二甲双胍对小鼠脑缺血再灌注损伤后认知功能的影响及其机制

Effect of metformin on cognitive function in mice with cerebral ischemia/reperfusion injury and its mechanism

目的探讨二甲双胍对脑缺血再灌注(I/R)小鼠认知功能的影响及其机制。方法采用随机数字表法将40只雄性C57BL/6小鼠[(23±2)g,7~8周龄]分为4组:sham组、I/R组、I/R+100 mg/kg二甲双胍组(低剂量组)和I/R+200 mg/kg二甲双胍组(高剂量组),每组10只。脑缺血组小鼠采用大脑中动脉阻断(MCAO)60 min后再灌注7 d,sham组除不插入细丝阻断外,其余手术步骤相同;低剂量组和高剂量组小鼠在脑缺血再灌注后4 h,每天分别用100,200 mg/kg二甲双胍溶液灌胃,持续7 d。采用Morris水迷宫实验评价小鼠学习和记忆相关指标;采用干湿质量法评估小鼠脑水肿情况;采用HE染色评估小鼠神经元形态变化;采用ELISA试剂盒检测小鼠脑组织脑源性神经营养因子(BDNF)含量和超氧化物歧化酶(SOD)活性。结果与sham组相比,I/R组小鼠自发交替正确率降低,逃避潜伏期增加,目标象限时间降低,穿越平台次数降低(均P<0.05);脑组织含水量增加(P<0.05);BDNF含量和SOD活性均降低(P<0.05);脑组织中变性神经元数量增多。与I/R组相比,低剂量组小鼠目标象限时间增加(P<0.05);高剂量组小鼠自发交替正确率增加(P<0.05),逃避潜伏期降低(P<0.05),目标象限时间增加(P<0.05),穿越平台次数增加(P<0.05),脑组织含水量降低(P<0.05),BDNF含量和SOD活性增加(P<0.05),神经元变性减少。结论200 mg/kg二甲双胍后处理可改善脑缺血再灌注小鼠认知功能,可能与脑水肿减轻、神经元变性改善、脑内BDNF含量和SOD活性增加有关。

Objective To evaluate the effect of metformin on cognitive function in cerebral ischemia/reperfusion(I/R)mice and its mechanism.Methods Forty male C57BL/6 mice,weighing(23±2)g,7-8 weeks old,were randomly divided into four groups:sham group,I/R group,I/R+100 mg/kg metformin group(low-dose group)and I/R+200 mg/kg metformin group(high-dose group),with 10 mice in each group.The mice in sham group underwent the same surgical procedures except for the absence of the insertion of the filament.In I/R group,the mice were subjected to middle cerebral artery occlusion(MCAO)for 60 min and then reperfusion for 7 d.Mice in low-dose group and high-dose group were intragastrically perfused with 100,200 mg/kg metformin solution every day for 7 d after I/R.The learning and memory-related indicators of mice in each group were evaluated using the Morris water maze,the brain edema of mice in each group was assessed using the dry-wet weight method,the morphological changes of neurons in mice in each group were evaluated using HE staining,the content of brain-derived neurotrophic factor(BDNF)and the activity of superoxide dismutase(SOD)in brain tissues of mice in each group were detected using ELISA kits.Results Compared with sham group,the spontaneous alternation accuracy,the target quadrant time and the number of crossing platforms were decreased in I/R group(P<0.05),the escape latency was increased(P<0.05),the water content of brain tissue was increased(P<0.05),BDNF content and SOD activity were decreased(P<0.05),and the neuronal degeneration were increased in I/R group.Compared with I/R group,the target quadrant time was increased in low-dose group(P<0.05).Compared with I/R group,the spontaneous alternation accuracy,the target quadrant time and the number of crossing platforms were increased in high-dose group(P<0.05),the escape latency was decreased(P<0.05),the water content of brain tissue was decreased(P<0.05),BDNF content and SOD activity were increased(P<0.05),and the neuronal degeneration were decreased in high-dose group.Conclusion Metformin(200 mg/kg)post-treatment could improve the cognitive function of cerebral ischemic mice,which may be related to the reduction of brain edema,the improvement of neuronal degeneration,and the increase of BDNF content and SOD activity in the brain.