Dietary omega-3 fatty acids decrease mortality and Kupffer cell prostaglandin E2 production in a rat model of chronic sepsis

Effect of Dietary Supplements with ω-3 Fatty Acids, Ascorbic Acid, and Polyphenolic Antioxidant Flavonoid on Gene Expression, Organ Failure, and Mortality in Endotoxemia-Induced Septic Rats

Sepsis syndrome develops through enhanced secretion of pro-inflammatory cytokines and the generation of reactive oxygen species (ROS). Sepsis syndrome is characterized by vascular hyperpermeability, hypotension, multiple organ dysfunction syndrome (MODS), and increased mortality, among others. Endotoxemia-derived sepsis is an important cause of sepsis syndrome. During endotoxemia, circulating endotoxin interacts with endothelial cells (ECs), inducing detrimental effects on endothelium function. The endotoxin induces the conversion of ECs into fibroblasts, which are characterized by a massive change in the endothelial gene-expression pattern. This downregulates the endothelial markers and upregulates fibrotic proteins, mesenchymal transcription factors, and extracellular matrix proteins, producing endothelial fibrosis. Sepsis progression is modulated by the consumption of specific nutrients, including ω-3 fatty acids, ascorbic acid, and polyphenolic antioxidant flavonoids. However, the underlying mechanism is poorly described. The notion that gene expression is modulated during inflammatory conditions by nutrient consumption has been reported. However, it is not known whether nutrient consumption modulates the fibrotic endothelial gene-expression pattern during sepsis as a mechanism to decrease vascular hyperpermeability, hypotension, MODS, and mortality. Therefore, the aim of this study was to investigate the impact of the consumption of dietary ω-3 fatty acids, ascorbic acid, and polyphenolic antioxidant flavonoid supplements on the modulation of fibrotic endothelial gene-expression patterns during sepsis and to determine the effects on sepsis outcomes. Our results indicate that the consumption of supplements based on ω-3 fatty acids and polyphenolic antioxidant flavonoids was effective for improving endotoxemia outcomes through prophylactic ingestion and therapeutic usage. Thus, our findings indicated that specific nutrient consumption improves sepsis outcomes and should be considered in treatment.

Narrative Review of n-3 Polyunsaturated Fatty Acid Supplementation upon Immune Functions, Resolution Molecules and Lipid Peroxidation

Fish oil supplementation is commonplace in human nutrition and is being used in both enteral and parenteral formulations during the treatment of patients with a large variety of diseases and immune status. The biological effects of fish oil are believed to result from their content of n-3 polyunsaturated fatty acids (PUFA), particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These fatty acids are known to have numerous effects upon immune functions and are described as immunomodulatory. However, immunomodulatory is a nondescript term that encompasses immunostimulation and immunosuppression. The primary goal of this review is to better describe the immune effects of n-3 PUFA as they relate to immunostimulatory vs. immunosuppressive effects. One mechanism proposed for the immune effects of n-3 PUFA relates to the production of specialized pro-resolving mediators (SPMs). A second goal of this review is to evaluate the effects of n-3 PUFA supplementation upon production of SPMs. Although n-3 PUFA are stated to possess anti-oxidative properties, these molecules are highly oxidizable due to multiple double bonds and may increase oxidative stress. Thus, the third goal of this review is to evaluate the effects of n-3 PUFA upon lipid oxidation. We conclude, based upon current scientific evidence, that n-3 PUFA suppress inflammatory responses and most cellular immune responses such as chemotaxis, transmigration, antigen presentation, and lymphocyte functions and should be considered immunosuppressive. n-3 PUFA induced production of resolution molecules is inconsistent with many resolution molecules failing to respond to n-3 PUFA supplementation. n-3 PUFA supplementation is associated with increased lipid peroxidation in most studies. Vitamin E co-administration is unreliable for prevention of the lipid peroxidation. These effects should be considered when administering n-3 PUFA to patients that may be immunosuppressed or under high oxidative stress due to illness or other treatments.

Clostridium difficile caused changes in fatty acids profile and resolvin D1 content in plasma of infected patients

OBJECTIVES

Clostridium difficile infection (CDI) is an acute gastrointestinal infection caused by anaerobic, toxin-producing bacteria. During the course of CDI, there is a general inflammatory state. In order to gain a deeper understanding of the role of fatty acids (FAs) in the pathogenesis of acute infection we analyzed their plasma content in both patients with CDI and controls.

METHODS

The study groups included 40 patients with CDI and 40 healthy volunteers. Plasma FA content was analyzed by gas chromatography, resolvin D1 (RvD1) level using ELISA assay, and we assessed the white blood cell (WBC) count, neutrophil count and C-reactive protein (CRP) level.

RESULTS

Patients with CDI were characterized by significantly higher values of WBC, neutrophils, platelets and CRP compared with the control group. The saturated FA index was statistically higher and total n-3 FA was significantly decreased in the plasma of CDI patients as compared with the control group. RvD1 content was significantly higher in the control group as compared with patients with CDI.

CONCLUSION

In patients with good outcomes, we probably observed the effective resolution of inflammation, as reflected in n-3 FA metabolism and their significant decrease in plasma. This may indicate the therapeutic role of n-3 FA in CDI infection.

Immunonutrition in Critical Illness: What Is the Role?

Acute illness-associated malnutrition leads to muscle wasting, delayed wound healing, failure to wean from ventilator support, and possibly higher rates of infection and longer hospital stays unless appropriate metabolic support is provided in the form of nutrition therapy. Agreement is still lacking about the value of individual immune-modulating substrates for specific patient populations. However, it has long been agreed that there are 3 primary targets for these substrates: 1) mucosal barrier function, 2) cellular defense function, and 3) local and systemic inflammation. These targets guide the multitude of interventions necessary to stabilize and treat the hypercatabolic intensive care unit patient, including specialized nutrition therapy. The paradigm shift that occurred 30 years ago created a unique role for nutrition as an agent to support host defense mechanisms and prevent infectious complications in the critically ill patient. This overview of immunonutrition will discuss the evidence for its role in critical illness today.

Docosahexaenoic acid, but not eicosapentaenoic acid, improves septic shock-induced arterial dysfunction in rats

Introduction

Long chain n-3 fatty acid supplementation may modulate septic shock-induced host response to pathogen-induced sepsis. The composition of lipid emulsions for parenteral nutrition however remains a real challenge in intensive care, depending on their fatty acid content. Because they have not been assessed yet, we aimed at determining the respective effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) during septic shock-induced vascular dysfunction.

Methods

In a peritonitis-induced septic shock model, rats were infused with EPA, DHA, an EPA/DHA mixture or 5% dextrose (D5) during 22 hours. From H18, rats were resuscitated and monitored during 4 hours. At H22, plasma, aorta and mesenteric resistance arteries were collected to perform ex vivo experiments.

