Eicosapentaenoic acid prevents atrial fibrillation associated with heart failure in a rabbit model

Eicosapentaenoic Acid Rescues Cav1.2-L-Type Ca2+ Channel Decline Caused by Saturated Fatty Acids via Both Free Fatty Acid Receptor 4-Dependent and -Independent Pathways in Cardiomyocytes

Dietary intake of omega-3 polyunsaturated fatty acids (eicosapentaenoic acid, EPA) exerts antiarrhythmic effects, although the mechanisms are poorly understood. Here, we investigated the possible beneficial actions of EPA on saturated fatty acid-induced changes in the L-type Ca2+ channel in cardiomyocytes. Cardiomyocytes were cultured with an oleic acid/palmitic acid mixture (OAPA) in the presence or absence of EPA. Beating rate reduction in cardiomyocytes caused by OAPA were reversed by EPA. EPA also retrieved a reduction in Cav1.2 L-type Ca2+ current, mRNA, and protein caused by OAPA. Immunocytochemical analysis revealed a distinct downregulation of the Cav1.2 channel caused by OAPA with a concomitant decrease in the phosphorylated component of a transcription factor adenosine-3',5'-cyclic monophosphate (cAMP) response element binding protein (CREB) in the nucleus, which were rescued by EPA. A free fatty acid receptor 4 (FFAR4) agonist TUG-891 reversed expression of Cav1.2 and CREB mRNA caused by OAPA, whereas an FFAR4 antagonist AH-7614 abolished the effects of EPA. Excessive reactive oxygen species (ROS) accumulation caused by OAPA decreased Cav1.2 and CREB mRNA expressions, which was reversed by an ROS scavenger. Our data suggest that EPA rescues cellular Cav1.2-Ca2+ channel decline caused by OAPA lipotoxicity and oxidative stresses via both free fatty acid receptor 4-dependent and -independent pathways.

Eicosapentaenoic Acid: between Cardiovascular Benefits and the Risk of Atrial Fibrillation

In recent years, scientific research has increasingly focused on the cardiovascular benefits of omega-3 polyunsaturated fatty acids (n-3 PUFAs) supplements. The most promising results emerged from the new trials on a high-dose eicosapentaenoic acid (EPA)-only approach, instead of the previously prescribed therapy with EPA + docosahexaenoic acid (DHA). The evidence of the reduction of cardiovascular events in patients at high cardiovascular risk with EPA is intriguing. However, physicians have expressed concern about the potential high risk of atrial fibrillation (AF) occurrence due to such an approach. This study aims to investigate the current evidence on the cardiovascular benefits of EPA and its association with atrial arrhythmogenesis. Current guidelines consider EPA (as IPE) treatment for selected patients but with no specific indication regarding AF risk evaluation. We propose a flowchart that could be a starting point for the future development of an algorithm to help clinicians to prescribe EPA safely and effectively, especially in patients at high risk of incipient AF.

Clinical significance of polyunsaturated fatty acids in the prevention of cardiovascular diseases

Cardiovascular diseases are one of the most important problems of modern medicine. They are associated with a large number of health care visits, hospitalizations and mortality. Prevention of atherosclerosis is one of the most effective strategies and should start as early as possible. Correction of lipid metabolism disorders is associated with definite clinical successes, both in primary prevention and in the prevention of complications of many cardiovascular diseases. A growing body of evidence suggests a multifaceted role for polyunsaturated fatty acids. They demonstrate a variety of functions in inflammation, both participating directly in a number of cellular processes and acting as a precursor for subsequent biosynthesis of lipid mediators. Extensive clinical data also support the importance of polyunsaturated fatty acids, but all questions have not been answered to date, indicating the need for further research.

Epicardial adipose tissue as a mediator of cardiac arrhythmias

Obesity is associated with higher risks of cardiac arrhythmias. Although this may be partly explained by concurrent cardiometabolic ill-health, growing evidence suggests that increasing adiposity independently confers risk for arrhythmias. Among fat depots, epicardial adipose tissue (EAT) exhibits a proinflammatory secretome and, given the lack of fascial separation, has been implicated as a transducer of inflammation to the underlying myocardium. The present review explores the mechanisms underpinning adverse electrophysiological remodeling as a consequence of EAT accumulation and the consequent inflammation. We first describe the physiological and pathophysiological function of EAT and its unique secretome and subsequently discuss the evidence for ionic channel and connexin expression modulation as well as fibrotic remodeling induced by cytokines and free fatty acids that are secreted by EAT. Finally, we highlight how weight reduction and regression of EAT volume may cause reverse remodeling to ameliorate arrhythmic risk.

Association of Plasma C1q/TNF-Related Protein 3 (CTRP3) in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is a highly prevalent cardiac arrhythmia characterized by atrial remodeling. Complement C1q tumor necrosis factor-related protein 3 (CTRP3) is one of the adipokines associated with obesity, diabetes, and coronary heart disease. The association between plasma CTRP3 levels and AF is uncertain. The aim of this study was to investigate whether plasma CTRP3 concentrations were correlated with AF. Our study included 75 AF patients who underwent catheter ablation at our hospital and 47 sinus rhythm patients to determine the difference in plasma CTRP3 concentrations. Blood samples before the ablation were collected, and ELISA was used to measure the concentrations of CTRP3. Plasma CTRP3 concentrations were significantly lower in AF patients compared with control group (366.9 ± 105.2 ng/ml vs. 429.1 ± 100.1 ng/ml, p = 0.002). In subgroup studies, patients with persistent AF had lower plasma CTRP3 concentrations than those with paroxysmal AF (328.3 ± 83.3 ng/ml vs. 380.0 ± 109.2 ng/ml, p = 0.037). The concentrations of plasma CTRP3 in the recurrence group after radiofrequency catheter ablation of AF were lower than those in the nonrecurrence group (337.9 ± 77.3 ng/ml vs. 386.6 ± 108.1 ng/ml, p = 0.045). Multivariate regression analysis revealed the independent correlation between plasma CTRP3 level and AF. Plasma CTRP3 concentrations were correlated with the presence of AF and AF recurrence.

