LDL and HDL subfractions, dysfunctional HDL: treatment options.

Low-density lipoproteins (LDL) are considered as important risk factors for cardiovascular diseases (CVD), while highdensity lipoproteins (HDL) are well recognized for their putative role in reverse cholesterol transport and other atheroprotective functions. Both LDL and HDL are heterogeneous in nature, including various subfractions depending on the method of isolation (≥ 7 LDL and 10 HDL subspecies, respectively). While it is established that small, dense LDL (sdLDL) have atherogenic potential, the role of different HDL subfractions is still largely unclear. The majority of clinical studies suggest an atheroprotective role of larger HDL particles, although recent work has highlighted the role of dysfunctional HDL within different subfractions. Several therapeutic approaches are able to primarily target cholesterol concentration in LDL or HDL. Certain drugs, such as niacin, statins and fibrates target multiple lipid traits (i.e. pleiotropic drug effects), while cholesterol ester transfer protein (CETP) inhibitors are able to increase plasma HDL cholesterol levels. Statins represent the most used lipid-lowering drugs, but there is a continued interest in the development of novel therapeutic approaches, including those that might affect dysfunctional HDL. Targeting distinct LDL and HDL subfractions may potentially reduce the residual risk seen in clinical endpoint trials.