Eicosapentaenoic acid modifies lipid composition in caveolae and induces translocation of endothelial nitric oxide synthase

Eicosapentaenoic Acid Improves Endothelial Nitric Oxide Bioavailability Via Changes in Protein Expression During Inflammation

BACKGROUND

Endothelial cell (EC) dysfunction involves reduced nitric oxide (NO) bioavailability due to NO synthase uncoupling linked to increased oxidation and reduced cofactor availability. Loss of endothelial function and NO bioavailability are associated with inflammation, including leukocyte activation. Eicosapentaenoic acid (EPA) administered as icosapent ethyl reduced cardiovascular events in REDUCE-IT (Reduction of Cardiovascular Events With Icosapent Ethyl-Intervention Trial) in relation to on-treatment EPA blood levels. The mechanisms of cardiovascular protection for EPA remain incompletely elucidated but likely involve direct effects on the endothelium.

METHODS AND RESULTS

In this study, human ECs were treated with EPA and challenged with the cytokine IL-6 (interleukin-6). Proinflammatory responses in the ECs were confirmed by ELISA capture of sICAM-1 (soluble intercellular adhesion molecule-1) and TNF-α (tumor necrosis factor-α). Global protein expression was determined using liquid chromatography-mass spectrometry tandem mass tag. Release kinetics of NO and peroxynitrite were monitored using porphyrinic nanosensors. IL-6 challenge induced proinflammatory responses from the ECs as evidenced by increased release of sICAM-1 and TNF-α, which correlated with a loss of NO bioavailability. ECs pretreated with EPA modulated expression of 327 proteins by >1-fold (P<0.05), compared with IL-6 alone. EPA augmented expression of proteins involved in NO production, including heme oxygenase-1 and dimethylarginine dimethylaminohydrolase-1, and 34 proteins annotated as associated with neutrophil degranulation. EPA reversed the endothelial NO synthase uncoupling induced by IL-6 as evidenced by an increased [NO]/[peroxynitrite] release ratio (P<0.05).

CONCLUSIONS

These direct actions of EPA on EC functions during inflammation may contribute to its distinct cardiovascular benefits.

Omega-3 polyunsaturated fatty acids and pulmonary arterial hypertension: Insights and perspectives

Pulmonary arterial hypertension (PAH) is a rare and progressive disorder that affects the pulmonary vasculature. Although recent developments in pharmacotherapy have extended the life expectancy of PAH patients, their 5-year survival remains unacceptably low, underscoring the need for multitarget and more comprehensive approaches to managing the disease. This should incorporate not only medical, but also lifestyle interventions, including dietary changes and the use of nutraceutical support. Among these strategies, n-3 polyunsaturated fatty acids (n-3 PUFAs) are emerging as promising agents able to counteract the inflammatory component of PAH. In this narrative review, we aim at analysing the preclinical evidence for the impact of n-3 PUFAs on the pathogenesis and the course of PAH. Although evidence for the role of n-3 PUFAs deficiencies in the development and progression of PAH in humans is limited, preclinical studies suggest that these dietary components may influence several aspects of the pathobiology of PAH. Further clinical research should test the efficacy of n-3 PUFAs on top of approved clinical management. These studies will provide evidence on whether n-3 PUFAs can genuinely serve as a valuable tool to enhance the efficacy of pharmacotherapy in the treatment of PAH.

Do patients benefit from omega-3 fatty acids?

Omega-3 fatty acids (O3FAs) possess beneficial properties for cardiovascular (CV) health and elevated O3FA levels are associated with lower incident risk for CV disease (CVD.) Yet, treatment of at-risk patients with various O3FA formulations has produced disparate results in large, well-controlled and well-conducted clinical trials. Prescription formulations and fish oil supplements containing low-dose mixtures of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have routinely failed to prevent CV events in primary and secondary prevention settings when added to contemporary care, as shown most recently in the STRENGTH and OMEMI trials. However, as observed in JELIS, REDUCE-IT, and RESPECT-EPA, EPA-only formulations significantly reduce CVD events in high-risk patients. The CV mechanism of action of EPA, while certainly multifaceted, does not depend solely on reductions of circulating lipids, including triglycerides (TG) and LDL, and event reduction appears related to achieved EPA levels suggesting that the particular chemical and biological properties of EPA, as compared to DHA and other O3FAs, may contribute to its distinct clinical efficacy. In vitro and in vivo studies have shown different effects of EPA compared with DHA alone or EPA/DHA combination treatments, on atherosclerotic plaque morphology, LDL and membrane oxidation, cholesterol distribution, membrane lipid dynamics, glucose homeostasis, endothelial function, and downstream lipid metabolite function. These findings indicate that prescription-grade, EPA-only formulations provide greater benefit than other O3FAs formulations tested. This review summarizes the clinical findings associated with various O3FA formulations, their efficacy in treating CV disease, and their underlying mechanisms of action.

The Role of Membrane Lipids in the Formation and Function of Caveolae

Caveolae are plasma membrane invaginations with a distinct lipid composition. Membrane lipids cooperate with the structural components of caveolae to generate a metastable surface domain. Recent studies have provided insights into the structure of essential caveolar components and how lipids are crucial for the formation, dynamics, and disassembly of caveolae. They also suggest new models for how caveolins, major structural components of caveolae, insert into membranes and interact with lipids.

Fatty acids act on vascular endothelial cells and influence the development of cardiovascular disease

Endothelial cells (ECs) maintain the health of blood vessels and prevent the development of cardiovascular disease (CVD). Free saturated fatty acids (FAs) induce EC damage and increase the risk of CVD by promoting arteriosclerosis. Conversely, polyunsaturated FAs (PUFAs), such as docosahexaenoic acid, are thought to suppress EC damage induced during the early stages of CVD. This review describes the effects of multiple dietary FAs on EC disorders involved in the development of CVD. The roles of FAs in atherosclerosis and CVD were analyzed by evaluating articles published in PubMed, Science Direct, and Web of Science. Saturated FAs were found to induce EC damage by reducing the production and action of EC-derived nitric oxide. Oxidative stress, inflammation, and the renin-angiotensin system were found to be involved in EC disorder. Furthermore, n-3 PUFAs were found to reduce EC dysfunction and prevent the development of EC disorder. These results indicate that FAs may affect EC failure induced during the early stages of CVD and reduce the risk of developing the disease.

Effects of Combining Docosahexaenoic Acid and Eicosapentaenoic Acid with Sesame Lignan on Vascular Endothelial Function

Vascular endothelial cells produce vasoactive substances, such as nitric oxide (NO), to regulate vascular relaxation and contraction. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) enhance NO production in endothelial cells, and sesamin, a sesame lignan contained in sesame seeds, also promotes NO production. This study examined DHA, EPA, and sesamin's combined effects since it was expected that combining them would further enhance NO production in endothelial cells. Using a human umbilical vein endothelial cell (HUVEC), the NO amount secreted in the culture supernatant was analyzed. Sesamin metabolite (SC1) was used in the experiments because it is a major metabolite in human blood after sesamin absorption. When cells were treated with DHA or EPA alone, they increased NO production in a concentration-dependent manner, whereas no change in NO production was observed for SC1. NO production increased when DHA and EPA were treated in combination with SC1, although the low DHA and EPA concentrations showed no difference in NO production. In the concentrations in which the combined effect was observed, SC1 activated eNOS via calcium signaling, whereas DHA and EPA activated eNOS via alterations in the membrane lipid environment. The combined effect of the two pathways was considered to have enhanced the eNOS activity. These results suggested that combining DHA, EPA, and sesamin might improve vascular endothelial function.

