Lipid peroxidation and antioxidant vitamins C and E in hypertensive patients

Obesity difference on association blood malondialdehyde level and diastolic hypertension in the elderly population: a cross-sectional analysis

AIMS

Although increased production of malondialdehyde (MDA), an end product of lipid oxidation caused by reactive oxygen species (ROS), has been found be elevated in hypertensive population, whether MDA contributed to a changed risk of hypertension is uncertain. We aimed to investigate whether elevated blood levels of MDA contribute to increased risk of hypertension and obesity has a modified effect on the association in an older Chinese population.

METHODS

Data were obtained from 2011 to 2012 of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), a national cohort of older adults in China. Associations between blood MDA level and systolic and diastolic blood pressure (BP) and risk of hypertension were performed by multivariable linear regression and logistic regression analysis.

RESULTS

The results of smooth curve revealed a gradual upward trend on association of blood MDA level with diastolic BP (P < 0.001), but not with systolic BP (P > 0.05). Logistic regression analysis suggested that elevated blood MDA levels were associated with increased risk of diastolic hypertension (OR = 1.079, 95% CI 1.039-1.122, P < 0.001) rather than systolic hypertension (OR = 0.978, 95% CI 0.943-1.015, P = 0.247) after adjustments of related confounding factors were made. Furthermore, we found the significant modification effect of obesity on the association between MDA level and risk of diastolic hypertension evaluated by body mass index (BMI, interaction P = 0.015) and by waist circumference (interaction P = 0.016).

CONCLUSION

Our results firstly identified that increased blood MDA levels were associated with elevated risk of diastolic hypertension, rather than systolic hypertension in the non-obese old population.

Erythrocyte Deformability and Na,K-ATPase Activity in Various Pathophysiological Situations and Their Protection by Selected Nutritional Antioxidants in Humans

The physicochemical and functional properties of erythrocytes are worsened in a variety of diseases. Erythrocyte deformability refers to their ability to adjust their shape according to external forces exerted against them in the circulation. It is influenced by the functionality of the Na,K-ATPase enzyme, which is localized in their membranes. The proposed review is focused on knowledge regarding changes in erythrocyte Na,K-ATPase activity, and their impact on erythrocyte deformability in various pathophysiological situations observed exclusively in human studies, as well as on the potential erytroprotective effects of selected natural nutritional antioxidants. A clear link between the erythrocyte properties and the parameters of oxidative stress was observed. The undesirable consequences of oxidative stress on erythrocyte quality and hemorheology could be at least partially prevented by intake of diverse antioxidants occurring naturally in foodstuffs. Despite intensive research concerning the effect of antioxidants, only a small number of investigations on erythrocyte properties in humans is available in databases. It is worth shifting attention from animal and in vitro experiments and focusing more on antioxidant administration in human studies in order to establish what type of antioxidant, in what concentration, and in which individuals it may provide a beneficial effect on the human organism, by protecting erythrocyte properties.

Association between Serum Vitamin C and the Blood Pressure: A Systematic Review and Meta-Analysis of Observational Studies

Background

Hypertension is regarded as a major and independent risk factor of cardiovascular diseases, and numerous studies observed an inverse correlation between vitamin C intake and blood pressure.

Aim

Our aim is to investigate the relationship between serum vitamin C and blood pressure, including the concentration differences and the correlation strength.

Method

Two independent researchers searched and screened articles from the National Library of Medicine, Cochrane Library, Web of Science, China National Knowledge Infrastructure, VIP databases, and WANFANG databases. A total of 18 eligible studies were analyzed in the Reviewer Manager 5.3 software, including 14 English articles and 4 Chinese articles.

Results

In the evaluation of serum vitamin C levels, the concentration in hypertensive subjects is 15.13 μmol/L lower than the normotensive ones (mean difference = −15.13, 95% CI [-24.19, -6.06], and P = 0.001). Serum vitamin C has a significant inverse relation with both systolic blood pressure (Fisher′s Z = −0.17, 95% CI [-0.20, -0.15], P < 0.00001) and diastolic blood pressure (Fisher′s Z = −0.15, 95% CI [-0.20, -0.10], P < 0.00001).

Conclusions

People with hypertension have a relatively low serum vitamin C, and vitamin C is inversely associated with both systolic blood pressure and diastolic blood pressure.

