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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Dietary (n-3) Fatty Acids Reduce Plasma F₂-Isoprostanes but Not Prostaglandin F₂ in Healthy Humans¹

Cecilia Nälsén^*,2, Bengt Vessby^*, Lars Berglund, Matti Uusitupa^**, Kjeld Hermansen, Gabrielle Riccardi, Angela Rivellese, Len Storlien, Arja Erkkilä^**, Seppo Ylä-Herttuala^**, Linda Tapsell and Samar Basu^*

The KANWU Study Group at ^* Clinical Nutrition and Metabolism, Department of Public Health and Caring Sciences and Uppsala Clinical Research Centre, Uppsala University, Uppsala, Sweden; ^** Department of Clinical Nutrition, University of Kuopio, Kuopio, Finland; Department of Clinical Endocrinology and Metabolism C, Aarhus Sygehus THG, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical and Experimental Medicine, School of Medicine, Federico II University, Naples, Italy; and Department of Biomedical Sciences and Medical Research Unit, University of Wollongong, Wollongong, Australia

² To whom correspondence should be addressed. E-mail: cecilia.nalsen{at}pubcare.uu.se.

	ABSTRACT

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
(n-3) Fatty acids are unsaturated and are therefore easily subject to oxidization; however, they have several beneficial health effects, which include protection against cardiovascular diseases. The aim of this study was to investigate whether (n-3) fatty acids, with a controlled fat quality in the background diet, affect nonenzymatic and enzymatic lipid peroxidation and antioxidant status in humans. A total of 162 men and women in a multicenter study (The KANWU study) were randomly assigned to a diet containing a high proportion of saturated fatty acids or monounsaturated fatty acids (MUFA) for 3 mo. Within each diet group, there was a second random assignment to supplementation with fish-oil capsules [3.6 g (n-3) fatty acids/d] or placebo. Biomarkers of nonenzymatic and enzymatic lipid peroxidation in vivo were determined by measuring 8-iso-prostaglandin F₂ (8-iso-PGF₂) and prostaglandin F₂ (PGF₂) concentrations in plasma at baseline and after 3 mo. Antioxidant status was determined by measuring plasma antioxidant capacity with an enhanced chemiluminescence assay. The plasma 8-iso-PGF₂ concentration was significantly decreased after 3 mo of supplementation with (n-3) fatty acids (P = 0.015), whereas the PGF₂ concentration was not affected. The antioxidant status was not affected by supplementation of (n-3) fatty acids, but was improved by the background diet with a high proportion of MUFA. We conclude that supplementation with (n-3) fatty acids decreases nonenzymatic free radical–catalyzed isoprostane formation, but does not affect cyclooxygenase-mediated prostaglandin formation.

KEY WORDS: • isoprostanes • prostaglandins • fatty acids • oxidative stress • antioxidant status

The (n-3) fatty acids including eicosapentaenoic (EPA)³ and docosahexaenoic acid (DHA) are highly unsaturated and might easily undergo oxidation to several bioactive compounds (1–3). These fatty acids were shown to reduce cardiovascular mortality in coronary heart disease patients (4) and affect several risk factors associated with cardiovascular disease by reducing triglyceride levels (5), reducing risk for arrhythmias and thrombosis (6), reducing inflammation, and improving endothelial function (7) through the modulation of several important biochemical pathways including eicosanoid formation (1).

Arachidonic acid, another important PUFA of the (n-6) series, can be converted enzymatically through the cyclooxygenase (COX) pathway to bioactive prostaglandins (PGF_2, PGE_2, PGI_2, among others) and thromboxanes (TX; Fig. 1) (8). Prostaglandin F₂ (PGF₂) controls several important physiologic functions in the body (9) and is also involved in acute and chronic inflammation in various species (10–14). 15-Keto-dihydro-prostaglandin F₂ (15-keto-dihydro-PGF₂), a major metabolite of prostaglandin F₂, can be used as a biomarker of enzymatically COX-mediated lipid peroxidation in vivo (9,15). Further, 15-keto-dihydro-PGF₂ was shown to be a reliable indicator of in vivo COX-mediated inflammation (10–15). To our knowledge, this study is the first to investigate the effect of supplementation with (n-3) fatty acids on basal plasma levels of PGF₂ metabolites as a biomarker of COX-mediated lipid peroxidation in vivo.

