FGF21 and Muscle Function

Fibroblast growth factor 21, FGF21, is one of many proteins to emerge as a target for further research during the past few decades of investigation into the biochemistry of calorie restriction. The practice of calorie restriction, reducing calorie intake by up to 40% while maintaining optimal micronutrient levels in the diet, has been found to reliably slow aging and extend life span in most of the species and lineages tested to date. The effect size is much larger in short-lived species than in long-lived species such as our own, unfortunately, and this is generally true of all interventions that upregulate beneficial stress responses. Calorie restriction spurs greater activity in cellular housekeeping processes such as autophagy, and otherwise makes cells more efficient and resilient. The outcome is a slowing of near all measures of aging.

Because calorie restriction produces sweeping changes in the operation of metabolism, it has been a slow and expensive process to determine the important controlling mechanisms, genes, and proteins. That process still continues today, but more of a focus is placed on well-known areas of study, those discovered some years ago. FGF21 and surrounding biochemistry is one such area - and a complicated area it is too. FGF21 levels increase with age, but also with calorie restriction, which clearly slows aging. Effects and processes relating to FGF21 seem different in obese individuals versus those of normal weight, and different again in aging.

So far it seems a bit of a mess, which probably means that any sort of therapy resulting from this research will have to be narrowly targeted to specific situations and specific tissues. An example of work that might be heading in that direction, eventually, is the role of FGF21 in muscle, as outlined in the open access paper noted below. FGF21 appears to control the reduction in muscle mass following inactivity and starvation, but is also involved in the beneficial cellular housekeeping process of mitophagy, necessary for effective muscle maintenance and function. So even here there are multiple processes to consider, and which appear to stand somewhat in opposition to one another.

Fibroblast growth factor 21 controls mitophagy and muscle mass

Exercise, nutritional changes, organelle dysfunction, and stress induce the systemic release of muscle-derived factors: cytokines (myokines) and metabolites (myometabolites) that exert autocrine, paracrine, or endocrine effects. Indeed, exercise preserves and ameliorates mitochondrial function and muscle metabolism, thereby affecting the release of myokines and metabolites, which might systemically counteract organ deterioration. In contrast, dysfunctional muscles can influence disease progression in other tissues.

The fibroblast growth factor 21 (FGF21) is a secreting myokine that can also be released in the bloodstream by other organs such as liver, heart, white adipose tissue (WAT), and brown adipose tissue (BAT). It is a starvation-like hormone with several metabolic functions aimed at overcoming nutrient deprivation by providing tissues with fuel. In skeletal muscle, FGF21 expression, in healthy conditions, is almost undetectable, and therefore, the circulating FGF21 is predominantly produced and released by the liver. In contrast, muscle-dependent systemic release of FGF21 increases with starvation, endoplasmic reticulum stress, mitochondrial dysfunction, obesity, mitochondrial myopathies, and aging. Moreover, FGF21 is a stress-induced myokine that has been proposed as a specific serum biomarker of muscle-specific mitochondrial disorders.

We and others recently demonstrated that in a muscle-specific OPA1 knockout animal model, characterized by mitochondrial dysfunction and by extensive muscle loss, the contribution of skeletal muscle to circulating FGF21 was predominant. In this model, FGF21 secreted from muscles mediates an integrated stress response that caused several systemic cell non-autonomous effects such as inflammation, metabolic alterations, and precocious senescence. Importantly, FGF21 deletion in OPA1 knockout muscles improved almost all systemic effects, while there was only a partial sparing of muscle mass. Injecting mice daily with exogenous FGF19, a closely related endocrine FGF member produced in the gut, increased skeletal muscle mass and strength. Remarkably, the skeletal muscle hypertrophy effects were not elicited by administrating FGF21. Thus, whether FGF21 is beneficial or detrimental for human health is still not clear, in part because the contribution of autocrine/paracrine-derived FGF21 signalling to muscle homeostasis has not been investigated yet.

In this study, muscle-specific FGF21 knockout mice were generated to investigate the consequences of FGF21 deletion concerning skeletal muscle mass and force. To identify the mechanisms underlying FGF21-dependent adaptations in skeletal muscle during starvation, the study was performed on muscles collected from both fed and fasted adult mice. In vivo overexpression of FGF21 was performed in skeletal muscle to assess whether FGF21 is sufficient per se to induce muscle atrophy.

We show that FGF21 does not contribute to muscle homeostasis in basal conditions in terms of fibre type distribution, fibre size, and muscle force. In contrast, FGF21 is required for fasting-induced muscle atrophy and weakness. The mass of isolated muscles from control-fasted mice was reduced by 15-25% compared with fed control mice. FGF21-null muscles, however, were significantly protected from muscle loss and weakness during fasting. Such important protection is due to the maintenance of protein synthesis rate in knockout muscles during fasting compared with a 70% reduction in control-fasted muscles, together with a significant reduction of the mitophagy flux via the regulation of the mitochondrial protein Bnip3. The contribution of FGF21 to the atrophy programme was supported by in vivo FGF21 overexpression in muscles, which was sufficient to induce autophagy and muscle loss by 15%. Bnip3 inhibition protected against FGF21-dependent muscle wasting in adult animals.

In summary, the current study elucidates by using gain and loss of function approaches, a novel role for FGF21 in the control of skeletal muscle mass through the regulation of the anabolic/catabolic balance. These findings are important for the understanding of the molecular pathways that control muscle mass. Moreover, this study also open several new avenues for future investigation to define the mechanisms mediated by FGF21 in the interplay between muscle and other tissues such as bones, heart, and WAT in whole body homeostasis.

Calorie Restriction Acts via p38 to Reduce Inflammation due to Innate Immune Activity

The practice of calorie restriction, reducing calorie intake by up to 40% while still obtaining optimal micronutrient intake, slows aging in most species tested to date. The effect on life span is much larger in short-lived species than in long-lived species, but the short-term health benefits are similar in mice and humans, even though mice live up to 40% longer when calorie restricted, and humans clearly do not. One component of the beneficial response to calorie restriction is a reduction in inflammation, particularly important given the prominent role that chronic inflammation plays in the aging process. In later life the immune system falls into an inflammatory, overly active, but ineffective state, a combination of the states known as inflammaging and immunosenescence. This disrupts tissue maintenance and accelerates the progression of all of the most common age-related diseases. Control over inflammation is a very desirable goal for older individuals.

Researchers have found that caloric restriction reduces levels of innate immunity by decreasing the activity of a regulatory protein called p38, triggering a chain reaction effect ending in a reduced immune response. Innate immunity is like the security guard of the body, keeping an eye out for any unwelcome bacteria or viruses. If the innate immune system spots something, it activates an acute immune response. We need some degree of both kinds of immunity to stay healthy, but an overactive innate immune system - which occurs more often as we age - means constant low-grade inflammation, which can lead to myriad health issues.

The research was conducted in the microscopic nematode worm C. elegans. The most fundamental genes and regulatory mechanisms found in these worms are typically simpler versions of those present in humans, making them a good model for studying human aging, genetics, and disease. Researchers analyzed the levels of proteins and actions of genetic pathways during periods of caloric restriction. They were able to zero in on a particular genetic pathway that was regulated by the p38 protein. They saw that when p38 was totally inactive, caloric restriction failed and had no impact on innate immunity. When it was active, but at lower levels than normal, it triggered the genetic pathways that turned down the innate immune response to an optimal level.

After making this discovery, the researchers were curious to know if the well-known longevity mechanism of reduced IGF1 signaling also acted on the immune system. For over 20 years, study after study in many different organisms have confirmed that lower levels of IGF1 signaling contributes to a longer lifespan. This is thought to be due to the activation of protective factors by a protein called FOXO (called DAF-16 in C. elegans). A reduction in the activity of the FOXO-like gene seems to tell the worms that they are in a fasting-like state, and that nutrients may be scarce. This directs the worms to conserve energy, leading to a reduction in food intake. This self-imposed caloric restriction then leads to the lowering of the innate immune response.

Link: https://www.joslin.org/news/lifespan-extension-linked-to-metabolic-regulation-of-immune-system.html

Comparing the Mitochondria of Mice and Long-Lived Bats

Like naked mole-rats, bats are outliers among mammals when it comes to metabolism and longevity. They live much longer than similarly-sized mammals. We can hypothesize that the demands of living in oxygen-poor underground environments, in the case of naked mole-rats, and the demands of flight, in the case of bats, leads to a more resilient cellular biochemistry. That in turn has the side-effect of greater longevity. Much of the investigation of this hypothesis is focused on mitochondria, the power plants of the cell, and their differing composition between species. The membrane pacemaker view of aging suggests that species differences in life span among mammals arise in large part due to the degree of resistance to oxidation of cell membranes, particularly those of mitochondria. Mitochondrial function is critical to tissue function, and aging is associated with a growing malaise in mitochondria: poor quality control, rising levels of damage and dysfunction.

Some common observations have been used to generate theories of ageing. The rate of living theory of ageing proposes to explain the variation in mammalian lifespans, it states that lifespan and metabolic rate are inversely correlated. Another theory is the mitochondrial free radical theory of ageing, this states that animals with high basal metabolic rates will generate greater levels of reactive oxygen species (ROS) and due to their detrimental effect, have shorter lifespans. Observed mammalian biology mostly aligns with these theories however there are a few notable exceptions, including the naked mole rat and microbats, that live much longer than their small body size and high metabolic rates would predict.

Microbats are exceptionally long-lived considering their small body size and high metabolic rates. For instance, the maximum lifespan for the bat; Myotis lucifugus (weight ~8g) is 34 years. In comparison the maximum lifespan of a mouse (Mus musculus) (weight ~30g) is 4 years. Bats have been shown to expend double the amount of energy in comparison to non-flying eutherian mammals and yet they live on average three times longer than non-flying eutherian mammals. This raises the question; how do bats maintain such high metabolic rates without succumbing to accumulating damage over their lifespan?

Oxidative stress has been a key focus for the majority of studies investigating longevity in bats. Mitochondrial dysfunction is evident in ageing and age-related diseases. Mitochondrial DNA (mtDNA) is considered to be more susceptible to mutagenesis due to the close proximity of mtDNA to ROS and also the high number of direct repeat regions prone to deletions. Bat mtDNA was found to have a lower number of repeat regions compared with other mammals. Bats were found to produce half to one third of the amount of hydrogen peroxide per oxygen molecular consumed compared to both shrews and mice. Research thus far indicates that bats produce less ROS and may also be more resistant to oxidative stress.

In this study we compared the mitochondrial lipidome and proteome of whole brain and skeletal tissues from adult Pipistrelle bats (maximal lifespan 12 years) with parallel sample types prepared from young and middle-aged Mus musculus. We used proteomics and ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry lipidomics, to interrogate mitochondrial fractions prepared from tissues. Fatty acid binding protein 3 (FABP3) was found at different levels in mouse and bat muscle mitochondria and its orthologues were investigated in Caenorhabditis elegans knock-downs for LBP 4, 5, and 6. In the bat, high levels of free fatty acids and N-acylethanolamine lipid species together with a significantly greater abundance of FABP3 in muscle were found. We show that decreased quantities of FABP3 orthologues are detrimental to mitochondrial health. The literature supports this as a mechanism associated with mitochondrial dysfunction across many tissues. Mechanisms to increase levels of FABP3 or fatty acids in the mitochondrial compartment may be of interest in supporting mitochondrial health through the lifespan.

Link: https://doi.org/10.18632/aging.101861

Why Does the Aging Metabolism Bias Towards Fat Accumulation and Lipid Deposition?

Irina Conboy's pithy description of what aging does to the operation of metabolism runs much as follows: "stem cells are sleeping, so damage is not regenerated. Instead you now make fibrous tissue, and deposit fat tissue to replace the damage. Then gradually over time, you just turn into this big scar and big fat blob." It is certainly the case that the older body seems to tend to hold on to lipids, create fat tissue, and put fats and other lipids into cells where they are usually not found in large amounts in youth. We might well ask why this happens. Is it the result of damage, some form of dysregulation of normal metabolism that is entirely harmful, or is it at least in part an evolved compensation that helps to attenuate some of the consequences of the underlying molecular damage that causes aging?

The authors of today's open access paper argue that both adaptive and maladaptive processes are in play. Nothing in biology is simple, and the observed redistribution of fat and changes in metabolism may be both harmful and protective when considered in various contexts, or when pieces of the whole are examined in isolation. That in later years it becomes challenging to maintain a good body weight, as the amount of work required to attain that goal ever increases, is no excuse for letting things slide, of course. While it may well be the case that some aspects of excess fat tissue are protective, the epidemiological evidence overwhelmingly demonstrates that, when taken as a whole, being even modestly overweight raises the risk of age-related disease, increases lifetime medical cost, increases mortality, and reduces life expectancy. Those negative effects scale up as the weight and excess fat tissue increase.

The Dual Role of the Pervasive "Fattish" Tissue Remodeling With Age

With advancing age, lean mass and bone mineral density decrease, while total fat mass increases and changes its distribution, particularly in the abdominal region, often without concomitant changes in body mass index (BMI). In mammals, fat mass accumulates as adipose tissue or ectopic lipid deposition. Adipose tissue is a dynamic organ involved in the regulation of energy homeostasis, mainly divided in three types, brown (BAT), white (WAT), and BEIGE which differ in embryogenesis, anatomy, and function. While BAT possesses high levels of mitochondria and is specialized in fat burning to generate heat, WAT is characterized by a low density of mitochondria and it is generally involved in lipid storage in two biological distinct compartments: subcutaneous (SAT) and visceral (VAT) adipose tissue. WAT is not only involved in the storage of lipids, but also plays an important role as immuno-endocrine organ.

With advancing age, BAT mass declines, while WAT increases reaching the maximum peak by early old age and changing its distribution toward a higher proportion of VAT. WAT redistribution is also accompanied by an accumulation of fat mass in non-adipose tissues and organs, such as muscle, liver, heart, pancreas and others, that normally contain only small amounts of fat, stored within lipid droplets (LDs). Adipose tissue shows also an extraordinary plasticity, in fact it can differentiate into another type of adipose tissue, such as BEIGE or replace the parenchyma of organs that undergo involution with age, such as the thymus.

The maintenance of a balanced amount of fat mass is crucial for health and survival. According to the "thrifty phenotype" theory, humans were selected to accumulate fat depots to face periods of food shortage. However, while a critical lower threshold of fat content exists, an upper threshold is apparently missing, and adipose tissue can accumulate in great amounts. The absence of an upper threshold for fat accumulation is probably due to the fact that this phenomenon did not occur in the wild frequently enough to undergo selection, or, alternatively, resulted neutral for the fitness of individuals.

With aging, the "thrifty phenotype" seems to emerge more dramatically, and the balance is tilted toward an increase of fat mass, at the level of VAT and SAT as well as in ectopic sites (liver, muscles, etc.). This increase in fat deposition at the level of SAT and VAT can be considered an adaptive response to modified health conditions interacting with contingent environmental conditions, leading eventually to decreased energy expenditure. However, in some cases the storage of surplus energy can not be claimed as the reason for fat accumulation, especially when this occurs ectopically at the expenses of other tissue types with important vital functions, as in the case of thymic involution or skeletal muscle infiltration.

In this case, it seems that fat deposition in the form of WAT is a sort of physiological program (genetically determined?) for organs and tissues undergoing age-related atrophy or involution. Different stem cell subpopulations such as muscle fibro-adipogenic progenitors and bone marrow mesenchymal stem cells preferentially differentiate to adipocyte with age, therefore, we are tempted to speculate that the pathway leading to this cell type is a sort of a default choice in involution processes. Should this speculation be verified, the reasons for this choice remain elusive.

The accumulation of WAT has been for long time viewed as detrimental, being the source of pro-inflammatory mediators and other important endocrine modulators and strongly associated with metabolic diseases such as insulin resistance and type II diabetes, cardiovascular diseases, and cancer. However, it is not totally clear whether this negative role is present also in extreme old age. Actually, data on body composition in nonagenarians and centenarians are largely missing, even though the BMI of these people is usually lower than that of younger (70-80 years-old) persons. It is possible that, as for other risk factors like lipid serum profile and inflammatory parameters, also the presence of a consistent amount of WAT can be important for survival at very advanced age. Further studies are needed to verify this hypothesis.

Does Klotho Act on Cognitive Function via FGF23?

Klotho is a longevity gene in that more of the protein it codes for acts to modestly extend life in mice. Levels of klotho protein decline with age, and increased amounts appear to produce beneficial outcomes in health and longevity in part via stem cell function. Klotho also influences cognition, and a number of research groups are working on approaches, such as gene therapies to upregulate klotho expression, or delivery of recombinant protein fragments of the full klotho molecule, that might at some point result in ways to enhance cognitive function in humans, old and young alike.

Klotho is known to be closely related to FGF23, and research into this relationship has uncovered roles for klotho throughout the body, in many organs. This popular science article focuses on the brain however, covering research results suggesting that the influence of klotho on cognitive function might be quite circuitous and indirect, involving other organs in the body. This isn't an unreasonable suggestion - it is certainly the case in other, better known systems of regulation.

The longevity gene klotho keeps memory keen, but how? New research raises the possibility that it might influence cognition through its signaling partners FGF23 and the fibroblast growth factor (FGF) receptor. Researchers recently reported that mice lacking FGF23 have memory problems similar to those seen in klotho knockouts. Meanwhile, another group reported that older people with high levels of FGF23 in their blood are at elevated risk of developing dementia. However, changes in circulating FGF23 levels are also known to impair kidney function. Kidney disease by itself can harm cognition, leaving it unclear if FGF23 acts directly in the brain or indirectly in the periphery.

Klotho levels dwindle with age, and drop off steeply with disease progression in mouse models of amyloidosis. Conversely, high levels of klotho boost cognitive performance in people, and memory in mice. Another recent study adds genetic evidence for klotho's protective effect in the brain. Researchers found that the klotho variant associated with high expression and longevity seemed to negate some effects of the ApoE4 allele. Among 82 people with this protective klotho variant, ApoE4 carriers accumulated no more brain amyloid than noncarriers. The mechanism is unclear.

Researchers have elucidated at least one signaling pathway through which klotho acts. Klotho spans the cell membrane, where it binds FGF receptors to form a pocket that captures extracellular FGF, triggering intracellular signaling. It is unknown what effect this has on the brain. In the kidney, the binding of klotho and FGF23 stimulates excretion of phosphate and vitamin D, hence functions in their homeostasis. FGF23 levels appear to be tightly regulated. Mice with too much of it develop the vitamin-D-deficient bone disease rickets. Those with too little accumulate mineral deposits throughout their bodies and age faster, as do klotho knockouts.

Were the learning defects of the FGF23 knockout mice due to FGF23 in the brain? Probably not. The authors searched intensively for FGF23 mRNA or protein in wild-type mouse brain, but were unable to find significant expression. Because of this, they believe that brain klotho acts via other mechanisms, independent of FGF23. The FGF23 knockouts develop kidney disease, grow slowly, and die by 9 weeks of age. Kidney problems are linked to cognitive deficits. In particular, high FGF23 levels predict progression of kidney disease and worse cognition. Researchers believe the take-home message from these studies is the importance of kidney function for cognition.

Link: https://www.alzforum.org/news/research-news/klothos-partner-fgf23-cognition-protein

Hijacking the Proteasome to Dispose of Unwanted Molecules in Age-Related Disease

Cells are equipped with a protein disposal system in the form of the proteasome. Damaged or excess proteins are tagged with ubiquitin, and shuttled to the proteasome where they are dismantled into component parts that can be reused to build new proteins. The popular science article noted here discusses an approach to interfacing with this cellular maintenance system that is presently under developement, delivering carefully designed molecules that ensure a specific protein is tagged with ubiquitin, thus persuading the cell to destroy it. Over the course of aging, cells become exposed to any number of unwanted forms of molecular waste, many of which are proteins of one sort or another, and it is possible that finding ways to deliver those molecules to the proteasome could prove to be an effective therapy.

The drug strategy, called targeted protein degradation, capitalizes on the cell's natural system for clearing unwanted or damaged proteins. These protein degraders take many forms, but the type that is heading for clinical trials this year is one that researchers have spent more than 20 years developing: proteolysis-targeting chimaeras, or PROTACs. Because they destroy rather than inhibit proteins, and can bind to them where other drugs can't, protein degraders could conceivably be used to go after targets that drug developers have long considered 'undruggable': cancer-fuelling villains such as the protein MYC, or the tau protein that tangles up in Alzheimer's disease.

In diagrams, PROTACs often look like dumb-bells. They are molecules made up of two binding ends connected by a thin tether. The action happens on the ends. One grabs on to the target protein, while the other latches on to a ubiquitin ligase - part of the cell's natural rubbish-disposal system that labels defective or damaged proteins by slapping a small protein called ubiquitin onto them. Ubiquitin tags act as sort of 'Please collect' stickers that instruct the cell's protein shredder, called the proteasome, to do its thing.

Proximity accounts for a lot in biology, so by simply bringing together the ligase and the target protein, a PROTAC ensures that the target will get marked for destruction. Ligases are efficient and ubiquitin, as the name suggests, is plentiful, so a single PROTAC should be able to perform its catch-and-release function repeatedly throughout the cell, suggesting that only a small amount of such a drug is needed for potent activity.

Link: https://www.nature.com/articles/d41586-019-00879-3

Phase II Clinical Trial Results for the Eidos Therapeutics Approach to Transthyretin Amyloidosis

The protein transthyretin can misfold and form solid deposits of amyloid. This occurs to an increasing degree with age, and it is becoming clear that transthyretin amyloid contributes meaningfully to a range of age-related conditions, and is not only a problem in the small minority of individuals who rise to the level of being diagnosed with transthyretin amyloidosis. Many of those have a mutation in the transthyretin gene that predisposes them to the formation of amyloid, but again, the accumulation of this amyloid is one of the contributing causes of aging and age-related disease for all of us: osteoarthritis, heart failure, spinal stenosis, and more. Thus we should all be quite interested in progress towards the development of therapies.

Eidos Therapeutics is working on a fairly traditional approach to the treatment of transthyretin amyloidosis, a small molecule drug AG10 that must be taken continuously, and that alters the behavior of transthyretin to prevent the formation of amyloid. The company recently raised a sizable amount of funding to support their later stage clinical trials. This was accomplished prior to the publication of phase 2 trial results, but at a point in time at which the company had enough data for the principals to feel quite confident in progressing to much larger phase 3 trials. The paper I'll point out here outlines the results of the phase 2 trial, in which both people with age-related and genetic transthyretin amyloidosis were given AG10. It appears to improve short-term measures of the condition, though it remains to be seen as to whether this approach can actually reverse existing amyloid deposition to any degree, or the consequent pathology.

When it comes to the role of transthyretin in aging, I'm much more in favor of approaches that remove transthyretin amyloid, such as the catalytic antibodies under development at Covalent Biosciences, rather than approaches such as that pioneered by Eidos Therapeutics, in which only the progression of the condition is slowed or stopped. Reversal of the damage via a form of repair is a treatment that can be applied every so often, perhaps once every few years at most, rather than having to be continuously applied. Furthermore it can be applied at any stage of the condition to improve matters for the patient, and can be applied repeated for greater effect. A way of halting the creation of new transthyretin amyloid is only marginally helpful for someone who is greatly impacted by large amounts of the stuff clogging up his or her cardiovascular system.

Transthyretin Stabilization by AG10 in Symptomatic Transthyretin Amyloid Cardiomyopathy

This study represents the first clinical experience with AG10 in the target patient population of transthyretin amyloidosis cardiomyopathy (ATTR-CM). Administration of AG10 was well tolerated and was not associated with safety signals of potential clinical concern. In the present study AG10 treatment increased serum TTR levels from baseline and brought those levels to within the normal range in all subjects, both mutant and wild-type. This included subjects whose baseline levels were markedly below the normal range. The 28-day treatment duration of the present study limits any assessment of clinical benefit.

The serum level of transthyretin, long recognized both as a sensitive index of overall nutritional status and as an acute phase reactant, is becoming more widely appreciated as an independent predictor of survival in ATTR-CM. In one recent study of patients with wild-type ATTR-CM, regression analysis suggested that a 1 mg/dL decrement in serum transthyretin level is associated with a 7-11% decrement in survival.

Patients with an established diagnosis of ATTR-CM and NYHA Class II-III symptoms aged 18-90 years were eligible for the study. Subjects were randomized in a 1:1:1 ratio to AG10, 400mg or 800mg, or matching placebo, administered twice daily. The primary objective of the study was to evaluate the safety and tolerability of AG10 compared to placebo. Secondary endpoints included pharmacokinetics (AG10 plasma concentrations), change from baseline in serum transthyretin concentration, and two distinct ex vivo measures of transthyretin stabilization. The study enrolled 49 subjects, of which 14 (29%) had known mutant ATTR-CM. Subjects ranged in age from 60-86 years, with a mean of 74.1 years, and 92% were male. All subjects had symptomatic, chronic heart failure due to ATTR-CM with NYHA Class II or III symptoms. Importantly, on average subjects had relatively low transthyretin at baseline.

AG10 plasma concentrations were determined at peak following the initial dose, and at peak and trough on Days 14 and 28 of the study. Subjects in the placebo group experienced a mean reduction of 7±15% in serum transthyretin concentration by Day 28 relative to baseline. Conversely, subjects administered either 400mg or 800mg AG10 bid showed a dose-dependent, mean increase in circulating transthyretin of 36±21% and 50±38%, respectively. There was a greater treatment effect observed in AG10-treated subjects with mutant ATTR-CM (67±42%) as compared to subjects with wild-type ATTR-CM (33±20%). This might be explained in part by the lower serum transthyretin levels in mutant ATTR-CM subjects measured at baseline.

Long-Term Aerobic Exercise Slows Age-Related Decline in Vascular Function

The study here measures vascular function in athletic and sedentary older individuals, finding that, as one might expect, long-term exercise produces a slower pace of decline in the ability of blood vessels to respond to circumstances by relaxing or contracting as needed. The molecular damage of aging impairs this function, and blood vessels stiffen, leading to rising blood pressure. Aerobic exercise slows the pace of many of the aspects of aging, this one included, though it doesn't appear to extend overall life span in mouse studies. Rather the period of life spent healthy is extended. Whether or not this holds up in humans is an interesting question; epidemiological studies show correlations between regular exercise and something like five years of additional life expectancy. People are not mice, and these two approaches to scientific discovery can't really be directly compared to one another, unfortunately.

Impaired vascular function as a result of aging occurs due to the coalition of environment, oxidative stress, and inflammation. These factors result in reduced nitric oxide (NO) bioavailability, causing a failure of the vasculature to dilate in response to increases in shear stress during hyperaemia. Furthermore, vascular structure is also compromised with age as wall stiffness increases, reducing flexibility. Therefore, vascular dysfunction promotes cardiovascular disease (CVD) risk and contributes both to a reduction in health span and overall life expectancy. Given this premise there is an increasingly important but unmet need for interventions which aim to reduce inflammation and oxidative stress, while developing an environment conducive to vascular function.

Modifiable lifestyle factors, such as increased physical activity (PA) and/or exercise have been advocated to reduce vascular impairment and restore NO dependent vasodilatation, even in apparently healthy older cohorts. Multiple lines of evidence, including both human and pre-clinical models demonstrate that those individuals who are regularly active enjoy superior vascular function, with lower levels of systemic inflammation and oxidative stress. Vascular function, or specifically endothelial function, is commonly assessed non-invasively using the flow mediated dilation (FMD) technique. As cardiovascular events can be independently predicted by endothelial compliance, FMD has emerged as a conventional method to determine vascular function.

We conducted a systematic review and meta-analysis of controlled studies examining flow mediated dilatation (FMD) of athletic older persons and otherwise healthy sedentary counterparts to (i) compare FMD as a determinant of endothelial function between athletes and sedentary individuals and, (ii) summarize the effect of exercise training on FMD in studies of sedentary aging persons. Studies were identified from systematic search of major electronic databases. Thirteen studies with age ranges from 62 to 75 years underwent quantitative pooling of data. The majority of study participants were male.

