What is Apolipoprotein B (ApoB)?

From the Guidelines

Apolipoprotein B (ApoB) is a protein that plays a crucial role in the transport of cholesterol and fat in the bloodstream, serving as the primary structural protein of several lipoproteins including very low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), and low-density lipoproteins (LDL).

Key Points

• ApoB is an accurate measure of the total number of potentially atherogenic particles in circulation, with each lipoprotein particle containing exactly one ApoB molecule 1.
• High levels of ApoB in the blood are strongly associated with an increased risk of cardiovascular disease, as these particles can contribute to the buildup of plaque in artery walls 1.
• ApoB works by binding to specific receptors on cell surfaces, particularly in the liver, facilitating the uptake and clearance of cholesterol from the bloodstream.
• Measuring ApoB levels can provide valuable information about cardiovascular risk, sometimes offering more precise risk assessment than traditional cholesterol measurements, especially in patients with conditions like diabetes or metabolic syndrome where standard lipid profiles might not fully capture risk 1.

Clinical Significance

• ApoB has been shown to be equal to LDL-C in risk prediction, and may even be a better treatment target than LDL-C in some cases 1.
• Non-HDL cholesterol, which is highly correlated with ApoB levels, has been shown to be a superior predictor of CHD risk compared to LDL cholesterol in several studies 1.
• The use of ApoB as a treatment target is supported by several studies, including the Treating to New Targets (TNT) and Incremental Decrease in End Points through Aggressive Lipid Lowering (IDEAL) trials, which found that on-treatment ApoB and non-HDL cholesterol were better predictors of reduced CVD events than levels of LDL cholesterol 1.

From the Research

Definition and Structure of Apolipoprotein B

• Apolipoprotein B (apoB) is a critical structural protein of atherogenic lipoproteins, with two major isoforms: apoB48 and apoB100 2.
• ApoB48 is found in chylomicrons and chylomicron remnants, while apoB100 is contained in very-low-density lipoprotein (VLDL), intermediate density lipoprotein, LDL, and lipoprotein(a) 2.
• The unique one apoB per particle ratio makes plasma apoB concentration a direct measure of the number of circulating atherogenic lipoproteins 2.

Role of Apolipoprotein B in Cardiovascular Risk

• ApoB is considered a more accurate indicator of cardiovascular risk than total cholesterol or LDL cholesterol 2.
• The 2019 European Society of Cardiology/European Atherosclerosis Society Guidelines concluded that apoB was a more accurate measure of cardiovascular risk and a better guide to the adequacy of lipid lowering than LDL-C or non-HDL-C 3.
• Studies have shown that on-treatment apoB is associated with residual vascular risk after treatment with potent statin therapy 4.

Measurement and Clinical Significance of Apolipoprotein B

• ApoB can be measured more accurately than LDL-C or non-HDL-C 3.
• The substitution of apoB for LDL-C in cardiovascular disease prevention guidelines has been deemed unjustified, but discussions continue 2.
• Meta-regression analyses have shown that reducing apoB levels is associated with decreased cardiovascular risk, with a relative risk of 0.93 for major adverse cardiovascular events per 10 mg/dL decrease in apoB 5.