Relationships among oxidation of low-density lipoprotein, antioxidant protection, and atherosclerosis

The role of paraoxonase 1 in regulating high-density lipoprotein functionality during aging

Pharmacological interventions to increase the concentration of high-density lipoprotein (HDL) have led to disappointing results and have contributed to the emergence of the concept of HDL functionality. The anti-atherogenic activity of HDLs can be explained by their functionality or quality. The capacity of HDLs to maintain cellular cholesterol homeostasis and to transport cholesterol from peripheral cells to the liver for elimination is one of their principal anti-atherogenic activities. However, HDLs possess several other attributes that contribute to their protective effect against cardiovascular diseases. HDL functionality is regulated by various proteins and lipids making up HDL particles. However, several studies investigated the role of paraoxonase 1 (PON1) and suggest a significant role of this protein in the regulation of the functionality of HDLs. Moreover, research on PON1 attracted much interest following several studies indicating that it is involved in cardiovascular protection. However, the mechanisms by which PON1 exerts these effects remain to be elucidated.

High prevalence of cardiovascular risk factors in children and adolescents with Williams-Beuren syndrome

Background

A high incidence of cardiovascular (CV) risk factors has been reported in adults with Williams-Beuren syndrome (WS). However, the prevalence of these factors in children and adolescents with WS is unknown. Therefore, the purpose of this study was to evaluate the prevalence of CV risk factors in these patients.

Methods

Thirty-two WS patients aged <18 years were enrolled in the study. Oxidized low-density lipoprotein levels (n = 32), oral glucose tolerance test results (n = 20), plasma renin and aldosterone levels (n = 31), 24-h ambulatory blood pressure (ABP; n = 24), carotid artery intima-media thickness (IMT; n = 15), and brachial artery flow-mediated dilatation (FMD; n = 15) were measured and analyzed.

Results

The lipid profile revealed hypercholesterolemia in 22 % and elevated oxidized low-density lipoprotein levels in 94 % of the patients. Glucose metabolism abnormalities were found in 70 % of the patients. Insulin resistance was observed in 40 % of the patients. High plasma renin and aldosterone levels were detected in 45 and 39 % of the patients, respectively. A mean systolic blood pressure above the 90th percentile was noted in 29 % of patients. High IMT (>0.65 mm) and low FMD (<9 %) were detected in 80 and 73 % of patients, respectively.

Conclusion

In patients with WS, CV risk factors are frequently present from childhood. In children with WS, screening tests for the early detection of CV risk factors and long-term follow-up are required to determine whether long-term exposure to these factors increases the risk for CV events in adulthood.

Effect of Ascorbate on Acrolein Modification of Very Low Density Lipoprotein and Uptake of Oxidized Apolipoprotein E by Hepatocytes

Acrolein modification of apolipoprotein (apo) E in human very low density lipoprotein (VLDL) was suppressed by ascorbate. Acrolein-modified apoE in VLDL was not taken up by human hepatoma cell whereas unmodified apoE in the presence of ascorbate was taken up. These results suggest that ascorbate can play an important role in maintaining proper lipoprotein metabolism by the antioxidant effect.

The blackberry fruit: a review on its composition and chemistry, metabolism and bioavailability, and health benefits

Blackberry (Rubus sp.) fruit contains high levels of anthocyanins and other phenolic compounds, mainly flavonols and ellagitannins, which contribute to its high antioxidant capacity and other biological activities. Blackberry phenolic composition and concentrations are known to be influenced by genetics, growing conditions, and maturation. Despite the current knowledge of their chemistry, research specific to blackberry phenolic compounds' health benefits, metabolism, bioavailability, and mechanism by which they confer health benefits is scarce. Blackberry phenolic compounds have protective effects on age-related neurodegenerative diseases and bone loss in vivo and can inhibit low-density lipoprotein and liposomal oxidation in vitro. Blackberry extracts have also exerted antimutagenic effects in vitro and in vivo by modifying cell signaling pathways and suppressing tumor promotion factors. However, the antiobesity, antidiabetic, antimicrobial, and anti-inflammatory properties of blackberry phenolic compounds need investigation. Similarly, studies that elucidate the in vivo physiologically effective concentrations of blackberry phenolic compounds are necessary.

Association between bipolar I disorder and the L55M and Q192R polymorphisms of the paraoxonase 1 (PON1) gene

BACKGROUND

The purpose of this work was to study the association between the PON1 L55M and Q192R polymorphisms and bipolar I disorder in Tunisian patients and to explore their relation to the sociodemographic, clinical and therapeutic characteristics of this disease.

PATIENTS AND METHODS

Our study included 109 patients with bipolar I disorder and 110 controls aged 39.4±11.8 and 37.3±9.2 years, respectively. L55M and Q192R of the PON1 gene polymorphisms were determined by multiplex polymerase chain reaction.

RESULTS

Significant difference was detected in the distribution of the genotype frequencies of L55M and Q192R polymorphisms (χ²=6.32, df=2, p=0.04; χ²=10.15, df=2, p=0.006 respectively) between patients and controls. We noted significant association between bipolar I disorder and QR and RR genotypes (OR 2.06, CI 95% 1.10-3.84, p=0.02; OR 1.72, CI 95% 1.07-2.75, p=0.02 respectively) and between this disease and LM and MM genotypes (OR 2.22, CI 95% 1.19-4.15, p=0.012; OR 3.04, CI 95% 1.60-5.77, p=0.01 respectively). There were no significant differences in gender, age at onset, illness episode and treatment among all genotypes. However, Q192R polymorphism was significantly associated with age and patients with RR genotype were the youngest.

CONCLUSION

Bipolar I disorder was significantly associated with L55M and Q192R polymorphisms, suggesting that these polymorphisms may play a role for development of bipolar I disorder. There was no significant association between the clinical and therapeutic characteristics of this population and these polymorphisms. Further studies are required to clarify the implication of these polymorphisms in the pathophysiology of bipolar I disorder.

Fast repair of protein radicals by urate

The repair of tryptophan and tyrosine radicals in proteins by urate was studied by pulse radiolysis. In chymotrypsin, urate repairs tryptophan radicals efficiently with a rate constant of 2.7 × 10(8)M(-1)s(-1), ca. 14 times higher than the rate constant derived for N-acetyltryptophan amide, 1.9 × 10(7)M(-1)s(-1). In contrast, no repair of tryptophan radicals was observed in pepsin, which indicates a rate constant smaller than 6 × 10(7)M(-1)s(-1). Urate repairs tyrosine radicals in pepsin with a rate constant of 3 × 10(8)M(-1)s(-1)-ca. 12 times smaller than the rate constant reported for free tyrosine-but not in chymotrypsin, which implies an upper limit of 1 × 10(6)M(-1)s(-1) for the corresponding rate constant. Intra- and intermolecular electron transfer from tyrosine residues to tryptophan radicals is observed in both proteins, however, to different extents and with different rate constants. Urate inhibits electron transfer in chymotrypsin but not in pepsin. Our results suggest that urate repairs the first step on the long path to protein modification and prevents damage in vivo. It may prove to be a very important repair agent in tissue compartments where its concentration is higher than that of ascorbate. The product of such repair, the urate radical, can be reduced by ascorbate. Loss of ascorbate is then expected to be the net result, whereas urate is conserved.

