Clinical studies suggest that intake of ω-3 polyunsaturated fatty acids (ω-3 PUFA) may lower the incidence of heart failure. Dietary supplementation with ω-3 PUFA exerts metabolic and anti-inflammatory effects that could prevent left ventricle (LV) pathology; however, it is unclear whether these effects occur at clinically relevant doses and whether there are differences between ω-3 PUFA from fish [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] and vegetable sources [α-linolenic acid (ALA)].
Methods and results
We assessed the development of LV remodelling and pathology in rats subjected to aortic banding treated with ω-3 PUFA over a dose range that spanned the intake of humans taking ω-3 PUFA supplements. Rats were fed a standard food or diets supplemented with EPA+DHA or ALA at 0.7, 2.3, or 7% of energy intake. Without supplementation, aortic banding increased LV mass and end-systolic and -diastolic volumes. ALA supplementation had little effect on LV remodelling and dysfunction. In contrast, EPA+DHA dose-dependently increased EPA and DHA, decreased arachidonic acid in cardiac membrane phospholipids, and prevented the increase in LV end-diastolic and -systolic volumes. EPA+DHA resulted in a dose-dependent increase in the anti-inflammatory adipokine adiponectin, and there was a strong correlation between the prevention of LV chamber enlargement and plasma levels of adiponectin (r = −0.78). Supplementation with EPA+DHA had anti-aggregatory and anti-inflammatory effects as evidenced by decreases in urinary thromboxane B2 and serum tumour necrosis factor-α.
Dietary supplementation with ω-3 PUFA derived from fish, but not from vegetable sources, increased plasma adiponectin, suppressed inflammation, and prevented cardiac remodelling and dysfunction under pressure overload conditions.
α-linolenic acid; Diet; Docosahexaenoic acid; Eicosapentaenoic acid; Heart failure
Polyunsaturated fatty acids (PUFAs) form an important constituent of all the cell membranes in the body. PUFAs such as arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) form precursors to both pro-inflammatory and anti-inflammatory compounds. Low-grade systemic inflammation occurs in clinical conditions such as insulin resistance, hypertension, type 2 diabetes mellitus, atherosclerosis, coronary heart disease, lupus, schizophrenia, Alzheimer's disease, and other dementias, cancer and non-alcoholic fatty liver disease (NAFLD) that are also characterized by an alteration in the metabolism of essential fatty acids in the form of excess production of pro-inflammatory eicosanoids and possibly, decreased synthesis and release of anti-inflammatory lipoxins, resolvins, protectins and maresins. We propose that low-grade systemic inflammation observed in these clinical conditions is due to an imbalance in the metabolism of essential fatty acids that is more in favour of pro-inflammatory molecules. In this context, transgenic fat-1 mouse that is designed to convert n-6 to n-3 fatty acids could form an ideal model to study the altered metabolism of essential fatty acids in the above mentioned conditions. It is envisaged that low-grade systemic inflammatory conditions are much less likely in the fat-1 mouse and/or these diseases will run a relatively mild course. Identifying the anti-inflammatory compounds from n-3 fatty acids that suppress low-grade systemic inflammatory conditions and understanding their mechanism(s) of action may lead to newer therapeutic strategies.
Dietary polyunsaturated fatty acids (PUFA), in particular the long chain marine fatty acids docosahexaenoic (DHA) and eicosapentaenoic (EPA), are linked to many health benefits in humans and in animal models. Little is known of the molecular response to DHA and EPA of the small intestine, and the potential contribution of this organ to the beneficial effects of these fatty acids. Here, we assessed gene expression changes induced by DHA and EPA in the wildtype C57BL/6J murine small intestine using whole genome microarrays and functionally characterized the most prominent biological process.
The main biological process affected based on gene expression analysis was lipid metabolism. Fatty acid uptake, peroxisomal and mitochondrial beta-oxidation, and omega-oxidation of fatty acids were all increased. Quantitative real time PCR, and -in a second animal experiment- intestinal fatty acid oxidation measurements confirmed significant gene expression differences and showed in a dose-dependent manner significant changes at biological functional level. Furthermore, no major changes in the expression of lipid metabolism genes were observed in the colon.
We show that marine n-3 fatty acids regulate small intestinal gene expression and increase fatty acid oxidation. Since this organ contributes significantly to whole organism energy use, this effect on the small intestine may well contribute to the beneficial physiological effects of marine PUFAs under conditions that will normally lead to development of obesity, insulin resistance and diabetes.
