ACEI改善糖尿病大鼠的糖代谢紊乱

目的 利用血管紧张素转换酶抑制剂(ACEI)阻断肾素-血管紧张素系统(RAS),研究阻断RAS改善胰岛素抵抗及糖代谢的作用机制,探讨脂肪组织局部RAS与胰岛素抵抗的关系.方法 30只雄性Wistar大鼠随机分为正常对照组(NC组)、高脂组(HF组)和高脂干预组(AE组),分别以基础饲料喂养、高脂喂养、高脂加培哚普利[4 mg/(kg·d)]干预喂养12周.干预结束后HF组和AE组给予链脲佐菌素(STZ)20 mg/kg小剂量腹腔注射诱导成模,2周后3组大鼠分别行口服葡萄糖耐量试验(OGTY)及计算稳态模型评估.胰岛素抵抗指数(HOMA-IR),评价胰岛素抵抗和糖代谢,处死大鼠,以RT-PCR法检测附睾和肾周脂肪组织脂联素、抵抗素、纤溶酶原激活物抑制剂(PAI)-1 mRNA的表达.结果 与NC组(n=10)比较,HF组(n=7)大鼠OGTY各时点血糖、血糖曲线下面积(AUC)、HOMA-IR显著升高,PAI-1、抵抗素mRNA表达显著增加,分别是NC组的1.50倍、1.47倍,脂联素mRNA的表达下降了40.8%(均P＜0.01);与HF组比较,AE组(n=9)大鼠OGTT各时点血糖有所下降,60、120 min血糖差异有显著性(P＜0.05),AUC、HOMA-IR显著减少,PAI-1、抵抗素mRNA表达较HF组分别下降了28%、38.1%,脂联素mRNA表达升高为HF组的1.62倍(P均＜0.05).结论 ACEI可以改善长期高脂喂养联合STZ诱导大鼠的胰岛素抵抗和糖代谢紊乱,其作用机制可能与改善内脏脂肪组织的脂肪因子表达相关.     

肾素血管紧张素系统在非酒精性脂肪性肝病发病机制中的实验研究

目的 探讨肝组织肾素血管紧张素系统在非酒精性脂肪性肝病(NAFLD)发病机制中的作用.方法 取Wistar大鼠24只均分为模型组和对照组.对照组予正常饮食,模型组予高脂饮食,8周后处死大鼠,测定血清肝功能、血脂、血糖和胰岛素,分别以HE染色和苦味酸-天狼星红染色进行肝组织病理学观察,ELISA法测定肝组织血管紧张素Ⅱ(AngⅡ)浓度,免疫组织化学法测定肝组织转化生长因子(TGF)-β1表达水平.结果 模型组大鼠高脂喂养8周后,体质量、肝指数、肝功能、血脂、血胰岛素显著高于对照组[体质量:(463.50±22.72)g比(405.12±10.32)g;肝指数:(3.75±0.21)比(2.66±0.15);ALT:(79.8±8.6)U/L比(58.8±11.6)U/L; AST:(200.01±51.72) U/L比(150.30±37.27)U/L;胆固醇:(3.67±0.48)mmol/L比(1.50±0.23)mmol/L;三酰甘油:(2.06±0.40) mmol/L比(0.71±0.34) mmo1/L;胰岛素:(17.37±2.89)pmol/L比(11.08±2.12) pmol/L],差异均有统计学意义(均P＜0.01).模型组大鼠病理组织学均出现明显的肝脂肪变性,且部分出现小叶内和汇管区炎性反应,部分肝组织出现明显的纤维化改变.模型组大鼠肝组织AngⅡ[(32.80±2.81) pg/ml]较对照组[(22.83±1.75)pg/ml]高(t=9.559,P＜0.01).免疫组织化学检测显示模型组TGFβ1表达量明显高于对照组(Z=--2.540,P=0.011).Spearman相关性分析显示,大鼠肝组织内AngⅡ浓度增加程度与肝脂肪变积分(r=0.644,P=0.002)和TGF-β1表达量(r=0.470,P=0.037)均呈正相关.结论 AngⅡ和TGF-β1在NAFLD模型大鼠的肝组织内浓度明显增加,肾素血管紧张素系统可能参与了NAFLD的发生和发展.     

