n-3 fatty acids: antiatherosclerotic effects

Effect of omega-3 polyunsaturated fatty acids in modulation of vascular tone under physiological and pathological conditions

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are mainly found in marine fish oils and commercially available fish oil supplements. Several studies have documented that n-3 PUFAs can reduce the risk of cardiovascular diseases through anti-inflammatory, anti-thrombotic, and anti-atherosclerotic properties. Notably, regulation of vascular tone is one of the most important bases of cardiovascular health and especially for maintaining blood pressure within optimal physiological ranges. Recent clinical and animal studies indicate an association between n-3 PUFAs and vascular functions. In this regard, many clinical trials and basic experimental studies have been conducted so far to investigate the influence of n-3 PUFAs on vascular tone. In this review, we have summarized the results obtained from both clinical and basic studies that evaluated the effect of n-3 PUFAs under physiological and pathological conditions. Moreover, we also focus on verifying the underlying basic molecular mechanism of n-3 PUFAs on the vascular system.

Improvement in serum lipids and liver morphology after supplementation of the diet with fish oil is more evident under regular feeding conditions than under high-fat or mixed diets in rats

BACKGROUND

Dietary n- 3 polyunsaturated fatty acids (PUFAs) have a role in preventing cardiovascular and hepatic diseases. However, their effects might differ significantly depending on individual dietary patterns. The aim of the present study was to evaluate the effects of dietary supplementation with ω-3 fatty acids (FA), administered in different schedules, on hepatic and aortic histological structure, lipid profile, and body weight (BW) in male Wistar rats under standard (SD), high-fat diet (HFD) and mixed feeding conditions.

METHODS

PUFA treatment consisted of the administration of 50 mg/kg fish oil (FO) daily by oral gavage. HFD was obtained by adding a suspension of 4% cholesterol, thiouracil and cholic acid to the animals' drinking water. The rats were maintained on the diets for 6 weeks, and different schedules of PUFA administration were used. At 14, 28, and 42 days, the morphology of liver and aortic samples and the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG) were assessed.

RESULTS

The HFD groups exhibited significant hyperlipidemia and aortic inflammation, with progression to atherogenesis after 6 weeks. Administration of PUFAs slightly attenuated the aortic changes in these groups and reduced the liver's tendency to steatosis. FO-induced metabolic improvement was more evident in SD than in HFD rats. For instance, after the first 2 weeks, SD animals that received PUFAs had significantly increased HDL levels vs. controls (62.375 ± 4.10 vs. 52.625 ± 8.38 mg/dL, P < 0.05), but HFD rats did not, and decreased TG levels were observed exclusively in the SD rats (57.6 ± 4.09 vs. 66 ± 4.69 mg/dL, P < 0.05). After 6 weeks of n- 3 PUFA administration, LDL was significantly lower in the SD rats than in controls (13.67 ± 4.13 vs. 30.83 ± 2.86 mg/dL, P < 0.001), but the decrease in the HFD rats, although significant (49.17 ± 5.85 mg/dL vs. 57.17 ± 4.96 g/dL, P < 0.05), was not as marked. In the mixed-diet groups, administration of 50 mg/kg/day FO for 14 days under SD conditions following 4 weeks of HFD slightly decreased TG (86.625 ± 11.67 vs. 73 ± 4.52 mg/dL, P < 0.05) and increased HDL (45.875 ± 5.28 vs. 56 ± 3.16 mg/dL). However, in these animals, n-3 PUFA administration had no effect on LDL or TC. Administration of half of the above dose failed to improve any biochemical parameters. FO protected against excessive weight gain mainly under SD conditions.

CONCLUSIONS

The results show that FO confers more protection against cardiovascular risk factors (increased LDL and TG, decreased HDL) and liver lipid accumulation when given to rats consuming regular diets than when given to rats consuming a high-fat diet. This argues that priority should be given to consumption of a healthy diet rather than to the use of supplements. The effectiveness of n-3 PUFAs might be reduced in the case of hyperlipidic intake or after consumption of a high-fat diet.

Nutrigenomic Functions of PPARs in Obesogenic Environments

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that mediate the effects of several nutrients or drugs through transcriptional regulation of their target genes in obesogenic environments. This review consists of three parts. First, we summarize current knowledge regarding the role of PPARs in governing the development of white and brown/beige adipocytes from uncommitted progenitor cells. Next, we discuss the interactions of dietary bioactive molecules, such as fatty acids and phytochemicals, with PPARs for the modulation of PPAR-dependent transcriptional activities and metabolic consequences. Lastly, the effects of PPAR polymorphism on obesity and metabolic outcomes are discussed. In this review, we aim to highlight the critical role of PPARs in the modulation of adiposity and subsequent metabolic adaptation in response to dietary challenges and genetic modifications. Understanding the changes in obesogenic environments as a consequence of PPARs/nutrient interactions may help expand the field of individualized nutrition to prevent obesity and obesity-associated metabolic comorbidities.

Sexual dimorphism of lipid metabolism in very long-chain acyl-CoA dehydrogenase deficient (VLCAD-/-) mice in response to medium-chain triglycerides (MCT)

Medium-chain triglycerides (MCT) are widely applied in the treatment of long-chain fatty acid oxidation disorders. Previously it was shown that long-term MCT supplementation strongly affects lipid metabolism in mice. We here investigate sex-specific effects in mice with very-long-chain-acyl-CoA dehydrogenase (VLCAD) deficiency in response to a long-term MCT modified diet. We quantified blood lipids, acylcarnitines, glucose, insulin and free fatty acids, as well as tissue triglycerides in the liver and skeletal muscle under a control and an MCT diet over 1 year. In addition, visceral and hepatic fat content and muscular intramyocellular lipids (IMCL) were assessed by in vivo(1)H magnetic resonance spectroscopy (MRS) techniques. The long-term application of an MCT diet induced a marked alteration of glucose homeostasis. However, only VLCAD-/- female mice developed a severe metabolic syndrome characterized by marked insulin resistance, dyslipidemia, severe hepatic and visceral steatosis, whereas VLCAD-/- males seemed to be protected and only presented with milder insulin resistance. Moreover, the highly saturated MCT diet is associated with a decreased hepatic stearoyl-CoA desaturase 1 (SCD1) activity in females aggravating the harmful effects of a saturated MCT diet. Long-term MCT supplementation deeply affects lipid metabolism in a sexual dimorphic manner resulting in a severe metabolic syndrome only in female mice. These findings are striking since the first signs of insulin resistance already occur in female VLCAD-/- mice during their reproductive period. How these metabolic adaptations are finally regulated needs to be determined. More important, the relevance of these findings for humans under these dietary modifications needs to be investigated.

