| Despite encouraging advances in sepsis treatment over the last decade, sepsis represents a challenging, although largely underrecognized, healthcare problem in both developing and developed world, with a high mortality ranging from 20% to 60%. It is agreed that sepsis deeply perturbs immune homeostasis by inducing an initial tremendous systemic inflammatory response which is accompanied by an anti-inflammatory response. Sepsis-induced immunosuppression or immunoparalysis involving both innate and adaptive immunity plays a central role in impaired clearance of microorganisms. As a result, persisting immunosupression could not only give rise to patients’ inability to fight primary bacterial infection but also make patients more susceptible to secondary infections. Consequently, therapies aimed at restoring immune functions, especially the lymphocyte function, now offer a perspective for a better care of septic patients.Increasing evidence indicates diets containing special fat composition may influence inflammation and modulate immune functions. The n-3 polyunsaturated fatty acids (PUFAs) including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are rich in fish oil (FO), while n-6 PUFAs are mainly contained in safflower and soybean oils (SO). It is currently assumed that many n-3 PUFAs-derived metabolites, including 5-series cysteinyl-leukotrienes, leukotriene B5, and thromboxane A3, possess markedly reduced inflammation and vasomotor potencies compared with n-6 PUFAs-derived lipid mediators and may even exert antagonistic functions. On this basis, dietary supplemented with n-3 and n-6 PUFA in different proportions have been employed in different clinical settings.To date, the impact of fish oil-supplemented TPN on clinical outcomes including infections, length of ICU and hospital stay, and mortality in septic patients was not clear.Given pretreatment may not be an ideal option in the clinical setting, we designed to treat rats with TPN containing either a standard SO emulsion or FO emulsion after inducing sepsis. The present study was performed to investigate whether PN containing FO prolongs survival and alters the fatty acids composition in plasma and erythrocyte membranes in a rat model of cecal ligation and puncture (CLP)-induced sepsis. Additionally, T lymphocyte subsets in spleen and blood, and plasma high-mobility group box 1 (HMGB1) and interleukin (IL)-10 concentrations were determined to explore the effects of FO-supplemented TPN on T lymphocytes and inflammation response. Meanwhile, the bacterial loads in the peritoneal lavage fluid, kidney, lung, and spleen were analyzed.This thesis is divided into three parts:PART 1:Effects of parenteral nutrition containing n-3 PUFAs on survival and bacterial loads of the key organs in a rat model of CLP induced-sepsisObjectives: Parenteral nutrition containing n-3 polyunsaturated fatty acids in sepsis is not fully clear. This study is to investigate the effects of parenteral fish oil on survival and bacterial loads of the key organs in a rat model of CLP induced-sepsis.Methods: Adult male Sprague-Dawley rats were subjected to cecal ligation and puncture-induced sepsis. For recovery, central venous catheterization was performed 2 days before sepsis induced. Rats were randomly assigned to receive normal saline (n=20), or total parenteral nutrition containing a standard soybean oil emulsion (n=20), or fish oil-supplemented total parenteral nutrition (n=20) at the onset of sepsis for 5 days. In the sham group, rats were challenged by sham operation and underwent appropriate control treatment (n=10).Results: Sepsis led to a high mortality and body weight lost compared with sham operation, although there was no significant difference between the SO and FO groups. Total parenteral nutrition containing fish oil, but not without fish oil, improved the survival compared with normal saline. Sepsis caused acute lung and spleen injury to a varying extent, and fish oil attenuated the histopathologic changes of the key organs compared with both fish oil and normal saline. In addition, parenteral fish oil decreased the bacterial loads in peritoneal lavage, kidney, lung, and spleen.Conclusions: Total parenteral nutrition containing n-3 PUFAs initiated at the onset of sepsis improves survival, attenuated the histopathologic injuries of the key organs, and decreased the local and systemic bacterial loads.PART 2:Ability of parenteral nutriotion with n-3 PUFAs to modulate immune function and regulate inflammatory responseObjectives: To evaluate the effects of n-3 PUFAs on immune function and inflammatory response in a rat model of CLP-induced sepsis.Methods:Flow cytometry was used to determine the proportions of the blood and spleen lymphocyte subsets. The comparisons in CD3+, CD3+CD4+, CD3+CD8+ and CD4+CD25high T lymphocytes subsets, as well as the ratio of CD3+CD4+ to CD3+CD8+ T cells, in all experimental animals at day 5 after CLP or sham operation were analyzed. Foxp3 mRNA and protein levels in all groups were determined by RT-PCR and Western-blot. The plasma HMGB1 and IL10 levels were tested by ELISA.Results: Total parenteral nutrition containing fish oil improved the percentages of CD3+ and CD3+CD4+ T cells, as well as the CD4+/CD8+ ratio in blood and spleen. Meanwhile, the percentage of regulatory T cells (CD4+CD25high) among CD4+ T cells was reduced by fish oil-supplemented total parenteral nutrition. Moreover, fish oil-supplemented total parenteral nutrition attenuated the production of high-mobility group box 1 and interleukin-10 in plasma.Conclusions: The present study suggests fish oil-supplemented total parenteral nutrition initiated at the onset of sepsis modulates immune function and regulates inflammatory response in a rat model.PART 3:Parenteral nutrition containg n-3 PUFAs improves survival while beneficially altering phospholipids fatty acids profile and modulating TLR4-NF-κB signal pathway in rat sepsisObjectives: To investigate the effects of n-3 PUFAs on alterations of the fatty acids composition in plasma and erythrocyte membranes and the modulation of TLR4, MYD88 and NF-κB after sepsis.Methods: Gas chromatography was used to analyze the fatty acids profile in plasma and erythrocyte membranes. TLR4, MYD88 and NF-κB mRNA and protein levels in all four groups were determined by RT-PCR and Western-blot.Results: Parenteral infusion of fish oil increased the concentrations of eicosapentaenoic acid and docosahexaenoic acid, as well as the ratio of (eicosapentaenoic acid + docosahexaenoic acid) to arachidonic acid both in plasma and erythrocyte membrane. Additionally, compared with the NS and SO groups, FO group decreased the levels of TLR4, MYD88 and NF-κB either in mRNA or protein.Conclusions:The present study demonstrates parenteral nutrition containg fish oil initiated at the onset of sepsis beneficially alters the lipids profile in plasma and erythrocyte membrane, and modulates TLR4-NF-κB signal pathway after sepsis. |
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