Fight Aging!

A reduced calorie intake produces beneficial changes to metabolism, promoting autophagy and cell maintenance, among other mechanisms, improving health and leading to a modestly slowed pace of aging. Interestingly, adjusting the time of eating in order to experience longer periods of hunger while still consuming the same calorie intake produces outcomes that are broadly similar at the high level, even if somewhat different at the detailed level of metabolism and cell biochemistry.

One might look at the great breadth of research into calorie restriction, time-restricted feeding, and intermittent fasting and conclude that one of the more important factors in the results achieved is the amount of time spent in a state of hunger. In other words that it is the hunger-associated signaling and cellular reactions to that signaling that provide a sizable fraction of the benefits observed when calories are consistently reduced. There are, must be, other mechanisms at work, of course. A low calorie diet sustained over time reduces the burden of harmful inflammatory visceral fat tissue, for example. Further, reducing specific dietary components such as methionine without reducing overall calorie intake can trigger nutrient sensors to induce some of the benefits of calorie restriction. It is an interesting area of study.

Effect of time-restricted eating and intermittent fasting on cognitive function and mental health in older adults: A systematic review

Nutrition is one of the modifiable lifestyle factors that has been identified as a potential target for interventions in older adults' cognitive health and mental well-being. Time Restricted Eating (TRE) and Intermittent Fasting (IFA) are two dietary approaches that have gained popularity in recent years due to their potential health benefits. Time Restricted Eating (TRE), an approach rooted in the alignment of eating patterns with circadian rhythms, centers on limiting the span of time during which food consumption occurs each day and emphasizes the importance of when we eat, along with underscoring the intricate interplay between nutrition and the body's internal clock within a disciplined time frame typically ranging from 8 to 12 hours.

On the other hand, IFA encompasses a spectrum of fasting regimens with the common thread of cycling between periods of food consumption and periods of calorie restriction or fasting. These dietary approaches, TRE and IFA, have demonstrated their efficacy in improving metabolic health by enhancing factors such as insulin sensitivity, glucose metabolism, and lipid profiles. Additionally, these approaches have been associated with factors linked to increased longevity, including improvements in cardiovascular health and a reduction in the risk of age-related diseases.

Studies have suggested that both IFA and TRE may have beneficial effects on cognitive function and mental health in older adults. The mechanisms underlying these effects are complex and multifaceted, but may involve improvements in glucose metabolism, inflammation, oxidative stress, and neuroplasticity. Both IFA and TRE involve periods of fasting, which can lead to a decrease in insulin resistance and an increase in insulin sensitivity. This can, in turn, improve glucose uptake in the brain, which is important for preserving cognitive function and minimizing the risk of cognitive decline. Additionally, improved glucose metabolism may have a protective effect on the brain, lowering the likelihood of neurodegenerative conditions like Alzheimer's and Parkinson's. IFA and TRE may also modulate the gut microbiome, which has been implicated in brain function and mental health.

Recent studies have delved into the association between TRE, cognitive function, and mental health in older adults, yielding somewhat mixed results. While our findings suggest a relationship between TRE and IFA practices and cognitive function and mental health among older adults, it is important to acknowledge the complexity of this relationship. Various factors, including the duration and timing of the eating window and the physical condition of older adults, or even specific subgroups like those aged 70 years and older, can influence the outcomes.

Our systematic review encompasses a range of study designs, each offering unique insights into the effects of fasting interventions on cognitive function and mental health in older adults. Cross-sectional studies revealed that individuals practicing TRE were less likely to exhibit signs of mental health distress, particularly those aged over 70 years. Experimental designs provided preliminary evidence regarding the feasibility and potential efficacy of fasting interventions. Cohort studies tracked participants over time and found that individuals regularly practicing IFA were more likely to revert to successful aging with no cognitive impairment compared to those with irregular or no IFA practice.

In this study, researchers assessed the effects of a healthy lifestyle on mortality in older people suffering from chronic conditions of aging. As noted in similar studies, the effect size is larger than that achieved via readily available pharmaceutical strategies used to treat chronic illness, such as antihypertensive and lipid-lowering drugs. It is never too late to adjust one's choices in order to reduce future health risks: regular exercise, lose excess weight, eat a better diet, and so forth.

Lifestyles are associated with all-cause mortality, yet limited research has explored the association in the elderly population with multimorbidity. We aim to investigate the impact of adopting a healthy lifestyle on reducing the risk of all-cause mortality in older individuals with or without multimorbidity in both China and UK. This prospective study included 29,451 and 173,503 older adults aged 60 and over from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and UK Biobank. Lifestyles and multimorbidity were categorized into three groups, respectively. Cox proportional hazards regression was used to estimate the Hazard Ratios (HRs) and dose-response for all-cause mortality in relation to lifestyles and multimorbidity, as well as the combination of both factors.

During a mean follow-up period of 4.7 years in CLHLS and 12.14 years in UK Biobank, we observed 21,540 and 20,720 deaths, respectively. For participants with two or more conditions, compared to those with an unhealthy lifestyle, adopting a healthy lifestyle was associated with a 27%-41% and 22%-42% reduction in mortality risk in the CLHLS and UK Biobank, respectively; Similarly, for individuals without multimorbidity, this reduction ranged from 18% to 41%. Among participants with multimorbidity, individuals with an unhealthy lifestyle had a higher mortality risk compared to those maintaining a healthy lifestyle, with HRs of 1.15 and 1.27 for two conditions, and 1.24 and 1.73 for three or more conditions in CLHLS and UK Biobank, respectively. Adherence to a healthy lifestyle can yield comparable mortality benefits for older individuals, regardless of their multimorbidity status. Furthermore, maintaining a healthy lifestyle can alleviate the mortality risks linked to a higher number of diseases.

Link: https://doi.org/10.1016/j.ssmph.2024.101673

Given that cardiovascular disease is the largest cause of human mortality, and the present dominant strategy of lowering LDL-cholesterol in the bloodstream has failed to change that fact, it is perhaps surprising to find that there exist only minor, exploratory attempts to break new ground and move beyond this approach. There is not great program of discovery, no sense of urgency, only small groups occasionally trying something new every few years or so. More generally, research into novel ways to address aging and age-related disease is far from adequately supported, given the great burden of suffering and mortality that accompanies old age.

It is widely accepted that atherosclerosis, a primary driver of cardiovascular disease (CVD), is primarily caused by inflammation at the endovascular level, yet most treatments fail to address their cause. Aging itself is a major independent risk factor for CVD, which remains one of the leading causes of disability and death. As shown in different studies, age-related arterial dysfunction was found in the absence of conventional cardiovascular risk factors, suggesting that age-related arterial dysfunction is a primary effect of advancing age. This phenomenon persists despite best efforts to promote healthy lifestyle and pharmacological treatments. Additionally, it is worth noting that as much as 20% of individuals who develop coronary heart disease lack conventional risk factors. This suggests there are still unaddressed factors missing from the current approach to patient management. Furthermore, another study showed that up to 70% of individuals who experienced myocardial infarctions were classified as low risk based on conventional 10-year coronary heart disease risk screening.

Recent evidence suggests that three finite physiological responses to numerous insults exist in the human body, attributing to the pathophysiology of CVD: oxidative stress, inflammation, and ultimately vascular dysfunction. This process, often referred to as vascular aging or "inflammaging", encompasses the complex interplay of molecular and cellular events like immune dysregulation associated with aging and the acceleration of age-related diseases. Consequently, it is essential to consider certain overlooked and novel factors that contribute to aging as a process also contributing to the origin of traditional risk factors. For example, the gut microbiome - a complex ecosystem of organisms located throughout our body organs, including the gastrointestinal tract, serving as a transducer of environmental signals to the rest of the body - contributing either to promoting or reducing systemic inflammation and age-related cardiovascular disease risk. Understanding such factors is needed to be able to address them.

Link: https://doi.org/10.2147/CIA.S457180

As the authors of today's open access paper note, their study is not the first to find a correlation between the diversity of the oral microbiome and cognitive function. The relative numbers of different microbial species present in the mouth can be assessed using 16S rRNA sequencing, where different species have slightly different 16S rRNA gene sequences. Given low cost assays to categorize a microbiome, there is a growing interest in the contributions to function and dysfunction made by the various distinct microbiomes situated throughout the body: gut, skin, mouth, and so forth. In this case, a greater diversity of microbial species present in the mouth correlates with a lesser age-related loss of cognitive function. Why is this the case?

The most well researched mechanism is inflammation generated by harmful species such as Porphyromonas gingivalis, responsible for gum disease. Gum disease allows leakage of bacteria and their products into the bloodstream. There is some evidence for this mechanism to underlie a relationship between gum disease and more serious issues such as atherosclerosis and dementia, though there is some debate over whether this is in fact a sizable effect versus other contributing factors. It is possible to speculate in other directions, however. For example, people who take worse care of their oral health probably also undertake less day to day maintenance of health and fitness in other ways, leading to greater age-related neurodegeneration. Or that age-related loss of cognitive function may contribute to a lesser effort in maintaining oral health. The challenge with human epidemiological data is that it does not show causation.

Association of the oral microbiome with cognitive function among older adults: NHANES 2011-2012

An association between the gut microbiome and cognitive function has been demonstrated in prior studies. However, whether the oral microbiome, the second largest microbial habitant in humans, has a role in cognition remains unclear. Using weighted data from the 2011 to 2012 National Health and Nutrition Examination Survey, we examined the association between oral microbial composition and cognitive function in older adults. The oral microbiome was characterized by 16S ribosomal RNA gene sequencing. Cognitive status was assessed using the Consortium to Establish a Registry for Alzheimer's Disease immediate recall and delayed recall, Animal Fluency Test, and Digit Symbol Substitution Test (DSST). Subjective memory changes over 12 months were also assessed. Linear regression and logistic regression models were conducted to quantify the association of α-diversity with different cognitive measurements controlling for potential confounding variables. Differences in β-diversity were analyzed using permutational analysis of variance.

A total of 605 participants aged 60-69 years were included in the analysis. Oral microbial α-diversity was significantly and positively correlated with DSST (β = 2.92). Participants with higher oral microbial α-diversity were more likely to have better cognitive performance status based on DSST (adjusted odds ratio = 2.35) and were less likely to experience subjective memory changes (adjusted odds ratio = 0.43). In addition, β-diversity was statistically significant for the cognitive performance status based on DSST and subjective memory changes.

One potential mechanism underlying oral microbial dysbiosis and cognitive function impairment is systemic inflammation. A recent meta-analysis concluded that the concentrations of plasma or cerebrospinal fluid inflammatory markers were higher in patients with mild cognitive impairment than in normal control individuals. Indeed, alternations in the oral microbiome, a potential source of low-grade systemic inflammation, may contribute to the development of cognitive impairment and dementia. Periodontal disease, a condition known to be linked to oral microbial dysbiosis, has been correlated with elevated levels of neutrophil counts as well as proinflammatory mediators, such as interleukin (IL)-1, IL-6, and C-reactive protein in the blood. Conversely, intensive periodontal treatment resulted in an attenuation of systemic inflammatory markers.

This research makes for interesting reading in the context of a recent paper discussing a mismatch between brain and body circadian clocks as a contributing factor to degenerative aging. Researchers here show that an accumulation of senescent cells in the adrenal gland disrupts its adherence to circadian rhythm, while targeted removal of those cells restores function. We might add this to the many good reasons to remove lingering senescent cells from the aging body. These cells secrete a potent mix of pro-inflammatory factors that are disruptive to surrounding cell and tissue function, and are an important contributing cause of degenerative aging throughout the body and brain.

Aging progresses through the interaction of metabolic processes, including changes in the immune system and endocrine system. Glucocorticoids (GCs), which are regulated by the hypothalamic-pituitary-adrenal (HPA) axis, play an important role in regulating metabolism and immune responses. However, the age-related changes in the secretion mechanisms of GCs remain elusive. Here, we found that corticosterone (CORT) secretion follows a circadian rhythm in young mice, whereas it oversecreted throughout the day in aged mice older than 18 months old, resulting in the disappearance of diurnal variation. Furthermore, senescent cells progressively accumulated in the zona fasciculata (zF) of the adrenal gland as mice aged beyond 18 months. This accumulation was accompanied by an increase in the number of Ad4BP/SF1 (SF1), a key transcription factor, strongly expressing cells (SF1-high positive, SF1-HP).

Removal of senescent cells with the senolytic treatment of dasatinib and quercetin resulted in the reduction of the number of SF1-HP cells and recovery of CORT diurnal oscillation in 24-month-old mice. Similarly, administration of a neutralizing antibody against IL1β, which was found to be strongly expressed in the adrenocortical cells of the zF, resulted in a marked decrease in SF1-HP cells and restoration of the CORT circadian rhythm. Our findings suggest that the disappearance of CORT diurnal oscillation is a characteristic of aging individuals and is caused by the secretion of IL1β, one of the senescence-associated secretory phenotype factors, from senescent cells that accumulate in the zF of the adrenal cortex. These findings provide a novel insight into aging. Age-related hypersecretory GCs could be a potential therapeutic target for aging-related diseases.

Link: https://doi.org/10.1111/acel.14206

A considerable amount of effort has gone into assessing the biochemical differences between old people and extremely old people, in search of protective mechanisms that might be used as a basis for therapies to modestly slow the pace of aging. This may not be the best approach from the point of view of size of effect achieved at the end of the day, as centenarians are still meaningfully impacted by aging, their physiology far removed from that of a young individual, but it is an approach well suited to the present environment of low cost omics technologies. Everything that can be measured attracts attention, and the cheaper the measure is to enact, the more that researchers will use it.

Previous studies of the aging human brain have shown dynamic gene expression changes that distinguish young adults from the aging population. Independent transcriptome analyses showed shifts in the expression of different glial-specific genes and indicated that inflammatory or immune-responsive genes are upregulated during aging in most brain regions, increasing the vulnerability of the brain to cognitive aging. Moreover, a recent transcriptomic study performed in frontal cortex samples of individuals organized in two different groups according to their age (≤80 vs. ≥85 years) showed that the ≥85 years group of age was associated with a distinct transcriptome signature in the cerebral cortex and revealed a protective mechanism of aging and longevity mediated by neural circuit activity.

Centenarians are a group that exhibits extreme longevity, which is commonly accompanied by better quality of life, physical independence, and cognitive function compared to older individuals dying in 70s or 80s. Omic approaches in blood samples from centenarians revealed that the transcriptome and the expression pattern of noncoding RNAs are more similar to young individuals than septuagenarians. Different studies have also described that centenarians present a reduced number of cases with neurodegenerative diseases, in some cases avoid dementia. Consistent with these ideas, our recent study characterizing Basque centenarians identified that they showed better biological profiles in blood analysis, required fewer use of medical resources, and developed fewer diseases including from the nervous system compared with non-centenarians.

We performed transcriptomic studies in hippocampus samples from individuals of different ages (centenarians, here meaning those ≥97 years of age, old, and young) and identified a differential gene expression pattern in centenarians compared to the other two groups. In particular, several isoforms of metallothioneins (MTs) were highly expressed in centenarians. Moreover, we identified that MTs were mainly expressed in astrocytes. Functional studies in human primary astrocytes revealed that MT1 and MT3 are necessary for their homeostasis maintenance. The concentration of zinc in the brain surpasses that of the body by 10-fold and it is essential for normal functioning. There is a link between zinc levels in the brain and cognitive function, and the decline in cognitive performance observed during aging has been linked to the dysregulation of zinc homeostasis. MTs, zinc transporters family (ZnTs), presenilins, and zinc-regulated and iron-regulated proteins (ZIPs) are responsible for the homeostasis of zinc in the brain. Overall, these results indicate that the expression of MTs specifically in astrocytes is a mechanism for protection during aging.

Link: https://doi.org/10.1111/acel.14201

The practice of calorie restriction, reducing calorie intake to as much as 40% below ad libitum intake while still maintaining optimal micronutrient levels, is well demonstrated to slow aging in a range of species. Relative extension of life span is smaller as species life span increases, however, for reasons that make sense from an evolutionary perspective. It is unclear as to how the observed, sweeping changes to metabolism conspire to produce this differing outcome, however. Evidence to date suggests that increased autophagy is the primary mechanism by which reduced calorie intake produces benefits, but a full understanding remains to be achieved despite decades of research.

The altered metabolic state produced by calorie restriction is triggered by sensors detecting the availability of specific dietary components, such as the essential amino acid methionine. It is possible to create some fraction of the benefits of calorie restriction with a low methionine diet. Similarly, experiments have demonstrated that a reduced intake of various other amino acids can also produce some degree of benefits similar to those resulting from calorie restriction. Human trials of mild degrees of calorie restriction have been conducted, and analysis of that data continues years after the trials completed. There has been little comparable work on human trials of amino acid restriction, however.

Amino acid restriction, aging, and longevity: an update

Ever since the discovery that restricting laboratory rodent food consumption relative to their ad libitum (henceforth ad lib) feeding amount reliably extended their lives, prevented or delayed a host of diseases, and generally enhanced later life health, researchers have been seeking to discover the mechanisms by which such restriction works. One way to investigate this question is to determine whether a key feature of what we call the dietary restriction (DR) effect, that is, improved health, reduced disease, and extended longevity due to diminished food consumption, is to restrict various components of the diet as contrasted with simply reducing food consumption itself. By now, experimental reduction of all dietary macronutrients has been performed many times in addition to macronutrient components, particularly essential amino acids, in multiple species. Various diets, from low calorie to low protein to low methionine, branched-chain amino acids (BCAAs), or isoleucine formulations, have shown that dietary modulation can affect later life health in laboratory species. Whether these dietary enhancements of later life health will be translatable to humans is a question begging to be answered.

So far surveys of humans on plant-based low methionine or low sulfur amino acid (methionine + cysteine) diets have been reported to be associated with several beneficial health outcomes such as lower cardiometabolic risk factors or diabetes-related mortality. Short-term (4-12 weeks) clinical trials indicate that low sulfur amino acid diets as in most animal studies lead to weight loss, lower total cholesterol and LDL cholesterol, and other salubrious changes. The cancer field has been particularly interested in low methionine diets as both cell-based and preclinical studies confirm that cancer cells hunger for methionine. Yet short-term trials of medical methionine restriction, especially when combined other cancer therapies, have been generally less than successful largely because of low palatability of the diet. Clearly if low methionine or low sulfur amino acid diets are to be sustainable, the plant-based approach is more likely to be successful.

It is time to determine in human studies whether these low these amino acid restricting diets unlike chronic DR, are sustainable over the long-term and what the long-term health consequences might be. It is also important to discover how the diets affect mood, energy, and interact with other healthy-enhancing lifestyle or pharmaceutical interventions such as exercise or geroprotective drugs. We have reached the "translation stage" of biological aging research. It will be curious to see how successful that translation will be.

Klotho is a longevity-associated protein. Studies in mice show that upregulation lengthens life, while downregulation shortens life. In humans, levels of the soluble circulating form of α-klotho correlate with many aspects of aging. More of it is better, less of it is worse. Here, researchers show this to be the case for inflammation related to osteoarthritis. Identification of the full panoply of mechanisms by which klotho acts to improve health remains a work in progress. It is predominantly active in the kidney, and is clearly protective of kidney health and function in later life. Kidney function is important to the rest of the body, and this may be enough to explain much of the effect on health, inflammation, life span, and so forth. Circulating α-klotho appears to have effects on the brain, however, improving cognitive function even in younger animals. It may be that it has meaningful effects on other organs as well.

The systemic immune-inflammation index (SII) is an indicator of neutrophil, lymphocyte, and platelet counts that is used to evaluate inflammation, and it can more objectively reflect changes in the level of inflammation in the body. The SII can be calculated through routine blood examination, which has the advantages of speed, efficiency, simplicity, and low cost. Previous studies have confirmed that the SII has good clinical value in diagnosing chronic diseases such as tumours, osteoporosis, kidney stones, and rheumatoid arthritis.

The Klotho gene (also known as the longevity gene) is related to ageing and is believed to exert antiaging effects through various biological mechanisms. With the increase in academic research on the Klotho gene, the function of the Klotho gene has gradually been elucidated. Previous studies have shown that the Klotho gene plays a key biological role in antioxidant, anti-inflammatory, and antiapoptotic mechanisms; kidney protection; and the improvement of calcium metabolism and phosphorus metabolism.

The association between the SII and serum Klotho has not yet been revealed. To fill this gap, we used data from the National Health and Nutrition Examination Survey (NHANES) database in the United States to explore the relationship between the SII and serum Klotho concentrations in osteoarthritis (OA) patients. This study revealed a significant negative linear relationship between the SII and serum Klotho concentration in OA patients, indicating that a higher SII is associated with lower Klotho concentration. The SII can serve as a predictive indicator of serum Klotho concentrations in OA patients, and Klotho may serve as a potential anti-inflammatory drug for OA treatment. The causal relationship between the SII and serum Klotho concentration still needs further prospective cohort studies or Mendelian randomised studies for verification.

Link: https://doi.org/10.1371/journal.pone.0300674

Oxidative stress is the presence of a damaging level of oxidative molecules, more than cells can cope with without resulting in harmfully altered behavior, dysfunction, cell death, and so forth. Increased levels of oxidative molecules is a feature of aging and inflamed tissue. As researchers here note, it appears in the context of degenerative disc disease. Targeting oxidative stress with antioxidant compounds has achieved some success for some conditions of local inflammation, such as the use of mitochondrially targeted antioxidants for uveitis, but the fine details of how a specific antioxidant interacts with cellular machinery matters greatly. A range of antioxidants have been tested in animal models for the treatment of degenerative disc disease, but little of this has progressed into human trials.

Intervertebral disc degeneration (IDD) is caused by aging, long-term sitting, long-term spinal load, and other factors. At the same time smoking, diet, and other factors can also lead to IDD. Abnormal accumulation of reactive oxygen species (ROS) occurs within the intervertebral disc, causing the production-clearance homeostasis to be disrupted, and excess ROS leads to activation of pathways downstream of ROS, which in turn triggers a range of symptoms.

When IDD occurs, the disc system undergoes intense, localized oxidative stress. From a molecular perspective, superoxide dismutase activity is significantly reduced in the plasma of IDD patients or rats, and levels of various biomarkers of oxidative stress, including phospholipase A, fructosamine, malondialdehyde, peroxide potential, total hydrogen peroxide, advanced oxidation protein products and NO, induce DNA damage, lipid metabolism, and protein synthesis disorder. From the cellular perspective, oxidative stress promotes the degeneration of normal nucleus pulposus cells in the IVD microenvironment, and impedes the function of collagen-secreting cells.

From a more macroscopic point of view, the degeneration of nucleus pulposus cells results in the decrease of type II collagen content, which is replaced by type I collagen. The annulus fibrosus is impacted by external force, and its effect of dispersing and relieving stress is weakened, which makes the annulus fibrosus easier to break, and causes the nucleus pulposus to expand and compress the nerve, resulting in more clinical symptoms.

Link: https://doi.org/10.1016/j.arr.2024.102323

Today's open access review paper goes back to the basics on aging and cancer, a first principles consideration of whether or not the evidence shows that we should think of cancer as a distinct process from aging. It is certainly the case that while cancer incidence increases with age, it doesn't keep on increasing ad infinitum. In very late life, 90 and older, those who are not already dead from one cause or another actually have lower rates of cancer than younger cohorts. This may not be a only matter of those most prone to cancer having died already, but also reflect something fundamental about the way in which cellular biochemistry changes at that age.

The majority of cancer risk scales with age-related disability of the immune system, and with a growing burden of mutational damage that spreads through tissue. That growing mutational damage enables the catastrophic final change to produce runaway cancerous replication, while immune aging prevents this first cancerous cells from being caught and destroyed by immune cells. One of the primary goals of the immune system is to destroy potentially cancerous cells, but growing levels of chronic inflammation, tissue damage, and cell dysfunction prevent that from happening efficiently in later life. Cancers that predominantly occur in children are a strange exception, not the rule.

Why does cancer risk start to drop at a very old age? Plausibly because cell activity diminishes across the board; less activity means less chance of mutational damage and the creation of a cancerous cells. These are overly simplistic summaries of a much more complex reality, but they are starting points for thinking about cancer and aging.

