INS and type 2 diabetes mellitus: Likewise, insulin-resistant elderly people [26,134], T2D patients with mild cognitive impairment [135,136], and even prediabetic patients with normal cognitive function [49,134] show brain hypometabolism quantified by a decreased uptake of [18F]-FDG (18-fluorodeoxyglucose) detected by PET (positron emission tomography) imaging.