Dietary fat, eicosanoids, and immunity

You are not always what you eat-Fatty acid bioconversion and lipid homeostasis in the larvae of the sand mason worm Lanice conchilega

The meroplanktonic larvae of benthic organisms are an important seasonal component of the zooplankton in temperate coastal waters. The larvae of the reef-building polychaete Lanice conchilega contribute up to 15% of the summer zooplankton biomass in the North Sea. Despite their importance for reef maintenance (which positively affects the benthic community), little is known about the trophic ecology of this meroplanktonic larva. Qualitative and quantitative estimates of carbon (C) transfer between trophic levels and of fatty acid (FA)-specific assimilation, biosynthesis, and bioconversion can be obtained by compound-specific stable isotope analysis of FA. The present work tested the hypothesis that the concept of fatty acid trophic markers (FATM), widely used for studies on holoplankton with intermediate to high lipid contents, is also applicable to lipid-poor organisms such as meroplanktonic larvae. The incorporation of isotopically-enriched dietary C by L. conchilega larvae was traced, and lipid assimilation did not follow FA-specific relative availabilities in the diet. Furthermore, FAs that were unavailable in the diet, such as 22:5(n-3), were recorded in L. conchilega, suggesting their bioconversion by the larvae. The results indicate that L. conchilega larvae preferentially assimilate certain FAs and regulate their FA composition (lipid homeostasis) independently of that of their diet. Their quasi-homeostatic response to dietary FA availability could imply that the concept of FATM has limited application in lipid-poor organisms such as L. conchilega larvae.

The comparative roles of polyunsaturated fatty acids in pig neonatal development

The present review focuses on the importance of polyunsaturated fatty acid (PUFA) provision for the normal development of the pig neonate. The review describes first the selected fatty acid composition of a range of porcine tissues including nervous tissues, muscle and adipose tissues, reproductive organs and immune-responsive organs and/or cells. The importance of PUFA to the functioning of the immune system of the neonate is considered briefly and is followed by an in-depth consideration of the sources of PUFA for the neonatal pig. The effects of different categories or specific types of fatty acid (i.e. non-essential, linoleic, α-linolenic, long-chain n-6 and n-3 PUFA) on various indices of pig neonatal growth are reviewed. The importance of n-3 PUFA supply to the fetal and early neonatal pig is underlined and evidence is presented for more attention to be given to the amounts available from maternal sources. Based on the material reviewed, recommendations are made on the dietary intake of PUFA in the gestating pig.

Tissue-specific, nutritional, and developmental regulation of rat fatty acid elongases

Of the six fatty acid elongase (Elovl) subtypes expressed in mammals, adult rat liver expresses four subtypes: Elovl-5 > Elovl-1 = Elovl-2 = Elovl-6. Overnight starvation and fish oil-enriched diets repressed hepatic elongase activity in livers of adult male rats. Diet-induced changes in elongase activity correlate with Elovl-5 and Elovl-6 mRNA abundance. Adult rats fed the peroxisome proliferator-activated receptor alpha (PPARalpha) agonist WY14,643 have increased hepatic elongase activity, Elovl-1, Elovl-5, Elovl-6, Delta5, Delta6, and Delta9 desaturase mRNA abundance, and mead acid (20:3,n-9) content. PPARalpha agonists affect both fatty acid elongation and desaturation pathways leading to changes in hepatic lipid composition. Elovl activity is low in fetal liver but increases significantly after birth. Developmental changes in hepatic elongase activity paralleled the postnatal induction of Elovl-5 mRNA and mRNAs encoding the PPARalpha-regulated transcripts, Delta5 and Delta6 desaturase, and cytochrome P450 4A. In contrast, Elovl-6, Delta9 desaturase, and FAS mRNA abundance paralleled changes in hepatic sterol regulatory element binding protein 1c (SREBP-1c) nuclear content. SREBP-1c is present in fetal liver nuclei, absent from nuclei immediately after birth, and reappears in nuclei at weaning, 21 days postpartum. In conclusion, changes in Elovl-5 expression may account for much of the nutritional and developmental control of fatty acid elongation activity in the rat liver.

Pilot study of dietary fatty acid supplementation in the treatment of adult periodontitis

The anti-inflammatory effects of both n-3 and n-6 polyunsaturated fatty acids (PUFA) have been demonstrated in vitro and in many disease states, in particular in the treatment of rheumatoid arthritis. The benefit of n-3 PUFA supplementation has been documented in animal models of periodontal inflammation and a trend towards reduced inflammation has been seen in human experimental gingivitis. The purpose of this study was to examine the potential anti-inflammatory effects of PUFA supplementation, by administration of fish oil as a source of the n-3 PUFA, eicosapentaenoic acid, and borage oil as a source of the n-6 PUFA, gamma-linolenic acid (GLA), to adults with periodontitis. Thirty adult human subjects with periodontitis were administered either fish oil 3000 mg daily; borage oil 3000 mg daily; fish oil 1500 and borage oil 1500 mg daily, or placebo. The modified gingival index, the plaque index (PI), periodontal probing depths and beta-glucuronidase levels in gingival crevicular fluid were measured at baseline and after 12 weeks of treatment. Improvement in gingival inflammation was observed in subjects treated with borage oil (P<0.016), with a trend apparent in subjects treated with fish oil or a combination of PUFA. There was no statistically significant improvement in PI, although a trend was apparent in those receiving borage oil. Improvement in probing depth was seen in those subjects treated with either fish oil alone or borage oil alone, but statistical significance was only seen for the comparison of borage oil and placebo (P<0.044). No change was seen in gingival crevicular fluid (GCF) beta-glucuronidase levels. The use of borage oil supplementation, a source of the n-6 PUFA, GLA, can have beneficial effects on periodontal inflammation. n-6 PUFA supplementation seemed to offer more impressive results than either n-3 PUFA supplementation or the combination of lower doses of the two supplements. Additional studies will be necessary to more fully assess the potential of these agents to favorably affect periodontal inflammation.

