Cardiovascular effects of omega-3 free Fatty acids

Omega-3 fatty acids are essential substances for the development and function of human organism. They cannot be synthesized in humans, and consequently have to be acquired from food, almost exclusively from fish. Omega-3 fatty acids exert potent anti-inflammatory and anti-atherosclerotic actions by interfering with the metabolism of arachidonic acid, modifying lipid composition (mainly lowering triglycerides), improving hemodynamics and reducing cardiac hypertrophy. Recently, clinical and experimental studies demonstrated an anti-arrhythmic effect and a significant impact on survival after myocardial infarction (MI). It follows that omega-3 fatty acids have been widely accepted for clinical use in patients with dyslipidemia or with atherosclerotic disease and in survivors of acute MI. This review briefly explores the metabolic mechanisms and the clinical effects of this class of substances and considers their use in patients with cardiovascular disease.     

Subdural hematoma after a fall in an elderly patient taking high-dose omega-3 fatty acids with warfarin and aspirin: case report and review of the literature

The elderly population is at an increased risk for major bleeding, possibly due to increased sensitivity to anticoagulation, multiple comorbidities, and polypharmacy. Elderly patients receiving antiplatelet and anticoagulant therapy have an additional risk for bleeding. Omega-3 fatty acids, also known as fish oil, have been used for hyperlipidemia, coronary heart disease, hypertension, and other conditions. Some studies have demonstrated that consumption of fish oil concentrate, n-3 polyunsaturated fatty acid (n-3 PUFA), results in cardiovascular benefits that include reductions in mortality, sudden death, nonfatal myocardial infarction, and thrombotic stoke, as well as improvement in graft patency. The mechanism of action of n-3 PUFA is not completely understood, but a dual antiplatelet and anticoagulant effect has been proposed. Few data exist on whether or not fish oil can be used safely with other antiplatelet or anticoagulant drugs. We report the case of a patient who after a minor fall developed a subdural hematoma requiring craniotomy that likely was precipitated by concomitant use of high-dose omega-3 fatty acids 6 g/day with both aspirin and warfarin. These findings are important because of the wide availability of omega-3 fatty acids and the propensity for use of complementary and alternative medicine in patients with cardiovascular disease who are already taking antiplatelet and/or anticoagulant agents. Judicious use of these combinations is advised, and pharmacists can play an important role in educating patients and other health care providers about the bleeding risks associated with combination therapy.     

n-3多不饱和脂肪酸在慢性肾脏疾病中的应用

数十年来的动物研究支持鱼油中的主要成分n-3多不饱和脂肪酸(n-3PUFA)在肾脏疾病治疗中的有效性,在一些人类肾小球疾病如IgA肾病中n-3PUFA也被证实有益,但临床试验结果并不一致。n-3PUFA应用能否成为肾脏疾病的一种新的治疗手段,仍需进一步的大规模临床研究。     

Omega-3 polyunsaturated fatty acids and cognition in a college-aged population

The cognitive influences of omega-3 polyunsaturated fatty acids (n-3 PUFA) remain unclear throughout the life span. Dietary n-3 PUFA appear cognitively beneficial prenatally and neuroprotective at later age; however, researchers using supplementation designs have reported disparate findings across age groups. Few studies have examined the cognitive impact of n-3 PUFA during young adulthood. This study assessed the cognitive effects of fish oil supplementation at college age, hypothesizing benefits on affect, executive control, inhibition, and verbal learning and memory. College-aged participants were assigned to active (n = 20, 5 men; age = 19.9, sage = 1.8) or placebo (n = 21, 7 men; age = 20.4, sage = 1.6) treatments, receiving fish oil (480 mg DHA/720 mg EPA) or coconut oil, respectively. Both groups completed four weeks of supplementation. At baseline and posttreatment, the researchers administered the Rey Auditory Verbal Learning Test (RAVLT; Lezak, 1995), Stroop Color and Word Test (SCWT; Golden & Freshwater, 2002), Trail Making Test (TMT; Corrigan & Hinkeldey, 1987; Gaudino, Geisler, & Squires, 1995; Lezak, 1995), and Positive and Negative Affect Schedule (PANAS; Watson, Clark, & Tellegen, 1988). Repeated-measures ANOVAs indicated no benefits of fish oil on the SCWT, RAVLT Stages 1 to 5, or PANAS. An interaction occurred between condition and time of measurement (i.e., baseline and posttreatment) on RAVLT Stages 6 and 7, and placebo significantly improved TMT performance over fish oil. The benefits of n-3 PUFA on RAVLT performance derived more from depreciated placebo performance than improved performance due to fish oil. The placebo gain on TMT performance likely derived from a learning effect. Together, these results present limited cognitive benefits of n-3 PUFA at college age; however, the treatment may have been subtherapeutic, with a larger sample needed to generalize these results.     

