HDL subfractions analysis: a new laboratory diagnostic assay for patients with cardiovascular diseases and dyslipoproteinemia.

Objective: The HDL family forms a protective part of plasma lipoproteins. It consists of large HDL, intermediate HDL, and small HDL subclasses. The large HDL and intermediate HDL subclasses are considered anti-atherogenic parts of the HDL family. The atherogenicity of the small HDL subclass is currently the subject of much discussion. In the patient group with the diagnosis of cardiovascular disease (arterial hypertension, coronary heart disease) and in individuals with a non-atherogenic hypercholesterolemia, a type of lipoprotein profile (either a non-atherogenic phenotype A, or an atherogenic phenotype B) was identified, and a concentration of small dense LDL (sdLDL) was analyzed. The aim of this study was to identify the major representative of the HDL subclasses in the individuals with cardiovascular diseases, who had an atherogenic lipoprotein phenotype B, and in the individuals with the diagnosis of non-atherogenic hyper-betalipoproteinemia LDL1,2, who had a non-atherogenic lipoprotein phenotype A.

Methods: Identification of the specific lipoprotein phenotype and a quantitative analysis of small dense LDL was performed by an electrophoresis method on polyacrylamide gel (PAG), using the Lipoprint LDL system. For a quantitative analysis of HDL subclasses, i.e., large HDL, intermediatete HDL, and small HDL, in subjects with newly diagnosed cardiovascular diseases (arterial hypertension and coronary heart disease), and in subjects with a non-atherogenic hypercholesterolemia (hyper-betalipoproteinemia LDL1,2), we used an innovative electrophoresis method on polyacrylamide gel (PAG), the Lipoprint HDL system. With regard to lipids, total cholesterol and triglycerides in plasma were analyzed by an enzymatic CHOD PAP method. A control group consisted of a group of healthy normolipidemic volunteers without signs of clinically manifested impairment of the cardiovascular system.

Results: In the patient group with the diagnosis of arterial hypertension (p<0.0002) and coronary heart disease (p<0.0001), (both are classified as cardiovascular diseases), the large HDL subclass was significantly decreased and the small HDL subclass was increased (p<0.0001). The concentration of the intermediate HDL subclass did not differ from that of the control group. These results were in accordance with an atherogenic lipoprotein phenotype B in individuals with the diagnosis of cardiovascular diseases, where, using a Lipoprint LDL analysis, a high concentration of atherogenic small dense LDL (p<0.0001) was found. Thus, it seems that the small HDL subclass represents an atherogenic part of the HDL family. Conversely, an increased concentration of total HDL (p<0.0001), large HDL (p<0.005), and intermediate HDL subclasses (p<0.0001) was found in a group of subjects with a non-atherogenic hyper-betalipoproteinemia LDL1,2.The concentration of the small HDL subclass did not differ from that of the control group. In this non-atherogenic lipoprotein profile, only traces of atherogenic small dense LDL were identified.

Conclusions: The advantages of this new method includes: (i) Identification of ten HDL subfractions with Lipoprint HDL analysis (large HDL1-3, intermediate HDL 4-7, and small HDL 8-10) . (ii) Discovery of a high concentration of small HDL in plasma lipoproteins in patients with cardovascular diseases with an atherogenic lipoprotein phenotype B, confirms that the atherogenic subclass of HDL family is attributable to small HDL. (iii) Presence of a low concentration of small HDL in non-atherogenic hypercholesterolemia also confirms the atherogenic characteristics of the small HDL subclass per se. (iv) Presence of small dense LDL is definitive to diagnose an atherogenic lipoprotein profile. It is valid for hyperlipidemia and for normolipidemia as well.