不同水平维生素E和β—胡萝卜素对Cu^2＋氧化修饰低密度脂蛋白的影响

研究不同浓度的维生素Ｅ（ＶＥ）和β－胡萝卜素（βＣ）对Ｃｕ＾２＋诱导的氧化修饰低密度脂蛋白（ＬＤＬ）作用的影响,通过测定硫代巴比妥酸反应物质（ＴＢＡＲＳ）、ＬＤＬ的电泳迁移率（Ｒｆ?以及荧光物质（Ｌｉｐｏｆｕｓｉｎ）扫描,反映ＬＤＬ的氧化修饰程度。结果表明：ＶＥ、βＣ均可减少ＴＢＡＲＳ的产生、减小ＬＤＬ的Ｒｆ,并且具有剂量－效应关系,随浓度增加,ＶＥ抑制作用加强而βＣ抑制作用减弱,而且ＶＥ对ＴＢＡ     

大豆异黄酮对低密度脂蛋白氧化修饰的抑制作用

为探讨大豆异黄酮 (SI)在体外及体内对低密度脂蛋白 (LDL)氧化修饰的作用特点及其与α 生育酚的异同 ,采用密度梯度超速离心法分离制备血清LDL后 ,建立了Cu2 + 诱导LDL氧化修饰反应模型 ,体外向模型中直接加入SI和α 生育酚后 ,通过监测反应体系中硫代巴比妥酸反应物质 (TBARS)和共轭双烯生成量的变化观察它们的作用。体内实验通过先补加SI于高脂饲料喂饲大鼠 ,再测定血中LDL对Cu2 + 诱导氧化的敏感性以反映SI的效果。结果表明 ,体外无论在启动LDL氧化反应前还是反应后加入SI,均显著降低体系中TBARS和共轭双烯的生成 ,并呈现剂量相关关系 ;仅在启动LDL氧化反应前加入α 生育酚显示良好的抑制效果 ,当启动LDL氧化反应后加入α 生育酚则未表现任何防护作用。在大鼠喂饲实验中 ,高脂饲料导致动物LDL对氧化修饰的敏感性增加 ,补加SI对此有明显的拮抗作用。可见 ,在体外SI是与α 生育酚作用有所区别的一类天然抗氧化剂 ,它在体外和体内均能显著抑制LDL的氧化修饰     

Retinol, alpha-tocopherol and carotenoids in diabetes.

OBJECTIVE: A case-control study was conducted to evaluate the effects of diabetes mellitus on serum levels of vitamin A, alpha-carotene, beta-carotene, alpha-tocopherol, serum and urine RBP. SUBJECTS: One hundred and seven patients with Type 2 diabetes mellitus (28-74 y) were recruited from those attending a primary health care clinic in King Khalid University Hospital in Riyadh City (Saudi Arabia). They were matched for age and sex with 143 healthy individuals. METHODS: Fasting blood samples and 10h urine collections were obtained from all subjects. Levels of vitamins and carotenoids in serum measured by high performance liquid chromatography (HPLC), and of retinol binding protein (RBP) in serum and urine by an enzyme-linked immunosorbent assay (ELISA). RESULTS: The mean serum concentrations of retinol, alpha-carotene, and alpha-tocopherol were similar in both groups after correction of lipid soluble vitamins for serum lipids levels. However, serum beta-carotene concentration was significantly higher in control subjects than diabetics (P = 0.002). Serum and urine RBP concentrations were significantly higher in diabetics than in controls (P = 0.0001). In normal subjects (but not diabetics) serum concentrations of retinol and RBP were higher in men than in women (P = 0.02, P = 0.0001 respectively). In both normal and diabetic subjects, serum levels of alpha-tocopherol (P = 0.007) and urine RBP (P = 0.005), were higher in men than women. Urinary excretion of RBP was significantly higher in diabetic patients with renal impairment than other diabetics or controls (P = 0.0001). There was a negative correlation between fasting blood glucose (FBG) concentration and serum beta-carotene (P = 0.008) in the total combined group and a positive correlation between FBG and urinary RBP/creatinine (P = 0.009) in diabetic patients. CONCLUSION: Serum beta-carotene concentration was significantly lower in diabetic patients than controls. Serum retinol concentration in patients with diabetes was normal, yet serum and urine RBP concentrations were significantly higher in diabetics than in controls.     