TGFβ1和CTGF在非酒精性脂肪性肝炎肝组织中的表达及意义

目的:探讨非酒精性脂肪性肝炎(NASH)患者肝脏转化生长因子β1(TGFβ1)和结缔组织生长因子(CTGF)的表达及二者在脂肪性纤维化发展过程中的相关性.方法:采用HE染色,光镜下观察21例非酒精性脂肪性肝炎组(NASH组)肝组织和10例正常肝组织组标本肝组织的病理改变;RT-PCR及免疫组织化学技术分别检测以上两组标本中TGFβ1和CTGF的表达情况.结果:光镜下非酒精性脂肪性肝炎组出现明显炎症反应和纤维化.免疫组化结果显示非酒精性脂肪性肝炎组肝脏TGFβ1和CTGF的表达显著高于正常肝脏组(109.52±4.50 VS 1 14.47±2.00,117.07±3.60 VS 125.05±3.37,均P＜0.01).NASH组TGFβ1和CTGF mRNA的表达水平升高明显,与对照组比较差异有统计学意义(0.66±0.07 VS 0.46±0.04,0.59±0.08VS 0.41±0.05,均P＜0.05).结论:TGFβ1和CTGF在非酒精性脂肪性肝炎中的表达升高可能参与了脂肪性肝炎向肝纤维化转变,CTGF可能在诊断和治疗非酒精性脂肪性肝炎中扮演重要的作用.     

肾素-血管紧张素系统与脂肪代谢研究进展

肾素-血管紧张素系统(RAS)的多种成分可在脂肪组织中表达。在鼠类动物模型中,RAS促进脂肪细胞生长、分化,甘油三酯储存,细胞肥大,体脂沉积;而在人类成熟脂肪细胞,血管紧张素Ⅱ抑制前体脂肪细胞分化,使脂肪异位沉积在肝脏、骨骼、胰岛组织,从而形成胰岛素抵抗。抑制RAS系统的药物,如血管紧张素转换酶抑制剂、血管紧张素受体拮抗剂可能改善肥胖相关的高血压、脂代谢紊乱、胰岛素抵抗,从而减少2型糖尿病的发生。     

二甲双胍对高糖高脂饮食诱导的糖尿病大鼠脂肪肝的干预作用

目的 观察高糖、高脂饮食诱导的糖尿病大鼠肝脏病理改变,探讨二甲双胍的干预作用.方法 40只SD大鼠随机分为正常对照(NC)组、糖尿病对照(DM-C)组和DM+二甲双胍干预(DM-M)组.比较各组生化指标、肝重及肝脏指数的改变.HE染色观察大鼠肝脏形态学变化;免疫组化法检测肿瘤坏死因子α(TNF-α)在肝脏的表达.结果 高糖、高脂饲养4周后诱导大鼠出现胰岛素抵抗;8周成功建立T2DM大鼠模型.18周末 DM-C 组大鼠肝脏出现严重脂肪变性,TNF-α在肝脏的蛋白表达水平增加(P<0.01).经二甲双胍治疗后,DM-M组大鼠肝脏脂肪变性程度明显减轻,TNF-α的蛋白表达水平下降(P<0.05).结论 二甲双胍可降低高糖、高脂饮食诱导的糖尿病大鼠肝脏脂肪含量,降低TNF-α在肝组织的蛋白表达,对治疗2型糖尿病脂肪肝具有一定的作用.     

