Question

Which of the following is a peroxisome proliferator-activated receptor-alpha (PPAR-\(\alpha\)) agonist:

• A. Ezetimibe
• B. Niacin
• C. Colesevelam
• D. Gemfibrozil

Hint:

Fibrates like Gemfibrozil and Fenofibrate are PPAR-\(\alpha\) agonists used to lower triglycerides and increase HDL levels in dyslipidemia patients.

Answer 1

The Correct Option is D

Step 1: Understanding PPAR-\(\alpha\) agonists. Peroxisome proliferator-activated receptor-alpha (PPAR-\(\alpha\)) is a nuclear receptor that regulates lipid metabolism. PPAR-\(\alpha\) agonists, also known as fibrates, are used to lower triglyceride levels and increase HDL cholesterol in patients with dyslipidemia. 

Step 2: Role of Gemfibrozil as a PPAR-\(\alpha\) agonist. Gemfibrozil is a fibrate class drug that activates PPAR-\(\alpha\), leading to: 
- Increased fatty acid oxidation. 
- Decreased triglyceride levels. 
- Increased HDL cholesterol levels. 

Step 3: Why other options are incorrect. - (A) Ezetimibe: Inhibits intestinal cholesterol absorption by blocking NPC1L1, not a PPAR-\(\alpha\) agonist. 
- (B) Niacin: Reduces triglycerides and LDL by inhibiting lipolysis but does not act on PPAR-\(\alpha\). 
- (C) Colesevelam: A bile acid sequestrant that lowers LDL cholesterol, unrelated to PPAR-\(\alpha\) activation.

Answer 2

The question asks which drug activates peroxisome proliferator-activated receptor-alpha (PPAR-\(\alpha\)), a nuclear receptor that governs fat and lipoprotein metabolism. Checking the actual mechanism of each lipid lowering drug identifies the one that works through this receptor.

1. Ezetimibe: This drug blocks the NPC1L1 transporter in the intestinal brush border, cutting down cholesterol absorption from the gut. Its target is a transport protein in the intestine, not a nuclear receptor, so it is not a PPAR-\(\alpha\) agonist.
2. Niacin: Niacin lowers triglycerides mainly by inhibiting lipolysis in adipose tissue through a separate receptor pathway, GPR109A, and by reducing hepatic VLDL production. This mechanism does not involve PPAR-\(\alpha\) activation.
3. Colesevelam: This is a bile acid sequestrant that binds bile acids in the intestine, forcing the liver to pull more cholesterol from the blood to make new bile acids. It lowers LDL through this bile acid pathway and has no PPAR-\(\alpha\) activity.
4. Gemfibrozil: This drug belongs to the fibrate class, and fibrates work precisely by activating PPAR-\(\alpha\) in liver and muscle tissue. This activation switches on genes that boost fatty acid oxidation and lipoprotein lipase activity, which together lower triglycerides and raise HDL cholesterol.

Only gemfibrozil works through direct activation of the PPAR-\(\alpha\) receptor, while the other three act through entirely separate mechanisms.

Therefore, the correct answer is Gemfibrozil.