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.

Dietary fat and breast cancer metastasis by human tumor xenografts

Human breast cancer cell lines growing as xenografts in athymic nude mice have been used to examine the effects of dietary fat and fatty acids on tumor progression. The estrogen independent MDA-MB-435 cell line has the advantage that it metastasizes consistently to the lungs and forms quantifiable secondary nodules when injected into the mammary fat pads. With these breast cancer cells, the stimulating effects of polyunsaturated omega-6 fatty acids on both primary tumor growth and metastasis were demonstrated; in contrast, the long-chain omega-3 fatty acids were inhibitory. The model can also be adapted to examine dietary fatty acids, and inhibitors of their metabolism, as experimental adjuvant therapy after surgical excision of the primary tumors. Unfortunately, estrogen dependent human breast cancer cells do not metastasize, or do so rarely, in nude mice; in consequence, it is not possible to use the model to study estrogen-fatty acid interactions on the metastatic process. In addition to metastasis from a primary location, intravenous injection of MDA-MB-435 cells into the nude mouse host, particularly when combined with studies using Matrigel-based in vitro invasion assays, permits further dissection of the steps in the metastatic cascade which are influenced by dietary fatty acids. The results obtained by these several approaches have demonstrated distinct roles for the cyclooxygenase and lipoxygenase-mediated products of omega-6 fatty acid metabolism, and suggest new approaches to experimental breast cancer therapy.

Inhibition of lipid absorption as an approach to the treatment of obesity

A reduction in fat intake may be achieved by making educated choices to reduce total calorie intake, to consume a lower quantity of total fats, or to modify the ratio of saturated-to-polyunsaturated lipids. Leptin agonists or NPY or CCK antagonists may prove to be useful to diminish appetite and thereby reduce the total intake of food. But eating has such cultural, social, and hedonistic attributes that such a single-pronged approach is unlikely to be successful. The use of fat substitutes may prove to be popular to provide a wide range of snack food options, but these are likely to be of minimal use in weight reduction programs because of their distribution of additives in only a limited number of foods. The inhibitors of lipid digestion will be modestly successful in the short term; their long-term success will be influenced by gastrointestinal adverse effects and the need to consume fat-soluble vitamin supplements to prevent the development of fat-soluble vitamin deficiencies. The inhibition of lipid absorption is an attractive targeted approach for the treatment of obesity, since this would reduce the uptake of visible as well as invisible fats, which would potentially offer convenient dosing, and could also be a means to inhibit secondarily the uptake of carbohydrate calories.

Efficacy of gamma-linolenic acid in the treatment of patients with atopic dermatitis

Of 60 patients with atopic dermatitis (30 males and 30 females, 15-30 years old) 30 were treated with gamma-linolenic acid of (C18:3 n-6) at a dosage of 274 mg twice a day; the other 30 patients were given placebo. The patients were treated for 12 weeks, during which their symptoms were assessed on a linear scale both by a dermatologist and by themselves every 4 weeks. The patients who received gamma-linolenic acid, showed gradual improvements in pruritus, erythema, vesiculation and oozing, which were statistically significant compared with the control group (P < 0.001). Only one patient had presented with scaling at the beginning of the study and this symptom appeared to be less influenced by the effects of gamma-linolenic acid. The assessments of symptoms made by the dermatologist were generally consistent with those made by the patients themselves. gamma-linolenic acid was found to be effective and without side-effects for the treatment of atopic dermatitis.

Breast cancer: weighing the evidence for a promoting role of dietary fat

It has been hypothesized that a high-fat diet promotes the development of postmenopausal breast cancer. This contention is supported by data showing high international correlations between fat intake and breast cancer rates, modest positive associations with a high-fat diet in case-control studies, and animal model studies that have consistently demonstrated that dietary fat influences mammary cancer development at several stages in the carcinogenic process. A number of plausible biologic mechanisms have been suggested that may explain such promotional effects. In contrast, dietary fat intake is unrelated to the risk of breast cancer in cohort studies. The conflicting findings from cohort studies have created uncertainty regarding nutritional recommendations and breast cancer prevention. After reviewing key scientific findings that are relevant to this issue, the following conclusion is drawn: In the absence of data from dietary intervention trials, the weight of available evidence suggests that the type and amount of fat in the diet is related to postmenopausal breast cancer and that the inability to detect associations within populations (cohort studies) is because of measurement error and the relative homogeneity of diets measured. It is expected that the results from intervention trials will clarify this issue.