Older athletes had more favorable FMD compared with sedentary controls. There was no significant improvement in the vascular function of sedentary cohorts following a period of exercise training. However, there was a significant increase in artery baseline diameter from pre to post intervention. In addition, there was no significant difference in endothelial independent vasodilation between the trained and sedentary older adults, or from pre to post exercise intervention. In conclusion, long-term aerobic exercise appears to attenuate the decline in endothelial vascular function, a benefit which is maintained during chronological aging. However, currently there is not enough evidence to suggest that exercise interventions improve vascular function in previously sedentary healthy older adults.

Link: https://doi.org/10.3389/fphys.2019.00031

On Adult Cardiac Stem Cells and their Aging

Does the adult mammalian heart contain a population of stem cells capable of tissue repair? If so, they are not very active; the heart is one of the least regenerative of organs, alongside the brain and the rest of the central nervous system. Opinions and study results differ on whether or not cardiac stem cells exist in any meaningful sense in the adult heart. If they do, there is the possibility of coercing them into greater efforts in tissue maintenance. This is possibly a faster path to regeneration of a damaged or aging heart than any of the other options. However, this would also require that these stem cells not only exist, but also survive into old age in a sizable enough population to produce regeneration. This is another area of study in which there are more questions than answers.

Until the new millennium, the adult heart was considered a postmitotic organ, but several recent studies have supported the notion that it possesses a population of endogenous cardiac stem/progenitor cells (CSCs) supporting myocardial cell turnover and regeneration due to their intrinsic potential to differentiate in all cardiac cell lineages. This discovery opened a new era for myocardial regeneration where endogenous cardiac stem/progenitor cells were introduced as direct regenerative agents and/or endogenous targets of regenerative therapy to effectively replenish the heart muscle cells, lost by injury and/or age, in order to improve/normalize myocardial function.

However, the pathological and pathophysiological cardiomyopathy that occurs with age also affects the stem cell microenvironment modifying adult stem cell biology and then their ability, during lifespan, to repair damaged tissues and organs. Accordingly, as shown for other stem cell types, cardiac stem cell (CSC) potential has also been found to be compromised or even lost with aging as a consequence of the accumulation and activation of senescence factors affecting myocardial homeostasis, producing DNA damage, and alteration of the telomere-telomerase system eventually leading to a senescent phenotype of CSCs. Despite this evidence, interesting studies have demonstrated that the old decompensated heart appears to maintain a functionally competent pool of CSCs during life and that the senescent phenotype of CSCs may be therefore reverted using growth factors or cardioprotective molecules. This accumulating knowledge is fundamental for the prospects of CSCs as main agents for myocardial regeneration because the majority of the patients in need of such therapy are indeed aged subjects.

During the late adulthood, the heart maintains a functionally competent CSC compartment, but the aged cardiac phenotype produces an accumulation of senescent CSCs. Aging and cellular senescence are a major hindrance to the endogenous regenerative efficacy of CSCs. However, the persistence in aged decompensated hearts of a population of functionally competent CSCs with long telomeres generates the hypothesis that endogenous CSCs may be indeed rejuvenated to regain robust regenerative potential. This population of functional yet old CSCs lacks senescent markers, expresses telomerase and cycling proteins, such as Ki67, and displays the capacity to migrate to injured zones generating a healthy progeny of young CMs. Indeed, as demonstrated in old humans, a pool of CSCs seems to maintain a growth reserve and self-renewing potential in the cardiac tissue, critical variables for effective cardiac homeostasis and repair during aging.

It is expected that a better understanding of the metabolic pathways and molecular mechanisms active in adult stem cells in old tissues may be helpful to develop genetic approaches or drugs to preserve their stemness potential during aging and to manipulate their quiescence, self-renewal, and differentiation. Several strategies able to decrease ROS levels, to restore or increase telomerase activity and telomere length in order to delay the natural aging process of the entire organism, have been studied in the past decade.

The present available evidence shows that the mammalian, including the human, myocardium possesses an "aged" CSC phenotype and this affects CSC self-renewal ability, differentiation, and regenerative potential. Thus, CSCs are not immortal. They undergo cellular aging in response to a variety of physiological and pathological demands. We can envision the phenomenon of CSC ageing as a result of a stochastic and therefore reversible cell autonomous process. Indeed, if CSC aging is really a stochastic cell autonomous process, then the possibility to rejuvenate the endogenous CSC population by stimulating their growth and self-renewing could be concrete. On the other hand, CSC aging could be a cell cycle-dependent process, affecting all or most of the endogenous CSC population, with a consequent irreversible loss of CSC regenerative capacity with time. If the latter is correct, it is predictable that the loss of CSC regenerative capacity with time progression is an inevitable phenomenon that cannot be rescued by stimulating their growth, which would only speed their progressive exhaustion. The determination of whether the aged phenotype of the CSCs is reversible or irreversible has importance for the future of myocardial regeneration.

Link: https://doi.org/10.1155/2019/5813147

Senescent Cells Cause a Sizable Fraction of the Consequences of Type 2 Diabetes

For the overwhelming majority of patients, type 2 diabetes is a self-inflicted condition. It is the consequence of excess visceral fat tissue, accumulated and held over the years. This type of fat is metabolically active and distorts the operation of metabolism in ways that accelerate the progression of many aspects of aging and age-related disease. Even quite late in the progression of the condition, patients can effectively turn back type 2 diabetes and its consequences via the use of a sustained low calorie diet and consequent weight loss. That more people do not do this is quite eye-opening, given that the alternative is unpleasant medications, side-effects, and the continuation of the disease process leading to an early death.

One of the primary ways in which visceral fat causes harm is via increased levels of chronic inflammation. Inflammation is a necessary part of the immune response to pathogens and injury, provided it lasts a short time only. But when it runs continually, it produces significant dysfunction in tissue maintenance and repair, and accelerates disease processes in all of the common age-related conditions. Visceral fat tissue can produce inflammation in numerous ways: because fat cells secrete signals similar to those of infected cells; fat cells tend to produce DNA debris that can provoke the immune system; and, relevant to research noted here, greater amounts of fat tissue encourage the creation of larger numbers of senescent cells.

The accumulation of lingering senescent cells in all tissues of the body is one of the fundamental causes of aging. Cells become senescent in large numbers constantly, day in and day out, largely resulting from somatic cells reaching the Hayflick limit on replication. Cells can also become senescent as the result of injury, DNA damage, a toxic environment, and the signals of other, nearby senescent cells. Near all senescent cells are quickly destroyed, either self-destructing via apoptosis, or removed by the immune system. It is the tiny fraction that evade this fate that contribute to aging. They largely achieve this end via a potent mix of secreted signals that spur chronic inflammation, destructive remodeling of the surrounding extracellular matrix, and altered behavior in normal cells. Wherever we see chronic inflammation in aging, we should be thinking of senescent cells.

Fortunately, senolytic therapies to selectively destroy senescent cells are presently under active development. New biotechnology companies and development programs are arriving in this part of the industry on a regular basis now, and a significant and growing amount of funding is now available for this work. Even better, a range of low-cost, easily obtained drugs and other compounds (such as the dasatinib and quercetin combination, fisetin, piperlongumine, and the FOXO4-DRI peptide) have been shown to remove a fair fraction of senescent cells in animal studies. Some are presently in initial human trials. Any older person suffering one or more of the many age-related conditions that appear likely to be actively maintained and driven by senescent cells, and who wishes to responsibly self-experiment with senolytics, can certainly do so with just a little knowledge and effort. These are interesting times.

Removal of 'zombie cells' alleviates causes of diabetes in obese mice

Inflammation and dysfunction of fat tissue cause some of the insulin resistance in obese people. In many cases, that dysfunction is caused by senescent cells that already have been shown to be responsible for conditions related to aging and illness, including osteoporosis, muscle weakness, nerve degeneration, and heart disease. These cells also accumulate in the fat tissues of obese and diabetic people and mice.

In this study, the researchers, using genetically modified mice and wild-type (normal) mice, removed senescent cells two ways: by causing genetically-mediated cell death and by administering a combination of senolytic drugs. Senolytic drugs selectively kill senescent cells but not normal cells. The result: glucose levels and insulin sensitivity improved. The mice also showed a decline in inflammatory factors and a return to normal fat cell function. The senolytic drugs also prompted improved kidney and heart function, both of which are common complications of diabetes.

Targeting senescent cells alleviates obesity-induced metabolic dysfunction

Cellular senescence is a cell fate that entails proliferative arrest and acquisition of a pro-inflammatory senescence-associated secretory phenotype (SASP). Although senescent cells exist in relatively small numbers in any particular tissue, they have been associated with multiple diseases of aging and are emerging as useful therapeutic targets for age-related diseases, including cardiovascular disease, pulmonary fibrosis, neurodegeneration, and osteoporosis. A number of stimuli, including potentially oncogenic, inflammatory, damage-related, and metabolic stimuli, can trigger a senescence response. Components of the SASP secreted by adipose-derived senescent cells have been postulated to confer insulin resistance upon metabolic tissues, inhibit adipogenesis, and attract immune cells that can exacerbate insulin resistance. Here, we determined whether removing senescent cells in the context of obesity improves metabolic phenotypes.

Recently, drugs that preferentially decrease senescent cell burden, termed senolytics, have been identified. We discovered the first senolytics based on our observation that senescent cells rely on several survival pathways to confer resistance to their pro-apoptotic SASP and intracellular cell damage signals. Knowing this, we identified dasatinib (D) and quercetin (Q) as orally bioactive drugs that transiently target these survival pathways to induce apoptosis preferentially in senescent cells.

We employed the combination of D plus Q (D + Q) in our studies for the following reasons. (a) In our hands, no senolytic investigated thus far targets all types of senescent cells. For example, unlike navitoclax (ABT263), fisetin, A1331852, A1155463, or Q on its own, D selectively targets senescent adipose progenitors, a key cell type for adipose tissue and metabolic function. (b) On the other hand, Q, unlike D, is effective against senescent endothelial cells, a cell type implicated in vascular complications of diabetes. (c) D + Q is effective in alleviating multiple age- and senescence-associated disorders, including many that are frequent complications or comorbidities of diabetes in preclinical animal models.

Here, we show that reducing senescent cell burden in obese mice, either by activating drug-inducible "suicide" genes driven by the p16Ink4a promoter or by treatment with senolytic agents, alleviates metabolic and adipose tissue dysfunction. These senolytic interventions improved glucose tolerance, enhanced insulin sensitivity, lowered circulating inflammatory mediators, and promoted adipogenesis in obese mice. Elimination of senescent cells also prevented the migration of transplanted monocytes into intra-abdominal adipose tissue and reduced the number of macrophages in this tissue. In addition, microalbuminuria, renal podocyte function, and cardiac diastolic function improved with senolytic therapy. Our results implicate cellular senescence as a causal factor in obesity-related inflammation and metabolic derangements and show that emerging senolytic agents hold promise for treating obesity-related metabolic dysfunction and its complications.

New Evidence for Adult Neurogenesis to Occur Even in Late Old Age in Humans

You might have missed it, but the past year has seen quite the debate in scientific circles over whether or not humans exhibit the same processes of neurogenesis in adult life that are observed in mice. Neurogenesis is the process by which new neurons are created in the brain and integrated into neural circuits. It is a part of the plasticity that allows for cognitive function and maintenance of that function in the face of damage. Obviously, this is a very important topic for those groups seeking ways to apply regenerative medicine to the brain.

Prior to the discovery of adult neurogenesis in the 1990s, it was thought that no such process took place after early development, and that the tissues of the adult brain were not maintained in this way. Since the 1990s an enormous amount of investigative work on this topic has taken place in mice, and comparatively little in human brains and brain tissue. In this context, much upheaval occurred in the wake of a study published last year that found no evidence of adult human neurogenesis. Shortly thereafter, another study was published with contradictory results, showing that there were signs of neurogenesis. The debate continues, and we will see more, ever more careful studies on this topic. Currently the weight of evidence leans in the direction of neurogenesis in adults, thankfully - if the process exists, then there is a path to enhance it in older individuals, in order to find ways to postpone and reverse portions of age-related neurodegeneration.

People keep making new brain cells throughout their lives (at least until the age of 97), according to a study on human brains. The idea has been fiercely debated, and it used to be thought we were born with all the brain cells we will ever have. The researchers also showed that the number of new brain cells tailed off with age. And it falls dramatically in the early stages of Alzheimer's disease - giving new ideas for treating the dementia.

Most of our neurons - brain cells that send electrical signals - are indeed in place by the time we are born. Studies on other mammals have found new brains cells forming later in life, but the extent of "neurogenesis" in the human brain is still a source of debate. The study looked at the brains of 58 deceased people who were aged between 43 and 97. The focus was on the hippocampus - a part of the brain involved in memory and emotion.

Neurons do not emerge in the brain fully formed, but have to go through a process of growing and maturing. The researchers were able to spot immature or "new" neurons in the brains that they examined. In healthy brains there was a "slight decrease" in the amount of this neurogenesis with age. "I believe we would be generating new neurons as long as we need to learn new things. And that occurs during every single second of our life."

But there was a different story in the brains from Alzheimer's patients. The number of new neurons forming fell from 30,000 per millimetre to 20,000 per millimetre in people at the beginning of Alzheimer's. "That's a 30% reduction in the very first stage of the disease. It's very surprising for us, it's even before the accumulation of amyloid beta, a hallmark of Alzheimer's, and probably before symptoms, it's very early. Larger studies will need to confirm these findings and explore whether they could pave the way for an early test to flag those most at risk of the disease."

Link: https://www.bbc.com/news/health-47692495

Proposing Physical, Neurological Explanations for Age-Related Differences in the Perception of the Passage of Time

Why does the perception of the passage of time change with age? Having glanced through the short paper referenced in these publicity materials, it has the look of another of the many airy theories on the operation of the mind that must wait around for however long it takes for neuroscience to advance to the point of being able to say anything sensible about how perceived experience relates to physical structure and cellular biology. Still, one has to start somewhere. Final answers and understanding must be preceded by theories that prompt lines of investigation. That theorizing will start out entirely unsupported, and only incrementally become better and more scientific. We shouldn't be holding our collective breath waiting on those final answers, of course. They are quite the long way away.

A researcher has suggested that the perception that days last longer in childhood can be blamed on the ever-slowing speed at which images are obtained and processed by the human brain as the body ages. This phenomenon is attributed to physical changes in the aging human body. As tangled webs of nerves and neurons mature, they grow in size and complexity, leading to longer paths for signals to traverse. As those paths then begin to age, they also degrade, giving more resistance to the flow of electrical signals. These phenomena cause the rate at which new mental images are acquired and processed to decrease with age. This is evidenced by how often the eyes of infants move compared to adults - because infants process images faster than adults, their eyes move more often, acquiring and integrating more information.

The end result is that, because older people are viewing fewer new images in the same amount of actual time, it seems to them as though time is passing more quickly. "The human mind senses time changing when the perceived images change. The present is different from the past because the mental viewing has changed, not because somebody's clock rings. Days seemed to last longer in your youth because the young mind receives more images during one day than the same mind in old age."

Link: https://pratt.duke.edu/about/news/its-spring-already-physics-explains-why-time-flies-we-age

The Relentless Focus on Amyloid Clearance for Later Stage Alzheimer's Disease is Disintegrating

In hindsight, the Alzheimer's research and development community of the past fifteen years or so has been a strange place. The vast, overwhelming majority of investment has gone towards attempts to clear amyloid-β in later stage Alzheimer's disease, largely via immunotherapies. This strategy has failed, over and again, long past the point at which it was defensible to blame that failure on the challenging nature of the underlying projects to first make immunotherapies work at all, and then to make them work in the brain. Enormous sums were spent on repeated attempts to clear amyloid-β even as the research community was settling on the consensus that aggregation of amyloid-β is a feature of early Alzheimer's. It only causes mild cognitive impairment on its own, but sets the stage for the later accumulation of hyperphosphorylated tau. It is tau aggregates and their surrounding biochemistry that cause the real harm, the severe dysfunction and death of neurons.

Where years of relentless failure did not move the leaders who determined strategy for Alzheimer's development at the large scale, the rise of plausible, much cheaper alternatives has finally produced motion. Large anti-amyloid programs are being cancelled, trial development halted. It is becoming apparent that low cost senolytics have a large effect on late stage Alzheimer's disease animal models, perhaps more so than many of the immunotherapies when they were tested in mice. Meanwhile, groups are working on drainage or filtration of cerebrospinal fluid, which should clear out a usefully large fraction of all of the protein aggregates involved in neurodegeneration, again much more cheaply than immunotherapies. Other researchers are focused on removing bacterial and viral contributions to amyloid buildup and neuroinflammation.

Ironically, just as this flourishing of alternative and potentially more cost effective development programs takes place, some of the anti-amyloid immunotherapies are finally starting to achieve their goals, to remove significant amounts of amyloid-β from the human brain. Yet they haven't moved the needle on patient outcomes. This upheaval, when taken as a whole, seems a positive development. The old industry is being disrupted by the growth of a new industry. Bad investments are being cleared out, and more productive new investments are being made. The Alzheimer's research community of the early 2020s will be a much more diverse ecosystem with a greater expectation of success.

Biogen/Eisai Halt Phase 3 Aducanumab Trials

Today, Biogen and Eisai announced they would terminate the Phase 3 ENGAGE and EMERGE trials of aducanumab for early Alzheimer's disease. A futility analysis run by an independent data-monitoring committee concluded that that trials would not reach their primary endpoint, the slowing of cognitive decline as measured by the Clinical Dementia Rating-Sum of Boxes (CDR-SB). Aducanumab is a monoclonal antibody that helps clear amyloid-β (Aβ) from the brain. The trials had recruited more than 3,200 patients around the world.

"This tells us that removal of amyloid in people with disease is too late. Amyloid is a disease trigger. Once the neurodegenerative disease process is up and running, it is up and running. Even though this trial was in the early symptomatic phase of AD, it is still in the phase when Aβ is no longer likely to be the driving process but where tau and inflammation probably are. I think Aβ is still a good target for the primary and maybe secondary prevention trials of AD, before tau and inflammation have started driving the disease. I think this solidifies the opinion that amyloid-targeted therapies do not have a clinical effect at the symptomatic stages of the disease process. Might anti-amyloid therapies work prior to the development of symptoms? Maybe, but with no symptomatic signal, it is risky to continue in that space. We clearly need other targets, and tau is the leading candidate for now."

Alzheimer's Drug Failure Leaves Scientists Seeking New Direction

The brain has been a black box for drug developers, but focusing on beta amyloid has long been viewed as the best hope for treating the mysterious ailment that affects millions of Americans and their families. For many, the hypothesis became an article of faith, motivating billions of dollars in research spending and putting thousands of patients through clinical trials. "It's not science anymore. It has turned into a religion."

Biogen and Eisai will discontinue two late-stage trials designed to evaluate the efficacy and safety of the drug, aducanumab, which has cost the partners more than $830 million over the past three years. The results showed that the drug was unlikely to help patients, the companies said in a statement, and the discontinuation wasn't related to safety concerns. The latest failure, following the unraveling of similar experimental beta amyloid drugs from Eli Lilly & Co., and Pfizer Inc. in large-scale trials, has scientists questioning whether the persistent focus on targeting the compound has prevented investment in testing drugs against other possible Alzheimer's targets. Even so, researchers had thought that perhaps the Biogen compound might be different from previous failures.

Senescent Cells as a Contributing Cause of Degenerative Disc Disease

At this point, I suspect it will surprise no-one who follows the field to learn that the accumulation of senescent cells is a significant cause of degenerative disc disease. The evidence from a mouse study that is provided in the open access paper here doesn't quite rise to establishing that claim, but it is compelling nonetheless. Given the role of cellular senescence in arthritis, a disease of localized chronic inflammation, it is logical to also expect a role in the degeneration of intervertebral discs, as this is also a condition of aging in which inflammation seems important.

Senescent cells, even while present in only comparatively small numbers, generate a potent mix of molecules that spurs chronic inflammation and is destructive of surrounding tissue structure. Fortunately early senolytic compounds, those shown to destroy a sizable fraction of senescent cells cells in animal studies, are cheap and readily available to anyone willing to try this self-experiment. It is just a pity that so few older people know this at the present time - the hundreds of millions worldwide who are suffering when perhaps they need not be.

Age-related changes in the intervertebral discs are the predominant contributors to back pain, a common physical and functional impairment experienced by older persons. Cellular senescence, a process wherein cells undergo growth arrest and chronically secrete numerous inflammatory molecules and proteases, has been reported to cause decline in the health and function of multiple tissues with age. Although senescent cells have been reported to increase in intervertebral degeneration (IDD), it is not known whether they are causative in age-related IDD.

To examine the impact of senescent cells on age-associated IDD, we used p16-3MR transgenic mice, which enables the selective removal of p16Ink4a-positive senescent cells by the drug ganciclovir. Disc cellularity, aggrecan content and fragmentation alongside expression of inflammatory cytokine (IL-6) and matrix proteases (ADAMTS4 and MMP13) in discs of p16-3MR mice treated with ganciclovir and untreated controls were assessed. In aged mice, reducing the percent of senescent cells decreased disc aggrecan proteolytic degradation and increased overall proteoglycan matrix content along with improved histological disc features. Additionally, reduction of senescent cells lowered the levels of MMP13, which is purported to promote disc degenerative changes during aging.

The findings of this study suggest that systemic reduction in the number of senescent cells ameliorates multiple age-associated changes within the disc tissue. Cellular senescence could therefore serve as a therapeutic target to restore the health of disc tissue that deteriorates with age.

Link: https://doi.org/10.1111/acel.12927

Decline in Cognitive Function is Small Prior to Age 65

Researchers here process the enormous set of health data found in the UK Biobank to conclude that there is comparatively little sign of cognitive decline in cohorts younger than age 65. After that, loss of function sets in quite rapidly, however. This is good news for those of us taking good care of our health, and who have a long time yet before reaching 65. Not so great for the older contingent in the population, but we really don't need any more incentives than already exist in order to forge ahead with the development of rejuvenation therapies. Repair of the damage that causes aging, and aging of the brain in particular, is the only path forward likely to produce meaningful results in the clinic over the next ten to twenty years.

Age is a key risk factor for cognitive performance. Cognitive decline is common in older ages but recently there has been interest in understanding the age at which significant decline in cognitive abilities begins. Such knowledge has implications for the design of behavioral or pharmacological interventions since they are more likely to work if they are applied when, or even years before, individuals first begin to experience decline. Efforts to date are often based on cross-sectional studies which may be confounded by 'cohort effects'. Longitudinal studies suggest evidence of cognitive decline in middle age but that age trajectories differ by sex and cognition domain or task.

Longitudinal data that span many decades generally report minimal cognitive decline before the age of 65, but such studies are rare and also subject to limitations including small sample size, selection attrition, and retest or practice effects. Researchers examined cognitive decline among ~2,500 participants aged 25 to 95 years at recruitment in the Midlife in the United States (MIDUS) study, and all cognitive domains measured showed significant but small declines over 9 years, with differences in the timing and extent of change. The largest analysis to-date included a 10 year follow-up of ~7,400 participants aged 45-70 at recruitment of the Whitehall Study. The design of this study allowed for cross-sectional and longitudinal analysis. For the former analysis, performance on several tests were progressively lower with older age categories. In longitudinal analyses, there was some evidence of greater decline at older ages and of a linear trend in decline with increasing age for some of the tests, particularly in men.

UK Biobank is a large population cohort of adults who underwent medical, sociodemographic, mental health and cognitive assessment in 2006-2010 and are being followed up at intervals. The large age-distribution and follow-up enables cross-sectional as well as longitudinal analysis of age. In the current study of individuals aged 38 to 73 at baseline, we observed significantly lower performance on memory, attention, and processing tasks across successive age groups. Reasoning scores, based on the fluid intelligence test, were higher with successive age group until 60, then dropped to less than that of under 45 year olds. Longitudinal analysis of a subset of individuals with repeated measures of four tests showed linear declines in visual memory and processing speed tasks with age but of a much lesser degree than those observed in cross-sectional analyses. Decline rates in reasoning and prospective memory did not significantly differ with age. Taken together, our findings suggest that decline in cognitive abilities before age 65 is evident but small, and that observed cross-sectional differences in cognition from middle to older adult years may be due largely to age cohort effects.

Link: https://doi.org/10.1371/journal.pone.0213948

Naked Mole Rats as the Outlier Species, Thriving with High Oxidative Stress

Rising levels of oxidative stress occur with aging. This term describes the presence of excessive numbers of oxidative molecules, reacting with surrounding molecular machinery to cause breakage and cellular dysfunction. It is significant enough in aging for the free radical theory of aging to have arisen some decades ago, postulating that oxidative damage was the cause of aging. Alas, matters are not that simple. Persistently raised levels of oxidative stress are a downstream consequence of deeper causes, such as mitochondrial dysfunction, chronic inflammation, cellular senescence, and the like. Further, oxidative molecules do in fact serve a necessary and useful role in healthy cellular metabolism. They act as signals to spur cellular maintenance, for example, and thus small or temporary increases in oxidative stress tend to be beneficial. This is one of the mechanisms by which exercise produces health benefits.

Naked mole rats are a strange species, an outlier among rodents. They are eusocial, like some insects. They live nine times longer than similarly sized rodent species, and show few signs of aging across most of that life span. They exhibit high levels of oxidative stress, but appear near completely immune to the consequences that would appear in rats or mice given the same flood of oxidative molecules. They show the presence of senescent cells, but appear largely unaffected by that as well, which is interesting given the very prominent role played by the harmful, inflammatory secretions of senescent cells in the aging and age-related diseases of mice. Finally, naked mole rats are near immune to cancer.

Needless to say, researchers are quite interested in learning how exactly of all this is possible. Might any of the findings result in biotechnologies that can be applied to humans, to shut down cancer, or resist aging? No-one knows. My suspicion is that it will take a while to find out, and there is a good chance that altering humans to be more like naked mole rats is not a near term project - something for the latter half of the century, not the next few decades. I would say we are better off trying to repair the metabolism we have rather than building a better one, given the present state of biotechnology. It is a much more plausible goal.

The Naked Mole Rat: A Unique Example of Positive Oxidative Stress

More than 60 years ago, it was first proposed that aging could be attributed to the deleterious effects of free radicals produced as natural by-products of aerobic metabolism. The free radical theory of aging (FRTA) is based on the hypothesis that dysfunctions observed during aging and a range of age-associated pathologies are due to the accumulation of oxidative damage to biological macromolecules (e.g., DNA damage, lipid peroxidation, and nonrepairable protein oxidation) by reactive oxygen and nitrogen species. A more precise version of the free radical theory of aging, called the mitochondrial free radical theory of aging (MFRTA), specifies that mitochondria are the main sources of reactive oxygen species (ROS) generation and are also the targets of deleterious effects: oxidative damages to mitochondrial DNA, mitochondrial proteins, or phospholipids are assumed to directly cause aging.

Naked mole rats (Heterocephalus glaber), first described in 1842, are the longest living rodents known. Several studies have investigated the production of free radicals and oxidative damages in the naked mole rat, and the results are puzzling. Despite remarkably long lives, some tissues of the naked mole rat, such as arteries, produce higher amounts of ROS (from cytoplasmic and mitochondrial sources) as compared to these tissues from the short-lived mouse. Importantly, the arteries of naked mole rats are highly resistant to the pro-apoptotic effects of ROS in vitro, whereas those of the mouse are not.

Furthermore, several studies have shown that naked mole rats have high levels of oxidative damages to macromolecules from a young age. Interestingly, these levels of damages are maintained over a 20-year period without increase. One hypothesis is that further damages are attenuated by an efficient repair system. A limit of these studies is that only damages to macromolecules were investigated: mitochondrial DNA damage has not been studied in naked mole rat tissues. Hence, further studies using this unique animal model are needed as it would be very informative to compare ROS-producing systems from cellular and mitochondrial sources and oxidative damage in nuclear, cytoplasmic, and mitochondrial targets in long-lived naked mole rat and short-lived rodents.

