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

Effects of Walnut-Rich Diet on Cation-Handling Proteins in the Heart of Healthy and Metabolically Compromised Male Rats

The transport of cations in the cardiomyocytes, crucial for the functioning of the heart, can be affected by walnut diet due to the high content of polyunsaturated fatty acids. Healthy and metabolically compromised rats (drinking 10% fructose solution) were subjected to a diet supplemented with 2.4 g of walnuts for 6 weeks to investigate the effect on proteins involved in cation transport in the heart cells. Fructose increased the level of the α1 subunit of Na+/K+-ATPase and the phosphorylation of extracellular signal-regulated kinase 1/2 in the heart of control and walnut-eating rats, while elevated L-type calcium channel α (LTCCα), sodium-calcium exchanger 1 (NCX1), and Maxi Kα level were observed only in rats that did not consume walnuts. However, walnuts significantly increased the cardiac content of LTCC, NCX1, and Maxi Kα, as well as Kir6.1 and SUR2B subunits of KATP channel, but only in fructose-naive rats. In animals that drank fructose, a significant increasing effect of walnuts was observed only in Akt kinase phosphorylation, which may be a part of the antiarrhythmic mechanism of decreasing cation currents in cardiomyocytes. The walnut diet-induced increase in LTCC and NCX1 expression in healthy rats may indicate intense cardiac calcium turnover, whereas the effect on Kir6.1 and SUR2B subunits suggests stimulation of KATP channel transport in the cardiac vasculature. The effects of walnuts on the cation-handling proteins in the heart, mostly limited to healthy animals, suggest the possible use of a walnut-supplemented diet in the prevention rather than the treatment of cardiological channelopathies.

Omega-3 fatty acids in bipolar patients with a low omega-3 index and reduced heart rate variability: the "BIPO-3" trial

Background

Research suggests that a low omega-3 index may contribute to the low heart rate variability and the increased risk of cardiovascular morbidity and mortality in bipolar disorders. However, so far, no intervention trial with EPA and DHA has been conducted in bipolar patients attempting to increase their heart rate variability.

Methods

119 patients with bipolar disorder according to DSM-IV were screened, with 55 euthymic bipolar patients—owing to inclusion criteria (e.g. low omega-3 index (< 6%), SDNN < 60 ms.)—being enrolled in a randomized, double-blind, 12-week parallel study design with omega-3 fatty acids (4 capsules of 530 mg EPA, 150 mg DHA) or corn oil as a placebo, in addition to usual treatment. Heart rate variability as well as the omega-3 index were measured at baseline and at the endpoint of the study.

Results

A total of 42 patients (omega-3: n = 23, corn oil: n = 19) successfully completed the study after 12 weeks. There was a significant increase in the omega-3 index (value at endpoint minus value at baseline) in the omega-3 group compared to the corn oil group (p < 0.0001). However, there was no significant difference in the change of the SDNN (value at endpoint minus value at baseline) between the treatment groups (p = 0.22). In addition, no correlation between changes in SDNN and change in the omega-3 index could be detected in the omega-3 group (correlation coefficient = 0.02, p = 0.94) or the corn oil group (correlation coefficient =  − 0.11, p = 0.91). Similarly, no significant differences between corn oil and omega-3 group regarding the change of LF (p = 0.19), HF (p = 0.34) and LF/HF ratio (p = 0.84) could be demonstrated.

Conclusions

In our randomized, controlled intervention trial in euthymic bipolar patients with a low omega-3 index and reduced heart rate variability no significant effect of omega-3 fatty acids on SDNN or frequency-domain measures HF, LF and LF/HF ratio could be detected. Possible reasons include, among others, the effect of psychotropic medication present in our trial and/or the genetics of bipolar disorder itself. Further research is needed to test these hypotheses.

Trial registration ClinicalTrials.gov, NCT00891826. Registered 01 May 2009–Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT00891826

Mechanisms Underlying Antiarrhythmic Properties of Cardioprotective Agents Impacting Inflammation and Oxidative Stress

The prevention of cardiac life-threatening ventricular fibrillation and stroke-provoking atrial fibrillation remains a serious global clinical issue, with ongoing need for novel approaches. Numerous experimental and clinical studies suggest that oxidative stress and inflammation are deleterious to cardiovascular health, and can increase heart susceptibility to arrhythmias. It is quite interesting, however, that various cardio-protective compounds with antiarrhythmic properties are potent anti-oxidative and anti-inflammatory agents. These most likely target the pro-arrhythmia primary mechanisms. This review and literature-based analysis presents a realistic view of antiarrhythmic efficacy and the molecular mechanisms of current pharmaceuticals in clinical use. These include the sodium-glucose cotransporter-2 inhibitors used in diabetes treatment, statins in dyslipidemia and naturally protective omega-3 fatty acids. This approach supports the hypothesis that prevention or attenuation of oxidative and inflammatory stress can abolish pro-arrhythmic factors and the development of an arrhythmia substrate. This could prove a powerful tool of reducing cardiac arrhythmia burden.

