Triglyceride-rich lipoproteins, remnants and atherosclerotic cardiovascular disease: What we know and what we need to know

Apolipoprotein B-containing triglyceride-rich lipoproteins (TRLs) -chylomicrons, very low-density lipoproteins (VLDL), their remnants, and intermediate-density lipoproteins (IDL) - are recognised as key contributors to atherosclerotic cardiovascular disease (ASCVD). On a per particle basis, genetic and clinical evidence indicates that TRL/remnants exhibit a greater atherogenic potential than LDL and evidence points to this being mediated by enhanced arterial wall retention of TRLs, the pro-inflammatory actions of their constituent apolipoproteins and cargo of cholesterol and bioactive lipids, and their capacity to induce endothelial dysfunction. Despite the strong association between plasma triglyceride levels and ASCVD, TRL-lowering trials have produced inconsistent, often negative results. The answer to this conundrum, as explored here, likely lies in the complexity of TRL structure, composition and metabolism, and in the dynamic influence that TRLs have on the properties of LDL, the most abundant atherogenic lipoprotein. The substantial heterogeneity in the TRL/remnant/IDL spectrum means that these particles present a wide range of potentially pathogenic factors to the artery wall in the form of major and minor lipids and a variety of surface apolipoproteins. Significant gaps exist in our knowledge: how are TRL remodelled during their lifetime in the bloodstream to become cholesterol-enriched lipoproteins; which are the most relevant TRL subspecies or TRL constituents, that initiate and progress the formation of atherosclerotic lesions; and what are the prime targets for effective intervention. Critical to the design of future triglyceride-lowering prevention trials will be the development of superior biomarkers of TRL/remnant atherogenicity and the development of a precision medicine approach to ASCVD prevention.