Treatment with the ω-3 polyunsaturated fatty acids (PUFAs) docosahexanoic acid (DHA) and eicosapentanoic acid (EPA) exerts cardioprotective effects, and suppresses Ca2+-induced opening of the mitochondrial permeability transition pore (MPTP). These effects are associated with increased DHA and EPA, and lower arachidonic acid (ARA) in cardiac phospholipids. While clinical studies suggest the triglyceride lowering effects of DHA and EPA are equivalent, little is known about the independent effects of DHA and EPA on mitochondria function. We compared the effects of dietary supplementation with the ω-3 PUFAs DHA and EPA on cardiac mitochondrial phospholipid fatty acid composition and Ca2+-induced MPTP opening. Rats were fed a standard lab diet with either normal low levels of ω-3 PUFA, or DHA or EPA at 2.5% of energy intake for 8 weeks, and cardiac mitochondria were isolated and analyzed for Ca2+-induced MPTP opening and phospholipid fatty acyl composition. DHA supplementation increased both DHA and EPA and decreased ARA in mitochondrial phospholipid, and significantly delayed MPTP opening as assessed by increased Ca2+ retention capacity and decreased Ca2+-induced mitochondria swelling. EPA supplementation increased EPA in mitochondrial phospholipids, but did not affect DHA, only modestly lowered ARA, and did not affect MPTP opening. In summary, dietary supplementation with DHA but not EPA, profoundly altered mitochondrial phospholipid fatty acid composition and delayed Ca2+-induced MPTP opening.
cardiac; eicosapentaenoic acid; docosahexaenoic acid; fish oil; heart; mitochondrial permeability transition pore
The relationship between omega-3 polyunsaturated fatty acids (n-3 PUFA) from seafood (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) or plant (alpha-linolenic acid, ALA) sources and risk of type 2 diabetes mellitus (DM) remains unclear. We systematically searched multiple literature databases through June 2011 to identify prospective studies examining relations of dietary n-3 PUFA, dietary fish and/or seafood, and circulating n-3 PUFA biomarkers with incidence of DM. Data were independently extracted in duplicate by 2 investigators, including multivariate-adjusted relative risk (RR) estimates and corresponding 95% CIs. Generalized least-squares trend estimation was used to assess dose-response relationships, with pooled summary estimates calculated by both fixed-effect and random-effect models. From 288 identified abstracts, 16 studies met inclusion criteria, including 18 separate cohorts comprising 540,184 individuals and 25,670 cases of incident DM. Consumption of fish and/or seafood was not significantly associated with DM (n=13 studies; RR per 100g/d=1.12, 95% CI=0.94, 1.34); nor were consumption of EPA+DHA (n=16 cohorts; RR per 250mg/d=1.04, 95% CI=0.97, 1.10) or circulating levels of EPA+DHA biomarkers (n=5 cohorts; RR per 3% of total fatty acids=0.94, 95% CI=0.75, 1.17). Both dietary ALA (n=7 studies; RR per 0.5g/d=0.93, 95% CI=0.83, 1.04) and circulating ALA biomarker levels (n=6 studies; RR per 0.1% of total fatty acid=0.90, 95% CI=0.80, 1.00, P=0.06) were associated with non-significant trend towards lower risk of DM. Substantial heterogeneity (I2~80%) was observed among studies of fish/seafood or EPA+DHA and DM; moderate heterogeneity (<55%) was seen for dietary and biomarker ALA and DM. In unadjusted meta-regressions, study location (Asia vs. North America/Europe), mean BMI, and duration of follow-up each modified the association between fish/seafood and EPA+DHA consumption and DM risk (P-Interaction ≤ 0.02 each). We had limited statistical power to determine the independent effect of these sources of heterogeneity due to their high collinearity. The overall pooled findings do not support either major harms or benefits of fish/seafood or EPA+DHA on development of DM, and suggest that ALA may be associated with modestly lower risk. Reasons for potential heterogeneity of effects, which could include true biologic heterogeneity, publication bias, or chance, deserve further investigation.
Polyunsaturated fatty acids (PUFAs) derived from marine sources, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are widely consumed as supplements within the community. However, the use of marine PUFAs in a therapeutic context is also increasing in patients receiving treatment for a range of cancer types. On balance, the literature suggests that marine PUFAs have potential as an effective adjuvant to chemotherapy treatment, may have direct anticancer effects, and may help ameliorate some of the secondary complications associated with cancer. Although a range of doses have been trialled, it would appear that supplementation of fish oil (>3 g per day) or EPA/DHA (>1 g EPA and >0.8 g DHA per day) is associated with positive clinical outcomes. However, further research is still required to determine the mechanisms via which marine PUFAs are mediating their effects. This review summarises our current understanding of marine PUFAs and cancer therapy.
polyunsaturated fatty acids; eicosapentaenoic acid; docosahexaenoic acid; chemotherapy; cachexia
There is increasing evidence that polyunsaturated fatty acids (PUFAs) play a role in cancer risk and progression. The n-3 family of PUFAs includes alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) while the n-6 family includes linolenic acid (LA) and arachidonic acid (AA). EPA and DHA are precursors for anti-inflammatory lipid mediators while AA is a precursor for pro-inflammatory lipid mediators. Collectively, PUFAs play crucial roles in maintaining cellular homeostasis, and perturbations in dietary intake or PUFA metabolism could result in cellular dysfunction and contribute to cancer risk and progression. Epidemiologic studies provide an inconsistent picture of the associations between dietary PUFAs and cancer. This discrepancy may reflect the difficulties in collecting accurate dietary data; however, it also may reflect genetic variation in PUFA metabolism which has been shown to modify physiological levels of PUFAs and cancer risk. Also, host-specific mutations as a result of cellular transformation could modify metabolism of PUFAs in the target-tissue. Clinical trials have shown that supplementation with PUFAs or foods high in PUFAs can affect markers of inflammation, immune function, tumor biology, and prognosis. Pre-clinical investigations have begun to elucidate how PUFAs may mediate cell proliferation, apoptosis and angiogenesis, and the signaling pathways involved in these processes. The purpose of this review is to summarize the current evidence linking PUFAs and their metabolites with cancer and the molecular mechanisms that underlie this association. Identifying the molecular mechanism(s) through which PUFAs affect cancer risk and progression will provide an opportunity to pursue focused dietary interventions that could translate into the development of personalized diets for cancer control.
