A rapid and simple method for measuring the susceptibility of low-density-lipoprotein and very-low-density-lipoprotein to copper-catalyzed oxidation

Effects of vitamin C supplementation on oxidative stress and serum paraoxonase/arylesterase activities in patients on long-term hemodialysis

BACKGROUND

Oxidative stress increases oxidizability of apolipoprotein-B containing lipoproteins and decreases paraoxonase (PON) activity in hemodialysis (HD) patients and plays an important part in the development of atherosclerotic cardiovascular diseases. In HD patients, plasma ascorbic acid (AA) levels are decreased either due to the loss by hemodialysis membranes or due to malnutrition and contribute to the imbalance of antioxidant defense mechanisms. We hypothesized that long-term ascorbic acid (AA) supplementation recovers oxidizability of lipoproteins in HD patients by reinforcing PON activity.

METHODS

Twenty-nine adult patients were treated with 100mg and 500mg AA at the end of each HD session thrice a week for two consecutive 16 weeks-periods, respectively. Blood samples were obtained before the first HD session and prior to the first HD sessions following the 100mg AA-supplemented and the 500mg AA-supplemented periods.

RESULTS

PON activities were significantly increased after 100mg (p<0.05) and 500mg AA (p<0.001) supplementation periods compared to the basal level. Apo-B lipoprotein oxidizability (Δ-MDA) was significantly decreased after 500mg AA supplementation compared to both basal (p<0.05) and 100mg AA supplementation periods (p<0.05). Plasma AA concentrations were negatively correlated with Δ-MDA levels (R=-0.327; p<0.01).

CONCLUSION

Our results suggest that long-term parenteral 500mg AA supplementation improves PON activity alleviating apo B-containing lipoproteins oxidizability in HD patients.

Evaluation of Antioxidant Activities and Phenolic Compounds of Scorzonera latifolia (Fisch. & Mey.) DC. Collected from Different Geographic Origins in Turkey

Objectives

The chemical composition of plants is considered to be affected by many parameters. Therefore, the region where the samples are collected is likely to have an influence on the composition of phenolic compounds, so that their biological activities. In the present study, evaluation of antioxidant activity potentials of Scorzonera latifolia (Fisch. & Mey.) DC. aerial parts and roots, which were collected from different regions of Turkey, was aimed.

Materials and Methods

1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method and measurement of malondialdehyde (MDA) levels were used for determining antioxidant capacities of the tested extracts. In order to observe variations in the chemical composition of the investigated samples qualitatively as well as quantitatively, high performance liquid chromatography analyses were performed.

Results

Quantitative analysis showed that the amounts of chlorogenic acid and hyperoside in plants vary according to the regions where the samples were collected. As a result aerial parts of the S. latifolia collected from the Kars region have found to contain higher amount of chlorogenic acid (1246.78±3.20 µg/g) as well as hyperoside (652.32±2.48 µg/g) than other samples. The highest DPPH radical scavenging activity was determined with the IC₅₀ value of 1.036 mg/mL for S. latifolia aerial parts of Kayseri sample. MDA level was detected as the lowest with treatment of S. latifolia Bayburt root sample (4.41 nmol/mL).

Conclusion

According to the antioxidant activity results, no significant difference was observed in the antioxidant potential between the samples collected from different locations except for S. latifolia collected from the Kars region.

First-episode psychosis is associated with oxidative stress: Effects of short-term antipsychotic treatment

AIMS

In the present study, our aim was to investigate the oxidative-antioxidative systems in unmedicated first-episode psychosis (FEP) patients at the beginning and after short-term treatment.

METHODS

This study consisted of 29 patients who experienced an FEP and 25 control subjects. In order to investigate the oxidative status, we determined plasma malondialdehyde (MDA) levels, oxidizability of red blood cells, oxidation and oxidizability of apolipoprotein B-containing lipoproteins (apo B-basal MDA and apo B-ΔMDA). In order to evaluate the antioxidative defense, we measured serum total antioxidative capacity, uric acid, albumin, total bilirubin and vitamin E levels and serum paraoxonase/arylesterase, whole blood glutathione peroxidase (GPx) and red blood cell superoxide dismutase activities before and after 6 weeks of treatment in patients with FEP.

RESULTS

Plasma MDA and apo B-basal MDA levels and red blood cell superoxide dismutase activity were significantly higher and serum arylesterase and whole blood-GPx activities were lower in the FEP group than those of the healthy control group. There were not any significant changes in the oxidative and antioxidative system parameters (except increased vitamin E levels) after treatment.

CONCLUSIONS

The results of this study suggest that FEP is accompanied by oxidative stress. However, further studies are needed to clarify the role of oxidative stress in the physiopathologic mechanisms of FEP, so that oxidative and antioxidative system parameters can be used in the management of these patients. In accordance with psychiatric evaluation, for a better management, patients with FEP may require a multidisciplinary approach, including oxidative and antioxidative system parameters.

Effect of oxidized low-density lipoprotein concentration polarization on human smooth muscle cells' proliferation, cycle, apoptosis and oxidized low-density lipoprotein uptake

To clarify the effect of concentration polarization of oxidative modification of low-density lipoproteins (ox-LDLs) on human smooth muscle cells (SMCs), the proliferation, ox-LDL uptake and apoptosis with SMCs cultured on permeable (the permeable group) or non-permeable membranes (the non-permeable group) were analysed by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay, spectrofluorometry and flow cytometry using a parallel-plate flow chamber technique. The concentration polarization of ox-LDLs at the surface of the cultured cell monolayer was assessed by confocal laser microscopy. The results showed that concentration polarization of ox-LDLs could indeed occur at the cultured cell monolayer surface of the permeable group, leading to an enhanced wall concentration of ox-LDLs that was over 15 per cent higher than the bulk concentration of the perfusion solution at a pressure of 100 mmHg. When concentration of ox-LDLs in the perfusion solution was less than or equal to 100 µg ml(-1), SMCs' proliferation was induced, while cell apoptosis was induced when its concentration was above 150 µg ml(-1). The uptake of ox-LDLs by the cultured cells was significantly higher for the permeable group than for the non-permeable group. In addition, the ox-LDL-induced cell death and apoptosis were much more severe in the permeable group than that in the non-permeable group. Therefore, the experimental study suggests that concentration polarization of ox-LDLs plays an adverse role in the vascular system owing to its toxicity to vascular cells, in turn enhance ox-LDL infiltration into the arterial wall and accelerate SMC apoptosis.

Effects of long-term antidepressant treatment on oxidative status in major depressive disorder: a 24-week follow-up study

PURPOSE

Major depressive disorder (MDD) is a devastating disease that afflicts large populations and has also been accepted to be an independent risk factor for cardiovascular disease (CVD). Oxidative stress seems to play an essential role in the relationship of MDD and CVD. We aimed to determine the level of oxidative stress in patients with MDD and to investigate the effects of long-term antidepressant (AD) treatment on the oxidative-antioxidative system parameters and CVD risk factors.

METHOD

Fifty patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 44 healthy control subjects were included in the study. Control visits of the patients were repeated 6weeks, 12weeks and 24weeks after beginning of the AD treatment. Lipid profiles, oxidation and oxidizability of apolipoprotein B-containing lipoproteins (expressed as apo B-b-MDA and apo B-Δ-MDA, respectively), levels of plasma malondialdehyde (p-MDA), total antioxidative capacity (TAOC), antioxidant molecules and antioxidant enzyme activities including paraoxonase/arylesterase, red blood cell superoxide dismutase (RBC-SOD) and glutathione peroxidase were determined during 24-week of follow-up period.

RESULTS

According to the results of the study, p-MDA, apo B-b-MDA and RBC-SOD activity were increased and arylesterase activity was decreased in MDD patients. Body mass index (BMI), vitamin A and total cholesterol levels in MDD patients increased after 24-weeks of AD treatment. RBC-SOD activity, TAOC, p-MDA and apo B-b-MDA levels were decreased; paraoxonase/arylesterase activities and apo B-Δ-MDA were increased at the end of 24th week.

CONCLUSION

Oxidative stress, demonstrated in MDD patients, was partly improved during 24weeks of AD treatment. Increase in paraoxonase/arylesterase activities and decrease in p-MDA and apo B-b-MDA levels after 24weeks seem to be beneficial for reduction of CVD risk in MDD patients. However increased BMI and apo B-Δ-MDA levels are negative cardiovascular effects of long-term AD treatment.

