LDL Receptor Regulates the Reverse Transport of Macrophage-Derived Unesterified Cholesterol via Concerted Action of the HDL-LDL Axis: Insight From Mouse Models

Lactiplantibacillus plantarum ATCC8014 Alleviates Postmenopausal Hypercholesterolemia in Mice by Remodeling Intestinal Microbiota to Increase Secondary Bile Acid Excretion

Hypercholesterolemia poses a significant cardiovascular risk, particularly in postmenopausal women. The anti-hypercholesterolemic properties of Lactiplantibacillus plantarum ATCC8014 (LP) are well recognized; however, its improving symptoms on postmenopausal hypercholesterolemia and the possible mechanisms have yet to be elucidated. Here, we utilized female ApoE-deficient (ApoE-/-) mice undergoing bilateral ovariectomy, fed a high-fat diet, and administered 109 colony-forming units (CFU) of LP for 13 consecutive weeks. LP intervention reduces total cholesterol (TC) and triglyceride (TG) accumulation in the serum and liver and accelerates their fecal excretion, which is mainly accomplished by increasing the excretion of fecal secondary bile acids (BAs), thereby facilitating cholesterol conversion. Correlation analysis revealed that lithocholic acid (LCA) is an important regulator of postmenopausal lipid abnormalities. LP can reduce LCA accumulation in the liver and serum while enhancing its fecal excretion, accomplished by elevating the relative abundances of Allobaculum and Olsenella in the ileum. Our findings demonstrate that postmenopausal lipid dysfunction is accompanied by abnormalities in BA metabolism and dysbiosis of the intestinal microbiota. LP holds therapeutic potential for postmenopausal hypercholesterolemia. Its effectiveness in ameliorating lipid dysregulation is primarily achieved through reshaping the diversity and abundance of the intestinal microbiota to correct BA abnormalities.

Dietary fat quality, plasma atherogenic lipoproteins, and atherosclerotic cardiovascular disease: An overview of the rationale for dietary recommendations for fat intake

The scientific evidence supporting the current dietary recommendations for fat quality keeps accumulating; however, a paradoxical distrust has taken root among many researchers, clinicians, and in parts of the general public. One explanation for this distrust may relate to an incomplete overview of the totality of the evidence for the link between fat quality as a dietary exposure, and health outcomes such as atherosclerotic cardiovascular disease (ASCVD). Therefore, the main aim of the present narrative review was to provide a comprehensive overview of the rationale for dietary recommendations for fat intake, limiting our discussion to ASCVD as outcome. Herein, we provide a core framework - a causal model - that can help us understand the evidence that has accumulated to date, and that can help us understand new evidence that may become available in the future. The causal model for fat quality and ASCVD is comprised of three key research questions (RQs), each of which determine which scientific methods are most appropriate to use, and thereby which lines of evidence that should feed into the causal model. First, we discuss the link between low-density lipoprotein (LDL) particles and ASCVD (RQ1); we draw especially on evidence from genetic studies, randomized controlled trials (RCTs), epidemiology, and mechanistic studies. Second, we explain the link between dietary fat quality and LDL particles (RQ2); we draw especially on metabolic ward studies, controlled trials (randomized and non-randomized), and mechanistic studies. Third, we explain the link between dietary fat quality, LDL particles, and ASCVD (RQ3); we draw especially on RCTs in animals and humans, epidemiology, population-based changes, and experiments of nature. Additionally, the distrust over dietary recommendations for fat quality may partly relate to an unclear understanding of the scientific method, especially as applied in nutrition research, including the process of developing dietary guidelines. We therefore also aimed to clarify this process. We discuss how we assess causality in nutrition research, and how we progress from scientific evidence to providing dietary recommendations.

Human PBMCs Form Lipid Droplets in Response to Spike Proteins

Intracellular lipid droplets (LDs) can accumulate in response to inflammation, metabolic stresses, and other physiological/pathological processes. Herein, we investigated whether spike proteins of SARS-CoV-2 induce LDs in human peripheral blood mononuclear cells (PBMCs) and in pulmonary microvascular endothelial cells (HPMECs). PBMCs or HPMECs were incubated alone or with endotoxin-free recombinant variants of trimeric spike glycoproteins (Alpha, Beta, Delta, and Omicron, 12 µg/mL). Afterward, cells were stained with Oil Red O for LDs, cytokine release was determined through ELISA, and the gene expression was analyzed through real-time PCR using TaqMan assays. Our data show that spikes induce LDs in PBMCs but not in HPMECs. In line with this, in PBMCs, spike proteins lower the expression of genes involving lipid metabolism and LD formation, such as SREBF1, HMGCS1, LDLR, and CD36. On the other hand, PBMCs exposed to spikes for 6 or 18 h did not increase in IL-1β, IL-6, IL-8, MCP-1, and TNFα release or expression as compared to non-treated controls. Thus, spike-induced LD formation in PBMCs seems to not be related to cell inflammatory activation. Further detailed studies are warranted to investigate in which specific immune cells spikes induce LDs, and what are the pathophysiological mechanisms and consequences of this induction in vivo.

Dysregulation of Cholesterol Homeostasis in Ovarian Cancer

Cholesterol plays an essential role in maintaining the rigidity of cell membranes and signal transduction. Various investigations confirmed empirically that the dysregulation of cholesterol homeostasis positively correlates with tumor progression. More specifically, recent studies suggested the distinct role of cholesterol in ovarian cancer cell proliferation, metastasis and chemoresistance. In this review, we summarize the current findings that suggest the contribution of cholesterol homeostasis dysregulation to ovarian cancer progression and resistance to anti-cancer agents. We also discuss the therapeutic implications of cholesterol-lowering drugs in ovarian cancer.

