Fight Aging!

If the activities of a cell appear precisely engineered and highly efficient, it is because every layer of cellular activity is monitored by some form of quality control mechanism. A cell is a collection of molecules moving at incredible speeds, where every possible collision happens countless times per second. All of the damaging, unwanted reactions that can occur between molecular structures in the cell do in fact happen constantly. Breakage happens constantly. Manufacture of new structures produces flawed outcomes constantly. But all of these issues are cleaned up as they occur. The processes of quality control and maintenance that undertake this cleanup work are collectively vital to cell health and cell function.

Messenger RNA is manufactured as the first stage of gene expression. The transcriptional machinery of the cell nucleus assembles messenger RNA molecules based on their genetic blueprints before sending them off to be translated into proteins. Following the remarks above, many flawed messenger RNA molecules result from the constant transcriptional activity in the cell nucleus and must be dealt with by a layer of messenger RNA quality control. As is the case for most of the processes involved in gene expression, this quality control is fairly well understood by the research community, likely becomes meaningfully less effective with advancing age, but measuring specific aspects of this quality control process can be challenging, leading to debate.

The function of mRNA quality control in aging and age-related diseases

Aging is accompanied by a gradual decline in physiological functions and an exponential increase in susceptibility to multiple age-associated diseases. Aging is caused by the impairment of biological systems at multiple levels. At the cellular level, the accumulation of senescent cells, which stably stop proliferation, is considered as a major cause of aging. At the molecular level, genomic instability and reduced proteostasis contribute to accelerating both cellular senescence and organismal aging. Recent studies also suggest important roles of messenger RNA (mRNA) quality control systems in aging. Studies using the nematode Caenorhabditis elegans demonstrated the important function of mRNA quality control and homeostatic regulation of splicing in organismal aging. In addition, age-dependent accumulation of stalled ribosomes, which are closely associated with co-translational mRNA quality control systems, contributes to aging and longevity in the budding yeast Saccharomyces cerevisiae and C. elegans.

Eukaryotic cells are equipped with multiple mRNA surveillance systems that eliminate abnormal transcripts. Nonsense-mediated mRNA decay (NMD), a key RNA surveillance process, targets mRNA transcripts that contain premature termination codons (PTCs). Nonstop decay (NSD) eliminates mRNAs without stop codons that cause ribosome stalling at the poly(A) tail, and conventionally no-go decay (NGD) removes mRNAs with internal stem-loop structures or rare codons that cause internal ribosome stalling. Although poly(A)-mediated ribosome stalling has been classically associated with NSD, recent studies showed that poly(A) stretches can also trigger ribosome collisions and activate NGD, indicating a partial mechanistic overlap between the two pathways. Slow elongation caused by non-optimal or rare codons activates a noncanonical mRNA surveillance pathway, codon-optimality-mediated decay, rather than NGD, and the decay of such mRNAs is mechanistically distinct from NGD.

Impairments of NMD, NSD, and NGD contribute to physiological defects such as premature aging and neurodegeneration, highlighting the importance of proper maintenance of mRNA quality control in organismal health. Here, we discuss the critical roles of these pathways in maintaining mRNA quality and preventing the accumulation of aberrant transcripts, which can contribute to aging and age-related disorders. Specifically, we discuss the function of NMD in aging processes and age-related diseases, including cancer and neurodegenerative disorders. We also review the safeguarding roles of NSD and NGD in preventing the accumulation of faulty mRNAs and proteins associated with various diseases. We explore the potential functions of additional mRNA surveillance and the associated signaling pathways, such as ribosome-associated quality control (RQC), in aging and age-related diseases. Understanding the intricate relationship between mRNA surveillance mechanisms and aging may provide key information for developing potential therapeutics that boost these pathways for delaying aging and treating age-related diseases.

Aging can be split up into specific categories in many different ways; age-related diseases as collections of symptoms, specific forms of cell and tissue damage that accumulate, dysfunctions separated by organ, and so forth. None of these categories exist in isolation from the others, however. All aspects of aging interact with one another. Kidney dysfunction affects the brain. Mitochondrial dysfunction influences the burden of cellular senescence. There are a hundred other interactions one might consider that blur the lines of any attempt at categorization of the progression of aging. Nothing is neat and contained, everything interacts.

Aging is accompanied by conserved hallmarks including genomic instability, epigenetic alterations, loss of proteostasis, and mitochondrial dysfunction, but how these processes emerge and become mechanistically linked remains unclear. Here we leverage a proteome-wide, single-cell, subcellular atlas of protein expression, localization, and aggregation across yeast replicative aging to map hallmark-linked remodeling in its spatial context.