Protective effect of L-arginine in experimentally induced myocardial ischemia: comparison with aspirin

OBJECTIVE

Coronary artery diseases including myocardial ischemia (MI) remain one of the leading causes of death worldwide. This study was designed to compare the protective effect of L-arginine versus aspirin from the biochemical changes associated with MI injury.

EXPERIMENTAL DESIGN

Four groups of male New Zealand white rabbits were investigated. Normal group (n = 8) rabbits were fed standard chow pellets, untreated MI group (n = 16), where hypercholesterolemia was induced by feeding the animals with a diet containing 2% cholesterol for 28 days, L-arginine group (n = 12) rabbits were fed a 2% cholesterol-enriched diet in conjunction with L-arginine (2.25 g %) in drinking water for 28 days, and aspirin group (n = 12) rabbits were fed 2% cholesterol-enriched diet in conjunction with aspirin administered orally (0.7 mg/kg per d) for 28 days. After 28 days, MI was induced in all groups, except the normal group, by a single subcutaneous (sc) injection of isoproterenol hydrochloride (0.2 mg/kg body weight [bw]). Animals were sacrificed 6 hours later.

RESULTS

Our results showed that L-arginine was more effective than aspirin in reducing platelet aggregation, reducing low-density lipoprotein (LDL) oxidizability, preventing aortic intimal thickening, and maintaining histological architecture of the myocardium. Both drugs, however, had similar positive effects on plasma fibrinogen levels and on the prevention of myocardial release of cardiac troponin I and creatine kinase-MB. The effect on hypercholesterolemia was insignificant for both drugs. Aspirin was more effective than L-arginine in prolonging prothrombin time.

CONCLUSION

L-arginine supplementation represents a potentially novel nutritional strategy for preventing and treating coronary artery diseases especially in cases of aspirin resistance and/or hypersensitivity.

Artichoke leaf extract reduces oxidative stress and lipoprotein dyshomeostasis in rats fed on high cholesterol diet

Hypercholesterolemia and lipid peroxidation play complementary role in atherosclerosis. Artichoke leaf extract (ALE) is rich in natural antioxidants and has a cholesterol-reducing effect. However, there is no study investigating the effect of ALE on lipid levels and lipid peroxidation in experimental hypercholesterolemic conditions. Rats were fed on 4% (w/w) cholesterol and 1% (w/w) cholic acid supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. Serum lipid composition, malondialdehyde (MDA) and diene conjugate (DC) levels and plasma antioxidant activity (AOA) were measured. In addition, endogenous DC and copper-induced MDA levels were determined in apo B-containing lipoproteins (LDL+VLDL fraction). Serum cholesterol and triglyceride levels and the ratio of cholesterol to HDL-cholesterol decreased due to ALE treatment in rats fed on HC diet. Significant decreases in serum MDA and DC levels and increases in plasma AOA were detected in serum in ALE-treated hypercholesterolemic rats. Endogenous DC and copper-induced MDA levels were also lower in LDL+VLDL fraction due to ALE-treatment in hypercholesterolemic rats. Our results indicate that ALE may be useful for the prevention of hypercholesterolemia-induced pro-oxidant state in LDL+VLDL fraction and the reduction of increased serum cholesterol and triglyceride levels.

Glycoxidative stress-induced damage on lipid profile in a fructose-enriched diet model of insulin resistance in rats

OBJECTIVE

To study alterations in plasma lipid profile and oxidative damage to lipoprotein fractions (LF) and their fatty acids during an early insulin-resistant and increased oxidative state developed by a fructose-rich diet (FRD).

METHODS AND RESULTS

Wistar rats were fed a commercial diet with (FRD) or without (CD) 10% fructose in the drinking water. After 3 weeks, plasma glucose, triglyceride (TG), insulin (I), fructosamine (F), free fatty acids (FFA) and lipid profile (total cholesterol [TC] and HDL-C, LDL-C and VLDL-C sub-fractions) were determined. The insulin sensitivity HOMA index was assessed. FRD-fed rats had higher plasma TG, I, and F levels; increased HOMA; decreased HDL-C and LDL-C; augmented VLDL-C and TC/HDL-C, and TG/HDL-C atherogenic risk scores. LF of FRD rats had increased oxidative damage on the fatty acyl profile and in copper-induced lipoperoxidation.

CONCLUSIONS

Fructose feeding early increases the atherogenic risk inducing an insulin resistant-glycoxidative state that affects plasma lipid profiles.

Susceptibility of apolipoprotein B-containing lipoproteins to oxidation and antioxidant status in acute coronary syndromes

BACKGROUND

Oxidized lipoproteins may play an important role in the pathogenesis of atherosclerosis, and it has been shown that antioxidants have a protective effect against the progression of atherosclerosis.

HYPOTHESIS

The aim of this study was to investigate the oxidative susceptibility of apolipoprotein B-containing lipoproteins and antioxidant status in patients with acute coronary syndromes and chronic stable angina pectoris.

METHODS

The study population included 70 patients with acute coronary syndromes (14 with recent acute myocardial infarction and 56 with unstable angina pectoris), 105 patients with stable angina pectoris, and 75 control subjects. In addition to conventional lipid and lipoprotein analysis, the susceptibility of apolipoprotein B-containing lipoproteins to in vitro oxidation (lag phase) and plasma vitamin E and total carotene levels was measured.

RESULTS

The lag phase was significantly shorter in patients with acute coronary syndromes (45 +/- 12 min) than in patients with stable angina pectoris (51 +/- 10 min) and in control subjects (58 +/- 9 min) (p < 0.0001). Both plasma vitamin E and total carotene levels were lowest in patients with acute coronary syndromes (1.11 +/- 0.32 mg/dl and 119 +/- 32 micrograms/dl, respectively), followed by patients with stable angina pectoris (1.25 +/- 0.37 mg/dl and 132 +/- 37 micrograms/dl) and then controls (1.52 +/- 0.31 mg/dl and 167 +/- 41 micrograms/dl).

CONCLUSIONS

These data suggest that there is an intense oxidative process and a lower antioxidant status in acute coronary syndromes. This may lead to plaque instability due to the activation of the inflammatory response in coronary atherosclerotic lesions.

Coronary artery disease risk factors in patients with schizophrenia: effects of short term antipsychotic treatment

The aim of the present study was to investigate serum paraoxonase/arylesterase activities and oxidation/oxidizability of apolipoprotein B-containing lipoproteins and several coronary artery disease risk factors, including homocysteine, high sensitive C-reactive protein, tumour necrosis factor-alpha, leptin and adiponectin in patients with schizophrenia. Oxidation of lipoproteins plays an important role in atherogenesis, and the enzyme paraoxonase has been shown to prevent lipoprotein oxidation. Furthermore, low paraoxonase activity has been suggested to predict coronary artery disease. Forty patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for schizophrenia and 35 healthy control subjects were included in the study. Serum paraoxonase/arylesterase activities were determined spectrophotometrically. Malondialdehyde levels of apolipoprotein B-containing lipoproteins were determined before and after incubation with copper-sulphate, which yielded basal- and Delta-malondialdehyde values, respectively. Homocysteine and highly sensitive C-reactive protein levels were determined using a fluorescence-polarization immunoassay and immunonephelometry, respectively. Leptin and adiponectin levels were measured with radioimmunoassay and tumour necrosis factor-alpha was determined by enzyme linked immunosorbent assay. Serum paraoxonase and arylesterase activities were significantly lower and Delta-malondialdehyde levels were significantly higher in the schizophrenia group compared with the control group. However, there were not any significant differences in other parameters of the study between the study groups. There was a significant increase in body mass index and serum triglyceride and very low density lipoprotein cholesterol levels in the schizophrenic group after 6 weeks of treatment. These parameters were significantly increased in patients treated with atypical antipsychotics but not in patients treated with typic or long acting antipsychotics. The results of the present study suggest that patients with schizophrenia might have increased risk for coronary artery disease related to reduced serum paraoxonase activity and increased oxidizability of apolipoprotein B-containing lipoproteins.

