Studies of dietary supplementation with omega 3 fatty acids in patients with rheumatoid arthritis

Lipopolysaccharide-stimulated RAW 264.7 macrophage inducible nitric oxide synthase and nitric oxide production is decreased by an omega-3 fatty acid lipid emulsion

BACKGROUND

Omega-3 fatty acids (omega-3 FA) have been demonstrated to have anti-inflammatory properties, postulated to occur through several principal mechanisms, including (1) displacement of arachidonic acid from the cellular membrane; (2) shifting of prostaglandin E(2) and leukotriene B(4) production; and (3) molecular level alterations including decreased activation of nuclear factor kappa B and activator protein-1. An additional regulator that is likely associated is the production of nitric oxide (NO) by nitric oxide synthetase. NO is a short-lived free radical involved in many biological functions. However, excessive NO production can lead to complications, suggesting that decreased NO production is a potential target for some inflammatory diseases. We hypothesized that pretreating with an omega-3 FA lipid emulsion would decrease the production of NO in macrophages and that this effect would occur through alterations in inducible nitric oxide synthetase (iNOS).

MATERIALS AND METHODS

Greiss reagent was used to assess NO production in RAW 264.7 macrophages following omega-3 or omega-6 FA treatment alone or in combination with lipopolysaccharide (LPS) stimulation for 12 h/24 h. iNOS levels were determined by Western blot. Tumor necrosis factor-alpha levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Following LPS-stimulation, omega-3 FA pretreatment at 12 and 24 h produced significantly less NO (P < 0.05) compared to omega-6 FA or media-only conditions. omega-3 FA pretreatment at 12 and 24 h also had less iNOS protein expression compared to omega-6 FA or media-only conditions. Tumor necrosis factor-alpha production was significantly decreased with omega-3 FA treatment compared to omega-6 FA treatment (P < 0.05) after 24 h LPS stimulation.

CONCLUSION

These experiments demonstrate that, in addition to other anti-inflammatory effects, omega-3 FA lipid emulsions also significantly lower NO production in LPS-stimulated macrophages through altered iNOS protein expression.

Attenuation of iNOS in an LPS-stimulated macrophage model by omega-3 fatty acids is independent of COX-2 derived PGE2

BACKGROUND

Omega-3 fatty acids (n-3 FA) demonstrate significant anti-inflammatory properties thought to occur through three principal mechanisms; (1) displacement of arachidonic acid from the cellular membrane, (2) differential prostaglandin E2 (PGE2) and LTB4 production, and (3) molecular level alterations such as diminished nuclear factor kappa B and AP-1 activation. Recently, n-3 FA have been demonstrated to significantly decrease nitric oxide (NO) production in a lipopolysaccharide (LPS)-stimulated M Phi model. We hypothesized that decreased NO production by n-3 FA occurs through inhibition of cyclooxygenase-2 (COX-2) derived PGE2 and that repletion of the system with PGE2 would obliterate these effects. Selective COX-2 inhibitor (L-748,731) experiments and separate PGE2 repletion studies were used to test this hypothesis.

METHODS

NO production was assessed following 24 h with or without LPS/PGE2 in the presence of n-3 FA, L-748,731 (a selective COX-2 inhibitor), or combination (n-3 FA + L-748,731) treatment. Western blots were used to assess inducible NO synthase protein expression.

RESULTS

Independently or in the presence of LPS, treatment with a COX-2 inhibitor significantly increased NO production compared with control, n-3 FA, and combination treatment. NO production in combination treatment is slightly increased compared to n-3 FA treatment. In control cells treated with LPS, PGE2 repletion resulted in a significant decrease in NO. All other treatment groups repleted with PGE2 demonstrated no significant alterations in NO production. Inducible NO synthase protein expression levels were similar to NO production across all treatments.

CONCLUSION

These experiments disproved our original hypothesis that the decrease in NO production associated with n-3 FA treatment occurs through a COX-2 derived PGE2 dependent mechanism. Eliminating COX-2 derived PGE2 by a selective inhibitor actually increased NO production. Exogenous PGE2 repletion did not restore the system. Therefore, mechanisms other than n-3 FA associated alterations in COX-2 derived PGE2 are likely involved in decreasing NO production in LPS stimulated M Phi.

