Tilapia skin collagen peptides‑calcium chelates:Structural characterization, stability, in vitro and in vivo anti-osteoporosis mechanism.

Tilapia (Oreochromis mossambicus) skin, as a by-product with high collagen, is an excellent source of calcium carriers to develop novel functional food for osteoporosis. In this study, tilapia skin collagen peptides (TSCP) were used to prepare peptides‑calcium chelates (TSCP-Ca), and the structural characteristics and stability were evaluated. The in vitro and in vivo anti-osteoporosis mechanisms of TSCP-Ca were investigated by Osteoblast hFoB1.19 cells and low calcium diet mice models. The results indicated that TSCP had high calcium chelating ability with value of 93.20 ± 1.23 mg/g, and NH and CO groups mainly participated in chelating calcium ions. TSCP-Ca showed favorable thermal and digestive stabilities. In vitro study demonstrated that TSCP-Ca could enhance calcium nodules formation and alkaline phosphatase (ALP) activity, and promote osteoblast differentiation by modulating OPG/RANKL and FGF2/RUNX2 signaling pathways in osteoblast hFoB1.19 cells. In vivo, TSCP-Ca significantly promoted calcium absorption and bone growth, improved femoral structure and density in calcium deficient mice, and the effect was significantly better than that of CaCO3. Meanwhile, TSCP-Ca treatment could regulate bone metabolism by regulating the relative abundance of probiotics like Bifidobacterium, Bacteroides, Blautia, Alistipes based on gut-bone axis, resulting to the increase of calcium absorption and bone formation in calcium deficient mice. These findings suggested that TSCP-Ca could be applied as potential dietary supplement or calcium supplement for treating osteoporosis.