DIETARY CASEIN PHOSPHOPEPTIDES PREVENT BONE LOSS AGED OVARIECTOMIZED RATS

The effect of dietary Ca-bound casein phosphopeptides (CaCPP) on the b ones of aged ovariectomized (OVX) rats was studied as a model for post menopausal bone loss. Three groups of ovariectomized rats were fed a c ontrol diet or one of two experimental diets, and one group of sham-op erated rats (SHAM) was fed the control diet. The experimental diets co ntained 0.5% Ca and 0.4% P. In one diet, CaCPP was the sole source of calcium and provided 62.5% of dietary phosphorus (CaCPP diet). In the other, Ca-free CPP provided 100% of dietary phosphorus (Ca-free CPP di et). In the control diet, CaCO3, and KH2PO4 were used. During a 17-wk feeding period, there was little change in femoral bone mineral densit ies (BMD) of ovariectomized rats fed CaCPP and Ca-free CPP, or in the SHAM rats fed the control diet, whereas the bone mineral densities in the control ovariectomized rats decreased with time. Some of the segme ntal bone mineral densities of the excised femurs from the rats fed Ca CPP were significantly higher than those from the control ovariectomiz ed rats, but the values of the Ca-free CPP group were similar to those of the control ovariectomized rats. In the Ca-free CPP group, the dis crepancy in bone mineral densities obtained between in vivo results an d excised specimens might have been the result of a loss in bone mass due to their significant loss in body weight. There were no significan t differences in serum inorganic phosphorus, alkaline phosphatase acti vity, osteocalcin or 1 alpha-25-dihydroxycholecalciferol concentration s among the ovariectomized groups. In the CaCPP and Ca-free CPP groups , urinary phosphorus excretion decreased and urinary calcium excretion increased significantly with time. The inhibitory effect on bone loss in aged ovariectomized rats could be due to the effects of dietary Ca CPP on phosphorus and calcium metabolism.