Lipoproteins 1.2: Le monde du cholesterol

Question 1

what apoprotein is bound to LDL?

Answer 1

Because VLDL is a precursor of LDL
VLDL -> IDL -> 50%LDL
As such, it will have the same apoprotein as LDL ->** apoB100**.

La LDL porte aussi fièrement, en héritage, son chapeau apoB100 qui lui permet de se lier à son récepteur hépatique. C’est sa seule composante protéinique

Question 2

What is the role of LDL?

Answer 2

This is the pizza delivery guy

It goes from one cell to another and provides cholesterol

Say the skin needs to produce vitamin D, well LDL will drop the delivery (cholesterol)

Question 3

Where does LDL return after the delivery?

Answer 3

Le LDL retourne au foie par liaison par leur apoB100 et ils sont dégradés en tous leurs constituants moléculaires

Question 4

Why and what is commonly called the “bad cholesterol”?

Answer 4

LDL

It is called so because in high quantities it can drop cholesterol in arteries leading to plaque buildup

Question 5

What happens if the liver senses an increased amount of cholesterol coming via LDLs?

Answer 5

1. It will secrete more cholesterol via the biliary route
2. It will reduce production of cholesterol by targeting HMG CoA Reductase

Question 6

PCSK-9 role and cascade

Answer 6

PCSK-9 is a protein produced by the liver
It’s role is related to its interaction with the R-LDLs (LDL receptors in the hepatocytes)

R-LDLs are essential in order to sense LDL, bind it, and eliminate it in an efficient way -> lowering cholesterol plasmic levels

As such, it is vital that we recycle our R-LDLs in order for this to happen

NOW,
La PCSK9 régule l’expression des R-LDL à la surface des hépatocytes en les dirigeant vers les lysosomes où ils seront dégradés

It binds to the LDL - R-LDLD couple and now the receptor is not recycled -> less elemination of LDL but also less sensing of LDL

The liver literally thinks that there are less LDL molecules because it cannot sense them -> it thinks it should produce more
Patient ends up with high cholesterol levels

Question 7

HDL role

Answer 7

Moi je passe le balei!
Cleanup janitor

It goes around and picks up cholesterol that is stuck around the body and sends it to the liver

Capte le cholestérol libre des surfaces cellulaires et le redonne aux VLDL et aux LDL
Ceci permet aux VLDL et surtout aux LDL de ramener le cholestérol vers le foie

Question 8

How does cholesterol and triglicerides enter enterocytes?

Answer 8

cholesterol:
special membrane transporter: NPCL1
triglicerides: micelles

Question 9

chylomicrons just like HDL, LDL, and VLDL are synthesized in the liver/

Answer 9

FALSE

chylomicrons in the enterocytes!!!!

Question 10

True or False,
Statin is a common treatment targeting cholesterol in all its forms.

Answer 10

FALSE
. Inhibiteurs de la HMG coA réductase partial
** Ils diminuent le C-LDL ( ET NON PAS LE C-HDL)**

Question 11

Why would a patient with statines, NPC1 blockers and anti-PCSK9 still have high trigliceride counts?

Answer 11

They do nothing for triglicerides only cholesterol

intead need to use fibrates
Fibrates: Ils augmentent l**’activité de la lipoprotéine lipase **ce qui permet de diminuer la concentration plasmatique des triglycérides