Summary
Vitamin E, a major lipid-soluble, chain-breaking antioxidant includes several tocopherols
having the biological activity of RRR-alpha-tocopherol. Vitamin E circulates in the
blood as free tocopherol bound to beta-lipoproteins and is present in cell membrane
where it exerts a potent defence against lipid peroxidation (1). Blood concentration
of vitamin E in humans ranges from 25 to 30 μM, depending on daily intake and body’s
ability to absorb fat (1). In the last decade the scientific interest on biological
activity of vitamin E increased because of a growing body of evidence linking this
vitamin with atherosclerosis and its complications (2). Thus, the oxidative hypothesis
of atherosclerosis suggests that LDL accumulates within vessel wall, in particular
in the macrophages, as a consequence of its oxidative modification mediated by resident
cells (3, 4). A reduced defence against LDL oxidation could favour this process and
accelerate atherosclerotic progression. Accordingly, patients with coronary heart
disease have lower plasma concentration of vitamin E than controls (2) and prospective
studies demonstrated that a daily assumption of vitamin E reduces cardiovascular events
(5). According to the oxidative hypothesis of atherosclerosis, this effect has been
attributed to the inhibition of LDL oxidation. Alternative mechanism potentially implicated
in the antiatherosclerotic activity of vitamin E includes its interference with the
activity of platelet and monocyte, in which the intracellular redox status plays an
important functional role (6, 7). As platelets and monocytes are both involved in
the pathophysiologic process leading to atherosclerotic lesion, the interference of
vitamin E with the biological function of these cells may represent another important
tool to explore the anti-atherosclerotic activity of vitamin E. This review will focus
on the open issues related to the use of vitamin E in clinical studies and the potential
usefulness in investigating platelet function and clotting activation in patients
treated with vitamin E.