Effects of different intensities of endurance training on serum fibroblast growth factor level, glucose, and insulin resistance in streptozotocindiabetic male rats

Background and aims: Fibroblast growth factor 21 (FGF21) is a myokine which is produced and secreted by skeletal muscle. Given the inconsistent results on the relationship between the intensity of training and the improvement of blood indices in diabetic patients, the current research investigated the effect of endurance training at different intensities on serum FGF21 level, glucose, and insulin resistance in streptozotocin (STZ)diabetic male rats. Methods: To this end, 50 rats (with a mean weight of 23.28±25.05 g) were randomly divided into healthy (nondiabetic) control, diabetic control, as well as low, moderate, and highintensity endurance training groups. Diabetes was induced in all rats by the injection of STZ. Three days after STZ injection, the blood samples were taken from the cut tip of the tails, and those rats with blood glucose levels above 300 mg/dL were considered diabetic and included in the study. The program included 8week aerobic training at different intensities. The blood samples (5 cc) were directly collected from the hearts 48 hours after the last training session, followed by measuring the serum FGF21 level, glucose, and insulin. Finally, the analysis of variance and Bonferroni posthoc test were used for intergroup comparison and the significance level was considered lt;0.05. Results: Based on the results, the serum glucose level, insulin resistance, and FGF21 reduced after eight weeks of endurance training. The reduction of FGF21 in higher intensity endurance training group was greater compared to the other groups (P lt;0.05) and the reduction of glucose in moderate intensity group was more significant in comparison to that of the other groups (P lt;0.001). However, the insulin level increased, which was more pronounced in the moderate intensity training group compared to the other groups (P=0.002). Conclusion: Overall, both moderate and highintensity endurance training led to a comparatively more effective reduction in blood glucose and insulin resistance. Therefore, these two parameters may have a protective effect on the complications associated with diabetes in the rats.