Additive effects of estrogen deficiency and diabetes on bone mineral density in rats

We investigated the combined effects of estrogen deficiency and diabetes on bone mineral density (BMD) and bone metabolism in rats. Ten-week-old, female rats were randomly divided into four groups: controls (C), an ovariectomized group (O), a streptozotocin-induced diabetic group (S), and a combined ovariectomy and streptozotocin-induced diabetic group (OS). The BMD of the lumbar spine and the femur were measured before grouping and at 23 weeks old. At the end of the experiment, blood samples were obtained via cardiac puncture, and bone gla protein (BGP), tartrate-resistant acid phosphatase (TRAP) and 1,25-dihydroxyvitamin D levels were measured. The rats in the C, O, S, and OS groups, in that order, had higher levels of BMD of the lumbar spine and femur at 23 weeks of age. The BGP levels in the S and OS groups were significantly lower than in C and O groups. Significantly higher 1,25-dihydroxyvitamin D was observed in the O group compared with the C, S and OS groups. No differences were obtained in TRAP among four groups. Our data suggest that the combined effects of estrogen deficiency and diabetes on BMD are not synergistic or counteractive but additive. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.