Ma, J.Pilichiewicz, A.Feinle-Bisset, C.Wishart, J.Jones, K.Horowitz, M.Rayner, C.2012-06-142012-06-142012Diabetic Medicine, 2012; 29(5):604-6080742-30711464-5491http://hdl.handle.net/2440/71522Aims:  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.en© 2011 The Authors. Diabetic Medicine © 2011 Diabetes UKglucagon-like peptide 1glucose-dependent insulinotropic polypeptideglycaemic controlJournal article002011873510.1111/j.1464-5491.2011.03496.x0003029086000082-s2.0-8485806464424721Feinle-Bisset, C. [0000-0001-6848-0125]Jones, K. [0000-0002-1155-5816]Horowitz, M. [0000-0002-0942-0306]Rayner, C. [0000-0002-5527-256X]