Role of the incretin system in the remission of type 2 diabetes following bariatric surgery.

AIMS: It has been observed, as a collateral outcome of bariatric surgery, that morbidly obese patients with frank type 2 diabetes mellitus or impaired glucose tolerance undergone Roux-en-Y Gastric Bypass (RYGB) or bilio-pancreatic diversion (BPD) became and remained euglycemic since surgery. But, most interestingly, the conversion to euglycemia happened within few days from the operation, long before a significant weight loss could intervene. The purpose of this viewpoint is to try to elucidate the mechanisms involved in the resolution/remission of diabetes after bariatric surgery, in particular highlighting the role played by the modifications in incretin secretion.

DATA SYNTHESIS: The effect of purely restrictive procedures in improving glucose control is directly proportional to the degree of weight loss. In contrast, either RYGB or BPD, the first a mainly restrictive and the second a quite purely malabsorptive bariatric technique, operate through a different mechanism, as a probable consequence of the small intestine bypass. The bypass of different intestinal portions covers a central role in the mechanisms of action of these two surgical procedures. In fact, while RYGB does not affect insulin resistance but increases insulin secretion via the stimulation of nutrient-mediated incretin secretion, BPD induces a full normalization of insulin resistance and, consequently, a significant reduction of insulin secretion. The insulin resistance reversion is only partially explained by the incretin level changes after BPD.

CONCLUSION: A role of incretins in type 2 diabetes improvement or resolution is ascertained although it is possible that other, not yet identified, hormone(s) can cooperate with them.