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Nutritional Neurosciences

Dietary Fat Type Affects Vitamins C and E and Biomarkers of Oxidative Status in Peripheral and Brain Tissues of Golden Syrian Hamsters¹

Nutrition and Neurocognition Laboratory and ^* Cardiovascular Nutrition Research Laboratory, Jean Mayer U.S. Department of Agriculture-Human Nutrition Research Center on Aging at Tufts University, Boston, MA

²To whom correspondence should be addressed. E-mail: antonio.martin{at}tufts.edu.

	ABSTRACT

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Oxidative stress is an important trigger in the complex chain of events leading to neurodegenerative diseases. On the other hand, dietary fatty acids play an essential role in brain function. The objectives of this study were to assess the effect of dietary fat type on vitamin C and vitamin E (-and -tocopherol) concentrations in peripheral and brain tissues and its effect on 8-epiPGF₂ (F₂-isoprostanes). Male Golden Syrian hamsters (n = 120, 8 wk old) were fed diets enriched in butter, hydrogenated fat (margarine), and canola and soybean oils. After 12 wk, hamsters were deprived of food, anesthetized with isoflurane, and killed via terminal exsanguination. Analyses of vitamins C, E, and 8-epiPGF₂ were performed in peripheral tissues and brain. Hamsters consuming the margarine-enriched diet had lower (P < 0.05) vitamin C and -tocopherol concentrations in liver, plasma, and brain, and higher (P < 0.02) plasma 8-epiPGF₂ than groups fed the butter, and the canola and soybean oil diets. Liver and plasma -tocopherol concentration was higher (P < 0.001) among the groups fed the soybean- and margarine-enriched diets compared with the other groups. -Tocopherol was higher (P < 0.05) and 8-epiPGF₂ lower (P < 0.01) among the groups fed the canola and soybean oil diets compared with the other groups. Across the groups, an inverse correlation between plasma levels of vitamin C and 8-epiPGF₂ (r = -0.37, P = 0.03) and a positive correlation between plasma levels of vitamin C and -tocopherol were observed (r = 0.341, P = 0.003). Hamsters fed the butter-enriched diet had a higher (P < 0.03) plasma uric acid concentration than the other groups. The results of this study provide new evidence concerning the effect of dietary fat on antioxidant status, which is important for the maintenance of good health.

KEY WORDS: • dietary fats • vitamin C • vitamin E • F₂-isoprostanes • Golden Syrian hamsters

During the past decade, reduction in fat intake has been the main focus of national dietary recommendations to decrease the risk of coronary heart disease (CHD)³ (1–3). Several lines of evidence, however, have indicated that certain type of fats have a more important role in determining the risk of CHD than the total amount of fat in the diet (4–6). The Golden Syrian hamster has been used frequently as a model with which to study diet-induced atherosclerosis. This experimental model provides the opportunity to investigate, in addition to the vascular changes, how dietary fat type alters nutrient status and oxidative stress levels. Recent evidence suggests that dietary fatty acid composition influences numerous behaviors including body temperature regulation, pain sensitivity, feeding behavior, and cognitive performance (7,8). However, the mechanisms of these effects remain poorly understood.

Both vitamins E and C have important roles in cell function and have been implicated in processes associated with aging including vascular changes, inflammatory damage, and cancer (9–11). At the molecular level, vitamin C acts as a cofactor for dopamine-ß-hydroxylase in the neurotransmitter synthesis, improves lysosomal protein degradation, and mediates glutamate uptake (12–14). Vitamin C has also been associated with decreased levels of oxidative stress (15). Vitamin E is the most important antioxidant in the lipid phase. Vitamin E acts to protect cells against the effects of free radicals, which are potentially damaging by-products of the body’s metabolism (16). Vitamin E was shown to have a neuroprotective effect (17). However, there are no studies documenting the effects of different types of fat on the levels of vitamin C and vitamin E in Golden Syrian hamsters.

Isoprostanes (8-epiPGF₂) are a family of eicosanoids of nonenzymatic origin; they are produced by the random oxidation of phospholipids by oxygen radicals and are elevated by oxidative stress (18). These compounds can act as vasoconstrictors (19) and are increased in the hepatorenal syndrome and pulmonary oxygen toxicity (20,21). Because of the characteristics of this study with diets containing high concentrations of PUFA, the assessment of the effect of dietary fat oxidative stress is relevant for the development of dietary interventions.

