TBL: choline Flashcards
the gene for the enzyme that catalyzes choline biosynthesis is induced by
estrogen
choline 3 functions
- source of methyl groups for SAM
- acetylcholine
- part of main phospholipid in membranes
dietary sources of choline
eggs
liver
wheat germ (membrane rich components)
betaine is a
choline metabolite
betaine can’t be converted to __ but can be used as a __, sparing some __
betaine can’t be converted to choline but can be used as a methyl donor, sparing some choline requirements
good source of betaine
beets
is human breast milk rich in choline?
YES
__ degrade choline to make __ and __ before it can be absorbed
gut bacteria degrade choline to make betaine and methylamines before it can be absorbed
free choline that survives the gut bacteria is absorbed by the __ by __ transport
free choline that survives the gut bacteria is absorbed by the intestine by carrier-mediated transport
what 2 items contain enzymes that hydrolyze phosphoatidylcholine in the diet
pancreatic secretions
intestinal mucosal cells
what enzyme hydrolyzes phosphatidylcholine
phospholipases (A1, A2, and B)
after hydrolyzing phsophatidylcholine, the free choline formed enters __
after hydrolyzing phsophatidylcholine, the free choline formed enters portal circulation of the liver
how is choline transported to the placenta?
in large amounts, choline is pumped against a concentration gradient
all tissues accumulate choline by __ and __
all tissues accumulate choline by diffusion and mediated transport
choline uptake is especially important in (5 tissues)
- liver
- kidney
- mammary gland
- placenta
- brain
only a small fraction of dietary choline is __ by __
only a small fraction of dietary choline is acetylated by choline acetyltransferase
availability of __ and __ influence choline acetyltransferase activity
availability of choline and CoA influence choline acetyltransferase activity
in the brain, what determines the rate of acetylcholine synthesis and why
choline availiability bc it is unlikely for choline acetyltranferase to be saturated
choline taken up by the brain may firest enter a __ before it is converted to __
choline taken up by the brain may firest enter a storage pool before it is converted to acetylcholine
methyl groups of choline can be used for (2)
- one-carbon metabolism
- conversion to betaine
main sites of choline oxidation
liver and kidney
purpose of choline oxidation
- decrease choline availability to tissues
- scavenges methyl groups
- ATP generation
in utero, fetus is exposed to __ concentrations of choline
in utero, fetus is exposed to high concentrations of choline
__ is one of the few non-nervous tissues to store large amounts of choline as __
placenta is one of the few non-nervous tissues to store large amounts of choline as acetylcholine
choline acetyltransferase acetyaltes a __ fraction of dietary choline
choline acetyltransferase acetyaltes a small fraction of dietary choline
choline acetyltransferase is concentrated in __ and __
choline acetyltransferase is concentrated in cholinergic neurons and placenta
choline acetyltransferase depends on availabilityof (2)
- choline
- CoA
large precursor pool of choline used for acetylcholine synthesis is found in __ in cholinergic neurons
large precursor pool of choline used for acetylcholine synthesis is found in choline phospholipids in cholinergic neurons
main sites of choline oxidation
liver and kidney
choline oxidation forms __
choline oxidation forms betaine
oxidation of choline steps
- Choline is oxidized to Betaine aldehyde in the inner mitochondrial membrane
- Betaine aldehyde dehydrogenase oxidizes betaine aldehyde to form betaine.
- Betaine cannot be reduced back to choline; oxidation pathway diminishes availability of
choline
mice without choline dehydrogenase couldn’t produce
ATP
making phosphatidylcholine: enzyme 1
choline kinase
making phosphatidylcholine: enzyme 2
CTP PC
rate limiting step in phosphatidylcholine biosynthesis
CTP PC
deficiency of CTP PC in lungs of premature infants causes
respiratory distress syndrome
cholesterol __ CTP PC
cholesterol inhibits transcription of CTP PC
cholesterol stimulates __, which __ transcription of CTP PC gene
cholesterol stimulates SRE, which inhibits transcription of CTP PC gene
alternative pathways of phosphatidylcholine production can occur in (3)
liver
brain
mammary glands
choline defieicny compromises __ and __ function
choline defieicny compromises liver and kidney function
choline is necessary for __ transport
choline is necessary for carnitine transport
when is demand for choline extra high?
pregnancy and lactation
premenopausal women have __ capacity for synthesis of choline
choline prevents __ dysfunction in them
estrogen
premenopausal women have enhanced capacity for synthesis of choline
choline prevents developing organ dysfunction in them
ppl with enough folate and B12, but not enough choline had
liver damage and muscle damage
choline and brain development
essential!
brain extracts choline best during neonatal period (first 4 weeks of life)
epigenetics: choline deficiency decreases __ concentrations, resulting in DNA __
epigenetics: choline deficiency decreases SAM concentrations, resulting in DNA hypomethylation
DNA methylation is necessary during __ development for __
DNA methylation is necessary during fetal development for neurogenesis
in adults, choline accelerates the synthesis and release of __ in nerve cells
in adults, choline accelerates the synthesis and release of acetylcholine in nerve cells
phosphatidylcholine is carried into neurons as part of
apolipoprotein E
reduced phosphatidylcholine and choline is associated with __
reduced phosphatidylcholine and choline is associated with Alzheimer’s disease
in mice, choline-rich diet diminished __ loss
in mice, choline-rich diet diminished memory loss
in rodents, choline (and methyl) deficiency led to __ in the liver which leads to liver __
in rodents, choline (and methyl) deficiency led to lipid accumulation in the liver which leads to liver fibrosis
choline deficiency sensitizes hepatocytes to __ and __ carcinogens
choline deficiency sensitizes hepatocytes to liver and breast carcinogens