Influence of n-6 and n-3 polyunsaturated fatty acids on the resistance to experimental tuberculosis

It has previously been shown that the n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (20:5(n-3)) and docosahexaenoic acid (22:6(n-3)) possess antiinflammatory properties and can interfere with immune functions. To evaluate whether this would affect resistance to infection, we studied the influence of different types of fatty acids (FAs) on experimental tuberculosis in an animal model. Three groups of 26 weanling guinea pigs were fed isocaloric diets with 26 cal% fat that differed in FA composition with respect to saturated FAs, linoleic acid (18:2(n-6)), eicosapentaenoic acid (20:5(n-3)), and docosanexaenoic acid (22:6(n-3)) as follows: (1) reference (REF) group: 14.8 cal% saturated FAs and 2.8 cal% linoleic acid; (2) n-6 group: 4.6 cal% saturated FAs and 15.4 cal% linoleic acid; (3) n-3 group: 6.3 cal% saturated FAs, 10 cal% linoleic acid, 1.4 cal% eicosapentaenoic acid, and 0.9 cal% docosahexaenoic acid. After 13 weeks, 18 animals from each group were intramuscularly injected with 180 colony-forming units (CFU) Mycobacterium tuberculosis strain H37Rv. Eight noninfected animals per group served as controls. Seven weeks later, the mean number of mycobacteria recovered from the spleens of the n-3 group (log 4.34 CFU, standard error of the mean [SEM], 0.12) was significantly higher than from the REF group (log 3.90 CFU; SEM, 0.15) and the n-8 group (log 3.93 CFU; SEM, 0.13; P < .05). In addition, the Root Index of Virulence (RIV) showed the most pronounced progression of the disease in the n-3 group. The mean size of the tuberculin reaction was larger in the n-3 group than in the other groups (P < .05). There was no significant difference between the n-6 group and the REF group. We conclude that supplementing the diet with n-3 FAs eicosapentaenoic acid and docosahexaenoic acid can affect resistance to M tuberculosis, whereas supplementing with n-6 FAs does not.

The influence of dietary lipids on the composition and membrane fluidity of rat hepatocyte plasma membrane

Weanling male Wistar rats were fed for five weeks on standard rat chow (23 g fat/kg diet) or one of four synthetic diets with butterfat, coconut oil, corn oil, or fish oil as the main lipid source (100 g fat/kg diet). In all diets, 10% of the fat was provided as corn oil to prevent essential fatty acid deficiency. Significant differences were observed in the saturated, monounsaturated, and polyunsaturated fatty acid composition, and in the ratio of cholesterol to phospholipid, in the hepatocyte membranes. The fluidity of hepatocyte plasma membranes was assessed using the fluorescence recovery after photobleaching technique and steady-state fluorescence anisotropy of diphenylhexatriene. No significant differences were found in the fluidity of plasma membranes between animals on the different fat diets, despite diet-induced changes in their fatty acid composition. However, the proportion of lipid free to diffuse in the plasma membrane varied with diet, being significantly greater (P < 0.05) in animals fed chow (63.7%), coconut oil (61.5%), and butterfat (57.6%) diets than in those fed the corn oil (47.3%) diet. Animals fed fish oil showed an intermediate (50.0%) proportion of lipid free to diffuse. The data support the hypothesis that dietary lipids can change both the chemical composition and lateral organization (lipid domain structure) of rat hepatocyte plasma membranes.

A randomized trial of isonitrogenous enteral diets after severe trauma. An immune-enhancing diet reduces septic complications

OBJECTIVE

The authors randomized patients to an enteral diet containing glutamine, arginine, omega-3 fatty acids, and nucleotides or to an isonitrogenous, isocaloric diet to investigate the effect of septic outcome. A third group of patients, without enteral access but eligible by severity of injury, served as unfed controls and were studied prospectively to determine the risk of infection.

SUMMARY BACKGROUND DATA

Laboratory and clinical studies suggest that diets containing specialty nutrients, such as arginine, glutamine, nucleotides, and omega-3 fatty acids, reduce septic complications. Unfortunately, most clinical trials have not compared these diets versus isonitrogenous, isocaloric controls. This prospective, blinded study randomized 35 severely injured patients with an Abdominal Trauma Index > or = 25 or a Injury Severity Score > or = 21 who had early enteral access to an immune-enhancing diet ([IED] Immun-Aid, McGaw, Inc., Irvine, CA; n = 17) or an isonitrogenous, isocaloric diet (Promote [Ross Laboratories, Columbus, OH] and Casec [Mead-Johnson Nutritionals, Evansville, IN]; n = 18) diet. Patients without early enteral access but eligible by severity of injury served as contemporaneous controls (n = 19). Patients were evaluated for septic complications, antibiotic usage, hospital and intensive care unit (ICU) stay, and hospital costs.

RESULTS

Two patients died in the treatment group and were dropped from the study. Significantly fewer major infectious complications (6%) developed in patients randomized to the IED than patients in the isonitrogenous group (41%, p = 0.02) or the control group (58%, p = 0.002). Hospital stay, therapeutic antibiotics, and the development of intra-abdominal abscess was significantly lower in patients receiving the IED than the other two groups. This improved clinical outcome was reflected in reduced hospital costs.

CONCLUSIONS

An IED significantly reduces major infectious complications in severely injured patients compared with those receiving isonitrogenous diet or no early enteral nutrition. An IED is the preferred diet for early enteral feeding after severe blunt and penetrating trauma in patients at risk of subsequent septic complications. Unfed patients have the highest complication rate.

