Beta-carotene inhibits atherosclerosis in hypercholesterolemic rabbits

β-Carotene accelerates the resolution of atherosclerosis in mice

β-Carotene oxygenase 1 (BCO1) catalyzes the cleavage of β-carotene to form vitamin A. Besides its role in vision, vitamin A regulates the expression of genes involved in lipid metabolism and immune cell differentiation. BCO1 activity is associated with the reduction of plasma cholesterol in humans and mice, while dietary β-carotene reduces hepatic lipid secretion and delays atherosclerosis progression in various experimental models. Here we show that β-carotene also accelerates atherosclerosis resolution in two independent murine models, independently of changes in body weight gain or plasma lipid profile. Experiments in Bco1-/- mice implicate vitamin A production in the effects of β-carotene on atherosclerosis resolution. To explore the direct implication of dietary β-carotene on regulatory T cells (Tregs) differentiation, we utilized anti-CD25 monoclonal antibody infusions. Our data show that β-carotene favors Treg expansion in the plaque, and that the partial inhibition of Tregs mitigates the effect of β-carotene on atherosclerosis resolution. Our data highlight the potential of β-carotene and BCO1 activity in the resolution of atherosclerotic cardiovascular disease.

β-carotene accelerates the resolution of atherosclerosis in mice

β-carotene oxygenase 1 (BCO1) catalyzes the cleavage of β-carotene to form vitamin A. Besides its role in vision, vitamin A regulates the expression of genes involved in lipid metabolism and immune cell differentiation. BCO1 activity is associated with the reduction of plasma cholesterol in humans and mice, while dietary β-carotene reduces hepatic lipid secretion and delays atherosclerosis progression in various experimental models. Here we show that β-carotene also accelerates atherosclerosis resolution in two independent murine models, independently of changes in body weight gain or plasma lipid profile. Experiments in Bco1-/- mice implicate vitamin A production in the effects of β-carotene on atherosclerosis resolution. To explore the direct implication of dietary β-carotene on regulatory T cells (Tregs) differentiation, we utilized anti-CD25 monoclonal antibody infusions. Our data show that β-carotene favors Treg expansion in the plaque, and that the partial inhibition of Tregs mitigates the effect of β-carotene on atherosclerosis resolution. Our data highlight the potential of β-carotene and BCO1 activity in the resolution of atherosclerotic cardiovascular disease.

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Exploring the Active Compounds of Traditional Mongolian Medicine Baolier Capsule (BLEC) in Patients with Coronary Artery Disease (CAD) Based on Network Pharmacology Analysis, Molecular Docking and Experimental Validation

Objective

Baolier Capsule (BLEC) is a Traditional Mongolian Medicine comprising fifteen herbs. This study aims to illustrate the synergistic mechanism of BLEC in the treatment of Coronary Artery Disease (CAD) by using network pharmacology method, molecular docking and experimental validation.

Methods

Searching and screening the active ingredients of different herbs in BLEC and target genes related to CAD in multiple databases. Subsequently, Protein-Protein Interactions Network (PPI-Net), gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment were used to identify the key targets. AutoDock was used to verify the binding ability between the active ingredient and key target through molecular docking. Reverse Transcription-Quantitative Real-Time Polymerase Chain Reaction (RT-qPCR) was used to verify the effect of active ingredient of BLEC on the key target gene. Finally, effect of BLEC on the degree of blood lipids and atherosclerosis was validated by animal experiment.

Results

There are 144 active components and 80 CAD-related targets that are identified in BLEC in the treatment of CAD. What is more, 8 core genes were obtained by clustering and topological analysis of PPI-Net. Further, GO and KEGG analysis showed that fluid shear stress and atherosclerosis are the key pathways for BLEC to treat CAD. These results were validated by molecular docking method. In vitro, active compounds of BLEC (Quercetin, luteolin, kaempferol, naringenin, tanshinone IIA, β-carotene, 7-O-methylisomucronulatol, piperine, isorhamnetin and Xyloidone) can inhibit 8 core gene (AKT1, EGFR, FOS, MAPK1, MAPK14, STAT3, TP53 and VEGFA) expression. Moreover, BLEC not only improve blood lipid levels but also inhibit the development of atherosclerosis in ApoE-knockout mice.

Conclusion

Our research first revealed the basic pharmacological effects and related mechanisms of in the treatment of CAD. The predicted results provide some theoretical support for BLEC or its important active ingredients to treat CAD.

Ageing, Age-Related Cardiovascular Risk and the Beneficial Role of Natural Components Intake

Ageing, in a natural way, leads to the gradual worsening of the functional capacity of all systems and, eventually, to death. This process is strongly associated with higher metabolic and oxidative stress, low-grade inflammation, accumulation of DNA mutations and increased levels of related damage. Detrimental changes that accumulate in body cells and tissues with time raise the vulnerability to environmental challenges and enhance the risk of major chronic diseases and mortality. There are several theses concerning the mechanisms of ageing: genetic, free radical telomerase, mitochondrial decline, metabolic damage, cellular senescence, neuroendocrine theory, Hay-flick limit and membrane theories, cellular death as well as the accumulation of toxic and non-toxic garbage. Moreover, ageing is associated with structural changes within the myocardium, cardiac conduction system, the endocardium as well as the vasculature. With time, the cardiac structures lose elasticity, and fibrotic changes occur in the heart valves. Ageing is also associated with a higher risk of atherosclerosis. The results of studies suggest that some natural compounds may slow down this process and protect against age-related diseases. Animal studies imply that some of them may prolong the lifespan; however, this trend is not so obvious in humans.

Effects of Dietary Supplementation of Garlic and Oregano Essential Oil on Biomarkers of Oxidative Status, Stress and Inflammation in Postweaning Piglets

The effects of two different concentrations of micro capsuled oregano essential oil (OEO) and purple garlic powder on biomarkers of oxidative status, stress, and inflammation, as well as on average daily gain (ADG) and feed conversion ratio (FCR), were evaluated in piglets during the postweaning period. The trial was carried out with 300 crossbred pigs of 21 days of age fed with different concentrations of OEO and purple garlic powder and ZnO. Saliva and serum samples were taken to evaluate a panel of biomarkers of oxidative status, stress, and inflammation. OEO and garlic powder at 0.4% did not produce significant changes in C-reactive protein (CRP) and cortisol and yielded higher levels of the antioxidant biomarker CUPRAC in serum than higher doses (p < 0.01); they yielded a better ADG than the control and ZnO diets. OEO and garlic powder at higher concentrations than 0.4% showed higher concentrations of CRP (p < 0.05). Overall, doses of OEO and garlic powder at 0.4% did not lead to inflammation, stress, or negative changes in oxidative biomarkers in piglets during the postweaning period and gave better productive performance than the control and ZnO diets. High doses of OEO and garlic powder were ineffective and could negatively affect the animals. Therefore, our results highlight the importance of the dose used when OEO or garlic are supplemented to piglets.

