vitamins

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Vitamin- A

• M.Prasad Naidu
• MSc Medical Biochemistry, Ph.D,.

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Vitamin- A

• Structure
• 6C beta-ionine ring with 11C polyprenoid side
  chain with alternate double bonds.
• Provitaminbeta carotene RetinalRetinal
• Active forms 1.Retinol
• 2.Retinal
• 3.Retinoic acid

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Poly isoprenoid side chain
RDA 0.7 mg
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Vitamin A

• Retinol Retinal retinoicacid
  All-trans Retinal A1 common in circulation.
• 11cis- Retinal form is present in rhodopsin.
• Active forms are heat stable and light sensitive.

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Vitamin A

• Sources
• Animal marine fish liver oils
• Plant - mango\papaya\carrot
• RDA 1000 ug \ day
• 1 RE 1ug of retinol 0.6 ug of betacarotene

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Vitamin A
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• FUNTIONS
• Retinal and Retinol vision
• Retinoic acid
• cell differentiation
  glycoprotein synthesis
  reproduction.
• 3.Beta-carotene- Anti-oxidant

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Walds visual cycle

• The Cyclic events that occur in the process of
  vision is visual cycle. .
• Rhodopsin is a photoreceptor present in retinal
  rod cells.
• Rhodopsin is a conjugated protein with 11-cis
  retinal and protein opsin.

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FUNCTIONS OF VIT A
WALDS VISUAL CYCLE
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Defeciency

• primary causes dietary
• secondarycausesmalabsorption
• Results in
• Night blindness
• Conjunctival xerosis
• Bitots spots
• Corneal xerosis
• keratomalasia
• Blindness

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.

• Toxicity of vit-A is either due to
• 1. over-dosage of vit-A supplements
• 2. excess dietary intake
• As vitamin A is not excreted from the body it
  isccumulated in liver producing toxic
• effects
• Toxicity produces headache , nausea , vomitings
  , liver damage alterations in the skin and mucous
  membranes etc.

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.

• Vit-A can be used to treat diseases where
  epithelial surface is damaged.
• Retinoic acid acts on cell differentiation and
  growth therefore used as a drug.
• It is used to treat diseases like Measles, Acne,
  Psoriasis , Leukemia etc.

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Visual cycle

• meta-rhodopsin
• Transducin Transducin A
• PDE
  PDE A
• CGMP
  GMP

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VISUAL CYCLE

• Decreased CGMP
• closes Na channels in rod cell membrane
• hyper polarization of rod cell membrane
• generation of nerve impulse to visual cortex

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Vitamin D

• Structure
• plants - Ergosterol Ergocalciferol
  D2
• Active form in animals is calcitriol

UV
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Vitamin D

• Sources
• 1. sunlight
• 2. animal sources fish liver oils \ eggs
• 3. plant sources
• 4. food fortification milk\ butter
• RDA
• 200-400 IU \ day

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Vitamin D

• Digestion \ absorption \ transport
• Digested and absorbed in small intestine
• using bile salts .
• Vit-D is transported from intestine to
  circulation by chylomicrons and stored in the
  liver.

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Vitamin D

• Synthesis of vit-D
• Regulation of synthesis by Ca and PO4.
• Low calcium stimulates PTH secretion which
  activates 1- hydroxylase

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functions

• Vit-D plays a major role in regulation of
  calcium and phosphate levels by mainly acting on
  3 different organs.
• Intestine increases absorption of Ca and PO4
• Bone increases deposition of CaPO4 thus
  increasing mineralization of bones .
• Kidneys reabsorbs Ca and decreases Ca
  excretion.

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Vitamin D

• Deficiency
• Children ---Rickets
• Adults ------ Osteomalacia

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Vitamin D

• Toxicity
• hyper-vitaminosis D causes toxic effects
• like de-mineralization , hyper-calcemia ,
  renal calculi etc.

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Absorption and Transport
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Iron deficiency anemia

• Laboratory findings
• Hypochromic microcytic anemia
• ? ferritin ( 30 to 300 Nanogm/ml)
• ? serum iron (50 to175 µgm/dl)
• ? TIBC (300 to 350 µgm/dl)
• ? transferrin (200 to 400 mg/dl)

Spoon-shaped nails (koilonychia)
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Dental fluorosis
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Thank q