polyunsaturated fatty acids; cancer; pre-clinical testing; epidemiologic studies; clinical trials as topic; clinical trials; phase II as topic; review of literature
Dietary intake of long-chain n-3 polyunsaturated fatty acids (n-3 PUFA) has been reported to decrease several markers of lymphocyte activation and modulate monocyte susceptibility to apoptosis. However most human studies examined the combined effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) using relatively high daily amounts of n-3 PUFA. The present study investigated the effects of increasing doses of DHA added to the regular diet of human healthy volunteers on lymphocyte response to tetradecanoylphorbol acetate (TPA) plus ionomycin activation, and on monocyte apoptosis induced by oxidized LDL (oxLDL). Eight subjects were supplemented with increasing daily doses of DHA (200, 400, 800 and 1600mg) in a triacylglycerol form containing DHA as the only PUFA, for two weeks each dose. DHA intake dose-dependently increased the proportion of DHA in mononuclear cell phospholipids, the augmentation being significant after 400mg DHA/day. The TPA plus ionomycin-stimulated IL-2 mRNA level started to increase after ingestion of 400mg DHA/day, with a maximum after 800mg intake, and was positively correlated (P<0.003) with DHA enrichment in cell phospholipids. The treatment of monocytes by oxLDL before DHA supplementation drastically reduced mitochondrial membrane potential as compared with native LDL treatment. OxLDL apoptotic effect was significantly attenuated after 400mg DHA/day and the protective effect was maintained throughout the experiment, although to a lesser extent at higher doses. The present results show that supplementation of the human diet with low DHA dosages improves lymphocyte activability. It also increases monocyte resistance to oxLDL-induced apoptosis, which may be beneficial in the prevention of atherosclerosis.
DHA enrichment; interleukin-2; mitochondrial membrane potential; oxidized LDL
The importance of n-3 long chain polyunsaturated fatty acids (LC-PUFAs) for human health has received more focus the last decades, and the global consumption of n-3 LC-PUFA has increased. Seafood, the natural n-3 LC-PUFA source, is harvested beyond a sustainable capacity, and it is therefore imperative to develop alternative n-3 LC-PUFA sources for both eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Genera of algae such as Nannochloropsis, Schizochytrium, Isochrysis and Phaedactylum within the kingdom Chromista have received attention due to their ability to produce n-3 LC-PUFAs. Knowledge of LC-PUFA synthesis and its regulation in algae at the molecular level is fragmentary and represents a bottleneck for attempts to enhance the n-3 LC-PUFA levels for industrial production. In the present review, Phaeodactylum tricornutum has been used to exemplify the synthesis and compartmentalization of n-3 LC-PUFAs. Based on recent transcriptome data a co-expression network of 106 genes involved in lipid metabolism has been created. Together with recent molecular biological and metabolic studies, a model pathway for n-3 LC-PUFA synthesis in P. tricornutum has been proposed, and is compared to industrialized species of Chromista. Limitations of the n-3 LC-PUFA synthesis by enzymes such as thioesterases, elongases, acyl-CoA synthetases and acyltransferases are discussed and metabolic bottlenecks are hypothesized such as the supply of the acetyl-CoA and NADPH. A future industrialization will depend on optimization of chemical compositions and increased biomass production, which can be achieved by exploitation of the physiological potential, by selective breeding and by genetic engineering.
Phaeodactylum tricornutum; long chain polyunsaturated fatty acid synthesis; metabolic engineering; elongases; desaturases; acyl-CoA synthetases; acyltransferases
Long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) are recommended for management of patients with wide-ranging chronic diseases, including coronary heart disease, rheumatoid arthritis, dementia, and depression. Increased consumption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is recommended by many health authorities to prevent (up to 0.5 g/day) or treat chronic disease (1.0 g/day for coronary heart disease; 1.2–4 g/day for elevated triglyceride levels). Recommendations for dietary intake of LC n-3 PUFAs are often provided for α-linolenic acid, and for the combination of EPA and DHA. However, many studies have also reported differential effects of EPA, DHA and their metabolites in the clinic and at the laboratory bench. The aim of this article is to review studies that have identified divergent responses to EPA and DHA, and to explore reasons for these differences. In particular, we review potential contributing factors such as differential membrane incorporation, modulation of gene expression, activation of signaling pathways and metabolite formation. We suggest that there may be future opportunity to refine recommendations for intake of individual LC n-3 PUFAs.
LC n-3 PUFAs; omega-3 fatty acids; eicosapentaenoic acid; docosahexaenoic acid; resolvin D1; differential response; omega-3 fatty acid metabolites
High consumption of fish carries a lower risk of cardiovascular disease as a consequence of dietary omega-3 long chain polyunsaturated fatty acid (n-3 PUFA; especially EPA and DHA) content. A controversy exists about the component/s responsible of these beneficial effects and, in consequence, which is the best proportion between both fatty acids. We sought to determine, in healthy Wistar rats, the proportions of EPA and DHA that would induce beneficial effects on biomarkers of oxidative stress, and cardiovascular disease risk.
