ApoB100

ApoB-100, or apolipoprotein B-100, is a major structural protein of atherogenic lipoproteins. It is encoded by the APOB gene on chromosome 2 and is produced in the liver as part of very-low-density lipoproteins (VLDL). A tissue-specific RNA editing event generates apoB-48 in enterocytes for chylomicron formation, resulting in two main isoforms: apoB-100 and apoB-48.

ApoB-100 plays a central role in lipoprotein assembly and metabolism. It acts as a scaffold for lipid incorporation into VLDL and contributes to the formation of low-density lipoprotein (LDL) after triglyceride lipolysis. A single apoB-100 molecule is present on each VLDL/LDL particle, and it functions as the ligand for the LDL receptor, enabling receptor-mediated endocytosis and hepatic clearance of cholesterol-rich particles. The presence of apoB-100 thus links particle number to cholesterol transport.

Genetics and disease relevance. Variants in APOB can affect lipoprotein production or receptor binding. Mutations that reduce apoB-100’s affinity for the LDL receptor cause familial defective apoB-100, leading to elevated LDL cholesterol and increased cardiovascular risk. Severe truncating variants can cause familial hypobetalipoproteinemia, with reduced LDL levels and potential fat malabsorption. More common polymorphisms can modestly influence lipid levels and cardiovascular risk, illustrating how apoB-100 relates to lipoprotein biology and disease.

Clinical implications. ApoB-100 concentration reflects the number of atherogenic particles and is used as a biomarker for cardiovascular risk, sometimes offering advantages over LDL cholesterol in certain patients. Measurement of apoB can aid in dyslipidemia assessment and guide therapeutic decisions aimed at reducing apoB-containing lipoproteins.