Therapeutic Effects of Specialized Pro-Resolving Lipids Mediators on Cardiac Fibrosis via NRF2 Activation

Heart disease is the number one mortality disease in the world. In particular, cardiac fibrosis is considered as a major factor causing myocardial infarction and heart failure. In particular, oxidative stress is a major cause of heart fibrosis. In order to control such oxidative stress, the importance of nuclear factor erythropoietin 2 related factor 2 (NRF2) has recently been highlighted. In this review, we will discuss the activation of NRF2 by docosahexanoic acid (DHA), eicosapentaenoic acid (EPA), and the specialized pro-resolving lipid mediators (SPMs) derived from polyunsaturated lipids, including DHA and EPA. Additionally, we will discuss their effects on cardiac fibrosis via NRF2 activation.

Mechanistic insights into cardiovascular protection for omega-3 fatty acids and their bioactive lipid metabolites

Patients with well-controlled low-density lipoprotein cholesterol levels, but persistent high triglycerides, remain at increased risk for cardiovascular events as evidenced by multiple genetic and epidemiologic studies, as well as recent clinical outcome trials. While many trials of low-dose ω3-polyunsaturated fatty acids (ω3-PUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) have shown mixed results to reduce cardiovascular events, recent trials with high-dose ω3-PUFAs have reignited interest in ω3-PUFAs, particularly EPA, in cardiovascular disease (CVD). REDUCE-IT demonstrated that high-dose EPA (4 g/day icosapent-ethyl) reduced a composite of clinical events by 25% in statin-treated patients with established CVD or diabetes and other cardiovascular risk factors. Outcome trials in similar statin-treated patients using DHA-containing high-dose ω3 formulations have not yet shown the benefits of EPA alone. However, there are data to show that high-dose ω3-PUFAs in patients with acute myocardial infarction had reduced left ventricular remodelling, non-infarct myocardial fibrosis, and systemic inflammation. ω3-polyunsaturated fatty acids, along with their metabolites, such as oxylipins and other lipid mediators, have complex effects on the cardiovascular system. Together they target free fatty acid receptors and peroxisome proliferator-activated receptors in various tissues to modulate inflammation and lipid metabolism. Here, we review these multifactorial mechanisms of ω3-PUFAs in view of recent clinical findings. These findings indicate physico-chemical and biological diversity among ω3-PUFAs that influence tissue distributions as well as disparate effects on membrane organization, rates of lipid oxidation, as well as various receptor-mediated signal transduction pathways and effects on gene expression.

Effect of fish oil on circulating asymmetric dimethylarginine and adiponectin in overweight or obese patients with atrial fibrillation

Obesity and adipose-derived peptides might be involved in the pathogenesis of atrial fibrillation (AF). Adiponectin plays a major role in the modulation of several metabolic pathways, and asymmetric dimethylarginine (ADMA) has been suggested to be predictive of AF and associated adverse events. The aim of this study was to investigate the effect of fish oil supplementation on circulating adiponectin and ADMA in overweight or obese patients with persistent AF. In this randomized, double-blind, placebo-controlled trial, 80 overweight or obese (body mass index (BMI) ≥ 25 kg/m2) patients with persistent AF were randomly assigned to two groups to receive either 2 g/day fish oil or placebo, for 8 weeks. Serum levels of adiponectin and ADMA, and anthropometric indexes were measured. This study showed that serum adiponectin concentrations increased significantly following fish oil supplementation compared with the placebo group (13.15 ± 7.33 vs. 11.88 ± 6.94 µg/ml; p = .026). A significant reduction was also observed in serum ADMA levels in the fish oil compared with the placebo group following the intervention (0.6 ± 0.13 vs. 0.72 ± 0.15 µmol/L; p = .001). The changes in serum adiponectin and ADMA concentrations remained significant after adjustments for baseline values, age, sex, and changes of BMI and waist circumference (p = .011 and p = .001, respectively). In conclusion,  8 weeks supplementation with fish oil increased serum adiponectin and decreased ADMA concentrations in overweight or obese patients with persistent AF. As adiponectin and ADMA are suggested to be involved in many pathways associated with AF, the current findings might be promising in the clinical management of this disease, an issue that needs further investigations.

Milk fat crystal network as a strategy for delivering vegetable oils high in omega-9, -6, and -3 fatty acids

As an alternative to the strategies currently used to deliver unsaturated fatty acids, especially, the essentials omega-6 and 3- fatty acids, the aim of this work was to investigate the effect of the incorporation of 25 e 50% (w/w) of olive, corn and linseed oil into the crystal structure of anhydrous milk fat (AMF). Fatty acid composition, atherogenicity (AI), and thrombogenicity (TI) index, crystallization kinetics, polymorphism by Rietveld method (RM), microstructure, thermal behavior, solid fat content, and lipid compatibility was evaluated. The addition of vegetable oils reduced the saturated fatty acids, and the AI and TI indices of AMF, and increased the concentration of unsaturated, specifically omega-6 and -3 fatty acids. Although vegetable oils caused changes in nucleation and crystallization kinetics, the spherulitic and crystalline morphology and the β' polymorphism of AMF were maintained. The study demonstrated the possibility of using the crystal structure of AMF as a vehicle for unsaturated fatty acids in food formulations, as an alternative to nutritional supplementation. In addition, studies on the use of RM in blends made with AMF and vegetable oil have not been found in literature, thus demonstrating the relevance of the present study.

Is epicardial fat tissue associated with atrial fibrillation recurrence after ablation? A systematic review and meta-analysis

INTRODUCTION

Although an undoubted association between epicardial fat tissue (EFT) and atrial fibrillation (AF) has been recently approved, the association between EFT and post-ablation AF recurrence is not evident yet. This study aimed to assess the association between EFT and AF recurrence after ablation.

METHODS

The present study was a systematic review and meta-analysis using related literature available in electronic databases until July 2018 via "atrial fibrillation" and "epicardial fat" as the main keywords. Considering the different methods of EFT measurement, three different pooled meta-analyses were conducted in this study including: 1) comparison of total EFT volume, 2) left atrium (LA)-EFT volume, and 3) EFT thickness between two groups with and without AF recurrence estimating standardized mean difference (SMD) through a random and non-random effect meta-analysis. Statistical analysis was also performed using Comprehensive Meta-analysis (CMA) Software.

RESULTS

Following a search into a total number of 518 articles, the findings of 12 studies published in 10 articles were enrolled in this meta-analysis. Accordingly, the results of meta-analysis showed that LA-EFT and total EFT volumes were higher in recurrent subjects (LA-EFT: SMD = 0.862 ml; I2 = 0.00, 95% confidence interval (CI) = 0.567-1.156; total EFT: SMD = 1.017 ml, I2 = 0.00, 95% CI = 0.748-1.286). Besides, a significant higher EFT thickness in patients with AF recurrence compared to those with no AF recurrence was observed (SMD = 0.808 mm, I2 = 91.07, 95% CI = 0.215-1401).

CONCLUSION

The total EFT and LA-EFT volumes, as well as EFT thickness, seemed to be associated with AF recurrence in patients undergoing AF ablation.

Epicardial adipose tissue and atrial fibrillation: pathophysiological mechanisms, clinical implications, and potential therapies

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is associated with increased cardiovascular morbidity and mortality. Epicardial adipose tissue (EAT) serves as a biologically active organ with important endocrine and inflammatory function. Review An accumulating body of evidence suggests that EAT is associated with the initiation, perpetuation, and recurrence of AF, but the precise role of EAT in AF pathogenesis is not completely elucidated. Pathophysiological mechanisms involve adipocyte infiltration, profibrotic and pro-inflammatory paracrine effects, oxidative stress, neural mechanisms, and genetic factors.

CONCLUSIONS

Notably, EAT accumulation seems to be associated with stroke and adverse cardiovascular outcomes in AF. Weight loss, specific medications and ablation of ganglionated plexi (GP) seem to be potential therapies in this setting.

Linking atrial fibrillation with non-alcoholic fatty liver disease: potential common therapeutic targets

Non-alcoholic fatty liver disease (NAFLD) and atrial fibrillation (AF) are common chronic non-infectious diseases with rising incidences. NAFLD is an independent risk factor for the onset of AF, after adjusting potentially related factors. The pathogenesis of these diseases share several mechanisms including reduced adiponectin level, insulin resistance, and renin angiotensin aldosterone system (RAAS) activation, in addition to activation of common disease pathways that promote inflammation, oxidative stress, and fibrosis. Furthermore, statins and RAAS blockers exert therapeutic effects concurrently on NAFLD and AF. The common pathogenesis of NAFLD and AF may serve as a potential therapeutic target in the future.

Long-Term Administration of Eicosapentaenoic Acid Improves Post-Myocardial Infarction Cardiac Remodeling in Mice by Regulating Macrophage Polarization

Background

Consumption of n‐3 fatty acids reduces the incidence of cardiovascular mortality in populations that consume diets rich in fish oil. Eicosapentaenoic acid (EPA) is an n‐3 fatty acid known to reduce the frequency of nonfatal coronary events; however, the frequency of mortality after myocardial infarction (MI) is not reduced. The aims of this study were to determine whether long‐term administration of EPA regulated cardiac remodeling after MI and to elucidate the underlying therapeutic mechanisms of EPA.

Methods and Results

C57BL/6J mice were divided into control (phosphate‐buffered saline–treated) and EPA‐treated groups. After 28 days of treatment, the mice were subjected to either sham surgery or MI by left anterior descending coronary artery ligation. Mortality due to MI or heart failure was significantly lower in the EPA‐treated mice than in the phosphate‐buffered saline–treated mice. However, the incidence of cardiac rupture was comparable between the EPA‐treated mice and the phosphate‐buffered saline–treated mice after MI. Echocardiographic tests indicated that EPA treatment attenuated post‐MI cardiac remodeling by preventing issues such as left ventricular systolic dysfunction and left ventricle dilatation 28 days after MI induction. Moreover, during the chronic remodeling phase, ie, 28 days after MI, flow cytometry demonstrated that EPA treatment significantly inhibited polarization toward proinflammatory M1 macrophages, but not anti‐inflammatory M2 macrophages, in the infarcted heart. Furthermore, EPA treatment attenuated fibrosis in the noninfarcted remote areas during the chronic phase.

Conclusions

Long‐term administration of EPA improved the prognosis of and attenuated chronic cardiac remodeling after MI by modulating the activation of proinflammatory M1 macrophages.

Hypoxia induces arginase II expression and increases viable human pulmonary artery smooth muscle cell numbers via AMPKα1 signaling

Pulmonary artery smooth muscle cell (PASMC) proliferation is one of the hallmark features of hypoxia-induced pulmonary hypertension. With only supportive treatment options available for this life-threatening disease, treating and preventing the proliferation of PASMCs is a viable therapeutic option. A key promoter of hypoxia-induced increases in the number of viable human PASMCs is arginase II, with attenuation of viable cell numbers following pharmacologic inhibition or siRNA knockdown of the enzyme. Additionally, increased levels of arginase have been demonstrated in the pulmonary vasculature of patients with pulmonary hypertension. The signaling pathways responsible for the hypoxic induction of arginase II in PASMCs, however, remain unknown. Hypoxia is a recognized activator of AMPK, which is known to be expressed in human PASMCs (hPASMCs). Activation of AMPK by hypoxia has been shown to promote cell survival in PASMCs. In addition, pharmacologic agents targeting AMPK have been shown to attenuate chronic hypoxia-induced pulmonary hypertension in animal models. The present studies tested the hypothesis that hypoxia-induced arginase II expression in hPASMCs is mediated through AMPK signaling. We found that pharmacologic inhibitors of AMPK, as well as siRNA knockdown of AMPKα1, prevented hypoxia-induced arginase II. The hypoxia-induced increase in viable hPASMC numbers was also prevented following both pharmacologic inhibition and siRNA knockdown of AMPK. Furthermore, we demonstrate that overexpression of AMPK induced arginase II protein expression and viable cells numbers in hPASMCs.

Pharmacological strategies for prevention of postoperative atrial fibrillation

Atrial fibrillation (AF) complicating cardiac surgery continues to be a major problem that increases the postoperative risk of stroke, myocardial infarction, heart failure and costs and can affect long-term survival. The incidence of AF after surgery has not significantly changed over the last two decades, despite improvement in medical and surgical techniques. The mechanism and pathophysiology underlying postoperative AF (PoAF) is incompletely understood and results from a combination of acute and chronic factors, superimposed on an underlying abnormal atrial substrate with increased interstitial fibrosis. Several anti-arrhythmic and non-anti-arrhythmic medications have been used for the prevention of PoAF, but the effectiveness of these strategies has been limited due to a poor understanding of the basis for the increased susceptibility of the atria to AF in the postoperative setting. In this review, we summarize the pathophysiology underlying the development of PoAF and evidence behind pharmacological approaches used for its prevention in the postoperative setting.

The Current Role of Omega-3 Fatty Acids in the Management of Atrial Fibrillation

Background: The main dietary source of omega-3 polyunsaturated fatty acids (n-3 PUFA) is fish, which contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In the present manuscript, we aimed to review the current evidence regarding the clinical role of n-3 PUFA in the prevention of atrial fibrillation (AF) and the possible underlying mechanisms. Methods: A literature search based on PubMed listings was performed using “Omega-3 fatty acids” and “atrial fibrilation” as key search terms. Results: n-3 PUFA have been shown to attenuate structural atrial remodeling, prolong atrial effective refractory period through the prevention of reentry and suppress ectopic firing from pulmonary veins. Dietary fish intake has been found to have no effect on the incidence of AF in the majority of studies. Circulating DHA has been consistently reported to be inversely associated with AF risk, whereas EPA has no such effect. The majority of studies investigating the impact of n-3 PUFA supplementation on the incidence of AF following cardiac surgery reported no benefit, though most of them did not use n-3 PUFA pretreatment for adequate duration. Studies using adequate four-week pretreatment with n-3 PUFA before cardioversion of AF showed a reduction of the AF incidence. Conclusions: Although n-3 PUFA have antiarrhythmogenic properties, their clinical efficacy on the prevention of AF is not consistently supported. Further well-designed studies are needed to overcome the limitations of the existing studies and provide robust conclusions.

Fatty acids and cardiac disease: fuel carrying a message

From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western-type high-fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time, advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish-oil derived FA-derivatives with anti-inflammatory properties, the so-called resolvins, and various G-protein-coupled receptors that recognize FA as ligands. In the present review, we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure.

TGF-β1 signal pathway in the regulation of inflammation in patients with atrial fibrillation

OBJECTIVE

To observe the expression changes of inflammatory markers TGF-β1, Smad3 and IL-6 in patients with atrial fibrillation (AF), and to explore the significance of TGF-β1 signaling pathway in the structural remodeling of AF.

METHODS

The expression of TGF-β1, Smad3 and IL-6 in 50 cases with AF and 30 normal cases were detected by RT-PCR and ELISA.

RESULTS

The TGF-β1, Smad3 and IL-6 mRNA and protein expression levels in patients with AF were significantly higher than that in the control group (P<0.05), but there was no significantly different between the paroxysmal AF group and the persistent AF group (P>0.05). The TGF-β1mRNA expression in the ⩾ 50 years subgroup was significantly higher than that in the <50 years subgroups, and it was higher in the NYHA III subgroup than in the I/II grade subgroup. It was also higher in the left ventricular ejection fraction (LVEF) <50% subgroup than in LVEF ⩾ 50% group, and it was significantly higher in the AF time ⩾ 36 months subgroup than that in <36 months subgroup (P<0.05). The Smad3 and IL-6 expressions in the in the LVEF <50% subgroup were both high that than that in LVEF ⩾ 50% group, and higher in the AF time ⩾ 36 months subgroup than that in <36 months subgroup (P<0.05). There were a positive correlation between TGF-β1, Smad3 and IL-6 (r=0.687, r=0.547). There were also a positive correlation between Smad3 and IL-6 mRNA (r=0.823).

CONCLUSIONS

AF is associated with inflammation, and the inflammation is also involved in the fibrillation and sustain of AF. The TGF-β1 signal pathway may be involved in the process of atrial structural remodeling in patients with AF, and iss related with the occurrence and maintenance of AF.

Fish oil constituent eicosapentaenoic acid inhibits endothelin-induced cardiomyocyte hypertrophy via PPAR-α

AIMS

A growing body of evidence shows the cardiovascular benefits of fish oil ingredients, including eicosapentaenoic acid (EPA), in humans and experimental animals. However, the effects of EPA on endothelin (ET)-1-induced cardiomyocyte hypertrophy and the involved signaling cascade are largely unknown. A previous study has demonstrated that peroxisomal proliferator-activated receptor (PPAR)-α ligand (fenofibrate) prevents ET-1-induced cardiomyocyte hypertrophy. Although EPA is a ligand of PPAR-α, to date, no study has examined a relationship between EPA and PPAR-α in cardiomyocyte hypertrophy. Here, we investigated whether EPA can block ET-1-induced cardiomyocyte hypertrophy and the possible underlying mechanisms.

MAIN METHODS

At day 4 of culture, neonatal rat cardiomyocytes were divided into four groups: control, control cells treated with EPA (10 μM), ET-1 (0.1 nM) administered only and EPA-pre-treated ET-1 administered groups. Also, the cardiomyocytes were treated with PPAR-α siRNA in order to elucidate the mechanisms that may underlie suppression of hypertrophy via the EPA-PPAR system.

