Vitamins and lipids (1.15) Flashcards
What are the 4 fat soluble vitamins?
A
D
E
K
What is the active form of vitamin A?
all-trans-retinol
What are the dietary forms of vitamin A? What foods?
Carotenoids
Retinyl-acyl esters
Red, yellow, and orange fruits and vegetables
How is dietary vitamin A converted into free carotenoid and free retinol in the intestine?
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
What happens in the intestine after free carotenoids and free retinols are formed? Why?
Fatty acids, phospholipids, monoacylglycerol, and/or cholesterol are added
Gets incorporated into micelle
In what two forms does vitamin A leave the intestinal cell?
Retinoic acid…to liver via blood albumin
CRBPII-retinyl-palmitate…lymphatics in chylomicron –> to liver as chylomicron-remnant
Why does retinoic acid go to the liver?
The liver stores vitamin A in stellate cells…controls vitamin A homeostasis (30-86ug/dL)
After retinyl esters enter a hepatic parenchymal cell, how can the leave?
Stellate cells (to/back to storage) VLDL (to tissues)
After retinyl esters enter a hepatic parenchymal cell, they can be converted to retinol. How does retinol leave?
Retinol complexes with transthyretin and retinol binding protein (RBP) to go out to the serum
After retinyl esters enter a hepatic parenchymal cell, they can be converted to retinoic acid. How does retinoic acid leav?
Goes out to serum complexed with albumin…like it did from the intestinal cell
What kind of receptors are Retinoic Acid Receptors (RAR), Retinoic X Receptors (RXR), and some Peroxisome proliferator activated receptor (PPAR)?
Ligand activated transcription factors
What are the effects of RAR, RXR, and PPAR?
Increased differentiation of goblet cells
Decreased keratinization
Apoptosis of cancer cells
Maturation of dendritic cells
Recruitment of antibody secreting B cells to small intestine
How can carotenes be helpful if they are not cut?
Act as antioxidants…their double bonds can neutralize singlet oxygen and free radicals
What are the symptoms of vitamin A deficiency?
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)*
How is vitamin A deficiency diagnosed?
The Relative Dose Response (RDR)
How is the RDR calculated?
At what point is an RDR indicative of a deficiency?
RDRs > 20%
What is the Tolerable Upper Limit (TUL) of vitamin A?
3000ug/day