New lessons in weight loss surgery
Understanding what happens after weight loss surgery may reveal new strategies to control diabetes
Weight loss surgery refers to a group of similar operations prescribed to treat morbid obesity (defined as a body mass index greater than 40) and type 2 diabetes. Most patients who undergo this massive intervention experience rapid resolution of type 2 diabetes after surgery. It is believed that this is not simply the result of gastric restriction and weight loss, but that other factors are in play. Researchers in Prof. Duan Chen's group at the Norwegian University of Science and Technology in Trondheim asked the question ‘How does the surgical rearrangement of the intestine improve diabetes?’ The "hindgut hypothesis" suggests that food in the rearranged hindgut stimulates the production a gut hormone called glucagon-like peptide 1 (GLP-1). This peptide increases production of insulin in the pancreas, and thereby has a beneficial effect on type 2 diabetes. Based on this hypothesis, a special surgical procedure called ileal interposition has been developed and successfully applied to patients. Researcher Helene Johannessen and her colleagues from Trondheim have established an animal model to help understand the mechanisms underlying the effects of weight loss surgery. She says "We have found evidence to support the hindgut hypothesis. Furthermore, when this procedure was combined with one of today’s most used weight loss surgeries, sleeve gastrectomy, the production of GLP-1 was increased not only in the ileum (a part of the hindgut), but also in the pancreatic islets." This may explain, at least in part, the remission of diabetes after weight loss surgery, and suggests a new strategy to control diabetes by targeting GLP-1 in the pancreatic islets. The mechanisms underlying postsurgical weight loss and/or weight regain in patients still remain unclear. A major point of controversy is whether this is due to biological or behavioral factors. It has been difficult to directly and precisely measure eating behavior in humans. Using a "Big Brother" type cage to observe animals after surgery, the research team found that the animals took more time to finish their meals. This is likely to be a beneficial behavior contributing to weight loss.
Eating Behavior and Glucagon-Like Peptide-1-Producing Cells in Interposed Ileum and Pancreatic Islets in Rats Subjected to Ileal Interposition Associated with Sleeve Gastrectomy. Obesity Surgery 2012 [Epub ahead of print] PMID 22949011