Increased oxidation resistance of atherogenic plasma lipoproteins at high vitamin E levels in non-vitamin E supplemented men

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Lycopene, lutein and beta-carotene as determinants of LDL conjugated dienes in serum

Oxidative modification of low-density lipoprotein (LDL) in the vascular endothelium is considered to be important in the development of early atherosclerosis. The aim of this study was to investigate the main determinants of serum LDL conjugated dienes in women (n=124) and men (n=225). We focused on the influence of fat-soluble vitamins and carotenoids on the concentration of conjugated dienes in LDL. In multivariate linear regression models, including age, body mass index, diastolic blood pressure, symptomatic ischaemic heart disease (IHD) or IHD history, statin medication, leukocytes and serum triglycerides as covariates, plasma lycopene (standardized beta=-0.33; P=0.002) and lutein (standardized beta=-0.22; P=0.027) concentrations were the strongest determinants of serum LDL conjugated dienes in women, whereas plasma beta-carotene (standardized beta=-0.23; P=0.002) was the most important factor in men. Furthermore, statin medication, diastolic blood pressure, age and serum triglycerides were significant determinants of LDL conjugated dienes. The regression model with lycopene contributed to 29% in women and 15% in men with beta-carotene of the variation of serum LDL conjugated dienes. Results of the present study suggest that plasma lycopene, lutein and beta-carotene are the most powerful antioxidants for explaining the content of in vivo oxidatively modified LDL in serum.

Local and systemic oxidant/antioxidant status before and during lung cancer radiotherapy

To examine local and systemic oxidative status of lung cancer (LC) and oxidant effects of radiotherapy (RT), this study evaluated antioxidants and markers of oxidative and nitrosative stress in bronchoalveolar lavage (BAL) fluid and in the blood of 36 LC patients and 36 non-cancer controls at baseline and during and after RT for LC. LC patients had higher baseline serum urate, plasma nitrite and lower serum oxidized proteins than controls (p = 0.016, p < 0.001 and p = 0.027, respectively), but BAL fluid oxidative stress markers were similar. RT tended to raise some antioxidants, however, significant increases were seen in serum urate, conjugated dienes and TBARS (p = 0.044, p = 0.034 and p = 0.004, respectively) 3 months after RT. High urate at baseline may compensate against the oxidative stress caused by LC. RT shifts the oxidant/antioxidant balance towards lipid peroxidation, although the antioxidant defense mechanisms of the body appear to counteract the increased oxidative stress rather effectively.

Modulation of Hepatic Inflammatory Risk Markers of Cardiovascular Diseases by PPAR–α Activators

Atherosclerosis is a long-term chronic inflammatory disease associated with increased concentrations of inflammatory hepatic markers, such as CRP and fibrinogen, and of peripheral origin, such as tumor necrosis factor (TNF)-α and interleukin (IL)-6. Peroxisome proliferator-activated receptor (PPAR-)-α is a ligand-activated transcription factor that regulates expression of key genes involved in lipid homeostasis and modulates the inflammatory response both in the vascular wall and the liver. PPAR-α is activated by natural ligands, such as fatty acids, as well as the lipid-lowering fibrates. PPAR-α agonists impact on different steps of atherogenesis: (1) early markers of atherosclerosis, such as vascular wall reactivity, are improved, (2) however, reduced expression of adhesion molecules on the surface of endothelial cells, accompanied by decreased levels of inflammatory cytokines, such as TNF-α, IL-1, and IL-6, leads to a decreased leukocyte recruitment into the arterial wall; (3) in later stages of the atherosclerotic process, PPAR-α agonists may promote plaque stabilization and reduce cardiovascular events, via effects on metalloproteinases, such as MMP9. Moreover, PPAR-α activation by fibrates also impairs proinflammatory cytokine-signaling pathways in the liver resulting in the modulation of the acute phase response reaction via mechanisms independent of changes in lipoprotein levels. Effective coronary artery disease (CAD) prevention requires the use of agents that act beyond low-density lipoprotein cholesterol-lowering. PPAR-α agonists appear to comprehensively address some of the abnormalities of the most common clinical phenotypes of the high CAD risk patient of the 21st century such as in the metabolic syndrome and type 2 diabetes: low high-density lipoprotein cholesterol, high triglycerides, small, dense low-density lipoprotein, and a proinflammatory, procoagulant state.