ω-3 fatty acid differentially modulated serum levels of IGF1 and IGFBP3 in men with CVD: a randomized, double-blind placebo-controlled study

OBJECTIVE

Studies have reported elevated serum insulin-like growth factor (IGF)-1 levels followed by ω-3 supplementation in various groups. Considering decreased level of IGF1 in patients with cardiovascular disease (CVD) and protective effects of IGF1 against CVD progression and myocardial infarctions mortality, this study was performed with the aim of determining effects of ω-3 supplementation on serum levels and gene expression of IGF1 and IGF binding protein-3 (IGFBP3) in men with CVD.

METHODS

Sixty-two middle-aged (55.9 ± 6.5 y) non-obese men with CVD followed the study protocol in two groups of ω-3 (n = 31) or placebo (n = 31) supplementation. Participants took ω-3 supplement or placebo (edible paraffin) for 8 wk and were asked not to change their diet or physical activity plan. Anthropometric and lipid profile characteristics, serum IGF1, serum IGFBP3 and also IGF1 and IGFBP3 gene expression in peripheral blood mononuclear cells (PBMCs) were measured in all participants before and after the intervention. Statistical analyses were performed using SPSS software.

RESULTS

There were no significant differences between the two study groups in age and body mass index at baseline. The groups also had no difference in baseline serum low-density lipoprotein, high-density lipoprotein, very low-density lipoprotein, triacylglycerols, and IGF1. Compared with placebo, ω-3 supplementation increased serum IGF1 levels (P = 0.01), and decreased serum level of IGFBP3 (P = 0.02). There was a trending toward an increase in IGF1 expression and nonsignificant decrease in IGFBP3 expression.

CONCLUSIONS

ω-3 supplementation in patients with CVD increases serum IGF1 levels and decreases serum IGFBP3. Further research is warranted to investigate the underlying mechanisms.

Plasma n-3 and n-6 fatty acids and inflammatory markers in Chinese vegetarians

Background

Polyunsaturated fatty acid (PUFA) intake favorably affects chronic inflammatory-related diseases such as cardiovascular disease; however, the relationship between the PUFA and inflammatory factors in the healthy vegetarians were not clear. We aimed to investigate the plasma fatty acids status, and its association with plasma inflammatory factors in Chinese vegetarians and omnivores.

Methods

A total of 89 male vegetarians and 106 male omnivores were participated the study. Plasma concentrations of inflammatory factors were detected by ELISA, and as standard methods fatty acids were extracted and determined by chromatography.

Results

Compared with omnivores, vegetarians have significant higher interleukin-6 (IL-6), plasma n-6 PUFA, n-6/n-3, and 18:3n-3; while they have significant lower leukotriene B4 (LTB4), cyclo-oxygenase-2 (COX2) and prostaglandin E2 (PGE2), 20:5n-3, 22:5n-3, 22:6n-3, and n-3 PUFA. In vegetarians, plasma 20:4n-6 was significant positively related to TNF-α. LTB4 was significantly positively related to plasma 22:6n-3, and negatively associated with n-6 PUFA.

Conclusion

Vegetarians have higher plasma n-6 PUFA and IL-6, but lower LTB4, n-3 PUFA, 22:6n-3, COX2 and PGE2 levels. It would seem appropriate for vegetarians to increase their dietary n-3 PUFA, while reduce dietary n-6 PUFA and thus reduce the risk of chronic inflammatory-related diseases.

Triolein and trilinolein ameliorate oxidized low-density lipoprotein-induced oxidative stress in endothelial cells

Uptake of oxidized low-density lipoprotein by endothelial cells is a critical step for the initiation of atherosclerosis. Triacylglycerol uptake in these cells is understood to be a part of the process. The present investigation, comparison among the effects of simple acylglycerol, including tristearin, triolein, and trilinolein, upon oxidized low-density lipoprotein -induced oxidative stress was undertaken. Results indicated that trilinolein (78 % ± 0.02) and triolein (90 % ± 0.01) increased cell viability of endothelial cells exposed to oxidized low-density lipoprotein, whereas tristearin decreased the cell viability (55 % ± 0.03) (P < 0.05). Oxidized low-density lipoprotein treatment significantly increased apoptosis (23 %), compared to cells simultaneously exposed to trilinolein (19 %) or triolein (16 %), where apoptosis was reduced (P < 0.05). On the other hand, exposure to tristearin further increased oxidized low-density lipoprotein -induced cell apoptosis (34 %). Treatment with trilinolein or triolein on oxidized low-density lipoprotein -stimulated endothelial cells inhibited the expression of ICAM-1 and E-selectin mRNA. Moreover, both trilinolein and triolein demonstrated a strong antioxidant response to oxidative stress caused by oxidized low-density lipoprotein. Taken together, the results indicate trilinolein and triolein possess anti-inflammatory properties, which are mediated via the antioxidant defense system.

Lipid profiling following intake of the omega 3 fatty acid DHA identifies the peroxidized metabolites F4-neuroprostanes as the best predictors of atherosclerosis prevention

The anti-atherogenic effects of omega 3 fatty acids, namely eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) are well recognized but the impact of dietary intake on bioactive lipid mediator profiles remains unclear. Such a profiling effort may offer novel targets for future studies into the mechanism of action of omega 3 fatty acids. The present study aimed to determine the impact of DHA supplementation on the profiles of polyunsaturated fatty acids (PUFA) oxygenated metabolites and to investigate their contribution to atherosclerosis prevention. A special emphasis was given to the non-enzymatic metabolites knowing the high susceptibility of DHA to free radical-mediated peroxidation and the increased oxidative stress associated with plaque formation. Atherosclerosis prone mice (LDLR^−/−) received increasing doses of DHA (0, 0.1, 1 or 2% of energy) during 20 weeks leading to a dose-dependent reduction of atherosclerosis (R² = 0.97, p = 0.02), triglyceridemia (R² = 0.97, p = 0.01) and cholesterolemia (R² = 0.96, p<0.01). Targeted lipidomic analyses revealed that both the profiles of EPA and DHA and their corresponding oxygenated metabolites were substantially modulated in plasma and liver. Notably, the hepatic level of F₄-neuroprostanes, a specific class of DHA peroxidized metabolites, was strongly correlated with the hepatic DHA level. Moreover, unbiased statistical analysis including correlation analyses, hierarchical cluster and projection to latent structure discriminate analysis revealed that the hepatic level of F₄-neuroprostanes was the variable most negatively correlated with the plaque extent (p<0.001) and along with plasma EPA-derived diols was an important mathematical positive predictor of atherosclerosis prevention. Thus, oxygenated n-3 PUFAs, and F₄-neuroprostanes in particular, are potential biomarkers of DHA-associated atherosclerosis prevention. While these may contribute to the anti-atherogenic effects of DHA, further in vitro investigations are needed to confirm such a contention and to decipher the molecular mechanisms of action.

