胰岛素抵抗与高血压病关系探讨

胰岛素抵抗与高血压病关系探讨福建省立医院内科严晓时胰岛素抵抗（Ｉｎｓｕｌｉｎｒｅｓｉｓｔａｎｃｅ，ＩＲ）高胰岛素血症与原发性高血压病（Ｅｓｓｅｎｔｉａｌｈｙｐｅｒｔｅｎｓｉｏｎ，ＥＨ）的关系密切，是近年研究的一个热点。本文通过对ＥＨ患者进行空腹血糖（...     

2型糖尿病大鼠模型GLUT4 mRNA表达的研究

目的：研究葡萄糖转运体4（GLUT4）mRNA表达在2型糖尿病胰岛素抵抗中的分子机制。方法：采用高脂高糖饲养，一次性腹腔注射链脲佐菌素（STZ）制备2型糖尿病大鼠模型。逆转录聚合酶链反应（RT-PCR）分析大鼠骨骼肌、心肌和脂肪组织中GLUT4 mRNA的表达量变化与差别。结果：正常对照组和2型糖尿病大鼠模型组GLUT4 mRNA在骨骼肌中有相对较高表达，在心肌中表达次之，在脂肪组织中表达相对偏低。2型糖尿病大鼠模型组骨骼肌中GLUT4 mRNA表达量只有对照组骨骼肌的48％、心肌的44％、脂肪组织的38％。结论：GLUT4 mRNA表达量下降导致骨骼肌、心肌和脂肪组织对葡萄糖摄取利用减少是胰岛素抵抗的重要分子基础，是诱发2型糖尿病原因之一。     

钒酸盐对糖尿病大鼠糖原的影响与cAMP的关系

目的在链脲佐菌素（ＳＴＺ）糖尿病大鼠模型观察钒酸盐（Ｖａ）对骨骼肌和肝脏糖原的影响与ｃＡＭＰ的关系。方法用正钒酸钠分别管饲正常对照大鼠和ＳＴＺ致糖尿病大鼠，观测肝脏和骨骼肌的糖原与ｃＡＭＰ的变化趋势。结果与正常对照组比较，糖尿病骨骼肌糖原含量下降（Ｐ＜０．０１），肝糖原含量升高（Ｐ＜０．０１）；Ｖａ使肌糖原上升４７％（Ｐ＜０．０１），肝糖原下降５０％（Ｐ＜０．０１），均恢复至正常水平，提示至少有部分肝糖原向骨骼肌转移。Ｖａ同时升高肝ｃＡＭＰ，降低骨骼肌ｃＡＭＰ，与糖尿病动物使用Ｖａ后肌肝糖原变化相反。结论本试验提示ｃＡＭＰ在Ｖａ导致的肝糖原向骨骼肌转移中发挥一定作用。     

水杨酸钠对胰岛素抵抗大鼠氧化应激水平的影响

目的探讨水杨酸钠对胰岛素抵抗大鼠胰岛素敏感性的影响及作用机制。方法分别给大鼠静脉输注脂肪乳＋肝素,脂肪乳＋肝素＋水杨酸钠和生理盐水7h,部分大鼠在输液的最后2h同时行清醒状态高胰岛素一正血糖钳夹试验,测定血浆葡萄糖、游离脂肪酸（FFA）、胰岛素、C肽、丙二醛（MDA）水平,检测肝脏、肌肉中MI）A含量及谷胱甘肽过氧化物酶（GSH—Px）活性。结果脂肪乳输注组葡萄糖输注率（GIR）是生理盐水输注组的45％,输注水杨酸钠可使GIR提高1．3倍（P〈0．01）。与生理盐水输注组比较,脂肪乳输注组血浆、肝脏、肌肉中MDA水平增加了2～4倍（P〈0．01）;GSH—PX活性降低45％～50％（P〈0．01）。水杨酸钠输注使MDA水平较脂肪乳输注组降低了62％-66％（P〈0．01）,GSH-PX活性升高35％～38％（P〈0．05）。结论FFA增高引起机体氧化应激增强,可能是导致胰岛素抵抗发生的机制之一。应用水杨酸钠后大鼠氧化应激减弱,胰岛素抵抗改善,故水杨酸钠可能通过降低氧化应激途径而发挥改善胰岛素抵抗的作用。     