Amiodarone inhibits tocopherol-mediated human lipoprotein peroxidation

It is unknown whether lipoprotein tocopherol-mediated peroxidation (TMP) is influenced by peculiar drug physicochemical properties such as hydrophobicity. Thus, we studied the effect of the extremely hydrophobic agent amiodarone on human non-HDL TMP. The drug, albeit devoid of specific radical-scavenging effects, inhibited TMP at therapeutic concentrations and with an efficiency similar to that of the physiological co-antioxidant ascorbic acid, showing indeed an IC(50) of 5microM. A comparable efficiency was observed with human LDL, and with a pure LDL-VLDL mixture. TMP was also inhibited by other hydrophobic cationic amphiphiles without radical-scavenging activity, namely desethylamiodarone, chlorpromazine, clomipramine, promethazine, promazine, verapamil, bromhexine, propranolol, mepivacaine, metoprolol, tramadol and ranitidine, whose anti-TMP potency was far lower than that of amiodarone and related to drug hydrophobicity degree. Further, TMP was strongly inhibited by butylhydroxytoluene, a lipophilic radical scavenger. Hydrophobic acidic (diclofenac, indomethacin, ibuprofen and ketoprofen) or neutral (n-hexane, anthracene, o-xylene and toluene) compounds could not instead inhibit TMP, indicating a stringent requirement for drug basicity in the pharmacological inhibition of TMP. Amiodarone effectiveness was lowered by lipoprotein alpha-tocopherol enrichment, suggesting some drug-alpha-tocopherol interaction and less lipid pharmacological protection at higher alpha-tocopheroxyl radical generation. Drug anti-TMP activity may so be related to electrostatic and hydrophobic interactions with lipoprotein alpha-tocopherol and lipid moiety, resulting in decreased radical phase transfer and lipid propensity to undergo radical-driven peroxidation. In conclusions, primarily drug basicity and then hydrophobicity are solely relevant to TMP inhibition. Amiodarone, at therapeutic concentrations, has anti-TMP properties, which could occur in the clinical setting.

Antioxidative effects of plant polyphenols: from protection of G protein signaling to prevention of age-related pathologies

The antioxidant potency of three natural polyphenols, resveratrol, curcumin, and genistein, was compared by using the two human models: oxymodified with H(2)O(2) and homocysteine (Hcy) G proteins in the postmortem frontal cortex (FC) membranes of age-matched control and Alzheimer's disease (AD) subjects; and Cu(2+)-induced oxidation of plasma low-density lipoproteins (LDL). In Co, 3-10 microM polyphenols dose-dependently depressed the G protein 25% stimulation induced by 10 microM H(2)O(2) or 500 microM Hcy. Resveratrol revealed significantly higher antioxidativity than curcumin or genistein. In AD, the antioxidativity of polyphenols showed no significant differences. Polyphenols (1 microM) significantly increased the LDL oxidation lag time (oxyresistance) as compared with control, the effect of resveratrol being most potent. Due to the dual antioxidant mechanism, the investigated polyphenols, particularly resveratrol, should have preferences for the preventive-therapeutic use in age-related oxidative stress-based pathologies.

Divergent in vitro and in vivo lipid peroxidation in the postprandial phase of patients with type I diabetes mellitus

OBJECTIVE

The two- to fourfold higher risk of cardiovascular disease in diabetes mellitus is more strongly predicted by the postprandial than by the fasting blood glucose and lipids. We aimed to investigate the impact of postprandial changes in serum lipoprotein fractions on lipid peroxidation in type I diabetes mellitus (T1DM).

DESIGN

This was a prospective observational study.

SETTING

The study was performed at Antwerp University Hospital, Belgium.

SUBJECTS

Twenty-three well-controlled T1DM patients were included.

INTERVENTION

Patients received a standard breakfast and lunch (>50% energy as fat). Blood was sampled at fasting (F), after the post-breakfast hyperglycemic peak (BP), just before lunch (B), after the post-lunch hyperglycemic peak (LP), after the post-lunch dale (LD) and 5 h after lunch (L) for the measurement of serum lipids, lipoprotein subfraction composition, alpha-tocopherol and lipid peroxidation in vivo and in vitro.

RESULTS

Serum triacylglycerols (Tgs) increased (from 1.03+/-0.40 at F to 1.60+/-0.87 mmol/l at LP, P=0.001), but cholesterol decreased by 12% in parallel with alpha-tocopherol (from 4.43+/-0.76 at F to 4.12+/-0.82 micromol/mmol total lipid at B, P=0.006). Although plasma malondialdehyde increased from 1.02+/-0.36 at F to 1.14+/-0.40 micromol/L at LP, P=0.03, copper-induced in vitro peroxidation decreased in the low-density lipoprotein and high-density lipoprotein fractions.

CONCLUSIONS

In well-controlled T1DM patients moderate postprandial increases in serum Tgs are accompanied by a relative deficiency in alpha-tocopherol. Lipid peroxidation in vivo increases but cannot be ascribed to changes in the susceptibility of lipoproteins to copper-induced in vitro peroxidation.

Effect of dietary supplementation of astaxanthin byPhaffia rhodozymaon lipid peroxidation, drug metabolism and some immunological variables in male broiler chicks fed on diets with or without oxidised fat

1. Effects of dietary supplementation of astaxanthin (Ax) provided from Phaffia rhodozyma on lipid peroxidation, hepatic drug metabolism, antibody titres to sheep red blood cells (SRBC) and splenocyte proliferation to mitogens were determined in male broiler chicks. 2. Chicks, one week old, were given diets with or without oxidised fat (0 or 3.7 meq of peroxide value (POV)/kg diet) and/or Ax (0 or 100 mg/kg diet) for 14 d, ad libitum. 3. Lipid peroxidation, estimated by 2-thiobarbituric acid reactants values in liver, spleen, heart, plasma and hepatic microsomes, were increased by feeding a diet containing oxidised fat (P<0.05) but were not affected by Ax feeding. 4. Cytochrome P-450 contents in hepatic microsome tended to be increased by feeding Ax. 5. Anti-SRBC titre was not affected by oxidised fat or Ax feeding, while plasma immunogloblin (Ig) G concentration was increased by Ax feeding but was not affected by oxidised fat feeding. 6. When chicks were fed on the diet without oxidised fat, Ax enhanced splenocyte proliferation stimulated by both concanavalin A and pokeweed mitogen, while in chicks fed on a diet containing oxidised fat, Ax reduced the proliferation (P<0.01 for Ax and oxidised fat interaction). 7. The results indicated that dietary supplementation of Ax from Phaffia rhodozyma had an impact on T cell proliferation and Ig G production as a part of acquired immunity, but was not effective in preventing lipid peroxidation in male broiler chicks.

Sialic acid and oxidizability of lipid and proteins and antioxidant status in patients with coronary artery disease

The aim of this study was to investigate the possible relationship between serum total sialic acid (TSA) concentration, recently shown to be a cardiovascular risk factor, and lipid and protein oxidation and antioxidant status and the severity of coronary artery disease (CAD) according to the obstructive vessel number in patients. The study was carried out on a total of 200 patients (142 men and 58 women) who were hospitalized for elective coronary angiographic evaluation with complaint of typical angina pectoris. According to the results of angiography, 150 patients had angiographically proven CAD (CAD group) and 50 patients had a history suggestive of angina pectoris but normal coronary angiograms (control group). The CAD group was further divided into single-, double- and triple-vessel disease groups according to the number of vessels involved. Lipid parameters were determined by routine laboratory methods. Plasma malondialdehyde (MDA) and vitamin E concentrations were determined by high-performance liquid chromatography. TSA and other oxidant and antioxidant parameters were studied spectrophotometrically. Our results demonstrated significant increases both in TSA levels and in indicators of oxidative stress in the patients with CAD compared with the controls. However, antioxidant parameters were decreased in the patients with CAD. We found strong positive correlations between TSA and plasma MDA, Delta-MDA which represents the degree of oxidative modification of apolipoprotein B-containing lipoproteins, serum protein carbonyls and apolipoprotein B and weak correlations between TSA and low density lipoprotein cholesterol, triacylglycerol, paraoxonase, glutathione peroxidase (GPx), vitamin C and vitamin E. In conclusion, TSA is related to markers of lipid and protein oxidation, paraoxonase and GPx activities, vitamin C and E levels and the severity of CAD.

Oxidation of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in major depressive disorder

Major depressive disorder (MDD) is blaimed to play a role in the onset of coronary artery disease (CAD). The aim of the present study was to investigate serum paraoxonase/arylesterase activities and oxidation of apolipoprotein B-containing lipoproteins in patients with MDD. Oxidation of lipoproteins plays an important role in atherogenesis and the enzyme paraoxonase, has been shown to prevent lipoprotein oxidation. Furthermore, low paraoxonase activity was suggested to predict CAD. Eighty-six patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 36 healthy control subjects were included in the study. Serum paraoxonase and arylesterase activities were determined spectrophotometrically. Malondialdehyde (MDA) levels of apolipoprotein B-containing lipoproteins were determined before (basal) and after incubation with copper-sulphate, that yielded basal- and Delta-MDA values, respectively. Serum paraoxonase/arylesterase activities were significantly reduced in the post-treatment group compared with the pre-treatment group. Basal-MDA (MDA) level was significantly higher in the MDD group compared with the control group. Delta-MDA level of the severe MDD group was significantly higher than that of the control group. There was a positive correlation between the oxidizability of apolipoprotein B-containing lipoproteins and the severity of the disease. Total cholesterol, HDL-cholesterol, LDL-cholesterol, apolipoprotein B levels were significantly higher and apolipoprotein AI levels were significantly lower in the MDD group compared with those of the control group. The findings of the present study suggest that: 1) antidepressant treatment might reduce serum paraoxonase activity/mass; 2) oxidation and oxidizability of apolipoprotein B-containing lipoproteins seem to be increased in MDD.

