Contribution of vitamin A to the oxidation resistance of human low density lipoproteins

Structural Features of Small Molecule Antioxidants and Strategic Modifications to Improve Potential Bioactivity

This review surveys the major structural features in various groups of small molecules that are considered to be antioxidants, including natural and synthetic compounds alike. Recent advances in the strategic modification of known small molecule antioxidants are also described. The highlight is placed on changing major physicochemical parameters, including log p, bond dissociation energy, ionization potential, and others which result in improved antioxidant activity.

Antioxidant Defense and Pseudoexfoliation Syndrome: An Updated Review

Oxidative stress (OS) affects the anterior ocular tissues, rendering them susceptible to several eye diseases. On the other hand, protection of the eye from harmful factors is achieved by unique defense mechanisms, including enzymatic and non-enzymatic antioxidants. The imbalance between oxidants and antioxidants could be the cause of pseudoexfoliation syndrome (PEXS), a condition of defective extracellular matrix (ECM) remodeling. A systematic English-language literature review was conducted from May 2022 to June 2022. The main antioxidant enzymes protecting the eye from reactive oxygen species (ROS) are superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which catalyze the reduction of specific types of ROS. Similarly, non-enzymatic antioxidants such as vitamins A, E and C, carotenoids and glutathione (GSH) are involved in removing ROS from the cells. PEXS is a genetic disease, however, environmental and dietary factors also influence its development. Additionally, many OS products disrupting the ECM remodeling process and modifying the antioxidative defense status could lead to PEXS. This review discusses the antioxidative defense of the eye in association with PEXS, and the intricate link between OS and PEXS. Understanding the pathways of PEXS evolution, and developing new methods to reduce OS, are crucial to control and treat this disease. However, further studies are required to elucidate the molecular pathogenesis of PEXS.

Bioactive Compounds of Edible Fruits with Their Anti-Aging Properties: A Comprehensive Review to Prolong Human Life

Aging is a complicated biological process in which functional and structural alterations in a living organism take place over time. Reactive oxygen species is one of the main factors responsible for aging and is associated with several chronic pathologies. The relationship between aging and diet is quite interesting and has attained worldwide attention. Healthy food, in addition to dietary antioxidants, are required to delay the process of aging and improve the quality of life. Many healthy foods such as fruits are a good source of dietary nutrients and natural bioactive compounds which have antioxidant properties and are involved in preventing aging and other age-related disorders. Health benefits linked with healthy consumption of fruit have drawn increased interest. A significant number of studies have documented the advantages of fruit intake, as it suppresses free-radical development that further reduces the oxidative stress created in the body and protects against several types of diseases such as cancer, type 2 diabetes, inflammatory disorders, and other cardiovascular diseases that ultimately prevent aging. In addition, fruits have numerous other properties like anti-inflammatory, anti-cancerous, anti-diabetic, neuroprotective, and have health-promoting effects. Mechanisms of various bioactive compounds that aids in preventing various diseases and increases longevity are also described. This manuscript provides a summary of various bioactive components present in fruits along with their health-promoting and antiaging properties.

Dietary Antioxidants and the Mitochondrial Quality Control: Their Potential Roles in Parkinson's Disease Treatment

Advances in medicine and dietary standards over recent decades have remarkably increased human life expectancy. Unfortunately, the chance of developing age-related diseases, including neurodegenerative diseases (NDDs), increases with increased life expectancy. High metabolic demands of neurons are met by mitochondria, damage of which is thought to contribute to the development of many NDDs including Parkinson’s disease (PD). Mitochondrial damage is closely associated with the abnormal production of reactive oxygen species (ROS), which are widely known to be toxic in various cellular environments, including NDD contexts. Thus, ways to prevent or slow mitochondrial dysfunction are needed for the treatment of these NDDs. In this review, we first detail how ROS are associated with mitochondrial dysfunction and review the cellular mechanisms, such as the mitochondrial quality control (MQC) system, by which neurons defend against both abnormal production of ROS and the subsequent accumulation of damaged mitochondria. We next highlight previous studies that link mitochondrial dysfunction with PD and how dietary antioxidants might provide reinforcement of the MQC system. Finally, we discuss how aging plays a role in mitochondrial dysfunction and PD before considering how healthy aging through proper diet and exercise may be salutary.

Free radicals, natural antioxidants, and their reaction mechanisms

The normal biochemical reactions in our body, increased exposure to the environment, and higher levels of dietary xenobiotic's result in the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Implication of vitamin A deficiency on vascular injury related to inflammation and oxidative stress. Effects on the ultrastructure of rat aorta

BACKGROUND

Vitamin A deficiency induces activation of NF-kB and impairs activities of antioxidant enzymes in aorta.

AIM OF THE STUDY

We study the effect of vitamin A deficiency on the aorta histoarchitecture and the possibly contribution of its prooxidant and inflammatory effects to artery alterations.

METHODS

Twenty-one-day-old Wistar male rats were fed during 3 months with vitamin A-deficient diet (-A, n = 8) or the same diet containing 8 mg of retinol palmitate/kg of diet (+A, control, n = 8). In aortas, thiobarbituric reactive substances and reduced glutathione levels were measured by spectrophotometry. Expressions of TNF-alpha, NOX-2, VCAM-1, and TGF-beta1 were assessed by RT-PCR and Western Blot. The morphology of aorta was examined by light and transmission electron microscopy.

