MIF表达与肥胖因素消除小鼠七氟醚预处理心肌保护作用的关系

Relationship between MIF expression and obese-induced abolition of sevoflurane preconditioning-induced cardioprotection in mice

目的 初步评价巨噬细胞移动抑制因子(MIF)表达与肥胖因素消除小鼠七氟醚预处理心肌保护作用的关系.方法 雄性C57BL∕6J小鼠48只,4周龄,采用随机数字表法分为2组(n=24):正常饮食组(Lean组)和高脂饮食组(Obese组).Lean组小鼠正常饮食(10%kcal)喂养12周;Obese组小鼠高脂饮食(60%kcal)喂养12周.测量小鼠体重;取尾静脉血样,检测血糖、血浆总胆固醇、甘油三酯、胰岛素和瘦素的浓度.上述指标测定完成后,采用随机数字表法将Lean组和Obese组分为3个亚组(n=8):假手术组(L-Sham组和O-Sham组)、心肌缺血再灌注组(L-IR组和O-IR组)和七氟醚预处理组(L-IR+Sev组和O-IR+Sev组).建立Langendorff离体心脏灌注模型,平衡灌注30 min后,L-Sham组和O-Sham组K-H液持续灌注115 min;L-IR组和O-IR组K-H液逆行灌注30 min后全心缺血25 min,再灌注60 min;L-IR+Sev组和O-IR+Sev组灌注含七氟醚(终浓度0.6 mmol∕L)的K-H液5 min,洗脱5 min,共循环3次,然后全心缺血25 min,再灌注60 min.于再灌注末,记录左心室舒张压(LVDP)、左心室舒张末压(LVEDP)和左心室内压上升∕下降最大速率(±dp∕dtmax).于再灌注末,取心脏,测定心肌梗死体积,采用Western blot法测定心肌组织MIF表达水平.结果 与Lean组比较,Obese组体重、血糖、血浆总胆固醇、甘油三酯、胰岛素和瘦素水平均升高(P<0.05).与L-Sham组比较,L-IR组和L-IR+Sev组LVDP和+dp∕dtmax降低,LVEDP和-dp∕dtmax升高,心肌梗死体积增加,心肌MIF表达上调,O-Sham组心肌MIF表达上调(P<0.05);与L-IR组比较,L-IR+Sev组LVDP和+dp∕dtmax升高,LVEDP和-dp∕dtmax降低,心肌梗死体积减少,心肌MIF表达上调,O-IR组心肌MIF表达上调(P<0.05);与O-Sham组比较,O-IR组和O-IR+Sev组LVDP和+dp∕dtmax降低,LVEDP和-dp∕dtmax升高,心肌梗死体积增加(P<0.05),MIF表达差异无统计学意义(P>0.05);O-IR组和O-IR+Sev组间上述各指标比较差异无统计学意义(P>0.05).结论 肥胖因素消除七氟醚预处理心肌保护作用的机制可能与其诱导MIF过表达有关.

Objective To evaluate the relationship between macrophage migration inhibitory factor ( MIF) expression and obese-induced abolition of sevoflurane preconditioning-induced cardioprotection in mice. Methods Forty-eight male C57BL∕6J mice, aged 4 weeks, were divided into 2 groups ( n=24 each) using a random number table method: normal diet group ( Lean group ) and high-fat diet group ( Obese group) . Lean group were fed a normal diet ( 10% kcal) for 12 weeks, while Obese group were fed a high-fat diet ( 60% kcal) for 12 weeks. The weight of mice was measured. Blood samples were collected from the tail vein for determination of blood glucose concentrations, and plasma concentrations of total cho-lesterol, triglyceride, insulin and leptin. After measurement of the parameters mentioned above, Lean group and Obese group were divided into 3 subgroups ( n=8 each) using a random number table method:sham operation groups (L-Sham group, O-Sham group), myocardial ischemia-reperfusion groups (L-IR group, O-IR group) and sevoflurane preconditioning groups (L-IR+Sev group, O-IR+Sev group). The mice were anesthetized and their hearts were immediately removed and retrogradely perfused in a Langendorff apparatus with an oxygenated K-H solution at 37 ℃. Hearts were continuously perfused with K-H solution for 115 min in L-Sham and O-Sham groups. Hearts were subjected to global ischemia for 25 min, followed by 60-min reperfusion after being retrogradely perfused with K-H solution in L-IR and O-IR groups. In L-IR+Sev and O-IR+Sev groups, hearts were subjected to 3 cycles of 5-min perfusion with sevoflurane-contai-ning K-H solution ( final concentration 0. 6 mmol∕L) and 5-min washout, and then hearts were subjected to global ischemia for 25 min, followed by 60-min reperfusion. Left ventricular developed pressure ( LVDP ) , left ventricular end-diastolic pressure ( LVEDP ) , and the maximum rate of increase or decrease in left ventricular pressure ( ±dp∕dtmax) were recorded at the end of reperfusion. Hearts were obtained at the end of reperfusion for determination of myocardial infarct size and expression of MIF ( by Western blot) . Results Compared with Lean group, the weight, blood glucose, levels of plasma total cholesterol, tri-glyceride, insulin and leptin were significantly increased in Obese group (P<0. 05). Compared with L-Sham group, the LVDP and +dp∕dtmax were significantly decreased, LVEDP and -dp∕dtmax were in-creased, myocardial infarct size was increased, and the expression of myocardial MIF was up-regulated in L-IR and L-IR+Sev groups, and the expression of myocardial MIF was up-regulated in O-Sham group ( P<0. 05) . Compared with L-IR group, LVDP and +dp∕dtmax were significantly increased, LVEDP and-dp∕dtmax were decreased, myocardial infarct size was decreased, and the expression of myocardial MIF was up-regulated in group L-IR+Sev, and the expression of myocardial MIF was significantly up-regulated in group O-IR (P<0. 05). Compared with O-Sham group, LVDP and +dp∕dtmax were significantly de-creased, LVEDP and-dp∕dtmax were increased, and myocardial infarct size was increased, and no signif-icant change was found in the expression of MIF in O-IR and O-IR+Sev groups ( P>0. 05) . Conclusion The mechanism by which obese abolishes sevoflurane preconditioning-induced cardioprotection may be relat-ed to inducing MIF over-expression in mice.