Plasma extracellular superoxide dismutase levels in an Australian population with coronary artery disease

ln vitro experiments suggest that free radicals may contribute importantly to atherogenesis. Superoxide dismutase (SOD), particularly extracellular SO D (EC-SOD), which accounts for the majority of SOD biological activity, is a major superoxide scavenger. We explored factors that may affect plasma EC -SOD levels measured by ELISA and assessed the association between plasma E C-SOD and coronary artery disease documented angiographically in 590 white Australian patients less than or equal to 65 years old. Mean+/-SEM plasma E C-SOD in female patients (113.6+/-13.2 ng/mL) was significantly higher than in male patients (86.6+/-5.1 ng/mL, P<0.0001), and all 19 patients with le vels >400 ng/mL were heterozygous for the Arg213-->Gly mutation at the EC-S OD gene; there was also a positive correlation with age (r=0.131, P=0.0016) . Plasma EC-SOD in current smokers (75.0+/-9.3 ng/mL) was much lower than i n nonsmokers (111.7+/-8.2 ng/mL, P<0.01), and ex-smokers had intermediate l evels (84.3+/-7.1 ng/mL). Levels were significantly lower in patients with than in those without a history of acute myocardial infarction (MI) (76.1+/ -7.5 versus 110.1+/-6.0 ng/mL, P<0.05), and low plasma EC-SOD was independe ntly associated with an increased likelihood of a history of MI (OR, 2.04; 95% CI, 1.10 to 3.82); higher EC-SOD levels also tended to be associated wi th delayed onset of MI. In conclusion,our study establishes that in patient s assessed by coronary angiography, circulating EC-SOD is lower in men than in women and in smokers of each sex and that low levels are independently associated with a history of MI. These findings are consistent with EC-SOD' s being protective and contributing to reduced coronary risk.