Raman spectroscopy for scavenging activity assay using nanoshell precursor nanocomposites as SERSprobes

In this work, we have developed a novel SERS-based approach to detect hydrogen peroxide (H2O2) scavenging activity by using gold nanoshell precursor nanocomposites (SiO2/GNPs) as nanoprobes. H2O2 can reduce AuCl4- to Au0 and enlarge the gold nanoparticles (GNPs) that attached on the surface of SiO2. As the concentration of H2O2 increases, the surface coverage of resultant gold on silica cores increases accordingly until continuous gold nanoshells (GNSs) are formed. During the growth process, there is a strong correlation between the SERS-activity of the GNSs and the amount of H2O2 that is used as reductant. When H2O2 reaches 250 μM, the resultant GNSs show the highest SERS-activity. H2O2 can be scavenged by antioxidants such as tannic acid and L-apple acid. Their H2O2 scavenging activities were determined by restraining the H2O2-mediated (250 μM) growth of SiO2/GNPs. The decrease of the SERS-activity was proportional to the H2O2 scavenging activity of the antioxidant. The results showed that tannic acid had a much higher H2O2 scavenging activity than that of L-apple acid.

Analysis of oxidative stress biomarkers using a simultaneous competitive/non-competitive micromosaic immunoassay

Immunoassays represent a core workhorse methodology for many applications ranging from clinical diagnostics to environmental monitoring. In traditional formats such as the enzyme linked immunosorbent assay (ELISA), analytes are measured singly or in small sets. As more biomarkers are identified for disease states, there is a need to develop methods that can measure multiple markers simultaneously. Immunoaffinity arrays are one such chemistry that can achieve multi-marker screening. Most arrays are performed in either competitive or non-competitive formats, where the former are used predominantly for small molecules and the later for macromolecules. To date, ELISA and immunoaffinity array methods have relied exclusively on one of these formats and not the other. Here an immunoaffinity array method capable of performing simultaneous competitive and non-competitive analysis generated using micromosaic immunoassay techniques is introduced for the analysis of metabolites and proteins. In this report, three markers of oxidative stress were used as a model system. The method described here demonstrates the simultaneous analysis of 3-nitrotyrosine, by indirect competitive immunoassay while the enzymes catalase and superoxide dismutase are analyzed by non-competitive sandwich immunoassay. The method requires less than 1 microL sample and 45 min for completion. Logistic curve fits and LOD (limits of detection) statistical analysis of the binding results are presented and show good agreement with published data for these antibody-antigen systems.

Influence of apolipoprotein E genotype and dietary α-tocopherol on redox status and C-reactive protein levels in apolipoprotein E3 and E4 targeted replacement mice

The molecular basis of the positive association between apoE4 genotype and CVD remains unclear. There is directin vitroevidence indicating that apoE4 is a poorer antioxidant relative to the apoE3 isoform, with some indirectin vivoevidence also available. Therefore it was hypothesised that apoE4 carriers may benefit from α-tocopherol (α-Toc) supplementation. Targeted replacement mice expressing the human apoE3 and apoE4 were fed with a diet poor (0 mg/kg diet) or rich (200 mg/kg diet) in α-Toc for 12 weeks. Neither apoE genotype nor dietary α-Toc exerted any effects on the antioxidant defence system, including glutathione, catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase activities. In addition, no differences were observed in mitogen-induced lymphocyte proliferation. α-Toc concentrations were modestly higher in plasma and lower in tissues of apoE4 compared with apoE3 mice, with the greatest differences evident in the lung, suggesting that an apoE4 genotype may reduce α-Toc delivery to tissues. A tendency towards increased plasma F2-isoprostanes in apoE4 mice was observed, while liver thiobarbituric acid-reactive substances did not differ between apoE3 and apoE4 mice. In addition, C-reactive protein (CRP) concentrations were reduced in apoE4 mice indicating that this positive effect on CRP may in part negate the increased CVD risk associated with an apoE4 genotype.

Relationship Between Plasma Total Antioxidant Capacity and Thoracic Aortic Intima-Media Thickness

It is known that antioxidants have an important role in the prevention of coronary artery disease (CAD). Low total antioxidant capacity (TAC) is a risk factor for ischemic heart disease. However, no data are available concerning the relationship between TAC and severity of thoracic aortic atherosclerosis. This study using multiplane transesophageal echocardiography (TEE) examined the relationship between atherosclerotic thoracic aortic intima-media thickness (TAIMT) and TAC. Twenty-nine patients (17 male, 12 female; mean age 36 +/- 8 years) without a history of atherosclerotic cardiovascular disease referred for TEE were included. The patients with obesity, hypertension, diabetes, and CAD were excluded. The TAC was measured for each patient using a more recently developed method. TAIMT and grade of thoracic aortic atherosclerosis were evaluated in each patient by using TEE. Mean TAC level was 1.91 +/- 0.53 mmol Trolox equiv/l. There was a negative and significant correlation between the TAC levels and TAIMT and grade of thoracic aortic atherosclerosis (r = -0.799, P < 0.001 versus r = -0.827, P < 0.001, respectively). Multiple linear regression analysis showed that TAIMT was independently associated with TAC (beta = -0.734, P < 0.001). The mean values of TAC in grade I, II, and III were 2.23 +/- 0.31, 1.58 +/- 0.31, and 1.04 +/- 0.27 mmol Trolox equiv/l, respectively (ANOVA P < 0.001). This study indicates that the TAC is an independent variable for TAIMT and it has a potential for an independent variable for atherosclerotic lesions in the major arterial locations.

Effects of elderberry juice on fasting and postprandial serum lipids and low-density lipoprotein oxidation in healthy volunteers: a randomized, double-blind, placebo-controlled study

BACKGROUND

In a recent pilot study, the intake of elderberry juice resulted in a significant decrease in serum cholesterol concentrations and an increase in low-density lipoprotein (LDL) stability. This study was designed to verify the preliminary results.

OBJECTIVE

We investigated the impact of elderberry juice on cholesterol and triglyceride concentrations as well as antioxidant status in a cohort of young volunteers.

DESIGN

Study A: The randomized, placebo-controlled trial for studying the effect of anthocyanes on lipid and antioxidant status, 34 subjects took capsules with 400 mg spray-dried powder containing 10% anthocyanes t.i.d. equivalent to 5 ml elderberry juice for 2 weeks. A subgroup of 14 subjects continued for an additional week to test for resistance to oxidation of LDL. Study B: To investigate the short-term effects on serum lipid concentrations, six subjects took a single dose of 50 ml of elderberry juice (equivalent to 10 capsules) along with a high-fat breakfast.

RESULTS

In the placebo-controlled study, there was only a small, statistically not significant change in cholesterol concentrations in the elderberry group (from 199 to 190 mg/dl) compared to the placebo group (from 192 to 196 mg/dl). The resistance to copper-induced oxidation of LDL did not change within 3 weeks. In the single-dose experiment increases in postprandial triglyceride concentrations were not significantly different when the six subjects were investigated with and without elderberry juice.

