Relationship of serum uric acid to measures of endothelial function and atherosclerosis in healthy adults

Although uric acid (UA) is considered as an antioxidant, the relationship between serum UA levels and cardiovascular diseases is not clear yet. Higher brachial artery resting diameter (BD), impaired brachial artery flow-mediated dilatation (FMD), increased carotid intima-media thickness (IMT), decreased aortic distensibility (AoD), and increased aortic stiffness index (AoSI) and elastic modulus (AoEM) are predictors for development and/or progression of atherosclerosis. In this study, BD, FMD, carotid IMT, AoD, AoSI and AoEM were studied in healthy subjects with UA concentrations in physiological range. One hundred 24 healthy volunteers between 26 and 55 years of age were included in this study. Each subject had a serum UA levels in normal range. Carotid IMT, BD and brachial FMD were measured by means of high-resolution vascular ultrasound. AoD, AoSI, AoEM were examined by transthoracic echocardiography. Endothelium-dependent dilatation (EDD) was assessed by establishing reactive hyperemia and endothelium-independent dilatation (EID) was determined by using sublingual isosorbide dinitrate. Although carotid IMT and EDD were significantly correlated with UA concentrations (r = 0.346, p < 0.0001; r = -0.255, p < 0.05, respectively), EID measurements were not significantly correlated with serum UA concentrations (r = - 0.105, p > 0.05). In addition, AoSI and AoEM were significantly correlated with serum UA levels (r = 0.368, p < 0.0001; r = -0.366, p < 0.0001, respectively), and there was a significant inverse correlation between AoD and serum UA concentrations (r = -0.366, p < 0.0001). Furthermore, in multivariate analysis, we found that serum UA concentrations were correlated with increased carotid IMT, reduced FMD and increased aortic stiffness independent of other cardiovascular risk factor (beta = 256, p = 0.002; beta = -193, p = 0.03; beta = 0.295, p < 0.0001, respectively). In healthy subjects, increased serum UA concentrations, even in physiological range, are a risk factor for increased carotid IMT, reduced FMD and increased aortic stiffness independent of other cardiovascular risk factor, and other factors related to the metabolic syndrome.