View larger version (9K): [in this window] [in a new window]   FIGURE 1  Schematic diagram of endogenous formation of 8-iso-PGF2 via free radical and 15-keto-dihydro-PGF2 via COX-catalyzed oxidation of arachidonic acid (44). Abbreviations: ROS, reactive oxygen species.

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Hypothetically, the (n-3) fatty acids (EPA and DHA) may compete with arachidonic acid for the generation of 3-series prostaglandins over 2-series prostaglandins through the COX pathway. However, clear evidence for this concept in humans is presently lacking. The aim of this study was to investigate whether supplementation of dietary EPA and DHA, the major long-chained (n-3) fatty acids, in the context of a background diet of controlled fat quality, affects both the nonenzymatic and enzymatic lipid peroxidation in humans measured as F₂-isoprostanes and a metabolite of prostaglandin F₂ in plasma, respectively. In addition, we analyzed antibodies against oxidized LDL (oxLDL) and antioxidant status determined as antioxidant capacity and tocopherol concentrations.

	SUBJECTS AND METHODS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The design, population, and diet in the study were described in detail previously (19).

Study design

The KANWU study was a multicenter study involving Kuopio (Finland), Aarhus (Denmark), Naples (Italy), Wollongong (Australia) and Uppsala (Sweden). After baseline assessment (see details below), the participants were randomly assigned to a diet containing a high proportion of either saturated fatty acids (SAFA diet) or monounsaturated fatty acids (MUFA diet) for a study period of 90 d. Within each diet group, there was a 2nd random assignment to either supplements of capsules containing fish-oil [3.6 g (n-3) fatty acids/d containing 2.4 g EPA 20:5 (n-3) and DHA 22:6 (n-3), corresponding to 3 capsules twice daily of Pikasol, Lube A/S] or to placebo capsules with the same amount of olive oil. Four groups were thus formed: SAFA + placebo (n = 42); SAFA + (n-3) (n = 41); MUFA + placebo (n = 40); and MUFA + (n-3) (n = 39). The same assessments as at baseline were performed again at the end of the 90-d diet period. The increased intake of EPA and DHA during the study was reflected in the fatty acid composition of the serum phospholipids as previously described (19).

Subjects

A total of 162 healthy subjects (86 men and 76 women) aged 30–65 y with normal or moderately increased body weight participated in the study. The subjects were instructed to avoid nutritional supplements from 2 wk before and during the study. They were not to take preparations containing acetylsalicylic acid (ASA) regularly during the last month before the start of the study and they had to avoid ASA in the last week before and during the study. They were asked not to change their lifestyle or physical activity patterns during the study. The study was approved by the ethics committee of the Medical faculty at each center and all participants gave their informed consent.

Diets

All participants were instructed to eat isoenergetic diets with the same proportions of the main nutrients, including similar a proportion of total fat, but with a high proportion of saturated (SAFA diet) or monounsaturated (MUFA diet) fatty acids, respectively. The diets were calculated to contain 37 energy percent (E%) fat with 17, 14, and 6 E% SAFA, MUFA, and PUFA, respectively, in the SAFA diet, and 8, 23, and 6E% in the MUFA diet. The changes in the dietary fat quality in the different diets during the study reflected the fatty acid changes in the serum phospholipids as previously described (19).

All participants were supplied with edible fats to be used as spreads on bread, for cooking, and in dressings. At some centers, food items such as bread, ice-cream, and ready-made dishes based on the appropriate type of fat were also provided. The participants were instructed to reduce their intake of high-fat food items and not to eat fat fish or products based on them.

Dietary analysis

The subjects were asked to keep weighed food records over 3 consecutive days (2 weekdays and 1 weekend day) once before and twice during the study. The intake during the study was calculated as the mean value of the two 3-d food records provided during mo 2 and 3 of the study. Local nutrient analysis software programs containing country-specific food databases and data on margarines and other specially prepared foods used in the diets were used in the analysis.

Blood sampling

Blood samples were taken from an antecubital vein after an overnight fast at baseline and after 3 mo. All plasma and serum samples were kept frozen at –70°C until analyzed or fresh samples were used.

