Parenteral administration of medium- but not long-chain lipid emulsions may increase the risk for infections by Candida albicans

Apolipoprotein E Gene Polymorphism, Serum Lipids, and Risk of Superficial Fungal Infections in Egyptian Patients - A Preliminary Case-Controlled Study

Background

Apolipoprotein E (APOE) gene isoforms have been found to affect the risk of superficial fungal infections (SFIs). However, the data only cover a few ethnicities.

Aims

The present work intended to investigate the association of APOE gene polymorphism and serum lipids with the susceptibility of SFIs among a group of Egyptian patients.

Materials and Methods

Standard laboratory methods were used to estimate the serum lipid profile, and polymerase chain reaction-restriction fragment length polymorphism was used to detect APOE gene polymorphism in deoxyribonucleic acid extracted from 150 SFI patients and an equal number of apparently healthy matched controls.

Results

Serum total cholesterol, triglycerides, and low-density lipoprotein cholesterol were significantly higher in the studied patients than in controls. The APOE gene ε2, ε4 alleles, and ε3/4 and ε3/2 genotypes were significantly distributed in the patients than in the controls. APOE ε3/3 genotype was predominant in dermatophytosis and tinea versicolour patients, and ε3/4 genotype was predominant in candidiasis.

Conclusions

ApoE alleles ε2 and ε4, and genotypes ε2/3 and ε3/4 are linked to SFI and may be risk factors, whereas allele ε3 and genotype ε3/3 may be protective for SFI in the Egyptian population studied. The lipid profile results suggest that hyperlipidemia may provide evidence for SFI pathogenesis. However; further large-scale studies are still needed to validate our results.

Disparate Candida albicans Biofilm Formation in Clinical Lipid Emulsions Due to Capric Acid-Mediated Inhibition

Receipt of parenteral nutrition (PN) remains an independent risk factor for developing catheter-related bloodstream infections (CR-BSI) caused by fungi, including by the polymorphic fungus Candida albicans, which is notoriously adept at forming drug-resistant biofilm structures. Among a variety of macronutrients, PN solutions contain lipid emulsions to supply daily essential fats and are often delivered via central venous catheters (CVCs). Therefore, using an in vitro biofilm model system, we sought to determine whether various clinical lipid emulsions differentially impacted biofilm growth in C. albicans We observed that the lipid emulsions Intralipid and Omegaven both stimulated C. albicans biofilm formation during growth in minimal medium or a macronutrient PN solution. Conversely, Smoflipid inhibited C. albicans biofilm formation by approximately 50%. Follow-up studies revealed that while Smoflipid did not impair C. albicans growth, it did significantly inhibit hypha formation and hyphal elongation. Moreover, growth inhibition could be recapitulated in Intralipid when supplemented with capric acid-a fatty acid present in Smoflipid but absent in Intralipid. Capric acid was also found to dose dependently inhibit C. albicans biofilm formation in PN solutions. This is the first study to directly compare different clinical lipid emulsions for their capacity to affect C. albicans biofilm growth. Results derived from this study necessitate further research regarding different lipid emulsions and rates of fungus-associated CR-BSIs.

Infection in central venous catheter led by parenteral nutrition of tumor patients

With the wide application of parenteral nutrition (PN) and central venous catheter (CVC) in tumor patients, the relative infection led by CVC has become a common and troublesome hospital infection in clinics. During infusion, PN fluid forms a high-sugar and high-fat microenvironment around CVC, facilitating the adhesion, growth, and diffusion of pathogenic bacteria. This condition forms a bacterial biofilm (BF) consisting of one or several kinds of pathogenic bacteria. Upon formation of the film, pathogens in the BF can resist antibacterial drugs and immune cells, causing repeated infections of bacteria or fungi and endangering the lives of patients. In this article, we summarize the applications of PN, characteristics of CVC infection in tumor patients, mixed BF, and related research methods to provide reference for studies of mixed BF infection of CVC.

A Short-Term Long-Chain Triglycerides Infusion Has No Influence on Immune Function of Adult Patients Undergoing Gastrointestinal Surgery

BACKGROUND

Parenteral nutrition (PN) support containing long-chain triglycerides (LCT) plays a critical supportive role in surgical patients' management. This study aims to investigate the effects of intravenous (IV) LCT emulsion on human immune function in adult patients receiving a gastrointestinal surgical procedure.

METHODS

Sixty adult patients were randomly assigned either to the LCT treatment group (n = 32) or to the control group (n = 28). After an abdominal operation, the subjects received PN treatment with or without LCT for 5 days. Neutrophil, peripheral blood mononuclear cell (PBMC), lymphocyte and CD4/CD8, serum immunoglobulin A (IgA), IgG, IgM, complement C3 and C4, interleukin (IL)-2, IL-4, IL-10, IL-12, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma were measured and statistically analyzed.

