Although some other factors, such as diabetic complications, may lead to increased risk of fall and fracture in these patients, the main reason may be attributed to the value of BMD.12 In the current study, we found the level of Apelin-13 in osteoporosis and osteopenia group was significantly lower than that in normal group, and multivariate analysis showed that in all included patients the level of Apelin-13 was positively correlated to the value of BMD, demonstrating that Apelin-13 may be a protective factor for osteoporosis in patients with Type-2 diabetes mellitus. Here, APLN is linked to type 2 diabetes mellitus.