Term
| What is generic descriptor of Vit A |
|
Definition
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|
Term
| Retinoids exhibit biological activity for retinOL or retinAL? |
|
Definition
|
|
Term
| Beta-ionine ring, isopreponoid units and conjugated double bond system are characteristics of what vitamin? |
|
Definition
|
|
Term
| Which three types of forms of does vit A come in? |
|
Definition
| Retinoid, Precursors or provitamins, synthetic form |
|
|
Term
| What are examples of retinoids and their chemical formula? |
|
Definition
- all trans- retiNOL (R- CH2OH)
- RetiNAl (R-CHO)
- Retinoic Acid ( R-COOH) |
|
|
Term
| Parent compounds have all cis or all trans configuration? |
|
Definition
|
|
Term
| What are examples of precursors or provitamins? |
|
Definition
- β-carotene
- other carotenoids |
|
|
Term
| What is Tretinoin and what is it used for? |
|
Definition
Tretinoin is all –trans retinoic acid used to treat
PSORASIS (skin condition that causes skin redness and irritation) and
APL (acute promyelocytic leukemia) |
|
|
Term
| What is Etretinate or Accutane and what is it used for? |
|
Definition
| It is a 13- cis retinoic acid used to treat ACNE |
|
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Term
| What carotenoids are MOST prevalent in diet? (six) |
|
Definition
alpha carotene beta carotene
Lycopene Lutein
Zeaxanthin beta-cryptozanthin |
|
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Term
| Which carotenoids are Provitamin A carotenoids? (3) |
|
Definition
a-carotene
b-carotene
b-cryptoxanthin |
|
|
Term
| Natural occurring are carotenoids in which form? |
|
Definition
|
|
Term
| What is dietary source of beta carotene? |
|
Definition
- green leafy vegetables, carrots, red palm oil.
Fruits: peaches, apricots, mango, papaya
- yellow orange veggies: sweet potato, squash, cassava
- High carotenoid rice |
|
|
Term
| What are dietary sources of alpha carotene? |
|
Definition
- green leafy vegetables, carrots, red palm oil.
Fruits: peaches, apricots, mango, papaya
- yellow orange veggies: sweet potato, squash, cassava
- High carotenoid rice |
|
|
Term
|
Definition
| Green leafy vegetables, peas, pepper, egg yolk |
|
|
Term
|
Definition
|
|
Term
|
Definition
| tomato, watermelon, pink grapefruit |
|
|
Term
| In the conversion of beta carotene to retiNOL,what enzymes are present and their function? |
|
Definition
Cleavage enzyme: 15,15- dioxygenase (in cytosol of mucosal cells- intestines)
Reduction enzyme: retinaldehyde reductase |
|
|
Term
| 15,15 dioxygenase and retinaldehyde reductase are involved in which reaction? |
|
Definition
| Conversion of beta carotene to retoNOL |
|
|
Term
| 1 μg retoNOL= how many IU |
|
Definition
| 3.33 IU vit A from retinol |
|
|
Term
| 1 RE = how many μg of all trans retinol? |
|
Definition
| 1 RE = 1 μg of all trans retinol |
|
|
Term
| 1 RE = how many μg of beta carotene? |
|
Definition
| 1 RE= 6 μg of beta carotene |
|
|
Term
| 1 RE = how many μg of other provitamin A carotenoids? |
|
Definition
| 1 RE = 12 μg of other provitamin carotenoids |
|
|
Term
| 1 RAE = ___ μg all trans retinol |
|
Definition
| 1 RAE = 1 μg all trans retinol |
|
|
Term
| 1 RAE= ____ μg of all trans beta carotene in OIL |
|
Definition
| 1 RAE = 2 μg of all trans beta carotene in OIL |
|
|
Term
| 1 RAE= ____ μg of FOOD BASED all trans beta carotene |
|
Definition
| 1 RAE = 12 μg of FOOD BASED all trans beta carotene |
|
|
Term
| 1 RAE = ___ μg of other food based pro vitamin A carotenoids |
|
Definition
| 1 RAE= 24 μg of other food based pro vitamin A carotenoids |
|
|
Term
|
Definition
1 μg all trans retinol
6 μg beta carotene
12 μg of other provitamin A carotenoids
1-6-12 |
|
|
Term
|
Definition
1 μg all trans
2 μg all trans beta carotene in OIL
12 μg FOOD BASED all trans beta carotene
24 μg of other food based PROVITAMIN A carotenoids
1-2-12-24 |
|
|
Term
| The RDA vit A for Male is? |
|
Definition
|
|
Term
| The RDA Vit A for Female is? |
|
Definition
|
|
Term
| Daily value for Vit A is? |
|
Definition
|
|
Term
| 10 IU of beta carotene =____ IU retinol |
|
Definition
| 10 IU of beta carotene = 3.33 IU of retinol |
|
|
Term
| When converting from IU beta carotene from fruits to vegetables to μg RAE, IU is divided by ___? (page 7 notes) |
