Dietary docosahexaenoic acid and immunocompetence in young healthy men

Role of Resolvins in Inflammatory and Neuropathic Pain

Chronic pain is an unpleasant experience associated with actual or potential tissue damage. Inflammatory pain alerts the body to inflammation and promotes healing; however, unresolved inflammation can lead to chronic pain. Conversely, neuropathic pain, due to somatosensory damage, can be a disease in itself. However, inflammation plays a considerable role in the progression of both types of pain. Resolvins, derived from omega-3 fatty acids, actively suppress pro-inflammatory mediators and aid in the resolution of inflammation. Resolvins alleviate various inflammatory and neuropathic pain models by reducing hypersensitivity and regulating inflammatory cytokines and glial activation in the spinal cord and dorsal root ganglia. Thus, resolvins are a promising alternative for pain management with the potential to reduce the side effects associated with conventional medications. Continued research is crucial to unlock the therapeutic potential of resolvins and integrate them into effective clinical pain management strategies. This review aimed to evaluate the literature surrounding the resolvins in inflammatory and neuropathic pain.

The Role of Lipids in the Regulation of Immune Responses

Lipid metabolism plays a major role in the regulation of the immune system. Exogenous (dietary and microbial-derived) and endogenous (non-microbial-derived) lipids play a direct role in regulating immune cell activation, differentiation and expansion, and inflammatory phenotypes. Understanding the complexities of lipid-immune interactions may have important implications for human health, as certain lipids or immune pathways may be beneficial in circumstances of acute infection yet detrimental in chronic inflammatory diseases. Further, there are key differences in the lipid effects between specific immune cell types and location (e.g., gut mucosal vs. systemic immune cells), suggesting that the immunomodulatory properties of lipids may be tissue-compartment-specific, although the direct effect of dietary lipids on the mucosal immune system warrants further investigation. Importantly, there is recent evidence to suggest that lipid-immune interactions are dependent on sex, metabolic status, and the gut microbiome in preclinical models. While the lipid-immune relationship has not been adequately established in/translated to humans, research is warranted to evaluate the differences in lipid-immune interactions across individuals and whether the optimization of lipid-immune interactions requires precision nutrition approaches to mitigate or manage disease. In this review, we discuss the mechanisms by which lipids regulate immune responses and the influence of dietary lipids on these processes, highlighting compelling areas for future research.

Specialized Pro-Resolving Mediators in Neuroinflammation: Overview of Studies and Perspectives of Clinical Applications

Specialized pro-resolving mediators (SPMs) are lipid mediators derived from poly-unsaturated fatty acids (PUFAs) which have been demonstrated to have an important role in the inflammation environment, preventing an overreaction of the organism and promoting the resolution of inflammation. Our purpose was to point out the current evidence for specialized pro-resolving mediators, focusing on their role in neuroinflammation and in major neurological diseases.

Determinants of Serum Immunoglobulin Levels: A Systematic Review and Meta-Analysis

Background

An up-to-date overview of determinants of serum immunoglobulins in adults is pivotal for clinical practice and research, but currently lacking. We therefore performed a systematic review and meta-analysis to identify determinants of serum immunoglobulin levels.

Methods

Embase, Web of Science, Medline, Cochrane, and Google Scholar were searched from inception to July 11th, 2019 for articles reporting on determinants of serum immunoglobulin A, G or M (IgA, IgG or IgM) in adult humans. Random and fixed effect models were applied to obtain pooled mean differences (MDs) and 95% confidence intervals (CIs) for the association of age and sex with serum immunoglobulins.

Results

We retrieved 117 articles reporting on determinants of serum immunoglobulins, of which 28 could be meta-analyzed. Older compared to younger individuals had higher IgA (MD: 0.38; CI: 0.18 - 0.58), but lower IgM levels (MD: -0.40; 95%: -0.66 - -0.14). Men had higher IgA (MD: 0.22; CI: 0.03 - 0.42), but lower IgM levels (MD: -0.21; CI: -0.32 - -0.10) than women. Age and sex did not influence IgG. Caucasian ethnicity was associated with lower IgA, IgG, and IgM. Smoking and corticosteroid use were associated with lower IgG. Positive associations were reported of probiotics with IgG, alcohol with IgA, hypertension with IgA and IgG, and acute psychological stress with IgA, IgG, and IgM.

Conclusions

Older age and male sex are associated with higher IgA, but lower IgM, and urge investigation of age- and sex-specific reference ranges of immunoglobulins. Other identified determinants were ethnicity, diet, lifestyle and cardio-metabolic factors.

Herring roe oil supplementation alters microglial cell gene expression and reduces peripheral inflammation after immune activation in a neonatal piglet model

Neonatal brain development can be disrupted by infection that results in microglial cell activation and neuroinflammation. Studies indicate that polyunsaturated fatty acids (PUFAs) and their metabolites can resolve inflammation. It is not known if dietary PUFA increases lipid metabolites in brain or reduces neuroinflammation in neonates. We hypothesized that dietary PUFAs might suppress neuroinflammation by inhibiting pro-inflammatory cytokine over-production and promoting inflammatory resolution in the periphery and brain. Piglets were obtained on postnatal day (PD) 2 and randomly assigned to herring roe oil (HRO) or control (CON) diet. HRO was included at 2 g/kg powdered diet. HRO increased DHA levels in occipital lobe and the DHA to arachidonic acid (ARA) ratio in hippocampal tissue. HRO decreased ARA metabolites in occipital lobe. HRO failed to attenuate microglial pro-inflammatory cytokine production ex vivo. HRO did not affect fever or circulating resolvin D1 levels. HRO decreased circulating neutrophils and liver inflammatory gene expression, but increased resolution marker gene expression in liver post LPS. HRO upregulated CXCL16, TGFBR1, and C1QA in microglial cells. HRO supplementation exerted beneficial effects on inflammation in the periphery, but further studies are needed to evaluate the specific effects of omega-3 supplementation on microglial cell physiology in the neonate.

The Physiological Role of Boron on Health

Boron is an essential mineral that plays an important role in several biological processes. Boron is required for growth of plants, animals, and humans. There are increasing evidences of this nutrient showing a variety of pleiotropic effects, ranging from anti-inflammatory and antioxidant effects to the modulation of different body systems. In the past few years, the trials showed disease-related polymorphisms of boron in different species, which has drawn attention of scientists to the significance of boron to health. Low boron profile has been related with poor immune function, increased risk of mortality, osteoporosis, and cognitive deterioration. High boron status revealed injury to cell and toxicity in different animals and humans. Some studies have shown some benefits of higher boron status, but findings have been generally mixed, which perhaps accentuates the fact that dietary intake will benefit only if supplemental amount is appropriate. The health benefits of boron are numerous in animals and humans; for instance, it affects the growth at safe intake. Central nervous system shows improvement and immune organs exhibit enhanced immunity with boron supplementation. Hepatic metabolism also shows positive changes in response to dietary boron intake. Furthermore, animals and human fed diets supplemented with boron reveal improved bone density and other benefits including embryonic development, wound healing, and cancer therapy. It has also been reported that boron affects the metabolism of several enzymes and minerals. In the background of these health benefits, low or high boron status is giving cause for concern. Additionally, researches are needed to further elucidate the mechanisms of boron effects, and determine the requirements in different species.

