Gastrointestinal in vitro digests of infant biscuits formulated with bovine milk proteins positively affect in vitro differentiation of human osteoblast-like cells

Infant biscuits (IBs) are part of complementary feeding from weaning up to the age of five years. They normally contain bovine milk proteins, which can influence bone development. This potential effect was investigated using experimental baked IBs, which were prepared from doughs containing different type of dairy proteins: milk protein concentrate (IB1), whey protein isolate (IB2), and skimmed milk powder (IB3). Dairy protein-free (IB0) and gluten-free (IB4) biscuits were also formulated. The in vitro gastrointestinal digests of IBs (IBDs) were tested on a co-culture of Caco-2/HT-29 70/30 cells as an in vitro model of human small intestine. None of the IBDs influenced cell viability and monolayer integrity, while IBD0 and IBD4 increased Peptide-YY production. The basolateral contents of Transwell plates seeded with Caco-2/HT-29 70/30 co-culture, mimicking metabolized IBDs (MIBDs), were tested on Saos-2 cells, an in vitro model of human osteoblast-like cells. After incubation, MIBD0, lacking dairy proteins, decreased the cell viability, while MIBD2, containing whey protein isolate, increased both the viability and the number of cells. MIBD2 and MIBD4, the latter containing both casein and whey proteins, increased alkaline phosphatase activity, a bone differentiation marker. These results highlight that IBs containing dairy proteins positively affect bone development.