胰岛素抵抗HepG2细胞模型的建立及鉴定

目的 建立呈胰岛素抵抗的ＨｅｐＧ２细胞模型。方法 将ＨｅｐＧ２细胞置于１０＾－７ｍｏｌ／Ｌ胰岛素培养液中２４小时,使ＨｅｐＧ２细胞胰岛素受体充分下调,检测燕比较下调和未下调的ＨｅｐＧ２细胞,糖,脂类代谢水平,发现：下调ＨｅｐＧ２细胞胰岛素受体减少了５６％,将ＤＲ－ＨｅｐＧ２细胞于不同浓度胰岛素培养液中,胰岛素受体数 明显减少,当培养液中胰岛素的浓度为１０＾－７ｍｏｌ／Ｌ时,ＤＲ－ＨｅｐＧ２细胞胰岛     

抵抗素对HepG2肝细胞胰岛素信号通路IRS-2/Akt的影响

目的探讨抵抗素对HepG2肝细胞中胰岛素信号通路IRS-2/Akt的影响及其与腺苷酸活化蛋白激酶(AMPK)通路之间的关系。方法50 ng/ml重组人抵抗素处理肝HepG2细胞株,siRNA技术抑制HepG2细胞AMPKα2亚基表达,采用实时RT-PCR技术检测胰岛素信号通路相关细胞信号抑制因子3(SOCS-3)和胰岛素受体底物2(IRS-2)mRNA的水平,采用蛋白印迹技术检测蛋白激酶B(Akt)的蛋白含量及磷酸化水平。结果在基础及胰岛素刺激状态下,抵抗素上调SOCS-3 mRNA的表达(P0.05),下调IRS-2 mRNA的表达(P0.05),仅在胰岛素刺激状态下降低Akt总蛋白含量及其磷酸化水平(P0.05),且未转染与转染AMPKα2 siRNA组比较,Akt总蛋白含量及其磷酸化水平差异无统计学意义(P0.05)。结论抵抗素对HepG2细胞胰岛素信号通路IRS-2/Akt起抑制作用,这可能是其导致肝脏胰岛素抵抗的机制之一;抵抗素对IRS-2/Akt信号通路与AMPK通路的影响可以相互独立。     

蛋白激酶C在软脂酸诱导HepG2细胞胰岛素抵抗中的作用

目的从蛋白激酶C(PKC)信号通路角度,探讨游离脂肪酸(FFA)引起肝脏胰岛素抵抗(IR)的可能机制。方法培养HepG2细胞,同时设立对照组、软脂酸(PA)组、高胰岛素组。软脂酸组、高胰岛素组分别用250μmol/L PA、5×10-7mol/L胰岛素处理24h。然后对照组、软脂酸组再根据胰岛素刺激前加( )与不加(-)PKC抑制剂白屈菜红碱盐酸盐(chelerythrine chloride,CC)5μmol/L预处理1h,随机分为两亚组:对照组(-)、对照组( )、PA组(-)、PA组( )。葡萄糖氧化酶法测定胰岛素刺激后12h葡萄糖消耗量,蒽酮法测定胰岛素刺激后3h点细胞内糖原含量,Western blotting技术检测15min点细胞内P-Ser473PKB、P-Ser21/9GSK-3α/β水平。结果PA组(-)与高胰岛素组葡萄糖消耗量无统计学差异(P=0.523)。葡萄糖消耗量、细胞内糖原含量、P-Ser473PKB、P-Ser21GSK-3α、P-Ser9GSK-3β水平均显示,PA组(-)与对照组(-)比较显著降低(P值依次为0.000,0.000,0.004,0.004,0.028),对照组( )与对照组(-)比较略有升高但无显著性差异;PA组( )与PA组(-)比较显著升高(P值依次为0.000,0.014,0.043,0.041,0.035)。结论PA(250μmol/L)体外成功诱导了HepG2细胞产生IR,PKC信号通路在FFA引起肝脏IR中起着重要作用。     