Hypothalamic integration of immune function and metabolism

The immune and neuroendocrine systems are closely involved in the regulation of metabolism at peripheral and central hypothalamic levels. In both physiological (meals) and pathological (infections, traumas and tumors) conditions immune cells are activated responding with the release of cytokines and other immune mediators (afferent signals). In the hypothalamus (central integration), cytokines influence metabolism by acting on nucleus involved in feeding and homeostasis regulation leading to the acute phase response (efferent signals) aimed to maintain the body integrity. Peripheral administration of cytokines, inoculation of tumor and induction of infection alter, by means of cytokine action, the normal pattern of food intake affecting meal size and meal number suggesting that cytokines acted differentially on specific hypothalamic neurons. The effect of cytokines-related cancer anorexia is also exerted peripherally. Increase plasma concentrations of insulin and free tryptophan and decrease gastric emptying and d-xylose absorption. In addition, in obesity an increase in interleukin (IL)-1 and IL-6 occurs in mesenteric fat tissue, which together with an increase in corticosterone, is associated with hyperglycemia, dyslipidemias and insulin resistance of obesity-related metabolic syndrome. These changes in circulating nutrients and hormones are sensed by hypothalamic neurons that influence food intake and metabolism. In anorectic tumor-bearing rats, we detected upregulation of IL-1beta and IL-1 receptor mRNA levels in the hypothalamus, a negative correlation between IL-1 concentration in cerebro-spinal fluid and food intake and high levels of hypothalamic serotonin, and these differences disappeared after tumor removal. Moreover, there is an interaction between serotonin and IL-1 in the development of cancer anorexia as well as an increase in hypothalamic dopamine and serotonin production. Immunohistochemical studies have shown a decrease in neuropeptide Y (NPY) and dopamine (DA) and an increase in serotonin concentration in tumor-bearing rats, in first- and second-order hypothalamic nuclei, while tumor resection reverted these changes and normalized food intake, suggesting negative regulation of NPY and DA systems by cytokines during anorexia, probably mediated by serotonin that appears to play a pivotal role in the regulation of food intake in cancer. Among the different forms of therapy, nutritional manipulation of diet in tumor-bearing state has been investigated. Supplementation of tumor bearing rats with omega-3 fatty acid vs. control diet delayed the appearance of tumor, reduced tumor-growth rate and volume, negated onset of anorexia, increased body weight, decreased cytokines production and increased expression of NPY and decreased alpha-melanocyte-stimulating hormone (alpha-MSH) in hypothalamic nuclei. These data suggest that omega-3 fatty acid suppressed pro-inflammatory cytokines production and improved food intake by normalizing hypothalamic food intake-related peptides and point to the possibility of a therapeutic use of these fatty acids. The sum of these data support the concept that immune cell-derived cytokines are closely related with the regulation of metabolism and have both central and peripheral actions, inducing anorexia via hypothalamic anorectic factors, including serotonin and dopamine, and inhibiting NPY leading to a reduction in food intake and body weight, emphasizing the interconnection of the immune and neuroendocrine systems in regulating metabolism during infectious process, cachexia and obesity.

Experimental studies defining omega-3 fatty acid antiinflammatory mechanisms and abrogation of tumor-related syndromes

Clinical and experimental evidence has supported a benefit for the inclusion of fish oils (a primary source of omega-3 fatty acids) as a component of a normal healthy diet. Polyunsaturated omega-3 fatty acids have been demonstrated to be of benefit in a number of inflammation-associated disease states, including atherosclerosis, autoimmune disorders, malignancy, and sepsis. The beneficial effects of omega-3 fatty acids are thought to occur through the postulated antiinflammatory actions of omega-3 fats; however, the specific mechanism(s) of action has not been completely defined. In this review, we discuss the recent progress made in our laboratory on defining the mechanisms of omega-3 fatty acids activity.

Inhibition of osteoporosis in autoimmune disease prone MRL/Mpj-Fas(lpr) mice by N-3 fatty acids

OBJECTIVE

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease involving the breakdown of cartilage and juxta-articular bone, which is often accompanied by decreased bone mineral density (BMD) and increased risk of fracture. Anti-inflammatory omega-3 fatty acids may prevent arthritis and bone loss in MRL/lpr mice model of arthritis and in humans.

