Integrative and Translational Physiology : Integrative Aspects of Energy Homeostasis and Metabolic Diseases Exacerbation of endothelial dysfunction during the progression of diabetes : role of oxidative stress

Huang A, Yang YM, Feher A, Bagi Z, Kaley G, Sun D. Exacerbation of endothelial dysfunction during the progression of diabetes: role of oxidative stress. Am J Physiol Regul Integr Comp Physiol 302: R674 –R681, 2012. First published January 18, 2012; doi:10.1152/ajpregu.00699.2011.—To test the deterioration of endothelial function during the progression of diabetes, shear stressinduced dilation (SSID; 10, 20, and 40 dyn/cm) was determined in isolated mesenteric arteries (80–120 m in diameter) of 6-wk (6W), 3-mo (3M), and 9-mo (9M)-old male db/db mice and their wild-type (WT) controls. Nitric oxide (NO)-mediated SSID was comparable in 6W WT and db/db mice, but the dilation was significantly reduced in 3M db/db mice and declined further in 9M db/db mice. Vascular superoxide production was progressively increased in 3M and 9M db/db mice, associated with an increased expression of NADPH oxidase. Inhibition of NADPH oxidase significantly improved NOmediated SSID in arteries of 3M, but not in 9M, db/db mice. Although endothelial nitric oxide synthase (eNOS) expression was comparable in all groups, a progressive reduction in shear stress-induced eNOS phosphorylation existed in vessels of 3M and 9M db/db mice. Moreover, inducible NOS (iNOS) that was not detected in WT, nor in 6W and 3M db/db mice, was expressed in vessels of 9M db/db mice. A significantly increased expression of nitrotyrosine in total protein and immunoprecipitated eNOS was also found in vessels of 9M db/db mice. Thus, impaired NO bioavailability plays an essential role in the endothelial dysfunction of diabetic mice, which becomes aggravated when endothelial nitrosative stress is further activated via perhaps, an additional iNOS-mediated pathway during the progression of diabetes.