Immunomodulation by n-3- versus n-6-rich lipid emulsions in murine acute lung injury--role of platelet-activating factor receptor

n-3 Polyunsaturated Fatty Acids Modulate LPS-Induced ARDS and the Lung-Brain Axis of Communication in Wild-Type versus Fat-1 Mice Genetically Modified for Leukotriene B4 Receptor 1 or Chemerin Receptor 23 Knockout

Specialized pro-resolving mediators (SPMs) and especially Resolvin E1 (RvE1) can actively terminate inflammation and promote healing during lung diseases such as acute respiratory distress syndrome (ARDS). Although ARDS primarily affects the lung, many ARDS patients also develop neurocognitive impairments. To investigate the connection between the lung and brain during ARDS and the therapeutic potential of SPMs and its derivatives, fat-1 mice were crossbred with RvE1 receptor knockout mice. ARDS was induced in these mice by intratracheal application of lipopolysaccharide (LPS, 10 µg). Mice were sacrificed at 0 h, 4 h, 24 h, 72 h, and 120 h post inflammation, and effects on the lung, liver, and brain were assessed by RT-PCR, multiplex, immunohistochemistry, Western blot, and LC-MS/MS. Protein and mRNA analyses of the lung, liver, and hypothalamus revealed LPS-induced lung inflammation increased inflammatory signaling in the hypothalamus despite low signaling in the periphery. Neutrophil recruitment in different brain structures was determined by immunohistochemical staining. Overall, we showed that immune cell trafficking to the brain contributed to immune-to-brain communication during ARDS rather than cytokines. Deficiency in RvE1 receptors and enhanced omega-3 polyunsaturated fatty acid levels (fat-1 mice) affect lung-brain interaction during ARDS by altering profiles of several inflammatory and lipid mediators and glial activity markers.

Preconditioning rats with three lipid emulsions prior to acute lung injury affects cytokine production and cell apoptosis in the lung and liver

BACKGROUND

Critically ill patients are at higher risk having acute lung injury (ALI) and more often in need of parenteral nutrition. We sought to study whether preconditioning with representative of lipid emulsions for one week could benefit rats from ALI.

METHODS

Using a lipopolysaccharide (LPS)-induced ALI rat model and techniques such as polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.

RESULTS

PGE₂ production in the serum was highest in the LPS group, followed with Intralipid group, and the PGE₂ level of these two groups was significantly (P < 0.05) higher than the rest. Intralipid conditioning caused significantly less production of LTB₄ than the LPS, Clinoleic, or Omegaven group. In contrast to Intralipid, rats pretreated with Clinoleic or Omegaven significantly decreased their production of inflammatory mediators (IL-1 β, IL-6 and TNF-α), had less apoptosis in the lung tissues, and Omegaven greatly improved liver function upon lipopolysaccharide (LPS) challenge.

CONCLUSIONS

In an ALI setting, preconditioning with Omegaven or Clinoleic was better than Intralipid in decreasing the intensity of the cytokine storm and apoptosis caused by LPS challenge, and Omegaven in addition had the potential to improve liver function. The results from the present study set a basis for further investigation of the molecular mechanisms of ALI, including the up- and downstream pathways of proinflammatory factor production, in search of (small) molecules intervening with the pathogenesis of ALI in order to translate relevant research findings into clinical benefit for patients with ALI. The use of Omegaven or Clinoleic, particularly in patients with ALI, is still characterized by uncertainty due to a lack of relevant studies. Future investigations must specifically focus on the route of administration and mode of application (enteral vs. parenteral/bolus vs. continuous), determining an optimal dose of Omegaven or Clinoleic, and the defining the best timepoint(s) for administration. Critically ill patients are at higher risk having acute lung injury (ALI) and more often in need of parenteral nutrition. The effect of lipid emulsion via parenteral nutrition on liver function was first time evaluated in rats in an ALI setting. The comparison of three forms of lipid emulsion in a rat model of acute lung injury was first time studied. The fish oil-based lipid emulsion decrease in PGE 2 and increase in LTB 4 was first time reported.

