Effects of dietary arachidonic acid on human immune response

Serum 25-hydroxyvitamin D and fatty acids in relation to the risk of microbial infections in children: The TRIGR Divia study

BACKGROUND & AIMS

Nutrient status may affect the risk of microbial infections and play a role in modulating the immune response against such infections. The aim of this study was to determine whether serum 25-hydroxyvitamin D [25(OH)D] and serum fatty acids in infancy are associated with microbial infections by the age of 18 months.

METHODS

Altogether 576 newborn infants from Trial to Reduce IDDM in the Genetically at Risk (TRIGR) born between 2002 and 2007 were included. The concentration of 25(OH)D vitamin and proportions of 26 fatty acids (presented as % of total fatty acids) were analyzed in cord blood serum and in sera taken at 6, 12, and 18 months of age. The cord blood samples and mean of 6-18-month values were used as exposures. Infections were detected by screening IgG antibodies against 10 microbes using enzyme immunoassay and antibodies against 6 coxsackievirus B serotypes by plaque neutralization assay in serum samples taken at 18 months of age.

RESULTS

A higher proportion of n-3 polyunsaturated fatty acids (PUFAs) and especially long-chain n-3 PUFAs at birth and at the age of 6-18 months was associated with decreased risk of coxsackievirus B2 infection unadjusted and adjusted for region, case-control status, and maternal type 1 diabetes. Higher proportion of docosapentaenoic acid (DPA, 22:5 n-3) at birth was associated with a decreased risk of respiratory syncytial virus infection. 25(OH)D vitamin concentration was not consistently associated with the risk of infections. When only infected children were included docosahexaenoic acid (DHA, 22:6 n-3) and arachidonic acid (20:4 n-6) proportions were positively associated with IgG antibody levels against influenza A virus. 25(OH)D vitamin concentration showed an inverse association with rotavirus IgG levels among children with rotavirus seropositivity.

CONCLUSIONS

In young children with increased susceptibility to type 1 diabetes, long-chain n-3 PUFAs may influence the risk of viral infections and immune response against the infections. However, this association may depend on the type of virus suggesting virus-specific effects.

SARS-CoV-2 vaccines: What we know, what we can do to improve them and what we could learn from other well-known viruses

In recent weeks, the rate of SARS-CoV-2 infections has been progressively increasing all over the globe, even in countries where vaccination programs have been strongly implemented. In these regions in 2021, a reduction in the number of hospitalizations and deaths compared to 2020 was observed. This decrease is certainly associated with the introduction of vaccination measures. The process of the development of effective vaccines represents an important challenge. Overall, the breakthrough infections occurring in vaccinated subjects are in most cases less severe than those observed in unvaccinated individuals. This review examines the factors affecting the immunogenicity of vaccines against SARS-CoV-2 and the possible role of nutrients in modulating the response of distinct immune cells to the vaccination.

Metabolomic and transcriptomic signatures of influenza vaccine response in healthy young and older adults

Seasonal influenza causes mild to severe respiratory infections and significant morbidity, especially in older adults. Transcriptomic analysis in populations across multiple flu seasons has provided insights into the molecular determinants of vaccine response. Still, the metabolic changes that underlie the immune response to influenza vaccination remain poorly characterized. We performed untargeted metabolomics to analyze plasma metabolites in a cohort of younger and older subjects before and after influenza vaccination to identify vaccine-induced molecular signatures. Metabolomic and transcriptomic data were combined to define networks of gene and metabolic signatures indicative of high and low antibody response in these individuals. We observed age-related differences in metabolic baselines and signatures of antibody response to influenza vaccination and the abundance of α-linolenic and linoleic acids, sterol esters, fatty-acylcarnitines, and triacylglycerol metabolism. We identified a metabolomic signature associated with age-dependent vaccine response, finding increased tryptophan and decreased polyunsaturated fatty acids (PUFAs) in young high responders (HRs), while fatty acid synthesis and cholesteryl esters accumulated in older HRs. Integrated metabolomic and transcriptomic analysis shows that depletion of PUFAs, which are building blocks for prostaglandins and other lipid immunomodulators, in young HR subjects at Day 28 is related to a robust immune response to influenza vaccination. Increased glycerophospholipid levels were associated with an inflammatory response in older HRs to flu vaccination. This multi-omics approach uncovered age-related molecular markers associated with influenza vaccine response and provides insight into vaccine-induced metabolic responses that may help guide development of more effective influenza vaccines.

Dietary intake and biomarkers of linoleic acid and mortality: systematic review and meta-analysis of prospective cohort studies

BACKGROUND

Current evidence on associations between intakes of linoleic acid (LA), the predominant n-6 (ω-6) fatty acid, and mortality is inconsistent and has not been summarized by a systematic review and meta-analysis.

OBJECTIVE

The aim was to perform a systematic review and meta-analysis of prospective cohort studies to examine associations between LA intake and mortality.

METHODS

We conducted a comprehensive search of MEDLINE and EMBASE databases through 31 July 2019 for prospective cohort studies reporting associations of LA (assessed by dietary surveys and/or LA concentrations in adipose tissue or blood compartments) with mortality from all causes, cardiovascular disease (CVD), and cancer. Multivariable-adjusted RRs were pooled using random-effects meta-analysis.

RESULTS

Thirty-eight studies reporting 44 prospective cohorts were identified; these included 811,069 participants with dietary intake assessment (170,076 all-cause, 50,786 CVD, and 59,684 cancer deaths) and 65,411 participants with biomarker measurements (9758 all-cause, 6492 CVD, and 1719 cancer deaths). Pooled RRs comparing extreme categories of dietary LA intake (high vs low) were 0.87 (95% CI: 0.81, 0.94; I2 = 67.9%) for total mortality, 0.87 (95% CI: 0.82, 0.92; I2 = 3.7%) for CVD mortality, and 0.89 (95% CI: 0.85, 0.93; I2 = 0%) for cancer mortality. Pooled RRs for each SD increment in LA concentrations in adipose tissue/blood compartments were 0.91 (95% CI: 0.87, 0.95; I2 = 64.1%) for total mortality, 0.89 (95% CI: 0.85, 0.94; I2 = 28.9%) for CVD mortality, and 0.91 (95% CI: 0.84, 0.98; I2 = 26.3%) for cancer mortality. Meta-regressions suggested baseline age and dietary assessment methods as potential sources of heterogeneity for the association between LA and total mortality.

CONCLUSIONS

In prospective cohort studies, higher LA intake, assessed by dietary surveys or biomarkers, was associated with a modestly lower risk of mortality from all causes, CVD, and cancer. These data support the potential long-term benefits of PUFA intake in lowering the risk of CVD and premature death.