RESULTS

The LCT and control groups did not differ significantly at entry in terms of general features. Except for a significant increase of neutrophil number at 24 hours after the surgery in both groups (p < .01), all parameters representing the patients' immune function had no significant difference between the LCT and the control groups with respect to neutrophil and PBMC count, lymphocyte, CD4/CD8, serum IgA, IgG, IgM, complement C3, C4, IL-2, IL-4, IL-10, IL-12, TNF-alpha, and IFN-gamma (p > .05, respectively) 24 hours before the operation, and 24 hours and 120 hours after the operation.

CONCLUSIONS

The regimens of LCT administration may have diverse effects on human immune function in different patient populations. However, LCT emulsion at an appropriate dose and infusion speed does not alter human immune function of adult patients undergoing moderate gastrointestinal surgery.

Immune activation by medium-chain triglyceride-containing lipid emulsions is not modulated by n-3 lipids or toll-like receptor 4

BACKGROUND

Saturated medium-chain triglycerides (MCT) as part of the parenteral lipid regimen (50% MCT and 50% long chain triglycerides (LCT)) activate the immune system in vitro. Fish oil (FO)-derived n-3 fatty acids (FA) inhibit saturated FA-induced immune activation via a toll-like receptor (TLR)-4 mediated mechanism. We hypothesized that effects of parenteral MCTs on immune cells involve TLR-4 signaling and that these effects are modulated by n-3 FA that are present in FO.

MATERIALS AND METHODS

To test this hypothesis we assessed effects of addition of various commercially available mixed parenteral lipid emulsions, n-3 FA and of TLR-4 inhibition on MCT-induced human immune cell activation by evaluation of the expression of leukocyte membrane activation markers and reactive oxygen species (ROS) production.

RESULTS

All MCT-containing lipid emulsions activated leukocytes by inducing changes in expression of membrane markers and stimulus induced ROS production, whereas MCT-free lipid emulsions lacked this effect. Moreover, addition of n-3 FA to LCT/MCT did not prevent MCT-induced immune activation. TLR-4 inhibitors did not distinctly modulate MCT-induced changes in immune function.

CONCLUSION

Taken together, these findings suggest that leukocyte activation by parenteral MCTs does not involve TLR-4 signaling and is not modulated by n-3 FA in FO-, but is exerted via different signaling pathways.

Addition of lipids to parenteral nutrition does not cause fungal infections

Parenteral nutrition (PN) that includes lipid emulsion is considered to increase both bacterial and fungal central venous catheter-related bloodstream infections. This concept is based on several erroneous metrics: Reports in age-old literature at a time when preparing PN admixtures lacked stringent quality control, when its infusion, the techniques of insertion, maintenance of vascular access devices, and delivery systems were not well identified or enforced. Additionally, concepts of glucohomeostasis were different and higher glucose levels were accepted. We provide updated information with supporting literature to show that associating PN with lipids with an increase in bloodstream infections is not justified.

Targeted gene deletion in Candida parapsilosis demonstrates the role of secreted lipase in virulence

Candida parapsilosis is a major cause of human disease, yet little is known about the pathogen's virulence. We have developed an efficient gene deletion system for C. parapsilosis based on the repeated use of the dominant nourseothricin resistance marker (caSAT1) and its subsequent deletion by FLP-mediated, site-specific recombination. Using this technique, we deleted the lipase locus in the C. parapsilosis genome consisting of adjacent genes CpLIP1 and CpLIP2. Additionally we reconstructed the CpLIP2 gene, which restored lipase activity. Lipolytic activity was absent in the null mutants, whereas the WT, heterozygous, and reconstructed mutants showed similar lipase production. Biofilm formation was inhibited with lipase-negative mutants and their growth was significantly reduced in lipid-rich media. The knockout mutants were more efficiently ingested and killed by J774.16 and RAW 264.7 macrophage-like cells. Additionally, the lipase-negative mutants were significantly less virulent in infection models that involve inoculation of reconstituted human oral epithelium or murine intraperitoneal challenge. These studies represent what we believe to be the first targeted disruption of a gene in C. parapsilosis and show that C. parapsilosis-secreted lipase is involved in disease pathogenesis. This efficient system for targeted gene deletion holds great promise for rapidly enhancing our knowledge of the biology and virulence of this increasingly common invasive fungal pathogen.

Lipase 8 affects the pathogenesis of Candida albicans

The production of lipases can affect microbial fitness and virulence. We examined the role of the lipase 8 (LIP8) gene in the virulence of Candida albicans by constructing Deltalip8 strains by the URA-blaster disruption method. Reverse transcription-PCR experiments demonstrated the absence of LIP8 expression in the homozygous knockout mutants. Reconstituted strains and overexpression mutants were generated by introducing a LIP8 open reading frame under control of a constitutive actin promoter. Knockout mutants produced more mycelium, particularly at higher temperatures and pH >or=7. Diminished LIP8 expression resulted in reduced growth in lipid-containing media. Mutants deficient in the LIP8 gene were significantly less virulent in a murine intravenous infection model. The results clearly indicate that Lip8p is an important virulence factor of C. albicans.

