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- Qualifying the Increased Mortality Risk Resulting from Metabolic Syndrome and Sarcopenia
- SPP1+ Macrophages are Implicated in Numerous Age-Related Conditions
- Some Bird Species May Have Evolved Ways to Resist Harmful Glycation
- Evidence for Low Frequency Ultrasound to Reverse Cellular Senescence
- The Concept of Bioenergetic Age in the Context of Neurodegeneration
- A Reminder of the Harms Done by Excess Visceral Fat Tissue
- XBP1 to Upregulate the Unfolded Protein Response Reduces Pathology in Mouse Models of Alzheimer's Disease
- Inducing a Torpor-Like State in Mice Slows Aging
- Differences in the Gut Microbiome and Immune Function in Male versus Female Centenarians
- Larger Volume White Matter Hyperintensities Correlate with Cognitive Decline
- The Interactions Between Aging, Circadian Rhythm, and Cancer Risk
- Cardiometabolic Index Correlates with Accelerated Biological Age
- Worse Cardiovascular Health Correlates with Raised Biomarkers of Neurodegeneration
- High Neutrophil to Lymphocyte Ratio as a Predictor of Muscle Loss
- The Finnish Twin Cohort's Odd Results for the Effects of Exercise on Mortality
Qualifying the Increased Mortality Risk Resulting from Metabolic Syndrome and Sarcopenia
https://www.fightaging.org/archives/2025/03/qualifying-the-increased-mortality-risk-resulting-from-metabolic-syndrome-and-sarcopenia/
Metabolic syndrome is the precursor to type 2 diabetes, and a direct consequence of being sufficiently overweight to experience the necessary disruptions to metabolism. Sarcopenia is the name given to severe loss of muscle mass and strength when it occurs in older people, though it is worth noting that these losses are universal. While a sizable fraction of the muscle atrophy observed in wealthier regions of the world results from a sedentary lifestyle, the other underlying causes resulting from aging occur for everyone. Everyone would reach a state of sarcopenia eventually, if they did not first die due to some other consequence of degenerative aging.
Since sarcopenia is in part driven by chronic inflammation, and chronic inflammation is characteristic of metabolic syndrome, these two conditions can coexist. In today's open access paper, epidemiologists examine data obtained for this patient population in order to quantify the excess mortality risk that these individuals experience as a result of (a) the underlying damage and dysfunction that contributes to these conditions, and (b) the secondary dysfunctions and further damage resulting from these conditions.
Additive impact of metabolic syndrome and sarcopenia on all-cause and cause-specific mortality: an analysis of NHANES
Metabolic syndrome (MetS) and sarcopenia (SP) are increasingly significant public health issues in aging societies, sharing common pathophysiological mechanisms and being associated with severe health consequences. This study analyzed data from the National Health and Nutrition Examination Survey (NHANES) conducted between 1999 and 2018. Mortality data were obtained from the National Death Index up to December 2019. Among the 21,962 participants, 61.5% had neither MetS nor SP (MetS-/SP-), 24.6% had MetS only (MetS+/SP-), 12.2% had SP only (MetS-/SP+), and 1.5% had both MetS and SP(MetS+/SP+).
Compared to the group without MetS and SP, the groups with MetS only, SP only, and both MetS and SP showed increased all-cause mortality, with adjusted hazard ratios (HR) of 1.23, 1.63, and 1.61, respectively. The MetS+/SP+ group had the highest overall mortality risk. For cause-specific mortality, the MetS+/SP+ group exhibited increased cardiovascular mortality (HR: 1.89), cardiac mortality (HR: 1.89), respiratory mortality (HR: 2.63), and diabetes mortality (HR: 8.79) compared to the group without MetS and SP.
SPP1+ Macrophages are Implicated in Numerous Age-Related Conditions
https://www.fightaging.org/archives/2025/03/spp1-macrophages-are-implicated-in-numerous-age-related-conditions/
The innate immune cells known as macrophages are found everywhere in the body, outside the brain. Inside the brain an analogous population known as microglia exists. A population of monocytes resides in the spleen and circulates in the bloodstream, capable of differentiating into macrophages and entering tissues when needed. But large numbers of tissue resident macrophages also exist, already in place. Macrophages undertake a wide range of tasks, including the destruction of infectious pathogens and senescent and cancerous cells, coordination of tissue regeneration following injury, and clearance of metabolic waste and debris. Macrophages are diverse in the sense that they can adopt different programs of expression and behavior in response to circumstances and environment. With advancing age, some of these behaviors can become maladaptive in response to the damaged tissue environment.
Today's open access paper is focused on one specific population of macrophages that is implicated as a source of inflammatory signaling in aging. Chronic inflammation is a feature of aging, with many contributing causes. When inflammation continues indefinitely without resolution, it changes cell behavior to cause disruption to tissue structure and function, contributing to the onset and progression of a range of age-related conditions. Since necessary short term inflammation and harmful long-term inflammation are governed by the same regulatory pathways, it is likely that the only truly effective solution to the problem of chronic inflammation in aged tissues involves removing the molecular damage that provokes it and either removing or altering the behavior of the immune cell populations that generate the largest amounts of inflammatory signaling.
SPP1 macrophages across diseases: A call for reclassification?
