Cardioprotective Properties of HDL: Structural and Functional Considerations

Dynamics of HDL-Cholesterol Following a Post-Myocardial Infarction Cardiac Rehabilitation Program

Background

Exercise-based cardiac rehabilitation programs (CRP) are recommended for patients following acute coronary syndrome to potentially improve high-density lipoprotein cholesterol (HDL-C) levels and prognosis. However, not all patients reach target HDL-C levels. Here we analyze the dynamics and predictors of HDL-C increase during CRP in patients following ST-segment elevation myocardial infarction or occlusion myocardial infarction.

Methods

We conducted a prospective study of myocardial infarction patients who completed exercise-based Phase 2 CRP. Data was collected on clinical variables, cardiovascular risk factors, treatment goals, pharmacological therapy, and health outcomes through questionnaires at the beginning and at the end of Phase 2 CRP. Lipid profile analysis was performed before discharge, 4 to 6 weeks after discharge, and at the end of Phase 2 CRP. Changes in lipid profiles were evaluated, and predictors of failure to increase HDL-C levels were identified by binary logistic regression analysis.

Results

Our cohort comprised 121 patients (mean age 61.67 ± 10.97 years, 86.8% male, and 47.9% smokers before admission). A significant decrease in total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) were noted, along with an increase in HDL-C (43.87 ± 9.18 vs. 39.8 ± 10.03 mg/dL, p < 0.001). Patients achieving normal HDL-C levels (>40 mg/dL in men and >50 mg/dL in women) significantly increased from 34.7% at admission to 52.9% the end of Phase 2. Multivariable analysis revealed smoking history (hazard ratio [HR] = 0.35, 95% confidence interval [CI], 0.11-0.96, p = 0.04), increased reduction in total cholesterol (HR = 0.94, 95% CI, 0.89-0.98, p = 0.004), and increased reduction in LDL-C (HR = 0.94, 95% CI, 0.89-0.99, p = 0.01) were inversely associated with failure to increase HDL-C levels. Conversely, higher HDL-C before CRP (HR = 1.15, 95% CI, 1.07-1.23, p < 0.001) and increased lipoprotein (a) (HR = 1.01, 95% CI, 1-1.02, p = 0.04) predicted failure to increase HDL-C levels. No significant correlations were found with Mediterranean diet adherence, weekly physical activity, training modalities, or physical fitness parameters.

Conclusions

Participation in an exercise-based Phase 2 CRP led to mild but significant increases in HDL-C. Smoking history and patients experiencing substantial reductions in total cholesterol and LDL-C were more likely to experience HDL-C increases, unlike those with higher HDL-C and lipoprotein (a) levels before CRP.

Cardiorespiratory Fitness Is Not Associated with Cardiovascular Disease Risk in Firefighters: A Cross-Sectional Study in South African Firefighters

Cardiovascular disease (CVD) risk factors are frequently reported among firefighters, yet no studies have compared these factors between male and female firefighters, specifically from a low- to middle-income country (LMIC). This study aimed to determine the prevalence of CVD risk factors and their relationship with cardiorespiratory fitness (VO2max) in 254 active career firefighters (mean age: 42.6 ± 7.8 years). The assessments included anthropometry, blood pressure, blood glucose, cholesterol, triglycerides, and VO2max. The results indicated that 48.0% and 51.8% of females and males were pre-hypertensive, respectively. Hypertension was identified in 15.8% of the firefighters. According to body mass index (BMI), 37.3% of males and 25% of females were found to be overweight, while an additional 44.9% of males and 45.7% of females were classified as obese. Only 17.3% of males and 18.2% of females were found to be of normal weight. These findings were corroborated by categories of central obesity using waist circumference (WC), which were 47.7% for males and 41.6% for females. Low HDL-C was found in 95.2% of males and 86.4% of females, with 28.3% of males also having elevated triglyceride levels (TG). VO2max was "excellent" in 48.8% of males and 12.6% of females, though it had no significant association with most CVD risk factors. The only notable link was a small correlation between VO2max and triglycerides (r = -0.215; p = 0.001). These findings suggest that while cardiorespiratory fitness may have no impact, additional factors likely contribute to the cardiovascular health of firefighters, necessitating the need for comprehensive health and fitness programmes.

