Vit. B12 defiency

Question 1

What is vitmian B12 involved in?

Answer 1

Methylation cycle of folate, takes methyl from folate to make it active, and conversion of methionine to homocysteine

Question 2

Where do we get B12 from?

Answer 2

Only bacteria produce, so things like meat, shellfish, milk and eggs

Question 3

How is B12 absorbed?

Answer 3

Binds to hepatocorrin, secreted by parietal cells, after it has been cleaved by pepsin.
IF binds to vit. B12 after pancreatic proteases break HC-B12, and is absorbed in terminal ileum due to IF receptors. IF is recycled and vit. B12 is taken to cells with high turnover (TC-B12) and is stored in the liver. (HC again)

Question 4

What disease is caused by vit. B12 deficiency?

Answer 4

Pernicious/megaloblastic anaemia, with large red blood cells.

Question 5

What can be a cause of low B12?

Answer 5

Lack of IF secreted
poor function of ileal absorption
lack pf acid to release
normal pancreatic secretion

Question 6

How can B12 binding by IF be interfered with?

Answer 6

R- binders in saliva bind to B12 however pancreatic secretions release B12 from them

Question 7

What is pernicious anaemia?

Answer 7

Autoimmune disorder where antibodies attach parietal cells and IF, lack of IF thus lack of B12 absorption

Can be diagnosed by blood test showing antibodies against IF, not just parietal cells, both??

Treatment: supplements, frequently

Question 8

How can B12 absorptio be impaired by the ileum?

Answer 8

Surgery to have removed ileum or Crohns where ileum is inflammed

Question 9

What else does the ileum absorb?

Answer 9

Bile salts, causing fat absorption