Effect of high-dose alpha-tocopherol supplementation on biomarkers of oxidative stress and inflammation and carotid atherosclerosis in patients with coronary artery disease

BACKGROUND: Oxidative stress and inflammation are crucial in atherogenesis. alpha-Tocopherol is both an antioxidant and an antiinflammatory agent. OBJECTIVE: We evaluated the effect of RRR-alpha-tocopherol supplementation on carotid atherosclerosis in patients with stable coronary artery disease (CAD) on drug therapy. DESIGN: Randomized, controlled, double-blind trial compared RRR-alpha-tocopherol (1200 IU/d for 2 y) with placebo in 90 patients with CAD. Intimal medial thickness (IMT) of both carotid arteries was measured by high-resolution B-mode ultrasonography at 0, 1, 1.5, and 2 y. At 6-mo intervals, plasma alpha-tocopherol concentrations, C-reactive protein (CRP), LDL oxidation, monocyte function (superoxide anion release, cytokine release, and adhesion to endothelium), and urinary F(2)-isoprostanes were measured. RESULTS: alpha-Tocopherol concentrations were significantly higher in the alpha-tocopherol group but not in the placebo group. High-sensitivity CRP concentrations were significantly lowered with alpha-tocopherol supplementation than with placebo (32%; P < 0.001). alpha-Tocopherol supplementation significantly reduced urinary F(2)-isoprostanes (P < 0.001) and monocyte superoxide anion and tumor necrosis factor release compared with baseline and placebo (P < 0.001). No significant difference was observed in the mean change in total carotid IMT in the placebo and alpha-tocopherol groups. In addition, no significant difference in cardiovascular events was observed (P = 0.21). CONCLUSIONS: High-dose RRR-alpha-tocopherol supplementation in patients with CAD was safe and significantly reduced plasma biomarkers of oxidative stress and inflammation but had no significant effect on carotid IMT during 2 y.     

Effects of supplementation with folic acid and antioxidant vitamins on homocysteine levels and LDL oxidation in coronary patients

Hyperhomocysteinemia is an important cardiovascular risk factor. Serum homocysteine levels are specially dependent on folate nutritional status. In addition, the oxidative modification of low-density lipoproteins (LDLs) in the endothelial microenvironment is a damaging factor that can be modified with fat-soluble antioxidant vitamins. The present study was done to assess the effect of a supplementation of folic acid and antioxidant vitamins on homocysteine levels and in vitro LDL oxidation in patients with coronary artery disease. Twenty-three patients with angiographically proven coronary artery disease were given supplements for 15 d consisting of one capsule twice a day of a multivitamin preparation containing 0.65 mg folic acid, 150 mg alpha-tocopherol, 150 mg ascorbic acid, 12.5 mg beta-carotene, and 0.4 microgram vitamin B12. Serum lipids, vitamin and homocysteine levels, and in vitro LDL oxidation were measured before and after the supplementation period. During the supplementation period, serum folate levels increased from 5.0 +/- 1.5 to 10.8 +/- 3.8 ng/mL (P < 0.001), vitamin B12 increased from 317.4 +/- 130.4 to 334.5 +/- 123.8 pg/mL (P < 0.05), and alpha-tocopherol increased from 8.2 +/- 5.1 to 13.7 +/- 7.9 mg/L (P < 0.001). Serum homocysteine levels decreased from 8.7 +/- 4.3 to 6.3 +/- 2.2 mumol/L (P < 0.001). In vitro LDL oxidation decreased from 2.6 +/- 1.1 to 1.6 +/- 1.1 nmol malondialdehyde/mg protein (P < 0.001). In comparing patients with healthy controls, basal levels of folate were lower in the patients, whereas vitamin B12, alpha-tocopherol, and homocysteine levels were similar. No changes in serum lipid levels or body weight were observed. In conclusion, a short-term supplementation with folic acid and antioxidant vitamins can reduce serum homocysteine levels and in vitro LDL oxidation in patients with coronary artery disease.     

alpha-tocopherol supplementation decreases production of superoxide and cytokines by leukocytes ex vivo in both normolipidemic and hypertriglyceridemic individuals