METHODS

In this study, the effect of long term feeding of 10% dietary n-3 (fish oil (FO)) and n-6 (corn oil (CO)) fatty acids begun at 6 weeks of age on bone mineral density (BMD) in different bone regions in an MRL/lpr female mouse model of RA was measured at 6, 9, and 12 months of age by dual energy x-ray absorptiometry (DEXA). After sacrificing the mice at 12 months of age, antioxidant enzyme activities were measured in spleen, mRNA for receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) was measured by RT-PCR in lymph nodes, and synovitis was measured in leg joints.

RESULTS

At 6, 9 and 12 months of age, BMD was significantly higher (p < 0.05) in distal femur, proximal tibia, and lumbar spine of FO fed mice than those of CO fed mice. Spleen catalase (CAT) and superoxide dismutase (SOD) activities were also significantly higher (p < 0.01) in FO fed mice than in CO fed mice. Histology of knee joints revealed mild synovitis in CO fed mice, which was not present in FO fed mice. RT-PCR analysis of lymph nodes revealed decreased RANKL mRNA (p < 0.001) expression and enhanced OPG mRNA expression (p < 0.01) in FO fed mice compared to CO fed mice.

CONCLUSIONS

These results suggest beneficial effects of long-term FO feeding in maintaining higher BMD and lower synovitis in this mouse model. These beneficial effects may be due, in part, to increased activity of antioxidant enzymes, decreased expression of RANKL, and increased expression of OPG in FO fed mice thereby altering the RANKL/OPG ratio. These significant beneficial effects on BMD suggest that FO may serve as an effective dietary supplement to prevent BMD loss in patients with RA.

Effects of omega-3 fatty acids on orexigenic and anorexigenic modulators at the onset of anorexia

In cancer anorexia, a decrease in food intake (FI) occurs concomitant with changes in orexigenic peptides such as neuropeptide Y (NPY) and anorexigenic peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) and anorexigenic neurotransmitter serotonin. omega-3 Fatty acid (omega-3FA) inhibits cytokine synthesis, and delays tumor appearance, tumor growth, and onset of anorexia in tumor-bearing rats. We hypothesize that, in cancer anorexia, omega-3FA is associated with quantitative reversal of hypothalamic NPY, alpha-MSH, and serotonin receptor (5-HT(1B)-receptor) enhancing FI. Fischer rats were divided into: MCA tumor bearing fed chow (TB-Chow) or omega-3FA diet (TB-omega-3FA) and controls: non-tumor bearing fed chow (NTB-Chow) or omega-3FA diet (NTB-omega-3FA). Rats were euthanized at anorexia and brains were removed for hypothalamic immunohistochemical study, using NPY, alpha-MSH, and 5-HT(1B)-receptor-specific antibodies and slides assessed by image analysis. Immunostaining specificity was controlled by omission of primary or secondary antibodies and pre-absorption test. At anorexia, FI decreased (P < 0.05) in TB-Chow but did not change in TB-omega-3FA rats. In TB-omega-3FA vs. TB-Chow, NPY immunoreactivity increased 38% in arcuate nucleus (ARC; P < 0.05), and 50% in magnocellular paraventricular nucleus (mPVN; P < 0.05). alpha-MSH decreased 64% in ARC and 29% in mPVN (P < 0.05). 5-HT(1B)-receptor immunoreactivity decreased 13% only in supraoptic nucleus (P < 0.05). No immunoreactivity was found in the control sections. omega-3FA modified hypothalamic peptides and 5-HT-(1B)-receptor immunoreactivity at anorexia, concomitant with an increase in FI, were probably mediated by omega-3FA inhibition of tumor-induced cytokines.

