Association between serum total antioxidant status and flow-mediated dilation in patients with systemic lupus erythematosus: an observational study

OBJECTIVE Endothelial dysfunction (ED) is a condition that involves increased oxidative stress and decreased total antioxidant status (TAS) levels. Systemic lupus erythematosus (SLE) is also associated with ED. We aimed to determine the association between serum TAS and ED as assessed by flow-mediated dilation (FMD) in patients with SLE. METHODS Thirty-four patients with stable SLE who were not undergoing any treatment and 39 healthy volunteers without any overt cardiovascular disease were included in this cross-sectional study. Doppler ultrasound was used to measure FMD to assess ED in the study groups. Serum TAS levels were measured using a TAS kit. High-sensitivity C-reactive protein (hs-CRP) and anticardiolipin antibody (aCLA) levels were also measured to assess the inflammatory state. The SLE group further was divided into 2 groups according to presence or absence of aCLA. SLE disease activity was assessed using the SLE disease activity index (SLEDAI). Regression analysis was used to define independent predictors. RESULTS The mean TAS levels were significantly lower in patients with SLE than in controls (1.60±0.11 versus 1.73±0.15 mmol/L, p<0.001). hs-CRP levels were significantly higher in patients with SLE than in controls (8.2±6.0 vs. 2.9±4.0 mg/L; p<0.001), particularly in SLE patients with positive aCLA when compared with SLE patients with negative aCLA (13.8±4.3 vs. 5.6±4.8 mg/L, p<0.001). The FMD percent was significantly lower in patients with SLE than in controls (8.1±4.9 vs. 10.6±4.7, p=0.04). There was a significant positive correlation between FMD and TAS in the SLE group (r=0.448, p=0.008) and the control group (r=0.367, p=0.03) and a significant negative correlation between FMD and serum hs-CRP (r=-0.368, p=0.04) in only the SLE group. In multiple linear regression analysis, TAS, hs-CRP, and SLEDAI were independently correlated with FMD (β=0.50, p=0.003; β=-0.33, p=0.03; and β=-0.36, p=0.03; respectively). CONCLUSION Patients with SLE who have no overt cardiovascular disease are at increased risk for ED and this may be associated with underlying inflammation and impairment of TAS.