Apolipoprotein B (Apo B) is the major apolipoprotein found in chylomicrons, very low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), and low-density lipoproteins (LDL). It is responsible for transporting lipid molecules (lipids). Due to differences in amino acid composition, Apo B can be divided into two subtypes: Apo B48 and Apo B100. Elevated levels of Apo B, particularly when combined with high levels of LDL, are a major driving force behind vascular diseases such as atherosclerosis. Excess Apo B in the liver leads to lipid-induced endoplasmic reticulum stress and insulin resistance. Studies have shown that the Apo B100/Apo A1 ratio is more effective in predicting the risk of cardiac events in patients with acute myocardial infarction compared to measuring Apo B-100 or Apo A1 alone.