Can inflammation be resolved in Alzheimer's disease?

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory loss and dementia. Accumulating evidence suggests that inflammation is involved in the pathogenesis of AD. Epidemiological studies suggest that use of anti-inflammatory drugs is associated with a lower incidence of AD. However, clinical trials with anti-inflammatory drugs have not been successful. Recent studies have shown that inflammation is resolved by a process that is mediated by a group of lipid mediators, so called specialized pro-resolving lipid mediators (SPMs). Unlike anti-inflammatory strategies, which usually involve inhibition of the synthesis of inflammatory mediators, stimulating the resolution of inflammation is aimed at ending inflammation in a similar fashion as under normal physiological conditions. We have previously shown that pathways of resolution are impaired in AD. Moreover, we found that SPMs can improve neuronal survival and increase microglial phagocytosis of amyloid beta (Aβ) in in vitro studies, indicating that stimulating resolution of inflammation may be a potential therapeutic target in AD. In this review, we summarize recent findings regarding resolution of inflammation in AD. We also discuss possible strategies to stimulate the resolution of inflammation in AD, specifically focusing on signaling pathways, including SPMs, their receptors and enzymes involved in their formation.

Preclinical Evaluation of the Short-Term Toxicity of 4-(N)-Docosahexaenoyl 2´, 2´- Difluorodeoxycytidine (DHA-dFdC)

PURPOSE

This study was designed to test the short-term toxicity of DHA-dFdC in a mouse model and its efficacy in a mouse model of leukemia at or below its repeat-dose maximum tolerated dose (RD-MTD).

METHOD

A repeat-dose dose-ranging toxicity study was designed to determine the tolerability of DHA-dFdC when administered to DBA/2 mice by intravenous (i.v.) injection on a repeat-dose schedule (i.e. injections on days 0, 3, 7, 10, and 13). In order to determine the effect of a lethal dose of DHA-dFdC, mice were injected i.v. with three doses of DHA-dFdC at 100 mg/kg on days 0, 3, and 5 (i.e. a lethal-RD). The body weight of mice was recorded two or three times a week. At the end of the study, major organs (i.e. heart, liver, spleen, kidneys, lung, and pancreas) of mice that received the lethal-RD or RD-MTD were weighed, and blood samples were collected for analyses. Finally, DHA-dFdC was i.v. injected into DBA/2 mice with syngeneic L1210 mouse leukemia cells to evaluate its efficacy at or below RD-MTD.

RESULTS

The RD-MTD of DHA-dFdC is 50 mg/kg. At 100 mg/kg, a lethal-RD, DHA-dFdC decreases the weights of mouse spleen and liver and significantly affected certain blood parameters (i.e. white blood cells, lymphocytes, eosinophils, and neutrophil segmented). At or below its RD-MTD, DHA-dFdC significantly prolonged the survival of L1210 leukemia-bearing mice.

CONCLUSION

DHA-dFdC has dose-dependent toxicity, affecting mainly spleen at a lethal-RD. At or below its RD-MTD, DHA-dFdC is effective against leukemia in a mouse model.

Immunomodulatory properties of shellfish derivatives associated with human health

Some vital components of marine shellfish are documented as an important source for both nutritional and pharmacological applications.

Update on the management of severe hypertriglyceridemia--focus on free fatty acid forms of omega-3

High levels of plasma triglycerides (TG) are a risk factor for cardiovascular diseases, often associated with anomalies in other lipids or lipoproteins. Hypertriglyceridemia (HTG), particularly at very high levels, significantly increases also the risk of acute pancreatitis. Thus, interventions to lower TG levels are required to reduce the risk of pancreatitis and cardiovascular disease. Several strategies may be adopted for TG reduction, including lifestyle changes and pharmacological interventions. Among the available drugs, the most commonly used for HTG are fibrates, nicotinic acid, and omega-3 polyunsaturated fatty acids (usually a mixture of eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA). These last are available under different concentrated formulations containing high amounts of omega-3 fatty acids, including a mixture of EPA and DHA or pure EPA. The most recent formulation contains a free fatty acid (FFA) form of EPA and DHA, and exhibits a significantly higher bioavailability compared with the ethyl ester forms contained in the other formulations. This is due to the fact that the ethyl ester forms, to be absorbed, need to be hydrolyzed by the pancreatic enzymes that are secreted in response to fat intake, while the FFA do not. This higher bioavailability translates into a higher TG-lowering efficacy compared with the ethyl ester forms at equivalent doses. Omega-3 FFA are effective in reducing TG levels and other lipids in hypertriglyceridemic patients as well as in high cardiovascular risk patients treated with statins and residual HTG. Currently, omega-3 FFA formulation is under evaluation to establish whether, in high cardiovascular risk subjects, the addition of omega-3 to statin therapy may prevent or reduce major cardiovascular events.

EPA, an omega-3 fatty acid, induces apoptosis in human pancreatic cancer cells: role of ROS accumulation, caspase-8 activation, and autophagy induction

In a recent study, we showed that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two common omega-3 fatty acids, can cause ROS accumulation and subsequently induce caspase-8-dependent apoptosis in human breast cancer cells (Kang et al. [2010], PLoS ONE 5: e10296). In this study, we showed that the pancreas has a unique ability to accumulate EPA at a level markedly higher than several other tissues analyzed. Based on this finding, we sought to further investigate the anticancer actions of EPA and its analog DHA in human pancreatic cancer cells using both in vitro and in vivo models. EPA and DHA were found to induce ROS accumulation and caspase-8-dependent cell death in human pancreatic cancer cells (MIA-PaCa-2 and Capan-2) in vitro. Feeding animals with a diet supplemented with 5% fish oil, which contains high levels of EPA and DHA, also strongly suppresses the growth of MIA-PaCa-2 human pancreatic cancer xenografts in athymic nude mice, by inducing oxidative stress and cell death. In addition, we showed that EPA can concomitantly induce autophagy in these cancer cells, and the induction of autophagy diminishes its ability to induce apoptotic cell death. It is therefore suggested that combination of EPA with an autophagy inhibitor may be a useful strategy in increasing the therapeutic effectiveness in pancreatic cancer.