降糖安脉胶囊治疗Ⅱ型糖尿病的实验研究

本实验用１％ＳＴＺ溶液注射于大鼠腹腔内，造成糖尿病动物模型，观察降糖发脉胶囊的治疗作用。结果表明：该方药可显著降低ＳＴＺ模型大鼠的空腹血糖；改善坐骨神经的传导功能；显著降低红细胞山梨醇含量；改善血液流变性和坐骨神经内微血管状态。提示降糖安脉胶囊可通过修复损伤的胰岛β细胞、促进胰岛素分泌、改善血液流变性和微循环、增加周围神经组织的血液供应和营养、抑制醛糖还原酶活性、阻断多元醇代谢通路等多种途径，实现     

盐知母降血糖活性部位对胰岛素抵抗作用的影响

目的：探讨盐知母降血糖活性部位对胰岛素抵抗作用的影响及其作用机制。方法：采用地塞米松诱导3T3-L1脂肪细胞胰岛素抵抗模型,比较盐知母降血糖活性部位对培养基中葡萄糖消耗的影响;采用STZ （链脲佐菌素）诱导大鼠胰岛素抵抗模型,给药14 d后测定大鼠空腹血糖值（FBG）,并用试剂盒测定胰岛素、血浆瘦素、血浆抵抗素等水平。比较盐知母不同降血糖活性部位对2型糖尿病大鼠胰岛素抵抗作用的影响。结果：盐知母降血糖活性部位均能显著增加胰岛素抵抗3T3-L1脂肪细胞培养基中的葡萄糖消耗量,且盐知母三氯甲烷层萃取组作用最佳;与模型组相比,各给药组均显著改善糖尿病大鼠FBG、OGTT、HbAlc、Homa-IR等水平及LEP、ADPN等胰岛素抵抗水平。结论：盐知母降血糖活性部位能够改善胰岛素抵抗作用,且三氯甲烷萃取层作用显著。     

姜黄素与格列本脲联用对2型糖尿病大鼠糖代谢的影响及其机制

目的：探讨姜黄素（Cur）与格列本脲（Gli）联用对2型糖尿病大鼠糖代谢的影响及其机制.方法：复制大鼠2型糖尿病模型,观察Cur（100 mg·kg^-1·d^-1 ig） ×5 d单用及与Gli（1 mg·kg-·d^-1ig） ×5 d联合应用对2型糖尿病大鼠空腹血糖、血浆胰岛素、胰岛素敏感性指数、肝糖原、肝毒性相关指标以及CYP3A活性的影响.结果：Cur能进一步增强Gli的降糖作用,应用Cur后比单用Gli进一步降低空腹血糖（22％至69％）,上调胰岛素及肝糖原水平（49％、19％至126％、81％）.Cur可显著下调肝损伤指标,对肝脏具有保护作用.Cur单用或与Gli联用均显著抑制CYP3A活性.结论：Cur可使Gli降糖效应增强,其机制可能与其抑制Gli代谢酶-CYP3A活性,使Gli代谢延缓,致使其降糖效应增强有关.     

解毒通络调肝散对实验性糖尿病大鼠肝脏IRS-2表达的影响

目的观察解毒通络调肝散对糖尿病胰岛素抵抗模型大鼠肝脏IRS-2的影响。方法采用高脂饮食加链脲佐菌素诱导糖尿病胰岛素抵抗大鼠模型。将造模成功的大鼠随机分为模型组、二甲双胍组、吡咯列酮组和解毒通络调肝组。给药8周后进行各指标检测。结果解毒通络调肝散能升高糖尿病胰岛素抵抗大鼠胰岛素敏感性指数,增加实验性糖尿病（DM）大鼠肝脏组织IRS-2的表达。结论解毒通络调肝散对大鼠IR有显著的改善作用,其机制可能与增加实验性糖尿病（DM）大鼠肝组织中IRS-2表达有关。     