Changes in Bone Marrow Fatty Acids Early after Ovariectomy-Induced Osteoporosis in Rats and Potential Functions

The aim of this study was to investigate the changes in bone marrow fatty acids early after ovariectomy-induced osteoporosis in rats, and explore the potential function of the bone marrow fatty acids. Ninety-six female Sprague Dawley rats (12 weeks) were randomly divided into an ovariectomized (OVX) group and Sham group (N = 48/group) and received ovariectomy or Sham surgery, respectively. After 3, 5, 7,14, 21 and 28 days, eight rats in each group were sacrificed to detect the composition of bone marrow fatty acids by means of gas chromatography-mass spectrometry and evaluate the trabecular bone microarchitecture by means of microCT. Bone marrow rinsing fluid and serum were collected for the detection of nitric oxide synthase/nitric oxide (NOS/NO) and bone metabolism related parameters, respectively. Our results demonstrated that the bone microstructure was damaged significantly from 14 days after OVX surgery onwards. Sample clustering and group separation were observed between the OVX group and Sham group 3 and 14 days after surgery, which suggested the role of bone marrow fatty acids in the early stage of postmenopausal osteoporosis. Palmitoleate, myristate and arachidonate were found to play an important role in classification between the OVX group and Sham group on the 3rd day after surgery (VIP > 1, p < 0.05). Palmitoleate, myristate, alpha linolenate, stearate and eicosenoate were found to play an important role in classification between the OVX group and Sham group on the 14th day after surgery (VIP > 1, p < 0.05). The levels of myristate, palmitoleate, alpha linolenate and eicosenoate were significantly decreased in the OVX group, while the levels of arachidonate and stearate were significantly increased in OVX group (p < 0.05). Additionally, myristate, palmitoleate, alpha linoleate and eicosenoate were negatively correlated with C-terminal telopeptide of type 1 collagen (CTX-1, a bone resorption marker), while arachidonate was negative correlated with osteocalcin (OCN, a bone formation marker) (p < 0.05). A significant correlation was also found between eicosenoate and NOS (p < 0.05). Profound bone marrow fatty acids changes have taken place in the early stage of post-menopausal osteoporosis. They may affect bone formation though affecting the differentiation and function of osteoclasts or osteoblasts, respectively. The NOS/NO system may mediate the influence of eicosenoate on bone formation.

The Importance of the Plasma Membrane in Atherogenesis

Atherosclerotic cardiovascular diseases are an important medical problem due to their high prevalence, impact on quality of life and prognosis. The pathogenesis of atherosclerosis is an urgent medical and social problem, the solution of which may improve the quality of diagnosis and treatment of patients. Atherosclerosis is a complex chain of events, which proceeds over many years and in which many cells in the bloodstream and the vascular wall are involved. A growing body of evidence suggests that there are complex, closely linked molecular mechanisms that occur in the plasma membranes of cells involved in atherogenesis. Lipid transport, innate immune system receptor function, and hemodynamic regulation are linked to plasma membranes and their biophysical properties. A better understanding of these interrelationships will improve diagnostic quality and treatment efficacy.

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.

The beneficial effects of omega-3 polyunsaturated fatty acids on controlling blood pressure: An umbrella meta-analysis

Several meta-analyses have revealed that n-3 PUFAs can lower blood pressure, but the findings are conflicting. In this regard, the present umbrella meta-analysis aimed was performed to clarify whether n-3 PUFAs have effects on blood pressure. PubMed, Scopus, Embase, Web of Science, and Google Scholar were used as international databases from inception to May 2022. To examine the effects of n-3 PUFA supplementation on blood pressure, a random-effects model was applied. The leave-one-out method was performed for the sensitivity analysis. The pooled estimate of 10 meta-analyses with 20 effect sizes revealed significant reductions in both systolic (ES = -1.19 mmHg; 95% CI: -1.76, -0.62, p < 0.001) and diastolic blood pressure (ES = -0.91 mmHg, 95% CI: -1.35, -0.47; p < 0.001) following n-3 PUFAs supplementation. In studies with a sample size of ≤ 400 participants and a mean age over 45, SBP and DBP were found to be substantially reduced. Overall, this umbrella meta-analysis indicates that n-3 PUFAs supplementation might play a role in improving DBP and SBP.

A biological rationale for the disparate effects of omega-3 fatty acids on cardiovascular disease outcomes

The omega-3 fatty acids (n3-FAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) rapidly incorporate into cell membranes where they modulate signal transduction pathways, lipid raft formation, and cholesterol distribution. Membrane n3-FAs also form specialized pro-resolving mediators and other intracellular oxylipins that modulate inflammatory pathways, including T-cell differentiation and gene expression. Cardiovascular (CV) trials have shown that EPA, administered as icosapent ethyl (IPE), reduces composite CV events, along with plaque volume, in statin-treated, high-risk patients. Mixed EPA/DHA regimens have not shown these benefits, perhaps as the result of differences in formulation, dosage, or potential counter-regulatory actions of DHA. Indeed, EPA and DHA have distinct, tissue-specific effects on membrane structural organization and cell function. This review summarizes: (1) results of clinical outcome and imaging trials using n3-FA formulations; (2) membrane interactions of n3-FAs; (3) effects of n3-FAs on membrane oxidative stress and cholesterol crystalline domain formation during hyperglycemia; (4) n3-FA effects on endothelial function; (5) role of n3-FA-generated metabolites in inflammation; and (6) ongoing and future clinical investigations exploring treatment targets for n3-FAs, including COVID-19.

Diversity of Lipid Function in Atherogenesis: A Focus on Endothelial Mechanobiology

Atherosclerosis is one of the most important problems in modern medicine. Its high prevalence and social significance determine the need for a better understanding of the mechanisms of the disease's development and progression. Lipid metabolism and its disorders are one of the key links in the pathogenesis of atherosclerosis. Lipids are involved in many processes, including those related to the mechanoreception of endothelial cells. The multifaceted role of lipids in endothelial mechanobiology and mechanisms of atherogenesis are discussed in this review. Endothelium is involved in ensuring adequate vascular hemodynamics, and changes in blood flow characteristics are detected by endothelial cells and affect their structure and function.