BACKGROUND: alpha-Tocopherol plays an important role in protecting LDL against oxidation. However, additional effects of alpha-tocopherol at the intracellular level may contribute to the clinical outcome of intervention studies. OBJECTIVE: We investigated whether alpha-tocopherol influences the inflammatory responses of immune cells in normolipidemic and hypertriglyceridemic subjects. DESIGN: RRR-alpha-Tocopherol was administered for 6 wk at a dose of 600 IU (402 mg)/d to 12 primary hypertriglyceridemic and 8 normolipidemic (fasting triacylglycerol >3.0 and <2.0 mmol/L, respectively) subjects. Cytokine production [tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, and IL-8] by mononuclear cells and superoxide production by polymorphonuclear cells and in diluted whole blood were determined before and after the intervention. RESULTS: Cytokine and superoxide production did not differ significantly between hypertriglyceridemic and normolipidemic subjects. alpha-Tocopherol supplementation resulted in a 2- to 3-fold increase in the concentration of alpha-tocopherol in plasma and LDL. Whereas superoxide production in response to phorbol 12-myristate 13-acetate decreased in all subjects, response to oxidized LDL increased in 19 of 20 subjects. Response to opsonized zymosan before alpha-tocopherol supplementation was not significantly different from that after supplementation. Lipopolysaccharide-induced cytokine production by mononuclear cells decreased after supplementation with alpha-tocopherol. CONCLUSIONS: alpha-Tocopherol differentially influences inflammatory responses of immune cells. These effects of alpha-tocopherol may be relevant in chronic inflammatory processes such as atherogenesis.     

Antioxidant supplementation effects on low-density lipoprotein oxidation for individuals with type 2 diabetes mellitus.

OBJECTIVE: This study compared susceptibility to oxidation of low-density lipoproteins (LDL) of non-diabetic and diabetic (Type 2) men and examined the response of diabetic men to antioxidant supplementation (alpha-tocopherol, beta-carotene and ascorbate). RESEARCH DESIGN AND METHODS: Twenty adult non-diabetic and 20 diabetic men were recruited. Oxidation of LDL was assessed by four different assay systems, and the extent of oxidation was assessed by four different measurements. Diabetic men received eight weeks of placebo ("baseline"), twelve weeks of antioxidant supplements ("treated") and eight weeks of placebo ("post-treatment"). Supplements provided 24 mg of beta-carotene, 1000 mg of ascorbate and 800 IU of alpha-tocopherol daily. RESULTS: With Cu oxidation at 37 degrees C, thiobarbituric reactive substances (TBARS) formation was significantly higher (p=0.032) and loss of free amine groups was significantly greater (p=0.013) in the LDL from diabetic subjects than controls. Antioxidant supplementation of diabetic subjects significantly decreased all parameters of LDL oxidation with Cu at 30 degrees C and 37 degrees C. At 30 degrees C the lag phase increased from 55 to 129 minutes (p<0.0001); conjugated diene formation decreased from 1.23 to 0.62 OD units (p<0.0001); TBARS formation decreased from 78 to 33 nmoles MDA/mg LDL protein (p<0.0001); and free amine loss decreased from 41 to 12% (p<0.0001). With Cu oxidation at 37 degrees C, similar changes occurred. CONCLUSIONS: These studies indicate that the LDL from diabetic subjects are more susceptible to oxidation than LDL from non-diabetic subjects. Supplementation of diabetic subjects with antioxidant vitamins significantly decreases susceptibility of LDL to oxidation by Cu. These studies are consistent with epidemiological and intervention studies suggesting that antioxidant vitamin use significantly decreases risk for coronary heart disease.     

Lower plasma alpha-carboxyethyl-hydroxychroman after deuterium-labeled alpha-tocopherol supplementation suggests decreased vitamin E metabolism in smokers

BACKGROUND: Cigarette smoking increases the fractional disappearance rates of alpha-tocopherol and is associated with increased oxidative stress, but its effects on alpha-tocopherol metabolism are unknown. OBJECTIVE: We hypothesized that smokers would have less alpha-tocopherol available and consequently lower plasma alpha-carboxyethyl-hydroxychroman (alpha-CEHC), the alpha-tocopherol metabolite produced by a cytochrome P450-mediated process. DESIGN: Smokers and nonsmokers (n = 10 per group) were supplemented with deuterium-labeled alpha-tocopheryl acetates (75 mg each d3-RRR-alpha-tocopheryl and d6-all-rac-alpha-tocopheryl acetate) from day -6 to day -1, and plasma tocopherols and CEHCs were measured (day -6 through day 17). RESULTS: After 6 d of supplementation, plasma d3- and d6-alpha-tocopherol concentrations did not differ significantly between groups. Plasma d3- and d6-alpha-CEHCs were detectable only from day -5 to day 5. Before supplementation, unlabeled alpha- and gamma-CEHCs were approximately 60% and 40% lower, respectively, in smokers than in nonsmokers (P < or = 0.05). In addition, d0-, d3-, and d6-alpha-CEHC areas under the curves were approximately 50% lower in smokers (P < 0.05), and smokers had lower maximal d3-alpha-CEHC (P = 0.004) and d6-alpha-CEHC (P = 0.0006) concentrations. Notably, 2.9-4.7 times as much alpha-CEHC was produced from all-rac-alpha-tocopherol than from RRR-alpha-tocopherol. During supplementation, smokers had about one-half (P < 0.05) the plasma total, d6-, or d3-alpha-CEHC concentrations that nonsmokers did given similar alpha-tocopherol concentrations. CONCLUSIONS: Smoking did not increase alpha-tocopherol disappearance through P450-mediated tocopherol metabolism. Therefore, the mechanism of increased alpha-tocopherol disappearance in smokers likely operates through oxidation pathways, which is consistent with alpha-tocopherol's antioxidant function. Consequently, evaluating the molecular mechanism or mechanisms responsible for tocopherol metabolism under conditions of oxidative stress and the mechanisms that regulate alpha-tocopherol status is warranted.     

