Susceptibility of plasma low density lipoprotein to cupric ion-induced peroxidation in patients with variant angina

Increased circulating malondialdehyde-modified low-density lipoprotein levels in patients with ergonovine-induced coronary artery spasm

OBJECTIVE

Coronary endothelial dysfunction is thought to underlie the development of coronary artery spasms. Malondialdehyde-modified low-density lipoprotein (MDA-LDL) was suggested as a marker of endothelial damage. This study investigated the diagnostic impact of MDA-LDL on ergonovine-induced coronary spasms.

METHODS

We included 152 patients with suspected coronary spastic angina. MDA-LDL levels were measured before an ergonovine provocation test. Coronary spasm was defined as total or subtotal occlusion, compared to the relaxed state after nitroglycerin, associated with ischemic ECG changes and concurrent chest pain. Changes in vessel diameter in response to ergonovine were evaluated with quantitative coronary angiography.

RESULTS

Coronary spasms were observed in 41 patients (27%). MDA-LDL levels were significantly higher in patients with spasms compared to those without spasms (139.9 ± 45.9 U/L vs. 109.6 ± 36.6 U/L, p<0.01). Univariate logistic regression analyses indicated significant relationships between coronary spasms and MDA-LDL (per 10 U/L, odds ratio (OR): 1.20; p<0.01), high-density lipoprotein (per 10 mg/dL, OR: 0.76; p=0.03), smoking (OR: 3.04; p<0.01), and male gender (OR: 3.51; p<0.01). In the multivariate model, MDA-LDL (per 10 U/L, OR: 1.17; p<0.01) remained a significant predictor of coronary spasm. Regression analysis showed a positive correlation between MDA-LDL levels and coronary luminal diameter changes induced by ergonovine (r=0.57, p<0.01). The optimal MDA-LDL threshold for predicting coronary spasm was 121.3 U/L, identified with a receiver operating characteristic curve.

CONCLUSIONS

Increased circulating MDA-LDL levels were associated with ergonovine-induced coronary artery spasm.

A Simple Density-Based Empirical Likelihood Ratio Test for Independence

We develop a novel nonparametric likelihood ratio test for independence between two random variables using a technique that is free of the common constraints of defining a given set of specific dependence structures. Our methodology revolves around an exact density-based empirical likelihood ratio test statistic that approximates in a distribution-free fashion the corresponding most powerful parametric likelihood ratio test. We demonstrate that the proposed test is very powerful in detecting general structures of dependence between two random variables, including non-linear and/or random-effect dependence structures. An extensive Monte Carlo study confirms that the proposed test is superior to the classical nonparametric procedures across a variety of settings. The real-world applicability of the proposed test is illustrated using data from a study of biomarkers associated with myocardial infarction.

Increased oxidative stress with elevated serum thioredoxin level in patients with coronary spastic angina

BACKGROUND

Increased oxidative stress has been implicated in the pathogenesis of coronary vasospasm. Thioredoxin (TRX) is a redox-active protein that is known to be induced by oxidative stress.

HYPOTHESIS

The serum TRX level may be high in patients with coronary vasospasm.

METHODS

The serum TRX level was determined using an enzyme-linked immunosorbent assay in 21 patients with the active stage of coronary spastic angina (CSA), in 18 patients with the inactive stage of CSA (iCSA), in 24 control subjects without coronary artery disease (Control), and in 20 patients with stable effort angina (SEA).

RESULTS

Serum TRX levels (mean +/- standard deviation ng/ml) were significantly higher in CSA (64 +/- 44) than in iCSA (28 +/- 26), in Control (34 +/- 15), and in SEA (36 +/- 16). In contrast, serum alpha-tocopherol levels (mg/g lipids) were significantly lower in CSA (2.8 +/- 0.7) than in Control (4.0 +/- 1.2) and in SEA (3.2 +/- 0.4). Current smoking was significantly more prevalent in CSA (76%) than in any of the other groups. No significant correlation was found between the serum level of TRX and alpha-tocopherol in the study subjects. In nine patients with CSA, the serum TRX level decreased (93 +/- 41 --> 41 +/- 35 ng/ml) and the alpha-tocopherol level increased (2.7 +/- 0.6 --> 3.2 +/- 0.7 mg/g lipids) significantly under medication with calcium entry blockers after an at least 3-month angina-free period.

