 40 million or 71% out of 56 million annual deaths globally, and 79% of all years lived with disability. Four common conditions, namely cardiovascular diseases, cancer, diabetes, and chronic respiratory diseases, account for 80% of chronic disease related deaths. The imposed socioeconomic burden is estimated to represent a $47 trillion loss over the last two decades. Fifty-eight percent of chronic disease-related mortality occurs in persons over 70 years of age. This growing age segment thus warrants special attention.

Age-associated outcomes are profoundly aggravated by frailty. Indeed, there is a recognized gap between lifespan, i.e., the total life lived, and healthspan, i.e., the period free from disease. Using health-adjusted life expectancy, that considers life expectancy, years lived with disability, and premature death from disease, the healthspan-lifespan gap is estimated at around 9 years. This gap appears refractory to current practice paradigms. In fact, one-fifth of an individual's life will be lived with morbidity. Extending lifespan alone without delaying disease onset and/or reducing disease severity would actually aggravate the healthspan-lifespan gap.

The insidious accumulation of chronic disease and frailty must engender disruptive innovation. Targeting the root cause at latent stages offers the prospect of implementing proactive, prophylactic actions. Growing regenerative options offer opportunities to boost innate healing, and address aging-associated decline. Diverse aging populations are thus at the cusp of a promising horizon.

Epigenetic clocks were developed by correlating observed changes in DNA methylation with age. Aging produces characteristic changes in cell behavior due to damage and dysfunction. While the nature of these changes is the same in every individual, the pace at which aging processes differs somewhat, the result of differing lifestyle choices and environmental exposures, such as particulate air pollution and persistent viral infection. When measured epigenetic age is greater than chronological age, this is referred to as epigenetic age acceleration, and this appears to be a useful measure of the degree to which an individual is aging more rapidly than the average. GrimAge is one of the better epigenetic clocks developed in recent years, judging from the data produced to support correlation between the measured epigenetic age acceleration and known risk factors for greater risk of age-related disease and mortality.

Here, researchers show that a sustained improvement in diet and exercise slows the rate at which the GrimAge epigenetic clock advances. It is most interesting to see the research community closing in, step by step, on a way to actually measure the effects of interventions on the aging process. Of note, however, GrimAge seems to have much the same issue in this study as was noted for first generation epigenetic clocks, in that it is insensitive to the metabolic changes brought about by exercise. There is clearly work yet to accomplish in the production of good, comprehensive biomarkers of aging!

Several biomarkers of healthy aging have been proposed in recent years, including the epigenetic clocks, based on DNA methylation (DNAm) measures, which are getting increasingly accurate in predicting the individual biological age. The recently developed "next-generation clock" DNAmGrimAge outperforms "first-generation clocks" in predicting longevity and the onset of many age-related pathological conditions and diseases. Additionally, the total number of stochastic epigenetic mutations (SEMs), also known as the epigenetic mutation load (EML), has been proposed as a complementary DNAm-based biomarker of healthy aging.

A fundamental biological property of epigenetic modifications, in particular DNAm, is the potential reversibility of the effect, raising questions about the possible slowdown of epigenetic aging by modifying one's lifestyle. Here, we investigated whether improved dietary habits and increased physical activity have favorable effects on aging biomarkers in healthy postmenopausal women. The study sample consists of 219 women from the "Diet, Physical Activity, and Mammography" (DAMA) study: a 24-month randomized factorial intervention trial with DNAm measured twice, at baseline and the end of the trial.

Women who participated in the dietary intervention had a significant slowing of the DNAmGrimAge clock, whereas increasing physical activity led to a significant reduction of SEMs in crucial cancer-related pathways. There was no significant slowing of DNAmGrim associated with the physical activity intervention nor reduced EML associated with the dietary intervention. Our study provides strong evidence of a causal association between lifestyle modification and slowing down of DNAm aging biomarkers. This randomized trial elucidates the causal relationship between lifestyle and healthy aging-related epigenetic mechanisms.

Link: https://doi.org/10.1111/acel.13439

Until fairly recently, it was impossible to accurately determine the age of a lobster found in the wild. This is one of a number of marine species that exhibits negligible senescence, meaning few signs of aging across the majority of its lifespan. How long can a lobster live? That used to be quite unclear until it was found that it is possible to count growth rings in the eye stalks in order to age specimens caught in the wild. There is an ongoing process of aging in this species, despite their negligible senescence, as demonstrated here. Researchers have been able to correlate lobster age to changes in DNA methylation, indicating that gene expression is changing over time in this species, and it is thus just as possible to produce an epigenetic clock for aging in this species as it is in the case of mammals.

Lobsters are notoriously difficult to age. Nobody knows exactly how old they can get, and some experts have estimated they could live on the ocean floor for as long as a century or more. "Until now, a lobster's age has usually been estimated using its size - but this is inaccurate as individual lobsters grow at different rates. For a long time, it appeared that there was no accurate way to quantify a lobster's age. Some research suggested that you could tell a lobsters age by counting the rings in parts of their eyestalks and stomach - a little like counting tree rings. But you can't do that for a living lobster."

"Lobsters have hard, inelastic shells and so in order to grow they must shed their old shell and replace it with a new one. However, lobsters of the same age don't always grow and moult at the same time. For example, lobsters with more food or in warmer waters can grow more quickly, which makes it really hard to know how old lobsters actually are. It is crucial to be able to estimate how many lobsters of particular ages are present in a given area so that they can be sustainably harvested. We wanted to develop a new, non-lethal method of determining the age of European lobsters that could be of better use for lobster fisheries management. The European lobster was an ideal species to study because it is economically and ecologically very important."

The research team used a method that relies on quantifying epigenetic changes that accumulate with age within a lobster. Lobsters raised from eggs, so that the exact ages of individuals was known, allowed the researchers to calibrate their methods. "We identified a very strong relationship between age and epigenetic modifications, which allowed us to accurately estimate the ages of individual lobsters. Applying this method to wild lobsters predicted ages that generally aligned with minimum estimates of age based on size."

Link: https://www.uea.ac.uk/news/-/article/ageing-the-unageable-uea-researchers-develop-new-way-to-age-lobsters

Chronic kidney disease leads to the state of end stage renal disease, kidney failure, and death. There are presently few options for effective treatment. Like many conditions, chronic kidney disease has a strong inflammatory component. Senescent cells in kidney tissue are implicated in the increasing fibrosis and declining kidney function exhibited by patients, as is the age-related decline of the immune system into an state of chronic inflammation. Kidney function is clearly very important to the function of organs and systems throughout the body, as demonstrated by the accelerated deterioration and increased mortality observed in chronic kidney disease patients.

It seems likely that the relationship between chronic kidney disease and inflammatory immune dysfunction is bidirectional. The degree to which this is mediated by senescent cells and their inflammatory secretions is unclear, but promising results have been achieved in animal studies based on the use of senolytic treatments capable of selectively destroying senescent cells. A human clinical trial is presently underway.

In today's open access paper, researchers ask whether addressing the decline of the immune system associated with chronic kidney disease might at least slow progression of this condition. That leads to a discussion of thymic involution as an important aspect of age-related immune system failure, and a catalog of some of the approaches to thymic regeneration that have been attempted over the past few decades. The thymus is where thymocytes mature into T cells of the adaptive immune system. The thymus atrophies with age, and the supply of new T cells is greatly diminished as a result. Absent reinforcements, the adaptive immune system becomes ever more dysfunctional. This is thought to be an important component of declining immune function in later life.

End-Stage Renal Disease-Related Accelerated Immune Senescence: Is Rejuvenation of the Immune System a Therapeutic Goal?

The chronic kidney disease (CKD) phenotype is very similar to premature ageing. Frailty, osteoporosis, muscle wasting, and cardiovascular disease occur at a younger age in CKD patients. Many factors such as oxidative stress, accumulation of uremic toxins, and inflammation are supposed to contribute to accelerated ageing. The immune system undergoes a similar premature ageing. Patients with end-stage renal disease (ESRD) frequently exhibit T cell lymphopenia and concomitantly have both a marked susceptibility for infections and a decreased response to vaccines suggesting a T cell immune defect. Finally, ESRD patients exhibit a low-grade inflammation status. This association is typical of the "inflammaging" state observed in elderly.

The term immune senescence clusters all the changes that occur in the immune system during ageing. Although this process mainly affects T lymphocytes, all aspects of innate and adaptive immunity are concerned. The ageing of the immune system is a more general concept including two different processes. The first one is what is specifically referred to by immune senescence, which is mainly linked to age-dependent thymic involution leading to reduced immune repertoire diversity and compounded oligo-clonal increase in memory immune cells. Sensitivity to infections, reduced vaccine immunity, and defect in tumour clearance observed in elderly are thought to be at least in part linked to these immune alterations. The second characteristics of aged immunity is inflammaging. Old age is associated with low-grade systemic inflammation. Chronic innate immune activation, pro-inflammatory cytokine profile secretion, and age-induced accumulation of self-reactive T cells contribute to age-related inflammation. Inflammaging is supposed to explain some degenerative disease associated with ageing.

Premature thymic involution is a key component of ESRD-associated immune senescence. It is reported that thymic output decreased with progression of CKD. Thymic output is comparable between 40-year-old uremic patients and 80 year-old non-uremic patients. Our group recently reported that, in ESRD patients, low thymic output was predictive of severe infections. The decrease in recent thymic emigrant cells could be the result of a reduction in the thymic output of naïve T cells and/or of a reduction in homeostatic proliferation. Premature loss of thymic function is likely to explain the decrease in naïve T cells in young patients with ESRD.

However, there are few data documenting potential causes for premature thymic involution during chronic kidney disease. Chronic inflammation is likely to markedly contribute to immune ageing. Of note, a recent study shows that C-reactive protein levels inversely correlates with naïve T cells in haemodialysis patients suggesting either that inflammation and immune senescence evolve in parallel or that one is driving the other one. Activation of innate immunity, characterised by monocyte activation and overproduction of inflammatory cytokines such as IL-6, is a key feature of the CKD immune system. Treating reversible source of inflammation is obviously a goal in CKD patients and such strategy may reduce premature ageing.

Immune senescence has deleterious consequences. Susceptibility to infection, premature cardiovascular disease, and increased cancer incidence are some of the most frequent and serious. A number of measures, from the simplest to the more complex, may be susceptible to reverse immune senescence, especially premature thymic involution.

Firstly, the impact of physical activity in maintaining thymic activity must not be neglected. It is one of the rare therapeutic strategies with consistent results in both animal and human studies. In an immunological ageing mouse model, 4 weeks of free-wheel running increased naïve T lymphocytes and reduced effector ratio of cytotoxic T lymphocytes. Concordant data also exist in humans. Physical activity is often reduced in CKD patients. Sedentary life, socio-economics conditions, comorbidities, and uremia-related asthenia contribute to the reduced physical activity. Although a large number of studies reported the beneficial effects of exercise in CKD patients, no data are available concerning the potential consequences on immune status. However, other benefits of physical exercise in ESRD patients have been largely reported and physical rehabilitation programs should be encouraged in these patients.

Secondly, many hormonal pathways play a role in thymic physiology. However, most of them are impaired during chronic renal failure. The IGF-1-GH pathway interferes with many aspects of thymus biology. The IGF-1-GH axis is profoundly altered in dialysis patients. ESRF patients have increased GH secretion, but normal IGF-1 concentrations, indicating GH resistance. This suggests that GH may be a therapeutic hope to reverse thymopoiesis defect in ESRD patients.

The effects of sex hormones on thymus are well-known. A number of studies demonstrated that sex steroid ablation delay or reverse thymus involution in both animals and humans. Surgical castration is obviously not a therapeutic option in humans, but LHRH analogues use is also associated with thymic rejuvenation. Nevertheless, some studies also suggest that castration-induced thymic rejuvenation is only transient and potentially hazardous. Despite some former results, the use of chemical castration to enhance thymic rejuvenation is consequently not a safe option.

Some cytokines may also promote thymic function. IL-7 is produced by both thymic stromal cells and bone marrow. IL-7 mediates lymphopoiesis of both T cells and B cells, and in the thymus, promotes proliferation, differentiation, and survival of thymocytes. Administration of IL-7 in mice expand both naïve and memory CD4 and CD8 peripheral T cells. IL-22 interacts with IL-2R on the surface of thymic epithelial cells and allows both survival and proliferation of thymocytes. IL-22 administration to mice having received total body irradiation increases both thymocytes and thymic epithelial cell recovery. Limitations in the therapeutic use of IL-22 are based on its dual effects, which strictly depend on the context. The pro-regenerative effects of IL-22 could be counterbalanced by its inflammatory and tumorigenic properties.

KGF belongs to the fibroblast growth factor family. This cytokine is involved in epithelial cell proliferation and differentiation in many tissues, including the thymus. KGF administration to mice enhance thymopoiesis and accelerate thymic recovery after irradiation.. In non-human primates, KGF enhances immune reconstitution after autologous hematopoietic progenitor cell transplantation. More recently, conflicting results made the benefits of KGF less clear. In HIV-infected patients, KGF was not effective in either improving thymic function or rising circulating CD4+ T cells.

Forced expression of FOXN1 in involuted thymus results in thymic regeneration with increased thymopoiesis and naïve T cell output. The structure of the regenerated thymus was very close to young thymus in terms of architecture and gene expression. These results suggests that up-regulation of FOXN1 is sufficient to reverse age-related thymic involution. Further, recombinant FOXN1 protein fused with cell-penetrating peptides increased the number of thymic epithelial cells and enhanced thymopoiesis after hematopoietic stem cell transplantation in mice. All together, these studies suggest that the FOXN1 axis research is a valuable strategy to reverse thymic involution. To date, there are no evaluation of FOXN1 expression during CKD.

The gut microbiota interferes with the immune system lifelong and its dysregulation results in inflammation. Whether microbiota interferes with immune senescence is challenging because the relative part of microbiota and health status are difficult to isolate. Moreover, even when dysbiosis may favour inflammation, inflammation may also promote dysbiosis asking the question of which came first. Dysbiosis is a hallmark of chronic kidney disease. Accumulation of uremic toxins in CKD causes substantial modifications in gut physiology. Evidence suggests that septic inflammation observed in ESRD is at least in part related to a shift toward more inflammatory microbiota.

In conclusion, premature thymic involution and chronic inflammation greatly contribute to increased morbidity and mortality in CKD patients. Mechanisms are likely to be multiple and interlinked. Even when the quest to fountain of youth is a pipe dream, there are many scientific opportunities to prevent or to, at least in part, reverse CKD-related immune senescence. Further studies should precisely define most important pathways driving premature immune ageing in CKD patients and best therapeutic options to control them.

An interesting idea is put forward in this open access paper, aimed at producing a greater and more useful unity of thought about the processes of aging. It is certainly the case that the field lacks a common conceptual foundation to build upon when it comes to working towards a better understanding of the mechanisms of aging. Hence the many theories of aging, focusing on quite different areas of molecular biology and evolutionary biology, and the persistent debate over whether aging is an evolved epigenetic program of late life dysfunction (the minority position), or an accumulation of damage that falls outside selection pressure for repair or prevention (the majority position).

We argue that some of the key principles of particle physics can be borrowed to study biological systems that age. Namely, these principles are: (a) Every interaction leads to a transformation of all interacting subjects. (b) Every process can be dissociated from the chronological time and considered as a sequence of discrete events. It is the order and the number of these events that predetermines the outcome, not time. (c) The threshold value is predetermined by a probability for a specific interaction to cause a specific transformation. An at-the-threshold event occurs not because of the accumulation of prior stimuli but because an increasing number of stimuli increased the probability of the observed event.

These principles can help understand the nature of aging or other biological processes. Cell functionality is determined by complex interactions of atoms within micro- and macromolecules with various cell structures and internal cell environments. During aging, discrete transformations in a cell eventually negatively affect cell system functionality. When atoms within molecules change their characteristics due to interactions and transformations, such as radioactivity, oxidation, reduction, etc., the macromolecule's whole functionality is altered. Alteration of functionality causes direct damage to a system by performing an alternative function or indirect damage defined by a loss of functionality.

In other words, systematic damage accumulation from the standpoint of a whole system leads to the decay of the system. Once damage in a system reaches a certain magnitude i.e. reaches a threshold, the system stops performing the originally designated function. When a cell can no longer maintain critical functionality, it finally transforms into a highly non-functional state. On an organism level, outcomes can look differently, e.g., senescence, cancer, coronary diseases, diabetes.

Therefore, biological aging may be defined as a sequence of highly discrete transformations caused by a combination of internal and external factors that lead to chronic damage accumulation and the consequent loss of functionality of a system. The transformations of damage repair mechanisms themselves may lead to their reduced functionality, representing critical thresholds since it would increase the rate of damage accumulation. However, some systems also exist where damage dilution, partitioning, clearance, decay and/or pre-emption support cell rejuvenation, thereby making the biological system appearing as non-aging (e.g. immortalized mammalian cell lines, germline, hydra).

Link: https://doi.org/10.18632/aging.203555

It is reasonable to think that intermittent treatment with senolytics can suppress cancer incidence by killing the senescent cells that are present in precancerous lesions, whether or not they are too small to be identified by present screening techniques. This should reduce the number of cells that can potentially go on to become cancerous, and also remove the contribution of senescent cell signaling to the growth and inflammatory status of the lesion. It should not be too challenging to prove this hypothesis in animal models, but prevention of cancer in the general sense is, unfortunately, a hard sell when it comes to clinical development. It is slow and expensive to run clinical trials for five or more years with cancer prevention in mind, and few organizations or investors would choose to take on that cost.

Senescence is a cell state that contributes to several homeostatic and pathological processes. In addition to being induced in somatic cells in response to replicative exhaustion (replicative senescence, RS) as part of organismal aging, senescence can also be triggered prematurely by oncogene hyperactivation or tumor suppressor dysfunction (oncogene-induced senescence, OIS). Consequently, senescent cells comprise a major component of precancerous lesions of skin, oral mucosa, nasopharynx, prostate, gut, and lung.

Unfortunately, invasive (or minimally invasive) interventions are currently the only available approach employed to eradicate premalignant lesions that carry the potential for cancer progression. Oncogene-Induced Senescence (OIS) is one form of senescence that occurs in response to oncogene overexpression in somatic cells and is present in precancerous lesions. While the contribution of OIS to disease progression is undetermined, recent evidence suggests that senescent cells are permissive for malignant transformation.

Senolytics are a newly emerging drug class capable of selectively eliminating senescent cells. While senolytics have been successfully demonstrated to mitigate a myriad of aging-related pathologies and to cull senescent cancer cells, there is a paucity of evidence for the potential use of senolytics as a novel approach to eliminate oncogene-induced senescent cells. This commentary will: (i) summarize evidence in established models of OIS including B-Raf-induced nevi, transgenic lung cancer, and pancreatic adenocarcinoma models as well as evidence from clinical precancerous lesions; (ii) suggest that OIS is targetable; and (iii) propose the utilization of senolytic agents as a revolutionary means to interfere with the ability of senescent premalignant cells to progress to cancer in vitro and in vivo. If proven to be effective, senolytics will represent an emerging tool to pharmacologically treat precancerous lesions.

Link: https://doi.org/10.1124/molpharm.121.000361

There are many different potential approaches to the treatment of aging as a medical condition. It is a sad truth, however, that funding the wrong type of project will almost certainly fail to move the needle on human aging. Further, it is almost certainly the case that most present effort in research and development is going towards the wrong type of project. A majority of the projects that could lead towards treatments for aging are focused on upregulation of the cellular stress response mechanisms triggered by exercise, calorie restriction, hypoxia, heat, and the like. We have a good idea as to the likely outcome of such approaches in humans: look at the results of structured exercise programs and calorie restriction, meaning a modest slowing of health that does little to change the present shape of a human life, and its decline into disability and mortality.

A different approach is needed if the goal is rejuvenation rather than a gentle slowing of the aging process. That approach should be to repair the various well-described accumulations of cell and tissue data that lie at (or close to) the root of aging, thereby allowing restored function. Clearance of senescent cells from aged tissues is an important example of this type of approach. Senescent cells secrete signals that provoke chronic inflammation and tissue dysfunction: their presence actively maintains a more aged, damaged state of organs. Targeted removal of even only a third of such errant cells produces quite startling demonstrations of rejuvenation in mice, reversals of age-related conditions that are greater and more rapid than can be obtained by even the best of stress response upregulation approaches (such as mTOR inhibition). And yet there is a great deal more of work analogous to mTOR inhibition taking place than work analogous to selective destruction of senescent cells.

Aubrey de Grey on Rejuvenation Policy at EARD2021

If we look at the maintenance approach, the damage repair approach, that, of course, I founded more than 20 years ago now, that has become very much the focus or one of the major focuses of the anti-aging research field. We can see that potentially, there is a bit of an issue, because there are lots of different types of damage that we have to go after.

Of course, the whole reason why geriatric medicine was originally seen to be a non-starter that would never really have all that much effect on the healthspan of the human race was because of that precise problem that there are so many things you have to fix. The maintenance approach kind of sidesteps that; it makes the divide-and-conquer problem more manageable in ways that I've talked about many times and I won't reiterate now.

But still, it's a divide-and-conquer problem. And that means that we have to make quite sure that the most difficult parts of that divide and conquer approach are not left behind and neglected. Of course, SENS Research Foundation was set up more than a decade ago, with exactly that in mind; we set it up as an independent charity, an independent nonprofit funded almost entirely by philanthropy.

We did that precisely in order to avoid the constraints that forced both industry and mainstream academia into short-termism into focusing on low-hanging fruit and neglecting the harder but equally important problems that otherwise they might work on. Of course, the past decade of work that we and others have done, has had great successes, and certainly some of those successes constitute progress in the most difficult areas of damage repair.

For example, in the area of mitochondrial mutations, in the area of extracellular matrix stiffening, these are areas which were completely stalled when we started, and they're not stalled anymore. But they're still nowhere near as far along as getting into clinical trials, for example. So we've got to make absolutely sure that that does not persist, that these things are continuing to be pushed forward.

That's where emerging challenge number one is: it is extraordinarily hard to get most people to not focus on the low-hanging fruit. In industry, of course, we know that people who want to make money, they want to make it soon, and therefore they are going to put pressure on to cause that to happen. Some of you who have long memories may recall a company called Elixir Pharmaceuticals, which were founded by two absolute demigods of gerontology, Cynthia Kenyon and Leonard Guarente. The reason why those of you with short memories will probably not remember Elixir is because it ended up being a complete waste of time. That was why: they took the wrong money, they got pressured into doing stuff that wasn't useful, and nobody remembers them at all.

It's, of course, exactly the same in academia, that short-termism arises from the need to publish or perish. And same result. The worst of it is that it's quite easy in biology in general, and certainly in our field, to identify areas where you can make quick progress and make a big splash and get a terribly interesting paper on the front page of Science Magazine. Unfortunately, it doesn't go anywhere, because there is no actual way to take it forward to something that would have clinical relevance in the long run.

And the final problem, a final aspect of this problem, is that most of the real visionaries who have money are actually capitalists: they are people who made their money in the private sector, and they believe in that kind of way of doing things. Many of them simply do not believe in philanthropy, or in charity in general.

Now, some of those people have been visionary enough to recognize that they have to bite that bullet. Of course, the person who gets the greatest credit for that in our world is Peter Thieltps://en.wikipedia.org/wiki/Peter_Thiel">Peter Thiel, who started funding Methuselah Foundation back in 2006. But the fact is now that these people have the opportunity to invest rather than to donate, they are very, very tempted to do exactly that. So we absolutely need to be vigilant in making sure that the most difficult components of the damage repair portfolio are not neglected.

To a first approximation, cells of the adaptive immune system are barred from the brain by the blood-brain barrier. This is only a first approximation, however, and more careful research has shown that a small number of adaptive immune cells do in fact enter the brain. This appears to be the case throughout life, a part of the normal interaction between immune system and central nervous system. The presence of adaptive immune cells in the brain in later life is also thought to be pathological, however, the result of age-related dysfunction of the blood-brain barrier, allowing unwanted cells into the brain to cause harm.

Neurodegenerative disease defines conditions in which there is progressive neuronal loss in the central nervous system (CNS), leading to either physical disability, cognitive deficits or both. Classical neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Aging is a major risk factor for neurodegenerative disease, and with a growing elderly population, its prevalence is continuously increasing. Beyond being a risk factor, aging also increases the severity of disease and results in an impaired recovery following insult. Although these diseases have different pathogenetic mechanisms such as protein aggregation, demyelination, ischaemia, or direct trauma, they all share a hallmark of neuroinflammation.

