GLP-1R signaling plays a critical role in the maintenance of glucose homeostasis as deletion of the GLP-1R in mice results in impaired glucose tolerance (Scrocchi et al., 1996) and physiological levels of GLP-1 enhance meal-related insulin secretion in humans (Kreymann et al., 1987; Mojsov et al., 1987). Here, GLP1R is linked to Impaired glucose tolerance.