Question

Which of the following is increased in lipoprotein lipase deficiency?

• A. VLDL
• B. LDL
• C. HDL
• D. Chylomicrons

Hint:

LPL clears triglyceride-rich particles; without it, the dietary fat carrier accumulates (Type I).

Answer 1

The Correct Option is D

Step 1: Lipoprotein lipase (LPL) is the enzyme on the capillary endothelium that hydrolyses triglycerides carried by chylomicrons and VLDL, releasing free fatty acids for tissue uptake. Apo CII, present on these particles, is the obligatory activator of LPL.

Step 2: When LPL (or its activator Apo CII) is deficient, the triglyceride-rich chylomicrons cannot be cleared from plasma. This is Type I hyperlipoproteinemia (familial chylomicronemia), in which the fasting plasma shows a creamy supernatant layer of chylomicrons.

Step 3: Therefore chylomicrons are the lipoprotein fraction that accumulates. Clinical features include eruptive xanthomas, hepatosplenomegaly and recurrent abdominal pain or pancreatitis. Management is restriction of dietary fat with medium chain triglyceride (MCT) supplementation, since MCTs are absorbed directly into the portal blood and do not need chylomicrons.

Step 4: VLDL, LDL and HDL are wrong because their metabolism does not depend chiefly on chylomicron clearance in this defect. LDL elevation is seen in Type II (LDL receptor defect), and VLDL excess characterises Type IV.