Recent studies showed a significant association between serum uric acid and cardiovascular mortality (22). Uric acid may have a direct injurious effect on the endothelium, altering endothelial cell function and reducing nitric oxide bioavailability, relevant to cardiovascular risk. However, there are no data examining the effect of dietary fat type on uric acid levels. Therefore, assessing the levels of uric acid in the context of different dietary fats and its association with the antioxidant concentration in vivo is important in evaluating the effect of dietary interventions on health status.

The objectives of this study were to assess the effects of dietary fat type representing a wide range of fatty acid profiles on vitamin C and E, and levels of 8-epiPGF₂ (F₂-isoprostanes) in peripheral and brain tissues of Golden Syrian hamsters.

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Animals and diets. Male Golden Syrian hamsters (n = 120, 8 wk old) were obtained from Charles River Laboratories. Hamsters were housed 4/cage in the animal care facility of the HNRCA, and were maintained at 25°C with a 12-h light:dark cycle throughout the experimental protocol. No differences in the food intake were observed throughout the experimental feeding period. Body weights did not differ among the diet groups, with an overall mean of 171.9 ± 2.0 g. The protocol followed the U.S. Code of Practice for the Care and Use of Animals for Scientific Purposes and was approved by the Animal Care Ethics Committee of the HNRCA.

The composition of diets consumed by the hamsters is reported in Table 1. The concentration of -tocopherol (d--tocopherol) in the hydrogenated oil (margarine) was only 16% of the -tocopherol present in the nonhydrogenated soybean oil. The lower -tocopherol concentration in the margarine accounted for the lower total vitamin E present in the margarine-enriched diet compared with the other diets.

    Plasma and tissue collection. Blood samples were collected into EDTA-coated tubes and centrifuged at 2000 x g for 15 min at 4°C. After plasma was collected, aliquots in triplicate were immediately mixed with an equal volume of cold 60 g/L metaphosphoric acid containing 1 mmol/L of the metal ion chelator diethylenetriaminepentaacetic acid (DTPA), for vitamin C and uric acid analysis. The remaining plasma was stored at -80°C for 8-epiPGF₂ analysis. The thorax was opened and the liver removed, weighed, sectioned into pieces, and placed in PBS containing 1 mmol/L DTPA (for vitamin E analysis), or in PBS containing 1 mmol/L DTPA and 60 g/L metaphosphoric acid (for vitamin C analysis). Hamsters were then decapitated and brain regions associated with motor and cognitive behavior (cortex, hippocampus, striatum, cerebellum) were immediately dissected on ice, sectioned into 2 pieces, and placed in PBS containing 1 mmol/L DTPA (for vitamin E analysis), or in PBS containing 1 mmol/L DTPA and 60 g/L metaphosphoric acid (for vitamin C analysis).

    Plasma cholesterol. Plasma total cholesterol was assayed on an Hitachi 911 automated analyzer (Roche Diagnostics) using enzymatic reagents as described by Dorfman et al. (23).

    Protein. Protein concentration in the tissues was determined by the Lowry method (24) using bovine serum albumin as a standard.

    Vitamin C. Ascorbate was analyzed in plasma and tissues by paired-ion, reversed-phase HPLC coupled with electrochemical detection. Briefly, 100 µL of plasma sample was mixed with an equal volume of cold 60 g/L metaphosphoric acid containing 1 mmol/L of the metal ion chelator DTPA (Sigma). An aliquot of plasma or tissue was analyzed on a LC8 column (150 mm x 4.6 mm i.d., 3-µm particle size, Supelco) using 99% deionized water and 1% methanol containing 40 mmol/L sodium acetate and 1.5 mmol/L dodecyltriathylammonium phosphate (Q12 ion pair cocktail, Regis) as the mobile phase delivered at a flow rate of 1 mL/min. Samples were injected with an autosampler (1100 series, Hewlett-Packard). Ascorbate was detected at an applied potential of +0.6 V with the gain set at 100 nA by a LC 4B amperometric electrochemical detector (Bioanalytical Systems). Ascorbate was eluted as a single peak with a retention time of 5.5 min. Peaks were integrated with a ChemStation (Hewlett-Packard). Ascorbate concentration was calculated on the basis of a calibration curve, and its concentration expressed in µmol/L or nmol/mg protein (25).

