Abstract
Protein-rich supplements are used widely for the prevention and management of malnutrition in older people. We have reported that healthy older, compared to younger, adults have less suppression of energy intake by whey-protein—effects on appetite-related hormones are unknown. The objective was to determine the effects of intraduodenally administered whey-protein on glucose, gut hormone, and amino acid concentrations, and their relation to subsequent ad libitum energy intake at a buffet meal, in healthy older and younger men. Hydrolyzed whey-protein (30 kcal, 90 kcal, and 180 kcal) and a saline control (~0 kcal) were infused intraduodenally for 60 min in 10 younger (19–29 years, 73 ± 2 kg, 22 ± 1 kg/m2) and 10 older (68–81 years, 79 ± 2 kg, 26 ± 1 kg/m2) healthy men in a randomized, double-blind fashion. Plasma insulin, glucagon, gastric inhibitory peptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), and amino acid concentrations, but not blood glucose, increased, while ghrelin decreased during the whey-protein infusions. Plasma GIP concentrations were greater in older than younger men. Energy intake correlated positively with plasma ghrelin and negatively with insulin, glucagon, GIP, GLP-1, PYY, and amino acids concentrations (p < 0.05). In conclusion, intraduodenal whey-protein infusions resulted in increased GIP and comparable ghrelin, insulin, glucagon, GIP, GLP-1, PYY, and amino acid responses in healthy older and younger men, which correlated to subsequent energy intake.
Highlights
A growing awareness of the extent and adverse effects of aging-related muscle loss, including reduced functional capacity and decreased quality of life [1,2,3], has stimulated the development of nutritional strategies designed to preserve and/or restore skeletal muscle mass and function
The aim of the study was to further characterize the effects of intraduodenal whey-protein loads on blood glucose, plasma insulin, glucagon, ghrelin, gastric inhibitory peptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), and amino acid concentrations, and their relationships with subsequent ad libitum energy intake, in older and younger men
We have further characterized the effects of these infusions on blood glucose, plasma insulin, glucagon, ghrelin, GIP, GLP-1, PYY, and amino acid concentrations, and their relationships with other measures, including with subsequent energy intake
Summary
A growing awareness of the extent and adverse effects of aging-related muscle loss, including reduced functional capacity and decreased quality of life [1,2,3], has stimulated the development of nutritional strategies designed to preserve and/or restore skeletal muscle mass and function. A ‘common’ nutritional strategy for management of malnutrition in older people is the use of nutritional supplements, which are usually high-energy drinks rich in whey protein (e.g., 10–30 g protein) [4,5,6]. Whey, when compared to casein or soy, protein results in greater muscle protein synthesis in young and older men [8]. Whey protein is a high-quality protein, high in essential, branched-chain amino acids and leucine, which are rapidly digested. Whey ingestion results in post prandial amino acid availability, which stimulates muscle anabolism [10]. It has been suggested that whey protein can be used in a clinical setting to improve health outcomes in those at risk of muscle loss [11]
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