Modulation of human immune and inflammatory responses by dietary fatty acids

Executive Summary: Conference on Dietary Supplement Use in the Elderly - Proceedings of the Conference Held January 14-15, 2003, Natcher Auditorium, National Institutes of Health, Bethesda, MD

Several issues prompted the need for this conference. Among these were the reported high prevalence (> 50%) of use of supplements among individuals over 50 years of age, inadequate scientific evidence supporting the safety and benefits of use among these individuals, and a report issued by the General Accounting Office (GAO) in 2001. This GAO report entitled "Health Products for Seniors: 'Anti-Aging' Products Pose Potential for Physical and Economic Harm," arose from concerns among legislators that seniors were spending money from their limited incomes on products that were not only ineffective but also potentially harmful. The conference was organized around three sessions to address the issues highlighted above, which were usage of dietary supplements among the elderly, age-related changes and issues that affect the use of supplements, and the evidence base supporting the use of supplements in disease prevention and health maintenance. Each session was followed by a panel discussion. This Executive Summary is organized around the three major discussion topics. The summary does not explicitly follow the order of the conference presentations; rather it is intended to capture and examine the current research gaps in knowledge and identify future research opportunities. These research opportunities, as expressed by the conference speakers, panelists, and attendees are summarized at the end of this paper under five thematic areas: usage behaviors, methodology, pre-clinical studies and clinical studies, informational databases, and education and dissemination.

Feeding Laying Hens Seal Blubber Oil: Effects on Egg Yolk Incorporation, Stereospecific Distribution of Omega-3 Fatty Acids, and Sensory Aspects

Seventy-two 26-wk-old Single Comb White Leghorn laying hens were randomly assigned to 36 cages (2 per cage) in a 3-orthogonal 4 x 4 latin square, with the fourth row suppressed, to assess the effect of feeding refined seal blubber oil (SBO, containing 22.2% omega-3 fatty acids) on the fatty acid composition and position in the egg yolk lipids. The experiment was conducted over a period of 9 wk. Eggs were collected and numbered, and the weights were recorded for each week and cage. Eggs collected at wk 5 and 9 were used for total lipid, lipid class, fatty acid, and positional analyses. Sensory evaluation was carried out on eggs collected at wk 6 and 7. Feeding SBO at 1.25% led to an increase (P < 0.0001) in the long-chain omega-3 polyunsaturated fatty acids (LCn3PUFA) and a concomitant decrease (P < 0.0001) in arachidonic acid (ARA) in the egg yolk lipids. Yet this amount of SBO in the diet had no effect (P > 0.1) on the sensory attributes of the egg and on production parameters such as egg weight, number of eggs laid, and feed intake (P > 0.05). When feeding SBO in amounts higher than 1.25% proportionately, a plateau effect of the LCn3PUFA content of the eggs was observed. This appears to be because the PUFA content in the sn-2 position of the phospholipids cannot exceed a certain amount. When this amount is reached, the LCn3PUFA will be increasingly stored in triglycerides. The results presented here clearly indicate how eggs can be produced with optimized composition of LCn3PUFA without affecting (P > 0.1) the sensory properties of the eggs. The procedures elaborated herein provide directly applicable consequences for the food industry.

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.

Effects of different dietary oils on inflammatory mediator generation and fatty acid composition in rat neutrophils