Association between depressive symptoms and serum concentrations of homocysteine in men: a population study

BACKGROUND

Results of studies of the association between blood concentrations of homocysteine and depression in general populations and among psychiatric patients are inconsistent.

OBJECTIVE

The objective was to study the association between depression and serum concentrations of total homocysteine (tHcy).

DESIGN

A cross-sectional study of a sample of 924 men aged 46-64 y was conducted as a part of the Kuopio Ischaemic Heart Disease Risk Factor Study. Those who had a history of psychiatric disorder (6.0%) were excluded. Depressive symptoms were assessed with the 18-item Human Population Laboratory Depression Scale. Those who scored > or =5 at baseline or at the 4-y follow-up were considered to have a tendency toward depression.

RESULTS

The participants were ranked according to their blood tHcy concentration and divided into tertiles. Those in the upper tertile for serum tHcy had a more than twofold (odds ratio: 2.30; 95% CI: 1.35, 3.90; P=0.002) higher risk of being depressed than did those in the lowest tertile for serum tHcy. The results remained significant after adjustment for the month of study, history of ischemic heart disease, smoking habits, alcohol consumption, marital status, education, and socioeconomic status in adulthood (odds ratio: 2.23; 95% CI: 1.30, 3.83; P=0.004).

CONCLUSION

High serum concentrations of tHcy may be associated with depression in middle-aged men.

Should antioxidant status be considered in interventional trials with antioxidants?

The last decade has seen many trials with antioxidants in patients with cardiovascular disease, with equivocal results. One possible explanation for the disappointing findings is the lack of identification criteria of patients who are potential candidates for antioxidant treatment. Several studies have been carried out in patients at risk of cardiovascular disease, indicating that enhanced oxidative stress is associated with the presence of diabetes, hypercholesterolaemia, hypertension, and smoking. This review analyses the data reported so far to determine whether they clearly support the premise that patients at risk of cardiovascular events may be candidates for antioxidant treatment.

Oxidative stress and smoking-induced vascular injury

The relative importance of mechanisms relevant to smoking-induced vascular injury is poorly understood. Cigarette smoke is a source of free radicals but also results in cellular activation and consequent generation of free radicals in vivo. Here we consider several approaches to estimating the consequences of free radical generation in vivo, using measurements of modified lipids, proteins, and DNA. Smoking appears to result in elevation of several biomarkers of oxidant stress, some in a dose-related fashion. There is also some evidence that disordered endothelial function in smokers may be partly attributable to oxidant stress. Other effects of smoking on hemostatic activation, sympathoadrenal function, and lipoprotein structure and function may also be modulated by smoking-induced oxidant stress. The emergence and application of rational quantitatively reliable indexes of oxidant stress in vivo is likely to elucidate the relative contribution of oxidant stress to smoking-induced vascular injury.

Uremia-related metabolic cardiac risk factors in chronic kidney disease

Growing evidence has been gathered over the last 15 years regarding the role of nontraditional or uremia-related risk factors in the pathogenesis of atherosclerosis in subjects with renal failure. Among those factors, dyslipidemia, inflammation, hyperhomocysteinemia, and oxidant stress have been extensively studied. However, the clinical significance of many of these factors remains controversial in light of reported studies. In this article, the existing evidence regarding the role of uremia-related risk factors in the pathogenesis of atherosclerosis is reviewed, with special emphasis on prevalence, cardiac risk, and management in patients with chronic kidney disease (CKD). Consensus treatment recommendations are provided for risk factors for which there is evidence to support preventive or therapeutic interventions.

