Diet and Medical Therapy Versus Bariatric Surgery in Type 2 Diabetes

It is generally held that ß-cell function is irreversibly lost already at the time the disease manifests itself and thereafter continues to decline linearly with time. Several studies, however, have documented the possibility that ß-cell function may be restored, at least partially, in type 2 diabetes. Of major relevance to the issue of ß-cell recovery in diabetes are the following findings: * bariatric surgery in morbidly obese patients with type 2 diabetes can restore euglycaemia, the acute insulin response to glucose and insulin sensitivity; * recent studies have reported that diabetic subjects return to euglycaemia and normal insulin levels within days after surgery, long before a significant weight loss has occurred; and * whereas gastric bypass (GBP) improves insulin sensitivity in proportion to weight loss, bilio-pancreatic diversion (BPD) improves insulin action out of proportion to weight loss, i.e., it normalizes it at a time when patients are still markedly obese. Because RYGB is a predominantly restrictive procedure involving the foregut, whereas BPD is a predominantly malabsorptive procedure involving the distal gastro-intestinal (GI) tract, these findings suggest that the control of both insulin action and ß-cell function is influenced by signals originating from the GI tract. The principal aim of this study is to verify the effect on type 2 diabetes mellitus (T2DM) of GBP and BPD, the two operations which have shown specific actions on glucose homeostasis control, in type 2 diabetic patients with BMI \> 35 kg/m2, and to compare this effect with matched T2DM control patients receiving the standard of medical care.