Results

We have shown that septic rats needed an active resuscitation with fluid challenge and norepinephrine treatment, while SHAM rats did not. In septic rats, norepinephrine requirements were significantly decreased in DHA and EPA/DHA groups (10.6±12.0 and 3.7±8.0 μg/kg/min respectively versus 17.4±19.3 μg/kg/min in D5 group, p<0.05) and DHA infusion significantly improved contractile response to phenylephrine through nitric oxide pathway inhibition. DHA moreover significantly reduced vascular oxidative stress and nitric oxide production, phosphorylated IκB expression and vasodilative prostaglandin production. DHA also significantly decreased polyunsaturated fatty acid pro-inflammatory mediators and significantly increased several anti-inflammatory metabolites.

Conclusions

DHA infusion in septic rats improved hemodynamic dysfunction through decreased vascular oxidative stress and inflammation, while EPA infusion did not have beneficial effects.

Single-blinded, randomized, and controlled clinical trial evaluating the effects of Omega-3 fatty acids among septic patients with intestinal dysfunction: A pilot study

Sepsis is a systemic inflammatory reaction, which is aggravated by aspects of the immune response that are thought to be inhibited by Omega-3 fatty acids. The aim of the present study was to determine if Omega-3 fatty acid could modulate immunological function and improve survival rate among septic patients with intestinal dysfunction. A total of 48 mechanically ventilated patients with intestinal dysfunction were included in this prospective, randomized and single-blind clinical study. Patients were randomly divided into control (group A) and treatment groups (group B). The treatment protocol for all the participants followed the Sepsis Survival Campaign guidelines, and group B received total parenteral nutrition containing 100 ml of Omega-3 fatty acids (containing 10 g refined fish oil) per day in addition to the standard treatment applied in group A. Group B had a significantly lower mortality rate compared with group A (12.5 vs. 41.7%, P<0.05) during the 28-day follow-up. Group B also had lower Acute Physiology and Chronic Health Evaluation II scores (P<0.05) and lower Marshall scores (P<0.05) at day 7. In addition, group B had a higher ratio of T helper to inducer lymphocytes as well as a higher ratio of CD4 to CD8 lymphocytes (P<0.01 for both) than group A. It was concluded that Omega-3 fatty acids improved T helper/inducer and CD4/CD8 ratios, and may have reduced mortality, among septic patients with intestinal dysfunction.

Temporal changes in hepatic antioxidant enzyme activities after ischemia and reperfusion in a rat liver ischemia model

This study investigated the hypothesis that administration of tilapia fish oil diet would attenuate warm liver ischemia/reperfusion injury (IRI) and whether fish oil modulates prooxidant/antioxidant status. Male Wistar rats were subjected to 30 min of approximately 70% hepatic ischemia followed by 1, 12, and 24 h reperfusion. Rats were randomly divided into three groups: sham-operated group (SO), control–warm hepatic ischemia (WI) group, and Oil–WI group given tilapia oil for 3 weeks followed by liver IRI. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured in the plasma. Levels of thiobarbituric acid reactive substances (TBARS) and antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured in liver fractions.

In the sham group, there was no enzymatic or histological change. I/R caused significant increase in serum AST, ALT, and tissue TBARS levels. As compared to the control group, animals treated with tilapia oil experienced a significant decrease ( p < 0.05) in AST and ALT levels in reperfusion periods. Tissue TBARS levels in Oil–WI group were significantly ( p < 0.05) reduced as compared to control group at 60 min after reperfusion. After ischemia, 1, 12, and 24 h of reperfusion, CAT, SOD, and GPx values were the lowest in the Oil–WI group and highest in the control group and were statistically significant ( p < 0.05). Histological analysis also revealed that fish oil provided some protection compared with the control group.

Tilapia oil exerts a protective effect during the early phase of reperfusion, and it modulates prooxidant/antioxidant status of rat liver subjected to warm IRI.

Dietary supplementation with omega-3 polyunsaturated fatty acids ameliorates acute pneumonia induced by Klebsiella pneumoniae in BALB/c mice

The immune benefits associated with the optimal intake of dietary fatty acids are widely known. The objective of the present investigation was to elucidate the role of omega-3 polyunsaturated fatty acids (n-3 PUFA) food source on acute pneumonia induced by Klebsiella pneumoniae. Three different n-3 PUFA preparations (cod liver oil, Maxigard, and flaxseed oil) were orally supplemented and infection was induced in different groups of experimental mice. Mice fed olive oil and normal saline served as oil and saline controls, respectively. After 2 weeks of fatty acid feeding, no effect on the establishment of infection was observed when acute pneumonia was induced in animals. On the other hand, 6 weeks of n-3 PUFA administration was found to improve resistance in mice, as reduced lung bacterial load coupled with significant improvement in pathology was seen in infected mice. Alveolar macrophages collected from all 3 groups of mice fed n-3 PUFA exhibited a significant decrease in the level of apoptosis following infection with K. pneumoniae and an enhanced in vitro phagocytic potential for the pathogen. Lower lung levels of nitric oxide, malondialdehyde, and lactate dehydrogenase were associated with a decrease in the severity of tissue damage. There was a significant increase in the lung levels of pro-inflammatory cytokines (tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β)). No significant change was observed in the levels of interleukin-10 (IL-10). This study highlights that dietary n-3 PUFA supplementation exerts an overall beneficial effect against acute experimental pneumonia. This mechanism is operative through upregulation of nonspecific and specific immune defenses of the host.

Lipids for intravenous nutrition in hospitalised adult patients: a multiple choice of options

Lipids used in parenteral nutrition provide energy, building blocks and essential fatty acids. Traditionally, these lipids have been based on n-6 PUFA-rich vegetable oils particularly soyabean oil. This may not be optimal because soyabean oil may present an excessive supply of linoleic acid. Alternatives to use of soyabean oil include its partial replacement by medium-chain TAG, olive oil or fish oil, either alone or in combination. Lipid emulsions containing these alternatives are well tolerated without adverse effects in a wide range of hospitalised adult patients. Lipid emulsions that include fish oil have been used in parenteral nutrition in adult patients' post-surgery (mainly gastrointestinal). This has been associated with alterations in patterns of inflammatory mediators and in immune function and, in some studies, a reduction in length of intensive care unit and hospital stay. These benefits are emphasised through recent meta-analyses. Perioperative administration of fish oil may be superior to post-operative administration. Parenteral fish oil has been used in critically ill adults. Here, the influence on inflammatory processes, immune function and clinical endpoints is not clear, since there are too few studies and those that are available report contradictory findings. However, some studies found reduced inflammation, improved gas exchange and shorter length of hospital stay in critically ill patients if they receive fish oil. More and better trials are needed in patient groups in which parenteral nutrition is used and where fish oil may offer benefits.

