Podcast
Questions and Answers
What is the first and rate-limiting reaction in the synthesis of bile salts?
What is the first and rate-limiting reaction in the synthesis of bile salts?
What percentage of bile acid molecules are present in the protonated form in the contents of the intestinal lumen?
What percentage of bile acid molecules are present in the protonated form in the contents of the intestinal lumen?
Which series of bile salts is produced from compounds with α-hydroxyl groups at positions 3, 7, and 12?
Which series of bile salts is produced from compounds with α-hydroxyl groups at positions 3, 7, and 12?
What is the pKa of the bile acids?
What is the pKa of the bile acids?
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What decreases the activity of 7α-hydroxylase, the enzyme catalyzing the first and rate-limiting reaction in bile salt synthesis?
What decreases the activity of 7α-hydroxylase, the enzyme catalyzing the first and rate-limiting reaction in bile salt synthesis?
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What is the remaining fragment attached to the ring structure after three carbons are removed from the side chain in bile salt synthesis?
What is the remaining fragment attached to the ring structure after three carbons are removed from the side chain in bile salt synthesis?
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Which lipoprotein particle contains specific apolipoproteins on its surface that act as ligands for specific plasma membrane receptors on target tissues?
Which lipoprotein particle contains specific apolipoproteins on its surface that act as ligands for specific plasma membrane receptors on target tissues?
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Which enzyme can remove triacylglycerol from HDL3 particles to regenerate HDL2 particles?
Which enzyme can remove triacylglycerol from HDL3 particles to regenerate HDL2 particles?
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What is the primary form of cholesterol esters in LDL?
What is the primary form of cholesterol esters in LDL?
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What process leads to the binding of the SREBP to the sterol-regulatory element of genes for the LDL receptor?
What process leads to the binding of the SREBP to the sterol-regulatory element of genes for the LDL receptor?
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What is the main mechanism of statin drugs in lowering blood LDL levels?
What is the main mechanism of statin drugs in lowering blood LDL levels?
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What happens when intracellular levels of cholesterol decrease?
What happens when intracellular levels of cholesterol decrease?
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What is the primary function of bile salts in the intestine?
What is the primary function of bile salts in the intestine?
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Where are over 95% of bile salts resorbed and recycled in the body?
Where are over 95% of bile salts resorbed and recycled in the body?
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What is the primary function of lipoproteins in the bloodstream?
What is the primary function of lipoproteins in the bloodstream?
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Which lipoprotein is assembled from dietary lipids within the epithelial cells of the small intestine?
Which lipoprotein is assembled from dietary lipids within the epithelial cells of the small intestine?
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What is the main function of ApoCII within the lipoprotein shell?
What is the main function of ApoCII within the lipoprotein shell?
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Which component of bile salts affects their solubility and ionization in the gut?
Which component of bile salts affects their solubility and ionization in the gut?
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What is the fate of VLDL remnants in the body?
What is the fate of VLDL remnants in the body?
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What is the consequence of excess LDL particles in the body?
What is the consequence of excess LDL particles in the body?
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What is the treatment for familial lipoprotein lipase deficiency?
What is the treatment for familial lipoprotein lipase deficiency?
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What is the role of VLDL in lipoprotein metabolism?
What is the role of VLDL in lipoprotein metabolism?
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What is the consequence of familial lipoprotein lipase deficiency?
What is the consequence of familial lipoprotein lipase deficiency?
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What happens to chylomicron remnants after being taken up by the liver?
What happens to chylomicron remnants after being taken up by the liver?
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What is the major benefit of HDL?
What is the major benefit of HDL?
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Which protein is involved in facilitating the directional movement of cholesterol from the cell to the lipoprotein particle?
Which protein is involved in facilitating the directional movement of cholesterol from the cell to the lipoprotein particle?
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What is the role of LCAT in HDL metabolism?
What is the role of LCAT in HDL metabolism?
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What is the consequence of mutations in the ABCA1 protein?
What is the consequence of mutations in the ABCA1 protein?
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How is mature HDL primarily cleared from the blood?
How is mature HDL primarily cleared from the blood?
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What is the purpose of CETP inhibitors in HDL metabolism?
What is the purpose of CETP inhibitors in HDL metabolism?
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Study Notes
HDL Metabolism and Function
- HDL takes on a more globular shape as the central hollow core fills with cholesterol esters, forming the mature HDL particle.
- HDL's major benefit is its ability to remove cholesterol from cells and return it to the liver, known as reverse cholesterol transport.
- Reverse cholesterol transport involves the directional movement of cholesterol from the cell to the lipoprotein particle, facilitated by the protein ABCA1.
- LCAT, acquired by the HDL particle from the circulation, catalyzes the transfer of a fatty acid from lecithin to cholesterol, trapping the cholesterol within the HDL core.
- Familial HDL deficiency and Tangier disease result from mutations in the ABCA1 protein, leading to low levels of HDL and early-onset coronary artery disease.
- Treatment with ezetimibe, a drug that blocks cholesterol absorption, was added to complement atorvastatin to lower blood LDL cholesterol levels in a patient with intermittent chest pain.
- Elevated levels of lipoprotein-associated cholesterol, particularly LDL, are associated with atherosclerotic plaque formation and cardiovascular events.
- Mature HDL particles can bind to specific receptors on hepatocytes and are primarily cleared from the blood through uptake by the scavenger receptor SR-B1.
- SR-B1 receptors transfer cholesterol and cholesterol esters into cells, dissociating the HDL particle when depleted and upregulating in cells that require cholesterol for biosynthesis.
- HDL exchanges apolipoproteins and lipids with other lipoproteins in the blood, transferring apoE and apoCII to chylomicrons and VLDL and obtaining free cholesterol from cell membranes.
- HDL either transports the free cholesterol and cholesterol esters directly to the liver or transfers them to circulating triacylglycerol-rich lipoproteins via CETP, exchanging triacylglycerols back to HDL.
- CETP inhibitors are being evaluated to increase HDL2 levels, as high concentrations of triacylglycerol-rich lipoproteins generate elevated levels of less atheroprotective HDL3.
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Description
Test your knowledge of HDL metabolism and function with this quiz. Explore the role of HDL in reverse cholesterol transport, its interaction with proteins like ABCA1 and LCAT, and the impact of mutations and treatments on HDL levels. Gain insights into the relationship between HDL and atherosclerosis, as well as its role in lipid exchange and cholesterol transport.
