La prééclampsie est caractérisée par une hypertension gestationnelle accompagnée d’une protéinurie détectable après 20 semaines de grossesse. Une invasion anormale de l’endomètre par le placenta est à l’origine de la pathophysiologie. L’apparition d’une condition hypoxique placentaire est associée à un stress oxydatif ainsi qu’à un dérèglement de la synthèse et du transport des acides gras polyinsaturés vers le fœtus. L’oxydation non enzymatique de l’acide arachidonique, un acide gras insaturé oméga-6, mène à la formation potentielle de soixante-quatre isomères de F₂-isoprostanes. Ces derniers sont d’excellents biomarqueurs du stress oxydatif et peuvent jouer un rôle de vasoconstricteurs, lorsque libérés des phospholipides des membranes cellulaires par les phospholipases A₂. J’ai étudié les niveaux d’acides gras intacts et oxydés libérés par les phospholipases A₂ ainsi que la voie du thromboxane A₂ dans le placenta de grossesses normotensives et prééclamptiques. Mes travaux ont mis en lumière que le plasmalogène, une classe particulière de phospholipides riche en acides gras polyinsaturés, est augmenté dans le placenta en prééclampsie. De plus, les F₂-isoprostanes libres se retrouvent en plus grandes concentrations dans le placenta des grossesses prééclamptiques. Parallèlement, l’expression génique de certaines phospholipases A₂ est plus élevée dans le placenta en prééclampsie que chez les contrôles. En résumé, une augmentation des F₂-isoprostanes à effet vasoconstricteur, additionné à une augmentation de l’expression génique du récepteur au thromboxane A₂, pourraient jouer un rôle important dans l’hypertension locale placentaire en cas de prééclampsie. / Preeclampsia is a complex disorder during pregnancy. It is characterized by hypertension and proteinuria detectable after twenty weeks of gestation. An abnormal placental development/invasion is believed to be the first step of the pathophysiology. Preeclampsia is associated with an hypoxic condition, oxidative stress and the deregulation of polyunsaturated fatty acid synthesis and transfer to the growing fetus. Lipid peroxidation of arachidonic acid, an omega-6 fatty acid, lead potentially to the formation of sixty-four isomers of F₂-isoprostanes. F₂-isoprostanes are reliable biomarkers of oxidative stress and some are vasoconstrictors when released from the phospholipids membranes by phospholipases A₂. I have studied intact and oxidized fatty acids liberated by phospholipases A₂ and the thromboxane A₂ pathways in the placenta of normotensives and preeclamptic placentas. We have observed that plasmalogen, a sub-class of phospholipids enriched in polyunsaturated fatty acids, is elevated in the placenta of preeclamptic pregnancies. Furthermore, concentration of free F₂-isoprostanes is higher in preeclamptic placentas compared to controls. The latter was accompanied by elevated mRNA expression of specific phospholipases A₂ in preeclamptic placentas when compared to normotensive controls. In brief, elevated levels of free F₂-isoprostanes in addition to higher expression of thromboxane A₂ receptors could be involved in the local placental hypertension in preeclampsia.