CONCLUSIONS

Patients with coronary spastic angina had a higher serum TRX level associated with a lower serum level of antioxidant vitamin E, with redox equilibrium appearing to be related to the disease activity of coronary vasospasm in these patients. Oxidative stress may be related to the genesis of coronary vasospasm.

Decreased plasma extracellular superoxide dismutase level in patients with vasospastic angina

OBJECTIVE

Extracellular superoxide dismutase (EC-SOD) is the major extracellular scavenger of superoxides, and one of the main regulators of nitric oxide bioactivity in vessel walls. Here, we examined whether plasma EC-SOD level was associated with vasospastic angina (VSA), and if it was a risk factor for VSA.

METHODS AND RESULTS

We assigned 105 patients with normal or mildly stenotic coronary arteries into either a VSA (n=58) or chest pain syndrome (CPS) (n=47) groups. Plasma EC-SOD and other biochemical variables were measured, and major coronary risk factors were assessed. Results showed that apart from smoking status there were no significant differences in patient characteristics and biochemical variables between the two groups. In the VSA group, prevalence of smoking was significantly higher (53% versus 26%, p=0.0055), and plasma EC-SOD level was significantly lower (68.9+/-18.5 ng/ml versus 83.8+/-25.9 ng/ml; p=0.0009). Not only smoking (OR 2.742, 95% CI 1.032-7.287, p=0.0431) but also plasma EC-SOD (OR 0.971, 95% CI 0.949-0.993, p=0.0102) was an independent risk factor for VSA.

CONCLUSIONS

In patients with VSA, plasma EC-SOD level was substantially reduced. Furthermore, plasma EC-SOD level followed by cigarette smoking was the most predictive risk factor for coronary spasms.

Serum thioredoxin and alpha-tocopherol concentrations in patients with major risk factors

BACKGROUND

Oxidative stress, which is thought to be increased in subjects with various coronary risk factors, induces thioredoxin (TRX), a redox-active protein.

METHODS AND RESULTS

To determine whether oxidative stress is increased, serum concentrations of both TRX and alpha-tocopherol (vitamin E) were determined in 12 control subjects without any coronary risk factors (CONTROL), 6 current smokers (SMOKING), 19 hypertensive patients (HT), 7 hypercholesterolemic patients (HC) and 14 subjects with multiple risk factors (MULTIPLE). Patients with diabetes mellitus were not included. The serum TRX concentrations (mean +/- SD ng/ml) were significantly higher in SMOKING (41+/-10), HT (41+/-17), HC (48+/-15) and MULTIPLE (46+/-15) than in CONTROL (24+/-11). The serum alpha-tocopherol concentrations (mg/g lipids) were not significantly different among CONTROL (4.0+/-0.7), SMOKING (4.0+/-0.8), HT (4.1+/-0.6) and HC (4.2+/-0.6), although the concentration was significantly lower in MULTIPLE (3.3+/-0.7) than in any of the other study groups.

CONCLUSIONS

SMOKING, HT, HC and MULTIPLE had significantly higher serum TRX concentrations than CONTROL, suggesting increased oxidative stress. MULTIPLE had a lower serum concentration of antioxidant alpha-tocopherol than any of the other study groups, suggesting impaired or exhausted defense against chronic oxidative stress in the presence of the multiple risk factors.

High remnant lipoprotein levels in patients with variant angina

BACKGROUND

Dyslipidemia with increased oxidative stress but without elevation of low-density lipoprotein cholesterol has been recently implicated in the pathogenesis of coronary vasospasm.

HYPOTHESIS

Disordered triglyceride-rich lipoprotein metabolism may be linked to the genesis of coronary artery spasm.

METHODS

Both serum remnant lipoprotein (RLP) and alpha-tocopherol levels were determined in 18 patients with the active stage of variant angina (VA), in 16 patients with the inactive stage of variant angina (IVA), and in 19 control subjects (CONTROL).