Recent advances in macrophage biology have revealed a remarkable diversity among these immune cells, highlighting the existence of specialized subpopulations with distinct functional roles in health and disease. Among these, SPP1+ macrophages, characterized by elevated osteopontin (SPP1) expression, have garnered significant attention due to their consistent association with pathological states. Originally identified in cancer as tumor-associated macrophages (TAMs), SPP1+ macrophages have since been implicated in various conditions, including aging, chronic inflammatory disorders, neurodegenerative diseases, and tissue remodeling.
Aging presents a compelling context in which SPP1+ macrophages emerge as key players. Single-cell RNA sequencing studies have revealed their abundance in the skeletal muscle of aged mice, where they exhibit hallmarks of senescence and enhanced angiogenic and lipid metabolic activity. Beyond musculoskeletal systems, SPP1+ macrophages also influence neurodegenerative diseases. In Alzheimer's disease, an upregulation of SPP1-positive microglia correlates with inflammation and synaptic loss. Perivascular macrophages with SPP1 profiles modulate microglial phagocytic activity, offering a potential mechanism underlying synapse degradation. This dual contribution to inflammation and neurodegeneration positions SPP1+ macrophages as central figures in aging-related pathologies.
Their conserved traits, such as promoting fibrosis, remodeling the extracellular matrix, and modulating immune responses, suggest they play a pivotal role in sustaining chronic inflammation and tissue dysfunction. Furthermore, their presence often correlates with poor clinical outcomes, underscoring their relevance as potential therapeutic targets. Despite these shared characteristics, SPP1+ macrophages exhibit functional adaptability across different disease contexts, raising questions about their classification and the underlying mechanisms that drive their diverse roles.
In this perspective, we briefly summarize recent discoveries on the multifaceted roles of SPP1+ macrophages across various pathological conditions, emphasizing their shared traits and the critical differences dictated by the tissue microenvironment and pathological inflammatory context. Based on our comparative literature investigation, we also propose a re-evaluation of their classification, advocating for their recognition as a distinct macrophage subtype linked to prolonged inflammatory states rather than specific to tumors. Such a shift in perspective could not only advance our understanding of macrophage biology but also open new avenues for targeted therapeutic interventions.
Some Bird Species May Have Evolved Ways to Resist Harmful Glycation
https://www.fightaging.org/archives/2025/03/some-bird-species-may-have-evolved-ways-to-resist-harmful-glycation/
Birds are much studied in the comparative biology of aging because they are long-lived for their size in comparison to mammals. The present consensus lumps birds and bats together, in that the evolution of flight and its high metabolic demand is thought to also require the evolution of a greater resistance to stresses placed on cells by oxidative molecules and other sources of molecular damage. One of those other forms of damage is glycation by sugar compounds. High blood sugar in mammals increases the production of a range of glycated molecules, such as the well-studied advanced glycation endproducts (AGEs), that can cause a variety of harms, from inflammation via the receptor for AGEs (RAGE) to cross-linking of the extracellular matrix to stiffen arteries.
Today's open access paper notes that birds exhibit high blood sugar relative to mammals, and that the relationship between blood sugar and species life span is not straightforward. It suggests that some longer lived species have evolved means to protect themselves from harmful glycation. This gives researchers something to look for; one of the long term goals in the study of the comparative biology of aging is to find mechanisms that might give rise to therapies that will slow aging in mammals. As ever, it is far to early to tell how this line of research will turn out in the end.
Birds' high blood sugar defies ageing expectations
The pace-of-life syndrome hypothesis proposes that an organism's metabolic rate, lifespan, reproductive strategies, and behaviour evolve in predictable ways. Under this framework, species with fast metabolisms, short lifespans, and high reproductive rates are expected to have higher blood sugar and glycation levels. Conversely, those with longer lifespans and slower developmental times should have lower blood sugar levels and greater resistance to glycation. However, it is unclear how glycation has coevolved with other traits across species, and so it is undetermined whether glycation fits into the framework of the pace of life hypothesis.
"Birds are particularly relevant in this context, given their relatively high blood sugar levels - on average almost twice as high as similarly sized mammals. This is thought to be an adaptation allowing flight, providing birds with the fuel needed to power intense bursts of aerobic exercise. But it is also paradoxical. Despite their higher blood sugar levels, birds show remarkable longevity compared to their mammalian counterparts, living up to three times longer."
Researchers conducted an analysis of 484 individual birds from 88 different species. They compared blood sugar levels and glycation rates in relation to the birds' life history traits. Their results revealed substantial variation in blood sugar levels across species. Smaller birds had the highest blood sugar levels, while larger species had the lowest. Glycation rates followed a similar trend, with smaller birds showing higher levels and larger birds displaying lower levels. However, the relationship between blood sugar levels and lifespan was more complex. While longer-lived birds generally had higher blood sugar levels, this increase plateaued beyond a certain point. This suggests that some species have evolved mechanisms to prevent glycation-related damage, rather than avoiding high blood sugar levels altogether.
Variation in albumin glycation rates in birds suggests resistance to relative hyperglycaemia rather than conformity to the pace of life syndrome hypothesis
The pace of life syndrome hypothesis (POLS) suggests that organisms' life history, physiological, and behavioural traits should co-evolve. In this framework, how glycaemia (i.e., blood glucose levels) and its reaction with proteins and other compounds (i.e. glycation) co-vary with life history traits remain relatively under-investigated, despite the well documented consequences of glucose and glycation on ageing, and therefore potentially on life history evolution. Birds are particularly relevant in this context given that they have the highest blood glucose levels within vertebrates and still higher mass-adjusted longevity when compared to organisms with similar physiology as mammals.