Interactions between vitamins C and E in human subjects

Despite convincing in vitro evidence, a vitamin C-E interaction has not been confirmed in vivo. This study was designed to examine the effects of supplementation with either vitamin C or E on their respective plasma concentrations, other antioxidants, lipids and some haemostatic variables. Fasting blood was collected before and after intervention from thirty healthy adults in a double-blinded crossover study. Baselines for measured variables were established after 2 weeks of placebo supplementation, followed by daily supplementation with 73.5 mg RRR-alpha-tocopherol acetate or 500 mg ascorbic acid, and placebo, for 6 weeks. A 2 month washout preceded supplement crossover. Mean values showed that plasma lipid standardised alpha-tocopherol increased with ascorbic acid supplementation: from 4.09 (sem 0.51) to 4.53 (sem 0.66) micromol/mmol total cholesterol plus triacylglycerol (P < 0.05), and plasma ascorbic acid increased from 62.8 (sem 14.9) to 101.3 (sem 22. 2) micromol/l (P < 0.005). Supplementation with (RRR)-alpha-tocopherol acetate increased plasma alpha-tocopherol from 26.8 (sem 3.9) to 32.2 (sem 3.8) micromol/l (P < 0.05), and lipid-standardised alpha-tocopherol from 4.12 (sem 0.48) to 5.38 (sem 0.52) micromol/mmol (P < 0.001). Mean plasma ascorbic acid also increased with vitamin E supplementation, from 64.4 (sem 13.3) to 76. 4 (sem 18.4) micromol/l (P < 0.05). Plasma ferric reducing (antioxidant) power and glutathione peroxidase (U/g haemoglobin) increased in both groups, while urate, total cholesterol and triacylglycerol levels decreased (P < 0.05 throughout). Results are supportive of an in vivo interaction between vitamins C and E.     

Evidence of hypolipemiant and antioxidant properties of argan oil derived from the argan tree (Argania spinosa)

BACKGROUND: Virgin argan oil is of interest in cardiovascular risk prevention due to its fat composition and antioxidant compounds. AIMS: We investigated with Moroccan subjects the effect of regular virgin argan oil consumption on lipid profile and antioxidant status and the in vitro effect of argan oil minor compounds (tocopherols, sterols and polyphenols) on LDL peroxidation. DESIGN: Healthy subjects (20 men, 76 women) were studied. Sixty-two were regular consumers of argan oil and 34 were non-consumers. METHODS: Fasting plasma lipids, antioxidant vitamins and LDL oxidation susceptibility were analyzed. In vitro LDL oxidation by phenolic and apolar compounds of virgin argan oil were performed. RESULTS: Diet composition of argan oil consumers has a higher significant content of polyunsaturated fatty acids than that of non-consumers (8.8 +/- 1.0 vs. 6.6 +/- 0.9 g, P < 0.05). Subjects consuming argan oil have lower levels of plasma LDL cholesterol (12.7%, P < 0.05) and Lp(a) (25.3%, P < 0.05) compared with the non-consumers. In argan oil consumers, plasma lipoperoxides were lower (58.3%, P < 0.01) and molar ratio alpha-tocopherol/total cholesterol (21.6%, P < 0.05) and alpha-tocopherol concentration (13.4%, P < 0.05) were higher compared with the non-consumers group. In spite of higher levels of plasma antioxidant and lower levels of lipoperoxides in argan oil consumers, LDL oxidation susceptibility remained fairly similar. A strong positive correlation was observed between increasing phenolic extract, sterol and tocopherol concentrations and the LDL-Lag phase (P < 0.05). CONCLUSIONS: Our findings suggest for the first time that regular consumption of virgin argan oil induces a lowering of LDL cholesterol and has antioxidant properties. This oil offers an additional natural food to reducing cardiovascular risk.     

Alpha-tocopherol supplementation for men with existing coronary artery disease: a feasibility study.

