Longevity Papers

An in-depth understanding of the molecular processes composing aging is crucial to develop therapeutic approaches that decrease aging as a key risk factor for cognitive decline. Herein, we present a spatio-temporal brain atlas (15 different regions) of microRNA expression across the mouse lifespan (7 time points) and two aging interventions. MicroRNAs are promising therapeutic targets, as they silence genes by complementary base-pair binding of messenger RNAs and mediate aging speed. We first established sex- and brain-region-specific microRNA expression patterns in young adult samples. Then we focused on sex-dependent and independent brain-region-specific microRNA expression changes during aging. We identified three sex-independent brain aging microRNAs (miR-146a-5p, miR-155-5p, and miR-5100). For miR-155-5p, we showed that these expression changes are driven by aging microglia and target mTOR signaling pathway components and other cellular communication pathways. In this work, we identify strong sex-brain-region-specific aging microRNAs and microglial miR-155-5p as a promising therapeutic target.

Despite calls for the development of consensus methods, most analyses of shotgun metagenomics data for microbiome studies use a single taxonomic classifier. In this study, we compare inferences from two broadly used classifiers, MetaPhlAn4 (marker-gene-based) and Kraken2 (k-mer-based), applied to stool metagenomic samples from participants in the Integrative Longevity Omics study to measure associations of taxonomic diversity and relative abundance with age, replicating analyses in an independent cohort. We also introduce consensus and meta-analytic approaches to compare and integrate results from multiple classifiers. While many results are consistent across the two classifiers, we find classifier-specific inferences that would be lost when using one classifier alone. When using a correlated meta-analysis approach across classifiers, differential abundance analysis captures more age-associated taxa, including 17 taxa robustly age-associated across cohorts. This study emphasizes the value of employing multiple classifiers and recommends novel approaches that facilitate the integration of results from multiple methodologies.

Immunosenescence dramatically reduces cancer vaccine efficacy in elderly patients, who represent the majority of cancer cases. Despite this clinical reality, age-related immune decline is rarely considered in preclinical testing. Therefore, novel in vitro models to test cancer vaccine efficacy, considering immunosenescence, are needed. Our novel lymph node paracortex on-a-chip (LNPoC) platform addresses this gap by recapitulating age-dependent immune responses against cancer vaccines, specifically antigen presentation, antigen-specific T cell activation, and antitumoral responses. Using this platform, we demonstrated that bone marrow-derived antigen-presenting cells (APCs) from young mice (6-7 weeks) displayed significantly enhanced ovalbumin (OVA) peptide presentation compared to APCs from older mice (35-36 weeks). This age-dependent difference translated to significantly greater OVA-specific CD8+ T cell activation and increased cytotoxicity against B16-OVA cancer cells. These age-dependent differences are unique to our LNPoC and undetectable in traditional 2D cultures, confirming that our LNPoC was more effective than 2D cultures at recapitulating immunosenescence-mediated immune responses against cancer vaccines in vitro. The in vivo validation confirms these findings, as young mice demonstrated higher OVA-specific CD8+ T cell responses and smaller tumors than older mice. Our LNPoC is a valuable tool for assessing immunosenescence\'s impact on cancer vaccines, potentially guiding more effective therapies for older adults.

Obesity and type 2 diabetes mellitus accelerate aging, shortening the duration of healthspan. Conversely, chronic calorie restriction (CR) extends healthspan. Research aimed at understanding the mechanism by which CR slows aging has focused heavily on insulin and downstream signaling cascades. Glucagon, a hormone that counter-regulates insulin, is commonly affected by these same interventions. To investigate the role of glucagon in aging we used dietary manipulation, global and liver- specific glucagon receptor knockout, and pharmacological glucagon receptor activation. We found that globally eliminating glucagon receptor signaling (Gcgr KO) decreases median lifespan by 35% in lean mice. These lifespan shortening effects are more robust in diet-induced obese mice (54%). Extending these findings to metabolic health, we found that glucagon receptor signaling is indispensable to the metabolic response to chronic CR in young and aged mice. While CR decreased liver fat, serum triglyceride, and serum cholesterol in WT mice, these metabolic benefits were absent in Gcgr KO mice. In line with these observations, we found that critical nutrient sensing pathways known to improve aging are dysregulated in mice lacking glucagon receptor signaling at the liver (Gcgrhep-/-). Liver-specific deletion of the glucagon receptor decreases hepatic AMP Kinase activation in aging mice, regardless of diet. Further, CR decreases hepatic mTOR activity in WT mice, but not in Gcgrhep-/- mice. Together, these findings propose that glucagon signaling plays a critical role in both normal aging and the lifespan and healthspan extension driven by caloric restriction.

