Follistatin Alleviates Hepatic Steatosis in NAFLD via the mTOR Dependent Pathway

Abstract

Junlu Tong1,2 *, Li Cong1 *, Yingbin Jia,3 Bai-Liang He,4 Yifan Guo,1 Jianzhong He,5 Decheng Li,3 Baojia Zou,3 Jian Li3 1Department of Endocrinology, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China; 2Department of Central Laboratory, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China; 3Department of Hepatobiliary Surgery, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China; 4Guangdong Provincial Key Laboratory of Biomedical Imaging, Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China; 5Department of Pathology, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jian Li; Baojia Zou, Department of Hepatobiliary Surgery, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People’s Republic of China, Tel [phone], Email [email protected]; [email protected]: In this study, we aimed to investigate the effect of follistatin (FST) on hepatic steatosis in NAFLD and the underlying mechanism, which has rarely been reported before.Methods: Liver samples from NAFLD patients and normal liver samples (from liver donors) were collected to investigate hepatic FST expression in humans. Additionally, human liver cells (LO2) were treated with free fatty acid (FFA) to induce lipid accumulation. Furthermore, lentivirus with FST overexpression or knockdown vectors were used to generate stable cell lines, which were subsequently treated with FFA or FFA and rapamycin. In the animal experiments, male C57BL/6J mice were fed with a high-fat diet (HFD) to induce NAFLD, after which the adeno-associated virus (AAV) gene vectors for FST overexpression were administered. In both cell culture and mice, we evaluated morphological changes and the protein expression of sterol regulatory element-binding protein1 (SREBP1), acetyl-CoA carboxylase1 (ACC1), carbohydrate-responsive element-binding protein (ChREBP), fatty acid synthase (FASN), and Akt/mTOR signaling. The body weight and serum parameters of the mice were also measured.Results: Hepatic FST expression level was higher in NAFLD patients compared to normal samples. In LO2 cells, FST overexpression alleviated lipid accumulation and lipogenesis, whereas FST knockdown aggravated hepatic steatosis. FST could regulate Akt/mTOR signaling, and the mTOR inhibitor rapamycin abolished the effect of FST knockdown on hepatic de novo lipogenesis (DNL). Furthermore, FST expression was increased in HFD mice compared to the corresponding controls. FST overexpression in mice reduced body weight gain, hyperlipidemia, hepatic DNL, and suppressed Akt/mTOR signaling.Conclusion: Hepatic FST expression increases in NAFLD and plays a protective role in hepatic steatosis. FST overexpression gene therapy alleviates hepatic steatosis via the mTOR pathway.Therefore, gene therapy for FST is a promising treatment in NAFLD.Keywords: follistatin, non-alcoholic fatty liver disease, free fatty acid, lipid synthesis

Keywords

• follistatin
• non-alcoholic fatty liver disease
• free fatty acid
• lipid synthesis