Therapeutic effect of exercise on nonalcoholic fatty liver disease induced by high-fat diet

Objective To observe the effect of exercise on nonalcoholic fatty liver disease (NAFLD) induced by high-fat diet and explore the mechanism.Methods Thirty healthy male rats were randomly divided into a normal control group( NC group) and a high-fat group( HF group), fed with normal chow and high-fat diet, respectively.Eighteen weeks later, the high-fat established as insulin resistance model and group was randomly divided into high-fat diet control group (HC group) and high-fat diet exercise group (HE group).HC group was continually given high-fat diet; HE group accepted swimming training for 6 weeks.After 24 weeks, the insulin sensitivity index (ISI) was calculated.After rats were sacrificed, weight of liver and body were measured to calculate liver mass index.Liver histology was detected by hematoxylin and eosin staining.Hepatic triglyceride content was detected.Phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) level was detected by Western blot technique.Results At the 18th week, compared to NC group, ISI of HF group decreased obviously.It suggested that insulin resistance appeared in HF group.At the 24th week, compared to NC group, ISI of HC group decreased significantly.But hepatic triglycefide content and liver mass index both increased.Pathology observation under light microscope showed obvious liver steatosis in HC group.Phosphorylation of AMPK level in HC group decreased to 50.8% of NC group.Exercise greatly improved the liver mass index, hepatic triglyceride content and ISI as well as liver steatosis compared to HC group.Phosphorylation of AMPK was also elevated to 78.1% of NC group in HE group.However,compared to NC group, liver mass index and hepatic triglyceride content increased simultaneously, while ISI and phosphorylation of AMPK level obviously decreased in HE group.Conclusion Elevated level of phosphorylation of AMPK contributed to improve insulin resistance and decrease the hepatic triglyceride content.Exercise could markedly improve NAFLD induced by high-fat diet through elevating phosphorylation of AMPK in liver. Key words: Exercise; Nonalcoholic fatty liver disease; Adenosine monophosphate-activated protein kinase; Insulin resistance