Influence of intravenous n-3 lipid supplementation on fatty acid profiles and lipid mediator generation in a patient with severe ulcerative colitis

Impact of lipid emulsions in parenteral nutrition on platelets: a literature review

Lipid emulsions are essential components of parenteral nutrition solutions that provide energy and essential fatty acids. The complexity of the formulations of lipid emulsions may lead to adverse outcomes such as platelet reactivity and changes in platelet aggregation and related coagulation. Platelets are responsible for haemostasis; they activate and demonstrate morphological changes upon extracellular factors to maintain blood fluidity and vascular integrity. Although parenteral nutrition lipid emulsions are generally found safe with regard to modulation of platelet activity, studies are still accumulating. Thus, this review aims to investigate platelet-related changes by parenteral nutrition lipid emulsions in human studies. Studies have pointed out patients at risk of bleeding and increased platelet aggregation responses due to the administration of lipid emulsions. Lipid emulsions may further benefit patients at high risk of thrombosis due to anti-thrombotic effects and should be cautiously used in patients with thrombocytopenia. The reported platelet-related changes might be associated with the fatty acid change in the plasma membranes of platelets following changes in platelet synthesis and plasma levels of eicosanoids. In conclusion, studies investigating platelets and parenteral nutrition should be supported to minimize the adverse effects and to benefit from the potential protective effects of parenteral nutrition lipid emulsions.

Use and Misuse of Parenteral Nutrition in Patients with Inflammatory Bowel Disease

Malnutrition is a very common and often underrecognized condition among patients with inflammatory bowel diseases (IBD). This is most commonly due to increased nutritional requirements and gastrointestinal losses, along with reduced oral intake. Screening for malnutrition is an essential component of managing both inpatients and outpatients with IBD. Although enteral nutrition is the preferred route of supplementation, parenteral nutrition (PN) remains an important strategy and should be considered in certain situations, such as cases with short-bowel syndrome, high-output intestinal fistula, prolonged ileus, or small-bowel obstruction. Appropriate use of PN is critical in order to prevent associated complications. This review addresses the common indications for use of PN, the composition of PN, and the possible complications encountered with PN use, as well as scenarios of inappropriate PN use among patients with IBD. A clinical management algorithm for utilizing PN among patients with IBD is proposed in this review.

Intravenous fish oil in critically ill and surgical patients - Historical remarks and critical appraisal

The purpose of this review is to explain the historical and clinical background for intravenous fish oil administration, to evaluate its results by using a product specific metaanalysis, and to stimulate further research in the immune-modulatory potential of fish oil. Concerning the immune-modulatory effects of fatty acids, a study revealed that ω-3 as well as ω-6 fatty acids would prolong transplant survival, and only a mixture with an ω-6:ω-3 ratio of 2.1:1 would give immune-neutral results. In 1998, the label of a newly registered fish oil emulsion also acknowledged this immune-neutral ratio in conjunction with ω-6 lipids. Also, two fish oil-supplemented fat emulsions, registered in 2004, used a similar ω-6:ω-3 ratio. Such an immune-neutral ω-6:ω-3 ratio denoted progress for most patients compared to pure ω-6 lipid emulsions. However, this immune-neutrality might on the other hand be responsible for the limited positive clinical results gained so far in critically ill and surgical patients where in most cases significance could only be shown for the pooled effect of numerous trials. Our product specific metaanalysis also did not reveal any differences, neither in infections rates nor in ICU or hospital length of stay. To evaluate the immune-modulatory effect of fish oil administered alone, new dose finding studies, reporting relevant clinical outcome parameters, are required. Precise mechanistic or physiological biomarkers for the indication of such a therapy should also be developed and validated.

Supplementation of Ω-3 Fatty Acids in Parenteral Nutrition Beneficially Alters Phospholipid Fatty Acid Pattern

BACKGROUND

The clinical safety and the uptake of omega-3 polyunsaturated fatty acids (PUFA) into the serum phospholipids and erythrocyte membranes after administration of fish-oil-supplemented parenteral nutrition (PN) was investigated in colorectal surgical patients.

METHODS

Forty patients undergoing colorectal surgery (n = 40) and with an indication for PN were enrolled in a prospective, double-blind, randomized study to receive an omega-3 PUFA-supplemented 20% lipid emulsion (Lipoplus; B. Braun Melsungen, Melsungen, Germany; test group, n = 19) for 5 days postoperatively. The control group received a standard 20% fat emulsion (Lipofundin MCT/LCT, B. Braun Melsungen, Melsungen, Germany, control group, n = 21). Clinical outcome parameters and safety were assessed by means of adverse events recording clinical parameters and hematologic analyses. The contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as arachidonic acid (AA), in phospholipid fractions in plasma and in erythrocytes were analyzed preoperatively, on postoperative days 1, 6, and 10 using liquid gas chromatography.

RESULTS

Both fat emulsions were well tolerated, and none of the adverse events was considered to be related to treatment. Postoperative infectious complications occurred in 4 patients of the omega-3 PUFA group vs 7 patients in the control group. As compared with the control group, the omega-3 PUFA group had significantly increased levels of EPA in the membranes of the erythrocytes in postoperative day 6 (2.0% +/- 0.9% vs 0.8% +/- 0.5% fatty acid methyl esters, [FAME]) and postoperative day 10 (2.1% +/- 0.8% vs 0.9% +/- 0.7% FAME, p < .05). Also, the EPA levels in the serum phospholipids were significantly higher than in the control group on the same postoperative days (7.0% +/- 2.6% vs 1.3% +/- 0.8% and 3.6% +/- 1.0% vs 1.0% +/- 0.4% FAME, p < .05). The DHA levels in the serum phospholipids were significantly higher in the omega-3 PUFA group compared with the control on postoperative days 6 and 10 (11.8% +/- 1.9% vs 8.4% +/- 1.5% and 11.2% +/- 1.6% vs 8.5% +/- 1.4% FAME, p < .05). AA levels were not significantly different in the both groups.

CONCLUSIONS

Omega-3-fatty-acids-supplemented fat emulsions for parenteral administration are safe and very well tolerated. This study demonstrates that parenteral administration of omega-3-PUFA-enriched fat emulsions leads to increased incorporation of EPA and DHA into phospholipids in serum and erythrocytes, whereas AA levels remain unchanged. Thus, postoperative parenteral administration of omega-3-PUFA-enriched lipid emulsions could have an impact on the postoperative inflammatory response after abdominal surgery and could be used in standard postoperative care when PN is indicated.

Docosahexaenoic acid inhibits Helicobacter pylori-induced STAT3 phosphorylation through activation of PPARγ

SCOPE

The health beneficial effects of docosahexaenoic acid (DHA) have been attributed to its anti-inflammatory properties. However, the molecular mechanism underlying anti-inflammatory effects of DHA remains largely elusive.