Immunometabolism and immune response regulate macrophage function in atherosclerosis

Macrophages are crucial in the progression of atherosclerotic cardiovascular disease (ASCVD). In the atherosclerotic lesions, macrophages play a central role in maintaining inflammatory response, promoting plaque development, and facilitating thrombosis. Increasing studies indicate that metabolic reprogramming and immune response mediate macrophage functional changes in all stages of atherosclerosis. In this review article, we explain how metabolic changes in glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, fatty acid synthesis, fatty acid oxidation, and cholesterol metabolism regulate macrophage function in atherosclerosis. We discuss how immune response to oxidized lipids regulate macrophage function in atherosclerosis. Additionally, we explore how abnormal metabolism leads to macrophage mitochondrial dysfunction in atherosclerosis.

Conferring liver selectivity to a thyromimetic using a novel nanoparticle increases therapeutic efficacy in a diet-induced obesity animal model

Optimization of metabolic regulation is a promising solution for many pathologies, including obesity, dyslipidemia, type 2 diabetes, and inflammatory liver disease. Synthetic thyroid hormone mimics-based regulation of metabolic balance in the liver showed promise but was hampered by the low biocompatibility and harmful effects on the extrahepatic axis. In this work, we show that specifically directing the thyromimetic to the liver utilizing a nanogel-based carrier substantially increased therapeutic efficacy in a diet-induced obesity mouse model, evidenced by the near-complete reversal of body weight gain, liver weight and inflammation, and cholesterol levels with no alteration in the thyroxine (T4) / thyroid stimulating hormone (TSH) axis. Mechanistically, the drug acts by binding to thyroid hormone receptor β (TRβ), a ligand-inducible transcription factor that interacts with thyroid hormone response elements and modulates target gene expression. The reverse cholesterol transport (RCT) pathway is specifically implicated in the observed therapeutic effect. Overall, the study demonstrates a unique approach to restoring metabolic regulation impacting obesity and related metabolic dysfunctions.

Intracellular Cholesterol Trafficking

Cholesterol is an essential lipid species of mammalian cells. Cells acquire it through synthesis in the endoplasmic reticulum (ER) and uptake from lipoprotein particles. Newly synthesized cholesterol is efficiently distributed from the ER to other organelles via lipid-binding/transfer proteins concentrated at membrane contact sites (MCSs) to reach the trans-Golgi network, endosomes, and plasma membrane. Lipoprotein-derived cholesterol is exported from the plasma membrane and endosomal compartments via a combination of vesicle/tubule-mediated membrane transport and transfer through MCSs. In this review, we provide an overview of intracellular cholesterol trafficking pathways, including cholesterol flux from the ER to other membranes, cholesterol uptake from lipoprotein donors and transport from the plasma membrane to the ER, cellular cholesterol efflux to lipoprotein acceptors, as well as lipoprotein cholesterol secretion from enterocytes, hepatocytes, and astrocytes. We also briefly discuss human diseases caused by defects in these processes and therapeutic strategies available in such conditions.

Cholesterol efflux capacity is increased in subjects with familial hypercholesterolemia in a retrospective case-control study

Familial Hypercholesterolemia (FH) is characterized by an increase in Low-Density Lipoprotein Cholesterol (LDL-C) and by premature Cardiovascular Disease (CVD). However, it remains to be fully elucidated if FH impairs cholesterol efflux capacity (CEC), and whether CEC is related to lipoprotein subfraction distribution. This study aimed at comparing FH patients and age, sex and BMI matched controls in terms of LDL and HDL subfraction distribution as well as CEC. Forty FH patients and 80 controls, matched for age, sex and BMI, were enrolled in this case-control study. LDL and HDL subfractions were analyzed using the Quantimetrix Lipoprint System. CEC was evaluated as aq-CEC and ABCA1-CEC. FH subjects showed a significantly higher concentration of all LDL subfractions, and a shift from large to small HDL subfraction pattern relative to controls. FH subjects with previous CVD event had smaller LDL lipoproteins than controls and FH subjects without previous CVD event. Both aq-CEC and ABCA1-CEC were increased in FH patients with respect to controls. To conclude, FH subjects had a metabolic profile characterized not only by higher LDL-C but also by shift from large to small HDL subfraction phenotype. However, FH subjects showed an increase CEC than controls.

Implantation of CPT1AM-expressing adipocytes reduces obesity and glucose intolerance in mice

Obesity and its associated metabolic comorbidities are a rising global health and social issue, with novel therapeutic approaches urgently needed. Adipose tissue plays a key role in the regulation of energy balance and adipose tissue-derived mesenchymal stem cells (AT-MSCs) have gained great interest in cell therapy. Carnitine palmitoyltransferase 1A (CPT1A) is the gatekeeper enzyme for mitochondrial fatty acid oxidation. Here, we aimed to generate adipocytes expressing a constitutively active CPT1A form (CPT1AM) that can improve the obese phenotype in mice after their implantation. AT-MSCs were differentiated into mature adipocytes, subjected to lentivirus-mediated expression of CPT1AM or the GFP control, and subcutaneously implanted into mice fed a high-fat diet (HFD). CPT1AM-implanted mice showed lower body weight, hepatic steatosis and serum insulin and cholesterol levels alongside improved glucose tolerance. HFD-induced increases in adipose tissue hypertrophy, fibrosis, inflammation, endoplasmic reticulum stress and apoptosis were reduced in CPT1AM-implanted mice. In addition, the expression of mitochondrial respiratory chain complexes was enhanced in the adipose tissue of CPT1AM-implanted mice. Our results demonstrate that implantation of CPT1AM-expressing AT-MSC-derived adipocytes into HFD-fed mice improves the obese metabolic phenotype, supporting the future clinical use of this ex vivo gene therapy approach.