RESULTS

The RLP levels were significantly (p < 0.05) higher in VA (6.4 +/- 2.7 mg/dl) than in IVA (4.4 +/- 1.5 mg/dl). In contrast, alpha-tocopherol levels were significantly lower in VA than that in CONTROL. Serum trigyceride levels were not significantly different among the study groups, although serum high-density lipoprotein cholesterol levels were significantly lower in VA than in CONTROL. Smoking was significantly (p < 0.05) more prevalent in VA (72%) than in IVA (25%) and CONTROL (37%). Serum RLP levels correlated positively with triglyceride levels (R = 0.73) and correlated inversely with alpha-tocopherol levels (R = -0.31) significantly in all study subjects.

CONCLUSIONS

Patients with active stage of variant angina had higher RLP levels than inactive patients with variant angina and lower alpha-tocopherol levels than control subjects. Disordered triglyceride-rich lipoprotein metabolism with increased oxidative stress appears to be linked to the activity of coronary vasospasm, suggesting a possible role in its pathogenesis.

Low Serum .ALPHA.-Tocopherol Concentrations in Subjects With Various Coronary Risk Factors

BACKGROUND

Oxidative stress may play an important role in the genesis and development of atherosclerosis.

METHODS AND RESULTS

To examine whether oxidative stress is increased in the presence of various coronary risk factors, serum alpha-tocopherol concentrations were determined in 168 apparently healthy subjects recruited from Daioh town (73 men and 95 women, mean age: 42+/-11 years). The alpha-tocopherol concentration (mg/g lipids) was significantly lower in men, older subjects (>or=50 years of age), smokers, those with hyper-low density lipoprotein (LDL)-cholesterolemia (C) (>or=160 mg/dl), hypertriglyceridemia (TG) (>or=150 mg/dl), hypo-high density lipoprotein (HDL)-C (<40 mg/dl), fasting hyperglycemia (>110 mg/dl) and obesity (body mass index >or=25 kg/m (2)) than in women, younger subjects, nonsmokers, those with normoLDL-C, normoTG, normoHDL-C, fasting normoglycemia and the non-obese. The concentration was not significantly different between hypertensives and nonhypertensives. Multivariate logistic regression analysis showed that the adjusted odds ratios (95% confidence interval) for hyperTG and hypoHDL-C as a factor for the lowest tertile of alpha-tocopherol concentration were 6.2 (1.6-24.4, p<0.01) and 6.0 (1.5-22.6, p<0.01), and those of the other risk factors were not significant. The alpha-tocopherol concentrations were significantly positively correlated with HDL-C concentrations (R=0.53) and negatively with TG concentrations (R=-0.53), BMI (R=-0.35), LDL-C concentrations (R=-0.25) and age (R=-0.22).

CONCLUSION

Increased oxidative stress, as shown by decreased alpha-tocopherol concentrations, was linked to the presence of various coronary risk factors, among which hyperTG and hypoHDL-C appeared to be most heavily associated with oxidative stress.

Increased lipid peroxidation during long-term intervention with high doses of n-3 fatty acids (PUFAs) following an acute myocardial infarction

OBJECTIVE

To assess the oxidative burden of a highly concentrated compound of n-3 PUFAs as compared to corn oil by measuring thiobarbituric acid-malondialdehyde complex (TBA-MDA) by HPLC. We also studied the influence on TBA-MDA of statins combined with n-3 PUFAs or corn oil.

DESIGN

A prospective, randomised, double-blind, controlled study.

SETTING

One hospital centre in Stavanger, Norway.

SUBJECTS

A total of 300 subjects with an acute myocardial infarction (MI).

INTERVENTIONS

Gelatine capsules, containing 850-882 mg EPA and DHA as concentrated ethylesters, or 1 g of corn oil, were ingested in a dose of two capsules twice a day for at least 1 y. Alpha-tocopherol (4 mg) was added to all capsules to protect the PUFAs against oxidation.

