Aging

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare genetic condition characterized by features of accelerated aging, with a life expectancy of less than two decades. HGPS is commonly caused by a point mutation in the LMNA gene which codes for lamin A, a vital component of the nuclear lamina. The HGPS mutation activates a cryptic splice site and leads to production of a truncated, farnesylated form of lamin A referred to as "progerin." Progerin is also produced in small amounts in healthy individuals and has been implicated in normal aging. HGPS is associated with an accumulation of genomic DNA double-strand breaks (DSBs), and alterations in DSB repair. DSB repair in mammalian cells normally occurs by either homologous recombination (HR), an accurate, templated form of repair, or by DNA end-joining (EJ), a non-templated rejoining of DNA ends. EJ is error-prone, although a portion of EJ events occurs precisely with no alteration to joined sequences. Previously, we reported that over-expression of progerin increased EJ relative to HR and decreased the precision of EJ. In our current work, we designed a novel model experimental system using derivatives of thymidine kinase (tk)-deficient mouse fibroblasts and incorporating a loss-of-function assay to further explore progerins impact on EJ. We established cell lines containing an integrated copy of a functional herpes tk gene with an embedded recognition site for endonuclease I-SceI. We examined EJ at the nucleotide level following induction of a DSB within the tk gene by expression of I-SceI and subsequent selection for cells that lost tk gene function. Comparison of EJ products recovered from cells expressing progerin versus from cells not expressing progerin revealed that progerin expression provoked larger DNA deletions associated with DSB repair as well as recovery of multiple repair products from individual cells, suggesting progerin impedes re-joining of DNA ends.

Senescence human bone marrow mesenchymal stem cells (BMSCs), vulnerable to age-related defects, is poor in tissue regeneration. Cells in bone marrow accumulated senescent contributing to the development of metabolic energy regulation hold prospects for therapeutic advances. This study aimed to evaluate energy metabolic changes in male bone marrow mesenchymal stem cells senescence process. Our research established cell specific surface marker and enzymes expression level changes, as well as ECAR and OCR resonance. Notably, CD14, HLA-DRB1 and CD90 upregulated, glycolysis-related genes are increased, tricarboxylic acid cycle-related genes are decreased. We firstly identified links between time-dependent cell aging process and energy metabolism in BMSCs.

Recent epidemiological studies suggest poor hydration is a modifiable risk factor for aging-related chronic disease. We tested whether serum sodium was associated with accelerated biological aging. We analyzed data from 363,286 adults (18-80 years) from 20 years of electronic medical records from a large healthcare system, as well as 24,611 adults (18-80 years) from National Health and Nutrition Examination Survey (NHANES) continuous (1999-2018). Seven key biomarkers were used to calculate biological age (BA) using the Klemera and Doubal method. We then reran the calculation using only the four variables with highest correlation with age as a robustness check. In both models, there was a significant linear association between age adjusted serum sodium and advanced biological aging, especially in the young cohorts. In the 7-variable model, in the Leumit dataset, the males in the highest sodium level versus the lowest, had a biological age that was 0.88 (95% CI 0.68-1.08) years accelerated and for females 2.32 (2.14-2.51) years. In NHANES dataset biological age of males at the highest sodium level was 1.92 (0.98-2.87) years accelerated as compared to those in the lowest sodium group. For females, the largest difference was for those 41-50 (1 year, .30-1.79). Increased serum sodium in the normal range is associated with accelerated biological aging in the general population, especially among people aged 18-50. Intervention studies are needed to confirm the link between hydration and biological aging.

