Aims Heme oxygenase-1 (HO-1) is an intracellular enzyme that catalyzes the oxidation of heme to generate CO, biliverdin, and iron. Since these products have antiatherogenic properties, HO-1 may play a protective role against the progression of atherosclerosis. However, plasma HO-1 levels in patients with atherosclerotic diseases, such as coronary artery disease (CAD) and peripheral artery disease (PAD), have not been clarified yet. Methods We investigated plasma HO-1 levels by ELISA in 410 consecutive patients undergoing elective coronary angiography who also had an ankle-brachial index (ABI) test for PAD screening. Results Of the 410 study patients, CAD was present in 225 patients (55%) (1-vessel (1-VD), n = 91; 2-vessel (2-VD), n = 66; 3-vessel disease (3-VD), n = 68). PAD (ABI < 0.9) was found in 36 (9%) patients. Plasma HO-1 levels did not differ between 225 patients with CAD and 185 without CAD (median 0.44 versus 0.35 ng/mL), but they were significantly lower in 36 patients with PAD than in 374 without PAD (0.27 versus 0.41 ng/mL, P < 0.02). After excluding the 36 patients with PAD, HO-1 levels were significantly higher in 192 patients with CAD than in 182 without CAD (0.45 versus 0.35 ng/mL, P < 0.05). HO-1 levels in 4 groups of CAD(−), 1-VD, 2-VD, and 3-VD were 0.35, 0.49, 0.44, and 0.44 ng/mL, respectively, and were highest in 1-VD (P < 0.05). In the multivariate analysis, HO-1 levels were inversely associated with PAD, whereas they were also associated with CAD. The odds ratios for PAD and CAD were 2.12 (95% CI = 1.03–4.37) and 0.65 (95% CI = 0.42–0.99) for the HO-1 level of <0.35 ng/mL, respectively. Conclusions Plasma HO-1 levels were found to be low in patients with PAD, in contrast to high levels in patients with CAD.

Background and Purpose— Heme oxygenase-1 (HO-1) catalyzes the oxidation of heme to generate carbon monoxide, biliverdin, and iron. Because these products have antiatherogenic properties, HO-1 may play a protective role against atherosclerosis. However, plasma HO-1 levels in patients with carotid atherosclerosis have not been reported. Methods— We investigated plasma HO-1 levels by ELISA in 136 subjects (age, 66±9 years) undergoing carotid ultrasonography. Results— Of the 136 study subjects, carotid plaque was found in 61 subjects (45%). Compared with 75 subjects without plaque, 61 with plaque were older and predominantly male ( P <0.05). Plasma HO-1 levels were higher in subjects with plaque than in those without plaque (median, 0.56 versus 0.44 ng/mL; P <0.05). The percentage of subjects with HO-1 level >0.50 ng/mL was higher in subjects with plaque than without plaque (66% versus 44%; P <0.025). In multivariate analysis, HO-1 level was a significant factor for carotid plaque independent of atherosclerotic risk factors. Odds ratio for plaque was 2.33 (95% CI, 1.15–4.75) for HO-1 level >0.50 ng/mL. Conclusions— Plasma HO-1 levels were high in subjects with carotid plaques, probably reflecting a protective response against carotid atherosclerosis.

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