慢性炎症状态下脂质代谢紊乱及肝脏、主动脉损害的分子机制

发布时间：2018-04-01 19:26

本文选题：慢性炎症　切入点：脂质代谢紊乱　出处：《重庆医科大学》2008年博士论文

【摘要】：目的低度慢性系统性炎症反应是代谢综合征（MS）的核心点和几项组成成份（如血糖、血脂及尿酸等）的连接点，炎症因子参与脂质代谢障碍的全过程。固醇调节元件结合蛋白（SREBPs）是核转录因子，SREBP裂解激活蛋白（SCAP）是内质网上的膜蛋白，SCAP对SREBPs的活性起着重要的调节作用；细胞是通过一个依赖于胞内胆固醇水平的反馈调节系统来控制胆固醇内稳态平衡，即主要通过SCAP-SREBPs-LDLR之间的相互作用实现对细胞内脂质稳态平衡的调节。体外实验证实炎症因子可通过干扰胆固醇介导的低密度脂蛋白受体反馈调节来促进外周细胞，如血管平滑肌细胞（VSMCs）的胆固醇摄入，从而导致胆固醇在外周细胞的异常聚集而形成泡沫细胞。乙酰CoA羧化酶（ACC）与脂肪酸合成酶（FAS）是甘油三酯（TG）合成的关键酶，肝脏TG的代谢是通过SCAP-SREBPs-ACC/FAS途径实现的，肝脏脂质代谢障碍主要是TG在肝细胞内异常聚集而形成以大泡性为主的肝细胞脂肪变性，可伴有炎症细胞浸润和/或纤维组织增生，炎症因子是否干扰ACC与FAS的表达而导致TG代谢障碍的机制目前仍不清楚。本实验在过去体外细胞实验的基础上，建立慢性炎症动物模型，探讨炎症状态下血脂代谢紊乱情况；炎症因子是否通过干扰SCAP-SREBPs介导的LDLR反馈调节促进脂质摄取，从而导致主动脉与肝脏脂质聚集。材料和方法利用8周龄C57BL/6J小鼠皮下注射酪蛋白（Casein）制作小鼠慢性炎症模型，分别给予普通饮食、高脂饮食饲养20周左右，提取血液、肝脏及主动脉进行下列实验；用酶学方法检测各组小鼠IL-6及血脂（包括TC、LDL-C、HDL-C及TG）水平；HE染色、ORO染色及Masson三色染色观察肝脏与主动脉形态学改变；根据NAFLD、NASH分级与分期标准对各组小鼠肝脏进行分级和分期；利用Real-time PCR技术定量检测肝脏LDLR、SCAP、SREBP2、SREBP1、ACC及FAS mRNA水平以及主动脉LDLR、SCAP、SREBP2mRNA水平； Western blotting检测肝脏LDLR、SCAP、SREBP1蛋白及主动脉LDLR、SCAP、SREBP2蛋白表达水平。结果1. C57BL/6J小鼠皮下注射Casein后，普通饮食和高脂饮食小鼠血清IL-6均显著升高。 2.在普通饮食组中除单纯普通饮食小鼠血清TC轻微下降外，LDL、HDL、及TG均明显下降；高脂饮食各项血脂指标（TC、LDL、HDL及TG）均明显下降。这些数据说明慢性炎症状态可导致血脂紊乱。 3.与普通饮食组相比，，单纯高脂饮食显著抑制主动脉和肝脏LDLR、SCAP和SREBP2mRNA与蛋白的表达，但在慢性炎症状态下，LDLR、SCAP和SREBP2mRNA与蛋白的显著提高，这提示慢性炎症状态可干扰细胞胆固醇代谢。 4.单纯高脂饮食组小鼠SREBP1、ACC及FAS基因表达升高，在慢性炎症状态下，SREBP1、ACC及FAS表达进一步提高，肝细胞摄取大量的TG，从而导致肝细胞脂肪变性、气球样变、肝细胞坏死及纤维组织增生，即形成NAFLD或者NASH。 5．单纯高脂饮食组小鼠主动脉根部内膜明显增厚，大量泡沫细胞形成及动脉粥样硬化斑块形成；在慢性炎症状态下，主动脉根部动脉粥样硬化斑块明显增厚，斑块面积更大，这说明炎症可加重主动脉损害。 1结论1．IL-6是炎症反应的敏感标记物，IL-6的高低与炎症反应程度密切相关,血清IL-6显著升高提示慢性炎症模型成功建立。 2．体内慢性炎症状态通过干扰SCAP-SREBP2-LDLR反馈调节系统，促进脂质摄取，从而导致主动脉与肝脏脂质聚集。这些数据表明慢性炎症状态可明显降低血脂水平；慢性炎症状态下没有一个安全的血浆胆固醇浓度，血浆胆固醇水平并不与细胞内胆固醇水平呈正相关。 3．炎症状态促进SREBP1、ACC及FAS的表达而使肝细胞内大量TG聚集，导致肝细胞脂肪变性，坏死及纤维化，故炎症状态可加重肝脏损害。
[Abstract]:The purpose of low-grade chronic systemic inflammation is a metabolic syndrome (MS) of the core and several components (such as blood glucose, blood lipid and uric acid) of the connection point, the whole process of inflammatory factors involved in lipid metabolism. The sterol regulatory element binding protein (SREBPs) is a nuclear transcription factor, SREBP cleavage activating protein (SCAP) is a membrane protein of the endoplasmic reticulum, SCAP activity of SREBPs plays an important role in regulating the cell; through a cholesterol level dependent on intracellular feedback to control cholesterol homeostasis balance system, mainly through the interaction between SCAP-SREBPs-LDLR to achieve the regulation of intracellular lipid homeostasis in vitro. Low density lipoprotein receptor in inflammatory cytokines by disrupting cholesterol mediated feedback regulation to promote peripheral cells, such as vascular smooth muscle cells (VSMCs) of the intake of cholesterol, resulting in cholesterol In the abnormal aggregation of peripheral cells and the formation of foam cells. Acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) is a key enzyme in the synthesis of triglycerides (TG), the liver metabolism of TG is achieved through SCAP-SREBPs-ACC/FAS pathway, liver lipid metabolism disorder is the main accumulation of TG in the liver cells and abnormal form bullous mainly fatty degeneration of liver cells, can be accompanied by inflammatory cell infiltration and / or hyperplasia of fibrous tissue, the expression of inflammatory cytokines ACC and FAS whether the interference caused by the mechanism of TG metabolism is not clear. In this experiment the past in vitro cell experiments, the establishment of animal model of chronic inflammation, investigate the disorder of blood lipid the metabolism of inflammation; inflammatory cytokines by SCAP-SREBPs mediated interference LDLR feedback regulation to promote lipid uptake, leading to aortic and hepatic lipid accumulation.