Selective suppression of endothelial cell activation by arachidonic acid

Endothelial cell (EC) activation plays a key role in inflammation, thrombosis and organ rejection. Normally, EC are in a quiescent state in which their function is to prevent coagulation and thrombosis, and to participate in the regulation of leukocyte migration from the bloodstream into the tissue. Upon activation with cytokines or other stimuli, EC up-regulate a number of genes, including E-selectin (ELAM-1), intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, interleukin (IL)-1, IL-8, tissue factor (TF), plasminogen activator inhibitor-1 (PAI-1), MCP-1 (monocyte chemoattractant protein-1) and endothelial cell inducible gene (ECI-6). Arachidonic acid (AA) is produced by several cell types, including EC, and acts on various cells. We report here that AA inhibits the up-regulation of some, but not all genes that are induced with EC activation in a dose-dependent manner. AA suppresses TNF-alpha, IL-1 alpha, LPS or PMA-induced E-selectin expression, as well as mRNA accumulation of E-selectin, ICAM-1 and IL-8 stimulated by TNF-alpha. The inhibition appears to be at the level of transcription. At the same time under the same conditions AA does not, repress mRNA accumulation for PAI-1, ECI-6, MCP-1 and VCAM-1. We suggest that the induced expression of AA with EC activation may result in a negative feedback loop regulating further activation.

Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal antiinflammatory drugs. Clinical and immune correlates

OBJECTIVE

To determine the following: 1) whether dietary supplementation with fish oil will allow the discontinuation of nonsteroidal antiinflammatory drugs (NSAIDs) in patients with rheumatoid arthritis (RA); 2) the clinical efficacy of high-dose dietary omega 3 fatty acid fish oil supplementation in RA patients; and 3) the effect of fish oil supplements on the production of multiple cytokines in this population.

METHODS

Sixty-six RA patients entered a double-blind, placebo-controlled, prospective study of fish oil supplementation while taking diclofenac (75 mg twice a day). Patients took either 130 mg/kg/day of omega 3 fatty acids or 9 capsules/day of corn oil. Placebo diclofenac was substituted at week 18 or 22, and fish oil supplements were continued for 8 weeks (to week 26 or 30). Serum levels of interleukin-1 beta (IL-1 beta), IL-2, IL-6, and IL-8 and tumor necrosis factor alpha were measured by enzyme-linked immunosorbent assay at baseline and during the study.

RESULTS

In the group taking fish oil, there were significant decreases from baseline in the mean (+/- SEM) number of tender joints (5.3 +/- 0.835; P < 0.0001), duration of morning stiffness (-67.7 +/- 23.3 minutes; P = 0.008), physician's and patient's evaluation of global arthritis activity (-0.33 +/- 0.13; P = 0.017 and -0.38 +/- 0.17; P = 0.036, respectively), and physician's evaluation of pain (-0.38 +/- 0.12; P = 0.004). In patients taking corn oil, no clinical parameters improved from baseline. The decrease in the number of tender joints remained significant 8 weeks after discontinuing diclofenac in patients taking fish oil (-7.8 +/- 2.6; P = 0.011) and the decrease in the number of tender joints at this time was significant compared with that in patients receiving corn oil (P = 0.043). IL-1 beta decreased significantly from baseline through weeks 18 and 22 in patients consuming fish oil (-7.7 +/- 3.1; P = 0.026).

CONCLUSION

Patients taking dietary supplements of fish oil exhibit improvements in clinical parameters of disease activity from baseline, including the number of tender joints, and these improvements are associated with significant decreases in levels of IL-1 beta from baseline. Some patients who take fish oil are able to discontinue NSAIDs without experiencing a disease flare.

Fish oil enhances macrophage tumor necrosis factor-alpha mRNA expression at the transcriptional level

Dietary supplementation with fish oil has previously been shown to enhance in vivo and in vitro (macrophage) synthesis of tumor necrosis factor-alpha (TNF-alpha) in response to bacterial lipopolysaccharide (LPS) stimulation. The studies reported here were conducted to gain insight into the molecular mechanisms of this nutrient-immune interaction by comparing the concentration, rate of synthesis, and rate of decay of TNF-alpha mRNA upon LPS stimulation of macrophages obtained from mice fed high-fat diets, rich in either fish oil, corn oil, or coconut oil, or a low-fat diet for a period of 4 weeks. The results indicate that compared with the other diet groups, LPS stimulation of macrophages from mice fed fish oil resulted in (1) enhanced levels of mRNA and protein for TNF-alpha, and (2) increased transcription of TNF-alpha mRNA as assessed by nuclear run-on assays. Posttranscriptional studies showed that the rate of decay of TNF-alpha mRNA did not vary significantly for macrophages from mice fed with fish oil as compared with corn oil. Further studies using actinomycin D and cycloheximide suggested that RNA synthesis, but not protein synthesis, was necessary for TNF-alpha mRNA accumulation. Taken together, the present studies suggest that fish oil enhances macrophage TNF-alpha mRNA expression at the transcriptional level. Although such TNF-alpha upregulation may provide a mechanism for the beneficial effects of fish oil in certain inflammatory and immune disorders, it can also underlie its potential deleterious effects if the degree of upregulation leads to exaggerated TNF-alpha production that exceeds the limits of benefit to reach toxic levels.

