高脂诱发C57BL/6J小鼠Ⅱ型糖尿病模型中胰岛素剪切的变化

[目的]通过建立高脂喂养糖尿病小鼠模型,探究高脂对胰岛素剪切成熟的影响。[方法]通过给C57BL/6J小鼠饲喂高脂饲料建立II型糖尿病小鼠模型,通过腹腔葡萄糖耐量试验(IPGTT)法测定高脂糖尿病小鼠血糖浓度,通过酶联接免疫吸附剂测定法检测糖负荷后糖尿病小鼠血液中胰岛素原在总胰岛素中所占的比例,采用Western-blot法检测高脂喂养糖尿病小鼠胰岛中激素原转化酶1(PC1)和激素原转化酶2(PC2)的表达水平及内质网应激(Endoplasmic reticulum stress,ER stress)信号通路相关分子表达。[结果]通过高脂喂养C57B6小鼠,当小鼠达10月龄时,IPGTT检测结果表明糖负荷后30、60、120 min高脂喂养组血糖水平与胰岛素原/总胰岛素均显著高于对照组,Western-blot结果表明,PC1和PC2表达水平均显著降低,其原因可能与ER stress信号通路激活相关。[结论]高脂喂养糖尿病小鼠血糖水平升高可能与PC1和PC2表达水平降低导致的胰岛素剪切障碍有关,PC1和PC2表达水平的降低是由ER stress引起的。     

Proapoptotic BAX and BAK modulate the unfolded protein response by a direct interaction with IRE1alpha

Accumulation of misfolded protein in the endoplasmic reticulum (ER) triggers an adaptive stress response-termed the unfolded protein response (UPR)-mediated by the ER transmembrane protein kinase and endoribonuclease inositol-requiring enzyme-1alpha (IRE1alpha). We investigated UPR signaling events in mice in the absence of the proapoptotic BCL-2 family members BAX and BAK [double knockout (DKO)]. DKO mice responded abnormally to tunicamycin-induced ER stress in the liver, with extensive tissue damage and decreased expression of the IRE1 substrate X-box-binding protein 1 and its target genes. ER-stressed DKO cells showed deficient IRE1alpha signaling. BAX and BAK formed a protein complex with the cytosolic domain of IRE1alpha that was essential for IRE1alpha activation. Thus, BAX and BAK function at the ER membrane to activate IRE1alpha signaling and to provide a physical link between members of the core apoptotic pathway and the UPR.     

Type 2 diabetes-a matter of beta-cell life and death?

In type 2 diabetes, the beta cells of the pancreas fail to produce enough insulin to meet the body's demand, in part because of an acquired decrease in beta-cell mass. In adults, pancreatic beta-cell mass is controlled by several mechanisms, including beta-cell replication, neogenesis, hypertrophy, and survival. Here, I discuss evidence supporting the notion that increased beta-cell apoptosis is an important factor contributing to beta-cell loss and the onset of type 2 diabetes. Interestingly, a key signaling molecule that promotes beta-cell growth and survival, insulin receptor substrate 2 (IRS-2), is a member of a family of proteins whose inhibition contributes to the development of insulin resistance in the liver and other insulin-responsive tissues. Thus, the IRS-2 pathway appears to be a crucial participant in the tenuous balance between effective pancreatic beta-cell mass and insulin resistance.     

Mitochondrial dysfunction and type 2 diabetes

Maintenance of normal blood glucose levels depends on a complex interplay between the insulin responsiveness of skeletal muscle and liver and glucose-stimulated insulin secretion by pancreatic beta cells. Defects in the former are responsible for insulin resistance, and defects in the latter are responsible for progression to hyperglycemia. Emerging evidence supports the potentially unifying hypothesis that both of these prominent features of type 2 diabetes are caused by mitochondrial dysfunction.     