β-Carotene Oxygenase 1 Activity Modulates Circulating Cholesterol Concentrations in Mice and Humans

BACKGROUND

Plasma cholesterol is one of the strongest risk factors associated with the development of atherosclerotic cardiovascular disease (ASCVD) and myocardial infarction. Human studies suggest that elevated plasma β-carotene is associated with reductions in circulating cholesterol and the risk of myocardial infarction. The molecular mechanisms underlying these observations are unknown.

OBJECTIVE

The objective of this study was to determine the impact of dietary β-carotene and the activity of β-carotene oxygenase 1 (BCO1), which is the enzyme responsible for the conversion of β-carotene to vitamin A, on circulating cholesterol concentration.

METHODS

In our preclinical study, we compared the effects of a 10-d intervention with a diet containing 50 mg/kg of β-carotene on plasma cholesterol in 5-wk-old male and female C57 Black 6 wild-type and congenic BCO1-deficient mice. In our clinical study, we aimed to determine whether 5 common small nucleotide polymorphisms located in the BCO1 locus affected serum cholesterol concentrations in a population of young Mexican adults from the Universities of San Luis Potosí and Illinois: A Multidisciplinary Investigation on Genetics, Obesity, and Social-Environment (UP AMIGOS) cohort.

RESULTS

Upon β-carotene feeding, Bco1-/- mice accumulated >20-fold greater plasma β-carotene and had ∼30 mg/dL increased circulating total cholesterol (P < 0.01) and non-HDL cholesterol (P < 0.01) than wild-type congenic mice. Our results in the UP AMIGOS cohort show that the rs6564851 allele of BCO1, which has been linked to BCO1 enzymatic activity, was associated with a reduction in 10 mg/dL total cholesterol concentrations (P = 0.009) when adjusted for vitamin A and carotenoid intakes. Non-HDL-cholesterol concentration was also reduced by 10 mg/dL when the data were adjusted for vitamin A and total carotenoid intakes (P = 0.002), or vitamin A and β-carotene intakes (P = 0.002).

CONCLUSIONS

Overall, our results in mice and young adults show that BCO1 activity impacts circulating cholesterol concentration, linking vitamin A formation with the risk of developing ASCVD.

Effect of tomato consumption on fasting blood glucose and lipid profiles: A systematic review and meta-analysis of randomized controlled trials

Tomato (Solanum lycopersicum) phytochemicals, which include phytoene, phytofluene, beta-carotene, flavonoids, lycopene, and polyphenols, have been shown to improve the effects of fasting on plasma triglyceride (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol (TC), and fasting blood sugar (FBS). The aim of this study was to systematically evaluate the effects of Tomato TC, TG, HDL, LDL, and FBS in humans. A systematic literature search was conducted in PubMed/MEDLINE, Web of sciences, and SCOPUS databases by two researchers for studies published until August of 2019 without language and time limitations. Results were combined with random effect models. Six studies were included in this meta-analysis. Combined results reveal a significant reduction in cholesterol (weighted mean difference [WMD]: -4.39 mg/dl, 95% CI: -7.09, -1.68, I² = % 48, p heterogeneity: .05), TG (WMD: -3.94 mg/dl, 95% CI: -7.67, -0.21, I² = % 90, p heterogeneity: .001), LDL levels (WMD: -2.09 mg/dl, 95% CI: -3.73, -0.81, I² = % 78, p heterogeneity: .001), and increasing in HDL levels (WMD: 2.25 mg/dl, 95% CI: 0.41, 4.10, I² = % 97, p heterogeneity: .001). Tomato was found to have a higher reduction effect on TG and LDL in younger participants. While pooled results indicate no significant effect on FBS levels (WMD: 0.59 mg/dl, 95% CI: -0.28, 1.46, I² = % 95, p heterogeneity: .001). In conclusion, the results indicate a significant reduction in total cholesterol, TG, and LDL and increase in HDL levels that is caused by tomato consumption.

The role of β-carotene and vitamin A in atherogenesis: Evidences from preclinical and clinical studies

Atherosclerotic cardiovascular disease (ASCVD) is the principal contributor to myocardial infarction, the leading cause of death worldwide. Epidemiological and mechanistic studies indicate that β-carotene and its vitamin A derivatives stimulate lipid catabolism in several tissues to reduce the incidence of obesity, but their roles within ASCVD are elusive. Herein, we review the mechanisms by which β-carotene and vitamin A modulate ASCVD. First, we summarize the current knowledge linking these nutrients with epidemiological studies and lipoprotein metabolism as one of the initiating factors of ASCVD. Next, we focus on different aspects of vitamin A metabolism in immune cells such as the mechanisms of carotenoid uptake and conversion to the vitamin A metabolite, retinoic acid. Lastly, we review the effects of retinoic acid on immuno-metabolism, differentiation, and function of macrophages and T cells, the two pillars of the innate and adaptive immune response in ASCVD, respectively. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Acyclic Isoprenoid Attenuates Lipid Anomalies and Inflammatory Changes in Hypercholesterolemic Rats

The present study was aimed to explore the antihyperlipidemic and anti-inflammatory effect of acyclic isoprenoid on high fat diet fed rats. Hypercholesterolemia was induced by the diet comprising of the normal rat chow 84.3%, lard 5%, yolk powder 10%, cholesterol 0.2% and 0.5% bile salt were fed to the rats for the period of 8 weeks. The results showed that abnormally elevated levels of plasma lipid profiles. Three different doses of acyclic isoprenoid (20, 40 and 80 mg/kg b.w/day) were administered orally to hypercholesterolemia suffering rats for the period of 30 days. Among these three doses of acyclic isoprenoid, the dose 80 mg/kg b.w. was significantly decreased the plasma lipid profiles when compared to other two doses. The effect produced by acyclic isoprenoid (80 mg/kg b.w) was comparable to that of simvastatin. Therefore, 80 mg/kg b.w was fixed as a effective dose and used for further analyses. Acyclic isoprenoid administration reinstated the elevated levels of cardiac and inflammatory markers in both blood and serum of hypercholesterolemic rats. In addition, acyclic isoprenoid administration decreased activity of 3-hydroxy 3-methyl-glutaryl-CoA reductase and increased the activity of lecithin cholesterol acyl transferase. These findings suggest that the administration of acyclic isoprenoid was potentially ameliorated the cardiac marker enzymes and inflammatory markers in addition to its antihypercholesterolemic effect.

Untargeted metabolomic analysis of the carotenoid-based orange coloration in Haliotis gigantea using GC-TOF-MS

Seafood coloration is typically considered an indicator of quality and nutritional value by consumers. One such seafood is the Xishi abalone (Haliotis gigantea), which displays muscle color polymorphism wherein a small subset of individuals display orange coloration of muscles due to carotenoid enrichment. However, the metabolic basis for carotenoid accumulation has not been thoroughly investigated in marine mollusks. Here, GC-TOF-MS-based untargeted metabolite profiling was used to identify key pathways and metabolites involved in differential carotenoid accumulation in abalones with variable carotenoid contents. Cholesterol was the most statistically significant metabolite that differentiated abalones with orange muscles against those with common white muscles. This observation is likely due to the competitive interactions between cholesterol and carotenoids during cellular absorption. In addition, the accumulation of carotenoids was also related to fatty acid contents. Overall, this study indicates that metabolomics can reflect physiological changes in organisms and provides a useful framework for exploring the mechanisms underlying carotenoid accumulation in abalone types.

