The effects of aurofusarin in the quail diet on the antioxidant systems of the developing embryo are investigated. Thirty eight 45-day-old Japanese quails (Coturnix japonica) were divided into two groups and were fed on a corn-soya diet or the same diet supplemented with aurofusarin at the level of 26.4 mg/kg feed in the form of Fusarium graminearum culture enriched with aurofusarin. Eggs obtained after 7 weeks of feeding were incubated. Samples of quail tissues were collected at day 17 of embryonic development and from day old hatchlings. Antioxidants and malondialdehyde were analysed by HPLC-based methods. Inclusion of aurofusarin in the maternal diet was associated with decreased concentrations of alpha- and gamma-tocopherols, alpha- and gamma-tocotrienols, retinol, lutein and zeaxanthin in egg yolk. The vitamin E (tocopherols and tocotrienols) concentration in the liver and yolk sac membrane (YSM) of the day 17 embryos and the hatchlings from aurofusarin-fed group was significantly decreased. Alpha-tocopherol concentration was also reduced in kidney, lung, heart, muscle and brain of day-old quails. In the liver of day-old quails, concentrations of lutein, zeaxanthin, retinol, retinyl linoleate, retinyl oleate, retinyl palmitate and retinyl stearate were also reduced. As a result of these diminished antioxidant concentrations, tissue susceptibility to lipid peroxidation was significantly increased. It is suggested that a compromised antioxidant system of the egg yolk and embryonic tissues could predispose quails to increased mortality at late stages of their embryonic development.
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Alpha- and gamma-tocopherol (α- and γ-T, respectively) metabolite analysis is of key relevance in the study of vitamin E metabolism. Whilst there is information on urinary excretion of the two major metabolites of these vitamin E homologues, namely the 2,5,7,8-tetramethyl-2-(β-carboxyethyl)-6-hydroxychroman (α-CEHC) and 2,7,8-trimethyl-2-(β-carboxyethyl)-6-hydroxychroman (γ-CEHC), their concentration and response to supplements in plasma remains poorly investigated. In this study we describe a gas chromatography-mass spectrometry (GC/MS)-based assay to measure both α and γ-T and their corresponding CEHC metabolites in human plasma. As an example of the application of this method we report data obtained following the supplemention of two healthy volunteers with 100 mg of deuterium-labeled _-T acetate (d2-γ-TAC). Under routine analytical conditions a good linearity in the range 0.0025–1µM was observed for both the α- and γ-CEHC deuterated standards. In plasma samples, the detection limit for α- and γ-CEHC was 2.5 and 5 nmol/l, respectively. The minimum amount of plasma required for the assay was 500 µl. The plasma concentrations of α-CEHC and γ-CEHC in unsupplemented healthy subjects were 12.6 ±7.5 and 160.7 ± 44.9 nmol/l, respectively. In the two volunteers supplemented with 100 mg of d2-γ-TAC, plasma d2-γ-T concentrations increased 250 to 450-fold 6 h postsupplementation. Plasma and urinary d2-γ-CEHC concentrations increased 20 to 40-fold 9–12 h postsupplementation. Interestingly, the acute increase in d2 γ-T did not significantly affect the baseline plasma concentrations of d0-γ-T and only slight lowered α-T concentrations. Likewise, plasma α-CEHC levels were not influenced and urinary excretion of α-CEHC were unaltered. This GC/MS method provides a versatile and accurate mean for assessing carboxyethyl-hydroxychroman metabolites of vitamin E in plasma.
Alpha-tocotrienol (alpha-T3) has been suggested to protect cellular membranes against free radical damage. This study was done to estimate the effect of alpha-T3 on free radical-induced impairment of erythrocyte deformability by comparing it to alpha-tocopherol (alpha-T). An erythrocyte suspension containing 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was forced to flow through microchannels with an equivalent diameter of 7 microm for measuring erythrocyte deformability. A higher concentration of AAPH caused a marked decrease in erythrocyte deformability with concomitant increase of membranous lipid peroxidation. Treatment of erythrocytes with alpha-T or alpha-T3 suppressed the impairment of erythrocyte deformability as well as membranous lipid peroxidation and they also increased erythrocyte deformability even in the absence of AAPH. In these cases, the protecting effect of alpha-T3 was significantly higher than that of alpha-T. We emphasize that higher incorporating activity of alpha-T3 into erythrocyte membranes seems to be the most important reason for higher protection against erythrocyte oxidation and impairment its deformability.
Does lack of tocopherols and tocotrienols put women at increased risk of breast cancer?
Schwenke DC.
J Nutr Biochem. 2002 Jan;13(1):2-20.
