ApoB, ApoA

ApoA and ApoB are essential proteins involved in lipid metabolism and transport within the body. ApoA, primarily found in high-density lipoproteins (HDL), plays a crucial role in the reverse cholesterol transport pathway, facilitating the removal of cholesterol from peripheral tissues to the liver for excretion. In contrast, ApoB is a key component of low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL), primarily responsible for transporting cholesterol and triglycerides from the liver to peripheral tissues. Together, these proteins play vital roles in maintaining lipid homeostasis and are integral to understanding cardiovascular health and disease risk.

ApoA is made in the gut as a part of compounds called chylomicrons. ApoB is made in the liver and gets released into the blood in the form of VLDL. VLDL loses fats called triglycerides to form IDL and eventually LDL. Apolipoprotein B helps LDL bind to receptors on cells and deliver cholesterol. It is also necessary for liver cells to bind LDL and remove it from the blood. Each molecule of VLDL, IDL, and LDL contains exactly one molecule of apoB, this makes apoB a measure of total non-HDL lipoproteins in circulation. In other words, apoB is a measure of lipoprotein carrying cholesterol. ApoB-containing lipoproteins are the main contributors to the hardening of the arteries (atherosclerosis) and heart disease. An increasing ratio of ApoB to ApoA represents increased cardiovascular risk due to a relative increase in atherogenic ApoB or a decrease in protective ApoA. The ratio is strongly related to risk of myocardial infarction and stroke, as well as other cardiovascular disorders.

The apoB to apoA ratio is considered a better predictor of cardiovascular risk compared to LDL and HDL cholesterol levels because it provides a direct assessment of the number of atherogenic particles relative to protective particles in the bloodstream.

Though there are some doctors who recommend getting ApoB as low as possible, this is not well supported. In fact, research supports that ApoB may help defend the body against harmful bacteria such as Staphylococcus aureus by interfering with a process called quorum sensing. Quorum sensing is how bacteria interact with each other to coordinate the necessary actions for survival.