Altered Distribution of Unesterified Cholesterol among Lipoprotein Subfractions of Patients with Diabetes Mellitus Type 2

Biomarkers are important tools to improve the early detection of patients at high risk for developing diabetes as well as the stratification of diabetic patients towards risks of complications. In addition to clinical variables, we analyzed 155 metabolic parameters in plasma samples of 51 healthy volunteers and 66 patients with diabetes using nuclear magnetic resonance (NMR) spectrometry. Upon elastic net analysis with lasso regression, we confirmed the independent associations of diabetes with branched-chain amino acids and lactate (both positive) as well as linoleic acid in plasma and HDL diameter (both inverse). In addition, we found the presence of diabetes independently associated with lower concentrations of free cholesterol in plasma but higher concentrations of free cholesterol in small HDL. Compared to plasmas of non-diabetic controls, plasmas of diabetic subjects contained lower absolute and relative concentrations of free cholesterol in all LDL and HDL subclasses except small HDL but higher absolute and relative concentrations of free cholesterol in all VLDL subclasses (except very small VLDL). These disbalances may reflect disturbances in the transfer of free cholesterol from VLDL to HDL during lipolysis and in the transfer of cell-derived cholesterol from small HDL via larger HDL to LDL.

Essential protein P116 extracts cholesterol and other indispensable lipids for Mycoplasmas

Mycoplasma pneumoniae, responsible for approximately 30% of community-acquired human pneumonia, needs to extract lipids from the host environment for survival and proliferation. Here, we report a comprehensive structural and functional analysis of the previously uncharacterized protein P116 (MPN_213). Single-particle cryo-electron microscopy of P116 reveals a homodimer presenting a previously unseen fold, forming a huge hydrophobic cavity, which is fully accessible to solvent. Lipidomics analysis shows that P116 specifically extracts lipids such as phosphatidylcholine, sphingomyelin and cholesterol. Structures of different conformational states reveal the mechanism by which lipids are extracted. This finding immediately suggests a way to control Mycoplasma infection by interfering with lipid uptake.

Liver X Receptor Agonist Inhibits Oxidized Low-Density Lipoprotein Induced Choroidal Neovascularization via the NF-κB Signaling Pathway

Age-related macular degeneration (AMD) is the most common blindness-causing disease among the elderly. Under oxidative stress, low-density lipoprotein in the outer layer of the retina is easily converted into oxidized low-density lipoprotein (OxLDL), which promotes the development of choroidal neovascularization (CNV), the main pathological change in wet AMD. Liver X receptor (LXR), a ligand-activated nuclear transcription factor, regulates various processes related to CNV, including lipid metabolism, cholesterol transport, inflammation, and angiogenesis. In this study, we evaluated the effects of the LXR agonist TO901317 (TO) on CNV. Our results demonstrated that the TO could inhibit OxLDL-induced CNV in mice as well as inflammation and angiogenesis in vitro. Using siRNA transfection in cells and Vldlr^-/- mice, we further confirmed the inhibitory effects of TO against the inflammatory response and oxidative stress. Mechanistically, the LXR agonist reduces the inflammatory response via the nuclear translocation of NF-κB p65 in the pathway for NF-κB activation and by enhancing ABCG1-dependent lipid transportation. Therefore, an LXR agonist is a promising therapeutic candidate for AMD, especially for wet AMD.

HDL Functions-Current Status and Future Perspectives

Cardiovascular disease (CVD) is the leading cause of death in Western countries. A low HDL-C is associated with the development of CVD. However, recent epidemiology studies have shown U-shaped curves between HDL-C and CVD mortality, with paradoxically increased CVD mortality in patients with extremely high HDL-C levels. Furthermore, HDL-C raising therapy using nicotinic acids or CETP inhibitors mostly failed to reduce CVD events. Based on this background, HDL functions rather than HDL-C could be a novel biomarker; research on the clinical utility of HDL functionality is ongoing. In this review, we summarize the current status of HDL functions and their future perspectives from the findings of basic research and clinical trials.

Design of Smart Aggregates: Toward Rapid Clinical Diagnosis of Hyperlipidemia in Human Blood

Molecular aggregates with environmental responsive properties are desired for their wide practical applications such as bioprobes. Here, a series of smart near-infrared (NIR) luminogens for hyperlipidemia (HLP) diagnosis is reported. The aggregates of these molecules exhibit a twisted intramolecular charge-transfer effect in aqueous media, but aggregation-induced emission in highly viscous media due to the restriction of the intramolecular motion. These aggregates, which can autonomously respond to different environments via switching the aggregation state without changing their chemical structures are described, as "smart aggregates". Intriguingly, these luminogens demonstrate NIR-II and NIR-III luminescence with ultralarge Stokes shifts (>950 nm). Both in vitro detection and in vivo imaging of HLP can be realized in a mouse model. Linear relationships exist between the emission intensity and multiple pathological parameters in blood samples of HLP patients. Thus, the design of smart aggregate facilitates rapid and accurate detection of HLP and provides a promising attempt in aggregate science.