Measurement of lipid peroxidation

    8-Iso-prostaglandin F₂. The plasma levels of 8-iso-prostaglandin F₂ (8-iso-PGF₂) were analyzed at 3 centers, Finland, Australia, and Sweden by using a validated RIA developed by Basu (20). Plasma samples from 2 centers (Denmark and Italy) were unfortunately inadequate to use for analysis of isoprostanes due to inappropriate sample handling and/or storage. The cross-reactivity between the 8-iso-PGF₂ antibody was 1.7% with 15-keto-13,14-dihydro-8-iso-PGF₂, 9.8% with 8-iso-PGF_2ß, 1.1% with PGF₂, 0.01% with 15-keto-PGF₂, 0.01% with 15-keto-13,14-dihydro-PGF₂, 0.1% with TXB₂, 0.03% with 11ß-PGF₂, 1.8% with 9ß-PGF₂, and 0.6% with 8-iso-PGF₃. The detection limit of the assay was 23 pmol/L.

    15-Keto-dihydro-PGF₂. The levels of 15-keto-dihydro-PGF₂ were analyzed in plasma from all centers using a validated RIA developed by Basu (15). The cross-reactivity with the antibody was 0.02% for PGF₂, 0.43% for 15-keto-PGF₂, <0.001% for PGE₂, 0.5% for 15-keto-13,14-dihydro-PGE₂, 1.7% for 8-iso-15-keto-13,14-dihydro-PGF₂, <0.001% for 11ß-PGF₂, <0.001% for TXB₂ and <0.01% for 8-iso-PGF₃. The detection limit of the assay was 45 pmol/L.

    Auto-antibodies against oxidized LDL (oxLDL). An ELISA was used to determine autoantibodies to oxLDL (21). The results are expressed as the ratio of binding to oxLDL to binding to native LDL (OxLDL:native LDL) after subtracting the mean background binding to the wells.

Measurement of antioxidant capacity, uric acid, and tocopherols

    Antioxidant capacity (AOC). The antioxidant capacity was measured in plasma with an enhanced chemiluminescent antioxidant assay (22,23). Plasma antioxidant capacity in the absence of uric acid was determined using uricase (Boehringer) to remove uric acid content in the plasma sample before antioxidant capacity was measured. Uricase solution (10 mL; 18 kU/L) was added to the diluted plasma. Thereafter, antioxidant capacity was measured as described previously. The antioxidant capacity without uric acid was shown to be correlated with the concentration of lipids, which may reflect the tocopherols that are transported by the lipid molecules; therefore, the results are presented with and without adjustment for the sum of cholesterol and triglycerides in serum (unpublished data).

    Uric acid. The concentration of uric acid was measured enzymatically in plasma (Instrumentation Laboratories) in a Monarch centrifugal analyzer (Instrumentation Laboratories).

    Tocopherols. HPLC with fluorescence detection was used to determine -, ß-, and -tocopherol in serum (24). Tocopherol levels were adjusted for the sum of cholesterol and triglycerides in serum (25).

Other biochemical and clinical analyses

Cholesterol and triglycerides in serum were measured by enzymatic colorimetric methods (Instrumentation Laboratories) in a Monarch centrifugal analyzer (Instrumentation Laboratories). LDL cholesterol was calculated according to Friedewald (26). Plasma glucose concentration was analyzed by a glucose oxidase assay (27). Blood pressure was measured in the supine position after a 10-min rest. BMI was calculated as body weight divided by height squared (kg/m²).

Statistical methods

Results for continuous variables are presented as means and SD. For variables with skewed distributions, a logarithmic transformation was made before the statistical analysis. The main outcome variables were the changes in 8-iso-prostaglandin F₂ and 15-keto-dihydro-PGF₂. For each outcome variable, the treatment effects were estimated from a statistical model in which treatment categories (SAFA diet/MUFA diet and the presence/absence of (n-3) fatty acids) and their interaction were analyzed. Factors and treatment center, age, sex, and the baseline value of the outcome variable were covariates. For outcome variables in which the interaction between the treatment factors was not significant (P 0.05), a limited model was used excluding that term. The difference in effect between the presence and absence of (n-3) fatty acids is presented with P-values combined over both diet groups, in which all subjects supplemented with (n-3) fatty acids were compared with all subjects given the placebo. Furthermore, the difference in effect between the 2 diet groups when combined over the presence/absence of (n-3) fatty acids groups is presented with P-values. The difference in effect within groups over time is also presented. Differences with P-values < 0.05 were regarded as significant. Statistical analyses were performed using JMP version 3.2 and SAS version 8.0 (SAS Institute).

	RESULTS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Clinical characteristics. The clinical characteristics of the participants at baseline did not differ among the groups (Table 1).

