Fish oil fatty acids improve postprandial vascular reactivity in healthy men

Efficacy and safety of n-3 fatty acids supplementation on depression: a systematic review and dose-response meta-analysis of randomised controlled trials

We aimed to investigate the effectiveness of n-3 fatty acids supplementation on the risk of developing depression, depressive symptoms and remission of depression. We searched PubMed, Scopus and Web of Science from inception to December 2022 to find randomised trials of n-3 fatty acids supplementation in adults. We conducted random-effects meta-analyses to estimate standardised mean differences (SMD) and 95 % CI for continuous outcomes and risk difference and 95 % CI for binary outcomes. A total of sixty-seven trials were included. Each 1 g/d n-3 fatty acids supplementation significantly improved depressive symptoms in adults with and without depression (moderate-certainty evidence), with a larger improvement in patients with existing depression. Dose-response analyses indicated a U-shaped effect in patients with existing depression, with the greatest improvement at 1·5 g/d. The analysis showed that n-3 fatty acid supplementation significantly increased depression remission by 19 more per 100 in patients with depression (low-certainty evidence). Supplementation with n-3 fatty acids did not reduce the risk of developing depression among the general population, but it did improve the severity of depression among patients with existing depression.

Metabolic fate of DHA from regio- and stereospecific positions of triacylglycerols in a long-term feeding trial in rats

This study investigated the impact of regio- and stereospecific position of docosahexaenoic acid (DHA) in dietary triacylglycerols (TAGs) on the fatty acid composition of tissues and organs in rats. Four-week feeding with TAGs containing DHA in sn-1, 2, or 3 position and palmitic acid in the remaining positions at a daily dosage of 500 mg TAG/kg body weight significantly increased the DHA content in all organs and tissues in rats, except in the brain, where the change in DHA level was not statistically significant. The group fed sn-1 DHA showed a significantly higher content of DHA in the plasma TAG than the group fed sn-3 DHA. The sn-3 DHA group had higher levels of DHA in the visceral fat compared to the sn-1, sn-2, as well as all other groups. This is the first study showing that DHA from sn-1 and sn-3 positions of dietary TAGs have differential accumulation in tissues. The new findings improved the current knowledge on the significance of TAG isomeric structure for the bioavailability and metabolic fate of DHA.

Post-Prandial Cognitive and Blood Pressure Effects of a DHA-Rich Omega-3 Powder in Middle-Aged Males: A Pilot Study

The use of omega-3 polyunsaturated fatty acid (ω-3 PUFA) supplements is increasingly common among middle-aged and older adults. Users of ω-3 PUFA supplements often report using such supplements to support cognitive health, despite mixed findings reported within the ω-3 PUFA literature. To date, very few studies have explored cognitive effects in distinctly middle-aged (40 to 60 years) adults, and none have examined the acute effects (in the hours following a single dose) on cognitive performance. The current study evaluated whether a single dose of ω-3 PUFA (4020 mg docosahexaenoic acid and 720 mg eicosapentaenoic acid) influences cognitive performance and cardiovascular function in middle-aged males. Cognitive performance and cardiovascular function were assessed before and 3.5-4 h after consumption of a high dose of ω-3 PUFA (DHA + EPA) or placebo, incorporated into a standardized meal (i.e., single serve of Greek yogurt). In this study of middle-aged males, no significant differential treatment effects were observed for cognitive performance. However, a significant reduction in aortic systolic blood pressure (pre-dose to post-dose) was apparent following consumption of the ω-3 PUFA (DHA + EPA) treatment (mean difference = -4.11 mmHg, p = 0.004) but not placebo (mean difference = -1.39 mmHg, p = 0.122). Future replication in a sample comprising females, as well as patients with hypertension, is merited.

Consumption of Nutritionally Enriched Hen Eggs Enhances Endothelium-Dependent Vasodilation via Cyclooxygenase Metabolites in Healthy Young People-A Randomized Study

OBJECTIVE

The present study aimed to evaluate the effects of enriched hen egg consumption on endothelium-dependent vasodilation (EDV) and the role of cyclooxygenases in EDV in the microcirculation of young healthy individuals. This study hypothesizes that Nutri4 eggs will improve endothelial function, which will be manifested by changes in microcirculatory flow measured by a laser Doppler flowmeter (LDF) during reactive hyperemia in response to vascular occlusion, in which n-3 PUFA plays an important role as well as its degradation pathway by cyclooxygenases.

MATERIALS AND METHODS

Participants consumed three eggs per day for three weeks: The control group (CTRL, n = 14) consumed regular hen eggs (approximately 0.330 mg of lutein, 1.785 mg of vitamin E, 0.054 mg of selenium and 438 mg of n-3 PUFAs daily) and Nutri4 group (n = 20) consumed enriched eggs (approximately 1.85 mg of lutein, 0.06 mg of selenium, 3.29 mg of vitamin E, and 1026 mg of n-3 PUFAs daily). Skin microvascular blood flow in response to EDV (post-occlusive reactive hyperemia (PORH) and iontophoresis of acetylcholine (AChID)) and sodium nitroprusside (SNPID; endothelium-independent) was assessed by laser Doppler flowmetry before and after dietary protocol and in a separate group of participants who were administered perorally 100 mg of indomethacin before microvascular response assessment. Arterial blood pressure, heart rate, serum lipid, and liver enzymes, anthropometric measurements, protein expression of cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2), neuronal nitric oxide synthases (nNOS), inducible nitric oxide synthases (iNOS), and endothelial nitric oxide synthases (eNOS) were measured before and after dietary protocol.

RESULTS

PORH and AChID were significantly enhanced, and SNPID remained unchanged in the Nutri4 group, while none was changed in the CTRL following a respective diet. PORH decreased after administration of indomethacin in Nutri4 after dietary protocol. Protein expression of COX-2 was significantly higher in the Nutri4 group compared to the CTRL after the dietary protocol.

CONCLUSION

Consumption of enriched eggs improves microvascular EDV in healthy young subjects. Results suggest an element of n-3 PUFAs metabolites via the cyclooxygenases pathway in enhanced reactive hyperemia.

Differential effects of single fatty acids and fatty acid mixtures on the phosphoinositide 3-kinase/Akt/eNOS pathway in endothelial cells

SCOPE

Dietary fat composition is an important modulator of vascular function. Non-esterified fatty acids (NEFA) enriched in saturated fatty acids (SFA) are thought to reduce vascular reactivity by attenuating insulin signalling via vasodilator pathways (phosphoinositide 3-kinase (PI3K)/Akt/endothelial nitric oxide synthase (eNOS)) and enhancing signalling via pro-inflammatory pathways.

METHODS

To examine the effects of fatty acids on these pathways, human aortic endothelial cells were incubated with single fatty acids, and mixtures of these fatty acids to mimic typical NEFA composition and concentrations achieved in our previous human study. RNA was extracted to determine gene expression using real-time RT-PCR and cell lysates prepared to assess protein phosphorylation by Western blotting.

RESULTS

Oleic acid (OA, 100 µM) was shown to down regulate expression of the insulin receptor, PTEN and a PI3K catalytic (p110β) and regulatory (p85α) subunit compared to palmitic, linoleic and stearic acids (P < 0.04), and promote greater eNOS phosphorylation at Ser¹¹⁷⁷. Both concentration and composition of the SFA and SFA plus n-3 polyunsaturated fatty acids (PUFA) mixtures had significant effects on genes involved in the PI3K/Akt pathway. Greater up-regulation was found with 800 than 400 µM concentration (respective of concentrations in insulin resistant and normal individuals), whereas greater down-regulation was evident with SFA plus n-3 PUFA than SFA mixture alone.

