Gut microbial enzymes and metabolic dysfunction-associated steatohepatitis: Function, mechanism, and therapeutic prospects.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent liver disease worldwide. The liver communicates with the intestine, in large part through the gut microbiota. Microbial enzymes are key mediators that affect the progression of MASLD and the more severe metabolic dysfunction-associated steatohepatitis (MASH). These enzymes contribute to the metabolism or biosynthesis of steroids, fatty acids, amino acids, ethanol, choline, and intestinal hormones that contribute to disease progression. Additionally, dysbiosis and functional alterations in the microbiota compromise the intestinal barrier, increasing its permeability to bacterial metabolites and liver exposure to microbial-associated molecular patterns (MAMPs), thereby exacerbating liver inflammation and fibrosis. Furthermore, functional alterations in the gut microbiota can modulate intestinal signaling pathways through metabolites or gut hormones, subsequently affecting hepatic metabolism. A deeper understanding of the roles of the gut microbiota and microbial enzymes in MASH will facilitate the development of personalized treatments targeting specific gut microbes or functional enzymes.