Swimming exercise increases serum irisin level and reduces body fat mass in high-fat-diet fed Wistar rats.

Background: It has been shown that irisin levels are reduced in skeletal muscle and plasma of obese rats; however, the effect of exercise training on irisin level remains controversial. We aim to evaluate the association of swimming exercise with serum irisin level and other obesity-associated parameters.

Methods: Forty healthy male Wistar rats were randomly assigned to 4 groups: a normal diet and sedentary group (ND group), normal diet and exercise group (NDE group), high-fat diet and sedentary group (HFD group), and high-fat diet and exercise group (HFDE group. After 8 consecutive weeks of swimming exercise, fat mass and serum irisin level was determined.

Results: Higher serum irisin levels were detected in the HFDE group (1.15 ± 0.28 μg/L) and NDE group (1.76 ± 0.17 μg/L) than in the HFD group (0.84 ± 0.23 μg/L) or the ND group (1.24 ± 0.29 μg/L), respectively (HFDE group vs. HFD group, P < 0.05; NDE group vs. ND group, P < 0.01). Pearson's correlation analysis showed that serum irisin level negatively correlated with TG level (r = -0.771, P < 0.05), percentage fat mass (r = -0.68, P < 0.05), fat mass (r = -0.576, P < 0.05), visceral fat mass (r = -0.439, P < 0.05) and TC level (r = -0.389, P < 0.05). The fat mass, visceral fat mass and percentage fat mass were lower in the HFDE group than the HFD group (all P values < 0.01).

Conclusion: Swimming exercise decreases body fat mass in high-fat-fed Wistar rats, which may be attributable to elevated irisin levels induced by swimming exercise.