胰岛β细胞的胰岛素抵抗

近年发现胰岛β细胞同样具有胰岛素的信号转导途径，同时也存在胰岛素抵抗。β细胞自身的胰岛素抵抗会导致葡萄糖刺激的一相胰岛素分泌异常，抑制β细胞增殖，促进β细胞凋亡。肥胖可以促进胰岛β细胞胰岛素抵抗的发生发展。胰岛β细胞自身胰岛素抵抗可能是2型糖尿病发病的中心环节。     

真胰岛素测定对胰岛β细胞功能和胰岛素抵抗的评价

目的　探讨血清真胰岛素 (TI)与免疫反应性胰岛素 (IRI)在反映胰岛 β细胞功能和胰岛素抵抗 (IR)方面的不同。 方法　测定正常糖耐量 (NGT)组 (75例 )、糖耐量减低 (IGT)组 (43例 )和 2型糖尿病 (T2DM )组 (54例 )的TI(ELISA法 )和IRI(RIA法 )水平 ,计算胰岛 β细胞功能指数 (HOMA β)和IR指数 (HOMA IR)。 结果　 (1 )HOMA βTI在IGT非肥胖组低于NGT非肥胖组 (P <0 0 5) ,T2DM非肥胖组低于NGT和IGT非肥胖组 (均P <0 0 1 ) ;在IGT和T2DM肥胖组低于NGT肥胖组 (均P <0 0 1 )。HOMA βIRI在IGT和T2DM非肥胖组低于NGT非肥胖组 (均P <0 0 5) ;在NGT、IGT和T2DM肥胖组之间无显著差异。(2 )HOMA IRTI和HOMA IRIRI在非肥胖组和肥胖组均显示T2DM有明显IR。结论　在反映胰岛 β细胞功能方面TI优于IRI,在反映IR方面TI与IRI有着相似的意义。     

罗格列酮对胰岛素抵抗大鼠β细胞作用形态学观察

目的　研究罗格列酮 (RSG)对胰岛素抵抗 (IR)大鼠 β细胞超微结构病变的作用。 方法高糖饲料喂养SD大鼠 6周复制IR大鼠模型。成模后用药组予RSG 10 μmol·kg-1·d-1,用药 6周。未用药IR大鼠模型为对照 (IR组 )。透射电镜观察胰岛 β细胞超微结构。 结果　与IR组相比 ,RSG组大鼠收缩压、血清甘油三酯、游离脂肪酸、胰岛素降低 (均P <0 .0 1) ,胰岛素敏感指数、血清高密度脂蛋白胆固醇升高 (均P <0 .0 1)。电镜观察IR大鼠 β细胞可见凋亡早期改变 ,细胞浆内脂质沉积以及细胞核和细胞器的病理变化。RSG组 β细胞超微结构病变明显减轻 ,未见凋亡的 β细胞及胞浆内脂质沉积。 结论　罗格列酮可有效防治高糖饲料诱导IR大鼠 β细胞的病理损害     

HIV-1蛋白酶抑制剂Nelfinavir降低大鼠胰岛素瘤INS-1细胞胰岛素释放

HIV 1蛋白酶抑制剂Nelfinavir处理 48h ,显著降低大鼠INS 1细胞基础胰岛素分泌和葡萄糖刺激的胰岛素释放 ,Nelfinavir对后者的抑制作用更强 ,提示Nelfinavir长期治疗可能导致胰岛 β细胞功能损害。     

胰岛β细胞胰岛素抵抗的证据

半个多世纪以来，研究胰岛素抵抗在2型糖尿病（DM）发病中的作用和近年来研究其在代谢综合征发生发展中的地位均取得了重大进展。尤其在2型DM发病机制方面，胰岛素抵抗和β细胞功能障碍为其必需的两大基础，这种多少年来建立的经典2型DM发病机制的“二元论”至今仍统治着糖尿病学界。此处所谓胰岛素抵抗是指传统概念的外周抵抗和肝胰岛素抵抗。然而，日益增多的事实表明胰岛，特别是β细胞的异常，     

胰岛β细胞自身胰岛素抵抗和2型糖尿病--胰岛素抵抗研究的新领域

2型糖尿病的发病机理尚未完全阐明,一般认为主要与胰岛素外周靶组织的胰岛素抵抗及胰岛β细胞分泌缺陷有关.但是二者在2型糖尿病发病机理中孰为原发孰为继发,以及各自在糖尿病发病中的地位一直是长期争论不休的问题.近年来发现β细胞膜上也存在胰岛素受体,即β细胞也是胰岛素的靶细胞,β细胞胰岛素信号转导障碍可导致胰岛素分泌缺陷,首次将胰岛素抵抗与β细胞分泌缺陷直接联系起来.为丰富胰岛素抵抗概念的内涵和外延,重新评价胰岛素抵抗在2型糖尿病发病中的作用提供了新的思路.     