Docosahexaenoic acid-induced alteration of Thy-1 and CD8 expression on murine splenocytes

Here we test whether the incorporation of docosahexaenoic acid (DHA, 22:6), an (n-3) fatty acid, into lymphocyte membranes affects the expression of the surface proteins Thy-1.2 and CD8. DHA was incorporated into splenocytes by three methods: feeding mice diets containing menhaden (fish) oil, fusing splenocytes with DHA-containing phosphatidylcholine vesicles, and culturing splenocytes with DHA. Thy-1.2 and CD8 expression were measured by flow cytometry and complement-mediated lysis using a panel of monoclonal antibodies. As (n-3) fatty acid incorporation into the lymphocytes increased, the expression of one Thy-1.2 epitope and one CD8 epitope decreased; the expression of two CD8 epitopes increased. Although diet-induced changes in surface protein expression may result from selective migration of cell populations or the diet's effect on protein biosynthesis, fusion with lipid vesicles demonstrated that DHA-containing phospholipids can mediate a direct and immediate effect. The decrease in Thy-1.2 expression was sustained for more than a week after removal of (n-3) fatty acids from the diet, most likely due to retention of membrane-bound (n-3) fatty acids. Because Thy-1.2 and CD8 participate in T cell activation, modulation of their expression by DHA suggests that DHA, when serving as a membrane structural element, may alter immune function.

Modulation of exercise-induced immunosuppression by dietary polyunsaturated fatty acids in mice

The possible interaction between intense exercise, known to suppress the immune response, and nutritive factors, such as polyunsaturated fatty acids (PUFA), was examined in inbred female C57Bl/6 mice. The animals received for 8 wk either a natural ingredient diet or a diet supplemented with 10 g/100 g linseed oil containing over 50% of 18:3 (n-3) alpha-linoleic acid. Other groups received PUFA containing only traces of 18:3 (n-3) fatty acid; beef tallow, containing mostly 18:1 (n-9) saturated fat, safflower oil, an 18:2 (n-6) PUFA, and fish oil, containing longer chain (n-3) PUFA. Each dietary group was divided into two subgroups: sedentary diet controls and exercised animals. Exercise consisted of continuous swimming at high intensity until exhaustion. It was shown in three separate experiments that (1) the primary humoral response to sheep red blood cells, determined by the plaque-forming cell (PFC) assay, was affected by PUFA diet in sedentary animals in the order beef tallow > control diet > safflower oil > fish oil > linseed oil, and (2) the PFC response was suppressed by the exhaustive exercise, as compared to sedentary controls, except for animals fed 18:3 (n-3) linseed oil, where the normal response was noted. Phagocytosis of fluorescent microspheres by peritoneal macrophages, determined by flow cytometry, was significantly lower in exercised animals receiving the linseed oil diet, whereas other diets either increased or did not significantly change the macrophage phagocytic activity, compared to the sedentary diet controls. Spleen lymphocyte subsets were unchanged in exercised animals except for a marked shift from the lymphoid peak toward the erythroid peak. Generally, our data showed a marked immunomodulatory effect of 18-3 (n-3) alpha-linoleic acid on the exhaustive exercise-related immunosuppression, as compared to the effects of other selected PUFA.

Effects of n-3 polyunsaturated fatty acids on the reacylation of arachidonic acid in peritoneal macrophages

Mouse peritoneal macrophages were prelabelled with [3H]AA and activated ex vivo with phorbol myristate acetate (PMA) in the presence or absence of added n-3 polyunsaturated fatty acids (n-3 PUFA). The n-3 PUFA did not affect the release of [3H]AA from stimulated macrophages. Added AA, enhanced, in a dose-dependent manner, the amount of free [3H]AA in the medium after activating the cells with PMA. Both n-3 PUFA and AA were actively acylated into the lipids of PMA activated macrophages, but the n-3 PUFA did not compete with reacylation of AA. In unstimulated cells, in the absence of PMA, n-3 PUFA effectively competed with AA for acylation into membrane phospholipids. These studies suggest that distinct pools of AA exist in macrophages.

Inhibition of cytokine-stimulated thymic lymphocyte proliferation by fatty acids: the role of eicosanoids

The effect of individual fatty acids on the proliferation of thymic lymphocytes in response to interleukin-1 (IL-1) was investigated. Proliferation was estimated by measuring [3H]thymidine incorporation into the acid insoluble fraction of the thymocytes. A concentration-dependent inhibition (in the range 1-100 microM) in the IL-1-stimulated proliferation was observed with the C20 fatty acids dihomo-gamma-linolenic acid (DGLA), arachidonic acid and eicosapentaenoic acid (EPA). A less pronounced concentration-dependent inhibitory response was observed with the C18 fatty acids linoleic acid, alpha-linolenic acid and gamma-linolenic acid. Palmitic acid and oleic did not have any effect on either basal or IL-1-stimulated proliferation at concentrations up to 100 microM. The potencies of each fatty acid for this effect at a concentration of 100 microM were: arachidonic acid > EPA > or = DGLA > linoleic acid. DGLA, arachidonic acid and EPA also attenuated IL-2-stimulated proliferation. The inhibitory action of these fatty acids was not mediated by conversion to prostaglandins or other eicosanoids as the cyclooxygenase inhibitor, ketoprofen and NDGA did not alter their action. Incubation of thymocytes with radiolabelled DGLA and EPA followed by reverse-phase HPLC analysis revealed that DGLA is predominantly converted to a more polar metabolite which is not PGE1 whereas EPA does not appear to be converted to any other detectable metabolite. The data indicate that the inhibitory actions of fatty acids on cell proliferation do not occur as a result of conversion to other metabolites but may be direct effects. The inhibition of cytokine-stimulated lymphocyte proliferation by unsaturated fatty acids would imply that they may attenuate cell-mediated immune reactions.

