Lipid composition of mononuclear cell membranes and serum from persons with high or low levels of serum HDL cholesterol.
High density lipoprotein (HDL) levels have been shown to be inversely correlated with the incidence of coronary artery disease (CAD). Since we have previously found that peripheral blood mononuclear cells (PBMC) from persons with high (n = 10) or low HDL (n = 10) have different functional properties, we wanted to examine the PBMC membrane lipid composition and fluidity, as well as to characterize the serum lipoproteins in greater detail. In persons with high HDL, PBMC membrane phospholipids were higher, and the cholesterol/phospholipid (CH/PL) ratio lower than in persons with low HDL. Membrane cholesterol and phospholipids were positively correlated with serum HDL2. The fatty acid composition of membrane phospholipids, and membrane fluidity was similar. The median saturated/unsaturated fatty acid (SFA/UFA) ratio tended to be lower in PBMC membranes and in serum from persons with high HDL; however this was not statistically significant. In serum, total phospholipids and HDL2 components (cholesterol, phospholipids and protein) were higher in persons with high HDL, whereas non-esterified fatty acids (NEFA) and very low density lipoprotein (VLDL) components (triglycerides, cholesterol, phospholipids and protein) were lower. Furthermore, serum cholesterol esters and the cholesterol esters/free cholesterol (CE/FC) ratio was higher, and the atherogenic index, i.e. (apoB X (total cholesterol-HDLc)/apoA-I X HDLc, lower in persons with high HDL. These results demonstrate that PBMC from persons with high or low serum HDL have a different lipid composition presumably of importance for cell function, lipid transport and atherogenesis.