高脂饮食豚鼠高密度脂蛋白代谢的特点

目的研究豚鼠高脂饮食后高密度脂蛋白代谢的特点,并与大鼠进行比较。方法将豚鼠和大鼠分别随机分为正常组（NC）和高脂组（HF）,正常组均给予普通饲料,高脂组给予高脂饲料诱导10周后,测定血清LDL-C、HDL-C水平,HDL3/HDL2比值和LCAT、CETP的表达;采用real-time RT-PCR方法检测肝脏SR-BI表达的变化。结果与正常组相比,豚鼠高脂组血清HDL-C水平显著升高,高密度脂蛋白亚型HDL3/HDL2的比值升高,血清CETP表达均显著增加,血清LCAT表达下降,肝脏SR-BI mRNA表达水平是正常组的2.27倍。而相同高脂饲料条件下,大鼠的上述指标均无明显变化。结论豚鼠摄入高脂饮食后HDL代谢与大鼠有所不同,主要表现为血清HDL-C升高,肝脏SR-BI受体表达增加,高密度脂蛋白亚型组分发生变化,大颗粒HDL2含量相对减少,小颗粒HDL3堆积,其机制与血清CETP、LCAT的变化密切相关。     

黄连素对高脂血症大鼠降血脂及抗氧化作用

目的:研究黄连素对高脂血症大鼠的降脂作用和抑制肝脏脂质过氧化的作用。方法:随机抽取10只大鼠作为对照组,其余大鼠制作大鼠高血脂模型。成模大鼠随机分为模型组,黄连素低、中、高剂量组和血脂康组,每组10只。各给药组大鼠每天一次给予相应药物灌胃,连续30 d。观察黄连素对高脂血症大鼠血清中总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL)、高密度脂蛋白(HDL)的影响和肝组织二脂酰甘油酰基转移酶(DGAT),羟甲基戊二酸单酰辅酶A(HMG-Co A),胆固醇7α-羟化酶(CYP7A),肝脏甘油三脂脂肪酶(HTGL)以及脂质过氧化产物丙二醛(MDA)含量、超氧化物歧化酶(SOD)与谷胱甘肽过氧化物酶(GSH-Px)活性的影响。结果:与正常组比较,高脂血症组大鼠的肝脏系数、TC、TG、LDL-C、DGAT、HMG-Co A和MDA显著升高(P0.01),HDL-C、CYP7A、HTGL、SOD和GSH-Px显著降低(P0.01)。与高脂血症组比较,黄连素中、高剂量组和血脂康组大鼠肝脏系数、TC、TG、LDL-C、DGAT、HMG-Co A和MDA明显减低(P0.01),HDL-C、CYP7A、HTGL、SOD和GSH-Px显著升高(P0.01);黄连素低剂量组TC、TG、LDL-C、DGAT、HMG-Co A和MDA含量显著降低(P0.05;P0.01),CYP7A和HTGL显著升高(P0.01)。结论:黄连素可降低高血脂大鼠的血脂水平,抑制肝脏脂质过氧化过程,减少肝脏损伤。     

非酒精性脂肪性肝病与MTP关系的实验研究

目的：探讨非酒精性脂肪性肝病( Non-alcoholic fatty liver disease, NAFLD)与微粒体甘油三酯转运蛋白(microsomal triglyceridetransfer protein,MTP）的关系。方法：将雄性Wistar 大鼠60只随机分为正常对照组（A 组）、高脂组（B 组）和MTP 抑制剂组（C 组）,每组各20 只。B 组、C组给予高脂饲料喂养,8 周后确认非酒精性脂肪肝建模成功,C组大鼠给予混有特异性小肠MTP抑制 剂JTT-130 的高脂饲料喂养,B 组大鼠建模过程始终喂养高脂饲料,A 组大鼠喂养普通饲料。于第12周,分别测定大鼠血清甘油 三酯(triglyceride,TG)、总胆固醇(total cholesterol,TC)、高密度脂蛋白胆固醇(high density lipoprotein-cholesterol,HDL-c)含量,以及 肝脏TC、TG、磷脂含量。同时测定肝脏中微粒体甘油三酯转运蛋白(MTP) 的活性与mRNA 表达量。结果：与正常对照组（A组）相 比,高脂组（B组）大鼠血清TC、TG、HDL-c 浓度和肝脏TC、TG含量明显提高（P＜0.05）,MTP 活性及mRNA 水平明显下调（P＜ 0.05）。与高脂组（B 组）比较,MTP 抑制剂组（C 组）大鼠血清TC、TG、HDL-c 浓度和肝脏TC、TG 含量明显下降（P＜0.05）,而 MTP 活性及mRNA 表达量比较无明显差别（P＞0.05）。结论：非酒精性脂肪性肝病存在MTP表达下调,特异性小肠MTP 抑制剂 JTT-130 可以有效抑制肠道对TG的转运,不影响肝脏TG分泌,并在降低高脂大鼠血浆TG和胆固醇水平的同时也降低肝脏TG 含量。     

