In familial hypercholesterolemia, cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma. Of particular concern is the oxidation of the excess LDL to form oxidized LDL (oxLDL). The oxLDL is taken up by macrophages, which become engorged to form foam cells. Which statement best describes the formation of foam cells?
A) cholesterol cannot be extracted from macrophages by HDL
B) expression of the receptors for oxLDL is increased in the macrophages
C) LDL enters by pinocytosis to form foam cells
D) LDL receptors on peripheral cells are upregulated
E) there is increased synthesis of cholesterol in macrophages as a result

Question

Quizplus · Accepted Answer

The formation of foam cells is primarily due to the increased uptake of oxidized LDL by macrophages through scavenger receptors, which are upregulated in response to oxLDL.  There are a number of cell surface receptors that bind lipoproteins of the LDL family, such as the classic LDL receptor and the LDL receptor-related proteins. Modified LDL, such as oxLDL, does not bind to the LDL receptor. Instead, these lipoprotein particles are taken up into macrophages via the scavenger receptor, FAT/CD36. Presentation of this receptor on macrophage plasma membranes is not downregulated in response to oxLDL uptake as is the case for the LDL receptor. Conversely, uptake of oxLDL by macrophages leads to increased density of FAT/ CD36 on these cells.

In Familial Hypercholesterolemia, Cholesterol Is Deposited in Various Tissues Because