METHODS AND RESULTS

In the present study, DHA was found to suppress the phosphorylation and nuclear translocation of signal transducer and activator of transcription 3 (STAT3) induced by Helicobacter pylori infection in human gastric cancer AGS cells. Notably, DHA induced expression of suppressor of cytokine signaling 3 (SOCS3), a negative regulator of STAT3. Knockdown of SOCS3 abolished the suppressive effect of DHA on STAT3(Tyr705) phosphorylation induced by H. pylori infection. DHA also induced nuclear translocation, DNA binding, and transcriptional activities of peroxisome proliferator-activated receptor gamma (PPARγ) in AGS cells. Knockdown of PPARγ inhibited the transcription of SOCS3 and attenuated the suppressive effect of DHA on phosphorylation of STAT3(Tyr705) induced by H. pylori. The PPARγ antagonist bisphenol A diglycidyl ether also mitigated the suppressive effect of DHA on H. pylori-induced phosphorylation of STAT3(Tyr705) . In addition, DHA inhibited the expression of c-Myc, which was attenuated in the AGS cells harboring SOCS3 specific siRNA. DHA also markedly decreased anchorage-independent growth of AGS cells infected by H. pylori.

CONCLUSION

DHA inhibits H. pylori-induced STAT3 phosphorylation in a PPARγ/SOCS3-dependent manner.

The study of n-3PUFAs protecting the intestinal barrier in rat HS/R model

BACKGROUND

N-3 PUFAs have been demonstrated in vitro it could prevent the intestinal tight junctions (TJs) from the ischemia/re-perfusion injury and the inflammatory reaction injury. The purpose of this study was to evaluate the protection of n-3 PUFAs on the intestinal TJs in the rat model of hemorrhagic shock followed by resuscitation.

METHODS

Male SD rats (n = 72; 250 ~ 300 g) were randomly divided into 6 groups: SHAM, hemorrhagic shock (HS), hemorrhagic shock/resuscitation (HS/R), ω-6 group, ω-3 group and ω-3 treatment group. Shock was induced, and a mean arterial pressure was maintained at 35 to 40 mmHg for 60 minutes. Resuscitation was carried out by returning half of the shed blood and Ringer's lactate solution. In ω-6 and ω-3 group, Intralipid or fish oil (0.2 g/Kg), respectively, was infused 30 minutes after shock. And fish oil was infused with resuscitation in ω-3 treatment group. Half of each group was killed at 30 minutes and 4 hours after resuscitation, respectively. The serum samples and the intestinal sample was collected for further examination.

RESULT

There is no difference between ω-3, ω-3 treatment and sham group in Chiu's score, but the other three groups have higher scores than they did. Compared with HS, HSR and ω-6 group, ω-3 and ω-3 treatment group showed most intact in intestinal mucoscal villi and TJs through HE, SEM and LSCM. The levels of IL-6 and TNF-α of bowel tissue in ω-3 and ω-3 treatment group were significantly lower than HS and HSR groups'. At the time point of 30 min, the levels of serum endotoxin were dramatically higher in HS、 HSR and ω-6 groups when compared with ω-3, ω-3 treatment and sham group. However, it in ω-3 group was greater than sham and HS group until 4 hours.

CONCLUSION

Fish oil pretreatment before resuscitation showed a beneficial effect to the intestinal TJs and atteunated inflammation after H/R in HS/R rat model and is better than ω-6 PUFAs did.

Impact of lipid emulsion containing fish oil on outcomes of surgical patients: systematic review of randomized controlled trials from Europe and Asia

OBJECTIVE

This study aimed to systematically review the clinical efficacy of lipid emulsion containing fish oil in surgical patients.

METHODS

Medline, SCI, Embase, Cochrane Library, and Chinese Biomedicine Database were searched for studies published before January 1, 2009 that were randomized controlled trials for postoperative patients. Parenteral nutrition with or without fish oil emulsion was the only difference between the intervention and control groups. Methodologic quality assessment was based on the Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.1 and Jadad's score scale. RevMan 5.0 statistical software was used for meta-analysis.

RESULTS

Six trials met all inclusion criteria and were enrolled for final meta-analysis. The aggregated results of the trails showed that fish oil was associated with no mortality advantage. There was a significant reduction in infectious complications in patients receiving fish oil (relative risk 0.49, 95% confidence interval 0.26-0.93, P=0.03). The result on length of hospital stay showed a trend of shortening by 3.06 d associated with receiving fish oil. However, the difference was not significant. When excluding one obviously heterogeneous study and aggregating the other three remaining studies, results showed significantly shortening of length of hospital stay associated with receiving fish oil. Fish oil also significantly shortened length of stay in the intensive care unit by 2.07 d.

CONCLUSION

The administration of lipid emulsion containing fish oil to patients undergoing elective major operations improves outcomes. The infectious complications are significantly fewer and length of hospitalization significantly shortened for patients treated with lipid emulsion containing fish oil. Further well-designed randomized controlled trials are needed to demonstrate the cost effectiveness of lipid emulsion containing fish oil to postoperative patients.

Effect of different lipid emulsions on the immunological function in humans: a systematic review with meta-analysis

BACKGROUND & AIMS

Reports regarding the pro- or anti-inflammatory effects of lipid emulsion used in parenteral nutrition are conflicting. Aim was to assess the effect of different intravenous lipid emulsions on immunological function in humans.

METHODS

We performed a computerized bibliographic search, searched reference lists in trial reports, hand-searched journals and contacted experts in the field. Randomized clinical trials evaluating the immunological effects of different parenteral lipid emulsions were included. Three authors independently performed data extraction, statistical processes were performed by two experts. Immunological parameters were classified by two immunologists as marker of improved or worsened immune function. A meta-analysis with standardized effect size estimation was performed for the comparison between long-chain triglycerides vs. glucose or other fat emulsions.

RESULTS

Of 682 assessed studies, 120 compared the immunological effects of intravenously applied lipid emulsions. Of 30 randomized trials, 14 were included in the meta-analysis. None of the lipid regimens showed any clear effect on the evolution of the immunological status or mortality in humans. Length of hospital stay and stay in the intensive care unit could not be evaluated.

CONCLUSION

We found no evidence that lipid emulsions and in particular those containing long-chain triglycerides have an unfavorable effect on immune function.

Free arachidonic versus eicosapentaenoic acid differentially influences the potency of bacterial exotoxins to provoke myocardial depression in isolated rat hearts

OBJECTIVE

Staphylococcal alpha-toxin and Escherichia coli hemolysin (ECH) evoke cardiac dysfunction in isolated rat hearts by provoking myocardial synthesis of arachidonic acid-derived thromboxane A2 or the cysteinyl-leukotrienes, LTC4, LTD4, and LTE4, respectively. We investigated whether low doses of either toxin, which fail to induce cardiac depression by themselves, induce cardiac dysfunction when combined with free arachidonic acid.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Isolated hearts from male Wistar rats.

INTERVENTIONS

Hearts were perfused with low doses of ECH or alpha-toxin in the absence or presence of arachidonic acid or the alternative eicosanoid precursor eicosapentaenoic acid (EPA).

