CCR2 Inhibition Promotes Muscle Regeneration in Aged Mice

Chronic inflammation is an important component of aging. The immune system becomes overactive, provoked by a range of problems that include persistent viral infections, increased amounts of molecular debris from dead and damaged cells, and the pro-inflammatory signaling of growing numbers of senescent cells. Inflammation is useful and even necessary in the short term, a part of the defense against pathogens and regeneration from injury. In youth, episodes of inflammation are resolved when no longer needed, but this progressively ceases to be the case in older individuals.

Today's open access paper reports on research into the disruption of regeneration by chronic inflammation. Researchers are attempting to decipher the regulatory mechanisms of inflammation in various tissues and cell types to try to find ways to sabotage inflammatory processes in a usefully selective way, as simply shutting down all inflammation is very likely do more harm than good. It is worth noting, as usual, that this goal ignores the root causes of the issue. It should always be more effective to identify and address what is provoking the immune system, such as the presence of senescent cells, rather than trying to prevent downstream consequences by adjusting the operation of cellular metabolism without repairing underlying causes.

Here, the focus is on the role of the receptor CCR2 in the effects of inflammation on muscle regeneration. Research into CCR2 in the context of inflammation and age-related disease is quite varied and has been going on for some years. Looking back in the archives, there is work related to Alzheimer's disease, heart regeneration, and ventricular hypertrophy in heart failure. Much of this is connected to inflammatory macrophages, which express CCR2 and thus react to signal molecules that promote activities on the part of these cells that are disruptive to tissue function. Given that evidence, inhibition of CCR2 activity appears to have potential as a basis for therapy.

Inhibition of inflammatory CCR2 signaling promotes aged muscle regeneration and strength recovery after injury

During tissue regeneration, the recruitment of inflammatory cells is a critical early response to injury. This recruitment aids in the establishment of a favorable environment for progenitor function and tissue regeneration. Chemokines play an important role in the recruitment of inflammatory cells to sites of injury; however, persistently elevated signaling contributes to chronic inflammation associated with impaired regeneration. Among the large chemokine superfamily members, Ccl2, Ccl7, and Ccl8 bind a shared receptor, Ccr2, and have key roles in the deleterious consequences of chronic chemokine activity. As such, inhibition of Ccr2 is being pursued as a clinical therapy in disease contexts.

As a G-protein coupled transmembrane receptor, ligand-mediated activation of Ccr2 mobilizes intracellular G-proteins that help activate several pathways, including Erk and p38Mapk. Abnormal activity in these intracellular mediators has been implicated in age-related stem cell and progenitor cell dysfunction. A role for Ccr2 has also been described during skeletal muscle regeneration.

The regenerative capacity of skeletal muscle relies on a population of non-hematopoietic Pax7-expressing muscle stem cells called satellite cells (SCs). In adults, SCs reside in a primarily quiescent state. In response to a degenerative insult, SCs activate, proliferate, differentiate, and the derived progenitor cells fuse to form multinucleated muscle fibers (myofibers); thus, fulfilling skeletal muscle regeneration. Analogous to other tissues and organs, the regenerative potential of skeletal muscle declines with age. Although features of this decline include loss of SC number and function, a sub-population persists with a regenerative potential that can be stimulated.

The role of Ccr2 in non-hematopoietic cells is largely understudied, especially in the context of tissue regeneration and aging. Here, we find inflammatory-related Ccr2 expression in non-hematopoietic myogenic progenitors (MPs) during regeneration. After injury, the expression of Ccr2 in MPs corresponds to the levels of its ligands, the chemokines Ccl2, Ccl7, and Ccl8. We find stimulation of Ccr2-activity inhibits MP fusion and contribution to myofibers. High levels of Ccr2 chemokines are a feature of regenerating aged muscle. Correspondingly, deletion of Ccr2 in MPs is necessary for proper fusion into regenerating aged muscle. Finally, opportune Ccr2 inhibition after injury enhances aged regeneration and functional recovery. These results demonstrate that inflammatory-induced activation of Ccr2 signaling in myogenic cells contributes to aged muscle regenerative decline.

The RNAAgeCalc Transcriptional Aging Clock

Omics data provides a wealth of metrics that correlate with age, quite well in some cases. Weighted combinations of CpG site methylation status, protein levels, and RNA transcript levels have all been found to measure age, and new and improved versions of these aging clocks are introduced on a regular basis. For people with a greater burden of damage and age-related disease, measured age tends to be greater than chronological age. So there is some hope that these approaches are actually measuring biological age, and can thus be used to speed up the development of rejuvenation therapies. Unfortunately it is unclear as to how the measurements made by aging clocks connect to the underlying damage of aging. Perhaps they reflect all of it, but perhaps not. Thus at the present time any given clock must still be calibrated for each specific approach to rejuvenation before the results can be taken at face value.

Increasing evidence has pointed to the interactions between genetics, epigenetics, and environmental factors in the aging process. Over the last decade, there has been a growing body of research in identifying genetic and epigenetic biomarkers of aging to decipher the molecular mechanisms underpinning disease susceptibility. For example, the genome-wide association studies (GWAS) have identified genetic loci associated with longevity and several aging-related diseases. As aging is a multifactorial process determined by the dynamic nature of static genetics as well as stochastic epigenetic variation and transcriptomics regulation, both DNA methylation and gene expression have emerged as promising hallmark for understanding the aging process and its associated diseases.

Numerous estimators have been developed to predict human aging from DNA methylation data. While the first generation DNA methylation age estimators including Horvath's clock and Hannum's clock were developed based on chronological age, the second generation DNA methylation age estimators were obtained by optimizing the prediction error on phenotypic age derived from clinical attributes associated with mortality and morbidity. This includes PhenoAge and GrimAge which aim to improve prediction of aging related outcomes (e.g., time-to-death, time-to-disease for cancer, Alzheimer's disease, and cardiovascular disease).

In addition to DNA methylation, changes in gene expression have been shown to be associated with aging and aging-related outcomes. Specifically, 56 consistently over-expressed and 17 genes consistently under-expressed with chronological age were identified by performing a meta-analysis on 27 microarray datasets from mice, rats, and human subjects. A closely related work was the development of the GenAge database of aging-related genes, including 307 genes potentially related to human aging.

Unlike DNA methylation in which several user-friendly software and computer programs are available for predicting epigenetic age across different tissues, there were limited transcriptional age predictors and the existing predictors have several pitfalls. First, most of the human transcriptional age predictors were developed based on microarray data and/or limited to only a few tissues. Second, the only predictor constructed using RNA-Seq data was derived based only on fibroblast data. To date, transcriptional studies on aging using RNA-Seq data across different human tissues was limited. Recognizing the gap in existing research of transcriptional aging based on RNA-Seq data, the aim of this study was twofold, first to identify common age-related genes across tissues; second to construct tissue-specific transcriptional age calculators for understanding how gene expression changed with age in different human tissues.

Based on our results, we introduce RNAAgeCalc, a versatile across-tissue and tissue-specific transcriptional age calculator. By performing a meta-analysis of transcriptional age signature across multi-tissues using the GTEx database, we identify 1,616 common age-related genes, as well as tissue-specific age-related genes. Based on these genes, we develop new across-tissue and tissue-specific age predictors. We show that our transcriptional age calculator outperforms other prior age related gene signatures as indicated by the higher correlation with chronological age as well as lower median and median error. Our results also indicate that both racial and tissue differences are associated with transcriptional age. Furthermore, we demonstrate that the transcriptional age acceleration computed from our within-tissue predictor is significantly correlated with mutation burden, mortality risk, and cancer stage in several types of cancer from the TCGA database, and offers complementary information to DNA methylation age.


Comparing the Genetics of Large and Small Long-Lived Rodents

Research into the comparative biology of aging seeks to identify important mechanisms determining life span and the progression of aging by comparing different near neighbor species with very different life spans. In this case, researchers are comparing the genetics of naked mole-rats, as a small long-lived rodent, with beavers, as a large long-lived rodent, in order to shed more light on mammalian aging.

Discerning the genetic factors that affect the aging process, in particular how they control lifespan, is one of the important yet unanswered questions in biology and evolution. Rodent species differ more than 10-fold in maximum lifespan, and long-lived rodents have been observed to show low susceptibility to certain age-related diseases. Therefore, analyses of their genomes could help discover genetic factors responsible for such diversity of lifespan. Motivated by this idea, an initial genome assembly of the naked mole rat (NMR), a rodent best known for its longevity (maximum lifespan of more than 35 years), was generated. It represented the first case of a mammalian genome being sequenced with the explicit purpose of providing insights into longevity. Analysis revealed several unique features and molecular mechanisms related to NMR phenotypes, such as cancer resistance, protein synthesis, visual function, etc.

The North American beaver has the second longest lifespan known for rodents, at more than 23 years. This species is famous for its ability to modify the environment by building complex dams and lodges, which sets them apart from other mammals. To date, two beaver genome assemblies have been reported, although extensive genome analyses have not been performed.

It should be noted that rodents have achieved long lives at least four times independently, and two contrasting combinations of longevity and body mass are recognized: i.e., species with large body mass and long lifespan (e.g., beaver and porcupine) and species with small body mass and long lifespan (e.g. naked mole-rat). Therefore, comparative analyses of these rodents and their closely related relatives that are characterized by small body mass and short lifespan could be useful for understanding how lifespan coevolved with body mass in rodents. It was proposed that the ability of organisms to effectively cope with both intrinsic and extrinsic stresses is linked with longevity.

With these goals in mind, we prepared high quality chromosome-level genome assemblies of the longest-lived rodents, the beaver and NMR. Our comparative genomic analyses reveal that amino acid substitutions at "disease-causing" sites are widespread in the rodent genomes and that identical substitutions in long-lived rodents are associated with common adaptive phenotypes, e.g., enhanced resistance to DNA damage and cellular stress. By employing a newly developed substitution model and likelihood ratio test, we find that energy metabolism and fatty acid metabolism pathways are enriched for signals of positive selection in both long-lived rodents.


Investigating the Cause of Irregular Heartbeat Following Cell Therapy for Regeneration of Heart Tissue

The promise of cell therapies is twofold. Firstly, the ability to regenerate from injuries that do not normally heal, such as severed nerves, or large loss of tissue mass. Secondly, the ability to restore more youthful function to aged tissues that suffer from a lack of replacement somatic cells due to the decline of stem cell activity. This decline is in part due to a loss of viable cells, and in part due to changes in the signaling environment or damage to stem cell niches that cause stem cells to become less active in response. Which of these processes is the dominant cause of loss of activity with age most likely differs from cell population to cell population.

As noted in the research materials below, there is considerable enthusiasm for the use of cell therapies to regenerate damage to the heart, particularly that occurring as a consequence of a heart attack. However, the heart is a highly structured organ with an electrical component to its activity, and regenerative strategies must avoid disruption of that structure and behavior. Do so and the heartbeat becomes irregular, or perhaps worse than that. This makes the heart a more challenging target than organs such as the kidney or liver, which are less stringent in their requirements for a very specific structure and balance of cell populations.

Heart regeneration using stem cells: Why irregular heartbeats occur after transplantation

Once a part of a heart tissue is injured due to restricted blood flow during a heart attack, treatment options are dire to fix the function of the heart to previous capacity. Stem cells are promising because they can be manipulated to generate healthy cells to replace diseased cells. No other cells hold this promise. There are a few issues to clear before stem cell treatments can be implemented clinically for heart regeneration and one major obstacle is to understand why irregular, abnormal heartbeats occur two to four weeks after induced pluripotent stem cell-derived heart muscle cells are transplanted to the heart. The heartbeat stabilizes on its own after 12 weeks but researchers set out to find out why the arrhythmia occurs.

It was thought that the arrhythmia occurs from the activity of the transplanted cells. Arrhythmia during a heart attacks is often noted as "re-entry" or when the electricity inside the heart goes haywire and loops around inside the heart. Two previous groups who studied arrhythmia in hearts of transplanted cells thought it was not caused by re-entry, but that it is the activity of the transplanted cells. Therefore, this team set out to find the cause through observing the properties of the various cells according to time points.

They created embryonic stem cell-derived cardiomyocyte cells and observed their electrical properties. There are two types of heart muscle cells made from induced pluripotent stem cells. "Working-type", which like the name implies, contracts and relaxes to produce exertion. The other is called "nodal-like", which acts like an electric pacemaker. After the twelfth week in vivo, the graft starts to grow, but immediately after transplantation it is very small. At the twelfth week the small graft has grown and consists mostly of working-type cells. The nodal-like cells has decreased significantly by then. The researchers believe that the arrhythmia decreases then, because the number of and activity of the nodal-like cells have decreased, causing extra electrical activity to decrease. So why does the population nodal-like cells decrease in vivo? Two weeks after transplantation, it was observed that nodal-like cells don't multiply after transplantation, while the working-type cells increase significantly after transplantation. "Perhaps if doctors could remove the nodal-like cells before transplantation, arrhythmia would not occur during future transplantation of heart cell grafts."

Increased predominance of the matured ventricular subtype in embryonic stem cell-derived cardiomyocytes in vivo

Accumulating evidence suggests that human pluripotent stem cell-derived cardiomyocytes can affect "heart regeneration", replacing injured cardiac scar tissue with concomitant electrical integration. However, electrically coupled graft cardiomyocytes were found to innately induce transient post-transplant ventricular tachycardia in recent large animal model transplantation studies. We hypothesised that these phenomena were derived from alterations in the grafted cardiomyocyte characteristics.

In vitro experiments showed that human embryonic stem cell-derived cardiomyocytes (hESC-CMs) contain nodal-like cardiomyocytes that spontaneously contract faster than working-type cardiomyocytes. When transplanted into athymic rat hearts, proliferative capacity was lower for nodal-like than working-type cardiomyocytes with grafted cardiomyocytes eventually comprising only relatively matured ventricular cardiomyocytes. RNA-sequencing of engrafted hESC-CMs confirmed the increased expression of matured ventricular cardiomyocyte-related genes, and simultaneous decreased expression of nodal cardiomyocyte-related genes. Temporal engraftment of electrical excitable nodal-like cardiomyocytes may thus explain the transient incidence of post-transplant ventricular tachycardia, although further large animal model studies will be required to control post-transplant arrhythmia.

Human Studies Link Calorie Restriction to Improved Cardiometabolic Status

The data noted here is not news to anyone who has followed calorie restriction research. It is well understood that the practice of calorie restriction is beneficial to long term health, reducing the impact of aging over time. It extends life by up to 40% in mice, but is nowhere near as effective as that in longer-lived mammals, such as our own species, even given similar short-term effects on metabolism. That said, it is interesting to note that enough robust studies of calorie restriction in humans have taken place over the past few decades to justify review papers on the topic.

Uncertainty remains about the risk/benefit balance of calorie restriction (CR) and its transferability to the current medical practice. Although during the last years different reviews and systematic reviews were published related effect of some type of CR on health, there are still no systematic reviews quantitatively summarizing the potential association between CR and multiple dimensions of health status. In fact, different systematic reviews have explored the association between CR and asthma, hypercholesterolemia, cardiovascular health, or bone health. Some systematic reviews have examined the general effects of diet or intermittent energy restriction on health, while others took in consideration specific populations such as intensive care units patients, athletes, or animal models. Hence, the aim of this study was to assess the effects of CR on dimensions of the WHO health concept, with a systematic review and meta-analyses of randomized controlled trials performed on this topic.

A total of 29 articles were retrieved including data from eight randomized controlled trials. All included trials were at low risk for performance bias related to objective outcomes. Collectively, articles included 704 subjects. Among the 334 subjects subjected to CR, the compliance with the intervention appeared generally high. Meta-analyses proved benefit of CR on reduction of body weight, BMI, fat mass, total cholesterol, while a minor impact was shown for LDL, fasting glucose, and insulin levels. No effect emerged for HDL and blood pressure after CR. Data were insufficient for other hormone variables in relation to meta-analysis of CR effects. Our conclusion is that CR is a nutritional pattern linked to improved cardiometabolic status. However, evidence is limited on the multidimensional aspects of health and requires more studies of high quality to identify the precise impact of CR on health status and longevity.


FOXO3a Suppresses Genomic Instability

FOXO3a is one of the very few genes for which an association with longevity has been identified in multiple human studies - though one should bear in mind that even though it shows up fairly reliably, the effect size is small. Still, near all such associations between human genetic variants and longevity cannot be replicated. Given this, there is an interest in understanding exactly how FOXO3a acts to influence life span. Here, researchers provide evidence that is suggestive of an effect on the burden of mutations in nuclear DNA, particularly double strand breaks. This is interesting in the context of recent work that links DNA repair activity for double strand breaks with the progressive detrimental shift in gene expression that takes place with age.

Genomic instability is one of the hallmarks of aging, and both DNA damage and mutations have been found to accumulate with age in different species. Certain gene families, such as sirtuins and the FoxO family of transcription factors, have been shown to play a role in lifespan extension. However, the mechanism(s) underlying the increased longevity associated with these genes remains largely unknown and may involve the regulation of responses to cellular stressors, such as DNA damage.

Here, we report that FOXO3a reduces genomic instability in cultured mouse embryonic fibroblasts (MEFs) treated with agents that induce DNA double-strand breaks (DSBs), that is, clastogens. We show that DSB treatment of both primary human and mouse fibroblasts upregulates FOXO3a expression. FOXO3a ablation in MEFs harboring the mutational reporter gene lacZ resulted in an increase in genome rearrangements after bleomycin treatment; conversely, overexpression of human FOXO3a was found to suppress mutation accumulation in response to bleomycin. We also show that overexpression of FOXO3a in human primary fibroblasts decreases DSB-induced γH2AX foci. Knocking out FOXO3a in mES cells increased the frequency of homologous recombination and non-homologous end-joining events. These results provide the first direct evidence that FOXO3a plays a role in suppressing genome instability, possibly by suppressing genome rearrangements.


Aging as a Target is a New Therapeutic Frontier

My attention was recently drawn to an open access commentary on the present early stage of the scientific initiative to treat aging as a medical condition. It was published earlier this year, and slipped past my notice amidst all of the other interesting papers emerging at the time. It is illustrative of a number of similar commentaries, in scientific journals, at conferences, and so forth, and is reflective of the present tenor of discussion among researchers. The scientific community is largely optimistic about the potential to intervene in the aging process, even if opinions vary widely as to how hard it will be, from a technical perspective, how much of a benefit to health and life span we can expect to engineer over the next few decades, and how much of a roadblock to progress is presented present systems of regulation, none of which yet recognize aging as a legitimate target for medical development.

We live in interesting times, witnessing the emergence of a new and very important field of scientific endeavor, concurrent with the emergence of a new and energetic medical industry of longevity, a period in which previously small scientific and advocacy communities blossom into large and earnest movements that overtake and transform existing institutions. The last five years and the next five years are a tipping point in the slow, decades-long cycles of business and technology, the prior phase of ineffective approaches to the diseases of aging giving way to and era of new biotechnologies and new approaches that will ensure longer, healthier lives for all. To my eyes that transformation is best explained as a shift to targeting the causes of aging, to repair the underlying damage to cells and tissues, rather than trying to treat the symptoms of aging caused by that damage. The next hundred years of medical development will be the focused on the control and reversal of aging; longevity assurance will be the defining industry of the 21st century, ultimately larger than all of the rest of medicine put together.

Aging: therapeutics for a healthy future

Many consider aging as a purely chronological phenomenon; it is an immutable fact that we all get older. However, this is a simplification as individuals all age functionally in different ways and the concept of "biological aging" is more relevant than chronological aging. When we consider biological aging, we have a therapeutic target, not simply targeting getting old, rather treating physiological decline that is manifested by dysfunction and morbidity in late life.

When biological aging becomes pathological, it can be considered as a failure of homeostasis. There is a progressive component, but ultimately a point is reached at which there is inability to counter the amassed toll on the body of time-dependent accumulation of cellular damage (DNA mutations, protein misfolding, oxidative stress, etc.), which occurs throughout life. With age, cellular processes (including stress response pathways invoked by damage) become less efficient, ultimately leading to cellular death and irreversible consequences. At younger ages, the body is able to mount compensatory responses and life is healthy. During middle age, the body's ability to maintain homeostasis declines, resulting in chronic diseases that accelerate the gradual degradation of life quality, resulting in severe detriments, frailty and, eventually, mortality. There are many ways that a homeostatic balance can be maintained, giving many opportunities for development of therapeutics.

Development of drugs in recent years has focused almost entirely on selectivity and specificity with a primary goal to reduce the risks of any side effects. Such an approach is highly valid when considering specific indications targeting selected organs. Aging is different; the body ages systemically, although not necessarily uniformly, and it may indeed be preferential to have broad, systemic anti-aging effects. Consideration of systemic therapies, broadly distributed targets or organ systems that can have wide impacts may be strong and viable strategies to take. Approaches of potential broad value are to modulate processes that are ubiquitous, systemic and that potentially have multiple impacts such as targeting the plasma proteome, cellular senescence, proteostasis, and metabolic processes.

Is a golden bullet of a single drug to impact aging biology a realistic scenario? The diversity of age-related disorders, the multitude of potential endpoints, the complexities of genetic risk factors and environmental challenges accumulating over a lifetime all make a single therapeutic unlikely. However, if there are fundamental underlying mechanisms, such as cellular senescence or failure of proteostatic maintenance, or a natural mixture, such as plasma or a fraction of plasma able to modulate multiple mechanisms, then potentially a single therapeutic could halt, or at least delay, most age-related disorders. It is still early for us to ascertain this, but the prospect will be tested in the clinic.

Regulatory issues pose some hurdles to the development of anti-aging therapeutics, but with a common goal in mind these can be navigated. Firstly, the FDA requires clinical trial endpoints be related to specifically impacting health or quality of life - survival, function, or feeling, not biomarkers. This must be kept in mind as we develop drugs, although biomarkers are going to be critical in assessing efficacy especially over extended time periods, they will not by themselves be sufficient for approval. Secondly, payers require a specific disease code for patient reimbursement, these will need much consideration as we move concepts from targeting specific indications to generalizing age-related diseases. These areas, which can be resolved by working together, should not be left too late for consideration.

We are at an exciting juncture where the realities of anti-aging therapies are upon us, and discussing how we can practically advance such approaches is a necessity. Even though a majority of research and therapeutic development focuses on individual domains such as neuroscience or behavior alone, thinking in the context of a systemic impact as we age provides wholly new opportunities, not only to tackle neurological disorders, but a spectrum of age-related ailments. The involvement of multiple disciplines, perspectives, and constituents in the field will be needed to be successful. This collaborative approach must be triggered so that quality of life for all can be improved in the near future.

Evidence for Klotho to Act on Life Span in Part via Resistance to Hypertension

Klotho is a longevity-associated protein. More of it in mice extends life, less of it shortens life. In humans, a number of studies have shown klotho levels to correlate with longevity. Beyond life span, a higher level of klotho also positively influences cognitive function, but the evidence to date shows the protein acting in the kidney. Researchers here demonstrate a link to hypertension, which is quite interesting, as the raised blood pressure of hypertension is strongly linked to both age-related mortality and cognitive decline. Increased blood pressure accelerates the progression of vascular conditions such as hypertension, leads to heart failure, and causes pressure damage to delicate tissues such as the brain. Sustained control of blood pressure is well demonstrated to reduce mortality in older people.

It has been known that high salt intake causes hypertension, but its exact mechanism was not understood until this study which found for the first time that Klotho deficiency, an anti-aging factor produced in the kidneys, causes aging-associated hypertension through high salt intake. Klotho acts as a hormone and is secreted into the blood from the kidneys. Its presence decreases with age causing the vascular and arterial system to stiffen. A recent study had shown the inverse relationship between the Klotho concentration and BP salt sensitivity. Hypertension is caused by excessive intake of salt, but the sensitivity of blood pressure to salt varies from individual to individual, and highly sensitive people are more likely to have high blood pressure.

In general, young people are less sensitive and are unlikely to develop hypertension, whereas older people are more sensitive to salt and are likely to develop hypertension. However, the mechanism of increased salt sensitivity with aging was unknown. Therefore, the research group first confirmed that salt sensitivity increased in aged mice, and revealed that the cause is that the blood concentration of the anti-aging factor Klotho protein decreases with age. Furthermore, the group clarified the molecular mechanism Wnt5a-RhoA pathway for the first time. In experiments using aged mice and cells, abnormal activation of this pathway could be reversed by supplementation with Klotho protein. As a result, it was possible to establish that the cause of salt-sensitive hypertension due to aging is Klotho protein decline.

The results of this experiment showed that Klotho supplementation could prevent the development of hypertension in the elderly and that Klotho levels could be a predictive marker for the development of hypertension. Trials for human verification is currently underway. Aging, a universal phenomenon, causes not only hypertension but dementia and frailty, and impairs the healthy life expectancy of individuals. The aging-related phenomenon of Klotho protein deficiency may be related to the onset of dementia and sarcopenia, or the loss of muscle-mass and usage associated with aging. Its onset mechanism is currently under investigation.


