Gamma-tocopherol Concentrations Research Articles

Ex vivo low-density lipoprotein oxidizability and in vivo lipid peroxidation in patients on CAPD

Chronic renal failure is associated with accelerated atherosclerosis and a high incidence of cardiovascular disease. Oxidative modification of low-density lipoprotein (LDL) is considered a key event in atherogenesis. We studied the ex vivo oxidizability of LDL exposed to Cu2+ ions (lag time, rate of propagation, maximum conjugated diene formation) and its relationship with LDL density, fatty acids, and antioxidants, along with plasma malondialdehyde (MDA) and autoantibodies against Cu2+-, MDA-, and hypochlorous acid-modified LDL and plasma antioxidants in 17 continuous ambulatory peritoneal dialysis (CAPD) patients and 21 healthy control subjects. LDL alpha- and gamma-tocopherol and total polyunsaturated fatty acid (PUFA) concentrations were significantly higher in the CAPD patients. LDL density was shifted to small, dense LDL. LDL oxidizability was comparable to that of healthy subjects. Lag time correlated positively with LDL alpha-tocopherol and inversely with both total PUFA concentrations and density; the rate of oxidation and LDL density correlated positively with total PUFA and total fatty acid concentrations, respectively. Ratios of autoantibody titers against oxidized to native LDL did not differ between the two groups. While plasma alpha- and gamma-tocopherol concentrations and tocopherol to cholesterol ratios were significantly higher, vitamin C concentrations were very low in the CAPD patients. MDA concentrations were 1.7 times higher than in healthy subjects. (1) Ex vivo LDL oxidizability is normal in CAPD patients as a result of efficient protection by LDL-associated lipophilic antioxidants, although the LDL composition is altered toward high oxidizability; and (2) the plasma antioxidant screen is insufficient due to impaired vitamin C status.

Association between alpha-tocopherol, gamma-tocopherol, selenium, and subsequent prostate cancer.

Selenium and alpha-tocopherol, the major form of vitamin E in supplements, appear to have a protective effect against prostate cancer. However, little attention has been paid to the possible role of gamma-tocopherol, a major component of vitamin E in the U.S. diet and the second most common tocopherol in human serum. A nested case-control study was conducted to examine the associations of alpha-tocopherol, gamma-tocopherol, and selenium with incident prostate cancer. In 1989, a total of 10,456 male residents of Washington County, MD, donated blood for a specimen bank. A total of 117 of 145 men who developed prostate cancer and 233 matched control subjects had toenail and plasma samples available for assays of selenium, alpha-tocopherol, and gamma-tocopherol. The association between the micronutrient concentrations and the development of prostate cancer was assessed by conditional logistic regression analysis. All statistical tests were two-sided. The risk of prostate cancer declined, but not linearly, with increasing concentrations of alpha-tocopherol (odds ratio (highest versus lowest fifth) = 0.65; 95% confidence interval = 0.32--1.32; P(trend) =.28). For gamma-tocopherol, men in the highest fifth of the distribution had a fivefold reduction in the risk of developing prostate cancer than men in the lowest fifth (P:(trend) =.002). The association between selenium and prostate cancer risk was in the protective direction with individuals in the top four fifths of the distribution having a reduced risk of prostate cancer compared with individuals in the bottom fifth (P(trend) =.27). Statistically significant protective associations for high levels of selenium and alpha-tocopherol were observed only when gamma-tocopherol concentrations were high. The use of combined alpha- and gamma- tocopherol supplements should be considered in upcoming prostate cancer prevention trials, given the observed interaction between alpha-tocopherol, gamma-tocopherol, and selenium.