Virgin olive oil (VOO) compared with fish oil (FO) and evening primrose oil (PO) on the ability of stimulated leukocytes to produce inflammatory mediators was investigated in rats. Weaned Wistar rats were fed a basal diet (BD) (2% by weight of corn oil) or diets containing 15% by weight of VOO, PO, or FO. After 8 weeks, glycogen-elicited peritoneal polymorphonuclear leukocytes, mainly neutrophils, were isolated. The calcium-ionophore stimulated neutrophils (2.5 x 10(6) cells/mL) obtained from rats fed the different oils produced a higher release of lysosomal enzymes (beta-glucuronidase, lysozyme, and myeloperoxidase [MPO]) compared with those fed BD. The production of reactive oxygen species (ROS) in response to the stimulant, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), by neutrophils from the VOO group (15.44 nmol of O(2)(-) and 6.56 nmol of H(2)O(2)) was similar to the BD group (12.01 nmol O(2)(-) and 8.49 nmol H(2)O(2)) and significantly lower than the PO (20.90 nmol O(2)(-) and 10.84 nmol H(2)O(2)) and FO (20.93 nmol O(2)(-) and 12.79 nmol H(2)O(2)) groups. The cyclooxygenase-derived eicosanoid production was reduced by the lipid enrichment of the diets. Whereas the generation of prostaglandin E(2) (PGE(2)) was significantly decreased in VOO (5.40 ng/mL), PO (4.95 ng/mL), and FO (1.44 ng/mL) groups compared with BD (8.19 ng/mL), thromboxane B(2) (TXB(2)) reduction was especially significant in neutrophils from the FO diet group (14.67 ng/mL compared with 26.69 ng/mL from BD). These experimental data suggest that FO and PO, as well as VOO, could be considered a valuable strategy in preventing the generation of some inflammatory mediators.

Location is everything: lipid rafts and immune cell signaling

The cells of both the adaptive and innate immune systems express a dizzying array of receptors that transduce and integrate an enormous amount of information about the environment that allows the cells to mount effective immune responses. Over the past several years, significant advances have been made in elucidating the molecular details of signal cascades initiated by the engagement of immune cell receptors by their ligands. Recent evidence indicates that immune receptors and components of their signaling cascades are spatially organized and that this spatial organization plays a central role in the initiation and regulation of signaling. A key organizing element for signaling receptors appears to be cholesterol- and sphingolipid-rich plasma membrane microdomains termed lipid rafts. Research into the molecular basis of the spatial segregation and organization of signaling receptors provided by rafts is adding fundamentally to our understanding of the initiation and prolongation of signals in the immune system.

Dietary supplementation with docosahexaenoic acid, but not with eicosapentaenoic acid, reduces host resistance to fungal infection in mice

The effect of dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on host resistance to Paracoccidioides brasiliensis infection was investigated. Mice fed palm oil supplemented with DHA showed reduced antifungal activity in the spleen and liver, as compared with mice fed palm oil or soybean oil without supplementation with DHA. Mice fed DHA-supplemented soybean oil also showed reduced antifungal activity in the liver, but the extent of reduction was less profound. This reduction in antifungal activity was not observed with EPA-supplemented palm or EPA-supplemented soybean oil. These results suggest that two factors, DHA and palm oil in combination, are involved in reducing the host resistance. DHA-enriched palm oil was also responsible for an increase in DHA concentration and a marked decrease in arachidonic acid content in the spleen and liver. However, this group did not show elevated spleen and liver phospholipid hydroperoxide levels compared with the other groups, excluding the possibility that the reduction in antifungal activity observed with DHA-enriched palm oil is due to acceleration of in vivo lipid peroxidation. Greater infection-induced increases in spleen and serum interferon-gamma concentrations were observed in mice fed DHA-enriched palm oil compared with the other groups.

Atopy and depression: results from the Northern Finland 1966 Birth Cohort Study

Several studies have suggested an association between IgE-mediated atopic allergies and depression. The present study extends our understanding about putative gender differences of this association and provides further epidemiological evidence for our previous finding that the association between atopy and depression may be characteristic for females only. In order to clearly determine the presence of atopic disorders and depression, we used more valid tools than had been employed earlier and we had access to a database (the Northern Finland 1966 Birth Cohort), in which individuals were followed up prospectively until the age of 31 years. The information on allergic symptoms, verified by skin-prick tests and comprising data of 5518 individuals, was used to ascertain the presence of atopy. Depression was assessed with the help of Hopkins' Symptom Checklist-25 and self-reported doctor-diagnosed depression. After adjusting for a father's social class, mother's parity, and place of residence, logistic regression analyses showed that the risk of developing depression increased in parallel with the increasing severity of depression and, when compared with nonatopic subjects, was 3.0 to 4.7-fold up in atopic females and statistically significant. In atopic males, the association between atopy and depression was statistically significant only in the highest depression scores, the odds ratio being 6.3-fold. The results indicate that females suffering from atopic diseases might possess an elevated risk of developing depression already during early adulthood. In males, the association between these two disorders is evident only among the most severe manifestations of depression. Possible background theories, that is, genetic abnormalities in serotonin metabolism, HPA-axis dysfunction, and histamine theory are discussed.

