Cholesteryl ester analogs inhibit cholesteryl ester but not triglyceride transfer catalyzed by the plasma cholesteryl ester-triglyceride transfer protein

Evidence for nonesterified fatty acids as modulators of neutral lipid transfers in normolipidemic human plasma

The relations between the level of plasma nonesterified fatty acid (NEFA) and both the mass concentration and activity of the cholesteryl ester transfer protein (CETP) were studied in fasted normolipidemic subjects. Plasma NEFA correlated positively with both CETP mass concentration (r = .50; P < .01) and the transfer of cholesteryl ester from HDL toward plasma VLDL+LDL (CETHDL-->VLDL+LDL activity) (r = .46; P < .05) but not with the transfer of cholesteryl ester from LDL toward plasma HDL (CETLDL-->HDL activity) (r = .05; NS). The high binding capacity of albumin for NEFA was used to investigate whether lipoprotein-bound NEFAs were implicated in the modulation of the cholesteryl ester transfer reaction. As compared with nonsupplemented controls, the addition of an excess of fatty acid-free albumin (8 g/L) to total normolipidemic plasmas reduced CETHDL-->VLDL+LDL activity (18.3 +/- 5.5% versus 9.8 +/- 3.1%; P < .0001) but not CETLDL-->HDL activity (22.3 +/- 4.5% versus 23.3 +/- 5.1%; NS). Moreover, CETHDL-->VLD+LDL and CETLDL-->HDL activities correlated negatively when measured in native plasma (r = -.45; P < .05) but positively when measured in albumin-supplemented plasma (r = .40; P < .05). In long-term incubation experiments, lipoprotein-bound NEFA increased the net mass transfer of cholesteryl esters from HDL toward VLDL+LDL but reduced the net mass transfer of triglycerides in the opposite direction, from VLDL+LDL toward HDL. Taken together, data of the present study brought strong and concordant arguments in favor of a dual effect of plasma NEFA in modulating both the mass and the activity of CETP in vivo.

Modulation of the plasma cholesteryl ester transfer by stachybotramide

Plasma cholesteryl ester transfer protein (CETP), which mediates the transfer and exchange of neutral lipids (cholesteryl esters (CE) and triglycerides (TG) and phospholipids between plasma lipoproteins, plays an essential role in reverse cholesterol transport system. We have found that a fungal metabolite, stachybotramide, modulates the activity of CETP. Stachybotramide stimulated the [14C]CE transfer from high density lipoprotein (HDL) to very low density lipoprotein (VLDL) and low density lipoprotein (LDL) by 1.3- to 1.5-fold at 0.2-0.5 mM. This stimulation was abolished in the presence of anti-CETP antibody. On the other hand, the transfer of [14C]CE from LDL and VLDL to HDL was slightly reduced by stachybotramide at 0.5 mM. Unlike the transfer of [14C]CE, the transfer of [3H]TG from HDL was not significantly affected by stachybotramide. These results suggest that stachybotramide preferentially stimulate the CETP-mediated transfer of CE from HDL to both VLDL and LDL.

Cholesteryl ester transfer protein inhibition by PD 140195

The presence of plasma cholesteryl ester transfer protein (CETP) activity may be atherogenic, and, therefore, strategies to inhibit its activity or production may result in a beneficial effect on lipoprotein profiles and the disease process. The current report describes 4-phenyl-5-tridecyl-4H-1,2,4- triazole-3-thiol (PD 140195), a novel CETP inhibitor. The concentration-dependent inhibition of CETP by PD 140195 and the inhibitory monoclonal antibody (Mab) TP2 is demonstrated in a variety of in vitro assay systems. Molecular models of PD 140195 suggest a spatial mimicry of the cholesteryl ester structure. Despite the structural similarity, kinetic studies with a fluorescent cholesteryl ester analog suggest that the inhibition of transfer is not competitive. PD 140195 also selectively inhibited cholesteryl ester but not triglyceride transfer, while the Mab TP2 blocked CETP transfer of both. Studies were carried out to determine whether CETP inhibition observed in vitro could also be demonstrated in vivo. When PD 140195 was intravenously infused to anesthetized rabbits (up to 20 mg/kg), only transient CETP inhibition was observed. In vitro reconstitution studies in the presence of bovine serum albumin resulted in marked reduction of PD 140195 inhibitory activity. Thus, the low activity of PD 140195 in whole plasma probably results from binding to other plasma proteins.