Circulating levels and bone contents of bone gamma-carboxyglutamic acid-containing protein are decreased in streptozocin-induced diabetes. Possible marker for diabetic osteopenia.

To investigate the pathophysiology of diabetic osteopenia, circulating levels and bone contents of bone gamma-carboxyglutamic acid-containing protein (BGP) were measured in streptozocin-induced diabetic rats . Plasma calcium and total protein were significantly decreased (P less than .01) in the diabetic group, and the plasma level of BGP in diabetic rats was 19.6 +/- 2.8 (mean +/- SE) ng/ml, which is significantly lower than the value of 89.2 +/- 14.0 ng/ml in control rats (P less than .01). Bone contents of calcium and hydroxyproline per femur were significantly decreased in the diabetic group (P less than .01), and the ratios of bone calcium to hydroxyproline were not different. Bone BGP content per femur in the diabetic group was 669 +/- 58 micrograms, which was also significantly lower compared with 1241 +/- 126 micrograms in control rats (P less than .01). The decreased bone content of BGP is consistent with the hypothesis that BGP synthesis is impaired in insulin-deficient diabetes. Because a relationship between plasma levels of BGP and bone turnover has been established, the low plasma BGP value suggests there is a decrease in bone turnover in diabetic rats. Therefore, we postulate that the low bone turnover is one of the pathological features of diabetic osteopenia and is at least partly responsible for the occurrence of this complication in diabetes mellitus.