RESULTS

After 1 y TBA-MDA increased modestly in the n-3 PUFA group (n=125), as compared to the corn oil group (n=130), P=0.027. Multiple linear regression analyses of fatty acids in serum total phospholipids (n=56) on TBA-MDA measured after 12 months intervention, showed no dependency. Performing best subsets regression, serum phospholipid concentration of arachidonic acid (20:4 n-6 PUFA) was identified as a predictor of TBA-MDA at 12 months follow-up, P=0.004. We found no impact of statins on TBA-MDA.

CONCLUSION

TBA-MDA increased modestly after long-term intervention with n-3 PUFAs compared to corn oil post-MI, suggesting biological changes induced by n-3 PUFAs, rather than simply reflecting their concentration differences. The peroxidative potential of n-3 PUFAs was not modified by statin treatment.

SPONSORSHIP

: Pharmacia A/S and Pronova A/S, Norway.

Significance of asymmetric dimethylarginine (ADMA) concentrations during coronary circulation in patients with vasospastic angina

The basal activity of nitric oxide (NO) is reduced in spastic arteries of patients with vasospastic angina (VSA). Elevated concentrations of ADMA are associated with reduced NO production and impaired endothelium-dependent vasodilatation. The aim of this study was to elucidate the role of ADMA and its relationship to NO end-products (NOx; nitrate + nitrite) during coronary circulation in patients with VSA. The plasma ADMA and NOx concentrations during coronary circulation were evaluated in 16 VSA and 16 control patients. Blood samples were obtained from the coronary sinus (V) and the ostium of the left coronary artery (A), and the (V-A) differences of ADMA and NOx were determined. The coronary sinus plasma ADMA concentration in patients with VSA was higher than that in the control. The coronary sinus - arterial (V-A) difference of NOx was negative in the VSA group and approximately zero in the control group (VSA group =-1.4 micromol/L, control group =-0.1 micromol/L, p=0.0005). Furthermore, in the VSA patients, there was a negative correlation between the (V-A) difference of NOx and the basal coronary artery tone at the site of spasm (r=-0.60, p=0.015). A significant negative correlation between the (V-A) differences of NOx and ADMA was observed in patients with VSA (r=-0.52, p<0.05), but not in those of the control. Higher ADMA concentrations might cause the reduced formation of NO that underlies the pathophysiology of coronary vasospasm.

Low density lipoprotein particles are small in patients with coronary vasospasm

Increased lipid oxidative stress has been recently implicated in the pathogenesis of coronary artery spasm. Small, dense LDL with high susceptibility to oxidation may be linked to the genesis of coronary vasospasm. The relative migratory distance of the predominant densitometric peak of LDL from that of VLDL to that of HDL in a 3% polyacrylamide gel electrophoresis was determined as a measure of LDL particle size in 49 patients with coronary spastic angina (CSA), in 56 patients with stable effort angina and a significant coronary artery stenosis (SEA) and also in 40 control subjects without coronary artery disease (Control). The incidence of detection of small, dense LDL (particle diameter <25.5 nm) or a relative migratory distance above 0.36 was significantly higher in CSA (57%) and also in SEA (39%) than in Control (20%). In SEA, a significantly higher serum level of triglyceride was noted in the subgroup with the small, dense LDL as compared with the subgroup without. In contrast, in CSA, the serum level of triglyceride was not significantly different between the subgroups with and without the small, dense LDL, although significantly lower serum levels of both HDL-cholesterol and alpha-tocopherol were noted in the former. In 16 patients of CSA, the detection of the small, dense LDL was significantly decreased after a >6-month angina-free period (69-->31%). We conclude that patients with coronary spastic angina had smaller LDL particles, associated not with hypertriglyceridemia but low serum levels of both HDL-cholesterol and vitamin E. Dyslipidemia with small, dense LDL may be related to the genesis of coronary vasospasm.

