小牛血清去蛋白注射液对2型糖尿病胰岛素抵抗大鼠模型骨骼肌GLUT4 mRNA表达的影响

目的观察小牛血清去蛋白注射液(DECB)对2型糖尿病胰岛素抵抗模型大鼠骨骼肌中葡萄糖转运因子4(GLUT4)的mRNA表达的影响。方法以高脂高糖饮食加链脲佐菌素制作2型糖尿病胰岛素抵抗大鼠模型,观察DECB对大鼠葡萄糖耐量(OGTT),运用RT-PCR方法检测大鼠模型骨骼肌中GLUT-4的mRNA表达。结果 DECB可改善OGTT,增加大鼠模型骨骼肌中GLUT4的mRNA表达。结论 DECB具有较好的降血糖、改善胰岛素抵抗、防治糖尿病并发症的作用。     

NIDDM大鼠骨骼肌组织GLUT4mRNA表达及其与胰岛素分泌关系的实验研究

目的 观察非胰岛素依赖型糖尿病（NIDDM）大鼠骨骼肌葡萄糖转运体4（glucose transporter4,GLUT4)mRNA表达及其与胰岛素分泌的关系。方法 制备NIDDM大鼠模型,用Northern blot方法测定骨骼肌组织中GLUT4mRNA表达量;放射免疫法测定血清胰岛素含量;免疫组化法观察胰岛素阳性β细胞。结果 NIDDM大鼠骨骼肌GLUT4mRNA表达显低下,仅为对照组的45％（P＜0.01);其空腹基础胰岛素水平正常,但葡萄糖耐量试验胰岛素水平较对照组明显降低,2h胰岛素分泌有延迟现象;免疫组化实验NIDDM大鼠胰岛体积减少一半以上,胰岛素阳性β细胞数量明显减少。结论 NIDDM大鼠骨骼肌GLUT4mRNA表达量低下,该反应与体内胰岛素分泌水平呈现一定的正相关性。     

白细胞介素6对2型糖尿病大鼠骨骼肌糖代谢的影响

目的：通过研究白细胞介素6（IL－6）对2型糖尿病（T2DM）大鼠骨骼肌葡萄糖转运体4（GLUT4）和糖原含量的影响,探讨其影响T2DM糖代谢的机制。方法：健康雄性SD大鼠随机分为4组：正常对照组（N组）10只,糖尿病IL-6抗原干预组（A组）10只,糖尿病IL－6抗体干预组（B组）8只,糖尿病对照组（C组）8只。测定血糖、血清胰岛素、血脂等指标;取股四头肌比色法测定肌糖原含量,免疫组化法测定骨骼肌GLUT4蛋白表达。结果：T2DM大鼠骨骼肌糖原含量和GLUT4蛋白表达较正常大鼠明显降低,IL-6抗体干预可以升高T2DM大鼠骨骼肌糖原含量和GLUT4蛋白表达。结论：T2DM大鼠骨骼肌GLUT4蛋白表达减少;IL－6抗体阻滞通过增加GLUT4蛋白表达促进骨骼肌对糖的利用。     