Beta-carotene supplementation increases antioxidant capacity of plasma in older women

The antioxidant effect of dietary beta-carotene supplementation on the peroxidation potential of plasma was investigated in a randomized double-blind, placebo-controlled study. Twelve healthy women (62-80 y) supplemented their usual daily diet with 90 mg of beta-carotene (n = 6) or placebo (n = 6) capsules for 3 wk. Plasma concentrations of beta-carotene, alpha- and gamma-tocopherol, ascorbate, urate, bilirubin and in vitro production of phosphatidylcholine hydroperoxides (PC-OOH) and utilization of plasma antioxidants in the presence of 50 mmol/L 2,2'-azobis (2-aminopropane) hydrochloride (AAPH), a free radical generator, at 37 degrees C were measured before and after dietary treatment. Plasma beta-carotene increased from 0.76 +/- 0.16 to 6.45 +/- 1.16 micromol/L (P < 0.05) in supplemented but not placebo-treated subjects. The plasma concentrations of other antioxidants did not change significantly in either group. beta-Carotene supplementation did not affect basal levels of plasma PC-OOH as measured by HPLC post-column chemiluminescence but did affect AAPH-induced production of PC-OOH. Before supplementation, the induction period of plasma PC-OOH production was 2.4 +/- 0.4 h, with levels reaching 5.39 +/- 1.50 micromol/L after 6 h of incubation. After supplementation, the induction period increased significantly to 4.2 +/- 0.4 h (P < 0.01), with a lower PC-OOH production of 2.16 +/- 0.90 micromol/L after 6 h (P < 0.05). In this system, plasma ascorbate concentrations were depleted first, followed by loss of bilirubin and alpha-tocopherol and then by the sequential loss of gamma-tocopherol, urate and beta-carotene. These results indicate that beta-carotene supplementation increases the plasma antioxidant capacity of older women.     

Comparison of the antioxidant effects of Concord grape juice flavonoids alpha-tocopherol on markers of oxidative stress in healthy adults

BACKGROUND: Concord grape juice (CGJ) is a rich source of flavonoids, which have greater antioxidant efficacy in vitro than does alpha-tocopherol; however, the efficacies of flavonoids and alpha-tocopherol in vivo have not been compared. OBJECTIVE: We compared the in vivo antioxidant efficacy of CGJ with that of alpha-tocopherol in healthy adults. DESIGN: Subjects were randomly assigned to receive either 400 IU RRR-alpha-tocopherol/d (n = 17) or 10 mL CGJ. kg(-1). d(-1) (n = 15) for 2 wk. Serum oxygen radical absorbance capacity, plasma protein carbonyls, urinary F(2)-isoprostanes, and resistance of LDL to ex vivo oxidation were measured before and after supplementation as markers of antioxidant status and oxidative stress. RESULTS: After supplementation, plasma alpha-tocopherol increased 92% in subjects who received alpha-tocopherol (P < 0.001); plasma total and conjugated phenols increased 17% (P < 0.01) and 22% (P < 0.001), respectively, in subjects who received CGJ. There was a significant change in plasma triacylglycerols in both groups, but the concentrations were within the normal range. CGJ supplementation was associated with significantly higher triacylglycerols than was alpha-tocopherol supplementation. Both supplementation regimens significantly increased serum oxygen radical absorbance capacity (P < 0.001) and LDL lag time (P < 0.001) and significantly decreased the LDL oxidation rate (P < 0.01), with no significant difference in effectiveness. Protein carbonyl concentrations in native plasma decreased 20% after CGJ supplementation, which was a significantly different response than that after alpha-tocopherol supplementation (P < 0.05). CONCLUSIONS: In healthy adults, 10 mL CGJ. kg(-1). d(-1) increased serum antioxidant capacity and protected LDL against oxidation to an extent similar to that obtained with 400 IU alpha-tocopherol/d but decreased native plasma protein oxidation significantly more than did alpha-tocopherol. CGJ flavonoids are potent antioxidants that may protect against oxidative stress and reduce the risk of free radical damage and chronic diseases.     

