Intriguingly, both ZDF and STZ rat models of DM have increased levels of the early endosome marker Rab5 and Aβ/β-CTF in the hippocampus, while high glucose up-regulates Aβ level through Rab5-dependent endosome enlargement co-localized with β-CTF and BACE1 in cultured cells (Chae et al., 2020). Here, BACE1 is linked to diabetes mellitus.