The therapeutic effect of exercise on insulin resistance induced by a high fat diet

Objective To observe the effect of exercise on insulin resistance induced by a high fat diet and to explore the underlying mechanism.Methods Thirty healthy male Wistar rats were randomly divided into a normal control group (NC group) and a high-fat group (HF group),fed with normal chow and a high fat diet respectively.Eighteen weeks later,insulin resistance had appeared in the HF group.The HF group was then randomly subdivided into a high-fat diet control group (HC group,fed a high fat diet) and an exercise group (HE group,fed a high fat diet and subjected to swimming training for 6 weeks).After 24 weeks,an insulin sensitivity index was calculated.Serum free fatty acid (FFA) and skeletal muscle triglyceride (TG) were detected.Phosphorylation of adenosine monophosphate kinase-α (AMPKα) in skeletal muscle was detected by Western blotting.Results At twenty-four weeks the insulin sensitivity of the HC group had decreased significantly compared to the NC group.Serum FFA level and skeletal muscle TG content had both increased.Average phosphorylation of AMPKα in the HC group decreased to 48.7% of the NC group average.Compared to the HC group,insulin sensitivity and phosporylation of AMPK-α were elevated significantly in the HE group.Serum FFA level and skeletal muscle TG content were both lower.However,compared to the NC group,both serum FFA level and skeletal muscle TG content had increased in the HE group,while insulin sensitivity and phosphorylation of AMPKα had significantly decreased.Conclusions Exercise can significantly improve insulin resistance induced by a high-fat diet through decreasing serum FFA level and ectopic li-pid accumulation in skeletal muscle. Key words: Exercise; Triglycerides; Adenosine monophosphate kinase; Free fatty acid; Insulin resistance