CONCLUSION

Our findings provide novel insights into the modulation of the PI3K/Akt/eNOS pathway by single fatty acids and fatty acid mixtures. In particular, OA appears to promote signalling via this pathway, with further work required to determine the primary molecular site(s) of action.

Does the Endothelium of Competitive Athletes Benefit from Consumption of n-3 Polyunsaturated Fatty Acid-Enriched Hen Eggs?

The present study aimed to determine the effect of n-3 polyunsaturated fatty acid (PUFA)-enriched hen eggs on microvascular vasodilation, microvascular responsiveness to a stress challenge and markers of oxidative stress in competitive athletes. Competitive athletes (n=23) were divided to a control group (n=9), who consumed three regular hens’ eggs daily (249 mg n-3 PUFAs/d), and n-3 PUFAs group (n=14), who consumed three n-3 PUFA-enriched hen eggs daily (1,053 g n-3 PUFAs/d) for 3 weeks. Endothelium-dependent responses [post-occlusive reactive hyperemia (PORH) and acetylcholine-induced dilation (AChID)] and endothelium-independent responses [sodium nitroprusside-induced dilation (SNPID)] of skin microvascular blood flow were assessed by laser Doppler flowmetry in pre- and post-acute exhausting exercise (AEE) sessions. Blood pressure, serum lipid, free fatty acids profiles, and biomarkers of oxidative stress were measured before and after each dietary protocol. Consumption of serum n-3 PUFAs significantly decreased the n-6/n-3 ratio and enhanced PORH and AChID, but did not affect SNPID at rest. Furthermore, serum glutathione peroxidase and superoxide dismutase activities were significantly decreased in the n-3 PUFAs group but remained unchanged in the control group. In both groups, PORH, AChID, and SNP were significantly reduced post-AEE compared with pre-AEE, both before and after consumption of each diet. Only AChID responsiveness to AEE (ΔAChID) significantly increased following consumption of n-3 PUFAs. Overall, n-3 PUFAs supplementation as n-3 PUFA-enriched hen eggs enhanced microvascular endothelial function at rest and may contribute to adaptation to AEE in competitive athletes.

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

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

High-dose omega-3 polyunsaturated fatty acid supplementation might be more superior than low-dose for major depressive disorder in early therapy period: a network meta-analysis

BACKGROUND

The application of n-3 Polyunsaturated Fatty Acids (n-3 PUFAs) supplementation for major depressive disorder (MDD) has been widely discussed in recent years, but its efficacy and application are still controversial. This network meta-analysis was conducted to compare the efficacy of different dosages of n-3 PUFAs on MDD patients in the early period of treatment.

METHODS

Randomized controlled trials (RCTs) exploring the efficacy of n-3 PUFA supplementation for patients with MDD were retrieved from the databases of Pubmed, Embase and the Cochrane Library. RCTs comparing the efficacy of n-3 PUFA for adult (≥18 years) MDD patients without comorbidity were eligible for our study. The score of depressive symptoms in early therapy period of the treatment (≤9 weeks) was extracted. Standardized mean deviations (SMDs) of all the sores from the eligible RCTs were synthesized in a pairwise meta-analysis in frequentist framework and a random-effects network meta-analysis in Bayesian framework for the overall and subgroups (high- and low-dose) efficacy of n-3 PUFAs.

RESULTS

A total of 910 MDD patients in 10 trials with 3 adjuvant therapy strategies (high-dose n-3 PUFAs, low-dose n-3 PUFAs and placebo) were included. Results of pairwise meta-analysis showed that n-3 PUFAs were superior to placebo (SMD: 1.243 ± 0.596; 95% CI: 0.060 ~ 2.414). Results of the network meta-analysis showed that both the high (SMD: 0.908 ± 0.331; 95% CI: 0.262 ~ 1.581) and the low-dose (SMD: 0.601 ± 0.286; 95% CI: 0.034 ~ 1.18) n-3 PUFAs were superior to placebo, and the efficacy of high-dose n-3 PUFAs is superior to that of low-dose.

CONCLUSIONS

High-dose n-3 PUFAs supplementation might be more superior than low-dose in the early therapy period for MDD. More head-to-head clinical trials need to be carried out to provide more direct comparison and enhance the evidence of the efficacy of n-3PUFAs for MDD.

Mediterranean Diet Increases Endothelial Function in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

The endothelium plays a key role in the maintenance of vascular health and represents a potential physiological target for dietary and other lifestyle interventions designed to reduce the risk of cardiovascular diseases (CVD) including stroke or coronary heart disease.

OBJECTIVE

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating the effects of the Mediterranean dietary pattern (MedDiet) on endothelial function.

METHODS

Medline, Embase, and Scopus databases were searched from inception until January 2019 for studies that met the following criteria: 1) RCTs including adult participants, 2) interventions promoting the MedDiet, 3) inclusion of a control group, and 4) measurements of endothelial function. A random-effects meta-analysis was conducted. Metaregression and subgroup analyses were performed to identify whether effects were modified by health status (i.e., healthy participants versus participants with existing comorbidities), type of intervention (i.e., MedDiet alone or with a cointervention), study duration, study design (i.e., parallel or crossover), BMI, and age of participants.

RESULTS

Fourteen articles reporting data for 1930 participants were included in the meta-analysis. Study duration ranged from 4 wk to 2.3 y. We observed a beneficial effect of the MedDiet on endothelial function [standardized mean difference (SMD): 0.35; 95% CI: 0.17, 0.53; P <0.001; I2 = 73.68%]. MedDiet interventions improved flow-mediated dilation (FMD)-the reference method for noninvasive, clinical measurement of endothelial function-by 1.66% (absolute change; 95% CI: 1.15, 2.17; P <0.001; I2 = 0%). Effects of the MedDiet on endothelial function were not modified by health status, type of intervention, study duration, study design, BMI, or age of participants (P >0.05).

CONCLUSIONS

MedDiet interventions improve endothelial function in adults, suggesting that the protective effects of the MedDiet are evident at early stages of the atherosclerotic process with important implications for the early prevention of CVD. This study has the PROSPERO registration number: CRD42018106188.

The Physiological Effect of n-3 Polyunsaturated Fatty Acids (n-3 PUFAs) Intake and Exercise on Hemorheology, Microvascular Function, and Physical Performance in Health and Cardiovascular Diseases; Is There an Interaction of Exercise and Dietary n-3 PUFA Intake?