Fish oil, but not soy bean or olive oil enriched infusion decreases histopathological severity of acute pancreatitis in rats without affecting eicosanoid synthesis

Different dietary fatty acids affect eicosanoid metabolism in different ways, thus influencing the pro- and anti-inflammatory balance of prostaglandins and leukotrienes. Therefore, we analyzed the impact of [n-3], [n-6], and [n-9] fatty acids on eicosanoid metabolism and histopathology in acute pancreatitis in rats. Seventy-five male Sprague-Dawley rats were randomized into five groups (n = 15). Group 1 underwent only laparotomy, while in groups, 2-5 pancreatitis was induced. Groups 1 and 2 were then given saline infusion, groups 3-5 received fat emulsion (group 3: rich in [n-6], group 4: rich in [n-9], group 5: rich in [n-3] fatty acids) for another 18 h. Infusion rich in [n-3] fatty acids significantly decreased histopathological severity of pancreatitis, compared to all other groups. There was no difference concerning the concentrations of prostaglandins and leukotrienes between all groups. Parenteral infusion rich in [n-3] fatty acids reduced histopathological severity of acute pancreatitis in rats without changing eicosanoid metabolism at the endpoint.

Innate immunity signaling pathways: links between immunonutrition and responses to sepsis

Septic infections in patients treated in intensive care units show the highest mortality rates. Despite advances in treatment methods, there is still no therapy available to efficiently reduce the excessive inflammatory response, which can increase the risk of multiple organ failure. One of the ways to discover new, more efficient treatment methods involves regulating the mechanisms of inflammatory response to a massive infection. Toll-like receptors (TLRs) that recognize pathogen-associated molecular patterns play a significant role in innate antibacterial and inflammatory responses. The regulatory impact of immunonutrition on TLR expression in septic patients seems to be a promising research direction. This paper presents the main mechanisms for the innate immune response to lipopolysaccharide, based on the research results for both TLR-dependent and independent signaling pathways. Special emphasis was put on the research results for the TLR-dependent immune response and the anti-bacterial/anti-inflammatory response after applying immunonutrition with increased concentrations of glutamine and unsaturated fatty acids.

The 2008 ESPEN Sir David Cuthbertson Lecture: Fatty acids and inflammation--from the membrane to the nucleus and from the laboratory bench to the clinic

Many chronic conditions involve excessive inflammation that is damaging to host tissues. Excessive or inappropriate inflammation and immunosuppression are components of the response to surgery, trauma, injury and infection in some individuals and these can lead, progressively, to sepsis and septic shock. Hyperinflammation is characterised by the production of inflammatory cytokines, eicosanoids and other inflammatory mediators, while the immunosuppression is characterised by impairment of antigen presentation and of certain T cell responses. N-6 fatty acids may contribute to the hyperinflamed and immunosuppressed states. N-3 fatty acids from fish oil decrease the production of inflammatory cytokines and eicosanoids. They act both directly (by replacing arachidonic acid as an eicosanoid precursor) and indirectly (by altering the expression of inflammatory genes through effects on transcription factor activation). Thus, these fatty acids are potentially useful anti-inflammatory agents and may be of benefit in patients with chronic inflammatory diseases or at risk of hyperinflammation and sepsis. An emerging application of n-3 fatty acids is in surgical or critically ill patients where they may be added to parenteral or enteral formulas. Studies to date are suggestive of clinical benefits from these approaches, although more robust data are needed especially in critically ill patients.

Rationale and use of n-3 fatty acids in artificial nutrition

Lipids traditionally used in artificial nutrition are based on n-6 fatty acid-rich vegetable oils like soyabean oil. This may not be optimal because it may present an excessive supply of linoleic acid. One alternative to the use of soyabean oil is its partial replacement by fish oil, which contains n-3 fatty acids. These fatty acids influence inflammatory and immune responses and so may be useful in particular situations where those responses are not optimal. Fish oil-containing lipid emulsions have been used in parenteral nutrition in adult patients post-surgery (mainly gastrointestinal). This has been associated with alterations in patterns of inflammatory mediators and in immune function and, in some studies, a reduction in length of intensive care unit (ICU) and hospital stay. Perioperative administration of fish oil may be superior to post-operative. Parenteral fish oil has been used in critically ill adults. Here the influence on inflammatory processes, immune function and clinical endpoints is not clear, since there are too few studies and those that are available report contradictory findings. Fish oil is included in combination with other nutrients in various enteral formulas. In post-surgical patients and in those with mild sepsis or trauma, there is clinical benefit from a formula including fish oil and arginine. A formula including fish oil, borage oil and antioxidants has demonstrated marked benefits on gas exchange, ventilation requirement, new organ failures, ICU stay and mortality in patients with acute respiratory distress syndrome, acute lung injury or severe sepsis.

Enhanced absorption of n-3 fatty acids from emulsified compared with encapsulated fish oil

Health benefits of n-3 fatty acids are well-established. However, consumption of adequate dietary sources of these fatty acids is inadequate. Oral fish oil supplements are an alternative means of consuming adequate long-chain n-3 fatty acids in individuals who do not consume sufficient dietary sources. However, palatability can present a problem with compliance. Emulsifying fish oil allows for production of a pleasant-tasting supplement and can enhance digestion and absorption of the fatty acids. We investigated the rate and extent of absorption of emulsified fish oil compared with capsular triglyceride fish oil supplements in humans. Participants subjectively rated palatability of these products. A randomized, crossover-designed, open-label trial was performed in which 10 healthy volunteers received emulsified fish oil and capsular triglyceride fish oil orally. Blood samples were collected at 0, 2, 4, 8, 24, and 48 hours to determine the absorption of individual fatty acids into plasma phospholipid fatty acids. At the completion of blood collection, subjects were asked to subjectively rate the tolerance and acceptability of the two supplements. During a 48-hour period, there was enhanced absorption of total n-3 and eicosapentaenoic acid (0.67%+/-0.16%, 0.45%+/-0.06%; P<0.01; 0.34%+/-0.05%, 0.23%+/-0.04%; P=0.05; emulsified fish oil and capsular triglyceride fish oil, respectively) observed for the emulsified fish oil treatment. Our findings indicate that a single dose of emulsified fish oil resulted in enhanced absorption of total n-3 eicosapentaenoic acid and docosahexaenoic acid as evidenced by changes in phospholipid fatty acids composition compared with the capsular triglyceride fish oil during the 48-hour observation period. Both supplements were subjectively rated and found to be well-tolerated by participants.

