AQP4 and diabetes mellitus: Diabetes compromises the integrity of the conceptual neurovascular unit in the hippocampus, leading to increased blood-brain barrier (BBB) permeability, vascular remodeling, higher levels of hippocampal cell mortality, greater astrocyte reactivity, disruption of the AQP4 polarity within the astrocytes, and ultimately impaired cognitive function (Ward et al., 2019; Zhang et al., 2019).