The goal of this project is to examine the physical mechanisms that contribute to improvements of glucose tolerance in type 2 diabetes mellitus (DM) following certain types of bariatric surgery.

The goal of this project is to examine the physiological mechanisms that contribute to improvements of glucose homeostasis in type 2 diabetes mellitus (DM) following gastric bypass Roux-en-Y bariatric surgery (GBP). The central hypotheses are: 1) that surgical changes in the anatomy of nutrient absorption achieved by GBP change incretin hormone secretion which in turn improves pancreatic islet function; and 2) that improvement in insulin secretion induced by the changes in incretin function, together with improvement in insulin resistance induced by weight loss, normalize glucose homeostasis in type 2 DM.

Funds are not available to pay for the surgery for patients, only to address research questions.

Inclusion Criteria:

• Patients who are at least 18 years of age and undergo bariatric surgery by a LABS certified surgeon.
• Enrollment in LABS-1 or LABS-2.
• Documented type 2 diabetes (fasting plasma glucose greater than 125 mg/dl) that is treated with lifestyle efforts (drug naïve) or taking acceptable oral medications (see appendix) with a HgA1c less than or equal to 8.5% and a fasting blood glucose less than or equal to 180 mg/dL. This will be one group.
• Non-diabetic (ND) with normal values for fasting glucose and HbA1c. This will be the second group.
• Adequate IV access.

Exclusion Criteria:

• Informed consent not obtained.
• Patient with diabetes with an HbA1c greater than 8.5% or a fasting blood glucose greater than 180 mg/dL.
• Creatinine greater than 1.7.
• Unlikely to comply with the 6 month follow-up (post-surgical) protocol (i.e. geographically inaccessible for study visits) or unable to communicate with local study staff.
• Use of unacceptable diabetic medications (see appendix) at baseline (see appendix).

Study participants will be selected from the LABS-2 cohort at participating LABS clinical centers.