脂联素影响骨骼肌胰岛素抵抗模型中葡萄糖转运蛋白4表达的研究

目的：通过建立骨骼肌L6细胞胰岛素抵抗模型,探讨骨骼肌L6细胞中脂联素（ APN）的分泌,以及脂联素对骨骼肌胰岛素抵抗模型中葡萄糖转运蛋白4（GLUT4）表达的影响。方法（1）体外培养大鼠L6成肌细胞,诱导分化后,给予不同浓度的棕榈酸（PA）,测定不同时间细胞培养上清液葡萄糖浓度,观察PA对L6细胞摄取葡萄糖的影响,建立胰岛素抵抗模型;（2）根据实验条件的不同分为三组：NC组（正常对照组,即骨骼肌L6细胞组）;IR组（胰岛素抵抗模型组）;IR＋PIO组（胰岛素抵抗模型＋吡格列酮组）。应用Western blot方法分别测定上述三组APN和GLUT4表达水平。结果（1）0．4 mmol· L^-1的棕榈酸在作用12、24、36 h以及0．6～0．8 mmol· L^-1棕榈酸作用8～36 h后,细胞培养上清液中葡萄糖含量,明显高于对照组。胰岛素抵抗模型建立;（2）Western blot结果显示：①与NC组比较,IR组APN和GLUT4表达均减少,差异有统计学意义;②与IR组比较,IR＋PIO组其APN和GLUT4表达均增加,差异有统计学意义。结论（1）大鼠L6成肌细胞培养并诱导分化后,经过一定条件下PA刺激,可以建立胰岛素抵抗模型;（2）大鼠L6细胞可分泌和表达脂联素,骨骼肌源性脂联素上调L6细胞GLUT4的表达;（3）吡格列酮作为PPAR-γ激动剂,可增加大鼠L6细胞脂联素的分泌,进而改善胰岛素敏感性。     

二甲双胍与罗格列酮对2型糖尿病大鼠GLUT4表达的比较

目的比较二甲双胍与罗格列酮对2型糖尿病大鼠骨骼肌葡萄糖转运蛋白4(GLUT4)mRNA表达的影响.方法以低剂量链脲佐菌素(STZ)加高热量饲料喂养制作模型,灌胃给药4周,检测糖耐量、空腹血清胰岛素(Ins)及骨骼肌GLUT4 mRNA表达量的变化.结果造模后大鼠注射葡葡糖后30,60,120min血糖显著升高,空腹Ins无明显变化,骨骼肌GLUT4 mRNA表达量显著降低.两药均可使注糖后120min血糖下降;罗格列酮尚可降低空腹血糖.二甲双胍可使骨骼肌GLUT4 mRNA表达量明显升高,但罗格列酮对骨骼肌GLUT4 mRNA表达的降低无影响.结论本造模方法可导致大鼠产生类似2型糖尿病的变化,两药均可改善此模型糖耐量异常,二甲双胍的作用与增强骨骼肌GLUT4基因表达有关,而罗格列酮的作用可能与其它环节有关.     

过表达KLF4对棕榈酸所致L6骨骼肌细胞胰岛素抵抗的影响

目的探讨Krtippel样因子4（KLF4）过表达对大鼠L6骨骼肌细胞胰岛素抵抗的影响。方法采用棕榈酸诱导法建立大鼠IJ6骨骼肌细胞的胰岛素抵抗模型,随机分为对照组和转染组。对照组转染腺病毒空载体（Ad）,转染组转染KLF4腺病毒表达载体（Ad—KLF4）。采用Real—timePCR和Western—blot检测两组KLF4、胰岛素受体（IR）和葡萄糖转运蛋白4（GLUT4）的表达水平,采用葡萄糖氧化酶法检测两组培养液中的葡萄糖浓度。结果与对照组比较,棕榈酸诱导组对葡萄糖的摄取量显著降低（P〈0．05）,KLF4、IR、GLUT4表达显著下调（P〈0．05）。KLF4过表达可显著提高细胞对胰岛素的敏感性,并上调IR、GLUT4表达。结论过表达KLF4可导致IR、GLUT4表达上调,并改善骨骼肌细胞的胰岛素抵抗。     

二甲双胍与罗格列酮对2型糖尿病大鼠GLUT4表达的比较

目的　比较二甲双胍与罗格列酮对2型糖尿病大鼠骨骼肌葡萄糖转运蛋白4(GLUT4)mRNA表达的影响。方法　以低剂量链脲佐菌素(STZ)加高热量饲料喂养制作模型,灌胃给药4周,检测糖耐量、空腹血清胰岛素(Ins)及骨骼肌GLUT4mR-NA表达量的变化。结果　造模后大鼠注射葡葡糖后30, 60, 120min血糖显著升高,空腹Ins无明显变化,骨骼肌GLUT4mR-NA表达量显著降低。两药均可使注糖后120min血糖下降;罗格列酮尚可降低空腹血糖。二甲双胍可使骨骼肌GLUT4mRNA表达量明显升高,但罗格列酮对骨骼肌GLUT4mRNA表达的降低无影响。结论　本造模方法可导致大鼠产生类似2型糖尿病的变化,两药均可改善此模型糖耐量异常,二甲双胍的作用与增强骨骼肌GLUT4基因表达有关,而罗格列酮的作用可能与其它环节有关。     