BackgroundDNA methylation-based biomarkers have enabled robust estimation of biological age across tissues, and longitudinally trained measures such as DunedinPACE provide estimates of the pace of aging from blood methylomes. However, longitudinal methylation data are often unavailable, particularly for minimally invasive tissues such as buccal mucosa. Here, we developed a pseudo-longitudinal framework to estimate a buccal mucosa-derived PACE-like aging-rate score from cross-sectional methylome data. MethodsWe used a buccal biological age estimator as an internal pseudo-time axis. Methylation beta-values were transformed to M-values, and CpG-specific smooth functions of biological age were fitted in cross-validation. Local derivatives of these functions were used to project each individuals buccal methylome forward by a small time step. The projected methylome was converted back to beta-values, biological age was recalculated, and the change in biological age per unit time was defined as a pseudo-aging velocity. This raw velocity was transformed to a non-negative PACE-like score centered at 1.0. We then trained cross-fitted models to predict the derived score from buccal CpG methylation profiles. ResultsIn 151 individuals, the proposed score was reproducibly predicted from buccal methylomes in out-of-fold analysis, with a Pearson correlation of 0.706 and Spearman correlation of 0.710 between observed and predicted PACE-like scores. Sensitivity analyses across CpG selection size and regression models showed broadly consistent performance. In contrast, the proposed buccal PACE-like score showed only modest association with measured DunedinPACE, and alternative attempts to reconstruct DunedinPACE from buccal methylomes, including supervised proxy modeling and buccal-to-blood CpG imputation, showed limited sample-level performance. ConclusionsThese results support the feasibility of deriving a tissue-specific PACE-like aging-rate score from cross-sectional buccal methylome data by treating biological age as a pseudo-time axis. The proposed score should not be interpreted as a replacement for blood-derived DunedinPACE, but rather as an exploratory buccal methylome dynamics index that may capture tissue-specific aging-related variation.

Accurate epigenetic age prediction from DNA methylation profiles is intrinsically high-dimensional, creating a need for parsimonious models that preserve predictive performance while reducing the number of assayed cytosine-phosphate-guanine (CpG) loci. This study introduces MOSurvivor, a population-based multi-objective search framework that jointly optimizes a weight-threshold CpG selector and eight XGBoost hyperparameters. Experiments used the GSE40279 whole-blood cohort (656 individuals profiled on the Illumina HumanMethylation450 platform). After retaining 1,000 age-correlated CpGs, five strategies were evaluated on the same 30 seeded 80:20 train/test splits: fixed-parameter XGBoost using all 1,000 CpGs, random search, a genetic algorithm, particle swarm optimization, and MOSurvivor. Internal fitness was estimated using three-fold cross-validation on each training set. Across the 30 held-out test sets, MOSurvivor achieved a mean absolute error (MAE) of 4.149 {+/-} 0.300 years, root mean squared error of 5.545 {+/-} 0.392 years, and R2 of 0.855{+/-} 0.027 while retaining 211.6 {+/-} 54.8 CpGs. Relative to full-feature XGBoost (MAE 4.095 {+/-} 0.285 years), MOSurvivor reduced the feature set by 78.8% at an MAE increase of only 0.054 years (1.3%). Paired Wilcoxon tests found no significant accuracy difference between MOSurvivor and any comparator (all unadjusted p > 0.05; all Holm-adjusted p [≥] 0.476). The most recurrent locus, cg16867657, appeared in 29 runs, whereas mean pairwise Jaccard similarity was 0.124, indicating a small stable core embedded in multiple near-equivalent feature subsets. MOSurvivor thus offers a competitive accuracy-parsimony trade-off rather than superior absolute accuracy. External validation and leakage-free nested feature preselection remain necessary before biological or clinical translation. Keywords: epigenetic clock, DNA methylation, feature selection, multi-objective optimization, XGBoost, metaheuristics, biological aging.

MicroRNAs (miRNAs) are small non-coding RNAs that play critical roles in regulating cellular senescence and aging. Our recent studies identified a conserved C. elegans miRNA cluster (miR-229/64/65/66) that is required for normal adult lifespan, with overexpression significantly extending longevity. Notably, cel-miR-229 is evolutionarily conserved in humans, with hsa-miR-425 sharing an identical seed sequence. Here, we investigated the role of miR-425 in mammalian cellular senescence. We found that miR-425 expression is markedly reduced in pharmacologically induced senescence in human lung cancer cells. Restoration of miR-425 expression attenuates senescence and suppresses the expression of senescence-associated secretory phenotype (SASP) cytokines following senescence induction. We further observed that miR-425 levels decline during replicative senescence, whereas stable overexpression in WI-38 fibroblasts delays senescence accumulation and preserves proliferative capacity. Mechanistically, miR-425 suppresses TGF-{beta} signaling, leading to reduced expression of the cyclin-dependent kinase inhibitor p21/CDKN1A and increased phosphorylation of the retinoblastoma (RB) protein, thereby promoting cell-cycle progression. We further identify PPP2CB, the catalytic subunit of protein phosphatase 2A (PP2A), as a direct target of miR-425. PPP2CB expression is downregulated in miR-425-5p overexpressing cells, even under senescence induction. Knockdown of PPP2CB using siRNA phenocopies the effects of miR-425 overexpression, reducing senescence, enhancing proliferative potential, and increasing RB phosphorylation. Collectively, our findings identify miR-425 as a conserved regulator of cellular senescence that acts through upregulation of RB phosphorylation. These results establish a novel miR-425-PPP2CB-RB regulatory axis controlling proliferation and senescence and suggest miR-425 as a potential therapeutic target for mitigating senescence to promote extended health span.

