Background/objective: A distinct suppressive effect of a whey protein (including glycomacropeptide)-enriched preload drink on subsequent food intake in comparison with a maltodextrin carbohydrate-enriched preload was demonstrated in an earlier companion study with the same female subjects; however, the potential mediators underlying the effect are unclear. The objective of this study was to investigate how the ingestion of a whey protein-enriched preload beverage affected postprandial plasma concentrations of several satiety-related gastrointestinal hormones and metabolites in comparison with a maltodextrin carbohydrate-enriched preload.
Subjects/methods: Eighteen normal-weight women were studied in a single-blind, randomized block design. Blood samples were collected at various time intervals for 120 min after consumption of a test drink (300 ml, ~1300 kJ) enriched (45 g) with either maltodextrin carbohydrate or whey protein containing naturally present glycomacropeptide.
Results: Plasma-active ghrelin concentrations decreased after both maltodextrin carbohydrate- and whey protein-enriched test drinks (P<0.05). The whey protein-enriched beverage led to increased plasma concentrations of cholecystokinin (CCK) at 60 and 75 min (P<0.05), glucagon-like peptide-1 (GLP-1) at 90 min (P<0.001), peptide tyrosine-tyrosine (PYY) at 90 and 120 min (P<0.01) and pancreatic polypeptide (PP) from 15 to 120 min (P<0.05) compared with maltodextrin carbohydrate. Total amino acid, urea and ammonia plasma concentrations were also higher after whey protein compared with maltodextrin carbohydrate ingestion (P<0.01).
Conclusions: Increased plasma concentrations of some gastrointestinal hormones related to satiety, particularly PP, and of amino acids and their metabolites, may have acted either singly or together to mediate the observed satiety response to whey protein.