妊娠期糖尿病患者网膜脂肪和肌肉组织GLUT4水平的研究

目的探讨妊娠期糖尿病（GDM）患者网膜脂肪组织与腹直肌葡萄糖转运蛋白4（GLUT4）表达的差异及其与胰岛素抵抗（IR）的关系。方法逆转录-聚合酶链反应（RT-PCR）检测23例GDM（GDM组）、21例正常孕妇（NGT组）网膜脂肪组织与腹直肌GLUT4mRNA的表达水平,测量空腹血糖（FPG）、空腹胰岛素（FINS）等指标,并计算胰岛素抵抗指数（HOMA-IR）值。结果2组腹直肌GLUT4mRNA表达量均高于对应组的网膜脂肪（P〈0.05）;GDM组网膜脂肪GLUT4mRNA表达量低于NGT组（P〈0.05）;2组腹直肌GLUT4mRNA表达量比较差别无统计学意义（P〉0.05）。网膜脂肪GLUT4mRNA表达量与孕前BMI、孕前腰臀比、FPG、FINS、HOMA-IR呈负相关（P〈0.05）;腹直肌GLUT4mRNA表达量与孕前BMI、孕前腰臀比、FPG、FINS、HOMA-IR均无相关性（P〉0.05）。结论在GDM患者网膜脂肪中GLUT4mRNA存在低表达,并且这种低表达可能与IR有关。     

小檗碱改善2型糖尿病大鼠胰岛素抵抗与PI-3K、GLUT4蛋白相关性的研究

目的观察小檗碱对2型糖尿病大鼠骨骼肌组织磷脂酰肌醇3激酶(phosphatidylinositol-3-kinase,PI-3K)之p85亚基、葡萄糖转运子4(glucose transporter4,GLUT4)蛋白表达的影响,以探讨小檗碱改善胰岛素抵抗,防治2型糖尿病的分子机制。方法采用尾静脉注射小剂量链脲佐菌素(streptozotocin,STZ,30mg.kg-1)加高脂高热量饲料喂养的方法建立2型糖尿病大鼠模型,以小檗碱干预10wk,检测血糖和血清胰岛素,用Western blot方法检测小檗碱干预后2型糖尿病大鼠骨骼肌组织PI-3K之p85亚基、GLUT4蛋白表达水平。结果小檗碱干预的2型糖尿病大鼠骨骼肌组织PI-3K之p85亚基、GLUT4蛋白表达水平均较模型组显著增加。结论小檗碱对2型糖尿病的治疗效应可能与提高骨骼肌组织中PI-3K之p85亚基、GLUT4蛋白表达水平有关。     

仙人掌果多糖降血糖作用及其机制

目的：研究仙人掌果多糖提取物（CFPE）的降血糖作用及其相关分子机制。方法：采用链脲佐菌素（STZ）复制糖尿病大鼠模型。连续给药8周,观察各组大鼠体重和糖化血红蛋白（GHb）的变化。运用RT-PCR技术,检测糖尿病大鼠肝组织和骨骼肌的胰岛素受体（IR）及骨骼肌葡萄糖转运蛋白4（GluT4）mRNA的表达。结果：与模型组比较,CFPE可明显降低糖尿病大鼠GHb含量,可使糖尿病大鼠体重明显回升;增加肝脏和骨骼肌IR及骨骼肌GluT4 mRNA的表达。结论：CFPE对糖尿病大鼠有明显的降血糖作用,其机制可能与其增加肝脏和骨骼肌IR以及骨骼肌GluT4 mRNA的表达有关。     

Toona sinensis Roem (Meliaceae) leaf extract alleviates hyperglycemia via altering adipose glucose transporter 4