莲心碱对实验性高脂血症大鼠血脂及脂质过氧化的影响

本文研究莲心碱对实验性高脂血症大鼠血脂和抗氧化能力的影响.将32只大鼠随机分为4组,对照组饲喂基础饲料;诱导组饲喂高脂饲料;试验组给予高脂饲料+莲心碱灌胃2.5和5.0 mg·kg-1.测血清中血脂和丙二醛(MDA)水平,以及谷胱甘肽过氧化物酶(GSH-Px)、超氧化物歧化酶(SOD)活性;取肝脏测绝对和相对肝重及MDA含量.结果表明莲心碱可显著降低实验性高脂血症大鼠血清中总胆固醇、甘油三酯、低密度脂蛋白胆固醇水平和动脉粥样硬化指数;显著升高血清高密度脂蛋白胆固醇、GSH-Px和SOD水平;同时还可显著降低血清和肝脏中MDA的含量;其绝对和相对肝重均低于诱导组.     

双歧杆菌三联活菌肠溶胶囊对高脂饮食所致大鼠非酒精性脂肪肝的疗效及机制探讨

目的 观察微生态制剂贝飞达(双歧杆菌三联活菌肠溶胶囊)治疗高脂饮食所致大鼠非酒精性脂肪肝的疗效并探讨其可能的作用机制.方法 雄性SD大鼠32只,适应性饲养1周后,随机分为3组,正常组:12只给予普通饲料喂养;模型组:12只,贝飞达治疗组:8只,均给予高脂饲料喂养;于喂养12周末正常组及模型组各处死4只,经肝组织HE染色确定造模成功后,贝飞达治疗组给予贝飞达[0.113 g/(kg·d)]灌胃,于16周末全部处死.检测大鼠血清AST、ALT、TC、TG、LDL、HDL、血清内毒素水平,观察其肝组织学变化.结果 模型组于高脂饲料喂养12周末出现脂肪肝,与正常组比较,模型组大鼠血清AST、ALT、TG、TC、LDL、HDL及血清内毒素水平均明显升高(P＜0.01).贝飞达治疗组大鼠各项指标较模型组均有显著改善,肝脏脂肪变性程度减轻.结论 微生态制剂贝飞达可能通过改善肠道菌群紊乱,减轻内毒素血症,从而调节肝脏脂质代谢紊乱,对非酒精性单纯性脂肪肝起到治疗作用.     

氧化鱼油对草鱼(Ctenopharyngodon idelluspond)肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响

