血小板源生长因子在糖尿病大鼠心肌的表达及意义

目的探讨血小板源生长因子-B（PDGF-B）在糖尿病心肌病发病机制中的作用。方法8周龄雄性sD大鼠60只,随机分为对照组30只、糖尿病组30只。链脲佐菌素（STZ）一次性腹腔注射建立糖尿病模型,每2周测量血糖、体重。在病程4周、8周、12周分别从两组大鼠中随机选择6只,称量并计算心体比（H／B）和左室重量指数（LVMI）。电镜观察比较12周糖尿病组与对照组大鼠心肌超微结构,光镜观察比较两组冠脉病变。RT～PCR比较不同病程各组大鼠心肌PDGF—B、纤维连接蛋白（FN）、Ⅲ型胶原（Colm）的mRNA表达情况。结果STZ诱导糖尿病SD大鼠在病程12周糖尿病心肌病已形成。在病程4周、8周、12周,糖尿病组H／B、LVMI逐渐增加,心肌PDGF—B mRNA表达显著上调（P〈0．01）,随着病程延长,呈逐渐增高趋势,与FN、Col Ⅲ表达进行性增高相平行。PDGF—B与FN、Col ⅢmRNA表达呈明显正相关（r=0．766,0．794,均P〈0．01）。结论糖尿病大鼠心肌PDGF—B表达上调与细胞外基质（ECM）的积聚密切相关,在糖尿病心肌病形成过程中起重要作用。     

高糖高脂对培养成年大鼠心肌细胞损伤观察及机制初探

目的建立成年大鼠心肌细胞培养模型,观察给予高糖、高脂刺激后是否发生心肌细胞损伤和凋亡,并分析其可能机制。方法将分离所得成年大鼠心肌细胞接种入培养皿后随机分为2组进行培养。正常对照组：以M199培养基（Media199）加入5mmol／L葡萄糖与20mmol／L甘露醇作为正常对照培养基培养细胞;高糖高脂组：以M199加入高糖（25mmol／L葡萄糖）高脂（600μmol／L软脂酸）作为培养基培养模拟糖尿病。培养48h后,分别收集培养基上清与细胞,进行心肌损伤和凋亡指标测定。结果高糖高脂组乳酸脱氢酶（LDH）,细胞凋亡蛋白caspase-3、caspase-8、caspase-9活性显著升高,与正常对照组比较,差异均具有统计学意义（P均〈0．01）。结论在培养的成年大鼠心肌细胞,高糖、高脂可引起心肌细胞损伤和凋亡,这种凋亡与easpase-8和caspase-9依赖的凋亡途径有关。     

二甲双胍对2型糖尿病大鼠心肌损伤的保护作用

目的 观察2型糖尿病(T2DM)大鼠心肌细胞凋亡、心肌间质胶原堆积及二甲双胍(MET)的干预作用.方法 8周龄SD大鼠高热量饮食1月后,腹腔注射小剂量链脲佐菌素(STZ,30 mg/kg)制备模型,成模后分别于12、24 w,采用光镜、原位末端标记法、流式细胞术检测心肌细胞凋亡,采用Masson染色观察胶原堆积程度,并分别检测各组大鼠心肌组织基质金属蛋白酶-2(MMP-2)、基质金属蛋白酶-9(MMP-9)、金属蛋白酶组织抑制物-1(TIMP-1) mRNA表达变化及MMP-2、MMP-9、TIMP-1蛋白水平的变化.结果 成模后12、24 w,T2DM组大鼠心肌凋亡细胞数明显增多,MET干预组大鼠的凋亡率降低.T2DM大鼠心肌间质胶原含量明显增加,MMP-2的表达明显减低,MMP-9、TIMP-1的表达均明显增加,但MMP-9/TIMP-1的比值下降.MET治疗组胶原含量明显减少,MMP-2表达明显上调,MMP-9和TIMP-1下调,但MMP-9/TIMP-1的比值增加.结论 T2DM大鼠心肌损伤表现为心肌细胞凋亡增加和间质纤维化,MMP-2、MMP-9及TIMP-1的调节失衡参与了T2DM心肌间质纤维化的发生与发展,MET可通过抑制糖尿病大鼠心肌细胞凋亡和心肌纤维化而减轻心肌损伤.     

