“…Bifidobacterium longum , known as a beneficial bacterium in humans, modulates host immune responses, suppresses inflammation, and restores intestinal mucosal barrier function ( Chichlowski et al., 2020 ; Yao et al., 2021 ; Mills et al., 2023 ). Recent research has also highlighted that metabolites of Bifidobacterium longum , such as 5-hydroxytryptamine, secondary bile acids, and short-chain fatty acids, mitigate liver inflammation, degree of fibrosis, and hepatocyte proliferation via the “gut-liver axis” ( Yu et al., 2023 ). Moreover, Bacteroidetes can express enzymes involved in bile acid metabolism, such as bile salt hydrolase, which facilitates the breakdown of primary conjugated bile acids into free bile acids in the intestine, contributing to the metabolism of primary bile acids and the production of secondary bile acids in the intestine ( Gérard, 2013 ; Wahlström et al., 2016 ).…”