Effects of n-3 and n-6 fatty acids on the activities and expression of hepatic antioxidant enzymes in autoimmune-prone NZBxNZW F1 mice

Menhaden fish oil (FO) containing n-3 fatty acids dramatically extends the life span and delays the onset and progression of autoimmune disease in (NZBxNZW)F1 (B/W) female mice as compared to those fed corn oil (CO) rich in n-6 lipids. As an inefficient antioxidant defense system has been linked to autoimmune diseases, the present study was undertaken to determine whether the protective action of n-3 lipids is mediated through their antioxidant defense system. Weanling B/W mice were fed a nutritionally adequate, semipurified diet containing CO or krill oil (KO) or FO at 10% level (w/w) ad libitum until the mice were 6.5 months old. All diets contained the same level of vitamin E (21.5 mg/100 g diet). We compared the effects of feeding n-6 and n-3 lipids on survival, kidney disease, hepatic microsomal lipid composition, peroxidation, and on the activity and mRNA expression of the antioxidant enzymes catalase, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in 6.5-month-old B/W mice. The results showed that when compared to livers from CO-fed mice, livers from KO- and FO-fed mice showed: (i) significantly higher (P < 0.001) activities and expression of CAT, GSH-Px and SOD; (ii) significantly lower (P < 0.001) arachidonic acid (20:4n-6) and linoleic acid (18:2n-6) and higher (P < 0.001) eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) levels in hepatic microsomes; and (iii) significantly lower (P < 0.001) estimated peroxidation indices and thiobarbituric acid reactive substances generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Parenteral nutrition: hospital to home

Parenteral nutrition support is the provision of essential nutrients intravenously, bypassing the intestinal tract. It is used in a variety of clinical settings and medical conditions. Parenteral nutrition is a complex technology that requires the input of many professionals, including dietitians. The role of the dietitian in parenteral nutrition support involves direct patient care, consultative services, education, program development, and research. Even though this field of practice is still developing, some common practices can be described. Nutrition assessment determination of macronutrient and micronutrient requirements, and monitoring are vital aspects of the provision of parenteral nutrition support that benefit from the knowledge and experience of a dietitian. The future of parenteral nutrition includes identification of preferred fuels for specific disease states, development of new lipid emulsions, and identification of conditionally essential nutrients.

Effects of dietary essential fatty acid deficiency on the development of the rat thymus and immune system

The paper describes an effect of essential fatty acid (EFA) deficiency on the development of the rat thymus and pups' immune system. From birth until being weaned (22nd day), the pups were hand-fed artificial milk diets containing a low (EFA-D) or high (EFA-R) proportion of EFA in the lipid fraction. The weight parameters of the body, thymus and spleen, the fatty acid composition of the individual thymus phospholipid subclasses, and mitogen-induced proliferation of thymus and spleen lymphocytes were studied. The results show that the total body weight of the EFA-deficient (EFA-D) fed animals was significantly decreased in comparison with the EFA-rich (EFA-R) and rat milk hand-fed animals. For the EFA-D group of young rats a high level of the (n-9) and (n-7) series fatty acids [mainly oleic 18:1(n-9) and eicosatrienoic 20:3(n-9) acids] was characteristic of the fatty acids in phosphatidylcholine and phosphatidylethanolamine in the thymus, compensating for the reduction of the content of arachidonic acid 20:4(n-6). The biochemical index of the EFA nutritional deficit in the thymus tissue was observable as early as on day 7. The mitogen-induced (Con A) proliferation of the thymus and spleen lymphocytes was decreased both on the 30th and 40th day of life. The results show that the EFA nutritional deficit in the early postnatal period caused damage to the structure of thymus in the young rats, most probably as a result of the change in the composition of the lipid fraction. These changes also affected the development of the immune system of the whole organism.

Short-term dietary lipid manipulation does not affect survival in two models of murine sepsis

Dietary lipid manipulation has been shown to have various effects on the immune system, depending on the amount of fat, degree of saturation, and type of fat used. In this study we investigated the role of different sources of fat at different levels on the survival of mice in two models of peritonitis, one with Pseudomonas aeruginosa and the other with Salmonella typhimurium. CF1 mice were pair-fed diets with 5% or 40% of total calories as fat. The source of fat used was coconut oil, oleic acid, safflower oil, or fish oil. Three other diets were tested as well, one with no fat, one with only 0.5% of total calories linoleic acid as the only source of fat, and a control diet that had 12% of total calories as corn oil. At the end of 2 weeks of feeding the experimental diets, mice were challenged with Ps aeruginosa intraperitoneally and mortality was recorded over 1 week. After 3 weeks of feeding the experimental diets, mice were challenged with S typhimurium and mortality was recorded over 2 weeks. No significant differences were seen on survival among groups fed different levels of fat, as well as different sources of fat. We conclude that, overall, 2- and 3-week manipulation of dietary fat does not affect outcome from infection in these models.

