Which mechanism best explains the antiatherogenic effect of high-density lipoprotein (HDL)?
- A ABCA1-mediated efflux of cholesterol from peripheral cells to apolipoprotein A-I, initiating reverse cholesterol transport ✓
- B Uptake of oxidized LDL by scavenger receptors on macrophages
- C Inhibition of hepatic LDL receptor expression
- D Direct activation of HMG-CoA reductase in hepatocytes
Correct answer: A. ABCA1-mediated efflux of cholesterol from peripheral cells to apolipoprotein A-I, initiating reverse cholesterol transport
Explanation
HDL mediates reverse cholesterol transport: ATP-binding cassette transporter B1 (ABCA1) transfers free cholesterol from peripheral cells, including foam cells, to lipid-poor apolipoprotein B-I to form nascent HDL, which delivers cholesterol to the liver via SR-BI. This removes cholesterol from atherosclerotic plaques. Scavenger receptor uptake of oxidized LDL promotes foam cell formation, the opposite effect. HDL also has antioxidant and anti-inflammatory actions, but ABCA1-dependent efflux is the central protective mechanism.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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