Plasma antioxidant status after high-dose chemotherapy: a randomized trial of parenteral nutrition in bone marrow transplantation patients

Chemotherapy and radiation therapy result in increased free radical formation and depletion of tissue antioxidants. It is not known whether parenteral nutrition (PN) administered during bone marrow transplantation (BMT) supports systemic antioxidant status. The aims of the study were to determine 1) whether high-dose chemotherapy decreases concentrations of major circulating antioxidants in patients undergoing BMT and 2) whether administration of standard PN maintains systemic antioxidant concentrations compared with PN containing micronutrients and minimal lipids alone. Twenty-four BMT patients were randomly assigned to receive either standard PN containing conventional amounts of dextrose, amino acids, micronutrients, and lipid (120 kJ/d) or a solution containing only micronutrients (identical to those in standard PN) and a small amount of lipid (12 kJ/d). Plasma antioxidant status was measured before conditioning therapy and serially at days 1, 3, 7, 10, and 14 after BMT. Plasma glutathione (GSH) and alpha- and gamma-tocopherol concentrations decreased and the GSH redox state became more oxidized after conditioning chemotherapy. Plasma cysteine concentrations were unchanged, whereas cystine concentrations increased. Plasma vitamin C and zinc concentrations and GSH peroxidase activity increased over time. Plasma alpha-tocopherol concentrations were lower in patients given standard PN. There were no differences in other plasma antioxidants between groups. A significant decline in GSH-glutathione disulfide, cysteine-cystine, and vitamin E status occurs after chemotherapy and BMT. Standard PN does not improve antioxidant status compared with administration of micronutrients alone. Further evaluation of PN formulations to support patients undergoing high-dose chemotherapy and BMT are needed.

Effects of various tocopherol-containing diets on tocopherol secretion into bile.

Gamma-tocopherol is abundant in common vegetable oil, but its concentration in plasma and liver is much lower than that of alpha-tocopherol. Discrimination between different forms of tocopherol is thought to take place via the hepatic alpha-tocopherol transfer protein (alpha-TTP). Gamma-tocopherol, with a low binding capacity to alpha-TTP, is thought to be excreted via the bile. Our previous studies showed that gamma-tocopherol administered with sesame seed exhibits significantly higher concentrations in the plasma and liver of rats than gamma-tocopherol alone. Thus, we attempted to confirm whether a much higher amount of gamma-tocopherol rather than alpha-tocopherol would be secreted in the bile, and whether sesame seed would suppress the secretion of gamma-tocopherol. In one experiment, we examined the concentrations of alpha- or gamma-tocopherol in the plasma, liver, and bile of rats fed diets containing 300 mg/kg of alpha-tocopherol, 300 mg/kg of gamma-tocopherol, or 300 mg/kg each of alpha-tocopherol + gamma-tocopherol, and in the other experiment, we compared the gamma-tocopherol concentrations of rats fed a diet of gamma-tocopherol alone to those of rats fed a gamma-tocopherol + sesame seed diet (each diet contained 300 mg/kg gamma-tocopherol). The bile collection was done over 6 h. The gamma-tocopherol concentration in the bile was markedly lower than that of alpha-tocopherol, paralleling the concentrations in the plasma and liver. Intake of alpha-tocopherol and gamma-tocopherol together further lowered the concentration of gamma-tocopherol in the bile as well as in the plasma and liver, compared to the intake of gamma-tocopherol alone. The gamma-tocopherol concentration in the bile, as well as in the plasma and liver, was markedly higher in the sesame seed-fed group than in the gamma-tocopherol alone group. We found that the concentrations of alpha- or gamma-tocopherol in the bile showed a good correlation with the concentrations of alpha- or gamma-tocopherol in the liver, though the concentrations in the bile were substantially lower than those in the liver. These findings suggest that secretion into the bile is not a major metabolic route of alpha- or gamma-tocopherol.

Serum α- and γ-tocopherols, retinol, retinyl palmitate, and carotenoid concentrations in captive and free-ranging bottlenose dolphins ( Tursiops truncatus)

Concentrations of retinol, retinyl palmitate, β-carotene, α-carotene, cryptoxanthin, lutein, lycopene, α-tocopherol, and γ-tocopherol were measured in blood samples collected from 15 captive and 55 free-ranging bottlenose dolphins ( Tursiops truncatus). From June 1991 to June 1994, blood samples were collected from captive animals residing at two locations; at Seven Seas (Brookfield Zoo, Brookfield, IL) and Hawk’s Cay (Marathon Key, FL). Blood samples were collected from free-ranging animals from June 1991 to June 1996. Retinol levels were not significantly different between captive dolphin groups. However, Seven Seas animals had higher ( P<0.01) serum retinol concentrations compared to free-ranging animals (0.061 vs 0.041 μg/ml). Retinyl palmitate was not detected in the serum of captive or free-ranging dolphins. Alpha-tocopherol levels were significantly ( P<0.05) higher for Seven Seas dolphins (16.4 μg/ml) than for Hawk’s Cay (13.0 μg/ml) and free-ranging dolphins (12.5 μg/ml). Gamma-tocopherol concentrations were similar among captive and free-ranging dolphins. Free-ranging dolphins showed levels of circulating carotenoids (lutein and β-carotene) while the captive animals did not. Additional carotenoids (lycopene, α-carotene and cryptoxanthin) were analyzed but not detected in any samples. Serum vitamin differences between captive and free-ranging dolphins may reflect the natural diet or indicate some potential biological or nutritional status significance.

