OGA and diabetes mellitus: AD is frequently associated with type 2 diabetes mellitus (T2DM) and decreased brain O-GlcNAc levels (Franco and Bronson, 2005; Accardi et al., 2012; Rasool et al., 2014; Arnold et al., 2018); Inhibition of O-GlcNAcase (OGA) has been shown to reduce tau aggregation and Aβ production (Yuzwa et al., 2012; Kim et al., 2013; Yuzwa et al., 2014a; Yuzwa et al., 2014b).