OPTN and type 2 diabetes mellitus: We found excitingly that among the above DEPs, only the elevated OPTN (Figure 5g) was significantly correlated with MMSE (r = −0.571, p = 0.011; Figure 5h), Aβ1‐42/Aβ1‐40 (r = 0.458, p = 0.049; Figure 5i), and rGSK‐3β (r = 0.532, p = 0.019; Figure 5j) in T2DM‐MCI patients, suggesting a strong power of OPTN as a biomarker for identifying MCI in T2DM patients.