Figure 2.

Plasma concentrations of glucose (A), insulin (B), C-peptide (C), GLP-1 (D), glucagon (E), and GIP (F) in patients examined before and after surgery. At t = 0 min, an oral mixed meal was ingested. Data are presented as means ± SEM. P values were calculated using repeated measures by ANOVA. Significant difference (P < 0.05) at individual time points (Bonferroni post hoc test). *Significant (P ≤ 0.05) differences at individual time points. Increased glucose levels (A) are consequent to decreased insulin and C-peptide levels after surgery (B and C). Incretin adaptation (D and F) to removal of duodenum and consequent reduction of GIP (E) are shown. The incretins showed an opposite trend after the surgery, i.e., a major reduction of GIP secretion and increase of GLP-1 release. The rise in glucagon concentration after the removal of duodenum reached the statistical significance after the first hour of the mixed-meal test.