We identify hundreds of previously unappreciated molecular changes that underlie major hallmarks of aging and show that hallmark phenotypes frequently manifest as compartment-specific erosion of spatial confinement, relocalization, and aggregation. 91.6% human orthologs of these hallmark-linked yeast proteins also change during human aging. Integrating these spatial phenotypes reveals many molecular connections linking different hallmarks. Temporal analysis suggests that disorganization of nucleolar ribosome biogenesis, proteostasis decline, and mitochondrial dysfunction precede other hallmarks. Together, our findings substantially deepen the molecular underpinnings of aging hallmarks and provide a framework for linking them into a hierarchical sequence of cellular failures.

Link: https://doi.org/10.64898/2026.02.26.708335

Sarcopenia is the name given to the characteristic age-related loss of muscle mass and strength, once the process enters more severe stages. The loss of strength and resilience is an important contribution to frailty, but muscle is also a metabolically active tissue and loss of muscle negatively affects metabolism as well as physical capacity. Chronic inflammation is a feature of aging, as the immune system reacts to cell and tissue dysfunction in maladaptive ways. That chronic inflammation contributes to all of the common age-related conditions by interfering in the maintenance of tissues; this includes muscle tissue and the development of sarcopenia.

Sarcopenia is a syndrome characterized by an age-related progressive decline in skeletal muscle mass, strength, and function. It represents a significant public health concern because of its adverse impact on the quality of life and prognosis of older adults. Chronic low-grade inflammation contributes to the pathophysiology of sarcopenia through multiple pathways, including cellular senescence, immunosenescence, oxidative stress, mitochondrial dysfunction, hormonal alterations, and gut microbiota dysbiosis. Moreover, obesity, a chronic inflammatory condition, is associated with sarcopenia, leading to sarcopenic obesity, which further exacerbates muscle loss and functional impairment.

In terms of interventions, exercise, nutritional supplementation, and combined approaches have demonstrated efficacy in improving muscle mass and function, as well as conferring demonstrable anti-inflammatory benefits. In addition to conventional hormonal therapies, pharmacological strategies, particularly anti-inflammatory agents and treatments targeting inflammatory pathways, show considerable therapeutic promise.

This review examines the central role of chronic inflammation in the development and progression of sarcopenia, as well as its underlying mechanistic basis. It also elaborates on the roles of key inflammatory cytokines, such as C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), in regulating muscle protein metabolic balance and their potential utility as biomarkers. A deeper understanding of the relationship between inflammation and sarcopenia will not only help elucidate its complex pathogenesis but also offer critical directions for the future development of early diagnostic tools and targeted anti-inflammatory interventions.

Link: https://doi.org/10.3389/fphar.2026.1733798

Senescent cells accumulate with age in tissues throughout the body, the result of a growing imbalance between the pace at which somatic cells enter the senescent state in response to damage, stress, and the Hayflick limit on the one hand and the pace of clearance of senescent cells by the immune system on the other. The growing burden of senescent cells disrupts tissue structure and function via inflammatory signaling. This is thought to produce a significant, important contribution to degenerative aging, and over the past fifteen years cellular senescence has become major focus of life science research and development.

Today the field of senotherapeutics, meaning anti-aging therapies that in some way target senescent cells, is in the strange superimposed state of both existing and yet to emerge. Senostatics slow the rate at which cells become senescent, and the low cost, generic mTOR inhibitor rapamycin appears to be a legitimate senostatic. Senolytics selectively destroy senescent cells, and the senolytic combination of dasatinib and quercetin, the subject of several early stage clinical trials, also costs little. Senomorphics impede the bad behavior of senescent cells, and many existing drugs might qualify as senomorphic to some degree.

The two named options above are readily available via off-label prescription to any older individual willing to try. Yet use is not widespread. The large clinical trials that would provide concrete demonstrations of efficacy (or lack of same) have not been conducted, and do not seem likely to be conducted. Generic drugs cannot command enough revenue to support the regulatory cost of large clinical trials. The research community and longevity industry is instead focused on the development of a wide range of novel senotherapeutics, and progress largely remains at a preclinical stage. Today's open access paper is an opinionated tour, but gives a sense of where things stand, the variety of approaches under consideration.