Tocopherol and fatty acid composition of twenty-five species of Onagraceae Juss.

Chemotaxonomic relationships in Onagraceae have been investigated at the level of leaf and flower compounds but not for seed traits. The objective of this study was to characterize a set of 26 accessions (25 species, 7 genera) of this family for seed oil content, fatty acid composition, tocopherol content and composition, and to evaluate the chemotaxonomic implications of the results. The accessions showed a large variation for all the traits. Gamma-linolenic acid was exclusively found in Oenothera spp. where two groups, showing different concentrations of gamma-linolenic acid and alpha-tocopherol, were observed. The species of Clarkia Pursh were markedly different to the rest of species, showing low alpha-linolenic acid and low gamma-tocopherol concentration. Circaea lutetiana L. had a characteristic tocopherol profile, with high levels (13%) of beta-tocopherol. Variation for fatty acid and tocopherol composition in Epilobium spp. suggested some phylogenetic relationships. The annual species E. pankulatum Nutt. showed a characteristic composition very similar to the closely related Boisduvalia densiflora (Lindl.) S. Watson. The accessions of the phylogenetically related E. fleischeri Hochst. and E. dodonaei Vill., also showed similar fatty acid and tocopherol composition. The results of this study suggest a potential chemotaxonomic value of seed fatty acids and tocopherols in Onagraceae.

Dietary acorns provide a source of gamma-tocopherol to pigs raised extensively

Pigs raised extensively and fed acorns and grass had a higher concentration of alpha and gamma-tocopherol in longissimus dorsi muscle and microsome extracts than pigs fed in confinement with mixed diets (P &lt; 0.001). This is attributable to the high concentration of alpha-tocopherol in grass (over 200 mg kg−1 DM) and gamma-toco-pherol in acorns (60–70 mg kg−1 DM). Key words: Pig, acorn, gamma-tocopherol, diet

Does vitamin C reduce blood pressure? Results of a large study of people aged 65 or older.

To characterize relationships among blood pressure, pulse rate, vitamin C status and other protective and risk factors for older British people, from a national survey. A cross-sectional analysis of survey data. A population study, representative of mainland Britain. Among 914 people of both sexes living in the community, 373 were taking blood-pressure-lowering drugs and were therefore excluded from the analyses. Completion of an interview on health, lifestyle and dietary habits, recording of a 4-day dietary record, anthropometry and taking of a blood sample to determine haematological and biochemical status. Systolic and diastolic blood pressures, pulse rate, indices of micronutrient status including plasma ascorbate concentration, nutrient intake and haematology. Plasma ascorbate concentration was inversely correlated to systolic and diastolic blood pressures and pulse rate. Other covariates of blood pressure included age, sex, domicile, plasma retinol, fibrinogen and gamma-tocopherol concentrations, erythrocyte count, prothrombin time and urine sodium: creatinine ratio. Covariates of pulse rate included sex, domicile, plasma fibrinogen and platelet count. Blood pressure was also correlated to intake of vitamin C. Plasma ascorbate concentration and intake of vitamin C are covariates of blood pressure in older people living in Britain. New intervention studies are now needed, to test for possible causalities.