Chronic co-exposure to chlorpyrifos and deltamethrin pesticides induces alterations in serum lipids and oxidative stress in Wistar rats: mitigating role of alpha-lipoic acid

The study evaluated the effect of combination of chlorpyrifos (CPF) and deltamethrin (DLT) on serum lipid profiles and oxidative stress in rats, and the mitigating role of alpha-lipoic acid (ALA). Thirty male rats were used for the 120-day study. Serum samples obtained at termination were evaluated for the levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL), malondialdehyde (MDA), and the activities of antioxidant enzymes. The levels of low-density lipoprotein-cholesterol (LDL), very low-density lipoprotein-cholesterol (VLDL), and atherogenic index (AI) were calculated. The pesticide combination elevated the levels of TG, TC, LDL, VLDL, AI, and MDA, and decreased HDL level, and activities of CAT, SOD, and GPx. The alterations induced by CPF and DLT were alleviated by ALA, partly through its antioxidant properties. In conclusion, co-exposure to DLT and CPF altered serum lipids and increased oxidative stress changes in the rats, which were ameliorated by ALA.

The relationship between dietary intake and other cardiovascular risk factors with blood pressure in individuals without a history of a cardiovascular event: Evidence based study with 5670 subjects

BACKGROUND AND AIM

Raised blood pressure is a leading cause of morbidity and mortality worldwide; improved nutritional approaches to population-wide prevention are required.We aimed to investigate the relationship between dietary intake and other cardiovascular risk factors with blood pressure in individuals without a history of a cardiovascular event in an Iranian cohort.

MATERIAL AND METHOD

A cross-sectional study of 5670 healthy subjects [approximately 40% (n=2179) males and 60% (n=3491) females] was undertaken in a sample from northeastern Iran. Subjects were recruited from an urban population, using a stratified-cluster method and derived from the Mashhad Stroke Heart Atherosclerosis Disorder (MASHAD) study, Mashhad, Iran. The age of the subjects was between 35 and 64 years. None of the subjects had a past history of major disease.

RESULTS

The mean ages for the male and female subgroups were 50.1± 8.1years and 48.2 ±7.8 y respectively. Not unexpectedly, subjects without hypertension (HTN) were younger than those with established HTN. Individuals with HTN were significantly more adipose than those without (p<0.01). We found no significant differences in crude or total energy adjusted intake of nutrients between the three groups (p>0.05), except for crude and energy adjusted phosphorus intake (p<0.05) and crude intake of the cholesterol (p<0.05). There was a significant correlation between the dietary intake of total fatty acids, phosphorus and vitamin E with both systolic blood pressure (SBP) and diastolic blood pressure (DBP). PUFA (odds ratio [OR] [95% confidence interval (CI)], 1.56 [1.05-1.06]; P<0.01), sodium (OR [95% CI], 1.00 [(1.00-1.01)]; P<0.01) and phosphorus (OR [95% CI], 1.00 [(1.00-1.01)]; P<0.01)were significant independent predictors of HTN after adjustment for energy intake.

CONCLUSION

In our representative population from North-Eastern Iran, it appears that in adults without a history of cardiovascular disease, crude or energy adjusted intake of phosphorus and total fatty acid intake were significant determinants of BP, however we found no association between sodium and potassium intake with BP.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

Oxidative stress in prehypertension: rationale for antioxidant clinical trials

Prehypertension has been recently described as an independent category of blood pressure. Mounting evidence suggests that blood pressure in the prehypertensive range is associated with an increased risk of developing hypertension and cardiovascular disease. Several reports have assigned a critical role for oxidative stress in these disease processes. This review focuses on the clinical and experimental studies done in prehypertension and hypertension within the context of oxidative stress. This article also provides insights into why diverse therapeutic interventions, which have in common the ability to reduce oxidative stress, can impede or delay the onset of hypertension in prehypertension subjects.

Impact of vitamin E and C supplementation on serum adhesion molecules in chronic degenerative aortic stenosis: a randomized controlled trial

BACKGROUND

An inflammatory component has been identified in degenerative aortic stenosis (AS). The combination of vitamins E and C has been shown to have anti-inflammatory properties. The aim of this study was to determine the impact of the combination of vitamins C and E or vitamin C only on serum levels of cell adhesion molecules and C-reactive protein in patients with chronic degenerative AS, with or without concomitant coronary artery disease.

