title: Effects of protein on glycemic and incretin responses and gastric emptying after oral glucose in healthy subjects.
abstract: BACKGROUND
  Dietary interventions represent a promising therapeutic strategy to optimize postprandial glycemia. The addition of protein to oral glucose has been reported to improve the glycemic profile.
  
  
  OBJECTIVE
  The aim of the current study was to evaluate the mechanisms by which protein supplementation lowers the blood glucose response to oral glucose.
  
  
  METHODS
  Nine healthy men were studied on 3 d each in a random order. Subjects consumed 300-mL drinks containing either 50 g glucose (Glucose), 30 g gelatin (Protein), or 50 g glucose with 30 g gelatin (Glucose + Protein) in water labeled with 150 mg [(13)C]acetate. Blood and breath samples were subsequently collected for 3 h to measure blood glucose and plasma insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations and gastric half-emptying time, which was calculated from (13)CO(2) excretion.
  
  
  RESULTS
  The blood glucose response was less after Glucose + Protein than after Glucose (P < 0.005); GIP was lower (P < 0.005), and there were no significant differences in plasma insulin or GLP-1. Protein alone stimulated insulin, GLP-1, and GIP (P < 0.05 for each) without elevating blood glucose. The gastric half-emptying time was greater after Glucose + Protein than after Glucose (P < 0.05) and tended to be greater for Glucose than for Protein (P = 0.06).
  
  
  CONCLUSIONS
  In healthy humans, the addition of protein to oral glucose lowers postprandial blood glucose concentrations acutely, predominantly by slowing gastric emptying, although protein also stimulates incretin hormones and non-glucose-dependent insulin release.
authors.affiliation: University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: Angela
authors.initials: A
authors.lastname: Karamanlis
authors.forename: Reawika
authors.initials: R
authors.lastname: Chaikomin
authors.forename: Selena
authors.initials: S
authors.lastname: Doran
authors.forename: Max
authors.initials: M
authors.lastname: Bellon
authors.forename: F Dylan
authors.initials: FD
authors.lastname: Bartholomeusz
authors.forename: Judith M
authors.initials: JM
authors.lastname: Wishart
authors.forename: Karen L
authors.initials: KL
authors.lastname: Jones
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Rayner
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005746:Gastric Emptying; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D054795:Incretins / Q000097:blood*; D007328:Insulin / Q000097:blood; D008297:Male
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D054795:Incretins; D007328:Insulin; D052216:Glucagon-Like Peptide 1; D005947:Glucose