Potential Biological Effects of Milk Protein Digests on In Vitro Cell Models of Human Intestine and Bone

Bovine milk proteins have gained considerable attention as nutritional supplements for athletes and the elderly. Indeed, casein and whey proteins are rich in essential, branched-chain, and antioxidant amino acids. Moreover, numerous biological functions have been attributed to these proteins, their hydrolysates, and derived peptides. The present work was aimed at evaluating the potential biological effects of milk protein in vitro digests on in vitro models of human intestinal cells and human osteoblast-like cells. Bovine powder micellar casein (C), whey protein isolate (W), and their mixture (80/20, w/w) (CW) were submitted to in vitro static gastrointestinal digestion. The digests were administered to a 70:30 coculture of Caco-2 and HT-29 cells to study proliferation, barrier integrity, and antioxidant properties. The intestinal metabolized digests were administered to osteoblast-like SaOS-2 cells to study proliferation. In vitro C digest increased the barrier integrity under physiological conditions. All milk protein digests displayed a protective role towards an impaired intestinal barrier, but the C digest was the most active. After prolonged exposure, the in vitro digests W and CW ameliorated the intestinal basal redox status. All in vitro digests exhibited scavenger activity, but the C and CW digests displayed a higher effect than the W digest at 60 and 75 min. All digests efficiently chelated iron ions, even if the W digest was the least effective. The administration of intestinal metabolized CW, C, and W digests enhanced osteoblast proliferation. These findings confirm the importance of milk proteins as ingredients for formulating supplements with potential benefits for the intestine and bones.