Vitamins B&B

Question 1

vitamin A, aka ______, is important for… (2)

Answer 1

vitamin A = retinol

1. vision (esp. rods - night vision)
2. cell differentiation (recall high doses of vitamin A can treat AML, among other cancers)

Question 2

the major source of vitamin A (retinol) is…

Answer 2

beta carotene (pro-vitamin A) - has antioxidant properties

can get from liver, dark green or yellow vegetables

Question 3

vitamin A is sometimes used as therapy for what type of cancer?

Answer 3

AML (acute promyelocytic leukemia) - classic finding is Auer rod

Vitamin A given as all-trans-retinoic acid —> induces malignant cells to complete differentiation

Question 4

vitamin C, aka _____, is important for… (4)

Answer 4

vitamin C = ascorbic acid, water soluble, required for:

1. iron absorption (non-heme - requires reduction)
2. collagen hydroxylation in ER
3. dopamine conversion to NE
4. antioxidant

Question 5

what are 2 major concerns of vitamin C excess?

Answer 5

1. iron overload (in predisposed patients) - Vitamin C enhances iron absorption
2. calcium oxalate kidney stones - Vitamin C metabolized into oxalate

Question 6

from where are the 2 forms of vitamin D found?

Answer 6

Vitamin D2 (ergocalciferol) - found in plants

Vitamin D3 (cholecalciferol) - found in fortified milk or synthesis induced via sunlight

Question 7

what must happen to Vitamin D for it to be activated?

Answer 7

must be hydroxylated, first in liver (step 1), then in kidney (step 2 - regulated by PTH)

recall active form is 1,25-OH Vitamin D (calcitriol)

Question 8

sarcoidosis can lead to rogue activation of which vitamin?

Answer 8

macrophages in sarcoidosis induce activation of vitamin D to 1,25-OH Vit. D (hydroxylated)

[recall normally this occurs in proximal tubule of kidney]

Question 9

describe the effects of vitamin D on the GI and bones

Answer 9

major mechanism is increased Ca2+ and PO4 absorption in GI

at abnormally high levels, paradoxical effect can occur in bones which causes Ca2+/PO4 resorption

Question 10

how does vitamin D deficiency present?

Answer 10

poor GI absorption of Ca2+/PO4 —> tetany and seizures due to hypocalcemia

also poor bone mineralization —> osteomalacia (adults), rickets (children)

[note that vitamin D deficiency is really just the same as having calcium deficiency]

Question 11

vitamin E, aka _____, has a key role in…

Answer 11

vitamin E = tocopherol

antioxidant, key role in protecting RBC from oxidative damage (scavenges free radicals)

Question 12

how would a vitamin E deficiency present?

Answer 12

vitamin E = tocopherol, antioxidant

deficiency (v rare) —> hemolytic anemia, muscle weakness, ataxia, loss of proprioception

Question 13

what are the vitamin K dependent clotting factors?

Answer 13

factors II (2), VII (7), IX (9), X (10), C, and S

require post-translational modification by vitamin K (deficiency —> bleeding)

Question 14

where does vitamin K come from?

Answer 14

green, leafy vegetables (K1 form - phylloquinone)

synthesized by GI bacteria (K2 form - menaquinone)

Question 15

what enzyme does warfarin inhibit to cause vitamin K antagonism?

Answer 15

warfarin blocks epoxide reductase, which reduces vitamin K

vitamin K in its reduced form is required because it is oxidized in the process of activating clotting factors (therefore, warfarin blocks the renewal of this resource!)

Question 16

how does zinc deficiency present in children vs adults?

Answer 16

children —> poor growth, impaired sexual development

adults —> poor wound healing, loss of taste, immune dysfunction, dermatitis

Question 17

acrodermatitis enteropathica

Answer 17

rare AR impairment in zinc absorption (mutations in zinc transportation)

—> dermatitis (hyperpigmented, classically perioral/perianal)
—> hair loss, diarrhea, poor growth, immune dysfunction (recurrent infection)

Question 18

what occurs from mild vs severe vitamin A deficiency?

Answer 18

mild: night blindness

severe: xerophthalmia (corneal scarring), hyperkeratosis, infections