|
Definition
| IU is divided by 20 (2x10) |
|
|
Term
| Compare Preformed vit A (retiNOL) with provitamin A? |
|
Definition
Preformed:
- animal food as retinol and retinyl ester
- toxic
- highly absorptive (70-90%)
Provitamin A:
- plant food as beta carotene and other carotenoids
- limited conversion to vit A
- carotenodermia is benign
- low absorptive efficiency |
|
|
Term
| What are some of the chemical properties of retinoids? |
|
Definition
Color: light yellow to redding
- soluble in organic solvents
- sensitive to oxidation, isomerization and polymerization by light, oxygen, and high temperatures
- stable in crystalline form and as an OIL stored in dark, cool place
- characteristics UV absorption spectrum |
|
|
Term
| What is REH and what role does it play in metabolism of retinoids? |
|
Definition
| REH is Retinyl Ester Hydrolase, it is found in pancreatic juices and it hydrolyzes retinyl esters |
|
|
Term
| Which enzymes are required to release proteins from vit A? |
|
Definition
| Release from protein requires PEPSIN and PROTEOLYTIC enzymes |
|
|
Term
| Which complex carries retinoids to different parts of the body? |
|
Definition
| TTR RBP 1:1 ratio (transthyretin or prealbumin) binds thyroxin |
|
|
Term
|
Definition
Re-esterification of retinol
LRAT (lecithing: retinol acyl transferase) |
|
|
Term
| Once retinol is re-esterified, it gets packaged into chylomicrons. T or F |
|
Definition
| True. its called Chylo RE (p 10) |
|
|
Term
| How are Chylo RE carried to the liver? |
|
Definition
|
|
Term
| How are Chylo RE taken up by the liver? |
|
Definition
| Chylo RE taken up by the liver in association with chylomicron remnant by RECEPTOR-MEDIATED ENDYCYTOSIS |
|
|
Term
| Where does hydrolysis and esterification of retinoids occur? |
|
Definition
|
|
Term
| What are two (2) esterificaton enzymes for retinoids and give brief description. |
|
Definition
1. LRAT
- uses ACYL groups from phosphotidylcholine
- high affinity
- involves retinol complexed to CRBP II
2. ARAT
- uses acyl groups from CoA
- low affinity
- non specific binding |
|
|
Term
|
Definition
LRAT: lecithin
- esterification enzyme
- uses ACYL groups from phosphotidylcholine
- high affinity
- involves retinol complexed to CRBP II |
|
|
Term
|
Definition
ARAT
- esterification enzyme
- uses acyl groups from CoA
- low affinity
- non specific binding |
|
|
Term
ARAT vs LRAT
a. Which one is high affinity enzyme?
b. Which one uses acyl group from CoA?
c. Which one envolves renitol complexed to CRBP II? |
|
Definition
|
|
Term
| Where is most (50-85 %) of Vit A stored? In what form? |
|
Definition
| Mostly as RE stored in LIVER hepatic stellate cells |
|
|
Term
| Vit A is excreted in bile but only after _______ and _______ ? |
|
Definition
| hydroxylation and glucoronidation |
|
|
Term
| Vit A is excreted in bile but only after _______ and _______ ? |
|
Definition
| hydroxylation and glucoronidation |
|
|
Term
| Vit A is excreted in bile but only after _______ and _______ ? |
|
Definition
| hydroxylation and glucoronidation |
|
|
Term
| Where is apo-retinol binding protein (apo- RBP) synthesized and what does it combine with to form a 1:1 complex? |
|
Definition
| apo-RBP is synthesized by hepatocytes and apo RBP combines with retinOL to form 1:1 complex called holo-RBP |
|
|
Term
| Draw diagram of transport and cellular metabolism in intestine, liver and target organs (VIt A) (p 10) |
|
Definition
|
|
Term
| Where is RBP- TTR complex formed? |
|
Definition
|
|
Term
|
Definition
| Transthyretin is a tetrameric protein whihc strongly binds four thyroxine molecules |
|
|
Term
| What is RBP (retinold binding protein) function in plasma? |
|
Definition
| to solubilize retinol and deliver it to cells |
|
|
Term
| Which protein limit "free" retinoid? |
|
Definition
|
|
Term
| Which protein channels retinoids to specific enzymes responsible for metabolic transformation and limits 'free' retinoids? |
|
Definition
|
|
Term
| In the nuclei, specific retinoid-receptor proteins have what function? |
|
Definition
| To regulate the activity of retinoid- responsive genes |
|
|
Term
Retinoid- binding protein and receptors?
