Dose‑dependent association of smoking exposure with HDL subfraction cholesterol content

Smoking has a significant effect on plasma lipid concentrations, especially high‑density lipoprotein (HDL)-associated cholesterol and its distribution across HDL subfractions, which are critical for cardiovascular health. The present study aimed to investigate the association between smoking and HDL‑cholesterol (HDL‑C) concentration, as well as the cholesterol distribution between different HDL subfractions, and other lipid parameters, including total cholesterol (TC), low‑density lipoprotein cholesterol (LDL‑C), triglycerides (TG), apolipoprotein AI (ApoAI), apolipoprotein B100 (ApoB100), and the TG/HDL‑C and ApoB100/ApoAI ratios, in a Hungarian cohort of 314 (137 nonsmokers and 177 smokers). HDL‑associated cholesterol was fractionated into ten electrophoretic subfractions (HDL‑1 to HDL‑10) and three subclasses (HDL‑L, HDL‑I, HDL‑S) using the Lipoprint^® HDL system. Smoking exposure was characterized using five indicators: current smoking status, cigarettes per day (CPD), duration of smoking (DoS), pack‑years, and the Heaviness of Smoking Index (HSI). Multiple regression models were applied, and significance was defined as p < 0.05 after Benjamini-Hochberg correction. All smoking‑related indicators were associated with a decrease in the cholesterol content of HDL subfractions. The strongest associations were observed for HDL‑4, HDL‑5, HDL‑6, and HDL‑7 (p < 0.001-0.033), as well as for the HDL‑I subclass (p < 0.001). Regarding the broader lipid profile, all indicators were significantly associated with lower HDL‑C (p < 0.001) and ApoAI (p = 0.001-0.003), and higher TG (p = 0.012-0.036), TG/HDL‑C ratio (p < 0.001-0.004), and ApoB100/ApoAI ratio (p < 0.001-0.015). In conclusion, smoking significantly reduces the cholesterol content of HDL subfractions, particularly within HDL‑4 to HDL‑7 and the HDL‑I subclass. Although total cholesterol levels were not significantly altered, smoking induced an atherogenic shift in lipid composition by lowering HDL‑C and increasing TG levels, which may contribute to or accelerate the development of atherosclerosis.