Vitamin E: the enigmatic one!

Abstract

Vitamin E was first identified more than 90 years ago by Evans and Bishop as an essential dietary factor that is required by rats to maintain normal reproduction (1). Unlike the other three fat-soluble vitamins that have very specific molecular targets and actions, vitamin E lacks specific pathways or specific molecular targets that account for its requirement from the diet. Considerable research had been focused on identifying specific molecular targets and actions for vitamin E (2). For instance, as it became clear that vitamins A and D act through cognate nuclear hormone receptors to regulate vitamin-responsive gene expression, investigators sought, without success, to identify similar activities for vitamin E. These investigations simply led back to the same understanding of vitamin E obtained from studies carried out between the 1930s and the 1980s, that vitamin E acts as a fat-soluble antioxidant. Vitamin E serves as a peroxyl radical scavenger that protects polyunsaturated fatty acids in membranes and lipoproteins from oxidative damage (3). Given that many dietary substances, as well as many substances synthesized within the body, have potent antioxidant properties, what selective pressures drove evolution to require humans and other higher animals to acquire vitamin E from the diet? Is this simply due to the physical properties and/or redox chemistry of vitamin E or is there something about vitamin E that we still do not understand? This issue of the Journal of Lipid Research contains the second installment of the JLR's Thematic Review Series on fat-soluble vitamins. The biology of vitamin E and its role in human cardiovascular disease will be considered in the two reviews that comprise this edition of the Thematic Review Series on fat-soluble vitamins.