What is the difference between Apolipoprotein B (ApoB) and Lipoprotein(a) (Lp(a))?

From the Guidelines

Apolipoprotein B and Lipoprotein(a) are distinct entities with different roles in lipid transport and cardiovascular risk, with Apolipoprotein B being a major structural protein of LDL and VLDL, and Lipoprotein(a) being a specialized lipoprotein with atherogenic properties. The key difference between the two lies in their structure and function, as well as their responsiveness to lifestyle factors and genetic determination. Apolipoprotein B (ApoB) is a primary protein component of LDL, essential for its assembly and secretion, and serves as a ligand for LDL receptor binding, facilitating cholesterol delivery to tissues 1. In contrast, Lipoprotein(a), or Lp(a), is a specialized lipoprotein consisting of an LDL-like particle with an additional protein called apolipoprotein(a) covalently bound to the ApoB-100 component, giving it unique atherogenic properties 1.

Some of the key points to consider when differentiating between Apolipoprotein B and Lipoprotein(a) include:

• Apolipoprotein B levels are more responsive to diet and lifestyle factors, whereas Lipoprotein(a) levels are largely genetically determined 1
• Elevated levels of both Apolipoprotein B and Lipoprotein(a) are associated with increased cardiovascular risk, but Lipoprotein(a) is considered an independent risk factor that remains elevated even when LDL is well-controlled with statins 1
• The measurement of Apolipoprotein B may have advantages in certain circumstances, particularly in patients with hypertriglyceridemia, and a level >130 mg/dL corresponds to an LDL-C level $160 mg/dL and constitutes a risk-enhancing factor 1
• Lipoprotein(a) levels are recommended to be measured in patients at high risk of cardiovascular disease, and a level $50 mg/dL or $125 nmol/L may be considered a risk-enhancing factor 1

Overall, understanding the differences between Apolipoprotein B and Lipoprotein(a) is crucial for assessing cardiovascular risk and guiding treatment decisions, with the most recent and highest quality evidence supporting the use of these biomarkers in clinical practice 1.

From the Research

Difference between Apolipoprotein B and Lipoprotein(a)

• Apolipoprotein B (apoB) and Lipoprotein(a) (Lp(a)) are two distinct lipoproteins that play a crucial role in cardiovascular risk assessment.
• ApoB is a primary component of low-density lipoprotein (LDL) and is recognized as a key lipid risk marker, reflecting the number of atherogenic lipoproteins 2.
• Lp(a), on the other hand, is a highly atherogenic lipoprotein characterized by apolipoprotein(a) covalently bounded to apoB-100 (apoB) 3.

Metabolic Pathways

• The fractional catabolism of Lp(a) is slower than that of LDL-apoB particles, implying that different metabolic pathways are involved in the catabolism of these lipoproteins 4.
• The metabolism of apo(a) and apoB within plasma Lp(a) particles in patients on statins remains unclear, but studies suggest that the apo(a) and apoB proteins within Lp(a) particles have similar fractional catabolic rates (FCR) and are therefore tightly coupled as an Lp(a) holoparticle 3.

Atherogenicity

• Lp(a) is recognized as a causal factor for coronary heart disease (CHD) and its atherogenicity relative to that of LDL on a per-particle basis is estimated to be approximately 6-fold greater 5.
• The atherogenicity of Lp(a) is substantially greater than that of LDL, making Lp(a) a key target for drug-based intervention in a significant proportion of the at-risk population 5.
• Elevated count of Lp(a) adds additional risk, and thus adequate assessment of atherogenic risk from dyslipidemia is best accomplished by consideration of both apoB-P and Lp(a) concentrations 6.