Omega-3 and omega-6 fatty acids have distinct effects on endothelial fatty acid content and nitric oxide bioavailability

Treatment with high dose icosapent ethyl (IPE), an ethyl ester of the omega-3 fatty acid eicosapentaenoic acid (EPA), significantly reduced ischemic events in patients with either cardiovascular disease (CV) or diabetes plus other risk factors (REDUCE-IT) but the mechanism is not well understood.  We compared the effects of EPA, docosahexaenoic acid (DHA), and the omega-6 fatty acid arachidonic acid (AA) on bioavailability of nitric oxide (NO) and fatty acid composition. Human umbilical vein endothelial cells (HUVECs) were pretreated with EPA, DHA, or AA (10 µM). Cells were stimulated with calcium ionophore and NO and peroxynitrite (ONOO^-) were measured using porphyrinic nanosensors. Levels of EPA, DHA, AA and other fatty acids were measured by gas chromatography (GC). EPA treatment caused the greatest NO release (18%, p < 0.001) and reduction in ONOO^- (13%, p < 0.05) compared to control; the [NO]/[ ONOO^-] ratio increased by 35% (p < 0.001). DHA treatment increased NO levels by 12% (p < 0.01) but had no effect on ONOO^- release. AA did not affect either NO or ONOO^- release.  Fatty acid treatments increased their respective levels in endothelial cells.  EPA levels increased 10-fold to 4.59 mg/g protein (p < 0.001) with EPA treatment and the EPA/AA ratio increased by 10-fold (p < 0.001) compared to vehicle.  Only EPA increased docosapentaenoic acid (DPA, omega-3) levels by 2-fold (p < 0.001). AA alone decreased the EPA/AA ratio 4-fold (p<0.001). These findings support a preferential benefit of EPA on endothelial function and omega-3 fatty acid content.

EPA and DHA containing phospholipids have contrasting effects on membrane structure

Omega-3 FAs EPA and DHA influence membrane fluidity, lipid rafts, and signal transduction. A clinical trial, Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial, demonstrated that high-dose EPA (4 g/d icosapent ethyl) reduced composite cardiovascular events in statin-treated high-risk patients. EPA benefits correlated with on-treatment levels, but similar trials using DHA-containing formulations did not show event reduction. We hypothesized that differences in clinical efficacy of various omega-3 FA preparations could result from differential effects on membrane structure. To test this, we used small-angle X-ray diffraction to compare 1-palmitoyl-2-eicosapentaenoyl-sn-glycero-3-phosphocholine (PL-EPA), 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PL-DHA), and 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PL-AA) in membranes with and without 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol. Electron density profiles (electrons/Å3 vs. Å) were used to determine membrane structure, including membrane width (d-space). PL-EPA and PL-DHA had similar membrane structures without POPC and/or cholesterol but had contrasting effects in the presence of POPC and cholesterol. PL-EPA increased membrane hydrocarbon core electron density over an area of ±0-10 Å from the center, indicating an extended orientation. PL-DHA increased electron density in the phospholipid head group region, concomitant with disordering in the hydrocarbon core and a similar d-space (58 Å). Adding equimolar amounts of PL-EPA and PL-DHA produced changes that were attenuated compared with their separate effects. PL-AA increased electron density centered ±12 Å from the membrane center. The contrasting effects of PL-EPA, PL-DHA, and PL-AA on membrane structure may contribute to differences observed in the biological activities and clinical actions of various omega-3 FAs.

Potential depression and antidepressant-response biomarkers in human lymphoblast cell lines from treatment-responsive and treatment-resistant subjects: roles of SSRIs and omega-3 polyunsaturated fatty acids

While several therapeutic strategies exist for depression, most antidepressant drugs require several weeks before reaching full biochemical efficacy and remission is not achieved in many patients. Therefore, biomarkers for depression and drug-response would help tailor treatment strategies. This study made use of banked human lymphoblast cell lines (LCLs) from normal and depressed subjects; the latter divided into remitters and non-remitters. Due to the fact that previous studies have shown effects on growth factors, cytokines, and elements of the cAMP-generating system as potential biomarkers for depression and antidepressant action, these were examined in LCLs. Initial gene and protein expression profiles for signaling cascades related to neuroendocrine and inflammatory functions differ among the three groups. Growth factor genes, including VEGFA and BDNF were significantly down-regulated in cells from depressed subjects. In addition, omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been reported to act as both antidepressants and anti-inflammatories, but the mechanisms for these effects are not established. Here we showed that n-3 PUFAs and escitalopram (selective serotonin reuptake inhibitors, SSRIs) treatment increased adenylyl cyclase (AC) and BDNF gene expression in LCLs. These data are consistent with clinical observations showing that n-3 PUFA and SSRI have antidepressant affects, which may be additive. Contrary to observations made in neuronal and glial cells, n-3 PUFA treatment attenuated cAMP accumulation in LCLs. However, while lymphoblasts show paradoxical responses to neurons and glia, patient-derived lymphoblasts appear to carry potential depression biomarkers making them an important tool for studying precision medicine in depressive patients. Furthermore, these data validate usefulness of n-3 PUFAs in treatment for depression.

Omega-3 Polyunsaturated Fatty Acids: Versatile Roles in Blood Pressure Regulation

Significance: Hypertension is characterized as the imbalance of vasoconstriction and vasodilatation. Hypertension is influenced by genetic variation and environmental risk factors, such as unhealthy diet. Clinical trial results suggest that increasing intake of foods rich in n-3 polyunsaturated fatty acids (PUFAs) is beneficial for hypertension. Recent Advances: We summarized recent clinical trials regarding supplementation with n-3 PUFAs to reduce blood pressure (BP) in untreated hypertensive and normotensive subjects and systematically discussed the antihypertension mechanisms of n-3 PUFAs/n-3 oxylipins, including reducing oxidative stress, altering functions of membrane-related proteins, and competing with n-6 PUFAs/n-6 oxylipins in regulating vasodilator release. Critical Issues: Previous studies considered n-3 PUFAs as single molecules with beneficial roles in hypertension. Recently, researchers have paid more attention to the metabolism of n-3 PUFAs and explored molecular mechanisms of n-3 PUFAs and oxylipins derived from n-3 PUFAs in hypertension interventions. Future Directions: Based on the metabolism of n-3 PUFAs/n-3 oxylipins and mechanisms in BP control, we suggested that supplementation of n-3 PUFAs combined with agents targeting PUFA metabolism or the related signal pathways may amplify their effects to treat hypertension and other cardiovascular diseases. Antioxid. Redox Signal. 34, 800-810.

Interactive Effects of Omega-3 Polyunsaturated Fatty Acids and Secondhand Smoke in Mice and Human Subjects

Active smoking and secondhand smoke (SHS) exposure increase the risk of cardiovascular morbidity and mortality. Active smoking is associated with reduced levels of omega-3 polyunsaturated fatty acids (n-3 PUFA) and studies show that n-3 PUFA supplementation can improve smoking-induced vascular dysfunction. However, the relationship between n-3 PUFA and SHS exposure has not been studied. Fat-1 transgenic mice, which convert n-6 to n-3 PUFA, were fed diets with n-3 PUFA or without (n-6 PUFA diet), exposed to air or SHS for 4 weeks, and vasoreactivity, antioxidant indices, and omega-3 index (percent eicosapentaenoic + docosahexaenoic acids in RBC) measured. Compared to air-exposed mice, SHS-enhanced aortic constriction in mice fed the n-6 PUFA diet (omega-3 index, 5.9 ± 0.2%; mean ± SE), but not in mice fed the n-3 PUFA diet (omega-3 index, 7.8 ± 0.6%). SHS also significantly induced mRNA expression of cytochrome P4501A1, NADPH:quinone oxidoreductase, heme oxygenase-1, and angiotensinogen in adipose tissue, and increased antioxidant capacity only in mice on the n-6 PUFA diet. Notably, SHS reduced the omega-3 index by 1.0 percentage point (p = 0.003), compared to air-exposed mice irrespective of diet. Additionally, we recruited human nonsmokers (NS) with and without SHS exposure (n = 40) 19-40 years old and measured the omega-3 index and antioxidant capacity. In human subjects SHS exposure was associated with a significantly lower omega-3 index (NS, 4.4 ± 1.1%; NS + SHS, 3.2 ± 1.0%; mean ± SD, p = 0.002) and higher antioxidant capacity (p < 0.001) than unexposed NS. Thus, SHS exposure is associated with lower levels of n-3 PUFA in mice and humans; however, an omega-3 index of ~ 8% in mice has vasoprotective and antioxidant properties.

