Dysbiosis-Driven Reprogramming of Secondary Bile Acid Metabolism in Metabolic Dysfunction-Associated Steatotic Liver Disease: Insights from an Ex Vivo Human Fecal Microbiota Model

Gut microbial dysbiosis-induced perturbations in bile acid (BA) metabolism are implicated in metabolic dysfunction–associated steatotic liver disease (MASLD), yet evidence remains largely associative. Using an optimized ex vivo fecal microbiota model, we modeled the metabolism kinetics of conjugated- and primary-BA between MASLD and healthy donors. Enzymes for known BA metabolic reactions were inferred using functional metagenomics. MASLD cultures exhibited impaired deconjugation capacity but preserved downstream primary-BA clearance and demonstrated a substrate-independent shift that favored oxidative metabolism over 7α-dehydroxylation. This was marked by increased formation clearance of 7-keto-deoxycholic acid (175%) and 3-oxo-cholic acid (51.7%) from cholic acid (CA) and 7-keto-lithocholic acid (77.9%) from chenodeoxycholic acid (CDCA). C7-oxidized BA constituted the major proportion of total BA clearance (CA = 56.0%, CDCA = 72.3%) in MASLD cultures. Enrichment of C3- and C7-hydroxysteroid dehydrogenases in MASLD compared to control corroborated the differential secondary BA profiles. Together, microbes catalyzing C7-oxidation warrants further investigation as potential pharmacological targets of MASLD.