We thus performed a comparative analysis on glucose and albumin glycation rates of 88 bird species from 22 orders, in relation to life history traits (body mass, clutch mass, maximum lifespan, and developmental time) and diet. Glucose levels correlated positively with albumin glycation rates in a non-linear fashion, suggesting resistance to glycation in species with higher glucose levels. Plasma glucose levels decreased with increasing body mass but, contrary to what is predicted to the POLS hypothesis, glucose levels increased with maximum lifespan before reaching a plateau. These results increase our knowledge about the diversity of glycaemia and glycation patterns across birds, pointing towards the existence of glycation resistance mechanisms within comparatively high glycaemic birds.
Evidence for Low Frequency Ultrasound to Reverse Cellular Senescence
https://www.fightaging.org/archives/2025/03/evidence-for-low-frequency-ultrasound-to-reverse-cellular-senescence/
The manipulation of cell state to produce positive outcomes via either electromagnetic fields or physical stimuli such as pressure are both understudied areas of cell biology, potentially applicable to the production of novel therapies, but with little concrete progress to that end goal. One of the challenges is that there are many, many different ways in which one can apply electromagnetic fields or physical stimuli to cells, and it seems fairly clear from a review of the fairly sparse literature on this topic that (a) most of the choices one can make in this large space of options will not produce the desired results, and (b) replication is hard because researchers do not adequately describe the exact protocol they are using. Small and even unintentional changes in the setup of the experiment can produce large differences in outcomes.
Today's open access paper is quite interesting. In it, researchers present evidence for the application of pulsed pressure to cells via low frequency ultrasound to be capable of reversing cellular senescence. Normally senescence is an irreversible transition, though in recent years researchers have found a few manipulations that can achieve this goal. Low frequency ultrasound is shown to affect mTOR signaling and boost autophagy. Pharmacological approaches to achieve this goal, such as use of rapamycin, do not reverse senescence. They do reduce the number of cells that become senescent, however, and thus allow the number of senescent cells in a tissue or in cell culture to become lower over time. Researchers tested the ultrasound approach in cell culture, but were careful to try to show that formerly senescent cells lost characteristics of senescence, it wasn't just a reduced onset of senescence. The researchers then tested the application of low frequency ultrasound to mice, and report a sizable gain in life span in mice treated with ultrasound throughout their lives, in the same ballpark as the use of senolytic drugs to clear senescent cells.
Rejuvenation of Senescent Cells, In Vitro and In Vivo, by Low-Frequency Ultrasound
Senescent cells, as rigorously defined by many markers, including the expression of β-galactosidase, can be mechanically rejuvenated by low frequency ultrasound (LFU) without transfection or other biochemical manipulations. The ultrasound pressure waves restore normal behavior irrespective of whether senescence is induced by chemical treatment or by repeated replication. There is no apoptosis with LFU, and videos of senescent cells show a dramatic increase in cell and mitochondrial motility, as well as in growth after LFU treatment. Many features of senescent cells are all reversed by LFU, including the increase in β-galactosidase activity, p16 and p21 expression, decreased telomere length, increased H3K9me3 levels, decreased 5mC levels, increased cell size, secretion of senescence-associated secretory phenotype (SASP), and inhibition of growth. Surprisingly, ultrasound treatment of normal cells causes secretion of growth-stimulating factors that partially restore normal behavior in senescent cells. Because replicatively senescent cells are restored to a normal phenotype by LFU, they can be cultured for longer periods to produce increased numbers of cells without major alteration in their phenotype.
It is perhaps surprising that fully senescent cells can be rejuvenated by pressure waves. This raises the question of how a senescent cell is defined. Cells that were made senescent by toxic compounds or repeated replications were incubated for long periods, and time-lapse video microscopy verified the absence of any growth. After such treatments, quiescent cells were not present since over 95% of the cells expressed β-galactosidase and many of the larger senescent cells grew and divided in the videos after LFU. By tracing individual cells, we were able to determine that growth was occurring in over 30% of the originally non-dividing cells after 4-5 days. Such robust growth is inconsistent with the growth of just a subpopulation of cells that are not senescent. Further, there is no apoptosis after LFU treatment of the senescent cells, and over fifteen characteristics of senescence are reversed. Thus, all of these objective criteria indicate that LFU reverses senescence, and we suggest that LFU actually rejuvenates senescent cells.
This opens many new possibilities in the aging research field, including the possibility of rejuvenating aged cells in vivo to inhibit age-dependent disorders, which appears to be true based on the results of the mouse studies reported here. 46 mice were treated over 300 days (some mice reached 3 years of age). In the five LFU-treated groups, the best survivors had the lowest doses of ultrasound with about 50% survival at 1000 days (~33 months of age) and 3 mice survived until 3 years. Autopsies of the mice that died revealed no tumors or obvious cause of death. In terms of the safety of LFU, half of the mice in the longevity study were treated daily with LFU for over 300 days without damage or evidence of harm from the LFU treatment. Further, the treated mice maintained a normal weight, whereas the weight of the sham mice was declining with age.
