Fig. 2: Pancreatic β cell-specific Senp2 knockout affects insulin processing and maturation.

a Immunohistochemical staining of the pancreas with insulin antibodies, scale bar: 100 μm. b Total β cell mass of the control and Senp2-βKO mice fed a 16-week HFD was measured with the following equation: β cell mass = pancreas weight × β cell area/pancreas area, which was determined by immunohistochemical staining with an insulin antibody. n = 3–4 mice. c GSIS of isolated islets from the control or Senp2-βKO mice. Islets were incubated under 2.8 mM (low) or 17.8 mM (high) glucose concentrations. n = 5–10 per group. *P < 0.05, t-test. d Relative insulin mRNA levels of the islets from the control and Senp2-βKO mice. The mRNA level of the control group was set to 1, and other values are expressed relative to this level. n = 7–9 per group. e Representative EM images (40000x) of isolated islets of the control and Senp2-βKO mice; scale bar: 500 nm. f, g Manual quantification and classification of insulin granules were performed on 5–6 areas/islet, >100 isolated islets/mouse. Total insulin granules per unit area (f) and distribution of insulin granule types (g), n = 3–4 mice per group, *P < 0.05, t-test. h Fasting serum insulin and proinsulin concentrations of the control and Senp2-βKO mice were measured after CD (20 weeks old) or 16 weeks of HFD (24 weeks old) feeding. Insulin (the left panel), proinsulin (the middle panel), and molar ratio of proinsulin to insulin (the right panel), n = 6–10 per group. *P < 0.05, t-test. All data are presented as the mean ± SEM.