Which apolipoprotein’s function includes acting as an LPL cofactor?

• A. Apolipoprotein C1
• B. Apolipoprotein C2
• C. Apolipoprotein C3
• D. Apolipoprotein E

Answer: (B)

Lipoprotein lipase needs a cofactor to function on triglyceride-rich lipoproteins. Apolipoprotein C-II is the partner that activates LPL on the surface of chylomicrons and VLDL, enabling the enzyme to hydrolyze triglycerides into free fatty acids and glycerol for tissue uptake. Without C-II, LPL activity drops and triglyceride-rich particles accumulate, leading to hypertriglyceridemia.

Apolipoprotein C-I and C-III modulate lipoprotein metabolism—C-III can actually inhibit LPL and slow TG clearance—while apolipoprotein E is key for receptor-mediated clearance of remnants, not LPL activation. So C-II is the specific cofactor that turns on LPL.