Lipid and protein oxidation and antioxidant status in patients with angiographically proven coronary artery disease

OBJECTIVES

We aimed to evaluate the association of lipid peroxidation, protein oxidation and antioxidant system, and to assess an association with the severity of the disease, in patients with and without coronary artery disease (CAD) documented by coronary angiography.

DESIGN AND METHODS

The population included 208 patients, undergoing clinically indicated coronary angiography. While the subjects with normal coronary angiograms (n=54) were evaluated as controls, the patients with CAD (n=154) were divided into three categories according to the number of diseased coronaries; one-vessel (n=50), two-vessels (n=51) and three-vessels (n=53). Lipid parameters were determined by routine laboratory methods. Plasma malondialdehyde and vitamin E concentrations were determined with the high-performance liquid chromatography. Other oxidant and antioxidant parameters were studied spectrophotometrically.

RESULTS

While plasma malondialdehyde levels, the susceptibilities of erythrocyte and apolipoprotein B containing lipoproteins to in vitro induced oxidative stress, serum protein carbonyls, low density lipoprotein-cholesterol, triglyceride, apolipoprotein B and lipoprotein (a) levels had significantly increased, high-density lipoprotein-cholesterol and apolipoprotein AI levels, erythrocyte glutathione peroxidase, glutathione reductase, glucose 6 phosphate dehydrogenase, serum catalase, paraoxonase and arylesterase activities, plasma vitamin E and C and carotenoid levels had significantly decreased. The odds ratios for one-, two-, and three-vessel disease increased across especially higher tertiles of concentrations for oxidation parameters and lower tertiles of concentrations for antioxidant parameters.

CONCLUSIONS

According to the results, we suggest that increased lipid and protein oxidation products and decreased antioxidant enzymes and vitamins contribute to increased oxidative stress which in turn is related to the severity of the disease.

Cell-mediated LDL oxidation: The impact of transition metals and transferrin

Activated monocytes release oxygen radicals by respiratory burst and oxidative damage can be accelerated by transition metals. We investigated the cell-mediated and metal-catalysed in vitro oxidation of low-density lipoproteins (LDL), as well as the impact of the metal-binding protein transferrin (Tf). LDL oxidation was measured by monitoring the increase in fluorescence (350/440 nm excitation/emission). Maximal respiratory burst by U937 cells was achieved after 96 h differentiation with retinoic acid and dihydroxyvitamin D3 followed by stimulation with opsonised zymosan. Addition of activated cells resulted in the LDL oxidation, even in the absence of transition metals. Moreover, activated cells greatly enhanced metal-catalysed oxidative modifications, especially in the presence of copper. By binding metals, Tf was able to strongly impair this process. In conclusion, by generating oxygen radicals, activated U937 cells were able to oxidise LDL. The oxidising process was most pronounced in the presence of copper and could be blocked by Tf.

Effects of micronized fenofibrate and vitamin E on in vitro oxidation of lipoproteins in patients with type 1 diabetes mellitus

OBJECTIVE

The primary objective was to compare the antioxidant activity of micronised fenofibrate 200 mg to 400 IU of vitamin E and placebo, on the LDL and VLDL particles of patients with type 1 diabetes. The secondary objective was to investigate the possible synergy between micronized fenofibrate and vitamin E and to compare the efficacy of these treatments on lipids.

METHODS

A double-blind, placebo-controlled trial in which patients were randomised into three treatment groups after a wash-out period of 8 weeks: the placebo group (Pla/Pla-group) in which patients received placebo during two consecutive periods of 8 weeks, the vitamin E group (Vit E/Vit E-group) in which patients received Vitamin E during two consecutive periods, and the fenofibrate/Vitamin E group (Fen/Fen + Vit E-group) in which patients received fenofibrate during the first period, followed by fenofibrate and vitamin E during the consecutive period. Blood samples taken at each visit, were analysed for routine biochemistry, blood lipids and copper mediated lipid peroxidation in vitro.

RESULTS

The lag time of the non-HDL lipoprotein oxidation increased in the group given fenofibrate. The lag-time increased further when fenofibrate and vitamin E were given in association. (This reached significance in the intention-to-treat population, P = 0.034). The AUC of TBARS formation in the Vit E/Vit E group decreased after the first period, but this effect was not enhanced by continuing vitamin E for another 8 weeks. The AUC of TBARS formation did not change significantly after the administration of fenofibrate. Only after the second period, when vit E was given in association, the AUC of TBARS formation decreased significantly (P = 0.004). Fenofibrate caused a significant decrease in total and LDL-cholesterol and triglycerides (P < 0.05). In contrast, vitamin E had no effect on lipids.

CONCLUSIONS

The combination of micronized fenofibrate 200 mg/day and vitamin E 400 IU/day tended to increase the resistance of non-HDL lipoproteins to copper-mediated oxidation, shown by a prolongation of the lag-time. Vitamin E administration only, decreased the oxidation of non-HDL lipoproteins shown by a reduction of TBARS formation. This protective effect of vitamin E tended to be amplified by micronized fenofibrate.

Evolution of Serum α-Tocopherol in the Postprandial and Postabsorptive Phases in Type 1 Diabetes Mellitus

Blood glucose, lipids, alpha-tocopherol, and malondialdehyde were monitored in type 1 diabetes mellitus patients for 8 hours after a standard fat-rich breakfast and lunch. Although glucose and triglycerides increased, alpha-tocopherol decreased and malondialdehyde increased in the postprandial phase. In the postabsorptive phase values returned to fasting levels. These results point to the possible relevance of postprandial alpha-tocopherol depletion and lipid peroxidation to an increased cardiovascular risk in these patients.

Oxidizability of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in preeclampsia

OBJECTIVES

Lipoprotein oxidation has been implicated in the pathogenesis of preeclampsia and paraoxonase, an antioxidant enzyme shown to protect lipoproteins from being oxidized. The aim of the present study was to evaluate oxidizability of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in preeclampsia.

DESIGN AND METHODS

Twenty-one women with mild preeclampsia, 21 women with severe preeclampsia, and 20 women with normal uncomplicated pregnancy were included in this study. Serum malondialdehyde (MDA) level, an indicator of lipid peroxidation, was measured by high-performance liquid chromatography (HPLC). The oxidizability of apolipoprotein B-containing lipoproteins was evaluated by copper-induced in vitro peroxidation of the isolated fraction of apolipoprotein B-containing lipoproteins coupled with the thiobarbituric acid-reactive substances assay and expressed as the difference between copper-treated MDA and basal MDA (DeltaMDA). The serum paraoxonase and arylesterase activities were determined spectrophotometrically.

RESULTS

Serum MDA and DeltaMDA levels of apolipoprotein B-containing lipoproteins were significantly higher in both mild and severe preeclampsia groups than in the normal pregnant group. Serum paraoxonase and arylesterase activities were not significantly different among the study groups.

CONCLUSIONS

Enhancement in oxidizability of apolipoprotein B-containing lipoproteins accompanying with dyslipidemia and increased serum MDA levels suggests that those lipoproteins play a role in the pathogenesis of preeclampsia. Further studies are needed to investigate serum paraoxonase activity in women with normal pregnancies and preeclampsia.

Oxidizability of apolipoprotein B-containing lipoproteins, levels of lipid peroxidation products and antioxidants in normal pregnancy

OBJECT

The object was to assess oxidizability of apolipoprotein B-containing lipoproteins, levels of lipid peroxidation products and antioxidants in normal pregnancy.

METHOD

Serum malondialdehyde, vitamin E, carotenoids, albumin, uric acid, bilirubin, triglyceride, total cholesterol levels and in vitro copper-induced oxidation of apolipoprotein B-containing lipoproteins were investigated in 21 healthy pregnant and 22 nonpregnant women. Mann-Whitney U test was used for the statistical analyses.

