New Insights Into the Regulation of HDL Metabolism and Reverse Cholesterol Transport

Shuttle/sink model composed of β-cyclodextrin and simvastatin-loaded discoidal reconstituted high-density lipoprotein for enhanced cholesterol efflux and drug uptake in macrophage/foam cells

Targeting drug delivery to macrophage/foam cells is challenged owing to the poor cell permeability and fluidity resulting from the massive accumulation of intracellular cholesterol in atherosclerosis (AS). Discoidal reconstituted high-density lipoprotein (d-rHDL) has been well regarded as a potential drug delivery system for AS by virtue of its plaque-targeting and cholesterol removal abilities, while the latter is compromised by the high activation energy of cholesterol efflux. It is reported that a low concentration of β-cyclodextrin (β-CD) can function as a cholesterol shuttle to promote cholesterol efflux from cells to the extracellular acceptors (cholesterol sink, such as HDL particles), but it is still unknown whether the combination of β-CD with a drug-loaded d-rHDL can function as a shuttle/sink model to promote the remodeling and drug release of the d-rHDL carrier after accelerating the cholesterol efflux. Furthermore, it is interesting to investigate whether enhanced cholesterol efflux can improve the cellular drug uptake by restoring the permeability and fluidity of the cell membrane. Here, simvastatin-loaded d-rHDL (ST-d-rHDL) was combined with different concentrations of β-CD. Compared with ST-d-rHDL alone, the cholesterol removal ability of ST-d-rHDL combined with 0.5 mM of β-CD increased by 31-fold after incubation for 6 h and the cumulative drug release of ST-d-rHDL increased by two-fold during the initial 1 h in an acellular mimetic system. In macrophage/foam cells, 0.5 mM of β-CD showed superior promoting effects in the cholesterol removal ability and remodeling of ST-d-rHDL compared to 0.1 mM of β-CD. The high concentration of β-CD at 2 mM displayed a low efficiency for accelerating cholesterol efflux, which might function as a cholesterol sink rather than a cholesterol shuttle. Moreover, the permeability and fluidity of the cell membrane were improved by combining 0.5 mM of β-CD with ST-d-rHDL, which exhibited an enhanced cellular drug uptake and inhibiting effect on the intracellular lipid deposition and secretion of inflammatory cytokine. Collectively, combination of β-CD and ST-d-rHDL as a shuttle/sink model could enhance cholesterol efflux and drug uptake to suppress inflammation in macrophage/foam cells.

Low-density lipoprotein nanomedicines: mechanisms of targeting, biology, and theranostic potential

Native nanostructured lipoproteins such as low- and high-density lipoproteins (LDL and HDL) are powerful tools for the targeted delivery of drugs and imaging agents. While the cellular recognition of well-known HDL-based carriers occurs via interactions with an HDL receptor, the selective delivery and uptake of LDL particles by target cells are more complex. The most well-known mode of LDL-based delivery is via the interaction between apolipoprotein B (Apo-B) - the main protein of LDL - and the low-density lipoprotein receptor (LDLR). LDLR is expressed in the liver, adipocytes, and macrophages, and thus selectively delivers LDL carriers to these cells and tissues. Moreover, the elevated expression of LDLR in tumor cells indicates a role for LDL in the targeted delivery of chemotherapy drugs. In addition, chronic inflammation associated with hypercholesterolemia (i.e., high levels of endogenous LDL) can be abated by LDL carriers, which outcompete the deleterious oxidized LDL for uptake by macrophages. In this case, synthetic LDL nanocarriers act as 'eat-me' signals and exploit mechanisms of native LDL uptake for targeted drug delivery and imaging. Lastly, recent studies have shown that the delivery of LDL-based nanocarriers to macrophages via fluid-phase pinocytosis is a promising tool for atherosclerosis imaging. Hence, the present review summarizes the use of natural and synthetic LDL-based carriers for drug delivery and imaging and discusses various mechanisms of targeting.

High-Density Lipoprotein (HDL) in Allergy and Skin Diseases: Focus on Immunomodulating Functions

From an evolutionary perspective, lipoproteins are not only lipid transporters, but they also have important functions in many aspects of immunity. High-density lipoprotein (HDL) particles are the most abundant lipoproteins and the most heterogeneous in terms of their composition, structure, and biological functions. Despite strong evidence that HDL potently influences the activity of several immune cells, the role of HDL in allergies and skin diseases is poorly understood. Alterations in HDL-cholesterol levels have been observed in allergic asthma, allergic rhinitis, atopic dermatitis (eczema), psoriasis, urticaria, and angioedema. HDL-associated apolipoprotein (apo) A-I, apoA-IV, and apoC-III, and lyso-phosphatidylcholines potently suppress immune cell effector responses. Interestingly, recent studies provided evidence that allergies and skin diseases significantly affect HDL composition, metabolism, and function, which, in turn, could have a significant impact on disease progression, but may also affect the risk of cardiovascular disease and infections. Interestingly, not only a loss in function, but also, sometimes, a gain in function of certain HDL properties is observed. The objective of this review article is to summarize the newly identified changes in the metabolism, composition, and function of HDL in allergies and skin diseases. We aim to highlight the possible pathophysiological consequences with a focus on HDL-mediated immunomodulatory activities.

Relationship of angiotensin converting enzyme (I/D) polymorphism (rs4646994) and coronary heart disease among a male Iraqi population with type 2 diabetes mellitus

BACKGROUND

Insertion deletion (I/D) polymorphism (rs4646994) in the angiotensin-converting enzyme (ACE) has a substantial effect on coronary heart disease (CHD). The amplification of an Alu repetitive element in an intron of the ACE has shown three potential genotypes of I/I and D/D as homozygous, and I/D as heterozygous.

OBJECTIVE

The objective of this study was to investigate the association between the ACE gene polymorphism and CHD among male Iraqi patients with and without type2 diabetes mellitus (T2DM).

METHODS

A case-control study of total 217 male subjects participated in this study, divided into three groups; Group 1 including 86 CHD patients with T2DM, group 2 including 78 CHD patients without T2DM, and group 3 including 53 age and sex-matched healthy individuals (as a control group). Genotyping of ACE (I/D) gene was performed using polymerase chain reaction (PCR) technique.

RESULTS

The II allele was significantly more frequent in CHD patients without T2DM compared to the control population, but not from those patients with T2DM (p < 0.05). Nonetheless, the ID allele was significantly more frequent in each of CHD with T2DM and control populations compared to the CHD without T2DM. The DD allele was significantly more frequent in CHD patients with T2DM compared to each of CHD patients without T2DM and control populations (p < 0.05).

CONCLUSION

We conclude that the D/D and I/D genotypes are implicated as risk factors for development of CHD with T2DM, but not CHD without T2DM among the male Iraqi population. However, larger sample sizes are needed to monitor the CHD patients and to validate this study.

Computational SNP Analysis and Molecular Simulation Revealed the Most Deleterious Missense Variants in the NBD1 Domain of Human ABCA1 Transporter

The ATP-binding cassette transporter A1 (ABCA1) is a membrane-bound exporter protein involved in regulating serum HDL level by exporting cholesterol and phospholipids to load up in lipid-poor ApoA-I and ApoE, which allows the formation of nascent HDL. Mutations in the ABCA1 gene, when presents in both alleles, disrupt the canonical function of ABCA1, which associates with many disorders related to lipid transport. Although many studies have reported the phenotypic effects of a large number of ABCA1 variants, the pathological effect of non-synonymous polymorphisms (nsSNPs) in ABCA1 remains elusive. Therefore, aiming at exploring the structural and functional consequences of nsSNPs in ABCA1, in this study, we employed an integrated computational approach consisting of nine well-known in silico tools to identify damaging SNPs and molecular dynamics (MD) simulation to get insights into the magnitudes of the damaging effects. In silico tools revealed four nsSNPs as being most deleterious, where the two SNPs (G1050V and S1067C) are identified as the highly conserved and functional disrupting mutations located in the NBD1 domain. MD simulation suggested that both SNPs, G1050V and S1067C, changed the overall structural flexibility and dynamics of NBD1, and induced substantial alteration in the structural organization of ATP binding site. Taken together, these findings direct future studies to get more insights into the role of these variants in the loss of the ABCA1 function.