Lipoxins in chronic inflammation

The discovery of endogenous molecules involved in counterregulation of inflammatory responses that may lead to tissue injury provides an opportunity to explore new therapeutic approaches based on manipulation of new pathways. Natural counterregulatory pathways may reduce the possibility of unwanted toxic side-effects. Lipoxins are trihydroxytetraene-containing eicosanoids that are generated within the vascular lumen during platelet-leukocyte interactions and at mucosal surfaces via leukocyte-epithelial cell interactions. During cell-cell interactions, transcellular biosynthetic pathways are the major lipoxin biosynthetic routes, and thus, in humans, lipoxins are formed in vivo during multicellular responses, such as inflammation and asthma. This branch of the eicosanoid cascade generates specific tetraene-containing products that serve as "stop signals" for neutrophils that regulate key steps in leukocyte trafficking and prevent neutrophil-mediated tissue injury. These novel anti-inflammatory lipid mediators also appear to facilitate the resolution of the acute inflammatory response. In this review, recent findings and new concepts pertaining to the generation of lipoxins and their impact on the resolution of acute inflammation, and organ protection from leukocyte-mediated injury, are presented. The parallels and possible associations with periodontal diseases are discussed.

Impact of high flaxseed diet on mitogen-induced proliferation, IL-2 production, cell subsets and fatty acid composition of spleen cells from pregnant and F1 generation Sprague-Dawley rats

Flaxseed (FS) being rich in alpha-linolenic acid may alter the immune parameters. Therefore, we assessed the impact of FS and defatted flaxseed meal (FLM) on fatty acid composition, cell subsets, proliferation and IL-2 production by splenic lymphocytes. Pregnant female Sprague-Dawley rats were fed diets containing 0% FS and FLM, 20 or 40% FS, 13 or 26% FLM during gestation or gestation, lactation and 8 week post-weaning period. FS and FLM resulted in up to 8.3 fold and 4.6 fold increase in splenic ALA among pregnant rats, 4.5 fold and 1.2 fold increase in splenic ALA among F(1) generation rats. Splenic linoleic acid (LA) and arachidonic acid (AA) were 18 and 40% lower in 40% FS fed pregnant rats, and AA was 15% lower in all the other groups. Among F(1) rats, splenic LA and AA were 16 and 48% lower in 40% FS group, and AA was 18% lower in 20% FS and 26% FLM groups. Concanavalin A and phytohemagglutinin mediated proliferation of spleen cells were 60 and 52% lower in 40% FS fed pregnant and F(1) generation rats, respectively. No significant changes were observed in the cell subsets or IL-2 production by splenic cells from different groups.

Dietary alpha-linolenic acid decreases C-reactive protein, serum amyloid A and interleukin-6 in dyslipidaemic patients

BACKGROUND

Inflammation plays an important role in the pathogenesis of coronary artery disease. We examined whether dietary supplementation with alpha-linolenic acid (ALA, 18:3n-3) affects the levels of inflammatory markers in dyslipidaemic patients.

