American Journal of Physiology vol:254 issue:4 Pt 1 pages:E496-504
The effect of diabetes on maternal bone mineral metabolism and fetal mineralization was studied in nonpregnant and pregnant BB rats fed two diets (0.85% calcium-0.7% phosphorus and 0.2% calcium-phosphorus). Non-pregnant female diabetic rats had normal total bone mineral content (BMC), despite decreased trabecular bone volume density (TBVD). Nondiabetic rats on the low calcium-phosphorus diet showed decreased TBVD, signs of increased bone turnover, and decreased BMC; plasma 1,25-dihydroxyvitamin D3 [1,25 (OH)2D3] was increased and urinary calcium excretion was decreased. A similar response was observed in diabetic rats with a further decrease in TBVD. Nondiabetic 21-day pregnant rats on high and low calcium-phosphorus diets had higher 1,25(OH)2D3 than nonpregnant rats (98 vs. 58 and 328 vs. 147 pg/ml, respectively). Maternal BMC did not change during pregnancy but was decreased by the low calcium-phosphorus diet; fetal mineral content was not influenced by the low calcium-phosphorus regime. No increase in 1,25(OH)2D3 was observed in pregnant diabetic rats (57 vs. 52 and 112 vs. 128 pg/ml in high and low calcium-phosphorus diet groups). Fetal mineralization was severely impaired in diabetes but was not further decreased by the low calcium-phosphorus diet. Thus nonpregnant diabetic rats respond normally to a low calcium-phosphorus diet, but pregnant diabetic rats do not show increased 1,25(OH)2D3 levels due to impairment of fetal mineralization.