Strain-Dependent Effects of Dietary Cholic Acid on Liver Fibrogenesis and Gut Microbiota in TSNO and TSOD Mice

Background: Metabolic dysfunction-associated steatohepatitis (MASH) is defined by hepatocellular damage accompanied by inflammation and fibrotic changes. Bile acids (BAs) and gut microbiota play pivotal roles in disease progression. However, the contribution of dietary cholic acid (CA), a primary BA, remains unclear. Methods: We investigated the effect of dietary CA supplementation in Tsumura–Suzuki obese diabetic (TSOD) and Tsumura–Suzuki non-obese (TSNO) mouse strains with distinct metabolic phenotypes. The mice were fed normal diet (ND) or 0.5% CA-supplemented ND. Liver injury, fibrosis, and macrophage dynamics were assessed by biochemical assays, histology, flow cytometry, and RT-qPCR. Gut microbiota composition and fecal BA profiles were analyzed using 16S rRNA sequencing and mass spectrometry. Results: CA supplementation induced hepatomegaly, liver injury, and lipid metabolism abnormalities in both strains. In TSNO mice, CA markedly enhanced hepatic fibrosis, increased Col1a1 and Timp1 expressions, and promoted CD11c+ monocyte-derived macrophage infiltration. In contrast, TSOD mice showed minimal fibrotic responses to CA but exhibited pronounced alterations in gut microbiota composition, including enrichment of Akkermansia muciniphila, along with changes in fecal BA profiles. Flow cytometry further revealed Kupffer cell numbers and increased macrophage recruitment in both strains after CA supplementation. Conclusions: Dietary CA exerts strain-dependent effects on MASH pathogenesis. CA promoted macrophage-driven hepatic fibrosis in TSNO mice, whereas it primarily modulated gut microbiota and BA metabolism in TSOD mice. These findings highlight the dual roles of CA in linking hepatic immune responses with intestinal homeostasis and suggest a context-dependent contribution to MASH progression.