The Function of the Islets of Langerhans

Abstract

The islets of Langerhans play an essential role in regulating nutrient homeostasis in man. They function to ensure that despite wide fluctuations in the supply of certain nutrients in the diet, the concentration of these nutrients in the blood is maintained at a level appropriate to the varying and competing needs of the tissues of the body. This is achieved largely by alterations in the rate of secretion of the islet cell hormones into the circulation. These hormones are released in response to changes in the concentration of metabolites and other hormones in the circulation and in response to the activity of the sympathetic and parasympathetic nervous systems. The relative amounts of insulin and glucagon in the circulation, determined largely by their rate of secretion, is an important factor in regulating the rate of flux of metabolites into and out of tissues such as liver, muscle and adipose tissue. Pancreatic polypeptide and somatostatin do not appear to have any direct effect on the metabolism of these tissues, and these hormones may play a role in determining the rate of entry of nutrients into the circulation from the gastrointestinal tract.