Transpo of glucose across a cell membrane occurs by facilitated diffusion. By this means of transpo glucose is transpoed down the concentration gradient. This transpo is accomplished by different isoforms of a super family of hydrophobic, integral membrane proteins referred to as glucose transpoers. GLUT4 receptors are found on skeletal muscle, cardiac muscle and adipocytes. This receptor is dependent on insulin. During fasting, level of insulin in the blood is low, which in-turn reduce the number of GLUT4 receptors. Ref: Applied Physiology in Intensive Care Medicine By Brochard, Jordi Mancebo, Page 2170; Bioenergetics Primer for Exercise Science By Jie Kang, Page 119