Dietary fats and cardiometabolic disease: mechanisms and effects on risk factors and outcomes

The effect of dietary fats on cardiometabolic diseases, including cardiovascular diseases and type 2 diabetes mellitus, has generated tremendous interest. Many earlier investigations focused on total fat and conventional fat classes (such as saturated and unsaturated fats) and their influence on a limited number of risk factors. However, dietary fats comprise heterogeneous molecules with diverse structures, and growing research in the past two decades supports correspondingly complex health effects of individual dietary fats. Moreover, health effects of dietary fats might be modified by additional factors, such as accompanying nutrients and food-processing methods, emphasizing the importance of the food sources. Accordingly, the rapidly increasing scientific findings on dietary fats and cardiometabolic diseases have generated debate among scientists, caused confusion for the general public and present challenges for translation into dietary advice and policies. This Review summarizes the evidence on the effects of different dietary fats and their food sources on cell function and on risk factors and clinical events of cardiometabolic diseases. The aim is not to provide an exhaustive review but rather to focus on the most important evidence from randomized controlled trials and prospective cohort studies and to highlight current areas of controversy and the most relevant future research directions for understanding how to improve the prevention and management of cardiometabolic diseases through optimization of dietary fat intake.

Comparison of different dietary sources of n-3 polyunsaturated fatty acids on immune response in broiler chickens

The study aims to research the effects of varied dietary sources of n-3 polyunsaturated fatty acids (PUFA) on the immune response in broiler chickens with stress on natural killer (NK) cell activity. Diets supplemented with one of the four sources of n-3 PUFA: linseed oil-, echium oil-, fish oil (FO) or algal biomass-enriched diets at levels of 18, 18, 50 and 15 g/kg fresh weight, were provided for one-d-old male Ross 308 broilers, totaling 340 in number, until they were slaughtered. The analyses included total lipid profile using gas chromatography (GC) for plasma, spleen, thymus, and blood. Additionally, NK cell activity and cell proliferation were investigated for thymocytes and splenocytes. The results indicated that the source of n-3 PUFA had a strong influence on fatty acid composition across all tissues. NK activity was highest in splenocytes and PBMCs from broilers fed linseed oil, followed by those fed algal biomass or echium oil, and lowest for those from broilers fed FO. The proliferative response of lymphocytes from algal biomass-fed chickens tended to be the highest, followed by those fed linseed oil in most cases. Lymphocytes from chickens fed fish oil showed the lowest proliferative response. These results could mean that a docosahexaenoic acid (DHA)-rich algal product might enrich chicken meat with n-3 PUFA without significant damaging effects on chicken immunity.

Interaction between dietary fatty acids and genotype on immune response in Atlantic salmon (Salmo salar) after vaccination: A transcriptome study

A pivotal matter to aquaculture is the sourcing of sustainable resources as ingredients to aquafeeds. Levels of plant delivered oils as source of fatty acids (FA) in aquafeeds have reached around 70% resulting in reduced levels of long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in salmon fillet composition. EPA and DHA can modulate inflammation and immune response, so it is crucial to understand how fish immune response is affected by low LC n-3 PUFA diet and if this diet can have a detrimental effect on vaccine response. Atlantic salmon (Salmo salar) can produce EPA/DHA from α-linolenic acid (ALA) and this endogenous capacity can be explored to develop families with higher tolerance to low LC n-3 PUFA diets. Here we analyze innate and adaptive immune response in Atlantic salmon to a commercial vaccine after being fed low levels of EPA and DHA, and we also compare three strains of salmon selected by their endogenous capacity of synthesizing LC- n-3 PUFA. A total of 2,890 differentially expressed genes (DEGs) were identified (p-value adjusted < 0.1) when comparing vaccinated fish against control non-vaccinated. Gene ontology (GO) and KEGG analysis with 442 up/downregulated genes revealed that most DEGs were both related to immune response as well as part of important immune related pathways, as "Toll-like receptor" and "Cytokine-Cytokine interaction". Adaptive response was also addressed by measuring antigen specific IgM, and titers were significantly higher than in the pre-immune fish at 62 days post-immunization. However, diet and strain had no/little effect on vaccine-specific IgM or innate immune responses. Atlantic salmon therefore display robustness in its response to vaccination even when feed low levels of LC n-3 PUFA.

The gut mucosal barrier of zebrafish (Danio rerio) responds to the time-restricted delivery of Lobosphaera incisa-enriched diets

Recent studies in mammalian models revealed compelling evidence that along with the intrinsic characteristics of diets, the time of their delivery could have a profound impact on their benefits. In this study, we explored a time-dependent modulation of the gut mucosal barrier by delivering diets enriched with the green microalga (Lobosphaera incisa) either in a time-restricted regime or randomly to zebrafish (Danio rerio). The basal diet was enriched with microalgal biomass through two inclusion levels (i.e., 10% and 15% w/w), and the feeding trial lasted for six weeks. The control group was fed with the basal diet. After collection of tissue samples at week 6, the remaining fish were challenged by intraperitoneal injection of Streptococcus inaie. A histological analysis of the gut structure revealed that the fish that received the microalgae randomly exhibited shorter villi length. Genes coding for immunity were modulated in the gut by dietary treatments. Notably, the transcript levels of lysozyme, β-defensin and hepcidin were significantly higher in the group subjected to the time-restricted feeding regime. Dietary microalgae affected the fatty acid content in the gut, particularly the level of arachidonic acid (ARA), and the time-restricted feeding influenced its accumulation. Groups that received diets enriched with 15% microalgae, regardless of the feeding strategy, displayed a significantly higher resistance to S. inaie 16 days post-infection, though differences between the delivery strategies were pronounced during the early stage of infection. In conclusion, the dietary inclusion of L. incisa modulated some of the features of the gut mucosal barrier of zebrafish, and the time of delivery appeared to have a considerable influence on immunomodulatory functions.

