Effects of fructooligosaccharide supplementation combined with aerobic exercise on gut microbiota, cecal venous metabolites, and lipid metabolism in rats

Fructooligosaccharides (FOS) are prebiotic food ingredients that can be fermented by beneficial gut bacteria, but whether their combined application with exercise confers greater metabolic benefits than either intervention alone remains poorly defined. This study evaluated the effects of FOS supplementation combined with moderate-intensity aerobic exercise on lipid metabolism, brown adipose tissue (BAT) markers, gut microbiota composition, and circulating microbial metabolites in rats. Female Wistar rats were assigned to four groups in a 2 × 2 factorial design: control (S), exercise (SE), FOS, and FOS plus exercise (FOSE), with a 28-day intervention period. The FOSE group showed lower final body weight, reduced peri-ovarian white adipose tissue (WAT) weight, a higher BAT index, and a more multilocular BAT morphology compared with other groups, although these BAT-related changes require further protein-level and functional validation. Consistently, combined intervention was associated with increased mRNA expression of thermogenesis-related genes (Ucp1, Pgc1a, Prdm16) and lipid droplet-mitochondrial coupling genes (Plin5, Mfn2) in BAT, while hepatic lipogenesis-related gene expression (Fas, Srebp-1c) was reduced. Microbiota analysis revealed Bifidobacterium enrichment in FOS-supplemented groups, and untargeted LC-MS/MS-based metabolomics of cecal venous serum identified indole-3-propionic acid (IPA) as a prominent differential metabolite. In correlation analyses, IPA levels were positively correlated with Bifidobacterium abundance and BAT-related gene-expression markers. These findings suggest that the combined intervention is associated with altered lipid metabolism markers, gut microbiota composition, and circulating microbial metabolites. Because the study was correlational and diets differed in energy density, causal studies with isocaloric controls and functional validation are needed.