METHODS AND RESULTS

One hundred patients with asymptomatic or mildly symptomatic moderate AS were randomized in 2:2:1 format in an open-label trial. Forty-one patients received vitamin E (400 IU) and vitamin C (1000 mg) daily, 39 patients received vitamin C (1000 mg) only, and 20 patients were followed as controls. Serum intracellular adhesion molecule (ICAM-1), E selectin, P selectin, vascular-cellular adhesion molecule (VCAM-1), C-reactive protein, and alpha-tocopherol (vitamin E) were measured by enzyme-linked immunosorbent assay at baseline and 6 months postsupplementation. Half of the patients from each of the 2 active groups were followed for further 6 months to determine any changes after cessation of therapy. In the vitamin E and C, group there was reduction in serum ICAM-1 (298 +/- 12 to 272 +/- 12 ng/mL at 6 months, P = .0015) with a return to base line 6 months after cessation of therapy. In the vitamin C only group, there was a reduction in serum P selectin (134 +/- 10 to 118 +/- 10 ng/mL at 6 months, P = .033). All the inflammatory markers were unchanged in control group over 6 months of follow-up.

CONCLUSION

Vitamin E and C supplementation had modest anti-inflammatory effect in chronic degenerative AS. The clinical relevance of this would require further clarification.

Associations between plasma antioxidants and hypertension in a community-based sample of 415 Australians aged 60-64

It has been suggested that increased oxidative stress may be both a cause as well as a consequence of hypertension. In vivo oxidation of low-density lipoproteins by oxygen-free radicals may increase hypertension-related atherogenesis, and antioxidants may be beneficial in this regard. Previous findings concerning associations between serum measures of antioxidants and hypertension have however been inconsistent. Plasma levels of beta-carotene, Vitamin A, E, uric acid, homocysteine and total antioxidant capacity, as well as two markers of oxidative stress, malondialdehyde (MDA) and protein carbonyls, were measured in morning fasting blood samples provided by 415 Australians aged 60-64 years, selected randomly from the community. Participants also provided information on sociodemographic attributes, mental and physical health, and provided two measures of resting blood pressure, allowing a diagnosis of definite or borderline hypertension. Those with hypertension had lower levels of beta-carotene and higher levels of uric acid and MDA compared to normotensive participants. The last two of these associations persisted when the analyses controlled for lifestyle and health factors. The findings from this study offer limited support for the proposition that lower antioxidant status and higher oxidative stress are associated with hypertension, and suggest the need for longitudinal studies to examine causality and intervention studies to determine the benefit of antioxidants in this group.

Systemic arterial pressure response to two weeks of Tempol therapy in SHR: involvement of NO, the RAS, and oxidative stress

The roles of nitric oxide (NO) and plasma renin activity (PRA) in the depressor response to chronic administration of Tempol in spontaneously hypertensive rats (SHR) are not clear. The present study was done to determine the effect of 2 wk of Tempol treatment on blood pressure [mean arterial pressure (MAP)], oxidative stress, and PRA in the presence or absence of chronic NO synthase inhibition. SHR were divided into four groups: control, Tempol (1 mmol/l) alone, nitro-L-arginine methyl ester (L-NAME, 4.5 mg x g(-1).day(-1)) alone, and Tempol + L-NAME or 2 wk. With Tempol, MAP decreased by 22%: 191 +/- 3 and 162 +/- 21 mmHg for control and Tempol, respectively (P < 0.05). L-NAME increased MAP by 16% (222 +/- 2 mmHg, P < 0.01), and L-NAME + Tempol abolished the depressor response to Tempol (215 +/- 3 mmHg, P < 0.01). PRA was not affected by Tempol but was increased slightly with L-NAME alone and 4.4-fold with L-NAME + Tempol. Urinary nitrate/nitrite increased with Tempol and decreased with L-NAME and L-NAME + Tempol. Tempol significantly reduced oxidative stress in the presence and absence of L-NAME. In conclusion, in SHR, Tempol administration for 2 wk reduces oxidative stress in the presence or absence of NO, but in the absence of NO, Tempol is unable to reduce MAP. Therefore, NO, but not changes in PRA, plays a major role in the blood pressure-lowering effects of Tempol. These data suggest that, in hypertensive individuals with endothelial damage and chronic NO deficiency, antioxidants may be able to reduce oxidative stress but not blood pressure.

