Differences in systemic oxidative stress based on race and the metabolic syndrome: the Morehouse and Emory Team up to Eliminate Health Disparities (META-Health) study

Abstract

Background: Classification schema such as metabolic syndrome may underestimate cardiovascular disease (CVD) risk in African Americans, despite a higher burden of CVD in African Americans. Oxidative stress results from an imbalance of prooxidants and antioxidants and leads to endothelial dysfunction that promotes vascular inflammation and atherosclerosis. Aminothiol markers of oxidative stress are associated with CVD risk factors and metabolic syndrome; however, little is known about racial differences in levels of oxidative stress. We sought to investigate whether oxidative stress would be higher in African Americans compared to whites independently of traditional risk factor burden.

Methods: We assessed oxidative stress in a biracial, community-based cohort. In 620 subjects (59% female, 52% African American) in the Morehouse and Emory Team up to Eliminate Health Disparities (META-Health) study, we measured plasma levels of glutathione, an intracellular antioxidant, and its redox potential as a ratio of reduced and oxidized glutathione (E(h) glutathione).

Results: African Americans had lower glutathione levels (P<0.001) compared to whites. There was a trend toward more oxidized E(h) glutathione (P = 0.07) in African Americans; however, this did not reach statistical significance. After adjustment for demographics and CVD risk factors, African-American race remained a significant correlate of lower glutathione levels (P<0.001) and a more oxidized E(h) glutathione (P = 0.04). After further adjustment for high-sensitivity C-reactive protein (hsCRP), glutathione remained significantly lower in African Americans (P = 0.001). African Americans with or without metabolic syndrome had lower glutathione levels compared to whites with or without metabolic syndrome, respectively (both P ≤ 0.001), and African Americans without metabolic syndrome had a more oxidized E(h) glutathione compared to whites without metabolic syndrome (P = 0.003).

Conclusions: African Americans have higher levels of oxidative stress than whites, even after adjustment for differences in CVD risk factors and inflammation. Racial differences in oxidative stress may play a key role in understanding observed racial disparities in CVD.

Fig. 1.

(A) Box plot of glutathione levels by race and absence or presence of metabolic syndrome. The band near the middle of the box is the median, whereas the top and bottom of the box are the upper and lower quartiles, respectively. The circles represent outliers. (**) P≤0.001. (B) Box plot of oxidized glutathione (E_h glutathione) levels by race and absence or presence of metabolic syndrome. The band near the middle of the box is the mean, whereas the top and bottom of the box are±1 standard deviation, respectively. The circles represent outliers. (*) P=0.02; (**) P=0.003.