Effects of dietary omega3 and omega6 lipids and vitamin E on proliferative response, lymphoid cell subsets, production of cytokines by spleen cells, and splenic protein levels for cytokines and oncogenes in MRL/MpJ-lpr/lpr mice

omega3 Fatty acid rich fish oil (FO) and vitamin E may delay the progress of certain autoimmune diseases. The present study examined the mechanisms of action of omega3 lipids and vitamin E in autoimmune-prone MRL/lpr mice suffering from extensive lymphoproliferation, lupus-like symptoms, and accelerated aging. To determine whether the effects of omega3 lipids in autoimmune disease is linked to vitamin E levels, weanling female MRL/lpr and congenic control MRL/++ mice were fed diets containing 10% corn oil (CO) or 10% FO at two levels of vitamin E (75 IU or 500 IU/kg diet) for 4 months. The appearance of lymph nodes was delayed in the mice fed FO, and higher levels of FO offered further protection against the appearance of lymph nodes. Analysis of the spleen cells revealed that the cells positive for Thy.1 and Fas were significantly higher in the MRL/++ mice. The groups fed high levels of vitamin E generally exhibited higher levels of Fas. The proliferative response of splenocytes of MRL/++ mice to mitogens was significantly higher compared with MRL/lpr mice. Interleukin (IL)-10 production by spleen cells was significantly higher in FO-fed MRL/lpr mice than in CO-fed mice. In mice fed a high level of vitamin E, the production of IL-12 and tumor necrosis factor-alpha was significantly lower and IL-2 was significantly higher than in animals fed a low level of vitamin E. Proinflammatory cytokines were higher in the MRL/lpr mice and both FO and vitamin E lowered the levels of proinflammatory cytokines and lipid mediators. Western blots revealed that c-myc and c-ras were significantly lower and IL-2 and transforming growth factor (TGF)-beta1 levels were significantly higher in the spleens of MRL/++ mice. FO lowered c-myc and high levels of vitamin E in the diets normalized the levels of TGF-beta1 in MRL/lpr mice. The observations from this study suggest that both FO and vitamin E modulate the levels of specific cytokines, decrease the levels of proinflammatory cytokines, inflammatory lipid mediators, and c-myc, and increase TGF-beta1 levels in spleens of MRL/lpr mice and thus may delay the progress of autoimmune diseases.

Omega-3 fatty acids in inflammation and autoimmune diseases

Among the fatty acids, it is the omega-3 polyunsaturated fatty acids (PUFA) which possess the most potent immunomodulatory activities, and among the omega-3 PUFA, those from fish oil-eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)--are more biologically potent than alpha-linolenic acid (ALA). Some of the effects of omega-3 PUFA are brought about by modulation of the amount and types of eicosanoids made, and other effects are elicited by eicosanoid-independent mechanisms, including actions upon intracellular signaling pathways, transcription factor activity and gene expression. Animal experiments and clinical intervention studies indicate that omega-3 fatty acids have anti-inflammatory properties and, therefore, might be useful in the management of inflammatory and autoimmune diseases. Coronary heart disease, major depression, aging and cancer are characterized by an increased level of interleukin 1 (IL-1), a proinflammatory cytokine. Similarly, arthritis, Crohn's disease, ulcerative colitis and lupus erythematosis are autoimmune diseases characterized by a high level of IL-1 and the proinflammatory leukotriene LTB(4) produced by omega-6 fatty acids. There have been a number of clinical trials assessing the benefits of dietary supplementation with fish oils in several inflammatory and autoimmune diseases in humans, including rheumatoid arthritis, Crohn's disease, ulcerative colitis, psoriasis, lupus erythematosus, multiple sclerosis and migraine headaches. Many of the placebo-controlled trials of fish oil in chronic inflammatory diseases reveal significant benefit, including decreased disease activity and a lowered use of anti-inflammatory drugs.

Modulation of lipopolysaccharide-stimulated macrophage tumor necrosis factor-alpha production by omega-3 fatty acid is associated with differential cyclooxygenase-2 protein expression and is independent of interleukin-10

BACKGROUND

The role of omega-3 fatty acids (FA) as anti-inflammatory agents involves the inhibition of macrophage (Mphi) cytokine production, but the mechanisms involved are not well defined. The effects of omega-3 FA on the transcription and translation of cyclooxygenase-2 (COX-2), the production of prostaglandin E(2) (PGE(2)), and the production of interleukin-10 (IL-10) were investigated as potential mechanisms for the down-regulation of lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha production.

METHODS

RAW 264.7 Mphi were incubated with Omegaven (10 mg% omega-3 FA), Lipovenos (10 mg% omega-6 FA), or DMEM for 4 h of pretreatment. The cells were then exposed to LPS (1 microg/ml) or medium alone for 3 h. COX-2 mRNA levels were determined by semi-quantitative reverse transcriptase polymerase chain reaction, and COX-2 protein levels were determined by Western blotting. The levels of PGE(2) and IL-10 proteins secreted into the medium were quantified using enzyme-linked immunosorbent assays.