Microalgal Derivatives as Potential Nutraceutical and Food Supplements for Human Health: A Focus on Cancer Prevention and Interception

Epidemiological studies are providing strong evidence on beneficial health effects from dietary measures, leading scientists to actively investigate which foods and which specific agents in the diet can prevent diseases. Public health officers and medical experts should collaborate toward the design of disease prevention diets for nutritional intervention. Functional foods are emerging as an instrument for dietary intervention in disease prevention. Functional food products are technologically developed ingredients with specific health benefits. Among promising sources of functional foods and chemopreventive diets of interest, microalgae are gaining worldwide attention, based on their richness in high-value products, including carotenoids, proteins, vitamins, essential amino acids, omega-rich oils and, in general, anti-inflammatory and antioxidant compounds. Beneficial effects of microalgae on human health and/or wellness could in the future be useful in preventing or delaying the onset of cancer and cardiovascular diseases. During the past decades, microalgal biomass was predominately used in the health food market, with more than 75% of the annual microalgal biomass production being employed for the manufacture of powders, tablets, capsules or pastilles. In this review, we report and discuss the present and future role of microalgae as marine sources of functional foods/beverages for human wellbeing, focusing on perspectives in chemoprevention. We dissected this topic by analyzing the different classes of microalgal compounds with health outputs (based on their potential chemoprevention activities), the biodiversity of microalgal species and how to improve their cultivation, exploring the perspective of sustainable food from the sea.

Raman spectroscopy imaging reveals interplay between atherosclerosis and medial calcification in the human aorta

Medial calcification in the human aorta accumulates during aging and is known to be aggravated in several diseases. Atherosclerosis, another major cause of cardiovascular calcification, shares some common aggravators. However, the mechanisms of cardiovascular calcification remain poorly understood. To elucidate the relationship between medial aortic calcification and atherosclerosis, we characterized the cross-sectional distributions of the predominant minerals in aortic tissue, apatite and whitlockite, and the associated extracellular matrix. We also compared the cellular changes between atherosclerotic and nonatherosclerotic human aortic tissues. This was achieved through the development of Raman spectroscopy imaging methods that adapted algorithms to distinguish between the major biomolecules present within these tissues. We present a relationship between apatite, cholesterol, and triglyceride in atherosclerosis, with the relative amount of all molecules concurrently increased in the atherosclerotic plaque. Further, the increase in apatite was disproportionately large in relation to whitlockite in the aortic media directly underlying a plaque, indicating that apatite is more pathologically significant in atherosclerosis-aggravated medial calcification. We also discovered a reduction of β-carotene in the whole aortic intima, including a plaque in atherosclerotic aortic tissues compared to nonatherosclerotic tissues. This unprecedented biomolecular characterization of the aortic tissue furthers our understanding of pathological and physiological cardiovascular calcification events in humans.

Anti-atherosclerotic effect of housefly (Musca domestica) maggot-derived protein-enriched extracts by dampened oxidative stress in apolipoprotein E-deficient mice

Despitemany therapeutic advances, atherosclerosis remains the leading cause of morbidity and mortality in developed countries.

Vitamin A Decreases Cytotoxicity of Oxidized Low-Density Lipoprotein in Patients with Atherosclerosis

BACKGROUND

Oxidized low-density lipoprotein (ox-LDL) is implicated in initiation and progression of atherosclerosis. Previously, we found that ox-LDL increases vulnerability of peripheral blood mononuclear cells (PBMCs) in atherosclerotic patients compared to controls. Vitamin A induces proliferation of PBMCs. The aim of this study was to determine the effect of vitamin A supplementation on PBMC survival against LDL and different doses of ox-LDL.

METHOD

In this double-blind placebo-controlled trial, we recruited 35 atherosclerotic patients and 38 healthy controls and randomly allocated them into placebo and vitamin A groups, which received either placebo or 25,000 IU/day of vitamin A for 3 months. PBMCs were isolated, cultured, and stimulated by 1 µg/mL LDL as well as 1 µg/mL and 50 µg/mL ox-LDL. The stimulation indexes (SIs) of PBMCs were calculated to identify cell viability. Additionally, the circulating ox-LDL levels were measured by ELISA.

RESULTS

Viability of PBMCs stimulated by 50 µg/mL ox-LDL significantly increased following vitamin A supplementation in patients (p < 0.01). The levels of circulating ox-LDL were not changed by vitamin A treatment. Ox-LDL levels were strongly and positively correlated to SI of PBMCs stimulated by 1 µg/mL LDL and1 µg/mL ox-LDL in all groups.

CONCLUSION

Vitamin A decreases cytotoxicity of high-dose ox-LDL and improves PBMC viability. The protective effect of vitamin A is not mediated by an antioxidative mechanism, but may instead have been due to intracellular protection of the apoptotic machinery or induction of proliferation of the cells. Higher levels of ox-LDL increase PBMC irritability in all participants.

Identification and activation of novel biosynthetic gene clusters by genome mining in the kirromycin producer Streptomyces collinus Tü 365

Streptomycetes are prolific sources of novel biologically active secondary metabolites with pharmaceutical potential. S. collinus Tü 365 is a Streptomyces strain, isolated 1972 from Kouroussa (Guinea). It is best known as producer of the antibiotic kirromycin, an inhibitor of the protein biosynthesis interacting with elongation factor EF-Tu. Genome Mining revealed 32 gene clusters encoding the biosynthesis of diverse secondary metabolites in the genome of Streptomyces collinus Tü 365, indicating an enormous biosynthetic potential of this strain. The structural diversity of secondary metabolisms predicted for S. collinus Tü 365 includes PKS, NRPS, PKS-NRPS hybrids, a lanthipeptide, terpenes and siderophores. While some of these gene clusters were found to contain genes related to known secondary metabolites, which also could be detected in HPLC-MS analyses, most of the uncharacterized gene clusters are not expressed under standard laboratory conditions. With this study we aimed to characterize the genome information of S. collinus Tü 365 to make use of gene clusters, which previously have not been described for this strain. We were able to connect the gene clusters of a lanthipeptide, a carotenoid, five terpenoid compounds, an ectoine, a siderophore and a spore pigment-associated gene cluster to their respective biosynthesis products.

Vitamin A-deficient diet accelerated atherogenesis in apolipoprotein E(-/-) mice and dietary β-carotene prevents this consequence

Vitamin A is involved in regulation of glucose concentrations, lipid metabolism, and inflammation, which are major risk factors for atherogenesis. However, the effect of vitamin A deficiency on atherogenesis has not been investigated. Therefore, the objective of the current study was to examine whether vitamin A deficiency accelerates atherogenesis in apolipoprotein E-deficient mice (apoE^−/−). ApoE^−/− mice were allocated into the following groups: control, fed vitamin A-containing chow diet; BC, fed chow diet fortified with Dunaliella powder containing βc isomers; VAD, fed vitamin A-deficient diet; and VAD-BC group, fed vitamin A-deficient diet fortified with a Dunaliella powder. Following 15 weeks of treatment, liver retinol concentration had decreased significantly in the VAD group to about 30% that of control group. Vitamin A-deficient diet significantly increased both plasma cholesterol concentrations and the atherosclerotic lesion area at the aortic sinus (+61%) compared to the control group. Dietary βc fortification inhibited the elevation in plasma cholesterol and retarded atherogenesis in mice fed the vitamin A-deficient diet. The results imply that dietary vitamin A deficiency should be examined as a risk factor for atherosclerosis and that dietary βc, as a sole source of retinoids, can compensate for vitamin A deficiency.

