The Role Of MTOR In Cognitive Dysfunction Of STZ-induced Diabetic Rats

OBJECTIVESStudy the connection of p-mTOR(Ser2448), t-mTOR changes and course of diabetes, diabetic cognitive dysfunction and apoptosis related protein on the diabetic rats induced by STZ(streptozocin, STZ).METHODSMale Sprague-Dawley(SD) rats were divided into two groups randomly as follows:diabetic group(DM group) and normal control group(Con group). After adaptive feeding for one week, DM group rats were injected intraperitoneally with STZ(60mg/kg), tail vein blood glucose was measured after3days, and established the STZ-induced diabetes models(n=30), the Con group rats were injected with the same amount of citric acid buffer(n=21). After eatablish the model successfully, fed the equal number of rats for11weeks,15weeks and20weeks. The Morris water maze test detect the cognitive function of rats prior to sacrifice. Blood was collected for measurement of blood glucose and lipids before the animals were decapitated. Left and right hippocampus of15diabetes rats and15normal rats were preserved by liquid nitrogen, in order to extract the hippocampus protein for taking Western bloting of p-mTOR, t-mTOR, Bax and Bcl-2, rats lefted were perfused with4%neutral formalin and taken brain, hippocampus from each group were processed for routine paraffin embedding. Paraffin-embedded sections were cut throughout the tissue and processed with immunohistochemical and TUNEL.RESULTS1. Morris water maze test showed that the escape latency and time spend in object quadrant were not significantly different in11-weeks diabetic rats from those in age-matched control rats(P>0.05). However, it was significantly different in the15-weeks and20-weeks diabetic rats(P<0.05), the escape latency incresed with the diabetes duration and the time spend in object quadrant decreased with the diabetes duration. During all the diabetic groups, the escape latency incresed with the diabetes duration(P<0.05) and the time spend in object quadrant was not.(P>0.05).2. TUNEL showed that the number of pyramidal cells in the hippocampal CA1region of15-weeks and20-weeks diabetic rats were obviously more than the age-matched control rats.3. Relevant protein expression of apoptosis, Bax, Bcl-2and Bax/Bcl-2ratio in hippocampus were not significantly different in11-weeks diabetic rats from those in age-matched control rats(P>0.05). However, the expression of Bax and the Bax/Bcl-2ratio were significantly different in the15-weeks and20-weeks diabetic rats from those in age-matched control rats(P<0.05) since Bcl-2was not, Bax and the Bax/Bcl-2ratio increased with the diabetes duration,4. Immunohistochemical showed that positive pyramidal cells of t-mTOR in the hippocampal CA1region were saw in15-weeks and20-weeks diabetic rats, but not in age-matched controls.5. The expression of p-mTOR, t-mTOR in hippocampus were not significantly different in11-weeks diabetic rats from those in age-matched control rats(P>0.05). However, the expression were significantly different in the15-weeks and20-weeks diabetic rats from those in age-matched control rats(P<0.05), they increased with the diabetes duration.CONCLUSIONS1. With the extension of the course of STZ-induced diabetic rats, the cognitive dysfunction became more and more serious..2. With the extension of the course of STZ-induced diabetic rats, the number of pyramidal cells and the Bax/Bcl-2ratio in the hippocampus gradually increased.3. With the extension of the course of STZ-induced diabetic rats, the expression of p-mTOR(Ser2448) and t-mTOR in the hippocampus gradually increased.