Female Wistar rats were fed for 13 weeks with 5 different dietary supplements of oils; 3 derived from fish (EPA/DHA ratios of 1:1, 2:1, 1:2) plus soybean and linseed as controls. The activities of major antioxidant enzymes (SOD, CAT, GPX, and GR) were determined in erythrocytes and liver, and the ORAC test was used to determine the antioxidant capacity in plasma. Also measured were: C reactive protein (CRP), endothelial dysfunction (sVCAM and sICAM), prothrombotic activity (PAI-1), lipid profile (triglycerides, cholesterol, HDLc, LDLc, Apo-A1, and Apo-B100), glycated haemoglobin and lipid peroxidation (LDL-ox and MDA values).
After three months of nutritional intervention, we observed statistically significant differences in the ApoB100/ApoA1 ratio, glycated haemoglobin, VCAM-1, SOD and GPx in erythrocytes, ORAC values and LDL-ox. Supplementation with fish oil derived omega-3 PUFA increased VCAM-1, LDL-ox and plasma antioxidant capacity (ORAC). Conversely, the ApoB100/ApoA1 ratio and percentage glycated haemoglobin decreased.
Our results showed that a diet of a 1:1 ratio of EPA/DHA improved many of the oxidative stress parameters (SOD and GPx in erythrocytes), plasma antioxidant capacity (ORAC) and cardiovascular risk factors (glycated haemoglobin) relative to the other diets.
Omega-3 polyunsaturated fatty acids (PUFA); Eicosapentaenoic acid (EPA); Docosahexaenoic acid (DHA); Fish oils; Oxidative stress; Antioxidant status; Cardiovascular disease risk; Insulin resistance
Pathological left ventricular (LV) hypertrophy frequently progresses to dilated heart failure with suppressed mitochondrial oxidative capacity. Dietary marine ω-3 polyunsaturated fatty acids (ω-3 PUFA) up-regulate adiponectin and prevent LV dilation in rats subjected to pressure overload. This study 1) assessed the effects of ω-3 PUFA on LV dilation and down-regulation of mitochondrial enzymes in response to pressure overload; and 2) evaluated the role of adiponectin in mediating the effects of ω-3 PUFA in heart.
Wild type (WT) and adiponectin-/- mice underwent transverse aortic constriction (TAC) and were fed standard chow ± ω-3 PUFA for 6 weeks. At 6 weeks, echocardiography was performed to assess LV function, mice were terminated, and mitochondrial enzyme activities were evaluated.
TAC induced similar pathological LV hypertrophy compared to sham mice in both strains on both diets. In WT mice TAC increased LV systolic and diastolic volumes and reduced mitochondrial enzyme activities, which were attenuated by ω-3 PUFA without increasing adiponectin. In contrast, adiponectin-/- mice displayed no increase in LV end diastolic and systolic volumes or decrease in mitochondrial enzymes with TAC, and did not respond to ω-3 PUFA.
These findings suggest ω-3 PUFA attenuates cardiac pathology in response to pressure overload independent of an elevation in adiponectin.
The type and quantity of dietary fat ingested contributes to the onset and progression of chronic diseases, like diabetes and atherosclerosis. The liver plays a central role in whole body lipid metabolism and responds rapidly to changes in dietary fat composition. Polyunsaturated fatty acids (PUFA) play a key role in membrane composition and function, metabolism and the control of gene expression. Certain PUFA, like the n-3 PUFA, enhance hepatic fatty acid oxidation and inhibit fatty acid synthesis and VLDL secretion, in part, by regulating gene expression. Our studies have established that key transcription factors, like PPARα, SREBP-1, ChREBP and MLX, are regulated by n-3 PUFA, which in turn control levels of proteins involved in lipid and carbohydrate metabolism. Of the n-3 PUFA, 22:6,n-3 has recently been established as a key controller of hepatic lipid synthesis. 22:6,n-3 controls the 26S proteasomal degradation of the nuclear form of SREBP-1. SREBP-1 is a major transcription factor that controls the expression of multiple genes involved fatty acid synthesis and desaturation. 22:6,n-3 suppresses nuclear SREBP-1 which, in turn suppresses lipogenesis. This mechanism is achieved, in part, through control of the phosphorylation status of protein kinases. This review will examine both the general features of PUFA-regulated hepatic gene transcription and highlight the unique mechanisms by which 22:6,n-3 impacts gene expression. The outcome of this analysis will reveal that changes in hepatic 22:6,n-3 content has a major impact on hepatic lipid and carbohydrate metabolism. Moreover, the mechanisms involve 22:6,n-3 control of several well-known signaling pathways, such as Akt, Erk1/2, Gsk3β and PKC (novel or atypical). 22:6,n-3 control of these same signaling pathways in non-hepatic tissues may help explain the diverse actions of n-3 PUFA on such complex physiological processes as visual acuity and learning.
docosahexaenoic acid (22:6,n-3); PPARα; SREBP-1; ChREBP; MLX; gene transcription; hepatic fatty acid metabolism
Omega-3 polyunsaturated fatty acids [ω-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] from fish oil ameliorate cardiovascular diseases. However, little is known about the effects of ω-3 PUFAs on cardiac fibrosis, a major cause of diastolic dysfunction and heart failure. The current study assessed the effects of ω-3 PUFAs on cardiac fibrosis.
