胆固醇结石患者肝脏LCRα基因的蛋白差异表达及意义

目的:研究胆囊胆固醇结石患者肝脏的核受体基因:肝脏x受体a(liver Xreceptor a,LXRα)、法尼醇受体(famesoid Xreceptor,FXR)、人类固醇异生物受体(steroid xenobiotic receptor,SXR)及肝受体同类物1(liver receptor homolog-1,LRH-1)的蛋白表达,探讨胆固醇结石病的发病机理.方法:23例胆囊胆固醇结石患者(胆石组),12例无胆石症的胆囊息肉患者为对照(对照组).测定胆石胆固醇成分和胆汁脂类成分(胆固醇、磷脂和胆汁酸),并计算胆汁总脂和胆汁胆固醇饱和指数.Western-Blot法测定肝脏LRH-1、FXR、SXR及LXRa基因的蛋白表达量.结果:胆石组胆汁呈胆固醇过饱和;胆汁胆固醇摩尔百分比浓度较对照组升高,P<0.01;胆汁总脂较对照组明显下降,P<0.05;胆汁中胆汁酸和磷脂成分2组比较差异均无统计学意义(P>0.05).胆石组LRH-1蛋白表达高于对照组(0.88±0.05vs 0.69±0.03),P<0.05,LXRa、FXR和SXR表达2组差异无统计学意义(P>0.05).结论:人类肝脏LRH-1的蛋白表达增高与胆囊胆固醇结石形成有关.     

普罗布考通过调控ABCA1、SR-BⅠ、ABCG5、ABCG8表达及抗炎作用抑制高胆固醇血症兔动脉粥样硬化（英文）

作为一种有效的降脂药物,普罗布考能够降低血浆高密度脂蛋白胆固醇(HDL-C)水平并抑制动脉粥样硬化,但其机制尚未完全阐明.本研究的目的旨在进一步阐明普罗布考降脂及抗动脉粥样硬化的机理.将新西兰白兔随机分为4组:正常饮食组、正常饮食+普罗布考组、高脂饮食组(HFD组)、高脂饮食+普罗布考组(HFD+P组).结果显示,处理7周后,与HFD组比较,H FD+P组动脉粥样硬化病变程度、肝脏脂质蓄积明显减轻,血浆甘油三脂、总胆固醇、低密度脂蛋白胆固醇及HDL-C水平降低,肝脏中清道夫受体-BⅠ(SR-BⅠ)以及肝脏与小肠中三磷酸腺苷结合盒转运体(ABC)G5(ABCG5)、ABCG8表达上调,肝脏中A BCA1表达下调,主动脉弓与血浆肿瘤坏死因子α、白介素1、白介素6、单核趋化蛋白1水平降低.这些结果表明普罗布考的抗动脉粥样硬化作用可能与其调控A BCA1、SR-BⅠ、ABCG5、ABCG8表达及抑制促炎介质的分泌有关.     

高胆固醇饲料对雄兔凝血和纤溶系统活性的影响

目的:探讨高胆回醇饲料喂养对兔血液凝血和纤溶系统活性的影响.方法:14只10～12周龄的健康雄性新西兰家兔,随机分为高胆固醇饲料喂养组(高胆固醇组)和普通饲料喂养组(对照组).高胆固醇组以含1%胆固醇的饲料喂饲,每天100 g,自由饮水,对照组给予不合胆固醇的普通饲料喂养,共喂养14周.所有雄兔均分别于高胆固醇饲料喂养前及不同饲料喂养后12周采耳缘静脉血分别测定血脂水平变化及血液凝血和纤溶系统活性变化.结果:①与对照组及基础值相比,高胆固醇组雄兔血中的甘油三酯、总胆固醇、低密度脂蛋白、脂蛋白(a)、载脂蛋白B水平显著升高;②高胆固醇组雄兔血小板活性显著增强、凝血酶原时间及活化部分凝血酶时间缩短、纤维蛋白原含量增加;③高胆固醇组纤溶酶原活性、α2-抗纤溶酶活性较普通组增强.结论:高胆固醇饮食不仅能直接导致高脂血症的形成,还可显著增强血液凝血活性和抑制血液纤溶活性,促进动脉粥样硬化的发生发展.     