玉米种胚内质网胁迫相关基因对人工老化处理的响应

【目的】在植物中,内质网胁迫（endoplasmic reticulum stress,ERS）和未折叠蛋白应答（unfolded protein response,UPR）参与环境胁迫响应过程,然而,玉米种子老化过程中内质网胁迫相关基因表达情况尚未见报道。文章利用基因数字表达谱技术探究玉米种子老化过程中内质网胁迫相关基因表达规律,以期为揭示种子衰老的分子机制提供理论依据。【方法】以玉米杂交种郑单958种子为材料,采用高温（45℃）高湿（相对湿度100%）的方法进行人工老化处理。分别提取未老化处理（对照）和老化处理3 d的玉米种胚总RNA,利用Illumina HiSeqTM 2000平台进行高通量测序。去除原始数据中的接头序列、包含模糊碱基的序列以及低质量序列,获得Clean reads,利用短序列比对软件SOAPaligner/ SOAP2将Clean Reads分别比对到玉米参考基因组和参考基因序列,采用RPKM（reads per kb per million reads）方法计算基因的表达量,根据FDR（false discovery rate）＜0.001和|log2 ratio(T/CK)|≥1的标准筛选差异表达的基因,对获得的差异表达基因（differentially expressed genes,DEGs）进行KEGG（kyoto encyclopedia of genes and genomes）数据库功能注释分析,筛选出响应人工老化的内质网胁迫相关差异表达基因。利用qRT-PCR技术定量分析内质网胁迫相关基因在不同人工老化时间内的表达特性。【结果】基因数字表达谱鉴定结果表明,有104个差异表达基因在人工老化过程中参与内质网蛋白质加工（protein processing in endoplasmic reticulum）通路,其中内质网胁迫相关基因有97个（81个上调表达,16个下调表达）。对差异表达基因功能注释分析表明,内质网胁迫的标志性蛋白基因BiP以及分子伴侣蛋白基因CRT、CNT和GRP94等显著上调表达。参与内质网相关性降解（endoplasmic reticulum-associated degradation,ERAD）途径的有83个差异表达基因（70个上调,13个下调）,其中启动ERAD途径的关键酶基因EDEM （ER degradation enhancing mannosidase I-like protein）下调,参与蛋白泛素化的E2泛素结合酶基因UbcH5、E3泛素连接酶基因Hrd1和Doa10等也发生显著的表达变化。qRT-PCR结果表明,内质网胁迫相关基因在不同人工老化时间内表现表达多样性和复杂性。【结论】人工老化处理能造成玉米种胚细胞发生内质网胁迫。细胞通过上调分子伴侣基因表达和诱导ERAD途径响应内质网胁迫,但ERAD途径受阻可能引起错误折叠蛋白聚集,从而进一步加剧细胞损伤,最终导致种子活力降低甚至丧失。     

Fish oil prevents insulin resistance induced by high-fat feeding in rats

Non-insulin-dependent diabetes mellitus is an increasingly prevalent disease in Western and developing societies. A major metabolic abnormality of non-insulin-dependent diabetes is impaired insulin action (insulin resistance). Diets high in fat from vegetable and nonaquatic animal sources (rich in linoleic acid, an omega-6 fatty acid, and saturated fats) lead to insulin resistance. In rats fed high-fat diets, replacement of only 6 percent of the linoleic omega-6 fatty acids from safflower oil with long-chain polyunsaturated omega-3 fatty acids from fish oil prevented the development of insulin resistance. The effect was most pronounced in the liver and skeletal muscle, which have important roles in glucose supply and demand. The results may be important for therapy or prevention of non-insulin-dependent diabetes mellitus.     

TRB3: a tribbles homolog that inhibits Akt/PKB activation by insulin in liver

Insulin resistance is a major hallmark in the development of type II diabetes, which is characterized by the failure of insulin to promote glucose uptake in muscle and to suppress glucose production in liver. The serine-threonine kinase Akt (PKB) is a principal target of insulin signaling that inhibits hepatic glucose output when glucose is available from food. Here we show that TRB3, a mammalian homolog of Drosophila tribbles, functions as a negative modulator of Akt. TRB3 expression is induced in liver under fasting conditions, and TRB3 disrupts insulin signaling by binding directly to Akt and blocking activation of the kinase. Amounts of TRB3 RNA and protein were increased in livers of db/db diabetic mice compared with those in wild-type mice. Hepatic overexpression of TRB3 in amounts comparable to those in db/db mice promoted hyperglycemia and glucose intolerance. Our results suggest that, by interfering with Akt activation, TRB3 contributes to insulin resistance in individuals with susceptibility to type II diabetes.     