Increased Levels of Methylmalonic Acid May Raise the Risk of Metastasis in Older People

The article here discusses the interesting possibility that comparatively simple differences in circulating factors may be at the root of the higher risk of cancer metastasis in older people. Metastasis is the process by which cancer cells migrate from the primary tumor to form new tumors elsewhere. It is what makes cancers in much of the body hard to treat and ultimately fatal rather than merely harmful, problematic, but manageable. Thus targets that might potentially interfere in metastasis are of interest.

As we get older, the risk that we will develop cancer increases, because we accumulate genetic mutations and are continually exposed to cancer-causing substances. Most cancer-causing agents are found in the environment, but some are produced by our own bodies. Researchers now report that methylmalonic acid (MMA) - a by-product of protein and fat digestion - can accumulate in the blood with age, and might promote the spread of tumours. Methylmalonic acid is produced in cells in very small amounts. Usually, it becomes linked to the molecule coenzyme A to form methylmalonyl-CoA, and is converted to succinyl-CoA in a reaction that involves vitamin B12 as a cofactor. Succinyl-CoA subsequently enters the TCA cycle - a series of chemical reactions that are a key part of energy production in the cell.

Researchers report that MMA levels are significantly higher in the blood of healthy people over the age of 60 than in those under 30. The elevated level of MMA had not caused ill health in the individuals studied. However, the authors found that treating human cancer cells with serum from the blood of the older group, or with high concentrations of MMA, led them to adopt characteristics of metastatic cancer cells - those that can spread from a primary tumour to seed cancers elsewhere in the body. These characteristics include a loss of cell-cell attachment and an increase in mobility. When injected into mice, the cells formed metastatic tumours in the lungs.

The authors examined the gene-expression profiles of cells treated with MMA, and compared them with those of untreated cells. One of the genes most highly upregulated in response to MMA was SOX4, which encodes a transcription factor involved in the regulation of embryonic development and cancer progression. The authors demonstrated that repressing SOX4 expression blocked the cancer-cell response to MMA, and prevented the formation of metastatic tumours in mice that received injections of cancer cells treated with old serum. Thus, MMA indirectly induces an increase in the expression of SOX4, which in turn elicits broad reprogramming of gene expression and subsequent transformation of cells into a metastatic state.


Age-Related Downregulation of Rubicon Causes Excessive Autophagy in Adipocytes, Contributing to Metabolic Dysfunction

Autophagy is a vital collection of cellular maintenance processes in which proteins and structures are broken down and recycled for their component parts. In short-lived laboratory species, dysfunctional autophagy shortens life span, while increased operation and efficiency of autophagy - as occurs in response to forms of stress such as heat, exercise, and calorie restriction - slows aging and extends life span.

The usual high level view of aging and autophagy is that autophagic activity declines with age, and that this loss of function contributes to cell and tissue dysfunction, and thus also to age-related disease and mortality. The picture is more complex, however. Different component mechanisms of autophagy decline in different ways and at different paces in different tissues, and this is a distinct issue from the question of whether or not autophagy is running at a given pace. The operation of autophagy is actually upregulated with age in at least some tissues. Too much autophagy can cause issues that are just as problematic as those resulting from too little autophagy, because it destroys necessary protein machinery in the cell, thus disrupting normal function.

Today's research materials present an interesting example of the perils of too much autophagy. Here, this is specifically occurring in fat cells, and the researchers involved identify a protein that appears to regulate this excessive autophagy in older fat tissue. It is known that fat cells change their behavior for the worse with age, and the changes in autophagy noted here may be one of the more important mechanisms in this aspect of aging.

Is turning back the clock in aging fat cells a remedy for lifestyle diseases?

"Adipocytes produce hormones and cytokines that regulate the function of other metabolic organs. Age-related changes in adipose tissue result in metabolic disorders that are closely associated with life-threatening cardiovascular diseases. However, no one really knows what causes adipocyte dysfunction in aged organisms." The research team decided to focus on autophagy, the process used by cells to eliminate unwanted or dysfunctional cellular components. Previous studies had shown that autophagy plays an important role in the prevention of various age-related disorders and is likely to be involved in the aging process. But most pertinent was the finding that autophagy is essential for the normal function and longevity of normal organs, such as liver or kidney.

"We previously showed that a protein called Rubicon, which inhibits autophagy, is upregulated in aging tissues. We therefore hypothesized that Rubicon likely accumulates in aged adipocytes, decreasing autophagic activity and contributing to the onset of metabolic disorders." Surprisingly though, the researchers found that Rubicon levels were actually decreased in the adipose tissue of aged mice, resulting in increased autophagic activity. "As a result, the mice developed lifestyle diseases such as diabetes and fatty liver and had significantly higher cholesterol levels, despite being fed the same diet as control animals." The researchers went on to identify the specific proteins affected by the increased levels of autophagy, showing that supplementation of these proteins restored adipocyte function.

Age-dependent loss of adipose Rubicon promotes metabolic disorders via excess autophagy

The systemic decline in autophagic activity with age impairs homeostasis in several tissues, leading to age-related diseases. A mechanistic understanding of adipocyte dysfunction with age could help to prevent age-related metabolic disorders, but the role of autophagy in aged adipocytes remains unclear. Here we show that, in contrast to other tissues, aged adipocytes upregulate autophagy due to a decline in the levels of Rubicon, a negative regulator of autophagy. Rubicon knockout in adipocytes causes fat atrophy and hepatic lipid accumulation due to reductions in the expression of adipogenic genes, which can be recovered by activation of PPARγ. SRC-1 and TIF2, coactivators of PPARγ, are degraded by autophagy in a manner that depends on their binding to GABARAP family proteins, and are significantly downregulated in Rubicon-ablated or aged adipocytes. Hence, we propose that age-dependent decline in adipose Rubicon exacerbates metabolic disorders by promoting excess autophagic degradation of SRC-1 and TIF2.

A Gene Therapy Approach to Clearing Persistent Herpesviruses

Approaches that might effectively clear herpesviruses from the body are of considerable interest, as there is good evidence for the burden of persistent infection to have a meaningful impact on the pace of aging, largely via detrimental effects on the operation of the immune system over the course of years and decades. This is particularly true for cytomegalovirus, which may be a major cause of immunosenescence in near all people, but one might also look at the (presently disputed) evidence for HSV-1 to be a primary contributing cause of Alzheimer's disease.

Infectious disease researchers have used a gene editing approach to remove latent herpes simplex virus 1, or HSV-1, also known as oral herpes. In animal models, the findings show at least a 90 percent decrease in the latent virus, enough researchers expect that it will keep the infection from coming back. The study used two sets of genetic scissors to damage the virus's DNA, fine-tuned the delivery vehicle to the infected cells, and targeted the nerve pathways that connect the neck with the face and reach the tissue where the virus lies dormant in individuals with the infection.

In the study, the researchers used two types of genetic scissors to cut the DNA of the herpes virus. They found that when using just one pair of the scissors the virus DNA can be repaired in the infected cell. But by combining two scissors - two sets of gene-cutting proteins called meganucleases that zero in on and cut a segment of herpes DNA - the virus fell apart. The dual genetic scissors are introduced into the target cells by delivering the gene coding for the gene-cutting proteins with a vector, which is a harmless deactivated virus that can slip into infected cells. The researchers injected the delivery vector into a mouse model of HSV-1 infection, and it finds its way to the target cells after entering the nerve pathways. The researchers found a 92% reduction in the virus DNA present in the superior cervical ganglia, the nerve tissue where the virus lies dormant. The reductions remained for at least a month after the treatment.

"This is the first time that scientists have been able to go in and actually eliminate most of the herpes in a body. We are targeting the root cause of the infection: the infected cells where the virus lies dormant and are the seeds that give rise to repeat infections. Most research on herpes has focused on suppressing the recurrence of painful symptoms, and the team is taking a completely different approach by focusing on how to cure the disease. The big jump here is from doing this in test tubes to doing this in an animal. I hope this study changes the dialog around herpes research and opens up the idea that we can start thinking about cure, rather than just control of the virus."


Cartilage Regrowth: Steering Microfracture to Provoke Regeneration of Fully Functional Cartilage

Microfracture surgery is a poor approach to producing the regrowth of cartilage. It is a procedure that causes minor damage, and that damage in turn provokes a more extensive regeneration of joint tissue. The tissue is unfortunately not the same as normal cartilage, but is better than nothing in cases of serious damage or wear. Researchers here asked how this response to damage works, and whether it can be steered to produce fully functional cartilage instead of the present less optimal tissue.

Damaged cartilage can be treated through a technique called microfracture, in which tiny holes are drilled in the surface of a joint. The microfracture technique prompts the body to create new tissue in the joint, but the new tissue is not much like cartilage. Microfracture results in what is called fibrocartilage, which is really more like scar tissue than natural cartilage. It covers the bone and is better than nothing, but it doesn't have the bounce and elasticity of natural cartilage, and it tends to degrade relatively quickly.

For a long time, people assumed that adult cartilage did not regenerate after injury because the tissue did not have many skeletal stem cells that could be activated. Working in a mouse model, researchers documented that microfracture did activate skeletal stem cells. Left to their own devices, however, those activated skeletal stem cells regenerated fibrocartilage in the joint. But what if the healing process after microfracture could be steered toward development of cartilage and away from fibrocartilage? The researchers knew that as bone develops, cells must first go through a cartilage stage before turning into bone. They had the idea that they might encourage the skeletal stem cells in the joint to start along a path toward becoming bone, but stop the process at the cartilage stage.

The researchers used a powerful molecule called bone morphogenetic protein 2 (BMP2) to initiate bone formation after microfracture, but then stopped the process midway with a molecule that blocked another signaling molecule important in bone formation, called vascular endothelial growth factor (VEGF). "What we ended up with was cartilage that is made of the same sort of cells as natural cartilage with comparable mechanical properties, unlike the fibrocartilage that we usually get. It also restored mobility to osteoarthritic mice and significantly reduced their pain."


A Two Part Interview with Greg Bailey of Juvenescence

Juvenescence and Life Biosciences are presently the two large business development companies in the growing longevity industry. They act much like venture funds, in that they create or take controlling positions in biotech startups, but are organized as companies in structure, with the ability to later go public. The resulting entity looks much like a Big Pharma company with many subsidiaries. It is quite possible to do this at a smaller scale and bootstrap towards much the same end goal - see Ichor Therapeutics and its portfolio companies, for example.

Greg Bailey is one of the cofounders of Juvenescence, alongside Jim Mellon and Declan Doogan. Today I'll point out a recent two part interview, covering a mix of what the company is doing and the present state of investor interest in the longevity industry. Juvenescence is very visible as a company, since Jim Mellon does a great deal of work to spread his views on (a) the merits of working to extend the healthy human life span, and (b) the enormous returns on investment that will be generated by even early and limited success in treating aging as a medical condition. The longevity industry will become the largest and most beneficial industry in the world, given that every adult human being is a potential customer, and without health and life little else matters. The present medical industry, the business of treating ill people, will become a sidebar to the far more extensive provision of preventative treatments to control aging.

Perceptions among investors and the public at large as to how far along we are towards that goal will rise and fall with the year to year successes and failures of Juvenescence and similar companies. In a young industry, whether it is fair or not, the fortunes of all fellow travelers are affected by the performance of the household names.

Juvenesence (1): from strength to strength in R&D and investment firepower

Juvenescence seems to be moving from success to success; we started by asking Greg to bring us up-to-speed on news so far.

Well, the good news is that we closed morphoceuticals [spontaneous tissue regeneration therapy] this year; the bad news is that they need access to their labs. So COVID-19 has slowed the process on our development of spontaneous regeneration of a limb or an organ using bioelectrics - but we have an amazing team working on this and hopefully will be back in the lab soon. We recently closed a joint venture with a company called G3, and the new company is called Juvenomics. Basically they have 2500 people's complete omics data - proteome, genome, etc., and they have another 4000 patients that they have partial omics data on. We have the use of all that data to try and generate new drugs and drug combinations for anti-aging and modifying aging. So it's really exciting to get access to that data, and our extraordinary machine learning team, which has made great strides on the data science side, will be the group that will use this data to create drugs, drug combinations and repurpose drugs.

We are on track to launch our first product in the end of September, Metabolic Switch; it is a ketone ester that in mammals is geroprotective, neuroprotective, and cardioprotective. I couldn't be more excited about that launch! And it should be relatively affordable, if you have a monthly subscription it's quite reasonable. We signed our second product for Juvenescence Life, our non-RX division. This a product that increases autophagy. It will improve cognition, boost your immunity, help your bones, your cardiac health, your skin, hair ... So I'm really excited about adding that one; hopefully we will be able to launch next year (and hopefully is the operative word there), which would be great news.

And how about research?

Our RX Division continues to move forward; it looks like we're going to have two to four drugs in the clinic next year and we are starting human trials for obesity, cachexia, and immunometabolism, fibrosis, as well as combinations of those products - when products move into trials, that's a time I find really exciting. In our regeneration division, LyGenesis starts its phase 1/2A clinic, to be able to regenerate a liver using lymph nodes, and that starts this year. We are on track to try and undertake thymus replacement using the lymph nodes, over the next few years. This is very exciting and would obviously be a great step forward for immuno-resilience, since it involutes at 3% a year every year after you turn 20. This is possibly why, unfortunately, 70 or 80-year-olds are dying from COVID-19.

When we spoke last we understood that you were fundraising - how's that going?

We're going out to raise $150m in our C round, which hopefully will be a prelude to an IPO, and, of course, we're talking to banks, to make sure that we have a balanced syndicate for that initiative. So all in all, it's been a little busy! There's still this wild discrepancy between how much money is made available to social apps and media apps and one of the most powerful transformative scientific opportunities that humanity has ever had to modify aging. I think it's like 10 times, maybe 20 times discrepancy in capital available from VCs, so, hopefully, the VCs and the sophisticated investors will understand that work to modify aging is happening now, not in 10 years' time.

Juvenescence (2): "It's all about prevention, and that's incredibly disruptive"

Are there other issues that you need to educate investors about, or are they becoming better informed as time goes on?

It's going in the right direction; there's already a difference response from when I talked to people in March compared with now. Maybe I'm getting better at telling the story, or maybe the company is moving along, and obviously the fact that biotech is on fire is certainly very helpful. However, I think that what still needs an enormous amount of education about is the scale of things. Tackling aging is very different from manufacturing a drug for breast cancer, cardiac disease, or inflammatory bowel disease. The population for breast cancer in Europe is probably in the 400,000s, but 400 million Europeans are getting older - it's just completely different metrics.

Most investors appear to prefer seed-to-early-stage investing; have you found this to be the case in your networks?

This is about talking to the banks again; this is not going to be biotech investors, because they'll think it's early stage and worth nothing. They don't understand that the patient population is 7.8 billion people. So, it's going to be thematic investors, ESG people [Environmental, Social & Governance], sustainable, environmental investors; it's going to be funds who understand the diversity of having non-RX, RX, and machine learning. It's a retail event, so crowd-funding has an opportunity to do well. Most people are petrified of biotech, but it's no different from mining: put some money in, if you're lucky you find gold; if you're not lucky, you don't. The share price either goes up if you found gold, or drops if you didn't. If we have a clinical trial, and it's run by smart, educated people, then it has a better-than-average chance of it being positive and, if it's right, there's a 10x return; historically, this is what we saw at Medivation and Biohaven, predecessor companies with which I've been involved.

IL-6 and TGFβ1 Upregulation with Age Cause Detrimental Changes in Hematopoiesis

Researchers here show that blocking the age-related upregulation of inflammatory signal molecules IL-6 and TGFβ1 can reverse some of the deterimental changes in the function of hematopoiesis. Hematopoiesis is the process by which hematopoietic stem cells and related progenitor cell populations generate immune cells and red blood cells. With age, the production of lymphoid immune cells declines, and this is an important component of the aging of the immune system.

It is interesting to note that both IL-6 and TGFβ1 are generated by senescent cells as a part of the senescence-associated secretory phenotype. Senescent cells accumulate with age throughout the body, and contribute to chronic inflammation, as well as to the progression of near all age-related conditions. Given this, we should perhaps expect senolytic treatments that selectively destroy senescent cells in old tissues to be capable of reversing those aspects of immune aging investigated here.

Hematopoietic ageing involves declining erythropoiesis and lymphopoiesis, leading to frequent anaemia and decreased adaptive immunity. How intrinsic changes to the hematopoietic stem cells (HSCs), an altered microenvironment and systemic factors contribute to this process is not fully understood. Here we use bone marrow stromal cells as sensors of age-associated changes to the bone marrow microenvironment, and observe up-regulation of IL-6 and TGFβ signalling-induced gene expression in aged bone marrow stroma.

Inhibition of TGFβ signalling leads to reversal of age-associated HSC platelet lineage bias, increased generation of lymphoid progenitors and rebalanced HSC lineage output in transplantation assays. In contrast, decreased erythropoiesis is not an intrinsic property of aged HSCs, but associated with decreased levels and functionality of erythroid progenitor populations, defects ameliorated by TGFβ-receptor and IL-6 inhibition, respectively. These results show that both HSC-intrinsic and HSC-extrinsic mechanisms are involved in age-associated hematopoietic decline, and identify therapeutic targets that promote their reversal.


Higher Body Mass Index Correlates with Reduced Cerebral Blood Flow

Vascular aging is an important contribution to neurodegeneration. The brain is an energy-hungry organ, and reductions in blood flow with age have a negative impact on brain tissue. These reductions can occur for obvious reasons such as the weakening of the heart in cases of heart failure, but there are other, more subtle processes at work to reduce the delivery of nutrients to the brain, such as the progressive stiffening of blood vessels and reductions in capillary density. Researchers here note that greater excess fat tissue, as measured by body mass index, correlates with reduced blood flow in the brain. It is plausible that this is mediated by the higher levels of chronic inflammation generated in people with larger than needed visceral fat deposits, as inflammation accelerates dysfunction in the vascular system, as well as dysfunction in tissue maintenance in general.

As a person's weight goes up, all regions of the brain go down in activity and blood flow, according to a new brain imaging study. One of the largest studies linking obesity with brain dysfunction, scientists analyzed over 35,000 functional neuroimaging scans using single-photon emission computerized tomography from more than 17,000 individuals to measure blood flow and brain activity. Low cerebral blood flow is the primary brain imaging predictor that a person will develop Alzheimer's disease. It is also associated with depression, ADHD, bipolar disorder, schizophrenia, traumatic brain injury, addiction, suicide, and other conditions.

Striking patterns of progressively reduced blood flow were found in virtually all regions of the brain across categories of underweight, normal weight, overweight, obesity, and morbid obesity. These were noted while participants were in a resting state as well as while performing a concentration task. In particular, brain areas noted to be vulnerable to Alzheimer's disease, the temporal and parietal lobes, hippocampus, posterior cingulate gyrus, and precuneus, were found to have reduced blood flow along the spectrum of weight classification from normal weight to overweight, obese, and morbidly obese.


Destroying Existing Microglia is Necessary for Replacement Strategies to Work

Today's open access research is a demonstration in mice of approaches to replace near all microglia in the central nervous system. Microglia are innate immune cells of the brain, involved not just in destroying pathogens and errant cells, but also in ensuring the correct function of neural connections. With the progression of aging, their behavior shifts to become more harmful and inflammatory, and their numbers include ever more senescent cells. Senescent cells generate tissue dysfunction and chronic inflammation via the senescence-associated secretory phenotype, but beyond that microglia tend to adopt a more aggressive and inflammatory set of behaviors even when not senescent. This detrimental change is the consequence of some mix of persistent infection, protein aggregates, and other forms of the underlying molecular damage that drives aging.

Microglial dysfunction contributes meaningfully to age-related neurodegeneration, as illustrated by the benefits produced in animal models by the selective destruction of senescent microglia. That approach has turned back the tau pathology characteristic of Alzheimer's disease in mice, for example. There is also evidence for inflammatory microglia to be involved in the progression of Parkinson's disease.

More than just the senescent cells need to be replaced, or otherwise have their behavior changed for the better, however. Approaches involving clearance of a large fraction of microglia, and allowing them to regenerate thereafter, have seemed viable. Efforts to replace microglia with transplanted cells have proven challenging, however: even hematopoietic stem cell transplantation, such as via a bone marrow transplant, doesn't replace more than a small fraction of the existing microglia. As researchers here demonstrate, it is necessary to first destroy near all microglia in order to leave an empty niche in the brain that will generate signals telling the body to replace these cells. Will replacement be necessary for the treatment of age-related microglial dysfunction, rather than genetic dysfunction? It seems plausible that hematopoietic stem cell replacement will be adopted as an approach to immune system rejuvenation, so why not pair it with clearance of cell populations that should be replaced?

Efficient Strategies for Microglia Replacement in the Central Nervous System

Microglia are important immune cells in the central nervous system (CNS). Dysfunctions of gene-deficient microglia contribute to the development and progression of multiple CNS diseases. Microglia replacement by nonself cells has been proposed to treat microglia-associated disorders. However, some attempts have failed due to low replacement efficiency, such as with the traditional bone marrow transplantation approach.

Engrafted cells in previous transplantation approaches do not extensively proliferate in the recipient brain, which explains the low efficiency of transplantation. Indeed, the proliferation-dependent turnover rate of microglia is rather slow in homeostatic conditions. In contrast, we have demonstrated that residual microglia exhibit an astonishing proliferation capacity after pharmacological depletion (~99%). This potentially suggests that microglial proliferation relies on an empty microglial niche. We therefore reasoned that the microglia-free niche is a vital prerequisite for successful engraftment of nonself microglia (or microglia-like cells). Colony-stimulating factor 1 receptor (CSF1R) is essential for microglia survival. PLX5622 is a CSF1R inhibitor with improved specificity compared to its analog, PLX3397. To create the microglia-free niche, we utilized PLX5622 to inhibit CSF1R.

We then developed highly efficient approaches for nonself microglia replacement that are effective in the adult normal mouse at the CNS-wide scale. First, microglia replacement by bone marrow transplantation (mrBMT) is capable of inducing allografted bone marrow cells (BMCs) to differentiate into microglia-like cells in the entire CNS, replacing 92.66% of resident microglia in the brain, 99.46% in the retina, and 92.61% in the spinal cord, respectively. Second, microglia replacement by peripheral blood (mrPB) is able to induce peripheral blood cells (PBCs) to microglia-like cells and replace 80.74% of resident microglia in the brain and 74.01% in the retina. Third, to precisely manipulate microglia in a specified brain region without affecting the rest of the brain, we further developed microglia replacement by microglia transplantation (mrMT). The engrafted microglia via mrMT resemble the natural characteristics of naive microglia.

When determining superiority of a strategy, replacement efficiency and source availability are the two most important dimensions to take into consideration. Among the three microglia replacement approaches, mrBMT achieves the highest replacement efficiency - 92.66% in the brain, 99.46% in the retina, and 92.61% in the spinal cord. However, mrBMT uses the BMC as the donor cell, which is clinically hard to acquire due to the invasive nature of the procedure and the aversive response from the donor. Such scarce availability of the source is likely to restrict its potential of becoming a widely used standard clinical method for microglial replacement. On the other hand, mrPB greatly broadens the donor source by using PBC, the largest donor cell pool, while maintaining high replacement efficiency CNS wide, just slightly inferior to mrBMT. Abundant availability of donor cells and the relatively high efficiency of cell replacement make mrPB an ideal approach to manipulate microglia at the whole-CNS scale.

DOK7 Gene Therapy Regrows Neuromuscular Junctions to Improve Aged Muscle Function

One of the numerous possible contributing causes to sarcopenia, the name given to the characteristic age-related decline in muscle mass and strength, is the dysfunction and loss of neuromuscular junctions. These structures link muscles and nerves, but how much of the lost strength of sarcopenia is due to this cause versus, say, declining muscle stem cell activity. The best way to assess the contribution of any given form of damage to any specific age-related condition is to repair that damage, and only that damage, and then observe the results. With that in mind, researchers here report on their implementation of a gene therapy approach to force the regrowth of neuromuscular junctions in aged mice. The treated mice exhibit increased strength in comparison to their untreated peers, which is a promising step towards an eventual therapy for humans.

Age-related decline in motor function has a major impact on quality of human life. The motor impairment involves age-related changes at least in the nerve and muscle systems, including a pathogenic loss of skeletal muscle mass and strength, known as sarcopenia. Accumulating evidence raises the possibility that the age-related decline in motor function is caused, at least in part, by functional impairment of the neuromuscular junction (NMJ), a cholinergic synapse essential for motoneural control of skeletal muscle contraction. Many studies with rodents have shown age-related denervation at NMJs in addition to degeneration of the presynaptic motor nerve terminals, where the neurotransmitter acetylcholine is released, and the postsynaptic endplate, where acetylcholine receptors (AChRs) densely cluster, suggesting an impaired neuromuscular transmission with aging.

