Chapter 21 The Endocrine System Pancreas Insulin and Diabetes How does the endocrine system regulate energy metabolism Anatomy of the Endocrine System Primary endocrine organs primary func on is the secre on of hormones Secondary endocrine organs also secrete hormones but it is secondary to some other func on Transport and Uptake of Biomolecules How does the body maintain an energy balance of equal energy input and energy output when energy input which is determined by feeding is intermiEent Absorp ve State For about 3 4 hours aGer ea ng a meal the body must absorb while nutrients are plenGful In this state energy input usually exceeds output and the energy is stored in macromolecules Post Absorp ve State Corresponds to the me between meals where the rate of energy expenditure is greater than energy intake Energy stores are mobilized to provide the energy that cells need As a result the body provides a constant supply of nutrients to cells Beta cells are directly sensi ve to the concentraGon of glucose in uid surrounding them How Does the Endocrine System Regulate this Process Metabolic adjustments as the body switches between these two states are triggered by the release of insulin and glucagon Insulin pep de hormone with A and B chains connected by disulphide bonds Structure of Insulin Kine cs of insulin release How does insulin trigger glucose uptake into cells so that it can be stored as energy Receptor tyrosine kinases The Insulin receptor is an example of a receptor tyrosine kinase Receptor tyrosine kinases The insulin receptor tyrosine kinase type receptor McGeTrick Feener and Kahn 2004 How does insulin binding to the receptor trigger cells to take up more glucose Insulin Receptor Ac va on The insulin receptor couples to intracellular signaling cascades to recruit GLUT4 transporters to the cell surface Facilitated Di usion of Glucose Glucose binds GLUT 4 on the exterior of the membrane and this binding causes a conformaGonal change in the proteins which transports glucose into the interior of the cell How does insulin recruit GLUT4 to the cell membrane GSC GLUT4 Storage Compartment of Vesicles Insulin dependent inser on of GFP labeled GLUT4 in adiposites Watson et al 2004 Regula on of Absorp ve Metabolism Majority of reac ons involve the synthesis of macromolecules that can store energy i e glycogen and especially fats The Diabetes Epidemic According to the American Diabetes Associa on in the U S 8 of the popula on 24 million people have diabetes In addi on another 57 million people are pre diabe c meaning there is a high probability that they will develop diabetes in the future Prevalence of Diabetes in the U S Diabetes Mellitus Diabetes mellitus consists of two types type 1 and type 2 Type 1 diabetes mellitus is also called juvenile onset diabetes because damage to the beta cells of the pancreas keeps them from secre ng enough insulin in the blood to regulate blood glucose Type 2 diabetes mellitus also called adult onset diabetes is characterized by failure to respond to insulin when its levels are normal Results in cells not gecng required glucose and blood glucose levels rising Diabetes Mellitus Regula on of Post absorp ve Metabolism Insulin s ac ons in the body are reinforced by opposing changes in Glucagon secre on decreased during the absorp ve state and increase during the post absorp ve state Evidence suggests that the release of insulin inhibits the produc on and secre on of glucagon from alpha cells Insulin and glucagon are antagonists