title: Accelerated protein digestion and amino acid absorption after Roux-en-Y gastric bypass.
abstract: BACKGROUND
  Roux-en-Y gastric bypass (RYGB) involves exclusion of major parts of the stomach and changes in admixture of gastro-pancreatic enzymes, which could have a major impact on protein digestion and amino acid absorption.
  
  
  OBJECTIVE
  We investigated the effect of RYGB on amino acid appearance in the systemic circulation from orally ingested protein and from endogenous release.
  
  
  METHODS
  Nine obese glucose-tolerant subjects, with a mean body mass index (in kg/m(2)) of 39.2 (95% CI: 35.2, 43.3) and mean glycated hemoglobin of 5.3% (95% CI: 4.9%, 5.6%), were studied before and 3 mo after RYGB. Leucine and phenylalanine kinetics were determined under basal conditions and during 4 postprandial hours by intravenous infusions of [3,3,3-(2)H3]-leucine and [ring-(2)D5]-phenylalanine combined with ingestion of [1-(13)C]-leucine intrinsically labeled caseinate as the sole protein source of the meal. Changes in body composition were assessed by dual-energy X-ray absorptiometry.
  
  
  RESULTS
  After RYGB, basal plasma leucine concentration did not change, but marked changes were seen postprandially with 1.7-fold increased peak concentrations (before—mean: 217 μmol/L; 95% CI: 191, 243 μmol/L; 3 mo—mean: 377 μmol/L; 95% CI: 252, 502 μmol/L; P = 0.012) and 2-fold increased incremental AUC (before-mean: 4.1 mmol ∙ min/L; 95% CI: 2.7, 5.5 mmol ∙ min/L; 3 mo-mean: 9.5 mmol ∙ min/L; 95% CI: 4.9, 14.2 mmol ∙ min/L; P = 0.032). However, the postprandial hyperleucinemia was transient, and concentrations were below basal concentrations in the fourth postprandial hour. These concentration differences were mainly caused by changes in leucine appearance rate from orally ingested caseinate: peak rate increased nearly 3-fold [before—mean: 0.5 μmol/(kg fat-free mass ∙ min); 95% CI: 0.4, 0.5 μmol/(kg fat-free mass ∙ min); 3 mo—mean 1.4 μmol/(kg fat-free mass ∙ min); 95% CI: 0.8, 1.9 μmol/(kg fat-free mass ∙ min); P = 0.002], and time to peak was much shorter (before—mean: 173 min; 95% CI: 137, 209 min; 3 mo—mean: 65 min; 95% CI: 46, 84 min; P < 0.001). Only minor changes were seen in endogenous leucine release after RYGB.
  
  
  CONCLUSIONS
  RYGB accelerates caseinate digestion and amino acid absorption, resulting in faster and higher but more transient postprandial elevation of plasma amino acids. Changes are likely mediated by accelerated intestinal nutrient entry and clearly demonstrate that protein digestion is not impaired after RYGB. This trial was registered at clinicaltrials.gov as NCT01559792.
authors.affiliation: Department of Endocrinology and Novo Nordisk Foundation Centre for Basic Metabolic Research and kirstine.bojsen-moeller@regionh.dk.
authors.forename: Kirstine N
authors.initials: KN
authors.lastname: Bojsen-Møller
authors.affiliation: Department of Endocrinology and Novo Nordisk Foundation Centre for Basic Metabolic Research and.
authors.forename: Siv H
authors.initials: SH
authors.lastname: Jacobsen
authors.affiliation: Department of Endocrinology and Novo Nordisk Foundation Centre for Basic Metabolic Research and.
authors.forename: Carsten
authors.initials: C
authors.lastname: Dirksen
authors.affiliation: Department of Endocrinology and Novo Nordisk Foundation Centre for Basic Metabolic Research and.
authors.forename: Nils B
authors.initials: NB
authors.lastname: Jørgensen
authors.affiliation: Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark;
authors.forename: Søren
authors.initials: S
authors.lastname: Reitelseder
authors.affiliation: Department of Endocrinology and.
authors.forename: Jens-Erik B
authors.initials: JE
authors.lastname: Jensen
authors.affiliation: Department of Surgical Gastroenterology, Hvidovre Hospital, Copenhagen, Denmark;
authors.forename: Viggo B
authors.initials: VB
authors.lastname: Kristiansen
authors.affiliation: Novo Nordisk Foundation Centre for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Holst
authors.affiliation: Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Clinical Metabolomics, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Gerrit
authors.initials: G
authors.lastname: van Hall
authors.affiliation: Department of Endocrinology and Novo Nordisk Foundation Centre for Basic Metabolic Research and.
authors.forename: Sten
authors.initials: S
authors.lastname: Madsbad
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D005260:Female; D015390:Gastric Bypass; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D007930:Leucine / Q000008:administration & dosage / Q000097:blood*; D008297:Male; D062407:Meals; D008875:Middle Aged; D009765:Obesity / Q000601:surgery; D010649:Phenylalanine / Q000008:administration & dosage / Q000097:blood*; D019518:Postprandial Period; D059748:Proteolysis; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002364:Caseins; D004044:Dietary Proteins; D006442:Glycated Hemoglobin; D007930:Leucine; D010649:Phenylalanine
keywords: amino acid absorption; bariatric surgery; caseinate; gastric emptying; glucagon; glucagon-like peptide-1; intrinsically labeled protein; milk protein; protein digestion