    Plasma uric acid. Plasma uric acid was analyzed by paired-ion, reversed-phase HPLC coupled with electrochemical detection, using the same procedure described for vitamin C determination, with the electrode potential of +0.6 V but with the gain set at 1 µA. Uric acid was eluted as a single peak with a retention time of 3.5 min. Peaks were integrated with a ChemStation (Hewlett-Packard). Uric acid concentration was calculated based on a calibration curve, and its concentration expressed in µmol/L (25).

    Vitamin E (- and -tocopherol). Tocopherol concentration of plasma and tissue was measured by reversed-phase HPLC. Tocol (a gift from Hoffmann-La Roche) was added to the mixture as an internal standard. Samples were centrifuged at 125 x g for 5 min at 4°C. The supernatant was collected and dried under a stream of nitrogen gas, and reconstituted in 100 µL of methanol. Tocopherols were separated by HPLC using a 3-mm C18 reversed-phase column (Perkin-Elmer). The mobile phase was delivered at a flow rate of 1.0 mL/min, consisting of 1% water in methanol, and containing 10 mmol/L lithium perchlorate. Samples were injected with an autosampler (1100 series, Hewlett Packard). Eluted peaks were detected at an applied potential of +0.6 V by a LC 4B amperometric electrochemical detector (Bioanalytical Systems). Tocopherols were eluted as well-separated peaks with a retention time from 2 to 6 min. Peaks were integrated with a ChemStation (Hewlett Packard) and tocopherol concentrations were expressed in µmol/L or pmol/mg protein (26).

    Plasma 8-isoprostane (8-epiPGF₂). Analysis of 8-isoprostane (8-epiPGF₂), which has been proposed as a marker of oxidative stress, was performed using an enzyme immunoassay (EIA) kit (27,28). This assay is based on the competition between 8-isoprostane and an 8-isoprostane-acetylcholinesterase conjugate (8-isoprostane tracer) for a limited number of 8-isoprostane–specific rabbit antiserum binding sites. The rabbit antiserum-8-isoprostane (either free or tracer) complex binds to the rabbit IgG mouse monoclonal antibody that has been previously attached to the well. First, samples (0.5–1 mL) were mixed gently with 50 µL of affinity sorbent (mouse anti-8-isoprostane covalently bound to Sepharose 4B) for 60 min at room temperature to purify samples before measurement by EIA. After incubation, samples were centrifuged briefly at 11,750 x g to sediment the sorbent (Cayman Chemical). The sorbent, which contains the bound 8-isoprostane, was rinsed with washing solution; after the supernatant was discarded, the sorbent pellet was resuspended in 300 µL of ethanol-elution solution. The ethanol washes were evaporated in a vacuum centrifugation and immediately dissolved in 125 µL EIA buffer. Samples were then analyzed in duplicate using the EIA kit. The concentration of 8-isoprostane in the test samples was interpolated from the standard curve using log transformation (20).

    Statistical analysis. Data are expressed as mean ± SD. All data were analyzed using 1-way ANOVA to determine whether there was a significant difference among the dietary treatment groups. When differences were detected, group means were compared with Tukey’s Honestly Significant Differences. Differences were considered to be significant at P < 0.05. The correlations between variables were examined by linear regression or by Spearman’s correlation as appropriate (29). All statistical analyses were performed with Systat 10 (SPSS).

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Plasma total cholesterol concentration was higher (P < 0.05) in hamsters fed the butter-enriched diet (7.5 ± 0.7 mmol/L) compared with the other groups (nonpurified diet: 3.5 ± 0.1 mmol/L, nonpurified diet + cholesterol, 4.8 ± 0.2 mmol/L; margarine, 5.9 ± 0.5 mmol/L; canola oil, 4.4 ± 0.2 mmol/L; soybean oil, 5.1 ± 0.2 mmol/L).

Hamsters consuming the two soybean oil–based diets, i.e., margarine and soybean oil, had lower (P < 0.05) plasma and liver vitamin C concentrations than the other groups (Table 2). However, only the hamsters consuming the margarine-enriched diet had significantly higher plasma 8-epiPGF₂ levels than the other groups. In addition, hamsters fed the margarine-enriched diet had lower levels of vitamin C in the cortex and striatum, but not hippocampus and cerebellum compared with hamsters fed the other diets (Table 3). There were significantly higher levels of vitamin C in the hippocampus of the hamsters fed the canola- and soybean oil–enriched diets than the other diets.

