Bariatric surgery: unstressing or boosting the beta-cell?

Bariatric surgery is the most effective therapy for severe obesity in terms of reduction of morbidity and mortality and quality of life improvement. Different bariatric procedures distinctly differ with regard to their effectiveness to reduce body weight and to improve morbidities, such as type 2 diabetes. In this regard, the most effective procedures are bilio-pancreatic diversion (BPD) and duodenal switch procedure curing 98.9% of the diabetes patients, followed by Roux-en-Y gastric bypass (RYGB) with 83.7% success rate, by gastroplasty with 71.6% and by gastric banding with 47.9%. Interestingly, a net improvement up to resolution of type 2 diabetes has been consistently reported few days after RYGB and BPD. RYGB promotes incretin secretion which, in turn, stimulates insulin secretion while insulin sensitivity is slightly improved. Rarely, the long-term effect of incretin hypersecretion might result in hypertrophy and hyperplasia of the islets of Langerhans, otherwise known as nesidioblastosis, associated with hyperinsulinaemia and severe postprandial hypoglycaemia. In contrast, BDP improves insulin resistance to a greater extent and results, in the long run, in supra-normal values of insulin sensitivity with subsequent reduction of insulin secretion. The mechanism allowing diabetes resolution after surgical intestinal manipulation is extremely interesting but only partially understood.