Biochemistry of Lipoprotein Metabolism

Biochemistry of Lipoprotein Metabolism

Lipoproteins are complex molecules made up of lipids and proteins that play a crucial role in the transport of fats throughout the body. They are classified based on their density, which is determined by the amount of protein they contain. The major classes of lipoproteins include chylomicrons, very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Each of these lipoproteins has a specific function in the body’s lipid metabolism.

Chylomicron Metabolism

Chylomicrons are the largest and least dense lipoproteins and are responsible for transporting dietary fats from the intestines to the liver and other tissues. Once the chylomicrons deliver their cargo, they are broken down by lipoprotein lipase, an enzyme found in the capillaries of adipose tissue and muscle. This releases free fatty acids and glycerol, which can be taken up by cells for energy or storage.

VLDL and LDL Metabolism

VLDLs are produced in the liver and are responsible for transporting endogenous triglycerides to tissues. As VLDLs circulate in the bloodstream, they undergo lipolysis by lipoprotein lipase, converting them into intermediate-density lipoproteins (IDLs) and eventually into LDLs. LDLs are often referred to as «bad cholesterol» because they can contribute to the buildup of plaque in the arteries, leading to atherosclerosis and cardiovascular disease.

HDL Metabolism

HDLs are produced in the liver and intestine and are responsible for picking up excess cholesterol from cells and tissues and transporting it back to the liver for excretion. HDLs are often referred to as «good cholesterol» because they help remove cholesterol from the bloodstream, reducing the risk of atherosclerosis. The process of transferring cholesterol from peripheral tissues to HDL is known as reverse cholesterol transport.