Plasma myeloperoxidase is inversely associated with endothelium-dependent vasodilation in elderly subjects with abnormal glucose metabolism

Myeloperoxidase (MPO), a biomarker related to inflammation, oxidative stress, and nitric oxide scavenging, has been shown to impair endothelium-dependent vasodilation. Because elevated hydrogen peroxide concentrations in diabetic vessels may enhance MPO activity, we hypothesized that a stronger association of MPO with flow-mediated dilation (FMD) may be found in subjects with abnormal glucose metabolism. Myeloperoxidase concentrations were measured in EDTA plasma samples from participants of a population-based cohort study, including 230 subjects with normal glucose metabolism and 386 with abnormal glucose metabolism. Vascular function was expressed as FMD and nitroglycerin-mediated dilation of the brachial artery. In subjects with abnormal glucose metabolism, MPO was negatively associated with FMD (−20.9 [95% confidence interval {CI}, −41.7 to −0.2] -μm change in FMD per SD increment of MPO). This association remained significant after adjustment for nitroglycerin-mediated dilation (−31.1 [95% CI, −50.0 to −12.3]) and was not attenuated after further adjustment for established risk factors. In subjects with normal glucose metabolism, MPO was not significantly associated with FMD (2.0 [95% CI, −16.0 to 20.0]). In conclusion, in subjects with abnormal glucose metabolism, plasma levels of MPO are inversely associated with endothelium-dependent vasodilation, possibly reflecting enhancement of MPO activity by vascular oxidative stress.