Effect of a diet rich in calcium on mineral and bone metabolism in rats

Abstract

Objetive: A diet rich in calcium has generally been recommended to maintain adequate bone health. However, recent studies have sparked controversy over its benefits. In this sense, most of the existing studies in animal models are carried out with diets deficient in vitamin D. In this study, the effect of a diet rich in calcium on mineral metabolism and bone his tomorphometry in rats is evaluated. In addition, in UMR‐106 cells, the direct effect of calcium supplementation on the expression of osteogenic genes is assessed. Material and methods: A group of male wistar rats of approximately 3 months of age was fed a normal calcium content diet (0.6%) while another group received a high calcium content diet (1.2%). After 20 days urine samples were collected 24h, blood for biochemical analysis and the femur for bone histomorphometry study. In vitro, the gene expression of Runx2, Osterix and Osteocalcin was studied in UMR‐106 cells cultured under conditions of high calcium content. Results: The ingestion of a diet rich in calcium reduced the concentration of PTH and calcitriol in plasma, increased calciuria and decreased phosphaturia. At the bone level, a drastic decrease in osteoblastic activity was observed, consistent with the decrease in PTH. However, the trabecular volume remained similar in both groups. In vitro, calcium supplementation did not decrease the expression of osteoblastic markers in UMR‐106, indicating that the in vivo effects are mostly indirect and due to the decrease in PTH. Conclusions: A high‐calcium diet reduces the concentration of PTH and calcitriol in plasma, which results in a decrease in osteoblastic activity.