Physical activity has a beneficial effect on systemic hemodynamics, physical strength, and cardiac function in cardiovascular (CV) patients. Potential beneficial effects of dietary intake of n-3 polyunsaturated fatty acids (n-3 PUFAs), such as α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid on hemorheology, vascular function, inflammation and potential to improve physical performance as well as other CV parameters are currently investigated. Recent meta-analysis suggests no effect of n-3 PUFA supplementation on CV function and outcomes of CV diseases. On the other hand, some studies support beneficial effects of n-3 PUFAs dietary intake on CV and muscular system, as well as on immune responses in healthy and in CV patients. Furthermore, the interaction of exercise and dietary n-3 PUFA intake is understudied. Supplementation of n-3 PUFAs has been shown to have antithrombotic effects (by decreasing blood viscosity, decreasing coagulation factor and PAI-1 levels and platelet aggregation/reactivity, enhancing fibrinolysis, but without effects on erythrocyte deformability). They decrease inflammation by decreasing IL-6, MCP-1, TNFα and hsCRP levels, expression of endothelial cell adhesion molecules and significantly affect blood composition of fatty acids. Treatment with n-3 PUFAs enhances brachial artery blood flow and conductance during exercise and enhances microvascular post-occlusive hyperemic response in healthy humans, however, the effects are unknown in cardiovascular patients. Supplementation of n-3 PUFAs may improve anaerobic endurance and may modulate oxygen consumption during intense exercise, may increase metabolic capacity, enhance endurance capacity delaying the onset of fatigue, and improving muscle hypertrophy and neuromuscular function in humans and animal models. In addition, n-3 PUFAs have anti-inflammatory and anti-nociceptive effects and may attenuate delayed-onset muscle soreness and muscle stiffness, and preserve joint mobility. On the other hand, effects of n-3 PUFAs were variably observed in men and women and they vary depending on dietary protocol, type of supplementation and type of sports activity undertaken, both in healthy and cardiovascular patients. In this review we will discuss the physiological effects of n-3 PUFA intake and exercise on hemorheology, microvascular function, immunomodulation and inflammation and physical performance in healthy persons and in cardiovascular diseases; elucidating if there is an interaction of exercise and diet.

The Postprandial Appearance of Features of Cardiometabolic Risk: Acute Induction and Prevention by Nutrients and Other Dietary Substances

The purpose of this review is to provide an overview of diets, food, and food components that affect postprandial inflammation, endothelial function, and oxidative stress, which are related to cardiometabolic risk. A high-energy meal, rich in saturated fat and sugars, induces the transient appearance of a series of metabolic, signaling and physiological dysregulations or dysfunctions, including oxidative stress, low-grade inflammation, and endothelial dysfunction, which are directly related to the amplitude of postprandial plasma triglycerides and glucose. Low-grade inflammation and endothelial dysfunction are also known to cluster together with insulin resistance, a third risk factor for cardiovascular diseases (CVD) and type-II diabetes, thus making a considerable contribution to cardiometabolic risk. Because of the marked relevance of the postprandial model to nutritional pathophysiology, many studies have investigated whether adding various nutrients and other substances to such a challenge meal might mitigate the onset of these adverse effects. Some foods (e.g., nuts, berries, and citrus), nutrients (e.g., l-arginine), and other substances (various polyphenols) have been widely studied. Reports of favorable effects in the postprandial state have concerned plasma markers for systemic or vascular pro-inflammatory conditions, the activation of inflammatory pathways in plasma monocytes, vascular endothelial function (mostly assessed using physiological criteria), and postprandial oxidative stress. Although the literature is fragmented, this topic warrants further study using multiple endpoints and markers to investigate whether the interesting candidates identified might prevent or limit the postprandial appearance of critical features of cardiometabolic risk.

Omega-3 polyunsaturated fatty acids-enriched hen eggs consumption enhances microvascular reactivity in young healthy individuals

The beneficial effect of omega-3 polyunsaturated fatty acids (PUFA) supplementation on the cardiovascular (CV) system is well supported in CV patients; however, the effect of the consumption of omega-3 PUFA-enriched functional food in healthy individuals is still not fully elucidated. This study aimed to determine the effect of the consumption of omega-3 PUFA-enriched hen eggs on the microvascular reactivity (primary outcome), blood pressure (BP), and serum lipid profile in young healthy individuals. The control group (N = 16) ate 3 ordinary hen eggs (277 mg of omega-3 PUFAs/day), and the OMEGA-3 group (N = 20) ate 3 omega-3 PUFA-enriched eggs containing 259 mg of omega-3 PUFAs/egg daily (α-linolenic acid (ALA), 167 mg/egg; eicosapentaenoic acid (EPA), 7 mg/egg; docosahexaenoic acid (DHA), 84 mg/egg) for 3 weeks (777 mg of omega-3 PUFA/day). Postocclusive reactive hyperemia (PORH) in skin microcirculation assessed by laser Doppler flowmetry, serum lipid profile, fasting blood glucose, high-sensitivity C-reactive protein (hsCRP), and arterial BP were measured in all subjects before and after the protocol. PORH was significantly enhanced, and triglycerides, hsCRP, and BP were significantly decreased in the OMEGA-3 group compared with baseline measurements, whereas there was no significant difference in the control group after the protocol when compared with baseline. To the best of our knowledge, this is the first study to demonstrate that consumption of a mixture of omega-3 PUFA (ALA + EPA + DHA), provided via enriched hen eggs, elicits changes in the microvascular reactivity, BP, and triglyceride level in healthy subjects that are associated with CV benefits, thus suggesting that daily consumption of omega-3 PUFA-enriched eggs in healthy individuals may potentially contribute to CV risk factor attenuation and disease prevention.

The Cognitive Ageing, Nutrition and Neurogenesis (CANN) trial: Design and progress

Introduction

The Cognitive Ageing, Nutrition and Neurogenesis trial hypothesizes that a combined intervention with long-chain n-3 polyunsaturated fatty acids (n-3) and cocoa flavan-3-ols (FLAV) will mitigate the cognitive decline anticipated to naturally occur over 1 year in older adults.

Methods

In a double-blinded, placebo-controlled parallel design, 259 individuals with mild cognitive impairment or subjective memory impairment were randomized to a control or n-3 FLAV group (1.5 g docosahexaenoic acid + eicosapentaenoic acid and 500 mg n-3 FLAV daily) for 12 months. Cognition was measured at 0, 3, and 12 months. The primary end-point is hippocampus-sensitive cognitive function (e.g., number of false-positives on the Picture Recognition Task of the Cognitive Drug Research test battery). Secondary outcomes include additional cognitive measures, brain atrophy and blood flow (assessed by magnetic resonance imaging), vascular function, circulating biomarkers of cardiovascular and cognitive health, gut microflora, red blood cell fatty acid status, and urine flavan-3-ol metabolites.

Results

Screening began in 2015, with all baseline visits completed in March 2017. The intervention was finished in March 2018.

Discussion

Cognitive Ageing, Nutrition and Neurogenesis aims to identify an effective diet-based intervention to prevent or delay cognitive impairment in cognitively at-risk individuals, which could ultimately contribute to a reduced population burden of dementia.

Clinicaltrials.gov

NCT02525198.

How does high DHA fish oil affect health? A systematic review of evidence

The health benefits of fish oil, and its omega-3 long chain polyunsaturated fatty acid content, have attracted much scientific attention in the last four decades. Fish oils that contain higher amounts of eicosapentaenoic acid (EPA; 20:5n-3) than docosahexaenoic acid (DHA; 22:6n-3), in a distinctive ratio of 18/12, are typically the most abundantly available and are commonly studied. Although the two fatty acids have traditionally been considered together, as though they were one entity, different physiological effects of EPA and DHA have recently been reported. New oils containing a higher quantity of DHA compared with EPA, such as fractionated and concentrated fish oil, tuna oil, calamari oil and microalgae oil, are increasingly becoming available on the market, and other oils, including those extracted from genetically modified oilseed crops, soon to come. This systematic review focuses on the effects of high DHA fish oils on various human health conditions, such as the heart and cardiovascular system, the brain and visual function, inflammation and immune function and growth/Body Mass Index. Although inconclusive results were reported in several instances, and inconsistent outcomes observed in others, current data provides substantiated evidence in support of DHA being a beneficial bioactive compound for heart, cardiovascular and brain function, with different, and at times complementary, effects compared with EPA. DHA has also been reported to be effective in slowing the rate of cognitive decline, while its possible effects on depression disorders are still unclear. Interestingly, gender- and age- specific divergent roles for DHA have also been reported. This review provides a comprehensive collection of evidence and a critical summary of the documented physiological effects of high DHA fish oils for human health.