Docosahexaenoic acid-enriched fish oil consumption modulates immunoglobulin responses to and clearance of enteric reovirus infection in mice

We hypothesized that consumption of the (n-3) PUFA, docosahexaenoic acid (DHA), modulates the mucosal immune response to enteric infection with respiratory enteric orphan virus (reovirus), a model intestinal pathogen. Mice were fed either AIN-93G control diet, containing 10 g/kg corn oil and 60 g/kg high oleic acid safflower oil, or AIN-93G, containing 10 g/kg corn oil and 60 g/kg DHA-enriched fish oil, for 4 wk and then orally gavaged with reovirus strain Type 1 Lang, (T1/L). Reovirus-specific IgA antibody was first detectable in the feces of mice fed a control diet at 6 d postinfection (PI) and was further elevated at 8 and 10 d PI. IgA responses in DHA-fed mice were similar at 6 and 8 d PI but greater at 10 d PI (P < 0.05). Both reovirus-specific serum IgA and IgG(2a) were comparably induced in mice fed control or DHA diets. Reovirus-specific IgA and IgG(2a) secretion by ex vivo Peyer's patch, lamina propria, and spleen cultures derived from control and DHA groups were comparable. Although both groups carried similar numbers of reovirus plaque forming units per intestine, DHA-fed mice shed nearly 10 times more viral RNA in feces than control mice at 2, 4, and 6 d PI (P < 0.05). However, viral RNA was not detectable in either group at 8 and 10 d. Taken together, these data suggest that DHA consumption did not markedly alter mucosal or systemic Ig responses to reovirus but delayed clearance of the virus from the intestinal tract.

Immune modulation by parenteral lipid emulsions

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

Use of fish oil in parenteral nutrition: Rationale and reality

Excessive or inappropriate inflammation and immunosuppression are components of the response to surgery, trauma, injury and infection in some individuals and can lead, progressively, to sepsis and septic shock. The hyperinflammation is characterised by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids and other inflammatory mediators, while the immunosuppression is characterised by impairment of antigen presentation and of T-helper lymphocyte type-1 responses. Long-chain n-3 fatty acids from fish oil decrease the production of inflammatory cytokines and eicosanoids. They act both directly (by replacing arachidonic acid as an eicosanoid substrate and by inhibiting arachidonic acid metabolism) and indirectly (by altering the expression of inflammatory genes through effects on transcription factor activation). Thus, long-chain n-3 fatty acids are potentially useful anti-inflammatory agents and may be of benefit in patients at risk of hyperinflammation and sepsis. As a consequence, an emerging application for n-3 fatty acids, in which they may be added to parenteral (or enteral) formulas, is in surgical or critically-ill patients. Parenteral nutrition that includes n-3 fatty acids appears to preserve immune function better than standard formulas and appears to diminish the extent of the inflammatory response. Studies to date are suggestive of clinical benefits from these approaches, especially in patients post surgery, although evidence of clinical benefit in patients with sepsis is emerging.

Effects of enteral feeding with eicosapentaenoic acid, γ-linolenic acid, and antioxidants in mechanically ventilated patients with severe sepsis and septic shock*

OBJECTIVES

Enteral diets enriched with eicosapentaenoic acid (EPA), gamma-linolenic acid (GLA), and antioxidants have previously been shown to improve outcomes in patients with acute respiratory distress syndrome. Several studies using animal models of sepsis demonstrate that enteral nutrition enriched with omega-3 fatty acids reduces mortality rate. This study investigated whether an enteral diet enriched with EPA, GLA, and antioxidant vitamins can improve outcomes and reduce 28-day all-cause mortality in patients with severe sepsis or septic shock requiring mechanical ventilation.

DESIGN

Prospective, double-blind, placebo-controlled, randomized trial.

SETTING

Three different intensive care units of a tertiary hospital in Brazil.

PATIENTS

The study enrolled 165 patients.

INTERVENTIONS

Patients were randomized to be continuously tube-fed with either a diet enriched with EPA, GLA, and elevated antioxidants or an isonitrogenous and isocaloric control diet, delivered at a constant rate to achieve a minimum of 75% of basal energy expenditure x 1.3 during a minimum of 4 days.

MEASUREMENTS AND MAIN RESULTS

Patients were monitored for 28 days. Patients who were fed with the study diet experienced a significant reduction in mortality rate compared with patients fed with the control diet, the absolute mortality reduction amounting to 19.4% (p = .037). The group who received the study diet also experienced significant improvements in oxygenation status, more ventilator-free days (13.4 +/- 1.2 vs. 5.8 +/- 1.0, p < .001), more intensive care unit (ICU)-free days (10.8 +/- 1.1 vs. 4.6 +/- 0.9, p < .001), and a lesser development of new organ dysfunctions (p < .001).

CONCLUSIONS

In patients with severe sepsis or septic shock and requiring mechanical ventilation and tolerating enteral nutrition, a diet enriched with EPA, GLA, and elevated antioxidants contributed to better ICU and hospital outcomes and was associated with lower mortality rates.

n-3, n-6, and n-9 polyunsaturated fatty acids--which composition in parenteral nutrition decreases severity of acute hemorrhagic necrotizing pancreatitis in rats?

BACKGROUND AND AIMS

Acute pancreatitis often requires parenteral nutrition. Thus, we analyzed, using a randomized trial, whether different fatty acids in parenteral nutrition influence lipidperoxidation and histopathology in acute pancreatitis in rats.

MATERIALS AND METHODS

Seventy-five male Sprague-Dawley rats were randomized into five groups (gr.) (n=15). Gr. 1 underwent a laparotomy followed by saline infusion, gr. 2-5 received intraductal glycodeoxycholic acid (GDOC) followed by intravenous cerulein. Six hours after induction of pancreatitis (IOP), gr. 2 received saline infusion, while gr. 3 was infused with standard lipovenous (rich in [n-6] polyunsaturated fatty acids (PUFA)), gr. 4 received ClinOleic (rich in [n-9] PUFA), while gr. 5 was infused with Omegaven (rich in [n-3] PUFA) for 18 h. After 24 h, all animals were sacrificed and the pancreas was determined histopathologically according to the severity of pancreatitis. Furthermore, pancreatic lipidperoxidation (TBARS) and activity of lipid production protective enzymes superoxide dismutase (SOD) and gluthationperoxidase (GSHPx) were analyzed.

RESULTS

Omegaven infusion reduced the severity of histopathologic changes in acute pancreatitis and decreased lipidperoxidation (TBARS) in pancreatic tissue samples. Furthermore, pancreatic activity of SOD was increased. However, standard PUFA and ClinOleic infusion did not influence the severity of pancreatitis and lipidperoxidation.

CONCLUSION

Parenteral nutrition high in n-3 PUFA seems to be superior to compositions of n-6 or n-9 PUFA in the treatment of acute hemorrhagic pancreatitis in rats.