a. in PLASMA
b. in CELLS
c. in NUCLEI |
|
Definition
1. in plasma RPB functions to solubilize retinOL and deliver it to cells
2. in CELLS: cellular retinoid binding protein limit "free" retinoid and channel retinoids to specific enzymes responsible for metabolic transformation
3. in NUCLEI: specific retinoid receptor protein regulate the activity of retinoid responsive genes |
|
|
Term
| Draw retinoid conversion reactions. Vit a (page 13) |
|
Definition
|
|
Term
| What are functions of vit A? |
|
Definition
a. 11-cis retinAL fucntions in retina. Convert light into neural signals necessary for vision
b. Ret. Acid maintains normal differentiation of the conjuctival membranes, cornea, and other cells to prevent xerophthalmia.
- cellular differentiation
- Development
- Immunity |
|
|
Term
| 11-cis-retiNAL (function in vision) |
|
Definition
| 11-cis retinAL fucntions in retina. Convert light into neural signals |
|
|
Term
| Retinoic Acid (function in vision) |
|
Definition
| Ret. Acid maintains normal differentiation of the conjuctival membranes, cornea, and other cells to prevent xerophthalmia. |
|
|
Term
| Function of Vit A in vision |
|
Definition
Light absorbing unit (chromophore): 11 cis retinal bound to opsin
- disk contain "visual pigment" or rhodopsin (in rods) and iodopsins (in cones)
-absorption of a photon light catalyzes the isomerization of 11-cis-retinal to all trans retinal and its release from opsin.
- this triggers a neuronal signaling cascase
- regeneration occurs in RPE (retinal pigment epithelium) |
|
|
Term
| Draw visual cycle . Vit A page 14 |
|
Definition
|
|
Term
| + or - Vitamin A in Basal Cells: cell differention |
|
Definition
+ A: Cuboidal, columnar, and goblet cells
- A: squamous (scale like) cells |
|
|
Term
| Role of Vit A (RA) in gene expression? |
|
Definition
1. Binding of RA to its nuclear receptor
2. Activation of receptor
3. Binding of the receptor to a RARE
4. Regulation of the expression of genes downstream |
|
|
Term
Retinoic Acid:
RAR, RXR: what do they bind? |
|
Definition
RAR: binds RA and 9-cis-RA
RXR: binds 9-cis-RA |
|
|
Term
|
Definition
Skin(keratin)
Matrix (laminin)
Enzymes( alcohol dehydrogenatse, etc) |
|
|
Term
|
Definition
Drying and ulceration of cornea
- night blindness
- conjuctival xerosis
- bitot's spots
- corneal xerosis
- ulceration
- necrosis/keratomalacia |
|
|
Term
| Immune function and Vit A |
|
Definition
Effects on the immune system
- infection
- morbidity
- growth
- mortality (Inf and Children, women of reproductive age) |
|
|
Term
| Follicular hyperkeratosis |
|
Definition
| in deficiency of Vit A, mucous secreting epithelial cells become keratinized |
|
|
Term
| Xerophthalamia: clinical deficiency and progression |
|
Definition
Clinical deficiency:
conjuctival xerosis, bitot spots
progression: corneal xerosis, ulceration, keratomalacia, blindness |
|
|
Term
|
Definition
Beta carotene:
- 18 % incr. lung cancer
- 8 % incre in lung cancer mortality
- more heart disease
Vit E:
- no effect in lung cancer mortality
- decrease death from eschemic heard disease and stroke
- increase death from hemorrhagic stroke |
|
|
Term
Vit A deficiency?
Who's at risk?
