title: Plasma Free Amino Acid Responses to Intraduodenal Whey Protein, and Relationships with Insulin, Glucagon-Like Peptide-1 and Energy Intake in Lean Healthy Men.
abstract: This study determined the effects of increasing loads of intraduodenal (ID) dairy protein on plasma amino acid (AA) concentrations, and their relationships with serum insulin, plasma glucagon-like peptide-1 (GLP-1) and energy intake. Sixteen healthy men had concentrations of AAs, GLP-1 and insulin measured in response to 60-min ID infusions of hydrolysed whey protein administered, in double-blinded and randomised order, at 2.1 (P2.1), 6.3 (P6.3) or 12.5 (P12.5) kJ/min (encompassing the range of nutrient emptying from the stomach), or saline control (C). Energy intake was quantified immediately afterwards. Compared with C, the concentrations of 19/20 AAs, the exception being cysteine, were increased, and this was dependent on the protein load. The relationship between AA concentrations in the infusions and the area under the curve from 0 to 60 min (AUC0-60 min) of each AA profile was strong for essential AAs (R² range, 0.61-0.67), but more variable for non-essential (0.02-0.54) and conditional (0.006-0.64) AAs. The AUC0-60 min for each AA was correlated directly with the AUC0-60 min of insulin (R² range 0.3-0.6), GLP-1 (0.2-0.6) and energy intake (0.09-0.3) (p < 0.05, for all), with the strongest correlations being for branched-chain AAs, lysine, methionine and tyrosine. These findings indicate that ID whey protein infused at loads encompassing the normal range of gastric emptying increases plasma concentrations of 19/20 AAs in a load-dependent manner, and provide novel information on the close relationships between the essential AAs, leucine, valine, isoleucine, lysine, methionine, and the conditionally-essential AA, tyrosine, with energy intake, insulin and GLP-1.
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. natalie.luscombe-marsh@csiro.au.|CSIRO Food and Nutrition, PO Box 10041 Adelaide BC, Adelaide SA 5000, Australia. natalie.luscombe-marsh@csiro.au.
authors.forename: Natalie D
authors.initials: ND
authors.lastname: Luscombe-Marsh
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. amy.hutchison@adelaide.edu.au.
authors.forename: Amy T
authors.initials: AT
authors.lastname: Hutchison
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. stijn.soenen@adelaide.edu.au.
authors.forename: Stijn
authors.initials: S
authors.lastname: Soenen
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. robert.steinert@adelaide.edu.au.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Steinert
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. Peter.Clifton@unisa.edu.au.|School of Pharmacology and Medical Sciences, University of South Australia, Adelaide 5001, Australia. Peter.Clifton@unisa.edu.au.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Clifton
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. michael.horowitz@adelaide.edu.au.
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.affiliation: NHMRC Centre of Research Excellence in Translating Nutritional Science to Good Health, The University of Adelaide Discipline of Medicine, Adelaide 5000, Australia. christine.feinle@adelaide.edu.
authors.forename: Christine
authors.initials: C
authors.lastname: Feinle-Bisset
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood*; D000597:Amino Acids, Branched-Chain / Q000097:blood; D000601:Amino Acids, Essential / Q000097:blood; D001069:Appetite Regulation / Q000187:drug effects*; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D004386:Duodenum / Q000378:metabolism*; D002149:Energy Intake / Q000187:drug effects*; D005746:Gastric Emptying; D005768:Gastrointestinal Hormones / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000097:blood*; D064368:Healthy Volunteers; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period; D012016:Reference Values; D000067816:Whey Proteins / Q000378:metabolism / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D000601:Amino Acids, Essential; D001786:Blood Glucose; D005768:Gastrointestinal Hormones; D007328:Insulin; D000067816:Whey Proteins; D052216:Glucagon-Like Peptide 1
keywords: appetite regulation; dairy; glycemic control; human; insulinotropic response; whey protein hydrolysate