Vitamins and Lipids - Skildum Flashcards
After ingestion, how do triacyglycerols travel through the gut lumen?
The gall bladder secretes bile salts that emulsify the TG’s.
What is the next step of TG’s after being emulsified by bile salts?
Lipase and colipase released from the pancreas breaks TG’s into a fatty acid and 2 monoacyglycerols.
They are then reemulsified in a bile salt micelle.
What happens to the micelle containing 2 Monacyglycerols and a TG?
They are taken up by intestinal epithelium and Triacyglycerols are reformed. Then they are packaged in chylomicrons and transported through the lymph to get to the blood.
What is the major apoprotein in chylomicrons?
ApoB-48
What is the difference between ApoB-48 in chylomicrons and the ApoB-100 found in hepatocytes?
They come from the same gene in DNA. The difference is that after transcription, the RNA that makes ApoB-48 is EDITED. A stop codon is added in producing a smaller mRNA and protein
How does HDL affect chylomicrons after they have entered the blood?
HDL transfers ApoCII and ApoE onto the nascent chylomicron transforming it into a mature chylomicron
Thats metamorphosis! (random comment to no one)
What activates Lipoprotein Lipase (LPL) ?
What does it do?
LPL is activated by ApoCII.
LPL is found in the capillary beds of muscle and adipose tissue.
LPL cleaves chylomicrons into FA’s, glycerol, and chylomicrons remnants
After LPL breaks up the chylomicron. Where do the FA’s, glycerol, and chylomicron remnants go?
FA’s: Oxidized in muscle or stored as TG’s in adipose tissue
Glycerol: Back to the liver
Chylo Remnants: Back to the liver
FA’s and cholesterol grabbed by the liver from chylo-remnants can be repackaged to serve a very similar function as chylomicrons. Explain
Can be repackaged with ApoB-100 as VLDL (very low density lipoprotein).
VLDL also delivers FA fuels to the body tissues
Why is it only possible for adipose tissue to store FA’s as TG’s in the fed state?
BECAUSE the glycerol-3-phosphate backbone required to form TG’s can only be produced by glycolysis in adipocytes
What kinds of cells serve as a storage reservoir for Vitamin A?
Stellate cells of the liver
What proteins are important for blood transport of retinol and retinoic acid?
Retinol = RBP (retinol binding protein)
Retinoic Acid = Complexes with albumin
Active form of Vitamin A?
All-trans-retinol
Rod cell rhodopsin is a complex of two molecules:
Opsin and _______.
When light strikes it a conformation change then converts _______ to _________.
Rod cell rhodopsin is a complex of two molecules:
Opsin and cis-retinal.
When light strikes it, a conformation change then converts cis-retinal to trans-retinal.
This conversion activates a g-protein and Na channel –> boom sight!
How does Vit A affect the immuen system?
Retinoic acid actually plays a role in maturing dendritic cells and recruiting antibody-secreting cells to the small intestine.
Complications of Vit A Deficiency?
Anorexia Retarded growth Infections Alopecia Epithelial cell keratinization Night blindness, xeropthalmia, Bitot's spots (keratin build-ups)
Most important complication to remember with Vit A toxicity?
Teratogenic effect
Vit E deficiency is rare unless you have an absorption problem. Premies, Chrohn’s, short bowel, etc.
What would the clinical manifestations include?
Myopathy
Hemolytic anemia
Peripheral neuropathy
Loss of vibratory sense - ataxia
Vit E function?
Cellular oxidative stress defense
Especially in membranes
Possibly why myopathy occurs without it
2 main forms of Vit K. Phylloquinone and Menaquinone. Where are they found?
Phylloquinone = leafy green vegetables
Menaquinone = produced by fermentation (in gut, or can be found in cheese)
Which vitamin inhibits Vitamin K absorption and metabolism?
Vit E
How could Vit K deficiency result in a patient with increased prothrombin time and increased bleeding?
(Rare, by the way)
Vitamin K acts as a cofactor for gamma-glutamyl carboxylase.
Which activates blood-clotting proteins
Factor 9, 7a, 10, and prothrombin are all Vit-K-Dependent!
What foods is Vitamin D found in?
Animal origins:
liver, eggs, fish, dairy products, shitake mushrooms
In order to synthesize Vit D de novo, what organs are required?
Skin, liver, kidney
Why is the parathyroid gland important vor Vit D synthesis?
In order for kidney to convert Vit D to its active form it must be acted upon by PTH, produced int he Parathyroid gland.
PTH is produced in response to low calcium conentrations
When Vit D binds to VDR it induces transcription events to increase Ca in the blood. What are some of these proteins created?
Ca channel TRPV6 at the intestinal brush border, calbindin in cytoplasm, Ca-ATPase pumps on basolateral membrane, and claudin to allow more Ca across tight junction.
Vit D is the most likely Vitamin to have toxic effects. What are the effects?
Calcification of soft tissues (kidneys, heart, lungs, vessels)
Hyperphosphatemia
Hypertension
Problems associated with Vit D deficiency?
Rickets - seizures, growth retardation, failure of bone mineralization
Osteomalacia is the adults form
most calorically dense food?
fat!
Which molecule’s function is to maintain cholesterol and apoprotein homeostasis.
HDL
