Fat Soluble Vitamins

Question 1

Vitamin A

Answer 1

Plays a key role in night vision, cell differentiation and growth regulation
Beta-carotene = precursor to Vitamin A, can be converted directly to retinal
Retinoids = preformed vitamin A in animals
Retinoids and carotenoids are transported from the intestine to the liver in chylomicrons
Some carotenoids can be converted to retinol (in the liver)
Retinol circulates in the blood
Retinal is important for vision
Retinol and Retinal can be interconverted
Retinoic acid (formed from retinal, but cannot be converted back to retinol or retinal) - used for modulation gene expression
Carotenoid that are not converted to vitamin A may act as antioxidants
Vitamin A is involved in the perception of light - the retinal form of the vitamin combines with opsin to form visual pigment rhodopsin
Retinoic Acid binds to regulatory region of DNA and alters the level of mRNA produced *only retinoic acid is used for gene expression
Vitamin A plays a role in maintaining immune function

Question 2

Vitamin A Deficiency

Answer 2

Threat to the health, sight, and lives of millions of children around the world
Can be caused by insufficiency intake of Vitamin A, fat, protein, or zinc
Deficiency can result in blindness - major cause of blindness in developing world

Question 3

Vitamin D

Answer 3

Can be produced in the skin by exposure to UV light - when UV light strikes the skin, 7-dehydrocholesterol (made from cholesterol in the body) is converted to Vitamin D3
Vitamin D travels in the blood to the liver –> In the liver enzymes add a hydroxyl group to carbon 25 to form 25, hydroxy vitamin D3 –> in the kidneys enzymes a hydroxyl group to carbon number 1 forming active vitamin D = 1,25-dihydroxy vitamin D3
Important for bone healthy, normal functioning of the parathyroid gland, and regulation of the immune system
Principle function is to maintain levels of Ca & Phosphorus in the blood to favor bone mineralization - when blood Ca drops, parathyroid gland releases PTH –> PTH stimulates kidneys to activate enzymes to convert to active vitamin D3
For blood Ca levels: increase intestinal calcium transport proteins to move Ca from intestinal lumen into the body, in bone vitamin D stimulates bone cells to breakdown bone to release Ca, in kidney vitamin D acts to increase the amount of Ca retained by kidneys and put back into the blood
Regulates genes

Question 4

Vitamin D Deficiency

Answer 4

When Vitamin D is deficient, dietary calcium cannot be absorbed efficiently and there can be improper bone mineralization and abnormalities in bone structure
In children, deficiency can result in rickets
In adults, deficiency can result in osteomalacia
(Over supplementation can result in high blood and urine calcium concentrations, depositing of calcium in blood vessels and kidneys, and cardiovascular damage)

Question 5

Vitamin E (Tocopherol)

Answer 5

Antioxidant properties - functions primarily as a fat-soluble antioxidant, donates electron to neutralize reactive molecules
Absorption depends on normal fat absorption
Incorporated into chylomicrons once absorbed

Question 6

Vitamin E (Tocopherol) Deficiency

Answer 6

At risk: premature infants, individuals with protein or fall malabsorption
Newborn infants have low blood tocopherol because little transfer of Vitamin E to fetus until last weeks of pregnancy
At risk for hemolytic anemia (red cells membranes rupture)

Question 7

Vitamin K

Answer 7

Needed for production of blood clotting proteins (needed to make fibrin)
Involved in proteins needed for bone mineralization and demineralization

Question 8

Vitamin K Deficiency

Answer 8

Major symptom: abnormal blood coagulation
Deficiency is common in newborns - little transfer to fetus, breast milk low in Vitamin K, and no bacteria in newborn gut
Newborn infants typically given a Vitamin K injection within 6 hours of birth