Aging and cancer

Aging is the most important risk factor of malignant disease, the prevalence of which dramatically increases as adults age, reaching a peak around 85 or 90 years, when the incidence of new cancer diagnoses starts to decline and that of cardiovascular and other diseases ramps up. Aging is, to some degree, modulable, meaning that chronological age (measured in years) and biological age (measured by biological tests and clinical status) can be uncoupled from each other. A young biological age is linked to a reduced risk of malignant disease. For this reason, it may even be argued - in a polemic fashion - that aging is a modifiable risk factor of cancer. This speculation is apparently supported by epidemiological data indicating that lifestyle factors that slow the aging process - such as leanness, an equilibrated mostly plant-based diet, voluntary physical activity and the avoidance of environmental mutagens - also reduce the probability to develop malignant disease. This observation suggests - but does not prove - that aging and cancer share common causes that are influenced by lifestyle or, in a slightly different vision, that manifest aging precipitates the development of clinically detectable tumors that then develop as 'age-related diseases'.

In this review, we will examine the mechanistic connections between aging and malignant disease. We will first discuss arguments in favor of the null hypothesis, namely, that aging and cancer just coincide as we become older because both are time-dependent processes but do not necessarily share a common biological basis. This null hypothesis would be in line with the existence of childhood cancers and progeroid (i.e., aging-accelerating) syndromes that do not increase the likelihood to develop cancer. We will then examine the likely more broadly applicable hypothesis that aging and cancer have common mechanistic grounds, as supported by the idea that both these processes share molecular and cellular characteristics that have been referred to as 'meta-hallmarks' or 'agonistic hallmarks'. However, this hypothesis does not explain why very old age (older than 90 years) is accompanied by a reduction of the incidence of cancers, perhaps because certain 'antagonistic hallmarks' of aging counteract carcinogenesis.

We conclude that aging and cancer are connected by common superior causes including endogenous and lifestyle factors, as well as by a bidirectional crosstalk, that together render old age not only a risk factor of cancer but also an important parameter that must be considered for therapeutic decisions.

An aneurysm is a weakened section of a major blood vessel wall that expands and remodels into a dilated bulge, vulnerable to rupture and subsequent death. Given that treatment often fails, prevention is of great interest to the research community. What are the contributing factors to the development of an aneurysm? Researchers here look at the contribution of inflammatory signaling, generally agreed upon to be central to the dysregulation of blood vessel tissue that leads to the creation of an aneurysm.

Abdominal aortic aneurysm (AAA) has been recognized as a serious chronic inflammatory degenerative aortic disease in recent years, and it is characterized by the progressive pathological dilatation of the abdominal aortic wall. Most patients who develop AAA are usually asymptomatic; however, when the aneurysm expands and ruptures, its mortality is extremely high. According to reports, even if ruptured AAAs are treated in time, the cases fatality rate is still as high as 50-70%, coupled with the cases without timely surgery, the ruptured AAAs' total mortality can be as high as 90%.

Modern studies have identified aortic extracellular matrix (ECM) degradation, the apoptosis of vascular smooth muscle cells (VSMCs), and vascular chronic inflammatory response as the three basic pathological processes in the pathogenesis of AAA. Of these, vascular chronic inflammatory response is the core process. The cytokines released by inflammatory cells not only exacerbate ECM degradation but also lead to the apoptosis of VSMCs. For example, interleukin (IL)-1β, IL-6, IL-33, and other stimuli prompt macrophages or VSMCs to secrete matrix metalloproteinases (MMPs) that degrade elastin and collagen, leading to the apoptosis of VSMCs and ECM degradation, thereby disrupting the stability of the aortic wall architecture.

It has been demonstrated in animal experiments that the use of an IL-1β receptor inhibitor (anakinra) can effectively inhibit mouse AAA formation induced by porcine pancreatic elastase (PPE) perfusion. Therefore, inflammasome regulation of the secretion of cytokines like IL-1β and IL-18 may significantly influence AAA progression, which has been recognized as a chronic inflammatory disease. This article reviews some mechanism studies to investigate the role of inflammasome in AAA and then summarizes several potential drugs targeting inflammasome for the treatment of AAA, aiming to provide new ideas for the clinical prevention and treatment of AAA beyond surgical methods.

Link: https://doi.org/10.3390/ijms25095001

The progression of Alzheimer's disease varies considerably between patients. Is this a matter of random chance in the complex dysfunction of a complex system, or should researchers be looking more closely at genetic and epigenetic differences between patients as a contributing cause of this variability? Researchers here argue for this conclusion based on what is presently known of the heritability of Alzheimer's disease risk and specific genetic variants that are correlated with Alzheimer's disease risk.

Alzheimer's disease (AD) has traditionally been considered first and foremost a neurodegenerative condition. This neuron-centric view of AD is not wholly unjustified, as synapse and neuronal loss are cornerstone features of the worsening cognitive outcomes associated with disease progression.In addition, two primary histopathological hallmarks, extracellular β-amyloid deposition and intraneuronal neurofibrillary tangles of hyperphosphorylated tau protein, have informed much of the research on AD pathogenesis and are still fundamental scoring criteria of present molecular attempts to stage disease trajectory. However, we now know that the disease is more multifaceted than this, comprising different cell types, inflammatory overloads, the vasculature, and uniquely vulnerable brain regions, among others. Therefore, the limited success of AD therapies, which have focused largely on mitigating β-amyloid pathology, may stem from our inability to tackle the complexity of the disease and the heterogenicity of those suffering from it.

The genome holds the key to many of these individual differences. Genetics account for up to 58%-79% of AD risk, and about 75 susceptibility loci have been discovered to date. For comparison, the genetic component of Parkinson's disease is about 15%. In fact, the heritability of AD is so great that parental disease history has been employed to identify AD-by-proxy cases in attempts to increase the power of genetic association studies. Still, it has not been trivial to translate these genetic links into mechanistic breakthroughs and therapeutic targets, as the resulting functional outcomes and causal genes linked to each polymorphism remain mostly unresolved.

Here, we explore how genomic research has advanced the understanding of late-onset AD. This is, for us, the first meaning of the "broken" AD genome, akin to unraveling a code. But various processes centered on our DNA become dysfunctional in AD, imparting an equally significant connotation to the term; i.e., "broken" in this context alludes to the genome as a driver of disease. We primarily highlight findings originating from human datasets, as existing disease models often fail to recapitulate the full pathological spectrum of AD. We recognize the importance of these tools and, when appropriate, reference insights obtained using them. We also identify challenges for the field and discuss strategies for amassing the wealth of genomic information now available for developing therapeutics and clinical tools.

Link: https://doi.org/10.1016/j.xgen.2024.100555

Macrophages are innate immune cells of the body, microglia the analogous innate immune cells of the central nervous system. All microglia and most macrophages depend on the function of colony stimulating factor 1 receptor (CSF1R); if this protein or its function are suppressed, the cells die. Following clearance of microglia and macrophages, the populations are restored within a few weeks. If this is carried out in an old animal, the new microglia and macrophages lack some of problems exhibited by the prior population, such as excessive inflammatory signaling, a high burden of cellular senescence, and so forth. There are well established CSF1R inhibitor drugs, such as pexidartinib (PLX3397), and so one can find a number of studies in which neurodegenerative conditions associated with microglial inflammation are improved by temporary clearance followed by repopulation.

Today's open access paper is an example of this sort of work. The authors provide evidence for clearance of microglia to improve the environment of a damaged retina in a mouse model of age-related macular degeneration. One might compare this to past animal studies in which clearance of microglia improves Alzheimer's disease and reduces injury following stroke. Beyond that, a considerable weight of evidence links increased numbers of pro-inflammatory microglia, whether activated or senescent, to the onset and progression of neurodegenerative conditions. It is plausible that short-term treatment with pexidartinib or a similar CSF1R inhibitor, avoiding most of the side-effects that accompany long-term use in cancer patients, will prove to be beneficial enough to enter widespread use.

Microglial repopulation restricts ocular inflammation and choroidal neovascularization in mice

Age-related macular degeneration (AMD) is a prevalent, chronic and progressive retinal degenerative disease characterized by an inflammatory response mediated by activated microglia accumulating in the retina. While robust evidence clearly identifies the beneficial effects of microglial repopulation in degenerative neurological diseases, the contributions of repopulating microglia in the retinal degenerative diseases AMD and the potential mechanisms remain incompletely understood.

In this study, we demonstrated that ten days of the CSF1R inhibitor PLX3397 treatment to induce microglial repopulation exacerbated neovascular leakage and angiogenesis formation. We also found that the accumulation of senescent cells in laser sites and treatment with microglial repopulation increased microglial phagocytosis and led to reduced cellular senescence. In addition, new microglia produced less CXCL2 and exhibited lower levels of activation markers than resident microglia, thereby ameliorating leukocyte infiltration and attenuating the inflammatory response in choroidal neovascularization lesions. Our study provides promising insights into the potential of microglial repopulation as a novel, promising therapeutic approach for the treatment of AMD using a mouse model of laser-induced CNV.

Microglia have been implicated to accumulate in the subretinal space, subsequently switching into an activated phenotype and undergoing significant changes in their function in both AMD patients and mouse models. These activated microglia cause the excessive release of inflammatory mediators and a prolonged inflammatory response, which may result in the growth of neovascular lesions and further tissue damage. As microglial survival and function are critically dependent upon CSF1R, CSF1R inhibition can effectively deplete microglia. Withdrawal of CSF1R inhibition results in the rapid repopulation of the whole retina with naïve microglia. Now that microglial activation in CNV has been identified as a symptom of inflammatory damage which in turn exacerbates retinal degeneration, it is plausible to hypothesize that the replacement of these overactivated microglia with new microglia resembling nonreactive homeostatic microglia may relieve the inflammatory response and promote retinal tissue repair in AMD.

Researchers here argue for neural stem cells in the hypothalamus to support a youthful environment in many other tissues via secreted factors carried into circulation in exosomes. To the degree that this signaling falters with age, it contributes to the burden of aging and age-related dysfunction - though as ever it is challenging to assign a relative importance to this mechanism versus all of the others identified to date, or a firm place in a network of cause and consequence. I don't think that describing either the signaling or its reduction with age as a program is helpful. We might expect component parts of a complex system to evolve a dependency on the behavior of other component parts. There are any number of well-established examples of the interdependence of internal organ function in the aging body. This is just the way things work.

In contrast to the hypothesis that aging results from cell-autonomous deterioration processes, the programmed longevity theory proposes that aging arises from a partial inactivation of a "longevity program" aimed at maintaining youthfulness in organisms. Supporting this hypothesis, age-related changes in organisms can be reversed by factors circulating in young blood. Concordantly, the endocrine secretion of exosomal microRNAs (miRNAs) by hypothalamic neural stem cells (htNSCs) regulates the aging rate by enhancing physiological fitness in young animals. However, the specific molecular mechanisms through which hypothalamic-derived miRNAs exert their anti-aging effects remain unexplored.

Using experimentally validated miRNA-target gene interactions and single-cell transcriptomic data of brain cells during aging and heterochronic parabiosis, we identify the main pathways controlled by these miRNAs and the cell-type-specific gene networks that are altered due to age-related loss of htNSCs and the subsequent decline in specific miRNA levels in the cerebrospinal fluid (CSF). Our bioinformatics analysis suggests that these miRNAs modulate pathways associated with senescence and cellular stress response, targeting crucial genes such as Cdkn2a, Rps27, and Txnip. The oligodendrocyte lineage appears to be the most responsive to age-dependent loss of exosomal miRNA, leading to significant derepression of several miRNA target genes.

Furthermore, heterochronic parabiosis can reverse age-related upregulation of specific miRNA-targeted genes, predominantly in brain endothelial cells, including senescence promoting genes such as Cdkn1a and Btg2. Our findings support the presence of an anti-senescence mechanism triggered by the endocrine secretion of htNSC-derived exosomal miRNAs, which is associated with a youthful transcriptional signature.

Link: https://doi.org/10.3390/ijms25105467

Popular science articles covering the longevity industry and research into the treatment of aging tend to be a grab-bag of different projects and people of wildly different value and characteristics, all given much the same weight in the narrative. It takes a year or two of work to come to some initial understanding of the state of the field of aging research, to be able to start to distinguish good ideas from bad ideas, and make arguments about what is likely to have larger versus smaller effects on aging. No popular science journalist has put in that time. If looking for a single point of blame, it may be that there is at present no agreed-upon way to measure efficacy of a treatment for aging in humans, coupled to the point that most approaches to slow aging via metabolic adjustment behave quite differently in long lived species (such as our own) versus short-lived species (such as laboratory mice). Absent a way to rapidly assess a treatment for aging in humans, people can continue to equate likely good and likely bad approaches without being called on it.

Longevity research is advancing - but slowly. Clinical trials are moving forward on select uses for longevity drugs, younger researchers are taking the field more seriously, and private organizations are pledging significant support to research: The Saudi-based Hevolution Foundation has promised up to $1 billion in funding annually for biotech startups and academic researchers.

But while there likely remain many promising treatment candidates that have yet to be identified, they would take decades to reach clinical trials. Even academics who are bullish on the promise of longevity research fear that, for all the fanfare, the field has become too fixated on a few drugs and lifestyle adjustments that have been under investigation for years, while neglecting the basic research that could reveal novel pathways to slow down human aging.

In the last two decades, scientists have performed hundreds of lab experiments - mostly on animals - on drugs like rapamycin, canagliflozin, acarbose, empagliflozin, metformin, and on interventions like calorie restriction in diets and removal of nondividing senescent cells. Instead of testing the effects of these treatments on specific illnesses, many of these studies test whether certain interventions slow down animals' aging processes and help them live longer.

The expansion of longevity research has unearthed some potentially useful information about which biological mechanisms control aging and how to alter them. In mice and other species, changing a single pathway has the power to extend life by significant margins, raising hopes that if humans respond similarly, certain drugs could extend human lives by years. The horizon for this future is still far off. Most researchers I spoke to didn't believe that humans were going to experience a rapid increase in life expectancy any time soon - or maybe ever. They believed progress would instead be made in healthspan, helping people stay healthier for longer and avoiding long periods of physical and cognitive decline as they get older.

Link: https://www.vox.com/the-highlight/24121932/anti-aging-longevity-science-health-drugs

Intervertebral disc degeneration is a feature of aging, and injury can produce further challenges. A range of approaches have been assessed to enhance the regenerative capacity of disc tissue, useful not just after injury, but also to reverse some of the declines in disc structure and function produced by aging. Stem cell therapies have been attempted, and are widely available via medical tourism, but unfortunately that diverse population of patients contributes next to no publicly available data to help researchers understand whether or not this is a viable approach, and how to improve on it. First generation stem cell therapies are gradually being replaced by exosome therapies, as these are logistically easier to manage. Exosomes can be harvested and stored, it is easier to produce consistent batches from one central location for manufacture, and the benefits of stem cell therapies are in any case mediated by the signaling produced by these cells, largely carried in extracellular vesicles such as exosomes.

Thus in today's open access paper, we see an example of researchers building on the exosome therapy approach rather than the cell therapy approach. Beyond the logistics, another advantage of exosomes is that they can be readily engineered to carry additional cargo into cells. In this case, researchers are delivery a DNA plasmid to express FOXF1. The usual challenge with DNA plasmids is that they express poorly, as passage into the cell nucleus and access to transcriptional machinery that can read the plasmid only efficiently occurs during cell division. The researchers used an injury model in mice, so there will tend to be more cellular replication in this circumstance as regeneration takes place. In any case, the researchers observed improvements in the treated mice versus controls. We are likely to see a range of similar approaches based on the use of extracellular vesicles as a gene therapy vector emerge in the years ahead.

Engineered extracellular vesicle-based gene therapy for the treatment of discogenic back pain

Painful musculoskeletal disorders such as chronic low back pain (LBP) are leading causes of disability worldwide and their prevalence and societal impact continues to rise with expansion of the aging population and growing opioid crisis. Intervertebral disc (IVD) degeneration is a major cause of LBP, often referred to as discogenic back pain (DBP), with epidemiological studies estimating that approximately 40% of cases are attributed to IVD degeneration. The IVD functions as an avascular and aneural joint, sandwiched between adjacent vertebral bodies of the spinal column. It is comprised of a gelatinous proteoglycan-rich nucleus pulposus (NP) core encapsulated by rings of collagen that form the annulus fibrosus (AF). In degeneration, mechanical imbalances, loss of critical extracellular matrix (ECM) components such as proteoglycans, increased catabolism, inflammation, and neurovascular invasion contribute to a detrimental shift in homeostasis that leads to the loss of tissue function and increased pain.

n previous studies, we have demonstrated the potential of developmental transfection factors such as Brachyury (T) and Forkhead Box F1 (FOXF1), both of which are healthy immature NP markers involved in growth during development, to drive cellular reprogramming of diseased human NP cells to a pro-anabolic phenotype in vitro. These studies also highlight the feasibility of using engineered extracellular vesicles (eEVs) to mediate the delivery of FOXF1 to diseased cells, and their potential to be used as a minimally invasive gene delivery mechanism.

Here we have developed a novel non-viral gene therapy, using eEVs to deliver FOXF1 to the degenerated IVD in an in vivo model. Injured IVDs treated with eEVs loaded with FOXF1 demonstrated robust sex-specific reductions in pain behaviors compared to control groups. Furthermore, significant restoration of IVD structure and function in animals treated with FOXF1 eEVs were observed, with significant increases in disc height, tissue hydration, proteoglycan content, and mechanical properties. This is the first study to successfully restore tissue function while modulating pain behaviors in an animal model of DBP using eEV-based non-viral delivery of transcription factor genes. Such a strategy can be readily translated to other painful musculoskeletal disorders.

Most of us put little thought into the muscles that control the movement of the eye. They just work. Researchers here ask the interesting question: why are these extraocular muscles so resilient? Why does their function decline so little with age, when other muscles throughout the body lose strength and mass, leading ultimately to sarcopenia? There is no complete answer to this question, but it is suggested here that this resilience might have something to do with the fact that the extraocular muscles are much more heavily innervated than other muscles in the body. That in turn might direct a greater focus towards the effects of aging on neuromuscular junctions and consequent loss of innervation in muscles elsewhere in the body. This loss of innervation has been suggested as a contributing cause of sarcopenia.

The extraocular muscles (EOMs) are unique in several aspects: They represent the fastest and most fatigue-resistant muscles within the human body. Extraocular muscles (EOMs) predominantly exhibit impairment in conditions such as myasthenia gravis and mitochondrial myopathies, yet, remarkably, they are spared from various muscular dystrophies, including Duchenne, Becker, limb-girdle, and congenital muscular dystrophies, as well as aging. Furthermore, EOMs demonstrate particular resistance to amyotrophic lateral sclerosis (ALS).

he complexity of the actions performed by the extraocular muscles (EOMs) is reflected in their anatomical and physiological characteristics. Morphologically and in terms of their molecular composition, they significantly differ from the muscle fibers (MFs) of other skeletal muscles. The gene expression profile of the EOMs is distinct from that of limb muscles, with differences encompassing over 330 genes involved in metabolic pathways, structural components, development markers, and regenerative processes. Unlike skeletal muscles, the EOMs predominantly utilize an aerobic pathway for carbohydrate metabolism and relies directly on the glucose influx from the blood. This metabolic strategy enables them to be among the fastest muscles in the body while also being exceptionally resistant to fatigue.

Notably, EOM fibers express a diverse array of myosin heavy-chain isoforms, retaining embryonic forms into adulthood. Moreover, their motor innervation is characterized by a high ratio of nerve fibers to muscle fibers and the presence of unique neuromuscular junctions. These features contribute to the specialized functions of EOMs, including rapid and precise eye movements. Understanding the mechanisms behind the resilience of EOMs to disease and aging may offer insights into potential therapeutic strategies for treating muscular dystrophies and myopathies affecting other skeletal muscles.

Link: https://doi.org/10.3390/ijms25094985

The practice of calorie restriction is well known to slow aging, though the effects on life span are much larger in short-lived species. In humans calorie restriction is demonstrated to be beneficial to long-term health, certainly on a par with the results obtained from maintenance of physical fitness. Calorie restriction has noteworthy effects on the distribution and biochemistry of fat tissue. Researchers here report that one aspect of this outcome is a slowing of age-related changes in adult stem cells associated with subcutaneous fat.

With advancing age, there is a gradual loss of subcutaneous adipose tissue volume, leading to diminished glucose and lipid uptake. This phenomenon is known as "lipid overflow hypothesis," which results in the ectopic deposition of lipids in muscles and the liver, ultimately contributing to the development of insulin resistance. Long-term calorie restriction (CR) has been found to result in reduced adipocyte size and a beneficial remodeling of body fat composition, shifting away from visceral white adipose tissue towards subcutaneous white adipose tissue. This shift is significant as subcutaneous fat tends to have positive effects on aging and obesity, whereas visceral is associated with detrimental health outcomes.

Adipose-derived stem cells (ASCs) are crucial for tissue regeneration, but aging diminishes their stemness and regeneration potential. Aging is associated with increased adipose tissue fibrosis but no significant change in adipocyte size was observed with age. Long term caloric restriction failed to prevent fibrotic changes but resulted in significant decrease in adipocytes size. Aged subcutaneous ASCs displayed an increased production of reactive oxygen species (ROS). Using mitochondrial membrane activity as an indicator of stem cell quiescence and senescence, we observed a significant decrease in quiescence ASCs with age exclusively in the subcutaneous adipose depot. In addition, aged subcutaneous adipose tissue accumulated more senescent ASCs having defective autophagy activity. However, long-term caloric restriction leads to a reduction in mitochondrial activity in ASCs. Furthermore, caloric restriction prevents the accumulation of senescent cells and helps retain autophagy activity in aging ASCs. These results suggest that caloric restriction and caloric restriction mimetics hold promise as a potential strategy to rejuvenate the stemness of aged ASCs.

Link: https://doi.org/10.18632/aging.205812

Senescent cells accumulate with age as the immune system falters in its ability to clear these cells in a timely fashion. Senolytic therapies selectively destroy some fraction of senescent cells, and first generation senolytic drugs have been demonstrated to rapidly and impressively reverse age-related disease and extend life in mice. The best of these first generation drugs are repurposed cancer therapeutics such as dasatinib and navitoclax, with the jury still out on whether plant extracts like fisetin can be competitive on their own rather than in combination with the chemotherapeutics.

The second generation senolytics presently under development aim to be more selective, have fewer side-effects, require lower or more infrequent doses, or be able to target a greater range of senescent cell types. It is becoming clear that senescence is a varied collection of states, and first generation senolytics are only effective in destroying senescent cells for some of those states, and in some tissues. With this in mind, today's popular science article takes a look at some of the companies and research groups working on a broad range of second generation senolytic treatments. There are promising programs under development; we might expect a much more diverse range of options to exist for patients and self-experimenters a decade from now than is presently the case.

Researchers are using new molecules, engineered immune cells and gene therapy to kill senescent cells and treat age-related diseases

Lurking throughout your body, from your liver to your brain, are zombie-like entities known as senescent cells. They no longer divide or function as they once did, yet they resist death and spew out a noxious brew of biological signals that can slow cognition, increase frailty and weaken the immune system. Worst of all, their numbers increase as you age. For more than a decade, researchers have been trying to see whether they can selectively destroy these cells with a variety of drugs. In a pivotal study published in 2015, a team discovered that a combination of two compounds, called dasatinib and quercetin, killed senescent cells in aged mice. The treatment made the mice less frail, rejuvenated their hearts and boosted their running endurance. The finding opened the door to a new area of medicine called senolytics.

Now, fresh results from animal studies and human clinical trials have added momentum to the field. In mice and monkeys, researchers are using genetic tools to reprogram and kill senescent cells. Others are engineering senolytic immune cells. And about 20 clinical trials are ongoing. Researchers are testing new and repurposed drugs that could have senolytic properties, in the hope of combating age-related conditions, including Alzheimer's disease, pulmonary fibrosis, and chronic kidney disease.

One key strategy in senolytics involves designing drugs that stop senescent cells from resisting apoptosis. Usually, the cells survive by producing anti-death proteins. Blocking these with drugs can force the cells to succumb to death. Unity Biotechnology is at the forefront of this approach. In a recent study, researchers found that senescent cells were more abundant in the retinas of diabetic mice than in those of healthy mice. It was possible, the team predicted, that senescent cells in the blood vessels of the eye play a part in diabetes-related vision loss. The researchers designed a drug, called foselutoclax, which blocks the action of BCL-xL, a key anti-death protein that is abundant in senescent cells. When they injected the drug into the eyes of diabetic mice, it killed senescent cells in the blood vessels supplying the retina, but not healthy cells.