Effect of dietary dl-alpha-tocopherol on tissue alpha- and gamma-tocopherol and pulmonary hypertension syndrome (ascites) in broilers

The objectives of this experiment were to determine the effects of high dietary levels of vitamin E on growth performance and pulmonary hypertension syndrome (PHS) mortality. Male broiler chicks (Cobb 500) were randomly assigned to one of four dietary treatments consisting of standard starter and grower diets supplemented with 0, 17, 46, and 87 mg dl-alpha-tocopherol acetate/kg. To encourage the development of PHS, air temperature in the house was 32 and 28 C for Weeks 1 and 2, dropped to 18 C during Week 3, and kept between 10 and 15 C during Weeks 4 through 7. Also, chicks were placed in floor pens on litter used for five previous flocks and ventilation reduced to increase dust and ammonia in the house. Ammonia levels increased from an initial 18 to 36 ppm on Day 42 with the increase in ammonia corresponding to an obvious increase in dust in the air. Lung and liver tissue obtained at 2, 5, and 7 wk of age were analyzed for tissue alpha- and gamma-tocopherol by liquid chromatography. Dietary vitamin E had no effect on body weight, feed intake, or feed efficiency. Cumulative PHS mortality through 7 wk of age was 21% and was also unaffected by dietary treatment. Liver and lung alpha-tocopherol concentrations exhibited a dose-response increase to dietary tocopherol and there was a high correlation between lung and liver tissue alpha-tocopherol (r = 0.72, P < 0.05). Whereas gamma-tocopherol concentrations in lung and liver were unaffected by dietary treatment, liver and lung exhibited age-dependent increases in both alpha- and gamma-tocopherol. Despite dose-dependent increases in tissue alpha-tocopherol, supplementation of diets with up to 87 mg dl-alpha-tocopherol acetate had no effect on growth performance or PHS mortality in broilers under the conditions used in this study.

Plasma retinol and plasma and lipoprotein tocopherol and carotenoid concentrations in healthy elderly participants of the Framingham Heart Study

Data on plasma concentrations of tocopherols and the major carotenoids in adults aged > or = 65 y, particularly in those > 80 y, are sparse. In the current study retinol, tocopherol (alpha- and gamma-tocopherols), and carotenoid (lutein/zeaxanthin, cryptoxanthins, lycopene, and alpha- and beta-carotene) concentrations were determined in 638 subjects, 230 men (aged 75 +/- 5 y) and 408 women (76 +/- 6 y), of the Framingham Heart Study. All subjects were free of clinical evidence of cardiovascular disease and cancer. Percentile ranges were comparable with those established in younger cohorts. Moreover, women had significantly higher plasma alpha-tocopherol and plasma and lipoprotein concentrations of beta-cryptoxanthin and alpha- and beta-carotene than did men. Lycopene concentrations were inversely correlated with age and lowest among subjects > or = 80 y. Total intakes (diet+supplements) of vitamin C and vitamin E, but not dietary intakes alone, were positively associated with plasma alpha-tocopherol and inversely associated with gamma-tocopherol concentrations. In multivariate analyses, plasma cholesterol and triacylglycerol concentrations and total intake of vitamins E and C predicted 64% and 55% of the plasma alpha-tocopherol concentrations in men and women, respectively. Important predictors for the majority of carotenoids included plasma cholesterol concentration, body mass index (negative effect), and smoking status (negative effect); for lycopene concentration they included cholesterol concentration and age (negative effect). In summary, percentile ranges and lipoprotein distributions were comparable with those established in younger cohorts, suggesting that overall antioxidant status is not altered in people between the ages of 67 and 96 y.

Effects of smoking on serum levels of lipid peroxides and essential fat-soluble antioxidants.

The effect of smoking on serum levels of the fat-soluble essential antioxidants (beta-carotene, alpha-tocopherol, gamma-tocopherol, and retinol) and lipid peroxides was studied in 31 smokers and 38 nonsmokers. The study subjects were male student, at King Saud University, aged 18-26 years. Smokers had significantly higher serum levels of lipid peroxides and significantly lower serum concentration of beta-carotene than nonsmokers (P < 0.05). Mean serum concentrations of retinol, alpha-tocopherol, gamma-tocopherol, and total vitamin E were lower among smokers than those of nonsmokers, but the differences were not statistically significant. The lower level of beta-carotene among smokers is probably brought about by the destruction of this antioxidant during neutralization of free radicals present in cigarette smoke. It seems possible that, during such oxidative stress, the interaction among antioxidants and their relative levels in serum are a crucial determinant of the concentration of a particular antioxidant. Therefore, the lower mean levels of alpha-tocopherol and gamma-tocopherol observed in smokers serum may also be related to cigarette smoking. This study has given rise to some concern about the adequacy of dietary beta-carotene, vitamin A and vitamin E of Saudis. The combination of cigarette smoking and low dietary intakes of essential antioxidants may provoke damage by oxidants present in cigarette smoke.

