Abstract: Objective To investigate the effect of mutation human proprotein convertase subtilism/kexin type 9(hPCSK9^D374Y) in PCSK9 gene on methionine choline deficiency diet (MCD)-induced nonalcoholic steato-hepatitis (NASH) in mice. Methods Sixteen C57BL/6J wild-type mice were selected and randomly divided into the hPCSK9^D374Y group and the control GFP group. MCD was fed for 6 weeks, and then the serum level of hepatic triglyceride, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was examined. Oil Red O and Sirius Red staining microscopy were used to identify hepatic lipid infiltration and fibrosis severity. F4/80-positive cell infiltration was analyzed using immunohistochemistry. Lipid synthesis and inflammatory response-related proteins were detected by Western blot and related mRNA expression was analyzed by RT-qPCR. Results Hepatic hPCSK9 protein and mRNA were significantly up-regulated, LDLR protein expression was down-regulated, and serum level of ALT and AST was significantly elevated in the hPCSK9^D374Y group of mice(P＜0.05). The degree of hepatic steatosis and fibrosis increased and F4/80-positive cells were significantly increased (P＜0.01). FASN and SCD1 proteins were significantly up-regulated and PPARα was down-regulated in the hPCSK9^D374Y group; The expression of TLR4 and p-P65 was elevated, whereas the expression of IκBα was decreased (P＜0.001). RT-qPCR results showed a significant increase of mRNA coding inflammatory factors TNF-α, IL-1β, IL-6, and MCP-1, and a significant up-regulation of fibrosis-associated mRNAs (collagen Ⅰα and collagen Ⅲα) was found (P＜0.001). Conclusions Functionally acquired mutation in the PCSK9 gene (hPCSK9^D374Y) exacerbates MCD-induced hepatic steatosis, inflammatory response and fibrosis in mice.

Key words: non-alcoholic steatohepatitis, proprotein convertase subtilisin/kexin type 9 (PCSK9), methionine choline deficiency diet, inflammatory factor