Calcium yak caseinate promotes calcium absorption to prevent osteoporosis in mice

Calcium is a pivotal mineral element in maintaining bone health. Absorption and metabolic balance of calcium are essential for the formation and maintenance of bones. In this study, we investigated the promotional effect of calcium yak caseinate (CYC) on calcium absorption and its mechanism in ovariectomized (OVX) mice induced by removal of bilateral ovaries. Here, after OVX mice were supplemented with CYC, their apparent calcium absorption rate was significantly improved by regulating serum 25-hydroxyvitamin D, the calcium/phosphorus ratio, and the ratios of phosphorus and calcium to creatinine in urine. Hematoxylin and eosin staining of the duodenum showed that CYC supplementation significantly increased the villus height and to some extent increased the intestinal wall thickness. The gut microbiota and functional prediction studies indicated that CYC altered the gut microbiota composition in OVX mice, characterized by a significant increase in the relative abundance of Lactobacillus. This leads to the upregulation of calcium absorption-related metabolic pathways, including mineral absorption, propanoate metabolism, and synthesis and degradation of ketone bodies. Further analysis showed that CYC promoted calcium absorption by upregulating the expression of TRPV6 protein in the duodenum and TRPV5 and Calbindin-D28k in the kidneys of OVX mice. This study shows that CYC improves the apparent absorption rate of calcium by promoting its absorption in the duodenum and the reabsorption in the kidneys, thereby preventing and improving osteoporosis in OVX mice.