Characterisation of the vasodilation effects of DHA and EPA, n-3 PUFAs (fish oils), in rat aorta and mesenteric resistance arteries

Background and purpose

Increasing evidence suggests that the omega-3 polyunsaturated acids (n-3 PUFA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are beneficial to cardiovascular health, promoting relaxation of vascular smooth muscle cells and vasodilation. Numerous studies have attempted to study these responses, but to date there has not been a systematic characterisation of both DHA and EPA mediated vasodilation in conduit and resistance arteries. Therefore, we aimed to fully characterise the n-3 PUFA-induced vasodilation pathways in rat aorta and mesenteric artery.

Methods

Wire myography was used to measure the vasomotor responses of freshly dissected rat mesenteric artery and aorta. Arteries were pre-constricted with U46619 and cumulative concentrations of either DHA or EPA (10 nM-30 μM) were added. The mechanisms by which n-3 PUFA relaxed arteries were investigated using inhibitors of vasodilator pathways, which include: nitric oxide synthase (NOS; L-NAME), cycloxygenase (COX; indomethacin), cytochrome P450 epoxygenase (CYP450; clotrimazole); and calcium-activated potassium channels (K_Ca), SK_Ca (apamin), IK_Ca (TRAM-34) and BK_Ca (paxilline).

Results

Both DHA- and EPA-induced relaxations were partially inhibited following endothelium removal in rat mesenteric arteries. Similarly, in aorta EPA-induced relaxation was partially suppressed due to endothelium removal. CYP450 also contributed to EPA-induced relaxation in mesenteric artery. Inhibition of IK_Ca partially attenuated DHA-induced relaxation in aorta and mesenteric artery along with EPA-induced relaxation in mesenteric artery. Furthermore, this inhibition of DHA- and EPA-induced relaxation was increased following the additional blockade of BK_Ca in these arteries.

Conclusions

This study provides evidence of heterogeneity in the vasodilation mechanisms of DHA and EPA in different vascular beds. Our data also demonstrates that endothelium removal has little effect on relaxations produced by either PUFA. We demonstrate IK_Ca and BK_Ca are involved in DHA-induced relaxation in rat aorta and mesenteric artery; and EPA-induced relaxation in rat mesenteric artery only. CYP450 derived metabolites of EPA may also be involved in BK_Ca dependent relaxation. To our knowledge this is the first study indicating the involvement of IK_Ca in n-3 PUFA mediated relaxation.

Effects of Montmorency tart cherry (Prunus Cerasus L.) consumption on vascular function in men with early hypertension

BACKGROUND

Tart cherries contain numerous polyphenolic compounds that could potentially improve endothelial function and reduce cardiovascular disease risk.

OBJECTIVE

We sought to examine the acute effects of Montmorency tart cherry (MC) juice on vascular function in subjects with early hypertension.

DESIGN

A placebo-controlled, blinded, crossover, randomized Latin square design study with a washout period of ≥14 d was conducted. Fifteen men with early hypertension [systolic blood pressure (SBP) ≥130 mm Hg, diastolic blood pressure ≥80 mm Hg, or both] received either a 60-mL dose of MC concentrate or placebo. Microvascular reactivity (laser Doppler imaging with iontophoresis), arterial stiffness (pulse wave velocity and analysis), blood pressure, and phenolic acid absorption were assessed at baseline and at 1, 2, 3, 5, and 8 h postconsumption.

RESULTS

MC consumption significantly lowered SBP (P < 0.05) over a period of 3 h, with peak reductions of mean ± SEM 7 ± 3 mm Hg 2 h after MC consumption relative to the placebo. Improvements in cardiovascular disease risk factors were closely linked to increases in circulating protocatechuic and vanillic acid at 1-2 h.

CONCLUSIONS

MC intake acutely reduces SBP in men with early hypertension. These benefits may be mechanistically linked to the actions of circulating phenolic acids. This study provides information on a new application of MCs in health maintenance, particularly in positively modulating SBP. This trial was registered at clinicaltrials.gov as NCT02234648.

Differential effects of EPA versus DHA on postprandial vascular function and the plasma oxylipin profile in men

Our objective was to investigate the impact of EPA versus DHA on arterial stiffness and reactivity and underlying mechanisms (with a focus on plasma oxylipins) in the postprandial state. In a three-arm crossover acute test meal trial, men (n = 26, 35-55 years) at increased CVD risk received a high-fat (42.4 g) test meal providing 4.16 g of EPA or DHA or control oil in random order. At 0 h and 4 h, blood samples were collected to quantify plasma fatty acids, long chain n-3 PUFA-derived oxylipins, nitrite and hydrogen sulfide, and serum lipids and glucose. Vascular function was assessed using blood pressure, reactive hyperemia index, pulse wave velocity, and augmentation index (AIx). The DHA-rich oil significantly reduced AIx by 13% (P = 0.047) with the decrease following EPA-rich oil intervention not reaching statistical significance. Both interventions increased EPA- and DHA-derived oxylipins in the acute postprandial state, with an (1.3-fold) increase in 19,20-dihydroxydocosapentaenoic acid evident after DHA intervention (P < 0.001). In conclusion, a single dose of DHA significantly improved postprandial arterial stiffness as assessed by AIx, which if sustained would be associated with a significant decrease in CVD risk. The observed increases in oxylipins provide a mechanistic insight into the AIx effect.

A single Mediterranean meal does not impair postprandial flow-mediated dilatation in healthy men with subclinical metabolic dysregulations

Cardiovascular risk factors are known to exacerbate high-saturated fatty acid meal (HSFAM)-induced endothelial dysfunction, but the influence of subclinical metabolic dysregulations and the acute impact of a single mixed Mediterranean-type meal (MMM) remains unknown. Thus, this study has the objective to evaluate the metabolic and vascular effect of such meals in healthy subjects with or without subclinical fasting metabolic dysregulations. Twenty-eight healthy males without overt cardiovascular risk factors randomly ingested 1 of 2 isocaloric meals on separate days. Plasma metabolic markers, fatty acid (FA) profile, and endothelial function (flow-mediated dilatation; FMD) were assessed at baseline and 2 and 4 h after meal ingestion. Unsupervised hierarchical clustering identified 2 subgroups of participants (n = 11 and 17) differing by their baseline metabolic profiles. The MMM did not significantly alter postprandial endothelial function in all subjects, irrespective of baseline metabolic parameters. In contrast, the HSFAM induced postprandial endothelial dysfunction (Δ%FMDabsolute = -5.28 ± 2.54, p < 0.01 vs. MMM) in a subgroup of individuals with significantly greater body mass index, fasting insulinemia, and lipid parameters (n = 11). Finally, the postprandial plasma FA profiles were differentially enriched by the HSFAM and MMM, notably with saturated FAs and omega-3 polyunsaturated FAs, respectively. Collectively, our results highlight the detrimental impact of a single HSFAM on endothelial function in healthy individuals displaying subclinical fasting metabolic dysregulations. Such individuals could benefit from MMM, demonstrated herein to be without any acute detriment to endothelial function.

Consumption of Fish Oil Providing Amounts of Eicosapentaenoic Acid and Docosahexaenoic Acid That Can Be Obtained from the Diet Reduces Blood Pressure in Adults with Systolic Hypertension: A Retrospective Analysis

BACKGROUND

Although many randomized controlled trials (RCTs) have examined the effects of the n-3 (ω-3) fatty acids eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) on blood pressure (BP) and vascular function, the majority have used doses of EPA+DHA of >3 g/d, which are unlikely to be achieved by dietary manipulation.