Emerging strategies in senotherapeutics: from broad-spectrum senolysis to precision reprogramming

Cellular senescence, originally described as a finite proliferative arrest in cultured somatic cells, has since been recognized as a central mechanism underlying aging and the development of age-associated disorders. The progressive accumulation of senescent cells (SnCs) promotes chronic inflammation through the senescence-associated secretory phenotype (SASP) and circumvents immune-mediated clearance by upregulating pro-survival and immune checkpoint pathways. Early "first-generation" senolytics, including navitoclax (ABT-263) and the dasatinib-quercetin (D + Q) combination, provided proof-of-concept that selective removal of SnCs can alleviate certain fibrotic, metabolic, and cardiovascular pathologies in preclinical studies. However, these agents exhibited notable drawbacks, such as dose-dependent thrombocytopenia, variable therapeutic efficacy, and the emergence of resistance mechanisms. Consequently, current research has shifted toward precision senotherapy, though significant translational challenges remain.

This review synthesizes three next-generation strategies developed to address limitations of early senolytic agents. (1) Immune-based senolysis: This approach applies immuno-oncology principles to counter immune evasion of SnCs. Strategies include blocking immunosuppressive ligands such as GD3 ganglioside, engineering chimeric antigen receptor (CAR) T cells to target senescence-specific surface markers like urokinase-type plasminogen activator receptor (uPAR), and exploiting metabolic vulnerabilities (e.g., glutaminolysis and ferroptosis) to sensitize SnCs to immune-mediated clearance. (2) Tissue-precision proteolysis-targeting chimeras (PROTACs): These agents recruit organ- or tissue-specific E3 ligases (e.g., von Hippel-Lindau (VHL)) to selectively degrade anti-apoptotic proteins such as BCL-xL. Localized activity may reduce systemic toxicity and mitigate dose-limiting effects observed with traditional inhibitors. (3) Microbiome-epigenetic interplay: This strategy modulates the gut-liver axis to enhance senolytic efficacy. Short-chain fatty acids (SCFAs), such as butyrate, epigenetically regulate drug transporter expression and suppress the SASP, while dietary interventions may create a microenvironment favorable to senolysis.

These approaches offer potentially more targeted and personalized therapeutic options but face significant challenges, including immunopathology, manufacturing complexity, off-target effects, and long-term safety concerns. The ongoing shift from broad inhibition to precision reprogramming represents a promising but preliminary step in the treatment of age-related diseases.

An increasing number of cells in aged tissues enter a senescent state, ceasing replication and generating pro-inflammatory signals that are disruptive to tissue structure and function. In the case of innate immune cells, however, there is some question as to whether they are in fact senescent or just adopting features of senescence, and that leads to debate over whether these cells are in fact harmful. Neutrophils, also known as polymorphonuclear leukocytes, are an important cell type in the innate immune system. Here, researchers show that neutrophils in aged individuals exhibit features of cellular senescence, but stop short of calling them senescent cells. They also show that this behavior is harmful, as it impedes the immune response to infection.

Aging drives increased susceptibility to respiratory infections by Streptococcus pneumoniae (pneumococci). Polymorphonuclear leukocytes (PMNs) are among the first responders in the lung following pneumococcal infection and are required for bacterial clearance. However, PMN antimicrobial function declines with age. To identify mechanisms underlying this decline, we performed RNA sequencing on PMNs in the lungs of young and old mice following pulmonary infection with S. pneumoniae. We observed significant transcriptomic differences across host age.

Transcriptional analysis followed by functional validation revealed that in infected mice, PMNs from aged hosts failed to upregulate several effector activities including glycolysis and subsequent mitochondrial reactive oxygen species (ROS) production, which are necessary for bacterial killing by PMNs. Conversely, PMNs in aged mice displayed a higher senescence-associated secretory phenotype (SASP) score and upregulated pathways involved in cellular senescence. Follow-up functional characterization found that in uninfected hosts, PMNs in aged mice expressed higher levels of SASP factors IL-10, TNFα, and ROS, had a lower incidence of apoptosis, and had a higher proportion of cells positive for senescence-associated β-galactosidase, features of a senescent-like phenotype.

Importantly, blocking TNFα, one of the SASP factors, altered the senescent-like phenotype and boosted the antibacterial activity of PMNs from aged hosts and increased host resistance to S. pneumoniae pulmonary infection. In conclusion, host aging is associated with altered PMN phenotype, including a shift toward senescent-like energy-deficient cells, which contribute to impaired host defense and represent potential targets for improved interventions against infection in older adults.

Link: https://doi.org/10.1111/acel.70435

The standard view of the evolution of aging is that aging exists because natural selection operates more strongly on features of young animals than on features of old animals. A faster time to reproductive success will be selected over a slower time to reproductive success. This leads to the evolution of biological systems that are front-loaded for early efficiency, but that decay to become dysfunctional over time. Aging is near universal but not actually universal, however. For example, varieties of hydra are in fact immortal, exhibiting no loss of function over time. How to explain the existence of the few immortal species in the presently dominant view of the evolution of aging? Here, researchers build a model of the evolution of aging in which a runaway feedback loop leading to immortality is a possible outcome.

