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IHN: Biochemistry 2 > Carnitine > Flashcards

Carnitine Flashcards

1
Q

dietary sources of carnitine

A

most foods
red meat
some plant foods

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2
Q

who has carnitine deficiency?

A

no one!

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3
Q

who has low carnitine levels? do they overcome it?

A

premature infants, but they make more and grow rapidly

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4
Q

humans have __ carnitine synthesis

A

humans have endogenous carnitine synthesis

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5
Q

carnitine uses __ and __ transport

A

carnitine uses active and passive transport

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

byproducts of carnitine degradation and how they are excreted

A

trimethylamine (urine)
gamma-butyrobetaine (feces)

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9
Q

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

A

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

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10
Q

rate of carnitine synthesis is regulated by availabiity of

A

E-N-trimethyl lysine

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11
Q

final enzyme of L-carnitine synthesis

A

gamma-butyrobetaine hydroxylasw

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12
Q

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

A

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

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13
Q

what 2 organs can’t synthesize carnitine

A

cardiac or skeletal muscle

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14
Q

rate of carnitine biosynthesis is NOT affected by (2)

A
  1. dietary intake of carnitine
  2. changes in renal handling of carnitine (more or less excretion)
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15
Q

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

A

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

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16
Q

97% of all carnitine is in

A

skeletal muscle

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17
Q

__ carnitine transporters exist

A

6 carnitine transporters exist

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18
Q

4 main carnitine transporters

A

OCTN1
OCTN2
OCTN3
Oat9s

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19
Q

OCTN stands for

A

organic cation transporter

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20
Q

OCTN1 is found in

A

most tissues

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21
Q

OCTN1 has __ affinity and is dependent on __

A

OCTN1 has low affinity and is dependent on pH

22
Q

OCTN1 is mostly responsible for

A

secretion of carnitine across renal epithelium

23
Q

OCTN2 is highly expressed in (7)

A

heart
muscle
placenta
kidneys
pancreas
testis
epididymic

24
Q

OCTN2 is weakly expressed in

A

brain
liver
lung

25
Q

OCTN2 has __ affinity

A

OCTN2 has high affinity

26
Q

OCTN2 is dependent on

A

Na+ gradient

27
Q

which OCTN is most important?

A

OCTN2
except in testes

28
Q

OCTN3 is highly expressed in

A

testes

29
Q

OCTN3 has the highest __ for carnitine

A

OCTN3 has the highest specificity for carnitine

30
Q

Oat9s is found in

A

mice

31
Q

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

A

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

32
Q

kidney must __ 95% of carnitine for proper carnitine homeostasis

A

kidney must reabsorb 95% of carnitine for proper carnitine homeostasis

33
Q

carnitine in metabolism

A

mitochondrial LCFA oxidation

34
Q

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

A

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

35
Q

carnitne in metabolism 2

A

acyl-CoA to CoA ratio

36
Q

which form of CoA is necessary

A

free CoA (non-esterified)

37
Q

carnitine can accept __ and __ residues to free __

A

carnitine can accept acyl and acetyl residues to free CoA

38
Q

when do we need free CoA

A

pyruvate dehydrogenase rxns

39
Q

assessment of carnitine status

A

plasma ratio of esterified to non-esterified carnitine

40
Q

high plasma ratio of esterified to non-esterfied indicates

A

abnormal carnitine metabolism

41
Q

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

A

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

42
Q

is there a test for functional carnitine deficiency?

A

no

43
Q

genetic carnitine deficiency

A

mutations of OCTN2

44
Q

OCTN2 symptoms

A

myopathies
hypoglycemia
hyperammonemia (protein metabolism)
fatal if untreated

45
Q

hyper-excretion of carnitine

A

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

46
Q

prolonged treatment with __ and __ can deplete circulating carnitine levels

A

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

47
Q

__ agents can also deplete carnitine

A

chemotherapeutic agents can also deplete carnitine

48
Q

2 uses or carnitine as a treatment

A
  1. in patients with OCTN2 mutation
  2. end stage renal disease
49
Q

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

A

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

50
Q

in who is carnitine a conditionally essential nutrient?

A

hospitalized premature infants

IHN: Biochemistry 2 (38 decks)

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