Integrated serum and fecal metabolomics identifies compartment-specific metabolic remodeling in mice fed high-fat and Western diets

Obesogenic diets induce systemic and gut luminal metabolic perturbations, but whether these alterations occur in parallel across biospecimens remains unclear. In particular, the extent to which high-fat diet (HFD) and Western diet (WD) produce shared or compartment-specific metabolic responses in circulation and feces has not been systematically compared. In this study, targeted LC-MS/MS-based metabolite profiling was performed using serum and fecal samples from mice fed a normal diet (ND), HFD, or WD. Serum samples were analyzed at the individual-animal level, whereas fecal samples were analyzed as cage-level pooled specimens and interpreted as exploratory. Group differences were assessed using non-parametric statistics with Benjamini-Hochberg false discovery rate correction, followed by cross-compartment comparison of HFD-versus-ND and WD-versus-ND directional changes among metabolites detected in both matrices. In serum, obesogenic diets were associated with significant alterations in branched-chain amino acid-related metabolites, phenylalanine, serotonin, butyrylcarnitine, and taurocholic acid. In exploratory fecal metabolomics, significant diet-associated differences were observed mainly in amino acid-related metabolites, cholic acid, and 3-indolepropionic acid. Cross-compartment comparison of HFD-versus-ND and WD-versus-ND responses showed that several amino acid-related metabolites, including valine, leucine, and phenylalanine, were decreased in serum but increased in feces. WD also showed fecal bile acid- and indole-related changes in the exploratory fecal dataset under the present conditions. These findings suggest that HFD and WD are associated with distinct and compartment-specific metabolic remodeling across circulating and luminal compartments and support the value of multi-compartment metabolomics in studies of diet-associated metabolic dysfunction.