KEY FINDINGS

Following ET-1 treatment, 2.12- and 1.92-fold increases in surface area and total protein synthesis rate in cardiomyocytes, respectively, were observed and these changes were greatly blocked by EPA pre-treatment. Further, the expression of PPAR-α increased in EPA-treated groups. PPAR-PPRE binding activity was suppressed in ET-1 administered cardiomyocyte and this suppression was improved by EPA treatment. Lastly, pre-treatment of cardiomyocytes with PPAR-α siRNA prior to EPA treatment attenuated the suppressing effects of EPA on cardiomyocyte hypertrophy.

SIGNIFICANCE

In conclusion, the present study shows that EPA attenuates ET-1 induced cardiomyocyte hypertrophy by up regulating levels of PPAR-α pathway.

Plasma phospholipid omega-3 fatty acids and incidence of postoperative atrial fibrillation in the OPERA trial

Background

Long‐chain polyunsaturated omega‐3 fatty acids (n‐3 PUFA) demonstrated antiarrhythmic potential in experimental studies. In a large multinational randomized trial (OPERA), perioperative fish oil supplementation did not reduce the risk of postoperative atrial fibrillation (PoAF) in cardiac surgery patients. However, whether presupplementation habitual plasma phospholipid n‐3 PUFA, or achieved or change in n‐3 PUFA level postsupplementation are associated with lower risk of PoAF is unknown.

Methods and Results

In 564 subjects undergoing cardiac surgery between August 2010 and June 2012 in 28 centers across 3 countries, plasma phospholipid levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) were measured at enrollment and again on the morning of cardiac surgery following fish oil or placebo supplementation (10 g over 3 to 5 days, or 8 g over 2 days). The primary endpoint was incident PoAF lasting ≥30 seconds, centrally adjudicated, and confirmed by rhythm strip or ECG. Secondary endpoints included sustained (≥1 hour), symptomatic, or treated PoAF; the time to first PoAF; and the number of PoAF episodes per patient. PoAF outcomes were assessed until hospital discharge or postoperative day 10, whichever occurred first. Relative to the baseline, fish oil supplementation increased phospholipid concentrations of EPA (+142%), DPA (+13%), and DHA (+22%) (P<0.001 each). Substantial interindividual variability was observed for change in total n‐3 PUFA (range=−0.7% to 7.5% after 5 days of supplementation). Neither individual nor total circulating n‐3 PUFA levels at enrollment, morning of surgery, or change between these time points were associated with risk of PoAF. The multivariable‐adjusted OR (95% CI) across increasing quartiles of total n‐3 PUFA at enrollment were 1.0, 1.06 (0.60 to 1.90), 1.35 (0.76 to 2.38), and 1.19 (0.64 to 2.20); and for changes in n‐3 PUFA between enrollment and the morning of surgery were 1.0, 0.78 (0.44 to 1.39), 0.89 (0.51 to 1.55), and 1.01 (0.58 to 1.75). In stratified analysis, demographic, medication, and cardiac parameters did not significantly modify these associations. Findings were similar for secondary PoAF endpoints.

Conclusions

Among patients undergoing cardiac surgery, neither higher habitual circulating n‐3 PUFA levels, nor achieved levels or changes following short‐term fish oil supplementation are associated with risk of PoAF.

Clinical Trial Registration

URL: Clinicaltrials.gov Unique identifier: NCT00970489

Fish oil and atrial fibrillation after cardiac surgery: a meta-analysis of randomized controlled trials

Background

Influence of fish oil supplementation on postoperative atrial fibrillation (POAF) was inconsistent according to published clinical trials. The aim of the meta-analysis was to evaluate the effects of perioperative fish oil supplementation on the incidence of POAF after cardiac surgery.

Methods

Pubmed, Embase and the Cochrane Library databases were searched. Randomized controlled trials (RCTs) assessing perioperative fish oil supplementation for patients undergoing cardiac surgery were identified. Data concerning study design, patient characteristics, and outcomes were extracted. Risk ratio (RR) and weighted mean differences (WMD) were calculated using fixed or random effects models.

Results

Eight RCTs involving 2687 patients were included. Perioperative supplementation of fish oil did not significantly reduce the incidence of POAF (RR = 0.86, 95%CI 0.71 to 1.03, p = 0.11) or length of hospitalization after surgery (WMD = 0.10 days, 95% CI: 0.48 to 0.67 days, p = 0.75). Fish oil supplementation also did not affect the perioperative mortality, incidence of major bleeding or the length of stay in the intensive care unit. Meta-regression and subgroup analyses indicated mean DHA dose in the supplements may be a potential modifier for the effects of fish oil for POAF. For supplements with DHA >1 g/d, fish oil significantly reduced the incidence of POAF; while it did not for the supplements with a lower dose of DHA.

Conclusions

Current evidence did not support a preventative role of fish oil for POAF. However, relative amounts of DHA and EPA in fish oil may be important for the prevention of POAF.

Fatty acids modulate cytokine and chemokine secretion of stimulated human whole blood cultures in diabetes

Fatty acids, uric acid and glucose are thought to contribute to subclinical inflammation associated with diabetes mellitus. We tested whether co-incubation of free fatty acids and uric acid or glucose influences the secretion of immune mediators from stimulated human whole blood in vitro. Fresh whole blood samples from 20 healthy subjects, 20 patients with type 1 diabetes and 23 patients with type 2 diabetes were incubated for 24 h with palmitic acid (PAL), linolenic acid (LIN) or eicosapentaenoic acid (EPA) alone or together with elevated concentrations of uric acid or glucose. Concentrations of proinflammatory cytokines interleukin (IL)-1β, IL-2, IL-12(p70), IL-18, IFN-γ, of regulatory cytokines IL-4, IL-10, IL-17 and chemokine CCL2 (MCP-1) were measured by multiplex-bead technology from supernatants. Co-incubation of fatty acids with uric acid resulted in a significant reduction of IL-10, IL-12(p70), IFN-γ and CCL2 (MCP-1) concentrations in supernatants compared to incubation with uric acid alone (P < 0·0001). In contrast, IL-18 was up-regulated upon co-stimulation with fatty acids and uric acid. Similarly, co-incubation of fatty acids with glucose diminished secretion of IL-10, IFN-γ and CCL2 (monocyte chemotactic protein-1), while IL-8 was up-regulated (P < 0·001). Samples from healthy and diabetic subjects did not differ after adjustment for age, sex, body mass index and diabetes type. All three fatty acids similarly influenced whole blood cytokine release in vitro and modulated uric acid or glucose-stimulated cytokine secretion. Although the ω-3-fatty acid EPA showed slightly stronger effects, further studies are required to elaborate the differential effects of PAL, LIN and EPA on disease risk observed previously in epidemiological studies.

