Background and aims: Irisin myokine whose secretion is induced by exercise is associated with an increase in thermogenesis. However, the effect of aerobic exercise with different intensities on the production and release of irisin in overweight individuals is controversial. This study aimed to investigate the effect of eight weeks of aerobic training with different intensities on PGC-1α, FNDC5, UCP1, and irisin in obese male Wistar rats. Methods: In this experimental study, 24 adult obese male Wistar rats (weight: 250-300 g; body mass index [BMI] >30 g/cm2) divided into three groups, including aerobic training with 28 m/min (moderate intensity [MI]), aerobic training with 34 m/min (high intensity [HI]), and control. All training groups exercised for eight weeks walking on a treadmill (five 60-min sessions per week). The paired sample t test and one-way ANOVA were used to determine the intra- and inter-group differences. Furthermore, Tukey’s post hoc test was used. Results: The levels of PGC-1α in muscle tissue in aerobic training groups with MI and HI increased (P=0.001 and F=11.81) compared to control group. The levels of irisin (P=0.006 and F=6.10) and UCP1 (P=0.04) were significantly increased in MI group. On the other hand, FNDC5 increased significantly in both MI and HI groups (P=0.001 and F=12.49). While irisin and UCP1 levels increased in HI group compared to the control group, the change was not statistically significant (P>0.05). The levels of irisin, UCP1, and FNDC5 increased more significantly in MI group than in HI group (P<0.05). Conclusion: Both types of aerobic training (MI and HI) had a beneficial effect on changes in irisin, UCP1, FNDC5, and PGC-1α levels. Accordingly, moderate exercise possibly changes the phenotype of white to brown adipose tissue leading to an increase in thermogenesis, body weight loss, and sensitivity to insulin.

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