Although mechanisms that would explain the link between high fasting plasma glucose and Alzheimer’s disease and other dementias were not fully understood, some authors suggested that vascular disease and alterations in glucose, insulin, mitochondrial dysfunction, hippocampal and amygdalar atrophy, inflammation, oxidative stress, and amyloid-β protein and tau protein metabolism underlie the pathophysiology; thus, recently it was put forward that Alzheimer’s disease can be regarded as “type 3 diabetes” [14,46,47,48,49]. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.