For instance, infusion of the GLP-1R antagonist Exendin-9 has been used to investigate the relative importance of GLP-1 secretion on postprandial gastric emptying rate, - glucose absorption and -glucose excursions (150), and the role of exaggerated GLP-1 secretion for improved β-cell function and glucose tolerance after Roux-en-Y gastric bypass (151). This evidence concerns the gene GCG and glucose measurement.