In this study we tested the effects of Toona sinensis leaf extracted with water (TSL1) on alloxan-induced (50 mg/kgBwt, i.v.) diabetic Long-Even rats. Diabetic rats given TS leaf with water (TSL1), with 50% alcohol (TSL3) or with H2O extract (TSL5) showed lower levels of plasma glucose. Normal rats given Glibenclamide (GC) had lower levels of plasma glucose, but TSL1 administration showed no significant effect on plasma glucose. By contrast, TSL1 or GC given to alloxan-induced diabetic rats showed a 40% reduction in plasma glucose compared to diabetic rats. Diabetic rats had lower levels of insulin. Interestingly, TSL1 or GC given to diabetic rats showed improvements in plasma insulin levels. Diabetic rats had lower expressions of glucose transporter 4 (GLUT4) mRNA (RT-PCR) and GLUT4 protein (Western blot) in brown and white adipose tissues; in contrast, diabetic rats given TSL1 or GC showed a significant increase in both GLUT4 mRNA and protein levels. Moreover, the expressions of GLUT4 mRNA in red and white muscles were not significantly different among diabetic rats, diabetic rats given TSL1 or GC, and the normal rats. Compared to diabetic rats, diabetic rats given TSL1 or GC had lower levels of GLUT4 protein in white muscle but not in red muscle. Conclusively, T. sinensis Roem (Meliaceae) leaf possesses the hypoglycemia effect underlying an increment of insulin to mediate the adipose glucose transporter 4 mechanism.     

Adipocyte-derived exosomal miR-27a induces insulin resistance in skeletal muscle through repression of PPARγ

OBJECTIVE To explore increasingly exosomal serum miR-27 a derived from adipocytes could be taken up by skeletal muscle tissue and induce insulin resistance in skeletal muscle in obese state. METHODS The association between miR-27 a and insulin resistance in skeletal muscle was determined in obese children,high-fat diet-induced miR-27 a knockdown obese mice,db/db mice and C2C12 cells overexpressing miR-27 a.The crosstalk mediated by exosomal miR-27 a between adipose tissue and skeletal muscle was determined in C2C12 cel s incubated with conditioned medium prepared from palmitate-treated 3 T3-L1 adipocytes. RESULTS After knockdown miR-27 a in obese insulin resistance mice,impaired insulin resistance, glucose intolerance and insulin resistance of skeletal muscle were partly restored. In high-fat diet group, the expressions of IRS-1 and GLUT4 in glucose uptake signal pathway of skeletal muscle were significantly decreased, while the expression of IRS-1 and GLUT4 was restored after miR-27 a knockdown. The content of FABP4, a marker specific for exosomes from adipocytes, was detected in sera, skeletal muscle, supernatant of adipocytes and co-cultured C2C12 cells; furthermore,exosomal miR-27 a in serum and adipocyte supernatants were detect, and fluorescence co-localization experiments were conducted to detect whether the exosomal miR-27 a in serum is mainly derived from adipocyte; finally,we used the supernatant of adipose tissue to construct conditioned media to treat with C2C12 cells, and detected whether adipocytes derived exosomal miR-27 a could impaired glucose uptake signaling pathway of skeletal muscle. the expressions of PPARγ silencing high-fat diet induced C57 BL/6 J obese mouse model and adenovirus intervention miR-27 a knockdown model were examined,and a C2C12 cell model overexpressing miR-27 a in the absence or presence with rosiglitazone(PPARγ activator)were established to test glucose consumption, glucose uptake, and glucose uptake signaling pathways of skeletal muscle cells. CONCLUSION These results identify a novel crosstalk signaling pathway between adipose tissue and skeletal muscle in the development of insulin resistance, and indicate that adipose tissue-derived miR-27 a may play a key role in the development of obesity-triggered insulin resistance in skeletal muscle.     