CONTEXT: Recent studies have considered the role of inflammation in the development of both cardiovascular disease (CVD) and musculoskeletal conditions, such as rheumatoid arthritis. Studies suggest that inflammation plays a significant role in the development of cardiovascular disease. In conditions of chronic pain, as with rheumatoid arthritis, inflammation has also been noted through elevated levels of inflammatory markers. There are currently no studies that examine the possible connection between inflammatory markers related to increased risk of cardiovascular disease and nonspecific chronic musculoskeletal pain (NCMP). OBJECTIVE: The purpose of this study was to determine whether urinary levels of microalbumin (MA) and F2-isoprostanes (F2-isoPs), inflammatory biomarkers associated with increased CVD risk, are elevated in persons with NCMP compared to nonpain case controls. NCMP refers to pain present for more than 3 days per week and for more than 12 weeks. This type of pain is not due to injury but is associated with interference of normal function. DESIGN: Nonrandomized observational study. METHODS: A cross-sectional study with 120 participants (60 pain subjects, 60 nonpain case-controls). A single first-morning void urine sample was collected from each subject. Urine specific gravity and total volume were measured and then a sample was sent to a lab for analysis of MA and F2-isoPs. Inflammatory biomarker levels in the pain and nonpain groups were compared. RESULTS: There were no significant differences in F2-isoPs levels between the chronic pain group (0.65ng/mg ± 0.05) and the nonpain group (0.80ng/mg ± 0.07) (95% CI (-0.32, 0.03)). However, MA levels were significantly higher in the chronic pain group (2.41mg/g ± 0.24) compared to the nonpain group (1.88mg/g ± 0.14) (95% CI (0.34, 1.68)). MACR levels were also significantly higher in the chronic pain group (2.07mg/g ± 0.31) compared to the nonpain group (1.14mg/g ± 0.14) (95% CI (0.32, 1.64)). CONCLUSION: These findings suggest a possible link between at least one inflammatory marker (microalbumin) and NCMP. This in turn allows for a limited but reasonable inference that NCMP may be a risk factor for cardiovascular disease, mediated through the MA inflammatory biomarker. Further research is needed to more fully understand the possible connection between NCMP and CVD.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2013-2014. / Un stress oxydatif survient lorsqu’il y a surproduction de dérivés actifs de l’oxygène par rapport aux défenses antioxydantes. Ce déséquilibre est associé, entre autres, à la prééclampsie, une pathologie de la grossesse. Les F2-isoprostanes regroupent soixante-quatre isomères issus de la peroxydation de l’acide arachidonique. Ceux-ci sont reconnus comme étant les biomarqueurs les plus fiables du stress oxydatif in vivo. Une méthode d’analyse par chromatographie liquide couplée à la spectrométrie de masse en tandem pour le dosage de sept isomères de F2-isoprostanes dans des échantillons de plasma, de sang et de membranes érythrocytaires a été mise au point et validée. Les F2-isoprostanes dans le plasma ont été corrélés positivement avec plusieurs acides gras trans plasmatiques au troisième trimestre de la grossesse. Contre toute attente, les F2-isoprostanes du plasma, du sang et des membranes érythrocytaires sont moins abondants en prééclampsie par rapport aux contrôles en fin de grossesse. / An oxidative stress is defined as an imbalance between the production of reactive oxygen species and antioxidant defenses of the organism. This imbalance has been associated with preeclampsia, a pathology of the mid-to-late pregnancy. Peroxidation of arachidonic acid generates sixty-four isomers of F2-isoprostanes. The latter are recognized as the most reliable biomarkers of oxidative stress in vivo. A method using liquid chromatography tandem mass spectrometry (HPLC-MS/MS) for the determination of seven isomers of F2-isoprostanes in plasma samples, whole blood and erythrocyte membranes has been developed and validated. The F2-isoprostanes correlated positively with several trans fatty acids in plasma at end of the pregnancy. Unexpectedly, F2-isoprostanes were less abundant in preeclampsia than in control pregnancies at the third trimester.

