Bariatric surgery procedures have now been firmly demonstrated to lead to significant improvement and even, in many cases, complete reversal of abnormal glucose homeostasis in type 2 diabetes (T2D). Various surgery procedures are can be performed to induce weight loss. The most striking anti-diabetic effects are observed with biliopancreatic diversion with duodenal switch (BPD-DS), followed by Roux-in-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). The first two procedures induce both a restriction of energy intake and a low absorption of dietary fatty acids while the latter exclusively targets energy intake restriction. The investigator and others have shown that improvement of T2D occurs within days after BPD-DS or RYGB in the vast majority of patients, prior to any significant weight loss. This very rapid metabolic recovery is explained by a normalization of β-cell function after meal challenges and ameliorated hepatic insulin sensitivity. The investigator and others have shown that these acute anti-diabetic effects are mostly recapitulated by matched caloric restriction, independent of changes in gastrointestinal hormones, showing the importance of gastrointestinal-derived energy fluxes for acute diabetes control. Muscle insulin sensitivity, on the other hand, improves more slowly in association with weight loss, demonstrating the heterogeneous metabolic response of the various organs to BPD-DS. Some preliminary studies also demonstrate a rapid reduction of NEFA levels and production rate upon i.v. administration of lipids during euglycemic hyperinsulinemic clamps. This very rapid improvement in NEFA tolerance strongly suggests that adipose tissue storage of circulating fatty acids also improves very rapidly, prior to any significant weight loss, after BPD-DS. It may also suggest an acceleration of oxidative fatty acid metabolism in organs such as the liver, the heart and/or skeletal muscles. Studies of the rapid metabolic changes after bariatric surgery conducted thus far rapidly improved the understanding of the fundamental pathogenic defects of T2D. However, much remains to be understood about the acute changes in gastrointestinal-derived metabolic fluxes, organ-specific metabolic responses to bariatric surgery and their relationship with the reversal of T2D. Using in vivo methodological approaches, the investigator proposes to investigate the early organ-specific changes in dietary fatty acid metabolism in response to BPD-DS vs. SG and their relation to improved systemic changes in glucose homeostasis, insulin sensitivity and β-cell function in patients with T2D.

Participants will undergo a metabolic study before and 8 to 12 days after bariatric surgery after a 12-hour fast and a three-day food and physical activity diary with accelerometry. The patients recover very rapidly from the surgery and will be able to participate to the proposed investigations the week after their hospitalization on an outpatient basis on the earliest week day between 8 and 12 days after the surgery procedure. The metabolic study is a 6-hour meal test using Positron Emitting Tomography (PET).

Inclusion Criteria:

Four groups of 11 subjects each: obese subjects with T2D or with normal glucose tolerance undergoing either BPD-DS or SG for treatment of obesity. T2D and control subjects will be matched for age (± 3 years), BMI (± 2 kg/m2) and gender across both BPD-DS and SG.

Exclusion Criteria:

• presence of overt cardiovascular disease, as assessed by history, physical exam, and abnormal EKG;
• treatment with a fibrate, a thiazolidinedione, a beta-blocker or other drugs known to affect lipid or carbohydrate metabolism (except statins, sulfonylurea, metformin, and other antihypertensive agents that can be temporarily stopped prior to the protocols);
• presence of liver or renal disease, uncontrolled thyroid disorder or other major illnesses;
• smoking (>1 cigarette/day) and/or consumption of more than 2 alcoholic beverages per day;
• prior history or current fasting plasma cholesterol level > 7 mmol/l or fasting TG > 6 mmol/l;
• any other contraindication to temporarily stop current medications for hyperglycemia, lipids, or hypertension.