Dynamic Expression Of GLUT1 And GLUT3 MRNA In Diabetic Rats With Cerebral Ischemia/Reperfusion

BackgroundDiabetes mellitus with cerebral infarction is one of diabetic vascular complications.It is also one of the major death causes of patients with diabetes mellitus.Glucose is almost the primary metabolic fuel for the central nervous system, and a constant supply is essential to maintain normal cerebral development and function.The delivery of glucose from the blood to the brain cell must be mediated by the facilitative glucose transport proteins GLUT1 and GLUT3.Most studies suggested that chronic hyperglycemia could induce the downregulation of glucose transporters in diabetic rats.Diabetes mellitus is often combined with ischemic cerebrovascular disease.Many researches have proved that acute hyperglycemia could aggravate ischemic brain damage and increase the cerebral infarction volumes. However,hypoglycemia decreases energy supply for brain,which may exacerbate the injury of the brain tissue and affect the prognosis.Whether the process is related with GLUT1 and GLUT3 is unknown,especially the dynamic expression of GLUT1 and GLUT3 mRNA in diabetic rats with cerebral ischemiaJreperfusion.ObjectivesTo investigate the expressions of GLUT1 and GLUT3 transcription level in diabetic rats with cerebral ischemia/reperfusion damage,and further to explore the relationship between the blood glucose levels,the GLUT gene expressions and the cerebral infarction volumes.MethodsA total of 175 healthy male wistar rats weighting 180-220g were used,10 rats were randomly chosen to be normal control group(group NC),the rest 165 rats were induced to be diabetes mellitus by injection of STZ intraperitondally,After the diabetic model was successfully established,the 150 rats were randomly divided into 3 groups:DM1 group(the blood glucose was not controlled),DM2 group(the blood glucose was general controlled),DM3 group(the blood glucose was good controlled). The three DM groups were treated with protamine zinc insulin(PZI)to control their blood glucose levels to 16.7～25.0mmol/L,10.0～14.0mmol/L,6.0～8.0mmol/L respectively.After six weeks,focal ischemic models of middle cerebral artery occlusion(MCAO)in three diabetic groups(DM1_MCAODM2_MCAOand DM3_MCAO) rats weighing 250～330g were established by inserting fishing thread.Another 50 rats were added as normal control group(NC_MCAO)and sham operation group.40 rats were decapitated at MCAO1.5h reperfusion 24h(Each group had ten rats.)to be made brain slices.The infarction area of brain was measured by TTC staining technique and then analyzed quantitively by image analysis system.Brain samples were harvested from ischemic penumbra at four groups MCAO1.5h/R3h,12h,24h and 72h (Each time point had ten rats.).The expression of GLUT1 mRNA and GLUT3 mRNA were determined by RT-PCR.Results1.During the experiment the weights of DM 1 and DM2 groups were lower than the NC group(P＜0.01),but the blood glucose was much higher than the NC group (P＜0.01).The rate of the weight growth of DM3 group was more rapid than DM1 and DM2 groups,and the control of blood glucose was better.2.The order of the changes in brain infarct volume was NC_MCAO＜DM3_MCAO＜DM2_MCAO＜DM1_MCAO.Compared with the NC_MCAOgroup,the cerebral infarction volumes of group DM1_MCAO,DM2_MCAOand DM3_MCAOwere increased by 38.84%,14.11%and 4.32%.NC_MCAOvs.DM1_MCAOand DM2_MCAO showed significantly differences(P＜0.05).DM3_MCAOvs.DM1_MCAOand DM2_MCAO also showed significantly differences(P＜0.05).There was no statistical significance between group DM3_MCAOand NC_MCAO(P＞0.05).There were positive correlation between the cerebral infraction volume and the blood glucose(r=0.941).3.The expressions of GLUT1 mRNA and GLTU3 mRNA in sham operation subgroup of NCMCAO were higher than that of in sham operation subgroups of DM1MCAO,DM2_MCAOand DM3_MCAO.The differences were significant(P＜0.05).4.In the four groups,the GLUT1 mRNA increased at 3h,reached a peak at 24h, and still maintained higher level than that of sham operation subgroup at 72h, meanwhile,at the corresponding time points the GLUT1mRNA of the DM1_MCAO group and DM2_MCAOgroup were inferior to the NC_MCAOgroup(P＜0.05).The order of increasing range of GLUT1 mRNA at MCAO1.5h/R24h was NC_MCAO＞DM3_MCAO＞DM2_MCAO＞DM1_MCAO.The trend of GLUT3 mRNA is similar to that of GLUT1 mRNA.5.Compared with the corresponding sham operation subgroups,the increasing range of GLUT1 mRNA in four groups were higher than that of GLUT3 mRNA.Conclusion1.Chronic hyperglycemia could induce the downregulation of the GLUT1 and GLUT3 mRNA expressions in the rat brain.After we controlled the blood glucose level using insulin,the expressions of GLUT 1 and GLUT3 mRNA increased.2.Proper control of blood glucose can reduce the cerebral infarction volumes of diabetic rats with ischemic brain damage.However,it doesn't suggest that the lower of blood glucose control,the smaller of cerebral infarction volumes.The mechanism may be related to the down regulation of brain glucose transporter protein.3.The up-regulation of the GLUT genes in the ischemic penumbra region can maintain the energy supply for the brain after cerebral ischemia hypoxic injury. Hyperglycemia can down-regulate the increasing range of GLUT1mRNA and GLUT3 mRNA expressions after cerebral ischemia hypoxic injury.4.The increasing range of GLUT1 mRNA in four groups was higher than that of GLUT3 mRNA,which suggests that GLUT1 is more sensitive than GLUT3 to cerebral ischemia/reperfusion.