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.
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
Purpose of review
To report recent data on the potential role of omega-3 fatty acids, in particular docosahexaenoic acid (DHA) and its derivatives, in the treatment of dry eye syndrome.
Dietary supplementation with polyunsaturated fatty acids (PUFAs) yields positive results in the improvement of dry eye signs and symptoms. Although several studies have shown this, evidence is still lacking as to which fatty acid or what combination constitutes the most effective treatment. Studies show that treatment with alpha-linoleic acid reduces dry eyeinduced inflammation. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derivatives, particularly resolvin E1 (RvE1) and neuroprotectin D1 (NPD1), appear to be responsible for DHA’s anti-inflammatory effect. This is supported in a study where topical RvE1 resulted in decreased inflammation in a mouse dry eye model. Topical administration of pigment epithelium derived factor (PEDF) in combination with DHA accelerates the regeneration of corneal nerves after their damage during corneal surgery, promoting the return of sensitivity and reducing the signs of dry eye. This combined treatment also reduces objective signs of dry eye, such as rose bengal staining.
No firm recommendations can be made regarding optimal dietary supplementation of essential fatty acids that benefit dry eye patients. Based on animal data and preliminary human studies, DHA and its derivatives appear to be a safe, effective topical treatment for dry eye patients. This may result from their role in the resolution of inflammation and the regeneration of damaged corneal nerves.
Dry eye; docosahexaenoic acid; omega-3 fatty acids; omega-6 fatty acids; corneal nerves; neuroprotectin D1
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
A growing body of clinical and epidemiological evidence suggests that low dietary intake and/or tissue levels of n-3 (omega-3) polyunsaturated fatty acids (PUFAs) are associated with postpartum depression. Low tissue levels of n-3 PUFAs, particularly docosahexaenoic acid (DHA), are reported in patients with either postpartum or nonpuerperal depression. Moreover, the physiological demands of pregnancy and lactation put childbearing women at particular risk of experiencing a loss of DHA from tissues including the brain, especially in individuals with inadequate dietary n-3 PUFA intake or suboptimal metabolic capabilities. Animal studies indicate that decreased brain DHA in postpartum females leads to several depression-associated neurobiological changes including decreased hippocampal brain-derived neurotrophic factor and augmented hypothalamic-pituitary-adrenal responses to stress. Taken together, these findings support a role for decreased brain n-3 PUFAs in the multifactorial etiology of depression, particularly postpartum depression. These findings, and their implications for research and clinical practice, are discussed.
Docosahexaenoic acid (DHA) is the major polyunsaturated fatty acid (PUFA) in the brain and a structural component of neuronal membranes. Changes in DHA content of neuronal membranes lead to functional changes in the activity of receptors and other proteins which might be associated with synaptic function. Accumulating evidence suggests the beneficial effects of dietary DHA supplementation on neurotransmission. This article reviews the beneficial effects of DHA on the brain; uptake, incorporation and release of DHA at synapses, effects of DHA on synapses, effects of DHA on neurotransmitters, DHA metabolites, and changes in DHA with age. Further studies to better understand the metabolome of DHA could result in more effective use of this molecule for treatment of neurodegenerative or neuropsychiatric diseases.
Docosahexaenoic acid (DHA); Polyunsaturated fatty acid (PUFA); Neurodegeneration; Depression; Anti-nociception
We reported that reduced dietary intake of polyunsaturated fatty acids (PUFA) such as arachidonic (AA,20:4n6, omega-6) and docosahexaenoic (DHA,22:6n3, omega-3) acids led to alcohol-induced fatty liver and fibrosis. This study was aimed at studying the mechanisms by which a DHA/AA-supplemented diet prevents alcohol-induced fatty liver.
Male Long-Evans rats were fed an ethanol or control liquid-diet with or without DHA/AA for 9 weeks. Plasma transaminase levels, liver histology, oxidative/nitrosative stress markers, and activities of oxidatively-modified mitochondrial proteins were evaluated.
