BDNF and Alzheimer disease: Rex et al. (2006) considered that BDNF and its receptor (TrkB) were impaired with age in AD patients. It was also suggested that β-amyloid protein was detrimental to the production and signaling of BDNF. In addition, exercise helps to increase the levels of BDNF, which can improve AD performance to some extent (Laurin et al., 2001; Etnier et al., 2016; Choi et al., 2018).