国产罗格列酮对实验性树鼩肝脂肪变性的保护作用

目的探讨国产罗格列酮对高糖高脂喂养诱导树鼩肝脂肪变性干预治疗的效果.方法36只树鼩分为对照组8只(A组),喂常规鼠饲料.另28只喂高糖高脂饲料,并于22周将血糖≥11.1mmol/L的19只动物再分为药物干预组8只(B组)和非干预组11只(C组).B组以国产罗格列酮按每天5 mg/kg的剂量清晨一次性给药,用药7周.实验前、后检测体重(Wt)、空腹血糖(FBG)、血脂4项[总胆固醇(TC),三酰甘油(TG),高密度脂蛋白胆固醇(HDL-C),低密度脂蛋白胆固醇(LDL-C)]、空腹血清胰岛素(FINS)和血清转氨酶水平.实验结束时剖腹取肝标本,光镜下观察肝脏形态学改变,以免疫组化法检测肝脏解偶联蛋白3(UCP3)和胰岛素受体β(IR-β)的表达水平,以计算机图像分析系统对UCP3、IR-β表达作细胞阳性计数和面积密度及灰度分析.结果(1)血生化改变B、C两组动物FBG均明显增高,实验结束时C组的血糖仍居高不下,同时血TC、TG增加值、FINS和自身稳定模型评估法胰岛素抵抗指数(HOMA-IR)也明显增高,而B组的FBG则显著下降,其他生化参数也均与对照组相似.(2)肝脏形态学B、C两组动物均出现弥漫性肝脂肪变性,脂肪变性的面积密度和肝细胞脂变率均在30%左右,两组差异均无显著性.实验结束时,B组肝脂肪变性显著改善,C组则进一步加重.(3)免疫组化分析C组IR-β表达明显强于A组(P＜0.01);正常肝细胞不表达UCP3,C组肝细胞表达UCP3的面积密度和细胞阳性率均明显小于B组(P＜0.01);肝肪脂变性面积密度与UCP3面积密度(r=-0.86,P=0.001)和细胞阳性率(r=-0.79,P＜0.001)呈负相关.结论国产罗格列酮可能通过改善胰岛素抵抗、提高胰岛素敏感性、促进肝脏UCP3的表达,对实验性树鼩肝脂肪变性起防治作用.     

阻断肾素血管紧张素系统通过下调iNOS改善糖尿病大鼠胰岛功能

目的 研究阻断肾素血管紧张素系统(RAS)对糖尿病大鼠胰岛功能的影响.方法 以高脂饮食结合小剂量腹腔注射链脲佐菌素(30 mg/kg)的方法建立糖尿病大鼠模型,分别以培哚普利4 mg·kg-1·d-1(AE组,n=10)和缬沙坦40 mg·kg-1·d-1(AR组,n=10)干预.8周后行静脉葡萄糖耐量试验检测胰岛β细胞功能,以RT-PCR检测胰岛血管紧张素原(AGT)和胰岛素mRNA的表达,以TUNEL法检测胰岛细胞凋亡,以免疫组化法检测胰岛局部诱导型NO合酶(iNOS)及细胞内胰岛素水平等.结果 与正常对照组(n=10)相比,糖尿病组(n=8)早期胰岛素分泌指数(EISI)降低了81.1%,胰岛AGT表达增加了69.2%,单位面积胰岛细胞凋亡计数增加了2.1倍,局部iNOS相对浓度增加了23.0%(均P＜0.01);培哚普利或缬沙坦干预后,EISI分别增加了1.84和1.74倍,胰岛AGT表达分别降低了21.4%和23.4%,胰岛凋亡细胞计数分别降低了79.0%和36.3%,局部iNOS相对浓度分别下降了16.5%和18.9%(均P＜0.01).AE、AR组之间差异无统计学意义.结论 阻断RAS可以改善糖尿病大鼠胰岛功能,其机制可能与下调胰岛局部iNOS表达,减弱氧化应激对胰岛的损伤有关.     

己酮可可碱对非酒精性脂肪肝大鼠肝组织线粒体解耦联蛋白表达的影响

目的 探讨己酮可可碱(PTX)对非酒精性脂肪肝性肝病(NAFLD)大鼠线粒体解耦联蛋白(UCP)-2 mRNA表达的影响. 方法 SD大鼠60只,正常喂养1周后随机分为3组,每组20只.其中对照组20只,以普通饲料喂养,实验组和干预组各20只,以高脂饲料喂养,干预组高脂饮食4周后,在饮水中加用已酮可可碱(PTX)(100 mg·Kg-1·d-1),于第24周处死,采用反转录聚合酶链反应(RT-PCR)技术检测肝脏UCP-2mRNA的表达. 结果 对照组大鼠肝脏UCP2mRNA呈微量表达(1.2±0.1),实验组大鼠肝脏UCP2mRNA呈强表达(4.0±0.3),干预组大鼠肝脏UCP2mRNA呈弱表达(3.0±0.2),3组间UCP-2mRNA表达差异有统计学意义(F=160.67,P＜0.01). 结论 己酮可可碱可下调NAFLD大鼠肝细胞UCP-2mRNA的表达.     