Similarities and differences between the effects of EPA and DHA on markers of atherosclerosis in human subjects

We have reviewed effects of long chain (LC) n-3 PUFA on markers of atherosclerosis in human subjects with a focus on individual effects of EPA and DHA. Initial results from epidemiological studies suggested that LC n-3 PUFA from fish oils (FO) reduced incidence of CVD; those results have been confirmed in interventional studies. Dietary intervention with n-3 PUFA decreased fasting and postprandial TAG, number of remnant-like chylomicron particles, large VLDL, and total and small dense LDL particles. It increased mean size of LDL particles by increasing number of large and decreasing those of small dense particles. With some exceptions, n-3 PUFA decreased blood pressure (BP) and heart rate (HR), flow-mediated dilation (FMD) and plasma concentrations of inflammatory markers. n-3 PUFA also decreased circulating adhesion molecules and intima-media thickness (IMT) in some but not other studies. For IMT, results varied with the sex and artery being examined. EPA effects on FMD are endothelial cell dependent, while those of DHA seem to be endothelial cell independent. Individually, both EPA and DHA decreased TAG and inflammatory markers, but only DHA decreased HR, BP and number of small dense LDL particles. Results varied because of dose and duration of n-3 PUFA, EPA:DHA, health status of subjects and other reasons. Future studies are needed to determine optimal doses of EPA and DHA individually, their synergistic, additive or antagonistic effects, and to understand underlying mechanisms. In conclusion, n-3 PUFA decreased several risk factors for atherosclerosis without any serious adverse effects.

Modulation of blood cell gene expression by DHA supplementation in hypertriglyceridemic men

Our previous study with docosahexaenoic acid (DHA) supplementation to hypertriglyceridemic men showed that DHA reduced several risk factors for cardiovascular disease, including the plasma concentration of inflammatory markers. To determine the effect of DHA supplementation on the global gene expression pattern, we performed Affymetrix GeneChip microarray analysis of blood cells [treated with lipopolysaccharide (LPS) or vehicle] drawn before and after the supplementation of DHA from the hypertriglyceridemic men who participated in that study. Genes that were significantly differentially regulated by the LPS treatment and DHA supplementation were identified. Differential regulation of 18 genes was then verified by quantitative real-time polymerase chain reaction (qRT-PCR). Both microarray and qRT-PCR data showed that DHA supplementation significantly suppressed the expression of low-density lipoprotein (LDL) receptor and cathepsin L1, both of which were also up-regulated by LPS. DHA supplementation also suppressed oxidized LDL (lectin-like) receptor 1 (OLR1). However, LPS did not induce OLR1 mRNA expression. Enrichment with Gene Ontology categories demonstrated that the genes related to transcription factor activity, immunity, host defense and inflammatory responses were inversely regulated by LPS and DHA. These results provide supporting evidence for the anti-inflammatory effects of DHA supplementation, and reveal previously unrecognized genes that are regulated by DHA and are associated with risk factors of cardiovascular diseases.

Zizyphus lotus L. (Desf.) modulates antioxidant activity and human T-cell proliferation

Background

Zizyphus lotus L. (Desf.) also known as Jujube, is a deciduous shrub which belongs to Rhamnaceae family. This plant is used in Algerian traditional medicine for its anti-diabetic, sedative, analgesic, anti-inflammatory and hypoglycaemic activities. In the present study, we determined the concentrations of different vitamins (vitamin A, C and E) and fatty acids in root, stem, leaves, fruit pulp and seed of Zizyphus lotus L. (Desf.) and assessed the effects of their aqueous extracts on antioxidant status and human T-cell proliferation.

Methods

Aqueous filtrates from different parts, i.e, root, leaf, stem, fruit pulp and seed, of Zizyphus lotus L. (Desf.) were prepared. Vitamin C levels were determined by precipitating with 10% trichloroacetic acid and vitamin A and E were assessed by HPLC. Lipid composition of these extracts was determined by gas-liquid chromatography. Anti-oxidant capacity was evaluated by using anti-radical resistance kit [Kit Radicaux Libres (KRL^@; Kirial International SA, Couternon, France)]. T-cell blastogenesis was assessed by the incorporation of ³H-thymidine. IL-2 gene expression was evaluated by RT-qPCR.

Results

Our results show that fruit pulp contained higher vitamin A and C contents than other parts of the plant. Furthermore, the fruit pulp was the richest source of linoleic acid (18:2n-6), a precursor of n-6 fatty acids. Fruit seeds possessed higher vitamin C levels than leaves, roots and stem. The leaves were the richest source of vitamin E and linolenic acid (18:3n-3), a precursor of n-3 fatty acids. The antioxidant capacity of the different extracts, measured by KRL^@ test, was as follows: pulp < seed<leaf<root < stem. As far as T-cell proliferation is concerned, we observed that the different extracts of Zizyphus lotus L. (Desf.) exerted immunosuppressive effects.

Conclusion

Seed extracts exerted the most potent immunosuppressive effects on T cell proliferation and IL-2 mRNA expression. The results of the present study are discussed in the light of their use to modulate the immune-mediated diseases.

n-3 polyunsaturated fatty acids--physiological relevance of dose

n-3 polyunsaturated fatty acids (PUFA) are widely used for chemotheraphy/chemoprevention of chronic diseases. However, the molecular mechanism(s) by which the bioactive n-3 PUFA (eicosapentaenoic acid and docosahexaenoic acid) modulate effector pathways are not fully elucidated. Multiple experimental approaches, including use of animal models, cell lines, and human clinical trials, have been utilized to dissect the complex effectors. It is imperative to link these different experimental approaches together in order to interpret outcomes in the context of human physiology and pathophysiology. Unfortunately, the adoption of a broad array of model systems and a wide range of fatty acid exposures (i.e. doses) has made it difficult to interpret biological outcomes. Therefore, in this mini-review we discuss the impact of (a) molecular structure of bioactive fatty acids, (b) dose relevance relative to human consumption, (c) enrichment of fatty acids in sera and tissues following dietary intake, and (d) limitations of cell/tissue culture studies.