Many, but not all, features of the naked mole rat defy the free radical theories of aging. However, there is a recent extension of the theory, called the membrane pacemaker theory of aging, which holds true in the naked mole rat. This theory predicts that membrane fatty acid composition has an influence on lipid peroxidation and consequently may be an important determinant of aging and lifespan. Indeed, a study showed that naked mole rat membranes from different tissues contain more fatty acids resistant to peroxidation than do membranes from mice. Thus, the cellular membrane composition of the naked mole rat could partially explain their exceptional longevity. Still, the "naked mole rat exception" raises the question of whether or not ROS (cytoplasmic and mitochondrial) are responsible for aging.

Changes in the Gut Microbiome as the Cause of Inflammation and Oxidative Stress Leading to Vascular Dysfunction

Chronic inflammation and oxidative stress disrupt the function of smooth muscle cells in blood vessel walls. This is one of the contributing causes of vascular stiffness with age, alongside cross-links, calcification, and loss of elastin, all of which alter the structural properties of blood vessel tissue to produce a reduction in elasticity. There is the question of the relative importance of these contributions, a question that exists for most aspects of aging at the present time, lacking easy ways to remove only one contributing factor to assess the outcome. Nonetheless, the research results noted here suggest that smooth muscle dysfunction is the most important factor in vascular stiffness, and that - in mice, at least - changes in gut bacteria populations are the cause of this issue. This might make us more optimistic about the prospects for near term therapies in humans.

Stiffening of blood vessels is important because it results in hypertension; the feedback mechanisms controlling blood pressure are disrupted by this type of damage and dysfunction. That in turn produces tissue damage throughout the body due to rupture of capillaries and other pressure-related issues. Hypertension also accelerates the progression of atherosclerosis, and makes it more likely for fatal structural failures in large blood vessels to occur in the later stages of that condition.

Why do blood vessels naturally stiffen and degrade as we age, boosting cardiovascular disease risk? Researchers gave young mice and old mice broad-spectrum antibiotics to kill off the majority of bacteria living in their gut, aka their gut microbiome. Then they assessed the health of their vascular endothelium (the inner lining of their blood vessels) and the stiffness of their large arteries. They also measured blood levels of inflammatory compounds, tissue-damaging free-radicals, antioxidants, and the blood-vessel-expanding compound nitric oxide in both groups. After three to four weeks of the treatment, the young mice saw no change in vascular health. The old mice, however, saw vast improvements on all measures. "When you suppressed the microbiome of the old mice, their vascular health was restored to that of young mice. This suggests there is something about those microorganisms that is causing vascular dysfunction."

To assess what that something may be, the researchers then took fecal samples from another set of mice and had them genetically sequenced, comparing the gut bacteria living in the old mice with that in the young. In the old mice, the researchers saw an increased prevalence of microbes that are pro-inflammatory and have been previously associated with diseases. For instance, the old mice hosted significantly more Proteobacteria, a phyla that includes Salmonella and other pathogens, and pro-inflammatory Desulfovibrio. To drill down further, the researchers measured blood levels of metabolites - small molecules produced by the gut microorganisms and absorbed into the bloodstream - in old and young mice. Old mice had three times as much TMAO (trimethylamine N-oxide), a metabolite shown in previous studies to be linked to increased risk of atherosclerosis, heart attack, and stroke.

"We have long known that oxidative stress and inflammation are involved in making arteries unhealthy over time, but we didn't know why arteries begin to get inflamed and stressed. Something is triggering this. We now suspect that, with age, the gut microbiota begins producing toxic molecules, including TMAO, which get into the blood stream, cause inflammation and oxidative stress and damage tissue." The researchers recently launched a human trial to explore how different diets impact the gut and, in turn, cardiovascular disease risk. They are also studying a compound called dimethyl butanol, which blocks the bacterial enzyme required to produce TMAO. Ultimately, it could be developed into a dietary supplement.

Link: https://www.colorado.edu/today/2019/03/19/fountain-youth-heart-health-may-lie-gut

Telomere Length and Mitochondrial DNA Copy Number Over the Mouse Lifespan

The science of intervention in aging has reached the point at which the research community should be undertaking a great deal more of the sort of work exhibited here. The authors of this open access paper have done the public service of producing reference data on telomere length and mitochondrial DNA copy number in multiple tissues over the mouse life span. Telomere length is a terrible metric for aging when measured in the immune cells taken from a blood sample; it varies widely between individuals, is dynamic for a given individual, dependent on day to day environmental and health factors, and trends with age only show up in statistical analyses carried out across sizable study populations - and sometimes not even then. Mitochondrial DNA copy number is more interesting, and a reference work here might be quite useful.

Both of these metrics, regardless of their quality or lack of same, are downstream consequences of lower-level forms of damage in aging. Average telomere length is a loose measure of stem cell activity, a proxy for the replacement rate for cells in a tissue. Stem cell activity declines with age, and thus so does the supply of new cells with long telomeres. Mitochondrial DNA copy number is generally thought to fall with age (though see the results below), and lower copy number counts correlate with poor health outcomes. Mitochondria, the power plants of the cell, undergo a general malaise with age, their function faltering, and this contributes to many age-related conditions, particularly in energy-hungry tissues like muscles and the brain. These processes have underlying causes, and go on to cause further issues themselves. A good fraction of the research community involved in aging seeks to override these evident declines without trying to address the root causes - an approach that may well produce some benefits, but will not solve the problem of aging in and of itself.

Our study aimed to provide chronological aging standard curves and slopes of telomere length and mitochondrial DNA copy number (mtDNAcn), which can help researchers objectively assess the degree of aging in target tissues in various studies using C57BL/6 male mice. C57BL/6 is one of the commonly used rodent models. To evaluate telomere length by qPCR, we used the telomere primer set telg and telc. Unlike previously suggested primers that generate PCR products of various lengths, the telg and telc set produced PCR products of constant length, resulting in stable amplification and clear chronological standard curves.

The telomere qPCR conditions proposed in this study resulted in reproducible and discriminating amplification outcomes, and the fidelity of the qPCR result was further confirmed by telomere restriction fragment (TRF) analysis. The telomere standard curves also showed significant changes with aging. To the best of our knowledge, this is the first report of the aging standard curves of mouse telomeres using the telg and telc set and integrating various tissues across the body.

All 12 tissues showed age-dependent changes in telomere length or mtDNAcn, indicating that we can estimate tissue-specific aging status using at least one of these aging markers. A variety of studies have indicated that telomere erosion occurs in aged human or animal subjects. In our study, all tissues showed telomere length decline with aging. However, the mtDNAcn showed a tendency to increase or decrease with aging depending on the tissue. We found increments in mtDNAcn in the retina, thoracic aorta, and spleen, but the other tissues showed a decreasing tendency with aging.

In addition to mitochondrial dysfunction due to a decreased mitochondrial genome, increased mtDNAcn has also been suggested to be detrimental to cells and eventually induces cellular senescence or apoptosis. Accumulation of mtDNA mutations induces high mtDNAcn in nucleoids (mtDNA-protein complexes), and results in nucleoid enlargement and subsequent mitochondria functional deficiency. Excessive mtDNA replication could be triggered by the activation of twinkle mtDNA helicase and mitochondrial transcription factor A. These previous studies support the notion that an increase in mtDNAcn is a normal phenomenon in aging, although the mechanism of tissue-specific increase or decrease with aging remains to be elucidated.

It is known that telomerase activity in adult tissues differs between human and rodents. Telomerase is constitutively expressed in various tissues of laboratory mice, whereas it is tightly regulated in human somatic cells. Therefore, the results of mouse experiments cannot be directly applied to humans. Nevertheless, animal model experiments are indispensable to understanding human diseases, and the results have to be compared with human data to infer the clinical symptoms of the human body.

Link: https://doi.org/10.3390/cells8030247

Intron Retention via Alternative Splicing as a Signature of Aging

In recent years researchers have investigated changes in alternative splicing in the context of aging and age-related disease. It is thought to be important in cellular senescence, for example, but that is just one line item in the bigger picture. A given gene can code for multiple different proteins, and alternative splicing is the name given to the processes by which those different proteins are produced. A gene contains discrete DNA sequences called exons and introns, the former passed into the protein production process, and the latter removed during RNA splicing. The canonical protein produced from this genetic blueprint contains all of the exons, joined in sequence, but alternative splicing may drop exons, resulting in a different protein.

The balance between the proteins produced from a given gene tends to shift with age. This might be a harmful downstream consequence of underlying molecular damage, or an evolved reaction to attempt to compensate for that damage in some way. All too little mapping of these age-related changes in alternative splicing has been carried out, but we might regard it as yet another form of gene expression regulation, akin to epigenetic changes that alter the pace of production of proteins.

Intron retention is another possible form of alternative splicing. Instead of an intron being removed, it is included in the process of producing a protein. This also results in a different protein with different characteristics. In today's open access paper, researchers look specifically at intron retention in flies, mice, and humans, finding that rates of this phenomenon correlate with age and neurodegenerative disease. The water is muddied somewhat by the point that this alternative splicing does take place to some degree in young individuals, as a normal part of the operation of cellular metabolism. Nonetheless, it seems likely that someone might produce an intron retention clock analogous to the epigenetic clocks presently demonstrated to measure age quite well.

Alternative splicing is a regulatory mechanism that generates multiple mRNA transcripts from a single gene. While this process is essential for many biological processes such as neurogenesis, alteration in the splicing patterns is also prevalent during aging and may contribute to many age-onset diseases like Alzheimer's disease (AD). Intron retention (IR) occurs when a specific intron remains unspliced in the mature polyadenylated mRNA. As an IR may trigger nonsense-mediated decay (NMD) of mRNA or introduce mutation in the translated protein, it has been widely considered as an aberrant splicing event that is associated with various diseases.

For instance, dysregulated IR is one of the drivers of transcriptome diversity in cancer and can lead to inactivation of different tumor-suppressor genes. IR in endoglin and EAAT2 gene also leads to cellular senescence and amyotrophic lateral sclerosis, respectively. Interestingly, dietary restriction in worms could reduce aberrant IR caused by defective splicing during aging, suggesting that IR at specific genes can be used as disease biomarkers or targets for therapeutic intervention. Accumulated evidence indicated that IR may also play an important regulatory role during normal development, including translational inhibition in response to hypoxic stress, regulation of mRNA expression patterns during hematopoiesis and neurogenesis. Therefore, defining age-associated changes to IR may allow a far better understanding into how IR may regulate the transition from healthy to the pathological state during aging.

To this end, we analyzed the in-house RNA-sequencing data of aging male Drosophila heads and observed a global increase in the level of IR as the animals aged. Interestingly, IR affects functionally distinct groups of genes at different stages of an adult lifespan. Consistent with the role of chromatin structure in regulating RNA splicing, we found that nucleosome positioning within a subset of introns in young flies correlated with their differential retention in older animals. Further analyses of transcriptome from mouse and human brain tissues suggest that the global increase in IR during aging may be evolutionarily conserved. The differentially retained introns identified from different species share several similar characteristics, including shorter length when compared to spliced introns and not susceptible to NMD.

Notably, several differential IR genes identified from aging Drosophila and human brain tissues are linked to AD-related pathways, postulating that the pattern of IR may undergo further changes during AD progression. To test this possibility, we analyzed AD datasets from the cerebellum and frontal cortex, and observed a global increase in the level of IR in AD brain tissues when compared to the control samples. These differentially retained introns have a shorter length and higher GC content compared to the spliced introns. Differential IR genes are enriched for functions associated with RNA processing and protein homeostasis, with more than a hundred of them having an altered level of protein expression in AD frontal cortex. Taken together, our results suggest that a global increase in IR may be a transcriptional signature of aging that is conserved across species and differential IR at specific genes may contribute to the etiology of late-onset sporadic AD.

Link: https://doi.org/10.1111/acel.12928

Chronic Inflammation as the Primary Cause of Declining Bone Regeneration with Age

Researchers here show that it is the chronic inflammation of aging that is the dominant contributing cause of loss of capacity in bone regeneration in later life. We should all feel a degree of relief whenever it turns out that chronic inflammation is the primary proximate cause of an age-related condition. Age-related inflammation is driven by senescent cells and immune system failure. Therapies to remove senescence cells are well advanced in clinical development, and there are many potential lines of work that will lead to ways to reverse the dysfunction of the aged immune system in years to come. The inflammatory profile of an old individual twenty years from now will look very different from the inflammatory profile of an old individual today.

A new study finds that increases in chronic inflammation - not the passage of time - is the main reason why injured bones do not heal as well with age. The results revolve around the known breakdown, due to wear and tear, of the protein machines and large molecules necessary for the life of human cells, the remnants of which trigger the immune system. First studied in its role in destroying invading microbes, this system also can react to the body's own proteins to cause inflammation, a response that fights infection at the site of injury and transitions into the healing process. The current study explains how this age-driven increase in immune signals diminishes the ability of stem cells - essential ingredients in bone repair - to multiply

The current study is based on the observation in human patients that stem cell number in the bone marrow significantly declines with increasing age, and that fractures take longer to heal as the stem cell number drops. The research team then moved to mouse models to explore the related mechanisms. The researchers found that exposing stem cells from young mice to the blood serum of the older mice made their stem cells four times less likely to divide and multiply, an irreversible state called senescence. Past studies had also shown that senescent stem cells send signals that encourage inflammation in a vicious circle.

Furthermore, treatment over time with sodium salicylate, an ingredient in aspirin, repressed NFκB signals and related aged-induced chronic inflammation, increasing the number and bone-healing contribution of skeletal stem cells. Further experiments revealed that anti-inflammatory treatment changed the action of thousands of genes in the stem cells, restoring them to a genetic profile seen in young skeletal stem cells. These results suggest that it is inflammation, not chronological age, that hinders bone healing in the elderly.

An obstacle to the translation of the findings into future treatments is that rejuvenating bone stem cells with anti-inflammatory drugs just after a bone fracture would also block the acute inflammation that is necessary for successful bone healing. This suggests that a more immediate application may be to use anti-inflammatory drugs to build up stem cell pools, not after bone breaks, but during the weeks before elective orthopedic surgeries like hip or knee replacements. In these cases, anti-inflammatory drugs would be used leading up to a surgery, but then be cut off just before to make way for the acute inflammation necessary to normal healing.

Link: https://www.eurekalert.org/pub_releases/2019-03/nlh-cl031319.php

More Evidence for Hypertension to Produce Brain Damage

Hypertension, raised blood pressure due to age-related dysfunction of blood vessels, is an important process in aging. It is one of the more important ways in which low-level biochemical damage and cellular malfunctioning is converted into high level structural damage to tissues. Pressure damage to the sensitive tissues of the brain, kidney, lungs, and more causes large degrees of functional loss when taking place over years. In the brain, rupture of capillaries leads to countless tiny, unnoticed strokes, each destroying a small volume of brain tissue. This slowly adds up to produce cognitive decline and dementia, one small loss at a time.

Elderly people with high blood pressure, or hypertension, who took medicine to keep their 24-hour systolic blood pressure around 130 mm Hg for three years showed significantly less accumulation of harmful brain lesions compared with those taking medicine to maintain a systolic blood pressure around 145 mm Hg, according to new research. However, the reduction in brain lesions, visible as bright white spots on a magnetic resonance imaging (MRI) scan, did not translate to a significant improvement in mobility and cognitive function. Researchers said it is likely that three years was too short a time for such benefits to become apparent.

The study, called INFINITY, is the first to demonstrate an effective way to slow the progression of cerebrovascular disease, a condition common in older adults that restricts the flow of blood to the brain. The study is also unique in its use of around-the-clock ambulatory blood pressure monitors, which measured participants' blood pressure during all activities of daily living, rather than only in the medical care environment. In addition to seeing beneficial effects in the brain, those who kept their blood pressure lower also were less likely to suffer major cardiovascular events, such as a heart attack or stroke.

"I think it's an important clinical finding, and a very hopeful one for elderly people who have vascular disease of the brain and hypertension. With the intensive 24-hour blood pressure treatment we reduced the accrual of this brain damage by 40 percent in a period of just three years. That is highly clinically significant, and I think over a longer time period intensive reduction of the ambulatory blood pressure will have a substantial impact on function in older persons, as well."

Link: https://www.acc.org/about-acc/press-releases/2019/03/17/22/15/lowering-blood-pressure-prevents-worsening-brain-damage-in-elderly

T Cell Senescence Is Involved in the Disruption of Glucose Metabolism in Type 2 Diabetes

Cellular senescence is an important contributing cause of aging. Senescent cells accumulate with age and secrete a potent mix of molecules and vesicles, the senescence associated secretory phenotype. This disrupts tissue function in a range of ways, and produces chronic inflammation that accelerates the progression of all of the common age-related conditions. All forms of cell in the body appear to be capable of senescence, and the cells of the immune system are no exception. With advancing age, an increasing number of T cells of the adaptive immune system become senescent, producing the same damaging secretions.

Exactly what damage is done by senescent T cells? Firstly, it appears that they contribute to autoimmunity - which is very interesting in light of other work showing that senescent cells of other varieties also contribute to the autoimmune condition of type 1 diabetes. Secondly, senescent T cells, like other senescent cells, produce the outcome of chronic inflammation in tissues throughout the body. The harms done by inflammation sustained over the long term really can't be overstated: it degrades function and accelerates most of the aspects of degenerative aging.

Researchers here find that, interestingly, senescent T cells appear to be quite influential in the pathology of type 2 diabetes. This is near entirely a self-inflicted condition produced by the presence of excess visceral fat tissue and its distorting effect on metabolism. Type 2 diabetes appears to also result in larger numbers of senescent T cells - which fits with other evidence suggesting that the pathway of obesity, metabolic syndrome, and type 2 diabetes tends to produce more senescent cells in general, particularly in fat tissue, and leads to a shorter life expectancy and earlier onset of age-related disease.

T-cell senescence contributes to abnormal glucose homeostasis in humans and mice

Chronic inflammation is strongly associated with metabolic diseases, including diabetes and atherosclerosis. Patients with insulin resistance are considered to be at greater risk of cardiovascular disease. Proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, play essential roles in the pathogenesis of insulin resistance. Moreover, patients with prediabetes show significantly lower insulin sensitivity and higher levels of inflammatory markers than metabolically normal individuals. In addition, low-grade inflammation in prediabetes is thought to increase the risk of a cardiovascular event.

Aging of the immune system also contributes to the development of chronic inflammation and has an important effect on metabolic disease and immunologic disorders in humans. In addition, low-grade chronic inflammation is a driver of immunosenescence. The chronic inflammatory environment that is a characteristic of metabolic diseases may also be induced by augmented secretion of proinflammatory cytokines, including TNF-α and IL-6, reactive oxygen species (ROS), and acute-phase reactants released from senescent immune cells. In human studies, several lines of evidence indicate that a senescent T-cell-mediated inflammatory response is associated with the pathogenesis of acute coronary syndrome and hypertension. However, any relationship between the immunosenescence of T cells and abnormal glucose homeostasis remains to be elucidated.

In the present study, we investigate whether T-cell senescence contributes to the systemic inflammatory response in patients with prediabetes and mice with diet-induced obesity by immunologically characterizing senescent T cells. We studied the patients visiting a hospital for routine health check-ups, who were divided into two groups: normal controls and people with prediabetes. Gene expression profiling of peripheral blood mononuclear cells from normal controls and patients with type 2 diabetes was undertaken using microarray analysis. We also investigated the immunometabolic characteristics of peripheral and hepatic senescent T cells in the normal subjects and patients with prediabetes. Moreover, murine senescent T cells were tested functionally in the liver of normal or mice with metabolic deterioration caused by diet-induced obesity.

Human senescent (CD28-CD57+) CD8+ T cells are increased in the development of diabetes and proinflammatory cytokines and cytotoxic molecules are highly expressed in senescent T cells from patients with prediabetes. Moreover, we demonstrate that patients with prediabetes have higher concentrations of reactive oxygen species (ROS) in their senescent CD8+ T cells via enhancing capacity to use glycolysis. These functional properties of senescent CD8+ T cells contribute to the impairment of hepatic insulin sensitivity in humans.

Furthermore, we found an increase of hepatic senescent T cells in mouse models of aging and diet-induced obesity. Adoptive transfer of senescent CD8+ T cells also led to a significant deterioration in systemic abnormal glucose homeostasis, which is improved by ROS scavengers in mice. This study defines a new clinically relevant concept of T-cell senescence-mediated inflammatory responses in the pathophysiology of abnormal glucose homeostasis. We also found that T-cell senescence is associated with systemic inflammation and alters hepatic glucose homeostasis. The rational modulation of T-cell senescence would be a promising avenue for the treatment or prevention of diabetes.

Age-Associated B Cells in Immunosenescence

The adaptive immune system consists of many different types of cell, undertaking many different tasks, all falling into the two broad categories of T cells and B cells. With age, the immune system falls into a chronic state of inflammation and overactivation (inflammaging) at the same time as it becomes ever less capable of defending tissues against pathogens and rogue cells (immunosenescence). Researchers have identified numerous potentially harmful subpopulations of both T and B cells in the aged immune system, and in the case of B cells have even selectively removed and replaced them, a procedure that resulted in improved immune function in mice.

That demonstration in mice was accomplished nearly a decade ago, and it is disappointing that comparatively little progress towards the clinical application of this sort of approach to immune aging has occurred since then. The evidence, from many animal studies and the few human trials of immune cell clearance undertaken, clearly shows that removing and replacing the immune system is beneficial because it destroys problem populations of immune cells. The challenge lies in producing a method of clearance that has few risks and side-effects, but the component parts of that technology certainly already exist - just look at Oisin Biotechnologies' target cell destruction platform for example.

Humoral immune responses mediated by B cells are important for adaptive immunity. B cells produce a diverse set of antibodies, which help in effectively eliminating antigens including pathogens. In addition, B cells play an indispensable role in the immune system via presentation of antigens and secretion of cytokines. In aged individuals, a spectrum of immune system alterations, termed "immune senescence," result in a blunted adaptive immune response, an increased tendency for inflammatory responses, enhanced susceptibility to infections, and an increased production of autoantibodies. Multiple factors may contribute to these immune activity changes. T cells have been shown to participate in immune senescence. However, the role of B cells in this respect remains unclear.

Recent findings illustrate conspicuous shifts in B cell subsets in the elderly, suggesting that age-related changes in B cells may contribute to immune senescence. The discovery of a subset of B cells that express T-bet, termed age-associated B cells (ABCs), has drawn significant attention in recent years. Initially isolated from aged donors and found to be closely associated with immune senescence, these cells were expected to provide a novel therapeutic avenue for autoimmune diseases.

These B cells first accumulated in the spleen and increased significantly in the bone marrow with age. ABC phenotypes are distinct from other B cell subsets. ABCs expressed similar levels of IgM and lower levels of IgD compared to follicular B cells. In addition, cell cycle analyses showed that ABCs were quiescent, suggesting that they are not a subset of self-renewing cells. Because ABCs were explored using mouse models, the existence of similar cells in aged humans may need confirmation. More interestingly, B cells with phenotypes similar to that of ABCs appear in both mice and humans, during the course of certain autoimmune diseases, and following some viral infections.

ABCs responded only to TLR7 and TLR9 stimuli in vitro. They were found to secrete antibodies upon TLR stimulation rather than upon BCR stimulation. Since TLRs are commonly associated with skewing toward inflammatory responses, increased numbers of ABCs may yield more innate immune responses, characterized by low-affinity antibody, and inflammatory processes. Furthermore, ABCs directly participate in producing autoantibodies, indicating that they are associated with serious autoimmunity seen in the aged. Considered together, ABCs appear to play multiple roles in age-associated alteration of immune activity. However, antigen-presentation ability is mainly displayed in in vitro assays. Interaction of ABCs with the other immune cells in vivo may need further exploration.

Link: https://doi.org/10.3389/fimmu.2019.00318

Light Physical Activity Correlates with Reduced Risk of Cardiovascular Disease

One of the more interesting findings in the epidemiology of exercise, enabled by the development of lightweight accelerometers to measure daily activity, is that even very modest levels of movement and exertion have a significant correlation with health outcomes in later life. People who cook, walk a little, and tinker in the garden have meaningfully lower mortality rates than those who do not, and the effect scales through different degrees of this sort of low-level exercise. The important question to ask here is whether or not physical activity causes health benefits. The alternative explanation is that people who are healthier and more robust naturally tend to be more active. Human data usually doesn't allow for any inspection of causation, as opposed to the discovery of correlations, but animal studies have definitively shown that exercise causes improved health - although it doesn't appear to extend overall life span to any meaningful degree.

Despite impressive declines in age-standardized coronary heart disease (CHD) mortality rates since the 1960s, cardiovascular disease (CVD) remains the leading cause of death in the United States and globally. More than half a million older American individuals die of CVD annually. Physical activity (PA) is a key candidate for reducing CHD risk in older women. The long-standing, prevailing paradigm in PA research is that moderate to vigorous PA (MVPA) for at least 150 minutes per week is needed to prevent CVD in adults. However, a meta-analysis of 9 epidemiologic studies found reduced risks of CHD associated with levels of self-reported MVPA (≥3 metabolic equivalent tasks [METs]) that were lower than the recommended guidelines.

Light PA at intensity levels of 1.5 to 3.0 METs is poorly measured by self-reported questionnaires because they fail to capture light movements performed habitually throughout the day. Recent reports reveal that light PA measured by accelerometry is associated with reduced risks of total and CVD mortality, as well as favorable levels of CVD risk factors. In this prospective cohort study of older women, light PA measured by accelerometry was associated with a dose-responsive, independent reduced risk of incident CHD and CVD events. The highest quartile of light PA was associated with a 42% reduced risk of myocardial infarction or coronary death and a 22% reduced risk of incident CVD events compared with the lowest quartile of light PA. These reduced risks persisted after multivariable adjustment that included physical functioning and other measures of health status, even though some covariates may themselves be altered by PA and thus dilute the associations.

Link: https://doi.org/10.1001/jamanetworkopen.2019.0419

Turn.bio: Transiently Reprogramming Cells to Near Pluripotence as a Therapy for Aging

Turn.bio is Gary Hudson's latest company, now that others are running the day to day development at Oisin Biotechnologies. The Turn.bio staff are working on a particular take on the idea of inducing pluripotence in cells in vivo as a form of compensatory therapy for aging. This is a concept that struck me as being fairly crazy the first time I saw it discussed in a research publication. It is certainly possible to reliably reprogram somatic cells of near any sort into what are known as induced pluripotent stem cells, capable of differentiating into any type of cell. This is the foundation for the production of arbitrary cell types for transplantation. But doing it inside a living animal? Surely a recipe for cancer and more cancer, as the pluripotent cells replicate uncontrollably outside the normal restraints of a structured tissue.

Oddly, however, the initial outcome in mice was not cancer and more cancer. It was a set of benefits to health and tissue function that looked a lot like the results of stem cell therapies, most likely achieved via the signaling produced by the newly induced pluripotent stem cells. It remains to be seen what the risks look like over the long term, but the result prompted some interest and following studies in the research community. Given this, what if it were possible to guide cells only part-way into a pluripotent state, and only temporarily, generating beneficial signals for a time without any meaningful risk of pluripotent cells floating around in tissues for the long term? That is what the Turn.bio staff are working on. The result may be a more controllable, guided way to achieve the benefits of stem cell therapy without the stem cells. The paper here is the basis for their current development program.

