INS and type 2 diabetes mellitus: Type 2 diabetes mellitus (T2DM) increases the risk of developing AD (Akter et al., 2011; Vagelatos and Eslick, 2013) and AD patients also exhibit disturbed energy metabolism and insulin resistant in the brain, possibly due to impairments of insulin signaling (Talbot et al., 2012; Chen and Zhong, 2013).