View this table: [in this window] [in a new window]   TABLE 2 Vitamin C and vitamin E (- and -tocopherol) concentration in liver and plasma, and plasma uric acid and 8-epiPGF2 concentration 12 wk after consumption of different dietary fats by Golden Syrian hamsters1

View this table: [in this window] [in a new window]   TABLE 3 Vitamin C and vitamin E (- and -tocopherol) concentration in cortex, hippocampus, striatum, and cerebellum 12 wk after consumption of different dietary fats by Golden Syrian hamsters1

In contrast to -tocopherol, -tocopherol in liver and plasma was significantly higher in the hamsters fed the two soybean oil–based diets (margarine and soybean oil) (Table 2). Demonstrating a similar pattern, -tocopherol levels were higher in all brain regions of hamsters fed the soybean oil–based diets (margarine and soybean oil) than the other dietary treatments (Table 3).

Plasma uric acid concentration was higher (P < 0.03) in hamsters fed the butter-enriched diet compared with the other groups.

Across groups, plasma concentrations of vitamin C and 8-epiPGF₂ levels were inversely correlated (r = -0.37, P = 0.03), whereas those of vitamin C and -tocopherol were positively correlated (r = 0.341, P = 0.003).

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The margarine-enriched diet, relative to butter, canola, and soybean oil, was associated with a less favorable antioxidant status and increased indices of oxidative stress. Hamsters fed the margarine-enriched diet had lower vitamin C and E concentrations and significantly higher 8-epiPGF₂ levels than any of the other diet groups. Whether this observation was attributable to lower antioxidant nutrient intakes, a more rapid consumption of the antioxidant nutrients, or impaired utilization of the antioxidant nutrients has yet to be determined. Although some studies reported elevated concentrations of oxidative stress in association with diets enriched in PUFA (30,31), other studies did not show changes in oxidative stress by feeding high-PUFA diets (32–34). Our results also show that hamsters fed the soybean oil diet did not have higher levels of 8-epiPGF₂ compared with controls and canola oil–fed hamsters. It was postulated that the degree of dietary fatty acid unsaturation increases the peroxidizability of the lipids, reduces the time required to develop symptoms of vitamin E deficiency (35), and increases oxidative stress. However, some studies showed a decrease in DNA damage in healthy subjects through dietary intervention (33). In this study, the soybean oil group had higher concentrations of -tocopherol and -tocopherol in peripheral and brain tissues, and vitamin C in brain, compared with controls and the group fed the margarine-enriched diet. This may have accounted for the decreased oxidative stress in hamsters fed the soybean oil–enriched diet. Both groups fed the canola- and soybean oil–enriched diets had similar concentrations of -tocopherol and vitamin C in blood and brain tissues. In addition, soybean oil–fed hamsters had higher -tocopherol in plasma and brain compared with the canola oil–fed hamsters. Thus, the higher levels of vitamin E in tissues reflected high concentrations of antioxidants in the soybean oil–fed hamsters, which may explain why these hamsters had lower levels of oxidative stress.

The less favorable effect of hydrogenated fat (margarine) feeding, relative to both saturated and unsaturated fats, on oxidative stress appears to be also associated with a higher degree of inflammation. In fact, Han et al. (36) showed that interleukin-6 and tumor necrosis factor- were significantly higher after consumption of a stick margarine diet compared with a soybean oil diet in a group of adults with moderate hypercholesterolemia. Consumption of a diet high in hydrogenated fat has been associated with increased production of proinflammatory cytokines and increased oxidative stress (36). The higher concentration of 8-epiPGF₂ in the margarine-fed hamsters in our study supports these previous reports.

An important finding of this study is that hamsters fed the canola oil– and soybean oil–enriched diets generally had higher -tocopherol and vitamin C levels in peripheral and brain tissues than hamsters fed the margarine-enriched diet. One explanation for the high vitamin C concentration in the brain in both canola- and soybean oil–fed hamsters is that vitamin C is consumed at a lower rate because of the lower oxidative stress in these groups. These results agree with other studies showing that high PUFA intake was associated with reduced oxidative stress in vivo (37).

