兔血浆脂蛋白-胆固醇代谢的房室模型研究

本文以胆固醇逆向转运机理为基础,运用房室模型方法,选取糖尿病兔与正常兔对照,研究血浆脂蛋白转运胆固醇能力的差异.辨识结果表明,糖尿病组HDL逆向转运胆固醇的两个环节,即HDL将胆固醇转运给VLDL和LDL的能力及后者将胆固醇带回肝脏的能力,均明显低于对照组;而糖尿病组LDL转运胆固醇至肝外组织的能力大于对照组.从而说明糖尿病将促进AS发病.     

胆固醇酯转运蛋白转基因动物的研究进展

胆固醇酯转运蛋白 (ＣＥＴＰ)是胆固醇代谢中的一种血浆酶 ,是胆固醇逆向转运系统中的关键蛋白质。ＣＥＴＰ催化血浆脂蛋白之间非极性脂质特别是胆固醇酯 (ＣＥ)的交换和平衡 ,关系到各种脂蛋白的颗粒大小和脂质组成 ,决定高密度脂蛋白 (ＨＤＬ)和低密度脂蛋白 (ＬＤＬ)质和量的变化 ,在胆固醇逆向转运中起关键作用 ,与动脉粥样硬化 (ＡＳ)的发生和发展密切相关。ＣＥＴＰ缺陷患者伴有明显的高α脂蛋白血症 (ＨＡＬＰ)的发现使人们对ＣＥＴＰ在脂代谢中的重要性有了更高认识。人ＣＥＴＰ遗传缺陷表型和ＣＥＴＰ转基因动物研究表明 ,ＣＥＴＰ…     

集落刺激因子与动脉粥样硬化

集落刺激因子（ＣＳＦｓ）可通过激活ＬＤＬ受体依赖性和非依赖性途径，使含ＡＰＯＢ－１００的脂蛋白水平降低。另一方面，动脉壁内ＣＳＦｓ则吸引循环单核细胞而聚集、衍化为巨噬细胞，并增强其摄取脂蛋白和酯化胆固醇的能力。提示ＣＳＦｓ对动脉粥样硬化可能具有抑制和促进双重作用。对ＷＨＨＬ兔的整体实验显示，Ｍ－ＣＳＦ能减缓其自发性动脉粥样硬化的进程。对ＣＳＦｓ的进一步研究可能有助于加深对动脉粥样硬化发病机理的认识，进而开辟防治新途径。     

胆固醇酯转运蛋白的基因多态性

胆固醇酯转运蛋白（cholesteryl ester transfer protein,CETP）通过介导胆固醇酯在高密度脂蛋白和富含载脂蛋白B的脂蛋白之间的交换,在胆固醇逆向转运过程中起着关键的作用。流行病学研究资料已经阐明CETP基因多态同血浆CETP浓度和脂蛋白水平相关联,因而CETP基因被认为是冠心病（coronary heart disease,CHD）的易感基因之一。本文重点阐述CETP基因单核苷酸多态与脂蛋白代谢及临床疾病易感性关系的最新研究进展。     

实验性高胆固醇血症家兔血液流变特性的改变与AS形成关系的研究

目的：了解实验性高胆固醇血症家兔血液流变特性的改变与动脉粥样硬化形成的关系。方法：健康家兔８０只,随机分为实验组（ＡＧ）６０只和对照组（ＣＧ）２０只。各组又均分为４个亚组,即ＡＧ１－ＡＧ４和ＣＧ１－ＣＧ４。ＡＧ组每只给予胆固醇粉１ｇ／ｄ,在喂养的第２、４、８和１２周分别观察ＡＧ１－ＣＧ１、ＡＧ２－ＣＧ２、ＡＧ３－ＣＧ３和ＡＧ４－ＣＧ４的主动脉粥样硬化（ＡＳ）病变及相应血液流变特性的变化。结果：在兔     