RESULTS

Pretreatment with omega-3 FA increased Mphi COX-2 protein expression levels without altering the levels of COX-2 mRNA in response to LPS stimulation. In addition, pretreatment with omega-3 FA dramatically decreased the PGE(2) and IL-10 production induced by LPS, whereas pretreatment with an equivalent dose of omega-6 FA only resulted in a modest increase in PGE(2) and a slight decrease in IL-10 production compared to controls.

CONCLUSION

As COX-2 protein levels were increased without a change in COX-2 mRNA levels with omega-3 FA pretreatment, this suggested that omega-3 FA did not upregulate COX-2 at the transcriptional level. The omega-3 FA may instead posttranscriptionally stabilize existing COX-2 mRNA. The increased COX-2 expression may thus be explained by increased translation of COX-2 and/or decreased COX-2 degradation. The decreased PGE(2) production could be attributed to the replacement of Mphi membrane omega-6 FA substrates by omega-3 FA and the competitive inhibition of COX-2 enzyme by omega-3 FA. The reduction of active COX-2 product associated with an increase in COX-2 enzyme implies the existence of a negative feedback mechanism. Surprisingly, IL-10 production was decreased by omega-3 FA pretreatment, indicating that the reduced IL-10 inhibition of Mphi cytokine production was superceded by the other actions of omega-3 FA.

Effects of dietary omega-3 and omega-6 lipids and vitamin E on serum cytokines, lipid mediators and anti-DNA antibodies in a mouse model for rheumatoid arthritis

OBJECTIVE

Omega-3 (omega-3) fatty acid rich-fish oil (FO) and vitamin E (vit-E) may delay the progress of certain autoimmune diseases. The present study examined the mechanism of action of omega-3 and omega-6 lipids and vit-E on the serum cytokines and lipid mediators in autoimmune-prone MRL/lpr mice (a model for rheumatoid arthritis, RA). The lpr (lymphoproliferative) gene is overexpressed in these mice causing extensive lymphoproliferation, lupus-like symptoms and accelerated aging.

METHODS

Weanling female MRL/lpr and congenic control MRL/++ mice were fed 10% corn oil (CO, omega6) or FO-based semipurified diets containing two levels of vitamin E (vit-E-75, I.U. and vit-E-500 I.U./Kg diet) for four months. At the end of the experiment, serum anti-DNA antibodies, cytokines and lipid mediators levels were determined.

RESULTS

The appearance of enlarged lymph nodes was delayed in the mice fed FO, and the FO-500 IU vit-E diet offered further protection against enlargement of lymph nodes. The MRL/lpr mice exhibited significantly higher levels of serum anti-dsDNA antibodies. The FO-fed mice had significantly lower serum IL-6, IL-10, IL-12, TNF-alpha, PGE2, TXB2 and LTB4 levels compared with CO-fed mice. In mice fed 500 IU vit-E diets, the serum IL-6, IL-10, IL-12 and TNF-alpha levels were significantly lower and serum IL-1beta was significantly higher compared to 75 IU-vit-E-fed mice in CO/FO or both. The levels of anti-DNA antibodies, IL-4, IL-6, TNF-alpha, IL-10 and IL-12 were higher in the sera of MRL/lpr mice. The FO diet lowered the levels of these cytokines (except IL-4) and lipid mediators. Adding 500 IU of vit-E to the FO diet further lowered the levels of IL-6, IL-10, IL-12, and TNF-alpha.

CONCLUSION

It is clear from our observations that the beneficial effects of FO can be enhanced by the addition of 500 IU of vit-E in the diet. The FO diet containing 500 IU of vit-E may specifically modulate the levels of IL-6, IL-10, IL-12 and TNF-alpha and thereby may delay the onset of autoimmunity in the MRL/lpr mouse model. The observations from this study may form a basis for selective nutrition intervention based on specific fatty acids and antioxidants in delaying the progress of RA.