The observation that hamsters fed both soybean oil–based diets (margarine and soybean oil) had higher levels of -tocopherol in peripheral and brain tissue is likely related to the higher concentration of -tocopherol in this oil. The brain of hamsters fed the soybean oil–based diets incorporated significantly more -tocopherol than the other groups, reflecting dietary intake (Table 3). Interestingly, the cerebellum accumulated the most, followed by striatum, cortex, and hippocampus. The role played by -tocopherol in the brain remains unknown. Some reports have demonstrated that -tocopherol is an efficient antioxidant against superoxide, decreasing platelet aggregation and arterial thrombogenesis, and therefore relevant to human health (38–40). Therefore, the high concentration of -tocopherol present in the margarine-enriched diet and in tissues of the hamsters fed this diet may have contributed to ameliorating the effects of the hydrogenated fat.

Soybean oil has 58% PUFA, 24% monounsaturated fatty acids, and no trans fatty acids, whereas canola oil and margarine contain 34, 53 and 2.2% and 34, 29 and 18% respectively. The soybean oil–enriched diet contained 41% more PUFA than the margarine- and canola oil–enriched diets. However, the levels of 8-epiPGF₂ were significantly higher in hamsters fed the margarine-enriched diet, suggesting that the trans fatty acids and/or the low vitamin E in the margarine diet may have contributed to the elevated oxidative stress in this group. Interestingly, this group’s diet had the lowest vitamin E concentration and 84% less -tocopherol than the nonhydrogenated soybean oil. There was no indication in this study that an elevated intake of PUFA, when the antioxidants were appropriate, was associated with higher concentrations of 8-epiPGF₂. Suzumura et al. (41) showed in hamsters that vitamin E deficiency significantly increased the levels of plasma oxidative stress markers such as 8-epiPGF₂ and hydroperoxides. Stein et al. (42) found higher plasma thiobarbituric acid reactive substances in vitamin E–deficient male Golden Syrian hamsters and a greater propensity of lipoproteins (d < 1.063 kg/L) to peroxidation in vitro than hamsters fed a vitamin E–supplemented diet. Kubow et al. (43) indicated that oxidative stress in Golden Syrian hamsters could play a causal role in dietary-induced hyperlipidemia, which can be inhibited by high vitamin E intake. In fact, Sarabi et al. (44) showed in women that the accumulation of lipid peroxidation products such as 8-epiPGF₂ seemed to be associated with an impaired vasodilation in general. Moreover, they showed a relationship between the levels of -tocopherol and endothelial vasodilatory function, suggesting that this nutrient has important health benefits in a healthy population.

Based on the literature, the elevated uric acid concentration associated with high cholesterol may contribute to the increased risk of cardiovascular events associated with high saturated fat intake (45–48).

Some limitations of this study should be acknowledged. Perhaps the most important of these is that because this is an animal study, the extrapolation of the results to humans must be done with caution. Similarly, the antioxidant nutrient content of the diets differed, again reflecting the levels available in common fats habitually consumed by humans. Although this makes it impossible to attribute the differences observed to a specific component of the diet, it does simulate potential effects resulting from current dietary guidelines.

In conclusion, vitamin C and vitamin E in plasma and brain were significantly decreased, and plasma levels of F₂-isoprostanes significantly increased in hamsters fed the margarine-enriched diet. Canola oil– and soybean oil–enriched diets were associated with a significant increase in vitamin E concentration in peripheral tissues and brain and lower F₂-isoprostanes. The results of this study provide new evidence concerning the relevant role that dietary fat and dietary antioxidant vitamins may play in the concentration of nutrients such as vitamins C and E in brain and peripheral tissues, and in antioxidant status, which may be important for reducing the risk of degenerative diseases.

	FOOTNOTES

 
¹ Supported in part by Grant T32 DK62032–11 and 1 T32 HL69772–01A1 from the National Institutes of Health, Bethesda, MD (S.E.D.) and a Fulbright/Ministry of Education, Culture and Sports Award for Postdoctoral Research in the United States of America, Visiting Scholar Program, Commission for Cultural, Educational and Scientific Exchange between the United States of America and Spain (C.S.-M.).

³ Abbreviations used: CHD, coronary heart disease; DTPA, diethylenetriaminepentaacetic acid; EIA, enzyme immunoassay; 8-epiPGF₂, 8-isoprostane; MUFA, monounsaturated fatty acids.

Manuscript received 12 September 2003. Initial review completed 3 October 2003. Revision accepted 1 December 2003.