In recent years, senescence is increasingly understood as a process of damage accumulation that accelerates with age throughout an organism's lifespan. That understanding has rarely been introduced to senescence evolution theory. In classic models, including Mutation accumulation and Antagonistic pleiotropy, the intensity of selection over genes is determined by the timing of their effect on mortality. They conclude senescence evolution occurs because of weak selection on late-acting genes. Despite the success of these classic explanations, several phenomena have not been fully addressed. One is the existence of species exhibiting negligible senescence - mortality rate that remains constant with age.

Here we explore, consistent with recent evidence, an alternative model: where genes affect mortality throughout an organism's lifespan, and the shape of this effect determines selection. We expanded Hamilton's classic model of senescence evolution using these notions. Our model takes into account evolutionary dynamics between external mortality risk, potential mortality risk from internal damage, reproduction start age, and reproduction rate. The analysis of the model suggests biological limitations on reducing the potential mortality risk from internal damage can lead to a positive feedback loop in senescence evolution where genes that slow senescence can increase selection for further senescence retardation. Our model sheds light on several phenomena, not fully explained by classic theory, including Peto's paradox, Strehler-Mildvan correlation, and negligible senescence.

Link: https://doi.org/10.1002/ece3.72988

Most programs aiming to produce therapies that treat aging involve some form of manipulation of cellular metabolism, usually via small molecules initially derived from screens that showed effects on function or survival in lower animals. Effect sizes are usually modest, and decrease relative to species life span as species life span increases; large increases in function and life span in a nematode worm translate to modest gains in a mouse. Where we have the ability to compare mice and humans, in the matter of growth hormone metabolism and calorie restriction, we know that sizable gains in mice do not translate to sizable gains in humans.

Researchers, particularly Brian Kennedy's team, have shown that most combinations of this sort of intervention fail to be useful. Any two marginally positive age-slowing changes to metabolism are far more likely to interfere with one another than they are to combine for a greater effect. Yet aging is a combination of forms of cell and tissue damage, and thus multiple treatments will be needed to address aging. To combine therapies is a desirable end goal, but it must be pursued rationally, using combinations made up of therapies that specifically address different forms of age-related damage. In principle, such combinations should be far less likely to interfere in one another's operation, and the outcome for health and longevity more likely to be additive and greater than any one therapy alone.

This view of combined therapies as the end goal was always implicit in the Strategies for Engineered Negligible Senescence (SENS) view of aging and how to go about the construction of rejuvenation therapies. One must repair the damage, and thus one must combine different repair strategies that address different forms of damage. This is the central point that the Longevity Escape Velocity (LEV) Foundation is attempting to demonstrate in their large, long-running mouse studies. The goal is to pick sensible combinations of therapies based on a damage repair philosophy, and show that these combinations can be additive. Nothing is ever straightforward, and there are clearly things to be learned along the way, but so far the LEV Foundation seems to be proving their point, a useful counterbalance to the work of Brian Kennedy.

Robust Mouse Rejuvenation: Breaking the Ceiling of Longevity Research

For decades, the field of biogerontology has largely focused on a single strategy: manipulating metabolism to slow down the rate at which we age. While approaches like caloric restriction have produced fascinating results in short-lived organisms like worms and flies, they have shown clear limits in mammals. At LEV Foundation, we are pursuing a distinct alternative: maintenance through damage repair. All age-related damage can be classified into a manageable number of categories. Since there are different types of damage, a single therapeutic intervention is insufficient. To achieve meaningful rejuvenation, we must move from isolation to synergy.

This necessity is the foundation of the Robust Mouse Rejuvenation (RMR) programme. We define RMR as a specific engineering benchmark: a multi-component intervention that increases both mean and maximum lifespan in mice by at least 12 months. This must be achieved in a mouse strain with a well-documented mean lifespan of at least 30 months, with treatment initiating only at the advanced age of 18 months. To hit this target, the RMR programme consists of large-scale studies designed to determine how leading-edge interventions behave when deployed together.

The RMR1 study served as a first test, operating at an unprecedented scale with 1000 middle-aged mice divided into 10 subgroups per sex. This granular design allowed us to map the complex web of interactions. We selected four interventions that had individually shown promise in extending mouse lifespan: rapamycin, senolytics, telomerase gene therapy, and hematopoietic stem cell transplantation. By administering these simultaneously, we sought to establish whether their combined impact could finally break through the lifespan ceiling that no single intervention has ever managed to overcome.