Fresh isolated erythrocyte ghost membranes and erythrocyte suspensions were incubated with an organic hydroperoxide, tert-butyl hydroperoxide, to establish the in vitro oxidative stress models. Circulating erythrocytes from normal individuals were fractionated into subpopulations of different ages by ultracentrifugation and used as an in vivo model. In these models, membrane iPF2alpha-III content accumulation was proportional to oxidative stress and correlated with decreased membrane fluidity. In circulating erythrocytes, membrane iPF2alpha-III increased with age and inversely correlated with membrane fluidity only in the core region. / Oxidative stress is involved in the pathophysiology of a wide variety of human diseases. Isoprostanes, a family of prostaglandin derivatives, are mainly derived from free radical peroxidation of specific polyunsaturated fatty acids (PUFA). Measurement of F2-isoprostanes (F2-iPs) or one specific biologically active isomer (iPF2alpha-III) is considered to be a reliable lipid peroxidation marker in human diseases. However, the association observed between increased plasma/urine F2-iPs and diseases does not necessarily reflect tissue oxidative damages. Circulating erythrocytes, a tissue with limited biosynthetic capacity and poor repair mechanism, would offer a number of advantages for assessment of in vivo oxidative damages. In this thesis, human erythrocyte membrane iPF2alpha-III content was investigated as a new marker for in vivo oxidative stress assessment. Membrane fluidity was used as an indirect marker of cellular function. / To use membrane iPF2alpha-III in a human disease with known oxidative stress burden, 49 Chinese patients on long-term haemodialysis and 31 healthy Chinese subjects were recruited. Both plasma and membrane iPF 2alpha-III showed that haemodialysis patients had increased oxidative stress. Only membrane iPF2alpha-III, but not the conventional used plasma iPF2alpha-III, correlated with membrane fluidity. Furthermore, the significant inverse correlation between membrane iPF 2alpha-III and the core region of membrane fluidity was observed for this group of patients too. Since membrane iPF2alpha-III was shown to provide a link between oxidative stress and erythrocyte function, it would be considered as a new marker of in vivo erythrocyte oxidative stress assessment. (Abstract shortened by UMI.) / Yu Xiongwen. / "July 2005." / Advisers: Wai Kei Christopher Lam; Chung Shun Ho. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3724. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 198-223). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

The aims were to investigate oxidative stress (I), angiogenesis (II) and inflammation (III-IV) in healthy women during pregnancy and postpartum. Oxidative stress was estimated by measurement of 8-iso-PGF2α and the antioxidants α- and γ-tocopherol. The angiogenic factors PlGF, VEGF-A and the antiangiogenic factor sFlt1 were measured to estimate angiogenesis. PTX3, IL-6, TNF-α and a PGF2α metabolite were measured to estimate inflammation. Out of 52 included women, 15 had minor pregnancy complications and 37 were classified as normal. In study III data from all 52 women were used. For the other studies (I, II and IV) only data from the 37 women with normal pregnancy were used. Pregnancy was associated with increased levels of 8-iso-PGF2α with advancing gestational age. The median postpartum value corresponded to values observed in early gestation and a significant decrease was observed from late pregnancy to postpartum. Lipid-adjusted α- and γ-tocopherol levels decreased with advancing gestational age (I). PlGF increased from early pregnancy until weeks 29–30 and thereafter decreased until week 40. sFlt1 levels were relatively constant until weeks 29–30, when they increased, reaching a peak at weeks 39–40. Postpartum levels were low. The sFlt1:PlGF ratio decreased from weeks 9–12, was constantly low from weeks 19–20 to 37–38 and then increased to weeks 39–40. VEGF-A was detectable in only 8 % of the samples during pregnancy and in 64 % postpartum (II). There was a continuous increase of PTX3 as pregnancy progressed. The increase was most evident after week 31 with the highest levels just before delivery (III). IL-6 increased throughout pregnancy and remained high postpartum. No change in TNF-α could be seen with advancing gestational age or postpartum. The PGF2α metabolite levels increased throughout pregnancy and decreased postpartum (IV). In conclusion, normal pregnancy is associated with mild oxidative stress and inflammation. This might have physiological effects for normal pregnancy development. By delineating how these mediators of oxidative stress, angiogenesis and inflammation fluctuate throughout normal pregnancy and postpartum, we have established a reference for studies of these factors in pregnancy complications.

