Term
| Vit. A: food sources: retinoids |
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Definition
| in liver and dairy (whole milk, cheese, butter), highly susceptible to oxidation |
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Term
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Definition
| commonly found as retinyl ester (palmitate) --> animal based food products; fish and fish liver oil; supplements contail all-trans-retinyl acetate/palmitate |
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Term
| Vit. A: food sources: carotenoids |
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Definition
-brightly colored fruits and veggies (sweet potatoes, butternut squash, papaya, mango)
-B-carotene: greatest pro vit activity, broccoli, spinach, peas
-B-cryptoxanthin: fruits
-lycopene: watermelon, tomatoes
-zeaxanthin: orange bell pepper, corn, egg
-lutein: beets, kiwi |
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Term
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Definition
-emulsification of fat globules
-needs to be released from proteins, and retinyl esters need esterases to get free retinol |
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Term
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Definition
- 70-90% of retinoids absorbed when 10g or more of fat is present
- 50-60% absorption of carotenoids
- pectin decreases carotenoid absorption (interferes with micelle formation) |
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Term
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Definition
-retinol absorbed via carrier
-carotenoids absorbed via transporters and passive diffusion
-need micelle for esterase to fxn
-fat->CCK->gallbladder->bile acids |
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Term
| Vit. A: in enterocyte: B carotene |
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Definition
1) enters and gets converted to two molecules of retinal by B carotene dioxygenase
2) retinal binds to CRBPII
3)retinal+CRBPII converted to retinol-CRBPII by NADPH dependent retinal reductase
4)retinol-CRBPII -> retinyl palmitate by LRAT
5)CRBPII-retinyl-palmitate packed into chylomicron
*retinal can be converted to retinoic acid by NAD and FAD dependent retinal oxidase and enter blood |
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Term
| Vit. A: in enterocyte: retinol |
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Definition
1) retinol bound to CRBPII
2) CRBPII-retinol eserified by LRAT to CRBPII-retinyl palmitate
3)packaged into chylomicron |
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Term
| Vit. A: in enterocyte: carotenoids |
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Definition
| get incorporated into chylomicron |
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Term
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Definition
-by RBP and TTR in blood
-carotenoids transported as part of lipoproteins (LDL has highest [], the HDL then VLDL) |
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Term
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Definition
1) retinol binds to RBP
2) haloRBP released into blood (from liver) and binds to transthyretin
3)complex goes to peripheral tissues, taken up by receptor mediated endocytosis
-TTR dissociates
- halo binds to receptor and taken up by endocytosis
-in cytoplams retinol and RBP separate
- ApoRBP released back into blood and degraded/recycled by kidney |
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Term
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Definition
When chylomicron taken up by hepatocytes
-retinyl ester hydrolase hydrolyzes retinyl to retinol + FFAs
-retinol binds to CRBPI
-retinol reesterified by either LRAT or ARAT
-retinyl esters stored in stellate cells until needed |
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Term
| Vit. A: metabolism: CRBPI |
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Definition
CRBPI retinol can:
A) converted into CRBP retinal by NADPH dependent retinol dehydrogenase; CRBPI-retinal can be converted to retinoic acid by retinal dehydrogenase
B) CRBPI-retinol can be attached to RBP and released into blood |
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Term
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Definition
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Term
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Definition
1) vision
2) cellular differentiation
3) gene expression
4) immunity |
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Term
| Vit. A: function: vision basics |
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Definition
-rhodopsin = opsin + cis-retinal
-rods --> dim light, have photoreceptor rhodopsin
-cones --> bright light |
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Term
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Definition
1) light touches retina, bleaches rhodopsin, breaks bond b/w opsin and cis-retinal
2) cis-retinal converted to trans-retinal
3)trans-retinal converts transducing-GDP to transducin-GTP
4)transducin_GTP actiates phosphodiesterase
5)phosphodiesterase converts cyclic guanosine monophosphate guanosine monophosphate |
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Term
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Definition
6)Na channels close, causing hyperpolarization of rod photoreceptor cell's membrane
7)hyperpolarization transmits visual signal to brain
8)regeneration of cis-retinal and rhodopsin |
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Term
| Vit. A: regeneration of 11-cis-retinal steps |
