Which lipoprotein has exogenous triglycerides as its major component?

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

Answer: (A)

Dietary fats are absorbed in the intestine and repackaged into triglycerides within enterocytes, forming chylomicrons. This makes chylomicrons the primary carrier of exogenous, or dietary, triglycerides. They enter the lymphatic system and then the bloodstream, where lipoprotein lipase on capillary walls hydrolyzes the triglycerides, releasing fatty acids to tissues such as muscle and adipose tissue for energy or storage. After delivering their triglycerides, chylomicrons shrink to remnants that are rich in cholesterol and are cleared by the liver via receptor-mediated uptake involving ApoE. Because they carry the largest share of dietary triglycerides, chylomicrons have the highest triglyceride content and the lowest density among the lipoproteins.

In contrast, other lipoproteins handle triglycerides from different sources: a liver-produced particle carries endogenous triglycerides synthesized by the liver; a particle primarily transports cholesterol esters; and another particle is rich in protein and participates in removing cholesterol from tissues and transferring it to the liver.