DPP4 and Alzheimer disease: Previously, it has been reported that the DPP-4 inhibitor saxagliptin exerted a neuroprotective effect by ameliorating memory and learning deficits, upregulating hippocampus GLP-1 and downregulating hippocampus Aβ, p-tau, TNF-α, and IL-1β in streptozotocin-induced AD rats [28].