Pleiotropic functions and clinical importance of circulating HDL-PON1 complex

High density lipoprotein (HDL) functions are mostly mediated through a complex proteome, particularly its enzymes. HDL can provide a scaffold for the assembly of several proteins that affect each other's function. HDL particles, particularly small, dense HDL3, are rich in paraoxonase 1 (PON1), which is an important enzyme in the functionality of HDL, so the antioxidant and antiatherogenic properties of HDL are largely attributed to this enzyme. There is an increasing need to represent a valid, reproducible, and reliable method to assay HDL function in routine clinical laboratories. In this context, HDL-associated proteins may be key players; notably PON1 activity (its arylesterase activity) may be a proper candidate because its decreased activity can be considered an important risk factor for HDL dysfunctionality. Of note, automated methods have been developed for the measurement of serum PON1 activity that facilitates its assay in large sample numbers. Arylesterase activity is proposed as a preferred activity among the different activities of PON1 for its assay in epidemiological studies. The binding of PON1 to HDL is critical for the maintenance of its activity and it appears apolipoprotein A-I plays an important role in HDL-PON1 interaction as well as in the biochemical and enzymatic properties of PON1. The interrelationships between HDL, PON1, and HDL's other components are complex and incompletely understood. The purpose of this review is to discuss biochemical and clinical evidence considering the interactions of PON1 with HDL and the role of this enzyme as an appropriate biomarker for HDL function as well as a potential therapeutic target.

Association between human blood metabolome and the risk of pre-eclampsia

Pre-eclampsia is a complex multi-system pregnancy disorder with limited treatment options. Therefore, we aimed to screen for metabolites that have causal associations with preeclampsia and to predict target-mediated side effects based on Mendelian randomization (MR) analysis. A two-sample MR analysis was firstly conducted to systematically assess causal associations of blood metabolites with pre-eclampsia, by using metabolites related large-scale genome-wide association studies (GWASs) involving 147,827 European participants, as well as GWASs summary data about pre-eclampsia from the FinnGen consortium R8 release data that included 182,035 Finnish adult female subjects (5922 cases and 176,113 controls). Subsequently, a phenome-wide MR (Phe-MR) analysis was applied to assess the potential on-target side effects associated with hypothetical interventions that reduced the burden of pre-eclampsia by targeting identified metabolites. Four metabolites were identified as potential causal mediators for pre-eclampsia by using the inverse-variance weighted method, including cholesterol in large HDL (L-HDL-C) [odds ratio (OR): 0.88; 95% confidence interval (95% CI): 0.83-0.93; P = 2.14 × 10-5), cholesteryl esters in large HDL (L-HDL-CE) (OR: 0.88; 95% CI: 0.83-0.94; P = 5.93 × 10-5), free cholesterol in very large HDL (XL-HDL-FC) (OR: 0.88; 95% CI: 0.82-0.94; P = 1.10 × 10-4) and free cholesterol in large HDL (L-HDL-FC) (OR: 0.89; 95% CI: 0.84-0.95; P = 1.45 × 10-4). Phe-MR analysis showed that targeting L-HDL-CE had beneficial effects on the risk of 24 diseases from seven disease chapters. Based on this systematic MR analysis, L-HDL-C, L-HDL-CE, XL-HDL-FC, and L-HDL-FC were inversely associated with the risk of pre-eclampsia. Interestingly, L-HDL-CE may be a promising drug target for preventing pre-eclampsia with no predicted detrimental side effects. The study consists of a two-stage design that conducts MR at both stages. First, we assessed the causality for the associations between 194 blood metabolites and the risk of pre-eclampsia. Second, we investigated a broad spectrum of side effects associated with the targeting identified metabolites in 693 non-preeclampsia diseases. Our results suggested that Cholesteryl esters in large HDL may serve as a promising drug target for the prevention or treatment of pre-eclampsia with no predicted detrimental side effects.

Effect of fixed-dose combination of insulin degludec and liraglutide on apoB-containing lipoprotein subclasses and HDL lipidome in type 2 diabetes

AIMS

Administration of insulin degludec and liraglutide (IDegLira) correlates to fasting lipid profile changes of diabetic patients, while data concerning apoB-containing lipoprotein subclasses and HDL lipidome are scarce. We evaluated its effect on fasting lipid parameters, apolipoproteins, apoB-containing lipoprotein subclasses and HDL lipidome in patients with type 2 diabetes.

METHODS

Sixty three patients with HbA1c > 7 % on oral glucose-lowering drugs received either IDegLira or insulin degludec for 3 months. Lipoprotein subfraction profile was determined through Lipoprint method, whereas HDL lipid composition via ¹H NMR.