Prevention of Endothelial Dysfunction and Cardiovascular Disease by n-3 Fatty Acids-Inhibiting Action on Oxidative Stress and Inflammation

BACKGROUND

Prospective cohort studies and randomized controlled trials have shown the protective effect of n-3 fatty acids against cardiovascular disease (CVD). The effect of n-3 fatty acids on vascular endothelial cells indicates their possible role in CVD prevention.

OBJECTIVE

Here, we describe the effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on endothelial dysfunction-caused by inflammation and oxidative stress-and their role in the development of CVD.

METHODS

We reviewed epidemiological studies done on n-3 fatty acids in CVD. The effect of DHA and EPA on vascular endothelial cells was examined with regard to changes in various markers, such as arteriosclerosis, inflammation, and oxidative stress, using cell and animal models.

RESULTS

Epidemiological studies revealed that dietary intake of EPA and DHA was associated with a reduced risk of various CVDs. EPA and DHA inhibited various events involved in arteriosclerosis development by preventing oxidative stress and inflammation associated with endothelial cell damage. In particular, EPA and DHA prevented endothelial cell dysfunction mediated by inflammatory responses and oxidative stress induced by events related to CVD. DHA and EPA also increased eNOS activity and induced nitric oxide production.

CONCLUSION

The effects of DHA and EPA on vascular endothelial cell damage and dysfunction may involve the induction of nitric oxide, in addition to antioxidant and anti-inflammatory effects. n-3 fatty acids inhibit endothelial dysfunction and prevent arteriosclerosis. Therefore, the intake of n-3 fatty acids may prevent CVDs, like myocardial infarction and stroke.

Omega-3 polyunsaturated fatty acids and hypertension: a review of vasodilatory mechanisms of docosahexaenoic acid and eicosapentaenoic acid

Hypertension is often characterised by impaired vasodilation involving dysfunction of multiple vasodilatory mechanisms. ω-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) can reduce blood pressure and vasodilation. In the endothelium, DHA and EPA improve function including increased NO bioavailability. However, animal studies show that DHA- and EPA-mediated vasodilation persists after endothelial removal, indicating a role for vascular smooth muscle cells (VSMCs). The vasodilatory effects of ω-3 PUFAs on VSMCs are mediated via opening of large conductance calcium-activated potassium channels (BK_Ca ), ATP-sensitive potassium channels (K_ATP ) and possibly members of the K_v 7 family of voltage-activated potassium channels, resulting in hyperpolarisation and relaxation. ω-3 PUFA actions on BK_Ca and voltage-gated ion channels involve electrostatic interactions that are dependent on the polyunsaturated acyl tail, cis-geometry of these double bonds and negative charge of the carboxyl headgroup. This suggests structural manipulation of ω-3 PUFA could generate novel, targeted, therapeutic leads.

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.

Dietary α-Linolenic Acid Counters Cardioprotective Dysfunction in Diabetic Mice: Unconventional PUFA Protection

Whether dietary omega-3 (n-3) polyunsaturated fatty acid (PUFA) confers cardiac benefit in cardiometabolic disorders is unclear. We test whether dietary -linolenic acid (ALA) enhances myocardial resistance to ischemia-reperfusion (I-R) and responses to ischemic preconditioning (IPC) in type 2 diabetes (T2D); and involvement of conventional PUFA-dependent mechanisms (caveolins/cavins, kinase signaling, mitochondrial function, and inflammation). Eight-week male C57Bl/6 mice received streptozotocin (75 mg/kg) and 21 weeks high-fat/high-carbohydrate feeding. Half received ALA over six weeks. Responses to I-R/IPC were assessed in perfused hearts. Localization and expression of caveolins/cavins, protein kinase B (AKT), and glycogen synthase kinase-3 β (GSK3β); mitochondrial function; and inflammatory mediators were assessed. ALA reduced circulating leptin, without affecting body weight, glycemic dysfunction, or cholesterol. While I-R tolerance was unaltered, paradoxical injury with IPC was reversed to cardioprotection with ALA. However, post-ischemic apoptosis (nucleosome content) appeared unchanged. Benefit was not associated with shifts in localization or expression of caveolins/cavins, p-AKT, p-GSK3β, or mitochondrial function. Despite mixed inflammatory mediator changes, tumor necrosis factor-a (TNF-a) was markedly reduced. Data collectively reveal a novel impact of ALA on cardioprotective dysfunction in T2D mice, unrelated to caveolins/cavins, mitochondrial, or stress kinase modulation. Although evidence suggests inflammatory involvement, the basis of this "un-conventional" protection remains to be identified.

Current Research Landscape of Marine-Derived Anti-Atherosclerotic Substances

Atherosclerosis is a chronic disease characterized by lipid accumulation and chronic inflammation of the arterial wall, which is the pathological basis for coronary heart disease, cerebrovascular disease and thromboembolic disease. Currently, there is a lack of low-cost therapeutic agents that effectively slow the progression of atherosclerosis. Therefore, the development of new drugs is urgently needed. The research and development of marine-derived drugs have gained increasing interest from researchers across the world. Many marine organisms provide a rich material basis for the development of atherosclerotic drugs. This review focuses on the latest technological advances in the structures and mechanisms of action of marine-derived anti-atherosclerotic substances and the challenges of the application of these substances including marine polysaccharides, proteins and peptides, polyunsaturated fatty acids and small molecule compounds. Here, we describe the theoretical basis of marine biological resources in the treatment of atherosclerosis.

The Anti-Inflammatory and Antioxidant Properties of n-3 PUFAs: Their Role in Cardiovascular Protection

Polyunsaturated fatty acids (n-3 PUFAs) are long-chain polyunsaturated fatty acids with 18, 20 or 22 carbon atoms, which have been found able to counteract cardiovascular diseases. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in particular, have been found to produce both vaso- and cardio-protective response via modulation of membrane phospholipids thereby improving cardiac mitochondrial functions and energy production. However, antioxidant properties of n-3 PUFAs, along with their anti-inflammatory effect in both blood vessels and cardiac cells, seem to exert beneficial effects in cardiovascular impairment. In fact, dietary supplementation with n-3 PUFAs has been demonstrated to reduce oxidative stress-related mitochondrial dysfunction and endothelial cell apoptosis, an effect occurring via an increased activity of endogenous antioxidant enzymes. On the other hand, n-3 PUFAs have been shown to counteract the release of pro-inflammatory cytokines in both vascular tissues and in the myocardium, thereby restoring vascular reactivity and myocardial performance. Here we summarize the molecular mechanisms underlying the anti-oxidant and anti-inflammatory effect of n-3 PUFAs in vascular and cardiac tissues and their implication in the prevention and treatment of cardiovascular disease.

