Both intestinal and hepatic lipoprotein production are stimulated by an acute elevation of plasma free fatty acids in humans

Role of ChREBP and its target gene PNPLA3 in pathogenesis of nonalcoholic fatty liver disease in rats

AIM: To explore the role of carbohydrate responsive element binding protein (ChREBP) and its target gene patatin-like phospholipase domain containing family member A3 (PNPLA3) in the pathogenesis of nonalcoholic fatty liver disease (NAFLD).

METHODS: Forty-eight adult male rats were randomly and equally divided into two groups to receive a normal fed diet (control group) or a high-fat diet (NAFLD model group). At the end of the 4th, 8th and 12th wk, 8 rats in each group were killed to determine serum biochemical parameters, observe pathological changes in hepatic tissue under a light microscope, detect the expression of ChREBP protein by immunohistochemistry, and detect the expression of ChREBP and PNPLA3 mRNAs in the liver by RT-PCR.

RESULTS: NAFLD was successfully induced in rats after feeding a high-fat diet. In the control group, rat liver lobule structure was intact under a light microscope, the biochemical parameters were in the normal ranges, and expression of ChREBP protein was weak in the liver tissue. Compared with the control group, rat weight was increased, the volume of the liver was obviously increased, fat drop deposition was visible in liver cells, and the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol (TC), triglycerides (TG), fasting blood glucose (FBG), and fasting serum insulin (FINS) were significantly elevated in the model group (P < 0.05 for all). With the prolongation of feeding time, blood AST, ALT, TC, TG FBG and FINS levels were gradually elevated and ISI significantly declined (P < 0.05). ChREBP protein expression and ChREBP and PNPLA3 mRNA expression in rat liver tissue were increased in the model group compared with the control group (P < 0.05). With the prolongation of feeding time, ChREBP protein expression and ChREBP and PNPLA3 mRNA expression were significantly increased (P < 0.05). ChREBP mRNA expression in the model group was positively correlated with PNPLA3 expression, serum levels of AST, ALT, and hepatic inflammatory activity score (r = 0.409, P < 0.05; r = 0.498, P < 0.05; r = 0.677, P < 0.01; r = 0.729, P < 0.01; r = 0.566, P < 0.01), but had a negative correlation with ISI (r = -0.611, P < 0.01).

CONCLUSION: High fat diet induces the expression of ChREBP, which may activate the expression of lipid synthesis related gene PNPLA3 and promote the formation of fatty liver through regulation of insulin resistance.