Impact of the bacterial colonic metabolism on fecal water toxicity as biomarkers of future colorectal cancer risk after bariatric surgery

Bariatric surgery is an effective way to treat obesity. Roux-en-Y gastric bypass (RYGB) reduces the gastric volume and bypasses parts of the small intestine so that malabsorption is induced whereasSleeve Gastrectomy (SG) only reduces the volume of the stomach without inducing malabsorption. Although bariatric surgery reduces overall cancer risk, evidence indicates that the risk for colorectal cancer (CRC) is increased and might depend on the type of surgery. We hypothesize that bariatric surgery modifies the bacterial colonic environment which contributes to the future CRC risk. A one-year follow-up study will be conducted in obese patients undergoing bariatric surgery and a control group of obese patients on a weight loss diet. Blood and fecal samples will be collected prior to and at specific time points after surgery or weight loss diet. We will characterize the colonic fermentation by analyzing metabolite profiles of the fecal samples, the composition of the microbiota and the bile acid composition and compare their capacity to induce toxicity in cultured colonic cells. Also the contribution of inflammation to toxicity will be taken into account. With multivariate statistical methods, we will identify those parameters that are associated with increased toxicity.