Protective Effects of Moderate Ca Supplementation against Cd-Induced Bone Damage under Different Population-Relevant Doses in Young Female Rats

Estimation of the skeleton-protective effects of Ca in Cd-induced bone damage is helpful in the assessment of Cd health risk. The aim of this study was to identify whether Ca supplementation during exposure to different population-relevant doses of Cd can prevent Cd-induced bone damage under the tolerable upper intake level of Ca supplementation. Young female Sprague-Dawley rats were given different population-relevant doses of Cd (1, 5, and 50 mg Cd/kg diet) and Ca supplementation (0.4% Ca supplementation) intervention. Ca supplementation significantly decreased Cd-induced bone microstructure damage, increased bone biomechanics (p < 0.05), serum bone formation marker level (p < 0.05) and expression of osteogenic gene markers exposure to the 5 and 50 mg Cd/kg diets. However, it had no impact on these indicators under the 1 mg Cd/kg diets, with the exception of expression of osteogenic marker genes. Ca supplementation significantly decreased serum Klotho level (p < 0.05), and fibroblast growth factor 23/Klotho-associated gene expression in the kidney and bone showed significant changes. In conclusion, Ca supplementation has a positive effect on bone formation and bone quality against the damaging impact of Cd, especially with exposure to the 5 mg and 50 mg Cd/kg diet, which may be related to its impact on the fibroblast growth factor 23/Klotho axis.