Lycopene, atherosclerosis, and coronary heart disease

Diets rich in fruits and vegetables containing carotenoids have been of interest because of their potential health benefit against chronic diseases such as cardiovascular diseases (CVD) and cancer. Interest particularly in lycopene is growing rapidly following the recent publication of epidemiological studies that have associated high lycopene levels with reductions in CVD incidence. Two studies were conducted. In the first one, we examined the role of lycopene as a risk-lowering factor with regard to acute coronary events and stroke in the prospective Kuopio Ischemic Heart Disease Risk Factor (KIHD) Study. The subjects were 725 middle-aged men free of coronary heart disease and stroke at the study baseline. In a Cox's proportional hazards' model adjusting for covariates, men in the lowest quartile of serum levels of lycopene had a 3.3-fold (P < 0.001) risk of the acute coronary event or stroke as compared with others. In the second study, we assessed the association between plasma concentration of lycopene and intima-media thickness of the common carotid artery wall (CCA-IMT) in a cross-sectional analysis of the Antioxidant Supplementation in the Atherosclerosis Prevention (ASAP) study data in 520 asymptomatic men and women. In a covariance analysis adjusting for common cardiovascular risk factors, low plasma levels of lycopene were associated with an 18% increase of IMT in men as compared with men in whom plasma levels were higher than median (P = 0.003 for difference). In women, the difference did not remain significant after the adjustments. On the basis of these works, it is evident that the circulating levels of lycopene play some role with regard to cardiovascular health in Finland, at least in men. We conclude that circulating levels of lycopene, a biomarker of tomato-rich food, may play a role in early stages of atherogenesis and may have clinical and public health relevance.

Supplementation with vitamin E but not with vitamin C lowers lipid peroxidation in vivo in mildly hypercholesterolemic men

Although the use of vitamin E supplements has been associated with a reduction in coronary events, assumed to be due to lowered lipid peroxidation, there are no previous long-term clinical trials into the effects of vitamin C or E supplementation on lipid peroxidation in vivo. Here, we have studied the long-term effects of vitamins C and E on plasma F2-isoprostanes, a widely used marker of lipid peroxidation in vivo. As a study cohort, a subset of the "Antioxidant Supplementation in Atherosclerosis Prevention" (ASAP) study was used. ASAP is a double-masked placebo-controlled randomized clinical trial to study the long-term effect of vitamin C (500 mg of slow release ascorbate daily), vitamin E (200 mg of D-alpha-tocopheryl acetate daily), both vitamins (CellaVie), or placebo on lipid peroxidation, atherosclerotic progression, blood pressure and myocardial infarction (n = 520 at baseline). Lipid peroxidation measurements were carried out in 100 consecutive men at entry and repeated at 12 months. The plasma F2-isoprostane concentration was lowered by 17.3% (95% CI 3.9-30.8%) in the vitamin E group (p = 0.006 for the change, as compared with the placebo group). On the contrary, vitamin C had no significant effect on plasma F2-isoprostanes as compared with the placebo group. There was also no interaction in the effect between these vitamins. In conclusion, long-term oral supplementation of clinically healthy, but hypercholesterolemic men, who have normal vitamin C and E levels with a reasonable dose of vitamin E lowers lipid peroxidation in vivo, but a relatively high dose of vitamin C does not. This observation may provide a mechanism for the observed ability of vitamin E supplements to prevent atherosclerosis.

