Since the protein expression of cathepsin D is significantly increased in the cortex of T2D but the activity is decreased, we assessed the 3 major forms of cathepsin D in the cortex to evaluate whether or not T2D alters the trafficking pattern of cathepsin D. We observed a significant increase in both the intermediate and mature forms of cathepsin D in T2D compared to the nondiabetic control (Fig. 2e, f). This evidence concerns the gene CTSD and type 2 diabetes mellitus.