The metabolic effects of surgery in type 2 diabetes

Abstract

The incidence of obesity and type 2 diabetes continues to rise by epidemic proportions. Metabolic surgery has been defined as the manipulation of a normal organ or organ system to achieve a potential health gain and used in addition to bariatric surgery. Currently, It is the only treatment modality that has the most positive and long-lasting effect on type 2 diabetes remission. Changes in the intestinal structure by surgery affect endocrine functions and digestive system physiology. A significant portion of its effects is related to weight loss. However, rapid changes, especially in gastrointestinal hormones, are responsible for the early glycemic effects. These effects occur with an increase in incretin hormone levels, a decrease in anti-incretin hormone levels, central effect through the vagus, changes in bile acid metabolism and microbiota. The reason for increase of incretin hormone levels is explained by the passage of large amounts of food into the ileum due to the anatomical alteration (hindgut hypothesis). The other alternative hypothesis is the foregut hypothesis. As a result of bypassing the upper intestinal tract, the decreased overstimulation with the interruption of the contact of foods with the duodenum and proximal jejunum probably causes the inactivation of anti-incretin factors. The clinical studies have confirmed these effects and therefore the indications for metabolic surgery have expanded. The standard recommended methods include sleeve gastrectomy, Roux-en-Y gastric bypass (RYGB) and its modifications, biliopancreatic diversion (BPD) and its modifications. Based on meta-analysis results, gastric bypass and its modifications is more effective than sleeve gastrectomy in improving short- and mid-term glycaemic control in patients with type 2 diabetes. The outcomes of new surgical interventions (ileal interposition in combination with sleeve gastrectomy (SG) and SG + transit bipartition procedures, etc.) are still insufficient for routine use, and long-term outcomes remain lacking. When and what method to use for which patient will be clarified by future studies.