亚毒性剂量毒死蜱降低新西兰兔ABCA1表达加重高脂诱导的动脉粥样硬化

为了探讨亚毒性剂量有机磷酸酯杀虫剂毒死蜱对高脂饮食诱导的动脉粥样硬化的影响及其机制,32只健康雄性新西兰兔随机分为对照组、毒死蜱组、高脂组、高脂+毒死蜱组.每天以20 mg/kg亚毒性剂量的毒死蜱灌胃处理6个月.动物处死后检测血脂水平和血清胆碱酯酶活性.收集腹腔巨噬细胞,测定其胆固醇流出率.苏丹Ⅳ染色观察胸主动脉粥样硬化斑块,定量分析动脉粥样硬化斑块占血管内表面积的百分比.颈总动脉石蜡切片,观察动脉粥样硬化斑块.采用实时定量PCR和蛋白质印迹检测,分别检测肝脏、血管和腹腔巨噬细胞中三磷酸腺苷结合盒转运体A1(ATP-binding cassette transporter A1,ABCA1)mRNA和蛋白质的表达.结果显示:与对照组相比,高脂饮食升高了血清总胆固醇和脂蛋白水平,主动脉和颈总动脉出现明显的动脉粥样硬化斑块,其肝脏、主动脉和腹腔巨噬细胞ABCA1的表达升高,腹腔巨噬细胞中胆固醇流出增加;与对照组相比,毒死蜱组血清胆碱酯酶活性降低,但没有出现明显的中毒症状和肝肾功能损伤,血清中高密度脂蛋白(HDL)水平降低,ABCA1的表达降低,腹腔巨噬细胞中胆固醇流出减少;高脂+毒死蜱组与高脂组相比,血清胆碱酯酶活性降低,也没有出现明显的中毒症状和肝肾功能损伤,ABCA1的表达降低,腹腔巨噬细胞中胆固醇流出减少,主动脉和颈总动脉粥样硬化斑块更加明显.结果提示长期暴露于亚毒性剂量的毒死蜱可加速高脂饮食的致动脉粥样硬化作用,其机制可能与毒死蜱降低体内ABCA1的表达和胆固醇流出有关.     

研究: 普罗布考通过调控ABCA1、SR-BⅠ、ABCG5、ABCG8表达及抗炎作用抑制高胆固醇血症兔动脉粥样硬化

作为一种有效的降脂药物,普罗布考能够降低血浆高密度脂蛋白胆固醇(HDL-C)水平并抑制动脉粥样硬化,但其机制尚未完全阐明．本研究的目的旨在进一步阐明普罗布考降脂及抗动脉粥样硬化的机理．将新西兰白兔随机分为4组：正常饮食组、正常饮食+普罗布考组、高脂饮食组(HFD组)、高脂饮食+普罗布考组(HFD+P组)．结果显示,处理7周后,与HFD组比较,HFD+P组动脉粥样硬化病变程度、肝脏脂质蓄积明显减轻,血浆甘油三脂、总胆固醇、低密度脂蛋白胆固醇及HDL-C 水平降低,肝脏中清道夫受体-BⅠ(SR-BⅠ)以及肝脏与小肠中三磷酸腺苷结合盒转运体(ABC)G5(ABCG5)、ABCG8表达上调,肝脏中ABCA1表达下调,主动脉弓与血浆肿瘤坏死因子α、白介素1、白介素6、单核趋化蛋白1水平降低．这些结果表明普罗布考的抗动脉粥样硬化作用可能与其调控ABCA1、SR-BⅠ、ABCG5、ABCG8表达及抑制促炎介质的分泌有关．     

乙醇预防兔胆囊胆固醇结石的实验研究

实验兔３０只平均分三组：Ａ组饲正常饲料,Ｂ组饲含１．２％胆固醇和０．５％胆盐的高胆固醇饲料,Ｃ组饲高胆固醇饲料和乙醇。乙醇提供总热卡的３０％。一个月后抽血测甘油三酯及胆固醇,并剖腹取胆囊及肝胆管胆汁,观察胆囊成石率和测各种胆汁成分。结果：Ｃ组胆囊内无结石形成,血清胆固醇和胆囊胆汁中的胆固醇、磷脂、钙等明显低于Ｂ组,提示乙醇对胆囊胆固醇结石有预防作用     

