FIS1 and fatty liver disease: In the present study, the decreased expression of Mfn1, Mfn2, and OPA1 was accompanied by a significant increased expression of FIS1 and Drp1 observed in the FLHS hens and the steatosis hepatic cells cultured in vitro, suggesting that the inhibition of mitochondrial fusion and the promotion of mitochondrial fission were induced by the fatty liver disease.