Incretin effect in relation to weight loss surgery
Rapid transit of nutrients from the gastric pouch to the distal ileum in those with Roux-en-Y anatomy or the duodenal switch causes increased release of incretins (glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide) with subsequent enhancement of glucose-stimulated insulin secretion and beta-cell sensitivity to oral glucose, especially in patients with type 2 diabetes, in whom this relationship is impaired. Similar effects are seen after the sleeve gastrectomy, although the results are less dramatic and substantial. This may indicate the possible role of ghrelin as an incretin hormone because this hormone level drops immediately after surgery. These early GI hormone changes likely explain much of the initial improvement in blood glucose levels after weight loss surgery. However, long-term data show that glycemic control can wane over time, likely as a result of weight regain or poor diet choices. This may also relate to the existing islet cell mass at the time of surgery because the best and most durable responses occur in patients with diabetes existing for < 5 years and not on insulin therapy.