A systematic review of the effects of increasing arachidonic acid intake on PUFA status, metabolism and health-related outcomes in humans

We conducted a systematic review of randomised controlled trials (RCT) of increased intake of arachidonic acid (ARA) on fatty acid status and health outcomes in humans. We identified twenty-two articles from fourteen RCT. Most studies were conducted in adults. These used between 80 and 2000 mg ARA per d and were of 1-12 weeks duration. Supplementation with ARA doses as low as 80 mg/d increased the content of ARA in different blood fractions. Overall there seem to be few marked benefits for adults of increasing ARA intake from the typical usual intake of 100-200 mg/d to as much as 1000 mg/d; the few studies using higher doses (1500 or 2000 mg/d) also report little benefit. However, there may be an impact of ARA on cognitive and muscle function which could be particularly relevant in the ageing population. The studies reviewed here suggest no adverse effects in adults of increased ARA intake up to at least 1000-1500 mg/d on blood lipids, platelet aggregation and blood clotting, immune function, inflammation or urinary excretion of ARA metabolites. However, in many areas there are insufficient studies to make firm conclusions, and higher intakes of ARA are deserving of further study. Based on the RCT reviewed, there are not enough data to make any recommendations for specific health effects of ARA intake.

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.

Potential Roles of n-3 PUFAs during Skeletal Muscle Growth and Regeneration

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), which are commonly found in fish oil supplements, are known to possess anti-inflammatory properties and more recently alter skeletal muscle function. In this review, we discuss novel findings related to how n-3 PUFAs modulate molecular signaling responsible for growth and hypertrophy as well as the activity of muscle stem cells. Muscle stem cells commonly known as satellite cells, are primarily responsible for driving the skeletal muscle repair process to potentially damaging stimuli, such as mechanical stress elicited by exercise contraction. To date, there is a paucity of human investigations related to the effects of n-3 PUFAs on satellite cell content and activity. Based on current in vitro investigations, this review focuses on novel mechanisms linking n-3 PUFA’s to satellite cell activity and how they may improve muscle repair. Understanding the role of n-3 PUFAs during muscle growth and regeneration in association with exercise could lead to the development of novel supplementation strategies that increase muscle mass and strength, therefore possibly reducing the burden of muscle wasting with age.

Dietary omega-6, but not omega-3, polyunsaturated or saturated fatty acids increase inflammation in primary lung mesenchymal cells

Obesity is an important risk factor for developing severe asthma. Dietary fatty acids, which are increased in sera of obese individuals and after high-fat meals, activate the innate immune system and induce inflammation. This study investigated whether dietary fatty acids directly cause inflammation and/or synergize with obesity-induced cytokines in primary human pulmonary fibroblasts in vitro. Fibroblasts were challenged with BSA-conjugated fatty acids [ω-6 polyunsaturated fatty acids (PUFAs) and ω-3 PUFAs or saturated fatty acids (SFAs)], with or without TNF-α, and release of the proinflammatory cytokines, IL-6 and CXCL8, was measured. We found that the ω-6 PUFA arachidonic acid (AA), but not ω-3 PUFAs or SFAs, upregulates IL-6 and CXCL8 release. Combined AA and TNF-α challenge resulted in substantially greater cytokine release than either alone, demonstrating synergy. Synergistic upregulation of IL-6, but not CXCL8, was mainly mediated via cyclooxygenase (COX). Inhibition of p38 MAPK reduced CXCL8 release, induced by AA and TNF-α alone, but not in combination. Synergistic CXCL8 release, following AA and TNF-α challenge, was not medicated via a single signaling pathway (MEK1, JNK, phosphoinositide 3-kinase, and NF-κB) nor by hyperactivation of NF-κB or p38. To investigate if these findings occur in other airway cells, effects of AA in primary human airway smooth muscle (ASM) cells and human bronchial epithelial cells were also investigated. We found proinflammatory effects in ASM cells but not epithelial cells. This study suggests that diets rich in ω-6 PUFAs might promote airway inflammation via multiple pathways, including COX-dependent and -independent pathways, and in an obese person, may lead to more severe airway inflammation.

Arachidonic acid supplementation modulates blood and skeletal muscle lipid profile with no effect on basal inflammation in resistance exercise trained men

Arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA), is the metabolic precursor to the eicosanoid family of lipid mediators. Eicosanoids have potent pro-inflammatory actions, but also act as important autocrine/paracrine signaling molecules in skeletal muscle growth and development. Whether dietary ARA is incorporated into skeletal muscle phospholipids and the resulting impact on intramuscular inflammatory and adaptive processes in-vivo is not known. In the current study, resistance trained men (≥1 year) received dietary supplementation with 1.5g/day ARA (n=9, 24 ± 1.5 years) or placebo (n=10, 26 ± 1.3 years) for 4-weeks while continuing their normal training regimen. Plasma and vastus lateralis muscle biopsies were collected in an overnight fasted state at baseline and week 4. ARA supplementation increased plasma content of ARA and gamma-linolenic acid, while decreasing relative abundance of linoleic acid, eicosapentaenoic acid, and dihomo-gamma-linolenic acid. In skeletal muscle, ARA and dihomo-gamma-linolenic acid content increased, whereas alpha-linolenic-acid was reduced. Compared to placebo, ARA supplementation reduced circulating platelet and monocyte number, and decreased the mRNA expression of the immune cell surface markers; neutrophil elastase/CD66b and interleukin 1-beta, in peripheral blood mononuclear cells. In muscle, ARA supplementation increased mRNA expression of the myogenic regulatory factors; MyoD and myogenin, but had no effect on a range of immune cell markers or inflammatory cytokines. These data show that dietary ARA supplementation can rapidly and safely modulate plasma and muscle fatty acid profile and promote myogenic gene expression in resistance trained men, without a risk of increasing basal systemic or intramuscular inflammation.

Gamma-linolenic acid, Dihommo-gamma linolenic, Eicosanoids and Inflammatory Processes

Gamma-linolenic acid (GLA, 18:3n-6) is an omega-6 (n-6), 18 carbon (18C-) polyunsaturated fatty acid (PUFA) found in human milk and several botanical seed oils and is typically consumed as part of a dietary supplement. While there have been numerous in vitro and in vivo animal models which illustrate that GLA-supplemented diets attenuate inflammatory responses, clinical studies utilizing GLA or GLA in combination with omega-3 (n-3) PUFAs have been much less conclusive. A central premise of this review is that there are critical metabolic and genetic factors that affect the conversion of GLA to dihommo-gamma linolenic acid (DGLA, 20:3n-6) and arachidonic acid (AA, 20:4n-6), which consequently affects the balance of DGLA- and AA- derived metabolites. As a result, these factors impact the clinical effectiveness of GLA or GLA/(n-3) PUFA supplementations in treating inflammatory conditions. Specifically, these factors include: 1) the capacity for different human cells and tissues to convert GLA to DGLA and AA and to metabolize DGLA and AA to bioactive metabolites; 2) the opposing effects of DGLA and AA metabolites on inflammatory processes and diseases; and 3) the impact of genetic variations within the fatty acid desaturase (FADS) gene cluster, in particular, on AA/DGLA ratios and bioactive metabolites. We postulate that these factors influence the heterogeneity of results observed in GLA supplement-based clinical trials and suggest that "one-size fits all" approaches utilizing PUFA-based supplements may no longer be appropriate for the prevention and treatment of complex human diseases.

