Nutrient Interactions and Toxicity
Dietary ( )-Catechin and BHT Markedly Increase -Tocopherol
Concentrations in Rats by a Tocopherol--Hydroxylase–Independent
Mechanism
1,2
Jan Frank,
3
Torbjo ¨ rn Lundh,* Robert S. Parker,
†
Joy E. Swanson,
†
Bengt Vessby**
and Afaf Kamal-Eldin
Department of Food Science, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden;
*Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences,
S-750 07 Uppsala, Sweden;
†
Division of Nutritional Sciences, Cornell University, Ithaca, NY;
and **Department of Public Health and Caring Sciences/Geriatrics, University of Uppsala,
S-751 25 Uppsala, Sweden
ABSTRACT The effects of dietary (+)-catechin (CAT) and BHT on plasma and tissue concentrations of -to-
copherol (-T), -tocopherol (-T) and cholesterol (C) were studied in male Sprague-Dawley rats. The rats were fed
the compounds during a 4-wk period at concentrations of 2 g/kg in standardized diets, low but adequate in vitamin
E, with 2 g/kg cholesterol. The CAT-regimen did not affect weight gain, feed intake or organ weights. BHT did not
affect feed intake but lowered the body weight and the amount of liver lipids and increased the weights of livers
and lungs relative to the body weight. Rats consuming CAT had 2.5–3.5-fold increased plasma, liver and lung -T
concentrations, but C concentrations remained unchanged. BHT-feeding resulted in 2.4- and 1.7-fold elevation in
-T but 50% decrease in -T concentrations in blood plasma and liver, respectively. BHT also lowered total C
in the liver without affecting the concentration of C in the liver lipids. To investigate whether the -T–sparing action
of the studied compounds was due to the inhibition of tocopherol--hydroxylase, HepG2 cells were incubated with
CAT or BHT in the presence of -tocopherol (-T) and the 3'- and 5'--carboxychromanol metabolites in the media
were analyzed by GC/MS. Neither CAT nor BHT inhibited tocopherol--hydroxylase activity in hepatocyte cultures;
CAT was also inactive in a rat microsomal assay. In conclusion, both dietary CAT and BHT markedly increased -T
concentrations in plasma and organs of Sprague-Dawley rats by a mechanism that apparently does not involve
inhibition of tocopherol--hydroxylase, a key enzyme in tocopherol catabolism. J. Nutr. 133: 3195–3199, 2003.
KEY WORDS: ● BHT ● catechin ● cytochrome P
450
● tocopherols ● tocopherol--hydroxylase.
Vitamin E was recognized as a factor essential for reproduc-
tion in rats by Evans and Bishop in 1922 and subsequently
acknowledged as a vitamin in 1925 (1). Vitamin E is a generic
name for all natural and synthetic substances exerting the
biological activity of -tocopherol (-T).
4
The eight natural
vitamin E compounds are derivatives of 6-chromanol and
classified into tocopherols, substituted with a saturated phytyl
side chain, and tocotrienols, substituted with an unsaturated
isoprenoid side chain. The prefixes -, -, - and - are added
according to the number and position of methyl groups sub-
stituted at the chromanol ring (2).
-T is the major lipid-soluble antioxidant (3) and the
predominant E-vitamer in human and animal tissues despite
the fact that -tocopherol (-T) is the major dietary form of
vitamin E (4,5). Among other things, the body specifically
retains -T due to the action of a hepatic -tocopherol trans-
fer protein, which has a higher affinity for -T than for the
other vitamers. Also, tocopherol--hydroxylase, the enzyme
catalyzing the initial step in the catabolism of tocopherols to
their water-soluble metabolites, has a much higher catalytic
activity toward -T than -T (6). Because the body makes use
of specific mechanisms to retain -T, it has been regarded as
the biologically most important form of the vitamin. Natural
-T also has the highest biological activity of all forms of
vitamin E, which traditionally has been assessed in animal
model systems, such as the rat fetal resorption-gestation test,
the curative myopathy test or the dialuric acid-induced test for
RBC hemolysis (5). One major concern with the values ob-
tained with these tests is that the animals are given experi-
mental feeds that do not reflect a natural diet but contain the
studied vitamer as the only antioxidant (7–9). The concen-
tration of a certain E-vitamer in the body (10 –12), its avail-
ability for physiological tasks, and, as a result, the values for its
1
Presented in part at the Oxygen Club Of California 2002 World Congress,
March 2002, Santa Barbara, CA [Frank, J., Kamal-Eldin, A., Lundh, T. & Vessby,
B. (2002) Sesamin, (+)-catechin, and butylated hydroxytoluene elevate vita-
min E levels in male Sprague-Dawley rats].
2
Supported by the Swedish Council for Forestry and Agricultural Research
(SJFR, Grant 50.0496/98).
3
To whom correspondence should be addressed.
E-mail: Jan.Frank@lmv.slu.se.
4
Abbreviations used: C, cholesterol; CAT, (+)-catechin; FBS, fetal bovine
serum; T, tocopherol; TAG, triacylglycerols.
0022-3166/03 $3.00 © 2003 American Society for Nutritional Sciences.
Manuscript received 4 June 2003. Initial review completed 3 July 2003. Revision accepted 24 July 2003.
3195
Downloaded from https://academic.oup.com/jn/article-abstract/133/10/3195/4687563 by guest on 30 May 2020