Step I Cholesterol question

[Phloston]

P. 120 of FA says, for HDL (to the right of the orange circle that says "mature HDL"): "transfer of cholesterol esters to VLDL, IDL, LDL."

HDL functions in reverse cholesterol transport (i.e. bringing it from the periphery to the liver [as specified on p. 121]), so why would it transfer cholesterol esters to LDL, considering LDL only brings cholesterol to the periphery?

Should p. 120 instead say "transfer of cholesterol esters to VLDL, IDL"?

 

[Chirurg]

P. 120 of FA says, for HDL (to the right of the orange circle that says "mature HDL"): "transfer of cholesterol esters to VLDL, IDL, LDL."

HDL functions in reverse cholesterol transport (i.e. bringing it from the periphery to the liver [as specified on p. 121]), so why would it transfer cholesterol esters to LDL, considering LDL only brings cholesterol to the periphery?

Should p. 120 instead say "transfer of cholesterol esters to VLDL, IDL"?

that's correct.

 

[tk0102]

P. 120 of FA says, for HDL (to the right of the orange circle that says "mature HDL"): "transfer of cholesterol esters to VLDL, IDL, LDL."

HDL functions in reverse cholesterol transport (i.e. bringing it from the periphery to the liver [as specified on p. 121]), so why would it transfer cholesterol esters to LDL, considering LDL only brings cholesterol to the periphery?

Should p. 120 instead say "transfer of cholesterol esters to VLDL, IDL"?

I think FA is right. Two other important functions of HDL are to 1) collect and transfer cholesterol esters to LDL via CEPT and 2) esterify free cholesterol/cholesterol on the surface of LDL via Apo A-> LCAT. In both cases, HDL does so to sequester cholesterol in VLDL/IDL/LDL by esterifying them and thus making them more hydrophobic. Remember, free cholesterol is dangerous, because it can modify cell membrane fluidity (among other things).

Regarding 1): There's a whole class of drugs under development that inhibit CEPT for the very reason of keeping cholesterol esters out of LDL, where they can get 'stranded' if B-100 gets oxidized or glycosylated. They also seem to increase HDL, probably by a removal of inhibition effect.

http://www.nejm.org/doi/full/10.1056/NEJMe078029