Figure 5. Supplementation with 3,3-dimethyl-1-butanol (DMB) improves endothelial function by enhancing nitric oxide (NO)-mediated dilatation and reducing superoxide-related suppression of endothelium-dependent dilatation (EDD).

A, carotid artery endothelium-independent dilatation (EID) in response to increasing doses of the NO donor sodium nitroprusside (SNP); and B, EID area under the curve (AUC) (both n = 17–21 per group). C, EDD to acetylcholine (ACh) in the presence of the NO synthase inhibitor N^G-nitro-l-arginine methyl ester (l-NAME); and D, NO-mediated dilatation, as assessed by the difference in peak EDD in the absence vs. presence of l-NAME (both n = 9–13 per group). E, superoxide production, measured in 1 mm aorta rings by electron paramagnetic resonance (EPR) spectroscopy, with representative tracings shown above (n = 11–22 per group). Aortic abundance of superoxide dismutase (SOD) 1 (F) and 2 (G) normalized to GAPDH with representative Western blot images generated from WES electropherograms shown above. H, peak EDD to ACh in the absence vs. presence of the superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL; n = 8–15 per group). Data are mean ± SD. Data are combined for mice aged 24 and 27 months. Statistics are two-way mixed (group dose) ANOVA with Tukey’s post hoc test (A and C), one-way ANOVA with Tukey’s post hoc test (B, D and E),×and two-way mixed (group × ACh alone or ACh + TEMPOL) with Šídák’s post hoc test (F). *P < 0.05 control vs. young 5 month reference group within dose/condition. †P < 0.05 control vs. DMB within dose/condition. ˆP < 0.01 DMB vs. young 5 month reference group within dose. Abbreviations: Y, young; OC, old control; OD, old DMB.