Which apolipoprotein mediates the uptake of chylomicron remnants and IDL remnants?

The correct answer is ApoE. ApoE is a key apolipoprotein involved in the metabolism of lipoproteins, specifically facilitating the uptake of chylomicron remnants and intermediate-density lipoprotein (IDL) remnants by the liver.

Chylomicrons, which are large lipoproteins formed in the intestines after ingestion of dietary fats, release triglycerides to tissues. After this process, the remnant particles remain, which are rich in cholesterol and are referred to as chylomicron remnants. Similarly, IDL particles are formed from very-low-density lipoproteins (VLDL) as they lose triglycerides.

ApoE plays a crucial role in the recognition and binding of these remnants to liver cell receptors. The liver has specific receptors, such as the low-density lipoprotein receptor (LDLR) and very-low-density lipoprotein receptor (VLDLR), that specifically recognize ApoE. Once the remnant lipoproteins bind to these receptors, they are internalized, allowing the liver to process these particles and clear them from circulation.

In contrast, ApoA-1 primarily facilitates the formation of high-density lipoproteins (HDL) and is involved in reverse cholesterol transport, ApoC-II is