Methods and Results
We assessed left ventricular (LV) fibrosis and pathology in mice subjected to transverse aortic constriction (TAC) subsequent to the consumption of a fish oil or a control diet. In control mice, four weeks of TAC induced significant cardiac dysfunction, cardiac fibrosis and cardiac fibroblast activation (proliferation and transformation into myofibroblasts). Dietary supplementation with fish oil prevented TAC-induced cardiac dysfunction and cardiac fibrosis, and blocked cardiac fibroblast activation. In heart tissue, TAC increased active TGF-β1 levels and phosphorylation of Smad2. In isolated adult mouse cardiac fibroblasts, TGF-β1 induced cardiac fibroblast transformation, proliferation, and collagen synthesis. EPA and DHA increased cGMP levels and blocked cardiac fibroblast transformation, proliferation, and collagen synthesis. EPA and DHA blocked phospho-Smad2/3 nuclear translocation. DT3, a PKG inhibitor, blocked the anti-fibrotic effects of EPA and DHA. EPA and DHA increased phospho-eNOS and eNOS protein levels and nitric oxide production.
ω-3 fatty acids prevent cardiac fibrosis and cardiac dysfunction by blocking TGF-β1-induced phospho-Smad2/3 nuclear translocation through activation of the cGMP/PKG pathway in cardiac fibroblasts.
transverse aortic constriction; ω-3 fatty acids; cardiac fibrosis; cGMP/PKG
The impact of polyunsaturated fatty acid (PUFA) supplementation on phospholipase D (PLD) trafficking and activity in mast cells was investigated. The enrichment of mast cells with different PUFA including α-linolenic acid (LNA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid (LA) or arachidonic acid (AA) revealed a PUFA-mediated modulation of the mastoparan-stimulated PLD trafficking and activity. All PUFA examined, except AA, prevented the migration of the PLD1 to the plasma membrane. For PLD2 no PUFA effects on trafficking could be observed. Moreover, PUFA supplementation resulted in an increase of mastoparan-stimulated total PLD activity, which correlated with the number of double bonds of the supplemented fatty acids. To investigate, which PLD isoform was affected by PUFA, stimulated mast cells were supplemented with DHA or AA in the presence of specific PLD-isoform inhibitors. It was found that both DHA and AA diminished the inhibition of PLD activity in the presence of a PLD1 inhibitor. By contrast, only AA diminished the inhibition of PLD activity in the presence of a PLD2 inhibitor. Thus, PUFA modulate the trafficking and activity of PLD isoforms in mast cells differently. This may, in part, account for the immunomodulatory effect of unsaturated fatty acids and contributes to our understanding of the modulation of mast cell activity by PUFA.
phospholipase D; polyunsaturated fatty acids; mast cells; exocytosis
Experimental studies suggest long-chain n-3 polyunsaturated fatty acids (n-3 PUFA) may reduce risk of atrial fibrillation (AF). Prior studies evaluating fish or n-3 PUFA consumption from dietary questionnaires and incident AF have been conflicting. Circulating levels of n-3 PUFA provide an objective measurement of exposure.
Methods and Results
Among 3,326 US men and women age≥65y and free of AF or heart failure at baseline, plasma phospholipid levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) were measured at baseline using standardized methods. Incident AF (789 cases) was prospectively identified from hospital discharge records and study visit electrocardiograms during 31,169 person-years of follow-up (1992-2006). In multivariable Cox models adjusted for other risk factors, the RR in the top versus lowest quartile of total n-3 PUFA (EPA+DPA+DHA) levels was 0.71 (95%CI=0.57-0.89, P-trend=0.004); and of DHA levels, 0.77 (95%CI=0.62-0.96, P-trend=0.01). EPA and DPA levels were not significantly associated with incident AF. Evaluated non-parametrically, both total n-3 PUFA and DHA showed graded and linear inverse associations with incidence of AF. Adjustment for intervening events such as heart failure or myocardial infarction during follow-up did not appreciably alter results.
In older adults, higher circulating total long-chain n-3 PUFA and DHA levels were associated with lower risk of incident AF. These results highlight the need to evaluate whether increased dietary intake of these fatty acids could be effective for primary prevention of AF.
atrial fibrillation; biomarkers; epidemiology; fatty acids
Dietary n−3 polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, and these effects have been attributed to their capability to modulate ion channels. In the present review, we will focus on the effects of PUFAs on a cardiac sodium channel (Nav1.5) and two potassium channels involved in cardiac atrial and ventricular repolarization (Kv) (Kv1.5 and Kv11.1). n−3 PUFAs of marine (docosahexaenoic, DHA and eicosapentaenoic acid, EPA) and plant origin (alpha-linolenic acid, ALA) block Kv1.5 and Kv11.1 channels at physiological concentrations. Moreover, DHA and EPA decrease the expression levels of Kv1.5, whereas ALA does not. DHA and EPA also decrease the magnitude of the currents elicited by the activation of Nav1.5 and calcium channels. These effects on sodium and calcium channels should theoretically shorten the cardiac action potential duration (APD), whereas the blocking actions of n−3 PUFAs on Kv channels would be expected to produce a lengthening of cardiac action potential. Indeed, the effects of n−3 PUFAs on the cardiac APD and, therefore, on cardiac arrhythmias vary depending on the method of application, the animal model, and the underlying cardiac pathology.
n−3 PUFAs; atrial fibrillation; arrhythmias; heart failure
The extent to which long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) from fish oil such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exert their anti-inflammatory effects by down-regulating intestinal inflammation in humans is unknown. We investigated the impact of LCn-3PUFA supplementation on inflammatory gene expression in the duodenum of obese patients with type 2 diabetes.