Enhancing the health-promoting effects of tomato fruit for biofortified food

Consumption of tomato fruits, like those of many other plant species that are part of the human diet, is considered to be associated with several positive effects on health. Indeed, tomato fruits are an important source of bioactive compounds with known beneficial effects including vitamins, antioxidants, and anticancer substances. In particular, antioxidant metabolites are a group of vitamins, carotenoids, phenolic compounds, and phenolic acid that can provide effective protection by neutralizing free radicals, which are unstable molecules linked to the development of a number of degenerative diseases and conditions. In this review, we will summarize the recent progress on tomatoes nutritional importance and mechanisms of action of different phytochemicals against inflammation processes and prevention of chronic noncommunicable diseases (e.g., obesity, diabetes, coronary heart disease, and hypertension). In addition, we will summarize the significant progress recently made to improve the nutritional quality of tomato fruits through metabolic engineering and/or breeding.

HDL and cholesterol: life after the divorce?

For decades, HDL and HDL-cholesterol (HDL-C) levels were viewed as synonymous, and modulation of HDL-C levels by drug therapy held great promise for the prevention and treatment of cardiovascular disease. Nevertheless, recent failures of drugs that raise HDL-C to reduce cardiovascular risk and the now greater understanding of the complexity of HDL composition and biology have prompted researchers in the field to redefine HDL. As such, the focus of HDL has now started to shift away from a cholesterol-centric view toward HDL particle number, subclasses, and other alternative metrics of HDL. Many of the recently discovered functions of HDL are, in fact, not strictly conferred by its ability to promote cholesterol flux but by the other molecules it transports, including a diverse set of proteins, small RNAs, hormones, carotenoids, vitamins, and bioactive lipids. Based on HDL's ability to interact with almost all cells and transport and deliver fat-soluble cargo, HDL has the remarkable capacity to affect a wide variety of endocrine-like systems. In this review, we characterize HDL's unique cargo and address the functional relevance and consequences of HDL transport and delivery of noncholesterol molecules to recipient cells and tissues.

Metabolic engineering of β-carotene in orange fruit increases its in vivo antioxidant properties

Orange is a major crop and an important source of health-promoting bioactive compounds. Increasing the levels of specific antioxidants in orange fruit through metabolic engineering could strengthen the fruit's health benefits. In this work, we have afforded enhancing the β-carotene content of orange fruit through blocking by RNA interference the expression of an endogenous β-carotene hydroxylase gene (Csβ-CHX) that is involved in the conversion of β-carotene into xanthophylls. Additionally, we have simultaneously overexpressed a key regulator gene of flowering transition, the FLOWERING LOCUS T from sweet orange (CsFT), in the transgenic juvenile plants, which allowed us to obtain fruit in an extremely short period of time. Silencing the Csβ-CHX gene resulted in oranges with a deep yellow ('golden') phenotype and significant increases (up to 36-fold) in β-carotene content in the pulp. The capacity of β-carotene-enriched oranges for protection against oxidative stress in vivo was assessed using Caenorhabditis elegans as experimental animal model. Golden oranges induced a 20% higher antioxidant effect than the isogenic control. This is the first example of the successful metabolic engineering of the β-carotene content (or the content of any other phytonutrient) in oranges and demonstrates the potential of genetic engineering for the nutritional enhancement of fruit tree crops.

Dietary intake of carotenoids and their antioxidant and anti-inflammatory effects in cardiovascular care

Cardiovascular disease related to atherosclerosis represents nowadays the largest cause of morbidity and mortality in developed countries. Due to inflammatory nature of atherosclerosis, several studies had been conducted in order to search for substances with anti-inflammatory activity on arterial walls, able to exert beneficial roles on health. Researches investigated the role of dietary carotenoids supplementation on cardiovascular disease, due to their free radicals scavenger properties and their skills in improving low-density lipoprotein cholesterol resistance to oxidation. Nevertheless, literature data are conflicting: although some studies found a positive relationship between carotenoids supplementation and cardiovascular risk reduction, others did not find any positive effects or even prooxidant actions. This paper aimed at defining the role of carotenoids supplementation on cardiovascular risk profile by reviewing literature data, paying attention to those carotenoids more present in our diet (β-carotene, α-carotene, β-cryptoxanthin, lycopene, lutein, zeaxanthin, and astaxanthin).

β-Carotene Attenuates Angiotensin II-Induced Aortic Aneurysm by Alleviating Macrophage Recruitment in Apoe(-/-) Mice

Abdominal aortic aneurysm (AAA) is a common chronic degenerative disease characterized by progressive aortic dilation and rupture. The mechanisms underlying the role of α-tocopherol and β-carotene on AAA have not been comprehensively assessed. We investigated if α-tocopherol and β-carotene supplementation could attenuate AAA, and studied the underlying mechanisms utilized by the antioxidants to alleviate AAA. Four-months-old Apoe^−/− mice were used in the induction of aneurysm by infusion of angiotensin II (Ang II), and were orally administered with α-tocopherol and β-carotene enriched diet for 60 days. Significant increase of LDL, cholesterol, triglycerides and circulating inflammatory cells was observed in the Ang II-treated animals, and gene expression studies showed that ICAM-1, VCAM-1, MCP-1, M-CSF, MMP-2, MMP-9 and MMP-12 were upregulated in the aorta of aneurysm-induced mice. Extensive plaques, aneurysm and diffusion of inflammatory cells into the tunica intima were also noticed. The size of aorta was significantly (P = 0.0002) increased (2.24±0.20 mm) in the aneurysm-induced animals as compared to control mice (1.17±0.06 mm). Interestingly, β-carotene dramatically controlled the diffusion of macrophages into the aortic tunica intima, and circulation. It also dissolved the formation of atheromatous plaque. Further, β-carotene significantly decreased the aortic diameter (1.33±0.12 mm) in the aneurysm-induced mice (β-carotene, P = 0.0002). It also downregulated ICAM-1, VCAM-1, MCP-1, M-CSF, MMP-2, MMP-9, MMP-12, PPAR-α and PPAR-γ following treatment. Hence, dietary supplementation of β-carotene may have a protective function against Ang II-induced AAA by ameliorating macrophage recruitment in Apoe^−/− mice.