BACKGROUND: Recent studies have suggested that alpha-tocopherol supplementation can help reduce the incidence of coronary disease. Our objectives were to determine the feasibility of providing alpha-tocopherol supplements to male veterans with existing coronary artery disease and determine its effects on alpha-tocopherol levels and the susceptibility of low-density lipoprotein (LDL) to oxidation. METHODS: Fifty-seven percent of 138 coronary disease patients were willing to participate in a placebo-controlled trial -25% were already taking antioxidants. Thirty-nine men were randomly assigned to either 400 mg/day of alpha-tocopherol (n = 27) or placebo (n = 12). alpha-Tocopherol levels and LDL oxidation (measured by formation of thiobarbituric acid-reactive substance) were measured at baseline and at 6 months. RESULTS: Thirty-three subjects (22 alpha-tocopherol, 11 placebo) completed the study; 3 subjects withdrew after suffering coronary disease events. Supplement compliance exceeded 90% and alpha-tocopherol was well tolerated. The alpha-tocopherol group had a significantly greater mean increase in lipid-adjusted alpha-tocopherol levels (73% vs. -4.6%, P < 0.0001), but oxidized LDL did not change significantly. CONCLUSIONS: A secondary prevention trial among veterans would be feasible because the rates of enrollment, completion, compliance, and clinical events were high. alpha-Tocopherol supplements did not decrease the susceptibility of LDL to oxidation, suggesting that higher dosages or longer duration of supplementation may be required for secondary prevention.     

Dietary fiber reduces the antioxidative effect of a carotenoid and α-tocopherol mixture on LDL oxidation ex vivo in humans

BACKGROUND: Antioxidant concentrations in low density lipoproteins (LDL) are an important determinant for their susceptibility to oxidation and can be modulated by dietary intake. AIM OF THE STUDY: In the present study, the influence of dietary fiber on the antioxidant enrichment and the oxidation resistance of LDL after antioxidant supplementation is investigated. METHOD: An antioxidant supplement consisting of beta-carotene, lycopene, lutein, canthaxanthin and alpha-tocopherol was given to six young women together with a standard meal. Using a cross-over study design, each subject received the standard meal without additional dietary fiber and enriched with pectin, guar, or cellulose in a random order. To determine the resistance of LDL against copper ion-induced oxidation, the formation of conjugated dienes was measured. RESULTS: Eight, 10, and 24 hours after antioxidant supplementation the isolated LDL revealed significantly (p < 0.05) increased antioxidant concentrations; addition of pectin, guar, or cellulose to the meal depressed this increase. Concomitantly, the observed increase in the resistance of LDL against oxidation (measured as lag phase) was lower with dietary fiber supplementation than that found without. On average, pectin, guar, and cellulose reduced the increase of the lag phase (measured without addition of dietary fiber) by 38%, 22%, and 18%, respectively. CONCLUSIONS: These results indicate that dietary fiber supplementation decreases the antioxidative effect of a supplement consisting of carotenoids and alpha-tocopherol in LDL, an effect that is likely to be mediated by a reduced bioavailability of these antioxidants in the gut.     

Plant- and marine-derived n-3 polyunsaturated fatty acids have differential effects on fasting and postprandial blood lipid concentrations and on the susceptibility of LDL to oxidative modification in moderately hyperlipidemic subjects

BACKGROUND: Dietary alpha-linolenic acid (ALA) can be converted to long-chain n-3 polyunsaturated fatty acids (PUFAs) in humans and may reproduce some of the beneficial effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on cardiovascular disease risk factors. OBJECTIVE: This study aimed to compare the effects of increased dietary intakes of ALA and EPA+DHA on a range of atherogenic risk factors. DESIGN: This was a placebo-controlled, parallel study involving 150 moderately hyperlipidemic subjects randomly assigned to 1 of 5 interventions: 0.8 or 1.7 g EPA+DHA/d, 4.5 or 9.5 g ALA/d, or an n-6 PUFA control for 6 mo. Fatty acids were incorporated into 25 g of fat spread and 3 capsules to be consumed daily. RESULTS: The change in fasting or postprandial lipid, glucose, or insulin concentrations or in blood pressure was not significantly different after any of the n-3 PUFA interventions compared with the n-6 PUFA control. The mean (+/- SEM) change in fasting triacylglycerols after the 1.7-g/d EPA+DHA intervention (-7.7 +/- 4.99%) was significantly (P < 0.05) different from the change after the 9.5-g/d ALA intervention (10.9 +/- 4.5%). The ex vivo susceptibility of LDL to oxidation was higher after the 1.7-g/d EPA+DHA intervention than after the control and ALA interventions (P < 0.05). There was no significant change in plasma alpha-tocopherol concentrations or in whole plasma antioxidant status in any of the groups. CONCLUSION: At estimated biologically equivalent intakes, dietary ALA and EPA+DHA have different physiologic effects.     

