Effect of the composition of very low and low density lipoproteins on the rate of cholesterylester transfer from high density lipoproteins in man, studied in vitro

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Abstract
The process of cholesterylester (CE) transfer is supposed to be a regulatory factor in the distribution of CE between lipoproteins. In addition to the activity of CE transfer protein, this process may be affected by acceptor lipoprotein characteristics. In this study the effect of the composition of different very low density lipoproteins (VLDL) and low density lipoproteins (LDL) on the ability to accept CE from HDL in vitro was investigated. [3H]-CE high density lipoprotein (HDL) (100 nmol CE) from one batch was incubated with VLDL (75 nmol CE), isolated from fifteen subjects for 4 h and separately with LDL (250 nmol CE), isolated from thirteen subjects for 16 h, both in the presece of lipoprotein-free plasma providing a source of cholesterylester transfer protein. The CE transfer rate to VLDL (range 1·34–2·84% [3H]-CE transferred h-1) was correlated to the triacylglycerol (TG):CE molar ratio (r: 0·63, P < 0·05), to the phospholipid (PL):CE molar ratio (r: 0·75, P < 0·01), to the protein (Pr):CE ratio (expressed in g nmol-1) (r: 0·72, P < 0·01) and to the free cholesterol (FC):CE molar ratio (r: 0·69, P < 0·01), but not to the FC:PL molar ratio (r: -0·08, NS). The CE transfer rate to LDL (range 1·18–3·59 nmol CE h-1) was correlated to the Pr:CE ratio (r: 0·72, P < 0·01) and inversely to the FRC:PL molar ratio (r: -0·88, P < 0·001), but not to the TG:CE molar ratio (r: 0·40, NS), nor to the FC:CE molar ratio (r: -0·37, NS). The correlation between CE transfer rate and PL:CE molar ratio almost reached significance (r: 0·54, 0·05 < P < 0·10). It is concluded that the ability of VLDL to accept CE is enhanced when it contains more TG and more surface constituent, relative to CE, while in LDL surface characteristics are involved in the process of CE transfer. An influence of VLDL and LDL composition and CE transport in human plasma is suggested.

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