Vit A Flashcards

1
Q

what was the first Vit discovered

A

Vit A

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2
Q

Vit a is a generic term for a large number of……

A

….related compounds with Vit A activity

called retinoide

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3
Q

what is an early sign of Vit A deficiency

A

night blindness…lack of Vit A in back of eye

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4
Q

what are the 3 key forms of retinoids

A
  • retinal (vision)
  • retinol (transport; converted to other forms)
  • retinoic acid (hormone)
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5
Q

Vit A interconversions

A

Vit A is esterified to FA in food

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6
Q

Carotenoids

A

plant derived
carotenoid blood concentrations can be used as biomarkers for fruit and veg intake
higher blood levels associated with lower risk of several chronic diseases
some have PROVit A activity

Beta carotene is most potent….

  • potential to cleave TWO molecules of Vit A
  • less efficient absorption than vit A
  • less bioavailable
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7
Q

which carotenoids have pro Vit An activity

A

alpha carotene
beta carotene
beta cryptoxanthin

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8
Q

can carotenoids be converted to retinAL?

A

yes

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9
Q

Vit A and Carotenoid good

A

Vit A (retinoids)

  • animal foods
  • liver, fish, milk products, butter, egg yolk

Carotenoids

  • plant foods
  • orange and yellow fruits and veggies
  • dark green leafy vegetables
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10
Q

Vit A bioavailability

A

the rate and extent at which a vitamin is absorbed and utilized

depends on amount in food and amount absorbed

animal sources (retinoids) are more bioavailable

RAE= retinol activity equivalents

vit A has best bioavailbility (all-trans-retinol)/aniaml source
then dietary beta carotene
then supplemental beta carotene
then other active carotenoids

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11
Q

metabolic functions of Vit A

A

VISION

  • retinAL
  • participates in visual cycle
  • initiated by light, end result is AP

REGULATION OF GENE EXPRESSION

  • retinOIC ACID
  • repro, growth, integrity of imune system, integrity of epithelial cells
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12
Q

Vit A-regulation of gene expression

A

retinoic acid can act as a steroid hormone
retinoic acid actually binds to the DNA and alter protein

most physiological effects of Vit A result from its role in regulating gene expression

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13
Q

process of vit A in gene expression

A

1) retinol travels to target cell membrane
2) retinol–>retinal –>retinoic acid
3) retinoic acid travels intracellularly to the nucleus by CRABP (cellular retinoic acid binding protein)
4) retinoic acid attaches to DNA receptors and alters transcription

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14
Q

regulation of gene expresion and Vit A WRT repro, growth, immunity and other epithelial cells

A

REPRO
supports sperm development
support normal fetal development

GROWTH
role in bone turnover
RA regulates the gene expression of growth hormone

IMMUNITY

  • maintains integrity of skin and mucosal cells
  • differentiation of white blood cells
  • “anti-infective” hormone

OTHER EPITHELIAL CELLS

  • role in differentiation
  • lungs, cornea, GI tract, skin
  • Vit A also contribute toward RBC formation
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15
Q

**Vit A nutrient interactions

A

ZINC**

  • Vit A need zinc
  • Zn deficiency interferes with Vit A
  • Zn needed for synthesis of RBP
  • Zn needed for release of Vit A from liver storage
  • Zn needed for conversion of retinOL to retinAL

IRON
-Vit A helps Iron
Combination of Vit A and iron reduces anemia more effectively than iron alone
-may relate to Vit A’s role in diffferentiation of RBD…hemoglobin

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16
Q

Vit A deficiency can lead to irreversible blindness

A

-xerophthalmia
lack of Vit A in FRONT of eye (cornea)
-ulcerations of the cornea
-leading cause of blindness in developing countries

17
Q

what is the leading cause of blindness in developed countries?

A

diabetes

18
Q

other effecets of Vit A deficiency

A
  • decreased growth
  • failure to reproduce
  • increased susceptibility to infection
  • keratinization of epithelial tissues
    • cells change shape and secrete keratin
19
Q

Vit A toxicity

A

can be toxic due to liver storage

-hypervitaminosis A
overconsumption of Vit A, NOT carotenoids

-Teratogenic risk
risk of birth defects if too much Vit A during pregnancy

harmful toxicity is due to Vit A not carotenoids