title: Transient, early release of glucagon-like peptide-1 during low rates of intraduodenal glucose delivery.
abstract: BACKGROUND
  The "incretin" hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), account for some 60% of the stimulation of insulin by oral glucose, but the determinants of their secretion from the small intestine are poorly understood. Cells which release GIP (K cells) are localized to the proximal small intestine, while GLP-1 releasing cells (L cells) predominate in the distal gut. It has been suggested that a threshold rate of duodenal glucose delivery (approximately 1.8 kcal/min) needs to be exceeded for stimulation of GLP-1.
  
  
  OBJECTIVE
  To determine whether a low intraduodenal glucose load (1 kcal/min) has the capacity to stimulate GLP-1, and if so, the characteristics of the response.
  
  
  METHODS
  Retrospective analysis of all studies in our laboratory involving healthy humans administered intraduodenal glucose at 1 kcal/min for 120 min.
  
  
  METHODS
  Clinical research laboratory.
  
  
  METHODS
  27 healthy subjects (24 male; age 36+/-3 years; BMI 25.2+/-0.7 kg/m(2)).
  
  
  METHODS
  Plasma GLP-1, GIP, insulin, and blood glucose concentrations, reported as mean+/-SEM.
  
  
  RESULTS
  During intraduodenal glucose, plasma GLP-1 increased at 15 and 30 min (P<0.001 for both) and returned to baseline thereafter. In contrast, there were sustained increases in plasma GIP (P<0.001), insulin (P<0.001), and blood glucose (P<0.001).
  
  
  CONCLUSIONS
  In healthy subjects, there is early, transient stimulation of GLP-1 by glucose loads hitherto believed to be "sub-threshold". The mechanisms underlying this effect, which could be attributed to initially rapid transit to jejunal L cells, or a duodeno-jejunoileal neural or hormonal loop, remain to be determined.
authors.affiliation: University of Adelaide, Discipline of Medicine, Royal Adelaide Hospital, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Kuo
authors.forename: Reawika
authors.initials: R
authors.lastname: Chaikomin
authors.forename: Amelia
authors.initials: A
authors.lastname: Pilichiewicz
authors.forename: Deirdre
authors.initials: D
authors.lastname: O'Donovan
authors.forename: Judith M
authors.initials: JM
authors.lastname: Wishart
authors.forename: James H
authors.initials: JH
authors.lastname: Meyer
authors.forename: Karen L
authors.initials: KL
authors.lastname: Jones
authors.forename: Christine
authors.initials: C
authors.lastname: Feinle-Bisset
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Rayner
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000187:drug effects; D004386:Duodenum / Q000187:drug effects; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000096:biosynthesis / Q000097:blood*; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D007328:Insulin / Q000097:blood*; D007421:Intestine, Small / Q000187:drug effects; D007441:Intubation, Gastrointestinal; D008297:Male; D012189:Retrospective Studies
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005947:Glucose