MEASUREMENTS AND MAIN RESULTS

Application of low-dose ECH with arachidonic acid increased coronary perfusion pressure, depressed left ventricular contractile function, provoked electrical instability, and induced a release of creatine kinase concomitant with the liberation of LTC4, LTD4, and LTE4 into the perfusate. All events were abolished when formation of cysteinyl-leukotrienes was blocked by the 5-lipoxygenase activity inhibitor MK-886, targeting 5-lipoxygenase activating protein. In the presence of arachidonic acid, low doses of alpha-toxin caused an increase in cerebral perfusion pressure and a decline of contractile performance, attributable to the release of thromboxane A2, as both events were mitigated by the cyclooxygenase-inhibitor indomethacin. High doses of ECH caused cardiac dysfunction even in the absence of arachidonic acid. However, in the presence of EPA, the cardiodepressant effect of ECH was blunted. Release of EPA-derived LTE5 at the expense of arachidonic acid-derived LTC4, LTD4, and LTE4 was noted in these hearts.

CONCLUSIONS

The potency of the bacterial exotoxins ECH and alpha-toxin to cause coronary vasoconstriction and myocardial depression is dependent on the availability of free arachidonic acid and may be influenced by supplying omega-3 fatty acids as alternative lipid precursors.

Short-Time Infusion of Fish Oil-Based Lipid Emulsions, Approved for Parenteral Nutrition, Reduces Monocyte Proinflammatory Cytokine Generation and Adhesive Interaction with Endothelium in Humans

Potential impact of omega-3 fatty acids, as contained in fish oil, on immunological function has been suggested because observations of reduced inflammatory diseases in Greenland Inuit were published. A fish oil-based lipid emulsion has recently been approved for parenteral nutrition in many countries. We investigated the influence of a short infusion course of fish oil-based (omega-3) vs conventional (omega-6) lipid emulsion on monocyte function. In a randomized design, twelve healthy volunteers received omega-3 or omega-6 lipid infusion for 48 h, with cross-over repetition of the infusion course after 3 mo. Fatty acid profiles, monocyte cytokine release and adhesive monocyte-endothelium interaction were investigated. Resultant omega-6 lipid emulsion increased plasma-free fatty acids including arachidonic acid, whereas the omega-3/omega-6 fatty acid ratio in monocyte membranes remained largely unchanged. It also caused a tendency toward enhanced monocyte proinflammatory cytokine release and adhesive monocyte-endothelium interaction. In contrast, omega-3 lipid emulsion significantly increased the omega-3/omega-6 fatty acid ratio in the plasma-free fatty acid fraction and in monocyte membrane lipid pool, markedly suppressing monocyte generation of TNF-alpha, IL-1, IL-6, and IL-8 in response to endotoxin. In addition, it also significantly inhibited both monocyte-endothelium adhesion and transendothelial monocyte migration, although monocyte surface expression of relevant adhesive molecules (CD11b, CD18, CD49 days, CCR2) was unchanged. Although isocaloric, omega-3 and omega-6 lipid emulsions exert differential impact on immunological processes in humans. In addition to its nutritional value, fish oil-based omega-3 lipid emulsion significantly suppresses monocyte proinflammatory cytokine generation and features of monocyte recruitment.

Omega-3 vs. omega-6 lipid emulsions exert differential influence on neutrophils in septic shock patients: impact on plasma fatty acids and lipid mediator generation

OBJECTIVE

To compare the effects of a conventional omega-6 lipid infusion and a fish oil based (omega-3) lipid infusion for parenteral nutrition on neutrophil function, lipid mediators, and plasma free fatty acids.

DESIGN AND SETTING

Open-label, randomized, pilot study in a university hospital medical intensive care unit and experimental laboratory.

PATIENTS AND PARTICIPANTS

Ten patients with septic shock and eight healthy controls.

INTERVENTIONS

Patients (five per group) requiring parenteral nutrition received intravenously either a omega-3 or a omega-6 lipid emulsion for a 10-day period.

MEASUREMENTS AND RESULTS

At baseline levels of plasma free fatty acids were elevated several-fold, including high concentrations of the omega-6 lipid precursor arachidonic acid (AA). Neutrophils isolated from septic patients displayed markedly reduced responsiveness to ex vivo stimulation, including lipid mediator generation [leukotrienes (LT), PAF], respiratory burst, and phosphoinositide hydrolysis signaling. Under the omega-6 lipid infusion regimen abnormalities in plasma free fatty acids and impairment of neutrophil functions persisted or worsened. In contrast, a rapid switch in the plasma free fatty acid fraction to predominance of the omega-3 acids eicosapentaenoic acid and docosahexaenoic acid over AA occurred in response to omega-3 lipid infusion. LTB(5), in addition to LTB(4), appeared upon neutrophil stimulation originating from these patients, and neutrophil function was significantly improved in the omega-3 lipid group.

CONCLUSIONS

omega-3 vs. omega-6 lipid emulsions differentially influence the plasma free fatty acid profile with impact on neutrophil functions. Lipid-based parenteral nutrition in septic patients may thus exert profound influence on sequelae and status of immunocompetence and inflammation.

Parenteral nutrition with fish oil modulates cytokine response in patients with sepsis

Infusion of fish oil-based (n-3) lipids may influence leukocyte function and plasma lipids in critical care patients. Twenty-one patients with sepsis requiring parenteral nutrition were randomized to receive an n-3 lipid emulsion rich in eicosapentaenoic acid and docosahexaenoic acid or a conventional (n-6) lipid emulsion (index fatty acid: arachidonic acid) for 5 days. The impact on plasma-free fatty acids, mononuclear leukocyte cytokine generation, and membrane fatty acid composition was examined. Cytokine synthesis by isolated mononuclear leukocyte was elicited by endotoxin. Before the onset of lipid infusion therapy, plasma-free fatty acid concentrations were greatly increased in septic patients, with arachidonic acid by far surpassing eicosapentaenoic acid and docosahexaenoic acid, a feature maintained during conventional lipid infusion. Within 2 days of fish oil infusion, free n-3 fatty acids increased, and the n-3/n-6 ratio was reversed, with rapid incorporation of n-3 fatty acids into mononuclear leukocyte membranes. Generation of proinflammatory cytokines by mononuclear leukocytes was markedly amplified during n-6 and was suppressed during n-3 lipid application. After termination of lipid administration, free n-3 fatty acid concentrations and mononuclear leukocyte cytokine synthesis returned to preinfusion values. Use of lipid infusions might allow us to combine intravenous alimentation with differential impact on inflammatory events and immunologic functions in patients with sepsis.

Effects of fish oil in parenteral nutrition

OBJECTIVE

Fish oil is a rich source of omega-3 fatty acids (FAs), especially eicosapentaenoic acid and docosahexaenoic acid. The existing data suggest that eicosapentaenoic acid and docosahexaenoic acid are the active agents in fish oil. A number of clinical trials have shown that dietary fish oil supplementation has antiatherogenic properties and immunomodulation effects. Fish oils are not used widely in parenteral nutrition because fish oil emulsions have not been commercially available until very recently. Studies concerning the use of fish oil in parenteral route are rare.

METHODS

We reviewed the effect of parenteral fish oil infusion on lipid metabolism and immune response in normal and disease conditions.