CONCLUSIONS

Elderberry spray-dried extract at a low dose exerts a minor effect on serum lipids and antioxidative capacity. Higher, but nutritionally relevant doses might significantly reduce postprandial serum lipids.

Inhibition by uric acid of free radicals that damage biological molecules

To clarify the antioxidative role of uric acid, its ability to scavenge carbon-centered and peroxyl radicals and its inhibitory effect on lipid peroxidation induced by various model systems were examined. Uric acid efficiently scavenged carbon-centered and peroxyl radicals derived from the hydrophilic free radical generator 2,2'-azobis-(2-amidinopropane)-dihydrochloride (AAPH). All damage to biological molecules, including protein, DNA and lipids induced by AAPH, was strongly prevented by uric acid. In contrast, alpha-tocopherol had little effect on damage to biological molecules. Lipid peroxidation by the lipophilic free radical generator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) was little inhibited by uric acid, but not by alpha-tocopherol. Copper-induced lipid peroxidation was inhibited by uric acid and alpha-tocopherol. NADPH- and ADP-Fe(3+)-dependent microsomal lipid peroxidation was efficiently inhibited by alpha-tocopherol, but not by uric acid. Uric acid seems to scavenge free radicals in hydrophilic conditions to inhibit lipid peroxidation on the lipid-aqueous boundary, and the antioxidation is only little in lipophilic conditions.

Probabilistic kinetic model of slow oxidation of low-density lipoprotein: I. Theory

The microscopic probabilistic model has been introduced to explain the kinetics of very slow oxidation of low-density lipoprotein (LDL) from human plasma. The LDL oxidation, carried out in very unfavorable conditions, is assumed to be initiated by the traces of the transition-metal ions associated with the lipoprotein. The substrates for the metal-ion attack are alpha-tocopherol and the pre-formed lipid hydroperoxide. The theory assumes oscillation of the metal ions and alpha-tocopherol from the oxidized to the reduced states. In this model alpha-tocopherol acts as a pro-oxidant. The entire oxidation process consists of rare bursts of events in individual LDL particles. The reactions within the particles are treated in terms of probabilities of individual active species to participate in a specified reaction. The circular flow of the radical reactions could be visualized as circular flow of microscopic probabilities. The empirical, macroscopic quantities are quantitatively related with the microscopic probabilities, determined by a set of five adjustable parameters. The differential equations describing the initial radical generation rate and the rates of change of concentration of oxygen, hydroperoxide, co-antioxidant and trapped radicals in an LDL system are numerically solved in a finite difference approach.

Aggregation of LDL with chondroitin-4-sulfate makes LDL oxidizable in the presence of water-soluble antioxidants

The content of plasma and arterial interstitial fluid in water-soluble antioxidants makes it unlikely for low-density lipoprotein (LDL) to oxidize by the oxidation mechanisms most frequently discussed. By aggregation of LDL in the presence of chondroitin-4-sulfate (C-4-S), but not with chondroitin-6-sulfate or sphingomyelinase, a complex arises which can oxidize in the presence of 20 microM ascorbate and 300 microM urate. This oxidation sensitivity even persists after the gel-filtration of an LDL/C-4-S/Cu(2+) complex, indicating entrapment of Cu(2+) within. This corresponds well to the known ability of C-4-S to bind copper ions and is a potential mechanism by which LDL oxidation in the arterial intima is facilitated after prolonged retention by the extracellular matrix.

Antioxidant vitamins and the risk of carotid atherosclerosis. The Perth Carotid Ultrasound Disease Assessment study (CUDAS)

OBJECTIVES

This study examined whether dietary intake or plasma levels of antioxidant vitamins were independently associated with common carotid artery intima-media (wall) thickness (IMT) or focal plaque, or both, in a large, randomly selected community population.

BACKGROUND

Oxidation of low-density lipoprotein (LDL) cholesterol is thought to be important in early atherogenesis. Antioxidant micronutrients may therefore protect against lipid peroxidation and atherosclerotic vascular disease.

METHODS

We studied 1,111 subjects (558 men and 553 women; age 52 +/- 13 years [mean +/- SD], range 27 to 77). We measured dietary vitamin intake and fasting plasma levels of vitamins A, C and E, lycopene and alpha- and beta-carotene and performed bilateral carotid artery B-mode ultrasound imaging. RESULTS; After adjustment for age and conventional risk factors, there was a progressive decrease in mean IMT, with increasing quartiles of dietary vitamin E intake in men (p = 0.02) and a nonsignificant trend in women (p = 0.10). Dietary vitamin E levels accounted for 1% of the variance in measured IMT in men. For plasma antioxidant vitamins, there was an inverse association between carotid artery mean IMT and plasma lycopene in women (p = 0.047), but not in men. None of the other dietary or plasma antioxidant vitamins, nor antioxidant vitamin supplements, were associated with carotid artery IMT or focal carotid artery plaque.

CONCLUSIONS

This study provides limited support for the hypothesis that increased dietary intake of vitamin E and increased plasma lycopene may decrease the risk of atherosclerosis. No benefit was demonstrated for supplemental antioxidant vitamin use.

Vitamin E: protective role of a Janus molecule

Since the discovery of vitamin E in 1922, its deficiency has been associated with various disorders, particularly atherosclerosis, ischemic heart disease, and the development of different types of cancer. A neurological syndrome associated with vitamin E deficiency resembling Friedreich ataxia has also been described. Whereas epidemiological studies have indicated the role of vitamin E in preventing the progression of atherosclerosis and cancer, intervention trials have produced contradictory results, indicating strong protection in some cases and no significant effect in others. Although it is commonly believed that phenolic compounds like vitamin E exert only a protective role against free radical damage, antioxidant molecules can exert other biological functions. For instance, the antioxidant activity of 17-beta-estradiol is not related to its role in determining secondary sexual characters, and the antioxidant capacity of all-trans-retinal is distinguished from its role in rhodopsin and vision. Thus, it is not unusual that alpha-tocopherol (the most active form of vitamin E) has properties independent of its antioxidant/radical scavenging ability. The Roman god Janus, shown in ancient coins as having two faces in one body, inspired the designation of 'Janus molecules' for these substances. The new biochemical face of vitamin E was first described in 1991, with an inhibitory effect on cell proliferation and protein kinase C activity. After a decade, this nonantioxidant role of vitamin E is well established, as confirmed by authoritative studies of signal transduction and gene regulation. More recently, a tocopherol binding protein with possible receptor function has been discovered. Despite such important developments in understanding the molecular mechanism and the targets of vitamin E, its new Janus face is not fully elucidated. Greater knowledge of the molecular events related to vitamin E will help in selecting the parameters for clinical intervention studies such as population type, dose response effects, and possible synergism with other compounds.