Consequences? |
|
Definition
125,000 to 250,000 million children (pre-school) and pregnant and lactating women
Consequences:
Leading cause of preventable childhood blindness
- night blindness and xerophthalmia
- 250,000-500,000 per year
Increase risk of mortality and morbidity in pre school children, and most likely in pregnant women
- Incresse risk of dying from childhood infections |
|
|
Term
| Where is Vit A deficiency in pre school children most prevalent *region |
|
Definition
| south east asia . 127 million |
|
|
Term
| What are contributing factors to Vit A deficiency? |
|
Definition
Low intake in diet or breast milk
High demand during infection
High losses with diarhhea |
|
|
Term
| How does immune responce changes due to Vit A deficiency? |
|
Definition
Lymphoid cellularity
- thymic atrophy
- reduced number of spleen cells
- reduced lymphocytes etc
Antibody responses
- reduced T cell dependent antigens
Cell mediated immunity
- reduced cytoxicity
- alterations in cytokine production
Innate Immunity
- decreased number of natural killer cells
- Reduced phagocytosis by macrophages |
|
|
Term
| What are risk factors of Vit A deficiency? |
|
Definition
Age
Gender
Physiological status
Diet
Socioeconomic conditions
Clusterin |
|
|
Term
Evaluation of Vit A status:
Clinical
Histological
Biochemical |
|
Definition
Clinical
- night blindness
- dark adaptaion tests
Histological
- conjuctival impression cytology
Biochemical:
Retinol levels in serum
Relative Dose Response (RDR)
Modified Relative Dose Response (MRDR) |
|
|
Term
| Relative Dose Response Test *Vit A assessment status |
|
Definition
Relative Dose Response Test:
As liver reserves of Vit A become low, conservation starts to increase efficiency of Vit A.
- At critical threshhold , rate of release is dimineshed and blood levels are low
- BUT, synthesis of carier protein RBP continues
- SO accumulation of a pool of preformed RBP
Procedure:
- Fasting blood sample is taken
- oily solution w/450-1000 micrograms of RETINYL PALMITATE is given orally
- Small meal with some fat is given
- After 5 hours, second blood test
- Blood analyzed and RDR is calculated:
RDR= ret (5 hr)- ret (0 hr)/ ret (5 hr)
RDR > 20% indicates of INAdequate hepatic stores |
|
|
Term
| Modified Relative dose response: Vit A assessment |
|
Definition
| - uses DEHYDRO- RETINOL for dosing and a single blood sample at 5 hours post dosing |
|
|
Term
| Public Health Measures to correct Vit A deficiency (3) |
|
Definition
Food Fortification
Supplementation
Dietary Diversificaton |
|
|
Term
| Supplement of Vit A (+ and -) |
|
Definition
+:
easy to implement
fast improvement in Vit A status
Easy to target vulnearable pop
low cost
easy to do
-:
short term approach
distribution every 6 months
requires heaby logistics |
|
|
Term
| What children are at high risk of deficiency of vit A? |
|
Definition
measles
diarrhea
chicken pox
protein energy malnutrition
severe infection |
|
|
Term
| Food Fortification of Vit A (+, -, main issues) |
|
Definition
+ :
- wide coverage
- easy to implement
- does not depend on active participation
- inexpensive
- :
- entire pop exposed
- target pop may not be reached
- requires a centralized food industry
- need effective surveillance
Main issues:
- selection of appropriate food vehicle
- Selection of appropriate level of fortification
- need for regulation
- sustanability
- economic implications |
|
|
Term
| What are clinical indicators to assess vit A deficiency? |
|
Definition
Clinical:
pre school: night blindress < 6 yo: >1 %
bitot spots (<6 yo: >0.5 %)
Pregnant women: night blindness (> 6%)
Sub clinical:
pre school: serum retinol <6 yo >20 % |
|
|
Term
Draw deficiency to toxicity curve of Vit A
page. 28 |
|
Definition
|
|
Term
| Toxicity and Vit A (symptoms) |
|
Definition
Hypervtiaminosis A
- bright red marginal discoloration of the gingiva
- Retinoid Embryopathy (during 1st trimester)
- malformation (limb)
- craniofacial defects in bones and oral clef
- cardiac, thymic, CNS defect
- microtia/anotia (ear)
- |
|
|
Term
|
Definition
Excess intake of Vit A leads to incrased risk of osteoporosis.
- May impair the ability of vit D to promote calcium absorption
- 1500 mcg/day --> reduced bone mineral density compare with who consumed <500 mcg
- effect of retinols is decresed with use of estrogens
- High vit A does not equal to high blood levels of retinol
- beta carotene intake is ok, esp from fruits and veggies
- only problems with retiNOL |
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