Effects of aerobic exercise on CNPY2-PERK pathway in the liver of mice with non-alcoholic fatty liver disease

Abstract

Objective: To investigate the effects of aerobic exercise on non-alcoholic fatty liver (NAFLD) induced by high fat and the mechanism of CNPY2-PERK pathway. Methods: Eight-week-old male C57BL/6J mice were randomly divided into four groups: the control group (C), the C+ aerobic exercise group (CE), the model group (M) and the M+ aerobic exercise group (ME). Mice in group C and CE were given normal diet, while mice in group M and ME were given high-fat diet (60 cal % fat). The mice were fed continuously for 18 weeks until the end of the experiment, and the serum and liver samples were collected. Both CE and ME group performed an aerobic treadmill training from the 10th week (12 m/min, 60 min/ day, 5 days/week, for 8 weeks). The serum levels of total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), alanine aminotransferase (ALT), aspartate aminotransferase (AST) were detected. The pathological morphology of the liver was observed. The relative expressions of CNPY2, PERK, p-eIF2a, CHOP, CNPY2 mRNA and PERK mRNA, and the positive expressions of CNPY2 and PERK were measured. Results: Compared with group C, the serum levels of LDL-c, TC, TG, ALT and AST in group M were increased significantly (P＜0.05), while the HDL-c level was decreased significantly (P＜0.05). The liver tissues of mice showed obvious hepatic steatosis, the number of lipid droplets in liver cells was increased, and the expressions of CNPY2, CNPY2mRNA, PERK, PERKmRNA, p-eIF2a, CHOP, and the positive expressions of both CNPY2 and PERK in liver were increased (P＜0.05). However, the above indexes showed no significant difference in CE group (P＞0.05). Compared with group M, the serum levels of LDL-c, TC, TG, ALT and AST in group ME were decreased (P＜0.05). The fatty degeneration of liver tissue and the number of lipid droplets in liver cells in mice was reduced, and the expressions of CNPY2, CNPY2 mRNA, PERK, PERK mRNA, p-eIF2a, CHOP, and the positive expressions of CNPY2 and PERK in liver tissue were decreased (P＜0.05). Conclusion: The CNPY2-PERK pathway is involved in the formation of NAFLD. Aerobic exercise can effectively ameliorate NAFLD, and the mechanisms may be related to the reduction of CNPY2-PERK pathway-related molecule expressions by aerobic exercise.