Effects of garlic extract consumption on blood lipid and oxidant/antioxidant parameters in humans with high blood cholesterol

Effects of garlic extract supplementation on blood lipid profile and oxidant/antioxidant status were investigated in volunteer subjects with high blood cholesterol. A total of 23 volunteer subjects with high blood cholesterol (>5.98 mmol/L) participated in the study. Of them, 13 patients were evaluated as a hypertensive group and the others a normotensive group. Before (first sample) and after (second sample) garlic extract consumption for 4 months, routine blood analyses including lipid parameters and liver and kidney function tests were performed. Additionally, blood oxidant (malondialdehyde [MDA], oxidation resistance [OR]), and antioxidant (antioxidant potential [AOP], nonenzymatic superoxide radical scavenger activity [NSSA]) parameters were measured. Serum total cholesterol, low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) cholesterols, and triglyceride levels were found to be significantly lowered, but HDL high-density lipoprotein cholesterol level increased after the extract use. The total:HDL cholesterol ratio was also found to be significantly decreased after the extract use. There were no meaningful differences with regard to other routine biochemical parameters. Additionally, blood AOP, OR, and NSSA values were found increased and MDA level decreased in the second samples relative to the first ones. Systolic and diastolic blood pressure values were also found to be significantly lowered after extract supplementation in the hypertensive group, but no similar changes were observed in the normotensive group. We conclude that garlic extract supplementation improves blood lipid profile, strengthens blood antioxidant potential, and causes significant reductions in systolic and diastolic blood pressures. It also leads to a decrease in the level of oxidation product (MDA) in the blood samples, which demonstrates reduced oxidation reactions in the body.

Vitamin E for the Treatment of Cardiovascular Disease: Is There a Future?

Oxidative stress seems to play a key role in the pathogenesis of atherosclerosis. Agents that protect low-density lipoprotein from oxidation have been shown in a range of in vitro and animal models to reduce the development and progression of atherosclerosis. These agents include antioxidant micronutrients such as vitamin E. They have gained wide interest because of the potential for prevention of atherosclerotic vascular disease in humans. In the last decade, many trials with antioxidants have been carried out in patients with cardiovascular disease, but the results are equivocal. The reason for the disappointing findings is unclear, but one possible explanation is the lack of identification criteria of patients who are potential candidates for antioxidant treatment. This review analyses the data reported so far to determine whether they clearly support the premise that patients at risk of cardiovascular disease may be candidates for antioxidant treatment.

Effects of garlic extract consumption on plasma and erythrocyte antioxidant parameters in atherosclerotic patients

Effects of ingesting garlic extract on plasma and erythrocyte antioxidant parameters of atherosclerotic patients were investigated in this study. Eleven patients with atherosclerosis participated in the study. They ingested a dose of 1 ml/kg body weight of garlic extract daily for 6 months (study period). Before and after this period, fasting blood samples were obtained, and oxidant (malondialdehyde, MDA and xanthine oxidase, XO) and antioxidant (superoxide dismutase, SOD and glutathione peroxidase, GSH-Px) parameters were studied in plasma and erythrocytes obtained from the patients. Blood samples obtained from 11 healthy subjects served as the controls. Plasma XO activity and MDA levels were higher, but plasma and erythrocyte GSH-Px activities were lower, in patients with atherosclerosis relative to those of the control group. Our results showed that ingestion of garlic extract leads to significantly lowered plasma and erythrocyte MDA levels in the patients even in the absence of changes in antioxidant enzyme activities. Our results also demonstrated the presence of oxidant stress in blood samples from patients with atherosclerosis, but ingesting garlic extract prevented oxidation reactions by eliminating this oxidant stress. Thus, it is possible that reduced peroxidation processes may play a part in some of the beneficial effects of garlic in atherosclerotic diseases.

Prevention of fructose-induced hypertension by dietary vitamins

Essential hypertension in humans may develop through a combination of genetic and environmental factors. Diet has long been under investigation as a potential effector of blood pressure. A diet high in sucrose or fructose can give rise to hyperlipidemia, insulin resistance and hypertension. Insulin resistance, glucose intolerance and oxidative stress are common features of hypertension. If glucose metabolism through the glycolytic pathway is impaired, as in insulin resistance, there will be a build-up of glyceraldehyde, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate with further metabolism to methylglyoxal, a highly reactive ketoaldehyde. Excess aldehydes can bind sulfhydryl groups of membrane proteins, altering membrane calcium channels, increasing cytosolic free calcium, peripheral vascular resistance and blood pressure. The presence of reactive aldehydes can also lead to oxidative stress. Dietary management through lower sucrose or fructose intake and increased consumption of vitamins improves glucose metabolism, lowers tissue aldehydes, increases anti-oxidant capacity and may also prevent hypertension.