心肌脂质过氧化反应程度对糖尿病大鼠缺血再灌注损伤的影响

目的测定链脲佐菌素(STZ)诱导的不同周期精尿病大鼠对心肌缺血／再灌注(I／ R)损伤的影响及其与心肌脂质过氧化反应程度及血浆一氧化氮(NO)变化的关系。方法阻断和开放左冠状动脉前降支建立大鼠急性心肌I／R模型。用TTC染色测定大鼠心肌 I／R后梗死面积;用T／BARS法测定脂质过氧化反应程度;用硝酸还原酶法测定NO含量结果 STZ处理后2周,糠尿病组(2WD)心肌梗死面积比对照组(2WC)明显缩小,STZ处理后16周(16WD),梗死面积比对照组(16WC)增加;心脏组织的脂质过氧化物反应产物 2WD组较2WC组低,但是在16WD组中较16WC组显著增加;血浆NO水平2WD组较 2WC组增高,但是16WD组较16WC组显著减少。结论 STZ诱导的大鼠急、慢性期糖尿病对心肌I／R损伤呈现相反的作用。这可能是由于大鼠急、慢性期糖尿病相反的心肌脂质过氧化反应程度及NO改变而引起。     

愈肾合剂对糖尿病肾病大鼠肾脏细胞凋亡及ERK信号转导系统的影响

目的观察愈肾合剂对糖尿病(DN)肾病大鼠肾脏细胞凋亡及ERK信号转导系统的影响。方法 SD大鼠单侧肾切除加腹腔注射链脲佐菌素(STZ)复制DN模型,每日愈肾合剂灌胃,8 w后流式细胞术检测肾脏皮质细胞凋亡数目及caspase-9和caspase-3蛋白表达,采用Western印迹方法检测肾脏皮质细胞内磷酸化ERK1/2蛋白质的表达。结果愈肾合剂明显减少DN大鼠肾脏皮质细胞凋亡数目,降低caspase-9和caspase-3的蛋白表达,激活ERK信号通路。结论愈肾合剂可通过抗凋亡途径发挥肾脏保护作用。     

益母草防治实验性糖尿病心肌损伤的研究

益母草注射液应用于STZ诱导的2型糖尿病大鼠，能抑制心肌细胞凋亡，改善心肌间隙连接蛋白43（Cx43）的表达和空间分布，防治糖尿病心肌损伤。     

糖尿病大鼠心力衰竭时心肌细胞凋亡的研究

目的探讨糖尿病大鼠心力衰竭时是否存在心肌细胞凋亡.方法建立STZ糖尿病大鼠模型,饲养12周,经心功能检测后确认为糖尿病心力衰竭的大鼠,采用TUNEL法及TEM法,检测糖尿病大鼠左室心肌的凋亡细胞.结果 糖尿病大鼠出现心功能异常并可见凋亡的心肌细胞,而对照组左室心肌组织中未见心肌细胞凋亡.结论心肌细胞凋亡与糖尿病大鼠心力衰竭密切相关.     

