Plasma levels of lipid and cholesterol oxidation products and cytokines in diabetes mellitus and cigarette smoking: effects of vitamin E treatment

To evaluate the role of both oxidation and inflammation in atherosclerosis, we compared LDL oxidizability, in vivo lipid and cholesterol oxidation, and basal and lipopolysaccharide (LPS)-stimulated production of various cytokines in normolipidemic patients with diabetes mellitus (DM; n=11), cigarettes smokers (n=12) and controls (n=14). In addition, the effects of vitamin E (600 I.U./day for 4 weeks) on these parameters were evaluated. Initial LDL oxidation characteristics before and after vitamin E were identical in the 3 groups. Plasma thiobarbituric acid reactive substances were higher in DM and smokers versus controls (0.77±0.22, 0.74±0.14 versus 0.62±0.10 μmol malondialdehyde equivalents/l, respectively; P versus controls <0.05) and normalized after vitamin E supplementation. Total plasma oxysterols were higher in smokers versus controls (354±104 versus 265±66 nmol/l, P<0.05) and unaffected by vitamin E. The basal and LPS-stimulated levels of interleukin-1β and tumour necrosis factor α (TNFα) and the basal level of interleukin-1-receptor antagonist (IL-1RA) were identical for the 3 groups. LPS-stimulated IL-1RA was higher in DM versus controls (10.7±2.0 versus 8.1±1.7 pmol/l, P<0.05). After vitamin E, TNFα dropped in controls and smokers, and IL-1RA in smokers only. Results suggest increased in vivo oxidative stress and inflammation in DM and smoking, which is partly overcome by vitamin E.