In humans, electrophysiological and muscle fiber-type studies suggested age-related denervation at NMJs. Indeed, it is reported that the denervation rate at NMJs increases upon aging, although age-related morphological changes at NMJs remain controversial. Moreover, a recent study suggests that the increased rate of NMJ denervation contributes to the reduction in muscle strength in patients with sarcopenia, supporting the idea that the NMJ is a possible therapeutic target for treating age-related motor dysfunction.

We previously generated AAV-D7, a recombinant muscle-tropic adeno-associated virus (AAV) serotype 9 vector carrying the human DOK7 gene under the control of the cytomegalovirus promoter, and demonstrated that therapeutic administration of AAV-D7 - DOK7 gene therapy - enlarges NMJs and improves impaired motor activity in a mouse model of familial amyotrophic lateral sclerosis (ALS). Given that NMJ denervation appears to play a crucial role in age-related decline in motor function, DOK7 gene therapy might also ameliorate age-related motor impairment by suppressing denervation at NMJs. Thus, in the present study, we examined whether DOK7 gene therapy improves the motor function in aged mice.

Here, we show that DOK7 gene therapy significantly enhances motor function and muscle strength together with NMJ innervation in aged mice. Furthermore, the treated mice showed greatly increased compound muscle action potential (CMAP) amplitudes compared with the controls, suggesting enhanced neuromuscular transmission. Thus, therapies aimed at enhancing NMJ innervation have potential for treating age-related motor impairment.


The Prospects for LANDO Upregulation as a Treatment for Alzheimer's Disease

Of late, researchers have identified a process known as LC3-associated endocytosis (LANDO) by which cells can ingest and then break down the amyloid-β deposits associated with Alzheimer's disease. This raises the idea that perhaps some form of upregulation of LANDO would at least slow the progression of Alzheimer's disease, though the balance of evidence to date is beginning to suggest that amyloid-β is the wrong target, at least in later stages of the condition. Researchers here show that, in animal models, LANDO can reduce the inflammation of brain tissue associated with neurodegenerative conditions, a finding that makes this approach perhaps more interesting. The chronic inflammation of aging is strongly implicated in the progression of neurodegeneration, and may be the primary mechanism linking various forms of early pathology and environment exposure to the much more harmful later stages of Alzheimer's disease.

The researchers previously discovered the LANDO pathway in microglial cells, the primary immune cells of the brain and central nervous system. Scientists found that when genes required for this pathway are deleted, Alzheimer's disease progression accelerates in a mouse model. The investigators also showed that LANDO protects against neuroinflammation, one of the hallmarks of Alzheimer's disease. While continuing to investigate LANDO, the researchers identified a novel function of the protein ATG16L. This protein is critical for autophagy, the normal process by which a cell recycles its components during periods of stress or energy deprivation. While ATG16L is important for autophagy, it can also play a role in LANDO. The investigators found that if a region of ATG16L called the WD domain is deleted, LANDO is inhibited while autophagy continues.

Most mouse models used in Alzheimer's disease research rely on making genetic changes to recreate the disease. For this work, researchers used a new model with a specific deficiency of just the WD domain of ATG16L. This means the model carries out autophagy normally but lacks the LANDO pathway. By the time the mice are 2 years old, they exhibit symptoms and pathology that mimic human Alzheimer's disease. This spontaneous age-associated model of Alzheimer's disease is the first created by deleting a single protein domain (WD on ATG16L) not previously associated with Alzheimer's disease. The researchers also analyzed human Alzheimer's disease tissue samples, looking at the expression of proteins that regulate LANDO, including ATG16L. Expression of these proteins is decreased by more than 50% in people with Alzheimer's disease. This finding shows a correlation between how deficiency in LANDO combined with aging may lead to Alzheimer's disease in the mouse model and in humans.

Reducing neuroinflammation has been proposed as a potential way to treat Alzheimer's disease. To treat their new mouse model, researchers used a compound that inhibits the inflammasome - a complex of proteins that activates pro-inflammatory immune reactions. Researchers profiled the model's behavior and found evidence of improved cognition and memory in addition to a decrease in neuroinflammation. "This work solidifies LC3-associated endocytosis as a pathway that prevents inflammation and inflammatory cytokine production in the central nervous system. While much of the data on LANDO suggests a significant role in neuroinflammatory and neurodegenerative diseases, there is also a strong possibility that it could be targeted as a therapy against cancer or even infectious diseases that rely on similar processes for survival."


Aging Research Should be Far More of a Priority than is Presently the Case

For our species, aging is by far the greatest single cause of suffering and death. It is presently inevitable, affects everyone, and produces a drawn out decline of pain and disability, leading to a horrible death through progressive organ failure of one sort or another. The integrity of the mind is consumed along with the vitality of the body. Aging is the cause of death of 90% or more of the people who live in wealthier regions of the world, and the majority of those even in the poorest regions. More than 100,000 lives every day are lost to aging, and hundreds of millions more are suffering on their way to that fate.

Yet very little funding goes towards medical research in general, and of that only a tiny fraction is devoted towards means to slow and reverse aging. If arriving from the outside, uninformed, one might think that this is rational on the part of funding entities, and assume that it indicates the lack of a clear path towards treatments to aging. But it is not rational. Finding ways to treat aging as a medical condition, and bring it under control to slow or reverse its consequences, is not a fishing expedition. It is not a blind hunt with slim hopes of success. On the contrary, the underlying mechanisms of aging are well cataloged and comparatively well understood. There is a clear road forward towards treatments that will greatly reduce the suffering and death that presently accompanies old age, and thus greatly extend the healthy human life span.

Every life lost is a tragedy. That we expect to be diminished, damaged, and killed by aging doesn't make it any less of a tragedy. Everyone who dies due to aging has friends and family who are hurt by their absence, achievements left undone, a shadow of a greater and longer life that he or she might have lived if given the chance. Every tragic story about lost potential, lost friends, and untimely ending is repeated millions of times each month around the world. And for the most part we all stand by and pretend that this does not happen, and pretend that there is nothing that can be done. The present poor state of funding and development for therapies to treat aging is irrational.

Where is the 'Operation Warp Speed' for Aging?

Perhaps you hope that the U.S. government will be able to accelerate COVID-19 vaccine development with its $10 billion program 'Operation Warp Speed'. Maybe it will. However, if these are your primary concerns, then getting funding for aging research should be a top priority, especially if you are an older adult, or if you have friends or family that are elderly. As you are probably aware, the COVID-19 pandemic disproportionately affects older adults. In fact, 80% of hospitalizations from Covid-19 are adults older than 65 years of age. Although the novel coronavirus may be your top concern at this time, I suggest you turn your attention to an underlying disease process ubiquitous in humans that receives far less attention: aging. If we could treat aging itself, the effects of this pandemic would certainly be muted.

To an outside observer, aging has a fairly obvious phenotype: hair graying and thinning, and skin wrinkling beginning in our third and fourth decades of life, some loss of height, tooth decay and the need for glasses in our fourth, fifth, and sixth decades of life, and age spots, loss of muscle tone and strength, diminished height, and aches and pains in the decades after that. We all know that these unwanted changes occur as we age, and yet we do not talk about aging as though it is a disease. If you walk into a doctor's office at the age of 65 and complain that you are old with a laundry list of age-related problems, the doctor may be able to help with some of your symptoms, but will have nothing to offer you to treat their underlying cause.

Appropriate funding and attention should be given to research in gerontology, the study of aging, but instead the issue is being sidelined while it continues to wreak havoc on humanity. Aging should be treated like any other disease, since the biological underpinnings of aging are becoming better understood every day and potential therapies are being investigated, albeit slowly.

What Causes Aging? How Much Have We Learned in Recent Years?

Scientists and aging researchers have garnered a great deal of knowledge regarding the biological mechanisms of aging in recent years. However, there is still much to learn about the drivers of aging, especially in regards to how the nine hallmarks of aging affect one another. The more we know about the biology of aging, the easier it will be to develop therapies that target the specific causes of aging. With the knowledge we have, scientists at universities and in the private sector are already at work developing potential treatments for aging.

Recent Breakthroughs in Research Give Hope in the Quest to Cure Aging

Recent research suggests that aging is treatable and potentially reversible. The identification of the nine inter-related hallmarks of aging in the 2013 review paper "The Hallmarks of Aging" brought the notion that aging could be addressed therapeutically into the mainstream and spawned a flurry of research into the aging process. At the time of this writing "The Hallmarks of Aging" has been cited over six thousand times. Additionally, the advent of new technologies for genetic programming, such as CRISPR-Cas9 in 2013, discoveries in the field of stem cells, most notably the discovery of Yamanaka factors, to generate Induced Pluripotent Stem Cells (IPSCs) from somatic cells in 2006, and technological advancements in the field of proteomics such as more precise and efficient microscopy, histology, and mass spectrometry, have given scientists the tools necessary to attempt to target the hallmarks of aging and repair them. Advances such as these have led to several anti-aging breakthroughs in recent years, with a central theme being that targeting just one hallmark of aging usually confers benefits to multiple other hallmarks.

Aging Research; Where is the Funding?

Federal funding for aging research comes from the National Institute on Aging (NIA). The NIA is a division of the National Institutes of Health (NIH), which is the largest biomedical research agency on Earth, and the medical research arm of the U.S. department of Health and Human Services (HHS). The NIA is requesting $3.2 billion for fiscal year (FY) 2021, a decrease of about 10% from FY 2020. The NIA will only allocate 10% of its budget, $322.6 million, to its Division of Aging Biology (DAB), which "supports research to determine the basic biochemical and genetic mechanisms underlying the processes of aging at the cell, tissue, and organ levels and the ways these are communicated among cells and tissues of the body."

The research done by the DAB is arguably closest to what we mean in regards to research on the biology of aging, yet it receives only 10% of the NIA budget. The NIA's requested budget for FY 2021 is only 0.24% of the United States proposed discretionary budget for 2021, and the NIA's DAB budget is only 0.024% of the United States discretionary budget. Aging research is far too valuable to only account for less than a quarter of a percent of discretionary funding. And research on the biology of aging through the DAB, which includes research on treating aging with therapies such as senolytics, is receiving a negligible amount of funding given the enormous potential of such therapies to slow or reverse aging.

Adenosine Signaling via the A1 Receptor Reverses Age-Related Decline in Neutrophil Function

Neutrophils are an important component of the innate immune system, mounting a first response to infectious pathogens. An insufficient neutrophil response leads to a far more serious infection. Researchers here report on an exploration of mechanisms responsible for rousing neutrophils to action, and how they change with age. They find that stimulation of a specific cell surface receptor can reverse the age-related decline in efficiency of the neutrophil response to at least one specific infectious pathogen. Thus this might prove to be the basis for therapies capable of improving the capacity of the aged immune system to protect against infectious disease.

Despite the availability of vaccines and antibiotics, Streptococcus pneumoniae remain the leading cause of community-acquired pneumonia in the elderly. Immunosenescence, the overall decline in immunity that occurs with age, contributes to the increased susceptibility of the elderly to infection. We and others previously found that neutrophils (polymorphonuclear leukocytes or PMNs) are required for host defense against S. pneumoniae infections as they are needed for initial control of bacterial numbers upon infection.

Extracellular adenosine (EAD) is key for host resistance to pneumococcal infection. Upon tissue injury triggered by a variety of insults, including infection, ATP is released from cells and metabolized to adenosine. EAD is recognized by four G protein-coupled receptors, A1, A2A, A2B, and A3. These receptors are ubiquitously expressed on many cell types including PMNs and can have opposing effects on immune responses.

Aging is accompanied by changes in EAD production and signaling. However, the role of the EAD pathway in immunosenescence remains practically unexplored. We previously found that triggering A1 receptor signaling in old mice significantly enhanced their resistance to pneumococcal lung infection and reduced the ability of S. pneumoniae to bind pulmonary epithelial cells. The objective of this study was to explore the age-driven changes in the EAD pathway and its impact on PMN function.

PMNs from old mice failed to efficiently kill pneumococci ex vivo; however, supplementation with adenosine rescued this defect. To identify which adenosine receptors is involved, we used specific agonists and inhibitors. We found that A1 receptor signaling was crucial for PMN function as inhibition or genetic ablation of A1 impaired the ability of PMNs from young mice to kill pneumococci. Importantly, activation of A1 receptors rescued the age-associated defect in PMN function. In exploring mechanisms, we found that PMNs from old mice failed to efficiently kill engulfed pneumococci and that A1 receptor controlled intracellular killing. In summary, targeting the EAD pathway reverses the age-driven decline in PMN antimicrobial function, which has serious implications in combating infections.


Adenosine Injected into Arthritic Joints Produces Cartilage Regrowth

Researchers here provide evidence for injections of adenosine into damaged joint tissue to provoke meaningful degrees of cartilage regrowth in an animal model of degenerative joint disease. Finding ways to force the regrowth of tissues, such as cartilage, that normally exhibit little regenerative capacity is an important goal for the research community. Many varied approaches are presently under development; this one has the merit of being comparatively simple when compared to the more logistically challenging cell therapy and tissue engineering strategies.

Previous research had shown that maintaining supplies of adenosine, known to nourish the chondrocyte cells that make cartilage, also prevented osteoarthritis in similar animal models of the disease. In a new study, researchers injected adenosine into the joints of rodents whose limbs had been damaged by inflammation resulting from either traumatic injury, such as a torn ligament, or from massive weight gain placing pressure on joints. The biological damage in these cases is similar to that sustained in human osteoarthritis. The study rodents received eight weekly injections of adenosine, which prompted regrowth rates of cartilage tissue between 50 percent and 35 percent as measured by standard laboratory scores.

Among the study's other key findings was that a cell-signaling pathway, known as transforming growth factor beta (TGF-beta) and involved in many forms of tissue growth, death, and differentiation, was highly active in cartilage tissue damaged by osteoarthritis, as well as in cartilage tissue undergoing repair after being treated with adenosine. Additional testing in lab-grown chondrocytes from people with osteoarthritis showed different chemical profiles of TGF-beta signaling during breakdown than during growth, providing the first evidence that the pathway switched function in the presence of adenosine, from assisting in cartilage breakdown to encouraging its repair.


The Public Cannot Distinguish Between Scientific versus Unscientific, Likely Good versus Likely Bad Approaches to Longevity

One of the challenges inherent in patient advocacy for greater human longevity, for more research into aging and rejuvenation, is that journalists and the public at large either cannot or will not put in the effort needed to distinguish between: (a) scientific, plausible, and likely useful projects, those with a good expectation of addressing aging to a meaningful degree; (b) scientific, plausible, and likely unhelpful projects, those that will do little to move the needle on life expectancy, and (c) products and programs that consist of marketing, lies, and little else. This last category is depressingly large, and the first category still depressingly small.

There are examples of useful, high-expectation scientific projects in the senolytics industry, working on the means of removing senescent cells from old tissues. In animal models this is far and away the most impressive approach to rejuvenation attempted to date, applicable to many age-related diseases. The first good senolytic therapy will be revolutionary for human health in later life. As a counterpoint, an example of a poor and unhelpful scientific project is the use of metformin as a geroprotective drug, an approach that appears to very modestly and unreliably slow the progression of aging. Beneficial effects in animal studies are haphazard and small. The single study in diabetic humans shows only a small effect size. If devoting vast expense to clinical trials that target the mechanisms of aging, then why do so for a marginal therapy? Lastly, for examples of marketing and lies, one has to look no further than the established "anti-aging" industry and all of its nonsense and magical thinking. Apple stem cells. Random peptides with cherry-picked studies. Clearly no meaningful effects in the many humans using these products.

As meaningful attempts to produce rejuvenation therapies progress, and begin to attract greater attention in the world at large, we continue to see articles such as the one I'll point out today, in which no attempt is made to differentiate between sleep strategies, stem cell therapies, senolytics, metformin, and other approaches good and bad. High expectation versus low expectation of gains in health, good data versus bad data in animal studies, scientific or unscientific, it is all just lumped into the same bucket. This is unfortunate, as it leads to the situation in which any arbitrary health-focused demagogue selling branded coffee is presented just as legitimate and useful to the field as an industry leader in the clinical development of actual rejuvenation therapies, or another industry leader working on projects that can in principle only produce small gains in late life health. Which is clearly not the case. As a 60-year-old, you can practice changing your sleep and coffee habits, you can take a calorie restriction mimetic, or you can take senolytics, and only one of those three things is going to make a very sizable difference to your health and remaining life expectancy.

Why Silicon Valley Execs Are Investing Billions to Stay Young

Dave Asprey, 48, is the founder of the Bulletproof wellness empire and a vocal champion of the movement to extend human life expectancy beyond 100 years. He's made millions by experimenting on his own body and packaging his home-brewed discoveries into books, a podcast, consulting services and consumer products (you may have even tried his butter-laced coffee). Thanks to a recent explosion of advances in longevity medicine, Asprey's vision of living healthfully into his second century might not be so crazy. In fact, for people in middle age right now, a handful of therapies in clinical trials have the potential, for the first time in human history, to radically transform what "old age" looks like. If the life extensionists are right, a person who's 40 today might reasonably expect to still be downhill skiing, running a 10K or playing singles tennis at 100.

It might be an exaggeration to say BioViva CEO Liz Parrish believes death is optional, but for her, Asprey's goal of living to 180 shows a distinct lack of ambition. "If you can reach homeostasis in the body, where it's regenerating itself just a little bit faster than it's degrading, then what do you die of? An accident or natural disaster, probably. There's no expiration date at 90 or 100 years old." Like Asprey, she has received criticism from the longevity research community for becoming "patient zero" in her own experimental drug trial, aimed at halting aging at the cellular level. In 2015, Parrish underwent telomerase and follistatin gene therapies in Bogotá, Colombia. The procedures involved receiving around a hundred injections of a cocktail of genes and a virus modified to deliver those new genes into her body's cells.

Humans have always aspired to find the fountain of youth, so "people might be skeptical about the fact that anti-aging technologies are working now," says British investor and businessman Jim Mellon. "But the fact is that this is finally happening, and we need to seize the moment." Mellon cofounded Juvenescence, a three-year-old pharmaceutical company that's investing in multiple technologies simultaneously to increase the odds of bringing winning products to market. Mellon, 63, has made his fortune betting on well-timed investment opportunities, and he predicts that a new "stock-market mania" for life extension is just around the corner. "This is like the internet dial-up phase of longevity biotech. If you'd invested in the internet in the very early days, you'd be one of the richest people on the planet. We're at that stage now, so the opportunity for investors is huge." One of Mellon's bets is on a class of drugs called senolytics, which destroy senescent cells. Senescent cells harm the body by secreting compounds that cause inflammation in surrounding tissues. Many age-related conditions - arthritis, diabetes, Alzheimer's, cancer - have an inflammatory component, and studies suggest that a buildup of senescent cells is a large part of the problem.

Eric Verdin, 63, is president and CEO of the Buck Institute, a globally renowned center for aging research just outside San Francisco in Marin County. Verdin is bullish on the promise of living healthfully to at least 100. Today. But 180? Don't count on it. "My prediction, based on everything we know today, is that getting to 120 is about the best we can do for the foreseeable future. I'll bet my house we're not going to see anyone live to 180 for another 200 years, if ever. But making everyone a healthy centenarian, this is something we can do today. And that's something to be excited about." Verdin's own lab at the Buck Institute studies the aging immune system and how it's affected by lifestyle factors, such as nutrition and exercise. Take, for instance, rapalogs, a class of drugs derived from rapamycin that interact with a protein called mTOR, which serves as a linchpin for multiple critical biological processes, including cell growth and metabolism. Rapalog drugs tamp down mTOR, possibly preventing age-related diseases such as diabetes, stroke, and some cancers. One of the many effects of rapamycin is that it mimics the mechanisms of calorie restriction. As Verdin's lab and others have shown, fasting provides a number of anti-aging benefits, including insulin regulation, reduced inflammation and, to put it colloquially, clearing out the gunky by-products of metabolism.

Centenarians are Comparatively Resistant to Age-Related Disease

Centenarians, people who survive to 100 years of age or more, are comparatively resistant to age-related disease. They are not in good shape in comparison to a much younger person, of course. They are much reduced in vigor and capacity, and aging has gnawed away at their bodies and minds. But nonetheless, the very modest goals of much of the aging research community - to slow aging and extend healthy life span by just a few years - leads to the view that centenarian biochemistry is an interesting place to look for the basis for treatments. If the goal is only a couple more years of life, then why not investigate how it is that some people manage to live a decade or more longer than their peers? If the goal is to achieve far greater results, however, meaning actual rejuvenation, reversal of aging, extending healthy and youthful life spans by decades or more, then we must look elsewhere, towards mechanisms and tools that do not naturally occur in the human body.

Although human life expectancy has increased over the past two decades, individuals in most countries do not appear to be living healthier. Disease prevalence, disability, and the number of years spent with disease or disability have all increased. Yet, in contrast, many centenarians do not follow this trend. Rather, exceptional longevity is associated with a reduced risk of morbidity and, on average, a delay in the onset of age-associated diseases including cancer, cardiovascular disease, stroke, and dementia. Throughout older adulthood, in comparison to their peers who do not survive to 100 years, centenarians have fewer diseases and limitations in performing activities of daily living and are less likely to be hospitalized. Moreover, living to extreme ages has been associated with compression of morbidity and disability, or shortening the proportion of life spent with disease and disability toward the end of life. In fact, supercentenarians, individuals aged 110+ years, spend only 5% of their lives on average with an age-related disease in comparison to 18% for younger controls with many maintaining functional independence up to the age of 100 years.

The exceptionality of centenarians (i.e., their extreme survival), is the reason that they are a powerful cohort among which to examine genetic contributions to longevity and healthy aging. The sensitivity of a genetic risk model to correctly classify individuals as long-lived increased with increasing age exceptionality (i.e., 71% specificity in classifying individuals aged older than 102 years and 85% specificity in classifying individuals aged older 105 years) indicating that the genetic contribution to longevity becomes stronger when looking at older ages. The ability to reach exceptional ages without an age-related disease is also considered an extreme phenotype which can increase the power to identify genetic variants associated with a reduced risk of disease. Using centenarians as extreme controls against cases with specific age-related diseases has been shown to increase the power to detect associations between genetic variants and risk of disease.

Unexpectedly it seems that centenarians do not achieve their exceptional longevity due to the absence of genetic variants associated with disease, as centenarians have been found to have variants related to increased risk of cancer, cardiac disease, and even neurodegenerative diseases. Rather, it seems that centenarians are enriched with protective genes, including variants related to a reduced risk of cardiovascular disease and hypertension as well as enhanced immunity and metabolism. Genetic comparisons with centenarians may also be helpful in evaluating the clinical significance of genetic variants found to be associated with disease as those that are present in centenarians clearly do not preclude long survival.


TREM2 Inhibition as a Potentially Broadly Effective Cancer Therapy

It remains the case that far too much of the extensively funded work on cancer therapies is only relevant to a tiny subset of cancers. This is no way to achieve success in the fight to control cancer: there is only so much funding, only so many researchers, and too many types of cancer for an incremental strategy to make earnest process over the next few decades. The important lines of research into cancer treatments are those that can in principle be applied to many (or preferably all) cancers, and that are in principle highly effective, such as inhibition of telomere lengthening. The ideal cancer therapy is one that can be delivered systemically throughout the body, and will effectively destroy any and all cancers that it encounters. That therapy could then be mass manufactured, at costs crushed down by the logistics of scale, and given to all cancer patients.

Immunotherapy has revolutionized cancer treatment by stimulating the patient's own immune system to attack cancer cells, yielding remarkably quick and complete remission in some cases. But such drugs work for less than a quarter of patients because tumors are notoriously adept at evading immune assault. Now a new study has found that the effects of a standard immunotherapy drug can be enhanced by blocking the protein TREM2, resulting in complete elimination of tumors. "An antibody against TREM2 alone reduces the growth of certain tumors, and when we combine it with an immunotherapy drug, we see total rejection of the tumor. The nice thing is that some anti-TREM2 antibodies are already in clinical trials for another disease. We have to do more work in animal models to verify these results, but if those work, we'd be able to move into clinical trials fairly easily because there are already a number of antibodies available."

T cells, a kind of immune cell, have the ability to detect and destroy tumor cells. To survive, tumors create a suppressive immune environment in and around themselves that keeps T cells subdued. A type of immunotherapy known as checkpoint inhibition wakes T cells from their quiescence so they can begin attacking the tumor. But if the tumor environment is still immunosuppressive, checkpoint inhibition alone may not be enough to eliminate the tumor. A protein called TREM2 is associated with underperforming immune cells in the brain in the context of Alzheimer's disease. Researchers realized that the same kind of immune cells, known as macrophages, are found in tumors, where they produce TREM2 and promote an environment that suppresses the activity of T cells.

