Background. Irisin is the result of the proteolysis of fibronectin type III domain-containing protein 5, the levels of which are determined by physical activity. Objective(s). This study aims to identify changes in FNDC5 gene expression and the heart muscle irisin levels in male rats following 8 weeks resistance and endurance training. Methods. Fifteen male rats (10-12 weeks old and 331.8±63.09 g in weight) were randomly assigned to three groups: control, resistance and endurance training groups (5 in each group). The endurance group performed activities on a treadmill for 8 weeks. The resistance group performed activities for 8 weeks on a one-meter-long ladder with a slope of 85○. The control group did not undergo any particular training. Sampling was carried out 72 h after the end of the training. The heart tissue were excised, cleaned and immediately frozen in liquid nitrogen, and stored at -70○C. FNDC5 gene expression and the heart muscle irisin levels were measured using Real-Time PCR and ELISA, respectively. Results. Kruskal-Wallis test showed a significant increase in the heart muscle FNDC5 expression in both training groups (P=0.004). One-way ANOVA showed a significant difference in heart muscle irisin levels among the groups (p=0.004). Conclusion. It can be concluded that both resistance and endurance training can significantly increase FNDC5 gene expression and the heart muscle irisin levels, suggesting that physical activity can prevent and cure cardiovascular diseases.

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