Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Scott W. Leonard^*, Eric Gumpricht, Michael W. Devereaux, Ronald J. Sokol and Maret G. Traber¹^,*

^* Linus Pauling Institute, Oregon State University, Corvallis, OR
Section of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, University of Colorado Health Sciences Center and The Children's Hospital, Denver, CO

^¹ To whom correspondence should be addressed. e-mail: maret.traber{at}oregonstate.edu

To evaluate vitamin E metabolism, a method was developed toquantitate liver ${alpha}$ - and ${gamma}$ -tocopherol metabolites, ${alpha}$ -carboxyethylhydroxychroman [ ${alpha}$ -CEHC; 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman]and ${gamma}$ -CEHC [2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman],respectively. Vitamin E supraenriched livers were obtained fromrats that were injected with vitamin E daily for 18 days. Liversamples ( $~$ 50 mg) were homogenized, homogenate CEHC-conjugateswere hydrolyzed, CEHCs were extracted with ethyl ether, andthen CEHCs were quantitated using liquid chromatography-massspectrometry (LC-MS). Precision, based on intersample variability,ranged from 1% to 3%. Recovery of ${alpha}$ - and ${gamma}$ -CEHCs added to liverhomogenates ranged from 77% to 87%. Detection limits of ${alpha}$ - and ${gamma}$ -CEHC were 20 fmol, with a linear detector response from 0.025to 20 pmol injected. Corresponding with an increase in liver ${alpha}$ -tocopherol, the MS peak for liver ${alpha}$ -CEHC (mass-to-charge ratio277.8) increased 80-fold (0.18 ± 0.01 to 15 ±2 nmol/g). Liver ${alpha}$ -CEHC concentrations were correlated with serum ${alpha}$ -CEHC, liver ${alpha}$ -tocopherol, and serum ${alpha}$ -tocopherol (P < 0.001for each comparison). ${alpha}$ -CEHC represented 0.5–1% of theliver ${alpha}$ -tocopherol concentration.

Thus, LC-MS can be successfully used to quantitate ${alpha}$ - and ${gamma}$ -CEHCin liver samples. These data suggest that in times of excessliver ${alpha}$ -tocopherol, increased metabolism of ${alpha}$ -tocopherol to ${alpha}$ -CEHCoccurs.

Abbreviations: CEHC, carboxyethyl hydroxychroman; LC-MS, liquid chromatography-mass spectrometry; MDR1, multidrug resistance protein-1; m/z, mass-to-charge ratio; SXR, steroid and xenobiotic receptor; UGT1A1, UDP-glucuronosyltransferase-1A1

Supplementary key words ${alpha}$ -carboxyethyl hydroxychroman • ${gamma}$ -carboxyethyl hydroxychroman • mass spectrometry • vitamin E metabolism • ${alpha}$ -tocopherol • ${gamma}$ -tocopherol • liquid chromatography-mass spectrometry

Add to CiteULike CiteULike Add to Complore Complore Add to Connotea Connotea Add to Del.icio.us Del.icio.us Add to Digg Digg Add to Reddit Reddit Add to Technorati Technorati What's this?

This article has been cited by other articles:

H. Freiser and Q. Jiang
{gamma}-Tocotrienol and {gamma}-Tocopherol Are Primarily Metabolized to Conjugated 2-({beta}-carboxyethyl)-6-Hydroxy-2,7,8-Trimethylchroman and Sulfated Long-Chain Carboxychromanols in Rats
J. Nutr., May 1, 2009; 139(5): 884 - 889.
[Abstract] [Full Text] [PDF]

S. W. Leonard, J. D. Joss, D. J. Mustacich, D. H. Blatt, Y. S. Lee, and M. G. Traber
Effects of vitamin E on cholesterol levels of hypercholesterolemic patients receiving statins
Am. J. Health Syst. Pharm., November 1, 2007; 64(21): 2257 - 2266.
[Abstract] [Full Text] [PDF]

Q. Jiang, H. Freiser, K. V. Wood, and X. Yin
Identification and quantitation of novel vitamin E metabolites, sulfated long-chain carboxychromanols, in human A549 cells and in rats
J. Lipid Res., May 1, 2007; 48(5): 1221 - 1230.
[Abstract] [Full Text] [PDF]

Methods

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration