Lipid Biochemistry USMLE Step 1 Practice Question
A 28-year-old man with familial hypertriglyceridemia presents with severe epigastric pain and recurrent acute pancreatitis. Vital signs show BP 128/82 mmHg, HR 102 bpm, RR 18/min, temp 37.8°C. Serum triglycerides are markedly elevated at 2000 mg/dL with normal cholesterol levels. Lipase is 450 U/L. Genetic testing reveals a mutation in the apolipoprotein C-III gene. Which mechanism best explains how this mutation contributes to severe hypertriglyceridemia?
Answer choices
- ADeficiency of apolipoprotein C-II cofactor for lipoprotein lipase
- BLoss of inhibitory effects on lipoprotein lipase, increasing its activityCorrect answer
- CImpaired binding of chylomicrons to hepatic receptors
- DIncreased synthesis of hepatic triglycerides and VLDL secretion
- EActivation of hepatic lipase in extrahepatic tissues
- FApoE loss-of-function reducing hepatic VLDL remnant clearance
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