The immune system plays a key role in CNS homeostasis and disease. The innate immune system is the first line of defense against pathogens and central nervous system (CNS)-resident macrophages, microglia, are of vital importance as early respondents to CNS alterations such as damage or infection but also in development and homeostasis. Microglia activation is also an important component of neuroinflammation, aging, and different neurodegenerative diseases either directly via phagocytosis and cytokine production, as shown by the identification of disease-specific microglia, or indirectly in response to cues from the adaptive immune system.

The adaptive immune system is an important component of the host defense against pathogens, through the recognition of non-self antigens. This defensive mechanism is mediated by B lymphocytes and T lymphocytes which display a diverse range of specific antigen receptors during humoral and cellular-mediated immunity. Although the CNS was once considered an 'immune-privileged' site, recent studies have indicated the presence and importance of the adaptive immune system in the CNS for immune-surveillance and defense against neurotropic viruses. Studies have also highlighted the role of adaptive immunity in maintaining CNS homeostasis and integrity, promoting neurogenesis and improving cognitive function.

In healthy individuals, this immune-CNS interaction is highly regulated to maintain the beneficial relationship. However, during both aging and neurodegenerative disease, the blood-brain barrier (BBB) is disrupted, leading to an increased infiltration of peripheral immune cells into the CNS, where they can potentiate further neurodegeneration or facilitate tissue regeneration. In both neurodegenerative disease and the normal aging process, there is a common theme of immune dysregulation and abnormal immune responses.

Link: https://doi.org/10.3389/fnagi.2020.572090

Tumor cells have identifying surface markers that the immune system can in principle attack, but vaccination against those surface markers in order to encourage an anti-tumor immune response has been hit and miss. Researchers here dig deeper into the mechanisms that may explain this variability in response, and thus allow a more viable approach to patient-specific cancer vaccines that will more effectively rouse the immune system to target cancerous cells.

When cells begin to turn cancerous, they start producing mutated proteins not seen in healthy cells. These cancerous proteins, also called neoantigens, can alert the body's immune system that something has gone wrong, and T cells that recognize those neoantigens start destroying the cancerous cells. Eventually, these T cells experience a phenomenon known as "T cell exhaustion," which occurs when the tumor creates an immunosuppressive environment that disables the T cells, allowing the tumor to grow unchecked.

Scientists hope that cancer vaccines could help to rejuvenate those T cells and help them to attack tumors. In recent years, they have worked to develop methods for identifying neoantigens in patient tumors to incorporate into personalized cancer vaccines. Some of these vaccines have shown promise in clinical trials to treat melanoma and non-small cell lung cancer. "These therapies work amazingly in a subset of patients, but the vast majority still don't respond very well. A lot of the research in our lab is aimed at trying to understand why that is and what we can do therapeutically to get more of those patients responding."

Previous studies have shown that of the hundreds of neoantigens found in most tumors, only a small number generate a T cell response. Now a new study helps to shed light on why that is. In studies of mice with lung tumors, the researchers found that as tumor-targeting T cells arise, subsets of T cells that target different cancerous proteins compete with each other, eventually leading to the emergence of one dominant population of T cells. After these T cells become exhausted, they still remain in the environment and suppress any competing T cell populations that target different proteins found on the tumor. However, researchers found that if they vaccinated these mice with one of the neoantigens targeted by the suppressed T cells, she could rejuvenate those T cell populations. "If you vaccinate against antigens that have suppressed responses, you can unleash those T cell responses. Trying to identify these suppressed responses and specifically targeting them might improve patient responses to vaccine therapies."

Link: https://news.mit.edu/2021/tumor-vaccine-t-cells-0916

The Rejuvenome project at the Astera Institute aims to fill an important gap in research and development aimed at the slowing or reversing mechanisms of aging. Very little work in academia or industry assesses the outcome of combined treatments. Are several different senolytic drugs targeting difference mechanisms of senescent cell death, at lower doses, much better than just one senolytic drug, at a higher dose, at clearing harmful senescent cells from old tissues? Do aged mice live longer in good health with senolytics to remove senescent cells plus flagellin immunization to improve the gut microbiome plus exosome therapy to spur greater regeneration of tissues? Does in vivo reprogramming to reset epigenetic marks in aged cells plus CDC42 inhibition to enhance hematopoiesis produce greater extension of life in mice than either alone?

Projects such as these could have been conducted a hundred times over, in dozens of ways, over the past decade. Yet they have not been. Intellectual property and perverse regulatory incentives make it hard enough to proceed to ensure that few groups pursue this path. Yet combining approaches to the treatment of aging is absolutely vital in order to achieve meaningful results. Aging is caused, at root, by a set of distinct processes, the creation of quite different forms of cell and tissue damage that arise out of the normal operation of healthy metabolism. Any one therapy can address only one of these processes, leaving the rest of aging to progress unaffected. The gains will be only incremental. The research and development communities are failing us in their neglect of this point.

Thus philanthropic funding must step in to conduct this sort of research, and that is what the Astera Institute principals intend. Rejuvenome plans to run large, robust mouse studies in aged mice. Some of their studies are planned to combine interventions known to or suspected to extend life in mice, in order to determine synergies. The work is expected to launch in earnest, once the mouse study population is old enough, in 2022. Rejuvenome expects to accept solicitations from the community in the near future as to the best combinations of interventions to assess in this fashion.

Rejuvenome

A key current limitation in the longevity field is that deep biological studies on individual interventions have primarily been investigated independently and in an ad hoc fashion, leading to a lack of comprehensive data on any one intervention. One project examines brain aging but doesn't measure lifespan, while another measures metabolism but doesn't track epigenetics, and yet another looks just at lifespan itself. This fractured approach makes it difficult to compare or combine aging interventions within a common framework.

To resolve this problem, the Rejuvenome will conduct a large-scale experiment in genetically diverse mice to measure system-wide multi-omics spanning a panel of rejuvenation interventions. By measuring multiple hallmarks of aging across the lifespan of mice, the project will provide a high-resolution description of the interconnection or independence of different aspects of the aging process and of how interventions alter these pathways. The resulting intervention-effect matrix will support the field in its advance towards better interventions.

Ultimately, the Rejuvenome will test combinations of interventions designed to target multiple aspects of aging simultaneously. There is good reason to believe such combinations will produce synergistic effects. Multiple gene knockouts in C. elegans have been shown to increase lifespan by 10x, and a combination of three compounds extended lifespan in flies beyond the effects of any of the individual components - a similar multifaceted approach could produce the longest living mice and suggest potential future multi-factorial therapies for humans.

Astera Institute

The Astera Institute was created to bring humanity the greatest imaginable good in the most efficient possible way. When your ambitions are boundless, but your resources are finite, leverage is your friend. In the words of Konrad Zuse, "I was too lazy to calculate, so I invented the computer." Inspired by such extreme examples of "work smarter," Astera seeks to activate the areas of exponential latent potential within science and technology. We want to create benevolent super-intelligence, live to 200, fix science, and do engineering worthy of Asimov. Astera Institute was established by Jed McCaleb. It is a 501c3 non-profit dedicated to developing high leverage technologies that can lead to massive returns for humanity. Astera's unusually high impact derives from housing moonshots and novel scientific research that have no other natural home in today's research and development landscape. Astera focuses on longevity, AGI, metascience, and frontier engineering.

Researchers here briefly review the ability of calorie restriction to improve stem cell function in various different tissues over the course of aging. This is thought to be one of the ways in which the practice of calorie restriction slows aging, quite significantly in short-life species, and much less so in longer-lived species. Since the short-term metabolic changes, and benefits to health, produced by calorie restriction are quite similar across mammals of different life spans, it remains an open question as to exactly why life expectancy is only modestly affected in long-lived species. Calorie restriction induces sweeping changes in near every aspect of cellular metabolism, and neither metabolism nor the effects of calorie restriction are completely mapped and understood. It will be a while yet before the research community has answers to the deeper questions about species differences in the long-term benefits produced by calorie restriction.

One of the most impactful and reproducible interventions that can slow down age-associated pathologies is calorie restriction (CR). CR is an intervention to prolong longevity, where the number of calories consumed is decreased but sufficient nutrition is maintained. Initially seen in a rodent study in 1935, recent findings have demonstrated its beneficial effect in mammals and primates. It has been thought that these advantages are mediated through stem cell proliferation and perseveration of stem cell activity, thus functioning as a regenerative therapy. Therefore, a thorough understanding of the mechanism, regulation, and signalling molecules underlying the advantages of CR for specific stem cells, such as muscle stem cells, intestinal epithelium stem cells, hematopoietic stem cells (HSCs) and hair follicle stem cells, would help in determining specific pharmacological and dietary intervention for regenerative therapy in the future. In addition, the structural and functional modifications observed can provide a more complete understanding of the numerous CR effects and thus be useful in therapy consideration.

One of the characteristics seen in age-related pathologies is stem cell exhaustion. Here, we review the various impacts of CR on mammalian health mediated through stem cell potency in various tissues. In the skeletal muscle, CR acts as an anti-inflammatory agent and increases the presence of satellite cells endogenously to improve regeneration, thus causing a metabolic shift to oxidation to meet oxygen demand. In the intestinal epithelium, CR suppresses the mechanistic target of rapamycin complex 1 (mTORC1) signalling in Paneth cells to shift the stem cell equilibrium towards self-renewal at the cost of differentiation. In haematopoiesis, CR prevents deterioration or maintains the function of HSCs depending on the genetic variation of the mice. In skin and hair follicles, CR increases the thickness of the epidermis and hair growth and improves hair retention through stem cells. CR mediates the proliferation and self-renewal of stem cells in various tissues, thus increasing its regenerative ability.

Link: https://doi.org/10.21315/mjms2021.28.4.2

Once one starts to investigate, tissue type by tissue type, the effects of interventions known to modestly slow aging, one finds differences. This could be a matter of differences in the biodistribution of a particular therapeutic agent, or it could be that various forms of age-related damage are more or less significant in different organs, or that the regulation of stress responses differs from tissue to tissue, such that some therapeutics target a regulatory pathway more relevant to a kidney than a lung, for example. All of this implies that great deal of work lies ahead, if every potential therapy must be mapped by its effects on every type of tissue in the body, and optimization proceeds tissue type by tissue type.

The ability to study and compare organ aging in the context of organismal aging has recently been documented using a geropathology approach. This concept consists of identifying and grading age-related histopathologic lesions so that a quantitative score is established for each organ allowing for comparison of lesion scores between all organs examined and between all animals in a specific cohort. Therefore, the contribution of each organ to aging can be assessed, in contrast to studying the effect of aging or age-related disease on each organ.

Geropathological interrogation of individual organs provides a powerful look at the morphologic changes associated with increasing age in an organ-dependent manner. For example, based on severity of age-related histopathologic lesion scores, it can be seen that different organs age at different rates with increasing age in C57BL/6 and CB6F1 mice. The heart ages earlier and more rapidly in CB6F1 mice from 8 months to 24 months compared to C57BL/6 mice. Surprisingly, there is no difference in aging of the lungs across this age span in the two strains. For the liver, age-related lesions are seen 8 months earlier in C57BL/6 mice and there is an increase in aging in C57BL/6 mice from 16 to 32 months. The pattern was similar for the kidney, with age-related lesions occurring earliest in C57BL/6 mice at 16 months and then progressing more rapidly.

The second example provides insight into how different organs respond to therapeutic drugs based on changes in severity of lesion scores. Studies with C57BL/6 mice treated for 3 months starting at 20 months of age have shown that organ response based on lesion scores is drug dependent in four major organs- heart, lungs, liver and kidney. For rapamycin, an mTOR inhibitor, kidney, heart and liver were most responsive in males but only kidney was responsive in females using a dose of 14 ppm in the feed. For acarbose, an antidiabetic drug, heart and kidney were most responsive in both genders at a dose of 1000 ppm in the feed. For phenyl butyric acid, an inhibitor of histone deacetylation, lungs and kidney were most responsive in both genders at a dose of 1000 ppm in the feed. In addition, published observations for fisetin, a natural product with senolytic activity, have shown lungs and kidney to be most responsive. It is worth noting that the kidney appears to be less drug dependent, suggesting it might serve as a sentinel organ in drug studies investigating effects on aging, at least in C57BL/6 mice of both genders. These types of observations will be invaluable for helping make decisions on selection of effective drug combinations for aging intervention studies.

Link: https://doi.org/10.15761/JTS.1000458

No feasible amount of funding that could be devoted to the research and development of rejuvenation therapies would be too much. If near all other projects were dropped, and institutions radically retooled on a short term basis, then the world might be able to devote $300 billion per year into medical research and development aimed at aging. That is an unachievable upper bound, of course. Given a few decades in which to train new researchers while rapidly and radically expanding existing institutions, then humanity might start to approach that scale of expenditure. Realistically it will take 20-30 years following the first unarguable successes in human rejuvenation for the economic incentives to meaningful start in on the creation of a suitably vast industry. Progress on this scale takes time.

The cost of the medical conditions, suffering, and mortality caused by aging, meanwhile, is staggeringly large. Researchers have estimated that slowing aging by one year worldwide is worth $38 trillion in productivity gains. Direct and easily measured medical and productivity costs of aging are more than $1 trillion per year in the US alone. Looking at the common estimates of the economic worth of a human life, the cost of the yearly death toll due to aging is well over $100 trillion, a vast destruction of the value of living individuals, their knowledge and capacity to make the world a better place. No feasible amount of funding devoted to achieving medical control over aging could be enough, given these numbers.

Today's short article is a fairly standard call for the US government to do more for a favored cause. Its novelty is that the cause is human longevity, the medical control of aging. The various patient advocacy, investor, academic, and biotechnology industry factions interested in the development of the means to treat aging have not yet developed an earnest lobbying arm - and are perhaps not yet large enough to produce more than the few initiatives that have emerged to date, such as the Longevity Dividend. It isn't only governments that fund medical research and development, however. Philanthropy and industry are just as important, and just as capable of contributions at the large scale.

The Case for a Longevity Moonshot

There has been tremendous progress in understanding aging and showing that it is possible to reverse it, and there is a growing longevity industry validating the approach to treat aging directly. Researchers are using a variety of approaches, from drugs that get rid of old cells to gene and stem cell therapies. Institutions researching aging include the nonprofit SENS Research Foundation, David Sinclair's lab at Harvard, and biotech companies including Calico (a sister company of Google), Rejuvenate Bio, BioAge, Cambrian, Unity Biotechnology, Juvenescence, Retro Biosciences, and Oisin Biotechnologies.

Both donors and investors see promise in reversing aging. However, there is research that the private sector will not do on its own because investors seek quick returns and donors have only so much money. It has taken seven years to fundraise for clinical trials to see if metformin slows down aging. And there has been more research in mice than in people, partly because clinical trials for people cost more. Basic research is risky, expensive, and without a certain payoff, so important research goes undone because the private sector is unwilling to fund it. The government needs to fill in the gap.

If we discovered a cure for aging, it would make society much wealthier, and the benefits to mankind would be enormous. Increasing life expectancy by one year alone by slowing down aging is worth $38 trillion, according to a recent study-more than the entire national debt of $29 trillion. Finding a cure for aging would significantly boost GDP by allowing people to work for longer. It would also lower the national debt, because higher GDP would lead to more tax revenue, and less would need to be spent on Medicare and Social Security because people would be healthier for longer.

Unfortunately, aging receives only 6% of government health research funding. There has been far more government spending on treating individual diseases, but as Vijay Pande and Kristen Fortney wrote for Andreessen Horowitz, curing cancer would add only four years to the average lifespan "because another major killer like stroke would be just around the corner. Only by targeting aging itself can we make significant impact on improving quality of life and healthspan." It would be more valuable to find a cure for aging than for individual diseases like cancer because it would stop those diseases from materializing in the first place. You're at much greater risk of cancer and Alzheimer's at age 70 than at age 30, and a cure for aging could fundamentally change that. U.S. life expectancy has been roughly stagnant, rising only 7% since 1980. We should target life expectancy as an important measure of national well-being, in addition to GDP. A cure for aging would boost life expectancy far more than finding a cure for individual diseases because aging increases people's risk of disease.

Researchers here note that structured exercise programs can reduce the burden of chronic inflammation in older individuals, a desirable outcome. The study is a reminder that being sedentary has a cost. Too little exercise and a lack of physical fitness in later life produces harmful consequences such as a raised level of chronic inflammation, and thus a faster progression towards all of the common and ultimately fatal age-related diseases. The fine details of our metabolism and its interaction with aging evolved in an environment of much greater regular physical exertion, all the way into later life, than is presently the case. When we fail to keep up with that level exercise, we suffer in its absence.

Increased basal low-grade inflammation is observed with advancing age, which is augmented by physical inactivity. However, data regarding the influence of lifelong exercise training and particularly high-intensity interval training (HIIT) on inflammatory mediators in older men are scarce. Therefore, we examined effects of 6 weeks of aerobic preconditioning followed by 6 weeks of HIIT on inflammatory mediators - interleukin (IL)-6, homocysteine, and high-sensitivity C-reactive protein (hsCRP) - in previously sedentary older men (SED) and masters athletes (LEX). Further, we investigated whether SED exhibited greater basal inflammatory biomarkers compared to LEX.

Twenty-two men (aged 62 ± 2 years) participated in the SED group, while 17 age-matched LEX men (aged 60 ± 5 years) also participated as a positive comparison group. In SED, preconditioning and HIIT caused a reduction in IL-6 compared to enrollment. SED homocysteine did not change throughout, while the decrease in hsCRP after preconditioning and after HIIT compared to enrollment was small. HIIT did not influence IL-6 or hsCRP in LEX. Homocysteine increased from enrollment to post-HIIT in LEX, but all other perturbations were trivial. IL-6 and hsCRP were greater in SED than LEX throughout the investigation, but homocysteine was not different.

Results of this study suggest moderate-intensity aerobic exercise and HIIT lowers IL-6 (and possible hsCRP) in previously sedentary older men. Moreover, lifelong exercise is associated with reduced concentrations of some inflammatory biomarkers in older males, and therefore, physical inactivity, rather than age per se, is implicated in chronic low-grade inflammation. Moreover, physical inactivity-induced inflammation may be partly salvaged by short-term exercise training.

Link: https://doi.org/10.3389/fphys.2021.702248

This research is a representative example of ongoing efforts to better understand changes in the gut microbiome with age, identifying how and why specific microbial species are either protective or harmful to health. The gut microbiome is responsible for generating a range of helpful metabolites, but can also interact with tissues and the immune system to provoke chronic inflammation. It has been noted that some known beneficial populations decline while some known harmful populations grow in number with advancing age - though there is a great deal of work remaining to produce a full map of the effects of microbial species on health and aging. Fortunately, some short-cut approaches have been shown to favorably adjust an aged gut microbiome, such as fecal microbiota transplantation and flagellin immunization. Widespread clinical use still lies in the future, even through such approaches are quite accessible to self-experimenters.

Bifidobacterium species are pioneer colonizers of the gut and have been associated with various health-promoting effects, although the precise modes of action remain largely unknown. The abundances of various Bifidobacterium species in the gut vary widely among individuals according to dietary habits, age, and physiological status. One exception is Bifidobacterium longum (B. longum subsp. longum), which belongs to the human core microbiome. This species accounts for a higher proportion of Bifidobacterium species in the gut regardless of host age, is distributed broadly across the human lifespan, and is among a small subset of gut commensals that can colonize the gut for years.

Using a conceptual framework based on evolution and the pathogen transmission theory, we showed that B. longum had formed at least three geographically related populations and established the active transmission of B. longum strains across different types of hosts and according to geography and proximity. Interestingly, we identified a strong and statistically significant association between host age and genetic variations in B. longum genomes.

Our data also provide a molecular basis for host-microbe coevolution, and this knowledge could feasibly be used to promote host health. The causal link between the gut microbiota and host aging has been investigated extensively, and microbiome-based therapies such as dietary interventions, probiotics, and fecal microbiota transplantation have been shown to efficiently alleviate host aging. Some bacteria have been associated with a long human lifespan by analyzing the gut microbiota of centenarians. No chronological threshold or age is associated with an abrupt change in the microbiota composition; rather, these changes proceed gradually over time.

We identified a strong negative association of the genus Bifidobacterium with host age, consistent with previous observations of reduced bifidobacterial counts in the elderly compared with the gut microbiota of two or three other age groups. We further investigated the bifidobacterial species-level composition and identified B. longum as the most dominant of the core bifidobacterial species in the studied cohort. We further determined that the relative abundance of B. longum was also significantly correlated with host age. Interestingly, efforts to associate the genotype of this aging-related species with host age revealed a robustly significant association with the bacterial arginine biosynthesis pathway.

Previous studies have demonstrated many molecular mechanisms by which microbiota may favorably affect host health and aging, based on principles designed to seek possible solutions to those changes experienced during the aging process, including (1) decreased immune system functioning (i.e., immunosenescence) and low-grade chronic inflammation (i.e., inflammaging); (2) inappropriate oxidative stress; (3) impaired gut barrier function; (4) decreased energy supply for colon epithelial cells; and (5) perturbed gut metabolism (e.g., lipid metabolism, glucose homeostasis, vitamin B and conjugated linoleic acid production). Here, we propose another potent mechanistic route that key players (B. longum) in the gut microbiota are capable of generating age-related genomic adaptations in the arginine metabolism pathway, enhancing the bacterial arginine-enriching ability, further modifying arginine flux and the overall metabolome in the gut microbiota, and ultimately achieving protection against host aging.

Link: https://doi.org/10.1186/s40168-021-01108-8

The earliest stages of Alzheimer's disease are characterized by increasing aggregation of misfolded amyloid-β, but there is considerable debate over the role played by amyloid-β in the onset and progression of the condition. The failure of amyloid-clearing immunotherapies to improve patient outcomes has spurred a great deal of alternative theorizing, some of which regards amyloid-β aggregation as a side-effect of other, more important processes, and some of which adjusts the details by which amyloid-β produces pathology, but retains it as a central pillar of disease onset.

Unfortunately all animal models of Alzheimer's pathology are highly artificial, as the usual laboratory species do not naturally develop anything resembling the Alzheimer's neurodegenerative processes in humans. Thus the models reflect preconceptions about which processes are important. If a researcher thinks that a specific subset of amyloid-β aggregation is vital to the progression of Alzheimer's disease, then that lab will generate mice that exhibit this specific biochemistry. This strategy is inefficient, to say the least. The hypothesis leads to the mouse model, which leads to therapies that can rescue the mouse model, which leads to treatments that so far don't work well in humans, because the hypothesis is in some way incorrect.

It seems fairly well established that there is a dynamic equilibrium between amyloid-β in the brain and in the rest of the body. Researchers have run human trials based on attempts to clear amyloid-β in the bloodstream, and thus cause amyloid-β to leave the brain via the equilibrium mechanisms. This seems to be working modestly well so far, though it is only slowing progression of Alzheimer's disease. Amyloid-β is created in both the brain and the body, but which of these is the important source when it comes to the onset of Alzheimer's disease? In today's research materials, scientists suggest that Alzheimer's may originate in amyloid-β production in the liver. So of course they engineered a highly artificial mouse model in which that happens, producing neurodegeneration as a consequence. Sadly, this alone should give us little confidence that the liver amyloid hypothesis is a true reflection of what is going on in humans, for the reasons given above.

The concept is interesting, however, given recent work on the origins of α-synuclein aggregates in Parkinson's disease. It appears that in some fraction of Parkinson's patients, the α-synuclein responsible for the onset of the condition originates in the gut and then spreads to the brain. Given that, it isn't outrageous to suggest a bodily origin of the amyloid-β aggregation in Alzheimer's disease. It does, however, need more and better evidence in order to become convincing.

Landmark study presents evidence Alzheimer's disease begins in the liver

For several decades it has been generally accepted that Alzheimer's disease is caused by the accumulation of amyloid proteins in the brain. These proteins form toxic aggregations known as plaques and it is these plaques that damage the brain. Although doubts are growing regarding the veracity of the "amyloid hypothesis," the build up of these plaques is still the most prominent physiological sign of Alzheimer's. And one of the more interesting hypotheses going around suggests these damaging amyloid proteins originate in the liver.

The big challenge in investigating this liver-amyloid hypothesis is that amyloid is also produced in the brain. Most mouse models used in Alzheimer's research involve engineering the animals to overexpress amyloid production in the central nervous system, which only really resembles the minority of humans suffering from hereditary early-onset Alzheimer's. The vast majority of people developing the disease instead experience what is known as sporadic Alzheimer's, where the disease develops in older age, with no familial or genetic history.