Cholesterol homeostasis: Researching a dialogue between the brain and peripheral tissues

Cholesterol homeostasis is a highly regulated process in human body because of its several functions underlying the biology of cell membranes, the synthesis of all steroid hormones and bile acids and the need of trafficking lipids destined to cell metabolism. In particular, it has been recognized that peripheral and central nervous system cholesterol metabolism are separated by the blood brain barrier and are regulated independently; indeed, peripherally, it depends on the balance between dietary intake and hepatic synthesis on one hand and its degradation on the other, whereas in central nervous system it is synthetized de novo to ensure brain physiology. In view of this complex metabolism and its relevant functions in mammalian, impaired levels of cholesterol can induce severe cellular dysfunction leading to metabolic, cardiovascular and neurodegenerative diseases. The aim of this review is to clarify the role of cholesterol homeostasis in health and disease highlighting new intriguing aspects of the cross talk between its central and peripheral metabolism.

Co-Administration of Propionate or Protocatechuic Acid Does Not Affect DHA-Specific Transcriptional Effects on Lipid Metabolism in Cultured Hepatic Cells

Long-chain n-3 polyunsaturated fatty acids (n-3 LC-PUFAs) are collectively recognized triglyceride-lowering agents, and their preventive action is likely mediated by changes in gene expression. However, as most studies employ fish oil, which contains a mixture of n-3 LC-PUFAs, the docosahexaenoic acid (DHA)-specific transcriptional effects on lipid metabolism are still unclear. The aim of the present study was to further elucidate the DHA-induced transcriptional effects on lipid metabolism in the liver, and to investigate the effects of co-administration with other bioactive compounds having effects on lipid metabolism. To this purpose, HepG2 cells were treated for 6 or 24 h with DHA, the short-chain fatty acid propionate (PRO), and protocatechuic acid (PCA), the main human metabolite of cyanidin-glucosides. Following supplementation, we mapped the global transcriptional changes. PRO and PCA alone had a very slight effect on the transcriptome; on the contrary, supplementation of DHA highly repressed the steroid and fatty acid biosynthesis pathways, this transcriptional modulation being not affected by co-supplementation. Our results confirm that DHA effect on lipid metabolism are mediated at least in part by modulation of the expression of specific genes. PRO and PCA could contribute to counteracting dyslipidemia through other mechanisms.

A novel apoA-I mimetic peptide suppresses atherosclerosis by promoting physiological HDL function in apoE-/- mice

BACKGROUND AND PURPOSE

Apolipoprotein A-I (apoA-I) mimetic peptides (AAMPs) are short peptides that can mimic the physiological effects of apoA-I, including the suppression of atherosclerosis by reversely transporting peripheral cholesterol to the liver. As the hydrophobicity of apoA-I is considered important for its lipid transport, novel AAMPs were designed and synthesized in this study by gradually increasing the hydrophobicity of the parent peptide, and their anti-atherosclerotic effects were tested.

EXPERIMENTAL APPROACH

Seventeen new AAMPs (P1-P17) with incrementally increased hydrophobicity were designed and synthesized by replacing the amino acids 221-240 of apoA-I (VLESFKVSFLSALEEYTKKL). Their effects on cholesterol efflux were evaluated. Their cytotoxicity and haemolytic activity were also measured. The in vitro mechanism of the action of the new peptides was explored. Adult apolipoprotein E^-/- mice were used to evaluate the anti-atherosclerotic activity of the best candidate, and the mechanistic basis of its anti-atherosclerotic effects was explored.

KEY RESULTS

Seventeen new AAMPs (P1-P17) were synthesized, and their cholesterol efflux activity and cytotoxicity were closely related to their hydrophobicity. P12 (FLEKLKELLEHLKELLTKLL) was the best candidate and most strongly promoted cholesterol efflux among the non-toxic peptides (P1-P12). With its phospholipid affinity, P12 facilitated cholesterol transport through the ATP-binding cassette transporter A1. In vivo, P12 exhibited prominent anti-atherosclerotic activity via coupling with HDL.

CONCLUSION AND IMPLICATIONS

P12 featured adequate hydrophobicity, which ensured its efficient binding with cytomembrane phospholipids, cholesterol and HDL, and provided a basis for its ability to reversely transport cholesterol and treat atherosclerosis.

Pathophysiology of Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2DM), one of the most common metabolic disorders, is caused by a combination of two primary factors: defective insulin secretion by pancreatic β-cells and the inability of insulin-sensitive tissues to respond appropriately to insulin. Because insulin release and activity are essential processes for glucose homeostasis, the molecular mechanisms involved in the synthesis and release of insulin, as well as in its detection are tightly regulated. Defects in any of the mechanisms involved in these processes can lead to a metabolic imbalance responsible for the development of the disease. This review analyzes the key aspects of T2DM, as well as the molecular mechanisms and pathways implicated in insulin metabolism leading to T2DM and insulin resistance. For that purpose, we summarize the data gathered up until now, focusing especially on insulin synthesis, insulin release, insulin sensing and on the downstream effects on individual insulin-sensitive organs. The review also covers the pathological conditions perpetuating T2DM such as nutritional factors, physical activity, gut dysbiosis and metabolic memory. Additionally, because T2DM is associated with accelerated atherosclerosis development, we review here some of the molecular mechanisms that link T2DM and insulin resistance (IR) as well as cardiovascular risk as one of the most important complications in T2DM.

Exosomes: Multifaceted Messengers in Atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis (AS) is a chronic inflammatory disease that contributes to the development of coronary artery disease, which has become a leading health burden worldwide. Though several strategies such as pharmacological treatment, exercise intervention, and surgery have been used in clinical practice, there is still no effective strategy to cure AS. Exosomes are extensively studied both as diagnostic markers as well as for therapeutic purposes due to their role in pathological processes related to AS. To elucidate the role of exosomes in AS and thus provide a new insight into AS therapy, we review recent advances concerning exosome targets and their function in mediating intercellular communication in AS, and expect to provide a reference for novel effective strategies to cure AS.

RECENT FINDINGS

Exosomes exert important roles in the diagnosis, development, and potential therapy of AS. For AS development, (1) activation of CD-137 in endothelial cells represses exosomal-TET2 production, causing a phenotypic switch of vascular smooth muscle cells (VSMC) and promoting plaque formation; (2) exosomal-MALTA1 derived from endothelial cells causes neutrophil extracellular traps (NETs) and M2 macrophage polarization, which aggravates AS; and (3) exosomal-miR-21-3p derived from macrophages inhibits PTEN expression and further promotes VSMC migration/proliferation, leading to AS development. For AS diagnosis, plasma exosomal-miR30e and miR-92a are considered to be potential diagnostic markers. For AS therapy, adipose mesenchymal stem cell-derived exosomes protect endothelial cells from AS aggravation, via inhibiting miR-342-5p. Exosome-mediated cross-talk between different cells within the vasculature exerts crucial roles in regulating endothelial function, proliferation and differentiation of vascular smooth muscle cells, and platelet activation as well as macrophage activation, collectively leading to the development and progression of AS. Exosomes can potentially be used as diagnostic biomarkers and constitute as a new therapeutic strategy for AS.

Control of Lipid Bilayer Phases of Cell-Sized Liposomes by Surface-Engineered Plasmonic Nanoparticles

Liquid-ordered (Lo)-phase domains, a cholesterol-rich area on lipid bilayers, have attracted significant attention recently because of their relevance to lipid rafts, the formation/collapse of which is associated with various kinds of information exchange through the plasma membrane. Here, we demonstrate that the formation/collapse of Lo-phase domains in cell-sized liposomes, that is, giant unilamellar vesicles (GUVs), can be controlled with bioactive plasmonic nanoparticles and light. The nanoparticles were prepared by surface modification of gold nanorods (AuNRs) using a cationized mutant of high-density lipoprotein (HDL), which is a natural cholesterol transporter. Upon the addition of surface-engineered AuNRs to GUVs with the mixed domains of Lo and liquid-disorder (Ld) phases, the Lo domains collapsed and solid-ordered (So)-phase domains were formed. The reverse phase transition was achieved photothermally, with the AuNRs loaded with cholesterol. During these transitions, the AuNRs appeared to be selectively localized on the less fluidic domain (Lo or So) in the phase-mixed GUVs. These results indicate that the phase transitions occur through the membrane binding of the AuNRs followed by spontaneous/photothermal transfer of cholesterol between the AuNRs and GUVs. Our strategy to develop bioactive AuNRs potentially enables spatiotemporal control of the formation/collapse of lipid rafts in living cells.

