Hepatic and Peripheral Insulin Sensitivity Do Not Improve 2 Weeks After Bariatric Surgery

Objective: Bariatric surgery has rapid metabolic effects on glucose metabolism before the occurrence of clinically significant weight loss. This suggests an acute effect of the surgery itself, e. g., resulting from bypassing the nutrient flow from the proximal gastrointestinal tract. Rapid effects of Roux-en-Y gastric bypass surgery (RYGB) on glucose metabolism were defined. Design and Methods: Glucose metabolism and total triglyceride hydrolysis in the basal state and during a hyperinsulinemic euglycemic clamp using stable isotopes 2 weeks were studied before and after RYGB. Results: Eighteen pre-menopausal women scheduled for RYGB were included. 2 weeks after RYGB median weight loss was 7.8 kg. Basal insulin and glucose levels decreased after surgery. Endogenous glucose production (EGP) was lower after surgery. In addition, insulin levels were lower during the clamp after surgery, suggesting enhanced clearance. Hepatic and peripheral insulin sensitivity did not change. Free fatty acid (FFA) levels increased after surgery both in the basal state and during the first step of the clamp. Total triglyceride hydrolysis did not change in the basal state and tended to be higher during hyperinsulinemia. Conclusions: Within 2 weeks, RYGB reduces basal EGP as well as insulin and glucose levels without an acute beneficial effect on hepatic or peripheral insulin sensitivity. The latter may be explained by higher rates of lipolysis and exposure to FFA induced by the hypocaloric state.