Antioxidant ability of various flavonoids against DPPH radicals and LDL oxidation

Flavonoids, a group of polyphenolic compounds, exist naturally and serve as antioxidants in vegetables, fruits, and so on. The inhibition of low density lipoprotein (LDL) oxidation may be an effective way to prevent or delay the progression of atherosclerosis. In the present study, we analyzed the radical scavenging capacity of 10 flavonoids (catechin, epicatechin [EC], epigallocatechin [EGC], epicatechin gallate [ECg], epigallocatechin gallate [EGCg], myricetin, quercetin, apigenin, kaempferol, and luteolin) toward 1,1-diphenyl-2-picryl-hydrazyl [DPPH]. After 20 min of incubation, EGCg was the most effective DPPH radical scavenger, luteolin being the least active of this flavonoid group. The mutual antioxidant effect of flavonoids with alpha-tocopherol (alpha-toc) on LDL oxidizability was investigated by using the lipophilic azo radical initiator 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) [AMVN-CH3O]. An inhibitory effect of flavonoids on LDL oxidation was observed in the order of luteolin>ECg>EC>quercetin>catechin>EGCg>EGC>myricetin>kaempferol> apigenin. The shortened lag time induced by higher doses of alpha-toc (6 mg/100 mL) was restored by flavonoids. These results suggest that 1) radical trapping effects of flavonoids differ according to their structure, and 2) flavonoids act as hydrogen donors to alpha-toc radical; furthermore, by interaction with alpha-toc, they have a greater potential to delay the oxidation of LDL.     

Effects of oral vitamin E and beta-carotene supplementation on ultraviolet radiation-induced oxidative stress in human skin

BACKGROUND: Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting. OBJECTIVE: We examined the ability of 2 lipid-soluble antioxidants, vitamin E and beta-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR. DESIGN: Sixteen healthy subjects took either alpha-tocopherol (n = 8; 400 IU/d) or beta-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/cm(2) UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed. RESULTS: Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 +/- 0.66 (x +/- SEM) to 18.2 +/- 0.64 mug/mL (P < 0.01), and the skin concentration increased from 0.55 +/- 0.09 to 1.6 +/- 0.19 ng/mg protein (P < 0.01). Supplementary beta-carotene increased plasma concentrations from 1 +/- 0.3 to 2.25 +/- 0.3 mug/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malondialdehyde concentration from 0.42 +/- 0.07 to 1.24 +/- 0.16 nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 +/- 0.4% to 12.0 +/- 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor beta-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin. CONCLUSIONS: Vitamin E or beta-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation.     

Eicosanoid production, thrombogenic ratio, and serum and LDL peroxides in normo- and hypercholesterolaemic post-menopausal women consuming two oleic acid-rich diets with different content of minor components

The present paper compares the effects of two monounsaturated oils, extra virgin olive oil (EVOO) and high-oleic acid sunflower oil (HOSO), on serum and LDL peroxides, eicosanoid production and the thrombogenic ratio (thromboxane (TX) B2:6-keto-prostaglandin F1alpha) in fourteen non-obese post-menopausal women. The subjects, mean age 63 (SD 11) years, were assigned to two consecutive oleic acid-rich 28 d dietary periods. EVOO and HOSO represented 62 % of the total lipid intake and were used as the only culinary fat during the first and second dietary periods respectively. Serum peroxides, plasma alpha-tocopherol and TXB2 levels in stimulated platelet-rich plasma (PRP-TXB2) were significantly higher (P < 0.01, P < 0.001, and P < 0.05, respectively) after the HOSO diet than after the EVOO diet. The relationship between the serum cholesterol level (< 6.21 mmol/l or > or = 6.21 mmol/l) and the type of dietary oil on eicosanoids, peroxides and alpha-tocopherol were evaluated by two-way ANOVA. Dietary oil significantly affected (P < 0.05) the PRP-TXB2 level, whereas serum and LDL peroxides were significantly affected (P < 0.001 and P < 0.01, respectively) by the serum cholesterol level. The plasma alpha-tocopherol level was significantly affected by the serum cholesterol level and the type of dietary oil (both P < 0.001). No significant relationships were found between serum cholesterol levels, serum peroxide or LDL peroxide levels, plasma alpha-tocopherol concentrations or alpha-tocopherol intakes with eicosanoid production or the thrombogenic ratio due to dietary changes. However, in spite of their higher alpha-tocopherol levels, hypercholesterolaemic subjects showed increased peroxidation in serum and LDL in comparison with normocholesterolaemic subjects on the HOSO diet in comparison with the EVOO diet. These findings suggest that differences in the type of minor compounds, as well as in the concentration of linoleic acid, in both these monounsaturated oils may play an important role in modulating eicosanoid production and lipoprotein peroxidation when they constitute a large proportion of the diet of post-menopausal women.     

