Gut Microbiota Changes in Metabolic Dysfunction-Associated Steatohepatitis and Inflammatory Bowel Disease: Common Pathogenic Features

Gut microbiota changes have emerged as central players in the pathogenesis of both metabolic dysfunction-associated steatohepatitis (MASH) and inflammatory bowel disease (IBD). Although these diseases affect distinct primary organs, they share converging mechanisms driven by dysbiosis, including loss of beneficial short-chain fatty acid-producing taxa such as Faecalibacterium prausnitzii and Roseburia, enrichment of pro-inflammatory Enterobacteriaceae, and disruption of bile acid and tryptophan metabolism. These shifts compromise epithelial barrier integrity, promote the translocation of microbial products such as lipopolysaccharide, and trigger toll-like receptor 4-mediated activation of inflammatory cascades dominated by tumor necrosis factor-alpha, interleukin-6, and transforming growth factor-beta. In MASH, this dysbiotic environment fuels hepatic inflammation, insulin resistance, and fibrogenesis, while in IBD it sustains chronic mucosal immune activation. Shared features include impaired butyrate availability, altered bile acid pools affecting farnesoid X receptor and Takeda G protein-coupled Receptor 5 signaling, and defective aryl hydrocarbon receptor activation, all of which link microbial dysfunction to host metabolic and immune dysregulation. Understanding these overlapping pathways provides a deeper understanding of the role of the gut-liver and gut-immune axes as unifying frameworks in disease progression. This narrative review synthesizes current evidence on gut microbiota in MASH and IBD, underscoring the need for longitudinal, multi-omics studies and microbiome-targeted strategies to guide personalized therapeutic approaches.