Increased PIP3 activity blocks nanoparticle mRNA delivery

The biological pathways that affect drug delivery in vivo remain poorly understood. We hypothesized that altering cell metabolism with phosphatidylinositol (3,4,5)-triphosphate (PIP3), a bioactive lipid upstream of the metabolic pathway PI3K (phosphatidylinositol 3-kinase)/AKT/ mTOR (mammalian target of rapamycin) would transiently increase protein translated by nanoparticle-delivered messenger RNA (mRNA) since these pathways increase growth and proliferation. Instead, we found that PIP3 blocked delivery of clinically-relevant lipid nanoparticles (LNPs) across multiple cell types in vitro and in vivo. PIP3-driven reductions in LNP delivery were not caused by toxicity, cell uptake, or endosomal escape. Interestingly, RNA sequencing and metabolomics analyses suggested an increase in basal metabolic rate. Higher transcriptional activity and mitochondrial expansion led us to formulate two competing hypotheses that explain the reductions in LNP-mediated mRNA delivery. First, PIP3 induced consumption of limited cellular resources, "drowning out" exogenously-delivered mRNA. Second, PIP3 triggers a catabolic response that leads to protein degradation and decreased translation.

Lipid efflux mechanisms, relation to disease and potential therapeutic aspects

Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.

High Density Lipoprotein and Its Precursor Protein Apolipoprotein A1 as Potential Therapeutics to Prevent Anthracycline Associated Cardiotoxicity

Cardiovascular disease and cancer are the leading causes of death in developed societies. Despite their effectiveness, many cancer therapies exhibit deleterious cardiovascular side effects such as cardiotoxicity and heart failure. The cardiotoxic effects of anthracyclines such as doxorubicin are the most well-characterized of cardiotoxic anti-cancer therapies. While other anti-neoplastic drugs also induce cardiotoxicity, often leading to heart failure, they are beyond the scope of this review. This review first summarizes the mechanisms of doxorubicin-induced cardiotoxicity. It then reviews emerging preclinical evidence that high density lipoprotein and its precursor protein apolipoprotein A1, which are known for their protective effects against ischemic cardiovascular disease, may also protect against doxorubicin-induced cardiotoxicity both directly and indirectly, when used therapeutically.

GPR120 facilitates cholesterol efflux in macrophages through activation of AMPK signaling pathway

Cholesterol efflux from macrophages is the initial step of reverse cholesterol transport, an important process for high-density lipoprotein-mediated atheroprotection. G protein-coupled receptor (GPR) 120, which functions as long-chain fatty acid receptor, is well known for its anti-inflammatory and insulin-sensitizing function in macrophages. However, the role of GPR120 on macrophage foam cell formation, the hallmark of atherosclerotic plaques, has not been verified. In this study, we found for the first time that stimulation of GPR120 by its agonist GW9508 elevated the expression of ATP-binding cassette transporters (ABC) A1 and ABCG1 in THP-1 macrophage-derived foam cells and Raw264.7 macrophages, and promoted ABCA1- and ABCG1-mediated cholesterol efflux and reduced cellular cholesteryl ester (CE) content as well. In addition, GPR120 activation was accompanied with the stimulation of AMPK pathway in macrophages; however, the effect of GPR120 on macrophage cholesterol efflux was largely abolished by AMPK inhibition. Moreover, the AMPK activity and the expression of ABCA1 and ABCG1 were markedly abrogated by knockdown of GPR120, or application of phospholipase C (PLC) inhibitor, calcium chelator, or CaMKK inhibitor. Because only free cholesterol can be effluxed from macrophages, we found that activation of AMPK could lead to increase both neutral CEs hydrolysis by upregulation of neutral cholesterol ester hydrolase expression and acid CEs hydrolysis by activation of ULK1. In conclusion, these results demonstrated that GPR120 facilitated ABCA1- and ABCG1-mediated cholesterol efflux through activation of PLC/Ca²⁺ /CaMKK/AMPK signaling pathway, which induced CE hydrolysis and elevated the expression of ABCA1 and ABCG1 in macrophages.

High-Density Lipoproteins Are Bug Scavengers

Lipoproteins were initially defined according to their composition (lipids and proteins) and classified according to their density (from very low- to high-density lipoproteins—HDLs). Whereas their capacity to transport hydrophobic lipids in a hydrophilic environment (plasma) is not questionable, their primitive function of cholesterol transporter could be challenged. All lipoproteins are reported to bind and potentially neutralize bacterial lipopolysaccharides (LPS); this is particularly true for HDL particles. In addition, HDL levels are drastically decreased under infectious conditions such as sepsis, suggesting a potential role in the clearance of bacterial material and, particularly, LPS. Moreover, "omics" technologies have unveiled significant changes in HDL composition in different inflammatory states, ranging from acute inflammation occurring during septic shock to low-grade inflammation associated with moderate endotoxemia such as periodontal disease or obesity. In this review, we will discuss HDL modifications associated with exposure to pathogens including bacteria, viruses and parasites, with a special focus on sepsis and the potential of HDL therapy in this context. Low-grade inflammation associated with atherosclerosis, periodontitis or metabolic syndrome may also highlight the protective role of HDLs in theses pathologies by other mechanisms than the reverse transport of cholesterol.

How will farmed populations of freshwater fish deal with the extreme climate scenario in 2100? Transcriptional responses of Colossoma macropomum from two Brazilian climate regions

Tambaqui (Colossoma macropomum Cuvier, 1818) is an endemic fish of the Amazon and Orinoco basins, and it is the most economically important native species in Brazil being raised in five climatically distinct regions. In the face of current global warming, environmental variations in farm ponds represent additional challenges that may drive new adaptive regional genetic variations among broodstocks of tambaqui. In an experimental context based on the high-emission scenario of the 5th Intergovernmental Panel on Climate Change (IPCC) report, we used two farmed tambaqui populations to test this hypothesis. RNA-seq transcriptome analysis was performed in the liver of juvenile tambaqui from northern (Balbina Experimental Station, Balbina, AM) and southeastern (Brumado Fish Farming, Mogi Mirim, SP) Brazilian regions kept for 30 days in artificial environmental rooms mimicking the current and extreme climate scenarios. Three Illumina MiSeq runs produced close to 120 million 500 bp paired-end reads; 191,139 contigs were assembled with N50 = 1595. 355 genes were differentially expressed for both populations in response to the extreme scenario. After enrichment analysis, each population presented a core set of genes to cope with climate change. Northern fish induced genes related to the cellular response to stress, activation of MAPK activity, response to unfolded protein, protein metabolism and cellular response to DNA damage stimuli. Genes biologically involved in regulating cell proliferation, protein stabilisation and protein ubiquitination for degradation through the ubiquitin-proteasome system were downregulated. Genes associated with biological processes, including the cellular response to stress, MAPK cascade activation, homeostatic processes and positive regulation of immune responses were upregulated in southeastern fish. The downregulated genes were related to cytoskeleton organisation, energy metabolism, and the regulation of transcription and biological rhythms. Our findings reveal the signatures of promising candidate genes involved in the regional plasticity of each population of tambaqui in dealing with upcoming climate changes.

New Perspectives on Atherogenic Dyslipidaemia and Cardiovascular Disease

Over the past few decades, atherogenic dyslipidaemia has become one of the most common phenotypic presentations of lipid abnormalities, being strongly and unequivocally associated with an increased risk of cardiovascular (CV) disease. Despite the excellent results achieved from statin and non-statin management of LDL cholesterol and CV events prevention, there still remains a significant residual risk, associated with the prevalence of non-LDL cholesterol lipid patterns characterised by elevated triglyceride levels, low HDL cholesterol, a preponderance of small and dense LDL particles, accumulation of remnant lipoproteins and postprandial hyperlipidaemia. These qualitative and quantitative lipid modifications are largely associated with insulin resistance, type 2 diabetes and obesity, the prevalence of which has grown to epidemic proportions throughout the world. In this review, we analyse the pathophysiology of this particular dyslipidaemia, its relationship with the development of atherosclerotic CV disease and, finally, briefly describe the therapeutic approaches, including changes in lifestyle and current pharmacological interventions to manage these lipid alterations aimed at preventing CV events.