Chronic alcohol administration increased the degree of fatty liver but fatty liver decreased significantly in rats fed the alcohol-DHA/AA-supplemented diet. Alcohol exposure increased oxidative/nitrosative stress with elevated levels of ethanol-inducible CYP2E1, nitric oxide synthase, nitrite and mitochondrial hydrogen peroxide. However, these increments were normalized in rats fed the alcohol-DHA/AA-supplemented diet. The number of oxidatively-modified mitochondrial proteins was markedly increased following alcohol exposure but significantly reduced in rats fed the alcohol-DHA/AA-supplemented diet. The suppressed activities of mitochondrial aldehyde dehydrogenase, ATP synthase, and 3-ketoacyl-CoA thiolase in ethanol-exposed rats were also recovered in animals fed the ethanol-DHA/AA-supplemented diet.
Addition of DHA/AA prevents alcohol-induced fatty liver and mitochondrial dysfunction in an animal model by protecting various mitochondrial enzymes most likely through reducing oxidative/nitrosative stress.
Alcoholic fatty liver; polyunsaturated fatty acids; Long-Evans rat; Oxidative/nitrosative stress; Protein oxidation; β-oxidation of fatty acids; Mitochondrial dysfunction
The anti-atherogenic effects of omega 3 fatty acids, namely eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) are well recognized but the impact of dietary intake on bioactive lipid mediator profiles remains unclear. Such a profiling effort may offer novel targets for future studies into the mechanism of action of omega 3 fatty acids. The present study aimed to determine the impact of DHA supplementation on the profiles of polyunsaturated fatty acids (PUFA) oxygenated metabolites and to investigate their contribution to atherosclerosis prevention. A special emphasis was given to the non-enzymatic metabolites knowing the high susceptibility of DHA to free radical-mediated peroxidation and the increased oxidative stress associated with plaque formation. Atherosclerosis prone mice (LDLR−/−) received increasing doses of DHA (0, 0.1, 1 or 2% of energy) during 20 weeks leading to a dose-dependent reduction of atherosclerosis (R2 = 0.97, p = 0.02), triglyceridemia (R2 = 0.97, p = 0.01) and cholesterolemia (R2 = 0.96, p<0.01). Targeted lipidomic analyses revealed that both the profiles of EPA and DHA and their corresponding oxygenated metabolites were substantially modulated in plasma and liver. Notably, the hepatic level of F4-neuroprostanes, a specific class of DHA peroxidized metabolites, was strongly correlated with the hepatic DHA level. Moreover, unbiased statistical analysis including correlation analyses, hierarchical cluster and projection to latent structure discriminate analysis revealed that the hepatic level of F4-neuroprostanes was the variable most negatively correlated with the plaque extent (p<0.001) and along with plasma EPA-derived diols was an important mathematical positive predictor of atherosclerosis prevention. Thus, oxygenated n-3 PUFAs, and F4-neuroprostanes in particular, are potential biomarkers of DHA-associated atherosclerosis prevention. While these may contribute to the anti-atherogenic effects of DHA, further in vitro investigations are needed to confirm such a contention and to decipher the molecular mechanisms of action.
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are functionally the most important omega-3 polyunsaturated fatty acids (PUFAs). Oral supply of these fatty acids increases their levels in plasma and cell membranes, often at the expense of the omega-6 PUFAs arachidonic acid (ARA) and linoleic acid. This results in an altered pattern of lipid mediator production to one which is less pro-inflammatory. We investigated whether short term intravenous supply of omega-3 PUFAs could change the levels of EPA, DHA, ARA and linoleic acid in plasma and erythrocytes in patients with hepatic colorectal metastases.
Twenty patients were randomised to receive a 72 hour infusion of total parenteral nutrition with (treatment group) or without (control group) omega-3 PUFAs. EPA, DHA, ARA and linoleic acid were measured in plasma phosphatidylcholine (PC) and erythrocytes at several times points up to the end of infusion and 5 to 12 days (mean 9 days) after stopping the infusion.
The treatment group showed increases in plasma PC EPA and DHA and erythrocyte EPA and decreases in plasma PC and erythrocyte linoleic acid, with effects most evident late in the infusion period. Plasma PC and erythrocyte EPA and linoleic acid all returned to baseline levels after the 5–12 day washout. Plasma PC DHA remained elevated above baseline after washout.
