Obesity and metabolic perturbations after loss of aquaporin 7, the adipose glycerol transporter

摘要

Adipocytes are a dynamic reservoir for storage of energy in the absorptive phase and release of energy in the postabsorptive phase. The flux of carbon into and out of adipocytes is a highly regulated, although incompletely understood, process. Whereas insulin-stimulated uptake of glucose has been extensively studied, research on the transport of fatty acids and glycerol has lagged. Discovery of the aquaporin (AQP) family of proteins significantly advanced the biology of glycerol transport. To date, there are 11 identified proteins in the AQP family. These proteins assemble as tetramers in the plasma membrane, with each monomer containing a channel. Although most members of the family are specific for water transport, a subset consisting of AQP3, AQP7, AQP9, and AQP10 are also permeated by other solutes, including glycerol. Of these proteins, only AQP7 is expressed at high abundance in adipose tissue. Recent articles, including one by Hibuse et al. in this issue of PNAS, provide strong evidence that AQP7 is required for efflux of glycerol from adipocytes, and lack of AQP7 influences not only adipocyte biology but also whole-body glucose homeostasis and insulin sensitivity.