RESULTS

Compared to insulin degludec, IDegLira administration resulted in significantly greater reduction of total and LDL-cholesterol. On the other hand, the effect of the two drugs on apolipoprotein-B-containing lipoprotein subfractions concentration was minimal and did not differ between the 2 interventions. IDegLira, but not insulin degludec, induced an atheroprotective shift in HDL's fatty acid composition and particle core depletion in triglycerides.

CONCLUSIONS

IDegLira administration is accompanied by total and LDL-cholesterol reduction, while sdLDL concentration only reduced in patients experiencing triglyceride reduction. IDegLira induced compositional changes of HDL particles. These changes may contribute to the cardioprotective properties of liraglutide.

Lipoprotein profiles associated with exposure to poly- and perfluoroalkyl substances (PFASs) in the EuroMix human biomonitoring study

Exposure to per- and polyfluoroalkyl substances (PFASs) is associated with increased blood cholesterol. Although elevated cholesterol is a well-established risk factor for cardiovascular diseases (CVD), it is not clear whether PFASs affect this risk. Lipoprotein subclasses are emerging biomarkers for disease risk and lipoprotein profiling may provide an insight to physiological implications of PFAS exposure. We explored the association between serum PFAS concentrations and lipoprotein subclasses in a cross-sectional study. We determined the concentrations and lipid composition of the major subclasses of lipoproteins in plasma samples from 127 adult participants of the EuroMix human biomonitoring study by nuclear magnetic resonance (NMR). Serum concentrations of 17 PFASs showed a detection frequency between 30 and 100% and were included in further analyses. We examined the associations between PFAS concentrations and lipoprotein subclasses by linear mixed-effect regression models, adjusted for confounders. In the adjusted models, positive associations were found between several PFASs and cholesterol concentrations in large to medium sized HDL and medium sized LDL particles. We found a 4-12% increase in HDL cholesterol per interquartile range (IQR) increase for several PFASs. In women the associations with PFNA, PFUnDA, PFDoDA and PFOS were significant after adjustment for multiple comparisons. Similar magnitude of change was observed between longer chained PFASs and LDL cholesterol, and a few of these associations reached significance for cholesterol in large to medium LDL particle sizes in women. No significant associations with plasma triglycerides were observed. However, most PFASs tended to be associated with reduction in VLDL (very low-density lipoproteins) particle number and VLDL triglyceride. Findings from this exploratory study, suggest that background PFAS exposures influence particle size distributions and lipid composition of plasma lipoprotein subclasses, and that these effects may be more prominent in women. A two-points lipoprofiling for all subjects indicated both low intra-individual variability and good analytical reproducibility.

Effect of renal function on high-density lipoprotein particles in patients with coronary heart disease

BACKGROUND

Although renal insufficiency and dyslipidemia are known to be closely associated, the effect of kidney function on the size and clinical value of high-density lipoprotein (HDL) particles remains largely unknown, especially in patients with coronary heart disease.

METHODS

A total of 419 coronary heart disease patients and 105 non-coronary heart disease patients were included. HDL particle size, represented by HDL-C/apoA-I, was compared between groups stratified by estimated glomerular filtration rate (eGFR) and Gensini scores using standard Student's t test and one-way ANOVA. Pearson's correlation test was performed to analyze the association between eGFR and HDL-C/apoA-I in patients with coronary heart disease. The relationship between HDL particle size and the occurrence of coronary heart disease was explored using Univariate logistic regression analysis.

RESULTS

In patients with coronary heart disease, between-group analysis revealed that HDL-C/apoA-I increased as eGFR declined, and significance appeared as eGFR declined to under 60 ml/min·1.73 m² (P < 0.001), and Pearson's correlation test also confirmed an inverse correlation between eGFR and HDL-C/apoA-I levels in coronary heart disease patients. When stratified by Gensini scores, in coronary heart disease patients with eGFR ≥ 90 mL/(min·1.73 m²), those with higher Gensini scores had smaller HDL-C/apoA-I. However, with or without kidney insufficiency, smaller HDL-C/apoA-I was associated with a higher occurrence of coronary heart disease (P < 0.05).

CONCLUSION

With the presence of renal insufficiency, HDL-C/apoA1 was higher in patients with coronary heart disease. Lower HDL-C/apoA1 was still associated with a higher occurrence of coronary heart disease, but the original association between lower HDL-C/apoA1 and more severe coronary artery stenosis was lost in patients with renal insufficiency.

