HDL phospholipid content and composition as a major factor determining cholesterol efflux capacity from Fu5AH cells to human serum

The relationships of cell cholesterol efflux to HDL phospholipid (PL) content and composition in human serum were analyzed in two groups of subjects selected on the basis of their HDL cholesterol (HDLC) levels: a norm-HDL group (1.10 mmol/L<HDGC<1.50 mmol/L) and a high-HDL group (HDL-C>1.75 mmol/L). In the high-HDL group, the relative fractional efflux was significantly higher than in the norm-HDL group, and in both groups, fractional efflux was correlated with a number of lipoprotein parameters, the best correlation and the only one that remained significant after multivariate analysis being with HDL phospholipid (HDL-PL). Analysis of the HDL-PL subclasses revealed that HDL in the high-HDL sera was enriched with phosphatidylethanolamine (HDL-PE) and relatively deficient in sphingomyelin (HDL-SM) compared with norm-HDL sera. Moreover, the fractional efflux values in the high-HDL group were negatively correlated with the proportion of HDL-PE (r=-.64, P<.0001) and positively correlated with the proportion of HDL-SM (r=.43, P<.01). Thus, this study provides evidence that HDL-PL concentration can be used to predict the capacity of serum to accept cellular cholesterol. Among the differences described between norm-HDL and high-HDL sera, the variability in PE to SM ratio might reflect changes in serum cholesterol accepters that modulate the first step of reverse cholesterol transport.