Serum Irisin is Associated with Bone Mineral Density in Postmenopausal T2dm Patients Complicated with Osteoporosis and in Mice with Diabetic Osteoporosis

Background: Osteoporosis is a systemic bone disease with low bone mass, destruction of bone microstructure, and increased bone fragility. Gender and metabolic status are well-known risk factors for osteoporosis. Irisin is a newly discovered myokine that is secreted by skeletal muscle and adipose tissue. Serum Irisin was reported to be decreased in type 2 diabetes mellitus (T2DM) and/or osteoporosis patients, and it is correlated with bone mineral density (BMD) of neck bone, but its role in postmenopausal T2DM with osteoporosis remains largely unknown. Methods: Postmenopausal T2DM patients with or without osteoporosis were recruited, and 50 agematched healthy postmenopausal women were employed as healthy control. C57BL/6J mice were intraperitoneally injected with 65 mg/kg Streptozotocin (STZ) daily for consecutive 5 days to induce diabetes, and 1 mg/kg recombinant Irisin protein was injected into diabetic mice through the tail vein once a week for 4 months. Results: Compared to that of healthy control, serum Irisin levels and BMD in L1–L4 lumbar spine, femoral neck, total hip, and Wards were decreased in postmenopausal T2DM patients and further decreased in T2DM patients with osteoporosis. Moreover, serum Irisin levels were also correlated with BMD in the above body parts in T2DM patients. Furthermore, recombinant Irisin protein improved diabetic osteoporosis and inflammation in STZ-induced diabetic mice with osteoporosis. Conclusion: Serum Irisin levels in postmenopausal T2DM patients with osteoporosis were significantly decreased, which may be related to the decreased BMD and the occurrence of osteoporosis in postmenopausal T2DM patients. The combined measurement of serum Irisin levels and BMD in patients with T2DM in the early stage has a certain effect on the diagnosis and treatment of osteoporosis.