Human plasma vitamin E kinetics demonstrate rapid recycling of plasma RRR-alpha-tocopherol

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 91; no. 21; pp. 10005 - 10008
• Main Authors: Traber, M.G. (University of California, Berkeley, CA.), Ramakrishnan, R, Kayden, H.J
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 11.10.1994; National Acad Sciences
• Subjects: administration & dosage; Administration, Oral; alpha-tocopherol; blood; Blood plasma; CARENCE EN VITAMINE; Carrier proteins; CATABOLISME; CATABOLISMO; CHYLOMICRON; chylomicrons; DEFICIENCIA DE VITAMINAS; Deuterium; enantiomers; ESTRUCTURA QUIMICA; GENERO HUMANO; GENRE HUMAIN; Humans; Intestinal Absorption; Kinetics; Lipids; LIPOPROTEINAS; LIPOPROTEINE; Lipoproteins; Liver; Liver - metabolism; mathematical models; metabolism; METABOLISME; METABOLISMO; MODELE MATHEMATIQUE; MODELOS MATEMATICOS; Models, Biological; pharmacokinetics; PLASMA SANGUIN; PLASMA SANGUINEO; QUILOMICRONES; Radioisotope Dilution Technique; Secretion; STRUCTURE CHIMIQUE; Time Factors; TOCOFEROLES; TOCOPHEROL; Tocopherols; very low density lipoprotein; vitamin deficiencies; Vitamin E; Vitamin E - administration & dosage; Vitamin E - blood; Vitamin E - pharmacokinetics; VITAMINA E; VITAMINE E
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.21.10005

A kinetic model of vitamin E transport in humans is described using data from our studies with deuterium-labeled stereoisomers of alpha-tocopherol (RRR-and SRR-). In normal subjects, both alpha-tocopherols are present at similar concentrations in chylomicrons, but by 24 hr, RRR-alpha-tocopherol is at higher plasma concentrations because RRR-alpha-tocopherol is preferentially incorporated into very low density lipoproteins, which are then secreted into plasma. In three nondiscriminator patients with familial isolated vitamin E deficiency, the fractional disappearance rates (mean +/-SD) of deuterium-labeled RRR- and SRR-alpha-tocopherols in plasma were 1.4 +/- 0.6 and 1.3 +/- 0.3 pools per day, respectively (difference, 0.1 +/- 0.3). In these patients, plasma concentrations of both RRR- and SRR-alpha-tocopherols decreased similarly to SRR-alpha-tocopherol in controls. In six controls, fractional disappearance rates of deuterium-labeled RRR-alpha-tocopherol (0.4 +/- 0.1 pool per day) were significantly (P 0.01) slower than for SRR- (1.2 +/-0.6). The differences (0.8 +/- 0.6 pool per day) between these two rates in controls estimate the rate at which RRR-alpha-tocopherol, which had left the plasma, was returned to the plasma. Although plasma labeled RRR-alpha-tocopherol concentrations in controls appear to change slowly, these data show that both RRR- and SRR-alpha-tocopherols leave the plasma rapidly, but only RRR-alpha-tocopherol is returned to the plasma, likely in nascent very low density lipoproteins. This recycling of RRR-alpha-tocopherol accounts for nearly 1 pool of alpha-tocopherol per day