Isoflavone phytoestrogens consumed in soy decrease F(2)-isoprostane concentrations and increase resistance of low-density lipoprotein to oxidation in humans

BACKGROUND: Oxidative damage to lipids may be involved in the etiology of atherosclerosis, cardiovascular disease in general, and cancer. The soy isoflavone phytoestrogens, genistein and daidzein, and equol (a daidzein metabolite produced by intestinal microflora) are antioxidants in vitro; equol is a particularly good inhibitor of LDL oxidation and membrane lipid peroxidation. OBJECTIVE: We sought to investigate the effects of a diet enriched with soy containing isoflavones on in vivo biomarkers of lipid peroxidation and resistance of LDL to oxidation, compared with a diet enriched with soy from which the isoflavones had been extracted. DESIGN:: A randomized, crossover design was used to compare diets enriched with soy that was low or high in isoflavones in 24 subjects. Plasma concentrations of an F(2)-isoprostane, 8-epi-prostaglandin F(2)(alpha) (8-epi-PGF(2)(alpha)), a biomarker of in vivo lipid peroxidation, and resistance of LDL to copper-ion-induced oxidation were determined. RESULTS: Plasma concentrations of 8-epi-PGF(2)(alpha) were significantly lower after the high-isoflavone dietary treatment than after the low-isoflavone dietary treatment (326 +/- 32 and 405 +/- 50 ng/L, respectively; P = 0.028) and the lag time for copper-ion-induced LDL oxidation was longer (48 +/- 2.4 and 44 +/- 1.9 min, respectively; P = 0.017). Lag time for oxidation of unfractionated plasma and plasma concentrations of malondialdehyde, LDL alpha-tocopherol, polyunsaturated fatty acids, and isoflavonoids did not differ significantly between dietary treatments. CONCLUSIONS: Consumption of soy containing naturally occurring amounts of isoflavone phytoestrogens reduced lipid peroxidation in vivo and increased the resistance of LDL to oxidation. This antioxidant action may be significant with regard to risk of atherosclerosis, cardiovascular disease in general, and cancer.     

Plasma antioxidant capacity in response to diets high in soy or animal protein with or without isoflavones

BACKGROUND: Several clinical trials have suggested that soy intake decreases oxidative stress. Soy isoflavones have antioxidant properties in vitro, but results of supplementation in clinical trials are inconclusive. OBJECTIVE: The objective was to evaluate the independent effects of soy protein and soy-derived isoflavones on plasma antioxidant capacity and biomarkers of oxidative stress. DESIGN: Forty-two hypercholesterolemic (LDL cholesterol > 3.36 mmol/L) subjects aged >50 y were provided with each of 4 diets in random order in a crossover design. Diets varied in protein source (10% of energy, soy or animal) and isoflavone content (trace or 50 mg/1000 kcal) and were consumed for 42 d each. Plasma antioxidants, protein carbonyls, malondialdehyde, total antioxidant performance, LDL oxidizability, and urinary F(2)-isoprostanes were measured at the end of each dietary phase. RESULTS: Plasma antioxidant concentrations were not significantly different, regardless of dietary treatment, except for isoflavones, which were higher after isoflavone supplementation (P = 0.0001). Although plasma total antioxidant performance was 10% higher with soy protein intake, regardless of dietary isoflavones (P = 0.0003), soy protein did not significantly affect most individual markers of oxidative stress (LDL oxidizability, urinary F(2)-isoprostanes, malondialdehyde, or protein carbonyls in native plasma). However, soy protein was associated with modestly lower concentrations of protein carbonyls in oxidized plasma. There was no significant effect of isoflavones on LDL oxidation, urinary F(2)-isoprostanes, or protein carbonyl groups, although, paradoxically, the plasma malondialdehyde concentration was significantly higher after the isoflavone-rich diets (P = 0.04). CONCLUSIONS: Diets relatively high in soy protein or soy-derived isoflavones have little effect on plasma antioxidant capacity and biomarkers of oxidative stress.     

