Low-density-lipoprotein (LDL) cholesterol, also known as "bad" cholesterol, is responsible for clogging arteries and can lead to cardiovascular disease. The LDL balance in your body is maintained in part by your liver. However, when you consume too much cholesterol, your liver can't handle the load, and LDL cholesterol is allowed to clog up your arteries. Knowledge of the liver's role in LDL regulation has led to the creation of drugs that specifically target cholesterol synthesis in the liver.
What Is LDL Cholesterol?
Low-density-lipoprotein (LDL) cholesterol is the kind of cholesterol doctors are referring to when they talk about "bad" cholesterol. It's primarily derived from foods that are high in saturated and trans-fats, and it's bad because it has a tendency to accumulate in your arteries, clogging them up and causing heart attacks or stroke. This is in contrast to high-density-lipoprotein (HDL), or "good" cholesterol, whose job it is to retrieve LDL cholesterol from your circulation, thereby preventing your arteries from becoming clogged.
Cholesterol Uptake Into the Liver
The fats and cholesterol you eat begin their journey in your intestines, where they are absorbed as "chylomicrons." Fats from these chylomicrons may be stored in your body's fatty tissues or used as fuel by your muscle. Alternatively, they may be taken to the liver, where they are taken up by liver cells and turned back into cholesterols that eventually get converted into LDL cholesterol.
How Does the Liver Produce LDL Cholesterol?
The liver is induced to release cholesterol when your body requires it. Cholesterol is released as very-low-density-lipoprotein (VLDL) particles. These are used to generate free fatty acids, which your body uses for energy. VLDL particles that are produced in excess are converted by enzymes in your blood into intermediate-density-lipoprotein (IDL) particles, and then into LDL. LDL is taken back up into your liver, and the process begins again.
What Happens When There Is Too Much LDL Cholesterol?
If there is too much LDL cholesterol for your liver to handle, it can be taken up by special cells in your blood called macrophages. These cells internalize LDL cholesterol and, in the process, wind up attaching to the walls of your arteries in areas that become "fatty streaks." These fatty streaks are the beginning of the process of atherosclerosis, which can cause your arteries to become clogged.
Medical Relevance of the Liver's Relationship With LDL Cholesterol
The fact that the liver produces cholesterol that eventually turns into LDL cholesterol has medical relevance. The statins--for example, simvastatin or rosuvastatin, also known as Crestor--are a group of drugs that were designed to inhibit one of the liver enzymes, known as HMG-Co A reductase, responsible for producing cholesterol. By taking a statin, you can lower the amount of cholesterol your liver produces, thereby lowering the amount of LDL cholesterol in your circulation.