Increased autoantibodies against oxidized low-density lipoprotein in coronary circulation in patients with coronary spastic angina

Oxidized low-density lipoproteins are important in the progression of atherosclerosis. Autoantibodies against malondialdehyde-modified low-density lipoproteins have been reported to be predictive of the progression of atherosclerosis. This study sought to examine whether plasma levels of autoantibodies against oxidized low-density lipoprotein increase in the coronary circulation in patients with coronary spastic angina. The authors examined plasma antioxidized low-density lipoprotein antibody levels (activity unit values (AcU)/mL) simultaneously in the coronary sinus and the aortic root in 20 patients with coronary spastic angina, 23 patients with stable exertional angina, and 15 control subjects by measuring plasma levels of immunoglobulin G (IgG) autoantibodies against malondialdehyde-modified low-density lipoproteins by enzyme-linked immunosorbent assay. The plasma antioxidized low-density lipoprotein antibody levels (AcU/mL) in the coronary sinus increased in coronary spastic angina (38 +/- 16) compared with stable exertional angina (23 +/- 7) and control subjects (20 +/- 6) (p < or = 0.0001). The levels (AcU/mL) in the aortic root also increased in coronary spastic angina (33 +/- 12) compared with stable exertional angina (23 +/- 7) and control subjects (20 +/- 6) (p < 0.005). Furthermore, the coronary sinus-arterial differences of the levels (AcU/mL) were also higher in coronary spastic angina (5 +/- 9) than in stable exertional angina (0 +/- 6) and healthy subjects (-1 +/- 5) (p < 0.05). The generation of malondialdehyde-modified low-density lipoproteins is reported to be associated with atherothrombosis. These findings suggest that elevated levels of autoantibodies against malondialdehyde-modified oxidized low-density lipoproteins in coronary circulation are associated with the development of atherothrombosis from the progression of atherosclerosis rather than with the extent of coronary atherosclerosis in patients with coronary spastic angina.

Detection of the "midband" lipoprotein in patients with coronary artery spasm

BACKGROUND

Dyslipidemia in patients with coronary vasospasm has been characterized by a low level of high-density lipoprotein (HDL) cholesterol without elevation of low-density lipoprotein (LDL) cholesterol, distinct from patients with organic coronary artery disease.

HYPOTHESIS

Disordered triglyceride-rich lipoprotein metabolism may be linked to the genesis of coronary artery spasm.

METHODS

The incidence of the "midband" lipoprotein observed between very low-density lipoprotein (VLDL) and LDL bands in the polyacrylamide disc gel electrophoretic analysis was determined in 48 patients with coronary spastic angina (CSA), in 50 patients with stable effort angina and a significant fixed coronary stenosis (SEA), and in 40 control subjects without coronary artery disease (Control).

RESULTS

The incidence was significantly (p<0.05) higher in CSA (71%) than in SEA (50%) and Control (25%). Smoking was significantly (p < 0.05) more prevalent in CSA (77%) than in SEA (50%) and Control (50%). In SEA, serum levels of triglyceride and apoproteins C-II, C-III, and E were all significantly higher, and the serum level of HDL cholesterol was significantly lower in the midband-positive than in the midband-negative subgroup. In CSA, no significant differences were found in these serum levels between the midband-positive and -negative subgroups, except for a significantly (p < 0.05) lower level of HDL cholesterol in the former. However, a significantly (p < 0.05) higher incidence of diabetes mellitus or impaired glucose tolerance was noted in the midband-positive (41%) than in the midband-negative subgroup (7%) in CSA. The incidence of the detected midband lipoprotein was significantly decreased in the blood samples obtained from 20 of CSA after a > 6-month angina-free period (70-->25%, p < 0.05).

CONCLUSIONS

The midband lipoprotein was frequently detected in patients with coronary vasospasm, suggesting that dyslipidemia with disordered triglyceride-rich lipoprotein metabolism may be linked to the genesis of coronary artery spasm.

Increase in plasma levels of oxidized low-density lipoproteins in patients with coronary spastic angina

Oxidized low-density lipoproteins (LDL) impair endothelium-dependent dilation and constrict arteries. This study examined possible relation of the circulating plasma levels of Ox-LDL to coronary spastic angina (CSA). The plasma levels of Ox-LDL were measured by ELISA in 37 consecutive patients with CSA and normal coronary angiograms and in 79 consecutive control patients. The Ox-LDL levels in patients with CSA were significantly higher than those in controls. In multivariate analysis, higher levels of Ox-LDL were a risk factor for CSA independently of other traditional risk factors. The Ox-LDL levels had a significant and positive correlation with constrictor response of coronary arteries to the intracoronary acetylcholine infusion. Thus, Ox-LDL may play a possible role in pathogenesis of coronary spasm.

