Nature Aging

Summary Background People with Type 2 diabetes mellitus (T2DM) are at increased risk of developing dementia. Evidence suggests that thiazolidinediones (TZDs) may be protective for dementia onset including Alzheimer's disease and vascular dementia, compared to other second-line antidiabetic medications (SAMs). However, causality remains uncertain due to methodological limitations. We examined the effect of TZD on the risk of vascular dementia and all-cause dementia in T2DM, compared to other second-line treatments. Methods We emulated a pragmatic randomised trial using UK primary care data, Clinical Practice Research Datalink Aurum, between 2003 and 2023 to estimate the comparative effectiveness of initiating a TZD, dipeptidyl peptidase-4 (DPP-4) inhibitors, sodium-glucose cotransporter-2 (SGLT2) inhibitors, or sulfonylurea (SU) against incident dementia in T2DM adults on metformin therapy. Patients were followed for up to 5 years from 180 days after their first SAM prescription. We used overlap weighting to adjust for baseline confounding and fitted double robust Cox models to estimate adjusted hazard ratios (aHRs). Findings This study included 124,311 participants (mean age 63 years, 61% males, and 20% whites), of whom 595 developed vascular dementia and 1,678 developed all-cause dementia during follow-up. On top of metformin, 8,669 initiated TZD, 30,216 initiated DPP-4 inhibitors, 55,997 initiated SU and 29,429 initiated SGLT2 inhibitors. TZD were associated with a similar risk of vascular dementia compared with DPP-4 inhibitors (aHR 0.89;95% CI 0.36-2.23) and SU (0.58;0.24-1.42). SGLT2 inhibitors were associated with a lower risk of vascular dementia than TZD (0.29;0.09-0.94), DPP-4 inhibitors (0.25;0.10-0.64), and SU (0.17;0.07-0.40). Most patterns persisted in all-cause dementia: SGLT2 inhibitors vs DPP-4 inhibitors (0.51;0.26-0.99) and SGLT2 inhibitors vs SU (0.35;0.18-0.67), with no difference observed between SGLT2 inhibitors and TZDs. Interpretation Dementia risk was similar for TZDs, DPP-4 inhibitors and SUs but was significantly lower for SGLT2 inhibitors, a finding that warrants further investigation. Considering potential cognitive effects when selecting therapies for T2DM is important in an ageing population.

Pet dogs share human-like environments while aging on a compressed timescale, making them a powerful translational model for aging research. Using genomic and phenotypic data from 7,627 dogs in the Dog Aging Project, including 976 profiled for 159 blood metabolites and clinical analytes, we generated the first GWAS catalog in dogs. Blood traits map to orthologous loci in dogs and humans, indicating deeply conserved pathways. Breed ancestry explains substantial variance in blood traits, and selection on visible characteristics such as fur type has pleiotropic metabolic effects. Leveraging mosaic ancestry in mixed-breed dogs and longitudinal mortality data, we identify blood traits elevated in short-lived breeds that predict individual mortality risk -- including globulin and potassium -- and protective traits enriched in long-lived breeds, such as ethanolamine. Although some aging-associated traits relate to growth hormone pathways, many do not, indicating that aging in dogs is multifactorial. These findings establish dogs as a translational system for identifying genetic determinants and biomarkers of aging relevant to extending healthy lifespans.