This placebo-controlled randomized crossover study included 12 men with type 2 diabetes. After a 4-week run-in period, patients received in a random sequence 5 g/d of fish oil (providing 3 g of EPA + DHA) and a placebo (corn and soybean oil) for 8 weeks each. The two treatment phases were separated by a 12-week washout period. Gene expression was assessed by real-time polymerase chain reaction in duodenal biopsy samples obtained in the fasted state at the end of each treatment phase. Intestinal mRNA expression levels of interleukin (IL)-6 and tumor-necrosis factor (TNF)-α were hardly detectable after either treatment (<100 copies/105 copies of the reference gene ATP5o). Intestinal mRNA expression of IL-18 and of the transcription factor signal transducer and activator of transcription 3 (STAT3) was higher (>5000 copies/105 copies ATP5o) but still relatively low. EPA + DHA supplementation had no impact on any of these levels (all P ≥ 0.73).
These data suggest that duodenal cells gene expression of pro-inflammatory cytokines is low in patients with type 2 diabetes and not affected by EPA + DHA supplementation. Further studies are warranted to determine if inflammatory gene expression in other tissues surrounding the intestine is modulated by EPA + DHA supplementation.
ClinicalTrials.gov ID: NCT01449773
Eicosapentaenoic acid (EPA); Docosahexaenoic acid (DHA); Signal transducer and activator of transcription 3 (STAT3); Inflammatory gene expression; n-3 supplementation; Placebo-controlled; Duodenum; Type 2 diabetes
Two families of polyunsaturated fatty acid (PUFA), omega-3 (ω-3) and omega-6 (ω-6), are required for physiological functions. The long chain ω-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have significant biological effects. In particular, DHA is a major component of cell membranes in the brain. It is also involved in neurotransmission. Spinal cord injury (SCI) is a highly devastating pathology that can lead to catastrophic dysfunction, with a significant reduction in the quality of life. Previous studies have shown that EPA and DHA can exert neuroprotective effects in SCI in mice and rats. The aim of this study was to analyze the mechanism of action of ω-3 PUFAs, such as DHA, in a mouse model of SCI, with a focus on the early pathophysiological processes.
In this study, SCI was induced in mice by the application of an aneurysm clip onto the dura mater via a four-level T5 to T8 laminectomy. Thirty minutes after compression, animals received a tail vein injection of DHA at a dose of 250 nmol/kg. All animals were killed at 24 h after SCI, to evaluate various parameters implicated in the spread of the injury.
Our results in this in-vivo study clearly demonstrate that DHA treatment reduces key factors associated with spinal cord trauma. Treatment with DHA significantly reduced: (1) the degree of spinal cord inflammation and tissue injury, (2) pro-inflammatory cytokine expression (TNF-α), (3) nitrotyrosine formation, (4) glial fibrillary acidic protein (GFAP) expression, and (5) apoptosis (Fas-L, Bax, and Bcl-2 expression). Moreover, DHA significantly improved the recovery of limb function.
Furthermore, in this study we evaluated the effect of oxidative stress on dorsal root ganglion (DRG) cells using a well-characterized in-vitro model. Treatment with DHA ameliorated the effects of oxidative stress on neurite length and branching.
Our results, in vivo and in vitro, clearly demonstrate that DHA treatment reduces the development of inflammation and tissue injury associated with spinal cord trauma.
DHA; Inflammation; Omega-3; Oxidative stress; Spinal cord injury
Polyisoprenylation is a set of secondary modifications involving proteins whose aberrant activities are implicated in cancers and degenerative disorders. The last step of the pathway involves an ester-forming polyisoprenylated protein methyl transferase- and hydrolytic polyisoprenylated methylated protein methyl esterase (PMPMEase)-catalyzed reactions. Omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) have been linked with antitumorigeneis and tumorigenesis, respectively. PUFAs are structurally similar to the polyisoprenyl groups and may interfere with polyisoprenylated protein metabolism. It was hypothesized that PUFAs may be more potent inhibitors of PMPMEase than their more polar oxidative metabolites, the prostaglandins. As such, the relative effects of PUFAs and prostaglandins on PMPMEase could explain the association between cyclooxygenase-2 (COX-2) expression in tumors, the chemopreventive effects of the non-steroidal anti-inflammatory (NSAIDs) COX-2 inhibitors and PUFAs. PUFAs such as arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids inhibited PMPMEase activity with Ki values of 0.12 to 3.7 μM. The most potent prostaglandin was 63-fold less potent than AA. The PUFAs were also more effective at inducing neuroblastoma cell death at physiologically equivalent concentrations. The lost PMPMEase activity in AA-treated degenerating cells was restored by incubating the lysates with COX-1 or COX-2. PUFAs may thus be physiological regulators of cell growth and could owe these effects to PMPMEase inhibition.
