Fig. 2: Conditional deletion of Pitpna in the pancreatic beta-cell impairs glucose-stimulated insulin secretion.

a Western blot analysis of Pitpna in isolated islets from Ins-Cre, Pitpna^flox/flox, and littermate control Ins-Cre, Pitpna^wt/wt (WT) mice at age 8 weeks (n = 3), P < 0.0001. Metabolic parameters were assessed in Ins-Cre, Pitpna^flox/flox, and WT male mice at age 8 weeks including: b random-fed and overnight 16-h fasted blood glucose and plasma insulin (n = 6), P = 0.0042. c plasma insulin and stimulation index after glucose bolus (n = 6), P_GSIS = 0.0272, P_{Stimulation index} = 0.0465. d blood glucose measurements after glucose bolus (n = 6), P_genotype = 0.0003. e Quantification of insulin release in response to 2.8 mM and 16.7 mM glucose concentrations and KCl (40 mM) from isolated islets of 10-week-old female Ins-Cre, Pitpna^flox/flox, and WT mice (n = 5), P_2.8 = 0.3695, P_16.7 = 0.008, P_Kcl = 0.0132. f Representative transmission electron micrographs of pancreatic beta-cells from 10-week-old Ins-Cre, Pitpna^flox/flox, and WT female mice. g–i Quantification of docked vesicles (g, P = 0.01), granules density (h, P = 0.0402), granule morphology (i) (immature secretory granule (ISG, blue box), mature secretory granules (MSG, red box), crystal-containing granules (CCG, yellow box), and empty secretory granules (ESG, orange box) in beta-cells of 10-week-old female Ins-Cre, Pitpna^flox/flox (n = 8), and WT mice (n = 8) shown in panel (f), P_ISG < 0.0001, P_MSG < 0.0001, P_CCG = 0.746, P_ESG = 0.0274. j Representative transmission electron micrographs of ER morphology and Golgi morphology of beta-cells from 10-week-old female Ins-Cre, Pitpna^flox/flox, and WT mice. White and red dashed boxes in the left panel identify high-magnification images of ER (center panel) and Golgi (right panel). k Immunostaining of insulin and glucagon (Gcg) in paraffin-embedded pancreata from 10-week-old female Ins-Cre, Pitpna^flox/flox, and WT mice. l Islet morphometric analysis including islet number per area pancreas (mm²), insulin⁺ cells per area pancreas, glucagon⁺ cells per area pancreas, and pancreatic beta-cell mass in 10-week-old female Ins-Cre, Pitpna^flox/flox and WT mice (WT, n = 7, 16, 5, 5 for islets number, insulin⁺ number, beta cell mass, Gcg⁺ number, respectively), (Ins-Cre^, Pitpna^flox/flox, n = 7, 13, 5, 5 for islets number, insulin⁺ number, beta cell mass, Gcg⁺ number, respectively), P_insulin⁺ _Nr. < 0.0001, P_{islets Nr.} = 0.0084, P_{beta-cell mass} = 0.0128, P_{Gcg+ Nr.} = 0.4698. Data are presented as mean values ± SEM for (b), (c), (d), (e), (g), (h), (i), (l). *P < 0.05, ***P < 0.001 and n.s. denotes not significant. Two-way repeated-measure ANOVA with Post-hoc multiple comparisons test (Sidak’s) was used for (c), (d). Two-tailed unpaired Student t-test were used for (a), (b), (c), (e), (g), (h), (i), (l). All primary source data are reported in the Source data file.