Dynamic Expression Of GLUT1 And GLUT3 Protein In Diabetic Rats With Cerebral Ischemic Reperfusion

Objectives:The diabetic cardiovascular or cerebrovascular complication is the major death cause of patients with diabetes mellitus. Then diabetic stroke accounted for most of diabetic cerebrovascular complications. But at present, there are controversies about the control standards of blood glucose level in the treatment of diabetic stroke. GLUT1 and GLUT3 were the principal factors which participate in glucose transport and metabolism in brain. Studies found that GLUT1 and GLUT3 expression were notably up-regulated in the penumbra region after cerebral ischemia, and chronic hyperglycemia can cause the decrease expression of GLUT1 and GLUT3 in brain namely down-regulation. The brain damage depended on the functional recovery of the brain cells in ischemic penumbra region. However, it is unclear whether there was the compensatory change of GLUT1 and GLUT3 in ischemic penumbra region of the diabetic stroke, which may be related to the blood glucose level and the ischemic time. So the study was aimed to evaluate the expression of GLUT1 and GLUT3 in diabetic rats with cerebral ischemic reperfusion, and futher to explore the relationship between the blood glucose levels, the GLUT protein expressions and the cerebral infarction volumes. That might help to determine the proper blood glucose threshold level in the treatment of diabetic apoplexy. Materials and Methods:A total of 220 healthy male Wistar rats weighting 180-220g were used, 50 rats were randomly chosen to be normal control group (group NC), the rest 170 rats were induced to be diabetes mellitus by STZ which was injected into the abdomens and only 150 rats became diabetes finally. When the diabetic model was successfully established, the diabetic rats were randomly divided into 3 groups: the DM1 group (the blood glucose was not controlled), the DM2 group (the blood glucose was general controlled), and the DM3 group (the blood glucose was good controlled). The three groups were treated with protamine zinc insulin (PZI) to control their blood glucose levels to >16.7mmol/L, 10.0-14.0mmol/L, 6.0-8.0mmol/L respectively. And focal ischemic rat model of middle artery occlusion (MCAO) was made by insertion of fishing thread in 6 weeks after diabetic model establishment. Each group was divided into 5 subgroups (n=10 each): four focal ischemic subgroups at different ischemic-reperfusion time (at 3h, 12h, 24h and 72h after reperfusion, respectively) and sham-operated subgroups. The protein expression of GLUT1 and GLUT3 was assessed by western blot. Results are presented as means±standard error (SE). The significance of differences between each part of the group were determined using one-way ANOVA and the significance of differences between each group were determined using SNK-q test by SPSS11.0. A value of p < 0.05 was considered statistically significant.Results:1. During the experiment the weights of DM groups were lower than the NC group (P<0.01), but the blood glucose was much higher than the NC group (P<0.01).2. The expressions of GLUT1 protein and GLTU3 protein in sham operation subgroup of NC_MCAO were higher than that of in sham operation subgroups of DM_MCAO- The differences were significant (P<0.01).3. GLUT1 protein in 4 groups all began to increase at 3h, peaking at 24h after reperfusion and still maintained higher level even at 72h than that of corresponding sham-operated subgroups, meanwhile, at the corresponding time points the GLUT1 protein of the DM1_MCAO group, DM2_MCAO and DM3_MCAO group were inferior to the NC_MCAO group(P<0.01). The trend of GLUT3 protein is similar to that of GLUT1 protein.4. Compared with the corresponding sham operation subgroups, the enhanced amplitude of GLUT1 protein is higher than that of GLUT3 protein significantly, expecially at the 24hour ischemic reperfusion.Conclusions:1. GLUT1 and GLUT3 expressions were notably up regulated in the penumbra region after cerebral ischemia, it may be a protective reaction against ischemic injury.2. The increasing amplitude of the GLUT1 protein expression in rat cerebral ischemia penumbra was higher than that of GLUT3, and this might indicate that GLUT1 reacts faster than GLUT3.3. The up-regulated amplitude of GLUT1 and GLUT3 in diabetic rats with cerebral ischemic injury became smaller than that of normal control.4. Therefore, in the therapy of diabetic patients with cerebral embolism, the blood glucose control should not be too strict, otherwise the up-regulation of GLUT1 and GLUT3 induced by cerebral ischemic injury might not be able to meet the needs of energy metabolism in cells, which would cause inadequate compensation and be detrimental to the reversible restoration of cerebral ischemic penumbra function.