Breast cancer is the leading site of new cancers in women and the second leading cause (after lung cancer) of cancer mortality in women. Observational studies that have collected data for dietary exposure to alpha-tocopherol with or without the other related tocopherols and tocotrienolshave suggested that vitamin E from dietary sources may provide women with modest protection from breast cancer. However, there is no evidence that vitamin E supplements confer any protection whatever against breast cancer. Observational studies that have assessed exposure to vitamin E by plasma or adipose tissue concentrations of alpha-tocopherol have failed to provide consistent support for the idea that alpha-tocopherol provides any protection against breast cancer. In addition, evidence from studies in experimental animals suggest that alpha-tocopherol supplementation alone has little effect on mammary tumors. In contrast, studies in breast cancer cells indicate that alpha- gamma-, and delta-tocotrienol, and to a lesser extent delta-tocopherol, have potent antiproliferative and proapoptotic effects that would be expected to reduce risk of breast cancer. Many vegetable sources of alpha-tocopherol also contain other tocopherols or tocotrienols. Thus, it seems plausible that the modest protection from breast cancer associated with dietary vitamin E may be due to the effects of the other tocopherols and the tocotrienols in the diet. Additional studies will be required to determine whether this may be the case, and to identify the most active tocopherol/tocotrienol.
Alpha-tocopherol and its esterified derivatives have been shown to be effective in reducing monocytic-endothelial cell adhesion. However, the effect of alpha-tocotrienol (alpha-T3) has not been characterized. In the present study, using human umbilical vein endothelial cells (HUVEC) as the model system, we examined the relative inhibitory effects of alpha-T3 and other vitamin E derivatives on cell surface adhesion molecule expression under TNF-alpha stimulation. Using enzyme-linked immunosorbent assay, we demonstrated that alpha-T3 markedly inhibited the surface expression of vascular cell adhesion molecule-1 in TNF-alpha activated HUVEC in a dose- and time-dependent manner. The optimal inhibition was observed at 25 micromol/l alpha-T3 within 24 h (77+/-5%) without cytotoxicity. In addition, the surface expression of intercellular adhesion molecule-1 and E-selectin were also reduced by 40+/-7 and 42+/-5%, respectively. In order to further evaluate the effects of alpha-T3 on the vascular endothelium, we investigated the ability of monocytes to adhere to endothelial cells. Interestingly, a 63+/-3% decrease in monocytic cell adherence was observed. Compared to alpha-tocopherol and alpha-tocopheryl succinate, alpha-T3 displayed a more profound inhibitory effect on adhesion molecule expression and monocytic cell adherence. This inhibitory action by alpha-T3 on TNF-alpha-induced monocyte adhesion was shown to be NF-kappaB dependent and was interestingly reversed with co-incubation with farnesol and geranylgeraniol, suggesting a role for prenylated proteins in the regulation of adhesion molecule expression. In summary, the above results suggest that alpha-T3 is a potent and effective agent in the reduction of cellular adhesion molecule expression and monocytic cell adherence.
Vitamin E inhibition of normal mammary epithelial cell growth is associated with a reduction in protein kinase C (alpha) activation
Sylvester PW, McIntyre BS, Gapor A, Briski KP.
Cell Prolif. 2001 Dec;34(6):347-57.
Tocopherols and tocotrienols represent the two subclasses within the vitamin E family of compounds. However, tocotrienols are significantly more potent than tocopherols in suppressing epidermal growth factor (EGF)-dependent normal mammary epithelial cell growth. EGF is a potent mitogen for normal mammary epithelial cells and an initial event in EGF-receptor mitogenic-signalling is protein kinase C (PKC) activation. Studies were conducted to determine if the antiproliferative effects of specific tocopherol and tocotrienol isoforms are associated with a reduction in EGF-receptor mitogenic signalling and/or PKC activation. Normal mammary epithelial cells isolated from midpregnant BALB/c mice were grown in primary culture, and maintained on serum-free media containing 10 ng/mL EGF as a mitogen, and treated with various doses (0-250 microm) of alpha-, gamma-, or delta-tocopherol or alpha-, gamma-, or delta-tocotrienol. Treatment with growth inhibitory doses of delta-tocopherol (100 microm), alpha-tocotrienol (50 microm), or gamma- or delta-tocotrienol (10 microm) did not affect EGF-receptor levels, EGF-induced EGF-receptor tyrosine kinase activity, or total intracellular levels of PKC(alpha). However, these treatments were found to inhibit EGF-induced PKC(alpha) activation as determined by its translocation from the cytosolic to membrane fraction. Treatment with 250 microm alpha- or gamma-tocopherol had no affect on EGF-receptor mitogenic signalling or cell growth. These findings demonstrate that the inhibitory effects of specific tocopherol and tocotrienol isoforms on EGF-dependent normal mammary epithelial cell mitogenesis occurs downstream from the EGF-receptor and appears to be mediated, at least in part, by a reduction in PKC(alpha) activation.
Tocopherols and tocotrienols (Vitamin E) are part of a group of “minor components” of main interest, present in the unsaponifiable fraction of many samples. Their importance in biological, metabolical and nutritional studies makes determination of tocopherols and related compounds of major interest. Present work critically reviews the different ways to perform sample pre-treatment and analysis of these compounds, related to the matrices, other analytes to be measured, sensitivity, and simplicity. The review includes well referenced tables that provide in-depth summaries of methodology for the chromatographic analysis of alpha-tocopherol and related compounds in foods, pharmaceuticals, plants, animal tissues and other matrices.