A detailed understanding of aging biology and the development of anti-aging therapeutic strategies remain imperative yet inherently challenging due to the protracted nature of aging. Cellular senescence arises naturally through replicative exhaustion and is accelerated by clinical treatments or environmental stressors. The accumulation of senescent cells-defined by a loss of mitogenic potential, resistance to apoptosis, and acquisition of a pro-inflammatory secretory phenotype-has been implicated as a key driver of chronic disease, tissue degeneration, and organismal aging. Recent studies have highlighted the therapeutic promise of senolytic drugs, which selectively eliminate senescent cells. Compelling results from preclinical animal studies and ongoing clinical trials underscore this potential. However, the clinical translation of senolytics requires further pharmacological validation to refine selectivity, minimize toxicity, and determine optimal dosing. Equally important is the evaluation of senolytics' potential to restore tissue structure and function by reducing the senescent cell burden. In vitro tissue culture models offer a powerful platform to advance these efforts. This review summarizes the current landscape of

Cockayne Syndrome (CS) is a premature aging disorder caused by mutations in the CSA and CSB genes involved in DNA metabolism and other cellular processes. CS patients display many features including premature aging, neurodegeneration, and kidney abnormalities. Nicotinamide dinucleotide (NAD

Diversity Outbred (DO) mice are a powerful model system for mapping complex traits due to their high genetic diversity and mapping resolution. However, while there are extensive tools available for standard genetic analysis in DO mice, fewer techniques have been implemented to facilitate integrated, cross-study analysis. Here, we implement Haseman-Elston regression to estimate genetic correlations among 7,233 phenotypes measured across eleven independent DO mouse studies. We used this network of genetic correlations to cluster phenotypes according to shared genetics, which enhanced the power to detect quantitative trait loci (QTL). This approach empowered the detection of 884 QTL for 383 meta-phenotypes, explaining an average of 40.36% of the total genetic variance per mega-analysis. We leveraged this network for insights into specific areas of biology, including lifespan, frailty, immune composition, histological and functional lung phenotypes, and histological phenotypes of the aorta. We found the genetics of lifespan to share limited correlation with the genetics of frailty but stronger correlation with the genetics of immune cell composition. Additionally, mega-analyses driven by genetic correlations identified candidate genes (e.g. Cdkn2b) associated with degraded extracellular matrix in the aorta. Finally, an ensemble of genetic analyses implicated pulmonary neuroendocrine cell signaling and/or differentiation as a key driver of multiple lung pathophenotypes.

Background: Cardiovascular disease (CVD) is the leading cause of global mortality, with recent increases attributed to demographic shifts in age and rising rates of obesity. Diminished contractile reserve is a hallmark of a diseased heart; assessing contractile reserve is pivotal in prognosticating and monitoring CVD progression. The Frank-Starling mechanism and sympathetic stimulation are key to enhance contractile reserve but have not been explored in vivo in old and obese mouse models of CVD. This project aims to use speckle tracking echocardiography (STE) to characterize the function of the heart at baseline, with increased preload, and with sympathetic stimulation. We hypothesize that along with blunted systolic function, diastolic function, and contractility, old and obese mice will have a blunted contractile reserve. Methods: STE was obtained for control (4-month-old), aged (24-month-old), and obese mice (high fat diet-induced). Mice received an intravenous injection of 150L saline to increase preload to assess the Frank-Starling response, followed by injection of {beta}1adrenergic receptor agonist dobutamine to assess sympathetic response. Results: At baseline, aging and obese mice demonstrated blunted systolic, diastolic function, and contractility. Endocardial and epicardial wall displacement differed between aging and obese mice with contractile reserve, indicating that they have functionally distinct cardiac phenotypes. Conclusions: This study is the first to demonstrate blunted systolic function, diastolic function, and contractility through STE in aging and obese mice. Our novel method for investigating the contractile reserve of mice demonstrated aging and obese mice have dissimilar responses when assessing contractile reserve, which could contribute to their distinct functional phenotypes.

