Apolipoprotein E (apoE) is a vital protein involved in the metabolism of lipids (fats) and cholesterol within the body. Encoded by the APOE gene, apoE plays a crucial role in the transportation, distribution, and clearance of cholesterol and other lipids in the bloodstream. It is a component of several lipoproteins, including chylomicrons, very low-density lipoproteins (VLDL), and high-density lipoproteins (HDL). There are three major isoforms of apoE (apoE2, apoE3, and apoE4), each resulting from different variations in the APOE gene. These isoforms have varying affinities for receptors and differ in their abilities to regulate cholesterol metabolism. ApoE4 is associated with an increased risk of cardiovascular diseases and Alzheimer's disease, while ApoE2 may offer some protective effects against certain conditions. ApoE is predominantly produced in the liver and brain, where it performs diverse functions beyond lipid transport, such as neuro-regulation, synaptic plasticity, and repair processes in the central nervous system. Its multifaceted roles make it a significant target for understanding and potentially treating various disorders related to lipid metabolism and neurological health.