Aging is characterized by changes in gut microbiome, metabolic imbalance and chronic inflammation, yet how these processes integrate to drive tissue degeneration remains poorly defined. Using age-related macular degeneration (AMD) as a model of tissue aging, we identify a diet-induced metabolic-immune axis that promotes systemic and retinal degeneration. In mice, a high-fat, cholesterol-enriched (HFC) diet induced perturbations in the gut structural integrity and microbiome repertoire, as well as systemic metabolic aging signatures, prominently marked by reduced circulating histidine. Plasma histidine levels were similarly decreased in AMD patients and inversely correlated with body mass index (BMI) in control donors. These diet-induced gut microbiome changes and subsequent metabolic alterations promoted peripheral innate immune reprogramming, with expansion of inflammatory neutrophils and monocytes that infiltrated the outer retina in a mouse model. Mechanistically, the gut-derived IGF1R/AKT2 signaling acts as a central regulator of global epigenetic remodeling and systemic immune aging under high-fat conditions in C. elegans. In a mouse model with an age-dependent dry AMD-like pathology, distinct retinal pigment epithelium (RPE) subpopulations exhibited downregulation of the histidine transporter SLC7A5, linking metabolic stress to activation of MIF/CD74-dependent inflammatory signaling between RPE and infiltrating immune cells. Histidine supplementation or AKT2 phospho-state modulation attenuated systemic immune activation and rescued retinal degeneration. These findings identify histidine-axis dysregulation as a mechanistic bridge between diet-induced microbiome changes, metabolic stress, immune aging, and retinal degeneration.

The circadian rhythm orchestrates gene expression and critical physiological processes but becomes disrupted with aging, contributing to disease. How this disruption interacts with cellular senescence--a key driver of aging pathology--remains poorly defined. We studied renal gene expression at four timepoints over 24hrs in 6- and 24-month-old genetically diverse UM-HET3 mice of both sexes and performed complementary analyses in synchronized fibroblasts sampled at seven timepoints. Aging dysregulated core clock relationships, including loss of the canonical anti-phase expression between Bmal1 and Per2. Senescence-associated genes were not static but exhibited pronounced oscillations, with senescence phenotypes varying by sex and time of day. Differential expression analysis revealed immune activation, metabolic rewiring, and epigenetic changes that were sex- and time-dependent. Variance analysis uncovered increased transcriptional noise in aging, particularly in circadian-regulated pathways such as RNA splicing, ribosome biogenesis, and TOR signaling. Single-nucleus RNA-Seq identified two cell populations lacking the normal Bmal1-Cdkn1a expression relationship: one senescent-like and another profibrotic, revealing distinct cell states linked to circadian dysregulation. Fibroblasts recapitulated key age-related circadian changes seen in the kidneys, including phase shifts in mTOR and oxidative phosphorylation. Together, this work demonstrates that senescence phenotypes are dynamic, sex-specific, and time-of-day dependent, and introduces a new framework for detecting senescent cells based on circadian gene relationships. These findings underscore the need to integrate temporal context into aging research and therapeutic strategies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=185 HEIGHT=200 SRC="FIGDIR/small/709919v1_ufig1.gif" ALT="Figure 1"> View larger version (86K): org.highwire.dtl.DTLVardef@ae008corg.highwire.dtl.DTLVardef@1a618eaorg.highwire.dtl.DTLVardef@1adcb4borg.highwire.dtl.DTLVardef@fdc268_HPS_FORMAT_FIGEXP M_FIG C_FIG

Aging is a complex multifactorial process that affects cellular function and tissue homeostasis over time. Despite extensive research, the molecular mechanisms driving cellular aging remain poorly understood1,2. Many studies have focused on changes in DNA methylation as an indicator of aging3. In particular, the degree of methylation at polycomb CpG islands has been shown to be predictive of phenotypic changes associated with aging4,5. Since many age-related pathological processes, are thought to be of single-cell origin (e.g. cancer), we questioned whether polycomb DNA methylation also occurs preferentially in a subset of cells within the overall population. Using single-cell whole-genome methylation data from multiple ages and tissues, we identify Average Polycomb CpG Methylation as a hallmark of cellular aging. This revealed that aging occurs at varying rates within specific cells, with faster proliferating cells showing accelerated levels. Gene expression analysis in "young" and "old" single cells identified changes in immune response, translation regulation, tumorigenesis, neurodegeneration and other cellular processes associated with aging. These results challenge traditional models of homogeneous cellular aging and suggest that aging itself is a highly individualized process at the single-cell level that may be driven by programmed changes in polycomb CpG island DNA methylation.

