Which of the following is the major source of extracellular cholesterol?
|A||Very-low-density lipoproteins VLDLs|
|B||Low –density lipoproteins LDLs|
|C||High –density lipoprotein HDLs|
a. The uptake of exogenous cholesterol by cells results in a marked suppression of endogenous cholesterol synthesis.
b. Low-density human lipoprotein not only contains the greatest ratio of bound cholesterol to protein but also has the greatest potency in suppress ing endogenous cholesterogenesis.
c. LDLs normally suppress cholesterol synthesis by binding to a specific membrane receptor that mediates inhibition of hydroxymethylglutaryl HMG coenzyme A reductase.
d. In familial hypercholesterolemia 143890, the LDL receptor is dysfunctional, with the result that cholesterol synthesis is less responsive to plasma cholesterol levels. Suppression of HMG CoA reductase is attained using inhibitors statins that mimic the structure of mevalonic acid, the natural feedback inhibitor of the enzyme.