Not all lipoproteins suppress HMG-CoA activity when supplied in culture medium. For example, HDL was not effective, but LDL was effective, even when present at low nanomolar concentrations. What clues about the mechanism for regulating cholesterol homeostasis by lipoproteins are suggested by these findings?

The latter concept provides the mechanism by which statins selectively lower plasma LDL, In patients with FH, the concentration of cholesterol in blood is elevated many. Not all lipoproteins could suppress HMG CoA reductase activity. The high affinity action of LDL suggested that a cell surface receptor was involved. The discovery of the LDL receptor: Clues to receptor-mediated endocytosis, lipoprotein particles, low density lipoprotein (LDL) and high density lipoprotein (HDL).