Long-chain polyunsaturated fatty acids modulate lung inflammatory response induced by Pseudomonas aeruginosa in mice

Polyunsaturated fatty acid (PUFA) immunomodulatory properties have been studied extensively in chronic infections. Few studies have focused on acute infection; thus, PUFA effects in a mouse model of Pseudomonas aeruginosa (PA)-induced lung injury were evaluated. C57BL/6 mice were randomized to be fed for 3 wk with an eicosapentaenoic acid (EPA) diet, an arachidonic acid (AA) diet, or a control diet [saturated fatty acids]. Lung injury was induced by intratracheal instillation of 10(7) CFU of PA per mouse. In each diet group, animals were studied either without or after PA-inducing lung injury. Evaluation criteria were early mortality; inflammatory response assessed with tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-6 and IL-10 levels in bronchoalveolar lavage; lung injury evaluation; and extravascular lung water, assessed 24 h after the injury. After PA-induced lung injury, no difference in early mortality was observed; TNF-alpha level was significantly higher in the EPA diet than in the other two diet groups. No difference for the other cytokines was found among the groups. Lung edema was also more important in the EPA group, consistent with the variations of TNF-alpha levels. Our study clearly shows that in PA-induced acute lung injury, n-3 PUFA induces differences in the inflammatory response with a higher level of lung edema. Modulation of the inflammatory response with n-3 PUFA can influence the response to a bacterial challenge.

n-3 fatty acids, inflammation, and immunity--relevance to postsurgical and critically ill patients

Excessive or inappropriate inflammation and immunosuppression are components of the response to surgery, trauma, injury, and infection in some individuals and these can lead, progressively, to sepsis and septic shock. The hyperinflammation is characterized by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids, and other inflammatory mediators, while the immunosuppression is characterized by impairment of antigen presentation and of T helper cell type-1 responses. Long-chain n−3 FA from fish oil decrease the production of inflammatory cytokines and eicosanoids. They act both directly (by replacing arachidonic acid as an eicosanoid substrate and by inhibiting arachidonic acid metabolism) and indirectly (by altering the expression of inflammatory genes through effects on transcription factor activation). Thus, long-chain n−3 FA are potentially useful anti-inflammatory agents and may be of benefit in patients at risk of developing sepsis. As such, an emerging application of n−3 FA is in surgical or critically ill patients where they may be added to parenteral or enteral formulas. Parenteral or enteral nutrition including n−3 FA appears to preserve immune function better than standard formulas and appears to partly prevent some aspects of the inflammatory response. Studies to date are suggestive of clinical benefits from these approaches, especially in postsurgical patients.

Methyl palmitate: inhibitor of phagocytosis in primary rat Kupffer cells

Kupffer cells are involved in phagocytosis and known to release biologically active mediators during early events of liver injury. Such functional properties of Kupffer cells can be modulated by methyl palmitate (MP). Therefore, efficacy of MP to modulate Kupffer cell function was evaluated in cultured primary Kupffer cells from rat liver. Phagocytic activity of Kupffer cells was measured by their capacity to phagocytize latex beads and the release of TNF-alpha, IL-10, IL-6, nitric oxide, and PGE2 was determined in cell culture medium after incubating the cells with various concentrations of MP for 24 h followed stimulation with lipopolysaccharide (LPS) for 6 h. To understand the mechanism of phagocytosis, we investigated the hydrolysis of MP, and determine ATP levels and activity of NF-kappaB in MP-inhibited Kupffer cells. A significant decrease was observed in phagocytosis. Phagocytosis evaluated at 0.5 mM MP was found to be time-dependent with a maximum decrease of 49% at 6 h. Exposure of Kupffer cells to MP followed by LPS stimulation showed a dose-dependent decrease in phagocytosis and reduced the release of TNF-alpha, IL-10, nitric oxide, and PGE2 but not of IL-6 levels in the supernatant as compared to the control. While ATP levels were unchanged, the nuclear factor NF-kappaB (p65) activity was inhibited in Kupffer cells treated with MP after LPS stimulation (35.6 RLU versus 49.6 RLU in control). Hydrolysis of MP was found to be time-dependent; maximum concentration of MP and palmitic acid (hydrolysis products) in the cell being at 3 and 6 h, respectively. In general, MP appears to reduce phagocytosis and levels of TNF-alpha, IL-10, nitric oxide, and PGE2 without affecting ATP levels and is probably mediated by NF-kappaB. This in vitro model is useful for detailed mechanistic studies of inhibition of phagocytosis by MP and other fatty acid esters.

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.

Omega-3 fatty acid lipid emulsion reduces LPS-stimulated macrophage TNF-alpha production

BACKGROUND

Omega-3 (omega-3) fatty acids (FA), specifically eicosapentaenoic acid (EPA), attenuate cytokine-mediated inflammation. Currently, in the United States, there is no commercial source of omega-3 lipid for clinical use. A clinically used European lipid emulsion, Omegaven, has been shown to have beneficial antiinflammatory effects; however, the mechanisms of its action are not well defined. In the present work, this omega-3 FA emulsion has been evaluated in order to define its effects on TNF-alpha production in a model of LPS-stimulated macrophages.

MATERIALS AND METHODS

RAW 264.7 cells (1 x 10(6) cell/well) were incubated with DMEM, Omegaven, or an isoenergetic omega-6 lipid emulsion, Lipovenos for 4 h. Cells were washed and then stimulated with LPS (1 microg/mL) or media alone for 3 h. Plate well supernatants were collected and assayed for TNF-alpha production by ELISA. Statistical analysis was performed by ANOVA and post-hoc analyses; the significance was defined as p < 0.05.

RESULTS

Unstimulated RAW cell TNF-alpha production was similar in all groups and < 60 pg/mL. Lipovenos pretreatment did not alter TNF-alpha production from that of baseline compared to LPS-stimulated cells. Four-hour Omegaven pretreatment significantly reduced TNF-alpha production in LPS-stimulated cells, with a 46% reduction in TNF-alpha from baseline observed.

CONCLUSION

Four-hour omega-3 FA emulsion pretreatment significantly attenuated LPS-stimulated macrophage TNF-alpha production. These data support the contention that antiinflammatory effects of omega-3 FA occur at least in part through the inhibition of macrophage TNF-alpha production in response to endotoxin. Further studies to define the antiinflammatory mechanisms of omega-3 FA on macrophages are warranted. The availability of Omegaven as an experimental treatment and Lipovenos as an equivalent control will be useful for future studies.