The breakthrough in this new research is the development of a new animal model of Alzheimer's disease. Here, the researchers engineered a mouse to produce human amyloid proteins solely in the liver, and this allowed for novel observations into how these proteins can enter the bloodstream and travel to the brain. This new study offers clear evidence of a "blood-to-brain pathway." Using the newly developed mouse model the study shows how amyloid produced in the liver can move to the brain and cause damage leading to pathological signs similar to those seen with Alzheimer's disease.

Synthesis of human amyloid restricted to liver results in an Alzheimer disease-like neurodegenerative phenotype

Several lines of study suggest that peripheral metabolism of amyloid beta (Aß) is associated with risk for Alzheimer disease (AD). In blood, greater than 90% of Aß is complexed as an apolipoprotein, raising the possibility of a lipoprotein-mediated axis for AD risk. In this study, we report that genetic modification of C57BL/6J mice engineered to synthesise human Aß only in liver (hepatocyte-specific human amyloid (HSHA) strain) has marked neurodegeneration concomitant with capillary dysfunction, parenchymal extravasation of lipoprotein-Aß, and neurovascular inflammation. Moreover, the HSHA mice showed impaired performance in the passive avoidance test, suggesting impairment in hippocampal-dependent learning. Transmission electron microscopy shows marked neurovascular disruption in HSHA mice. This study provides causal evidence of a lipoprotein-Aß /capillary axis for onset and progression of a neurodegenerative process.

There is much less interest in analysis of saliva than of blood or urine when it comes to mining metabolite and protein data in search of biomarkers of aging. Saliva has less to work with in terms of useful molecules. Nonetheless, some groups are making inroads in the analysis of biomolecules in saliva, as noted here. It should be expected that any sufficiently diverse set of biological data will exhibit characteristic changes with the accumulation of age-related damage and dysfunction. Somewhere in all of these options lies a simple, low-cost test that accurately reflects the state of that damage and dysfunction, and can thus be used to rapidly assess the degree to which any potential rejuvenation therapy actually works.

Researchers have conducted a comprehensive analysis of the metabolites that make up human saliva using samples given voluntarily from a group of 27-to-33-year-old individuals and a group of 72-to-80-year-old individuals. The sample collection was easy and noninvasive. Twenty-seven volunteers supplied their saliva, which they collected themselves at home. These were transferred to the laboratory for analysis. In general, the concentration of metabolites in saliva is very low compared to that in blood and urine, making it more challenging to detect them. However, using a comprehensive method, the researchers identified 99 metabolites, some of which were previously unreported in saliva. They also found that saliva contains information that reflects biological aging. Twenty metabolites, including those related to antioxidative activity, energy synthesis, and muscle maintenance, were lower in the elderly individuals than the young people, whereas one metabolite actually increased.

"It's interesting that ATP, the metabolite related to energy production, increased 1.96-fold in the elderly. This is possibly due to reduced ATP consumption in the elderly individuals. Amongst the metabolites that declined in quantity were two that are related to taste, suggesting that the elderly lose some ability to taste, and others that are related to muscle activity such as swallowing. These age-linked salivary metabolites together illuminate a metabolic network that reflects a decline of oral function during human aging."

Although this is the first comprehensive analysis to be performed on the metabolites of saliva, the researchers are planning to continue this work. In the future, they hope that saliva will be a sample that can be given readily and easily but could provide an enormous amount of information about an individual's health. "In saliva, age-linked metabolites are related to relatively broad metabolic conditions so that age-related information obtained from salivary metabolites may be distinct from that of blood and urine."

Link: https://www.oist.jp/news-center/press-releases/how-we-age-told-spit

Researchers here report on their view of amyloid accumulation in the brains of older people, as established by PET scans. They suggest that there is a tipping point after which further accumulation and the consequent development of Alzheimer's disease becomes predictable. It is interesting to consider what is going on under the hood to produce this behavior. Most aspects of age-related disease involve mutual interactions between different processes of damage and dysfunction, leading to feedback loops that change behavior at different stages of disease progression. In a system in which there is some capacity for maintenance, there may well be thresholds of damage and dysfunction after which maintenance cannot keep up, and pathology develops more rapidly as a result.

In those who eventually develop Alzheimer's dementia, amyloid silently builds up in the brain for up to two decades before the first signs of confusion and forgetfulness appear. Amyloid PET scans already are used widely in Alzheimer's research, and now an algorithm developed by researchers represents a new way of analyzing such scans to approximate when symptoms will arise. Using a person's age and data from a single amyloid PET scan, the algorithm yields an estimate of how far a person has progressed toward dementia - and how much time is left before cognitive impairment sets in.

Researchers analyzed amyloid PET scans from 236 people participating in Alzheimer's research studies. The participants were an average of 67 years old at the beginning of the study. All participants underwent at least two brain scans an average of 4½ years apart. The researchers applied a widely used metric known as the standard uptake value ratio (SUVR) to the scans to estimate the amount of amyloid in each participant's brain at each time point. The researchers also accessed over 1,300 clinical assessments on 180 of the participants. The assessments typically were performed every one to three years. Most participants were cognitively normal at the start of data collection, so the repeated assessments allowed the researchers to pinpoint when each participant's cognitive skills began to slip.

Researchers spent years trying to figure out how to use the data in amyloid PET scans to estimate the age at which symptoms would appear. The breakthrough came when they realized that amyloid accumulation has a tipping point and that each individual hits that tipping point at a different age. After this tipping point, amyloid accumulation follows a reliable trajectory. "You may hit the tipping point when you're 50; it may happen when you're 80; it may never happen. But once you pass the tipping point, you're going to accumulate high levels of amyloid that are likely to cause dementia. If we know how much amyloid someone has right now, we can calculate how long ago they hit the tipping point and estimate how much longer it will be until they are likely to develop symptoms."

Link: https://medicine.wustl.edu/news/time-until-dementia-symptoms-appear-can-be-estimated-via-brain-scan/

The ribosome is a cellular structure responsible for the translation stage of protein manufacture, in which proteins are assembled from amino acids according to the blueprint provided by a messenger RNA molecule. In today's research materials, scientists report that a small change in a ribosomal protein, found in heat-tolerant organisms, has interesting effects when introduced into short-lived laboratory species via genetic engineering. The outcome is a reduction in the error rate for protein manufacture, an increased heat tolerance, and a modestly extended life span.

It is worth noting that life span increases of this degree in very short-lived species such as yeast, flies, and worms should not be expected to appear in humans when the same approach is taken in our species. Very short-lived species have highly plastic life spans, particularly when it comes to approaches that improve the quality control of proteins in the cell, such as by increasing the efficiency of autophagy or proteasomal function in order to clear damaged proteins. As species life span increases, the effects of such interventions diminish. This is likely because longer-lived species have already evolved mechanisms that compensate in other ways, a necessary precondition for their longer life spans.

Nonetheless, this work on the ribosome, at the other end of the spectrum of protein quality control mechanisms, is interesting when considered in the context of the naked mole-rat, which lives nine times as long as similarly sized mammalian species. The much longer life span of the naked mole-rat is likely a result of the combination of many favorable differences in many areas of metabolism. That said, a few years ago it was found that this species has unusually efficient ribosomes, and therefore a lower rate of errors in protein manufacture. Today's results in flies and worms really only provide a starting point for debate over the degree to which the exceptional life span of the naked mole-rat is dependent on improved protein synthesis. While we should likely be leaning towards a smaller fraction of the overall effect rather than a larger fraction, there is clearly much more work to be accomplished on this topic.

Antiaging advice from single-celled creatures: Build better proteins

Many studies of the causes of aging and disease have focused on the accumulation of mutations in genes - the blueprints for a cell's proteins and other molecules. Far fewer have looked at glitches in how each blueprint gets translated, which can create faulty proteins. Key to translation is the ribosome, the cellular machinery that uses DNA's instructions to assemble amino acids into proteins. When the ribosome makes a mistake, the resulting proteins may fold improperly, stick to other proteins, and sometimes cause damage to cells.

Researchers looked to a part of the ribosome known to be critical for accurate translation: a protein called RPS23. While analyzing genetic data from species across the tree of life-from cows to gut microbes - the researchers found the same amino acid at a key position in this ribosomal protein. But there was an exception: Certain species of single-celled organisms called archaea that thrive in extremely hot and acidic environments had a mutation that replaced this amino acid with another.

Curious about the effects of this mutation, the researchers used the gene editor CRISPR to swap it into RPS23 genes of yeast, fruit flies, and the tiny roundworm Caenorhabditis elegans. Organisms with the mutation had fewer protein synthesis errors than unmodified controls. All three types of organisms could also survive at higher temperatures. Most strikingly, the yeast cells, flies, and worms lived between 9% and 23% longer. The mutants also seemed healthier as they aged: Compared with the control counterparts, older flies with the mutation were better able to climb and older modified worms produced more offspring.

Increased fidelity of protein synthesis extends lifespan

Loss of proteostasis is a fundamental process driving aging. Proteostasis is affected by the accuracy of translation, yet the physiological consequence of having fewer protein synthesis errors during multi-cellular organismal aging is poorly understood. Our phylogenetic analysis of RPS23, a key protein in the ribosomal decoding center, uncovered a lysine residue almost universally conserved across all domains of life, which is replaced by an arginine in a small number of hyperthermophilic archaea. When introduced into eukaryotic RPS23 homologs, this mutation leads to accurate translation, as well as heat shock resistance and longer life, in yeast, worms, and flies. Furthermore, we show that anti-aging drugs such as rapamycin, Torin1, and trametinib reduce translation errors, and that rapamycin extends further organismal longevity in RPS23 hyperaccuracy mutants. This implies a unified mode of action for diverse pharmacological anti-aging therapies. These findings pave the way for identifying novel translation accuracy interventions to improve aging.

Mitophagy is a quality control process that removes damaged and worn mitochondria, sending them to a lysosome for disassembly. Mitochondria are essential to cell function, a herd of hundreds of these bacteria-like organelles present in every cell. Active mitophagy ensures that this population of mitochondria remains usefully functional, providing the cell with a sufficient supply of the energy store molecule adenosine triphosphate (ATP). When mitophagy falters, as occurs throughout the body with age, for reasons that remain incompletely understood, the outcome is that mitochondrial function, cell function, and tissue function are all negatively affected. A better understanding of the triggers of the mitophagy process could lead to the development of compensatory therapies that at least partially restore lost mitochondrial function, and thus improve health and turn back aging in the old.

Mitochondria form a complex, interconnected reticulum that is maintained through orchestrated remodeling processes, such as biogenesis, dynamic fission and fusion, and targeted degradation of damaged/dysfunctional mitochondria, called mitophagy. These remodeling processes are collectively known as mitochondrial quality control and are initiated by various cues to maintain energetic homeostasis, which is particularly important for tissues with high-energy demands (e.g., skeletal muscle and heart). While the reticulum appears to respond to energetic demand uniformly, mitochondrial quality control acts with remarkable subcellular precision. For example, in both skeletal muscle and heart, impaired or damaged regions of mitochondria are separated from the functional reticulum in response to certain cellular signals, setting the stage for their degradation by mitophagy. However, what governs the spatial specificity of this process is poorly understood.

The cellular energy sensor AMPK senses cellular energy status by monitoring AMP and/or ADP levels. AMP and/or ADP bind to the γ subunit of AMPK, resulting in a conformational change. Muscle-specific knockout of both α subunit isoforms impairs exercises capacity and mitochondrial oxidative capacity, clearly linking energy sensing of AMPK to mitochondrial function as well as tissue function. Indeed, AMPK activation promotes mitochondrial fission in vitro through its direct substrate mitochondrial fission factor (Mff). We and others have previously demonstrated that induction of mitophagy in response to energetic stress (e.g., exercise, fasting, etc.) is controlled by AMPK-dependent mechanisms.

To reconcile the subcellular specificity of mitochondrial quality control with the fact that exercise and other energetic stresses increase ADP and AMP, the known activators of AMPK, we hypothesized that a proportion and/or subtype of AMPK is localized at mitochondria. This pool of AMPK may serve as a gauge of energetic cues, particularly when and where ATP production through oxidative phosphorylation becomes limited. Herein, we uncovered that a particular combination of subunits of AMPK are localized to mitochondria in a variety of tissues, including skeletal muscle and heart in both mice and humans, which we term mitoAMPK.

We show that mitoAMPK is localized to the outer mitochondrial membrane and is activated in response to various stimuli of mitochondrial energetic stress. mitoAMPK activity and activation are spatially variable across the mitochondrial reticulum. Finally, we present evidence that suggests activation of mitoAMPK in skeletal muscle is required for mitophagy in vivo. Discovery of a pool of AMPK on mitochondria and its importance for mitochondrial quality control highlights the complexity of energetic monitoring in vivo and could facilitate development of strategies of targeting mitochondrial energetics to treat diseases related to impaired mitochondrial function.

Link: https://doi.org/10.1073/pnas.2025932118

Researchers here demonstrate that molecules designed to supply hydrogen sulfide to mitochondria in skin cells can slow the progression of photoaging, the damage done to skin tissue by UV radiation. This offers some insight into the role of mitochondria in the reaction to UV radiation that produces lasting structural damage in skin. The publicity materials speculate on the ability to reverse existing photoaging damage, but that is unsupported by the work presented in the paper, which only shows the outcome of the topical application of the treatment to skin prior to exposure to ultraviolet radiation.

Two new molecules, AP39 and AP123, that generate minute amounts of the gas hydrogen sulfide have been found to prevent skin from ageing after being exposed to ultraviolet light found in sunlight. Researchers exposed adult human skin cells and the skin of mice to ultraviolet radiation (UVA). UVA is the part of natural sunlight which damages unprotected skin and can penetrate through windows, and even through some clothes. It causes skin to age prematurely by turning on skin digesting enzymes called collagenases. These enzymes eat away at the natural collagen, causing the skin to lose elasticity and sag, resulting in wrinkles

In the experiments, the compounds AP39 and AP123 did not protect the skin in the same way traditional sun creams prevent sunburn, but instead penetrated the skin to correct how skin cells' energy production and usage was turned off by UVA exposure. This then prevented the activation of skin-degrading collagenase enzymes and subsequent skin damage.

The compounds AP39 and AP123 specifically target the energy generating machinery inside our cells, the mitochondria, and supply them with minute quantities of alternative fuel, hydrogen sulfide, to use when skin cells are stressed by UVA. The direct result of this was the activation of two protective mechanisms. One is a protein call PGC-1α, which controls mitochondria number inside cells and regulates energy balance. The other is Nrf2, which turns on a set of protective genes that mitigate UVA damage to skin and turn off the production of collagenase, the main enzyme that breaks down collagen in damaged skin tissue and causes skin to look significantly more "aged".

Link: https://www.exeter.ac.uk/research/news/articles/newdrugmoleculescouldprev.html

Blood vessels passing through the central nervous system are sheathed by specialized cells that form the blood-brain barrier. The barrier controls the passage of cells and molecules into the brain. This protection is essential to the normal function of the brain, which operates in a biological environment that is very different to that of the result of the body. Unfortunately, and like all systems in the body, the blood-brain barrier deteriorates with age. This allows harmful molecules and cells to leak into the brain, provoking a damaging state of chronic inflammation in brain tissue. Inflammation is thought to be an important component of age-related neurodegenerative conditions, and to the degree that blood-brain barrier dysfunction contributes to the overall state of inflammation in brain tissue, it can be considered one of the important causes of neurodegeneration.

What to do about this problem? There is the question. The blood-brain barrier is a complex system, and thus its failure is also complex, when considered in detail. As is the case for much of aging, it is presently somewhere between challenging and impossible to accurately assess the relative importance of the many changes, failures, and forms of damage that can be measured in the cells of the blood-brain barrier. Even determining the direction of cause and effect for a few of these line items can be a hard task, an undertaking of years for teams of scientists. This is why the easier path to knowledge is to start with what is known of the root causes of aging, attempt to repair those causes one by one, and then observe the results on the dysfunction of critical biological systems such as the blood-brain barrier.

For example, senescent cells that accumulate in old tissues can now be cleared to a sizable degree via the application of senolytic therapies. Will this help to restore lost blood-brain barrier integrity? If so, it is then possible to look at specific differences before and after treatment in order to ask why this outcome the case. That may then inform researchers about the arrangement and relationships of blood-brain barrier pathologies in a more general sense. A working, narrowly focused rejuvenation therapy is the best of tools with which to explore the details of the aging process.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

Blood vessels are essential to transport oxygen and nutrients, remove CO2 and other waste products, and, thus, maintain homeostasis in the body. Blood vessels that vascularize the central nervous system (CNS) acquire specific anatomical and functional characteristics that collectively form the blood-brain barrier (BBB). At the cellular level, the BBB is developed by continuous non-fenestrated endothelial cells (ECs) encompassed by pericytes, smooth muscle cells, astrocytes, microglia, oligodendroglia, and neurons that are altogether called the neurovascular unit (NVU). At the molecular level, the BBB ECs are compacted by claudins, occludins, and ZO-1 [tight junction (TJ) proteins] and junction adhesion molecule (JAM) proteins to restrict the paracellular and transcellular diffusion of molecules in the CNS.

In addition, the BBB ECs mediate influx transporters to select metabolite uptake from the blood and efflux transporters to remove toxins and waste products from the brain into the blood. In BBB ECs, leukocyte adhesion molecules (LAMs) express very low to suppress immune surveillance in the brain. Thus, the BBB confines the access of neurotoxic compounds, blood cells, and pathogens to the brain. In addition, the BBB sustains the homeostasis of the brain through tight regulation of the transport of molecules between the brain parenchyma and peripheral circulation.

Hence, the BBB is a fundamental and crucial element of normal and healthy brain function. Any impairment in the cellular or molecular components causes BBB breakdown that results in BBB dysfunction. Aging is one of several factors involved in the breaking of the BBB and was first observed in aged patients reported in the 1970s. In dysfunctional BBBs, the possibility of permeability increases; thus, toxic and blood-borne inflammatory substances that infiltrate the brain could change the biochemical microenvironment of the neurons, thus leading to neurodegenerative diseases and dementia. It has been reported that BBB disruption in aged people is strongly related to Alzheimer's disease (AD) and cognitive impairment.

Although researchers have reported the contributions of BBB disruption to the pathogenesis of cognitive impairment associated with normal aging and dementia, more research is needed to elucidate the precisely causing factors and the cellular and molecular mechanisms of BBB maintenance, breakdown, and repair correlated with neurodegeneration and cognition decline. In the future, how aging and dementia affect BBB function in health and disease state, thus leading to neurodegeneration and cognitive impairment, should be explored in living organisms. Clinical research pertaining to this will boost our knowledge and help us better understand the association between BBB breakdown and cognitive decline. Such studies pave the way for the use of the BBB as a novel biomarker and therapeutic target to treat dementia and other neurological diseases associated with cognitive impairment.

Stem cells maintain tissue by providing a supply of daughter somatic cells to replace losses. This stem cell activity declines with age, and a sizable fraction of that decline in the most studied populations appears to be a reaction to the aged signaling environment rather than intrinsic dysfunction, at least in earlier old age. The behavior of cells lacking damage is controlled by their epigenetic state, alterations to the genomic machinery that governs the production of specific proteins. Could long term health be significantly improved by altering the epigenetic state of old stem cells, overriding their reaction to the aged tissue environment, and maintaining function at youthful levels? The consensus view of stem cell aging is that loss of function is an evolved response that serves to minimize cancer risk, but equally the evidence to date from animal studies suggests that there is considerable room to improve stem cell function and tissue maintenance in later life without greatly raising cancer risk.

Researchers have been looking at epigenetics as a cause of ageing processes for some time. Epigenetics looks at changes in genetic information and chromosomes that do not alter the sequence of the genes themselves, but do affect their activity. One possibility is changes in proteins called histones, which package the DNA in our cells and thus control access to DNA. A research group has now studied the epigenome of mesenchymal stem cells. These stem cells are found in bone marrow and can give rise to different types of cells such as cartilage, bone, and fat cells.

"We wanted to know why these stem cells produce less material for the development and maintenance of bones as we age, causing more and more fat to accumulate in the bone marrow. To do this, we compared the epigenome of stem cells from young and old mice. We could see that the epigenome changes significantly with age. Genes that are important for bone production are particularly affected."

The researchers then investigated whether the epigenome of stem cells could be rejuvenated. To do this, they treated isolated stem cells from mouse bone marrow with a nutrient solution which contained sodium acetate. The cell converts the acetate into a building block that enzymes can attach to histones to increase access to genes, thereby boosting their activity. The treatment caused the epigenome to rejuvenate, improving stem cell activity and leading to higher production of bone cells. To clarify whether this change in the epigenome could also be the cause of the increased risk in old age for bone fractures or osteoporosis in humans, the researchers studied human mesenchymal stem cells from patients after hip surgery. The cells from elderly patients who also suffered from osteoporosis showed the same epigenetic changes as previously observed in the mice.

Link: https://www.mpg.de/17468019/fountain-of-youth-for-ageing-stem-cells-in-bone-marrow

Researchers here demonstrate the creation of artificial pseudo-organelles capable of generating adenosine triphosphate (ATP). ATP is a chemical energy store molecule that is produced by mitochondria. It is vital to cell function. Mitochondrial production of ATP falters with age, as well as in tissues that become poorly supplied with nutrients. Finding a way to provide additional ATP could be quite helpful as a compensatory therapy, though whether or not a constant oversupply of ATP has meaningful negative consequences will have to be explored in greater detail than has been the case to date.

Cells have small compartments known as organelles to perform complex biochemical reactions. These compartments have multiple enzymes that work together to execute important cellular functions. Research have now successfully mimicked these nano spatial compartments to create 'artificial mitochondria'. This was achieved through reprogramming of 'exosomes', which are small vesicles (diameter ~120 nm) that cells use for intercellular signaling. The researchers carried out the experiments using microfluidic droplet reactors, which generated small droplets that were of similar size as typical cells. The researchers first aimed to facilitate controlled fusion of these exosomes within the droplets while preventing unwanted fusions.

These customized exosomes were then preloaded with different reactants and enzymes, which turned them into biomimetic nano factories. The team demonstrated this multienzyme biocatalytic cascade function by encapsulating glucose oxidase (GOx) and horseradish peroxidase (HRP) inside the exosomes. The GOx first converts glucose into gluconic acid and hydrogen peroxide. The HRP in turn uses the hydrogen peroxide generated in the first reaction to oxidize Amplex Red to a fluorescent product, resorufin. Next, the researchers wanted to know exactly how well these mini reactors can be uptaken and internalized by the cells. The cells derived from human breast tissues were fed with fused exosome nanoreactors, and their internalization over the next 48 hours was observed. It was found that cells were able to uptake these customized exosomes primarily through endocytosis, along with multiple other mechanisms.

Armed with this knowledge, the team sought to create functional artificial mitochondria that are capable of producing energy inside the cells. To achieve this, ATP synthase and bo3 oxidase were reconstituted into the earlier exosomes containing GOx and HRP, respectively. These exosomes were in turn fused to create nanoreactors that can produce ATP using glucose and dithiothreitol (DTT). It was found that the fused exosomes were capable of penetrating deep into the core part of a solid spheroid tissue and produce ATP in its hypoxic environment.

Link: https://www.ibs.re.kr/cop/bbs/BBSMSTR_000000000738/selectBoardArticle.do?nttId=20413

In today's open access paper, researchers report a modest improvement in cerebral blood flow and cognitive performance in a small study of older individuals suffering cognitive impairment as a result of sustained hyperbaric oxygen treatment over a period of months. This seems a compensatory approach to therapy, in that improvements in cerebral blood flow should be expected to improve cognitive function at any age. This is the mechanism by which exercise rapidly improves memory function, for example. A direct comparison of hyperbaric oxygen treatment and exercise would be interesting.

This result might help to inform discussions of the degree to which loss of blood supply to the brain contributes to cognitive decline in patients diagnosed with neurodegenerative conditions. Vascular dementia is an acknowledged and well-researched condition, but to what degree is the impairment of Alzheimer's patients at various stages due to vascular aging and consequent reduced blood flow to the brain, versus the harmful protein aggregation and neuroinflammation characteristic of Alzheimer's? Absent a way to remove just one of these pathologies, it is hard to answer that question.