老年大鼠心肌组织中促凋亡蛋白Omi/HtrA2的表达改变及可能意义

目的验证老年大鼠心肌细胞凋亡程度；测定老年心肌组织中内源性线粒体后凋亡调节蛋白Omi／HtrA2和XIAP的表达及其与心肌细胞凋亡的关系。方法分别选取雄性成年SD大鼠[体重（278±10）g，4-6个月]和老年SD大鼠[体重（525±8）g，22-24个月]。随机分为以下4组：正常成年组（40只）；正常老年组（40只）；老年ucf～101组（10只），腹腔注射ucf-101（1．5μmol／kg）；老年DMSO组（10只），腹腔注射DMSO（1．5μmol／kg）。采用Caspase-3活性测定法检测大鼠心肌组织中心肌细胞凋亡发生情况；用Western—blot蛋白印记法检测大鼠心肌组织中Omi／HtrA2和XIAP的表达水平。结果以成年大鼠caspase-3比活性（1．00±0．04）为1，老年大鼠的caspase-3的比活性（2．31±0．43，P〈0．01）显著增高。老年大鼠心肌组织中Omi／HtrA2表达明显增高，XIAP表达明显下降。给予特异性Omi／HtrA2的抑制剂ucf-101，可显著减少老年大鼠心肌组织caspase-3的表达。结论老年大鼠心肌组织中表达增多的Omi／HtrA2，可能导致了XIAP的降解以及随后的caspase-3活化和细胞凋亡。     

链脲佐菌素诱导糖尿病大鼠心肌缺血/再灌注损伤

目的 研究链脲佐菌素(STZ)诱导的糖尿病大鼠缺血/再灌注(I/R)心肌的损伤,从心电图、心肌梗死面积、心肌大体和超微结构观察损伤的程度并分析其可能的作用机制.方法 采用STZ(45 mg/kg)诱导大鼠糖尿病4周后制备心肌缺血30 min再灌注120 min模型,连续检测心电图变化,用2,3,5-氯化三苯基四氮唑(TTC)染色法测定心肌梗死面积、HE染色和电镜下观察心肌组织结构的改变.结果 糖尿病大鼠由I/R损伤引起的心肌梗死面积并没有增加,但是HE染色和电镜下均发现糖尿病心肌损伤更为严重,肌纤维结构消失、心肌细胞膜和细胞核损伤、线粒体降解、血管淤滞、内皮损伤.结论 STZ诱导糖尿病4周的大鼠缺血/再灌注后心肌损伤较非糖尿病大鼠加重.     

牛磺酸对糖尿病心肌病大鼠的保护作用

目的:探讨牛磺酸对糖尿病大鼠心肌的保护作用机制。方法:用Wistar大鼠52只,高糖高脂饮食 喂养4周造成胰岛素抵抗后,随机选其中7只腹腔注射枸橼酸钠缓冲液为对照组1;其余用链脲菌素(STZ)腹腔 注射诱发2型糖尿病,20周后成功复制糖尿病心肌病,通过颈动脉插管将等容舒张期左室内压下降的最大速率 (-dp/dtmax)≤93.1kPa/s的糖尿病大鼠(24只)分组:7只用双蒸水腹腔注射,为对照组2;8只通过腹腔注射 AT2激动剂(CGP42112A),为实验组1;9只腹腔注射牛磺酸,为实验组2。以上注射每天1次,连续4周。称心 脏重量(HW),通过凋亡试剂盒检测心肌细胞凋亡指数(CAI),用WesternBlot法、免疫组化染色法检测心肌细胞 上AT2和bcl 2蛋白质量。结果:实验组1和2、对照组2,-dp/dtmax、显著低于对照组1(均P<0.01);三组糖尿 病大鼠心肌CAI、AT2的蛋白质表达量及HW均显著高于对照组1(P<0.01);实验组1、2心肌CAI、AT2的蛋 白质表达量分别显著高于、显著低于对照组2(均P<0.01);实验组1心肌CAI、AT2的蛋白质表达量及心脏重 量测定分别显著高于实验组2(均P<0.01);bcl 2变化正好与AT2变化相反。结论:AT2高表达促进糖尿病大 鼠心肌细胞的凋亡,是糖尿病心肌病的重要促发因素之一;牛磺酸通过下调AT2的高表达保护糖尿病     

