Apo B/apo A-I ratio and cardiovascular risk prediction.

Apolipoproteins are proteins associated with lipids in lipoprotein particles. They play important roles in lipoprotein metabolism, such as transport of these hydrophobic molecules in plasma aqueous medium, binding to specific receptors in cell surface to correctly direct lipids to target organs and body tissues, and activation or inhibition of enzymes involved in lipid metabolism. Apolipoprotein A-I (apo A-I) is the largest component of the high density lipoprotein (HDL) particle, representing approximately 45% of its molecular mass. Moreover, it acts as a co-factor for the enzyme lecithin cholesterol acyl transferase and as a mediator in transfer of cholesterol from cells to HDL particles, which are important processes for the reverse transport of cholesterol to the liver. Apolipoprotein B (apo B) is present in chylomicrons, such as apo B-48, and in very low density lipoproteins (VLDL), intermediate density lipoprotein (IDL) and low density lipoprotein (LDL), such as apo B-100, which is responsible for binding the lipoprotein to its specific tissue receptor. Apo B is the main functional protein for transporting cholesterol to peripheral cells. About 90% of protein in LDL is composed of apo B.