HIF-1α induction suppresses excessive lipid accumulation in alcoholic fatty liver in mice

Background & Aims: Chronic alcohol intake stimulates hepatic oxygen consumption and subsequently causes liver hypoxia, leading to activation of hypoxia inducible factor-1 (HIF-1). Although HIF-1 plays a crucial role in the metabolic switch from aerobic to anaerobic metabolism in response to hypoxia, its roles in the regulation of lipid metabolism in alcoholic fatty liver remain unknown. Methods: Wild-type and hepatocyte-specific HIF-1α-null mice were subjected to a 6% ethanol-containing liquid diet for 4 weeks, and functional effects of loss of the HIF-1α gene on lipid metabolism were examined in the liver. Results: Hepatocyte-specific HIF-1α-null mice developed severe hypertriglyceridemia with enhanced accumulation of lipids in the liver of mice exposed to a 6% ethanol-containing liquid diet for 4 weeks. Sterol regulatory element-binding protein 1c (SREBP-1c) and its downstream target acetyl-CoA carboxylase were greatly activated as the hepatic steatosis progressed, and these alterations were inversely correlated with the expression of the HIF-1-regulated gene DEC1. Overexpression of DEC1 in the mutant liver abrogated the detrimental effects of loss of HIF-1α gene on ethanol-induced fatty liver with reduced SREBP-1c expression. Conversely, co-administration of the HIF hydroxylase inhibitor dimethyloxalylglycine for the last 2 weeks improved markedly the ethanol-induced fatty liver in mice. Conclusions: The current results provide direct evidence for protective roles of HIF-1 induction in the development of ethanol-induced fatty liver via activation of the HIF-1-regulated transcriptional repressor DEC1.