title: Insulin sensitivity and secretion changes after gastric bypass in normotolerant and diabetic obese subjects.
abstract: OBJECTIVE
  To elucidate the mechanisms of improvement/reversal of type 2 diabetes after Roux-en-Y gastric bypass (RYGB).
  
  
  METHODS
  Fourteen morbidly obese subjects, 7 with normal glucose tolerance and 7 with type 2 diabetes, were studied before and 1 month after RYGB by euglycemic hyperinsulinemic clamp (EHC), by intravenous glucose tolerance test (IVGTT) and by oral glucose tolerance test (OGTT) in 3 different sessions. Intravenous glucose tolerance test IVGTT and OGTT insulin secretion rate (ISR) and sensitivity were obtained by the minimal model. Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured. Six healthy volunteers were used as controls.
  
  
  RESULTS
  Total ISR largely increased in diabetic subjects only when glucose was administered orally (37.8 ± 14.9 vs 68.3 ± 22.8 nmol; P < 0.05, preoperatively vs postoperatively). The first-phase insulin secretion was restored in type 2 diabetic after the IVGTT (Φ1 × 10: 104 ± 54 vs 228 ± 88; P < 0.05, preoperatively vs postoperatively; 242 ± 99 in controls). Insulin sensitivity by EHC (M × 10) was slightly but significantly improved in both normotolerant and diabetic subjects (1.46 ± 0.22 vs 1.37 ± 0.55 mmol·min·kg; P < 0.05 and 1.53 ± 0.23 vs 1.28 ± 0.62 mmol·min·kg; P < 0.05, respectively). Quantitative insulin sensitivity check index was improved in all normotolerant (0.32 ± 0.02 vs 0.30 ± 0.02; P < 0.05) and diabetic subjects (0.33 ± 0.03 vs 0.31 ± 0.02; P < 0.05). GIP and GLP-1 levels increased both at fast and after OGTT mainly in type 2 diabetic subjects.
  
  
  CONCLUSIONS
  The large increase of ISR response to the OGTT together with the restoration of the first-phase insulin secretion in diabetic subjects might explain the reversal of type 2 diabetes after RYGB. The large incretin secretion after the oral glucose load might contribute to the increased ISR.
authors: Department of Computer and System Science, University of Rome Sapienza, Rome, Italy. salinari@dis.uniroma1.it
authors: Serenella
authors: S
authors: Salinari
authors: Alessandro
authors: A
authors: Bertuzzi
authors: Caterina
authors: C
authors: Guidone
authors: Elena
authors: E
authors: Previti
authors: Francesco
authors: F
authors: Rubino
authors: Geltrude
authors: G
authors: Mingrone
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications*; D005260:Female; D015390:Gastric Bypass / Q000379:methods*; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*; D000078790:Insulin Secretion; D008297:Male; D009767:Obesity, Morbid / Q000097:blood / Q000150:complications / Q000601:surgery*; D016896:Treatment Outcome
chemical_list: D001786:Blood Glucose; D007328:Insulin; D052216:Glucagon-Like Peptide 1