Effect of fish oil supplementation for two generations on changes of lymphocyte function induced by Walker 256 cancer cachexia in rats

Fish oil supplementation has been shown to improve the cachectic state of tumor-bearing animals and humans. Our previous study showed that fish oil supplementation (1 g per kg body weight per day) for 2 generations had anticancer and anticachetic effects in Walker 256 tumor-bearing rats as demonstrated by reduced tumor growth and body weight loss and increased food intake and survival. In this study, the effect of fish oil supplementation for 2 generations on membrane integrity, proliferation capacity, and CD4/CD8 ratio of lymphocytes isolated from mesenteric lymph nodes, spleen, and thymus of Walker 256 tumor-bearing animals was investigated. We also determined fish oil effect on plasma concentration and ex vivo production of cytokines [tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-6, and IL-10]. Lymphocytes from thymus of tumor-bearing rats presented lower viability, but this change was abolished by fish oil supplementation. Tumor growth increased proliferation of lymphocytes from all lymphoid organs, and fish oil supplementation abolished this effect. Ex vivo production of TNF-alpha and IL-6 was reduced in supplemented animals, but IL-4 and IL-10 secretion was stimulated in both nontumor and tumor-bearing rats. IL-10 and IFN-gamma plasma levels was also decreased in supplemented animals. These results suggest that the anticachetic effects of fish oil supplementation for a long period of time (2 generations) in Walker 256 tumor-bearing rats may be associated to a decrease in lymphocyte function as demonstrated by reduced viability, proliferation capacity, and cytokine production.

Toxicology and safety of DHA

Docosahexaenoic acid (DHA) is a long-chain polyunsaturated fatty acid with activities in both infants and adults. The objective of the current work was to evaluate the published literature concerning the toxicological assessment of DHA-rich oils in animals and the safety profile of DHA consumption in humans. Structured literature searches concerning DHA toxicology and DHA effects on platelet function, lipid levels, oxidative potential, glycemic control, and immune function were conducted. The toxicological profile of DHA derived from single-cell organisms demonstrates that these oils are safe in rats (up to a consumption level of 3290 mg/kg body weight/d) in 90-d toxicology evaluations, as well as in reproductive and developmental toxicology studies. The maximum DHA level in human breast milk exceeds 1% of total fatty acids in high-fish-consuming populations. Consumption of DHA-rich human milk as sole source of nutrition provides approximately 315 mg/d in infants 1-6 months of age, and appears to be a safe level of intake. DHA supplementation studies in adults have employed doses ranging from less than 1 to 7.5 g/d, and have not resulted in any consistent adverse responses in platelet function, lipid levels, in vivo oxidation parameters, glycemic control, or immune function. In conclusion, DHA consumption does not result in consistent adverse events in infants or adults. Safe intake levels may be modeled on DHA intake from human milk in infants, and may be at least as high as the upper doses studied in adults.

DHA supplementation decreases serum C-reactive protein and other markers of inflammation in hypertriglyceridemic men

Dietary (n-3) PUFA reduce inflammation, an independent risk factor for cardiovascular disease. The antiinflammatory effects of docosahexaenoic acid (DHA) in hypertriglyceridemic men have not been previously reported, to our knowledge, and were the focus of this study. Hypertriglyceridemic men (n = 17 per group) aged 39-66 y, participated in a double-blind, randomized, placebo-controlled parallel study. They received no supplements for the first 8 d and then received either 7.5 g/d DHA oil (3 g DHA/d) or olive oil (placebo) for the last 90 d. Blood samples were collected from fasting men on study days -7, 0, 45, 84, and 91. DHA supplementation for 45 and 91 d decreased the number of circulating neutrophils by 11.7 and 10.5%, respectively (P < 0.05). It did not alter the circulating concentrations of other inflammatory markers tested within 45 d, but at 91 d it reduced (P < 0.05) concentrations of C-reactive protein (CRP) by 15%, interleukin-6 by 23%, and granulocyte monocyte-colony stimulating factor by 21% and DHA increased the concentration of antiinflammatory matrix metalloproteinase-2 by 7%. The number of circulating neutrophils was positively associated with the weight percent (wt %) of 20:4(n-6) in RBC lipids, and negatively to the wt % of 20:5(n-3) and 22:6(n-3). Concentrations of CRP and serum amyloid A were positively associated with the sum of SFA and negatively with the wt % of 18:1(n-9) and 17:0 in RBC lipids; CRP was also positively associated with the wt % of 20:2(n-6). The mean size of VLDL particles was positively associated with plasma concentrations of neutrophils and CRP. In conclusion, DHA may lessen the inflammatory response by altering blood lipids and their fatty acid composition.

Comparative effects of DHA and EPA on cell function

Fish oil supplementation has been reported to be generally beneficial in autoimmune, inflammatory and cardiovascular disorders. Most researchers have attributed these beneficial effects to the high content of omega-3 fatty acids in fish oil (FO). The effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are not differentiated in most studies. In fact, up to 1990, purified DHA was not available for human use and there was no study regarding its effects on human immune response. In this review, the differences in the effects of these two fatty acids on cell function are discussed. Studies have shown that EPA and DHA have also different effects on leukocyte functions such as phagocytosis, chemotactic response and cytokine production. DHA and EPA modulate differently expression of genes in lymphocytes. Activation of intracellular signaling pathways involved with lymphocyte proliferation is also differently affected by these two fatty acids. In relation to insulin producing cell line RINm5F, DHA and EPA are cytotoxic at different concentrations and the proteins involved with cell death are differently modulated by these two fatty acids. Substantial improvement in the therapeutic usage of omega-3 fatty acid-rich FO will be possible with the discovery of the different mechanisms of actions of DHA and EPA.

Nutrient intake and immune function of elderly subjects

OBJECTIVE

Food intake, aging, and immune function share complex influences. Therefore, the purpose of this study was to examine relationships between nutrient intakes from food and dietary supplements and a biomarker of immune function.

DESIGN

Data were collected from participants in a cross-sectional study as well as baseline data from a longitudinal study (n=89). Subjects completed 24-hour food recalls, including supplement intake. Polyclonal mitogen phytohemmagluttin (PHA) was the immune function stimulator used. Height and weight were used to calculate body mass index.

STATISTICAL ANALYSES PERFORMED

Descriptive, bivariate correlation, Spearman's rho for nonparametric data, t tests, and stepwise regression with nutrient intakes as independent variables and T-cell proliferation as dependent variables.

RESULTS

Significant positive correlations (P< or =0.05) were found between PHA-induced proliferation and intake of docosahexaenoic acid (DHA), eicosahexaenoic acid (EPA), sodium, and selenium, although intakes of DHA plus EPA were inadequate when compared to recommended intakes. A significant negative correlation with total vitamin A, with many vitamin A levels being above the upper limit of safety. Regression analyses found these nutrients to be variables significant in explaining the variance in PHA (P=0.005).

CONCLUSIONS

Selenium, sodium, DHA, EPA, and vitamin A intake from diet and supplements were associated with PHA-induced proliferative responses. Clients may be counseled to have adequate selenium, EPA, DHA intake, and vitamin A, but avoid excess vitamin A.