Phospholipids of Animal and Marine Origin: Structure, Function, and Anti-Inflammatory Properties

In this review paper, the latest literature on the functional properties of phospholipids in relation to inflammation and inflammation-related disorders has been critically appraised and evaluated. The paper is divided into three sections: Section 1 presents an overview of the relationship between structures and biological activities (pro-inflammatory or anti-inflammatory) of several phospholipids with respect to inflammation. Section 2 and Section 3 are dedicated to the structures, functions, compositions and anti-inflammatory properties of dietary phospholipids from animal and marine sources. Most of the dietary phospholipids of animal origin come from meat, egg and dairy products. To date, there is very limited work published on meat phospholipids, undoubtedly due to the negative perception that meat consumption is an unhealthy option because of its putative associations with several chronic diseases. These assumptions are addressed with respect to the phospholipid composition of meat products. Recent research trends indicate that dairy phospholipids possess anti-inflammatory properties, which has led to an increased interest into their molecular structures and reputed health benefits. Finally, the structural composition of phospholipids of marine origin is discussed. Extensive research has been published in relation to ω-3 polyunsaturated fatty acids (PUFAs) and inflammation, however this research has recently come under scrutiny and has proved to be unreliable and controversial in terms of the therapeutic effects of ω-3 PUFA, which are generally in the form of triglycerides and esters. Therefore, this review focuses on recent publications concerning marine phospholipids and their structural composition and related health benefits. Finally, the strong nutritional value of dietary phospholipids are highlighted with respect to marine and animal origin and avenues for future research are discussed.

Lipids in the intensive care unit: Recommendations from the ESPEN Expert Group

This article summarizes the presentations given at an ESPEN Workshop on "Lipids in the ICU" held in Tel Aviv, Israel in November 2014 and subsequent discussions and updates. Lipids are an important component of enteral and parenteral nutrition support and provide essential fatty acids, a concentrated source of calories and building blocks for cell membranes. Whilst linoleic acid-rich vegetable oil-based enteral and parenteral nutrition is still widely used, newer lipid components such as medium-chain triglycerides and olive oil are safe and well tolerated. Fish oil (FO)-enriched enteral and parenteral nutrition appears to be well tolerated and confers additional clinical benefits, particularly in surgical patients, due to its anti-inflammatory and immune-modulating effects. Whilst the evidence base is not conclusive, there appears to be a potential for FO-enriched nutrition, particularly administered peri-operatively, to reduce the rate of complications and intensive care unit (ICU) and hospital stay in surgical ICU patients. The evidence for FO-enriched nutrition in non-surgical ICU patients is less clear regarding its clinical benefits and additional, well-designed large-scale clinical trials need to be conducted in this area. The ESPEN Expert Group supports the use of olive oil and FO in nutrition support in surgical and non-surgical ICU patients but considers that further research is required to provide a more robust evidence base.

Pretreatment with Fish Oil-Based Lipid Emulsion Modulates Muscle Leukocyte Chemotaxis in Murine Model of Sublethal Lower Limb Ischemia

This study investigated the effects of a fish oil- (FO-) based lipid emulsion on muscle leukocyte chemotaxis and inflammatory responses in a murine model of limb ischemia-reperfusion (IR) injury. Mice were assigned randomly to 1 sham (sham) group, 2 ischemic groups, and 2 IR groups. The sham group did not undergo the ischemic procedure. The mice assigned to the ischemic or IR groups were pretreated intraperitoneally with either saline or FO-based lipid emulsion for 3 consecutive days. The IR procedure was induced by applying a 4.5 oz orthodontic rubber band to the left thigh above the greater trochanter for 120 min and then cutting the band to allow reperfusion. The ischemic groups were sacrificed immediately while the IR groups were sacrificed 24 h after reperfusion. Blood, IR-injured gastrocnemius, and lung tissues were collected for analysis. The results showed that FO pretreatment suppressed the local and systemic expression of several IR-induced proinflammatory mediators. Also, the FO-pretreated group had lower blood Ly6C^hiCCR2^hi monocyte percentage and muscle M1/M2 ratio than the saline group at 24 h after reperfusion. These findings suggest that FO pretreatment may have a protective role in limb IR injury by modulating the expression of proinflammatory mediators and regulating the polarization of macrophage.