Section Review—Cardiovascular & Renal: n-3 Fatty Acids as Adjuvants to Conventional Therapy in Patients with Coronary Artery Disease

Whether dietary supplementation with n-3 polyunsaturated fatty acids (PUFA) (also called omega-3 fatty acids or fish oils) may be beneficial in patients with coronary artery disease (CAD) is at the present time a matter of debate. In this review, we consider some basic concepts of n-3 PUFA, discuss epidemiological data, animal experiments and the effects of n-3 PUFA on cardiovascular risk factors. The studies on clinical outcome in patients with CAD and safety aspects are reviewed in order to provide a basis for further understanding of the potential value of dietary supplementation with n-3 PUFA. Some recommendations for daily clinical practice and suggestions for future research are also given.     

Biological mechanisms and cardiovascular effects of omega-3 fatty acids

The mechanisms and cardiovascular effects of omega-3 fatty acids are reviewed. Omega-3 polyunsaturated fatty acids are the major ingredient found in commercially available fish oil products. The incidence of many diseases, including coronary heart disease, diabetes mellitus, and psoriasis, is lower in Eskimos, who ingest diets rich in omega-3 fatty acids, compared with European controls. Potential mechanisms by which these fatty acids cause their many physiologic effects include competing with omega-6 fatty acids for prostaglandin and leukotriene pathways and enhancing cell membrane fluidity by virtue of the high degree of unsaturation. Numerous studies have documented longer bleeding times and decreased platelet aggregation in subjects ingesting omega-3 fatty acids. Omega-3 fatty acids may reduce serum cholesterol concentrations by decreasing the synthesis of very low density lipoprotein and, therefore, low-density lipoprotein. Blood viscosity is significantly and uniformly lower in subjects receiving omega-3 fatty acids compared with controls. Potential risks of supplementation with fish oils include hypervitaminosis A and D, vitamin E deficiency, increased bleeding times, decreased platelets, and ingestion of contaminated fish. Supplementation with moderate amounts of omega-3 fatty acids appears to be relatively safe. Possible adverse effects include nausea, diarrhea, and a "fishy" taste. Properly controlled, long-term clinical trials are needed to determine whether supplementation with omega-3 fatty acids would be therapeutically beneficial in various patient populations and disease states.     

Cognitive enhancement by omega-3 fatty acids from child-hood to old age: Findings from animal and clinical studies

Omega-(n)-3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are major components of neuronal membranes and have a wide range of functions, from modulating synaptic plasticity and neurochemistry, to neuroimmune-modulation and neuroprotection. Thus, it is not surprising that n-3 PUFA are widely acknowledged to have cognitive-enhancing effects. Although clinical evidence is somewhat conflicting, probably in large part due to methodological issues, animal studies have consistently demonstrated that n-3 PUFA are indispensable for proper brain development, may enhance cognitive function in healthy, adult individuals and attenuate cognitive impairment in aging and age-related disorders, such as dementia. This review discusses and integrates up to date evidence from clinical and animal studies investigating the cognitive-enhancing effects of n-3 PUFA during development, child- and adult-hood, as well as old-age with associated neurodegenerative diseases, such as Alzheimer's disease. Furthermore, we cover the major underlying biochemical and neurophysiological mechanisms by which n-3 PUFA mediate these effects on cognition. This article is part of a Special Issue entitled 'Cognitive Enhancers'.     

Dietary n-6 and n-3 polyunsaturated fatty acids and colorectal carcinogenesis: results from cultured colon cells, animal models and human studies

During the past few decades, many studies have been conducted to evaluate the effects of n-6 and n-3 polyunsaturated fatty acids (PUFAs) on colorectal carcinogenesis. This report provides a brief overview of the recent studies that have been performed in cultured colon cells, animal models as well as of the population-based and short-term biomarker studies with humans. No differential effect between n-6 and n-3 PUFAs has been observed in vitro. Results from animal models indicate that n-6 PUFAs have a tumor enhancing effect, predominantly during the post-initiation phase. n-3 PUFAs may protect against colorectal carcinogenesis during both the initiation and post-initiation phase. Population-based human studies show little or no associations between n-6 or n-3 PUFA intake and colorectal cancer. Short-term biomarker studies in humans suggest though that fish oil (FO) supplementation with high amounts of n-3 PUFAs may protect against colorectal carcinogenesis and that n-6 PUFA supplementation may increase the risk.     

Dietary n-6 and n-3 polyunsaturated fatty acids and colorectal carcinogenesis: results from cultured colon cells, animal models and human studies

During the past few decades, many studies have been conducted to evaluate the effects of n-6 and n-3 polyunsaturated fatty acids (PUFAs) on colorectal carcinogenesis. This report provides a brief overview of the recent studies that have been performed in cultured colon cells, animal models as well as of the population-based and short-term biomarker studies with humans. No differential effect between n-6 and n-3 PUFAs has been observed in vitro. Results from animal models indicate that n-6 PUFAs have a tumor enhancing effect, predominantly during the post-initiation phase. n-3 PUFAs may protect against colorectal carcinogenesis during both the initiation and post-initiation phase. Population-based human studies show little or no associations between n-6 or n-3 PUFA intake and colorectal cancer. Short-term biomarker studies in humans suggest though that fish oil (FO) supplementation with high amounts of n-3 PUFAs may protect against colorectal carcinogenesis and that n-6 PUFA supplementation may increase the risk.     

The role of n-3 polyunsaturated fatty acids in the prevention and treatment of cardiovascular disease

Growing evidence has suggested an important role of n-3 polyunsaturated fatty acids in reducing risk of cardiovascular disease in the general population and patients with preexisting heart disease. In particular, several long-term epidemiologic studies have found an inverse association between fish consumption and risk of coronary heart disease or stroke. Two secondary prevention trials have found that increasing fish consumption or fish oil supplementation significantly reduced coronary death among patients with existing myocardial infarction. In addition, epidemiologic and clinical studies have suggested that alpha-linolenic acid (ALA), a short-chain n3-3 fatty acid from plant sources, may have similar cardiac benefits as long-chain n-3 fatty acids from fish. Potential mechanisms through which n-3 polyunsaturated fatty acids protect against CVD include their antiarrhythmic and antithrombotic effects, and improving insulin sensitivity and endothelial function. (c) 2001 Prous Science. All rights reserved.     

Therapeutic potential of marine n-3 fatty acids in CABG patients

Dietary intake of marine n-3 polyunsaturated fatty acids (PUFA) has beneficial effects in various cardiac disorders. Few studies have, however, investigated the therapeutic potential of n-3 PUFA in patients undergoing coronary artery bypass grafting (CABG). Five heterogeneous randomized studies on n-3 PUFA for prevention of postoperative atrial fibrillation have yielded conflicting results. Increased venous graft patency rates following CABG were seen in another study in patients treated with n-3 PUFA. Finally, supplements with n-3 PUFA postoperatively have been associated with a lower risk of repeat revascularization and lower mortality in patients with poor ventricular function. Data are still few, and more studies are needed to clarify the therapeutic potential of n-3 PUFA in patients undergoing CABG.     

Effect of supplementation of n-3 polyunsaturated fatty acids on oxidative stress-induced DNA damage of rat hepatocytes

The effect of supplementation of n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat hepatocytes was examined. Male Wistar rats were fed a diet containing safflower oil (control n-6 PUFA diet) or fish oil (n-3 PUFA diet) in 50 g/kg of dried diet and an equal amount of vitamin E in 59 mg/kg of dried diet for 6 weeks. The liver of rats fed safflower oil was rich in n-6 PUFA, whereas that of rats fed fish oil was rich in n-3 PUFA. Isolated hepatocytes were treated in vitro with ADP/Fe (II) ion or hydrogen peroxide at 37 degrees C for 30 min to induce oxidative stress. The degree of lipid peroxidation was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances. The degree of oxidative DNA damage was assessed based on comet-type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-deoxyguanosine levels. In both ADP/Fe(II) ion and hydrogen peroxide oxidation, the degree of lipid peroxidation of hepatocytes increased in both diet groups, and the level of increase in the fish oil diet group was slightly higher than that in the safflower oil diet group. In ADP/Fe(II) ion oxidation, the degree of DNA damage increased in both diet groups, but there were no significant differences in the level of increase. In contrast, in hydrogen peroxide oxidation, the degree of DNA damage increased in both diet, and the increase in the fish oil diet group was significantly lower than that in the safflower oil diet group. It is unlikely that an n-3 PUFA-rich diet enhances oxidative stress-induced hepatocyte DNA damage as compared with the control n-6 PUFA-rich diet.     

Polychlorinated biphenyls (PCBs) contamination and aryl hydrocarbon receptor (AhR) agonist activity of Omega-3 polyunsaturated fatty acid supplements: Implications for daily intake of dioxins and PCBs

Omega-3 polyunsaturated fatty acid (n-3 PUFA) rich oils derived primarily from fish are frequently consumed as supplements. Due to the tendency of persistent organic pollutants (POPs) to accumulate in exposed organisms, n-3 PUFA supplements can contain sufficient POPs to present a risk to consumers. Here we investigated PCB concentrations and aryl hydrocarbon receptor (AhR) agonist activity in 17 n-3 PUFA supplements available in Canada. PCBs ranged from <0.8 to 793 ng g⁻¹ oil, with salmon- and seal-derived products yielding the highest values. AhR agonist activity from a reporter gene assay ranged from 1.3 to 72.2 pg TEQ g⁻¹ oil, with salmon and tuna yielding the highest values. When consumed at the recommended doses and as a supplement to the average Canadian diet, seal-derived oil can contribute to exceedance of the tolerable daily intake of 20 ng PCBs kg-BW⁻¹ day⁻¹, and salmon-, tuna-, and sea herring-derived oils can contribute to exceedance of the tolerable daily intake limit of 2.3 pg TEQ kg-BW⁻¹ day⁻¹. The beneficial properties of fish and n-3 PUFA supplements, and the results of this study suggest that it is prudent to consume supplements derived from small, cold-water fatty fish. Further research will be necessary to draw firm conclusions.     

Electrophysiologic properties of lidocaine, cocaine, and n-3 fatty-acids block of cardiac Na+ channels

Lidocaine and cocaine, two local anesthetics, and n-3 polyunsaturated fatty acids in fish oils, inhibit the voltage-gated Na(+) channels of cardiomyocytes. This inhibition by lidocaine and n-3 fish oil is associated with antiarrhythmic effects, whereas with cocaine lethal arrhythmias may occur. These electrophysiologic studies show that at the concentrations tested, the n-3 fish oil fatty acids and lidocaine share three actions on I(Na): a potent inhibition of I(Na); a strong voltage-dependence of this inhibition; and a large shift of the steady-state inactivation to hyperpolarized potentials. By contrast cocaine shares only the potent inhibition of I(Na). The voltage-dependence of the inhibition is much decreased with cocaine, which produces only a very small leftward shift of the voltage-dependence of inactivation. The large leftward shift of the steady-state inactivation seems very important in the prevention of fatal arrhythmias by the n-3 fatty acids. Thus, we suggest that it is lack of this effect by cocaine, which is one factor, that eliminates its ability to prevent fatal cardiac arrhythmias. Further we report that in cultured neonatal rat cardiomyocytes n-3 fish oil fatty acids terminate the tachycardia induced by the alpha(1) adrenergic agonist, phenylephrine, whereas cocaine accelerates the tachycardia and causes bouts of tachyarrhythmias.     

Fish oils and vascular disease prevention: an update

Considerable epidemiological data confirmed the existence of favorable associations between fish consumption and mortality from cardiovascular disease. Accumulating evidence suggests that n-3 polyunsaturated fatty acids supplementation is an effective additive treatment for the primary and secondary prevention of cardiovascular disease. Another indication for the use of n-3 PUFA is the treatment of hypertriglyceridemia as monotherapy or in combination with other lipid lowering agents (e.g. statins or fibrates). However, high doses of n-3 PUFA are required for this effect (e.g. 3-4 g/day). Fish oils may be acting via several mechanisms that include antiarrhythmic, antithrombotic and anti-inflammatory effects as well as plaque stabilization. Despite the current evidence supporting a beneficial effect of fish oils on vascular disease, more definitive studies than the ones already performed are required. Some ongoing trials may provide further insight into the indications for fish oil supplementation. This review considers the mechanisms accounting for the cardioprotective properties of n-3 polyunsaturated fatty acids. We also discuss the epidemiological and interventional studies evaluating the relationship between n-3 polyunsaturated fatty acids consumption and cardiovascular disease.     

A comparative study on the effect of algal and fish oil on viability and cell proliferation of Caco-2 cells.

Polyunsaturated fatty acid (PUFA) rich micro-algal oil was tested in vitro and compared with fish oil for antiproliferative properties on cancer cells in vitro. Oils derived from Crypthecodinium cohnii, Schizochytrium sp. and Nitzschia laevis, three commercial algal oil capsules, and menhaden fish oil were used in cell viability and proliferation tests with human colon adenocarcinoma Caco-2 cells. With these tests no difference was found between algal oil and fish oil. The nonhydrolysed algal oils and fish oil showed a much lower toxic effect on cell viability, and cell proliferation in Caco-2 cells than the hydrolysed oils and the free fatty acids (FFAs). Eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) were used as samples for comparison with the tested hydrolysed and nonhydrolysed oils. The hydrolysed samples showed comparative toxicity as the free fatty acids and no difference between algal and fish oil. Oxidative stress was shown to play a role in the antiproliferative properties of EPA and DHA, as alpha-tocopherol could partially reverse the EPA/DHA-induced effects. The results of the present study support a similar mode of action of algal oil and fish oil on cancer cells in vitro, in spite of their different PUFA content.     

n-3多不饱和脂肪酸类药物在心血管疾病中的临床应用进展

许多临床试验表明n-3多不饱和脂肪酸(n-3 PUFAs)对于冠心病、血脂异常和心力衰竭等人群均具有保护作用,而且已有建议推荐心肌梗死后患者和高甘油三酯血症人群口服此类提纯药物。但在应用过程中,仍有一些值得临床关注的问题,如药物安全性、药物成分和用量等。笔者认为,随着对n-3 PUFAs药物的深入研究,其将有更广阔的应用前景。     

