Gut microbial signatures for aging-related sarcopenia and dietary links among community-dwelling old-old adults: A metagenomic study

BACKGROUND AND OBJECTIVES: Sarcopenia, characterized by progressive loss of muscle mass, strength and function, poses a major aging-related health challenge. While a gut-muscle axis is implicated, microbiota-sarcopenia associations in the old-old (≥80 years) remain unexplored. METHODS: This cross-sectional analysis included 315 community-dwelling adults aged ≥80 years from a longitudinal cohort at the 20-year follow-up timepoint, of whom 180 met the inclusion criteria. Gut microbiota was profiled by shotgun metagenomic sequencing alongside sarcopenia assessment. Microbial taxa associated with sarcopenia were identified using MaAsLin2, and dietary associations were assessed by partial Spearman correlation. RESULTS: The prevalence of sarcopenia in this old-old cohort (mean age 86.8 ± 4.3 years) was 51.7%. Sarcopenic individuals showed lower nutrition scores, reduced microbial richness and altered β-diversity (all P < 0.05). Multivariable analysis identified six differentially abundant species associated with sarcopenia (FDR < 0.10), including two positively associated (Ruthenibacterium lactatiformans and Catenibacillus scindens), and four negatively associated (Phascolarctobacterium faecium, Pyramidobacter piscolens, Lacrimispora saccharolytica and Limosilactobacillus mucosae). Random forest and LEfSe analysis validated R. lactatiformans and P. faecium as the most discriminative signatures for sarcopenia. After adjusting for obesity, these signatures remained significant (P < 0.05). These alterations were linked to functional dysregulation, including increased purine degradation and reduced biotin biosynthesis potential. R. lactatiformans abundance negatively correlated with dietary maltose intake (P < 0.05). CONCLUSION: In old-old adults, we identified distinct gut microbiota signatures associated with sarcopenia. R. lactatiformans and P. faecium emerged as candidate features. The dietary-microbiota correlations suggest potential nutrition strategies. These findings provide a basis for exploring microbiota-based approaches in advanced aging.