High-density lipoprotein revisited: biological functions and clinical relevance

Previous interest in high-density lipoproteins (HDLs) focused on their possible protective role in atherosclerotic cardiovascular disease (ASCVD). Evidence from genetic studies and randomized trials, however, questioned that the inverse association of HDL-cholesterol (HDL-C) is causal. This review aims to provide an update on the role of HDL in health and disease, also beyond ASCVD. Through evolution from invertebrates, HDLs are the principal lipoproteins, while apolipoprotein B-containing lipoproteins first developed in vertebrates. HDLs transport cholesterol and other lipids between different cells like a reusable ferry, but serve many other functions including communication with cells and the inactivation of biohazards like bacterial lipopolysaccharides. These functions are exerted by entire HDL particles or distinct proteins or lipids carried by HDL rather than by its cholesterol cargo measured as HDL-C. Neither does HDL-C measurement reflect the efficiency of reverse cholesterol transport. Recent studies indicate that functional measures of HDL, notably cholesterol efflux capacity, numbers of HDL particles, or distinct HDL proteins are better predictors of ASCVD events than HDL-C. Low HDL-C levels are related observationally, but also genetically, to increased risks of infectious diseases, death during sepsis, diabetes mellitus, and chronic kidney disease. Additional, but only observational, data indicate associations of low HDL-C with various autoimmune diseases, and cancers, as well as all-cause mortality. Conversely, extremely high HDL-C levels are associated with an increased risk of age-related macular degeneration (also genetically), infectious disease, and all-cause mortality. HDL encompasses dynamic multimolecular and multifunctional lipoproteins that likely emerged during evolution to serve several physiological roles and prevent or heal pathologies beyond ASCVD. For any clinical exploitation of HDL, the indirect marker HDL-C must be replaced by direct biomarkers reflecting the causal role of HDL in the respective disease.

Fabry disease: Mechanism and therapeutics strategies

Fabry disease is a monogenic disease characterized by a deficiency or loss of the α-galactosidase A (GLA). The resulting impairment in lysosomal GLA enzymatic activity leads to the pathogenic accumulation of enzymatic substrate and, consequently, the progressive appearance of clinical symptoms in target organs, including the heart, kidney, and brain. However, the mechanisms involved in Fabry disease-mediated organ damage are largely ambiguous and poorly understood, which hinders the development of therapeutic strategies for the treatment of this disorder. Although currently available clinical approaches have shown some efficiency in the treatment of Fabry disease, they all exhibit limitations that need to be overcome. In this review, we first introduce current mechanistic knowledge of Fabry disease and discuss potential therapeutic strategies for its treatment. We then systemically summarize and discuss advances in research on therapeutic approaches, including enzyme replacement therapy (ERT), gene therapy, and chaperone therapy, as well as strategies targeting subcellular compartments, such as lysosomes, the endoplasmic reticulum, and the nucleus. Finally, the future development of potential therapeutic strategies is discussed based on the results of mechanistic studies and the limitations associated with these therapeutic approaches.

The berberine-enriched gut commensal Blautia producta ameliorates high-fat diet (HFD)-induced hyperlipidemia and stimulates liver LDLR expression

Berberine (BBR) is an effective cholesterol-lowering drug. Although gut microbiota has been implicated in the pharmacological activities of BBR, little evidence exists on the specific species of gut microbiota involved in its therapeutic effects, nor on linking gut bacteria to its recognized hypercholesterolemia-alleviating mechanism-upregulation of the low-density lipoprotein receptor (LDLR) in the liver. The present study was performed to identify the specific species of gut microbiota involved in the anti-hyperlipdemic effect of BBR, and interpret its mechanism through linking the gut microbiota and LDLR. The BBR-enriched gut bacterial species were identified by whole genome shotgun sequencing. Pure cultured B. producta was orally administered to C57BL/6 mice to evaluate its anti-hyperlipdemic effect. The LDLR-upregulating effect of B. producta was evaluated both in vitro and in vivo. Orally administration of BBR (200 mg/kg) decreased serum and liver lipid levels in HFD-induced hyperlipidemic mice. Microbiome analysis indicated that Blautia was closely associated with BBR's lipid-modulating activities. Further analysis revealed that BBR selectively promoted the growth of Blautia producta. Orally treatment of HFD mice with live B. producta reduced obesity and alleviated hyperlipidemia. Notably, the B. producta significantly increased LDLR expression in the liver, and its spent culture supernatant upregulated the LDLR level and promoted LDL uptake by HepG2 cells. Simultaneously, B. producta also linked butyrate-producing and bile salt hydrolase (BSH)-inhibiting effect of BBR. The gut microbiota, especially B. producta, may confers the hypercholesterolemia-alleviating effects of berberine. B. producta represents a novel probiotic that may be used for the treatment of dyslipidemia.

Cholesterol Chip for the Study of Cholesterol-Protein Interactions Using SPR

Cholesterol, an important lipid in animal membranes, binds to hydrophobic pockets within many soluble proteins, transport proteins and membrane bound proteins. The study of cholesterol-protein interactions in aqueous solutions is complicated by cholesterol's low solubility and often requires organic co-solvents or surfactant additives. We report the synthesis of a biotinylated cholesterol and immobilization of this derivative on a streptavidin chip. Surface plasmon resonance (SPR) was then used to measure the kinetics of cholesterol interaction with cholesterol-binding proteins, hedgehog protein and tyrosine phosphatase 1B.

Effect of a PCSK9 inhibitor and a statin on cholesterol efflux capacity: A limitation of current cholesterol-lowering treatments?

BACKGROUND

Cellular cholesterol efflux is a key step in reverse cholesterol transport that may impact on atherosclerotic cardiovascular risk. The process may be reliant on the availability of apolipoprotein (apo) B-100-containing lipoproteins to accept cholesterol from high-density lipoprotein. Evolocumab and atorvastatin are known to lower plasma apoB-100-containing lipoproteins that could impact on cholesterol efflux capacity (CEC).

METHODS

We conducted a 2-by-2 factorial trial of the effects of subcutaneous evolocumab (420 mg every 2 weeks) and atorvastatin (80 mg daily) for 8 weeks on CEC in 81 healthy, normolipidaemic men. The capacity of whole plasma and apoB-depleted plasma, including ATP-binding cassette transporter A1 (ABCA1)-mediated and passive diffusion, to efflux cholesterol, was measured.

