Gut microbiota and diabetes remission after metabolic surgery

Humans carry up to 200 bacterial species in the gastrointestinal tract. Important contribution of these genes is in carbohydrate degradation. The main task of the gut microbiota is digestion of food. The dominant gut bacteria are degradates of complex polysaccharides and releasing SCFA which are the sources for energy, cholesterol synthesis and gluconeogenesis. The mutual interaction of gut microbiota and host immune system is necessary for maintaining their symbiotic relationship. Microbial compositions differ in different metabolic conditions. Firmicutes are dominant in obese subjects while Akkermansia muciniphila which protect against adiposity, low grade inflammation in adipose tissue and insulin resistance is reduced in this population. Intestinal dysbiosis is associated with insulin resistance and diabetes type 2. Betaproteobacteria was highly enriched in diabetic population. The ratio of Bacteriodetes to Firmicutes and the Bacteroides-Prevotella group to the C.coccoides-E.rectale group are reduced. Gastrointestinal rearrangements after RYGB promote substantial changes on the gut microbiota. Gut microbota manipulation in favor of Akkermansia spp. may contribute in antidiabetic effect of metformin and could be potential treatment for T2D. Changes in gut bacteria after RYGB (Roux-en-Y gastric bypass) alter the body weight independent of other effects of bariatric/metabolic surgery. Mechanism for diabetes remission after bariatric surgery is still not clear. Besides change in incretin secretion and bile acid recirculation, potential mechanism is change of gut microbiota content. Possible improvement of glucose regulation following bariatric surgery may be related to butyrate and propionate production by some bacteria species, which influence glucose metabolism independently of bile acids recirculation.