The Concept of Bioenergetic Age in the Context of Neurodegeneration
https://www.fightaging.org/archives/2025/03/the-concept-of-bioenergetic-age-in-the-context-of-neurodegeneration/
The brain requires a lot of energy to function. Like muscle tissue, it is particularly vulnerable to age-related dysfunction in energy metabolism, the various pathways by which cells make use of nutrients to supply energy for the operation of vital biochemical processes. The brain primarily makes use of glucose as a nutrient, but this process of deriving energy from glucose becomes dysfunctional with age, and this dysfunction tends to be particularly pronounced in patients exhibiting neurodegenerative conditions such as Alzheimer's disease. An alternative to glucose readily used elsewhere in the body is β-oxidation of fatty acids. There are reasonable explanations as to why the brain has evolved not to favor this path, such as the greater degree of oxidative stress it generates. But at the end of the day, if the brain had more access to compensatory sources of energy, dysfunction would be slowed with aging.
So to today's research materials, in which the scientists involved show that people with higher degrees of β-oxidation of fatty acids throughout the body tend to suffer less as glucose metabolism in the brain runs awry with age. Thus one could use biomarkers of β-oxidation and call it a measure of the age of energy metabolism, as the researchers do here, but I think that to be an unhelpful framing obscures the relationships between the underlying processes and capacities. As the researchers note, the beneficial effects of present anti-amyloid immunotherapies are small enough, only a modest slowing of disease progression, that a shift in metabolism to favor β-oxidation can produce a similar outcome. What one should take away from this is not that we should all jump up and focus research efforts on upregulation of β-oxidation of fatty acids, which can be achieved to a reasonable degree by ketogenic and calorie restricted diets, but rather that there remains a great unmet need for actually effective therapies to turn back the progression of neurodegenerative conditions.
Lowering Bioenergetic Age May Help Fend Off Alzheimer's
A person's "bioenergetic age" - or how youthfully their cells generate energy - might be a key indicator of whether they're at risk of developing Alzheimer's disease, new research shows. One of the early warning signs of Alzheimer's is that brain cells start losing their ability to produce and use energy efficiently, such as metabolizing glucose. But some people don't show disease symptoms for years. This delay between abnormalities in energy pathways and the onset of symptomatic disease suggests there is a "bioenergetic capacity" that provides a buffer for these individuals. Their bodies and brains are better at keeping energy levels up even when problems start.
Researchers turned to a group of molecules called acylcarnitines, which are associated with declining cognition and breaking down or metabolizing fats and proteins for energy. To test if high acylcarnitine levels in the blood could predict who's at risk of developing Alzheimer's, the researchers used data from a large-scale study called the Alzheimer's Disease Neuroimaging Initiative. This led the researchers to define a bioenergetic clock based on acylcarnitines - how old a person's metabolism acts, compared to actual age. Higher bioenergetic age is linked to higher acylcarnitine levels, worsened Alzheimer's pathology, cognitive decline, and brain atrophy.
The researchers also quantified cognitive decline using a common test called the mini-mental state examination, on which a score below 24 out of 30 points indicates impairment. They found that people with low acylcarnitine levels to begin with declined more slowly, losing about 0.5 points less per year than people with high acylcarnitine levels. The benefit is on par with the Alzheimer's drug lecanemab. To some degree, a person's bioenergetic clock ticks forward at a rate determined by their genetics, but having a healthy lifestyle - for example, eating a plant-based diet and exercising - can help keep acylcarnitine levels low, which means a younger bioenergetic age.
Individual bioenergetic capacity as a potential source of resilience to Alzheimer's disease
Impaired glucose uptake in the brain is an early presymptomatic manifestation of Alzheimer's disease (AD), with symptom-free periods of varying duration that likely reflect individual differences in metabolic resilience. We propose a systemic "bioenergetic capacity", the individual ability to maintain energy homeostasis under pathological conditions. Using fasting serum acylcarnitine profiles from the AD Neuroimaging Initiative as a blood-based readout for this capacity, we identified subgroups with distinct clinical and biomarker presentations of AD.
Our data suggests that improving beta-oxidation efficiency can decelerate bioenergetic aging and disease progression. The estimated treatment effects of targeting the bioenergetic capacity were comparable to those of recently approved anti-amyloid therapies, particularly in individuals with specific mitochondrial genotypes linked to succinylcarnitine metabolism. Taken together, our findings provide evidence that therapeutically enhancing bioenergetic health may reduce the risk of symptomatic AD. Furthermore, monitoring the bioenergetic capacity via blood acylcarnitine measurements can be achieved using existing clinical assays.
A Reminder of the Harms Done by Excess Visceral Fat Tissue
https://www.fightaging.org/archives/2025/03/a-reminder-of-the-harms-done-by-excess-visceral-fat-tissue/
Being overweight correlates with an increased risk of age-related disease and mortality in later life. The greater the excess weight, the greater the risk. A sizable fraction of this risk appears to be mediated by the metabolic activity of visceral fat cells, which promote chronic inflammation through a range of mechanisms. These include an increased burden of cellular senescence, visceral fat cells mimicking the signaling associated with infected cells, and an greater amount of debris from dying and dead cells that provokes a maladaptive inflammatory response from immune cells. Chronic inflammation is characteristic of aging, and is disruptive to tissue structure and function.