Rather than making senolytics from scratch, some scientists are testing drugs that already exist. In a 2019 study, researchers used dasatinib and quercetin to remove senescent brain cells in a mouse model of Alzheimer's disease. Mice treated with the senolytics had reduced brain inflammation and improved memory compared with animals that were given a placebo. Spurred on by these promising data from mice, researchers last year conducted the first safety trial of the drug combination in people with early stage Alzheimer's disease. The team gave five people dasatinib and quercetin intermittently for three months. The researchers found that the drugs were safe and that dasatinib was present in samples of cerebrospinal fluid, suggesting it could cross into the brain. Quercetin was not detected in brain fluid samples, but researchers suspect that it did reach the brain and was rapidly broken down. The team is now conducting a larger trial to track the cognition of people with and without Alzheimer's disease for nine months after they take a placebo or the drug combination. The results should be released in 2025.

When it comes to killing cells in the body, the immune system could be of help. And some researchers have latched on to the idea of using genetically engineered immune cells called chimeric antigen receptor (CAR) T cells. These can target and kill specific cells on the basis of the molecules they display on their surface. Researchers found that old mice treated with the CAR T cells selective for a marker of senescence had reduced blood-sugar levels - a sign of improved metabolic health - and that the animals ran faster and for longer. But CAR-T-cell therapies are expensive to make. Deciduous Therapeutics is also developing a more affordable approach that harnesses a different kind of immune cell called a natural killer T cell. In 2021, researchers at Deciduous Therapeutics demonstrated the senolytic role of these cells, which naturally become less effective with age. They also found that drugs that can activate the immune cells helped to eliminate senescent cells in the damaged lungs of mice, reducing lung scarring and improving survival. Safety tests will be conducted in dogs and non-human primates later this year, and clinical trials should begin in the next two years.

Other teams such as Oisin Biotechnologies are using gene therapy to kill senescent cells. In this approach, researchers package a gene that encodes a lethal protein called caspase-9 into fatty capsules studded with proteins derived from a virus. In mice and monkeys, the capsules have been found to deliver the gene to cells in the lungs, heart, liver, spleen and kidneys. Healthy cells are spared, because the gene is activated only in senescent cells that have high levels of one of two proteins called p16 and p53. The researchers found that, over four months, a monthly dose of the therapy reduced frailty and cancer rates in old mice without causing harmful side effects.

T cell senescence is a noted feature of the aging immune system. T cells mature in the thymus, which atrophies with age. Absent a supply of new T cells, the existing populations are forced into greater cellular replication in order to (a) maintain a steady number of cells, and (b) continue to respond to infection with an expansion of the number of T cells equipped to attack the pathogen. Cellular senescence occurs when a cell reaches the Hayflick limit to replication. With each cell division, telomeres at the ends of chromosomes shorten. When telomeres become too short, a cell either self-destructs or becomes senescent. In some subsets of the immune cell population, almost half of all T cells are senescent in old people.

Senescent cells generate a pro-inflammatory, pro-growth mix of signals, the senescence-associated secretory phenotype (SASP). These cells serve a purpose when present in the short term, but when they linger the SASP becomes highly disruptive to tissue structure and function. As today's open access paper points out, even though T cells are not present in the brain in any great number, their state of senescence does matter. Inflammatory signaling moves throughout the body, and can and does link the distinct immune systems of the body and brain.

With the increasing proportion of the aging population, neurodegenerative diseases have become one of the major health issues in society. Neurodegenerative diseases (NDs), including multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), are characterized by progressive neurodegeneration associated with aging, leading to a gradual decline in cognitive, emotional, and motor functions in patients. The process of aging is a normal physiological process in human life and is accompanied by the aging of the immune system, which is known as immunosenescence.

T-cells are an important part of the immune system, and their senescence is the main feature of immunosenescence. The appearance of senescent T-cells has been shown to potentially lead to chronic inflammation and tissue damage, with some studies indicating a direct link between T-cell senescence, inflammation, and neuronal damage. The role of these subsets with different functions in NDs is still under debate. A growing body of evidence suggests that in people with a ND, there is a prevalence of CD4+ T-cell subsets exhibiting characteristics that are linked to senescence. This underscores the significance of CD4+ T-cells in NDs. In this review, we summarize the classification and function of CD4+ T-cell subpopulations, the characteristics of CD4+ T-cell senescence, the potential roles of these cells in animal models and human studies of NDs, and therapeutic strategies targeting CD4+ T-cell senescence.

Link: https://doi.org/10.3390/cells13090749

In a tissue bank of more than 5,000 donated brains, researchers found 12 in which there were signs of Alzheimer's disease pathology but for which the donors had exhibited none of the symptoms of Alzheimer's disease. Here find a report on some of the biochemical differences found in these resilient brains; it is hoped that pursuing this line of research might aid in the understanding of the condition and strategies for the development of effective therapies.

Some individuals show a discrepancy between cognition and the amount of neuropathological changes characteristic for Alzheimer's disease (AD). This phenomenon has been referred to as 'resilience'. The molecular and cellular underpinnings of resilience remain poorly understood. To obtain an unbiased understanding of the molecular changes underlying resilience, we investigated global changes in gene expression in the superior frontal gyrus of a cohort of cognitively and pathologically well-defined AD patients, resilient individuals, and age-matched controls (n = 11-12 per group).

897 genes were significantly altered between AD and control, 1121 between resilient and control and 6 between resilient and AD. Gene set enrichment analysis (GSEA) revealed that the expression of metallothionein (MT) and of genes related to mitochondrial processes was higher in the resilient donors. Weighted gene co-expression network analysis (WGCNA) identified gene modules related to the unfolded protein response, mitochondrial processes and synaptic signaling to be differentially associated with resilience or dementia.

As changes in MT, mitochondria, heat shock proteins, and the unfolded protein response (UPR) were the most pronounced changes in the GSEA and/or WGCNA, immunohistochemistry was used to further validate these processes. MT was significantly increased in astrocytes in resilient individuals. A higher proportion of the mitochondrial gene MT-CO1 was detected outside the cell body versus inside the cell body in the resilient compared to the control group and there were higher levels of heat shock protein 70 (HSP70) and X-box-binding protein 1 spliced (XBP1s), two proteins related to heat shock proteins and the UPR, in the AD donors.

Finally, we show evidence for putative sex-specific alterations in resilience, including gene expression differences related to autophagy in females compared to males. Taken together, these results show possible mechanisms involving MTs, mitochondrial processes, and the UPR by which individuals might maintain cognition despite the presence of AD pathology.

Link: https://doi.org/10.1186/s40478-024-01760-9

Exercise is known to improve cognitive function and neurogenesis, the process by which new neurons are created by neural stem cells and then mature to integrate into existing neural networks. Neurogenesis is best studied in the hippocampus, where it is necessary for learning and memory function to take place. It is also likely important in the very limited ability of the central nervous system to recover from injury and in general maintenance of brain tissue over time.

In today's open access paper, researchers demonstrate that exercise reverses age-related changes in the gene expression and behavior of microglia, innate immune cells of the brain that are analogous to macrophages elsewhere in the body. They also show that microglia are necessary for the benefits of exercise to emerge. Microglia assist neurons in altering and maintaining synaptic connections in the brain, and this is one way in which the aging of microglia might be detrimental to cognitive function.

Microglia also become more inflammatory with age, however, and chronic inflammation tends to change cell behavior for the worse in all tissues. In this context, it is worth noting that exercise is known to dampen inflammation, among its many other benefits. The study here says little about the signaling mechanisms by which exercise might induce a temporary rejuvenation in microglia, however.

Exercise rejuvenates microglia and reverses T cell accumulation in the aged female mouse brain

Exercise may be useful for preventing (or reversing) age-related hippocampal deterioration and maintaining neuronal health. However, the mechanisms underlying the beneficial effects of exercise on the ageing brain remain poorly defined. We provide here a comprehensive single cell RNA-seq dataset and unbiased analyses characterising the effects of both natural ageing and exercise on cell types within the female mouse hippocampus. We show that ageing alters the relative abundance and transcriptional phenotypes of different cell types in the hippocampus.

We further demonstrate that exercise profoundly and specifically impacts the transcriptional state of microglia, reverting the gene expression signature of aged microglia towards that observed in young animals. In particular, the transcriptional profile of disease-associated microglia was markedly rejuvenated by exercise. We went on to demonstrate that microglia are required for the pro-neurogenic effects of exercise in the aged hippocampus. Importantly, however, global depletion of microglia did not affect the cognitive benefits conferred by exercise in our experimental paradigm.

Prior analyses of microglia have indicated that ageing is associated with increased expression of inflammatory factors. Here, we identified similar microglial differentially expressed genes in association with ageing, including type II interferon and immune genes Ccl2, Ccl3, Ccl4, Ccl5, Ccl7, and Ccl8. We also identified pathways enriched in aged microglia, including those regulating the TYROBP causal network, chemokine signalling, and type II interferon signalling. Strikingly, the number of microglial differentially expressed genes identified between young sedentary mice and aged exercising mice was small, reflecting their transcriptional similarity and hence the restorative impact of exercise on the microglial phenotype. Indeed, our linear regression analyses revealed that exercise had a profound and specific effect on the transcriptional signature of aged microglia, reverting their gene expression profile back towards that seen in young microglia.

Recent work from our group highlighted that microglial phenotypes can profoundly influence hippocampal neurogenesis in the injured brain. The process of adult neurogenesis itself is otherwise also well known to be regulated and/or influenced by exercise. We previously demonstrated that exercise supports both the activity and survival of neural precursors, and that microglia may play a role therein. With our unbiased single-cell transcriptomics analyses identifying microglia as the cells mostly modulated by exercise, we probed the in vivo significance of this phenomenon in relation to hippocampal neurogenesis. Here, our depletion experiments showed that the loss of microglia annulled any stimulatory effects of exercise on hippocampal neurogenesis. As technological advances progress, future studies could explore more specifically what microglial subset (or state) inhibits adult neurogenesis and/or drives the pro-neurogenic effects of exercise.

There is considerable interest in developing biomarkers to detect the earliest stages of Alzheimer's disease, well prior to symptoms. To the degree that Alzheimer's is a lifestyle condition, it might be postponed or averted if discovered early on. To the degree that it is not a lifestyle condition, then the first viable anti-amyloid immunotherapies offer some chance, the odds yet to be determined, of averting Alzheimer's in the earliest stages. Some progress has been made on predictive biomarkers that can be assessed a decade or more prior to symptoms, but work continues to broaden and improve upon these options.

A recent study has identified a new biomarker for Alzheimer's disease in asymptomatic stages of the disease. The molecule is miR-519a-3p, a microRNA directly linked to the expression of the cellular prion protein (PrPC), which is dysregulated in people suffering from some neurodegenerative diseases such as Alzheimer's. The search for biomarkers that are stable and easily detectable in biofluids, such as microRNAs, offers hope for detecting Alzheimer's disease in its early, asymptomatic stages. Early detection could significantly improve the diagnosis and treatment of this disease, which affects more than 35 million people worldwide.

The amount of PrPC changes over the course of Alzheimer's disease, with higher levels in the early stages of the disease and lower levels as the disease progresses. Although the mechanism responsible for these changes is not known in detail, it has been observed that certain microRNAs bind to a specific region of the PRNP gene that controls PrPC expression, reducing it. For this reason, and based on comparisons of previous studies and computational analyses in various genomic databases, the researchers selected the microRNA miR-519a-3p for their study.

"If our goal is to use miR-519a-3p as a biomarker to detect Alzheimer's dementia in hypothetically healthy people, it is essential to ensure that its levels are not altered in other neurodegenerative diseases. In our study, we compared the levels of this biomarker in samples from other tauopathies and Parkinson's disease, confirming that the changes in miR-519a-3p are specific to Alzheimer's disease. The next step is to validate miR-519a-3p as a biomarker in blood samples from different cohorts of patients, in order to start using it in the clinical diagnosis of Alzheimer's disease in peripheral samples."

Link: https://ibecbarcelona.eu/new-biomarker-to-diagnose-alzheimers-in-asymptomatic-stages/

Thrombosis is the inappropriate clumping of platelets to form blood clots in blood vessels, leading to potential blockage and serious injury as tissues are deprived of blood flow. This undesirable situation occurs more readily with age. Platelets are produced by megakaryocyte cells, and the count of platelets in the blood tends to increase in older people. Why does this happen? Researchers here dig in to some of the details, and find that age-related changes in hematopoiesis in the bone marrow produce a distinct population of megakaryocytes that manufacture a greater number of platelets. Further, those platelets are more easily triggered into clot formation. Restoration of youthful hematopoiesis is already an important goal in the treatment of aging, and this adds one more reason for that to be the case.

Platelet dysregulation is drastically increased with advanced age and contributes to making cardiovascular disorders the leading cause of death of elderly humans. Here, we reveal a direct differentiation pathway from hematopoietic stem cells into platelets that is progressively propagated upon aging. Remarkably, the aging-enriched platelet path is decoupled from all other hematopoietic lineages, including erythropoiesis, and operates as an additional layer in parallel with canonical platelet production. This results in two molecularly and functionally distinct populations of megakaryocyte progenitors.

The age-induced megakaryocyte progenitors have a profoundly enhanced capacity to engraft, expand, restore, and reconstitute platelets in situ and upon transplantation and produce an additional platelet population in old mice. The two pools of co-existing platelets cause age-related thrombocytosis and dramatically increased thrombosis in vivo. Strikingly, aging-enriched platelets are functionally hyper-reactive compared with the canonical platelet populations. These findings reveal stem cell-based aging as a mechanism for platelet dysregulation and age-induced thrombosis.

Link: https://doi.org/10.1016/j.cell.2024.04.018

In recent years, it has become clear that the gut microbiome contributes meaningfully to long-term health, perhaps to much the same degree as exercise, diet, and other common lifestyle choices. Unlike those choices, the composition of the gut microbiome is more inscrutable, however. While commercial services employing 16S rRNA sequencing can cost-effectively list the microbial species present in the intestines, and their relative proportions, it remains a work in progress to (a) reliably connect differences in the list to pathologies of aging, and (b) reliably alter the gut microbiome in deterministic and lasting ways.

Which is not to say that we know nothing! It is clear that the relative proportions of the microbial species making up the gut microbiome change with age, and some of those changes provoke chronic inflammation. Pro-inflammatory microbes grow in number at the expense of microbial species responsible for producing beneficial metabolites such as butyrate. It is also clear that fecal microbiota transplantation from a young individual produces a lasting reset of the gut microbiome, and consequent improvements in health, even if the full details of what matter in that reset have yet to be determined.

Aging amplifies a gut microbiota immunogenic signature linked to heightened inflammation

Aging is associated with low-grade inflammation that increases the risk of infection and disease, yet the underlying mechanisms remain unclear. Gut microbiota composition shifts with age, harboring microbes with varied immunogenic capacities. We hypothesized the gut microbiota acts as an active driver of low-grade inflammation during aging. Microbiome patterns in aged mice strongly associated with signs of bacterial-induced barrier disruption and immune infiltration, including marked increased levels of circulating lipopolysaccharide (LPS)-binding protein (LBP) and colonic calprotectin.

Ex vivo immunogenicity assays revealed that both colonic contents and mucosa of aged mice harbored increased capacity to activate toll-like receptor 4 (TLR4) whereas TLR5 signaling was unchanged. We found patterns of elevated innate inflammatory signaling (colonic Il6, Tnf, and Tlr4) and endotoxemia (circulating LBP) in young germ-free mice after 4 weeks of colonization with intestinal contents from aged mice compared with young counterparts, thus providing a direct link between aging-induced shifts in microbiota immunogenicity and host inflammation. Additionally, we discovered that the gut microbiota of aged mice exhibited unique responses to a broad-spectrum antibiotic challenge, with sustained elevation in Escherichia (Proteobacteria) and altered TLR5 immunogenicity 7 days post-antibiotic cessation.

Together, these data indicate that old age results in a gut microbiota that differentially acts on TLR signaling pathways of the innate immune system. We found that these age-associated microbiota immunogenic signatures are less resilient to challenge and strongly linked to host inflammatory status. Gut microbiota immunogenic signatures should be thus considered as critical factors in mediating chronic inflammatory diseases disproportionally impacting older populations.

Angiogenesis, the complex set of processes by which new blood vessels are produced, becomes less efficient with advancing age. One important consequence is a loss of capillary density, which has a range of detrimental effects on tissue function, particularly in energy-hungry tissues such as the brain and muscle. Regeneration from injury is also dependent on the quality and efficiency of angiogenesis. Researchers here take a narrow focus on the question of angiogenesis relevant to bone tissue maintenance and regeneration, and the use of exosome therapies to improve angiogenesis. To the degree that treatment with exosomes harvested from stem cells can improve angiogenesis throughout the body, this approach to therapy should produce broad benefits.

Bone is a metabolically dynamic structure that is generally remodeled throughout the lifetime of an individual but often causes problems with increasing age. A key player for bone development and homeostasis, but also under pathological conditions, is the bone vasculature. This complex system of arteries, veins, and capillaries forms distinct structures where each subset of endothelial cells has important functions. Starting with the basic process of angiogenesis and bone-specific blood vessel formation, coupled with initial bone formation, the importance of different vascular structures is highlighted with respect to how these structures are maintained or changed during homeostasis, aging, and pathological conditions.

After exemplifying the current knowledge on bone vasculature, this review will move on to exosomes, a novel hotspot of scientific research. Exosomes will be introduced starting from their discovery via current isolation procedures and state-of-the-art characterization to their role in bone vascular development, homeostasis, and bone regeneration and repair while summarizing the underlying signal transduction pathways. With respect to their role in these processes, especially mesenchymal stem cell-derived extracellular vesicles are of interest, which leads to a discussion on patented applications and an update on ongoing clinical trials. Taken together, this review provides an overview of bone vasculature and bone regeneration, with a major focus on how exosomes influence this intricate system, as they might be useful for therapeutic purposes in the near future.

Link: https://doi.org/10.3390/ijms25105204

One of the consequences of the COVID-19 pandemic is that the biotech industry is now geared up for the use of messenger RNA (mRNA) as a basis for therapy. The broadest use at present is vaccination, as doses can be very low and the experience gained during the pandemic is directly applicable, but many other forms of mRNA gene therapy are under development. Given the ability to produce novel mRNA vaccines, the most obvious use beyond infectious disease is to force the immune system to engage with cancerous tissue. This line of development appears to be making good progress.

In a first-ever human clinical trial of four adult patients, an mRNA cancer vaccine quickly reprogrammed the immune system to attack glioblastoma, the most aggressive and lethal brain tumor. While too early in the trial to assess the clinical effects of the vaccine, the patients either lived disease-free longer than expected or survived longer than expected. The results mirror those in 10 pet dog patients suffering from naturally occurring brain tumors whose owners approved of their participation, as they had no other treatment options, as well as results from preclinical mouse models. The breakthrough now will be tested in a Phase 1 pediatric clinical trial for brain cancer.

This is a potential new way to recruit the immune system to fight notoriously treatment-resistant cancers using an iteration of mRNA technology and lipid nanoparticles, similar to COVID-19 vaccines, but with two key differences: use of a patient's own tumor cells to create a personalized vaccine, and a newly engineered complex delivery mechanism within the vaccine. "Instead of us injecting single particles, we're injecting clusters of particles that are wrapping around each other like onions, like a bag full of onions. The reason we've done that in the context of cancer is these clusters alert the immune system in a much more profound way than single particles would."

In a cohort of four patients, RNA was extracted from each patient's own surgically removed tumor, and then messenger RNA, or mRNA - the blueprint of what is inside every cell, including tumor cells - was amplified and wrapped in the newly designed high-tech packaging of biocompatible lipid nanoparticles, to make tumor cells "look" like a dangerous virus when reinjected into the bloodstream and prompt an immune-system response. The vaccine was personalized to each patient with a goal of getting the most out of their unique immune system.

Link: https://ufhealth.org/news/2024/uf-developed-mrna-vaccine-triggers-fierce-immune-response-to-fight-malignant-brain-tumor

In today's open access paper, researchers discuss the role of bone marrow aging in the chronic inflammation observed in the aging brain. This inflammation is clearly of great importance in the onset and development of neurodegenerative conditions such as Alzheimer's disease; it is disruptive to the function of the brain. The immune system of the body originates in the hematopoietic cell populations of bone marrow, where cells of the innate immune system are created, as well as the thymocyte precursors to adaptive immune cells. With age, the production of immune cells becomes biased towards innate immune cells (myeloid cell lineages) over adaptive immune cells (lymphoid lineage), but this is far from the only change that takes place.

The immune system of the brain is distinct from that of the body, and originates from different progenitor populations established during early development. Microglia of the central nervous system, for example, are analogous to the macrophages found in the rest of the body, but are thought to originate in the yolk sac during embryonic growth. Still, the immune system of the brain is influenced by that of the body, both by the passage of inflammatory signal molecules, and by the transport of some small number of immune cells into the brain. This transfer appears to increase with age, either due to dysfunction of the blood-brain barrier, or as an adaptive process in response to some aspect of aging. Regardless, while the immune system of the brain is distinct, it is far from isolated from the state of the body, and is thus affected by aspects of aging taking place in the bone marrow.

Aging brain: exploring the interplay between bone marrow aging, immunosenescence, and neuroinflammation

Aging is a complex process characterized by a myriad of physiological changes, including alterations in the immune system termed immunosenescence. It exerts profound effects on both the bone marrow and the central nervous system, with significant implications for immunosenescence in neurological contexts. Our mini-review explores the complex relationship between bone marrow aging and its impact on immunosenescence, specifically within the context of neurological diseases.

The bone marrow serves as a crucial hub for hematopoiesis and immune cell production, yet with age, it undergoes significant alterations, including alterations in hematopoietic stem cell function, niche composition, and inflammatory signaling. These age-related shifts in the bone marrow microenvironment contribute to dysregulation of immune cell homeostasis and function, impacting neuroinflammatory processes and neuronal health.

In our review, we aim to explore the complex cellular and molecular mechanisms that link bone marrow aging to immunosenescence, inflammaging, and neuroinflammation, with a specific focus on their relevance to the pathophysiology of age-related neurological disorders. By exploring this interplay, we strive to provide a comprehensive understanding of how bone marrow aging impacts immune function and contributes to the progression of neurological diseases in aging individuals. Ultimately, this knowledge can hold substantial promise for the development of innovative therapeutic interventions aimed at preserving immune function and mitigating the progression of neurological disorders in the elderly population.

The composition of the gut microbiome influences health and aging. In addition to variations between individuals, the relative abundances of different microbial populations making up the gut microbiome change with age in ways that contribute to chronic inflammation and the loss of useful metabolite production. Researchers here demonstrate that it is possible to correlate aspects of this gut microbiome aging with changes in behavior normally observed in aged mice. The gut microbiome is becoming an attractive target for intervention, given that strategies such as fecal microbiota transplantation can produce a lasting restoration of a more youthful gut microbe configuration.

In this study, we evaluated the locomotor activity, sensory function, and cognitive level of young (3 month old) and aged (22 month old) female C57BL/6J mice through a series of behavioral tests. The physiological functions, gut microbiota, and their metabolites of young and aged mice were comparatively analyzed from the perspective of the microbiota-gut-brain axis (MGBA). Our study focused on the alterations in the microbiota and metabolites induced by aging, and whether such alterations affect systemic inflammation and inflammation of related brain region through the MGBA to mediate abnormal behaviors.

Decreased locomotor activity, decreased pain sensitivity, and reduced respiratory metabolic profiling were observed in aged mice. High-throughput sequencing revealed that the levels of genus Lactobacillus and Dubosiella were reduced, and the levels of genus Alistipes and Bacteroides were increased in aged mice. Certain bacterial genus were directly associated with the decline of physiological behaviors in aged mice. Furthermore, the amount of fecal short-chain fatty acids (SCFAs) in aged mice was decreased, accompanied by an upregulation in the circulating pro-inflammatory cytokines and increased expression of inflammatory factors in the brain.

Aging-induced microbial dysbiosis was closely related with the overall decline in behavior, which may attribute to the changes in metabolic products, e.g., SCFAs, caused by an alteration in the gut microbiota, leading to inflammaging and contributing to neurological deficits. Investigating the MGBA might provide a novel viewpoint to exploring the pathogenesis of aging and expanding appropriate therapeutic targets.

Link: https://doi.org/10.3389/fnins.2024.1362239

That it is possible to produce aging clocks from omics data, that some omics changes map very well to chronological age, biological age, and risk and presence of age-related disease, has been used to argue for aging to be an evolved program. Researchers here use a modeling approach to show that random events, the accumulation of molecular damage, can still produce the outcome observed in aging clocks.

Aging clocks have provided one of the most important recent breakthroughs in the biology of aging, and may provide indicators for the effectiveness of interventions in the aging process and preventive treatments for age-related diseases. The reproducibility of accurate aging clocks has reinvigorated the debate on whether a programmed process underlies aging. Here we show that accumulating stochastic variation in purely simulated data is sufficient to build aging clocks, and that first-generation and second-generation aging clocks are compatible with the accumulation of stochastic variation in DNA methylation or transcriptomic data.