Should antioxidant status be considered in interventional trials with antioxidants?

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

Childhood and adult dietary vitamin E intake and cardiovascular risk factors in mid-life in the 1946 British Birth Cohort

OBJECTIVES

To determine whether dietary vitamin E intake in childhood or mid-life was predictive of adult hypertension and high waist circumference, as two important risk factors for cardiovascular disease.

DESIGN

Longitudinal study of a social class stratified random sample of all the legitimate, singleton births in the week of 3-9 March 1946.

SETTINGS

England, Scotland and Wales.

SUBJECTS

The 2980 survey members who provided information on diet, health and sociodemographic information at two time points; age 4 y in 1950 (24-h dietary recall) and 43 y in 1989 (48-h dietary recall).

MAIN OUTCOME MEASURES

Outcomes were adjusted odds ratios (ORs) for hypertension and high waist circumference at age 43 y by thirds of vitamin E intake, relative to the highest intake thirds at both ages.

RESULTS

The lowest consumers of vitamin E in both childhood and adulthood were more likely to be hypertensive (OR 1.8, 95% confidence interval (CI): 1.03-3.08) and have high waist circumference (OR 1.6, 95% CI: 1.02-2.43) than those consuming high levels at both ages. A low intake of vitamin E at just one time point was not associated with a statistically significant increased risk of hypertension or high waist circumference. Social class was also an independent and equally strong predictor of these coronary risk factors, indicating that the relation between social class and cardiovascular risks was not mediated solely by the current measures of diet and lifestyle.

CONCLUSIONS

Unique data on vitamin E intake from foods in both childhood and adulthood have indicated that relatively low intake of vitamin E at both ages predicted hypertension and high waist circumference at age 43 y.

Vitamin C lowers blood pressure and alters vascular responsiveness in salt-induced hypertension

The present study was undertaken to investigate the effect of vitamin C treatment on blood pressure and vascular reactivity in salt-induced hypertension. Male Sprague-Dawley rats were fed a normal rat diet, a high-sodium (8% NaCl) diet, a normal rat diet plus vitamin C treament (100 mg x kg(-1) x day(-1)), or a high-sodium diet plus vitamin C treatment for 6 weeks. Salt loading significantly increased blood pressure, which was attenuated by vitamin C treatment. Aortic rings from the different groups were suspended for isometric-tension recording. The contractile response to noradrenaline was significantly increased in the salt-loaded rats. Vitamin C reduced the sensitivity of aortic rings to noradrenaline in rats on normal and high-sodium diets. In noradrenaline-precontracted rings, the relaxation response to acetylcholine, which was attenuated in the salt-loaded rats, was restored by vitamin C treatment. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME) abolished the enhanced response to acetylcholine caused by vitamin C. The results suggest that the antihypertensive effect of vitamin C is associated with a reduction in vascular sensitivity to noradrenaline and enhancement of endothelium-dependent relaxation due to increased nitric oxide bioavailability.

Dietary vitamin E and C supplementation prevents fructose induced hypertension in rats

In fructose-induced hypertension in Wistar-Kyoto (WKY) rats, excess endogenous aldehydes bind sulfhydryl groups of membrane proteins, altering membrane Ca2+ channels and increasing cytosolic free calcium and blood pressure. The thiol compound N-acetyl cysteine prevents fructose-induced hypertension by binding excess endogenous aldehydes and normalizing membrane Ca2+ channels and cytosolic free calcium. The aim of the present study was to investigate whether dietary supplementation of vitamin E and vitamin C which are known to increase tissue glutathione, a storage form of cysteine, prevents this hypertension and its associated biochemical and histopathological changes. Starting at 7 weeks of age, animals were divided into four groups of six animals each and treated as follows: control group, normal diet and normal drinking water; fructose group, normal diet and 4% fructose in drinking water; fructose + vitamin E group, diet supplemented with vitamin E (34 mg/ kg feed) and 4% fructose in drinking water; fructose + vitamin C group, diet supplemented with vitamin C (1,000 mg/kg feed) and 4% fructose in drinking water. At 14 weeks, systolic blood pressure, platelet [Ca2+]i and kidney and aortic aldehyde conjugates were significantly higher in the fructose group. These animals also displayed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidneys. Dietary vitamin E and C supplementation in fructose-treated WKY rats prevented the increase in systolic blood pressure by normalizing cytosolic [Ca2+]i and kidney and aortic aldehyde conjugates and preventing adverse renal vascular changes.

