Background: Bariatric surgery is currently the most effective treatment for weight loss. Its metabolic effects of weight loss and improvement of type 2 diabetes are mediated mainly through the postprandial elevation of gut hormones such as GLP-1, which suppresses food intake and improves insulin secretion.
Aim: To characterize the longitudinal changes in fasting and postprandial secretion of glucose, insulin and gut hormones (GLP-1 and GIP) in patients before and after Roux-en-Y gastric bypass (RYGB).
Subjects and Methods: Twenty-one obese patients with type 2 diabetes (Age: 48.2±13.2 years, BMI: 43.2±6.2 kg/m2) were studied before and at 1, 3 and 12 months after RYGB. Glucose, Insulin, GLP-1 and GIP levels were measured at fasting state and during a Mixed Meal Tolerance Test.
Results: There was a significant reduction in fasting and postprandial levels of glucose and insulin as early as 1 month post-RYGB. An earlier peak of glucose and insulin was observed at 30 minutes as opposed to the one at 60 minutes prior to bariatric surgery. There was a steady increase in peak GLP-1 levels secreted in response to a mixed meal test (MMT) with time after surgery with an earlier peak at 15 minutes versus the peak seen at 30 minutes preoperatively. There was no significant difference in GIP responses to MMT before and after surgery.
Conclusions: Our results confirm, in concordance with the literature, a reduction in fasting and postprandial glucose and insulin levels and an increase in postprandial secretion of GLP-1 after surgery which increases in magnitude with time whereas there is no significant change in GIP secretion with surgery. Interestingly, there is an earlier peak of GLP-1 levels followed by an earlier peak of glucose and insulin levels post-RYGB.