The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment

Although epidemiological studies provide strong evidence for an inverse relationship between omega-3 polyunsaturated fatty acids (n-3 PUFAs) and cardiac mortality, inconsistent and often conflicting results have been obtained from both animal studies and clinical prevention trials. Despite these heterogeneous results, some general conclusions can be drawn from these studies: 1) n-PUFAs have potent effects on ion channels and calcium regulatory proteins that vary depending on the route of administration. Circulating (acute administration) n-3 PUFAs affect ion channels directly while incorporation (long-term supplementation) of these lipids into cell membranes indirectly alter cardiac electrical activity via alteration of membrane properties. 2) n-3 PUFAs reduce baseline HR and increase HRV via alterations in intrinsic pacemaker rate rather than from changes in cardiac autonomic neural regulation. 3) n-3 PUFAs may be only effective if given before electrophysiological or structural remodeling has begun and have no efficacy against atrial fibrillation. 5) Despite initial encouraging results, more recent clinical prevention and animal studies have not only failed to reduce sudden cardiac death but actually increased mortality in angina patients and increased rather than decreased malignant arrhythmias in animal models of regional ischemia. 6) Given the inconsistent benefits reported in clinical and experimental studies and the potential adverse actions on cardiac rhythm noted during myocardial ischemia, n-3 PUFA must be prescribed with caution and generalized recommendations to increase fish intake or to take n-3 PUFA supplements need to be reconsidered.

Antifibrotic effects of ω-3 fatty acids in the heart: one possible treatment for diastolic heart failure

Half of heart failure patients have diastolic heart failure, which has no effective treatments. Several studies indicate a role for ω-3 polyunsaturated fatty acids (PUFAs) in heart failure. Recent studies suggest that ω-3 PUFAs inhibit cardiac fibrosis and attenuate diastolic dysfunction. This opens up possible new avenues for treatment of diastolic heart failure. In this review, we focus on the antifibrotic effects of ω-3 PUFAs in heart and the underlying cellular and molecular mechanisms.

Effect of Omega-3 Polyunsaturated Fatty Acid Supplementation in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia conferring a higher morbidity and mortality. Despite the increasing incidence of AF; available therapies are far from perfect. Dietary fish oils, containing omega 3 fatty acids, also called polyunsaturated fatty acid [PUFA] have demonstrated beneficial electrophysiological, autonomic and anti-inflammatory effects on both atrial and ventricular tissue. Multiple clinical trials, focusing on various subsets of patients with AF, have studied the role of PUFA and their potential role in reducing the incidence of this common arrhythmia. While PUFA appears to have a beneficial effect in the primary prevention of AF in the elderly with structural heart disease, this benefit has not been universally observed. In the secondary prevention of AF, PUFA seems to have a greater impact in the reducing AF in patients with paroxysmal or persistent AF, stages of AF associated with less atrial fibrosis and negative structural remodeling. However, AF suppression has not been consistently demonstrated in clinical trials. In patients undergoing heart surgery, increasing PUFA intake has yielded mixed results in terms of AF prevention post-operatively; however, increased PUFA has been associated with a reduction in hospital stay. Therefore recommending the use of PUFA for the purpose of AF reduction remains controversial. This is in part attributable to the complexity of AF. Other conflicting variables include: heterogeneous patient populations studied; variable dosing; duration of follow-up; comorbidities; and, concomitant pharmacotherapy. This review article reviews in detail available basic and clinical research studies of fish oil in the treatment of AF, and its role in the treatment of this common disorder.

ABBREVIATIONS

AF=Atrial fibrillation, CHS=Cardiovascular Health Study,CABG=Coronary artery bypass surgery, d=Day, DHA=Docosahexaenoic acid, EPA=Eicosapentaenoic acid, ERP= Effective refractory period, g=Gram, PAF= Paroxysmal atrial fibrillation, PeAF= Persistent atrial fibrillation PUFA= Polyunsaturated fatty acid.

DHA derivatives of fish oil as dietary supplements: a nutrition-based drug discovery approach for therapies to prevent metabolic cardiotoxicity

INTRODUCTION

During the early 1970s, Danish physicians Jorn Dyerberg and colleagues observed that Greenland Eskimos consuming fatty fishes exhibited low incidences of heart disease. Fish oil is now one of the most commonly consumed dietary supplements. In 2004, concentrated fish oil was approved as a drug by the FDA for the treatment of hyperlipidemia. Fish oil contains two major omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). With advancements in lipid concentration and purification techniques, EPA- or DHA-enriched products are now commercially available, and the availability of these components in isolation allows their individual effects to be examined. Newly synthesized derivatives and endogenously discovered metabolites of DHA exhibit therapeutic utility for obesity, metabolic syndrome and cardiovascular disease.

AREAS COVERED

This review summarizes our current knowledge on the distinct effects of EPA and DHA to prevent metabolic syndrome and reduce cardiotoxicity risk. Since EPA is an integral component of fish oil, we will briefly review EPA effects, but our main theme will be to summarize effects of the DHA derivatives that are available today. We focus on using nutrition-based drug discovery to explore the potential of DHA derivatives for the treatment of obesity, metabolic syndrome and cardiovascular diseases.