白藜芦醇衍生物改善2型糖尿病大鼠血糖及胰岛素抵抗作用的研究

目的探讨白藜芦醇衍生物BTM-0512对2型糖尿病大鼠血糖及胰岛素抵抗作用的影响。方法单次腹腔注射链脲佐菌素（STZ,35mg·kg^-1）结合高脂饮食建立2型糖尿病大鼠模型。糖尿病大鼠分为3组（模型组、BTM-0512低剂量组、BTM-0512高剂量组）,药物灌胃3周。检测空腹血糖（FBG）、糖基化血红蛋白（HblAC）、空腹血清胰岛素（Fins）和口服糖耐量（OGTT）;计算HOME．IR、胰岛素敏感指数（1AD、胰岛素分泌指数（IS）,以此评价胰岛素抵抗（IR）。结果BTM-0512能剂量依赖性降低2型糖尿病大鼠FBG和HblAC,改善HOME．IR和IAI,但对OGTT与IS没有影响。结论BTM0512可以降低2型糖尿病大鼠血糖并改善IR。     

葛根素对高胰岛素环境下大鼠肝细胞一氧化氮合成的影响

目的：观察葛根素对高胰岛素环境下大鼠肝细胞一氧化氮（NO）合成的影响。方法：体外培养BRL大鼠肝细胞株,用高胰岛素诱导其形成胰岛素抵抗细胞模型,观察葛根素对肝细胞一氧化氮合成的影响。结果：葛根素可调节高胰岛素环境下大鼠肝细胞一氧化氮合酶（NOS）的活性,增加肝细胞NO的合成。结论：葛根素可通过适度调节肝细胞NO的产生,从而促进肝细胞对葡萄糖转化,改善肝细胞胰岛素抵抗的作用。     

Inhibition of the transmembrane protein tyrosine phosphatase lar by 3S-peptide-I enhances insulin receptor phosphorylation in intact cells

3S-peptide-I, a tris-sulfotyrosyl dodecapeptide that corresponds to the major autophosphorylation domain within the insulin receptor beta-subunit, selectively enhances insulin signal transduction by specifically inhibiting dephosphorylation of the insulin receptor catalyzed by protein tyrosine phosphatases (PTPases). Because of the potential role of the transmembrane PTPase LAR in the regulation of insulin signaling, we assessed the effect of 3S-peptide-I on recombinant LAR PTPase activity and in McA-RH7777 rat hepatoma cells overexpressing full-length LAR protein (McA4B/LAR). 3S-peptide-I significantly reduced insulin receptor dephosphorylation by recombinant LAR (p < 0.001) while blocking dephosphorylation of the insulin receptor by approximately 72% in semi-permeabilized McA4B/LAR cells (p < 0.001). Increased LAR expression resulted in 40% reduction in ligand-mediated phosphorylation of the insulin receptor compared with null vector control (p < 0.001). However, treatment of intact McA4B/LAR cells with a fatty acid derivative of 3S-peptide-I (50 microM) led to an enhancement of insulin-stimulated receptor phosphorylation by 89% (p < 0.001). As a result, control and McA4B/LAR cells showed comparable steady-state levels of insulin receptor phosphorylation in the presence of insulin. These findings provide evidence that 3S-peptide-I may improve insulin responsiveness in intact cells by inhibiting LAR, an enzyme whose activity has been implicated in the pathogenesis of insulin resistance.     

Influence of umbelliferone on membrane-bound ATPases in streptozotocin-induced diabetic rats

The activities of membrane-bound ATPases are altered both in erythrocytes and tissues of streptozotocin (STZ)-induced diabetic rats and diabetic patients. Umbelliferone (UMB), a natural antioxidant, is a benzopyrone occurring in nature, and it is present in the fruits of golden apple (Aegle marmelos Correa) and bitter orange (Citrus aurantium). Earlier we evaluated and reported the effect of UMB on plasma insulin and glucose, and this study was designed to evaluate the effect of umbelliferone on membrane-bound ATPases in erythrocytes and tissues (liver, kidney and heart) of STZ-induced diabetic rats. Adult male albino rats of Wistar strain, weighing 180-200 g, were made diabetic by an intraperitonial administration of STZ (40 mg/kg). Normal and diabetic rats were treated with UMB dissolved in 10% dimethyl sulfoxide (DMSO) and diabetic rats were also treated with glibenclamide as drug control, for 45 days. In our study, diabetic rats had increased level of blood glucose and lipid peroxidation markers, and decreased level of plasma insulin and decreased activities of total ATPases, (Na(+)+K(+))-ATPase, low affinity Ca(2+)-ATPase and Mg(2+)-ATPase in erythrocytes and tissues. Restoration of plasma insulin and glucose by UMB and glibenclamide seemed to have reversed insulin, glucose and lipid peroxidation markers, and diabetes-induced alterations in the activities of membrane-bound ATPases. Thus, our results show that the normalization of membrane-bound ATPases in various tissues, is due to improved glycemic control and antioxidant activity by UMB.     

