Diabetes Remission and Insulin Secretion After Gastric Bypass in Patients with Body Mass Index <35 kg/m2

Most morbidly obese patients who undergo gastric bypass experience rapid remission of type 2 diabetes mellitus (T2DM) but the response in non-morbidly obese patients is not clear. This trial prospectively assessed the effect of diabetes remission, glucose metabolism, and the serial changes of insulin secretion after gastric bypass in inadequately controlled T2DM patients with a BMI of 23-35 kg/m(2). A total of 62 consecutive patients with T2DM and a BMI of 23-35 kg/m(2) underwent gastric bypass. Data were prospectively collected before surgery and 1, 4, 12, 26, and 52 weeks and 2 years after surgery. Insulin secretion was measured by insulinogenic index and area under the curve (AUC) during a standard oral glucose tolerance test (OGTT). Remission of type 2 diabetes was defined as fasting glucose level < 110 mg/dl and HbA1c < 6.0% without any glycemic therapy. Of the 62 patients, 24 were men and 38 were women (age 43.1 +/- 10.8 years). Their preoperative characteristics were as follows: BMI 30.1 +/- 3.3 kg/m(2), waist circumference 99.6 +/- 9.6 cm, C-peptide 3.1 +/- 1.4 ng/ml, and duration of T2DM 5.4 +/- 5.1 years. The mean BMI decreased postoperatively to 22.6 +/- 2.3 kg/m(2) in 1 year and 23.0 +/- 2.7 kg/m(2) in 2 years. The mean HbA1c decreased from 9.7 +/- 1.9% to 5.8 +/- 0.5% in 1 year and 5.9 +/- 0.5% in 2 years. Complete remission of T2DM was achieved in 57% in 1 year and 55% in 2 years after surgery. Before surgery, the OGTT test showed a blunted insulin secretion pattern with an insulinogenic index of 0.1 +/- 0.2 and AUC of 2,324 +/- 1,015 mu IU min/ml. In 1 week after surgery, the insulinogenic index increased to 0.16 and AUC decreased to 1,366 mu IU min/ml along with a rapid drop of insulin resistance. The insulinogenic index and AUC gradually increased to 0.27 and 3,220, respectively, 1 year after surgery and remained stable up to 2 years with a very low insulin resistance. Laparoscopic gastric bypass facilitates immediate improvement in the glucose metabolism of inadequately controlled non-severe obese T2DM patients, and the benefit is sustained up to 2 years after surgery. The benefit is regulated by the decrease in insulin resistance, increase in early insulin response, and total insulin secretion to glucose load.