It is worth noting that this study was conducted and published by the same groups who put together the poor study and accompanying overhyped media materials regarding the effects of hyperbaric oxygen treatment on measures of metabolism related to aging. It is most likely a good idea to treat this and any future work conducted by these researchers with an appropriately greater level of scrutiny and skepticism.

Hyperbaric oxygen therapy alleviates vascular dysfunction and amyloid burden in an Alzheimer's disease mouse model and in elderly patients

Vascular dysfunction is entwined with aging and the pathogenesis of Alzheimer's disease (AD), and contributes to reduced cerebral blood flow (CBF) and consequently, hypoxia. Hyperbaric oxygen therapy (HBOT) is in clinical use for a wide range of medical conditions. In the current study, we exposed 5XFAD mice, a well-studied AD model that presents impaired cognitive abilities, to HBOT and then investigated the therapeutical effects. HBOT increased arteriolar luminal diameter and elevated CBF, thus contributing to reduced hypoxia. Furthermore, HBOT reduced amyloid burden by reducing the volume of pre-existing plaques and attenuating the formation of new ones. This was associated with changes in amyloid precursor protein processing, elevated degradation and clearance of amyloid-ß protein and improved behavior of 5XFAD mice. Hence, our findings are consistent with the effects of HBOT being mediated partially through a persistent structural change in blood vessels that reduces brain hypoxia.

To understand whether the ability of HBOT to change CBF and affect cognitive function also applied to elderly people, we performed a human study in which six elderly patients (age 70.00 ± 2.68 years) with significant memory loss at baseline (memory domain score < 100) were treated with HBOT (60 daily HBOT sessions within 3 months). CBF and cognitive function were evaluated before and after HBOT. CBF was measured by MRI, while cognitive functions were evaluated using computerized cognitive tests. Following HBOT, there were significant CBF increases in several brain areas.

At baseline, patients attained a mean global cognitive score (102.4±7.3) similar to the average score in the general population normalized for age and education level (100), while memory scores were significantly lower (86.6 ± 9.2). Cognitive assessment following HBOT revealed a significant increase in the global cognitive score (102.4 ± 7.3 to 109.5 ± 5.8), where memory, attention and information processing speed domain scores were the most ameliorated. Moreover, post-HBOT mean memory scores improved to the mean score (100.9 ± 7.8), normalized per age and education level (100). The improvements in these scores correlate with improved short and working memory, and reduced times of calculation and response, as well as increased capacity to choose and concentrate on a relevant stimulus.

The analysis of the effects of genetic variants on human life expectancy has employed ever large databases in recent years: more genes, more sequences, more people. As the data grows, the likely size of the effect of genetic variation on human longevity has become smaller. Outside of a few interesting genes, such as those relating to blood cholesterol levels and cardiovascular disease risk, he picture is one of countless variants with small, interacting, environment-dependent effects, different in every study population.

How much of this picture is a true assessment versus a consequence of larger effects being hidden in the interactions between gene variants? Past studies have near all focused on a variant by variant analysis, considering each variant alone - and so this is an interesting question. Interesting or not, it remains the case that there may be no practical application here, however. Old people are still aged, damaged, and increasingly frail, whether or not they carry rare gene variants associated with longevity. Finding ways to emulate survivors to old age is an inherently poor approach to the treatment of aging, at least in comparison to working towards the repair of the underlying molecular damage that causes aging, in order to produce rejuvenation.

A major goal of aging research is identifying genetic targets that could be used to slow or reverse aging - changes in the body and extend limits of human lifespan. However, the majority of genes that showed the anti-aging and pro-survival effects in animal models were not replicated in humans, with few exceptions. Potential reasons for this lack of translation include a highly conditional character of genetic influence on lifespan, and its heterogeneity, meaning that better survival may be result of not only activity of individual genes, but also gene-environment and gene-gene interactions, among other factors.

In this paper, we explored associations of genetic interactions with human lifespan. We selected candidate genes from well-known aging pathways (IGF1/FOXO growth signaling, P53/P16 apoptosis/senescence, and mTOR/SK6 autophagy and survival) that jointly decide on outcomes of cell responses to stress and damage, and so could be prone to interactions. We estimated associations of pairwise statistical epistasis between SNPs in these genes with survival to age 85+ in the Atherosclerosis Risk in Communities study, and found significant effects of interactions between SNPs in IGF1R, TGFBR2, and BCL2 on survival to age 85 and older. We validated these findings in the Cardiovascular Health Study sample, using survival to age 85+, and to the 90th percentile, as outcomes.

Our results show that interactions between SNPs in genes from the aging pathways influence survival more significantly than individual SNPs in the same genes, which may contribute to heterogeneity of lifespan, and to lack of animal to human translation in aging research.

Link: https://doi.org/10.3389/fcell.2021.692020

Researchers here report on a broad comparison of protein sequences across many mammalian species, conducted in order to search for small differences between individual proteins that correlate with species life span. They find that humans, as one of the longer-lived mammals, already have most of these differences present across most of the the population. Further, the nature of these differences between proteins, meaning the specific functions of differing proteins in cell metabolism, is argued to support the hypothesis that quality control processes responsible for maintaining protein structure and removing damaged proteins make a sizable contribution to species differences in life span.

A key mechanism that may contribute to differences in lifespan between species is the maintenance of the proteostasis network. Protein stability or proteostasis refers to the capacity to protect protein structures and functions against environmental stressors, including aging. In fact, dysfunction of the protein quality control mechanisms is a hallmark of aging and there is substantial evidence linking proteostasis and longevity. For instance, improved protein stability is determinant for longevity in exceptionally long-lived mollusks and in the naked mole-rat, the longest-living rodent. In addition, interventions that enhance proteome stability can improve health or increase lifespan in model organisms, such as pharmacological chaperones that have been investigated as potential therapeutic targets to reduce the adverse effects of misfolding of aging-related proteins.

A mammalian-wide study of the genomic underpinnings of lifespan has never been carried out with the combined goals of identifying individual mutations linked to longevity; analyzing the functional properties of their genes and the pathways in which they take part; and studying how the stability of proteins coded by these genes may differentiate long- and short-lived species. Here, we performed the largest phylogeny-based genome-phenotype analysis to date, focusing on the detection of individual mutations and genes that underlie the enormous variation of lifespan in mammals. We report the discovery of more than 2,000 longevity-related genes and show that, overall, they present a trend towards increased protein stability in long-lived organisms. In addition, we successfully show that our findings enhance the interpretation of the results of longevity genome-wide association studies that have been carried out in humans.

We discovered a total of 2,737 single amino acid differences (AA) in 2,004 genes that distinguish long- and short-lived mammals, significantly more than expected by chance. These genes belong to pathways involved in regulating lifespan, such as inflammatory response and hemostasis. Among them, a total 1,157 AA showed a significant association with maximum lifespan in a phylogenetic test. Interestingly, most of the detected AA positions do not vary in extant human populations (81.2%) or have allele frequencies below 1% (99.78%). Consequently, almost none of these putatively important variants could have been detected by genome-wide association studies. Additionally, we identified four more genes whose rate of protein evolution correlated with longevity in mammals. Crucially, SNPs located in the detected genes explain a larger fraction of human lifespan heritability than expected, successfully demonstrating for the first time that comparative genomics can be used to enhance interpretation of human genome-wide association studies. Finally, we show that the human longevity-associated proteins are significantly more stable than the orthologous proteins from short-lived mammals, strongly suggesting that general protein stability is linked to increased lifespan.

Link: https://doi.org/10.1093/molbev/msab219

Rejuvenation takes place very early in embryonic development. The germline cells that go into the creation of an embryo are well protected and maintained in comparison to the average somatic cell in the adult body. Nonetheless, there is an accumulation of age-related epigenetic changes and molecular damage. Cells purge themselves of as much of this change and damage as possible, in order to ensure that the young are born with young somatic cells and tissues. This is primarily a resetting of epigenetic controls over gene expression, decorations on the structure of the genome that control shape and access to specific genes by the molecular machinery responsible for producing proteins from genetic blueprints.

A cell is a state machine, largely governed in operation by the matter of which proteins are produced, and in what quantities. Not completely governed: some damage, such as mutations to nuclear DNA, is irreversible. Some molecular waste cannot be managed even by cells in a youthful epigenetic state, and will degrade normal function. In a collection of replicating cells, that waste can be diluted via cell division, or even passed off entirely to a sacrificial daughter cell in a process of asymmetric division. So long as no one cell or small number of cells are vital, even serious mutation can be evaded by replication, provided that mutated cells are rejected. This is how single celled life, such as bacteria, can continue indefinitely. Further, a few lower organisms, such as the hydra, essentially a tiny bundle of stem cells in which every structure is replaceable, use this strategy in order to achieve individual immortality. Higher animals, with complex central nervous systems that include many non-replicating cells that cannot be sacrificed, cannot use this strategy, and so suffer from degenerative aging.

Embryonic rejuvenation is a process that can be understood, induced, and manipulated. The creation of induced pluripotent stem cells from normal adult somatic cells via reprogramming is one example of what becomes possible given sufficient knowledge and technical aptitude. This combines, in the same way as occurs in the early embryo, both an epigenetic reset and loss of somatic cell state, such as the shape and function of a skin cell or a brain cell, producing dedifferentiation into a pluripotent stem cell state. Researchers are presently looking beyond experiments in cell cultures towards the application of reprogramming in living animals. An epigenetic reset is a desirable outcome for somatic tissues throughout the aged body, likely able to reverse to some degree many age-related issues, such as loss of mitochondrial function. Dedifferentiation of somatic cells in an adult individual, on the other hand, is a roadblock and a challenge. It will lead to cancer where it occurs to a lesser degree, and it will cause pathology and death if prevalent. Differentiated cell state is vital to normal tissue function.

Thus an important question currently under investigation is whether or not these two aspects of reprogramming are inseparable. Is there an approach to reprogramming that will produce maximal epigenetic rejuvenation with minimal dedifferentiation? If so, that could prove to the the basis for a very useful approach to the treatment of aging. It likely cannot help much in the case of stochastic nuclear DNA damage leading to somatic mosaicism, and it cannot help with the accumulation of some forms of persistent molecular waste in long-lived cells, but it could nonetheless be beneficial enough to be interesting.

Cellular reprogramming and epigenetic rejuvenation

A recent addition to the anti-ageing strategies being developed comes from cellular reprogramming approaches. Induced pluripotency studies provided evidence that age-related cellular phenotypes such as mitochondrial morphology, function and number, as well as nuclear envelope integrity, are not irreversible. However, developmental cellular reprogramming turns a cell to a pluripotent state, where it has the potential to generate any somatic cell type. This process is not appropriate for an anti-ageing therapy in vivo because it requires not only the loss of the original cellular identity, but also the re-establishment of self-renewal capabilities. Therefore, induction of pluripotency or the direct injection of pluripotent cells in vivo, invariably lead to cancer in mice. For a cellular reprogramming-based intervention to be considered rejuvenative (turning an old cell into a younger cell), we need to uncouple its effects from dedifferentiation (loss of somatic cell identity).

Cellular reprogramming has demonstrated potential not only in regenerative medicine, but also in the ageing field through the amelioration of both physiological and cellular ageing hallmarks. While partial reprogramming might be used as a catch-all term to describe this type of rejuvenation, it does not reflect the fact that the described interrupted cellular reprogramming techniques are applied with the aim of (epigenetic) rejuvenation as opposed to inducing pluripotency (loss of cell identity). Reprogramming-induced rejuvenation (RIR) is a better term, capturing the nature of the utilised process and final aim of the interventions.

RIR has shown promise as a treatment to safely reverse ageing whilst retaining the ability to revert to or maintain original cell identity, both in vivo and in vitro. However, the precise nature of RIR still needs to be fully understood before it can be safely implemented as an anti-ageing treatment. For example, tracking any traces of pluripotency in partially reprogrammed cells (particularly in vivo) is a necessary precaution to minimise long-term cancer risk. Additionally, can rejuvenated partially reprogrammed cells be cultured long-term? The rejuvenated phenotype of some OSKM-treated cells lasts at least four weeks, but does this phenotype remain stable or eventually start to deteriorate at a rate faster than normal ageing?

Other important RIR safety concerns include how the reprogramming factors are introduced in vivo. Retroviruses are commonly used to integrate reprogramming factors into the genome. However, this method bears risks, such as insertional mutagenesis, residual expression and re-activation of reprogramming factors, and retrotransposon activation, all of which could increase cancer risk in vivo. Non-integrative delivery methods, such as transient transfection, non-integrating viral vectors, and RNA transfection are safer alternatives. For example, researchers have successfully used mRNA transfection to non-integratively conduct RIR. Another safe alternative is chemical-based reprogramming, which involves direct conversion of a somatic cell to a pluripotent state by use of small molecules and growth factors. It is conceivable that, in the future, chemical-based reprogramming could be adapted to achieve rejuvenation, however, this reprogramming approach currently only works for mice.

While RIR applied to skeletal muscle stem cells appears effective in improving regenerative capacity and muscle function in immunocompromised mice, further analysis is required regarding the somatic mosaicism of partially reprogrammed stem cells. Somatic variants at a stem or early progenitor cell level in turn can cause lineage bias, reduced stem cell function, and increased risk of developing haematologic cancer (e.g. age-related clonal haematopoesis). This can lead to the development of pre-malignant cells, which have a higher propensity to transform to a malignant state, the effect of which could be attenuated or exacerbated by RIR.

It also remains to be further explored whether and how RIR would work on post-mitotic terminally differentiated cells, such as neurons, cardiomyocytes, or adipocytes, but also other non-dividing cells such as quiescent or senescent cells. Pilot work has been done in the latter two states, demonstrating that a rejuvenated phenotype is achievable after restoration of cell division. These results may point to a scenario where proliferation is an essential requirement for rejuvenation. Indeed, induced pluripotency of postnatal neurons was only possible after forced cell proliferation via p53 expression. Coincidentally, the natural rejuvenation event in the early mouse embryo spans over stages of very active cell proliferation.

Overall, RIR is currently the best prospect to achieve epigenetic rejuvenation. Further studies are required to fully determine its limitations and efficacy.

Loss of hair cells in the inner ear is thought to be the primary mechanism behind the progression of age-related hearing loss, though there is some debate over whether it is in fact loss of cells versus loss of the connections that link hair cells to the brain. For some years, the research community has investigated whether or not it is possible to generate new hair cells in a living animal, bypassing the usual inability to replace losses in this cell population. Various approaches to signaling and cell therapy have been attempted, but despite interesting technology demonstrations, there is as yet little progress towards clinical translation of this research.

Various mechanisms can cause sensorineural hearing loss, among which irreversible damage to inner ear hair cells is the main cause. Although the commonly used hearing aids and cochlear implants in clinical practice improve the hearing of patients, their effect depends on the quantity and quality of residual hair cells and spiral neurons. Therefore, the ideal way to treat sensorineural hearing loss is to regenerate hair cells, through the use of stem cells to repair the structure and function of the cochlea, so as to fundamentally restore hearing.

Stem cell therapy in the auditory field has been a research hotspot in recent years. Although some progress has been made, almost all are results at the animal level, and there is still a long way to go before clinical transformation. The microenvironment of inner ear stem cells and the interaction with neighboring cells are very important for inner ear stem cells or sensory precursor cells to induce differentiation into mature inner ear hair cells. In the reported studies, the efficiency of differentiation of inner ear stem cells or sensory precursor cells into hair cells is still low. An insufficient number of new hair cells, immature new hair cells without the function of mature hair cells, and long-term survival of new hair cells are all key problems and difficulties that need to be solved urgently.

These results indicate that it is more difficult to regulate a single signal pathway to regenerate functional hair cells, and it may require coordinated regulation of multiple genes to effectively promote hair cell regeneration and the functional maturity and survival of new hair cells. Still, inducing the committed differentiation of stem cells into hair cells or nerve cells, the exploration of the methods of stem cell transplantation into the inner ear, and the safety research of stem cell transplantation have collectively laid the foundation for the transplantation of stem cells in vivo.

Link: https://doi.org/10.3389/fncel.2021.732507

Researchers here note that reduction in the calorie content in the diet is the important trigger for the benefits of calorie restriction, not reductions in the quantity of food ingested. The practice of calorie restriction, reducing calorie intake while still obtaining optimal micronutrient intake, has been shown to extend life span in near all species and lineages tested to date. Firm data on human life span has yet to be obtained, and is expected to be modest, on the order of a few years only, but short-term beneficial changes to the operation of metabolism are quite similar between mice and humans. Research into calorie restriction has given rise to a broad field of development of calorie restriction mimetic drugs, targeting many of the same cellular stress response mechanisms that are triggered by a low calorie intake. One shouldn't expect miracles from this line of work: we know the limits of calorie restriction in humans, and while it is certainly beneficial, it doesn't greatly change the duration of a human life.

Although calorie restriction has been reported to extend lifespan in several organisms, animals subjected to calorie restriction consume not only fewer calories but also smaller quantities of food. Whether it is the overall restriction of calories or the coincidental reduction in the quantity of food consumed that mediates the anti-aging effects is unclear. Here, we subjected mice to five dietary interventions. We showed that both calorie and quantity restriction could improve early survival, but no maximum lifespan extension was observed in the mice fed isocaloric diet in which food quantity was reduced.

Mice fed isoquant diet with fewer calories showed maximum lifespan extension and improved health among all the groups, suggesting that calorie intake rather than food quantity consumed is the key factor for the anti-aging effect of calorie restriction. Midlife liver gene expression correlations with lifespan revealed that calorie restriction raised fatty acid biosynthesis and metabolism and biosynthesis of amino acids but inhibited carbon metabolism, indicating different effects on fatty acid metabolism and carbohydrate metabolism. Our data illustrate the effects of calories and food quantity on the lifespan extension by calorie restriction and their potential mechanisms, which will provide guidance on the application of calorie restriction to humans.

Link: https://doi.org/10.18632/aging.203493

The processes of autophagy act to remove damaged molecular machinery and structures in the cell. Autophagy becomes dysfunctional with age, however. This is likely downstream of underlying causes of aging that cause changes in gene expression that degrade the function of autophagic processes in one way or another. For example mitophagy, the clearance of damaged mitochondria by autophagy, is indirectly negatively impacted by changes in mitochondrial dynamics resulting from altered gene expression. Equally, age-related changes in gene expression produce defects in the formation of autophagosomes, and this affects all aspects of autophagy.

Many of the known interventions that slow aging in animal models appear to improve the efficiency of autophagy, and functional autophagy is required for the extension of healthy life span via calorie restriction to take place. While improvement of autophagy has been a goal in the research community for quite some time, surprisingly little concrete progress has been made towards the development of therapies that specifically target dysfunction in autophagic processes.

Calorie restriction mimetics such as mTOR inhibitors improve autophagy, and mitochondrially targeted antioxidants and NAD+ upregulation may act to restore mitophagy. These were not designed with the enhancement of autophagy in mind; rather, it has been found to be one of their outcomes. The research and development communities have yet to see success in the development of narrowly targeted means of restoring a youthful function of autophagy in old tissues, though a few groups, such as the startup Selphagy Therapeutics that emerged from work on LAMP2A upregulation in the liver, are working in that area.

Selective Autophagy as a Potential Therapeutic Target in Age-Associated Pathologies

Cellular garbage disposal is critical for recycling defective cell constituents, such as proteins and organelles, towards the maintenance of cellular homeostasis. One of the main degradative molecule pathways is autophagy, which is a physiological catabolic process shared by all eukaryotes. Derived from the Greek words 'auto' meaning self, and 'phagy', meaning eating, autophagy, it was initially considered to be a bulk degradation process, while now its highly selective nature is increasingly appreciated. This self-digestive mechanism relieves the cell from proteotoxic, genotoxic, oxidative, and nutrient stress. It is accomplished in an intricate stepwise manner, which leads to clearance of damaged cell constituents, in the degradative organelle, the lysosome. Failure to complete this procedure has been implicated in many age-related diseases.

Homeostatic mechanisms that respond to mitochondrial damage are less efficient during aging. Mitophagy is a physiological eukaryotic pathway, which involves the degradation of superfluous or damaged mitochondria. When perturbed, normal mitochondrial function is hindered, resulting in the production of excessive reactive oxygen species (ROS). This ultimately leads to cellular dysfunction and tissue damage. Defective mitophagy is evident in a variety of age-related pathologies such as neurodegeneration, metabolic syndromes, and myopathies.

Aggrephagy degrades aggregation-prone proteins via targeted macroautophagy, in addition to chaperone-mediated autophagy and the proteasomal pathway. These proteins typically form aggresomes near the nucleus, which are surrounded by intermediate filament cytoskeleton, and are further processed to be degraded by autophagy. Protein aggregation usually occurs due to misfolding and can cause, among others, dysregulation of calcium homeostasis, inflammation, neurotoxicity.

Recycling of peroxisomes is also regulated by autophagy. These small dynamic single membrane organelles regulate fatty acid oxidation, production of bile acid and other lipids, while also producing ROS, which is neutralized by catalase. Moreover, peroxisomes interact with a multitude of other cellular constituents, such as lipids, the endoplasmic reticulum (ER), and mitochondria. Pexophagy and peroxisome biogenesis have recently been implicated with disease. During aging, peroxisomal targeting signal 1 (PTS1) protein import deteriorates and catalase function is diminished. Peroxisomes become more abundant and PEX5 accumulates on their membranes. This causes increased production of ROS, which further blocks peroxisomal protein import and contributes to aging.

With regard to therapeutic intervention, several pharmacological compounds have been shown to activate mitophagy and alleviate symptoms of age-related diseases, dependent on dysfunctional mitochondria. Rapamycin activates AMPK, while blocking mTOR, maintaining energetic demands and preventing neurological symptoms, such as neuroinflammation. Metformin and pifithrin induce Parkin by inhibiting p53 activity and alleviating diabetic phenotypes. Resveratrol, mainly found in grape skin, as well as, NAD+ precursors found in natural compounds activate mitophagy and mitochondrial biogenesis through the sirtuin 1 (SIRT1)-PGC-1α axis. Urolithin A, an intestinal microbiome-derived metabolite from dietary intake, induces both mitochondrial degradation and biogenesis, and increases health span of model organisms such as C. elegans and mice.

Selective autophagic induction by genetic intervention or chemical compound administration is currently being investigated in multiple diseases as potential therapeutic approach, although no drug has reached the clinic yet. Indeed, clinical studies concerning druggable autophagy targets remains limited. This highlights the complexity and intricacies of selective autophagic pathways, which in humans, cannot be easily targeted due to context-dependence and extensive crosstalk with other functional networks. Thus, initial optimism has subsided, with research now focusing on specific compounds that could target specific aspects of selective autophagy. An important objective of the collective efforts of the research community and pharmaceutical companies is to achieve targeting selective autophagy mediators, while not affecting other cellular processes.

Are there many strategies that can reverse cellular senescence? There are certainly strategies that can lower levels of cellular senescence over time, both in cell cultures and in living animals, but very few are actually reprogramming senescent cells into normal cells. It isn't clear that this reversal of the senescent state is a good idea, given that there is usually a good reason for at least some of such cells to be senescent, such as potentially cancerous mutations. The strategy described here is probably not causing senescent cells to become normal cells in any great number, but rather lowering the rate at which cells become senescent or encouraging senescent cells to self-destruct more rapidly, as well as encouraging normal cells to replicate more rapidly, thus diluting the senescent fraction of the population.

Cellular rejuvenation occurs naturally in embryonic development when sperm and egg (each having a certain chronological age) fuse to each other to form an embryo of age zero. Similarly, reprogramming of somatic cells to pluripotency, producing induced pluripotent stem cells (iPSCs), resets their biological clock as well. At this stage, a core network of transcription factors including NANOG, OCT4, and SOX2 maintains pluripotency in embryonic stem cells (ESCs) and iPSCs. In particular, the pluripotency factor NANOG is essential for maintaining the self-renewal of ESCs over many population doublings.

Although overexpression of NANOG does not confer pluripotency to somatic cells, it has been shown to restore several cellular functions that are compromised by aging including proliferation and differentiation of senescent fibroblasts and mesenchymal stem cells. In vivo endogenous expression of this transcription factor in stratified epithelia of adult mice showed that systemic overexpression of NANOG induces hyperplasia without initiating tumors.

Recently, we discovered that expression of NANOG in myoblasts restored their myogenic differentiation potential, as evidenced by expression of myogenic regulatory factors and the ability to form myotubes, which was impaired by replicative senescence. This result prompted us to investigate the anti-aging effects of NANOG on primary human myoblasts and in skeletal muscle tissue in vivo. Here, we show that overexpression of NANOG reversed the hallmarks of cellular senescence in muscle progenitors in vitro and restored the satellite cell abundance in the skeletal muscle of progeroid mice.

