αGLP-1R−/− mice show glucose intolerance and disturbed glucagon secretion in response to i.p. glucose administration. αGLP-1R−/− mice show glucose intolerance and disturbed glucagon secretion in response to i.p. glucose administration. A: Female αGLP-1R−/− KO mice (ko, red) and their WT littermates (wt, gray), 4–5 months old (n = 8–10), were used in these assays. A: ipGTT with glucose at 2 g/kg body weight after overnight fasting. B: Area under the curve (AUC) of the ipGTT. C: Circulating insulin levels of the ko and wt mice during ipGTT. D: First-phase insulin secretion after glucose injection. E: ITT with insulin at 0.5 units/kg body weight after 6 h fasting. F: Glucagon secretion after glucose injection in the same setting as ipGTT. Only two time points were examined because glucagon measurements require a large amount of blood (50 μL), and the Institutional Animal Care and Use Committee guidelines have a limit on live blood collection from each mouse.*P < 0.05; **P < 0.01. Yanqing Zhang et al. Diabetes 2019;68:34-44 ©2019 by American Diabetes Association