Body fat distribution in women changes as menopause progresses and estrogen levels decrease, causing the adipose tissue concentrated in the hips and thighs to gradually shift to the midsection as harmful visceral fat. This predisposes women to low-grade inflammation and cardiovascular diseases, which increase significantly after menopause. A study investigated the connection between health behaviours and low-grade inflammation. Health behaviours in this study include sleeping, eating and physical activity, and related disorders.
"In line with previous studies, a higher amount of visceral fat was, as expected, associated with low-grade inflammation. Visceral fat accumulated in the midsection secretes cytokines that increase inflammation, and this can increase the risk of metabolic diseases." The results show that those individuals who exhibit more disordered eating behaviour, as well as those who were physically less active, had more visceral fat, and thus the risk of low-grade inflammation was also higher. When eating and physical activity behaviours were examined together, higher physical activity was associated with lower visceral fat, especially in those women who did not display disordered eating behaviour.
XBP1 to Upregulate the Unfolded Protein Response Reduces Pathology in Mouse Models of Alzheimer's Disease
https://www.fightaging.org/archives/2025/03/xbp1-to-upregulate-the-unfolded-protein-response-reduces-pathology-in-mouse-models-of-alzheimers-disease/
Overexpression of the transcription factor XBP1 has been shown to extend life in flies. It is thought to achieve this outcome by increasing the efficiency of the unfolded protein response, a cell maintenance process. Its diverse other effects may also be important, as its regulation of transcription touches on immune function, lipid metabolism, glucose metabolism, and other mechanisms. This extensive portfolio of influences is often the case for transcription factors. Here, researchers apply brain-specific XBP1 overexpression to mouse models of Alzheimer's disease, and observe a reduction in pathology.
The decay of the proteostasis network has been pointed out as a primary hallmark of aging, a phenomenon that may contribute to Alzheimer's disease (AD) pathogenesis. Strategies to improve proteostasis have been tested in multiple models of neurodegenerative diseases, observing outstanding protective effects. One of the central nodes of the proteostasis network altered during aging involves the function of the endoplasmic reticulum (ER), the main site for protein production in the cell. The ER is also highly altered in AD. To cope with ER stress, cells activate an evolutionarily conserved pathway known as the unfolded protein response (UPR), which aims to re-establish proteostasis. The UPR reinforces many processes involved in the function of the secretory pathway to improve protein production and sustain cell function, whereas chronic ER stress results in neurodegeneration and cell death.
The most conserved UPR signaling branch is initiated by the ER stress sensor IRE1, which catalyzes the unconventional splicing of the mRNA encoding XBP1. This event results in the expression of an active transcription factor, termed XBP1s, which enables transcriptional reprogramming. We recently reported that the activity of the IRE1/XBP1 pathway declines in the brain during normal aging in mammals and strategies to enhance the activity of the UPR extend brain healthspan. Importantly, we showed that strategies to express XBP1s in neurons either using transgenic mice or gene therapy delayed synaptic dysfunction and cognitive decline during normal aging, in addition to reducing the content of senescence cells in the brain.
With the idea of testing the effects of artificially enforcing UPR adaptive responses in the AD brain, we overexpressed the active XBP1s form in the nervous system using transgenic mice, in addition to the hippocampus using adeno-associated viral (AAV) vectors. Overexpression of XBP1s dramatically reduced the content of amyloid plaques in the brain and improved cognitive performance and synaptic plasticity in a model of familial AD (5xFAD transgenic animals expressing mutant APP and presenilin-1). Additionally, XBP1s overexpression in the brain improved memory performance on a model of sporadic AD based on the injection of amyloid β oligomers. The beneficial effects of XBP1s expression in the context of experimental AD and normal aging involve a substantial correction of gene expression patterns associated with synaptic function, neuronal morphology, and connectivity. Thus, we speculate that a major protective mechanism of XBP1s in AD relates to its function as a regulator of neuronal physiology that may parallel its effects in reducing amyloid deposition.
Inducing a Torpor-Like State in Mice Slows Aging
https://www.fightaging.org/archives/2025/03/inducing-a-torpor-like-state-in-mice-slows-aging/
Torpor is characteristic of hibernating mammals, involving reduced body temperature and slowed metabolism. Researchers have discovered a way to induce this state in mice, and demonstrate that implementing a schedule of intermittent repeated periods of torpor produces an extension of healthspan. This ties in to an established literature on the relationships between metabolic rate, body temperature, and lifespan in mammals, in that one would expect reduced body temperature to produce a modest slowing of aging.
Torpor is a state of profoundly decreased metabolic rate, driving a decrease in core body temperature that can last from hours to days, whereas hibernation is a seasonal behavior comprising multiple bouts of torpor interrupted by periodic arousals to euthermia. These extraordinary adaptations raise many unanswered fundamental questions of homeotherm biology, one of the most compelling being the link between torpor and longevity. Natural torpor is characterized by tightly coupled, extreme physiological changes that have been individually implicated in aging and longevity, such as decreased core body temperature and metabolic rate, and caloric restriction. Indeed, hibernating species exhibiting long torpor bouts show extended longevity compared to closely related non-hibernators and longer lifespan than would be expected based on body mass alone.