Researchers injected cancerous cells into mice to induce the development of a sarcoma. The mice were divided into four groups. In one group, the mice received an antibody that blocked TREM2; in another group, a checkpoint inhibitor; in the third group, both; and the fourth group, placebo. In the mice that received only placebo, the sarcomas grew steadily. In the mice that received the TREM2 antibody or the checkpoint inhibitor alone, the tumors grew more slowly and plateaued or, in a few cases, disappeared. But all of the mice that received both antibodies rejected the tumors completely. The researchers analyzed immune cells in the tumors of the mice treated with the TREM2 antibody alone. They found that suppressive macrophages were largely missing and that T cells were plentiful and active, indicating that blocking TREM2 is an effective means of boosting anti-tumor T cell activity. Further experiments revealed that macrophages with TREM2 are found in many kinds of cancers.


Immune System Aging as an Important Contributing Factor in the Progression of Many Age-Related Diseases

The immune system influences the function of tissues throughout the body. Immune cells are involved in tissue maintenance and wound healing, in the necessary day to day clearance of senescent cells, in the removal of cell debris and molecular waste. In some organs they have even more vital functions, such as assisting in the maintenance of synaptic connections in the brain. Further, immune cells produce inflammatory and anti-inflammatory signals that influence the behavior of other cells in numerous ways. Thus when the immune system runs awry and falters with age, the downstream consequences are pervasive and consequential.

The most obvious issue in immune system aging is a failing capacity to defend against pathogens. When all infections become more serious, causing more harm, this combines poorly with the diminished resilience of an older individual. But there is far more to immune aging than just this. A poor defense against infection is just one slice of the consequences. Arguably the most problematic issue is chronic inflammation, the continual inappropriate activation of immune cells and inflammatory signaling, normally beneficial and useful in the short term, but very harmful when maintained over the long term. Chronic inflammation accelerates the onset and progression of near all of the common fatal age-related conditions. It makes atherosclerosis worse, it drives the pathology of neurodegenerative conditions, it disrupts tissue maintenance.

All of this makes rejuvenation of the aged immune system a very desirable goal. Numerous possible approaches to this challenge are at various stages of development. Regrowth of the atrophied thymus in older individuals would restore the failing supply of new T cells of the adaptive immune system. Replacing damaged hematopoietic stem cell populations would boost the production of all types of immune cell. Selectively destroying damaged or misconfigured immune cells would prevent them from causing further harm. There are many different problem populations: age-associated B cells; senescent immune cells; exhausted T-cells; cells that have become reactive to proteins in ways that lead to autoimmunity; overly inflammatory microglia; and so forth.

The interplay between immunosenescence and age-related diseases

Aging is a major risk factor for the higher incidence and prevalence of chronic conditions, such as cardiovascular diseases, metabolic diseases, and neurodegenerative diseases. Chronic systemic sterile inflammation is crucially involved with the etiology and progression of these conditions. In the elderly, these conditions are often presented with multimorbidity and may finally lead to organ failure and death. With the advance of immunosenescence (aging of the immune system), older adults also become more susceptible to infectious diseases and cancer. Of note, T cell aging and low-grade inflammation (inflammaging) are implicated with several age-related conditions. The expansion of late-differentiated T cells (CD28-), regulatory T cells, increased serum levels of autoantibodies, and pro-inflammatory cytokines were implicated with morbidities during aging. Features of accelerated immunosenescence can be identified in adults with chronic inflammatory conditions, such as rheumatoid arthritis, and are predictive of poor clinical outcomes. Therefore, there is an interplay between immunosenescence and age-related diseases.

First of all, it is important to differentiate acute from chronic inflammatory processes. Acute inflammation is a transient and useful process aiming the elimination of pathogens and tissue regeneration, orchestrated by cells of the innate immunity. It is a self-regulated process with alarm, leukocyte mobilization, and resolution phases. But aging starts a chronic inflammatory process, known as "inflammaging", with persistent and non-resolved production of pro-inflammatory mediators (cytokines, chemokines, and acute phase proteins) that increases the risk for age-related morbidity and mortality.

Although there are many sources of inflammaging, some evidence indicates the presence of overt infections during life to fuel inflammaging. Age-related intrinsic factors may also contribute to the inflammaging. When cells reach senescence, they produce cytokines, chemokines, growth factors, proteases, and angiogenic factors that characterize a senescence-associated secretory phenotype (SASP). As senescent cells accumulate during aging, SASP may also contribute to inflammaging. Inflammaging can be therefore interpreted as the complex result of the interplay between SASP, lifestyle factors, and of dysregulated innate immune cell functions with aging.

Not surprisingly, immunosenescence and SASP have been observed in older adults and during the developmental course of many immune-mediated conditions. Age-related diseases such as neurodegenerative diseases, rheumatoid arthritis, cardiovascular diseases, metabolic disorders, and cancer share common features of immunosenescence. Adverse effects of chronic low-grade inflammation increase the risk for the early appearance of diseases associated with age, suggesting that both aging and chronic (immune-mediated) diseases are interconnected states with common characteristics.

Considering the Use of DNA Methylation Clocks

Assessment of biological age via patterns of DNA methylation is an active area of development. Methylation of CpG sites on the genome is a form of epigenetic mark that regulates the expression of specific proteins. Methylation status of these sites changes constantly, cell by cell, in response to environmental circumstances. Some of these changes are characteristic of aging, and the ability to assess DNA methylation across the whole genome thus led to the discovery of weighted combinations of CpG site methylation status that strongly correlate with age and disease status. The process of understanding what these combinations actually represent, in terms of underlying processes of damage and reaction to damage, has only barely started, however.

In contrast to the steady pace of chronological age, the pace of biological age varies among individuals and may predict distinct aspects of aging at different life stages. As chronological age does not sufficiently represent fundamental aging processes, methods to measure biological aging have been developed, which is important for assessing strategies to slow down biological aging and extend healthspan. Technical breakthroughs have led to the discovery of several molecular markers of aging, including epigenetic biomarkers.

Among biomarkers of aging, such as telomere length (TL), metabolomic, transcriptomic, and proteomic variations, the most promising are based on the DNA methylation (DNAm) of cytosines at CpG dinucleotides, representing one of the key epigenetic mechanisms altering gene expression or splicing. The cumulative assessment of DNAm levels at age-related CpGs could be used as a DNAm clock, which may mirror biological aging. Although some clinical biomarkers outperform DNAm clocks in reflecting morbidity and mortality, the advantage of DNAm clocks is their ability to measure either multitissue or cell-/tissue-specific aging. DNAm clocks could help explain why some individuals stay healthy, whereas others develop age-related neurodegenerative diseases.

Several studies support the link between DNAm clocks and biological age. DNAm-age acceleration (difference between DNAm-age and chronological age) was associated with major neurodegenerative diseases. Similarly, HIV-infected individuals exhibit premature aging based on methylome-wide changes. Furthermore, individuals with Werner syndrome or Down syndrome also display accelerated DNAm clocks. In contrast, DNAm-age in centenarians is on average 9 years younger than their chronological age. However, it is mostly unclear what the underlying molecular mechanisms of DNAm clocks are. Do they reflect similar aspects of the aging process? What is their capacity to predict risk of decline before disease onset and therapeutic effectiveness aiming to extend healthspan? Various confounders may influence the outcome of these age predictors, including genetic and environmental factors, as well as technical differences in the selected DNAm arrays. These factors should be taken into consideration when interpreting DNAm clock predictions.


Evaluating the Electrical Stimulation of Neurogenesis as a Regenerative Therapy in Rats

Electromagnetic approaches to medical treatment are only lightly explored in comparison to pharmacology, but it is possible that some could turn out to be as effective as the results of the average drug development program. The example here involves the use of electrical stimulation to increase neurogenesis in rats. Neurogenesis is the generation of new neurons in the brain by neural stem cell populations, followed by the integration of these neurons into neural circuits. This is essential for the function of memory, among other cognitive functions, as well as the ongoing maintenance and repair of brain tissue. Greater levels of neurogenesis appear to be beneficial across the board, and it seems worthwhile to keep an eye on progress in the various approaches aimed at achieving that goal.

The major aim of stroke therapies is to stimulate brain repair and to improve behavioral recuperation after cerebral ischemia. Despite remarkable advances in cell therapy for stroke, stem cell-based tissue replacement has not been achieved yet, stimulating the search for alternative strategies for brain self-repair using the neurogenic zones of the brain, the dentate gyrus and the subventricular zone (SVZ). However, during aging, the potential of the hippocampus and the SVZ to generate new neuronal precursors, declines. We hypothesized that electrically stimulation of endogenous neurogenesis in aged rats could increase the odds of brain self-repair and improve behavioral recuperation after focal ischemia.

Following stroke in aged animals, the rats were subjected to two sessions of electrical non-convulsive stimulation using ear-clip electrodes, at 7- and 24 days after injury. Animal were sacrificed after 48 days. We report that electrical stimulation (ES) stimulation of post-stroke aged rats led to an improved functional recovery of spatial long-term memory (T-maze), but not on the rotating pole or the inclined plane, both tests requiring complex sensorimotor skills. Surprisingly, ES had a detrimental effect on the asymmetric sensorimotor deficit.

Histologically, there was a robust increase in the number of doublecortin-positive cells in the dentate gyrus and SVZ of the infarcted hemisphere and the presence of a considerable number of neurons expressing tubulin beta III in the infarcted area. Among the genes that were unique to ES, we noted increases in the expression of seizure related 6 homolog like, which is one of the physiological substrate of the β-secretase BACE1 involved in the pathophysiology of Alzheimer's disease, and Igfbp3 and BDNF receptor mRNAs which has been shown to have a neuroprotective effect after cerebral ischemia. However, ES was associated with a long-term down regulation of cortical gene expression after stroke in aged rats suggesting that gene expression in the peri-infarcted cortical area may not be related to electrical stimulation induced-neurogenesis in the subventricular zone and hippocampus.


Unity Biotechnology Fails Phase II Trial of Localized Senolytics for Knee Osteoarthritis

UNITY Biotechnology is the largest of the handful of biotech startups working on senolytics, therapies capable of selectively destroying a sizable fraction of the senescent cells that accumulate in old tissues. The company entered clinical trials with a first generation senolytic drug quite early in the development of this presently small industry, with so far only the Mayo Clinic and Betterhumans also running trials in humans. This week, UNITY announced the failure of a phase II study for knee osteoarthritis, an outcome that was half expected by some observers and competitors, but which will no doubt prove to be a burden for senolytic companies seeking to raise funds for further development.

UNITY Biotechnology Announces 12-week data from UBX0101 Phase 2 Clinical Study in Patients with Painful Osteoarthritis of the Knee

UNITY Biotechnology, Inc., a biotechnology company developing therapeutics to extend healthspan by slowing, halting or reversing diseases of aging, today announced the 12-week results from the Phase 2 study of UBX0101, a p53/MDM2 interaction inhibitor, in patients with moderate-to-severe painful osteoarthritis (OA) of the knee. There was no statistically significant difference between any arm of UBX0101 and placebo at the 12-week endpoint for change from baseline in WOMAC-A, an established measurement of pain in OA. Given these results, UNITY does not anticipate progressing UBX0101 into pivotal studies and will narrow the company's near-term focus to its ongoing ophthalmologic and neurologic disease programs.

"Developing novel treatments that selectively eliminate or modulate senescent cells is at the heart of what we do, and we have generated valuable data that will enable us to learn from this study and inform future studies in diseases of aging. While these are not the results we had hoped for, the evidence that senescent cells contribute to diseases of aging remains compelling, and we are excited to advance UBX1325 for retinal diseases, which inhibits Bcl-xL, a distinct senolytic target. Diabetic macular edema and diabetic retinopathy are attractive not only because of the strength of underlying biology, but also because of the sensitive, quantitative, and objective clinical assessments available. The burden of senescent cells in various diseases of aging is increasingly evident, which together with our research gives us great conviction in our science and the future of our pipeline."

It has been a topic for discussion - sometimes quite pointed discussion - in the industry that UNITY adopted a single dose localized injection approach for their delivery of senolytics, delivering their drug to the knee joint directly. Many people have thought that this was a poor choice. On the one hand this means much lower amounts of the drug in question can be used, which is a desirable characteristic when the drug is a toxic chemotherapeutic compound. On the other hand, it is far from clear that the harm done by senescent cells is local to a significant enough degree for this strategy to work. These cells secrete inflammatory and other signals, and much of that is carried throughout the body. If one destroys only half of the senescent cells in the knee joint, does that in fact both meaningfully and reliably alter the character of inflammatory damage, given what is going on in the rest of the body?

There are a few reasons as to why this attempt could have failed. Firstly, the small molecule drug used may just not work reliably enough in humans in comparison to mice. It would be far from the first time that has happened, if so: promising phase I data can evaporate in phase II, just because more and different patients are involved. Mayo Clinic data from the use of the dasatinib and quercetin senolytic combination in patients with idiopathic pulmonary fibrosis suggests that the results, in terms of destruction of senescent cells, are similar in humans and mice, but that is not the drug being used by UNITY, and it targets a different set of mechanisms to induce apoptosis in senescent cells.

Secondly, as noted above, local administration may be a poor strategy if the goal is to reduce inflammatory burden, given that senescent cells throughout the body are capable of contributing to that burden. Maybe it works in some people, but it will be unreliable given the wide variation in status of the systemic inflammatory burden. Unreliability is always a good possibility when trying to explain early success leading to later failure in clinical trials. The Mayo Clinic and Betterhumans trials of the dasatinib and quercetin combination used oral administration, and thus the drug goes everywhere in the body, globally reducing senescent cell counts and the inflammatory signaling that they generate.

Thirdly, the specific mechanism targeted by UNITY may not be as useful as hoped. It is inhibition of the interaction between p53 and MDM, and has the look of something that suppresses or alters the activity of senescent cells as much as destroys them. This can appear good if measuring specific markers of senescent cell signaling, but it might not actually be as helpful as hoped if the cells are still there, and still undertaking activities that are not being measured. The complexity of cell signaling is another point at which mice and humans might differ enough to make a particular type of signaling suppression more effective in one species than another.

Overall, the animal data, and other human data, for the use of senolytics to reverse age-related pathology is compelling. Very compelling. It is unfortunate that the first attempt at bringing an approach to the clinic failed, but numerous other groups are out there working on the problem, and most of them have what look to be better approaches to the challenge. We'll see how the next few trials progress.

A Plasma Proteomic Profile of Frailty

Some proteins in the blood change in characteristic ways with age and physical decline, and that change can be measured. Numerous research groups have put forward various proposed biomarkers of biological age that are based on the proteomic analysis of blood samples. The work here is an illustrative example, focused specifically on frailty in old age. While frailty is regularly measured via tests of physical function, as the researchers note, it is a complicated state that involves not just physical weakness, but also chronic inflammation, immune dysfunction, cognitive decline, and other components. Having a more rigorous measure will assist in the development of rejuvenation therapies capable of reversing frailty, and work continues towards achievement of that goal.

Frailty is a late life phenotype, which is associated with low physiologic reserve and increased vulnerability to adverse outcomes such as disability, hospitalization, and death. Frailty is a multidimensional construct and involves several components, including physical, psychological, cognitive, and social domains. The complexity of this clinical syndrome has made it difficult to elucidate its biology. Although both genetic and proteomic approaches have been applied, previous studies have been inconclusive regarding the biology of frailty. To date, no large-scale proteomic study has been carried out in regard to frailty. An additional challenge is to distinguish the biological antecedents of frailty from aging. Since frailty is strongly associated with chronological age, both may share a common biological signature.

To elucidate the proteomic signature associated with frailty, 4265 proteins were measured in plasma of older adults, of which 55 were positively associated and 88 were negatively associated with frailty. The proteins most strongly associated with frailty were fatty acid-binding proteins, including FABP and FABPA, leptin, and ANTR2. Pathway analysis with the top 143 frailty-associated proteins revealed enrichment for proteins in pathways related to lipid metabolism, musculoskeletal development and function, cell-to-cell signaling and interaction, cellular assembly, and organization. A frailty prediction model utilizing 110 proteins demonstrated a correlation between predicted frailty and observed frailty. Predicted frailty was also more strongly correlated with chronological age than observed frailty.


Luciferase Visualization of Age-Related Loss of Mitochondrial Membrane Potential in Mice

Researchers here demonstrate a way to visualize mitochondrial membrane potential, a measure of mitochondrial function, in living animals. A tailored genetic modification causes luciferase activity to correlate with mitochondrial membrane potential: engineered mice with better functioning mitochondria glow more brightly. This, in principle, allows for rapid testing of approaches that will restore mitochondrial function in old mice.

Tiny factories float inside our cells and provide them with almost all the energy they need: the mitochondria. Their effectiveness decreases when we get older. Mitochondria are almost like cells within the cell. Like their host, they have a membrane that protects their genetic material and, above all, filters exchanges with the outside. The difference in electrical charge between the inside and the outside of the mitochondria, called "membrane potential", allow certain molecules to go through, while others remain at bay. As between the two poles of a used electric battery, the membrane potential of the mitochondria can sometimes drop. For scientists, this is an unmistakable clue that its functions are impaired.

We know how to measure the phenomenon on cultured cells. But until now, you couldn't really see it on live animals. Now researchers have found a way to study the phenomenon in live mice. They use animals that are genetically modified to express luciferase - an enzyme that produces light when combined with another compound called luciferin. This is how fireflies sometimes light up our summer evenings. Scientists have developed two molecules that, when injected into the rodent, pass into the mitochondria, where they activate a chemical reaction. The mitochondria then produce luciferin and eject it outwards. Luciferin combines with luciferase in mouse cells to produce light.

Researchers need only measure light intensity to get a clear picture of how well the mitochondria are functioning. When they function less well, their membrane lets in less chemical compounds. The production of luciferin decreases, and therefore the luminosity too. To demonstrate the potential of their method, the researchers carried out several experiments. For example, they observed that older rodents produce significantly less light. This drop in light reflects a drop in the activity of mitochondria - their membrane potential is much lower than in younger rodents. The team also tested a chemical known to rejuvenate mitochondria: nicotinamide riboside. This molecule is non-toxic and commercially available as a dietary supplement. Mice given this compound produced more light, a sign of increased mitochondrial activity.


Towards Better Vaccines and a Lower Burden of Infectious Disease in Old People

Over a lifetime, the burden of infectious disease - and particularly persistent infections such as cytomegalovirus - influences the pace of aging via its detrimental impact on immune function in later life. The slow upward trend in life expectancy over the past two centuries is due in no small part to reductions in infectious disease that accompanied improvements in sanitation and then medicine. In addition, in old age, once the immune system declines into ineffectieness, infectious disease becomes a much more serious concern. Infections that a young person defeats with ease become life-threatening. The primary strategy to address this issue presently adopted by the research community is to expand and improve on vaccines for older people, as the authors of today's open access paper outline. The issue with this approach is that the aged immune system is ineffective, and thus while there are some techniques that can improve vaccine performance, that performance is always going to be poor.

If we want older people to exhibit a much lower burden of infectious disease, and to respond well to vaccines, the only viable way forward is to rejuvenate the immune system. Forms of therapy that might achieve this goal include regrowth of the thymus, the organ responsible for the maturation of T cells of the adaptive immune system, and which atrophies near entirely by age 50 or so. Additionally, damaged and dysfunctional hematopoietic stem cell populations of the bone marrow must be restored to a youthful capacity to generate immune cells. Further, growing populations of exhausted, senescent, and misconfigured immune cells must be selectively destroyed. Development of each of these approaches is a major undertaking, even given that meaningful inroads have been made towards a basis for therapies.

Preventing infectious diseases for healthy ageing: The VITAL public-private partnership project

People at an older age mainly die of three causes, accounting for 85% of them: cardiovascular disease, cancer, and respiratory system diseases. Although infection constitutes only a secondary cause of death in that group, happening mainly during the winter periods because of influenza infection and pneumonia disease, it is a major threat for aging adults in cluster environments like rest homes or health care facilities. People from that age group arriving in hospitals with a secondary diagnosis of infection monopolize the beds for a long period, recover badly and remain weak when leaving the health care facility. This results in a long-term poor overall health condition with a high cost for society.

Healthcare systems will have to deal with increasing numbers of ageing adults with severe infections, not only because of the higher number of individuals living longer but also because of the decline in their immune response, called immunosenescence, which makes them more vulnerable to pathogens. Ageing adults may thereby also become a new source of infection. However, an effective medical act to safeguard individuals and populations against infectious diseases is vaccination, which has proven its effectiveness in children and young adults. The ambition is to achieve a similar level of infectious disease control in ageing adults. This would be fundamental for enhancing healthy ageing. However, many recommended vaccines for ageing adults do not maintain an effective and/or sustained immune response, as is the case for influenza, pneumococcal disease or pertussis, for example.

Therefore, there is a need to better understand the aetiology of the major infectious diseases affecting this population. There is also a need to decipher the mechanisms underlying immunosenescence, which should lead to improved vaccine effectiveness and to the development of more efficient vaccination strategies for this age group (whom to vaccinate, when, where, how frequently, and at what price). Finally, there is a need to provide dedicated educational programs to healthcare professionals. Over the next decade, local decision makers will need to have a clear view on this healthcare problem, with access to effective tools to manage the growing healthcare burden they need to control.

Glucose, Methionine, and the Study of Calorie Restriction in Yeast

Beneficial changes to metabolism take place in response to a lowered intake of nutrients, upregulating cell maintenance processes and extending life span. This evolved a very long time ago indeed, a way to ensure greater odds of survival in the face of famine. As a consequence of its distant origins, the mechanisms of the calorie restriction response are similar in near all species, from single celled yeast through to higher animals such as mammals.

The research noted here reinforces this point: calorie restriction in yeast cells in culture is usually achieved by reducing the surrounding amount of glucose, a far cry from the sort of diet and dietary restriction found in mammals. Nonetheless, researchers show that this glucose restriction causes a loss of methionine in the yeast cells, and the downstream reaction to that loss of methionine includes the usual beneficial adaptation to a lack of nutrients. In mammals, methionine is an essential amino acid that must be obtained from the diet, and it is the lack of methionine that is the primary trigger for the response to calorie restriction. Thus the cellular response in the two very different species is nonetheless quite similar.

Since the discovery in the early 1930s that reduced food intake extends the life span of rats, caloric restriction (CR), defined as a reduction in calorie intake without causing malnutrition, has been shown to extend the life span of a range of species. While the effect on life span for humans remains to be determined, studies in nonhuman primates indicate that CR confers health benefits and possibly extends life span in rhesus monkeys, and short-term CR studies in humans evoke metabolic health benefits.

While the life span phenotype of CR was first observed in laboratory rats, much of the insight into molecular mechanisms has derived from simpler model organisms including the budding yeast Saccharomyces cerevisiae. Budding yeast has been a canonical model for aging research due to its short replicative life span (defined as the number of daughter cells produced by a mother cell prior to senescence) and ease of genetic manipulation. In addition, yeast cells can grow on synthetic media of precisely controlled composition, making it possible to isolate the effect of an individual nutrient on life span. For example, CR has been implemented by simply reducing the glucose concentration of the media without affecting other nutrients.

In this work, we investigate the molecular mechanism of life span extension by glucose restriction (GR) in yeast, using an approach that combines global gene expression profiling, microfluidics-based single-cell analysis, and candidate-based genetic manipulations. Using ribosome profiling and RNA-seq, we systematically compared the translational and transcriptional profiles of cells grown in GR and normal media, uncovering groups of functionally related genes that are up- or down-regulated. We observed a cross-talk from glucose sensing to the regulation of intracellular methionine: methionine biosynthetic enzymes and transporters were significantly down-regulated by GR, leading to the decreased intracellular methionine level, and external supplementation of methionine cancels the life span extension by GR without affecting the life span in the normal media. With additional evidence from systematic manipulations of methionine pathway genes and bioinformatic analyses of other long-lived mutants, we were able to place intracellular methionine at a central position for life span regulation.


A Cell Based Approach to Regeneration of the Atrophied Thymus

Researchers here report on a cell based approach to regeneration of the aged thymus. The thymus is responsible for maturation of T cells of the adaptive immune system. Unfortunately, this organ atrophies with age for reasons that appear connected to chronic inflammation, but are far from fully explored. This loss of active thymic tissue greatly reduces the pace at which the adaptive immune system is supplied with replacement cells, and is a major contributing factor to the loss of immune function that emerges with advancing age.