Biomarker Discovery in Atherosclerotic Diseases Using Quantitative Nuclear Magnetic Resonance Metabolomics

Despite great progress in the management of atherosclerosis (AS), its subsequent cardiovascular disease (CVD) remains the leading cause of morbidity and mortality. This is probably due to insufficient risk detection using routine lipid testing; thus, there is a need for more effective approaches relying on new biomarkers. Quantitative nuclear magnetic resonance (qNMR) metabolomics is able to phenotype holistic metabolic changes, with a unique advantage in regard to quantifying lipid-protein complexes. The rapidly increasing literature has indicated that qNMR-based lipoprotein particle number, particle size, lipid components, and some molecular metabolites can provide deeper insight into atherogenic diseases and could serve as novel promising determinants. Therefore, this article aims to offer an updated review of the qNMR biomarkers of AS and CVD found in epidemiological studies, with a special emphasis on lipoprotein-related parameters. As more researches are performed, we can envision more qNMR metabolite biomarkers being successfully translated into daily clinical practice to enhance the prevention, detection and intervention of atherosclerotic diseases.

High-density lipoprotein remodeling by phospholipid nanoparticles improves cholesterol efflux capacity and protects from atherosclerosis

The efficiency of cholesterol efflux from cells promoted by high-density lipoproteins (HDLs) depends on HDL concentration and functional properties. The term "dysfunctional HDL" describes HDLs with impaired protective properties. Cholesterol efflux capacity (CEC) of HDL is reduced in patients with atherosclerosis, but the exact mechanisms underlying this impairment are not well characterized. Enriching HDLs with phospholipids (PLs) improves CEC. Herein, we assessed the potential of PL nanoparticles in improving HDL functionality. We lipidated HDL subfractions by incubating with PL nanoparticles containing soybean polyunsaturated phosphatidylcholine. Incubating blood plasma with PL nanoparticles resulted in the dose-dependent lipidation of all HDL subfractions. Changes in apolipoprotein A1 (apoA-1) and PL concentrations were the most prominent in the HDL₂ fraction. Concentrations of PL in the HDL₃ fraction and the fraction with a density > 1.21 g/mL increased by 30-50%, whereas apoA-1 levels decreased. We hypothesized that PL nanoparticles may cause HDL remodeling that can improve their functions. The CECs of lipidated HDLs were analyzed by incubating apolipoprotein B (apoB)-depleted plasma with ³H-cholesterol-labeled THP-1 macrophages. The findings revealed a two-fold increase in cholesterol efflux compared with native apoB-depleted plasma. Moreover, intravenous administration of PL nanoparticles restored lipid profiles and effectively protected blood vessels from atherosclerosis progression in cholesterol-fed rabbits compared with that of fenofibrate and atorvastatin. PL nanoparticles also protected against atherosclerosis and decreased the atherogenic index. Altogether, these results indicate that PL nanoparticles can be used to correct the lipid composition and CEC of HDLs. DATA AVAILABILITY: Additional data can be provided upon reasonable request from the date of publication of this article within 5 years. The request should be sent to the author-correspondent at the address cd95@mail.ru.

Efficacy and safety of liraglutide in type 2 diabetes mellitus patients complicated with coronary artery disease: A systematic review and meta-analysis of randomized controlled trials

To evaluate the efficacy and safety of liraglutide in patients with Type 2 Diabetes Mellitus (T2DM) complicated with Coronary Artery Disease (CAD), we searched PubMed, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), Chinese VIP Information (VIP), Wanfang Database and Chinese Biomedical Literature database (CBM) for relevant randomized controlled trials (RCTs) from inception to 7 October 2020. A total of 18 RCTs including 1557 patients with T2DM complicated with CAD were included. Meta-analysis revealed liraglutide reduced hemoglobin A1c (HbA1c) (WMD = -0.67; 95% CI[-0.94 to -0.39]; P < 0.00001), fasting plasma glucose (FPG) (WMD = -0.80; 95% CI[-1.06 to -0.54]; P < 0.00001) and 2 h plasma glucose (2hPG) (WMD = -1.64; 95% CI[-2.12 to -1.16]; P＜0.00001); improved left ventricular ejection fraction(LVEF) (WMD = 4.79; 95% CI[4.08-5.51]; P < 0.00001), left ventricular end-diastolic diameter (LVEDD) (WMD = -5.70; 95% CI[-6.67 to -4.72]; P＜0.00001), E/A (WMD = 0.13; 95% CI[0.11-0.14]; P < 0.00001) and left ventricular posterior wall thickness (LVPWT) (WMD = -1.86; 95% CI[-2.16 to -1.55]; P < 0.00001); reduced total cholesterol (TC) (WMD = -0.48; 95% CI[-0.56 to -0.39]; P < 0.00001), triglycerides (TG) (WMD = -0.42; 95% CI[-0.59 to -0.26]; P < 0.00001), low-density lipoprotein cholesterol (LDL-C) (WMD = -0.41; 95% CI[-0.55 to -0.26]; P < 0.00001), and increased high-density lipoprotein cholesterol (HDL-C) (WMD = -0.19; 95% CI[0.13-0.24]; P = 0.0005). As for safety assessment, liraglutide did not increase the incidence of hypoglycemia (OR = 0.75, 95% CI[0.32-1.77], P = 0.51) and gastrointestinal (OR = 1.15, 95% CI[0.72-1.85], P = 0.55) events. Consequently, liraglutide had favorable effects on blood glucose, cardiac function, lipid profile and an acceptable safety profile.