熊果酸与胰岛素抵抗研究综述

随着世界经济的快速发展,生活方式的改变,Ⅱ型糖尿病的发病率逐年升高。胰岛素抵抗作为Ⅱ型糖尿病的显著特征,成为研究的热点。熊果酸属于五环三萜类化合物,具有多种生物学效应。近来研究发现,熊果酸可以通过降低血糖、调节血脂、清除体内自由基、保护胰腺β细胞,缓解机体的胰岛素抵抗,从而具有医药开发潜力。     

PI-3K转导通路在Ⅱ型糖尿病发病机制中作用的研究进展

胰岛素是通过胰岛素信号的转导通路来发挥其调节血糖并且促进其代谢合成的,其中磷脂酰肌醇-3激酶（PI-3K）在胰岛素信号转导中起关键性作用,而胰岛素信号转导通路障碍所引起的胰岛素抵抗在Ⅱ型糖尿病治疗中有着至关重要的作用．从胰岛素抵抗的发病机制、影响PI-3K的因素等几个方面综述了PI-3K在Ⅱ型糖尿病发病机制中的作用．     

Mitochondrial dysfunction in the elderly: possible role in insulin resistance

Insulin resistance is a major factor in the pathogenesis of type 2 diabetes in the elderly. To investigate how insulin resistance arises, we studied healthy, lean, elderly and young participants matched for lean body mass and fat mass. Elderly study participants were markedly insulin-resistant as compared with young controls, and this resistance was attributable to reduced insulin-stimulated muscle glucose metabolism. These changes were associated with increased fat accumulation in muscle and liver tissue assessed by 1H nuclear magnetic resonance (NMR) spectroscopy, and with a approximately 40% reduction in mitochondrial oxidative and phosphorylation activity, as assessed by in vivo 13C/31P NMR spectroscopy. These data support the hypothesis that an age-associated decline in mitochondrial function contributes to insulin resistance in the elderly.     

Increased insulin sensitivity and obesity resistance in mice lacking the protein tyrosine phosphatase-1B gene

Protein tyrosine phosphatase-1B (PTP-1B) has been implicated in the negative regulation of insulin signaling. Disruption of the mouse homolog of the gene encoding PTP-1B yielded healthy mice that, in the fed state, had blood glucose concentrations that were slightly lower and concentrations of circulating insulin that were one-half those of their PTP-1B+/+ littermates. The enhanced insulin sensitivity of the PTP-1B-/- mice was also evident in glucose and insulin tolerance tests. The PTP-1B-/- mice showed increased phosphorylation of the insulin receptor in liver and muscle tissue after insulin injection in comparison to PTP-1B+/+ mice. On a high-fat diet, the PTP-1B-/- and PTP-1B+/- mice were resistant to weight gain and remained insulin sensitive, whereas the PTP-1B+/+ mice rapidly gained weight and became insulin resistant. These results demonstrate that PTP-1B has a major role in modulating both insulin sensitivity and fuel metabolism, thereby establishing it as a potential therapeutic target in the treatment of type 2 diabetes and obesity.     

A family with severe insulin resistance and diabetes due to a mutation in AKT2

Inherited defects in signaling pathways downstream of the insulin receptor have long been suggested to contribute to human type 2 diabetes mellitus. Here we describe a mutation in the gene encoding the protein kinase AKT2/PKBbeta in a family that shows autosomal dominant inheritance of severe insulin resistance and diabetes mellitus. Expression of the mutant kinase in cultured cells disrupted insulin signaling to metabolic end points and inhibited the function of coexpressed, wild-type AKT. These findings demonstrate the central importance of AKT signaling to insulin sensitivity in humans.     

2型糖尿病患者微血管病变与血液流变学变化、胰岛素抵抗的相关性

目的 :研究血液流变学变化和胰岛素抵抗与 2型糖尿病微血管病变的关系。方法 :检测 10 6例 2型糖尿病患者 ,其中有微血管并发症 5 3例 ,无微血管并发症 5 3例 ,以及 5 3例正常对照组的血液流变学、空腹血糖、空腹胰岛素 ,计算胰岛素敏感性指数 (ISI) ,并进行比较。结果 :糖尿病两组全血粘度和血浆粘度均显著高于正常对照组 ;ISI则显著低于正常对照组 (P<0 .0 1)。糖尿病有微血管病变组全血粘度和血浆粘度显著高于无微血管病变组 ;ISI显著低于无微血管病变组 (P<0 .0 1)。多元逐步回归分析显示 ,2型糖尿病微血管病变与糖尿病病程、血糖、全血粘度和血浆粘度呈显著正相关 (r=0 .62 4,0 .42 8,0 .3 46,0 .3 82 ,P值分别 <0 .0 0 1,0 .0 1,0 .0 5 ,0 .0 1) ,与 ISI呈显著负相关 (r=-0 .3 5 2 ,P<0 .0 5 )。结论 :2型糖尿病微血管病变患者存在持续性的高血糖、高血液粘度 ,糖尿病病程的延长 ,严重的胰岛素抵抗为 2型糖尿病微血管病变的主要危险因素。     

