Vitamin A MUHAMMAD MUSTANSAR

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  • Figure 11.4: Mucous Membrane Integrity.
  • Vitamin A MUHAMMAD MUSTANSAR

    1. 1. 1
    2. 2. 3VITAMIN AVITAMIN A :- Is widely distributed inanimal and plant foodsanimals –pre-formed – Retinol.plants – pro-formed - carotene
    3. 3. VITAMIN A Exits in 3 forms:all trans-retinollong chain fatty acyl ester of retinol (mainstorage form)retinal (the active form in the retina) retinoic acid is also considered to bephysiologically active provitamin A or carotene can be converted toretinol in vivo
    4. 4. CH3CH3H3CCH3H3C CH3H3CCH3CH3CH3β-caroteneCH3CH3H3CCH3CH3OHCH3CH3H3CCH3CH3OHliverO2retinal (active form in vision)CH3CH3H3CCH3CH3OCOOHCH3CH3H3CCH3CH3retinoic acid ("hormonally-activeform")ROvitamin A acetate (R = CH3)vitamin A palmitate (R = C16H33retinol (from diet)
    5. 5. Vitamin A6Lots of double bonds, good anti-oxidant
    6. 6. SOURCES
    7. 7. VITAMIN A & CAROTENOIDSSourcesRetinoids - liver, dairy, fishCarotenoids - brightly coloredfruits & vegetablesβ-carotene - greatest provitamin Aactivity2009 Cengage-Wadsworth
    8. 8. 9pre-formed vitaminA:: meat, liver &dairy productsPRO-FORM VITAMIN A :Yellow, red and greenvegetables and fruitsDietary Sources of Vitamin A
    9. 9. CH3CH3H3CCH3CH2OHCH3VITAMIN A (RETINOL)Vitamin A contains 5 conjugated double bondswhich arekey to some biological actionsIsolated in impure form by McCollum in 1915RDA: 0.7 mg
    10. 10. VITAMIN A (RETINOL)Retinol and beta–carotene preformedvitamin A.Beta carotene can be converted toretinol in the body; 6mg of beta caroteneis equivalent to 1mg of retinol.
    11. 11. VITAMIN A & CAROTENOIDSCarotenoidsAntioxidant functionsCarotenoids & eye healthCarotenoids & heart diseaseCell proliferation, growth, &differentiationCarotenoids & cancerCarotenoids & health claims2009 Cengage-Wadsworth
    12. 12. VITAMIN A & CAROTENOIDSDigestion & absorptionVitamin A requires digestionRetinol bound to fatty acid estersRetinyl esters & carotenes oftencomplexed with protein2009 Cengage-Wadsworth
    13. 13. Emulsification of fat globulesRetinol absorbed via proteincarrierCarotenoids absorbed viatransporters & passive diffusion
    14. 14. VITAMIN A & CAROTENOIDSCarotenoids & retinoids metabolizedin enterocytes to some extentRetinol esterified & incorporated intochylomicrons for transportCellular retinol-binding protein(CRBP) II2009 Cengage-Wadsworth
    15. 15. Transport, metabolism, &storageChylomicrons carry to liverAdditional metabolism in liver
    16. 16. Carotenoids transported as partof lipoproteinsCarotenoids stored in liver &adipose
    17. 17. VITAMIN A & CAROTENOIDSRetinol that is esterified may bestored in the liver Stellate cells & parenchymal cellsTransported in blood via 2proteins Retinol-binding protein (RBP) Tranthyretin (TTR)2009 Cengage-Wadsworth
    18. 18. 19 Approximately 80% is absorbed. It is passed along with fat through thelymphatic system into blood stream. absorption is poor in case of diarrhea,jaundice and abdominal disorder.
    19. 19. absorption increases if taken withfat. vitamin A which is not absorbed isexcreted within 1 or 2 days in feces .
    20. 20. 21ABSORPTION & STORAGE The liver has enoromous capacity tostore – in the form of retinolpalmitate. under normal conditions a well-fedperson has sufficient Vitamin Areserves to meet his need for 6 to 9months or more. Free retinol is highly active buttoxic & therefore transported inblood stream in combination withretinol binding protein (liver)
    21. 21. VITAMIN A & CAROTENOIDSFunctions & mechanisms of actionVitamin A Vision - rhodopsin Cellular differentiation Gene expression Growth Other functions - reproduction, bonemetabolism2009 Cengage-Wadsworth
    22. 22. ADDITIONAL ROLE OF RETINOLretinol also functions in the synthesis ofcertain glycoproteins andmucopolysaccharides necessary formucous production and normal growthregulationthis is accomplished by phosphorylationof retinol to retinyl phosphate whichthen functions similarly to dolicholphosphate
    23. 23. BIOLOGICAL ROLE OF VITAMIN-A1. Retinol and retinoic acid have rolein normal reproduction2. Retinal has a role in visual cycle3. Retinoic acid has a role inglycoprotein synthesis4. Roll in MPS synthesis
    24. 24. 5. Vitamin-A is needed formitochondrial membrane function6. Anti cancer role: β-carotene is anantioxidant and trap peroxy free radicalsin tissues at low partial pressure of O27. Bone and teeth formation
    25. 25. 27DAILY REQUIRMENT Men and women – 600 mcg. Pregnancy and lactation – 950 mcg. Infants – 350mcg. Children – 600mcg.(RECOMMENDE BY ICMR – 1989)
    26. 26. (VISUAL CYCLE) Rhodopsin darkness lightOpsin Opsin + retinal + 11cis retinal isomerase trans retinal
    27. 27. Walds Visual cycleRhodopsinPhotorhodopsinBathorhodopsinLumirhodopsinMetarhodopsin IMetarhodopsin IIMetarhodopsin III
    28. 28. PHYSIOLOGICAL FUNCTIONS OFVITAMIN AVisionEpithelial cell"integrity’ReproductionResistance toinfectious diseaseBone remodelingGrowth