胰岛β细胞自身胰岛素抵抗和2型糖尿病——胰岛素抵抗研究的新领域

2型糖尿病的发病机理尚未完全阐明，一般认为主要与胰岛素外周靶组织的胰岛素抵抗及胰岛β细胞分泌缺陷有关。但是二者在2型糖尿病发病机理中孰为原发孰为继发，以及各自在糖尿病发病中的地位一直是长期争论不休的问题。近年来发现β细胞膜上也存在胰岛素受体，即β细胞也是胰岛素的靶细胞，β细胞胰岛素信号转导障碍可导致胰岛素分泌缺陷，首次将胰岛素抵抗与β细胞分泌缺陷直接联系起来。为丰富胰岛素抵抗概念的内涵和外延，重新评价胰岛素抵抗在2型糖尿病发病中的作用提供了新的思路。     

胰岛素抵抗细胞模型的胰岛素降解酶表达

目的 了解胰岛素降解酶（ＩＤＥ）基因、酶蛋白表达水平与胰岛素敏感性的关系,并初步探讨胰岛素降解抑制剂氯喹改善胰岛素敏感性的分子机制。方法 以的代大鼠肝细胞胰岛抵抗（ＩＲ）模型为研究对象,分别采用免疫印迹技术和逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）技术检测ＩＲ细胞模型的ＩＤＥ酶蛋白表达（ＥＩＰ）及基因表达水平（ＥＩＧ）,同时检测ＩＤＥ活性和反映细胞胰岛素敏感性的＾１４Ｃ－２－脱氧葡萄糖掺入率及＾１４Ｃ     

不同糖代谢状态人群胰岛素抵抗和胰岛β细胞功能研究

目的探讨从正常糖耐量到糖尿病(DM)不同糖代谢水平,胰岛素抵抗(IR)与胰岛β细胞功能的演变.方法青岛市区30～74岁的正常糖耐量(NGT)447例;空腹血糖受损(IFG)142例;糖耐量受损(IGT)93例;IFG合并IGT(IFG+IGT)42例;新诊DM 153例.采用HOMA-IR评价IR,HOMA-β、ΔI30/ΔG30分别评价基础状态下及糖负荷后的早期胰岛β细胞功能.结果 IFG组HOMA-IR为1.14±0.06,明显高于NGT组的0.93±0.03(P＜0.05),IFG组HOMA-β为4.53±0.06,低于NGT组5.10±0.04(P＜0.05),两组间△I30/△G30差异无显著性(4.86±0.11 vs 4.99±0.11);IGT组HOMA-IR为1.12±0.07,明显高于NGT(P＜0.05),两组间HOMA-β差异无显著性,IGT组△I30/△G30 为4.62±0.14,低于NGT组的4.99±0.11(P＜0.05);DM组HOMA-IR为1.55±0.05,明显高于NGT、IGT和IFG组(P＜0.05),DM组HOMA-β和△I30/△G30 分别为3.94±0.06、3.93±0.12,明显低于其他各组(P＜0.05),DM组基础与糖负荷后的胰岛β细胞功能均明显受损.结论 IFG患者主要表现β细胞功能缺陷,IGT为胰岛素早期分泌受损,DM患者兼有严重的IR和β细胞缺陷.从NGT到DM,随着糖代谢的不断恶化,IR逐渐加重,胰岛β细胞功能进行性减退,最终发生胰岛β细胞功能衰竭.     

