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Fat Soluble Vitamins. Fat soluble vitamins include: A and carotenoids, E, K, D Associated with fat absorption Needed in small amounts Stored in fatty tissues Excess intake has toxic consequences. Retinol and caroteinoids Lipid-soluble red, orange, and yellow pigments produced by plants

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fat soluble vitamins
Fat Soluble Vitamins
  • Fat soluble vitamins include: A and carotenoids, E, K, D
  • Associated with fat absorption
  • Needed in small amounts
  • Stored in fatty tissues
  • Excess intake has toxic consequences
slide2

Retinol and caroteinoids

  • Lipid-soluble red, orange, and yellow pigments produced by plants
  • Fewer than 10% have vitamin A activity
  • B carotene, a carotene, b cryptoxanthin
  • Others also have physiological importance
    • Lycopene
    • Canthaxanthin
    • Zeaxanthin

Fig. 10-1a, p. 327

slide4

70-90% vitamin A absorption if fat is present

<5% to 60% for carotenoids; vitamin E interferes

CRBPII = cellular retinol binding protein

LRAT = lecithin retinol acyl transferase

Specfic protein carrier- vitamin A

Passive diffusion - carotenoids

Fig. 10-2, p. 329

slide5

‘‘Outer limiting

membrane’’

Photoreceptor

(rod) cell

Müller cell

Outer segment

Inner

segment

Capillary

Outer of photoreceptor (rod) cell Segment

Pigment epithelium

Nucleus

  • Functions: Vitamin A
    • Vision
    • Cell differentiation, growth, reproduction
    • Bone development
    • Immune system

Fig. 10-7, p. 334

slide8

Functions: Vitamin A

    • Vision
    • Cell differentiation, growth, reproduction
    • Bone development
    • Immune system

Fig. 10-9, p. 335

slide9

Functions: Vitamin A

    • Vision
    • Cell differentiation, growth, reproduction
    • Bone development
    • Immune system
slide10

Functions: Vitamin A

    • Vision
    • Cell differentiation, growth, reproduction
    • Bone development
    • Immune system
  • Function: Carotenoids
  • Antioxidants for singlet oxygen;
  • Lycopene > vitamin E >  carotene > cryptoxanthin > zeaxanthin,  carotene > lutein
  • (also work better when used together)
  • Antioxidant for lipid peroxides (works with vitamin E)
  • Lower incidence of atherosclerosis through prevention of oxidation of LDLs
slide11

Interaction with other nutrients:

  • Vitamins E and K (inversely related; high A, low E and K)
  • Zinc and iron
  • Protein
  • Excretion: most in urine as oxoretinoic acid, small amounts in expired air, some in feces

Fig. 10-10, p. 339

slide12

Deficiency:

  • increased morbidity in children under age 5 with no evident clinical signs of deficiency
  • Signs, when present include xeropthalmia, anorexia, retarded growth, increased susceptibility to infections, enlargement of hair follicle, and keratinization of epithelial (mucous cells) of the skin.
  • Toxicity:
  • Hypervitaminosis A
    • Nausea, vomiting, double vision, headache, dizziness, and desquamation of the skin
  • Teratogen
slide13

Vitamin D (a seco-steroid)

plants

animals

Fig. 10-11, p. 344

slide15

Dietary Vitamin D is absorbed from a micelle, along with other fats.

  • About 50% of dietary D3 is absorbed. Most absorbed in distal small intestine.
  • Incorporated into chylomicrons
  • Cholecalciferol from the skin is bound to DBP and travels primarily to the liver, but can be picked up by other tissues as well (muscle and adipose)
  • Blood is the major storage site; half-life of 10-21 days
  • Hydroxylases generate the active form of the vitamin (25-OH cholecalciferol)
  • Release by the kidney of active forms; a half-life of 4-6 hours in the blood

Fig. 10-12, p. 346

slide16

Functions:

    • Acts as a steroid hormonein calcium homeostasis
      • Intestinal effects
      • Effects on the kidney
      • Effects on bone

Fig. 10-13, p. 347

slide19

Deficiency: rickets, osteomalacia

  • Interaction with other nutrients:
  • Calcium, phosphorus, vitamin K
  • Excretion:
  • Bile > feces > urine
  • Toxicity:
  • Not possible from excess exposure to sunlight
  • Few cases; calcification of soft tissues, hypertension, anorexia, renal dysfunction
slide21

Digestion and Transport:

  • Synthetic forms are de-esterified
  • Free alcohol forms are absorbed passively in micelles; non-saturable
  • 20-80% absorption; better with fats
  • Incorporated into chylomicrons in intestinal cell and sent out into lymph
  • Transfer between chylomicrons, HDLs and LDLs occurs in the blood. HDLs and LDLs contain highest concentration of the vitamin
  • Half-life of about 48 hrs.
  • Some stored in adipose, liver, lung, heart, muscle, adrenals

Table 10-3, p. 354

slide22

Functions:

  • Maintenance of membranes - prevents oxidation of unsaturated fatty acids contained in the phospholipids (includes membranes of mitochondria and ER)
    • Reduced LDL oxidation; decreased plaque formation
    • Reduction in cataract formation
    • Reduced oxidation in diabetics
  • Suppression of activity of HMGcoA reductase (cholesterol synthesis)

1

2

Fig. 10-18, p. 356

slide23

Regeneration

  • Nutrient Interactions:
  • Function closely linked to selenium (needed for GSH peroxidase), vitamin C, sulfur containing amino acids,
  • Inhibits carotene absorption and conversion to retinol; may impair vitamin K absorption; may cause vitamin -D dependent bone mineralization problems
  • Deficiency:
  • Rare except in populations with fat malabsorption (cystic fibrosis)
  • myopathy and weakness, croid pigment accumulation, and degenerative neurologic problems
  • Toxicity: one of the least toxic; bleeding problems

Fig. 10-19, p. 356

slide24

Vitamin K

    • Absorption: in micelles; incorporated into chylomicrons, then chylomicron remnants, then VLDLs, then HDLs and LDLs.
    • Found mainly in liver and heart. Turnover is once every 2.5 hrs.

Synthetic form

From green plants

Synthesized by bacteria

Fig. 10-20, p. 361

slide27

Vitamin K cycle

Needed for protein carboxylation

Vit. K usually only present in this form in the body

Osteocalcin or Bone Gla protein

Matrix Gla protein

Fig. 10-23, p. 364

slide28

Deficiency: rare in adults; newborns, chronic antibiotic administration, and malabsorption can result in deficiency

Bleeding episodes

Osteoporosis

Toxicity: none known

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