OBJECTIVETo explore the role of NF-E2-related factor 2(Nrf2) and its related factors in the progression of nonalcoholi steatohepatitis (NASH) by investigating the alterations of lipid metabolism and liver histopathology as well as the changes of mRNA and protein expression levels of Nrf2 and its related factors in rats during NASH progression.

METHODSMale SD rats were randomly divided into normal group and model group, which were administrated with high fat diet to establish nonalcoholic steatohepatitis model. The rats from both groups were randomly killed at the end of 4, 12 weeks respectively. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) were detected in the serum and liver tissue; Changes in fat deposition in liver tissue were determined by oil red O staining. HE staining were used to observe the pathological changes of liver tissue and to calculate nonalcoholic fatty liver disease (NAFLD) activity score (hepatic steatosis, inflammation and ballooning degeneration of liver cells). The expression of Nrf2 in liver was detected by immunohistochemical staining. The mRNA and protein levels of Nrf2 and related factors in liver were determined by Realtime PCR and Western blot, respectively.

RESULTSAfter 4 weeks of high fat diet, the levels of ALT, AST, TC in rat serum and TC, TG, LDL-C in liver were significantly increased compared with that of the normal group (P < 0.01, P < 0.05). After 4 weeks of high fat diet, the levels of ALT, AST, TC, TG in serum and TC, TG, LDL- C in liver increased further (P < 0.01, P < 0.05). Until the 12th week, the content of HDL-C in liver was significantly lower than that of the normal group (P < 0.05). At the end of the 4th or the 12th week, lipid droplets in the model rat liver cells were heavily dyed red and hepatic steatosis increased severely, with ballooning degeneration of liver cells. With the extension of high fat diet feeding time, fat deposition in the liver tissue, hepatic steatosis, NAFLD score, Nrl2 expression were significantly increased (P < 0.01). Expression levels of mRNA and protein of Nrf2, heme oxyenase 1(HO1), NADPH quinone oxidoreductase 1(NQO1), γ-glutamylcysteine synthethase (γ-GCS), glutathione S-transferase (GST) in the model rats increased or decreased at the end of the 4th or the 12th week differentially, (P < 0.01, P < 0.05) with the more significant changes at the end of the 4th week than the 12th week.

CONCLUSIONNrf2 and its related factors may be involved in the occurrence and development of nonalcoholic fatty liver disease, which may play an important role in the process of NASH formation.