Intravenous supply of omega-3 PUFAs results in a rapid increase of EPA and DHA in plasma PC and of EPA in erythrocytes. These findings suggest that infusion of omega-3 PUFAs could be used to induce a rapid effect especially in targeting inflammation.
http://www.clinicaltrials.gov identifier NCT00942292
Parenteral nutrition; Fish oil; Omega-3 fatty acids; Eicosapentaenoic acid; Docosahexaenoic acid; Arachidonic acid; Liver metastases
Macrophages play a key role in obesity-induced inflammation. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exert anti-inflammatory functions in both humans and animal models, but the exact cellular signals mediating the beneficial effects are not completely understood. We previously found that two nutrient sensors AMP-activated protein kinase (AMPK) and SIRT1 interact to regulate macrophage inflammation. Here we aim to determine whether ω-3 PUFAs antagonize macrophage inflammation via activation of AMPK/SIRT1 pathway. Treatment of ω-3 PUFAs suppresses lipopolysaccharide (LPS)-induced cytokine expression in macrophages. Luciferase reporter assays, electrophoretic mobility shift assays (EMSA) and Chromatin immunoprecipitation (ChIP) assays show that treatment of macrophages with ω-3 PUFAs significantly inhibits LPS-induced NF-κB signaling. Interestingly, DHA also increases expression, phosphorylation and activity of the major isoform α1AMPK, which further leads to SIRT1 over-expression. More importantly, DHA mimics the effect of SIRT1 on deacetylation of the NF-κB subunit p65, and the ability of DHA to deacetylate p65 and inhibit its signaling and downstream cytokine expression require SIRT1. In conclusion, ω-3 PUFAs negatively regulate macrophage inflammation by deacetylating NF-κB, which acts through activation of AMPK/SIRT1 pathway. Our study defines AMPK/SIRT1 as a novel cellular mediator for the anti-inflammatory effects of ω-3 PUFAs.
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.
Numerous studies on perinatal long chain polyunsaturated fatty acid nutrition have clarified the influence of dietary docosahexaenoic acid (DHA) and arachidonic acid (ARA) on central nervous system PUFA concentrations. In humans, omnivorous primates, and piglets, DHA and ARA plasma and red blood cells concentrations rise with dietary preformed DHA and ARA. Brain and retina DHA are responsive to diet while ARA is not. DHA is at highest concentration cells and tissues associated with high energy consumption, consistent with high DHA levels in mitochondria and synaptosomes. DHA is a substrate for docosanoids, signaling compounds of intense current interest. The high concentration in tissues with high rates of oxidative metabolism may be explained by a critical role related to oxidative metabolism.
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
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
The purpose of this study is to evaluate the effects of docosahexaenoic acid (DHA), a major omega-3-polyunsaturated fatty acid (ω-3-PUFAs), in the development of experimental choroidal neovascularization (CNV) in rodents.
Experimental second generation Long Evans rats fed with diets of varying ω-3-PUFA content designed to produce significantly different retinal DHA levels were used in our studies. A transgenic mouse model (fat-1) engineered to over-produce DHA was also studied. CNV was induced by rupture of Bruch's membrane using laser photocoagulation. At 7 days after induction, animals were euthanatized, and eyes were collected. RPE/choroid flatmounts were labeled with isolectin IB4 to determine CNV lesion volumes using confocal microscopy and high-performance 3D imaging software.
The median of CNV complex volumes of animals with DHA-adequate diets was lower by 63% relative to that of animals with DHA-deficient diets. The median of CNV complex volumes in fat-1 transgenic mice was decreased by 59% relative to that of wild type controls.
Dietary intake or genetic manipulation to increase the sources of DHA significantly diminished the volume of induced CNV lesions in rodents. They suggest that consumption of ω-3-PUFAs may serve to prevent CNV.
