Changes in Serum Osteocalcin are Not Associated with Changes in Glucose or Insulin for Osteoporotic Patients Treated with Bisphosphonate

BACKGROUND Bisphosphonate is used in osteoporosis treatment to repress osteoclast activity, which then decreases levels of osteocalcin (OC). OC, a protein secreted by osteoblasts and released from the bone matrix during osteoclastic bone resorption, has been found to control blood glucose levels by increasing insulin production and sensitivity. The question addressed in this study is whether decreasing OC through bisphosphonate treatment will provoke a change in glucose homeostasis. METHODS Eighty-four patients with osteoporosis were treated with once-weekly risedronate 35 mg and cholecalciferol 5,600 IU. We measured fasting plasma glucose (FPG), insulin, and undercarboxylated (Glu) and carboxylated (Gla) OC levels at baseline and after 16 weeks. To estimate insulin resistance (IR) and β-cell function (B)%, homeostasis model assessment (HOMA)-IR and HOMA-B% were also calculated, respectively. RESULTS The mean FPG level in total subjects increased significantly from 5.3 to 5.5 mmol/L, but no changes in blood glucose were noted in the 24 subjects with impaired fasting glucose. Glu and Gla OC levels declined significantly after treatment. No correlations were observed between changes in OC and changes in glucose, however. CONCLUSIONS Bisphosphonate treatment for osteoporosis reduced OC, but this change was not associated with changes in glucose metabolism.