Flashcards in L-Carnitine Deck (21)
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1
Zwitterionic quaternary amino acid
L-carnitine
2
How much L-carnitine does the body contain and where is it stored?
20-25 g and 98 % is found in skeletal and cardiac muscle
3
What kind of diet should maintain normal carnitine biosynthesis?
a vegetarian diet with lysine, methionine, and micronutrients
4
L-carnitine is absorbed in intestine using what?
sodium dependent transport called 'organic cation transport number 2' (OCTN2)
- 2 gram = saturation dose
5
Synthesis of L-carnitine begins with what?
methylation of L-lysine by S-adenosylmethionine (SAMe) to form trimethyllysine
6
Biosynthesis of L-carnitine requires what 5 cofactors?
SAMe, vit C, iron, vit B6, and Niacin
7
What is the last enzyme in L-carnitine synthesis?
y-butyrobetaine hydroxylase
(found only in liver and kidney cells)
8
95% of L-carnitine is reabsorbted by?
renal tubules
9
Why do vegetarians have a reduced capacity to uptake carnitine into skeletal muscle?
downreg of carnitine transporter OCTN2
10
What are the two biochemical functions of L-carnitine?
1. mitochondrian long-chain fatty acid transport
2. modulation of acetyl-coenzyme A/coenzyme A ratio
11
What is L-carnitine's primary function?
transformation of free long-chain fatty acids into long-chain acylcarnitine for transport into mito matrix for beta-oxidation
12
How does L-carnitine protect cells against toxic accumulation of acetyl-CoA?
by acting as a reservoir for excess acetyl residues which may be generating high rates of beta-oxidation
13
CPT l catalyzes the rate-limiting step in what reaction?
transfer of long-chain fatty acids into mito
14
CPT l is inhibited by what?
malonyl-CoA during fatty acid synthesis
15
What can cause an L-carnitine deficiency?
inborn errors of metabolism
16
Pathological manifestations of chronic L-carnitine deficiency include?
accumulation of lipids in skeletal/cardiac m., and liver
17
What nutrient can decrease L-carnitine synthesis?
choline
18
What medications can decrease L-carnitine plasma concentrations?
anticonvulsant meds
19
What acts as a competitive inhibitor of L-carnitine intestinal absorption?
D-carnitine (biologically inactive)
20
L-carnitine supplementation is associated with what?
27% reduction in all-cause mortality and 65% reduction in ventricular arrhythmias
21
