Iron Physiology

Summary

This video explains the essential role of iron in the body, focusing on its absorption, transportation, and storage. Iron is crucial for many physiological processes, especially in red blood cell production. The transcript covers the forms of iron, how it’s absorbed in the small intestine, and how it’s transported by proteins like transferrin. Key enzymes, such as Vitamin C ferroreductase, and transporters like DMT1 and ferroportin, play important roles in iron metabolism. The video also discusses regulation through hepcidin and the impact of genetic mutations like hereditary hemochromatosis, which causes iron overload.

Takeaways

• 😀 Iron is an essential element in the body, required for many physiological processes.
• 🍽️ The daily dietary requirement of iron is between 10 to 20 mg.
• 🧑‍⚕️ Iron comes in two main forms: ferrous (Fe2+) and ferric (Fe3+) iron, which are crucial for absorption and transport.
• 🔬 In the small intestine, ferric iron (Fe3+) is reduced to ferrous iron (Fe2+) by vitamin C and the enzyme ferroreductase for absorption.
• ⚙️ The transporter DMT1 is responsible for moving ferrous iron into enterocytes, where it can be used or stored.
• 🛑 Once absorbed, ferrous iron is often oxidized back to ferric iron and stored as ferritin in cells.
• 💉 Transferrin is a key protein that carries ferric iron (Fe3+) in the blood to various tissues, including the liver and bone marrow.
• 🔄 Approximately 75% of absorbed iron goes to erythropoiesis (red blood cell production) in the bone marrow.
• 🩸 In the liver, iron is stored as ferritin and can be released back into circulation when needed, bound to transferrin.
• ⚖️ Hepcidin, a key iron regulator produced by the liver, controls iron levels by inhibiting ferroportin, which regulates iron release from cells.
• 🧬 A mutation in the HFE gene can cause hereditary hemochromatosis, a condition where excessive iron accumulates in tissues due to improper regulation.
• 🍖 Iron can also be obtained from hemoglobin and myoglobin found in red blood cells, broken down to release iron.
• 📉 Lack of iron can lead to iron-deficiency anemia, with menstrual bleeding being a common cause of iron loss in women, who need more iron than men.

Q & A

What are the two main forms of iron found in the body?

The two main forms of iron in the body are ferric iron (Fe3+) and ferrous iron (Fe2+).

Why can't the body absorb ferric iron (Fe3+) directly?

The body cannot absorb ferric iron (Fe3+) directly because it needs to be reduced to ferrous iron (Fe2+) for absorption in the small intestine.

What enzyme is involved in converting ferric iron to ferrous iron in the small intestine?

The enzyme Vitamin C ferroreductase is responsible for converting ferric iron (Fe3+) to ferrous iron (Fe2+) in the small intestine.

What role does the divalent metal transporter 1 (DMT1) play in iron absorption?

DMT1 is a co-transporter that facilitates the absorption of ferrous iron (Fe2+) into intestinal cells, also allowing hydrogen ions to enter the cell.

How is iron transported around the body once absorbed into the bloodstream?

Once absorbed, iron is transported by the protein transferrin, which binds to two ferric iron (Fe3+) ions and carries them through the bloodstream to various cells.

What are the primary fates of absorbed iron in the body?

Most absorbed iron (about 75%) is used for erythropoiesis in the bone marrow to produce red blood cells. Some iron is also transported to the liver for storage.

What happens to transferrin once it has delivered iron to cells, such as in the liver?

After transferrin delivers iron to cells, it binds to transferrin receptors, is endocytosed, and the iron is either used, stored as ferritin, or released back into circulation.

What is the role of hepcidin in regulating iron levels in the body?

Hepcidin is the master regulator of iron levels. It inhibits ferroportin, the transporter that releases iron into circulation, and decreases iron absorption from the small intestine.

How does inflammation affect iron regulation in the body?

Inflammatory cytokines, such as interleukin 6, stimulate the production of hepcidin, which lowers plasma iron levels by inhibiting iron release from cells and absorption from the intestine.

What is hereditary hemochromatosis, and how is it related to iron regulation?

Hereditary hemochromatosis is a condition caused by mutations in the HFE gene, leading to an inability to regulate iron properly. This results in excessive iron absorption and iron overload in tissues.

What is the role of heme iron in iron metabolism?

Heme iron, derived from hemoglobin and myoglobin, is broken down into iron and biliverdin in the small intestine. The iron can be absorbed and stored or used for erythropoiesis.