PPAR在动脉粥样硬化发生与发展中的作用

动脉粥样硬化(AS)是一种以动脉壁脂质蓄积为特征的复杂病变过程。过氧化酶体增殖物激活型受体(PPAR)是核内孤儿受体家族成员,它作为脂质和脂蛋白代谢的调节物,可以调控血浆胆固醇及甘油三酯的水平、促进脂肪细胞分化、影响巨噬细胞内胆固醇内稳态、稳定斑块、抑制血小板聚积从而影响AS的发生和发展。PPAR可通过对基因转录的调控来调理脂质代谢紊乱,并在血管壁水平直接产生抗AS作用。     

极低密度脂蛋白受体研究进展

极低密度脂蛋白受体 (VLDL R)属于低密度脂蛋白受体 (LDL R)超家族 ,结构上与LDL R极为相似 ,而在结合特性、组织分布及生理功能上存在较大的差异 .近年来的研究表明 ,VLDL R配体结合域中的重复序列参与配体的结合 ,并已初步确定受体N端的 4个重复序列中含有与配体结合的重要位点 ;在哺乳动物体内 ,VLDL R主要分布于脂代谢活跃的组织细胞 ,如 :心肌、骨骼肌和脂肪组织等 ,表明其与脂质尤其是甘油三酯的代谢密切相关 ;动脉粥样硬化 (AS)的病变斑块组织中该受体的表达量很高 ,推测VLDL R参与了AS的病变过程 ;在不同的细胞内 ,VLDL R及其亚型的表达并不一致 ,并发现与各种生理、病理变化相关 ,已经发现多种转录因子参与VLDL R表达的调控 ;基因敲除研究也不断揭示VLDL R新的功能意义 ,特别是发现了VLDL R在脑的发育过程中的重要信号作用 ,这些研究已使人们对VLDL R有了新的更全面的认识     

原发性肾病综合征高脂血症发生机制的研究进展

原发性肾病综合征高脂血症主要表现为血浆总胆固醇（Ch）和低密度脂蛋白胆固醇（LDL—Ch）明显升高,甘油三酯（TG）和极低密度脂蛋白胆固醇（VLDL—Ch）升高。高密度脂蛋白胆固醇（HDL—Ch）浓度可降低或不变,但HDL的亚型分布异常,即HDL3增加而HDL2减少。这提示我们HDL3转变为富含CH的HDL2成熟障碍。不过,关于高脂血症在肾病综合征的发生机制较为复杂,还不十分清楚。但是目前有关该机制的观点主要集中在（1）低白蛋白血症刺激肝脏合成胆固醇、甘油三酯、脂蛋白增加,（2）外周脂蛋白的清除障碍,（3）高密度脂蛋白（HDL）的成熟障碍,本文就此做一综述。     

低密度脂蛋白胆固醇升高在家兔动脉粥样硬化发生发展中的意义

目的：观察低密度脂蛋白胆固醇（LDL-c）对家兔动脉粥样硬化（AS）形成的影响,探讨AS的发生机制.方法：以高脂饲料复制家兔实验性AS模型,分阶段检测家兔血清胆固醇（TC）、甘油三脂（TG）、高密度脂蛋白胆固醇（HDL-c）和低密度脂蛋白胆固醇（LDL-c）含量;观察主动脉内膜病理学变化;分析主动脉内膜增生程度及AS斑块面积与血浆脂蛋白水平的相关性.结果：高脂组家兔主动脉粥样硬化面积和内膜增生程度明显较对照组增加（P〈0.01）,血浆LDL-c水平明显较对照组升高（P〈0.01）;动脉内膜增生程度及AS斑块面积均与血浆LDL-c水平呈非常显著正相关（r=0.837,P〈0.001）.结论：提示血浆LDL-c水平升高,是致AS发生发展的重要原因.     