缬沙坦对2型糖尿病大鼠心肌细胞凋亡的影响

目的探讨缬沙坦对糖尿病大鼠心肌细胞凋亡的作用。方法随机选择29只健康雄性SD大鼠中的21只,以高糖高脂饲料喂养4周后腹腔注射链脲佐菌素30mg/kg,3d后测血糖≥16.7mmol/L者（n=19）入选糖尿病大鼠模型,并随机分为糖尿病组（DM组,n=9）和缬沙坦治疗组（VAL组,n=10）,另外8只健康雄性SD大鼠为对照组（CN组,n=8）。VAL组给予缬沙坦（20mg/kg.d）治疗6周,检测各组大鼠血生化和胰岛素水平,各组大鼠于第12周末处死,取部分左心室前壁组织以TUNEL法检测大鼠心肌细胞凋亡,免疫组化法检测Caspase-3、NF-κB的表达。结果与CN组相比,DM组和VAL组大鼠心肌细胞凋亡及Caspase-3和NF-κB的阳性表达显著增多,差异具有统计学意义（P〈0.05）;与DM组相比,VAL组大鼠心肌细胞凋亡及Caspase-3和NF-κB的阳性表达明显减少,差异具有统计学意义（P〈0.05）。结论缬沙坦能够抑制糖尿病大鼠心肌细胞的凋亡,具有心肌保护作用。     

血管钠肽抑制内质网应激减轻糖尿病大鼠缺血/再灌注心肌损伤

目的 观察人工合成的钠尿肽——血管钠肽（VNP）对糖尿病（DM）大鼠心肌缺血/再灌注（MI/R）损伤的影响及机制。方法 高脂饲料喂养SD大鼠4周后,注射链脲霉素STZ（25 mg/kg,i.p.）,1周后随机血糖≥11.1 mmol/L为DM模型构建成功,常规制备MI/R（30 min/4 h）模型。将大鼠随机分为4组:假手术组、MI/R组、DM+假手术组、DM+MI/R组。多导生理记录仪检测左室压上升/下降最大速率（±LVdP/dtmax）,Evans blue-TTC双染色法检测心肌梗死面积,TUNEL法进行心肌细胞凋亡测试、试剂盒检测caspase-3活性,Western blot检测GRP78、Chop和PKG等蛋白表达。结果 与对照组相比,DM大鼠MI/R心肌损伤加重。VNP治疗（再灌前10 min,给予100 μg/kg,i.v）可显著减轻DM大鼠MI/R损伤,包括增强±LVdP/dtmax,降低心梗范围、死亡率与Caspase-3活性（n=8,P<0.05）。此外,VNP可降低内质网应激相关蛋白GRP78、CHOP表达（n=3,P<0.01）。VNP上述效应可同时被PKG阻断剂KT-5823（再灌前20 min,给予0.5 mg/kg,i.p）抑制、并被cGMP衍生物8-Br-cGMP（1 mg/kg）模拟（P<0.05,P<0.01）。用内质网应激抑制剂TUDCA（50 mg/kg）预处理DM大鼠,并不能增强VNP的心肌保护作用。结论 VNP治疗可减轻DM性MI/R损伤,其机制可能与通过cGMP-PKG信号抑制内质网应激有关,提示VNP对DM性缺血性心脏病具有潜在治疗价值。     

Suppression of apoptosis is responsible for increased thickness of intestinal mucosa in streptozotocin-induced diabetic rats

