AQP2 and nephrogenic diabetes insipidus: Dysregulation of AQP2 as well as genetic mutations in AQP2 [23] and the AVP receptor [24,25,26,27], are key in many water balance disorders including nephrogenic diabetes insipidus (NDI), which is the inability to appropriately respond to circulating levels of AVP, acute kidney injury [28], chronic kidney injury [29], chronic heart failure [30], and many others.