RESULTS

Studies showed that the main effects of parenteral infusion of fish oil are: 1) incorporation of omega-3 FAs into cellular membranes of many cell populations that consequently influence the disease process of some disease conditions, 2) an effect on eicosanoid metabolism leading to a decrease in platelet aggregation and thrombosis, 3) amelioration of the severity of diet-induced hepatic steatosis, 4) less accumulation of lipid peroxidation products in liver tissue, and 5) immunomodulation effects and therapeutic benefits in animal disease models or various disease conditions of humans. Most of these studies suggested that parenteral infusion of omega-3 FAs have clinical beneficial effects comparable to those of dietary administration. However, different effects of omega-3 and omega-6 FAs in some situations has been reported. For example, plasma triacylglycerol levels were not lowered after fish oil infusion in normal or diabetic rats when compared with those of safflower oil or soybean oil infusion. The reason for the difference remain unclear.

CONCLUSION

The metabolic and immunologic effects of parenteral use of omega-3 FAs requires further evaluation, especially in some disease conditions.

Inflammatory bowel diseases: principles of nutritional therapy

Inflammatory Bowel Diseases - ulcerative colitis and Crohn's disease- are chronic gastrointestinal inflammatory diseases of unknown etiology. Decreased oral intake, malabsorption, accelerated nutrient losses, increased requirements, and drug-nutrient interactions cause nutritional and functional deficiencies that require proper correction by nutritional therapy. The goals of the different forms of nutritional therapy are to correct nutritional disturbances and to modulate inflammatory response, thus influencing disease activity. Total parenteral nutrition has been used to correct and to prevent nutritional disturbances and to promote bowel rest during active disease, mainly in cases of digestive fistulae with high output. Its use should be reserved for patients who cannot tolerate enteral nutrition. Enteral nutrition is effective in inducing clinical remission in adults and promoting growth in children. Due to its low complication rate and lower costs, enteral nutrition should be preferred over total parenteral nutrition whenever possible. Both present equal effectiveness in primary therapy for remission of active Crohn's disease. Nutritional intervention may improve outcome in certain individuals; however, because of the costs and complications of such therapy, careful selection is warranted, especially in patients presumed to need total parenteral nutrition. Recent research has focused on the use of nutrients as primary treatment agents. Immunonutrition is an important therapeutic alternative in the management of inflammatory bowel diseases, modulating the inflammation and changing the eicosanoid synthesis profile. However, beneficial reported effects have yet to be translated into the clinical practice. The real efficacy of these and other nutrients (glutamine, short-chain fatty acids, antioxidants) still need further evaluation through prospective and randomized trials.

Effect of arachidonic and eicosapentaenoic acids on acute lung injury induced by hypochlorous acid

BACKGROUND

Hypochlorous acid (HOCl) is the main oxidant of activated polymorphonuclear neutrophil granulocytes (PMN) and generated by myeloperoxidase during respiratory burst. This study investigates the effects of HOCl on pulmonary artery pressure (PAP) and vascular permeability and characterises the influence of arachidonic acid (AA) and eicosapentaenoic acid (EPA) on the observed effects.

METHODS

HOCl (500, 1,000, 2,000 nmol/min) was continuously infused into the perfusate (Krebs-Henseleit buffer solution, KHB). AA or EPA in subthreshold doses (both 2 nmol/min) or buffer were simultaneously infused using a separate port. PAP, pulmonary venous pressure (PVP), ventilation pressure, and lung weight gain were continuously recorded. The capillary filtration coefficient (Kf,c) was calculated before and 30, 60, and 90 minutes after starting the HOCl infusion.

RESULTS

HOCl application resulted in a dose dependent increase in PAP and Kf,c. The onset of these changes was inversely related to the HOCl dose used. The combined infusion of AA with HOCl resulted in a significant additional rise in pressure and oedema formation which forced premature termination of all experiments. The combination of EPA with HOCl did not result in an enhancement of the HOCl induced rise in pressure and oedema formation.

CONCLUSIONS

Changes in the pulmonary microvasculature caused by HOCl are differently influenced by omega-6 and omega-3 polyunsaturated free fatty acids, suggesting a link between neutrophil derived oxidative stress and pulmonary eicosanoid metabolism.

A fish oil emulsion used for parenteral nutrition attenuates monocyte-endothelial interactions under flow

Monocyte adhesion contributes to perfusion abnormalities, tissue damage, and activation of the coagulation system seen during trauma, shock, or overwhelming inflammation. This study was performed to determine whether an intravenous fish oil emulsion used for parenteral nutrition attenuates monocyte-endothelial interactions under flow and reduces procoagulant activity, measured as tissue factor (TF) expression on adherent monocytes in vitro. Endothelial cell monolayers were incubated with either an intravenous fish oil emulsion or a conventional omega-6 lipid emulsion at 0.05 to 1 mg/ml for 24 h. Six hours following activation with TNFalpha (25 ng/ml), expression of endothelial cell adhesion molecules was measured by flow cytometry. Adhesion of isolated monocytes to pretreated endothelium was examined in a parallel plate flow chamber at a shear stress of 1.5 dynes/cm2. Following perfusion, the cells were cocultured for an additional 4 h and TF expression on monocytes was determined by flow cytometry. In contrast to omega-6 lipids, fish oil down-regulated E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in a dose-dependent manner. P-selectin, however, remained unchanged. In addition, firm adhesion was reduced to 54%, whereas rolling interactions remained unchanged. Fish oil exhibited no effect on the TF expression on cocultured monocytes. We conclude that intravenous fish oil emulsions reduce both endothelial cell adhesion molecule expression and monocyte adhesion. However, under postcapillary flow conditions, rolling interactions via P-selectin remain unaltered. The functional importance of this effect is illustrated by the corresponding upregulation of TF in response to residual monocyte-endothelial interactions.

Omega-3 fatty acids suppress monocyte adhesion to human endothelial cells: role of endothelial PAF generation

Monocyte-endothelium interaction is a fundamental process in many acute and chronic inflammatory diseases. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are fish oil-derived alternative (omega-3) precursor fatty acids implicated in the suppression of inflammatory events. We investigated their influence on rolling and adhesion of monocytes to human umbilical vein endothelial cells (HUVEC) under laminar flow conditions in vitro. Exposure of HUVEC to tumor necrosis factor (TNF-alpha) strongly increased 1) surface expression of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and E-selectin, 2) platelet-activating factor (PAF) synthesis as assessed by thrombin challenge, and 3) rate of rolling and adhesion of monocytes. Preincubation of HUVEC with EPA or DHA markedly suppressed PAF synthesis, monocyte rolling, and adherence, whereas expression of endothelial adhesion molecules was unchanged. Also, PAF receptor antagonists markedly suppressed the adhesion rate of monocytes, and EPA or DHA revealed no additional inhibitory capacity. In contrast, arachidonic acid partially reversed the effect of the antagonist. We conclude that omega-3 fatty acids suppress rolling and adherence of monocytes on activated endothelial cells in vitro by affecting endothelial PAF generation.