We find that accumulating stochastic variation is sufficient to predict chronological and biological age, indicated by significant prediction differences in smoking, calorie restriction, heterochronic parabiosis, and partial reprogramming. Although our simulations may not explicitly rule out a programmed aging process, our results suggest that stochastically accumulating changes in any set of data that have a ground state at age zero are sufficient for generating aging clocks.

Link: https://doi.org/10.1038/s43587-024-00619-x

The Pace of Aging biomarker emerged from analysis of the Dunedin Study data. It is analogous to epigenetic clocks or phenotypic age, in that it is produced by a machine learning approach, working backwards from a large database of parameters and their changes with age in the study population. Instead of being an assessment of biological age, however, it is an assessment of the pace of biological aging.

In today's open access paper, the Pace of Aging developers improve on their original design. They expand the study populations used and reduce the number of individual assays needed to construct the Pace of Aging marker. They also show correlations between Pace of Aging and aspects of aging such as life expectancy, mortality risk, and risk of developing age-related disease. Interestingly, Pace of Aging increases with advancing age, much as one might expect given the way in which age-related loss of function is observed to progress.

Pace of Aging in older adults matters for healthspan and lifespan

Our original Pace of Aging method was developed from analysis of health changes from young adulthood to midlife in the Dunedin Study 1972-73 birth cohort. To be most useful for comparative biodemographic analysis used by planners to evaluate efforts to promote healthy longevity, the Pace of Aging method needs to be adapted to a different context: samples of individuals representing a wide range of birth cohorts for whom follow-up begins later in the life course. In addition, whereas the Dunedin Study collected extensive biochemical and physical examination data from participants, the studies used by planners typically have access to much sparser measurement panels. Here, we introduce an adapted method for calculation of Pace of Aging in a sample composed of a wide range of birth cohorts with follow-up in midlife and older age and a sparse panel of biomarkers.

We compiled data from dried-blood spot, physical exam, and functional test protocols conducted by the US Health and Retirement Study (HRS) during 2006-2016 (six assessment waves). We identified nine parameters measured at all six waves that met criteria for inclusion in the Pace of Aging analysis: C-reactive protein (CRP), Cystatin-C, glycated hemoglobin (HbA1C), diastolic blood pressure, waist circumference, lung capacity (peak flow), tandem balance, grip strength, and gait speed. A total of 13,626 individuals provided data on at least six of these nine biomarkers across at least two of the follow-up assessments. We modeled longitudinal change in these biomarkers to estimate person-specific slopes for each of them. Then we combined slope information across biomarkers to compute each participants' Pace of Aging.

The adapted Pace of Aging measure reveals stark differences in rates of aging between population subgroups and demonstrates strong and consistent prospective associations with incident morbidity, disability, and mortality. Pace of Aging accelerates at more advanced ages. HRS participants who were older at their baseline biomarker assessment showed more rapid change across subsequent follow-ups as compared to those who were younger. This observation is consistent with biodemographic data showing that mortality risk accelerates at older ages. Pace of Aging is faster in sociodemographic groups characterized by shorter lifespan. Men tended to experience faster Pace of Aging as compared with women. Those with less education tended to experience faster Pace of Aging as compared to those with more education, consistent with observations of a socioeconomic gradient in the pace of aging from the Dunedin Cohort and a Swiss cohort.

Midlife and older adults with faster Pace of Aging were at increased risk of incident chronic disease, disability, and mortality. Older adults with faster Pace of Aging more often developed new chronic diseases and disabilities and were at increased risk of death. Moreover, these associations were independent of smoking, obesity, and educational attainment.

Epigenetic marks such as DNA methylation control expression of genes and cell behavior. They change with age, a reflection of the processes of damage and dysfunction that occur with age. Researchers here focus on DNA methylation in one organ in mice to demonstrate that age-related changes are not linear over time. The individual goes through stages and phase transitions from one state of cellular behavior to another. This is worth considering when thinking about how epigenetic clocks that measure biological age might work in practice, especially when used as a way to evaluate the efficacy of potential rejuvenation therapies.

Analyzing the data of aging mouse colon tissues, we have identified multiple sets of CpG sites exhibiting sudden methylation changes at two different time points. One group of sets undergoes a rapid methylation change during the early-to-midlife transition, while another group exhibits accelerated methylation changes during the mid-to-late-life transition. Interestingly, DNA methylation switches at similar time points were observed in rat peripheral blood DNA. Notably, the division of the lifespan into three stages is already supported by the raw methylation data.

Our data goes in line with a digital aging hypothesis which views aging as a process consisting of discrete steps resulting from mechanisms showing variation in rate during lifespan. The existence of transitions between discrete stages reveals the more controlled, or even programmed, nature of epigenetic aging and opens questions about the regulation and consequences of these abrupt changes. It also indicates that essential insights into the nature of aging may be missed when comparing only two ages.

Link: https://doi.org/10.1038/s41467-024-47316-2

Epigenetic age is most commonly measured via blood sample, assessing the epigenetic markers of immune cells in that sample. Unfortunately the present mainstream epigenetic clocks will provide different ages for different immune cell populations. This leads to meaningful variation in assessments of the same individual, because different cell populations might be present in somewhat different proportions in each blood sample. We might also question which of the cell populations provide the most useful epigenetic age when it comes to responsiveness to interventions that might slow or reverse aspects of aging. This is a well known problem at this point in the continued development of epigenetic clocks, but there is as yet little consensus on what to do about it.

Aging is a significant risk factor for various human disorders, and DNA methylation clocks have emerged as powerful tools for estimating biological age and predicting health-related outcomes. Methylation data from blood DNA has been a focus of more recently developed DNA methylation clocks. However, the impact of immune cell composition on epigenetic age acceleration (EAA) remains unclear as only some clocks incorporate partial cell type composition information when analyzing EAA.

We investigated associations of 12 immune cell types measured by cell-type deconvolution with EAA predicted by six widely-used DNA methylation clocks in data from more than 10,000 blood samples. We observed significant associations of immune cell composition with EAA for all six clocks tested. Across the clocks, nine or more of the 12 cell types tested exhibited significant associations with EAA. Higher memory lymphocyte subtype proportions were associated with increased EAA, and naïve lymphocyte subtypes were associated with decreased EAA. To demonstrate the potential confounding of EAA by immune cell composition, we applied EAA in rheumatoid arthritis.

Our research maps immune cell type contributions to EAA in human blood and offers opportunities to adjust for immune cell composition in EAA studies to a significantly more granular level. Understanding associations of EAA with immune profiles has implications for the interpretation of epigenetic age and its relevance in aging and disease research.

Link: https://doi.org/10.1111/acel.14071

If you've ever wondered why so much effort goes towards the development of supplements and other only marginally effective interventions based on the use of plant extracts, the answer is quite simple: it is usually far cheaper to gain regulatory approval for commercial sale via this approach. From the point of view of many developers, it doesn't much matter how good the result is, as sales in the supplement space are driven by marketing, not efficacy. Thus keep the costs low. So much of this industry is trapped in a cycle in which the search for the lowest regulatory cost produces a market packed with marginal interventions, where competition is driven by branding and marketing rather than product efficacy, and that in turn educates developers and consumers to work towards more of the same.

That said, there are a few plant extracts that might actually be useful enough to pay attention to. Clearance of senescent cells in aged tissues is an important goal, as these cells actively harm tissue function and promote chronic inflammation. A few plant extracts appear to be able to selectively kill senescent cells, most notably piperlongumine and fisetin when used on their own. Quercetin is more widely known, but only because it is a part of the well studied dasatinib and quercetin combination; on its own quercetin isn't meaningfully senolytic. For piperlongumine and fisetin there is an absence of published human data (despite the existence of a clinical trial in the case of fisetin).

Still, all of these compounds are comparatively poorly bioavailable, which has led to groups attempting formulations with varieties of nanocarrier, such as encapsulation in liposomes, that will enable better distribution into the desired target cells. Time will tell as to whether this is a useful line of research and development that will lead to senolytic therapies that are both cheaper and comparably effective to the more sophisticated therapies under development in the longevity industry.

Nanocarriers for natural polyphenol senotherapeutics

Senescence is a heterogenous and dynamic process in which various cell types undergo cell-cycle arrest due to cellular stressors. While senescence has been implicated in aging and many human pathologies, therapeutic interventions remain inadequate due to the absence of a comprehensive set of biomarkers in a context-dependent manner. Polyphenols have been investigated as senotherapeutics in both preclinical and clinical settings. However, their use is hindered by limited stability, toxicity, modest bioavailability, and often inadequate concentration at target sites.

To address these limitations, nanocarriers such as polymer nanoparticles and lipid vesicles can be utilized to enhance the efficacy of senolytic polyphenols. Focusing on widely studied senolytic agents - specifically fisetin, quercetin, and resveratrol - we provide concise summaries of their physical and chemical properties, along with an overview of preclinical and clinical findings. We also highlight common signaling pathways and potential toxicities associated with these agents. Addressing challenges linked to nanocarriers, we present examples of senotherapeutic delivery to various cell types, both with and without nanocarriers. Finally, continued research and development of senolytic agents and nanocarriers are encouraged to reduce the undesirable effects of senescence on different cell types and organs.

This review underscores the need for establishing reliable sets of senescence biomarkers that could assist in evaluating the effectiveness of current and future senotherapeutic candidates and nanocarriers.

Atherosclerosis is the buildup of fatty plaques in blood vessel walls that narrow and weaken those vessels, leading to rupture and a heart attack or stroke. While it is the innate immune cells known as macrophages that are responsible for removing excess lipids from blood vessel walls, clearing up the damage that leads to atherosclerotic plaques, atherosclerosis is a broadly inflammatory condition. Any contribution to systemic inflammatory signaling makes it harder for macrophages to do their job, and the aged adaptive immune system is just as much a source of inflammation as the aged innate immune system.

Whereas initiation of atherosclerotic plaques often occurs upon damage to the endothelium and subsequent infiltration of lipids into the vessel wall, its progression is marked by the infiltration of immune components leading to chronic inflammation of the plaque. Over time, the formation of necrotic debris, plaque destabilization and eventual rupture drive potentially fatal acute cardiovascular events such as a myocardial infarction or stroke. In light of the gradual functional decline of the aging immune system, it comes as no surprise that the incidence of acute cardiovascular events also greatly increases with age, even though atherosclerotic vascular changes already start occurring during early adolescence.

The hallmark feature of atherosclerotic plaque initiation is considered to be the accumulation of low density lipoproteins (LDL) in the tunica intima. This can occur due to a "leaky" endothelial cell layer of the vessel wall in response to damage, for example at sites of shear stress. Modification of LDL, primarily oxidation (oxLDL), promotes the recruitment and infiltration of monocytes into the vessel wall, and the subsequent accumulation of cholesterol-enriched foam cells that contribute to plaque growth and necrotic core formation. Adaptive immune responses, carried out by T cells and B cells, play a crucial role in atherosclerosis progression.

Distinct subsets of T cells, both effector memory T cells and regulatory T cells (Tregs), influence plaque development and stability. Notably, interferon gamma (IFNγ) secreting T helper (Th) 1 cells are the most common T cells found in atherosclerotic plaques. Th1 cells are considered pro-atherogenic, partially due to their role in stimulating macrophage polarization towards pro-inflammatory M1 effector cells. Advances in single cell technology further support the importance of adaptive immunity in atherosclerosis and revealed T-cells to be the most abundant leukocyte present in human carotid atherosclerotic plaques, outnumbering myeloid populations. Additionally, T cell receptor (TCR) sequencing has exposed plaque specific clonal expansion of CD4+ effector T cells with transcriptome profiles indicative of recent antigen-mediated T cell activation, thus suggesting an autoimmune component in atherosclerosis pathology.

Aging not only induces the expansion of pro-inflammatory and cytotoxic T cell subsets, but also stimulates an increase in T cells with regulatory phenotypes. An overall increase of Tregs was observed in the atherosclerotic aorta of aged LDLR knockout mice alongside a heightened expression of functional Treg markers and genes encoding for the IL-35 cytokine as compared to young mice. Similar upregulation of genes indicative of Treg activity was demonstrated in ex vivo human plaques. Moreover, Tregs show clonal expansion in the human carotid plaque. Previously, it has been reported that Treg functionality can decrease upon aging. Whether aging also impacts the immunosuppressive capacity of Tregs in the atherosclerotic environment, remains to be elucidated.

Link: https://doi.org/10.3389/fimmu.2024.1350471

Much of past research into age-related disease involves looking at changes in gene expression in the diseased organ, a very low-level laundry list of alterations. This is somewhat decoupled from the approach of looking at changes in cell behavior, a high-level laundry list of alterations. A sizable fraction of life science research involves trying to make firm connections between these two sets of data, to better steer development efforts towards interfering in more relevant rather than less relevant mechanisms. Here, as an example of this sort of work, researchers link PAR2 expression in the kidney to cellular senescence in that organ. Senescent cells accumulate with age to produce chronic inflammation and other tissue dysfunction. There is considerable interest in finding ways to both selectively remove these cells, or prevent their creation in the first place.

Cellular senescence contributes to inflammatory kidney disease via the secretion of inflammatory and profibrotic factors. Protease-activating receptor 2 (PAR2) is a key regulator of inflammation in kidney diseases. However, the relationship between PAR2 and cellular senescence in kidney disease has not yet been described. In this study, we found that PAR2-mediated metabolic changes in renal tubular epithelial cells induced cellular senescence and increased inflammatory responses.

Using an aging and renal injury model, PAR2 expression was shown to be associated with cellular senescence. Under in vitro conditions in a kidney epithelial cell line, PAR2 activation induces tubular epithelial cell senescence and senescent cells showed defective fatty acid oxidation (FAO). Cpt1α inhibition showed similar senescent phenotype in the cells, implicating the important role of defective FAO in senescence. Finally, we subjected mice lacking PAR2 to aging and renal injury. PAR2-deficient kidneys are protected from adenine- and cisplatin-induced renal fibrosis and injury, respectively, by reducing senescence and inflammation. Moreover, kidneys lacking PAR2 exhibited reduced numbers of senescent cells and inflammation during aging.

These findings offer fresh insights into the mechanisms underlying renal senescence and indicate that targeting PAR2 or FAO may be a promising therapeutic approach for managing kidney injury.

Link: https://doi.org/10.1111/acel.14184

The various approaches to restricting calorie intake remain a popular area of scientific study, as periods of low calorie intake produce broadly beneficial effects on the operation of metabolism. They are protective when it comes to the effects of aging. In animal studies, life-long calorie restriction has been shown to slow aging and extend life span. A great deal of work has gone into the production of calorie restriction mimetic drugs that recreate a small fraction of the metabolic response to low calorie diets and fasting, but as of yet none of these are demonstrated to improve on the practice of calorie restriction.

In humans, the evidence suggests that health benefits resulting from even comparatively mild calorie restriction are sizable enough to make it worth considering as a lifestyle choice. That said, the effects on life span are clearly smaller in longer-lived species. Mice live up to 40% longer when calorie restricted, and that is not the case in humans. Exactly why this difference exists remains a mystery, particularly given that the short term metabolic changes that occur when calorie intake is reduced are broadly similar across mammalian species. As today's open access paper notes, when comparing the beneficial changes to the liver that result from calorie restriction, the biochemistry looks very similar in mice and humans.

Intermittent fasting protects against liver inflammation and liver cancer / Drug partially mimics fasting effects

When experimenting with different variants of intermittent fasting, it was found that several parameters determine protection against liver inflammation: The number and duration of fasting cycles play a role, as does the start of the fasting phase. A 5:2 dietary pattern works better than 6:1; 24-hour fasting phases better than 12-hour ones. A particularly unhealthy diet requires more frequent dieting cycles.

Researchers now wanted to find out the molecular background of the response to fasting. To this end, the researchers compared protein composition, metabolic pathways and gene activity in the liver of fasting and non-fasting mice. Two main players responsible for the protective fasting response emerged: the transcription factor PPARα and the enzyme PCK1. The two molecular players work together to increase the breakdown of fatty acids and gluconeogenesis and inhibit the build-up of fats.

The fact that these correlations are not just a mouse phenomenon was shown when tissue samples from metabolic dysfunction-associated steatohepatitis (MASH) patients were examined: Here, too, the researchers found the same molecular pattern with reduced PPARα and PCK1. Are PPARα and PCK1 actually responsible for the beneficial effects of fasting? When both proteins were genetically switched off simultaneously in the liver cells of the mice, intermittent fasting was unable to prevent either chronic inflammation or fibrosis.

The drug pemafibrate mimics the effects of PPARα in the cell. Can the substance also mimic the protective effect of fasting? The researchers investigated this question in mice. Pemafibrate induced some of the favorable metabolic changes that were observed with 5:2 fasting. However, it was only able to partially mimic the protective effects of fasting. "This is hardly surprising, as we can only influence one of the two key players with pemafibrate. Unfortunately, a drug that mimics the effects of PCK1 is not yet available."

A 5:2 intermittent fasting regimen ameliorates NASH and fibrosis and blunts HCC development via hepatic PPARα and PCK1

The role and molecular mechanisms of intermittent fasting (IF) in metabolic dysfunction-associated steatohepatitis (MASH) and its transition to hepatocellular carcinoma (HCC) are unknown. Here, we identified that an IF 5:2 regimen prevents NASH development as well as ameliorates established MASH and fibrosis without affecting total calorie intake. Furthermore, the IF 5:2 regimen blunted MASH-HCC transition when applied therapeutically. The timing, length, and number of fasting cycles as well as the type of NASH diet were critical parameters determining the benefits of fasting.

Combined proteome, transcriptome, and metabolome analyses identified that peroxisome-proliferator-activated receptor alpha (PPARα) and glucocorticoid-signaling-induced PCK1 act co-operatively as hepatic executors of the fasting response. In line with this, PPARα targets and PCK1 were reduced in human MASH. Notably, only fasting initiated during the active phase of mice robustly induced glucocorticoid signaling and free-fatty-acid-induced PPARα signaling. However, hepatocyte-specific glucocorticoid receptor deletion only partially abrogated the hepatic fasting response. In contrast, the combined knockdown of PPARα and Pck1 in vivo abolished the beneficial outcomes of fasting against inflammation and fibrosis. Moreover, overexpression of Pck1 alone or together with PPARα in vivo lowered hepatic triglycerides and steatosis. Our data support the notion that the IF 5:2 regimen is a promising intervention against MASH and subsequent liver cancer.

The immune system declines with age, becoming both less effective (immunosenescence) and at the same time overly inflammatory and active (inflammaging). It isn't just less effective when it comes to defending against infectious pathogens, but also in the matter of destroying senescent and potentially cancerous cells. Meanwhile, constant unresolved inflammatory signaling is disruptive to tissue structure and function, altering cell behavior for the worse. There are many possible approaches to at least somewhat reverse the underlying causes of these age-related dysfunctions of the immune system: restoring active thymic tissue; improving hematopoietic function; clearing malfunctioning and senescent immune cells; and so forth. More effort should be devoted to bringing these potential therapies to the clinic.

A stem-cell researchers didn't trust what they were seeing. Their elderly laboratory mice were starting to look younger. They were more sprightly and their coats were sleeker. Yet all the researchers had done was to briefly treat them - many weeks earlier - with a drug that corrected the organization of proteins inside a type of stem cell. In two papers, in 2020 and 2022, the team described how the approach extends the lifespan of mice and keeps them fit into old age. The target of this elixir is the immune system. The stem cells she treated are called haematopoietic, or blood, stem cells (HS cells), which give rise to all immune cells. As blood circulates, the mix of cells pervades every organ, affecting all bodily functions.

But the molecular composition of the HS cells changes with age, and this distorts the balance of immune cells that they produce. Recently another team showed that restoring the balance between two key types of immune cell gives old mice more youthful immune systems, improving the animals' ability to respond to vaccines and to stave off viral infections. Other scientists have used different experimental approaches to draw the same conclusion: rejuvenating the immune system rejuvenates many organs in an animal's body, at least in mice. And, most intriguingly, evidence suggests that immune system ageing might actually drive the ageing of those organs.

The potential - helping people to remain healthy in their later years - is seductive. But translating this knowledge into the clinic will be challenging. Interfering with the highly complex immune system can be perilous, researchers warn. So, at first, pioneers are setting their sights on important yet low-risk goals such as improving older people's responses to vaccinations and improving the efficiency of cancer immunotherapies. "The prospect that reversing immune ageing may control age-related diseases is enticing. But we are moving forward cautiously."

Link: https://doi.org/10.1038/d41586-024-01274-3

The immune system is complex and undertakes many activities in the body beyond mounting a defense against pathogens. Immune cells are involved in many of the normal processes of tissue maintenance. Even where there is no direct involvement, the secreted signals produced by inflammatory immune cells produce changes in the behavior of other cell populations. Thus we should not be surprised to find it possible to draw connections between the state of the immune system and the structural properties of tissue that arise from the behavior of the cells making up that tissue. This is one of many reasons why change and dysfunction in the immune system is an important component of aging, and one that should be addressed as a part of any broad attempt to produce rejuvenation.

It is well known that during the aging process, the immune system changes, that is, the disorder and decline of immune system function. In the aging state, the immune system usually shows a relatively continuous state of low activation. When stimulated by the outside world, its dynamic response becomes weaker and the amplitude is reduced, and this combination of chronic inflammatory state and reduced effective defense ability is often referred to as immune aging.

Studies have found that immune aging is associated with increased morbidity and mortality in the elderly. With the increase of age, T cells with aging phenotypes will continue to accumulate, further promoting immune aging, resulting in a decrease in immune function and an increase in pro-inflammatory function.

It has been found that aging T cells may promote pathological changes in the tissue structure of various systems of the human body through a variety of mechanisms, thereby leading to related diseases and fundamentally affecting the health of the elderly. First, aging T cells continue to produce cytokines that directly promote inflammation. Secondly, aging T cells may not be able to perform the function of monitoring aging, so that they cannot clear the irreversibly damaged cells that become senescent cells. In addition, aging T cells can lead to the loss of autoimmune tolerance and secrete cytotoxic substances that directly damage tissues. Finally, aging T cells can also indirectly participate in various changes by regulating intestinal homeostasis.

Link: https://doi.org/10.1186/s12979-024-00433-4

Klotho is one of the few longevity-associated genes shown to work in both directions; lower expression shortens life span in animal studies, while increased expression modestly slows aging. Despite several decades of research, scientists have yet to reach a full understanding of how klotho influences life span. The klotho gene produces a transmembrane protein that operates inside and on the surface of cells, as well as a section of the protein, α-klotho, that detaches to act as a signal molecule outside the cell. Study has primarily focused on the protective role of klotho in the kidneys, with the hypothesis that kidney function is important enough to organs throughout the body that slowed kidney aging has a global effect on healthspan. Since the discovery that increased circulating α-klotho improves cognitive function, even in younger animals, however, researchers have increasingly focused on how klotho might be slowing aging in the brain.

The study here is one of a number to examine human data in order to provide support for the ongoing development of therapies based on delivery of an optimized α-klotho version. Does the evidence in humans suggest that the broad base of animal study data will hold up in our species? Largely yes. Levels of α-klotho in blood can be measured, and those individuals with less circulating α-klotho appear to experience increased risk of age-related disease and mortality. At this point it seems likely that therapies to increase circulating α-klotho levels will emerge before a complete understanding of why it is that this increase is beneficial.

The prognostic value of serum α-klotho in age-related diseases among the US population: A prospective population-based cohort study

α-Klotho is a potential biological marker of aging with satisfactory clinical applicability. However, its prognostic significance in age-related diseases has largely been undermined. Therefore, we aimed to report the prognostic value of serum α-klotho levels in age-related diseases.

Participants with available serum α-klotho data from the National Health and Nutrition Examination Survey (2007-2016) were included. Their survival status was collected at 7.62 ± 2.99 years after serum α-klotho data was collected, and the endpoint was all-cause and cardiovascular mortality. A Cox regression model was established to examine the association between serum α-klotho levels and all-cause and cardiovascular mortality.

The present study included 13,746 U.S. adults with a survey-weighted mean age of 56.19 ± 10.42 years old. The optimal cutoff value of serum α-klotho for predicting all-cause mortality risk in the general population was 603.5 pg/ml. Individuals with low serum α-klotho (less than 603.5 pg/ml) had a significantly higher risk of all-cause (adjusted hazard ratio: 1.34) and cardiovascular mortality (adjusted hazard ratio: 1.63). Subgroup analysis showed that low serum α-klotho level was an independent risk factor for all-cause and cardiovascular mortality in people with hypertension, congestive heart failure, diabetes mellitus, and emphysema, while it was an independent risk factor for all-cause mortality in patients with renal insufficiency.