Maternal dietary fatty acids and their roles in human placental development

Fatty acids are essential for feto-placental growth and development. Maternal fatty acids and their metabolites are involved in every stage of pregnancy by supporting cell growth and development, cell signaling, and modulating other critical aspects of structural and functional processes. Early placentation process is critical for placental growth and function. Several fatty acids modulate angiogenesis as observed by increased tube formation and secretion of angiogenic growth factors in first-trimester human placental trophoblasts. Long-chain fatty acids stimulate angiogenesis in these cells via vascular endothelium growth factor (VEGF), angiopoietin-like protein 4 (ANGPTL4), fatty acid-binding proteins (FABPs), or eicosanoids. Inadequate placental angiogenesis and trophoblast invasion of the maternal decidua and uterine spiral arterioles leads to structural and functional deficiency of placenta, which contributes to preeclampsia, pre-term intrauterine growth restriction, and spontaneous abortion and also affects overall fetal growth and development. During the third trimester of pregnancy, placental preferential transport of maternal plasma long-chain polyunsaturated fatty acids is of critical importance for fetal growth and development. Fatty acids cross the placental microvillous and basal membranes by mainly via plasma membrane fatty acid transport system (FAT, FATP, p-FABPpm, & FFARs) and cytoplasmic FABPs. Besides, a member of the major facilitator superfamily-MFSD2a, present in the placenta is involved in the supply of DHA to the fetus. Maternal factors such as diet, obesity, endocrine, inflammation can modulate the expression and activity of the placental fatty acid transport activity and thereby impact feto-placental growth and development. In this review, we discuss the maternal dietary fatty acids, and placental transport and metabolism, and their roles in placental growth and development.

Ageing enhances the shedding of splenocyte microvesicles with endothelial pro-senescent effect that is prevented by a short-term intake of omega-3 PUFA EPA:DHA 6:1

BACKGROUND

Ageing is associated with progressive endothelial senescence and dysfunction, and cardiovascular risk. Circulating endothelial microvesicles (MVs) are pro-senescent and pro-inflammatory endothelial effectors in acute coronary syndrome. Omega-3 PUFA intake was claimed beneficial in cardiovascular prevention.

PURPOSE

To investigate whether the intake of the omega-3 formulation EPA:DHA 6:1 by middle-aged and old rats reduces the shedding of pro-senescent microvesicles from cultured spleen leukocytes (SMVs) and clarify the underlying mechanisms in target coronary primary endothelial cells (ECs).

METHODS

Middle-aged male Wistar rats (M, 48-week old) received 500 mg/kg/d of either EPA:DHA 6:1, EPA:DHA 1:1, or vehicle (CTL) for 7 days, old rats (72-week old) for 14 days. Spleen-derived leukocytes were prepared and cultured for 24 h and MVs collected from supernatants (SMVs). Cultured ECs were prepared from freshly isolated porcine coronary arteries. Senescence-associated β-galactosidase activity (SA-β-gal) was assessed by C12FDG, protein expression by Western blot analysis, oxidative stress by dihydroethidium using confocal microscopy, and procoagulant MVs by prothrombinase assay. The pro-senescent potential of SMVs from middle-aged rats (M-SMVs) was analyzed by comparison with young (Y, 12-week) and old (O) rats.

RESULTS

The shedding of SMVs significantly increased with age and was inhibited by EPA:DHA 6:1 intake that also prevented ROS accumulation in spleen. Incubation of ECs with 10 nM SMVs from middle-aged and old but not those from young rats induced premature senescence after 48 h. The pro-senescent effect of M-SMVs was prevented by Losartan and associated with endothelial oxidative stress. M-SMVs induced an up-regulation of senescence markers (p16, p21, p53), pro-atherothrombotic (VCAM-1, ICAM-1, tissue factor) and pro-inflammatory markers (pNF-κB, COX-2) and proteins of the angiotensin system (ACE, AT1-R). Conversely, endothelial NO synthase was down-regulated. Intake of EPA:DHA 1:1 and 6:1 by middle-aged rats decreased SMV shedding by 14% and 24%, respectively. Only EPA:DHA 6:1 intake abolished the M-SMVs-induced endothelial senescence and reduced the pro-senescent action of O-SMVs by 45%. Protection of ECs was not observed in response to SMVs from EPA:DHA 1:1 treated rats.

CONCLUSION

Ingestion of EPA:DHA 6:1 by middle-aged or old rats, respectively abolished or limited both the shedding of SMVs and their pro-senescent, pro-thrombotic and pro-inflammatory effects in ECs, most likely by triggering the local angiotensin system. EPA:DHA 6:1 may help to delay ageing-related endothelial dysfunction.

Pathophysiological Role of Caveolae in Hypertension

Caveolae, flask-shaped cholesterol-, and glycosphingolipid-rich membrane microdomains, contain caveolin 1, 2, 3 and several structural proteins, in particular Cavin 1-4, EHD2, pacsin2, and dynamin 2. Caveolae participate in several physiological processes like lipid uptake, mechanosensitivity, or signaling events and are involved in pathophysiological changes in the cardiovascular system. They serve as a specific membrane platform for a diverse set of signaling molecules like endothelial nitric oxide synthase (eNOS), and further maintain vascular homeostasis. Lack of caveolins causes the complete loss of caveolae; induces vascular disorders, endothelial dysfunction, and impaired myogenic tone; and alters numerous cellular processes, which all contribute to an increased risk for hypertension. This brief review describes our current knowledge on caveolae in vasculature, with special focus on their pathophysiological role in hypertension.

Conjugated Linoleic Acid Modulates Clinical Responses to Oral Nitrite and Nitrate

Dietary NO₃^- (nitrate) and NO₂^- (nitrite) support ˙NO (nitric oxide) generation and downstream vascular signaling responses. These nitrogen oxides also generate secondary nitrosating and nitrating species that react with low molecular weight thiols, heme centers, proteins, and unsaturated fatty acids. To explore the kinetics of NO₃^-and NO₂^-metabolism and the impact of dietary lipid on nitrogen oxide metabolism and cardiovascular responses, the stable isotopes Na¹⁵NO₃ and Na¹⁵NO₂ were orally administered in the presence or absence of conjugated linoleic acid (cLA). The reduction of ¹⁵NO₂^- to ¹⁵NO was indicated by electron paramagnetic resonance spectroscopy detection of hyperfine splitting patterns reflecting ¹⁵NO-deoxyhemoglobin complexes. This formation of ¹⁵NO also translated to decreased systolic and mean arterial blood pressures and inhibition of platelet function. Upon concurrent administration of cLA, there was a significant increase in plasma cLA nitration products 9- and 12-¹⁵NO₂-cLA. Coadministration of cLA with ¹⁵NO₂^- also impacted the pharmacokinetics and physiological effects of ¹⁵NO₂^-, with cLA administration suppressing plasma NO₃^-and NO₂^-levels, decreasing ¹⁵NO-deoxyhemoglobin formation, NO₂^-inhibition of platelet activation, and the vasodilatory actions of NO₂^-, while enhancing the formation of 9- and 12-¹⁵NO₂-cLA. These results indicate that the biochemical reactions and physiological responses to oral ¹⁵NO₃^-and ¹⁵NO₂^-are significantly impacted by dietary constituents, such as unsaturated lipids. This can explain the variable responses to NO₃^-and NO₂^-supplementation in clinical trials and reveals dietary strategies for promoting the generation of pleiotropic nitrogen oxide-derived lipid signaling mediators. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT01681836.