Fish Oil-Based Fat Emulsion Reduces Acute Kidney Injury and Inflammatory Response in Antibiotic-Treated Polymicrobial Septic Mice

Acute kidney injury (AKI) is a common complication in sepsis. This study compared the effects of a fish oil-based with a mixed oil fat emulsion on remote renal injury in an antibiotic-treated septic murine model. Mice were randomly assigned to a normal control (NC) group and three septic groups. Sepsis was induced by cecal ligation and puncture (CLP). The antibiotic was injected intraperitoneally (IP) after CLP and then daily till the time of sacrifice. Three hours after antibiotic treatment, one of the septic groups was injected IP with a fish oil-based emulsion (FO), while the other two groups were given either a mixed oil emulsion (MO) or saline (SC). The septic groups were further divided into two separate time groups, with blood and kidneys samples collected at 24 h or 72 h post-CLP. The results showed that sepsis leads to the activation of neutrophils, T helper (Th)1/Th-2/Th-17 and Treg cells (p < 0.05). Plasma NGAL and mRNA expressions of renal MyD88 and TLR4 were also enhanced (p < 0.05). Compared to the SC group, the group given the fish oil-based emulsion had decreased plasma NGAL by 22% and Treg by 33%. Furthermore, renal gene expressions of MyD88 and TLR4 reduced by 46% and 62%, respectively, whereas heat shock protein 70 and peroxisome proliferator-activated receptor-γ increased by 158% and 69%, respectively (p < 0.05), at Day 3 after CLP. These results suggest that administration of a fish oil-based emulsion has favorable effects, maintaining blood T cell percentage, downregulating Treg expression, attenuating systemic and local inflammation and offering renal protection under conditions of antibiotic-treated polymicrobial sepsis.

Immunomodulation by lipid emulsions in pulmonary inflammation: a randomized controlled trial

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is a major cause of mortality in intensive care units. As there is rising evidence about immuno-modulatory effects of lipid emulsions required for parenteral nutrition of ARDS patients, we sought to investigate whether infusion of conventional soybean oil (SO)-based or fish oil (FO)-based lipid emulsions rich in either n-6 or n-3 fatty acids, respectively, may influence subsequent pulmonary inflammation.

METHODS

In a randomized controlled, single-blinded pilot study, forty-two volunteers received SO, FO, or normal saline for two days. Thereafter, volunteers inhaled pre-defined doses of lipopolysaccharide (LPS) followed by bronchoalveolar lavage (BAL) 8 or 24 h later. In the murine model of LPS-induced lung injury a possible involvement of resolvin E1 (RvE1) receptor ChemR23 was investigated. Wild-type and ChemR23 knockout mice were infused with both lipid emulsions and challenged with LPS intratracheally.

RESULTS

In volunteers receiving lipid emulsions, the fatty acid profile in the plasma and in isolated neutrophils and monocytes was significantly changed. Adhesion of isolated monocytes to endothelial cells was enhanced after infusion of SO and reduced by FO, however, no difference of infusion on an array of surface adhesion molecules was detected. In neutrophils and monocytes, LPS-elicited generation of pro-inflammatory cytokines increased in the SO and decreased in the FO group. LPS inhalation in volunteers evoked an increase in neutrophils in BAL fluids, which decreased faster in the FO group. While TNF-α in the BAL was increased in the SO group, IL-8 decreased faster in the FO group. In the murine model of lung injury, effects of FO similar to the volunteer group observed in wild-type mice were abrogated in ChemR23 knockout mice.