析因设计评价血管紧张素转换酶抑制剂与血管紧张素Ⅱ1型受体拮抗剂单用及联用治疗不同分期糖尿病肾病的效果

糖尿病肾病(DN)的早期干预可望逆转肾功能.肾素-血管紧张素系统(RAS)参与了DN的发生发展,血管紧张素转换酶抑制剂(ACEI)和血管紧张素Ⅱ(AngⅡ)1型受体拮抗剂(ARB)分别阻断RAS的不同环节发挥肾功能保护作用.本研究采用2×3析因设计分别观察DN不同分期以及RAS单纯阻断和双重阻断的干预效果.     

沙库巴曲缬沙坦对老年射血分数中间值的心力衰竭患者左心室射血分数和重构的影响

目的对比分析沙库巴曲缬沙坦、肾素血管紧张素系统(RAS)阻滞剂对老年射血分数中间值的心力衰竭(HFmrEF)患者临床疗效。方法选取中国心力衰竭数据库中老年HFmrEF患者278例,根据抗心力衰竭口服药分为血管紧张素转换酶抑制剂(ACEI)组99例、血管紧张素受体拮抗剂(ARB)组84例、血管紧张素受体脑啡肽酶抑制剂(ARNI)组95例,对比分析各组治疗前、治疗1、3个月LVEF、左心室舒张末期内径(LVEDD)及N末端B型钠尿肽前体(NT-proBNP)水平。结果 ACEI组、ARB组、ARNI组NT-proBNP、LVEDD均呈逐渐下降趋势,LVEF呈逐渐上升趋势(P_(时间)=0.000);3组LVEF和LVEDD的变化趋势,差异有统计学意义(F_(交互)=9.459,P=0.000;F_(交互)=3.043,P=0.027)。与ARNI组比较,ACEI组和ARB组治疗1、3个月LVEF明显升高[(46.70±5.06)%和(47.09±5.39)%vs(44.88±7.07)%,(49.28±5.38)%和(50.77±6.02)%vs(45.08±7.77)%,P0.05],ACEI组治疗1个月LVEDD明显降低,但治疗3个月LVEDD明显升高(P0.05)。结论 RAS阻滞剂较沙库巴曲缬沙坦能更有效的提高HFmrEF患者LVEF,而对于逆转左心室大小方面,可能稍劣于沙库巴曲缬沙坦。     

二甲双胍降低大鼠肝脏胆固醇和甘油三酯含量的机制探讨

目的 观察二甲双胍对长期高饱和脂肪酸饲养大鼠肝脏腺苷酸活化蛋白激酶α(AMPKα)和PPARα表达和活性的影响,探讨二甲双胍降低肝脏胆固(TC)和甘油三酯(TG)含量的可能机制.方法 Wistar雄性大鼠30只,随机等分为:对照组(C组)、高脂组(HF组)和高脂加二甲双胍组(Met组,高脂喂养4个月,第5个月加用二甲双胍胃1个月),喂养共5个月,测定血清、肝脏组织中的TC和TG含量;分别应用实时PCR、Western印迹检测肝脏AMPKα 和PPARα 的基因转录、蛋白表达和活性水平;PPARα 转录因子DNA结合活性测定用ELISA法.结果 与C组比较,HF组大鼠肝脏AMPKα2和PPAα mRNA表达水平显著降低(均P＜0.05);AMPKα 蛋白表达及活性显著降低(均P＜0.05),PPARα蛋白表达及DNA结合活性分别降低 48.6%、21.6%(均P＞0.05); 肝脏TC、TG含量(均P＜0.05)和血TC、TG水平(均P＜0.01)均显著增高.与HF组比较,Met组肝脏AMPKα2 mRNA和蛋白表达及活性显著增高(均P＜0.05),PPARα蛋白表达增高56.5%(P＞0.05),其DNA结合活性显著增高(P＜0.05);肝脏TC、TG含量血TC、TG水平均显著降低(均P＜0.05).结论 二甲双胍降低长期高脂饲养所致的大鼠肝脏、血中TC、TG水平的增高,可能与其激活肝细胞AMPKα及PPARα有关.     