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	DISCUSSION

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

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OxLDL are present in atherosclerotic lesions (36), and LDL particles rich in PUFA may be more easily oxidized in vitro (37). Furthermore, autoantibodies against oxLDL were detected in human serum and atherosclerotic lesions (38). However, the titers of autoantibodies against oxLDL in this study were not affected by supplementation of (n-3) fatty acids or by the background diet.

The serum concentrations of -tocopherols increased and -tocopherols decreased in all groups, probably due to the increased amount -tocopherol–containing fat in the diet during the study. Another possible explanation for the increased levels of -tocopherol in this study might be that the subjects were influenced by the participation in a dietary intervention with generally improved dietary habits. Because this increase occurred in all groups, it could not be related to the reduced levels of F₂-isoprostanes, which occurred only in subjects supplemented with (n-3) fatty acids. The increased lipid adjusted antioxidant capacity without uric acid in the subjects that consumed the MUFA diet might also reflect an increased content of -tocopherol–containing fat or improved dietary habits due to participation in the study. Other studies examining the antioxidant capacity of subjects consuming fish oil supplements or higher intakes of PUFA reported an increased or unaffected effect on antioxidant capacity (39,40). The inverse relation between - and -tocopherols in this study agrees with other studies in which increased intake of -tocopherols was shown to decrease the levels of -tocopherols (23,41). The diverging effects on the levels of ß-tocopherol in the diets were of interest, with a decreased concentration of ß-tocopherol after consumption of the SAFA diet and increased concentration after the MUFA diet. Earlier studies showed decreased levels of ß-tocopherol after intake of a diet rich in rapeseed oil or olive oil (42), and after intake of an almond-enriched diet (43), whereas the levels of ß-tocopherol were unaffected after supplementation with -tocopherol (23).

Arachidonic acid can be converted by COX to primary PG and TX, which regulate several important physiologic and pathophysiologic processes in the body such as inflammation, gastrointestinal and renal function, pain, fever, platelet aggregation, and reproduction (8,9,11–14,44). This pathway could be modulated by major (n-3) fatty acids; EPA may compete with structurally related arachidonic acid for bioconversion by COX to PG of the F3-series (45,46). Based on this assumption, we hypothesized in this study that supplementation of (n-3) fatty acids may modulate enzymatic conversion of arachidonic acid and thereby the COX-mediated PGF₂ formation. However, although the nonenzymatically free radical–catalyzed lipid peroxidation in vivo was affected, COX-mediated lipid peroxidation was unchanged. Recently, it was reported that the inflammatory biomarkers C-reactive protein, interleukin-6, and tumor necrosis factor- were unaffected after supplementation with (n-3) fatty acids in hypertensive subjects treated for type 2 diabetes (34). On the contrary, it was shown that consumption of (n-3) fatty acids lowers the levels of several other biomarkers of inflammation and endothelial activation (7). In addition, (n-3) fatty acids exert potent anti-inflammatory effects (3,47). However, the current study was performed in healthy subjects and the basal levels of PGF₂ were not affected. This does not confirm that (n-3) fatty acids have any profound effect on PG formation. Subjects with higher levels of PGF₂ such as patients with type 2 diabetes (13), smokers (14), and patients with rheumatoid arthritis (44) should be studied to determine the role of (n-3) fatty acids in the regulation of the enzymatic conversion of arachidonic acid to primary PGF₂.

Free radicals are involved in acute and chronic inflammation (11,12,44), and (n-3) fatty acids have anti-inflammatory effects (1,2,7,47). Recent work from Serhan et al. (2) suggested that resolvins, oxygenated products from (n-3) fatty acids, possess potent anti-inflammatory activity. In this study, we showed that irrespective of background diet, supplementation of (n-3) fatty acids decreased free radical–mediated isoprostane formation rather than COX-mediated PG formation. This observation is of notable biological importance due to the anti-inflammatory properties of (n-3) fatty acids, which might be related to the regulation of isoprostane formation in basal state in humans. Because PGF₂ formation was unaffected, but F₂-isoprostane formation was lowered, we contend that (n-3) fatty acids might preferentially counteract free radical–catalyzed isoprostane formation rather than COX-mediated PGF₂ formation. However, it was shown earlier that (n-3) fatty acids might convert to F₃- and F₄-isoprostanes through the free radicals (48,49). Thus, reduction of F₂-isoprostane levels after supplementation of (n-3) fatty acids might occur through several unidentified pathways.