OBJECTIVE

The objective was to examine, by using a retrospective analysis from a multicenter RCT, the impact of recommended EPA+DHA intakes achievable through diet on systolic and diastolic BPs and microvascular function in adults in the United Kingdom.

METHODS

In a double-blind, placebo-controlled RCT, healthy men and women (n = 312) consumed a control oil or fish oil (FO) providing 0.7 or 1.8 g EPA+DHA/d, in random order, each for 8 wk. Fasting BP and microvascular function (using laser Doppler iontophoresis) were assessed and plasma collected for the quantification of markers of vascular function. Participants were retrospectively genotyped for the endothelial nitric oxide synthase (eNOS) rs1799983 variant.

RESULTS

No effects of n-3 fatty acid treatment or any treatment × eNOS genotype interactions were evident in the group as a whole for any of the clinical or biochemical outcomes. Assessment of response according to hypertension status at baseline indicated a significant (P = 0.046) FO-induced reduction (mean: 5 mm Hg) in systolic BP, specifically in those with isolated systolic hypertension (n = 31). No dose response was observed.

CONCLUSIONS

These findings indicate that in adults with isolated systolic hypertension, daily doses of EPA+DHA as low as 0.7 g show clinically meaningful BP reductions, which, at a population level, could be associated with lower cardiovascular disease risk. Confirmation of findings in an RCT in which participants are prospectively recruited on the basis of BP status is required to draw definite conclusions.

Influence of fish oil supplementation and strength training on some functional aspects of immune cells in healthy elderly women

Immune function changes with ageing and is influenced by physical activity (strength training, ST) and diet (fish oil, FO). The present study investigated the effect of FO and ST on the immune system of elderly women. Forty-five women (64 (sd 1·4) years) were assigned to ST for 90 d (ST; n 15), ST plus 2 g/d FO for 90 d (ST90; n 15) or 2 g/d FO for 60 d followed by ST plus FO for 90 d (ST150; n 15). Training was performed three times per week, for 12 weeks. A number of innate (zymosan phagocytosis, lysosomal volume, superoxide anion, peroxide of hydrogen) and adaptive (cluster of differentiation 4 (CD4), CD8, TNF-α, interferon-γ (IFN-γ), IL-2, IL-6 and IL-10 produced by lymphocytes) immune parameters were assessed before supplementation (base), before (pre-) and after (post-) training. ST induced no immune changes. FO supplementation caused increased phagocytosis (48 %), lysosomal volume (100 %) and the production of superoxide anion (32 %) and H2O2 (70 %) in the ST90. Additional FO supplementation (ST150) caused no additive influence on the immune system, as ST150 and ST90 did not differ, but caused greater changes when compared to the ST (P< 0·05). FO increased CD4+ and CD8+ lymphocytes in the ST150, which remained unchanged when training was introduced. The combination of ST and FO reduced TNF-α in the ST150 from base to post-test. FO supplementation (ST150, base–pre) when combined with exercise (ST150, pre–post) increased IFN-γ, IL-2, IL-6 and IL-10 production. The immune parameters improved in response to FO supplementation; however, ST alone did not enhance the immune system.

A select review reporting the quality of studies measuring endothelial dysfunction in randomised diet intervention trials

A quality assessment of the primary studies reported in the literature carried out using select dietary ingredients (DI) purported to affect vascular endothelial function was conducted through a systematic PubMed search from January 2000 to August 2012. A total of seventy randomised controlled trials with defined DI (folic acid (fifteen), n-3 fatty acids (twenty), cocoa (fifteen) and isoflavones (twenty)) and standardised measures of vascular endothelial function were evaluated. Jadad scores, quality scoring parameters for DI and flow-mediated dilation (FMD) methodology used were ascertained. A total of 3959 randomised subjects, mean age 51 (se 0·21) years (range 9-79 years), were represented in the dataset. The mean Jadad scores did not differ statistically among the DI studies, with the majority of the studies being of good quality. Higher DI quality scores were achieved by studies using the botanical ingredients cocoa and isoflavones than by those using the nutrient ingredients folic acid and n-3 fatty acids. The mean DI quality scores were 4·13 (se 0·34), 5·20 (se 0·47), 6·13 (se 0·41) and 6·00 (se 0·59) for the folic acid, n-3 fatty acid, cocoa and isoflavone intervention studies, respectively (and significantly different). The mean Corretti FMD scores were 7·27 (se 0·56), 7·46 (se 0·79), 6·29 (se 0·61) and 7·11 (se 0·56) for the folic acid, n-3 fatty acid, cocoa and isoflavone intervention studies, respectively (NS). FMD studies failed to adequately describe the equipment used and more than half failed to provide an adequate description of the procedures used for vascular image acquisition and measurement. DI can be utilised for dietary intervention studies; however, the methodology should be clearly reported using the guidelines for assessment for both DI and FMD.

High-fat meals rich in EPA plus DHA compared with DHA only have differential effects on postprandial lipemia and plasma 8-isoprostane F2α concentrations relative to a control high-oleic acid meal: a randomized controlled trial

BACKGROUND

Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) supplementation has beneficial cardiovascular effects, but postprandial influences of these individual fatty acids are unclear.

OBJECTIVES

The primary objective was to determine the vascular effects of EPA + DHA compared with DHA only during postprandial lipemia relative to control high-oleic acid meals; the secondary objective was to characterize the effects of linoleic acid-enriched high-fat meals relative to the control meal.

DESIGN

We conducted a randomized, controlled, double-blind crossover trial of 4 high-fat (75-g) meals containing 1) high-oleic acid sunflower oil (HOS; control), 2) HOS + fish oil (FO; 5 g EPA and DHA), 3) HOS + algal oil (AO; 5 g DHA), and 4) high-linoleic acid sunflower oil (HLS) in 16 healthy men (aged 35-70 y) with higher than optimal fasting triacylglycerol concentrations (mean ± SD triacylglycerol, 1.9 ± 0.5 mmol/L).

RESULTS

Elevations in triacylglycerol concentration relative to baseline were slightly reduced after FO and HLS compared with the HOS control (P < 0.05). The characteristic decrease from baseline in plasma nonesterified fatty acids after a mixed meal was inhibited after AO (Δ 0-3 h, P < 0.05). HLS increased the augmentation index compared with the other test meals (P < 0.05), although the digital volume pulse-reflection index was not significantly different. Plasma 8-isoprostane F2α analysis revealed opposing effects of FO (increased) and AO (reduced) compared with the control (P < 0.05). No differences in nitric oxide metabolites were observed.

CONCLUSIONS

These data show differential postprandial 8-isoprostane F2α responses to high-fat meals containing EPA + DHA-rich fish oil compared with DHA-rich AO, but these differences were not associated with consistent effects on postprandial vascular function or lipemia. More detailed analyses of polyunsaturated fatty acid-derived lipid mediators are required to determine possible divergent functional effects of single meals rich in either DHA or EPA. This trial was registered at clinicaltrials.gov as NCT01618071.

