Expression Of Aldose Reductase And Antioxidant Enzyme MRNA In Brain Tissue Of Diabetic Rats

[Objective]To establish type2diabetic rat model,and through the analysis of relevant indicators, the characteristic and the stability of this rat model is evaluated.[Methods]A total of160male Sprague-Dawley(SD)rats,were randomly divided into model group and control group. The control group was given a normal diet, whereas the model group was given a diet with high fat and sugar content.After4weeks and8weeks,the rats of the model group were injected with1%mmol/L streptozotocin(STZ) by two steps whereas the rats of the control group were inject with0.lmmol/L citric acid-citrate buffer of the same volume as the STZ used for the model group.The random blood glucose level of the rat higher than13.8mmol/L was used as the criterion for achieving an effective model.Rats were detected at different time points for their body weight and blood glucose level, and at16weeks the levels of indicators in rats, such as the levels of glycosylated hemoglobin, blood lipid, serum insulin, and insulin resistance index.[Results]1.Blood glucose levels of the model group increased. After becoming the diabetes model,the blood glucose level of the rats in model group was18.83±6.82mmol/L,which was significantly different as compared to the control group(P<0.01). The insulin level of the control group increased,39.51±1.60, which was significantly different as compared to the control group(P<0.01).The insulin sensitivity was reduced in the model group,42.92±4.35,which was statistically significant as compared to the control group(P<0.01).The level of glycosylated hemoglobin(GHb) of the model group (6.67±0.28%)was significantly higher as compared to the control group(P<0.01).2. The level of blood lipids were elevated in diabetes rats, with LDL at0.78±0.07mmol/L, TC at1.53±0.18mmol/L, TG at1.80±0.30mmol/L, which were statistically significant compared to the control group (P<0.01). [Conclusion]1. STZ combined with the diet of high fat and sugar content can reproduce the rat model which has the characteristics of insulin resistance and develops diabetes in a process similar to the type2diabetes in human.The model is of high levels of blood sugar,blood lipids,hyperinsulinemia and insulin resistance and other features, which tend to result in the diabetic brain lesion. It is an ideal animal mode for the study of type2diabetes and the mechanism of its associated complications in brain.2. The relevant indicators of the diabetic rat model had constant changes, and the blood glucose level was stable, which indicated that this method was stable for reproducing the diabetic rat model, and can be used for long term study. [Objective]To measure the expression levels of antioxidant enzymes (SOD, CAT, GPx) and AR mRNA in the brain tissue of the diabetic rats at different periods (8weeks,12weeks,16weeks) and with different blood glucose levels (13.8-16.7mmol/L (group L(low)), group H (high)>16.7mmol/L).To elucidate at the gene level the process of the abnormal changes of antioxidants in the microenvironment of brain tissue.To identify the relation between the changes of antioxidant enzymes and the ARmRNA, and the high blood glucose level and oxidative stress.[Methods]60diabetic rat models established in Part I and10normal rats in control group,were divided into six treatment groups(8H,8L,12H,12L,16H,16L)and a control group, according to different stages of the disease (8weeks,12weeks,16weeks)and different blood glucose levels(13.8-16.7mmol/L (group L),(group H)>16.7mmol/L). The mRNA expression of SOD, CAT, GPx and AR in the brain tissue of rats in each group were detected with RT-PCR method respectively.[Results]RT-PCR results showed that the relative expression levels of the GPxmRNA of the treatment groups were statistically different as compared to the control group(P<0.05). Along with the progression of the disease, the expression levels of GPxmRNA of the treatment groups gradually reduced after a first increase.The GPx levels of Groups H and L did not achieve statistically significant difference (P>0.05) during the same time periods, except at8weeks (P<0.05).The treatment groups, as compared to the control group, all had significantly lower relative expression of SOD mRNA (P<0.05), which gradually reduced with the progression of the disease.There is no significant difference in SOD mRNA expression between the groups H and L in the same period (P>0.05).The treatment groups, as compared to the control group, all had significantly lower relative expression of CAT mRNA (P<0.05), except for the group L at8 weeks.With the progression of the disease, the expression of CAT mRNA gradually decreased.There is no significant difference in CAT mRNA expression between the groups H and L in the same period (P>0.05).The treatment groups, as compared to the control group, all had significantly lower relative expression of CAT mRNA (P<0.05), except for the group L at8weeks. With the progression of the disease, the expression of CAT mRNA gradually decreased.There is no significant difference in CAT mRNA expression between the groups H and L in the same period (P>0.05).The treatment groups, as compared to the control group, all had significantly higher relative expression of AR mRNA (P<0.05). There is significant difference in AR mRNA expression between the groups H and L in the same period (P<0.05).[Conclusion]1. In the brain tissue of diabetes rats, along the progression of the disease, the expression of mRNA of antioxidant enzymes SOD, CAT decreased gradually, whereas the expression of GPxmRNA decreased after a frist increase.This indicated that the oxidative stress is tightly related to the diabetic encephalopathy and it may be the main factor of brain injury.2. AR mRNA expression increased gradually with the progression of the disease, which indicated that AR as main activation factor could be an important mechanism in the diabetic encephalopathy by influencing sugar metabolic pathway of body.3. The expressions of the mRNA of GPx and AR were different under different blood glucose levels, which indicated a possible dependence of the expression of GPx and AR on the level of blood glucose,and prompted the change of GPx and AR may be an important reason that different blood glucose levels caused the brain injury.