Obstructive sleep apnea and dyslipidemia: from animal models to clinical evidence

Lipid metabolism deregulation constitutes the pathogenic basis for the development of atherosclerosis and justifies a high incidence of cardiovascular-related morbidity and mortality. Some data suggest that dyslipidemia may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to alterations in fundamental biochemical processes, such as intermittent hypoxia (IH). The aim of this systematic review was to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and alterations in lipid metabolism. Much evidence shows that, during the fasting state, OSA and IH increase lipid delivery from the adipose tissue to the liver through an up-regulation of the sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1, increasing the synthesis of cholesterol esters and triglycerides. In the postprandial state, lipoprotein clearance is delayed due to lower lipoprotein lipase activity, probably secondary to IH-up-regulation of angiopoietin-like protein 4 and decreased activity of the peroxisome proliferator-activated receptor alpha. Moreover, oxidative stress can generate dysfunctional oxidized lipids and reduce the capacity of high-density lipoproteins (HDL) to prevent low-density lipoprotein (LDL) oxidation. In the clinical field, several observational studies and a meta-regression analysis support the existence of a link between OSA and dyslipidemia. Although there is evidence of improved lipid profile after apnea-hypopnea suppression with continuous positive airway pressure (CPAP), the majority of the data come from observational studies. In contrast, randomized controlled trials evaluating the effects of CPAP on lipid metabolism present inconclusive results and two meta-analyses provide contradictory evidence.

Site-specific 5-hydroxytryptophan incorporation into apolipoprotein A-I impairs cholesterol efflux activity and high-density lipoprotein biogenesis

Apolipoprotein A-I (apoA-I) is the major protein constituent of high-density lipoprotein (HDL) and a target of myeloperoxidase-dependent oxidation in the artery wall. In atherosclerotic lesions, apoA-I exhibits marked oxidative modifications at multiple sites, including Trp⁷² Site-specific mutagenesis studies have suggested, but have not conclusively shown, that oxidative modification of Trp⁷² of apoA-I impairs many atheroprotective properties of this lipoprotein. Herein, we used genetic code expansion technology with an engineered Saccharomyces cerevisiae tryptophanyl tRNA-synthetase (Trp-RS):suppressor tRNA pair to insert the noncanonical amino acid 5-hydroxytryptophan (5-OHTrp) at position 72 in recombinant human apoA-I and confirmed site-specific incorporation utilizing MS. In functional characterization studies, 5-OHTrp⁷² apoA-I (compared with WT apoA-I) exhibited reduced ABC subfamily A member 1 (ABCA1)-dependent cholesterol acceptor activity in vitro (41.73 ± 6.57% inhibition; p < 0.01). Additionally, 5-OHTrp⁷² apoA-I displayed increased activation and stabilization of paraoxonase 1 (PON1) activity (μmol/min/mg) when compared with WT apoA-I and comparable PON1 activation/stabilization compared with reconstituted HDL (WT apoA-I, 1.92 ± 0.04; 5-OHTrp⁷² apoA-I, 2.35 ± 0.0; and HDL, 2.33 ± 0.1; p < 0.001, p < 0.001, and p < 0.001, respectively). Following injection into apoA-I-deficient mice, 5-OHTrp⁷² apoA-I reached plasma levels comparable with those of native apoA-I yet exhibited significantly reduced (48%; p < 0.01) lipidation and evidence of HDL biogenesis. Collectively, these findings unequivocally reveal that site-specific oxidative modification of apoA-I via 5-OHTrp at Trp⁷² impairs cholesterol efflux and the rate-limiting step of HDL biogenesis both in vitro and in vivo.

Postprandial dyslipidemia in insulin resistant states in adolescent populations

Obesity and the metabolic syndrome are becoming increasingly prevalent not only in adults, but also in adolescents. The metabolic syndrome, a complex cluster of metabolic abnormalities, increases one's risk of developing type 2 diabetes and cardiovascular disease (CVD). Dyslipidemia, a key component of the metabolic syndrome, is highly associated with insulin resistance and contributes to increased CVD risk. Dyslipidemia has traditionally been assessed using a fasting lipid profile [i.e. fasting triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C)]. However, the postprandial state predominates over the course of a day and non-fasting triglycerides independently predict CVD risk. In insulin resistant states, the intestine overproduces triglyceride-rich lipoprotein (TRL) particles, termed chylomicrons (CMs), following ingestion of a fat-containing meal, as well as in the fasting state. Along with elevated hepatic TRLs (i.e. very-low density lipoproteins), CMs contribute to remnant lipoprotein accumulation, small dense LDL particles, and reduced HDL-C, which collectively increase CVD risk. Given the early genesis of atherosclerosis and physiological metabolic changes during adolescence, studying postprandial dyslipidemia in the adolescent population is an important area of study. Postprandial dyslipidemia in the pediatric population poses a significant public health concern, warranting a better understanding of its pathogenesis and association with insulin resistance and CVD. This review discusses the metabolic syndrome, focusing on the link between insulin resistance, postprandial dyslipidemia, and CVD risk. Furthermore, the clinical significance and functional assessment of postprandial dyslipidemia, specifically in the adolescent population, is discussed in more detail.

Methionine sulfoxide reductase A attenuates atherosclerosis via repairing dysfunctional HDL in scavenger receptor class B type I deficient mice

High-density lipoprotein (HDL), a well-known atheroprotective factor, can be converted to proatherogenic particles in chronic inflammation. HDL-targeted therapeutic strategy for atherosclerotic cardiovascular disease (CVD) is currently under development. This study aims to assess the role of methionine sulfoxide reductase A (MsrA) in abnormal HDL and its related disorders in scavenger receptor class B type I deficient (SR-BI^-/- ) mice. First, we demonstrated that MsrA overexpression attenuated ROS level and inflammation in HepG2 cells. For the in vivo study, SR-BI^-/- mice were intravenously injected with lentivirus to achieve hepatic MsrA overexpression. High-level hepatic MsrA significantly reduced the plasma free cholesterol contents, improved HDL functional proteins apolipoprotein A-I (apoAI), apoE, paraoxonase1 (PON1), and lecithin:cholesterol acyltransferase (LCAT), while decreased the pro-inflammatory property of dysfunctional HDL, contributing to reduced atherosclerosis and hepatic steatosis in Western diet-fed mice. Furthermore, the study revealed that hepatic MsrA altered the expression of several genes controlling HDL biogenesis, cholesterol esterification, cholesterol uptake mediated by low-density lipoprotein receptor (LDLR) and biliary excretion, as well as suppressed nuclear factor κB (NF-κB) signaling pathway, which largely relied on liver X receptor alpha (LXRα)-upregulation. These results provide original evidence that MsrA may be a promising target for the therapy of dysfunctional HDL-related CVD.

Recent Advances in the Critical Role of the Sterol Efflux Transporters ABCG5/G8 in Health and Disease

Cardiovascular disease is characterized by lipid accumulation, inflammatory response, cell death, and fibrosis in the arterial wall and is the leading cause of morbidity and mortality worldwide. Cholesterol gallstone disease is caused by complex genetic and environmental factors and is one of the most prevalent and costly digestive diseases in the USA and Europe. Although sitosterolemia is a rare inherited lipid storage disease, its genetic studies led to identification of the sterol efflux transporters ABCG5/G8 that are located on chromosome 2p21 in humans and chromosome 17 in mice. Human and animal studies have clearly demonstrated that ABCG5/G8 play a critical role in regulating hepatic secretion and intestinal absorption of cholesterol and plant sterols. Sitosterolemia is caused by a mutation in either the ABCG5 or the ABCG8 gene alone, but not in both simultaneously. Polymorphisms in the ABCG5/G8 genes are associated with abnormal plasma cholesterol metabolism and may play a key role in the genetic determination of plasma cholesterol concentrations. Moreover, ABCG5/G8 is a new gallstone gene, LITH9. Gallstone-associated variants in ABCG5/G8 are involved in the pathogenesis of cholesterol gallstones in European, Asian, and South American populations. In this chapter, we summarize the latest advances in the critical role of the sterol efflux transporters ABCG5/G8 in regulating hepatic secretion of biliary cholesterol, intestinal absorption of cholesterol and plant sterols, the classical reverse cholesterol transport, and the newly established transintestinal cholesterol excretion, as well as in the pathogenesis and pathophysiology of ABCG5/G8-related metabolic diseases such as sitosterolemia, cardiovascular disease, and cholesterol gallstone disease.