Regeneration of the thymus is thus an important project for human rejuvenation, and numerous approaches to this goal are at various, largely early stages of development. Like most demonstrations in mice carried out to date, the cell therapy in this case involves direct introduction of material into the thymus. This requirement makes a strategy more challenging to use as a basis for therapies intended to prevent immune aging. The thymus is very inconveniently located, under the sternum and over the heart, and any sort of direct injection into the depths of the chest is likely to have too high a rate of complication and mortality in older people for regulators to allow it to be applied preventatively to a large fraction of the population.

Age-associated systemic, chronic inflammation is partially attributed to increased self (auto)-reactivity, resulting from disruption of central tolerance in the aged, involuted thymus. This involution causally results from gradually decreased expression of the transcription factor FOXN1 in thymic epithelial cells (TECs), while exogenous FOXN1 in TECs can partially rescue age-related thymic involution. Given the findings that TECs induced from FOXN1-overexpressing embryonic fibroblasts can generate an ectopic de novo thymus under the kidney capsule and intra-thymically injected naturally young TECs can lead to middle-aged thymus regrowth, we attempted to extend these two findings by combining them as a novel thymic rejuvenation strategy with two types of promoter-driven FOXN1-reprogrammed embryonic fibroblasts (FREFs).

We engrafted these two-types of FREFs directly into the aged murine thymus. We found significant regrowth of the native aged thymus with rejuvenated architecture and function in both males and females, exhibiting increased thymopoiesis and reinforced thymocyte negative selection, along with reduced senescent T cells and auto-reactive T cell-mediated inflammation in old mice. Therefore, this strategy has preclinical significance and presents a strategy to potentially rescue decreased thymopoiesis and perturbed negative selection to significantly, albeit partially, restore defective central tolerance and reduce subclinical autoimmune symptoms in the elderly.


Reviewing the Mechanisms of Longevity in Long-Lived Bats

Today's open access research is a good companion piece to a recent paper that investigates biochemical differences between long-lived and short-lived bats. Bats are renowned for, firstly, an exceptional resistance to classes of virus that are fatal to other mammals, allowing bat populations to act as reservoirs for potentially dangerous pathogens, and secondly for an exceptional longevity in comparison to other mammalian species of a similar size. In mammals, species longevity tends to scale up with size, with a few notable and well-studied long-lived exceptions such as naked mole-rats, humans, and some bats.

In terms of asking why longevity occurs in these species, for naked mole-rats (and near relative species) it may be a side-effect of tolerating oxygen-poor underground environments, providing greater resistance to mechanisms of cell damage that also occur with age. For we humans, the grandmother hypothesis suggests that our culture and intelligence allows older individuals to contribute to the fitness of descendants in ways that other primates do not, and thus there is selection pressure for a longer, slower decline after menopause. As for bats (and birds, which are also, as a rule, long-lived for their size) the high metabolic demands of flight are thought to provide the side-effect of greater longevity for similar reasons to the longevity of naked mole rats, a resistance to cellular damage that occurs with both exertion and aging.

Finding out whether or not these proposals are in fact the case requires a deep analysis of cellular biochemistry, comparing long-lived and short-lived mammals. That analysis is very much a work in progress, providing a great many potential mechanisms to consider and compare, while the present consensus on what is important and what is relevant remains subject to being overturned at short notice. Today's open access paper is a good review of what is known of bat longevity, with the added bonus of a discussion of viral resistance in these species, which may well turn out to be relevant to the question of life span, given the interactions between infection, inflammation, and aging.

The World Goes Bats: Living Longer and Tolerating Viruses

One of the most amazing properties of bats is their longevity. Many bat species such as little brown bat, Brandt's bat, mouse-eared bat, and Indian flying fox have maximum lifespans of 30-40 years. Other bat species have maximum lifespans around 20 years, which is still very long for species of this size. Extreme longevity has arisen at least four separate times during bat speciation. These findings suggest that long lifespan is no accident; it either arose because long lifespan has fitness benefits for bats or because some other phenotype is selected that also precipitates longevity, one of which being a dampened immune response.

The reasons behind the long lifespan of bats remain debated, with scientists developing hypotheses based either on evolutionary life history or molecular studies testing known longevity pathways. Bats have several features that would favor selection for low mortality rates, including small litters, the capacity of flight (which permits escape from predators), and (in many species) the ability to hibernate, or enter into a low-energy torpor state. Torpor is linked to longevity in bats and other species and may protect the animal from bouts of starvation and/or promote homeostatic maintenance during periods of low metabolic rate. Consistent with a beneficial role for hibernation, other species that can enter hibernation, such as gray mouse lemurs and 13-lined squirrels, have longer lifespan than mice of similar size.

Genomic studies have pointed to some longevity clues. For instance, the genome of the Brandt's bat and several other species has a mutation in the growth hormone receptor gene that may interfere with transmembrane domain function. Growth hormone receptor loss of function mutations are associated with protection from diabetes and cancer in humans and long lifespan in mice. Indeed, bats have physiologic (e.g., pancreatic structure) and transcriptomic changes that resemble growth hormone receptor knockout mice. There are also intriguing changes in the transmembrane region of the IGF1 receptor, which is associated with longevity in a range of model organisms and in centenarians. Both of these hormonal signaling pathways are intimately linked to nutrient signaling, one of the most robust pillars of aging.

Genome maintenance is an important longevity assurance mechanism and another recognized pillar of aging. In an 8-year longitudinal study of blood samples from free-living greater mouse-eared bats (Myotis myotis), it was reported that DNA repair and DNA damage signaling pathways are maintained throughout lifespan, consistent with the low levels of cancer in bat species. Among DNA repair pathways, DNA double-strand break repair shows the strongest correlation with longevity. Remarkably several DNA double-strand break repair genes were shown to be under positive selection in two species of bats. Interestingly, some of these DNA repair genes, such as DNA-PK and Rad50, also function as DNA sensors in innate immune response. Hence, the genetic changes that evolved in bats may modulate both processes simultaneously and the innate immune response may be an evolutionary driver of positive selection.

Mitochondrial dysfunction is a feature of aging across the evolutionary spectrum and another highly supported pillar of aging. Energetic demands associated with flight in bats require enhanced mitochondrial respiratory metabolism, which is expected to generate excess oxidative damage. To counteract this damage, bats have evolved more efficient mitochondria, producing less H2O2 per unit oxygen consumed. Bat fibroblasts have also been shown to have lower levels of oxidative damage to proteins and to be resistant to acute oxidative stress. To help maintain proteostasis upon oxidative stress, bats express major heat shock proteins at higher levels. This may simultaneously permit bats to endure high temperatures with flight and maintain protein homeostasis with age. Bats also exhibit enhanced autophagy activity with advancing age, suggesting that their cells are better able to clear damaged proteins and organelles. Increased mitochondrial oxidative stress would also be expected to generate mitochondrial DNA alterations, or heteroplasmy. However, oxidative lesions in M. myotis are found only at low rates in an age-independent manner, suggesting better repair or removal of damaged mitochondria.

As they age, bats avoid upregulation of genes involved in chronic inflammation, which is typically not observed in mammals. This likely results from the multitude of mechanisms that evolved to suppress inflammation due to viral infections. Microbiome studies indicate that Myotis myotis may have stable microbiome composition that does not change over time in contrast to mice and humans, where the microbiome undergoes significant changes with age. As aging-related gut dysbiosis triggers inflammation, the ability of bats to maintain stable microbiome may contribute to the lack of age-related inflammation, or by contrast, low levels of inflammation may promote a more stable microbiome.

One major unanswered question is the extent to which cell senescence occurs with age in bats. Since cell senescence may be a major driver of chronic inflammation during mammalian aging, it will be important to determine whether cell senescence, another pillar, is altered with age in bat species. In-depth studies are needed to address this question in vivo and in cell culture. Among other hallmarks of aging, telomere attrition has been addressed to a limited extent, with mixed results. The shorter-lived bat species, Rhinolophus ferrumequinum and Miniopterus schreibersii, do exhibit telomere shortening, but no evidence was found in the longest-lived species, Myotis myotis. This bat apparently does not express telomerase but exhibits differential expression of genes involved in telomere maintenance and the alternative lengthening of telomeres (ALT) pathway.

A majority of the mechanisms that have evolved to protect bats from viruses likely contribute to their longevity. Bats evolved multiple strategies to combat inflammation, such as dampened NLRP3 inflammasome activity. Inflammation has emerged as a driver of multiple age-related pathologies, including cardiovascular diseases, cancer, Alzheimer's disease, and diabetes. This led to the concept of inflammaging, defined as the long-term result of the chronic physiological stimulation of the innate immune system, which becomes damaging during aging. Factors that trigger inflammaging include viruses, microbiome bacteria, senescent cells, and self-products of cellular damage such as debris containing cellular DNA and proteins. Reducing inflammation due to any of these factors can be beneficial for longevity; however, bat evolution seems to have attenuated mechanisms of cytoplasmic DNA sensing specifically.

Remarkably, bats are unique in their ability to tolerate DNA transposable elements. DNA transposons move in the genome via a cut-and-paste mechanism involving DNA intermediates. Such transposons are found in invertebrates but are generally inactivated and fossilized in the genomes of mammals. Only the vespertilionid family of bats is known to harbor significant levels of active DNA transposable elements. This bat family includes genus Myotis, which contains the longest-lived bats, which suggests that these animals are exceptionally healthy. The ability to tolerate active DNA transposons is likely linked to dampened cytoplasmic DNA sensing.

In the continuing arms race against pathogens, evolutionary fitness requires a functional immune system. However, a highly active immune system may increase fitness in young age but limit longevity. Why did bat evolution result in adjusted immune system functions in a way that favors longevity? We speculate that bats' exceptionally high exposure to viral pathogens forced them to develop ways to co-exist with viruses rather than to fight them. Bats are unique among mammals in the size and density of their colonies, and in their ability to fly long distances, a trait that further increases pathogen exposure. Modern humans living in large metropolises and enjoying air travel may be coming close to the bat level of viral exposure. However, humans have only been enjoying this lifestyle for less than 100 years, while bats evolved 60-70 million years ago.

Astaxanthin as a Geroprotective Compound

Astaxanthin, a pigment compound produced by some types of algae and yeast, has been investigated for its effects on the expression and activity of proteins known to be related to the pace of aging, such as FOXO3 and klotho. At least one company is working on drug candidates derived from astaxanthin. Given the behavior of other candidate geroprotective compounds with these targets, we shouldn't be holding our collective breath waiting on sizable benefits to lifespan. The effect size on aging as a whole tends to be modest at best, even given clinically useful benefits for specific medical conditions. The open access paper here provides a summary of recent work on this topic.

In recent years, the scientific interest in natural compounds with geroprotective activities has grown exponentially. Among the various naturally derived molecules, astaxanthin (ASX) represents a highly promising candidate geroprotector. By virtue of the central polyene chain, ASX acts as a scavenger of free radicals in the internal membrane layer and simultaneously controls oxidation on the membrane surface. Moreover, several studies have highlighted ASX's ability to modulate numerous biological mechanisms at the cellular level, including the modulation of transcription factors and genes directly linked to longevity-related pathways.

One of the main relevant evolutionarily-conserved transcription factors modulated by astaxanthin is the forkhead box O3 gene (FOXO3), which has been recognized as a critical controller of cell fate and function. Moreover, FOXO3 is one of only two genes shown to robustly affect human longevity. Due to its tropism in the brain, ASX has recently been studied as a putative neuroprotective molecule capable of delaying or preventing brain aging in different experimental models of brain damage or neurodegenerative diseases. Astaxanthin has been observed to slow down brain aging by increasing brain-derived neurotrophic factor (BDNF) levels in the brain, attenuating oxidative damage to lipids, protein, and DNA and protecting mitochondrial functions. Emerging data now suggest that ASX can modulate Nrf2, FOXO3, Sirt1, and Klotho proteins that are linked to longevity. Together, these mechanisms provide support for a role of ASX as a potential geroneuroprotector.


Mitochondrial Dysfunction in Monocytes of the Innate Immune System Contributes to Inflammaging

Inflammaging is the name given to the constant activation of the immune system that occurs in older individuals. Inflammation is useful and necessary in the short term, for the destruction of pathogens and damaged cells, or to recruit immune cells to aid in regeneration and clearance of metabolic waste. When inflammation continues without resolution, however, it becomes very harmful to tissue function. The chronic inflammation of aging has many contributing causes: the accumulation of senescent cells and their pro-inflammatory signaling; changes in the gut microbiome that favor inflammatory microbial species; persistent infections by viral pathogens such as cytomegalovirus; and so forth. Here, researchers look at how monocytes of the innate immune system change with age, becoming more inflammatory in response to the aging tissue environment.

Monocytes are circulating cells of the innate immune system which participate in a breadth of host defense and inflammatory processes, including antigen presentation, phagocytosis, inflammatory cytokine and chemokine production, and extravasation into tissue followed by differentiation to macrophages or dendritic cells. As a principal circulating inflammatory cell, monocytes have long been speculated to be major contributors to the age-associated chronic inflammatory state often termed "inflammaging". Because inflammaging is thought to underlie the bulk of age-related chronic diseases, monocytes are potential therapeutic targets for strategies meant to ameliorate aging-related disease.

Within the context of aging, multiple previous studies have found profound monocyte and macrophage dysfunction, including increased basal inflammation, impaired inflammatory activation, altered phagocytosis, and impaired migration/chemotaxis. In recent years, a variety of cellular metabolic programs have been shown to be linked to immune cell functions. However, immunometabolic studies have not been extensively undertaken in the aging field, and whether aging triggers shifts in immune cell metabolic programs is not well-understood.

We were the first to demonstrate that aging impaired mitochondrial function in monocytes when we showed that isolated human classical monocytes displayed reduced mitochondrial respiratory capacity. Now researchers have demonstrated a gene transcription pattern in isolated CD14+ classical monocytes from older individuals suggestive of a decrease in mitochondrial function and oxidative phosphorylation and, concomitantly, an increase in glycolytic energy production. Subsequent experiments found increased reactive oxygen species (ROS) production and enhanced glucose uptake in unstimulated monocytes from older adults.

In addition to increased ROS and decreased mitochondrial spare capacity, the researchers noted trends toward increased mitochondrial mass and reduced mitochondrial membrane potential in monocytes from older adults, and using these assays in tandem demonstrated that mitochondrial membrane potential was substantially decreased on a per mitochondrion basis. Overall, classical monocytes from older adults appeared to have a degree of mitochondrial dysfunction which may increase reliance on glycolytic metabolism during a quiescent state, and this may cause the increase in basal inflammatory activity in monocytes demonstrated here and in previous studies.


Reviewing Associations Between Physical Activity and Loss of Average Telomere Length with Age

Telomeres are repeated DNA sequences at the ends of chromosomes. With each cell division a little telomere length is lost, and this is an important part of the countdown mechanism that limits replication of somatic cells. Somatic cells with short telomeres become senescent or self-destruct. Stem cells, on the other hand, use telomerase to lengthen their telomeres, and thus produce daughter somatic cells with long telomeres throughout a lifetime. This two-tier system of privileged stem cells and limited somatic cells, present in near all animals, keeps the risk of cancer low enough for evolutionary success, while still allowing for tissue maintenance and cell turnover.

Average telomere length in tissues declines with age, and this is largely a function of loss of stem cell activity. There are fewer replacement cells with long telomeres. Telomere length is usually measured in immune cells in a blood sample, however, and here there are many more factors at work to muddy the waters. Immune cells will replicate at quite different rates from day to day, depending circumstances ranging from stress to infection. In human studies, telomere length only exhibits associations with aging - or with interventions known to modestly slow aging - in the statistics of large groups. Even then many studies fail to find a good correlation with diet, exercise, and the like. Thus for any given individual there usually isn't much to learn from a measure of telomere length, or a change in that measure over time.

Physical activity, a modulator of aging through effects on telomere biology

Telomere length (TL) varies greatly between species. At birth, every human individual has a specific TL that ranges between 5 to 15 kb. Throughout life telomeres shorten continuously with a rate between 20-50 bp due to the end-replication phenomenon, oxidative stress, and other modulating factors. However, telomere shortening rates and consequently also average TL vary amongst different tissue types, which is at least partly explained by tissue-specific proliferation rates. In dividing cells, the end replication problem is an important driver of telomere shortening that can be modified by other factors, such as oxidative stress or inflammation. In postmitotic cells instead oxidative stress can directly damage telomeric DNA and drive cells into senescence.

The TL of peripheral blood leucocytes (LTL) has gained substantial interest as a potential marker of biological age. Mean LTL in adults is approximately 11 kb and declines with an annual rate of 30-35 bp. Telomere attrition is most pronounced during the first two years of life, which are characterized by rapid somatic growth. The shortening of telomeres is not a unidirectional process since the reverse-transcriptase telomerase is capable of adding to telomeric ends. However, most somatic cells do not express telomerase. Detectable levels of telomerase activity can typically be found in germ line and embryonic stem cells, immune cells, and in cancer cells.

Regular exercise is a well-established approach to reduce the risk of morbidity and premature mortality. Prospective cohort studies demonstrate that men and women who regularly exercise, have a 30% lower all-cause mortality risk than sedentary individuals. In the older persons the beneficial effects of regular physical activity (above 200 minutes a day) are even more pronounced reaching up to 40% or more mortality risk reduction. Besides a substantial reduction of mortality, regular exercise also reduces the incidence and progression of coronary heart disease, hypertension, stroke, diabetes, metabolic syndrome, colon cancer, breast cancer, and depression. Despite the existence of robust evidence for multiple health benefits of regular exercise, the underlying mechanisms are insufficiently understood. General key mechanisms that drive the process of aging include the accumulation of genetic damage, epigenetic modifications, and shortening of telomeres. It has been speculated that exercise can help preserve TL through the induction of telomerase.

Despite robust evidence from cross-sectional and prospective intervention studies, not all previously published analyses support a relationship between exercise and telomere biology, however. For example, in a cross-sectional and longitudinal analyses of 582 older adults, researchers found no consistent relationship between physical activity and LTL.

Telomere research has gained much attention in the previous decade for its potential use and promise as a future therapeutic target, disease management, and measurement of genomic aging. Interventions, such as physical activity, that target the deleterious processes of aging have concomitantly created interest in the area of lifestyle and aging related research. Largely, the available physical activity data do not exclude that an association between regular exercise and TL exists. However, to date, the observed results from human studies are skewed largely by associations and observational or cross-sectional data. In light of the limited data, available evidence suggests altogether, that regular, and consistent physical activity over an extended period of time may assist with preservation of telomeres and cellular aging. Nevertheless, conflicting and a lack of consistent findings from the existing evidence, and particularly from the few available mechanistic studies means there is much more to explore and understand, prior to measurements such as TL will be adopted clinically.

Exercise May Aid in Resisting Frailty and Cognitive Decline in Part via Effects on the Gut Microbiome

The gut microbiome is influential on long-term health, and its quality declines with age. Microbial populations that produce beneficial metabolites such as butyrate or propionate decline in number, replaced by microbial populations that invade tissue and cause chronic inflammation. Physical exercise influences health and the gut microbiome, but as noted here, the evidence for exercise to beneficially regulate these microbial populations largely results from animal studies. Data in humans is still comparatively lacking, even though epidemiological studies strongly suggest a relationship between exercise and a better gut microbiome.

Although the general characteristics of the gut microbiome in healthy people are not yet completely defined, the gut microbiomes of people with disease (e.g. metabolic syndrome, physical frailty, cognitive dysfunction, etc.) show a gradual change toward an imbalanced composition compared to those in healthy people. These imbalanced microbiome characteristics may contribute to disease onset and may play a role in a vicious cycle.

Age-related changes in the composition and diversity of the gut microbiome aggravate the immune system to regulate inflammatory responses. Collapse of the immune system causes age-related diseases. The gut microbiome is related to the immune system in that both vary in composition with age. Although the gut microbiota of humans is determined to some extent at birth, the composition continually changes throughout life according to the external environment. This age-dependent gut microbiome is closely correlated with host inflammation and pathophysiology as the host ages. The gut physiology induced by this altered gut microbiome can cause host sensitivity to microbiota, leading to chronic and severe inflammatory responses.

Exercise can significantly alter the composition of the gut microbiome, although the mechanism by which this occurs remains unclear. Some studies have assessed the effects of exercise as a treatment on metabolic disorders in mice with diabetes. When db/db (type 2 diabetes) and db/+ (control) mice were made to exercise at a low intensity, the proportion of Bifidobacterium spp. increased in the db/+ mice that exercised. In another study, wild-type mice were subjected to voluntary wheel running for 12 weeks. After the exercise intervention, the Bacteroidetes:Firmicutes ratio increased, preventing diet-induced obesity. In addition, 4-week-old C57BL/6J mice that were made to exercise on a treadmill had an increased relative abundance of Butyricimonas and Akkermansia.

It is difficult to elucidate the long-term effects of exercise in humans because the gut microbiota is influenced by several genetic and environmental factors. For this reason, previous studies have primarily sought to demonstrate the correlation between the gut microbiome and physical function. These studies have shown that the gut microbiome has distinct characteristics. This led to the hypothesis that improvements in physical function through exercise training could also be associated with the gut microbiome. Therefore, it is important to study alterations in the gut microbiome according to the type and intensity of exercise. However, to our knowledge, no studies have determined which exercise types (e.g., resistance or aerobic exercise) are more effective in influencing the gut microbiome.


Should Rapamycin be Prescribed Ubiquitously as an Anti-Aging Supplement?

Should rapamycin be prescribed ubiquitously as an anti-aging supplement? That is the question the authors of this commentary ask after a short overview of what is known of the beneficial effects of rapamycin on mechanisms relevant to aging. Research into inhibition of the two mTOR complexes, mTORC1 and mTORC2, via compounds such as rapamycin, is well funded at the present time. Numerous companies are attempting to push mTOR inhibitors through clinical trials. It is perhaps the largest outgrowth of research into the slowing of aging produced by the practice of calorie restriction, in which benefits are largely mediated by an increased efficiency of the cellular housekeeping processes of autophagy. The question at the end of the day is whether the effect sizes here are large enough to chase hard, in comparison to those that can be obtained via exercise or calorie restriction, given that we know that exercise and calorie restriction have only a limited effect on the shape of human aging. We should aim higher.

mTOR (mammalian target of rapamycin) plays a significant role in age-related stem cell dysfunction through various mechanisms highlighting its potential as an anti-aging target to rejuvenate stem cell function. In fact, mTOR regulates many of the hallmarks of aging. A breakthrough study in 2009 showing the lifespan extending properties of rapamycin in genetically heterogenous mice led to significant research into rapamycin as an anti-aging intervention. Since that time, rapamycin has been well studied in aging and age-related functional decline mainly through the modulation of autophagy, mitochondrial function, insulin signaling, and senescence.

TOR is a heavily conserved serine/threonine kinase with homologues in several eukaryotes from yeast to humans, highlighting its importance in cellular processes. The mammalian version, mTOR exists as two distinct complexes, mTOR1 and mTOR2 that are structurally and functionally different. The mTOR1 complex acts as a central nutrient sensor and regulator of cell proliferation, growth, and survival. mTOR2 activity is usually preserved during acute rapamycin treatment but prolonged exposure can reduce mTOR2 activity as well. Hyperactive mTOR activity with aging seems to have deleterious consequences in somatic stem cells, especially muscle-derived stem cells.

Rapamycin and other compounds have been demonstrated to have significant senotherapeutic effects (i.e. selective ability to restore or eliminate senescent cells). Not only has rapamycin has been demonstrated to reduce senescence in muscle-derived stem cells by our group, but others have demonstrated that blocking mTOR reduces stem cell senescence and associated secretory phenotypes.

Should rapamycin be prescribed ubiquitously as an anti-aging supplement? There is certainly a preponderance of evidence demonstrating the safety of rapamycin in healthy and aged humans that has been well reviewed. Since its approval in 1999 by the FDA, rapamycin has been used by millions of patients with very few mild but reversible side effects. However, one possible strategy is likely intermittent treatment at higher doses for prolonged periods of time. We additionally propose that a combinatorial approach may be in order to target senescence at multiple nodes (inhibition of anti-apoptotic pathways and mTOR) directly through the use of multiple senotherapeutic agents such as fisetin and rapamycin. Overall, the plethora of preclinical and clinical data using rapamycin strongly suggests that targeting mTOR and/or senescence is a promising therapeutic strategy to mitigate aging-related phenotypes and restore stem cell health and function.


Reducing LDL Cholesterol is the Wrong Target for Cardiovascular Disease

When people say "cardiovascular disease" in the context of blood cholesterol, they mean atherosclerosis. This is the name given to the build up of fatty deposits that narrow and weaken blood vessels, leading to heart failure and ultimately some form of disabling or fatal rupture - a stroke or heart attack. The primary approach to treatment is the use of lifestyle choices and drugs such as statins to lower cholesterol carried by LDL particles in the blood. Unfortunately, the evidence strongly suggests that this is the wrong approach, in that the benefits are small and unreliable.

