What is Apolipoprotein B (Apo B)?

From the Guidelines

Apolipoprotein B (ApoB) is a protein that serves as the primary component of low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL), playing a crucial role in the transport of cholesterol and triglycerides in the bloodstream, with levels providing a more accurate assessment of cardiovascular risk than traditional LDL cholesterol measurements 1. ApoB levels in the blood are a good estimate of the number of atherogenic particles, including VLDL, IDL, and LDL, with each particle containing exactly one ApoB molecule. Key points about ApoB include:

• ApoB is a similar risk marker to LDL cholesterol and a better index of the adequacy of LDL-lowering therapy 1.
• Normal ApoB levels are typically below 100 mg/dL, with optimal levels being under 80 mg/dL for high-risk individuals 1.
• Elevated ApoB levels indicate an increased number of atherogenic particles and a higher risk of atherosclerosis and cardiovascular disease.
• Management of high ApoB levels includes lifestyle modifications and medications that can lower ApoB, such as statins, PCSK9 inhibitors, and ezetimibe.
• ApoB testing is particularly valuable for patients with diabetes, metabolic syndrome, or family history of premature cardiovascular disease, as these conditions can have discordance between LDL-C and ApoB levels 2. The most recent and highest quality evidence suggests that ApoB levels should be <80 and <100 mg/dL for subjects with very high or high CVD risk, respectively 1.

From the Research

Definition and Role of Apolipoprotein B

• Apolipoprotein B (Apo B) is a key component in lipid metabolism, with a single Apo B molecule present in every particle of very low-density lipoprotein, intermediate density lipoprotein, low density lipoprotein, and lipoprotein(a) 3.
• Apo B is a more accurate measure of cardiovascular risk and a better guide to the adequacy of lipid lowering than low-density lipoprotein cholesterol (LDL-C) or non-high-density lipoprotein cholesterol (HDL-C) 4.
• Apo B predicts ischemic cardiovascular events in both genders and is better than LDL cholesterol in this respect 5.

Measurement and Comparison with LDL-C

• Apo B can be measured more accurately than LDL-C or non-HDL-C 4.
• The use of LDL-C to guide the adequacy of lipid lowering therapy represents an interpretive error of the results of the statin/ezetimibe/PCSK9 inhibitor randomized clinical trials, and Apo B should be the primary metric to guide statin/ezetimibe/PCSK9 therapy 4.
• There is growing support for the idea that addition of Apo B measurement to the routine lipid panel for assessing and monitoring patients at risk for cardiovascular disease (CVD) would enhance patient management 6.

Association with Cardiovascular Disease

• High plasma levels of Apo B are a risk factor for atherosclerosis, whereas low levels may provide protection 5.
• Apo B is closely related to atherosclerosis and directly reflects the number of atherogenic lipoprotein particles 7.
• Per SD increment of Apo B was associated with an elevated risk of cardiovascular mortality (HR, 1.13; 95% CI, 1.03-1.24) 7.

Clinical Significance

• Apo B is a single atherogenic lipid marker present in all lipids sub-fractions except HDL-C, and thus, Apo B integrates and extends the information from triglycerides and cholesterol 3.
• The relationship of Apo B with all-cause mortality was U-shaped, and the threshold value was 108 mg/dL 7.
• Apo B was linearly associated with increased risk of cardiovascular mortality and non-linearly associated with all-cause mortality in a U-shaped manner, independently of other cardiovascular risk factors 7.