胆固醇逆转运相关蛋白基因在骨骼肌的表达

构建载脂蛋白ＡＩ（ａｐｏＡＩ）、载脂蛋白Ｅ（ａｐｏＥ）和卵磷脂胆固醇酰基转移酶（ＬＣＡＴ）的病毒或非病毒载体,分别转染离体成肌细胞或直接注入小鼠骨骼肌,观察其表达程序及分泌人血等情况,探讨借用骨骼肌异源表达这些在胆固醇逆转运中起关键作用的重要候选基因,进而发展一种简易安全基因治疗方法的可能性。结果显示,质粒表达载体ｐＣＭＶａｐｏＥ３和重组腺病毒载体Ａｄ－ＲＳＶ－ａｐｏＡＩ在原代培养小鼠成肌细胞和成     

基于脂代谢特点建立豚鼠动脉粥样硬化模型优势的研究进展

动脉粥样硬化（AS）在全球的发病率逐年升高,有关AS 的研究也越来越深入,合适的动物模型是研究动脉粥样硬化机制和 药物研发的关键环节。在众多动物模型中豚鼠作为动脉粥样硬化的研究对象存在众多优势,主要体现在血浆脂蛋白的构成比例、 胆固醇的转运形式、肝脏中胆固醇的存在形式与比例、对外源性胆固醇的敏感性、胆固醇与脂蛋白代谢过程中关键酶的活性变化 等方面。本综述基于脂代谢特点,对比分析这几个方面内容来阐述豚鼠作为动脉粥样硬化动物模型的优势。     

清道夫受体A基因的表达和调控研究进展

Ａ类清道夫受体（ＳＲ－Ａ）的表达具有巨噬细胞特异性,这与ＳＲ－Ａ启动子上的ＰＵ．１／Ｓｐｉ－１识别位点有关,ＳＲ－Ａ具有广泛的配体结合活性,在机体的防御,细胞粘附及信息转导等过程中起重要作用,对修饰脂蛋白的介导,内吞可能是动脉粥样硬化斑块形成的重要原因。     

卵磷脂胆固醇酰基转移酶基因的多态性和突变与动脉粥样硬化关系

卵磷脂胆固醇酰基转移酶(Lecithin cholesterol acyltransferase,LCAT)催化血浆中绝大多数胆固醇的酯化—外周组织胆固醇逆向转运(Reverse cholesterol transportation,RCT)到肝脏进一步分解的关键步骤,同时调节血浆高密度胎蛋白(high density lipoprotein,HDL)等脂蛋白的成熟与代谢。对其基因多态性和突变的研究表明：LCAT在RCT、脂代谢和动脉粥样硬化发生发展中起重要作用,有可能作为预防或治疗动脉粥样硬化的靶基因。     

天然和氧化修饰型LDL、VLDL及HDL对培养人动脉平滑肌细胞原癌基因fos及myc表达的影响

动脉平滑肌细胞（ＳＭＣ）是动脉粥样硬化（ＡＳ）斑块中的主要细胞,它的增殖在ＡＳ形成过程中极其重要。脂蛋白和氧化修饰型脂蛋白对ＳＭＣ增殖的影响以及ＳＭＣ增殖与原癌基因异常表达的关系是当前ＡＳ发病机制研究的热点之一。我们在建立人主动脉ＳＭＣ体外培养方法的基础上,观察了ＬＤＬ,ＶＬＤＬ及ＨＤＬ和相应的氧化修饰型脂蛋白对培养人ＳＭＣｆｏｓ,ｍｙｃ,ｅｒｂ－Ｂ原癌基因转录表达的影响。结果表明：①ＨＤＬ对ＳＭＣｆｏｓ,ｍｙｃ基因表达无影响;②ＬＤＬ和ＶＬＤＬ有使这些基因表达增加的趋势,但与对照比较差异不显著（Ｐ＞０．０５）;③ＯＸ－ＶＬＤＬ,ＯＸ－ＶＬＤＬ和ＯＸ－ＨＤＬ有使ＳＭＣｆｏｓ,ｍｙｃ基因表达显著增强的作用（Ｐ＜０．０１）,且其作用较相应的天然脂蛋白大（Ｐ＜０．０１）．上述结果说明：ＬＤＬ,ＶＬＤＬ,ＯＸ－ＬＤＬ,ＯＸ－ＶＬＤＬ和０Ｘ－ＨＤＬ的致ＡＳ作用可能与刺激ＳＭＣｆｏｓ和ｍｙｃ癌基因表达增加有关。     