Ramipril increases the protein level of skeletal muscle IRS-1 and alters protein tyrosine phosphatase activity in spontaneously hypertensive rats

To investigate mechanisms by which angiotensin converting enzyme (ACE)-inhibition increases insulin sensitivity, spontaneously hypertensive (SH) rats were treated with or without ramipril (1 mg/kg per day) for 12 weeks. Insulin binding and protein levels of insulin receptor substrate-1 (IRS-1), p85-subunit of phosphatidylinositol 3'-kinase (p85) and Src homology 2 domain-containing phosphatase-2 (SHP2) were then determined in hindlimb muscle and liver. Additionally, protein tyrosine phosphatase (PTPase) activities towards immobilized phosphorylated insulin receptor or phosphorylated IRS-1 of membrane (MF) and cytosolic fractions (CF) of these tissues were measured. Ramipril treatment increased IRS-1-protein content in muscle by 31+/-9% (P<0.05). No effects were observed on IRS-1 content in liver or on insulin binding or protein expression of p85 or SHP2 in both tissues. Ramipril treatment also increased dephosphorylation of insulin receptor by muscle CF (22.0+/-1.0%/60 min compared to 16.8+/-1.5%/60 min; P<0.05), and of IRS-1 by liver MF (37.2+/-1.7%/7.5 min compared to 33.8+/-1.7%/7.5 min; P<0.05) and CF (36.8+/-1.0%/7.5 min compared to 33.2+/-1.0%/7.5 min; P<0.05). We conclude that the observed effects of ACE-inhibition by ramipril on the protein expression of IRS-1 and on PTPase activity might contribute to its effect on insulin sensitivity.     

Lithium regulates protein tyrosine phosphatase activity in vitro and in vivo

RATIONALE: Lithium has been shown to regulate multiple intracellular signaling pathways by affecting various protein kinases. However, the counterpart of protein kinases, i.e., protein phosphatases may play an important role in lithium-regulated cellular signaling and functions. OBJECTIVES: The present work was designed to test the effect of lithium on protein phosphatases in vitro and in vivo. METHODS: PC12 cells were used as an in vitro model to characterize the effect of lithium on protein phosphatase activity. Rats treated with a lithium-containing diet were used to examine the in vivo effect of the drug on brain protein phosphatase activity.RESULTS. Lithium stimulated protein tyrosine phosphatase (PTPase) activity in a dose- and time-dependent manner in PC12 cells. A maximal stimulation of 87% was observed after 6 h of incubation with 3 mM LiCl. In contrast, protein serine phosphatase (PSPase) activity was not changed by lithium. The stimulatory effect on PTPase was not due to a direct action of the ion on the enzymes, but its selectivity was noted since treatment of cells with other monovalent cations exhibited no effect on PTPase activity. Lithium appeared to target specific PTPase(s) as it stimulated membrane-associated PTPase activity without affecting cytosolic or nuclear enzymatic activities. Moreover, the stimulation of PTPase activity in PC12 cells by lithium is independent of de novo protein synthesis. In the rat, 3 weeks of lithium treatment significantly elevated PTPase activity in hippocampus, striatum and cortex. CONCLUSION: The present findings provide the first evidence that lithium treatment selectively increases membrane-associated PTPase activity and suggest that this action may contribute to the pharmacotherapeutic actions of lithium.     

The effect of insulin on expression level of nucleoside transporters in diabetic rats

Evidence that the time course of insulin-induced changes in adenosine level in diabetic rats is different from that observed for expression of adenosine kinase prompted us to study the insulin effect on expression of nucleoside transporters in tissues of diabetic rats. RNase protection assay demonstrated that mRNA levels of equilibrative (rENT) and Na+-dependent nucleoside transporters (rCNT) were altered in diabetic tissues. The rENT1 mRNA level with respect to values obtained in age- and sex-matched nondiabetic rats was decreased by 45, 32, and 10% in diabetic heart, liver, and kidney, respectively. The level of rENT2 mRNA was lowered by 40% in diabetic kidney and heart, and by 24% in diabetic liver. Changes in the expression pattern of rCNT1 and rCNT2 in diabetic tissues differed significantly from that observed for rENT. The levels of rCNT1 and rCNT2 mRNA did not change significantly in diabetic kidney. In diabetic heart, the mRNA levels of rCNT1 and rCNT2 increased 1.7- and 2-fold, respectively. Changes in expression of nucleoside transporters were accompanied by alterations in adenosine content. Administration of insulin to diabetic rats resulted in a drop in adenosine concentration in examined tissues and return of the rCNT1, rCNT2, and rENT2 but not rENT1 mRNA levels to values observed in nondiabetic rats. In summary, these data demonstrate that insulin affects expression of nucleoside transporters in a cell-specific manner. We conclude that change in the expression level of the nucleoside transporters occurring in tissues of diabetic rat is an important factor influencing adenosine levels in the cell.     