Intestinal mucosal growth is a common, but uncharacterized, observation associated with diabetes mellitus. Epithelial homeostasis is balanced by regulation of cell proliferation and cell death. To determine the contribution of apoptosis to the overall maintenance of intestinal growth, we examined intestinal apoptosis in the well-characterized streptozotocin (STZ)-induced diabetes rat model. Rats were injected with STZ (75 mg/kg body weight), thereafter they were allowed free feeding or restricted feeding for 3 weeks. Food intake and intestinal mucosal height were evaluated. In a second experiment, additional groups of animals were injected with STZ and were fed ad libitum for 1 or 3 weeks. Ornithine decarboxylase (ODC) activity, ratio of fragmented DNA to total DNA, electrophoresis of fragmented DNA, and Western blot analysis of caspase-3 were examined. Food intake gradually increased in free-feeding rats after induction of diabetes. Intestinal mucosal height in free-feeding diabetic rats was approximately 25% longer than controls, but this increase in mucosal height was not observed in restricted-fed diabetic rats (25 g/d). ODC activity in intestinal mucosa in diabetic rats did not differ from that of control rats. Percent fragmented DNA of diabetic rats 1 week after STZ injection was significantly lower than that of control rats, and this decrease returned to the control level 3 weeks after STZ treatment. Active form of caspase-3 was attenuated 1 week after drug treatment. Attenuated effect of diabetic rats on intestinal apoptosis did not affect increased apoptosis after ischemia-reperfusion. Suppression of apoptosis in the early days of STZ-induced diabetes was responsible for the increased mucosal height in the small intestine in STZ-induced diabetic animals.     

糖尿病大鼠心肌细胞凋亡与Caspase-8及蛋白激酶C-β表达的相关性研究

目的 通过研究糖尿病大鼠心脏中的细胞凋亡,Caspase-8及蛋白激酶C(PKC)-β的表达来探讨糖尿病心肌病(DCM)的组织学改变与细胞分子水平改变的相互关系.方法 实验大鼠分为4组:(1)糖尿病组,64只,用高糖高脂饲料喂养,予链脲佐菌素(STZ)30 mg/L一次性腹腔注射复制糖尿病模型.(2)正常对照组,37只,饲以普通饲料,腹腔注射柠檬酸盐缓冲液代替STZ.(3)STZ组,42只,饲以普通饲料,腹腔注射STZ.(4)高糖高脂组,37只,饲以高糖高脂饲料,腹腔注射柠檬酸盐缓冲液.在不同时段,抽样检查动物:观察心脏病理组织学变化;用实时荧光定量(PCR)等技术检测心肌Caspase-8及PKC-β的表达;用流式细胞术检测心肌的凋亡.比较不同组间的差异.结果 (1)造模型成功后,糖尿病组大鼠体质量较对照组明显下降(P＜0.05),且随着病程的进展呈下降趋势.高糖高脂组体质量一直较高,各时间段无明显改变.糖尿病组的血糖一直都高于对照组、STZ组及高糖高脂组(P＜0.05);高糖高脂组和对照组血糖差异无统计学意义.(2)糖尿病组细胞凋亡有随着病程延长而增高的趋势.(3)造模型成功后,Caspase-8、PKC-β的表达,糖尿病组高于对照组,而且有随着病程的延长增加的趋势.(4)糖尿病组发生心肌肥大、纤维化,随着病程的延长,病变有逐渐加重的病理特点.(5)相关分析提示,糖尿病组16周时,血糖和心肌细胞凋亡与Caspase-8、PKC-β的表达呈正相关.结论 Caspase-8表达失衡与DCM的发病有关.PKC-β在DCM中起到了一定的作用.高血糖在DCM的发病中起重要的作用.