The role of oxidative stress in postprandial endothelial dysfunction

Endothelial dysfunction is a turning point in the initiation and development of atherosclerosis and its complications and is predictive of future cardiovascular events. Ingestion of high-carbohydrate or high-fat meals often results in postprandial hyperglycaemia and/or hypertriacylglycerolaemia that may lead to a transient impairment in endothelial function. The present review will discuss human studies evaluating the impact of high-carbohydrate and high-fat challenges on postprandial endothelial function as well as the potential role of oxidative stress in such postprandial metabolic alterations. Moreover, the present review will differentiate the postprandial endothelial and oxidative impact of meals rich in varying fatty acid types.

Effects of two different types of fast food on postprandial metabolism in normal and overweight subjects

BACKGROUND/OBJECTIVES

The aim was to investigate the effects of a conventional and an unconventional fast-food meal on postprandial metabolism in normal and in overweight subjects.

SUBJECTS/METHODS

Twenty-five healthy normal (n = 12) and overweight (n = 13) volunteers (21-39 years) participated in this randomized, dietary cross-over study and received two test meals (matched in energy and energy giving nutrients) after an overnight fast with 1 week between test days. The conventional fast-food meal was a hamburger meal (hamburger, bacon, cola drink, calculated glycemic load = 48.7), the unconventional fast food was a salmonburger meal (fiber-rich sourdough rye bread, salad with vinegar, orange juice, glycemic load = 46.0). Blood samples were taken before and after the meal and analyzed for glucose (before 20, 40, 60 and 80 min) and insulin (before 1, 2 and 3 h).

RESULTS

Postprandial increases in glucose and insulin were 44% lower after the unconventional meal (P<0.001 and P = 0.003, respectively). The difference between meals in insulin response (that is, conventional meal higher than unconventional) correlated with body mass index (BMI) (r = 0.538, P = 0.006).

CONCLUSIONS

Unconventional fast food can have less effect on blood insulin and glucose postprandially compared with conventional fast food matched in energy and energy giving nutrients. The difference between meals in insulin response is associated with higher BMI. Thus, improvement in food quality might help to control postprandial increases in blood glucose and blood insulin.

Glu298Asp polymorphism influences the beneficial effects of fish oil fatty acids on postprandial vascular function

Our objective was to determine whether the endothelial nitric oxide synthase (eNOS) Glu298Asp polymorphism influences vascular response to raised NEFA enriched with saturated fatty acids (SFA) or long-chain (LC) n-3 polyunsaturated fatty acids (PUFA). Subjects were prospectively recruited for genotype (Glu298, n = 30 and Asp298, n = 29; balanced for age and gender) consumed SFA on two occasions, with and without the substitution of 0.07 g fat/kg body weight with LC n-3 PUFA, and with heparin infusion to elevate NEFA. Endothelial function was measured before and after NEFA elevation (240 min), with blood samples taken every 30 min. Flow-mediated dilation (FMD) decreased following SFA alone and increased following SFA+LC n-3 PUFA. There were 2-fold differences in the change in FMD response to the different fat loads between the Asp298 and Glu298 genotypes (P = 0.002) and between genders (P < 0.02). Sodium nitroprusside-induced reactivity, measured by laser Doppler imaging with iontophoresis, was significantly greater with SFA+LC n-3 PUFA in all female subjects (P < 0.001) but not in males. Elevated NEFA influences both endothelial-dependent and endothelial-independent vasodilation during the postprandial phase. Effects of fat composition appear to be genotype and gender dependent, with the greatest difference in vasodilatory response to the two fat loads seen in the Asp298 females.

The Glu298Asp single nucleotide polymorphism in the endothelial nitric oxide synthase gene differentially affects the vascular response to acute consumption of fruit and vegetable puree based drinks

SCOPE

Diets low in fruits and vegetables (FV) are responsible for 2.7 million deaths from cardiovascular diseases (CVD) and certain cancers annually. Many FV and their juices contain flavonoids, some of which increase endothelial nitric oxide synthase (eNOS) activity. A single nucleotide polymorphism in the eNOS gene, where thymine (T) replaces guanine (G) at position 894 predicting substitution of glutamate for aspartate at codon 298 (Glu298Asp), has been associated with increased CVD risk due to effects on nitric oxide synthesis and subsequently vascular reactivity. Individuals can be homozygous for guanine (GG), thymine (TT) or heterozygous (GT).

METHODS AND RESULTS

We investigated the effects of acute ingestion of a FV-puree-based-drink (FVPD) on vasodilation and antioxidant status in subjects retrospectively genotyped for this polymorphism. Healthy volunteers (n = 24; 11 GG, 11 GT, 2 TT) aged 30-70 were recruited to a randomized, controlled, crossover, acute study. We showed that acute consumption of 400 mL FVPD differentially affected individuals depending on their genotype. There was a significant genotype interaction for endothelium-dependent vasodilation measured by laser Doppler imaging with iontophoresis (P < 0.05) and ex vivo low-density lipoproteins (LDL) oxidation (P = 0.002). GG subjects had increased endothelium-dependent vasodilation 180 min (P = 0.028) and reduced ex vivo LDL oxidation (P = 0.013) after 60 min after FVPD compared with control, no differences were observed in GT subjects.

CONCLUSION

eNOS Glu298Asp genotype differentially affects vasodilation and ex vivo LDL oxidation after consumption of FV in the form of a puree-based drink.

A comparison of the changes in cardiac output and systemic vascular resistance during exercise following high-fat meals containing DHA or EPA

Long-chain n-3 PUFA can lower blood pressure (BP) but their acute effects on cardiac output, BP and systemic vascular resistance (SVR) in response to dynamic exercise are uncertain. We compared the effects of high-fat meals rich in EPA (20 : 5n-3), DHA (22 : 6n-3) or oleic acid (control) on cardiac output, BP and SVR in response to exercise stress testing. High-fat meals (50 g fat) containing high-oleic sunflower oil enriched with 4·7 g of either EPA or DHA v. control (high-oleic sunflower oil only) were fed to twenty-two healthy males using a randomised cross-over design. Resting measurements of cardiac output, heart rate and BP were made before and hourly over 5 h following the meal. A standardised 12 min exercise test was then conducted with further measurements made during and post-exercise. Blood samples were collected at fasting, 5 h postprandially and immediately post-exercise for the analysis of lipid, glucose and 8-isoprostane-F2α (8-iso-PGF2α). Plasma concentrations of EPA and DHA increased by 0·22 mmol/l 5 h following the EPA and DHA meals, respectively, compared with the control (P < 0·001). Resting cardiac output and 8-iso-PGF2α increased similarly following all meals and there were no significant differences in cardiac output during exercise between the meals. SVR was lower at 5 h and during exercise following the DHA but not EPA meal, compared with the control meal, by 4·9 % (95 % CI 1·3, 8·4; P < 0·01). Meals containing DHA appear to differ from EPA with regard to their effects on cardiovascular haemodynamics during exercise.

Effects of acute ingestion of different fats on oxidative stress and inflammation in overweight and obese adults

Background

Studies show that obese individuals have prolonged elevations in postprandial lipemia and an exacerbated inflammatory response to high fat meals, which can increase risk for cardiovascular diseases. As epidemiological studies indicate an association between type of fat and circulating inflammatory markers, the purpose of this study was to investigate the acute effect of different fat sources on inflammation and oxidative stress in overweight and obese individuals.

Methods

Eleven overweight and obese subjects consumed three high fat milkshakes rich in monounsaturated fat (MFA), saturated fat (SFA), or long-chain omega 3 polyunsaturated fat (O3FA) in random order. Blood samples collected at baseline, 1, 2, 4, and 6 hours postprandial were analyzed for markers of inflammation (soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor- α (TNF-α), and C-reactive protein (CRP)), oxidative stress (8-epi-prostaglandin-F2α (8-epi) and nuclear factor-κB (NF-κB)), and metabolic factors (glucose, insulin, non-esterified free fatty acids, and triglycerides (TG)).