Ceruloplasmin as low-density lipoprotein oxidase: activation by ascorbate and dehydroascorbate

The ability of ceruloplasmin (Cp) to oxidize low-density lipoproteins (LDL) in the presence of water-soluble antioxidants was investigated and a reaction mechanism proposed. Ascorbate strongly enhanced LDL oxidation, but only after its rapid consumption. Dehydroascorbate enhanced Cp-mediated LDL oxidation even more strongly. Lipid-soluble antioxidants and water-soluble peroxides did not show noticeable activation. However, loading of LDL with lipid hydroperoxides increased the initial oxidation rate. We conclude that Cp mediates a localized redox cycle, where reduction of Cp-Cu2+ is effected by water-soluble reductants and reoxidation by liposoluble hydroperoxides.

Comparison of a vitamin E-rich diet and supplemental vitamin E on measures of vitamin E status and lipoprotein profile

OBJECTIVE

To determine whether dietary modification rather than use of supplements can raise indices of vitamin E status to potentially cardioprotective levels.

DESIGN

Eight week randomised controlled trial with parallel treatments to compare increased use of vitamin E-rich foods, supplementation with 200 IU of vitamin E, and a placebo.

SETTING

Dunedin, New Zealand.

SUBJECTS

Ninety subjects were recruited, of whom 82 non-smoking, free-living individuals aged 22-72 y with plasma cholesterol <7.5 mmol/l completed the trial.

MAIN OUTCOME MEASURES

Dietary intakes, plasma alpha tocopherol, plasma alpha tocopherol/cholesterol ratio and lipoprotein cholesterol.

RESULTS

Consumption of an additional 12 mg of vitamin E (alpha tocopherol equivalents) from dietary sources was primarily achieved through the replacement of saturated fat-rich foods with unsaturated fats rich in vitamin E, nuts and vegetables. This resulted in a 3.4 micromol/l increase in plasma alpha tocopherol at week 6 (95% CI 1.6-5.3), and 0.9 micromol/mmol in plasma alpha tocopherol/cholesterol at weeks 4 and 6 (95% CI 0.3-1.4 and 0.4-1.4, respectively) when compared with the placebo group. In the supplement group, plasma alpha tocopherol and plasma alpha tocopherol/cholesterol were significantly increased within 2 weeks and remained so throughout the 8 week intervention.

CONCLUSION

Increasing dietary vitamin E intake can increase plasma alpha tocopherol levels, although factors other than dietary intake are also important determinants. The extent of dietary modification required to achieve potentially cardioprotective levels of plasma alpha tocopherol is difficult in practice.

SPONSORSHIP

The study was supported through the Otago Medical Research Foundation Laurenson Award.

Differential inhibition by alpha- and beta-tocopherol of human erythroleukemia cell adhesion: role of integrins

The effect of alpha- and beta-tocopherol on human erythroleukemia cell (HEL) adhesion induced by phorbol 12-myristate 13-acetate (PMA) has been studied. Adhesion induced by PMA stimulation was prevented by 44.5% by physiological concentrations of alpha-tocopherol. Under the same experimental conditions, beta-tocopherol, an analogue of alpha-tocopherol, produced 11% inhibition of adhesion. Cell response gradually increased from 0 to 24 h of alpha-tocopherol treatment. Only a slight time dependency of beta-tocopherol inhibition was observed. Another human erythroleukemia cell line (K562) and the human monocyte tumor cell line U937 showed 5.0 and 11.2% inhibition, respectively. Similar to alpha-tocopherol, the protein kinase C inhibitor, Calphostin C, and the MAPK inhibitor, PD98059, prevented PMA-induced cell adhesion. An inhibition of ERK-1 phosphorylation was observed for alpha-tocopherol only in HEL, implying that MAP kinase pathway is involved in this cell line. Fluorescence-activated cell sorting (FACS), by using various integrin-specific monoclonal antibodies, has shown that alpha (1-6), beta1, and alphav integrins are less expressed at the cell surface after alpha-tocopherol treatment. Beta-tocopherol treatment was less effective.

The hyperlipemic hamster - a model for testing the anti-atherogenic effect of amlodipine

Male Golden Syrian hamsters were subjected to a hyperlipemic diet. At intervals ranging from 2 to 14 weeks, the animals were examined for changes in serum constituents and structural modifications of lesion-prone areas: the cardiac valves, coronary arteries and aortic arch. Serum was characterized by a gradual increase in cholesterol, triglycerides and a decrease in total peroxyl-radical trapping potential. The sequence of modifications of the endothelial cells, smooth muscle cells, and migrating plasma monocytes as well as of the extracellular matrix were established. Amlodipine treatment of hyperlipemic hamster was assessed. Amlodipine exhibited an athero-protective effect, acting as antioxidant, reducing the LDL uptake by the vessel wall and consequently, limiting the size and extent of lesioned areas. The hyperlipemic hamster is a reliable model to unravel the cellular alterations leading to atheroma formation, and for testing the effect of drugs in this process.

The nitric oxide donor pentaerythritol tetranitrate can preserve endothelial function in established atherosclerosis

Recent results suggested that long-term treatment with a low dose of the organic nitrate pentaerythritol tetranitrate (PETN, 6 mg kg(-1) per day) for 16 weeks slightly decreases aortic superoxide production in normal rabbits. We sought to determine if PETN can preserve endothelium dependent relaxation (EDR) in atherosclerotic rabbits. Three groups of 9 - 10 New Zealand White rabbits received a cholesterol chow (0.75%) for 16 weeks. One group (CHOL16) served as control and two groups were fed for another 16 weeks a cholesterol-chow without (CHOL32) or with 6 mg PETN kg(-1) per day (PETN32). Isolated aortic rings of CHOL16 showed a typical impairment of EDR with a maximal relaxation at 1 microM acetylcholine of 28+/-16%. In CHOL32-rings EDR was completely impaired. In striking contrast, EDR in PETN32 (24+/-15%) was similar to that of CHOL16 indicating a protective effect of PETN on endothelial function. Vascular superoxide production measured with the lucigenin method was not different between the groups. Aortic lesion formation in PETN32 was smaller than in CHOL32 (P<0.008). The onset of copper-induced LDL-oxidation (lag-time) after 16 weeks of cholesterol feeding (214+/-9 min) was reduced in CHOL32 (168+/-24 min, P=0.035) but not in PETN32 (220+/-21 min). This indicates prevention of increased LDL oxidation by PETN. The halfmaximal effective vasodilator concentrations of PETN (in -logM) were identical in CHOL16 (7.9+/-0.1), CHOL32 (7.6+/-0.2) and PETN32 (7.7+/-0.2). Similar results were obtained with S-nitroso-N-acetyl-D,L-penicillamine. These data suggest that PETN can reduce the progression of lesion formation, endothelial dysfunction and of LDL-oxidation in established atherosclerosis.