Transient non-integrative nuclear reprogramming promotes multifaceted reversal of aging in human cells

The process of nuclear reprogramming to induced pluripotent Stem cells (iPSCs) is characterized, upon completion, by the resetting of the epigenetic landscape of cells of origin, resulting in reversion of both cellular identity and age to an embryonic-like state. Notably, if the expression of the reprogramming factors is applied only for a short time and then stopped - before the so-called Point of No Return (PNR) - the cells return to the initiating somatic cell state. These observations suggest that if applied for a short enough time (transient reprogramming), the expression of reprogramming factors fails to erase the epigenetic signature defining cell identity; however, it remains unclear whether any substantial and measurable reprogramming of cellular age can be achieved before the PNR and if this can result in any amelioration of cellular function and physiology. To test this, we first evaluated the effect of transient reprogramming on the transcriptome of two distinct cell types - fibroblasts and endothelial cells - from aged human subjects, and we compared it with the transcriptome of the same cell types isolated from young donors.

We utilized a non-integrative reprogramming protocol that we optimized, based on a cocktail of mRNAs expressing OCT4, SOX2, KLF4, c-MYC, LIN28 and NANOG (OSKMLN). Our protocol consistently produces induced pluripotent stem cell (iPSC) colonies, regardless of age of the donors, after 12-15 daily transfections; we reasoned that the PNR in our platform occurs at about day 5 of reprogramming, based on the observation that the first detectable expression of endogenous pluripotency-associated lncRNAs occurs at day 5. Therefore, we adopted a transient reprogramming protocol where OSKMLN were daily transfected for four consecutive days, and performed gene expression analysis two days after the interruption.

Analysis of transcriptomic signatures revealed that transient reprogramming triggers a more youthful gene expression profile, while retaining cell identity. Epigenetic clocks based on DNA methylation levels are the most accurate molecular biomarkers of age across tissues and cell types and are predictive of a host of age-related conditions including lifespan. Exogenous expression of canonical reprogramming factors (OSKM) is known to revert the epigenetic age of primary cells to a prenatal state. To test whether transient expression of OSKMLN could reverse the epigenetic clock, we used two epigenetic clocks that apply to human fibroblasts and endothelial cells: Horvath's original pan-tissue epigenetic clock, and the more recent skin and blood clock. According to the pan-tissue epigenetic clock, transient OSKMLN significantly reverted the DNA methylation age.

This data demonstrates that transient expression of OSKMLN can induce a rapid, persistent reversal of cellular age in human cells at the transcriptomic, epigenetic, and cellular levels . Importantly, these data demonstrate that the process of "cellular rejuvenation" - that we name Epigenetic Reprogramming of Aging, or "ERA" - is engaged very early and rapidly in the iPSC reprogramming process. These epigenetic and transcriptional changes occur before any epigenetic reprogramming of cellular identity takes place, a novel finding in the field.

Sarcopenia is an age-related condition that is characterized by loss of muscle mass and force production. We wanted to test whether transient reprogramming of aged muscle stem cells (MuSCs) would improve a cell-based treatment in restoring physiological functions of muscle of older mice. To test this, we first performed electrophysiology to measure tetanic force production in tibialis anterior (TA) muscles isolated from young (4 months) or aged (27 months) immunocompromised mice. We found that TA muscles from aged mice have lower tetanic forces compared to young mice, suggesting an age-related loss of force production. Next, we isolated MuSCs from aged mice (20-24 months). After treating aged MuSCs, we transplanted them into injured TA muscles of aged (27 months) immunocompromised mice. We waited 30 days to give enough time to the transplanted muscles to fully regenerate. We then performed electrophysiology to measure tetanic force production.

Muscles transplanted with untreated aged MuSCs showed forces comparable to untransplanted muscles from aged control mice. Conversely, muscles that received treated aged MuSCs showed tetanic forces comparable to untransplanted muscles from young control mice. These results suggest that transient reprogramming in combination with MuSC-based therapy can restore physiological function of aged muscles to that of youthful muscles.

Chronic Periodontitis Only Modestly Raises the Risk of Dementia

Periodontitis is the later stage of gum disease, an inflammatory condition largely caused by particular strains of bacteria found in the mouth. While there is a fair amount of promising work related to destroying or sabotaging the disease-causing mechanisms of those bacterial species, nothing has yet made the leap to earnest clinical development. It is thought, based on epidemiological data showing an association with mortality, and on a reasonable examination of the mechanisms involved, that periodontitis can spread inflammatory signaling elsewhere in the body, particularly to the heart and the brain, and thereby accelerate the progession of age-related conditions. The research here, however, using study data for a large number of patients, shows only a modest effect on the incidence of dementia due to the presence of periodontitis.

Gum disease (gingivitis) that goes untreated can become periodontitis. When this happens, the infection that affected your gums causes loss in the bone that supports your teeth. Periodontitis is the main cause of tooth loss in adults. Interestingly, periodontitis is also a risk factor for developing dementia, one of the leading causes for disability in older adults. Recently, researchers in South Korea studied the connection between chronic periodontitis and dementia. The research team examined information from the National Health Insurance Service-Health Screening Cohort (NHIS-HEALS). In South Korea, the NHIS provides mandatory health insurance covering nearly all forms of health care for all Korean citizens. The agency also provides health screening examinations twice a year for all enrollees aged 40 years or older and maintains detailed health records for all enrollees.

The researchers looked at health information from 262,349 people aged 50 or older. All of the participants were grouped either as being healthy (meaning they had no chronic periodontitis) or as having been diagnosed with chronic periodontitis. The researchers followed the participants from January 1, 2005 until they were diagnosed with dementia, died, or until the end of December 2015, whichever came first. The researchers learned that people with chronic periodontitis had a 6 percent higher risk for dementia than did people without periodontitis. This connection was true despite behaviors such as smoking, consuming alcohol, and remaining physically active.

Link: https://www.healthinaging.org/blog/periodontitis-may-raise-the-risk-for-developing-dementia/

David Sinclair on the Academy for Health and Lifespan Research

The Academy for Health and Lifespan Research was recently announced, an initiative analogous to that of the long-running Longevity Dividend group, but hopefully more energetic and more focused on at least some rejuvenation biotechnologies such as senolytic therapies. The principals include many of the researchers now involved in startup biotech companies working on ways to intervene in the mechanisms of aging, and the goal is to generate greater support for development of means to slow or reverse aging and age-related disease. David Sinclair is associated with Life Biosciences and its collection of portfolio companies, and here discusses the Academy and its future role.

Tell me about the academy. Is it intended to be mainly an advocacy organization?

The academy has been formed because our field of aging and longevity research has reached a point of maturity where the leaders in the field believe that we can have - or will have - a big impact on the planet. That impact will be in medicine, in health span, and in its knock-on effect on everything from human productivity to Social Security. We wanted to come together to speak with one voice, to be able to help corporations and governments understand what things they should be thinking about now and give realistic projections of what life is going to be like 10, 20, 50 years from now. Because it's not a question of if there's going to be an impact, it's really a question of what kind of a future we want to build when this happens.

What kind of impact are we talking about? When you think about 10, 20, 50 years in the future, how do you see aging being transformed in the U.S. and around the world?

By impact, I mean that instead of tackling one disease at a time, which is the way 20th-century medicine and pharmaceutical development was practiced, we believe we can develop medicines that will treat aging at its source and thereby have a much greater impact on health and lifespan than drugs that target a single disease. Heart disease medicine may keep your heart healthy for an extra five or 10 years, but does nothing for your brain. So, we're ending up with a population of people who live longer but not better and who need a lot of help, if they're not completely in the grip of dementia. We don't think that's necessarily the only or the best approach.

Now, we have the knowledge. We're developing the technologies to not just delay these diseases of aging but actually reverse aspects of them. Imagine you have a treatment for heart disease, but as a side effect you'd also be protected against Alzheimer's, cancer, and frailty. You'd live a longer and healthier life. The reason we can extend the lifespan of animals is not because we can just make them live longer, but we keep them healthy. The animals don't get heart disease, cancer, Alzheimer's, until sometimes 20 percent later in their life. And so that's 20 percent longer youth, not just 20 percent longer life.

Are there regulatory hurdles? When we've spoken in the past, you've mentioned that the FDA considers aging a natural process and therefore won't approve drugs to treat it.

Opinions are changing rapidly about whether aging should be a condition that a doctor can prescribe a medicine for. We currently live in a world where aging is so common that it's considered by most of the world, including the medical community, as something that's natural and inevitable. And if something's considered inevitable, typically you don't focus on it in the same way as something you can treat. Cancer was a natural part of life at one time, in the same way that aging is today. A hundred years ago, doctors didn't focus on treating cancer as much as we do now, because then you couldn't do much, if anything, about it.

There are now dozens of companies working on therapies that could potentially extend overall human health and lifespan, but none of them are working specifically toward an approval for aging because the FDA wouldn't even know where to start. But that may be changing quickly. I've been part of a group that talked with the FDA, and they are willing and also quite enthusiastic about considering a change that defines aging as a disease. They would like us, first, to show that it's possible to change the rate of aging, which in my view is backward, but that's what they want. In Australia, the government is 100 percent behind this, at the FDA level and in the Ministry for Health. I'm hopeful that one country in the world - it may be Australia, it may be the U.S., it may be an Asian country - will change its definition of aging. Once one country changes its definition, then it will be a domino effect and the others will follow.

Link: https://news.harvard.edu/gazette/story/2019/03/anti-aging-research-prime-time-for-an-impact-on-the-globe/

The Importance of Preventing High Blood Pressure in Aging

Raised blood pressure with age, hypertension, is a major downstream consequence of low-level biochemical damage and cellular dysfunction, converting it into high-level structural damage in the body and brain. Hypertension is an important proximate contributing cause of ultimately fatal age-related conditions of the cardiovascular system, kidneys, brain, and lungs, among others. Pressure damage in delicate tissues degrades function in many organs, particularly in the central nervous system where there is little to no regeneration capable of reversing that damage. More subtly, hypertension also causes heart muscles to enlarge and weaken, contributing to heart failure. Hypertension also accelerates the development of atherosclerosis, through mechanisms independent of other factors such as chronic inflammation.

Hypertension is so great a contribution to age-related disease, such an important mediating mechanism, that it is possible to produce sizable reductions in mortality by forcing a lower blood pressure, even without addressing the underlying causes in any way. The widespread use of antihypertensive medications to achieve this goal is one of the success stories of mainstream medicine in recent decades. There are, sadly, not all that many mechanisms that rise to this level of importance as single downstream consequences of low-level biochemical damage in aging. Chronic inflammation is another, but beyond that the only way to make significant progress towards control of aging is to repair the underlying damage. Attempting to address downstream consequences is largely very hard and of limited utility. Control of blood pressure and inflammation are outliers in this context.

Sustained blood pressure control and coronary heart disease, stroke, heart failure, and mortality: An observational analysis of ALLHAT

Treatment and control of high blood pressure (BP) is a key strategy for reducing coronary heart disease (CHD), stroke, heart failure (HF), and all-cause mortality among adults with hypertension. Accordingly, clinical practice guidelines provide recommendations for accurately identifying adults with hypertension, initiating appropriate antihypertensive therapy, and achieving predefined BP goals that have been shown to be associated with lower cardiovascular disease (CVD) and all-cause mortality event rates in randomized trials. However, less is known about the role of sustaining BP control over time.

In clinical practice, patients may be followed over many years and often experience times of controlled as well as uncontrolled BP. There are several reasons why BP control may change over time, including changes in patients' health status or medication adherence, variability in BP measurement from visit to visit, or reduction in antihypertensive medication intensity due to concerns about overtreatment on the part of the provider. The proportion of visits at which patients achieve BP control can easily be calculated, could be used to facilitate discussions with patients about treatments goals, and could be used as a performance measure for quality improvement. Also, data on the effects of maintaining sustained BP control could be used to support greater treatment consistency over time or conversely, to allow higher BP levels at some visits.

Findings from a limited number of studies suggest that having BP control at a greater proportion of visits over time is associated with a lower CVD risk. However, prior studies included primarily white participants, those with existing coronary heart disease (CHD), or with multiple CVD risk factors. The purpose of the current study was to determine the association of sustained BP control with CHD, stroke, HF, and mortality in an observational analysis of a demographically and clinically diverse population within a large clinical trial, the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). Participation was restricted to 24,309 participants with four to seven visits with systolic BP (SBP) measurements during a 22-month period. Participants were as having sustained BP control (SBP lower than 140 mm Hg) at 100%, 75% to 100%, 50% to 75%, and fewer than 50% of visits during this period.

In this observational analysis of participants from ALLHAT, those with SBP control, defined as SBP lower than 140 mm Hg at fewer than 50% of study visits, were more likely to have a stroke, develop HF, or experience the combined outcome of fatal CHD/nonfatal myocardial infarction, stroke, or HF. These associations were present after adjustment for potential confounders. Compared to those with SBP control at 100% visits, adjusted hazard rations among those with SBP control at fewer than 50% of visits was 1.16 for fatal CHD/nonfatal myocardial infarction, 1.71 for stroke, 1.63 for heart failure, 1.39 for the composite CVD outcome, and 1.14 for mortality. Sustained SBP control may be beneficial for preventing stroke, heart failure, and CVD outcomes in adults taking antihypertensive medication.

Improvement in Heart Attack Incidence and Outcomes Over the Past Twenty Years

The story of the past few decades has been a steady reduction in the incidence and mortality of the major age-related diseases that dominated old age in the last century. This has been a strange triumph, in the sense that it was achieved using very inefficient strategies for medical research and development, coupled with an aggressive push towards prevention through lifestyle choice. At no point were the causes of aging deliberately targeted; instead medical efforts focused on tinkering with the downstream consequences of the late disease state. That this combination nonetheless achieved the results that it did is a testament to the dedication of researchers and clinicians. Imagine how much could be achieved given a better research and development strategy, one capable of producing rejuvenation via repair of the causes of aging.

Heart attack prevention and outcomes have dramatically improved for American adults in the past two decades. Compared to the mid-1990s, Americans today are less likely to have heart attacks and also less likely to die from them. Tracking more than four million Medicare patients between 1995 and 2014, this is the largest and most comprehensive study of heart attacks in the United States to date. Its two key findings are that hospitalizations for heart attacks have declined by 38%, and the 30-day mortality rate for heart attacks is at an all-time low of 12%, down by more than a third since 1995.

The researchers believe these gains are no accident. The last 20 years have been marked by national efforts to prevent heart attacks and improve care for those who suffer them. The Centers for Medicare and Medicaid Services, the American College of Cardiology, and the American Heart Association - along with other organizations and "legions of researchers and clinicians and public health experts" - have focused on reducing risk by promoting healthy lifestyles, addressing risk factors, and improving the quality of care.

While the study tallies the impressive overall gains, it also sheds light on the health outcome disparities in America on a county by county basis. "Priority health areas," which were previously identified as lagging areas, saw little or no change in their 30-day mortality rates following heart attack in the past two decades - indicating that they should receive particular attention in future healthcare improvement activities. "We are now at historic lows in the rates of heart attacks and deaths associated with heart attacks. However, this is no time to be complacent. We document extraordinary gains - but the effort is far from finished. The goal is to one day relegate heart attacks to the history of medicine."

Link: https://news.yale.edu/2019/03/15/1990s-heart-attacks-have-become-less-deadly-frequent-americans

Restoring Sight by Making Retinal Ganglion Cells Light Sensitive via Gene Therapy

Retinal degeneration causes blindness by destroying the photoreceptor cells in the retina. Some forms of degenerative blindness leave intact other cell populations, however. What if those populations could be granted some of the same mechanisms used by photoreceptor cells to pass signals to the optic nerve? Researchers here demonstrate a gene therapy that does just this, a most interesting feat of engineering. It is still a poor alternative to prevention of the condition, or restoration of lost photoreceptor cells, but it is no less impressive for it. This is truly an age of biotechnology.

Scientists inserted a gene for a green-light receptor into the eyes of blind mice and, a month later, they were navigating around obstacles as easily as mice with no vision problems. They were able to see motion, brightness changes over a thousandfold range and fine detail on an iPad sufficient to distinguish letters. The researchers say that, within as little as three years, the gene therapy - delivered via an inactivated virus - could be tried in humans who've lost sight because of retinal degeneration, ideally giving them enough vision to move around and potentially restoring their ability to read or watch video.

Correcting the genetic defect responsible for retinal degeneration is not straightforward, because there are more than 250 different genetic mutations responsible for retinitis pigmentosa alone. About 90 percent of these kill the retina's photoreceptor cells - the rods, sensitive to dim light, and the cones, for daylight color perception. But retinal degeneration typically spares other layers of retinal cells, including the bipolar and the retinal ganglion cells, which can remain healthy, though insensitive to light, for decades after people become totally blind. In their trials in mice, the team succeeded in making 90 percent of ganglion cells light sensitive.

To reverse blindness in these mice, the researchers designed a virus targeted to retinal ganglion cells and loaded it with the gene for a light-sensitive receptor, the green (medium-wavelength) cone opsin. Normally, this opsin is expressed only by cone photoreceptor cells and makes them sensitive to green-yellow light. When injected into the eye, the virus carried the gene into ganglion cells, which normally are insensitive to light, and made them light-sensitive and able to send signals to the brain that were interpreted as sight.

Link: https://news.berkeley.edu/2019/03/15/with-single-gene-insertion-blind-mice-regain-sight/

Ccna2 as a Novel Regulator of Cellular Senescence

Given the present wave of investment into the treatment of aging, in both the business and research communities, and given the significant valuations put on the first companies working on senolytic drugs to clear senescent cells, it should come as no surprise to see a land rush underway in the investigation of the biochemistry of cellular senescence. The state of funding for any specific field of research is to a sizable degree steered by what is going on in the world of startups and venture capital. When finding a new mechanism is a potential ticket to valuable intellectual property, a startup company, and production of clinical therapies, then there will be more funding available for researchers involved in the search for mechanisms, and more researchers joining in.

Senescent cells are clearly significant in all aspects of aging, and removing them is proving, in mice at least, to produce robust reversal of aging and age-related disease. Senescent cells, while small in number even in old individuals, produce a potent mix of signals known as the senescence-associated secretory phenotype, or SASP. This SASP generates chronic inflammation, changes the behavior of normal cells for the worse, destructively remodels the extracellular matrix, and more. In some ways it might be considered an actively maintained aspect of aging. Removing senescent cells removes this signaling, and restores tissue function as a result. Other researchers are interested in modulating or suppressing the SASP, but I have to think that this is a much more challenging proposition, given the complexity of SASP signaling.

The open access paper here is an illustrative example of the sort of detailed investigation of the mechanisms of cellular senescence that is taking place today. Some will give rise to efforts to develop new therapies to destroy, prevent, or alter the behavior of senescent cells. This sort of work is spreading and well funded to a degree that would have been unimaginable prior to the noted 2011 demonstration of the relevance of senescent cells to aging. All of this is driven by success in showing that removal of senescent cells reverses aging and age-related disease, and by the significant investment in clinical development that followed.

The p53/miRNAs/Ccna2 pathway serves as a novel regulator of cellular senescence: Complement of the canonical p53/p21 pathway

It is demonstrated that the presence and progressive accumulation of senescent cells contribute to overall organism aging; senescent cells aggregate in aging tissues have been considered as a causal factor for aging-related disorders. Senescent cells are characterized as irreversible growth arrest, increased senescence-associated β-galactosidase activity, and undergo distinctive phenotypic alterations, including profound chromatin and secretome changes. Research over last three decades has uncovered a variety of signaling pathways that are involved in the regulation of cellular senescence and determine the lifespan in a manner conserved across species, including insulin growth factor 1 (IGF-1) signaling (IIS), rapamycin (mTOR) signaling, and the sirtuin family. Additionally, p53 activation exerts critical roles in modulating cellular senescence and organismal aging. Senescence-induction stressors including DNA lesions, telomere shortening, oxidative stress, and oncogene activation, initially halt cell cycle progression through p53-mediated induction of p21 and finally trigger cellular senescence.

MicroRNAs (miRNAs) are conserved tiny noncoding RNAs generated from endogenous hairpin-shaped precursors, which have emerged as novel and fundamental actors in gene regulation. These small RNA molecules can direct bind to specific sites presented in target messenger RNA (mRNA). As the recognition of target mRNAs mainly depends on the seed region of the mature miRNA, one single miRNA might regulate hundreds of target mRNAs; meanwhile, distinct miRNAs might co-regulated the same mRNA, thus orchestrating a large variety of physiological and cellular processes. Recently, a growing body of evidence has suggested the potential role of miRNAs in modulating the aging process and cellular senescence. In this work, we evaluated the miRNA and mRNA profile in the physiological aging 20-month-old mouse model by high-throughput analysis.

The data showed that various p53 responsive miRNAs, including miR-124, miR-34a and miR-29a/b/c, were up-regulated in the aging mouse compared to the young mouse. Further investigation unraveled that, similarly to miR-34a and miR-29, miR-124 significantly promoted cellular senescence. As expected, mRNA microarray and gene co-expression network analysis unveiled that the most down-regulated mRNAs were enriched in the regulatory pathways of cell proliferation. Fascinatingly, among these down-regulated mRNAs, Ccna2 stood out as a common target of several p53 responsive miRNAs (miR-124 and miR-29), which functioned as the antagonist of p21 in cell cycle regulation.

Silencing of Ccna2 remarkably triggered the cellular senescence, while Ccna2 overexpression delayed cellular senescence and significantly reversed the senescence-induction effect of miR-124 and miR-29. Moreover, these p53 responsive miRNAs were significantly up-regulated during the senescence process of p21-deficient cells; overexpression of p53 responsive miRNAs or knockdown of Ccna2 evidently accelerated the cellular senescence in the absence of p21. Taken together, our data suggested that the p53/miRNAs/Ccna2 pathway might serve as a novel senescence modulator independent of p53/p21 pathway.

Proposing the IMM-AGE Metric to Measure the Aging of the Immune System

Determinations of biological age based on ever more detailed measurements of human cellular biochemistry are known as clocks. Biological age is distinct from chronological age, as different people age at somewhat different rates. Aging is an accumulation of cell and tissue damage and the consequences of that damage; more damage means a higher biological age. The best known clock examples are the well known varieties of epigenetic clock, based on patterns of DNA methylation that decorate the genome. In recent years, researchers have been rapidly developing other sorts of clock, using other measures of cellular biochemistry and metabolism. The one here is an example of the type, focused on immune system function.

The immune system is the critical function in the body for managing health. It is a complex system with hundreds of different cell-types. Until now, no metric had existed to quantify an individual's immune status. New data, while requiring further development, describes a metric (called IMM-AGE) by which we can accurately understand a person's immune status, providing increased information for accurate prediction and management of risks for disease and death.

This new capability will have drug development implications: Given the importance of immune status in vaccine response, this new data could play a significant role in both the design of future vaccine trials and in re-evaluating past vaccine trials. Moreover, this new metric for immune aging could see chronological age augmented by "immune age" as a way of improving drug development programs - providing for enhanced clinical trial entry/exclusion criteria that can elicit a more homogenous response and greater likelihood of success.

The researchers developed their unique data by following a group of 135 healthy volunteers for nine years, taking annual blood samples which were profiled against a range of 'omics' technologies (cell subset phenotyping, functional responses of cells to cytokine stimulations and whole blood gene expression). This captured population- and individual-level changes to the immune system over time, which when analyzed using a range of novel, immune aligned, machine learning analytical technologies, enabled identification of patterns of cell-subset changes, common to those in the study, despite the large amount of variation in their immune system states. The data and metrics generated was then validated against a cohort of more than 2,000 patients from the Framingham Heart Study.

Link: https://www.eurekalert.org/pub_releases/2019-03/c-ndu031119.php

Burden of Age-Related Disease Varies Broadly Between Regions of the World

Researchers here present an interesting view of the variance in the burden of age-related disease exhibited by populations around the world. Unsurprisingly, the impact of age falls most heavily on those living in the poorest and least developed regions. Modern medicine and the other comforts of technology, for all that they do not directly target the causes of aging, do manage to have a sizable influence on the pace at which aging and age-related disease progresses over a lifetime. The largest gaps are mostly likely due to a combination of sanitation, particulate exposure from fires, and control of pathogens - akin to the difference between today and the 19th century. But the underlying reasons for the differences between wealthier nations, such as Japan versus countries of Western Europe, tend to be harder to pin down.

A 30-year gap separates countries with the highest and lowest ages at which people experience the health problems of a 65-year-old. Researchers found 76-year-olds in Japan and 46-year-olds in Papua New Guinea have the same level of age-related health problems as an "average" person aged 65. These negative effects include impaired functions and loss of physical, mental, and cognitive abilities resulting from the 92 conditions analyzed, five of which are communicable and 81 non-communicable, along with six injuries.

The study is the first of its kin. Where traditional metrics of aging examine increased longevity, this study explores both chronological age and the pace at which aging contributes to health deterioration. The study uses estimates from the Global Burden of Disease study (GBD). Researchers measured "age-related disease burden" by aggregating all disability-adjusted life years (DALYs), a measurement of loss of healthy life, related to the 92 diseases. The findings cover 1990 to 2017 in 195 countries and territories. For example, in 2017, people in Papua New Guinea had the world's highest rate of age-related health problems with more than 500 DALYs per 1,000 adults, four times that of people in Switzerland with just over 100 DALYs per 1,000 adults. The rate in the United States was 161.5 DALYs per 1,000, giving it a ranking of 53rd, between Algeria at 52nd with 161.0 DALYs per 1,000 and Iran at 54th with 164.8 DALYs per 1,000.

Using global average 65-year-olds as a reference group, researchers also estimated the ages at which the population in each country experienced the same related burden rate. They found wide variation in how well or poorly people age. Ranked first, Japanese 76-year-olds experience the same aging burden as 46-year-olds in Papua New Guinea, which ranked last across 195 countries and territories. At 68.5 years, the United States ranked 54th, between Iran (69.0 years) and Antigua and Barbuda (68.4 years).

Link: http://www.healthdata.org/news-release/what-age-do-you-feel-65

SGLT-2 Inhibitors as Calorie Restriction Mimetics

SGLT-2 inhibitors, or gliflozins, are a newer and still expensive class of anti-diabetic drug. They work by interfering in the trafficking of glucose, preventing the kidney from reclaiming glucose and introducing it back into the bloodstream. The glucose is instead excreted. Analogously to metformin, another anti-diabetic drug, it is proposed that inhibition of SGLT-2 in some ways mimic the effects of calorie restriction, triggering beneficial cellular housekeeping mechanisms that usually only turn on during periods of fasting or low calorie intake. Size of effect and degree of side-effects are always the questions in these matters, however. One should hold back any nascent enthusiasm until able to find reliable answers in the literature.

Evidently, a faction of the research community thinks that metformin has a large enough effect size to run a human trial versus aging, in order to push the FDA into accepting aging as an indication. Following that same line of thinking, these researchers would probably also consider this strategy for one or more SGLT-2 inhibitors. That said, one of the points of using metformin as the lever, to try to make the FDA reconsider aging as a medical condition that can be treated, is that metformin is very widely used and has a long history of use. Not that it is particularly effective in the grand scheme of things. It is hard for the FDA to object to it on any grounds other than aging not being a formally defined and approved medical condition that people are permitted to treat, which is exactly the battle that researchers wish to take place.

SGLT-2 inhibitors induce a fasting state that triggers metabolic benefits

SGLT-2 inhibitors are a relatively new class of diabetes drugs that have shown many benefits for people with type 2 diabetes who have not responded well to previous interventions. Researchers set out to understand how these benefits happen. They found that SGLT-2 inhibitors induce a fasting state in the body without requiring the patient to sharply cut back on food intake.

The researchers studied SGLT-2 inhibitors in a series of animal studies. First, they split the animals into two groups. One ate a normal diet and the other consumed a high fat diet. The high fat diet induced an insulin-resistant, diabetes-like state. They then split the animals into the three different cohorts. One group maintained their original diets. The second group maintained their original diets but also took SGLT-2 inhibitors. The third group matched the weight loss of group two through other methods, to confirm that any beneficial effects seen in group two were a result of SGLT-2 inhibitors and not weight loss in general. The researchers confirmed that the group given the medication saw a large boost to their metabolic processes due to the activation of pathways associated with fasting. "Lowering glucose by this mechanism shifts metabolism toward beneficial pathways that help to reduce fat accumulation in tissues. It causes the liver to think that it's in a fasting state and therefore a lot of pathways and genes are turned on that are similar to what you would see when someone is fasting."