RESULTS

In -A rats, high levels of TBARS in serum and aorta and low levels of GSH in aorta were found. An increased expression of TNF-alpha, NOX-2, VCAM-1, and TGF-beta1 in aorta from -A rats was observed. Examination of the intimal layer by light microscopy indicated the presence of an irregular surface in -A aortas. TEM studies showed large vacuoles and multivesicular bodies along the endothelium and also multivesicular bodies in the subendothelial space of aortas from -A rats. Furthermore, the histological appearance of internal elastic lamina was different from control. Small vesicles in the medial layer were observed in aortas from vitamin A-deficient rats.

CONCLUSIONS

Vitamin A deficiency produces histoarchitectural alterations in aorta, which can be associated, at least in part, to the oxidative stress and inflammation induced by vitamin A deficiency.

Intestinal β-carotene 15,15′-dioxygenase activity is markedly enhanced in copper-deficient rats fed on high-iron diets and fructose

The purpose of the present work was to examine effects of the Cu–Fe interaction on intestinal β-carotene 15,15′-dioxygenase activity when a wide range of dietary Fe (deficiency to excess) was used in relation to Cu status of rats. The effect of dietary carbohydrates was also examined since they play a role in the Cu–Fe interactionin vivo. Weanling male Sprague-Dawley rats (n72) were divided into twelve dietary groups, which were fed on either low-, normal-, or high-Fe levels (0·9, 9·0, and 90·0 mmol Fe/kg diet respectively) combined with Cu-adequate or -deficient levels (0·94 and 0·09 mmol Cu/kg diet respectively) and with starch or fructose in the diets. The data showed that both Fe concentration and β-carotene 15,15′-dioxygenase activity in small intestinal mucosa were enhanced with increasing dietary Fe and with Cu deficiencyv. Cu adequacy. Dietary fructose did not aggravate the Fe-enhancement, related to Cu deficiency, in the small intestine; however, fructose increased the intestinal dioxygenase activity in rats fed on normal- or high-Fe diets when compared with starch controls. Thus, the highest intestinal dioxygenase activity associated with the lowest hepatic retinol (total) concentration was found in rats fed on the Cu-deficient, high-Fe, fructose-based diet. Finally, a positive linear relationship was found between the dioxygenase activity and Fe concentration in intestinal mucosa. In conclusion, the data indicate that β-carotene 15,15′-dioxygenase activity requires Fe as cofactorin vivoand the enzyme is modulated by the three dietary components: Cu, Fe, and fructose.

Alterations in the Lipid Metabolism of Rat Aorta: Effects of Vitamin A Deficiency

Antioxidants are known to reduce cardiovascular disease by reducing the concentration of free radicals in the vessel wall and by preventing the oxidative modification of low-density lipoproteins. The prooxidative effect of a vitamin-A-deficient diet on the aorta has previously been demonstrated by us. In this study, the lipid metabolism in the aorta of rats fed on a vitamin-A-deficient diet was evaluated. Vitamin A deficiency induced a hypolipidemic effect (lower serum triglyceride and cholesterol levels) and a decreased serum paraoxonase 1/arylesterase activity. The concentrations of triglycerides, total cholesterol, free and esterified cholesterol, and phospholipids were increased in the aorta of vitamin-A-deficient rats. The phospholipid compositions showed an increase in phosphatidylcholine (PC), phosphatidylinositol plus phosphatidylserine and phosphatidylethanolamine, a decrease in sphingomyelin, and no change in phosphatidylglycerol. In the aorta, the increase in triglycerides was associated with an increased fatty acid synthesis and mRNA expression of diacylglycerol acyltransferase 1. The increased PC content was attributed to an increased synthesis, as measured by [methyl-(14)C]choline incorporation into PC and high CTP:phosphocholine cytidylyltransferase-alpha mRNA expression. The cholesterol synthesis, evaluated by [1-(14)C]acetate incorporated into cholesterol and mRNA expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase, did not change. The lipoprotein lipase and lectin-like oxidized low-density lipoprotein receptor 1 mRNA expression levels increased in the aorta of vitamin-A-deficient animals. The incorporation of vitamin A into the diet of vitamin-A-deficient rats reverted all the changes observed. These results indicate that a vitamin-A-deficient diet,in addition to having a prooxidative effect, alters the aorta lipid metabolism.

Enzymatic O-methylation of flavanols changes lag time, propagation rate, and total oxidation during in vitro model triacylglycerol-rich lipoprotein oxidation

3'-O-Methyl derivatives of flavan-3-ols, (+)-catechin (C), (-)-epicatechin (EC), and (-)-catechin gallate (CG) were prepared enzymatically. Hexanal (EC and CG family, 5 mmol/L) and conjugated diene (C and EC family, 0.25-10 mmol/L) formation following CuSO4-mediated triacylglycerol-rich lipoprotein oxidation was measured. All EC and CG compounds significantly reduced hexanal formation (p < 0.02). O-Methylation improved the ability of CG (more polar) while reducing the ability of EC (less polar) to limit hexanal formation. 3'-O-methyl EC was 18% (p < 0.001) and 4'-O-methyl 65% (p < 0.001) less able than EC to suppress hexanal formation. At >1 micromol/L all EC and C compounds significantly increased lag time. Parent compounds were more effective (> 4-fold increase) than metabolites (1.5-fold increase). Parent compounds did not influence propagation rate (DeltaOD/min). At >1 mmol/L O-methylated EC and C reduced propagation by 20-40% (p < 0.01). Notably, at 0.25 mmol/L O-methylated EC and C increased propagation rates 22% (p < 0.01) despite prolonging lag time.