Effect of dietary supplementation with increasing doses of docosahexaenoic acid on neutrophil lipid composition and leukotriene production in human healthy volunteers

n-3 PUFA supplementation helps in the prevention or treatment of inflammatory diseases and CVD. However, many supplementations reported so far are either a combination of n-3 PUFA or used large daily amounts of n-3 PUFA dosages. The present study investigated the influence of increasing dose intake of DHA on the fatty acid composition of phospholipids in neutrophils and on their capability to produce leukotrienes (LT) B4 and B5in vitro. Twelve healthy volunteers were supplemented with increasing daily doses of DHA (200, 400, 800 and 1600 mg, each dose in TAG containing DHA as the only PUFA and for a 2-week period). At the end of each supplementation period, neutrophil fatty acid composition, and LTB4 and LTB5 production were determined by GC and liquid chromatography–tandem MS, respectively. The DHA/arachidonic acid ratio increased in a dose-dependent manner with respect to the increasing doses of DHA supplementation and was significantly different from baseline after supplementation with either 400, 800 or 1600 mg DHA. The LTB5/LTB4 ratio was significantly increased compared to baseline after supplementation with 800 and 1600 mg DHA. LTB5/LTB4 and DHA/arachidonic acid ratios were correlated (r 0·531, P < 0·0001). The present data suggest that both changes in neutrophil lipid composition and LT production occurred with daily supplementation with 800 and 1600 mg DHA. The clinical benefits associated with these doses of DHA in inflammatory diseases remain to be investigated.

Effects of increasing docosahexaenoic acid intake in human healthy volunteers on lymphocyte activation and monocyte apoptosis

Dietary intake of long-chain 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 DHA and 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 plus ionomycin activation, and on monocyte apoptosis induced by oxidized LDL. Eight subjects were supplemented with increasing daily doses of DHA (200, 400, 800, 1600 mg) in a TAG form containing DHA as the only PUFA, for 2 weeks each dose. DHA intake dose-dependently increased the proportion of DHA in mononuclear cell phospholipids, the augmentation being significant after 400 mg DHA/d. The tetradecanoylphorbol acetate plus ionomycin-stimulated IL-2 mRNA level started to increase after ingestion of 400 mg DHA/d, with a maximum after 800 mg intake, and was positively correlated (P < 0.003) with DHA enrichment in cell phospholipids. The treatment of monocytes by oxidized LDL before DHA supplementation drastically reduced mitochondrial membrane potential as compared with native LDL treatment. Oxidized LDL apoptotic effect was significantly attenuated after 400 mg DHA/d 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 oxidized LDL-induced apoptosis, which may be beneficial in the prevention of atherosclerosis.

The content of favorable and unfavorable polyunsaturated fatty acids found in commonly eaten fish

Changes in diet during the past century have caused a marked increase in consumption of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFAs) with a concomitant decrease in the intake of n-3 PUFAs. Increased fish consumption has been shown to be the only realistic way to increase dietary quantities of beneficial long-chain n-3 PUFAs such as eicosapentaenoic acid and docosahexaenoic acid and re-establish more balanced n-6:n-3 ratios in the diets of human beings. Our objective in this research was to characterize some of the relevant fatty acid chemistry of commonly consumed fish, with a particular focus on the four most commonly consumed farmed fish. To do this, 30 commonly consumed farmed and wild fish were collected from supermarkets and wholesalers throughout the United States. Fatty acid composition of samples from these fish was determined using gas chromatography. The 30 samples studied contained n-3 PUFAs ranging from fish having almost undetectable levels to fish having nearly 4.0 g n-3 PUFA per 100 g fish. The four most commonly farmed fish, Atlantic salmon, trout, tilapia, and catfish, were more closely examined. This analysis revealed that trout and Atlantic salmon contained relatively high concentrations of n-3 PUFA, low n-6:n-3 ratios, and favorable saturated fatty acid plus monounsaturated fatty acid to PUFA ratios. In contrast, tilapia (the fastest growing and most widely farmed fish) and catfish have much lower concentrations of n-3 PUFA, very high ratios of long chain n-6 to long chain n-3 PUFAs, and high saturated fatty acid plus monounsaturated fatty acid to PUFA ratios. Taken together, these data reveal that marked changes in the fishing industry during the past decade have produced widely eaten fish that have fatty acid characteristics that are generally accepted to be inflammatory by the health care community.

Is boron nutritionally relevant?

Evidence from numerous laboratories using a variety of experimental models, including humans, shows that boron is a bioactive beneficial element. Much evidence has come from studies that did not require nutritional or environmental stressors or fastidious methods in diet preparation or environmental control. The evidence includes deprivation studies showing that boron is necessary for some higher animals to complete the life cycle, and that realistic low boron intakes result in impaired bone health, brain function, and immune response. Thus, low boron intake is a relevant nutritional concern, which diets rich in fruits, vegetables, nuts, and pulses can prevent.

Leukocyte numbers and function in subjects eating n-3 enriched foods: selective depression of natural killer cell levels

Introduction

While consumption of omega-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) has been recommended for those at risk of inflammatory disease such as rheumatoid arthritis, the mechanism of their anti-inflammatory effect remains to be clearly defined, particularly in relation to the dose and type of n-3 LCPUFA. The objective of this study was to determine whether varying the levels of n-3 LCPUFA in erythrocyte membrane lipids, following dietary supplementation, is associated with altered numbers and function of circulating leukocytes conducive to protection against inflammation.

Methods

In a double-blind and placebo-controlled study, 44 healthy subjects aged 23 to 63 years consumed either standard or n-3 LCPUFA-enriched versions of typical processed foods, the latter allowing a target daily consumption of 1 gram n-3 LCPUFA. After six months, peripheral blood leukocyte and subpopulation proportions and numbers were assessed by flow cytometry. Leukocytes were also examined for lymphoproliferation and cytokine production, neutrophil chemotaxis, chemokinesis, bactericidal, adherence and iodination activity. Erythrocytes were analyzed for fatty-acid content.

Results

Erythrocyte n-3 LCPUFA levels were higher and absolute leukocyte and lymphocyte numbers were lower in subjects consuming n-3 enriched foods than in controls. There were no changes in the number of neutrophils, monocytes, T cells (CD3⁺), T-cell subsets (CD4⁺, CD8⁺) and B cells (CD19⁺). However, natural killer (NK) (CD3^-CD16⁺CD56⁺) cell numbers were lower in n-3 supplemented subjects than in controls and were inversely related to the amount of eicosapentaenoic acid or docosahexaenoic acid in erythrocytes. No significant correlations were found with respect to lymphocyte lymphoproliferation and production of IFN-γ and IL-2, but lymphotoxin production was higher with greater n-3 LCPUFA membrane content. Similarly, neutrophil chemotaxis, chemokinesis, bactericidal activity and adherence did not vary with changes in erythrocyte n-3 LCPUFA levels, but the iodination reaction was reduced with higher n-3 LCPUFA content.