The transcriptional complex Mondo/Max-like, MML-1/MXL-2, acts as a convergent transcriptional regulatory output of multiple longevity pathways in Caenorhabditis elegans. These transcription factors coordinate nutrient sensing with carbohydrate and lipid metabolism across the evolutionary spectrum. While most studies have focused on the downstream outputs, little is known about the upstream inputs that regulate these transcription factors in a live organism. Here, we found that knockdown of various glucose metabolic enzymes decreases MML-1 localization in the nucleus and identified two hexokinase isozymes, hxk-1 and hxk-2, as the most vigorous regulators of MML-1 function. Upon hexokinase knockdown, MML-1 redistributes to mitochondria and lipid droplets (LD) and concomitantly, transcriptional targets are downregulated and germline longevity is abolished. Further, we found that hxk-1 regulates MML-1 through mitochondrial {beta}oxidation, while hxk-2 regulates MML-1 by modulating the pentose phosphate pathway (PPP) and its coordinated association with lipid droplets. Similarly, inhibition of the PPP rescues mammalian MondoA nuclear translocation and transcriptional function upon starvation. These studies reveal how metabolic signals and organellar communication regulate a key convergent metabolic transcription factor to promote longevity.

Aging leads to functional decline across tissues, often accompanied by profound changes in cellular composition and cell-intrinsic molecular states. However, a comprehensive catalog of how the population of individual cell types change with age and the associated epigenomic dynamics is lacking. Here, we constructed a single-cell chromatin accessibility atlas consisting of ~7 million cells from 21 tissue types spanning three age groups in both sexes. This dataset revealed 536 main cell types and 1,828 finer-grained subtypes, defined by unique chromatin accessibility landscapes at ~1.3 million cis-regulatory elements. We observed widespread remodeling of immune lineages, with increases in plasma cells and macrophages, and depletion of T and B cell progenitors. Additionally, non-immune cell populations, including kidney podocytes, ovary granulosa cells, muscle tenocytes and lung aerocytes, showed marked reductions with age. Meanwhile, many subtypes changed synchronously across multiple organs, underscoring the potential influence of systemic inflammatory signals or hormonal cues. At the molecular level, aging was marked by thousands of differentially accessible regions, with the most concordant changes shared across cell types linked to genes related to inflammation or development. Putative upstream factors, such as intrinsic shifts in transcription factor usages and extrinsic cytokine signatures, were identified. Notably, around 40% of aging-associated main cell types and subtypes showed sex-dependent differences, with tens of thousands of chromatin accessibility peaks altered exclusively in one sex. Together, these findings present a comprehensive framework of how aging reshapes the chromatin landscape and cellular composition across diverse tissues, offering a comprehensive resource for understanding the molecular and cellular programs underlying aging and supporting the exploration of targeted therapeutic strategies to address age-related dysfunction.

Growth differentiation factor 15 (GDF-15) levels are emerging as a candidate biomarker of aging. The present study aimed to: (1) characterize the association of GDF-15 with the continuum of arterial stiffening, assessed as carotid-femoral pulse wave velocity, as age increases; (2) determine the predictive role of serum GDF-15 levels on mortality; and (3) identify genetic determinants of serum GDF-15 levels.

This study investigated the impact of anti-aging protein α-Klotho on cardiometabolic diseases (CMDs) among middle-aged and elderly population. A total of 11,198 participants aged 40-79 years were included in the National Health and Nutrition Examination Survey (NHANES) spanning 2007-2016. Serum α-Klotho levels were quantified via enzyme-linked immunosorbent assays. CMDs comprised cardiovascular disease (CVD), and four metabolic disorders: type 2 diabetes (T2DM), obesity, chronic kidney disease (CKD), and non-alcoholic fatty liver disease (NAFLD). Weighted logistic regression analysis, subgroup analysis, mediation analysis, restricted cubic splines (RCS), and Cox proportional hazards regression analysis were used. α-Klotho exhibited negative associations with each single CMD except T2DM, and RCS showed U-shape and L-shape dose-response relationships of α-Klotho with risk of T2DM and CKD, respectively. Ordered logistic regression analysis revealed that higher levels of Klotho markedly reduced the cumulative number of metabolic comorbidities complicating CVD (OR 0.56 (0.35, 0.91)). Simple mediation analysis showed CKD may explain up to 20.42% of the association between Klotho and CVD. Notably, α-Klotho's association with cardiometabolic comorbidities was particularly evident among individuals who were widowed/divorced/separated, non-Hispanic Black, lower-income, or less educated, with hypertension, current smokers, lower leisure and commuting physical activity, but higher work-related physical activity. Regarding long-term effects, higher α-Klotho levels were associated with lower all-cause mortality among participants with CMDs, but not among those without CMDs. Higher α-Klotho levels were associated with lower CMD prevalence, particularly in high-risk cardiovascular populations with lower socioeconomic status and unfavorable lifestyles and reduced all-cause mortality risk among CMD patients.