Abstract：

Objective To study the roles of abnormal expressions of Caspase-8 and protein kinase C(PKC)-β of cardiomyocytes in the development of the apoptosis of cardiomyocyte in diabetic rat. Methods Rats were divided into 4 groups:(1)normal control (NC, n=37),(2)rats given STZ injection and normal diet(STZ,n= 42), (3) rats fed with high fat and high sngar ( HFS, n= 37), (4)rats given STZ injection and high fat and high sugar diet (type 2 DM, n=64). Plasma glucose, insulin and lipids were detected. At the end of experiment, the animals were sacrificed, and their hearts were examined. Pathological changes were observed and the expressions of Caspase-8, PKC-β mRNA were determined by real time-PCR method; apoptosis was analyzed by flow cytometry. Results (1)The body weight was higher in HFS group than in other three groups, and progressively decreased in type 2 diabetes group. The glucose level was highest in diabetic group, and was similar between groups of HFS and NC. (2)The apoptosis showed tendency to ascend during course of disease in diabetes model group. (3)The expressions of Caspase-8 and PKC-β mRNA were significantly enhanced in diabetes model group than in normal control group, and had a tendency to ascend during the course of disease.(4)The myocardial cells of the diabetic rats were rarified and swelling, fibrosis was observed. (5)At the 16th week, the level of plasma glucose was correlated positively with the expressions of Caspase-8 and PKC-β mRNA. Conclusions The enhancement of expressions of Caspase-8 amd PKC-β may play iportat rols in the pathogenesis of diabetic cardiomyopathy,in which apoptosis of the cardiomyocytes increased.     

PERK/eIF2α通路在酒精性肝损伤大鼠肝细胞凋亡中的作用

目的 探讨内质网类似激酶(PERK)/真核生物翻译起始因子(eIF)2α信号通路在酒精性肝损伤大鼠肝细胞凋亡中的作用.方法 建立大鼠酒精性肝损伤模型.设4、6、10周和12周4个时间点,动态观察肝组织病理变化;流式细胞术检测肝细胞凋亡率;酶联免疫吸附法检测血清同型半胱氨酸(tHCY)水平;实时荧光定量聚合酶链反应和Western blot检测肝组织PERK/eIF2α通路信号分子mRNA和蛋白的表达水平.多组样本均数的两两比较采用One-Way ANOVA分析.结果 4周时造模大鼠发生急性肝损伤改变,12周时则出现慢性肝损伤改变;6周时造模大鼠肝细胞凋亡率较正常组显著增加(P＜0.05),随着造模时间的延长,肝细胞凋亡程度逐渐加剧,12周时早期和总凋亡率分别达到26%和29%;自6周起,造模大鼠血清tHCY水平明显高于正常大鼠(P＜0.01);自4周起,造模大鼠肝组织eIF-2α蛋白发生明显磷酸化,12周时peIF-2α蛋白表达量上升了2.81倍(P＜0.01),葡萄糖调节蛋白(GRP) 78/Bip、GRP94、caspase 12和caspase-3则表现为过度活化,12周时基因和蛋白表达量分别为正常大鼠的4.70、12.95、3.83、4.05倍和3.93、6.93、9.88、3.31倍(P＜0.01).结论 PERK/eIF2α通路的活化与酒精性肝损伤大鼠肝细胞凋亡的发生和持续发展密切相关.     

