Relationships between Endothelium-Dependent Vasodilation, Serum Vitamin E and Plasma Isoprostane 8-Iso-PGF2α Levels in Healthy Subjects

Abstract

Due to the reported associations between a low intake of vitamin E and atherosclerosis on one hand, and between endothelial dysfunction and atherosclerosis on the other hand, we investigated the relationship between endothelium-dependent vasodilation and serum levels of vitamin E (α- and γ-tocopherol) as well as the lipid peroxidation markers malondialdehyde and 8-iso-PGF_2α in a healthy population. Healthy subjects (31 men and 25 women), aged between 20 and 69 years, underwent measurements of forearm blood flow (FBF) at rest and during local infusion of 2 and 4 μg/min of methacholine (Mch, to evaluate endothelium-dependent vasodilation) and 5 and 10 μg/min of sodium nitroprusside (SNP, to evaluate endothelium-independent vasodilation, and during reactive hyperemia using venous occlusion plethysmography. Serum α-tocopherol concentration was significantly related to the index of endothelial function (r = 0.46, p < 0.01), defined as the ratio between the maximal dilatations during Mch and SNP infusions. Serum γ-tocopherol levels were positively related to the maximal FBF during reactive hyperemia (r = 0.54, p < 0.01) in women only. Furthermore, in women only, plasma 8-iso-PGF_2α levels were inversely related to the relative increases in FBF during both Mch and SNP infusions (r = –0.58 and r = –0.59, p < 0.01 for both). The results show a relationship between the levels of α-tocopherol and endothelial vasodilatory function, suggesting a beneficial role for this potent lipid-soluble antioxidant also in a population sample of apparently healthy subjects. Furthermore, in women, the accumulation of lipid peroxidation products such as 8-iso-PGF_2α seems to be associated with an impaired vasodilation in general.