脂蛋白(a)与动脉粥样硬化及脑梗死的研究进展

脂蛋白(a)是由载脂蛋白(a)和低密度脂蛋白构成的。脂蛋白(a)不随血浆中同型半胱氨酸、载脂蛋白A、高密度脂蛋白的变化而变化,是一种相对独立的脂蛋白。脂蛋白(a)的合成过程主要是在肝脏中完成的,脂蛋白(a)可以抑制NO介导的血管舒张,破坏血管壁中促凝与抗凝因子的平衡,参与动脉粥样硬化斑块的形成。动脉粥样硬化是脑梗死最基本的病因之一,在临床工作中我们应当重视脂蛋白(a)与脑梗死的关系,我们可以通过测定血清中脂蛋白(a)的水平来预测脑梗死的患病风险,尤其能对病变损害程度重,病变累及范围广的脑梗死的发生提出预警。高水平的血浆脂蛋白(a)是脑梗死及动脉粥样硬化的独立危险因素,本文就脂蛋白(a)与动脉粥样硬化及脑梗死研究中的进展做一综述,为脑梗死的预防提供参考和研究依据。     

载脂蛋白(a)单克隆抗体的制备及其性能研究

载脂蛋白(a)简称 apo(a),是脂蛋白(a)(Lp(a))中特征性蛋白成分,分子量在400—700kD,apo(a)以二硫键与低密度脂蛋白(LDL)的载脂蛋白 B100相连构成 Lp(a),分子量在1 200—1 500kD。近年来国内外学者认为 Lp(a)和 apo(a)是研究动脉粥样硬化危险因素的重要指标。我们为了探索脂质代谢紊乱引起的心血管系统疾病,进行了apo(a)的单克隆抗体研究。apo(a)提取的脂蛋白 Lp(a)经密度为     

降脂蛋白(a)研究

脂蛋白(a)[Lp(a)]是由载脂蛋白(a)(apo(a))与载脂蛋白B100(apoB100)通过共价键连接的脂蛋白。高血浆水平Lp(a)是心血管疾病的独立风险因子,Lp(a)的血浆水平主要受遗传因素调控,主要有LPA[lipoprotein,Lp(a)]基因的三环结构域kringle IV/2拷贝数和单核苷酸多态性(SNP)。欧洲动脉粥样硬化协会(EAS)和美国心脏病协会(AHA)建议对于高Lp(a)的人群应当考虑降高Lp(a)的治疗。目前已有多种降高Lp(a)的药物和方法,如血浆分离置换法、雌激素治疗、反义核苷酸治疗、类法尼醇X核内受体(farnesoid X receptor,FXR)激动治疗等,但应用于临床的降高Lp(a)的药物和方法依然缺乏。本文拟就降Lp(a)的药物和方法进展情况进行综述。     

脂蛋白（a）的研究进展──生物化学与分子生物学方面

脂蛋白（ａ）［Ｌｐ（ａ）］是一种与低密度脂蛋白类似的脂蛋白,其特殊处在于多含一种具明显多态性的糖蛋白──载脂蛋白（ａ）［Ａｐｏ（ａ）］。Ａｐｏ（ａ）与血浆纤溶酶原有很大同源性。Ｌｐ（ａ）由肝合成,其分解可能主要经非特异途径。Ａｐｏ（ａ）大小及血浆Ｌｐ（ａ）浓度主要由Ａｐｏ（ａ）基因决定。Ｌｐ（ａ）易沉积于血管壁,并可促进平滑肌细胞生长及抑制纤维蛋白溶解,这可能是其促动脉粥样硬化和血栓形成的机理所在。Ｌｐ（ａ）的生理功能尚不清楚。     

载脂蛋白B的分子生物学基础

载脂蛋白B(apoB)是富含甘油三酯和胆固醇的脂蛋白(CM、VLDL和LDL)特有的蛋白质成分。apoB₁₀₀是LDL受体的专一性配基,介导血中LDL-胆固醇(LDL-Ch)被外周组织细胞摄取和清除。载脂蛋白B基因遗传变异和apoB异常,血中LDL-Ch堆积,导致动脉粥样硬化发生是冠心病危险因素。     