Lipoprotein(a) is a risk factor for occurrence of acute myocardial infarction in patients with coronary vasospasm

OBJECTIVES

The purpose of this study is to determine whether lipoprotein(a) (Lp[a]) is an independent risk factor for coronary spasm and occurrence of acute myocardial infarction (AMI) in patients with coronary spasm.

BACKGROUND

Although elevated serum Lp(a) levels are known to be associated with coronary atherosclerosis and AMI, the association between the elevated level of this lipoprotein and coronary spasm remains to be elucidated.

METHODS

Serum Lp(a) levels were measured using a latex immunoassay in 77 patients with coronary spasm but without a significant (>75%) fixed coronary stenosis, including 16 with prior myocardial infarction (MI), in 177 patients with a fixed stenosis but without rest angina, including 114 with prior MI and in 81 control subjects without coronary artery disease.

RESULTS

The serum Lp(a) level in patients with coronary spasm (median; 17 mg/dl) was higher (p < 0.01) than in control subjects (12 mg/dl) but lower (p < 0.01) than in patients with a fixed stenosis (23 mg/dl). The incidence of subjects with higher (>25 mg/dl) serum Lp(a) levels was higher in patients with a fixed stenosis (46%, p < 0.01) but not in patients with coronary spasm (27%), compared with control subjects (21%). Among the patients with coronary spasm, the incidence of higher Lp(a) levels was higher in patients with than in those without a history of prior MI (56% vs. 21%, p < 0.05). The patients with higher Lp(a) levels had a higher incidence of prior MI than those without (41% vs. 13%, p < 0.05). The multivariate analysis confirmed that higher serum Lp(a) level is an independent determinant for prior MI in these patients (odds ratio, 4.19; 95%, confidence interval, 1.03 to 17.00).

CONCLUSIONS

Elevated serum level of Lp(a) was found to be associated with a history of prior MI in patients with coronary spasm, suggesting that Lp(a) may play an important role in the genesis of thrombotic coronary occlusion and the occurrence of AMI subsequent to coronary spasm.

Possible role of high susceptibility of high-density lipoprotein to lipid peroxidative modification and oxidized high-density lipoprotein in genesis of coronary artery spasm

Recent study demonstrated high susceptibility of plasma LDL to lipid peroxidative modification in patients with variant angina. Oxidized stress state, especially oxidized LDL, may induce coronary artery spasm by its impairing effect of endothelium-dependent arterial relaxation, but precise mechanisms remain unclear. Study subjects included 93 patients who underwent coronary angiographic examination: 12 patients with coronary artery spasm provoked by ergonovine without organic stenosis (group I), 11 patients who did not demonstrate coronary artery spasm or organic stenosis (group II) and 70 patients with organic coronary artery stenosis (group III). Levels of plasma HDL-cholesterol and apoA-I in group I were similar to those in III but were significantly lower than those in II, although the other plasma lipid parameters were not different among the three groups. The levels of TBARS in plasma and HDL were significantly higher in group I than in II or III (2.94+/-1.56 vs. 1.91+/-0.35 or 2.23+/-0.89 nmol MDA/ml and 1.23+/-1.00 vs. 0.54+/-0.37 or 0.70+/-0.63 nmol MDA/mg protein; P < 0.05), although the levels of TBARS in LDL were not significantly different. In the monitoring curve of diene production during copper-induced lipid peroxidation of HDL, its propagation slope was steeper and levels of maximum diene absorbance was higher in group I as compared with that in II or III, but not found in those of LDL. These results suggested that high susceptibility of HDL to lipid peroxidative modification in group I may contribute to the genesis of coronary artery spasm, and oxidized HDL rather than oxidized LDL is more likely to be related to coronary artery spasm.

