Correlation of endothelin 1 plasma levels with plasma antioxidant capacity in elderly patients treated for hypertension

Experimental studies confirmed that reactive oxygen species increase endothelin-1 (ET-1) synthesis, and modulate ET-1 signaling pathway resulting in vasoconstriction and vascular remodeling. The aim of this study was to evaluate the relationship between plasma ET-1 concentration and antioxidant status in patients with essential hypertension and type 2 diabetes mellitus. Methods: 78 hypertensive patients, 53.8% diabetic, mean age 72.1 +/- 7.07 were examined. The plasma concentration of glucose, creatinine, uric acid, bilirubin, cholesterol, insulin, HbA1c and ET-1 were measured. Antioxidant status was assessed by Ferric Reducing Ability of Plasma (FRAP), vitamin C concentration and erythrocyte superoxide dismutase (SOD) activity. Results: With diabetes ET-1 concentration was higher (1.35 +/- 0.51 vs 1.12 +/- 0.46 pg/mL, p=0.04). The negative correlations between ET-1 concentration and FRAP (r=-0.50, p<0.0001), vitamin C (r=-0.296, p=0.01) and SOD (r=-0.44, p=0.001) were found. Concentration of ET-I correlated positively with SBP (r=0.33, p=0.005) but not with DBP. The relationship between DBP and ET-I only in subjects with DBP>110 mm Hg and FRAP<0.40 mmol/L was found. In multiple regression analysis plasma ET-I levels were associated independently with FRAP (beta=-0.583, p=0.003) and plasma vitamin C (beta=-0.407, p=0.04). Conclusions: In hypertensive and diabetic patients higher plasma endothelin-1 level was independently associated with lower plasma antioxidant status measured by FRAP and decreased vitamin C concentration, which may be a result of increased oxidative stress in these diseases. (C) 2008 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.