Low serum lycopene concentration is associated with an excess incidence of acute coronary events and stroke: the Kuopio Ischaemic Heart Disease Risk Factor Study

A number of epidemiological studies have shown an association between beta-carotene and the risk of cardiovascular diseases, whereas only a few studies are available concerning the association of lycopene with the risk of coronary events, and no studies have been undertaken concerning lycopene and stroke. Thus, we tested the hypothesis that low serum levels of lycopene are associated with increased risk of acute coronary events and stroke in middle-aged men previously free of CHD and stroke. The subjects were 725 men aged 46-64 years examined in 1991-3 in the Kuopio Ischaemic Heart Disease Risk Factor Study. Forty-one men had either a fatal or a non-fatal acute coronary event or a stroke by December 1997. In a Cox' proportional hazard's model adjusting for examination years, age, systolic blood pressure and three nutritional factors (serum folate, beta-carotene and plasma vitamin C), men in the lowest quarter of serum lycopene levels (< or =0.07 micromol/l) had a 3.3-fold (95 % CI 1.7, 6.4, risk of acute coronary events or stroke compared with the others. Our study suggests that a low serum level of lycopene is associated with an increased risk of atherosclerotic vascular events in middle-aged men previously free of CHD and stroke.

Low plasma lycopene concentration is associated with increased intima-media thickness of the carotid artery wall

Although a number of epidemiological studies have evaluated the association between ss-carotene and the risk of cardiovascular diseases, there has been little research on the role of lycopene, an acyclic form of ss-carotene, with regard to the risk of cardiovascular disease. We investigated the relationship between plasma concentrations of lycopene and intima-media thickness of the common carotid artery wall (CCA-IMT) in 520 middle-aged men and women (aged 45 to 69 years) in eastern Finland. They were examined from 1994 to 1995 at the baseline of the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study, a randomized trial concerning the effect of vitamin E and C supplementation on atherosclerotic progression. The subjects were classified into 2 categories according to the median concentration of plasma lycopene (0.12 micromol/L in men and 0.15 micromol/L in women). Mean CCA-IMT of the right and left common carotid arteries was 1.18 mm in men and 0.95 mm in women with plasma lycopene levels lower than the median and 0.97 mm in men (P:<0.001 for difference) and 0.89 mm in women (P:=0.027 for difference) with higher levels of plasma lycopene. In ANCOVA adjusting for cardiovascular risk factors and intake of nutrients, in men, low levels of plasma lycopene were associated with a 17.8% increment in CCA-IMT (P:=0.003 for difference). In women, the difference did not remain significant after the adjustments. We conclude that low plasma lycopene concentrations are associated with early atherosclerosis, manifested as increased CCA-IMT, in middle-aged men living in eastern Finland.

Antioxidative efficacy of parallel and combined supplementation with coenzyme Q10 and d-alpha-tocopherol in mildly hypercholesterolemic subjects: a randomized placebo-controlled clinical study

It has been claimed that coenzyme Q10 (Q10) would be an effective plasma antioxidant since it can regenerate plasma vitamin E. To test separate effects and interaction between Q10 and vitamin E in the change of plasma concentrations and in the antioxidative efficiency, we carried out a double-masked, double-blind clinical trial in 40 subjects with mild hypercholesterolemia undergoing statin treatment. Subjects were randomly allocated to parallel groups to receive either Q10 (200 mg daily), d-alpha-tocopherol (700 mg daily), both antioxidants or placebo for 3 months. In addition we investigated the pharmacokinetics of Q10 in a separate one-week substudy. In the group that received both antioxidants, the increase in plasma Q10 concentration was attenuated. Only vitamin E supplementation increased significantly the oxidation resistance of isolated LDL. Simultaneous Q10 supplementation did not increase this antioxidative effect of vitamin E. Q10 supplementation increased and vitamin E decreased significantly the proportion of ubiquinol of total Q10, an indication of plasma redox status in vivo. The supplementations used did not affect the redox status of plasma ascorbic acid. In conclusion, only vitamin E has antioxidative efficiency at high radical flux ex vivo. Attenuation of the proportion of plasma ubiquinol of total Q10 in the vitamin E group may represent in vivo evidence of the Q10-based regeneration of the tocopheryl radicals. In addition, Q10 might attenuate plasma lipid peroxidation in vivo, since there was an increased proportion of plasma ubiquinol of total Q10.

