What are Apolipoprotein B (Apo B) and Lipoprotein(a) (Lp(a))?

From the Guidelines

ApoB and Lp(a) are crucial blood markers that help assess heart disease risk, with ApoB being a protein on harmful cholesterol particles like LDL and Lp(a) being a specialized type of LDL cholesterol with an extra protein attached, both providing valuable information beyond standard cholesterol tests. ApoB (Apolipoprotein B) is a protein found on the surface of harmful cholesterol particles like LDL, and it gives a more accurate picture of risk than standard cholesterol tests because each particle has exactly one ApoB molecule 1. High ApoB levels mean more particles that can deposit in artery walls, increasing heart attack and stroke risk.

Key Points About ApoB and Lp(a)

• Lp(a), or Lipoprotein(a), is a specialized type of LDL cholesterol with an extra protein attached, and it's largely determined by genetics and doesn't respond well to lifestyle changes 1.
• Lp(a) is particularly dangerous because it promotes blood clots and accelerates plaque buildup in arteries, and unlike regular cholesterol, Lp(a) levels stay relatively constant throughout life 1.
• Both markers provide valuable information beyond standard cholesterol tests, helping doctors better assess cardiovascular risk and potentially guide more personalized treatment decisions.
• If either is elevated, your doctor might recommend more aggressive cholesterol-lowering strategies or closer monitoring, with a relative indication for ApoB measurement being triglyceride $200 mg/dL and an Lp(a) level $50 mg/dL or $125 nmol/L being considered a risk-enhancing factor 1. Some of the key factors to consider when evaluating ApoB and Lp(a) include:
• Family history of premature ASCVD or personal history of ASCVD not explained by major risk factors, which are relative indications for Lp(a) measurement 1.
• The level of ApoB and Lp(a), with a level >130 mg/dL corresponding to an LDL-C level $160 mg/dL and constituting a risk-enhancing factor for ApoB, and an Lp(a) level $50 mg/dL or $125 nmol/L being considered a risk-enhancing factor 1.

Importance of ApoB and Lp(a) in Clinical Practice

• The measurement of ApoB and Lp(a) can provide valuable information for assessing cardiovascular risk and guiding treatment decisions, especially in patients with hypertriglyceridemia or a family history of premature ASCVD 1.
• The European Society of Cardiology (ESC) guidelines recommend measuring Lp(a) in patients at high risk of cardiovascular disease (CVD) and to target levels below 50 mg/dL 1. Overall, ApoB and Lp(a) are important markers that can help identify individuals at high risk of cardiovascular disease, and their measurement can inform treatment decisions and guide personalized care.

From the Research

Apolipoprotein B (Apo B) and Lipoprotein(a) (Lp(a)) Explained

• Apolipoprotein B (Apo B) is a protein that is part of low-density lipoprotein (LDL) cholesterol, also known as "bad" cholesterol 2, 3, 4.
• Apo B is the main structural protein of LDLs, triglyceride-rich lipoproteins, and lipoprotein(a), and is crucial for their formation, metabolism, and atherogenic properties 3.
• Lipoprotein(a) (Lp(a)) is a type of LDL cholesterol-like particle that is bound to apolipoprotein(a) 5.
• Lp(a) is considered a novel marker of cardiovascular disease and acts through induction of vascular inflammation, atherogenesis, calcification, and thrombosis 5.
• Elevated levels of Lp(a) are associated with an increased risk of cardiovascular disease, including atherosclerotic cardiovascular disease and calcific aortic valve stenosis 5.

Role of Apo B in Cardiovascular Disease

• Apo B is a more accurate indicator of cardiovascular risk than either total cholesterol or LDL cholesterol 2, 4, 6.
• Apo B levels indicate the atherogenic particle concentration independent of the particle cholesterol content, which is variable 4.
• The number of apo B-containing lipoproteins is a direct measure of the number of circulating atherogenic lipoproteins 4.

Lp(a) and Cardiovascular Risk

• Elevated Lp(a) levels are associated with a residual cardiovascular risk despite traditional risk factor optimization, including LDL cholesterol reduction 5.
• Compelling evidence from pathophysiological, observational, and genetic studies suggests a potentially causal association between high Lp(a) levels and cardiovascular disease 5.
• Emerging nucleic acid-based therapies, such as antisense oligonucleotides and small interfering RNAs, are being developed to lower Lp(a) levels and reduce cardiovascular risk 5.