GLUT4 is the facilitated glucose transporter expressed exclusively in adipocytes and muscle cells, and 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. The total cellular content of GLUT4 is significantly decreased in adipose cells from many patients with Type II diabetes mellitus, and animals with some types of experimental diabetes.