Hepicidin and its role in iron metabolism.

Among various micro-nutrients, iron plays a major role not only for hemoglobin alone but also for oxidative metabolism and energy production. Hemoglobin functions as a chief oxygen carrier while other iron containing mitochondrial enzymes and respiratory chain proteins are involved in oxidative metabolism and release of energy from carbohydrates and fats. Iron salts have very low bioavailability and have potential for toxicity. Therefore iron absorption and its metabolism in humans is highly regulated process. Its regulation at cellular levels is through iron responsive proteins via ironresponsive elements in messenger RNA from genes encoding proteins of iron metabolism. Regulation of iron metabolism along with iron mobilization from macrophages, tissue stores and synthesis of transferrin receptor and ferritin is a complex process. It has been observed that hepatocytes produce hormone peptide hepcidin which plays a major role in the systemic regulation of iron metabolism by its action on target cells at various sites including the liver. Zhang and Enns have recently concluded that hepicidin plays a key of role in the regulation of iron metabolism.1 Several experimental and other clinical studies have demonstrated that hepicidin controls the release of iron from variety of cells such as macrophages, hepatocytes, enterocytes etc to plasma.2-5 Hepcidin primarily controls the iron absorption. However, the recycling of iron from red cell lysis and release of iron from tissue iron stores is carried by the interaction of hepicidin with ferroportin which is a cellular iron exporter in vertebrates.5 Ferroportin is primarily expressed by enterocytes and macrophages. It has been shown that release of ferroportin is also controlled by hepicidin.