Role of SNARE's in the GLUT4 translocation response to insulin in adipose cells and muscle

Insulin stimulates glucose transport in skeletal muscle, heart, and adipose tissue by promoting the appearance of GLUT4, the major glucose transporter isoform present in these tissues, on the cell surface. This is achieved by differentially modulating GLUT4 exocytosis and endocytosis, between a specialized intracellular compartment and the plasma membrane. Ligands which activate the heterotrimeric GTP-binding proteins Gs and Gi appear to modulate insulin-stimulated glucose transport through effects on the fusion of docked GLUT4-containing vesicles with the plasma membrane. In insulin resistance states, reduced cellular GLUT4 levels in adipose cells fully account for the decreased glucose transport response to insulin in these cells. In contrast, although insulin-stimulated GLUT4 translocation is also impaired in muscle, total cellular levels of GLUT4 are not altered. The defect in muscle has been attributed to a GLUT4 trafficking problem and thus studies of this mechanism could provide clues as to the nature of the impairment. The movement of GLUT4-containing vesicles from an intracellular storage site to the plasma membrane and the fusion of docked GLUT4-containing vesicles with the plasma membrane are conceptually similar to some secretory processes. A general hypothesis called the SNARE hypothesis (soluble NSF attachment protein receptors where NSF stands for N-ethylmaleimide-sensitive fusion protein) postulates that the specificity of secretory vesicle targeting is generated by complexes that form between membrane proteins on the transport vesicle (v-SNARE's) and membrane proteins located on the target membrane (t-SNARE's). Several v- and t-SNARE's have been identified in adipose cells and muscle. VAMP2 and VAMP3/cellubrevin (v-SNARE's) have been shown to interact with the t-SNARE's syntaxin 4 and SNAP-23. The cytosolic protein NSF has the characteristic of binding to the v-/t-SNARE complex through its interaction with alpha-SNAP, another soluble factor. Furthermore, recent studies have demonstrated that VAMP2/3, syntaxin 4, SNAP-23, and NSF are functionally involved in insulin-stimulated GLUT4 translocation in adipose cells and thus are likely to be involved in the Gs- and Gi-mediated modulation of the glucose transport response to insulin as well. This review summarizes recent advances on the normal mechanism of GLUT4 translocation and discusses how this process could be affected in insulin resistant states such as type II diabetes.     

Karanjin from Pongamia pinnata induces GLUT4 translocation in skeletal muscle cells in a phosphatidylinositol-3-kinase-independent manner

Insulin-stimulated glucose uptake in skeletal muscle is decreased in type 2 diabetes due to impaired translocation of insulin-sensitive glucose transporter 4 (GLUT4) from intracellular pool to plasma membrane. Augmenting glucose uptake into this tissue may help in management of type 2 diabetes. Here, the effects of an identified antihyperglycemic molecule, karanjin, isolated from the fruits of Pongamia pinnata were investigated on glucose uptake and GLUT4 translocation in skeletal muscle cells. Treatment of L6-GLUT4myc myotubes with karanjin caused a substantial increase in the glucose uptake and GLUT4 translocation to the cell surface, in a concentration-dependent fashion, without changing the total amount of GLUT4 protein and GLUT4 mRNA. This effect was associated with increased activity of AMP-activated protein kinase (AMPK). Cycloheximide treatment inhibited the effect of karanjin on GLUT4 translocation suggesting the requirement of de novo synthesis of protein. Karanjin-induced GLUT4 translocation was further enhanced with insulin and the effect is completely protected in the presence of wortmannin. Moreover, karanjin did not affect the phosphorylation of AKT (Ser-473) and did not alter the expression of the key molecules of insulin signaling cascade. We conclude that karanjin-induced increase in glucose uptake in L6 myotubes is the result of an increased translocation of GLUT4 to plasma membrane associated with activation of AMPK pathway, in a PI-3-K/AKT-independent manner.     

