From bariatric to metabolic surgery: Looking for a "disease modifier" surgery for type 2 diabetes

In this review the recent evolution of the comprehension of clinical and metabolic consequences of bariatric surgery is depicted. At the beginning bariatric surgery aim was a significant and durable weight loss. Later on, it became evident that bariatric surgery was associated with metabolic changes, activated by unknown pathways, partially or totally independent of weight loss. Paradigm of this "metabolic" surgery is its effects on type 2 diabetes mellitus (T2DM). In morbid obese subjects it was observed a dramatic metabolic response leading to decrease blood glucose, till diabetes remission, before the achievement of clinically significant weight loss, opening the avenue to search for putative anti-diabetic "intestinal" factors. Both proximal duodenal (still unknown) and distal (GLP1) signals have been suggested as hormonal effectors of surgery on blood glucose decrease. Despite these findings T2DM remission was never considered a primary indication for bariatric surgery but only a secondary one. Recently T2DM remission in obese subjects with body mass index (BMI) greater than 35 has become a primary aim for surgery. This change supports the idea that "metabolic surgery" definition could more appropriate than bariatric, allowing to explore the possibility that metabolic surgery could represent a "disease modifier" for T2DM. Therefore, several patients have undergone surgery with a primary aim of a definitive cure of T2DM and today this surgery can be proposed as an alternative therapy. How much surgery can be considered truly metabolic is still unknown. To be truly "metabolic" it should be demonstrated that surgery could cause T2DM remission not only in subjects with BMI > 35 but also with BMI < 35 or even < 30. Available evidence on this topic is discussed in this mini-review.