INSR and diabetes mellitus: Neuronal apoptosis is the main cause of brain dysfunction in diabetes, and dysregulation of the insulin receptor (IR) and insulin‐like growth factor‐1 receptor (IGF‐1R) signaling pathways in the hippocampus plays an important role in the induction of neuronal apoptosis and consequently the occurrence and development of diabetic encephalopathy (Hoffman et al., 2010; Ito et al., 2012).