为了研究氧化鱼油对草鱼肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响,本研究以豆油、鱼油、氧化鱼油作为饲料脂肪源,分别设计鱼油组(6F)、豆油组(6S)、2%氧化鱼油(2OF)、4%氧化鱼油(4OF)及6%氧化鱼油(6OF)5组等氮、等能半纯化饲料,在池塘网箱养殖平均体重为(74.8±1.2)g草鱼72 d。采用实时荧光定量PCR(q RT-PCR)的方法,测定了草鱼肝胰脏、肠道组织中四种胆固醇合成相关酶HMGCR、SREBP2、CETP、ABCA1和胆汁酸合成关键酶CYP7A1的基因表达活性,结合血清、肝胰脏和肠道TC、TBA含量分析了胆固醇、胆汁酸的合成强度的变化。结果显示:(1)添加氧化鱼油后,草鱼肝胰脏HMGCR基因表达活性显著上调(p0.05),ABCA1和CYP7A1基因表达活性显著下调(p0.05),肝胰脏TC、TBA含量显著增加(p0.05);(2)添加氧化鱼油后,草鱼肠道HMGCR基因表达活性显著上调(p0.05),CYP7A1基因表达活性显著下调(p0.05),肠道TC含量显著增加(p0.05),而TBA含量显著减少(p0.05);(3)添加鱼油或氧化鱼油后,饲料∑PUFA含量与肝胰脏ABCA1基因表达活性呈显著正相关关系(p0.05),饲料MDA含量与肠道ABCA1基因表达活性呈显著负相关关系(p0.05)。结果表明,随着饲料氧化鱼油添加量的增加,在饲料∑PUFA含量减少和鱼油氧化产物MDA含量增加的交互影响下,肝胰脏和肠道细胞胆固醇合成能力、向细胞内转运胆固醇的能力增强,向细胞外转运胆固醇的能力、以胆固醇为原料合成胆汁酸的能力减弱,致使肝胰脏、肠道、血清胆固醇含量增加、而血清、肠道胆汁酸含量减少。肝胰脏胆汁酸含量增加,显示肝胰脏有胆汁酸淤积的发展趋势。预示着鱼体生理代谢可能需要更多的胆固醇以满足生理代谢的需要,而鱼体胆汁酸可能出现供给不足。     

火麻仁油、藻油混合油软胶囊对高胆固醇血症动物模型血脂及脂质过氧化的影响

目的：探讨火麻仁油、藻油混合油软胶囊对高胆固醇血症大鼠血脂及脂质过氧化的影响。方法：50只大鼠随机分为5组,分别是空白对照组、模型对照组、火麻仁油藻油低剂量组（85mg/kg）、火麻仁油藻油中剂量组（170mg/kg）、火麻仁油藻油高剂量组（340mg/kg）,饲喂以高脂饲料及不同剂量火麻仁油藻油,测大鼠体重、脂肪,计算Lees指数、脂体比,检测血清中总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白-胆固醇（LDL-C）、高密度脂蛋白-胆固醇（HDL-C）,以及血清和肝脏中丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性。结果：与正常组相比,模型组大鼠体重、Lees指数、肾脂体比、睾脂体比、总脂体比显著增加（P＜0.01或P＜0.05）,TG、TC、LDL-C含量显著升高,HDL-C显著降低（P＜0.01或P＜0.05）,血清和肝脏中MDA显著升高,SOD显著降低（P＜0.01或P＜0.05）。与模型组比较,火麻仁油、藻油高、中剂量组大鼠体重、睾脂肪比、肾周脂肪比、总脂体比显著降低,TG、TC、LDL-C含量显著降低,HDL-C显著升高（P＜0.01或P＜0.05）,血清和肝脏中MDA含量显著降低,SOD活性升高（P＜0.01或P＜0.05）。结论：对于高胆固醇血症模型大鼠,中、高剂量火麻仁油、藻油混合油的摄入能够有效起到调节血脂、抑制脂质过氧化学作用。     

霍山石斛胶囊对高脂血症大鼠血脂和脂质过氧化水平的影响

目的：探讨霍山石斛胶囊（Dendrobium huoshenese capsule,DHC）对高脂血症大鼠的血脂影响及脂质过氧化水平作用。方法：采用高脂饲料建立实验性高脂血症大鼠模型,而后进行低、中、高三种剂量的DHC和阳性对照药血脂康实验性治疗,实验8周后,取大鼠血清、肝脏,检测模型大鼠血清总固醇（Total cholesterol,TC）、甘油三酯（Triglyceride,TG）、低密度脂蛋白胆固醇（Low density lipoprotein cholesterol,LDL—C）、高密度脂蛋白胆固醇（High density lipoprotein cholesterol,HDL—C）含量,并计算动脉粥样硬化指数（Atherosclerosis index,AI）;同时测定血清和肝脏超氧化物歧化酶（Superoxide dismutase,SOD）活性及丙二醛（Malondialdehyde,MDA）含量;并计算肝系数,制备大鼠肝脏石蜡切片观察其病理学变化。结果：与高脂血症模型组相比,DHC中、高剂量组和血脂康组能显著降低高脂血大鼠血清TC、TG、LDL-C,升高HDL—C,表现为AI降低;低剂量的DHC能升高HDL—C,但在降低血清TC、TG、LDL．C和AI上无统计学差异（P〉0．05）;除DHC低剂量组对血清SOD活性升高作用不显著外（P〉0．05）,其他各浓度给药组均能显著升高血清和肝脏SOD活性,降低血清和肝脏MDA含量及肝系数（P〈0．05,P〈0．01）;同时,DHC各给药组还可不同程度降低高脂血症大鼠肝细胞的脂肪变性程度。结论：霍山石斛胶囊能调节血脂代谢异常,增强抗氧化能力,具有防治脂肪肝和抗动脉粥样硬化作用。     

