Vitamin E: non-antioxidant roles

Vitamin E was originally considered a dietary factor of animal nutrition es pecially important for normal reproduction. The significance of vitamin E h as been subsequently proven as a radical chain breaking antioxidant that ca n protect the integrity of tissues and play an important role in life proce sses. More recently alpha-tocopherol has been found to possess functions th at are independent of its antioxidant/ radical scavenging ability. Absorpti on in the body is alpha-tocopherol selective and other tocopherols are not absorbed or are absorbed to a lesser extent. Furthermore, pro-oxidant effec ts have been attributed to tocopherols as well as an anti-nitrating action. Non-antioxidant and non-pro-oxidant molecular mechanisms of tocopherols ha ve been also described that are produced by alpha-tocopherol and not by bet a-tocopherol. alpha-Tocopherol specific inhibitory effects have been seen o n protein kinase C, on the growth of certain cells and on the transcription of some genes (CD36, and collagenase). Activation events have been seen on the protein phosphatase PP2A and on the expression of other genes (alpha-t ropomyosin and Connective Tissue Growth Factor). Non-antioxidant molecular mechanisms have been also described for gamma-tocopherol, delta-tocopherol and tocotrienols. (C) 2000 Elsevier Science Ltd. All rights reserved.