Dietary fats modify vascular fat composition, eNOS localization within lipid rafts and vascular function in obesity

We tested whether dietary fatty acids alter membrane composition shifting localization of signaling pathways within caveolae to determine their role in vascular function. Wild type (WT) and caveolin-1-deficient mice (cav-1 KO), required for vascular caveolae formation, were fed low fat (LF), high saturated fat (HF, 60% kcal from lard), or high-fat diet with 50:50 lard and n-3 polyunsaturated fatty acid-enriched menhaden oil (MO). HF and MO increased body weight and fat in WT but had less effect in cav-1 KO. MO increased unsaturated fatty acids and the unsaturation index of aorta from WT and cav-1 KO. In LF WT aorta, endothelial nitric oxide synthase (eNOS) was localized to cav-1-enriched low-density fractions which shifted to actin-enriched high-density fractions with acetylcholine (ACh). HF and MO shifted eNOS to high-density fractions in WT aorta which was not affected by ACh. In cav-1 KO aorta, eNOS was localized in low-density non-caveolar fractions but not shifted by ACh or diet. Inducible NOS and cyclooxygenase 1/2 were not localized in low-density fractions or affected by diet, ACh or genotype. ACh-induced dilation of gracilis arteries from HF WT was similar to dilation in LF but the NOS component was reduced. In WT and cav-1 KO, dilation to ACh was enhanced by MO through increased role for NOS and cyclooxygenase. We conclude that dietary fats affect vascular fatty acid composition and membrane localization of eNOS but the contribution of eNOS and cyclooxygenase in ACh-mediated vascular responses is independent of lipid rafts.

Replication of a Gene-Diet Interaction at CD36, NOS3 and PPARG in Response to Omega-3 Fatty Acid Supplements on Blood Lipids: A Double-Blind Randomized Controlled Trial

BACKGROUND

Modulation of genetic variants on the effect of omega-3 fatty acid supplements on blood lipids is still unclear.

METHODS

In a double-blind randomized controlled trial, 150 patients with type 2 diabetes (T2D) were randomized into omega-3 fatty acid group (n = 56 for fish oil and 44 for flaxseed oil) and control group (n = 50) for 180 days. All patients were genotyped for genetic variants at CD36 (rs1527483), NOS3 (rs1799983) and PPARG (rs1801282). Linear regression was used to examine the interaction between omega-3 fatty acid intervention and CD36, NOS3 or PPARG variants for blood lipids.

FINDINGS

Significant interaction with omega-3 fatty acid supplements was observed for CD36 on triglycerides (p-interaction = 0.042) and PPAGR on low-density lipoprotein-cholesterol (p-interaction = 0.02). We also found a significant interaction between change in erythrocyte phospholipid omega-3 fatty acid composition and NOS3 genotype on triglycerides (p-interaction = 0.042), total cholesterol (p-interaction = 0.013) and ratio of total cholesterol to high-density lipoprotein cholesterol (p-interaction = 0.015). The T2D patients of CD36-G allele, PPARG-G allele and NOS3-A allele tended to respond better to omega-3 fatty acids in improving lipid profiles. The interaction results of the omega-3 fatty acid group were mainly attributed to the fish oil supplements.

INTERPRETATION

This study suggests that T2D patients with different genotypes at CD36, NOS3 and PPARG respond differentially to intervention of omega-3 supplements in blood lipid profiles.

Omega-3 Polyunsaturated Fatty Acids Protect Against Cigarette Smoke-Induced Oxidative Stress and Vascular Dysfunction

In cigarette smokers endothelial dysfunction, measured by flow-mediated dilation (FMD), precedes cardiovascular disease (CVD) and can be improved by supplementation with n - 3 polyunsaturated fatty acids (PUFAs). We developed a mouse model of cigarette smoke (CS)-induced endothelial dysfunction that resembles impaired FMD observed in human cigarette smokers and investigated the mechanism by which n - 3 PUFAs mediate vasoprotection. We hypothesized that loss of nitric oxide (NO)-dependent vasodilation in CS-exposed mice would be prevented by dietary n - 3 PUFAs via a decrease in oxidative stress. C57BL/6 mice were fed a chow or n - 3 PUFA diet for 8 weeks and then exposed to mainstream CS or filtered air for 5 days, 2 h/day. Mesenteric arterioles were preconstricted with U46619 and dilated by stepwise increases in pressure (0-40 mmHg), resulting in increases in flow, ± inhibitor of NO production or antioxidant, Tempol. Markers of oxidative stress were measured in lung and heart. CS-exposed mice on a chow diet had impaired FMD, resulting from loss of NO-dependent dilation, compared with air exposed mice. Tempol restored FMD by normalizing NO-dependent dilation and increasing NO-independent dilation. CS-exposed mice on the n - 3 PUFA diet had normal FMD, resulting from a significant increase in NO-independent dilation, compared with CS-exposed mice on a chow diet. Furthermore, n - 3 PUFAs decreased two CS-induced markers of oxidative stress, 8-epiprostaglandin-F2α levels and heme oxygenase-1 mRNA, and significantly attenuated CS-induced cytochrome P4501A1 mRNA expression. These data demonstrate that dietary n - 3 PUFAs can protect against CS-induced vascular dysfunction via multiple mechanisms, including increasing NO-independent vasodilation and decreasing oxidative stress.

Pretreatment with fish oil attenuates heart ischaemia consequences in rats

NEW FINDINGS

What is the central question of this study? We investigated whether pretreatment with fish oil could prevent the major consequences of ischaemic injury to the heart. What is the main finding and its importance? Fish oil pretreatment attenuated the consequences of ischaemic injury as indicated by the small infarction area and the preservation of systolic function and coronary blood flow. These findings support the use of fish oil in order to reduce the impact of heart ischaemia. ω-3 Polyunsaturated fatty acid (ω-3 PUFA)-rich fish oil supplementation has protective effects on heart ischaemic injury. Left ventricular (LV) ischaemia was induced in rats by permanent ligation of the left descending coronary artery. Saline, fish oil or soybean oil was administered daily by gavage [3 g (kg body weight)^-1 ] for 20 days before inducing ischaemia. Outcomes were assessed 24 h after left descending coronary artery ligation. Pretreatment with fish oil decreased the ω-6/ω-3 fatty acid ratio in the LV. A reduction in infarct size and in the intensity of ventricular systolic dysfunction was found in the fish oil group compared with the saline or soybean oil groups through echocardiographic evaluation. Before infarction, LV glycogen concentrations were decreased in the fish oil group compared with the saline group. Soybean oil pretreatment led to a further increase in the LV levels of CINC-2/αβ, IL-1β and TNF-α induced by the heart infarction. In heart-infarcted rats, fish oil pretreatment decreased creatine kinase and caspase-3 activities; prevented the decrease in the coronary blood flow; increased LV contents of ATP and lactate; increased the mRNA levels of iNOS, eNOS, HIF1α, GLUT1, VEGF-α and p53 in the LV as measured by RT-PCR; and did not change LV pro-inflammatory cytokine concentrations compared with the control group. Fish oil protected the heart from ischaemia, as indicated by the decrease in the heart infarction area and systolic dysfunction associated with increased LV ATP concentrations and maintenance of the coronary blood flow with no change in pro-inflammatory cytokine levels.