Conclusion

The data show that regular long-term consumption of n-3 enriched foods leads to lower numbers of NK cells and neutrophil iodination activity but higher lymphotoxin production by lymphocytes. These changes are consistent with decreased inflammatory reaction and tissue damage seen in patients with inflammatory disorders receiving n-3 LCPUFA supplementation.

Effects of the fish-oil supplementation on the immune and inflammatory responses in elite swimmers

The effect of fish-oil supplementation (FO-S) on the immune responses of elite swimmers was investigated. In a randomized placebo-controlled trial, swimmers received either fish-oil capsules (n=10) containing long chain polyunsaturated fatty acids (FA) of n-3 (LCPUFA n-3) or placebo capsules (n=10), both for 6 weeks. Plasma FA, immunological markers, insulin and cortisol were evaluated. The FO-S resulted in an increase in LCPUFA n-3 and a decrease in arachidonic n-6 FA in plasma and a reduction in the production of interferon-gamma by cultured cells. A reduction in the production of tumor necrosis factor-alpha was observed in both groups. An increase in interleukin-2 production and no significant difference in interleukin-4 were also observed. FO-S was able to attenuate the exercise-induced increases in prostaglandin E2. Circulating concentrations of insulin did not change, while cortisol and glucose showed increase after the study period. These results suggest that FO-S influence exercise-associated immune responses in competitive swimmers.

Differential immunomodulation with long-chain n-3 PUFA in health and chronic disease

The balance of intake of n-6 and n-3 PUFA, and consequently their relative incorporation into immune cells, is important in determining the development and severity of immune and inflammatory responses. Some disorders characterised by exaggerated inflammation and excessive formation of inflammatory markers have become among the most important causes of death and disability in man in modern societies. The recognition that long-chain n-3 PUFA have the potential to inhibit (excessive) inflammatory responses has led to a large number of clinical investigations with these fatty acids in inflammatory conditions as well as in healthy subjects. The present review explores the presence of dose-related effects of long-chain n-3 PUFA supplementation on immune markers and differences between healthy subjects and those with inflammatory conditions, because of the important implications for the transfer of information gained from studies with healthy subjects to patient populations, e.g. for establishing dose levels for specific applications. The effects of long-chain n-3 PUFA supplementation on ex vivo lymphocyte proliferation and cytokine production by lymphocytes and monocytes in healthy subjects have been studied in twenty-seven, twenty-five and forty-six treatment cohorts respectively, at intake levels ranging from 0.2 g EPA+DHA/d to 7.0 g EPA+DHA/d. Most studies, particularly those with the highest quality study design, have found no effects on these immune markers. Significant effects on lymphocyte proliferation are decreased responses in seven of eight cohorts, particularly in older subjects. The direction of the significant changes in cytokine production by lymphocytes is inconsistent and only found at supplementation levels > or =2.0 g EPA+DHA/d. Significant changes in inflammatory cytokine production by monocytes are decreases in their production in all instances. Overall, these studies fail to reveal strong dose-response effects of EPA+DHA on the outcomes measured and suggest that healthy subjects are relatively insensitive to immunomodulation with long-chain n-3 PUFA, even at intake levels that substantially raise their concentrations in phospholipids of immune cells. In patients with inflammatory conditions cytokine concentrations or production are influenced by EPA+DHA supplementation in a relatively large number of studies. Some of these studies suggest that local effects at the site of inflammation might be more pronounced than systemic effects and disease-related markers are more sensitive to the immunomodulatory effects, indicating that the presence of inflamed tissue or 'sensitised' immune cells in inflammatory disorders might increase sensitivity to the immunomodulatory effects of long-chain n-3 PUFA. In a substantial number of these studies clinical benefits related to the inflammatory state of the condition have been observed in the absence of significant effects on immune markers of inflammation. This finding suggests that condition-specific clinical end points might be more sensitive markers of modulation by EPA+DHA than cytokines. In general, the direction of immunomodulation in healthy subjects (if any) and in inflammatory conditions is the same, which indicates that studies in healthy subjects are a useful tool to describe the general principles of immunomodulation by n-3 PUFA. However, the extent of the effect might be very different in inflammatory conditions, indicating that studies in healthy subjects are not particularly suitable for establishing dose levels for specific applications in inflammatory conditions. The reviewed studies provide no indications that the immunomodulatory effects of long-chain n-3 PUFA impair immune function or infectious disease resistance. In contrast, in some conditions the immunomodulatory effects of EPA+DHA might improve immune function.

Omega-3 polyunsaturated fatty acids affect lipopolysaccharide-induced maturation of dendritic cells through mitogen-activated protein kinases p38

OBJECTIVE

The omega-3 polyunsaturated fatty acids (PUFAs) play a key role as immune response modulators and suppressors of immunologic functions, such as lymphocyte proliferation, cytokine production, and cell surface molecular expression in T lymphocytes, monocytes, and natural killer cells. However, little is known about the effect of omega-3 PUFAs on dendritic cells (DCs). We studied the effect of omega-3 PUFAs on DCs and the related intracellular signal transduction pathway.

METHODS

Dendritic cells were generated from human peripheral blood monocytes in the presence of granulocyte-macrophage colony-stimulating factors and interleukin (IL)-4 and treated with eicosapentaenoic acid (EPA), docosahexanoic acid (DHA), and stearic acid for 24 h. Lipopolysaccharide (LPS) was used for maturation of the DCs. The expressions of CD40, CD80, CD86, and human leukocyte antigen-DR (HLA-DR) were analyzed by flow cytometry; production of IL-12 and tumor necrosis factor-alpha were detected by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. The proliferative ability of allogeneic T cells stimulated by DCs was evaluated by tritiated thymidine ((3)H-TdR). Western blot analysis of p38 mitogen-activated protein kinase was conducted.

RESULTS

The omega-3 PUFAs reduced expression levels of costimulatory molecules CD80 and CD86 and major histocompatibility complex HLA-DR. IL-12 and tumor necrosis factor-alpha levels decreased significantly in the EPA and DHA groups. EPA and DHA also significantly reduced the proliferative ability of allogeneic T cells stimulated by DCs. The omega-3 PUFAs significantly inhibited LPS-induced p38 phosphorylation.

CONCLUSION

The omega-3 PUFAs may inhibit LPS-induced DC maturation and upregulate cytokine production. Impaired p38 mitogen-activated protein kinase activity is a potential critical intracellular signaling transduction mechanism.