The effect of tibolone treatment on lipid profile in women: A systematic review and dose-response meta-analysis of randomized controlled trials

Inconsistencies exist with regard to influence of tibolone treatment on the lipid profile. The reasons for these inconsistencies might derive from several factors, i.e., differences in baseline variables, intervention duration, participants' health status or baseline body mass index (BMI). To address these inconsistencies, based on a systematic search in Scopus, PubMed/Medline, Web of Science, and Embase for papers published until 21 December 2020, we conducted the current dose-response meta-analysis of randomized controlled trials (RCTs) to determine the impact of tibolone treatment on the lipid profile. The overall findings were derived from 26 RCTs. Tibolone administration decreased total cholesterol (TC) (weighted mean difference, WMD: -18.55 mg/dL, CI: -25.95 to -11.16, P < 0.001), high-density lipoprotein-cholesterol (HDL-C) (WMD: -9.42 mg/dL, CI: -11.83 to -7.01, P < 0.001) and triglyceride (TG) (WMD: -21.43 mg/dL, CI: -27.15 to -15.70, P < 0.001) levels. A significant reduction in LDL-C occurred when tibolone was prescribed for ≤ 26 weeks (WMD: -7.64 mg/dL, 95% CI: -14.58 to -0.70, P = 0.031) versus > 26 weeks (WMD: -8.84 mg/dL, 95% CI: -29.98, 12.29, P = 0.412). The decrease in TG (WMD: -22.64 mg/dL) and TC (-18.55 mg/dL) concentrations was more pronounced in patients with BMI ≥ 25 kg/m2versus BMI < 25 kg/m2. This systematic review and meta-analysis discovered that tibolone decreases TC, HDL-C and TG levels. LDL-C concentrations are significantly reduced when tibolone administration lasts for ≤ 26 weeks.

[Plasma high density lipoproteins phospholipds as an indirect indicator of their cholesterol efflux capacity - new suspected atherosclerosis risk factor]

High density lipoproteins (HDL) are a unique natural structure, protecting the body from the development of atherosclerotic vascular lesions and cardiovascular diseases due to this ability to remove cholesterol from cells. Plasma HDL level estimated by their cholesterol content, is a common lipid parameter, and its decrease is considered as an established atherosclerosis risk factor. However, a number of studies have shown the absence of positive clinical effects after drug-induced increase in HDL cholesterol. There is increasing evidence that not only HDL concentration, but also HDL properties, considered in this review are important. Many studies showed the decrease of HDL cholesterol efflux capacity in patients with coronary heart diseases and its association with disease severity. Some authors consider a decrease of this HDL capacity as a new additional risk factor of atherosclerosis. The review summarizes existing information on various protein and lipid components of HDL with a primary emphasis on the HDL. Special attention is paid to correlation between the HDL cholesterol efflux capacity and HDL phospholipids and the ratio "phospholipids/free cholesterol". The accumulated information indicates importance of evaluation in the HDL fraction not only in terms of their cholesterol, but also phospholipids. In addition to the traditionally used lipid criteria, this would provide more comprehensive information about the activity of the reverse cholesterol transport process in the body and could contribute to the targeted correction of the detected disorders.

Improved risk assessment of coronary artery disease by substituting paraoxonase 1 activity for HDL-C: Novel cardiometabolic biomarkers based on HDL functionality

BACKGROUND AND AIMS

Developing laboratory assays to evaluate HDL functions and improve cardiovascular disease (CVD) risk assessment has recently emerged as a challenge. The present study was conducted to help predict the risk of coronary artery disease (CAD) by investigating new cardiometabolic risk factors based on substituting paraoxonase 1 (PON1) as a critical enzyme in the functionality of HDL for that of HDL-C.