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

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

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

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

Inhibition of human low-density lipoprotein oxidation by flavonoids in red wine and grape juice

In the presence of red wine or grape juice, low-density lipoprotein was significantly resistant to oxidation; the biological activity of flavonoids, but not ethanol or nonflavonoid phenolic compounds, appeared to contribute to the antioxidant properties of red wine and grape juice. A significant antioxidant activity was also confirmed in low-density lipoprotein from humans after ingesting red wine but not grape juice, suggesting that flavonoids in red wine can be absorbed from the intestine more efficiently than those in grape juice.

Clinical predictors of oxidized low-density lipoprotein in patients with coronary artery disease

Oxidized low-density lipoprotein (LDL) may play a key role in the initiation and progression of atherosclerosis. Risk factors for elevated levels of oxidized LDL are not well established and may be important in identifying individuals who may benefit from antioxidant supplementation or interventions to reduce oxidant stress. The purpose of this study was to determine if clinical parameters predict levels of oxidized LDL. We evaluated the relation between clinical parameters and oxidized LDL in 45 nonsmoking, nondiabetic patients (39 men and 6 women) with coronary artery disease. Oxidized LDL was assessed by measurement of conjugated dienes, lipid peroxides, and thiobarbituric reactive substances (TBARS) at 0 hours to evaluate baseline oxidant stress and postincubation with an oxidizing agent to assess the capacity of LDL for peroxidation. Results were lipid standardized and were not materially altered by multivariate adjustment. Significant predictors of increased oxidized LDL included female sex, family history of premature cardiovascular disease, increased percent body fat, increased body mass index, increased heart rate at rest, history of smoking, exercise <4 times per week, and no regular wine consumption. These data suggest that clinical parameters correlate with levels of oxidized LDL and may be useful in identifying patients at risk for increased oxidant stress.

Association between cigarette smoking and lipid peroxidation in a controlled feeding study

BACKGROUND

Cigarette smoke may promote atherogenesis by producing oxygen-derived free radicals that damage lipids. However, evidence in support of this hypothesis is inconsistent because most studies did not control for aspects of diet (antioxidants and lipid substrate) that may confound the association between smoking and measures of lipid peroxidation.

METHODS AND RESULTS

The relationships between cigarette smoking and two measures of lipid peroxidation, breath ethane (an in vivo assay) and thiobarbituric acid-reactive substances (TBARS, an in vitro assay), were examined in 123 adults (11% of whom were smokers) participating in a controlled feeding study. After 3 weeks of controlled feeding on a common diet (36% total fat, 14% saturated fats, 6% polyunsaturated fats, and 12% monounsaturated fats), breath and fasting serum samples were collected for measurement of ethane and TBARS, respectively. Baseline characteristics of smokers and nonsmokers were similar, including several indices related to diet and nutritional status (albumin, cholesterol, body mass index, and oxygen radical-absorbing capacity). Cigarette smokers had significantly higher breath ethane (8.88 versus 1.71 pmol/L; P<.0001) and TBARS (24.0 versus 20.7 micromol/mL; P=.008) than nonsmokers. The interval between breath collection and the time the last cigarette was smoked was significantly and inversely correlated with breath ethane. Neither measure of lipid peroxidation was associated with measures of serum cholesterol or albumin, body mass index, or serum oxygen radical-absorbing capacity.

CONCLUSIONS

Cigarette smokers have higher rates of in vivo and in vitro lipid peroxidation. These results support the hypothesis that the atherogenic effects of smoking are mediated in part by free radical damage to lipids.

Antioxidant nutrient supplementation reduces the susceptibility of low density lipoprotein to oxidation in patients with coronary artery disease

OBJECTIVE

This study sought to determine the effect of antioxidant supplementation on the susceptibility of low density lipoprotein (LDL) to oxidation in patients with established cardiovascular disease (CVD).

BACKGROUND

Data are inconsistent regarding the role of antioxidant nutrients in the prevention of CVD.

METHODS

The study design was a 12-week, double-blind, placebo-controlled clinical trial. Patients with CVD (n = 45) were randomized to 1) placebo control; 2) 400 IU of vitamin E, 500 mg of vitamin C, 12 mg of beta-carotene (mid-dose); or 3) 800 IU of vitamin E, 1,000 mg of vitamin C, 24 mg of beta-carotene (high dose) daily. Reduced susceptibility of LDL to oxidation was estimated by an increase in lag phase (minutes). Baseline and 6- and 12-week measurements of lipoproteins and lag phase were obtained. Plasma levels of antioxidants were measured at baseline and 12 weeks.

