We studied the effects of a 2-day walk exercise (6 h+6 h) on the serum concentration of circulating moderately oxidized LDL (LDL baseline conjugated dienes), lipids (total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride), antioxidants (alpha-tocopherol, gamma-tocopherol, beta-carotene, and ubiquinol-10), and antioxidant potential in serum (S-TRAP) and LDL (LDL-TRAP) in healthy well-trained men. The exercise was performed twice with an interval of 14 days. While 6 h walking the subjects drank 6 cl . kg (-1) water which contained either carbohydrate (CHO trial) or placebo (PLA trial). During the 2-day exercise the level of oxidized LDL decreased by 25 % (p=0.001) in the PLA trial. At the same time serum gamma-tocopherol decreased by 20 % (p=0.049), while the other measured antioxidants remained unchanged and the serum antioxidant potential increased by 22 % (p=0.018). Serum total cholesterol decreased by 3 % (p=0.017), serum triglycerides by 22 % (p=0.001), and LDL-cholesterol by 14 % (p=0.045). HDL cholesterol increased by 9 % (p=0.001). The results in the carbohydrate trial were similar to the ones in the PLA trial. The findings suggest that exercise of long duration but of low, non-exhaustive intensity decreases the concentration of circulating oxidized LDL simultaneously with an increase in serum antioxidant potential in healthy trained men. Carbohydrate ingestion during the exercise does not have any further effect on these changes.

Both alpha-lipoic acid (LA) and ascorbic acid (vitamin C) have been shown to improve endothelial dysfunction, a precursor of atherosclerosis. Since oxidant stress can cause endothelial dysfunction, we tested the interaction and efficacy of these antioxidants in preventing oxidant damage to lipids due to both intra- and extracellular oxidant stresses in EA.hy926 endothelial cells. LA spared intracellular ascorbate in culture and in response to an intracellular oxidant stress induced by the redox cycling agent menadione. Extracellular oxidant stress generated by incubating cells for 2 h in with 0.2 mg/ml LDL and 5 muM Cu2+ caused a time-dependent increase of the lipid peroxidation product malondialdehyde in both cells and LDL, preceded by rapid disappearance of; alpha-tocopherol in LDL. alpha-Lipoic acid at concentrations of 40-80 microM blunted these effects. Similarly, intracellular ascorbate concentrations of 1-2 mM also prevented Cu2+-induced lipid peroxidation in LDL and cells. Cu2+-dependent oxidation of LDL in the presence of ascorbate-loaded cells decreased intracellular ascorbate by 20%, but this decrease was not reversed by LA. Both LA and ascorbate protect endothelial cells and LDL from either intra- or extracellular oxidant stress, but that LA does not spare ascorbate in oxidatively stressed cells.

The intake of phenolic acids and related polyphenolic compounds has been inversely associated with the risk of heart disease, but limited information is available about their bioavailability or mechanisms of action. Polyphenolics, principally avenanthramides, and simple phenolic acids in oat bran phenol-rich powder were dissolved in HCl:H(2)O:methanol (1:19:80) and characterized by HPLC with electrochemical detection. The bioavailability of these oat phenolics was examined in BioF1B hamsters. Hamsters were gavaged with saline containing 0.25 g oat bran phenol-rich powder (40 micromol phenolics), and blood was collected between 20 and 120 min. Peak plasma concentrations of avenanthramides A and B, p-coumaric, p-hydroxybenzoic, vanillic, ferulic, sinapic, and syringic acids appeared at 40 min. Although absorbed oat phenolics did not enhance ex vivo resistance of LDL to Cu(2+)-induced oxidation, in vitro addition of ascorbic acid synergistically extended the lag time of the 60-min sample from 137 to 216 min (P

The effect of broccoli extract (BE)-enriched diet was studied in order to evaluate its ability to counteract liver cholesterol oxidation products (COPs) induced by acute strenuous exercise in rats. Thirty-two female Wistar rats were randomly divided into four groups: control diet without exercise (C), BE-enriched diet without exercise (B), control diet with acute exhaustive exercise (S) and BE-enriched diet with acute exhaustive exercise (BS). The study lasted 45days and on the last day, rats of S and BS groups were forced to run until exhaustion on a treadmill. Glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT) and cholesterol oxidation products (COPs) were determined in liver. Exhaustive exercise was clearly responsible for tissue damage, as evidenced by the increase of lactate dehydrogenase (LDH) plasma activity in the S group. Moreover, the exercise protocol reduced CAT activity in liver, while it did not affect GST, GR and GPx. BE-enriched diet raised GST, GR and CAT activities in rats of BS group. The main COPs found were 7α-hydroxycholesterol, 7β-hydroxycholesterol, 7-ketocholesterol, cholestanetriol, 24-hydroxycholesterol and 27-hydroxycholesterol. The BE-enriched diet led to reduced cholesterol oxidation following exhaustive exercise; the highest level of COPs was found in the S group, whereas the BS rats showedthe lowest amount. This study indicates that the BE-enriched diet increases antioxidant enzyme activities and exerts an antioxidant effect towards cholesterol oxidation in rat liver, suggesting the use of phytochemicals in the prevention of oxidative damage and in the modulation of the redox environment.

