Dalcetrapib in patients with an acute coronary syndrome

Crosstalk between high-density lipoproteins and endothelial cells in health and disease: Insights into sex-dependent modulation

Atherosclerotic cardiovascular disease is the leading cause of death worldwide. Intense research in vascular biology has advanced our knowledge of molecular mechanisms of its onset and progression until complications; however, several aspects of the patho-physiology of atherosclerosis remain to be further elucidated. Endothelial cell homeostasis is fundamental to prevent atherosclerosis as the appearance of endothelial cell dysfunction is considered the first pro-atherosclerotic vascular modification. Physiologically, high density lipoproteins (HDLs) exert protective actions for vessels and in particular for ECs. Indeed, HDLs promote endothelial-dependent vasorelaxation, contribute to the regulation of vascular lipid metabolism, and have immune-modulatory, anti-inflammatory and anti-oxidative properties. Sex- and gender-dependent differences are increasingly recognized as important, although not fully elucidated, factors in cardiovascular health and disease patho-physiology. In this review, we highlight the importance of sex hormones and sex-specific gene expression in the regulation of HDL and EC cross-talk and their contribution to cardiovascular disease.

HDL and Cholesterol Ester Transfer Protein (CETP)

Cholesterol ester transfer protein (CETP) is important clinically and is one of the major targets in cardiovascular disease studies. With high conformational flexibility, its tunnel structure allows unforced movement of high-density lipoproteins (HDLs), VLDLs, and LDLs. Research in reverse cholesterol transports (RCT) reveals that the regulation of CETP activity can change the concentration of cholesteryl esters (CE) in HDLs, VLDLs, and LDLs. These molecular insights demonstrate the mechanisms of CETP activities and manifest the correlation between CETP and HDL. However, animal and cell experiments focused on CETP give controversial results. Inhibiting CETP is found to be beneficial to anti-atherosclerosis in terms of increasing plasma HDL-C, while it is also claimed that CETP weakens atherosclerosis formation by promoting RCT. Currently, the CETP-related drugs are still immature. Research on CETP inhibitors is targeted at improving efficacy and minimizing adverse reactions. As for CETP agonists, research has proved that they also can be used to resist atherosclerosis.

Effect of selective BET protein inhibitor apabetalone on cardiovascular outcomes in patients with acute coronary syndrome and diabetes: Rationale, design, and baseline characteristics of the BETonMACE trial

After an acute coronary syndrome (ACS), patients with diabetes remain at high risk for additional cardiovascular events despite use of current therapies. Bromodomain and extra-terminal (BET) proteins are epigenetic modulators of inflammation, thrombogenesis, and lipoprotein metabolism implicated in atherothrombosis. The BETonMACE trial tests the hypothesis that treatment with apabetalone, a selective BET protein inhibitor, will improve cardiovascular outcomes in patients with diabetes after an ACS. DESIGN: Patients (n = 2425) with ACS in the preceding 7 to 90 days, with type 2 diabetes and low HDL cholesterol (≤40 mg/dl for men, ≤45 mg/dl for women), receiving intensive or maximum-tolerated therapy with atorvastatin or rosuvastatin, were assigned in double-blind fashion to receive apabetalone 100 mg orally twice daily or matching placebo. Baseline characteristics include female sex (25%), myocardial infarction as index ACS event (74%), coronary revascularization for index ACS (80%), treatment with dual anti-platelet therapy (87%) and renin-angiotensin system inhibitors (91%), median LDL cholesterol 65 mg per deciliter, and median HbA1c 7.3%. The primary efficacy measure is time to first occurrence of cardiovascular death, non-fatal myocardial infarction, or stroke. Assumptions include a primary event rate of 7% per annum in the placebo group and median follow-up of 1.5 years. Patients will be followed until at least 250 primary endpoint events have occurred, providing 80% power to detect a 30% reduction in the primary endpoint with apabetalone. SUMMARY: BETonMACE will determine whether the addition of the selective BET protein inhibitor apabetalone to contemporary standard of care for ACS reduces cardiovascular morbidity and mortality in patients with type 2 diabetes. Results are expected in 2019.