基因修饰小鼠在脂代谢紊乱与动脉粥样硬化研究中的新进展

近十余年来,载脂蛋白(ApoE)与低密度脂蛋白(LDL)受体 (LDLr)基因敲除小鼠已成为研究脂代谢和动脉粥样硬化最为常用的模型.在这两种小鼠模型基础上,通过与不同的转基因、基因敲除小鼠杂交,产生了多种脂代谢紊乱和动脉粥样硬化小鼠模型,为发现调控血浆脂蛋白以及动脉粥样硬化发生的机制,创造了有利条件.此外,新的严重高甘油三酯血症小鼠模型也制备成功,本文笔者研究组研究了其中的脂蛋白脂酶缺陷模型与代谢性疾病的关系,得到了许多有意义的结果.而利用不同转基因和去基因小鼠作为供体, 以及ApoE或LDL受体缺陷小鼠作为接受体的骨髓移植技术,则大大丰富了人们对于巨噬细胞中不同基因在动脉粥样硬化发生、发展和消退过程中作用的认识.动脉粥样硬化的易损斑块形成是近年来的一个研究热点,应用小鼠模型进行模拟也取得了一定的成功.然而,小鼠与人类在脂代谢和动脉粥样硬化中存在很大的种系差异,本文对此也予以评述.     

人血清脂蛋白(a)中纤维蛋白溶酶原位点测定

用单克隆抗载脂蛋白(a)抗体为包被抗体,酶标抗纤维蛋白溶酶原(Pg)抗体为检测抗体建立了人血清脂蛋白(a)［Lp(a)］中Pg位点的酶联免疫吸附试验法.方法特异,测定范围为28～880 mg/L,变异系数批内为4%～6%,批间为7%～9%.检测了正常人、冠心病(CHD)和肾衰血透患者(CRF)血清Lp(a)、Lp(a)中Pg位点和Pg/Lp(a)比值.结果示正常人血清Lp(a)水平分别同Pg、Pg/Lp(a)呈正、负相关.CHD和CRF患者Lp(a)、Pg位点和Pg/Lp(a)比值明显高于正常人,认为Lp(a)中Pg位点测定对于动脉粥样硬化的病理生理研究具有特殊的价值.     

脂代谢的测定对老年2型糖尿病患者临床意义

目的探讨老年2型糖尿病与血脂、载脂蛋白、脂蛋白(a)之间的关系及其临床测定的意义。方法对97例老年2型糖尿病患者及65例老年对照组进行了血清总胆固醇(TC)、甘油三脂(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、载脂蛋白AI(ApoAI)、载脂蛋白B(ApoB)及脂蛋白(a)[Lp(a)]的测定。结果老年2型糖尿病患者血清TC、TG、LDL-C、ApoB及Lp(a)水平均显著高于老年对照组。而血清HDL-C和ApoAI水平老年2型糖尿病组显著低于老年对照组。结论老年2型糖尿病患者由于体内胰岛素相对不足及胰岛素抵抗,使血脂、载脂蛋白、脂蛋白浓度和组成成分发生变化及功能发生异常,从而促进动脉粥样硬化,并伴随着血管并发症的发生。因此,在对老年糖尿病并发症的预防和控制上,应在控制血糖的基础上减少脂肪的摄入,以降低高脂血症的发生,从而降低血管并发症的发生。     

脂蛋白、载脂蛋白和脂蛋白受体与衰老

本文观察了新生儿(脐带血),青年(18—24岁),老年(55—65岁)各40例的血脂、脂蛋白、载脂蛋白和低密度脂蛋白LDL受体功能的变化。结果表明,新生儿的血脂,脂蛋白和载脂蛋白含量在各年龄组中最低(P<0.01),其LDL受体结合水平最高,(P<0.01)。血清TC,TG,LDL-C,apo B和CII随增龄上升,但LDL受体水平和HDL-C,apo AI,AII的增龄变化不明显。该结果指出,衰老对LDL受体的结合水平和HDL-C,apo AI,AII的影响似乎不大。另方面说明,TC,LDL-C和apo B浓度随增龄增加而不伴有相应的LDL受体结合水平及HDL-C,APO AI,AII浓度的上升,使老年期的脂蛋白代谢平衡被打破,因而促使高胆固醇血症和动脉粥样斑块的形成。     