In conclusion, supplementation with (n-3) fatty acids decreases free radical–catalyzed isoprostane formation, but the enzymatic COX-mediated PG formation is not affected in healthy subjects. Future studies are warranted to clarify the mechanism by which EPA and DHA reduce nonenzymatic free radical–catalyzed lipid peroxidation in vivo.

	ACKNOWLEDGMENTS

 
We thank Rawya Mohsen for data handling.

	FOOTNOTES

 
¹ Supported by a grant from the Swedish Nutrition Foundation.

³ Abbreviations used: AOC, antioxidant capacity; ASA, acetylsalicylic acid; COX, cyclooxygenase; DHA, docosahexaenoic acid; E%, energy percent; EPA, eicosapentaenoic acid; 8-iso-PGF₂, 8-iso-prostaglandin F₂;15-keto-dihydro-PGF₂, 15-keto-dihydro-prostaglandin F₂; MUFA, monounsaturated fatty acid; oxLDL, oxidized LDL; PGF₂, prostaglandin F₂; SAFA, saturated fatty acid; TX, thromboxane.

Manuscript received 14 October 2005. Initial review completed 3 January 2006. Revision accepted 7 February 2006.

	LITERATURE CITED

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Leaf A, Weber PC. Cardiovascular effects of n-3 fatty acids. N Engl J Med. 1988;318:549–57.[Medline]

2. Serhan CN. Novel eicosanoid and docosanoid mediators: resolvins, docosatrienes, and neuroprotectins. Curr Opin Clin Nutr Metab Care. 2005;8:115–21.[Medline]

3. Serhan CN, Arita M, Hong S, Gotlinger K. Resolvins, docosatrienes, and neuroprotectins, novel omega-3-derived mediators, and their endogenous aspirin-triggered epimers. Lipids. 2004;39:1125–32.[Medline]

4. Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet. 1999;354:447–55.[Medline]

5. Harris WS. n-3 fatty acids and serum lipoproteins: human studies. Am J Clin Nutr. 1997;65:1645S–54.[Abstract/Free Full Text]

6. Connor WE. Importance of n-3 fatty acids in health and disease. Am J Clin Nutr. 2000;71:171S–5S.[Abstract/Free Full Text]

7. Lopez-Garcia E, Schulze MB, Manson JE, Meigs JB, Albert CM, Rifai N, Willett WC, Hu FB. Consumption of (n-3) fatty acids is related to plasma biomarkers of inflammation and endothelial activation in women. J Nutr. 2004;134:1806–11.[Abstract/Free Full Text]

8. Samuelsson B, Granstrom E, Green K, Hamberg M, Hammarstrom S. Prostaglandins. Annu Rev Biochem. 1975;44:669–95.[Medline]

9. Basu S, Kindahl H, Harvey D, Betteridge KJ. Metabolites of PGF2 alpha in blood plasma and urine as parameters of PGF2 alpha release in cattle. Acta Vet Scand. 1987;28:409–20.[Medline]

10. Mutschler DK, Eriksson MB, Wikstrom BG, Lind L, Larsson A, Bergren-Kiiski R, Lagrange A, Nordgren A, Basu S. Microdialysis-evaluated myocardial cyclooxygenase-mediated inflammation and early circulatory depression in porcine endotoxemia. Crit Care Med. 2003;31:1780–5.[Medline]

11. Basu S, Eriksson M. Oxidative injury and survival during endotoxemia. FEBS Lett. 1998;438:159–60.[Medline]

12. Basu S, Nozari A, Liu XL, Rubertsson S, Wiklund L. Development of a novel biomarker of free radical damage in reperfusion injury after cardiac arrest. FEBS Lett. 2000;470:1–6.[Medline]

13. Helmersson J, Vessby B, Larsson A, Basu S. Association of type 2 diabetes with cyclooxygenase-mediated inflammation and oxidative stress in an elderly population. Circulation. 2004;109:1729–34.[Abstract/Free Full Text]

14. Helmersson J, Larsson A, Vessby B, Basu S. Active smoking and a history of smoking are associated with enhanced prostaglandin F(2alpha), interleukin-6 and F(2)-isoprostane formation in elderly men. Atherosclerosis. 2005;181:201–7.[Medline]

15. Basu S. Radioimmunoassay of 15-keto-13,14-dihydro-prostaglandin F₂alpha: an index for inflammation via cyclooxygenase catalysed lipid peroxidation. Prostaglandins Leukot Essent Fatty Acids. 1998;58:347–52.[Medline]

