Apolipoprotein E (ApoE) is a polymorphic protein that plays a vital role in the metabolism and transport of lipids in the body. Specifically, ApoE is a major component of plasma lipoproteins, including chylomicrons (CM), very low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), and some high-density lipoproteins (HDL). ApoE is primarily synthesized in the liver, but it is also produced in other tissues such as the brain, kidneys, bones, adrenal glands, and macrophages. It participates in the transport, storage, and excretion of lipids, including cholesterol and triglycerides. It also serves as a ligand for low-density lipoprotein (LDL) receptors and chylomicron remnant receptors on hepatocytes, facilitating the clearance of these lipoproteins from the circulation. This process plays a crucial role in maintaining lipid homeostasis. Furthermore, ApoE has been implicated in various other biological processes, including neuroprotection, immune regulation, and tissue repair. Recent studies have suggested that ApoE may play a role in the development of neurological disorders such as Alzheimer's disease.