isoprenylation; polyunsaturated fatty acids; prostaglandins; arachidonic acid; COX-2
Randomized trials of omega-3 polyunsaturated fatty acid (PUFA) treatment for depression have differed in outcome. Recent meta-analyses ascribe discrepancies to differential effects of eicosapentaenoic acid (EPA) vs. docosahexaenoic acid (DHA) and to diagnostic heterogeneity. This meta-analysis tests the hypothesis that EPA is the effective component in PUFA treatment of major depressive episodes.
PubMed was searched (1960 through June 2010) using terms “Fish Oils”[Mesh] AND (“Depressive Disorder”[Mesh] OR “Bipolar Depression”) AND “Randomized Controlled Trial”[Publication Type], for placebo-controlled trials of PUFA supplementation, a depressive episode as primary disorder, published in English, supplemented by manual bibliography review.
The search yielded 15 trials involving 916 participants.
Sample sizes; PUFA doses; mean ages, baseline and endpoint depression ratings and standard deviations; and p values were extracted.
In a mixed-effect model, percentage of EPA in the supplements was the fixed-effect predictor, dichotomized into two groups: EPA < 60% or EPA ≥ 60% of EPA + DHA. Secondary analyses explored relevance of treatment duration, age, and EPA dose.
Supplements with EPA ≥ 60% showed benefit on standardized mean depression scores (SMD, for EPA ≥ 60% = 0.558, 95% CI = (0.277, 0.838), z = 4.195, p = 0.001; for EPA < 60% = −0.026, 95% CI = (0.200, 0.148), z = −0.316, p =0.756), with negligible contribution of random effects or heteroscedasticity, and no effects of treatment duration or age. Supplements with EPA < 60% were ineffective. Exploratory analyses supported a non-linear model, with improvement determined by the dose of EPA in excess of DHA, within the range 200 to 2200 mg EPA.
Supplements containing EPA ≥ 60%, in dose range 200 to 2200 mg EPA in excess of DHA, were effective against primary depression. Translational studies are needed to determine mechanisms of EPA’s therapeutic benefit.
n-3 PUFA; docosahexaenoic acid; eicosapentaenoic acid; clinical trials; depression; meta-analysis
Dietary very long chain omega (ω)-3 polyunsaturated fatty acids (PUFA) have been associated with reduced CVD risk, the mechanisms of which have yet to be fully elucidated. LDL receptor null mice (LDLr-/-) were used to assess the effect of different ratios of dietary ω-6 PUFA to eicosapentaenoic acid plus docosahexaenoic acid (ω-6:EPA+DHA) on atherogenesis and inflammatory response. Mice were fed high saturated fat diets without EPA and DHA (HSF ω-6), or with ω-6:EPA+DHA at ratios of 20:1 (HSF R=20:1), 4:1 (HSF R=4:1), and 1:1 (HSF R=1:1) for 32 weeks. Mice fed the lowest ω-6:EPA+DHA ratio diet had lower circulating concentrations of non-HDL cholesterol (25%, P<0.05) and interleukin-6 (IL-6) (44%, P<0.05) compared to mice fed the HSF ω-6 diet. Aortic and elicited peritoneal macrophage (Mϕ) total cholesterol were 24% (P=0.07) and 25% (P<0.05) lower, respectively, in HSF R=1:1 compared to HSF ω-6 fed mice. MCP-1 mRNA levels and secretion were 37% (P<0.05) and 38% (P<0.05) lower, respectively, in elicited peritoneal Mϕ isolated from HSF R=1:1 compared to HSF ω-6 fed mice. mRNA and protein levels of ATP-binding cassette A1, and mRNA levels of TNFα were significantly lower in elicited peritoneal Mϕ isolated from HSF R=1:1 fed mice, whereas there was no significant effect of diets with different ω-6:EPA+DHA ratios on CD36, Mϕ scavenger receptor 1, scavenger receptor B1 and IL-6 mRNA or protein levels. These data suggest that lower ω-6:EPA+DHA ratio diets lowered some measures of inflammation and Mϕ cholesterol accumulation, which was associated with less aortic lesion formation in LDLr-/- mice.
ω-6:EPA+DHA ratio; ω-3 fatty acids; atherosclerosis; inflammation; macrophage cholesterol accumulation; LDLr-/- mouse; diet; elicited peritoneal Mϕ
Peroxisome proliferator-activated receptor gamma (PPAR γ) is a transcription factor, which is abundantly expressed in adipose tissue and has a direct link to adiposity. It seems that long-chain polyunsaturated fatty acids (LC-PUFAs) can regulate PPAR γ expression. The purpose of this study was to investigate the effects of n-3LC PUFA supplementation on plasma levels of PPAR γ and thyroid hormones in obesity.
