Focus on Lipids: High-Density Lipoprotein Cholesterol and Its Associated Lipoproteins in Cardiac and Renal Disease

High-density lipoprotein cholesterol (HDL-C) contains dozens of apoproteins that participate in normal cholesterol metabolism with a reliance on renal catabolism for clearance from the body. The plasma pool of HDL-C has been an excellent inverse predictor of cardiovascular events. However, when HDL-C concentrations have been manipulated with the use of niacin, fibric acid derivatives, and cholesteryl ester transferase protein inhibitors, there has been no improvement in outcomes in patients where the low-density lipoprotein cholesterol has been well treated with statins. Apolipoprotein L1 (APOL1) is one of the minor apoproteins of HDL-C, newly discovered in 1997. Circulating APOL1 is a 43-kDa protein mainly found in the HDL3 subfraction. In patients with chronic kidney disease (CKD), mutant forms of APOL1 have been associated with rapidly progressive CKD and end-stage renal disease (ESRD). Because mutant forms of APOL1 are more prevalent in African Americans compared to Caucasians, it may explain some of the racial disparities seen in the pool of patients with ESRD in the United States. Thus, HDL-C is an important lipoprotein carrying apoproteins that play roles in vascular and kidney disease.