Atherosclerosis, dyslipidemia, and inflammation: the significant role of polyunsaturated Fatty acids

Phospholipids play an essential role in cell membrane structure and function. The length and number of double bonds of fatty acids in membrane phospholipids are main determinants of fluidity, transport systems, activity of membrane-bound enzymes, and susceptibility to lipid peroxidation. The fatty acid profile of serum lipids, especially the phospholipids, reflects the fatty acid composition of cell membranes. Moreover, long-chain n-3 polyunsatured fatty acids decrease very-low-density lipoprotein assembly and secretion reducing triacylglycerol production. N-6 and n-3 polyunsatured fatty acids are the precursors of signalling molecules, termed "eicosanoids," which play an important role in the regulation of inflammation. Eicosanoids derived from n-6 polyunsatured fatty acids have proinflammatory actions, while eicosanoids derived from n-3 polyunsatured fatty acids have anti-inflammatory ones. Previous studies showed that inflammation contributes to both the onset and progression of atherosclerosis: actually, atherosclerosis is predominantly a chronic low-grade inflammatory disease of the vessel wall. Several studies suggested the relationship between long-chain n-3 polyunsaturated fatty acids and inflammation, showing that fatty acids may decrease endothelial activation and affect eicosanoid metabolism.

LC/ESR/MS study of pH-dependent radical generation from 15-LOX-catalyzed DPA peroxidation

Docosapentaenoic acid (DPA) is a unique fatty acid that exists in two isomeric forms (n-3 and n-6), which differ in their physiological behaviors. DPA can undergo free radical-mediated peroxidation via lipoxygenase (LOX). 15-LOX, one of the LOX isomers, has received much attention in cancer research because of its very different expression level in normal tissues compared to tumors and some bioactive fatty acid metabolites modulating the tumorigenic pathways in cancer. However, the mechanism linking 15-LOX, DPA metabolites, and their bioactivities is still unclear, and the free radicals generated in DPA peroxidation have never been characterized. In this study, we have studied radicals formed from both soybean and human cellular (PC3-15LOS cells) 15-LOX-catalyzed peroxidation of DPAs at various pH's using a combination of LC/ESR/MS with the spin trapping technique. We observed a total of three carbon-centered radicals formed in 15-LOX-DPA (n-3) stemming from its 7-, 17-, and 20-hydroperoxides, whereas only one formed from 17-hydroperoxide in DPA (n-6). A change in the reaction pH from 8.5 (15-LOX enzyme optimum) to 7.4 (physiological) and to 6.5 (tumor, acidic) not only decreased the total radical formation but also altered the preferred site of oxygenation. This pH-dependent alteration of radical formation and oxygenation pattern may have significant implications and provide a basis for our ongoing investigations of LOXs as well as fatty acids in cancer biology.

The fatty acid oxidation product 15-A3t-isoprostane is a potent inhibitor of NFκB transcription and macrophage transformation

Fatty acids such as eicosapentaenoic acid (EPA) have been shown to be beneficial for neurological function and human health. It is widely thought that oxidation products of EPA are responsible for biological activity, although the specific EPA peroxidation product(s) which exert these responses have not yet been identified. In this work we provide the first evidence that the synthesized representative cyclopentenone IsoP, 15-A(3t)-IsoP, serves as a potent inhibitor of lipopolysaccharide-stimulated macrophage activation. The anti-inflammatory activities of 15-A(3t)-IsoP were observed in response not only to lipopolysaccharide, but also to tumor necrosis factor alpha and IL-1b stimulation. Subsequently, this response blocked the ability of these compounds to stimulate nuclear factor kappa b (NFκB) activation and production of proinflammatory cytokines. The bioactivity of 15-A(3t)-IsoP was shown to be dependent upon an unsaturated carbonyl residue which transiently adducts to free thiols. Site directed mutagenesis of the redox sensitive C179 site of the Ikappa kinase beta subunit, blocked the biological activity of 15-A(3t)-IsoP and NFκB activation. The vasoprotective potential of 15-A(3t)-IsoP was underscored by the ability of this compound to block oxidized lipid accumulation, a critical step in foam cell transformation and atherosclerotic plaque formation. Taken together, these are the first data identifying the biological activity of a specific product of EPA peroxidation, which is formed in abundance in vivo. The clear mechanism linking 15-A(3t)-IsoP to redox control of NFκB transcription, and the compound's ability to block foam cell transformation suggest that 15-A(3t)-IsoP provides a unique and potent tool to provide vaso- and cytoprotection under conditions of oxidative stress.

Consumption of polyunsaturated fatty acids, fish, and nuts and risk of inflammatory disease mortality

BACKGROUND

n-3 (omega-3) Polyunsaturated fatty acids (PUFAs), fish, and nuts can regulate inflammatory processes and responses.

OBJECTIVE

We investigated whether dietary intakes of PUFAs [n-3, n-6 (omega-6), and α-linolenic acid], fish, and nuts were associated with 15-y mortality attributed to noncardiovascular, noncancer inflammatory diseases.

DESIGN

The analyses involved 2514 participants aged ≥49 y at baseline. Dietary data were collected by using a semiquantitative food-frequency questionnaire, and PUFA, fish, and nut intakes were calculated. Inflammatory disease mortality was confirmed from the Australian National Death Index.

RESULTS

Over 15 y, 214 subjects died of inflammatory diseases. Women in the highest tertiles of total n-3 PUFA intake, compared with those in the lowest tertile of intake at baseline, had a 44% reduced risk of inflammatory disease mortality (P for trend = 0.03). This association was not observed in men. In both men and women, each 1-SD increase in energy-adjusted intake of α-linolenic acid was inversely associated with inflammatory mortality (hazard ratio: 0.83; 95% CI: 0.71, 0.98). Subjects in the second and third tertiles of nut consumption had a 51% and 32% reduced risk of inflammatory disease mortality, respectively, compared with those in the first tertile (reference). Dietary intakes of long-chain n-3 and n-6 PUFAs and fish were not associated with inflammatory disease mortality.

CONCLUSIONS

We report on a novel link between dietary intake of total n-3 PUFA and risk of inflammatory disease mortality in older women. Furthermore, our data indicate a protective role of nuts, but not fish, against inflammatory disease mortality.

