Impact of exercise-induced irisin on bones of osteoporotic male rat model

This study aimed to evaluate the impact of exercise-induced irisin on bone mineral density (BMD), bone turnover and bone microarchitecture in normal and glucocorticoid-induced osteoporotic rats. Four groups of rats (10 rats each) were included in the study; group1 (control group), group 2 (normal exercised) which its rats underwent an exercise protocol, group 3 (osteoporotic rats) where Methylprednisolone was administered intravenously to the rats in order to induce osteoporosis. And group 4 (osteoporotic exercised rats), its rats underwent the same exercise protocol as group 2 after induction of osteoporosis by methylprednisolone. At the end of the study, BMD was measured then the rats were sacrificed and their serum levels of irisin, alkaline phosphatase (ALP), total calcium, serum C-terminal telopeptide of type I collagen (CTX1) were measured, Osteocalcin (OCN) and Osterix (OSX) mRNA in bone tissues were also assessed. Bone microarchitecture was also histologically examined. The study results revealed that exercise improved BMD, increased the levels of serum irisin, ALP, total calcium, (OCN) and (OSX) mRNA levels with decreased serum CTX1 levels. Furthermore there was significant difference in microarchitecture of bone in normal exercised and osteoporotic exercised rats as compared to control and osteoporotic rats, respectively. Moreover, significant positive correlations were found between serum irisin levels and each of BMD, OCN and OSX mRNA and osteocytes and osteoblasts numbers. Conversely, a negative correlation was found between serum irisin level and CTX1.In conclusion, this study highlighted irisin as a new target for preservation of bone in glucocorticoid-induced osteoporosis.