METHODS AND RESULTS

The present study recruited 274 subjects undergoing diagnostic coronary angiography, 92 without significant CAD (non-CAD), and 182 with a severe CAD. The diagnostic accuracy of the new biomarkers in non-CAD versus multi-vessel disease was obtained in descending order of AUC as 0.72 (P < 0.001) for log (TG/PON1), 0.70 (P < 0.001) for nonHDL-C/PON1, and 0.67 (P < 0.001) for LDL-C/PON1. After performing a multivariate adjustment for age, gender, BMI, statin therapy, and diabetes mellitus, the increased odds of CAD remained significant for the new cardiometabolic ratios as independent variables [adjusted OR = 1.47 (1.15-1.88), p = 0.002 for LDL-C/PON1; adjusted OR = 2.15 (1.41-3.5), p = 0.009 for nonHDL-C/PON1; adjusted OR = 5.03 (2.14-13.02), p = 0.004 for log (TG/PON1)]. CAD was diagnosed with an optimal discriminating cutoff of 1.84 for LDL-C/PON1, 2.8 for nonHDL-C/PON1, and 0.48 for log (TG/PON1).

CONCLUSIONS

To improve CAD's risk assessment, the PON1 activity was proposed as an alternative to HDL-C in the commonly used atherogenic lipid ratios. Substituting the PON1 activity for the HDL-C concentration can provide an index of the HDL activity. The present study sought to exploit the lipoprotein-related risk factors of CAD from a more effective perspective.

Fetal High-Density Lipoproteins: Current Knowledge on Particle Metabolism, Composition and Function in Health and Disease

Cholesterol and other lipids carried by lipoproteins play an indispensable role in fetal development. Recent evidence suggests that maternally derived high-density lipoprotein (HDL) differs from fetal HDL with respect to its proteome, size, and function. Compared to the HDL of adults, fetal HDL is the major carrier of cholesterol and has a unique composition that implies other physiological functions. Fetal HDL is enriched in apolipoprotein E, which binds with high affinity to the low-density lipoprotein receptor. Thus, it appears that a primary function of fetal HDL is the transport of cholesterol to tissues as is accomplished by low-density lipoproteins in adults. The fetal HDL-associated bioactive sphingolipid sphingosine-1-phosphate shows strong vasoprotective effects at the fetoplacental vasculature. Moreover, lipoprotein-associated phospholipase A2 carried by fetal-HDL exerts anti-oxidative and athero-protective functions on the fetoplacental endothelium. Notably, the mass and activity of HDL-associated paraoxonase 1 are about 5-fold lower in the fetus, accompanied by an attenuation of anti-oxidative activity of fetal HDL. Cholesteryl ester transfer protein activity is reduced in fetal circulation despite similar amounts of the enzyme in maternal and fetal serum. This review summarizes the current knowledge on fetal HDL as a potential vasoprotective lipoprotein during fetal development. We also provide an overview of whether and how the protective functionalities of HDL are impaired in pregnancy-related syndromes such as pre-eclampsia or gestational diabetes mellitus.

The Role of the ATP-Binding Cassette A1 (ABCA1) in Human Disease

Cholesterol homeostasis is essential in normal physiology of all cells. One of several proteins involved in cholesterol homeostasis is the ATP-binding cassette transporter A1 (ABCA1), a transmembrane protein widely expressed in many tissues. One of its main functions is the efflux of intracellular free cholesterol and phospholipids across the plasma membrane to combine with apolipoproteins, mainly apolipoprotein A-I (Apo A-I), forming nascent high-density lipoprotein-cholesterol (HDL-C) particles, the first step of reverse cholesterol transport (RCT). In addition, ABCA1 regulates cholesterol and phospholipid content in the plasma membrane affecting lipid rafts, microparticle (MP) formation and cell signaling. Thus, it is not surprising that impaired ABCA1 function and altered cholesterol homeostasis may affect many different organs and is involved in the pathophysiology of a broad array of diseases. This review describes evidence obtained from animal models, human studies and genetic variation explaining how ABCA1 is involved in dyslipidemia, coronary heart disease (CHD), type 2 diabetes (T2D), thrombosis, neurological disorders, age-related macular degeneration (AMD), glaucoma, viral infections and in cancer progression.

