Figure 1.

ARFRP1 is required for appropriate insulin secretion in mice. (A) Western blot analysis from isolated islets from ad libitum fed male Arfrp1^flox/flox and Arfrp1^{β-cell−/−} mice probed with indicated antibodies. (B) Immunostaining of dispersed islet cells from ad libitum fed Arfrp1^flox/flox and Arfrp1^{β-cell−/−} mice stained for ARFRP1 (white), insulin (red), and glucagon (green). Nuclei were visualized with DAPI (blue). Scale bar = 40 μm. (C) Blood glucose levels of 13-weeks-old ad libitum fed male Arfrp1^flox/flox (n = 12) and Arfrp1^{β-cell−/−} mice (n = 14). (D) Plasma insulin levels of 13 weeks old ad libitum male Arfrp1^flox/flox (n = 11) and Arfrp1^{β-cell−/−} mice (n = 13). (E) Total pancreatic insulin levels of ad libitum fed male Arfrp1^flox/flox (n = 11) and Arfrp1^{β-cell−/−} mice (n = 10). (F) Oral glucose tolerance test in 4h fasted male Arfrp1^flox/flox (n = 6) and Arfrp1^{β-cell−/−} mice (n = 9). Blood glucose was measured at indicated time points. Data is shown as mean ± SEM (∗ = p ≤ 0.05 2-way ANOVA). (G) Area under the curve of (F). (H) Plasma insulin levels after oGTT described in (F). (I) Area under the curve of (H). (J) Glucose stimulated insulin secretion from isolated islets of ad libitum fed 12- to 14-week-old male Arfrp1^flox/flox (n = 6) and Arfrp1^{β-cell−/−} (n = 7) mice treated with indicated glucose concentrations was measured at indicated time points in perifusion experiments. The first phase is marked in light gray, and the second phase is marked in dark grey. (K) Calculated area under the curve of first and second phase of glucose-stimulated insulin secretion measured in (J). Data are presented as mean ± SEM, ∗p ≤ 0.05 (unpaired Student's t-test, Welch's correction).