Oxidative stress : relationship with exercise and training

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection - the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson's disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

Protecting against anthracycline-induced myocardial damage: a review of the most promising strategies

Over the last 40 years, great progress has been made in treating childhood and adult cancers. However, this progress has come at an unforeseen cost, in the form of emerging long-term effects of anthracycline treatment. A major complication of anthracycline therapy is its adverse cardiovascular effects. If these cardiac complications could be reduced or prevented, higher doses of anthracyclines could potentially be used, thereby further increasing cancer cure rates. Moreover, as the incidence of cardiac toxicity resulting in congestive heart failure or even heart transplantation dropped, the quality and extent of life for cancer survivors would improve. We review the proposed mechanisms of action of anthracyclines and the consequences associated with anthracycline treatment in children and adults. We summarise the most promising current strategies to limit or prevent anthracycline-induced cardiotoxicity, as well as possible strategies to prevent existing cardiomyopathy from worsening.

Increased resistance to oxidation of betalain-enriched human low density lipoproteins

Betalains are natural pigments recently considered as compounds with potential antioxidative properties. In this work, ex vivo plasma spiking of pure either betanin or indicaxanthin, followed by isolation of low density lipoprotein (LDL), and measurement of its resistance to copper-induced oxidation, has been used to research if these betalains can bind to LDL and prevent oxidation of LDL lipids. When pooled human plasma from 10 healthy volunteers was incubated in the presence of 25-100 microM either betanin or indicaxanthin, incorporation of both compounds in LDL was observed, with a maximum binding of 0.52 +/- 0.08, and 0.51 +/- 0.06 nmoles of indicaxanthin and betanin, respectively, per mg LDL protein. Indicaxanthin-enriched and betanin-enriched LDL were more resistant than homologous native LDL to copper-induced oxidation, as assessed by the elongation of the induction period. The incorporated indicaxanthin, however, appeared twice as effective as betanin in increasing the length of the lag phase, while both compounds did not affect the propagation rate. Both betalains were consumed during the inhibition period of lipid oxidation, and delayed consumption of LDL-beta carotene. Indicaxanthin, but not betanin, prevented vitamin E consumption at the beginning of LDL oxidation, and prolonged the time of its utilization. The resistance of LDL to oxidation when vitamin E and indicaxanthin acted separately in a sequence, was lower than that measured when they were allowed to act in combination, indicating some synergistic interaction between the two molecules. No prooxidant effect over a large concentration range of either betanin or indicaxanthin was observed, when either betalain was added to the LDL system undergoing a copper-induced oxidation. These results show than indicaxanthin and betanin may bind to LDL, and are highly effective in preventing copper-induced lipid oxidation. Interaction with vitamin E appears to add a remarkable potential to indicaxanthin in the protection of LDL. Although molecular mechanisms remain uncompletely understood, various aspects of the action of betanin and indicaxanthin in preventing LDL lipid oxidation are discussed.

Importance of the kidneys in metabolism of vitamins A1 and A2 and their fatty acyl esters in mink feeding on fish-based diets and exposed to Aroclor 1242

Two-month-old female mink (Mustela vison) were fed diets based on freshwater smelt (Osmerus eperlanus), Baltic herring (Clupea harengus membras), or North-Atlantic herring (Clupea harengus harengus) for 21 weeks. Half of the smelt-fed mink were exposed to the commercial polychlorinated biphenyl (PCB) preparation Aroclor 1242 (1 mg/day) in the feed. Retinol (vitamin A(1)), 3,4-didehydroretinol (vitamin A(2)), their fatty acyl esters, and vitamin E were studied in the kidneys by reversed-phase high-performance liquid chromatography. Exposure to Aroclor 1242 resulted a significant decrease in the alcoholic and esterified vitamin A(2). Levels of the A(1) analogs did not change due to the PCBs and were the same in mink fed either smelt or Baltic herring. In mink fed very fatty Atlantic herring, the renal levels of vitamin A(1) and E were significantly lower than in the other mink and apparently consumed by lipid peroxidation. The vitamins were located mainly in the cortex, and the fatty acyl esters showed a fatty acid composition that differed from those in liver and plasma. In the kidneys of the smelt-fed mink (control or Aroclor-exposed) the ratio of vitamin A(2) to A(1) was much lower than the ratios in the liver or plasma, suggesting inefficient uptake of A(2) in the kidneys. In the PCB-exposed mink, in which vitamin losses are increased, tissue levels of vitamin A(2) may be more difficult to maintain than levels of vitamin A(1).

Effects of Aroclor 1242 and different fish-based diets on vitamins A1 (retinol) and A2 (3,4-didehydroretinol), and their fatty acyl esters in mink plasma

The effects of a 21-week exposure to Aroclor 1242 (1mg per day in feed) on plasma concentrations of vitamins A(1) (retinol) and A(2) (3,4-didehydroretinol) and their principal fatty acyl esters (A(1)-16:0, A(2)-16:0 (palmitates), A(1)-18:1n-9; A(2)-18:1n-9 (oleates), and A(1)-18:0; A(2)-18:0 (stearates)) were studied in young female mink (Mustela vison) fed a diet based on freshwater smelt. These vitamin levels were also examined in mink fed diets containing Baltic herring or fatty marine fish. In the Aroclor-exposed smelt-fed mink, the plasma concentrations of A(1) and A(2) esters were significantly lower than the levels in controls fed the uncontaminated smelt diet. In addition, the A(2) esters reacted more sensitively to the polychlorinated biphenyls than did A(1) esters. In contrast, in the plasma of the exposed mink the level of alcoholic A(1) was normal, and transport of thyroxine (T(4)) and nonspecific lipoprotein transport of major lipids were not impaired. Despite the large dietary supply of vitamin A(2) and high levels of plasma A(2) esters, the mink fed freshwater smelt had only trace amounts of alcoholic vitamin A(2) in their plasma. The concentrations of A(1) and A(2) esters in the plasma of all the mink studied correlated with the hepatic total concentrations of the vitamins. Thus, in carnivores that have nonspecific lipoprotein transport of vitamin A esters, determination of plasma levels of the esterified vitamins may be a useful nondestructive way to estimate stores of the vitamin A analogs in the body and to assess the organochlorine-induced decrease in the vitamin stores.