Randomized controlled trial of the effect of n-3 fatty acid supplementation on the metabolism of apolipoprotein B-100 and chylomicron remnants in men with visceral obesity

BACKGROUND: Lipid abnormalities may contribute to the increased risk of atherosclerosis and coronary disease in visceral obesity. Fish oils lower plasma triacylglycerols, but the underlying mechanisms are not fully understood. OBJECTIVE: We studied the effect of fish oils on the metabolism of apolipoprotein B-100 (apo B) and chylomicron remnants in obese men. DESIGN: Twenty-four dyslipidemic, viscerally obese men were randomly assigned to receive either fish oil capsules (4 g/d, consisting of 45% eicosapentaenoic acid and 39% docosahexaenoic acid as ethyl esters) or matching placebo (corn oil, 4 g/d) for 6 wk. VLDL, intermediate-density lipoprotein (IDL), and LDL apo B kinetics were assessed by following apo B isotopic enrichment with the use of gas chromatography-mass spectrometry after an intravenous bolus injection of trideuterated leucine. Chylomicron remnant catabolism was measured with the use of an intravenous injection of a chylomicron remnant-like emulsion containing cholesteryl [(13)C]oleate, and isotopic enrichment of (13)CO(2) in breath was measured with isotope ratio mass spectrometry. Kinetic values were derived with multicompartmental models. RESULTS: Fish oil supplementation significantly (P < 0.05) lowered plasma concentrations of triacylglycerols (-18%) and VLDL apo B (-20%) and the hepatic secretion of VLDL apo B (-29%) compared with placebo. The percentage of conversions of VLDL apo B to IDL apo B, VLDL apo B to LDL apo B, and IDL apo B to LDL apo B also increased significantly (P < 0.05): 71%, 93%, and 11%, respectively. Fish oils did not significantly alter the fractional catabolic rates of apo B in VLDL, IDL, or LDL or alter the catabolism of the chylomicron remnant-like emulsion. CONCLUSION: Fish oils effectively lower the plasma concentration of triacylglycerols, chiefly by decreasing VLDL apo B production but not by altering the catabolism of apo B-containing lipoprotein or chylomicron remnants.     

Ascorbate is depleted by smoking and repleted by moderate supplementation: a study in male smokers and nonsmokers with matched dietary antioxidant intakes

BACKGROUND: Lack of reliable dietary data has hampered the ability to effectively distinguish between effects of smoking and diet on plasma antioxidant status. As confirmed by analyses of comprehensive food-frequency questionnaires, the total dietary intakes of fruit and vegetables and of dietary antioxidants were not significantly different between the study groups in the present study, thereby enabling isolation of the effect of smoking. OBJECTIVE: Our objective was to investigate the effect of smoking on plasma antioxidant status by measuring ascorbic acid, alpha-tocopherol, gamma-tocopherol, beta-carotene, and lycopene, and subsequently, to test the effect of a 3-mo dietary supplementation with a moderate-dose vitamin cocktail. DESIGN: In a double-blind, placebo-controlled design, the effect of a vitamin cocktail containing 272 mg vitamin C, 31 mg all-rac-alpha-tocopheryl acetate, and 400 microg folic acid on plasma antioxidants was determined in a population of smokers (n = 37) and nonsmokers (n = 38). The population was selected for a low intake of fruit and vegetables and recruited from the San Francisco Bay area. RESULTS: Only ascorbic acid was significantly depleted by smoking per se (P < 0.01). After the 3-mo supplementation period, ascorbic acid was efficiently repleted in smokers (P < 0.001). Plasma alpha-tocopherol and the ratio of alpha- to gamma-tocopherol increased significantly in both supplemented groups (P < 0.05). CONCLUSIONS: Our data suggest that previous reports of lower concentrations of plasma vitamin E and carotenoids in smokers than in nonsmokers may primarily have been caused by differences in dietary habits between study groups. Plasma ascorbic acid was depleted by smoking and repleted by moderate supplementation.     

The effect of vitamin E and vitamin C supplementation on LDL oxidizability and neutrophil respiratory burst in young smokers