The overarching conclusion following the completion of RMR1 is a qualified win for synergy. RMR1 successfully demonstrated that combining damage-repair interventions with metabolic modulation (rapamycin) yields additive benefits. Specifically, we observed a distinct rectangularisation of the survival curve. This means that we significantly increased mean lifespan by ensuring more mice survived into late life. However, we must be clear about the limits of this result. We did not observe a radical extension of maximum lifespan (the age of the oldest survivors). While the all-four combination group outperformed both the naive and mock controls, the "robust" goal of shifting the entire mortality window remains the target for future iterations.

RMR1 demonstrated that a single dose of damage repair has a limited window of efficacy. The damage re-accumulates. Future protocols must likely incorporate repeated dosing for interventions like senolytics and gene therapy. However, the male data revealed that combinatorial treatments extend this window significantly when supported by metabolic stability. We have used these critical lessons to design RMR2. The new study replaces the single-dose approach with cyclic treatments using mesenchymal stem cells and an expanded panel of eight interventions. With the blueprint for this next phase complete, funding is the only remaining bottleneck.

Autophagy is the name given to a collection of cellular processes responsible for recycling damaged or otherwise unwanted proteins and structures. The materials to be recycled are conveyed to a lysosome where they are broken down into raw materials that can be reused for further protein synthesis. Many of the most well studied approaches to slowing aging in laboratory species involve increased autophagy. Greater autophagy improves cell function and is demonstrated to reduce the pace at which cells in aged tissues enter the harmful senescent state. Nothing in biology is simple, however. Here, researchers discuss the role of excessive autophagy in sustaining the inflammatory, disruptive signaling that is generated by lingering senescent cells in aged tissues.

Autophagy and cellular senescence are fundamental stress-response programs that critically shape aging and disease progression, yet their functional relationship has remained paradoxical. Autophagy is traditionally viewed as a cytoprotective process that preserves cellular homeostasis and delays senescence. In contrast, emerging evidence demonstrates that autophagy is also indispensable for the survival and pathological activity of established senescent cells. In this review, we propose a "threshold model" to reconcile these opposing roles and to provide a unified framework linking signal transduction, organelle quality control, and therapeutic intervention.

According to the threshold model, autophagy exerts stage-dependent functions governed by stress intensity and disease progression. Below a critical damage threshold, robust autophagic flux suppresses senescence initiation by maintaining mitochondrial integrity, limiting oxidative stress, and preserving proteostasis. Once this threshold is exceeded, autophagy is functionally reprogrammed to sustain the metabolic and biosynthetic demands of senescent cells, including production of the senescence-associated secretory phenotype (SASP).

We highlight key signaling nodes that regulate this transition, including mTORC1, AMPK, p53, and p62, as well as spatial and organelle-specific mechanisms such as the TOR-autophagy spatial coupling compartment (TASCC), mitophagy failure, lipophagy blockade, and aberrant nucleophagy. These processes converge on innate immune pathways, notably cGAS-STING and NF-κB signaling, to drive chronic inflammation and tissue dysfunction. Importantly, we extend this mechanistic framework to clinical translation, synthesizing evidence from ongoing trials in cancer, neurodegeneration, metabolic liver disease, and fibrosis. We argue that effective targeting of the autophagy-senescence axis requires precision gerontology, integrating dynamic biomarkers to guide stage-specific interventions-autophagy activation for prevention and autophagy inhibition or senolysis for established disease.

Link: https://doi.org/10.1016/j.redox.2026.104079

As researchers continue to map the changing composition of the gut microbiome in aging and disease, in ever more detail, they increasingly uncover the problematic activities of specific microbial species and specific mechanisms by which the aging of the gut microbiome can contribute to age-related loss of function throughout the body. This opens the door to the development of means of targeted adjustment of the gut microbiome's composition, and also to the development of therapies that interfere in specific interactions between the microbiome and tissues that cause issues.

Ageing is accompanied by declining memory function, with extremely heterogeneous manifestation in the human population. Brain-extrinsic factors influencing cognitive decline, such as gastrointestinal signals, have emerged as attractive targets for peripheral interventions, but the underlying mechanisms remain largely unclear. Here, by charting a high-resolution map of microbiome ageing and its functional consequences throughout the lifespan of mice, we identify a mechanism by which inhibition of gut-brain signalling during ageing results in impaired neuronal activation in the hippocampus and loss of memory encoding.