β3-Adrenoceptor activation upregulates apolipoprotein A-I expression in HepG2 cells, which might further promote cholesterol efflux from macrophage foam cells

Objective

The aim of this study was to explore the effects of β₃-adrenoceptor (β₃-AR) activation on HepG2 cells and its influence on cholesterol efflux from macrophage foam cells.

Materials and methods

HepG2 cells were cultured and treated with the β₃-AR agonist, BRL37344, and antagonist, SR52390A, and the expression of apolipoprotein (Apo) A-I, ApoA-II, ApoB, and β₃-AR in the supernatants and cells was determined. The expression of peroxisome proliferator-activated receptor (PPAR) γ and PPARα in the HepG2 cells was also assessed. Next, using the RAW264.7 macrophage foam cell model, we also assessed the influence of the HepG2 cell supernatants on lipid efflux. The cholesterol content of the foam cells was also measured, and the cholesterol efflux from the macrophages was examined by determining ³H-labeled cholesterol levels. Expression of ATP-binding cassette transporter (ABC) A1 and ABCG1 of the macrophage foam cells was also assessed.

Results

β₃-AR activation increased ApoA-I expression in both the HepG2 cells and the supernatants; PPARγ expression was upregulated, but PPARα expression was not. Treatment with GW9662 abolished the increased expression of ApoA-I induced by the β₃-AR agonist. The HepG2 cell supernatants decreased the lipid accumulation and increased the cholesterol efflux from the macrophage foam cells. ABCA1 expression, but not ABCG1 expression, increased in the macrophage foam cells treated with BRL37344-treated HepG2 cell supernatants.

Conclusion

Activation of β₃-AR in HepG2 cells upregulates ApoA-I expression, which might further promote cholesterol efflux from macrophage foam cells. PPARγ might be required for the induction of ApoA-I expression.

Studies on the regulation of lipid metabolism and its mechanism of the iridoids rich fraction in Valeriana jatamansi Jones

Valeriana jatamansi Jones, a plant with heart-shaped leaves in the Valeriana genus of Valerianaceae, is widely used in Chinese folk medicine. Iridoid is an important constituent of V. jatamansi that contributes to the pharmacological efficacy of the herb. This study aims to investigate the regulation of lipid metabolism and its mechanism of the iridoids rich fraction in V. jatamansi (IRFV). A high fat diet was used to establish the hyperlipidemia rat model, with 2mg/kg/d of simvastatin as a positive control, fed with 7.5, 15, and 30mg/kg/d of IRFV for 20days to investigate the lipid regulation activity and mechanism of IRFV. Body weight, liver index, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) in both serum and liver, as well as total bile acid (TBA), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) in serum were measured. The lipoprotein lipase (LPL) and hepatic lipase (HL) activities and the apoprotein A5 (ApoA5), peroxisome proliferator-activated receptor α (PPAR-α), sterol regulatory element-binding proteins (SREBP-1c), and liver X receptor α (LXR-α) protein expressions were observed. Liver pathology was described through hematoxylin-eosin (HE) staining. Compared with the model group, three different IRFV dosages can slow down the weight gain of rats, reduce the contents of TG, and increase the contents of HDL-C in serum. Low IRFV dosage can significantly reduce the AST and ALT contents in serum, liver index, and the TG contents in liver, enhance LPL activity. Medium IRFV dosage can significantly decrease the TG and LDL-C contents in liver. High IRFV dosage can significantly reduce LDL-C, TBA, AST, and ALT contents in serum, and enhance HL activity. Three different IRFV dosages can significantly increase the ApoA5 and PPAR-α protein expression and decrease the SREBP-1c protein expression. Furthermore, the LXR-α protein expression decreased in low- and high-dose groups. Liver tissue pathological observation showed that IRFV can improve cell degeneration to a certain extent. These results strongly suggest that IRFV play significant roles in regulating lipid metabolism, the mechanism may be related to the increased ApoA5 protein expression.