Effects of cod liver oil on tissue antioxidant pathways in normal and streptozotocin-diabetic rats

Lipid disorders and increased oxidative stress may exacerbate some complications of diabetes mellitus. Previous studies have implicated the beneficial effects of some antioxidants, omega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the protection of cells from the destructive effect of increased lipids and lipid peroxidation products. This study, therefore, was designed to investigate the effects of cod liver oil (CLO, Lysi Ltd. Island), which comprises mainly vitamin A, PUFAs, EPA and DHA. Effects were monitored on plasma lipids, lipid peroxidation products (MDA) and the activities of antioxidant enzymes, glutathione peroxidase (GSHPx) and catalase in heart, liver, kidney and lung of non-diabetic control and streptozotocin (STZ)-induced-diabetic rats. Two days after STZ-injection (55 mg kg(-1) i.p.), non-diabetic control and diabetic rats were divided randomly into two groups as untreated or treated with CLO (0.5 ml kg(-1) rat per day) for 12 weeks. Plasma glucose, triacylglycerol and cholesterol concentrations were significantly elevated in 12-week untreated-diabetic animals; CLO treatment almost completely prevented these abnormalities in triacylglycerol and cholesterol, but hyperglycaemia was partially controlled. CLO also provided better weight gain in diabetic animals. In untreated diabetic rats, MDA markedly increased in aorta, heart and liver but was not significantly changed in kidney and lung. This was accompanied by a significant increase in both GSHPx and catalase enzyme activities in aorta, heart, and liver of diabetic rats. In kidney and lung, diabetes resulted in reduced catalase while GSHPx was significantly activated. In aorta, heart, and liver, diabetes-induced changes in MDA were entirely prevented by CLO treatment. In the tissues of CLO-treated diabetic animals, GSHPx activity paralleled those of control animals. CLO treatment also caused significant improvements in catalase activities in every tissue of diabetic rats, but failed to affect MDA and antioxidant activity in control animals. The current study suggests that the treatment of diabetic rats with CLO provides better control of glucose and lipid metabolism, allows recovery of normal growth rate, prevents oxidative/peroxidative stress and ameliorates endogenous antioxidant enzyme activities in various tissues. Because CLO contains a plethora of beneficial compounds together, its use for the management of diabetes-induced complications may provide important advantages.

Effects of vitamin A and insulin on the antioxidative state of diabetic rat heart: a comparison study with combination treatment

Because elevated oxidative stress may exacerbate cardiovascular complications of diabetes mellitus, the current study aimed to investigate the effects of treatment with either vitamin A, an antioxidant, or with insulin on lipid peroxidation products and antioxidant enzyme activities of diabetic rat heart. Also to evaluate whether a combination of vitamin A and insulin exerts more beneficial effects than treatment with each agent alone. Rats were made diabetic with a single injection of streptozotocin (STZ, 55 mg kg(-1) i.p.). Two days after STZ-injection, one group of diabetic rats was treated with vitamin A (retinol acetate, 30 mg kg(-1) day(-1) i.o.) for 12 weeks. A second group of diabetic rats was untreated for 6 weeks and then treated for another 6 weeks with insulin (8-10 IU rat(-1) day(-1) s.c.). Both therapies were applied to another group of diabetic rats for assessment of combined therapy with vitamin A plus insulin. Hearts from 12-week untreated diabetic animals showed about a four-fold increase in the level of thiobarbituric acid reactive substances (TBARS), indicative of increased lipid peroxidation. This was accompanied by approximately 100% increase in both catalase and glutathione peroxidase (GSHPx) enzyme activities. Therapy with insulin alone caused a small but significant improvement in plasma TBARS as well as GSHPx activities, but no significant change in plasma catalase in diabetic animals. Diabetes-induced disturbance in TBARS was almost completely prevented by vitamin A therapy. Although, a similar degree of activities for GSHPx was determined in diabetic animals treated with each agent alone, combination therapy was found to be more effective than single therapies in the recovery of GSHPx of diabetic heart. In contrast to insulin single therapy, vitamin A alone significantly prevented an increase in catalase activity of diabetic heart, and a combination of these agents did not supply any further benefit. Superoxide dismutase (SOD) activity was not found significantly different among the experimental groups. STZ-diabetes also resulted in less plasma retinol and retinol-binding protein (RBP), which was significantly improved by insulin single therapy while vitamin A used alone, failed to increase plasma retinol and RBP levels of diabetic animals. Our findings suggest that single therapy with insulin is unable to preclude oxidative reactions in diabetic heart to the same extent as obtained by vitamin A therapy alone, in spite of allowing recovery of normal growth rate and improved vitamin A metabolism in diabetic rats. A combination of insulin with vitamin A may provide more benefits than use of either agent alone in the treatment of general characteristics of diabetes and the maintenance of antioxidant defence of diabetic heart and thus in the reduction of peroxidative stress-induced cardiac injury.

