Many diabetic patients who have Roux-en-Y gastric bypass (RYGB) have rapid improvements in their blood sugars within days of their surgery, even before they have lost much weight. It typically takes much longer for these improvements to occur after adjustable gastric banding (AGB), despite an equally low caloric intake. Changes in levels of hormones released by the small intestine as a consequence of the particular type of surgery may be an important factor in the rapid improvement of blood sugars. One of these hormones, glucagon-like peptide-1 (GLP-1), has an important effect on insulin secretion from the pancreas. This study seeks to determine whether changes in GLP-1 are responsible for the improvement in blood sugar after certain types of weight loss surgeries. In order to meet inclusion criteria, participants must have type 2 diabetes for less than 10 years and be approved by insurance to undergo RYGB or AGB at the Hospital of the University of Pennsylvania or Penn Presbyterian Medical Center. We will obtain several measurements of GLP-1 and other hormones that affect glucose levels during the three study visits: 1) Visit 1 (2-3 weeks before surgery); 2) Visit 2 (after 10% of body weight is lost); and 3) Visit 3 (5-10 days after Visit 2). To see if the improvement in blood sugar after surgery is due to changes in GLP-1, we will block its effect on insulin release by giving either salt water or a medication that blocks the activity of GLP-1 during the two visits that take place after surgery (Visits 2 and 3). Each visit will last for 4-6 hours and participants will be compensated for their time.
The purpose of this study is to see how hormones that control blood sugar change in response to two different weight loss surgeries (gastric bypass and gastric banding). We believe that changes in a hormone called glucagon-like peptide-1 (GLP-1) may account for the greater improvement in blood sugar after certain types of surgeries. GLP-1 makes the pancreas release insulin, a hormone that lowers blood sugar. The study will consist of one screening visit and three study visits in which the glucose response will be measured after drinking a liquid meal: 1) Visit 1 (2-3 weeks before surgery); 2) Visit 2 (after 10% of body weight is lost); and 3) Visit 3 (5-10 days after Visit 2). Hormone levels will be measured during the three study visits. To see if the improvement in blood sugar after surgery is due to changes in GLP-1, we will block its effect on insulin release by giving either salt water or a medication that blocks the activity of GLP-1 during the two visits that take place after surgery (Visits 2 and 3).