BACKGROUND AND OBJECTIVE: Several epidemiological and experimental studies have associated the intake of antioxidants, which are abundant in the Mediterranean diet, with a low incidence of cardiovascular disease. One possible mechanism of this action is the oxidative protection in low density lipoproteins (LDL). The aim of our study was to compare the antioxidative activity of diverse phenolic compounds present in virgin olive oil on these lipoproteins.

SUBJECTS AND METHOD: LDL was isolated from blood plasma of healthy volunteers by sequential ultracentrifugation. This was followed by oxidation with CuC12 in the presence of different concentrations of phenolic compounds and virgin olive oil extract. Production of conjugated dienes was determined by the continuous monitoring of increased absorbency at 234 nm as an indicator of LDL oxidation.

RESULTS: Virgin olive oil extract prolonged the latency phase and significantly lowered the progression rate (p<0.05) at low concentrations (2 g/ml). This antioxidative effect was also observed with low concentrations (2 M) of caffeic acid and oleuropein (p<0.05). However, it was necessary to increase the concentration of flavone up to 50 times to observe a similar effect (p<0.05).

CONCLUSION: Both virgin olive oil extract enriched in phenolic compounds and phenolic compounds present in olive oil (caffeic acid and oleuropein) are potent antioxidants at very low concentrations. Thus, the beneficial effects of a Mediterranean diet may be partly due to the protective action of these compounds.

There is increasing evidence to support the hypothesis that free radical-mediated oxidative processes contribute to atherogenesis. More recently the ability of antioxidant nutrients to affect cell response and gene expression has been reported in vitro, providing a novel mechanistic perspective for the biological activity of antioxidants. Sea buckthorn (Hippophaë rhamnoides L.) is a rich source of antioxidants both aqueous and lipophilic, as well as polyunsaturated fatty acids. The objective of the study was to characterize the antioxidant profile of Sea buckthorn juice (SBJ) and to evaluate its effect on plasma lipids, LDL oxidation, platelet aggregation and plasma soluble cell adhesion protein concentration. Twenty healthy male volunteers were given either a placebo or SBJ for 8 weeks. Additional daily intakes of vitamin C, alpha-tocopherol, beta-carotene and flavonoids through SBJ supplementation were 462, 3.2, 1.0 and 355 mg respectively. There were no significant changes in plasma total cholesterol, LDL-C, platelet aggregation or plasma intercellular cell adhesion molecule 1 (ICAM-1) levels between treatment groups. Although not significant, a 20% and 17% increase in plasma HDL-C and triacylglycerol (TAG) concentrations were observed. SBJ supplementation also resulted in a moderate decrease in the susceptibility of LDL to oxidation.

Oxidized low-density lipoproteins (ox-LDLs) appear to play a significant role in atherogenesis. In fact, circulating ox-LDL concentrations have been recognized as a risk factor for cardiovascular disease (CVD). A higher intake of some nutrients and specific food compounds such as monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and flavonoids have also been associated with a lower risk of CVD. These dietary factors could be associated to a lower risk of CVD through a reduction of the atherogenicity of LDL particles through limited oxidation. Therefore, the purpose of this article is to review human clinical studies that evaluated effects of dietary antioxidant vitamins, fatty acids (MUFA, PUFA) and specific flavonoid-rich foods on LDL particle oxidation and describe potential mechanisms by which dietary factors may prevent oxidation of LDL particles. Antioxidant vitamin supplements such as alpha-tocopherol and ascorbic acid as well as beta-carotene and fish-oil supplements have not been clearly demonstrated to prevent oxidation of LDL particles. Moreover, inconsistent documented effects of flavonoid-rich food such as olive oil, tea, red wine and soy on LDL particle oxidizability may be explained by difference in variety and quantity of flavonoid compounds used among studies. However, a healthy food pattern such as the Mediterranean diet, which includes a combination of antioxidant compounds and flavonoid-rich foods, appears effective to decrease LDL particle oxidizability, which may give some insight of the cardiovascular benefits associated with the Mediterranean diet.