Study on the lipid composition of aging Fischer-344 rat lymphoid cells: effect of long-term calorie restriction

Long-term calorie restriction (LCR) is widely known to increase the survival rate of laboratory rodents and appears to retard the aging and senescence process. The present study was undertaken in Fischer-344 male rats maintained on ad libitum (AL) or LCR (40% less food intake than AL starting at 6 weeks of age). Age-associated changes in the proliferative response of lymphoid cells to mitogenic stimuli were studied in relation to alterations in the fatty acid composition of adherent and non-adherent-enriched subpopulations of spleen cells. Increases in spleen cell long-chain highly unsaturated fatty acids (20:4, 22:4 and 22:5) were accompanied by decreases in linoleic acid (18:2) in aging AL-fed rats. However, LCR stabilized levels of 18:2 and prevented the rise in highly unsaturated fatty acids. In addition, LCR markedly modulated the fatty acid profiles of thymocytes and bone marrow cells. A 70% decline in concanavalin A (Con A) stimulated [3H]thymidine uptake of spleen cells from AL animals was normalized by LCR. Splenic reduced glutathione (GSH), a potential modulator of the mitogenic response, was unaffected by age and nutritional regimen. Thus, normalization of lymphoid cell fatty acid composition by LCR parallels the preservation of mitogenic responsiveness to Con A.

Implications for cancer epidemiology of differences in dietary intake associated with alcohol consumption

Several dietary factors are thought to modify risk for cancers that are known to be associated with alcohol intake. In this study, we sought to identify and describe alcohol-related differences in dietary and nutritional factors that are potential independent predictors of cancer risk or effect modifiers or confounders of alcohol-cancer relationships. Data were obtained from a large hospital-based case-control study that was designed to estimate the cancer risk from various tobacco products. Study subjects consisted of 465 male and 300 female incident lung cancer cases and 870 male and 556 female hospitalized patient controls matched on age (+/- 5 yrs). Nutritional data were analyzed as log-transformed frequencies of 30 food items, 9 factor scores generated to describe overall patterns of dietary intake, and nutrient scores estimating daily intake of fat, vitamin A, fiber, and cholesterol. We observed many more significant differences in nutritional exposures by alcoholic beverage intake than would be expected merely by chance. For males, the most striking relationships included increased meat and egg consumption with increasing alcohol consumption and higher intake of cantaloupe and cold cereal among lighter drinkers. For females, we observed strong inverse relationships between alcohol consumption and reported intake of fruit, cold cereal, and ice cream. We also observed a direct association between alcohol and meat consumption, though it was weaker than that found among men. Findings based on factors and nutrients followed the pattern observed for the individual food items, with highest fat scores and lowest fruit scores among the heaviest drinkers. Implications for nutrient-alcohol interactions and statistical considerations are discussed.

Dietary fish oil and olive oil supplementation in patients with rheumatoid arthritis. Clinical and immunologic effects

Forty-nine patients with active rheumatoid arthritis completed a 24-week, prospective, double-blind, randomized study of dietary supplementation with 2 different dosages of fish oil and 1 dosage of olive oil. Clinical evaluations were performed at baseline and every 6 weeks thereafter, and immunologic variables were measured at baseline and after 24 weeks of study. The 3 groups of patients were matched for age, sex, disease severity, and use of disease-modifying antirheumatic drugs (DMARDs). Subjects continued receiving DMARDs and other background medications without change during the study. Twenty patients consumed daily dietary supplements of n3 fatty acids containing 27 mg/kg eicosapentaenoic acid (EPA) and 18 mg/kg docosahexaenoic acid (DHA) (low dose), 17 patients ingested 54 mg/kg EPA and 36 mg/kg DHA (high dose), and 12 patients ingested olive oil capsules containing 6.8 gm of oleic acid. Significant improvements from baseline in the number of tender joints were noted in the low-dose group at week 24 (P = 0.05) and in the high-dose group at week 18 (P = 0.04) and 24 (P = 0.02). Significant decreases from baseline in the number of swollen joints were noted in the low-dose group at weeks 12 (P = 0.003), 18 (P = 0.002), and 24 (P = 0.001) and in the high-dose group at weeks 12 (P = 0.0001), 18 (P = 0.008), and 24 (P = 0.02). A total of 5 of 45 clinical measures were significantly changed from baseline in the olive oil group, 8 of 45 in the low-dose fish oil group, and 21 of 45 in the high-dose fish oil group during the study (P = 0.0002). Neutrophil leukotriene B4 production decreased by 19% from baseline in the low-dose fish oil group (P = 0.0003) and 20% in the high-dose group (P = 0.03), while macrophage interleukin-1 production decreased by 38.5% in the olive oil group (P not significant), 40.6% in the low-dose group (P = 0.06), and 54.7% in the high-dose group (P = 0.0005). Tritiated thymidine incorporation in peripheral blood mononuclear cells after stimulation with concanavalin A increased significantly in all 3 groups after 24 weeks, compared with baseline values. We conclude that the clinical benefits of dietary supplementation with omega-3 fatty acids are more commonly observed in patients consuming higher dosages of fish oil for time intervals that are longer than those previously studied. Dietary supplementation with olive oil is also associated with certain changes in immune function, which require further investigation.

