Choline Flashcards
Explain the methionine synthase pathway.
in cytosol, B12 is cofactor for methionine synthase to act on cosubstrates of homocysteine and 5-CH3-THf to transfer CH3 group to homocysteine and THF(active form of folate). B12 is cofactor for enzyme that acts on homocysteine to pick up up methyl group to form methionine.
What are choline roles (4)?
1) neurotransmission as acetylcholine, 2)one-carbon metabolism (directlyY and as betaine, 3)phospholipid biosynthesis and 4)sphingomyyelin synthesis
What are choline functions when it is phosphatidyl choline?
~as phophatidyl choline: cell membrane structure/integrity, critical for VLDL synthesis and export of fat from liver, predominant phospholipid in bile, signal molecule in cell membrane, endogenous ligand for nuclear receptors (THIS IS SUPER IMPORTANT)
What are choline functions as one-carbon metabolism (methionine synthase pathway)?
choline is a methyl donor directly, indirectly via betaine
major source of methyl groups for epigenetic modifications of DNA
what are choline functions as synthesis of sphingomyelin?
cell membrane structure, signaling structure
What are choline acetycholine functions?
NT and cell signaling
Which pathway is a major consumer of SAM?
sequential methylation of phosphastidylemethanolamine (endogenous choline synthesis)
What vitamin is sensitive to methyl group status?
choline
which vitamin is tx for nonalcoholic fattyy liver disease?
choline
What are helath effects of choline with inadequate intake?
increased hepatic steatosis and increased liver enzymes, cognitive impairment, neural tube defects (INDEPENDENT OF FOLATE), both high homocysteine and low choline associated with CVD (when methylation pathway is not occurring well_. Role of trimethylamine
What vitamins cause neural tube defects?
folate and choline, independent of each other
What are food sources of choline?
main source is phosphatidyl choline (PTDCHO), animal sources contain more choline than plants (meat, eggs, legumes, nuts/seeds, milk, grains, vegetables), plants provide betaine that can spare choline in some reactions
Water form: free choline, glycerophosphocholine, phosphocholine
Fat form: phosphotidyl choline, lyso phosphatidtyl choline, sphingomyelin
Why do neonates need choline?
they need to support growth and development, choline in human milk increases from birth to 2 wks then remainst stable
who is at risk of choline deficiency?
PN pts. (fatty liver and hepatocellular damage occur), pts with cystic fibrosis, pregnant women
what are the key roles summary of choline?
membrane structure and function, lipid transport via VLDL, methyl donation, neurotransmission, cell signaling
it is difficult to attribute disease to deficiency