Comparison of the effects of linseed oil and different doses of fish oil on mononuclear cell function in healthy human subjects

Studies on animal and human subjects have shown that greatly increasing the amount of linseed (also known as flaxseed) oil (rich in the n−3 polyunsaturated fatty acid (PUFA) α-linolenic acid (ALNA)) or fish oil (FO; rich in the long-chain n−3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) in the diet can decrease a number of markers of immune function. The immunological effects of more modest doses of n−3 PUFA in human subjects are unclear, dose–response relationships between n−3 PUFA supply and immune function have not been established and whether ALNA has the same effects as its long-chain derivatives is not known. Therefore, the objective of the present study was to determine the effect of enriching the diet with different doses of FO or with a modest dose of ALNA on a range of functional responses of human monocytes and lymphocytes. In a randomised, placebo-controlled, double-blind, parallel study, forty healthy males aged 18–39 years were randomised to receive placebo or 3·5 g ALNA/d or 0·44, 0·94 or 1·9 g (EPA+DHA)/d in capsules for 12 weeks. The EPA:DHA ratio in the FO used was 1·0:2·5. ALNA supplementation increased the proportion of EPA but not DHA in plasma phospholipids. FO supplementation decreased the proportions of linoleic acid and arachidonic acid and increased the proportions of EPA and DHA in plasma phospholipids. The interventions did not alter circulating mononuclear cell subsets or the production of tumour necrosis factor-α, interleukin (IL) 1β, IL-2, IL-4, IL-10 or interferon-γ by stimulated mononuclear cells. There was little effect of the interventions on lymphocyte proliferation. The two higher doses of FO resulted in a significant decrease in IL-6 production by stimulated mononuclear cells. It is concluded that, with the exception of IL-6 production, a modest increase in intake of either ALNA or EPA+DHA does not influence the functional activity of mononuclear cells. The threshold of EPA+DHA intake that results in decreased IL-6 production is between 0·44 and 0·94 g/d.

Fish oil ameliorates the allograft arteriosclerosis of intestine on rats

Fish oil had been shown to have an immunomodulating effect and had favorable effect on the pathogenesis of atherosclerosis. The aim of this study was to estimate the effect of fish oil on the graft arteriosclerosis and graft immune response after rat allogenic small intestinal transplantation. Since two wk pretransplantation, the Lewis rats were supplemented by gavage with: (i) phosphate buffer saline, 0.6% volume of body weight (V/W), as control group; (ii) fish oil (0.6%, V/W); (iii) fish oil (0.3%, V/W). Total intestine from donor F344 was heterotopically transplanted into the Lewis recipient. The recipient rats were killed on the 60th day post-transplantation. The cytokine levels, the activity of NF-kappa B and the arteriosclerosis of grafts were analyzed. Intragastrical supplementation with 0.6% fish oil induced pronounced inhibition of the pro-inflammtory cytokine expression of interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, and the increase of anti-inflammtory cytokine expression of IL-10 in graft. Suppression of the TNF-alpha and IL-6 expression by fish oil was attributed to its inhibitory effect on NF-kappaB activation. Intragastric 0.6% fish oil infusion ameliorated the development of graft arteriosclerosis. Fish oil was therefore considered to have an immunosuppressive effect on rat allogenic small intestinal transplant model based on the intra-graft IL-6, TNF-alpha and IL-10 levels. It might result in ameliorating the arteriosclerosis of the grafts.

Effect of docosahexaenoic acid-rich fish oil supplementation on human leukocyte function

BACKGROUND

The effect of a docosahexaenoic acid (DHA)-rich fish oil (FO) supplementation on human leukocyte function was investigated.

METHODS

Ten male volunteers were supplemented with 3g/day FO containing 26% eicosapentaenoic acid (EPA, 20:5, n-3) and 54% DHA (22:6, n-3) for 2 months.

RESULTS

FO supplementation changed the fatty acid (FA) composition of leukocytes resulting in an increase of n-3/n-6 ratio from 0.18 to 0.62 in lymphocytes and from 0.15 to 0.70 in neutrophils. DHA-rich FO stimulated an increase in phagocytic activity by 62% and 145% in neutrophils and monocytes, respectively. Neutrophil chemotactic response was increased by 128%. The rate of production of reactive oxygen species by neutrophils was also increased, as it was with lymphocyte proliferation. These changes were partially reversed after a 2-month wash out period. With respect to cytokine production by lymphocytes, interleukin (IL)-4 release was not altered, whereas secretions of IL-10, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were raised. These results are in contrast to those described by others using EPA-rich FO supplementation. Lymphocyte pleiotropic gene expression was analyzed by a macroarray technique. Of the analyzed genes (588 in total), 77 were modified by the supplementation. FO supplementation resulted in up-regulation of 6 genes (GATA binding protein 2, IL-6 signal transducer, transforming growth factor alpha, TNF, heat shock 90kDa protein 1-alpha and heat shock protein 70kDa 1A) and a down regulation of 71 genes (92.2% of total genes changed). The largest functional group of altered genes was that related to signaling pathways (22% of the total modified genes).

CONCLUSIONS

Therefore, although EPA and DHA are members of n-3 FA family, changes in the proportion of DHA and EPA exert different effects on neutrophil, monocyte and lymphocyte function, which may be a result of specific changes in gene expression.

Omega-3 Fatty Acids as Adjunctive Therapy in Crohns Disease

Crohns disease is an inflammatory bowel disease that can have a significant impact on the health of those afflicted. The etiology of the disease is unknown, but genetic, environmental, dietary, and immunological factors are thought to be involved. Multiple nutrients can become depleted during active disease due to inadequate intake or malabsorption. Preventing these deficiencies is paramount in the care of those suffering from Crohns disease. Often the traditional treatments (medications) have limited effectiveness and negative side effects that inhibit their use. Enteral nutrition has promising therapeutic benefits, but its use is often limited to the pediatric population due to poor patient acceptability. Omega-3 fatty acids have been investigated for their anti-inflammatory properties as an alternative to traditional care. This article reviews the etiology of Crohns disease, nutritional deficiencies, traditional treatments, and the use of omega-3 fatty acids in the prevention of Crohns recurrence. The results from clinical trials have been conflicting, but a new fish oil preparation that limits the side effects of traditional fish oil therapy shows promise as an adjunctive treatment for Crohns disease. Continued research is needed to validate these findings.

