Deletion of steroid receptor coactivator-3 gene ameliorates hepatic steatosis

Background & aims: Excess dietary fat can cause hepatic steatosis, which can progress into severe liver disorders including steatohepatitis and cirrhosis. Steroid receptor coactivator-3 (SRC-3), a member of the p160 coactivator family, is reported as a key regulator of adipogenesis and energy homeostasis. We sought to determine the influence of SRC-3 on hepatic steatosis and the mechanism beneath. Methods: The influence of siRNA-mediated SRC-3 silencing on hepatic lipid accumulation was assessed in HepG2 cells. The molecular mechanism of SRC-3 regulation of hepatic lipid metabolism was also studied. Moreover, the effect of SRC-3 ablation on hepatic steatosis was examined in SRC-3 deficient mice. Results: In this study, we report that SRC-3 ablation reduces palmitic acid-induced lipid accumulation in HepG2 cells. Moreover, deletion of SRC-3 ameliorates hepatic steatosis and inflammation response in mice fed a high fat diet (HFD). These metabolic improvements can presumably be explained by the reduction in chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) expression and the subsequent elevation in peroxisome proliferator-activated receptor alpha (PPAR alpha) level. At the molecular level, SRC-3 interacts with retinoic receptor a (RAR alpha) to activate COUP-TFII expression under all-trans retinoic acid (ARTA) treatment. Conclusions: These findings indicate a crucial role for SRC-3 in regulating hepatic lipid metabolism and provide the possible novel inner mechanisms. (C) 2011 Published by Elsevier B.V. on behalf of the European Association for the Study of the Liver.