| Objectives: Lipid disorders which are defined as abnormity of quanlity orquantity of lipid and its metabolites in blood, tissues and organs, caused bysome congenital or acquired factors. Researchers consider that insulinresistance has played an important role in the mechanism of lipid mediatedorgan injury, but recently more people believe that chronic inflammation isthe central link. The inflmmation is the low grade, systemic and chronicinflammation response, is different from general inflammation which canproduce redness, swelling, fever and pain. The choronic inflammation canwork together with lipid, and cause the pathological damage in manyorgans and lipid metabolism diseases through many molecular signalingpathways. To simulate the low grade, systemic and chronic inflammatorymodel, we injected subcutaneously10%casein into C57BL/6J mice for14weeks. Through the inflammation model, we observed the lipid contentand distribution in serum and tissues.Methods:53male C57BL/6J mice of8week old were selected, the mice were randomly assigned to4groups for different diet and treatingmethods: normal chow diet group(NCD, n=12), high cholesterol dietgroup(HCD, n=12), casein treating group(NCD+Casein, n=14) and highcholesterol diet and casein treating group(HCD+Casein, n=15). Highcholesterol diet contains1.25%cholesterol,0.5%cholate and21%fat. Thecasein treating group mice were suncutaneously injected with0.5mLcasein every other day while the control mice were injected with0.5mLnormal saline. After14weeks, all mice were sacrificed and the bloodplasma, skeletal muscle, fat and kidney were collected. After centrifugingplasma, we tested the level of SAA and IL-6in serum by ELISA. Then wetested the level of serum FFA by ELISA. Parts of skeletal muscle, fat andkidney were cut and made to frozen sections, while parts of the tissues toparaffin sections. The lipid level in the tissues was tested by oid red Ostaining, quantified by measuring TG and FFA content.Results:(1) Casein injection elevated the serum levels of SAA andIL-6, whether mice were fed with normal chow diet or high cholesterol diet.(2) Casein injection or high cholesterol diet induced the increase of thelevel of serum FFA. The level of serum FFA in HCD+Casein group micewas raised compared with HCD group.(3) Through oil red O staining andtesting TG and FFA level, lipid accumulation appeared in skeletal muscle,adipose and kidney tissues of HCD group mice. Lipid further accumulated in skeletal muscle and kidney tissues of HCD+casein group mice, but therewas no change in fat tissue.Conclusion: Subcutaneous injection of casein to mice can build asuccessful inflammation model, the model can simulate the low grade,systemic and chronic inflammatory condition in human body. A studyfound, when a T lymphocytes aggregates in visceral fat of obese patients,may form adipose inflammation, which cause the happening of metabolicsyndrome. In the inflammation model, blood FFA level had increasedsignificantly, TG and FFA increased in skeletal muscle and kidney tissues,but there was no change in fat tissues. Perhaps the main reason of thedistribution difference of lipid between tissues is: the adipose tissue is thetarget and source organ of chronic inflammatory response, lipidaccumulation mediated by inflammation first occurs in adipose tissue, andadipose tissue as a fat storage organ, can well modulate compensatorylylipid metabolism and distribution. Studies reported chronic inflammationpromotes fat decomposition within white adipose tissue but fat depositionin other tissues, which is an important mechanism of fat redistribution andclosely related to many metabolic diseases, but it is still unclear if somemolecular signaling pathways are involving in the process. It is also unclearif some membrane proteins are expressed, which transport lipid from fattissue into other tissues, and cause lipid redistribution in inflammatoryconditions. Objective: Numerous molecular signaling pathways of inflammationmediate lipid metabolic disorders in various tissues, Researchers observedlipid ectopic deposition between tissues in inflamed model mice, indicatedthat inflammatory stress upregulated the expression of sterol regulatoryelement binding protein1and downstream targets genes in non-fattytissues, while inhibited these genes expression and increased adiposetriglyceride lipase