1.1.4 Lipoprotein Structure and Metabolism Flashcards
What is the role of HDL in the transport of cholesterol?
HDL can take cholesterol from the tissues an bring it to the liver where is can be excreted in bile; or it can load it to VLDL which will go back into the tissues or go back to liver
What is the general structure of a lipoprotein?
Polar surface envelope and a neutral lipid core
What is the substrate and site of action of lipoprotein lipase?
Triacylglycerol is substrate at the site of capillary surfaces
What is the substrate and site of action of hepatic triglyceride lipase?
Triacylglycerol and phospholipids at the site of liver sinusoids
What is the role of the LDL receptor-related protein?
It binds apo-E and has a function in uptake of cholesterol-loaded chylomicron remnants and HDL and the delivery of cholesterol to liver for excretion
What is the role of the scavenger receptor (SR-B1)?
Selective uptake of cholesteryl esters - can lead to creation of foam cells
Where is apoE found and what is its function?
Chylomicron, VLDL and HDL and is the ligand for the LDL receptor
What do LDL and VLDL contain that HDL does not?
Apo-B
Where is apoB-100 found and what is its function?
VLDL and LDL and it is the ligand for the LDL receptor
Cutaneous Xantoma is a result of what and how can it be treated?
This is a result from extremely elevated levels of cholesterol - was treated with apheresis.
What is the process of HDL genesis?
Nascent HDL can be produced from the liver or the intestine. It will be filled with free cholesterol which will then be esterfied by LCAT. This will cause the cholesteryl esters to migrate to the core of the HDL
What is the process of biliary lipid secretion?
Cholesterol is transported by ABCG5/G8 across the canalicular membrane. ABCB11 transports bile acid into canaliculi. ABCB4 transports phospholipid into the canaliculi. This will create a micelle.
Why is elevated LDL a major risk for atherosclerosis?
It migrates into vascular intima which can be taken up by phagocytes and injure endothelial cells, or cause accumulation of foam cell necrosis.
What is the function of the LDL receptor?
It binds to apoB-100 or apoE and in involved in the regulation of LDL levels, redistribution of cholesterol and ultilization of cholestrol
What is revese cholesterol transport and what is HDL’s role in it?
Reverse cholesterol transport is a multi-step process resulting in the net movement of cholesterol from peripheral tissues back to the liver via the plasma. Cholesterol from non-hepatic peripheral tissues is transferred to HDL by the ABCA1 (ATP-binding cassette transporter). Apolipoprotein A1 (ApoA-1), the major protein component of HDL, acts as an acceptor, and the phospholipid component of HDL acts as a sink for the mobilised cholesterol.
What is the role of chylomicrons and VLDL in the transport of triglycerides?
Triglycerides from the intestinal lumen are loaded into chylomicrons which make fatty acids that can be used for adipose tissue or muscle
Triglycerides from the liver can be loaded into VLDL and thus make fatty acids that are used for adipose tissue or muscle
What is the substrate and site of action of LCAT?
Cholesterol and phosphatidylcholine (nascent HDL) at the site of lipoproteins
Where is apoA-1 found and what does it do?
HDL and activates LCAT (Lecithin:cholesterol acyltransferase)
Describe the process of VLDL remnant metabolism
VLDL remnants can be uptaken by the liver, or it can be hydrolyzed by HTGL which will lead to LDL formation.
Why is HDL considered to be good cholesterol?
It decreases the amount of cholesterol available for tissue deposition by removing it from macrophages and promoting return to the liver.
Going to largest to smallest rank the size of the human plasma lipoproteins
Chylomicrons, VLDL, LDL, and HDL
What is the role of oxidized LDL and arterial plaque formation?
Oxidized LDL in the intima of blood vessels can promote the chemotaxis of monocytes. The oxidized LDL can be taken up via scavenger receptor on macrophages leading to foam cell formation.This can injure endothelial cells, but can also damage intima via foam cell necrosis.
Describe the process of cholesterol transport and metabolism
Dietary cholesterol can be either excreted or loaded into a chylomicron. This turns into a chylomicron remnant which can then be brought to the tissues or excreted.
What are the ABC transporters and their role in HDL metabolism?
These are important proteins in the efflux of cholesterol to HDL particles. This is integral to reverse cholesterol transport.
Defects in the LDL receptor can lead to what?
This is FH and it can lead to elevated levels of cholesterol similar to how defective apoB-100 would
Where is apoB-48 found and what does it do?
Chylomicron and has a structural role
Describe the process of intravascular VLDL metabolism
Nascent VLDL can be loaded with cholesteryl esters from HDL to become a mature VLDL. This can then be used to transport fatty acids to the tissues. The VLDL remnant will then go to the liver
Familial alpha-lipoprotein deficiency is known as what?
Tangier Disease - caused by a defective ABCA1
Where is apoC-II found and what is its function?
Chylomicron and VLDL and is a activator of lipprotein lipase
What is the substrate and site of action for acid lipase?
Triacylglycerols and cholesteryl esters at the site of Lysosomes