Using 30-second voice recordings from 7,081 adults aged 40-70, we trained gender-specific models to estimate voice-predicted age (Voice Age). Voice Age correlated with chronological age comparably to established omic and physiological aging clocks, while capturing an independent dimension of biological aging. Accelerated vocal aging showed association with higher adiposity, impaired sleep physiology, and cardiometabolic risk markers, supporting voice as a scalable, non-invasive functional aging biomarker.

Quantifying cellular age in vitro in a scalable and biologically meaningful manner is essential for the discovery of pharmacological interventions that modulate aging. We developed imAgeScore, a machine-learning model trained on high-content Cell Painting features to predict the phenotypic age of primary human dermal fibroblasts. imAgeScore correlates with chronological and DNA methylation-based age estimates and captures coordinated morphological changes across nuclear and cytoplasmic compartments. The model detected age acceleration during serial propagation and age reduction following partial reprogramming. Pharmacological interventions targeting distinct aging hallmarks induced predictable shifts in predicted age and enabled classification of damaging versus rejuvenating cellular states. Application of imAgeScore in an automated high-throughput screening pipeline identified candidate age-modulating compounds, revealed inter-individual variability in response magnitude, and detected additive rejuvenation effects in selected combinatorial treatments. Functional validation in a scratch wound assay confirmed enhanced cellular repair by leading candidates, supporting the biological relevance of morphology-derived age reduction. Together, these results demonstrate that image-based morphological profiling provides a scalable platform for quantifying cellular aging and screening for candidate rejuvenation interventions.

Reduction in the Indy (Im not dead yet) gene, a plasma membrane citrate transporter, in Drosophila and its homolog in worms extends lifespan by promoting metabolic homeostasis. Indy reduction delays the onset of aging-associated pathology in the fly midgut, including preservation of intestinal barrier integrity and intestinal stem cell homeostasis. Gut microbiota has broad impacts on host metabolism, health, and aging. Age-related dysbiosis impairs intestinal barrier function and drives mortality. However, the underlying mechanisms that link increased microbial load to frailty and negative effects on health remain mostly unclear. Here we show that Indy heterozygote flies have significantly lower bacterial load and increased diversity during aging compared to controls. However, the presence of the microbiome was not required for Indy lifespan extension, though removal of microbes did enhance the effects of Indy reduction on longevity, suggesting potential interactions between the microbiome and Indy. Indy down-regulation was linked to reduced expression of the JAK/STAT signaling ligands Upd3 and Upd2 in the midgut of young flies, which likely contributes to preserved intestinal stem cell homeostasis. Altogether, our results suggest that Indy reduction impacts microbiome load and composition, which preserves gut homeostasis and extends lifespan through impacts on JAK/STAT signaling pathway. Significance StatementIndy is a fly homologue of mammalian SLC13A5 (mSLC13A5) plasma membrane citrate transporter, a central metabolic regulator involved in health, longevity, and disease. Reduction of fly Indy gene activity preserves metabolic and intestinal stem cell homeostasis and extends longevity. Gut microbiota impacts host metabolism, health, and aging. Here we show that Indy reduction prevents age-associated increases in bacterial load and expression of the JAK/STAT signaling ligands Upd3, and Upd2, while maintaining microbiome diversity. These changes likely slow activation of epithelial cell turnover in the gut and contribute to downstream lifespan effects. As the role of INDY and microbiome are conserved across organisms, our study provides a framework to study underlying mechanisms of the effects of reduced Indy and the microbiome on health and longevity.

Dietary restriction extends lifespan across model organisms, but the plasma molecular changes mediating this effect remain incompletely characterized. We present a longitudinal multiomic analysis of 2,234 plasma samples from 960 Diversity Outbred mice subjected to intermittent fasting or caloric restriction and followed to natural death. Using mass spectrometry, we quantified 1,512 metabolites, lipids, and proteins and mapped their associations with diet, age and longevity. DR-induced molecular changes scale with caloric intake and modulate inflammatory, lipid catabolism, and oxidative stress pathways. Aging showed a biphasic signature with sharp acceleration beyond 85% of lifespan, demarcating terminal decline. Mediation and survival modeling both identified superoxide dismutase (SODE) and vascular cell adhesion molecule (VCAM1) as top lifespan predictors. Genetic analysis revealed 9,599 QTL, nine of which coincided with previously identified lifespan QTLs, and were largely related to immune regulation. These findings provide a rich multiomic and genetic resource for the aging research community.

