Cholesterol ester transfer protein (CETP) and atherosclerosis

How anacetrapib inhibits the activity of the cholesteryl ester transfer protein? Perspective through atomistic simulations

Cholesteryl ester transfer protein (CETP) mediates the reciprocal transfer of neutral lipids (cholesteryl esters, triglycerides) and phospholipids between different lipoprotein fractions in human blood plasma. A novel molecular agent known as anacetrapib has been shown to inhibit CETP activity and thereby raise high density lipoprotein (HDL)-cholesterol and decrease low density lipoprotein (LDL)-cholesterol, thus rendering CETP inhibition an attractive target to prevent and treat the development of various cardiovascular diseases. Our objective in this work is to use atomistic molecular dynamics simulations to shed light on the inhibitory mechanism of anacetrapib and unlock the interactions between the drug and CETP. The results show an evident affinity of anacetrapib towards the concave surface of CETP, and especially towards the region of the N-terminal tunnel opening. The primary binding site of anacetrapib turns out to reside in the tunnel inside CETP, near the residues surrounding the N-terminal opening. Free energy calculations show that when anacetrapib resides in this area, it hinders the ability of cholesteryl ester to diffuse out from CETP. The simulations further bring out the ability of anacetrapib to regulate the structure-function relationships of phospholipids and helix X, the latter representing the structural region of CETP important to the process of neutral lipid exchange with lipoproteins. Altogether, the simulations propose CETP inhibition to be realized when anacetrapib is transferred into the lipid binding pocket. The novel insight gained in this study has potential use in the development of new molecular agents capable of preventing the progression of cardiovascular diseases.

Cardiovascular disease is a leading cause of morbidity and mortality in Western societies. One of the most encouraging treatment methods to prevent the generation and progression of cardiovascular disease is the elevation of high density lipoprotein (HDL) levels in circulation, as high HDL levels have been found to correlate negatively with the risk of cardiovascular disease. HDL elevation is attainable through inhibition of cholesteryl ester transfer protein (CETP). A novel molecular agent, anacetrapib, fulfills the requirements with an acceptable side-effect profile. In this study, our objective is to gain more detailed information regarding the interactions between CETP and anacetrapib in order to unlock the inhibitory mechanism of the drug that has, to date, remained unclear. Our results point out the primary binding site of anacetrapib and highlight the ability of the drug to regulate the structure-function relationship of those structural regions of CETP that are considered important in CETP inhibition. Our findings could be exploited in the development of new and more efficient molecular agents against cardiovascular disease.

Lipid exchange mechanism of the cholesteryl ester transfer protein clarified by atomistic and coarse-grained simulations

Cholesteryl ester transfer protein (CETP) transports cholesteryl esters, triglycerides, and phospholipids between different lipoprotein fractions in blood plasma. The inhibition of CETP has been shown to be a sound strategy to prevent and treat the development of coronary heart disease. We employed molecular dynamics simulations to unravel the mechanisms associated with the CETP-mediated lipid exchange. To this end we used both atomistic and coarse-grained models whose results were consistent with each other. We found CETP to bind to the surface of high density lipoprotein (HDL) -like lipid droplets through its charged and tryptophan residues. Upon binding, CETP rapidly (in about 10 ns) induced the formation of a small hydrophobic patch to the phospholipid surface of the droplet, opening a route from the core of the lipid droplet to the binding pocket of CETP. This was followed by a conformational change of helix X of CETP to an open state, in which we found the accessibility of cholesteryl esters to the C-terminal tunnel opening of CETP to increase. Furthermore, in the absence of helix X, cholesteryl esters rapidly diffused into CETP through the C-terminal opening. The results provide compelling evidence that helix X acts as a lid which conducts lipid exchange by alternating the open and closed states. The findings have potential for the design of novel molecular agents to inhibit the activity of CETP.

Coronary heart disease is a major cause of death in the Western societies. One of the most promising interventions to prevent and slow down the progress of coronary heart disease is the elevation of high density lipoprotein (HDL) levels in circulation. Animal models together with early clinical studies have shown that the inhibition of cholesteryl ester transfer protein (CETP) is a promising strategy to achieve higher HDL levels. However, drugs with acceptable side-effects for CETP-inhibition do not yet exist, although the next generation CETP inhibitor (anacetrapib) has great potential in this regard. In this study, our objective is to gain more detailed information regarding the interactions of CETP with lipoprotein particles. We show how the CETP-lipoprotein complex is formed and how lipid exchange between CETP and lipoprotein particles takes place. Our findings help to understand in a mechanistic way how CETP-mediated lipid exchange occurs and how it could be exploited in the design of new and more efficient molecular agents against coronary heart disease.