16. Morrow JD, Hill KE, Burk RF, Nammour TM, Badr KF, Roberts LJ 2nd. A series of prostaglandin F₂-like compounds are produced in vivo in humans by a non-cyclooxygenase, free radical-catalyzed mechanism. Proc Natl Acad Sci U S A. 1990;87:9383–7.[Abstract/Free Full Text]

17. Basu S. Isoprostanes: novel bioactive products of lipid peroxidation. Free Radic Res. 2004;38:105–22.[Medline]

18. Basu S, Helmersson J. Factors regulating isoprostane formation in vivo. Antioxid Redox Signal. 2005;7:221–35.[Medline]

19. Vessby B, Uusitupa M, Hermansen K, Riccardi G, Rivellese AA, Tapsell LC, Nälsen C, Berglund L, Louheranta A, et al. Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU Study. Diabetologia. 2001;44:312–9.[Medline]

20. Basu S. Radioimmunoassay of 8-iso-prostaglandin F2alpha: an index for oxidative injury via free radical catalysed lipid peroxidation. Prostaglandins Leukot Essent Fatty Acids. 1998;58:319–25.[Medline]

21. Narvanen O, Erkkila A, Yla-Herttuala S. Evaluation and characterization of EIA measuring autoantibodies against oxidized LDL. Free Radic Biol Med. 2001;31:769–77.[Medline]

22. Whitehead TP, Thorpe GHG, Maxwell SRJ. Enhanced chemiluminescent assay for antioxidant capacity in biological fluids. Anal Chim Acta. 1992;266:265–77.

23. Öhrvall M, Nälsén C, Vessby B. Vitamin E improves the antioxidative capacity but not the insulin sensitivity in elderly men. Nutr Metab Cardiovasc Dis. 1997; Nutr Metab Cardiovasc Dis. 7:9–15.

24. Öhrvall M, Tengblad S, Vessby B. Lower tocopherol serum levels in subjects with abdominal adiposity. J Intern Med. 1993;234:53–60.[Medline]

25. Thurnham DI, Davies JA, Crump BJ, Situnayake RD, Davis M. The use of different lipids to express serum tocopherol: lipid ratios for the measurement of vitamin E status. Ann Clin Biochem. 1986;23:514–20.[Medline]

26. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;18:499–502.[Abstract]

27. Hjelm M. A methodological study of the enzymatic determination of glucose in blood. Scand J Clin Lab Invest. 1963;15:415–28.[Medline]

28. Gopaul NK, Anggard EE, Mallet AI, Betteridge DJ, Wolff SP, Nourooz-Zadeh J. Plasma 8-epi-PGF2 alpha levels are elevated in individuals with non-insulin dependent diabetes mellitus. FEBS Lett. 1995;368:225–9.[Medline]

29. Reilly MP, Pratico D, Delanty N, DiMinno G, Tremoli E, Rader D, Kapoor S, Rokach J, Lawson J, et al. Increased formation of distinct F2 isoprostanes in hypercholesterolemia. Circulation. 1998;98:2822–8.[Abstract/Free Full Text]

30. Morrow JD, Frei B, Longmire AW, Gaziano JM, Lynch SM, Shyr Y, Strauss WE, Oates JA, Roberts LJ 2nd Increase in circulating products of lipid peroxidation (F2-isoprostanes) in smokers. Smoking as a cause of oxidative damage. N Engl J Med. 1995;332:1198–203.[Abstract/Free Full Text]

31. Higdon JV, Liu J, Du SH, Morrow JD, Ames BN, Wander RC. Supplementation of postmenopausal women with fish oil rich in eicosapentaenoic acid and docosahexaenoic acid is not associated with greater in vivo lipid peroxidation compared with oils rich in oleate and linoleate as assessed by plasma malondialdehyde and F(2)-isoprostanes. Am J Clin Nutr. 2000;72:714–22.[Abstract/Free Full Text]

32. Mori TA, Puddey IB, Burke V, Croft KD, Dunstan DW, Rivera JH, Beilin LJ. Effect of omega 3 fatty acids on oxidative stress in humans: GC-MS measurement of urinary F2-isoprostane excretion. Redox Rep. 2000;5:45–6.[Medline]

33. Mori TA, Dunstan DW, Burke V, Croft KD, Rivera JH, Beilin LJ, Puddey IB. Effect of dietary fish and exercise training on urinary F2-isoprostane excretion in non-insulin-dependent diabetic patients. Metabolism. 1999;48:1402–8.[Medline]