Dynamic action of carotenoids in cardioprotection and maintenance of cardiac health

Oxidative stress has been considered universally and undeniably implicated in the pathogenesis of all major diseases, including those of the cardiovascular system. Oxidative stress activate transcriptional messengers, such as nuclear factor-κB, tangibly contributing to endothelial dysfunction, the initiation and progression of atherosclerosis, irreversible damage after ischemic reperfusion, and even arrhythmia, such as atrial fibrillation. Evidence is rapidly accumulating to support the role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as intracellular signaling molecules. Despite this connection between oxidative stress and cardiovascular disease (CVD), there are currently no recognized therapeutic interventions to address this important unmet need. Antioxidants that provide a broad, "upstream" approach via ROS/RNS quenching or free radical chain breaking seem an appropriate therapeutic option based on epidemiologic, dietary, and in vivo animal model data. Short-term dietary intervention trials suggest that diets rich in fruit and vegetable intake lead to improvements in coronary risk factors and reduce cardiovascular mortality. Carotenoids are such abundant, plant-derived, fat-soluble pigments that functions as antioxidants. They are stored in the liver or adipose tissue, and are lipid soluble by becoming incorporated into plasma lipoprotein particles during transport. For these reasons, carotenoids may represent one plausible mechanism by which fruits and vegetables reduce the risk of chronic diseases as cardiovascular disease (CVD). This review paper outlines the role of carotenoids in maintaining cardiac health and cardioprotection mediated by several mechanisms including redox signaling.

Dietary values of astaxanthin and canthaxanthin in Penaeus monodon in the presence and absence of cholesterol supplementation: effect on growth, nutrient digestibility and tissue carotenoid composition

Penaeus monodon (mean initial wet weight 1·19 (se 0·01) g) were fed seven diets in triplicate: a control diet (D1) without carotenoids; three diets formulated to supply 0·1 % astaxanthin alone (D2), 0·2 % astaxanthin alone (D3), and a combination of 0·1 % astaxanthin and 1 % cholesterol (D4); three diets with 0·07 % canthaxanthin alone (D5), 0·13 % canthaxanthin alone (D6), and a combination of 0·07 % canthaxanthin and 1 % cholesterol (D7). Weight gain (WG, %), specific growth rate (SGR, %/d) and survival were chosen as parameters of shrimp growth performance. Total antioxidant status (TAS), superoxide dismutase (SOD), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were chosen as indices of shrimp plasma antioxidant capacity. Meanwhile, digestibility, retention efficiency and tissue carotenoids were also investigated to determine the additive effect of cholesterol on the efficiency of astaxanthin and canthaxanthin. After 74 d rearing, WG and SGR of shrimp fed D2–D4 and D7 were higher than those of shrimp fed D1 (P < 0·05). Shrimp fed D4 had the highest survival. The apparent digestibility coefficients (ADC) of astaxanthin in D2–D4 were higher than those of canthaxanthin in D5–D7 (P < 0·05). Although ADC of astaxanthin were quite high (>98 %) in D2–D4 and no differences were found among them (P>0·05), the carotenoid retention efficiencies in the whole body, muscle and shell (D2–D3 treatments) were considerably low; however, cholesterol supplementation significantly improved the carotenoid retention efficiencies in the whole body, muscle and shell (D4 treatment). Accordingly, the addition of cholesterol also significantly enhanced the carotenoid contents of tissues. Shrimp fed supplemented carotenoid diets (D2–D7) had higher TAS and lower SOD, ALT and AST than shrimp fed D1 (P < 0·05). A low dissolved oxygen stress test was conducted for 7 d after the rearing trial and shrimp survival was also compared among the treatments. The survival of shrimp fed the diets supplemented with astaxanthin or canthaxanthin was higher than that of shrimp fed D1 during the stress test (P < 0·05). In conclusion, all data suggested that astaxanthin was better than canthaxanthin as the dietary carotenoid source in the commercial diet of P. monodon, and the supplement of cholesterol could positively enhance the efficiency of astaxanthin and canthaxanthin.

Antitumor and antioxidant activity of protocatechualdehyde produced from Streptomyces lincolnensis M-20

We characterized the biological functions of protocatechualdehyde (PA) isolated from the butanol extract of culture supernatant from Streptomyces lincolnensis M-20. Following butanol extraction, it was purified by silica gel and Sephadex LH-20 column chromatography. PA was analyzed by Furier Transform Infrared Spectroscopy (FT-IR), Gas chromatograph-Mass Spectrometer (GC-MS), and Nuclear Magnetic Resonance (NMR). PA had potent antioxidant activity, as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Antitumor activity against MCF-7 human breast cancer cells was evaluated by the 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide (MTT) assay. PA treatment (0 approximately 150 muM) dose-dependently blocked apoptosis, as shown by improved cell viability and inter-nucleosomal DNA fragmentation. Our findings suggest that Streptomyces lincolnensis M-20, a lincomycin producer, also produces protocatechualdehyde.

A 9-cis beta-carotene-enriched diet inhibits atherogenesis and fatty liver formation in LDL receptor knockout mice

Our aim was to study the effect of 9-cis beta-carotene-rich powder of the alga Dunaliella bardawil on lipid profile, atherogenesis, and liver steatosis in high-fat diet-fed LDL receptor knockout mice. In 4 sets of experiments, mice were distributed into the following groups: control, fed an unfortified diet; Dunaliella 50, fed a diet composed of 50% 9-cis and 50% all-trans beta-carotene; Dunaliella 25, fed a diet containing 25% 9-cis and 75% all-trans beta-carotene; beta-carotene-deficient Dunaliella, fed beta-carotene-deficient Dunaliella powder; and all-trans beta-carotene, fed a synthetic all-trans beta-carotene. All fortified diets contained 0.6% total beta-carotene. Algal 9-cis beta-carotene was absorbed by the mice and accumulated in the liver. Synthetic all-trans beta-carotene was not converted to 9-cis beta-carotene. Dunaliella 50 inhibited high-fat diet-induced plasma cholesterol elevation by 40-63% and reduced cholesterol concentrations in the atherogenic VLDL and LDL. Atherosclerotic lesion area in mice treated with Dunaliella 50 was 60-83% lower compared with mice fed the high-fat diet alone. beta-Carotene-deficient Dunaliella did not influence plasma cholesterol and atherogenesis, suggesting that beta-carotene is essential for a Dunaliella protective effect. Moreover, by administrating Dunaliella powder containing different levels of 9-cis and all-trans beta-carotene isomers, we found that the effect on plasma cholesterol concentration and atherogenesis is 9-cis-dependent. Dunaliella 50 also inhibited fat accumulation and inflammation in the livers of mice fed a high-fat diet, which was accompanied by reduced mRNA levels of inflammatory genes. These results in mice suggest that 9-cis beta-carotene may have the potential to inhibit atherogenesis in humans.

A carotenoid algal preparation containing phytoene and phytofluene inhibited LDL oxidation in vitro

The antioxidative effect of the carotenoids phytoene and phytofluene in biological systems has not yet been studied. We therefore sought to investigate the effect of these carotenoids, isolated from the alga Dunaliella bardawil, in a biological system and used the in vitro low density lipoprotein (LDL) oxidation method to assay their antioxidative effects. We found that similar to beta-carotene and alpha-tocopherol, a carotenoid algal preparation containing phytoene and phytofluene inhibited LDL oxidation. These findings and the presence of phytoene and phytofluene in human tissues suggest that they can be part of the defense system against oxidative stress.

