Is RCT (Reverse Cholesterol Transport) Ready for an RCT (Randomized Controlled Trial)?

Association of high-density lipoprotein levels with baseline coronary plaque volumes by coronary CTA in the EVAPORATE trial

BACKGROUND AND AIMS

Dyslipidemia with elevated triglycerides (TGL) and low high-density lipoprotein cholesterol (HDL-C) predicts residual cardiovascular risk, despite goal LDL-C levels and optimal statin therapy. Coronary plaque characterization by CCTA can provide mechanistic understanding of coronary artery disease and associated prognosis. The role of HDL-C in the pathogenesis of atherosclerosis is not well understood in statin-treated patients with elevated TGL. We sought to examine the association of HDL-C levels with baseline coronary plaque volumes, namely total plaque (TP) and total non-calcified plaque (TNCP) volumes by CCTA in participants enrolled in the EVAPORATE trial.

METHODS

We analyzed 80 participants who were enrolled in the trial. Linear regression analysis as a univariate and multivariate model adjusted for significant cardiovascular risk factors was performed to evaluate independent association of HDL-C and baseline coronary plaque volumes. In an exploratory analysis, stratified by sex, we compared the association of serum HDL-C levels with baseline coronary plaque volumes in males and females.

RESULTS

Mean (SD) age of participants (n = 80) was 57.1 (8.6) years and 43% were male. Median (Inter Quartile Range/IQR) log-TNCP volume was 83.0 (0.1-7.3) mm³ and median (IQR) log-TP volume was 144.8 (0.1-7.1) mm³. After adjustment for relevant clinical covariates including age, gender, BMI, hypertension, diabetes, past smoking and baseline TGL levels, increasing levels of HDL-C remain independently associated with lower baseline log-TNCP volumes (β: 0.043 ± 0.021, p = 0.042) and baseline log-TP volumes (β: 0.046 ± 0.022, p = 0.035) on CCTA. On stratifying by sex in a multivariable regression analysis, HDL-C levels were inversely associated with baseline log-TNCP volumes (β: 0.066 ± 0.026, p = 0.018) and log-TP volumes (β: 0.077 ± 0.025, p = 0.004) in females, but not in males (log-TNCP volumes β: 0.038 ± 0.034, p = 0.282) and log-TP volumes (β: -0.033 ± 0.036, p = 0.364).

CONCLUSIONS

In a cohort of statin treated patients with known atherosclerosis and residually elevated TGL, there was a significant inverse relationship between HDL-C levels and baseline coronary plaque, TP and TNCP volumes on CCTA. Our findings provide more detailed mechanistic evidence regarding the protective role of HDL-C in coronary atherosclerosis in a high-risk cohort. Further investigation to evaluate the interaction of HDL-C levels and coronary plaque volumes on differential CVD risk in statin-treated patients with elevated TGL levels is warranted.

Modulation of cholesterol efflux capacity in patients with myocardial infarction

PURPOSE OF REVIEW

Epidemiologic studies consistently demonstrated that patients with coronary artery disease (CAD) and low HDL cholesterol (HDL-C) are more likely to develop major adverse cardiovascular events as compared with those with normal or high HDL. However, several large randomized trials failed to demonstrate that a substantial, pharmacological-based, increase of HDL-C concentrations results in a clinically significant reduction of ischemic outcomes. This has been largely attributed to the fact that, although these drugs are able to raise the HDL-C concentration, they have no effect on HDL-C atheroprotective function. Subsequently, the 'HDL hypothesis' evolved, and the focus shifted from raising the concentration of HDL-C to raising the reverse cholesterol transport (RCT) function by increasing patients cholesterol efflux capacity (CEC) instead. Indeed, new data suggest that HDL-C metabolism and the ability of the HDL molecule to transport cholesterol from the atherosclerotic plaque to the liver, measured by the CEC, is more important than steady-state HDL-C levels. Modulation of the CEC has become, therefore, a promising therapeutic target in CAD patients. This article reviews the current data on the 'cholesterol efflux hypothesis' and discuss its ability to be modulated has a potential therapeutic target.

RECENT FINDINGS

Recent data have demonstrated that impaired serum CEC was associated with increased mortality after a myocardial infarction (MI). Thus, therapeutic intervention aiming to improve CEC and RCT may reduce the risk of recurrent events. Early phase clinical studies targeting CEC showed promising results and a megatrial is ongoing testing the hypothesis that an improved RCT trough a modulation of the CEC can modify patient's prognosis after an acute MI.

SUMMARY

The 'cholesterol efflux hypothesis' is now supported by several clinical studies and is being tested with a therapeutic candidate in a megatrial enrolling high-risk patient with MI.

Bariatric Surgery Improves HDL Function Examined by ApoA1 Exchange Rate and Cholesterol Efflux Capacity in Patients with Obesity and Type 2 Diabetes

Bariatric surgery improves glycemic control better than medical therapy; however, the effect of bariatric surgery on HDL function is not well characterized. Serum samples were available at baseline, 1-, and 5-years post procedures, for 90 patients with obesity and type 2 diabetes who were randomized to intensive medical therapy (n = 20), Roux-en-Y gastric bypass (RYGB, n = 37), or sleeve gastrectomy (SG, n = 33) as part of the STAMPEDE clinical trial. We examined serum HDL function by two independent assays, apolipoprotein A-1 exchange rate (AER) and cholesterol efflux capacity (CEC). Compared with baseline, AER was significantly higher at 5 years for participants in all treatment groups, but only increased significantly at 1 year in the RYGB and SG groups. CEC was divided into ABCA1-dependent and independent fractions, and the later was correlated with AER. ABCA1-independent CEC increased significantly only at 5 years in both surgical groups, but did not significantly change in the medical therapy group. There was no significant change in ABCA1-dependent CEC in any group. The increase in AER, but not ABCA1-independent CEC, was correlated with the reduction in body mass index and glycated hemoglobin levels among all subjects at 5 years, indicating that AER as a measure of HDL function would be a better reflection of therapy versus CEC.