A comparison of the kinetics of low-density lipoprotein oxidation induced by copper or by γ-rays: Influence of radiation dose-rate and copper concentration

The oxidation of low-density lipoproteins is the first step in the complex process leading to atherosclerosis. The aim of our study was to compare the kinetics of low density lipoprotein oxidation induced by copper ions or by oxygen free radicals generated by60Co γ-rays. The effects of copper concentration and irradiation dose-rate on LDL peroxidation kinetics were also studied. The oxidation of LDL was followed by the measurement of conjugated diene, hydroperoxides, and thiobarbituric acid reactive substance formation as well as α-tocopherol disappearance. In the case of gamma irradiation, the lag-phase before the onset of lipid peroxidation was inversely correlated to the radiation dose-rate. The radiation chemical rates (v) increased with increasing dose-rate. Copper-induced LDL peroxidation followed two kinetic patterns: a slow kinetic for copper concentrations between 5–20 µM, and a fast kinetic for a copper concentration of 40 µM. The concentration-dependent oxidation kinetics suggest the existence of a saturable copper binding site on apo-B. When compared with γ-rays, copper ions act as drastic and powerful oxidants only at higher concentrations ([Formula: see text]40 µM).Key words: LDL, peroxidation, kinetics, copper, γ-radiolysis, dose-rate.

The effect of pharmacological doses of different antioxidants on oxidation parameters and atherogenesis in hyperlipidaemic rabbits

The oxidation hypothesis of atherosclerosis implies that antioxidants are able to inhibit lipoprotein oxidation in the arterial wall and thereby retard atherogenesis. Since most of the animal studies performed have used very high doses of antioxidants, it is to date unknown whether antioxidants are effective antiatherosclerotic agents when given in pharmacological doses. Here we addressed this question using homozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits as an animal model of atherosclerosis. The rabbits were divided into four groups, each consisting of ten animals. They received either a standard diet or a diet containing 4.3 mg ubiquinone-10, or 4.3 mg vitamin E or 15 mg probucol/kg body weight daily. After 12 months, the extent of aortic atherosclerosis was assessed as the intima thickness, media thickness and intima-to-media ratio in 14 cross sections equally distributed over the whole aorta. To evaluate the antioxidant effects of the diet, lipophilic and hydrophilic antioxidants, lipids, fatty acids and plasma oxidizability were measured after 0, 3 and 6 months of feeding. We found that supplementation with probucol significantly decreased aortic intima-to-media ratio compared to controls. The antiatherosclerotic action of probucol was accompanied by its beneficial action on plasma oxidizability and some plasma antioxidants. No decrease in aortic atherosclerosis was measured in ubiquinone-10- and vitamin E-supplemented rabbits, despite the fact that both antioxidants decreased plasma oxidizability and ubiquinone-10 increased the plasma levels of antioxidants. Taken together, these data suggest that pharmacological doses of probucol retard atherogenesis in WHHL rabbits by an antioxidant mechanism, while ubiquinone-10 and vitamin E at these dosages are ineffective in this highly hyperlipidaemic model. The measurement of some oxidation-related parameters in plasma, such as lipophilic antioxidants, polyunsaturated fatty acids and lipoprotein oxidizability, may be useful in assessing the risk of atherogenesis in humans.

Soy protein isolate reduces the oxidizability of LDL and the generation of oxidized LDL autoantibodies in rabbits with diet-induced atherosclerosis

The incidence of atherosclerosis can be modified by diet, and plant-derived proteins have a beneficial effect, but the underlying mechanisms remain unclear. It has been suggested that oxidized LDL (oxLDL) and autoantibodies against oxLDL are important in the development of atherosclerosis. We analyzed these factors in rabbits fed a nonpurified diet supplemented with high cholesterol (10.0 g/kg) containing either 270.0 g/kg casein (CAS, n = 10) or 270.0 g/kg soy protein isolate (SPI, n = 10) for 2 mo. Plasma and purified serum LDL from rabbits were analyzed at d 0, 15, 30, 45 and 60 of treatment, and the size of atherosclerotic lesions was evaluated at d 60 of treatment. CAS-fed rabbits had significantly higher plasma cholesterol at d 15-45 and LDL cholesterol levels at d 15 and 30. Levels of trilinolein and phosphatidylcholine hydroperoxides were higher in the LDL fraction of rabbits fed CAS than in those fed SPI. Also, CAS-fed rabbits had higher levels of highly oxidized LDL [monoclonal antibody (mAb) 24-reactive oxLDL] in plasma at d 60, whereas SPI-fed rabbits had higher levels of minimally oxidized LDL (mAb 28-reactive oxLDL) at d 45. These results were consistent with the earlier formation of anti-oxLDL antibodies and the presence of a larger area of atherosclerotic lesion in rabbits fed the CAS diet. These data indicate the importance of both the type of dietary protein used in the induction of atherosclerosis and the relevance of immunologic mechanisms in addition to biochemical and physiologic factors in the pathogenesis of atherosclerosis.

Human, but not bovine, oxidized cerebral spinal fluid lipoproteins disrupt neuronal microtubules

Cerebral spinal fluid (CSF) lipoproteins have become a focus of research since the observation that inheritance of particular alleles of the apolipoprotein E gene affects the risk of Alzheimer's disease (AD). There is evidence of increased lipid peroxidation in CSF lipoproteins from patients with AD, but the biological significance of this observation is not known. A characteristic of the AD brain is a disturbance of the neuronal microtubule organization. We have shown previously that 4-hydroxy-2(E)-nonenal, a major product of lipid peroxidation, causes disruption of neuronal microtubules and therefore tested whether oxidized CSF lipoproteins had the same effect. We exposed Neuro 2A cells to human CSF lipoproteins and analyzed the microtubule organization by immunofluorescence. In vitro oxidized human CSF lipoproteins caused disruption of the microtubule network, while their native (nonoxidized) counterparts did not. Microtubule disruption was observed after short exposures (1 h) and lipoprotein concentrations were present in CSF (20 microg/mL), conditions that did not result in loss of cell viability. Importantly, adult bovine CSF lipoproteins, oxidized under identical conditions, had no effect on the microtubule organization of Neuro 2A cells. Comparison of human and bovine CSF lipoproteins revealed similar oxidation-induced modifications of apolipoproteins E and A-I as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Fatty acid analysis revealed substantially lower amounts of unsaturated fatty acids in bovine CSF lipoproteins, when compared to their human counterparts. Our data therefore indicate that oxidized human CSF lipoproteins are detrimental to neuronal microtubules. This effect is species-specific, since equally oxidized bovine CSF lipoproteins left the neuronal microtubule organization unchanged.

Specific cellular responses to alpha-tocopherol

In the last 10 years precise cellular functions of alpha-tocopherol, some of which are independent of its antioxidant/radical-scavenging ability, have been revealed. Absorption of alpha-tocopherol from the gut is a selective process. Other tocopherols are not absorbed or are absorbed to a lesser extent. At the post-translational level, alpha-tocopherol inhibits protein kinase C and 5-lipoxygenase and activates protein phosphatase 2A and diacylglycerol kinase. Some genes [platelet glycoprotein IV/thrombospondin receptor/class B scavenger receptor (CD36), alpha-tocopherol transfer protein (alpha-TTP), alpha-tropomyosin, connective tissue growth factor and collagenase] are affected by alpha-tocopherol at the transcriptional level. alpha-Tocopherol also inhibits cell proliferation, platelet aggregation, monocyte adhesion and the oxygen burst in neutrophils. Other antioxidants, such as beta-tocopherol and probucol, do not mimic these effects, suggesting a nonantioxidant, alpha-tocopherol-specific molecular mechanism.