Dietary supplementation with an extract of lycopene-rich tomatoes does not reduce atherosclerosis in Watanabe Heritable Hyperlipidemic rabbits

Tomatoes are rich in lycopene and other carotenoids which have shown beneficial effects on CVD in epidemiological and intervention studies. In the present study the effect of an extract of lycopene-rich tomatoes, Lyc-O-Mato®on atherosclerosis was studied in Watanabe Heritable Hyperlipidemic rabbits. The rabbits were fed a control diet, a control diet supplemented with the tomato extract or a control diet supplemented with a mixture of plant oils for 16 weeks. Lycopene was detected only in plasma of rabbits receiving tomato extract. The tomato extract had no effect on cholesterol and triacylglycerol levels measured in total plasma, lipoprotein fractions and on aortic atherosclerosis evaluated biochemically and by microscopy. Oxidation of lipids in unfractionated plasma also was unaffected by the intake of tomato extract. In conclusion, the tomato extract increased plasma levels of lycopene in rabbits, but had no effect on hypercholesterolaemia, oxidation of plasma lipids or aortic atherosclerosis.

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.

9-cis beta-carotene-rich powder of the alga Dunaliella bardawil increases plasma HDL-cholesterol in fibrate-treated patients

The effect of fibrates on high density lipoprotein (HDL)-cholesterol levels is suggested to be mediated by its binding to peroxisome proliferator-activated receptor-alpha (PPARalpha). Upon ligand binding, PPARalpha heterodimerizes with the 9-cis retinoic acid receptor (RXR) and it is this heterodimer which regulates gene expression. We assessed the hypothesis that a combined treatment with fibrate plus 9-cis beta-carotene-rich powder of the alga Dunaliella bardawil, as a source of 9-cis retinoic acid, would improve the drug's effect on HDL-cholesterol levels. In an open-labeled first trial, 20 fibrate-treated men with plasma HDL-cholesterol levels below 40 mg/dl were given Dunaliella capsules, providing 60 mg beta-carotene/day, containing all-trans and 9-cis beta-carotene (1:1 ratio, w/w). Twenty-two fibrate-treated patients participated in a double-blind placebo-controlled second trial. Eleven patients were treated with Dunaliella capsules, and 11 patients were treated with beta-carotene-deficient Dunaliella capsules. Following 6 weeks of the dual treatment plasma HDL-cholesterol increased by 24.5 and 12.7% in the first and second trials, respectively (P=0.002 and 0.012). The dual treatment also increased HDL-cholesterol levels in human apolipoprotein A-I transgenic mice by 87.5% (P=0.021). The results show that a combination treatment of fibrate plus 9-cis beta-carotene-rich Dunaliella powder amplifies the effect of the drug on HDL-cholesterol levels.

Effect of Antioxidants on Atherosclerotic Plaque Formation in Balloon-Denuded and Irradiated Hypercholesterolemic Rabbits

The oxidative modification of low-density lipoprotein (LDL) hypothesis implies that antioxidants should be effective in suppressing atherosclerosis. This study is designed to test the potential of antioxidants to inhibit atherosclerotic plaque progression in balloon-denuded and irradiated hypercholesterolemic rabbits. Rabbits were fed with a 1% cholesterol diet supplemented with or without a mixture of antioxidants (vitamin E, vitamin C, selenium, zinc, copper, manganese, N-acetylcysteine, glutamine). At 7 days both iliac arteries were balloon denuded, and 4 weeks later, 1 iliac artery underwent endovascular irradiation (n=12), while the contralateral was sham treated (n=12). Four weeks after irradiation, animals were euthanized, and arteries were fixed and processed for histo- or immunohistochemistry for determining the plaque area, macrophage count, and oxidized LDL-positive areas. Plasma antioxidant levels were significantly higher in the animals fed with antioxidant diet. Plasma (thiobarbituric acid-reactive substances) and arterial tissue oxidized LDL (immunoreactive to specific oxidized LDL antibody) levels were significantly higher in the irradiated as compared with nonirradiated animals (0.69+/-0.09 and 31.05+/-4.21 versus 0.24+/-0.04 and 18.42+/-4.62, P<0.001 and 0.05), and antioxidants partially lowered the oxidized LDL levels (0.35+/-0.14 and 25.41+/-4.82, P<0.001 and 0.01). Plaque area in the irradiated animals was 175% greater than in nonirradiated animals (P<0.05). Antioxidant supplementation resulted in a 50% decrease in plaque area of both control and irradiated animals. Antioxidants reduced both the cholesterol-induced and radiation-enhanced circulating and tissue oxidized LDL levels, resulting in reduced plaque.

Evidence for a non-antioxidant, dose-dependent role of alpha -lipoic acid in caspase-3 and ERK2 activation in endothelial cells

Endothelial cell apoptosis contributes to atherosclerosis and may be exacerbated by oxidative stress. Results from clinical trials using antioxidant supplementation are equivocal and could be enhanced by antioxidants with additional non-antioxidant properties such as alpha -lipoic acid and alpha -tocopherol. The aim of this study was to investigate the effects of these antioxidants on cytoprotective pathways and endothelial apoptosis. Endothelial cells were incubated with alpha -lipoic acid and alpha -tocopherol, alone or in combination, prior to incubation with H(2)O(2) or staurosporine. alpha -lipoic acid pre-treatment alone increased caspase-3 activity in a dose-dependent manner. Both H(2)O(2) and staurosporine increased DNA fragmentation and caspase-3 activity and pre-treatment of cells with alpha -lipoic acid and/or alpha -tocopherol failed to prevent stress-induced apoptosis. Neither antioxidant treatments nor apoptotic inducers alone altered expressions of Bcl-2, Bax, HSP70 or pERK1/2 or pJNK. alpha -lipoic decreased pERK2 in staurosporine-treated cells in a dose-dependent manner. These findings indicate that pre-incubation with alpha -lipoic acid and alpha -tocopherol, alone or in combination, does not protect against oxidative- or non-oxidative-induced apoptosis in endothelial cells. Moreover, we have demonstrated a non-antioxidant, dose-dependent role of alpha -lipoic acid in caspase-3 and ERK2 activation. These data provide an insight and indicate caution in the use of high doses of alpha -lipoic acid as an antioxidant.

Beta-carotene supplementation results in adverse ventricular remodeling after acute myocardial infarction

OBJECTIVE

We studied the effects of beta-carotene (BC) on ventricular remodeling after myocardial infarction.

METHODS

Myocardial infarction was induced in Wistar rats that were then treated with a BC diet (500 mg/kg of diet per day; MI-BC; n = 27) or a regular diet (MI; n = 27). Hearts were analyzed in vivo and in vitro after 6 mo.