Effect of enzymatic randomization on positional distribution and stability of seal blubber and menhaden oils

In an effort to investigate the effect of positional distribution on oxidative stability of menhaden and seal blubber oils, Novozyme 435 was used as a random biocatalyst. Positional distribution of fatty acids was determined using gas chromatography. As some of the α-tocopherol was lost during randomization, its content was adjusted to the level prior to the process to eliminate this effect on oxidative stability of oils tested. Conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) were used as indicators of oxidative stability. The results showed that the polyunsaturated fatty acids were distributed predominantly at terminal positions in randomized menhaden oil, whereas they were distributed more evenly among all positions in enzymatically randomized seal blubber oil, compared to their unrandomized counterparts. Results of CD and TBARS values indicated that randomized menhaden oil was more stable than the original oil, whereas randomized seal blubber oil was more vulnerable to oxidation compared to its counterpart. Changes of oxidative stability after randomization were mainly due to positional redistribution of fatty acids, especially those of the polyunsaturated types.

Docosahexanoic acid-induced coronary arterial dilation: actions of 17S-hydroxy docosahexanoic acid on K+ channel activity

Despite extensive studies, the mechanisms mediating the cardiovascular actions of ω-3 polyunsaturated fatty acids has not yet been fully understood. The present study determined the possible actions of an endothelium-derived lipoxygenase product of docosahexanoic acid (DHA), 17S-hydroxy DHA (17S-HDHA), in bovine coronary arteries. High-performance liquid chromatography (LC) analysis demonstrated that bovine coronary arterial endothelial cells can metabolize DHA via lipoxygenases, and one of the major products was confirmed to be 17S-HDHA by LC-tandem mass spectrometry. In isolated perfused small bovine coronary arteries, 17S-HDHA (10⁻⁹ to 10⁻⁵ M) caused a concentration-dependent dilation with a maximum dilator response of 87.8 ± 2.5%, which is much more potent than the dilator response of its precursor, DHA. Moreover, 17S-HDHA-induced vasodilatations were significantly blocked by iberiotoxin, a large conductance Ca²(+)-activated K(+) (BK(Ca)) channel blocker, but not altered by an ATP-sensitive K(+) channel blocker, glibenclamide. In patch-clamp whole-cell recording, 17S-HDHA markedly increased K(+) currents in coronary arterial smooth muscle cells. In the inside-out mode, but not in the cell-attached mode, 17S-HDHA dramatically increased the BK(Ca) channel activity, which was substantially blocked by iberiotoxin. Collectively, our findings indicate that 17S-HDHA, an endothelium-derived DHA product via lipoxygenase, activates BK(Ca) channels in coronary arterial smooth muscle cells, leading to coronary vasodilation, which may represent an important mechanism mediating the beneficial actions of DHA in coronary circulation.

Endogenously Decreasing Tissue n-6/n-3 Fatty Acid Ratio Reduces Atherosclerotic Lesions in Apolipoprotein E –Deficient Mice by Inhibiting Systemic and Vascular Inflammation

Objective— To use the fat-1 transgenic mouse model to determine the role of tissue n-6/n-3 fatty acid ratio in atherosclerotic plaque formation. Although it has been suggested that a low ratio of n-6/n-3 polyunsaturated fatty acids (PUFAs) is more desirable in reducing the risk of atherosclerotic cardiovascular disease, the role of tissue n-6/n-3 fatty acid ratio in atherosclerosis has not been sufficiently tested in a well-controlled experimental system. The fat-1 transgenic mouse model, expressing an n-3 fatty acid desaturase, is capable of producing n-3 PUFAs from n-6 PUFAs and thereby has a ratio of n-6/n-3 fatty acids close to 1:1 in tissues and organs.

Methods and Results— To generate apolipoprotein E–deficient plus fat-1 transgenic mice ( apoE −/− / fat-1 ), we crossed heterozygous fat-1 mice with apoE −/− mice. After 14 weeks of a Western-type diet rich in n-6 PUFAs, the apoE −/− / fat-1 mice showed a lower ratio of n-6/n-3 fatty acids than the apoE −/− mice in all organs and tissues tested. The aortic lesion area in apoE −/− / fat-1 mice was significantly reduced when compared with that of apoE −/− littermates (7.14±0.54% versus 13.49±1.61%). There were no differences in plasma cholesterol or high- and low-density lipoprotein levels between the 2 groups, except for a higher triglyceride level in the apoE −/− / fat-1 mice. A significant reduction of interleukin 6 and prostaglandin E 2 in both plasma and aorta culture medium was observed in apoE −/− / fat-1 mice. RT-PCR analysis also indicated that the expression of intercellular adhesion molecule-1, monocyte chemoattractant protein-1, interleukin 6, and cyclooxygenase-2 was lower in the aortas and the circulating monocytes from apoE −/− / fat-1 mice. In addition, the expression of nuclear factor κB/p65 in the aorta and the recruitment of macrophages into atherosclerotic plaques were reduced in apoE −/− / fat-1 mice, compared with apoE −/− mice.

Conclusion— To our knowledge, this is the first study to provide direct evidence for the role of tissue n-6/n-3 ratio in atherosclerosis using the fat-1 transgenic mouse model. Our findings demonstrate that a decreased n-6/n-3 fatty acid ratio reduces atherosclerotic lesions in apoE −/− mice. This protective effect may be attributed to the antiinflammatory properties of n-3 fatty acids, rather than their lipid-lowering effect.

Effect of chemical randomization on positional distribution and stability of omega-3 oil triacylglycerols

Randomization has been commonly used to modify the chemical and physical properties of natural fats and oils. In this study, seal blubber oil (SBO) and menhaden oil (MHO) were modified through chemical randomization using sodium methoxide, and the effect on positional distribution of fatty acids was investigated using gas chromatography (GC) and (13)C nuclear magnetic resonance (NMR) spectroscopy. The effect of randomization on the stability of the original oils and their randomized counterparts was analyzed by comparing conjugated dienes and thiobarbituric acid reactive substances (TBARS) values after accelerated oxidation at 60 degrees C for 4 days. The omega-3 polyunsaturated fatty acids (PUFA) were distributed more evenly among the terminal sn-1,3 positions and the middle sn-2 position in chemically randomized oils when compared to the starting oils. The effect was more pronounced for SBO with omega-3 PUFA attached preferentially to sn-1,3 positions of triacylglycerols before randomization, and it was less pronounced for MHO, which contained omega-3 PUFA more evenly distributed before randomization. However, different levels of commonly known omega-3 fatty acids, namely, docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), eicosapentaenoic acid (EPA), and stearidonic acid (STA), were obtained in both original and randomized oils from GC and (13)C NMR spectroscopy. The stability of the randomized oils was also affected to different degrees, depending on the storage time.