Link: https://doi.org/10.1126/sciadv.abe5671

Researchers here demonstrate that introducing an antioxidant into the diet, one that accumulates in cell lysosomes, helps to prevent macrophage dysfunction and thus reverse atherosclerotic plaque in an animal model of atherosclerosis. The hypothesis is that oxidized LDL particles, ingested and carried to lysosomes for degradation, are an important component of dysfunction in the macrophage cells responsible for clearing out lipid accumulations in blood vessel walls. Macrophages function well in youth, but are challenged and made dysfunctional in later life by the age-related increase in levels of oxidation of lipids and lipid carriers such as LDL particles. Strategies in clinical use to slow atherosclerosis have so far not directly targeted this challenge of oxidation and macrophage function, which may well be why they are of only limited benefit.

Multiple studies suggest that the presence of lysosomal cholesterol accumulation in macrophages, and not the total amount of intracellular lipids, is critical for the observed inflammatory response. We have shown that lysosomes in macrophages are a site of low-density lipoprotein (LDL) oxidation. Seven days after taking up mechanically aggregated LDL or sphingomyelinase aggregated LDL, mouse or human macrophage-like cells and human monocyte-derived macrophages generated ceroid in their lysosomes. Ceroid (lipofuscin) is a polymerized product of lipid oxidation found within foam cells in atherosclerotic lesions.

The lysosomal oxidation of LDL is catalyzed by oxidation-reduction active iron present in the lysosomes of macrophages through the generation of hydroperoxyl radicals at the lysosomal pH of 4.5. This oxidation is inhibited by cysteamine (2-aminoethanethiol), an antioxidant that accumulates in lysosomes. Cysteamine is used in patients for the lysosomal storage disease cystinosis, caused by the absence of the lysosomal cystine transporter cystinosin. Recently, we have shown that cysteamine reduces atherogenic conditions caused by lysosomal LDL oxidation, such as lysosomal dysfunction, cellular senescence, and secretion of various proinflammatory cytokines, such as interleukin-1β, TNF-α, and interleukin-6, and chemokines, such as CCL2, in human macrophages.

LDL receptor-deficient mice were fed a high-fat diet to induce atherosclerotic lesions. They were then reared on chow diet and drinking water containing cysteamine or plain drinking water. Aortic atherosclerosis was assessed, and samples of liver and skeletal muscle were analyzed. There was no regression of atherosclerosis in the control mice, but cysteamine caused regression of between 32% and 56% compared with the control group, depending on the site of the lesions. Cysteamine substantially increased markers of lesion stability, decreased ceroid, and greatly decreased oxidized phospholipids in the lesions. The liver lipid levels and expression of cluster of differentiation 68, acetyl-coenzyme A acetyltransferase 2, cytochromes P450 (CYP)27, and proinflammatory cytokines and chemokines were decreased by cysteamine. Skeletal muscle function and oxidative fibers were increased by cysteamine. There were no changes in the plasma total cholesterol, LDL cholesterol, high-density lipoprotein cholesterol, or triacylglycerol concentrations attributable to cysteamine.

In conclusion, inhibiting the lysosomal oxidation of LDL in atherosclerotic lesions by antioxidants targeted at lysosomes causes the regression of atherosclerosis and improves liver and muscle characteristics in mice and might be a promising novel therapy for atherosclerosis in patients.

Link: https://doi.org/10.1161/JAHA.120.017524

The scientific community is very broad, and there are many groups within that community whose members intermittently produce studies that are either poorly designed, poorly conducted, or poorly presented and explained. Or all three, for all of the usual reasons. Constraints of time and funding, institutional pressure to publish, the involvement of external interests, and so forth. Bad papers do get published, provided that the authors are subtle enough. This does tend to be a self-correcting problem, when considered over a sufficiently long span of time to allow errant individuals and institutions to blacken their reputations with the community at large. Still, at any given moment, one should expect to see that some small fraction of published scientific papers are problematic, rather than merely incorrect.

The problematic paper for today's discussion was published last year, reporting on a study of the effects of hyperbaric oxygen treatment on areas of metabolism that are connected to the study of aging. At the time, claims of reversal of aging were circulating in the media. The paper itself was of poor quality, but far less offensive than the related and entirely unfounded hype. It was the usual circus of ignorant commentary, yes, but also a matter of hyperbaric oxygen treatment providers pushing claims that were completely unsupported by the evidence. Serious researchers will think twice about working with anyone who was involved in this exercise. I talked about this a little at the time, focusing as much on the ridiculous claims being made by institutions involved in the work, and by the media at large, as on issues with the study and interpretation of data. Relatedly, I see that the SENS Research Foundation team have chosen to pick apart the scientific details in a recent article. A little more shaming can't hurt in this case!

Hyperbolic Hyperbaric "Age Reversal"

Lower-quality, clickbait-hungry media outlets love sensationalist claims, but one does expect better from the public relations department of an internationally-respected research university. And it was an easy jump from the already-overstated "In First, Aging Stopped in Humans" and "treatments can reverse two processes associated with aging and its illnesses" to saying that a treatment "can reverse aging process" - and to then land in a mud-pit of self-parody with "Human ageing reversed in 'Holy Grail' study, scientists say."

The actual findings of a recent study on hyperbaric oxygen treatment (HBOT) were much more limited. Despite some intriguing indicators, the actual impact of HBOT on aging based on this study is entirely unclear, quite plausibly negligible, and in any case objectively less impressive than that of (say) regular exercise, which certainly does not "reverse aging."

The actual details of the study show that even the narrow claims of the study abstract aren't fully justified. It's not clear that blood-cell telomeres were lengthened any more than they would have been without HBOT; it's not clear that "senescent" T-cells were reduced in numbers, let alone actually destroyed; and if "senescent" T-cells had been destroyed, it would not demonstrate a senolytic effect of HBOT. Despite the fact that it's standard terminology in the immunology world, "senescent" T-cells aren't actually "senescent cells" in the sense usually used in the geroscience world. Jumping from post-HBOT reductions in the number of these "senescent" T-cells to potential effects on classical senescent cells is really just a misunderstanding of what kinds of cells are involved in each case.

Even if the study had robustly demonstrated that every one of the points above really did occur, it would not constitute "reversing aging" - or even justify the more restrained claims that "blood cells actually grow younger as the treatments progress" or "that the aging process can in fact be reversed at the basic cellular-molecular level."

Aging has comparatively simple root causes, forms of cell and tissue damage that accumulate as a side-effect of the normal operation of metabolism. These comparatively simple causes take effect on a very, very complex system, however. The result is an intricate web of interacting consequences, and ultimately a dysfunctional, failing mess in which it is very hard to pinpoint which of the countless observed mechanisms are actually important. The complexity of the outcome is a result of the complexity of a living organism, not of the complexity of the root causes of aging. Metabolism is incompletely understood, and for so long as that is the case, inspecting the progression of aging will continue to reveal new subtleties. This is why interventions should focus on the causes of aging, far better understood at the present time, and not on manipulating later stages of the process, much of which remains a dark forest.

Researchers have made a surprising discovery about the connection between protein shape and mitochondrial health, providing a piece of evidence for yet another theme in aging research: it's always more complicated than we thought. Proteins within the mitochondria are intricately involved in mitochondrial function, and are protected by the mitochondrial unfolded protein response (UPRmt). When proteins misfold in the mitochondria, which can be caused by external threats like pathogens or mitochondrial toxins, the UPRmt gets activated which helps restore protein shape and function. Past research on the microscopic worm C. elegans has demonstrated that boosting the UPRmt during development contributes to better mitochondrial health and a longer lifespan for the worms.

Consistently, pharmacologically boosting UPRmt has been shown to slow down diseases with mitochondrial dysfunction, such as Alzheimer's. The new research has found that activating the UPRmt in adult worms has the opposite effect: adult worms with a boosted unfolded protein response have worse health and a shorter lifespan. Digging into the details of this surprising outcome led the team to examine the mitochondrial permeability transition pore. Most of the time this pore is closed, keeping the interior of the mitochondria separate from the rest of the cell. Under stress, though, it opens to release calcium into the rest of the cell, signaling that it's time to cut its losses and induce cell death. It turns out that methods to boost the UPRmt in adult C. elegans are caused indirectly - the UPRmt is initiated in response to the opening of the transition pore. While the UPRmt is busy trying to clean things up, the signals coming from the opened pore are too strong for the cell to ignore and result in cell death. Researchers think this is what contributes to the early death of the adult worms.

Research in C. elegans forms the basis of much aging research, but what does this mean for efforts to boost health and prevent disease in people? While the mitochondrial permeability transition pore is already implicated in conditions like stroke and heart attack, the role of the UPRmt is not as well understood. Researchers liken the UPRmt to inflammation, which has a specific purpose and is useful under some conditions, but causes damage under others. One possibility is that, in a stressed cell, the UPRmt uses valuable cellular resources, hastening the already inevitable cell death.

Link: https://www.buckinstitute.org/news/aging-its-more-complicated-than-we-thought/

Immunotherapies that have successfully targeted amyloid-β have failed to help Alzheimer's patients to any meaningful degree. This may be because amyloid-β is only relevant in the earliest stages of the condition, or because the most visible amyloid-β aggregation outside cells is a side-effect of neurodegeneration rather than a core disease process. The research community has in recent years turned increasing attention to immunotherapies that target tau aggregation, characteristic of the later stages of Alzheimer's disease. There appears to be a bidirectional relationship between neuroinflammation and the accumulation of toxic, altered forms of tau. As noted here, targeting tau in human trials is starting to produce data that is more suggestive of patient benefits. Still, this is a painfully incremental process, and the results are still only a marginal improvement. We can hope that targeting inflammatory processes, such as those connected to senescent supporting cells in the brain, may produce better outcomes.

In a first for the field, there is now a hint that a tau immunotherapy may have slightly benefited people with Alzheimer's disease (AD). Semorinemab, a monoclonal antibody specific for tau's N-terminus, stemmed cognitive decline by almost half among people with mild to moderate AD, according to topline results from the Phase 2 LAURIET trial. The findings are a welcome reprieve after most tau immunotherapies thus far, including semorinemab itself, have come up short in trials. In a previous Phase 2 study, called TAURIEL, semorinemab brought no cognitive or functional benefit to people with prodromal AD or mild cognitive impairment. Despite this negative result among people in earlier stages of the disease, the companies moved forward with LAURIET, which enrolled participants in the mild to moderate stages of AD.

LAURIET enrolled 272 participants whose Mini-Mental State Examination (MMSE) scores were between 16 and 21 and who had brain amyloid at baseline. After receiving three doses spaced two weeks apart, participants received monthly intravenous infusions of semorinemab, or placebo, for the remainder of the trial. The study enrolled two cohorts, which received treatment for either 48 or 60 weeks. For both enrolled cohorts, between baseline and 49 weeks, those in the semorinemab groups declined 43.6 percent less on the ADAS-Cog11 than did those in the placebo groups, satisfying one primary outcome. The same was not true for the other primary endpoint, the Alzheimer's Disease Cooperative Study-Activities of Daily Living. Both groups declined similarly on the ADCS-ADL, in which an appointed caregiver scores the participant on how they perform a variety of tasks.

Why a possible efficacy signal in LAURIET, but not a peep in TAURIEL? Researchers think that the difference could come down to which species of tau predominate in different stages of the disease. Perhaps specific hyperphosphorylated forms drive the earlier stages of disease, and semorinemab might not bind them.

Link: https://www.alzforum.org/news/research-news/first-cognitive-signal-tau-immunotherapy-works

The Longevity.technology team has been publishing notes on the recent Aging Research and Drug Discovery (ARDD) conference, one of the few events at the end of this year to be held in person again after the long pandemic hiatus. It was a challenge for conference organizers to look into the crystal ball six to twelve months in advance and commit to a late 2021 event, but some did. The 2022 conference season will no doubt be interesting, as restrictions relax sufficiently for reliable travel and advance scheduling, and a few years of the suppressed urge to network is finally unleashed. The ARDD conferences are more focused on academic science and the established pharmaceutical industry than on investment and entrepreneurship, at least in comparison to say, the Undoing Aging conference series, but it can nonetheless be an interesting event for both investors and entrepreneurs.

For my part, I feel that there is too much of a focus on incremental, unambitious programs and interventions, such as metformin and other calorie restriction mimetics. These unambitious programs may turn out to provide sufficient proof of principle, in animal studies and preclinical drug discovery, for those leaders in the pharmaceutical industry who still find the idea of treating aging a novelty. The outcomes in the clinic will be modest to the point of pointlessness, however. No-one should be spending billions on the development of drugs that cannot in principle do any more for health than exercise and or a reduction in calorie intake. The opportunity cost here is vast, a loss of attention and effort that should have gone towards the development of true rejuvenation therapies with potentially sizable effects on health and life span. This is a complaint that can be directed at the field as a whole, and ARDD only happens to be a representative sampling of that field.

ARDD 2021 kicks off: sessions to cover longevity topics from AI and senolytics to mitochondria and stem cell rejuvenation.

With the goal of building better connections between pharma companies and the longevity field, ARDD's organisers are conscious of the importance of showcasing the most credible research and development in aging. "People want to believe in longevity, but it's important to maintain a stringent a scientific focus as possible. We haven't shown a single molecule working in humans and, while we've been able to slow aging down in mammals, we have never been able to stop it. But I'm very enthusiastic and positive about some of these challenges that we're facing. Years ago, the aging field was many disconnected fields. But the industry and the science has started taking shape, and the conference has evolved through the integration of multiple fields with key hallmarks of aging."

Lots to learn about longevity at ARDD 2021: from pharma and startups to physicians and high schoolers.

The theme of education continues throughout this year's conference, which has its roots in bridging the gap between the longevity field and major pharmaceutical companies. "From the very beginning, we have tried to make this conference very friendly towards the pharmaceutical industry, which needs to buy into this field. There has been a lot of activity in early stage drug discovery in the pharmaceutical industry, specifically on aging and age-associated biology that can be purposed towards multiple diseases."

Focus on frailty over aging

Anne-Ulrike Trendelenburg from the Novartis Institutes for Biomedical Research gave a brilliant presentation on pathways that should be targeted to treat age-related diseases, and how her research is shifting away from aging and towards defining and targeting frailty. Novartis' research has highlighted five recommendations to guide the future of age-related disease targeting. Firstly, focusing on healthspan as opposed to lifespan, which will have the biggest impact on patient lives, adding quality of life to years, over adding years to life. Trendelenburg also highlighted targeting multimorbidity, rather than continuing to focus on treating each individual disease, which is said to be ineffective and expensive. The team from Novartis want to develop better multimorbidity models in order to progress another of their recommendations, which is to target frailty over age through clinical trials.

ARDD 2021: DNA repair, mitochondrial enhancement, gene editing, and how a new era for longevity will help us beat age-related disease.

The day showcased a variety of longevity research, we heard more about the importance of focussing on mitochondrial targets in relation to finding age-related therapies. Karl Lenhard Rudolph from the Leibniz Institute on Aging spoke on mitochondrial enhancement and its relationship with late life dietary restriction, enabling improvements in stem cells and lifespan. While recognising the positive effects seen with dietary restriction across organisms, Rudolph addressed the worrying data that saw this method losing efficacy when restriction is started late in life. When looking at reduction of mortality rates lifelong dietary restriction shows a reduction in mortality rate, however late life dietary restriction has very little effect.

The combination of dasatinib and quercetin was the first practical senolytic therapy explored in mice and human trials. Treatments tended to be one-time (a few doses a few days apart) or weekly over a period of a few months. Here, researchers try a longer term approach, weekly intervals for much of the adult life of mice.

Senolytic therapies produce rejuvenation in animal studies by selectively destroying senescent cells, which cause pathology as they accumulate in tissues. Present thinking is that this accumulation is more a matter of increased creation and slowed clearance rather than individual senescent cells lingering for the long term. Is the best dosing strategy a frequent one or an infrequent one. Or does it not much matter, so long as cells are periodically cleared?

That the study here shows greater benefits in terms of slowed disc degeneration when the senolytic treatement is started earlier in adult life suggests a few things. Firstly that some forms of structural damage do not tend to recover, even when their causes are removed. Secondly that senescent cells are causing some degree of harm earlier in adult life than we might otherwise have suspected. Assessments of the burden of cellular senescence by age do exist, but are not yet robust. Results like this might cause some reassessment of the ideal strategy for those who would like to take advantage of the existence of readily available senolytic drugs.

Studies of human tissues and mouse models have shown an increased incidence of senescent cells during intervertebral disc aging and degeneration. Intervertebral disc degeneration is highly prevalent within the elderly population and is a leading cause of chronic back pain and disability. Due to the link between disc degeneration and senescence, we explored the ability of the Dasatinib and Quercetin drug combination (D + Q) to prevent an age-dependent progression of disc degeneration in mice.

We treated C57BL/6 mice beginning at 6, 14, and 18 months of age, and analyzed them at 23 months of age. Interestingly, 6- and 14-month D + Q cohorts show lower incidences of degeneration, and the treatment results in a significant decrease in senescence markers p16INK4a, p19ARF, and SASP molecules IL-6 and MMP13. Treatment also preserves cell viability, phenotype, and matrix content. Although transcriptomic analysis shows disc compartment-specific effects of the treatment, cell death and cytokine response pathways are commonly modulated across tissue types.

Our results show that the D + Q combination could target senescence in the mouse disc, and these results provide proof of principle that senolytics may be useful in mitigating age-dependent disc degeneration by decreasing local senescence status, fibrosis and matrix degradation, while promoting cell viability, healthy matrix deposition and lower levels of systemic inflammation.

Link: https://doi.org/10.1038/s41467-021-25453-2

Much of the communication between cells is carried in extracellular vesicles, membrane-wrapped packages of signaling molecules. Vesicles are classified by size at present, though the nomenclature is often used confusingly and inconsistently. Exosomes are one class of smaller and frequently studied vesicle. Since it is now comparatively cheap to analyze the contents of vesicles obtained from blood samples, there exists a wealth of data related to changes in vesicle sizes, types, and contents that take place with age. It remains to be seen as to what can be achieved with this data beyond the construction of biomarkers to measure biological age.

Almost every cell, including stem cells, naturally release extracellular vesicles (EVs) responsible for cell-to-cell communication. They are split into three categories: microvesicles or ectosomes are submicron vesicles with a diameter of 100nm-1000nm, distinguished by biogenesis mechanisms including cytoskeleton remodeling and phosphatidylserine externalization. These microvesicles are formed by the outward budding and fission of the plasma membrane after cell stimulation or stress. Exosomes are the most common EVs studied and the smallest ones with a diameter of 30nm-100nm.

Exosomes are considered key regulators of many biological settings and are present in several extracellular fluids to mediate cellular communication. Recently, they were suggested as biomarkers for several diseases to set up diagnosis and disease progression. Their characteristics hold a great interest in designing therapeutic purposes in metabolic and genetic disorders, neurodegenerative and cardiovascular diseases, and cancer.

The first signature of human aging is the decrease of tissue regeneration and repair, leading to the accumulation of senescent cells. These cells have been described to release more exosomes with different compositions than a normal cell. A cellular transcriptional program is induced whereby the number and composition of exosomes are changed, consequently reflecting the current parent cell profile. Much evidence has increasingly involved exosomes and exosome-derived miRNAs in both normal and pathological aging processes. Evidence has also increasingly involved exosome-derived miRNAs in aging-associated diseases. In this work, we review exosome biogenesis and its involvement in the mechanisms related to aging with a focus on the different pathways described for their secreted miRNAs.

Link: https://doi.org/10.3390/biomedicines9080968

Biochemistry is complex, and particularly so in the brain. The amyloid cascade hypothesis of Alzheimer's disease essentially states that slow aggregation of amyloid-β over years causes the onset of later and much more severe stages of Alzheimer's disease, meaning the chronic inflammation in brain tissue and tau aggregation that kills neurons. The hypothesis has so far survived the failure of amyloid-β clearance via immunotherapy to produce patient benefits, as well as the evidence for a subset of older individuals to exhibit high levels of amyloid-β without progressing to Alzheimer's disease. Researchers continue to explore and modify their hypotheses regarding how exactly amyloid-β leads to later issues.

At present, the research community appears to be leaning towards the idea that once the later stages of inflammation and tau aggregation take hold, they form a self-sustaining feedback loop of increasing pathology, and amyloid-β becomes largely irrelevant after that point. In this case early use of immunotherapies should reduce disease risk, but trials focused on prevention will take a long time to run to completion. It is still possible that the most visible amyloid-β aggregation outside cells is only a side-effect of chronic infection or other processes that generate inflammation and pathology. In that case, targeting amyloid-β will not help. In either case, therapies that target the mechanisms of inflammation or tau aggregation will be the next focus. There is a good chance that senolytic treatments to remove senescent cells in the brain will help, for example.

PET Firms Up Amyloid Cascade: Plaques, Inflammation, Tangles

In the Alzheimer's cascade hypothesis, plaques unleash tangles; alas, where neuroinflammation fits in has been hazy. Now, the first study to combine imaging of microglial activation with amyloid and tau PET in the human brain places neuroinflammation squarely in between the two. Researchers report PET findings from 108 adults who range from cognitively healthy to Alzheimer's disease (AD) dementia. Across this cohort, the regional distribution of microglial activation mirrored Braak staging, and correlated with tangle load. Moreover, the extent of microglial activation predicted the spread of tangles into later Braak regions, suggesting it drove this pathology. Notably, the relationship between neuroinflammation and tangles only occurred in the presence of amyloid plaques, and all three pathologies were required for cognitive decline.

"Amyloid potentiates microglial activation to drive tau propagation in the brain. The data suggest neuroinflammation should be included in biological definitions of AD. This is a very compelling study, and certainly advances our understanding of the crosstalk between microglial activation, amyloid, and tau burden in the clinical context."

PET imaging studies have consistently shown that as plaques spread into cortex, tangles break out of the medial temporal lobe to rampage across the brain, attacking cognition as they go. But the mechanistic connection between the pathologies remained mysterious. The medial temporal lobe contains little amyloid, making a direct interaction unlikely. Animal and in vitro studies hinted that microglia might be the missing link. In mice, activation of the NLRP3 inflammasome in microglia caused the cells to spew cytokines that triggered tau phosphorylation in neurons. Further, microglia isolated from AD brains contained tau seeds, which the cells released into the culture medium. The data implied that microglia phagocytose aggregated neuronal tau present in aging brain, then try but fail to digest it, and instead end up strewing it across the brain.

Most cancer treatments produce a lot of senescent cells in the course of killing cancerous cells. This is thought to be the primary reason as to why cancer survivors have a reduced life expectancy and greater burden of age-related disease. Senescent cells secrete disruptive, inflammatory signals that harm tissue function when consistently present. Growing numbers of senescent cells in old tissues are an important contribution to degenerative aging.

The straightforward approach to this issue would be to treat cancer patients with senolytic therapies to clear senescent cells after the anti-cancer treatment is complete. Whether or not one can usefully interfere during the anti-cancer treatments is an interesting question, and one that likely lacks a simple answer. Here researchers conduct a preliminary investigation of one potential point of intervention that appears to bias cells towards destruction rather than senescence, but only in some cancer types and treatment types. A great deal of further work would need to take place in order to determine whether this is actually safe in the scenario of cancer therapies.

A number of anti-cancer strategies, which are based on chemotherapy, radiotherapy, and immunotherapy or the use of CDK4/CDK6 inhibitors and epigenetic modulators may promote cellular senescence in cancer and normal cells and tissues as an adverse side effect. Cellular senescence, a state of permanent cell cycle arrest with well characterized biochemical and molecular biomarkers, is considered to be a tumor suppressor mechanism and tissue repair and regeneration modulator. However, in some circumstances, cellular senescence may also stimulate chronic inflammation and tumorigenesis in aged organisms.

DNMT2/TRDMT1 methyltransferase is implicated in the regulation of cellular lifespan and DNA damage response (DDR). It was suggested that DNMT2/TRDMT1 might be considered as a novel target in cancer therapy as the loss of DNMT2/TRDMT1 sensitized cancer cells to PARP inhibitors. In the present study, the responses to senescence-inducing concentrations of doxorubicin and etoposide in different cancer cells with DNMT2/TRDMT1 gene knockout were evaluated, including changes in the cell cycle, apoptosis, autophagy, interleukin levels, genetic stability and DDR.

