Abstract
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 (non-diabetic) control, diabetic
control, as well as low, moderate, and high-intensity 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 8-week 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 post-hoc test were used for inter-group comparison and
the significance level was considered <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<0.05) and the reduction of
glucose in moderate intensity group was more significant in comparison to that of the other groups (P<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 high-intensity 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.