Diet and overall survival in a cohort of very elderly people

We conducted a 5-year cohort study among 162 self-sufficient residents in a public home for the elderly in Rome, Italy, to evaluate the association between the consumption of specific food groups and nutrients and overall 5-year survival. We used a validated, semiquantitative food-frequency questionnaire to assess diet at baseline. Individuals consuming citrus fruit at least twice a week had an adjusted risk of dying that was half that of individuals who consumed citrus fruit less than once a week [relative risk (RR) = 0.52; 95% confidence interval (CI) = 0.28-0.95] (with adjustment for gender, age, education, body mass index, smoking status, cognitive function, and chronic diseases). The adjusted RRs of mortality were 0.38 (95% CI = 0.14-1.01) for consumption of milk and yogurt at least three times a week vs less than once a week; 0.21 (95% CI = 0.08-0.35) for moderate consumption of espresso coffee (1-2 cups weekly) vs less than once a week; and 0.35 (95% CI = 0.17-0.69) for > 2 cups a week of espresso coffee vs less than once a week. High levels of intake of ascorbic acid, riboflavin, and linoleic acid were associated with 50-60% decreases in mortality risk. High consumption of meat was associated with a higher risk of mortality (RR = 9.72; 95% CI = 2.68-35.1) among subjects with chronic diseases. Our findings indicate that frequent consumption of citrus fruit, milk, and yogurt; low consumption of meat; and high intake of vitamin C, riboflavin, and linoleic acid are associated with longevity.

Relationship between classic risk factors, plasma antioxidants and indicators of oxidant stress in angina pectoris (AP) in Tehran

Cardiovascular disease (CVD) in general seems to be the leading cause of death in the Eastern Mediterranean Region (EMR) including Iran. This may be due to classic risk factors such as high triglyceride (TG), high total cholesterol (TC), and low levels of high density lipoprotein cholesterol (HDL-C). The impact of antioxidants as potentially protective risk factors against early coronary heart disease (CHD) is unknown in Iran. Therefore, relationships between angina and plasma antioxidants and indicators of lipid peroxidation were investigated in a case-control study. In this study, 82 cases of previously undiagnosed angina pectoris (AP), identified by a modified WHO Rose chest pain questionnaire and verified by electrocardiography during treadmill exercise testing, were compared with 146 controls selected from the same population of over 4000 male civil servants aged 40-60 years. Subjects with AP declared significantly less physical activity and had higher serum TG [means (S.E.M.) 2.32 (0.18) versus 1.61 (0.07) mmol/l] but lower HDL-C [1.01 (0.04) versus 1.18 (0.03) mmol/l] than age-matched controls. Levels of total serum cholesterol, low-density lipoprotein cholesterol (LDL-C) and lipoprotein(a) [Lp(a)] were not significantly different between the two groups, while the ratio of LDL-C/HDL-C was significantly higher [4.51 (0.23) versus 3.54 (0. 11)] for subjects with AP than for the controls. There was no significant difference in plasma levels of alpha-tocopherol, vitamin C, alpha- and beta-carotene. However, retinol [1.90 (0.06) versus 2. 09 (0.05)] and beta-cryptoxanthin [0.398 (0.04) versus 0.467 (0.03)] were significantly lower in AP. Furthermore, angina cases exhibited a higher index of lipid peroxidation than controls (e.g. malondialdehyde, MDA; 0.376 (0.010) versus 0.337 (0.009) micromol/l). On multiple logistic regression analysis, retinol with odds ratio (OR) of 0.644 [95% confidence interval (CI; 0.425-0.978)], beta-cryptoxanthin, with an OR of 0.675 (CI; 0.487-0.940), oxidation indices, MDA with OR of 1.612 (95% CI; 1.119-2.322) and LDL-C/HDL-C ratio with OR of 2.006 (95% CI; 1.416-2.849) showed the most significant independent associations with AP in this group of Iranians. In conclusion, the state of lipid peroxidation as well as the status of special antioxidants may be co-determinants of AP in Iran, in parallel with the influence of classical risk factors for cardiovascular disease.

Extra-virgin olive oil increases the resistance of LDL to oxidation more than refined olive oil in free-living men with peripheral vascular disease

Patients with peripheral vascular disease (Fontaine stage II) are characterized by ischemia of the lower extremities, atherosclerosis and alteration of blood coagulation and fibrinolysis. A randomized, two-period, crossover design was used to compare the effects of extra-virgin (VO) and refined olive (RO) oils on plasma lipids and lipoprotein composition and LDL oxidation susceptibility in free-living men with peripheral vascular disease. The oils differed in their antioxidant profile (alpha-tocopherol: 300 vs. 200 mg/kg; phenolic compounds 800 vs. 60) and concentration but not in their fatty acid composition. Subjects were randomly assigned to two groups. The first group (n = 12) received VO with which to freely cook all meals for 3 mo, followed by a 3-mo wash-out period; they then received RO for the final 3 mo. The second group (n = 12) consumed the oils in the opposite order. Energy, fat, polyunsaturated fatty acids (PUFA) and alpha-tocopherol intakes were not different when patients consumed the two oils. Profiles of the major fatty acids in plasma and LDL were not different after consumption of VO and RO. The slope of the line for LDL oxidation vs. the line for copper concentration was significantly higher after the intake of RO than after the intake of VO. Total LDL taken up by macrophages was significantly greater when the men consumed RO rather than VO. We suggest that antioxidants present in VO may protect LDL against oxidation more than does RO in men with peripheral vascular disease.

Oxidative stress induced in pathologies: the role of antioxidants

Exposure to oxidant molecules issued from the environment (pollution, radiation), nutrition, or pathologies can generate reactive oxygen species (ROS for example, H2O2, O2-, OH). These free radicals can alter DNA, proteins and/or membrane phospholipids. Depletion of intracellular antioxidants in acute oxidative stress or in various diseases increases intracellular ROS accumulation. This in turn is responsible for several chronic pathologies including cancer, neurodegenerative or cardiovascular pathologies. Thus, to prevent against cellular damages associated with oxidative stress it is important to balance the ratio of antioxidants to oxidants by supplementation or by cell induction of antioxidants.

