Human fibroblasts express the insulin-responsive glucose transporter (GLUT4)

The transport of glucose across the plasma membrane of nonepithelial cells is mediated by a family of facilitative glucose transporters. One glucose transporter is insulin-responsive (GLUT4) and is found in muscle, heart, and fat cells, differentiated cells which are difficult to maintain and study in culture. Cultured dermal fibroblasts, on the other hand, also are insulin-responsive, can be easily maintained in culture, and retain the genetic complement of the donor. In this paper, we evaluate RNA isolated from cultured human fibroblasts for the expression of four different glucose transporters. Northern blot analysis indicated that human fibroblasts expressed the erythrocyte (GLUT1), the fetal skeletal muscle (GLUT3), and the insulin-responsive (GLUT4) glucose transporters, but not the liver glucose transporter (GLUT2). To confirm the presence of GLUT4 mRNA, cDNA was synthesized from human fibroblast RNA, amplified using primers specific for GLUT4 by the polymerase chain reaction, and sequenced. The sequence was identical to that of GLUT4 cDNA. These data indicate that cultured human fibroblasts express at least three genetically distinct facilitative glucose transporters.