RESULTS

Serum malondialdehyde, vitamin E, triglyceride and total cholesterol levels were significantly higher; albumin and uric acid levels and vitamin E/triglyceride + total cholesterol and carotenoids/triglyceride + total cholesterol ratios were significantly lower in the pregnant group. Basal malondialdehyde concentrations of apolipoprotein B-containing lipoprotein fraction and Delta-malondialdehyde values determined at 30, 60, 90, 120, 150 and 180th minutes of incubation were significantly lower in the pregnant group compared to those in the non-pregnant group.

CONCLUSION

Although greater lipid peroxidation product levels reflect an enhanced lipid peroxidation status in normal pregnancy, apolipoprotein B-containing lipoprotein fraction of normal pregnant women compared with the nonpregnant subjects seems to be protected from oxidation.

Effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men

Although there is a general consensus concerning the lower risk for cardiovascular disease in moderate drinkers, the mechanisms responsible for the cardioprotective effect of red wine remain unknown. It has been proposed that increased serum paraoxonase activity may be a mechanism of action underlying reduced cardiovascular disease risk in moderate drinkers, since paraoxonase inhibits lipoprotein oxidation. The aim of this study was to investigate the effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men. Fourteen healthy-men were included in the study. The subjects consumed 0.375 g alcohol / kg body weight for 3 weeks. Paraoxonase and arylesterase activities were studied spectrophotometrically. Oxidizability of apolipoprotein B-containing lipoproteins were determined, after separating them with precipitation method, by incubating with copper-sulfate. Paraoxonase activity did not change, however arylesterase activity significantly decreased after red wine consumption (P < 0.01). There was a reduced susceptibility of apolipoprotein B-containing lipoproteins to copper-sulfate induced oxidation after red wine consumption (P < 0.01). Our results support that red wine protects lipoproteins against oxidation, however there was not any significant change in serum paraoxonase activity after red wine consumption.

Effects of Atorvastatin on LDL sub-fractions and peroxidation in type 1 diabetic patients: a randomised double-blind placebo-controlled study

BACKGROUND

Patients with diabetes have an increased risk of both developing and dying from cardiovascular disease, and, currently, more aggressive lipid-lowering targets are being recommended for these patients. Statins are widely and successfully used to correct dyslipidemia and prevent acute coronary episodes, but their effects on lipoprotein composition and peroxidation have not been fully investigated. We aimed to address this issue in type 1 diabetes mellitus.

METHODS

T1DM patients with atherogenic index (total/HDL-cholesterol > 4) were randomised double-blindly to group A (n = 12) that received Atorvastatin 40 mg/day and group P (n = 12) that received placebo. They were monitored for blood biochemistry, LDL sub-fractions and lipid peroxidation at inclusion, after 6 and after 12 weeks.

RESULTS

In group A, the 40% decrease in serum total and LDL cholesterol and 20% decrease in triglycerides was accompanied by a decrease in serum alpha-tocopherol from 46.4 +/- 16.3 (mean +/- SD) at inclusion to 32.2 +/- 11.8 and 32.6 +/- 14.0 micromol/L after 6 and 12 weeks respectively (p < 0.001 compared to group P by repeated-measures ANOVA). Relative to LDL + VLDL cholesterol, alpha-tocopherol increased by 40% (p < 0.001). Copper-induced LDL + VLDL peroxidation increased from 4891 +/- 1325 at inclusion to 6821 +/- 2291 and 7040 +/- 1712 nmol TBARS/mg LDL + VLDL cholesterol produced in 3 h (p = 0.004). LDL sub-fractions shifted towards the less dense regions (p = 0.03).

CONCLUSIONS

These results suggest that Atorvastatin lowers the antioxidant capacity of LDL and VLDL in T1DM. The mechanisms underlying these changes merit further investigation and should be taken into account when planning long-term primary prevention of CHD in diabetes.

Antioxidative probiotic fermented goats' milk decreases oxidative stress-mediated atherogenicity in human subjects

The increasing interest in a healthy diet is stimulating innovative development of novel scientific products in the food industry. The viable lactic acid bacteria in fermented milk products, such as yoghurt, have been associated with increased lactose tolerance, a well-balanced intestinal microflora, antimicrobial activity, stimulation of the immune system and antitumoural, anticholesterolaemic and antioxidative properties in human subjects. Recently, we have studied a human Lactobacillus spp. strain that possesses antioxidative activity. The aim of the present pilot study was to develop goats' milk fermented with the human antioxidative lactobacilli strain, Lactobacillus fermentum ME-3, and to test the effect of the fermented probiotic goats' milk on oxidative stress markers (including markers for atherosclerosis) in human blood and urine and on the gut microflora. Twenty-one healthy subjects were assigned to two treatment groups: goats' milk group and fermented goats' milk group (150 g/d) for a period of 21 d. Consumption of fermented goats' milk improved anti-atherogenicity in healthy subjects: it prolonged resistance of the lipoprotein fraction to oxidation, lowered levels of peroxidized lipoproteins, oxidized LDL, 8-isoprostanes and glutathione redox ratio, and enhanced total antioxidative activity. The consumption of fermented goats' milk also altered both the prevalence and proportion of lactic acid bacteria species in the gut microflora of the subjects. We conclude that the goats' milk fermented with our special antioxidative lactobacilli strain Lactobacillus fermentum ME-3 exhibits anti-atherogenic effects.

Influence on hazelnut oil administration on peroxidation status of erythrocytes and apolipoprotein B 100-containing lipoproteins in rabbits fed on a high cholesterol diet

Hazelnut oil (HO) is rich in monounsaturated fatty acids (MUFA). The effect of a high cholesterol (HC) diet with and without HO on lipids and lipid peroxide levels in plasma, apolipoprotein B 100-containing lipoproteins (VLDL + LDL), and erythrocytes as well as hematological data was investigated in rabbits. A HC diet caused significant increases in lipid peroxide levels in plasma and apo B-containing lipoproteins together with histopathological atherosclerotic findings in aorta. In addition, this diet resulted in hemolytic anemia associated with increased endogenous diene conjugate (DC) levels, but H(2)O(2)-induced malondialdehyde (MDA) levels remained unchanged in erythrocytes. HO supplementation reduced lipid peroxide levels in plasma and apolipoprotein B 100-containing lipoproteins as well as aortic atherosclerotic lesions in rabbits fed an HC diet without any decreasing effect on lipid levels. In addition, HO was found to reduce hemolytic anemia together with significant decreases in DC and H(2)O(2)-induced MDA levels.

The consumption of processed tomato products enhances plasma lycopene concentrations in association with a reduced lipoprotein sensitivity to oxidative damage

Lycopene, the predominant carotenoid in tomatoes, is hypothesized to mediate the health benefits of tomato products. We designed a study to examine the change in plasma lycopene and resistance of lipoproteins to ex vivo oxidative stress. Healthy individuals (n = 60; age >40 y; 30 men/30 women) consumed a lycopene-free diet for 1 wk and were subsequently randomized to receive 35 +/- 1, 23 +/- 1 or 25 +/- 1 mg lycopene/d from Campbell's Condensed Tomato Soup (CS), Campbell's Ready To Serve Tomato Soup (RTS) or V8 Vegetable Juice (V8), respectively, for 15 d. Total plasma lycopene concentrations decreased from 0.499 +/- 0.044 to 0.322 +/- 0.027 (35%, P < 0.0001) micro mol/L for the 60 participants during the 7-d washout period. After intervention, total lycopene concentrations increased for those consuming CS, RTS and V8 (compared with the washout period for each group) to 0.784 +/- 0.083 (123%, P < 0.0001), 0.545 +/- 0.061 (57%, P < 0.01) and 0.569 +/- 0.061 (112%, P < 0.0001) micro mol/L, respectively. The concentrations of all lycopene isomers decreased during the washout period. As a percentage of plasma total lycopene isomers for the 60 subjects, all-trans-lycopene decreased from 44.4 +/- 1.2 to 39.6 +/- 1.2 (P < 0.0001), whereas total cis-lycopene isomers increased from 55.6 +/- 1.2 to 60.4 +/- 1.2 (P < 0.0001) during the washout period, a shift that was reversed by consumption of tomato products for 15 d. The ex vivo lipoprotein oxidation lag period, used as a measure of antioxidant capacity, increased significantly from 64.7 +/- 2.4 min at the end of the washout period (all groups) to 70.1 +/- 4.0 (P < 0.05), 68.3 +/- 2.4 (P < 0.05) and 71.7 +/- 4.0 min (P < 0.01) after treatment for the CS, RTS and V8 groups, respectively. This study shows that lycopene concentrations and isomer patterns change rapidly with variation in dietary intake. In addition, 15 d of tomato product consumption significantly enhanced the protection of lipoproteins to ex vivo oxidative stress.