Effects of 6-month eicosapentaenoic acid treatment on postprandial hyperglycemia, hyperlipidemia, insulin secretion ability, and concomitant endothelial dysfunction among newly-diagnosed impaired glucose metabolism patients with coronary artery disease. An open label, single blinded, prospective randomized controlled trial

Background

Recent experimental studies have revealed that n-3 fatty acids, such as eicosapentaenoic acid (EPA) regulate postprandial insulin secretion, and correct postprandial glucose and lipid abnormalities. However, the effects of 6-month EPA treatment on postprandial hyperglycemia and hyperlipidemia, insulin secretion, and concomitant endothelial dysfunction remain unknown in patients with impaired glucose metabolism (IGM) and coronary artery disease (CAD).

Methods and results

We randomized 107 newly diagnosed IGM patients with CAD to receive either 1800 mg/day of EPA (EPA group, n = 53) or no EPA (n = 54). Cookie meal testing (carbohydrates: 75 g, fat: 28.5 g) and endothelial function testing using fasting-state flow-mediated dilatation (FMD) were performed before and after 6 months of treatment. The primary outcome of this study was changes in postprandial glycemic and triglyceridemic control and secondary outcomes were improvement of insulin secretion and endothelial dysfunction. After 6 months, the EPA group exhibited significant improvements in EPA/arachidonic acid, fasting triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C). The EPA group also exhibited significant decreases in the incremental TG peak, area under the curve (AUC) for postprandial TG, incremental glucose peak, AUC for postprandial glucose, and improvements in glycometabolism categorization. No significant changes were observed for hemoglobin A1c and fasting plasma glucose levels. The EPA group exhibited a significant increase in AUC-immune reactive insulin/AUC-plasma glucose ratio (which indicates postprandial insulin secretory ability) and significant improvements in FMD. Multiple regression analysis revealed that decreases in the TG/HDL-C ratio and incremental TG peak were independent predictors of FMD improvement in the EPA group.

Conclusions

EPA corrected postprandial hypertriglyceridemia, hyperglycemia and insulin secretion ability. This amelioration of several metabolic abnormalities was accompanied by recovery of concomitant endothelial dysfunction in newly diagnosed IGM patients with CAD.

Clinical Trial Registration UMIN Registry number: UMIN000011265 (https://www.upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&type=summary&recptno=R000013200&language=E)

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0437-y) contains supplementary material, which is available to authorized users.

Lack of effect of supplementation with EPA or DHA on platelet-monocyte aggregates and vascular function in healthy men

BACKGROUND AND AIMS

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fish oil are postulated to have favourable effects on platelet, endothelial and vascular function. We investigated whether EPA has differential effects on in vivo platelet aggregation and other markers of cardiovascular risk compared to DHA.

METHODS AND RESULTS

Following a 2 wk run-in taking encapsulated refined olive oil, 48 healthy young men were randomly allocated using a parallel design to receive EPA-rich (3.1 g EPA/d) or DHA-rich (2.9 g DHA/d) triglyceride concentrates or refined olive oil (placebo), for a total supplementary lipid intake of 5 g/d. The specified primary outcome was change in platelet monocyte aggregates (PMA); secondary outcomes were capillary density, augmentation index, digital pulse volume measurements, 24 h ambulatory BP, plasma 8-isoprostanes-F2α. Changes in the proportions of DHA and EPA in erythrocytes and non-esterified fatty acid composition indicated compliance to the intervention. There was no significant treatment effect on PMA (P = 0.382); mean changes (%) (95% CI) were placebo -0.5 (-2.0, 1.04), EPA 0.4 (-0.8, 1.6), DHA 0.3 (-1.5, 2.0). R-QUICKI, an index of insulin sensitivity, was greater following EPA compared to placebo (P < 0.05). No other significant differences were noted.

CONCLUSION

Neither EPA- nor DHA-rich fish oil supplementation influence platelet-monocyte aggregation or several markers of vascular function after 6 wk in healthy young males. This trial was registered at clinicaltrials.gov as NCT01735357.

Potential of Food and Natural Products to Promote Endothelial and Vascular Health

Endothelial dysfunction is now well established as a pivotal early event in the development of major cardiovascular diseases including hypertension, atherosclerosis, and diabetes. The alteration of the endothelial function is often triggered by an imbalance between the endothelial formation of vasoprotective factors including nitric oxide (NO) and endothelium-dependent hyperpolarization, and an increased level of oxidative stress involving several prooxidant enzymes such as NADPH oxidase and, often also, the appearance of cyclooxygenase-derived vasoconstrictors. Preclinical studies have indicated that polyphenol-rich food and food-derived products such as grape-derived products, black and red berries, green and black teas and cocoa, and omega-3 fatty acids can trigger activating pathways in endothelial cells promoting an increased formation of nitric oxide and endothelium-dependent hyperpolarization. Moreover, intake of such food-derived products has been associated with the prevention and/or the improvement of an established endothelial dysfunction in several experimental models of cardiovascular diseases and in humans with cardiovascular diseases. This review will discuss both experimental and clinical evidences indicating that different types of food and natural products are able to promote endothelial and vascular health, as well as the underlying mechanisms.

Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease

Essential polyunsaturated fatty acids (PUFAs) have profound effects on brain development and function. Abnormalities of PUFA status have been implicated in neuropsychiatric diseases such as major depression, bipolar disorder, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder. Pathophysiologic mechanisms could involve not only suboptimal PUFA intake, but also metabolic and genetic abnormalities, defective hepatic metabolism, and problems with diffusion and transport. This article provides an overview of physiologic factors regulating PUFA utilization, highlighting their relevance to neuropsychiatric disease.

Role of CYP1A1 in modulating the vascular and blood pressure benefits of omega-3 polyunsaturated fatty acids

The mechanisms that mediate the cardiovascular protective effects of omega 3 (n-3) polyunsaturated fatty acids (PUFAs) have not been fully elucidated. Cytochrome P450 1A1 efficiently metabolizes n-3 PUFAs to potent vasodilators. Thus, we hypothesized that dietary n-3 PUFAs increase nitric oxide (NO)-dependent blood pressure regulation and vasodilation in a CYP1A1-dependent manner. CYP1A1 wild-type (WT) and knockout (KO) mice were fed an n-3 or n-6 PUFA-enriched diet for 8 weeks and were analyzed for tissue fatty acids and metabolites, NO-dependent blood pressure regulation, NO-dependent vasodilation of acetylcholine (ACh) in mesenteric resistance arterioles, and endothelial NO synthase (eNOS) and phospho-Ser1177-eNOS expression in the aorta. All mice fed the n-3 PUFA diet showed significantly higher levels of n-3 PUFAs and their metabolites, and significantly lower levels of n-6 PUFAs and their metabolites. In addition, KO mice on the n-3 PUFA diet accumulated significantly higher levels of n-3 PUFAs in the aorta and kidney without a parallel increase in the levels of their metabolites. Moreover, KO mice exhibited significantly less NO-dependent regulation of blood pressure on the n-3 PUFA diet and significantly less NO-dependent, ACh-mediated vasodilation in mesenteric arterioles on both diets. Finally, the n-3 PUFA diet significantly increased aortic phospho-Ser1177-eNOS/eNOS ratio in the WT compared with KO mice. These data demonstrate that CYP1A1 contributes to eNOS activation, NO bioavailability, and NO-dependent blood pressure regulation mediated by dietary n-3 PUFAs.