Long-term effects of vitamin E, vitamin C, and combined supplementation on urinary 7-hydro-8-oxo-2'-deoxyguanosine, serum cholesterol oxidation products, and oxidation resistance of lipids in nondepleted men

We studied the long-term effects of vitamins E and C and their combination on lipid peroxidation in vivo and in vitro. The Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) trial is a double-masked placebo-controlled randomized clinical trial to study the effects of vitamin C (500 mg of slow release ascorbate per day), vitamin E (182 mg of RRR-alpha-tocopherol acetate per day), and the combination of both antioxidants. Lipid peroxidation measurements were carried out for 48 male participants at entry and at 12 and 36 months. Compared with placebo, vitamin E and the vitamin combination increased plasma lipid-standardized alpha-tocopherol during the first 12 months by 68.2% and 65.2% (P:<0. 001 for both), respectively, and reduced serum 7beta-hydroxycholesterol by 50.4% (P:=0.013) and 44.0% (P:=0.041), respectively. The net change of lipid standardized alpha-tocopherol was 63.8% after 36 months of vitamin E supplementation and 43.3% for the combination. Vitamin C supplementation elevated plasma total ascorbate level by 30.1% (P:=0.043) in 12 months and by 91.1% (P:=0. 001) in 36 months. Neither vitamin E, vitamin C, nor the combination influenced the urinary excretion rate of 7-hydro-8-oxo-2'-deoxyguanosine or the antioxidative capacity of plasma. Vitamin E and the combination of vitamins E and C enhanced the oxidation resistance of isolated lipoproteins and total serum lipids. Our data indicate that long-term supplementation of nondepleted men with a reasonable dose of vitamin E alone or in combination with slow release vitamin C reduces lipid peroxidation in vitro and in vivo, whereas a relatively high dose of vitamin C alone does not.

Anti-oxidant therapy for the treatment of coronary artery disease

Coronary artery disease is the most common cause of death in developed countries. It may present in many different ways, but most frequently as a myocardial infarction, sudden death, angina or heart failure. Preventive measures in relation to coronary artery disease are particularly important because of its high incidence, high mortality and because most patients die outside hospital. Since the oxidation of low density lipoprotein cholesterol (LDL-C) is a critical early step in the process of atheroma formation, taking anti-oxidants to prevent LDL-C oxidation may prove a very effective means of reducing coronary artery disease mortality. However, the role of anti-oxidants in coronary artery disease prevention needs to be evaluated as part of an overall strategy that includes pharmacological and non-pharmacological measures, which are described in this review. In addition, a more structured and scientific approach to anti-oxidant therapy needs to be adopted. This requires that evidence for oxidative stress in a particular condition is obtained, the nature and severity determined and an appropriate anti-oxidant is administered, in an effective dose, which can be shown to correct the oxidative stress. When this is achieved, meaningful clinical trials should be possible, which will determine the place of anti-oxidant therapy for the specified condition.

Antioxidants and lipoprotein metabolism

Lipoprotein metabolism plays a significant role in the pathogenesis of atherosclerosis and risk of vascular disease. Elevated levels of LDL and low levels of HDL are linked to the risk of cardiovascular disease. It is now widely accepted that oxidative modification of LDL affects the metabolism of lipoproteins, leading to their increased accumulation in arterial intima. The present paper will examine some of the accumulating evidence from studies showing relationships between dietary intake of antioxidant nutrients, i.e. vitamins E and C, the carotenoids and the flavonoids, and their influence on lipoprotein metabolism. In particular, the present paper will review the available literature on the affect of antioxidant supplementation on lipoprotein oxidation, and hence metabolism of LDL in human subjects.

