“Dietary factor X (is) indispensable for the production of healthy young.” That is how Herbert McLean Evans and Katharine Scott Bishop described vitamin E in their 1922 paper in the journal Science reporting their discovery of the essential nutrient.
Vitamin E is the common name that refers to a group of eight vitamers that include four tocopherols* and four tocorienols. Vitamin E deficiency causes cholestatic liver disease in children, neurological abnormalities and impaired immune response. Due to its strong antioxidant function, this fat-soluble vitamin is used as a supplement to decrease the risk of heart disease.
Continuing the Journal of Lipid Research’s thematic series on fat-soluble vitamins, the September issue addresses vitamin E with two reviews covering current research on this topic. In his introduction to the series, editorial board member William S. Blaner describes vitamin E as “the enigmatic one,” because we still do not know specific pathways or molecular targets of vitamin E that help explain its role as an essential nutrient.
Of the eight forms of vitamin E, the human body preferentially uses only the alpha-tocopherol form. The liver plays a major role in the control of uptake and circulation of vitamin E into the plasma. The review by Maret G. Traber of the Linus Pauling Institute at Oregon State University describes regulatory mechanisms that prevent vitamin E buildupthrough the interplay of two separate hepatic systems — the alpha-tocopherol uptake and secretion into the plasma and the cytochrome P450 oxidation systems — that degrade the nontocopherol forms.
The second review, by Moshe Vardi, Nina S. Levy and Andrew P. Levy of the Technion-Israel Institute of Technology, addresses the controversy regarding the cardioprotective effects of vitamin E. After reviewing various vitamin E intervention studies and their clinical outcomes related to cardiovascular morbidity and mortality, the authors conclude that “the answer appears to be a resounding no when one provides vitamin E indiscriminately to unselected populations.”
Using a pharmacogenomics approach, Vardi et al. identified a subgroup for which vitamin E is highly cardioprotective: those individuals who are either on hemodialysis or are diabetic and carry a haptaglobin genotype, Hp 2-2. The article emphasizes the importance of proper patient selection to observe vitamin-E-based protection against the development of cardiovascular disease.
* “Tocos” in Greek means “childbirth,” “ferein” means “bring forth,” and “-ol” represents the presence of an OH group.
Preethi Chander (email@example.com) earned a Ph.D. in structural biology from Purdue University and completed a postdoctoral fellowship at the National Institutes of Health.