Vitamin D

Question 1

vitamin D3 is also called

Answer 1

cholecalciferol

Question 2

vitamin D3 is synthesized from

Answer 2

7-dehydrocholesterol

Question 3

what are the two ways hydroxylation of vitamin D3 happens in the liver via 25-hydroxylase

Answer 3

1. microsomal cytochrome P-450 enzyme called CYP2R1

2. mitochondrial cytochrome P-450 enzyme called - CYP27A1

Question 4

vitamin D3 -> 25-hydroxylase ->

Answer 4

calcidiol
25-hydroxycholecalciferol
25-OH cholecalciferol
25-OH vitamin D

Question 5

how is vitamin D3 hydroxylated in the kidney via 1 alpha - hydroxylase

Answer 5

mitochondrial cytochrome P-450 enzyme called CYP27B1

Question 6

vitamin D3 -> 1alpha-hydroxylase ->

Answer 6

calcitriol

Question 7

____ is released from the kidney and bound to DBP in the blood

Answer 7

calcitriol

Question 8

when sufficient amounts of calcitriol are present, the activity of ______ is decreased through negative feedback

Answer 8

1alpha-hydroxylase

Question 9

_____ stimulates 1alpha-hydroxylase activity

Answer 9

PTH (parathyroid hormone)

Question 10

_____ inhibits 1alpha-hydroxylase activity

Answer 10

FGF-23 (fibroblast like growth factor 23)

Question 11

high concentrations of calcitriol stimulate

Answer 11

24-hydroxylase

Question 12

calcitriol -> 24-hydroxylase ->

Answer 12

calcitetrol and calcitroic acid

Question 13

vitamin D and calcitriol are NOT the same thing

Answer 13

T

Question 14

_______ is a pleiotropic steroid hormone

Answer 14

calcitriol

Question 15

calcitriol binds to a cell membrane VDR or a receptor called

Answer 15

MARRS (membrane associated rapid response steroid binding protein)

Question 16

serum calcium homeostasis: calcitriol up regulates the transcription of the genes

Answer 16

TRPV6, calbindin D9K, Ca 2+ -ATPase, and claudins

Question 17

in the kindey, calcitriol up-regulates the genes for BRUSH BORDER

Answer 17

TRPV5, calbindin D28K, and basolateral border Ca 2+ -ATPase

Question 18

________ are responsible for bone resorption by releasing hydrochloric acid, alkaline phosphatases and collagenase which dissolve and catabolize the bone matrix

Answer 18

mature osteoclast

Question 19

vitamin d deficiencies are linked to _____% of global annual death rate

Answer 19

60-65%

Question 20

what 6 ways does calcitriol prevent cancer

Answer 20

1. • stimulates cell differentiation by stimulating E-cadherin *
2. inhibits cell proliferation by inhibiting oncogenes like Myc
3. promotes tumor cell apoptosis by activating caspases and bax
4. prevents tumor angiogenesis by inhibiting VEGF
5. increases NK cell activity
6. increases macrophage chemotaxic and phagocytic activity

Question 21

why is prostate cancer and serum vitamin d related

Answer 21

dysfunctional prostate cells have down-regulated the production of the enzyme 1alpha-hydroxylase

Question 22

______ regulates the expression and production of several cytokines (vitamin d and autoimmune)

Answer 22

calcitriol

Question 23

_______ influence the immune system in a positive way and can further suppress the destructive activity of Th1 cells

Answer 23

Th2 cells and Treg cells

Question 24

______ enhances calcium uptake and thus intracellular Ca 2+ concentrations

Answer 24

calcitriol

Question 25

what is a toxic amount of vitamin d taken daily

Answer 25

50,000IU day/month