Vitamins and lipids (1.15)

Question 1

What are the 4 fat soluble vitamins?

Answer 1

A
D
E
K

Question 2

What is the active form of vitamin A?

Answer 2

all-trans-retinol

Question 3

What are the dietary forms of vitamin A? What foods?

Answer 3

Carotenoids
Retinyl-acyl esters

Red, yellow, and orange fruits and vegetables

Question 4

How is dietary vitamin A converted into free carotenoid and free retinol in the intestine?

Answer 4

Dietary protein-bound carotenoids and retinyl esters enter stomach –proteases–> carotenoid and retinyl esters enter duodenum –hydrolases, esterases, and lipases–> free carotenoids and free retinol

Question 5

What happens in the intestine after free carotenoids and free retinols are formed? Why?

Answer 5

Fatty acids, phospholipids, monoacylglycerol, and/or cholesterol are added

Gets incorporated into micelle

Question 6

In what two forms does vitamin A leave the intestinal cell?

Answer 6

Retinoic acid…to liver via blood albumin

CRBPII-retinyl-palmitate…lymphatics in chylomicron –> to liver as chylomicron-remnant

Question 7

Why does retinoic acid go to the liver?

Answer 7

The liver stores vitamin A in stellate cells…controls vitamin A homeostasis (30-86ug/dL)

Question 8

After retinyl esters enter a hepatic parenchymal cell, how can the leave?

Answer 8

Stellate cells (to/back to storage)
VLDL (to tissues)

Question 9

After retinyl esters enter a hepatic parenchymal cell, they can be converted to retinol. How does retinol leave?

Answer 9

Retinol complexes with transthyretin and retinol binding protein (RBP) to go out to the serum

Question 10

After retinyl esters enter a hepatic parenchymal cell, they can be converted to retinoic acid. How does retinoic acid leav?

Answer 10

Goes out to serum complexed with albumin…like it did from the intestinal cell

Question 11

What kind of receptors are Retinoic Acid Receptors (RAR), Retinoic X Receptors (RXR), and some Peroxisome proliferator activated receptor (PPAR)?

Answer 11

Ligand activated transcription factors

Question 12

What are the effects of RAR, RXR, and PPAR?

Answer 12

Increased differentiation of goblet cells
Decreased keratinization
Apoptosis of cancer cells
Maturation of dendritic cells
Recruitment of antibody secreting B cells to small intestine

Question 13

How can carotenes be helpful if they are not cut?

Answer 13

Act as antioxidants…their double bonds can neutralize singlet oxygen and free radicals

Question 14

What are the symptoms of vitamin A deficiency?

Answer 14

Anorexia
Retarded growth
Increased susceptibility to infections
Alopecia
Keratinization of epithelial cells
Night blindness*
Xeropthalmia (dry eyes d/t keratinization)*
Bitot's spots (something with eyes)*

Question 15

How is vitamin A deficiency diagnosed?

Answer 15

The Relative Dose Response (RDR)

Question 16

How is the RDR calculated?

Answer 16

Measure plasma retinol –> give an oral bolus of retinyl-palmitate –wait 5 hours–> measure plasma retinol…bb for “before bolus” and ab for “after bolus”

RDR = retinol - retinol / retinol

Question 17

At what point is an RDR indicative of a deficiency?

Answer 17

RDRs > 20%

Question 18

What is the Tolerable Upper Limit (TUL) of vitamin A?

Answer 18

3000ug/day

Question 19

What can happen if vitamin A TUL is exceeded for a period of time?

Answer 19

Nausea/Vomiting
Blurred vision*
Headache
Desquamation of skin
Alopecia
Ataxia
Liver damage (from excess stellate cell growth and proliferation)
Conjunctivitis/eye pain
Teratogen at very high doses (Accutane--an acne medication)

Question 20

What are the two forms of vitamin E? What food?

Answer 20

Tocopherols (saturated 16C acyl chains)
Tocotrienols (polyunsaturated 16C acyl chains)

Plant oils and wheat germ

Question 21

How does vitamin E get into the liver?