Materials and methods using 8 week old C57BL/6J mice by subcutaneous injection of casein (Casein) production of chronic inflammation model in mice, which were fed with normal diet, high fat diet for 20 weeks or so, extraction of blood, liver and aorta of the experimental mice were detected by enzymatic method; IL-6 and blood lipid (including TC, LDL-C, HDL-C and TG) level; HE staining, to observe the changes of liver and aortic morphology ORO staining and Masson staining; according to NAFLD, on mice liver grading and staging NASH grading and staging criteria; using quantitative Real-time PCR detection of liver LDLR, SCAP, SREBP2, SREBP1, ACC and FAS mRNA level and SCAP level of SREBP2mRNA, aortic LDLR, Western; blotting detection of liver LDLR, SCAP, SREBP1, SCAP, LDLR protein and aortic, the expression of SREBP2 protein.
Results after subcutaneous injection of Casein in 1. C57BL/6J mice, the serum IL-6 of the normal diet and the high fat diet mice increased significantly.
2., in the general diet group, except for a slight decrease in serum TC level, LDL, HDL and TG decreased significantly. The blood lipid indexes (TC, LDL, HDL and TG) of high-fat diet decreased significantly. These data indicate that chronic inflammation can lead to dyslipidemia.
3., compared with the normal diet group, the high-fat diet significantly inhibited the expression of LDLR, SCAP and SREBP2mRNA and protein in aorta and liver, but in chronic inflammatory state, LDLR, SCAP and SREBP2mRNA increased significantly with protein. This indicates that chronic inflammation can interfere with cholesterol metabolism in cells.
4. simple high-fat diet group mice SREBP1, ACC and FAS gene expression increased, SREBP1 in chronic inflammatory conditions, ACC, and FAS expression to further improve the hepatic uptake amounts of TG, which leads to hepatic steatosis, ballooning degeneration, necrosis of liver cells and fibrous tissue hyperplasia, the formation of NAFLD or NASH.
5. simple high-fat diet group mice aortic intima was obviously thickened, a large number of foam cell formation and the formation of atherosclerotic plaque; in chronic inflammatory conditions, aortic atherosclerotic plaque thickening, larger plaque area, suggesting that inflammation can aggravate the main artery damage.
1 conclusion 1.IL-6 is a sensitive marker of inflammatory reaction. The level of IL-6 is closely related to the degree of inflammatory reaction. Serum IL-6 is significantly elevated, suggesting that the chronic inflammation model is successfully established.
2. in the state of chronic inflammation by interfering with SCAP-SREBP2-LDLR feedback regulation system, promote lipid uptake, resulting in accumulation of aorta and liver lipid. These data suggest that chronic inflammation can significantly reduce blood lipid level; chronic inflammation is not a safe plasma cholesterol concentration, plasma cholesterol levels and not intracellular cholesterol levels were positively correlated.
3., inflammatory state promotes the expression of SREBP1, ACC and FAS, and makes a large number of TG aggregation in liver cells, resulting in steatosis, necrosis and fibrosis of liver cells. Therefore, inflammation can aggravate liver damage.

【学位授予单位】：重庆医科大学
【学位级别】：博士
【学位授予年份】：2008
【分类号】：R363

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