These include pathways typically activated during situations that cause a lack of available nutrients in the body, such as exercise or calorie intake reduction. SGLT-2 inhibitors also blocked a pathway that can cause insulin resistance. The researchers also identified a new hormone mediator of SGLT-2 inhibitor treatment. Mice treated with SGLT-2 inhibitor medication had elevated levels of FGF-21, a hormone known to induce beneficial metabolic effects. Using mice lacking FGF-21, they found that FGF-21 was required for the weight loss and reduced body fat. FGF-21 did not play any role in the reduction of fat deposition in the liver. One mystery still remains, however: what are the specific mechanisms behind the reduction in cardiovascular disease risk observed in humans? This will be an important question for future studies.

SGLT2 inhibition reprograms systemic metabolism via FGF21-dependent and -independent mechanisms

SGLT2 inhibitors (SGLT2i) are unique antidiabetic drugs that promote urinary glucose loss and increase the urinary threshold for glucose reabsorption. As a result, plasma glucose levels are reduced and overall glycemic control is improved. Intriguingly, SGLT2i, including canagliflozin (CANA), have recently been shown to reduce cardiovascular and all-cause mortality in type 2 diabetes (T2D) and may improve hepatic steatosis and nonalcoholic fatty liver disease. The cellular actions of SGLT2i are distinct from those of other medications for T2D, such as insulin sensitizers and insulin secretagogues, which reduce blood glucose but increase glucose uptake and promote weight gain. By contrast, SGLT2i act in an insulin-independent manner to cause modest weight loss, promote fatty acid oxidation and ketogenesis, and increase hepatic glucose production, even after a single dose. The unique induction of fatty acid oxidation and ketogenesis by SGLT2i may contribute to not only beneficial outcomes, but also ketoacidosis reported with this medication class.

Here, we utilize an integrated transcriptomic-metabolomics approach to identify molecular mediators of CANA in nondiabetic mice with diet-induced obesity. We demonstrate that CANA modulates key nutrient-sensing pathways, with activation of 5′ AMP-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin (mTOR), without changing insulin or glucagon sensitivity or signaling. Moreover, CANA induces transcriptional reprogramming to activate catabolic pathways, increase fatty acid oxidation, reduce hepatic steatosis, and increase hepatic and plasma levels of the hepatokine FGF21. FGF21 is an important coordinator of fasting-induced metabolic responses and reduction in adiposity via increasing lipolysis, hepatic fatty acid oxidation, and ketogenesis. Given that these effects mirror many phenotypes induced by CANA, we hypothesized that FGF21 would be required for CANA action. Using FGF21-null mice, we demonstrate that FGF21 is not required for the metabolic switch toward a fasting-like catabolic state but is required to promote lipolysis and reduction in adiposity in response to SGLT2i.

A Review of DNA Methylation Based Epigenetic Clocks as a Measure of Aging

Epigenetic clocks measure DNA methylation of sites on the genome that are patterned in much the same way in every individual of a given age. DNA methylation is an epigenetic marker that serves to regulate the production of protein from a specific gene. A range of different clocks have been constructed based on weighted assessments of methylation at various points on the genome, and the best of them can measure age quite accurately, to within a few years.

The clocks were built by working backwards from DNA methylation and age data, and it was discovered along the way that people with methylation patterns characteristic of an older age have a worse prognosis for age-related disease and mortality, or have a greater tendency to already exhibit age-related diseases. It is unclear, however, as to what exactly epigenetic clocks really are measuring. Which of the underlying forms of damage and consequent dysfunction, outlined in the SENS rejuvenation research proposals, lead to these DNA methylation changes? Some of them? All of them? No-one can presently say, and that is a challenge if the research community is to use epigenetic clocks to assess potential rejuvenation therapies.

The development of tools to diagnose and predict age-dependent risks has enormous significance in preventing age-related diseases and improving the health status of the elderly. The process of aging results in multiple changes at both the molecular and cellular level, including cellular senescence, telomere attrition, and epigenetic alterations. Among these hallmarks, telomere length, which experiences progressive shortening during replication of somatic cells, is a remarkable characteristic of aging and linked with age-related health status. However, recent evidence has revealed that the correlation between telomere length and age-related outcomes of individuals is low. Thus, investigators are still searching for other biomarkers that can be used in the prediction of age-related outcomes with higher accuracy.

Current studies have indicated that epigenetic changes comprise a significant component of the aging process. Epigenetics refer to the modulation of gene activity without any change in the genomic sequence. Well-studied epigenetic modifications include DNA methylation, histone modification, and non-coding RNA, with changes in dynamic DNA methylation found to be most associated with the aging process. In general, age-dependent changes in DNA methylation include global hypomethylation and region-specific hypermethylation.

Abundant studies have demonstrated a close relationship between DNA methylation and aging and longevity. These findings have impelled researchers to develop age predictors based on the correlation between methylation changes and chronological age. DNA methylation age, evaluated by these predictors, reflects the biological age of a person, which has a close association with individuals' health status and can be changed by multiple risk factors, such as smoking and obesity. Therefore, the difference between DNA methylation age and chronological age may be a promising tool in predicting disease risk and longevity potential in early life.

Link: https://doi.org/10.3389/fgene.2019.00107

Greater Fitness in Old Age Correlates with Greater Ten Year Survival Rates

The research materials here make a good companion piece to a recent study showing that exercise performance, physical fitness in other words, predicts mortality more accurately than age. In the study here, much the same analysis is carried in a different patient population, a sizable group with an average age of 75 at the study outset. Ten years after fitness testing was carried out, mortality data for the study population shows that those of greater fitness were significantly more likely to survive. We shouldn't need any more incentives than already exist to stay active and fit for as long as we can in live, but add this one to the mountain of evidence on the topic.

Doctors use cardiovascular risk factors to help guide decisions about preventive measures and medications. Previous studies have shown that quitting smoking and controlling blood pressure, cholesterol, and diabetes can reduce heart disease risk. However, most studies of cardiovascular risk factors have focused on middle-aged people, leaving a knowledge gap regarding the importance of these risk factors in older people.

The team analyzed medical records from more than 6,500 people aged 70 years and older who underwent an exercise stress test between 1991 and 2009. They assessed fitness based on patients' performance during the exercise stress test, which required patients to exercise on a treadmill as hard as they could. They divided patients into three groups reflecting their fitness based on the number of METs (metabolic equivalents, a measure of exercise workload) they achieved during the test: most fit (10 or more METs), moderately fit (six to 9.9 METs) and least fit (six or fewer METs). For this study, the researchers grouped patients with zero, one, two, or three or more cardiovascular risk factors.

On average, participants were 75 years old when they underwent the stress test. Researchers tracked the patients for an average of just under 10 years, during which time 39 percent of them died. Over this period, the researchers found higher fitness was associated with significantly increased rates of survival. The most fit individuals were more than twice as likely to be alive 10 years later compared with the least fit individuals. In contrast, a patient's total number of cardiovascular risk factors was not associated with their risk of death and patients with zero risk factors had essentially the same likelihood of dying as those with three or more risk factors. The study did not account for any changes in fitness level that the participants may have experienced over time. However, previous studies have suggested that improving fitness can help improve heart health, even late in life.

Link: https://www.eurekalert.org/pub_releases/2019-03/acoc-hfl030519.php

Signs of Cellular Senescence in Aged Bone Marrow, Contributing to Impaired Generation of Immune Cells

The accumulation of lingering senescence cells with age is apparently there to be discovered in every tissue in the body, and researchers are gathering a great deal of data now that it is generally accepted that these errant cells are one of the causes of aging. The overt signs of cellular senescence in a tissue are much the same throughout the body, even if there may well be significantly different classes of senescent cell still to be categorized. All senescent cells examined to date generate inflammatory, harmful secreted molecules that rouse the immune system, disrupt surrounding cell activities, destructively remodel the extracellular matrix, and more. All of this is a necessary part of regeneration when it takes place over the short term, but when the secretions of senescent cells continue without resolution, over years, the diseases, declines, and chronic inflammation of aging emerge.

In today's open access paper, researchers identify signs of cellular senescence in bone marrow cell populations as a contributing factor to the age-related decline of hematopoietic activity, the very necessary creation of immune and blood cells by hematopoietic stem cells. A reduced supply of new immune cells is one of the major contributing causes of age-related immunosenescence, the faltering of the immune system. The immune system is so fundamental to health that its fall into chronic inflammation and ineffectiveness may be a primary driver of human late-life mortality. Certainly, there is a wide range of evidence linking aspects of immune function with mortality in human cohorts.

What do we do about cellular senescence? We deploy senolytic therapies systemically throughout the body, targeting senescent cells for destruction by triggering apoptosis. The initial set of senolytic compounds used in research and early testing seem moderately effective in mice, clearing up to half of senescent cells from some tissues, and human data is starting to arrive this year. These compounds are cheap and easily obtained by those who don't wish to wait five to ten years for an expensive (and only maybe improved) version to emerge from the regulatory pathway of clinical trials. The research community will be kept quite busy in the years ahead by assessing cellular senescence, and then the removal of senescent cells, in the context of each and every decline of aging. But anyone willing to accept the risks of self-experimentation, after reading through the existing evidence and making an informed decision, can always choose to forge ahead today and try for themselves, to see what happens to their own age-related conditions.

An early-senescence state in aged mesenchymal stromal cells contributes to hematopoietic stem and progenitor cell clonogenic impairment through the activation of a pro-inflammatory program

Hematopoietic stem and progenitor cells (HSPC) can self-renew and differentiate into all blood components thus serving as a reservoir for mature blood cells throughout life. However, as we age, HSPC functionality is impaired with cells displaying a reduced capacity to maintain tissue homeostasis. Hematopoietic stem and progenitor cells reside in the bone marrow (BM) niche, and their function is supported by a variety of both hematopoietic and nonhematopoietic cell types, such as osteoblasts, adipocytes, endothelial, and mesenchymal stromal cells (MSC). Several studies highlighted the key role of MSC in regulating HSPC fate and promoting engraftment of the rare and more primitive hematopoietic stem cells (HSC). Indeed, changes in the cellular composition of the HSC niche during aging contribute to hematologic decline and involve decreased bone formation, enhanced adipogenesis, increased BM inflammation, and altered HSPC-MSC crosstalk.

Senescent cells accumulate during aging and contribute to tissue dysfunction and impaired tissue regeneration. Senescence is also characterized by increased SA-β-Gal activity, persistent DNA damage repair activation, and telomeric attrition. Moreover, senescent cells exhibit transcriptional activation of a senescent-associated secretory inflammatory phenotype collectively known as SASP. The robust secretion of SASP chemokines/cytokines triggers an inflammatory response that could reinforce senescence in a cell-autonomous fashion and be transferred to surrounding cells through paracrine mechanisms, to amplify the senescence response.

To date, the activation of a senescence program in human aged MSC and the interplay between aged MSC and HSPC remain to be elucidated. In this study, we successfully established human BM-derived MSC from young and elderly healthy donors. We investigated the effects of chronological age on MSC properties and found that MSC derived from aged healthy subjects show senescence-like features comprising an enlarged morphology, reduced proliferation capacity, delayed cell cycle progression, and increased levels of SA-β-Gal and lipofuscin. Importantly, we found that aged MSC activate a SASP-like program that contributes in a non cell autonomous manner to impair young HSPC clonogenicity by mediating an inflammatory state in HSPC.

Over the past decade, a growing body of evidence revealed that inflammatory stimuli alter HSPC fate and functionality by affecting HSPC proliferation/quiescence status, differentiation potential, or HSPC-niche interactions. In particular, it has been reported that chronic inflammation drives HSPC myeloid skewing and leads to HSPC exhaustion during aging. Our data indicate that the secretome of aged MSC may as well contribute to boost inflammation in HSPC in a paracrine fashion. However, further investigations are needed to dissect the role of individual SASP factors secreted by aged MSC on HSPC biology and to determine whether chronic exposure of young HSPC to MSC-derived inflammatory molecules may induce paracrine senescence in HSPC as previously described in other settings.

Fasting Mimicking Diet as a Treatment for Inflammatory Bowel Disease

Forms of intermittent fasting and calorie restriction are quite effective at reducing inflammation, and the work done on fasting mimicking diets has gone a long way towards quantifying this effect. The goal was to find the 80/20 point on the line between mild calorie restriction and fasting, the most food one can eat and still obtain lasting benefits to metabolic health due to the usual reaction to an extended period of restricted calorie intake. (Which, per that research, is one day at 1000 kcal followed by four more days at 750 kcal per day, provided those calories are in the form of healthy food). Since lowered calorie intake has anti-inflammatory effects, it isn't surprising to see researchers investigating it in the context of inflammatory diseases. The work here is largely interesting for the continued focus on the degree to which the benefits of fasting emerge during the period of increased calorie intake afterwards, rather than during the fast.

A new study reports on the health benefits of periodic cycles of the diet for people with inflammation and indicated that the diet reversed inflammatory bowel disease (IBD) pathology in mice. Results showed that fasting-mimicking diet caused a reduction in intestinal inflammation and an increase in intestinal stem cells in part by promoting the expansion of beneficial gut microbiota. Study authors say the reversal of IBD pathology in mice, together with its anti-inflammatory effects demonstrated in a human clinical trial, indicate that the regimen has the potential to mitigate IBD.

For people with a poor diet, a "once in a while" fix is the periodic use of a low-calorie, plant-based diet that causes cells to act like the body is fasting. Earlier clinical trials allowed participants to consume between 750 and 1,100 calories per day over a five-day period and contained specific proportions of proteins, fats, and carbohydrates. Participants saw reduced risk factors for many life-threatening diseases. "We know that the fasting-mimicking diet is safer and easier than water-only fasting, but the big surprise from this study is that if you replace the fasting-mimicking diet, which includes pre-biotic ingredients, with water, we don't see the same benefits."

In the study, one group of mice adhered to a four-day fasting-mimicking diet by consuming approximately 50 percent of their normal caloric intake on the first day and 10 percent of their normal caloric intake from the second through fourth days. Another group fasted with a water-only diet for 48 hours. The study demonstrated that two cycles of a four-day fasting-mimicking diet followed by a normal diet appeared to be enough to mitigate some, and reverse other, IBD-associated pathologies or symptoms. In contrast, water-only fasting came up short, indicating that certain nutrients in the fasting-mimicking diet contribute to the microbial and anti-inflammatory changes necessary to maximize the effects of the fasting regimen.

The research team observed activation of stem cells and a regenerative effort in the colon and the small intestine, which increased significantly in length only in the presence of multiple cycles of the fasting-mimicking diet. They concluded that fasting primes the body for improvement, but it is the "re-feeding" that provides the opportunity to rebuild cells and tissues. "We've determined that the dietary components are contributing to the beneficial effects; it's not just about the cells of the human body but it's also about the microbes that are affected by both the fasting and the diet. The ingredients in the diet pushed the microbes to help the fasting maximize the benefits against IBD."

Link: https://news.usc.edu/154847/fasting-mimicking-diet-ibd-usc-stody/

Fewer Calories, Better Cell Performance

Calorie restriction, reducing calorie intake by 40% or so while maintaining optimal micronutrient intake, is the most reliable way to upregulate all of the cellular maintenance processes that act to improve cell and tissue function. This response to famine evolved very early on in the history of life on our planet, and near all organisms assessed by the research community have a cellular metabolism that operates more efficiently when calories intake is restricted. While everyone should consider trying calorie restriction, given the health benefits it conveys, and given that it costs nothing, it isn't the path to a sizable extension of life span in our species. Efforts to recreate even thin slices of the metabolic response to calorie restriction have proven to be challenging, despite an investment of billions and decades, and even the best present development programs achieve little in the grand scheme of what might be possible given better approaches to the problem of aging. They will only modestly slow aging, not radically change the length of human life.

The number of calories a person eats directly influences the performance of different cells. One experiment on mice shows how a low calorie diet can protect the brain from neuronal cell death associated with diseases such as Alzheimer's, Parkinson's, epilepsy, and cerebral vascular accident (CVA). The mice were divided into two groups. The researchers calculated the average number of calories the group with no caloric restrictions would eat and then fed the other group 40% fewer calories. After 14 weeks, mice belonging to the two groups were given an injection containing a substance known to cause seizures, damage, and neuronal cell death.

While the animals in the group that had no dietary restrictions had seizures, the animals whose calories had been restricted did not. The researchers then studied what occurred in vitro. To do that, they isolated the organelles called mitochondria of the brain cells of the mice, which were also divided into two groups: those that had unrestricted diets and those that had restricted diets. When calcium was introduced to the medium, they noted that uptake was greater in the mitochondria belonging to the group that had ingested fewer calories. Mitochondria are the organelles responsible for energy generation in cells. In the case of the mice subjected to a calorie restricted diet, mitochondria increased the calcium uptake capacity in situations where the level of that mineral was pathologically high.

In the pancreas, caloric restriction has shown to be capable of improving cell response to increased levels of blood glucose. The researchers reached this conclusion after conducting experiments using beta cells that remain in the pancreatic islets and are responsible for producing insulin. Blood serum from mice subjected to a variety of diets, similar to the study on the effects of caloric restriction on neurons, was used to nourish the cells cultivated in vitro. In the cells treated with the serum of animals that ate fewer calories, insulin secretion through the beta cells occurred normally: low when glucose was low and high when glucose was elevated. This did not occur in the animals that ate more calories (and became obese). The experiment showed that there may be a circulating blood factor that acutely modifies beta cell function.

Researchers have again raised the hypothesis of whether the phenomenon is related to the mitochondria, since insulin secretion depends on the availability of ATP (adenosine triphosphate, the molecule that stores energy) in the cell. When they measured oxygen consumption by the two groups of cells, they observed that it was higher in cells that received serum from animals subjected to caloric restriction. Since respiration is responsible for the release of insulin during peak glucose, it was a sign that the cells generated more ATP under that condition. Other experiments have also shown that the mitochondria of cells treated with serum from animals subjected to caloric restriction exchanged more material with each other, which made them more efficient.

Link: http://fapesp.br/week2019/london/news/diets-consisting-of-fewer-calories-improve-cell-performance

The Engineering of Kidney Organoids Proceeds Apace

This is the organoid era of tissue engineering. Researchers are making earnest progress in establishing the recipes that allow cells to be grown into small, functional tissue sections. They lack a network of capillaries, however, so must be no more than a millimeter or so in thickness in order for nutrients to perfuse sufficiently through the tissue to support all of its cells. Every organ, every tissue has a significantly different recipe, but it is usually something that can be derived from an examination of the biochemistry of embryonic growth, with enough time and funding. Given the large number of different tissues versus the smaller number of research groups working on tissue engineering, this process of discovery will be going on for a while yet. It has taken a great deal of time and effort to produce the first functional organoids, and it will take longer yet to manage complete coverage of the human body.

Today I'll point out a couple of recent articles that focus on kidney organoids specifically. Kidney function is not independent of structure and location as is the case for the liver, so one can't just put kidney organoids into a patient's lymph nodes, as Lygenesis is doing with liver sections. It is nonetheless plausible to transplant some number of kidney organoids into a failing kidney and have them integrate usefully to support overall kidney function. It may be the case that this becomes a widespread mode of therapy before a reliable solution is found for construction of capillary networks in engineered tissue, a challenge that presently blocks the way towards building larger tissue sections and whole organs from a patient's own cells. Or it may not; the future is hard to predict at the best of times, never mind when the research is moving as fast as it is these days.

Engineered mini-kidneys come of age

With organs-in-a-dish a growing success story, research with organoids has increasingly proved its worth. Already, scientists can create organoids that have many of the cell types and complex architectures of human organs such as the kidney, liver, guts, and even the brain. Most organoids grown in vitro, however, have lacked the vasculature to provide the cells with oxygen and nutrients, remove metabolic waste, and facilitate communication between cell types - functions that drive their maturation into working tissue-building blocks.

When it comes to kidney organoids, that shortcoming has kept researchers from reproducing key functions, such as blood filtration, reabsorption, and urine production. A vascularized organoid could better model kidney diseases, enhance renal drug toxicity testing, and ultimately lead to building blocks for replacement therapies. To answer that need, a team of researchers has developed a powerful new approach. By exposing stem cell-derived organoids to fluidic shear stress, they have significantly expanded their vascular networks and improved the maturation of kidney compartments. They hypothesized that fluid flow could help the models form blood vessels from precursor endothelial cells found in growing kidney organoids - and successfully, for the first time, demonstrated that by exposing the organoids to fluid flow, their vascularization and maturation can be enhanced in vitro, rather than in an animal host.

"The vascular networks form close to the epithelial structures that build the glomerular and tubular compartments, and in turn promote epithelial maturation. This integrated process works really like a two-way street. Our method may pave the way to also vascularize other types of organoids, such as the liver organoids."

Researchers develop mini kidneys from urine cells

Thanks to revolutionary developments in stem cell research, scientists can grow mini intestines, livers, lungs and pancreases in the lab. Recently, by growing so-called pluripotent stem cells, they have also been able to do this for kidneys. In a study, researchers used adult stem cells, directly from the patient, for the first time. Cells from urine also proved to be ideal for this purpose. A mini kidney from the lab doesn't look like a normal kidney. But the simple cell structures share many of the characteristics of real kidneys, so researchers can use them to study certain kidney diseases.

"We can use these mini kidneys to model various disorders: hereditary kidney diseases, infections, and cancer. This allows us to study in detail what exactly is going wrong. This helps us to understand the workings of healthy kidneys better, and hopefully, in the future, we will be able to develop treatments for kidney disorders. In the lab, we can give a mini kidney a viral infection which some patients contract following a kidney transplant. We can then establish whether this infection can be cured using a specific drug. And we can also use mini kidneys created from the tissue of a patient with kidney cancer to study cancer."

Correlating CMV Infection and Markers of Inflammation in Older Individuals

Cytomegalovirus (CMV) is a highly prevalent herpesvirus, and cannot be effectively cleared from the body by the immune system. Nearly everyone is infected by the time old age rolls around. While most people have no obvious symptoms of infection, over decades CMV corrodes the immune system. Ever more cells of the limited number available to the adaptive immune system become uselessly specialized to fight CMV, which leaves ever fewer cells for other tasks. This is one of the contributing causes of immune system aging. A range of studies have demonstrated correlations between CMV infection and markers of immune system decline, such as chronic inflammation. The open access paper noted here is an example of the type.

What to do about CMV? A way to clear it from the body will prevent future issues for those who are young, but won't do much to fix the disruption of the immune system in those already old. Since CMV doesn't appear to cause much damage other than this slow breakage of immune function, it might be better to use targeted cell killing technologies to clear out the adaptive immune cells that are specialized to CMV, and then replace them via some form of cell therapy, or regeneration of the thymus, or another approach with a similar outcome of increased creation of new adaptive immune cells.

Aging has been linked to persistent low-grade systemic inflammation that is characterized by a chronic increase in the levels of circulating pro-inflammatory cytokines, whose presence is highly related to age-related metabolic, cardiovascular, and neurodegenerative diseases. To underscore the importance of pro- and anti-inflammatory homeostasis in aging, and the role of chronic low-grade inflammation in shaping the aging phenotype, a term "inflammaging" has been coined.

Cytokines are signaling molecules possessing unique modulatory functions. Among numerous pro- and anti-inflammatory cytokines, some stand out as influential contributors to age-related differences in health, immunity, and cognition. The tumor necrosis factor (TNF) that plays a key role in several neuroimmune functions is associated with the increased risk for neurodegeneration. IL-6 that is produced mostly by adipose tissue macrophages is elevated in persons of advanced age and people suffering from obesity. IL-10, an anti-inflammatory cytokine, suppresses, in turn, the release of TNF and other inflammatory cytokines. Another prominent pro-inflammatory cytokine, IL-1β is primarily produced by monocytes. Alone or in synergy with TNF, IL-1β affects nearly every cell in the organism.

To complicate matters, the interrelated effects of all surveyed cytokines as well as their influence on immune and neuroendocrine functions can be modified by chronic activity of an infectious agent. A lifelong persistent infection influences immunosenescence and can significantly alter the course of cognitive aging when it acts in conjunction with individual differences in cytokine production and release. Currently, consensus seems to be building around the CMV as such a chronic modifier of cytokine action. CMV exerts significant influence on the aging immune system and thus acts as a driving factor of inflammaging. In older adults, CMV has been linked to increased frailty, accelerated cognitive decline, and an increased risk of cardiovascular and Alzheimer's diseases.

The present study posited four major goals. First, we aimed to measure and characterize the baseline inflammatory status of aged individuals recruited for an intervention study of active aging before starting the cognitive and physical training. Specifically, we assessed main inflammatory and anti-inflammatory biomarkers, such as circulating cytokines. Second, we aimed to explore the influence of gender and CMV-seropositivity on the immune and metabolic markers measured at baseline. Third, we examined the associations among inflammatory and metabolic factors, and assessed whether CMV-seropositivity modifies these relationships. Fourth, we explored the influence of the measured inflammatory factors on the cognitive abilities, such as fluid intelligence, episodic memory, speed, and working memory, in the context of CMV-serostatus and gender.

In the present study we found that both gender and CMV-seropositivity modulate circulating peripheral biomarkers, and that CMV infection modifies associations among the latter. In CMV-seropositive individuals, episodic memory and fluid intelligence correlated negatively with pro-inflammatory IL-6; and episodic memory, fluid intelligence, and working memory correlated negatively with anti-inflammatory IL-1RA. We conclude that both CMV-serostatus and gender may modulate neuroimmune factors, cognitive performance, and the relationship between the two domains.

Link: https://dx.doi.org/10.3390/ijms20040990

More on Poor Sleep and Levels of Tau in the Brain

You might recall that researchers recently connected poor sleep with raised levels of tau in the brain. Sleep is needed to clear out tau, the amount of which rises during the active use of the brain while waking. Altered forms of tau protein can aggregate in the aging brain to form the neurofibrillary tangles that occur in later stages of Alzheimer's disease, and this might explain some of the known correlation between sleep disruption and neurodegeneration. The study here provides more data on this correlation, linking higher levels of tau with sleep apnea specifically, a common form of sleep disturbance. This is still a correlation in search of definitive proof of causation in humans, however, even if the recent animal study seems fairly compelling on the point of poor sleep causing raised tau levels.

People who stop breathing during sleep may have higher accumulations of the toxic protein tau, a biological hallmark of Alzheimer's disease, in part of the brain that manages memory, navigation, and perception of time. Recent evidence has supported an association between an increased risk for dementia and sleep disruption. That's particularly true for obstructive sleep apnea, which is a potentially serious disorder where breathing repeatedly stops during sleep. However, it remains unclear what could be driving this association.

Using the population-based Mayo Clinic Study of Aging, researchers identified 288 people 65 and older who did not have dementia. Their bed partners were asked whether they noticed if their partners stopped breathing during sleep. Positron emission tomography brain scans of study participants looked for buildup of the toxic protein tau in the entorhinal cortex, which is the part of the brain that is deep behind the nose and susceptible to accumulating tau. The entorhinal cortex stores and retrieves information related to visual perception and when experiences happen. The dysfunctional tau protein forms tangles in the brains of people with Alzheimer's disease, contributing to cognitive decline.

Fifteen percent of the study group, or 43 participants, had bed partners who witnessed sleep apnea. Participants with witnessed apneas had about 4.5 percent higher levels of tau in the entorhinal cortex than those who have not been observed to have apneas during sleep. "Our research results raise the possibility that sleep apnea affects tau accumulation. But it's a chicken and egg problem." Does sleep apnea cause an accumulation of tau, a toxic protein that forms into tangles in the brains of people with Alzheimer's disease? Or does the accumulation of tau in certain areas cause sleep apnea?

