Glucose uptake of hepatocytes and pancreatic beta cells (in mice, but GLUT1 in human beta cells; see Reference 1). The high Km of GLUT2 allows for glucose sensing; rate of glucose entry is proportional to blood glucose levels. GLUT4 transporters are insulin sensitive, and are found in muscle and adipose tissue. As muscle is a principal storage site for glucose and adipose tissue for triglyceride (into which glucose can be converted for storage), GLUT4 is important in post-prandial uptake of excess glucose from the bloodstream. Moreover, several recent papers show that GLUT 4 is present in the brain also. The drug metformin
Alpha cell Alpha cell Alpha cells (more commonly alpha-cells or α-cells) are endocrine cells in the pancreatic islets of the pancreas. They make up to 20% of the human islet cells synthesizing and secreting the peptide hormone glucagon, which elevates the glucose levels in the blood. To elevate glucose levels, glucagon binds to receptors on hepatocytes (liver cells) and some other cells (e.g. kidney cells). This activates an enzyme, glycogen phosphorylase, inside the hepatocyte to hydrolyse glycogen to glucose. This process is called glycogenolysis. In rodents, alpha cells are located in the periphery of the islets, however in humans the islet architecture