RESULTS

BC caused decreased left ventricular wall thickness (MI = 1.49 +/- 0.3 mm, MI-BC = 1.23 +/- 0.2 mm, P = 0.027) and increased diastolic (MI = 0.83 +/- 0.15 cm2, MI-BC = 0.98 +/- 0.14 cm2, P = 0.020) and systolic (MI = 0.56 +/- 0.12 cm2, MI-BC = 0.75 +/- 0.13 cm2, P = 0.002) left ventricular chamber areas. With respect to systolic function, the BC group presented less change in fractional area than did controls (MI = 32.35 +/- 6.67, MI-BC = 23.77 +/- 6.06, P = 0.004). There was no difference in transmitral diastolic flow velocities between groups. In vitro results showed decreased maximal isovolumetric systolic pressure (MI = 125.5 +/- 24.1 mmHg, MI-BC = 95.2 +/- 28.4 mmHg, P = 0.019) and increased interstitial myocardial collagen concentration (MI = 3.3 +/- 1.2%, MI-BC = 5.8 +/- 1.7%, P = 0.004) in BC-treated animals. Infarct sizes were similar between groups (MI = 45.0 +/- 6.6%, MI-BC = 48.0 +/- 5.8%, P = 0.246).

CONCLUSION

Taken together, these data suggest that BC has adverse effects on ventricular remodeling after myocardial infarction.

Analysis of the variable effect of dietary vitamin E supplements on experimental atherosclerosis

Vitamin E inhibits processes thought to be important in the development of atherosclerosis but clinical trials to determine its effect on cardiovascular disease have given variable results, the majority being negative. The reasons for this are unclear. Animal trials can be better controlled and use more rigorous measures of lesion progression than human trials. The present study reviewed trials using rabbits and mice to determine whether they also are variable and, if so, to uncover methodological differences that may account for the different outcomes. A large number of trials examining the effect of vitamin E supplements on experimental atherosclerosis were identified. Using rigorous selection criteria, a well-defined group was selected for further investigation. Almost all the mice trials showed a significant effect of vitamin E, but only around one-third of the rabbit trials did so. When the rabbit trials were divided into those that did and those that did not observe significant effects, no single factor was found that could account for the dichotomy. However, when the percentage reduction in disease was considered, rather than the within-trial significance level, there were clear dose-dependent effects of vitamin E on disease severity in heritable hyperlipidaemic rabbits, and in genetically normal rabbits made hyperlipidaemic with cholesterol alone; the dose dependence was different in the two groups, the heritable hyperlipidaemic rabbits showing a near ten-fold lower sensitivity. The high doses required to affect experimental atherosclerosis may, if applicable to other species, help explain the absence of effects in many human trials.

Inhibition of lipoprotein lipid oxidation

According to the oxidative modification hypothesis, antioxidants that inhibit the oxidation of low-density lipoprotein (LDL) are expected to attenuate atherosclerosis, yet not all antioxidants that inhibit LDL oxidation in vitro inhibit disease in animal models of atherosclerosis. As with animal studies, a benefit with dietary supplements of antioxidants in general and vitamin E in particular was anticipated in humans, yet the overall outcome of large, randomized controlled studies has been disappointing. However, in recent years it has become clear that the role of vitamin E in LDL oxidation and the relationship between in vitro and in vivo inhibition of LDL oxidation are more complex than previously appreciated, and that oxidative events in addition to LDL oxidation in the extracellular space need to be considered in the context of an antioxidant as a therapeutic drug against atherosclerosis. This review focuses on some of these complexities, proposes a novel method to assess in vitro 'oxidizability' of lipoprotein lipids, and summarizes the present situation of development of antioxidant compounds as drugs against atherosclerosis and related cardiovascular disorders.

Dietary antioxidants and paraoxonases against LDL oxidation and atherosclerosis development

Oxidative modification of low-density lipoprotein (LDL) in the arterial wall plays a key role in the pathogenesis of atherosclerosis. Under oxidative stress LDL is exposed to oxidative modifications by arterial wall cells including macrophages. Oxidative stress also induces cellular-lipid peroxidation, resulting in the formation of 'oxidized macrophages', which demonstrate increased capacity to oxidize LDL and increased uptake of oxidized LDL. Macrophage-mediated oxidation of LDL depends on the balance between pro-oxidants and antioxidants in the lipoprotein and in the cells. LDL is protected from oxidation by antioxidants, as well as by a second line of defense--paraoxonase 1 (PON1), which is a high-density lipoprotein-associated esterase that can hydrolyze and reduce lipid peroxides in lipoproteins and in arterial cells. Cellular paraoxonases (PON2 and PON3) may also play an important protective role against oxidative stress at the cellular level. Many epidemiological studies have indicated a protective role for a diet rich in fruits and vegetables against the development and progression of cardiovascular disease. A large number of studies provide data suggesting that consumption of dietary antioxidants is associated with reduced risk for cardiovascular diseases. Basic research provides plausible mechanisms by which dietary antioxidants might reduce the development of atherosclerosis. These mechanisms include inhibition of LDL oxidation, inhibition of cellular lipid peroxidation and consequently attenuation of cell-mediated oxidation of LDL. An additional possible mechanism is preservation/increment of paraoxonases activity by dietary antioxidants. This review chapter presents recent data on the anti-atherosclerotic effects and mechanism of action of three major groups of dietary antioxidants-vitamin E, carotenoids and polyphenolic flavonoids.

Ex vivo measures of LDL oxidative susceptibility predict carotid artery disease

AIM

The purpose of the study was to assess whether ex vivo measures of low-density lipoprotein (LDL) oxidation improved prediction of carotid artery disease (CAAD) case-control status compared to standard lipid and smoking measures.

METHODS

One hundred and forty cases with a high degree of carotid artery stenosis aged 40-83 years and an equal number of controls without stenosis or other vascular disease were matched by censored age within 2 years. Matched logistic regression evaluated the significance of copper-induced oxidative measures with and without covariates. The relationship of LDL oxidation measures with statin use and current smoking was also evaluated.

RESULTS

Logistic regression demonstrated a significant effect of the three correlated measures of oxidative susceptibility (lag time, oxidation rate and maximal rate of oxidation) separately on disease prediction (all p<0.05). These oxidative measures remained significant predictors of case-control status when other cardiovascular disease predictors (age; LDL-C, HDL-C and ApoAI levels; current smoking, ever smoking and pack-years smoked) were jointly considered. This relationship was not attributable to the effects of statin use on LDL oxidation.

CONCLUSIONS

Ex vivo measures of oxidation improved the prediction of carotid artery disease status, suggesting that this is an important determinant of atherosclerotic risk in this older population.

Retardation of atherosclerosis by overexpression of catalase or both Cu/Zn-superoxide dismutase and catalase in mice lacking apolipoprotein E

Oxidative stress has been suggested to potentiate atherogenesis. However, studies that have investigated the effect of antioxidants on atherosclerosis showed inconsistent results, ie, atherosclerosis was either retarded or not changed by dietary antioxidants. This report directly examined the effect of overexpressing Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and/or catalase on atherosclerosis and lipid peroxidation in mice lacking apolipoprotein E (ApoE-/-). Based on lipid staining of the en face of the aorta tree and the serial sections of the proximal aorta, ApoE-/- mice overexpressing catalase or both Cu/Zn-SOD and catalase had smaller and relatively early stages of atherosclerotic lesions (eg, foam cells and free lipids) when compared with ApoE-/- mice, who developed more advanced lesions (eg, fibrous caps and acellular areas). In addition, the retarded development of atherosclerosis was correlated with a reduced F2-isoprostanes in the plasma and aortas in ApoE-/- mice overexpressing catalase or both Cu/Zn-SOD and catalase. In contrast, the levels of F2-isoprostanes and atherosclerosis in the ApoE-/- mice overexpressing Cu/Zn-SOD alone were comparable to ApoE-/- control mice. These observations implied that endogenously produced hydrogen peroxide, but not superoxide anions, contributed to the formation of oxidized lipids and the development of atherosclerosis in ApoE-/- mice.

