FASN and fatty liver disease: Our results demonstrated that F. prausnitzii can significantly downregulate the hepatic lipid-regulating enzyme activity, including fatty acid synthase, malic enzyme, carnitine palmitoyltransferase and β-oxidation in the livers of db/db mice, indicating that the reduced hepatic triglyceride levels produced by F. prausnitzii are accounted for by the decrease in hepatic lipogenesis and responsible in improving hepatic steatosis.