Dietary vitamin E supplementation lowers blood pressure in spontaneously hypertensive rats

In spontaneously hypertensive rats (SHRs) excess endogenous aldehydes bind sulfhydryl groups of membrane proteins, altering membrane Ca2+ channels and increasing cytosolic free calcium and blood pressure. The thiol compound, N-acetyl cysteine, normalizes elevated blood pressure in SHRs by binding excess endogenous aldehydes. Vitamin E increases tissue glutathione levels--a storage form of cysteine. The aim of the present study was to investigate whether a dietary supplementation of vitamin E lowers blood pressure and prevents renal vascular changes by normalizing tissue aldehyde conjugates and cytosolic [Ca2+] in SHRs. Starting at 12 weeks of age, animals were divided into three groups of six animals each. Animals in the WKY-control group and SHR-control group were given a normal diet and the SHR-vitamin E group a diet supplemented with vitamin E (34 mg/ kg feed) for the next 9 weeks. After 9 weeks, systolic blood pressure, platelet [Ca2+]i, and liver, kidney and aortic aldehyde conjugates were significantly higher in SHR controls as compared to WKY controls and the SHR-vitamin E group. SHR-controls also showed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidney. Dietary vitamin E supplementation in SHRs lowered the systolic blood pressure, cytosolic [Ca2+], tissue aldehyde conjugates and attenuated adverse renal vascular changes.

Blood oxidant/antioxidant status of atherosclerotic patients

In the present study, it is aimed to investigate oxidant/antioxidant status of plasma and erythrocytes from atherosclerotic patients and to establish the possible role of oxidant stress in the formation and progression of atherosclerosis. Antioxidant potential (AOP) values and malondialdehyde (MDA) levels were studied in erythrocyte and plasma samples from 40 atherosclerotic patients and 38 healthy controls. A total of 13 subjects in each group were smokers. AOP was found unchanged in erythrocytes but lower in plasma samples (P<0.0005) from atherosclerotic patients as compared with those of the controls. MDA levels were however higher in erythrocyte hemolysate (P<0.025), erythrocyte membrane (P<0.0005) and blood plasma samples (P<0.0005) from atherosclerotic patients than those of the controls. Moreover, AOP was found to be lower in plasma samples of smoker patients than that of non-smoker patients (P<0.05). In the control group, erythrocyte MDA level was higher in smoker group than that of non-smoker group (P<0.05). Results reveal the presence of oxidant stress in the blood samples from patients with atherosclerosis. It seems antioxidant therapy might give beneficial results for atherosclerotic patients.

Dietary vitamin C supplementation lowers blood pressure in spontaneously hypertensive rats

In spontaneously hypertensive rats (SHRs) excess endogenous aldehydes bind sulfhydryl groups of membrane proteins, altering membrane Ca2+ channels and increasing cytosolic free calcium and blood pressure. The thiol compound, N-acetyl cysteine, normalizes elevated blood pressure in SHRs by binding excess endogenous aldehydes. Vitamin C can increase tissue cysteine and glutathione levels. The aim of the present study was to investigate whether a dietary supplementation of vitamin C can lower tissue aldehydes and blood pressure and normalize associated biochemical and histopathological changes in SHRs. Starting at 12 weeks of age, animals were divided into 3 groups of 6 animals each. Animals in the WKY-control group and SHR-control group were given a normal diet and the SHR-vitamin C group a diet supplemented with vitamin C (1000 mg/kg feed) for the next 9 weeks. After nine weeks, systolic blood pressure, platelet [Ca2+]i, plasma insulin and liver, kidney and aortic aldehyde conjugates were significantly higher in SHR controls as compared to WKY controls and the SHR-vitamin C group. SHR-controls also showed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidneys. Dietary vitamin C supplementation in SHRs lowered the systolic blood pressure, tissue aldehyde conjugates and attenuated adverse renal vascular changes.

