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Annals of Surgery:
doi: 10.1097/SLA.0b013e318269cf5c
Original Articles

Insulin Sensitivity and Secretion Changes After Gastric Bypass in Normotolerant and Diabetic Obese Subjects

Salinari, Serenella DSC*; Bertuzzi, Alessandro DSC; Guidone, Caterina MD; Previti, Elena MSC*; Rubino, Francesco MD§; Mingrone, Geltrude PhD

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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 × 10−9: 104 ± 54 vs 228 ± 88; P < 0.05, preoperatively vs postoperatively; 242 ± 99 in controls). Insulin sensitivity by EHC (M × 102) was slightly but significantly improved in both normotolerant and diabetic subjects (1.46 ± 0.22 vs 1.37 ± 0.55 mmol·min−1·kg−1; P < 0.05 and 1.53 ± 0.23 vs 1.28 ± 0.62 mmol·min−1·kg−1; 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.

© 2013 Lippincott Williams & Wilkins, Inc.

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