Functionally defective high density lipoprotein is pro-oxidant : a deviation from normal atheroprotective character

High-density lipoprotein is a potential life saving antiatherogenic molecule. However, not all HDL is functionally similar, it can become dysfunctional and may increase atherosclerotic risk. At present, it is unknown, which structural alterations of HDL are essential accounting for its defective functionality and the precise pro-atherogenic mechanisms of action. This study is aimed at identification of the possible prevalence of dysfunctional HDL in subjects and its compositional and functional characterization in comparison to that of functional HDL. HDL was isolated from serum by ultracentrifugation and subjected to functional assays. HDL from majority of healthy subjects showed remarkable antioxidant property by inhibiting LDL oxidation. However, in those healthy subjects with systemic oxidative stress and inflammatory response as well as in those with known coronary heart disease, HDL was dysfunctional and promoted LDL oxidation. Dysfunctional HDL was truly pro-oxidant as it induced intracellular reactive oxygen species formation in cultured monocytes/macrophages. Functional deficiency in HDL did not show any association with HDL-cholesterol content. However, its characterization showed an enrichment of triglycerides, phospholipids, lipid peroxides, and diminished activity of paraoxonase-1, compared to functional HDL, which might render the particle dysfunctional and pro-oxidant.This study demonstrates the prevalence of dysfunctional HDL even among healthy subjects, despite normal HDL-C level, and in majority of subjects with known CHD, which is pro-oxidant in nature that might promote vascular inflammation and atherogenesis. The functional assay of HDL could lead to improved predictive accuracy of cardiovascular disease risk associated with circulating HDL.