    29. 29. 31VISION Retinal is a necessarystructural component ofrhodopsin or visual purple,the light sensitive pigmentwithin rod and cone cells ofthe retina. If inadequatequantities of vitamin A arepresent, vision is impaired.
    30. 30. 32EPITHELIAL CELL "INTEGRITY Many epithelial cells appear to require vitaminA for proper differentiation and maintenance. Lack of vitamin A leads to dysfunction of manyepithelia - the skin becomes keratinized andscaly, and mucus secretion is suppressed. Itseems likely that many of these effects are dueto impaired transcriptional regulation due todeficits in retinoic acid signalling.
    31. 31. Fig. 11-4, p. 372Vitamin A maintainshealthy cells in themucous membranes.Without vitamin A, thenormal structure andfunction of the cells inthe mucous membranesare impaired.Mucus Goblet cellsStepped Art
    32. 32. 34Reproduction: Normal levels of vitamin A is required for spermproduction, Normal reproductive cycles in females require adequateavailability of vitamin A.Bone remodeling: Normal functioning of osteoblasts and osteoclasts isdependent upon vitamin A.
    33. 33. 35DEFICIENCYSYMPTOMS
    34. 34. Deficiency symptoms Xeropthalmia Follicular conjunctivitis Keratomalacia Nyctalopia (night blindness) Follicular hyperkeratosis and keratizing metaplasia Urolithiasis
    35. 35. SYMPTOMS Alteration of skin and mucousmembrane Hepatic dysfunction Headache Drowsiness Peeling of skin about the mouth andelsewhere
    36. 36. Follicular Hyperkeratosis
    37. 37. 40RESISTANCE TO INFECTIOUS DISEASE In almost every infectious disease studied,vitamin A deficiency has been shown toincrease the frequency and severity ofdisease.
    38. 38.  Several large trials with malnourishedchildren have demonstrated dramaticreductions in mortality from diseases such asmeasles by the simple and inexpensiveprocedure of providing vitamin Asupplementation.
    39. 39. 42THE SIGNS OF VITAMIN A DEFICIENCYOcular Night blindness. Conjunctival xerosis bitot’s spot Corneal xerosis keratomalaciaExtra ocular Retarded growth Skin disorders Effect onreproductive organs. Effect on bone
    40. 40. 43NIGHT BLINDNESS Lack of vitamin A causes nightblindness or inability to see indim light. night blindness occurs as a resultof inadequate pigment in theretina. It also called tunnel vision. Night blindness is also found inpregnant women in someinstances, especially during thelast trimester of pregnancy whenthe vitamin A needs areincreased.
    41. 41. RETINOPATHY
    42. 42. 47BITOTS SPOTSThese are foamy andwhitish cheese-liketissue spots thatdevelop around theeye ball, causingsevere dryness in theeyes. These spots donot affect eye sight inthe day light.
    43. 43. 48CONJUNCTIVAL XEROSIS Conjunctiva becomes dryand non wettable. Instead of looking smoothshiny it appears muddy &wrinkled.
    44. 44. KERATOMALACIA
    45. 45. 50KERATOMALACIA One of the major causefor blindness in India. cornea becomes soft andmay burst open . The process is rapid If the eye collapsesvision is lost.
    46. 46. 51INCREASED RISK OF MORTALITYFROM INFECTIOUS DISEASEIt has been best studied in malnourished children,but also is seen in animals. In such cases,supplementation with vitamin A has beenshown to substantially reduce mortality fromdiseases such as measles and gastrointestinalinfections.
    47. 47. HYPERVITAMINOSIS AExcess of vitamin A induce series of toxiceffects known as hypervitaminosis Asyndrome. Seen usually amongEskimos who consume livers of polarbear and arctic foxes.
    48. 48. 53HYPRRVITAMINOSIS AIf the daily dose > 30,000mcgtoxic symptoms:- painful joint thickening of long bones.
    49. 49.  anorexia low grade fever rashes irregular menstruation fatigue. loss of hair
    50. 50. 55CAROTENEMIA A condition in which conversionof carotene to vitamin A isimpaired by inborn metabolic erroror hepatic diseases generalized yellowish skin andmucosa. excessive deposition of carotenewhich is result of high intake offoods containing carotene.
    51. 51. SUMMARY
    52. 52. SUMMARY VITAMIN A
    53. 53. VITAMIN ASOURCESAnimal sources•Liver oil•Butter•Milk•Cheese•Egg yolkPlant sources•Tomatoes•Carrot•Green-yellow vegetables•Spinach•Mangoes•Papaya•Corn•Sweet potatoRDA: Adults 3000-5000 IU/dayChildren, pregnant and lactating women
    54. 54. sources:Retinol is found in liver, wholemilk, cheese and butter.Carotenes are found in milk,carrots, dark green leafyvegetables and orange colouredfruits, e.g. mango and apricots.
    55. 55. 60TREATMENT vitamin deficiency should be treated urgently . depending upon deficiency symptoms it is given inthe dose of 7,500 to 15,000 mcg per day for onemonth nearly all of the early stages of xerophthalmia can bereversed by administration of a massive dose –2,00000 IU or 110mg orally on two successive days(30). If Hypervitaminosis restriction of diet

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