胰岛素、胰岛素原对胰岛素抵抗状态下HepG2细胞PAI-1分泌的影响

目的研究胰岛素、胰岛素原对胰岛素抵抗状态下ＨｅｐＧ２细胞ＰＡＩ１分泌的影响。方法选择在合成ＰＡＩ１方面与肝细胞相似的ＨｅｐＧ２细胞，以高浓度胰岛素诱导胰岛素抵抗后，分别用生理浓度的胰岛素、胰岛素原刺激２４小时，以观察胰岛素抵抗状态下ＰＡＩ１活性的变化。结果基础状态下胰岛素抵抗ＨｅｐＧ２细胞与非胰岛素抵抗ＨｅｐＧ２细胞相比，ＰＡＩ１活性差异不明显；胰岛素、胰岛素原刺激后，胰岛素抵抗ＨｅｐＧ２细胞ＰＡＩ１活性明显高于非胰岛素抵抗ＨｅｐＧ２细胞。当培液中同时加入１０－４Ｍ二甲双胍后，胰岛素、胰岛素原介导的ＰＡＩ１过量分泌得到明显抑制。结论在胰岛素抵抗状态下，胰岛素、胰岛素原刺激后ＨｅｐＧ２细胞ＰＡＩ１活性明显增加，而二甲双胍可明显抑制此现象。     

软脂酸诱导HepG2细胞胰岛素抵抗及花生四烯酸防治作用的机制研究

目的 探讨高浓度软脂酸(PA)诱导HepG2细胞胰岛素抵抗(IR)的机制及花生四烯酸(AA)对IR的防治作用。方法 (1)用高浓度软脂酸(PA)或10^-7mol／L高胰岛素(HI)培养HepG2细胞建立具有IR的细胞模型，测定培养液中葡萄糖含量及细胞内糖原含量作为鉴定指标；(2)用Western blot检测胞内糖原合酶(GS)和蛋白激酶B(PKB)蛋白水平；(3)用磷脂酰肌醇3激酶(P13K)抑制剂Wortmannin(WT)探讨其对胰岛素信号通路的影响；(4)观察AA是否对PA引起的IR有防治作用。结果 (1)0．20mmol／L PA或川培养HepG2细胞36h后，培养液中葡萄糖含量极显著增高，细胞内糖原含量极显著减少；(2)高浓度PA使磷酸化的PKB(P-Ser473)蛋白水平显著减少，磷酸化的糖原合酶(P-Ser641 GS)蛋白水平极显著增加；(3)WT使对照组GS活性及胞内糖原含量极显著减少，HI组和PA组胞内糖原含量均无统计学差异，但各实验组PKB活性都极显著减少；(4)PA AA组培养液中葡萄糖含量显著低于PA组，GS和PKB活性及胞内糖原含量显著增加。结论 高浓度PA或HI培养HepG2细胞能够诱导IR，其机制可能是其引起胰岛素信号传递途径中自PKB下游到GS之间的信号通路受阻所致。AA能改善PA引起的IR。     

胰岛素,胰岛素原对胰岛素抵抗状态下HepG2细胞PAI—1分泌？…

研究胰岛素，胰岛素原对胰岛素抗状下ＨｅｐＧ２细胞ＰＡＩ－１分泌的影响。方法选择在合成ＰＡＩ－１方面与肝细胞相似的ＨｅｐＧ２细胞，以高浓度胰岛素诱导胰岛素抵抗后，分别用生理浓度的胰岛素、胰岛素原刺激２４小时，以观察胰岛素抵抗状态下ＰＡＩ－１活性的变化。     

不同浓度葡萄糖、胰岛素对HK-2细胞转化生长因子β1表达的影响

用不同浓度葡萄糖和胰岛素干预人近端肾小管上皮细胞（HK-2），ELISA法测培养液上清中TGF-β1浓度，RT—PCR检测HK-2细胞中TGF—β1mRNA表达水平。结果显示高浓度葡萄糖和胰岛素通过不同途径上调HK-2细胞TGF—β1的表达。     