Cellular senescence contributes to the progression of many age related musculoskeletal diseases. Cellular senescence is a biological state that arises from replicative exhaustion and various cellular stressors, including elevated oxidative stress, mitochondrial dysfunction, mechanical overload, and chronic exposure to pro-inflammatory cytokines and proteases. Although senolytic agents show promise for eliminating senescent cells, their translation has been hindered by the lack of physiologically relevant and scalable in vitro screening methods. In the present study, we developed a standardized, physiologically relevant senescence-induction model and validated a metabolic activity assay as a rapid, scalable method for screening senolytic compounds. We used primary human intervertebral disc cells (IVD) as an example, but the workflow applies to many other cell types. To mimic inflammatory and oxidative stress, we used a combination of TLR-2 activation (Pam2CSK4) and tert-butyl hydroperoxide (tBHP), a potent ROS generator. Senescence induction was validated by quantifying {beta}-galactosidase fluorescence intensity, {beta}-gal enzymatic activity, and the expression of the p16 senescence marker across 3 IVD cell types: nucleus pulposus (NP), inner annulus fibrosus (iAF), and outer annulus fibrosus (oAF) cells. The combined Pam2CSK4 + tBHP exposure generated a robust senescent phenotype across all 3 IVD cell types, with oAF cells exhibiting the strongest increases in {beta}-gal fluorescence, {beta}-gal enzymatic activity, and p16 expression. We then used oAF cells to evaluate if the metabolic activity assay (Alamar Blue) could be used to determine both cytotoxicity of senolytic drugs in non-senescent cells and senolytic activity in a mixed population of senescent and non-senescent cells. We validate the method by comparing metabolic activity results with {beta}-gal enzymatic activity and p16 expression in induced and noninduced cells following exposure to three known senolytics (o-Vanillin, RG-7112, and ABT-199). The metabolic activity assay reliably identified a therapeutic window in which the three senolytics were non-toxic to non-senescent cells while selectively reducing metabolic activity in a mixed population of senescent and non-senescent cells. The reductions in metabolic activity in the mixed population correlated with decreases in SA {beta}-gal enzymatic activity and p16 expression, validating metabolic activity as a sensitive and scalable senolytic readout.

Immune decline in older adults is associated with increased susceptibility to infection and chronic inflammatory diseases. Macrophages are critical innate immune cells that show reduced capacity for phagocytosis and migration with age. Our previous work shows that reduced levels of MYC and USF1 transcription factors are drivers of macrophage age-related functional decline. Here we show that macrophage-specific Myc overexpression improves macrophage migration and, more importantly, is able to improve physical performance at older age in Drosophila, while lifespan remains unaffected. Treatment of human primary macrophages from older individuals with the geroprotective supplement fisetin reverses the decline in MYC expression and improves phagocytosis of pathogens and cell migration functions towards levels seen in younger individuals. Mechanistically, fisetin acts via MYC, by restoring expression levels of MYC targets in human macrophages that are altered with age. Finally, fisetin feeding in older mice improves motor activity and reduces frailty, as well as restoring primary macrophage function and Myc expression in vitro. These findings reveal that restoration of MYC in macrophage ageing is responsible, at least in part, for improvement in physical performance with age and identify this pathway as a rational target to reverse age-related immune decline. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=185 SRC="FIGDIR/small/731325v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@1a1935org.highwire.dtl.DTLVardef@16d2119org.highwire.dtl.DTLVardef@197f838org.highwire.dtl.DTLVardef@294839_HPS_FORMAT_FIGEXP M_FIG C_FIG

