Which protein transfers lipid from HDL to LDL to the liver, connecting forward and reverse transport?

Which protein transfers lipid from HDL to LDL to the liver, connecting forward and reverse transport?

• A. ATP-binding cassette transporter A1
• B. Lecithin cholesterol acyltransferase
• C. CETP
• D. Apolipoprotein B

Answer: (C)

Cholesteryl ester transfer protein mediates lipid exchange in the bloodstream, moving cholesteryl esters from HDL to LDL and VLDL in exchange for triglycerides. This transfer bridges the reverse transport pathway—where HDL gathers cholesterol from tissues for return to the liver—and the forward pathway, by delivering cholesterol via LDL/VLDL to the liver for clearance. The other proteins have different roles: ABCA1 helps load cholesterol onto ApoA-I to form HDL; LCAT esterifies cholesterol on HDL to aid maturation; ApoB is a core structural protein of VLDL/LDL involved in assembly and receptor recognition, not lipid transfer between HDL and LDL.

Cholesteryl ester transfer protein mediates lipid exchange in the bloodstream, moving cholesteryl esters from HDL to LDL and VLDL in exchange for triglycerides. This transfer bridges the reverse transport pathway—where HDL gathers cholesterol from tissues for return to the liver—and the forward pathway, by delivering cholesterol via LDL/VLDL to the liver for clearance. The other proteins have different roles: ABCA1 helps load cholesterol onto ApoA-I to form HDL; LCAT esterifies cholesterol on HDL to aid maturation; ApoB is a core structural protein of VLDL/LDL involved in assembly and receptor recognition, not lipid transfer between HDL and LDL.