Remnant lipoproteins: are they equal to or more atherogenic than LDL?

PURPOSE OF REVIEW: To critically appraise new insights into the biology of remnant lipoproteins and their putative role in the pathophysiology of atherosclerotic cardiovascular disease, and to compare the atherogenicity of remnant particles with that of low-density lipoproteins (LDL). RECENT FINDINGS: New in-vivo stable isotope tracer studies of the kinetics of apoB48 and apoB100-containing lipoproteins in postprandial conditions have revealed that apoB48-containing very low-density lipoproteins (VLDL) accumulated markedly in hypertriglyceridemic patients. These intestinally-derived particles were cleared slowly, and represented up to 25% of circulating VLDL; as part of the remnant particle population, they may increase cardiovascular risk. Importantly, the PCSK9 inhibitor, evolocumab, was shown to reduce remnant levels (-29%) during the postprandial period in diabetic patients on statin therapy - an effect which may be additive to that of LDL-cholesterol reduction in conferring cardiovascular benefit. In recent Mendelian randomization studies, the effect of lowering triglyceride-rich lipoproteins or LDL-cholesterol translated to similar clinical benefit per unit of apoB. Finally, in randomized trials involving statin-treated patients with atherosclerotic cardiovascular disease, remnant cholesterol levels were associated with coronary atheroma progression independently of LDL-cholesterol. SUMMARY: Overall, data from observational studies in large cohorts, Mendelian randomization studies, meta-regression analyses, and post-hoc analyses of randomized trials are consistent with the contention that remnants are highly atherogenic particles and contribute to the atherosclerotic burden in an equivalent manner to that of LDL.

The ATP-binding cassette transporter subfamily A member 1 (ABC-A1) and type 2 diabetes: an association beyond HDL cholesterol.

Recent findings from several groups demonstrate that ABC-A1 participates in the pathogenesis of the metabolic syndrome and type 2 diabetes. A variant of the ABC-A1 gene (R230C) is associated with the metabolic syndrome and its co-morbidities in Mexicans. Its presence is associated with an increased risk for obesity, the metabolic syndrome and type 2 diabetes. R230C is found exclusively in Amerindian and Amerindian-derived populations. Moreover, animal models confirm the participation of ABC-A1 in the pathogenesis of diabetes. Mice lacking AbcA1 specifically in beta cells had glucose intolerance at 8 weeks of age. The absence of ABC-A1 led to cholesterol accumulation within the beta cell plasma membrane, suggesting that cholesterol may play a role in the insulin secretory pathway. In conclusion, ABC-A1 may be more than a determinant of HDL-cholesterol. It may provide a link between components of the metabolic syndrome and atherosclerosis.