Natural health products, modulation of immune function and prevention of chronic diseases

The immune system is increasingly found to be involved in the development of several chronic illnesses, for which allopathic medicine has provided limited tools for treatment and especially prevention. In that context, it appears worthwhile to target the immune system in order to modulate the risk of certain chronic illnesses. Meanwhile, natural health products (NHPs) are generating renewed interest, particularly in the prevention and treatment of several chronic diseases. Over 20 scientists from fields related to immune function and NHPs were thus convened to establish the state of knowledge on these subjects and to explore future research directions. This review summarizes the result of discussions held during the symposium. It thus seeks to be thought provoking rather than to comprehensively cover such broad areas of research. Notably, a brief overview of the immune system is presented, including potentially useful targets and strategies to keep it in an equilibrated state, in order to prevent certain disorders. The pertinence and limitations of targeting the immune system to prevent chronic diseases is also discussed. The paper then discusses the usefulness and limitations of current experimental tools available to study the immune modulating effects of NHPs. Finally, a concise review of some of the most studied NHPs showing promising immunomodulatory activity is given, and avenues for future research are described.

Nutritional Intervention With Omega-3 Fatty Acids in a Case of Malignant Fibrous Histiocytoma of the Lungs

We present a case of a 78-yr-old man with malignant fibrous histiocytoma with multiple lesions in both lungs. Following diagnosis, he declined conventional chemotherapy and elected nutritional intervention by increasing intake of omega-3 fatty acids and lowering intake of omega-6 fatty acids. We estimated that he consumed 15 g of the long-chain omega-3 fatty acids eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) per day, and the ratio of linoleic acid/long-chain omega-3 fatty acids in his diet was 0.81. Serial computed tomography scans and pulmonary x-rays revealed remarkably a slow and steady decrease in the size and number of bilateral nodules. He has no apparent side effects from consuming large quantities of fish and algae oils rich in DHA and EPA and he remains asymptomatic.

Fish consumption: recommendations versus advisories, can they be reconciled?

Consumption of at least two servings of fish per week is recommended by the American Heart Association (AHA) to achieve cardio-protective effects. However, some fish are contaminated with methylmercury, which may counteract the positive effect of the omega-3 fatty acids, and numerous governments have issued advisories for certain fish species. These mixed messages may be a source of confusion to the consumer and to the health professional. This paper reviews whether it is possible to follow the AHA recommendation for fish consumption while avoiding the risks associated with consuming mercury in amounts in excess of government thresholds.

Food components and immune function

PURPOSE OF REVIEW

Enhancing immune function or alternatively dampening inflammatory processes by specific food components has received a lot of interest. The purpose of this review is to summarize recent findings with the emphasis on underlying mechanisms.

RECENT FINDINGS

Dietary beta-glucans are relatively new candidates in the field of immune modulation by diet. In-vitro and animal studies suggest that beta-glucans shift inflammatory profiles to a Th1 type, which may enhance resistance against bacterial and parasitic infections. Regarding polyunsaturated fatty acids, there is evidence that n-3 fatty acids from fish oils (eicosapentaenoic acid and docosahexaenoic acid) dampen inflammatory responses. Whether eicosapentaenoic acid or docosahexaenoic acid is responsible for this phenomenon remains controversial. It is also inconclusive whether the plant-derived n-3 fatty acid alpha-linolenic acid has the same antiinflammatory effects as observed for fish oils. Saturated fatty acids may activate toll-like receptors and consequently the inflammatory pathway. The effect of total fat intake is controversial, since high-fat diets have been found to suppress immune function, while also improving intestinal barrier function. Finally, Gingko biloba was found to lower nuclear factor kappaB and activator protein 1 activation, possibly due to its high content of polyphenols.

SUMMARY

In this review we discuss the nutritional components able to enhance immune function or show antiinflammatory effects. It can be concluded that diet certainly has the potential to direct immune responses. Apart from studies on fish oils, however, evidence from human studies is limited.

Effects of EPA and DHA on proliferation, cytokine production, and gene expression in Raji cells

The effects of EPA and DHA on the function and gene expression of a B-lymphocyte cell line (Raji) were investigated. Proliferation; production of interleukin-10 (IL-10), tumor necrosis factor (TNF)-alpha, and interferon (INF)-gamma; and expression of pleiotropic genes were evaluated. Cell proliferation was increased in the presence of 12.5 microM EPA (approximately twofold) and 12.5 microM DHA (approximately 1.5-fold). EPA and DHA (25 microM) also decreased production of the key immunoregulatory cytokines IL-10, TNF-alpha, and INF-gamma. EPA and DHA changed the expression of specific genes, but this effect was more marked for EPA (25.9% of genes investigated) compared with DHA (8.4% of genes investigated). EPA and DHA affected the expression of genes clustered as: cytokines, signal transduction, transcription, cell cycle, defense and repair, apoptosis, cell adhesion, cytoskeleton, and hormones. The most remarkable changes were observed in the genes of signal transduction and transcription. These results led us to conclude that the mechanism of DHA and EPA effects on B-lymphocyte functions includes regulation of gene expression. Thus, the ingestion of fish oil, a rich source of EPA and DHA, may have a strong effect on B-lymphocyte function in vivo. However, remarkable differences were observed between DHA and EPA, demonstrating that specific effects of these FA may be responsible for the marked differences in edible oil effects on immune function in vivo reported by others.

Fatty acids and the immune system: from basic science to clinical applications

Over the last 25 years, the effects of fatty acids on the immune system have been characterized using in vitro, animal and human studies. Advances in fatty acid biochemistry and molecular techniques have recently suggested new mechanisms by which fatty acids could potentially modify immune responses, including modification of the organization of cellular lipids and interaction with nuclear receptors. Possibilities for the clinical applications of n-3 PUFA are now developing. The present review focuses on the hypothesis that the anti-inflammatory properties of n-3 PUFA in the arterial wall may contribute to the protective effects of n-3 PUFA in CVD, as suggested by epidemiological and secondary prevention studies. Studies are just beginning to show that dietary n-3 PUFA can be incorporated into plaque lipid in human subjects, where they may influence the morphology and stability of the atherosclerotic lesion.

Fish and shellfish as dietary sources of methylmercury and the omega-3 fatty acids, eicosahexaenoic acid and docosahexaenoic acid: risks and benefits

Fish and shellfish supply the human diet with not only complex nutrients including the omega-3 fatty acids, but also highly toxic chemicals including methylmercury. The dietary essential fatty acids are linoleic and alpha-linolenic acid. Two omega-3 fatty acids with longer carbon chains, eicosahexaenoic acid (EPA) and docosahexaenoic acid (DHA), can be synthesized in humans from alpha-linolenic precursors. Though not required in the diet per se, EPA and DHA have important roles in metabolism. The almost exclusive source of preformed dietary DHA is fish and shellfish. These foods are also an important source of EPA. In marked contrast to the benefits of fish and shellfish as sources of preformed omega-3 fatty acids, fish and shellfish are almost exclusively the dietary source of methylmercury. Fortunately, these chemicals are not uniformly distributed across many species of fish and shellfish. The purpose of this article is to provide information on the comparative distribution of these chemicals and nutrients to help groups formulating dietary recommendations.