Orientador: Patrícia Moriel / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T00:37:20Z (GMT). No. of bitstreams: 1 Freitas_BetaniadeJesuseSilvadeAlmendra_D.pdf: 2657931 bytes, checksum: d4646bbc60ccc13e11ca7d806b4f75dc (MD5) Previous issue date: 2014 / Resumo: Estudos acerca da influência do estresse oxidativo sobre o equilíbrio cutâneo, sobretudo por seus efeitos devastadores sobre a integridade da pele, são essenciais para a proposição de estratégias de intervenção preventivas para o desenvolvimento do câncer de pele. O objetivo do estudo foi comparar o estresse oxidativo de indivíduos que tiveram e não tiveram câncer de pele não melanoma e avaliar o efeito da suplementação combinada de vitaminas C, E e mineral Zinco no estresse oxidativo de indivíduos que apresentaram a doença. O estudo foi dividido em duas fases: a fase 1 foi um estudo transversal com controles, cuja população foi constituída por pessoas saudáveis (n = 24) e o grupo caso constituído por indivíduos que apresentaram câncer de pele não melanoma já submetidas a tratamento cirúrgico (n = 60). E a fase 2, um ensaio clínico randomizado e duplo cego, no qual os pacientes do grupo caso foram randomizados em dois subgrupos: grupo placebo (n = 34) e grupo suplementado (n = 26) com 50 mg de vitamina C, 60 mg de vitamina E e 40 mg de Zinco durante 8 semanas. As amostras de sangue dos sujeitos foram obtidas no período basal e após intervenção para a avaliação dos biomarcadores de estresse oxidativo (F2-isoprostano, nitrito, substâncias reativas ao ácido tiobarbitúrico (TBARS) e capacidade antioxidante total). O consumo alimentar habitual e o estado nutricional dos sujeitos foram avaliados. Para identificação dos fatores associados ao câncer de pele foi utilizada a análise de regressão logística univariada e multivariada. O nível de significância adotado para este estudo foi de 5%. A maioria dos pacientes estudados foram do sexo feminino com idade superior a 50 anos. Os pacientes do grupo caso apresentaram mais elevadas concentrações séricas dos biomarcadores de estresse oxidativo, sendo que as concentrações de F2-isoprostano estavam significativamente mais elevadas em comparação com os controles. Após suplementação não houve diferença estatística entre os grupos placebo e suplementado em relação aos marcadores de estresse oxidativo. A idade e o F2-isoprostano podem ser marcadores de risco para o câncer de pele não melanoma, a cada ano a mais para o fator idade aumenta em 12% a chance de câncer e cada unidade a mais na medida do marcador aumenta em 4% a chance de câncer. Os resultados mostraram prevalência de sobrepeso no grupo controle com diferença estatística significativa em relação ao grupo caso. As concentrações dietéticas dos minerais antioxidantes zinco, cobre e selênio do grupo caso foram estatisticamente inferiores em relação aos controles e não houve diferença estatística nas concentrações dietéticas dos nutrientes antioxidantes entre os grupos suplementado e placebo. Este estudo sugere que pessoas diagnosticadas com câncer de pele não melanoma e que no momento da realização da pesquisa não mais apresentavam a doença, mostravam elevado estresse oxidativo, quando comparadas a pessoas saudáveis. A suplementação de antioxidantes pelo período de tempo realizado no trabalho não provocou redução significativa nas concentrações dos marcadores de estresse oxidativo dos pacientes. O estudo ainda sugere que o marcador de estresse oxidativo F2-isoprostano pode ser utilizado como um fator de risco para o desenvolvimento do câncer de pele não melanoma / Abstract: Studies investigating the influence of oxidative stress on skin homeostasis, especially for its devastating effects on skin integrity, are essential for the development of preventive intervention strategies for skin cancer. The goal of this study was to compare the concentrations of oxidative stress biomarkers in blood between individuals with and without non-melanoma skin cancer and evaluate the effect of combined supplementation with vitamins C, E, and the mineral zinc on oxidative stress in skin-cancer patients. The study was divided into two stages: stage 1 was cross-sectional study with controls, whose population consisted of healthy individuals (n = 24) and the case group included individuals who had non-melanoma skin cancer undergoing surgery (n = 60). And the second phase a randomized, double blind clinical trial where patients in the case group were randomized into two subgroups: placebo (n =34) and a supplemented group (n = 26) who received 50 mg of vitamin C, 60 mg of vitamin E, and 40 mg of zinc for 8 wk. Blood samples were taken from the subjects before and after intervention to evaluate levels of oxidative stress biomarkers (F2-isoprostane, nitrite, thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity. The usual food consumption and nutritional state of the subjects were also evaluated. Multivariate and univariate logistics regression analysis were used to identify factors associated with the development of skin cancer. The level of significance adopted for this study was 5%. The majority of participants were women