Inflammatory bowel disease and environmental influences

Some environmental factors have been established firmly as influences on the development of IBD, such as smoking and appendectomy. Other behaviors, such as oral contraceptive use and sugar intake, have been suggested as risk factors, but he data conflict sharply. The importance of other behaviors, such as breast-feeding, is even murkier with sharply divergent data. Some issues studied may not be factors in themselves but rather markers for other unidentified influences. The conflicting evidence in many of these studies may be clarified as specific genes are identified and the interplay between these environmental factors and genetic subtypes is investigated.

n-3 fatty acids in psoriasis

Increased concentrations of free arachidonic acid (AA) and its proinflammatory metabolites have been observed in psoriatic lesions. Replacement of arachidonic acid by alternative precursor polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA), which can be metabolized via the same enzymatic pathways as AA, might be a therapeutic option in psoriasis. However the results of studies evaluating the therapeutic benefit of dietary fish oil have been conflicting and not clearly dose-dependent. To overcome the slow kinetics and limited availability of oral supplementation, we have performed three studies to assess the efficacy and safety of an intravenously administered fish oil derived lipid emulsion on different forms of psoriasis. Patients received daily infusions of either an n-3 fatty acid-based lipid emulsion (Omegaven) or a conventional n-6 lipid emulsion (Lipoven) in different time and dose regimens. In addition to an overall assessment of the clinical course of psoriasis, EPA- and AA-derived neutrophil 5-lipoxygenase (LO)--products, thromboxane (TX) B2/B3, PAF and plasma free fatty acids were investigated. Treatment with n-3 fatty acids resulted in a considerably higher response rate than infusion of n-6 lipids. A more than 10-fold increase in neutrophil EPA-derived 5-LO product formation was noted in the n-3 group, accompanied by a rapid increase in plasma-free EPA within the first days. In conclusion, intravenous n-3-fatty acid administration causes reduction of psoriasis, which may be related to changes in inflammatory eicosanoid generation. The rapidity of the response to intravenous n-3 lipids exceeds by orders of magnitude the hitherto reported kinetics of improvement of psoriatic lesions upon use of oral supplementation.

[Immunonutrition in experimental colitis: beneficial effects of omega-3 fatty acids]

BACKGROUND

Recent data have given emphasis to the benefits of immunonutrition with omega-3 fatty acids (n-3 FA) in various clinical situations. This work presents the results of parenteral administration of different lipid emulsions in experimental acute colitis and reviews the pertinent literature.

METHODS

Seventy-four adult male Wistar rats were randomized in six groups that had 10% acetic acid-induced colitis (except CS). During 7 days, control groups CS (without colitis) and CC (with colitis) received physiological solution and the others received specific lipid emulsion by a central venous catheter (0.5 mL/h). The n-3/n-6 FA ratio and lipidic compositions were: group L--1:7.7 (LCT, n = 12), M--1:7.0 (MCT and LCT, n = 12), LW-3--1:4.5 (LCT plus FO, n = 12) and MW-3--1:3.0 (MCT and LCT plus FO, n = 13). Rats were evaluated to assess abdominal and intestinal alterations, macrophage cellularity and colonic concentrations of LTB4, LTC4, PGE2 and TXB2.

RESULTS

N-3 FA treated rats (LW-3 and MW-3) presented less inflammatory abdominal alterations than CC rats. Mucosal ulcer formation in MW-3 group was the only comparable to CS group. Only CS, M and MW-3 rats presented smaller cellularity than CC group. Comparing to CC group, there were found smaller averages of LTB4 in CS, LW-3 and MW-3 groups, of PGE2 in CS, M and MW-3 groups, and of TXB2 in CS and MW-3 groups. LTC4 averages were not different.

CONCLUSIONS

1) LCT-containing lipid emulsion with low n-3/n-6 ratio do not modify inflammatory colitis derived manifestations; 2) the association of MCT/LCT-containing lipid emulsion with fish oil with high n-3/n-6 ratio impels great beneficial impact, attenuating morphological and inflammatory consequences and decreasing colonic concentrations of proinflammatory mediators.

Impact of parenteral n-3 fatty acids on experimental acute colitis

The present study was undertaken to investigate the effects of parenteral lipid emulsions (LE) enriched with n-3 fatty acids (n-3 FA) in experimental acute colitis. Seventy-four adult male Wistar rats were randomized into six groups, five of which had acetic acid-induced colitis. The animals received a fat-free diet and water ad libitum in individual metabolic cages. By a central venous catheter, saline was infused (0.5 ml/h) into the control groups CS (without colitis) and CC (with colitis), while the test groups received specific LE for 7 days. The n-3/n-6 FA ratio and the lipidic compositions regarding long chain (LCT) and medium chain (MCT) triglycerides were: group L--1:7.7 (LCT, n = 12), M--1:7.0 (MCT and LCT, n = 12), LW-3--1:4.5 (LCT plus n-3 FA, n = 12) and MW-3--1:3.0 (MCT and LCT plus n-3 FA, n = 13). The frequency of diarrhea, oral intake/body weight ratio, intestinal alterations, macrophage cellularity were evaluated and colonic concentrations of leukotrienes (LTB4, LTC4), prostaglandins (PGE2) and thromboxanes (TXB2) were measured. Groups M, MW-3 and LW-3 had less diarrhea than the CC group (P<0.05). Average oral intake/body weight ratio in MW-3 animals was comparable to the CS and better than the CC group. n-3 FA treated rats (LW-3 and MW-3) presented less intestinal inflammatory alterations than CC rats. Mucosal ulcer formation in MW-3 group did not differ from CS rats. M and MW-3 rats had less macrophages in the colon than the CC group. Compared with CC group, lower concentrations of LTB4 in the CS, LW-3 and MW-3 groups; of PGE2 in the CS, M and MW-3 groups; and of TXB2 in the CS and MW-3 groups were found. Mean concentrations of LTC4 did not differ among the groups. Thus, a LCT-containing LE with a low n-3-n-6 ratio does not modify inflammatory colitis manifestations; LE with a high n-3-n-6 ratio reduces diarrhea, preserves oral intake-weight ratio, attenuates morphological consequences and decreases colonic concentrations of inflammatory mediators; MCT/LCT-containing LE with 1:3 n-3-n-6 ratio exerts the most profound beneficial impact on the inflammatory response.

Review: the role of omega 3 fatty acids in intestinal inflammation

The role of polyunsaturated fatty acids (PUFAs) in inflammatory lesions of the intestines is the subject of increasing research. This review begins with a background discussion of the source, elongation, and desaturation of PUFAs, as well as the role they have played in the human diet through evolution. The available data and hypotheses as to how manipulation of PUFAs might effect the various components of the immune system are then provided. Possible mechanisms by which PUFAs result in immunomodulation include alterations in eicosanoid synthesis, membrane fluidity, signal transduction, intraluminal bacteria, and gene expression. Attention is then turned to the known effects that these polyunsaturated fatty acids have on the various individual components of the immune system including lymphocytes, neutrophils, and antigen presenting cells, as well as the immunoregulatory process of apoptosis. Finally, laboratory data on the role of PUFAs in necrotizing enterocolitis, and to a greater extent inflammatory bowel disease, first as demonstrated in animal models of the disease, and second in human studies are then summarized.

