aka: apoB100-calc / ApoB 100 / Apoprotein B100

Apolipoprotein B100 (apoB100) is a building block of very low-density lipoproteins (VLDLs), intermediate-density lipoproteins (IDLs), and low-density lipoproteins (LDLs). These related molecules all transport fats and cholesterol in the bloodstream.

Low-density lipoproteins are the primary carriers of cholesterol in the blood. Apolipoprotein B-100 allows these particles to attach to specific receptors on the surface of cells, particularly in the liver. The receptors transport low-density lipoproteins into the cell, where they are broken down to release cholesterol. The cholesterol is then used by the cell, stored, or removed from the body.

Lipoproteins are composed of the following:

– proteins (apolipoproteins)
– phospholipids
– triglycerides
– cholesterol

The lipoproteins vary in the major lipoprotein present, and the relative contents of the different lipid components. ApoB is an important component of many of the most atherogenic lipoprotein particles.

ApoB occurs in 2 main forms, apoB 48 and apoB 100. ApoB 48 is synthesized mainly by the small intestine. ApoB 100 is the apolipoprotein found in lipoproteins synthesized by the liver. Therefore, from the viewpoint of atherosclerosis and cardiovascular risk, apoB100 is the important one. ApoB 48 is primarily found in chylomicrons.

ApoB 100 is found in chylomicrons, VLDL, IDL, LDL and LP(a) particles. All these particles are atherogenic. Each of these particles contains a single apoB molecule. Therefore, measurements of apoB represent the total burden of the main lipoprotein particles involved in the atherosclerotic process.

Usually, 85-90 percent of apoB represent LDL particles. Thus, apoB reflects particle concentration, similar to LDL-P. Although measurements of apoB are not widely available, the assay has been standardized and does not require a fasting sample.

Several studies have shown that apoB may be a better predictor of cardiovascular disease risk than LDL-C. Furthermore, it has been shown that apoB may be elevated despite normal or low concentrations of LDL-C. ApoB also appears to predict on-treatment risk, when LDL-C has been lowered by statin therapy. The INTERHEART study found that the apoB/apoA1 ratio is more effective at predicting heart attack risk, than either the apoB or apoA1 measure alone.

Apo B containing lipoproteins are the ones that are most likely to enter the wall of the arteries. They are capable of trafficking cholesterol into the artery wall, and if present in increased numbers they may be the main initiating factor in atherosclerosis. Retention of ApoB containing lipoprotein particles within the arterial wall is an essential part of the process.

Normal Range For ApoB:

– Usually less than 100 mg/dL is considered desirable in low or intermediate risk individuals.

– Less than 80 mg/dL is desirable in high risk individuals, such as those with cardiovascular disease or diabetes.

References:
– https://www.ncbi.nlm.nih.gov/pubmed/8759066
– https://www.ncbi.nlm.nih.gov/pubmed/11755609
– https://www.theheart.org/article/155691.do
– https://www.ncbi.nlm.nih.gov/pubmed/15345795
– https://www.ncbi.nlm.nih.gov/pubmed/21960651
– https://www.ncbi.nlm.nih.gov/books/NBK22336/#A3634
– https://ghr.nlm.nih.gov/gene/APOB