Here we demonstrate that the activity of a spatially defined neuronal population in the preoptic area, which has previously been identified as a torpor-regulating brain region, is sufficient to induce a torpor-like state (TLS) in mice. Prolonged induction of TLS slows epigenetic aging across multiple tissues and improves healthspan. We isolate the effects of decreased metabolic rate, long-term caloric restriction, and decreased core body temperature on blood epigenetic aging and find that the decelerating effect of the TLS on aging is mediated by decreased body temperature. Taken together, our findings provide novel mechanistic insight into the decelerating effects of torpor and hibernation on aging and support the growing body of evidence that body temperature is an important mediator of the aging processes.
Differences in the Gut Microbiome and Immune Function in Male versus Female Centenarians
https://www.fightaging.org/archives/2025/03/differences-in-the-gut-microbiome-and-immune-function-in-male-versus-female-centenarians/
Why are there more female than male centenarians? The difference in life expectancy between men and women is well known and well explored. The long list of potential causative mechanisms all come with supportive evidence, but are incompletely understood at the detail level. In particular it remains unclear as to the relative importance of each these contributing factors versus all of the others. Here, researchers focus on differences in immune function and the composition of the gut microbiome in extremely old individuals. These are connected items, as the immune system gardens the gut microbiome by removing potentially problematic microbes, while those problematic microbes can induce chronic inflammation and dysfunction in the immune system.
Extreme longevity, particularly reaching the age of 100 years, is an exceptionally rare trait in the human population, exhibiting significant variations in prevalence between genders. Women generally exhibit greater survival rates than men across all age groups, including centenarians, with the gender gap in life expectancy ranging from 4.2 to 6.2 years. Genetic factors and immune responses play a crucial role in achieving longevity; however, there is limited information regarding the mechanisms that regulate the differences in biological aging between men and women.
A strong immune system is a key factor in determining lifespan, and sex plays an important role in its composition and activity. The sex-based diversity in immunity between males and females is regulated by several mechanisms, including X chromosome inactivation, mosaicism, skewing, and dimorphism in the expression of X chromosome-encoded genes, as well as regulatory genes on the Y chromosome. Generally, women exhibit stronger innate and adaptive immune responses than men.
An additional factor that may contribute to gender differences in the immune system is the gut microbiota. Composition of gut microbiota varies between males and females providing sex-specific differences in immune responses. Notably, it has been demonstrated that the ratio of bacterial cells to human cells differs between males and females, with a ratio of approximately 1.3:1 for males and 2.2:1 for females. However, the mechanisms by which the gut microbiome contributes to conditions conducive to successful aging remain unclear. Consequently, future research should prioritize investigating the causal relationship between sexually dimorphic immunity and the microbiota.
Larger Volume White Matter Hyperintensities Correlate with Cognitive Decline
https://www.fightaging.org/archives/2025/03/larger-volume-white-matter-hyperintensities-correlate-with-cognitive-decline/
White matter hyperintensities are small volumes of damage and scarring in the white matter of the brain, named for the way they appear in MRI images of brain tissue. They can be caused by rupture of small blood vessels, but also by any other localized cause of cell death and inflammation. Greater numbers of white matter hyperintensitives are generally indicative of a higher risk of neurodegenerative conditions and cognitive decline. Interestingly, researchers here note that the correlation with cognitive decline only exists for larger white matter hyperintensities.
The association between white matter integrity and adverse brain health outcomes is well-established. Increased white matter lesion burden has consistently been linked to higher risk of stroke, cognitive impairment, dementia, and mortality in cross-sectional and longitudinal studies involving diverse patient populations and healthy older adult cohorts.
This study investigates the relationship between white matter hyperintensities (WMHs) and longitudinal cognitive decline in older adults. Using data from The Irish Longitudinal Study on Ageing (TILDA), we examined WMH characteristics, including volume, location, and microstructural integrity, in a community-dwelling population of 497 individuals over a six-year period. WMHs were categorised into phenotypes based on their size, fractional anisotropy (FA), and mean diffusivity (MD), with subtypes for periventricular and deep white matter lesions. We hypothesised that larger, microstructurally compromised lesions would be associated with accelerated cognitive decline.
We isolated 11,933 WMHs, with an average of 24 WMHs per individual. Of these lesions, 6,056 (51%) were classified as Low Volume - High FA, 3193 (27%) were classified as Low Volume - Low FA and 2684 (22%) were classified as High Volume, Low FA. Our findings demonstrate that high-volume, low FA deep and periventricular lesions were significantly linked to cognitive decline, whereas small periventricular lesions with near normal microstructural properties do not predict cognitive decline. These results suggest that distinct WMH phenotypes may serve as markers for differential risks of cognitive impairment, providing potential targets for early intervention in at-risk populations.
The Interactions Between Aging, Circadian Rhythm, and Cancer Risk
https://www.fightaging.org/archives/2025/03/the-interactions-between-aging-circadian-rhythm-and-cancer-risk/
This open access review paper outlines what is known of the way in which aging, circadian rhythm, and cancer risk interact with one another. Cancer is a well known as an age-related disease; among other contributing mechanisms, the mutation burden in somatic cells increases with age, while the surveillance conducted by the immune system, intended to destroy cancerous cells long before they form a tumor, declines with age. Separately, circadian rhythm regulation also becomes dysfunctional with advancing age, though the causative mechanisms in this case are little understood in comparison to what is known of the causes of cancer. Lastly, circadian rhythm interacts with cancer risk in potentially complex ways, again an area in which more research is needed before we might be able to say it is well understood.