HDL/LDL 比值、LP（a）及s-CRP 与冠脉病变程度相关性分析

目的:研究高密度脂蛋白/低密度脂蛋白比值(HDL/LDL比值)、脂蛋白a(LP(a))及超敏C反应蛋白(s-CRP)与冠脉病变程度之间的关系。方法:对120名初发急性STEMI行急诊冠脉造影术并支架植入术患者(<12小时),并于次日晨检测空腹生化血脂分析,测得HDL/LDL比值、LP(a)及s-CRP等相关指标,冠脉造影结果根据Gensini积分系统分轻、中、重度三组,比较三组之间上述三项指标有无差异,并选取冠脉造影正常20例为对照组,比较各组间有无差异。结果:与正常组相比,心梗组HDL/LDL比值明显降低(P<0.05),各组间HDL/LDL比值亦存在差异(P<0.05),LP(a)及s-CRP在不同冠脉分级上亦存在着差异(P<0.05),以上差异均有统计学意义。结论:上述三项指标对冠脉病变严重程度有一定的预测价值。     

Lipoprotein(a) accelerates atherosclerosis in uremic mice

Uremic patients have increased plasma lipoprotein(a) [Lp(a)] levels and elevated risk of cardiovascular disease. Lp(a) is a subfraction of LDL, where apolipoprotein(a) [apo(a)] is disulfide bound to apolipoprotein B-100 (apoB). Lp(a) binds oxidized phospholipids (OxPL), and uremia increases lipoprotein-associated OxPL. Thus, Lp(a) may be particularly atherogenic in a uremic setting. We therefore investigated whether transgenic (Tg) expression of human Lp(a) increases atherosclerosis in uremic mice. Moderate uremia was induced by 5/6 nephrectomy (NX) in Tg mice with expression of human apo(a) (n = 19), human apoB-100 (n = 20), or human apo(a) + human apoB [Lp(a)] (n = 15), and in wild-type (WT) controls (n = 21). The uremic mice received a high-fat diet, and aortic atherosclerosis was examined 35 weeks later. LDL-cholesterol was increased in apoB-Tg and Lp(a)-Tg mice, but it was normal in apo(a)-Tg and WT mice. Uremia did not result in increased plasma apo(a) or Lp(a). Mean atherosclerotic plaque area in the aortic root was increased 1.8-fold in apo(a)-Tg (P = 0.025) and 3.3-fold (P = 0.0001) in Lp(a)-Tg mice compared with WT mice. Plasma OxPL, as detected with the E06 antibody, was associated with both apo(a) and Lp(a). In conclusion, expression of apo(a) or Lp(a) increased uremia-induced atherosclerosis. Binding of OxPL on apo(a) and Lp(a) may contribute to the atherogenicity of Lp(a) in uremia.     

Recombinant adenovirus vector mediated expression of lipoprotein (a) [Lp(a)] in rabbit plasma.

Lipoprotein (a) [Lp(a)] is a heterodimer of apolipoprotein (a) [apo(a)] and apolipoprotein B-100 (apoB-100) of low density lipoprotein linked by a disulfide bond. Apo(a) and apoB-100 are synthesized by the liver and covalently associate or couple to form Lp(a) extracellularly. Elevated plasma Lp(a) is an independent risk factor for vascular injury disorders such as restenosis after balloon angioplasty and accelerated graft atherosclerosis following heart transplantation. Lp(a) is not expressed in laboratory animals making studies of its pathophysiology difficult. To overcome this problem, we explored the possibility of generating Lp(a) in rabbit plasma using replication-deficient adenovirus vector mediated gene delivery. Rabbits were chosen because of their large vessels and unlike mouse or rat, rabbit apoB-100 could interact with apo(a) to generate Lp(a). The recombinant (r) adenovirus vector construct used encoded a 200 kDa apo(a) [Ad-apo(a)]. Ad-apo(a) injection into the rabbit marginal vein caused the appearance of plasma rLp(a). Injection of a r adenovirus vector expressing the bacterial LacZ gene (Ad-LacZ) or PBS (vehicle) did not result in detectable plasma rLp(a). These are the first results to demonstrate plasma expression of rLp(a) in rabbits using adenovirus vector mediated gene transfer. Therefore, this system may be suitable for investigating Lp(a)'s role in the development of vascular injury diseases in a rabbit model.     

