Abstract 626: The ABCA1 Agonist Peptides CS-6253 and ATI-5261 Replicate ApoA-I Function and Generate nHDL Particles that Are Remodeled and Maturated Within the Plasma Compartment, Resulting in Efficient Cholesterol SR-BI Delivery to Hepatic Cells

Novel apolipoprotein (apo) mimetic peptides are potent mediators of ABCA1-mediated cholesterol efflux, mimicking native apoA-I. We investigated CS-6253 (CS) and ATI-5261 (ATI) in their ability to promote lipid transfer between nascent (n)HDL particles and plasma lipoproteins and examined cholesterol influx from remodelled HDL-like particles to hepatic cells through the SR-BI receptor. nHDL-like lipoproteins nHDL-CS and nHDL-ATI were generated by incubating CS or ATI in the presence of BHK cells expressing ABCA1 labelled with 3 [H]cholesterol and 3 [H] choline; native apoA-I was used as control. These nHDL particles were incubated with plasma at 37°C. Both CS and ATI increased LCAT activity significantly, although were approximately 50% less efficient than nHDL-apoA-I (fractional esterification rate (FER) =22.32±0.86%/h; vs nHDL-CS and nHDL-ATI; FER=11.40±0.045%/h; p<0.05). The majority of 3 [H]cholesterol from nHDL mimetics was esterified by LCAT, resulting in an increase in α1-migrating HDL-like particles in plasma (as shown by 2D-PAGGE). The ability of nHDL mimetics to transfer 3 [H]-phosphatidyl choline to plasma apoB-containing lipoproteins is (76±20%) in HDL-apoA-I, (38±0.5%) in nHDL-ATI and (54±13%) in nHDL-CS. These data show that nHDL mimetics are actively remodelled in the presence of plasma lipoproteins. We then investigated cholesterol delivery from HDL-CS and HDL-ATI mimetic to hepatic tissue via SR-BI using Fu5AH cells, having HDL-apoA-I as control. Kinetic parameters for SR-BI-mediated cholesterol influx are as follows: HDL-CS ( K m = 0.30±0.05 ug/ml; p<0.05) efficient as HDL apoA-I at promoting cholesterol uptake into Fu5AH cells ( K m = 0.37±0.13 ug/ml), while HDL-ATI was least efficient ( K m = 1.03±0.20 ug/ml). The inhibition of SR-BI selective uptake with BLT-1 affected the uptake of cholesterol from apoB precipitated plasma containing either HDL-CS, HDL-ATI or apoA-I. Here we present an in-vitro model of nHDL-CS and nHDL-ATI that actively undergo remodelling and maturation in plasma and replicate the function of apoA-I. These mature HDL mimetics generated from ABCA1 agonist peptides deliver cholesterol efficiently to hepatocytes specifically through the SR-BI receptor.

Fractional Esterification Rate of Cholesterol and Ratio of Triglycerides to HDL-Cholesterol Are Powerful Predictors of Positive Findings on Coronary Angiography

Background: We examined the predictive value of various clinical and biochemical markers for angiographically defined coronary artery disease (aCAD). Specifically, we assessed the value of the ratio of plasma triglyceride (TGs) to HDL-cholesterol (HDL-C) and the fractional esterification rate of cholesterol in plasma depleted of apolipoprotein B (apoB)-containing lipoproteins (FERHDL), a functional marker of HDL and LDL particle size. Methods: Patients (788 men and 320 women) undergoing coronary angiography were classified into groups with positive [aCAD(+)] and negative [aCAD(−)] findings. Patient age, body mass index, waist circumference, blood pressure (BP), medications, drinking, smoking, exercise habits, and plasma total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-unesterified cholesterol, HDL-C, TGs, FERHDL, apoB, log(TG/HDL-C), and TC/HDL-C were assessed. Lipids and apoproteins were measured by standard laboratory procedures; FERHDL was determined by a radioassay. Results: Members of the aCAD(+) group were older and had a higher incidence of smoking and diabetes than those in the aCAD(−) group. The aCAD(+) group also had higher TG, apoB, FERHDL, and log(TG/HDL-C) and lower HDL-C values. aCAD(+) women had greater waist circumference and higher plasma TC and TC/HDL-C. aCAD(+) men, but not women, had higher plasma LDL-C. In the multivariate logistic model, the significant predictors of the presence of aCAD(+) were FERHDL, age, smoking, and diabetes. If only laboratory tests were included in the multivariate logistic model, FERHDL appeared as the sole predictor of aCAD(+). Log(TG/HDL-C) was an independent predictor when FERHDL was omitted from multivariate analysis. Conclusions: FERHDL was the best laboratory predictor of the presence of coronary atherosclerotic lesions.