Correlation analysis in the T2D group (Figure 3, Diabetes) revealed that the levels of Tau, Asp, Glu, and Ala showed a strong positive correlation with CCL27, CD2AP, CTSD, LACTB2, MARCO, NADK, PAG1, PDGFA, PLXNB3, PPP1R2, SCARF1, SDC4, SERPINE1, SORT1, SOST, and ST6GAL1 proteins. Here, CTSD is linked to diabetes mellitus.