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Definition
| all-trans-retinal -> all-trans-retinol -> into IRBP -> all-trans retinol -> all-trans-retinyl esters -> 11-cis-retinol > 11-cis-retinal |
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Term
| Vit. A: function: cell differentiation |
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Definition
use retinoic acid
retinoic acid induces differentiation of keratinocytes into mature epidermal cells by switching on gene for keratin, it also induces differentiation of squamous epithelial cells into goblet cells |
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Term
| Vit. A: functions: gene expression |
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Definition
1) RXR binds to cis-retinoic acid, RAR binds to trans-retinoic acid
2)A receptor complexes form homodiamers or heterodiamers
-RAR/RAR or RXR/RXR, or RXR/RAR or RXR/VDR
3)diamers bind to specific DNA nucleotide sequense, referred to as retinoic acid response elements (RARE) in promoter regions of specific genes |
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Term
| Vit. A: carotenoid fxn, antioxidant |
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Definition
-most found in membranes
-lycopene has highest antioxidant activity
-lycopene > alpha carotene > B cryptoxanthin > zeaxanthin > B carotene > lutein |
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Term
| Vit. A: carotenoids fxn, immunity |
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Definition
| needed for T-lymphocyte fxn, antibody response to infection, stimulates phagocytic activity, cytokine production, and maintains killer cell activity |
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Term
| Vit. A: carotenoids fxn, eye health |
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Definition
| AMD-macula in retina, lutein and zeaxanthin help prevent UV induced oxidative damage of membrane macula |
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Term
| Vit. A: carotenoids fxn, random |
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Definition
| lycopene inhibits cell proliferation, growth; stimulate differentiation |
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Term
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Definition
interaction w/ other nutrients
-excess dietary A decreases absorption of K -> bleeding
-increased B carotene intake reduces absorption of E
-erythrocyte required for syntesis of RBC, and EP not synthesized in absence of A (A turns on transcription of EP -> macrocytic anemia) |
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Term
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Definition
-kidney main organ where A is broken down
-excreted in urine (60%), lungs, feces (40%)
-carotenoids metabolized to cariety of compounds and excreted into bile, removed from body in feces
-some undergo enterohepatic recirculation |
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Term
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Definition
1 RAE = 1 micro g retinol = 12 micro g B carotene = 24 micro g alpha carotene and B cryptozanthin
Men: 900 micro g RAE
Women: 700 micro g RAE
1 IU = o.3 mcg retinal = 3.6 mcg B carotene |
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Term
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Definition
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Term
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Definition
-commonly seen in children <5 years
-one of cause of mortality and increased infectious morbidity
-anorexia, retarded growth, increased susceptibility to infections, and keratinization of epithelial (mucous) cells |
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Term
| Vit. A: deficiency, 3 symptoms |
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Definition
1) night blindness
2) xerophthalmia - dryness of eye, not enough mucous
3) corneal perforeation (keratomalacia) |
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Term
| Vit. A: deficiency, at risk |
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Definition
-malabsorption disorder
-pancreatic (bile), liver (RBP), or gall bladder (bile) disease
-acute protein deficiency
-measles infections (reduce absoprtion and increase urninary excretion |
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Term
| Vit. A: toxicity, acute hypervitaminosis |
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Definition
| -large doses in short time, shedding of skin |
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Term
| Vit. A: toxicity, chronic hypervitaminosis A |
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Definition
(3-4 times higher than RDA over several months or yrs)
-desquamation of skin (shedding)
-alopecia
-bone and muscle pain
-increased bone fractures
-conjunctivitis
-liver damage |
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Term
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Definition
-teratogenic effects
-carotenoids (B carotene) results in hypercarotenosis in ppl ingesting 3mg or more of B carotene daily, yellow discoloration of skin (fatty ares of palms and soles)
-no UL |
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Term
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Definition
-conjunctival impression cytology (CIC), eye exam looking for reduction of Goblet cells and epithelial cells
-plasma retinol [], depends on protein and zinc (RBP synthesis) and energy status, infection and inflammation will decrease it |
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