INS and hyperinsulinism: For instance, hyperinsulinemia (a characteristic of DM type 2 as a consequence of insulin resistance) is known to reduce the level of insulin in the central nervous system via downregulation of insulin transport at the blood brain barrier which ultimately reduced insulin signalling (a neuronal functioning which facilitates learning and memory) and weakened glucose transport resulting in neurodegenerative disorders, namely, AD [55,56].