Relation of cardiovascular risk factors to atherosclerosis in type III hyperlipoproteinemia

The familial lipoprotein disorder type III hyperlipoproteinemia (HPL) carries a marked increase in the risk of accelerated and premature atherosclerosis, but there is considerable variation among affected individuals in susceptibility to cardiovascular disease (CVD). We studied the influence of independent risk factors for atherosclerosis in 67 patients with clinically overt type III HPL and homozygosity for apolipoprotein (apo) E2. Among the different risk factors (lipid and lipoprotein levels, age, sex, body mass index, smoking status, hypertension, and diabetes mellitus) there was only a statistically significant difference in age between 25 patients with atherosclerosis and 42 patients without atherosclerosis. Serum lipoprotein (a), [Lp, (a)], levels were 30.6% higher in the atherosclerosis group, but this was not statistically significant. We conclude that (in contrast to familial hypercholesterolemia) elevated Lp (a) concentrations may not be regarded as a component of the clinical syndrome of type III HPL.     

A PvuII polymorphism of the low density lipoprotein receptor gene is not associated with plasma concentrations of low density lipoproteins including LP(a)

Lipoprotein(a) [Lp(a)] is a low density lipoprotein (LDL), in which apolipoprotein B-100 (apo B-100) is attached to apolipoprotein(a) [apo(a)], a glycoprotein of variable size. Lp(a) may be as atherogenic as LDL. In normal populations, Lp(a) concentrations in plasma are largely determined by the apo(a) gene locus on chromosome 6, but regulation of synthesis and catabolism of Lp(a) is poorly understood. In some studies, a PvuII restriction fragment length polymorphism (RFLP) in the LDL receptor gene seems to affect concentrations of LDL in plasma, and other studies have indicated that Lp(a) catabolism could be mediated by the LDL receptor. We therefore expected that the PvuII polymorphism in the LDL receptor gene might be associated with Lp(a) levels in 170 Caucasian men aged 40 years, selected to have a high representation of low molecular weight apo(a) phenotypes. However, plasma concentrations of cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and Lp(a) were all unrelated to the LDL receptor gene PvuII polymorphism both in the group as a whole and when it was subgrouped by apo(a) phenotype. Therefore our data do not support the concept that this particular LDL receptor gene polymorphism is associated with LDL receptor function, and our data therefore neither support nor rule out a role for the LDL receptor in Lp(a) catabolism.     

High-level lipoprotein [a] expression in transgenic mice: evidence for oxidized phospholipids in lipoprotein [a] but not in low density lipoproteins

Efforts to elucidate the role of lipoprotein [a] (Lp[a]) in atherogenesis have been hampered by the lack of an animal model with high plasma Lp[a] levels. We produced two lines of transgenic mice expressing apolipoprotein [a] (apo[a]) in the liver and crossed them with mice expressing human apolipoprotein B-100 (apoB-100), generating two lines of Lp[a] mice. One had Lp[a] levels of approximately 700 mg/dl, well above the 30 mg/dl threshold associated with increased risk of atherosclerosis in humans; the other had levels of approximately 35 mg/dl. Most of the LDL in mice with high-level apo[a] expression was covalently bound to apo[a], but most of the LDL in the low-expressing line was free. Using an enzyme-linked sandwich assay with monoclonal antibody EO6, we found high levels of oxidized phospholipids in Lp[a] from high-expressing mice but not in LDL from low-expressing mice or in LDL from human apoB-100 transgenic mice (P <0.00001), even though all mice had similar plasma levels of human apoB-100. The increase in oxidized lipids specific to Lp[a] in high-level apo[a]-expressing mice suggests a mechanism by which increased circulating levels of Lp[a] could contribute to atherogenesis.     

