Aerobic exercise training alters gastrointestinal microbiota and enhances exercise capacity in UM-HET3 mice

Aerobic exercise attenuates age-related physiological decline, potentially through favorable modulation of gut microbiota diversity. The purpose of this study was to characterize aerobic exercise training (ET)-induced alterations in the gut microbiome of aging, genetically heterogeneous UM-HET3 mice and examine associations between microbial shifts and changes in body composition (body weight, lean mass, and fat mass) and exercise capacity (total work, distance, and duration). Male UM-HET3 mice were assigned to sedentary (SED; n = 16) or ET (n = 17) groups. ET mice trained 5 days per week for 4 weeks at 65% of maximal work output. Body composition and exercise capacity were assessed before and after the intervention. Post-intervention fecal samples were analyzed by 16S rRNA gene sequencing (SED, n = 13; ET, n = 13). ASVs were taxonomically classified using QIIME2 with the SILVA 138.1 reference database. Alpha and beta diversity analyses were conducted in R, and Spearman's correlations assessed relationships between phylum-level abundances and physiological outcomes. ET mice exhibited greater alpha diversity, with a higher median richness (219.5), although differences were not statistically significant. Principal coordinate analysis of beta diversity demonstrated significant separation between groups (P = 0.01), indicating distinct microbial community composition. At the phylum level, ET was associated with modest shifts in gut microbial composition, characterized by higher relative abundances of Firmicutes and Verrucomicrobiota and lower abundances of Bacteroidota and Desulfobacterota compared to SED mice. Collectively, these findings indicate that aerobic exercise training induces distinct shifts in gut microbiota composition in middle-aged UM-HET3 mice despite underlying genetic heterogeneity.