Figure 2.

Pancreatic islets in a DIO model exhibit NIK hyperactivation and display a net β cell secretory defect. (A) Blood glucose and AUC were determined in 12 chow (dotted line) and 15 DIO (solid line) fed C57BL/6 WT mice (16 wk old) after i.p. injection of d-glucose. Data are representative of three independent mouse cohorts tested. ****, P < 0.0001. (B) Insulin levels and AUC (10 min after injection) were determined for 5 chow (dotted line) and 15 DIO (solid line) fed C57BL/6 WT mice (16 wk old) after i.v. injection of d-glucose. Data are representative of three independent mouse cohorts tested. *, P < 0.05. (C) Total β cell area was determined for 5 chow- and 5 HFD-fed WT mice by quantification of insulin-positive area in serial graft sections as a percentage of total pancreatic exocrine area (*, P < 0.05). (D) Data are mean and SEM showing percentage of net insulin secretion normalized to mean β cell area determined for mice in C. (left) Net fasted insulin levels; (right) net secretion (AUC) for 10 min after d-glucose injection. *, P < 0.05; ****, P < 0.0001. (E) Protein levels of NIK, IKKα/β phosphorylation, IκBα, p100 to p52 processing, and RelB in one islet isolate from a chow-fed and a DIO C57BL/6 WT mouse were assessed by immunoblotting. A representative of four independent experiments is shown. Histogram data depict cumulative densitometry relative to β-actin of the four independent experiments. (F and G) Protein levels of p100 to p52 processing and RelB in one (F) TNF- and (G) RANKL-stimulated mouse islet isolate at 0, 1, and 4 h after stimulation. IκBα levels at 0, 15, 30, 60, and 240 min after stimulation were assessed by immunoblotting. A representative of four independent experiments is shown. Histogram data shows cumulative densitometry relative to β-actin of the four independent experiments. All data are represented as mean ± SEM; p-values were determined using Student’s t test.