白藜芦醇对大鼠非酒精性脂肪肝的疗效及其机制

目的 观察白藜芦醇对非酒精性脂肪肝的治疗效果,并初步探讨其机制. 方法 Wistar大鼠3组(每组10只):正常对照(NC)组以标准饲料喂养,高脂饲料喂养(HF)组和白藜芦醇治疗(RT)组以高脂饲料喂养,RT组第7周开始加用白藜芦醇治疗(100mg·kg-1·d).在第16周结束实验,以正糖-高胰岛素钳夹术评价大鼠胰岛素抵抗;肝脏石蜡切片HE染色观察病理学改变;Western blot技术检测肝脏内5'-磷酸腺苷活化白激酶(AMPK)的磷酸化水平. 结果 HF组与NC组相比,内脏脂肪和肝指数增高(P<0.05);空腹胰岛素水平增高,葡萄糖输注率下降(t=10.554,P<0.01);光学显微镜下肝脏出现明显脂肪变性;肝组织内AMPK磷酸化水平降低到NC组的45.8%(t=8.384,P<0.01).白藜芦醇干预后,内脏脂肪指数显著下降(P<0.01);空腹胰岛素水平降低,葡萄糖输注率明显增高(t=5.866,P<0.01);光学显微镜下的肝脏脂肪变性得到明显改善;肝组织内的AMPK磷酸化水平提高到NC组的70.2%(t=3.816,P<0.01).结论 白藜芦醇通过AMPK途径可以同时改善胰岛素抵抗和减少肝脏脂质沉积,从而改善脂肪肝.     

白藜芦醇对高脂饮食大鼠骨骼肌不同线粒体亚群氧化、抗氧化水平和胰岛素敏感性的影响

目的 观察白藜芦醇对高脂饮食大鼠骨骼肌不同线粒体亚群氧化、抗氧化水平及胰岛素敏感性的影响.方法 8周龄雄性SD大鼠分为普通饮食组(NC组)、高脂饮食组(HF组)及白藜芦醇干预高脂饮食组(HFR组);干预8周后检测各组大鼠骨骼肌肌膜下(SS)及肌纤维间(IMF)线粒体氧化应激及抗氧化水平,并观察各组大鼠整体及骨骼肌胰岛素敏感性的变化.结果 与NC组相比,HF组大鼠胰岛素敏感性明显下降(P＜0.05),SS及IMF线粒体活性氧簇(ROS)和丙二醛的水平明显增加,SS线粒体抗氧化酶活性均下降,而IMF线粒体抗氧化酶活性均增高(均P＜0.05).与HF组相比,HFR组胰岛素敏感性明显改善,SS及IMF线粒体的抗氧化酶活性均明显增高,ROS和丙二醛的含量明显下降到NC组水平(均P＜0.05).结论 白藜芦醇对高脂饮食大鼠骨骼肌不同线粒体亚群氧化应激水平均有明显的改善作用,并且显著增加其胰岛素敏感性.     

Oxidative stress,KLF6 and transforming growth factor-beta up-regulation differentiate non-alcoholic steatohepatitis progressing to fibrosis from uncomplicated steatosis in rats

BACKGROUND/AIMS: Pathogenesis of non-alcoholic steatohepatitis (NASH) remains poorly understood. Cytochrome P450 2E1 (CYP 2E1), cytokines, oxidative stress and activation of hepatic stellate cells seem to play a role in this process. The aim was to determine the potential implication of these factors in the progression from uncomplicated steatosis to steatohepatitis with progressive fibrosis. METHODS: Animals were fed a standard diet, a 5% orotic acid-diet (OA) developing hepatic steatosis, or the methionine-choline deficient (MCD) diet inducing steatohepatitis for 2 and 6 weeks. Lipid peroxidation, CYP 2E1 expression and activity, expression of UCP-2, interleukin (IL)-6, transforming growth factor (TGF)beta1, KLF6 mRNAs, and activation of hepatic stellate cells were examined by gas chromatography, high-performance liquid chromatography, Western blotting, quantitative polymerase chain reaction and immunohistochemistry. RESULTS: Lipid peroxidation increased in the MCD model whereas only minor changes occurred in the OA model. KLF6 and TGFbeta1 mRNAs were selectively up-regulated in MCD animals. Stellate cell activation, inflammation and collagen deposition only occurred in the MCD group. CYP 2E1 expression and activity increased in the OA group while both decreased in MCD animals. UCP-2 and IL-6 mRNA increased in both groups. CONCLUSIONS: In the context of steatosis, lipid peroxidation is associated with inflammation and stellate cell activation with concomitant increase in TGFbeta1 production, possibly through up-regulation of KLF6.     

