RF Atmeh¹, SI Almuhtaseb², MA Al-Sulaibi², WA Alananzeh², BM Kana’an^1
1Jordan University of Science and Technology, Irbid, Jordan
²Al-Balqa` Applied University, Al-Salt, Jordan

Background: High density lipoproteins (HDLs) have a role in the progression and regression of atherosclerosis, but their exact function is not well established yet. Measurement of plasma HDL cholesterol is of low predictive value and its use as a biomarker in assessing the individual’s risk of cardiovascular diseases is now questionable. Objective: We believe that some of HDL subclasses are better candidates as biomarkers especially the small ones. Alteration in the chemical composition of HDL subclasses may impair function and reduce their antiatherogenic properties. However, data about the proportions of lipid components and their fatty acid constituents in HDL subclasses are scarce in the literature and are not consistent.

Procedure: We analyzed the apolipoproteins and the lipid classes: triacylglycerols, cholesteryl esters and phospholipids, and their fatty acid composition in seven HDL subclasses isolated by the new method of electrofiltration. Results: All the subclasses contained apolpipoprotein A-I, cholesteryl esters, triacylglycerols, Phosphatidylcholine, and sphingomyelin, whereas other polipoproteins, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine were detected in some subclasses. There was a wide variation in the phospholipids distribution in the subclasses. We identified ten fatty acids in these lipid classes where six of them were saturated and four were unsaturated. The fatty acids 16:0 and 18:0 were the most abundant in all lipids of all the subclasses, whereas the other fatty acids showed variable distribution.

Conclusion: Our results show the variability of the chemical composition of HDL subclasses and explain the microheterogeneity of HDL particles due to differences in composition especially the fatty acids. We suggest that the proportion of phosphatidylethanolamine among HDL subclasses can be related to the impaired clearance of the small HDL subclasses in cases of hyperlipoproteinemia, diabetes, and alcohol intake. Studying the detailed composition of HDL subclasses is crucial for better understanding of their role in atheroprotection and other pathological conditions.

Keywords: cholesterol, High density lipoproteins (HDL), atherosclerosis, fatty acids composition
Schlüsselwörter: Cholesterin, HDL, Arteriosklerose, Fettsäurenzusammensetzung