Olive oil consumption increases HDL-cholesterol levels, while decreasing LDL-cholesterol levels, LDL susceptibility to oxidation and lipid peroxidation. The reduction of cellular oxidative stress, thrombogenicity and the formation of atheroma plague can explain the preventive effects of olive oil on atherosclerosis development. In addition to reducing risk factors for coronary heart disease, olive oil might also help prevent certain types of cancers, and beneficially modify immune and inflammatory responses.

Oxidative stress in the central nervous system (CNS) may cause oxidation of lipoprotein particles. The oxidized lipoproteins may damage cellular and subcellular membranes, leading to tissue injury and cell death. Human low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) are oxidized by transition metal ions, such as Cu2+. Using PC 12 cells, we tested the cytotoxicity of oxidized LDL and VLDL. Cell death was increased in a dose-dependent manner. Antioxidants added to the incubation medium, such as vitamins E or C, or resveratrol showed some protection. Results indicated that oxidized lipoproteins may serve as an oxidative stressor, which may initiate the neuronal cell death leading to the manifestation of Alzheimer disease (AD).

Vascular cell death is a key feature of atherosclerotic lesions and may contribute to the plaque "necrotic" core, cap rupture, and thrombosis. Oxidatively modified low-density lipoproteins (LDLs) are implicated in the pathogenesis of atherosclerosis, and dietary antioxidants are thought to protect the vasculature against LDL-induced cytotoxicity. Because LDL oxidative modification may vary within atherosclerotic lesions, we examined the effects of defined, oxidatively modified LDL species on human arterial smooth muscle cell apoptosis and the cytoprotective effects of vitamin C. Moderately oxidized LDL (0 to 300 microg protein/mL), which has the highest content of lipid hydroperoxides, induced smooth muscle cell apoptosis within 6 hours, whereas native LDL and mildly and highly oxidized LDL had no effect. Moderately oxidized LDL increased cellular DNA fragmentation, release of fragmented DNA into the culture medium, and annexin V binding and decreased mitochondrial dehydrogenase activity and expression of the antiapoptotic mediator Bcl-x(L). Treatment of cells with native LDL together with the lipid hydroperoxide 13(S)-hydroperoxyoctadeca-9Z,11E-dienoic acid (HPODE, 200 micromol/L, 6 to 24 hours) also induced apoptotic cell death. Pretreatment of smooth muscle cells with vitamin C (0 to 100 micromol/L, 24 hours) attenuated the cytotoxicity and apoptosis induced by both moderately oxidized LDL and HPODE. Our findings suggest that moderately oxidized LDL, with its high lipid hydroperoxide content, rather than mildly or highly oxidized LDL, causes apoptosis of human smooth muscle cells and that vitamin C supplementation may provide protection against plaque instability in advanced atherosclerosis.

BACKGROUND: Previously, a novel formulation of vitamin C-lipid metabolites (PureWay-C) was shown to be more rapidly taken-up by human T-lymphocytes and more rapidly stimulate neurite outgrowth, fibroblast adhesion and inhibition of xenobiotic-induced T-cell hyperactivation. Here, PureWay-C serum levels were measured in healthy volunteers after oral supplementation. Plasma C-reactive protein and oxidized low density lipoprotein levels (LDL) were also measured. MATERIAL/METHODS: Healthy volunteers maintained a low vitamin C diet for 14 days and, following an overnight fast, received a single oral dose of (vitamin C) 1000 mg of either ascorbic acid (AA), calcium ascorbate (CaA), vitamin C-lipid metabolites (PureWay-C), or calcium ascorbate-calcium threonate-dehydroascorbate (Ester-C). Blood samples were collected immediately prior to the oral dose administration and at various times post ingestion. Twenty-four-hour urine collections were saved for oxalate and uric acid assays. RESULTS: PureWay-C supplementation leads to the highest absolute serum vitamin C levels when compared to AA, CaA and Ester-C. PureWay-C provides a statistically significant greater serum level than calcium ascorbate at 1, 2, 4, and 6 hours post oral supplementation whereas Ester-C shows a less but slightly statistically significant increase at only 1 and 4 hours. Oral supplementation with PureWay-C also led to a greater reduction in plasma C-reactive protein and oxidized LDL levels compared to the other vitamin C formulations. CONCLUSIONS: PureWay-C is more rapidly absorbed and leads to higher serum vitamin C levels and greater reduction of plasma levels of inflammatory and oxidative stress markers than other forms of vitamin C, including Ester-C.