鐵恆定的新知──鐵調素與鐵轉運蛋白之角色與檢測

Iron homeostasis- role and significance of hepcidin and erythroferrone

鐵恆定是平衡鐵質在體內的狀態，除了體內有足夠的鐵質，也避免鐵質過度累積。因為鐵質在體內沒有特殊的代謝途徑；因此，鐵循環機制在各個環節調控了鐵質的吸收與再利用。在人體中，鐵質的濃度會以轉錄後調控方式促進或抑制各種鐵質相關的蛋白質的生成；有核紅血球自血流中獲得鐵質則是在運鐵蛋白（transferrin）循環中嚴謹的被調控著。鐵質的吸收與鐵質的再利用則是透過鐵調節激素-鐵調素（hepcidin）與鐵轉運蛋白（ferroportin）之相互作用來調控的。鐵轉運蛋白是鐵質自細胞輸出的通道；鐵調素可經由結合鐵轉運蛋白而降解之，來抑制鐵質自細胞內游移至血漿中。另外，有核紅血球產生的荷爾蒙赤鐵酮（erythroferrone）可以抑制肝細胞製造分泌鐵調素，進而增加食物鐵的吸收和自細胞游移出儲存鐵。本篇綜論主要是介紹鐵調素與赤鐵酮在紅血球生成中如何調節鐵恆定、兩者的檢驗以及其未來展望。

Iron homeostasis is the balance of iron in the body. It ensures adequate iron in the body and prevents excessive iron accumulation. Iron has no specific metabolic pathway in the body; therefore, the iron levels strictly regulate the absorption and reuse of iron. In the human body, iron post-transcriptionally regulates the biosynthesis of several iron-related proteins. The nucleated red blood cells at various stage obtain iron to synthesize hemoglobin through the strict regulation of the transferrin cycle. Iron absorption and iron reuse are regulated through interaction between the iron regulatory hormone hepcidin and ferroportin. Ferroportin is a transporter through which iron is exported from cells; and hepcidin binds to and degrades the ferroportin via endocytosis, thereby inhibiting the movement of iron from cells into plasma. On the other hand, the hormone erythroferrone produced by nucleated red blood cells inhibit the production and secretion of hepcidin by hepatocytes, thus increasing dietary iron absorption and mobilization of the stored iron from cells. This mini-review focus on the role of hepcidin and erythroferrone in the regulation of iron homeostasis, as well as their significance in erythropoiesis and their future prospects.