阿霉素对HepG2细胞G6PD表达和活性的影响

目的探讨化疗药物阿霉素（ADM）在体外对HepG2细胞6-磷酸葡萄糖脱氢酶（G6PD）表达和活性的影响。方法将0.5μg/ml ADM作用于HepG2细胞,MTT法检测HepG2细胞的生长抑制情况;Beutler改良法测定胞内还原型谷胱甘肽（GSH）的含量,速率法测定G6PD活性,实时荧光定量RT-PCR法观察G6PD mRNA表达水平的变化。结果24h实验组的抑制率为46.1%。ADM作用4h和24h后,G6PD mRNA的表达增强,G6PD活性高于未加药对照组（P〈0.05）。4h实验组GSH含量低于对照组（P〈0.05）。结论ADM在体外能明显抑制HepG2细胞生长,能诱导HepG2细胞G6PD mRNA表达增加、活性增强;其机制可能与G6PD参与肿瘤细胞内抵抗氧化压力有关。     

高浓度葡萄糖条件下罗格列酮对NIT-1细胞增殖、胰岛素分泌水平及IRS-2表达的影响

目的探讨高浓度葡萄糖条件下罗格列酮对胰岛B细胞增殖、胰岛素分泌功能的影响及机制。方法取对数生长期NOD鼠胰岛β细胞株NIT-1,以胰酶消化离心、收集细胞,按5×10^4个细胞／孔移至24孔培养板,继续培养48h后分别用葡萄糖浓度为5．6—27．6mmol／L的RPMI1640培养基处理,24h后随机分为对照组、罗格列酮1～3组,分别加入浓度为0～10^-5mol／L的罗格列酮培养;分别于干预24h和48h时收集细胞培养上清液,采用MTT法检测各组细胞增殖活性,放射免疫法检测胰岛素水平;Western blot技术检测胰岛素受体底物（IRS）-2蛋白表达水平。结果①四组细胞增殖活性及胰岛素分泌水平均随葡萄糖浓度升高而降低,其中罗格列酮1-3组细胞增殖活性和胰岛素分泌量均显著高于对照组（P〈0．05、0．01）。②罗格列酮3组在葡萄糖浓度为22．5、27．6mmol／L培养24h及葡萄糖浓度为11．1mmol/L培养48h时胰岛素分泌水平均显著高于对照组（P〈0．05、0．01）;不同浓度葡萄糖培养下罗格列酮3组细胞中IRS-2蛋白水平均显著高于对照组（P〈0．05、0．01）,且变化趋势同上。结论在高浓度葡萄糖条件下罗格列酮可促进NIT-1细胞增殖、胰岛素分泌,机制可能与其上调IRS2表达有关。     