2型糖尿病大鼠并发心肌病的研究

目的 在大鼠中复制类似人类2型糖尿病模型,观察并发糖尿病性心肌病的情况.方法 取健康雄性SD大鼠120只,体质量180～220 g,按体质量及血糖值分为4组:(1)糖尿病组:40只,高糖高脂饲料喂养,一次性腹腔注射30 mg/kg链脲佐菌素(STZ)溶液;(2)STZ组:30只,普通饲料喂养,一次性腹腔注射30 mg/kg STZ溶液;(3)高糖高脂饲料组:25只,高糖高脂饲料喂养,一次性腹腔注射等容积柠檬酸盐缓冲液溶液;(4)对照组:25只,普通饲料喂养,一次性腹腔注射等容积柠檬酸盐缓冲液溶液.腹腔注射STZ溶液或柠檬酸盐缓冲液溶液后,观察动物饮水、进食及尿量变化.注射后4、8、12、16周,各组分批抽样检查,称取体质量,取血检测空腹血糖、空腹胰岛素、三酰甘油、总胆固醇;处死动物取心脏称质量,取心肌组织行光镜及透射电镜观察.结果 实验饲料喂养1周,各组大鼠体质量、血糖差异无统计学意义(P>0.05);喂养4周,STZ或柠檬酸盐缓冲液注射前,糖尿病组和高糖高脂饲料组大鼠体质量、空腹胰岛素、胰岛素抵抗指数较对照组和STZ组明显升高(P<0.05);糖尿病组与高糖高脂饲料组相比、STZ组和对照组相比差异均无统计学意义(P>0.05).注射后4个时段,糖尿病组和高糖高脂饲料组大鼠血糖、体质量、心脏质量、血三酰甘油、总胆固醇比同时段的对照组和STZ组增高(P<0.05),糖尿病组大鼠的上述指标较高糖高脂饲料组大鼠增加更显著,差异有统计学意义(P<0.05),STZ组和对照组相比差异无统计学意义(P>0.05).心肌光镜和电镜检查结果显示,糖尿病组大鼠心肌细胞肥厚并出现变性、凋亡等显著病变,间质胶原纤维增生;STZ组大鼠心肌无明显病理改变;高糖高脂饲料组大鼠心肌呈现类似糖尿病大鼠病理改变,但与糖尿病组大鼠相比,改变较不明显.结论 2型糖尿病大鼠成模4周后,心脏发生糖尿病性心肌病的病理改变,表现为心肌细胞肥大、变性,间质纤维组织增生,其发生率为100%.     

Reduced silent information regulator 1 signaling exacerbates myocardial ischemia–reperfusion injury in type 2 diabetic rats and the protective effect of melatonin

Diabetes mellitus (DM) increases myocardial oxidative stress and endoplasmic reticulum (ER) stress. Melatonin confers cardioprotective effect by suppressing oxidative damage. However, the effect and mechanism of melatonin on myocardial ischemia–reperfusion (MI/R) injury in type 2 diabetic state are still unknown. In this study, we developed high‐fat diet‐fed streptozotocin (HFD‐STZ) rat, a well‐known type 2 diabetic model, to evaluate the effect of melatonin on MI/R injury with a focus on silent information regulator 1 (SIRT1) signaling, oxidative stress, and PERK/eIF2α/ATF4‐mediated ER stress. HFD‐STZ treated rats were exposed to melatonin treatment in the presence or the absence of sirtinol (a SIRT1 inhibitor) and subjected to MI/R surgery. Compared with nondiabetic animals, type 2 diabetic rats exhibited significantly decreased myocardial SIRT1 signaling, increased apoptosis, enhanced oxidative stress, and ER stress. Additionally, further reduced SIRT1 signaling, aggravated oxidative damage, and ER stress were found in diabetic animals subjected to MI/R surgery. Melatonin markedly reduced MI/R injury by improving cardiac functional recovery and decreasing myocardial apoptosis in type 2 diabetic animals. Melatonin treatment up‐regulated SIRT1 expression, reduced oxidative damage, and suppressed PERK/eIF2α/ATF4 signaling. However, these effects were all attenuated by SIRT1 inhibition. Melatonin also protected high glucose/high fat cultured H9C2 cardiomyocytes against simulated ischemia–reperfusion injury‐induced ER stress by activating SIRT1 signaling while SIRT1 siRNA blunted this action. Taken together, our study demonstrates that reduced cardiac SIRT1 signaling in type 2 diabetic state aggravates MI/R injury. Melatonin ameliorates reperfusion‐induced oxidative stress and ER stress via activation of SIRT1 signaling, thus reducing MI/R damage and improving cardiac function.     