Antioxidant potentials of vitamin A and carotenoids and their relevance to heart disease

Despite being one of the first vitamins to be discovered, the full range of biological activities for vitamin A remains to be defined. Structurally similar to vitamin A, carotenoids are a group of nearly 600 compounds. Only about 50 of these have provitamin A activity. Recent evidence has shown vitamin A, carotenoids and provitamin A carotenoids can be effective antioxidants for inhibiting the development of heart disease. Vitamin A must be obtained from the diet: green and yellow vegetables, dairy products, fruits and organ meats are some of the richest sources. Within the body, vitamin A can be found as retinol, retinal and retinoic acid. Because all of these forms are toxic at high concentrations, they are bound to proteins in the extracellular fluids and inside cells. Vitamin A is stored primarily as long chain fatty esters and as provitamin carotenoids in the liver, kidney and adipose tissue. The antioxidant activity of vitamin A and carotenoids is conferred by the hydrophobic chain of polyene units that can quench singlet oxygen , neutralize thiyl radicals and combine with and stabilize peroxyl radicals. In general, the longer the polyene chain, the greater the peroxyl radical stabilizing ability. Because of their structures, vitamin A and carotenoids can autoxidize when O2 tension increases, and thus are most effective antioxidants at low oxygen tensions that are typical of physiological levels found in tissues. Overall, the epidemiological evidence suggests that vitamin A and carotenoids are important dietary factors for reducing the incidence of heart disease. Although there is considerable discrepancy in the results from studies in humans regarding this relationship, carefully controlled experimental studies continue to indicate that these compounds are effective for mitigating and defending against many forms of cardiovascular disease. More work, especially concerning the relevance of how tissue concentrations, rather than plasma levels, relate to the progression of tissue damage in heart disease is required. This review assembles information regarding the basic structure and metabolism of vitamin A and carotenoids as related to their antioxidant activities. Epidemiological, intervention trials and experimental evidence about the effectiveness of vitamin A and carotenoids for reducing cardiovascular disease is also reviewed.

Antioxidant vitamins and coronary artery disease risk in South African males

Decreased antioxidant-vitamin nutritional status may increase lipid peroxidation and susceptibility of low-density lipoprotein (LDL) to oxidative modification. The aim of this study was to evaluate the vitamin nutritional status of coronary artery disease (CAD) patients and to assess the risk of CAD related to each individual antioxidant vitamin. The study was performed as a case-control study with 41 patients with angiographically demonstrated CAD and 41 apparently healthy age- and smoking status-matched controls. Plasma vitamin E, C and A concentrations were significantly decreased in CAD patients compared with controls (p < 0.001) after correcting for significant covariates. Per quartile decrease in vitamin A and E concentrations was associated with increased risk of CAD, even after adjusting for CAD risk factors, while per quartile decrease in vitamin C concentrations was not associated with significant CAD risk after adjusting for CAD risk factors. Decreased vitamin A and E concentrations are independently associated with increased risk of CAD independent from other CAD risk factors in white male South Africans and dietary intervention strategies are advocated.

The antioxidative effects of the isoflavan glabridin on endogenous constituents of LDL during its oxidation

The effect of the consumption of glabridin, an isoflavan isolated from Glycyrrhiza glabra (licorice) root, on the susceptibility of low density lipoprotein (LDL) to oxidation was studied in atherosclerotic apolipoprotein E deficient (E[o] mice) and was compared with that of the known flavonoids, quercetin and catechin. Glabridin inhibitory activity on in vitro oxidation of human LDL was also investigated by determining the formation of lipid peroxides and oxysterols and the consumption of LDL-associated lipophilic antioxidants. Determination of the extent of LDL oxidation by measuring the formation of thiobabituric acid reactive substances (TBARS) after 2 h of LDL incubation with CuSO4 (10 microM) or 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH) (5 mM), revealed that glabridin or quercetin consumption resulted in a 53 and 54% reduction in copper ion induced oxidation, respectively, and a 95 and 83% reduction in AAPH induced LDL oxidation, respectively. No inhibition was obtained with consumption of catechin. About 80% of glabridin was found to bind to the LDL human particle. In the in vitro oxidation of LDL induced by AAPH (5 mM), glabridin inhibited the formation of TBARS, lipid peroxides and cholesteryl linoleate hydroperoxide (CLOOH) at all the concentrations tested (5-60 microM), while in oxidation induced by copper ions (10 microM), glabridin exhibited a pro-oxidant activity at concentrations lower than 20 microM, and a clear antioxidant activity at concentrations greater than 20 microM. Glabridin (30 microM) inhibited the formation of cholest-5-ene-3,7-diol (7-hydroxycholesterol), cholest-5-ene-3-ol-7-one (7-ketocholesterol) and cholestan-5,6-epoxy-3-ol (5,6-epoxycholesterol) after 6 h of AAPH induced LDL oxidation, by 55, 80 and 40%, respectively, and after 6 h of copper ion induced LDL oxidation, by 73, 94 and 52%, respectively. Glabridin also inhibited the consumption of beta-carotene and lycopene by 38 and 52%, respectively, after 0.5 h of LDL oxidation with AAPH, but failed to protect vitamin E. The in vivo and in vitro reduction of the susceptibility of LDL to oxidation obtained with glabridin, may be related to the absorption or binding of glabridin to the LDL particle and subsequent protection of LDL from oxidation by inhibiting the formation of lipid peroxides and oxysterols, and by protecting LDL associated carotenoids.

