| Vitamin E: action, metabolism and perspectives. | |
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MedLine Citation:
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PMID: 11519885 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Natural vitamin E includes four tocopherols and four tocotrienols. RRR-alpha-tocopherol is the most abundant form in nature and has the highest biological activity. Although vitamin E is the main lipid-soluble antioxidant in the body, not all its properties can be assigned to this action. As antioxidant, vitamin E acts in cell membranes where prevents the propagation of free radical reactions, although it has been also shown to have pro-oxidant activity. Non-radical oxidation products are formed by the reaction between alpha-tocopheryl radical and other free radicals, which are conjugated to glucuronic acid and excreted through the bile or urine. Vitamin E is transported in plasma lipoproteins. After its intestinal absorption vitamin E is packaged into chylomicrons, which along the lymphatic pathway are secreted into the systemic circulation. By the action of lipoprotein lipase (LPL), part of the tocopherols transported in chylomicrons are taken up by extrahepatic tissues, and the remnant chylomicrons transport the remaining tocopherols to the liver. Here, by the action of the "alpha-tocopherol transfer protein", a major proportion of alpha-tocopherol is incorporated into nascent very low density lipoproteins (VLDL), whereas the excess of alpha-tocopherol plus the other forms of vitamin E are excreted in bile. Once secreted into the circulation, VLDL are converted into IDL and LDL by the action of LPL, and the excess of surface components, including alpha-tocopherol, are transferred to HDL. Besides the LPL action, the delivery of alpha-tocopherol to tissues takes place by the uptake of lipoproteins by different tissues throughout their corresponding receptors. Although we have already a substantial information on the action, effects and metabolism of vitamin E, there are still several questions open. The most intriguing is its interaction with other antioxidants that may explain how foods containing small amounts of vitamin E provide greater benefits than larger doses of vitamin E alone. |
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Authors:
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E Herrera; C Barbas |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Review |
Journal Detail:
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Title: Journal of physiology and biochemistry Volume: 57 ISSN: 1138-7548 ISO Abbreviation: J. Physiol. Biochem. Publication Date: 2001 Mar |
Date Detail:
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Created Date: 2001-08-24 Completed Date: 2002-02-08 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9812509 Medline TA: J Physiol Biochem Country: Spain |
Other Details:
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Languages: eng Pagination: 43-56 Citation Subset: IM |
Affiliation:
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Facultad de Ciencias Experimentales y Técnicas, Universidad San Pablo-CEU, Madrid, Spain. eherrera@ceu.es |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Antioxidants / metabolism, pharmacology Arteriosclerosis / etiology, metabolism, prevention & control Carrier Proteins / metabolism Chylomicrons / metabolism Humans Intestinal Absorption Liver / metabolism Molecular Structure Oxidants / metabolism, pharmacology Oxidation-Reduction Vitamin E / chemistry, metabolism*, pharmacology* |
| Chemical | |
Reg. No./Substance:
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0/Antioxidants; 0/Carrier Proteins; 0/Chylomicrons; 0/Oxidants; 0/alpha-tocopherol transfer protein; 1406-18-4/Vitamin E |
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