Apolipoprotein B (Apo B) is the primary apolipoprotein of chylomicrons, very low-density lipoprotein (VLDL), Intermediate-density lipoprotein (IDL), and Low-density lipoprotein (LDL) particles, which is responsible for carrying fat molecules (lipids). Apo B is divided into two subgroups: Apo B48 and Apo B100, according to the difference in amino acid composition. High levels of Apo B, especially associated with the higher LDL particle concentrations, are the primary driver of plaques that cause vascular disease (atherosclerosis). Overproduction of apolipoprotein B can result in lipid-induced endoplasmic reticulum stress and insulin resistance in the liver. Study showed that the Apo B100 / Apo A1 ratio is more effective at predicting heart attack risk, in patients who had had an acute myocardial infarction, than either the Apo B100 or Apo A1 measure alone.