A comparison of the function of the brain insulin–PI3K–Akt signaling pathway in the frontal cortices among subjects with AD, type 2 diabetes, type 2 diabetes and AD, and control subjects showed that the deficiency in the insulin–PI3K–Akt signaling was more significant in subjects with both type 2 diabetes and AD [98]. The gene discussed is AKT1; the disease is type 2 diabetes mellitus.