Atherosclerosis does occur more readily with very high levels of LDL cholesterol, as illustrated by the early onset of the condition in patients with genetic disorders such as homozygous familial hypercholesterolemia, in which blood cholesterol can be as high as ten times normal. Yet reducing LDL cholesterol levels, even to as much as ten times lower than normal, does very little for patients with established atherosclerotic lesions. One has to look at the mechanisms of the disease in more detail to (a) see why this is the case, and (b) identify which classes of therapy should be attempted instead.

Atherosclerosis is essentially a consequence of the failure of a process called reverse cholesterol transport. When cholesterol becomes stuck in excessive amounts in blood vessel walls, macrophage cells of the innate immune system are called to the site. The macrophages ingest cholesterol and then hand it off to HDL particles. The HDL cholesterol is then carried to the liver to be excreted. This all works just fine in young people. Older people, however, exhibit growing levels of oxidized cholesterols such as the toxic 7-ketocholesterol. Even small amounts of these oxidized cholesterols disrupt macrophage function in ways that are otherwise only achievable through very sizable amounts of cholesterol. The macrophages become inflammatory, cease their work, become loaded down with cholesterol, and die. An atherosclerotic lesion is essentially a self-sustaining macrophage graveyard that will keep pulling in and destroying ever more cells, growing larger as it does so.

The right point of intervention in atherosclerosis is therefore macrophage function. Make macrophages resistant to oxidative cholesterol and cholesterol overload, as Repair Biotechnologies is doing. Or remove oxidized cholesterols from the body, as Underdog Pharmaceuticals is doing. The crucial goal is to allow macrophages to operate normally in the toxic environment of the atherosclerotic lesion; given enough time, it is in principle possible for these cells to dismantle even advanced and sizable lesions. That they do not normally do this is because of oxidized cholesterols or sheer amount of cholesterol, not any other inherent limit.

Doubt cast on wisdom of targeting 'bad' cholesterol to curb heart disease risk

Setting targets for 'bad' (LDL) cholesterol levels to ward off heart disease and death in those at risk might seem intuitive, but decades of research have failed to show any consistent benefit for this approach, reveals a new analysis. If anything, it is failing to identify many of those at high risk while most likely including those at low risk, who don't need treatment, say the researchers, who call into question the validity of this strategy.

Cholesterol-lowering drugs are now prescribed to millions of people around the world in line with clinical guidelines. Those with poor cardiovascular health; those with LDL cholesterol levels of 190 mg/dl or higher; adults with diabetes; and those whose estimated risk is 7.5% or more over the next 10 years, based on various contributory factors, such as age and family history, are all considered to be at moderate to high risk of future cardiovascular disease. But although lowering LDL cholesterol is an established part of preventive treatment, and backed up by a substantial body of evidence, the approach has never been properly validated, say the researchers.

Hit or miss: the new cholesterol targets

This analysis highlights the discordance between a well-researched clinical guideline written by experts and empirical evidence gleaned from dozens of clinical trials of cholesterol reduction. It further underscores the ongoing debate about lowering cholesterol in general and the use of statins in particular. In this analysis over three-quarters of the cholesterol lowering trials reported no mortality benefit and nearly half reported no cardiovascular benefit at all.

The widely held theory that there is a linear relationship between the degree of LDL-C reduction and the degree of cardiovascular risk reduction is undermined by the fact that some randomized controlled trials with very modest reductions of LDL-C reported cardiovascular benefits while others with much greater degrees of LDL-C reduction did not. This lack of exposure-response relationship suggests there is no correlation between the percent reduction in LDL-C and the absolute risk reduction in cardiovascular events.

Moreover, consider that the Minnesota Coronary Experiment, a 4-year long randomized controlled trial of a low-fat diet involving 9423 subjects, actually reported an increase in mortality and cardiovascular events despite a 13% reduction in total cholesterol. What is clear is the lack of clarity of these issues. In most fields of science the existence of contradictory evidence usually leads to a paradigm shift or modification of the theory in question, but in this case the contradictory evidence has been largely ignored simply because it doesn't fit the prevailing paradigm.

Considering the Use of Lasers to Break Down Harmful Protein Aggregates

It is possible to tailor the frequency of laser light to selectively disrupt the bonds or structure of particular arrangements of molecules - such as, say, the harmful protein aggregates found in neurodegenerative and other age-related conditions. Researchers here showcase early work into the disruption of amyloids, a class of altered of proteins that feature prominently in numerous conditions. The challenge in this sort of approach is usually not that of achieving the desired disruption, but rather doing so without the delivery of so much energy, released as heat, that the process kills surrounding cells and tissues. Past early stage efforts have floundered on that problem.

A notable characteristic of several neurodegenerative diseases, such as Alzheimer's and Parkinson's, is the formation of harmful plaques that contain aggregates - also known as fibrils - of amyloid proteins. Unfortunately, even after decades of research, getting rid of these plaques has remained a herculean challenge. Thus, the treatment options available to patients with these disorders are limited and not very effective.

In recent years, instead of going down the chemical route using drugs, some scientists have turned to alternative approaches, such as ultrasound, to destroy amyloid fibrils and halt the progression of Alzheimer's disease. Now, a research team has used novel methods to show how infrared-laser irradiation can destroy amyloid fibrils. While laser experiments coupled with various microscopy methods can provide information about the morphology and structural evolution of amyloid fibrils after laser irradiation, these experiments have limited spatial and temporal resolutions, thus preventing a full understanding of the underlying molecular mechanisms. On the other hand, though this information can be obtained from molecular simulations, the laser intensity and irradiation time used in simulations are very different from those used in actual experiments. It is therefore important to determine whether the process of laser-induced fibril dissociation obtained through experiments and simulations is similar."

The scientists used a portion of a yeast protein that is known to form amyloid fibrils on its own. In their laser experiments, they tuned the frequency of an infrared laser beam to that of the "amide I band" of the fibril, creating resonance. Scanning electron microscopy images confirmed that the amyloid fibrils disassembled upon laser irradiation at the resonance frequency, and a combination of spectroscopy techniques revealed details about the final structure after fibril dissociation. For the simulations, the researchers employed a technique that a few members of the current team had previously developed, called "nonequilibrium molecular dynamics (NEMD) simulations." Its results corroborated those of the experiment and additionally clarified the entire amyloid dissociation process down to very specific details. Through the simulations, the scientists observed that the process begins at the core of the fibril where the resonance breaks intermolecular hydrogen bonds and thus separates the proteins in the aggregate. The disruption to this structure then spreads outward to the extremities of the fibril.


A Fisetin Variant, CMS121, Slows Disease Progress in an Alzheimer's Mouse Model

The research materials here are of interest because fisetin has been shown to be a senolytic compound in mice, capable of selectively destroying harmful senescent cells. Other senolytics have reversed the progression of Alzheimer's disease pathology in mouse models of the condition. Destroying senescent cells in the brain reduces inflammatory signaling, and chronic inflammation is a significant mechanism in neurodegenerative conditions such as Alzheimer's disease. Whether this compound works well as a senolytic in humans has yet to be established - a clinical trial is underway, so hopefully we'll find out in the next year or two.

The researchers here are not interested in cellular senescence at all, however, and instead base their work on the effects of fisetin and fisetin-like molecules on lipid metabolism in the brain. Back in 2014, they showed that fisetin slowed the onset of Alzheimer's like symptoms in mice. The present work is much the same, except with an improved version of fisetin called CMS121. This all raises the question of whether their approach is working for the reasons that they think it is working.

Over the last few decades, researchers have studied how a chemical called fisetin, found in fruits and vegetables, can improve memory and even prevent Alzheimer's-like disease in mice. More recently, the team synthesized different variants of fisetin and found that one, called CMS121, was especially effective at improving the animals' memory, and slowing the degeneration of brain cells.

In the new study, researchers tested the effect of CMS121 on mice that develop the equivalent of Alzheimer's disease. The team gave a subset of the mice daily doses of CMS121 beginning at 9 months old - the equivalent of middle age in people, and after the mice have already begun to show learning and memory problems. The timing of the lab's treatment is akin to how a patient who visits the doctor for cognitive problems might be treated, the researchers say. After three months on CMS121, at 12 months old, the mice were given a battery of memory and behavior tests. In both types of tests, mice with Alzheimer's-like disease that had received the drug performed equally well as healthy control animals, while untreated mice with the disease performed more poorly.

To better understand the impact of CMS121, the team compared the levels of different molecules within the brains of the three groups of mice. They discovered that when it came to levels of lipids - fatty molecules that play key roles in cells throughout the body - mice with the disease had several differences compared to both healthy mice and those treated with CMS121. In particular, the researchers pinpointed differences in something known as lipid peroxidation - the degradation of lipids that produces free radical molecules that can go on to cause cell damage. Mice with Alzheimer's-like disease had higher levels of lipid peroxidation than either healthy mice or those treated with CMS121.


Telomerase Gene Therapy May Treat Fibrosis via a Reduced Burden of Cellular Senescence

A number of research groups are quite enthusiastic about the prospects for telomerase gene therapy as a treatment for aging and numerous age-related diseases. This is based on more than a decade of work in mice, showing extended life spans and improved metabolism. Over the past few years, reversal of fibrosis via telomerase gene therapy has been demonstrated in mice. The evidence for this to be an approach worth bringing to the clinic continues to accumulate. Fibrosis is a disruption of tissue maintenance, associated with chronic inflammation, in which an inappropriate deposition of scar-like collagen takes place, degrading normal tissue structure and function. Today's research materials are the latest on this topic, in which scientists dig deeper into the mechanisms by which telomerase upregulation might be acting on fibrosis in the lung.

The primary function of telomerase is to extend telomeres, caps of repeated DNA at the ends of chromosomes. Telomere length shortens with every cell division, but only stem cells normally express telomerase and thus have the capability to maintain long telomeres. The vast majority of somatic cells in the body lose their telomere length until hitting the Hayflick limit, at which point their shortened telomeres trigger cell death or cellular senescence. All tissues are in a state of turnover, losing cells to the Hayflick limit, while replacements with long telomeres are generated by stem cells.

Telomerase upregulation might produce benefits in a number of ways. Firstly, if all cells express telomerase, then there will tend to be more functional cells in any given tissue, postponing age-related declines in function that occur due to a slowing of stem cell activity. A concern here is that this will allow damaged cells to function for longer, and thus raise cancer risk. That raised risk doesn't occur in mice with upregulated telomerase, possibly because immune system function is improved by telomerase gene therapy in the same way as other tissue function, and improved cancer suppression by immune cells outweighs the increased risk due to lengthening the telomeres of damaged and potentially cancerous cells. Whether or not the same balance of factors will occur in humans is still to be determined.

Secondly, telomerase upregulation may reduce the burden of senescent cells in tissues, both by preventing cells from replicative senescence, and by improving the operation of mechanisms that clear senescent cells. Senescent cells are important in aging, as demonstrated by the extension of life and reversal of age-related disease produced in mice via senolytic therapies that selectively remove these errant cells. Interestingly, senescent cells are strongly implicated in the progression of fibrosis, and their removal has been shown to reverse the condition in mice. In the research noted here, telomerase gene therapy reduces measures of senescence in fibrotic lungs. It is entirely plausible that this is the primary mechanism by which increased telomerase activity reverses fibrosis.

Researchers pave the way for a future gene therapy to reverse pulmonary fibrosis associated with ageing

Idiopathic pulmonary fibrosis is a potentially lethal disease for which there is currently no cure and that is associated with certain mutations or advanced age. Resesarchers had previously developed an effective therapy for mice with fibrosis caused by genetic defects. Now they show that the same therapy can successfully be used to treat mice with age-related fibrosis. The treatment tested in mice is a gene therapy that activates the production of telomerase in the body. Telomerase is an enzyme that repairs the telomeres at the end of chromosomes.

The new study describes the effects of ageing on lung tissue in detail. One such effect is that alveolar type II cells stop doing their job. In addition to regenerating tissue, these cells produce and release a lipid-protein complex called pulmonary surfactant that facilitates the mechanical work done by the lungs. "Lung tissue must expand when we breathe in, six to ten times per minute, which means a great deal of physical effort. Pulmonary surfactant plays an important role in lubricating lung tissue, retaining its elasticity, and reducing the amount of work required to expand and contract it. If type II pneumocytes fail to regenerate, the surfactant is not produced, which results in lung stiffness and fibrosis."

In 2018, researchers developed a gene therapy that reversed pulmonary fibrosis in mice lacking the telomerase gene. This therapy was based on activating telomerase expression temporarily. A virus used as a telomerase gene carrier was injected intravenously into the mice. The effect - alveolar type II cells with long telomeres - was temporary, but lung tissue regeneration was successfully induced. The same therapy was now used in aging mice. And it worked in them too. "The telomerase-activating gene therapy prevented the development of fibrosis in all mice, including the ones without genetic alterations that only underwent physiological ageing."

Telomerase treatment prevents lung profibrotic pathologies associated with physiological aging

We determined the impact of AAV9-Tert gene therapy in rescuing DNA damage, apoptosis, and senescence in Tert+/+ and Tert-/- lungs treated with either AAV9-Tert or AAV9-null virus particles. We found that both Tert+/+ and Tert-/- mice treated with AAV9-Tert showed significantly decreased numbers of γ-H2AX-positive cells in the lung parenchyma compared with the corresponding cohorts treated with the null vector, indicating decreased DNA damage upon telomerase treatment. Similarly, we detected significantly decreased numbers of activated caspase3-positive cells in the alveolar parenchyma of both Tert+/+ and Tert-/- lungs treated with AAV9-Tert compared with those treated with the null vector. Interestingly, increased senescence as detected by p16-positive cells specifically in the case of aveolar macrophages was also rescued in both Tert+/+ and Tert-/- lungs treated with AAV9-Tert compared with those treated with the null vector.

Finally, by performing double immunostainings with the proliferation marker Ki67 and the specific markers for alveolar type II cells, club cells, and aveolar macrophages, we observed that proliferation of alveolar type II cells, club cells, and aveolar macrophages was significantly increased in both Tert+/+ and Tert-/- lungs treated with AAV9-Tert compared with those treated with the null vector. Interestingly, the number of SOX2-positive differentiating club cells was also significantly reduced in Tert+/+ and Tert-/- lungs upon telomerase gene therapy.

Finally, to address whether treatment with telomerase gene therapy also prevented expression of proinflammatory and anti-inflammatory markers, we determined mRNA expression of Tnf, Il1b, Il6, Il4, Il10, and Il13 in total lung extracts from Tert+/+ and Tert-/- mice. We observed significantly decreased expression of these markers in both Tert+/+ andTert-/- mice treated with AAV9-Tert compared with those treated with the null vector.

Overexpression of VRK-1 Extends Life Span in Nematode Worms

A great many approaches exist to slow aging in short-lived laboratory species such as nematodes, flies, and mice. The example here is an illustrative example, similar to dozens of other discoveries regarding life span and upregulation or downregulation of the expression of specific proteins. Since cellular biochemistry is a connected web of interactions, most such methods involve adjusting different parts of the same underlying system of regulation. An increased operation of cellular stress responses is the most common such regulator of the pace of aging. Unfortunately this type of intervention has much larger effects on life span in short-lived species than it does in long-lived species. This has led to much of the field of aging research focusing on projects that appear interesting in mice, but cannot possibly produce large gains in human life span.

Mitochondria are essential subcellular organelles for cellular energy production. Mitochondria also play important functions in a wide array of other cellular processes, ranging from cellular signaling to apoptosis. In addition, mitochondria play crucial roles in organismal aging, and functional declines in mitochondria are associated with age-related diseases. However, mild inhibition of mitochondrial respiration has been shown to promote longevity in multiple species. In Caenorhabditis elegans, the genetic inhibition of mitochondrial respiration genes prolongs life span. Inhibition of mitochondrial respiration also increases life span in Drosophila and mammals.

Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK), a critical cellular energy sensor that increases life span in multiple species, is one of the factors required for the enhanced longevity caused by inhibition of mitochondrial respiration in C. elegans. The vaccinia virus-related kinase (VRK) family consists of three serine-threonine protein kinases (VRK1 to VRK3) in mammals, which are related to casein kinases. Among these three, the best characterized is VRK1, a cell cycle regulator that is abundant in proliferative tissues. Unlike mammals, C. elegans has a single VRK ortholog, VRK-1, whose function in cell proliferation is relatively well established. However, it remains unknown whether VRK-1 acts in postmitotic cells or has a role in adult life span.

In this study, we sought to elucidate the role of VRK-1 in regulation of adult life span in C. elegans. We found that overexpression of VRK-1::GFP (green fluorescent protein), which was detected in the nuclei of cells in multiple somatic tissues, including the intestine, increased life span. Conversely, genetic inhibition of vrk-1 decreased life span. We further showed that vrk-1 was essential for the increased life span of mitochondrial respiratory mutants. We demonstrated that VRK-1 was responsible for increasing the level of active and phosphorylated form of AMPK, thus promoting longevity.


The Gut Microbiome Changes Shortly Before Death in Centenarians

Extremely old people have such high mortality rates that studies such as this one here become practical, answering the question of how the gut microbiome changes in the final decline into death. It is well established that the gut microbiome is influential on health, and undergoes detrimental changes across the course of adult life, although it remains to be determined as to which of the possible mechanisms are most important. In particular, it is unclear as to whether gut microbiome changes provoke inflammatory immune dysfunction or whether age-related immune dysfunction allows more inflammatory microbes to prosper. Or whether both directions of causation are relevant.

Several studies have revealed certain unique characteristics of gut microbiome in centenarians. We established a prospective cohort of fecal microbiota and conducted the first metagenomics-based study among centenarians. The objective was to explore the dynamic changes of gut microbiota in healthy centenarians and centenarians approaching end of life and to unravel the characteristics of aging-associated microbiome. Seventy-five healthy centenarians participated in follow-up surveys and collection of fecal samples at intervals of 3 months. Data pertaining to dietary status, health status scores, cause of disease and death, and fecal specimens were collected for 15 months.

Twenty participants died within 20 months during the follow-up period. The median survival time was 8-9 months and the mortality rate was 14.7% per year. The health status scores before death were significantly lower than those at 3 months before the end of the follow-up period. At this time, the participants mainly exhibited symptoms of anorexia and reduced dietary intake and physical activity. Metagenomics sequencing and analysis were carried out to characterize the gut microbiota changes in the centenarians during their transition from healthy status to death.

Analysis showed a significant change in gut microbiota from 7 months prior to death. All participants were grouped with 7 months before death as cut-off; no significant difference in α diversity was found between the two groups. Analysis revealed significant changes in the abundance of ten bacterial species before death; of these, eight species were significantly reduced (Akkermansia muciniphila, Alistipes finegoldii, Alistipes shahii, Bacteroides faecis, Bacteroides intestinalis, Butyrivibrio crossotus, Bacteroides stercoris, and Prevotella stercorea) while two were significantly increased before death (Bifidobacterium longum and Ruminococcus bromii). We speculate that these changes might occur before the clinical symptoms of deterioration in health status.


30% to 40% of Dementia Might be Avoided via Lifestyle Choices

Today's open access research materials present a statistical exercise that uses broad epidemiological data to determine the impact of individual lifestyle choices and environmental factors to the incidence of dementia. The results are not declaring that, say, particulate air pollution is responsible for 2% of dementias. Rather if the statistics point out that particulate air pollution is associated with 2% of cases, smoking with 5%, and hearing loss with 8%, then one starts to see priorities in the choices that people should be making to better manage their health over the long term.

Summing all of the impacts together - to see a 30-40% contribution of lifestyle and environment to incidence of dementia - also provides an assessment of the degree to which dementia is a lifestyle disease. To which it is avoidable with sensible choices regarding health and surrounding environment. Alzheimer's disease in particular involves a number of mechanisms that look suspiciously like those involved in type 2 diabetes, a condition that is near entirely a lifestyle issue resulting from excess fat tissue. Nonetheless, Alzheimer's disease and other dementias are clearly not determined by obesity to the same degree. The risk spreads out over choices and influences that touch on chronic inflammation (fat, smoking, air pollution), cognitive reserve (education), physical damage to brain tissue and surrounding channels for cerebrospinal fluid drainage (hypertension, head injury). It is a matter of many smaller contributions that cause harm through a range of quite different mechanisms.

While senolytic drugs that remove senescent cells in the brain will probably make a sizable difference to dementia incidence, via greatly reducing inflammation in brain tissue, it remains the case that comparatively little else can be done at present other than slowing the decline through better life-long health. More and better regenerative therapies, and more and better therapies that target the underlying molecular damage of brain aging are needed.

Dementia prevention, intervention, and care: 2020 report of the Lancet Commission

Overall, a growing body of evidence supports the nine potentially modifiable risk factors for dementia modelled by the 2017 Lancet Commission on dementia prevention, intervention, and care: less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact. We now add three more risk factors for dementia with newer, convincing evidence. These factors are excessive alcohol consumption, traumatic brain injury, and air pollution. We have completed new reviews and meta-analyses and incorporated these into an updated 12 risk factor life-course model of dementia prevention. Together the 12 modifiable risk factors account for around 40% of worldwide dementias, which consequently could theoretically be prevented or delayed. The potential for prevention is high and might be higher in low-income and middle-income countries (LMIC) where more dementias occur.

The number of people with dementia is rising. Predictions about future trends in dementia prevalence vary depending on the underlying assumptions and geographical region, but generally suggest substantial increases in overall prevalence related to an ageing population. For example, according to the Global Burden of Diseases, Injuries, and Risk Factors Study, the global age-standardised prevalence of dementia between 1990 and 2016 was relatively stable, but with an ageing and bigger population the number of people with dementia has more than doubled since 1990.

However, in many high income countries (HIC) such as the USA, the UK, and France, age-specific incidence rates are lower in more recent cohorts compared with cohorts from previous decades collected using similar methods and target populations and the age-specific incidence of dementia appears to decrease. All-cause dementia incidence is lower in people born more recently, probably due to educational, socio-economic, health care, and lifestyle changes. However, in these countries increasing obesity and diabetes and declining physical activity might reverse this trajectory. In contrast, age-specific dementia prevalence in Japan, South Korea, Hong Kong, and Taiwan looks as if it is increasing, as is Alzheimer's in LMIC, although whether diagnostic methods are always the same in comparison studies is unclear.

Cognitive reserve is a concept accounting for the difference between an individual's clinical picture and their neuropathology. It is divided into neurobiological brain reserve (eg, numbers of neurons and synapses at a given timepoint), brain maintenance (as neurobiological capital at any timepoint, based on genetics or lifestyle reducing brain changes and pathology development over time) and cognitive reserve as adaptability enabling preservation of cognition or everyday functioning in spite of brain pathology. Early-life factors, such as less education, affect the resulting cognitive reserve. Midlife and old-age risk factors influence age-related cognitive decline and triggering of neuropathological developments. Consistent with the hypothesis of cognitive reserve is that older women are more likely to develop dementia than men of the same age, probably partly because on average older women have had less education than older men. Cognitive reserve mechanisms might include preserved metabolism or increased connectivity in temporal and frontal brain areas.

Risk factors in early life (education), midlife (hypertension, obesity, hearing loss, traumatic brain injury, and alcohol misuse) and later life (smoking, depression, physical inactivity, social isolation, diabetes, and air pollution) can contribute to increased dementia risk. Good evidence exists for all these risk factors although some late-life factors, such as depression, possibly have a bidirectional impact and are also part of the dementia prodrome. Our new life-course model and evidence synthesis has paramount worldwide policy implications. It is never too early and never too late in the life course for dementia prevention. Early-life (younger than 45 years) risks, such as less education, affect cognitive reserve; midlife (45-65 years), and later-life (older than 65 years) risk factors influence reserve and triggering of neuropathological developments.

IGF-1R Inhibition Reduces Neuroinflammation in an Alzheimer's Mouse Model

Chronic inflammation in brain tissue is an important component of the progression of neurodegenerative conditions such as Alzheimer's disease. It is important enough that some researchers propose inflammation resulting from persistent infection and cellular senescence to be the primary mechanism in Alzheimer's disease, and the characteristic accumulation of amyloid-β deposits only a side-effect. Given the failure to achieve meaningful benefits in patients through removal of amyloid-β, researchers are turning their eyes towards ways to suppress inflammatory signaling in the brain. Removal of senescent cells, the source of a great deal of that inflammatory signaling, is one promising avenue, but other efforts focus on interference in specific signaling pathways, as is the case here.