高脂血症的合理治疗

血脂即血中所含脂质的总称,其中主要包括胆固醇(TC)、甘油三酯(TG)、磷脂和脂肪酸。由于脂质代谢或运转异常使血浆中一种或几种脂质高于正常称为高脂血症,可表现为高胆固醇血症、高甘油三酯血症或两者兼有(混合型高脂血症)。脂质不溶于水或微溶于水,必须与载脂蛋白结合以脂蛋白形式存在,才能在血液循环中运转,因此高脂血症常为高脂蛋白血症的反映。     

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。     

脂蛋白脂酶与糖尿病心肌病

脂蛋白脂酶(lipoprotein lipase,LPL)通过水解血浆中富含甘油三酯(triglyceride,TG)的脂蛋白,为心肌组织提供游离脂肪酸(free fatty acid,FFA)供能。糖尿病期间,由于心肌组织减弱对葡萄糖的利用能力,导致心脏供能不足。此时,机体通过一系列机制上调心肌LPL活性,促进血浆极低密度脂蛋白(very low density lipoprotein,VLDL)和乳糜微粒(chylomicrons,CM)的水解,以增强FFA为心肌组织代偿性供能。糖尿病患者通过上调心肌LPL活性,进而促使血浆FFA浓度显著升高,导致大量活性氧、脂质等在心肌细胞内蓄积,并潜在地诱发糖尿病心肌病(diabetic cardiomyopathy,DCM)。因此,本文主要针对糖尿病对心肌LPL的调控机制及LPL如何潜在地诱发DCM做一综述,以期为DCM提供新的治疗靶点和途径。     

磷脂转移蛋白的功能及其表达调节

磷脂转移蛋白（PLTP）是调控脂蛋白代谢的间接影响物质,它被认为是高密度脂蛋白（HDL）代谢的关键酶。PLTP不但特异性介导脂蛋白间磷脂的转移和交换,还介导HDL的转化及修饰HDL的大小和组成。此外,PLIP还能调节极低密度脂蛋白（VLDL）的分泌,促进VLDL转化成HDL。最近研究报道,PLTP能够有助于胆固醇外流,起到抗动脉粥样硬化分子作用。因此,PLTP的基因表达间接地调控脂蛋白的代谢。     

肝脏在高甘油三酯血症中的作用

高甘油三酯血症(HTG)是心脑血管疾病的独立危险因子。肝脏在甘油三酯的合成和分解代谢过程中起着十分重要的作用,肝脏甘油三酯合成过剩或／和甘油三酯分解障碍,均能使血浆甘油三酯升高,形成HTG。肝脏甘油三酯合成过剩的因素包括一些参与甘油三酯合成的酶活性增加;甘油三酯分解代谢延缓的因素包括Angpt13和肝脏X受体(LXR)功能加强,肝脂酶活性受抑制,ApoE2和ApoCⅢ含量升高;既能使甘油三酯合成增加,也能使甘油三酯分解代谢延缓的因素包括餐后,ApoAⅡ与胆固醇酯转移蛋白(CETP)的协同作用等。     

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…     

Hepatic denervation impairs the assembly and secretion of VLDL-TAG

VLDL secretion is a regulated process that depends on the availability of lipids, apoB and MTP. Our aim was to investigate the effect of liver denervation upon the secretion of VLDL and the expression of proteins involved in this process. Denervation was achieved by applying a 85% phenol solution onto the portal tract, while control animals were treated with 9% NaCl. VLDL secretion was evaluated by the Tyloxapol method. The hepatic concentration of TAG and cholesterol, and the plasma concentration of TAG, cholesterol, VLDL-TAG, VLDL-cholesterol and HDL-cholesterol were measured, as well as mRNA expression of proteins involved in the process of VLDL assembly. Hepatic acinar distribution of MTP and apoB was evaluated by immunohistochemistry. Denervation increased plasma concentration of cholesterol (125.3 +/- 10.1 vs. 67.1 +/- 4.9 mg dL(-1)) and VLDL-cholesterol (61.6 +/- 5.6 vs. 29.4 +/- 3.3 mg dL(-1)), but HDL-cholesterol was unchanged (45.5 +/- 6.1 vs. 36.9 +/- 3.9 mg dL(-1)). Secretion of VLDL-TAG (47.5 +/- 23.8 vs. 148.5 +/- 27.4 mg dL h(-1)) and mRNA expression of CPT I and apoB were reduced (p < 0.01) in the denervated animals. MTP and apoB acinar distribution was not altered in the denervated animals, but the intensity of the reaction was reduced in relation to controls.     

