DPP4 and Alzheimer disease: Combinations of the key terms were used for data retrieval, including “atopic dermatitis,” “adipokine,” “leptin,” “adiponectin,” “resistin,” “visfatin,” “dipeptidyl peptidase-4,” “fatty acid binding protein,” “apelin,” and “zinc-α2-glycoprotein.” Studies that reported the expressions of the mentioned adipokines and adipokines-related genetic variations in patients with AD as well as animal and in vitro experiments focused on the molecular mechanism of adipokines in AD were involved.