敌百虫对兔食饵性动脉硬化加速作用

目的:观察低剂量敌百虫对高脂模型兔动脉粥样硬化的作用.方法:新西兰兔32只,随机分为A组:喂饲高脂高胆固醇饲料加敌百虫清晨空腹灌胃(18mg·kg-1·d-1);B 组:单纯喂饲高脂高胆固醇饲料.检测喂饲饲料前和喂饲后5周、10周、15周血清PON1、胆碱酯酶(CHE)、血清总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)、C反应蛋白(CRP)和血糖(GLU):实验第5周、第10周每组处死5只兔,第15周处死全部剩余兔,取主动脉全段,苏丹Ⅳ染色,Photoshop系统测定粥样斑块面积占内膜面积的百分比:检测肝PON1活性及血管内皮依赖性舒张功能(EDRR).结果:喂饲高脂高胆固醇后,A组和B组动物的TC、TG、HDL、LDL、CRP、GLU水平明显增高,但A、B组检测值差异无显著意义(P＞0.05);血清PON1、肝PON1活性降低,但A组PON1活性明显低于B组(P＜0.05);A组和B组动物主动脉EDRR均降低,A组EDRR降低大于B((P＜0.05);喂饲高脂高胆固醇饲料各组动物主动脉均见粥样硬化斑块形成,但A组动脉粥样斑块面积/内膜面积百分比明显高于B组(P＜0.05).结论:敌百虫加速实验性高脂血症动物动脉粥样硬化斑块形成,其机制可能与降低PONl活性有关.     

肝康Ⅳ号对脂肪肝大鼠肝组织脂质含量及形态学的影响

目的探讨肝康Ⅳ号（Gankang Ⅳ,GKⅣ）对脂肪肝（FL）组织胆固醇（TC）、甘油三脂（TG）、超氧化物歧化酶（SOD）、丙二醛（MDA）及形态学的影响。方法64只SPF级Wistar大鼠,随机分为A组、B1组、B2组、B3组、C组、D组。A组、B1组、B2组、B3组、C组给予高脂饲料（84.4%标准饲料＋10%猪油＋0.5%胆固醇＋0.1%胆盐＋5%蛋黄粉）和白酒复合复制大鼠FL模型,B1组、B2组、B3组、C组分别给予肝康Ⅳ号低、中、高剂量和东宝肝泰灌胃干预,设空白对照D组。第6周末处死动物取肝脏制备10%的肝匀浆检测TC、TG、SOD、MDA。检测肝脏病理学。结果（1）TC、TG：B1组、B2组、B3组、C组与A组比较,TC、TG含量明显下降（P〈0.05～0.01）,B2组、B3组与C组比较差异有显著（P〈0.05）。（2）SOD、MDA：B1组、B2组、B3组、C组与A组比较,MDA含量明显下降（P〈0.05～0.01）,SOD水平明显升高（P〈0.05～0.01）;在SOD方面,B1组与C组比较差异有非常显著性（P〈0.01）,B2组与C组比较差异有显著（P〈0.05）;在MDA方面,B1组、B2组、B3组与C组比较差异有非常显著性（P〈0.01）。（3）肝脏病理学：A组为重度脂肪肝,C组、B1组为中度脂肪肝,B2组、B3组脂肪肝程度轻于C组、B1组。结论GKIV能有效降低肝脏组织脂质沉积,防止MDA的升高,SOD的下降;减轻FL程度,呈现量效关系。     

