Blood Metabolites Reveal Sex-Specific Biological Signatures of Frailty in Aging Mice
A longitudinal mouse study identifies sex-specific plasma metabolite biomarkers of frailty, pointing to B vitamins in females and lipids in males.
Summary
Researchers tracked plasma metabolites and frailty scores in aging male and female mice across five time points, identifying distinct sex-specific metabolic signatures. In females, B vitamin metabolism markers—flavin-adenine dinucleotide and pyridoxate—were linked to frailty, while in males, lipid-related metabolites including sphingomyelins and glycerophosphocholines dominated. Across both sexes, ergothioneine and tryptophan emerged as robust frailty-associated metabolites. A metabolomics-based frailty clock outperformed age and sex alone in males. These findings, validated in a separate cohort, suggest that frailty has distinct metabolic underpinnings by sex and offer candidate biomarkers for future clinical translation.
Detailed Summary
Frailty—a syndrome of accumulated health deficits with aging—lacks accepted molecular biomarkers, limiting early detection and mechanistic understanding. This study addresses that gap by combining longitudinal plasma metabolomics with frailty index (FI) measurements in naturally aging C57BL/6NIA mice, offering a controlled, repeated-measures design rarely achieved in human studies.
The discovery cohort comprised 20 female and 24 male untreated mice assessed at up to five time points spanning roughly 13 months to 2.5 years of age. A panel of 781 plasma metabolites was quantified. Principal component analysis showed clear separation by both time point and sex, confirming that aging and biological sex are dominant sources of metabolic variation. Of 781 metabolites, 527 changed significantly over the time course. Co-abundance network analysis distilled these into two core aging-related subsets: one enriched in amino acid metabolism (subset 1, n=200) and one in lipid metabolism (subset 2, n=125), both showing generally declining abundance with age. Eighty-six hub metabolites—including guanidinoacetate, methylmalonate, and sphingomyelin species—were designated core age-related metabolites, with lipid-pathway metabolites predominating.
For frailty-specific analysis, machine learning feature selection identified metabolites whose variation tracked FI independently of chronological age. Frailty-related metabolites were enriched in amino acid metabolism and metabolism of cofactors and vitamins. Key pan-sex frailty metabolites included ergothioneine (a dietary antioxidant), tryptophan, and alpha-ketoglutarate—all declining with greater frailty. Critically, sex-stratified analyses revealed divergent frailty metabolite profiles: females showed frailty associations with B vitamin metabolism markers flavin-adenine dinucleotide (FAD) and pyridoxate (vitamin B6 metabolite), while males showed frailty associations with lipid-related metabolites including sphingomyelins, glycerophosphoethanolamine, and glycerophosphocholine.
A metabolomics-based frailty clock built from these features outperformed a model using age and sex alone, but this improvement was statistically significant only in male mice, suggesting the metabolic signal for frailty may be more metabolomically tractable in males or that female frailty involves pathways less well captured by current metabolite panels. Validation in a separate cohort of NMN-treated mice confirmed associations for 9 candidate biomarkers, with ergothioneine and perfluorooctanesulfonate (PFOS) identified as the most robust cross-cohort frailty biomarkers.
These findings carry several implications. The sex specificity of frailty metabolites argues strongly for sex-stratified analyses in future biomarker and intervention studies. The prominence of B vitamin and cofactor metabolism in female frailty points toward mitochondrial energy metabolism as a potential mechanistic target. The lipid-centric male frailty signature aligns with known sex differences in cardiovascular and metabolic disease risk. Ergothioneine's consistent inverse association with frailty across sexes and cohorts makes it a particularly compelling candidate for clinical biomarker development and possibly dietary intervention research.
Key Findings
- Ergothioneine and tryptophan were robustly inversely associated with frailty across both sexes and validated in a second cohort.
- Female frailty was specifically linked to B vitamin metabolism markers FAD and pyridoxate.
- Male frailty was specifically linked to lipid metabolites: sphingomyelins, glycerophosphoethanolamine, and glycerophosphocholine.
- A metabolomics-based frailty clock outperformed age+sex prediction, but only significantly so in male mice.
- Lipid metabolism dominated age-related metabolite changes, while amino acid and cofactor metabolism dominated frailty-related changes.
Methodology
Longitudinal study of 44 untreated C57BL/6NIA mice (20 female, 24 male) with plasma metabolomics (781 metabolites) and frailty index measured at up to 5 time points. Co-abundance network analysis, machine learning feature selection, linear mixed models, and a metabolomics frailty clock were applied; findings were validated in a separate NMN-treated cohort of 43 mice.
Study Limitations
The study used inbred C57BL/6NIA mice, limiting direct translation to genetically diverse human populations. Sample sizes, especially at later time points, were small due to natural attrition. The validation cohort consisted of NMN-treated mice, introducing a potential confound when confirming biomarkers identified in untreated animals.
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