Processing Methodologies of Wet Microalga Biomass Toward Oil Separation: An Overview

One of the main goals of Mankind is to ensure food system sustainability-including management of land, soil, water, and biodiversity. Microalgae accordingly appear as an innovative and scalable alternative source in view of the richness of their chemical profiles. In what concerns lipids in particular, microalgae can synthesize and accumulate significant amounts of fatty acids, a great fraction of which are polyunsaturated; this makes them excellent candidates within the framework of production and exploitation of lipids by various industrial and health sectors, either as bulk products or fine chemicals. Conventional lipid extraction methodologies require previous dehydration of microalgal biomass, which hampers economic feasibility due to the high energy demands thereof. Therefore, extraction of lipids directly from wet biomass would be a plus in this endeavor. Supporting processes and methodologies are still limited, and most approaches are empirical in nature-so a deeper mechanistic elucidation is a must, in order to facilitate rational optimization of the extraction processes. Besides circumventing the current high energy demands by dehydration, an ideal extraction method should be selective, sustainable, efficient, harmless, and feasible for upscale to industrial level. This review presents and discusses several pretreatments incurred in lipid extraction from wet microalga biomass, namely recent developments and integrated processes. Unfortunately, most such developments have been proven at bench-scale only-so demonstration in large facilities is still needed to confirm whether they can turn into competitive alternatives.

Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of T-Wave Vector

Ventricular arrhythmias and sudden cardiac death during long-term space missions are a major concern for space agencies. Long-duration spaceflight and its ground-based analog head-down bed rest (HDBR) have been reported to markedly alter autonomic and cardiac functioning, particularly affecting ventricular repolarization of the electrocardiogram (ECG). In this study, novel methods are developed, departing from previously published methodologies, to quantify the index of Periodic Repolarization Dynamics (PRD), an arrhythmic risk marker that characterizes sympathetically-mediated low-frequency oscillations in the T-wave vector. PRD is evaluated in ECGs from 42 volunteers at rest and during an orthostatic tilt table test recorded before and after 60-day –6° HDBR. Our results indicate that tilt test, on top of enhancing sympathetic regulation of heart rate, notably increases PRD, both before and after HDBR, thus supporting previous evidence on PRD being an indicator of sympathetic modulation of ventricular repolarization. Importantly, long-term microgravity exposure is shown to lead to significant increases in PRD, both when evaluated at rest and, even more notably, in response to tilt test. The extent of microgravity-induced changes in PRD has been associated with arrhythmic risk in prior studies. An exercise-based, but not a nutrition-based, countermeasure is able to partially reverse microgravity-induced effects on PRD. In conclusion, long-term exposure to microgravity conditions leads to elevated low-frequency oscillations of ventricular repolarization, which are potentiated following sympathetic stimulation and are related to increased risk for repolarization instabilities and arrhythmias. Tested countermeasures are only partially effective in counteracting microgravity effects.

The role of antioxidants in the chemistry of oxidative stress: A review

This Review Article is focused on the action of the reactive oxygenated species in inducing oxidative injury of the lipid membrane components, as well as on the ability of antioxidants (of different structures and sources, and following different mechanisms of action) in fighting against oxidative stress. Oxidative stress is defined as an excessive production of reactive oxygenated species that cannot be counteracted by the action of antioxidants, but also as a perturbation of cell redox balance. Reactive oxygenated/nitrogenated species are represented by superoxide anion radical, hydroxyl, alkoxyl and lipid peroxyl radicals, nitric oxide and peroxynitrite. Oxidative stress determines structure modifications and function modulation in nucleic acids, lipids and proteins. Oxidative degradation of lipids yields malondialdehyde and 4-hydroxynonenal, but also isoprostanes, from unsaturated fatty acids. Protein damage may occur with thiol oxidation, carbonylation, side-chain oxidation, fragmentation, unfolding and misfolding, resulting activity loss. 8-hydroxydeoxyguanosine is an index of DNA damage. The involvement of the reactive oxygenated/nitrogenated species in disease occurrence is described. The unbalance between the oxidant species and the antioxidant defense system may trigger specific factors responsible for oxidative damage in the cell: over-expression of oncogene genes, generation of mutagen compounds, promotion of atherogenic activity, senile plaque occurrence or inflammation. This leads to cancer, neurodegeneration, cardiovascular diseases, diabetes, kidney diseases. The concept of antioxidant is defined, along with a discussion of the existent classification criteria: enzymatic and non-enzymatic, preventative or repair-systems, endogenous and exogenous, primary and secondary, hydrosoluble and liposoluble, natural or synthetic. Primary antioxidants are mainly chain breakers, able to scavenge radical species by hydrogen donation. Secondary antioxidants are singlet oxygen quenchers, peroxide decomposers, metal chelators, oxidative enzyme inhibitors or UV radiation absorbers. The specific mechanism of action of the most important representatives of each antioxidant class (endogenous and exogenous) in preventing or inhibiting particular factors leading to oxidative injury in the cell, is then reviewed. Mutual influences, including synergistic effects are presented and discussed. Prooxidative influences likely to occur, as for instance in the presence of transition metal ions, are also reminded.

