Over-expression of HNF4 alpha attenuated lipotoxicity in non-alcoholic fatty liver disease model

Abstract

Background: Hepatocyte nuclear factor 4α (HNF4α) is known as a master regulator of liver-specific gene expression. The effects of HNF4α on non-alcohol fatty liver disease (NAFLD) at transcriptional level are largely unknown. In this study, we evaluated the role of HNF4α in NAFLD model. Methods: High fat (HF) diet was fed to rats for 20 weeks to induce NAFLD. To make vitro NAFLD model, palmatic acid (PA) treated in HepG2 cells for 24 hours. Later, liver-specific gene expressions were evaluated. Using microporator, a transcription factor, HNF4α was over-expressed in HepG2 cells. After transfection, MTT assay, Tunnel assay, FACS, Nile-red staining, and qPCR gene evaluation were performed. Results: Hepatic gene expression of Foxa2 and GATA4 were up regulated in HF diet fed rats compared to control group. But HNF4α mRNA expression was decreased in diet induced fatty disease model. In HepG2 cells, palmatic acid treatment also decreased HNF4α mRNA expression; however, interestingly, the oleic acid treatment did not affect the HNF4α mRNA expression. HepG2 cells over-expressing HNF4α through transfection showed a protective effect against palmatic acid-induced apoptosis. HNF4α over-expression was also associated with increased fatty acid oxidation and VLDL secretion. The HepG2 cells over-expressing HNF4α also exhibited increased the mRNA expression of enzymes related to VLDL secretion (MTTP and ApoB) and fatty acid oxidation (ACOX and CYP4A1). Moreover HNF4α over-expression was also involved in decreased fatty acid uptake. The HepG2 cells over-expressing HNF4α also exhibited decreased the mRNA expression of fatty acid uptake mediator (CD36 and FATP2). Conclusions: HNF4α attenuated lipotoxicity by increased VLDL secretion and fatty acid oxidation in NASH model. Disclosures: The following authors have nothing to disclose: Jai Sun Lee, Dae Won Jun, Seung Min Lee, Yong Kyun Cho, Eun Chul Jang, Sang Bong Ahn