The Gut-Liver Axis in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Mechanisms, Microbiome...

Metabolic dysfunction-associated steatotic liver disease (MASLD) is increasingly recognized as a multifactorial condition in which the gut-liver axis plays a central pathogenic role. While a large body of literature has described associations between gut microbiota alterations and MASLD, a critical synthesis of the mechanistic pathways linking microbial activity to liver injury remains lacking. This review specifically focuses on gut-derived microbial metabolites as key mediators of disease progression. We examine how short-chain fatty acids, bile acids, lipopolysaccharide (LPS), trimethylamine-N-oxide (TMAO) and microbially derived ethanol influence hepatic lipid metabolism, inflammation and fibrogenesis through defined molecular pathways, including FXR signaling, TLR4 activation and immune-metabolic crosstalk. Importantly, we highlight inconsistencies in human microbiome studies, limitations in establishing causality and the challenges in translating preclinical findings into effective therapies. Although microbiome-targeted interventions such as probiotics, bile acid modulators and fecal microbiota transplantation show promise, their clinical efficacy remains variable due to interindividual heterogeneity and lack of mechanistic precision.By integrating current mechanistic evidence with translational insights, this review identifies critical knowledge gaps and proposes future directions for metabolite-focused therapeutic strategies. A more precise understanding of gut-derived signaling pathways will be essential to move from associative microbiome research toward targeted and personalized interventions in MASLD.