Vitamins E plus C and interacting conutrients required for optimal health. A critical and constructive review of epidemiology and supplementation data regarding cardiovascular disease and cancer

Antioxidants are crucial components of fruit/vegetable rich diets preventing cardiovascular disease (CVD) and cancer: plasma vitamins C, E, carotenoids from diet correlate prevalence of CVD and cancer inversely, low levels predict an increased risk of individuals which is potentiated by combined inadequacy (e.g., vitamins C + E, C + carotene, A + carotene); self-prescribed rectification of vitamins C and E at adequacy of other micronutrients reduce forthcoming CVD, of vitamins A, C, E, carotene and conutrients also cancer; randomized exclusive supplementation of beta-carotene +/- vitamin A or E lack benefits except prostate cancer reduction by vitamin E, and overall cancer reduction by selenium; randomized intervention with synchronous rectification of vitamins A + C + E + B + minerals reduces CVD and counteracts precancerous lesions; high vitamin E supplements reveal potentials in secondary CVD prevention. Plasma values desirable for primary prevention: > or = 30 mumol/l lipid-standardized vitamin E (alpha-tocopherol/cholesterol > or = 5.0 mumol/mmol); > or = 50 mumol/l vitamin C aiming at vitamin C/vitamin E ratio > 1.3-1.5; > or = 0.4 mumol/l beta- (> or = 0.5 mumol/l alpha+ beta-) carotene.

CONCLUSIONS

In CVD vitamin E acts as first risk discriminator, vitamin C as second one; optimal health requires synchronously optimized vitamins C + E, A, carotenoids and vegetable conutrients.

Low-density lipoprotein and oxidised low-density lipoprotein: their role in the development of atherosclerosis

Oxidation of low-density lipoprotein (LDL) may be implicated in the development of atherosclerotic disease. Oxidised LDL is taken up more readily by monocyte-derived macrophages than LDL. Antibodies to oxidised LDL are found in atherosclerotic lesions, Increased risk of ischaemic heart disease is associated with a preponderance of small dense LDL particles, which are more susceptible to oxidation. Proatherogenic alterations in cell biochemistry and signalling pathways occur in the presence of LDL and more markedly oxidised LDL. In vitro antioxidants inhibit changes in cell biochemistry, while in vivo, they have been shown to attenuate or reverse development of atherosclerosis.

Possible antioxidant effect of vitamin A supplementation in premature infants

BACKGROUND

Increased lipid peroxidation caused by oxygen free radicals is thought to be one of the common pathogenetic mechanisms for the so-called oxygen radical diseases of prematurity. Since in vitro studies have shown that various forms of vitamin A can exert antioxidant effects that are more potent than those of vitamin E (treatment with which has been ineffective in these diseases), the purpose of this prospective, controlled study was to determine whether administration of supplemental vitamin A to premature infants deficient in this vitamin would have an antioxidant effect in vivo.

METHODS

Fourteen infants (1181 +/- 35 g; gestational age 29 +/- 0.04 weeks) with a serum retinol concentration at 7 +/- 2 days of age in the deficient range, lower than 0.7 mumol/l (< 20 micrograms/dl), were enrolled in the study. Infants were randomized to receive the standard amount of vitamin A or standard plus supplemental (2.6 mumol/l [2500 IU] orally each day) vitamin A, beginning at 1 week of age. Antioxidant effects of supplementation were assessed by a decrease in lipid peroxidation, quantified by the ethane content of expired air.

RESULTS

Three weeks after study enrollment, total daily vitamin A intake in the infants receiving supplements was 4.565 +/- 0.236 mumol (4354 +/- 225 IU) versus 1.879 +/- 0.317 mumol/l (1792 +/- 302 IU) in infants receiving standard amounts of the vitamin. In spite of the difference in intake of vitamin A, 3 weeks after study enrollment, serum retinol concentrations did not differ between the infants given supplements and those receiving standard amounts of vitamin A, 0.70 +/- 0.21 versus 0.66 +/- 0.07 mumol/l (20 +/- 6 micrograms/dl versus 19 +/- 2 micrograms/dl, respectively). In the infants receiving supplemental vitamin A, breath ethane values declined from baseline values. There was an inverse correlation between the number of weeks of supplementation and breath ethane values, whereas there was no significant correlation between the duration of the study and breath ethane values in the infants not given supplements.

CONCLUSIONS

Our data suggest that supplementation with vitamin A in a small group of vitamin A-deficient preterm infants was associated with an antioxidant effect. Although no immediate clinical benefits were associated with supplementation, the data provide the rationale for future investigations of possible antioxidant effects of (larger amounts?) of vitamin A in higher risk premature infants born with subnormal serum retinol concentrations.