CONCLUSIONS

After infusion of conventional lipid emulsions, leukocytes exhibited increased adhesive and pro-inflammatory features. In contrast, FO-based lipid emulsions reduced monocyte adhesion, decreased pro-inflammatory cytokines, and neutrophil recruitment into the alveolar space possibly mediated by ChemR23-signaling. Lipid emulsions thus exert differential effects in human volunteers and mice in vivo.

TRIAL REGISTRATION

DRKS00006131 at the German Clinical Trial Registry, 2014/05/14.

Modulation of endothelial cell integrity and inflammatory activation by commercial lipid emulsions

Background

Thrombosis and immune dysfunction are two important complications that result from the administration of parenteral nutrition. Endothelial cells within the vasculature are crucial components necessary for maintenance of normal coagulation and immune function.

Methods

We compared the effects of three commercial lipid emulsions (LEs; Intralipid®, ClinOleic® [or Clinolipid®], and Omegaven®) differing in the levels of omega-6 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, omega-9 monounsaturated fatty acids, and saturated fatty acids upon endothelial cell fatty acid composition using Gas chromatography, endothelial cell integrity by assessing measurement of apoptosis and necrosis using flow cytometry, endothelial cell inflammatory activation by assessing the induction of ICAM-1 by lipopolysaccharide [LPS]), and transcription factor activation (phosphorylation of NF-κB) using western blot analysis.

Results

Gas chromatographic analysis confirmed cellular uptake of the fatty acids within the LEs; furthermore, these fatty acid changes reflected the composition of the oils and egg phosphatides used in the manufacturing of these emulsions. However, the kinetics of fatty acid uptake and processing differed between LEs. Fish oil LE negatively impacted cell viability by doubling the percentage of apoptotic and necrotic cell populations quantified by flow cytometry using Annexin V/Fluorescein and propidium iodide. The soybean oil LE did not alter cell viability, while the olive oil-predominate emulsion improved cell viability. All LEs were capable of suppressing LPS-induced ICAM-1 expression; however, the fish oil LE was more potent than the other emulsions. Fish oil LE supplementation of cells also suppressed LPS-induced phosphorylation of NF-κB, while the soybean oil and olive predominant LE had no effect upon NF-κB phosphorylation.

Conclusions

Lipid emulsions are readily incorporated and stored in the form of triacylglycerols. Soybean oil-based, olive oil-predominant and fish-oil based LEs differentially affected endothelial cell integrity. Importantly, these three LEs were capable of suppressing endothelial cell inflammatory response despite their fatty acid content.

Immunomodulation by fish-oil containing lipid emulsions in murine acute respiratory distress syndrome

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is a major cause of mortality in intensive care units. Patients with ARDS often require parenteral nutrition with lipid emulsions as essential components. Besides being an energy supply, these lipid emulsions might display differential modulatory effects on lung integrity and inflammation.

METHODS

In a pre-emptive strategy, we investigated the impact of three different intravenously infused lipid emulsions on lung morphology, leukocyte invasion, protein leakage and cytokines in a murine model of ARDS. Mice received an infusion of normal saline solution, a pure long-chain triglycerides (LCT) emulsion, a medium-chain triglycerides (MCT) containing mixed emulsion (LCT/MCT), or a fish oil (FO) containing mixed emulsion (LCT/MCT/FO) before lipopolysaccharide (LPS) challenge.

RESULTS

Mice pre-infused with fish oil-containing lipid emulsion showed decreased leukocyte invasion, protein leakage, myeloperoxidase activity, and cytokine production in their alveolar space after LPS challenge compared to mice receiving LCT or LCT/MCT. In line with these findings, lung morphology assessed by histological staining after LPS-induced lung injury improved faster in the LCT/MCT/FO group. Concerning the above mentioned parameters, no significant difference was observed between mice infused with LCT or the combination of LCT and MCT.

CONCLUSION

Fish oil-containing lipid emulsions might exert anti-inflammatory and pro-resolving effects in the murine model of acute lung injury. Partial replacement of n-6 fatty acids with n-3 fatty acids may thus be of benefit for critically ill patients at risk for ARDS which require parenteral nutrition.