A paradox： Insulin inhibits expression and secretion of resistin which induces insulin resistance

AIM： To confirm whether insulin regulates resistin expression and secretion during differentiation of 3T3-L1 preadipocytes and the relationship of resistin with insulin resistance both in vivo and in vitro. METHODS： Supernatant resistin was measured during differentiation of 3T3-L1 preadipocytes. L6 rat myoblasts and hepatoma cell line H4IIE were used to confirm the cellular function of resistin. Diet-induced obese rats were used as an insulin resistance model to study the relationship of resistin with insulin resistance. RESULTS： Resistin expression and secretion were enhanced during differentiation 3T3-L1 preadipocytes. This cellular differentiation stimulated resistin expression and secretion, but was suppressed by insulin. Resistin also induced insulin resistance in H4IIE hepatocytes and L6 myoblasts. In diet-induced obese rats, serum resistin levels were negatively correlated with insulin sensitivity, but not with serum insulin. CONCLUSION： Insulin can inhibit resistin expression and secretion in vitro, but insulin is not a major regulator of resistin in vivo. Fat tissue mass affects insulin sensitivity by altering the expression and secretion of resistin.     

Selenium overexposure induces insulin resistance: In silico study

Background and aimsSeveral studies raise concerns about the possible association of high selenium exposure with insulin resistance and type 2 diabetes. This in silico study proposes a possible mechanism of insulin resistance in the case of overexposure to selenium.MethodA study was carried out using molecular modeling, where cysteines of the insulin-receptor are replaced by selenocysteines. Calculation of the interaction energy of the receptor was performed in both cases with Auto Dock Tools and Vina 4.2 software to predict whether the substitution of amino acid could lead to destabilization of the protein-ligand complex and therefore possibly insulin resistance. Finally, the docked complex was analyzed by using BIOVIA Discovery Studio Visualizer to show the type of interactions between the ligands and insulin-receptor, and to determine the distance of the ligands from the binding site on insulin-receptor.ResultsThe results show that the substitution of cysteine by selenocysteine in the insulin receptor does not lead to stabilization of the complex receptor/insulin, but to its disruption.In addition, the types and the number of bonds between insulin and its receptor in the two cases are different, where 7 strong bonds between insulin and its receptor were found in the case of the cysteine complex compared to 6 weak bonds in the second case.ConclusionFindings of this study suggest that misincorporation of selenocysteines in insulin receptor could lead to destabilization of the insulin-receptor complex and therefore may possibly cause an insulin resistance.     

Resistin is expressed in human hepatocytes and induces insulin resistance

Resistin, known as an adipocyte-specific secretory factor (ADSF), is implicated to modulate insulin resistance in rodents. However, the precise role of this factor for human insulin resistance has remained elusive. Here, we investigate the relationship between human resistin and insulin resistance in hepatocytes and the effect of Metformin on resistin. In this study, the expression of resistin in human hepatocytes and hepatic tissues was examined, and the human resistin eukaryotic expression vector was constructed and stably transfected in HepG2 cells. Data showed that resistin is expressed in human hepatocytes and hepatic tissues. Overexpression of human resistin impaired significantly insulin-stimulated glucose uptake and glycogen synthesis in HepG2 cells. It also decreased the expression of insulin receptor substrate 2 (IRS-2) and c-cbl associated protein (CAP), whereas increased the expression of glycogen synthetase kinase 3beta (GSK-3beta). The result suggested that human resistin induced insulin resistance in hepatocytes by blocking the two insulin signal transduction pathways of PI-3K/Akt and of CAP/c-cbl. We also concluded that Metformin reversed the effect of resistin and downregulated the expression of resistin in hepatocytes.     

阿司匹林对游离脂肪酸引起的大鼠肝细胞胰岛素抵抗的保护作用

探讨游离脂肪酸和阿司匹林对大鼠肝细胞胰岛素受体底物2(IRS -2)的蛋白质含量及其酪氨酸残基磷酸化水平的影响,结果提示游离脂肪酸可能通过抑制IRS- 2酪氨酸残基磷酸化和降低IRS -2蛋白质含量引起肝细胞胰岛素抵抗,阿司匹林能防治游离脂肪酸引起的肝细胞胰岛素抵抗。     