Effect of combined coenzyme Q10 and d-alpha-tocopheryl acetate supplementation on exercise-induced lipid peroxidation and muscular damage: a placebo-controlled double-blind study in marathon runners

To test the effects of combined coenzyme Q10 (Q10) and d-alpha-tocopheryl acetate supplementation on exercise-induced oxidative stress and muscular damage we conducted a double-blind study in 37 moderately trained male marathon runners. These were randomly allocated to receive either an antioxidant cocktail: 90 mg of Q10 and 13.5 mg of d-alpha-tocopheryl acetate daily (18 men) or placebo (19 men) for three weeks before a marathon (42km) run. Just before the run, plasma Q10 was 282% (p < 0.0001) and plasma vitamin E 16% (p < 0.007) higher in the supplemented group, than in the placebo group. Also the proportion of plasma ubiquinol of total Q10, an indication of plasma redox status in vivo, was significantly higher in the supplemented group. Furthermore, the susceptibility of the VLDL + LDL fraction, to copper-induced oxidation, was significantly reduced in the supplemented group, compared to the placebo group. The exercise increased lipid peroxidation significantly in both study groups, as assessed by the elevated proportion LDL of LDL and the increased susceptibility of lipoproteins to copper induced oxidation. However, the supplementation had no effect on lipid peroxidation or on the muscular damage (increase in serum creatine kinase activity or in plasma lactate levels) induced by exhaustive exercise. Plasma ascorbate, Q10, whole blood glutathione and serum uric acid concentrations increased during the exercise, elevating significantly the TRAP value of plasma by 10.3% and the proportion of plasma ubiquinol of total Q10 by 4.9%. These results suggest that even though exercise increases plasma lipid peroxidation, it also elevates the antioxidative capacity of plasma, as assessed by the increased plasma TRAP and the proportion of Q10H2 of total Q10. However, prior supplementation with small doses of Q10 and d-alpha-tocopheryl acetate neither attenuates the oxidation of lipoproteins nor muscular damage induced by exhaustive exercise such as encountered in a marathon run.

Copper can promote oxidation of LDL by markedly different mechanisms

Oxidation of LDL (0.1 microM) in PBS with copper concentrations ranging from 0.03 to 10 microM, equal to 0.3-100 Cu2+/LDL, was investigated by monitoring the formation of conjugated dienes at 234 nm. With all 8 LDL samples examined, the kinetics changed strongly at submicromolar Cu2+ concentrations. Based on time-course of the formation of conjugated dienes, cholesteryl linoleate hydroxides and hydroperoxides as well as the antioxidant consumption, two oxidation types were distinguished. Type A oxidations, observed at relatively high Cu2+ concentrations of 10-100 Cu2+/ LDL, represented the conventional kinetics of LDL oxidation with an inhibition period (= lag-time) followed by a propagation phase. In contrast, type C oxidations proceeded after a negligibly short lag time followed by a distinct propagation phase. The rate of this propagation increased rapidly to 0.5 mol diene/mol LDL and then slowed down in the presence of alpha-,gamma-tocopherols and carotenoids, which were consumed faster than tocopherols. The increase in diene absorption was due to the formation of both hydroxides and hydroperoxides suggesting a high initial decomposition of hydroperoxides. At submicromolar concentrations of about 0.1 to 0.5 microM, type C and type A oxidation can be combined resulting in 4 consecutive oxidation phases, i.e. 1st inhibition and 1st propagation (belonging to type C), followed by 2nd inhibition and 2nd propagation (belonging to type A). Increasing copper concentrations lowered the 1st propagation and shortened the 2nd inhibition periods until they melted into one apparent kinetic phase. Decreasing [Cu2+] increased the 1st propagation and 2nd inhibition but lowered the 2nd propagation phase until it completely disappeared. A threshold copper concentration, denoted as Cu(lim), can be calculated as a kinetic constant based on the Cu2+-dependence for the rate of 2nd propagation. Below Cu(lim), LDL oxidation proceeds only via type C kinetics. The Cu2+-dependence of the oxidation kinetics suggests that LDL contains two different Cu2+ biding sites. Cu2+ at the low-affinity binding sites, with half-saturation at 5-50 Cu2+/LDL, initiates and accelerates the 2nd propagation by decomposing lipid hydroperoxides. Cu2+ bound to the high-affinity binding sites, with half-saturation at 0.3-2.0 Cu2+/LDL, is responsible for the 1st propagation. Arguments in favor and against this propagation being due to tocopherol mediated peroxidation (TMP) are discussed. If the lag-time concept is extended to the conjugated diene curves seen for combined oxidation profiles, then a true inhibition phase does not apply to this time interval, but instead represents the time elapsed before the onset of the 2nd propagation phase.