Diverse responses were revealed that was based on type of cancer cells (breast and cervical cancer, osteosarcoma and glioblastoma cells) and anti-cancer drugs. DNMT2/TRDMT1 gene knockout in drug-treated glioblastoma cells resulted in decreased number of apoptotic and senescent cells, IL-8 levels, and autophagy, and increased number of necrotic cells, DNA damage, and affected DDR compared to drug-treated glioblastoma cells with unmodified levels of DNMT2/TRDMT1. We suggest that DNMT2/TRDMT1 gene knockout in selected experimental settings may potentiate some adverse effects associated with chemotherapy-induced senescence.

Link: https://doi.org/10.18632/aging.203203

Progeria is a rare genetic condition in which cells throughout the body become misshapen, dysfunctional, and damaged due to the accumulation of a broken form of the structural protein lamin A, called progerin. This produces outcomes that in some ways resemble accelerated aging. Aging is, after all, the accumulation of cell and tissue damage and dysfunction - just not this particular type of damage, to any great degree. Interestingly, progerin is observed in low levels in genetically normal older individuals, so it is possible that there is some contribution from this mechanism to normal aging. The studies needed to establish whether or not this contribution is sizable enough to care about have yet to be carried out, however. Nonetheless, it is interesting to keep an eye on the development of therapies for progeria that involve suppression of progerin or its activities.

Children with Hutchinson-Gilford progeria syndrome (HGPS) age rapidly due to a rare de novo mutation which causes accumulation of a shortened form of prelamin A - called progerin - at the nuclear envelope. Progerin is toxic and causes misshapen nuclei, cell senescence, a host of aging-related disease phenotypes, and death in the teenage years from myocardial infarction or stroke. Because progerin is methylated by the enzyme ICMT, earlier studies hypothesized that targeting ICMT might be an effective anti-HGPS therapy. These studies showed that targeting ICMT with genetic strategies improves phenotypes and extends survival in mouse models of progeria and that early-stage ICMT inhibitors can overcome senescence and improve phenotypes of cells from HGPS patients.

However, further studies were not possible due to the lack of ICMT inhibitors with ample bioavailability and pharmacological properties. Scientists have now taken a big step forward by synthesizing and validating a potent ICMT inhibitor (UCM-13207, Cpd21) that can be used in vivo. Their drug improves both cellular and in vivo phenotypes of HGPS, including parts of the vascular phenotype, and extends survival of mice with progeria. The study represents an important step in the preclinical validation of this therapeutic strategy and raises hopes that clinical trials might be possible in the not-too-distant future.

Both the current and previous studies show that targeting ICMT mislocalizes progerin, alleviates senescence, and stimulates proliferation of cells from mice and children with HGPS. Both also show that targeting ICMT does not influence the characteristic nuclear blebbing phenotype of progerin-expressing cells. Moreover, the magnitude of the effects of these three approaches is comparable. Whereas the earlier studies find that blocking progerin methylation reduces its turnover and causes the protein to accumulate in the nucleoplasm, Cpd21 was found to increase progerin turnover and reduce its levels in cells and tissues. The latter result - reducing the levels of a toxic protein - is obviously more attractive from a therapeutic perspective, and it raises the questions of whether Cpd21 causes off-target effects that trigger progerin degradation or whether it influences LMNA transcription, splicing, or mRNA turnover. The current study did not distinguish between these possibilities.

Link: https://doi.org/10.1021/acscentsci.1c00828

Thymic involution is the process of atrophy observed to take place in the thymus with age. The thymus is a small, but critical organ. Thymocytes produced in the bone marrow migrate to the thymus where they mature into T cells of the adaptive immune system. As active thymic tissue is replaced with fat, the supply of T cells falls to a fraction of youthful levels. This loss of replacement cells is an important contributing factor in the age-related decline of the adaptive immune system. T cell populations come under increasing replicative stress as they strive to maintain a consistent number of circulating cells, while pathological subpopulations of broken and malfunctioning T cells accumulate.

Why does the thymus atrophy? Researchers have studied the signaling involved, and it is reasonable to put much of the blame on rising levels of chronic inflammation with age. That is likely not the whole story, however, as chronic inflammation is a very broad set of mechanisms and interactions, as well as being associated with many other forms of immune dysfunction. We should expect to see discoveries such as that reported in today's open access paper, in which the authors delve into a very specific aspect of immune function that can both correlate with chronic inflammation, and gradually deplete thymic tissue over a lifetime.

Circulating mature dendritic cells homing to the thymus promote thymic epithelial cells involution via the Jagged1/Notch3 axis

The thymus is the central immune organ of the body and critical for T-cell differentiation and development. Many different cell types including thymocytes and thymic stromal cells such as thymic epithelial cells (TECs), resident macrophages, and dendritic cells (DCs) are present in the thymus. As the most crucial stromal cells in the thymus, TECs consist of the cortex and medulla TECs and control the positive and negative selection of T cells. The volumes of the thymic epithelium (cortex and medulla) show a continuous involution from the first year to the end of life. During thymus degeneration, TECs are replaced by fibrocytes and adipocytes. Decreased thymopoiesis leads to a decreased output of naïve T cells with reduced TCR repertoire and diversity. In addition, the number of naïve T cells in peripheral blood decreases gradually.

The increasing evidence demonstrated that peripheral DCs can migrate into the thymus. It was reported that two of the three major subsets of thymic DCs originate extrathymically and continually migrate to the thymus. It has been demonstrated that bone marrow derived antigen-presenting cells (APCs) carrying antigens from the periphery migrate into the thymus and delete autoreactive cells. Futher studies noted that circulating DCs migrated into the thymus and interacted with thymocytes.

In this study, mature DCs (mDCs), generated from the GM-CSF and IL-4 induced bone marrow cells, were intravenously injected into wild-type mice. Three days later, assays showed that the mDCs were indeed able to return to the thymus. Homing DCs have been mainly reported to deplete thymocytes and induce tolerance. However, medullary TECs (mTECs) play a crucial role in inducing immune tolerance. Thus, we evaluated whether the mDCs homing into the thymus led to TECs depletion. We cocultured mDCs with mTEC1 cells and found that the mDCs induced the apoptosis and inhibited the proliferation of mTEC1 cells. These effects were only achieved via direct cell-cell contact between mDCs and mTEC1 cells. Furthermore, we observed that an intrathymic injection of the mDCs resulted in acute thymic atrophy and reduced thymocytes and TECs substantially in vivo. In sum, this demonstrated that circulating mDCs migrated into the thymus and induced the degeneration of the thymus.

Overall, the findings of this study improve our understanding of the mechanisms underlying thymus degeneration. During infection, activated DCs are mature, and migrate into different lymph nodes through afferent lymphatic vessels. DCs, residing in tissues, can reach the periphery and carry antigens to secondary lymphoid organs through blood. A small number of circulating DCs, capturing pathogens, can migrate into thymus. Although the number of thymic homing DCs is relatively small, given numerous mild or severe infections throughout our lifetime, the cumulative effects may contribute to age-related thymus degeneration.

In summary, our results provided evidence that circulating mDCs return to the thymus and interact directly with TECs to activate Notch signaling through the Jagged1/Notch3 axis. Long-term Notch signaling activation of TECs results in their apoptosis and growth inhibition, thus leading to the degeneration of the thymus. These results also provide insights into the mechanisms underlying age-related thymic atrophy or infection, organ transplant rejection, and other diseases related acute thymic atrophy and help to develop novel strategies in clinical thymus and T-cell reconstruction.

I wholeheartedly approve of the approach taken by the organizers of the Impetus Grants project. If one has the funds to influence the course of science, then this is a smart way to go about it. Pick a field and a goal that interests you, and place funds in the hands of researchers with as little red tape and infrastructure as possible. Arrange for publication of data in advance, to ensure that all that is learned will be propagated to the rest of the field. The only real challenge in setting up such a venture is to learn enough about the field in order to be able to pick a good supporting team of scientific advisors and reviewers, people who are willing to be something other than conservative. The overhead to direct as much as tens of millions of dollars into constructive fundamental research can be quite minimal in this model.

Impetus Grants provides funding for scientists to start working on what they consider the most important problems in aging biology, without delay. Such work should not be held up by red tape: we offer grants of up to $500,000, with decisions made within 3 weeks. Our review process asks "what's the potential for impact" rather than "could this go wrong".

Our goal is to have a broad impact on the field, by supporting projects that challenge assumptions, develop new tools and methodologies, discover new ways to reverse aging processes, and/or synthesize isolated manifestations of aging into a systemic perspective. To ensure that we learn from every project, we're organizing a special issue of GeroScience to provide an opportunity to publish both positive and negative results from funded studies. We would rather fund the work you are most excited about doing, even if it might fail, than work that is certain to produce results but with limited impact on the field. But we realize that proposed projects will be done in the context of existing publication incentives.

We provide anywhere from $10,000 to $500,000. We do consider the amount requested during review; all else equal, projects that require less funding will be favored. We will pay a maximum of 10% institutional overhead, in line with the Gates Foundation precedent. Your application will be reviewed by at least two reviewers with more than a decade of experience in aging research, and at least one reviewer who is a topic expert for your proposal. All of our reviewers are under NDA to preserve confidentiality of your proposal. All projects will be evaluated on the clarity and quality of their experimental plans, and on the scope and immediacy of their potential impact on the longevity field. We ask 'could this work' rather than 'could this fail', and are not looking for complete consensus among reviewers; if at least one reviewer is strongly supportive of the project, we will tend to fund it.

Link: https://www.impetusgrants.com/

This review takes a look at a number of peptides related to mitochondrial function, and which are thought to potentially provide therapeutic benefit. Some are interesting in the context of aging. As is the case for most peptides with enough scientific literature to justify a review paper, availability and use is somewhat ahead of the science. Peptide manufacture is easy enough and cheap enough that most studied peptides can be purchased from established manufacturers. That certainly doesn't mean that they are in fact useful at the end of the day! This marketplace is very much like the supplement marketplace in that respect: there is a great deal more marketing than there is truth and robust evidence of benefits. That a mechanism exists, and connects to aspects of aging, such as mitochondrial dysfunction, is no guarantee that manipulating it will have a large enough effect to matter.

Mitochondria-derived peptides (MPDs) are a class of recently identified peptides, which are found within other known mitochondrial genes and encoded by small open reading frames (ORFs). The first MDP, Humanin (HN), was discovered in 2001 in patients with Alzheimer's disease and described as a neuroprotective peptide with a high therapeutic potential for neurodegenerative diseases. After HN, two other types of MDPs were discovered: mitochondrial ORF of the 12S rDNA type-c (MOTS-c) and small Humanin-like peptide, 1 to 6 (SHLP1-6).

MDPs are widely presented in different tissues, such as the kidney, skeletal muscle, colon, vascular wall, and heart. MDPs are released into the body via paracrine and endocrine pathways and have diverse functions as cytoprotective agents, such as maintaining cell viability and mitochondrial function under stress, are involved in cellular metabolism and cell survival and act in response to inflammation and oxidative stress. Recently, the role of MDPs was highlighted for many senescence and ageing-associated diseases, chronic inflammation diseases, cancer and neurodegenerative diseases, and retinal and fertility diseases.

In this review, we focus on the role of on MDPs as crucial peptides, modulating and regulating mitochondrial function and involved in pathological changes in cardiovascular disease via different molecular mechanisms. We also discuss the application of MDPs, modified MDPs and synthetic MDPs as uprising pharmaceutical tools for the treatment of cardiovascular diseases and other conditions. Further understanding the role of MDPs in various signalling pathways related to CVD would improve its medical significance and therapeutic potential.

Link: https://doi.org/10.3390/ijms22168770

Aging is the accumulation of molecular damage and the consequences of that damage. This molecular damage and its immediate consequences are comparatively simple to describe, but the damage takes place in a fantastically complex system of cells, cellular interactions, tissues, organs, organ interactions, and more. Every problem causes cascading, interacting chains of cause and effect, hard to pick apart via inspection and hard to reason about. Cellular metabolism and tissue structure and function are far from fully mapped, and aging involves sweeping changes throughout the organism and its countless subsystems.

Today's open access paper is an interesting attempt to layer the known hallmarks of aging (which are not all necessarily deeper causes of aging) by how they emerged over time in the evolution of life from unicellular to multicellular and higher organisms. This may well be a useful mental tool when considering the merits of various approaches to the treatment aging, but again, the system as a whole is fundamentally hard to reason about.

The enormous complexity and incomplete understanding of the overlap between aging and cellular biochemistry is why many people are in favor of repair-based interventions as the most effective path forward. There is a better understanding of root causes in aging than there is of how these causes connect in detail to the end consequences of aging. This produces an environment in which the most cost-effective approach is to repair a form of fundamental cell and tissue damage, and see whether or not it produces impressive results in animal studies. Then figure out the details regarding how and why it produces impressive results.

This is how the present focus on senolytic therapies to clear senescent cells emerged. Prior to producing the first demonstration studies of senescent cell removal in mice, not even the researchers who suggested this as a promising line of work thought that this approach to aging would produce rejuvenation in mice to the degree that it does. The exploration of why and how this is so beneficial will take considerably longer than the process of bringing the first useful senolytics into widespread use. Aging is hard to reason about.

The Evolution of the Hallmarks of Aging

The evolutionary theory of aging has set the foundations for a comprehensive understanding of aging. The biology of aging has listed and described the "hallmarks of aging," i.e., cellular and molecular mechanisms involved in human aging. The present paper is the first to infer the order of appearance of the hallmarks of bilaterian and thereby human aging throughout evolution from their presence in progressively narrower clades. Its first result is that all organisms, even non-senescent, have to deal with at least one mechanism of aging - the progressive accumulation of misfolded or unstable proteins. Due to their cumulation, these mechanisms are called "layers of aging."

The first layer of aging is the accumulation of unfolded or unstable proteins. As it appears as early as in unicellular organisms, it is universal. In other terms, no species is devoid of at least one mechanism of aging, although in some, its effects are efficiently countered by mechanisms of anti-aging. The first mechanism of anti-aging is disposal of unfolded or unstable proteins by cell division.

The second layer of aging is epigenetic alterations under the form of chromatin remodeling and histone modifications. It has appeared with the evolution of a more sophisticated support for DNA and does not seem to be causally related to the first layer. It concerns all archaea and eukaryotes.

The third layer of aging contains mitochondrial dysfunction, more specifically, ROS damage and the progressive degradation of mitochondrial integrity and biogenesis, damage to mitochondrial DNA and damage to the nuclear architecture, and finally the progressive degradation of proteolytic systems. The appearance of these mechanisms of aging is apparently unrelated to the existence of the previous ones. Yet, interactions are likely: the generation of ROS may increase the number of misshaped proteins, the loss of mitochondrial integrity may increase the generation of ROS. The mechanisms of the third layer result from the appearance of the characteristics of eukaryotic life, the existence of a nucleus, of mitochondria (and chloroplasts), and the appearance of autophagy. All eukaryotes share the mechanisms of this third layer - except those who have possibly lost one of its components.

The fourth layer of aging contains all the mechanisms grouped under the label of 'nutrient sensing': sirtuins and the TOR, AMPK and Insulin - IGF-1 pathways. These mechanisms also appeared independently from mechanisms of the first three layers. However, the level of interactions increases dramatically with this layer, which may be interpreted as a mechanism focused on the management of the available energy sources that happens to control many of the mechanisms of aging of the first three layers (directly with the regulation of autophagy or mitochondrial activity, indirectly through the double role of sirtuins in the regulation of this mechanism and in genomic maintenance), and thereby modulate the rate of aging. These mechanisms characterize opisthokonts, but not all eukaryotes, as their components do not seem to be involved in aging in bikonts, although most of them are present.

These first four layers of aging together constitute the hallmarks of unicellular aging. Unicellular organisms contain some or all of them and most multicellular opisthokonts still contain all of them. In unicellular organisms, the problem of unicellular aging is mainly solved through reproduction, sexual or clonal, which resets the aging clock for at least one of the two cells that result from cell division.

The fifth layer of aging contains DNA methylation and transcriptional alterations. In general, these epigenetic mechanisms, appeared early during the evolution of unicellular organism, have the effect of modulating the expression of genes in a cell, which is necessary to the coordination of individual cells in multicellular life. There is evidence that they are involved as mechanisms of aging in metazoans but it is plausible that they are involved in the aging of a colony in holozoans.

The sixth layer of aging is the decline in the regenerative potential of tissues. It appears with the distinction between stem cells and somatic cells in metazoans. Importantly, this duality of cells is an elegant multicellular solution to the problems of unicellular aging, as long as damaged somatic cells can be renewed, and as the renewal of stem cells can outpace the accumulation of damage as efficiently as prokaryotes get rid of accumulated protein aggregates by sequestrating them into one lineage. When the renewal of cells is insufficient, multicellular organisms age.

The seventh layer of aging contains both inflammation and the accumulation of senescent cells. The mechanisms of aging in this layer are likely to be strongly dependent on the existence of a lower rate of renewal of the cells in a multicellular organism, although they probably originate in some of the specificities of eumetazoans. Inflammation, cell senescence, and the decline in the regenerative potential of tissues together form the engine of aging in most senescent multicellular organisms.

The eighth and last layer of aging contains the accumulation of mutations in nuclear DNA, telomere attrition, and alterations of other forms of intercellular communications as those involved in inflammation. These mechanisms of aging do not depend on the appearance of new entities with bilaterians, but on the considerable complexification of intercellular communication and mutual dependency that appears at this stage, under the constraint of the existence of a complex organization.

The last four layers of aging together constitute the hallmarks of metacellular aging, that is, the aging of the cells of the organism that happens in multicellular life only. Metacellular aging is the problem of aging left unsolved by evolution in many metazoans. It basically consists in the failure to control the effects of unicellular aging, so that they progressively affect the whole multicellular organism, which eventually dies.

In the end, although the multilayer view of aging casts considerable light on the general process of aging, there are three important limitations, that all stem from the essentially 'basic cell biology' approach to aging. The first is that it ignores potentially important non-cellular factors of multicellular aging, like the continuous remodeling, and progressive structural degradation, of the extracellular matrix. The second is that it does not describe how variations of the general mechanism of aging explain the huge variety of the rate of aging among bilaterians. The third is that the importance, and maybe even the implication of some mechanisms of aging may depend on environmental factors.

A little cellular senescence is a good thing. When a cell enters the state of senescence in response to potentially cancerous mutational damage it shuts down replication and secretes signals that attract the immune system. Immune cells destroy any such senescent, damaged, potentially dangerous cells that fail to destroy themselves. When senescent cells accumulate with age, however, as the immune system falters in its task of clearance, the inflammatory secretions of these errant cells - the senescence-associated secretory phenotype (SASP) - make the environment much more favorable for the creation and growth of cancer.

Cellular senescence provides a significant benefit to the host by inducing irreversible cell cycle arrest and eliciting potent immune-mediated incipient tumor cell clearance, which is characterized by reduced incidence of cancer and halted tumor development. Senescence provides an alternative strategy to overcome the limitations of traditional cancer treatment because low dose of drugs can achieve the purpose of inducing senescence. However, senescent cells and SASP components can directly or indirectly promote tumor cells growth, invasion, and metastasis, and tumor vascularization. The senescence phenotype is complicated, and the production rate and clearance rate of senescent cells may be the influencing factors of the effects of senescence on tumor progression. One of the possibilities is that senescent cells are only beneficial when they are transient, and the accumulation of senescent cells and SASP cause increased susceptibility to tumorigenesis.

The in-depth understanding and utilization of senescence in cancer therapy has gained increasing attention and has become an important research field. A growing number of studies have convincingly demonstrated a paradoxical role for spontaneous senescence and therapy-induced senescence (TIS), that senescence may involve both cancer prevention and cancer aggressiveness. Previous findings have indicated that TIS is a positive outcome of therapy, since senescence is a state of growth arrest reflecting the loss of reproductive potential. In order to overcome the negative effects of TIS in cancer treatment, the concept of combining senescence-inducing therapies and removal of senescent cells, both normal and tumor derived, via senolytic therapies, or manipulating the paracrine effects of SASP is proposed. However, before clinical application, we must balance the validity and potential risks, and determine the overall advantages of this treatment concept.

Link: https://doi.org/10.3389/fcell.2021.722205

One of the more interesting developments of recent years in work on the beneficial effects of calorie restriction in humans is the establishment of an optimal boundary of reduced calorie intake. Can one obtain near all the benefits of fasting by eating a little, and how much is "a little" in this context? That question led to the fasting mimicking diet, supported by evidence for "a little" to be something like 750 calories per day for an averagely sized human, when considering a five day fast or low-calorie diet. As researchers note here, improvements in many metabolic parameters are not very different when considering fasting versus a fasting mimicking low calorie intake on this time frame. A range of other topics are also under exploration, such as how long the benefits to metabolism last following a fast, how long one has to fast to obtain those lasting benefits, how frequently to fast, and so forth. But it is always good to see an accumulation of more data and more robust data on these topics.

Fasting is known to have many health benefits such as prolonging lifespan and suppression of tumorigenesis. In the present study, we systematically evaluated the effects of water-only fasting on metabolic-syndrome and age-related risk markers in 45 normal-weight individuals. As shown, a 4.59 kg reduction in body weight, 9.85 cm reduction in waist circumference, and 1.64 kg/m2 reduction in body mass index (BMI) were observed during a 5-day water-only fast. After refeeding for 1 month (day 38), body weight, waist circumference, and BMI were still lower than the baseline level.

Blood pressure (BP) significantly declined during water-only fasting with diastolic BP declining more than systolic BP and gradually both increased to the baseline level by 98 days. Considering many fasting studies showed diastolic BP reduction did not exceed systolic BP reduction, future studies are needed on water-only fasting and BP reduction. Insulin dropped approximately 2.8-fold lower than the baseline level during water-only fasting. Insulin-like growth factor 1 (IGF-1) decreased by a total of 26% during water-only fasting and decreased more in females than males.

The number of pan T cells, CD4+T cells, CD8+T cells, and B cells decreased during water-only fasting. In contrast, the frequency of Treg cells significantly increased during fasting and still exceeded the baseline level 3 months after refeeding. This is an important benefit, since Treg cells have anti-inflammation effects. With regard to thyroid hormones, T4 increased rapidly during fasting, whereas T3 and TSH decreased. The decreased level of T3 during water-only fasting is of particularly importance since a low T3 level, without impairing thyroid function, is strongly associated with longevity.

The present study suggested that water-only fasting for many parameters was similar to calorie restriction and a fasting-mimic diet.The results of the present study are very promising as 5-day water-only fasting has many critical beneficial effects without toxicity.

Link: https://doi.org/10.1002/ctm2.502

You might recall a Chinese study from a few years back claiming a sizable effect on atherosclerotic plaque for supplementation with nattokinase. The result was a 36% reversal in plaque size, which is several times larger than can be reliably achieved with approaches such as statins and their successors, drugs that lower blood cholesterol. The dose was 6000FU/day for 6 months. My attention was recently drawn to the publication of results for a US study using dose of 2000FU/day for several years. In that study, there was no effect on the progression of atherosclerosis, and certainly no marked reversal.

Medicine in general has a serious replication issue, in that all too many claimed results evaporate when a more rigorous study is undertaken. One only has to look at the NIA Interventions Testing Program to see many claims of longer mouse life spans refuted by more careful work. Problems with replication and study quality are particularly the case for clinical work conducted outside the US and Western Europe. One can find a great many researchers in wealthier nations who are immediately and reflexively skeptical of studies in their field that were conducted in other parts of the world.

That aside, is this a question of different doses and patients with a different severity of disease? Perhaps, but when one sees data with this sort of inconsistency, it casts doubt on whether there is or can be an effect size large enough to be interesting. Nattokinase does appear to have an effect on mammalian biochemistry and cell behavior that could influence atherosclerosis, but that is never the point. Mechanisms are what they are, the question is always whether or not the effect size of manipulating the mechanism in this way, with this treatment, is large enough to pursue.

