Implications of aquaglyceroporins 7 and 9 in glycerol metabolism and metabolic syndrome

The discovery of water channel protein (aquaporin [AQP]) has made a great impact on life sciences. So far, 13 AQPs have been identified in human. AQP3, 7, 9, and 10 are subcategorized as aquaglyceroporins which permeabilize glycerol as well as water. Many investigators have demonstrated that AQPs play a crucial role in the maintenance of water homeostasis, but the physiological significance of some AQPs as glycerol channels remains elusive. Adipocyte is a major source of glycerol, which is one of the substrates for hepatic gluconeogenesis. This review focuses on recent studies on glycerol metabolism through AQP7 and AQP9, and briefly discusses the importance of glycerol channel in adipocytes, liver, and heart.