Macrophage lipoprotein lipase modulates the development of atherosclerosis but not adiposity

The role of macrophage lipoprotein lipase (LpL) in the development of atherosclerosis and adiposity was examined in macrophage LpL knockout (MLpLKO) mice. MLpLKO mice were generated using cre-loxP gene targeting. Loss of LpL in macrophages did not alter plasma LpL activity or lipoprotein levels. Incubation of apolipoprotein E (ApoE)-deficient β-VLDL with peritoneal macrophages from ApoE knockout mice lacking macrophage LpL (MLpLKO/ApoEKO) led to less cholesteryl ester formation than that found with ApoEKO macrophages. MLpLKO/ApoEKO macrophages had reduced intracellular triglyceride levels, with decreased CD36 and carnitine palmitoyltransferase-1 mRNA levels compared with ApoEKO macrophages, when incubated with VLDL. Although both MLpLKO/ApoEKO and ApoEKO mice developed comparable hypercholesterolemia in response to feeding with a Western-type diet for 12 weeks, atherosclerosis was less in MLpLKO/ApoEKO mice. Epididymal fat mass and gene expression levels associated with inflammation did not differ between the two groups. In conclusion, macrophage LpL plays an important role in the development of atherosclerosis but not adiposity.     

The recycling of apolipoprotein E in primary cultures of mouse hepatocytes. Evidence for a physiologic connection to high density lipoprotein metabolism

Internalization of apoE-containing very low density protein (VLDL) by hepatocytes in vivo and in vitro leads to apoE recycling and resecretion. Because of the role of apoE in VLDL metabolism, apoE recycling may influence lipoprotein assembly or remnant uptake. However, apoE is also a HDL protein, and apoE recycling may be related to reverse cholesterol transport. To investigate apoE recycling, apoE(-/-) mouse hepatocytes were incubated (pulsed) with wild-type mouse lipoproteins, and cells and media were collected at chase periods up to 24 h. When cells were pulsed with VLDL, apoE was resecreted within 30 min. Although the mass of apoE in the media decreased with time, it could be detected up to 24 h after the pulse. Intact intracellular apoE was also detectable 24 h after the pulse. ApoE was also resecreted when cells were pulsed with HDL. When apoA-I was included in the chase media after a pulse with VLDL, apoE resecretion increased 4-fold. Furthermore, human apoE was resecreted from wild-type mouse hepatocytes after a pulse with human VLDL. Finally, apoE was resecreted from mouse peritoneal macrophages after pulsing with VLDL. We conclude that 1) HDL apoE recycles in a quantitatively comparable fashion to VLDL apoE; 2) apoE recycling can be modulated by extracellular apoA-I but is not affected by endogenous apoE; and 3) recycling occurs in macrophages as well as in hepatocytes, suggesting that the process is not cell-specific.     

ApoAⅠ促进THP-1源性泡沫细胞ApoE分泌的研究

目的通过建立动脉粥样硬化损伤部位细胞模型,观察ApoAI对THP—l源性泡沫细胞ApoE分泌的影响,探讨ApoAI与ApoE之间是否存在相互关系以及这种关系对动脉粥样硬化的影响。方法采用聚乙二醇-6000（PEG-6000）沉淀法制备人血浆HDL,再利用凝胶过滤柱层析法分离ApoA I;佛波酯（PMA）诱导THP-1单核细胞分化为巨噬细胞,氧化型低密度脂蛋白（oxidized low density lipoprotein,OXLDL）使分化后THP-1细胞荷脂,建立动脉粥样硬化细胞模型;ELISA检测不同浓度ApoAI（0,5,10,15,25ug／m1）及不同孵育时间（0．3,6,12,24h）,THP—1源性泡沫细胞ApoE的分泌;RT—PCR检测细胞ApoEmRNA的表达情况。结果ApoAI增加THP-1源性泡沫细胞ApoE的分泌量;且ApoE蛋白质的分泌随着ApoAI孵育时间增加而增加,在24hApoE的分泌量达最大;在剂量试验中,ApoE的分泌量随着ApoAI剂量的增加有增加趋势,ApoAI浓度为25μmol／L时,ApoE分泌量最大;而却oE基因的表达不受ApoAI的影响。结论-定浓度的ApoAI促进THP-1源性泡沫细胞ApoE的分泌,且具有时间及剂量依赖性。而在基因水平上,ApoAI对ApoEmRNA表达没有影响。     