Exercise-induced galanin release facilitated GLUT4 translocation in adipocytes of type 2 diabetic rats

Although galanin has been shown to increase insulin sensitivity in skeletal muscle of rats, there is no literature available about the effect of galanin on Glucose Transporter 4 (GLUT4) translocation from intracellular membrane pools to plasma membranes in adipocytes of type 2 diabetic rats. In the present study M35, a galanin antagonist was used to elucidate whether exercise-induced galanin release increased GLUT4 translocation in adipocytes of streptozotocin-induced diabetic rats. The present findings showed that plasma galanin levels after swimming training in all four trained groups were higher compared with each sedentary control. M35 treatment had an inhibitory effect on glucose infusion rates in the euglycemic-hyperinsulinemic clamp test and GLUT4 mRNA expression levels in adipocytes. Moreover, M35 treatment reduced GLUT4 concentration in both plasma membranes and total cell membranes. The ratios of GLUT4 contents in plasma membranes to total cell membranes in four drug groups were lower compared with each control. These data demonstrate a beneficial role of endogenous galanin to transfer GLUT4 from internal stores to plasma membranes in adipocytes of type 2 diabetic rats. Galanin plays a significant role in regulation of glucose metabolic homeostasis and is an important hormone relative to diabetes.     

虫草多糖对2型糖尿病小鼠InsR／IRS-1通路及糖代谢的影响

目的：观察虫草多糖对2型糖尿病小鼠InsR／IRS—1通路及糖代谢的影响。方法：采用高脂饲料联合腹腔注射小剂量链脲佐菌素（STZ,25mg·kg-1）建立胰岛素抵抗2型糖尿病模型,每日给予不同剂量虫草多糖（200,400mg·kg-1）治疗,28d后．免疫印迹法检测实验小鼠骨骼肌内胰岛素受体（1nsR）、胰岛素受体底物（IRS-1）及葡萄糖转运蛋白（GLUT4）的表达水平。检测肝脏葡萄糖激酶（GK）、磷酸果糖激酶（PFK）活性水平。结果：虫草多糖治疗组可显著改善糖尿病小鼠InsR／IRS一1及GLUT4蛋白的畀常表达（P〈0．05）;并呈剂量依赖性地增强小鼠肝脏GK及PFK酶活性,与糖尿病模型组比较差畀有统计学意义（P〈0．05或0．01）。结论：虫草多糖可增强胰岛素信号通路敏感性,改善葡萄糖代谢,从而缓解糖尿病小鼠胰岛素抵抗及高血糖症状,为胰岛素抵抗2型糖尿病的临床治疗提供新的依据。     

Effects of losartan in combination with or without exercise on insulin resistance in Otsuka Long–Evans Tokushima Fatty rats

Hypertension often complicates type 2 diabetes mellitus, and angiotensin converting enzyme inhibitor treatment has been shown to improve insulin resistance in such cases. However, the effect of angiotensin II type-1 (AT₁) receptor antagonists on insulin resistance is still controversial. To gain further information on this effect, we examined the effect of losartan on insulin resistance in Otsuka Long–Evans Tokushima Fatty (OLETF) rats, a model of type 2 diabetes mellitus. Losartan administration alone lowered systolic blood pressure, but did not improve oral glucose tolerance test or insulin resistance in OLETF rats. However, the administration of losartan with exercise significantly improved both systolic blood pressure and insulin resistance relative to control OLETF rats. On the other hand, losartan treatment, regardless of exercise, increased glucose uptake in excised soleus muscle and fat cells. To explore the beneficial effect of losartan on skeletal muscle glucose uptake, we examined intracellular signaling of soleus muscle. Although Akt activity and glucose transporter type 4 (GLUT4) expressions were not affected by losartan with or without exercise, extracellular signal-regulated kinase (ERK1/2) and p38 mitogen-activated protein (MAP) kinase activities were increased by both interventions. These results indicate that angiotensin AT₁ receptor antagonist improved local insulin resistance, but not systemic insulin resistance. These findings may explain the controversy over the effect of angiotensin AT₁ receptor antagonists on insulin resistance in clinical use. The enhancing effect of angiotensin AT₁ receptor antagonist on skeletal muscle glucose uptake may be attributable to MAP kinase activation or other mechanisms rather than phosphatidylinositol 3-kinase activation.