Incretin Levels and Effect Are Markedly Enhanced 1 Month After Roux-en-Y Gastric Bypass Surgery in Obese Patients With Type 2 Diabetes

TLDR

Limited data suggest that insulin secretion improves rapidly after Roux‑en‑Y gastric bypass, potentially beyond weight loss alone. The study aimed to determine whether RY‑GBP alters incretin levels and their effect on insulin secretion in obese type 2 diabetic patients. Researchers measured fasting and stimulated GLP‑1 and GIP concentrations and calculated the incretin effect as the difference in insulin AUC between an oral glucose tolerance test and an isoglycemic intravenous glucose test, before and one month after RY‑GBP. One month after RY‑GBP, patients lost an average of 9.2 kg, showed significant increases in GLP‑1 and GIP secretion, and the previously blunted incretin effect rose to 42.5 %, comparable to controls, indicating enhanced incretin‑mediated insulin secretion.

Abstract

Limited data on patients undergoing Roux-en-Y gastric bypass surgery (RY-GBP) suggest that an improvement in insulin secretion after surgery occurs rapidly and thus may not be wholly accounted for by weight loss. We hypothesized that in obese patients with type 2 diabetes the impaired levels and effect of incretins changed as a consequence of RY-GBP.Incretin (gastric inhibitory peptide [GIP] and glucagon-like peptide-1 [GLP-1]) levels and their effect on insulin secretion were measured before and 1 month after RY-GBP in eight obese women with type 2 diabetes and in seven obese nondiabetic control subjects. The incretin effect was measured as the difference in insulin secretion (area under the curve [AUC]) in response to an oral glucose tolerance test (OGTT) and to an isoglycemic intravenous glucose test.Fasting and stimulated levels of GLP-1 and GIP were not different between control subjects and patients with type 2 diabetes before the surgery. One month after RY-GBP, body weight decreased by 9.2 +/- 7.0 kg, oral glucose-stimulated GLP-1 (AUC) and GIP peak levels increased significantly by 24.3 +/- 7.9 pmol x l(-1) x min(-1) (P < 0.0001) and 131 +/- 85 pg/ml (P = 0.007), respectively. The blunted incretin effect markedly increased from 7.6 +/- 28.7 to 42.5 +/- 11.3 (P = 0.005) after RY-GBP, at which it time was not different from that for the control subjects (53.6 +/- 23.5%, P = 0.284).These data suggest that early after RY-GBP, greater GLP-1 and GIP release could be a potential mediator of improved insulin secretion.