Gut microbial metabolites of amino acids in liver diseases.

Due to the unique anatomical connection between the gut and liver, metabolites derived from gut microbiota are closely linked to hepatic health and disease. Among these microbial metabolites, amino acid derivatives have emerged as crucial mediators in gut-liver communication, influencing liver pathophysiology through their bioactive properties. Accumulating evidence demonstrates that amino acid metabolites, including amines, indoles, aromatic derivatives, branched-chain fatty acids (BCFAs), and sulphur-containing compounds (SCCs), function as critical signaling molecules within the gut-liver axis. These metabolites modulate immune responses, inflammation, and metabolic homeostasis, thus affecting the progression and severity of liver diseases. Understanding the specific microbial metabolic pathways responsible for producing these metabolites is essential to reveal novel pathological mechanisms and identify promising biomarkers and therapeutic targets. In this review, we summarize recent advances in microbial amino acid metabolism and highlight the diverse roles of amino acid-derived metabolites in liver disease progression. Furthermore, we discuss the translational potential and current challenges associated with targeting microbial amino acid metabolism in clinical settings. A deeper understanding of these metabolic interactions may ultimately facilitate the development of innovative diagnostic tools and effective therapeutic strategies for liver diseases.