Associations of dietary long-chain n-3 polyunsaturated fatty acids and fish with biomarkers of inflammation and endothelial activation (from the Multi-Ethnic Study of Atherosclerosis [MESA])

The cardioprotective effects of long-chain n-3 polyunsaturated fatty acids (PUFAs) and fish consumption have been observed. However, data on the specific associations of these dietary factors with inflammation and endothelial activation are sparse. A cross-sectional study was conducted of 5,677 men and women from the Multi-Ethnic Study of Atherosclerosis (MESA) cohort, including African Americans, Caucasians, Chinese, and Hispanics aged 45 to 84 years and free of clinical cardiovascular disease. Dietary information was collected using a self-administered food frequency questionnaire. Multivariate linear regression analyses were used to examine relations between the intake of long-chain n-3 PUFAs, nonfried fish, and fried fish and biomarkers of inflammation and endothelial activation. Long-chain n-3 PUFA intake was inversely associated with plasma concentrations of interleukin-6 (p = 0.01) and matrix metalloproteinase-3 (p = 0.03) independent of age, body mass index, physical activity, smoking, alcohol consumption, and dietary variables. Nonfried fish consumption was inversely related to C-reactive protein (p = 0.045) and interleukin-6 (p <0.01), and fried fish consumption was inversely related to soluble intercellular adhesion molecule-1 (p <0.01) but was not associated with other biomarkers after adjustment for potential confounders. In conclusion, the results of this study suggest that the dietary intake of long-chain n-3 PUFAs and fish is inversely associated with concentrations of some biomarkers, reflecting lower levels of inflammation and endothelial activation. These results may partially explain the cardioprotective effects of fish consumption.

Enzymes and receptors of prostaglandin pathways with arachidonic acid-derived versus eicosapentaenoic acid-derived substrates and products

Dietary fish oil containing omega 3 highly unsaturated fatty acids has cardioprotective and anti-inflammatory effects. Prostaglandins (PGs) and thromboxanes are produced in vivo both from the omega 6 fatty acid arachidonic acid (AA) and the omega 3 fatty acid eicosapentaenoic acid (EPA). Certain beneficial effects of fish oil may result from altered PG metabolism resulting from increases in the EPA/AA ratios of precursor phospholipids. Here we report in vitro specificities of prostanoid enzymes and receptors toward EPA-derived, 3-series versus AA-derived, 2-series prostanoid substrates and products. The largest difference was seen with PG endoperoxide H synthase (PGHS)-1. Under optimal conditions purified PGHS-1 oxygenates EPA with only 10% of the efficiency of AA, and EPA significantly inhibits AA oxygenation by PGHS-1. Two- to 3-fold higher activities or potencies with 2-series versus 3-series compounds were observed with PGHS-2, PGD synthases, microsomal PGE synthase-1 and EP1, EP2, EP3, and FP receptors. Our most surprising observation was that AA oxygenation by PGHS-2 is only modestly inhibited by EPA (i.e. PGHS-2 exhibits a marked preference for AA when EPA and AA are tested together). Also unexpectedly, TxA(3) is about equipotent to TxA(2) at the TP alpha receptor. Our biochemical data predict that increasing phospholipid EPA/AA ratios in cells would dampen prostanoid signaling with the largest effects being on PGHS-1 pathways involving PGD, PGE, and PGF. Production of 2-series prostanoids from AA by PGHS-2 would be expected to decrease in proportion to the compensatory decrease in the AA content of phospholipids that would result from increased incorporation of omega 3 fatty acids such as EPA.

Gender-related response of lipid metabolism to dietary fatty acids in the hamster

Gender and dietary fatty acids are involved in the regulation of lipid metabolism, disturbances of which can lead to pathologies such as metabolic syndrome or CVD. Possible interactions between these factors were investigated in male and female hamsters fed diets rich in either saturated fatty acids (‘butter’ diet) or in α-linolenic acid (‘linseed oil’ diet). Gender effect predominated over the diet effect on cholesterol (CH) metabolism; compared to males, females exhibited lower concentrations of plasma total CH (−20%,P<0·001), LDL-CH (−40%,P<0·001) and HDL-CH (−16%,P<0·001), together with higher LDL receptor (+40%) and lower HDL receptor (−60%) hepatic content. Triacylglycerol (TG) metabolism was affected by diet above all: compared to animals fed the ‘butter’ diet, those fed the ‘linseed oil’ diet exhibited lower plasma (−23%,P=0·046) and liver TG (−20%,P=0·026) concentration which may result from both an increased β-oxidation (P<0·001), without any change in PPARα mRNA, and a decreased hepatic lipogenesis (P=0·023), without increased sterol response element binding protein 1c (SREBP1c) mRNA. The response to diet was much more pronounced in males than in females, without gender effect on the transcription level of PPARα and SREBP1c. Finally, the ‘linseed oil’ diet decreased the insulin resistance index (−80%,P<0·001) with a more marked effect in males, in relation to their higher hepatic PPARγ expression (+90%,P=0·012). In conclusion, in our model, the response of either TG or CH to dietary fatty acids is modulated differently by gender. The possible relevance of these interactions to dietary practice should be taken into account in man.

Impaired Filterability of Erythrocytes from Patients with Chronic Hepatitis C and Effects of Eicosapentaenoic Acid on the Filterability

Although erythrocyte filterability plays a key role in microcirculation, it is unknown whether the filterability of erythrocytes from patients with chronic hepatitis C (CH-C) is impaired. This study aimed to investigate erythrocyte filterability in CH-C patients in relation to medical treatment. The mean erythrocyte filterability (%) for all 24 patients with CH-C (69.2 +/- 10.8%) was significantly lower than that for 5 normal controls (80.5 +/- 1.7%, P < 0.03). In 8 patients, the combination therapy of ribavirin (RBV) and interferon improved liver function but caused anemia. The filterability after treatment (57.8 +/- 12.8%) was lower than that before treatment (70.8 +/- 9.7%, P < 0.05). Decreased filterability showed no correlation with the mean corpuscular volume or mean corpuscular Hb concentration during treatment, suggesting that the decrease in filterability mainly arises from changes in erythrocyte membrane properties. We investigated the protective effects of eicosapentaenoic acid (EPA) on the RBV-induced anemia. Filterability in 7 responders was markedly improved from 68.4 +/- 4.6% to 77.4 +/- 2.4% (P < 0.001), but not in 3 nonresponders. In the responders, the progression of anemia was restrained. In conclusion, we found an obvious impairment of the filterability of erythrocytes from CH-C patients, further impairment of the filterability induced by oxidative membrane damage caused by RBV leading to hemolytic anemia, and amelioration of the filterability caused by the antioxidative effects of EPA.

