As stated above, increasing evidence reveals that the downregulation of DHCR24 could be induced by a lot of risk factors from AD, including Aβ, aging, diabetes-related factors, hypoxia, oxidative stress, chronic inflammation, insufficiency of brain neurotrophic substances, and metabolic syndrome, etc. Intriguingly, above data obviously suggests a causative link between DHCR24 downregulation and major risk factors from AD (Fig. 2). Here, DHCR24 is linked to diabetes mellitus.