METHODS

We recruited 76 male dyslipidaemic patients (mean age=51+/-8 years) following a typical Greek diet. They were randomly assigned either to 15 ml of linseed oil (rich in ALA) per day (n=50) or to 15 ml of safflower oil (rich in linoleic acid (LA, 18:2n-6)) per day (n=26). The ratio of n-6:n-3 in linseed oil supplemented group was 1.3:1 and in safflower oil supplemented group 13.2:1. Dietary intervention lasted for 3 months. Blood lipids and C-reactive protein (CRP), serum amyloid A (SAA), and interleukin-6 (IL-6) levels were determined prior and after intervention. CRP and SAA were measured by nephelometry and IL-6 by immunoassay.

RESULTS

Dietary supplementation with ALA decreased significantly CRP, SAA and IL-6 levels. The median decrease of CRP was 38% (1.24 vs. 0.93 mg/l, P=0.0008), of SAA 23.1% (3.24 vs. 2.39 mg/l, P=0.0001) and of IL-6 10.5% (2.18 vs. 1.7 pg/ml, P=0.01). The decrease of inflammatory markers was independent of lipid changes. Dietary supplementation with LA did not affect significantly CRP, SAA and IL-6 concentrations but decreased cholesterol levels.

CONCLUSIONS

Dietary supplementation with ALA for 3 months decreases significantly CRP, SAA and IL-6 levels in dyslipidaemic patients. This anti-inflammatory effect may provide a possible additional mechanism for the beneficial effect of plant n-3 polyunsaturated fatty acids in primary and secondary prevention of coronary artery disease.

Diet and asthma: has the role of dietary lipids been overlooked in the management of asthma?

OBJECTIVE

This article discusses the role of diet in the management of asthma. Readers will gain an understanding of how evolution of the western diet has contributed to increased asthma prevalence and how dietary modification that includes management of dietary lipids may reduce symptoms of asthma.

DATA SOURCES

Relevant studies published in English were reviewed.

STUDY SELECTION

Medline search to identify peer-reviewed abstracts and journal articles.

RESULTS

Asthma and obesity, which often occur together, have increased in prevalence in recent years. Studies suggest adaption of a western diet has not only contributed to obesity, but that increased intake of specific nutrients can cause changes in the frequency and severity of asthma. Increased asthma prevalence has also been proposed to arise from increased exposure to diesel particles or lack of exposure to infectious agents or endotoxins during childhood, generating a biased Th2 immune response, and increased cytokine and leukotriene production. Antagonists directed against these pro-inflammatory mediators include anticytokines and antileukotrienes. A reduction in the levels of inflammatory mediators associated with asthma has also been seen with dietary interventions, such as the administration of oils containing gamma-linolenic acid and eicosapentaenoic acid.

CONCLUSIONS

Evidence suggests elevated body mass index and dietary patterns, especially intake of dietary lipids, contribute to symptoms of asthma. Dietary modification may help patients manage their asthma as well as contribute to their overall health.

Dietary docosahexaenoic acid is more optimal than eicosapentaenoic acid affecting the level of cellular defence responses of the juvenile grouper Epinephelus malabaricus

The combined effects of dietary docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids on phagocytic, respiratory burst, and leucocyte proliferative activities of the juvenile grouper, Epinephelus malabaricus, were investigated. The test fish were fed for 12wk on test diets containing 1g 100g(-1) diet of DHA and EPA in combinations (DHA/EPA: 3/1, 2/1, 1/1, 0.7/1, 0.3/1). In addition to promoting fish growth, high dietary DHA/EPA ratio significantly enhanced phagocytic and respiratory burst activities of grouper head-kidney leucocytes compared with low ratio. Significant correlations were found between leucocyte phagocytic or respiratory burst activities and concentrations of 20:3(n-3), DHA and EPA in fish liver and muscle tissues. Leucocyte proliferation was significantly higher (P< 0.05) when the diets were high in DHA/EPA ratio than low in DHA/EPA ratio, when stimulated by Con A and PHA-P, but not by LPS. Tissue DHA concentrations and leucocyte proliferation were significantly and positively correlated. Fortification of dietary DHA, thus increased T-cell proliferation and phagocytic function of grouper leucocytes. DHA is the only member in the (n-3) highly unsaturated fatty acid family that stimulated phagocytic functions of leucocytes and T-cell proliferation, and is more optimal than EPA affecting the cellular defence responses of the E. malabaricus juveniles.