High molecular weight adiponectin reduces apolipoprotein B and E release in human hepatocytes

Low circulating levels of high molecular weight adiponectin (HMW-Apm) have been linked to dyslipidaemia and systemic HMW-Apm negatively correlates with very low density lipoprotein (VLDL), apolipoprotein B (ApoB), and ApoE and is positively associated with ApoA-I. Therefore, it was investigated whether HMW-Apm alters the hepatic synthesis of ApoB, ApoE, and ApoA-I or the activity of the hepatic ATP-binding cassette transporter A1 (ABCA1), as the main determinant of plasma HDL. HMW-Apm reduces hepatic ApoB and ApoE release whereas ABCA1 protein, activity and ApoA-I were not altered. Global gene expression analysis revealed that hepatic nuclear factor 4-alpha (HNF4-alpha) and HNF4-alpha regulated genes like ApoB are downregulated by HMW-Apm and this was confirmed at the mRNA and protein level. Therefore it is concluded that HMW-adiponectin may ameliorate dyslipidaemia by reducing the hepatic release of ApoB and ApoE, whereas ABCA1 function and ApoA-I secretion are not influenced.     

Insulin suppression of VLDL apo B secretion is not mediated by the LDL receptor

Insulin inhibits hepatic very low density lipoprotein (VLDL) apo B secretion in rats. Current studies test whether the insulin effect is LDL receptor-mediated by examining the effect of insulin on VLDL apo B secretion in hepatocytes derived from Ldlr-/- and control mice. Primary hepatocytes were incubated overnight with media containing 14C-leucine and either 0.1nM (basal) or 200nM insulin. Afterwards, secreted VLDL B100 and B48 were quantitated. Insulin reduced 14C-labeled B100 and B48 comparably in control and Ldlr-/- hepatocytes with a 62+/-12% vs. 59+/-12% decrease in B100, and a 56+/-11% vs. 61+/-9% decrease in B48. Results indicate: (1) mouse hepatocytes respond to insulin by reducing VLDL apo B output; (2) both VLDL B100 and B48 secretion are suppressed; and (3) insulin inhibition of VLDL apo B secretion is retained in Ldlr-/- hepatocytes.     

Remnant lipoprotein particles are taken up into myocardium through VLDL receptor--a possible mechanism for cardiac fatty acid metabolism

The VLDL (very low-density lipoprotein) receptor is a peripheral lipoprotein receptor expressing in fatty acid active tissues abundantly. In the Balb/c fasting mice, VLDL receptor as well as LPL (lipoprotein lipase), FAT (fatty acid translocase)/CD36, H-FABP (heart-type fatty acid-binding protein), ACS (acyl-CoA synthetase) and LCAD (long-chain acyl-CoA dehydrogenase) expressions increased. An electron microscopic examination indicated the lipid droplets that accumulated in the hearts of fasting Balb/c mice. During the development of SD (Sprague-Dawley) rats, VLDL receptor, LPL, FAT/CD36, H-FABP, ACS, and LCAD mRNAs concomitantly increased with growth. However, PK (pyruvate kinase) mRNA expression was negligible. In cultured neonatal rat cardiomyocytes, VLDL receptor expression increased with days in culture. Oil red-O staining showed that cardiomyocytes after 7 days in culture (when the VLDL receptor protein is present) accumulated beta-migrating VLDL. Thereby, we showed that the cardiac VLDL receptor pathway for delivery of remnant lipoprotein particles might be part of a cardiac fatty acid metabolism.     

