DPP4 and Cognitive impairment: Previous preclinical studies show that DPP-4 inhibitors counteract stroke in the normal and diabetic mouse brain [10], ameliorate cognitive impairment in streptozotosin-induced diabetic rat [11], high-fat fed mice [12], and a mouse model of chronic cerebral hypoperfusion [13], lessen the development of cerebral infarction induced by temporally focal ischemia in non-diabetic normal mice [14], improve cognition in high-fat diet induced insulin resistant rats [15], and delay some forms of Alzheimer’s disease pathology in Alzheimer’s prone mice [16].