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IHN: Biochemistry 2 > Vitamin E > Flashcards

Vitamin E Flashcards

1
Q

what forms of vitamin E are in the diet?

A
  1. alpha-tocopherol (oils and nuts)
  2. gamma-tocopherol (soybean and corn oil)
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2
Q

food form of vit E

A

free tocopherol AND
esterified tocotrienols

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3
Q

vit E food source

A

bran/germ of grains, nuts, and palm oil

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4
Q

do pregnant and lactating women need additional vit E?

A

no

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5
Q

what happens when you reach the UL for vit E?

A

increased bleeding and GI distress

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6
Q

vit E interferes with absorption and metabolism of __, which is necessary for clotting

A

vit E interferes with absorption and metabolism of vit K, which is necessary for clotting

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7
Q

excess vit E in diet can cause __

A

excess vit E in diet can cause bleeding

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8
Q

how is vit E metabolized before absorption in enterocyte

A

it is a lipid SO
bile salts required for emulsification, solubilization, and spontaneous packaging into the micelle

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9
Q

__ is the only form of vit E that is actively maintained in the human body

A

alpha-tocopherol is the only form of vit E that is actively maintained in the human body

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10
Q

__ is the form of vit E found in the largest quantity in blood and tissues

A

alpha-tocopherol is the form of vit E found in the largest quantity in blood and tissues

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11
Q

how is vitamin E absorbed into the enterocyte?

A
  1. primarily in jejunum by passive diffusion
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12
Q

the rate of vit E absorption is

A

highly variable (10-80%)

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13
Q

factors that interfere with intestinal absorption of vit E

A
  1. retinoids
  2. plant sterols
  3. EPA
  4. alcohol
  5. dietary fiber
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14
Q

2 methods of vit E absoprtion into enterocyte

A
  1. passive diffusion
  2. NPC1L1, SR-B1, CD36
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15
Q

vit E passive diffusion requires __ for emulsification, solubilization, and __ formation

A

vit E passive diffusion requires bile salts for emulsification, solubilization, and micelle formation

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16
Q

micelles carrying vit E __ into enterocyte

A

micelles carrying vit E passively diffuse into enterocyte

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17
Q

other receptors that play a role in vit E absorption

A

NPC1L1
SR-B1
CD36

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18
Q

how is vitamin E absorbed in the enterocyte?

after absorption, vit E is packaged into __ and released into __

A

after absorption, vit E is packaged into chylomicrons and released into lymph

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19
Q

fate of vit E packed into chylomicrons

A
  1. after absorption, vit E packed into chylomicrons and released into lymph
  2. vit E delivered to extra-hepatic tissues as LPL degrades lipoprotein
  3. vit E in chylomicron remnant reaches liver
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20
Q

how does enterocyte excrete vit E?

A

exocytosis (bc it is packaged into chylomicrons)

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21
Q

fate of vit E that reaches liver (from chylomicron remnant)

A

alpha-TTP selectively transports alpha-tocopherol into liver lipoproteins (mainly VLDL)

  • excess alpha-tocopherols transferred to HDL
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22
Q

alpha-tocopherol transfer protein transfers

A

alpha-tocopherol into liver-secreted plasma lipoproteins

23
Q

why does the liver only accept alpha-tocopherol form of vit E

A

bc alpha-TTP

24
Q

excess vit E is __

A

excess vit E is secreted into bile

25
Q

most alpha-tocopherol is incorporated into

A

VLDL

26
Q

excess alpha-tocopherol is secreted into

A

bile

27
Q

90% of vit E is stored in __ of __

A

90% of vit E is stored in lipid droplets of adipocytes

28
Q

changes in adipose tissue cause problems with

A

vit E homeostasis

29
Q

alpha-TTP is expressed highly in __ and at lower levels in (4)

A

alpha-TTP is expressed highly in liver and at lower levels in brain, kidney, lung, and spleen

30
Q

plasma levels: alpha-tocopherol is __ more elevated than __

A

plasma levels: alpha-tocopherol is 10x more elevated than gamma-tocopherol

31
Q

mutated or deleted alpha-TTP causes __ and __

A

mutated or deleted alpha-TTP causes ataxia and AVED (vit E deficiency)

32
Q

what does vit E do as an antioxidant?

