| Objective:To observe the effects of liraglutide on the mitochondrial ATP-sensitive potassium channel(mitoKATP)in diabetic rats with focal cerebral ischemia,and to further investigate the protective effects and potential mechanism of liraglutide.Methods:Sixty male Sprague-Dawley rats（8-10 weeks old,weighing 280-320 g）were randomly divided into 5 groups:cerebral ischemia（CI）group,diabetic cerebral ischemia（DCI）group,and insulin（Ins）group,liraglutide（Lir）group and 5-hydroxydecanoic acid+liraglutide（5-HD+Lir）group,12 in each group.The diabetic rat model was first induced by streptozotocin（STZ）,and then the middle cerebral artery occlusion（MCAO）model was established by modified Longa suture method.The Ins group was intraperitoneally injected with corresponding insulin（<22.0 mmol/L,1.0 IU/kg;22.0-28.0mmol/L,1.5 IU/kg;>28.0 mmol/L,2 IU/kg）after MCAO.In the Lir group,liraglutide（700μg/kg,ip）was intraperitoneally injected 1 hour after MCAO;5-HD（30 mg/kg）was administered intraperitoneally30 minutes before MCAO in 5-HD+Lir group,1 hour after MCAO liraglutide（700μg/kg,ip）was intraperitoneally injected;rats in the CI group and the DCI group were intraperitoneally injected with an equal volume of normal saline at the same time.Fasting blood glucose was measured before injection of streptozotocin and 1-3 days after injection,3 h and 24 h after ischemia,respectively.After 24 hours of MCAO,the neurological deficits of the rats were evaluated,then the rats were sacrificed,and the heads were decapitated to detect cerebral infarction volume by 2,3,5-chlorinated diphenyltetrazolium（TTC）staining;the MPO and SOD activities were measured by tissue;the relative expression levels of Kir6.2and SUR1 in the ischemic brain tissue were detected by protein immunoblotting.Results:（1）Fasting blood glucose changes:blood glucose in the diabetic cerebral ischemia group,insulin group,liraglutide group,5-HD+liraglutide group was significantly increased after injection of STZ（P<0.05）;In the insulin group,insulin was significantly decreased after the injection of insulin again（P<0.05）;the blood glucose was significantly decreased after the injection of liraglutide in the 5-HD+liraglutide group and liraglutide group（P<0.05）;there was no significant change in blood glucose in the cerebral ischemia group.（2）Neurological deficit score:compared with the cerebral ischemia group,the neurological deficit score in the diabetic cerebral ischemia group was significantly increased（P<0.05）;compared with the diabetic cerebral ischemia group,liraglutide group were significantly lower（P<0.05）,but there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,5-HD+liraglutide group were significantly increased（P<0.05）.（3）Cerebral infarction volume:compared with cerebral ischemia group,the volume of cerebral infarction in diabetic cerebral ischemia group was significantly increased（P<0.05）;compared with diabetic cerebral ischemia group,liraglutide group was significantly reduced（P<0.05）,but there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,the 5-HD+liraglutide group was increased significantly（P<0.05）.（4）Determination of SOD activity:compared with the cerebral ischemia group,the SOD activity in the diabetic cerebral ischemia group was significantly decreased（P<0.05）.Compared with the diabetic cerebral ischemia group,the activity of SOD in the liraglutide group was significantly higher（P<0.05）,but there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,the SOD activity of the5-HD+liraglutide group was significantly higher（P<0.05）.（5）Determination of MPO activity:compared with cerebral ischemia group,MPO activity was significantly increased in diabetic cerebral ischemia group（P<0.05）;compared with diabetic cerebral ischemia group,liraglutide group MPO activity significantly decreased（P<0.05）,while there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,MPO activity in the 5-HD+liraglutide group significantly increased（P<0.05）.（6）The expression of Kir6.2:compared with the cerebral ischemia group,the expression of Kir6.2 in the diabetic cerebral ischemia group was significantly down-regulated（P<0.05）;compared with the diabetic cerebral ischemia group,liraglutide group was significantly up-regulated（P<0.05）,but there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,the 5-HD+liraglutide group was significantly down-regulated（P<0.05）.（7）The expression of SUR1:compared with the cerebral ischemia group,the expression of SUR1 in the diabetic cerebral ischemia group was significantly down-regulated（P<0.05）.Compared with the diabetic cerebral ischemia group,the expression of SUR1 was significantly higher in the liraglutide group（P<0.05）,but there was no significant difference in the insulin group（P>0.05）.Compared with the liraglutide group,the expression of SUR1 was significantly down-regulated in the 5-HD+liraglutide group（P<0.05）.Conclusion:1.Liraglutide has a direct protective effect on diabetic cerebral ischemia injury.2.Activation of the mitoKATPTP channel to inhibit oxidative stress and inflammatory response may be one of the important mechanisms of liraglutide in the neuroprotective effects of diabetic cerebral ischemic injury. |