Efficacy of a complex multivitamin supplement

OBJECTIVES: Multivitamin supplements are often sold to consumers with the claim that supplements modify risk factors associated with disease. Because few products are validated scientifically, we examined the effects of a 24-ingredient multivitamin formula in an open-label pilot investigation. METHODS: We examined 150 subjects for specific endpoints including blood concentrations of selected vitamins, homocysteine, lipids, and low-density lipoprotein (LDL) oxidation indices at baseline and at 12 and 24 wk. RESULTS: One hundred forty-one subjects were successfully assayed for and showed significant time effects for homocysteine and vitamin B6 (as pyridoxal-5'-phosphate), B12, and folic acid concentrations during treatment (P < 0.0001). Vitamin B6, B12, and folic acid concentrations were significantly elevated at weeks 12 and 24 (P < 0.05). Homocysteine concentration decreased significantly during the same periods (7.9 +/- 2.4 versus 6.7 +/- 1.7 versus 6.7 +/- 1.9 mM/mL; P < 0.05). There were correlations relating homocysteine to vitamins B6 (P = 0.001, r(2) = 0.03), B12 (P < 0.001, r(2) = 0.09), and folic acid (P = 0.001, r(2) = 0.10). Significant time effects were noted for 121 subjects successfully assayed for vitamin C, E, beta-carotene, LDL oxidation rate, and LDL lag time (P < 0.0001). Post hoc assessment showed elevations in vitamin C, E, and beta-carotene concentrations at 12 and 24 wk (P < 0.05). LDL oxidation lag time at baseline (57.5 +/- 13.9 min) increased by 12 wk (63.5 +/- 19.0 min; P < 0.05) and 24 wk (63.8 +/- 16.3 min; P < 0.05). LDL oxidation rate at baseline (9.7 +/- 3.0 microM x min(-1). g(-1)) was reduced at 12 wk (7.1 +/- 2.5 microM x min(-1) x g(-1); P < 0.05) and 24 wk (6.0 +/- 2.0 microM x min(-1) x g(-1); P < 0.05). Only vitamin C was significantly correlated with LDL oxidation rate (P = 0.05, r(2) = 0.003). CONCLUSIONS: A multi-ingredient vitamin formula with antioxidant properties has measurable effects on homocysteine and LDL oxidation indices.     

Multivitamin-mineral supplementation prevents lipid peroxidation during "the Marathon des Sables"

OBJECTIVE: We investigated the effect of a moderate mutivitamin and mineral supplementation containing mainly vitamin C (150.0 mg.day(-1)), vitamin E (24.0 mg.day(-1)) and beta-carotene (4.8 mg.day(-1)) prior to and during an extreme running competition -the Marathon des Sables (MDS)- that consisted of six long races in the desert. METHODS: Seventeen athletes participated in our double blind, placebo-controlled study. Blood samples were collected prior to the supplementation i.e. three weeks before the competition (D-21), two days prior to the MDS (D-2), after the third race (D3) and at the end of the competition (D7). Erythrocyte antioxidant enzyme activity (glutathione peroxidase (GPx), superoxide dismutase (SOD)), erythrocyte glutathione level (GSH), plasma non-enzymatic antioxidant status (uric acid, vitamin C, alpha-tocopherol, retinol, beta-carotene), markers of plasma lipid peroxidation (thiobarbituric reactive substances (TBARS)), reactive carbonyl derivatives (RCD) and membrane damage (creatine kinase and lactate dehydrogenase activities) were measured. RESULTS: In both groups, GSH levels, uric acid levels and membrane damage significantly increased during the competition while SOD activity significantly decreased. In Supplemented group, plasma alpha-tocopherol, beta-carotene and retinol levels significantly increased after three weeks of supplementing. In contrast to Placebo group, alpha-tocopherol, vitamin C and retinol levels were significantly affected by the competition in Supplemented group. Moreover, no increase in TBARS was observed in Supplemented group during the competition, whereas TBARS significantly increased at D3 in the placebo group. CONCLUSION: The moderate multivitamin-mineral supplementation prevented the transient increase in TBARS levels during this extreme competition.     

