The indirect pathway of HDL cholesterol return to the liver involves CETP-mediated exchange. Which option best describes this pathway?

• A. Indirect pathway
• B. Direct pathway
• C. Both direct and indirect
• D. Neither

Answer: (A)

The idea being tested is how HDL can return cholesterol to the liver through different routes. In the indirect pathway, HDL donates its cholesteryl esters to apoB-containing lipoproteins (like VLDL and LDL) via the cholesteryl ester transfer protein, CETP, in exchange for triglycerides. The resulting triglyceride-rich remnants are then taken up by the liver, delivering cholesterol indirectly. This CETP-mediated exchange is the hallmark of the indirect route.

In contrast, the direct pathway involves HDL transferring cholesterol straight to hepatocytes through receptors like SR-BI without CETP involvement, so it’s not the route described here. Hence, describing the CETP-mediated, indirect transfer correctly identifies the indirect pathway as the mechanism in question.