Cancer, one of the worlds leading causes of death, is characterized by a complex metabolic reprogramming that features the Warburg effect as one of its hallmarks. The Warburg effect involves increased glucose and amino acid metabolism, which promotes tumor proliferation and progression. Although cancer has historically been attributed to genetic mutations, recent studies suggest a possible metabolic origin. However, a key characteristic of cancer cells is their greater adaptability than normal cells, as evidenced by their resistance to chemotherapy, which stems from their high mutability. This underscores the need to examine the relationship between metabolic reprogramming and cancer development from both metabolic and evolutionary perspectives. In this context, Saccharomyces cerevisiae snf1{Delta} strain has emerged as an ideal cellular model for studying the Warburg effect. This study aimed to determine whether deletion of the SNF1 gene in S. cerevisiae affects its chronological aging and competitiveness in a glucose and amino acid-dependent manner. Herein, we provide evidence that the snf1{Delta} strain changes the chronological aging depending on nutrimental condition, under low-nutrient levels shortens (0.1% glucose + 0.1x amino acids), and increases under high-nutrient levels (5% glucose + 3x amino acids). Competitiveness of the snf1{Delta} strain in co-cultivation with wild-type was also improved in 5% glucose + 3x amino acids, by approximately 2 Log10. These results indicate that snf1{Delta} strain aging and competitiveness are also sensitive to nutrimental status, as was observed in cancer cells.

Osteocytes are long-lived cells that play a central role in bone homeostasis, yet age-related changes in their functional states remain poorly understood, particularly because skeletal aging involves multiple processes beyond cellular senescence. We generated an osteocyte-specific MepeCre mouse line and combined osteocyte ablation in young and middle-aged mice with skeletal phenotyping, single-cell transcriptomics, and senolytic treatment. MepeCre-driven recombination was largely confined to osteocytes, with minimal off-target activity. Osteocyte ablation increased bone mass at both ages, indicating that osteocytes constrain bone accrual as part of their role in skeletal homeostasis. However, the accompanying remodeling changes differed with age: enhanced osteoblast activity predominated in young mice, whereas reduced osteoclast-mediated bone resorption predominated in middle-aged mice. Single-cell transcriptomics revealed distinct osteocyte subpopulations whose relative abundance shifted with age, from a predominantly matrix-enriched state in young mice to an expanded aging-transitional state in middle-aged mice. Although this state showed partial enrichment of senescence-associated transcriptional signatures, senolytic treatment failed to recapitulate the increase in bone mass induced by osteocyte ablation. Osteocyte therefore regulate bone mass through age-dependent mechanisms that coincide with shifts in osteocyte-state composition. These changes emerge by middle age and may contribute to early remodeling imbalance before overt cellular senescence during skeletal aging. Graphical AbstractGraphical summary of the findings of this study. AA, amino acids; NA, nucleic acid; UA, uric acid; TCA, tricarboxylic acid.

Abstract Background: Disability prediction in elderly with cardiometabolic multimorbidity (CMM) is limited. We developed a dynamic nomogram and addressed three questions: predictive value of routine blood markers, depression vs. physical function, and plateau in CMM count.Methods: Using CHARLS data (46 predictors), disability defined as ADL/IADL impairment or self-report. LASSO and logistic regression built the nomogram, with mediation, RCS, trend tests, machine learning, and SHAP.Results: Six predictors (depression, cognition, stroke, CMM number, age, falls) formed a good-performing nomogram (https://xjbsashjtdx.shinyapps.io/DynamicNomogram/). Left-hand grip strength mediated 12.3% of strokes effect. Cognition showed an inverted U-shape (inflection point=12.043). CMM count plateaued after 3 diseases. Depression outranked grip strength and walking speed. SHAP identified HbA1c, creatinine, uric acid, hematocrit, fasting glucose, TyG, and CVAI as risk markers.Conclusions: The nomogram enables personalized risk stratification. Routine blood markers predict disability, depression dominates over physical function, and the CMM-disability relationship plateaus at CMM[≥]3.

Astrocytes assume multiple phenotypes in the brain in response to stress, injury, inflammation, and aging. Given the complexity of this critical cell type in the CNS, it is important to gain a greater understanding of the differences between these phenotypes and to potentially identify therapeutic approaches to modifying astrocyte function in the context of disease and aging. We compared senescent and reactive astrocytes using a strictly defined paradigm to induce these phenotypes in human astrocytes. Gene expression profiling reveals overlapping but distinct expression profiles. Reactive astrocytes predominantly express genes involved in inflammatory responses while senescent astrocytes express genes and a secretome that suggests a role in synaptic pruning. Unexpectedly, functional analysis in a simplified neurite outgrowth assay suggests that senescent astrocytes retain the ability to support neurite outgrowth while reactive astrocytes lose this capacity. The data suggests that senescent and reactive astrocytes play distinct functional roles in the physiology of the aging brain. However, the overlapping inflammatory nature of senescent and reactive astrocytes makes it difficult to discriminate between them using existing toolsets designed to identify senescent cells.