Replicative senescence occurs in response to shortened telomeres and is triggered by ATM and TP53-mediated DNA damage signaling that blocks replication. hTERT lengthens telomeres, which is thought to block damage signaling and the onset of senescence. We find that normal diploid fibroblasts expressing hTERT mutants unable to maintain telomere length do not initiate DNA damage signaling and continue to replicate, despite having telomeres shorter than senescent cells. The TRF1 and TRF2 DNA binding proteins of the shelterin complex stabilize telomeres, and we find that expression of different mutant hTERT proteins decreases levels of the Siah1 E3 ubiquitin ligase that targets TRF2 to the proteasome, by increasing levels of the CDC20 and FBXO5 E3 ligases that target Siah1. This restores the TRF2:TRF1 ratio to block the activation of ATM and subsequent activation of TP53 that is usually associated with DNA damage-induced senescence signaling. All hTERT variants reduce DNA damage signaling, and this occurs concomitantly with telomeres assuming a more compact, denser conformation than senescent cells as measured by super-resolution microscopy. This indicates that hTERT variants induce TRF2-mediated telomere compaction that is independent of telomere length, and it plays a dominant role in regulating the DNA damage signaling that induces senescence and blocks replication of human fibroblasts. These observations support the idea that very short telomeres often seen in cancer cells may fail to induce senescence due to selective stabilization of components of the shelterin complex, increasing telomere density, rather than maintaining telomere length via the reverse transcriptase activity of hTERT.

By dissecting metabolic and epigenetic features imposed by ageing in cardiomyocyte conversion from fetal and adult mouse fibroblasts, Santos et al. describe that metabolic modulation can enhance direct cardiac reprogramming.

DNA damage is a serious threat to cellular viability, and it is implicated as the major cause of normal ageing. Hence, targeting DNA damage therapeutically may counteract age-related cellular dysfunction and disease, such as neurodegenerative conditions and cancer. Identifying novel DNA repair mechanisms therefore reveals new therapeutic interventions for multiple human diseases. In neurons, non-homologous end-joining (NHEJ) is the only mechanism available to repair double-stranded DNA breaks (DSB), which is much more error prone than other DNA repair processes. However, there are no therapeutic interventions to enhance DNA repair in diseases affecting neurons. NHEJ is also a useful target for DNA repair-based cancer therapies to selectively kill tumour cells. Protein disulphide isomerase (PDI) participates in many diseases, but its roles in these conditions remain poorly defined. PDI exhibits both chaperone and redox-dependent oxidoreductase activity, and while primarily localised in the endoplasmic reticulum it has also been detected in other cellular locations. We describe here a novel role for PDI in DSB repair following at least two types of DNA damage. PDI functions in NHEJ, and following DNA damage, it relocates to the nucleus, where it co-localises with critical DSB repair proteins at DNA damage foci. A redox-inactive mutant of PDI lacking its two active site cysteine residues was not protective, however. Hence, the redox activity of PDI mediates DNA repair, highlighting these cysteines as targets for therapeutic intervention. The therapeutic potential of PDI was also confirmed by its protective activity in a whole organism against DNA damage induced in vivo in zebrafish. Hence, harnessing the redox function of PDI has potential as a novel therapeutic target against DSB DNA damage relevant to several human diseases.

Meiotic segregation errors in human oocytes are the leading cause of miscarriages and trisomic pregnancies and their frequency increases exponentially for women in their thirties. One factor that contributes to increased segregation errors in aging oocytes is premature loss of sister chromatid cohesion. However, the mechanisms underlying age-dependent deterioration of cohesion are not well-defined. Autophagy, a cellular degradation process critical for cellular homeostasis, is known to decline with age in various organisms and cell types. Here we quantify basal autophagy in Drosophila oocytes and use GAL4/UAS inducible knockdown to ask whether disruption of autophagy in prophase oocytes impacts the fidelity of chromosome segregation. We find that individual knockdown of autophagy proteins in Drosophila oocytes during meiotic prophase causes a significant increase in segregation errors. In addition, Atg8a knockdown in prophase oocytes leads to premature loss of arm cohesion and missegregation of recombinant homologs during meiosis I. Using an oocyte aging paradigm that we have previously described, we show that basal autophagy decreases significantly when Drosophila oocytes undergo aging. Our data support the model that a decline in autophagy during oocyte aging contributes to premature loss of meiotic cohesion and segregation errors.

