Insulin resistance-induced hyperglycemia decreased the activation of Akt/CREB in hippocampus neurons: Molecular evidence for mechanism of diabetes-induced cognitive dysfunction

• In GK rats and STZ-induced diabetic model, we detected the variation of dendritic spine density in hippocampus neurons.
• The insulin resistance-induced hyperglycemia is performed in both GK rats and STZ-induced diabetic model.
• The phosphorylated Akt/CREB is downregulated in these two diabetic models.

Several previous studies have indicated that diabetic have higher risk of suffering from Alzheimer's disease, which severely induced cognitive dysfunction. However, the underlying molecular mechanism and more details on the cognitive deficits induced by hyperglycemia have not been elucidated. Here in our present study, on the basis of Goto-Kakizaki (GK) rats and streptozotocin (STZ)-induced diabetic model, we detected the variation of dendritic spine density in hippocampus as well as the differential expression of some important signal transduction molecules that were of relevance in learning and memory function. We found that the magnitude of escape latency time was significantly increased in such diabetic animals; the phosphorylated Akt/CREB; SYP and BDNF as well as other downstream molecules in hippocampus neurons were also downregulated in both diabetic groups compared to the normal groups. Thus, all of these data indicate the obstacle of neuronal pathology and the Akt/CREB signaling pathway caused by hyperglycemia that may suppress cognitive behavior, which may provide a novel way for the prevention of diabetic encephalopathy and the cognitive deficits of Alzheimer's disease.