Diets, dietary supplements, and nutritional therapies in rheumatic diseases

Rheumatoid arthritis and many other systemic rheumatic diseases remain illnesses of unknown cause for which current therapy is often inadequate. This leads patients to seek questionable remedies, prominent among which are dietary manipulations. Is there a role for dietary modifications in the routine therapy for patients with rheumatic diseases? This article discusses the relationships between diets, fasting, elemental nutrition, vitamins, minerals, and foods for rheumatic diseases. Known scientific-based evidence for the use, safety, and efficacy of diets and dietary-related practices subscribed by patients with rheumatic diseases are presented. Studies that link diet with arthritis offer the possibility of identifying new therapeutic approaches for selected patients and of developing new insights to disease pathogenesis. Dietary therapy for arthritis, however, is still being investigated.

The influence of membrane fluidity, TNF receptor binding, cAMP production and GTPase activity on macrophage cytokine production in rats fed a variety of fat diets

The effects of different dietary fats on peritoneal macrophage plasma membrane fluidity, intracellular cyclic AMP (cAMP) production, GTP hydrolysis and TNF binding and TNF-induced IL1 and IL6 production was investigated. After a four week period, fluidity, as determined by both fluorescence recovery after photobleaching (FRAP) and anisotropy was lowest and highest in animals fed corn and fish oil respectively. After eight weeks feeding, lateral membrane movements were decreased substantially in fish, olive and coconut oil fed dietary groups, whereas an increase in the corn oil fed group was observed, no effect was observed in macrophages from the butter fed group. However, an increase in the packing was observed in macrophages from all dietary groups except in the olive oil fed group. GTPase values for the coconut oil and butter groups were higher than in any other dietary group. After receiving the diet for 8 weeks these differences between the groups were no longer apparent. Exposure of macrophages to TNF had no effect on the rate of GTP hydrolysis. A major enhancement of cAMP production became apparent between weeks 4 and 8 of dietary treatment. After 4 weeks on the diet, values were significantly higher from cells of animals fed corn and olive oils than from animals fed fish oil. After 8 weeks, while there was a general enhancement of production, further differences became apparent. Feeding corn and coconut oils resulted in the highest values and olive oil and chow in the lowest. It is proposed that fats rich in n-3 fatty acids (fish oils) alter membrane fluidity, decrease TNF binding affinity, GTPase activity and cAMP production which appears not to modify cytokine production after short term dietary supplementation. However, after long term feeding it appears that increases in the sensitivity of the TNF receptors plays a major role in modifying cytokine production.

Alteration of n-3 fatty acid composition in lung tissue after short-term infusion of fish oil emulsion attenuates inflammatory vascular reaction

OBJECTIVES

To investigate whether modulation of the fatty acid profile can be achieved by the short-term infusion of a fish oil emulsion which may attenuate the pulmonary response to inflammatory stimulation. Changes of fatty acid pattern in-lung tissue and perfusate were analyzed and correlated with physiologic data after a 3-hr infusion of fish oil in comparison with a soybean oil preparation.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Experimental laboratory in a university teaching hospital.

SUBJECTS

Forty standard breed rabbits of either gender.

INTERVENTIONS

Isolated lungs from anesthetized rabbits were ventilated and recirculation-perfused (200 mL/min) with 200 mL of cell-free buffer solution to which either 2 mL of saline (control, n = 6), 2 mL of a 10% soybean oil preparation (n = 6), or 2 mL of a 10% fish oil emulsion (n = 6) were added. Samples of perfusate and lung tissue were collected for analysis of fatty acid composition. Tissue and perfusate fatty acid composition were analyzed by capillary gas chromatography. To study metabolic alterations in states of inflammatory stimulation, lungs of each group were stimulated with small doses of the calcium ionophore, A23187 (10(-8) M), during the 180-min lipid perfusion period and again after washing out the lipids by exchanging the perfusion fluid. Pulmonary arterial pressure and lung weight gain were monitored, and eicosanoids were analyzed in the perfusate.

MEASUREMENTS AND MAIN RESULTS

Free eicosapentaenoic acids increased several-fold in lung tissue and perfusate during a 3-hr infusion with fish oil. The intravenously administered n-3 fatty acids were rapidly hydrolyzed, as indicated by the appearance of substantial quantities of eicosapentaenoic acid in the perfusate free fatty acid fraction. This increase of perfusion levels of eicosapentaenoic acid was paralleled by an attenuated pressure increase and edema formation due to calcium ionophore challenge and an altered eicosanoid spectrum determined in the perfusate compared with soybean oil-treated lungs.