Exercise, cachexia, and cancer therapy: a molecular rationale

Evidence from recent publications indicates that repeated exercise may enhance the quality of life of cancer patients. The lack of reported negative effects and the consistency of the observed benefits lead one to conclude that physical exercise may provide a low-risk therapy that can improve patients' capacity to perform activities of daily living and improve their quality of life. Repeated physical activity may attenuate the adverse effects of cancer therapy, prevent or reverse cachexia, and reduce risk for a second cancer through suppression of inflammatory responses or enhancement of insulin sensitivity, rates of protein synthesis, and anti-oxidant and phase II enzyme activities. These results most likely come about through the ability of physical exercise to attenuate a chronic inflammatory signaling process and to transiently activate the mitogen-activated protein kinase, c-Jun NH2-terminal kinase, c-Jun NH2-terminal kinase-mitogen-activated protein kinase, and nuclear factor-kappa B pathways and through its ability to enhance insulin sensitivity. Expanded molecular-based research into these areas may provide new insights into the biological mechanisms associated with cancer rehabilitation and endogenous risk.

Metabolic aging and predicted longevity: results of a cross-sectional study in post-menopausal women

BACKGROUND AND AIMS

The extent to which general characteristics of metabolic aging contribute to differences in life span among individuals remains uncertain. The objective of this study was to examine the association of age-related physiological and metabolic variables with predicted longevity in postmenopausal women.

METHODS

Subjects were 33 healthy women aged 55-65 years. Total and resting energy expenditure, body temperature, immune function as assessed by a delayed-type hypersensitivity skin test (DTH), lipid profile, and reported dietary intake were measured.

RESULTS

There were no significant associations between longevity, energy expenditure, body temperature, lipid profile, or dietary intake. However, there was a significant association of predicted longevity with DTH (partial r=0.44, p=0.023).

CONCLUSIONS

These results suggest that immune function may predict familial differences in longevity, while energy expenditure, body temperature, lipid profile, and dietary intake are unrelated. Although the small sample size may have limited the ability to detect metabolic effects on longevity in this study, the general approach may be broadly applicable to examinations of metabolic aging in humans.

Dietary effects of arachidonate-rich fungal oil and fish oil on murine hepatic and hippocampal gene expression

BACKGROUND

The functions, actions, and regulation of tissue metabolism affected by the consumption of long chain polyunsaturated fatty acids (LC-PUFA) from fish oil and other sources remain poorly understood; particularly how LC-PUFAs affect transcription of genes involved in regulating metabolism. In the present work, mice were fed diets containing fish oil rich in eicosapentaenoic acid and docosahexaenoic acid, fungal oil rich in arachidonic acid, or the combination of both. Liver and hippocampus tissue were then analyzed through a combined gene expression- and lipid- profiling strategy in order to annotate the molecular functions and targets of dietary LC-PUFA.

RESULTS

Using microarray technology, 329 and 356 dietary regulated transcripts were identified in the liver and hippocampus, respectively. All genes selected as differentially expressed were grouped by expression patterns through a combined k-means/hierarchical clustering approach, and annotated using gene ontology classifications. In the liver, groups of genes were linked to the transcription factors PPARalpha, HNFalpha, and SREBP-1; transcription factors known to control lipid metabolism. The pattern of differentially regulated genes, further supported with quantitative lipid profiling, suggested that the experimental diets increased hepatic beta-oxidation and gluconeogenesis while decreasing fatty acid synthesis. Lastly, novel hippocampal gene changes were identified.

