INS and diabetes mellitus: Diabetes appears to be an important risk factor for developing AD (Baumgart et al., 2015) with several studies linking diabetes and impaired insulin signaling in the brain to AD pathogenesis (Biessels et al., 2006; Bomfim et al., 2012; Talbot et al., 2012; Zhao et al., 2017; Kim et al., 2019).