The metabolism of tocotrienol remains unclear. We studied the distribution of tocotrienol in rats fed the tocotrienol-rich fraction extracted from palm oil. We have previously shown that dietary sesame seeds markedly elevate the tocopherol concentration in rats. In this study, we also examined the effect of dietary sesame seeds on the tocotrienol concentration. In experiment 1, rats (4-wk-old) were fed the diet with alpha-tocopherol alone or with alpha- and gamma-tocotrienols. In experiment 2, the effect of dietary sesame seeds on tocopherol and tocotrienol concentrations in rats fed the diet with tocopherol and tocotrienol was studied. The rats were fed the experimental diet for 8 wk in both experiments. alpha- and gamma-Tocotrienols accumulated in the adipose tissue and skin, but not in plasma or other tissues, of the rats fed tocotrienols. Dietary sesame seeds elevated (P < 0.05) tocotrienol concentrations in the adipose tissue and skin, but did not affect their concentrations in other tissues or in plasma. The gamma-tocopherol concentration in all tissues and plasma of rats fed gamma-tocopherol was extremely low but was elevated (P < 0.05) in many tissues by feeding sesame seeds. These data suggest that the transport and tissue uptake of vitamin E isoforms are different. Dietary sesame seeds elevate the concentrations of both tocopherols and tocotrienols.
Vitamin E consists of a number of compounds, tocopherols and tocotrienols, that function as lipid-soluble antioxidants. A hypothesis is that vitamin E may slow the progression of atherosclerosis by blocking the oxidative modification of low-density lipoprotein cholesterol and thus decrease its uptake into the arterial lumen. Basic science and animal studies have generally supported this hypothesis. Observational studies have primarily assessed patients with no established coronary heart disease (CHD), and results have generally supported a protective role of vitamin E in CHD. Early primary and secondary prevention clinical trials (Alpha-Tocopherol, Beta-Carotene Cancer Protection study and Cambridge Heart Antioxidant Study) showed mixed results. Despite years of encouraging evidence from basic science and observational studies, 3 large randomized clinical trials (Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto miocardico, Heart Outcomes Prevention Evaluation, and Primary Prevention Project) with a combined total of more than 25,000 patients failed to show a significant benefit with vitamin E taken as a dietary supplement for the prevention of CHD. Four large randomized primary prevention trials currently under way should add to our knowledge. The American Heart Association has recommended consumption of a balanced diet with emphasis on antioxidant-rich fruits and vegetables but has made no recommendations regarding vitamin E supplementation for the general population. Although vitamin E supplementation seems to be safe for most people, recommendations from health care professionals should reflect the uncertainty of established benefit as demonstrated in clinical trials.
We are studying novel tocotrienols, which have a number of activities that might interfere with the formation of atherosclerotic plaques, including hypocholesterolemic, antioxidant, anti-inflammatory and antiproliferation effects. This study compared the effects of alpha-tocopherol, the tocotrienol-rich fraction (TRF(25)) and didesmethyl tocotrienol (d-P(25)-T3) of rice bran on the pathogenesis of atherosclerotic lesions in C57BL/6 apolipoprotein (apo)E-deficient (-/-) mice. These mice are an excellent model because they become hyperlipidemic even when they consume a low fat diet and they develop complex atherosclerotic lesions similar to those of humans. These compounds were also tested in wild-type C57BL/6 apoE (+/+) and (+/-) mice fed low or high fat diets. When a high fat diet was supplemented with alpha-tocopherol, TRF(25) or d-P(25)-T3 and fed to mice (+/+) for 24 wk, atherosclerotic lesion size was reduced 23% (P = 0.33), 36% (P = 0.14) and 57% (P < 0.02), respectively, and in mice (+/-) fed for 18 wk, lesions were reduced by 19% (P = 0.15), 28% (P < 0.01) and 33% (P < 0.005), respectively, compared with mice fed a control diet. A low fat diet did not cause atherosclerotic lesions in these mice. The low fat diet supplemented with TRF(25) or d-P(25)-T3 fed to apoE-deficient (-/-) mice for 14 wk decreased atherosclerotic lesion size by 42% (P < 0.04) and 47% (P < 0.01), respectively, whereas alpha-tocopherol supplementation resulted in only an 11% (P = 0.62) reduction. These results demonstrate the superior efficacy of tocotrienols compared with alpha-tocopherol. Althoughtocotrienols decreased serum triglycerides, total and LDL cholesterol levels, the decreases in atherosclerotic lesions seem to be due to the other activities. Serum tocol concentrations in various groups are also described. This is the first report of a significant reduction in the atherosclerotic lesion size in all three genotypes of apoE mice fed a novel tocotrienol (d-P(25)-T3) of rice bran. Dietary tocotrienol supplements may provide a unique approach to promoting cardiovascular health.