During patient selection for this proteomic analysis, we payed special attention to ApoE genetype, olfactory function, and rGSK‐3β(T/S9), because changes of these factors are correlated to the cognitive decline in T2DM patients (Michaelson, 2014; Rahayel et al., 2012; Zhang et al., 2018). Here, APOE is linked to type 2 diabetes mellitus.