An apolipoprotein A-I mimetic dose-dependently increases the formation of prebeta1 HDL in human plasma

Prebeta1 HDL is the initial plasma acceptor of cell-derived cholesterol in reverse cholesterol transport. Recently, small amphipathic peptides composed of D-amino acids have been shown to mimic apolipoprotein A-I (apoA-I) as a precursor for HDL formation. ApoA-I mimetic peptides have been proposed to stimulate the formation of prebeta1 HDL and increase reverse cholesterol transport in apoE-null mice. The existence of a monoclonal antibody (MAb 55201) and a corresponding ELISA method that is selective for the detection of the prebeta(1) subclass of HDL provides a means of establishing a correlation between apoA-I mimetic dose and prebeta1 HDL formation in human plasma. Using this prebeta1 HDL ELISA, we demonstrate marked apoA-I mimetic dose-dependent prebeta1 HDL formation in human plasma. These results correlated with increases in band density of the plasma prebeta1 HDL, when observed by Western blotting, as a function of increased apoA-I mimetic concentration. Increased prebeta1 HDL formation was observed after as little as 1 min and was maximal within 1 h. Together, these data suggest that a high-throughput prebeta1 HDL ELISA provides a way to quantitatively measure a key component of the reverse cholesterol transport pathway in human plasma, thus providing a possible method for the identification of apoA-I mimetic molecules.     

Kinetics and plasma concentrations of 26-hydroxycholesterol in baboons

26-Hydroxycholesterol (26OHC), a major oxysterol in human blood, is believed to play an important role in reverse cholesterol transport, bile acid formation, and regulation of various cellular processes. Using isotope dilution mass spectrometry, we measured plasma 26OHC concentrations in baboons fed either a high cholesterol/saturated fat (HC-SF) or normal chow diet. Plasma 26OHC levels in baboons were comparable to those reported for humans and were positively correlated with plasma cholesterol concentrations. Animals on the HC-SF diet had significantly higher 26OHC levels (0.274+/-0.058 microM, mean+/-S.D.) than those on the chow diet (0.156+/-0.046 microM). In separate experiments, [(3)H]26OHC was injected into four tethered baboons, and multiple blood samples drawn over a 1-h period were analyzed for [(3)H]26OHC and 26OHC. Fitting the specific radioactivity data to a two-pool compartmental model indicated a rapidly turning over plasma compartment (t(1/2) 2.9-6.0 min) and a second compartment with slow turnover (t(1/2) 76-333 min). The calculated 26OHC production rate was 2.5 micromol/kg body weight/day. Assuming all 26OHC is converted to bile acids, the 26OHC production rate corresponds to about 10% of total bile acid production in adult baboons. These results indicate that rapid turnover of plasma 26OHC at submicromolar concentrations could significantly contribute to bile acid synthesis.     

ADP-ribosylation factor (ARF)-like 7 (ARL7) is induced by cholesterol loading and participates in apolipoprotein AI-dependent cholesterol export

Here, we identify ADP-ribosylation factor (ARF)-like 7 (ARL7) as the only ARF- and ARL-family member whose mRNA-expression is induced by liver X-receptor/retinoid X-receptor agonists or cholesterol loading in human macrophages. Moreover, subcellular distribution of mutant and wild type ARL7-enhanced green fluorescent protein (EGFP) supports that ARL7 may be involved in a vesicular transport step between a perinuclear compartment and the plasma membrane. Therefore, we investigated the effect of ARL7 over-expression on the cholesterol secretory pathway. We found that expression of wild type and dominant active ARL7-EGFP stimulated the rate of apolipoprotein AI-specific cholesterol efflux 1.7- and 2.8-fold. In contrast, expression of the dominant negative form of ARL7-EGFP led to approximately 50% inhibition of cholesterol efflux. This data is consistent with a model in which ARL7 is involved in transport between a perinuclear compartment and the plasma membrane apparently linked to the ABCA1-mediated cholesterol secretion pathway.     