Higher plasma docosahexaenoic acid is associated with reduced progression of coronary atherosclerosis in women with CAD

Fish intake, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and in some cases alpha-linolenic acid (ALA) have been associated with reduced risk of cardiovascular events and death. The association between n-3 fatty acids in plasma lipids and the progression of coronary artery atherosclerosis was assessed among women with established coronary artery disease (CAD). A prospective cohort study involved postmenopausal women (n = 228) participating in the Estrogen Replacement and Atherosclerosis Trial. Quantitative coronary angiography was performed at baseline and after 3.2 +/- 0.6 (mean +/- SD) years. Women with plasma phospholipid (PL) DHA levels above the median, compared with below, exhibited less atherosclerosis progression, as expressed by decline in minimum coronary artery diameter (-0.04 +/- 0.02 and -0.10 +/- 0.02 mm, respectively; P = 0.007) or increase in percentage stenosis (1.34 +/- 0.76% and 3.75 +/- 0.74%, respectively; P = 0.006), and had fewer new lesions [2.0% (0.5-3.5%) of measured segments (95% confidence interval) and 4.2% (2.8-5.6%), respectively; P = 0.009] after adjustments for cardiovascular risk factors. Similar results were observed for DHA in the triglycerides (TGs). EPA and ALA in plasma lipids were not significantly associated with atherosclerosis progression. Consistent with higher reported fish intake, higher levels of plasma TG and PL DHA are associated with less progression of coronary atherosclerosis in postmenopausal women with CAD.

Fatty acid-induced changes in vascular reactivity in healthy adult rats

Dietary fatty acids (FAs) are known to modulate endothelial dysfunction, which is the first stage of atherosclerosis. However, their exact role in this initial phase is still unclear. The effects of isolated or combined (by 2) purified FAs from the main FA families were studied on the vascular response of isolated thoracic aorta in healthy rats to get a better understanding of the mechanisms of action of dietary FAs in regulating vascular endothelial function. Cumulative contraction curves to phenylephrine and relaxation curves to carbachol and then to sodium nitroprusside were obtained in the absence or presence of the FAs studied allowing endothelium-dependent and endothelium-independent ability of the smooth muscle to relax to be assessed in each experimental group. The endothelium-dependent vasodilator response to carbachol was lowered by eicosapentaenoic acid, whereas it was not altered either by docosahexaenoic acid alone or by combined eicosapentaenoic acid-docosahexaenoic acid, oleic acid, or stearic acid, and it was increased by linoleic acid (LA). A decreased phenylephrine-induced contraction was observed after incubation with arachidonic acid and with stearic acid. On the other hand, the endothelium-dependent relaxation was reduced by the addition of combined LA-arachidonic acid and LA-oleic acid. In conclusion, these data point out the differential effects of different types of FAs and of FAs alone vs combined on vascular reactivity. The complex nature of these effects could be partially linked to metabolic specificities of endothelial cells and to interactions between some FAs.

Omega-3 Fatty Acids and the Regulation of Expression of Endothelial Pro-Atherogenic and Pro-Inflammatory Genes

By partially replacing the corresponding omega-6 analogues in membrane phospholipids, omega-3 fatty acids have been shown to decrease the transcriptional activation of genes--e.g., adhesion molecules, chemoattractants, inflammatory cytokines--involved in endothelial activation in response to inflammatory and pro-atherogenic stimuli. This regulation occurs, at least in part, through a decreased activation of the nuclear factor-kappaB system of transcription factors, secondary to decreased generation of intracellular hydrogen peroxide. Such regulation by omega-3 fatty acids is likely linked to the presence of a higher number of double bonds in the fatty acid chain in omega-3 compared with omega-6 fatty acids. By similar mechanisms, omega-3 fatty acids have been recently shown to reduce gene expression of cyclooxygenase-2, an inflammatory gene involved, through the activation of some metalloproteinases, in plaque angiogenesis and plaque rupture. The quenching of gene expression of pro-inflammatory pro-atherogenic genes by omega-3 fatty acids has consequences on the extent of leukocyte adhesion to vascular endothelium, early atherogenesis and later stages of plaque development and plaque rupture, ultimately yielding a plausible comprehensive explanation for the vasculoprotective effects of these nutrients.

Contrasting effect of fish oil supplementation on the development of atherosclerosis in murine models

OBJECTIVE

Increased fish oil intake is associated with protection against coronary heart disease and sudden death, while effects on atherosclerosis are controversial. We explored the effects of supplementing fish oil (rich in n-3 polyunsaturated fatty acids, PUFA) or corn oil (rich in n-6 PUFA) in two different models of atherosclerosis.

METHODS AND RESULTS

Sixty-three low density lipoprotein receptor-deficient (LDLR(-/-)) mice and sixty-nine apolipoprotein E-deficient (apoE(-/-)) mice were fed diets without supplementations or supplemented with either 1% fish oil or 1% corn oil. In apoE(-/-) mice, neither fish oil nor corn oil had any major impact on plasma lipids or atherosclerosis. In LDLR(-/-) mice, conversely, the fish oil and the corn oil group had lower levels of LDL-cholesterol and triglycerides and had lesser atherosclerosis in the aortic root and in the entire aorta (p < 0.01 versus unsupplemented group). Atherosclerosis was significantly less in the fish oil group compared with the corn oil group when evaluated en face in the aortic arch (area positive to lipid staining: 32% with fish oil versus 38% with corn oil; 48% with unsupplemented diet).

CONCLUSIONS

n-3 and n-6 PUFA supplementation retarded the development of atherosclerosis in LDLR(-/-) mice, with a stronger effect seen with n-3 PUFA. There was an important strain-dependence of the effect, with no protection against atherosclerosis in apoE(-/-) mice.

Soluble adhesion molecules and marine n-3 fatty acids in patients referred for coronary angiography

OBJECTIVE

To investigate the relationship between soluble cellular adhesion molecules (sCAMs) and the extent of coronary artery disease (CAD) in patients with stable angina pectoris.

METHODS AND RESULTS

Two hundred and ninety-one subjects had fasting levels of circulating intercellular adhesion molecule-1(sICAM-1), vascular cellular adhesion molecule-1 (sVCAM-1), sP-selectin and contents of n-3 polyunsaturated fatty acids (n-3 PUFA) in granulocyte membranes and adipose tissue determined before undergoing elective coronary angiography. Levels of soluble VCAM-1 (983+/-216 versus 893+/-196 ng/l, p<0.001), ICAM-1 (318+/-140 versus 290+/-75 ng/l, p<0.05) and P-selectin (90+/-27 versus 80+/-23 ng/l, p<0.01) were significantly increased in subjects with significant CAD compared to subjects with no significant stenoses. In a linear regression analysis, both sVCAM-1 and sP-selectin, but not sICAM-1, correlated to the presence and the severity of CAD. Both sICAM-1 and sP-selectin were significantly correlated to current smoking status and a history of myocardial infarction. The content of total n-3 PUFA and docosahexaenoic acid in adipose tissue was marginally, but significant positively correlated to VCAM-1.