Development of Wistar rat model of insulin resistance

AIM: To establish a simplified and reliable animal model of insulin resistance with low cost in Wistar rats. METHODS: Wistar rats were treated with a high fat emulsion by ig for 10 d. Changes of the diets, drinking and body weight were monitored every day and insulin resistance was evaluated by hyperinsulinemic-euglycemic clamp techniques and short insulin tolerance test using capillary blood glucose. Morphologic changes of liver, fat, skeletal muscles, and pancreatic islets were assessed under light microscope. mRNA expressions of GLUT2 and α-glucosidase in small intestine epithelium, GLUT4 in skeletal muscles and Kir6.2 in beta cell of islets were determined by in situ hybridization. RESULTS: KITT was smaller in treated animals (4.5±0.9) than in untreated control Wistar rats (6.8±1.5), and so was glucose injection rate. Both adipocyte hypertrophy and large pancreatic islets were seen in high fat fed rats, but no changes of skeletal muscles and livers were observed. mRNA levels of GLUT2, α-glucosidase in small intestinal epithelium and Kir6.2 mRNA in beta cells of islets increased, whereas that of GLUT4 in skeletal muscles decreased in high fat fed group compared with normal control group. CONCLUSION: An insulin resistance animal model in Wistar rats is established by ig special fat emulsion.     

胰岛素的糖基化作用及其与胰岛素抵抗的关系

人胰岛素在体外与不同浓度葡萄糖溶液孵育，利用氯化硝基四唑氮蓝还原反应证实胰岛素能被糖基化；利用抗胰岛素抗体分离３３例Ⅱ型糖尿病患者血清胰岛素，比色测定糖基化胰岛素水平。结果表明：糖尿病患者糖基化胰岛素水平显著升高，且与血糖呈显著正相关，与空腹血胰岛素／血糖比值和糖负荷后曲线下胰岛素／血糖面积比值呈显著负相关。说明糖基化胰岛素水平取决于血糖控制状况。且可能参与胰岛素抵抗的形成。     

胰岛素对大鼠骨骼肌细胞脂联素受体基因表达的影响

目的了解体外胰岛素对原代培养大鼠骨骼肌细胞脂联素受体1表达的影响。方法体外原代培养骨骼肌细胞,应用SYBRGreenⅠ染料建立一种快速、可靠的实时定量PCR,对其主要要素进行优化。观察不同胰岛素浓度不同作用时间下,大鼠骨骼肌细胞脂联素受体基因表达水平的动态变化。结果建立敏感、特异、快速检测脂联素受体1mRNA的实时定量PCR方法,随着胰岛素浓度的增加,脂联素受体1表达逐渐降低。在较低浓度（胰岛素浓度〈1nmol/L）时,脂联素受体1表达的降低无统计学意义,当胰岛素浓度增加到10nmol/L及以上时,骨骼肌细胞脂联素受体1表达的降低有统计学意义（P〈0.05）,这种抑制作用1h后出现,24h后达到高峰。结论成功地建立SYBRGreenⅠ实时定量PCR检测脂联素受体基因的表达方法,体外高胰岛素对骨骼肌细胞脂联素受体1mRNA表达有抑制作用,并呈时间和剂量依赖性。     

吸烟减少大鼠骨骼肌细胞胰岛素受体基因表达

应用RT-PCR及免疫组化技术分别检测实验大鼠骨骼肌细胞胰岛素受体基因mRNA及蛋白表达.结果显示正常吸烟组、高脂饲养吸烟组及糖尿病吸烟组大鼠骨骼肌细胞胰岛索受体基因mRNA的表达显著低于各自对照组(0.50±0.06对0.84±0.09,0.38±0.01对0.59±0.05,0.37±0.05对0.55±0.05,均P<0.01),蛋白含量亦明显低于各自对照组(6.99±0.53对8.89±0.36,5.17±0.29对7.53±0.53,2.16±0.56对5.03±0.79,均P<0.01),这可能是长期吸烟导致胰岛素抵抗的分子机制之一.     

胰岛素抵抗与高血压的关系

研究表明胰岛素抵抗与高血压密切相关,胰岛素抵抗是高血压的一个独立危险因子,二者存在理论上的因果关系.胰岛素抵抗在高血压的发病机制中起至关重要的作用,而高血压也可影响胰岛素的代谢,造成胰岛素抵抗,两者相辅相成,导致一系列严重慢性并发症的发生.同时,多种降压药物可通过影响糖代谢从而改善胰岛素抵抗,另一方面,部分改善胰岛素抵抗的药物可用于治疗原发性高血压.因此,了解胰岛素抵抗与高血 压之间的关系对于胰岛素抵抗及高血压的防治有重要意义.