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Vitamin E


Vitamin E refers to a group of eight fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which .-tocopherol is the most common in the North American diet.

-Tocopherol can be found in corn oil, soybean oil, margarine and dressings. In the North American diet,

-Tocopherol, the most biologically active form of vitamin E, is the second most common form of vitamin E. This variant of vitamin E can be found most abundantly in wheat germ oil, sunflower, and safflower oils. It is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation.

Vitamin E has many biological functions; the antioxidant function being the most important and/or best known. Other functions include enzymatic activities, gene expression and neurological function(s).

It's also been suggested that the most important function of vitamin E is in cell signaling (and, that it may not have a significant role in antioxidant metabolism).

As an antioxidant, vitamin E acts as a peroxyl radical scavenger, preventing the propagation of free radicals in tissues, by reacting with them to form a tocopheryl radical which will then be oxidized by a hydrogen donor (such as Vitamin C) and thus return to its reduced state. As it is fat-soluble, it is incorporated into cell membranes, which protects them from oxidative damage.

. As an enzymatic activity regulator, for instance, protein kinase C (PKC), which plays a role in smooth muscle growth, can be inhibited by .-tocopherol. .-Tocopherol has a stimulatory effect on the dephosphorylation enzyme, protein phosphatase 2A, which in turn, cleaves phosphate groups from PKC leading to its deactivation, bringing the smooth muscle growth to a halt.

Vitamin E also has an effect on gene expression. Macrophages rich in cholesterol are found in the atherogenetic tissue. Scavenger receptor CD36 is a class B scavenger receptor found to be up-regulated by oxidized low density lipoprotein (LDL) and binds it. Treatment with alpha tocopherol was found to downregulate the expression of the CD36 scavenger receptor gene and the scavenger receptor class A (SR-A) and modulates expression of the connective tissue growth factor (CTGF). CTGF gene, when expressed, is responsible for the repair of wounds and regeneration of the extracellular tissue that is lost or damaged during atherosclerosis.

. Vitamin E also plays a role in neurological functions, and inhibition of platelet aggregation.

Vitamin E also protects lipids and prevents the oxidation of polyunsaturated fatty acids (PUFAs.)

Vitamin E deficiency can cause:
  • spinocerebellar ataxia
  • myopathies
  • peripheral neuropathy
  • ataxia
  • skeletal myopathy
  • retinopathy
  • impairment of the immune response
  • erythrocyte hemolysis

References


Ref: ^ Brigelius-Flohe, B; Traber (1999). "Vitamin E: function and metabolism". FASEB 13: 1145.1155.

. ^ Traber, MG (1998). "The biological activity of vitamin E". The Linus Pauling Institute. Retrieved 6 March 2011.

. ^ Bieri, JG; Evarts (1974). ".-Tocopherol: metabolism, biological activity and significance in human vitamin E nutrition". American Journal of Clinical Nutrition 27 (9): 980.986. PMID 4472121.

. ^ a b c Brigelius-Flohé R, Traber MG (1 July 1999). "Vitamin E: function and metabolism". FASEB J. 13 (10): 1145.55. PMID 10385606.

. ^ Reboul E, Richelle M, Perrot E, Desmoulins-Malezet C, Pirisi V, Borel P (15 November 2006). "Bioaccessibility of carotenoids and vitamin E from their main dietary sources". Journal of Agricultural and Food Chemistry 54 (23): 8749.8755. doi:10.1021/jf061818s. PMID 17090117.

. ^ a b c d e f g h i National Institute of Health (4 May 2009). "Vitamin E fact sheet".

. ^ a b Herrera; Barbas, C (2001). "Vitamin E: action, metabolism and perspectives". Journal of Physiology and Biochemistry 57 (2): 43.56. doi:10.1007/BF03179812. PMID 11579997.

. ^ Packer L, Weber SU, Rimbach G (2001). "Molecular aspects of .-tocotrienol antioxidant action and cell signalling". Journal of Nutrition 131 (2): 369S.73S. PMID 11160563.

. ^ a b c d Bell, EF (1987). "History of vitamin E in infant nutrition". American Journal of Clinical Nutrition 46 (1 Suppl): 183.186. PMID 3300257.

. ^ Azzi (2007). "Molecular mechanism of alpha-tocopherol action". Free radical biology & medicine 43 (1): 16.21. doi:10.1016/j.freeradbiomed.2007.03.013. PMID 17561089.

. ^ Zingg; Azzi, A (2004). "Non-antioxidant activities of vitamin E". Current medicinal chemistry 11 (9): 1113.33. PMID 15134510.

Fri May 19 12:17:44 CDT 2006




 

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