CONCLUSION

Short-term n-3 lipid application (fish oil emulsion) exerts anti-inflammatory effects on lung vasculature, which may be due to the metabolism of eicosapentaenoic acid resulting in the generation of less potent inflammatory eicosanoids.

Anorexia during acute and chronic disease

Anorexia is associated with disorders of all systems. Anorexia represents a consistent clinical manifestation during acute and chronic pathophysiological processes (infection, inflammation, injury, toxins, immunological reactions, malignancy and necrosis). Anorexia during disease can be beneficial or deleterious depending on the timing and duration. Temporary anorexia during acute disease may be beneficial to an organism since a restriction in the intake of micro- and macro-nutrients will inhibit bacterial growth. Long-term anorexia during chronic disease, however, is deleterious to an organism and may be associated with cachexia, which can ultimately result in death. Various mechanisms participate in the anorexia observed during disease, including cytokine action. Anorexia induced by cytokines is proposed to involve modulation of hypothalamic-feeding associated sites, prostaglandin-dependent mechanisms, modifications of neurotransmitter systems, gastrointestinal, metabolic, and endocrine factors. In addition, the anorexia-cachexia syndrome is multifactorial and may involve chronic pain, depression or anxiety, hypogeusia and hyposmia, chronic nausea, early satiety, malfunction of the gastrointestinal system, metabolic alterations, cytokine action, production of other anorexigenic substances and/or iatrogenic causes (chemotherapy, radiotherapy). Cachexia may result not only from anorexia and a decreased caloric intake, but also from malabsorption and losses from the body (ulcers, hemorrhage, effusions), or a change in body metabolism. Research has focused on potential interventions to modify anorexia during disease and the anorexia-cachexia syndrome. Nutritional modifications and the use of specific steroids (such as megestrol acetate) are being tested in the clinical setting. Understanding the specific mechanisms responsible for anorexia during disease as well as their interactions is essential to develop interventions for the control of anorexia (during a critical time in a specific disease), and to devise less toxic immunotherapeutic regimens using cytokines.

Fish oil may impede tumour angiogenesis and invasiveness by down-regulating protein kinase C and modulating eicosanoid production

Inhibition of angiogenesis shows considerable promise as a strategy for treating solid malignancies. Induction of collagenase by protein kinase C plays an important role in the angiogenic process as well as in metastasis. Lipoxygenase products are required for endothelial cell mitosis, and also promote collagenase production. By down-regulating hormonal activation of protein kinase C and modulating eicosanoid metabolism, ingestion of omega-3-rich fish oils may impede angiogenesis and reduce tumor invasiveness-thus rationalizing the growth-retardant and anti-metastatic effects of fish oil feeding almost invariably seen in animal tumour models. Certain other anti-inflammatory agents-including cromolyn (an inhibitor of protein kinase C activation) and gamma-linolenic acid (which indirectly inhibits lipoxygenase) may have analogous tumour-retardant activity. Clinical application of supplemental fish oil in cancer therapy is long overdue.

Influence of unsaturated fatty acids on the production of tumour necrosis factor and interleukin-6 by rat peritoneal macrophages