Activation state alters the effect of dietary fatty acids on pro-inflammatory mediator production by murine macrophages

Studies investigating the effect of dietary fats on pro-inflammatory cytokine production by macrophages (M phis) have yielded conflicting results. We hypothesised that this may be due to the different capacities of the M phis studied commonly (resident, thioglycollate-elicited) to produce prostaglandin E(2)(PGE(2)) and leukotriene B(4)(LTB(4)) which inhibit and stimulate, respectively, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) production. To investigate this, male C57Bl6 mice were fed for 6 weeks on a low fat (LF) diet or on high fat diets which contained coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO) as the main fat source. Production of TNF-alpha, IL-1 beta, PGE(2)and LTB(4)by lipopolysaccharide-stimulated resident and thioglycollate-elicited (i.e. inflammatory) peritoneal M phis was measured. PGE(2)production by both inflammatory and resident M phis was significantly decreased by FO feeding. FO also decreased LTB(4)production by resident M phis compared with LF feeding. Production of both cytokines by inflammatory M phis decreased with increasing unsaturation of the high fat diets, such that cells from FO-fed mice showed significantly decreased production of TNF-alpha and IL-1 beta compared to those from mice fed on each of the other diets. In contrast, resident M phis from mice fed FO showed increased TNF-alpha production compared to those from CO-fed mice. Thus, FO feeding decreases production of TNF-alpha and IL-1 beta by inflammatory M phis and increases production of TNF-alpha by resident M phis, at least in comparison to some other dietary fats. These results indicate the mechanisms by which dietary fats exert their effects upon pro-inflammatory cytokine production are most likely different for resident and inflammatory M phis.

E. coli hemolysin-induced lipid mediator metabolism in alveolar macrophages: impact of eicosapentaenoic acid

Escherichia coli hemolysin (HlyA) is a prototype of a large family of pore-forming proteinaceous exotoxins that have been implicated in the pathogenetic sequelae of severe infection and sepsis, including development of acute lung injury. In the present study in rabbit alveolar macrophages (AMs), subcytolytic concentrations of purified HlyA evoked rapid synthesis of platelet-activating factor, with quantities approaching those in response to maximum calcium ionophore challenge. In parallel, large quantities of leukotriene (LT) B(4) and 5-, 8-, 9-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE) were liberated from HlyA-exposed AMs depending on exogenous arachidonic acid (AA) supply. Coadministration of eicosapentaenoic acid (EPA) dose dependently suppressed generation of the proinflammatory lipoxygenase products LTB(4) and 5-, 8-, 9-, and 12-HETE in parallel with the appearance of the corresponding EPA-derived metabolites LTB(5) and 5-, 8-, 9-, and 12-hydroxyeicosapentaenoic acid (HEPE). At equimolar concentrations, EPA turned out to be the preferred substrate over AA for these AM lipoxygenase pathways, with the sum of LTB(5) and 5-, 8-, 9-, and 12-HEPE surpassing the sum of LTB(4) and 5-, 8-, 9-, and 12-HETE by >80-fold. In contrast, coadminstration of EPA did not significantly reduce HlyA-elicited generation of the anti-inflammatory AA lipoxygenase product 15-HETE. We conclude that AMs are sensitive target cells for HlyA attack, resulting in marked proinflammatory lipid mediator synthesis. In the presence of EPA, lipoxygenase product formation is shifted from a pro- to an anti-inflammatory profile.

Effects of parenteral infusion with fish-oil or safflower-oil emulsion on hepatic lipids, plasma amino acids, and inflammatory mediators in septic rats

This study was designed to investigate the effects of preinfusion with total parenteral nutrition (TPN) using fish-oil (FO) versus safflower-oil (SO) emulsion as fat sources on hepatic lipids, plasma amino-acid profiles, and inflammatory-related mediators in septic rats. Normal rats, with internal jugular catheters, were assigned to two different groups and received TPN. TPN provided 300 kcal. kg(-1). d(-1), with 40% of the non-protein energy as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fat emulsion, which was made of SO or FO. After receiving TPN for 6 d, each group of rats was further divided into control and sepsis subgroups. Sepsis was induced by cecal ligation and puncture; control rats received sham operation. All rats were classified into four groups as follows: FO control group (FOC; n = 7), FO sepsis group (FOS; n = 8), SO control group (SOC; n = 8), and SO sepsis group (SOS; n = 9). The results of the study demonstrated that plasma concentrations of triacylglycerol and non-esterified fatty acids did not differ between the FO and SO groups, regardless of whether the animals were septic. SOS had significantly higher total lipids and cholesterol content in the liver than did the SOC group. The FOS group, however, showed no difference from the FOC group. Plasma leucine and isoleucine levels were significantly lower in the SOS group than in the SOC group, whereas no difference in these two amino acids was observed between the FOC and FOS groups. Plasma arginine levels were significantly lower in both septic groups than in the groups without sepsis when either FO or SO was infused. Plasma glutamine levels, however, did not differ across groups. No differences in interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, or leukotriene B(4) concentrations in peritoneal lavage fluid were observed between the two septic groups. These results suggest that catabolic reaction in septic rats preinfused with FO is not as obvious as those preinfused with SO. Compared with SO emulsion, TPN with FO emulsion prevents liver fat accumulation associated with sepsis. However, parenterally administered FO had no beneficial effect in lowering cytokines and LTB(4) levels in peritoneal lavage fluid in septic rats induced by cecal ligation and puncture.

PAF-induced synthesis of tetraenoic and pentaenoic leukotrienes in the isolated rabbit lung

In an isolated rabbit lung model, we tested the hypothesis that platelet-activating factor (PAF)-induced leukotriene (LT) synthesis is critically dependent on the free precursor fatty acid supply and the possible substitution of arachidonic acid (AA) by eicosapentaenoic acid (EPA). To augment the intravascular polymorphonuclear neutrophils (PMNs) in the isolated lung, human PMNs were infused into the pulmonary artery. LTs and hydroxyeicosatetra(penta)enoic acids were quantified with HPLC techniques. Application of PAF (5 microM) or AA (10 microM) provoked the generation of limited quantities of 4-series LTs and 5-hydroxyeicosatetraenoic acid (total sum of 5-lipoxygenase products approximately 7 and approximately 27 pmol/ml in lungs both with and without infused PMNs, respectively). Combined administration amplified 5-lipoxygenase product formation, with a predominance of cysteinyl-LT synthesis in lungs both without (total sum approximately 67 pmol/ml) and, much more strikingly, with (total sum approximately 308 pmol/ml) an infusion of neutrophils. EPA (10 microM) elicited exclusive generation of 5-series LTs and 5-hydroxyeicosapentaenoic acid (total sum approximately 82 pmol/ml). Dual stimulation with PAF and EPA provoked amplification of EPA-derived 5-lipoxygenase product formation, again with predominance of cysteinyl-LTs in lungs without (total sum approximately 224 pmol/ml) and, in particular, with (total sum approximately 545 pmol/ml) preceding microvascular PMN entrapment. Combined application of PAF, AA, and EPA resulted in the synthesis of LTs derived from both fatty acids, with a predominance of 5-series products. We conclude that the PAF-evoked 5-lipoxygenase product formation in the neutrophil-harboring lung capillary bed is critically dependent on intravascular precursor fatty acid supply, with EPA representing the preferred substrate compared with AA. PMN-related transcellular eicosanoid synthesis is suggested to underlie the predominant generation of cysteinyl-LTs. The supply of n-3 versus n-6 precursor fatty acid may thus have a major impact on inflammatory mediator generation.

