Effect of glycomacropeptide fractions on cholecystokinin and food intake

Glycomacropeptide (GMP) is the hydrophilic 64-amino acid C-terminal glycopeptide released into cheese whey when kappa-casein is cleaved by chymosin. GMP exists as a mixture of different glycoforms due to the carbohydrates sialic acid (N-acetylneuraminic acid, NeuNAc), galactose (Gal), galactosamine and glucosamine attached by O-glycosidic linkages. GMP reportedly stimulates the release of cholecystokinin (CCK), which may promote satiety. The objectives of the present study were to manufacture three glycoforms of GMP, minimally glycosylated GMP (3.5 (sd 0.1) % NeuNAc and 1.5 (sd 0.1) % Gal), glycosylated GMP (12.0 (sd 0.3) % NeuNAc and 4.2 (sd 0.2) % Gal) and a GMP-depleted whey protein concentrate, and to assess the effects of these fractions relative to glucose on CCK, subjective measures of satiety and food intake. In a randomised double-blind acute study, twenty overweight/obese males (56.9 (sd 7.2) years, 97.4 (sd 8.1) kg, 31.5 (sd 3.0) kg/m2) were recruited to consume four 50 g preloads (two GMP preparations, GMP-depleted whey and glucose) containing 895 kJ. Blood samples and subjective measures of satiety were collected before and at 15, 30, 60, 90, 120 and 180 min after the consumption of preload, and CCK levels were measured. A lunchtime meal of hot food was provided from which subjects ate ad libitum until satisfied. Energy and nutrient intakes from the food consumed were calculated. There was no significant difference in CCK levels, subjective measures of satiety or food intake between treatments at the given preload level. These results suggest that the protein fractions at the dose employed do not influence satiety, CCK levels or energy intake at a subsequent meal.