METABOLISM IN DIABETIC COMA PRODUCED BY ALLOXAN

Alloxan given parenterally produces in the rat a state of diabetic coma which is analogous to the severe coma of human diabetes. Such animals, moreover, show a rise in plasma inorganic phosphate and blood sugar. They also show in the liver a decrease in glycogen and in the total acid-soluble phosphates. An increase in liver inorganic phosphate occurs with a concurrent fall in adenosine pyrophosphate and other organo-phosphates. Hence the rise in plasma inorganic phosphate during coma is at least partially due to a loss of liver phosphate. It is probable that this rise in plasma inorganic phosphate results from a breakdown of organo-phosphates which result from the depressed oxidations associated with insulin lack. Insulin, when administered in exceptionally large doses, tends to cause improvement in both the clinical and chemical state of comatose rats.     

A selective inhibitor of eIF2alpha dephosphorylation protects cells from ER stress

Most protein phosphatases have little intrinsic substrate specificity, making selective pharmacological inhibition of specific dephosphorylation reactions a challenging problem. In a screen for small molecules that protect cells from endoplasmic reticulum (ER) stress, we identified salubrinal, a selective inhibitor of cellular complexes that dephosphorylate eukaryotic translation initiation factor 2 subunit alpha (eIF2alpha). Salubrinal also blocks eIF2alpha dephosphorylation mediated by a herpes simplex virus protein and inhibits viral replication. These results suggest that selective chemical inhibitors of eIF2alpha dephosphorylation may be useful in diseases involving ER stress or viral infection. More broadly, salubrinal demonstrates the feasibility of selective pharmacological targeting of cellular dephosphorylation events.     

门冬胰岛素30注射液强化治疗Ⅱ型糖尿病的临床观察

目的观察门冬胰岛素30（诺和锐30）注射液强化治疗Ⅱ型糖尿病的效果.方法Ⅱ型糖尿病患者86例,给予生活方式干预,包括健康教育,低热量、低脂肪饮食,中等体力活动,戒烟、限酒,血压高者给予降压等,血脂异常者给予调脂.治疗组给予诺和锐30注射液3餐前皮注（根据血糖监测结果调整胰岛素剂量）,对照组给予诺和灵30R笔芯,早、晚餐前30 min皮注.观察6个月,观察治疗前后患者的FBG、2hPBG、HbA1c及低血糖发生率的变化.结果Ⅱ型糖尿病患者用诺和锐30强化治疗后,FBG、2hPBG、HbA1c等指标均好于对照组,低血糖发生率较对照组减少,P〈0.01,经比较有统计学意义.结论对Ⅱ型糖尿病患者应用诺和锐30强化治疗,血糖平稳,低血糖发生率减低,疗效肯定.     

运动对骨骼肌胰岛素功能影响

随着经济发展、人们生活方式改变,糖尿病已严重威胁人类健康。胰岛素抵抗是2型糖尿病发生的关键因素,从胰岛素合成后与胰岛素受体结合到实现生理效应的一系列过程中,都可能发生异常。运动疗法能够提高组织对胰岛素的敏感性,提高机体维持血糖稳定的激素调节能力。查阅了近年来国内外有关运动干预骨骼肌胰岛素功能的研究情况,分析了运动对骨骼肌胰岛素影响的主要因素,以及不同运动形式对骨骼肌胰岛素的影响。     

持续气道正压通气治疗阻塞型睡眠呼吸暂停低通气综合征合并2型糖尿病的疗效观察

目的通过观察持续气道正压通气（CPAP）治疗对合并2型糖尿病（T2DM）的阻塞型睡眠呼吸暂停低通气综合征（OSAHS）患者的胰岛素抵抗（IR）的影响。方法 46例合并T2DM的OSAHS患者随机分为2组,对照组（22例）行保守治疗,而实验组（24例）加用CPAP治疗。观察所有患者治疗前及治疗后1、3、6个月的临床指标变化,采用稳态模式评估（HOMA）指数评价IR。结果实验组患者治疗1个月后,其最低SaO 2水平明显高于治疗前及同一时段的对照组（P〈0.01）;治疗3个月后,其呼吸暂停低通气指数明显低于治疗前及同一时段的对照组（P〈0.01）;治疗6个月后,其空腹胰岛素及HOMA水平明显低于治疗前及同一时段的对照组（P〈0.01）。结论长期CPAP治疗可显著改善合并T2DM的OSAHS患者的IR。