LIPID-PEROXIDATION OF CIRCULATING LOW-DENSITY LIPOPROTEINS WITH AGE, SMOKING AND IN PERIPHERAL VASCULAR-DISEASE

In this study, lipid peroxides in plasma and the low density lipoprotein (LDL) fraction and plasma concentrations of vitamin E, lipids and lipoproteins were measured in 22 smokers (mean age 35 years), 26 non-smoking patients with peripheral vascular disease (PVD, mean age 66 years), and 23 younger (ages less than or equal to 55 years) and 26 older (ages >55 years) healthy subjects. Plasma lipid peroxide concentrations in the PVD patients (105.9 +/- 20.6 vs. 91.8 +/- 15.8 ng malondialdehyde (MDA)/ml plasma, mean +/- S.D.) and the smokers (94.1 +/- 16.5 vs. 74.0 +/- 13.9 ng MDA/ml plasma) were significantly elevated compared with levels in the appropriate control subjects and levels were significantly higher in older compared with younger control subjects. Plasma LDL lipid peroxides were also significantly raised in patients with PVD and smokers compared with control values (PVD: 37.1 +/- 7.7 vs. 26.3 +/- 4.1 ng MDA/ml plasma; smokers: 30.4 +/- 6.9 vs. 24.9 +/- 7.5 ng MDA/ml plasma). The ratio of LDL lipid peroxides:LDL-cholesterol was significantly higher in the smokers, and plasma cholesterol and LDL-cholesterol were significantly higher in patients with PVD compared with other groups of subjects. The ratio of vitamin E:total lipid was not significantly different between the study groups. These data show that lipid peroxide levels in the plasma LDL fraction are elevated along with raised circulating levels in patients with PVD and smokers but that LDL lipid peroxide concentrations were independent of age in the healthy subjects. Elevated LDL lipid peroxide concentrations may be mainly due to abnormally high LDL levels in PVD patients, whereas in smokers, the concentration of lipid peroxides in the LDL particles is raised and might render the lipoprotein more atherogenic.