RESULTS

Evolocumab and atorvastatin independently decreased whole plasma CEC (main effect p < .01 for both). However, there were no significant effects of evolocumab and atorvastatin on apoB-depleted plasma, ABCA1-mediated and passive diffusion-mediated CEC (p > .05 in all). In the three intervention groups combined, the reduction in whole plasma CEC was significantly correlated with the corresponding reduction in plasma apoB-100 concentration (r = .339, p < .01). In the evolocumab monotherapy group, the reduction in whole plasma CEC was also significantly correlated with the corresponding reduction in plasma lipoprotein(a) concentration (r = .487, p < .05).

CONCLUSIONS

In normolipidaemic men, evolocumab and atorvastatin decrease the capacity of whole plasma to efflux cellular cholesterol. These effects may be chiefly owing to a fall in the availability of apoB-100-containing lipoproteins. Reduction in circulating lipoprotein(a) may also contribute to the decrease in whole plasma cholesterol efflux with evolocumab monotherapy.

Alisol B 23-acetate adjusts bile acid metabolisim via hepatic FXR-BSEP signaling activation to alleviate atherosclerosis

BACKGROUND

Postmenopausal women have a high incidence of atherosclerosis. Phytosterols have been shown to have cholesterol-lowering properties. Alisa B 23-acetate (AB23A) is a biologically active plant sterol isolated from Chinese herbal medicine Alisma. However, the atherosclerosis effect of AB23A after menopause and its possible mechanism have not been reported yet.

PURPOSE

To explore whether AB23A can prevent atherosclerosis by regulating farnesoid X receptor and subsequently increasing fecal bile acid and cholesterol excretion to reduce plasma cholesterol levels.

METHODS

Aortic samples from premenopausal and postmenopausal women with ascending aortic arteriosclerosis were analyzed, and bilateral ovariectomized (OVX) female LDLR^-/- mice and free fatty acid (FFA)-treated L02 cells were used to analyze the effect of AB23A supplementation therapy.

RESULTS

AB23A increased fecal cholesterol and bile acids (BAs) excretion dependent on activation of hepatic farnesoid X receptor (FXR) in ovariectomized mice. AB23A inhibited hepatic cholesterol 7α-hydroxylase (CYP7A1) and sterol 12α-hydroxylase (CYP8B1) via inducing small heterodimer partner (SHP) expression. On the other hand, AB23A increased the level of hepatic chenodeoxycholic acid (CDCA), and activated the hepatic BSEP signaling. The activation of hepatic FXR-BSEP signaling by AB23A in ovariectomized mice was accompanied by the reduction of liver cholesterol, hepatic lipolysis, and bile acids efflux, and reduced the damage of atherosclerosis. In vitro, AB23A fixed abnormal lipid metabolism in L02 cells and increased the expression of FXR, BSEP and SHP. Moreover, the inhibition and silencing of FXR canceled the regulation of BSEP by AB23A in L02 cells.

CONCLUSION

Our results shed light into the mechanisms behind the cholesterol-lowering of AB23A, and increasing FXR-BSEP signaling by AB23A may be a potential postmenopausal atherosclerosis therapy.

Monitoring Atheroprotective Macrophage Cholesterol Efflux In Vivo

This chapter provides details on the methodologies currently used to monitor macrophage cholesterol efflux in vivo in mice. The general principles and techniques described herein can be applied to evaluate the effect of different experimental pathophysiological conditions or the efficacy of different therapeutic strategies on the modulation of in vivo cholesterol efflux to plasma acceptors and the rate of reverse transport of unesterified cholesterol from macrophages to feces in mice.

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

OBJECTIVE

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

APPROACH AND RESULTS

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

CONCLUSIONS

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

Children with familial hypercholesterolemia display changes in LDL and HDL function: A cross-sectional study

BACKGROUND

The functional status of lipoprotein particles contributes to atherogenesis. The tendency of plasma low-density lipoprotein (LDL) particles to aggregate and the ability of igh-density lipoprotein (HDL) particles to induce and mediate reverse cholesterol transport associate with high and low risk for cardiovascular disease in adult patients, respectively. However, it is unknown whether children with familial hypercholesterolemia (FH) display lipoprotein function alterations.

HYPOTHESIS

We hypothesized that FH children had disrupted lipoprotein functions.

METHODS

We analyzed LDL aggregation susceptibility and HDL-apoA-I exchange (HAE), and activity of four proteins that regulate lipoprotein metabolism (cholesteryl ester transfer protein, lecithin-cholesterol acyltransferase, phospholipid transfer protein, and paraoxonase-1) in plasma samples derived from children with FH (n = 47) and from normocholesterolemic children (n = 56). Variation in lipoprotein functions was further explored using an nuclear magnetic resonance-based metabolomics profiling approach.

RESULTS

LDL aggregation was higher, and HAE was lower in FH children than in normocholesterolemic children. LDL aggregation associated positively with LDL cholesterol (LDL-C) and negatively with triglycerides, and HAE/apoA-I associated negatively with LDL-C. Generally, the metabolomic profile for LDL aggregation was opposite of that of HAE/apoA-I.

CONCLUSIONS

FH children displayed increased atherogenicity of LDL and disrupted HDL function. These newly observed functional alterations in LDL and HDL add further understanding of the risk for atherosclerotic cardiovascular disease in FH children.