Long-chain n-3 fatty acids and inflammation: potential application in surgical and trauma patients

Lipids used in nutritional support of surgical or critically ill patients have been based on soybean oil, which is rich in the n-6 fatty acid linoleic acid (18:2n-6). Linoleic acid is the precursor of arachidonic acid (20:4n-6). In turn, arachidonic acid in cell membrane phospholipids is the substrate for the synthesis of a range of biologically active compounds (eicosanoids) including prostaglandins, thromboxanes, and leukotrienes. These compounds can act as mediators in their own right and can also act as regulators of other processes, such as platelet aggregation, blood clotting, smooth muscle contraction, leukocyte chemotaxis, inflammatory cytokine production, and immune function. There is a view that an excess of n-6 fatty acids should be avoided since this could contribute to a state where physiological processes become dysregulated. One alternative is the use of fish oil. The rationale of this latter approach is that fish oil contains long chain n-3 fatty acids, such as eicosapentaenoic acid. When fish oil is provided, eicosapentaenoic acid is incorporated into cell membrane phospholipids, partly at the expense of arachidonic acid. Thus, there is less arachidonic acid available for eicosanoid synthesis. Hence, fish oil decreases production of prostaglandins like PGE2 and of leukotrienes like LTB4. Thus, n-3 fatty acids can potentially reduce platelet aggregation, blood clotting, smooth muscle contraction, and leukocyte chemotaxis, and can modulate inflammatory cytokine production and immune function. These effects have been demonstrated in cell culture, animal feeding and healthy volunteer studies. Fish oil decreases the host metabolic response and improves survival to endotoxin in laboratory animals. Recently clinical studies performed in various patient groups have indicated benefit from this approach.

Dietary modification of inflammation with lipids

The n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in high proportions in oily fish and fish oils. The n-3 PUFA are structurally and functionally distinct from the n-6 PUFA. Typically, human inflammatory cells contain high proportions of the n-6 PUFA arachidonic acid and low proportions of n-3 PUFA. The significance of this difference is that arachidonic acid is the precursor of 2-series prostaglandins and 4-series leukotrienes, which are highly-active mediators of inflammation. Feeding fish oil results in partial replacement of arachidonic acid in inflammatory cell membranes by EPA. This change leads to decreased production of arachidonic acid-derived mediators. This response alone is a potentially beneficial anti-inflammatory effect of n-3 PUFA. However, n-3 PUFA have a number of other effects which might occur downstream of altered eicosanoid production or might be independent of this activity. For example, animal and human studies have shown that dietary fish oil results in suppressed production of pro-inflammatory cytokines and can decrease adhesion molecule expression. These effects occur at the level of altered gene expression. This action might come about through antagonism of the effects of arachidonic acid-derived mediators or through more direct actions on the intracellular signalling pathways which lead to activation of transcription factors such as nuclear factor kappa B (NFB). Recent studies have shown that n-3 PUFA can down regulate the activity of the nuclear transcription factor NFB. Fish oil feeding has been shown to ameliorate the symptoms in some animal models of chronic inflammatory disease and to protect against the effects of endotoxin and similar inflammatory challenges. Clinical studies have reported that oral fish oil supplementation has beneficial effects in rheumatoid arthritis and among some patients with asthma, supporting the idea that the n-3 PUFA in fish oil are anti-inflammatory. There are indications that inclusion of n-3 PUFA in enteral and parenteral formulas might be beneficial to patients in intensive care or post-surgery.

(n-3) Fatty acids and infectious disease resistance

The current view of the manner in which (n-3) polyunsaturated fatty acids (PUFA) affect the immune system is centered on their ability to alter cytokine production and secondarily to diminish eicosanoid biosynthesis. The purpose of this article is to review the evidence that (n-3) PUFA affect host infectious disease resistance. Although there have been a few human clinical trials involving (n-3) PUFA and human infectious disease, the data are equivocal and the study designs confounded by the simultaneous inclusion of other immunonutrients (i.e., arginine and nucleotides) with the (n-3) PUFA. Thus, this review focuses on animal feeding trials that include an in vivo challenge of the host with a live infectious agent. Host survival and pathogen clearance are the most common end points measured in these studies. The data suggest that (n-3) PUFA can both improve and impair host resistance to a number of pathogens. However, the data are still quite limited in breadth and depth. For those pathogens for which data exist, the number of published studies in general does not exceed two or three. Emphasis is placed on defining important microbiological and immunological differences in various host-pathogen interactions that might help explain the incongruity in the findings published to date. The authors believe that direct examination of (n-3) PUFA on human infectious disease resistance is warranted.

Prostaglandin E(2) modulation of vascular endothelial growth factor production in murine macrophages

We have previously shown that dietary (n-3) fatty acids decrease mammary tumor vascularization and PGE(2) production. One possible mechanism may be the modulation of vascular endothelial growth factor (VEGF) production by PGE(2). Macrophages are major producers of VEGF, and thus we assessed the role of PGE(2) in vitro and in vivo on their VEGF production. When added to macrophages, pharmacological (10(-7) M) but not physiological (10(-9) to 10(-11) M) concentrations of PGE(2) increased VEGF mRNA and protein levels. That increased expression was relatively rapid and sustained up to 8 hrs, but declined by 24 hrs. Similarly, dibutryl cAMP increased production of VEGF protein which was completely inhibited by H89. Addition of cAMP-elevating agents further potentiated the production of VEGF by PGE(2). Next, (n-3) and (n-6) fatty acids were added to macrophages in vitro or provided in the diet. Macrophages of mice fed safflower oil (n-6) had 2- to 4-fold greater copy number of VEGF transcripts after lipopolysaccarhide (LPS) stimulation compared to fish oil (n-3). A decreasing trend was seen in LPS-induced VEGF secretion from macrophages in vitro after docosahexaenoic acid or eicosapentaenoic acid incubation compared to arachidonic acid. While pharmacological concentrations of PGE(2) modulate VEGF expression, physiological alterations did not alter VEGF protein production by macrophages.

Parenteral supplementation with a fish-oil emulsion prolongs survival and improves rat lymphocyte function during sepsis

Nutritional intervention with omega-3 fatty acids during trauma and infection has been shown to improve the clinical outcome of patients and the survival rate in laboratory animals. This study evaluated the effects of parenteral administration of lipid emulsions containing fish oil (FO) or soybean oil (SBO) on survival and T-lymphocyte response during sepsis. Male Sprague-Dawley rats (250-275 g) were prepared for parenteral feeding 4 d before inducing sepsis by cecal ligation and puncture (CLP). Standard resuscitation was provided with normal saline. Thirty minutes after completing CLP, sham control or CLP rats were infused continuously with saline or a parenteral diet containing SBO or a 1:1 FO:SBO emulsion. The survival rate was significantly improved in rats receiving the FO-supplemented diet, with 50% alive by 120 h in comparison with the saline-infused, chow-fed rats (0% alive by 120 h) or the SBO-fed rats (12% alive at 120 h). The T-lymphocyte response was evaluated at 24 h after CLP. Sepsis led to a decline in lymphocyte proliferation in rats infused with saline or the SBO emulsion, which was associated with a greater release of splenocyte interleukin-10, transforming growth factor-beta and prostaglandin E2. Administering the 1:1 FO:SBO parenteral diet during sepsis improved the survival rate and prevented the sepsis-induced suppression of lymphocyte proliferation and interleukin-2 release. The FO effect on lymphocyte function was associated with decreased splenocyte release of transforming growth factor-beta and prostaglandin E2.

