title: Correlation of the incretin effect with first- and second-phase insulin secretions in Koreans with various glucose tolerance statuses.
abstract: OBJECTIVE
  To examine the relationship between beta-cell function and the incretin effect.
  
  
  METHODS
  We performed a 180-min hyperglycaemic clamp study with oral glucose administration at 60 min in Korean subjects with normal glucose tolerance (NGT, n = 9), impaired fasting glucose (IFG, n = 6) and type 2 diabetes mellitus (T2DM, n = 6).
  
  
  METHODS
  First- and second-phase insulin secretions were measured during the first 60 min. The insulin response to intravenous glucose during the 60- to 120-min interval (Insiv) was calculated using a prediction method. The insulin response to oral glucose (Ins(oral)) was calculated by subtracting the Insiv from the overall insulin response during the 60- to 120-min interval (Ins(overall)). The incretin effect under the hyperglycaemic clamp condition (IE(clamp)) was calculated by the equation: 100 × [(Ins(overall) - Insiv)/Ins(overall)].
  
  
  RESULTS
  The IE(clamp) was comparable among the three groups (46.3 ± 6.4%, 35.7 ± 8.8% and 51.4 ± 7.4% for the NGT, IFG and T2DM group, respectively, P = 0.327) and was not correlated with the first- and second-phase insulin secretions. However, the Ins(oral) (mU/l 60 min) was significantly different between the NGT, IFG and T2DM groups (5199 ± 1185, 2164 ± 956 and 1034 ± 355, respectively; P = 0.010) and was well correlated with the first- and second-phase insulin secretions.
  
  
  CONCLUSIONS
  The incretin effect measured by the hyperglycaemic clamp with oral glucose loading was neither correlated with beta-cell function nor different between NGT, IFG and T2DM groups in Koreans.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Tae Jung
authors.initials: TJ
authors.lastname: Oh
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kyong Soo
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Young Min
authors.initials: YM
authors.lastname: Cho
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D001786:Blood Glucose / Q000378:metabolism*; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D015309:Glucose Clamp Technique; D018149:Glucose Intolerance / Q000378:metabolism*; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism; D054795:Incretins / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D054795:Incretins; D007328:Insulin