Lack of antioxidant adaptation to short-term aerobic training in human muscle.

The effects of 8 wk of 35 min of aerobic cycle training (3 times/wk) on indexes of male and female human vastus lateralis muscle antioxidant status were investigated. Training resulted in significant elevations in whole body maximal O2 consumption and muscle citrate synthase activity. Despite this, muscle superoxide dismutase, catalase, and glutathione peroxidase activities were not significantly altered by the training protocol. In addition, training did not affect muscle vitamin E (alpha- and gamma-tocopherol) concentrations. Glutathione status determined as the concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), total glutathione (GSH + 2 x GSSG), and GSH/GSSG ratio was unaffected by the training protocol. There were no significant differences between males and females in any indexes of muscle antioxidant status. These results indicate that the moderate aerobic training typically performed by regularly exercising humans did not positively alter endogenous antioxidant status. This suggests that short-term aerobic training increases capacity for flux through the citric acid cycle without necessarily increasing the ability to handle potential free radicals generated by the enhanced electron flux.

Lack of correlation between the alpha-tocopherol content of plasma and LDL, but high correlations for gamma-tocopherol and carotenoids

In 59 healthy human subjects (37 male and 22 female) the concentrations of the lipid-soluble antioxidants alpha- and gamma-tocopherol, alpha- and beta-carotene, lycopene, cryptoxanthin, canthaxanthin, and lutein + zeaxanthin were determined in plasma (mumol/L) and in isolated low density lipoproteins (LDL) (mumol/mmol cholesterol). Plasma alpha-tocopherol concentrations were significantly correlated with plasma total cholesterol concentrations (r2 = 0.51, P < 0.0001) yet not with the LDL alpha-tocopherol content (r2 = 0.05, ns). Plasma gamma-tocopherol concentrations were weakly correlated with plasma total cholesterol (r2 = 0.12, P < 0.003) and both absolute and cholesterol standardized plasma gamma-tocopherol concentrations correlated strongly with the LDL gamma-tocopherol content (r2 = 0.58 and r2 = 0.72, respectively). In contrast, carotenoid concentrations did not correlate with cholesterol concentrations, but their LDL content correlated significantly with the respective plasma concentrations (r2 = 0.67 to 0.92, all P < 0.0001). In a subgroup of study subjects (n = 13) the distribution of vitamin E and carotenoids among LDL was calculated. The proportion of plasma alpha- and gamma-tocopherol found in LDL was 48 +/- 7 (range, 36-61%) and 41 +/- 7%, respectively, suggesting that LDL was in most of these subjects not the main carrier for these antioxidants. The lipophilic carotenoids, however, were predominantly carried by LDL (e.g., beta-carotene: 87 +/- 10%), whereas the proportion of the more polar ones carried by LDL was much smaller (e.g., lutein + zeaxanthin: 36 +/- 6%). The results of this study show that plasma alpha-tocopherol concentrations are not predictive for the alpha-tocopherol content of LDL in nonsupplemented individuals. This finding could have implications in interpreting the cause of the inverse relationship between plasma alpha-tocopherol and risk of atherosclerosis.

Variability of vitamin E content in pumpkin seeds (Cucurbita pepo L.).

Pumpkin (Cucurbita pepo L.) seed oil is a common salad oil which is produced in the southern parts of Austria, Slovenia and Hungary. It is dark green and has a high content of free fatty acids. Due to its colour, the oil cannot be used for cooking. The content of vitamin E, especially gamma-tocopherol, is very high. The oil content of the pumpkin seed is about 50%. The seed itself can be eaten. Therefore a pumpkin variety with high vitamin E content is desirable. The aim of this work was to find a variety of Cucurbita pepo which has a high oil yield and a high vitamin E content. A total of 100 breeding lines were tested for their tocopherol content. The tocopherols and tocotrienols are extracted with hexane and analysed by NP-HPLC/FLD with hexane/dioxan (96/4) as eluent, with fluorescence detection at 292/335 nm. The gamma-tocopherol content, which is about 5-10 times as much as that of alpha-tocopherol varies over a broad range (41-620 mg/kg dry pumpkin seeds). Beta- and delta-tocopherol are found at low levels.

