Effect of glycomacropeptides (GMP) on satiety hormones and food intake

Glycomacropeptide (GMP) is the hydrophilic 63 amino acid C-terminal glycopeptide released into cheese whey when x-casein is cleaved by chymosin. GMP exists as a mixture of different glycoforms due to the carbohydrates sialic acid (NeuNAc), galactose (Gal), galactosamine (GalNAc) and glucosamine (GlcNAc) attached by O-glycosidic linkages. It has been reported that GMP stimulates the release of cholecystokinin (CCK) which may influence satiety. The objectives of this study were to manufacture different glycoforms of GMP (a poorly glycosylated GMP-approximately 3.5% NeuNAc and similar to 1.5% Gal) and highly glycosylated GMP (approximately 12% NeuNAc and 4% Gal) and assess the effects of these glycoforms relative to glucose on CCK, subjective measures of satiety and food intake. In a randomised double blind acute satiety study, 20 overweight or obese males (56.9+/-7.2 yr, 97.4+/-8.1 kg, 31.5+/-3.0 kg/m(2)) were recruited to consume four 50 g preloads (two GMP preparations, GMP depleted whey and glucose) with a three day interval between treatments. The energy content of the preloads was kept constant at 895 kJ. Blood samples were collected at baseline before and at 15, 30, 60, 90, 120 and 180 minutes after the preload and the CCK levels were measured. Subjective measures of satiety were recorded at the same time points. Three hours after the preload a lunch meal of hot food was provided from which subjects ate ad libitum until satisfied. Energy and nutrient intake from the food consumed was 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.