Brain entropy (BEN), a measure of the complexity and irregularity of neural has emerged as a promising marker for cognitive and clinical traits. However, normative lifespan trajectories of BEN remain underexplored. In this study, we investigated age-related changes in BEN across the human lifespan using Sample Entropy (SampEn). BEN was estimated from resting-state fMRI data collected from multiple Human Connectome Project cohorts (N = 2,415, ages 8-89 years), and normative growth curves were modeled using the GAMLSS framework. Results revealed a nonlinear increase in average BEN from childhood to older adulthood, with females exhibiting significantly higher BEN than males. Regional and network-level analyses confirmed similar age-related patterns.

Intrinsic capacity (IC) refers to physical and mental capacities that determine healthy aging. IC is the central element of the World Health Organization care pathway 'Integrated Care for Older People' (ICOPE). However, the operationalization of a composite IC measurement in clinical settings remains to be defined. We used screening data from ICOPE implementation in a real-life population of 27,706 adults 60 years or older that were users of primary care services to elaborate and cross-validate IC scores and centile values for men and women. Here, we show that IC centiles were cross-sectionally associated with comorbidity, frailty and limitations in both activities of daily living and instrumental activities of daily living. External validation using populations from high-income (French INSPIRE-T cohort) and upper-middle-income (ICOPE Brazil) countries validated the associations between IC centiles and clinical outcomes. The IC centiles developed using ICOPE screening data constitute a standardized parameter to monitor individual and population IC through a clinically friendly approach.

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DNA-protein crosslinks (DPCs) are toxic DNA lesions that block all DNA transactions including replication and transcription, and the consequences of impaired DNA-Protein Crosslink Repair (DPCR) are severe. At the cellular level, impaired DPCR leads to the formation of double strand breaks, genomic instability and cell death, while at the organismal level, it is associated with cancer, aging and neurodegeneration. Despite its importance, the mechanisms of DPCR at the organismal level are largely unknown. Proteases play a central role in DPCR, as they remove proteinaceous part of the DPCs, while the peptide remnant crosslinked to DNA is subsequently removed by other repair factors. We characterized the role of putative protease ACRC/GCNA (ACidic Repeat Containing/Germ Cell Nuclear Antigen) in DPCR at the organismal level. For this purpose, we have created new animal models with CRISPR/Cas system: two zebrafish lines with inactive Acrc. We were able to overcome the early embryonic lethality caused by Acrc inactivation by injecting Acrc-WT mRNA and have created a viable animal model to study the role of Acrc in adult tissues. We identified histone H3, topoisomerases 1 and 2, Dnmt1, Parp1, Polr3a and Mcm2 as DPC substrates of Acrc. We have proven that Acrc is absolutely essential for vertebrate development, and that the mechanism behind it is DPC proteolysis.

Cell death mediated by the abnormal activation of autophagy has been observed in many neurodegenerative diseases. Dual leucine zipper kinase (DLK), a member of the mitogen-activated protein kinase cascade, plays a key role in regulating cellular autophagy and the progression of neurodegenerative diseases. However, its role in age-related hearing loss has not been reported. In this study, we found that DLK, phosphorylated c-Jun N-terminal kinase (p-JNK), and JNK3 expression increased in the cochleae of C57BL/6J mice during aging. The DLK/JNK pathway and autophagy are excessively activated in the House Ear Institute-Organ of Corti 1 (HEI-OC1) senescent hair cell line. After DLK was upregulated in HEI-OC1 cells, autophagy was activated, and cell aging was initiated. Inhibiting the DLK/JNK pathway in senescent HEI-OC1 cells can reduce autophagy activation and senescence, and inhibiting autophagy activation can also alleviate senescence. The inhibition of DLK or JNK3 in vivo significantly reduced age-related cochlear structural damage and hearing loss in C57BL/6J mice. The results of the present study showed that DLK/JNK3 may play a key role in cochlear hair cell senescence and age-related hearing loss through the abnormal activation of autophagy within cochlear hair cells, suggesting that DLK or JNK3 may be potential targets for alleviating age-related hearing loss.