	LITERATURE CITED

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Expert Panel (1993) Summary of the second report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II). J. Am. Med. Assoc. 269:3015-3023.[Medline]

2. Kennedy, E., Meyers, L. & Layden, W. (1996) The 1995 dietary guidelines for Americans: an overview. J. Am. Diet. Assoc. 96:234-237.[Medline]

3. Krauss, R. M., Deckelbaum, R. J., Ernst, N., Fisher, E., Howard, B. V., Knopp, R. H., Kotchen, T., Lichtenstein, A. H., McGill, H. C., Pearson, T. A., Prewitt, T. E., Stone, N. J., Horn, L. V. & Weinberg, R. (1996) Dietary guidelines for healthy American adults. A statement for health professionals from the Nutrition Committee, American Heart Association. Circulation 94:1795-1800.[Free Full Text]

4. Krauss, R. M., Eckel, R. H., Howard, B., Appel, L. J., Daniels, S. R., Deckelbaum, R. J., Erdman, J. W., Jr, Kris-Etherton, P., Goldberg, I. J., Kotchen, T. A., Lichtenstein, A. H., Mitch, W. E., Mullis, R., Robinson, K., Wylie-Rosett, J., St Jeor, S., Suttie, J., Tribble, D. L. & Bazzarre, T. L. (2000) AHA dietary guidelines: revision 2000: a statement for healthcare professionals from the Nutrition Committee of the American Heart Association. Circulation 102:2284-2299.[Free Full Text]

5. Dwyer, J. T. & Lichtenstein, A. H. (2001) ABC’s of dietary guidelines 2000 for clinicians. Nutr. Clin. Care 3:359-370.

6. Expert Panel (2001) Executive summary of the third report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). J. Am. Med. Assoc. 285:2486-2497.[Free Full Text]

7. Kaplan, R. J. & Greenwood, C. E. (1998) Dietary saturated fatty acids and brain function. Neurochem. Res. 23:615-626.[Medline]

8. Winocur, G. & Greenwood, C. E. (1999) The effects of high fat diets and environmental influences on cognitive performance in rats. Behav. Brain Res. 101:153-161.[Medline]

9. Frei, B. (1991) Ascorbic acid protects lipids in human plasma and low-density lipoprotein against oxidative damage. Am. J. Clin. Nutr. 54:1113S-1118S.[Medline]

10. van Popel, G. & van den Berg, H. (1997) Vitamins and cancer. Cancer Lett 114:195-202.[Medline]

11. Block, G., Henson, D. E. & Levine, M. (1991) Vitamin C: a new look. Ann. Intern. Med. 114:909-910.

12. Martín, A., Cherubini, A., Andrés-Lacueva, C., Paniagua, M. & Joseph, J. A. (2002) Effects of fruits and vegetables on levels of vitamins E and C in the brain and their association with cognitive performance. J. Nutr. Health Aging 6:392-404.[Medline]

13. Menniti, F. S., Knoth, J. & Diliberto, E. J., Jr (1986) Role of ascorbic acid in dopamine beta-hydroxylation. The endogenous enzyme cofactor and putative electron donor for cofactor regeneration. J. Biol. Chem. 261:16901-16908.[Abstract/Free Full Text]

14. Levine, M., Dhariwal, K. R., Welch, R. W., Wang, Y. & Park, J. B. (1995) Determination of optimal vitamin C requirements in humans. Am. J. Clin. Nutr. 62:1347S-1356S.[Abstract/Free Full Text]

15. Sánchez-Moreno, C., Cano, M. P., de Ancos, B., Plaza, L., Olmedilla, B., Granado, F. & Martín, A. (2003) Effect of orange juice intake on vitamin C concentrations and biomarkers of antioxidant status in humans. Am. J. Clin. Nutr. 78:454-460.[Abstract/Free Full Text]

16. Traber, M. G. & Arai, H. (1999) Molecular mechanisms of vitamin E transport. Annu. Rev. Nutr. 19:343-355.[Medline]

17. Engelhart, M. J., Geerlings, M. I., Ruitenberg, A., van Swieten, J. C., Hofman, A., Witteman, J. C. & Breteler, M. M. (2002) Dietary intake of antioxidants and risk of Alzheimer disease. J. Am. Med. Assoc. 287:3223-3229.[Abstract/Free Full Text]

18. Delanty, N., Reilly, M. P., Pratico, D., Lawson, J. A., McCarthy, J. F., Wood, A. E., Ohnishi, S. T., Fitzgerald, D. J. & FitzGerald, G. A. (1997) 8-epi PGF₂ alpha generation during coronary reperfusion. A potential quantitative marker of oxidant stress in vivo. Circulation 95:2492-2499.[Abstract/Free Full Text]

19. Banerjee, M., Kang, K. H., Morrow, J. D., Roberts, L. J. & Newman, J. H. (1992) Effects of a novel prostaglandin, 8-epi-PGF₂ alpha, in rabbit lung in situ. Am. J. Physiol. 263:H660-H663.