Effects of tomato juice consumption on plasma and lipoprotein carotenoid concentrations and the susceptibility of low density lipoprotein to oxidative modification

Effects of tomato juice supplementation on the carotenoid concentration in lipoprotein fractions and the oxidative susceptibility of LDL were investigated in 31 healthy Japanese female students. These subjects were randomized to one of three treatment groups; Control, Low and High. The Control, Low and High groups consumed 480 g of a control drink, 160 g of tomato juice plus 320 g of the control drink, and 480 g of tomato juice, providing 0, 15 and 45 mg of lycopene, respectively, for one menstrual cycle. The ingestion of tomato juice, rich in lycopene but having little beta-carotene, increased both lycopene and beta-carotene. Sixty-nine percent of lycopene in plasma was distributed in the LDL fraction and 24% in the HDL fraction. In the Low group, the lycopene concentration increased 160% each in the VLDL+IDL, LDL and HDL fractions (p<0.01). In the High group, the lycopene concentration increased 270% each in the VLDL+IDL and LDL fractions, and 330% in the HDL fraction (p<0.01). Beta-carotene also increased 120% and 180% in LDL fractions of the Low and the High groups, respectively. Despite these carotenoid increases in LDL, the lag time before oxidation was not prolonged as compared with that of the Control group. The propagation rate decreased significantly after consumption in the High group. Multiple regression analysis showed a positive correlation between lag time changes and changes in the alpha-tocopherol concentration per triglyceride in LDL, and a negative correlation between propagation rate changes and changes in the lycopene concentration per phospholipid in LDL. These data suggest that alpha-tocopherol is a major determinant in protecting LDL from oxidation, while lycopene from tomato juice supplementaion may contribute to protect phospholipid in LDI, from oxidation. Thus, oral intake of lycopene might be beneficial for ameliorating atherosclerosis.     

Vitamin C inhibits lipid oxidation in human HDL

HDL are susceptible to oxidation, which affects their cardioprotective properties. Although several studies have reported inhibition of HDL oxidation by vitamin E, none has determined the potential protective effect of vitamin C, another important blood antioxidant. We investigated whether vitamin C protects HDL from oxidation by incubating HDL (0.2 g of protein/L) at 37 degrees C with cupric (Cu2+) ions (10 micromol/L) in the absence (control) or presence of vitamin C (20-200 micromol/L). In the absence of vitamin C, lipid oxidation in HDL began immediately and proceeded rapidly. Cholesteryl linoleate declined to a minimum, whereas lipid oxidation products (lipid dienes and TBARS) increased to near-maximal levels within 1 h. Vitamin C (50-200 micromol/L) retarded initiation of lipid oxidation for at least 4 h under the same conditions. The ability of vitamin C to preserve the cardioprotective antioxidant function of HDL was also assessed. HDL (0.5 g of protein/L) preincubated with Cu2+ (10 micromol/L) for 2 h in the absence of vitamin C lost antioxidant activity (45.4 +/- 6.2% inhibition of LDL oxidation compared with 93.2 +/- 3.6% for native HDL, P < 0.05). The addition of vitamin C (50-200 micromol/L) during preincubation of HDL with Cu2+, however, resulted in no significant loss of HDL antioxidant activity (77.3 +/- 0.3 to 89.8 +/- 5.4% inhibition of LDL oxidation, P > 0.05 compared with native HDL). Our results demonstrate that vitamin C inhibits lipid oxidation in HDL and preserves the antioxidant activity associated with this lipoprotein fraction.     

Daily intake of a formulated tomato drink affects carotenoid plasma and lymphocyte concentrations and improves cellular antioxidant protection