Polyunsaturated fatty acids up-regulate hepatic scavenger receptor B1 (SR-BI) expression and HDL cholesteryl ester uptake in the hamster.

Diets rich in polyunsaturated fatty acids lower plasma HDL cholesterol concentrations when compared to diets rich in saturated fatty acids. We investigated the mechanistic basis for this effect in the hamster and sought to determine whether reduced plasma HDL cholesterol concentrations resulting from a high polyunsaturated fat diet are associated with a decrease in reverse cholesterol transport. Animals were fed semisynthetic diets enriched with polyunsaturated or saturated fatty acids for 6 weeks. We then determined the effect of these diets on the following parameters: 1) hepatic scavenger receptor B1 (SR-BI) mRNA and protein levels, 2) the rate of hepatic HDL cholesteryl ester uptake, and 3) the rate of cholesterol acquisition by the extrahepatic tissues (from de novo synthesis, LDL and HDL) as a measure of the rate of reverse cholesterol transport. Compared to saturated fatty acids, dietary polyunsaturated fatty acids up-regulated hepatic SR-BI expression by approximately 50% and increased HDL cholesteryl ester transport to the liver; as a consequence, plasma HDL cholesteryl ester concentrations were reduced. Although dietary polyunsaturated fatty acids increased hepatic HDL cholesteryl ester uptake and lowered plasma HDL cholesterol concentrations, there was no change in the cholesterol content or in the rate of cholesterol acquisition (via de novo synthesis and lipoprotein uptake) by the extrahepatic tissues.These studies indicate that substitution of polyunsaturated for saturated fatty acids in the diet increases SR-BI expression and lowers plasma HDL cholesteryl ester concentrations but does not affect reverse cholesterol transport.     

Cholesterol transport between cells and high-density lipoproteins

Various types of studies in humans and animals suggest strongly that HDL is anti-atherogenic. The anti-atherogenic potential of HDL is thought to be due to its participation in reverse cholesterol transport, the process by which cholesterol is removed from non-hepatic cells and transported to the liver for elimination from the body. Extensive studies in cell culture systems have demonstrated that HDL is an important mediator of sterol transport between cells and the plasma compartment. The topic of this review is the mechanisms that account for sterol movement between HDL and cells. The most prominent and easily measured aspect of sterol movement between HDL and cells is the rapid bidirectional transfer of cholesterol between the lipoprotein and the plasma membrane. This movement occurs by unmediated diffusion, and in most situations its rate in each direction is limited by the rate of desorption of sterol molecules from the donor surface into the adjacent water phase. The net transfer of sterol mass out of cells occurs when there is either a relative enrichment of sterol within the plasma membrane or a depletion of sterol in HDL. Recent studies suggest that certain minor subfractions of HDL (with pre-beta mobility on agarose gel electrophoresis and containing apoprotein A-I but no apo A-II) are unusually efficient at promoting efflux of cell sterol. To what extent efflux to these HDL fractions is balanced by influx from the lipoprotein has not yet been established clearly. The prevention and reversal of atherosclerosis require the mobilization of cholesterol from internal (non-plasma membrane) cellular locations. To some extent, this may involve the retroendocytosis of HDL. However, most mobilization probably involves the transport of internal sterol to the plasma membrane, followed by desorption to extracellular HDL. Several laboratories are investigating the transport of sterol from intracellular locations to the plasma membrane. Studies on biosynthetic sterol (probably originating mostly in the smooth endoplasmic reticulum) suggest that there is rapid transport to the plasma membrane in lipid-rich vesicles. Important features of this transport are that it bypasses the Golgi apparatus and may be positively regulated by the specific binding of HDL to the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)     