Link: https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-study-shows-sleep-apnea-may-be-tied-to-increased-alzheimers-biomarker-in-brain/

Have Specific Genetic Examples of Antagonistic Pleiotropy Been Identified in Humans?

Pleiotropy occurs when a single gene affects more than one distinct and seemingly unrelated trait. Antagonistic pleiotropy occurs when one of those traits is harmful. It is widely considered to be an important foundation for the evolution of aging, in that natural selection operates strongly during early life, a period characterized by tooth and claw battles for survival and reproductive success. Evolution will select for genes, mechanisms, and biological systems that operate well early and run down later, or otherwise cause harm in later life. The adaptive immune system is an example of the type, a system that works very well right out of the gate in youth, but cannot possibly function indefinitely. It devotes resources to all pathogens encountered, and eventually simply runs out of capacity. The decline of the immune system is much more complex than that simple sketch, of course, and has numerous distinct causes, but the example serves.

In the broader sense, why doesn't the body repair itself indefinitely? The antagonistic pleiotropy hypothesis suggests that the fierce selection pressure in early life will strip away anything that isn't absolutely vital to immediate survival and reproductive success. Long-term investment in repair and maintenance simply cannot survive this evolutionary arms race, in which even a tiny loss of advantage may well lead to extinction of the lineage. This might lead us to wonder how the lowly hydra manages to be functionally immortal, actually ageless - but it is only one among countless species that all undergo degenerative aging. Perhaps we are seeing the hydra shortly before its inevitable extinction at the hands of a slightly more efficient rival.

The two commentaries here follow on from a recent paper that discussed antagonistic pleiotropy and the evidence for it. Everyone involved in the exchange appears to support the antagonistic pleiotropy hypothesis; the debate is over whether or not specific named genes in humans are clearly pleiotropic in this way, and whether the evidence in support of that position is robust. As the authors of the original paper note, the challenge inherent in human data is that it produces correlations rather than the definitive causation that can be obtained from a well-designed animal study.

Byars and Voskarides: Genes that improved fitness also cost modern humans, evidence for genes with antagonistic effects on longevity and disease

Austad and Hoffmann reviewed the current state-of-the-art on what support there is for the theory of antagonistic pleiotropy and what implications this has for modern medicine regarding improving human health and longevity. Although the authors focus on examples in both wild populations and laboratory conditions, the review states that there are no compelling examples in humans where the underlying genes or alleles that carry this tradeoff have been identified. This fails to acknowledge recent studies, mostly published the last two years, where excellent progress has been made in identifying such genes and below, we describe several examples.

Two studies in 2017 uncovered evidence for antagonistic pleiotropy in genes related to coronary heart disease (CAD) and fitness, and diseases related to ageing. The first found that CAD genes in humans are significantly enriched for fitness (increased lifetime reproductive success) relative to the rest of the genome, with evidence that the direction of their effects on CAD and fitness are antagonistic. This study provides a possible reason why genes carrying health risks have persisted in human populations. The second found evidence for multiple variants in genes related to ageing that exhibited antagonistic pleiotropic effects. They found higher risk allele frequencies with large effect sizes for late-onset diseases (relative to early-onset diseases) and an excess of variants with antagonistic effects expressed through early and late life diseases.

There also exists other recent tangible evidence of antagonistic pleiotropy in specific human genes. The SPATA31 gene has been found under strong positive genomic selection. Long-lived individuals carry fewer SPATA31 copy numbers. On the other hand, its overexpression in fibroblast cells leads to premature senescence, this being the case in people having multiple copies of the gene. During human evolution, more copies of this gene have likely been favored since this protein is important in sensing and repairing UV-induced DNA damage. Unfortunately, the cost is cell senescence and premature aging.

Austad and Hoffmann: Response to genes that improved fitness also cost modern humans: evidence for genes with antagonistic effects on longevity and disease

Byars and Voskarides, responding to our review of empirical support for the antagonistic pleiotropy theory of the evolution of aging, feel that we have 'failed to acknowledge' recent human studies supporting the theory. Indeed, we mentioned no human studies because we had intended our review to present only the strongest evidence supporting the theory which has been done almost entirely in laboratory model organisms. For this reason, while we mentioned a few studies from natural populations, we emphasized how such nonexperimental studies could be consistent with the antagonistic pleiotropy mechanisms, but could not be cleanly attributed to it. Experimental studies establish cause-and-effect in a way that correlational studies cannot.

It is an unfortunate truth about research on humans that because experimental studies are often impossible, results are almost inevitably correlational, which in our view makes virtually any single study highly suggestive at best, but never compelling. To illustrate why, we consider one of the studies adduced by Byars and Voskarides, although we could have chosen any of the others. That study identifies numerous human alleles pre-disposing individuals to coronary artery disease (CAD) but also conferring reproductive advantages early in life. This is a very nice study given the limitations of human research. The best that could be done with available data was done. Note, however, that one of the first lessons of statistical reasoning is that correlation does not equal causation and, yes, genomic associations are correlations.

Our point in noting these things is certainly not to denigrate the study by Byars et al. or the other studies cited. These are some very fine studies using state-of-the-art genomic analyses. We simply wanted to explain why we consider such studies less compelling as support for the antagonistic pleiotropy theory than experimental studies done in model laboratory organisms with specific and purposeful manipulation of specific individual genes.

Aging and Oxidative Signaling in Muscle Tissue

Today's open access review discusses oxidative signaling and damage in aging muscles. All considerations of oxidative molecules in aging are complex, but then nothing in biology is simple. Decades ago, the research community proposed that aging was caused by oxidative damage, but the data that led to that theory of aging was only a small part of the overall story. The original theory has since fallen to the wayside. Yes, there is oxidative damage in old tissues, cell components disrupted by reacting with oxidizing molecules. But cells also use oxidative molecules as signals, and respond to rising levels of oxidation with greater repair efforts. A number of the ways to slow aging in short-lived laboratory species work because they cause a modest increase in the production of oxidative molecules by mitochondria, and any greater level of damage to cellular mechanisms is outweighed by increased activity of cellular maintenance processes.

Mitochondria are the primary source of oxidative molecules, but the process may be fairly indirect, even given the loss of mitochondrial quality and function that is characteristic of aging. In the SENS view of mitochondrial dysfunction, a small fraction of cells become overtaken by broken mitochondria and, as a consequence, export significant volumes of oxidative molecules into surrounding tissue. It is a multi-step process that only begins with mitochondrial damage. Further, consider that levels of oxidative molecules in circulation go hand in hand with inflammation. The immune system declines with age, falling into a state of ineffective chronic inflammatory activity. This may also be an important source of age-related oxidative stress. It is usually challenging to pick apart the degree to which specific mechanisms contribute to aging, as it is hard to alter any one mechanism in complete isolation.

The skeletal muscle is the largest organ in the body comprising ~40% of its mass. It plays fundamental roles in movement, posture, and energy metabolism. The loss of skeletal muscle mass and function with age can have a major impact on quality of life and results in increased dependence and frailty. Age-related decline of skeletal muscle function (sarcopenia) results in strength loss. This loss stems from two major sources, reductions in muscle mass (i.e., quantity) and decrease in its intrinsic capacity for producing force (i.e., quality). Both can be the consequence of several factors, including oxidative stress that is the result of the accumulation of reactive oxygen and nitrogen species (ROS/RNS). The free-radical theory of aging was established more than 60 years ago and has become one of the most studied theories to have been proposed. It is now accepted that this theory and its various spin-offs cannot alone explain the aging process. Nevertheless, huge amounts of data indicate that ROS-mediated aging phenotypes and age-related disorders exist

During physiological homeostasis the overall oxidative balance is maintained by the production of ROS/RNS from several sources and their removal by antioxidant systems, including endogenous or exogenous antioxidant molecules. At physiological concentrations ROS/RNS play essential roles in a variety of signaling pathways. There is an optimal level of ROS/RNS to sustain both cellular homeostasis and adaptive responses, and both too low and too high levels of ROS/RNS are detrimental to cell functions. The skeletal muscle consumes large quantities of oxygen and can generate great amounts of ROS and also reactive nitrogen species. Mitochondria are one of the most important sources of ROS in the skeletal muscle.

The origin of the increased ROS production and oxidative damage is mitochondrial dysfunction with aging, caused by age-related mitochondrial DNA mutations, deletions, and damage>, as well as the impaired ability of muscle cells to remove dysfunctional mitochondria. Oxidative phosphorylation impairment can lead to decreased ATP production and further generation of ROS. Interestingly, aging is associated not only with an increase in oxidative damage but also with an upregulation of antioxidant enzymes in the skeletal muscle. Furthermore, the iron content of the mitochondria in the skeletal muscle increases with aging, amplifying the oxidative damage with the generation of ROS. Increased ROS production, mitochondrial DNA damage, and mitochondrial dysfunction was observed in aged muscles.

The skeletal muscle is highly plastic and shows several adaptations towards mechanical and metabolic stress. Oxidative stressors, like ROS, have long been taken into account as harmful species with negative effects in the skeletal muscle. Proteins are frequently affected by oxidation; thus, elevated ROS levels can cause reversible or irreversible posttranslational modification of cysteine, selenocysteine, histidine, and methionine. Oxidative posttranslational modifications of proteins are characteristic in the aged muscle, such as carbonylation which alters protein function. The oxidative capacity of muscles is strongly associated with health and overall well-being. Enhanced oxidative capacity in the skeletal muscle protects against several pathological phenomena (insulin resistance, metabolic dysregulation, muscle loss with aging, and increased energetic deficits in myopathies). These protective effects are largely associated with enhanced mitochondrial function and elevated numbers of mitochondria, which can protect against cellular stress.

Link: https://doi.org/10.1155/2019/4617801

More of Just one Component Part of a Proteasome Extends Life in Worms and Flies

Proteasomes are structures the cell, complex assemblies of a number of different proteins, that are responsible for breaking down damaged and excess proteins into small chunks that can be reused as raw materials. As is true of other cell maintenance processes, more proteasomal activity leads to better cell and tissue function, the creation of lesser amounts of downstream damage and dysfunction over time. Aging is modestly slowed. By way of following on from a recent review of upregulated proteasomal activity as a path to the treatment of aging, I'll point out this recent research in which scientists expand upon a very selective way to improve the operation of the proteasome. The production of more copies of just one component part of a proteasome improves overall function to a great enough degree to affect life span in short-lived species, an interesting finding.

Proteasome activity has been shown to decline with age and increasing proteasome function is known to provide benefits to lifespan. Given the multiple roles that the proteasome plays, however, including roles in metabolism, cell proliferation, and cell signaling, among others, discerning which aspects of proteasome function are limiting specifically for aging is necessary for further targeted investigations into the molecular consequences of aging. The major proteolytic activity associated with the proteasome is the chymotrypsin-like activity provided by the β5 subunit, and artificial impairment of only the chymotrypsin-like activity of the proteasome in mice has been shown to be sufficient to cause multiple early aging phenotypes, including shortened lifespans, reduced body weight, altered metabolism, muscle atrophy, and accumulation of ubiquitinated peptides.

The β5 subunit of the proteasome has been shown in worms and in human cell lines to be regulatory. In these models, β5 overexpression results in upregulation of the entire proteasome complex which is sufficient to increase proteotoxic stress resistance, improve metabolic parameters, and increase longevity. However, fundamental questions remain unanswered, including the temporal requirements for β5 overexpression and whether β5 overexpression can extend lifespan in other species.

To determine if adult-only overexpression of the β5 subunit can increase proteasome activity in a different model, we characterized phenotypes associated with β5 overexpression in Drosophila melanogaster adults. We find that adult-only overexpression of the β5 subunit does not result in transcriptional upregulation of the other subunits of the proteasome as they do in nematodes and human cell culture. Despite this lack of a regulatory role, boosting β5 expression increases the chymotrypsin-like activity associated with the proteasome, reduces both the size and number of ubiquitinated protein aggregates in aged flies, and increases longevity. Surprisingly, these phenotypes were not associated with increased resistance to acute proteotoxic insults or improved metabolic parameters.

Link: https://doi.org/10.1038/s41598-019-39508-4

Insulin and IGF-1 in Human Aging and Longevity

The area of cellular metabolism surrounding growth hormone, IGF-1, and insulin is arguably the most studied set of mechanisms linking the operation of metabolism and the pace of aging. It is impacted by calorie restriction, an intervention that reliably slows aging. The longest lived engineered mice are those in which growth hormone signaling is disabled, and there is an equivalent human population with a similar inherited mutation to study. Many of the early attempts at producing long-lived nematode worms involved manipulation of IGF-1/insulin signaling. A greater number of centenarians than younger individuals appear to have favorable IGF-1/insulin signaling, suggesting some survival advantage.

But is this of any practical use when it comes to producing therapies that treat aging and meaningfully lengthen human life spans? After going on for thirty years of study, one has to think that the answer might be no. There is no way forward to radical life extension of decades and restored youth via mimicking calorie restriction, or trying to make metabolism more like that of long-lived people. Most people with the same biochemistry as centenarians die long before reaching that point - the survival advantage doesn't have to be large for centenarians to exhibit a larger proportion of a given trait than the general population. Human growth hormone mutants don't seem to live any longer than the rest of us. And so forth.

These and other, similar points have long led me to think that altering metabolism to age slightly more slowly - via IGF-1 signaling or other aspects of the response to calorie restriction - is just not a good use of research and development funds. It will not help those already aged in any meaningful way. It is a poor strategy for the research community to be undertaking, and it is a major problem that this strategy remains the dominant recipient of resources and attention. If enormous funding is to be invested in this field, let it go towards true rejuvenation research based on repair of the causes of aging, not tinkering with metabolism to produce minor adjustments in aging.

Centenarians are considered the best human model to study biological determinants of longevity having reached the very extremes of the human lifespan. Several studies compared circulating insulin and IGF-1 levels in centenarians with those of younger controls. Metabolic age-dependent remodeling is a physiological process occurring in the whole population. Aging is frequently associated with a decline in glucose tolerance secondary to an increased insulin resistance, but an exception occurs in long-lived people. Researchers found that insulin resistance increased with aging and declined in subjects older than 90 years. Indeed, long-lived subjects showed a higher insulin sensitivity and a better preservation of beta-cell function than younger subjects.

Data on the IGF-1 system in relation to longevity are still controversial in long-lived subjects. One team described an increased plasma IGF-1/IGFBP-3 ratio in healthy centenarians compared to elderly subjects. They hypothesized that this elevated ratio was indicative of a higher IGF-1 bioavailability which contributed to the improved insulin action in centenarians. In contrast, others reported that subjects with at least an A allele of the IGF-1 receptor gene had low levels of free plasma IGF-1 and were more represented among long-lived people.

These conflicting results probably reflect the complexity of the IGF-1 system and ethnic differences in enrolled populations. In addition, centenarians have often been compared to a control group of younger subjects. Therefore, in most of these studies it was not possible to conclude if IGF-1 differences between both groups were related to a different lifespan or reflected a physiological age-dependent IGF-1 decline.

While it is well known that enhanced insulin sensitivity and low insulin levels are associated with an improved survival, there is evidence showing that attenuation of the growth hormone/IGF-1 axis may have beneficial effects in extending lifespan in humans. However, it is still unknown which are the optimal IGF-1 levels during life to live longer and healthier. In addition, IGF-1 receptor sensitivity and activation of the post-receptor pathway were not evaluated in the majority of the study enrolling long-lived subjects. Therefore, it is not possible to define the real activation status of the IGF-1 receptor signaling through the mere dosage of circulating IGF-1 levels. This renders more difficult the identification of pharmacological or environmental strategies targeting this system for extending lifespan and promoting healthy aging.

Nonetheless, striking similarities have been described concerning the endocrine profile between centenarians and subjects after a calorie-restricted diet. The endocrine and metabolic adaptation observed in both models may be a physiological strategy to increase life span through a slower cell growing/metabolism, a slower loss of physiologic reserve capacity, a shift of cellular metabolism from cell proliferation to repair activities and a decrease in accumulation of senescent cells. These mechanisms seem to be, at least in part, mediated through the modulation of the growth hormone/IGF-1/insulin system.

Link: https://doi.org/10.3389/fendo.2019.00027

Immune Function as a Determinant of Aging and Longevity

The state of the immune system is an important determinant of aging. With age, immune function both declines in effectiveness and becomes inflammatory. Chronic inflammation accelerates the progression of all of the common age-related diseases. It disrupts tissue maintenance and regeneration, to pick one of many examples. It is likely that a sizable component of variation in aging arises from the differences between individuals in the degree to which the immune system has become damaged and dysfunctional.

Some of this immune aging is a matter of the burden of exposure to more rather than fewer pathogens over a lifetime: persistent infections in particular, such as cytomegalovirus and other herpesviruses, appear to drive immune aging. Some immune aging stems from the atrophy of the thymus, the organ responsible for maturation of T cells. A lesser volume of active thymic tissue means fewer new T cells to take up an effective defense of the body. Some immune aging is due to failure of barriers in the gut, allowing gut bacteria to trigger inflammatory activity. Some immune aging arises from cellular senescence among immune cells, turning them into harmful centers of inflammatory signaling. All of these issues have potential solutions, but, as in all matters related to aging, far too little funding and attention are given to the relevant development programs.

Pro-inflammatory immune responses are our first line of defence against infectious non-self. Inflammation however, has a cost. During the life-history of a human, low-grade inflammation, develops gradually and contributes to the pathogenesis of a range of age-related diseases from leaky gut to neurodegeneration. Conversely, ageing through cell senescence, can influence immune function with the depletion of the pool of naïve T-cells ready to respond to infection making older individuals more vulnerable to viral disease and less responsive to vaccination regimes. This can in turn, influence human lifespan. In the apparent complexity of this dual relationship it is difficult to arrive at a mechanism of causality because cause and consequence are intimately linked.

Compromised intestinal barrier function in humans has been associated with conditions such as Crohn's disease. Changes in the permeability of the mouse gut, which results in "leaky gut" has consequences on health span. In this context, increased age-associated levels of Tumour Necrosis Factor (TNF) have a negative impact on gut permeability and impacts on lifespan while IL-10 knockout mice have (along with their immune defects) increased intestinal permeability and develop early colitis compromising health span and lifespan. In contrast, TNF-deficient mice are protected from age-associated inflammation.

There is now increasing evidence that inflammation regulates ageing. But which tissues contribute to this is less clear. Brain neuroinflammation represents a critical factor contributing to progression of neurodegeneration. NF-κΒ is the major regulator of inflammation and its sustained activation in forebrain neurons elicits a selective inflammatory response accompanied by decreased neuronal survival and impaired learning and memory. More recent experiments of transient NF-κΒ activation in astrocytes (a type of microglia) through a diverse array of inflammatory cues (infection or application of pro-inflammatory cytokines), resulted in non-cell autonomous neurodegeneration. The central position of microglia innate immunity in neurodegeneration and especially in the risk for late on-set Alzheimer's Disease (AD) is exemplified in human genome-wide association studies. Loss of TREM2 has been associated with increased risk of late on-set AD and increased TREM2 expression in mouse microglia had an anti-inflammatory rescuing effect with the downregulation of several pro-inflammatory markers. This ameliorated the neuropathological and behavioural deficits of AD mouse models.

T cells and B cells undergo immune senescence. Senescence is age-dependent and is the driving force for immune ageing. During ageing, both T and B cells will be depleted and the memory B cells, long-lived plasma cells and peripheral T-cells show defects. In addition, the provision by the thymus of naïve T-cells for the adaptation to new pathogens is limited. The mechanisms of these age-related defects are not fully elucidated but reduced autophagy, is a major driving force for immune senescence. In murine T cells, neutrophils and macrophages, autophagy is attenuated during ageing and autophagy-deficient cells display premature ageing traits.

Germ-free mice live almost 100% to 600 days in contrast to their conventionally-reared counterparts that reach this point with a 60% survival probability. In addition, germ free mice do not display age-associated inflammation while their macrophages retain their antimicrobial activity. This indicates that age-associated changes of the microbiota are a significant driver of lifespan where TNF-mediated inflammation acting as an effector of morbidity. Indeed, treatment of mice with anti-TNF antibodies reversed age-associated changes in the microbiota and ameliorated life expectancy. Therefore, reversing these age-related microbiota changes represents a potential strategy for reducing age-associated inflammation and the accompanying morbidity.

Link: https://doi.org/10.1007/s10522-019-09801-w

The Shared Mechanisms of Osteoporosis and Alzheimer's Disease

Aging is at root a matter of accumulated cell and tissue damage. There are a comparatively small number of such forms of damage at the lowest level, the origins of aging. In that sense, all age-related diseases share their mechanisms. When researchers talk about shared mechanisms of age-related disease, they are usually considering processes further downstream from the sort of damage considered in the SENS rejuvenation research proposals, however. In this short commentary, the authors consider what is shared between osteoporosis and Alzheimer's disease, which, on the face it, might not be expected to have much in common at all once one passes beyond the fundamental damage of aging. One is a condition of the bones, and the other a condition of the brain, and the proximate causes in each case just don't seem to have much to do with one another. Nonetheless, read on.

Bone loss and Alzheimer's disease make an unexpected, but increasingly common combination in the aging population. The vastly different clinical presentations of these conditions made it hard to envision that a complex brain disease known for destroying our most advanced cognitive abilities could also impact the fundamental framework of the human body. This bias has likely contributed to the dearth of investigation into mechanisms of bone loss in Alzheimer's disease (AD) - which presents as a very real and unique problem for these patients.

Osteoporosis and bone fracture are estimated to occur in AD patients at over twice the rate as similarly-aged neurotypical adults. Occurring across international demographics and in both sexes, skeletal problems in AD patients are not a coincidence of aging, nor are they the result of disease-related immobility, as they often precede AD diagnosis. In fact, studies have used bone mineral density (BMD) to stratify neurotypical subjects 65 years and older into groups at greatest risk for developing dementia - with those exhibiting the lowest bone densities most likely to receive an AD diagnosis within 5-10 years.

The little empirical evidence that does exist on this subject makes a compelling case that the neuropathophysiological features of AD may also drive bone loss. To date, three genetic mouse models of AD have been characterized with a "pre-clinical" low BMD; however, there are possibly many more among the 150+ available AD models that have not been investigated for bone loss. What has been found is a low bone mass phenotype at ages just preceding the onset of significant hallmark brain pathology and detectable across models representing each hallmark pathology of AD: amyloid beta (Aβ) and phosphorylated tau (ptau) - with data implicating separate mechanisms by which each pathology disrupts skeletal homeostasis.

Data from amyloid-β mouse models support a bone-cell-autonomous role for Aβ in damaging bone tissue, with evidence that Aβ interfaced directly with bone cells to enhance the bone-resorbing activity of osteoclasts and inhibit the bone-building function of osteoblasts. Data obtained from studies with mouse models which selectively develop ptau and neurofibrillary tangle brain pathology showed that ptau - which is largely relegated to the neuronal cytoskeleton - damages the serotonergic dorsal raphe nucleus (DRN) of the brainstem. Serotonergic inputs from the DRN to the hypothalamus form a circuit that is essential for maintaining healthy bone mass in adult mammals; hence these findings suggest this circuit is compromised by ptau pathology.

Link: https://doi.org/10.18632/aging.101828

The Significance of Senescent Astrocytes in the Aging Brain

The best way to establish significance of a given form of damage or dysfunction in aging is to repair it and then observe the results of that repair. This form of investigation is now well underway for the accumulation of senescent cells in aging, as the research community has established numerous means of selectively destroying senescent cells in animals. These range from genetically engineered INK-ATTAC mice to senolytic small molecule drugs to programmable suicide gene therapies, and more are being added with each passing year. Recent demonstrations in mice (using navitoclax, dasatinib and quercetin, and piperlongumine as senolytic agents) have made it quite clear that senescent cells in the brain contribute to the progression of neurodegenerative conditions such as Alzheimer's disease, as removing those cells greatly improves matters.

Today's open access review paper looks at senescence in just one of the many populations of cells in the brain, the astrocytes. Previous work has examined glial cells in general in the context of cellular senescence and its detrimental effects on the brain, a category that includes astrocytes but also a range of other cell types. Astrocytes are support cells, and undertake a wide range of tasks to help ensure that neurons thrive and function correctly. It is not a loss of cells capable of carrying out these tasks that causes harm as a result of a small fraction of astrocytes becoming senescent. Rather it is that senescent cells produce a potent mix of inflammatory and other signals, and even a comparatively small number of them can produce significant disruption of tissue function as a result. It is well known that chronic inflammation in the brain is an important contributing factor to the progression and pathology of neurodegenerative conditions.

Astrocyte senescence: Evidence and significance

Aging is characterized as a time-dependent deterioration in the physiological integrity of living organisms. This functional decline has become incredibly relevant in the modern era, where advances in medicine have allowed humans to live longer than ever before. In light of the economic and social impact of aging and age-associated diseases, there has been extensive research into the underlying cellular mechanisms of aging. In fact, substandard results from clinical trials aimed at ameliorating age-associated neurodegenerative diseases suggest that aging is not only a risk factor for disease, but may rather be an underlying cause. In fact, the central nervous system (CNS) undergoes numerous detrimental changes as one ages including mitochondrial dysfunction, oxidative stress, and chronic inflammation. Therefore, targeting the mechanisms of CNS aging may be therapeutically prudent.

In order to examine possible mechanisms, definition of criteria to determine hallmarks of aging is critical. A landmark report has classified nine hallmarks of aging based on three criteria: (a) the hallmark should manifest during normal aging; (b) its experimental augmentation should accelerate aging; and (c) its experimental attenuation should hamper normal aging, thus increasing healthy lifespan. These hallmarks are genomic instability, telomere attrition, epigenetic alterations, stem cell exhaustion, altered intercellular communication, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, and cellular senescence. There is an intimate relationship between these hallmarks with fluctuations to one instigating changes in another. The most notable instance of this interconnectedness is with cellular senescence, a state of irreversible growth arrest coupled with stereotyped changes in phenotype and gene expression that represent all of the other hallmarks. In fitting with the above criteria, cellular senescence increases with age, and its augmentation and reduction, respectively, accelerate or diminish aging.

As studies concerning the role of cellular senescence in age-related disorders become increasingly common, senescence in the CNS is emerging as a new research topic. Taking into consideration that many neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and other types of dementia have age as a primary risk factor; the possibility that cellular senescence of CNS cell types may be a contributing factor can no longer be overlooked. Of the CNS cells, astrocytes are potential candidates for involvement in neurological disorders given their myriad roles in the maintenance of brain homeostasis. The loss of astrocyte function or the gain of neuroinflammatory function as a result of cellular senescence could have profound implications for the aging brain and neurodegenerative disorders, and we propose the term "astrosenescence" to describe this phenotype.

Astrocytes have been shown to undergo replicative cellular senescence in vitro and can senesce prematurely in response to various stressors. In vivo, senescent astrocytes have been shown to accumulate with age and in the context of neurological disorders. The detrimental impact these cells could contribute to the tissue microenvironment suggests that astrosenescence may contribute to the pathology of age-associated neurological diseases. Within a senescent cell, there can be various disruptions to normal cellular physiology including increases in reactive oxygen species (ROS), mitochondrial dysfunction, and inflammation. Notably, these are features also associated with neurodegenerative disorders.

An alternative line of therapy for the treatment of these disorders may be the clearance of senescent cells. This concept has been demonstrated with great success in transgenic mice that express constructs capable of inducible senescent cell clearance in order to extend healthy lifespan and reduce the effects of several age-associated disorders. Most recently, this concept has successfully been tested in a mouse model of tau-dependent neurodegeneration. Mice in this study accumulate senescent astrocytes and microglia, clearance of which prevents tau deposition and degeneration of cortical and hippocampal neurons, the very first study to demonstrate a causal link between glial senescence and neurodegeneration. In humans a similar effect might be conceivable using a new class of drugs known as senolytics. The previous study of tau-dependent neurodegeneration also demonstrated therapeutic potential with senolytic treatment, suggesting that senolytics to clear senescent astrocytes could be beneficial to age-associated neurogenerative diseases.