Rosmarinic Acid Exhibits a Lipid-Lowering Effect by Modulating the Expression of Reverse Cholesterol Transporters and Lipid Metabolism in High-Fat Diet-Fed Mice

Hyperlipidemia is a potent risk factor for the development of cardiovascular diseases. The reverse cholesterol transport (RCT) process has been shown to alleviate hyperlipidemia and protect against cardiovascular diseases. Recently, rosmarinic acid was reported to exhibit lipid-lowering effects. However, the underlying mechanism is still unclear. This study aims to investigate whether rosmarinic acid lowers lipids by modulating the RCT process in high-fat diet (HFD)-induced hyperlipidemic C57BL/6J mice. Our results indicated that rosmarinic acid treatment significantly decreased body weight, blood glucose, and plasma total cholesterol and triglyceride levels in HFD-fed mice. Rosmarinic acid increased the expression levels of cholesterol uptake-associated receptors in liver tissues, including scavenger receptor B type 1 (SR-B1) and low-density lipoprotein receptor (LDL-R). Furthermore, rosmarinic acid treatment notably increased the expression of cholesterol excretion molecules, ATP-binding cassette G5 (ABCG5) and G8 (ABCG8) transporters, and cholesterol 7 alpha-hydroxylase A1 (CYP7A1) as well as markedly reduced cholesterol and triglyceride levels in liver tissues. In addition, rosmarinic acid facilitated fatty acid oxidation through AMP-activated protein kinase (AMPK)-mediated carnitine palmitoyltransferase 1A (CPT1A) induction. In conclusion, rosmarinic acid exhibited a lipid-lowering effect by modulating the expression of RCT-related proteins and lipid metabolism-associated molecules, confirming its potential for the prevention or treatment of hyperlipidemia-derived diseases.

High-density lipoproteins, reverse cholesterol transport and atherogenesis

Plasma HDL-cholesterol concentrations correlate negatively with the risk of atherosclerotic cardiovascular disease (ASCVD). According to a widely cited model, HDL elicits its atheroprotective effect through its role in reverse cholesterol transport, which comprises the efflux of cholesterol from macrophages to early forms of HDL, followed by the conversion of free cholesterol (FCh) contained in HDL into cholesteryl esters, which are hepatically extracted from the plasma by HDL receptors and transferred to the bile for intestinal excretion. Given that increasing plasma HDL-cholesterol levels by genetic approaches does not reduce the risk of ASCVD, the focus of research has shifted to HDL function, especially in the context of macrophage cholesterol efflux. In support of the reverse cholesterol transport model, several large studies have revealed an inverse correlation between macrophage cholesterol efflux to plasma HDL and ASCVD. However, other studies have cast doubt on the underlying reverse cholesterol transport mechanism: in mice and humans, the FCh contained in HDL is rapidly cleared from the plasma (within minutes), independently of esterification and HDL holoparticle uptake by the liver. Moreover, the reversibility of FCh transfer between macrophages and HDL has implicated the reverse process - that is, the transfer of FCh from HDL to macrophages - in the aetiology of increased ASCVD under conditions of very high plasma HDL-FCh concentrations.

High Free Cholesterol Bioavailability Drives the Tissue Pathologies in Scarb1-/- Mice

Objective: Overall and atherosclerosis-associated mortality is elevated in humans with very high HDL (high-density lipoprotein) cholesterol concentrations. Mice with a deficiency of the HDL receptor, Scarb1 (scavenger receptor class B type 1), are a robust model of this phenotype and exhibit several additional pathologies. We hypothesized that the previously reported high plasma concentration of free cholesterol (FC)-rich HDL in Scarb1-/- mice produces a state of high HDL-FC bioavailability that increases whole-body FC and dysfunction in multiple tissue sites. Approach and Results: The higher mol% FC in Scarb1-/- versus WT (wild type) HDL (41.1 versus 16.0 mol%) affords greater FC bioavailability for transfer to multiple sites. Plasma clearance of autologous HDL-FC mass was faster in WT versus Scarb1-/- mice. FC influx from Scarb1-/- HDL to LDL (low-density lipoprotein) and J774 macrophages was greater ([almost equal to]4x) than that from WT HDL, whereas FC efflux capacity was similar. The higher mol% FC of ovaries, erythrocytes, heart, and macrophages of Scarb1-/- versus WT mice is associated with previously reported female infertility, impaired cell maturation, cardiac dysfunction, and atherosclerosis. The FC contents of other tissues were similar in the two genotypes, and these tissues were not associated with any overt pathology. In addition to the differences between WT versus Scarb1-/- mice, there were many sex-dependent differences in tissue-lipid composition and plasma FC clearance rates. Conclusions: Higher HDL-FC bioavailability among Scarb1-/- versus WT mice drives increased FC content of multiple cell sites and is a potential biomarker that is mechanistically linked to multiple pathologies.

Cholesterol efflux pathways, inflammation, and atherosclerosis

Plasma levels of high-density lipoprotein (HDL) inversely correlate with the incidence of cardiovascular diseases (CVD). The causal relationship between plasma HDL-cholesterol levels and CVD has been called into question by Mendelian randomization studies and the majority of clinical trials not showing any benefit of plasma HDL-cholesterol raising drugs on CVD. Nonetheless, recent Mendelian randomization studies including an increased number of CVD cases compared to earlier studies have confirmed that HDL-cholesterol levels and CVD are causally linked. Moreover, several studies in large population cohorts have shown that the cholesterol efflux capacity of HDL inversely correlates with CVD. Cholesterol efflux pathways exert anti-inflammatory and anti-atherogenic effects by suppressing proliferation of hematopoietic stem and progenitor cells, and inflammation and inflammasome activation in macrophages. Cholesterol efflux pathways also suppress the accumulation of cholesteryl esters in macrophages, i.e. macrophage foam cell formation. Recent single-cell RNASeq studies on atherosclerotic plaques have suggested that macrophage foam cells have lower expression of inflammatory genes than non-foam cells, probably reflecting liver X receptor activation, upregulation of ATP Binding Cassette A1 and G1 cholesterol transporters and suppression of inflammation. However, when these pathways are defective lesional foam cells may become pro-inflammatory.