Connection between the Altered HDL Antioxidant and Anti-Inflammatory Properties and the Risk to Develop Alzheimer's Disease: A Narrative Review

The protein composition of high-density lipoprotein (HDL) is extremely fluid. The quantity and quality of protein constituents drive the multiple biological functions of these lipoproteins, which include the ability to contrast atherogenesis, sustained inflammation, and toxic effects of reactive species. Several diseases where inflammation and oxidative stress participate in the pathogenetic process are characterized by perturbation in the HDL proteome. This change inevitably affects the functionality of the lipoprotein. An enlightening example in this frame comes from the literature on Alzheimer's disease (AD). Growing lines of epidemiological evidence suggest that loss of HDL-associated proteins, such as lipoprotein phospholipase A2 (Lp-PLA2), glutathione peroxidase-3 (GPx-3), and paraoxonase-1 and paraoxonase-3 (PON1, PON3), may be a feature of AD, even at the early stage. Moreover, the decrease in these enzymes with antioxidant/defensive action appears to be accompanied by a parallel increase of prooxidant and proinflammatory mediators, in particular myeloperoxidase (MPO) and serum amyloid A (SAA). This type of derangement of balance between two opposite forces makes HDL dysfunctional, i.e., unable to exert its "natural" vasculoprotective property. In this review, we summarized and critically analyzed the most significant findings linking HDL accessory proteins and AD. We also discuss the most convincing hypothesis explaining the mechanism by which an observed systemic occurrence may have repercussions in the brain.

Losartan and azelastine either alone or in combination as modulators for endothelial dysfunction and platelets activation in diabetic hyperlipidemic rats

AIM

The present study aimed mainly to demonstrate the effect of the antihistamine azelastine (AZ) and Angiotensin receptor blocker ( ARB), represented by losartan (LOS) either alone or in combined form on certain metabolic aspects, endothelial dysfunction and platelets activation markers in diabetic hyperlipidemic rat model.

METHODS

Rats were randomly classified to five groups: One group fed normal chow diet (NC). Four groups received alloxan and CCT-diet. One group received no treatment (DHC while the other three groups received AZ, LOS and their combination form, respectively for 8 weeks. Serum and tissue samples were collected for biochemical and histological evaluations.

RESULTS

DHC rats demonstrated significant hyperglycaemia, dyslipidemia, disturbances in endothelial and platelet activation markers. AZ or LOS administration demonstrated hypoglycaemic and hypolipidemic effects. VCAM-1 and sE-selectin (Endothelial function markers) along with CD63 (Platelet activation marker) showed significant decrease as compared to control group. AZ administration exerted little prominent effects than that of LOS, while their combination demonstrated remarkable changes compared to monotherapy. Histopathological findings were in agreement to certain extent with the biomarkers results.

CONCLUSIONS

Both drug categories may be expressed as suitable therapeutic tools for atherosclerotic complications either alone or along with other hypolipidemic drugs.

Myeloperoxidase as cardiovascular risk marker in pre-pubertal preterm children?

BACKGROUND AND AIMS

To evaluate the biomarkers related to cardiovascular risk in pre-pubertal preterm children with a birth weight of less than 1,500 g and relate them to current nutritional status, insulin resistance, and inflammation.

METHODS & RESULTS

This is a cross-sectional, controlled study with pre-pubertal preterm children aged 5-9 years with a birth weight of less than 1500 g (Preterm group, n = 44) compared to full term children of adequate weight for gestational age (Control group, n = 30). Clinical evaluation: anthropometry and pubertal staging. Laboratory tests: total cholesterol and fractions, triglycerides, paraoxonase 1, apolipoproteins A-I and B, myeloperoxidase (MPO), high sensitivity C-reactive protein (hs-CRP), glycemia and insulin (to calculate HOMA-IR). In the preterm group, 19 (43.2%) were male, with mean birth weight and gestational age of 1157 ± 242 g and 30.0 ± 2.3 weeks, respectively. The preterm group showed lower concentrations of HDL-c (60.1 ± 10.1 vs. 69.0 ± 10.0 mg/dL; p < 0.001); higher concentrations of hs-CRP [0.55 mg/dL (0.30; 39.4) vs. 0.30 mg/dL (0.30; 10.80); p = 0.043], of MPO [21.1 ng/mL (5.7; 120.0) vs. 8.1 ng/mL (2.6; 29.6); p < 0.001] and of MPO/HDL-c ratio [0.39 (0.09; 2.07) ng/mg vs. 0.11 (0.05; 0.58)]. The MPO/HDL-c ratio was the variable that showed the best discriminatory power between the groups (AUC = 0.878; 95% CI; 0.795-0.961). MPO concentrations in the preterm group were correlated with those of hs-CRP (r = 0.390; p = 0.009), insulin (r = 0.448; p = 0.002) and HOMA-IR (r = 0.462; p = 0.002).