Vitamin E: non-antioxidant roles

Vitamin E was originally considered a dietary factor of animal nutrition especially important for normal reproduction. The significance of vitamin E has been subsequently proven as a radical chain breaking antioxidant that can protect the integrity of tissues and play an important role in life processes. More recently alpha-tocopherol has been found to possess functions that are independent of its antioxidant/radical scavenging ability. Absorption in the body is alpha-tocopherol selective and other tocopherols are not absorbed or are absorbed to a lesser extent. Furthermore, pro-oxidant effects have been attributed to tocopherols as well as an anti-nitrating action. Non-antioxidant and non-pro-oxidant molecular mechanisms of tocopherols have been also described that are produced by alpha-tocopherol and not by beta-tocopherol. alpha-Tocopherol specific inhibitory effects have been seen on protein kinase C, on the growth of certain cells and on the transcription of some genes (CD36, and collagenase). Activation events have been seen on the protein phosphatase PP2A and on the expression of other genes (alpha-tropomyosin and Connective Tissue Growth Factor). Non-antioxidant molecular mechanisms have been also described for gamma-tocopherol, delta-tocopherol and tocotrienols.

The steady-state levels of oxidative DNA damage and of lipid peroxidation (F2-isoprostanes) are not correlated in healthy human subjects

Oxidative damage to DNA in human tissues can be determined by measuring multiple products of oxidative damage to the purine and pyrimidine bases using gas chromatography-mass spectrometry (GC-MS). Oxidative damage to lipids (lipid peroxidation) can be quantitated by the mass spectrometry-based determination of F2-isoprostanes, specific end-products of the peroxidation of arachidonic acid residues in lipids. For both DNA base damage products and 8-epi prostaglandin F2alpha (PGF2alpha), there is a wide variation in levels between different healthy human subjects. We measured multiple products of oxidative damage to DNA bases in white cells, and 8-epi PGF2alpha in plasma, from blood samples obtained from healthy human subjects in the UK and in Portugal. No correlation of 8-epi PGF2alpha levels with levels of any modified DNA base (including 8-hydroxyguanine) was observed. We conclude that no single parameter can be measured as an index of "oxidative stress" or "oxidative damage" in vivo.

Protective effect of oleuropein, an olive oil biophenol, on low density lipoprotein oxidizability in rabbits

On the basis of the results obtained with pilot studies conducted in vitro on human low density lipoprotein (LDL) and on cell cultures (Caco-2), which had indicated the ability of certain molecules present in olive oil to inhibit prooxidative processes, an in vivo study was made of laboratory rabbits fed special diets. Three different diets were prepared: a standard diet for rabbits (diet A), a standard diet for rabbits modified by the addition of 10% (w/w) extra virgin olive oil (diet B), a modified standard diet for rabbits (diet C) differing from diet B only in the addition of 7 mg kg(-1) of oleuropein. A series of biochemical parameters was therefore identified, both in the rabbit plasma and the related isolated LDL, before and after Cu-induced oxidation. The following, in particular, were selected: (i) biophenols, vitamins E and C, uric acid, and total, free, and ester cholesterol in the plasma; (ii) proteins, triglycerides, phospholipids, and total, free, and ester cholesterol in the native LDL (for the latter, the dimensions were also measured); (iii) lipid hydroperoxides, aldehydes, conjugated dienes, and relative electrophoretic mobility (REM) in the oxidized LDL (ox-LDL). In an attempt to summarize the results obtained, it can be said that this investigation has not only verified the antioxidant efficacy of extra virgin olive oil biophenols and, in particular, of oleuropein, but has also revealed a series of thus far unknown effects of the latter on the plasmatic lipid situation. In fact, the addition of oleuropein in diet C increased the ability of LDL to resist oxidation (less conjugated diene formation) and, at the same time, reduced the plasmatic levels of total, free, and ester cholesterol (-15, -12, and -17%, respectively), giving rise to a redistribution of the lipidic components of LDL (greater phospholipid and cholesterol amounts) with an indirect effect on their dimensions (bigger by about 12%).

Quantification of the alpha- and gamma-tocopherol metabolites 2,5,7, 8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman and 2,7, 8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman in human serum

alpha- and gamma-tocopherol are the major vitamin E compounds found in human blood and tissues. The metabolites are 2,5,7, 8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC) and 2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC, LLU-alpha), respectively. alpha-CEHC is excreted mainly as glucuronide or sulfate conjugates in the urine. Here we describe a sensitive and reliable method to analyze alpha- and gamma-CEHC in human serum. The concentration of alpha-CEHC in human serum is in the range of 5-10 pmol/ml but increases significantly up to 200 pmol/ml upon supplementation with RRR-alpha-tocopherol. About one-third of the alpha-CEHC circulating in the blood is present as a glucuronide conjugate. Baseline levels of gamma-CEHC are about 50 to 85 pmol/ml.

Incorporation of esterified soybean isoflavones with antioxidant activity into low density lipoprotein

We have recently reported that dietary intake of soybean isoflavone phytoestrogens resulted in increased oxidation resistance of isolated low density lipoprotein (LDL). In order to explore the underlying mechanisms we designed two types of in vitro experiments. First, we prepared several different isoflavone fatty acid esters to increase their lipid solubility and studied their incorporation into LDL. Second, the oxidation resistance of the isoflavone-containing LDLs was investigated with Esterbauer's 'conjugated diene' method using Cu2+ as prooxidant. Unesterified daidzein and genistein as well as genistein stearic acid esters were incorporated into LDL to a relatively small extent (0.33 molecules per LDL particle, or less) and they did not significantly influence oxidation resistance. The oleic acid esters of isoflavones were incorporated more effectively, reaching a level of 2.19 molecules per LDL particle or more, and the 4',7-O-dioleates of daidzein and genistein exhibited prolongations of lag times by 46% (P<0.05) and 202% (P<0.01), respectively. A smaller but significant increase in lag time (20.5%, P<0.01) was caused by daidzein 7-mono-oleate. In summary, esterification of soybean isoflavones daidzein and genistein with fatty acids at different hydroxyl groups provided lipophilicity needed for incorporation into LDL. Some isoflavone oleic acid esters increased oxidation resistance of LDL following their incorporation.

Copper-induced LDL peroxidation: interrelated dependencies of the kinetics on the concentrations of copper, hydroperoxides and tocopherol

Excessive uptake of oxidized low density lipoprotein plays a role in the onset of atherosclerosis. Lipid-associated antioxidants, the most abundant of which is tocopherol (vitamin E), are therefore believed to have anti-atherogenic properties. By contrast, hydroperoxides enhance the peroxidation of low density lipoprotein. We demonstrate that none of these compounds markedly affect the maximal rate of oxidation of low density lipoprotein, whereas the lag preceding rapid oxidation is prolonged by tocopherol but shortened by hydroperoxides. The corresponding 'prolongation' and 'shortening' can be compensated by each other in low density lipoprotein preparations enriched with both these compounds. The dependence of the balance between the effects of tocopherol and hydroperoxides on the copper concentration indicates that the antioxidative effect of vitamin E increases with the oxidative stress.