Aging is a multifaceted process that occurs on the background of and is significantly driven by transcriptional changes. Aging-related transcriptional changes may include reduced transcription of maintenance, repair and DNA methylation genes, de-differentiation, or increased transcription of transposons. Unbiased detection of these changes and full understanding of their physiological effects requires single-cell resolution. We studied single-nuclei transcriptomes of a model microcrustacean Daphnia magna sampled from 3 age- and reproduction status groups: young, old reproductively senescent, and old, regaining reproductive function late in life. We detected 17 cell clusters, some identifiable as ovary or fat body-, midgut-, epithelium-, and neural tissue-related, some escaping unambiguous identification. We detect significant changes of cell type abundance with age and with reproductive "rejuvenation" in ovary- and gut-related clusters. We also detect several patterns of functional transcriptional differences between treatment groups with nearly all cell types, with changes between old reproductive and old non-reproductive Daphnia often reversing age-related changes.

Earlier menopause is a risk factor for several age-related diseases, including dementia. The biological pathways linking menopause timing to later-life brain aging are not understood. Leveraging large-scale plasma proteomics in postmenopausal women from the UK Biobank (N=15,012), earlier menopause was associated with upregulation of pro-inflammatory and extracellular matrix degradation pathways, plus accelerated aging across proteomic clocks of organ and cellular aging, including brain and oligodendrocyte aging. Elevated GDF15, a canonical aging marker, was the top protein correlate of earlier menopause. We observed robust replication of menopause timing proteomic shifts in the Womens Health Initiative Long Life Study (N=1,210). In UKB, proteins associated with earlier menopause, including GDF15, exhibited concordant associations with incident dementia risk and brain atrophy, cerebral small vessel disease burden, and white matter microstructural integrity. Collectively, our findings identify proteomic signatures linking ovarian aging to brain aging, providing a framework to inform interventions to reduce dementia risk.

Biological aging clocks are typically evaluated through competitive benchmarking, implicitly assuming that a single metric can sufficiently capture the complexities of aging1-6. Here, we tested an alternative hypothesis: that distinct clock types capture orthogonal dimensions of aging and therefore yield greater value when integrated. Using the Framingham Heart Study, we compared the immune-aging metric, IMM-AGE, with established DNA methylation clocks and found that integrated models consistently outperformed single-clock approaches. To investigate the basis of this complementarity, we derived IMMAGE-Epi, a 22-CpG methylation surrogate of IMM-AGE which exhibited minimal overlap with canonical epigenetic clock CpGs, suggesting that immune aging is associated with a distinct methylomic feature and pathway space rather than representing a reformulation of existing clock architectures. Together, our findings support an emerging multidimensional model of biological aging in which integrating orthogonal biological clocks may offer greater translational utility than competitive single-clock optimization.

Whether distinct visible aging traits, e.g., wrinkling, pigmentation, and inflammation, reflect shared or independent epigenetic programs remains unknown; existing clocks compress aging into a single chronological axis, leaving the phenotype-specific architecture of cutaneous aging uncharacterized. Here, we integrate AI-derived facial phenotypes with skin DNA methylation profiles from 706 individuals to develop EpiVision, a panel of 21 epigenetic predictors spanning structural, pigmentary, inflammatory, and textural aging traits. Predictors reveal shared and trait-specific pathways, including developmental patterning, epithelial remodeling, hormonal signaling, and UV damage responses, and capture environmentally induced acceleration in sun-exposed skin alongside lifestyle and topical treatment-associated variation. These findings establish that visible skin aging comprises molecularly distinct axes with shared regulatory substrates and trait-specific drivers, providing a scalable epigenetic framework for intervention evaluation and aging biology research.

