Effect of Swimming on Serum Irisin Levels in Experimentally-Induced Rat Model of Postmenopausal Osteoporosis

Background: Irisin is a new myokine that has been linked to many metabolic diseases. Postmenopausal osteoporosis is a metabolic disease manifested by decreased bone mineral density; and physical exercise may play a role in its prevention and treatment. The relationship between irisin and physical exercise, and the role of irisin in osteoporosis are not clear yet. Aim of Study: The present study was performed to clarify the effect of swimming training on serum irisin levels in a rat model of postmenopausal osteoporosis induced in female albino rats. Material and Methods: Forty eight adult female rats were divided into 4 equal groups: Control (CONT), swimming (SWIM), ovariectomized (OVX), and ovariectomized plus swimming (OVX + SWIM). Serum levels of irisin, estradiol, calcium, phosphorus alkaline phosphatase, and bone calcium, phosphorus, and femoral ash weights were measured and histopathological examination of femoral bones were performed in all groups. Results: Serum irisin levels were significantly increased in SWIM group compared with CONT group, and decreased in OVX group compared with CONT and SWIM groups. In OVX + SWIM group, they were significantly increased compared with those of CONT and OVX groups; but, insignificantly changed compared with SWIM group. Positive correlations were found between serum irisin and serum levels of estradiol, bone calcium and phosphorus, femoral bone ash weights in all groups; and with serum alkaline phosphatase in SWIM and OVX + SWIM groups. Conclusion: Swimming training increased serum irisin levels in ovariectomized rats and guarded against the occurrence of osteoporotic changes. So, the beneficial effects of swimming training on bone may be mediated by irisin.