Npas4 Is a Novel Activity–Regulated Cytoprotective Factor in Pancreatic β-Cells

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FIG. 3.
FIG. 3.

Npas4 is induced and Ins2 reduced after 72-h infusion of glucose into live, conscious rats. Under general anesthesia, indwelling catheters were inserted into the left carotid artery and right jugular vein of 6-month-old Wistar rats. The catheters were tunneled subcutaneously and exteriorized at the base of the neck, and the animals recovered for 5 days after surgery. The animals were randomized into three groups, receiving 0.9% saline (control), 70% glucose, or 20% intralipid with heparin (20 units/mL). Initial glucose infusions rates were 3.3 mL ⋅ kg−1 ⋅ h−1 and were then adjusted to maintain 13.8–16.7 mmol/L over the 72 h. Lipid infusion rates were 1.7 mL ⋅ kg−1 ⋅ h−1, which were maintained throughout the 72-h infusion. After infusions, islets were isolated, RNA was extracted and reverse transcribed, and Taqman analyses were carried out. Rats infused with glucose had significantly increased Npas4 expression (A) as well as significantly reduced insulin 2 expression (B) (n = 4–5). For further evidence of regulation of Npas4 expression in vivo, we examined a model of type 2 diabetes that expresses human IAPP on the heterozygous viable yellow agouti background (hIAPP-Avy/A). Compared with littermate controls (Avy/A mice), at 14 weeks of age, there was significantly higher Npas4 staining in the transgenic group; however, at 24 weeks of age, there was no discernible difference between the two groups (red, insulin; green, Npas4; blue, TO-PRO-3 nuclear dye). Scale bars, 50 μm. Significance was established using a one-way ANOVA with Dunnett post hoc analysis. **P ≤ 0.01; ***P ≤ 0.001.

This Article

  1. Diabetes vol. 62 no. 8 2808-2820