豚鼠：一种良好的高脂血症模型动物

从豚鼠血浆脂蛋白组成、胆固醇和脂蛋白代谢特点等方面阐述了豚鼠与人类的相似性,并对其高脂血症模型的优势进行了评价,为构建豚鼠高脂血症模型并应用于降脂及抗动脉粥样硬化药物的研究提供参考。     

SC-435, an ileal apical sodium-codependent bile acid transporter inhibitor alters mRNA levels and enzyme activities of selected genes involved in hepatic cholesterol and lipoprotein metabolism in guinea pigs

We have demonstrated that SC-435, an apical sodium codependent bile acid transporter (ASBT) inhibitor, lowers plasma low-density lipoprotein cholesterol (LDL-C) concentrations in guinea pigs. The purpose of this study was to further examine the hypocholesterolemic effects of SC-435, by measuring the activity and RNA expression of regulatory enzymes of hepatic cholesterol and lipoprotein metabolism. In addition, the use of a combination (COMBO) therapy with simvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, was also tested. Male Hartley guinea pigs were randomly allocated to one of three diets (n=10 per group), for 12 weeks. The control diet contained no ASBT inhibitor or simvastatin. The monotherapy diet (ASBTi) contained 0.1% of SC-435. The COMBO therapy consisted of a lower dose of SC-435 (0.03%) and 0.05% simvastatin. Cholesterol ester transfer protein (CETP) and HMG-CoA reductase mRNA abundance were determined using RT-PCR techniques. Hepatic HMG-CoA reductase and cholesterol 7-hydroxylase (CYP7) activities were measured by radioisotopic methods. Compared to the control group, CETP activity was 34% and 56% lower with ASBTi and COMBO, respectively. Similarly, CETP mRNA expression was reduced by 36% and 73% in ASBTi and COMBO groups, respectively. Cholesterol 7-hydroxylase and HMG-CoA reductase activities were increased 2-fold with ASBTi and COMBO treatments, respectively. Likewise, HMG-CoA reductase mRNA expression was increased 33% with ASBTi treatment. These results suggest that both SC-435 monotherapy and combination therapy lower LDL cholesterol concentrations by altering both hepatic cholesterol homeostasis and the intravascular processing of lipoproteins in guinea pigs.     

Tissue-specific knockouts of ACAT2 reveal that intestinal depletion is sufficient to prevent diet-induced cholesterol accumulation in the liver and blood

Acyl-CoA:cholesterol acyltransferase 2 (ACAT2) generates cholesterol esters (CE) for packaging into newly synthesized lipoproteins and thus is a major determinant of blood cholesterol levels. ACAT2 is expressed exclusively in the small intestine and liver, but the relative contributions of ACAT2 expression in these tissues to systemic cholesterol metabolism is unknown. We investigated whether CE derived from the intestine or liver would differentially affect hepatic and plasma cholesterol homeostasis. We generated liver-specific (ACAT2(L-/L-)) and intestine-specific (ACAT2(SI-/SI-)) ACAT2 knockout mice and studied dietary cholesterol-induced hepatic lipid accumulation and hypercholesterolemia. ACAT2(SI-/SI-) mice, in contrast to ACAT2(L-/L-) mice, had blunted cholesterol absorption. However, specific deletion of ACAT2 in the intestine generated essentially a phenocopy of the conditional knockout of ACAT2 in the liver, with reduced levels of plasma very low-density lipoprotein and hepatic CE, yet hepatic-free cholesterol does not build up after high cholesterol intake. ACAT2(L-/L-) and ACAT2(SI-/SI-) mice were equally protected from diet-induced hepatic CE accumulation and hypercholesterolemia. These results suggest that inhibition of intestinal or hepatic ACAT2 improves atherogenic hyperlipidemia and limits hepatic CE accumulation in mice and that depletion of intestinal ACAT2 is sufficient for most of the beneficial effects on cholesterol metabolism. Inhibitors of ACAT2 targeting either tissue likely would be beneficial for atheroprotection.     

