Lipid Biochemistry USMLE Step 1 Practice Question
A 67-year-old man with established coronary artery disease presents with BP 138/82, HR 78, on high-dose atorvastatin. PCSK9 inhibitor is initiated due to persistently elevated cardiovascular risk. Recent labs show LDL cholesterol decreasing from 55 mg/dL to 20 mg/dL and apolipoprotein B at 45 mg/dL. Carotid ultrasound shows stable atherosclerotic plaque without progression. No muscle pain or hepatic dysfunction reported. Which mechanism best explains the LDL reduction achieved by PCSK9 inhibitors?
Answer choices
- AIncreased activation of hepatic lipase in extrahepatic tissues
- BDirect inhibition of hepatic cholesterol synthesis via HMG-CoA reductase
- CEnhanced conversion of VLDL to LDL particles
- DInhibition of lipoprotein lipase-mediated triglyceride hydrolysis
- EPrevention of PCSK9-mediated degradation of LDL receptors, increasing hepatic LDL uptakeCorrect answer
- FUpregulation of hepatic SR-BI increasing selective HDL cholesterol uptake
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