Researchers from the University of Cincinnati, the Cincinnati Children’s Hospital Medical Center and University of Gothenburg in Sweden report that it’s not just the size of a patient’s stomach that causes weight loss after a bariatric surgical procedure, but the change in their gut metabolism makeup.
Published in Nature, an online medical journal, on March 26, the study found that after vertical sleeve gastrectomy procedure, there was a change in the bile acids that bind to FXR nuclear receptors in the gut. With the absence of the FXR, the researchers found weight loss success and improvement or reduction in diabetes cases.
During a vertical sleeve gastrectomy, 80% of the stomach is removed to create a sleeve which restricts the amount of food that a patient can eat at once. According to Randy Seeley, a professor in the endocrinology, diabetes and metabolism division at UC and director of the Cincinnati Diabetes and Obesity Center, the smaller the stomach is made the more weight patients lose because they have less room to put food and eat fewer calories. However, the reason that vertical sleeve gastrectomies work is because there is major changes in the bile acids in the gut.
The study’s researchers believe that the therapeutic value of VSG isn’t just the result of a mechanical restriction because of a smaller stomach, but because of increased circulation of the bile acids that bind to the FXR nuclear receptor. This discovery was made in a mouse model where obese mice had their FXR receptors removed and undergone the same vertical sleeve gastrectomy procedure a human does. Despite their sleeve, rodents who didn’t have those receptors did not lose weight.
Ultimately because these bile acids and receptors interact with gut microbial communities, the researchers also evaluated the gut bacteria of vertical sleeve patients. Their research found that the surgery made dramatic changes in the gut bacteria of these patients. According to Karen Ryan, lead author of the study, manipulating gut bacteria is another way that we can mimic how this surgery works without having to actually do the procedure.
The study shows how important further exploration is needed on future obesity treatments and Type II Diabetes cases. Ultimately there are not enough surgeons available to treat this obesity epidemic, so we need to understand how the surgery works so we can offer more scalable solutions, Seeley said.
This study was done from grants from the Torsten Söderberg and Novo Nordisk foundations, UNIK Food Fitness and Pharma for Health and Disease research programme, Ethicon Endo-Surgery and the National Institute of Health’s National Institute of Diabetes and Digestive and Kidney Diseases and National Heart, Lung and Blood Institute.
NOTE: Seeley has also received research support directly from Ethicon Surgical Care as well as Novo Nordisk. He has served as a paid speaker and consultant for the company in the past.