RESUMEN
Aim To investigate the effects of acid sphingomyelinase(ASMase)on high-fat induced nonalcoholic fatty liver disease in mice and its regulation of PPARα- PGC-1α pathway. Methods ASMase knockout mice based on C57BL/6 background were constructed. Closed group heterozygotes were obtained through hybridized with wild-type mice(ASMase+/-),together with the littermate WT mice were prepared for NAFLD model in this study. The experiment was divided into four groups:WT+Chow:the WT mice were fed with normal diet for 12 weeks; WT+HFD:the WT mice were fed with high-fat diet for 12 weeks; ASMase+/-+Chow:the ASMase+/- mice were fed with normal diet for 12 weeks; ASMase+/- +HFD:the ASMase+/- mice were fed with high fat diet for 12 weeks. Biochemical method was used to detect serum TC,TG and liver TC,TG contents and liver function such as ALT and AST. Oil red staining,HE staining,Masson staining and Sirius red staining were performed to detect liver lipid accumulation,hepatocyte morphology and liver fibrosis. AmplexTM red sphingomyelinase kit was applied to detect ASMase activity. Western blot was performed to detect protein expressions of ASMase,PPARα,PGC-1α and CPT1. Results WT+HFD group displayed hypercholesterolemia and liver dysfunction. Levels of liver triglyceride(TG)were significantly higher than those in WT+Chow group(P<0.05 or P<0.01). Meanwhile,the hepatocytes showed marked steatosis,balloon-like changes,and fibrosis. Protein expression and activity of ASMase in liver increased significantly(P<0.01 or P<0.001),whereas CPT1,PPARα and PGC-1α expressions were not statistically significant compared with matched control group. Heterozygously ASMase-deficient mice reduced the elevated liver TG induced by HFD,as well as improving balloon-like changes and liver fibrosis. Furthermore,the expressions of PPARα,PGC-1α and CPT1 were up-regulated in ASMase+/- +HFD mice compared with WT+Chow group.Conclusions ASMase promotes hepatic steatosis and fibrosis,which may be related to its inhibition of PPARα-PGC-1α pathway.