The salutary characteristics of the tomato are normally related to its content of carotenoids, especially lycopene, and other antioxidants. Our purpose was to verify whether the daily intake of a beverage prototype called Lyc-o-Mato((R)) containing a natural tomato extract (Lyc-o-Mato((R)) oleoresin 6 %) was able to modify plasma and lymphocyte carotenoid concentrations, particularly those of lycopene, phytoene, phytofluene and beta-carotene, and to evaluate whether this intake was sufficient to improve protection against DNA damage in lymphocytes. In a double-blind, cross-over study, twenty-six healthy subjects consumed 250 ml of the drink daily, providing about 6 mg lycopene, 4 mg phytoene, 3 mg phytofluene, 1 mg beta-carotene and 1.8 mg alpha-tocopherol, or a placebo drink. Treatments were separated by a wash-out period. Plasma and lymphocyte carotenoid and alpha-tocopherol concentrations were determined by HPLC, and DNA damage by the comet assay. After 26 d of consumption of the drink, plasma carotenoid levels increased significantly: concentrations of lycopene were 1.7-fold higher (P<0.0001); of phytofluene were 1.6-fold higher (P<0.0001); of phytoene were doubled (P<0.0005); of beta-carotene were 1.3-fold higher (P<0.05). Lymphocyte carotenoid concentrations also increased significantly: that of lycopene doubled (P<0.001); that of phytofluene was 1.8-fold higher (P<0.005); that of phytoene was 2.6-fold higher (P<0.005); that of beta-carotene was 1.5-fold higher (P<0.01). In contrast, the alpha-tocopherol concentration remained nearly constant. The intake of the tomato drink significantly reduced (by about 42 %) DNA damage (P<0.0001) in lymphocytes subjected to oxidative stress. In conclusion, the present study supports the fact that a low intake of carotenoids from tomato products improves cell antioxidant protection.     

HDL oxidability and its protective effect against LDL oxidation in Type 2 diabetic patients

Low density lipoprotein (LDL) oxidation is a crucial step in the atherosclerotic process. High density lipoprotein (HDL)-associated enzymes such as paraoxonase could exert a protective effect on LDL oxidation in the arterial wall, an effect which could be impaired in Type 2 diabetes mellitus (T2DM). We studied copper-induced oxidation in LDL and HDL isolated from 17 T2DM patients with fair glycaemic control and HDL-cholesterol within normal range and 17 healthy normolipidaemic control subjects. To evaluate the effect of HDL on LDL oxidation in diabetic and control subjects, we assessed copper-induced oxidation in HDL/LDL mixtures, with each lipoprotein isolated from the same subject. Relationships with HDL chemical composition, alpha-tocopherol content and serum paraoxonase activity were investigated. Oxidation was promoted by lipoprotein incubation with copper and then thiobarbituric acid reactive substances (TBARS), conjugated diene production and electrophoretic mobility in agarose gel were measured. In T2DM subjects HDL oxidation was higher than in controls. However, HDL from diabetics was as effective as control HDL to inhibit LDL oxidation. Neither HDL chemical composition nor serum paraoxonase activity showed any difference as compared to control subjects. In contrast, HDL from T2DM subjects showed a higher alpha-tocopherol content which positively correlated with HDL oxidability. Paraoxonase activity positively and strongly correlated with HDL inhibitory effect on LDL oxidation in patients and controls belonging to the heterozygous activity phenotype. Besides, LDL oxidability showed no differences between patients and controls. These results suggest that fairly-controlled T2DM patients with HDL-cholesterol levels within normal range show: 1) normal HDL ability to inhibit LDL oxidation related to normal paraoxonase activity; 2) higher HDL oxidability in spite of its high alpha-tocopherol content, which could favour tocopherol-mediated peroxidation and 3) normal LDL oxidability possibly due to the lack of significant lipoprotein structural alterations.     

Extreme running competition decreases blood antioxidant defense capacity

OBJECTIVE: We tested whether an extreme running competition ("Marathon of Sands") might alter the blood's enzymatic and non-enzymatic antioxidant status in 6 well-trained athletes. METHODS: The Marathon of Sands is a competition consisting of six long duration races in the desert in which the athletes carry their own food. Blood samples were collected from an antecubital vein while the athletes were at rest before the competition and then again 72 hours after. Erythrocyte antioxidant enzyme activity (glutathione peroxidase, superoxide dismutase), erythrocyte glutathione level, plasma non-enzymatic status (vitamin C, alpha-tocopherol, retinol, beta-carotene and carotenoids) and plasma lipid peroxidation marker (TBARS) were measured. RESULTS: The Marathon of Sands induced a significant alteration of the blood antioxidant defense capacity. Indeed, 72 hours after the race, significant decreases were recorded in erythrocyte superoxide dismutase activity and in plasma concentrations of retinol, beta-carotene and other carotenoids. These changes were associated with a concomitant increase in erythrocyte glutathione and in plasma TBARS levels. CONCLUSION: This study indicated that such extreme competition induced an imbalance between oxidant and antioxidant protection.     