Parenteral lipids modulate leukocyte phenotypes in whole blood, depending on their fatty acid composition

To characterize the immunological effects of various lipids that are applied as part of total parenteral nutrition (TPN) formulations, we analyzed phenotypical changes in leukocytes following lipid exposure. Importantly, the study was performed with whole blood in order to prevent the functional changes that are induced by isolation procedures. Briefly, blood samples from 10 healthy volunteers were incubated with lipids containing pure long-chain triglycerides (L), mixed long- and medium-chain triglycerides (LM), synthetic structured lipids (SL), or emulsions based on olive oil (OO), or fish oil (FO). After immune fluorescent staining, leukocyte phenotype characteristics were analyzed by flowcytometry. Exposure to LM increased in a dose-dependent manner the expression of membrane surface markers for adhesion (CD11b) and degranulation (CD66b), while decreasing CD62L, on neutrophils and monocytes. These findings demonstrate that LM activates leukocytes in peripheral whole blood. On the other hand, decreased expression of activation markers was observed with L and FO. Lipids effects on the phenotype of T lymphocytes and Natural Killer cells were not seen during incubation for up to 4 h. These results indicate that (i) the composition of TPN formulations with regard to lipid structure has implications for the function of exposed immune competent cells and (ii) medium-chain triglycerides, which have been regarded as functionally inert deliverers of fuel calories, have distinct biological effects.

Lipid effects on neutrophil calcium signaling induced by opsonized particles: platelet activating factor is only part of the story

BACKGROUND & METHODS

Total parenteral nutrition is frequently used in clinical practice to improve the nutritional status of patients. However, the risk for infectious complications remains a drawback in which immune-modulating effects of the lipid component may play a role. To characterize these lipid effects we investigated neutrophil activation by opsonized yeast particles under influence of lipid emulsions derived from fish oil (VLCT), olive oil (LCT-MUFA), soybean oil (LCT), and a physical mixture of coconut and soybean oil (LCT-MCT).

RESULTS

Serum-treated zymosan (STZ) evoked a biphasic increase in cytosolic Ca2+ concentration ([Ca2+]c) with an initial slow rise that turned into a second fast rise until a plateau was reached. LCT-MCT (5 mM) pretreatment markedly increased the rate of [Ca2+]c rise during the initial phase, abolished the second phase and lowered the plateau. These effects of LCT-MCT were mimicked by the protein kinase C (PKC) activating phorbol ester PMA. LCT, LCT-MUFA and VLCT, on the other hand, decreased the rate of [Ca2+]c rise during both phases and lowered the plateau. The platelet-activating factor (PAF) receptor antagonist WEB 2086 inhibited the second phase, demonstrating that PAF acts as an intercellular messenger in STZ-induced Ca2+ mobilization, but did not interfere with the stimulatory effect of LCT-MCT or PMA on the initial rate of [Ca2+]c rise.

CONCLUSIONS

Structurally different lipids act only in part through PAF to distinctively modulate neutrophil calcium signaling in response to activation by opsonized particles.

The Contribution of the Toll-Like/IL-1 Receptor Superfamily to Innate and Adaptive Immunity to Fungal Pathogens In Vivo

In vitro studies have indicated the importance of Toll-like receptor (TLR) signaling in response to the fungal pathogens Candida albicans and Aspergillus fumigatus. However, the functional consequences of the complex interplay between fungal morphogenesis and TLR signaling in vivo remain largely undefined. In this study we evaluate the impact of the IL-1R/TLR/myeloid differentiation primary response gene 88 (MyD88)-dependent signaling pathway on the innate and adaptive Th immunities to C. albicans and A. fumigatus in vivo. It was found that 1) the MyD88-dependent pathway is required for resistance to both fungi; 2) the involvement of the MyD88 adapter may occur through signaling by distinct members of the IL-1R/TLR superfamily, including IL-1R, TLR2, TLR4, and TLR9, with the proportional role of the individual receptors varying depending on fungal species, fungal morphotypes, and route of infection; 3) individual TLRs and IL-1R activate specialized antifungal effector functions on neutrophils, which correlates with susceptibility to infection; and 4) MyD88-dependent signaling on dendritic cells is crucial for priming antifungal Th1 responses. Thus, the finding that the innate and adaptive immunities to C. albicans and A. fumigatus require the coordinated action of distinct members of the IL-1R/TLR superfamily acting through MyD88 makes TLR manipulation amenable to the induction of host resistance to fungi.