20. Vacchiano, C. A. & Tempel, G. E. (1994) Role of nonenzymatically generated prostanoid, 8-iso-PGF₂ alpha, in pulmonary oxygen toxicity. J. Appl. Physiol. 77:2912-2917.[Abstract/Free Full Text]

21. Reilly, M. P., Pratico, D., Delanty, N., DiMinno, G., Tremoli, E., Rader, D., Kapoor, S., Rokach, J., Lawson, J. & FitzGerald, G. A. (1998) Increased formation of distinct F₂ isoprostanes in hypercholesterolemia. Circulation 98:2822-2828.[Abstract/Free Full Text]

22. Meisinger, C., Thorand, B., Schneider, A., Stieber, J., Doring, A. & Lowel, H. (2002) Sex differences in risk factors for incident type 2 diabetes mellitus: the MONICA Augsburg cohort study. Arch. Intern. Med. 162:82-89.[Abstract/Free Full Text]

23. Dorfman, S., Smith, D., Osgood, D. & Lichtenstein, A. (2003) Study of diet-induced changes in lipoprotein metabolism in two strains of Golden-Syrian hamsters. J. Nutr. 133:4183-4188.[Abstract/Free Full Text]

24. Lowry, O. H., Rosebrough, N. J., Farr, A. L. & Randall, R. J. (1951) Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193:265-269.[Free Full Text]

25. Martín, A. & Frei, B. (1997) Both intracellular and extracellular vitamin C inhibit atherogenic modification of LDL by human vascular endothelial cells. Arterioscler Thromb. Vasc. Biol. 17:1583-1590.[Abstract/Free Full Text]

26. Martín, A., Foxall, T., Blumberg, J. B. & Meydani, M. (1997) Vitamin E inhibits low-density lipoprotein-induced adhesion of monocytes to human aortic endothelial cells in vitro. Arterioscler. Thromb. Vasc. Biol. 17:429-436.[Abstract/Free Full Text]

27. Pradelles, P., Grassi, J. & Maclouf, J. (1985) Enzyme immunoassays of eicosanoids using acetylcholine esterase as label: an alternative to radioimmunoassay. Anal. Chem. 57:1170-1173.[Medline]

28. Sánchez-Moreno, C., Cano, M. P., de Ancos, B., Plaza, L., Olmedilla, B., Granado, F. & Martín, A. (2003) Effect of high-pressurized orange juice consumption on plasma vitamin C, antioxidative status and inflammatory markers in healthy humans. J. Nutr. 133:2204-2209.[Abstract/Free Full Text]

29. Bland, J. M. & Altman, D. G. (1995) Calculating correlation coefficients with repeated observations: Part 1. Correlation within subjects. Br. Med. J. 310:446.[Free Full Text]

30. Maziere, C., Conte, M. A., Degonville, J., Ali, D. & Maziere, J. C. (1999) Cellular enrichment with polyunsaturated fatty acids induces an oxidative stress and activates the transcription factors AP1 and NFkappaB. Biochem. Biophys. Res. Commun. 265:116-122.[Medline]

31. Jenkinson, A., Franklin, M. F., Wahle, K. & Duthie, G. G. (1999) Dietary intakes of polyunsaturated fatty acids and indices of oxidative stress in human volunteers. Eur. J. Clin. Nutr. 53:523-528.[Medline]

32. O’Farrell, S. & Jackson, M. J. (1997) Dietary polyunsaturated fatty acids, vitamin E and hypoxia/reoxygenation-induced damage to cardiac tissue. Clin. Chim. Acta 267:197-211.[Medline]

33. Chen, L., Bowen, P. E., Berzy, D., Aryee, F., Stacewicz-Sapuntzakis, M. & Riley, R. E. (1999) Diet modification affects DNA oxidative damage in healthy humans. Free Radic. Biol. Med. 26:695-703.[Medline]