Nattokinase atherothrombotic prevention study: A randomized controlled trial

Described to be antithrombotic and antihypertensive, nattokinase is consumed for putative cardiovascular benefit. However, no large-scale, long-term cardiovascular study has been conducted with nattokinase supplementation. To determine the effect of nattokinase on subclinical atherosclerosis progression and atherothrombotic biomarkers. In this double-blinded trial, 265 individuals of median age 65.3 years, without clinical evidence of cardiovascular disease (CVD) were randomized to oral nattokinase 2,000 fibrinolytic units (FU) daily or matching placebo. The primary outcome was rate of change in subclinical atherosclerosis measured by serial carotid ultrasound every 6 months as carotid artery intima-media thickness (CIMT) and carotid arterial stiffness (CAS). Additional outcomes determined at least every 6 months were clinical parameters including blood pressure and laboratory measures including metabolic factors, blood rheology parameters, blood coagulation and fibrinolysis factors, inflammatory markers and monocyte/macrophage cellular activation markers.

After median 3 years of randomized treatment, annualized rate of change in CIMT and CAS did not significantly differ between nattokinase supplementation and placebo. Additionally, there was no significant effect of nattokinase supplementation on blood pressure or any laboratory determination. The results of this trial show that nattokinase supplementation has a null effect on subclinical atherosclerosis progression in healthy individuals at low risk for CVD.

Nattokinase Atherothrombotic Prevention Study (NAPS)

The potential for nattokinase to "thin" blood and to reduce blood clotting by positive antithrombotic and fibrinolytic effects presents a unique opportunity to safely study such effects on cardiovascular disease and cognition. Using nattokinase under primary prevention conditions, the investigators propose to conduct a randomized, double-blinded, placebo-controlled trial to determine whether decreasing atherothrombotic risk can reduce the progression of atherosclerosis and cognitive decline. The investigators propose to randomize 240 healthy non-demented women and men to nattokinase supplementation or to placebo for three years. The primary trial endpoints will be measurement of carotid arterial wall thickness and arterial stiffness, early changes of atherosclerosis that can be measured safely by non-invasive imaging techniques.

At the conclusion of this trial, the investigators expect to have sufficient evidence as to whether reducing the propensity for thrombus formation and/or increasing fibrinolytic activity can prevent the progression of atherosclerosis and cognitive decline. These results will provide novel and important data that will be informative concerning primary prevention through the atherothrombotic pathway. Providing evidence for a reduction in atherosclerosis progression and cognitive decline with nattokinase is likely to shift the current clinical paradigm for the prevention of these chronic age-related processes. In addition, such evidence will serve to create a new field of discovery and opportunity for prevention of cardiovascular disease and dementia.

In the course of examining gender differences on fly longevity, researchers here find sizable variations in life span between repeated studies. This variation is thought to derive from differences in maintaining a fly population, such as the dietary composition and season of the year. They suggest that this calls into question the detailed data obtained from much of the work involving aging and age-slowing interventions in flies. Reproducibility is critical to establishing whether or not observed effects are real. Flies may thus be a poor choice of model organism for any initial investigation of means to slow or reverse aging.

While our original goal was to understand how genetic variation played a role in costs of reproduction, we discovered strong cohort effects from one study to the next, especially across years. While we did not interrogate environmental and husbandry effects during the course of this experiment, we can surmise that these two factors were the major drivers of the differences we saw between the two replicate experiments, as genetic backgrounds were mostly comprised of iso-female lines.

The largest discrepancies between two years were seen with regards to maximum lifespans. While median lifespans were not changed to a large degree between years/seasons, maximum lifespans were significantly longer in summer 2019 in both sexes. We have several hypotheses, all related to fly husbandry, that could potentially explain this discrepancy. Our most likely, and anecdotally supported, hypothesis is that flies living in the summer are able to maintain better water homeostasis than those in the winter. Even though the incubators were set to approximately 60% humidity, we know that these often fluctuate. A second hypothesis for our observations is that the two experiments were done on slightly different media. As fly diet can have a huge impact on health and longevity, this could be contributing to our observed differences.

This lack of reproducibility in significant results between our two cohorts suggests that for certain questions the use of iso-female strains for determining genes that affect different phenotypes will require exquisite attention to husbandry details. The Drosophila Genetics Reference Panel (DGRP) has been used over the past decade to measure dozens of different biological phenotypes with conclusions about the genes playing a causal role in the phenotypes in question. However, if small environmental perturbations can make such differences in something a fundamental as sex differences in longevity, it is possible that many phenotypes may be more sensitive to subtle environmental variation than is generally supposed. As the fruit fly is used as the primary model organism to test novel compounds for their lifespan-extending effect, our results suggest that reproducibility between and even within laboratories might prove difficult.

Link: https://doi.org/10.1098/rsos.210273

Older mammals are prone to impaired thermoregulation, such as the inability to generate sufficient warmth in response to cold temperature. Researchers here find that changes in the population of ICL2 immune cells in fat tissue are important in this dysfunction. Transplanting young immune cells into old mice appears to help, but that demonstration is just the starting point. Researchers will now have to work their way down the long road to a sufficient understanding of the underlying mechanisms to enable a cost-effective forms of intervention. How does this dysfunction connect to the underlying cell and tissue damage of aging? That question will likely remain open for some years.

Human evolution has provided us a level of protection from the existential threat of cold temperature with the capacity to produce heat from fat stored in the body. However, with age, people become more susceptible to cold as well as inflammation and metabolic problems which can lead to a host of chronic diseases. In a new study, researchers find that the fat tissue of older mice loses the immune cell group 2 innate lymphoid cells (ILC2) which restore body heat in presence of cold temperatures. But in a cautionary tale for those seeking easy treatments for diseases of aging, they also found that stimulating production of new ILC2 cells in aging mice actually makes them more prone to cold-induced death.

Researchers were curious about why fat tissue harbors immune system cells, which are usually concentrated in areas often exposed to pathogens like nasal passages, lungs, and skin. When they sequenced genes from cells of old and young mice they found that older animals lacked ILC2 cells, a deficit which limited their ability to burn fat and raise their body temperature in cold conditions. When scientists introduced a growth factor that boosts the production of ILC2 in aging mice, the immune system cells were restored but the mice were surprisingly even less tolerant of cold temperatures.

"The simple assumption is that if we restore something that is lost, then we are also going to restore life back to normal. But that is not what happened. Instead of expanding healthy cells of youth, the growth factor ended up multiplying the bad ILC2 cells that remained in fat of old mice." But when researchers took ILC2 cells from younger mice and transplanted them into older mice, they found that the older animals' ability to tolerate cold was restored.

Link: https://news.yale.edu/2021/09/01/immune-cell-betrayal-explains-why-it-gets-colder-we-age

A recent popular science article from the Lifespan.io team provides a high level introduction to cellular reprogramming as a potential approach to the treatment of aging. Since the discovery that somatic cells can be reprogrammed to become induced pluripotent stem cells, essentially the same as embryonic stem cells, most exploration has focused on the cost-effective production of specific cell types for use in research and cell therapies. More recently, however, researchers have applied reprogramming strategies directly to tissues in living animals in order to improve heath and turn back aspects of aging and age-related disease.

Reprogramming is achieved by inducing expression of a few or all of the Yamanaka factors, genes regulating pluripotency. Scientists have observed that reprogramming of cells from old tissues reverses age-related epigenetic marks, gene expression changes, and mitochondrial dysfunction. It is a process that recapitulates some of the rejuvenation that takes place in early embryonic development, as cells clear out molecular damage and reset themselves for the task of building an embryo. Some studies have shown that delivering reprogramming factors into adult animals as a therapy produces benefits to health and signs of reversal of age-related pathology. There are clearly safety concerns in taking this approach to therapy, in that the production of even small numbers of pluripotent cells can lead to cancer, even as those cells improve tissue function via their signaling, in much the same way as the transplanted cells of first generation stem cell therapies. It isn't just a matter of producing a sort of in situ stem cell therapy, however; somatic cells exposed to lesser amounts of reprogramming factors can exhibit improved function without transforming into stem cells.

Reprogramming is not an instant event, not a switch. It is a process of change that requires sustained expression of reprogramming factors over some period of time, typically days. Shorter, lesser exposure to reprogramming factors can improve cell function by reversing age-related epigenetic changes and mitochondrial dysfunction without resulting in a transformation of cell type. This useful outcome of partial reprogramming may or may not prove to be challenging to reliably and safely achieve in living tissues. Different cell types require different timing, different recipes for effective reprogramming, and every aging organ in the body is made up of many different cell types. This is a work in progress.

Yamanaka Factors and Making Old Cells Young

In 2006, a study showed that it was possible to reprogram cells using just four master genes named Oct4, Sox2, Klf4, and c-Myc, or OSKM for short. These four reprogramming factors are often called the Yamanaka factors. This discovery paved the way for research into how these Yamanaka factors might be used for cellular rejuvenation and a potential way to combat age-related diseases. In 2011, a team first reported cellular rejuvenation using the Yamanaka factors. During their life, cells express different patterns of genes, and those patterns are unique to each phase in a cell's life from young to old; this gene expression profile makes it easy to identify an old or young cell.

In 2016, researchers showed for the first time that the cells and organs of a living animal could be rejuvenated via reprogramming. For the study, the researchers used a progeric mouse designed to age more rapidly than normal as well as a normally aging mouse strain. Both types of mice were engineered to express the Yamanaka factors when they came into contact with the antibiotic doxycycline, which was given to them via their drinking water. After just six weeks of this treatment, which steadily reprogrammed the cells of the mice, the researchers noticed improvements in their appearance, including reduced age-related spinal curvature. The treated mice also experienced a 50% increase in their mean survival time in comparison to untreated progeric control mice. It should be noted that not all aging signs were affected by partial cellular reprogramming, and if treatment was halted, the aging signs returned.

In 2020, another study howed that partial cellular reprogramming improves memory in old mice. As the previous studies have shown, partial cellular reprogramming is a balancing act between epigenetically rejuvenating cells and resetting their aging clocks, without completely resetting their cell identity so they forget what kind of cell they are. Also in 2020, researchers published a study that showed that they had managed to restore lost vision to old mice, and mice with damaged retinal nerves, using partial cellular reprogramming.

By far the biggest hurdle to translating partial cellular reprogramming to people is the need to find a way to activate the Yamanaka factors in our cells without needing to engineer our bodies to react to a drug such as doxycycline. Doing this may require us to develop drugs capable of activating OSKM, editing every cell in our body to respond to a particular compound like doxycycline, which would be extremely challenging though plausible. The rapid progress of medical technology could potentially mean that such partial cellular reprogramming therapies may become available in the not too distant future. We certainly hope so.

All other things being equal, more cells in the body undertaking more activity means a larger risk in any given period of time of one of those cells undergoing a cancerous mutation. Given this, larger and longer-lived species have necessarily evolved superior mechanisms of cancer suppression in order to avoid early death by cancer. The protein p53 is a cancer suppressor, produced from the gene TP53. Large mammals such as elephants maintain a low risk of cancer, despite having many more cells than smaller mammals, in part via having many copies of TP53 in the genome. It isn't just copy number, however. The sequence of p53 varies in small ways from species to species, and researchers here show that some of those differences appear to correlate with species longevity.

p53 is a critical sensor of cellular stress and thus, the dictator of cell fates. Depending on the types of stress, which include DNA damage, oncogene activation, nutrient deprivation, reactive oxygen species accumulation, and telomere shortening, p53 either (1) transiently stops cell proliferation, initiates the DNA repair machinery, and induces cell death when the damage cannot be repaired, or (2) pushes cells to replicative senescence, which is a permanent proliferation arrest.

Long-lived, cancer-free African elephants have 20 copies of the TP53 gene, including 19 retrogenes (38 alleles), which are partially active, whereas humans possess only one copy of TP53 and have an estimated cancer mortality rate of 11-25%. The mechanism through which p53 contributes to the resolution of Peto's paradox of cancer incidence remains vague. Thus, in this work, we took advantage of the available datasets and inspected the p53 amino acid sequence of phylogenetically related organisms that show variations in their lifespans.

We discovered new correlations between specific amino acid deviations in p53 and the lifespans across different animal species. We found that species with extended lifespans have certain characteristic amino acid substitutions in the p53 DNA-binding domain that alter its function. In addition, the loop 2 region of the human p53 DNA-binding domain was identified as the longest region that was associated with longevity. A 3D model revealed variations in the loop 2 structure in long-lived species when compared with human p53. We speculate that in long-lived species, L2 affects the p53 binding to DNA and/or other transcription factors and, consequently, affects the replicative senescence program.

Link: https://doi.org/10.3390/ijms22168512

The epidemiological evidence of recent years shows that a greater control of blood pressure is beneficial, reducing mortality and incidence of age-related conditions. Hypertension, raised blood pressure, is characteristic of age and very damaging to fragile tissues throughout the body. That damage adds up over time, and is a major contribution to age-related degeneration. A sizable component of age-related hypertension is lifestyle related, rather than an inexorable consequence of the mechanisms of aging, and thus avoidable. Further, a range of comparatively safe drugs can force a lowering of blood pressure, overriding dysfunction in blood pressure regulation. Even without addressing underlying causes related to the mechanisms of aging, this can produce a meaningful reduction in mortality and cardiovascular disease.

Aggressive blood pressure treatment in older hypertensive patients lowers the incidence of cardiovascular events compared to standard therapy, without increasing adverse outcomes. More than one billion people have hypertension worldwide. The overall prevalence in adults is around 30-45%, rising to more than 60% of people over 60 years of age. As populations age, adopt more sedentary lifestyles, and increase their body weight, the prevalence of hypertension worldwide will continue to rise. Elevated blood pressure was the leading global contributor to premature death in 2015, accounting for almost 10 million deaths.

The STEP study was conducted to provide new evidence on the benefits of blood pressure lowering in older patients with hypertension. Specifically, it examined whether intensive treatment targeting a systolic blood pressure (SBP) below 130 mmHg could reduce the risk of cardiovascular disease compared with a SBP target below 150 mmHg. The study enrolled 8,511 older essential hypertensive patients from 42 clinical sites in China. All participants were aged 60-80 years, with a SBP of 140-190 mmHg during three screening visits or taking antihypertensive medication. Patients with prior stroke were excluded.

Participants were randomly assigned to 1) intensive treatment (SBP target below 130 mmHg but no lower than 110 mmHg); or 2) standard treatment (SBP target 130-150 mmHg). uring a median 3.34-year follow-up period, the average decrease in SBP from baseline was 19.4 mmHg in the intensive treatment group and 10.1 mmHg in the standard treatment group. Average SBP reached 126.7 mmHg and 135.9 mmHg in the intensive and standard groups, respectively, with an average between-group difference of 9.2 mmHg.

The primary outcome was a composite of stroke, acute coronary syndrome, acute decompensated heart failure, coronary revascularisation, atrial fibrillation, or death from cardiovascular causes. A total of 196 primary outcome events were documented in the standard treatment group (4.6%) compared to 147 events in the intensive treatment group (3.5%), with a relative risk reduction of 26%.

Link: https://www.escardio.org/The-ESC/Press-Office/Press-releases/Intensive-blood-pressure-lowering-benefits-older-patients-with-hypertension

It has to be said, today's research materials make for a fascinating read. A group of scientists, in 2021, a decade into the general acceptance of the importance of cellular senescence as a phenomenon, conducts a study of lung fibrosis in which they achieve a reversal of that fibrosis using a bcl-2 inhibitor, venetoclax, and then publish a paper that fails to mention cellular senescence even once.

Fibrosis is a dysfunction of tissue maintenance, producing scar-like collagen deposits that disrupt tissue function. There is a weight of evidence for fibrosis as a phenomenon to be driven by the presence of senescent cells, including the use of various senolytic therapies in animal studies to reverse fibrosis. Initial human trials for one of those senolytic therapies are ongoing, and one of those trials was an attempt to treat lung fibrosis.

Many of the senolytic therapies established in animal studies are bcl-2 inhibitors, such as navitoclax, a close relative of venetoclax. Inhibition of BCL2 family proteins has the effect of driving senescent cells into self-destruction, reducing their resistance of programmed cell death stimuli. This was the one of the first approaches to the selective destruction of senescent cells to be validated in the laboratory, and is widely studied and appreciated in the research community.

So it is to my eyes a little odd for a research group to run a study using a senolytic drug, targeting a well-known apoptosis-related pathway, on a condition that is generally acknowledged to involve senescent cells, and then focus on everything other than senescence as a possible mechanism. Not even a mention in the discussion section. The exploration of bcl-2 in macrophages in the lung is certainly interesting, as macrophages are likely involved in everything that touches upon tissue maintenance, including fibrosis, but without addressing cellular senescence in some way it is hard to take the conclusions at face value here.

Reversal of lung fibrosis in mouse model suggests a novel therapeutic target for pulmonary fibrosis

Mice were given bleomycin for 12 days to establish lung fibrosis, and then treated daily until 21 days with ABT-199, whose medical form is known as Venetoclax, a medication approved by the FDA for use in several forms of leukemia. Control bleomycin mice had lung fibrosis with widespread collagen deposition. The bleomycin mice that received ABT-199 had normal lung architecture at 21 days and no collagen deposition.

Pulmonary fibrosis is a chronic disease showing aberrant remodeling of lung tissue. Idiopathic pulmonary fibrosis is the most common form of pulmonary fibrosis and has a high mortality rate within three to five years. Currently approved medications have limited efficacy. ABT-199 acts by inducing apoptosis, or programmed cell death, in monocyte-derived macrophages in the lung. Macrophages are large white blood cells that engulf and digest anything that does not have the surface proteins of healthy cells. Targets can include cancer cells, microbes, and cellular debris.

Researchers isolated macrophages from people with IPF. They found a marked increase in the macrophage mitochondrial protein Bcl-2 - a regulator of apoptosis - as compared to lung macrophages from people without IPF. Mitochondrial Bcl-2 was also elevated in lung macrophages from bleomycin-exposed mice that have lung fibrosis. Researchers found that mice with a conditional deletion of Bcl-2 in lung macrophages were protected from pulmonary fibrosis in the bleomycin model, and they were also protected from asbestos-induced lung fibrosis. These conditional deletion results set the stage for the experiments showing that the Bcl-2 inhibitor ABT-199 was able to reverse fibrosis in the mouse bleomycin model.

Targeting Cpt1a-Bcl-2 interaction modulates apoptosis resistance and fibrotic remodeling

Fibrosis progression is associated with apoptosis resistance in lung macrophages; however, the mechanism by which apoptosis resistance occurs is poorly understood. Here, we found a marked increase in mitochondrial B-cell lymphoma-2 (Bcl-2) in lung macrophages from subjects with idiopathic pulmonary fibrosis (IPF). Similar findings were seen in bleomycin-injured wild-type (WT) mice, whereas Bcl-2 was markedly decreased in mice expressing a dominant-negative mitochondrial calcium uniporter (DN-MCU). Carnitine palmitoyltransferase 1a (Cpt1a), the rate-limiting enzyme for fatty acid β-oxidation, directly interacted with Bcl-2 by binding to its BH3 domain, which anchored Bcl-2 in the mitochondria to attenuate apoptosis. This interaction was dependent on Cpt1a activity.

Lung macrophages from IPF subjects had a direct correlation between CPT1A and Bcl-2, whereas the absence of binding induced apoptosis. The deletion of Bcl-2 in macrophages protected mice from developing pulmonary fibrosis. Moreover, mice had resolution of fibrosis when Bcl-2 was deleted or was inhibited with ABT-199 (venetoclax) after fibrosis was established. These observations implicate an interplay between macrophage fatty acid β-oxidation, apoptosis resistance, and dysregulated fibrotic remodeling.

It remains to be seen as to whether Altos Labs is the new, large venture that patient advocates for the treatment of aging have been alluding to cryptically in recent months. It is apparently backed by a number of the high net worth individuals in the Left Coast business and philanthropy communities who are known to have a growing interest in the application of biotechnology to aging. Sadly, recent history suggests we should not expect much from such initiatives. Neither the Ellison Medical Foundation nor Calico Labs have done more than take on more of the same fundamental research into the progression of aging that is carried out at the NIA, at great expense, but no great gain. This is work that will not lead to rejuvenation therapies, and in many cases cannot even in principle achieve much in the matter of treating aging. The path to rejuvenation is to repair the known causes of aging and see what happens as a result. Unfortunately, most of the field spends most of its time trying to decipher how exactly aging proceeds in its complex later stages of cell and tissue dysfunction, without attempting to address those causes. Perhaps Altos Labs will be a different beast, given the apparent focus on cellular reprogramming. We can certainly hope so.

Last October, a large group of scientists made their way to Yuri Milner's super-mansion in the Los Altos Hills above Palo Alto. They were tested for covid-19 and wore masks as they assembled in theater on the property for a two-day scientific conference. Others joined by teleconference. The topic: how biotechnology might be used to make people younger. Milner previously started the glitzy black-tie Breakthrough Prizes, $3 million awards given each year to outstanding physicists, biologists, and mathematicians. But Milner's enthusiasm for science was taking a provocative and specific new direction. As the scientific sessions progressed, experts took the stage to describe radical attempts at "rejuvenating" animals.

That meeting has now led to the formation of an ambitious new anti-aging company called Altos Labs, according to people familiar with the plans. Altos hasn't made an official announcement yet, but it was incorporated in Delaware this year and a securities disclosure filed in California in June indicates the company has raised at least $270 million. Altos is pursuing biological reprogramming technology, a way to rejuvenate cells in the lab that some scientists think could be extended to revitalize entire animal bodies, ultimately prolonging human life. The new company, incorporated in the US and in the UK earlier this year, will establish several institutes in places including the Bay Area, San Diego, Cambridge, UK and Japan, and is recruiting a large cadre of university scientists with lavish salaries and the promise that they can pursue unfettered blue-sky research on how cells age and how to reverse that process.

Altos is certain to draw comparisons to Calico Labs, a longevity company announced in 2013 by Google co-founder, Larry Page. Calico also hired elite scientific figures and gave them generous budgets, although it's been questioned whether the Google spinout has made much progress. Calico has also started a lab whose focus is reprogramming; it published its first preprint on the topic this year.

Link: https://www.technologyreview.com/2021/09/04/1034364/altos-labs-silicon-valleys-jeff-bezos-milner-bet-living-forever/

Atherosclerosis, the buildup of fatty plaques in blood vessel walls, is an inevitable outcome of aging, driven by chronic inflammation, oxidative stress, and other processes that cannot be evaded without the development of new approaches to medical biotechnology. The pace at which this becomes a fatal condition is heavily driven by lifestyle choices, however. All of the usual activities and decisions that physicians tell us to avoid will, over time, lead to a faster progression of atherosclerosis, and a greater risk of mortality due to the rupture or blockage of blood vessels. It is quite possible that many people will be saved from their own neglect by new medical therapies that emerge in the years ahead. Equally, why roll the dice on the speed of medical progress, when you can postpone that need?

As much as 90% of the risk of a heart attack, stroke, or peripheral arterial disease (PAD) can be explained by smoking, poor eating habits, lack of physical activity, abdominal obesity, high blood pressure, raised blood lipid levels, diabetes, psychosocial factors, or alcohol. These guidelines focus on atherosclerotic cardiovascular disease (CVD), which affects the arteries. As the inside of the arteries become clogged up by fatty deposits, they can no longer supply enough blood to the body. This process is the main cause of heart attacks, strokes, PAD and sudden death where arteries become completely blocked. The most important way to prevent these conditions is to adopt a healthy lifestyle throughout life, especially not smoking, and to treat risk factors.

Targets for blood lipids, blood pressure, and glycaemic control in diabetes remain as recommended in recent guidelines on dyslipidaemias, hypertension, or diabetes. The current guidelines introduce a stepwise approach to intensifying preventive treatments, while always taking into consideration potential benefit, other conditions, psychosocial factors and patient preferences. In healthy people, for example, the stepwise approach starts with recommendations for everyone: smoking cessation, adopting a healthy lifestyle, and maintaining a systolic blood pressure below 160 mmHg.

Stopping smoking is potentially the most effective of all preventive measures, with substantial reductions in heart attacks or death. The CVD risk in smokers under 50 years of age is five-fold higher than in non-smokers. Quitting must be encouraged in all smokers, and passive smoking should be avoided where possible. Regarding nutrition, a healthy diet is recommended for all individuals to prevent CVD. This should emphasise plant-based foods including whole grains, fruits, vegetables, pulses, and nuts. New recommendations include the adoption of a Mediterranean or similar diet.

In terms of body weight, it is recommended that overweight and obese people lose weight to lower blood pressure, blood lipids, and the risk of diabetes, and thereby reduce the likelihood of CVD. For the first time, the guidelines state that bariatric surgery should be considered for obese individuals at high risk of CVD when a healthy diet and exercise do not result in maintained weight loss.