Clofibric acid or diethylmaleate supplemented diet decrease blood pressure in DOCA-salt treated male Sprague Dawley rats--relation with liver antioxidant status

The effects of 8-week diethylmaleate (DEM) and clofibric acid (CFA) supplemented diet on blood pressure, body and liver weights, liver antioxidant status and nitric oxide synthase (NOS) activity were investigated in 8-week DOCA-salt treated and untreated Sprague-Dawley male rats. It appeared that DEM and particularly CFA treatments were associated with a significant decrease in blood pressure in DOCA-salt treated rats, and an accentuation of the decreases in body weights in both diet supplemented groups. This was not associated with increases in NO production in the liver. In contrast, hepatic lipid peroxidation was significantly decreased in both DOCA-salt treated and untreated groups on DEM and particularly on CFA supplemented diet. The protective effects of CFA and DEM against hepatic cellular damage could be involved in the decreases in blood pressure in DOCA-salt treated rats, where CFA was more efficient than DEM. In CFA supplemented groups, there was a strong increase in hepatic superoxide dismutase (SOD), glutathione-peroxidase (GSH-Px), and catalase (CAT) activities and in DEM supplemented groups, increases in SOD and CAT activities and in GSH levels were observed. Our data suggest that normalization of blood pressure in DOCA-salt treated rats by CFA was due to an enhancement of the half-life of NO while DEM increased its availability.

Coenzyme Q versus hypertension: does CoQ decrease endothelial superoxide generation?

Reports from several research groups--including two small double-blind clinical studies--indicate that supplemental coenzyme Q10 (CoQ) is moderately effective as a treatment for hypertension, in humans and in animals. Its efficacy is associated with a decrease in total peripheral resistance, and appears to reflect a direct impact of CoQ on the vascular wall. A reasonable interpretation of these findings is that CoQ is acting as an antagonist of vascular superoxide--either scavenging it, or suppressing its synthesis. By improving the efficiency of shuttle mechanisms that transfer high-energy electrons from the cytoplasm to the mitochondrial respiratory chain, CoQ may decrease cytoplasmic NADH levels and thereby diminish the reductive power that drives superoxide synthesis in endothelium and vascular smooth muscle. If CoQ therapy does indeed lower vascular superoxide levels, it can be expected to decrease the atherothrombotic risk associated with hypertension, and may have broader utility in the management of disorders characterized by endotheliopathy.

Optimal nutrition: vitamin E

Interest in the role of vitamin E in disease prevention has encouraged the search for reliable indices of vitamin E status. Most studies in human subjects make use of static markers, usually alpha-tocopherol concentrations in plasma or serum. Plasma or serum alpha-tocopherol concentrations of < 11.6, 11.6-16.2, and > 16.2 mumol/l are normally regarded as indicating deficient, low and acceptable vitamin E status respectively, although more recently it has been suggested that the optimal plasma alpha-tocopherol concentration for protection against cardiovascular disease and cancer is > 30 mumol/l at common plasma lipid concentrations in combination with plasma vitamin C concentrations of > 50 mumol/l and > 0.4 mumol beta-carotene/l. Assessment of vitamin E status has also been based on alpha-tocopherol concentrations in erythrocytes, lymphocytes, platelets, lipoproteins, adipose tissue, buccal mucosal cells and LDL, and on alpha-tocopherol: gamma-tocopherol in serum or plasma. Erythrocyte susceptibility to haemolysis or lipid oxidation, breath hydrocarbon exhalation, oxidative resistance of LDL, and alpha-tocopheryl quinone concentrations in cerebrospinal fluid have been used as functional markers of vitamin E status. However, many of these tests tend to be non-specific and poorly standardized. The recognition that vitamin E has important roles in platelet, vascular and immune function in addition to its antioxidant properties may lead to the identification of more specific biomarkers of vitamin E status.

Malondialdehyde, lipofuscin and activity of antioxidant enzymes during physical exercise in patients with essential hypertension

DESIGN

To clarify the role of oxidative damage in essential hypertension, levels of lipid peroxidation products (malondialdehyde and lipofuscin) and activity of antioxidant enzymes (superoxide dismutase and glutathione peroxidase) were examined during a short period of physical exercise.

PATIENTS AND METHODS

We studied 11 male patients with mild to moderate essential hypertension in World Health Organization classes I or II and 10 healthy male controls. Physical exercise was performed on a bicycle ergometer at graded intensities of 1.0, 1.5 and 2.0 W/kg body weight Plasma concentrations of lipofuscin, malondialdehyde, epinephrine, norepinephrine, insulin, free fatty acids and glucose were determined. Superoxide dismutase activity was analysed in erythrocytes and glutathione peroxidase activity in whole blood.

RESULTS

Concentrations of lipofuscin and malondialdehyde were significantly elevated in hypertensive patients. Superoxide dismutase activity was not different between groups, while glutathione peroxidase activity was significantly decreased in hypertensive subjects. During exercise, the concentration of malondialdehyde and antioxidant enzyme activities increased significantly in both groups. No differences were found in absolute increases between the normotensive and hypertensive subjects. The levels of glucose, insulin and free fatty acids were similar in both groups. Basal concentrations of catecholamines and also the exercise-induced increases were lower in hypertensive patients.