Familial Hypercholesterolemia: Do HDL Play a Role?

Cardiovascular disease (CVD) in heterozygous familial hypercholesterolemia (HeFH), the most frequent monogenic disorder of human metabolism, is largely driven by low-density lipoprotein (LDL) cholesterol concentrations. Since the CVD rate differs considerably in this population, beyond the lifetime LDL cholesterol vascular accumulation, other classical risk factors are involved in the high cardiovascular risk of HeFH. Among other lipoprotein disturbances, alterations in the phenotype and functionality of high-density lipoproteins (HDL) have been described in HeFH patients, contributing to the presence and severity of CVD. In fact, HDL are the first defensive barrier against the burden of high LDL cholesterol levels owing to their contribution to reverse cholesterol transport as well as their antioxidant and anti-inflammatory properties, among others. In this context, the present narrative review aimed to focus on quantitative and qualitative abnormalities in HDL particles in HeFH, encompassing metabolic, genetic and epigenetic aspects.

Canagliflozin Facilitates Reverse Cholesterol Transport Through Activation of AMPK/ABC Transporter Pathway

BACKGROUND AND PURPOSE

Cholesterol is an essential lipid and its homeostasis is a major factor for many diseases, such as hyperlipidemia, atherosclerosis, diabetes, and obesity. Sodium-glucose cotransporter 2 (SGLT2) inhibitor canagliflozin (Cana) is a new kind of hypoglycemic agent, which decreases urinary glucose reabsorption and reduces hyperglycemia. Cana has been shown to regulate serum lipid, decrease serum triglyceride and increase serum high-density lipoprotein-cholesterol (HDL-C), and improve cardiovascular outcomes. But evidence of how Cana impacted the cholesterol metabolism remains elusive.

METHODS

We treated Cana on mice with chow diet or western diet and then detected cholesterol metabolism in the liver and intestine. To explore the mechanism, we also treated hepG2 cells and Caco2 cells with different concentrations of Cana.

RESULTS

In this study, we showed that Cana facilitated hepatic and intestinal cholesterol efflux. Mechanically, Cana via activating adenosine monophosphate-activated protein kinase (AMPK) increased the expression of ATP-binding cassette (ABC) transporters ABCG5 and ABCG8 in liver and intestine, increased biliary and fecal cholesterol excretion.

CONCLUSION

This research confirms that Cana regulates cholesterol efflux and improves blood and hepatic lipid; this may be a partial reason for improving cardiovascular disease.

(r)HDL in theranostics: how do we apply HDL's biology for precision medicine in atherosclerosis management?

High-density lipoproteins (HDL) are key players in cholesterol metabolism homeostasis since they are responsible for transporting excess cholesterol from peripheral tissues to the liver. Imbalance in this process, due to either excessive accumulation or impaired clearance, results in net cholesterol accumulation and increases the risk of cardiovascular disease (CVD). Therefore, significant effort has been focused on the development of therapeutic tools capable of either directly or indirectly enhancing HDL-guided reverse cholesterol transport (RCT). More recently, in light of the emergence of precision nanomedicine, there has been renewed research interest in attempting to take advantage of the development of advanced recombinant HDL (rHDL) for both therapeutic and diagnostic purposes. In this review, we provide an update on the different approaches that have been developed using rHDL, focusing on the rHDL production methodology and rHDL applications in theranostics. We also compile a series of examples highlighting potential future perspectives in the field.

Reverse Cholesterol Transport Dysfunction Is a Feature of Familial Hypercholesterolemia

PURPOSE OF REVIEW

We seek to establish whether high-density lipoprotein HDL metabolism and reverse cholesterol transport (RCT) impairment is an intrinsic feature of familial hypercholesterolemia (FH).

RECENT FINDINGS

RCT from macrophages (m-RCT), a vascular cell type of major influence on atherosclerosis, is impaired in FH due to defective low-density lipoprotein receptor (LDLR) function via both the HDL- and LDL-mediated pathways. Potential mechanisms include impaired HDL metabolism, which is linked to increased LDL levels, as well as the increased transport of cellular unesterified cholesterol to LDL, which presents a defective catabolism. RCT dysfunction is consistently associated with mutation-positive FH linked to decreased HDL levels as well as impaired HDL remodeling and LDLR function. It remains to be explored whether these alterations are also present in less well-characterized forms of FH, such as cases with no identified mutations, and whether they are fully corrected by current standard treatments.

The effect of transgender hormonal treatment on high density lipoprotein cholesterol efflux capacity

BACKGROUND AND AIMS

A decrease in high-density lipoprotein (HDL)-cholesterol concentrations during transgender hormone therapy has been shown. However, the ability of HDL to remove cholesterol from arterial wall macrophages, termed cholesterol efflux capacity (CEC), has proven to be a better predictor of cardiovascular disease (CVD) largely independently of HDL-concentrations. In addition, the serum capacity to load macrophages with cholesterol (cholesterol loading capacity, CLC) represents an index of pro-atherogenic potential. As transgender individuals are exposed to lifelong exogenous hormone therapy (HT), it becomes of interest to study whether HDL-CEC and serum CLC are affected by HT. HDL-CEC and serum CLC have been evaluated in 15 trans men treated with testosterone and in 15 trans women treated with estradiol and cyproterone acetate at baseline and after 12 months of HT.