Specifically, accumulation of gut bacteria that produce medium-chain fatty acids, such as Parabacteroides goldsteinii, can drive peripheral myeloid cell inflammation through GPR84 signalling. As a result, the function of vagal afferent neurons is impaired, the interoceptive signal received by the brain is weakened and hippocampal function declines. We leverage this pathway to define interventions that enhance memory in aged mice, such as phage targeting of Parabacteroides, GPR84 inhibition and restoration of vagal activity. These findings indicate a key role for interoceptive dysfunction in brain ageing and suggest that interoceptomimetics that stimulate gut-brain communication may counteract age-associated cognitive decline.

Link: https://doi.org/10.1038/s41586-026-10191-6

The gut microbiome changes with age in ways that negatively affect tissue function and health. This is known because we live in an age in which it costs little to accurately measure the composition of the gut microbiome from a stool sample: which microbial species, and the relative abundance of each species. Bacterial species can be distinguished from one another by differing sequences of the 16S rRNA gene, so low-cost and relatively unsophisticated gene sequencing approaches can be used to characterize an individual's gut microbiome. The result is something of a golden age in the identification of new ways to adjust the gut microbiome to improve health.

Today's open access paper stands out as interesting, in that the authors establish a correlation between the prevalence of a single bacterial species, Roseburia inulinivorans, and muscle strength in mice and humans. The Roseburia inulinivorans population diminishes with age. Increasing the Roseburia inulinivorans population size via supplementation with live bacteria enhances muscle strength in mice. The size of that increase in strength was on the order of 30%, more than large enough to expect the emergence of a deluge of Roseburia inulinivorans live probiotic supplements in the years ahead. A trial of those supplements will be needed to determine the size of the effect on human muscle strength, but given the low cost of single species probiotic manufacture, that seems worth the effort.

Roseburia inulinivorans increases muscle strength

Gut bacteria have been implicated in a wide range of health conditions, yet their potential role in preventing and treating muscle-wasting disorders remains largely unexplored. We aimed to investigate whether specific gut microbial species are associated with muscle strength and to explore underlying mechanisms linking the gut microbiota to muscle health. We conducted metagenomic analyses in cohorts of younger and older adults extensively phenotyped for muscle strength. Associations were tested between bacterial taxa and performance measures. Causality was assessed by oral supplementation of candidate species in antibiotic-treated mice. Metabolomic profiling and muscle phenotyping were performed to elucidate mechanisms.

The relative abundance of Roseburia inulinivorans, but not other Roseburia species, was positively associated with multiple strength measures including handgrip, leg press, and bench press in humans. Supplementation of R. inulinivorans in mice significantly enhanced forelimb grip strength, whereas other Roseburia species had no effect. Metabolomic analyses revealed that R. inulinivorans reduced amino acid concentrations in the caecum and plasma, while activating the purine and pentose phosphate pathway in muscle. These changes coincided with increased muscle fibre size and a shift from type I to type II fibres. Accordingly, we observed that the relative abundance of R. inulinivorans is lower in older adults compared with young adults.

R. inulinivorans emerges as a species-specific modulator of muscle strength, linking gut microbiota to muscle metabolism and function. These findings support its potential as a probiotic candidate for nutraceutical interventions targeting age-related muscle-wasting diseases.

The aging of the brain is characterized by the formation of solid aggregates of misfolded amyloid-β peptides. This is a foundation for later loss of cognitive function and the development of the more severe, inflammatory dysfunction of late stage Alzheimer's disease. Researchers here provide data from cell studies to suggest that the innate immune cells known as microglia maladaptively manufacture amyloid-β aggregates in the process of attempting to clear amyloid. Microglia have been the target of increasing interest in the context of the aging of the brain and development of neurodegenerative conditions, though much of that has focused on growing inflammation driven by this cell population. It seems we might have to consider that the normal operation of microglia becomes pathological when faced with protein aggregates, a part of the complex opening stages of Alzheimer's disease and perhaps other neurodegenerative conditions.

A new study shows that immune cells called microglia can actively promote the formation of plaques in Alzheimer's disease, challenging the long-standing view that these cells serve only as defenders against plaque buildup. "Most studies suggest that microglia are there to clean up the brain and remove the amyloid plaques. What we discovered is that actually they're part of the problem. They generate plaques. It was thought that plaques aggregate by themselves. And it seems that the microglia, by trying to deal with the problem, amplify it."

The research team shows that microglia can remodel soluble amyloid-beta (Aβ42) into extracellular fibrils with potent seeding activity. Seeding is a key problem in disease: it is the process by which one aggregate gives rise to multiple new aggregates. These are the same type of structures that accumulate in the brains of patients with Alzheimer's disease. "Our results suggest that many plaques in Alzheimer's brains may arise through cellular processes rather than spontaneous aggregation. We think this highlights a second role for microglia we were previously unaware of. Using seeding assays, we showed that cell-generated amyloid more closely resembles brain-derived amyloid and triggers disease-relevant cellular responses, establishing a model that better reflects what happens in patients."

