Dual elimination of the glucagon and GLP-1 receptors in mice reveals plasticity in the incretin axis - PubMed (original) (raw)

Islet insulin secretion was assessed by preincubation of islets in KRB for 60 minutes at 2.8 mM glucose at 37°C before distribution in batches of 10 islets per condition into wells containing 16.7 mM glucose with or without (A) exendin-4 (Ex-4, 10 nM), [

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-Ala2]GIP (GIP, 10 nM), (B) PACAP (10 nM), tolbutamide (Tol, 100 μM), or

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-arginine (L-arg, 10 mM) for 1 hour at 37°C. Levels of insulin in the secretion medium were normalized to levels of islet insulin content and are expressed as a fold change in insulin secretion relative to WT high-glucose treatment. Insulin content values averaged approximately 30–40 ng/islet for Glp1r–/– and WT mice and 15–25 ng/islet for Gcgr–/– and Gcgr–/–Glp1r–/– mice (n = 3 mice per group). Data shown are representative of 2–3 independent experiments, each with 3 replicates per condition. (C) Total cellular and media cAMP in islets from WT, Glp1r–/–, Gcgr–/–, and Gcgr–/–Glp1r–/– mice was quantified following treatment of the islets with 0, 1, 3, or 10 nM [

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-Ala2]GIP. Levels of cAMP in the secretion medium were normalized to levels of islet insulin content and are expressed as a fold change in islet cAMP levels relative to WT high-glucose treatment (n = 3 mice per group). Values are expressed as mean ± SEM. §P < 0.05, Glp1r–/– versus Gcgr–/–Glp1r–/– mice; #P < 0.05, Gcgr–/– versus Gcgr–/–Glp1r–/– mice; ‡P < 0.05, Gcgr–/–Glp1r–/– versus WT mice; †P < 0.05, Glp1r–/– versus WT mice; *P < 0.05, Gcgr–/– versus WT mice.