A low serum α-klotho concentration (less than 603.5 pg/ml) could serve as a marker of all-cause and cardiovascular mortality in the general population and in people with age-related diseases, including hypertension, congestive heart failure, diabetes mellitus, and emphysema.

Researchers here show that bile acid metabolism makes a meaningful contribution to age-related neurodegeneration and cognitive decline. Bile acids produced by the gut microbiome leave the intestines in growing amounts with advancing age, and cause harm to the brain. In animal models, the researchers demonstrate a that sequestering bile acids in the intestine with suitable molecules can reduce the bile acid contribution to brain aging. It is plausible that adjusting the balance of populations in the aged gut microbiome via fecal microbiota transplant from a young individual could produce similar benefits, but that has yet to be rigorously assessed.

Recent studies have suggested a link between changes in bile acids (BAs) and age-related cognitive impairment. Investigations into Alzheimer's disease and Parkinson's disease reveal that lower serum levels of unconjugated primary BAs (UPBAs), such as cholic acid and chenodeoxycholic acid, along with elevated levels of glycochenodeoxycholic acid, a conjugated primary BA metabolite, are closely associated with the severity of cognitive decline symptoms.

Current understanding suggests that the gut microbiota, which produces secondary BAs in the gastrointestinal lumen, undergoes age-related alterations. These changes significantly impact the levels of BAs circulating in the body and present within the brain. Additionally, there is a notable correlation between certain serum BA metabolites, particularly increased levels of glycolithocholic acid and tauro-lithocholic acid, which are bacterially derived secondary BAs, and elevated cerebrospinal fluid total tau levels. BAs can communicate between the periphery and the brain either through specific BA transporters or by passive diffusion across the blood-brain barrier.

In this study, we observe elevated levels of serum conjugated primary bile acids (CPBAs) and ammonia in elderly individuals, mild cognitive impairment, Alzheimer's disease, and aging rodents, with a more pronounced change in females. These changes are correlated with increased expression of the ileal apical sodium-bile acid transporter (ASBT), hippocampal synapse loss, and elevated brain CPBA and ammonia levels in rodents. In vitro experiments confirm that a CPBA, taurocholic acid, and ammonia induced synaptic loss. Manipulating intestinal BA transport using ASBT activators or inhibitors demonstrates the impact on brain CPBA and ammonia levels as well as cognitive decline in rodents. Additionally, administration of an intestinal BA sequestrant, cholestyramine, alleviates cognitive impairment, normalizing CPBAs and ammonia in aging mice.

Link: https://doi.org/10.1016/j.xcrm.2024.101543

Researchers here report on continued investigation of a bacterial peptide capable of disrupting misfolded α-synuclein aggregation. This aggregation is the driving pathology of Parkinson's disease. In other cases, such as for transthyretin amyloid, it has been possible to design small molecule drugs that interfere in harmful protein aggregation. While the bacterial peptide is toxic to cells, it is hoped that better understanding its interaction with α-synuclein will lead to non-toxic small molecules that can achieve the same disruption of protein aggregation, and thus a viable treatment for Parkinson's disease and other synucleinopathies.

Alpha-synuclein aggregation is a hallmark of Parkinson's disease and other synucleinopathies. It is a dynamic process in which the protein self-assembles to form oligomers that eventually develop toxic amyloid fibrils, which accumulate in the patient's brain. Alpha-synuclein oligomers play a key role in the development and progression of the disease and, therefore, are promising therapeutic and diagnostic targets, particularly in the early stages of the disease, but their transient and highly dynamic nature limits the study of their structure and hinders the development of therapies aimed at blocking them.

Researchers had observed in a previous study that a small molecule, the bacterial peptide PSMα3, inhibited the aggregation of alpha-synuclein in binding to oligomers, blocking the conversion to fibrils and inhibiting neurotoxicity. In this study, they identified where, how and when this binding occurs in the oligomers, uncovering a key region for the structural conversion process associated with the pathogenesis of Parkinson's disease. Researchers observed that PSMα3 acts by binding to one end of the alpha-synuclein (N-terminus) that regulates the oligomer-to-fibril conversion process. Upon binding, the peptide covers two small adjacent regions of the protein which have been found to be critical for this pathogenic transition.

"We identified the structure's sequence that is essential for the conversion of oligomers to fibrils, thus opening a new field of exploration in the design of molecules aimed at targeting oligomers. By leveraging this region, we can develop new molecules that mimic the properties of PSMα3 with a much higher affinity and efficacy."

Link: https://www.uab.cat/web/newsroom/news-detail/therapeutic-target-identified-to-neutralise-toxic-forms-of-parkinson-s-associated-protein-1345830290613.html?detid=1345915929138

Repair Biotechnologies was invited to present at this year's Rejuvenation Startup Summit in Berlin, and so my CSO Mourad Topors and I attended. There were more people present this year than were at the already busy 2022 event. This is perhaps an indication of a still growing interest in the longevity industry as it expands, particularly given the present poor market for investment in biotechnology companies. Investors are tending to stay home this year, but nonetheless there was a fair sized crowd in attendance.

Michael Greve's Forever Healthy Foundation hosts the Rejuvenation Startup Summit, and he gave the opening talk, framing the point of the exercise. The longevity industry will clearly become one of the world's largest industries, growing to become the majority of all medicine, given that every older individual is a potential customer. The hundred or more biotech startups that presently make up the longevity industry will collectively demonstrate that this field works, that it is viable, that we can slow and reverse aging. The first proven therapies will usher in a great increase in interest, investment, and participation in the longevity industry. The purpose of this conference series is to help to make that future happen: networking makes the world turn, particularly in the world of biotech investment.

The keynote was provided by Mehmood Khan of the Hevolution Foundation, slowly but steadily deploying Saudi Arabian sovereign wealth into aging research and the longevity industry. Hevolution is a non-profit organization, and plans to put the returns from its investments into further research and development to advance the field. The organization has a fairly conservative viewpoint that is focused on addressing the failure of increases in healthy life span to keep up with overall life span - a focus on compression of morbidity. The financial burden of a growing older population is unsustainable, the existence of the present demographic transition to a larger older population is a driving concern. The current approach to age-related disease isn't working and must change. This conservative viewpoint is one that sees it as very hard to make a gain of few years of healthy life when that gain must be made across the population as a while. Making the technology is perhaps the easier part when compared against the social, realpolitik considerations of how to scale the technology and provide access to it as a public health measure, a low cost therapy. This philosophy explains much of why they focus on the technologies and approaches that they do: mTOR inhibitors that might add a year of life at low cost can better meet their goals than the development of much more advanced therapies that could achieve greater extension of life, but would require decades of work to bring down in cost and scale out to mass availability. Khan made the point that scaling requires the participation of Big Pharma, but Big Pharma is not yet a part of the longevity industry; bringing them into the fold is a task yet to be accomplished. He closed by noting the scale of the disconnect between the cost of aging and the funds available for research. Hevolution has provided $250m in the past 18 months to research institutions that include the Buck Institute, making them the second largest source of funds after the US government - and this is woefully little for the task at hand.

Otto Kanzler of Rockfish Bio opened with an outline of just how bad degenerative aging is: the cost of coping, the disability, the mortality, the lost productivity. The company works on clearance of senescent cells, but while noting that senolytic therapy development is overall very promising, there are barriers to clinical translation. Senescent cells differ considerably by origin, tissue, and stage of senescence. Thus first generation therapies are not effective in clearing all senescent cell types, not selective enough. Further, indication choice is a challenge for any senolytics company, as it might initially seem that there are many options, few are in fact good options from the point of view of cost, difficulty of the discussion with regulators, ability to directly connect senescence to disease mechanisms, and so forth. A big problem is that there are no good non-invasive biomarkers for the burden of senescent cells, either globally or in specific tissues. The company's development program is derived from the realization that senescent cells have increased phospholipase A2 (PLA2) activity. PLA2 is an inducer of apoptosis, but senescent cells convert PLA2 to evade that fate. This is similar to a number of other mechanisms in senescent cells: the cells appear primed for apoptosis, but actively resist it. Rockfish Bio targets this PLA2 conversion with a small molecule, selectively inducing apoptosis in senescent cells as a result. Treatment of mice has produced an extension of life. Rockfish Bio is also collaborating with another industry company to produce a biomarker based on circulating miRNA levels that can measure burden of senescent cells.

Marco Quarta of Rubedo Life Sciences, another senolytics company, also noted the heterogenity of the senescence state, and the problems that this causes in the search for effective therapies. Rubedo has create a drug discovery platform to identify targets for different senescent cell types, and have built up a portfolio of targets and drug candidates. They recently raised significant funding for their first clinical program, focused on skin condition such as atopic dermatitis and psoriasis in which senescent cells are likely important, and where topical therapies can be applied. Like other senolytics companies Rubedo is motivated by the poor selectivity of existing therapies like the dasatinib and quercetin combination, and the off-target effects on non-senescent cells. The goal for Rubedo is to produce drug candidates that are far more selective for specific subsets of senescent cells. At this point, the company expects to start clinical trials in 2025.

Alexander Schueller of cellvie discussed the origins of the company's work on mitochondrial transplantation. Mitochondrial transplantation was used in a clinical trial for children with ischemic heart injury that put them on life support, and the results demonstrated that this approach can work to prevent death and permanent injury. The company was formed to broaden the use of mitochondrial transplantation for all forms of ischemia-reperfusion (IR) injury. A key part of IR injury is dysfunction and damage to mitochondria, but timely delivery of replacement mitochondria prevents much of the cascade of damage resulting from IR injury. The company aims at kidney transplantation as first IR injury situation, as preserving the function of donor kidneys provides the fastest path to a clinical proof of concept that will encourage others to expand this field. The company is presently working towards the development of good manufacturing practice (GMP) protocols for manufacture of harvested mitochondria, with the aim of moving from the use of autologous mitochondria to off the shelf mitochondria that are frozen for storage. Tests have been conducted in pig models that undergo 90 minutes of ischemia to the kidneys followed by treatment with human mitochondria. Biomarkers of kidney function have shown considerable improvement in the treated pigs. Schueller commented on some of the challenges inherent in obtaining funding, in part because the mechanisms underlying the benefits of mitochondrial transplantation are not fully understood. The company has thus been working on obtaining a better understanding, and has shown that uptake of new mitochondria via endocytosis triggers both mitophagy and mitogenesis, improving the situation for native mitochondria. This may not be the only mechanism. The company has also conducted proof of concept research into using mitochondria as a vector for gene therapy, as mitochondria tend to accumulate in the first downstream major organ after intravenous delivery.

Greg Fahy of Intervene Immune gave an update on their work on the reversal of thymic involution. The thymus atrophies, first after puberty, and then more slowly throughout the rest of life, leading to a near complete lack of active tissue as early as age 50 in many cases. The capabilities of the adaptive immune system slowly collapse, lacking the supply of new T cells generated in the thymus - and so the risk of death from immune-related causes rises precipitously after age 50. Thymus transplant from young donors to aged animals has been shown to extend life and restore immune function. Intervene Immune used a growth hormone / DHEA / metformin combination in small human trials, the choice of approach chosen in part to try to gain a rapid approval from regulators. The results from the first TRIIM trial were published in 2019, and included modest reductions in extrinsic and intrinsic epigenetic age. TRIIM-XA was an extension and expansion of that trial, including 26 participants. It is now complete and results are being analyzed. The COVID-19 pandemic occurred during TRIIM-XA, and Fahy speculated on whether this would have had any impact on the results via consequences of vaccination. In preliminary data, TRIIM-XA showed epigenetic age and phenotypic age reversal in a number of different clocks, as well as lower inflammatory markers, increased recent thymic emigrant naive T cells, improved strength and fitness as measured via exercise tolerance, standing test, and VO2max, and lowered body fat percentage and blood pressure. The company is starting to consider adding more agents to the protocol; Fahy tested the addition of a new option on himself recently with positive results.

Eric Verdin of the Buck Institute for Research on Aging gave the second keynote, a selection of ongoing work at the Buck Institute and its relevance to geroscience. He started with the role of senescent cells in aging via their contribution to chronic inflammation and the generation of secondary senescent cells via paracrine signaling. An important implication is that senescent immune cells generate secondary senescence in tissues throughout the body, linking immune aging to near all other aspects of aging. One of the Buck Institute projects focuses on characterizing and measuring senescent cells in the immune system, and finding ways to address it. The researchers have discovered considerable complexity over the course of aging in the changing populations of immune cells of various types and behaviors. Generic markers of cellular senescence show that large proportions of some subpopulations of immune cells have become senescent, for example up to 40% of some memory T cells. These markers of senescence need to be improved upon, however, given the diversity of senescent states. Verdin then moved on to discuss the buildup of lipofuscin with age. The researchers see it as a marker of senescence, at least in the immune system - it is actually a marker of lysosomal stress, characteristic of senescent cells. Their data demonstrates a correlation between lipofuscin burden, age, and other markers of senescence status in T cells. This detailed assessment of immune cell populations has also shown that epigenetic clocks produce different results in different subpopulations of immune cell. As a result, the clocks can be split into measures of extrinsic age (quite variable across immune cell types) versus intrinsic age (not so variable). The intrinsic age clock may be measuring the proportion of senescent cells in immune populations, but this has yet to be robustly demonstrated.

Lou Hawthorne of NaNotics works on targeting the soluble proteome for selective clearance. Nanots are engineered nanoscale sponges that can bind and soak up specific soluble proteins outside cells only, and are then cleared from the body by macrophages. Nanot binding represents an improvement over antibody approaches, both in specificity and in controlling the degree of depletion. The company can engineer nanots to, in principle, bind near any soluble protein. The initial clinical focus is on clearing soluble forms of TNF and TNF receptor (TNF-R1 and TNF-R2), as well as various interleukins to inhibit runaway inflammation. Inflammatory autoimmune conditions and cancers are the initial indications. All cancers shed TNF receptor fragments as soluble TNF-R1 and TNF-R2 in order to decoy TNF as a part of their immune suppression strategy. Clearing these decoys helps to make the cancer visible to the immune system. There used to be a clinic that employed apheresis to clear soluble TNF receptor fragments in terminal cancer patients, a treatment that achieved 60% response rates. The hope is that the nanot approach will improve on this. Soluble TNF receptor proteins are an undruggable target, so small molecules can't be used here, as they would interfere in necessary functions mediated by the receptors. NaNotics has also collaborated on clearing soluble PD-L1, showing benefits in models. Beyond cancer, the company works on clearance of soluble TNF to treat multiple sclerosis, as soluble TNF and soluble TNF-R1 both interfere in oligodendrocyte-mediated remyelination. In MS there is too much soluble TNF. In closing, Hawthorne mentioned that the company is now working on a polymer core nanot that will be able to last for a long time in circulation. They would like to use this to treat endothelial barrier dysfunction and inflammaging by clearing out the best-known circulating signal molecules involved in these processes.

Dobri Kiprov of Circulate started with an outline of the recent history of parabiosis research, starting with a collaboration with the Conboys. Further research after that supported the use of therapeutic plasma exchange as an approach to treat aspects of aging, the practical way to implement something like parabiosis in humans. Clinicians can remove plasma and substitute in young plasma, but this can produce side-effects. So they instead use 5% albumin in saline. Albumin comes from donor plasma, where the average age of donors is 25 or so. Kiprov argued for the quality of the albumin to likely be an important factor in the effects of parabiosis, given it has immunomodulatory, anti-inflammatory, and antioxidant effects. He outlined a recent clinical trial of therapeutic plasma exchange, which is double blinded and enrolled 40 patients. There was only one adverse reaction over the course of 360 procedures conducted during the trial. The clinicians assessed hand grip and similar values of physical condition, measures of cognitive function, and senescence-associated secretory phenotype (SASP) proteins in circulation. Treatment resulted in some improvement versus controls in all of these. The company continues to analyze the copious study data. Important goals include answering the question of how long the effects last for, as well as how to identify which patients will respond positively to the therapy.

Alejandro Ocampo of Epiterna spent some of his presentation on a sketch of the incentives shaping the longevity industry. Companies are focused on applying their work to specific age-related diseases rather than to aging; they typically don't even test to see if life span is extended in mice as a result of their treatment. This is because of regulatory concerns, in that trials to assess aging will be very costly, and no-one wants to be first to try to take the TAME trial design and convince the FDA to let them do it. So instead companies aim at regulator approval for one age-related disease followed by off-label use. Ocampo is concerned that this approach will leads to the failure of trials for viable anti-aging therapies that happen to be a poor fit for the chosen disease. Also, founders tend to lose control of the company as it moves forward, and if it starts working on one disease it may never change to focus on life extension; this has already happened. Learning from this, Epiterna tries to deliberately work on longevity rather than disease. The company is focused on aging in dogs, and are working to develop supplement based approaches to slowing aging. Why dogs? Because it is the largest companion animal market and there is a much lower regulatory cost and risk than is the case for human medicine, particularly given recent efforts to make regulators accept aging as an indication in animals. Additionally, dogs have a short enough life span to allow proof of effects on aging with a feasible cost. Why supplements? Because of the faster path to market and lower regulatory hurdles. The company has developed a low-cost screening platform that screens compounds for life extension in numerous short-lived species, working through yeast, worms, filies, killifish, and mice. In one year they can run ~3000 molecules in yeast and narrow down to a final 20 in mice that are consistently extending life across these species. The output of this screening will lead to trials in companion dogs, currently planned to last 2-3 years and include as many as a thousand animals.

Lorna Harries of SENISCA works on reprogramming cells by designing and screening oligonucleotides and small molecules that can suppress detrimental alternative splicing of RNA characteristic of aging and cellular senescence. This is a way to produce senotherapeutics that reprogram senescent cells into behaving better, or possibly even exit the senescent state if they are in early stage senescence. This screening platform can in principle be more selective about what type or stage of senescent cells are targeted than existing senolytic drugs. The SENISCA program originated with the unbiased screening of age-related changes in gene expression in samples from hundreds of people, where the results pointed to the importance of RNA processing pathways and altered expression of splicing factors. The company is developing oligonucleotides as therapeutics to target aging in general, and have a codevelopment partnership to develop small molecules for topical use in skin aging. The researchers have developed their own assays for senescent cell burden in tissues and cell cultures, as well as making it possible to distinguish between early and late senescent cell states. SENISCA is initially focused on idiopathic pulmonary fibrosis (IPF) as an indication, and has shown shown reduced senescence, fibrotic markers, collagen deposition, and DNA damage in human IPF patient cells in vitro following treatment. The company has tested intranasal delivery of naked oligonucleotides in mice, and show delivery to lungs, a promising start.

Stephanie Dainow of Lifespan.io gave, I'm told, an interesting presentation, particularly given that SENS Research Foundation and Lifespan.io are now merging. Unfortunately I had to miss this one. Apologies!

Phil Newman of Longevity.Technology discussed the demographic aging trend as a motivation to work on the treatment of aging as a medical condition, where even a modest slowing of aging could greatly reduce the vast economic cost of ill health in later life. There is a clearly a trend in the science and development, age-slowing, and age-reversing therapies will come into being, and things are going to become very interesting as average life expectancy increases step by step to be far greater than 100 years of age. That future is being built now, but what will it look like, where will the greatest focus fall? We can all speculate, and will all likely be surprised in many ways. Newman moved on to an overview of the present system of medical regulation and reimbursement; how the money flows, the economic incentives for Big Pharma, medical insurance companies, and governments. Chronic disease costs a lot, and therapies to effectively slow or reverse aging will improve the economics for everyone. How long will it be until effective therapies to treat aging exist? This is difficult to predict, but we might be pessimistic when looking at the decades it has taken for some currently popular therapies to move from fundamental research to recognition of value to active clinical development.

Lukas Langenegger of Hemotune showcased their approach to plood purification, improving dialysis techniques to remove specific molecules in blood. As for the NaNotics technology, this offers the ability to selectively remove multiple specific molecules and thus address multiple mechanisms at one time in the case of complex conditions. Hemotune make a machine that allows better, selective blood purification. As in all dialysis, blood runs through the machine. At the core is an exchangeable cartridge of engineered magnetic nanoparticles decorated with antibodies or other binders specific to selected molecules in blood. These nanoparticles, and the molecules newly bound to them, are removed by magnets before blood is returned to the patient. Hemotune is initially targeting sepsis-induced immunosuppression, a lasting condition that follows sepsis, and are working towards a clinical trial to be conducted in a few hundred patients. Secondly, the company has developed a proof of concept for the removal of anti-AAV antibodies. This will in principle enable AAV-based gene therapy to work in patients with existing antibodies. Antibodies prevent repeat dosing, but many patients have preexisting anti-AAV antibodies even prior to a first dose.

Robin Mansukhani of Deciduous Therapeutics presented on their senolytic immunotherapy, a small molecule treatment that produces a lasting alteration in the behavior of invariant natural killer T cells (iNKT cells) to increase their ability to clear senescent cells. iNKT cells coordinate the removal of senescent cells. Explaining the origin of the program, Mansukhani explained that the realization that accumulation of senescent cells is driven by failure of the immune system to clear these cells in a timely fashion led to research aimed at identifying which immune cells were dysfunctional and why. That in turn pointed the way to an intervention to reverse that dysfunction. The animal data generated by Deciduous demonstrates the effective lasting clearance of senescent cells, and a consequent sizable reduction in fibrosis in mouse models of idiopathic pulmonary fibrosis, a far greater effect than is produced by the current standard of care treatment of nintedanib. The company has also shown improvement in type 2 diabetes mouse models. In general, an effective senolytic should have a large value, as it can be applied to near every age-related disease in some way. The next steps for Deciduous are to scale up manufacturing processes and conduct IND-enabling studies. They are also looking into how to replicate the iNKT intervention in the brain, where the immune system is isolated and different, and would thus require identifying a different cell population and form of dysfunction to correct.

Matthew O'Connor of Cyclarity showed a sampling of studies demonstrating that 7-ketocholesterol, a harmful altered form of cholesterol, is associated with cardiovascular disease. At the SENS Research Foundation the staff spent some time looking into how to clear this molecule, and settled on a cyclodextrin based approach - finding ways to adapt existing cholesterol-binding cyclodextrins to only bind 7-ketocholesterol. In the process they produced a platform for cyclodextrin design that might be applied to other goals. Cyclodextrins have many uses, and existing cyclodextrin drugs bind various unwanted molecules to remove them from the body. The industry has a lot of experience in working with them. Cyclarity has shown in vitro that their cyclodrextrin drug can restore function in macrophages induced by 7-ketocholesterol to become foam cells. The company is headed to the clinic: the first GMP batch is produced, and a phase 1 safety trial in healthy volunteers and a smaller number of patients with plaque is set to start this year in Australia.

I presented on our work at Repair Biotechnologies, starting with a brief tour of the data showing that the risk of cardiovascular disease and mortality via stroke and heart attack rises with the burden of atherosclerotic plaque present in the arteries. For example, a Dutch study showed that 5-6 arterial plaques identified by imaging indicates a five-fold increase in risk over those with no visible plaques. The lipid-lowering standard of care (meaning long-term treatment with statins, PCSK9 inhibitors, and the like) does not meaningfully reduce plaque size, however. As little as a 1% reduction in plaque volume leads to a ~20% reduction in stroke and heart attack, but only a fraction of patients can achieve even this much plaque reduction after a year or more of treatment. The average improvement is close to zero. In comparison, the Repair Biotechnologies LNP-mRNA gene therapy can produce a 17% reduction in aortic plaque volume after six weeks of treatment in the LDLR knockout mouse model of accelerated atherosclerosis. Additionally, the therapy removes plaque lipids and encourages plaque stability in the APOE knockout mouse model of atherosclerosis. This therapy works by clearing a toxic excess of free cholesterol in the liver, restoring the liver to homeostasis and producing systemic beneficial effects throughout the body. The company is planning a series A round to fund the path to a first clinical trial in the rare genetic condition of homozygous familial hypercholesterolemia in 2026, with a potential fast track approval leading to off-label use for severe atherosclerosis in the general population.

