What is the mechanism of action of statins?

• A. They increase cholesterol synthesis
• B. They inhibit HMG-CoA reductase
• C. They promote LDL receptor activity
• D. They enhance HDL formation

Answer: (B)

Statins primarily work by inhibiting HMG-CoA reductase, an enzyme that plays a crucial role in the cholesterol biosynthesis pathway. By blocking this enzyme, statins effectively reduce the liver's production of cholesterol. This decrease in cholesterol synthesis prompts the liver to increase the number of LDL receptors on its surface, enhancing the uptake of LDL cholesterol from the bloodstream. As a result, the overall levels of LDL cholesterol in the blood decrease, contributing to a lower risk of cardiovascular disease.

While the other options mention aspects related to cholesterol and lipid metabolism, they do not accurately describe how statins exert their therapeutic effects. For example, increasing cholesterol synthesis contradicts the primary purpose of statins, which is to lower cholesterol levels. Promoting LDL receptor activity is a secondary effect of the reduction in cholesterol synthesis rather than the direct mechanism of action. Similarly, enhancing HDL formation is not a primary function of statins; they mainly focus on reducing LDL levels. Thus, the correct understanding of statins' mechanism ties back to their role as inhibitors of HMG-CoA reductase, leading to a cascade of effects that lower LDL cholesterol.