Polyunsaturated fatty acids and risk of preterm delivery

Preterm delivery (PD) is characterized both by increased neonatal morbidity and mortality and by important late pathologic sequelae. From a clinical stand-point, PD may results from a medical condition where the continuation of pregnancy could bring about a marked risk for the foetus and/or for the mother, or from an adverse event where the pregnancy is going to end spontaneously before 37 weeks of gestation. In the past few years some epidemiological studies have shown that diet may interfere with complex multifactorial processes contributing to the preterm triggering of labour. The attention has been focused on polyunsaturated fatty acids (PUFA) such as alpha-linoleic acid, precursor of Omega-3 series, and linoleic acid, precursor Omega-6 series. Their importance in modulating Prostaglandin concentrations at different levels is already known. Moreover, it has been reported that in clinical situation, such as PD, the endogenous levels of PUFA are unbalanced, with a Omega-6 predominance. Experimental, observational and clinical studies suggest that dietary intake of Omega-3 fatty acids is capable of significantly prolonging the duration of gestation in the range of 4-7 days; such prolongation would possibly occur through the inhibition of prostaglandins E2 and F2 alpha. In Western population dietary intake of Omega-3 appears to be marginal, and recommended assumption could be reached only by a ten-fold increase in blue fish ingestion. The recommended intake of EPA + DHA should be 1.4 g/daily with a 1:2.5 EPA:DHA. It is therefore possible to conclude that in light of controlled clinical studies and of the actual categories of risk for preterm delivery, the dietary supplementation of Omega-3, in addition to other pharmacological measures (17alpha-hydroxyprogesterone caproate), could be implemented for the secondary and/or tertiary prophylaxis of preterm delivery.     

Role of ω3 long-chain polyunsaturated fatty acids in reducing cardio-metabolic risk factors

Cardiovascular disease is the leading cause of mortality in many economically developed nations, and its incidence is increasing at a rapid rate in emerging economies. Diet and lifestyle issues are closely associated with a myriad of cardiovascular disease risk factors including abnormal plasma lipids, hypertension, insulin resistance, diabetes and obesity, suggesting that diet-based approaches may be of benefit. Omega-3 longchain-polyunsaturated fatty acids (ω3 LC-PUFA) are increasingly being used in the prevention and management of several cardiovascular risk factors. Both the ω3 and ω6 PUFA families are considered essential, as the human body is itself unable to synthesize them. The conversion of the two precursor fatty acids - linoleic acid (18:2ω6) and α-linoleic acid (α18:3ω3) - of these two pathways to longer (≥C(20)) PUFA is inefficient. Although there is an abundance of ω6 PUFA in the food supply; in many populations the relative intake of ω3 LC-PUFA is low with health authorities advocating increased consumption. Fish oil, rich in eicosapentaenoic (EPA, 20:5ω3) and docosahexaenoic (DHA, 22:6ω3) acids, has been found to cause a modest reduction in blood pressure at a dose level of >3g/d both in untreated and treated hypertensives. Whilst a multitude of mechanisms may contribute to the blood pressure lowering action of ω3 LC-PUFA, improved vascular endothelial cell function appears to play a central role. Recent studies which evaluated the potential benefits of fish oil in type-2 diabetes have helped to alleviate concerns raised in some previous studies which used relatively large dose (5-8 g/d) and reported a worsening of glycemic control. Several meta-analyses have confirmed that the most consistent action of ω3 LC-PUFA in insulin resistance and type-2 diabetes is the reduction in triglycerides. In some studies, fish oil has been found to cause a small rise in LDL-cholesterol, but a change in the LDL particle size, from the smaller more atherogenic form to the larger, less damaging particle size, have also been noted. ω3 LC-PUFA are effective modulators of the inflammation that accompanies several cardio-metabolic abnormalities. Taking into consideration the pleiotropic nature of their actions, it can be concluded that dietary supplementation with ω3 LC-PUFA will lead to improvements in cardio-metabolic health parameters. These fatty acids pose only minor side effects and more importantly, do not interact adversely with the common drug therapies used in the management and treatment of hypertension, dyslipidemia, type-2 diabetes, and obesity/metabolic syndrome, but in some instances work synergistically, thereby providing additional cardiovascular benefits.