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

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

Effect of olive and sunflower oils on low density lipoprotein level, composition, size, oxidation and interaction with arterial proteoglycans

The atherogenicity of low density lipoproteins (LDL) may be modulated by its serum levels, structure and affinity for components of the intima, all properties that can be altered by diet. Linoleic acid-rich diets (n-G, 18:2) reduce the levels of LDL whereas those rich in oleic (n-9,18:1) are considered 'neutral'. However, LDL enriched in linoleic acid have been reported to be more vulnerable to free radical-mediated oxidation than those enriched in oleic, a potentially atherogenic property. The effect of dietary fats on other properties of LDL that may also modulate atherogenesis, such as size and capacity to interact with intima components, are not well established. We explored here how a change from an olive oil-rich diet (OO) to a sunflower oil-rich one (SFO) affects these parameters in a community with a traditional Mediterranean diet. Eighteen free-living volunteers were placed for 3 weeks on a diet with 31% of caloric intake as sunflower oil and then shifted for an additional 3 weeks to a diet in which OO provided 30.5% of the calories. The LDL after SFO had a fatty acids ratio of (18:2 + 18:3 + 20:4) to (16:0 + 16:1 + 18:0 + 18:1) of 1.06 +/- 0.11 compared to 0.73 +/- 0.06 after the OO period. Serum LDL was significantly lower after SFO than after OO. Unexpectedly, copper-catalyzed oxidation of LDL from the SFO period was significantly less than that of the particles from the OO period. The resistance to oxidation of LDL of the SFO and OO period related to alterations in content of the antioxidants alpha-tocopherol, beta-carotene and retinol, in addition to changes in size and fatty acids composition. In vitro binding of LDL to human arterial proteoglycans was also significantly lower for the SFO-LDL than the OO-LDL, a result that can also be attributed to the larger size of the SFO-LDL. Therefore, three properties of LDL: circulating levels, oxidizability, and affinity with intima proteoglycans, that may modulate its atherogenicity, were shifted in a favorable direction by diets rich in linoleic acid and natural antioxidants.

Inhibition of low density lipoprotein oxidation by myrigalone B, a naturally occurring flavonoid

The influence of myrigalone B, a flavonoid from the fruit exudate of Myrica gale L. on Cu(2+)-induced oxidation of low density lipoprotein from cholesterol fed rabbits was investigated. Myrigalone B was an effective antioxidant, as shown by its ability to dose-dependently prolong the lag time for the formation of conjugated dienes. A 100% increase in lag time corresponds to a myrigalone B concentration of 1.4 +/- 1.1 microM. For alpha-tocopherol, used as a reference, this effect corresponds to a concentration of 1.9 +/- 1.2 microM. Myrigalone B also dose-dependently reduced the maximum rate of formation of conjugated dienes, 1.4 microM causing a 15 +/- 5% reduction, but it had no influence on the maximal amount of conjugated dienes formed.

Factors affecting resistance of low density lipoproteins to oxidation

Oxidation resistance (OR) of low density lipoproteins (LDL) is frequently determined by the conjugated diene (CD) assay, in which isolated LDL is exposed to CU2+ as prooxidant in the range of 1-10 microM. A brief review on major findings obtained with this assay will be given. A consistent observation is that vitamin E supplements or oleic acid-rich diets increase OR. Oxidation indices measured by the CD assay and effects of antioxidants very significantly depended on the Cu2+ concentration used for LDL oxidation. For medium and high Cu2+ concentrations, the relationship between lag time and propagation rate can be described by a simple hyperbolic saturation function, which has the same mathematical form as the Michaelis-Menten equation. At medium and high Cu2+ concentrations (0.5 to 5 microM), vitamin E increases lag time in a dose-dependent manner. The increase is higher for 0.5 microM Cu2+ as compared to 5 microM. At low Cu2+ concentrations (0.5 microM or less), the mechanism of LDL oxidation changes. Significant oxidation occurs in a preoxidation phase, which commences shortly after addition of Cu2+. Preoxidation is not inhibited by vitamin E. It is concluded that much additional work is needed to validate the importance of oxidation indices derived from CD and similar assays.

How different constituents of low density lipoprotein determine its oxidizability by copper: a correlational approach

Although low density lipoprotein (LDL) susceptibility to oxidation is expected to be primarily related to its composition, the individual contributions of different constituents to its oxidizability remain unclear. The present study was undertaken to elucidate how different constituents of isolated LDL determine its susceptibility to oxidation induced by Cu2+ under conditions close to those of well-known Cu2(+)-oxidation assay (H. Esterbauer, G. Striegl, H. Puhl and M. Rotheneder (1989) Free Radical Research Communications, 6, 67-75). We characterized antioxidant, fatty acid and total lipid composition of human LDL from healthy donors (n = 22) and compared each with LDL oxidizability by Cu2+. LDL oxidizability was evaluated as oxidizability of antioxidant-containing LDL (rate of lipid peroxidation measured before total consumption of alpha-tocopherol, the major LDL antioxidant), oxidizability of antioxidant-depleted LDL (maximal rate of lipid peroxidation and maximal production of conjugated dienes within the propagation, antioxidant-depleted phase of oxidation) and overall LDL resistance to oxidation (duration of the lag-phase before the onset of the propagation phase). We found that the oxidizability of antioxidant-containing LDL correlated negatively with LDL content of ubiquinol-10 and free cholesterol, and positively with that of n-3 polyunsaturated fatty acids (PUFAs). LDL n-3 PUFAs, ubiquinol-10 and free cholesterol were the most important determinants of the oxidizability of antioxidant-containing LDL, contributing to about 35%, 25% and 25% of its total variability, respectively. Oxidizability of antioxidant-depleted LDL was largely determined by LDL PUFA content. The overall LDL resistance to oxidation correlated weakly with LDL chemical composition. alpha-Tocopherol was found to be only a minor contributor to the oxidizability of isolated LDL under oxidative conditions used (7.5 or 14 mol Cu2+ / mol LDL). It appears that the oxidizability of antioxidant-containing LDL represents a parameter highly sensitive to changing LDL composition, whereas the overall LDL resistance to oxidation combines contributions from different LDL constituents more uniformly, being weaker sensitive to individual factors. It is suggested that PUFAs, ubiquinol-10 and free cholesterol are the most important determinants of LDL oxidizability of Cu2+.