Lipid modulation and systemic inflammation

N-6 and n-3 PUFAs from the diet are absorbed and reach the cell where they interact with fatty acid binding proteins within cell membranes and cytoplasm. They are processed in the endoplasmic reticulum (desaturation-elongation reactions, lipid synthesis, eicosanoid and epoxide production) and in peroxisomes (beta-oxidation, synthesis, oxidation products). They interact with receptors, ion channels, and nuclear elements; the result is modulation of gene expression. PUFA-induced alterations result in modulation of local and systemic inflammation and inflammatory disease activity.

The scientific basis of immunonutrition

Substrates with immune-modulating actions have been identified among both macro- and micronutrients. Currently, the modes of action of individual immune-modulating substrates, and their effects on clinical outcomes, are being examined. At present, some enteral formulas are available for the clinical setting which are enriched with selected immune-modulating nutrients. The purpose of the present paper is to review the scientific rationale of enteral immunonutrition. The major aspects considered are mucosal barrier structure and function, cellular defence function and local or systemic inflammatory response. It is notable that in critical illness the mucosal barrier and cellular defence are impaired and a reinforcement with enteral immunonutrition is desirable, while local or systemic inflammatory response should be down regulated by nutritional interventions. The results available from clinical trials are conflicting. Meta-analyses of recent trials show improvements such as reduced risk of infection, fewer days on a ventilator, and reduced length of intensive care unit and hospital stay. Thus, a grade A recommendation was proclaimed for the clinical use of enteral immune-modulating diets. Improvement in outcome was only seen when critical amounts of the immune-modulating formula were tolerated in patients classified as being malnourished. However, in other patients with severe sepsis, shock and organ failure, no benefit or even disadvantages from immunonutrition were reported. In such severe conditions we hypothesize that systemic inflammation might be undesirably intensified by arginine and unsaturated fatty acids, directly affecting cellular defence and inflammatory response. We therefore recommend that in patients suffering from systemic inflammatory response syndrome great caution should be exercised when immune-enhancing substrates are involved which may aggravate systemic inflammation.

Lipid mediators in the pathophysiology of critical illness

Inflammatory lipid mediators are produced by the metabolism of membrane phospholipids following a number of different stimuli. These mediators lead to a variety of cellular and systemic responses which contribute to the manifestations of the systemic inflammatory response syndrome in the critically ill patient. These mediators include platelet-activating factor and the eicosanoids, including prostaglandins, thromboxanes, leukotrienes, and HETEs. This review seeks to evaluate the current role of these mediators in the pathophysiology of critical illness. We will focus on recent studies concerning the modulation of these pathways as a potential therapeutic strategy for management of these critically ill patients. This includes the gamut from nutritional strategies to alter the cellular membrane lipid composition, thereby effecting the substrate available to produce these lipid byproducts, to intracellular inhibitors to alter production of these mediators, to receptor blockage and enhanced clearance to inhibit their effects.

Fish oil augments macrophage cyclooxygenase II (COX-2) gene expression induced by endotoxin

BACKGROUND

Fish oil-supplemented diets have anti-inflammatory and immunomodulating effects. Although fish oil is readily incorporated into the cell membrane and influences the production of eicosanoids, the exact mechanism is not clear. This study was designed to investigate the effects of eicosapentaenoic acid (EPA), a major component of fish oil, on macrophage (Mphi) cyclooxygenase (COX) gene expression induced by LPS.

METHODS

RAW 264.7 cells, a mouse Mphi cell line, were grown in EPA-rich media for 24 h. Mphi were washed and exposed to Escherichia coli LPS (10 microg/ml). Membrane lipid profile was determined by gas chromatographic analysis. COX-1 and COX-2 mRNA expressions were determined by Northern blot assays with mouse-specific cDNA probes. PGE(2) production of Mphi was measured by ELISA. Mphi production of COX-2 protein was determined by Western blot assays with an anti-COX-2 antibody.

RESULTS

Incubation in EPA-rich media increased membrane EPA and decreased arachidonic acid (AA) composition. COX-2 mRNA expression was induced by EPA and further augmented by LPS stimulation. EPA also augmented Mphi production of COX-2 protein. In comparison, COX-1 mRNA expression was not affected by either LPS stimulation or EPA incubation. EPA reduced PGE(2) production by LPS-stimulated Mphi. To further support that COX-2 mRNA was regulated by COX product, exogenous PGE(2) was added to Mphi prior to LPS stimulation. PGE(2) reduced COX-2 mRNA of LPS-stimulated Mphi.

CONCLUSION

EPA displaces AA and reduces PGE(2) production by LPS-stimulated Mphi. Fish oil inhibition of Mphi PGE(2) production induces COX-2 mRNA expression through a COX-2 product-mediated feedback mechanism.

Gadolinium blocks rat Kupffer cell calcium channels: relevance to calcium-dependent prostaglandin E2 synthesis and septic mortality

Hepatic Kupffer cells (KC), the major tissue macrophage population, produce the septic response mediators, tumor necrosis factor alpha (TNF-alpha) and prostaglandin E2 (PGE2), and have been shown to internalize gadolinium chloride (GD), a rare earth metal of the lanthanide series. Because GD pretreatment of rats has been shown to inhibit the mortality of sepsis, we studied the secretory response to lipopolysaccharide (LPS) by KC isolated from rats injected with either saline or GD (7 mg/kg, intravenously) on the 2 days before KC isolation. Using culture conditions modified to reflect the intrasinusoidal milieu of arginine (RPMI-1640 media with 10 or 100 micromol/L arginine), KC from GD-treated rats responded to LPS (0. 0025 microg/mL) with significantly (P <.01) reduced PGE2 release. In contrast, TNF-alpha release by treated KC was significantly (P <.05) enhanced, consistent with the loss of PGE2 autocoid inhibition of TNF-alpha. Calcium flux is an early signaling event in eicosanoid synthesis, and GD is known to block calcium channels. Therefore, KC were loaded with fura-2-AM to study the effect of GD on KC calcium flux. GD prevented ionomycin and platelet-activating factor (PAF)-mediated [Ca++]i increase and calcium-dependent PGE2 synthesis, while GD did not affect PGE2 synthesis when protein kinase C (PKC) was directly activated with tetradecanoylphorbolacetate (TPA). The inhibition of calcium flux and calcium-dependent PGE2 synthesis in the major cell of the monocytic phagocytic system by GD may explain the previously reported ability of this lanthanide to prevent the mortality of endotoxemia.

Early enteral nutrition in surgical patients

There is increasing evidence that delivery of nutrients via the gastrointestinal tract reduces the septic morbidity in severely injured patients. This article reviews the most current data and also reviews the importance of the gut-associated lymphoid tissue as an important factor in maintaining the host defenses.