OBJECTIVE: The purpose of this study was to determine the effect of vitamin E and/or vitamin C supplementation on low-density lipoprotein (LDL) oxidizability and neutrophil (PMN) superoxide anion production in young smokers. METHODS: Thirty smokers with a <5 pack-year history were randomly assigned to take placebo; vitamin C (1 g/day); vitamin E (400 IU/day), or both vitamins in a double-blind fashion. Subjects took the supplements for 8 weeks. At weeks 0 and 8, blood was collected for isolation of LDL and PMN, and for antioxidant vitamin analysis. LDL was oxidized with a copper (Cu) catalyst, and oxidation was measured by formation of conjugated dienes over a 5-hour time course. Lag times and maximum oxidation rates were calculated from the time course data. PMN superoxide anion release was assessed by respiratory burst after stimulation with phorbol ester and opsonized zymosan, and their ability to oxidize autologous LDL following treatment with the above stimuli was measured with the conjugated diene assay. RESULTS: Subjects who received vitamin E alone had a significant increase in the lag phase of Cu-catalyzed LDL oxidation (week 0, 118+/-31 min vs. week 8, 193+/-80 min, mean +/- SD, p < 0.05), whereas the vitamin C and placebo groups had no changes in LDL oxidation kinetics. The group receiving both vitamins E and C had a significant reduction in oxidation rate (week 0. 7.4+/-2.3 vs. week 8, 5.1+/-2.1, p < 0.05). There were no significant changes for any group in PMN superoxide anion production or PMN LDL oxidation after stimulation with either phorbol ester or opsonized zymosan. Plasma and LDL vitamin E concentrations were significantly increased in both groups that received vitamin E. The subjects who received vitamin C alone had no significant change in plasma vitamin C concentrations; however, when data were pooled from both groups who received vitamin C, the increases were significant. CONCLUSION: Vitamin E supplementation of young smokers was effective in reducing Cu-catalyzed LDL oxidizability; however, vitamin E and/or C supplementation showed few significant effects on the more physiologically relevant PMN function. This casts doubt on the ability of antioxidant supplementation to reduce oxidative stress in smokers in vivo. Therefore, smoking cessation remains the only means by which young smokers can prevent premature coronary heart disease.     

Protective activity of tomato products on <Emphasis Type="Italic">in vivo</Emphasis> markers of lipid oxidation

Summary.Background: It has been suggested that regular consumption of tomato products improves antioxidant defenses due to their endogenous antioxidant compounds, notably lycopene.Aim of the study: We evaluated the effects of tomato consumption on parameters of lipid oxidation in healthy human volunteers.Methods: Twelve females (enrolled at T-7), after a one-week of carotenoid-poor diet (T0), were instructed to supplement the same diet with different tomato products (raw, sauce, and paste), thereby providing approximately eight mg lycopene/day for three weeks (T21). Blood samples were periodically collected in order to evaluate plasma carotenoid concentrations, plasma antioxidant capacity, and susceptibility of LDL to metal ion-induced oxidation. Furthermore, 8-iso-PGF₂, a marker of in vivo oxidative stress, was analyzed in the 24-hour urine.Results: Carotenoid concentrations decreased significantly during the carotenoid-poor diet (P < 0.05), while lycopene concentrations increased significantly after tomato consumption (P < 0.001). The antioxidant capacity of plasma did not vary during the study. Conversely, LDL oxidizability decreased after tomato consumption, as demonstrated by a shortening of the lag phase (P < 0.001). This parameter was significantly correlated with lycopene concentration (r = 0.36, P < 0.05). The excretion of 8-iso-PGF₂ in urine was also significantly lower (–53%, P < 0.05 compared with T0) after tomato supplementation.Conclusions: These results further support a role for tomato products in the prevention of lipid peroxidation, a risk factor of atherosclerosis and cardiovascular disease.     

Flavonoids from almond skins are bioavailable and act synergistically with vitamins C and E to enhance hamster and human LDL resistance to oxidation

Consumption of tree nuts such as almonds has been associated with a reduced risk of coronary heart disease. Flavonoids, found predominantly in the skin of almonds, may contribute to their putative health benefit, but their bioactivity and bioavailability have not previously been studied. Almond skin flavonoids (ASF) were extracted with HCl:H2O:methanol (1:19:80) and their content of catechins and flavonols identified by HPLC with electrochemical detection. ASF bioactivity was assessed in vitro by their capacity to increase the resistance of human LDL to oxidation induced by 10 micromol/L Cu2+. ASF from 0.18 to 1.44 mumol gallic acid equivalent (GAE)/L increased the lag time to LDL oxidation in a dose-dependent manner (P < or = 0.0001). Combining ASF with vitamin E or ascorbic acid extended the lag time >200% of the expected additive value (P < or = 0.05). The bioavailability and in vivo antioxidant activity of 40 micromol ASF were examined in BioF1B hamsters. Peak plasma concentrations of catechin, epicatechin, and flavonols (quercetin, kaempferol, and isorhamnetin) occurred at 60, 120, and 180 min, respectively. The concentration of isorhamnetin was significantly elevated in liver at 180 min. Absorbed ASF enhanced the ex vivo resistance of hamster LDL collected at 60 min to oxidation by 18.0% (P = 0.028), and the in vitro addition of 5.5 micromol/L vitamin E synergistically extended the lag time of the 60-min sample by 52.5% (P < or = 0.05). Thus, ASF possess antioxidant capacity in vitro; they are bioavailable and act in synergy with vitamins C and E to protect LDL against oxidation in hamsters.