Dietary fats affect macrophage-mediated cytotoxicity towards tumour cells

In the present study, the effects of feeding mice diets of different fatty acid compositions on the production of TNF-alpha and nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages and on macrophage-mediated cytotoxicity towards L929 and P815 cells were investigated. C57Bl6 mice were fed on a low-fat (LF) diet or on high-fat diets (21% fat by weight), which included coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO) as the principal fat source. The fatty acid composition of the macrophages was markedly influenced by that of the diet fed. Lipopolysaccharide (LPS)-stimulated macrophages from FO-fed mice showed significantly lower production (up to 80%) of PGE2 than those from mice fed on each of the other diets. There was a significant positive linear correlation between the proportion of arachidonic acid in macrophage lipids and the ability of macrophages, to produce PGE2. Lipopolysaccharide-stimulated TNF-alpha production by macrophages decreased with increasing unsaturated fatty acid content of the diet (i.e. FO < SO < OO < CO < LF). Macrophages from FO-fed mice showed significantly lower production of TNF-alpha than those from mice fed on each of the other diets. Nitrite production was highest for LPS-stimulated macrophages from mice fed on the LF diet. Macrophages from FO-fed mice showed significantly higher production of nitrite than those from mice fed on the OO and SO diets. Compared with feeding the LF diet, feeding the CO, OO or SO diets significantly decreased macrophage- mediated killing of P815 cells (killed by nitric oxide). Fish oil feeding did not alter killing of P815 cells by macrophages, compared with feeding the LF diet; killing of P815 cells was greater after FO feeding than after feeding the other high fat diets. Compared with feeding the LF diet, feeding the OO or SO diets significantly decreased macrophage-mediated killing of L929 cells (killed by TNF). Coconut oil or FO feeding did not alter killing of L929 cells by macrophages, compared with feeding the LF diet. It is concluded that the type of fat in the diet affects macrophage composition and alters the ability of macrophages to produce cytotoxic and immunoregulatory mediators and to kill target tumour cells.

Nutrition and inflammatory bowel disease

This article reviews the nutritional aspects of inflammatory bowel disease (IBD) including the mechanisms and manifestations of malnutrition and the efficacy of nutritional therapies. Nutrient deficiencies in patients with IBD occur via several mechanisms and may complicate the course of the disease. Nutritional status is assessed by clinical examination and the use of nutritional indices such as the Subjective Global Assessment of nutritional status. Nutritional intervention may improve outcome in certain individuals; however, because of the costs and complications of such therapy, careful selection is warranted, especially in patients presumed to need parenteral nutrition.

Lipid treatment of inflammatory bowel disease

The aetiology of inflammatory bowel disease remains unclear. Local mediators such as arachidonic acid metabolites and peptide mediators (cytokines) appear to contribute to the disease process. The successful administration of neutralizing antibodies against TNF-alpha has confirmed a pathophysiological role for this cytokine in Crohn's disease. Established therapy of inflammatory bowel disease with 5-aminosalicylic acid compounds has been shown to reduce local leukotriene B4 formation by inhibiting lipoxygenases. This therapeutic mechanism formed one rationale for examining the effect of n-3 fatty acids, which also inhibit leukotriene B4 formation, on the course of these diseases. In the first study, published in 1989, we found no beneficial effects of n-3 fatty acids in patients with Crohn's disease; however, there was clinical improvement, just falling short of significance, in patients with ulcerative colitis. Since then two uncontrolled and five controlled studies have further investigated the therapeutic effect of n-3 fatty acids in patients with ulcerative colitis. The size of the patient population in the controlled studies ranged from 10 to 96 patients in the largest study. Two of these studies showed a significant improvement in clinical activity and a steroid-sparing effect, respectively. Another study found only a trend towards improvement and one trial, which also included a treatment group receiving evening primrose oil, found no beneficial effect in the 16 patients receiving n-3 fatty acids. A large, 2 year trial of n-3 fatty acids in patients with ulcerative colitis off steroids, which was recently completed at the Universities of Munich and Mainz, showed a delay of the first episode of relapse, but no reduction in the cumulative relapse rate at 2 years. Controversial results have been published for Crohn's disease. A new enteric-coated formulation reportedly increased the proportion of patients in remission where as another trial using a conventional preparation found no significant effect.

Pharmacological nutrition after burn injury

Burn patients develop pathophysiological alterations, which include extensive nitrogen loss, malnutrition, markedly increased metabolic rate and immunologic deficiency. This predisposes burn patients to frequent infections, poor wound healing, increased length of hospitalization and increased mortality. The nutritional support requires high protein and high energy diets preferably administered enterally soon after injury. The effects of increased dietary components such as glutamine, arginine and (n-3) fatty acids and related compounds have been evaluated in burn victims. These components, when supplied in quantities two to seven times of those in normal diets of healthy persons, appear to have beneficial pharmacological effects on the pathophysiological alterations associated with burns. However, the efficacy of immune-enhancing diets remains to be convincingly shown.

Omega-3 fatty acid-based lipid infusion in patients with chronic plaque psoriasis: results of a double-blind, randomized, placebo-controlled, multicenter trial

BACKGROUND

Profound changes in the metabolism of eicosanoids with increased concentrations of free arachidonic acid (AA) and its proinflammatory metabolites have been observed in psoriatic lesions. Free eicosapentaenoic acid (EPA) may compete with liberated AA and result in an antiinflammatory effect.

OBJECTIVE

Our purpose was to assess the efficacy and safety of intravenously administered fish-oil-derived lipid emulsion on chronic plaque-type psoriasis.

METHODS

A double-blind, randomized, parallel group study was performed in eight European centers. Eighty-three patients hospitalized for chronic plaque-type psoriasis with a severity score of at least 15 according to the Psoriasis Area and Severity Index (PASI) participated in a 14-day trial. They were randomly allocated to receive daily infusions with either a omega-3 fatty acid-based lipid emulsion (Omegavenous; 200 ml/day with 4.2 gm of both EPA and docosahexaenoic acid (DHA); 43 patients) or a conventional omega-6-lipid emulsion (Lipovenous; EPA+DHA < 0.1 gm/100 ml; 40 patients). The groups were well matched with respect to demographic data and psoriasis-specific medical history. Efficacy of therapy was evaluated by changes in PASI, in an overall assessment of psoriasis by the investigator, and a self-assessment by the patient. In one center neutrophil 4- versus 5-series leukotriene (LT) generation and platelet 2- versus 3- thromboxane generation were investigated and plasma-free fatty acids were determined.

RESULTS

The total PASI score decreased by 11.2 +/- 9.8 in the omega-3 group and by 7.5 +/- 8.8 in the omega-6 group (p = 0.048). In addition, the omega-3 group was superior to the omega-6 group with respect to change in severity of psoriasis per body area, change in overall erythema, overall scaling and overall infiltration, as well as change in overall assessment by the investigator and self-assessment by the patient. Response (defined as decrease in total PASI of at least 50% between admission and last value) was seen in 16 of 43 patients (37%) receiving the omega-3 emulsion and 9 of 40 patients (23%) receiving omega-6 fatty acid-based lipid emulsion. No serious side effects were observed. Within the first few days of omega-3 lipid administration, but not in the omega-6 supplemented patients, a manifold increase in plasma-free EPA concentration, neutrophil leukotriene B5 and platelet thromboxane B3 generation occurred.

