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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

How can L-carnitine improve insulin sensitivity?

L-carnitine facilitates transport of fatty acids into mito for oxidation which reduces lipid overload