Oxidative stress before and after exercise conditioning in patients following surgical revascularization of the myocardium

The main purpose of the study was to evaluate changes in the extent of oxidative stress and its associations with the indices of cardiorespiratory reserve and functional capacity in 35 patients enrolled in a 12-week exercise conditioning programme 2-4 weeks after surgical revascularization of the myocardium. The following markers of oxidative stress were measured spectrophotometrically before and after the programme: lipid peroxidation products (thiobarbituric acid reactive substances, diene conjugates and lipid hydroperoxide) and markers of blood antioxidant status (blood glutathione markers, blood antioxidative capacity and lag phase of low-density lipoprotein (LDL)). To evaluate the functional indices of the cardiorespiratory system the patients underwent bicycle cardiopulmonary testing before entering and after completing the programme. On the basis of peak oxygen consumption (peak VO2) +/- 1 SD, three subgroups with different aerobic capacity were identified: >/=19 ml/min per kg (GR I, n = 7), 11-19 ml/min per kg (GR II, n = 24) and </=11 ml/min per kg (GR III, n = 5). The extent of oxidative stress was markedly elevated in all subgroups. The most significant improvement occurred at the level of lipid peroxidation products and lag phase of LDL. The indices of cardiorespiratory reserve and exercise capacity demonstrated highly significant increases, while the most favourable modifications, considering both the biochemical and functional indices, were observed in patients with the lowest aerobic capacity.

Effects of intravenous supplementation with alpha-tocopherol in patients receiving total parenteral nutrition containing medium- and long-chain triglycerides

OBJECTIVE

To compare the effects of a lipid emulsion containing medium-chain triglycerides (MCT) and supplemented with alpha-tocopherol to a conventional long-chain triglyceride (LCT) emulsion.

DESIGN

Randomised double blind study.

SETTING

Department of Internal Medicine, Antwerp University Hospital.

SUBJECTS AND INTERVENTIONS

Twenty-four patients with an indication for total parenteral nutrition for a minimum of 10 days were randomly assigned to two groups: group E received as lipid source MCT/LCT (50/50) suplemented with 100 mg DL-alpha-tocopherol/day and group C received LCT. Blood samples were analysed at inclusion, after 4-6 and after 9-11 days.

RESULTS

In group E, serum alpha-tocopherol doubled from 11.4+/-6.9 at inclusion to 20.9+/-7.9 and to 23.8+/-8.8 microg/ml after 4 and 9 days, respectively, but did not change in group C (P=0.008). Production of thiobarbituric acid-reacting substances (TBARS) after 120 min incubation with copper decreased from 66+/-34 at inclusion to 29+/-25 nmol MDA/mg LDL and VLDL-cholesterol after 4 and to 42+/-17 after 9 days (P=0.022 when compared to group C, which underwent no significant changes). Velocity of production of fluorescent products decreased in group E but not in group C (P=0.026).

CONCLUSIONS

Supplementation of TPN containing MCT/LCT with 100 mg DL-alpha-tocopherol/day leads to a doubling in serum alpha-tocopherol and to a decrease in the susceptibility of LDL and VLDL to peroxidation in vitro.

SPONSORSHIP

This study was partly financed by B Braun Medical NVSA, Diegem, Belgium.

Vanadyl as a catalyst of human lipoprotein oxidation

Lipoprotein oxidation, which is relevant to atherogenesis, can be induced by redox-active transition metals, such as copper. Vanadium is a metal usually used as vanadyl to improve metabolic control in diabetic patients; given its redox-active properties, we have investigated possible oxidative effects of the metal on lipoproteins from healthy and diabetic subjects. Beginning from 10 microM, vanadyl, but not vanadate, induced oxidation of the non-HDL fraction, which was inhibited by EDTA, butylated hydroxytoluene and Vitamins E and C, but not by mannitol, SOD and catalase. Differently from copper, vanadyl could oxidize directly lipoprotein lipids, although it showed a lower oxidant activity against critical tryptophan residues of the lipoprotein protein moiety. Moreover, the non-HDL fraction of diabetic patients was more susceptible to vanadyl-dependent oxidation than that of controls. Thus, vanadium, in its reduced form which may be used in humans, can oxidize the non-HDL fraction through oxidative effects exerted especially on lipoprotein lipids; the specific pro-oxidant activity of vanadyl is more evident with lipoproteins of diabetic patients. Given also the tissue accumulating capacity of vanadium conceivably in a reduced form, its prolonged administration to humans, especially to diabetic patients without adequate antioxidant supplementation, needs caution.

Oxidative stress and endothelial function in chronic renal failure

This study aimed to investigate the relationship between oxidative stress and endothelium-dependent vasodilation in patients with chronic renal failure (CRF). Thirty-seven patients with CRF underwent evaluation of endothelium-dependent vasodilation and endothelium-independent vasodilation by means of forearm blood flow measurements with venous occlusion plethysmography during local intra-arterial infusions of methacholine (evaluating endothelium-dependent vasodilation) and sodium nitroprusside (evaluating endothelium-independent vasodilation). Lag phase of lipoprotein fraction to oxidation, total antioxidative activity, diene conjugates, thiobarbituric acid reactive substances, lipid hydroperoxide, reduced glutathione (GSH), oxidized GSH (GSSG), and the GSH redox ratio (GSSG/GSH) were all measured as markers of oxidative stress. Two groups of healthy subjects (61 and 37 subjects, respectively) were used as controls. In one group, oxidative stress markers were measured, whereas endothelium-dependent vasodilation and endothelium-independent vasodilation were assessed in the other group. Compared with controls, the patients with renal insufficiency had an impaired endothelium-dependent vasodilation, a shorter lag phase of lipoprotein fraction, and higher levels of diene conjugates, lipid hydroperoxide, and GSSG levels. The GSSG/GSH ratio was lower in patients with CRF. Endothelium-dependent vasodilation was positively correlated with total antioxidative activity (r = 0.41, P = 0.016), GSH (r = 0.44, P < 0.0098), and lag phase of LDL (r = 0.35, P = 0.036) and negatively correlated with GSSG (r = -0.40, P < 0.018), GSSG/GSH (r = -0.47, P = 0.0057), and diene conjugates (r = -0.53 P < 0.0015) in patients with CRF. These results show that an impaired endothelium vasodilation function and oxidative stress are related to each other in patients with CRF.

Determination of quantity and quality of polyphenol antioxidants in foods and beverages

The methods described in this article are quick, simple, and inexpensive to perform. The Folin quantitation method can determine both free and total polyphenol antioxidants in foods and beverages as described, as well as botanical extracts. This assay may also be used to estimate the daily per capita consumption of polyphenols in foods. The dose-response in vitro lower density lipoprotein antioxidant activity measurement (IC50) can be employed to compare antioxidants as pure compounds, or in mixtures after quantitating the polyphenols. The ex vivo lipoprotein-binding antioxidant activity can be measured simply and rapidly to determine possible in vivo binding of pure compounds or extracts from foods. Supplementation and epidemiology studies can utilize the rapid and inexpensive affinity column isolation method of lower density lipoproteins for the determination of lipoprotein oxidative susceptibility.

Antioxidant activity of amiodarone on human lipoprotein oxidation

Lipoprotein oxidation is crucial in atherogenic processes. Amiodarone is a lipophilic antiarrhythmic/antianginal drug which is able to influence the physicochemical status of biological lipid components. Since oxidation of lipids is affected by their physicochemical state and amiodarone binds to lipoproteins, we hypothesized that the drug may exert an antioxidant activity on human lipoprotein oxidation. Dose-dependent effects of therapeutically achievable amiodarone concentrations (1.5, 3, 5, 7 and 10 microM) were studied on copper-catalysed oxidation of the non-HDL fraction in vitro. Amiodarone inhibited oxidation as judged by generation of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and fluorescent products of lipoperoxidation (FPL) as well as from the kinetics of conjugated diene formation. This antioxidant activity was significant at 1.5 microM with total inhibition at 10 microM and an IC(50) of 4 microM. The primary in vivo metabolite of amiodarone, namely desethylamiodarone, also exhibited specific antioxidant properties although it was less effective than amiodarone with an IC(50) of 7 microM. In further in vivo experiments, susceptibility to copper-mediated oxidation of the non-HDL fraction was investigated before and 4 weeks after oral amiodarone administration to humans. Following treatment, significant inhibition of TBARS, LOOH and FPL generation was observed in comparison with baseline levels and a placebo-treated control group, highlighting an effective antioxidant capacity of amiodarone in vivo. Amiodarone did not change lipoprotein vitamin E and phospholipid content in vivo and did not show scavenging effects on oxidizing species involved in lipoprotein oxidation, such as peroxyl radicals, nor metal-binding/inactivating properties, suggesting that physicochemical modifications of lipoprotein lipids induced by the lipophilic drug may be involved in its antioxidant activity. In conclusion, amiodarone, and its primary metabolite desethylamiodarone, show previously unrecognized antioxidant activity on human lipoprotein oxidation. This effect is also evident in vivo and at therapeutically achievable drug concentrations. Thus, amiodarone may act as an antioxidant/antiatherosclerotic agent in humans, although this issue warrants further clinical study.

