**Question:** In well-fed state, which of the following inhibit CPT1 on the outer membrane of mitochondria:

A. Rosuvastatin
B. Fenofibrate
C. Gemfibrozil
D. Glycogenolysis

**Core Concept:**

CPT1 (Carnitine Palmitoyl-Transferase 1) is an enzyme responsible for the transport of long-chain fatty acids into mitochondria for beta-oxidation. In well-fed states, the inhibition of CPT1 can lead to reduced fatty acid oxidation, which has implications for lipid management and treatment of hyperlipidemia.

**Why the Correct Answer is Right:**

CPT1 is inhibited by specific drugs in the context of well-fed states. Rosuvastatin (A) and fenofibrate (B) are examples of statins and fibrates, respectively, which are commonly used lipid-lowering medications. These drugs inhibit CPT1, reducing fatty acid oxidation and contributing to their therapeutic effect (lowering cholesterol and triglycerides).

Gemfibrozil (C) is also a fibrate drug, which inhibits CPT1 and has similar effects to fenofibrate in reducing fatty acid oxidation.

Glycogenolysis (D) is the process of breaking down glycogen into glucose, which is not relevant to CPT1 inhibition or fatty acid oxidation in the context of well-fed states.

**Why Each Wrong Option is Incorrect:**

Glycogenolysis does not inhibit CPT1; rather, it is the primary process responsible for glucose production in the liver. This process is activated during fasting states, not well-fed conditions, where CPT1 inhibition is more relevant.

Rosuvastatin (A) and fenofibrate (B) are medications. Rosuvastatin is a statin, while fenofibrate belongs to the fibrate class of drugs, which are lipid-lowering agents. Both drugs inhibit CPT1, thus reducing fatty acid oxidation.

Gemfibrozil (C) is a fibrate drug, which is similar to fenofibrate in inhibiting CPT1, leading to reduced fatty acid oxidation.

The question specifically asks about well-fed states, and since glycogenolysis (D) is activated during fasting, it is not relevant to the context of well-fed states and fatty acid oxidation.

**Clinical Pearl:** Inhibition of CPT1 by statins and fibrates is a crucial pharmacological action that contributes to their lipid-lowering effect. These medications are used for hyperlipidemia management, particularly in well-fed states where fatty acid oxidation is a critical aspect.