Antioxidant enzyme activity is associated with blood pressure and carotid intima media thickness in black men and women: The SABPA study

- Glutathione reductase (GR) activity was higher in black men and women when compared to their white counterparts.
- Higher GR activity in black men was independently associated with thickening of the carotid intima media.
- Glutathione peroxidase (GPx) activity was lower in black women when compared to white women.
- Lower GPx activity in black women was independently associated with increased blood.
- GPx and GR activity are important role players in arterial remodelling and hypertension development in a black population.

In the urbanized black population of South Africa, oxidative stress may play a crucial role in the development of hypertension. Since oxidative stress may result from impaired antioxidant capacity we aimed to investigate antioxidant enzyme activity as well as its associations with vascular function and structure in a bi-ethnic population. Participants included 409 subjects almost equally stratified by ethnicity and sex. Blood pressure and carotid intima media thickness (cIMT) were measured and glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD) and catalase (CAT) enzyme activities were determined. GR activity was significantly higher in black men (7.71 nmol/min/ml vs 2.23 nmol/min/ml) and women (6.46 nmol/min/ml vs 2.86 nmol/min/ml) (p < 0.001) when compared to their white counterparts. In black women, GPx activity was significantly lower (p < 0.001) when compared to white women (31.9 nmol/min/ml vs 37.1 nmol/min/ml). In black men, cIMT was positively and independently associated with GR activity (R2 = 0.30; β = 0.18; p = 0.048). In black women, systolic blood pressure (R2 = 0.21; β = −0.24; p = 0.014), diastolic blood pressure (R2 = 0.11; β = −0.20; p = 0.044) and mean arterial pressure (R2 = 0.20; β = −0.31; p = 0.002) were inversely associated with GPx activity. No associations were found in the white groups. The positive association between GR activity and cIMT in black men may be the result of a compensatory response to prevent arterial remodelling. The inverse association between GPx activity and blood pressure in black women may indicate a role for decreased GPx activity in hypertension development in this population.