Chicken sternum cartilage protein-chelated calcium: enhance bone density in vivo and in vitro, with insights into chelation mechanism.

Calcium deficiency is a common health issue that can lead to metabolic bone diseases. Chelated calcium with bone protein and peptide improves bone mineral density (BMD), but chicken sternum cartilage protein (CSCP) as a calcium chelator, its bone health effects, and its chelation mechanism remain unelucidated. This study prepared and characterized CSCP-chelated calcium (CSCP-Ca) and evaluated its effects on BMD in MC3T3-E1 cells and low-calcium-fed rats. Molecular docking and molecular dynamics simulations revealed the possible chelation mechanism. Results showed CSCP-Ca2+ reached a maximum chelation rate of 76.91 ± 0.53 % at 40 min. Zeta potential and particle size distribution analysis indicated Ca2+ interacted with CSCP's surface negative charges, improving dispersion and reducing agglomeration. In vitro, compared with the control group, CSCP-Ca2+ increased ALP activity, OCN, Col-I content, and promoted mineralized nodules (P < 0.05). In vivo, CSCP-Ca2+ improved the skeletal structure of low-calcium-fed rats, reduced the apparent calcium absorption rate (55.84 ± 0.30 %, P < 0.05), and increased BMD (0.31 ± 0.04 g/cm3, P < 0.05). It also enhanced gut microbial α-diversity, altered β-diversity, and dose-dependently increased Bifidobacterium, Roseburia, and Faecalibacterium and decreased Helicobacter, Desulfovibrio, and Escherichia-Shigella, promoting short-chain fatty acids. Molecular docking and molecular dynamics simulations showed Ca2+ formed a stable structure with CSCP's undenatured type II collagen, and the binding sites were PRO14 and GLU13. This study confirms CSCP-Ca2+'s positive effects on bone and supports its development as a novel calcium supplement.