METHODS

Total HDL-CEC from macrophages and its major contributors, the ATP-binding cassette transporters (ABC) A1 and ABCG1 HDL-CEC and HDL-CEC by aqueous diffusion were determined by a radioisotopic assay. CLC was evaluated in human THP-1 macrophages.

RESULTS

In trans women, total HDL-CEC decreased by 10.8% (95%CI: -14.3;-7.3; p < 0.001), ABCA1 HDL-CEC by 23.8% (-34.7; -12.9; p < 0.001) and aqueous diffusion HDL-CEC by 4.8% (-8.4;-1.1; p < 0.01). In trans men, only aqueous diffusion HDL-CEC decreased significantly, -9.8% (-15.7;-3.9; p < 0.01). ABCG1 HDL-CEC did not change in either group. Serum CLC and HDL subclass distribution were not modified by HT in both groups.

CONCLUSIONS

Total HDL-CEC decreased during HT in trans women, with a specific reduction in ABCA1 CEC. This finding might contribute to a higher CVD risk.

High Density Lipoprotein Cholesterol Efflux Capacity and Atherosclerosis in Cardiovascular Disease: Pathophysiological Aspects and Pharmacological Perspectives

Over the years, the relationship between high-density lipoprotein (HDL) and atherosclerosis, initially highlighted by the Framingham study, has been revealed to be extremely complex, due to the multiple HDL functions involved in atheroprotection. Among them, HDL cholesterol efflux capacity (CEC), the ability of HDL to promote cell cholesterol efflux from cells, has emerged as a better predictor of cardiovascular (CV) risk compared to merely plasma HDL-cholesterol (HDL-C) levels. HDL CEC is impaired in many genetic and pathological conditions associated to high CV risk such as dyslipidemia, chronic kidney disease, diabetes, inflammatory and autoimmune diseases, endocrine disorders, etc. The present review describes the current knowledge on HDL CEC modifications in these conditions, focusing on the most recent human studies and on genetic and pathophysiologic aspects. In addition, the most relevant strategies possibly modulating HDL CEC, including lifestyle modifications, as well as nutraceutical and pharmacological interventions, will be discussed. The objective of this review is to help understanding whether, from the current evidence, HDL CEC may be considered as a valid biomarker of CV risk and a potential pharmacological target for novel therapeutic approaches.

Nicotinamide Prevents Apolipoprotein B-Containing Lipoprotein Oxidation, Inflammation and Atherosclerosis in Apolipoprotein E-Deficient Mice

The potential of nicotinamide (NAM) to prevent atherosclerosis has not yet been examined. This study investigated the effect of NAM supplementation on the development of atherosclerosis in a mouse model of the disease. The development of aortic atherosclerosis was significantly reduced (NAM low dose: 45%; NAM high dose: 55%) in NAM-treated, apolipoprotein (Apo)E-deficient mice challenged with a Western diet for 4 weeks. NAM administration significantly increased (1.8-fold) the plasma concentration of proatherogenic ApoB-containing lipoproteins in NAM high-dose (HD)-treated mice compared with untreated mice. However, isolated ApoB-containing lipoproteins from NAM HD mice were less prone to oxidation than those of untreated mice. This result was consistent with the decreased (1.5-fold) concentration of oxidized low-density lipoproteins in this group. Immunohistochemical staining of aortas from NAM-treated mice showed significantly increased levels of IL-10 (NAM low-dose (LD): 1.3-fold; NAM HD: 1.2-fold), concomitant with a significant decrease in the relative expression of TNFα (NAM LD: −44%; NAM HD: −57%). An improved anti-inflammatory pattern was reproduced in macrophages cultured in the presence of NAM. Thus, dietary NAM supplementation in ApoE-deficient mice prevented the development of atherosclerosis and improved protection against ApoB-containing lipoprotein oxidation and aortic inflammation.

Increased ABCA1 (ATP-Binding Cassette Transporter A1)-Specific Cholesterol Efflux Capacity in Schizophrenia

Objective:

Patients with schizophrenia have increased long-term mortality attributable to cardiovascular disease and commonly demonstrate features of mixed dyslipidemia with low HDL-C (high-density lipoprotein cholesterol). The removal of cholesterol from cells by HDL via specific ATP-binding cholesterol transporters is a major functional property of HDL, and its measurement as cholesterol efflux capacity (CEC) can predict cardiovascular risk. Whether HDL function is impaired in patients with schizophrenia is unknown.

Approach and Results:

We measured basal and ABCA1 (ATP-binding cassette transporter A1)- and ABCG1 (ATP-binding cassette transporter G1)-dependent CEC, comparing patients with schizophrenia with age- and sex-matched healthy controls, and related our findings to nuclear magnetic resonance analysis of lipoprotein subclasses. Total plasma cholesterol and LDL-C (low-density lipoprotein cholesterol) were comparable between healthy controls (n=51) and patients (n=120), but patients with schizophrenia had increased total plasma triglyceride, low HDL-C and apo (apolipoprotein) A-I concentrations. Nuclear magnetic resonance analysis indicated a marked (15-fold) increase in large triglyceride-rich lipoprotein particle concentration, increased small dense LDL particles, and fewer large HDL particles. Despite lower HDL-C concentration, basal CEC was 13.7±1.6% higher, ABCA1-specific efflux was 35.9±1.6% higher, and ABCG1 efflux not different, in patients versus controls. In patients with schizophrenia, ABCA1-specific efflux correlated with the abundance of small 7.8 nm HDL particles but not with serum plasminogen or triglyceride levels.

Conclusions:

Patients with schizophrenia have increased concentrations of atherogenic apoB-containing lipoproteins, decreased concentrations of large HDL particles, but enhanced ABCA1-mediated CEC. In this population, preventative strategies should focus on reducing atherogenic lipoproteins rather than increasing CEC.