Abstract Background: The influence of taurine on biological ageing remains unclear, particularly whether it acts as a causal driver or a functional biomarker. We aimed to disentangle the distinct roles of plasma taurine relative abundance, dietary taurine supply, and genetic metabolic capacity on all-cause mortality and unhealthy ageing. Methods: This prospective study used data from the Korean Genome and Epidemiology Study (2001~2022). A subcohort of 2,321 participants (mean age 56.5 years; 51.4% female) with complete metabolomic, dietary, and genomic data was analyzed. Three independent pathways were evaluated: (1) plasma taurine/total amino acid (AA) ratio, (2) dietary taurine to protein ratio, and (3) a weighted genetic risk score (GRS) from 21 SNPs in taurine biosynthesis and transport genes. Primary outcomes were all-cause mortality and unhealthy ageing (Physiological Healthy Ageing Index [PHAI] score [≤] 25th percentile). Results: A higher plasma taurine/total AA ratio was consistently associated with improved ageing outcomes. Participants in the highest quartile showed 29% lower all-cause mortality (Hazard Ratio [HR], 0.71; 95% Confidence Interval [CI], 0.52-0.98; P for trend = .04) and lower risk of PHAI-based unhealthy ageing (HR, 0.77; 95% CI, 0.59-1.00; P for trend = .04) versus the lowest quartile. Dietary taurine-to-protein ratio was not associated with mortality (P for trend = .70), nor was the GRS (P for trend = .74). Conclusions: The protective association of taurine was linked to its relative abundance within the systemic amino acid pool, rather than dietary intake or genetic predisposition, supporting taurine as a functional biomarker of metabolic efficiency rather than a deterministic causal driver of ageing.

Fasting-based dietary interventions are conserved regulators of aging that extend lifespan across species, including Caenorhabditis elegans. However, fasting studies in C. elegans are sensitive to experimental variables that can independently influence lifespan and health, including FUdR, antibiotic treatment, germline-less mutants, and the use of UV- or heat-killed bacteria. FUdR can alter lifespan, age-associated pathology, and stress responses, while antibiotics used to prevent bacterial growth during fasting may directly affect worm physiology. To minimize these confounding factors, we developed a simple adult-onset intermittent fasting paradigm that does not require FUdR, antibiotics, or bacterial killing. Wild-type worms were subjected to daily fasting periods of 5 h, 6 h, or 18 h until day 10 of adulthood and compared with continuously fed controls. Daily intermittent fasting robustly extended lifespan by 24-57%, demonstrating that repeated fasting windows during adulthood are sufficient to promote longevity under minimally confounded conditions. These findings establish a straightforward and experimentally tractable intermittent fasting paradigm for C. elegans and underscore the importance of limiting pharmacological and microbial conditions in dietary-intervention experiments.

BACKGROUNDAlong with advancing age comes declines in physical, cognitive, and cardiovascular function. This diminished capacity may lead to decreased ability to perform activities of daily living, disability onset, and loss of independence. Exercise is a regenerative medicine therapy that can mitigate this loss of function. High intensity interval training (HIIT) is an aerobic exercise paradigm consisting of intense activity periods interspersed with bouts of active recovery. Previously we demonstrated that HIIT preserved physical function in adult, middle-aged, and older male mice. However, whether HIIT preserves physical, cognitive, and cardiovascular function, mitigates frailty, and improves brain and heart health in older adult female mice remains unknown. HYPOTHESISCognitive, physical, and cardiovascular function in older adult female C57BL/6 will be preserved in exercised mice (HIIT) versus sedentary control (SED). METHODSMice (HIIT and SED, both n=9, 24m at end) were tested pre/post-intervention for physical (rotarod, treadmill, grip meter, inverted cling, voluntary wheel running, activity monitor), cognitive (open field, novel object recognition, puzzle box, y-maze), and cardiovascular (blood pressure, echocardiogram) function, body composition, and whole body calorimetry. The mice underwent 14-weeks of HIIT training with progressive volume and intensity. RESULTSHIIT significantly (p<0.05) increased or preserved function in many tests including: aerobic capacity (+71% HIIT versus, vs, no change, NC, in SED), four limb strength/endurance (-67% SED vs -28% HIIT), forelimb strength (-16% SED vs NC HIIT), overall motor function (NC SED vs +39% HIIT), executive function (NC SED vs +73% HIIT), and exploratory behavior, which improved across multiple tests with HIIT while remaining unchanged in SED. HIIT also reduced both systolic blood pressure by 12% (-17 mmHg) and mean arterial pressure by -16 mmHg. In addition, HIIT significantly reduced cardiac fibrosis, increased muscle fiber type 2a percentage, reduced IL-1{beta} expression in the hypothalamus, and mitigated frailty onset. CONCLUSIONHIIT significantly reduced age-related functional loss in all three domains assessed while preventing frailty onset in older adult females and improving markers of brain and heart health.

