Vitamin D Flashcards
vitamin D3 is also called
cholecalciferol
vitamin D3 is synthesized from
7-dehydrocholesterol
what are the two ways hydroxylation of vitamin D3 happens in the liver via 25-hydroxylase
- microsomal cytochrome P-450 enzyme called CYP2R1
2. mitochondrial cytochrome P-450 enzyme called - CYP27A1
vitamin D3 -> 25-hydroxylase ->
calcidiol
25-hydroxycholecalciferol
25-OH cholecalciferol
25-OH vitamin D
how is vitamin D3 hydroxylated in the kidney via 1 alpha - hydroxylase
mitochondrial cytochrome P-450 enzyme called CYP27B1
vitamin D3 -> 1alpha-hydroxylase ->
calcitriol
____ is released from the kidney and bound to DBP in the blood
calcitriol
when sufficient amounts of calcitriol are present, the activity of ______ is decreased through negative feedback
1alpha-hydroxylase
_____ stimulates 1alpha-hydroxylase activity
PTH (parathyroid hormone)
_____ inhibits 1alpha-hydroxylase activity
FGF-23 (fibroblast like growth factor 23)
high concentrations of calcitriol stimulate
24-hydroxylase
calcitriol -> 24-hydroxylase ->
calcitetrol and calcitroic acid
vitamin D and calcitriol are NOT the same thing
T
_______ is a pleiotropic steroid hormone
calcitriol
calcitriol binds to a cell membrane VDR or a receptor called
MARRS (membrane associated rapid response steroid binding protein)
serum calcium homeostasis: calcitriol up regulates the transcription of the genes
TRPV6, calbindin D9K, Ca 2+ -ATPase, and claudins
in the kindey, calcitriol up-regulates the genes for BRUSH BORDER
TRPV5, calbindin D28K, and basolateral border Ca 2+ -ATPase
________ are responsible for bone resorption by releasing hydrochloric acid, alkaline phosphatases and collagenase which dissolve and catabolize the bone matrix
mature osteoclast
vitamin d deficiencies are linked to _____% of global annual death rate
60-65%
what 6 ways does calcitriol prevent cancer
- stimulates cell differentiation by stimulating E-cadherin *
- inhibits cell proliferation by inhibiting oncogenes like Myc
- promotes tumor cell apoptosis by activating caspases and bax
- prevents tumor angiogenesis by inhibiting VEGF
- increases NK cell activity
- increases macrophage chemotaxic and phagocytic activity
why is prostate cancer and serum vitamin d related
dysfunctional prostate cells have down-regulated the production of the enzyme 1alpha-hydroxylase
______ regulates the expression and production of several cytokines (vitamin d and autoimmune)
calcitriol
_______ influence the immune system in a positive way and can further suppress the destructive activity of Th1 cells
Th2 cells and Treg cells
______ enhances calcium uptake and thus intracellular Ca 2+ concentrations
calcitriol