The effects of statins with a high hepatoselectivity rank on the extra-hepatic tissues; New functions for statins

Statins, as the most common treatment for hyperlipidemia, exert effects beyond their lipid-lowering role which are known as pleiotropic effects. These effects are mainly due to the inhibition of isoprenoids synthesis and consequently blocking prenylation of proteins involved in the cellular signaling pathways regulating cell development, growth, and apoptosis. Statins target cholesterol synthesis in the liver as the major source of cholesterol in the body and so reduce whole-body cholesterol. The reduced level of cholesterol forces other organs to an adaptive homeostatic reaction to increase their cholesterol synthesis capacity, however, this only occurs when statins have unremarkable access to the extra-hepatic tissues. In order to reduce the adverse effects of statin on the skeletal muscle, most recent efforts have been towards formulating new statins with the highest level of hepatoselectivity rank and the least level of access to the extra-hepatic tissues; however, the inaccessibility of statins for the extra-hepatic tissues may induce several biological reactions. In this review, we aim to evaluate the effects of statins on the extra-hepatic tissues when statins have unremarkable access to these tissues.

High-density lipoprotein or cyclodextrin extraction of cholesterol from aggregated LDL reduces foam cell formation

Low-density lipoprotein (LDL) deposition, aggregation and retention in the endothelial sub-intima are critical initiating events during atherosclerosis. Macrophages digest aggregated LDL (agLDL) through a process called exophagy. High-density lipoprotein (HDL) plays an atheroprotective role, but studies attempting to exploit it therapeutically have been unsuccessful, highlighting gaps in our current understanding of HDL function. Here, we characterized the role of HDL during exophagy of agLDL. We find that atherosclerotic plaque macrophages contact agLDL and form an extracellular digestive compartment similar to that observed in vitro During macrophage catabolism of agLDL in vitro, levels of free cholesterol in the agLDL are increased. HDL can extract free cholesterol directly from this agLDL and inhibit macrophage foam cell formation. Cholesterol-balanced hydroxypropyl-β-cyclodextrin similarly reduced macrophage cholesterol uptake and foam cell formation. Finally, we show that HDL can directly extract free cholesterol, but not cholesterol esters, from agLDL in the absence of cells. Together, these results suggest that the actions of HDL can directly extract free cholesterol from agLDL during catabolism, and provide a new context in which to view the complex relationship between HDL and atherosclerosis.

Metabolic syndrome and lung function in Korean children and adolescents: A cross-sectional study

This study aimed to investigate whether obesity and metabolic syndrome (MetS) are associated with pulmonary function in Korean children and adolescents. Data from the 2009–2011 Korea National Health and Nutrition Examination Survey which is cross-sectional, nationwide, and representative survey were used. Adjusted regression analysis was performed to evaluate the association of obesity and MetS with lung function in children and adolescents. A total of 763 children and adolescents aged 10–18 years were evaluated. We found no significant difference in FEV₁% predicted, FVC% predicted, and FEV₁/FVC ratio among the obesity groups. Subjects with MetS showed a significantly lower FEV₁ predicted (91.54 ± 0.74% vs 94.64 ± 0.73%, P = 0.004), lower FVC% predicted (91.86 ± 0.63% vs 95.20 ± 0.63%, P < 0.001), and lower FEV₁/FVC ratio (76.76 ± 0.43% vs 80.13 ± 0.43%, P < 0.001) than those without MetS. Elevated waist circumference (WC), systolic blood pressure, fasting glucose, and lower high-density lipoprotein cholesterol (HDL-C) were independently associated with lower FEV₁/FVC ratio (all P < 0.05, respectively). Among MetS components, increased WC was the most important factor influencing lower FEV₁/FVC ratio. In conclusion, lung function in MetS patients was significantly lower, and the MetS component was independently associated.

CXCL12 promotes atherosclerosis by downregulating ABCA1 expression via the CXCR4/GSK3β/β-cateninT120/TCF21 pathway

CXC chemokine ligand 12 (CXCL12) is a member of the CXC chemokine family and mainly acts on cell chemotaxis. CXCL12 also elicits a proatherogenic role, but the molecular mechanisms have not been fully defined yet. We aimed to reveal if and how CXCL12 promoted atherosclerosis via regulating lipid metabolism. In vitro, our data showed that CXCL12 could reduce ABCA1 expression, and it mediated cholesterol efflux from THP-1-derived macrophages to apoA-I. Data from the luciferase reporter gene and chromatin immunoprecipitation assays revealed that transcription factor 21 (TCF21) stimulated the transcription of ABCA1 via binding to its promoter region, which was repressed by CXCL12. We found that CXCL12 increased the levels of phosphorylated glycogen synthase kinase 3β (GSK3β) and the phosphorylation of β-catenin at the Thr120 position. Inactivation of GSK3β or β-catenin increased the expression of TCF21 and ABCA1. Further, knockdown or inhibition of CXC chemokine receptor 4 (CXCR4) blocked the effects of CXCL12 on TCF21 and ABCA1 expression and the phosphorylation of GSK3β and β-catenin. In vivo, the overexpression of CXCL12 in Apoe^-/- mice via lentivirus enlarged the atherosclerotic lesion area and increased macrophage infiltration in atherosclerotic plaques. We further found that the overexpression of CXCL12 reduced the efficiency of reverse cholesterol transport and plasma HDL-C levels, decreased ABCA1 expression in the aorta and mouse peritoneal macrophages (MPMs), and suppressed cholesterol efflux from MPMs to apoA-I in Apoe^-/- mice. Collectively, these findings suggest that CXCL12 interacts with CXCR4 and then activates the GSK-3β/β-catenin^T120/TCF21 signaling pathway to inhibit ABCA1-dependent cholesterol efflux from macrophages and aggravate atherosclerosis. Targeting CXCL12 may be a novel and promising strategy for the prevention and treatment of atherosclerotic cardiovascular diseases.

History of cardiovascular disease and cardiovascular biomarkers are associated with 30-day mortality in patients with hip fracture

Hip fractures are associated with increased mortality and it is important to identify risk factors. This study demonstrates that preexisting cardiovascular disease as well as cardiovascular biomarkers that are associated with increased 30-day mortality. These findings can be used to identify high-risk patients who might benefit from specialized care.

INTRODUCTION

This study investigates the association between cardiovascular disease (CVD), cardiovascular biomarkers, and 30-day mortality following a hip fracture.

METHODS

The Danish National Patient Registry was used to investigate the association between CVD and mortality following hip fracture in a nationwide population-based cohort study. In a subset of the included patients (n = 355), blood samples were available from a local biobank. These samples were used for analyzing the association between specific biochemical markers and mortality. The primary outcome was 30-day mortality.

RESULTS

A total of 113,211 patients were included in the population-based cohort study. Among these, heart failure was present in 9.4%, ischemic heart disease in 15.9%, and ischemic stroke in 12.0%. Within 30 days after the hip fracture, 11,488 patients died, resulting in an overall 30-day mortality of 10.1%. The 30-day mortality was significantly increased in individuals with preexisting CVD with multivariably adjusted odds ratios of 1.69 (95% confidence interval, 1.60-1.78) for heart failure, 1.23 (1.17-1.29) for ischemic heart disease, and 1.06 (1.00-1.12) for ischemic stroke. In the local database including 355 patients, 41 (11.5%) died within 30 days. The multivariably adjusted odds ratio for 30-day mortality increased with increasing NT-proBNP (2.36 [1.53-3.64] per quartile) and decreased with increasing HDL cholesterol (0.58 [0.41-0.82] per quartile). On this basis, we established a model for predicting the probability of death based on the biochemical markers.

CONCLUSION

Preexisting CVD was associated with increased 30-day mortality after a hip fracture. Furthermore, high levels of NT-proBNP and low levels of HDL cholesterol were associated with increased 30-day mortality.

Prevalence and associated risk factors of peripheral artery disease in virologically suppressed HIV-infected individuals on antiretroviral therapy in Kwara state, Nigeria: a cross sectional study

BACKGROUND

The association between HIV and cardiovascular disease (CVD) has been reported in several studies. However, there is paucity of information on the prevalence of subclinical disease as well as its associated risk factors in sub-Saharan African population. The aim of this study was to determine the prevalence and associated risk factors of peripheral artery disease (PAD) among virologically suppressed HIV-infected participants in Kwara State, Nigeria.

