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What is the main purpose of lipoproteins?
to transport lipids and fat-soluble vitamins in the blood
What is the structural protein for chylomicrons and chylomicron remnants?
Apo B-48, made in the intestine
What is the activator of lipoprotein lipase?
Apo C-II ("borrowed from HDL)
What are the two functions of Apo B-100?
- Structural component of VLDL, IDL, and LDL
- Ligand for LDL receptor
What are the two functions of Apo A-I?
- Structural component of HDL
- Activator of PCAT enzyme
What is the function of Apo E?
- Ligand for hepatic Apo E receptor for CM remnants clearing
- Ligand for Apo E receptor for IDL clearing
What receptor in the liver binds to the chylomicron remnant?
Apo E receptor
What receptor in extrahepatic tissue and the liver binds to LDL?
Apo B-100 receptor
What do bile acid resins (like cholestyramin) do to the absorption of bile salts?
Prevents the re-absorption of bile salts and forces the liver to use more cholesterol for bile salt synthesis.
What two effects will the decrease in cytosolic cholesterol result in?
- Increase in LDL receptor expression (decrease in serum cholesterol)
- Increase in HMG-CoA reductase expression (increase in de novo synthesis of cholesterol)
What are the three main functions of HDL?
- Resevoir for apolipoproteins (Apo C-II and Apo E)
- HDL uptake of unesterified cholesterol
- Esterification of cholesterol (by PCAT)
What is the function of CETP?
moves CEs from HDL to VLDL in exchange for TG
Where does HDL get its cholesterol?
- Peripheral cells
- Macrophages (foam cells) --> antiatherogenic