Apolipoprotein A-I (ApoA-I) is a protein that plays a crucial role in lipid metabolism. It is the main component of high-density lipoprotein (HDL), often referred to as "good cholesterol." ApoA-I helps transport cholesterol from the tissues back to the liver for excretion, thus contributing to the regulation of cholesterol levels in the body. Additionally, ApoA-I is involved in the formation of HDL particles and enhances the activity of enzymes that break down fats. Higher levels of ApoA-I are associated with a lower risk of cardiovascular diseases, making it an important factor in heart health and overall metabolic function.