METHODS

This study was conducted between July 2018 and December 2018. A total of 150 HIV-infected participants aged between 20 and 55 years and 50 HIV non-infected age-matched controls were randomly recruited in the study. Sociodemographic, anthropometric and clinical data were collected using a well-structured questionnaire. Ankle brachial index (ABI) was measured, PAD was defined as ABI of < 0.9. Cryopreserved serum was used to evaluate lipid profile parameters. Student's t-test and Chi-square were used to compare continuous and categorical variables. Associations of CVD risk factors and clinical data, and lipid profile with low ABI were assessed using logistic regression analysis.

RESULTS

The study participants had a mean age of 43.73 ± 8.74, majority were females (72.7%) with a mean duration on ART of 7.73 ± 3.52 years. Hypertension was present in 15.9%, diabetes 4%, family history of CVD 8.6% and metabolic syndrome 17.3% in the study group. The study participants recorded significantly lower mean values for ABI, HDL-C and significantly higher mean values of TG (P < 0.05) compared to the control group. The prevalence of low ABI (14.6%) was higher in the study group compared to the control group (2%). A significantly negative correlation between ABI and duration on ART (r = - 0.163, P = 0.041) and a positive correlation between viral load and TG were observed in the study group. TC (OR 1.784, P = 0.011), LDL-C (OR 1.824, P = 0.010) and CD4 cell count < 200 cells/mm3 (OR 2.635, P = 0.364) were associated with low ABI in the participants.

CONCLUSION

Viral suppression with combined antiretroviral therapy and long term treatment is associated with dyslipidaemia, with increased risk of PAD. Prevalence of PAD in virologically-suppressed individuals does not differ from the controls in the population studied.

Lipoprotein Lipase Inhibitor, Nordihydroguaiaretic Acid, Aggravates Metabolic Phenotypes and Alters HDL Particle Size in the Western Diet-Fed db/db Mice

Lipoprotein lipase (LPL) hydrolyzes triglycerides in lipoprotein to supply fatty acids, and its deficiency leads to hypertriglyceridemia, thereby inducing metabolic syndrome (MetSyn). Nordihydroguaiaretic acid (NDGA) has been recently reported to inhibit LPL secretion by endoplasmic reticulum (ER)-Golgi redistribution. However, the role of NDGA on dyslipidemia and MetSyn remains unclear. To address this question, leptin receptor knock out (KO)-db/db mice were randomly assigned to three different groups: A normal AIN76-A diet (CON), a Western diet (WD) and a Western diet with 0.1% NDGA and an LPL inhibitor, (WD+NDGA). All mice were fed for 12 weeks. The LPL inhibition by NDGA was confirmed by measuring the systemic LPL mass and adipose LPL gene expression. We investigated whether the LPL inhibition by NDGA alters the metabolic phenotypes. NDGA led to hyperglycemia, hypertriglyceridemia, and hypercholesterolemia. More strikingly, the supplementation of NDGA increased the percentage of high density lipoprotein (HDL)_small (HDL_3a+3b+3c) and decreased the percentage of HDL_large (HDL_2a+2b) compared to the WD group, which indicates that LPL inhibition modulates HDL subclasses. was NDGA increased adipose inflammation but had no impact on hepatic stress signals. Taken together, these findings demonstrated that LPL inhibition by NDGA aggravates metabolic parameters and alters HDL particle size.

Biological Consequences of Dysfunctional HDL

Epidemiological studies have suggested an inverse correlation between high-density lipoprotein (HDL) cholesterol levels and the risk of cardiovascular disease. HDLs promote reverse cholesterol transport (RCT) and possess several putative atheroprotective functions, associated to the anti-inflammatory, anti-thrombotic and anti-oxidant properties as well as to the ability to support endothelial physiology. The assumption that increasing HDL-C levels would be beneficial on cardiovascular disease (CVD), however, has been questioned as, in most clinical trials, HDL-C-raising therapies did not result in improved cardiovascular outcomes. These findings, together with the observations from Mendelian randomization studies showing that polymorphisms mainly or solely associated with increased HDL-C levels did not decrease the risk of myocardial infarction, shift the focus from HDL-C levels toward HDL functional properties. Indeed, HDL from atherosclerotic patients not only exhibit impaired atheroprotective functions but also acquire pro-atherogenic properties and are referred to as "dysfunctional" HDL; this occurs even in the presence of normal or elevated HDL-C levels. Pharmacological approaches aimed at restoring HDL functions may therefore impact more significantly on CVD outcome than drugs used so far to increase HDL-C levels. The aim of this review is to discuss the pathological conditions leading to the formation of dysfunctional HDL and their role in atherosclerosis and beyond.

Targeted Deletion of Hepatocyte Abca1 Increases Plasma HDL (High-Density Lipoprotein) Reverse Cholesterol Transport via the LDL (Low-Density Lipoprotein) Receptor

OBJECTIVE

The role of hepatocyte Abca1 (ATP binding cassette transporter A1) in trafficking hepatic free cholesterol (FC) into plasma versus bile for reverse cholesterol transport (RCT) is poorly understood. We hypothesized that hepatocyte Abca1 recycles plasma HDL-C (high-density lipoprotein cholesterol) taken up by the liver back into plasma, maintaining the plasma HDL-C pool, and decreasing HDL-mediated RCT into feces. Approach and Results: Chow-fed hepatocyte-specific Abca1 knockout (HSKO) and control mice were injected with human HDL radiolabeled with ¹²⁵I-tyramine cellobiose (¹²⁵I-TC; protein) and ³H-cholesteryl oleate (³H-CO). ¹²⁵I-TC and ³H-CO plasma decay, plasma HDL ³H-CO selective clearance (ie, ³H-¹²⁵I fractional catabolic rate), liver radiolabel uptake, and fecal ³H-sterol were significantly greater in HSKO versus control mice, supporting increased plasma HDL RCT. Twenty-four hours after ³H-CO-HDL injection, HSKO mice had reduced total hepatic ³H-FC (ie, ³H-CO hydrolyzed to ³H-FC in liver) resecretion into plasma, demonstrating Abca1 recycled HDL-derived hepatic ³H-FC back into plasma. Despite similar liver LDLr (low-density lipoprotein receptor) expression between genotypes, HSKO mice treated with LDLr-targeting versus control antisense oligonucleotide had slower plasma ³H-CO-HDL decay, reduced selective ³H-CO clearance, and decreased fecal ³H-sterol excretion that was indistinguishable from control mice. Increased RCT in HSKO mice was selective for ³H-CO-HDL, since macrophage RCT was similar between genotypes.

CONCLUSIONS

Hepatocyte Abca1 deletion unmasks a novel and selective FC trafficking pathway that requires LDLr expression, accelerating plasma HDL-selective CE uptake by the liver and promoting HDL RCT into feces, consequently reducing HDL-derived hepatic FC recycling into plasma.

Relationship Between HDL Functional Characteristics and Cardiovascular Health and Potential Impact of Dietary Patterns: A Narrative Review

Cardiovascular disease is a leading cause of death around the world. Overall diet quality and dietary behaviors are core contributors to metabolic health. While therapeutic targets have traditionally focused on levels of lipoprotein cholesterol when evaluating cardiovascular risk, current perspectives on high-density lipoprotein (HDL) have shifted to evaluating the functionality of this lipoprotein particle. Effects of diet on cardiovascular health are mediated through multiple pathways, but the impact on HDL composition and function deserves greater attention. Potential areas of investigation involve changes in particle characteristics, distribution, microRNA cargo, and other functional changes such as improvements to cholesterol efflux capacity. Various dietary patterns like the Mediterranean diet and Dietary Approaches to Stop Hypertension (DASH) diet have beneficial effects on cardiovascular health and may prevent cardiovascular events. These healthful dietary patterns tend to be rich in plant-based foods, with cardiovascular benefits likely resulting from synergistic effects of the individual dietary components. The purpose of this review is to summarize current perspectives on selected functions of HDL particles and how various dietary patterns affect cardiovascular health biomarkers, with a focus on HDL functionality.