EXPERT OPINION

The safety and efficacy evaluation of DHA derivatives will provide novel biomolecules for the drug discovery arsenal. Novel nutritional-based drug discoveries of DHA derivatives or metabolites may provide realistic and alternative strategies for the treatment of metabolic and cardiovascular disease.

Fish, Marine n-3 Fatty Acids, and Atrial Fibrillation - Experimental Data and Clinical Effects

Marine n−3 polyunsaturated fatty acids (PUFA) may have beneficial effects in relation to atrial fibrillation (AF) with promising data from experimental animal studies, however, results from studies in humans have been inconsistent. This review evaluates the mechanisms of action of marine n−3 PUFA in relation to AF based on experimental data and provides a status on the evidence obtained from observational studies and interventional trials. In conclusion, there is growing evidence for an effect of marine n−3 PUFA in prevention and treatment of AF. However, further studies are needed to establish which patients are more likely to benefit from n−3 PUFA, the timing of treatment, and dosages.

Omega-3 Fatty acids: anti-arrhythmic, pro-arrhythmic, or both?

This review focuses on developments after 2008, when the topic was last reviewed by the author. Pertinent publications were found by medline searches and in the author’s personal data base. Prevention of atrial fibrillation (AF) was investigated in a number of trials, sparked by one positive report on the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), considerations of upstream therapy, data from electrophysiologic laboratories and animal experiments. If EPA + DHA prevent postoperative AF, the effect is probably smaller than initially expected. The same is probably true for maintenance of sinus rhythm after cardioversion and for new-onset AF. Larger trials are currently ongoing. Prevention of ventricular arrhythmias was studied in carriers of an implanted cardioverter-defibrillator, with no clear results. This might have been due to a broad definition of the primary endpoint, including any ventricular arrhythmia and any action of the device. Epidemiologic studies support the contention that high levels of EPA + DHA prevent sudden cardiac death (SCD). However, since SCD is a rare occurrence, it is difficult to conduct an adequately powered trial. In patients with congestive heart failure, EPA + DHA reduced total mortality and rehospitalizations, but not SCD or presumed arrhythmic death. Of three trials in patients after a myocardial infarction, two were inadequately powered, and in one, the dose might have been too low. Taken together, while epidemiologic studies support an inverse relation between EPA + DHA and occurrence of SCD or arrhythmic death, demonstrating this effect in intervention trials remained elusive so far. A pro-arrhythmic effect of EPA + DHA has not been seen in intervention studies, and results of epidemiologic and animal studies also rather argue against such an effect. A different, and probably more productive, perspective is provided by a standardized analytical assessment of a person’s status in EPA + DHA by use of the omega-3 index, EPA + DHA in red cell fatty acids. In populations with a high omega-3 index, SCD is rare. Intervention trials can become more effective by including a low omega-3 index into the inclusion criteria, thus creating a study population more likely to demonstrate an effect of EPA + DHA. This is especially relevant in case of rare endpoints, like new-onset AF or SCD.

Association of plasma phospholipid long-chain ω-3 fatty acids with incident atrial fibrillation in older adults: the cardiovascular health study

BACKGROUND

Experimental studies suggest that long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs) may reduce the risk of atrial fibrillation (AF). Prior studies evaluating fish or n-3 PUFA consumption from dietary questionnaires and incident AF have been conflicting. Circulating levels of n-3 PUFAs provide an objective measurement of exposure.

METHODS AND RESULTS

Among 3326 US men and women ≥65 years of age and free of AF or heart failure at baseline, plasma phospholipid levels of eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid were measured at baseline by use of standardized methods. Incident AF (789 cases) was identified prospectively from hospital discharge records and study visit ECGs during 31 169 person-years of follow-up (1992-2006). In multivariable Cox models adjusted for other risk factors, the relative risk in the top versus lowest quartile of total n-3 PUFAs (eicosapentaenoic acid+docosapentaenoic acid+docosahexaenoic acid) levels was 0.71 (95% confidence interval, 0.57-0.89; P for trend=0.004) and of DHA levels was 0.77 (95% confidence interval, 0.62-0.96; P for trend=0.01). Eicosapentaenoic acid and docosapentaenoic acid levels were not significantly associated with incident AF. Evaluated nonparametrically, both total n-3 PUFAs and docosahexaenoic acid showed graded and linear inverse associations with incidence of AF. Adjustment for intervening events such as heart failure or myocardial infarction during follow-up did not appreciably alter results.

CONCLUSIONS

In older adults, higher circulating total long-chain n-3 PUFA and docosahexaenoic acid levels were associated with lower risk of incident AF. These results highlight the need to evaluate whether increased dietary intake of these fatty acids could be effective for the primary prevention of AF.

Health benefits of n-3 polyunsaturated fatty acids: eicosapentaenoic acid and docosahexaenoic acid

Marine-based fish and fish oil are the most popular and well-known sources of n-3 polyunsaturated fatty acids (PUFAs), namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These n-3 PUFAs are known to have variety of health benefits against cardiovascular diseases (CVDs) including well-established hypotriglyceridemic and anti-inflammatory effects. Also, various studies indicate promising antihypertensive, anticancer, antioxidant, antidepression, antiaging, and antiarthritis effects. Moreover, recent studies also indicate anti-inflammatory and insulin-sensitizing effects of these fatty acids in metabolic disorders. Classically, n-3 PUFAs mediate some of these effects by antagonizing n-6 PUFA (arachidonic acid)-induced proinflammatory prostaglandin E₂ (PGE₂) formation. Another well-known mechanism by which n-3 PUFAs impart their anti-inflammatory effects is via reduction of nuclear factor-κB activation. This transcription factor is a potent inducer of proinflammatory cytokine production, including interleukin 6 and tumor necrosis factor-α, both of which are decreased by EPA and DHA. Other evidence also demonstrates that n-3 PUFAs repress lipogenesis and increase resolvins and protectin generation, ultimately leading to reduced inflammation. Finally, beneficial effects of EPA and DHA in insulin resistance include their ability to increase secretion of adiponectin, an anti-inflammatory adipokine. In summary, n-3 PUFAs have multiple health benefits mediated at least in part by their anti-inflammatory actions; thus their consumption, especially from dietary sources, should be encouraged.