Gamma, but not alpha, tocopherol levels in serum are reduced in coronary heart disease patients.

Low concentrations of alpha tocopherol are claimed to be associated with an increased prevalence of coronary heart disease. This study was undertaken to see whether measurements of serum tocopherol concentrations can contribute to discrimination between subjects with and without coronary heart disease. All patients had been referred to the department of cardiology of the University Hospital in Uppsala, Sweden. Male patients (n = 69) below 60 years of age with coronary heart disease (CHD) and healthy age-matched reference subjects (n = 138) were compared. Lipid-corrected alpha tocopherol concentrations did not differ significantly between the groups, but the CHD group had a lower mean concentration of gamma tocopherol and a higher alpha/gamma ratio. In a stepwise logistic regression analysis, the LDL/HDL ratio was the best independent discriminator between the groups, followed by the proportion of palmitic acid in the cholesterol esters and the alpha/gamma tocopherol ratio. The lower gamma tocopherol concentration and the high ratio between alpha and gamma tocopherol in the CHD group indicate a difference in antioxidative status between CHD patients and healthy subjects. The lipid-lowering treatment of these CHD patients is far from optimal.

Effect of Chronic Ethanol Feeding on Hepatic and Extrahepatic Distribution of Vitamin E in Rats

The effect of chronic ethanol feeding on the status of alpha- and gamma-tocopherol in plasma, liver, lung, and testes of Sprague-Dawley rats was characterized. Rats were pair-fed liquid diets containing 36% of total calories either as ethanol or isocaloric carbohydrates. After 3 weeks, ethanol ingestion resulted in a significant (p less than or equal to 0.05) increase in liver weight and induced fatty liver without affecting total body weight. Ethanol feeding did not affect the plasma concentration of alpha-tocopherol but doubled that of gamma-tocopherol. When expressed per milligram of tissue, liver alpha-tocopherol did not vary with ethanol ingestion, whereas gamma-tocopherol concentration increased 2.5 times that of control animals. However, the concentration of alpha-tocopherol expressed per milligram of total lipids was significantly (p less than or equal to 0.01) decreased in the liver with ethanol feeding. In contrast to the liver, ethanol feeding significantly increased alpha- and gamma-tocopherol levels per milligram of total lipids in the testes. The concentration of gamma-tocopherol (but not alpha-tocopherol) per milligram of lung tissue and per total lung was significantly (p less than or equal to 0.05) increased with ethanol feeding. These data indicate that chronic ethanol ingestion significantly alters the distribution of alpha-tocopherol and gamma-tocopherol in hepatic and extrahepatic tissues of the rat.

Postprandial Changes in the Plasma Concentration of α- and γ-Tocopherol in Human Subjects Fed a Fat-Rich Meal Supplemented with Fat-Soluble Vitamins

The plasma concentrations of alpha (alpha)- and gamma (gamma)-tocopherol in 10 male and 15 female subjects (n = 14) received 1 g fat/kg body wt as soybean oil, and the meal was supplemented with 100% of the RDA for fat-soluble vitamins. In expt. 2, the subjects (n = 11) received 1 g fat/kg body wt as 50% soybean oil + 50% cream, and the meal was supplemented with 200% of the RDA for fat-soluble vitamins. The ratio of gamma- :alpha-tocopherol given in the test meal of expt. 1 was 2.8:1 and in expt. 2 was 0.9:1. Blood samples were obtained 0, 3, 6, 9 and 12 h after the meal. Tocopherol concentration was measured in plasma and lipoprotein fractions. In both studies, plasma triglyceride concentration increased significantly after the meal (P less than 0.001). Mean plasma cholesterol and alpha-tocopherol concentrations were unchanged, but plasma gamma-tocopherol concentration was significantly increased at 6, 9 and 12 h after the meal (P less than 0.05). The increase in plasma gamma-tocopherol was due to increases within the triglyceride-rich lipoprotein (TRL) fraction (d less than 1.006 g/ml) at earlier timepoints, followed by a sustained increase within low density lipoprotein (LDL) and high density lipoprotein (HDL) fractions at later timepoints. In contrast, alpha-tocopherol in LDL and HDL decreased postprandially, concomitant with a rise in TRL alpha-tocopherol. Our results are consistent with the concept that there are differences in the distribution of alpha- and gamma-tocopherol in postprandial lipoproteins.

