The Microbiology of Bariatric Surgery

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Obesity and its associated diseases are increasing worldwide. However, the mechanisms behind the development of obesity is not fully understood. There is evidence that intestinal bacteria may play a role in the development and perpetuation of obesity through regulation of energy and fat storage.

Bariatric surgery is currently the most effective modality for treating severe obesity with evidence to support long-term sustained weight loss and improvement in obesity-related comorbidities. The two most commonly performed bariatric surgical procedures are the Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). RYGB leads to greater weight loss than SG and improved diabetes control in patients following surgery. Despite the success of RYGB and SG in inducing weight loss and improving comorbidities, the underlying mechanisms leading to clinical improvement following these operations is not completely understood. Multiple factors are thought to play a role including reduced caloric intake, decreased nutrient absorption, increased satiety, release of hormones and shifts in bile acid metabolism.

Recent evidence has suggested that the gut bacteria mediates a number of the beneficial effects of bariatric surgery. Small studies have demonstrated changes in the composition and diversity of the gut microbiota after RYGB and SG in humans. One study also confirmed long-term microbial changes for RYGB. However, comparative trials have been small (less than 15 participants per treatment group) and important differences between specific bacterial populations have not been well elucidated. Furthermore, no human study has examined the differences in bacterial composition following RYGB and SG in relation to their metabolic consequences.

The aim of this study is to investigate and compare the metabolic and microbial changes that occur with RYGB, SG, and dietary controls. Specifically, we aim to use a systems biology approach utilizing powerful analytic techniques including metagenomics, metabolomics, and multiplex immune profiling to define the combined microbial, metabolic and immunologic changes that occur after bariatric surgery.