DHA; Omega-3 fatty acids; Choroidal neovascularization; Diet; Fat-1; Laser-induced CNV
Regular consumption of food enriched in omega3 polyunsaturated fatty acids (ω3 PUFAs) has been shown to reduce risk of cognitive decline in elderly, and possibly development of Alzheimer's disease. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the most likely active components of ω3-rich PUFAs diets in the brain. We therefore hypothesized that exposing mice to a DHA and EPA enriched diet may reduce neuroinflammation and protect against memory impairment in aged mice. For this purpose, mice were exposed to a control diet throughout life and were further submitted to a diet enriched in EPA and DHA during 2 additional months. Cytokine expression together with a thorough analysis of astrocytes morphology assessed by a 3D reconstruction was measured in the hippocampus of young (3-month-old) and aged (22-month-old) mice. In addition, the effects of EPA and DHA on spatial memory and associated Fos activation in the hippocampus were assessed. We showed that a 2-month EPA/DHA treatment increased these long-chain ω3 PUFAs in the brain, prevented cytokines expression and astrocytes morphology changes in the hippocampus and restored spatial memory deficits and Fos-associated activation in the hippocampus of aged mice. Collectively, these data indicated that diet-induced accumulation of EPA and DHA in the brain protects against neuroinflammation and cognitive impairment linked to aging, further reinforcing the idea that increased EPA and DHA intake may provide protection to the brain of aged subjects.
Paracrine interactions between adipocytes and macrophages contribute to chronic inflammation in obese adipose tissue. Dietary strategies to mitigate such inflammation include long-chain polyunsaturated fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, which act through PPARγ-dependent and independent pathways. We utilized an in vitro co-culture model designed to mimic the ratio of macrophages:adipocytes in obese adipose tissue, whereby murine 3T3-L1 adipocytes were cultured with RAW 264.7 macrophages in direct contact, or separated by a trans-well membrane (contact-independent mechanism), with 125 µM of albumin-complexed DHA, EPA, palmitic acid (PA), or albumin alone (control). Thus, we studied the effect of physical cell contact versus the presence of soluble factors, with or without a PPARγ antagonist (T0070907) in order to elucidate putative mechanisms. After 12 hr, DHA was the most anti-inflammatory, decreasing MCP1 and IL-6 secretion in the contact system (−57%, −63%, respectively, p≤0.05) with similar effects in the trans-well system. The trans-well system allowed for isolation of cell types for inflammatory mediator analysis. DHA decreased mRNA expression (p<0.05) of Mcp1 (−7.1 fold) and increased expression of the negative regulator, Mcp1-IP (+1.5 fold). In macrophages, DHA decreased mRNA expression of pro-inflammatory M1 polarization markers (p≤0.05), Nos2 (iNOS; −7 fold), Tnfα (−4.2 fold) and Nfκb (−2.3 fold), while increasing anti-inflammatory Tgfβ1 (+1.7 fold). Interestingly, the PPARγ antagonist co-administered with DHA or EPA in co-culture reduced (p≤0.05) adiponectin cellular protein, without modulating other cytokines (protein or mRNA). Overall, our findings suggest that DHA may lessen the degree of MCP1 and IL-6 secreted from adipocytes, and may reduce the degree of M1 polarization of macrophages recruited to adipose tissue, thereby decreasing the intensity of pro-inflammatory cross-talk between adipocytes and macrophages in obese adipose tissue.
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
Niacin, also known as nicotinic acid, is an organic compound that has several cardio-beneficial effects. However, its use is limited due to the induction of a variable flushing response in most individuals. Flushing occurs from a niacin receptor mediated generation of prostaglandins from arachidonic acid metabolism. This study examined the ability of docosahexaenoic acid, eicosapentaenoic acid, and omega-3 polyunsaturated fatty acids (PUFAs), to attenuate niacin-induced prostaglandins in THP-1 macrophages. Niacin induced both PGD2 and PGE2 generation in a dose-dependent manner. Niacin also caused an increase in cytosolic calcium and activation of cytosolic phospholipase A2. The increase in PGD2 and PGE2 was reduced by both docosahexaenoic acid and eicosapentaenoic acid, but not by oleic acid. Omega-3 PUFAs efficiently incorporated into cellular phospholipids at the expense of arachidonic acid, whereas oleic acid incorporated to a higher extent but had no effect on arachidonic acid levels. Omega-3 PUFAs also reduced surface expression of GPR109A, a human niacin receptor. Furthermore, omega-3 PUFAs also inhibited the niacin-induced increase in cytosolic calcium. Niacin and/or omega-3 PUFAs minimally affected cyclooxygenase-1 activity and had no effect on cyclooxygenase -2 activity. The effects of niacin on PGD2 generation were further confirmed using Langerhans dendritic cells. Results of the present study indicate that omega-3 PUFAs reduced niacin-induced prostaglandins formation by diminishing the availability of their substrate, as well as reducing the surface expression of niacin receptors. In conclusion, this study suggests that the regular use of omega-3 PUFAs along with niacin can potentially reduce the niacin-induced flushing response in sensitive patients.
