Fig. 5

GRK2 +/− mice display increased GLP-1R-dependent insulin release in vivo and in isolated islets. Insulin (a) and glucose (b) levels were assessed in serum samples of fasted mice (basal) and 15 min after the administration of an intraperitoneal glucose bolus (ipGTT, 2 g/kg) with or without the GLP-1 analog Exendin-4 (Ex4, 5 μg/kg (for ipGTT or ipGTT+Ex4, respectively, WT n = 7 or 8; for GRK2+/− n = 6 or 6; same mice were used to assess insulin and glucose levels). Analysis of glucose levels (c) and bar graph representing the area under the curve (AUC) (d) after insulinogenic stimuli are shown; WT: n = 8 for ipGTT and ipGTT + Ex4 and GRK2+/− n = 8 for ipGTT and 7 for ipGTT + Ex4. Insulin secretion in isolated pancreatic islets stimulated with high glucose (HG, 17 mM) or high glucose with Exendin-4 (HG + Ex4 100 nM) from WT and GRK2+/− mice, expressed as % of insulin content, n = 4 mice (2–3 different 5-islets pool were assessed per mice as technical replicas) (e). Amount of total islet insulin content as obtained by acidic extraction, n = 5 mice (8–11 5-islets pools were assessed per mice as technical replicas) (f). Means ± SEM data are represented. Statistical analysis was performed using repeated measures 2-way ANOVA (c) or 1-way ANOVA (a, b, d, and e) followed by Bonferroni’s post hoc test and unpaired t test (f); (*) was used for comparisons between WT and GRK2+/− mice, (#) was used for comparisons between basal vs ipGTT or ipGTT vs ipGTT + Ex4 (C). *p < 0.05; *** ^###p < 0.001