Link: https://vib.be/en#/news/brain-immune-cells-may-help-build-not-just-clear-alzheimers-plaques

One of the avenues by which regular exercise produces health benefits is through adjustment of the composition of the gut microbiome, favoring the production of metabolites that improve health. A range of metabolites produce by gut-resident microbial species influence important cell types in the body and brain, and are to some degree necessary for normal tissue function. Here, for example, researchers trace the influence of exercise through its effects on the abundance of various bacterial species in the gut to alterations to tryptophan metabolism to effects on memory function and mood in the brain.

Exercise exerts beneficial effects on mood and memory. One emerging pathway through which exercise influences brain health is via the gut microbiota, which produces metabolites that can influence host brain functions. However, it is not yet known which exercise-induced alterations in the gut microbiota are associated with alterations in systemic metabolites that may affect the brain. We investigated the effect of exercise on the gut microbiota and serum metabolomics profile in adult male rats and examined the association of these microbial-mediated changes with brain processes.

Exercise decreased the relative abundance of two tryptophan-metabolizing bacterial genera, Alistipes and Clostridium. Serum metabolomics revealed that exercise enhanced tryptophan metabolism, with a greater abundance of the serotonin catabolite 5-hydroxytryptophol identified. The abundance of genus Clostridium was negatively nominally associated with serum levels of 2-oxindole, an indole derivative. Analysis of the gut-brain modules also revealed that tryptophan metabolism was enhanced by exercise. Furthermore, exercise decreased hippocampal expression of the aryl hydrocarbon receptor, a mediator of the effects of tryptophan-metabolizing gut microbes on neuronal function.

Taken together, results suggest that exercise modulates gut microbes associated with systemic tryptophan metabolism, which may exert beneficial effects on memory and mood via regulation of the aryl hydrocarbon receptor.

Link: https://doi.org/10.61373/bm026r.0009

On the matter of cellular senescence as a contributing cause of degenerative aging, there is a school of thought whose members argue that at least some senescent cells are doing something useful by existing, despite their problematic behavior. Therefore therapeutic approaches should focus on prevention of senescence (senostatics) or reducing the harmful senescence-associated secretory phenotype (SASP) (senomorphics) rather than on outright destruction of senescent cells (senolytics). Within the array of possible ways to reduce the pace at which cells become senescence, sabotaging the ability of senescent cells to encourage their neighbors to also become senescent has been little explored, so it is interesting to note recent work on this topic.

Today's open access paper represents is an early step on the path to finding ways to block bystander senescence. It is likely that the relevant interactions differ by cell type and tissue, making it a more challenging exercise than would otherwise be the case. Here, the focus is on the brain, and the researchers outline potential target interactions that might be blocked to reduce the spread of cellular senescence in an aged brain. As an approach to therapy, this does have the look of an intervention that could increase risk of cancer, however. The ability of the senescent state to spread from cell to cell is one of the ways in which early cancers are suppressed before they can become an issue. But at the end of the day, the only practical way to assess hypothetical benefits versus hypothetical risks is to build a therapy and test it in animal studies.

Characterizing the SASP-Dependent Paracrine Spreading of Senescence Between Human Brain Cell Types

One of the defining phenotypes of a senescent cell is the senescence-associated secretory phenotype (SASP), which can propagate senescence in neighboring cells both in vitro and in vivo. Importantly, this paracrine spreading of senescence can act in a cell non-autonomous manner, influencing neighboring cell populations and contributing to immune cell recruitment. As cellular senescence has recently been linked to both age-related neurodegenerative phenotypes and local inflammation and is more clearly defined across brain cell types in a cell-type-dependent manner, an urgent question remains regarding how a cell-type-specific paracrine spreading of senescence occurs in the brain.

Here, we sought to unravel the relationship between key brain cell types (astrocytes, endothelial cells, microglia, oligodendrocytes, and neurons) in the context of a paracrine spreading of senescence via the SASP. We utilized our previously established in vitro DNA damage-induced human brain cell line senescence model and conditioned media experiments to profile the cell-type-dependent SASP, characterize the directionality of a paracrine spreading of senescence between the relevant cell types, identify key SASP ligands and receptors that mediate the cell-type-specific spread, and target these factors using various inhibitors in an attempt to prevent the paracrine spreading of senescence.

