In our studies, which have evaluated the effects of direct intraduodenal infusion of glucose at rates spanning the normal range for GE in health and T2D, GIP secretion was shown to increase in proportion to the rate of nutrient delivery, whereas stimulation of GLP-1 was only evident at a higher threshold (3-4 kcal/min) (15, 16). This evidence concerns the gene GCG and type 2 diabetes mellitus.