Reduced insulin/IGF-1 signaling (IIS) can greatly extend lifespan in C. elegans. However, its effects on the duration of healthy life (healthspan) remain unclear, with several reports of either morbidity expansion or scaled effects, though none of morbidity compression. Moreover, life-extension by IIS reduction is particularly inter-individually variable within populations, confounding efforts to understand the intra-individual biology of such interventions. Here, we performed a longitudinal investigation at individual nematode resolution, of IIS reduction on aging-related health and lifespan, through temporally-controlled auxin-induced degradation (AID) of the DAF-2 insulin/IGF-1 receptor. Our results show how inter-individual variation in aging rate within control populations explains the complex demographic effects of age-specific DAF-2 AID on population lifespan. Strikingly, adult-limited IIS reduction causes an inter-individually homogeneous increase in lifespan (reducing Gompertz rather than {beta}) that is driven by healthspan expansion and compression of morbidity. Unexpectedly, cessation of DAF-2 AID in decrepit elderly individuals rejuvenates locomotory capacity and extends lifespan, showing that higher levels of IIS are optimal for health and survival towards the end of life. We also document a memory effect of transient IIS reduction during early adulthood, that is sufficient to fully extend lifespan (+189% median lifespan). Together, these findings demonstrate that both lifespan and healthspan can be maximized by appropriate temporal and directional modulation of IIS.

Alzheimers disease (AD) is characterized not only by tau and amyloid-{beta} aggregation but also by systemic disruptions in circadian rhythms, metabolism, and gut-brain communication that exacerbate neuroinflammation and neurodegeneration. While glial cells play central roles in inflammatory signaling and proteostasis, the contribution of the gut microbiome to glia-driven AD pathology remains poorly understood. Here, we used Drosophila models with glial-specific expressions of human tau and amyloid-associated transgenes to investigate how microbiome integrity influences disease progression. AD models exhibited significant shifts in gut microbial composition, particularly in Lactobacillus and Acetobacter species, suggesting an adaptive microbial response to pathological stress. Strikingly, microbiome depletion (axenic condition) markedly worsened behavioral and physiological outcomes, including disrupted sleep-circadian rhythms, impaired memory, and reduced locomotor function. These deficits were accompanied by amplified neuroinflammatory signaling (Upd-Dome-Hop-Stat92e axis), increased apoptotic gene expression, lipid dysregulation, and altered synaptic markers. Moreover, microbiome loss induced energy stress marked by elevated phospho-AMPK (p-AMPK), yet failed to restore proteostasis, as evidenced by accumulation of ubiquitinated proteins and the autophagy adaptor Ref2p, indicating impaired autophagic flux. This dysfunction correlated with increased tau, phospho-tau, and A{beta}42 accumulation. Together, our findings demonstrate that microbiome depletion exacerbates glial-mediated inflammation, disrupts circadian and metabolic homeostasis, impairs, and accelerates cognitive and motor decline. This work highlights a previously underappreciated role of the gut microbiome in restraining glial dysfunction and mitigating AD-like pathology, positioning microbial homeostasis as a critical modulator of neurodegenerative disease progression.

The role of the peripheral immune system in Alzheimers Disease (AD) remains insufficiently resolved, limiting the understanding of systemic disease effects and mechanisms. Here, we employed three high-resolution single-cell techniques, including flow cytometry, single-cell RNA- and ATAC-sequencing, to investigate peripheral immunity in AD dementia and earlier stages of the AD trajectory in over 100 patients. We identified reduced humoral immune responses in AD, characterized by a diminished B cell compartment displaying an impaired activation phenotype. Classical monocytes expanded in mild cognitive impairment and early AD dementia, acquiring a NF-kB/AP-1-mediated low-grade inflammation phenotype. Our findings link peripheral dysregulation in innate and adaptive immunity at cell frequency, transcriptional and epigenetic levels to the AD trajectory and provide insights into distinct phenotypes that define AD progression in contrast to healthy aging across cohorts.