大米蛋白调控成熟期大鼠LDLR基因及蛋白表达

为了探讨大米蛋白对成熟期大鼠胆固醇代谢调控因子一低密度脂蛋白受体（low—densitv lipoprotein receptor．LDLR）的调控作用,以18周龄雄性Wistar成熟期大鼠为研究对象,应用大米蛋白及酪蛋白为食物蛋白源,饲喂无胆固醇及富含胆固醇饲料,经18日自由摄食后,测定实验鼠血浆总胆固醇、血浆高密度胆固醇水平及肝脏LDLR基因及蛋白表达水平。对照酪蛋白,大米蛋白均能显著降低大鼠血浆总胆固醇、血浆非高密度胆固醇水平及动脉粥样硬化指数,并且,显著刺激肝脏LDL基因及蛋白表达水平。实验结果表明,大米蛋白降低成熟期大鼠血浆胆固醇水平的作用功效与膳食胆固醇添加与否无关,大米蛋白降胆固醇的作用机制之一是能够有效刺激LDLR的表达,从而抑制LDL—C的转运入血。     

银灵通胶囊调节实验性高脂饮食大鼠血脂的研究

目的:探究银灵通胶囊对脂质代谢的影响及其机制。方法:建立大鼠高脂模型,用药后检测其血脂、丙二醛(MDA)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)的活性,检测肝脏组织的高密度脂蛋白受体SR-BI、低密度脂蛋白受体(LDLR)、氧化低密度脂蛋白(ox-LDH)受体CD36蛋白表达的mRNA表达水平,检测血管组织学变化。结果:高脂饮食明显升高大鼠血清中总胆固醇(CH)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)和动脉硬化指数(AI值),银灵通胶囊组可降低上述指标,且呈一定的浓度依赖;高脂饮食可增加肝脏中SR-BI及CD36表达,降低LDLR表达,银灵通胶囊引起SR-BI的过度表达,使LDLR表达增加,CD36表达下降。高脂饮食使血清中MDA的含量增加,给予银灵通胶囊后,明显降低血清MDA的含量。结论:银灵通胶囊具有调节脂质代谢,抗动脉粥样硬化(AS)及抗脂质过氧化作用。其机制与银灵通胶囊能引起肝脏中SR-BI的过度表达及LDLR表达增加,降低肝脏中CD36表达和血清MDA含量有关。     

高脂饮食性非酒精性脂肪性肝病小鼠肝脏脂代谢相关基因的改变

目的:分析非酒精性脂肪性肝病(NAFLD)小鼠肝脏中脂代谢相关基因的表达变化。方法:12周龄成年雄性C57BL/J6小鼠,随机分为对照组及NAFLD组。对照组予以普通饲料,NAFLD组予以高脂饮食喂养8周。分别测定两组小鼠肝功能、血脂及肝脂的变化,苏木精-伊红(HE)及油红O染色后光学显微镜下观察肝脏的形态结构和脂肪变性情况,并用实时荧光定量PCR(qPCR)法检测肝脏脂代谢重要基因的变化。结果:与对照组比较,NAFLD组小鼠的血清总甘油三酯(TG)、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)及肝脏TG、肝脏TC水平均显著升高(P0.05)。HE和油红O染色显示NAFLD组小鼠发生了显著的肝脏脂质沉积。此外,NAFLD组小鼠肝脏中脂肪酸转位酶(CD36)表达水平显著高于对照组,而硬脂酰辅酶A去饱和酶1(SCD1)、固醇调控元件结合蛋白(SREBP1c)表达水平在两组小鼠中无统计学差异。结论:高脂饮食诱导的脂肪肝中CD36表达上调,可能参与了NAFLD的发病机制。     

