Functionality of postprandial larger HDL2 particles is enhanced following CETP inhibition therapy.

OBJECTIVE: To evaluate the impact of CETP inhibition on the capacity of individual postprandial HDL subspecies to promote key steps of the reverse cholesterol transport pathway. METHODS: The capacity of HDL particles to mediate cellular free cholesterol efflux and selective hepatic uptake of cholesteryl esters was evaluated throughout postprandial phase (0-8 h) following consumption of a standardised mixed meal before and after treatment for 6 weeks with atorvastatin alone (10 mg/d) and subsequently with combination torcetrapib/atorvastatin (60/10 mg/d) in 16 patients displaying low HDL-C levels (<40 mg/dl). RESULTS: The larger HDL2b and HDL2a subfraction displayed a superior capacity to mediate cellular free cholesterol efflux via both SR-BI and ABCG1-dependent pathways than smaller HDL3 subspecies. CETP inhibition specifically enhanced the capacity of HDL2b subfraction for both SR-BI and ABCG1 dependent efflux. However, only the SR-BI-dependent efflux to HDL2b subspecies can be further enhanced during postprandial lipemia following CETP inhibition. Concomitantly, postprandial lipemia was associated with a reduced capacity of total HDL particles to deliver cholesteryl esters to hepatic cells in a drug independent manner. CONCLUSION: CETP inhibition specifically improves postprandial SR-BI and ABCG1-dependent efflux to larger HDL2b subspecies. In addition, CETP inhibition improves HDL-CE delivery to hepatic cells and maintains an efficient direct return of cholesteryl esters to the liver during postprandial lipemia.

Atheroprotective reverse cholesterol transport pathway is defective in familial hypercholesterolemia.

OBJECTIVE: Low high-density lipoprotein (HDL) cholesterol levels are frequently observed in familial hypercholesterolemia (FH) and might be associated with functional alterations of HDL particles that may influence their efficaciousness in the reverse cholesterol transport pathway. METHODS AND RESULTS: We evaluated key steps of the reverse cholesterol transport, ie, cellular free cholesterol efflux, cholesteryl ester transfer protein-mediated cholesteryl ester (CE) transfer from HDL to apolipoprotein B-containing lipoproteins, and hepatic HDL-CE uptake, in patients displaying FH (n = 12) and in healthy normolipidemic control subjects (n = 12). Large HDL2 particles isolated from FH patients displayed a reduced capacity to mediate free cholesterol efflux via both scavenger receptor-BI- and ABCG1-dependent pathways. A significant inverse relationship between scavenger receptor-BI-dependent HDL2 efflux capacity and carotid intima-media thickness (r = -0.473; P = 0.0186), as well as between ABCG1-dependent HDL2 efflux capacity and carotid intima-media thickness (r = -0.485; P = 0.0212), was detected. We also observed an elevated cholesteryl ester transfer protein-mediated CE transfer from HDL2 and HDL3 particles to low-density lipoprotein and a reduced capacity of HDL particles to deliver CEs to the liver. CONCLUSIONS: We demonstrated that the centripetal movement of cholesterol from peripheral tissues, including the vessel wall, to feces is defective in FH, thereby emphasizing its atherogenicity.

Postprandial lipemia enhances the capacity of large HDL2 particles to mediate free cholesterol efflux via SR-BI and ABCG1 pathways in type IIB hyperlipidemia.

Lipid and cholesterol metabolism in the postprandial phase is associated with both quantitative and qualitative remodeling of HDL particle subspecies that may influence their anti-atherogenic functions in the reverse cholesterol transport pathway. We evaluated the capacity of whole plasma or isolated HDL particles to mediate cellular free cholesterol (FC) efflux, cholesteryl ester transfer protein (CETP)-mediated cholesteryl ester (CE) transfer, and selective hepatic CE uptake during the postprandial phase in subjects displaying type IIB hyperlipidemia (n = 16). Postprandial, large HDL2 displayed an enhanced capacity to mediate FC efflux via both scavenger receptor class B type I (SR-BI)-dependent (+12%; P < 0.02) and ATP binding cassette transporter G1 (ABCG1)-dependent (+31%; P < 0.008) pathways in in vitro cell systems. In addition, the capacity of whole postprandial plasma (4 h and 8 h postprandially) to mediate cellular FC efflux via the ABCA1-dependent pathway was significantly increased (+19%; P < 0.0003). Concomitantly, postprandial lipemia was associated with elevated endogenous CE transfer rates from HDL2 to apoB lipoproteins and with attenuated capacity (-17%; P < 0.02) of total HDL to deliver CE to hepatic cells. Postprandial lipemia enhanced SR-BI and ABCG1-dependent efflux to large HDL2 particles. However, postprandial lipemia is equally associated with deleterious features by enhancing formation of CE-enriched, triglyceride-rich lipoprotein particles through the action of CETP and by reducing the direct return of HDL-CE to the liver.