Lipids and Lipoproteins in 2020 – JAMA

The 2019 European Society of Cardiology/European Atherosclerosis Society guidelines for the management of dyslipidaemia became the first major inter- national guideline to state that measurement of apoB levels “is recommended” to help assess ASCVD risk and to estimate the expected clinical benefit from lipid-lowering therapy.

Cholesterol and triglycerides are the major lipids in humans and are transported in plasma by lipoproteins. A lipoprotein is composed of cholesterol, triglycerides, and a single apolipoprotein B100 molecule (apoB) when secreted into plasma by the liver, and is referred to as a very low- density lipoprotein (VLDL). (Figure – step 1)

The triglycerides are rapidly removed by the enzyme lipoprotein lipase and used for energy consumption and storage. As triglycerides are being progressively removed, the lipoprotein is referred to as a VLDL remnant particle. After most of the triglycerides have been removed, the lipoprotein becomes denser and is referred to as a low-density lipoprotein (LDL). (Figure – step 2)

However, it is important to recognize that a VLDL particle, a remnant particle, and an LDL particle are merely different names for the same circulating apoB lipoprotein at different stages in its lifecycle, depending on the lipid content that it carries.

At any point in its lifecycle, regardless of its lipid content, an apoB lipoprotein less than 70 nm in diameter can flux across the endothelial barrier. The trapping of an apoB lipoprotein in the artery wall and subsequent release of its cholesterol content to macrophages is the necessary step for the initiation and progression of an atherosclerotic plaque.2 Over time, the atherosclerotic plaque slowly enlarges as more apoB-containing VLDL, remnant, and LDL particles become trapped in the artery wall (Figure)