Recent improvements in human longevity have highlighted the challenge of maintaining health throughout extended lifespans. This review examines how organisms regulate nutrient intake and metabolism, focusing on dietary protein's unique role in health and longevity. While caloric restriction enhances longevity, adherence to a low-calorie diet is challenging. Protein restriction represents an alternate nutritional intervention that improves longevity and health in model organisms and may be easier to translate to humans. However, its impacts are complex, and its mechanisms are poorly understood. The beneficial effects of protein restriction on metabolism and longevity may come at a cost to lean mass and physical resilience. Conversely, while public health recommendations often emphasize high protein intake, human epidemiological data and work on model organisms suggest that excessive protein consumption correlates with increased mortality. Understanding this paradox is crucial for developing evidence-based protein intake recommendations that balance longevity with physical performance.

Proper regulation of inflammatory responses is essential for organismal health. Dysregulation can lead to accelerated development of the diseases of aging and the aging process itself. Here, we identify a novel enzymatic activity of the mitochondrial sirtuin SIRT4 as a lysine deitaconylase that regulates macrophage inflammatory responses. Itaconate is a metabolite abundantly produced in activated macrophages. We find it forms a protein modification called lysine itaconylation. Using biochemical and proteomics approaches, we demonstrate that SIRT4 efficiently removes this modification from target proteins both in vitro and in vivo. In macrophages, elevated protein itaconylation increases upon LPS stimulation, coinciding with elevated SIRT4 expression. SIRT4-deficient macrophages exhibit significantly increased IL-1{beta} production in response to LPS stimulation. This phenotype is intrinsic to macrophages, as demonstrated by both lentiviral over-expression and acute SIRT4 knockdown models. Mechanistically, we identify key enzymes in branched-chain amino acid (BCAA) metabolism as targets of hyperitaconylation in SIRT4-deficient macrophages. The BCKDH complex component dihydrolipoamide branched chain transacylase E2 (DBT) is hyperitaconylated and has reduced BCKDH activity in SIRT4KO macrophages. Physiologically, SIRT4-deficient mice exhibit significantly delayed wound healing, demonstrating a consequence of dysregulated macrophage function. Our data reveal a novel protein modification pathway in immune cells and establish SIRT4 as a critical regulator at the intersection of metabolism and inflammation. These findings have implications for understanding immune dysregulation in aging and metabolic disease.

Frailty is an underappreciated but modifiable clinical syndrome, but little about how air quality improvements could influence frailty progression is known. Here, we utilized two Chinese cohorts with repeated follow-up visits to address this knowledge gap and explored the underlying DNA methylation mechanisms. We first conducted a multistate modeling analysis in the Chinese Longitudinal Healthy Longevity Study (CLHLS), a nationwide cohort with 21,654 older adults who had participated in at least two survey waves. An interquartile range reduction in PM

Tests that can predict whether a drug is likely to extend mouse lifespan could speed up the search for anti-aging drugs. We have applied a machine learning algorithm, XGBoost regression, to seek sets of plasma metabolites that can discriminate control mice from mice treated with an anti-aging diet (caloric restriction) or any of four anti-aging drugs. When the model is trained on any four of these five interventions, it predicts significantly higher lifespan extension in mice exposed to the intervention which was not included in the training set. Plasma peptide data sets also succeed at this task. Models trained on drug-treated normal mice also discriminate long-lived mutant mice from their respective controls, and models trained on males can discriminate drug-treated from control females. Triglycerides are over-represented among the most influential features in the regression models. Triglycerides with longer fatty acid chains tend to be higher in the slow-aging mice, while triglycerides with shorter fatty acid chains tend to decrease. Plasma metabolite patterns may help to select the most promising anti-aging drugs in mice or in humans, and may give new leads into physiological and enzymatic targets relevant to discovery of new anti-aging drugs.

Age and APOE genotype are the strongest known risk factors for late-onset Alzheimer's disease (AD), but the mechanisms linking them to neuronal loss remain incompletely defined. Using multiomic data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), we propose a unified hypothesis in which two interdependent failure modes--saturation of microglial lipid flux capacity and disruption of the astrocyte--neuron lactate shuttle (ANLS) due to excess astrocytic membrane cholesterol--drive disease progression upstream of amyloid and tau pathology. Stratifying participants by cognitive score quartiles, we find consistent associations linking impaired lipid clearance, metabolic stress, and genetic variants regulating cholesterol handling. These processes appear to reinforce each other, resulting in accelerating neurodegeneration. Our hypothesis reframes AD as a systems-level collapse in metabolic coordination, rather than a purely linear pathological cascade. These insights emerged during the development of digital twin models for personalized interventions, highlighting the power of systems approaches to reveal hidden drivers of neurodegeneration.