Extracellular amyloid β (Aβ) plaques and intracellular neurofibrillary tangles are Alzheimer's disease (AD) pathological features hypothesized to lead to neuronal death and cognitive dysfunction. Since aging is the main risk factor for AD, slowing down this process may delay disease onset or progression. The growth hormone (GH)/insulin-like growth factor (IGF-1) signaling pathway is hypothesized to be one of the primary pathways regulating lifespan in general. Partial inactivation of the IGF-1 receptor (IGF-1R) gene or insulin-like signaling extends longevity and postpones age-related dysfunction in nematodes, flies, and rodents.

The role of IGF-1 in regulating age-associated AD remains unclear. For instance, lower serum IGF-1 levels correlate with increased cognitive decline and risk of AD. Also, patients with familial AD demonstrate lower levels of circulating IGF-1 compared to controls. An ex vivo study revealed IGF-1 resistance along with insulin resistance through the PI3K pathway in AD patient brains. Finally, IGF-1 treatment diminished Aβ accumulation by improving its transportation out of the brains of AD mouse models while IGF-1R inhibition aggravated both behavioral and pathological AD symptoms in mice. On the other hand, the administration of a potent inducer of circulating IGF-1 levels failed to delay AD progression in a randomized trial. Also, acute or chronic delivery of IGF-1 exerted no beneficial effect on AD pathological hallmarks in rodent models in vivo. Moreover, high levels of serum IGF-1 were detected in individuals diagnosed with AD or other forms of dementia in one study.

Presumably, this dichotomy of effects is, in part, mediated through the effects of IGF-1 on its receptor. The IGF-1R and the insulin receptor (IR) are homologous tyrosine kinase proteins with remarkably different functions. In our previous work, AβPP/PS1 transgenic mice, which express human mutant amyloid precursor protein (APP) and presenilin-1 (PS-1), demonstrated a decrease in brain IGF-1 levels when they were crossed with IGF-1 deficient Ames dwarf mice. Subsequently, a reduction in gliosis and amyloid-β (Aβ) plaque deposition were observed in this mouse model. This supported the hypothesis that IGF-1 may contribute to the progression of the disease.

To assess the role of IGF-1 in AD, 9-10-month-old male littermate control wild type and AβPP/PS1 mice were randomly divided into two treatment groups: control and picropodophyllin (PPP), a selective, competitive, and reversible IGF-1R inhibitor. Mice were sacrificed after 7 days of daily injection and the brains, spleens, and livers were collected to quantify histologic and biochemical changes. The PPP-treated AβPP/PS1 mice demonstrated attenuated insoluble amyloid-β. Additionally, an attenuation in microgliosis and protein p-tyrosine levels was observed due to drug treatment in the hippocampus. Our data suggest IGF-1R signaling is associated with disease progression in this mouse model. More importantly, modulation of the brain IGF-1R signaling pathway, even at mid-life, was enough to attenuate aspects of the disease phenotype. This suggests that small molecule therapy targeting the IGF-1R pathway may be viable for late-stage disease treatment.


Arguing for DNA Methylation Changes to be a Contributing Cause of Aging

Contributing mechanisms of aging form an interconnected network of cause and consequence. For most such mechanisms there is considerable debate over relative importance to the manifestations of aging, as well as over whether a mechanism is upstream or downstream of its peers. The step by step "A causes B causes C causes D" view of aging and age-related disease is very unclear in the middle reaches of the chain of cause and effect, despite a good list of first causes and a growing understanding of proximate causes for many age-related conditions. Progress is slow, as no biochemical mechanism exists in isolation, and it is a challenge to pick apart the complexities of cellular metabolism to find the important relationships.

Thus for DNA methylation, epigenetic changes that alter expression of proteins, at the high level one can argue that this is downstream of forms of damage and dysfunction, a response on the part of cells. One can also argue that some of these changes are harmful and cause further issues. Connecting DNA methylation to causes and consequences is an enormous undertaking, given the number of methylation sites that are now connected to aging as a result of work on epigenetic clocks. Nonetheless, some inroads are being made.

During aging, predefined genes constantly undergo epigenetic modifications and exhibit altered expression in response to internal and external environmental stress. Changes in DNA methylation may occur hundreds of times over the lifespan of an individual in the form of a fully adaptive response. However, in some cases, this methylation acts as a switch for the acceleration of pathological aging, resulting in negative consequences. Thus, global fluctuations in DNA methylation are not only a consequence but also a cause of aging. Understanding the biological mechanisms underlying the observed associations may reveal novel targets for reversing aging-related phenotypes and ultimately prolonging lifespan.

Evidence has emerged showing that decreased autophagic activity is involved in DNA methylation. DNA methylation inhibits autophagy processes in two ways, one of which is the direct modification and silencing of autophagy-related genes by DNA methyltransferases. The promoter regions of Atg5 and LC3 are hypermethylated in aged mice, which suppresses gene expression and disrupts the completion of autophagosomes. Whole-body overexpression of Atg5 results in antiaging phenotypes, extending the median lifespan of mice by 17.2%. Furthermore, researchers have recently shown that DNA methylation inhibitors can rescue phenotypic changes associated with aging by reactivating autophagy-related genes.

Identification of the target genes modified by DNA methylation-related regulatory elements in aging individuals is highly informative to figure out the hormone-like effectors and signal pathways that mediate these alterations as well as related diseases. The interaction among epigenetic regulators during aging should also be highly valued. Further studies should focus on the cross-talk among these epigenetic regulators, such as DNA methylation, RNA methylation, histone methylation, and noncoding RNAs, which will aid in providing a full picture of epigenetics and aging. The results of such studies may pave the way for antiaging interventions as well as treatments for related diseases, enabling human life extension.


Short Term Cdc42 Inhibition In Middle Aged Mice Extends Median and Maximum Life Span

An interesting study of mouse life span extension via a novel methodology was recently published. The researchers developed a small molecule approach to inhibition of Cdc42, a protein with numerous functions throughout the cell. This is a target for intervention because - at least in cell cultures - loss of Cdc42 activity appears to restore youthful function to aged hematopoietic stem cells. This is the cell population responsible for producing blood and immune cells, and declining immune function with age is driven at least in part by dysfunction in hematopoietic stem cells. Ways to restore immune function in older individuals should prove to be broadly beneficial to health in later life, given that the immune system has roles in tissue maintenance and function that extend far beyond merely defending against pathogens.

The effect size in mice for Cdc42 inhibition is here shown to be somewhere in the range of a 12-16% gain in median and maximum life spans, along with a reversal of age-related changes in some inflammatory cytokine levels. This gain in life span isn't large in the grand scheme of things, given that lifelong calorie restriction can result in a 40% increase in mouse life span, but the point of interest here is that this result was achieved with a single four day treatment carried out in middle aged mice, already well on the way towards being aged. Only rapamycin and senolytics have robustly achieved similar outcomes based on short term late life treatment.

We might hypothesize that, in these aging mice, the generation of new immune cells by hematopoietic stem cells was increased for long enough via this intervention to provide the lasting benefits of a renewed and bolstered immune system. Even if raised rates of immune cell generation don't last, the additional cells created will last. An aging immune system should be in an incrementally better state going forward as the result of any intervention capable of providing more new immune cells for a time. Unfortunately a full assessment of immune cell populations wasn't carried out in this study; only proximate measures of immune system activity such as cytokine levels were assessed.

Inhibition of Cdc42 activity extends lifespan and decreases circulating inflammatory cytokines in aged female C57BL/6 mice

Cdc42 is involved in multiple and diverse functions of eukaryotic cells, including actin cytoskeleton reorganization, cell polarity, and cell growth. The activity of Cdc42 is significantly elevated in blood of elderly humans and in several tissues of aged C57BL/6 mice. We recently identified a specific small-molecule inhibitor of Cdc42 activity termed CASIN. Administration of CASIN in vivo did not show signs of toxicity. Previously, we reported that a brief ex vivo exposure of aged hematopoietic stem cells (HSCs) to CASIN that reduced the activity of Cdc42 in aged cells to the level found in young cells resulted in long-lasting youthful function of HSCs in vivo, likely due to epigenetic remodeling of aged cells upon modulation of Cdc42 activity. Consequently, we hypothesized that maybe a short-term systemic reduction of Cdc42 activity in aged animals in vivo might be also beneficial for lifespan, as an elevated activity of Cdc42 upon aging is causatively linked to a shorter lifespan in mice.

To determine whether a short-term systemic CASIN treatment of aged animals might indeed influence lifespan, we administered CASIN via intraperitoneal injection every 24 hours for 4 consecutive days to 75-week-old female C57BL/6 mice. 4 days of consecutive injections did not induce acute toxicity, and as well, none of the treated mice died within 4 weeks after CASIN injections, rendering chronic toxicity issues unlikely. Quantification of Cdc42 activity 24 hours after the last injection on day 5 demonstrated a reduction of Cdc42 activity in aged bone marrow cells to the level seen in young, confirming that CASIN is indeed reducing Cdc42 activity after a systemic in vivo treatment. Notably, aged mice treated with CASIN for only 4 consecutive days showed extension of their average and also maximum lifespan.

We performed analyses to investigate the extent to which aging-associated inflammatory cytokines in serum of aged mice were affected by CASIN treatment. Data showed a marked increase in the concentrations of INFγ, IL-1β, and IL-1α on aging and the concentrations for these cytokines were similar to concentrations in young animals upon CASIN treatment of aged mice. It is thus a possibility that a reduction in the concentrations of these cytokines upon CASIN treatment might contribute to the increase in lifespan observed in these animals.

Previously, the methylation status of CpG sites within the genes Prima1, Hsf4, and Kcns1 was shown to qualify as likely predictor of biological age of C57BL/6 mice. Applying this C57BL/6-trained DNA methylation marker panel to blood cells from aged animals treated with CASIN 9 weeks after treatment, we observed that epigenetic age predictions did not correlate anymore to the chronological age as in aged control animals, but resulted in a biological age prediction that was on average 9 weeks younger than their chronological age. These data imply that epigenetic changes underlie the extended longevity of aged CASIN-treated mice, while reinforcing the necessity to mechanistically validate tissues, cells, and biological pathways involved in the extension of longevity.

Accelerated Osteoporosis in Mitochondrial Mutator Mice

Mitochondria are the power plants of the cell, the evolved descendants of ancient symbiotic bacteria. They generate the chemical energy store molecules needed to power cellular processes. The herd of hundreds of mitochondria in every cell replicate like bacteria, and carry a small remnant circular genome, the mitochondrial DNA. Mice engineered to lack a functional PolgA gene exhibit defective mitochondrial DNA repair, and as a consequence accumulate mutations in their mitochondrial DNA at a rapid pace. Random mutation and declining mitochondrial function is a feature of aging, and these mitochondrial mutator mice exhibit accelerated aging as a consequence of the more rapid damage they suffer to this vital cell component.

Here, researchers examine just one feature of this accelerated aging, the more rapid onset of osteoporosis, the characteristic loss of bone mass and strength that occurs with age. Bone is a dynamic tissue, constantly remodeled by osteoblasts that create bone and osteoclasts that break it down. Damage to mitochondrial function causes a decline in osteoblast activity, favoring bone destruction over bone creation. Over time this leads to osteporosis and all of its consequences.

The pathogenesis of declining bone mineral density, a universal feature of ageing, is not fully understood. Somatic mitochondrial DNA (mtDNA) mutations accumulate with age in human tissues and mounting evidence suggests that they may be integral to the ageing process. To explore the potential effects of mtDNA mutations on bone biology, we compared bone microarchitecture and turnover in an ageing series of wild type mice with that of the PolgA mitochondrial DNA 'mutator' mouse.

In vivo analyses showed an age-related loss of bone in both groups of mice; however, it was significantly accelerated in the PolgA mice. This accelerated rate of bone loss is associated with significantly reduced bone formation rate, reduced osteoblast population densities, increased osteoclast population densities, and mitochondrial respiratory chain deficiency in osteoblasts and osteoclasts in PolgA mice compared with wild-type mice. In vitro assays demonstrated severely impaired mineralised matrix formation and increased osteoclast resorption by PolgA cells.

Finally, application of an exercise intervention to a subset of PolgA mice showed no effect on bone mass or mineralised matrix formation in vitro. Our data demonstrate that mitochondrial dysfunction, a universal feature of human ageing, impairs osteogenesis and is associated with accelerated bone loss.


Too Much Mitochondrial Fission in the Aging Germline Stem Cells of Flies

Mitochondria are bacteria-like organelles responsible for producing chemical energy store molecules to power cellular processes. Hundreds of them exist in every cell, constantly undergoing fusion and fission, swapping component parts with one another, and being culled when damaged by the quality control mechanism of mitophagy. Past work has indicated that there is too little mitochondrial fission in old cells, leading to mitochondria that are too large to be effectively removed when damaged. The research here suggests that there is instead too much mitochondrial fission in stem cells, though it is focused specifically on germline stem cells in flies. Mitochondrial dynamics is a balance, and disruption in either direction is problematic. Age-related disruption may well be different in different species and cell types, so it is a little early to say whether or not the work here is relevant to mammals.

Mitochondria frequently undergo coordinated cycles of fusion and fission (known as mitochondrial dynamics) to properly adjust the shape, size, and cellular distribution of the organelle to meet specific cellular requirements. Fusion produces elongated mitochondria by respectively joining the outer and inner membranes of two mitochondria. The closely related Dynamin-related GTPases, Mfn1 and Mfn2, mediate outer membrane fusion, while Opa1 is integral for fusion of the inner membrane. On the other hand, excessive mitochondrial fission produces fragmented mitochondria and is mediated by another Dynamin-related GTPase, called Drp1. Drp1 is recruited by its receptors on the outer membrane and oligomerizes along the mitochondrial constriction site to constrict the organelle and induce scission.

Mitochondrial dynamics are known to influence several mitochondria-dependent biological processes, such as lipid homeostasis, calcium homeostasis, and ATP production. Recent studies have also proposed a role for mitochondrial fusion and fission in regulating stem cell fate. In one interesting example, murine neural stem cells were shown to exhibit elongated mitochondria, and depletion of Mfn1 or Opa1 impaired their self-renewal. Despite tantalizing observations such as these, the overall impact of mitochondrial dynamics in aging stem cells and the mechanisms by which mitochondrial dynamics might affect stem cell function remain unclear.

Here, we report that mitochondrial dynamics are shifted toward fission during aging of Drosophila ovarian germline stem cells (GSCs), and this shift contributes to aging-related GSC loss. We found that as GSCs age, mitochondrial fragmentation and expression of the mitochondrial fission regulator Drp1 are both increased, while mitochondrial membrane potential is reduced. Moreover, preventing mitochondrial fusion in GSCs results in highly fragmented depolarized mitochondria, decreased BMP stemness signaling, impaired fatty acid metabolism, and GSC loss. Conversely, forcing mitochondrial elongation promotes GSC attachment to the niche. Importantly, maintenance of aging GSCs can be enhanced by suppressing Drp1 expression to prevent mitochondrial fission or treating with rapamycin, which is known to promote autophagy via TOR inhibition.


Delivery of BDNF Reverses Inflammatory Microglial Activation in Old Mice

Brain-derived neurotrophic factor (BDNF) shows up in many aspects of the interaction between health practices, mechanisms of aging, and mechanisms of neurodegeneration. Most research is focused on the effects of BDNF on neural plasticity, meaning the generation of new neurons from neural stem cell populations, followed by the integration of those new neurons into neural networks, such that they participate in the functioning of the brain. Plasticity is necessary for memory, learning, and maintenance and repair of brain tissue, and in this context the presence of higher levels of BDNF appears to be entirely beneficial.

Unfortunately, BDNF levels decline with age, for reasons that are yet to be fully explored. Exercise is known to improve memory function in older individuals, and there is good evidence for increased BDNF to be an important mechanism in this effect. Similarly, gut microbes generate butyrate, which increases BDNF, establishing a link between changes in the gut microbiome and age-related cognitive decline. Various interventions that improve memory in old mice, such as upregulation of osteocalcin or RbAp48 have also been shown to produce their effects via increased expression of BDNF.

So why not just delivery BDNF as a therapy to improve cognitive function in later life? This does indeed work, as illustrated in today's open access research materials. Interestingly, the authors are focused on the effects of BDNF on inflammatory behavior in the immune cells of the brain rather than on neuroplasticity. It is becoming clear that chronic inflammation in brain tissue is an important contributing cause of neurodegenerative conditions. Among other process, chronic inflammation in the brain involves the inappropriate inflammatory activation of microglia, a specialized type of innate immune cell resident to the brain. Beyond the usual functions one would expect for such cells - chasing down pathogens, destroying errant cells, and so forth - microglia also aid in the maintenance of synaptic connections in various ways. So it is entirely plausible that more inflammatory microglia could mean a greater disruption of neural function in numerous ways, both via inflammatory signaling that changes cell behavior for the worse, and through neglect of normal microglial duties.

BDNF reverses aging-related microglial activation

Microglial activation is implicated in the pathogenesis of multiple neurodegenerative diseases. Under physiological conditions, microglia are in a resting state characterized by ramified morphology, and they function as homeostatic keepers of the central nervous system. Resting microglia are not dormant; their processes are constantly and actively scanning a defined territory of brain parenchyma. After they have been exposed to stimulatory signals, microglia undergo various degrees of activation, such as changing their morphology, gene expression, and functional behavior. Depending upon the type, intensity, and duration of the exposure to the stimuli, activated microglia can be neuroprotective or neurotoxic. Activated microglia can release various inflammatory cytokines and toxins that together might injure or even cause neuronal death.

Brain-derived neurotrophic factor (BDNF), a versatile member of the neurotrophin family, is widely and highly expressed in the brain and is a chief regulator of axonal growth, neuronal differentiation, survival, and synaptic plasticity. In the central nervous system, BDNF and downstream prosurvival pathways have been demonstrated to protect neurons from damage and enhance neuronal network reorganization after injury. It has also been reported that BDNF treatment could reduce degrees of microglial activation in certain brain injury models, albeit these responses were considered a consequence of reduced neuronal injury and death elicited by BDNF. The direct effect of BDNF on microglia has rarely been explored.

This study aimed to characterize the role of BDNF in age-related microglial activation. Initially, we found that degrees of microglial activation were especially evident in the substantia nigra (SN) across different brain regions of aged mice. The levels of BDNF and TrkB in microglia decreased with age and negatively correlated with their activation statuses in mice during aging. Interestingly, aging-related microglial activation could be reversed by chronic, subcutaneous perfusion of BDNF. Peripheral lipopolysaccharide (LPS) injection-induced microglial activation could be reduced by local supplement of BDNF, while shTrkB induced local microglial activation in naïve mice. Thus in conclusion, decreasing BDNF-TrkB signaling during aging favors microglial activation, while upregulation BDNF signaling inhibits microglial activation via the TrkB-Erk-CREB pathway.

An Update on Single Issue Political Advocacy for Longevity in Europe

In most European countries, electoral rules are such that it is possible to conduct effective advocacy for a cause via a single issue political party. Successful examples include the Green Party and the Pirate Party, but there are many others. In the matter of patient advocacy for investment into rejuvenation research, to treat aging as a medical condition and greatly reduce the suffering that occurs in old age, a number of European advocates have formed single issue political parties to raise awareness. The Party for Health Research in Germany is one such initiative. Here, the European Longevity Initiative is discussed, an alliance of single-issue parties and non-profits across Europe.

There is ample need to communicate fresh facts, principles and arguments around aging research and longevity technology opportunities within the European Union, with the single message that only these new technologies will provide a long-term solution to the problems presented by aging and general health. The last decade yielded a complete change of the paradigm around the understanding of the main hallmarks of aging and the malleability of the overall aging process. Building upon accumulating research in the previous decades, aging research has gone completely mainstream, and the paradigm of translational geroscience has gained strong supporters working on interventions directly targeting the root causes of biological aging to prevent - the biggest killer - age-associated diseases, and to extend healthy lifespan, aka healthspan, significantly.

Cross-European single issue longevity politics has an actual birth date, or rather period, the Members of the European Parliament elections of 2019. That is when multiple actors, in different countries stood at the elections focusing on the issue of working towards preventing age-associated diseases with healthy longevity technologies. Let me highlight here a dedicated, single-issue, one of its kind, political party, the German Party for Health Research and myself who stood as an independent candidate in the East of England Region. We got 0.2% of the votes with an almost zero budget, virtually unknown, meaning 1 in 500 voters thought the mission and programme are worth their votes.

The European Longevity Initiative (ELI) is a loose association of mainly EU citizens and residents coming together to form a healthy longevity advocacy group particularly targeting EU level legislation and EU wide public. Its associates are currently covering the following EU countries: Germany, Slovenia, France, Czech Republic, Belgium, Hungary, Greece, Austria, Poland. Moreover, current ELI associates are representatives of at least six existing European longevity advocacy groups. (1) The already-mentioned German The Partei für Gesundheitsforschung - The Party for Health Research; (2), funded by longevity supporters in the Czech Republic; (3) UK-based Longevity International running the pioneering All Party Parliamentary Group (APPG) for Longevity in the UK; (4) International Institute of Longevity based in Poland and Liechtenstein; (5) Društvo za vitalno podaljševanje življenja Slovenije - Slovenian society for vital life extension; (6) Heales Société pour l'Extension de la Vie - The Healthy Life Extension Society, based in Belgium.


The Reasons to Study Aging

I point out this open access paper not for the content, but for the preamble, in which the author offers a view on why the research community should study aging. Not to learn how it works, but to learn how to intervene in order to make the world a better place, in which people suffer less than is presently the case. This, at root, is why we work on treating aging as a medical condition - because it is by far the greatest source of suffering and death in the world.

Aging is characterized by the progressive deterioration of the body's physiological function, which leads to decreased health, increased incidence of degenerative diseases and, finally, a progressive increase in the risk of death. Aging is classically approached as an inevitable phenomenon whose problems are treated in a timely and palliative way, aiming only to minimize the suffering of the elderly or extend their life span. In addition, these illnesses, usually manifested by chronic diseases associated with aging, tend to be treated individually. That is, individuals with cancer will be treated to eliminate the tumor, while diabetics will be treated with drugs to lower blood glucose levels. As much as it is obvious that these people should be treated, these treatments are still palliative, since even with the cure of one of these diseases, the elderly individual continues to be at an increased risk for other diseases that will inevitably kill them. That is why the main health agencies in the world started to approach aging itself as a clinical entity that deserves to be treated as such. Not by chance, the first clinical study that aims to delay aging itself has recently started.

The impact of having aging as a target for treatment is enormous, not only because aging is the main risk factor for death among humans, but also because it tends to be one of the main expenses of elderly individuals and governments, and it is potentially a major cause of social inequality. If health systems maintain their current policy, public health costs are expected to double by 2050, creating a burden that many countries will not be able to sustain. In addition to health gains, intervening with aging would represent savings of approximately 7 trillion US dollars over 50 years in the US alone, while disease retardation scenarios would lead to minimal savings, since the risk of individuals acquiring other chronic disabling diseases remain.

But is it even possible to delay the aging process itself, or even reverse it as some propose? In 2016, it was suggested that there is a maximum limit to human life span, and that this limit is around 115 years old. This article, however, has been challenged in regard to the statistical analysis, and some are convinced that the proposed limit on human longevity proposed is not real. In fact, a more recent study of Italian centenarians showed that, surprisingly, the risk of death stops increasing with time when individuals reach the age of 105 years. The progressive increase in the risk of death is what characterizes the aging process in living beings. Thus, eliminating this increase means, in practice, that aging stops happening after a certain age. According to the study, at 105 years of age, the chance of death remains fixed at around 50% per year. This leads to the conclusion that at a given moment the balance between damage and repair stabilizes, preserving vital functions as they are, ceasing, however without reversing, the aging process. Although the estimates are still up for debate, the question remains: if it is possible to stabilize and mitigate the aging process at some point in life, why wouldn't it be possible to do it at a younger age?

Evidence that indicates this is possible is abundant in nature. There are several species that show negligible aging, i.e. which do not present an increased risk of death (or hazard rate) with age. For example, some species of turtles live for decades and show no signs of senescence. The Greenland shark is yet another vertebrate of extreme longevity and can live more than 400 years. Even among closer species and with similar habits, the lifespan can vary greatly. The naked mole-rat is a rodent that lives up to 30 years and practically does not develop cancer, unlike other rats and rodents that live a maximum of 5 years. Some species, such as the hydra, are even considered "immortal", or "amortal", because they do not die from causes related to aging. Even in humans, there are cells that can be considered amortal, such as germline cells. In other words, nature offers us examples of how aging and lifespan can be controlled. Looking at these examples, understanding how individual's senescence rate is determined, and proposing strategies to delay aging are the goals of a growing field called biogerontology.


Biotech Startup SENISCA Develops a RNA Splicing Approach to the Treatment of Aging

In recent years, increasing attention has been given to RNA splicing as a mechanism of interest in aging. RNA splicing is the process of combining intron and exon regions derived from a gene's DNA sequence into the final RNA sequence transcribed from that gene. Introns are usually dropped, exons are usually included, but this process of combination allows multiple proteins to be derived from one gene.

