外源性胰岛素对体外循环兔胰岛素抵抗时心肌组织内质网应激的影响

Effect of exogenous insulin on endoplasmic reticulum stress in myocardial tissues during insulin resistance in rabbits undergoing cardiopulmonary bypass

目的评价外源性胰岛素对体外循环(CPB)兔胰岛素抵抗时心肌组织内质网应激的影响。方法健康成年新西兰大白兔40只,雌雄不拘,体重2.5~3.0 kg。采用随机数字表法分为4组(n=10):对照组(C组)、CPB组、CPB+胰岛素组(I组)和CPB+生理盐水组(NS组)。C组不作任何处理;CPB组建立CPB胰岛素抵抗模型;I组从建立CPB开始至术后1 d持续泵入胰岛素(根据血糖值调节胰岛素给药速率);NS组建立CPB从手术开始至术后1 d持续泵入等量生理盐水。分别于CPB前(T1)、主动脉开放后15、30和60 min(T2-4)时取左股动脉血样和心肌组织。采用氧化酶法检测血糖水平,放免法检测胰高血糖素水平,计算胰岛素抵抗指数,Western blot法检测兔心肌组织肌醇需求激酶1α(IRE1α)、X-盒结合蛋白-1(XBP1)和caspase-12的表达,实时荧光定量PCR法检测兔心肌组织IRE1、XBP1和caspase-12的mRNA表达,TUNEL法检测心肌细胞凋亡情况。结果与C组比较,CPB组、I组和NS组T2-4时血糖、血浆胰高血糖素、胰岛素抵抗指数和T4时心肌细胞凋亡指数升高,T4时心肌IRE1α、XBP1和caspase-12及其mRNA表达上调(P<0.05);与CPB组比较,I组T2-4时血糖、血浆胰高血糖素、胰岛素抵抗指数和T4时心肌细胞凋亡指数降低,T4时心肌IRE1α、XBP1和caspase-12及其mRNA表达下调(P<0.05)。结论外源性胰岛素可显著改善CPB兔心肌组织胰岛素抵抗,其机制与抑制内质网应激,减少细胞凋亡有关。

Objective To evaluate the effect of exogenous insulin on endoplasmic reticulum stress in myocardial tissues during insulin resistance in the rabbits undergoing cardiopulmonary bypass(CPB).Methods Forty healthy adult New Zealand white rabbits of both sexes,weighing 2.5-3.0 kg,were divided into 4 groups(n=10 each)using a random number table method:control group(group C),CPB group,CPB plus insulin group(group I)and CPB plus normal saline group(group NS).Group C received no treatment.An insulin resistance model was established in group CPB.Insulin was continuously infused(the infusion rate was adjusted according to the blood glucose)starting from establishing CPB to 1 day after operation in group I.The equal volume of normal saline was given starting from establishing CPB to 1 day after operation in group NS.Blood samples were collected from the left femoral artery,and myocardial tissues obtained before CPB(T1)and at 15,30 and 60 min after aortic opening(T2-4).The level of blood glucose was determined using oxidase method,the level of glucagon was detected by the radioimmunoassay method,and the insulin resistance index was calculated.The expression of inositol-requiring protein-1α(IRE1α),XBP1 and caspase-12 was measured by Western blot.The expression of IRE1α,XBP1 and caspase-12 mRNA was measured by fluorescent quantitative real-time polymerase chain reaction.Cell apoptosis was detected by TUNEL.Results Compared with group C,blood glucose and glucagon levels at T2-4 and insulin resistance index at T4 were significantly increased,and the expression of inositol-requiring protein-1α(IRE1α),XBP1 and caspase-12 protein and mRNA was up-regulated at T4 in CPB,I and NS groups(P<0.05).Compared with group CPB,blood glucose and glucagon levels at T2-4 and insulin resistance index at T4 were significantly decreased,and the expression of IRE1α,XBP1 and caspase-12 protein and mRNA was down-regulated at T4 in group I(P<0.05).Conclusion Exogenous insulin significantly improves insulin resistance in myocardial tissues,and the mechanism is related to inhibiting endoplasmic reticulum stress and reducing cell apoptosis in the rabbits undergoing CPB.