STARD4 knockdown in HepG2 cells disrupts cholesterol trafficking associated with the plasma membrane,ER, and ERC

STARD4, a member of the evolutionarily conserved START gene family, has been implicated in the nonvesicular intracellular transport of cholesterol. However, the direction of transport and the membranes with which this protein interacts are not clear. We present studies of STARD4 function using small hairpin RNA knockdown technology to reduce STARD4 expression in HepG2 cells. In a cholesterol-poor environment, we found that a reduction in STARD4 expression leads to retention of cholesterol at the plasma membrane, reduction of endoplasmic reticulum-associated cholesterol, and decreased ACAT synthesized cholesteryl esters. Furthermore, D4 KD cells exhibited a reduced rate of sterol transport to the endocytic recycling compartment after cholesterol repletion. Although these cells displayed normal endocytic trafficking in cholesterol-poor and replete conditions, cell surface low density lipoprotein receptor (LDLR) levels were increased and decreased, respectively. We also observed a decrease in NPC1 protein expression, suggesting the induction of compensatory pathways to maintain cholesterol balance. These data indicate a role for STARD4 in nonvesicular transport of cholesterol from the plasma membrane and the endocytic recycling compartment to the endoplasmic reticulum and perhaps other intracellular compartments as well.     

Antisense oligonucleotide inhibition of cholesteryl ester transfer protein enhances RCT in hyperlipidemic,CETP transgenic,LDLr-/- mice

Due to their ability to promote positive effects across all of the lipoprotein classes, cholesteryl ester transfer protein (CETP) inhibitors are currently being developed as therapeutic agents for cardiovascular disease. In these studies, we compared an antisense oligonucleotide (ASO) inhibitor of CETP to the CETP small molecule inhibitor anacetrapib. In hyperlipidemic CETP transgenic (tg) mice, both drugs provided comparable reductions in total plasma cholesterol, decreases in CETP activity, and increases in HDL cholesterol. However, only mice treated with the antisense inhibitor showed an enhanced effect on macrophage reverse cholesterol transport, presumably due to differences in HDL apolipoprotein composition and decreases in plasma triglyceride. Additionally, the ASO-mediated reductions in CETP mRNA were associated with less accumulation of aortic cholesterol. These preliminary findings suggest that CETP ASOs may represent an alternative means to inhibit that target and to support their continued development as a treatment for cardiovascular disease in man.     

Composition and ultrastructure of size subclasses of normal human peripheral lymph lipoproteins: quantification of cholesterol uptake by HDL in tissue fluids

Peripheral lymph lipoproteins have been characterized in animals, but there is little information about their composition, and none about their ultrastructure, in normal humans. Therefore, we collected afferent leg lymph from 16 healthy males and quantified lipids and apolipoproteins in fractions separated by high performance-size exclusion chromatography. Apolipoprotein B (apoB) was found almost exclusively in low density lipoproteins. The distribution of apoA-I, particularly in lipoprotein A-I (LpA-I) without A-II particles, was shifted toward larger particles relative to plasma. The fractions containing these particles were also enriched in apoA-II, apoE, total cholesterol, and phospholipids and had greater unesterified cholesterol-to-cholesteryl ester ratios than their counterparts in plasma. Fractions containing smaller apoA-I particles were enriched in phospholipid. Most apoA-IV was lipid poor or lipid free. Most apoC-III coeluted with large apoA-I-containing particles. Electron microscopy showed that lymph contained discoidal particles not seen in plasma. These findings support other evidence that high density lipoproteins (HDL) undergo extensive remodeling in human tissue fluid. Total cholesterol concentration in lymph HDL was 30% greater (P < 0.05) than could be explained by the transendothelial transfer of HDL from plasma, providing direct confirmation that HDL acquire cholesterol in the extravascular compartment. Net transport rates of new HDL cholesterol in the cannulated vessels corresponded to a mean whole body reverse cholesterol transport rate via lymph of 0.89 mmol (344 mg)/day.