Article

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

Department of Medicine, New York University School of Medicine, New York 10016.
Journal of Clinical Investigation (Impact Factor: 13.22). 03/1990; 85(2):397-407. DOI: 10.1172/JCI114452
Source: PubMed

ABSTRACT

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.

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    • "The natural form of vitamin E is RRR-alpha-tocopherol in which chiral carbons are in the R conformation at positions 2, 4, and 8 [9]. The alphatocopherol transfer protein modulates the release of vitamin E through the liver into the plasma [10] [11]. Vitamin E is metabolized by cytochrome P450, followed by conjugation, and excretion in urine [12] or bile [13]. "
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