Moxibustion at CV4 alleviates atherosclerotic lesions through activation of the LXRα/ABCA1 pathway in apolipoprotein-E-deficient mice

Objectives:

To investigate the anti-atherogenic effect of moxibustion and whether it is mediated through the reverse cholesterol transport process.

Methods:

8-week-old male apolipoprotein E deficient (ApoE^−/− knockout) mice were randomly divided into two groups (n=10 per group): atherosclerosis (AS) and AS plus moxibustion (AS+M). C57BL/6J mice of the same background (n=10) were selected as controls. Mice in the AS+M group received indirect moxibustion with an ignited moxa stick held over CV4. Mice of the AS and control groups were restrained in the same holder with an unlit moxa stick held over CV4. All treatments were performed for 20 min per day, 6 days per week for 12 weeks. After the treatment, the mice were euthanased and their serum lipids were measured. The aortic roots and thoracic aortas were collected for haematoxylin and eosin and red oil O staining, respectively, to analyse the atherosclerotic lesions. Expression of adenosine triphosphate binding cassette (ABCA)A1/G1 and liver X receptor α (LXRα) in the thoracic aorta were examined with Western blotting.

Results:

The moxibustion-treated (AS+M) mice showed a significantly lower plaque area percentage in the aortic root and thoracic aorta, and higher expression of LXRα and ABCA1 in the thoracic aorta compared with the AS mice. No significant differences were found in average lipid area percentage in the thoracic aorta, or ABCG1 expression in the thoracic aorta, between mice in the AS+M and AS groups.

Conclusion:

Moxibustion treatment at CV4 suppressed the progression of atherosclerotic lesions in ApoE^−/− mice. The anti-atherogenic effect of moxibustion may be achieved by: (1) regulation of lipid metabolism, and thus prevention of lipid accumulation; and (2) upregulation of LXRα- and ABCA1-mediated cholesterol efflux in the lesion area.

Time-resolved small-angle neutron scattering as a probe for the dynamics of lipid exchange between human lipoproteins and naturally derived membranes

Atherosclerosis is the main killer in the western world. Today’s clinical markers include the total level of cholesterol and high-/low-density lipoproteins, which often fails to accurately predict the disease. The relationship between the lipid exchange capacity and lipoprotein structure should explain the extent by which they release or accept lipid cargo and should relate to the risk for developing atherosclerosis. Here, small-angle neutron scattering and tailored deuteration have been used to follow the molecular lipid exchange between human lipoprotein particles and cellular membrane mimics made of natural, “neutron invisible” phosphatidylcholines. We show that lipid exchange occurs via two different processes that include lipid transfer via collision and upon direct particle tethering to the membrane, and that high-density lipoprotein excels at exchanging the human-like unsaturated phosphatidylcholine. By mapping the specific lipid content and level of glycation/oxidation, the mode of action of specific lipoproteins can now be deciphered. This information can prove important for the development of improved diagnostic tools and in the treatment of atherosclerosis.

Different mechanisms for selective transport of fatty acids using a single class of lipoprotein in Drosophila

In mammals, lipids are selectively transported to specific sites using multiple classes of lipoproteins. However, in Drosophila, a single class of lipoproteins, lipophorin, carries more than 95% of the lipids in the hemolymph. Although a unique ability of the insect lipoprotein system for cargo transport has been demonstrated, it remains unclear how this single class of lipoproteins selectively transports lipids. In this study, we carried out a comparative analysis of the fatty-acid composition among lipophorin, the CNS, and CNS-derived cell lines and investigated the transport mechanism of fatty acids, particularly focusing on the transport of PUFAs in Drosophila We showed that PUFAs are selectively incorporated into the acyl chains of lipophorin phospholipids and effectively transported to CNS through lipophorin receptor-mediated endocytosis of lipophorin. In addition, we demonstrated that C14 fatty acids are selectively incorporated into the diacylglycerols (DAGs) of lipophorin and that C14 fatty-acid-containing DAGs are spontaneously transferred from lipophorin to the phospholipid bilayer. These results suggest that PUFA-containing phospholipids and C14 fatty-acid-containing DAGs in lipophorin could be transferred to different sites by different mechanisms to selectively transport fatty acids using a single class of lipoproteins.

Promoter Methylation Regulates ApoA-I Gene Transcription in Chicken Abdominal Adipose Tissue

As a central constituent of HDL (high-density lipoprotein), apolipoprotein A-I (ApoA-I) has a vital function in lipid metabolism. Our previous studies confirmed that ApoA-I was differentially expressed in the adipose tissue of the abdomen of lean and fat broilers. The aim of the current work was to evaluate whether the transcription of ApoA-I in chicken abdominal adipose tissue was regulated by DNA methylation. The methylation status of ApoA-I promoter CpG island (PCGI) and promoter non-CpG island (PNCGI) as well as the ApoA-I expression level in adipose tissue of lean and fat broilers were determined using Sequenom MassARRAY and real-time PCR. The correlation analysis results showed that the methylation level of PCGI and the ApoA-I mRNA expression level were negatively correlated. Bisulfite sequencing PCR was used to assess the methylation level of ApoA-I promoter in the ICP1 cells treated with 5-aza-2'-deoxycytidine (5-Aza-CdR: an inhibitor of DNA methyltransferase). The result showed that 5-Aza-CdR caused a reduction in the methylation level of the ApoA-I promoter, thereby causing an increase in expression of the ApoA-I mRNA. Meanwhile, luciferase reporter assays indicated that in vitro methylation of the ApoA-I promoter containing CpG island with CpG methyltransferase led to transcriptional repression. Furthermore, the noticeable activation of NRF1 on ApoA-I transcription was largely enhanced  by the demethylation of the ApoA-I PCGI region. These observations indicated that the differential expression of ApoA-I gene in the adipose tissue of broilers could be mediated by transcription regulation, at least in part by DNA methylation in its PCGI region.

Residual cardiovascular risk among people with diabetes

Type 2 diabetes (T2D) is a growing health concern across both developed and developing countries. Cardiovascular disease (CVD) remains the major cause of increased mortality in this patient population. In recent years, effective low density lipoprotein lowering treatments and other risk reduction strategies have substantially reduced the risk of atherosclerotic CVD, yet patients with T2D continue to remain at increased risk for atherosclerotic CVD. Here, we will briefly review various proposed underlying mechanisms for this residual risk with a more in-depth focus on the potential role of triglyceride-rich lipoproteins in residual risk and potential avenues to target this pharmacologically.

Phospholipids in lipoproteins: compositional differences across VLDL, LDL, and HDL in pregnant women

Objective

The aim of this study was to analyse the differences in the phospholipid composition of very low density (VLDL), low density (LDL) and high density lipoprotein (HDL) monolayers in pregnant lean and obese women.

Methods

LDL, HDL, and VLDL were isolated from plasma samples of 10 lean and 10 obese pregnant women, and their species composition of phosphatidylcholines (PC) and sphingomyelins (SM) was analysed by liquid-chromatography tandem mass-spectrometry. Wilcoxon-Mann-Whitney U test and principal component analysis (PCA) were used to investigate if metabolite profiles differed between the lean/obese group and between lipoprotein species.

Results

No significant differences have been found in the metabolite levels between obese and non-obese pregnant women. The PCA components 1 and 2 separated between LDL, HDL, and VLDL but not between normal weight and obese women. Twelve SM and one PCae were more abundant in LDL than in VLDL. In contrast, four acyl-alkyl-PC and two diacyl-PC were significantly higher in HDL compared to LDL. VLDL and HDL differed in three SM, seven acyl-alkyl-PC and one diacyl-PC (higher values in HDL) and 13 SM (higher in VLDL). We also found associations of some phospholipid species with HDL and LDL cholesterol.

Conclusion

In pregnant women phospholipid composition differs significantly in HDL, LDL and VLDL, similar to previous findings in men and non-pregnant women. Obese and lean pregnant women showed no significant differences in their lipoprotein associated metabolite profile.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-0957-z) contains supplementary material, which is available to authorized users.

Association between the LIPG polymorphisms and serum lipid levels in the Maonan and Han populations

Introduction

The Maonan population is a relatively isolated minority in China. Little is known about endothelial lipase gene (LIPG) single nucleotide polymorphisms (SNPs) and serum lipid levels in the Chinese populations. The present study aimed to detect the association of several LIPG SNPs and environmental factors with serum lipid levels in the Chinese Maonan and Han populations.

