**Core Concept**
Fibrates are a class of hypolipidemic drugs that primarily work by activating peroxisome proliferator-activated receptor-alpha (PPAR-alpha), which leads to the reduction of very-low-density lipoprotein (VLDL) production in the liver. This action decreases the levels of triglycerides in the blood.

**Why the Correct Answer is Right**
Fibrates, such as fenofibrate and gemfibrozil, act by activating PPAR-alpha, which in turn increases the expression of lipoprotein lipase (LPL) and decreases the expression of apolipoprotein C-III (APOC3). LPL breaks down triglycerides in VLDL, while APOC3 inhibits LPL activity. By decreasing VLDL production and increasing LPL activity, fibrates effectively lower triglyceride levels in the blood.

**Why Each Wrong Option is Incorrect**
**Option B:** Nicotinic acid (niacin) primarily acts by inhibiting the release of free fatty acids from adipose tissue and increasing the clearance of VLDL from the bloodstream, but it does not primarily decrease VLDL production.
**Option C:** Statins, such as atorvastatin and simvastatin, primarily act by inhibiting the enzyme HMG-CoA reductase, which is involved in cholesterol synthesis, and not directly by decreasing VLDL production.
**Option D:** Cholestyramine is a bile acid sequestrant that primarily acts by binding to bile acids in the intestine and preventing their reabsorption, which leads to increased excretion of bile acids and decreased cholesterol levels, but it does not primarily decrease VLDL production.

**Clinical Pearl / High-Yield Fact**
Fibrates are particularly useful in patients with hypertriglyceridemia, as they can effectively lower triglyceride levels and reduce the risk of pancreatitis.

**✓ Correct Answer: A. Fibrates**