Introduction to iron metabolism

1. IRON METABOLISM
Manoj Sigdel
Asst Prof

2. What are minerals?
•Inorganic substances
•Form important part of human nutrition
•Not synthesized in the body
•Obtained through the food
•Do not produce energy
•Easily absorbed through intestine and are excreted
in urine and to a lesser extent in feces
•About 20-30 g of minerals are excreted per day

3. Types of Minerals
Based on the requirement minerals are divided
into :
1. Bulk Elements (macro nutrients)
• Required in large amounts (>100 mg per day)
• Examples are Na, K, Cl, Ca, P and Mg
• Represents 80% of body inorganic matter
2. Trace Elements (micro nutrients)
•Required in small amounts (<100 mg/day)
•Examples are Fe, Zn, Cu, I, F, Se, Mn, Mb, Co & Cr

4. What are Trace Elements?
•Dietary minerals required in minute quantities
(<100 mg/day) e.g. Cr, Co, Cu, F, I, Fe, Mn, Se
•Collectively comprise <1% of total body mass.
•Mostly serve as structural components or
cofactors of enzymes/proteins
•Absorbed from the GI tract and mainly stored in
liver
•Deficiencies cause reproducible, structural or
biochemical deficits

5. Iron (Fe)
•Also known as metal of life (total body store
is ~3 -5 gm)
Two types of iron-containing proteins
1) Haemoproteins
2) Non-haem iron proteins

6. Iron in Haemoproteins
•Cytochromes of the mitochondrial respiratory
chain (100 mg of iron)
•Haemoglobin: more than one half of total body
iron (2.5 grams)
•Myoglobin: about 0.3 grams Fe, muscle oxygen
storage protein
•Cytochrome P450: most abundant haemoprotein
of the liver (about 1 mg) detoxifies foreign
compounds
•Catalase

7. Non - heme iron proteins
•Ferritin: iron storage protein
•Transferrin: iron transport protein
•Aconitase: Enzyme
•Hemosiderin: iron storage protein

8. Requirement of iron
•Adult men : 10 mg/day
•Adult women : 18 mg/day
•Pregnant women: 40 mg/day

9. Iron Requirements in Pregnancy

10. Dietary sources of iron
Main sources: Green vegetables (e.g. spinach),
avocado, lentils, potatoes, jaggery, liver and
meat
Two types of dietary irons:
 Hem iron (animal origin) and
 non-hem iron (plant origin)

11. Distribution of Iron in Adult Human Body

12. Iron (Fe)
•Exists in two major valence states: Fe2+ and
Fe3+

13. Body Distribution of Iron
Protein Oxidation state Amount (mg) % total
Hb 2 2600 65
Mb 2 130 6
Transferrin 3 3 0.1
Ferritin 3 520 13
Hemosiderin 3 480 12
Catalase, Peroxidase 2 - -
Cytochromes 2/3 - -
Aconitase 4Fe.4S cluster - -
Ferrochelatase 2Fe•2S cluster - -
Others - 140 3.6

14. Iron absorption
•Iron kept soluble and in ferrous state by
gastric acid
•Absorbed mainly in duodenum
•Quantity absorbed regulated by enterocyte
•Multiple proteins involved in control of iron
transport
•Haem iron enters the enterocyte through
different process than inorganic iron

15. Absorption and Transport of Iron
Ferro
reductase Ferroxidase
*
Ferroxidase II
Ceruloplasmin
*

17. Hepcidin
•Iron regulatory hormone
•Block iron export from cells
•Produced by liver cells
•Coded in HAMP gene on chromosome 19
•Hepcidin production is increased by high iron stores
and inflammation

18. Mechanism of action of hepicidin
•The major mechanism of hepicidin is the regulation
of transmembrane iron transport.
•It binds to FERROPORTIN ,forms hepicidin-
ferroportin complex ,which is degraded in the
lysosomes and iron is locked inside the cells (mainly
enterocytes, hepatocytes and macrophages).

20. Effect of Iron Status on Iron Absorption
Manoj Sigdel

21. Factors Influencing the Iron Absorption

22. Iron is a one way substance
•lron metabolism is unique as it operates in a closed
system.
•lt is very efficiently utilized and reutilized by the body.
Further, iron losses from the body are minimal (< 1
mg/day) which may occur through bile, sweat, hair loss
etc.
• lron is not excreted into urine. Thus, iron differs from
the vitamins or other organic and inorganic substances
which are either inactivated or excreted during the
course of metabolic function.
•Hence, iron is appropriately regarded as a one-way
substance

23. Iron is a one way substance
•lron entry into the body is controlled at the absorption
level, depending on the body needs.
•Thus the periodical blood loss in menstruating women
increases its requirements. Increased iron demands are
also observed in pregnancy, lactation, and in growing
children.

24. Thank you