title: Effects of variations in duodenal glucose load on glycaemic, insulin, and incretin responses in type 2 diabetes.
abstract: OBJECTIVE
  Postprandial glucagon-like peptide-1 (GLP-1) secretion and the 'incretin effect' have been reported to be deficient in Type 2 diabetes, but most studies have not controlled for variations in the rate of gastric emptying. We evaluated blood glucose, and plasma insulin, GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) responses to intraduodenal glucose in Type 2 diabetes, and compared these with data from healthy controls.
  
  
  METHODS
  Eight males with well-controlled Type 2 diabetes, managed by diet alone, were studied on four occasions in single-blind, randomized order. Blood glucose, and plasma insulin, GLP-1, and GIP were measured during 120-min intraduodenal glucose infusions at 1 kcal/min (G1), 2 kcal/min (G2) and 4 kcal/min (G4) or saline control.
  
  
  RESULTS
  Type 2 patients had higher basal (P < 0.0005) and incremental (P < 0.0005) blood glucose responses to G2 and G4, when compared with healthy controls. In both groups, the stimulation of insulin and GLP-1 by increasing glucose loads was not linear; responses to G1 and G2 were minimal, whereas responses to G4 were much greater (P < 0.005 for each) (incremental area under the GLP-1 curve 224 ± 65, 756 ± 331 and 2807 ± 473 pmol/l.min, respectively, in Type 2 patients and 373 ± 231, 505 ± 161 and 1742 ± 456 pmol/l.min, respectively, in healthy controls). The GLP-1 responses appeared comparable in the two groups. In both groups there was a load-dependent increase in plasma GIP with no difference between them.
  
  
  CONCLUSIONS
  In patients with well-controlled Type 2 diabetes, blood glucose, insulin and GLP-1 responses are critically dependent on the small intestinal glucose load, and GLP-1 responses are not deficient.
authors: University of Adelaide, Discipline of Medicine, Royal Adelaide Hospital, Adelaide, Australia.
authors: J
authors: J
authors: Ma
authors: A N
authors: AN
authors: Pilichiewicz
authors: C
authors: C
authors: Feinle-Bisset
authors: J M
authors: JM
authors: Wishart
authors: K L
authors: KL
authors: Jones
authors: M
authors: M
authors: Horowitz
authors: C K
authors: CK
authors: Rayner
mesh_terms: D000704:Analysis of Variance; D001786:Blood Glucose / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D004386:Duodenum / Q000378:metabolism* / Q000503:physiopathology; D005746:Gastric Emptying; D005749:Gastric Inhibitory Polypeptide / Q000097:blood* / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D005947:Glucose / Q000008:administration & dosage* / Q000378:metabolism*; D006801:Humans; D054795:Incretins / Q000097:blood* / Q000378:metabolism; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period; D016037:Single-Blind Method
chemical_list: D001786:Blood Glucose; D054795:Incretins; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005947:Glucose