Effect of Eight Weeks of High Intensity Interval Training on Insulin Resistance and IRS1 Gene Expression in Gastrocnemius Muscle of Obese Wistar Rats

Background and objectives: The role of genetic components in expression of proteins involved in signaling pathways of fat and carbohydrate metabolism has been well-demonstrated. The aim of this study was to determine effects of high intensity interval training (HIIT) on glucose, insulin, and insulin resistance levels as well as IRS1 expression in gastrocnemius muscle of obese Wistar rats. Methods: The study included 14 male, Wistar rats (aged 10 weeks) weighting 220 ± 20 g. Obesity was induced in all rats via exposure to a high-fat diet for six weeks. Then, the rats were randomly divided into a HIIT group (n=7) and a control group (n=7). The rats in the HIIT group performed treadmill running, five sessions a week, for eight weeks. Levels of fasting glucose, serum insulin, insulin resistance, and IRS1 expression in the gastrocnemius muscle of the rats were measured after the last training session. Data were analyzed by the independent t-test at statistical significance of 0.05. Results: The HIIT intervention significantly decreased fasting glucose compared with the control group (p<0.0001). It also resulted in a significant decrease in serum insulin levels and insulin resistance compared with the control group (p<0.0001). Moreover, the HIIT training significantly increased IRS1 expression (p=0.030) in the gastrocnemius muscle of rats. Conclusion: Based on the available evidence, the increase in insulin function and the decrease in insulin resistance can be attributed to increased IRS1 expression in the gastrocnemius muscle following HIIT training.