Hepatobiliary, salivary glands and pancreas aquaporins in health and disease

Aquaporins (AQPs) are channel proteins largely present in mammals where they facilitate the permeation of water and a variety of substrates across cellular membranes. AQPs exert pleiotropic roles in both health and disease. This chapter addresses the most recent acquisitions in terms of expression and regulation, as well as physiological and pathophysiological rolesof AQPs in the hepatobiliary tract, salivary glands and pancreas. A number of AQPs are found in liver, bile ducts and gallbladder where they are playing roles in bile formation, secretion and reabsorption. Liver AQPs are also implicated in energy homeostasis by acting in hepatic gluconeogenesis and fat metabolism, and in important processes such as ammonia detoxification and mitochondrial release of hydrogen peroxide. Hepatobiliary AQPs are involved in clinical disorders including cholestasis, gallstone formation, insulin resistance, fatty liver disease, hepatic cirrhosis and hepatocarcinoma. Salivary and exocrine pancreas AQPs exert main roles in fluid secretion and contribute to the pathogenesis of xerostomia and pancreatic insufficiencies. Endocrine pancreas AQPs are suggested to be key regulators of intra-islet glycerol content as well as insulin production and secretion, and to contribute to the pathogenesis of diabetes. This body of knowledge represents the mainstay of present and future research in a rapidly expanding field.