Compositional and Metabolomic Shifts of the Gut Microbiome in Alcohol-Related Liver Disease

Alcohol-related liver disease (ALD) is a major global health concern characterized by steatosis and liver inflammation due to chronic alcohol consumption. Emerging evidence suggests that ALD is not solely a liver pathology but also involves dysfunction of the gut-liver axis, where alterations in the gut microbiota play a significant role. Although alcohol-associated dysbiosis has been extensively studied, whether these microbial changes contribute to ALD development or are merely a consequence of alcohol exposure remains unclear. To prove causation, it is essential to decipher which specific taxa and their metabolites drive the maladaptation of host-microbiota interactions upon alcohol exposure. In this review, we summarize the compositional changes in the gut microbiome after alcohol exposure, identifying traits of alcohol-induced dysbiosis and distinguishing them from those associated with liver disease. The effects of alcohol-induced dysbiosis on microbial metabolism and host responses are reviewed, focusing on the key classes of microbiota-derived metabolites, notably free fatty acids, tryptophan and its indole derivatives, and secondary bile acids. We discuss how alterations in these metabolites disrupt intestinal barrier function, immune responses, and metabolic signaling pathways, thereby exacerbating alcohol-induced injury. Advanced omics technologies and microbiome modulation strategies will help further investigation into these mechanisms. Detailed mechanistic insights into host-microbiota interactions could unveil novel therapeutic targets, offering potential strategies to prevent or mitigate ALD by modulating the gut microbiome and its metabolites.