Brian Kennedy of the National University of Singapore (NUS) opened his presentation with a complaint about the lack of preventitive treatment taking place in the period of healthy life. We have a sickcare system that focuses only the part of life when people are demonstrably unwell. Doing nothing while people are healthy is in fact causing harm, because aging is still progressing towards sickness while people are ostensibly healthy. The programs at NUS focus on the interface between biomarkers and interventions. One example of their work is a broad set of combinatorial studies, in which it was shown that the combination of any two supplements or small molecules that are modestly good on their own can produce any sort of result, bad or good, often bad, and no-one can yet predict in advance what the outcome will be. The NUS researchers conduct various simple interventions in mice while assessing life span and biomarkers, attempting to be rigorous in setting up a cost-effective system to better evaluate the effects of these interventions. Kennedy went on to make the point that we don't know much about widely used medical tourism treatments, meaning stem cell therapies, exosomes, and so forth, and he wants to work with clinics in order to gather data on the outcomes in people undergoing these studies - a matter of using rich people as model organisms, as he said. He also made the point that older people who are in a worse state of health, with an accelerated biological age relative to chronological age, appear to respond better to some interventions. He offered the example of a human alpha-ketoglutarate (AKG) study in supplement users (lacking a control group) in which epigenetic age was reduced. It is unknown as to whether a better relative outcome in less healthy individuals is the case for all interventions. The NUS researchers are repeating this AKG study with a control group, and should have results in 2025. Kennedy noted that AKG delays fertility decline in mice, and speculated on whether this could be a general effect across many interventions, because mechanisms that slow aging should have evolved to specifically slow reproductive aging, while everything else is a side-effect of that outcome. Moving on to aging clocks, the NUS team has produced a metabolomic aging clock, and along the way demonstrated that AKG levels in circulation decline with age. The researchers are also working on several other different clocks built out of combinations of clinical parameters, similar to phenotypic age and using data from the NHANES study, on the grounds that a clock of this nature should produce results that are more directly comprehensible and useful to clinicians.

Alexander Leutner of Cellbricks outlined their approach to tissue engineering. The company has developed a light-based bioprinting process. Laser light is projected into into a dish of bioink, each pulse of light making a tiny volume of the ink solidify. In this way the researchers can construct complex structures layer by layer: build a layer, raise it out of the bioink, build the next layer, and so forth. They can produce vascularized blocks of tissue in this way, and have manufactured functional cartilage, liver, pancreas, breast tissue, and others. They can also create tumor models or other forms of diseased tissue. The company aims to create implantable blocks for reconstructive surgery, such as following breast surgery, or tissue resections to remove tumors, or to restore function in aged livers by implanting a patch of functional liver tissue. The company has conducted a great deal of work to demonstrate that their tissue blocks are functional and stable over time, and match the strutural properties of native tissue as much as possible. They are presently conducting tests in animal models, and working towards partnerships with large pharma companies, which seems to be the standard approach for tissue engineering companies.

Matthew Scholz of Oisin Biotechnologies discussed their platform for genetic medicine based on LNP-mediated DNA delivery. At this point their first indications are sarcopenia and frailty, accumulation of unwanted fat, and accumulation of senescent cells. The company started with a focus on senescent cells, but that was not much discussed in this presentation, as Oisin obtained more support, funding, and interest for the other indications. The platform for delivery is the Entos Pharmaceuticals fusogenic LNPs, lipid nanoparticles that use a fusion protein derived from a virus to enable cell entry directly into the cytoplasm. This is distinct from the usual LNP path of endocytosis into a membrane-wrapped vesicle that must then be escaped to enter the cytoplasm. Fusogenic LNPs have no cell preference, and will enter any cell they encounter. This can be used as a starting point to build versions with some selectivity, but the unmodified LNP is the closest anyone has come to a vector that has broad body-wide distribution without the major organs taking up most of it. The company uses DNA machinery as a cargo for the LNP to engineer very selective expression of transgenes in specific tissues. The first application is to upregulate follistatin in to produce muscle growth. The team has demonstrated this outcome in mice, including in very old mice. The second application is to destroy unwanted fat cells, and the technology can selectively target specific fat pads via promoters that are only active in those tissues. They can also change the fusogenic LNP to more selectively target fat cells specifically. In effect the result is liposuction without surgery. In the future Oisin wants to broaden this technology platform to many other potential uses. The company is presently raising an A round led by Abbvie Ventures.

Jean Hebert of BE Therapeutics presented on tissue engineering for the brain. Permanent brain damage is a problem in many contexts, such as aging, injury, and cancer, and there is no approach at present to replace that tissue. The company is trying to develop a way to regrow brain tissue based on the recreation of developmental processes. Starting with the neocortex, the team analyzed precursor cells, and can now assemble an architecturally correct, vascularized neocortex organoid prototype from cell populations derived from induced pluripotent stem cells. The neocortex is a very dynamic part of the brain, with connections and usage changing constantly, so it seems possible to put in new tissue and have it be used appropriately to encode information. The team has implanted prototype tissues in mice, replacing a part of the neocortex that was surgically removed. They are now proceeding with work on human tissues, testing the function of developing neurons in preparation to optimize the form and function of the prototype tissues. The initially targeted indications involve damage to the neocortex, such as that resulting from stroke and dementia. The company is in the early preclinical stage, and has yet to conduct studies in animal models of those conditions.

Janine Sengstack of Junevity talked about the platform that she developed during her PhD, enabling discovery of transcription factors that alter cell behavior into more youthful phenotypes. Gene expression changes with age, the large number of individual changes can be mapped and measured, and thus one can screen and identify transcription factors that affect a large faction of this network of genes. The company uses siRNA to downregulate specific transcription factor expression, and have demonstrated proof of principle in vitro for liver cells. The treatment improved cell function along with resetting some of the map of changed gene expression. The team has used the platform to determine candidate transcription factors to suppress in the aging liver and fat tissue, and are working on skin aging as well. They are collaborating with a pharma company for target discovery in obesity. They have shown improved liver function, improved mitochondrial function, and lowered liver fat in obese mice using siRNA suppression of one transcription factor candidate. In skin, they have found a way to improve collagen production and restore more youthful gene expression across thousands of genes via siRNA suppression of a single transcription factor.

Joanna Bensz of Longevity Center Europe, Petr Sramek of the Healthy Longevity Clinic and LongevityTech.fund and Elisabeth Roider of the AYUN Health & Longevity Center presented on their respective longevity clinics. The most interesting of these projects, the one that isn't just a provision of boutique medical services, is the Healthy Longevity Clinic. This group are trying something new, a fusion of investing in companies, giving those companies a path to clinical trials outside the US, and clinics to offer services that will eventually include new therapies created by portfolio companies. They have established a number of clinics, in Praque and Florida, with a subsidiary in the Bahamas set up to conduct clinical trials there. Medical development is slow, and so it will take some time to see whether this proves to be a viable and helpful approach in practice: it would require a sizable fraction of companies to step away from the present well-beaten and thus safe path with regulators.

A panel of investors discussed the industry: Jens Eckstein of the Hevolution Foundation; Jan Adams of Apollo Health Ventures; Sergey Jakimov of LongeVC; Marc P. Bernegger of the company builder maximon; Alex Colville of age1; Patrick Burgermeister of Kizoo Technology Capital. The group offered a considerable diversity of opinions on what is important in the field. A lesson to take away is that the natural size of a faction of investors is one investor; they are all quite different.

Jürgen Reeß of Mogling Bio talked on the development of new, recently patented CDC42 inhibitors based on CASIN, a molecule that has been used to demonstrate reversal of stem cell aging and improved immune function in mice. The team sees CASIN as having too low a bioavailability to be a viable drug, too much of it is needed per dose. The new CDC42 inhibitors have similar effects, but with lower doses. The team has shown that CDC42 inhibition with CASIN can slow tumor growth in mouse models to the same degree as a PD1 checkpoint inhibitor, and the data suggests that this is an immunomodulatory effect achieved via altered regulatory T cell behavior. If combining CASIN and a PD1 inhibitor, tumors shrink and vanish in a mouse model. Thus cancer will be the company's first indication. The company is working towards IND-enabling studies in 2025, and are meanwhile running a number of collaboration programs to broaden the set of possible indications with proof of concept data.

Aaron Cravens of Revel Pharmaceuticals put advanced glycation end-products (AGEs) such as carboxymethylysine (CML) and glucosepane cross-links into the contxt of a damage-based view of aging. Aging is accumulated molecule damage, and repairing that damage is rejuvenation. AGEs are known to contribute to many aspects of aging, and Revel develops a platform to discover enzymes that can break down specific AGEs. Going into detail on the present programs, CML exists in a free circulating form and a bound form in the extracellular matrix, both of which provoke inflammatory reactions. In the last few years the company has developed enzymes that are much more effective than the initial 2019 candidates when it comes to clearing free CML. Cravens sees success with free CML as a stepping stone to the harder task of success with bound CML in the extracellular matrix. The company has considered which AGEs offer the fastest to get to the clinic; while the Revel started with a focus on glucosepane, it is a harder prospect. CML is less challenging, and this is now an initial focus. In principle, an early success with CML will build momentum for further investment for work on the more challenging AGEs.

Aaron Friedman of Reservoir Neuroscience started his presentation by noting that aging is complex and brain aging is particularly complex. Yet the research and development mainstream has ignored this complexity in favor of a relentless focus on just a few things, as in the case of amyloid and Alzheimer's disease. He suggested that the evidence suggests that Alzheimer's is largely a lifestyle disease, and thus interventions derived from lifestyle factors can postpone or slow Alzheimer's. In particlar, people who exercise have a 45% reduction in Alzheimer's risk, somewhat better than the effects of current anti-amyloid antibody treatments. Additionally, imaging data shows that loss of vascular health is the largest factor contributing to Alzheimer's; vascular aging appears before the increase in amyloid burden, and is a larger and easier signal to detect. Thus the industry should be focused on treating poor vascular health. The company intends to develop drugs that target this vascular dysfunction, and has built a drug discovery platform using organ-on-a-chip screening in blood vessel organoids. The team is in the early stages of lead optimization for one candidate inhibitor of the prostaglandin E2 receptor 2 (EP2), which is upregulated in aged and damaged blood vessels. This is a master regulator of inflammatory responses, and so suppressing it effectively should reduce chronic inflammation. Friedman notes that the beneficial effect of long-term NSAID use (specifically ibuprofen in the study referenced) on Alzheimer's risk may be mediated by indirect inhibition of EP2.

Chris Bradley of MatterBio works on advanced sequencing. There are many genomes in the body, as every cell is a little different, genetically and epigenetically. Unrepaired DNA damage accumulates constantly. Most of this is neither good nor bad, it is just noise that increases with age. Researchers think that the greater the mutational burden, the bigger the impact on aging. Speed of mutation accumulation is correlated with species life span, and regardless of species life span every cell has 1000 to 5000 mutations in old age. One consequence of mutational damage is cancer. The MatterBio plan is to (a) read the DNA, (b) identify mutations, then (c) either reverse mutations directly or replace bad cells. The team has developed a novel approach to next generation sequencing in order to see single cell mutations; this is a commercial technology being sold now. They are designing DNA editing machinery that can fix a mutation, and this is still a very early stage project. Lastly, the team has engineered bacteria and markers that allow the destruction of mutated cells, and this is heading into to the clinic as a treatment for cancer. They have shown both pancreatic cancer and ovarian cancer reduction in metastatic preclinical mouse studies.

Nikolina Lauc of GlycanAge discussed the company's aging clock based on measures of changing glycan levels. Glycosylation is a posttranslational modification that produces glycans. Immunoglobulin G glycans are among those that change significantly with age. Few labs work with glycans, but this group has at this point generated more than 160,000 glycomes from human samples. Interestingly, glycan changes can indicate early signs of later chronic disease up to a decade in advance for many conditions, including hypertension and autoimmune conditions. The GlycanAge clock compares well with the best epigenetic clocks in predication power for mortality, but the accelerations are different for age measured by glycans versus age measured by epigenetic changes. A few interesting differences are noted: GlycanAge shows that metformin has no effect on aging, while professional athletes have poor GlycanAge measures in comparison to those who undertake only moderate exercise.

Sophie Chabloz of AVEA presented on their development of a collegen precursor for skin aging. This has all of the slick marketing appearance of a very standard skin anti-aging company at the less reputable end of the industry, but they do at least have an interesting scientific program under all of that cover. After noting the existing industry strategies for adding collagen to skin and diet, and the drawbacks, Chabloz discussed the company's development program. Work started in in C. elegans before moving to cell models of skin. The company has tested their collagen precursor in combination with alpha-ketoglutarate in C. elegans, showing a modest extension of life span.

The last panel of the conference was led by Nina Ruge, a science journalist and author. I was on that panel with (in no particular order) Eric Verdin of the Buck Institute, Brian Kennedy of the National University of Singapore, and Phil Newman of Longevity.Technology. We talked about longevity clinics and what they can offer to the industry; to my mind the most interesting thing that clinics can do for us all is to free up their data and help organize clinical trials. Ruge asked us our opinions on the most interesting part of the industry, and we all had radically different answers on that topic, just as we differed on where we would invest funds for the best outcome, given the power to do so. It is characteristic of the aging and longevity field that almost everyone is in their own group of one when it comes to what the next steps should be.

It remains to be seen as to when the next conference in this series will be held - probably in 2026. I recommend attending. This remains an event at the core of the longevity industry. Many of the most interesting presenting founders and attendees have been involved in some way since the start of this great endeavor. Many of the presentations offered a strong identification with the Strategies for Engineered Negligible Senescence (SENS) viewpoint of aging as accumulated cell and tissue damage, and thus damage repair is the way to treat aging. Consider adding the next Rejuvenation Startup Summit to your calendar when it is announced.

This article serves as a high level overview of the present state of bioprinting of three-dimensional sections of living tissue. The field has stalled at the hurdle of vascularization for more than a decade now; it has proven to be challenging to make the leap from tiny functional organoid tissues to something larger. It isn't just the matter of building in capillary and larger blood vessel networks, however. Organoids are largely only approximations to real structured tissue, good enough to be functional in many respects, but not the final goal. In order to build sizable sections of organs with bioprinters, a great deal of work remains in order to be able to create structures that more closely, usefully match those of the body, even given that many of the pieces of that puzzle already exist.

Bioprinting is still in its infancy and bogged down by various challenges related to different aspects of the bioprinting process. The primary challenge is developing an ideal bioink that is apt for the tissue of interest to be printed. Maintaining adequate cell density and viability following extrusion, obtaining air bubble-free extruded filaments, achieving adequate mechanical strength post-printing, achieving vascularization and innervation of the tissue constructs, and printing complete organs are the major challenges slowing down the bioprinting process. Research is being conducted to overcome these hurdles and provide personalized treatment solutions for regenerating the lost tissues.

Gaining in-depth knowledge regarding the organogenesis process, the tissue structure, composition, and behavior of each tissue, ways to maintain cell viability, and tissue integration with the native tissue post-printing would enable us to overcome these challenges one step at a time. 4D bioprinting has recently emerged, where time is considered the fourth dimension of printing. The printed scaffold modulates their organization and behavior according to time-dependent external stimuli. The future is moving toward five-dimensional (5D) printing, which will occur in multiple rotational axes.

Advanced bioprinting technologies would greatly reduce the demand for organ donations. Government organizations and regulators are still working toward achieving a balance between the need for organ donation through early prevention and management of diseases and improved procurement of organs. Application of bioprinting technologies would greatly reduce the burden on the governments and buy us time till every nation becomes self-sufficient to manage the need for organ donations. Though the setting up of a bioprinting center of excellence is a costly affair, in terms of obtaining the infrastructural and biologics support, the number of lives saved through its applications in regenerative and rehabilitative medicine is of paramount significance.

Link: https://doi.org/10.7759/cureus.58029

Unresolved, constant inflammatory signaling is a feature of aging, the consequence of accumulated senescent cells and other maladaptive reactions to various forms of molecular damage and cellular dysfunction. This inflammation drives the onset and progression of many age-related conditions, particularly neurodegenerative diseases. The immune system is deeply integrated with the structure, function, and maintenance of neural tissue, and the age-related shift into a constant inflammatory state is increasingly disruptive to normal brain function.

Neuroinflammation refers to a highly complicated reaction of the central nervous system (CNS) to certain stimuli such as trauma, infection, and neurodegenerative diseases. This is a cellular immune response whereby glial cells are activated, inflammatory mediators are liberated and reactive oxygen species and reactive nitrogen species are synthesized. Neuroinflammation is a key process that helps protect the brain from pathogens, but inappropriate, or protracted inflammation yields pathological states such as Parkinson's disease, Alzheimer's, Multiple Sclerosis, and other neurodegenerative disorders that showcase various pathways of neurodegeneration distributed in various parts of the CNS.

This review reveals the major neuroinflammatory signaling pathways associated with neurodegeneration. Additionally, it explores promising therapeutic avenues, such as stem cell therapy, genetic intervention, and nanoparticles, aiming to regulate neuroinflammation and potentially impede or decelerate the advancement of these conditions. A comprehensive understanding of the intricate connection between neuroinflammation and these diseases is pivotal for the development of future treatment strategies that can alleviate the burden imposed by these devastating disorders.

Link: https://doi.org/10.3389/fnagi.2024.1347987

Intravenous, high-dose AAV gene therapy to upregulate VEGF has been shown to extend life in mice. This is perhaps a demonstration of the importance of loss of capillary density in tissue as a result of age-related disruption to angiogenesis, the multi-step process by which new blood vessels branch from existing vessels. Upregulation of VEGF is one of the possible approaches to restoring maintenance of capillary networks via improved angiogenesis, as VEGF is one of the important signal molecules involved in this process.

A similar AAV gene therapy is being assessed in clinical trials for the treatment of coronary artery disease, the progressive blockage of blood flow to heart tissue by atherosclerotic plaque. Preliminary results were recently announced for the EXACT phase II trial. The idea here is to incrementally improve blood flow by encouraging the body to produce alternative paths. The therapy is locally delivered to heart tissue, and thus uses a much lower dose than would be needed for intravenous injection for delivery to much of the body. Nonetheless, the principle is much the same. One could argue that all older individuals would likely benefit from some form of VEGF upregulation delivered to much of the body.

Gene therapy treatment increasing body's signal for new blood vessel growth shows promise

Final 12-month data from the EXACT trial demonstrates safety and efficacy results for a vascular endothelial growth factor (VEGF) gene therapy treatment for patients who have advanced coronary artery disease (CAD). CAD, also known as coronary heart disease or ischemic heart disease, affects about 20.5 million U.S. adults - making it the most common type of heart disease in the United States. Often, the first sign of CAD is a heart attack, triggered by a rupture of plaque accumulated in the arteries supplying blood to the heart. Over time, plaque narrows these arteries, blood flow diminishes, leading to angina - a condition characterized by chest pain due to insufficient oxygen-rich blood supply to the heart muscle. In patients with the most severe form, angina can be disabling, and additional medications, procedures or surgery may not be effective. There is a need for therapies for such a serious condition.

The EXACT trial assesses the safety and preliminary efficacy of the gene therapy XC001 in patients with "no option" refractory angina (NORA). The gene vector is designed to more effectively and safely increase the body's own signal for new blood vessel growth. Effectiveness was measured primarily by exercise capacity, degree of impairment of blood flow to the heart, and angina frequency and severity. Among the 32 patients with NORA, the gene therapy XC001 appeared safe with no serious adverse effects due to the drug. Surgical delivery was generally well-tolerated. Early benefits of XC001 are promising in relation to improvements in exercise duration, decreased symptoms, and improved blood flow in patients' hearts.

Total exercise duration increased from a mean of 359.9 seconds at baseline to 448.2 at three months, 449.2 at six months, and 477.6 at 12 months. Total myocardial perfusion deficit on positron emission tomography imaging decreased by 10.2% at three months, 14.3% at six months, and 10.2% at 12 months - demonstrating a reduction in impaired blood flood. The time to onset of ST depression during exercise tolerance testing increased by 105.2 at three months, 113.6 at six months, and 103.1 seconds at 12 months. Angina frequency decreased by -7.7 at three months, -6.6 at six months, and -8.8 episodes at 12 months. Angina class improved in 81% of participants at six months.

Being more physically fit at a given age reliably correlates with a lower future mortality risk. While human epidemiological data can only provide correlations, animal studies can and do provide evidence for physical fitness and exercise to modestly slow aspects of aging and reduce age-related mortality. In general, maintaining physical fitness into later life appears to be a good idea, based on the evidence.

Cardiorespiratory fitness (CRF) is a physical trait that reflects the integrated function of numerous bodily systems to deliver and use oxygen to support muscle activity during sustained, rhythmic, whole-body, large muscle physical activity. CRF can be objectively measured using direct (usually by maximal exercise testing with concomitant gas exchange analysis) or indirect (exercise predicted equations) methods with a variety of maximal or submaximal protocols.

Low CRF is considered a strong chronic disease risk factor that is not routinely assessed in clinical practice. Evidence suggests that the inclusion of CRF as a clinical vital sign would enhance patient management by improving the classification of those at high risk of adverse outcomes. The evidence supporting CRF as an important risk factor has accumulated since the 1980s through large cohort studies that investigated the prospective risk of all-cause mortality and cardiovascular events associated with CRF. Research has linked CRF to the incidence of some cancers, type 2 diabetes, metabolic syndrome, stroke, and depression. Higher CRF may even improve the prognosis in those with chronic conditions such as cancer, peripheral artery disease, heart failure, and chronic kidney disease.

The objective of this study was to conduct an overview of systematic reviews with meta-analyses from cohort studies that investigated relationships between CRF and prospective health-related outcomes among adults. We identified 26 systematic reviews with meta-analysis representing over 20.9 million observations from 199 unique cohort studies. CRF had the largest risk reduction for all-cause mortality when comparing high versus low CRF (hazard ratio, HR=0.47). A dose-response relationship for every 1-metabolic equivalent of task (MET) higher level of CRF was associated with a 11%-17% reduction in all-cause mortality (HR=0.89). The certainty of the evidence across all studies ranged from very low-to-moderate according to Grading of Recommendations, Assessment, Development and Evaluations.

Link: https://doi.org/10.1136/bjsports-2023-107849

Researchers here present an interesting view of age-related circadian dysfunction, focusing on mismatched regulation between the central circadian clock and somewhat independent peripheral clocks. The regulation of circadian rhythm in tissues results from the activities of these complex systems of multiple parts - and like all complex systems they begin to exhibit dysfunction with advancing age. The novel aspect of this research is the concept of multiple mismatched circadian regulators as a cause of further dysfunction in tissues.

Discovered in the 1970s, circadian clocks are essential for the regulation of biological time in most cells in the human body. These internal mechanisms adjust biological processes to a 24-hour cycle, allowing the synchronisation of cellular functions with daily variations in the environment. Circadian rhythms, which are coordinated by a central clock in the brain that communicates with clocks in different peripheral tissues, influence many functions, from our sleep patterns to our ability to metabolise food.

A study on the communication between the brain and muscle confirmed that the coordination between the central and peripheral clocks is crucial for maintaining daily muscle function and preventing the premature ageing of this tissue. Restoration of the circadian rhythm reduces the loss of muscle mass and strength, thereby improving deteriorated motor functions in experimental mouse models.

The results of the study have also demonstrated that time-restricted feeding (TRF), which involves eating only in the active phase of the day, can partially replace the central clock and enhance the autonomy of the muscle clock. More relevant still is that this restoration of the circadian rhythm through TRF can mitigate muscle loss, the deterioration of metabolic and motor functions, and the loss of muscle strength in aged mice.

"It is fascinating to see how synchronisation between the brain and peripheral circadian clocks plays a critical role in skin and muscle health, while peripheral clocks alone are autonomous in carrying out the most basic tissue functions. Our study reveals that minimal interaction between only two tissue clocks (one central and the other peripheral) is needed to maintain optimal functioning of tissues like muscles and skin and to avoid their deterioration and ageing. Now, the next step is to identify the signalling factors involved in this interaction, with potential therapeutic applications in mind."

Link: https://www.irbbarcelona.org/en/news/scientific/synchronisation-between-central-circadian-clock-and-circadian-clocks-tissues

Transposable elements in the genome are the remnants of ancient viral infections, capable of hijacking cellular machinery to copy themselves haphazardly across the genome, causing damage to existing genes. They can further provoke inflammation and cell dysfunction via the presence of the viral machinery that these transposable element sequences code for; innate immune mechanisms in cells have evolved to detect such apparently foreign molecules. Transposable elements are effectively suppressed in youth, but with age this suppression breaks down. It has been suggested that activation of transposable elements is an important contributing factor in age-related conditions, particularly in neurodegenerative conditions such as Alzheimer's disease.

