How do statins help in lowering cholesterol levels?

Statins lower cholesterol levels primarily by inhibiting HMG-CoA reductase, an enzyme that plays a crucial role in the cholesterol biosynthesis pathway. This enzyme is responsible for converting HMG-CoA to mevalonate, which is a precursor in the synthesis of cholesterol. By blocking this enzymatic activity, statins effectively reduce the overall production of cholesterol in the liver.

As a result of decreased cholesterol synthesis, the liver compensates by increasing the expression of LDL (low-density lipoprotein) receptors on its surface. This leads to enhanced uptake of LDL cholesterol from the bloodstream, subsequently lowering plasma levels of LDL cholesterol. This mechanism is fundamental to the therapeutic effects of statins in managing hyperlipidemia and reducing the risk of cardiovascular diseases.

In contrast to the other options, enhancing bile acid secretion pertains to medications like bile acid sequestrants, which work differently; blocking intestinal cholesterol absorption is the primary action of ezetimibe, not statins; and promoting apolipoprotein B synthesis would lead to increased LDL particles, countering the goal of lowering cholesterol levels.