title: The incretin effect in Korean subjects with normal glucose tolerance or type 2 diabetes.
abstract: BACKGROUND
  The incretin effect is known to be decreased in type 2 diabetes. However, there are limited data on the incretin effect in non-Caucasian subjects. Because Asian patients with type 2 diabetes are characterized by decreased insulin secretion, this study set out to examine the incretin effect in Korean subjects with normal glucose tolerance (NGT) or type 2 diabetes.
  
  
  METHODS
  We performed 75-g oral glucose tolerance tests (OGTTs) and corresponding isoglycaemic intravenous glucose infusion (IIGI) studies in Korean subjects with NGT (n = 14) or type 2 diabetes (n = 16). The incretin effect was calculated based on the incremental area under the curves (iAUCs) of the plasma levels of insulin, C-peptide or insulin secretion rate (ISR). The plasma levels of total glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) were measured by ELISA.
  
  
  RESULTS
  The incretin effect was not different between the subjects with NGT and type 2 diabetes (43 ± 6% vs 47 ± 4%, P = 0·575 by insulin; 29 ± 7% vs 38 ± 4%, P = 0·253 by C-peptide; 28 ± 7% vs 35 ± 5%, P = 0·372 by ISR, respectively). However, the gastrointestinally mediated glucose disposal (GIGD) was markedly decreased in type 2 diabetes (28·5 ± 4·2% vs 59·0 ± 4·3%, P < 0·001). The plasma levels of the total GLP-1 and GIP during the OGTTs were comparable between the two groups.
  
  
  CONCLUSIONS
  In Koreans, the secretion of GLP-1 or GIP during OGTTs and the incretin effect were comparable between subjects with NGT and type 2 diabetes, whereas the GIGD was significantly decreased in patients with type 2 diabetes.
authors: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors: Tae Jung
authors: TJ
authors: Oh
authors: Min Young
authors: MY
authors: Kim
authors: Ji Yon
authors: JY
authors: Shin
authors: Jung Chan
authors: JC
authors: Lee
authors: Sungwan
authors: S
authors: Kim
authors: Kyong Soo
authors: KS
authors: Park
authors: Young Min
authors: YM
authors: Cho
mesh_terms: D000328:Adult; D044466:Asian People; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000208:ethnology; D005749:Gastric Inhibitory Polypeptide / Q000097:blood; D005934:Glucagon / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D005951:Glucose Tolerance Test; D006801:Humans; D054795:Incretins / Q000097:blood*; D007328:Insulin / Q000097:blood / Q000378:metabolism; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D054795:Incretins; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon