Phenol-Enriched Virgin Olive Oil Promotes Macrophage-Specific Reverse Cholesterol Transport In Vivo

The Lipid Intensive Drug Therapy for Sepsis Phase II Pilot Clinical Trial

OBJECTIVES

Low cholesterol levels in early sepsis patients are associated with mortality. We sought to test if IV lipid emulsion administration to sepsis patients with low cholesterol levels would prevent a decline or increase total cholesterol levels at 48 hours.

DESIGN

Phase II, adaptive, randomized pilot clinical trial powered for 48 patients.

SETTING

Emergency department or ICU of an academic medical center.

PATIENTS

Sepsis patients (first 24 hr) with Sequential Organ Failure Assessment greater than or equal to 4 or shock.

INTERVENTIONS

Patients meeting study criteria, including screening total cholesterol levels less than or equal to 100 mg/dL or high-density lipoprotein cholesterol (HDL-C) + low-density lipoprotein cholesterol (LDL-C) less than or equal to 70 mg/dL, were randomized to receive one of three doses of lipid emulsion administered twice in 48 hours or no drug (controls). The primary endpoint was a change in serum total cholesterol (48 hr - enrollment) between groups.

MEASUREMENTS AND MAIN RESULTS

Forty-nine patients were enrolled and randomized. Two patients randomized to lipid emulsion were withdrawn before drug administration. Data for 24 control patients and 23 lipid emulsion patients were analyzed. The mean change in total cholesterol from enrollment to 48 hours was not different between groups and was 5 mg/dL ( sd 20) for lipid emulsion patients, and 2 mg/dL ( sd 18) for control patients ( p = 0.62). The mean changes in HDL-C and LDL-C were similar between groups. Mean change in triglycerides was elevated in lipid emulsion patients (61 mg/dL, sd 87) compared with controls (20 mg/dL, sd 70, p = 0.086). The 48-hour change in SOFA score was -2 (interquartile range [IQR] -4, -1) for control patients and -2 (IQR -3, 0) for lipid emulsion patients ( p = 0.46).

CONCLUSIONS

Administration of IV lipid emulsion to early sepsis patients with low cholesterol levels did not influence change in cholesterol levels from enrollment to 48 hours.

Electronegative LDL Is Associated with Plaque Vulnerability in Patients with Ischemic Stroke and Carotid Atherosclerosis

Owing to the high risk of recurrence, identifying indicators of carotid plaque vulnerability in atherothrombotic ischemic stroke is essential. In this study, we aimed to identify modified LDLs and antioxidant enzymes associated with plaque vulnerability in plasma from patients with a recent ischemic stroke and carotid atherosclerosis. Patients underwent an ultrasound, a CT-angiography, and an ¹⁸F-FDG PET. A blood sample was obtained from patients (n = 64, 57.8% with stenosis ≥50%) and healthy controls (n = 24). Compared to the controls, patients showed lower levels of total cholesterol, LDL cholesterol, HDL cholesterol, apolipoprotein B (apoB), apoA-I, apoA-II, and apoE, and higher levels of apoJ. Patients showed lower platelet-activating factor acetylhydrolase (PAF-AH) and paraoxonase-1 (PON-1) enzymatic activities in HDL, and higher plasma levels of oxidized LDL (oxLDL) and electronegative LDL (LDL(-)). The only difference between patients with stenosis ≥50% and <50% was the proportion of LDL(-). In a multivariable logistic regression analysis, the levels of LDL(-), but not of oxLDL, were independently associated with the degree of carotid stenosis (OR: 5.40, CI: 1.15-25.44, p < 0.033), the presence of hypoechoic plaque (OR: 7.52, CI: 1.26-44.83, p < 0.027), and of diffuse neovessels (OR: 10.77, CI: 1.21-95.93, p < 0.033), indicating that an increased proportion of LDL(-) is associated with vulnerable atherosclerotic plaque.

MiR-125b downregulates macrophage scavenger receptor type B1 and reverse cholesterol transport

OBJECTIVE

To determine whether miR-125b regulates cholesterol efflux in vivo and in vitro through the regulation of scavenger receptor type B1 (SR-B1).

APPROACH AND RESULTS

We demonstrated that miR-125b is up-regulated in the human aortas of patients with CAD and is located in macrophages and vascular smooth muscle cells (VSMCs). We identified SCARB1 as a direct target of miR-125b by repressing the activity of the SCARB1 3'-untranslated region reporter construct. Moreover, the overexpression of miR-125b in both human and mouse macrophages as well as VSMCs was found to downregulated the expression of the SCARB1 and the SR-B1 protein levels, thereby impairing α-HDL-mediated macrophage cholesterol efflux in vitro. The in vivo reverse cholesterol transport (RCT) rate from non-cholesterol-loaded macrophages transfected with miR-125b to feces was also found to be decreased when compared with that of control mimic-transfected macrophages.