大黄素通过激活PPARγ促进HepG2细胞葡萄糖摄取

目的 构建PPARγ和PPARγ应答元件（PPRE）荧光素酶系统，并确定大黄单体成分大黄素是否能够通过激活PPARγ促进HepG2肝细胞葡萄糖摄取。方法 （1）构建PPARγ和PPRE荧光素酶系统并对20余种中药成分进行筛选；（2）将能够激活PPARγ和PPRE系统的大黄素与HepG2肝细胞进行培养，分别用RT-PCR／Southern杂交测定PPARγmRNA的表达；（3）用Western印迹法测定大黄素处理后的HepG2细胞的PPARγ和葡萄糖转运蛋白2（Glut2）的表达水平；（4）测定大黄素作用后的HepG2细胞对2-脱氧-[^3H]-D-葡萄糖摄取率。结果 （1）在筛查的中药成分中，大黄素作用24h后，呈剂量（0．04～180μmol／L）依赖性地增强COS-7细胞PPRE荧光素酶活性，其中90μmol／L浓度时达到最高值，为对照组的4倍（P〈0．01），而10μmol／L浓度的吡格列酮作用强度为对照组的6倍（P〈0．01）；（2）大黄素在90μmol／L浓度时刺激HepG2细胞PPARγmRNA表达水平增加2．7倍（P〈0．01）；（3）大黄素的作用呈剂量和时间依赖性地刺激HepG2细胞PPARγ和Glut2蛋白的表达水平。其中，PPARγ蛋白水平在90μmol／L和作用16h刺激作用最强，约为对照组的3．1—3．8倍（P〈0．01）；Glut2蛋白水平在90μmol／L和作用16h刺激作用最强，约为对照组的2．5—4．3倍（P〈0．01）；（4）HepG2细胞的葡萄糖摄取率在90μmol／L浓度的大黄素作用24h后，约为对照组的5倍（P〈0．01）。结论 研究结果显示大黄素刺激HepG2肝细胞PPARγ和Glut2蛋白表达，并促进葡萄糖的摄取。     

The role of protein kinase C in insulin biosynthesis

Activation of protein kinase C (PKC) by the phorbol ester 4-phorbol myristate acetate (4-PMA) stimulated (pro)insulin biosynthesis in collagenase-isolated rat islets of Langerhans, as assessed by measuring the incorporation of [³⁵S]cysteine into proinsulin and insulin after fractionation by high performance liquid chromatography. The stimulatory effects of 4-PMA were observed at a substimulatory concentration of glucose (2 mM) but were not additive to the stimulatory effects of 20 mM glucose on insulin biosynthesis. Prolonged exposure to 4-PMA caused a marked down-regulation of PKC activity in islets. PKC-depleted islets showed a much reduced biosynthetic response to 20 mM glucose, but this was caused, at least in part, by an enhanced basal rate of (pro)insulin synthesis. These elevations in the basal rate of insulin synthesis were not secondary to an inerease in the amount of preproinsulin mRNA in PKC-depleted islets since Northern blot analysis showed that prolonged exposure to 4-PMA, and the subsequent loss of PKC activity, did not detectably alter basal levels of preproinsulin mRNA. These results suggest that the activation of PKC stimulates (pro)insulin synthesis in rat islets by enhancing translation of existing preproinsulin mRNA, and that this may play some part in the biosynthetic responses of -cells to glucose.     

Contrasting insulin dose-dependent defects in activation of atypical protein kinase C and protein kinase B/Akt in muscles of obese diabetic humans

Aims/hypothesis Insulin-stimulated glucose transport in muscle is impaired in obesity and type 2 diabetes, but alterations in levels of relevant signalling factors, i.e. atypical protein kinase C (aPKC) and protein kinase B (PKB/Akt), are still uncertain. Clamp studies using maximal insulin concentrations have revealed defects in activation of aPKC, but not PKB, in both obese non-diabetic and obese diabetic subjects. In contrast, clamp studies using submaximal insulin concentrations revealed defects in PKB activation/phosphorylation in obese non-diabetic and diabetic subjects, but changes in aPKC were not reported. The aim of this study was to test the hypothesis that dose-related effects of insulin may account for the reported differences in insulin signalling to PKB in diabetic muscle.Subjects and methods We compared enzymatic activation of aPKC and PKB, and PKB phosphorylation (threonine-308 and serine-473) during hyperinsulinaemic–euglycaemic clamp studies using both submaximal (400–500 pmol/l) and maximal (1400 pmol/l) insulin levels in non-diabetic control and obese diabetic subjects.Results In lean control subjects, the submaximal insulin concentration increased aPKC activity and glucose disposal to approximately 50% of the maximal level and PKBβ activity to 25% of the maximal level, but PKBα activity was not increased. In these subjects, phosphorylation of PKBα and PKBβ was increased to near-maximal levels at submaximal insulin concentrations. In obese diabetic subjects, whereas aPKC activation was defective at submaximal and maximal insulin concentrations, PKBβ activation and the phosphorylation of PKBβ and PKBα were defective at submaximal, but not maximal, insulin concentrations.Conclusions/interpretations Defective PKBβ activation/phosphorylation, seen on submaximal insulin stimulation in diabetic muscle, may largely reflect impaired activation of insulin signalling factors present in concentrations greater than those needed for full PKB activation/phosphorylation. Defective aPKC activation, seen at all insulin levels, appears to reflect, at least partly, an impaired action of distal factors needed for aPKC activation, or poor aPKC responsiveness.     

