Mechanism analysis of promoting calcium absorption and bone formation of peptides from different casein fractions

The development towards breastfeeding of infant formula has been studied on differences between different fractions of protein addition. Casein (CN), a phosphate calcium binding protein in bovine milk including α-CN, β-CN and κ-CN, could affect calcium absorption. However, few studies about effects of different CN fractions on bone forming function, so this study analyzed the influences of different casein fractions on calcium absorption and bone formation via amino acid content, peptide omics and molecular weight to obtain the differences on peptide after simulation of gastrointestinal digestion in vitro. The differential effects of CN fractions with simulated gastrointestinal digestion on calcium absorption were evaluated by calcium transport analysis in Caco-2 transepithelial cell and protein expression via Western blot. In addition, the influences on the activity of bone mineralized among peptides from different casein fractions were studied through MC3T3-E1 cells alkaline phosphatase (ALP) activity measurement and alizarin red staining experiments. At last, the bone formation of the femur, 8–12 vertebrae and mandible of mice fed with different CN fractions were observed via microcomputed tomography (Micro-CT). The results indicated that the significant differences existed in amino acid content, peptide composition of different CN fractions after digestion. Importantly, β+κ-CN group has the best calcium absorption promoting activity obtained from cell and mice experiment. Additionally, κ-CN group also exhibited outstanding effective on bone mineralize activity. Therefore, this study provides a new theoretical basis for the production and development of infant formula with promoting calcium absorption and bone mineralized function.