As today's open access paper notes, one way to obtain evidence for this proposition is to look at the long term outcome of antiretroviral drug use. These drugs are used to treat patients and animals infected with retroviruses, most prominently HIV, but also a number of others. In additional to suppressing infectious retroviruses, antiretroviral drugs also suppress the activity of transposable elements. After thirty years of a strong focus on treating AIDS, there is now a sizable patient population in later life, at the point at which transposable elements would be expected to become active.

Nucleoside Reverse Transcriptase Inhibitor Exposure Is Associated with Lower Alzheimer's Disease Risk: A Retrospective Cohort Proof-of-Concept Study

Alzheimer's disease (AD) is the most common form of dementia, affecting an estimated 6.5 million Americans including more than 10% of Americans over 65 years of age. There are no therapies that demonstrably stop the disease despite hundreds of clinical trials. The recent identification of reverse transcriptase (RT)-mediated somatic gene recombination (SGR) in the human brain, which becomes dysregulated in sporadic AD, implicates FDA-approved reverse transcriptase inhibitors (RTIs) as potential therapeutics for AD.

Multiple FDA-approved RTIs, the first of which was approved in 1987, are currently used to treat human immunodeficiency virus (HIV) and hepatitis B. RTIs can be orthosteric (bind to the active site) nucleoside RTIs (NRTIs) or allosteric non-NRTIs (NNRTIs), and together with integrase inhibitors and protease inhibitors (PIs), represent the components of combined antiretroviral therapy (cART). Because of effective cART, tens of thousands of people with HIV have lived to older ages but are now at risk for AD, providing an opportunity to retrospectively examine the incidence of AD by assessing medical claims databases.

This retrospective, proof-of-concept study evaluated the incidence of AD in people with HIV with or without exposure to NRTIs using de-identified medical claims data. Eligible participants were aged ≥60 years, without pre-existing AD diagnoses, and pursued medical services in the United States from October 2015 to September 2016. Cohorts 1 (N = 46,218) and 2 (N = 32,923) had HIV. Cohort 1 had prescription claims for at least one NRTI within the exposure period; Cohort 2 did not. Cohort 3 (N = 150,819) had medical claims for the common cold without evidence of HIV or antiretroviral therapy.

We identified a statistically significant positive association between NRTI exposure and decreased risk for sporadic AD in patients with HIV and ≥60 years of age. Age-adjusted and sex-adjusted hazard ratio (HR) showed a significantly decreased risk for AD in Cohort 1 compared with Cohorts 2 (HR 0.88) and 3 (HR 0.84). Post-marketing surveillance of NRTIs has shown acceptable safety data sufficient to allow NRTIs to be prescribed, as a class, continuously since 1987, and tens of thousands of patients ≥60 years of age are currently taking these medications, providing support that these agents will be well tolerated in aged patients. The data presented here support controlled clinical trials using NRTIs on patients with mild cognitive impairment (MCI), pre-symptomatic familial AD, Down syndrome, and sporadic AD, along with asymptomatic APOE4 carriers.

Researchers here report on the importance of molecular chaperones, and cyclophilin A in particular, to the function of hematopoietic stem cells. These cells generate red blood cells and immune cells, and thus age-related changes in hematopoietic function have important consequences for health. The immune system runs awry with age, and altered hematopoiesis is one of the contributing factors. If, as researchers here suggest, upregulation of cyclophilin A can improve hematopoietic stem cell function, then using this as a basis for therapy may produce health benefits in older individuals.

Hematopoietic stem cells (HSCs) are remarkably long-lived. HSCs typically remain dormant within the bone marrow, yet they possess the ability to activate and replenish blood cells continuously, maintaining a relatively youthful profile throughout the life of an organism. A driving force of cellular aging is the accumulation of proteins that have reached the end of their useful life. With age, proteins tend to misfold, aggregate, and accumulate inside the cell, which leads to toxic stress that can disrupt cell function. Cells that frequently engage in cell division, like progenitor cells, can dispose of protein aggregates through dilution. On the other hand, long-lived HSCs, which do not divide often, face the problem of the accumulation of misfolded proteins and subsequent toxic stress. Nevertheless, HSCs remain impervious to aging. How do they do it?

Previous studies have shown that mammalian cells express hundreds of molecular chaperones, proteins that preserve or change the three-dimensional conformation of existing proteins. Cyclophilins, one of the most abundant chaperones, have been implicated in the aging process. However, how they affect cellular proteins has not previously been studied. Working with mice, the researchers first characterized the protein content of HSCs and discovered that cyclophilin A is a prevalent chaperone. Further experiments showed that the expression of cyclophilin A was significantly decreased in aged HSCs, and genetically eliminating cyclophilin A accelerated natural aging in the stem cell compartment. In contrast, reintroducing cyclophilin A into aged HSCs enhanced their function. Together, these findings support cyclophilin A as a key factor in the longevity of HSCs.

Link: https://blogs.bcm.edu/2024/04/30/from-the-labs-uncovering-the-secret-of-long-lived-stem-cells/

Researchers here report on their efforts to interfere in a mechanism causing loss of the myelin that sheathes nerves. The driving goal is to produce a therapy for the severe demyelinating disease of multiple sclerosis rather than to reverse the lesser degree of myelin loss that occurs for everyone in later life. The animal evidence suggests that it may also prove to be useful in the general population of older individuals, however, which is promising. Loss of myelin is thought to contribute to some fraction of age-related loss of cognitive function, and so reversing that loss is an important goal.

Oligodendrocytes (OLs) are responsible for producing myelin sheaths that wrap around cable-like parts of nerve cells called axons, much like the plastic insulation around a wire. When the protective myelin gets damaged, be it by disease or the wear and tear of age, nerve signaling gets disrupted. Depending on where the damaged nerves lead, the disruptions can affect movement, vision, thinking and so on.

Analysis of stored autopsy tissues revealed that OLs within multiple sclerosis (MS) lesions lacked an activating histone mark called H3K27ac, while expressing high levels of two other repressive histone marks H3K27me3 and H3K9me3 associated with silencing gene activity. The research team scoured a library of hundreds of small molecules known to target enzymes that could modify gene expression and influence the silenced OLs. The team determined that the compound ESI1 (epigenetic-silencing-inhibitor-1) was nearly five times more powerful than any other compounds they considered.

The compound tripled the levels of the desired H3K27ac histone mark in OLs while sharply reducing levels of the two repressive histone marks. In both aging mice and mice mimicking MS, the ESI1 treatment prompted myelin sheath production and improved lost neurological function. Testing included tracking gene activation, measuring the microscopic new myelin sheaths surrounding axons, and observing that treated mice were quicker at navigating a water maze.

Link: https://www.eurekalert.org/news-releases/1043326

One of the important points made by advocates for the treatment of aging is that one cannot distinguish between aging and age-related disease. They are one and the same. There is no magical state of "healthy aging" in which one doesn't suffer eventual disease. A decline of function in aging that does not rise to the level required to call it a disease is the subclinical stage of that disease; all the same damage has taken place under the hood, just less of it. Conversely, an age-related disease is just another facet of aging, a collection of damage and consequences of damage that becomes sizable enough to reach the definition of disease. Whether or not any specific age-related dysfunction is called a disease is just a matter of whether the degree of dysfunction is on one side or another of an arbitrary line drawn in the sand.

The authors of today's open access paper take this point and then build on it to suggest that the most robust age-slowing approaches demonstrated in animal models should be tested more rigorously in patients with common, hard-to-treat conditions such as Alzheimer's disease. The approaches with the best data include calorie restriction and all of the calorie restriction mimetic interventions that seek to replicate some part of the sweeping cellular reaction to a reduced intake of calories. Interestingly, this hasn't been well tested in Alzheimer's patients. Perhaps it should be, even given that the research community expects effects on aging to be lower in long-lived species than in short-lived species. While calorie restriction extends mouse life span by as much as 40%, it certainly doesn't do that well in humans. The actual number has yet to be established, but it would be surprising to see that the effect of long-term calorie restriction or equivalent intermittent fasting in humans is larger than a few years of additional life span.

Aging as a target for the prevention and treatment of Alzheimer's disease

Alzheimer's disease (AD), the most common etiology of dementia in older adults, is projected to double in prevalence over the next few decades. Current treatments for AD manage symptoms or slow progressive decline, but are accompanied by significant inconvenience, risk, and cost. Thus, a better understanding of the risk factors and pathophysiology of AD is needed to develop novel prevention and treatment strategies.

While a mayfly has a lifespan of one day, an elephant's lifespan may exceed 100 years. Clearly, lifespan and aging are biological traits regulated by genetics and molecular signaling pathways - that may be exploited as a therapeutic target. Aging, however, is not recognized as a disease by the U.S. Food and Drug Administration. Thus, there are no FDA-approved treatments specifically for aging. Aging, however, is the most important risk factor for multiple diseases, including dementia and AD. As molecular mechanisms regulating aging are coming to light and signaling pathways uncovered, novel therapeutic targets present an alternative approach: instead of targeting one disease at a time - leading to the inconvenience, cost, and risk of polypharmacy - targeting aging directly may prevent or slow multiple age-related diseases. Calorie restriction (CR) may be a promising preventive or therapeutic option for individuals at risk for AD or already within the AD spectrum. However, current data are limited and human studies are scarce. Additional preclinical and human studies are now warranted to discover the pathways regulated by CR and to identify pharmacophores that mimic the beneficial effects of CR.

Hypotheses linking CR and weight loss to alterations in biomarkers of aging and AD may suggest novel treatment targets and strategies-and not just for AD. Newly discovered therapies may be safe and effective for prevention and/or as an adjunct to FDA-approved treatments for individuals in the AD spectrum. Prevention and treatment strategies targeting aging may be safer and more effective than the currently available treatments targeting more downstream pathways. While several studies are in progress (listed above), more are needed. In the meantime, AD trials should consider including biomarkers of aging and aging studies should include AD biomarkers.

Microglia are innate immune cells resident in the brain, analogous to macrophages elsewhere in the body, but with the addition of a portfolio of duties relating to the maintenance of neural function. With age ever more microglia become overly inflammatory, contributing to disruptive, unresolved inflammatory signaling, and abandoning their tissue maintenance tasks. This is thought to be an important contribution to neurodegenerative conditions and loss of cognitive function more generally. Researchers here report that the adoption of an inflammatory state is a progressive dysfunction for individual microglia, not just a matter of how many microglia have switched over to undertake inflammatory behavior.

Numerous studies have indicated that aged microglia are inflamed, have reduced phagocytic capacity, and have decreased motility. Microglia exhibit several hallmarks of aging that potentially contribute to their age-related dysfunction, such as shortened telomeres, altered intercellular communication, molecular alterations, and a loss of proteostasis. Furthermore, many recent studies have started to reveal the molecular changes that define microglial aging. Single cell RNA-Seq (scRNA-Seq) analyses indicate that microglia isolated from the entire brain lose homeostasis and activate inflammatory transcriptional profiles with age. Data rich studies have also revealed partial overlaps between aging microglia and those from disease models, including Alzheimer's disease.

Studies using aged plasma administration and heterochronic blood exchange demonstrate that microglia aging is in part driven by the aged systemic environment. However, the genesis of age-related dystrophic microglial phenotypes has not been extensively investigated. So, we set out to characterize the progression of age-related hippocampal microglial dysfunction, aiming to uncover intermediate states that could be intrinsic to the aging process. To do so, we undertook complementary cellular and molecular analyses of microglia across the adult lifespan and in heterochronic parabiosis - an experimental model of aging in which the circulatory systems of young adult and aged animals are joined.

In this study, we report that microglia in the adult mouse hippocampus, a brain region responsible for learning and memory and susceptible to age-related cognitive decline, advance through intermediate states that drive inflammatory activation during aging. We utilize scRNA-Seq across the adult lifespan to identify intermediate transcriptional states of microglial aging that emerge following exposure to an aged systemic environment. Functionally, we tested the role of these intermediate states using in vitro microglia approaches and an in vivo temporally controlled adult microglia-specific Tgfb1 conditional genetic knockout mouse model to demonstrate that intermediates represent checkpoints in the progression of microglia from homeostasis to inflammatory activation, with functional implications for hippocampal-dependent cognitive decline.

Link: https://doi.org/10.1101/2024.04.09.588665

As an atherosclerotic plaque grows into a hotspot of inflammation and cell dysfunction in a blood vessel wall, it starts to draw in the nearby vascular smooth muscle cells that wrap the outside of the vessel. As researchers here note, these smooth muscle cells are altered by the plaque environment in ways that are analogous to the behavior of cancerous cells. They change, multiply, and accelerate the growth of a fatty plaque that will eventually rupture to cause a stroke or heart attack by blocking a downstream blood vessel.

Atherosclerosis is the major cause of heart attacks and stroke around the world and occurs when fat deposits build up inside the arteries. Atherosclerosis can be reduced with a healthy diet or drugs called statins that slow or reverse the buildup of deposits. Previous studies had found that smooth muscle cells metamorphose into different types of cells inside these atherosclerotic plaques and multiply to make up most cells within the plaques. Yet until now, few studies had examined the cancer-like properties of the cells and if these changes contributed to atherosclerosis. To learn more, researchers closely tracked the development of transformed smooth muscle cells in mice with atherosclerosis and sampled plaques of people with atherosclerosis. They found striking parallels between changes in the smooth muscle cells and tumor cells, including hyperproliferation, resistance to cell death, and invasiveness.

DNA damage, another hallmark of cancer, accumulated in the mouse and human smooth muscle cells and appears to accelerate atherosclerosis, the researchers found. The researchers could further accelerate atherosclerosis in mice by introducing a genetic mutation that increased DNA damage within the smooth muscle cells. Vascular tissue from healthy mice and people had no signs of smooth muscle cells with the DNA damage found in atherosclerotic plaques. "The cells stay inside existing plaques, which makes us think that they behave mostly like benign tumor cells, but more work needs to be done in humans and animal models to address this hypothesis." If atherosclerosis is driven by cancer-like cells, anticancer therapies may be a potential new way to treat or prevent the disease.

Link: https://www.eurekalert.org/news-releases/1043152

Chronic, unresolved inflammation is a feature of aging. When the immune system is constantly active in this way, the consequent altered cell behavior throughout the body becomes disruptive to tissue and organ function, harmful to the individual. Chronic inflammation accelerates the onset and progression of all of the common fatal age-related conditions. This unwanted inflammatory signaling arises from many different roots, including the growing presence of senescent cells, but also the interaction of innate immune sensors with other forms of age-related dysfunction. For example, damage-associated molecular patterns such as mislocalized fragments of mitochondrial DNA leaking from dysfunctional mitochondria into the cell cytosol can trigger cGAS/STING signaling. This mechanism evolved to detect the presence of bacterial DNA, and unfortunately runs awry with age.

The challenge inherent in dampening age-related chronic inflammation is that, so far, it appears to use exactly the same pathways that are involved in the normal, necessary, short-term inflammatory response to injury, pathogens, potentially cancerous cells, and so forth. All of the approaches developed to date to suppress the overactivity of an immune system also suppress necessary functions, and that produces unpleasant long-term consequences. This is well established via the use of immunosuppressant drugs in patients with autoimmune disease. There was some hope that targeting aspects of cGAS/STING function would prove to be a better option, but as researchers note in today's open access paper, an operating cGAS/STING pathway appears to be necessary for long-term health.

STING promotes homeostatic maintenance of tissues and confers longevity with aging

Local immune processes within aging tissues are a significant driver of aging associated dysfunction, but tissue-autonomous pathways and cell types that modulate these responses remain poorly characterized. The cytosolic DNA sensing pathway, acting through cyclic GMP-AMP synthase (cGAS) and Stimulator of Interferon Genes (STING), is broadly expressed in tissues, and is poised to regulate local type I interferon (IFN-I)-dependent and independent inflammatory processes within tissues. Recent studies suggest that the cGAS/STING pathway may drive pathology in various in vitro and in vivo models of accelerated aging.

To date, however, the role of the cGAS/STING pathway in physiological aging processes, in the absence of genetic drivers, has remained unexplored. This remains a relevant gap, as STING is ubiquitously expressed, implicated in multitudinous disorders, and loss of function polymorphisms of STING are highly prevalent in the human population (an incidence of more than 50%). Here we reveal that, during physiological aging, STING-deficiency leads to a significant shortening of murine lifespan, increased pro-inflammatory serum cytokines and tissue infiltrates, as well as salient changes in histological composition and organization.

We note that aging hearts, livers, and kidneys express distinct subsets of inflammatory, interferon-stimulated gene (ISG), and senescence genes, collectively comprising an immune fingerprint for each tissue. These distinctive patterns are largely imprinted by tissue-specific stromal and myeloid cells. Using cellular interaction network analyses, immunofluorescence, and histopathology data, we show that these immune fingerprints shape the tissue architecture and the landscape of cell-cell interactions in aging tissues. These age-associated immune fingerprints are grossly dysregulated with STING-deficiency, with key genes that define aging STING-sufficient tissues greatly diminished in the absence of STING. This altered homeostasis in aging STING-deficient tissues is associated with a cross-tissue loss of homeostatic tissue-resident macrophage (TRM) populations in these tissues. Ex vivo analyses reveal that basal STING- signaling limits the susceptibility of TRMs to death-inducing stimuli and determines their in situ localization in tissue niches, thereby promoting tissue homeostasis.

Collectively, these data upend the paradigm that cGAS/STING signaling is primarily pathological in aging and instead indicate that basal STING signaling sustains tissue function and supports organismal longevity. Critically, our study urges caution in the indiscriminate targeting of these pathways, which may result in unpredictable and pathological consequences for health during aging.

Dasatinib and quercetin used in combination clears a fraction of lingering senescent cells in aging mice, producing a sizable degree of rejuvenation, and reversal of aspects of many different age-related conditions. In humans, clinical trials are underway at a sedate pace. Dasatinib is a chemotherapeutic small molecule, while quercetin is a plant extract flavonol. Here, researchers discuss their search for plant extract alternatives that mimic the effects of dasatinib, in the hopes of producing a less regulated alternative to the use of a small molecule drug, thereby lowering the barrier to entry somewhat. Size of effect is important, however, and it is yet to be demonstrated that any of their proposed alternatives can replicate the degree to which dasatinib impacts senescent cells.

The major risk factor for chronic disease is chronological age, and age-related chronic diseases account for the majority of deaths worldwide. Targeting senescent cells that accumulate in disease-related tissues presents a strategy to reduce disease burden and to increase healthspan. The senolytic combination of the tyrosine-kinase inhibitor dasatinib and the flavonol quercetin is frequently used in clinical trials aiming to eliminate senescent cells.

Here, our goal was to computationally identify natural senotherapeutic repurposing candidates that may substitute dasatinib based on their similarity in gene expression effects. The natural senolytic piperlongumine (a compound found in long pepper), and the natural senomorphics parthenolide, phloretin, and curcumin (found in various edible plants) were identified as potential substitutes of dasatinib. The gene expression changes underlying the repositioning highlight apoptosis-related genes and pathways. The four compounds, and in particular the top-runner piperlongumine, may be combined with quercetin to obtain natural formulas emulating the dasatinib + quercetin formula.

Link: https://doi.org/10.1038/s41598-024-55870-4

Researchers have found evidence of cellular senescence in neurons in the aging brain. How do neurons become senescent, given that they are post-mitotic, non-dividing cells? Cellular senescence is state primarily associated with excessive cell division, in which a cell reaches the Hayflick limit, though cells can become senescent in response to damage or toxicity. Here, researchers provide evidence to show that in the aging brain, and particularly in the context of neurodegenerative conditions, ever more neurons re-enter the cell cycle, which inevitably leads to senescence. This is an interesting line of research, adding another argument for the use of senolytic drugs to treat neurodegenerative conditions.

Increasing evidence indicates that terminally differentiated neurons in the brain may recommit to a cell cycle-like process during neuronal aging and under disease conditions. Because of the rare existence and random localization of these cells in the brain, their molecular profiles and disease-specific heterogeneities remain unclear. Through a bioinformatics approach that allows integrated analyses of multiple single-nucleus transcriptome datasets from human brain samples, these rare cell populations were identified and selected for further characterization.

Our analyses indicated that these cell cycle-related events occur predominantly in excitatory neurons and that cellular senescence is likely their immediate terminal fate. Quantitatively, the number of cell cycle re-engaging and senescent neurons decreased during the normal brain aging process, but in the context of late-onset Alzheimer's disease (AD), these cells accumulate instead. Transcriptomic profiling of these cells suggested that disease-specific differences were predominantly tied to the early stage of the senescence process, revealing that these cells presented more proinflammatory, metabolically deregulated, and pathology-associated signatures in disease-affected brains. Similarly, these general features of cell cycle re-engaging neurons were also observed in a subpopulation of dopaminergic neurons identified in the Parkinson's disease (PD)-Lewy body dementia (LBD) model.

An extended analysis conducted in a mouse model of brain aging further validated the ability of this bioinformatics approach to determine the robust relationship between the cell cycle and senescence processes in neurons in this cross-species setting.

Link: https://doi.org/10.1371/journal.pbio.3002559

Transdifferentiation is the use of various techniques to convert a somatic cell of one type directly into a somatic cell of another type. This is an alternative to first using Yamanaka factors to dedifferentiate somatic cells into induced pluripotent stem cells, then guiding differentiation into the desired final somatic cell type. For both differentiation from pluripotency to somatic cell and transdifferentiation between somatic cells, a suitable recipe of factors and altered gene expression must be discovered for any given destination. A few of these protocols are now well known, but the vast majority have yet to be robustly established, or even attempted at all.

In today's open access paper, researchers refer to transdifferentiation as direct reprogramming, not to be confused with the various forms of reprogramming via Yamanaka factors, either to produce induced pluripotent stem cells, or to restore youthful epigenetic patterns via what is known as partial reprogramming or epigenetic reprogramming. Transdifferentiation offers the potential to treat aspects of aging and age-related disease that involve the loss of small, specific cell populations, such as dopaminergenic neurons or sensory hair cells. These critical populations are surrounded by other, more numerous, less critical cells, which might be targets for transdifferentiation given a sufficiently selective therapy. Proof of concept in these and a few other cases has been achieved in animal studies, and it remains to be seen as to how rapidly this can advance to the clinic.

Next-generation direct reprogramming

While the concept that mature cell states are stable holds the key for homeostasis of an organism, the long-held believe was that this state cannot ever be reversed. This fallacy has gradually broken down. Now, the Yamanaka factors are now widely used not only for reprogramming but also for partial reprogramming that leads to rejuvenation of tissues. Yet another kind of reprogramming was emerging from the basic science field, now dubbed direct reprogramming, or transdifferentiation (we use the terms interchangeably from here on). During transdifferentiation a differentiated cell changes its fate to another, more desired differentiated cell type, without entering a pluripotent stage. The first identified transcription factor capable of directly reprogramming fibroblasts to skeletal muscles was MyoD. Many other lineage-specific transcription factors capable of transdifferentiating a target cell have since been identified.

Whether induced or endogenous process, in general, pioneer factors (PF) act as the first responders in direct reprogramming by binding and opening closed chromatin. It is not clear if each transdifferentiation lineage is regulated by a specific pioneer factor, or if a universal PF for transdifferentiation (capable of initiating multitude of direct lineage reversions) is still to be identified. Transdifferentiation studies have unveiled the opportunities and offer applications in regenerative therapies, such as cell replacement therapy or immunotherapy. The key question, and the topic of this review is to identify new, feasible methods to induce specific, high efficiency and targeted transdifferentiation.

These next-generation transdifferentiation approaches will come with better efficiency and plausibly with potential to treat diseases like Alzheimer's disease, muscle injury, diabetes, or myocardial infarction, resulting in elimination of the unsurmountable treatment issues at the moment (for example, finding a right donor or graft rejections). These novel approaches will enhance the efficacy and safety of direct reprogramming, allowing the ultimate decoding of the process towards plausibly resulting in 21st century personalized regenerative medicine.

Both cancer and aging impair the activity of T cells of the adaptive immune system, forcing these cells into exhaustion and senescence. The state of exhaustion is incompletely understood, but appears as an issue in immunotherapies making use of engineered T cells, as well as in the natural population of the aged body. Since researchers are already altering the T cells used in cancer therapies, why not alter them further to make them more able to resist the effects of aging cancer on T cell populations in the body? This is an interesting and plausible goal, but one that requires a greater understanding of T cell exhaustion than presently exists.

Cellular immunotherapy is revolutionizing oncology by harnessing T cells' unique ability to specifically target and potentially cure metastatic cancer, a feat not achievable with traditional treatments. Living T cells have proven they can eradicate even the most stubborn metastatic cells. However, challenges persist, as these therapies sometimes fail when T cells do not endure, often succumbing to exhaustion or senescence. This issue is being addressed by researchers who are exploring methods to enhance T cell resilience and functionality.

