Iron Metabolism

WHAT IS IRON METABOLISM?

Did you know that the usual iron intake is 10-20 mg per day for a person but the absorption is only 1-2 mg per day? Yes, it is that little! Iron can be obtained from the food we eat, such as meat and vegetables. Iron is an important element and is needed for the production of erythrocytes (erythropoiesis), as well as other important processes. It requires a tightly regulated process and takes place in the duodenum. In this article, we will go deeper about the process involved in iron metabolism which include iron absorption, transportation, and storage.

From the diagram above, you can see the enterocyte. The left side is apical membrane and the other side is basolateral membrane. Let me tell you the process one by one so it will be easier to understand.

When the iron intake is from the animal source like the meat we eat, which contains both haemoglobin and myoglobin, both of them contain heme. Inside the heme, there is iron. This iron which is in heme form is transported directly through a heme transporter (HCP1). HCP1 transfers iron in heme form from the intestine to the enterocyte and iron (Fe2+) is released inside. 

When we take food from plant sources such as vegetables, there is no heme, and iron will be mostly in Ferric form (Fe3+). But before that, it must be converted to Ferrous form (Fe2+) for absorption. This is done by DCYTB. In order to change, they need Vitamin C and an enzyme called Ferric Reductase. It then will be transported by DMT1, which are only specific for ferrous,  into the enterocyte.

These iron may be stored or kept in the cell as Ferritin or go out of the cell and be  transported across the basolateral membrane  by the iron exporter, Ferroportin (FPN). This FPN is inhibited by Hepcidin, which is the main regulator of iron homeostasis, and is secreted by the liver. It transports iron from enterocytes to blood vessels. Transferrin takes iron from the Feroportin and will send them to the liver, muscle, bone marrow and so on. This Ferrous form is  converted to Ferric form by Hephaestin (Hp). In order to change, they need Cuprum and Hp. It is then transported in the blood alongside transferrin.  

So, what is the role of a hepcidin? As we discussed earlier, Hepcidin is a peptide hormone which also acts as the key regulator of iron in our body. The function of Hepcidin is to decrease iron release from cells (hepatocytes and macrophages), and decrease iron absorption in enterocytes or intestine. 

https://www.researchgate.net/figure/Hepcidin-regulates-cellular-iron-export-into-plasma-When-hepcidin-concentrations-are_fig1_6572598/download

The main mechanism of Hepcidin is the regulation of transmembrane iron transport. Hepcidin also binds to ferroportin to produce  Hepcidin-ferroportin complex, which results in the closing of the entrance or 'gate' that keeps the iron from being released out from the cells. 

When Hepcidin levels are low, iron exporting cells have abundant ferroportin and release iron into plasma. But it is different when the Hepcidin increases. When Hepcidin concentration increases, it binds to ferroportin and thus iron is kept in the cells.

Unfortunately, if there is any excessive or lack of Hepcidin in the body, we are at high risk of getting diseases. When there is too much Hepcidin, all the cells will keep the iron or easily said, it will be locked up in the cell. Iron release will be decreased.  Meaning to say, there will be no iron in the blood, and this will lead to iron deficiency anemia. 

Iron Deficiency Anemia: Symptoms, Causes, and Treatment. (2019, August 20). Scientific Animations. 

I'm sure all of you already know that too much iron in your body is not good. When the Hepcidin is reduced, it will lead to the increasing of iron absorption and release. In this case, Hemochromatosis will occur. It causes your body to absorb too much iron from the food you eat.

https://healthjade.net/neonatal-hemochromatosis/

Considering all the things mentioned above, iron metabolism is very important to maintain a healthy body. If you suspect any of these diseases on your own body, make sure to consult your doctor on the iron intake and medication.

That's all from me for this time. I hope you enjoy this article. Bye!

BY: AMANI KHADIJAH BINTI FAUZI