First-Phase Insulin Secretion Restoration And Differential Response To Glucose Load Depending On The Route Of Administration In Type 2 Diabetic Subjects After Bariatric Surgery

Abstract

Objective: To elucidate the mechanisms of diabetes reversibility after malabsorptive bariatric surgery.

Research design and methods: Peripheral insulin sensitivity and beta-cell function after either intravenous (IVGTT) or oral glucose (OGTT) tests and minimal model analysis were assessed in 9 obese, type 2 diabetic subjects before and 1 month after bilio-pancreatic diversion (BPD) as compared with 6 normal-weight controls. Insulin-dependent whole-body glucose disposal was also measured by the euglycemic clamp. Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured.

Results: The first phase of insulin secretion after the IVGTT was fully normalized following the operation. The disposition index (DI), from OGTT data, was increased about tenfold and became similar to the values found in controls, while the DI, from IVGTT data, increased about 3.5 fold similarly to what happened after the euglycemic clamp. The AUC_GIP decreased about 4 times (from 3,000±816 to 577±155 pM·min P<0.05). On the contrary, the AUC_GLP1 was almost triplicate (from 150.4±24.4 to 424.4±64.3 pM·min P<0.001). No significant correlation was found between GIP or GLP1 % changes and modification of the sensitivity indexes independently of the route of glucose administration.

Conclusions: The restoration of the first-phase insulin secretion as well as the normalization of insulin sensitivity in type 2 diabetic subjects after malabsorptive bariatric surgery seem to be related to the reduction of the effect of some intestinal factor/s due to intestinal bypass.