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

Abstract
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 per-formed 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 com-pared with those of CONT and OVX groups; but, insignifi-cantly changed compared with SWIM group. Positive corre-lations 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 occur-rence of osteoporotic changes. So, the beneficial effects of swimming training on bone may be mediated by irisin.