flushing; prostaglandin E2; phospholipids; GPR109A; cardiovascular; docosahexaenoic acid; arachidonic acid
The inflammatory response is designed to help fight and clear infection, remove harmful chemicals, and repair damaged tissue and organ systems. Although this process, in general, is protective, the failure to resolve the inflammation and return the target tissue to homeostasis can result in disease, including the promotion of cancer. A plethora of published literature supports the contention that dietary n-3 polyunsaturated fatty acids (PUFA), and eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) in particular, are important modulators of a host's inflammatory/immune responses. The following review describes a mechanistic model that may explain, in part, the pleiotropic anti-inflammatory and immunosuppressive properties of EPA and DHA. In this review, we focus on salient studies that address three overarching mechanisms of n-3 PUFA action: (i) modulation of nuclear receptor activation, i.e., nuclear factor-κB (NF-κB) suppression; (ii) suppression of arachidonic acid–cyclooxygenase-derived eicosanoids, primarily prostaglandin E2-dependent signaling; and (iii) alteration of the plasma membrane micro-organization (lipid rafts), particularly as it relates to the function of Toll-like receptors (TLRs), and T-lymphocyte signaling molecule recruitment to the immunological synapse (IS). We propose that lipid rafts may be targets for the development of n-3 PUFA-containing dietary bioactive agents to down-modulate inflammatory and immune responses and for the treatment of autoimmune and chronic inflammatory diseases.
Long chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are considered essential omega-3 fatty acids in human nutrition. In marine microalgae EPA and/or DHA are allegedly involved in the regulation of membrane fluidity and thylakoid membrane functioning. The cellular content of EPA and DHA may therefore be enhanced at low temperature and irradiance conditions. As a result, polar and cold temperate marine microalgal species might potentially be suitable candidates for commercial EPA and DHA production, given their adaptation to low temperature and irradiance habitats.
In the present study we investigated inter- and intraspecific EPA and DHA variability in five polar and (cold) temperate microalgae. Intraspecific EPA and DHA content did not vary significantly in an Antarctic (Chaetoceros brevis) and a temperate (Thalassiosira weissflogii) centric diatom after acclimation to a range of irradiance levels at two temperatures. Interspecific variability was investigated for two Antarctic (Chaetoceros brevis and Pyramimonas sp. (Prasinophyceae)) and three cold-temperate species (Thalassiosira weissflogii, Emiliania huxleyi (Prymnesiophyceae) and Fibrocapsa japonica (Raphidophyceae)) during exponential growth. Interspecific variability was shown to be much more important than intraspecific variability. Highest relative and absolute levels of DHA were measured in the prymnesiophyte E. huxleyi and the prasinophyte Pyramimonas sp., while levels of EPA were high in the raphidophyte F. japonica and the diatoms C. brevis and T. weissflogii. Yet, no significant differences in LC-PUFA content were found between polar and cold-temperate species. Also, EPA and DHA production rates varied strongly between species. Highest EPA production rate (174 μg L-1 day-1) was found in the Antarctic diatom Chaetoceros brevis, while DHA production was highest in the cold-temperate prymnesiophyte Emiliania huxleyi (164 μg L-1 day-1). We show that, following careful species selection, effective mass cultivation of marine microalgae for EPA and DHA production may be possible under low temperature and irradiance conditions.
Eicosapentaenoic acid; Docosahexaenoic acid; Thalassiosira weissflogii; Chaetoceros brevis; Fibrocapsa japonica; Emiliania huxleyi; Pyramimonas sp.
Dietary fatty acids may modulate inflammation in macrophages of the atherosclerotic plaque, affecting its stability. The n-6 polyunsaturated fatty acid (PUFA) arachidonic acid (AA) generally promotes inflammation, while the PUFAs of the n-3 series eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) are considered anti-inflammatory. We determined how these PUFAs influence MMP-9 expression and secretion by the human monocytic cell line (MonoMac 6) at baseline and after 24-hour exposure. MMP-9 protein was measured by zymography and relative levels of MMP-9 mRNA were determined using quantitative real time PCR.