Effects of long-term supplementation with moderate pharmacologic doses of vitamin E are saturable and reversible in patients with type 1 diabetes

BACKGROUND

Vitamin E supplementation has been proposed as adjunctive therapy to counteract the increased LDL oxidation in diabetes and thus prevent or delay cardiovascular complications.

OBJECTIVE

The objective of this study was to investigate the effect of a moderate pharmacologic dose of vitamin E for </=1 y in patients with type 1 diabetes.

DESIGN

The study was double blind and the subjects were randomly assigned to 2 groups: the supplemented group (group S; n = 22) received 250 IU (168 mg) RRR-alpha-tocopherol 3 times/d for 1 y and the placebo group (group P; n = 22) received a placebo for 6 mo followed by 250 IU (168 mg) RRR-alpha-tocopherol 3 times/d for an additional 6 mo.

RESULTS

Serum vitamin E doubled after 3 mo of supplementation, from a mean (+/-SD) of 36.9 +/- 10.9 to 66.4 +/- 18.3 micromol/L (P: < 0.0005). Although lipid profiles, glycated hemoglobin, and blood biochemistry values did not change significantly, copper-induced in vitro peroxidizability of LDL and VLDL decreased after 3 mo of supplementation: the production of thiobarbituric acid-reactive substances decreased by 30-60% (P: < 0. 005) and the lag time for the appearance of fluorescent products increased from 107 +/- 25 to 123 +/- 30 min in group S (P: = 0.002 compared with group P). Vitamin E supplementation for an additional 3-9 mo resulted in no further changes in serum vitamin E and lipoprotein peroxidizability. Values returned to baseline after supplementation ended.

CONCLUSIONS

Because the improvement in lipoprotein peroxidizability is saturable and reversible, life-long supplementation with vitamin E should be considered in patients with type 1 diabetes.

Effects of dietary antioxidant supplementation on oxidative damage and resistance to oxidative damage during prolonged exercise in sled dogs

OBJECTIVES

To determine effects of dietary antioxidant supplementation on plasma concentrations of antioxidants, exercise-induced oxidative damage, and resistance to oxidative damage during exercise in Alaskan sled dogs.

ANIMALS

62 Alaskan sled dogs.

PROCEDURE

Dogs were matched for age, sex, and ability and assigned to 1 of 3 groups: sedentary and nonsupplemented (control [C]; n = 21), exercised and supplemented (S; 22), and exercised and nonsupplemented (N; 19). Dogs in group S were given 400 units of alpha-tocopherol acetate, 3 mg of beta-carotene, and 20 mg of lutein orally per day for 1 month, then dogs in groups S and N completed 3 days of exercise. Blood samples were collected before and after 1 and 3 days of exercise and after 3 days of rest. Plasma antioxidant concentrations were determined, and oxidative damage to DNA (plasma 7,8 dihydro-8-oxo-2'deoxyguanosine [8-oxodG] concentration) and membrane lipids (plasma hydroperoxide concentration) and resistance of plasma lipoproteins to oxidation were assessed.

RESULTS

Supplementation increased plasma concentrations of alpha-tocopherol, beta-carotene, and lutein. Plasma concentration of alpha-tocopherol increased and concentration of lutein decreased in group S with exercise. Concentration of 8-oxodG decreased in group S but increased in group N during and after exercise. Lag time of in vitro oxidation of lipoprotein particles increased with exercise in group S only.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary supplementation with antioxidants resulted in increased plasma concentrations of antioxidants. Moreover, supplementation decreased DNA oxidation and increased resistance of lipoprotein particles to in vitro oxidation. Antioxidant supplementation of sled dogs may attenuate exercise-induced oxidative damage.

Relation between lipoprotein (a) and in vitro oxidation of apolipoprotein B-containing lipoproteins

OBJECTIVES

To assess the relationship between lipoprotein (a) [Lp (a)] and lipoprotein oxidation in patients with coronary artery disease (CAD).

DESIGN AND METHODS

Oxidation of apolipoprotein (apo)B-containing lipoproteins, vitamin E, carotenoids, lipid-lipoprotein levels were determined in 171 CAD and 70 non-CAD subjects.

RESULTS

In CAD patients with Lp (a) concentrations >/= 30 mg/dL; total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), malondialdehyde (MDA), and apo B levels were significantly higher and lag-time and age were significantly lower than those of CAD patients with Lp (a) concentrations < 30 mg/dL. In non-CAD subjects with Lp (a) concentrations >/= 30 mg/dL; TC, LDL-C, and vitamin E levels were significantly higher and lag-time was significantly lower than those of non-CAD subjects with Lp (a) concentrations < 30 mg/dL. In CAD patients, Lp (a) correlated negatively with lag-time and positively with MDA levels. Lp (a) correlated negatively with lag-time and vitamin E levels in non-CAD subjects.

CONCLUSIONS

We have shown that plasma apo B-containing lipoproteins of both CAD and non-CAD subjects with Lp (a) levels >/= 30 mg/dL are more susceptible to in vitro oxidative modification than those of subjects with Lp (a) levels < 30 mg/dL. The relationship between Lp (a) and enhanced susceptibility of apo B-containing lipoproteins to oxidation, appears to support routine investigation of Lp (a).

Magnesium status and parameters of the oxidant-antioxidant balance in patients with chronic fatigue: effects of supplementation with magnesium

OBJECTIVE

Magnesium deficiency and oxidative stress have both been identified as pathogenic factors in aging and in several age-related diseases. The link between these two factors is unclear in humans although, in experimental animals, severe Mg deficiency has been shown to lead to increased oxidative stress.

METHODS

The relationship between Mg body stores, dietary intakes and supplements on the one hand and parameters of the oxidant-antioxidant balance on the other was investigated in human subjects.

RESULTS

The study population consisted of 93 patients with unexplained chronic fatigue (median age 38 years, 25% male, 16% smokers and 54% with Chronic Fatigue Syndrome (CFS). Mg deficient patients (47%) had lower total antioxidant capacity in plasma (p=0.007) which was related to serum albumin. Mg deficient patients whose Mg body stores did not improve after oral supplementation with Mg (10 mg/kg/day) had persistently lower blood glutathione levels (p=0.003). In vitro production of thiobarbituric acid reactive substances (TBARS) by non-HDL lipoproteins incubated with copper was related to serum cholesterol (p<0.001) but not to Mg or antioxidants and did not improve after Mg supplementation. In contrast, velocity of formation of fluorescent products of peroxidation (slope) correlated with serum vitamin E (p<0.001), which was, in turn, related to Mg dietary intakes. Both slope and serum vitamin E improved after Mg supplementation (p<0.001).

CONCLUSIONS

These results show that the lower antioxidant capacity found in moderate Mg deficiency was not due to a deficit in Mg dietary intakes and was not accompanied by increased lipid susceptibility to in vitro peroxidation. Nevertheless, Mg supplementation was followed by an improvement in Mg body stores, in serum vitamin E and its interrelated stage of lipid peroxidation.

Effect of LDL+VLDL oxidizability and hyperglycemia on blood cholesterol, phospholipid and triglyceride levels in type-I diabetic patients

Oxidative modification of low-density lipoproteins has been implicated in impaired lipid metabolism and its deposition in the arterial wall, and atherosclerosis. This study was carried out to determine the relationship between the in vitro oxidizability of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) and the cholesterol, phospholipid and triglyceride (TG) levels in the blood of Type-I diabetic patients. LDL+VLDL was isolated using a micro-affinity column from serum of diabetic patients (n = 34) and age-matched normal individuals (n = 22). The oxidative susceptibility of LDL+VLDL was determined by treatment with 25 microM CuCl(2) for 1.5 h. The levels of total-, LDL-, and HDL-cholesterol, phospholipids and triglycerides, as well as glycated hemoglobin (HbA(t)), were measured in the blood using standard methods. The diabetics had significantly higher levels of triglycerides and phospholipids, but cholesterol levels were similar between Type-I diabetics and age-matched normals. However, among diabetics, there was a significant correlation between the in vitro oxidation of LDL+VLDL at 1.5 h and total cholesterol (r = 0.49, P<0.002), and LDL cholesterol (r = 0.54, P<0.001) and TG (r = 0.34, P<0.05) levels. The level of in vitro oxidizability of LDL+VLDL did not have any correlation with HDL-cholesterol or phospholipid levels. The level of glycemic control (HbA(1)) did not have any correlation with levels of LDL- or HDL-cholesterol or triglycerides, but was significantly correlated with phospholipid levels (r = 0.48, P<0.005). This study suggests that the levels of LDL-cholesterol and triglycerides in the blood are directly related to the degree of in vitro oxidative susceptibility of low-density lipoproteins in Type-1 diabetic patients.