over the age of 50. The patients in the case group had higher serum concentrations of oxidative stress biomarkers, and the levels of F2-isoprostane were significantly higher than the controls. After antioxidant supplementation there was no statistical difference in the markers of oxidative stress among the placebo and supplemented groups. Age and F2-isoprostane may be effective biomarkers for estimating the risk of non-melanoma skin cancer development. Moreover, the risk of cancer increases with age at a rate of 12% per year, while an increase in concentration of these biomarker in blood increases the risk of cancer by 4%. These results showed a prevalence of excess weight in the control group with significant statistical difference from the case group. The dietary intake of the mineral antioxidants zinc, copper, and selenium of the case group were significantly lower than the control group, and there was no statistical difference in the dietary intake of the antioxidant nutrients among the supplemented and placebo groups. This study suggests that people diagnosed with non-melanoma skin cancer and those in remission at the time of the study, exhibited higher concentration oxidative stress than healthy individuals. The antioxidant supplementation by period the work performed did not cause significant reduction in serum concentrations of oxidative stress biomarkers of the patients. The results suggest that the concentration of the oxidative stress biomarker, F2-isoprostane, may serve as risk factor for non-melanoma skin cancer development / Doutorado / Ciencias Biomedicas / Doutora em Ciências Médicas

<p>Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of ageing, but its measurement <i>in vivo</i> has been difficult. The aim of this thesis was to evaluate methods for measurement of lipid peroxidation <i>in vivo</i> that are suitable for clinical investigations, and to apply these methods in animal and human studies investigating basal conditions and situations associated with increased lipid peroxidation.</p><p>The ferrous oxidation in xylenol orange assay for quantification of total plasma lipid hydroperoxides was re-evaluated regarding sample handling and storage. It was shown to be a useful tool for analyses of fresh but not stored plasma samples.</p><p>A methodology for measurement of the total amount (sum of free and esterified) of an F₂-isoprostane, 8-iso-prostaglandin F_2α, in tissues using alkaline hydrolysis in combination with an existing radioimmunoassay was developed. High levels of 8-iso-prostaglandin F_2α in rat liver tissue were quantified by this technique both at basal conditions and in an experimental model of increased lipid peroxidation induced by carbon tetrachloride.</p><p>Supplementation with vitamin E to rats decreased both non-enzymatic and enzymatic lipid peroxidation as measured by 8-iso-prostaglandin F_2α and a major prostaglandin F_2α metabolite. This was verified both in the urine at basal conditions, and in the urine and liver tissue after carbon tetrachloride induced lipid peroxidation.</p><p>In a randomised cross-over study in humans, a rapeseed oil-based diet with an increased proportion of easily oxidised polyunsaturated fatty acids was compared to a control diet rich in saturated fats. The rapeseed oil-based diet did not seem to increase the degree of lipid peroxidation in plasma and urine as measured by 8-iso-prostaglandin F_2α, hydroperoxides and malondialdehyde, presumably due to a sufficient content of antioxidants in the rapeseed oil diet.</p><p>In conclusion, the simultaneous measurement of several biomarkers of lipid peroxidation is a promising approach for future studies investigating the possible role of lipid peroxidation <i>in vivo</i> under basal conditions and in the pathology of diseases.</p>

<p>Numerous diseases are associated with reduced antioxidant defence and oxidative stress. The antioxidant defence includes dietary and endogenous antioxidants and involves complex interactions between them. The effects of dietary factors on antioxidant status and oxidative stress of healthy humans were investigated in the studies described in this thesis. Assays of plasma antioxidant capacity encompass interactions between various antioxidants. Although uric acid has an unclear function as an antioxidant, it is a major determinant of antioxidant capacity. We measured antioxidant capacity in the presence and absence of uric acid to provide more information on the application of measures of antioxidant capacity. Individuals with high dietary intakes of various antioxidants and antioxidant rich foods, especially when combined, had higher plasma antioxidant capacities than those with lower antioxidant intakes. However, there were no associations between dietary intake of antioxidants or antioxidant rich foods and the plasma concentration of F₂-isoprostanes, which is considered a reliable biomarker for oxidative stress. Intakes of various doses of a mixture of bilberry juice and black tea, rich in flavonoids for four weeks, increased antioxidant capacity in some groups, but urine levels of F₂-isoprostanes were not