Ascorbate and urate are the strongest determinants of plasma antioxidative capacity and serum lipid resistance to oxidation in Finnish men

Copper-induced plasma lipoprotein oxidation resistance has usually been determined in separated low density lipoprotein (LDL) fractions, that do not contain water-soluble antioxidants present in blood plasma. The aim of this study was to find the main determinants of the measurements of copper-induced lipid oxidation resistance (lag time) in whole serum and plasma total peroxyl radical trapping capacity (TRAP) in a population sample of smoking (n = 25) or non-smoking (n = 26) middle aged men at high risk of cardiovascular diseases. Smokers had significantly lower plasma ascorbic acid values, but only slightly lower alpha-tocopherol, beta-carotene and serum urate values than non-smokers. Plasma ascorbic acid concentration explained 23.5% of the lag time variation (standardized regression coefficient beta = 0.48; P = 0.004) in smokers and 5.6% in non-smokers. Serum urate concentration was the strongest determinant of lag time in non-smokers (beta = 0.64, P < 0.001). In addition, serum albumin, lipid standardized alpha-tocopherol and serum high density lipoprotein (HDL) cholesterol entered the multivariate regression mode for lag time. For plasma TRAP, only urate and ascorbic acid entered the multivariate regression model. Lag times in serum and in isolated very low density lipoprotein (VLDL) and LDL fraction did not correlate, but the maximal rate of these reactions correlated significantly. These results confirm that lipid peroxidation resistance in serum or plasma are associated with ascorbic acid, urate, alpha-tocopherol, albumin and HDL concentrations. The measurement of lipid oxidation resistance in whole serum might be more physiological than in isolated lipoprotein fraction, as the effects of water-soluble antioxidants are not artificially removed.

Effect of oral coenzyme Q10 supplementation on the oxidation resistance of human VLDL+LDL fraction: absorption and antioxidative properties of oil and granule-based preparations

Coenzyme Q10 (Q10) is supposed to be an important endogenous lipid-soluble antioxidant. We studied 60 healthy 46 +/- 7 (mean +/- SD)-year-old smoking men. They were randomized into three groups to receive oil-based or granular Q10 (90 mg/d) or placebo for 2 months. Oil-based capsule elevated Q10 in plasma by 178% and in VLDL+LDL fraction by 160%. The granular preparation increased Q10 in plasma by 168% and in VLDL+LDL by 127%. However, the 2-month Q10 supplementation did not increase the oxidation resistance of VLDL+LDL fraction, as assessed by copper induced VLDL+LDL oxidation, haemin+H(2)O(2)-induced VLDL+LDL oxidation, total antioxidative capacity of LDL, and plasma malondialdehyde measurements. The first and the last dose was used to carry out a 12 h pharmacokinetic study (five subjects per group), which indicated that only a small part of supplemented Q10 was absorbed to the circulation in 12 h and that the absorption varied extensively between subjects. Our results suggest that at least among smoking men, 90 mg of orally supplemented Q10 daily does not increase the oxidation resistance of VLDL+LDL. Bioavailability of both the granular and the oil-based Q10 preparation was similar during the long-term supplementation, but one dose of 30 mg had only a marginal effect on the plasma levels of Q10.