Introduction: Oxidative stress associates with cardiovascular disease risk. Various biochemical measurements have been identified as indicators of oxidative stress. In CARDIA, multiple measures of oxidative stress were performed over 2 exams, allowing comparisons among indicators. We hypothesized that the indicators would be highly correlated with each other.
Methods: Blood and urine samples were collected in the year 15 (2000-2001) and year 20 exams of CARDIA. CARDIA is a cohort study that began in 1985-1986 with black and white men and women at 4 sites in the US. The samples were processed under stable conditions and frozen at -70oC until analysis. Analysis was performed for F2-isoprostanes (GC-MS); the carotenoids α- and β-carotene, β-cryptoxanthin, and zeaxanthin/lutein which were summed to form (Sum4Carot, HPLC); urate (enzymatic); γ-tocopherol (HPLC); γ-glutamyl transferase (GGT, enzymatic); and oxidized LDL (ELISA).
Results: Correlations between the various indictors of oxidative stress are tabulated. See Table 1. F2-isoprostanes, urate, and γ-tocopherol were in the range 0.21-0.29, and all three were also inverse with Sum4Carot (range -0.18 to -0.29). Oxidized LDL correlated with urate and γ-tocopherol, but not with F2-isoprostanes or GGT, and GGT had correlations<0.1 with all indicators.
Conclusion: Several indicators (F2-isoprostanes, Sum4Carot, γ-tocopherol, and urate) correlated as predicted; e.g. an inverse relationship between F2-isoprostanes and Sum4Carot. Urate and γ-tocopherol have weak antioxidant properties, but are associated with oxidative stress in some situations and have a positive correlation with F2-isoprostanes herein. Nonetheless, the indicators cannot replace each other and each indicator provides a unique view of oxidative stress. Oxidized LDL and GGT appear to reflect alternative aspects of oxidative stress. Thus, the indicators cannot be interpreted in a universal manner. These observations reflect the complexity of oxidative stress. Further assessment is needed.