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Dig > L11: Absorption Of Iron And Gastrointestinal Disease > Flashcards

L11: Absorption Of Iron And Gastrointestinal Disease Flashcards

1
Q

Why is iron important

A

Oxygen transport
Electron transport by cytochromes
Regulation of enzymes
Cell cycle control

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2
Q

Can iron be actively excreted

A

No so the process of iron has to be tightly regulated for balance

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3
Q

What happens when erythrocytes become old

A

Engulfed by macrophages

Haem is Brocken to biliverdin then to bilirubin to produce bile

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4
Q

What is the major organ for iron storage

A

Liver

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5
Q

How can iron be lost in females

A

Menstruation (periods)

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6
Q

What are dietary iron

A

Inorganic

Haem

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7
Q

What form is iron in within inorganic

A

Ferric (fe3+)

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8
Q

Is ferric iron absorbed well

A

No because it has to be reduces to ferrous iron (fe2+)

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9
Q

Is haem absorbed well

A

Yes

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10
Q

Where is most of the iron absorbed in the body

A

Duodenum

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11
Q

How is iron absorbed in enterocytes

A

1) fe3+ is reduced to fe2+ by Dcytb enzyme and acid in the stomach
2) fe2+ is absorbed by DMT1
3) in the cell fe2+ is used in the cell or stored in the cell by binding to ferritin so iron does not drive free radicals (gives damage)
4) or fe2+ can be effluxed out of the enterocyte into the blood
5) FPN effluxes fe2+ out
6) fe2+ is oxidised to fe3+ to hephaestin
7) fe3 becomes bound to transferrin so iron is inert

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12
Q

How is circulating iron absorbed in a non-enterocyte cell

A

1) transferrin bound iron is taken in by a transferrin receptor
2) cells express transferrin receptor on the cell surface to take in iron

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13
Q

How is haem iron absorbed into enterocytes

A

1) HCP1 takes in haem iron into the cell
2) haem iron is then Brocken down by HO-1 enzyme to release biliverdin and free iron (can become bound to ferritin or used)

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14
Q

What happens when HO-1 releases biliverdin from haem iron

A

Biliverdin is catalysed by biliverdin reductase to give bilirubin

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15
Q

What does build up of bilirubin give

A

Jaundice

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16
Q

Which major hormone regulates iron levels

A

Hepcidin

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17
Q

Which organ is hepcidin produced in

A

Liver

18
Q

What is the action of hepcidin

A

Inhibit iron absorption

19
Q

How does hepcidin inhibit iron absorption

A

Hepcidin binds on the iron efflux transporter Fpn to block iron efflux

20
Q

What happens when there is high levels of iron

A

High Iron is sensed by protein called TfR2, HFE, HJV on hepatocytes
Hepcidin is produced by hepatocytes
Hepcidin binds to FNP1 on enterocytes to block iron absorption
Hepcidin binds to FNP1 on other cells to block iron absorption

21
Q

What happens when there is low levels of iron

A

Hepcidin production is suppressed

22
Q

What happens to hepcidin in infection and inflammation

A

IL-6 stimulates hepcidin transcription
Hepcidin acts on FNP1 on enterocytes to block iron absorption
Hepcidin acts on FNP1 on macrophages (that recycle iron) so iron is trapped within the macrophage

23
Q

Why is hepcidin switched on in infection and inflammation

A

Bacteria needs iron to live

Stopping iron efflux limits the damage of bacteria

24
Q

What can infection and inflammation result in

A

Anaemia of an chronic disease

25
Q

Why does infection and inflammation result in anaemia of chronic disease

A

Iron is stored in macrophages

26
Q

Why do obese patients have poor iron status

A

Due to chronic low grade inflammation and high hepcidin levels

27
Q

How do you differentiate between anaemia chronic disease and iron deficiency anaemia

A

Low serum ferritin indicates iron deficiency anaemia

High serum ferritin indicates anaemia of chronic disease

28
Q

What is ferritin

A

A protein that binds to iron to make it inert

29
Q

What happens when you cant make hepcidin

A

Hereditary haemochromatosis

30
Q

What is hereditary haemochromatosis

A

Iron overload that results in liver failure and diabetes mellitus

31
Q

How do you treat hereditary haemochromatosis

A

Phlebotomy because the patient has high levels of iron so you remove iron

32
Q

What causes hereditary haemochromatosis

A

Mutation of HFE protein
Mutation of HJV protein
Mutation of TFR2 protein
Mutation of hepcidin

33
Q

What does HFE, TFR2 and HJV do

A

Sense high levels of iron and switch on iron

34
Q

Which reaction of iron gives free radicals that lead to damage

A

Fenton reactions

35
Q

How is iron deficiency anaemia treated

A

200mg twice daily and 250mg ascorbate

36
Q

What are the causes of iron deficiency anaemia

A 
Menstrual blood 
Vegan diet (not a lot of iron in diet) 
Blood loss from gastrointestinal tract
37
Q

What is coeliac disease

A

Autoimmune disorder of the small bowel that results in villus atrophy due to a reaction of a gluten protein

38
Q

What are the symptoms of coeliac disease

A

Iron deficiency anaemia
Diarrhoea
Weight loss
Fatigue

39
Q

How do you test for coeliac disease

A

Trans glutaminase antibodies

Bowel biopsy

40
Q

What is the treatment for coeliac disease

A

Lifelong gluten free diet

Dig (20 decks)

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