Cancer, circadian rhythms, and aging are three biological processes closely associated with health and disease. While they may appear to be independent, increasing evidence suggests that there are complex interactions among them. The relationship between aging and cancer is very clear. Aging remains to represent the foremost risk factor across various cancer types, correlating with an elevated incidence of cancer that typically reaches its peak around the age of 85 years. On the mechanism, aging and cancer share many common hallmarks, including genomic instability, epigenetic alterations, chronic inflammation, cellular senescence, and so on, which serve as intermediaries between aging and cancer.
Circadian rhythms are 24-hour cycles that govern a range of physiological processes in living organisms, such as sleep-wake cycles, hormone release, metabolism, and cell proliferation. Disruption of circadian rhythms has also been shown to contribute importantly to the development and progression of cancers, although the exact mechanisms are not yet fully understood. Mechanistically, circadian rhythm proteins exhibit physical interactions with molecules implicated in cancer-related pathways, thus exerting influence over cancer initiation and progression.
Furthermore, there also exist complex and multifaceted relationships between aging and circadian rhythms. On the one hand, the aging process reduces the resilience of circadian rhythms, resulting in disrupted sleep-wake cycles, a diminished ability to synchronize circadian rhythms in peripheral tissues, and changes in the molecular functioning of circadian clock outputs. On the other hand, circadian rhythm dysfunction can accelerate the aging process by compromising essential bodily functions. These disruptions lead to increased oxidative stress, which refers to cellular damage caused by an imbalance between the production of reactive oxygen species (ROS) and the cell's ability to neutralize them. This imbalance of ROS can lead to DNA damage, protein denaturation, and lipid peroxidation, ultimately contributing to inflammation and the development of age-related health issues
Cardiometabolic Index Correlates with Accelerated Biological Age
https://www.fightaging.org/archives/2025/03/cardiometabolic-index-correlates-with-accelerated-biological-age/
The research community is steadily accumulating data on the relationship between aging clocks to assess biological age and existing measures of disease and dysfunction. For example, cardiometabolic index is a combined measure of obesity and lipid metabolism dysfunction, and associated with age-related metabolic diseases and consequent mortality. We should expect a good approach to assessing biological age to tend to produce higher biological ages in patients with a higher cardiometabolic index, and researchers here show that this is the case for the Klemera and Doubal aging clock.
The cardiometabolic index (CMI) combines clinical measures of triglycerides, high-density lipoprotein cholesterol, and waist-height ratio. CMI has been related to several metabolic disorders, including diabetes mellitus, atherosclerosis, ischemic stroke, and hypertension. Several studies have investigated the clinical significance of CMI in metabolic disorders, and more significant increases in CMI over time were significantly associated with a greater risk for subsequent cardiovascular events.
Cross-sectional data were obtained from participants with comprehensive CMI and biological age data in the National Health and Nutrition Examination Survey from 2011 to 2018. Biological age acceleration (BioAgeAccel) is calculated as the differences between biological age (determined via the Klemera and Doubal method) and chronological age. Weighted multivariable regression, sensitivity analysis, and smoothing curve fitting were performed to explore the independent association between CMI and the acceleration of biological age. Subgroup and interaction analyses were performed to investigate whether this association was consistent across populations.
In 4,282 subjects ≥ 20 years of age, there was a positive relationship between CMI and biological age. The BioAgeAccel increased 1.16 years for each unit CMI increase, and increased 0.99 years for per standard deviation increase in CMI. Participants in the highest CMI quartile had a BioAgeAccel that was 2.49 years higher than participants in the lowest CMI quartile. In stratified studies, the positive correlation between CMI and biological age acceleration was not consistent across strata. This positive correlation was stronger in female, diabetic patients, and non-hypertensive populations.
Worse Cardiovascular Health Correlates with Raised Biomarkers of Neurodegeneration
https://www.fightaging.org/archives/2025/03/worse-cardiovascular-health-correlates-with-raised-biomarkers-of-neurodegeneration/
At this point it is well established that cardiovascular aging correlates with neurodegenerative disease. Even setting aside the point that varied age-related diseases arise from common forms of underlying damage and so tend to loosely correlate with one another, we should note that the brain has high energy requirements. Any sustained reduction in the delivery of oxygen and nutrients to brain tissue via cerebral blood flow, resulting from loss of capillary density, other aspects of cerebral small vessel disease, and heart failure, for example, will contribute to existing issues. Researchers here add to the existing evidence, demonstrating that measures of cardiovascular health correlate with increased levels of established biomarkers of neurodegeneration.
The American Heart Association developed a 7-item tool, Life's Simple 7, to promote cardiovascular health (CVH) in the general population. Life's Simple 7 comprises lifestyle and vascular risk factors, including not smoking; maintaining a normal body mass index (BMI); engaging in regular physical activity; consuming a healthy diet; and managing dyslipidemia, diabetes, and hypertension. An optimal CVH characterized by a higher Life's Simple 7 score is associated with a reduced risk of cardiovascular disease (CVD).