We demonstrate that a cell-type-specific SASP profile of each brain cell type drives differential induction of secondary senescence, where some cell types can induce senescence in themselves as well as in other cell types, while other cell types are only capable of receiving secondary senescence induction, but cannot spread. Importantly, we identified both cell-type-specific and common SASP ligands and receptors, which we successfully targeted to prevent the induction of secondary senescence depending on the cell types communicating with one another. Taken together, this work gives key insights into the mechanisms of paracrine spreading of senescence between brain cell types in vitro and offers potential therapeutic targets to prevent this spreading, which may in turn help to alleviate age-related tissue decline and inflammaging.

Researchers here provide data on the correlations between (a) secreted proteins circulating in blood that are distinct to senescent cells of various types, and (b) a number of different age-related conditions. Some cell types are better than others when it comes to the strength of correlation between the burden of senescence as assessed by circulating proteins and status of given age-related condition. This process of mapping the landscape of senescence and aging sets the stage for the development of better assays that can inform patients as to the risk resulting from the burden of senescence, and later the degree of improvement produced by therapies capable of reducing the burden of senescent cells.

Senescence is characterized in part by proteomic expression changes, including the secretion of pro-inflammatory cytokines and other proteins, which become amplified during sustained senescence and in large part drive its deleterious effect in a chronic, age-related context. These senescence-associated proteins (SAPs) have since proven to be heterogeneous by cell type and senescence-inducing stimulus.

One promising technique in assessing individual senescence burden is through the quantification of SAPs in circulating plasma. The plasma senescence burden has previously demonstrated compelling clinical associations, including with age, frailty, and mortality. In recent years, a group of senescence-targeting compounds collectively known as senotherapeutics has been investigated for their limited and context dependent senescence-attenuating effects. Senotherapeutic drugs have demonstrated an ability to lower circulating SAPs in human trials, and to partially alleviate some aging phenotypes.

A remarkable recent finding is that beyond general clinical traits such as age and mortality, organ-specific proteins can be tracked in circulation and used to model organ age and organ-specific clinical traits. Considering the previously demonstrated clinical relevance of circulating canonical senescence signatures, examining cell type-specific senescence signatures in circulation could similarly shed light on the unique clinical relevance of organ-specific senescence.

In this study, senescence signatures from the Senescence Catalog (SenCat), including 14 human cell types such as peripheral blood mononuclear cells, renal epithelial cells, vascular smooth muscle cells, among others, are examined for their clinical relevance in circulation in two longitudinal studies: 1,275 participants of the Baltimore Longitudinal Study of Aging (BLSA) and 997 participants of the Invecchiare in Chianti (InCHIANTI) study. Notably, pooled senescence proteins outperformed non-senescence proteins in predicting many clinical parameters such as age and hypertension, and in many instances cell type senescence signatures mapped most strongly to their corresponding health domain. Importantly, the immune cell senescence signature is associated with future onset of several diseases such as diabetes.

Link: https://doi.org/10.64898/2026.02.06.26345739

Senescent cells accumulate in tissues with age to promote degenerative aging. Senescent cells cause harm via the signals that they send to other cells, the senescence-associated secretory phenotype (SASP). The SASP is by no means fully understood, and while it clearly contains many pro-inflammatory and pro-growth signals, it probably has many other effects as well. Here, researchers provide evidence for one specific SASP signal molecule to interfere in the benefits of exercise. Clearance of senescent cells should therefore produce an enhanced response to exercise in old individuals, in addition to the other benefits already demonstrated in a sizeable number of animal studies.

Adaptation to physiological stress is fundamental to health but varies widely among individuals. In humans, this heterogeneity is evident in markedly different gains in fitness in response to identical exercise training. The molecular determinants of this variable "trainability" remain poorly understood. Here we identify insulin-like growth factor binding protein-7 (IGFBP7), a senescence-associated secreted protein, as a circulating constraint on exercise adaptation.

Plasma proteomics in older adults enrolled in a randomized exercise trial revealed that IGFBP7 levels inversely predicted fitness gains after one year of high-intensity interval training despite similar baseline fitness. In mice, genetic deletion of IGFBP7 markedly amplified training-induced gains in exercise capacity across distinct training protocols, whereas somatic overexpression abolished this advantage. In the UK Biobank, lower IGFBP7 levels were associated with reduced mortality and multiple incident age-related diseases, mirroring the breadth of ties between fitness and healthspan.

Together, these findings identify circulating IGFBP7 as a molecular brake on physiological plasticity in response to exercise, linking training responsiveness, aging biology, and health outcomes.

Link: https://doi.org/10.64898/2026.02.09.26345899