Effects of Momordica charantia on insulin resistance and visceral obesity in mice on high-fat diet

We examined the preventive effect of Momordica charantia L. fruit (bitter melon) on hyperglycemia and insulin resistance in C57BL/6J mice fed with a high-fat (HF) diet. Firstly, mice were divided randomly into two groups: the control group was fed low-fat (LF) diet, whereas the experimental group was fed with a 45% HF diet last for 12 weeks. After 8 week of induction, the HF group was subdivided into six groups and was given orally with or without M. charantia or rosiglitazone 4 weeks afterward. We demonstrated that bitter melon was effective in ameliorating the HF diet-induced hyperglycemia, hyperleptinemia, and decreased the levels of blood glycated hemoglobin (HbA1c) and free fatty acid (FFA) (P < 0.01, P < 0.05, P < 0.05, respectively), whereas increased the adipose PPARγ and liver PPARα mRNA levels. Additionally, bitter melon significantly decreased the weights of epididymal white adipose tissue and visceral fat, and decreased the adipose leptin and resistin mRNA levels. It is tempting to speculate that at least a portion of bitter melon effects is due to be through PPARγ-mediated pathways, resulting in lowering glucose levels and improving insulin resistance, and partly be through PPARα-mediated pathways to improve plasma lipid profiles. This is the first report demonstrating that bitter melon, is a food factor, but not a medicine, itself could influence dual PPARα/PPARγ expression and the mediated gene expression, is effective in ameliorating insulin resistance and visceral obesity.     

马来酸罗格列酮干预高脂饲养大鼠脂肪肝的研究

目的观察高脂饲养所致正常SD大鼠脂肪肝与胰岛素抵抗的关系及罗格列酮干预脂肪肝的效果。方法将8周龄雄性SD大鼠随机分为三组，每组各11只：正常饲养组（NC）、高脂饲养组（HF）、高脂＋罗格列酮组（HF4-Ros）。饲养8周后取空腹血测定血糖、脂联素，胰岛素敏感性用正常血糖高胰岛素钳夹术稳态时的葡萄糖输注率（GIR）来评价，测定肝脏中TG含量，并对大鼠肝脏组织做HE染色。结果高脂饲养8周后，与NC组相比，HF组肝脏呈现明显脂肪肝，肝脏中TG明显增加达154．2％（NC组3．89mg／g，HF组9．89mg／g，P〈0．01）；与HF组相比，HF4-Ros组肝脏中TG显著降低达46．6％（5．28mg／g，P〈0．01），脂肪肝减轻。结论马来酸罗格列酮能明显改善高脂饲养大鼠的脂肪肝。     

Expression of the adiponectin receptors AdipoR1 and AdipoR2 in lean rats and in obese Zucker rats

The adiponectin receptors, AdipoR1 and AdipoR2, are thought to transmit the insulin-sensitizing effects of adiponectin, an adipokine secreted by adipocytes. Modifications of their expression in insulin-sensitive tissues (skeletal muscle, liver, and adipose tissue) could therefore play a role in the control of insulin sensitivity and the development of insulin resistance. Recent data in mice supported this possibility. We examined whether the expression of adiponectin receptors (messenger RNA [mRNA] concentrations) is controlled in vivo in rats (Wistar) by nutritional factors (high-fat [HF] vs high-carbohydrate diet, fasting vs fed state) and whether this expression is decreased in an experimental model of insulin resistance, the obese Zucker rat. In Wistar rats, neither an HF diet nor fasting modified the mRNA concentrations of AdipoR1 in muscle, liver, or adipose tissue; the only modification observed was a decrease (P < .05) in AdipoR2 mRNA level in the liver of rats fed with an HF diet. In obese Zucker rats compared with their lean controls, neither AdipoR1 nor AdipoR2 expression was modified in muscle. AdipoR2 expression was slightly decreased in adipose tissue, whereas the expression of both AdipoR1 and AdipoR2 was increased (P < .05) in the liver of obese Zucker rats. In conclusion, contrary to what was reported in mice, the expression of adiponectin receptors in rats is poorly responsive to changes in nutritional conditions and is not decreased in a model of insulin resistance. These results do not support an important role for the expression of AdipoR1 and AdipoR2 in the modulation of sensitivity to insulin.     

