Dysfunctional high-density lipoprotein: an updated review

High-density lipoprotein (HDL) has earned its reputation as "good" cholesterol in cardiovascular health, primarily because of its strong inverse association with cardiovascular disease. A potential mechanism for this association is its ability to promote cholesterol efflux capacity (CEC) and consequently reduce the buildup of cholesterol in arterial plaque. However, recent research underscores the importance of not only maintaining high HDL cholesterol (HDL-C) levels but also ensuring the functionality and quality of HDL particles. HDL particles exhibit various other atheroprotective activities, including anti-inflammatory, antioxidant, and vasodilatory properties. Collectively, these functions are thought to contribute to reducing cardiovascular risk beyond mere cholesterol transport. Both acute and chronic inflammation can induce structural and functional changes in HDL, potentially rendering the particles pro-inflammatory. Factors that increase inflammation, such as lifestyle choices, autoimmune diseases, and oxidative stress, can adversely affect HDL functionality. Dysfunctional HDL, such as electronegative HDL H5 or HDL isolated from patients with cardiovascular disease (CVD), may lose its protective properties and even contribute to CVD progression by promoting inflammation, oxidative stress, and endothelial damage. Recent studies indicate that the CEC of HDL particles may serve as a more critical determinant of atheroprotection than the absolute concentration of HDL-C. This review emphasizes the need to focus on both quantity and quality of HDL to reduce cardiovascular risk more effectively. Understanding the mechanisms behind HDL's protective effects provide valuable insights into heart health and potential therapeutic strategies.