Diabetes is a chronic and metabolic disease characterized by hyperglycemia resulting from defective insulin secretion and/or insulin resistance . Diabetics are at a significantly elevated risk for nephropathy, peripheral neuropathy, and retinopathy. In the central nervous system (CNS), chronic hyperglycemia leads to the enhanced formation of advanced glycation end products (AGEs), which have potentially toxic effects on neurons, causing dementia . Hyperglycemia also causes a significant increase in generation of reactive oxygen species (ROS), resulting in cerebral angiopathy and abnormalities of neurons and glia in the brain, and subsequent dementia . The degree to which the neuronal abnormality is caused directly by hyperglycemia remains unclear . Moreover, the development of diabetes-induced dementia is not only closely associated with hyperglycemia but also with the action of insulin .