The Essentiality of Arachidonic Acid in Infant Development

Arachidonic acid (ARA, 20:4n-6) is an n-6 polyunsaturated 20-carbon fatty acid formed by the biosynthesis from linoleic acid (LA, 18:2n-6). This review considers the essential role that ARA plays in infant development. ARA is always present in human milk at a relatively fixed level and is accumulated in tissues throughout the body where it serves several important functions. Without the provision of preformed ARA in human milk or infant formula the growing infant cannot maintain ARA levels from synthetic pathways alone that are sufficient to meet metabolic demand. During late infancy and early childhood the amount of dietary ARA provided by solid foods is low. ARA serves as a precursor to leukotrienes, prostaglandins, and thromboxanes, collectively known as eicosanoids which are important for immunity and immune response. There is strong evidence based on animal and human studies that ARA is critical for infant growth, brain development, and health. These studies also demonstrate the importance of balancing the amounts of ARA and DHA as too much DHA may suppress the benefits provided by ARA. Both ARA and DHA have been added to infant formulas and follow-on formulas for more than two decades. The amounts and ratios of ARA and DHA needed in infant formula are discussed based on an in depth review of the available scientific evidence.

Efficacy and safety of arachidonic acid for treatment of school-age children in Schistosoma mansoni high-endemicity regions

Arachidonic acid (ARA), an omega-6 fatty acid, is a potent schistosomicide that displayed significant and safe therapeutic effects in Schistosoma mansoni-infected schoolchildren in S. mansoni low-prevalence regions. We here report on ARA efficacy and safety in treatment of schoolchildren in S. mansoni high-endemicity areas of Kafr El Sheikh, Egypt. The study was registered with ClinicalTrials.gov (NCT02144389). In total, 268 schoolchildren with light, moderate, or heavy S. mansoni infection were assigned to three study arms of 87, 91, and 90 children and received a single dose of 40 mg/kg praziquantel (PZQ), ARA (10 mg/kg per day for 15 days), or PZQ combined with ARA, respectively. The children were examined before and after treatment for stool parasite egg counts and blood biochemical, hematological, and immunological parameters. ARA, like PZQ, induced moderate cure rates (50% and 60%, respectively) in schoolchildren with light infection and modest cure rates (21% and 20%, respectively) in schoolchildren with high infection. PZQ and ARA combined elicited 83% and 78% cure rates in children with light and heavy infection, respectively. Biochemical and immunological profiles were either unchanged or ameliorated after ARA therapy. Combination of PZQ and ARA might be useful for treatment of children with schistosomiasis in high-endemicity regions.

LTC4 synthase polymorphism modifies efficacy of botanical seed oil combination in asthma

Botanical seed oils reduce the generation of leukotrienes in patients with asthma.

Our objective was to determine the efficacy of a botanical seed oil combination against airflow obstruction in asthma, and to determine the pharmacogenomic effect of the leukotriene C₄ synthase (LTC₄S) polymorphism A-444C.

We conducted a randomized, double-blind, placebo-controlled, cross-over clinical trial in mild to moderate asthmatics to determine the change in FEV₁ after 6 weeks of therapy with borage and echium seed oils versus corn oil placebo. We also examined the effect of the variant LTC₄S -444C allele on the change in lung function.

We did not identify a difference in FEV₁ in the study cohort as a whole (n = 28), nor in the group of A homozygotes. In the C allele carriers (n = 9), FEV₁ improved by 3% after treatment with borage and echium seed oils and declined by 4% after placebo corn oil (p = 0.02). All 9 C allele carriers demonstrated an improvement in their FEV₁ on active treatment compared to placebo as compared to only 7 out of 19 A allele homozygotes (p = 0.007). We observed transient differences in ex vivo leukotriene generation from circulating basophils and granulocytes. We did not observe significant differences in urinary LTE₄ levels.

We conclude that compared to corn oil, a combination of borage and echium seed oils improves airflow obstruction in mild to moderate asthmatics who carry the variant allele in the LTC₄S gene (A-444C). Botanical oil supplementation may have therapeutic potential in asthma if used in a personalized manner.

Trial registration: This trial was registered at http://www.clinicaltrials.gov as NCT00806442.

Circulating omega-6 polyunsaturated fatty acids and total and cause-specific mortality: the Cardiovascular Health Study

BACKGROUND

Although omega-6 polyunsaturated fatty acids (n-6 PUFA) have been recommended to reduce coronary heart disease (CHD), controversy remains about benefits versus harms, including concerns over theorized proinflammatory effects of n-6 PUFA. We investigated associations of circulating n-6 PUFA including linoleic acid (the major dietary PUFA), γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid, with total and cause-specific mortality in the Cardiovascular Health Study, a community-based U.S. cohort.

METHODS AND RESULTS

Among 2792 participants(aged ≥65 years) free of cardiovascular disease at baseline, plasma phospholipid n-6 PUFA were measured at baseline using standardized methods. All-cause and cause-specific mortality, and total incident CHD and stroke, were assessed and adjudicated centrally. Associations of PUFA with risk were assessed by Cox regression. During 34 291 person-years of follow-up (1992-2010), 1994 deaths occurred (678 cardiovascular deaths), with 427 fatal and 418 nonfatal CHD, and 154 fatal and 399 nonfatal strokes. In multivariable models, higher linoleic acid was associated with lower total mortality, with extreme-quintile hazard ratio =0.87 (P trend=0.005). Lower death was largely attributable to cardiovascular disease causes, especially nonarrhythmic CHD mortality (hazard ratio, 0.51; 95% confidence interval, 0.32-0.82; P trend=0.001). Circulating γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid were not significantly associated with total or cause-specific mortality (eg, for arachidonic acid and CHD death, the extreme-quintile hazard ratio was 0.97; 95% confidence interval, 0.70-1.34; P trend=0.87). Evaluated semiparametrically, linoleic acid showed graded inverse associations with total mortality (P=0.005). There was little evidence that associations of n-6 PUFA with total mortality varied by age, sex, race, or plasma n-3 PUFA. Evaluating both n-6 and n-3 PUFA, lowest risk was evident with highest levels of both.

CONCLUSIONS

High circulating linoleic acid, but not other n-6 PUFA, was inversely associated with total and CHD mortality in older adults.