Cardiovascular health (CVH) has been associated with a low risk of Alzheimer disease and less vascular dementia. However, the association between CVH and biomarkers of neurodegeneration remains less understood. This study investigate the association of CVH, assessed by Life's Simple 7 score, with serum biomarkers of neurodegeneration, including neurofilament light chain (NfL) and total tau (t-tau). This cohort study was conducted within the Chicago Health and Aging Project (CHAP) of adults aged 65 years or older between 1993 and 2012. Participants who had measured serum NfL and t-tau levels and data on all components of the CVH score were included.
A total of 1,018 CHAP participants were included in the analysis (mean age, 73.1 ± 6.1 years). Compared with participants with low CVH scores (0-6 points), those with high CVH scores (10-14 points) had significantly lower serum levels of NfL (relative difference, -18.9%). A higher CVH score was associated with a slower annual increase in NfL levels as participants aged (relative difference in rate, -1.7%). Cardiovascular health was not associated with serum levels of t-tau. These findings suggest that promoting CVH in older adults may help alleviate the burden of neurodegenerative diseases.
High Neutrophil to Lymphocyte Ratio as a Predictor of Muscle Loss
https://www.fightaging.org/archives/2025/03/high-neutrophil-to-lymphocyte-ratio-as-a-predictor-of-muscle-loss/
Greater numbers of the innate immune cells known as neutrophils are characteristic of inflammation, whether transient or chronic. A complete blood count of different immune cell populations in circulation can be used to derive the neutrophil to lymphocyte ratio, and this can be used as a measure of chronic inflammation in older individuals. While there is a lot of variety from individual to individual, on balance either significantly more neutrophils than the average (common) or significantly fewer lymphocytes than the average (uncommon) indicates a worse prognosis for health in the years ahead. Chronic inflammation is disruptive to tissue structure and function, and drives the onset and progression of all of the major age-related conditions, including the progressive loss of muscle mass leading to sarcopenia. Thus one might expect to see correlations like the one noted here, between pace of muscle loss and neutrophil to lymphocyte ratio in older individuals.
Inflammation plays a pivotal role in the age-related decline of skeletal muscle mass, leading to sarcopenia in the elderly. The prevalence of sarcopenia notably increases among males aged ≥ 70. However, it remains unclear whether inflammatory indexes are associated with the reduction in skeletal muscle mass in the elderly population. Thirty-one males aged ≥ 70, without severe diseases or dementia, were enrolled in the study. They underwent muscle mass measurements, physical measurements, and hematological tests at the onset of the study and after a one-year follow-up.
Twenty-eight participants were successfully followed for one year. Appendicular skeletal muscle mass index (ASMI) decreased by 3.30 ± 2.41% in 14 participants and increased by 2.66 ± 1.61% in the other 14 participants compared to baseline levels. The baseline neutrophil-to-lymphocyte ratio (NLR) was 2.14 ± 0.56 in the ASMI-decreased group and 1.66 ± 0.62 in the ASMI-increased group. A statistically significant negative correlation was found between baseline NLR and the change in ASMI in linear regression analyses. NLR emerged as a potential prognostic marker for ASMI reduction in elderly males. However, further studies are necessary to assess its clinical utility.
The Finnish Twin Cohort's Odd Results for the Effects of Exercise on Mortality
https://www.fightaging.org/archives/2025/03/the-finnish-twin-cohorts-odd-results-for-the-effects-of-exercise-on-mortality/
You might recall that the Horvath epigenetic clock did not exhibit differences in biological age when comparing twins, given one twin that is sedentary versus one twin that is active. I blamed that on the epigenetic clock at the time, and it is certainly true that these clocks do exhibit quirks. The results noted here exonerate the Horvath clock and focus instead on the study population itself, however. The observed long-term relationship between exercise and mortality in this group is not what one would expect given the dose-response curve for exercise that has been established by many other, larger epidemiological studies.
Researchers investigated the links between long-term leisure-time physical activity and mortality, as well as whether physical activity can mitigate the increased risk of mortality due to genetic predisposition to diseases. Moreover, they examined the relationship between physical activity and later biological aging. The study included 22,750 Finnish twins born before 1958 whose leisure-time physical activity was assessed in 1975, 1981 and 1990. Mortality follow-up continued until the end of 2020.
Four distinct sub-groups were identified from the data, which was based on leisure-time physical activity over the 15-year follow-up: sedentary, moderately active, active and highly active groups. When the differences in mortality between the groups were examined at the 30-year follow-up, it was found that the greatest benefit - a 7% lower risk of mortality - was achieved between the sedentary and moderately active groups. A higher level of physical activity brought no additional benefit. When mortality was examined separately in the short and long term, a clear association was found in the short-term: the higher the level of physical activity, the lower the mortality risk. In the long term, however, those who were highly active did not differ from those who were sedentary in terms of mortality.
The researchers also investigated whether following the World Health Organization's physical activity guidelines affects mortality and genetic disease risk. The guidelines suggest 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous activity weekly. The study found that meeting these guidelines did not lower mortality risk or alter genetic disease risk. Even for twins who met the recommended levels of PA over a 15-year period, no statistically significant difference in mortality rates was found compared to their less active twin pair.
View the full article at FightAging