Serum beta-carotene, lycopene and alpha-tocopherol levels of healthy people in northeast Thailand

Human serum contains many different antioxidants which may be important in the maintenance of antioxidant status. beta-carotene and lycopene are carotenoids with potent antioxidant activity. Carotenoids intake probably protects against cancers and may affect the risk of several chronic conditions. alpha-tocopherol is well known for its function as antioxidant and in reduction of heart disease and cancer risk. We aimed to establish baseline values for serum beta-carotene, lycopene and alpha-tocopherol concentrations in healthy northeast Thais. Fasting serum beta-carotene, lycopene and alpha-tocopherol levels from 294 subjects aged 23-75 years old in northeast Thailand were determined by high performance liquid chromatography (HPLC). The mean serum beta-carotene, lycopene and alpha-tocopherol levels were 0.53 +/- 0.32 micromol/L, 0.57 +/- 0.37 micromol/L, and 26.64 +/- 14.85 micromol/L respectively. Serum beta-carotene and lycopene levels in females (N = 118) were significantly higher than the value for males (N = 176), ie 0.60 +/- 0.31 micromol/L versus 0.48 +/- 0.32 micromol/L (p = 0.002) for beta-carotene and 0.74 +/- 0.38 micromol/L versus 0.46 +/- 0.33 micromol/L (p<0.001) for lycopene whereas alpha-tocopherol level in males (28.60 +/- 14.34 micromol/L) was significantly higher than in females (23.72 +/- 15.16 micromol/L) (p = 0.006). beta-carotene level was positively correlated with alpha-tocopherol (r = 0.22, p<0.001) and lycopene levels (r = 0.63, p<0.001). The results from this study give the baseline data of serum beta-carotene, lycopene and alpha-tocopherol levels in healthy northeast Thai population and also suggest future study on the relationship of dietary intake.     

No antioxidant effect of combined HRT on LDL oxidizability and oxidative stress biomarkers in treated post-menopausal women

OBJECTIVE: To compare oxidative stress and LDL oxidizability in postmenopausal women with and without HRT. METHODS: In a cross sectional study, two groups of women, with or without combined per os HRT (1.5-2 mg estrogen associated with 10 mg dydrogesteron), were age and duration of menopause matched. Women were recruited after medical examination at LBSO (Oxidative Stress Laboratory), Joseph Fourier University, Grenoble, and Department of Gynecology, Grenoble University Hospital, France. Main outcome measures included determination of lipid profile and oxidative stress biomarkers (TBARS, LDL oxidizability, autoantibodies against oxidized-LDL). Measurement of circulating levels of vitamin C, E, beta-carotene, lycopene and total antioxidant plasma capacity. RESULTS: HRT led to decreased plasma total and LDL cholesterol (p < 0.05), but did not affect oxidizability and oxidation of LDL. Circulating levels of antioxidant vitamins (beta-carotene, vitamin C, vitamin E/triglycerides) and total antioxidant capacity of plasma and lipid peroxidation, assessed by plasma TBARs, were not different from controls in postmenopausal women receiving HRT. CONCLUSION: This study suggests that even if combined HRT modifies the blood lipid profile, it does not appear to influence oxidative status.     

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.     

Walnut polyphenolics inhibit in vitro human plasma and LDL oxidation.