34. Mori TA, Woodman RJ, Burke V, Puddey IB, Croft KD, Beilin LJ. Effect of eicosapentaenoic acid and docosahexaenoic acid on oxidative stress and inflammatory markers in treated-hypertensive type 2 diabetic subjects. Free Radic Biol Med. 2003;35:772–81.[Medline]

35. Tholstrup T, Hellgren LI, Petersen M, Basu S, Straarup EM, Schnohr P, Sandstrom B. A solid dietary fat containing fish oil redistributes lipoprotein subclasses without increasing oxidative stress in men. J Nutr. 2004;134:1051–7.[Abstract/Free Full Text]

36. Yla-Herttuala S, Palinski W, Rosenfeld ME, Parthasarathy S, Carew TE, Butler S, Witztum JL, Steinberg D. Evidence for the presence of oxidatively modified low density lipoprotein in atherosclerotic lesions of rabbit and man. J Clin Invest. 1989;84:1086–95.[Medline]

37. Reaven P, Parthasarathy S, Grasse BJ, Miller E, Steinberg D, Witztum JL. Effects of oleate-rich and linoleate-rich diets on the susceptibility of low density lipoprotein to oxidative modification in mildly hypercholesterolemic subjects. J Clin Invest. 1993;91:668–76.[Medline]

38. Salonen JT, Yla-Herttuala S, Yamamoto R, Butler S, Korpela H, Salonen R, Nyyssonen K, Palinski W, Witztum JL. Autoantibody against oxidised LDL and progression of carotid atherosclerosis. Lancet. 1992;339:883–7.[Medline]

39. Roberts WG, Gordon MH, Walker AF. Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil. Eur J Clin Nutr. 2003;57:1303–10.[Medline]

40. Tapsell LC, Gillen LJ, Patch CS, Batterham M, Owen A, Bare M, Kennedy M. Including walnuts in a low-fat/modified-fat diet improves HDL cholesterol-to-total cholesterol ratios in patients with type 2 diabetes. Diabetes Care. 2004;27:2777–83.[Abstract/Free Full Text]

41. Handelman GJ, Machlin LJ, Fitch K, Weiter JJ, Dratz EA. Oral alpha-tocopherol supplements decrease plasma -tocopherol levels in humans. J Nutr. 1985;115:807–13.[Abstract/Free Full Text]

42. Nydahl M, Gustafsson IB, Ohrvall M, Vessby B. Similar effects of rapeseed oil (canola oil) and olive oil in a lipid-lowering diet for patients with hyperlipoproteinemia. J Am Coll Nutr. 1995;14:643–51.[Abstract]

43. Jambazian PR, Haddad E, Rajaram S, Tanzman J, Sabate J. Almonds in the diet simultaneously improve plasma alpha-tocopherol concentrations and reduce plasma lipids. J Am Diet Assoc. 2005;105:449–54.[Medline]

44. Basu S, Whiteman M, Mattey DL, Halliwell B. Raised levels of F(2)-isoprostanes and prostaglandin F(2alpha) in different rheumatic diseases. Ann Rheum Dis. 2001;60:627–31.[Abstract/Free Full Text]

45. Fischer S, von Schacky C, Schweer H. Prostaglandins E3 and F3 alpha are excreted in human urine after ingestion of n - 3 polyunsaturated fatty acids. Biochim Biophys Acta. 1988;963:501–8.[Medline]

46. Corey EJ, Shih C, Cashman JR. Docosahexaenoic acid is a strong inhibitor of prostaglandin but not leukotriene biosynthesis. Proc Natl Acad Sci U S A. 1983;80:3581–4.[Abstract/Free Full Text]

47. Calder PC. Omega 3 polyunsaturated fatty acids, inflammation and immunity. World Rev Nutr Diet. 2001;88:109–16.[Medline]

48. Nourooz-Zadeh J, Halliwell B, Anggard EE. Formation of a novel class of F3-isoprostanes during peroxidation of eicosapentaenoic acid (EPA). Adv Exp Med Biol. 1997;433:185–8.[Medline]

49. Roberts LJ 2nd, Fessel JP, Davies SS. The biochemistry of the isoprostane, neuroprostane, and isofuran pathways of lipid peroxidation. Brain Pathol. 2005;15:143–8.[Medline]

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