Efficacy and safety of arachidonic acid for treatment of Schistosoma mansoni-infected children in Menoufiya, Egypt

Arachidonic acid (ARA), an omega-6 fatty acid, kills juvenile and adult schistosomes in vitro and displays highly significant and safe therapeutic effects in mice and hamsters infected with Schistosoma mansoni or S. haematobium. This study aims to examine the efficacy and safety of ARA in treatment of school-age children infected with S. mansoni. In total, 66 S. mansoni-infected schoolchildren (20-23 children/study arm) received a single dose of 40 mg/kg praziquantel (PZQ), ARA (10 mg/kg per day for 15 days), or PZQ combined with ARA. The children were examined before and after treatment for worm egg counts in stool and blood biochemical and immunological parameters. ARA proved to be as efficacious as PZQ in treatment of schoolchildren with low infection intensity (78% and 85% cure rates, respectively). For moderate-intensity infection, the ARA and PZQ combination led to 100% cure rate. Biochemical, hematological, and immunological parameters were either unchanged or ameliorated after ARA therapy.

The relationship between dietary fatty acids and inflammatory genes on the obese phenotype and serum lipids

Obesity, a chronic low-grade inflammatory condition is associated with the development of many comorbidities including dyslipidemia. This review examines interactions between single nucleotide polymorphisms (SNP) in the inflammatory genes tumor necrosis alpha (TNFA) and interleukin-6 (IL-6) and dietary fatty acids, and their relationship with obesity and serum lipid levels. In summary, dietary fatty acids, in particular saturated fatty acids and the omega-3 and omega-6 polyunsaturated fatty acids, impact the expression of the cytokine genes TNFA and IL-6, and alter TNFα and IL-6 production. In addition, sequence variants in these genes have also been shown to alter their gene expression and plasma levels, and are associated with obesity, measures of adiposity and serum lipid concentrations. When interactions between dietary fatty acids and TNFA and IL-6 SNPs on obesity and serum lipid were analyzed, both the quantity and quality of dietary fatty acids modulated the relationship between TNFA and IL-6 SNPs on obesity and serum lipid profiles, thereby impacting the association between phenotype and genotype. Researching these diet–gene interactions more extensively, and understanding the role of ethnicity as a confounder in these relationships, may contribute to a better understanding of the inter-individual variability in the obese phenotype.

Elevated immune-inflammatory signaling in mood disorders: a new therapeutic target?

Converging translational evidence has implicated elevated immune-inflammatory signaling activity in the pathoetiology of mood disorders, including major depressive disorder and bipolar disorder. This is supported in part by cross-sectional evidence for increased levels of proinflammatory eicosanoids, cytokines and acute-phase proteins during mood episodes, and prospective longitudinal evidence for the emergence of mood symptoms in response to chronic immune-inflammatory activation. In addition, mood-stabilizer and atypical antipsychotic medications downregulate initial components of the immune-inflammatory signaling pathway, and adjunctive treatment with anti-inflammatory agents augment the therapeutic efficacy of antidepressant, mood stabilizer and atypical antipsychotic medications. Potential pathogenic mechanisms linked with elevated immune-inflammatory signaling include perturbations in central serotonin neurotransmission and progressive white matter pathology. Both heritable genetic factors and environmental factors including dietary fatty-acid composition may act in concert to sustain elevated immune-inflammatory signaling. Collectively, these data suggest that elevated immune-inflammatory signaling is a mechanism that is relevant to the pathoetiology of mood disorders, and may therefore represent a new therapeutic target for the development of more effective treatments.

Design of foods with bioactive lipids for improved health

Numerous studies have found an association between the consumption of certain bioactive lipids and improved human health, e.g., the prevention, delay, or treatment of chronic and acute diseases, such as cancer, cardiovascular disease (CVD), osteoporosis, and immune disorders. In this review, we discuss food-based sources and potential beneficial attributes of major dietary bioactive lipids: polyunsaturated fatty acids; carotenoids; phytosterols and phytostanols; and fat-soluble vitamins. We summarize the various challenges associated with incorporating these bioactive lipids into foods and beverages, such as poor water solubility, high melting point, and low chemical stability. Finally, we propose several techniques that have been used to solve the challenges and integrate dietary bioactive lipids into foods for improved health.

Markers of endogenous desaturase activity and risk of coronary heart disease in the CAREMA cohort study

Background

Intakes of n-3 polyunsaturated fatty acids (PUFAs), especially EPA (C20∶5n-3) and DHA (C22∶6n-3), are known to prevent fatal coronary heart disease (CHD). The effects of n-6 PUFAs including arachidonic acid (C20∶4n-6), however, remain unclear. δ-5 and δ-6 desaturases are rate-limiting enzymes for synthesizing long-chain n-3 and n-6 PUFAs. C20∶4n-6 to C20∶3n-6 and C18∶3n-6 to C18∶2n-6 ratios are markers of endogenous δ-5 and δ-6 desaturase activities, but have never been studied in relation to incident CHD. Therefore, the aim of this study was to investigate the relation between these ratios as well as genotypes of FADS1 rs174547 and CHD incidence.

Methods

We applied a case-cohort design within the CAREMA cohort, a large prospective study among the general Dutch population followed up for a median of 12.1 years. Fatty acid profile in plasma cholesteryl esters and FADS1 genotype at baseline were measured in a random subcohort (n = 1323) and incident CHD cases (n = 537). Main outcome measures were hazard ratios (HRs) of incident CHD adjusted for major CHD risk factors.

Results

The AA genotype of rs174547 was associated with increased plasma levels of C204n-6, C20∶5n-3 and C22∶6n-3 and increased δ-5 and δ-6 desaturase activities, but not with CHD risk. In multivariable adjusted models, high baseline δ-5 desaturase activity was associated with reduced CHD risk (P for trend = 0.02), especially among those carrying the high desaturase activity genotype (AA): HR (95% CI) = 0.35 (0.15–0.81) for comparing the extreme quintiles. High plasma DHA levels were also associated with reduced CHD risk.

Conclusion

In this prospective cohort study, we observed a reduced CHD risk with an increased C20∶4n-6 to C20∶3n-6 ratio, suggesting that δ-5 desaturase activity plays a role in CHD etiology. This should be investigated further in other independent studies.

Polyunsaturated fatty acids. Immunomodulators in older adults

The immune system tends to become less efficient as people age, and nutrition plays a significant role in older adults' immune responses. In particular, dietary fatty acids are precursors to important immune system components. Certain fatty acids, predominantly those that are polyunsaturated, also tend to decrease the risk of certain neurological diseases in older adults. This article describes the impact of dietary polyunsaturated fatty acids (PUFA) on older adults' immune system and discusses the roles of age and immune status with regard to PUFA supplements.

Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet

Our genome adapts slowly to changing conditions of existence. Many diseases of civilisation result from mismatches between our Paleolithic genome and the rapidly changing environment, including our diet. The objective of the present study was to reconstruct multiple Paleolithic diets to estimate the ranges of nutrient intakes upon which humanity evolved. A database of, predominantly East African, plant and animal foods (meat/fish) was used to model multiple Paleolithic diets, using two pathophysiological constraints (i.e. protein < 35 energy % (en%) and linoleic acid (LA) >1.0 en%), at known hunter-gatherer plant/animal food intake ratios (range 70/30-30/70 en%/en%). We investigated selective and non-selective savannah, savannah/aquatic and aquatic hunter-gatherer/scavenger foraging strategies. We found (range of medians in en%) intakes of moderate-to-high protein (25-29), moderate-to-high fat (30-39) and moderate carbohydrates (39-40). The fatty acid composition was SFA (11.4-12.0), MUFA (5.6-18.5) and PUFA (8.6-15.2). The latter was high in α-linolenic acid (ALA) (3.7-4.7 en%), low in LA (2.3-3.6 en%), and high in long-chain PUFA (LCP; 4.75-25.8 g/d), LCP n-3 (2.26-17.0 g/d), LCP n-6 (2.54-8.84 g/d), ALA/LA ratio (1.12-1.64 g/g) and LCP n-3/LCP n-6 ratio (0.84-1.92 g/g). Consistent with the wide range of employed variables, nutrient intakes showed wide ranges. We conclude that compared with Western diets, Paleolithic diets contained consistently higher protein and LCP, and lower LA. These are likely to contribute to the known beneficial effects of Paleolithic-like diets, e.g. through increased satiety/satiation. Disparities between Paleolithic, contemporary and recommended intakes might be important factors underlying the aetiology of common Western diseases. Data on Paleolithic diets and lifestyle, rather than the investigation of single nutrients, might be useful for the rational design of clinical trials.

Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet

We recently showed that a hypocaloric carbohydrate restricted diet (CRD) had two striking effects: (1) a reduction in plasma saturated fatty acids (SFA) despite higher intake than a low fat diet, and (2) a decrease in inflammation despite a significant increase in arachidonic acid (ARA). Here we extend these findings in 8 weight stable men who were fed two 6-week CRD (12%en carbohydrate) varying in quality of fat. One CRD emphasized SFA (CRD-SFA, 86 g/d SFA) and the other, unsaturated fat (CRD-UFA, 47 g SFA/d). All foods were provided to subjects. Both CRD decreased serum triacylglycerol (TAG) and insulin, and increased LDL-C particle size. The CRD-UFA significantly decreased plasma TAG SFA (27.48 ± 2.89 mol%) compared to baseline (31.06 ± 4.26 mol%). Plasma TAG SFA, however, remained unchanged in the CRD-SFA (33.14 ± 3.49 mol%) despite a doubling in SFA intake. Both CRD significantly reduced plasma palmitoleic acid (16:1n-7) indicating decreased de novo lipogenesis. CRD-SFA significantly increased plasma phospholipid ARA content, while CRD-UFA significantly increased EPA and DHA. Urine 8-iso PGF_2α, a free radical-catalyzed product of ARA, was significantly lower than baseline following CRD-UFA (−32%). There was a significant inverse correlation between changes in urine 8-iso PGF_2α and PL ARA on both CRD (r = −0.82 CRD-SFA; r = −0.62 CRD-UFA). These findings are consistent with the concept that dietary saturated fat is efficiently metabolized in the presence of low carbohydrate, and that a CRD results in better preservation of plasma ARA.

Chain reactions: early-life stress alters the metabolic profile of plasma polyunsaturated fatty acids in adulthood

The rat maternal separation paradigm can be used to examine the biological consequences of early-life stress. Immunomodulatory polyunsaturated fatty acids (PUFAs) have recently attracted attention in the study of stress-related disorders. We established the plasma PUFA profile of maternally separated rodents compared to controls. Our results identify a proinflammatory PUFA profile as a persistent consequence of early-life stress and suggest new avenues of investigation in stress-related disorders.

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.

The health implications of changing linoleic acid intakes

Linoleic acid is the most prominent polyunsaturated fatty acid (PUFA) in the Western diet. It is virtually found in every food we eat and is the predominant PUFA in land-based meats, dairy, vegetables, vegetable oils, cereals, fruits, nuts, legumes, seeds and breads. Because linoleic acid is the metabolic precursor of arachidonic acid and bioactive eicosanoids derived from arachidonic acid, there is concern that dietary linoleic acid could augment tissue arachidonic acid content, eicosanoid formation and subsequently enhance the risk of and/or exacerbate conditions associated with acute and chronic diseases (i.e., cancers, cardiovascular disease, inflammation, neurological disorders, etc.). The following series of papers examines the impact of modifying dietary levels of linoleic acid on health outcomes. The authors were asked to start with current intakes of linoleic acid (adults) and determine if health outcomes would change if linoleic acid intake increased or decreased. The authors addressed changes in tissue arachidonic acid content and eicosanoid formation, cardiovascular disease, inflammation, and psychiatric disorders.

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.

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.

Arachidonic acid-and docosahexaenoic acid-enriched formulas modulate antigen-specific T cell responses to influenza virus in neonatal piglets

BACKGROUND

Whereas the immunomodulatory effects of feeding either arachidonic acid (AA) or docosahexaenoic acid (DHA) separately have been previously investigated, little is known about the immunomodulatory efficacy of AA or DHA when they are fed in combination as infant formula ingredients.

OBJECTIVE

The objective of this study was to investigate the ability of AA- and DHA(AA/DHA)-enriched infant formula to modulate immune responses in the neonate in response to an inactivated influenza virus vaccine.

DESIGN

Neonatal piglets (n = 48) were weaned on day 2 of age and distributed into 16 blocks of 3 littermate piglets each. Within each block, piglets were randomly assigned to a control formula, AA/DHA-enriched formula (0.63% AA and 0.34% DHA), or sow milk for 30 d. On day 9, 8 blocks of piglets were immunized with an inactivated influenza virus vaccine. On days 0, 9, 16, 23, and 30 after weaning, we measured influenza virus-specific T cell proliferation and phenotype of T subsets in peripheral blood. A delayed-type hypersensitivity reaction test was administered on day 28. Cytokine messenger RNA expression was determined by quantitative real time reverse transcriptase-polymerase chain reaction on day 30.