PCSK9/LDLR通路介导姜黄素烟酸酯促进HepG2摄取脂质

为研究PCSK9/LDLR通路介导姜黄素烟酸酯(CurTn)降低血浆低密度脂蛋白胆固醇(LDL-C),减少动脉内膜下脂质沉积的分子机制,用5、10、15μmo/L姜黄素烟酸酯与25 mg/L LDL共孵育Hep G2细胞24 h,分别采用油红O染色、胆固醇荧光定量试剂盒、Di I-LDL摄取检测细胞内胆固醇含量及LDL摄取情况,用逆转录定量聚合酶链反应(RT-Q-PCR)检测LDLR及SREBP2的m RNA表达,蛋白质印迹检测LDLR、SREBP2及PCSK9蛋白表达.随姜黄素烟酸酯作用浓度的增高细胞内脂滴显著增多,细胞内游离胆固醇(FC)、总胆固醇(TC)含量增高,细胞内胆固醇摄取增多;RT-Q-PCR和蛋白质印迹检测发现,与对照组(Control)比较,5、10、15μmo/L姜黄素烟酸酯处理组LDLR蛋白表达增高,SREBP2 mRNA表达水平升高,PCSK9蛋白表达降低,但对LDLR mRNA及SREBP2蛋白表达无影响.结果表明:姜黄素烟酸酯通过降低PCSK9、减少LDLR降解、升高LDLR蛋白表达,促进HepG2细胞胆摄取胆固醇.初步说明CurTn可能通过抑制PCSK9介导LDLR溶酶体降解,促进肝脏清除血浆LDL-C水平.     

Susceptibility to murine cholesterol gallstone formation is not affected by partial disruption of the HDL receptor SR-BI

High density lipoprotein (HDL) promotes reverse cholesterol transport from peripheral tissues to the liver where its cholesterol is secreted preferentially into bile. The scavenger receptor class B type I (SR-BI) is believed to play a pivotal role in unloading HDL cholesterol and its ester to hepatocytes. Here, using male SR-BI "att" mice with a dysfunctional mutation in the Sr-b1 promoter, we studied whether approximately 50% of normal SR-BI expression influences gallstone susceptibility in these mice fed a lithogenic diet containing 1% cholesterol, 0.5% cholic acid and 15% butterfat. Our results showed that the disruption of SR-BI expression reduced cholesterol secretion by 37% in the chow-fed state and 10% on the lithogenic diet, and while delaying incidence slightly, did not influence cumulative susceptibility to cholesterol gallstones. The lithogenic diet induced marked increases in biliary cholesterol and phospholipid secretion rates but not of bile salts. Basal expression of hepatic SR-BI protein was dissimilar in both wild-type and SR-BI mice, and remained unaltered in response to the lithogenic diet. By two independent dual isotope methods, intestinal cholesterol absorption was unimpaired by attenuation of the SR-BI which also displays low-density expression on small intestinal enterocytes. We conclude that although HDL cholesterol is a principal source of biliary cholesterol in the basal state, uptake of cholesterol from chylomicron remnants appears to be the major contributor to biliary cholesterol hypersecretion during diet-induced cholelithogenesis in the mouse.     

Effect of beta-muricholic acid on the prevention and dissolution of cholesterol gallstones in C57L/J mice

This study investigated whether beta-muricholic acid, a natural trihydroxy hydrophilic bile acid of rodents, acts as a biliary cholesterol-desaturating agent to prevent cholesterol gallstones and if it facilitates the dissolution of gallstones compared with ursodeoxycholic acid (UDCA). For gallstone prevention study, gallstone-susceptible male C57L mice were fed 8 weeks with a lithogenic diet (2% cholesterol and 0.5% cholic acid) with or without 0.5% UDCA or beta-muricholic acid. For gallstone dissolution study, additional groups of mice that have formed gallstones were fed chow with or without 0.5% beta-muricholic acid or UDCA for 8 weeks. One hundred percent of mice fed the lithogenic diet formed cholesterol gallstones. Addition of beta-muricholic acid and UDCA decreased gallstone prevalence to 20% and 50% through significantly reducing biliary secretion rate, saturation index, and intestinal absorption of cholesterol, as well as inducing phase boundary shift and an enlarged Region E that prevented the transition of cholesterol from its liquid crystalline phase to solid crystals and stones. Eight weeks of beta-muricholic acid and UDCA administration produced complete gallstone dissolution rates of 100% and 60% compared with the chow (10%). We conclude that beta-muricholic acid is more effective than UDCA in treating or preventing diet-induced or experimental cholesterol gallstones in mice.     