Bioprinting Skin Directly Onto a Wound

Bioprinting directly onto the body seems a logical evolution of the state of the art in this part of the field, given the emerging ability to bioprint full thickness skin, or at least a living structure very close to that. It is interesting to consider how bioprinting in situ could be made to work for internal organs. We might envisage something akin to keyhole surgery with a machine-guided printing head. The easier initial applications might include printing a patch of tissue directly onto the heart, akin to the present development of heart patches that are grown outside the body and then transplanted. The Lygenesis approach of liver or thymus organoids inside lymph nodes might also be amenable to this sort of evolution, given suitable printing hardware.

Imagine a day when a bioprinter filled with a patient's own cells can be wheeled right to the bedside to treat large wounds or burns by printing skin, layer by layer, to begin the healing process. That day is not far off. Scientists have created such a mobile skin bioprinting system - the first of its kind - that allows bi-layered skin to be printed directly into a wound. Affecting millions of Americans, chronic, large or non-healing wounds such as diabetic pressure ulcers are especially costly because they often require multiple treatments.

The major skin cells - dermal fibroblasts and epidermal keratinocytes - are easily isolated from a small biopsy of uninjured tissue and expanded. Fibroblasts are cells that synthesize the extracellular matrix and collagen that play a critical role in wound healing while keratinocytes are the predominant cells found in the epidermis, the outermost layer of the skin. The cells are mixed into a hydrogel and placed into the bioprinter. Integrated imaging technology involving a device that scans the wound, feeds the data into the software to tell the print heads which cells to deliver exactly where in the wound layer by layer. The bioprinter deposits the cells directly into the wound, replicating the layered skin structure, and accelerating the formation of normal skin structure and function.

The researchers demonstrated proof-of-concept of the system by printing skin directly onto pre-clinical models. The next step is to conduct a clinical trial in humans. "The technology has the potential to eliminate the need for painful skin grafts that cause further disfigurement for patients suffering from large wounds or burns."

Link: https://school.wakehealth.edu/Research/Institutes-and-Centers/Wake-Forest-Institute-for-Regenerative-Medicine/Awards-Honors-and-Media-Coverage/Mobile-Bedside-Bioprinter-Can-Heal-Wounds

Blame Tau for Much of the Harm Caused by Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy, as the name might suggest, is an amyloidosis. It involves the build up of amyloid-β, and in some cases significant amounts of other forms of amyloid, in blood vessel walls in the brain, and dysfunction results. As the brain is a nutrient-hungry organ, any disruption of the blood supply will cause issues over the long term, contributing to the development of dementia. As most readers here no doubt know, amyloid-β deposits are the primary feature of early Alzheimer's disease, at the stages leading into mild cognitive impairment. Amyloid deposition and the changes in cellular biochemistry that result form the foundation for the later aggregation of hyperphosphorylated tau protein into neurofibrillary tangles, and it is tau and its surrounding harmful biochemistry that causes cell death and major neurological dysfunction. So perhaps it isn't too surprising to find that in cerebral amyloid angiopathy, it is also tau that is doing the real damage.

Cerebral amyloid angiopathy (CAA) is typified by the cerebrovascular deposition of amyloid. Currently, there is no clear understanding of the mechanisms underlying the contribution of CAA to neurodegeneration. Despite the fact that CAA is highly associated with accumulation of , other types of amyloids have been shown to associate with the vasculature. Interestingly, in many cases, vascular amyloidosis is accompanied by significant tau pathology. However, the contribution of tau to neurodegeneration associated to CAA remains to be determined.

We used a mouse model of Familial Danish Dementia (FDD), a neurodegenerative disease characterized by the accumulation of Danish amyloid (ADan) in the vasculature, to characterize the contribution of tau to neurodegeneration associated to CAA. We performed histological and biochemical assays to establish tau modifications associated with CAA in conjunction with cell-based and electrophysiological assays to determine the role of tau in the synaptic dysfunction associated with ADan. We demonstrated that ADan aggregates induced hyperphosphorylation and misfolding of tau.

Moreover, in a mouse model for CAA, we observed tau oligomers closely associated to astrocytes in the vicinity of vascular amyloid deposits. We finally determined that the absence of tau prevents synaptic dysfunction induced by ADan oligomers. In addition to demonstrating the effect of ADan amyloid on tau misfolding, our results provide compelling evidence of the role of tau in neurodegeneration associated with ADan-CAA and suggest that decreasing tau levels could be a feasible approach for the treatment of CAA.

Link: https://doi.org/10.1186/s40478-019-0680-z

RAGE Knockout Reduces Age-Related Kidney Damage in Mice

RAGE is the receptor for advanced glycation end-products (AGEs), the mechanism by which cells react to the presence of AGEs. AGEs are metabolic byproducts that are both created in the body and present in the diet; cooking animal fat produces AGEs, for example. Diets heavy in meat and the related, fun, unhealthy products so prevalent in this modern calorie-packed world of ours are also heavy in AGEs of various sorts. It remains a topic for discussion as to the degree to which dietary AGEs are a problem, however. Do they contribute significantly to the issues caused by AGEs in general, or only in conditions in which metabolism is already aberrant, such as metabolic syndrome and type 2 diabetes? Opinions differ.

There are two quite distinct classes of harm associated with AGEs in aging. The first, and not the topic of today's research, is the creation of persistent cross-links in the extracellular matrix by the AGE glucosepane. A cross-link shackles together two of the complex molecules the extracellular matrix, thereby altering its properties by preventing free movement of those molecules. Significant cross-linking degrades elasticity, strength, and other necessary properties of various tissues. In the case of blood vessels, this loss of elasticity leads to hypertension and consequent cardiovascular disease. Glucosepane cross-links cannot be effectively broken down by our biochemistry, and thus will have to be dealt with via some form of therapy.

The second form of harm associated with AGEs is chronic inflammation. Chronic inflammation causes disarray and damage throughout the body, degrading tissue maintenance and encouraging dysfunction in organs and biological systems. AGEs produce inflammation in part by their interaction with RAGE, triggering it relentlessly and thus spurring other inflammatory signaling. The more AGEs there are in circulation, even if they are short-lived varieties, easily dealt with by the body, the more inflammation. Metabolic disorders of obesity, such as the aforementioned metabolic syndrome and type 2 diabetes, are characterized by excessive AGEs and excessive inflammation - though it is worth noting that there are plenty of other ways by which excess fat tissue generates inflammation.

Here, researchers demonstrate that the burden of inflammation and resulting organ damage occurring due to a raised level of AGEs is reduced when RAGE is disabled. The study uses normal and genetically engineered mice lacking RAGE, the mice fed either a normal diet or a diet containing large amounts of dietary AGEs. To the point I raised above about opinions on the effects of dietary AGEs, choice of diet didn't make much difference here. But RAGE knockout mice are better off in old age in either case, most likely due to reduced inflammatory consequences arising from the AGE-RAGE interaction.

Knockout of receptor for advanced glycation end-products attenuates age-related renal lesions

The impact of advanced glycation end-products (AGEs) on chronic kidney disease (CKD), especially through binding to their main receptor RAGE (receptor for AGEs), has received significant research attention. The AGEs form a heterogeneous group of molecules resulting from permanent binding of reducing sugars to a range of amino-compounds. Their endogenous formation occurs under various conditions such as hyperglycemia and oxidative stress, but also aging. Their presence is moreover clearly identified in foods: daily intake of Nɛ-carboxymethyllysine (CML, the most studied AGE) can be as high as 252 µg/kg body weight in a typical European diet.

Evidence has recently accumulated incriminating the endogenous AGE/RAGE axis in age-related diseases. RAGE is a multiligand, transmembrane receptor activating major pro-inflammatory and pro-oxidative signaling pathways. Its expression in numerous cell types increases with aging and pathological conditions such as diabetes, but a role for this receptor has been postulated in the premature dysfunction of several organs, even in the absence of diabetes. The impact of chronic exposure to dietary AGEs on aging remains poorly studied, however.

Considering the preferential accumulation of CML in the kidneys under a CML-enriched diet and studies linking dietary AGEs and kidney damage, we hypothesized that kidneys are target organs for accelerated aging induced by AGE/RAGE interactions. In order to study this question, histologic markers of renal aging were analyzed in 2-month-old male wild-type (WT) and RAGE knockout mice fed a control or a CML-enriched diet over 18 months.

Compared to controls, we observed higher CML levels in the kidneys of both CML WT and CML RAGE knockout mice, with a predominantly tubular localization. The CML-rich diet had no significant impact on the studied renal parameters, whereby only a trend to worsening glomerular sclerosis was detected. Irrespective of diet, RAGE knockout mice were significantly protected against nephrosclerosis lesions and renal senile apolipoprotein A-II (ApoA-II) amyloidosis. Compared with old WT mice, old RAGE knockout mice exhibited lower expression of inflammation markers and activation of AKT, and greater expression of Sod2 and SIRT1. Overall, nephrosclerosis lesions and senile amyloidosis were significantly reduced in RAGE knockout mice, indicating a protective effect of RAGE deletion with respect to renal aging. This could be due to reduced inflammation and oxidative stress in RAGE-/- mice, suggesting RAGE is an important receptor in so-called inflammaging.

Modeling and then Realizing a Restoration of Stem Cell Activity in the Brain

Every month sees the passage of a great many papers describing the computational modeling of cells, protein biochemistry, tissue function, and so forth. All too few of those efforts go any further, moving into real cells and tissues in order to test predictions. Here, it is pleasant to see a group of researchers doing just that and obtaining promising results that add to the growing body of work regarding loss of stem cell activity with age, and means to at least partially reverse that loss. We all have the intuition that, yes of course greatly improved computational capacity has to be helping scientific initiatives move towards rejuvenation in some way, but good demonstrations of real progress remain all too thin on the ground. We are afloat in computational capacity in this modern, connected age, but effective use of those countless processing cycles is quite the different topic.

Researchers have been able to rejuvenate stem cells in the brain of aging mice. The revitalised stem cells improve the regeneration of injured or diseased areas in the brain of old mice. The researchers expect that their approach will provide fresh impetus in regenerative medicine and facilitate the development of stem cell therapies. In order to create as accurate as possible computational models of stem cell behaviour, researchers applied a novel approach. "Stem cells live in a niche where they constantly interact with other cells and extra-cellular components. It is extremely difficult to model such a plethora of complex molecular interactions on the computer. So we shifted perspective. We stopped thinking about what external factors were affecting the stem cells, and started thinking about what the internal state of a stem cell would be like in its precisely defined niche."

The novel approach led to in a new computational model. "Our model can determine which proteins are responsible for the functional state of a given stem cell in its niche - meaning whether it will divide or remain in a state of quiescence. Our model relies on the information about which genes are being transcribed. Modern cell biology technologies enable profiling of gene expression at single cell resolution." From their computational model, researchers identified a molecule called sFRP5 that keeps the neuronal stem cells inactive in old mice, and prevents proliferation by blocking the Wnt pathway crucial for cell differentiation.

Studying stem cells first in a dish and then later directly in mice, a collaborating team then experimentally validated the computational prediction. When neutralising the action of sFRP5, quiescent stem cells did indeed start proliferating more actively. Thus, they were available again to be recruited for the regeneration processes in the aging brain. "With the deactivation of sFRP5, the cells undergo a kind of rejuvenation. As a result, the ratio of active to dormant stem cells in the brain of old mice becomes almost as favourable as in young animals."

Link: https://wwwen.uni.lu/university/news/latest_news/rajeunir_les_cellules_souches_dans_le_cerveau_de_souris_agees

Clearance of Senescent Cells Prevents Type 1 Diabetes in Animal Models

This result is unexpected, I have to say. Type 1 diabetes is not an age-related disease in any way; the majority of cases appear early. It is also understood to be an autoimmune condition, in which the immune system mistakenly attacks a particular tissue type or cell population. Yet researchers here show that senescent cells are a primary driver of the pathology of the condition, the death of beta cells in the pancreas and consequent severe metabolic dysfunction due to a lack of insulin. The accumulation of senescent cells is a mechanism associated with aging, not early life. This work raises many questions, such as will researchers find cellular senescence to be a critical part of other autoimmune conditions? Is the relevance of cellular senescence in mouse models definitely going to be the case in humans as well?

If cellular senescence is important in human type 1 diabetes, and if it is possible to achieve the same sort of results in humans as were obtained in mice in this study, then we will find out quite quickly. Senolytic therapies to clear as much as half of the senescent cells present in many tissues already exist: dasatinib and quercetin, possibly fisetin and piperlongumine. All of these are cheap and readily available for anyone who wishes to self-experiment. I'm sure that a number of type 1 diabetes patients will choose to do so. Further, the market for drugs for type 1 diabetes is so large that trials of senolytics for this condition will commence soon, given this research as a starting point and wake up call.

Type 1 diabetes (T1D) results from the loss of pancreatic beta cells, leading to insulin deficiency and disruption of glucose metabolism. The loss of beta cells is thought to be driven by an underlying autoimmune disorder in which peripheral tolerance is lost and mature autoreactive CD4+ and CD8+ cytotoxic T cells carry out progressive destruction of beta cells with support from innate immune cells. As a consequence, the major focus of current experimental therapies for T1D is to restore normal immune system function. In contrast, comparatively little is known about how beta cells themselves could actively participate and initiate the disease process.

Previous work has established that activation of the terminal unfolded protein response (UPR) in beta cells precedes symptoms of overt T1D. Indeed, inhibitors of the terminal UPR preserve beta cell mass and can reverse diabetes in the non-obese diabetic (NOD) mouse model, the classic model for spontaneous autoimmune diabetes, which recapitulates most of the features of T1D in humans. While it is generally accepted that apoptosis is the main response to terminal UPR, whether a beta cell mounts a protective or destructive stress response depends on the nature and duration of the stress as well as the competence of the beta cell to respond. Recent work has shown that intrinsic beta cell fragility is an underlying feature of both type 1 and 2 diabetes, prompting a closer investigation into the outcomes of the stress responses of beta cells in these diseases.

Cellular stress responses can induce a senescent fate and acquisition of a secretome composed of cytokines, chemokines, growth factors, proteases, and extracellular matrix factors, known as the senescence-associated secretory phenotype (SASP). A growing body of work supports the notion that SASP is beneficial when resolved efficiently, such as during embryonic development, wound healing, and tissue regeneration. However, the accumulation of senescent cells can disrupt tissue architecture and lead to dysfunction. Hence, a variety of age-related diseases in which senescent cell burden is high can be ameliorated either by genetic ablation of senescent cells or by the administration of small molecules that kill senescent cells.

Here, we report that in the NOD mouse model and in human T1D, a subpopulation of beta cells undergoes a stress response leading to senescence and SASP. Elimination of senescent beta cells from NOD mice afforded robust protection against diabetes, indicating that this subpopulation of cells contributes to disease progression. Remarkably, senolytic treatment had no apparent effect on the major lymphoid or myeloid populations infiltrating the islets, in the spleen or pancreatic lymph nodes, suggesting that in these experiments ablation of senescent beta cells does not affect immune cells. Taken together, these findings demonstrate that SASP is a pathogenic mechanism in T1D and that targeted elimination of senescent beta cells prevents this disease.

Link: https://doi.org/10.1016/j.cmet.2019.01.021

Apollo Ventures Funds Autophagy Enhancement Startup Samsara Therapeutics

As I noted recently, it is somewhat surprising to see so little movement towards the clinic in the field of autophagy enhancement over these past two decades. It has been an area of strong interest in the research community for at least that long. It is well known that upregulation of the cellular maintenance process of autophagy is an important part of the calorie restriction response, a sweeping change to metabolism that slows aging and improves health. Sizable investment in the development of calorie restriction mimetic drugs has taken place in the past fifteen years. Why then has the research and development community failed to do all that much with the direct upregulation of autophagy, despite a steady flow of papers and interest? I don't have the answer to that question, but I'll note that it isn't an unusual situation. There are many areas of research relating to aging in which all that is lacking, it seems, is the will and funding to make the leap to commercial development.

Given that, we are now at the point at which the first rejuvenation therapies worthy of the name, senolytic treatments that can clear senescent cells, has energized the investment community. Suddenly quite large amounts of funding are available for any line of work that might slow aging. The people managing venture funds, who are on a countdown of just a few years when it comes to finding placements for funding, are now sifting through the entirety of the scientific output related to aging from the past three decades, looking for possibilities. Autophagy upregulation is an obvious one, even if only on the basis of the sheer volume of research on this topic, and so companies focused on autophagy are now being founded and funded.

Taking a brief and partial glance at what is out there, Life Biosciences has Selphagy Therapeutics as a portfolio company, and as noted here Apollo Ventures has funded Samsara Therapeutics. I suspect this may be more to do with seeking a platform for small molecule drug discovery that autophagy specifically; if you look at Juvenescence and possibly other funds, the first point of entry into this field has been to invest in companies that will provide a drug discovery pipeline, not just a focus on one target.

Do I think that autophagy upregulation is a good use of resources? Well, yes, autophagy declines with age and it is widely agreed that this is a bad thing. But it is a matter of luck and happenstance at this stage when it comes to finding compounds that might produce greater upregulation than is achieved by the practice of calorie restriction. Even then, we know that calorie restriction does good things for health but little for life expectancy in humans. When the treatment exists and is free, then yes, go for it. But if we are to pour countless millions and entire careers into developing novel therapies for aging, why build things that can at best only shift more people into the higher end of natural variations in human longevity? That is aiming low, and we don't have to aim low. Those of you reading the articles below and thinking "where can I get this compound" should instead be asking "what is the size of this effect?" and probably choosing to eat less instead.

Samsara Therapeutics Closes Seed Round Led by Apollo Ventures

Samsara Therapeutics, Inc. ("Samsara,") a platform biotechnology startup engaged in the discovery and development of compounds that address the primary molecular causes of aging, announced today the closing of a seed financing round. The financing was led by Apollo Ventures, a life sciences venture capital firm and company builder working across Europe and North America. Additionally Nature Communications published a peer-reviewed paper, "The flavonoid 4,4′-dimethoxychalcone promotes autophagy-dependent longevity across species" authored by Samsara's scientific team. The paper demonstrates the capability of the Samsara platform to identify novel geroprotective small molecules that extend healthy lifespan across species and which are protective in mammalian models of disease.

The particular molecule (4,4'-dimethoxychalcone) is a natural product derived from the Japanese longevity herb known as Ashitaba. Samsara Therapeutics is conducting medicinal chemistry optimization of this compound and other Samsara platform-identified compounds in collaboration with Evotec. "This paper moves us closer to our goal of conducting the largest-ever exploration of the chemical space around natural products that extend healthy lifespan. Virtually all of the known geroprotectors have been natural products or derived thereof, and were identified via phenotypic screening. The time is ripe for this comprehensive approach due to methodological advances in phenotypic screening, target ID, and molecular mechanism of action analysis."

The flavonoid 4,4′-dimethoxychalcone promotes autophagy-dependent longevity across species

Ageing constitutes the most important risk factor for all major chronic ailments, including malignant, cardiovascular and neurodegenerative diseases. However, behavioural and pharmacological interventions with feasible potential to promote health upon ageing remain rare. Here we report the identification of the flavonoid 4,4′-dimethoxychalcone (DMC) as a natural compound with anti-ageing properties. External DMC administration extends the lifespan of yeast, worms and flies, decelerates senescence of human cell cultures, and protects mice from prolonged myocardial ischaemia. Concomitantly, DMC induces autophagy, which is essential for its cytoprotective effects from yeast to mice.

This pro-autophagic response induces a conserved systemic change in metabolism, operates independently of TORC1 signalling and depends on specific GATA transcription factors. Notably, we identify DMC in the plant Angelica keiskei koidzumi, to which longevity- and health-promoting effects are ascribed in Asian traditional medicine. In summary, we have identified and mechanistically characterised the conserved longevity-promoting effects of a natural anti-ageing drug.

An Outline of the OncoAge Consortium

The OncoAge consortium is a scientific interest group focused on the overlap between cancer and aging. Like many factions in the broader aging research community, its members are apparently giving cellular senescence a great deal of their attention these days. Better late than never, I'd say, but this focus is arguably less of an example of scrambling to catch up in their case than for purely aging-focused researchers. After all, the cancer research community studied cellular senescence to a significant degree well prior to the 2011 proof of concept study that finally persuaded gerontologists that accumulation of senescence cells is an important cause of degenerative aging.

My usual complaint about this situation is that clear evidence for that position on cellular senescence and aging was out there in plain view for two to three decades prior to that point, and simply dismissed. It wasn't until the SENS movement started to agitate on the topic in the early 2000s that matters started to move forward. Scientists are just as irrational en masse as the rest of humanity, be assured. The current development of senolytics as a rejuvenation therapy could have started twenty years ago, given a world in which different people were in charge of scientific strategy and funding. How many lives has that cost?

Chronological age is the most important single risk factor for the development of a variety of cancers and chronic diseases that account for the majority of societal morbidity, mortality, and public health costs. Recent findings suggest that changes in certain basic biological processes are shared in physiological aging, cancer, and degenerative pathologies. Importantly, similar processes can be altered in diseases as diverse as cancer, neurodegeneration, cardiovascular disorders, chronic obstructive pulmonary disease (COPD), osteoarthritis, and diabetes, to name a few.

For instance, at the cellular level, the accumulation in tissues of senescent cells (permanent cell cycle arrest in response to various types of stress or tissue remodeling) emerges as an important contributor to aging and age-related pathologies, through both cell autonomous and non-autonomous mechanisms driving inflammation, immunosenescence, and tissue degeneration. Therefore, a key challenge now is to rapidly improve our knowledge on the biological processes in common that lead to malignant transformation and degenerative pathologies.

From a cellular standpoint, the mechanisms that drive degenerative diseases and cancer are shared at an initial phase (e.g., during the accumulation of senescent cells), before adopting a particular direction and specific genetic and epigenetic modifications that orient cells toward distinct fates (e.g., escape of cellular checkpoints for cancer cells). Thus, schematically, degenerative aging and cancer can be considered as two sides of the same coin, involving many common fundamental biological mechanisms. Hence, the progressive degeneration of tissues can lead to transformation into cancer after activation of chronic inflammation and immunosenescence.

Although cancer and aging biology are closely related, they are often investigated separately. Thus, whereas a number of fundamental and translational research centers or institutes worldwide have oriented their research in the direction of aging, only a few of them have really focused their studies on the links between aging and cancer. This is the case for the Institute for Research on Cancer and Aging, Nice (IRCAN) in France, which bases its overarching strategy on combining the research developed by scientists and physicians on cancer and aging mechanisms. It is within this context that the OncoAge consortium was launched in Nice to facilitate the transfer of this growing knowledge on cancer and aging to medical innovation and current medical practice.

This consortium was certified and recognized in 2015 as a Hospital-University Federation (HUF). The global aim of the HUF program in France is to develop excellence within the university hospitals by targeting medical topics optimizing care, research, and education in these subject areas. In short, OncoAge is a HUF based on the expertise of medical and scientific teams oriented toward cancer pathologies associated with aging. The key aim of OncoAge is to improve the care of elderly patients, in particular those with cancer, to set up research projects, and develop training and educational programs in this domain. These efforts should not only deepen our understanding of the mechanisms underlying cancer and aging, but also improve the daily well-being of the patients.

Link: https://doi.org/10.3390/cancers11020250

Targeted Delivery of GDNF to Areas of the Brain Improves Parkinson's Symptoms

The overt Parkinson's disease are in part caused by the loss of a small but critical population of dopamine-generating neurons in the brain. As is the case for many neurodegenerative diseases, however, the creation of protein aggregates and resultant dysfunctional biochemistry is also important in Parkinson's. That causes a range of further issues beyond loss of motor control. The focus here is nonetheless on an attempt to regenerate lost dopamine-generating neurons, accomplished by delivering the protein GDNF into the brain over a sustained period of time, and in a very precise, narrowly targeted way. Trial results indicate an improvement in the condition of patients, providing additional support for use of the strategy of restoring lost neurons, even in the absence of any attempt to address the protein aggregation of Parkinson's disease. Though that said, I have to think that meaningful, long-term reversal of the condition will require the protein aggregates to be cleared.

A pioneering clinical trials program that delivered an experimental treatment directly to the brain offers hope that it may be possible to restore the cells damaged in Parkinson's disease. Six patients took part in the initial pilot study to assess the safety of the treatment approach. A further 35 individuals then participated in the nine-month double blind trial, in which half were randomly assigned to receive monthly infusions of Glial Cell Line Derived Neurotrophic Factor (GDNF) and the other half placebo infusions. After the initial nine months on GDNF or placebo, the open-label extension study took place, which explored the effects and safety of continued exposure to GDNF for another 40 weeks in the patients previously receiving GDNF (80 weeks in total) and the effects of 40 weeks of open label GDNF in those subjects who had previously received placebo for the first 40 weeks.

A specially designed delivery system was implanted using robot-assisted neurosurgery. This delivery system allowed high flow rate infusions to be administered every four weeks. Four tubes were carefully placed into each patient's brain, which allowed GDNF to be infused directly to the affected areas with pinpoint accuracy via a skull-mounted transcutaneous port behind the ear. After implantation and over the following several years the trial team administered more than 1000 brain infusions, once every four weeks over 18 months to study participants.

After nine months, there was no change in the PET scans of those who received placebo, whereas the group who received GDNF showed an improvement of 100% in a key area of the brain affected in the condition, offering hope that the treatment was starting to reawaken and restore damaged brain cells. By 18 months, when all participants had received GDNF, both groups showed moderate to large improvements in symptoms compared to before they started the study and that GDNF was safe when administered over this length of time. "This trial has shown that we can safely and repeatedly infuse drugs directly into patients' brains over months or years. This is a significant breakthrough in our ability to treat neurological conditions."

Link: https://www.iospress.nl/ios_news/new-treatment-offers-potentially-promising-results-for-the-possibility-of-slowing-stopping-or-even-reversing-parkinsons-disease/

Video of Investor Jim Mellon Presenting at Abundance 360 Summit 2019

Jim Mellon's Juvenescence venture is at present one of the few major venture organizations focused on approaches to treat aging as a medical condition. Mellon and his colleagues outlined their take on the field in a 2017 book, also called Juvenescence. We are fortunate in that he is among the first few high net worth individuals to both agree with the SENS philosophy of damage repair, and then, much more importantly, follow through in action as well as word. He is not just seeing a massive market opportunity in treating aging, though that is certainly there, but is doing this because he wishes to achieve the goal of radical life extension - far longer, healthier lives for all.

Jim Mellon is a relentless promoter once he has entered a field. As the science progresses to clinical development, we need someone like this. He will pull in the largest, most conservative investment concerns who presently have next to no interest in treating aging, and his funds will enable the startups and development programs needed to produce therapies. This is the necessary next stage in the evolution of rejuvenation research and development: moving from the laboratory to the clinic, moving from startup with data to fully funded company with human trials underway. It is an enormous amount of work, and requires large amounts of funding. That funding doesn't just happen by magic; considerable effort goes into lining up all of the necessary moving parts.

Jim Mellon - Abundance 360 Summit 2019

Thank you ladies and gentlemen for listening at this relatively late hour in the conference. I'm absolutely delighted to be here. I'm a non-scientist, so when I do something new, which is what I'm doing in longevity at the moment with my partners, I like to write a book about the subject, so that I can organize my thoughts and get access to key opinion leaders. A year and a half or so ago, I wrote a book called Juvenesence, which is also the name of our recently formed company, and I traveled around the United States, 8,000 miles in an old Honda, which I kept in San Francisco.

The Honda has now been sold, sadly, but the information that I garnered was extraordinary, and I'm really pleased for the first time in my career - and it has been quite a long career - to have found something where I am actually able to, in a very small way, move the dial as opposed to just jump on a bandwagon, as I've done before. I started off as a fund manager, and then I got into mining, German property, and, latterly, biotech. I've been involved in the biotech business for twelve years, and what is amazing to me is that in just those short twelve years, there has been an enormous change in biotech - particularly in the last six or seven years.