Characteristic changes in splicing take place with age, such as alterations in the proportions of different proteins produced from the same gene via different combinations of introns and exons. The regulation of splicing becomes more ragged in general, such as by allowing introns into RNA sequences when they should be excluded, and this is thought to contribute to metabolic disarray, cellular senescence, and other manifestations of aging. As for many of the mechanisms implicated in aging, there is as yet no robust placement of splicing changes in a chain of cause and consequence. It is unclear as to why exactly splicing runs awry, or the degree to which it contributes to specific higher level manifestations of aging.

The fastest way to achieve this understanding is most likely to selectively suppress splicing changes and see what happens as a result. This strategy has the added bonus of offering a chance at a treatment of aging if successful. Suppression of age-related changes in splicing is the intent of the founders of SENISCA, one of many biotech startup companies recently founded to swell the ranks of the growing longevity industry. They have found that forcing a reversal of some splicing changes can reverse cellular senescence, a normally irreversible cell state, and thus stop the senescent cells that accumulate with age from producing inflammatory secretions that cause great harm to old tissues. There is some debate over whether this is a good idea, versus forcing the destruction of these cells via senolytic treatments, as senescent cells are likely damaged in ways that might increase cancer risk if left alive and actively non-senescent. But again, the studies will be carried out and we'll see what results.

SENISCA seeks funding for senescence reversal

Deep in the labs at the University of Exeter's College of Medicine and Health (CMH), a new company is emerging. Co-founded by Professor Lorna Harries, SENISCA is developing "senotherapeutic interventions" that reverse cellular senescence. Through modulation of RNA splicing, the company has developed a way to effectively turn back the aging clock in old cells and is working on developing new treatments for the diseases and aesthetic aspects of aging.

"I'm an academic, but my ambition also has always been that anything that we discover that shows clinical potential is pursued and followed through to the clinic. Having shown that splicing regulation declines during aging, the million dollar question for me then was - what happens if you turn it back on?" This question led Harries to the study, which showed that cells could not only be brought out of senescence but that, by doing so, the cells were also rejuvenated.

"When we did that, we were utterly, utterly amazed. While there had been research that showed aging could be reversed in animal models by removing senescent cells, this was different. So we're not removing senescent cells, we are rejuvenating them. The cells regain pretty much all of the features of young cells. They're still old cells, but they're not senescent, so they're not throwing out inflammatory proteins, which is what's doing the damage to our bodies. We learned that yes, you can target those pathways and you can reverse senescence. The molecules were used to do that were already in the clinic as anti-cancer agents, so we knew they were safe and specific, so that proved that we'd found the right pathway."


Our founders have discovered that levels of splicing factors change during ageing, compromising our ability to carry out this 'fine tuning' of gene expression. This is a fundamental reason why cells become senescent. Compromised molecular resilience is a major cause of the ill health and frailty that accompanies ageing. We have demonstrated that restoration of splicing factor levels to those seen in younger cells is able to effectively turn back the ageing clock in old cells, bringing about reversal of senescence.

At SENISCA, we are taking a two-faceted approach for modulation of splicing factor levels. Firstly, we are identifying small molecules capable of restoring splicing factor levels. Secondly, we are targeting the genes that control splicing factor levels directly. Both approaches will reset splicing factor levels and reverse senescence. We anticipate that understanding the molecular basis of rejuvenation will highlight new treatments for the diseases and aesthetic aspects of ageing. More importantly, it is likely that preventative approaches based on rejuvenation will be developed reducing both disease incidence and severity.

Microtubule Activity in Dopaminergic Neurons Affects the Pace of Aging in Flies

In an interesting discovery, researchers here note evidence for the behavior of dopamine generating neurons in the fly brain to have an sizable influence on the pace of aging and longevity in this species. This effect on aging appears to depend on microtubule activity in these cells, but the work leaves open the question of how exactly this change to a very specific population of neurons alters life span. Much more is left to accomplish in order to even begin to speculate on relevance to human biochemistry.

Dopaminergic neurons, a critical modulatory system in the brain, are greatly affected by age, but it is unclear whether it can impact the aging process in animals. During the course of studying a putative scaffolding protein, Mask, a novel role was discovered for dopaminergic neurons in regulating longevity and aging in fruit flies. Overexpressing Mask in dopaminergic neurons leads to a ∼40% increase in lifespan in flies. This effect seems to be specific to the dopaminergic neurons, as overexpressing Mask in neither the entire body nor the nervous system (neurons or glial cells) showed significant effects on the lifespan.

Although the dopaminergic system provides essential modulation on various behaviors and physiological functions, flies devoid of dopamine in their brains and worms lacking the rate-limiting enzymes for dopamine synthesis live a normal lifespan. These results suggest that dopamine systems is not required to drive normal aging. Overexpressing Mask in specific dopaminergic neurons possibly induces a gain-of-function cellular effect, which consequently confers a beneficial outcome on aging and longevity.

The lifespan extension induced by Mask-overexpressing is accompanied by sustained adult locomotor and fecundity in the long-lived flies; and other physiological functions in the adult flies include food intake and insulin production in the brain are not consistently altered by overexpressing Mask in either group of dopaminergic neurons. The recent finding that Mask promotes microtubule dynamics in fly larval motor neurons and body wall muscles led to the postulation that altered microtubule dynamics in the Mask-expressing dopaminergic neurons is the key mediator. Overexpressing the Kinesin heavy chain Unc-10427 or knocking down a component of the Dynein/Dynactin complex, p150Glued28 are two interventions that have been previously shown to impact MT dynamics. Overexpressing Unc-104 or moderately reducing p150Glued level in the same groups of dopaminergic neurons also extend lifespan in flies, thus demonstrating that increasing MT dynamics and reducing microtubule stability in dopaminergic neurons is sufficient to induce lifespan extension in flies.


GDF15 Helps to Resist Age-Related Chronic Inflammation

Aging is accompanied by rising levels of sustained inflammation, a chronic overactivation of the immune system. This inappropriate activity on the part of immune cells disrupts tissue function in numerous ways, contributing to onset and progression of all of the common and ultimately fatal age-related conditions, from atherosclerosis to Alzheimer's disease. Ways to control this inflammation without disrupting other, necessary immune functions are thus likely to be broadly beneficial. Numerous age-related changes contribute to chronic inflammation; one of the most relevant for near term intervention is the accumulation of senescent cells in tissues throughout the body. These cells are near all destroyed quite rapidly in youth, with with age the processes of removal become less efficient. Senescent cells secrete pro-inflammatory signal molecules, and the more of them there are, the worse the outcome. Fortunately, senolytic therapies to selectively destroy senescent cells are presently in active development. Other approaches to inflammation will also be needed, however.

Mitochondrial dysfunction is associated with aging-mediated inflammatory responses, leading to metabolic deterioration, development of insulin resistance, and type 2 diabetes. Growth differentiation factor 15 (GDF15) is an important mitokine generated in response to mitochondrial stress and dysfunction; however, the implications of GDF15 to the aging process are poorly understood in mammals.

In this study, we identified a link between mitochondrial stress-induced GDF15 production and protection from tissue inflammation on aging in humans and mice. We observed an increase in serum levels and hepatic expression of GDF15 as well as pro-inflammatory cytokines in elderly subjects. Circulating levels of cell-free mitochondrial DNA were significantly higher in elderly subjects with elevated serum levels of GDF15. In the BXD mouse reference population, mice with metabolic impairments and shorter survival were found to exhibit higher hepatic Gdf15 expression.

Mendelian randomization links reduced GDF15 expression in human blood to increased body weight and inflammation. GDF15 deficiency promotes tissue inflammation by increasing the activation of resident immune cells in metabolic organs, such as in the liver and adipose tissues of 20-month-old mice. Aging also results in more severe liver injury and hepatic fat deposition in Gdf15-deficient mice. Although GDF15 is not required for Th17 cell differentiation and IL-17 production in Th17 cells, GDF15 contributes to regulatory T-cell-mediated suppression of conventional T-cell activation and inflammatory cytokines. Taken together, these data reveal that GDF15 is indispensable for attenuating aging-mediated local and systemic inflammation, thereby maintaining glucose homeostasis and insulin sensitivity in humans and mice.


An Aged Hematopoietic System can Cause Cognitive Decline via SASP Component CyPA

Today's open access paper outlines an investigation into how the aging of hematopoietic stem cell populations in bone marrow, responsible for producing blood and immune cells, can contribute to age-related dysfunction in the brain. The authors find that detrimental effects are mediated by circulating levels of CyPA, a signaling factor that is a part of the senescence-associated secretory phenotype (SASP), an inflammatory mix of signal molecules produced by senescent cells. The focus here is on direct inhibition of CyPA as an approach to therapy, but senolytic treatments to clear senescent cells may be the more useful approach if these errant cells are indeed the source of raised levels of CyPA. This seems reasonable, but is yet to be proven rigorously.

The aging of hematopoietic stem cells takes several forms. The population of functional stem cells declines due to damage, leading to a drop in the number of immune cells produced. This lack of reinforcements is one of the reasons why the aging immune system becomes dysfunctional, cluttered with exhausted, senescent, and malfunctioning cells. In addition, age-related changes in signaling and the stem cell niche in bone marrow cause detrimental changes in the distribution of types of immune cell produced. More myeloid cells and fewer lymphoid cells are produced, a change known as myeloid skew.

The aged hematopoietic system promotes hippocampal-dependent cognitive decline

In mice and humans, the hematopoietic system undergoes many functional and structural changes during aging, characterized by myeloid expansion, decreased immunity, and chronic low-grade inflammation. We hypothesized that these cellular changes contribute to hippocampal aging through the accumulation of pro-aging immune factors in old blood. Many of the age-related changes observed in old blood have roots in hematopoietic stem cell (HSC) aging.

We employed a heterochronic HSC transplantation model to test how exposure to an aged hematopoietic system contributes to hippocampal aging. Young (2 months) recipient mice were sublethally irradiated to destroy their native HSCs and transplanted with HSCs isolated from young (2 months) or old (24 months) donors, generating isochronic (Iso) and heterochronic (Het) HSC-reconstituted young mice. Blood chimerism was assessed by measuring the proportion of CD45.2 donor cells in CD45.1 recipient mouse blood by flow cytometry. Blood derived from old HSCs exhibited characteristic age-related myeloid bias 4.5 months post-transplantation. Animals showed no signs of illness or weight loss regardless of treatment.

To gain mechanistic insight into how the old hematopoietic system exerts its deleterious effects on cognition, we assessed peripheral immune cell infiltration into the hippocampus. Immunohistochemical identification of CD45.2+ hematopoietic cells in the dentate gyrus of CD45.1 recipient mice revealed low and equivalent levels of immune cell infiltration in Het and Iso HSC-reconstituted young mice. While we cannot exclude the possible contribution of these small numbers of peripheral immune cells, we hypothesized that the pro-aging effects of the old hematopoietic system are predominantly mediated through peripheral changes in circulating blood factors.

We performed unbiased proteomic analysis on blood plasma collected from Het and Iso HSC-reconstituted young mice 4.5 months post-transplantation. Using label-free mass spectrometry, we identified 22 factors that were differentially expressed between Het and Iso HSC-reconstituted young mice. Of these, the most significantly upregulated cytokine was cyclophilin A (CyPA, encoded by Ppia) - an intracellular protein that is secreted in response to inflammatory stimuli.

To test whether increasing systemic CyPA levels are sufficient to elicit age-related cognitive or cellular impairments, young (2 months) mice were intravenously injected with overexpression constructs encoding either CyPA or GFP control. Increased systemic levels of CyPA impair cognition in young mice, while inhibition of CyPA in aged mice improves cognition. Cumulatively, our data demonstrate that age-related changes in the hematopoietic system promote molecular, cellular, and cognitive hallmarks of hippocampal aging.

Notably, inhibiting CyPA has been demonstrated to be neuroprotective in a mouse model of amyotrophic lateral sclerosis. In humans, elevated cerebrospinal fluid CyPA levels have recently been associated with cognitive impairments in Alzheimer's disease patients expressing apolipoprotein E4. Moreover, in humans elevated CyPA plasma levels accompany a number of inflammatory age-related diseases, including diabetes, and cardiovascular disease. In these studies, CyPA plasma levels were also found to be elevated with aging. While little is known about the role of CyPA in aging, recent proteomic analysis using mass spectrometry has identified CyPA as part of the senescence-associated secretory phenotype (SASP). Ultimately, our data identify the aged hematopoietic system, and downstream circulating immune factors, as potential therapeutic targets to restore cognitive function in the elderly.

MicroRNA miR-218-5p in Follicle Regeneration for Hair Regrowth

As a general rule, people care too much about their hair and too little about their blood vessels. One can live without hair. It is interesting to see both (a) just how much work goes into the regeneration of lost hair, and (b) just how little is known of the fine details by which the capacity to grow hair fades with age. It is this lack of knowledge that leads to the present state of uncertain and largely ineffective interventions for hair growth. No-one is entirely sure as to where the root of the problem lies, or where the most effective points of intervention might be. A great deal of exploration takes place, but success is all too much a matter of luck rather than design. With that in mind, the research materials here bridge a number of approaches to regeneration that are broadly used in the field: cell therapies, exosome therapies as a way of mimicking the effects of a cell therapy that primarily acts via cell signaling, and identification of specific signaling molecules that can change native cell behavior.

Hair growth depends on the health of dermal papillae (DP) cells, which regulate the hair follicle growth cycle. Current treatments for hair loss can be costly and ineffective, ranging from invasive surgery to chemical treatments that don't produce the desired result. Recent hair loss research indicates that hair follicles don't disappear where balding occurs, they just shrink. If DP cells could be replenished at those sites, the thinking goes, then the follicles might recover.

Researchers cultured DP cells both alone (2D) and in a 3D spheroid environment. A spheroid is a three-dimensional cellular structure that effectively recreates a cell's natural microenvironment. In a mouse model of hair regeneration, the team looked at how quickly hair regrew on mice treated with 2D cultured DP cells, 3D spheroid-cultured DP cells in a keratin scaffolding, and the commercial hair loss treatment Minoxidil. In a 20-day trial, mice treated with the 3D DP cells had regained 90% of hair coverage at 15 days.

"The 3D cells in a keratin scaffold performed best, as the spheroid mimics the hair microenvironment and the keratin scaffold acts as an anchor to keep them at the site where they are needed. But we were also interested in how DP cells regulate the follicle growth process, so we looked at the exosomes, specifically, exosomal miRNAs from that microenvironment." Exosomes are tiny sacs secreted by cells that play an important role in cell to cell communication. Those sacs contain miRNAs, small molecules that regulate gene expression. The team measured miRNAs in exosomes derived from both 3D and 2D DP cells. In the 3D DP cell-derived exosomes, they pinpointed miR-218-5p, a miRNA that enhances the molecular pathway responsible for promoting hair follicle growth. They found that increasing miR-218-5p promoted hair follicle growth, while inhibiting it caused the follicles to lose function.


A Type of Phosphorylated Tau in Blood Samples Indicates Amyloid-β Aggregation Prior to Symptoms

Presently available methods of determining whether or not amyloid-β aggregates exist in the brain are expensive and invasive. Amyloid-β forms solid deposits in and around cells in the brain for decades prior to the first obvious signs of neurodegeneration, and people with raised levels of these protein aggregates are more likely to progress to dementia. Early, accurate, low-cost measurements of amyloid-β prior to symptoms could lead to the identification of lifestyle choices that minimize risk, as well as to the development of preventative therapies. Absent assays that can achieve this goal, there is little pressure to develop such treatments, however. Thus it is always good news to see progress towards cost-effective ways to measure amyloid-β burden.

Alzheimer's disease begins with a silent phase lasting two decades or more during which amyloid plaques slowly collect in the brain without causing obvious cognitive problems. For decades, researchers have been searching for an easy and affordable way to identify people in the so-called preclinical stage so that, once effective drugs are available, they could be treated and, ideally, never develop symptoms at all. Positron emission tomography (PET) brain scans can identify people with amyloid plaques, but they are too time-consuming and expensive to be widely used for screening or diagnosis.

Researchers previously had discovered that people with amyloid plaques tend to have certain forms of tau in the cerebrospinal fluid that surrounds their brains and spinal cords. Sampling the cerebrospinal fluid requires a spinal tap, which some participants are reluctant to undergo, but proteins in the cerebrospinal fluid can spill over into the blood, which is easier to obtain. If these specific forms of tau could be found in a person's blood, they reasoned, that might be an indication that the person has the consequences of amyloid plaques in his or her brain.

Researchers analyzed blood samples and brain scans from 34 people participating in Alzheimer's research studies. Nineteen of the participants had no amyloid in their brains, five had amyloid but no cognitive symptoms, and 10 had amyloid and cognitive symptoms. The researchers used mass spectrometry to identify and measure the different forms of tau in the blood samples. They found that levels of a form of tau known as phosphorylated tau 217 correlated with the presence of amyloid plaques in the brain. People with amyloid in their brains had two to three times more of the protein in their blood than people without amyloid. These high levels were evident even in people with no signs of cognitive decline.

To verify their findings, the researchers repeated the analysis in a separate group of 92 people: 42 with no amyloid, 20 with amyloid but no cognitive symptoms, and 30 with amyloid and symptoms. In this analysis, levels of phosphorylated tau 217 in the blood correlated with the presence of amyloid in the brain with more than 90% accuracy. When the researchers looked only at people with no cognitive symptoms, blood levels of phosphorylated tau 217 distinguished those in the early, asymptomatic stage of Alzheimer's disease from healthy people with 86% accuracy.


How Calorie Restriction Improves Intestinal Stem Cell Function

The practice of calorie restriction, eating up to 40% fewer calories while still maintaining an optimal intake of micronutrients, is well demonstrated to slow aging and extend healthy life span in near all species and lineages tested to date. It produces sweeping effects on the operation of metabolism - near everything changes, which has made it something of a challenge to identify the principal points of action. Nonetheless, more efficient operation of the cellular housekeeping mechanisms of autophagy is the most plausible mechanism to account for the majority of the benefits. That calorie restriction fails to extend life when autophagy is disabled is the most telling evidence.

The open access paper that I'll point out today is illustrative of a great many similar lines of work, in which researchers dig deeper into one narrow aspect of calorie restriction and its benefits. Here, the focus is on the function of stem cells supporting intestinal tissue. The lining of the intestine, the intestinal barrier, is important in aging. Its decline in effectiveness allows unwanted microbes and compounds to enter tissue and the bloodstream, where they contribute to rising levels of chronic inflammation.

This decline is in part similar to that of tissues throughout the body, caused by a loss of stem cell function. Every tissue is supported by stem cell and progenitor cell populations that provide a steady flow of new somatic cells to make up losses and repair damage. Stem cell activity falls off with age, due to a mix of damage to these cells and reactions to a changing signaling environment. As the supply of new somatic cells declines, so too does tissue function. The process is slowed by calorie restriction, as appears to be the case for all other processes of aging assessed in the context of calorie restriction. Researchers here ask why exactly that is the case for intestinal stem cells, supporting a cell population known to have a high rate of replacement.

Calorie Restriction Increases the Number of Competing Stem Cells and Decreases Mutation Retention in the Intestine

Aging and age-related pathologies such as cancer are the consequence of deleterious changes in cells and tissues over time, including the progressive accumulation of DNA mutations. Calorie restriction (CR) can prevent many age-related changes, resulting in extended lifespan and reduced age-related pathologies. Several intracellular mechanisms through which CR can reduce the accumulation of mutations have been identified, including attenuating oxidative stress and enhancing DNA repair. In addition to these intracellular mechanisms, mechanisms that act at the tissue level may be at play. For example, in Drosophila, CR enhances intestinal cellular fitness through outcompetition of less fit cells, thereby preventing age-related decline of intestinal integrity. Whether related mechanisms upon CR in mammals exist that act at a tissue level is currently unknown.

The mammalian intestinal wall is a single layer of epithelial cells curved into so-called crypt-villus units. As a protective barrier against the external environment, this epithelial sheet is constantly exposed to potentially DNA-damaging substances. However, most mutated cells are naturally lost due to the highly dynamic self-renewing nature of the epithelium. Lgr5+ stem cells at the bottom of crypts are long-lived and can thus accumulate mutations. However, these Lgr5+ stem cells compete for niche occupancy, resulting in continuous replacement and loss of neighboring stem cells, which is often referred to as stem cell competition. As a result, most stem cells, including those carrying mutations, will be lost while the progeny of one stem cell ultimately replaces all other stem cells in the crypt. Therefore, mutations will only be retained in the intestine if they are acquired by stem cells that win the stem cell competition.

We and others have recently shown that the chance that a stem cell can outcompete its neighbors can be manipulated by lowering the number of stem cells through pharmacologically inhibiting WNT protein gradients. Mutated stem cells can more rapidly spread within crypts when there are less competing stem cells. Interestingly, CR has been shown to increase the number of stem cells in intestinal crypts. Here we find that CR leads to increased numbers of functional Lgr5+ stem cells that compete for niche occupancy, resulting in slower but stronger stem cell competition. Consequently, stem cells carrying mutations encounter more wild-type competitors, thus increasing the chance that they get displaced from the niche to get lost over time. Thus, our data show that CR not only affects the acquisition of mutations but also leads to lower retention of mutations in the intestine.

Long-Lived Trees are Not Immortal

Trees can adopt a range of strategies not available to animals in order to live for very long periods of time, but they are not immune to mechanisms of aging. That said, those mechanisms are only broadly similar to the biochemistry of aging in animals. It isn't clear that there is anything useful to learn from long-lived plants insofar as human medicine is concerned. Nonetheless, it is an interesting area of study.

The oldest trees on Earth have stood for nearly five millennia, and researchers have long wondered to what extent these ancient organisms undergo senescence, physically deteriorating as they age. A recent paper studying ginkgoes, one of the world's longest-lived trees, even found that they may be able to "escape senescence at the whole-plant level," raising questions about the apparent lack of aging in centuries-old trees. However, researchers argues that although signs of senescence in long-lived trees may be almost imperceptible to people, this does not mean that they're immortal.

"When we try to study these organisms, we're really astonished that they live so long. But this doesn't mean that they're immortal. They live so long because they have many mechanisms to reduce a lot of the wear and tear of aging. They have limits. There are physical and mechanical constraints that limit their ability to live indefinitely." However, due to the difficulty of conducting research on trees with such long lifespans, little is known about what the process of senescence looks like. Simply finding enough millennial trees to study can be challenging. "When a species of tree can live for five millennia, it's very difficult to find even two trees that are between two and five millennia." For these long-lived trees, dying of senescence is a possibility, but the probability of dying from other causes is significantly higher.

Trees have a variety of ways to reduce their chances of death from aging alone, from compartmentalizing risk in complex branch structures to "building life on death" by growing new shoots from trunks composed of 90% nonliving biomass. But researchers maintain that even though long-lived trees can survive for millennia through these methods, the stress associated with aging, although little, will ultimately prevent immortality.


Influenza Vaccine Use Correlates with Lower Risk of Alzheimer's Disease

Researchers here note a correlation between receiving influenza vaccination, even once, and the later risk of Alzheimer's disease. This is interesting in the context of the present debate over the mechanisms of Alzheimer's, particularly regarding whether or not persistent viral infection is an important driver of the condition. Inflammation and immune system dysfunction are also clearly important in the progression of neurodegenerative conditions. How exactly influenza vaccines might influence this complex decline is an open question. One might hypothesize that this is mediated by something other than biology - that people more likely to take care of their overall health, and thus have a lesser degree of chronic inflammation and lesser incidence of Alzheimer's disease, are also more likely to make use of influenza vaccines.

People who received at least one flu vaccination were 17% less likely to get Alzheimer's disease over the course of a lifetime, according to new research. "Because there are no treatments for Alzheimer's disease, it is crucial that we find ways to prevent it and delay its onset. About 5.8 million people in the United States have this disease, so even a small reduction in risk can make a dramatic difference. We began our study by looking for ways we could reduce this risk."

"Our role was to sort through enormous amounts of de-identified patient data in the Cerner Health Facts database to see whether there are drugs that could be repurposed to reduce the risk of Alzheimer's disease. Once we identified the flu vaccine as a candidate, we used machine learning to analyze more than 310,000 health records to study the relationship between flu vaccination and Alzheimer's disease."

The research team also found that more frequent flu vaccination and receiving vaccination at younger ages were associated with even greater decreases in risk. "One of our theories of how the flu vaccine may work is that some of the proteins in the flu virus may train the body's immune response to better protect against Alzheimer's disease. Providing people with a flu vaccine may be a safe way to introduce those proteins that could help prepare the body to fight off the disease. Additional studies in large clinical trials are needed to explore whether the flu shot could serve as a valid public health strategy in the fight against this disease."