高脂饲养大鼠脂代谢调控基因的表达与胰岛素抵抗的关系及机制

目的探讨高脂饲养SD大鼠脂代谢基因表达的改变与胰岛素抵抗（IR）的关系。方法8周龄雄性SD大鼠随机分为3组：正常饲养组（NC,10只）、高脂饲养组（HF,10只）、高脂饲养＋吡格列酮15mg·kg^-1·d^-1进行灌胃组（HP,12只）。饲养20周时测定血清、肝脏及肌肉组织中TG含量,3组均行正常血糖高胰岛素钳夹试验,并用实时定量PCR方法分析脂肪、肝脏和肌肉中脂代谢调控基因mRNA表达的变化。结果饲养20周时,与NC组比较,HF组血清TG增加45．0％（P〈0．01）,肝脏和肌肉TG含量增加2．28倍和9．31倍（P〈0．01）;HF组葡萄糖的输注率（GIR）下降61％（P〈0．01）,存在明显的IR;脂肪组织脂肪酸合成酶、激素敏感酯酶表达分别增高21．3％、28．2％（P〈0．05）;肝脏乙酰辅酶A羧化酶表达增高48．3％（P〈0．05）、肉毒碱脂酰转移酶1（CPT-1）表达呈增高趋势（P〉0．05）;肌肉乙酰辅酶A羧化酶表达增加101．1％、CPT-1表达减少71．0％（P〈0．01）。HP组与HF组比较,血TG、肝脏TG、肌肉TG分别下降66．0％、64．5％及59．6％,GIR增加1．54倍,脂代谢基因的表达也发生了明显的改变。结论高脂饲养可引起sD大鼠肝脏和肌肉组织脂肪异位沉积及IR,吡格列酮干预可以改善,可能与脂代谢调控基因的改变有关。     

Ezetimibe decreases SREBP-1c expression in liver and reverses hepatic insulin resistance in mice fed a high-fat diet

Ezetimibe inhibits intestinal cholesterol absorption, thereby reducing serum cholesterol. Recent studies suggest that ezetimibe affects liver steatosis and insulin resistance. We investigated the impact of ezetimibe on insulin sensitivity and glucose metabolism in C57BL/6 mice. We analyzed 4 mouse groups fed the following diets: normal chow (4% fat) for 12 weeks, normal chow for 10 weeks followed by normal chow plus ezetimibe for 2 weeks, high-fat chow (32% fat) for 12 weeks, and high-fat chow for 10 weeks followed by high-fat chow plus ezetimibe for 2 weeks. In the normal chow + ezetimibe group, ezetimibe had no impact on body weight, fat mass, lipid metabolism, liver steatosis, glucose tolerance, or insulin sensitivity. In the high-fat chow + ezetimibe group, ezetimibe had no impact on body weight or fat mass but significantly decreased serum low-density lipoprotein cholesterol, triglyceride, and glutamate pyruvate transaminase levels; liver weight; hepatic triglyceride content; and hepatic cholesterol content and increased the hepatic total bile acid content. In association with increases in IRS-2 and Akt phosphorylation, ezetimibe ameliorated hepatic insulin resistance in the high-fat chow + ezetimibe group, but had no effect on insulin sensitivity in primary cultured hepatocytes. A DNA microarray and Taqman polymerase chain reaction revealed that ezetimibe up-regulated hepatic SREBP2 and SHP expression and down-regulated hepatic SREBP-1c expression. SHP silencing mainly in the liver worsened insulin resistance, and ezetimibe protected against insulin resistance induced by down-regulation of SHP. Ezetimibe down-regulated SREBP-1c in the liver and reversed hepatic insulin resistance in mice fed a high-fat diet.