Effect of a fish oil structured lipid-based diet on prostaglandin release from mononuclear cells in cancer patients after surgery

BACKGROUND

The authors compared the effect on eicosanoid production (prostaglandin E2 [PGE2], 6-keto PGF 1 alpha, and thromboxane B2) from peripheral blood mononuclear cells (PBMC) of feeding an enteral diet containing a fish oil/medium-chain triglyceride structured lipid (FOSL-HN) vs an isonitrogenous, isocaloric formula (O-HN) in patients undergoing major abdominal surgery for upper gastrointestinal malignancies. A previous study, which used the same formulas and experimental design, suggested improved renal and liver function as well as a reduced number of gastrointestinal and infectious complications with the use of fish oil structured lipids. This study sought to investigate the potential mechanism for these effects by assessing eicosanoid production from PBMC with the two diets.

METHODS

This prospective, blinded, randomized trial was conducted in 20 patients who were jejunally fed either FOSL-HN or O-HN for 7 days. Serum chemistries, hematology, urinalysis, gastrointestinal complications, liver and renal function, and eicosanoid production from isolated PBMC, either unstimulated or stimulated with endotoxin, were measured at endotoxin baseline and on day 7. Comparisons were made in 10 and 8 evaluable patients based a priori on the ability to reach a tube feeding rate of > 40 mL/h.

RESULTS

Patients receiving FOSL-HN experienced no untoward side effects compared with patients given O-HN and demonstrated the same general trend toward improved hepatic, renal and immune function found in the previous study. There was a significant reduction in PGE2 (p < .03) and 6-keto PGF 1 alpha (p < .01) production from PBMC with endotoxin stimulation in patients receiving FOSL-HN.

CONCLUSIONS

The results of early enteral feeding with FOSL-HN after surgery in this follow-up study provide further support to claims of safety, tolerance, and improved physiologic function. There was an associated reduction in eicosanoid production from PBMCs, which is presumed to be the principal mechanism for these effects.

Fish oil-supplemented feeding does not attenuate warm liver ischemia and reperfusion injury in the rat

Liver ischemia and reperfusion injury is mediated by oxygen free radicals, cytokines, and prostanoids produced by Kupffer cells and infiltrating neutrophils. Fish oil-supplemented diets alter membrane phospholipid composition and modify prostanoids and cytokine production in response to ischemia and reperfusion. This study tested the hypothesis that a fish oil-supplemented diet would attenuate warm liver ischemia and reperfusion injury in the rat. Male Sprague-Dawley rats were fed Vital HN supplemented with either fish oil (FO) or corn oil (CO) by the continuous duodenal infusion for 5 days. Total dietary fat (26% of total calories), caloric intake (70 cal/day), and volume (60 ml/day) were identical between two groups. Plasma eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels increased significantly in rats fed fish oil (0 to 16.3% for EPA and 2 to 12% for DHA). Liver histology was similar in both groups before ischemia. On Day 6, rats were subjected to 60 min of reversible hepatic ischemia. Plasma TNF levels, 1 and 24 hr after reperfusion, were not different between FO and CO rats. Liver injury assessed by bile flow, histology, plasma ALT, and bile glutathione efflux did not differ between groups. We conclude that our fish oil-supplemented enteral diet does not attenuate warm liver ischemia and reperfusion injury in rats.

Recovery of gut-associated lymphoid tissue and upper respiratory tract immunity after parenteral nutrition

OBJECTIVE

The authors characterize the recovery of parenteral nutrition-induced changes in gut-associated lymphoid tissue (GALT) and upper respiratory tract immunity with enteral nutrition and provide further information defining the effects of enteral feeding on mucosal immunity.

SUMMARY BACKGROUND DATA

The small intestine plays a prominent role in development and maintenance of mucosal immunity, both intestinal and extraintestinal, primarily through immunoglobulin A (IgA)-mediated mechanisms. Prior research has shown that mice fed total parenteral nutrition (TPN) have reduced GALT T and B cells, the cells responsible for IgA production, as well as impaired upper respiratory tract immunity to viral challenge of previously immunized animals. The recovery of TPN-induced changes in GALT and upper respiratory tract immunity after enteral refeeding is studied.

METHODS

Male institute of Cancer Research mice received 5 days of TPN followed by 0 to 4 days of chow. Small intestinal GALT was characterized by flow cytometry. In a second experiment, animals were immunized intranasally with moused-adapted influenza virus. Three weeks later, one group received a 5-day course of TPN followed by enteral refeeding for 5 days. A second group received TPN alone. Both groups were challenged with intranasal virus and killed 40 hours postchallenge to determine viral shedding from the upper respiratory tract.

RESULTS

Animals fed TPN only had significantly fewer GALT lymphocytes compared with those chow-fed control subjects. Peyer's patch counts increased after a single day of refeeding, returning to normal levels by 48 hours. Lamina propria counts remained significantly depressed after 24 hours of refeeding, but also returned to normal after 48 hours of refeeding. The T-cell and B-cell populations mimicked total cell patterns. Lamina propria CD4+/CD8+ ratio returned to normal only after 72 hours of refeeding. None of the 9 animals refed enterally for 5 days were positive for viral shedding, compared with 8 of 12 matched TPN-fed animals.

CONCLUSIONS

Enteral refeeding after TPN is associated with rapid repletion of GALT cellularity, initially within Peyer's patches and subsequently within the lamina propria. Refeeding corrects the impairment of IgA-mediated upper respiratory tract antiviral immunity occurring with TPN administration. This work further enhances the authors' knowledge of the underlying immunologic differences influenced by routes of nutrition.

Immune-enhancing enteral formulas: are they beneficial in critically ill patients?

Over the last decade there has been considerable interest in the use of specific nutrients to alter the metabolic response to injury and infection, to improve immune function, and to prevent or reverse the severe catabolism and wasting of the lean body mass that accompanies critical illness. In this review, representative animal studies and, when available, human studies examining the potential benefits of these individual nutrients are summarized. The overview of basic investigations is by no means all-inclusive, and the emphasis of this manuscript is a review of the currently available clinical trials examining the potential benefits of combinations of these individual immunity-enhancing nutrients in human patients.

The value of peri-operative nutrition in the sick patient

In summary, therefore, the provision of TPN to malnourished patients in the pre-operative period reduces the incidence of post-operative complications, but does not affect post-operative mortality. It is likely that the provision of nutrition by the enteral route is as effective as that by the parenteral route, and may have the extra benefit of resulting in a reduction in infectious complications when compared with patients receiving TPN. Furthermore, the use of enteral nutritional support in the post-operative period may also reduce both septic and major complications, but does not alter mortality. The use of specific combinations of nutrients appears to offer the greatest promise in the use of peri-operative nutritional support. The initial studies reported to date demonstrate reductions in post-operative morbidity, but again there are no benefits on mortality. However, further studies to determine the optimal combinations of nutrients for use in patients in the peri-operative period are urgently required.