CONCLUSION

sVCAM-1 and sP-selectin may serve as markers of CAD in patients with stable angina pectoris. Only sVCAM-1 was weakly correlated to n-3 PUFA in adipose tissue.

Omega-3 fatty acids and inflammation

Dietary omega-3 (n-3) fatty acids have a variety of anti-inflammatory and immune-modulating effects that may be of relevance to atherosclerosis and its clinical manifestations of myocardial infarction, sudden death, and stroke. The n-3 fatty acids that appear to be most potent in this respect are the long-chain polyunsaturates derived from marine oils, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and this review is restricted to these substances. A variety of biologic effects of EPA and DHA have been demonstrated from feeding studies with fish or fish oil supplements in humans and animals. These include effects on triglycerides, high-density lipoprotein cholesterol, platelet function, endothelial and vascular function, blood pressure, cardiac excitability, measures of oxidative stress, pro- and anti-inflammatory cytokines, and immune function. Epidemiologic studies provide evidence for a beneficial effect of n-3 fatty acids on manifestations of coronary heart disease and ischemic stroke, whereas randomized, controlled, clinical feeding trials support this, particularly with respect to sudden cardiac death in patients with established disease. Clinically important anti-inflammatory effects in man are further suggested by trials demonstrating benefits of n-3 fatty acids in rheumatoid arthritis, psoriasis, asthma, and inflammatory bowel disorders. Given the evidence relating progression of atherosclerosis to chronic inflammation, the n-3 fatty acids may play an important role via modulation of the inflammatory processes.

Effects of omega-3 fatty acids on cytokines and adhesion molecules

The dietary intake of omega-3 (n-3) polyunsaturated fatty acids has emerged, over the past 20 years, as an important way to modify cardiovascular risk. This likely occurs through beneficial effects at all stages in the natural history of vascular disease, from the inception of atherosclerotic lesions, to their growth and acute complications (plaque rupture in most instances), up to protection of myocardium from the consequences of ensuing acute myocardial ischemia. This review specifically focuses on the modulating effects of n-3 fatty acids on biologic events involved in early atherogenesis, including important properties of these natural substances on endothelial expression of adhesion molecules and cytokines, processes collectively denoted as "endothelial activation." By decreasing the endothelial responsiveness to proinflammatory and proatherogenic stimuli, n-3 fatty acids act on molecular events not targeted by any other drugs or interventions, and thereby complementary to those of already implemented pharmacologic treatments.

Comparison of conventional and fast gas chromatography in human plasma fatty acid determination

A fast gas chromatographic technique for the determination of fatty acids in human plasma was developed. Its validation and comparison to a conventional method are here reported. The fast method significantly reduced the time required for analysis by a factor of 5 (total time of 3.2 min) while maintaining a similar resolution. Reproducibility of qualitative and quantitative data was measured in both applications. The results demonstrated that the applied fast gas chromatography (GC) conditions do not affect the analytical quality of the assays, allowing a short analysis time.

Nutrition and the endothelium

Growing evidence suggests that dietary factors play an important role in modulating endothelial function. Epidemiologic and clinical studies have related intake of alpha-linolenic acid and long-chain n-3 fatty acids to lower plasma concentrations of inflammatory cytokines and endothelial adhesion molecules, both of which are considered markers of endothelial dysfunction. In contrast, trans fatty acid intake and a higher dietary glycemic load have been associated with increased plasma concentrations of these biomarkers. Recently, several epidemiologic and intervention studies have examined the relationship between overall dietary patterns and endothelial dysfunction. In general, a "prudent diet," characterized by higher intake of fruits, vegetables, legumes, fish, poultry, and whole grains, is associated with a beneficial effect on the endothelium. Conversely, a "Western diet," characterized by higher intake of red and processed meats, sweets, desserts, French fries, and refined grains, is associated with an impairment of the endothelial function. These findings provide additional biological mechanisms through which dietary factors influence the risk of cardiovascular diseases.

Consumption of (n-3) fatty acids is related to plasma biomarkers of inflammation and endothelial activation in women

We evaluated the hypothesis that intake of (n-3) fatty acids is inversely associated with biomarkers of inflammation and endothelial activation. We conducted a cross-sectional study of 727 women from the Nurses' Health Study I cohort, aged 43-69 y, apparently healthy at time of a blood draw in 1990. Dietary intake was assessed by a validated FFQ in 1986 and 1990. C-reactive protein (CRP) levels were 29% lower among those in the highest quintile of total (n-3) fatty acids, compared with the lowest quintile; interleukin-6 (IL-6) levels were 23% lower, E-selectin levels 10% lower, soluble intracellular adhesion molecule (sICAM-1) levels 7% lower, and soluble vascular adhesion molecule (sVCAM-1) levels 8% lower. The intake of alpha-linolenic acid was inversely related to plasma concentrations of CRP (beta = -0.55, P = 0.02), Il-6 (beta = -0.36, P = 0.01), and E-selectin (beta = -0.24, P = 0.008) after controlling for age, BMI, physical activity, smoking status, alcohol consumption, and intake of linoleic acid (n-6) and saturated fat. Long-chain (n-3) fatty acids (eicosapentaenoic and docosahexaenoic) were inversely related to sICAM-1 (beta = -0.11, P = 0.03) and sVCAM-1 (beta = -0.17, P = 0.003). Total (n-3) fatty acids had an inverse relation with CRP (beta = -0.44, P = 0.007), IL-6 (beta = -0.26, P = 0.009), E-selectin (beta = -0.17, P = 0.004), sICAM-1 (beta = -0.07, P = 0.02), and sVCAM-1 (beta = -0.10, P = 0.004). These associations were not modified by intake of vitamin E, dietary fiber, trans fatty acids, or by the use of postmenopausal hormone therapy. In conclusion, this study suggests that dietary (n-3) fatty acids are associated with levels of these biomarkers reflecting lower levels of inflammation and endothelial activation, which might explain in part the effect of these fatty acids in preventing cardiovascular disease.

