Carnitine

Question 1

dietary sources of carnitine

Answer 1

most foods
red meat
some plant foods

Question 2

who has carnitine deficiency?

Answer 2

no one!

Question 3

who has low carnitine levels? do they overcome it?

Answer 3

premature infants, but they make more and grow rapidly

Question 4

humans have __ carnitine synthesis

Answer 4

humans have endogenous carnitine synthesis

Question 5

carnitine uses __ and __ transport

Answer 5

carnitine uses active and passive transport

Question 6

active and passive caritine transport occurs at __ surface of enterocyte, but NOT __

Answer 6

active and passive caritine transport occurs at apical surface of enterocyte, but NOT basal

Question 7

75% of consumed carnitine is __, the rest is degraded by __ in __

Answer 7

75% of consumed carnitine is absorbed, the rest is degraded by bacteria in large intestine

Question 8

byproducts of carnitine degradation and how they are excreted

Answer 8

trimethylamine (urine)
gamma-butyrobetaine (feces)

Question 9

humans synthesize carnitine using __ and __ (both __ amino acids)

Answer 9

humans synthesize carnitine using lysine and methionine (both essential amino acids)

Question 10

rate of carnitine synthesis is regulated by availabiity of

Answer 10

E-N-trimethyl lysine

Question 11

final enzyme of L-carnitine synthesis

Answer 11

gamma-butyrobetaine hydroxylasw

Question 12

gamma-butyrobetaine hydroxylase is abundant in __ and __, but does not exist in __ and __

Answer 12

gamma-butyrobetaine hydroxylase is abundant in liver and testes, but does not exist in cardiac and skeletal muscle

Question 13

what 2 organs can’t synthesize carnitine

Answer 13

cardiac or skeletal muscle

Question 14

rate of carnitine biosynthesis is NOT affected by (2)

Answer 14

1. dietary intake of carnitine
2. changes in renal handling of carnitine (more or less excretion)

Question 15

carnitine is concentrated in __ tissues, but most abundant in __ and __

Answer 15

carnitine is concentrated in most tissues, but most abundant in liver and muscle

Question 16

97% of all carnitine is in

Answer 16

skeletal muscle

Question 17

__ carnitine transporters exist

Answer 17

6 carnitine transporters exist

Question 18

4 main carnitine transporters

Answer 18

OCTN1
OCTN2
OCTN3
Oat9s

Question 19

OCTN stands for

Answer 19

organic cation transporter

Question 20

OCTN1 is found in

Answer 20

most tissues

Question 21

OCTN1 has __ affinity and is dependent on __

Answer 21

OCTN1 has low affinity and is dependent on pH

Question 22

OCTN1 is mostly responsible for

Answer 22

secretion of carnitine across renal epithelium

Question 23

OCTN2 is highly expressed in (7)

Answer 23

heart
muscle
placenta
kidneys
pancreas
testis
epididymic

Question 24

OCTN2 is weakly expressed in

Answer 24

brain
liver
lung

Question 25

OCTN2 has __ affinity

Answer 25

OCTN2 has **high** affinity

Question 26

OCTN2 is dependent on

Answer 26

Na+ gradient

Question 27

which OCTN is most important?

Answer 27

OCTN2 except in testes

Question 28

OCTN3 is highly expressed in

Answer 28

testes

Question 29

OCTN3 has the highest __ for carnitine

Answer 29

OCTN3 has the highest **specificity** for carnitine

Question 30

Oat9s is found in

Answer 30

mice

Question 31

carnitine and acylcarnitine esters are excreted by __ excretion increases with higher

Answer 31

carnitine and acylcarnitine esters are excreted by **kidney** excretion increases with higher **concentrations in blood**

Question 32

kidney must __ 95% of carnitine for proper carnitine homeostasis

Answer 32

kidney must **reabsorb** 95% of carnitine for proper carnitine homeostasis

Question 33

carnitine in metabolism

Answer 33

mitochondrial LCFA oxidation

Question 34

carnitine is essential for mitochondrial use of __ and for __ production

Answer 34

carnitine is essential for mitochondrial use of **LCFAs** and for **energy** production

Question 35

carnitne in metabolism 2

Answer 35

acyl-CoA to CoA ratio

Question 36

which form of CoA is necessary

Answer 36

free CoA (non-esterified)

Question 37

carnitine can accept __ and __ residues to free __

Answer 37

carnitine can accept **acyl** and **acetyl** residues to free **CoA**

Question 38

when do we need free CoA

Answer 38

pyruvate dehydrogenase rxns

Question 39

assessment of carnitine status

Answer 39

plasma ratio of esterified to non-esterified carnitine

Question 40

high plasma ratio of esterified to non-esterfied indicates

Answer 40

abnormal carnitine metabolism

Question 41

carnitine deficiency is caused by hyper-__ or decreased __ of carnitine by __

Answer 41

carnitine deficiency is caused by hyper-**excretion** or decreased **reabsorption** of carnitine by **kidneys**

Question 42

is there a test for functional carnitine deficiency?

Answer 42

no

Question 43

genetic carnitine deficiency

Answer 43

mutations of OCTN2

Question 44

OCTN2 symptoms

Answer 44

myopathies hypoglycemia hyperammonemia (protein metabolism) fatal if untreated

Question 45

hyper-excretion of carnitine

Answer 45

abnormal amounts of SCFA produced and removed from body by excretion as acylcarnitine esters rate of excretion > endogenous synthesis

Question 46

prolonged treatment with __ and __ can deplete circulating carnitine levels

Answer 46

prolonged treatment with **valproic acid** and **pivalic acid** can deplete circulating carnitine levels

Question 47

__ agents can also deplete carnitine

Answer 47

**chemotherapeutic** agents can also deplete carnitine

Question 48

2 uses or carnitine as a treatment

Answer 48

1. in patients with OCTN2 mutation 2. end stage renal disease

Question 49

why is carnitine used as a treatment in end stage renal disease

Answer 49

patients with renal disease have abnormally high ratio of eseterified carnitine to free carnitine corrected by L-carnitine treatment

Question 50

in who is carnitine a conditionally essential nutrient?

Answer 50

hospitalized premature infants