IGF1 and Alzheimer disease: Consequently, dysregulated insulin/IGF signaling and insulin resistance in the CNS have been linked to an increased risk of dementia, including AD, which is sometimes referred to as type 3 diabetes (Biessels et al., 2006; Whitmer et al., 2008; Zemva and Schubert, 2011; Banks et al., 2012; Smolina et al., 2015; Biessels and Despa, 2018; Kuo et al., 2018; Shinjyo et al., 2020).