Methods

In total, 773 subjects of Maonan ethnicity and 710 participants of Han ethnicity were randomly selected from our previous stratified randomized samples. Genotypes of the LIPG rs2156552, rs4939883 and rs7241918 SNPs were determined by polymerase chain reaction‐restriction fragment length polymorphism, and then confirmed by direct sequencing.

Results

The allelic (rs2156552, rs4939883 and rs7241918) and genotypic (rs2156552 and rs4939883) frequencies were different between the two ethnic groups (p < 0.05–0.01). The minor allele carriers had lower apolipoprotein (Apo)A1/ApoB ratio (rs2156552 and rs7241918), high‐density lipoprotein cholesterol (HDL‐C) and apolipoprotein (Apo)A1 (rs2156552) levels and higher ApoB levels (rs4939883) in the Han population, and lower HDL‐C (rs2156552, rs4939883 and rs7241918) levels in the Maonan minority than the minor allele non‐carriers (p < 0.0167 after Bonferroni correction). Subgroup analyses according to sex showed that the minor allele carriers had a lower ApoA1/ApoB ratio (rs2156552 and rs7241918) and higher ApoB levels (rs7241918) in Han males, and lower ApoA1 and HDL‐C levels in Maonan females than the minor allele non‐carriers (p < 0.0167–0.001).

Conclusions

The present study demonstrates the association between the LIPG polymorphsims and serum lipid levels in the two ethnic groups. These associations might have an ethnic‐ and or/sex‐specificity.

Disentangling the genetic overlap between cholesterol and suicide risk

Suicide is major public health concern; one million individuals worldwide die by suicide each year of which there are many more attempts. Thus, it is imperative that robust and reliable indicators, or biomarkers, of suicide risk be identified so that individuals at risk can be identified and provided appropriate interventions as quickly as possible. Previous work has revealed a relationship between low levels of circulating cholesterol and suicide risk, implicating cholesterol level as one such potential biomarker, but the factors underlying this relationship remain unknown. In the present study, we applied a combination of bivariate polygenic and coefficient-of-relatedness analysis, followed by mediation analysis, in a large sample of Mexican-American individuals from extended pedigrees [N = 1897; 96 pedigrees (average size = 19.17 individuals, range = 2-189) 60% female; mean age = 42.58 years, range = 18-97 years, sd = 15.75 years] with no exclusion criteria for any given psychiatric disorder. We observed that total esterified cholesterol measured at the time of psychiatric assessment shared a significant genetic overlap with risk for suicide attempt (ρ_g = -0.64, p = 1.24 × 10^-04). We also found that total unesterified cholesterol measured around 20 years prior to assessment varied as a function of genetic proximity to an affected individual (h² = 0.21, se = 0.10, p = 8.73 × 10^-04; β_suicide = -0.70, se = 0.25, p = 8.90 × 10^-03). Finally, we found that the relationship between total unesterified cholesterol and suicide risk was significantly mediated by ABCA-1-specific cholesterol efflux capacity (β_{suicide-efflux} = -0.45, p = 0.039; β_{efflux-cholexterol} = -0.34, p < 0.0001; β_indirect = -0.15, p = 0.044). These findings suggest that the relatively well-delineated process of cholesterol metabolism and associated molecular pathways will be informative for understanding the neurobiological underpinnings of risk for suicide attempt.

Specific Cholesterol Binding Drives Drastic Structural Alterations in Apolipoprotein A1

Proteins typically adopt a multitude of flexible and rapidly interconverting conformers, many of which are governed by specific protein interaction domains. Whereas disc-shaped oligomeric HDL and its major protein component ApoA1 have been the focus of several investigations, the structural properties of monomeric ApoA1 remain poorly understood. Using tens of independent molecular simulations (>50 μs), we reveal that ApoA1 adopts a compact conformation. Upon the addition of a physiological concentration of cholesterol to ApoA1, the monomeric protein spontaneously formed a circular conformation. Remarkably, these drastic structural perturbations are driven by a specific cholesterol binding site at the C-terminal and a novel cholesterol binding site at the N-terminal. We propose a mechanism whereby ApoA1 opens in a stagewise manner and mutating the N-terminal binding site destroys the open "belt-shaped" topology. Complementary experiments confirm that the structural changes are induced by specific association of cholesterol with ApoA1, not by the nonspecific hydrophobic effect.

Transcriptome from Pacific cod liver reveals types of apolipoproteins and expression analysis of AFP-IV, structural analogue with mammalian ApoA-I

Apolipoproteins (Apos), transporting the lipids through the lymphatic and circulatory systems, are associated with kinds of diseases. Additionally, type IV antifreeze protein (AFP-IV) was related evolutionarily with apolipoproteins. However, the information of Apos in fish was limited. In this study, ApoA-I, ApoA-I-2, ApoA-IV, Apo E, ApoB-100-like and AFP-IV were sequenced from Pacific cod (Gadus macrocephalus) liver transcriptome using Illumina HiSeq 2000, and their 3-D models were constructed based on the most confidence templates ever reported in mammals. Interestingly, the model of G. macrocephalus AFP-IV, named GmAFPIV, is quite similar to the structure of ApoA-I. GmAFPIV includes 689 bases with a complete open reading frame encoding 125 amino acids. Sequence alignment of GmAFPIV showed 30% to 50% similarity with that of other species except Gadus sp. Expression levels of GmAFPIV were found in a decreasing manner in liver, intestine, gill, brain and gonad. Heterologously expression of the GmAFPIV protein was expressed in Escherichia coli and purified to immunize New Zealand rabbits. The survivors of E. coli in 60 μg/mL of GmAFPIV are more than that in the 30 μg/mL group after stored in -20 °C and -80 °C, indicating high concentration of GmAFPIV could protect E. coli avoiding the damage from ice crystal. The subcellular localization of GmAFPIV showed that the green fluorescence was mainly observed in the cytoplasm, indicating GmAFPIV play roles in the cytoplasm. It was concluded that GmAFPIV may function not only as an antifreeze protein but also as an apolipoprotein transporting lipids in fish.

ABCA1 Overexpression in Endothelial Cells In Vitro Enhances ApoAI-Mediated Cholesterol Efflux and Decreases Inflammation

Atherosclerosis, a disease of blood vessels, is driven by cholesterol accumulation and inflammation. Gene therapy that removes cholesterol from blood vessels and decreases inflammation is a promising approach for prevention and treatment of atherosclerosis. In previous work, we reported that helper-dependent adenoviral (HDAd) overexpression of apolipoprotein A-I (apoAI) in endothelial cells (ECs) increases cholesterol efflux in vitro and reduces atherosclerosis in vivo. However, the effect of HDAdApoAI on atherosclerosis is partial. To improve this therapy, we considered concurrent overexpression of ATP-binding cassette subfamily A, member 1 (ABCA1), a protein that is required for apoAI-mediated cholesterol efflux. Before attempting combined apoAI/ABCA1 gene therapy, we tested whether an HDAd that expresses ABCA1 (HDAdABCA1) increases EC cholesterol efflux, whether increased cholesterol efflux alters normal EC physiology, and whether ABCA1 overexpression in ECs has anti-inflammatory effects. HDAdABCA1 increased EC ABCA1 protein (∼3-fold; p < 0.001) and apoAI-mediated cholesterol efflux (2.3-fold; p = 0.007). Under basal culture conditions, ABCA1 overexpression did not alter EC proliferation, metabolism, migration, apoptosis, nitric oxide production, or inflammatory gene expression. However, in serum-starved, apoAI-treated EC, ABCA1 overexpression had anti-inflammatory effects: decreased inflammatory gene expression (∼50%; p ≤ 0.02 for interleukin [IL]-6, tumor necrosis factor [TNF]-α, and vascular cell adhesion protein-1); reduced lipid-raft Toll-like receptor 4 (80%; p = 0.001); and a trend towards increased nitric oxide production (∼55%; p = 0.1). In ECs stimulated with lipopolysaccharide, ABCA1 overexpression markedly decreased inflammatory gene expression (∼90% for IL-6 and TNF-α; p < 0.001). Therefore, EC ABCA1 overexpression has no toxic effects and counteracts the two key drivers of atherosclerosis: cholesterol accumulation and inflammation. In vivo testing of HDAdABCA1 is warranted.