affected. There were substantial individual variations in responses to the drinks related to baseline antioxidant capacity. Supplementation with eicosapentaenoic acid and docosahexaenoic acid decreased the plasma levels of F₂-isoprostanes, but not prostaglandin F_2α formation or antioxidant capacity. </p><p>It was concluded that a high intake of foods rich in antioxidants is related to improved antioxidant status. After intake of foods rich in antioxidants, the antioxidant status may increase, but with considerable individual variation in the responses, which warrants further investigation. Lipid peroxidation <i>in vivo</i> is not easily affected by dietary antioxidants in healthy humans. Although n-3 fatty acids are highly unsaturated, they reduce nonenzymatic free radical-catalyzed lipid peroxidation, but not enzymatic lipid peroxidation.</p>

Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of ageing, but its measurement in vivo has been difficult. The aim of this thesis was to evaluate methods for measurement of lipid peroxidation in vivo that are suitable for clinical investigations, and to apply these methods in animal and human studies investigating basal conditions and situations associated with increased lipid peroxidation. The ferrous oxidation in xylenol orange assay for quantification of total plasma lipid hydroperoxides was re-evaluated regarding sample handling and storage. It was shown to be a useful tool for analyses of fresh but not stored plasma samples. A methodology for measurement of the total amount (sum of free and esterified) of an F2-isoprostane, 8-iso-prostaglandin F2α, in tissues using alkaline hydrolysis in combination with an existing radioimmunoassay was developed. High levels of 8-iso-prostaglandin F2α in rat liver tissue were quantified by this technique both at basal conditions and in an experimental model of increased lipid peroxidation induced by carbon tetrachloride. Supplementation with vitamin E to rats decreased both non-enzymatic and enzymatic lipid peroxidation as measured by 8-iso-prostaglandin F2α and a major prostaglandin F2α metabolite. This was verified both in the urine at basal conditions, and in the urine and liver tissue after carbon tetrachloride induced lipid peroxidation. In a randomised cross-over study in humans, a rapeseed oil-based diet with an increased proportion of easily oxidised polyunsaturated fatty acids was compared to a control diet rich in saturated fats. The rapeseed oil-based diet did not seem to increase the degree of lipid peroxidation in plasma and urine as measured by 8-iso-prostaglandin F2α, hydroperoxides and malondialdehyde, presumably due to a sufficient content of antioxidants in the rapeseed oil diet. In conclusion, the simultaneous measurement of several biomarkers of lipid peroxidation is a promising approach for future studies investigating the possible role of lipid peroxidation in vivo under basal conditions and in the pathology of diseases.

Numerous diseases are associated with reduced antioxidant defence and oxidative stress. The antioxidant defence includes dietary and endogenous antioxidants and involves complex interactions between them. The effects of dietary factors on antioxidant status and oxidative stress of healthy humans were investigated in the studies described in this thesis. Assays of plasma antioxidant capacity encompass interactions between various antioxidants. Although uric acid has an unclear function as an antioxidant, it is a major determinant of antioxidant capacity. We measured antioxidant capacity in the presence and absence of uric acid to provide more information on the application of measures of antioxidant capacity. Individuals with high dietary intakes of various antioxidants and antioxidant rich foods, especially when combined, had higher plasma antioxidant capacities than those with lower antioxidant intakes. However, there were no associations between dietary intake of antioxidants or antioxidant rich foods and the plasma concentration of F2-isoprostanes, which is considered a reliable biomarker for oxidative stress. Intakes of various doses of a mixture of bilberry juice and black tea, rich in flavonoids for four weeks, increased antioxidant capacity in some groups, but urine levels of F2-isoprostanes were not affected. There were substantial individual variations in responses to the drinks related to baseline antioxidant capacity. Supplementation with eicosapentaenoic acid and docosahexaenoic acid decreased the plasma levels of F2-isoprostanes, but not prostaglandin F2α formation or antioxidant capacity. It was concluded that a high intake of foods rich in antioxidants is related to improved antioxidant status. After intake of foods rich in antioxidants, the antioxidant status may increase, but with considerable individual variation in the responses, which warrants further investigation. Lipid peroxidation in vivo is not easily affected by dietary antioxidants in healthy humans. Although n-3 fatty acids are highly unsaturated, they reduce nonenzymatic free radical-catalyzed lipid peroxidation, but not enzymatic lipid peroxidation.