CONCLUSION

Prepubertal preterm children show high MPO concentrations and MPO/HDL-c ratio that are associated with inflammation and oxidative stress, which, in turn, may be associated with atherosclerosis.

Short-term treatment with high dose liraglutide improves lipid and lipoprotein profile and changes hormonal mediators of lipid metabolism in obese patients with no overt type 2 diabetes mellitus: a randomized, placebo-controlled, cross-over, double-blind clinical trial

OBJECTIVE

Long-term treatment with up to 1.8 mg liraglutide improves cardiovascular and all-cause mortality in patients with type 2 diabetes at high risk for cardiovascular disease (CVD) and is currently under investigation in subjects without diabetes. Aim of our study was to investigate whether high dose (3 mg) short-term (5 weeks) treatment with liraglutide in obese patients with no overt type 2 diabetes affects metabolites, lipid and lipoprotein profile and components of activin-follistatin axis in cardiovascular beneficial or detrimental way.

RESEARCH DESIGN AND METHODS

Twenty obese patients participated in a randomized, placebo-controlled, cross-over, double-blind study and were administrated liraglutide 3 mg or placebo for 5 weeks. Metabolites, fatty acids, lipid-lipoprotein profile and concentrations of activins and follistatins (250 parameters) were assessed in serum at start and completion of each treatment.

RESULTS

Concentrations of important cardiovascular markers such as total, free and remnant cholesterol were reduced with liraglutide before and after adjusting for weight loss. Similarly, reductions in number of small and medium size LDL particles and in their total lipid concentration were observed with liraglutide and partially weight-loss related. Tyrosine levels were reduced and behenic acid levels were increased whereas only minor changes were observed in HDL, VLDL and IDL. Concentrations of activin AB and follistatin were significantly reduced in liraglutide-treated group.

CONCLUSIONS

Treatment of obese patients without overt type 2 diabetes with high dose of liraglutide for a short period of time induces changes in lipid-lipoprotein and hormonal profile that are suggestive of lower risk of atherosclerosis and CVD. Trial registration ClinicalTrials.gov Identifier: NCT02944500. Study ID Number 2015P000327. Registered November 2016.

Angiopoietin-1 aggravates atherosclerosis by inhibiting cholesterol efflux and promoting inflammatory response

OBJECTIVE

Angiopoietin-1 (Ang-1), a secreted protein, mainly regulates angiogenesis. Ang-1 has been shown to promote the development of atherosclerosis, whereas little is known about its effects on lipid metabolism and inflammation in this process.

METHOD

Ang-1 was transfected into ApoE^-/- mice via lentiviral vector or incubated with THP-1 derived macrophages. Oil red O and HE staining were performed to measure the size of atherosclerotic plaques in ApoE^-/- mice. Immunofluorescence was employed to show the expression of target proteins in aorta. [³H] labeled cholesterol was performed to examine the efficiency of cholesterol efflux and reverse cholesterol transport (RCT) both in vivo and vitro. Western blot and qPCR were used to quantify target proteins both in vivo and vitro. ELISA detected the levels of pro-inflammatory cytokines in mouse peritoneal macrophage.

RESULTS

Our data showed that Ang-1 augmented atherosclerotic plaques formation and inhibited cholesterol efflux. The binding of Ang-1 to Tie2 resulted in downregulation of LXRα, ABCA1 and ABCG1 expression via inhibiting the translocation of TFE3 into nucleus. In addition, Ang-1 decreased serum HDL-C levels and reduced reverse cholesterol transport (RCT) in ApoE-/- mice. Furthermore, Ang-1 induced lipid accumulation followed by increasing TNF-α, IL-6, IL-1β，and MCP-1 produced by MPMs, as well as inducing M1 phenotype macrophage marker iNOS and CD86 expression in aorta of ApoE^-/- mice.

CONCLUSION

Ang-1 has an adverse effect on cholesterol efflux by decreasing the expression of ABCA1 and ABCG1 via Tie2/TFE3/LXRα pathway, thereby promoting inflammation and accelerating atherosclerosis progression.