So the first book I wrote on this subject was called Cracking the Code. It is available in the remainder bins of some bookshops around the world. Still available, low price. Then the second book I wrote is Juvenescence, which I mentioned earlier on. In that time frame, six or seven years, we've heard the dawn of artificial intelligence, you've heard about In Silico Medicine as an example, for the discovery of novel compounds. That didn't exist six years ago. We've had the cure for hepatitis C in the last six years. This was a terrible scourge, and now if you've got $80,000, you can be cured, and many people have been cured of it. The Gilead drug was the best selling drug in the world for a while, selling at its peak $20 billion a year. We've had cancer immunotherapy that did not exist just six years ago, and this year it is going to breach all expectations. Sales of cancer immunotherapies, which have had biblical results in some cancers, will be over $100 billion. That was just an idea six years ago. Of course everyone is familiar with CRISPR/Cas9, Cas12 and Cas13, and so forth, and its variants, and that did not exist, even in published papers, six years ago when I wrote the book Cracking the Code.

In those six years, so much has happened. New industries have been created. What is going to happen in the next six years? Well, the answer is that none of us really know. In our own company Juvenescence, which is the fourth company my partners and I have started in the biotech space in the last decade or so, we don't really know, and so we're trying to put together a load of subsidiaries that cover most of the ground of this area. Because, for sure, out of eighteen projects, which is what we have, surely something will work and produce returns for our investors, and most importantly benefit patients, and lead us all to live a healthier and longer life, which is the aspiration of most people on the planet.

It was mentioned that life expectancy has increased dramatically over the last century or so. It has stalled a bit in the United States and the UK, and that is because the environmental factors that led to the improvement in life expectancy, including such things as antibiotics and vaccinations, have run their course. Things like opioid addiction are now taking a toll on life expectancy in countries such as the United States and the UK. But it is a fact that nothing has changed biologically in the last century: you take someone out of 1900 and put them in today's environment, they will live just as long as we do. Nothing has changed in our fundamental biology. But today we're on the cusp of a major change. The biological engineering of humans, the rearrangement of our atoms and molecules to effect longer lives is with us. There are human trials going on at the moment, this is not science fiction, and one of our own products will be in humans in the first quarter of next year. We have very high hopes for that. So I say with confidence, that I believe that life expectancy at birth will reach 115 within 20 or 30 years. That will change the entire trajectory of our lives. We'll no longer just be born, learn, earn, retire, and expire. There will be a whole fundamental change to our lives, with Peter Diamandis in his various books has described admirably.

We all known of Jeanne Calment, was she a fraud or not? In my opinion she did live to 122. People can live very long lives, we're not destined to die, but there are various factors that lead to the aging process. Some people have geroprotective genes, such as Jeanne Calment, and those genes will eventually be inculcated into the broader population, and those genes - using gene editing - will be the thing that keep people alive to 115 and beyond. But for the moment, it is small molecules, stem cells, and organ regeneration that we're focusing on.

We know now that aging is largely caused by antagonistic pleiotropy and hyperfunctioning. Genes that work well in our early days work against us as we get older. That is now a converging theory, and it is very important one, and we also know that there are some creatures out there that display negligible senescence, that really don't die except from predation. We are similarly made from atoms and molecules, and when rearranged, in due course, our pattern of death will be a very different one. However, we need to stay on the bridge. We need to stay healthy, because in the next ten years there will be phenomenal stuff that will keep us alive longer, and in a healther condition, and that is a statement of the obvious. Don't smoke, floss your teeth, eat some chocolate, drink some red wine, but not in vast quantities, and exercise in moderation. The astonishing breakthroughs, the terminologies that some of you are familiar with, such as NAD+, p53, autophagy, mTOR, and so forth, will come to the fore as science accelerates and develops as rapidly as it is today.

But we are still in the primitive phase of this. We are still very early in the science, and hence the opportunity for investors such as myself, Peter Diamandis, and other collaborative colleagues in this industry. There are some things out there that we can do now. I don't recommend hooking yourself up to a young person along the Ambrosia lines. Elevian are doing great work in seeing what factors in young blood could be applied to older people. I also don't recommend caloric restriction: it might add 5% to your life span if you starve yourself, if you eat 25% fewer calories, but it will feel like a very, very, very long life. Mimetics of caloric restriction are being developed, such as by ourselves in conjunction with the Buck Institute, and they will be in wide dispersal in the relatively near future. Then of course there are things like Elysium's Basis, there is metformin, for which a trial is going on at the moment under FDA auspices and Nir Barzilai. Then there is rapamycin, which is now being applied in dogs with some stunning effects, and rapalogs will be in human beings. My own Jack Russell terrier, Horatio, who is twelve years old, is now on the rapamycin, and I can tell you he is running around like a young puppy. So if it works for him, I'll taking it myself in the relatively near future.

Coming soon, we have senolytic drugs. Many of you may be familiar with senescent cells, these cells that are somewhere between healthy functioning and apoptosis. They cause a large burden of inflammation in human beings. Unity Biotechnology has a senolytic drug in human trials at the moment. There are other people developing senolytic trials including ourselves, via our company FoxBio in conjunction with Ichor Therapeutics in New York. Senolytic drugs are going to be, in my opinion, the front line of aging technology in the relatively near future, and will be in wide dispersal within the next three to five years for specific indications, and beyond that for longevity purposes.

I think there are about twenty senolytic companies out there, of which about five are serious ones. We own 50% of something called FoxBio, and we are further back from Unity Biotechnology, but we think we've got a better compound, we just don't know. We've invested $10 million in that so far. As we grow older we develop more senescent cells, as I said earlier, and that is because the body puts these cells into a state of arrest, probably to stop cancer. The removal of those senescent cells in animals seems to reverse the process of aging, not just just halt or slow. The mouse photograph I'm showing has been very useful in our fundraising efforts. On the right hand side you see the same mouse, this is a mouse that is about equivalent to 95 years old in a human. It is treated with a senolytic drug to remove these senescent cells, which account for less than 1% of the cell population, but account for almost all the inflammation. So osteoporosis, osteoarthritis, frailty, lack of balance, all that sort of stuff. This mouse treated with this senolytic drug goes from being 95 back to being middle aged. So it is an actual reversal of aging.

Whether it works in humans or not, we don't know, but it is in human trials for osteoarthritis and also for age-related macular degeneration. We're not sure what indication we'll go for, but I'm very optimistic about this. This is a small molecule, this is our specialization in the companies that we've formed so far. I think that this is going to be a very, very large selling product category in the drug field in the relatively near future.

So there are lots of things going on. You are familiar, this audience, with Samumed, which I visited last year in San Diego. I think it is a fabulous company. That is an indication of how much money is coming in to the space. They have raised $685 million and a $12 billion rumored pre-money valuation. The FOXO family is being interfered with, so our company FoxBio is an indication of that. Then of course you've got stem cells. We have our own company AgeX Therapeutics, which is now public here in the United States, we own about half of that company. I think stem cells are going to be the second major factor in the armatorium of fighting aging. Then down the pipe there is gene therapy, which undoubtably will be the way in which some of us will live to over 115 and beyond.

My partners and I have done several biotech companies, the most recent one is listed on the New York Stock Exchange. It is called Biohaven, and we started it four years ago. It has an approvable drug for migraine. Chairman Declan Doogan was formally the head of R&D at Pfizer, and latterly the CEO of Amarin, which was a huge success as some of you will know, with a drug for heart health. So we have a great seasoned team, and we have a personal motivation, because we are all of a certain age, to accelerate this process. So the aging acceleration of course includes artificial intelligence, which is one of Peter Diamandis' specializations, and we, Juvenescence, are the largest outside investor in In Silico Medicine, which has been mentioned a couple of times here today. This is a very exciting thing.

In the last few minutes I wanted to talk about Lygenesis. This is the first company that will be in humans, in the first quarter of next year. One year away - it is not very far. It will be in sick patients, so we can see immediately in a phase 2 trial whether it works or not. The idea is to take a cadaver liver, donated by someone, probably someone who fell off a motorbike, unfortunately, and divide it into 75 pieces. Those 75 pieces are implanted into 75 patients, and put it into a lymph node, and hope that the liver fully vascularizes and works and takes over from the patient's failing liver. There are plenty of people in the work who have failing livers. It costs $700,000 for a liver transplant here in the United States. It takes fifteen hours, and has a high mortality rate associated with it. Lygenesis has a twenty minute outpatient procedure, and it will cost less than $100,000 dollars to do. It expands the number of potential liver transplants, and there are seven million people in the US and Europe who have failing livers to the point at which it is going to kill them.

Now it hasn't been done in patients yet, but the FDA has accepted that this will be in patients in the first quarter of next year. In animal models, that is dogs, pigs, and mice, 450 plus trials have been done, and there has been a 100% success rate, which is absolutely remarkable in the context of scientific research. So I'm super excited about this company, which we own half of, because very importantly, this could be done not just in the liver, it could also be done for the thymus. The thymus is where your T cells are grown or matured, so your T cells come out of the thymus. As you get older the thymus involutes to nothing, it becomes very small, and that is why very old people have impaired immune systems. This could be a way of restoring immune systems in human beings.

We are at the dawn of the internet equivalent in this industry. As I said earlier, it is primitive, but it is accelerating, largely as a result of the efforts of people such as Peter Diamandis and other proselytizers, and you will remember, vaguely, in the 1980s and the 1990s, the geeky Bill Gates and others of this world, and none us thought that they would be as successful as they have been. We're at that stage in the longevity industry at the moment. Markets develop very quickly; I mentioned cancer immunotherapy taking over in cancer therapy as a gold standard, while biologics were nothing in 1995 and now are a third of all drug sales around the world. So this could be the same for longevity products. Of course, people are willing to spend money to gain extra years of healthy life. Eventually this will be available to everyone, even if at the beginning it will be available only at an expensive level, for the people who have money. But therapies come off patent, and will be widely available to everyone around the world. That is why I say with confidence that we are going to live a much longer life, and in good health.

The last thing I wanted to say is that if you take a stadium like this, and you dribble 1ml of water into it, and then you double that amount every minute, then it will take just 40 minutes for the whole stadium to be covered by 10cm of water. If you then wait for another four minutes, you will fill the entire stadium. This is equivalent to this science; at moment it is not widely known, it is only very nascent, it is in its early days. We are so lucky to be the first cohort on the planet to experience this science, but it is going to hit us very hard in the face if we are not prepared for it, because everything in the world is going to change as a result of changes due to biologically engineered life expectancy. It is going to happen very fast.

No-one, if I ask them, really knows how long it is going to take for the stadium to fill. Most people would say five days or ten days. It actually only takes 44 minutes, because you are doubling all the time, and this is where we are at in the science of longevity. At the moment longevity drugs and products are all snake oil, and sell about $140 billion around the world on an annual basis. None of them work. Imagine how big this market will be when the products start to work - and they are starting to work, they are in human trials, and I am super excited to be part of this.

Frailty Dramatically Increases Mortality Risk at any Age

Frailty syndrome is known to be associated with risk of death. It is a collection of signs of an advanced stage of damage and consequent dysfunction in the body, to the point at which loss of strength prevents most activities and the immune system can barely defend against pathogens. Researchers here add to the body of evidence demonstrating that frailty is linked to mortality; frail individuals at any age are in a worse position than their less frail age-matched peers. For all of the obvious reasons, the banishment of frailty from the human condition is one of the more important near term goals for the rejuvenation research community. It may be possible to achieve this to a fair degree through a narrow focus on the comprehensive control over chronic inflammation, as many of the components of frailty appear to be greatly influenced by the growing inflammation and incapacity of the immune system with age.

The concept of frailty is well established. Many clinicians diagnose it and know that it may negatively impact on a patient's clinical condition. However, it is often diagnosed in a subjective 'end of the bed' test rather than by using specific diagnostic criteria, despite being recognised as a factor influencing outcomes in geriatric research for many years. Frailty is a state in which a vulnerable individual, has a diminished physiological capacity to respond to external stress such as infection or trauma.

There are many instruments used to measure frailty, with variation in their composition. Development of these tools, and frailty research generally, have historically focused on older populations, but the recent publication finding the existence of frailty and its' negative impact on outcomes in younger adults (aged over 40 years) admitted as a surgical emergency suggests that frailty is not a diagnosis exclusive to older adults. The exact prevalence of frailty is currently unknown, recent studies have reported this between 8% and as high as 37%, but any estimate is a combination of heterogeneous subgroups and shows variation depending on the tool used to detect frailty.

This study aimed to evaluate the prevalence of frailty its associated risk of mortality, readmission rate and length of hospital stay in all adults, regardless of age, admitted as a surgical emergency. To evaluate the impact of frailty across the full range of the frailty spectrum the 7-point Clinical Frailty Scale was used and the outcome measures assessed for each incremental point increase. The cohort included 2,279 patients (median age 54 years; 56% female). Frailty was documented in patients of all ages: 1% in the under 40s to 45% of those aged 80+. We found that each incremental step of worsening frailty was associated with an 80% increase in mortality at Day 90, supporting a linear dose-response relationship. In addition, the most frail patients were increasingly likely to stay in hospital longer, be readmitted within 30 days, and die within 30 days.

Link: https://doi.org/10.1093/ageing/afy217

Control of Inflammation May Contribute to the Longevity of Bats

Bat species tend to be very long lived in comparison to other mammalian species of a similar size. The usual explanation for this involves evolutionary adaptation to the metabolic demands of flight. Bats and birds exhibit similar biochemical and metabolic features, despite their evolutionary distance from one another. Bats may have evolved mitochondria, the power plants of the cell, that are more efficient and more resilient to oxidative damage than their closest mammalian relatives that do not fly, and it is generally acknowledged that mitochondrial function and metabolic rate are important determinants of species longevity.

Here, however, researchers argue for greater control over inflammatory responses to be a noteworthy contributing factor in the longevity of bats versus other small mammals. Chronic inflammation is certainly a major issue in human aging; the immune system becomes progressively ever more overactive and incapable. Inflammation is useful and necessary in short bursts, whether defending against pathogens or assisting in regeneration from injury, but those same mechanisms cause considerable harm when turned on all the time.

Bats live very long and host numerous viruses that are extremely harmful when they infect humans and other animals. Researchers wanted to find out how bats can harbour so many of these pathogens without suffering from diseases. The key, they found, is in the bat's ability to limit inflammation. Bats do not react to infection with the typical inflammatory response that often leads to pathological damage. In humans, while the inflammatory response helps fight infection when properly controlled, it has also been shown to contribute to the damage caused by infectious diseases, as well as to aging and age-related diseases when it goes into overdrive.

The researchers found that the inflammation sensor that normally triggers the body's response to fight off stress and infection, a protein called NLRP3, barely reacts in bats compared to humans and mice, even in the presence of high viral loads. The researchers compared the responses of immune cells from bats, mice and humans to three different RNA viruses - influenza A virus, MERS coronavirus, and Melaka virus. The inflammation mediated by NLRP3 was significantly reduced in bats compared to mice and humans.

Digging further, they found that 'transcriptional priming', a key step in the process to make NLRP3 proteins, was reduced in bats compared with mice and humans. They also found unique variants of NLRP3 only present in bats that render the proteins less active in bats than in other species. These variations were observed in two very distinct species of bats - Pteropus alecto, a large fruit bat known as the Black Flying Fox, and Myotis davadii, a tiny vesper bat from China - indicating that they have been genetically conserved through evolution. Further analysis comparing 10 bat and 17 non-bat mammalian NLRP3 gene sequences confirmed that these adaptations appear to be bat-specific. What this implies is that rather than having a better ability to fight infection, bats have a much higher tolerance for it. The dampening of the inflammatory response actually enables them to survive.

Link: https://www.duke-nus.edu.sg/news/duke-nus-researchers-discover-secret-bats%E2%80%99-immunity

Upregulation of Autophagy to Attenuate Age-Related Declines in Muscle Regeneration

As a companion piece to another recently published open access paper, noted earlier this week, today's review paper considers the therapeutic upregulation of autophagy as a possible approach to reduce the deleterious impact of aging on muscle regeneration. Autophagy is the name given to a collection of cellular housekeeping processes responsible for ensuring that excess and broken cellular components are transported to a lysosome for recycling. Lysosomes are membrane-bound vesicles packed with enzymes capable of breaking down near all structures and molecular waste they are likely to encounter. The remnant molecules are released back into the broader cell as raw materials.

Autophagy is known to decline with age. Many of the approaches shown to slow aging in short-lived laboratory species either involve increased autophagy, or, as is the case for calorie restriction, appear to depend on increased autophagy for the beneficial effects on health and life span. Increased autophagy is a feature of many forms of cellular stress response: heat, cold, lack of nutrients, oxidative damage, and so forth. Mild or short-lived stress or damage can provoke a reaction that lasts for a while and produces an overall gain in cell function. Since autophagy removes damaged components, it limits the opportunity for damage to spread and produce downstream effects. When that is happening in every cell in the body on a regular basis, the result is a longer life span.

Unfortunately, what we know of the effects of calorie restriction in mice and humans tells us that stress responses such as upregulated autophagy have a much larger effect on life span in short-lived species than they do in long-lived species such as our own. Calorie restriction can increase maximum mouse life span by 40%. In humans an effect size of more than five years would be surprising, given that any reliable gain much larger than that would have been discovered in antiquity and very well explored by now. Which is not to say that calorie restriction is worthless: it produces a larger reliable gain in long term health - for basically healthy people - than any readily available, well understood medical technology. Given the advent of senolytics as a rejuvenation therapy, that statement probably won't remain true for very much longer, but it is worth considering.

Autophagy as a Therapeutic Target to Enhance Aged Muscle Regeneration

Skeletal muscle has remarkable regenerative capacity, relying on precise coordination between resident muscle stem cells (satellite cells) and the immune system. The age-related decline in skeletal muscle regenerative capacity contributes to the onset of sarcopenia, prolonged hospitalization, and loss of autonomy. Although several age-sensitive pathways have been identified, further investigation is needed to define targets of cellular dysfunction. Autophagy, a process of cellular catabolism, is emerging as a key regulator of muscle regeneration affecting stem cell, immune cell, and myofiber function.

The pharmacological induction of autophagy represents a promising strategy to improve stress resistance and regeneration of skeletal muscle. Spermidine and rapamycin are two examples of drugs that have been studied for their autophagy-inducing effects and lifespan extension in rodent models. While rapamycin acts directly on mTOR, spermidine's polyamine effects on histone acetylation status upregulates various autophagy-related transcripts and suppresses necrosis. The positive benefits of spermidine in muscle tissues of mice and rats have been shown by mitigating age-related muscular atrophy as well as functional myopathies that originate from autophagy failure.

Spermidine also modulates macrophage polarization in mice towards reduced inflammation, though some evidence suggests the autophagy inducing effects of rapamycin more directly target T lymphocytes. Taken together, these agents act as "caloric restriction mimetics" to induce autophagy and contribute to improvements in lifespan of mice. Specifically, the effects of autophagy induction show promise as it related to therapies targeting muscle stem cell myogenic capacity.

Muscle stem cells and monocytes/macrophages are essential for skeletal muscle homeostasis and regeneration. A common theme among these cell populations is the idea that autophagy is a key process that is altered in aged cells leading to functional decline. Autophagy is no longer an emerging regulator of cellular function but has consistently been shown to play a central and important role, especially in the context of aging. Stem cells, in particular, show dysfunctional autophagy during initial stages of activation while caloric restriction and physical activity allow a sensitization to autophagy with beneficial outcomes in cellular activation and function. The exact role for autophagy in muscle regeneration will be complex considering the temporal nature and diverse cell types contributing to the regenerative program. However, global induction of autophagy appears beneficial to the regenerative capacity in the aged muscle. Continuing to uncover the molecular events responsible for age-related perturbations in these pathways is critical for exposing pharmaceutical targets to combat the aging process and improve tissue regeneration in aged individuals.

Aneuploidy and Cellular Senescence in Aging

Aneuploidy is not very well studied in the context of aging, but at least a few research groups are looking into it. Aneuploidy describes the state of cellular dysfunction that arises from one or more missing or extra chromosomes, a problem that can occur as the result of malfunctions during cellular replication. Like all such issues in which an individual cell becomes damaged, the extent to which it causes downstream harm is largely governed by the degree to which a cell with aneuploidy can replicate, spreading its disordered state into a greater fraction of tissues. Alternatively, if aneuploidy occurs spontaneously with a great enough frequency, and also drives cells into senescence, then this might also be a path to significant harm in the course aging. Senescent cells contribute to aging via signaling, and even a comparatively small number of senescent cells can be very damaging.

This paper, I think, is an example of a fairly prevalent recent phenomenon: researchers retrofitting their current line of work on aging to more clearly build a link to cellular senescence. Cynically, I would say that this burst of rethinking is driven by the sizable influx of funding into the research and development of means to destroy or reprogram senescent cells. Now that it is broadly acknowledged that cellular senescence is a contributing cause of aging, there is funding for related projects, and the activities of researchers tend to be steered by the availability of funds.

Aging is characterized by a progressive loss of physiological integrity and function over time. Being the largest risk factor for the incidence of cancer, cardiovascular, and neurological diseases, it results from several interconnected molecular processes that decline with advancing age and that are commonly categorized in nine "aging hallmarks". Among these hallmarks, which are nevertheless interdependent, epigenetic alterations and cellular senescence have gained increased relevance, as they have been modulated by the current mainstream anti-aging therapies.

Although a single universal marker for cellular senescence is still to be unveiled, senescent cells present several distinguishing features in vitro, such as flattened morphology and enlarged nuclear size, and increased senescence-associated β-galactosidase (SA-β-Gal) activity. Moreover, cellular senescence is accompanied by the development of a senescence-associated secretory phenotype (SASP), a distinctive cell-specific secretome. There has been intensive research examining the regulatory mechanisms behind cellular senescence and SASP. It is now clear that this occurs on two fronts; while p53 and pRB are responsible for halting cell cycle progression during cell senescence, the regulation of the secretory component seems to be mainly mediated by the NF-κB signaling pathway.

For several decades, many observations have demonstrated an incidence of aneuploidy along human chronological aging. Aneuploidy is defined as an abnormal chromosome number resultant from chromosome mis-segregation during cell division, in both gametes and somatic cells. The molecular mechanisms behind the age-associated aneuploidy globally point to alterations in the expression levels of genes that are involved in the cell cycle and in the mitotic apparatus. Interestingly, genomic instability, telomere erosion, epigenetic drift, and defective proteostasis, which are the primary hallmarks of aging acting as initiating triggers leading to secondary hallmarks, have all been reported to induce mitotic defects and aneuploidization. Moreover, aneuploidy resulting from lagging chromosomes/weakened mitotic checkpoint has been associated with cellular senescence and premature aging.

While we are left to learn more what a truly senescent cell is, if there is the need of long- or short-term clearance from the organism, and, more importantly, if we can rescue the still proliferative "pre-senescent" cells. In this context, a new candidate hallmark for aging arises, aneuploidy, an abnormal chromosomal number that results from mis-segregation events during mitosis, which has been linked to normative aging and age-associated diseases, with the underlying mechanisms being poorly understood. Recently, aneuploidy was shown to increase with advancing age due to an overall dysfunction of the mitotic machinery. Furthermore, several reports have uncovered the impact of aneuploidy on cellular fitness and proliferative capacity, with several characteristics of aneuploid cells overlapping with those that are found in aged cells.

Our latest work provided insight as to how senescent cells arise, by demonstrating that elderly proliferative cells, primed with the expression of a senescence core gene signature, evolved into permanent cell cycle arrest (full senescence) following passage through a faulty mitosis. This further supports that improving mitotic fitness may be used as a potential anti-aging strategy, thereby counteracting the SASP-induced inflammatory microenvironment and helping to protect stem cell and parenchymal cell functions.

Link: https://doi.org/10.3390/ijms20040938

Acid Sphingomyelinase in Age-Related Blood-Brain Barrier Dysfunction

The blood-brain barrier is a lining of specialized cells that wraps all blood vessels passing through the central nervous system. It allows only certain molecules to pass, keeping the biochemistry of the central nervous system distinct from that of the rest of the body. Unfortunately, the blood-brain barrier begins to leak in later life, and the inappropriate passage of cells and molecules into the brain results in both chronic inflammation and more subtle processes of damage and disarray. The consensus is that this contributes to the development of neurodegenerative conditions and consequent dementia, though there is some debate over where exactly this fits in the hierarchy and causality of effects.

What causes the blood-brain barrier to break down? That is a question without a definitive answer, as for so many of the manifestations of aging. Researchers here provide evidence for rising levels of acid sphingomyelinase (ASM) to be important, demonstrating this in mice via artificially increased and decreased levels of ASM. We might then ask what causes increased ASM in old mice, but it usually takes years for researchers to follow the chain of cause and consequence to to the next point of interest, when working backwards from the end state in this manner.

Aging is related to progressive deterioration of central nervous system function and contributes to the pathogenesis of neurodegenerative disease. Previous studies have implicated alterations in the molecular mechanisms of aging with changes in the brain environment such as abnormal aggregation of proteins, neuronal loss, neuroinflammation, and cognitive deficits. The dysfunctions in aging could lead to neurodegenerative disease including mild cognitive impairment, cerebrovascular disease, Parkinson's disease, and Alzheimer's disease. In particular, disruption of the blood-brain barrier (BBB) is one of several major pathological features of these age-related neurodegenerative diseases. Moreover, many studies have demonstrated that BBB dysfunction may be a cause or consequence of neurodegeneration.

Acid sphingomyelinase (ASM), encoded by the Smpd1 gene, plays an important housekeeping role in sphingolipid metabolism and is known to regulate cell apoptosis, proliferation, and differentiation. Although ASM is expressed in virtually all cell types under normal conditions, ASM secreted from endothelial cells (ECs) is significantly associated with numerous diseases. ECs are the major cell type forming the BBB, along with pericytes and astrocytes, and the interaction between ECs and other neuronal cells is critical for the maintenance of neurological health in the brain. Previous studies have suggested that an increase in ASM activity may contribute to age-related brain damage. Nevertheless, the specific role of ASM in maintaining the integrity of the BBB and/or age-related neurodegeneration remains unclear.

In a recent study, we for the first time demonstrated that ASM derived from ECs plays a central role in aging-induced BBB disruption and neurodegeneration. Higher ASM activity was detected in plasma from older individuals (65-90 years) compared with plasma from their younger counterparts (24-45 years). We also confirmed similar results in plasma derived from old mice (20-months). The robust elevation in ASM levels in the brains of old mice was associated with microvessels, and ECs derived from microvessels were the main contributors for elevated ASM activity. These results indicated that ASM activity increased in aged plasma and brain ECs, and could affect brain dysfunction in the process of aging.

Old Smpd1 +/- mice, in which ASM is genetically inhibited, exhibited a significant reduction in ASM activity in the plasma and brain ECs. In addition, capillary density in the brains of older mice was decreased by EC death, while old Smpd1 +/- mice exhibited higher capillary density. BBB permeability was also increased in the brains of old mice. In contrast, a substantial decrease in permeability in old Smpd1 +/- mice was observed. Moreover, the leakiest vessels in the brain did not exhibit an apoptotic signal in both old mice and old Smpd1 +/- mice, indicating that the death of ECs caused by ASM was not the main cause of BBB disruption in aging.

In conclusion, our findings suggest a central role for ASM as a regulator of BBB integrity and neuronal function in aging, as well as highlight the potential of ASM as a drug target for anti-aging. To date, few inhibitors that can directly inhibit ASM have been found; nevertheless, highly potent and selective ASM inhibitors are anticipated to be developed in the future. Therefore, further studies investigating the development of functional ASM inhibitors may be highly valuable for understanding the anti-aging process and for the treatment of various age-related neurodegenerative diseases.

Link: http://submit.bmbreports.org/Search/View.html?tmp_tr_num=4521