Valid animal models are needed to evaluate how age-related changes in kidney function influence healthspan. Aging marmosets frequently develop renal insufficiency with anemia and exhibit reductions in body mass and metabolic rate. However, it remains unclear which age-related changes predict survival and which thresholds indicate increased mortality risk. We prospectively evaluated age, body composition, resting energy expenditure, hematology, and blood chemistry as predictors of 3-year survival in female and male marmosets (n = 66), 2-16 years of age. Objectives were to identify prognostic markers, define high-risk thresholds, and to develop and test a composite risk-factor scale for mortality screening in captivity. A 10-variable model showed the best predictive performance in multivariable Cox proportional hazards modeling, and was retained for further analysis (concordance = 0.881, p < 0.001). ROC curves using Youdens Index and AUC identified high-risk thresholds for predictors in the multivariable model, and threshold-defined categories were evaluated by Kaplan-Meier survival analysis. The 10 binary risk-factors were combined into a composite scale scored from 0 to 10 and tested with Cox regression. The scale explained approximately 42% of variance in survival and each additional risk factor increased mortality risk 1.75-fold (95% CI: 1.43-2.14, p < 0.001). Marmosets with [&ge;]7 risk factors exhibited a 19-month reduction in survival, and this high-risk threshold predicted 3-year survival with 89.4% accuracy. Results support the scale as a screening tool for mortality risk and highlight the high prevalence of age-associated renal disease and anemia in marmosets.

Background: Crohn's disease is a chronic relapsing inflammatory bowel disease with an unpredictable clinical course that may lead to recurrent hospitalizations and surgery, making early identification of patients at risk a key challenge in longitudinal monitoring. Objective: To evaluate the prognostic value of blood biomarkers for anticipating hospitalizations in patients with Crohn's disease by moving beyond exclusive reliance on conventional reference intervals toward the analysis of personalized biological drift. The underlying premise is that fluctuations that remain within standard reference ranges (and are therefore invisible to conventional thresholds) may still carry a risk signal when interpreted relative to an individual's optimal baseline. Design: We conducted a retrospective study of 993 patients with Crohn's disease followed at the University Hospital of Liege between 2005 and 2023. Longitudinal laboratory measurements were linked to Crohn's disease-related hospitalizations. Biomarkers were transformed into z-scores relative to optimized and personalized reference populations and classified into drift categories. Time to first hospitalization was analyzed using the Kaplan-Meier method, and recurrent hospitalizations were modeled using Cox models. Results: Hospitalization-free survival differed significantly across drift categories, including for deviations within conventional reference ranges (e.g., albumin, global log-rank p<0.0001). Among 57 biomarkers screened, 32 were significant in the global log-rank analysis, including 5 that were significant for intra-reference drift classes: low lymphocytes (%), low monocytes (%), low albumin, high potassium, and low aspartate aminotransferase. Conclusion: Personalized biomarker drift detects clinically meaningful risk signals that are missed by conventional reference-interval thresholds and may enable earlier risk stratification in Crohn's disease.