Effects of long-term thyroid hormone level alterations, n-3 polyunsaturated fatty acid supplementation and statin administration in rats

Thyroid hormones (THs) play multiple roles in the organism and alterations of their levels can result in many pathological changes. Currently, we use hyperthyroid and hypothyroid rats as "models of a diseased organism" and analyze whether n-3 polyunsaturated fatty acids (n-3 PUFA) administration can ameliorate TH-induced pathophysiological changes. We investigate myosin heavy chain composition, calsequestrin levels, changes in cardiac tissue remodeling and cell-to-cell communication, expression of protein kinases, mitochondrial functions, oxidative stress markers and cell death, changes in serum lipid levels, activities of key enzymes of thyroid hormone metabolism, activity of acetylcholine esterase and membrane anisotropy, as well as mobile behavior and thermal sensitivity. Additionally we also mention our pilot experiments dealing with the effect of statin administration on skeletal muscles and sensory functions. As THs and n-3 PUFA possess multiple sites of potential action, we hope that our complex research will contribute to a better understanding of their actions, which can be useful in the treatment of different pathophysiological events including cardiac insufficiency in humans.

Antioxidant supplementations for prevention of atrial fibrillation after cardiac surgery: an updated comprehensive systematic review and meta-analysis of 23 randomized controlled trials

This systematic review with meta-analysis sought to determine the impact of antioxidants (N-acetylcysteine [NAC], polyunsaturated fatty acids [PUFAs] and vitamins) on incidence of postoperative atrial fibrillation (POAF) and duration of length of hospital stay. Medline, Embase, Elsevier, Sciences online database and Google Scholar literature search was made for studies in randomized controlled trials. The effect sizes measured were odds ratio (OR) for categorical variable and standard mean difference (SMD) with 95% confidence interval (CI) for calculating differences between mean values of duration of hospitalization in intervention and control groups. A value of P < 0.1 for Q-test or I(2) > 50% indicated significant heterogeneity between the studies. Literature search of all major databases retrieved 355 studies. After screening, a total of 23 trials were identified that reported outcomes of 4278 patients undergoing cardiac surgery. Pooled effects estimates on POAF showed a significant reduction after NAC (OR: 0.56, 95% CI: 0.40-0.77, P < 0.001), PUFA (OR: 0.84, 95% CI: 0.71-0.99, P = 0.03) and vitamin C treatment (OR: 0.50, 95% CI: 0.27-0.91, P = 0.02). Hospital length of stay was not reduced after NAC therapy (SMD: 0.082, 95% CI -0.09 to 0.25, P = 0.3), but could be decreased with PUFA (SMD: -0.185, 95% CI: -0.35 to -0.018, P = 0.03) and vitamin C (SMD: -0.325, 95% CI -0.50 to -0.14, P < 0.01). In conclusion, perioperative antioxidant supplementations with NAC, PUFA and vitamin C prevent atrial fibrillation after cardiac surgery. Moreover, PUFA and vitamin C are capable to reduce hospital stay, whereas NAC lacks this capacity.

U-shaped relationship between tissue docosahexaenoic acid and atrial fibrillation following cardiac surgery

BACKGROUND/OBJECTIVES

Randomised controlled trials (RCTs) evaluating the effect of fish oil supplementation on postoperative atrial fibrillation (POAF) following cardiac surgery have produced mixed results. In this study, we examined relationships between levels of red blood cell (RBC) n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) and the incidence of POAF.

SUBJECTS/METHODS

We used combined data (n=355) from RCTs conducted in Australia and Iceland. The primary end point was defined as POAF lasting >10 min in the first 6 days following surgery. The odds ratios (ORs) for POAF were compared between quintiles of preoperative RBC n-3 LC-PUFA levels by multivariable logistic regression.

RESULTS

Subjects with RBC docosahexaenoic acid (DHA) in the fourth quintile, comprising a RBC DHA range of 7.0-7.9%, had the lowest incidence of POAF. Subjects in the lowest and highest quintiles had significantly higher risk of developing POAF compared with those in the fourth quintile (OR=2.36: 95% CI; 1.07-5.24 and OR=2.45: 95% CI; 1.16-5.17, respectively). There was no association between RBC eicosapentaenoic acid levels and POAF incidence.

CONCLUSIONS

The results suggest a 'U-shaped' relationship between RBC DHA levels and POAF incidence. The possibility of increased risk of POAF at high levels of DHA suggests an upper limit for n-3 LC-PUFAs in certain conditions.