Regulation of Mitochondrial Dynamics Ameliorates Hepatic Steatosis through TFEB Activation

Nonalcoholic fatty liver disease (NAFLD) is a common cause of liver disease that is closely related to metabolic syndromes, obesity, and type 2diabetes. There is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Recently, growing evidence suggests that the TFEB plays a pivotal role in mitochondrial dynamics. In this study, we investigated that mitochondrial dynamics play the potential role and mechanisms of TFEB in the amelioration of NAFLD. FFA increased expression of mitochondrial fission proteins p-Drp1, Fis1 and decreased expression of fusion proteins OPA1, Mfn2 and inhibition of TFEB activation. Mitotracker stain significantly increased in the proportion of cells with fragmented mitochondria in FFA-treated cells. HFD-fed mice displayed histology consistent with pathological hepatic steatosis. EM analysis indicated that HFD-fed mitochondria tended to be shorter and more round than ND-fed mitochondria. Western blot analyses reveal increased expression of the fission proteins, p-Drp1, Fis1, and significantly decreased in the fusion protein, Mfn2 and OPA1 in HFD-fed group. In vivo Tfeb knockout dramatically increased hepatic fat accumulation, liver ballooning in HFD-fed mice. EM analysis showed that HFD-fed Tfeb knockout mice had more rounded and swollen mitochondria, indicating that TFEB was dependent on the regulation of mitochondrial fragmentation. In vivo Tfeb knockout reveal significantly increased expression of the fission proteins in HFD-fed group. To demonstrated the direct regulatory mechanism of mitochondrial dynamics and TFEB activation, we used siRNA DRP1 and Mdivi-1. Inhibition of Drp1 promotes mitochondrial fusion, increased expression of fusion protein and reduced fat accumulation and activated TFEB. These results suggest a role in improving hepatic steatosis through regulation of TFEB-mediated mitochondrial dynamics in NAFLD. Disclosure J.Yoo: Other Relationship; American Diabetes Association. Y.Hwang: None. Funding National Research Foundation of Korea (2022R1I1A1A01069899)