Regulation of rat hepatocyte protein kinase C beta isoenzymes by the lipid peroxidation product 4-hydroxy-2,3-nonenal: A signaling pathway to modulate vesicular transport of glycoproteins

A major aldehydic end product of the peroxidation of arachidonic acid, 4-hydroxy-2,3-nonenal (HNE), has recently been considered for its potential involvement in a variety of cell functions. Here we report on the differential regulation of rat hepatocyte protein kinase C (PKC) isoforms by concentrations of HNE actually detectable in specific biological fluids or tissues. PKC betaI and, to a much greater extent, PKC betaII activities were markedly increased by 0.1 micromol/L HNE (final concentration in cell medium) whereas they were unaffected or even inhibited by 1 to 10 micromol/L HNE. On the contrary, the calcium independent PKC delta activity was inhibited by 0.1 micromol/L and increased by 1 and 10 micromol/L. Further, we show here that HNE-induced stimulation of PKC betaI and betaII activities, both in cytosolic and in membrane fractions, is paralleled by a marked stimulation of the anterograde transport of a lysosomal enzyme within the central vacuolar system. In fact, the treatment with 0.1 micromol/L HNE accelerated the PKC-dependent transport of lysosomal procathepsin D from the trans-Golgi network to the endosomal-lysosomal compartment and, in addition, increased the exocytosis of mature cathepsin D (CD) from these compartments. On the other hand, hepatocyte cotreatment with a selective inhibitor of classic PKCs prevented the aldehyde-induced activation of CD transport. These results support the possible involvement of HNE in the PKC-dependent regulation of the traffic of secretory glycoproteins, and point to remarkable implications of this aldehyde in the pathophysiology of various exocytic processes including hepatocyte lipoprotein secretion.

Fenofibrate protects lipoproteins from lipid peroxidation: synergistic interaction with alpha-tocopherol

One of the earliest steps of atherosclerotic plaque formation is an increase of circulating apolipoprotein B-containing lipoproteins which, after infiltrating the subendothelial space, undergo oxidative modification. Fenofibrate is an effective cholesterol- and triglyceride-lowering agent which has been shown to be beneficial in the treatment of atherosclerosis. Vitamin E, or alpha-tocopherol, is a powerful antioxidant which has been shown in a variety of studies to prevent lipoprotein peroxidation. The purpose of the present study was to investigate the effect of fenofibrate treatment, either alone or in combination with alpha-tocopherol, in reducing the susceptibility of lipoproteins to oxidative modification. Rats fed a normal diet were treated for up to 27 d with fenofibrate, either alone or in combination with equimolar doses of alpha-tocopherol. Combined VLDL (very low density lipoproteins) and LDL (low density lipoproteins) isolated after fenofibrate treatment were more resistant to copper-mediated oxidation, as assessed by conjugated diene formation. Lag time was prolonged up to 3.2-fold, while the maximal rate of diene production was significantly decreased by up to 2.2-fold. Treatment of rats with alpha-tocopherol alone at the selected dose had no significant effect on lag time, while the propagation rate was slightly decreased. Coadministration of fenofibrate with alpha-tocopherol prolonged the lag phase to a greater extent than fenofibrate alone, showing a synergistic interaction between the two compounds. Finally, the combination of fenofibrate and alpha-tocopherol was significantly more effective in modifying lipoprotein oxidation parameters than what was observed with alpha-tocopherol and bezafibrate or gemfibrozil. Thus, in addition to its well-established effects on lipoprotein concentrations and atherogenic parameters, fenofibrate reduces the susceptibility of VLDL and LDL to oxidative modification and exerts its action synergistically with alpha-tocopherol.

Ascorbate prevents prooxidant effects of urate in oxidation of human low density lipoprotein

Uric acid and ascorbic acid are important low molecular weight antioxidants in plasma. Their interactions and combined effect on Cu(2+)-catalysed oxidation of human low density lipoprotein were studied in vitro. It was found that uric acid alone becomes strongly prooxidant whenever it is added to low density lipoprotein shortly after the start of oxidation (conditional prooxidant). Ascorbic acid, which is present in human plasma at much lower concentrations (20-60 microM) than urate (300-400 microM), is in itself not a conditional prooxidant. Moreover, ascorbate prevents prooxidant effects of urate, when added to oxidising low density lipoprotein simultaneously with urate, even at a 60-fold molar excess of urate over ascorbate. Ascorbate appears to have the same anti-prooxidant effect with other aqueous reductants, which, besides their antioxidant properties, were reported to be conditionally prooxidant. Such interactions between ascorbate and urate may be important in preventing oxidative modification of lipoproteins in the circulation and in other biological fluids.

Validation of the peroxidative indicators, cis-parinaric acid and parinaroyl-phospholipids, in a model system and cultured cardiac myocytes

cis-Parinaric acid is increasingly being used in eukaryotic cells as a very sensitive marker for the initial stages of lipid peroxidation. Despite the increased application of this probe, no extensive validation, especially in cellular systems, has been performed. cis-Parinaric acid can either be inserted freely into biomembranes or incorporated (bio)synthetically into lipids (parinaroyl-lipid). Therefore, a direct comparison was made between the peroxidative behaviour of the two parinaroyl probes and the endogenous polyunsaturated fatty acids arachidonic and linoleic acid, in both an artificial lipidic system and in cultured neonatal rat heart cells. Three different radical generating systems were used, i.e., hydrogen peroxide, cumene hydroperoxide and the thermo-labile 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH). The data demonstrate that the peroxidation rate of cis-parinaric acid is higher than that of the parinaroyl, arachidonoyl and linoleoyl lipids. The latter three displayed comparable peroxidation rates, showing that the peroxidative decay of parinaroyl-lipid is a good marker for the degradation of endogenous polyunsaturated fatty acids. Experimental results using the freely inserted cis-parinaric acid could potentially lead to an overestimation of the inflicted damage and should be interpreted with care. In addition, a comparison was made with the measurement of conjugated dienes and malon dialdehyde as thiobarbituric acid reactive substances. The results demonstrate that measurement of conjugated dienes and malon dialdehyde only provide information on peroxidative processes in vitro, but are not suitable for in-depth studies in cultured cells. In contrast, the use of the parinaroyl probes is a suitable, straightforward, sensitive and reproducible method for detecting the initial stages of lipid peroxidation in living cells.

Linoleic acid peroxidation--the dominant lipid peroxidation process in low density lipoprotein--and its relationship to chronic diseases

Modern separation and identification methods enable detailed insight in lipid peroxidation (LPO) processes. The following deductions can be made: (1) Cell injury activates enzymes: lipoxygenases generate lipid hydroperoxides (LOOHs), proteases liberate Fe ions--these two processes are prerequisites to produce radicals. (2) Radicals attack any activated CH2-group of polyunsaturated fatty acids (PUFAs) with about a similar probability. Since linoleic acid (LA) is the most abundant PUFA in mammals, its LPO products dominate. (3) LOOHs are easily reduced in biological surroundings to corresponding hydroxy acids (LOHs). LOHs derived from LA, hydroxyoctadecadienoic acids (HODEs), surmount other markers of LPO. HODEs are of high physiological relevance. (4) In some diseases characterized by inflammation or cell injury HODEs are present in low density lipoproteins (LDL) at 10-100 higher concentration, compared to LDL from healthy individuals.