CONCLUSIONS

Our results indicate increased oxidative damage in patients with essential hypertension, which might be caused by a decrease in the activity of glutathione peroxidase. The ability of superoxide dismutase and glutathione peroxidase to respond to increased production of reactive oxygen species during a short period of physical exercise was not impaired in hypertensive subjects.

Modulation of alpha-tropomyosin expression by alpha-tocopherol in rat vascular smooth muscle cells

The effect of alpha-tocopherol (vitamin E) on gene expression in rat vascular smooth muscle cells was studied by the differential display technique. One gene out of about 1000 genes analyzed, identified as alpha-tropomyosin, showed an increased transcription level caused by alpha-tocopherol treatment. Northern and Western blot analysis revealed a time-dependent transient up-regulation of the amount of mRNA (peak between 2 and 3 h) and protein (peak at 5 h) in alpha-tocopherol-treated cells. No effect was observed in cells treated with beta-tocopherol.

Low-density lipoprotein oxidation and vitamins E and C in sustained and white-coat hypertension

Low-density lipoprotein oxidation and antioxidant vitamins E and C were investigated in white-coat hypertension in comparison with sustained hypertension and normotension. We selected 21 sustained hypertensive subjects, 21 white-coat hypertensive subjects, and 21 normotensive subjects matched for gender, age, and body mass index. White-coat hypertension was defined as clinical hypertension and daytime ambulatory blood pressure <139/90 (subjects were also reclassified using 134/90 and 135/85 mm Hg as cutoff points for daytime blood pressure). Blood samples were drawn for lipid profile determination, assessment of fluorescent products of lipid peroxidation in native LDL, evaluation of susceptibility to LDL oxidation in vitro (lag phase and propagation rate), and determination of LDL vitamin E and plasma vitamins E and C contents. Compared with sustained hypertensive subjects, white-coat hypertensives had significantly lower fluorescent products of lipid peroxidation (15.4+/-3.4 versus 10.2+/-3 units of relative fluorescence/mg LDL protein, P<.05), longer lag phase (54+/-10 versus 88+/-10 minutes, P<.05), lower propagation rate (8.2+/-2.5 versus 5.95+/-2.1 nmol diene/min per mg LDL cholesterol, P<.05), higher LDL vitamin E content (8.3+/-1.1 versus 10.1+/-1.8 nmol/mg LDL cholesterol, P<.05), and plasma vitamin C content (40+/-13 versus 57+9 micromol/L, P<. 05). No significant difference was observed between white-coat hypertensive and normotensive subjects. The results did not change after reclassification of subjects. Our data show that white-coat hypertensive subjects do not show an enhanced propensity to LDL oxidation or reduction in antioxidant vitamins. Given the role of LDL oxidation in the development of atherosclerosis and that of vitamin E and C in protecting against it, these findings suggest that white-coat hypertension per se carries a low atherogenic risk.

alpha-Tocopherol enhances the peroxidase activity of hemoglobin on phospholipid hydroperoxide

We have used direct separation of phospholipid hydroperoxide and phospholipid hydroxide by high performance liquid chromatography to examine the phospholipid hydroperoxide peroxidase activity of hemoglobin (Hb) in the presence of hydrogen donors. Hb exhibits phospholipid hydroperoxide peroxidase activity and rapidly breaks down phospholipid hydroperoxide to thiobarbituric acid-reactive substances. However, in the presence of alpha-tocopherol, some phospholipid hydroperoxide is converted to phospholipid hydroxide, which is more stable than the hydroperoxide and is much less reactive with thiobarbituric acid. Other electron donors such as glutathione and ascorbate are less effective than alpha-tocopherol. Free cysteine also shows some ability to reduce phospholipid hydroperoxides to corresponding hydroxides, but cys-93 beta of Hb did not participate in the reaction, as shown by N-ethylmaleimide modification. Hemin alone catalysed the reaction, in the absence of protein. The results therefore show that Hb catalyses an apparent phospholipid hydroperoxide alpha-tocopherol peroxidase reaction due to bound hemin, and that the reduction depends on the ability of hydrogen donors to react with the intermediate phospholipid alkoxyl radical and does not involve reduction by deprotonated sulfhydryl groups.