胰岛素抵抗大鼠骨骼肌中蛋白激酶B表达及葡萄糖转运蛋白4转位的改变

目的研究高脂饮食喂养的胰岛素抵抗(IR)大鼠骨骼肌中蛋白激酶B(PKB)表达和葡萄糖转运蛋白4(GluT4)转位的改变及饮食治疗、葛根素、罗格列酮干预的影响。方法将雄性SD大鼠50只随机分为正常饮食(A)组和高脂饮食(B)组,2个月后再将B组大鼠随机分为高脂饮食(C)组、正常饮食干预(D)组、葛根素干预(E)组和罗格列酮干预(F)组。干预1个月后检测骨骼肌中PKB的表达及转位至质膜的GluT4含量。结果C组大鼠产生了明显的IR,骨骼肌中PKB的表达较A组显著降低(P<0.01),转位到质膜上的GluT4含量显著减低(P<0.01);D、E、F组大鼠IR明显改善,骨骼肌中PKB的表达较C组大鼠显著增加(P<0.01),GluT4含量较C组大鼠显著升高(P<0.01)。结论高脂饮食喂养的SD大鼠骨骼肌产生明显的IR,骨骼肌中Ins诱导的PKB表达降低,Ins刺激的GluT4向质膜的转位减少。饮食治疗及葛根素、罗格列酮干预能增加骨骼肌中Ins刺激的PKB表达及GluT4向质膜的转位。     

间歇低氧对大鼠胰岛素抵抗及骨骼肌细胞GLUT4、Akt2的影响

目的 检测不同间歇低氧暴露时间对骨骼肌葡萄糖转运蛋白(GLUT)4与蛋白激酶B(PKB/Akt)2表达的影响,探讨二者在间歇低氧导致胰岛素抵抗中的作用.方法 选取健康雄性Sprague-Dawley大鼠40只,按照随机数字表法分为5组:常氧对照组(NC组),间歇低氧2周组(IH2组),间歇低氧4周组(IH4组),间歇低氧6周组(IH6组),间歇低氧8周组(IH8组),每组8只.IH2组、IH4组、IH6组、IH8组每天给予8h间歇低氧暴露(9:00～17:00),NC组室内环境正常饲养.检测各组空腹血糖和空腹胰岛素水平,计算稳态模型评估-胰岛素抵抗指数(HOMA-IR).采用免疫组织化学法检测大鼠骨骼肌GLUT4及Akt2蛋白的表达,蛋白表达量用平均灰度值表示,并分析GLUT4与Akt2的相关性.结果 与NC组相比,IH2组、IH4组、IH6组、IH8组空腹血糖、HOMA-IR升高,骨骼肌GLUT4与Akt2灰度值升高,并且随间歇低氧暴露时间的延长而升高明显(F =87.67～288.63,P均＜0.05);与NC组相比,IH2组、IH4组、IH6组、IH8组空腹胰岛素升高,其中IH2组、IH4组、IH6组,随间歇低氧暴露时间的延长而升高明显,IH8组较IH6组下降(F=86.04,P＜0.01).Pearson相关分析显示GLUT4与Akt2的表达呈正相关(r=0.895,P ＜0.05).结论 随着间歇低氧暴露时间的延长胰岛素抵抗程度增加,GLUT4与Akt2蛋白表达水平下降,二者在间歇低氧导致胰岛素抵抗的过程中起协同作用.     