Supplementation with AA (but not the n-3 fatty acids) increased, in a dose-dependent manner, expression of MMP-9 protein. This stimulation was regulated at the mRNA level. MMP-9 secretion started after 1 h of incubation and could not be prevented by simultaneous presence of n-3 series fatty acids. Finally, the secretion could be attenuated by LY 294002, a specific phosphatidylinositol-3-kinase (PI3K) inhibitor and by SH-5, a selective Akt inhibitor, suggesting that activation of PI3K by AA leads to augmented and sustained MMP-9 production.
This study shows that of the PUFA studied, AA alone influences the expression of MMP-9, which might have implications in MMP-9 induced plaque rupture.
Fatty acid metabolism is altered in colorectal cancer (CRC). We aimed to investigate incorporation of dietary n-6 and n-3 polyunsaturated fatty acids (PUFAs) into plasma phospholipids (PLs), tumour tissue, and normal mucosa in young CRC patients. We also aimed to study differences in PUFA composition between tumour and normal mucosa, and PUFA status associated with cancer stage. Sixty-five CRC patients younger than 55 years were included in a multicenter study. We assessed dietary fatty acid composition by food-frequency questionnaire. Fatty acid composition in plasma PL (n = 65) and tumour and normal colonic biopsies (n = 32) were analysed by gas chromatography. We observed a significant correlation for docosahexaenoic acid (DHA) between dietary intake and concentration in plasma PL (weight%) (r = 0.42; P = 0.001), but not for any n-6 PUFA. Tissue concentrations of arachidonic acid, eicosapentaenoic acid, and DHA (weight%) were 1.7–2.5 times higher in tumour than normal mucosa (P ≤ 0.001). Concentrations of n-3 and n-6 PUFA in plasma PL and tissues were not related to Duke's stage, although patients with more severe cancer stage reported higher intake of n-3 PUFA. In conclusion, we found accumulation of the long-chained n-3 and n-6 PUFA in tumour tissue in young CRC patients.
Accumulating evidence suggests that the pathophysiology of depression might be associated with neuroinflammation, which could be attenuated by pharmacological treatment for depression. Omega-3 polyunsaturated fatty acids (PUFAs) are anti-inflammatory and exert antidepressant effects. The aim of this study was to identify the molecular mechanisms through which docosahexaenoic acid (DHA), the main omega-3 PUFA in the brain, modulates oxidative reactions and inflammatory cytokine production in microglial and neuronal cells. The results of this study showed that DHA reduced expressions of tumor necrosis factor-α, interleukin-6, nitric oxide synthase, and cyclo-oxygenase-2, induced by interferon-γ, and induced upregulation of heme oxygenase-1 (HO-1) in BV-2 microglia. The inhibitory effect of DHA on nitric oxide production was abolished by HO-1 inhibitor zinc protoporphyrin IX. In addition, DHA caused AKT and ERK activation in a time-dependent manner, and the DHA-induced HO-1 upregulation could be attenuated by PI-3 kinase/AKT and MEK/ERK inhibitors. DHA also increased IKKα/β phosphorylation, IκBα phosphorylation, and IκBα degradation, whereas both nuclear factor-κB and IκB protease inhibitors could inhibit DHA-induced HO-1 expressions. The other major n-3 PUFA, eicosapentaenoic acid, showed similar effects of DHA on inflammation and HO-1 in repeated key experiments. In connecting with inflammation hypothesis of depression and clinical studies supporting the antidepressant effects of omega-3 PUFAs, this study provides a novel implication of the antidepressant mechanisms of DHA.
omega-3 fatty acids; docosahexaenoic acid (DHA); heme oxygenase-1 (HO-1); antidepressant; microglia; inflammation; biological psychiatry; depression, unipolar/bipolar; molecular & cellular neurobiology; psychopharmacology; omega-3 fatty acids; docosahexaenoic acid (DHA); heme oxygenase-1 (HO-1); antidepressant; microglia, inflammation
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