β-cell-selective knockout of the GLP-1R in mice with impaired glucose tolerance after intraperitoneal injection of glucose and exogenous supplementation of GLP-1 did not induce insulin secretion, but glucose tolerance returned to normal after oral glucose, suggesting that the extra-islet GLP-1R plays a regulatory role in oral glucose tolerance (Smith et al., 2014). The gene discussed is GLP1R; the disease is Impaired glucose tolerance.