MAPT and diabetes mellitus: Interestingly, intracerebroventricular (ICV) administration of STZ at low doses (< 1–3 mg/kg) that did not induce systemic diabetes resulted in cognitive impairment, oxidative stress, neurodegeneration, intracerebral glucose metabolism, cholinergic impairment, neuroinflammation, and abnormal phosphorylation of tau protein [48–50].