Cobalamin

Question 1

What are the 2 active coenzymes that our bodies can convert B12 into?

Answer 1

5-deoxyadenosylcobalamin

Methylcobalamin (CH3)

Question 2

What is the main B12 formed by microorganisms?

Answer 2

Cyanocobalamin

Question 3

Cyanocobalamin is found in what sources?

Answer 3

It’s the form in vitamins and added to cereals

Question 4

What does B12 from blue-green algae (spirulina) produce mostly, and what is it’s metabolic effects?

Answer 4

Pseudovitamin B12. Not active in humans

Question 5

Intrinsic factor is secreted from what, where?

Answer 5

Parietal cells of the stomach

Question 6

How is Vitamin B12 digested and absorbed?

Answer 6

See slide 228

Question 7

What conditions can decrease vitamin B12 digestion & absorption?

Answer 7

Zollinger-Ellison syndrome (too much HCl)

Medications for GERD (not enough HCl)

Pancreatic insufficiency (not enough proteases to release B12 from R proteins)

Malabsorptive syndromes

Question 8

50% of B12 is absorbed where?

Answer 8

Ileum

Question 9

B12+IF is released where and becomes what?

Answer 9

Enterocyte, becomes B12

Question 10

After the enterocyte, where does B12 go and how?

Answer 10

To the liver bound to transcobalamins in blood

Question 11

After the liver where does B12 go?

Answer 11

Leaves liver bound to transcobalamins in blood, then goes to be stored in bone, liver (50% storage here), brain, muscles.

Question 12

What significant compound and function is made as a product of the coenzymatic function of methylcobalamin

Answer 12

As methylcobalamin turns into cobalamin, homocysteine turns to methionine, which then turns into SAMe, an important factor in myelination

Question 13

What is the B12 coenzyme called and what does it mediate?

Answer 13

Adenosylcobalamin. Threonine and isoleucine metabolism or metabolism of odd-chain fatty acids.

Question 14

What is the RDA for B12?

Answer 14

Adults = 2.4 mcg

Question 15

What are the sources of B12?

Answer 15

Shellfish
Meats
Poultry
Fish
Dairy (some lost through pasteurization)
Fortified cereals

Question 16

How much B12 is lost from cooking?

Answer 16

33%

Question 17

What 2 conditions are associated with B12 deficiency?

Answer 17

Megaloblastic anemia

Pernicious anemia

Question 18

If you have a B12 deficiency, but you are good on folate, what symptoms of megaloblastic anemia will be taken care of and what ones remain?

Answer 18

Folate can get rid of hematologic symptoms, but not neurologic symptoms due to demyelination of nervers

Question 19

What is the direct cause of megaloblastic anemia with B12 deficiency?

Answer 19

Decreased DNA synthesis

Question 20

What is pernicious anemia?

Answer 20

Type of megaloblastic anemia. Autoimmune condition where antibodies attack gastric, parietal and mucosal cells.

Question 21

What happens with HCl secretion in pernicious anemia?

Answer 21

Decrease in HCl secretion (achlorydia) causes impaired B12 release from food proteins

Question 22

What happens with IF in pernicious anemia?

Answer 22

Impaired IF secretion causes inability to absorb B12

Question 23

What is the tx for pernicious anemia?

Answer 23

B12 injections

Question 24

What is the cause of B12 deficiency, inadequate absorption or intake?

Answer 24

Inadequate absorption

Question 25

What is the toxicity levels for B12

Answer 25

None

Question 26

T/F

Vegans will develop B12 deficiency relatively quick

Answer 26

False

May take 5-10 years before deficiency

Question 27

If you are elderly and 15% deficient, what is the best way to alleviate the problem?

Answer 27

Take IM injection or nasal spray