RESULTS

The influenza virus-specific CD4(+) and CD8(+) T cell ex vivo lymphoproliferative responses were significantly lower on day 23 after immunization in piglets receiving dietary AA/DHA supplementation and sow milk than in those receiving the unsupplemented control formula. The immunomodulatory effects of AA/DHA-enriched formulas were consistent with up-regulation of interleukin 10 in peripheral blood mononuclear cells.

CONCLUSION

Overall, it appears that the AA/DHA-enriched formula modulated antigen-specific T cell responses in part through an interleukin 10-dependent mechanism.

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.

Effects of polyunsaturated fatty acids on the proliferation of mitogen stimulated bovine peripheral blood mononuclear cells

The present study aimed at analysis of the effects of polyunsaturated fatty acid (PUFA), linoleic acid (LA, C18:2n - 6) and linolenic acid (LNA, C18:3n - 3) on bovine peripheral blood mononuclear cells (PBMC) in vitro. Both mitogen (ConA)-induced proliferative lymphocyte responsiveness during 4 days of culture and eicosanoid (prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4))) production during 36 h were determined in relation to the absence or presence of various concentrations of LA and LNA (0, 1, 5, 25, 125 and 250 microM). Mitogen-driven proliferative responses of lymphocytes tended to be uninfluenced in the presence of lower concentrations of LA, whereas significant inhibition was observed at the higher concentrations of LA (125 and 250 microM). However, increasing amounts of LNA did not affect the proliferation. ConA stimulation induced a clear PGE(2) response, which significantly decreased in the presence of 250 microM of LA. In addition, increasing amounts of LNA, but not LA, led to a significant decrease in LTB(4) levels. However, The production of LTB(4) did not alter due to mitogenic stimulation. In conclusion, the present study shows that bovine mononuclear cells may functionally be influenced by the presence of PUFA in their environment. Further studies need to be conducted to clarify in vivo consequences of these findings in a situation of PUFA enriched rations in ruminants.

Effects of supplementation with vitamins A, C, and E, selenium, and zinc on immune function in a murine sensitization model

OBJECTIVE

We compared the effects of supplementing with vitamins A, C, and E, selenium, and zinc on a range of innate and specific T-helper 1 (Th1) and Th2-driven adaptive immune responses.

METHODS

BALB/c mice were fed semi-purified AIN93 diets and randomly assigned to receive a diet supplemented with 120 mg/kg of vitamin A, 2500 mg/kg of vitamin C, 1000 mg/kg of vitamin E, 2 mg/kg of selenium, and 500 mg/kg of zinc (n = 15/group). After 4 wk of supplementation, mice were sensitized by topical application of di-nitro-chlorobenzene (DNCB); 2 wk later mice were challenged; and 5 d later they were killed to assess the effect on a range of innate responses (phagocytic activity, oxidative burst and tumor necrosis factor-alpha), adaptive Th1-driven responses (delayed-type hypersensitivity, DNCB-specific immunoglobulin [Ig] G2a and IgG2b, and interferon-gamma [IFN-gamma]), and adaptive Th2-driven responses (DNCB-specific IgE and IgG1 and interleukin-4 [IL-4]).

RESULTS

Immune function was affected only in the vitamin A group. These mice gained less weight and were less capable of resolving the inflammatory response elicited during sensitization. The oxidative burst of blood cells was increased, but production of IFN-gamma and IL-4 and the ratio of IFN-gamma to IL-4 were markedly depressed. In concordance with the latter result, production of Th1-driven IgG2a antibodies was decreased, whereas Th2-driven isotypes were not affected (IgG1, IgE) and mucosal IgA was increased.

CONCLUSIONS

These findings confirmed that supplementary amounts of vitamin A above dietary requirements enhance inflammatory responses accompanied by decreased Th1 and increased mucosal responses. However, supplementation of these sufficiently fed, non-stressed, young adult mice with vitamins C and E, selenium, or zinc had no effect on immune function. We speculate that using this model in aged, physiologically, or nutritionally stressed mice may provide outcomes more similar to those in sensitive human populations. If so, this would improve the usefulness of the model to assess, characterize, and rank effects of foods or nutrients on a range of immune functions, including Th1/Th2 polarization.

Effect of a Dietary n-6 Polyunsaturated Fatty Acid Supplement on Distinct Immune Functions of Goats

The aim of this study was to investigate whether dietary n-6 polyunsaturated fatty acids (PUFA) alter immune functions as lymphocyte blastogenesis, expression of lymphocyte and monocyte markers, and cell adhesion molecules of the integrin family in goats. Dutch White castrated male goats received a diet either rich in olive oil (control group, n = 4) or rich in corn oil (test group, n = 4) over a period of 3 weeks. The animals in the test group had significantly higher linoleic acid (LA, 18:2n-6) levels in plasma on days 7, 14 and 21 of the diet than control animals. This was also true for washed erythrocyte membranes at day 21. A significant reduction in the percentage of alpha-4 integrin (CD49d) expressing lymphocytes was observed in goats fed LA rich corn oil at day 21. However, no changes were observed in either lymphocyte proliferative responses to ConA and PHA or the expression of other lymphocyte/monocyte markers. In conclusion, feeding corn oil rich in LA caused significant increases in the proportion of LA in the fatty acid composition of plasma and erythrocyte membranes and was accompanied by a significant decrease of the adhesion molecule alpha-4 integrin (CD49d) on lymphocytes but not on monocytes.

Fatty acids as gatekeepers of immune cell regulation

Fatty acids have diverse roles in all cells. They are important as a source of energy, as structural components of cell membranes, as signalling molecules and as precursors for the synthesis of eicosanoids. Recent research has suggested that the organization of fatty acids into distinct cellular pools has a particularly important role in cells of the immune system and that forms of lipid trafficking exist, which are as yet poorly understood. This Review examines the nature and regulation of cellular lipid pools in the immune system, their delivery of fatty acids or fatty acid derivatives to specific locations and their potential role in health and disease.