Comparison of the therapeutic effects of human and mouse adipose-derived stem cells in a murine model of lipopolysaccharide-induced acute lung injury

INTRODUCTION

Adipose-derived stem cells (ASCs) have emerged as important regulators of inflammatory/immune responses in vitro and in vivo and represent attractive candidates for cell-based therapies for diseases that involve excessive inflammation. Acute lung injury (ALI) is an inflammatory condition for which treatment is mainly supportive due to lack of effective therapies. In this study, the therapeutic effects of ASC-based therapy were assessed in vivo by comparison of the anti-inflammatory properties of both human and murine ASCs in a mouse model of lipopolysaccharide (LPS)-induced ALI.

METHODS

Human ASCs (hASCs) or mouse ASCs (mASCs) were delivered to C57Bl/6 mice (7.5 × 105 total cells/mouse) by oropharyngeal aspiration (OA) four hours after the animals were challenged with lipopolysaccharide (15 mg/kg). Mice were sacrificed 24 and 72 hours after LPS exposure, and lung histology examined for evaluation of inflammation and injury. Bronchoalveolar lavage fluid (BALF) was analyzed to determine total and differential cell counts, total protein and albumin concentrations, and myeloperoxidase (MPO) activity. Cytokine expression in the injured lungs was measured at the steady-state mRNA levels and protein levels for assessment of the degree of lung inflammation.

RESULTS

Both human and mouse ASC treatments provided protective anti-inflammatory responses. There were decreased levels of leukocyte (for example neutrophil) migration into the alveoli, total protein and albumin concentrations in BALF, and MPO activity after the induction of ALI following both therapies. Additionally, cell therapy with both cell types effectively suppressed the expression of proinflammatory cytokines and increased the anti-inflammatory cytokine interleukin 10 (IL-10). Overall, the syngeneic mASC therapy had a more potent therapeutic effect than the xenogeneic hASC therapy in this model.

CONCLUSIONS

Treatment with hASCs or mASCs significantly attenuated LPS-induced acute lung injury in mice. These results suggest a potential benefit for using an ASC-based therapy to treat clinical ALI and may possibly prevent the development of acute respiratory distress syndrome (ARDS).

Acute lung injury: how macrophages orchestrate resolution of inflammation and tissue repair

Lung macrophages are long living cells with broad differentiation potential, which reside in the lung interstitium and alveoli or are organ-recruited upon inflammatory stimuli. A role of resident and recruited macrophages in initiating and maintaining pulmonary inflammation in lung infection or injury has been convincingly demonstrated. More recent reports suggest that lung macrophages are main orchestrators of termination and resolution of inflammation. They are also initiators of parenchymal repair processes that are essential for return to homeostasis with normal gas exchange. In this review we will discuss cellular cross-talk mechanisms and molecular pathways of macrophage plasticity which define their role in inflammation resolution and in initiation of lung barrier repair following lung injury.

Enteral n-3 fatty acids and micronutrients enhance percentage of positive neutrophil and lymphocyte adhesion molecules: a potential mediator of pressure ulcer healing in critically ill patients

n-3 Fatty acids are recognised as influencing both wound healing and immunity. We assessed the impact of a fish oil- and micronutrient-enriched formula (study formula) on the healing of pressure ulcers and on immune function in critically ill patients in an intensive care unit. A total of forty patients with pressure ulcers and receiving nutritional support were enrolled (intervention group, n 20, received study formula; and a control group, n 20, received an isoenergetic formula). Total and differential leucocyte count and percentage of adhesion molecule positive granulocyte and lymphocyte cells (CD11a, CD11b, CD18 and CD49b) were measured on days 0, 7 and 14. Percentage of positive lymphocytes for CD54, CD49b, CD49d and CD8 were also measured on days 0, 7 and 14. The state of pressure ulcers was assessed by using the pressure ulcer scale for healing tool score on days 7, 14 and 28 of treatment. No between-group differences in patient demographics, anthropometry or diagnostic class were observed. Patients who received the study formula showed significant increases in the percentage of positive CD18 and CD11a lymphocytes and of CD49b granulocytes as compared to controls (P < 0·05). While the severity of pressure ulcers was not significantly different between the two groups on admission, severity increased significantly over time for the control group (P < 0·05), but not for the study group. The present study suggests that a fish oil- and micronutrient-enriched formula may prevent worsening of pressure ulcers and that this effect may be mediated by an effect on adhesion molecule expression.

