Lower serum BDNF levels have been linked to the severity of cognitive impairment (Shimada et al., 2014; Siuda et al., 2017), and numerous investigations have revealed that individuals with T2DM have considerably lower BDNF levels than healthy subjects (Zhen et al., 2013, 2018; Sun et al., 2018; Anita et al., 2022). Here, BDNF is linked to type 2 diabetes mellitus.