34. Yehuda, S., Rabinovitz, S., Carasso, R. L. & Mostofsky, D. I. (2002) The role of polyunsaturated fatty acids in restoring the aging neuronal membrane. Neurobiol. Aging 23:843-853.[Medline]

35. Valk, E. E. & Hornstra, G. (2000) Relationship between vitamin E requirement and polyunsaturated fatty acid intake in man: a review. Int. J. Vitam. Nutr. Res. 70:31-42.[Medline]

36. Han, S. N., Leka, L. S., Lichtenstein, A. H., Ausman, L. M., Schaefer, E. J. & Meydani, S. N. (2002) Effect of hydrogenated and saturated, relative to polyunsaturated, fat on immune and inflammatory responses of adults with moderate hypercholesterolemia. J. Lipid Res. 43:445-452.[Abstract/Free Full Text]

37. Mori, T. A., Puddey, I. B., Burke, V., Croft, K. D., Dunstan, D. W., Rivera, J. H. & Beilin, L. J. (2000) Effect of omega 3 fatty acids on oxidative stress in humans: GC-MS measurement of urinary F₂-isoprostane excretion. Redox Rep 5:45-46.[Medline]

38. Saldeen, T., Li, D. & Mehta, J. L. (1999) Differential effects of alpha- and gamma-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis. J. Am. Coll. Cardiol. 34:1208-1215.[Abstract/Free Full Text]

39. Li, D., Saldeen, T. & Mehta, J. L. (1999) -Tocopherol decreases ox-LDL-mediated activation of nuclear factor-B and apoptosis in human coronary artery endothelial cells. Biochem. Biophys. Res. Commun. 259:157-161.[Medline]

40. Li, D., Saldeen, T., Romeo, F. & Mehta, J. L. (2001) Different isoforms of tocopherols enhance nitric oxide synthase phosphorylation and inhibit human platelet aggregation and lipid peroxidation: implications in therapy with vitamin E. J. Cardiovasc. Pharmacol. Ther. 6:155-161.[Abstract/Free Full Text]

41. Suzumura, K., Ohashi, N., Oka, K., Yasuhara, M. & Narita, H. (2001) Fluvastatin depresses the enhanced lipid peroxidation in vitamin E-deficient hamsters. Free Radic. Res. 35:815-823.[Medline]

42. Stein, O., Dabach, Y., Hollander, G., Halperin, G., Thiery, J. & Stein, Y. (1996) Relative resistance of the hamster to aortic atherosclerosis in spite of prolonged vitamin E deficiency and dietary hypercholesterolemia. Putative effect of increased HDL?. Biochim. Biophys. Acta 1299:216-222.[Medline]

43. Kubow, S., Goyette, N., Kermasha, S., Stewart-Phillip, J. & Koski, K. G. (1996) Vitamin E inhibits fish oil-induced hyperlipidemia and tissue lipid peroxidation in hamsters. Lipids 31:839-847.[Medline]

44. Sarabi, M., Vessby, B., Basu, S., Millgard, J. & Lind, L. (1999) Relationships between endothelium-dependent vasodilation, serum vitamin E and plasma isoprostane 8-iso-PGF(₂) levels in healthy subjects. J. Vasc. Res. 36:486-491.[Medline]

45. Culleton, B. F., Larson, M. G., Kannel, W. B. & Levy, D. (1999) Serum uric acid and risk for cardiovascular disease and death: the Framingham Heart Study. Ann. Intern. Med. 131:7-13.[Abstract/Free Full Text]

46. Fang, J. & Alderman, M. H. (2000) Serum uric acid and cardiovascular mortality the NHANES I epidemiologic follow-up study, 1971–1992: National Health and Nutrition Examination Survey. J. Am. Med. Assoc. 283:2404-2410.[Abstract/Free Full Text]

47. Lu, P., Hu, D., Lu, J., Wang, W. & Chen, B. (2002) The association between uric acid and coronary heart disease. Zhonghua Nei Ke Za Zhi 41:526-529.[Medline]

48. Bickel, C., Rupprecht, H. J., Blankenberg, S., Rippin, G., Hafner, G., Daunhauer, A., Hofmann, K. P. & Meyer, J. (2002) Serum uric acid as an independent predictor of mortality in patients with angiographically proven coronary artery disease. Am. J. Cardiol. 89:12-17.[Medline]

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