A growing body of literature has investigated the relationship between age and biomolecular changes, leading to conclusions that aging occurs in discrete molecular "waves." Data summary tools such as LOESS and sliding window analyses like DE-SWAN are common approaches that have gained acceptance in recent years. We demonstrate via simple simulations that these tools can identify non-linear patterns of aging where they do not exist. Specifically, we show that (i) clustering of molecular trajectories using LOESS can lead to artifactual characteristic patterns of molecular aging, (ii) "waves" of aging identified using the combination of LOESS and DE-SWAN in real data are not robust to changes in the underlying age distribution and are not supported by valid permutation testing, and (iii) DE-SWAN alone can generate pronounced "waves" of nonlinear molecular aging in linear data due to differences in statistical power along the age continuum. Our results specifically challenge the statistical support for discrete aging crests inferred in the literature, but do not rule out nonlinear molecular aging or age-associated transitions that may be detectable using other cohorts and statistical models.

Transcriptome analyses are widely used for biomarker discovery and to gain insights into normal processes and diseases. Age-related changes in gene expression inferred from RNA-seq are typically reported relative to the transcriptome composition using library-size normalisation. As such, absolute changes in transcript abundance with age remain poorly characterised. Here, using external spike-in normalisation in the Tabula Muris Senis dataset, we quantify age-related variation in total mRNA content and gene expression across mouse cell types. We observe widespread changes in total mRNA abundance, with decreases predominantly in non-immune cell types and increases predominantly in immune cell types. In parallel, the number of genes expressed declines across most cell types, including immune populations. Differential expression analysis based on spike-in-normalised counts identifies genes consistently downregulated across cell types, enriched for functions in RNA metabolism and protein processing. Furthermore, genes downregulated during ageing and during proliferation arrest show partial overlap, suggesting that these transcriptional changes may share regulatory processes. Together, these results are consistent with a general repression of transcriptional and metabolic activity with age, modulated by immune-specific responses. More broadly, our results demonstrate that conclusions drawn from transcriptomic ageing studies can depend strongly on whether gene expression is interpreted in relative or absolute terms, highlighting the importance of absolute normalisation approaches for the analysis of age-related transcriptomic change

Background: Elevated C-Reactive Protein (CRP), interleukin-6 (IL-6) and testosterone deficiency are associated with advanced age and chronic inflammatory diseases; while normal testosterone levels have been shown to decrease inflammation through several mechanisms. Cross-sectional studies have shown an inverse relationship between CRP, IL-6 and total testosterone (TT) levels, yet mixed findings have been reported when individual components of metabolic syndrome are considered. We evaluated the relationship between CRP, IL-6 and TT levels in men from 2004-2018 using the Baltimore Longitudinal Study of Aging to determine if low testosterone status is associated with a high inflammatory profile. Methods: Participants were selected from the Baltimore Longitudinal Study of Aging. Male participants with serum TT level measured during at least three visits were included in our cohort. Common measures of inflammatory disease such as CRP, High-Density Lipoprotein (HDL) and Triglyceride levels were collected via blood specimens. Comorbidity data were documented at each visit. Panel regression was used to analyze the relationship of a series of independent variables collected in pooled cross-sectional observations over time with a dependent variable for modeling. Results: A total of 347 patients were included in this study (median age = 70, IQR = 18, average follow up time = 6.7 +/- 3.2 years). Participants had a median CRP level of 1.0 mg/dL, median IL-6 level of 3.6, a median TT level of 446 ng/dL. On univariable analysis, increasing TT and HDL levels were associated with a decline in CRP, while high Body Mass Index (BMI), congestive heart failure (CHF), Diabetes, and increased serum triglycerides were associated with increased CRP. Age was not associated with CRP. On multivariable analysis, we found that increasing TT level was associated with a decline in CRP levels, independent of comorbidities (p = 0.018; Table 1). As expected, increased BMI was associated with a significant increase in CRP (p = 0.001, Table 1). Age, CHF, Diabetes, HDL, and Triglycerides were not significant predictors of CRP on multivariable analysis. Similarly, on multivariable analysis, increasing TT levels were independently associated with lower IL-6 levels. Higher HDL cholesterol levels were also associated with lower IL-6 levels, whereas increasing age was associated with higher IL-6 levels. BMI, CHF, diabetes, and triglycerides were not significant predictors of IL-6. Conclusions: Lower levels of serum total testosterone are associated with an increase in CRP in older men over time, independent of chronic inflammatory disease. Given the importance of CRP in pathogenesis of chronic disease, we highlight the potential benefits of using total testosterone as a biomarker of chronic inflammatory states.