Effect of dietary garlic and onion on biliary proteins and lipid peroxidation which influence cholesterol nucleation in bile

Formation of cholesterol gallstones in gallbladder is controlled by procrystallizing and anticrystallizing factors present in bile. Dietary garlic and onion have been recently observed to possess anti-lithogenic potential in experimental mice. In this investigation, the role of biliary proteins from rats fed lithogenic diet or garlic/onion-containing diet in the formation of cholesterol gallstones in model bile was studied. Cholesterol nucleation time of the bile from lithogenic diet group was prolonged when mixed with bile from garlic or onion groups. High molecular weight proteins of bile from garlic and onion groups delayed cholesterol crystal growth in model bile. Low molecular weight (LMW) proteins from the bile of lithogenic diet group promoted cholesterol crystal growth in model bile, while LMW protein fraction isolated from the bile of garlic and onion groups delayed the same. Biliary LMW protein fraction was subjected to affinity chromatography using Con-A and the lectin-bound and unbound fractions were studied for their influence on cholesterol nucleation time in model bile. Major portion of biliary LMW proteins in lithogenic diet group was bound to Con-A, and this protein fraction promoted cholesterol nucleation time and increased cholesterol crystal growth rate, whereas Con-A unbound fraction delayed the onset of cholesterol crystallization. Biliary protein from garlic/onion group delayed the crystallization and interfered with pronucleating activity of Con-A bound protein fraction. These data suggest that apart from the beneficial modulation of biliary cholesterol saturation index, these Allium spices also influence cholesterol nucleating and antinucleating protein factors that contribute to their anti-lithogenic potential.     

Disruption of the sterol carrier protein 2 gene in mice impairs biliary lipid and hepatic cholesterol metabolism.

Hepatic up-regulation of sterol carrier protein 2 (Scp2) in mice promotes hypersecretion of cholesterol into bile and gallstone formation in response to a lithogenic diet. We hypothesized that Scp2 deficiency may alter biliary lipid secretion and hepatic cholesterol metabolism. Male gallstone-susceptible C57BL/6 and C57BL/6(Scp2(-/-)) knockout mice were fed a standard chow or lithogenic diet. Hepatic biles were collected to determine biliary lipid secretion rates, bile flow, and bile salt pool size. Plasma lipoprotein distribution was investigated, and gene expression of cytosolic lipid-binding proteins, lipoprotein receptors, hepatic regulatory enzymes, and intestinal cholesterol absorption was measured. Compared with chow-fed wild-type animals, C57BL/6(Scp2(-/-)) mice had higher bile flow and lower bile salt secretion rates, decreased hepatic apolipoprotein expression, increased hepatic cholesterol synthesis, and up-regulation of liver fatty acid-binding protein. In addition, the bile salt pool size was reduced and intestinal cholesterol absorption was unaltered in C57BL/6(Scp2(-/-)) mice. When C57BL/6(Scp2(-/-)) mice were challenged with a lithogenic diet, a smaller increase of hepatic free cholesterol failed to suppress cholesterol synthesis and biliary cholesterol secretion increased to a much smaller extent than phospholipid and bile salt secretion. Scp2 deficiency did not prevent gallstone formation and may be compensated in part by hepatic up-regulation of liver fatty acid-binding protein. These results support a role of Scp2 in hepatic cholesterol metabolism, biliary lipid secretion, and intracellular cholesterol distribution.     

