In nonalcoholic fatty liver disease (NAFLD) mice, the relative abundance of A. muciniphila was decreased, as was the level of tryptophan metabolites, such as indole, indole-3-acetic acid, and indole-3-propionic acid, which act as ligands for aryl hydrocarbon receptor (AHR) to protect intestinal mucosal homeostasis [7]. Here, AHR is linked to metabolic dysfunction-associated steatotic liver disease.