ABSTRACT
AIM: To determine the role of G0/G1 switch gene 2 (G0S2) and its transcriptional regulation in palmitate-induced hepatic lipid accumulation. METHODS: HepG2 cells were treated with palmitate, or palmitate in combination with CCAAT/enhancer binding protein (C/EBP)ß siRNA or G0S2 siRNA. The mRNA expression of C/EBPß, peroxisome proliferator-activated receptor (PPAR)γ and PPARγ target genes (G0S2, GPR81, GPR109A and Adipoq) was examined by qPCR. The protein expression of C/EBPß, PPARγ, and G0S2 was determined by Western blotting. Lipid accumulation was detected with Oil Red O staining and quantified by absorbance value of the extracted Oil Red O dye. Lipolysis was evaluated by measuring the amount of glycerol released into the medium. RESULTS: Palmitate caused a dose-dependent increase in lipid accumulation and a dose-dependent decrease in lipolysis in HepG2 cells. In addition, palmitate increased the mRNA expression of C/EBPß, PPARγ, and PPARγ target genes (G0S2, GPR81, GPR109A, and Adipoq) and the protein expression of C/EBPß, PPARγ, and G0S2 in a dose-dependent manner. Knockdown of C/EBPß decreased palmitate-induced PPARγ and its target genes (G0S2, GPR81, GPR109A, and Adipoq) mRNA expression and palmitate-induced PPARγ and G0S2 protein expression in HepG2 cells. Knockdown of C/EBPß also attenuated lipid accumulation and augmented lipolysis in palmitate-treated HepG2 cells. G0S2 knockdown attenuated lipid accumulation and augmented lipolysis, while G0S2 knockdown had no effects on the mRNA expression of C/EBPß, PPARγ, and PPARγ target genes (GPR81, GPR109A and Adipoq) in palmitate-treated HepG2 cells. CONCLUSION: Palmitate can induce lipid accumulation in HepG2 cells by activating C/EBPß-mediated G0S2 expression.