Omega-3 fatty acids and cardiovascular disease: effects on risk factors, molecular pathways, and clinical events

We reviewed available evidence for cardiovascular effects of n-3 polyunsaturated fatty acid (PUFA) consumption, focusing on long chain (seafood) n-3 PUFA, including their principal dietary sources, effects on physiological risk factors, potential molecular pathways and bioactive metabolites, effects on specific clinical endpoints, and existing dietary guidelines. Major dietary sources include fatty fish and other seafood. n-3 PUFA consumption lowers plasma triglycerides, resting heart rate, and blood pressure and might also improve myocardial filling and efficiency, lower inflammation, and improve vascular function. Experimental studies demonstrate direct anti-arrhythmic effects, which have been challenging to document in humans. n-3 PUFA affect a myriad of molecular pathways, including alteration of physical and chemical properties of cellular membranes, direct interaction with and modulation of membrane channels and proteins, regulation of gene expression via nuclear receptors and transcription factors, changes in eicosanoid profiles, and conversion of n-3 PUFA to bioactive metabolites. In prospective observational studies and adequately powered randomized clinical trials, benefits of n-3 PUFA seem most consistent for coronary heart disease mortality and sudden cardiac death. Potential effects on other cardiovascular outcomes are less-well-established, including conflicting evidence from observational studies and/or randomized trials for effects on nonfatal myocardial infarction, ischemic stroke, atrial fibrillation, recurrent ventricular arrhythmias, and heart failure. Research gaps include the relative importance of different physiological and molecular mechanisms, precise dose-responses of physiological and clinical effects, whether fish oil provides all the benefits of fish consumption, and clinical effects of plant-derived n-3 PUFA. Overall, current data provide strong concordant evidence that n-3 PUFA are bioactive compounds that reduce risk of cardiac death. National and international guidelines have converged on consistent recommendations for the general population to consume at least 250 mg/day of long-chain n-3 PUFA or at least 2 servings/week of oily fish.

Cytochrome P450-dependent eicosanoid production and crosstalk

PURPOSE OF REVIEW

This review highlights recent advances in eicosanoid biology, especially linked to the cytochrome P450 (CYP)/soluble epoxide hydrolase (sEH) axis in vascular biology and disease.

RECENT FINDINGS

Since the first reports that CYP-derived metabolites of arachidonic acid can elicit vascular smooth muscle hyperpolarization and relaxation, it has become clear that fatty acid epoxides and diols are important lipid signaling molecules. Targeting CYP epoxygenases in vivo is difficult as these enzymes are involved in the metabolism of many currently used clinical agents. However, targeting the sEH which metabolizes fatty acid epoxides to their corresponding diols is a highly effective way of manipulating levels of these lipid mediators in vivo. Indeed, sEH-/- mice are protected against the development of some forms of hypertension, and have altered adipocyte metabolism and insulin resistance, phenomena reproduced by selective sEH inhibitors.

SUMMARY

Given that elevated epoxide levels have been linked with decreased blood pressure and inflammation in animal models, inhibitors of the sEH are currently being developed for the treatment of human hypertension and inflammation/atherosclerosis. This review focuses on outlining recent insights gained in the beneficial as well as the potentially adverse aspects of interfering with the CYP/sEH axis.

Eicosapentaenoic acid protects against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced hepatic toxicity in cultured rat hepatocytes

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent and ubiquitous environmental contaminant. The health impact of TCDD exposure is of great concern to the general public. Recent reports have implied that eicosapentaenoic acid (EPA) might be a potential chemopreventive agent and influence hepatotoxicity. The aim of the current study was to explore the effectiveness of EPA in alleviating the toxicity of TCDD on primary cultured rat hepatocytes. EPA (5, 10 and 20 μM) was added to cultures alone or simultaneously with TCDD (5 and 10 μM). Rat hepatocytes were treated with TCDD and EPA for 48 h, and then cytotoxicity was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (LMN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD but not EPA decreased cell viability. TCDD also increased TOS level and significantly decreased TAC level in rat hepatocytes in a clear dose dependent manner. On the basis of increasing doses, the dioxin caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG as compared to control culture. Whereas, in cultures treated with EPA alone, TOS level did not change and the level of TAC significantly increased. The presence of EPA with TCDD minimized the toxic effects of the dioxin on primary hepatocytes cultures. Noteworthy, EPA has a protective effect against TCDD-mediated DNA damages.

CYP-eicosanoids--a new link between omega-3 fatty acids and cardiac disease?

Fish oil omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) protect against arrhythmia and sudden cardiac death by largely unknown mechanisms. Recent in vitro and in vivo studies demonstrate that arachidonic acid (AA) metabolizing cytochrome P450-(CYP) enzymes accept EPA and DHA as efficient alternative substrates. Dietary EPA/DHA supplementation causes a profound shift of the cardiac CYP-eicosanoid profile from AA- to EPA- and DHA-derived epoxy- and hydroxy-metabolites. CYP2J2 and other CYP epoxygenases preferentially epoxidize the ω-3 double bond of EPA and DHA. The corresponding metabolites, 17,18-epoxy-EPA and 19,20-epoxy-DHA, dominate the CYP-eicosanoid profile of the rat heart after EPA/DHA supplementation. The (ω-3)-epoxyeicosanoids show highly potent antiarrhythmic properties in neonatal cardiomyocytes, suggesting that these metabolites may specifically contribute to the cardioprotective effects of omega-3 fatty acids. This hypothesis is discussed in the context of recent findings that revealed CYP-eicosanoid mediated mechanisms in cardiac ischemia-reperfusion injury and maladaptive cardiac hypertrophy.