Varying dietary fat type of reduced-fat diets has little effect on the susceptibility of LDL to oxidative modification in moderately hypercholesterolemic subjects

The effect of the fatty acid composition of reduced-fat diets on the in vitro oxidation of LDL was examined in 14 moderately hypercholesterolemic [low density lipoprotein (LDL) > 3.36 mmol/L] postmenopausal female and male subjects (age 44-78 y). Each subject consumed each of five reduced-fat diets [30 energy percent (E%) fat, 17 E% protein and 53 E% carbohydrate] enriched in beef tallow, canola oil, corn oil, olive oil or rice bran oil (20 E%) for 32-d periods. In vitro oxidation of LDL was assessed by incubating LDL with hemin and hydrogen peroxide, and measuring the time required for the reaction to reach maximum velocity (lag time). LDL lag times were 93.2 +/- 25.8, 95.9 +/- 26.4, 104.2 +/- 32.7, 108.0 +/- 26.6 and 113.1 +/- 24.0 min for corn oil, beef tallow, rice bran oil, canola oil and olive oil periods, respectively. When the data from all dietary phases were pooled, LDL alpha-tocopherol level (r = 0.30, P = 0.01) and plasma 18:1/18:2 ratio (r = 0.22, P = 0.08) were positively related to resistance of LDL to oxidation. Differences induced by the dietary perturbations in LDL content of beta-cryptoxanthin, lutein/zeaxanthin, lycopene, alpha-carotene or beta-carotene, and LDL particle size were not related to resistance of LDL to oxidation. In conclusion, in middle-aged and elderly moderately hypercholesterolemic subjects, the consumption of reduced-fat diets enriched in animal fat or vegetable oils with a relatively wide range of fatty acid profiles did not alter the in vitro susceptibility of LDL to oxidation. The advantages of reducing the saturated fat content of the diet were reflected in lower total and LDL cholesterol levels.

Age-related increased susceptibility of high-density lipoproteins (HDL) to in vitro oxidation induced by gamma-radiolysis of water

In the present study, we investigated the age-related susceptibility of high-density lipoproteins (HDL) to oxidation. HDL were obtained from healthy, normolipidemic young, middle-aged and elderly subjects. Oxidation of HDL was induced in vitro by oxygen free radicals generated by water gamma-radiolysis, and followed by the decrease of endogenous vitamin E and the formation of conjugated dienes and thiobarbituric acid-reactive substances, as well as the alterations of apolipoproteins A-I/A-II. The resistance of HDL to oxidation, evaluated by the length of the lag phase, decreased with aging. This increased oxidizability of HDL with aging could have a dramatic impact on the development of atherosclerosis in the elderly population.

Very slow autoxidation of low-density lipoprotein spares alpha-tocopherol

Low-density lipoprotein (LDL) in solution, supplemented with EDTA, is spontaneously oxidized at physiological temperature. In closed systems, three distinct phases of oxidation are present. In the lag period no change of any of the usually measured 'markers' of oxidation have been detected. In the second phase oxygen is consumed and subsequently the level of lipid hydroperoxides is increased. In the third phase, after consumption of oxygen, hydroperoxides decrease in concentration and the apoprotein-associated free radicals are formed. In the entire process alpha-tocopherol is conserved. The participation and preservation of alpha-tocopherol in the process is interpreted in terms of the tocopherol-mediated peroxidation. In the latter two phases alpha-tocopherol oscillates between the oxidized and reduced states.

Oxidation resistance of LDL is correlated with vitamin E status in beta-thalassemia intermedia

The alteration of the oxidant/antioxidant balance may affect the susceptibility of low density lipoproteins (LDL) to oxidation in haemolytic disorders such as thalassemia. Thirty patients affected by beta-thalassemia intermedia were examined, and compared with age-matched healthy controls. The mean amount of vitamin E in the thalassemic LDL was lower than control (p < 0.0001), either when it was calculated on the base of LDL protein (61% decrease) or cholesterol (25% decrease). The LDL resistance to Cu2+-induced oxidation, evaluated as the length of the lag phase before the onset of conjugated diene (CD) lipid hydroperoxide production, was 20% lower than control. Other parameters of LDL susceptibility to oxidation, such as the rate of lipid peroxidation, Rp, and the total amount of conjugated dienes produced, CDmax, were only slightly lower than control, which can be explained by a lower content of peroxidable lipids in the thalassemic LDL. Total LDL cholesterol was 1.08 x 10(3) and 2.07 x 10(3) mol/mol LDL in thalassemic and in control LDL, respectively. The length of the lag phase in thalassemic LDL shows a strongly positive correlation with its vitamin E content (r = 0.732; p < 0.0001). The r2-value of 0.53 provides evidence that more than 50% of the lag phase is determined by vitamin E. Oxidizability of LDL lipids may explain 22-24% of the lag phase, as calculated by the inverse correlation between the length of the lag phase and CDmax (r = -0.474; p = 0.008; r2 = 0.22) and Rp (r = -0.499; p = 0.005; r2 = 0.24). In multiple regression analysis, the lag phase was predictable to 66% by vitamin E plus CDmax, and to 60% by vitamin E plus Rp. Plasma vitamin E was 53% lower in thalassemia patients compared to control and positively correlated with vitamin E in the LDL (r = 0.677; p < 0.0001). None of the correlations above were observed in control subjects. In conclusion, beta-thalassemia is associated with very low levels of vitamin E in plasma and in LDL, a condition that renders these particles more susceptible to in vitro oxidative modification and may account for atherogenesis-related vascular diseases described in thalassemia. The present data on a statistically significant correlation between abnormally low vitamin E and oxidizability of LDL contribute substantially to the hypothesis that vitamin E is a pathophysiologically important determinant of antioxidative protection of LDL.

Objectives, design and recruitment of a familial and longitudinal cohort for studying gene-environment interactions in the field of cardiovascular risk: the Stanislas cohort

The main objective of the Stanislas cohort is to study the role and the contribution of genetic and environmental factors to cardiovascular status. We plan: a) to describe the degree of association of a large number of cardiovascular risk indicators with cardiovascular endpoints, b) to evaluate the contribution of genetic and that of environmental factors to this association, c) to follow the evolution of these risk indicators during a period of at least ten years, d) to search for the determinants influencing this evolution. The principal variables studied are: a) blood pressure, cardiac mass, and wall thickness of carotid and femoral arteries, b) obesity and fat mass, c) indicators of lipid metabolism, d) genetic polymorphisms of several cardiovascular risk candidate genes, e) food, tobacco and alcohol consumption, f) consumption of drugs and anti-oxidant vitamins. Between September 1993 and August 1995, 1006 families consisting of the two biological parents with at least two children were recruited totalling 4295 individuals. This cohort will be followed up until 2004. There will be two health examinations five and ten years after the initial examination. A bank of blood samples (serum and plasma) in liquid nitrogen and DNA (-80 degrees C) has been established.