expression in white adipose tissue. Those evidenceselaborate neither the character of organism response to inflammatory stress,nor the interaction mechanisms of different organs.FFA increased in the early process of lipid metabolism disorders, it isespecially important to research on FFA related metabolic enzymes.FAT/CD36as one of important fatty acid metabolic enzymes, widelydistributes in all kinds of tissues and cells. Testing the FAT/CD36expression can better to observe the molecular regulation process ofinflammatory response. The experiment detected FAT/CD36expression inmice muscle, fat and kidney tissues through the inflammation model.Methods: We extracted protein from0.1g of the tissues, determinedthe concentration by BCA method, and tested the FAT/CD36protein expression in the tissues according to Western Blot orimmunohistochemical staining in the paraffin sections.Results: Through Western Blot and immunohistochemical staining,FAT/CD36protein expression in the tissues of HCD+Casein group micewas obviously increased.Conclusion: Many studies show that excess FFA can spill fromadipose tissue to non-adipose tissues, be translated into TG and be stored inthese not-adipose tissues in pathologic state. Experiments have found thatthe expression increase of sterol regulatory element binding protein may beclosely related with fat ectopic deposition. Through the animal experiment,this research observed FAT/CD36expression increased in skeletal muscle,adipose and kidney tissues in the inflammatory condition. FAT/CD36as animportant membrane protein, can promote fatty acids intake in skeletalmuscle, adipose and kidney tissues, and can modulate inflammatoryresponse in various tissues. Adipose tissue as a lipid storage organ, cansecrete inflammation factors together with other tissues. inflammatoryfactors promote FAT/CD36expression, prompt transporting fatty acidsthrough membrane in the tissues, cause lipid redistribution. Objective: Transmembrane transporting in the kidney cells, free fattyacid (FFA) has played an important role in the development of chronickidney disease (CKD). Fatty acid translocase FAT/CD36is an importantfatty acid transmembrane transport protein, which plays an important rolein cellular fatty acid transport. However, it remains unclear that themolecular mechanisms of kidney damage mediate by the FFAtransmembrane transport in the pathological state, such as lipid metabolismdisorders and chronic inflammation. This study observed the effect ofinflammatory cytokines on the expression of fatty acid translocase(FAT/CD36) in renal cells loaded by fatty acids.Methods: HMCs and HK-2cells were treated with palmitate atconcentrations of0mmol/L,0.02mmol/L,0.04mmol/L,0.08mmol/L,0.16mmol/L and0.32mmol/L respectively for24h. Then renal cells weretreated with palmitate at concentration of0.04mmol/L combined with orwithout cytokines (TNF-α (25ug/L) or IL-6(20ug/L)) for24h. ThemRNA and protein expression of FAT/CD36were detected by real-timepolymerase chain reaction (PCR) and western blotting. Oil red O stainingwas used to observe the intracellular lipid droplet formation. Theintracellular TG and FFA were determined by enzymic assays and ELISArespectively. Results: Palmitate loading dose dependently increased the expressionof FAT/CD36mRNA and protein in both HMCs and HK-2cells. Theinflammatory cytokines further increased the expression of FAT/CD36mRNA and protein levels in both cells loaded by palmitate. Oil red Ostaining, TG and FFA assays showed that inflammatory cytokines increasedintracellular lipid levels in in both HMCs and HK-2cells.Conclusion: The pathogenesis of lipid metabolism disorders in thepatient of chronic renal failure is still not completely clear, it is generallybelieved that hyperlipidemia may cause deterioration in kidney function,studies have confirmed lipid metabolism disorders can cause chronickidney disease through the mesangial cells, endothelial cells andmacrophages. Inflammatory cytokines up-regulate the expression ofFAT/CD36in renal cells loaded by fatty acids and exacerbate theintracellular lipid accumulation through HMCs and HK-2cells model.Inflammation as the center link of lipid mediated kidney injury, raised theFAT/CD36expression, FAT/CD36further increased the intake of fattyacids, aggravated the lipid nephrotoxicity. |
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