The effect of individual unsaturated fatty acids on the release of tumour necrosis factor (TNF) and interleukin 6 (IL6) was investigated in thioglycollate-induced rat peritoneal macrophages. The intracellular mechanisms associated with the changes of cytokine production in response to fatty acids were also studied. Incubation of macrophages with 100 microM docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) increased TNF (21% and 15% respectively) and IL6 (69% and 40% respectively) production. Linoleic acid (LA) diminished TNF production by 16%. At 100 microM oleic acid (OA), LA and EPA concentration an increase in macrophage adenylate cyclase activity (110%, 72% and 39% respectively) and a decrease (14%) in the presence of DHA was observed. PGE2 production in the presence of 100 microM DHA was reduced by 36%, whereas in the presence of 100 microM LA an increase (75%) was observed. Phospholipase A2 (PLA2) activity was also found to be modified in the presence of EPA and DHA at 50 microM (20% and 60% respectively) and 100 microM (34% and 62% respectively) concentrations. The activities of both protein kinase A (PKA) and protein kinase C (PKC) were effected by the different fatty acids. At 50 microM all fatty acids suppressed PKA activity except OA which enhanced PKA activity by 14%. At 100 microM fatty acid concentration, EPA suppressed PKA activity by 40%. PKC activity was enhanced by LA and OA, by 18% and 21% respectively. However, at 100 microM EPA and DHA, PKC activity was suppressed by 37% and 17% respectively, whereas PKC activity was enhanced by 146% in the presence of 100 microM LA. These results show for the first time that unsaturated fatty acids have an effect on macrophage PLA2 activity and that PGE2 may be a potent modulator of IL6 production. From these studies it is tempting to speculate that macrophage TNF and IL6 release may, in part, occur via a PKC and PKA independent pathway and that PLA2 activity and PGE2 concentration are inversely related to production of TNF and IL6.

Eicosanoids and essential fatty acid modulation in chronic disease and the chronic fatigue syndrome

Abnormalities of Essential Fatty Acid (EFA) incorporation into phospholipid are found in chronic diseases. More recently changes in circulating EFA metabolites (EFAM) together with EFAM hypo-responsiveness of immune cells and EFAM production from cells have been found associated with disease. We hypothesize that changes in ratio of EFAMs are the normal physiological responses to stressors, but when stressors are excessive or prolonged, EFAM systems may become unpredictably hypo-responsive owing to factors such as receptor down regulation and substrate depletion. In time, many homeostatic system become deranged and held in that state by minor stressors. Literature review of chronic fatigue syndrome (CFS) shows hyper and hypo-responsiveness in immune function, several Hypothalamo-Pituitary (HP) axes and sympathetic nervous system, all relatable to dysfunctional changes in EFA metabolism. For the first time, we explain chronic immune system activation and hypo-responsive immune function in CFS; through EFAMs. Dietary EFA modulation (DEFA) can alter ratios of both membrane EFAs and produced EFAMs, and if maintained can restore hypo-responsive function. We discuss dietary strategies and relevance in CFS, and a case series of CFS patients applying DEFA with other titrated published managements which saw 90% gaining improvement within 3 months and more than 2/3 fit for full time duties. This hypothesis and DEFA may have relevance in other chronic conditions.

Dietary n-3 fatty acid effects on neutrophil lipid composition and mediator production. Influence of duration and dosage

Healthy volunteers supplemented their usual Western diets with Promega fish oil supplement (eicosapentaenoic acid [EPA], 0.28 g; docosahexaenoic acid [DCHA], 0.12 g; other n-3 fatty acids 0.10 g per capsule) using three protocols. Initial experiments (protocol 1 and 2) investigated the kinetics of incorporation of n-3 fatty acids into serum and neutrophil lipids after 10 capsules/d of Promega. EPA was rapidly detected in both serum and neutrophil lipids; the arachidonic acid (AA) to EPA ratio in neutrophil phospholipids showed a maximal reduction of 49:1 to 8:1 within 1 wk of beginning supplementation. EPA was preferentially incorporated into phosphatidyl-ethanolamine and phosphatidylcholine but not phosphatidylinositol. Long-term supplementation for up to 7 wk did not influence the AA/EPA ratio or the distribution of EPA among neutrophil phospholipids in a manner that was not observed after the first week. Neutrophils produced similar quantities of platelet-activating factor and slightly lower quantities of leukotriene B4 during long-term supplementation when compared with presupplementation values. Experiments examining the influence of Promega dosage indicated that the AA/EPA ratio in neutrophil lipids decreased in a dose-dependent manner. Only when the dose was increased to 15 capsules/d was there a reduction in the AA/DCHA ratio in neutrophil lipids. The quantity of AA in neutrophil lipids remained relatively constant at all supplement doses. Taken together, the current study demonstrates the capacity of n-3 fatty acids provided with a Western diet to be rapidly incorporated into neutrophil lipids. However, dietary n-3 fatty acids appear not to significantly reduce arachidonate content within neutrophil phospholipids. Constant arachidonate levels may account for the lack of large reductions in the biosynthesis of lipid mediators by neutrophils after fish-oil supplementation.