CONCLUSIONS

Together, these results provide evidence that miR-125b downregulates SCARB1 and SR-B1 in both human and mouse macrophages as well as VSMCs, thereby impairing macrophage cholesterol efflux in vitro and the whole macrophage-specific RCT pathway in vivo.

HDL and reverse cholesterol transport in humans and animals: Lessons from pre-clinical models and clinical studies

The ability to accept cholesterol from cells and to promote reverse cholesterol transport (RCT) represents the best characterized antiatherogenic function of HDL. Studies carried out in animal models have unraveled the multiple mechanisms by which these lipoproteins drive cholesterol efflux from macrophages and cholesterol uptake to the liver. Moreover, the influence of HDL composition and the role of lipid transporters have been clarified by using suitable transgenic models or through experimental design employing pharmacological or nutritional interventions. Cholesterol efflux capacity (CEC), an in vitro assay developed to offer a measure of the first step of RCT, has been shown to associate with cardiovascular risk in several human cohorts, supporting the atheroprotective role of RCT in humans as well. However, negative data in other cohorts have raised concerns on the validity of this biomarker. In this review we will present the most relevant data documenting the role of HDL in RCT, as assessed in classical or innovative methodological approaches.

The Capacity of APOB-Depleted Plasma in Inducing ATP-Binding Cassette A1/G1-Mediated Macrophage Cholesterol Efflux-But Not Gut Microbial-Derived Metabolites-Is Independently Associated with Mortality in Patients with ST-Segment Elevation Myocardial Infarction

Impaired HDL-mediated macrophage cholesterol efflux and higher circulating concentrations of trimethylamine N-oxide (TMAO) levels are independent risk factors for cardiovascular mortality. The TMAO precursors, γ-butyrobetaine (γBB) and Trimethyllysine (TML), have also been recently associated with cardiovascular death, but their interactions with HDL-mediated cholesterol efflux remain unclear. We aimed to determine the associations between APOB depleted plasma-mediated macrophage cholesterol efflux and plasma TMAO, γBB, and TML concentrations and explore their association with two-year follow-up mortality in patients with acute ST-elevation myocardial infarction (STEMI) and unstable angina (UA). Baseline and ATP-binding cassette transporter ABCA1 and ABCG1 (ABCA1/G1)-mediated macrophage cholesterol efflux to APOB-depleted plasma was decreased in patients with STEMI, and the latter was further impaired in those who died during follow-up. Moreover, the circulating concentrations of TMAO, γBB, and TML were higher in the deceased STEMI patients when compared with the STEMI survivors or UA patients. However, after statistical adjustment, only ABCA1/G1-mediated macrophage cholesterol efflux remained significantly associated with mortality. Furthermore, neither the TMAO, γBB, nor TML levels altered the HDL-mediated macrophage cholesterol efflux in vitro. We conclude that impaired ABCA1/G1-mediated macrophage cholesterol efflux is independently associated with mortality at follow-up in STEMI patients.

Uncurtaining the pivotal role of ABC transporters in diabetes mellitus

The metabolic disorders are the edge points for the initiation of various diseases. These disorders comprised of several diseases including diabetes, obesity, and cardiovascular complications. Worldwide, the prevalence of these disorders is increasing day by day. The world's population is at higher threat of developing metabolic disease, especially diabetes. Therefore, there is an impregnable necessity of searching for a newer therapeutic target to reduce the burden of these disorders. Diabetes mellitus (DM) is marked with the dysregulated insulin secretion and resistance. The lipid and glucose transporters portray a pivotal role in the metabolism and transport of both of these. The excess production of lipid and glucose and decreased clearance of these leads to the emergence of DM. The ATP-binding cassette transporters (ABCT) are important for the metabolism of glucose and lipid. Various studies suggest the key involvement of ABCT in the pathologic process of different diseases. In addition, the involvement of other pathways, including IGF signaling, P13-Akt/PKC/MAPK signaling, and GLP-1 via regulation of ABCT, may help develop new treatment strategies to cope with insulin resistance dysregulated glucose metabolism, key features in DM.

Impact of Dietary Lipids on the Reverse Cholesterol Transport: What We Learned from Animal Studies

Reverse cholesterol transport (RCT) is a physiological mechanism protecting cells from an excessive accumulation of cholesterol. When this process begins in vascular macrophages, it acquires antiatherogenic properties, as has been widely demonstrated in animal models. Dietary lipids, despite representing a fundamental source of energy and exerting multiple biological functions, may induce detrimental effects on cardiovascular health. In the present review we summarize the current knowledge on the mechanisms of action of the most relevant classes of dietary lipids, such as fatty acids, sterols and liposoluble vitamins, with effects on different steps of RCT. We also provide a critical analysis of data obtained from experimental models which can serve as a valuable tool to clarify the effects of dietary lipids on cardiovascular disease.