Importance of Small Bowel Peptides for the Improved Glucose Metabolism 20 Years after Jejunoileal Bypass for Obesity

Background: Obese patients operated with jejunoileal bypass (JIB) have reduced plasma concentrations of insulin and glucose. Gastric inhibitory peptide/glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) have been found to have a profound incretin effect in humans. The aim of the present study was to examine the long-term effect of JIB on glucose metabolism. Methods: Four groups (lean, nonoperated obese, obese 9 months after JIB and obese 20 years after JIB) of six females each were given a mixed meal (280 kcal). Plasma samples were obtained every 10 min for 60 min postprandially and were analyzed for glucose, insulin, GIP and GLP-1. Results: A reduction in body mass index (kg/m²) was seen for the two patient groups operated with JIB (12.1, at 9 months post-op; 13.1, at 20 years post-op). Surgery by JIB resulted in a reduction of glucose and insulin values. Concomitantly there was an elevation of postprandial GIP and GLP-1 plasma concentrations. In the obese subjects 20 years after JIB both fasting and postprandial GIP and GLP-1 values were markedly elevated compared with the other three groups; and plasma glucose and insulin concentrations were maintained at normal levels. Conclusions: The improvement in glucose metabolism seen after JIB may be due to reduced insulin resistance after weight loss and/or increased levels of the incretin hormones GIP and GLP-1. Progressively, elevated levels of GIP and GLP-1 seem to be necessary to maintain glucose homeostasis at longterm follow-up after this procedure.