Role of oxidative modifications in atherosclerosis

This review focuses on the role of oxidative processes in atherosclerosis and its resultant cardiovascular events. There is now a consensus that atherosclerosis represents a state of heightened oxidative stress characterized by lipid and protein oxidation in the vascular wall. The oxidative modification hypothesis of atherosclerosis predicts that low-density lipoprotein (LDL) oxidation is an early event in atherosclerosis and that oxidized LDL contributes to atherogenesis. In support of this hypothesis, oxidized LDL can support foam cell formation in vitro, the lipid in human lesions is substantially oxidized, there is evidence for the presence of oxidized LDL in vivo, oxidized LDL has a number of potentially proatherogenic activities, and several structurally unrelated antioxidants inhibit atherosclerosis in animals. An emerging consensus also underscores the importance in vascular disease of oxidative events in addition to LDL oxidation. These include the production of reactive oxygen and nitrogen species by vascular cells, as well as oxidative modifications contributing to important clinical manifestations of coronary artery disease such as endothelial dysfunction and plaque disruption. Despite these abundant data however, fundamental problems remain with implicating oxidative modification as a (requisite) pathophysiologically important cause for atherosclerosis. These include the poor performance of antioxidant strategies in limiting either atherosclerosis or cardiovascular events from atherosclerosis, and observations in animals that suggest dissociation between atherosclerosis and lipoprotein oxidation. Indeed, it remains to be established that oxidative events are a cause rather than an injurious response to atherogenesis. In this context, inflammation needs to be considered as a primary process of atherosclerosis, and oxidative stress as a secondary event. To address this issue, we have proposed an "oxidative response to inflammation" model as a means of reconciling the response-to-injury and oxidative modification hypotheses of atherosclerosis.

Effects of alpha-tocopherol and astaxanthin on LDL oxidation and atherosclerosis in WHHL rabbits

The aim of this study was to evaluate the influence of -tocopherol and astaxanthin on low-density lipoprotein (LDL) oxidation lag time and atherosclerotic lesion formation in Watanabe heritable hyperlipidemic (WHHL) rabbits. Thirty-one, 3-month-old WHHL rabbits were divided into three experimental groups. One group (n=10) was fed standard rabbit feed alone and served as a control, a second group (n=11) was supplied with the same feed containing 500 mg alpha-tocopherol/kg and a third group (n=10) was given a feed containing 100 mg astaxanthin/kg. Plasma lipids, lipoproteins and LDL oxidation lag time were followed for 24 weeks. At the end of the treatment period, the animals were killed and the thoracic aorta was used for evaluation of the degree of atherosclerosis. Colour photographs of the intimal surface of the vessel were taken for determination of the atherosclerotic area. Cross-sections of the thoracic aorta were used for histological examination and for determination of intimal thickening. Specimens of the vessel were used for determination of the tissue cholesterol content. Plasma cholesterol remained at a high level during the time of the experiment and there were no differences between the experimental groups. After 24 weeks, the LDL oxidation lag time was 53.7+/-1.7 min, 109+/-4 min (P<0.001) and 56.4+/-3.4 min (P=0.47) in the control, alpha-tocopherol and astaxanthin groups, respectively. In the thoracic aorta, the atherosclerotic area was 80.7+/-5.1%, 67.1+/-6.7% (P=0.13) and 75.2+/-5.7% (P=0.49) in the control, alpha-tocopherol and astaxanthin groups, respectively. The intimal thickening was 45.6+/-3.2%, 44.0+/-4.1% (P=0.89) and 40.0+/-4.5% (P=0.33) in the control, alpha-tocopherol and astaxanthin groups, respectively. Finally, the cholesterol content was 107+/-9 mol/g, 95.7+/-11.5 mol/g (P=0.31) and 101+/-5 mol/g (P=0.33) in the control, alpha-tocopherol and astaxanthin groups, respectively. It can be concluded that alpha-tocopherol but not astaxanthin prolonged the LDL oxidation lag time. The two antioxidative substances did not prevent atherogenesis in WHHL rabbits in this setting.

HeLp, a heme-transporting lipoprotein with an antioxidant role

Plasma lipoproteins involved in lipid transport are target for free radical-evoked pathological conditions in several mammalian models. The main hemolymphatic protein of Boophilus microplus is a heme-binding lipoprotein (HeLp, for Heme LipoProtein) that carries dietary heme produced from degradation of vertebrate hemoglobin to tissues of the tick. Addition of heme to phospholipid liposomes resulted in intense lipid peroxidation, which was inhibited by addition of HeLp. HeLp prevented lysis of red blood cells by heme. HeLp also inhibited reactions of heme with tert-butyl hydroperoxide (t-BOOH) or hydrogen peroxide. HeLp, quite differently from other lipoproteins, presents a protective intrinsic mechanism to counteract heme toxicity, while preserving the heme molecule to be reused by the tick. This is the first report of a lipoprotein acting as an antioxidant particle against heme-induced radical damage.

The antiatherogenic effect of DiNAC: experimental findings supporting immunomodulation as a new treatment for atherosclerosis related diseases

Inflammatory processes in the arterial wall are important in atherogenesis. The present review discusses the development of DiNAC as a potential new treatment modality for atherosclerosis related diseases. DiNAC, N,N'-diacetyl-L-cystine, is the disulphide dimer of N-acetyl cysteine, NAC. It was selected as an immunomodulating drug candidate due to its ability to modify contact sensitivity/delayed type hypersensitivity (CS/DTH) reactions in vivo. Initial structure-activity relationship (SAR) studies indicated that an intact disulfide bridge was essential for this effect. Antioxidants, like probucol and some close analogs with two sulphurs in close proximity (but not disulphides), were also found to have similar effects on CS/DTH reactions. These antioxidants have antiatherosclerotic effects, while structurally related compounds without sulphurs do not. Therefore, it was hypothesized that DiNAC might also possess antiatherosclerotic effects. This was investigated in WHHL rabbits and mice. In both species, DiNAC had antiatherosclerotic activity similar to that of probucol. The effect of DiNAC was not due to an alteration of lipid metabolism. Impaired endothelium mediated relaxation is known to be associated with atherosclerosis. DiNAC was shown to reverse this process in WHHL rabbits with advanced atherosclerosis, probably due to an action on the vessel wall itself that is not related to the extent of atherosclerosis or to plasma lipid levels. Preliminary data from a clinical investigation in hypercholesterolemic subjects suggest that DiNAC is likely to have similar effects also in patients. Taken together, these findings suggest immunomodulation to be a potential new therapy for atherosclerosis related diseases. DiNAC may represent a new treatment modality for such diseases.