Objective: To investigate the effects of exercise on insulin receptor, glucose transporter 4 (GLUT4) gene expression and protein content in skeletal muscle cells of streptozotocin-induced diabetic rats.
Methods: All rats were randomized into three groups: normal, diabetic and diabetic exercise groups. Diabetic exercise rats were swim-trained for 6 weeks. The GLUT4 mRNA of skeletal muscle was determined with dot blot and GLUT4 protein was detected by Western blotting.
Results: After 6 weeks of exercise training, plasma glucose level of diabetic rats decreased from 18.5 mmol/L +/- 1.9 mmol/L to 14.0 mmol/L +/- 3.3 mmol/L (P < 0.01). The dot blot revealed that GLUT4 mRNA decreased by 54.9% in skeletal muscle cells of diabetic rats compared with the normal rats. The Western blotting showed that GLUT4 protein of skeletal muscle cell in diabetic rats decreased by 30.7% compared with the control rats. GLUT4 mRNA and the protein of skeletal muscle in diabetic exercise group increased by 56% and 60.8% respectively as compared with the diabetic rats. However, the maximum binding of insulin receptor of skeletal muscle cells in diabetic exercise group decreased significantly compared with diabetic group.
Conclusion: The weaker expression of GLUT4 gene and the lower level of GLUT4 protein may be one of the causes of hyperglycemia in diabetic rats. Exercise training may raise the GLUT4 gene expression and the amount of GLUT4 protein in diabetic rats, contributing to the main mechanism of improved post-receptor insulin resistance and decreased hyperglycemia in diabetic rats.