Impact of glycerol gateway molecule in adipocytes.

Glycerol is one of the essential nutrients in the mammalian body. Glycerol released from adipocytes is delivered to the liver and used for gluconeogenesis. The molecular mechanism of glycerol transport across the cell membrane remains unclear. AQPadipose, which we identified in human adipose cDNA project and later found to be human AQP7, is expressed in adipose tissue, and upregulated during fasting. AQP7 belongs to the aquaglyceroporin subfamily to permealize glycerol as well as water. Loss of function mutation of AQP7 in human caused disturbance of normal rise of plasma glycerol. Disruption of AQP7 gene in mice resulted in profound hypoglycemia during prolonged fasting because of impaired glycerol supply to the liver. In obesity, AQP7 is overexpressed in visceral fat,accompanied by portal hyperglycerolemia and systemic hyperglycemia. Considered together, these works indicate that AQP7 functions as a glycerol gateway molecule in adipocytes.