CONCLUSIONS

Examining the broad transcriptional effects of LC-PUFAs confirmed previously identified PUFA-mediated gene expression changes and identified novel gene targets. Gene expression profiling displayed a complex and diverse gene pattern underlying the biological response to dietary LC-PUFAs. The results of the studied dietary changes highlighted broad-spectrum effects on the major eukaryotic lipid metabolism transcription factors. Further focused studies, stemming from such transcriptomic data, will need to dissect the transcription factor signaling pathways to fully explain how fish oils and arachidonic acid achieve their specific effects on health.

Inhibitions of histamine release and prostaglandin E2 synthesis by mangosteen, a Thai medicinal plant

The fruit hull of mangosteen, Garcinia mangostana L. has been used as a Thai indigenous medicine for many years. However, its mechanism of action as a medicine has not been elucidated. The present study was undertaken to examine the effects of mangosteen extracts (100% ethanol, 70% ethanol, 40% ethanol and water) on histamine release and prostaglandin E2 synthesis. We found that the 40% ethanol extract of mangosteen inhibited IgE-mediated histamine release from RBL-2H3 cells with greater potency than the water extract of Rubus suavissimus that has been used as an anti-allergy crude drug in Japan. All extracts of mangosteen potently inhibited A23187-induced prostaglandin E2 synthesis in C6 rat glioma cells, while the water extract of Rubus suavissimus had no effect. The 40% ethanol extract of mangosteen inhibited the prostaglandin E2 synthesis in a concentration-dependent manner with relatively lower concentrations than the histamine release. In addition, passive cutaneous anaphylaxis (PCA) reactions in rats were significantly inhibited by this ethanol extract as well as by the water extract of Rubus suavissimus. These results suggest that the 40% ethanol extract of mangosteen has potent inhibitory activities of both histamine release and prostaglandin E2 synthesis.

Association between skin test diagnosed atopy and professionally diagnosed depression: a Northern Finland 1966 Birth Cohort study

BACKGROUND

Several studies have suggested an association between IgE-mediated atopic allergies and depression, although thus far no epidemiologic evidence involving a large, unselected, general-population sample and valid methods in diagnosing atopy support this putative association.

METHODS

We used the Northern Finland 1966 Birth Cohort, which was followed prospectively to age 31. Of the total cohort, 5428 individuals underwent skin tests for three of the most common allergens (i.e., cat, birch, and timothy grass) and for dust mites (Dermatophagoides pteronyssinus). Data on doctor-diagnosed lifetime depression were obtained from questionnaires.

RESULTS

After adjusting for social class, mothers' parity, place of residence, and psychiatric morbidity, the logistic regression analysis showed that the risk of developing depression when compared with nonatopic subjects increased up to 1.8-fold in atopic women (adjusted odds ratio 1.8, 95% confidence interval [CI] 1.2-2.6) and, when compared with skin-test-negative female subjects without allergic symptoms, reached 2.7-fold increases (95% CI 1.6-4.6) in those suffering from clinically manifest atopic disorders. Corresponding associations were not found among male subjects.

CONCLUSIONS

Our results indicate that women suffering from atopic diseases may possess an elevated risk for developing depression during early adulthood. Possible background theories (i.e., genetic abnormalities in serotonin metabolism, hypothalamic-pituitary-adrenal axis dysfunction, and histamine theory) are discussed.

Recent studies on interactions between n-3 and n-6 polyunsaturated fatty acids in brain and other tissues

Recent literature provides a basis for understanding the behavioral, functional, and structural consequences of nutritional deprivation or disease-related abnormalities of n-3 polyunsaturated fatty acids. The literature suggests that these effects are mediated through competition between n-3 and n-6 polyunsaturated fatty acids at certain enzymatic steps, particularly those involving polyunsaturated fatty acid elongation and desaturation. One critical enzymatic site is a delta6-desaturase. On the other hand, an in-vivo method in rats, applied following chronic n-3 nutritional deprivation or chronic administration of lithium, indicates that the cycles of de-esterification/re-esterification of docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) within brain phospholipids operate independently of each other, and thus that the enzymes regulating each of these cycles are not likely sites of n-3/n-6 competition.