Results

O3FA enhanced NF-kB activation compared to SFA, but did not increase any inflammatory factors measured. Conversely, SFA led to higher ICAM-1 levels than MFA (p = 0.051), while MFA increased TG more than SFA (p < 0.05). CRP increased while TNF-α and 8-epi decreased with no difference between treatments.

Conclusions

While most of the inflammatory factors measured had modest or no change following the meal, ICAM-1 and NF-κB responded differently by meal type. These results are provocative and suggest that type of fat in meals may differentially influence postprandial inflammation and endothelial activation.

Pro- and anti-oxidant effects of polyunsaturated fatty acid supplementation in HepG2 cells

PUFA are bioactive nutrients thought to be effective in the prevention of many chronic diseases. PUFA susceptibility to free radical oxidation represents the other side of the coin, and the role of PUFA as pro- or anti-oxidants is still an unanswered question. In this study we supplemented HepG2 cells with different PUFA, and observed different effects on cytotoxicity, oxidation and modulation of antioxidant defenses. These were not simply related to the length of carbon chain, or to the number and position of double bonds. ARA supply evidenced the induction of oxidative damage, while DHA supplemented cells appeared richer in antioxidant defenses. To our knowledge, our study is the first evidencing the different pro- or anti-oxidant effect of different fatty acids when supplemented to cells. Overall, this points out the importance of not generalizing dietary recommendations considering PUFA as one category, but to extend them to the individual fatty acids.

DHA-rich fish oil reverses the detrimental effects of saturated fatty acids on postprandial vascular reactivity

BACKGROUND

Experimental elevation of nonesterified fatty acids (NEFAs) impairs endothelial function, but the effect of NEFA composition is unknown.

OBJECTIVE

The objective was to test the effect of acute elevation of NEFAs enriched with either saturated fatty acids (SFAs) or SFAs with long-chain (LC) n-3 (omega-3) PUFAs on vascular function measured via flow-mediated dilatation (FMD), laser Doppler iontophoresis (LDI), and digital volume pulse (DVP).

DESIGN

In 59 subjects (30 men and 29 women), repeated oral fat feeding of either palm stearin (SFA) or palm stearin with DHA-rich fish oil (SFA + LC n-3 PUFA) was performed on 2 separate occasions with continuous heparin infusion to elevate NEFAs for a duration of 60 to 240 min. Vascular function was measured at baseline and at the end of NEFA elevation; venous blood was collected for measurement of lipids and circulating markers of endothelial function.

RESULTS

NEFA elevation during consumption of the SFA-rich drinks was associated with a marked impairment of FMD, whereas consumption of SFAs + LC n-3 PUFAs improved FMD response, with a mean (±SEM) difference of 2.06 ± 0.29% (P < 0.001). Positive correlations were found with percentage weight of LC n-3 PUFAs in circulating NEFAs and change in FMD response [Spearman's rho (r(s)) = 0.460, P < 0.001]. LDI measures increased during both treatments (P ≤ 0.026), and there was no change in DVP indexes.

CONCLUSIONS

The composition of NEFAs can acutely affect FMD. The beneficial effect of LC n-3 PUFAs on postprandial vascular function warrants further investigation but may be mediated by nitric oxide-independent mechanisms. This trial is registered at clinicaltrials.gov as NCT01351324.

The assessment of vascular function during dietary intervention trials in human subjects

The potential to reduce cardiovascular morbidity through dietary modification remains an area of intense clinical and scientific interest. Any putatively beneficial intervention should be tested within a randomised controlled trial which records appropriate endpoints, ideally incident CVD and death. However, the large sample sizes required for these endpoints and associated high costs mean that the majority of dietary intervention research is conducted over short periods among either healthy volunteers or those at only slightly increased risk, with investigators using a diverse range of surrogate measures to estimate arterial health in these studies. The present review identifies commonly employed techniques, discusses the relative merits of each and highlights emerging approaches.

Impact of n-3 fatty acids on endothelial function: results from human interventions studies

PURPOSE OF REVIEW

Dysfunction of the endothelium plays an integral role in atherogenesis. This review summarizes recent findings on the effects of marine [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] and plant [alpha-linolenic acids (ALA)] n-3 polyunsaturated fatty acids (PUFAs) on endothelial function in healthy individuals and in patients with cardiovascular disease (CVD) risk factors or manifest CVD.

RECENT FINDINGS

We identified 33 intervention trials investigating the effects of n-3 PUFA on fasting and/or postprandial endothelial function. In healthy individuals regular supplementation of EPA/DHA or ALA shows inconsistent results on endothelial function, whereas markers of endothelial function seem to be improved in overweight dyslipidaemic patients and type 2 diabetics. Conflicting results are observed in CVD patients. Reasons for discrepancies between the study results include the health status and age of participants, duration of supplementation, dose and fatty acid composition of the administered n-3 PUFAs as well as methods used to assess endothelial function.

SUMMARY

In individuals with CVD risk factors including overweight, dyslipidemia and type 2 diabetes n-3 PUFAs may improve endothelial function. However, the evidence for a clinical efficacy is not strong enough to make final recommendations with respect to a specific dose and the duration of supplementation.

The impact of the catechol-O-methyltransferase genotype on the acute responsiveness of vascular reactivity to a green tea extract

The beneficial effects of green tea catechins, such as the proposed improvement in endothelial function, may be influenced by phase II metabolism during and after absorption. The methylation enzyme, catechol-O-methyltransferase (COMT), has a missense mutation rs4680 (G to A), proposed to result in a 40 % reduction in enzyme activity. In the present pilot study, twenty subjects (ten of each homozygous COMT genotype) were recruited. Green tea extract capsules (836 mg green tea catechins) were given in a fasted state, and a high-carbohydrate breakfast was given after 60 min. Blood samples and vascular function measurements were taken at regular intervals. The change in digital volume pulse stiffness index (SI) from baseline was shown to be different between genotype groups at 120 and 240 min, with a lower SI in the GG individuals (P ≤ 0·044). The change in blood pressure from baseline also differed between genotype groups, with a greater increase in systolic (P = 0·023) and diastolic (P = 0·034) blood pressure at 120 min in the GG group. The GG [corrected] group was shown to have a greater increase in insulin concentrations at 120 min (P = 0·019) and 180 min (P = 0·008) compared with baseline, despite similar glucose profiles. No genotypic differences were found in vascular reactivity measured using laser Doppler iontophoresis, total nitrite, lipids, plasma total antioxidant capacity or inflammatory markers after ingestion of the green tea extract. In conclusion, SI and insulin response to the glucose load differed between the COMT genotype groups, and this may be suggestive of a green tea extract and genotype interaction.

The effect of acute fish-oil supplementation on endothelial function and arterial stiffness following a high-fat meal

This study examined whether a commercially available fish-oil supplement offers protection from the acute effects of a high-fat meal (HFM) on endothelial function and arterial stiffness. An HFM causes acute impairments in endothelial function, whereas the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have a variety of cardioprotective effects. However, little is known about the efficacy of moderate fish-oil supplementation on the endothelial dysfunction induced by an HFM. Endothelial function (brachial artery flow-mediated dilation (FMD)), forearm blood flow (FBF), total hyperemia, central and peripheral blood pressure, and central artery stiffness were assessed in 20 healthy men (n = 10) and women (n = 10) at rest and 4 h after an HFM supplemented with either placebo or approximately 1 g EPA and DHA. Brachial artery FMD normalized for shear rate was significantly impaired (p = 0.033) following the HFM with placebo but remained unchanged compared with baseline following the HFM with the fish-oil supplement (p = 0.039; condition x time interaction). Resting FBF (p = 0.020) and total hyperemia (p = 0.014) were elevated following the HFM. All other vascular and hemodynamic measurements were unchanged in both trials. Commercially available fish-oil supplements taken with an HFM appear to preserve endothelial function following an HFM.