Evolution has shaped T cells to occasionally dampen their function in chronic viral infections to prevent autoimmunity and mitigate potential harm from an overly aggressive immune response. For example, the immune system's complete elimination of a hepatitis virus could cause significant liver damage. Chronic activation can also drive T cells toward senescence and exhaustion, weakening the immune response to cancer. To address these challenges, researchers have developed checkpoint inhibitors and engineered T cells to create synthetic T cells that can reverse or bypass these evolutionary constraints with great success in some indications.

Researchers have developed a synthetic T cell state they call TIF (T cells with an immortal-like and functional state). TIF cells are the product of disrupting the BCOR and ZC3H12A genes, a result that is surprising because these genes are typically expressed at low levels in T cells and lack dynamic regulation. This approach is aimed at addressing the traditional trade-off in T cell therapies between longevity and potency, offering cells that not only persist longer but also retain robust anti-tumor capabilities. TIF cells demonstrate enhanced survival and can enter a reversible dormant state, like memory cells, providing long-term immunity. Without BCOR, and in combination with ZC3H12A deficiency, genes that are usually repressed might become active, enhancing both stemness- and cytotoxicity-associated genes. This could potentially remove brakes on the T cell stemness and cytotoxic programs, enhancing therapeutic efficacy.

Link: https://doi.org/10.1084/jem.20240258

Here find an open access review of the present landscape of biomarkers of aging, both single measures and composite measures of various sorts, such as the aging clocks developed over the past fifteen years. The development of a good, consensus measure of biological age would accelerate efforts to treat aging as a medical condition, as assessing the ability of various classes of treatment to slow or reverse aging is at present a slow and expensive process - the only proven approach is a life span study. Unfortunately, all present approaches to the assessment of biological age have their challenges. The accumulation of large amounts of data for analysis proceeds in parallel with the development of better aging clocks that seek to address the known issues.

One major barrier to longevity research is evaluating the impact of interventions that improve human health and longevity because they are complex processes that occur over long time scales. Instead, measurable phenotypic traits or proxies of longevity, termed longevity biomarkers, may be used to assess the effectiveness of longevity interventions, or prognosticate clinical outcomes. Longevity biomarkers are critical tools for predicting lifespan and susceptibility to age-related diseases, but there exist a dizzying array of options, with at times contradictory readouts, and other key weaknesses.

Strengths of longevity biomarkers include providing insight into an individual's biological age, as opposed to chronological age, which is pivotal in evaluating targeted interventions that address aging and age-related conditions. However, most longevity biomarkers also exhibit notable weaknesses, such as a lack of specificity and lack of standardization across different studies and applications. These weaknesses underscore the need for more research to enhance their accuracy and reliability in long-term longitudinal studies.

In the present review, we discuss key strengths and weaknesses of popular clinical biomarkers used to predict morbidity and mortality associated with advanced age, identify existing bottlenecks, and integrate the field consensus on further directions for robust lifespan and healthspan estimation.

Link: https://doi.org/10.55277/ResearchHub.dxewpyv0

There are many different ways to conceptualize programs of research and development aimed at the treatment of aging. The Strategies for Engineered Negligible Senescence (SENS) is focused on aging as damage accumulation, and treatment is thus damage repair: remove senescent cells, restore mitochondrial function, clear out harmful protein aggregates, and so forth. Programmed aging viewpoints instead focus on ways to alter what are suspected to be evolved programs that drive aging, with this line of thought most often centered around the reversal of epigenetic changes that are observed to occur with age.

In today's open access paper, the authors propose a viewpoint that they call juventology, the study of youth, in analogy to gerontology, the study of aging. Clearly calorie restriction and related interventions adjust the operation of metabolism to slow aging and prolong the period of youthful life in many species. This might be taken as the existence of youth-maintaining programs, a delay of aging programs, or a slowing of damage accumulation. People tend to see their own view of aging reflected in the data for calorie restriction. It causes such a broad set of changes in cellular biochemistry, where that biochemistry is itself not fully mapped, that it is hard to mount arguments in support of one theory of aging versus another.

Is this really a good choice of strategy, however? Do we believe that calorie restriction is a starting point for a field that will in time engineer some form of altered metabolism that is far more effective when it comes to prolonging youthful life? In principle this has to be the case, as similar species with radically different life spans exist in the wild. Compare mice with naked mole-rats, for example, a nine-fold difference in life expectancy. In practice, I suspect that engineering human cellular metabolism to this degree is a far future prospect, however. The advantage of the damage repair approach is that it does seem to offer goals that can be achieved in the near future, without a full understanding of cellular biochemistry, and which will achieve meaningful gains in life span and reduction in the burden of age-related disease.

Exploring juventology: unlocking the secrets of youthspan and longevity programs

The paradigm of longevity programs opens up new vistas for understanding interventions that extend lifespan without instigating adverse effects. While traditional aging research has often fixated on combating free radicals and oxidative stress, juventology suggests that the most effective pro-longevity interventions induce alternate survival phases. The exploration of longevity programs in model organisms reveals a complex network of cellular responses and adaptive strategies that challenge the somewhat conventional theories of aging. Especially, the interplay between nutrient availability and the activation of specific longevity programs is not just a passive response but instead highlights a sophisticated network of cellular events that over the course of the lifespan can result in a healthier aging phenotype and increased longevity. In E. coli, Saccharomyces cerevisiae, and C. elegans, starvation, the most severe form of dietary restriction, causes a major lifespan extension.

Juventology is fundamentally different from "aging-centered" theories of aging for two reasons: (1) alternative lifespan programs, such as those entered in response to starvation, can be independent (or are at least partially independent) of aging itself. As an example, one could visualize the use of target-specific pharmaceuticals or systemically broader acting periodic fasting intervals modulate the mTor-S6K and PKA pathways, which in turn can promote regeneration and rejuvenation. Notably, this can be achieved even in an organism with a high rate of aging. Thus, even in an accelerated aging phenotype, a longer healthspan and lifespan may be accomplished by periodically activating regenerative and rejuvenating processes. (2) Juventology shifts the focus from an "old or older age" paradigm characterized by high degrees of dysfunction and subsequent high morbidity and mortality, instead to the period in life during which both morbidity and mortality are very low and only difficult to detect.

Diseases in humans are generally rare before the (biological) age 40, but comorbidities are common after age 65, yet no specific field of science is focusing on how evolution resulted in a program that is extremely efficient in preventing disease for the first 40 years of life and how that program may be modulated and extended by dietary, pharmacological, or other interventions. On the one hand, developmental biology focuses on the biological process from embryo to (young) adult stage and generally does not include this important field. On the other hand, biogerontology the biological basis of aging and age-related diseases. Thus, juventology presents a complementary field to both gerontology and developmental biology that focuses on the period of organismal life when the force of natural selection is high and body functions remain maximized.

Periodic fasting and calorie restriction promote cells to enter into a stress resistance state which is characterized by the activation of cell protection, regeneration, and rejuvenation processes. Across multiple species, these protective and regenerative mechanisms are activated in part by the down-regulation of growth hormone, IGF-1, mTor-S6K, and PKA signaling cascades, which in turn induces the extension of healthspan. Because these states have evolved to withstand periods of extreme nutrient starvation, they can be viewed as alternative longevity programs activated to maintain cellular "youthspan" until resources that promote proliferative processes become available again. Here, we propose that these juventology-based approaches provide complementary strategies to the classic biogerontology approaches to focus on the earlier (i.e., biologically younger) functional period while also studying the later progressively dysfunctional processes that affect health and longevity.

Researchers here demonstrate an approach to cell therapy for an injured heart that produces lesser degrees of abnormal function than prior efforts. There has been some concern that delivering new cells to the heart to spur greater regeneration will disrupt the electrical regulation of heartbeats, as animal studies suggested an unacceptable risk of arrhythmia following treatment. This work still makes use of cardiomyocytes generated from induced pluripotent stem cells, already accomplished by a number of other groups, but differences in the details of the approach appear to make a positive change in the outcome.

In a recent study, a research team tested a new strategy for regenerative heart therapy that involves injecting 'cardiac spheroids' derived from human induced pluripotent stem cells (HiPSCs) into monkeys with myocardial infarction. First, the team verified the correct reprogramming of HiPSCs into cardiomyocytes. They observed, via cellular-level electrical measurements, that the cultured cells exhibited potential patterns typical of ventricular cells. The cells also responded as expected to various known drugs. Most importantly, they found that the cells abundantly expressed adhesive proteins such as connexin 43 and N-cadherin, which would promote their vascular integration into an existing heart. Afterwards, the cells were transported from the production facility. The cardiac spheroids, which were preserved at 4°C in standard containers, withstood the four-hour journey without problem. This means that no extreme cryogenic measures would be needed when transporting the cells to clinics, which would make the proposed approach less expensive and easier to adopt.

Finally, the monkeys received injections of either cardiac spheroids or a placebo directly into the damaged heart ventricle. During the observation period, the researchers noted that arrythmias were very uncommon, with only two individuals experiencing transient tachycardia (fast pulse) in the first two weeks among the treatment group. Through echocardiography and computed tomography exams, the team confirmed that the hearts of monkeys that received treatment had better left ventricular ejection after four weeks compared to the control group, indicating a superior blood pumping capability. Histological analysis ultimately revealed that the cardiac grafts were mature and properly connected to pre-existing existing tissue. "The favorable results obtained thus far are sufficient to provide a green light for our clinical trial. We are already employing the same cardiac spheroids on patients with ischemic cardiomyopathy."

Link: https://www.shinshu-u.ac.jp/english/topics/2024/04/using-stem-cell-deri.html

While researchers here focus specifically on stair climbing as a form of physical activity to compare against risk of mortality in later life, there are any number of other studies that focus on activity more generally, or on other forms of moderate to vigorous exercise. The consensus across epidemiological studies is that physical activity correlates with reduced mortality. Animal studies have been used to demonstrate that the exercise in fact causes that reduced mortality, and it is reasonable to consider that the same is true in humans.

Cardiovascular disease is largely preventable through actions like exercise. However, more than one in four adults worldwide do not meet recommended levels of physical activity. Stair climbing is a practical and easily accessible form of physical activity which is often overlooked. This study investigated whether climbing stairs, as a form of physical activity, could play a role in reducing the risks of cardiovascular disease and premature death.

The authors collected the best available evidence on the topic and conducted a meta-analysis. Studies were included regardless of the number of flights of stairs and the speed of climbing. There were nine studies with 480,479 participants in the final analysis. The study population included both healthy participants and those with a previous history of heart attack or peripheral arterial disease. Ages ranged from 35 to 84 years old and 53% of participants were women.

Compared with not climbing stairs, stair climbing was associated with a 24% reduced risk of dying from any cause and a 39% lower likelihood of dying from cardiovascular disease. Stair climbing was also linked with a reduced risk of cardiovascular disease including heart attack, heart failure, and stroke.

Link: https://www.eurekalert.org/news-releases/1042193

Atherosclerosis is the growth of fatty lesions in blood vessel walls, ultimately leading to a heart attack or stroke when an unstable lesion ruptures. Atherosclerosis is primarily a condition of macrophage dysfunction, in which these cells fail to keep up with their task of removing excess cholesterol from blood vessel walls in order to return it to to the bloodstream for transport back to the liver. The local excess of cholesterol is largely the proximate cause of this macrophage dysfunction, so as the amount of cholesterol grows, macrophages become ever less capable of dealing with it. They die, adding their mass to the lesion, while signaling for reinforcements that will suffer the same fate.

That said, this is a description of how atherosclerosis progresses once it gets started. How do the initial small excesses of cholesterol form in the first place? Most of the underlying root causes of aging are involved in the growing inability of macrophages to keep up with the task of cholesterol transport. Further, altered behavior of other cell populations with advancing age, in the liver and blood vessel walls, may be capable of disrupting cholesterol transport from the liver to the rest of the body, leading to excess deposits in blood vessels. In today's open access paper, researchers focus in on the age-related decline in mitochondrial function in the context of atherosclerosis: would improving mitochondrial function help?

Effects of mitochondrial dysfunction on cellular function: Role in atherosclerosis

Atherosclerosis is the basis of a large proportion of fatal cardiovascular events, and a significant number of cardiovascular-related deaths can be attributed to the rupture of atherosclerotic plaques. Thinning of the covered fibrous cap formed by vascular smooth muscle cells (VSMCs) results in cap rupture and erosion, which is responsible for the majority of cardiovascular-related deaths from myocardial infarction and stroke. Atherosclerosis is an age-associated disorder; however, with the development of non-invasive diagnostic methods and the accumulation of knowledge in postmortem research, asymptomatic lesions have been described in young adults, suggesting that atherosclerosis is a chronic disease that develops at a much younger age than previously thought.

Atherosclerosis is now widely accepted to begin with endothelial dysfunction and lipid deposits, which progress through macrophage infiltration. In atherosclerosis-prone areas, the chronic inflammatory response and impaired lipoprotein metabolism are among the major contributors to atherosclerotic lesion formation. The first idea linking mitochondria to atherosclerosis was reported in 1970, but it is only recently that increasing evidence has highlighted the key role of mitochondrial dysfunction in the pathogenesis of atherosclerosis. Mitochondrial dysfunction can induce high levels of oxidative stress and high rates of apoptosis, which can cause endothelial dysfunction and increase the vascular disease burden. The increase in reactive oxygen species (ROS) production in mitochondria, accumulation of mitochondrial DNA damage, and progressive respiratory chain dysfunction are all related to atherosclerosis.

Mitochondrial dysfunction is believed to result in an increase in reactive oxygen species, leading to oxidative stress, chronic inflammation, and intracellular lipid deposition, all of which can contribute to the pathogenesis of atherosclerosis. Critical cells, including endothelial cells, vascular smooth muscle cells, and macrophages, play an important role in atherosclerosis. Mitochondrial function is also involved in maintaining the normal function of these cells. To better understand the relationship between mitochondrial dysfunction and atherosclerosis, this review summarizes the findings of recent studies and discusses the role of mitochondrial dysfunction in the risk factors and critical cells of atherosclerosis.

The author of this paper is an advocate for programmed aging. This is the view that degenerative aging is actively selected by evolutionary processes, perhaps because it helps to reduce the risk of runaway population growth, or perhaps because aging species better adapt to ecological change, rather than being a side-effect of selection effects focused on early life reproductive success that tend to produce systems that accumulate damage to fail over time. In some programmed aging views, epigenetic change is close to being the root cause of aging, being the implementation of an evolutionarily selected program. It is interesting to see an outline of perceived challenges in epigenetic clock development from the programmed aging viewpoint, to contrast with the challenges seen by other researchers, which are focused on the lack of understanding of how specific epigenetic changes reflect underlying damage and dysfunction.

Late in life, the body is at war with itself. There is a program of self-destruction (phenoptosis) implemented via epigenetic and other changes. I refer to these as type (1) epigenetic changes. But the body retains a deep instinct for survival, and other epigenetic changes unfold in response to a perception of accumulated damage (type (2)).

In the past decade, epigenetic clocks have promised to accelerate the search for anti-aging interventions by permitting prompt, reliable, and convenient measurement of their effects on lifespan without having to wait for trial results on mortality and morbidity. However, extant clocks do not distinguish between type (1) and type (2). Reversing type (1) changes extends lifespan, but reversing type (2) shortens lifespan. This is why all extant epigenetic clocks may be misleading.

Separation of type (1) and type (2) epigenetic changes will lead to more reliable clock algorithms, but this cannot be done with statistics alone. New experiments are proposed. Epigenetic changes are the means by which the body implements phenoptosis, but they do not embody a clock mechanism, so they cannot be the body's primary timekeeper. The timekeeping mechanism is not yet understood, though there are hints that it may be (partially) located in the hypothalamus. For the future, we expect that the most fundamental measurement of biological age will observe this clock directly, and the most profound anti-aging interventions will manipulate it.

Link: https://doi.org/10.1134/S0006297924020135

The progressive dysfunction of sweat glands in the skin is probably not high on the list of items that people think about in the context of degenerative aging, at least not until they experience it. A reduced capacity of sweat glands leads to heat intolerance, and it is one of the contributing causes of the raised mortality rate among the elderly in heat waves. Here, researchers examine some of the biochemistry of sweat gland cells in aging mice. They focus in on a number of proteins that may turn out to be viable targets for drugs to force sweat glands in aged skin back to a more youthful degree of function. It is a long road from fundamental investigations of this sort to that outcome, however.

Evaporation of sweat on the skin surface is the major mechanism for dissipating heat in humans. The secretory capacity of sweat glands (SWGs) declines during aging, leading to heat intolerance in the elderly, but the mechanisms responsible for this decline are poorly understood. We investigated the molecular changes accompanying SWG aging in mice, where sweat tests confirmed a significant reduction of active SWGs in old mice relative to young mice.

We first identified SWG-enriched messenger RNAs (mRNAs) by comparing the skin transcriptome of Eda mutant Tabby male mice, which lack SWGs, with that of wild-type control mice by RNA-sequencing analysis. This comparison revealed 171 mRNAs enriched in SWGs, including 47 mRNAs encoding 'core secretory' proteins such as transcription factors, ion channels, ion transporters, and trans-synaptic signaling proteins. Among these, 28 SWG-enriched mRNAs showed significantly altered abundance in the aged male footpad skin, and 11 of them, including Foxa1, Best2, Chrm3, and Foxc1 mRNAs, were found in the 'core secretory' category.

Consistent with the changes in mRNA expression levels, immunohistology revealed that higher numbers of secretory cells from old SWGs express the transcription factor FOXC1, the protein product of Foxc1 mRNA. In sum, our study identified mRNAs enriched in SWGs, including those that encode core secretory proteins, and altered abundance of these mRNAs and proteins with aging in mouse SWGs.

Link: https://doi.org/10.18632/aging.205776

Robust modern forms of vaccination that were developed in the 20th century remain one of the most important forms of medical technology. Infectious diseases are not going away any time soon, and continue to cause a sizable fraction of human mortality, even though that fraction is much reduced in our era. Unfortunately, effective vaccination depends on an effective immune system, and thus vaccines tend to perform increasingly poorly with advancing age. As we age our immune system becomes ever less capable, a decline into immunosenescence caused by a range of contributing processes: involution of the thymus, where T cells of the adaptive immune system mature; a growing presence of senescent, exhausted, and malfunctioning immune cells; a shift in cell populations of the bone marrow to produce more myeloid and fewer lymphoid cells; and so forth.

As today's open access paper points out, the approach to improving vaccination in the old has long been to find ways to work around the growing incapacity of the aged immune system. Developing better adjuvants to vaccines, for example. This produces only incremental gains. The yearly toll of influenza deaths is much larger than the estimates of prevented deaths due to widespread vaccination. For the 2022-2023 season those numbers show 21,000 estimated deaths versus 3,600 estimated prevented deaths. Most of those deaths are old people, not only less able to defend against an infectious pathogen, but also less able to benefit from vaccination. Something must change! That change must be to focus on ways to repair the aged immune system, restore its function to more youthful capabilities.

There are any number of approaches presently under development that show promise. Restoration of active thymic tissue would help by providing a supply of new T cells. Use of CASIN can produce lasting improvements in hematopoietic stem cell function in the bone marrow following a single treatment. Clearance of populations of malfunctioning immune cells has been demonstrated to improve immune function in animal models. Clearance of senescent cells can reduce the burden of unresolved inflammatory signaling that puts stress on the aged immune system. There are more in various stages of development.

Insights into vaccines for elderly individuals: from the impacts of immunosenescence to delivery strategies

The global population is entering an era of aging. Older people are more susceptible to pathogens and have higher rates of morbidity and mortality. Despite the significant success of current vaccine products, many commercial vaccines fail to generate effective and long-lasting immune protection in elderly individuals. With increasing age, the reasons for the decline in vaccine potency are multifactorial. Age-related dysregulation of lymph nodes, and crucial immune cells jointly reduces the efficiency of vaccination. With the continuous emergence of new pathogens, it is urgent to create strategies to improve vaccination-mediated protection for elderly individuals.

The existing approaches are primarily aimed at optimizing the vaccine delivery system rather than inhibiting the immunosenescence of the immune microenvironment in elderly individuals. Inhibiting the immunosenescence of elderly individuals can evoke strong and long-lasting immune protection, which serves as a critical measure to improve vaccine-induced immunity. Although inhibition of immunosenescence most likely requires continuous intervention/treatment and is complicated to achieve, we believe that sustained-release vaccination/adjuvants or booster immunizations may sustainably ameliorate immunosenescence in the elderly. Once the immunosenescence of the elderly is corrected, their immune efficacy against various antigens can be improved.

An attractive research direction will be discovering immunomodulators and vaccine formulations that can inhibit immunosenescence. The selection of adjuvants can greatly impact the type and magnitude of the immune response. Considering the special immune status of elderly individuals, designing tailored vaccine adjuvants is indispensable for the development of next-generation vaccines for older individuals. A chronic inflammatory state also accompanies immunosenescence. However, the common opinion is that adjuvants promote immunity by inducing local inflammation. Therefore, more in-depth studies are needed to explain the role of inflammation in vaccine-induced immunity and tune the contradictory perspectives.

Most studies focus on one or several cell types or certain processes of the immune response. However, our immune system is a complex and coordinated comprehensive network. More new technologies and advances will help reveal the complexity underlying the human immune system. We must pay more attention to the impacts of versatile cells or multiple immune cascade processes. Future research should focus on developing scientific methods to build more convincing models of aging and study the profound mechanisms underlying age-related alterations that impact the immune responses of older people.

One the important themes of the research and development at Repair Biotechnologies is that localized excesses of cholesterol arise with age, leading to excess intracellular cholesterol, which is a pathological mechanism that disrupts cell behavior and kills cells. Getting rid of these localized excesses of cholesterol is challenging, however, unless resorting to some form of engineered protein machinery or gene therapy. Cells cannot break down cholesterol and there is no good way to bind enough of the excess cholesterol to some form of small molecule for sequestration and disposal without also targeting vital cholesterol in cell membranes and elsewhere. As this paper notes, excess cholesterol is clearly a meaningful problem in aging.

Although dysregulated cholesterol metabolism predisposes aging tissues to inflammation and a plethora of diseases, the underlying molecular mechanism remains poorly defined. Here, we show that metabolic and genotoxic stresses, convergently acting through liver X nuclear receptor, upregulate CD38 to promote lysosomal cholesterol efflux, leading to nicotinamide adenine dinucleotide (NAD+) depletion in macrophages. Cholesterol-mediated NAD+ depletion induces macrophage senescence, promoting key features of age-related macular degeneration (AMD), including subretinal lipid deposition and neurodegeneration.

NAD+ augmentation reverses cellular senescence and macrophage dysfunction, preventing the development of AMD phenotype. Genetic and pharmacological senolysis protect against the development of AMD and neurodegeneration. Subretinal administration of healthy macrophages promotes the clearance of senescent macrophages, reversing the AMD disease burden. Thus, NAD+ deficit induced by excess intracellular cholesterol is the converging mechanism of macrophage senescence and a causal process underlying age-related neurodegeneration.

Link: https://doi.org/10.1016/j.celrep.2024.114102

Improved autophagy is implicated in many of the approaches shown to slow aging in animal models. An open question is whether more targeted approaches to altering the regulation of autophagy in aged cells can improve matters to a greater degree than, for example, exercise or the practice of calorie restriction, both of which are known to produce general improvements in autophagy. Researchers here show that improvement of autophagy via increased expression of TRP53INP2 in old mice can reduce the age-related loss muscle mass and function that leads to sarcopenia. It seems an interesting target for further development of therapies.

Sarcopenia is a major contributor to disability in older adults, and thus, it is key to elucidate the mechanisms underlying its development. Increasing evidence suggests that impaired macroautophagy/autophagy contributes to the development of sarcopenia. However, the mechanisms leading to reduced autophagy during aging remain largely unexplored, and whether autophagy activation protects from sarcopenia has not been fully addressed.

Here we show that the autophagy regulator TP53INP2/TRP53INP2 is decreased during aging in mouse and human skeletal muscle. Importantly, chronic activation of autophagy by muscle-specific overexpression of TRP53INP2 prevents sarcopenia and the decline of muscle function in mice. Acute re-expression of TRP53INP2 in aged mice also improves muscle atrophy, enhances mitophagy, and reduces reactive oxygen species (ROS) production. In humans, high levels of TP53INP2 in muscle are associated with increased muscle strength and healthy aging. Our findings highlight the relevance of an active muscle autophagy in the maintenance of muscle mass and prevention of sarcopenia.

Link: https://doi.org/10.1080/15548627.2024.2333717