BDNF and Alzheimer disease: Increasing evidence has shown that BDNF is associated with the etiology and pathogenesis of AD. Studies have found that BDNF exerts a potential protective effect based on neurotoxicity caused by the amyloid β protein (Aβ) in AD mouse models, with the serum and brain BDNF levels in mice (a mouse model of Tauopathy) found to be downregulated (27).