Fish oil in critical illness: mechanisms and clinical applications

Fish oil is rich in omega-3 fatty acids, which have been shown to be beneficial in multiple disease states that involve an inflammatory process. It is now hypothesized that omega-3 fatty acids may decrease the inflammatory response and be beneficial in critical illness. After a review of the mechanisms of omega-3 fatty acids in inflammation, research using enteral nutrition formulas and parenteral nutrition lipid emulsions fortified with fish oil were examined. The results of this research to date are inconclusive for both enteral and parenteral omega-3 fatty acid administration. More research is required before definitive recommendations can be made on fish oil supplementation in critical illness.

Acute lung injury is reduced in fat-1 mice endogenously synthesizing n-3 fatty acids

RATIONALE

Acute lung injury (ALI) remains an important cause of mortality in intensive care units. Inflammation is controlled by cytokines and eicosanoids derived from the n-6 fatty acid (FA) arachidonic acid (AA). The n-3 FA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and mediators derived from EPA and DHA possess reduced inflammatory potency.

OBJECTIVES

To determine whether the ability of fat-1 mice to endogenously convert n-6 to n-3 FA, and thus generate an increased ratio of n-3 to n-6 FA, impacts experimental ALI.

METHODS

We investigated ALI induced by intratracheal instillation of endotoxin in fat-1 and wild-type (WT) mice, assessing leukocyte numbers, protein concentration, and prostaglandin and cytokine levels in bronchoalveolar lavage fluid, as well as free FA in plasma, and lung ventilator compliance. Body temperature and motor activity of mice--markers of sickness behavior--were also recorded.

MEASUREMENTS AND MAIN RESULTS

In ALI, fat-1 mice exhibited significantly reduced leukocyte invasion, protein leakage, and macrophage inflammatory protein-2 and thromboxane B(2) levels in lavage fluid compared with WT mice. Free AA levels were increased in the plasma of WT mice in response to endotoxin, whereas EPA and DHA were increased in the fat-1 group. Ventilator compliance was significantly improved in fat-1 mice. Body temperature and motor activity were decreased in ALI. fat-1 Mice recovered body temperature and motor activity faster.

CONCLUSIONS

fat-1 Mice exhibited reduced features of ALI and sickness behavior. Increasing the availability of n-3 FA may thus be beneficial in critically ill patients with ALI.

Intravenous injection of siRNA directed against hypoxia-inducible factors prolongs survival in a Lewis lung carcinoma cancer model

Different routes for the in vivo administration of synthetic siRNA complexes targeting lung tumors were compared, and siRNA complexes were administered for the inhibition of hypoxia-inducible factor (HIF-1alpha and HIF-2alpha). Intravenous jugular vein injection of siRNA proved to be the most effective means of targeting lung tumor tissue in the Lewis lung carcinoma (LLC1) model. In comparison, intraperitoneal injection of siRNA was not suitable for targeting of lung tumor and intratracheal administration of siRNA exclusively targeted macrophages. Inhibition of HIF-1alpha and HIF-2alpha by siRNA injected intravenously was validated by immunohistofluorescent analysis for glucose-transporter-1 (GLUT-1), a well-established HIF target protein. The GLUT-1 signal was strongly attenuated in the lung tumors of mice treated with siRNA-targeting HIF-1alpha and HIF-2alpha, compared with mice treated with control siRNA. Interestingly, injection of siRNA directed against HIF-1alpha and HIF-2alpha into LLC1 lung tumor-bearing mice resulted in prolonged survival. Immunohistological analysis of the lung tumors from mice treated with siRNA directed against HIF-1alpha and HIF-2alpha displayed reduced proliferation, angiogenesis and apoptosis, cellular responses, which are known to be affected by HIF. In conclusion, intravenous jugular vein injection of siRNA strongly targets the lung tumor and is effective in gene inhibition as demonstrated for HIF-1alpha and HIF-2alpha.

