title: Intragastric administration of leucine or isoleucine lowers the blood glucose response to a mixed-nutrient drink by different mechanisms in healthy, lean volunteers.
abstract: The branched-chain amino acids leucine and isoleucine lower blood glucose after oral glucose ingestion, and the intraduodenal infusion of leucine decreases energy intake in healthy, lean men.
  
  
  
  We investigated the effects of the intragastric administration of leucine and isoleucine on the gastric emptying of, and blood glucose responses to, a physiologic mixed-macronutrient drink and subsequent energy intake.
  
  
  
  In 2 separate studies, 12 healthy, lean subjects received on 3 separate occasions an intragastric infusion of 5 g leucine (leucine-5g) or an intragastric infusion of 10 g leucine (leucine-10g), an intragastric infusion of 5 g isoleucine (isoleucine-5g) or an intragastric infusion of 10 g isoleucine (isoleucine-10g), or a control. Fifteen minutes later, subjects consumed a mixed-nutrient drink (400 kcal, 56 g carbohydrates, 15 g protein, and 12 g fat), and gastric emptying (13C-acetate breath test) and blood glucose, plasma insulin, C-peptide, glucagon, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (leucine study only) were measured for 60 min. Immediately afterward, energy intake from a cold, buffet-style meal was assessed.
  
  
  
  Compared with the control, leucine-10g decreased the blood glucose area under the curve (AUC) (P < 0.05) and tended to reduce peak blood glucose (P = 0.07), whereas effects of leucine-5g were NS. Leucine-10g, but not leucine-5g, increased plasma insulin and C-peptide AUCs (P < 0.01 for both), but neither dose affected glucagon, GLP-1, GIP, cholecystokinin, gastric emptying, or energy intake. Compared with the control, isoleucine-10g reduced the blood glucose AUC and peak blood glucose (P < 0.01), whereas effects of isoleucine-5g were NS. Neither load affected insulin, C-peptide, glucagon, GLP-1, or GIP. Isoleucine-10g, but not isoleucine-5g, slowed gastric emptying (P < 0.05), but gastric emptying was not correlated with the blood glucose AUC. Isoleucine did not affect energy intake.
  
  
  
  In healthy subjects, both leucine and isoleucine reduced blood glucose in response to a mixed-nutrient drink but did not affect subsequent energy intake. The mechanisms underlying glucose lowering appear to differ; leucine stimulated insulin, whereas isoleucine acted insulin independently. These trials were registered at www.anzctr.org.au as 12613000899741 and 12614000837628.
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia.
authors.forename: Sina S
authors.identifier: 0000-0002-8667-7316
authors.initials: SS
authors.lastname: Ullrich
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia.
authors.forename: Penelope Ce
authors.initials: PC
authors.lastname: Fitzgerald
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Schober
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia.
authors.forename: Robert E
authors.identifier: 0000-0001-7884-5036
authors.initials: RE
authors.lastname: Steinert
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia.
authors.forename: Michael
authors.identifier: 0000-0002-3067-7157
authors.initials: M
authors.lastname: Horowitz
authors.affiliation: Discipline of Medicine, University of Adelaide, Adelaide, Australia; and National Health and Medical Research Council of Australia Center of Research Excellence in Translating Nutritional Science to Good Health, Adelaide, Australia christine.feinle@adelaide.edu.au.
authors.forename: Christine
authors.identifier: 0000-0001-6848-0125
authors.initials: C
authors.lastname: Feinle-Bisset
mesh_terms: D000328:Adult; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D002766:Cholecystokinin / Q000097:blood; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D005260:Female; D005746:Gastric Emptying; D005749:Gastric Inhibitory Polypeptide / Q000097:blood; D005934:Glucagon / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D064368:Healthy Volunteers; D006801:Humans; D007328:Insulin / Q000097:blood; D007532:Isoleucine / Q000008:administration & dosage* / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood; D008297:Male; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D007328:Insulin; D007532:Isoleucine; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D002766:Cholecystokinin; D007930:Leucine
keywords: GIP; GLP-1; branched-chain amino acids; energy intake; food intake; gastric emptying; glucagon; gut hormones; humans; insulin