Apolipoprotein E (ApoE) is a protein that plays a crucial role in lipid metabolism and the transport of fats in the bloodstream. It is primarily produced in the liver and brain and helps to carry cholesterol and other lipids to cells throughout the body. ApoE is essential for the proper functioning of lipoproteins, which are particles that transport fats and cholesterol. There are three main genetic variants of ApoE: ApoE2, ApoE3, and ApoE4. These variants can influence an individual's risk of developing certain diseases, particularly Alzheimer's disease. Research has shown that the ApoE4 variant is associated with a higher risk of cognitive decline, while ApoE2 may offer some protective effects.