Redox-sensitive induction of Src/PI3-kinase/Akt and MAPKs pathways activate eNOS in response to EPA:DHA 6:1

Aims

Omega-3 fatty acid products containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have vasoprotective effects, in part, by stimulating the endothelial formation of nitric oxide (NO). This study determined the role of the EPA:DHA ratio and amount, and characterized the mechanism leading to endothelial NO synthase (eNOS) activation.

Methods and Results

EPA:DHA 6∶1 and 9∶1 caused significantly greater endothelium-dependent relaxations in porcine coronary artery rings than EPA:DHA 3∶1, 1∶1, 1∶3, 1∶6, 1∶9, EPA and DHA alone, and EPA:DHA 6∶1 with a reduced EPA + DHA amount, which were inhibited by an eNOS inhibitor. Relaxations to EPA:DHA 6∶1 were insensitive to cyclooxygenase inhibition, and reduced by inhibitors of either oxidative stress, Src kinase, PI3-kinase, p38 MAPK, MEK, or JNK. EPA:DHA 6∶1 induced phosphorylation of Src, Akt, p38 MAPK, ERK, JNK and eNOS; these effects were inhibited by MnTMPyP. EPA:DHA 6∶1 induced the endothelial formation of ROS in coronary artery sections as assessed by dihydroethidium, and of superoxide anions and hydrogen peroxide in cultured endothelial cells as assessed by electron spin resonance with the spin probe CMH, and the Amplex Red based assay, respectively.

Conclusion

Omega-3 fatty acids cause endothelium-dependent NO-mediated relaxations in coronary artery rings, which are dependent on the EPA:DHA ratio and amount, and involve an intracellular activation of the redox-sensitive PI3-kinase/Akt and MAPKs pathways to activate eNOS.

Role of dietary fish oil on nitric oxide synthase activity and oxidative status in mice red blood cells

The consumption of n-3 polyunsaturated fatty acids derived from fish oil is associated with cardiovascular benefits, which may result from the participation of nitric oxide.

Eicosapentaenoic acid (EPA) reduces cardiovascular events: relationship with the EPA/arachidonic acid ratio

The clinical efficacy of fish oil and high-purity eicosapentaenoic acid ethyl ester (hp-EPA-E) for treating cardiovascular disease (CVD) has been reported. Fish oil contains saturated and monounsaturated fatty acids that have pharmacological effects opposite to those of ω3 fatty acids (ω3). Moreover, ω3, such as EPA and docosahexaenoic acid (DHA), do not necessarily have the same metabolic and biological actions. This has obscured the clinical efficacy of ω3. Recently, the Japan EPA Lipid Intervention Study (JELIS) of hp-EPA-E established the clinical efficacy of EPA for CVD, and higher levels of blood EPA, not DHA, were found to be associated with a lower incidence of major coronary events. A significant reduction in the risk of coronary events was observed when the ratio of EPA to arachidonic acid (AA) (EPA/AA) was > 0.75. Furthermore, the ratio of prostaglandin (PG) I3 and PGI2 to thromboxane A2 (TXA2) ([PGI2 + PGI3]/TXA2) was determined to have a linear relationship with the EPA/AA ratio as follows: (PGI2 + PGI3)/TXA2 =λ + π＊ (EPA/AA). Like PGI2, PGI3 not only inhibits platelet aggregation and vasoconstriction, but also is assumed to reduce cardiac ischemic injury and arteriosclerosis and promote angiogenesis. Thus, the effects of EPA in reducing the risk of CVD could be mediated by biological action of PGI3 in addition to hypotriglyceridemic action of EPA. Compared with DHA, EPA administration increases the EPA/AA ratio and the (PGI2 + PGI3)/TXA2 balance to a state that inhibits the onset and/or progression of CVD.

Platelet redox balance in diabetic patients with hypertension improved by n-3 fatty acids

OBJECTIVE

Patients with type 2 diabetes mellitus (T2DM) are at increased risk of developing cardiovascular disease, largely as a result of defective production of cardioprotective nitric oxide and a concomitant rise in oxidative stress. Dietary interventions that could reverse this trend would be extremely beneficial. Here we investigated whether dietary n-3 polyunsaturated fatty acid (n-3 PUFA) supplementation positively affected platelet nitroso-redox imbalance.

RESEARCH DESIGN AND METHODS

We randomized hypertensive T2DM patients (T2DM HT; n = 22) and age-and-sex matched hypertensive study participants without diabetes (HT alone; n = 23) in a double-blind, crossover fashion to receive 8 weeks of n-3 PUFAs (1.8 g eicosapentaenoic acid and 1.5 g docosahexaenoic acid) or identical olive oil capsules (placebo), with an intervening 8-week washout period. Platelet nitrite and superoxide were measured and compared before and after treatment; 8-isoprostane was determined by ELISA and subcellular compartmentalization of the NAD(P)H oxidase subunit p47-phox examined by Western blotting.

RESULTS

The n-3 PUFA supplementation reduced 8-isoprostane and superoxide levels in platelets from T2DM HT, but not HT alone, participants, without effect on nitrite production. This coincided with a significant decrease in p47-phox membrane localization and a similar reduction in superoxide to that achieved with apocynin. At baseline, a subcohort of T2DM HT and HT alone participants showed evidence of nitric oxide synthase (NOS)-derived superoxide production, indicating defective enzymatic activity. This was reversed significantly in T2DM HT participants after treatment, demonstrating improved NOS function.

CONCLUSIONS

Our finding that n-3 PUFAs diminish platelet superoxide production in T2DM HT patients in vivo suggests a therapeutic role for these agents in reducing the vascular-derived oxidative stress associated with diabetes.

Autophagy regulates trans fatty acid-mediated apoptosis in primary cardiac myofibroblasts

Trans fats are not a homogeneous group of molecules and less is known about the cellular effects of individual members of the group. Vaccenic acid (VA) and elaidic acid (EA) are the predominant trans monoenes in ruminant fats and vegetable oil, respectively. Here, we investigated the mechanism of cell death induced by VA and EA on primary rat ventricular myofibroblasts (rVF). The MTT assay demonstrated that both VA and EA (200μM, 0-72 h) reduced cell viability in rVF (P<0.001). The FACS assay confirmed that both VA and EA induced apoptosis in rVF, and this was concomitant with elevation in cleaved caspase-9, -3 and -7, but not caspase-8. VA and EA decreased the expression ratio of Bcl2:Bax, induced Bax translocation to mitochondria and decrease in mitochondrial membrane potential (Δψ). BAX and BAX/BAK silencing in mouse embryonic fibroblasts (MEF) inhibited VA and EA-induced cell death compared to the corresponding wild type cells. Transmission electron microscopy revealed that VA and EA also induced macroautophagosome formation in rVF, and immunoblot analysis confirmed the induction of several autophagy markers: LC3-β lipidation, Atg5-12 accumulation, and increased beclin-1. Finally, deletion of autophagy genes, ATG3 and ATG5 significantly inhibited VA and EA-induced cell death (P<0.001). Our findings show for the first time that trans fat acid (TFA) induces simultaneous apoptosis and autophagy in rVF. Furthermore, TFA-induced autophagy is required for this pro-apoptotic effect. Further studies to address the effect of TFA on the heart may reveal significant translational value for prevention of TFA-linked heart disease.