Nutrition Fat Soluble Vitamins

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Vitamins A

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retinol
e. Role of vitamin A: as an anti-inflammatory substance, this is a recent finding.

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Retinoids

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i. Retinol: primary alcohol
ii. Retinal: aldehyde derivative of retinol
iii. Retinoic acid: results from oxidation of retinal
iv. Beta Carotene: found in plant food, cleavage in the intestine yields 2 retinal. Has less vitamin A activity than retinol

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Action of retinoid

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i. Behaves like steroid in the nucleus
ii. Retinoic acid binds to the chromatin Involved in synthesis of specific proteins, especially keratin

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deficiency in vitamin A

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i. Night blindness
ii. xeropthalmia (corneal dryness that leads to blindness)
iii. Large amounts of vitamin A (>7.5 mg/day) of retinol are toxic and results in hypervitaminosis A
iv. Good source of retinol is butter and egg yolk
v. Yellow and dark green vegetables are good sources of carotene

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Absorption, transport, and storage of vitamin A

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i. Visual pigment is all trans retinal. When light strikes, trans retinal takes 11 cis retinal configuration. Travels to the optic nerve of the brain. In vitamin A def, the travel is compromised so cannot see dimming clearly.
ii. Retanoic acid is NOT involved in vision at all. It is only involved in gene transcription from nucleus where it is oxidized and converted.

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dietary sources of vitamin A

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Beta carotene from diet goes into intestinal wall, converted to retinal, retinol acting with fatty acyl CoA and it will be stored in the liver.

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What is the storage site for vitamin A

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a. Liver is storage site for Vitamin A
b. Liver also synthesizes retinol binding protein. When there is vitamin A in any tissue outside of liver, retinol binding protein binds retinol and transports it to the cell that needs it.
c. If there is a liver problem and liver is not making retinol binding protein, the tissue will be deficient of vitamin A. In most cases of inflammation, retinol in plasma is compartmentalized into the cells hidden away from microorganisms.

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Vitamin D

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chalecalciferol, ergocalciferol
a. Active form: 1,25-dihydroxycholecalciferol

Function: responsible for calcium uptake
Important in inflammation, bone structure, pregnancy because it comprises immunological development of the fetus.

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vitamin D deficiency and High levels

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c. Deficiency: rickets, osteomalacia, symptoms are soft pliable bones
i. Bowed legs
d. High levels are toxic

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Sources of Vitamin D

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i. Ergocalciferol from Diet
ii. Cholecalciferol from skin and sun

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Vitamin D metabolism and actions

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i. 25 hydroxycholecalciferol is NOT the active form. Must be hydroxylated in kidney.
ii. When phosphate levels in blood drop, PTH stimulates increase in blood Ca. Resorption of the bone
iii. 1-25 HCF stimulates phosphate in diet

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3 control points of Vitamins D

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1. Stabilize and reduce loss of calcium in urine
2. PTH hormone function
3. Promote, increase absorption of Ca. Needs increased synthesis of calcium binding protein in the intestine.

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Vitamin K forms and function

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a. Forms of vitamin K:
i. From plant, phylloquinone
ii. From intestinal bacterial flora, menaquinone
iii. As a synthetic derivative: menadione
b. Function: carboxylation of glutamic acid residues in post translational modification of blood clotting factor.

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Deficiency in Vitamin K

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c. Deficiency: common in unsupplemented newborns and can cause bleeding
i. Microorganisms in the gut make vitamin K
ii. Newborns have sterile gut which is why they are given vitamin K immediately after birth

People who abuse antibiotics run into problems with vitamin K. Generally, it is not very common except drug induced and in new born.

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Carboxylation of glutamate

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i. Precursors of clotting factors with glutamyl residues
ii. Carboxylation of the residue will result in mature clotting factors
1. Vitamin K promotes gamma carboxylation of the glutamyl residue in blood cloting factors
a. Biotin (water soluble vitamin) works in carboxylation as well
iii. In some cases where people use anticoagulants, it is suspected that warfarin can block the pathway of vitamin K leading to unstoppable bleeding.

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Role of vitamin K in blood coagulation

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i. Factors are precursors for blood coagulation. Vitamin K comes and allows gamma carboxylation of the factors. Transnationally, becomes mature clotting factor which engages calcium and membrane phospholipids of platelets leading to formation of blood clots.

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Vitamin E

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a. Active form: several forms but alpha tocopherol is most active
b. Function: antioxidant
c. Deficiency: can lead to RBC fragility and hemolytic anemia

Hemolytic anemia is same as microcytic anemia

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Vitamin Supplementation

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a. Multivitamins are effective to prevent certain deficiencies
b. Supplementation is a contraindicative for some vitamins
c. Natural sources of vitamin (foods) are better than pills