Preferential incorporation of alpha-tocopherol vs gamma-tocopherol in human lipoproteins

Approximately 12 h after the ingestion of a single dose containing 1000 mg each of all-rac-alpha-tocopherol and RRR-gamma-tocopherol, the plasma and lipoproteins of normal subjects contained equal increases of both tocopherols; by 24 h the concentration of gamma-tocopherol, but not the alpha-tocopherol, decreased sharply. Similar studies in hyperlipidemic subjects demonstrated that the plasma and the chylomicron fraction from lipoprotein lipase-deficient patients (with elevated chylomicrons) contained both tocopherols up to 24 h, whereas plasma from a patient with dysbetalipoproteinemia (with elevated beta very-low-density lipoproteins) displayed the decrease in gamma-tocopherol at 24 h. These studies demonstrate that both alpha- and gamma-tocopherols are absorbed and secreted by the intestine in chylomicrons, and suggest that alpha-tocopherol is preferentially secreted by the liver in nascent lipoproteins. Furthermore, studies in post-gall bladder surgery patients suggest a preferential secretion of gamma-tocopherol in bile. Thus, the liver rather than the intestine appears to discriminate between alpha- and gamma-tocopherols.

Vitamin E in human milk from mothers of preterm and term infants.

The content of vitamin E (alpha- and beta + gamma-tocopherol) was analyzed in 63 human milk samples obtained from 13 mothers of preterm infants ("preterm" milk) and in 59 milk samples obtained from nine mothers of full-term infants ("term" milk). The changing pattern of the alpha- and beta + gamma-tocopherol content during the course of lactation was identical for both groups. Total vitamin E, alpha- as well as beta + gamma-tocopherol, decreased during the first 2 weeks of lactation and remained constant thereafter. The ratio of alpha- to beta + gamma-tocopherol decreased from about 10:1 to 4:1. At days 3 and 36 of lactation, vitamin E contents (median values and ranges) expressed as milligrams alpha-tocopherol equivalent per 100 ml were 1.45 (0.64-6.4) and 0.29 (0.17-0.48), respectively, for preterm and 1.14 (0.63-4.21) and 0.28 (0.19-0.86), respectively, for term human milk. The vitamin E, alpha-tocopherol and beta + gamma-tocopherol content of preterm human milk did not differ significantly (p less than or equal to 0.05) from that of term human milk at each sampling day. Based on these findings we conclude that the increased requirement of prematures for vitamin E is not reflected in the vitamin E content of milk from mothers delivering preterm infants.

Vitamin E in foods from high and low linoleic acid diets

As part of a human diet study, vitamin E activity was estimated in foods used in seven daily menus. Each menu was designed to contain 35% fat calories with either 10 or 30 gm/day of linoleic acid (18:2) and 500 mg/day of cholesterol. To estimate vitamin E activity, each food used in the menus was analyzed for alpha and gamma tocopherol content by high-pressure liquid chromatography with fluorescence detection. This article reports the alpha and gamma tocopherol contents of those foods, tocopherol contributions from each food in one sample 2,400-kcal menu, and the mean daily vitamin E activity (milligram alpha tocopherol equivalents) of all seven menus at five caloric levels. Major sources of alpha tocopherol (greater than 10% of the RDA) common to both diets (10 and 30 gm linoleic acid) were olive oil and a few fruits and vegetables. Additional major sources in the 30-gm linoleic acid diets were polyunsaturated fatty acid (PUFA) vegetable oils and margarine. Contrary to a common assumption, increasing the level of PUFA in the menus did not necessarily result in higher milligram equivalents of alpha tocopherol because soybean oil, with a tocopherol composition that is predominantly gamma tocopherol, was the major source of linoleic acid in the diets. Thus, vitamin E activity was not necessarily increased when soybean oil was substituted for a less saturated fat such as olive oil, which has mostly alpha tocopherol.