MAPT and Alzheimer disease: GK-2 counteracts the impaired cognitive functions in two AD rat models: (1) a surgical one (transection of the septo-hippocampal pathway), resulting in the development of cholinergic deficiency; and (2) a neurotoxic one (streptozotocin), reproducing the main pathological hallmarks (Aβ accumulation and tau phosphorylation) (Table 2) [234].