Alternatively, insulin is known to play several roles within the CNS including regulation of neuronal survival, feeding behavior, cognition, and most importantly regulation of tissue metabolism by controlling cellular glucose uptake—accessing CNS regions by crossing the BBB via insulin receptor (InsR)-mediated transport, and has been shown to be altered in post-mortem brain tissue from AD patients (Griffith et al., 2018). Here, INSR is linked to Alzheimer disease.