Fatty acids and lymphocyte functions

The immune system acts to protect the host against pathogenic invaders. However, components of the immune system can become dysregulated such that their activities are directed against host tissues, so causing damage. Lymphocytes are involved in both the beneficial and detrimental effects of the immune system. Both the level of fat and the types of fatty acid present in the diet can affect lymphocyte functions. The fatty acid composition of lymphocytes, and other immune cells, is altered according to the fatty acid composition of the diet and this alters the capacity of those cells to produce eicosanoids, such as prostaglandin E2, which are involved in immunoregulation. A high fat diet can impair lymphocyte function. Cell culture and animal feeding studies indicate that oleic, linoleic, conjugated linoleic, gamma-linolenic, dihomo-gamma-linolenic, arachidonic, alpha-linolenic, eicosapentaenoic and docosahexaenoic acids can all influence lymphocyte proliferation, the production of cytokines by lymphocytes, and natural killer cell activity. High intakes of some of these fatty acids are necessary to induce these effects. Among these fatty acids the long chain n-3 fatty acids, especially eicosapentaenoic acid, appear to be the most potent when included in the human diet. Although not all studies agree, it appears that fish oil, which contains eicosapentaenoic acid, down regulates the T-helper 1-type response which is associated with chronic inflammatory disease. There is evidence for beneficial effects of fish oil in such diseases; this evidence is strongest for rheumatoid arthritis. Since n-3 fatty acids also antagonise the production of inflammatory eicosanoid mediators from arachidonic acid, there is potential for benefit in asthma and related diseases. Recent evidence indicates that fish oil may be of benefit in some asthmatics but not others.

Influence of dietary supplementation with long-chain n-3 or n-6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults

Greatly increasing the amounts of flaxseed oil [rich in alpha-linolenic acid (ALNA)] or fish oil (FO); [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in the diet can decrease inflammatory cell functions and so might impair host defense. The objective of this study was to determine the effect of dietary supplementation with moderate levels of ALNA, gamma-linolenic acid (GLA), arachidonic acid (ARA), DHA, or FO on inflammatory cell numbers and functions and on circulating levels of soluble adhesion molecules. Healthy subjects aged 55 to 75 yr consumed nine capsules per day for 12 wk. The capsules contained placebo oil (an 80:20 mix of palm and sunflowerseed oils) or blends of placebo oil with oils rich in ALNA, GLA, ARA, or DHA or FO. Subjects in these groups consumed 2 g ALNA; approximately 700 mg GLA, ARA, or DHA; or 1 g EPA plus DHA (720 mg EPA + 280 mg DHA) daily from the capsules. Total fat intake from the capsules was 4 g per day. None of the treatments affected inflammatory cell numbers in the bloodstream; neutrophil and monocyte phagocytosis or respiratory burst in response to E. coli; production of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 in response to bacterial lipopolysaccharide; or plasma concentrations of soluble intercellular adhesion molecule-1. In contrast, the ALNA and FO treatments decreased the plasma concentrations of soluble vascular cell adhesion molecule-1 (16 and 28% decrease, respectively) and soluble E-selectin (23 and 17% decrease, respectively). It is concluded that, in contrast to previous reports using higher amounts of these fatty acids, a moderate increase in consumption of long-chain n-6 or n-3 polyunsaturated fatty acids does not significantly affect inflammatory cell numbers or neutrophil and monocyte responses in humans and so would not be expected to cause immune impairment. Furthermore, we conclude that moderate levels of ALNA and FO, which could be incorporated into the diet, can decrease some markers of endothelial activation and that this mechanism of action may contribute to the reported health benefits of n-3 fatty acids.

Polyunsaturated fatty acids, inflammation, and immunity

The fatty acid composition of inflammatory and immune cells is sensitive to change according to the fatty acid composition of the diet. In particular, the proportion of different types of polyunsaturated fatty acids (PUFA) in these cells is readily changed, and this provides a link between dietary PUFA intake, inflammation, and immunity. The n-6 PUFA arachidonic acid (AA) is the precursor of prostaglandins, leukotrienes, and related compounds, which have important roles in inflammation and in the regulation of immunity. Fish oil contains the n-3 PUFA eicosapentaenoic acid (EPA). Feeding fish oil results in partial replacement of AA in cell membranes by EPA. This leads to decreased production of AA-derived mediators. In addition, EPA is a substrate for cyclooxygenase and lipoxygenase and gives rise to mediators that often have different biological actions or potencies than those formed from AA. Animal studies have shown that dietary fish oil results in altered lymphocyte function and in suppressed production of proinflammatory cytokines by macrophages. Supplementation of the diet of healthy human volunteers with fish oil-derived n-3 PUFA results in decreased monocyte and neutrophil chemotaxis and decreased production of proinflammatory cytokines. Fish oil feeding has been shown to ameliorate the symptoms of some animal models of autoimmune disease. Clinical studies have reported that fish oil supplementation has beneficial effects in rheumatoid arthritis, inflammatory bowel disease, and among some asthmatics, supporting the idea that the n-3 PUFA in fish oil are anti-inflammatory and immunomodulatory.

Dietary supplementation with conjugated linoleic acid increased its concentration in human peripheral blood mononuclear cells, but did not alter their function

The purpose of this study was to examine if conjugated linoleic acid (CLA) supplementation of diets would alter fatty acid (FA) composition and function of peripheral blood mononuclear cells (PBMC). Seventeen women, 20-41 yr, participated in a 93-d study conducted at the Metabolic Research Unit. The same diet (19, 30, and 51% energy from protein, fat, and carbohydrate, respectively) was fed to all subjects throughout the study. Seven subjects (control group) supplemented their diet with six daily capsules (1 g each) of placebo oil (sunflower) for 93 d. For the other 10 subjects (CLA group), the supplement was changed to an equivalent amount of Tonalin capsules for the last 63 d of the study. Tonalin provided 3.9 g/d of a mixture of CLA isomers (trans-10,cis-12, 22.6%; cis-11,trans-13, 23.6%; cis-9,trans-11, 17.6%; trans-8,cis-10, 16.6%; other isomers 19.6%), and 2.1 g/d of other FA. PBMC isolated on study days 30 and 90 were used to assess intracellular cytokines by flow cytometry, secreted cytokines, and eicosanoid by enzyme-linked immonosorbent assay, and FA composition by gas-liquid chromatography. After supplementation, total CLA concentration increased from 0.012 to 0.97% (P < 0.0001) in PBMC lipids, but it did not significantly alter the concentration of other FA. CLA supplementation did not alter the in vitro secretion of prostaglandin E2, leukotriene B4, interleukin-1beta (IL-1beta), or tumor necrosis factor alpha (TNFalpha) by PBMC simulated with lipopolysaccharide, and the secretion of IL-2 by PBMC stimulated with phytohemagglutinin. Nor did it alter the percentage T cells producing IL-2, interferon gamma, and percentage of monocytes producing TNFalpha. The intracellular concentration of these cytokines was also not altered. None of the variables tested changed in the control group. Our results show that CLA supplementation increased its concentration in PBMC lipids, but did not alter their functions.