Natural killer cell activity in a longitudinal dietary fat intervention trial

It has been hypothesized that dietary fat may affect natural killer (NK) cell activity, a factor of potential importance in early tumor surveillance. Fourteen men successfully completed an intervention trial designed to test the effect of dietary fat on NK activity in humans. Study subjects lowered their fat intake to an average of 22% of calories as fat and consumed two dietary supplements (of coconut and safflower oils), in a cross-over design. These supplements resulted in large changes in the ratio of polyunsaturated to saturated fatty acids (1.73 to 0.34, on average). Results of a general linear model in which we fitted covariates on exercise, body mass, intervention sequence, and various dietary predictors revealed a significant effect of decreased total dietary fat intake on increased NK activity at an E/T ratio of 100:1 (about 0.79% increase for each absolute percent of calories as fat, P = 0.04). Similar results were obtained at E/T ratios of 50:1 and 25:1. No other nutritional predictor was significantly associated with NK activity at any E/T ratio.

Dietary fat and tumor metastasis

Evidence from several types of studies indicates a relationship between fat intake and occurrence of malignant tumors at specific sites. When rodents are fed high-fat diets, the incidence of mammary tumors sharply increases and latency of tumor appearance is greatly diminished, as compared with the same parameters in animals fed low levels of fat. Despite advances in surgical technique and the development of aggressive therapies for the treatment of primary cancers, most deaths in humans with cancer are caused by metastasis. Accordingly, we have reviewed the process of metastasis and have focused on the question of whether dietary fat can play a role. Metastasis is a complex, multistep, progressive process, and dietary fats may affect specific events such as implantation, survival, and proliferation of tumors. Finally, we discuss possible mechanisms by which dietary fat can modulate metastasis. Available data lead us to stress the importance of assessment of metastasis in studies of the effects of dietary fat on tumorigenesis.

Role of plasma fatty acids, prostaglandins and antioxidant balance in bovine mastitis

Plasma levels of free fatty acids (FFA) were measured in cows with mastitis. FFA levels are known to be elevated in milk of affected cows, and similar increases were now observed in blood plasma. Of the long-chain polyunsaturated fatty acids which serve as precursors for prostaglandins (PGs), leukotrienes (LT) and related eicosanoids, arachidonic acid (C20: 4 omega-6) was elevated by 156 per cent and C20: 3 (consisting of both omega-3 and omega-6) 153 per cent; eicosapentaenoic acid (20: 5 omega-3), not present in the plasma of healthy animals, was detected in blood of mastitic animals. Arachidonic acid correlated positively with the plasma levels of PGs. Total plasma phospholipids were increased as well, and they were positively correlated with the levels of linoleic and arachidonic acids. Changes in FFA levels correlated positively with parameters of inflammation, like bovine serum albumin and serum N-acetyl-beta-D-glucosaminidase, but negatively with the antioxidant status of the animals (vitamin E, glutathione peroxidase). As PGs and LTs are mediators of inflammation, and products of lipid peroxidation, the increase of plasma FFA could be related to tissue damage caused by oxygen free radicals. Similar processes are, however, involved also in host defence, e.g. in oxidative killing of pathogens.

Membrane fluidity of guinea pig lymphocytes and the dysfunction of the respiratory airway and lymphocyte beta-adrenergic systems of the guinea pig

The beta-adrenergic receptor responsiveness of isolated guinea pig tracheal spirals can be negatively affected by intraperitoneal administration of the Gram-negative bacterium Haemophilus influenzae, four days prior to the experiment. The reduction in tracheal relaxation is accompanied by a decrease in beta-adrenergic receptor binding sites in splenic lymphocyte membranes and by a decrease in the fluidity of these membranes. The H. influenzae-induced dysfunction of both the respiratory airway and lymphocyte beta-adrenergic systems can be mimicked by modulating the amount of linoleic acid in the diet. This linoleic acid induced dysfunction of the beta-adrenergic system is also accompanied by a decrease in the plasma membrane fluidity of the splenic lymphocyte membranes of the guinea pigs. The role for plasma membrane fluidity in asthma is discussed in relation to current concepts for atopy.

Effect of the quality of dietary fat on tumor growth and metastasis from a rat mammary adenocarcinoma

Experiments were performed to investigate whether the type of dietary fat might affect metastasis from the 13,762 mammary tumor. Female Fischer 344 retired breeder rats were placed into one of five dietary groups: 23% (wt/wt) and 5% (wt/wt) corn oil (HFCO, LFCO), 20% (wt/wt) and 5% (wt/wt) olive oil (HFOO and LFOO), or 20% (wt/wt) beef tallow (HFBT). After four weeks on the diets, each rat had a 2-mm3 piece of the tumor subcutaneously implanted. Primary tumor growth and body weight were monitored weekly for 40 days. At necropsy, the average volume of pulmonary metastases in the HFCO animals (n = 30) was significantly greater than in the other four groups. Among the four groups that did not differ significantly from each other, the rank order in average volume of pulmonary metastasis was as follows: HFOO (n = 25), HFBT (n = 26), LFOO (n = 25), and LFCO (n = 18). Growth of the primary tumor did not vary appreciably among the five groups despite the significant difference in pulmonary metastasis volume. The diets varied considerably in fatty acid content; the most salient difference was that the HFCO diet, which stimulated metastasis significantly more than the other diets did, contained about four times more linoleic acid (18:2) than the other diets. The relevance of this difference and other fatty acid differences is discussed. These results suggest that the quality of dietary fat can be an important determinant of pulmonary metastasis from the 13,762 mammary tumor in retired breeder rats.