Effect of a bisphosphonate and selective estrogen receptor modulator on bone remodeling in streptozotocin-induced diabetes and ovariectomized rat model.

BACKGROUND CONTEXT

Diabetes and menopause can cause severe osteoporosis. In general, menopause and diabetes can lead to an imbalance in bone turnover, which results in secondary osteoporosis. However, the efficacy of antiresorptive drugs against this form of osteoporosis has not been extensively evaluated.

OBJECTIVE

The aim of this study was to determine the changes in vertebral bone remodeling when postmenopausal osteoporosis is accompanied by diabetes and to compare the efficacy of bisphosphonates and selective estrogen-receptor modulators (SERMs) against these outcomes.

STUDY DESIGN

Streptozotocin-induced diabetic, ovariectomized Sprague-Dawley rats were used as the disease model. Alendronate and raloxifene were used as the bisphosphonate and SERM, respectively.

METHODS

We divided 62 female rats into five groups: (1) control (n=14), (2) DM (diabetes) (n=12), (3) DM+OVX (diabetes+ovariectomy) (n=12), (4) DM+OVX+A (diabetes+ovariectomy+alendronate) (n=12), and (5) DM+OVX+R (diabetes+ovariectomy+raloxifene) (n=12). Serum biochemical markers of bone turnover, including osteocalcin and the C-telopeptide of type I collagen (CTX-1), were analyzed. We measured histomorphometric parameters of the fourth lumbar vertebrae using microcomputed tomography. Mechanical strength was evaluated by a compression test.

RESULTS

In the DM and DM+OVX group, only the levels of osteocalcin significantly decreased compared with those of the control group at 8 weeks after OVX. At 12 weeks, the serum CTX-1 levels in the DM+OVX+A and DM+OVX+R groups were significantly lower than those of the DM+OVX group, but there were no changes in the levels of osteocalcin. Bone mineral density and mechanical strength were higher in the DM+OVX+A and DM+OVX+R groups than in the DM and DM+OVX groups (p<.05).

CONCLUSIONS

Even if postmenopausal osteoporosis is accompanied by diabetes in this animal model, both alendronate and raloxifene seem to show antiresorptive effects, decreased bone turnover rates, and improved bone mechanical strength. Therefore, alendronate and raloxifene are effective in the treatment of osteoporosis even for bone loss caused by DM and postmenopausal osteoporosis.