A patient with recurrent pancreatitis and eruptive xanthomata has fasting triglycerides of 4500 mg/dL. Lipoprotein electrophoresis shows a creamy supernatant layer with no clear plasma. LPL activity in post-heparin plasma is markedly reduced. The primary metabolic defect is impaired hydrolysis of triglycerides in which lipoprotein?

• A LDL
• B Chylomicrons and VLDL ✓
• C HDL
• D IDL only

Explanation

Lipoprotein lipase (LPL), located on capillary endothelium (especially in adipose, muscle, and heart), hydrolyzes triglycerides in both chylomicrons (exogenous pathway) and VLDL (endogenous pathway). LPL deficiency (familial hyperchylomicronemia, type I hyperlipoproteinemia) results in massive accumulation of both chylomicrons and VLDL, causing severe hypertriglyceridemia with the classic creamy plasma. Apo CII is the essential activator of LPL; deficiency of either LPL or apo CII produces the same phenotype.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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