Rosiglitazone ameliorates abnormal expression and activity of protein tyrosine phosphatase 1B in the skeletal muscle of fat-fed, streptozotocin-treated diabetic rats

Protein tyrosine phosphatase 1B (PTP1B) acts as a physiological negative regulator of insulin signaling by dephosphorylating the activated insulin receptor (IR). Here we examine the role of PTP1B in the insulin-sensitizing action of rosiglitazone (RSG) in skeletal muscle and liver. Fat-fed, streptozotocin-treated rats (10-week-old), an animal model of type II diabetes, and age-matched, nondiabetic controls were treated with RSG (10 micromol kg(-1) day(-1)) for 2 weeks. After RSG treatment, the diabetic rats showed a significant decrease in blood glucose and improved insulin sensitivity. Diabetic rats showed significantly increased levels and activities of PTP1B in the skeletal muscle (1.6- and 2-fold, respectively) and liver (1.7- and 1.8-fold, respectively), thus diminishing insulin signaling in the target tissues. We found that the decreases in insulin-stimulated glucose uptake (55%), tyrosine phosphorylation of IRbeta-subunits (48%), and IR substrate-1 (IRS-1) (39%) in muscles of diabetic rats were normalized after RSG treatment. These effects were associated with 34 and 30% decreases in increased PTP1B levels and activities, respectively, in skeletal muscles of diabetic rats. In contrast, RSG did not affect the increased PTP1B levels and activities or the already reduced insulin-stimulated glycogen synthesis and tyrosine phosphorylation of IRbeta-subunits and IRS-2 in livers of diabetic rats. RSG treatment in normal rats did not significantly change PTP1B activities and levels or protein levels of IRbeta, IRS-1, and -2 in diabetic rats. These data suggest that RSG enhances insulin activity in skeletal muscle of diabetic rats possibly by ameliorating abnormal levels and activities of PTP1B.     

丹皮多糖-2b降血糖作用的实验研究

目的：研究丹皮多糖－2b（CMP－2b)降血糖作用及作用机制。方法：用小鼠和大鼠建立葡萄糖性高血糖及四氧嘧啶性糖尿病模型，氢化可的松琥珀酸纳（HCSS)诱导胰岛素抵抗，观察丹皮多糖－2b对正常和高血糖模型动物的影响，并测定糖尿病动物SOD、Insulin、GHb、ApoA1等水平。结果：CMP－2b可降低葡萄糖和四氧嘧啶诱发的鼠高血糖，并能升高糖尿病小鼠SOD和大鼠ApoA1水平，降低GHb水平，改善小鼠胰岛素抵抗。结论：CMP－2b可有效地控制实验性高血糖，其降糖机理可能与改善机体对胰岛素的敏感性，促进外周组织对葡萄糖的利用有关。     

Divalent and trivalent alpha-ketocarboxylic acids as inhibitors of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPases) are important targets for the treatment of insulin resistance in patients with type II diabetes and as antibacterial agents. As a result, there is a growing interest in the development of potent and specific inhibitors for these enzymes. This paper describes a series of inhibitors that contain two or three alpha-ketocarboxylic acid groups that are designed to form multiple contacts with residues inside or near the active site of phosphatases. The inhibitors have been assayed against three PTPases: the Yersinia PTPase, PTP1B, and LAR. The best of the inhibitors has IC(50) values against the Yersinia PTPase and PTP1B of 0.7 and 2.7 microM, respectively. These divalent and trivalent compounds are significantly more potent than their corresponding monovalent analogues. In addition, they show good selectivity for PTP1B and the Yersinia PTPase as compared to LAR.