Reduced high density lipoprotein cholesterol in severe hypertriglyceridemic ApoCIII transgenic mice via lowered hepatic ApoAI synthesis

Clinical and epidemiological investigations confirm that patients with loss-of-function mutations (R19X, etc.) in Apolipoprotein CIII (ApoCIII) showed beneficial lipid profile including decreased plasma triglyceride and increased high density lipoprotein (HDL) levels. However, whether HDL level would be reduced in hypertriglyceridemia (HTG) induced by high ApoCIII expression has not been demonstrated yet. Here we showed, ApoCIII transgenic mice (ApoCIIItg) displayed severe HTG and had significantly lower HDL level. Analysis of apolipoproteins in lipoprotein fractions by SDS-PAGE revealed marked decrease of apolipoprotein AI (ApoAI) in HDL in transgenic mice compared with the wild type mice (WT) as controls. Further examination demonstrated that hepatic but not intestinal ApoAI mRNA was significantly reduced. Therefore, the decreased ApoAI synthesis might be accounted for the lower plasma HDL level in ApoCIII transgenic mice.

Effects of established hypolipidemic drugs on HDL concentration, subclass distribution, and function

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10%). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15%). Niacin is the most potent available drug in increasing HDL-C levels (up to 30%), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties.

Quantification of HDL proteins, cardiac events, and mortality in patients with type 2 diabetes on hemodialysis

BACKGROUND AND OBJECTIVES

Impairment of HDL function has been associated with cardiovascular events in patients with kidney failure. The protein composition of HDLs is altered in these patients, presumably compromising the cardioprotective effects of HDLs. This post hoc study assessed the relation of distinct HDL-bound proteins with cardiovascular outcomes in a dialysis population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The concentrations of HDL-associated serum amyloid A (SAA) and surfactant protein B (SP-B) were measured in 1152 patients with type 2 diabetes mellitus on hemodialysis participating in The German Diabetes Dialysis Study who were randomly assigned to double-blind treatment of 20 mg atorvastatin daily or matching placebo. The association of SAA(HDL) and SP-B(HDL) with cardiovascular outcomes was assessed in multivariate regression models adjusted for known clinical risk factors.

RESULTS

High concentrations of SAA(HDL) were significantly and positively associated with the risk of cardiac events (hazard ratio per 1 SD higher, 1.09; 95% confidence interval, 1.01 to 1.19). High concentrations of SP-B(HDL) were significantly associated with all-cause mortality (hazard ratio per 1 SD higher, 1.10; 95% confidence interval, 1.02 to 1.19). Adjustment for HDL cholesterol did not affect these associations.

CONCLUSIONS

In patients with diabetes on hemodialysis, SAA(HDL) and SP-B(HDL) were related to cardiac events and all-cause mortality, respectively, and they were independent of HDL cholesterol. These findings indicate that a remodeling of the HDL proteome was associated with a higher risk for cardiovascular events and mortality in patients with ESRD.

An in-silico model of lipoprotein metabolism and kinetics for the evaluation of targets and biomarkers in the reverse cholesterol transport pathway

High-density lipoprotein (HDL) is believed to play an important role in lowering cardiovascular disease (CVD) risk by mediating the process of reverse cholesterol transport (RCT). Via RCT, excess cholesterol from peripheral tissues is carried back to the liver and hence should lead to the reduction of atherosclerotic plaques. The recent failures of HDL-cholesterol (HDL-C) raising therapies have initiated a re-examination of the link between CVD risk and the rate of RCT, and have brought into question whether all target modulations that raise HDL-C would be atheroprotective. To help address these issues, a novel in-silico model has been built to incorporate modern concepts of HDL biology, including: the geometric structure of HDL linking the core radius with the number of ApoA-I molecules on it, and the regeneration of lipid-poor ApoA-I from spherical HDL due to remodeling processes. The ODE model has been calibrated using data from the literature and validated by simulating additional experiments not used in the calibration. Using a virtual population, we show that the model provides possible explanations for a number of well-known relationships in cholesterol metabolism, including the epidemiological relationship between HDL-C and CVD risk and the correlations between some HDL-related lipoprotein markers. In particular, the model has been used to explore two HDL-C raising target modulations, Cholesteryl Ester Transfer Protein (CETP) inhibition and ATP-binding cassette transporter member 1 (ABCA1) up-regulation. It predicts that while CETP inhibition would not result in an increased RCT rate, ABCA1 up-regulation should increase both HDL-C and RCT rate. Furthermore, the model predicts the two target modulations result in distinct changes in the lipoprotein measures. Finally, the model also allows for an evaluation of two candidate biomarkers for in-vivo whole-body ABCA1 activity: the absolute concentration and the % lipid-poor ApoA-I. These findings illustrate the potential utility of the model in drug development.