Roux-en-Y gastric bypass corrects hyperinsulinemia implications for the remission of type 2 diabetes.

CONTEXT Roux-en-Y gastric bypass (RYGB) has been shown to induce rapid and durable reversal of type 2 diabetes. OBJECTIVE The aim of the study was to investigate a possible mechanism for the remission of type 2 diabetes after RYGB. DESIGN A cross-sectional, nonrandomized, controlled study was conducted. Surgery patients were studied before RYGB and 1 wk and 3 months after surgery. SETTING This study was conducted at East Carolina University. SUBJECTS Subjects were recruited into three groups: 1) lean controls with no surgery [body mass index (BMI) < 25 kg/m²; n = 9], 2) severely obese type 2 diabetic patients (BMI > 35 kg/m²; n = 9), and 3) severely obese nondiabetic patients (BMI > 35 kg/m²; n = 9). INTERVENTION Intervention was RYGB. RESULTS One week after RYGB, diabetes was resolved despite continued insulin resistance (insulin sensitivity index was approximately 50% of lean controls) and reduced insulin secretion during an iv glucose tolerance test (acute insulin response to glucose was approximately 50% of lean controls). Fasting insulin decreased and was no different from lean control despite continued elevated glucose in the type 2 diabetic patients compared with lean. CONCLUSIONS After RYGB, fasting insulin decreases to levels like those of lean control subjects and diabetes is reversed (fasting blood glucose < 125 mg/dl). This leads us to propose that 1) exclusion of food from the foregut corrects hyperinsulinemia and 2) fasting insulin is dissociated from the influence of fasting glucose, insulin resistance, and BMI. The mechanisms for reversal of diabetes in the face of reduced insulin remain a paradox.