The Syrian golden hamster strain LPN: a useful animal model for human cholelithiasis

The purpose of this study was to specify the main mechanisms at the origin of gallstone formation in very young (5-week old) or young adult (9-week old) LPN hamsters fed a sucrose-rich (normal lipid) lithogenic diet for one and four weeks, respectively. It was also to compare these mechanisms in the two strains of hamsters (LPN and Janvier) or when an anti-lithiasic diet was given by substituting 10% of the sucrose by beta cyclodextrin. The LPN strain of hamsters showed a very high incidence of cholesterol gallstones (73%) after receiving the lithogenic diet. The gallstone formation is very rapid and occurs in less than one week in very young hamsters which show a high cholesterol synthesis rate in the liver. The cholesterol and phospholipid concentrations in the bile, cholesterol saturation index (CSI) and hydrophobic index (HI) increased significantly, concomitantly with a higher liver cholesterol synthesis in very young hamsters and with a lower bile acid synthesis (neutral pathway: cholesterol 7alpha-hydroxylase, CYP7A1 and acidic pathway: sterol 27 hydroxylase, CYP27A1) in young adult hamsters. No significant changes in the lipoprotein receptor expression (LDLr, SR-BI) were observed after feeding the lithogenic diet. Adding ten per cent beta-cyclodextrin, a cyclic oligosaccharide that binds cholesterol and bile acids to the lithogenic diet at the expense of sucrose, induced a decrease in cholesterol bile secretion and in the CSI and HI and prevented cholesterol gallstone formation. Similarly, another strain of Syrian Golden hamsters (" Janvier ") which originally exhibited a smaller bile cholesterol concentration, lower liver cholesterol synthesis and higher CYP7A1/CYP27A1 activity ratio did not carry cholesterol gallstones when fed the lithogenic diet. The main parameters always found at the origin of cholelithiasis in the Hamster are discussed: a higher hepatic cholesterogenesis (HMGCoAR), a higher HMGCoAR/CYP7A1 activity ratio, a lower cholesterol ester storage capacity, a higher CYP27A1/CYP7A1 activity ratio correlated to a higher cholesterol secretion in the bile and higher CSI and HI. In LPN hamsters, the incidence of cholesterol gallstones is nil when CSI + HI < 0.8 and positive for CSI + HI > 0.9. An overall comparison of the data obtained in LPN Hamsters and in Man suggests that this hamster strain appears to be an interesting model for human cholelithiasis.     

Increased expression of LXR alpha, ABCG5, ABCG8, and SR-BI in the liver from normolipidemic, nonobese Chinese gallstone patients

Cholesterol supersaturation of bile is one prerequisite for gallstone formation. In the present study of Chinese patients with gallstones, we investigated whether this phenomenon was correlated with the hepatic expression of genes participating in the metabolism of cholesterol and bile acids. Twenty-two nonobese, normolipidemic patients (female-male, 11:11) with gallstones were investigated with 13 age- and body mass index-matched gallstone-free controls (female-male, 10:3). The bile from the gallstone patients had higher cholesterol saturation than that from the controls. The mRNA levels of ABCG5, ABCG8, and liver X receptor alpha (LXRalpha) in the gallstone patients were increased by 51, 59, and 102%, respectively, and significantly correlated with the molar percentage of biliary cholesterol and cholesterol saturation index (CSI). The mRNA and protein levels of the hepatic scavenger receptor class B type I (SR-BI) were increased, and a significant correlation was found between the protein levels and the CSI. No differences were recorded between the two groups concerning the hepatic synthesis of cholesterol, bile acids, and esterification of cholesterol. Our results suggest that the upregulation of ABCG5/ABCG8 in gallstone patients, possibly mediated by increased LXRalpha, may contribute to the cholesterol supersaturation of bile. Our data are consistent with the possibility that increased amounts of biliary cholesterol may originate from plasma HDL cholesterol by enhanced transfer via SR-BI.     