Materials and Methods:
In a randomized double-blind controlled trial, 66 subjects with obesity were assigned to 2 groups. Participants in intervention group consumed omega3 capsules contained 1000 mg n-3 fatty acids (180 mg of eicosapentaenoic acid [EPA] and 120 mg of docosahexaenoic acid [DHA]) and placebo group consumed placebo capsules contained paraffin twice a day for 4 wk. Fasting blood samples and weight measurements were collected at the baseline and at the end of the trial. Plasma PPAR γ and thyroid hormones were measured by ELISA. Data were analyzed using a repeated measure model-two factor for comparing two groups in two times.
No significant changes were observed in PPAR γ levels between and within the groups after supplementation (P>0.05). N-3LC PUFA supplementation significantly increased T4 levels after 4 wk (P<0.05) but T3 and TSH did not change significantly.
Our study showed that n-3LC PUFAs supplementation increased T4 levels. However, no significant changes in T3, TSH and PPAR γ plasma levels were observed in obese adults.
Docosahexaenoic acid; eicosapentaenoic acid; N-3 LC PUFAs supplementation; obesity; peroxisome proliferator activated receptor gamma; thyrotropin; thyroxin; triiodothyronine
Docosahexaenoic acid (DHA) is required for normal brain function. The concentration of DHA in the brain depends on both diet and liver metabolism.
To determine rat brain DHA concentration and consumption in relation to dietary n-3 (omega-3) polyunsaturated fatty acid (PUFA) content and liver secretion of DHA derived from circulating α-linolenic acid (α-LNA).
Following weaning, male rats were fed for 15 weeks either: (1) a diet with a high DHA and α-LNA content, (2) an n-3 PUFA “adequate” diet containing 4.6% α-LNA but no DHA, or (3) an n-3 PUFA “deficient” diet containing 0.2% α-LNA and no DHA. Brain DHA consumption rates were measured following intravenous infusion in unanesthetized rats of [1-14C]DHA, whereas liver and brain DHA synthesis rates were measured by infusing [1-14C]α-LNA.
Brain DHA concentrations equaled 17.6 μm/g, 11.4 μm/g and 7.14 μm/g in rats on diets 1, 2 and 3, respectively. With each diet, the rate of brain DHA synthesis from α-LNA was much less than the brain DHA consumption rate, whereas the liver synthesis-secretion rate was 5-10 fold higher. Higher elongase 2 and 5 and desaturase Δ5 and Δ6 activities in liver than in brain accounted for the higher liver DHA synthesis rates; these enzymes were transcriptionally upregulated in liver but not in brain of rats fed the deficient diet.
While DHA is essential to normal brain function, this need might be covered by dietary α-LNA when liver metabolic conversion machinery is intact and the diet has a high α-LNA content.
docosahexaenoic acid; liver; brain; rat; n-3; omega-3; PUFA; imaging; metabolism; diet; synthesis; α-linolenic acid
Long-chain n-3 polyunsaturated fatty acids (n3-PUFA), including eicosapentaenoic acid (EPA/20:5n-3), docosapentaenoic acid (DPA/22:5n-3), and docosahexaenoic acid (DHA/22:6n-3), experimentally reduce cardiovascular risk. Yet, effects on cause-specific and total mortality and potential dose-responses remain controversial. Most observational studies have assessed self-reported dietary intakes, rather than objective biomarkers; while most randomized trials have tested effects of adding supplements to background dietary intake and evaluated secondary prevention, limiting inference for dietary n3-PUFA or primary prevention.
We investigated associations of plasma phospholipid EPA, DPA, DHA, and total n-3 PUFA with total and cause-specific mortality among generally healthy older adults not taking fish oil supplements.
Prospective cohort, 1992–2008.
Four U.S. communities.
2,692 U.S. adults age 75±5 years, free of prevalent coronary heart disease (CHD), stroke, or heart failure.
Phospholipid fatty acids and cardiovascular risk factors were measured in 1992 using standardized methods. Relationships with total and cause-specific mortality through 2008, and incident total (fatal+nonfatal) CHD and stroke, were assessed using Cox proportional-hazards.
During 30,829 person-years, 1,625 deaths (including 570 cardiovascular deaths), 359 fatal and 371 nonfatal CHD events, and 130 fatal and 276 nonfatal strokes occurred. After multivariable-adjustment, n3-PUFA biomarkers associated with lower total mortality, with extreme-quintile hazard ratios (95% CI) of 0.83 for EPA (0.71–0.98), 0.77 for DPA (0.66–0.90), 0.80 for DHA (0.67–0.94), and 0.73 for total n3-PUFA (0.61–0.86) (P-trend≤0.008 each). Lower risk was largely attributable to fewer cardiovascular, rather than noncardiovascular, deaths, in particular fewer arrhythmic cardiac deaths (total n3-PUFA: hazard ratio=0.52, 95%CI=0.31–0.86; P-trend=0.008). Based on relations with total mortality, individuals in the highest quintile of phospholipid n3-PUFA, versus the lowest, experienced 2.22 greater years of life (95%CI=0.75–3.13) after age 65.
Temporal changes in fatty acid levels and misclassification of death causes may cause underestimated associations; and unmeasured/imperfectly measured covariates, residual confounding.
Circulating individual and total n3-PUFA are associated with lower total mortality, especially CHD death, in older adults.
Primary Funding Source
National Institutes of Health.