CONCLUSION

Intravenous omega-3-fatty acid administration is effective in the treatment of chronic plaque-type psoriasis. This effect may be related to changes in inflammatory eicosanoid generation.

Effects of variations in the proportions of saturated, monounsaturated and polyunsaturated fatty acids in the rat diet on spleen lymphocyte functions

To obtain further information about the immunomodulatory effects of specific dietary fatty acids, weanling male rats were fed for 6 weeks on high-fat (178 g/kg) diets which differed according to the principal fatty acids present. The nine diets used differed in their contents of palmitic, oleic, linoleic and alpha-linolenic acids; as a result the total polyunsaturated fatty acid (PUFA) content and the PUFA:saturated fatty acid ratio varied (from 17.8 to 58.5 g/100 g fatty acids and from 0.28 to 5.56 respectively). The n-6 PUFA:n-3 PUFA ratio was kept constant in all diets at approximately 7.0. The fatty acid composition of the serum and of spleen lymphocytes were significantly influenced by that of the diet fed. The ex vivo proliferation of spleen lymphocytes decreased as the level of oleic acid in the diet increased. Spleen natural killer cell activity decreased as the oleic acid content of the diet increased and increased as the palmitic acid content of the diet increased. The extent of the effects of these fatty acids on lymphocyte functions was modified by the nature of the background fatty acid composition of the diet.

Nutrition and ulcerative colitis

The role of diet in the aetiology and pathogenesis of ulcerative colitis (UC) remains uncertain. Impaired utilization by colonocytes of butyrate, a product of bacterial fermentation of dietary carbohydrates escaping digestion, may be important. Sulphur-fermenting bacteria may be involved in this impaired utilization. Oxidative stress probably mediates tissue injury but is probably not of causative importance. Patients with UC are prone to malnutrition and its detrimental effects. However, there is no role for total parenteral nutrition and bowel rest as primary therapy for UC. The maintenance of adequate nutrition is very important, particularly in the peri-operative patient. In the absence of massive bleeding, perforation, toxic megacolon or obstruction, enteral rather than parenteral nutrition should be the mode of choice. Nutrients may be beneficial as adjuvant therapy. Butyrate enemas have improved patients with otherwise recalcitrant distal colitis in small studies. Non-cellulose fibre supplements are of benefit in rats with experimental colitis. Eicosapentaenoic acid in fish oil has a steroid-sparing effect which, although modest, is important, particularly in terms of reducing the risk of osteoporosis, but it seems to have no role in the patient with inactive disease. gamma-Linolenic acid and anti-oxidants also are showing promise. Nutrients may also modify the increased risk of colorectal carcinoma. Oxidative stress can damage tissue DNA but there are no data published at present on possible protection from oral anti-oxidants. Butyrate protects against experimental carcinogenesis in rats with experimental colitis. Folate supplementation is weakly associated with decreased incidence of cancer in UC patients when assessed retrospectively. Vigilance should be maintained for increased micronutrient requirements and supplements given as appropriate. Calcium and low-dose vitamin D should be given to patients on long-term steroids and folate to those on sulphasalazine.

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.

Fish oil fatty acids and human platelets: dose-dependent decrease in dienoic and increase in trienoic thromboxane generation

Dietary enrichment of membrane phospholipids with n-3 (fish-oil-derived) fatty acids has attracted attention as a putative therapeutic regimen for suppression of inflammatory and coagulatory events. Use of n-3 fatty-acid-enriched lipid infusions for parenteral nutrition results in micromolar concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DCHA) in the plasma-free fatty acid fraction. We investigated the influence of free EPA and DCHA on platelet thromboxane (Tx) A2 and A3 formation by using a recently developed high performance liquid chromatography-ELISA technique for separate quantification of the stable hydrolysis products TxB2 and TxB3. Washed human thrombocytes were incubated with free arachidonic acid (AA; 1 microM), A23187 (0.1 microM) or thrombin (5 U/mL) for stimulation; all regimens provoked large quantities of TxA2 in the absence of TxA3. Simultaneous admixture of free EPA or free DCHA to the incubation medium (concentration range, 0.01-50 microM) largely suppressed platelet TxA2 generation in response to all stimuli used in a dose-dependent manner. The effective concentration with 50% influence of arachidonic acid was 4.2 microM, whereas the inhibitory concentration with 50% effect of EPA and DCHA were both in the same order of magnitude but differed with the nature of the agonist (0.2-7 microM). Platelet (co-)incubation with EPA, but not DCHA, provoked dose-dependent synthesis of n-3-lipid-derived thromboxane: kinetics of formation and absolute quantities of TxA3 approximated 20% of the respective TxA2 data upon stimulation with AA. Both EPA and DCHA dose-dependently suppressed U46619-provoked platelet aggregation. We conclude that EPA and DCHA are potent competitive inhibitors of TxA2 generation by intact platelets, with EPA acting as poor substrate and DCHA being no substrate for the cyclooxygenase/thromboxane synthase complex. Enrichment of the plasma-free fatty acid fraction with n-3 lipids may offer a therapeutic regimen to suppress the synthesis of the potent proaggregatory and vasoconstrictory agent TxA2.

n-3 fatty acids only delay early relapse of ulcerative colitis in remission

Relapse prevention by dietary n-3 fatty acids (5.1 g/day) was studied in a double-blind, placebo-controlled trial of 64 patients with ulcerative colitis in remission and off steroids. 5-ASA compounds were stopped three months after randomization and clinical disease activity monitored for two years. Macroscopic and histologic activity and extension was assessed by colonoscopy at entry and at exit. Both treatment groups were well matched at start. Nine patients on placebo and eight on n-3 fatty acids stopped taking their medication prematurely. Actuarial relapse-free survival was improved by n-3 fatty acids only during months 2 and 3 (2P < 0.05-0.01), but cumulative relapse rate at two years was similar for those taking placebo (18/33 = 55%) and n-3 fatty acids (18/31 = 58%). There was also no consistent difference in clinical, macroscopic, and histologic disease activity between treatment groups. The n-3 fatty acids temporarily retard, but do not prevent, relapse of ulcerative colitis.

Eicosanoids and the gastrointestinal tract

Determining the role of eicosanoids in gastrointestinal physiology and pathophysiology has been an active area of investigation over the past 20 years. The landmark discovery of prostaglandin endoperoxide synthase and other enzymes involved in the production of arachidonic acid products (lipoxygenases and epoxygenases) ushered in a new era of research. The goal of this review is to distill a large body of work pertaining to studies of eicosanoids in the gastrointestinal tract. This review has been organized according both to functional (secretion and motility) and disease-related (inflammation, mucosal injury, and neoplasia) effects. The aim of this article is to present a clear summary of this area of gastroenterology so that future research can be directed in a logical and productive manner.