Functional signatures of the gut microbiome in middle-aged regular runners: insights from a metagenomic study.

INTRODUCTION: Exercise influences host metabolism and inflammation, but its functional effects on the gut microbiome in middle-aged populations remain unclear. This study used shotgun metagenomics to investigate the associations between long-term endurance running and the gut microbial ecosystem and its functional potential in middle-aged adults.

METHODS: We conducted a cross-sectional analysis comparing 33 middle-aged regular runners with 33 sedentary controls. No significant differences in age, BMI, dietary intake between groups. Fecal samples underwent metagenomic sequencing at an average depth of 10.97 Gb per sample. Following stringent quality control, taxonomic profiling, diversity analyses, and differential abundance testing were performed. Functional potential was annotated using GO, eggNOG, KEGG, CARD, VFDB, and CAZy databases.

RESULTS AND DISCUSSION: The gut microbiota of middle-aged regular runners (RG, n = 33) and sedentary controls (CG, n = 33) was compared using metagenomic sequencing. No significant differences were observed between the two groups in terms of age, BMI, or self-reported dietary patterns. Although no significant differences in α-diversity or β-diversity were found, taxonomic profiling revealed differences in microbial community composition between the groups. Runners exhibited an increased relative abundance of carbohydrate-fermenting and short-chain fatty acid (SCFA)-producing species, including Prevotella copri, Lachnospira eligens, and Collinsella intestinalis. KEGG functional analysis revealed enrichment of genes associated with antibiotic biosynthesis pathways in runners, whereas the control group was enriched in genes related to lipid metabolism and xenobiotic degradation. The total abundance of antibiotic resistance genes (ARGs) and virulence factors (VFs) was significantly lower in runners. Carbohydrate-active enzyme (CAZy) profiling further indicated that runners harbored higher abundances of carbohydrate-binding modules and glycosyltransferase families, while controls were enriched in complex polysaccharide-degrading enzymes. Nonetheless, the cross-sectional design, qualitative dietary assessment, residual sex imbalance, and lack of metabolomic validation limit causal inference. Longitudinal intervention studies incorporating metabolomic analyses are warranted to confirm these associations and elucidate the directional adaptation of the gut microbiota to long-term regular exercise.