Role of nuclear receptors in the regulation of gene expression by dietary fatty acids (review)

Long chain fatty acids, derived either from endogenous metabolism or by nutritional sources play significant roles in important biological processes of membrane structure, production of biologically active compounds, and participation in cellular signaling processes. Recently, the structure of dietary fatty acids has become an important issue in human health because ingestion of saturated fats (containing triglycerides composed of saturated fatty acids) is considered harmful, while unsaturated fats are viewed as beneficial. It is important to note that the molecular reason for this dichotomy still remains elusive. Since fatty acids are important players in development of pathology of cardiovascular and endocrine system, understanding the key molecular targets of fatty acids, in particular those that discriminate between saturated and unsaturated fats, is much needed. Recently, insights have been gained on several fatty acid-activated nuclear receptors involved in gene expression. In other words, we can now envision long chain fatty acids as regulators of signal transduction processes and gene regulation, which in turn will dictate their roles in health and disease. In this review, we will discuss fatty acid-mediated regulation of nuclear receptors. We will focus on peroxisome proliferators-activated receptors (PPARs), liver X receptors (LXR), retinoid X receptors (RXRs), and Hepatocyte Nuclear Factor alpha (HNF-4alpha), all of which play pivotal roles in dietary fatty acid-mediated effects. Also, the regulation of gene expression by Conjugated Linoleic Acids (CLA), a family of dienoic fatty acids with a variety of beneficial effects, will be discussed.

Arachidonic acid-dependent inhibition of adipocyte differentiation requires PKA activity and is associated with sustained expression of cyclooxygenases

Arachidonic acid inhibits adipocyte differentiation of 3T3-L1 cells via a prostaglandin synthesis-dependent pathway. Here we show that this inhibition requires the presence of a cAMP-elevating agent during the first two days of treatment. Suppression of protein kinase A activity by H-89 restored differentiation in the presence of arachidonic acid. Arachidonic acid treatment led to a prolonged activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), and suppression of ERK1/2 activity by the addition of U0126 rescued differentiation. Upon induction of differentiation, expression of cyclooxygenase-2 (COX-2) was transiently induced and then declined, whereas COX-1 expression declined gradually as differentiation progressed. Treatment with arachidonic acid led to sustained expression of COX-1 and COX-2. Omission of a cAMP-elevating agent or addition of H-89 or U0126 prevented sustained expression of COX-2. Unexpectedly, we observed that selective COX-1 or COX-2 inhibitors rescued adipocyte differentiation in the presence of arachidonic acid as effectively as did the nonselective COX-inhibitor indomethacin. De novo fatty acid synthesis, diacylglycerol acyltransferase (DGAT) activity, and triacylglycerol accumulation were repressed in cells treated with arachidonic acid. Indomethacin restored DGAT activity and triacylglycerol accumulation without restoring de novo fatty acid synthesis, resulting in an enhanced incorporation of arachidonic acid into cellular triacylglycerols.

Effect of eicosapentaenoic acid and docosahexaenoic acid on oxidative stress and inflammatory markers in treated-hypertensive type 2 diabetic subjects

n-3 fatty acids reduce the risk of cardiovascular disease via a number of possible mechanisms. Despite this, there has been concern that these fatty acids may increase lipid peroxidation. The data in vivo are inconclusive, due in part to limitations in the methodologies. In this regard, the measurement of F2-isoprostanes provides a reliable assessment of in vivo lipid peroxidation and oxidant stress. This study aimed to assess the effects of supplementation with purified eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), the two major n-3 fatty acids, on urinary F2-isoprostanes and markers of inflammation, in type 2 diabetic patients. In a double-blind, placebo controlled trial of parallel design, 59 nonsmoking, treated-hypertensive, type 2 diabetic subjects, were randomized to 4 g daily of purified EPA, DHA, or olive oil for 6 weeks, while maintaining their usual diet. F2-isoprostanes, measured using gas chromatography-mass spectrometry in 24 h urines and C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), were measured before and after intervention. Thirty-nine men and 12 women aged 61.2 +/- 1.2 years, with body mass index (BMI), 29.5 +/- 0.5 kg/m2; 24 h blood pressure, 138/73 mmHg; HbA1c, 7.3 +/- 0.1% and fasting glucose, 7.9 +/- 0.2 mmol/l completed the intervention. Baseline urinary F2-isoprostanes were positively associated with HbA1c (p=.011) and fasting glucose (p=.032). Relative to the olive oil group, postintervention urinary F2-isoprostanes were decreased 19% by EPA (p=.017) and 20% by DHA (p=.014). There were no significant changes in CRP, IL-6, and TNF-alpha following EPA or DHA supplementation. In regression analysis, Delta F2-isoprostanes were positively associated with Delta HbA1c (p=.007) independent of treatment group; and with Delta TNF-alpha (p=.034) independent of age, gender, BMI, and treatment group. There were no associations with Delta CRP or Delta IL-6. This study is the first report demonstrating that either EPA or DHA reduce in vivo oxidant stress without changing markers of inflammation, in treated hypertensive, type 2 diabetic subjects.

Cardiovascular protective effects of n-3 polyunsaturated fatty acids with special emphasis on docosahexaenoic acid

It is widely accepted that n-3 polyunsaturated fatty acids (PUFAs) rich in fish oils protect against several types of cardiovascular diseases such as myocardial infarction, arrhythmia, atherosclerosis, or hypertension. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may be the active biological components of these effects. Although the precise cellular and molecular mechanisms underlying the beneficial effects are still uncertain, the protective effects of n-3 PUFAs are attributable to their direct effects on vascular smooth muscle cell (VSMC) functions. These n-3 PUFAs activate K(+)(ATP) channels and inhibit certain types of Ca(2+) channels, probably via at least 2 distinct mechanisms. N-3 PUFAs favorably alter the eicosanoid profile and regulate cytokine-induced expression of inducible nitric oxide synthase and cyclooxygenase-2 via mechanisms involving modulation of signaling transduction events. N-3 PUFAs also modulate VSMC proliferation, migration, and apoptosis. These recent data suggest that modulation of these VSMC functions contribute to the beneficial effects of n-3 PUFAs on various cardiovascular disorders. Furthermore, recent studies strongly suggest that DHA has more potent and beneficial effects than EPA. However, many questions about the cellular and molecular mechanisms still remain to be answered.

The role of omega-3 fatty acids in cardiovascular disease

Plant-derived alpha-linolenic acid has been studied in a limited number of investigations. So far, some epidemiologic and a few mechanistic studies suggest a potential of protection from cardiovascular disease, but this potential remains to be proven in intervention studies. In contrast, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are prevalent in fish and fish oils, have been studied in thousands of investigations. A consistent body of evidence has been elaborated in various types of investigations, ultimately demonstrating reduction in total mortality, cardiovascular mortality, and morbidity by ingestion of roughly 1 g/d of EPA plus DHA. Current guidelines, however, do not discern between the omega-3 fatty acids mentioned; in fact, most even do not differentiate polyunsaturated fatty acids at all. Unfortunately, this complicates efficient implementation of an effective means of prophylaxis of atherosclerosis.