Short term citrus flavonoid supplementation of type II diabetic women: no effect on lipoprotein oxidation tendencies

Flavonoids, which are dietary components and have possible drug uses, inhibit lipoprotein oxidation in vitro. The present study considered whether flavonoid supplementation in humans could influence lipoprotein vulnerability to oxidation. Citrus flavonoid supplementation (about 1g/day, 3 weeks), or placebo, was given to 40 Type II diabetic women, a population prone to oxidative stress. Absorbance spectra of plasma from 4 subjects revealed that some flavonoid absorption occurred. When tested in vitro, a supplement extract, with spectrum peak height similar to that of plasma samples, completely inhibited copper-induced oxidation of very low plus low density lipoproteins. In contrast, neither flavonoid supplementation nor placebo influenced lipoprotein susceptibility to copper-stimulated oxidation in vitro (lag time or propagation rate). Thus, this study demonstrated that increased flavonoid consumption by humans does not necessarily alter lipoprotein susceptibility to oxidation assessed in vitro.

The in vitro oxidizability of lipoprotein particles in obese and non-obese subjects

There exists much evidence suggesting a major role for the oxidized low density lipoprotein (LDL) and VLDL particles in the pathogenesis of atherosclerosis. Although obesity is characterized by dyslipidemia, less is known about the oxidation capacity of lipoproteins in obese subjects. We measured the oxidizability in vitro in 21 premenopausal women with a BMI of 36.7+/-5.4 and compared them to 18 age-matched controls (BMI 21.9+/-1.8). The oxidizability of the non-HDL fraction is evaluated by measuring the fluorescence and thiobarbituric acid reactive substances (TBARS; MDA nM/mg non-HDL) at different time intervals of incubation. TBARS formation increased linearly with the increase of lipids both in non-obese and obese subjects. TBARS, measured every 30 min, increased in non-obese controls up to a maximum of 59.6 at 180' in contrast to a maximum of 77.1 at 180' (P < 0.001) in obese, but healthy, normocholesterolemic subjects. At each measurement the TBARS were significantly higher (P < 0.01-0.001) in obese subjects. Also the lag-time (period from zero to the start of the particle oxidation process) was significantly lower (92.5 vs. 123.4; P < 0.001) in obese subjects, when compared to lean controls. BMI correlates significantly with TBARS formation and its log transformed values (maximum P < 0.001). The lag-time was negatively related (n=39 total group, r=- 0.57, P < 0.001) to body weight and BMI. A significant relationship exists between TBARS formation (up to r=0.59) and triglyceride levels and a negative relationship exists with HDL-cholesterol levels. In vitro oxidizability of non-HDL lipoproteins is significantly increased in obese, non-diabetic subjects and related to increased body weight and triglyceride levels. Further studies are necessary to explore the underlying mechanisms for this phenomenon.

Hyperketonemia (acetoacetate) increases the oxidizability of LDL + VLDL in Type-I diabetic patients

The reason for the disproportionately higher level of vascular disease in patients with diabetes is not known. Oxidative modification of low-density lipoproteins has been implicated in impaired cholesterol uptake and its deposition in the arterial wall and atherosclerosis. The present study has examined the effects of hyperketonemia, glycemic control and duration of diabetes on the in vitro oxidative susceptibility to Cu++ of low-density lipoprotein (LDL) + very low-density lipoprotein (VLDL) from 34 Type-I diabetic patients without any clinical sign of vascular disease and 22 age-matched normal individuals. LDL + VLDL was isolated from plasma using a micro-affinity column. LDL + VLDL isolated from diabetic patients and age-matched normal individuals was treated with 25 mM CuCl2 for 1.5, 3 and 5 h. The ketone bodies acetoacetate (AA) and beta-hydroxybutyrate (BHB), as well as glycated hemoglobin (HbA1), were measured in the blood by standard methods. There was no difference in the in vitro oxidative susceptibility of LDL + VLDL at all time periods between Type-I diabetics (n = 34) and age-matched normal individuals (n = 22). However, among diabetics, when patients were separated into normoketonemic (NK) and hyperketonemic (HK) groups, in vitro oxidation of LDL + VLDL at 1.5 h from hyperketonemic diabetics was a 69% greater (p < .02) compared with that of normoketonemic diabetics and 80% greater (p < .02) compared with that of normal individuals. There was a significant correlation (r = 0.38, p < .03) between the in vitro oxidation of LDL + VLDL at 1.5 h and AA levels in diabetic patients. The level of in vitro oxidizability of LDL + VLDL did not have any correlation with levels of BHB (r = 0.20, p > .26), HbA1 (r = 0, p > .99), glucose (r = 0.06, p > .75) or duration of diabetes (r = 0.15, p > .40) in diabetic patients. In vitro incubation of normal plasma with AA resulted in an increase in the Cu + induced lipid peroxidation of LDL + VLDL. This study suggests that frequent episodes of ketosis and elevated levels of AA constitute a risk factor for the oxidative modification of low-density lipoproteins and development of vascular disease in diabetic patients.

Antioxidant activity of allopurinol on copper-catalysed human lipoprotein oxidation

We found that allopurinol, at therapeutically relevant concentrations (9-58 microM), significantly counteracted copper-catalysed human non-HDL lipoprotein oxidation, as assessed by thiobarbituric acid reactant content and kinetics of conjugated diene formation. Oxypurinol was ineffectual. Both drugs had no activity on metal-independent, peroxyl radical-induced lipoprotein oxidation. Specific fluorescence-quenching experiments revealed that only allopurinol could interact with copper antagonizing metal binding to lipoproteins. Thus, therapeutic allopurinol concentrations can inhibit copper-catalysed lipoprotein oxidation through metal complexation, suggesting some antioxidant-antiatherogenic activity of the drug in vivo.

Human low-density lipoproteins: oxidative modification and its relation to age, gender, menopausal status and cholesterol concentrations

Recently much evidence has accumulated indicating that oxidative modification of atherogenic lipoproteins plays an important role in atherogenesis. The goal of this study was to ascertain whether any association exists between this and the previously incriminated risk factors of atherosclerotic cardiovascular disease like age, gender and cholesterol concentration. Serum lipid profile, low-density lipoprotein (LDL) composition and indicators of LDL oxidation were examined in a cohort of healthy, predominantly middle aged men and women. LDL oxidation was assessed using the copper catalysis method, and monitored routinely by the increase in conjugated dienes over 4 to 24 hours. A more objective computer-aided technique was used to estimate the oxidative indices based on the sigmoidal fit to data. No marked differences between men and women were found with respect to mean age, total and LDL cholesterol, LDL protein and oxidation of LDL. The post-menopausal as compared to pre-menopausal status was associated with a greater extent of LDL oxidation, as well as with higher total serum cholesterol and its fractions, LDL cholesterol and LDL protein. No such differences were found in the data for men appropriately separated according to age. In a group with high risk LDL cholesterol, the total LDL oxidation was higher, as well as age and total cholesterol. Lag time and half-time of LDL oxidation were significantly shorter, while the oxidation rate of LDL was significantly faster when compared with data in the lower quartile. About six percent of participants had a considerably prolonged initial oxidation phase. These persons also showed low total and LDL cholesterol. High oxidation resistance was reversible and most probably caused by very low pre-existent oxidation products. Multiple regression analysis showed that the closest association among age, gender, lipid profiles and LDL oxidation indices existed between LDL cholesterol and conjugated diene production in both sexes (men: r = 0.93; women: r = 0.81). This association remained high even if adjusted for age. As in earlier epidemiological studies using logistic regression and showing age- and gender-related rising frequency of coronary heart disease, the present paper demonstrated age- and gender-related rising frequency of highly oxidized LDL. In both cases it was closely associated with an increasing LDL cholesterol concentration.