State of lipid metabolism in children and adolescents with insulin-dependent diabetes. I. Evaluation of lipoprotein (A) behavior in children and adolescents with insulin-dependent diabetes]

The level of lipoprotein Lp(a), one of the risk factors of atherosclerosis, was determined in 91 children and adolescents of age ranging from 3.3 to 22 years suffering from insulin-dependent diabetes. The changes in Lp(a) were analyzed in relation to the group of patients, the duration of diabetes, possible genetic factors, other factors predisposing to early onset of atherosclerosis, and occurrence of obesity in the analyzed group. The relation between the level of Lp(a) and other parameters of lipid metabolism (total cholesterol, triglycerides, phospholipids, HDL-cholesterol and apolipoprotein B) as well as a degree of metabolic normalization of diabetes (as assessed by the determination of glycosylated hemoglobin and fructosamine) was studied in addition. No relation between Lp(a) and the factors mentioned above, with exception of glycosylated hemoglobin and fructosamine concentrations, could be demonstrated. The elevated level of Lp(a) in children and adolescents during the period of poor metabolic control of diabetes may constitute an additional risk factor for early onset of atherogenic changes.     

Lipoprotein(a) and its position among other risk factors of atherosclerosis

Lipoprotein(a) [Lp(a)] comprises of an LDL particle and apolipoprotein(a) [apo(a)] and its elevated levels are considered a risk factor for atherosclerosis. The aim of our study was to find out whether elevated Lp(a) levels are associated with increased risk of atherosclerosis in patients with multiple other risk factors. We further tested the association of three polymorphisms of the apo(a) gene promoter with Lp(a) levels. No significant correlation was detected between Lp(a) levels and lipid and clinical parameters tested. The study demonstrated a significantly (p=0.0219) elevated Lp(a) level (mean 28+/-35 mg/dl, median 0.14) in patients with coronary heart disease (CHD). In a group with premature CHD the correlation was not significant anymore. There was a significant correlation between polymorphic loci of the promoter region of apo(a) gene and Lp(a) levels (+93C T, p=0.0166, STR, p<0.0001). Our study suggests that elevated Lp(a) level is an independent risk factor of CHD in carriers of other important CHD risk factors. Observed association of sequence variants of the promoter of apo(a) gene with Lp(a) levels is caused in part due to linkage to a restricted range of apo(a) gene length isoforms.     

Apolipoproteins and atherosclerosis. Apolipoprotein E and apolipoprotein(a) as candidate genes of premature development of atherosclerosis

Apolipoprotein E (apoE) is a plasma lipoprotein which plays a basic role in the degradation of particles rich in cholesterol and triglycerides. It is able to bind to LDL receptors, but also to receptors for chylomicron remnants. There are three major apoE isoforms, E2, E3, and E4. Their role in lipoprotein metabolism is related to their affinity for receptors. Allele E3 is predominant and apoE3 affects metabolism of lipoproteins in a standard way. When compared to allele E3, allele E2 is associated with lower LDL levels, whereas allele E4 with higher LDL levels. This has an impact on the progression of atherosclerosis. Allele E2 exhibits a protective role, whereas allele E4 is associated with a high risk factor. Lipoprotein(a) [Lp(a)] is a plasma lipoprotein, consisting of apolipoprotein(a), linked by a covalent bond with the LDL particle. Increased Lp(a) levels are associated with an increased incidence of diseases based on atherosclerosis, namely the ischemic heart disease. Another effect of Lp(a) is its competition with plasminogen, resulting in a decrease of fibrinolysis and thrombogenic activity. ApoE and Lp(a) are independent risk factors for premature development of atherosclerosis and therefore can be considered as candidate genes of premature atherosclerosis.     

Protein composition of Lp(a) lipoprotein from human plasma

The apolipoprotein composition of purified human Lp(a) lipoprotein was investigated by SDS--polyacrylamide gel electrophoresis and immunochemically. The lipoprotein contains two different polypeptides. One is identical by its app. Mr of approximately 250 000 and immunologically with apolipoprotein B of LDL (B-100). The other polypeptide has a higher app. Mr (approximately 350 000) and stains strongly with the periodate-Schiff's reagent. This high-Mr glycoprotein contains the specific Lp(a) immunoreactivity but does not react with antibodies against apo B. Apo B and Lp(a)-protein seem to be linked by disulfide bonds in the native lipoprotein. The unreduced detergent delipidized protein moiety from Lp(a) lipoprotein shows a single band of Mr approximately 700 000 in SDS--polyacrylamide gel electrophoresis and the immunoprecipitates formed against anti-Lp(a) and anti-apo B by the unreduced protein show a reaction of immunological identity.