Glucose transporter type 4 (GLUT4 or SLC2A4) is the facilitated glucose transporter exclusively expressed in adipocytes (brown and white fat) and muscle cells. GLUT4 is also known as the insulin-responsive glucose transporter. GLUT4 translocates from an ill-defined intracellular compartment to the plasma membrane in response to insulin. Defects in GLUT4 is a cause of noninsulin-dependent diabetes mellitus.