Link: https://www.eurekalert.org/news-releases/926798

It is thought that an appreciable fraction of the chronic inflammation of aging is caused by changes in the gut microbiome. There is a bidirectional interaction between the immune system and the microbial populations of the intestinal tract. The immune system gardens these populations, destroying problematic microbes. Microbes secrete metabolites and other molecules that can either benefit or harm the function of the immune system, the harms caused particularly by those microbes capable of provoking a sustained inflammatory response. The immune system declines with age for a range of reasons, and reduced efficacy in immune surveillance of gut microbes allows harmful microbial populations to grow in number, in turn further degrading immune function by inducing a state of chronic inflammation.

Many of the common, ultimately fatal age-related conditions are driven by chronic inflammation and the resulting disruption of normal tissue function. This is very much the case for neurodegenerative conditions. Inflammation in the brain is a prominent feature of tauopathies such as Alzheimer's disease, for example, in which toxic aggregates of altered tau protein form and spread in parallel with the inflammation of brain tissue. Researchers have shown that removing pro-inflammatory senescent cells from the brain, using senolytic drugs, reverses pathology in animal models of tauopathy. How much of inflammation in the brain is the result of senescent cells versus the gut microbiome versus other causes? The only way to find out is to remove each potential cause individually and observe the outcome.

In the case of the gut microbiome, strategies exist to reverse age-related changes. Fecal microbiota transplantation from young individuals to old individuals is the most studied of these approaches, well proven in animal models to reset the balance of microbial populations, reduce inflammation, and improve health. It is already used in humans to tackle cases in which pathological bacteria take over the intestines, and thus, given the will and the funding, it would be a comparatively short path to deploy fecal microbiota transplantation in clinical trials involving patients with inflammatory neurodegenerative conditions.

Fecal Microbiota Transplantation: A Microbiome Modulation Technique for Alzheimer's Disease

The gut microbiota plays a key role in modulating the gut-brain axis, which is a bidirectional communication network that involves the central nervous system, the autonomic nervous system (sympathetic and parasympathetic branches), the enteric nervous system, and the hypothalamic-pituitary-adrenal axis. Recent advances have revealed that the microbiota of the human gut has numerous beneficial functions, such as immune system development, resistance to pathogens, vitamin synthesis, production of metabolites such as short-chain fatty acids (SCFAs), nutrient and drug metabolism, and maintenance of the structural integrity of the intestinal mucosal barrier.

In humans, dysbiosis and changes in gut microbiome composition have been found to contribute to inflammatory bowel disease, type 2 diabetes, metabolic syndrome, obesity, colorectal cancer, Alzheimer's disease (AD), and numerous other diseases. AD is a disastrous neurological disorder affecting 5.8 million Americans (aged 65 years or older) in 2020. AD was the sixth most common cause of death in 2017, accounting for 121,404 deaths in the United States, and the fifth most common cause of death among elderly Americans (65+ years). The sizeable economic burden of AD, as well as its growing prevalence, are leading researchers to look for preventive or disease-modifying treatments.

There are various gut microbiota modulation interventions such as diet modification, prebiotics, probiotics, synbiotics, or fecal microbiota transplantation (FMT). FMT includes the transplantation of the gut microbiota from a donor to a recipient to refurbish the intestinal microflora of the recipient. It has been proven to be a successful treatment for recurrent Clostridium difficile infections. In this review, we summarize the procedure of FMT and its application in the treatment of various neurological disorders with a special emphasis on AD.

Osteoporosis, the age-related loss of bone mass and strength, is a serious condition. Bone is constantly remodeled, created by osteoblasts and removed by osteoclasts. With age, the balance of these activities tips towards favoring the osteoclasts, and bone mineral density declines over time as a consequence. It is becoming clear that inflammatory signaling is an important contributing factor in this dysregulation of the normal balance. The chronic inflammation that accompanies aging, the consequence of rising numbers of senescent cells, as well as of the presence of molecular damage that provokes the immune system, can be blamed for a great deal of the burden of aging.

Osteoporosis or porous bone disorder is the result of an imbalance in an otherwise highly balanced physiological process known as 'bone remodeling'. The immune system is intricately involved in bone physiology as well as pathologies. Inflammatory diseases are often correlated with osteoporosis. Inflammatory mediators such as reactive oxygen species (ROS), and pro-inflammatory cytokines and chemokines directly or indirectly act on the bone cells and play a role in the pathogenesis of osteoporosis.

Recently, researchers have coined the term "immunoporosis" to emphasize the role of immune cells in the pathology of osteoporosis. Accumulated evidence suggests both innate and adaptive immune cells contribute to osteoporosis. However, innate cells are the major effectors of inflammation. They sense various triggers to inflammation such as pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), cellular stress, etc., thus producing pro-inflammatory mediators that play a critical role in the pathogenesis of osteoporosis.

Cells of the myeloid lineage, including macrophages, monocytes, and dendritic cells, explicitly influences the skeletal system by the action of production of pro-inflammatory cytokines and can transdifferentiate into osteoclasts. Other cells of the myeloid lineage, such as neutrophils, eosinophils, and mast cells, largely impact osteoporosis via the production of pro-inflammatory cytokines. Further, cells of the lymphoid lineage, including natural killer cells and innate lymphoid cells, share innate-like properties and play a role in osteoporosis.

Link: https://doi.org/10.3389/fimmu.2021.687037

Researchers here identify a point of intervention in the age-related dysregulation of smooth muscle cell activity and surrounding extracellular matrix structure in blood vessel walls. Blood vessels stiffen with age, which leads to hypertension and consequent pressure damage to delicate structures throughout the body. The damage caused by hypertension is an important component of aging, a significant contribution to loss of function and mortality. Loss of elastin, cross-linking of extracellular matrix molecules, and the chronic inflammation generated by senescent cells are all known to contribute to vascular stiffening. Linking together various causes and consequences of aging are the diverse mechanisms of cell signaling and regulation of cell behavior, a layer of greater complexity. That complexity makes it challenging to piece together exactly how individual discoveries relate to one another, so the work noted here stands in isolation, with further research needed in order to better understand it in the broader context.

The muscle cells in healthy blood vessels are elastic and can stretch like rubber bands, allowing high volumes of blood to pump through. When the blood vessel tissues lose their elasticity, the vessels stiffen, forcing the heart to work harder to pump blood throughout the body. While diet, exercise and medication can improve overall heart health, there are no drugs on the market to treat underlying stiffening in blood vessels.

Most research into blood vessel stiffening has focused on the material surrounding the living cells - called the extracellular matrix - as the most important contributor to this condition. However, researchers now lay out evidence that smooth muscle cells independently contribute to vascular stiffening. To study this connection, the researchers first had to cut the line of communication between cells and the surrounding matrix. They used a gene editing tool called CRISPR to breed mice lacking the gene that produces transglutaminase (TG2), an enzyme enabling this crosstalk to take place.

Compared with mice that had normal TG2 production, the researchers found that in mice with no TG2 - where the crosstalk between the matrix and vascular smooth muscle cells was uncoupled - the development of vascular stiffening was reduced by nearly 70% at age 15 months. This is old age for a mouse and, generally, the time when blood vessels stiffen. The researchers say this indicates smooth muscle cells independently contribute to vascular stiffening, and that crosstalk influences vascular aging. Researchers suspect that severe vascular stiffening, like that seen in humans of old age, could be caused by out-of-control feedback between smooth muscle cells and their surrounding matrix.

Link: https://www.hopkinsmedicine.org/news/newsroom/news-releases/stiff-blood-vessels-linked-to-enzyme-that-fosters-cell-chatter

Now that we find ourselves in an era in which there is growing support and funding for the treatment of aging as a medical condition, the battle ceases to be one of persuading people to take the idea seriously, and more a matter of convincing research and development concerns to focus on projects that are more likely rather than less likely to produce meaningful gains. Rejuvenation and many added years is the desired goal, not merely a gentle slowing of aging that is little better than the results of optimal exercise and diet. Unfortunately, most of the research and development community is indeed working on projects that will, at best, produce that gentle slowing of aging. A panoply of drugs and mechanisms relate to cellular stress responses, those triggered by calorie restriction and exercise, and which produce a gentle slowing of aging when triggered independently of those lifestyle choices. Far too much attention is directed towards ways to induce these stress responses, and far too little to more ambitious projects.

Metformin remains something of a poster child for these efforts. It is a very safe drug, with decades of widespread human use, and hence it was picked as the vehicle for the TAME trial, an effort to persuade the FDA to run a clinical trial with endpoints that represent aging, a blueprint for later trials. Metformin has terrible animal data, however: there is very little consistency to support a claim that it slows aging, and the most robust studies show no effect on life span. Where it does extend life in animal studies, the effect size is less than that of calorie restriction. There is a large human trial that produced a small extension of life in diabetic patients taking metformin, but there is no data for metformin to have any such effects in metabolically normal humans. Further, the effect is modest. One can do better with exercise. This is not the road to meaningful interventions in aging; it is a distraction from better paths forward.

A Critical Review of the Evidence That Metformin Is a Putative Anti-Aging Drug That Enhances Healthspan and Extends Lifespan

The numerous beneficial health outcomes associated with the use of metformin to treat patients with type 2 diabetes (T2DM), together with data from pre-clinical studies in animals including the nematode, C. elegans, and mice have prompted investigations into whether metformin has therapeutic utility as an anti-aging drug that may also extend lifespan. Indeed, clinical trials, including the MILES (Metformin In Longevity Study) and TAME (Targeting Aging with Metformin), have been designed to assess the potential benefits of metformin as an anti-aging drug.

Preliminary analysis of results from MILES indicate that metformin may induce anti-aging transcriptional changes; however it remains controversial as to whether metformin is protective in those subjects free of disease. Furthermore, despite clinical use for over 60 years as an anti-diabetic drug, the cellular mechanisms by which metformin exerts its actions remain unclear. In this review, we have critically evaluated the literature that has investigated the effects of metformin on aging, healthspan, and lifespan in humans as well as other species. In preparing this review, particular attention has been placed on the strength and reproducibility of data and quality of the study protocols with respect to the pharmacokinetic and pharmacodynamic properties of metformin.

We conclude that despite data in support of anti-aging benefits, the evidence that metformin increases lifespan remains controversial. However, via its ability to reduce early mortality associated with various diseases, including diabetes, cardiovascular disease, cognitive decline, and cancer, metformin can improve healthspan thereby extending the period of life spent in good health. Based on the available evidence we conclude that the beneficial effects of metformin on aging and healthspan are primarily indirect via its effects on cellular metabolism and result from its anti-hyperglycemic action, enhancing insulin sensitivity, reduction of oxidative stress and protective effects on the endothelium and vascular function.

Muscle mass and strength declines with age, leading to sarcopenia and contributing to frailty. Many distinct mechanisms are thought to be involved, from stem cell inactivity to chronic inflammation. Most of these mechanisms are favorably impacted by the sweeping metabolic changes induced by the practice of calorie restriction. The study here adds to past evidence for calorie restriction to slow the onset of sarcopenia, yet another of the many reasons to consider it as a lifestyle choice.

Aging causes loss of skeletal muscle mass and function, which is called sarcopenia. While sarcopenia impairs the quality of life of older adults and is a major factor in long-term hospitalization, its detailed pathogenic mechanism and preventive measures remain to be identified. Caloric restriction (CR) suppresses age-related physiological and pathological changes in many species and prolongs the average and healthy life expectancy. It has recently been reported that CR suppresses the onset of sarcopenia; however, few studies have analyzed the effects of long-term CR on age-related skeletal muscle atrophy. Thus, we investigated the aging and CR effects on soleus (SOL) muscles of 9-, 24-, and 29-month-old ad libitum-fed rats (9AL, 24AL, and 29AL, respectively) and of 29-month-old CR (29CR) rats.

The total muscle cross sectional area (mCSA) of the entire SOL muscle significantly decreased in the 29AL rats, but not in the 24AL rats, compared with the 9AL rats. SOL muscle of the 29AL rats exhibited marked muscle fiber atrophy and increases in the number of muscle fibers with a central nucleus, in fibrosis, and in adipocyte infiltration. Additionally, although the decrease in the single muscle fiber cross-sectional area (fCSA) and the muscle fibers' number occurred in both slow-type and fast-type muscle fibers, the degree of atrophy was more remarkable in the fast-type fibers.

However, CR suppressed the muscle fiber atrophy observed in the 29AL rats' SOL muscle by preserving the mCSA and the number of muscle fibers that declined with aging, and by decreasing the number of muscle fibers with a central nucleus, fibrosis, and denervated muscle fibers. Overall, these results revealed that advanced aging separately reduces the number and fCSA of each muscle fiber type, but long-term CR can ameliorate this age-related sarcopenic muscle atrophy.

Link: https://doi.org/10.1016/j.exger.2021.111519

Senescent cells accumulate with age, but are never more than a tiny fraction of somatic cells in most tissues, even in very late life. Senescent cells nonetheless cause considerable harm via the signals that they produce, the senescence-associated secretory phenotype (SASP). These signals provoke chronic inflammation, harmful remodeling of tissue, and dysfunctional activity in nearby cells. That comparatively few senescent cells can cause an outsized level of pathology simply by existing is why the strategy of selectively destroying senescent cells with senolytic therapies produces such impressive results in animal studies. Removing accumulated senescent cells turns back degenerative aging. A meaningful fraction of the inflammatory, disrupted state of aged tissue is actively maintained by the SASP generated by senescent cells.

A number of features of senescence have been characterized, which could be used as proper biomarkers or potential therapeutic targets. Senescent cells generally display dramatically morphological changes, increased β-galactosidase activity, stable cell cycle arrest, persistent DNA damage response, metabolic reprogramming, and significant chromatin remodeling. The secretion of senescence-associated secretory phenotype (SASP) factors change the tissue microenvironment and affect even remote tissue via paracrine mechanisms, which is believed to contribute to organ degeneration with aging.

The phenotypic manifestations of SASP are heterogeneous and induced by different internal and external stimulus including telomere attrition, DNA damage, oncogenic activation, mitochondrial dysfunction, or epigenetic alterations. The SASP factors are mainly made of different types of soluble components including pro-inflammatory cytokines, growth factors, chemokines, and extracellular matrix-degrading proteins. This particular combination of signaling factors and the proteases that degrade extracellular matrix (ECM) to facilitate signal transduction has made SASP a powerful mechanism to modulate intercellular communication. The secretion of SASP factors is considered as a major detrimental aspect of senescence because it promotes chronic inflammation, induces fibrosis, and causes stem cell exhaustion.

However, it has also been shown to favor embryonic development or wound healing, suggesting whether beneficial or detrimental effects the SASP exerts depends on the physiological and pathological context. For example, a recent study has shown that transiently exposing the primary mouse keratinocytes to SASP factors increased cell stemness and regenerative capacity in vivo, while prolonged exposure caused secondary senescence and hindered regeneration. This suggests senescence has more complicated physiological roles than currently understood.

Senescence and its secretion phenotype SASP are the most fundamental player that could systematically change physiological functions at the intercellular level and reshape the tissue microenvironment toward aging. They directly change compositions of cell population by arresting the proliferation of progenitor cells or release pro-inflammatory factors to chronically elevate basal inflammation level causing systematic inflammaging. The effects of senescence and SASP are "erosive." Once it starts, it has the potential to spread via the flowing cytokines to induce remote secondary senescence.

Elimination of senescent cells by senolytic drugs has been proven to be effective to counteract senescence in natural aging or age-related disease model. Recently, the first clinical trial of senolytic drug was conducted in human with idiopathic pulmonary fibrosis (IPF). Surprisingly, instead of rescuing lung functions, there was significant improvement in locomotor function such as walking distance or gait speed. Although it is a mystery why the drug failed to take effect in lungs where the most of senescent cells exist in IPF patients, it is still exciting to see the improvement in motor functions which proved senescence communicates at inter-tissue levels. In the future, increasing the specificities of senolytic drugs might help to better cure aging-related diseases.

Link: https://doi.org/10.3389/fphys.2021.702276

It is indisputably the case that regular exercise and maintenance of physical fitness into later life lowers the incidence and slows the progression of neurodegenerative disease. One can write any number of reviews akin to today's open access paper, walking through the evidence for cellular pathways involved in neurodegeneration to be beneficially influenced by physical activity, as well as the epidemiological data linking fitness and exercise with a reduced burden of neurodegeneration in the broader population. There is a great deal of evidence, even even we restrict ourselves to only those studies published in the past twenty years or so.

The focus in today's paper is the effects of exercise on epigenetic regulation via DNA methylation. The nuclear genome is methylated at numerous distinct CpG sites, an ever-changing pattern of decorations that shift the structure of the genome in ways that enable or disable expression of specific genes. DNA methylation status is maintained by a complex array of machinery and feedback loops that react to the circumstances a cell finds itself in. Since aging occurs for the same underlying reasons in all of us, the pattern of methylation status changes in characteristic ways with age. This has allowed the production of epigenetic clocks to measure the burden of biological aging, constructed via machine learning approaches.

It is interesting to note that, as the authors of this paper point out, there are any number of specific instances one can point to in which physical activity has been shown to alter DNA methylation machinery in ways that affect neurodegenerative processes. Further, physical activity and fitness clearly reduces mortality and disease incidence, a modest slowing of aging. Yet the original Horvath epigenetic clock is insensitive to differences in physical fitness, despite performing well in many other circumstances. Later clocks such as GrimAge appear to be better in this regard, but it is certainly a concern.

This highlights the major issue with epigenetic clocks, as well as related measures of aging produced from other biological data. Given that they were produced by mining omics data in search of patterns, it is unclear as to what exactly they measure. Aging consists of numerous interacting processes, proceeding largely in parallel in any given individual. Any given clock implementation may well reflect the consequences of only some of those processes, and thus may be a bad choice if used to assess the results of any given approach to treating aging as a medical condition. The only sure way to calibrate a clock in order to validate its use for a specific scenario is the hard way: run a life span study.

Roles of physical exercise in neurodegeneration: reversal of epigenetic clock

The lack of physical exercise (PE) is a common phenomenon in modern society and has become a risk factor for many diseases, including cardiovascular diseases, metabolic dysfunctions, cancers, and neurodegenerative diseases. Appropriate exercise shapes the athletic figure and improves the body's basal metabolic rate. PE also plays a vital role in brain health, especially in preventing and alleviating the decline of cognitive function as well as the occurrence of some neurodegenerative diseases. The positive effects of regular, long-term physical activities and exercise interventions on cognition have been reported in the literature. Since only limited therapies are available for cognitive impairment, exercise may serve as a promising non-pharmaceutical treatment.

The process of brain aging, which is one of the risk factors for neurodegeneration, has been found to involve epigenetic mechanisms. Epigenetics, by definition, refers to a set of heritable mechanisms and phenomena that determine cell phenotypes without changing the genome. Epigenetic modifications such as abnormal DNA methylation (DNAm), microRNAs, and histone modifications are closely associated with damage to brain health and neurodegenerative diseases. As individuals age, the age-related changes are often linked to the fluctuating methylation levels of specific genes.

The DNAm has been proposed as a potential multi-tissue estimator of biological age and the concept of epigenetic clock (i.e., DNAm clock) has been developed with a suitable regression model to systemically measure the biological age. This tool has been extensively applied to distinguish between chronological age and biological age, as well as to estimate the corresponding health/disease status. While healthy individuals have almost identical chronological age and biological age (normal aging), patients with cancer and neurodegenerative diseases are biologically older (pathologic aging) and the offspring of centenarians are biologically younger (delayed aging). Therefore, the epigenetic clock is capable of assessing the state of aging among populations. Moreover, DNAm is associated with environmental and lifestyle factors, which have the capacity for regulating epigenetic variability in the brain. Given the effects of such factors as PE in slowing down the epigenetic age acceleration or even resetting the aging clock, the epigenetic clock has progressively become an exciting area of research.

In this review, we summarize brain-specific, disease-related mechanisms involving DNAm, through which PE reverses epigenetic changes to ameliorate neurodegeneration in aging, AD, and PD. We also integrate data from muscular-related molecule cascades in the periphery, which are directly induced by PE to affect the central nervous system (CNS). Furthermore, as a potential mediator of motor skills, DNAm can be modulated to improve the pathological symptoms of dyskinesia-related neurodegenerative diseases. The role of PE in neurodegeneration is further explored from the perspective of epigenetic-related mechanisms, and PE can be viewed as a potential rejuvenation therapy.

Mitochondria are vital cellular components, a herd of hundreds of these organelles in every cell working to produce the adenosine triphosphate (ATP) needed to power cellular processes. A side effect of this activity is the production of free radicals, which can increase to the point of causing oxidative stress to a cell when mitochondria are damaged. The herd is culled by the mechanisms of mitophagy, which clear out damaged mitochondria in order to maintain function. With age, mitophagy declines in efficiency, mitochondria become more damaged and dysfunctional, and oxidative stress rises. But in which direction is the arrow of causation? Evidence from the use of mitochondrially targeted antioxidants suggests that reducing oxidative stress improves mitophagy. Equally, improving mitophagy via other means, such as NAD+ upregulation, also seems to reduce oxidative stress.

Mitochondrial dysfunction is a hallmark of aging. Dysfunctional mitochondria are recognized and degraded by a selective type of macroautophagy, named mitophagy. One of the main factors contributing to aging is oxidative stress, and one of the early responses to excessive reactive oxygen species (ROS) production is the induction of mitophagy to remove damaged mitochondria. However, mitochondrial damage caused at least in part by chronic oxidative stress can accumulate, and autophagic and mitophagic pathways can become overwhelmed. The imbalance of the delicate equilibrium among mitophagy, ROS production, and mitochondrial damage can start, drive, or accelerate the aging process, either in physiological aging, or in pathological age-related conditions, such as Alzheimer's and Parkinson's diseases.

The interplay between mitophagy, ROS production, and aging is complex and far from being completely elucidated. The central role of ROS production and consequent damage to mitochondria in the aging process has been clearly established in the last 50 years, despite some objections to this theory over the past 15 years, and mitophagy is a key mechanism for mitochondrial quality and quantity control, as it limits the production of ROS, the damage to mitochondrial DNA of transmembrane potential loss, and the decrease in ATP production.

Evidence indicates that the imbalance of the delicate equilibrium among mitophagy, ROS production, and mitochondrial damage can start, drive, or accelerate the aging process, either in physiological or pathological conditions. It remains to be determined which is the prime mover of this imbalance, i.e., whether it is the mitochondrial damage caused by ROS that initiates the dysregulation of mitophagy, thus activating a vicious circle that leads to the reduced ability to remove damaged mitochondria, and further damage from ROS, or if, on the other hand, an alteration in the regulation of mitophagy constitutes one of the initial events leading to the main of the excessive production of ROS.

Link: https://doi.org/10.3390/antiox10050794

MicroRNAs are involved in the regulation of gene expression, increasing or decreasing the production of proteins for specific genes, and thereby changing cell behavior. Researchers here find a microRNA that acts to reduce cartilage degeneration in osteoarthritis. Levels are reduced in human osteoarthritic cartilage, and delivering this microRNA as a therapy reduces the level of pathology in a mouse model of injury-induced osteoarthritis. The delivery of manufactured microRNA, intended to alter cell behavior in advantageous ways, is a growing area of development. There is enough industry support to encourage more basic research into this approach to manipulating cell activity. It is a step up from small molecule approaches in terms of off-target effects and size of therapeutic effect, but remains considerably more expensive.

Osteoarthritis (OA), the most common aging-related joint disease, is caused by an imbalance between extracellular matrix synthesis and degradation. Here, we discover that both strands of microRNA-455 (miR-455), -5p and -3p, are up-regulated by Sox9, an essential transcription factor for cartilage differentiation and function. Both miR-455-5p and -3p are highly expressed in human chondrocytes from normal articular cartilage and in mouse primary chondrocytes.

We generate miR-455 knockout mice, and find that cartilage degeneration mimicking OA and elevated expression of cartilage degeneration-related genes are observed at 6-months-old. Using a cell-based miRNA target screening system, we identify hypoxia-inducible factor-2α (HIF-2α), a catabolic factor for cartilage homeostasis, as a direct target of both miR-455-5p and -3p. In addition, overexpression of both miR-455-5p and -3p protect cartilage degeneration in a mouse OA model, demonstrating their potential therapeutic value. Furthermore, knockdown of HIF-2α in 6-month-old miR-455 knockout cartilage rescues the elevated expression of cartilage degeneration-related genes.

This data strongly implicates miR-455-5p and -3p in supporting articular cartilage homeostasis by targeting Hif-2α.

Link: https://doi.org/10.1038/s41467-021-24460-7