Effects of short-term culturing on islet phosphoinositide and insulin secretory responses to glucose and carbachol

The ability of glucose and carbachol, alone or in combination, to stimulate islet cell phosphoinositide (PI) hydrolysis and insulin secretory responses in freshly isolated or in 20–24 h cultured rat islets was assessed. In freshly isolated,³H-inositol-prelabeled islets, 20 mM glucose alone or 1 mM carbachol alone stimulated significant increments in³H-inositol efflux and inositol phosphate (IP) accumulation. When stimulated with both agonists, a dramatic and synergistic effect on IP accumulation was noted. Carbachol (1 mM) alone had no sustained stimulatory effect on insulin secretion. Glucose (20 mM) alone induced a biphasic insulin secretory response. When compared to prestimulatory secretory rates of 18±4 pg/islet/min, peak first and second phase responses of freshly isolated islets to 20 mM glucose averaged 126±24 and 520±82 pg/islet/min, respectively. In the presence of both glucose (20 mM) and carbachol (1 mM), peak first and second phase responses now averaged 422±61 and 1016±156 pg/islet/min, respectively. In contrast to freshly studied islets, culturing islets for 20–24 h in CMRL-1066 medium attenuated all measured responses. The increases in³H-inositol efflux rates in response to glucose, carbachol, or their combination were significantly less than those observed with fresh islets. The IP responses were also attenuated. Second phase insulin secretory responses to 20 mM glucose alone (68±9 pg/islet/min) or the combination of 20 mM glucose plus 1 mM carbachol (358±85 pg/islet/min) were also significantly decreased when compared with fresh islets. We conclude from these studies that the process of culturing islets for one day in CMRL-1066 significantly decreases islet cell PI hydrolysis and insulin secretory responsiveness. These observations may help to explain the discordant conclusions reached concerning the involvement of PI hydrolysis and protein kinase C activation in the regulation of insulin release from freshly isolated versus cultured islets.     

蛋白激酶C和Ca2+在心肌细胞预处理中的作用

目的：探讨心肌细胞缺氧预处理、蛋白激酶C（PKC）和细胞内钙离子在心肌细胞预处理中的作用。方法：在培养乳鼠心肌细胞缺氧预处理的模型上，观察缺氧预处理以及PKC抑制剂Chelerythrine和钙离子螯合剂BAPTA／AM对缺氧预处理的影响。结果：缺氧预处理可以减少缺氧／复氧对心肌细胞的损伤。PKC抑制剂Chelerythrine和钙离子螯合剂BAPTA／AM可以抑制缺氧预处理的心肌保护作用。结论：PKC和钙离子介导心肌细胞的缺氧预处理。     

高糖对大鼠脂肪细胞胰岛素信号蛋白磷酸化的影响

目的 探讨高浓度葡萄糖（高糖）对原代培养大鼠脂肪细胞的葡萄糖转运活动、胰岛素信号蛋白磷酸化及表达的影响。方法 分离的大鼠脂肪细胞在5，10，15和25mmol/L葡萄糖中孵育24h，然后测定：糖转运活动；胰岛素受体（IR）、胰岛素受体底物（IRS）1、2及蛋白激酶B（PKB）的磷酸化；IRS1，IRS2，肌醇磷脂－3－激酶85亚单位（p85)和PKB的蛋白表达。结果 高糖抑制了这些细胞的葡萄糖转运活动，削弱了IR、IRS1的酪氨酸磷酸化及PKB的丝氨酸磷酸化；下调IRS1而上调IRS2蛋白表达。结论 高糖能抑制脂肪细胞的糖转运活动，诱导胰岛素抵抗。其作用机制与影响胰岛素信号蛋白多部位的磷酸化及蛋白表达有关。