Abstract 69: The Increase in Dalcetrapib-Induced HDL Remodeling Is Dependent on Cysteine 13 of Cholesteryl Ester Transfer Protein and Does Not Involve Phospholipid Transfer Protein

Abstract

Introduction: Inhibition of the cholesteryl ester transfer between HDL and apoB-containing lipoproteins by dalcetrapib requires cysteine 13 (C13) of CETP. In contrast to the CETP inhibitors torcetrapib or anacetrapib, the CETP modulator dalcetrapib stimulates CETP-dependent generation of pre-β-HDL in human plasma or isolated HDL in vitro . Hypothesis: We hypothesized that the effects of dalcetrapib on CETP-dependent HDL remodeling also require C13 of CETP and are not the result of interaction with the other cysteine-containing phospholipid transfer protein (PLTP). Results: The CETP C13S mutant was as active as wild-type (wt) CETP both i) in transferring cholesteryl ester between HDL and apoB-containing lipoproteins and ii) in generating pre-β1-HDL. Dalcetrapib inhibited the transfer of cholesteryl ester between HDL and apoB-containing lipoproteins by wtCETP (IC 50 = 200 nM) but increased pre-β1-HDL formation from isolated HDL, and ABCA1-mediated efflux (3-fold and 2.5-fold increase at 10 μM, respectively, p<0.01). These properties of dalcetrapib were not observed with the CETP C13S mutant. Native HDL was remodeled by wtCETP as evidenced by the formation of large and small particles; a process further enhanced by dalcetrapib. When reconstituted HDL (rHDL), containing only apoA-I and phospholipids, was substituted for isolated HDL, dalcetrapib did not increase wtCETP-induced pre-β1-HDL or ABCA1-dependent efflux (0.9-fold at 10 μM). PLTP induced pre-β1-HDL generation and ABCA1 efflux from native HDL and rHDL. PLTP-dependent HDL remodeling was not affected by dalcetrapib (0.9- and 1-fold at 10 μM for HDL and rHDL respectively). Conclusions: The enhanced generation of pre-β1-HDL by wtCETP and dalcetrapib was associated with an increase in ABCA1-specific efflux and HDL remodeling. As observed for cholesteryl ester transfer activity, dalcetrapib effects on CETP-dependent HDL remodeling required C13 of CETP and dalcetrapib had no effect on PLTP-dependent HDL remodeling.