Endothelial cells as targets for chylomicron remnants

Endothelial dysfunction is characterised by pro-inflammatory/pro-coagulant changes in the endothelium and supports leukocyte adhesion and transmigration, key steps in early atherogenesis. There is emerging evidence that triacylglycerol-rich lipoproteins (TGRLs) present in the circulation during the postprandial phase influence vascular inflammation but the specific contribution of the remnant lipoprotein component of TGRLs is largely unexplored and the mechanistic basis of their actions poorly defined. This article provides a brief overview of the evidence supporting direct actions of these particles on endothelial cells and highlights the importance of their fatty acid composition and oxidative state as determinants of their cellular actions.

Fatty acid-genotype interactions and cardiovascular risk

Cardiovascular disease (CVD) risk and rate of progression is determined by genetic, environmental and behavioural factors. Majority of genotype-diet-CVD phenotype research till date has focussed on the interactive impact of single nucleotide polymorphisms (SNP) and dietary fat composition, on blood lipids levels, with strong evidence of the existence of hypo- and hyper-responders. However, a recognised concern in the field of nutrigenetics is a lack of consistency between findings of different studies. This apparent lack of consistency is likely to be attributable to the impact of factors such as ethnicity and gender on the 'size' of nutrigenetic interactions, a clear understanding of which needs to be gained. Although not yet ready for widespread use, in the future a greater use of genetic profiling is likely to enhance current strategies of CVD prediction, and improve the design of more personalised approaches to minimise risk in the individual.

Long chain n-3 PUFA-rich meal reduced postprandial measures of arterial stiffness

BACKGROUND & AIMS

The consumption of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) is known to be cardio-protective. Data on the influence of LC n-3 PUFA on arterial stiffness in the postprandial state is limited. The aim of this study was to investigate the acute effects of a LC n-3 PUFA-rich meal on measures of arterial stiffness.

METHODS

Twenty-five healthy subjects (12 men, 13 women) received a control and a LC n-3 PUFA-rich meal on two occasions in a random order. Arterial stiffness was measured at baseline, 30, 60, 90, 120, 180 and 240 min after meal consumption by pulse wave analysis and digital volume pulse to derive an augmentation index and a stiffness index respectively. Blood samples were taken for measurement of lipids, glucose and insulin.

RESULTS

Consumption of the LC n-3 PUFA-rich meal had an attenuating effect on augmentation index (P=0.02) and stiffness index (P=0.03) compared with the control meal. A significant treatment effect (P=0.036) was seen for plasma non-esterified fatty acids concentrations.

CONCLUSIONS

These data indicate that acute LC n-3 PUFA-rich meal consumption can improve postprandial arterial stiffness. This has important implications for the beneficial properties of LC n-3 PUFA and cardiovascular risk reduction.

Moderate Champagne consumption promotes an acute improvement in acute endothelial-independent vascular function in healthy human volunteers

Epidemiological studies have suggested an inverse correlation between red wine consumption and the incidence of CVD. However, Champagne wine has not been fully investigated for its cardioprotective potential. In order to assess whether acute and moderate Champagne wine consumption is capable of modulating vascular function, we performed a randomised, placebo-controlled, cross-over intervention trial. We show that consumption of Champagne wine, but not a control matched for alcohol, carbohydrate and fruit-derived acid content, induced an acute change in endothelium-independent vasodilatation at 4 and 8 h post-consumption. Although both Champagne wine and the control also induced an increase in endothelium-dependent vascular reactivity at 4 h, there was no significant difference between the vascular effects induced by Champagne or the control at any time point. These effects were accompanied by an acute decrease in the concentration of matrix metalloproteinase (MMP-9), a significant decrease in plasma levels of oxidising species and an increase in urinary excretion of a number of phenolic metabolites. In particular, the mean total excretion of hippuric acid, protocatechuic acid and isoferulic acid were all significantly greater following the Champagne wine intervention compared with the control intervention. Our data suggest that a daily moderate consumption of Champagne wine may improve vascular performance via the delivery of phenolic constituents capable of improving NO bioavailability and reducing matrix metalloproteinase activity.

The impact of age on the postprandial vascular response to a fish oil-enriched meal

Although chronic fish oil intervention had been shown to have a positive impact on vascular reactivity, very little is known about their acute effects during the postprandial phase. Our aim was to examine the impact of a fish oil-enriched test meal on postprandial vascular reactivity in healthy younger ( < 50 years) v. older ( > or = 50 years) men. Vascular reactivity was measured at baseline (0 h), 2 and 4 h after the meal by laser Doppler iontophoresis and blood samples taken at 0 and 4 h for the measurement of plasma lipids, total nitrite, glucose and insulin. Acetylcholine- (ACh, endothelial-dependent vasodilator) and sodium nitroprusside (SNP, endothelial-independent vasodilator)-induced reactivities were greater at 4 h than at baseline or 2 h in the younger men (P < 0.04). These changes were not observed in the older men. Comparison of the male groups revealed significantly greater responses to ACh (P = 0.006) and SNP (P = 0.05) at 4 h in the younger compared with the older males. Postprandial NEFA concentrations were also greater at 4 h in the younger compared with the older men (P = 0.005), with no differences observed for any of the other analytes. Multiple regression analysis revealed age to be the most significant predictor of both ACh and SNP induced reactivity 4 h after the meal. In conclusion, the ingestion of a meal enriched in fish oil fatty acids was shown to improve postprandial vascular reactivity at 4 h in our younger men, with little benefit evident in our older men.

Dietary saturated and unsaturated fats as determinants of blood pressure and vascular function

The amount and type of dietary fat have long been associated with the risk of CVD. Arterial stiffness and endothelial dysfunction are important risk factors in the aetiology of CHD. A range of methods exists to assess vascular function that may be used in nutritional science, including clinic and ambulatory blood pressure monitoring, pulse wave analysis, pulse wave velocity, flow-mediated dilatation and venous occlusion plethysmography. The present review focuses on the quantity and type of dietary fat and effects on blood pressure, arterial compliance and endothelial function. Concerning fat quantity, the amount of dietary fat consumed habitually appears to have little influence on vascular function independent of fatty acid composition, although single high-fat meals postprandially impair endothelial function compared with low-fat meals. The mechanism is related to increased circulating lipoproteins and NEFA which may induce pro-inflammatory pathways and increase oxidative stress. Regarding the type of fat, cross-sectional data suggest that saturated fat adversely affects vascular function whereas polyunsaturated fat (mainly linoleic acid (18 : 2n-6) and n-3 PUFA) are beneficial. EPA (20 : 5n-3) and DHA (22 : 6n-3) can reduce blood pressure, improve arterial compliance in type 2 diabetics and dyslipidaemics, and augment endothelium-dependent vasodilation. The mechanisms for this vascular protection, and the nature of the separate physiological effects induced by EPA and DHA, are priorities for future research. Since good-quality observational or interventional data on dietary fatty acid composition and vascular function are scarce, no further recommendations can be suggested in addition to current guidelines at the present time.