Recent epidemiologic studies have associated nut consumption with a reduced incidence of cardiovascular mortality. However, little is known about the contribution of nut polyphenols to antioxidant and cardiovascular protection. In this investigation, polyphenol-rich extracts from English walnuts (Juglans regia) were studied and compared with ellagic acid for their ability to inhibit in vitro plasma and LDL oxidation, as well as their effects on LDL alpha-tocopherol during oxidative stress. In addition, the Trolox equivalent antioxidant activity (TEAC) was determined and liquid chromatography electrospray detection mass spectrometry (LC-ELSD/MS) analyses of the walnut extracts were performed. 2,2'-Azobis'(2-amidino propane) hydrochloride (AAPH)-induced LDL oxidation was significantly inhibited by 87 and 38% with the highest concentration (1.0 micromol/L) of ellagic acid and walnut extract, respectively. In addition, copper-mediated LDL oxidation was inhibited by 14 and 84% in the presence of ellagic acid and walnut extract, respectively, with a modest, significant LDL alpha-tocopherol sparing effect observed. Plasma thiobarbituric acid reacting substance (TBARS) formation was significantly inhibited by walnut extracts and ellagic acid in a dose-dependent manner, and the extracts exhibited a TEAC value greater than that of alpha-tocopherol. LC-ELSD/MS analysis of the walnut extracts identified ellagic acid monomers, polymeric ellagitannins and other phenolics, principally nonflavonoid compounds. These results demonstrate that walnut polyphenolics are effective inhibitors of in vitro plasma and LDL oxidation. The polyphenolic content of walnuts should be considered when evaluating their antiatherogenic potential.     

No significant effects of lutein, lycopene or beta-carotene supplementation on biological markers of oxidative stress and LDL oxidizability in healthy adult subjects.

OBJECTIVE: The objective of this study was to determine the effect of individual carotenoid supplementation on biochemical indices of oxidative status in apparently healthy adult males. METHODS:The study was a placebo controlled single blind study. Healthy male volunteers (n= 175) were assigned to four groups. They received daily supplements of beta-carotene (15 mg), lutein (15 mg), lycopene (15 mg) and placebo for three months. The effects of the supplementation on antioxidant status were monitored by plasma carotenoid, vitamin C and A levels, glutathione (GSH and GSSG) concentrations, protein SH groups. erythrocyte antioxidant enzyme activities (Cu-Zn SOD, Se-GSH-Px) and susceptibility of LDL to copper-induced oxidation. RESULTS: beta-carotene, lycopene and lutein supplementation led to significant plasma and LDL increases in each of these carotenoids, without modifications of other carotenoid levels in plasma or in LDL. The supplementation failed to enhance the resistance of LDL to oxidation or to modify the LDL polyunsaturated/ saturated fatty acid ratio. Vitamin C, GSH, protein SH groups and antioxidant metalloenzyme activities were also unchanged. CONCLUSION: We did not observe beneficial or adverse effects of lutein, lycopene or beta-carotene supplementation on biomarkers of oxidative stress. In apparently healthy subjects, carotenoid supplementation does not lead to significantly measurable improvement in antioxidant defenses.     

Do iron and vitamin C co-supplementation influence platelet function or LDL oxidizability in healthy volunteers?

OBJECTIVE: To examine the effect of co-supplementation with iron and vitamin C on antioxidant status, platelet function and low density lipoprotein oxidation in normal healthy volunteers. DESIGN: The study was carried out with two groups of 20 subjects each acting as their own control, comparing presupplemention with postsupplemention. One group was supplemented with iron and the RDA level of vitamin C and the second group with iron and 260 mg/d vitamin C. SETTING: The International Antioxidant Research Centre, The Guy's, King's College and St Thomas's School of Biomedical Science, Guy's Campus, London. SUBJECTS: Forty normal healthy volunteers, recruited from the staff of the Medical School and Hospital in which two volunteers withdrew during the study. INTERVENTIONS: Subjects in both studies were randomly assigned to one of two groups (5 males and 5 females group) and received supplements containing iron (14 mg/d) and either 60 mg/d (Group A) or 260 mg/d (Group B) vitamin C for 12 wk. Blood samples were taken at 6 wk and 12 wk, and prior to supplementation and analysed for iron and antioxidant status (transferrin bound iron, vitamin C and E, and beta-carotene levels) in both studies. Samples from the first study were analysed for the susceptibility of LDL isolated from plasma to Cu2+-induced oxidation and samples from the second for platelet function. RESULTS: Transferrin-bound iron was significantly increased (P < 0.05) at 12 wk, in Group A subjects (from 14.9+/-5.3 micromol/1 to 19.5+/-2.3 micromol/l; mean+/-s.d.; n=19), whereas those in Group B showed a significant increase (P < 0.05) after 6 wk (from 15.8+/-4.5 micromol/l to 20.4+/-6.6 micromol/l; n = 19) which decreased at 12 wk (16.3+/-5.0 micromol/l). Plasma total ascorbate significantly increased from an initial level of 59.3+/-21.3 micromol/l to 87.6+/-29.0 micromol/l after 6 wk and 81.7+/-11.4 micromol/l after 12 wk following the Group B supplementation, but only after 12 wk in Group A (from 64.0+/-24.8 micromol/l to 77.2+/-13.2 micromol/l). Plasma alpha-tocopherol concentrations were significantly increased after 6 wk and 12 wk with both levels of supplementation (from 24.2+/-5.71 micromol/l Group A and 23.4+/-5.3 micromol/l Group B to 26.3+/-5.5 micromol/l and 25.71+/-4.7 micromol/1 respectively at 12wk). The mean lag phase to oxidation of low density lipoprotein (LDL) was significantly increased in subjects in Group B after 12 wk ingestion of iron and 260 mg vitamin C (from 80.0+/-14.8 min to 97.2+/-16.9 min; n = 9). Platelet sensitivity to ADP-induced aggregation was significantly decreased (P < 0.05) by 12 wk in Group A (from EC50 2.3 < or = 1.3 microM to 3.7+/-2.2 microM; n = 10), whereas those receiving higher vitamin C showed a significant decrease (P < 0.05; from EC50 1.9+/-0.6 microM to 3.1+/-1.8 microM) after 6wk which subsequently increased towards presupplemental levels (2.6+/-1.6 microM). Platelets from the latter subjects showed a significant reduction in ADP-induced ATP secretion at both 6wk and 12 wk. CONCLUSION: The results show modest beneficial effects on LDL oxidation and platelet function following supplementation with iron and vitamin C. No evidence for pro-oxidant effects was observed.     