A

quenches free radicals and absorbs energy of free radicals

33
Q

unlike carotenes, vit E reamins a __ radical

A

unlike carotenes, vit E reamins a low-energy radical

34
Q

alpha-tocopherol has __ properties

A

alpha-tocopherol has antioxidant properties

35
Q

vit C recycles alpha-tocopherol by __

A

vit C recycles alpha-tocopherol by accepting alpha-tocopherol radical’s electron

36
Q

regeneration of vit E steps

A
  1. vit E accepts alpha-tocopherol radical’s electron
  2. vit C –> ascorbate radical (harmless radical)
  3. glutathione reduces ascorbate radical to reconstitute vit C
  4. NADPH oxidizes reduced glutathione
37
Q

since alpha-tocopherol is an antioxidant, it is found more in tissue with higher rates of __, such as __ and __

A

since alpha-tocopherol is an antioxidant, it is found more in tissue with higher rates of oxygen metabolism, such as brain and lung

38
Q

2 main functions of vit E in target tissues

A
  1. antioxidant
  2. regulatory (non-oxidant) functions
39
Q

__ is necessary for recycling of alpha-tocopherol

A

vit C is necessary for recycling of alpha-tocopherol

40
Q

2 regulatory (non-oxidant) functions of vit E

A
  1. regulation of gene expression
  2. cell signaling (PKC, Akt, tyrosine kinases, phosphatases)
41
Q

what form of vit E is excreted in urine?

A

conjugated form with glucouronic acid

42
Q

main organ responsible for vit metabolism and excretion

A

liver

43
Q

process for urinary excretion of vit E

A
  1. alpha-tocopherol oxidized into alpha-CEHC
  2. alpha-CEHC conjugated with glucouronic acid
  3. excreted in urine
44
Q

vit E assessment

A
  1. mainly blood analyses
45
Q

symptoms of vit E toxicity

A

inhibited platelet aggregation
easy bruising and bleeding

46
Q

risks of vit E deficiency

A

atherosclerosis
heart attack
cancer

47
Q

populations at risk for vit E deficiency

A
  • preemies
  • genetic abnormalities (AVED, apolipoproteinemia B)
  • fat malabsorption syndromes (cholestasis, cystic fibrosis, pancreatic insuffiency)
  • total parenteral nutrition
48
Q

alpha-tocopherol inhibits oxidation of __ which decreases prevalence of __

A

alpha-tocopherol inhibits oxidation of LDL-cholesterol which decreases prevalence of atherosclerosis

49
Q

vit E has __ function that quenches __ and protects from __

A

vit E has antioxidant function that quenches free radicals and protects from cancer

50
Q

vit E can help prevent formation of __ that can lead to heart attack or venous thromboembolism

A

vit E can help prevent formation of blood clots that can lead to heart attack or venous thromboembolism

51
Q

vit E may prevent formation of __ formed in stomach

A

vit E may prevent formation of carcinogenic nitrosamines formed in stomach

52
Q

4 properties of alpha-tocopherol in disease

A
  1. alpha-tocopherol inhibits oxidation of LDL-cholesterol (decreased atherosclerosis)
  2. vit E as an antioxidant prevents cancer development
  3. vit E prevents blood clots (could lead to heart attack or venous thromboembolism)
  4. vit E blocks formation of carcinogenic nitrosamines formed in stomach
53
Q

HOPE study

A

long term had increased risk of CVD

54
Q

vit E and cancer risk study

A

increased risk of prostate cancer with vit E treatment

IHN: Biochemistry 2 (38 decks)

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