INS and diabetes mellitus: In recent years, some scholars have also proposed the insulin hypothesis, that is, diabetes is a high risk factor for AD (Silva et al., 2019), the glucose metabolism and blood flow in the cognitively related brain area of AD patients have significant changes (Dukart et al., 2013), and the reversal of cerebral glucose metabolism rate and insulin resistance can promote the recovery of learning and memory ability in animal models (Kang et al., 2017).