Expression levels of ACAT1 and ACAT2 genes in the liver and intestine of baboons with high and low lipemic responses to dietary lipids

Acyl–coenzyme A:cholesterol acyltransferase (ACAT) 1 and ACAT2 play an important role in cellular cholesterol esterification and thus modulate intestinal cholesterol absorption and hepatic lipoprotein secretion. The relative expression levels of ACAT1 and ACAT2 in human tissues differ from those in other animals, including nonhuman primates. The present study compared the relative expression levels of ACAT1 and ACAT2 in baboons with high and low lipemic responses to dietary lipids. We isolated RNA and prepared cDNA from frozen liver and small intestine from high- and low-responding pedigreed baboons necropsied after consuming a high-cholesterol and high-fat diet for 18 months. The expression of ACAT1 and ACAT2 was measured by TaqMan real-time quantitative PCR normalized to 18s ribosomal RNA. The expression of ACAT1 was higher than that of ACAT2 in the liver, whereas the expression of ACAT2 was higher than that of ACAT1 in the duodenum and jejunum. There was no difference in the expression of ACAT1 or ACAT2 in the liver and intestine between high- and low-responding baboons except that the expression of ACAT1 was higher in the duodenum of high responders than in that of low responders. Western blot analysis also showed a higher level of ACAT1 protein in the duodenum of high responders than in that of low responders. There was a significant correlation between duodenal ACAT expression levels and total plasma cholesterol concentration in baboons. These results suggest that differences in ACAT1 expression may affect plasma cholesterol concentration and partly affect diet-induced hyperlipidemia.     

缺乏抗坏血酸对豚鼠胆固醇代谢的影响

边缘性缺乏抗坏血酸之豚鼠,于三周内其肝脏及小肠粘膜3-羟-3-甲基戊二酰辅酶A还原酶(HMGR)活力均下降到原有水平的50％,但肝脏胆固醇7α-羟化酶活力尚无显著性改变。坏血病豚鼠(三周内)上述几种酶活力都下降至原有水平的50％左右。豚鼠摄取抗坏血酸不足,其血清总胆固醇浓度显著增加,而血清高密度脂蛋自胆固醇浓度显著减少,其改变程度与抗坏血酸缺乏状况一致。     

肝纤维化动物模型探讨

目的 寻找肝纤维化最佳模型.方法 将Wistar大鼠随机分成血清组、四氯化碳皮下注射组、四氯化碳腹腔注射组,每组30只,各组分别给予猪血清腹腔注射、40%四氯化碳皮下和腹腔注射造模(每周2次),观察造模过程中大鼠死亡情况以及4周及6周各组大鼠肝纤维化的程度.结果 3种方法都能成功制备肝纤维化模型.从动物死亡情况来看,四氯化碳腹腔注射组死亡率明显高于前两组;血清组死亡率最低,但与四氯化碳皮下注射组比较无显著差异;从模型形成时间来看,血清组造模时间较长,明显高于其他两组,四氯化碳皮下注射组与四氯化碳腹腔注射组在模型形成时间上无明显差异.结论 四氯化碳皮下注射组制备肝纤维化模型动物死亡率较低,肝纤维化形成时间较短,是一种制作肝纤维化模型较好的方法.     

Regulation of guinea pig hepatic acyl-coa:cholesterol acyltransferase activity by dietary fat saturation and cholesterol