Metabolism of two forms of apolipoprotein B of VLDL by rat liver

Apolipoprotein B (apoB) is composed of metabolically distinct fractions of higher molecular weight (apoBh) and lower molecular weight (apoBl). When 125I-labeled very low density lipoprotein (VLDL) prepared from recirculating liver perfusates was injected into rats, labeled apoBl was preferentially removed from the plasma and apoBh entered low density lipoprotein (LDL). The time-related movement of labeled apoBh into higher density fractions was independent of that of labeled apoBl. When 125I-labeled triglyceride-rich lipoprotein (TRL) prepared from sucrose-fed rats was incubated with plasma from rats injected with heparin and then studied in a recirculating liver perfusion, apoBl was preferentially removed compared to apoBh. Thus, the loss of apoBl of hepatic VLDL in vivo was similar to the loss of apoBl of lipase-treated TRL in vitro. In control perfusions where TRL was incubated with heat-treated postheparin plasma, not only was there less initial hepatic clearance of apoB but the early phase of preferential apoBl removal during 30 min of perfusion was not observed. ApoE removal from perfusates was the same whether or not the TRL had been treated with heparin-releasable lipases. Apoprotein degradation, as indicated by the appearance in the perfusate of labeled degradation products, occurred 30 min after the preferential phase of apoBl removal. These results suggest that hepatic clearance of VLDL and TRL remnants is favored by lipolysis and by the presence of apoBl on the particle that enhances their hepatic binding and degradation.     

兔主动脉平滑肌细胞低密度脂蛋白受体相关蛋白(LRP)的诱导表达调节

在兔主动脉平滑肌细胞 ( SMC)培养基中分别加入正常低密度脂蛋白 ( N- LDL)、氧化低密度脂蛋白 ( ox- LDL)、正常极低密度脂蛋白 ( N- VLDL)、氧化极低密度脂蛋白 ( ox- VLDL)和 β-极低密度脂蛋白 (β- VLDL )培养 2 4 h后 ,用定量 RT- PCR和配体结合实验检测平滑肌细胞 LRP的m RNA和蛋白质水平的表达 .结果表明 :五种脂蛋白均能在转录和翻译水平诱导兔主动脉平滑肌细胞的 LRP表达 ,尤以富含胆固醇的 N- LDL ,ox- LDL和β- VLDL的刺激作用更明显 .用胆固醇单独或与脂蛋白共同温育 SMC后 ,发现胆固醇本身可促进 SMC的 LRP蛋白水平的表达 ,脂蛋白与胆固醇的共同刺激作用更为显著 .结果提示 :上述五种脂蛋白对 SMC上 LRP的表达有上调作用 ,其机制可能主要是通过其中的胆固醇来实现的 .     

Lactoferrin effects on phagocytic cell function. I. Increased uptake and killing of an intracellular parasite by murine macrophages and human monocytes

Mouse peritoneal macrophages (MPM) or human blood monocytes (HBM) co-cultured with intracellular (amastigote; AMA) forms of Trypanosoma cruzi in the presence of human lactoferrin (LF) took up greater numbers of organisms than in the absence of LF; the proportion of phagocytes taking up AMA was also significantly increased. Pretreatment of either MPM or AMA with LF also enhanced cell-parasite association. By immunofluorescence, HBM, MPM, and AMA were found to bind LF. By using 125I-labeled LF, each AMA was determined to have an average 1.1 X 10(6) surface receptors for LF. The enhancing effect of LF on cell-parasite association was inhibited when either rabbit anti-LF IgG or alpha-methyl mannoside (alpha-MM) was present during the incubation of MPM or AMA with LF, or when AMA pretreated with LF were then incubated with either of the LF blocking agents. Although these findings seemed to suggest that LF increased MPM-AMA association by bridging these cells, the LF effect was not inhibited when MPM pretreated with LF were subsequently incubated with either alpha-MM or anti-LF. Furthermore, LF stimulated phagocytosis, as denoted by a significant increase in latex particle uptake after LF treatment of MPM. The intracellular killing capacity of HBM or MPM was also stimulated by LF and was denoted by increased AMA destruction after LF treatments. The possibility that LF only appeared to increase the rate of AMA killing by simply promoting the engulfment of greater numbers of AMA that would then be destroyed intracellularly seemed unlikely because untreated MPM that had already taken up untreated AMA killed greater numbers of AMA when they were subsequently incubated with LF. The results of experiments with scavengers of oxygen reduction intermediates and of nitroblue tetrazolium reduction tests indicated that H2O2, O2- and 1O2 were involved in the killing of AMA by LF-treated MPM. These results suggest that LF, a glycoprotein secreted by neutrophils in greater than normal amounts during inflammation, may contribute to macrophage clearance of AMA released from infected host cells.