Sustained cardiomyocyte apoptosis and left ventricular remodelling after myocardial infarction in experimental diabetes

Aims/hypothesis Diabetes is known to reduce survival after myocardial infarction. Our aim was to examine whether diabetes is associated with enhanced cardiomyocyte apoptosis and thus interferes with the post-infarction remodelling process in myocardium in rat.Methods Four weeks after intravenous streptozotocin (diabetic groups) or citrate buffer (controls) injection, myocardial infarction was produced by ligation of left descending coronary artery. Level of cardiomyocyte apoptosis was quantified by TUNEL and caspase-3 methods. Collagen volume fraction and connective tissue growth factor were determined under microscope. Left ventricular dimensions were evaluated by echocardiography and planimetry.Results The number of apoptotic cardiomyocytes was equally high in diabetic and non-diabetic rats after 1 week from infarction. At 12 weeks after infarction the number of apoptotic cells was higher in the diabetic as compared to non-diabetic rats both in the border zone of infarction and in non-infarcted area. Correspondingly, left ventricular end diastolic diameter, relative cardiac weight, connective tissue growth factor-expression and fibrosis were increased in diabetic compared with non-diabetic rats with myocardial infarction.Conclusion/interpretation Sustained cardiomyocyte apoptosis, left ventricular enlargement, increased cardiac fibrosis and enhanced profibrogenic connective tissue growth factor expression were detected after myocardial infarction in experimental diabetes. Apoptotic myocyte loss could be an important mechanism contributing to progressive dilatation of the heart and poor prognosis after myocardial infarction in diabetes.Abbreviations STZ streptozotozin - MI myocardial infarction - CTGF connective tissue growth factor - LV left ventricular - LVEDD LV end-diastolic diameter - BNP B-type natriuretic peptide     

糖尿病大鼠缺血/再灌注心肌细胞凋亡及相关基因表达的研究

目的观察链脲佐菌素(STZ)诱导的糖尿病大鼠缺血/再灌注(I/R)模型心肌细胞凋亡及相关基因的表达。方法采用STZ(45 mg/kg)诱导大鼠糖尿病4周后制备心肌缺血30 min再灌注120 min模型,用2,3,5-氯化三苯基四氮唑染色法(TTC)测定心肌梗死面积,用TUNEI法检测细胞凋亡,用免疫组化方法检测凋亡相关基因的表达,透射电镜观察心肌组织超微结构的凋亡改变。结果与非糖尿病组相比,糖尿病组大鼠由I/R损伤引起的心肌梗死面积并没有增加,但是细胞凋亡指数增加(17%±3%比26%±3%,P<0.001)、Bcl-2表达降低(11.0%±3.8%比3.8%±2.5%,P<0.001)、Bax表达升高(26%±3%比36%±7%,P<0.001)、超微结构观察心肌凋亡损伤更为严重。结论糖尿病大鼠I/R心肌细胞凋亡增加,这可能与凋亡相关基因Bcl-2表达降低、Bax表达升高有关。     

The role of programmed cell death in streptozotocin-induced early diabetic nephropathy

The mechanism of autophagy in diabetic nephropathy (DN) is still unclear. The study was performed on streptozotocin (STZ) rats to investigate whether programmed cell death contribute to the pathogenesis and progression of DN. STZ rats were induced by an single intravenous injection of STZ dissolved in citrate buffer, early DN (E-DN) for STZ rats was defined as the stage from modeling to the end of the 8th week according to previous studies. A total of 36 male Sprague-Dawley rats were randomly divided into two groups: an E-DN group and a control group. After the 1st, 4th, and 8th week, the rats were sacrificed. Beclin1 and microtubule associated protein 1 light chain 3 (LC3) were examined, apoptosis level in renal tissue was detected by Tunnel assay detected as the apoptotic index. An electron microscopic examination of kidney tissues was performed at end of the 4th and 8th week. Compared with the control group, Beclin1 expression increased since the 1st week after modeling in STZ rats kidney and peaked at the end of the 8th week in western blotting and immunohistochemical stain. Meanwhile the level of LC3-II in DN group was significantly lower from the end of the 1st to the 8th week. A small amount of autophagosomes were observed in both E-DN group and control group under electron microscopic examination, and there was no significant difference between the groups. These findings indicate that an abnormality on autophagy may play an important role in the pathogenesis of E-DN.