Answer 21

Similar to vitamin A

Pancreatic lipase does its thing so vitamin E can enter intestinal epi cells…leaves as chylomicron for tissues…then to the liver in a chylomicron remnant

Question 22

How is vitamin E sent to the tissues after being in the liver?

Answer 22

RRR steroisomers can be incorporated into and exported in VLDL

Question 23

What is vitamin E’s function?

Answer 23

Antioxidant activity (d/t phenolic hydroxyl) in lipid bilayers

Question 24

What other two vitamins does vitamin E interact with?

Answer 24

Vitamin C reduces oxidized vitamin E to active form

Vitamin K absorption and metabolism are INHIBITED by vitamin E

Question 25

What are the symptoms of vitamin E deficiency?

Answer 25

Myopathy Hemolytic anemia Peripheral neuropathy Ataxia...loss of vibratory sense

Question 26

What can cause vitamin E deficiency?

Answer 26

Absorptive problems--premies, Crohn's, short bowel syndrome | Inherited lipoprotein disorders

Question 27

What are the two main forms of dietary vitamin K?

Answer 27

Phylloquinone (main form...in leafy greens) | Menaquinones (produced by fermentation...cheese)

Question 28

What is a synthetic form of vitamin K used in animal feed that can be toxic to humans?

Answer 28

Menadione (liver toxicity)

Question 29

What is the digestion/absorption process for vitamin K?

Answer 29

Same as E...which is the same as A...which is the same as fat

Question 30

Where is vitamin K stored?

Answer 30

Cellular membranes--lung, kidney, bone marrow, and adrenal glands

Question 31

What is vitamin K's function?

Answer 31

Co-factor for gamma-glutamyl carboxylase --> activates clotting proteins (Factors IX, VIIa, and X)

Question 32

What are the symptoms of vitamin K deficiency?

Answer 32

Coagulation disorder (increased PTT and bleeding)

Question 33

What foods contain vitamin D?

Answer 33

Foods of animal origin

Question 34

Besides the diet, how else can vitamin D be obtained?

Answer 34

Synthesized de novo from cholesterol

Question 35

What is needed to make active vitamin D3?

Answer 35

Metabolism of skin, liver, and kidney

Question 36

What is the main function of vitamin D?

Answer 36

Calcium homeostasis

Question 37

Vitamin D is taken to the liver via the expected route, but how is it activated (start with de novo steps)?

Answer 37

Cholesterol + sunlight (skin) --> dietary form of vitamin D --liver--> 25-Hydroxycholecalciferol (main form circulating in blood) --kidney (PTH 1-alpha hydroxylase--> 1,25-OH D3 (active form)

Question 38

When does the parathyroid secrete the PTH necessary to activate vitamin D?

Answer 38

When serum calcium is low (<8.5mg/dL)

Question 39

How does vitamin D increase serum calcium levels?

Answer 39

Reabsorption from bones | Increased absorption in the gut

Question 40

How does vitamin D increase intestinal calcium absorption?

Answer 40

Vitamin D Receptor acts as a ligand activated transcription factor --> tsl of calcium transport proteins (TRPV6 at brush border, calbindin in cytoplasm, and Ca ATPases at basolateral membrane...and alters claudin--tight junctions--to be more permeable to calcium)

Question 41

If vitamin D causes increased translation of proteins, how can there be a response within seconds to minutes?

Answer 41

There is a transcription-independent rapid response... binds to other plasma membrane receptors

Question 42

What are the symptoms of vitamin D deficiency?

Answer 42

Rickets (seizures, growth retardation, osteomalacia)

Question 43

What can cause vitamin D deficiency?

Answer 43

Diet Genetics Absorption problem (Crohn's)

Question 44

What are the symptoms of vitamin D toxicity (most likely vitamin toxicity)?

Answer 44

Calcification of soft tissues Hyperphosphatemia Hypertension

Question 45

What is the TUL of vitamin D in people >9?

Answer 45

4000IU