In vitro comparison of whey protein isolate and hydrolysate for their effect on glucose homeostasis markers

Research on new strategies to regulate glucose homeostasis to prevent or manage type 2 diabetes is a critical challenge. Several studies have shown that protein-rich diets could improve glucose homeostasis. Whey protein hydrolysis allows the release of amino acids and bioactive peptides, which exert numerous well-documented bioactivities. This study evaluates and compares the hypoglycemic potential of a whey protein hydrolysate and a whey protein isolate after static in vitro simulated gastrointestinal digestion (SGID) using the INFOGEST protocol. The peptide molecular mass distributions of the digested samples were evaluated by size exclusion chromatography and show that after digestion, the whey hydrolysate is significantly more hydrolyzed. After SGID, the whey protein hydrolysate induces a significative greater secretion of GLP-1 after two hours of contact with the enteroendocrine STC-1 cell line than the whey protein after isolation. In addition, the digested whey hydrolysate increases preproglucagon (GCG) and pro-convertase-1 (PCSK1) expression. The digested hydrolysate also inhibits the DPP-IV activity after an intestinal barrier passage challenge using a Caco-2/HT29-MTX mixed-cell model. Our results highlight that the prehydrolysis of whey proteins modify the intestinal peptidome, leading to a potentially greater hypoglycemic effect. This study confirms the previously observed in vitro hypoglycemic effect of this hydrolysate and evidences the beneficial impact of the industrial hydrolysis process.