Phosphatidylcholine-enriched diet prevents gallstone formation in mice susceptible to cholelithiasis

Cholesterol gallstones affect approximately 10-15% of the adult population in North America. Phosphatidylcholine (PC) is considered to be the main cholesterol solubilizer in bile. This study examined the effect of a PC-enriched diet on gallstone incidence in mice susceptible to cholelithiasis. The result obtained showed that the feeding of a lithogenic (LG) diet for 4 weeks or 8 weeks resulted in cholesterol gallstone incidences of 47% and 89%, respectively. These gallstone incidences were either reduced or prevented when the LG diet was enriched with 2% or 6% PC, respectively. The cholesterol saturation index (CSI) was reduced only in mice fed with LG + 6% PC diet as compared with mice fed the LG diet alone. However, in all groups, the CSI was significantly higher than in mice fed Purina chow diet. The biliary anionic polypeptide fraction (APF) was significantly increased in mice fed the LG + 2% PC diet and was reduced in those fed with LG + 6% PC diet. In conclusion, prevention or delay of gallstone formation was not due to a consistent effect on biliary lipid composition, suggesting a direct effect of PC on cholesterol solubilization and/or the effect of an additional nonlipid biliary component such as APF.     

Secretory phospholipase A2 increases SR-BI-mediated selective uptake from HDL but not biliary cholesterol secretion

High density lipoprotein cholesterol represents a major source of biliary cholesterol. Secretory phospholipase A2 (sPLA2) is an acute phase enzyme mediating decreased plasma HDL cholesterol levels. Clinical studies reported a link between increased sPLA2 expression and the presence of cholesterol gallstones. The aim of our study was to investigate whether the overexpression of human sPLA2 in transgenic mice affects biliary cholesterol secretion and gallstone formation. Liver weight (P < 0.01) and hepatic cholesterol content (P < 0.01) were significantly increased in sPLA2 transgenic mice compared with controls as a result of increased scavenger receptor class B type I (SR-BI)-mediated hepatic selective uptake of HDL cholesterol (P < 0.01), whereas hepatic SR-BI expression remained unchanged. However, biliary cholesterol secretion as well as fecal neutral sterol and fecal bile salt excretion remained unchanged in sPLA2 transgenic mice. Furthermore, gallstone prevalence in response to a lithogenic diet was identical in both groups. These data demonstrate that i) increased flux of cholesterol from HDL into the liver via SR-BI as a result of phospholipase modification of the HDL particle translates neither into increased biliary and fecal sterol output nor into increased gallstone formation, and ii) increased sPLA2 expression in patients with cholesterol gallstones might be a consequence rather than the underlying cause of the disease.     

Antilithiasic effect of beta-cyclodextrin in LPN hamster: comparison with cholestyramine

Beta-Cyclodextrin (BCD), a cyclic oligosaccharide that binds cholesterol and bile acids in vitro, has been previously shown to be an effective plasma cholesterol lowering agent in hamsters and domestic pigs. This study examined the effects of BCD as compared with cholestyramine on cholesterol and bile acid metabolism in the LPN hamster model model for cholesterol gallstones. The incidence of cholesterol gallstones was 65% in LPN hamsters fed the lithogenic diet, but decreased linearly with increasing amounts of BCD in the diet to be nil at a dose of 10% BCD. In gallbladder bile, cholesterol, phospholipid and chenodeoxycholate concentrations, hydrophobic and lithogenic indices were all significantly decreased by 10% BCD. Increases in bile acid synthesis (+110%), sterol 27-hydroxylase activity (+106%), and biliary cholate secretion (+140%) were also observed, whereas the biliary secretion of chenodeoxycholate decreased (-43%). The fecal output of chenodeoxycholate and cholate (plus derivatives) was increased by +147 and +64%, respectively, suggesting that BCD reduced the chenodeoxycholate intestinal absorption preferentially. Dietary cholestyramine decreased biliary bile acid concentration and secretion, but dramatically increased the fecal excretion of chenodeoxycholate and cholate plus their derivatives (+328 and +1940%, respectively). In contrast to BCD, the resin increased the lithogenic index in bile, induced black gallstones in 34% of hamsters, and stimulated markedly the activities of HMG-CoA reductase (+670%), sterol 27-hydroxylase (+310%), and cholesterol 7alpha-hydroxylase (+390%). Thus, beta-cyclodextrin (BCD) prevented cholesterol gallstone formation by decreasing specifically the reabsorption of chenodeoxycholate, stimulating its biosynthesis and favoring its fecal elimination. BCD had a milder effect on lipid metabolism than cholestyramine and does not predispose animals to black gallstones as cholestyramine does in this animal model.