Neuronal aging pace varies markedly between individuals, but what drives this variation remains unknown. Using cell-type-specific transcriptomic clocks applied to single-nucleus RNA sequencing data from 226 adults (ages 20-90), we quantified neuronal aging residuals as a donor-dominant phenotype. Variance decomposition revealed that microglial transcriptional programs predict inter-individual variation in neuronal aging residuals, a directional asymmetry consistent with a non-cell-autonomous relationship between microglial states and neuronal aging trajectories. This asymmetry is accompanied by an age-dependent shift from homeostatic to inflammatory microglial dominance beginning in midlife, with inflammatory dominance probability rising from 26% at age 35 to 92% by age 65, replicated in an independent cohort. IFN{gamma} signaling emerges as the dominant microglial program associated with accelerated neuronal aging in late adulthood. Candidate regulators of microglial IFN{gamma} activity (HIF1A, CEBPB, and EZH2) are computationally prioritized as intervention targets warranting functional validation.

Age-associated functional decline is partly driven by progressive chromatin degeneration. Maintenance of chromatin integrity preserves cell identity and promotes healthy aging, but through different mechanisms in proliferating and non-proliferating cells. However, specific mechanisms of chromatin maintenance and their compensatory capacity in proliferating and non-proliferating cells are undefined. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication-independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA-H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes, including cell identity genes. Partial hepatectomy, associated with induced proliferation, restores identity of HIRA knockout livers with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration and associated cell proliferation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/710643v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@a2a26aorg.highwire.dtl.DTLVardef@154e5aeorg.highwire.dtl.DTLVardef@b315a7org.highwire.dtl.DTLVardef@152bca4_HPS_FORMAT_FIGEXP M_FIG C_FIG

The postmenopausal ovary is commonly viewed as a passive organ, and its biology and cell composition remain incompletely characterized. Here, we generated a single-nucleus atlas of the aging postmenopausal human ovary comprising 439,011 nuclei across 64 ovarian samples from 28 donors. We resolved 37 fine cell states, revealing extensive stromal, vascular, and immune heterogeneity in the postmenopausal ovary. Aging was associated with stromal stress-state expansion, vascular and immune depletion, and enrichment of steroidogenic programs consistent with ovarian androgenization. Several major age-associated compositional shifts were supported in an independent GTEx ovary bulk RNA-seq cohort. Notably, the number of live births broadly opposed age-associated transcriptional and compositional remodeling. Together, our findings show that the postmenopausal ovary remains an actively remodeled aging tissue and that reproductive history leaves durable molecular and cellular imprints on ovarian aging.

Sleep disruption increases with age and is associated with adverse age-related outcomes, yet the molecular mechanisms linking these phenomena remain unclear. Here, through integrative analysis of human and mouse transcriptomic and proteomic datasets, we identify proteostasis-related pathways whose aging trajectories align with transcriptional responses to chronic sleep disruption across tissues and cell types. In the human prefrontal cortex, gene expression exhibits coherent age-associated directional shifts. Across human peripheral blood following sleep restriction and multiple aging mouse tissues and cell types, proteostasis pathways exhibit concordant downregulation. Among these, heat shock response pathways emerge as the most persistent and cross-modal signatures, with components of the heat shock factor 1 (HSF1)-mediated proteostasis network displaying diminished inducibility with age and chronic sleep insufficiency, in contrast to transient activation following short-term sleep deprivation. This attenuation is particularly pronounced in neurons, where age-associated suppression of HSF1 target programs indicates selective vulnerability of neuronal proteostasis. Spatial and single-cell analyses map this vulnerability to hippocampal circuits during aging and to superficial cortical layers and glutamatergic neurons in Alzheimers disease. These findings support a model in which repeated sleep disruption progressively reduces the inducible capacity of proteostatic stress responses, shifting from adaptive activation to progressive attenuation and accelerating age-related decline in proteome maintenance. Consistent with emerging functional evidence, this identifies HSF1-mediated proteostasis as an integrative axis linking sleep stability and molecular aging, suggesting a self-reinforcing relationship in which sleep disruption and proteostasis decline reciprocally exacerbate one another. These results connect transient molecular responses to sleep perturbations with long-term aging trajectories, revealing a systems-level mechanism through which cumulative sleep disruption may increase vulnerability during aging.