The Molecular Basis of Inherited Diabetes Insipidus

Diabetes insipidus is a disease characterized by the excretion of an abnormally large amount of dilute urine that results from a failure of the water-conserving mechanism in the collecting ducts of the kidney. Inherited diabetes insipidus is a rare disorder, but the study of affected individuals and families has provided unique insights into the normal mechanisms involved in regulation of water balance. Water conservation in the kidney is regulated primarily by the hormone vasopressin. This hormone interacts with renal vasopressin receptors that cause intracellular water channels to be inserted into the luminal membrane of the cells lining the collecting duct to allow water resorption from the renal ultrafiltrate. Inherited forms of diabetes insipidus have been described that affect each of the key components in this water resorption system. Autosomal-dominant neurohypophyseal diabetes insipidus results from disruption of vasopressin production, X-linked diabetes insipidus results from abnormalities in the vasopressin receptor, and autosomal recessive diabetes insipidus results from defective water channels. A fourth inherited disease, Wolfram syndrome, involves inherited diabetes insipidus as one component of a cluster of abnormalities, and the molecular basis of this syndrome is being elucidated, but is not yet well understood. This article will explore the molecular biology of each of these inherited forms of diabetes insipidus and the current state of knowledge of the molecular mechanisms of production of vasopressin and action of vasopressin in the kidney.