Inclusion of 10% fish oil in mixed medium-chain triacylglycerol-long-chain triacylglycerol emulsions increases plasma triacylglycerol clearance and induces rapid eicosapentaenoic acid (20:5n-3) incorporation into blood cell phospholipids

BACKGROUND

Lipolysis of a fish oil (FO) emulsion is much slower than that of a soybean [long-chain triacylglycerol (LCT)] emulsion; in contrast, emulsions containing medium-chain triacylglycerol (MCT) are efficiently hydrolyzed by lipoprotein lipase.

OBJECTIVES

We questioned whether incorporating 10% FO in a mixed MCT-LCT emulsion would affect plasma triacylglycerol clearance and provide efficient delivery of n-3 polyunsaturated fatty acids to cells and tissues.

DESIGN

This prospective crossover study was conducted in 8 normolipidemic subjects with the use of the hypertriglyceridemic clamp model and compared plasma triacylglycerol clearance of a lipid emulsion (5:4:1) made of 50% MCT, 40% LCT, and 10% FO (wt:wt:wt) to a control (5:5) preparation with 50% MCT and 50% LCT. Subjects were daily infused for 5 h, over 4 consecutive days. Fatty acyl pattern was daily measured in plasma phospholipids as well as in leukocyte and platelet phospholipids.

RESULTS

Inclusion of 10% FO in mixed emulsion particles enhanced plasma clearance of infused triacylglycerols (18%; P < 0.0001). The faster elimination of the 5:4:1 emulsion appears related to an enhanced uptake of remnant particles rather than to faster intravascular lipolysis. Each infusion of 5:4:1 raised the eicosapentaenoic acid (C20:5n-3) concentration in blood cell phospholipids to reach a 7-fold enrichment in platelets and a >2-fold enrichment in leukocytes after 4 infusions. In contrast, the docosahexaenoic acid (C22:6n-3) concentration remained unchanged in blood cell phospholipids.

CONCLUSIONS

Infusion of a mixed emulsion with MCTs, soy LCTs, and FO is associated with efficient plasma triacylglycerol clearance and results in rapid incorporation of C20:5n-3 but not C22:6n-3 in leukocyte and platelet phospholipids.

Fish oil in critical illness

PURPOSE OF REVIEW

The aim of this review is to discuss recent advances in the role of n-3 lipids derived from fish oil in clinical nutrition in an intensive care setting.

RECENT FINDINGS

Fish oil supplies n-3 fatty acids which compete with arachidonic acid (n-6) for the conversion to lipid mediators, influence lipid-bound second messenger generation and dependent cellular functions, and are a source for resolvins necessary for the resolution of inflammation. Enteral nutrition with n-3 fatty acids improved ventilation time in patients with acute lung injury and in one study reduced mortality in septic patients. Using a high-dose short-term infusion of fish oil-based lipid emulsion, rapid immunologic changes and effects on the endotoxin-induced stress response may be achieved. Inclusion of n-3 fatty acids in parenteral nutrition improved immunologic parameters and length of stay in surgical patients.

SUMMARY

Inclusion of fish oil in nutrition may influence the immune response and clinical outcomes by balancing the negative effects of n-6 fatty acids. Application as a part of enteral immunonutrition in surgical or acute respiratory distress syndrome patients and in lipid emulsions in surgical patients has beneficial effects. In septic patients, data on enteral use are highly controversial. Prospective data from randomized trials, however, are lacking.