Article de synthese sur la vitamine E. Etude de son activite antioxydante sous la forme de α-tocopherol et de son role dans la peroxidation des lipides, sur les radicaux libres. Cinetique et mecanismes d'action dans les organes et les tissus; forme active. Pour mesurer l'absorption et le transport de la vitamine E, utilisation d'un isotope stable marque et analyse par chromatographie gazeuse et spectrometrie de masse. Mesure de sa biodisponibilite. Transport de la vitamine E et lipoproteine chez l'homme

Vitamin E: Antioxidant Activity, Biokinetics, and Bioavailability

Vitamin E: A critical review.

Absorption, transport, and tissue delivery of vitamin E

Vitamin E is the term used for eight naturally occurring fat-soluble nutrients called tocopherols. alpha-Tocopherol is essential, has the highest biological activity and predominates in many species. In humans vitamin E is the most important lipid soluble antioxidant and deficiency may cause neurological dysfunction, myopathies and diminished erythrocyte life span. alpha-Tocopherol is absorbed via the lymphatic pathway and transported in association with chylomicrons. In plasma, alpha-tocopherol is found in all lipoprotein fractions but mostly is associated with apo B-containing lipoproteins. alpha-Tocopherol is associated with very-low-density lipoprotein when it is secreted from the liver. In the rat, about 90% of total body mass of alpha-tocopherol is recovered in the liver, skeletal muscle and adipose tissue. Most alpha-tocopherol is located in the mitochondrial fractions and in the endoplasmic reticulum, whereas little is found in cytosol and peroxisomes. New clinical evidence from heavy drinkers and from experimental work in rats suggests that alcohol may increase oxidation of alpha-tocopherol. Increased demand for vitamin E has also been observed in premature infants and patients with malabsorption, but there is little evidence that the healthy population requires supplementation of vitamin E to a well-balanced diet.

Absorption, transport and distribution of vitamin E.

Plasma and lipoprotein alpha-tocopherol concentrations of four patients with familial isolated vitamin E deficiency and six control subjects were observed for 4 d after an oral dose (approximately 15 mg) of RRR-alpha-tocopheryl acetate labeled with six deuterium atoms (d6-tocopherol). Chylomicron d6-tocopherol concentrations were similar in the two groups. d6-Tocopherol concentrations of plasma, very low (VLDL), low (LDL), and high (HDL) density lipoproteins were similar in the two groups only during the first 12 h; then these were significantly lower, and the rate of disappearance faster, in the patients. The times (tmax) of the maximum chylomicron d6-tocopherol concentrations were similar for the two groups, but tmax values in the controls increased in the order: chylomicrons less than VLDL less than or equal to LDL approximately HDL, while the corresponding values in the patients were similar to the chylomicron tmax. Thus, plasma d6-tocopherol in controls increased during chylomicron and VLDL catabolism, whereas in patients it increased only during chylomicron catabolism, thereby resulting in a premature and faster decline in the plasma tocopherol concentration due to a lack of d6-tocopherol secretion from the liver. We suggest that these patients are lacking or have a defective liver "tocopherol binding protein" that incorporates alpha-tocopherol into nascent VLDL.

/pdf/impaired-ability-of-patients-with-familial-isolated-vitamin-4ccf8ytwq9.pdf

Impaired ability of patients with familial isolated vitamin E deficiency to incorporate alpha-tocopherol into lipoproteins secreted by the liver.

Transport and distribution of α-tocopherol in lymph, serum and liver cells in rats

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Transport and distribution of α-tocopherol in lymph, serum and liver cells in rats