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.