This study evaluated the stability of casein phosphopeptides (CPP) and obtained peptide-calcium complex by heating and chelating the peptide with CaCl2 in a neutral solution. To assess the bioavailability of various calcium formulations, the calcium transport models were established in Caco-2 cells, and the transcellular transport pathways of various calcium formulations were studied by RT-PCR and Western blotting. Results of circular dichroism showed that CPP was a stable polypeptide. The ultraviolet absorption spectrum and Fourier transform-infrared spectrum (FT-IR) indicated that calcium could be chelated by carboxyl oxygen and amino nitrogen atoms of CPP to form peptide calcium chelate, and the calcium bioavailability of peptide calcium chelate was significantly higher than that of CaCl2 , calcium l-aspartate, and casein phosphopeptides mixed with CaCl2 . Four calcium sources increased the expression of TRPV5 and TRPV6 genes and proteins. The study intended to provide a basis for developing a novel calcium supplement. PRACTICAL APPLICATIONS: This paper examined the bioavailability of casein phosphopeptides calcium complex, CaCl2 , calcium l-aspartate, and casein phosphopeptides mixed with CaCl2 in Caco-2 cells, and the mechanisms were detected by western blotting. The results provide theoretical knowledge for the selection of calcium supplement raw materials and lay a foundation for the development of compound calcium preparations and drugs in the future.
Keywords: Caco-2 cells; bioavailability; calcium supplement; casein phosphopeptides; characterization; transcellular pathway.
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