Relationships between different types of fruit and vegetable consumption and serum concentrations of antioxidant vitamins

Increased fruit and vegetable consumption has become a health priority in many countries. Therefore, data investigating the influence of different types of fruits and vegetables on serum antioxidant levels would be useful. The objective of the study was to assess the relationship between fruit and vegetable consumption and vitamin serum antioxidant concentrations. Specific fruit and vegetable groups are evaluated. A total of 3521 subjects (1487 men and 2034 women), aged 35-60 years, participating in the SU.VI.MAX cohort were included in this study. Blood samples of participants were analysed for beta-carotene, vitamin C and alpha-tocopherol. Each subject had completed at least six dietary records during the first 2 years of the study. It was found that women had higher mean beta-carotene and vitamin C serum concentrations than men, but lower alpha-tocopherol serum concentrations. Serum beta-carotene and vitamin C concentrations were positively correlated with consumption of both fruit and vegetables, as well as with most of the fruit and vegetable groups tested. These relationships persisted after adjustment for confounding factors. Regression analysis showed a linear dose-response relationship. Root vegetables and citrus fruits were particularly associated with beta-carotene serum status as were citrus fruits for vitamin C. Fruit and vegetable consumption was either not or weakly associated with alpha-tocopherol serum concentrations. These results describe antioxidant serum concentrations according to fruit and vegetable consumption in a large sample and support the findings of previous studies involving a more limited number of subjects.     

beta-Carotene and alpha-tocopherol concentration and antioxidant status in buccal mucosal cells and plasma after oral supplementation

The uptake of alpha-tocopherol and beta-carotene and their antioxidative effect in plasma and buccal mucosal cells after oral application in twelve subjects is demonstrated in our study. The effect on the antioxidative status was evaluated using a modified thiobarbituric acid-reactive substance (TBARS) method. As expected, the supplement of 134.2 mg alpha-tocopherol/d and 25 mg beta-carotene/d for 7 d resulted in a significant increase of alpha-tocopherol and beta-carotene concentration in plasma (P<0.05). In buccal mucosal cells, the concentration of beta-carotene increased after supplementation (P<0.05), whereas the concentration of alpha-tocopherol remained constant. A decrease in TBARS (P<0.05) was found in buccal mucosal cells but not in plasma. In conclusion, an uptake of the supplemented antioxidants was detected in plasma and in buccal mucosal cells. There was significant change in beta-carotene concentration and oxidative stress as measured using a modified TBARS test in buccal mucosal cells, but not in the plasma.