RESULTS

Concentrations of alpha-tocopherol, vitamin C and beta-carotene significantly increased in the mid- and high dose groups during the trial. Lag phase significantly increased from baseline (190.1 +/- 63.8 min [mean +/- SD]) to 12 weeks (391.1 +/- 153.0 min) in the high dose group (p < 0.01). A nonsignificant increase in lag phase in the mid-dose group was observed during the same time interval. A dose response was found for mean percent change from baseline to 12 weeks for lag phase for the placebo, mid- and high dose groups (p = 0.004 for trend).

CONCLUSIONS

A high dose combination of antioxidant nutrients reduces the susceptibility of LDL to oxidation in patients with CVD and may be useful in secondary prevention.

Plasma lipid oxidation and susceptibility of low-density lipoproteins to oxidation in male patients with stable coronary artery disease

OBJECTIVES

Oxidative modifications of low-density lipoproteins (LDL) are considered to be important in the pathogenesis of atherosclerosis. However, the data on the association between LDL oxidation and severity of clinical manifestations of coronary artery disease (CAD) are contradictory. Previous reports were concerned mostly with unstable angina patients. The present study was undertaken to evaluate plasma lipid oxidation status in patients with stable CAD.

DESIGN AND METHODS

37 male patients with angiographically confirmed CAD (asymptomatic or suffering from stable angina pectoris) and 32 control subjects were used in the study. Plasma levels of vitamin E and products of lipid peroxidation, as well as parameters of the test for oxidizability of LDL in vitro were measured.

RESULTS

We did not find differences between 2 groups of individuals regarding the levels of products of lipid peroxidation, vitamin E levels, lag time, maximal rate of oxidation, and total amount of conjugated dienes in the test for oxidizability of LDL.

CONCLUSION

The results of our study challenge, but do not disprove, the oxidative hypothesis of atherosclerosis. Real atherosclerotic modifications of plasma LDL occur apparently in the vascular wall after trapping of LDL by the interstitial matrix. The rise in oxidative parameters in unstable angina reported in the literature may not be the cause of the disease but, rather, the consequence of the multiple brief episodes of ischemia-reperfusion.

Vitamin E deficiency in variant angina

BACKGROUND

Oxidative modification of LDL has been suggested to increase coronary vasoreactivity to agonists. A deficiency of vitamin E, a major antioxidant, may be related to the occurrence of coronary artery spasm.

METHODS AND RESULTS

Vitamin E levels were determined with the use of high-performance liquid chromatography in normolipidemic subjects, including 29 patients with active variant angina (group 1), 13 patients with inactive stage of variant angina without anginal attacks during the past 6 months (group 2), 32 patients with a significant (>75%) organic coronary stenosis and stable effort angina (group 3), and 30 patients without coronary artery disease (group 4). Total lipid levels in blood were calculated as total cholesterol plus triglyceride levels. The plasma alpha-tocopherol levels as well as alpha-tocopherol/lipids were significantly lower in group 1 than in groups 2 through 4. Also, the plasma gamma-tocopherol levels were significantly lower in group 1 than in groups 2 through 4. The vitamin E levels were not significantly different between group 1 patients with and those without a significant organic stenosis. In group 1, both alpha- and gamma-tocopherol levels were significantly elevated after a > or = 6-month angina-free period. The alpha-tocopherol levels in the LDL fraction were significantly lower in group 1 than in group 4. Plasma alpha-tocopherol levels were significantly correlated with those in the LDL fractions. In 6 patients of group 1 still having anginal attacks while receiving calcium channel blockers, the addition of vitamin E acetate (300 mg/d) significantly elevated plasma alpha-tocopherol levels and inhibited the occurrence of angina.

CONCLUSIONS

Plasma vitamin E levels were significantly lower in patients with active variant angina than in subjects without coronary spasm, suggesting an association between vitamin E deficiency and coronary artery spasm.