We measured the interactive effects of dietary cholesterol and fat on the regulation of hepatic acyl-CoA:cholesterol acyltransferase (ACAT) activity and its relationship to hepatic microsomal lipid composition in guinea pigs fed 15 g/100 g (w/w) fat diets (corn oil, olive oil, or lard) with 0.01, 0.08, 0.17, or 0.33 g/100 g (w/w) added cholesterol. Guinea pigs exhibited a dose dependent increase in hepatic microsomal ACAT activity, with increasing levels of cholesterol intake (P < 0.001) in all dietary fat groups. Animals fed monounsaturated olive oil had the highest hepatic ACAT activity with the exception of the 0.33 g/100 g cholesterol diet (P < 0.001). There were no differences in ACAT activity with intake of polyunsaturated corn oil or saturated lard. Dietary cholesterol resulted in increased microsomal free cholesterol (FC) concentrations in a dose dependent manner but had no effects on microsomal phosphatidylcholine (PC) concentrations. Guinea pigs fed olive oil generally had the highest microsomal FC/PC molar ratios, and hepatic ACAT activities correlated significantly with this parameter. After modification of the lipid compositions of the microsomes from guinea pigs fed the 12 test diets with FC/PC liposome treatment, microsomal ACAT activities remained significantly related to the microsomal FC/PC molar ratios, and dietary fat type did not affect this correlation. Our findings do not support the hypothesis that the stimulation of hepatic ACAT activity with cholesterol intake is enhanced by polyunsaturated fat intake. The data demonstrate that although dietary fat type and cholesterol amount have differential effects on hepatic ACAT activity, substrate availability, expressed as microsomal FC/PC molar ratio, is a major regulator of hepatic microsomal ACAT activity.     

FXR-mediated down-regulation of CYP7A1 dominates LXRalpha in long-term cholesterol-fed NZW rabbits

We investigated how cholesterol feeding regulates cholesterol 7alpha-hydroxylase (CYP7A1) via the nuclear receptors farnesoid X receptor (FXR) and liver X receptor alpha (LXRalpha) in New Zealand white rabbits. After 1 day of 2% cholesterol feeding, when the bile acid pool size had not expanded, mRNA levels of the FXR target genes short-heterodimer partner (SHP) and sterol 12alpha-hydroxylase (CYP8B) were unchanged, indicating that FXR activation remained constant. In contrast, the mRNA levels of the LXRalpha target genes ATP binding cassette transporter A1 (ABCA1) and cholesteryl ester transfer protein (CETP) increased 5-fold and 2.3-fold, respectively, associated with significant increases in hepatic concentrations of oxysterols. Activity and mRNA levels of CYP7A1 increased 2.4 times and 2.2 times, respectively. After 10 days of cholesterol feeding, the bile acid pool size increased nearly 2-fold. SHP mRNA levels increased 4.1-fold while CYP8B declined 64%. ABCA1 mRNA rose 8-fold and CETP mRNA remained elevated. Activity and mRNA of CYP7A1 decreased 60% and 90%, respectively. Feeding cholesterol for 1 day did not enlarge the ligand pool size or change FXR activation, while LXRalpha was activated highly secondary to increased hepatic oxysterols. As a result, CYP7A1 was up-regulated. After 10 days of cholesterol feeding, the bile acid (FXR ligand) pool size increased, which activated FXR and inhibited CYP7A1 despite continued activation of LXRalpha. Thus, in rabbits, when FXR and LXRalpha are activated simultaneously, the inhibitory effect of FXR overrides the stimulatory effect of LXRalpha to suppress CYP7A1 mRNA expression.     

Cholesteryl ester transfer protein activity and atherogenic parameters in rabbits supplemented with cholesterol and garlic powder

The current study was conducted to examine the effect of garlic supplementation on CETP activity, along with its anti-atherosclerotic effect in cholesterol-fed rabbits. Rabbits were fed a 1% cholesterol diet for 12 weeks, including a 1% garlic powder supplement. The garlic-supplemented group exhibited significantly lower CETP activity than the control group during the experimental period (P < 0.05). Among the atherogenic parameters, the total cholesterol, TG, LDL-C, VLDL-C, and atherogenic index were all significantly lower in the garlic group than in the control group during the experimental period (P < 0.05), whereas the HDL-C concentration was significantly higher in the garlic group than in the control group after 12 weeks (P < 0.05). Atherosclerotic lesion area in the aorta arch was also significantly lower in the garlic group (P < 0.05). In the morphological examination, the garlic-supplemented group exhibited far fewer fat droplet deposits than the control group. Furthermore, the garlic supplement also lowered the aortic and hepatic cholesterol, and triglyceride. Accordingly, the current results suggest that garlic exerts hypocholesterolemic and/or antiatherogenic and that plasma CETP activity might be a risk marker related with atherogenesis. As such, the inhibition of CETP activity may delay the progression of atherosclerosis, thereby supporting the atherogenicity of CETP and the inhibitory activity of garlic supplementation against CETP.