Differential lipid metabolism in monocytes and macrophages: influence of cholesterol loading

Dysregulated cytokine and oxidative response in hyper-glycolytic monocytes in obesity

Introduction

Obesity is associated with a plethora of health complications, including increased susceptibility to infections or decreased vaccine efficacy, partly due to dysregulated immune responses. Monocytes play a crucial role in innate immunity, yet their functional alterations in obesity remain poorly understood.

Methods

Here, we employed proteomic and metabolomic analyses to investigate monocyte characteristics in individuals with overweight, obesity, impaired glucose tolerance (IGT), and type 2 diabetes (T2D), compared to lean donors.

Results and discussion

Our results revealed distinct molecular signatures in monocytes from individuals with obesity, with significant alterations in pathways related to metabolism, cellular migration, and phagocytosis. Moreover, LPS-induced activation of monocytes unveiled heightened metabolic reprogramming towards glycolysis in subjects with obesity accompanied by dysregulated cytokine responses and elevated oxidative stress. Additionally, monocytes from donors with obesity exhibited increased lipid droplet accumulation. These findings shed light on the immunometabolic dysregulation underlying obesity-associated immune dysfunction, highlighting potential targets for therapeutic intervention.

Joint multi-omics discriminant analysis with consistent representation learning using PANDA

Integrative multi-omics analysis provides deeper insight and enables better and more realistic modeling of the underlying biology and causes of diseases than does single omics analysis. Although several integrative multi-omics analysis methods have been proposed and demonstrated promising results in integrating distinct omics datasets, inconsistent distribution of the different omics data, which is caused by technology variations, poses a challenge for paired integrative multi-omics methods. In addition, the existing discriminant analysis-based integrative methods do not effectively exploit correlation and consistent discriminant structures, necessitating a compromise between correlation and discrimination in using these methods. Herein we present PAN-omics Discriminant Analysis (PANDA), a joint discriminant analysis method that seeks omics-specific discriminant common spaces by jointly learning consistent discriminant latent representations for each omics. PANDA jointly maximizes between-class and minimizes within-class omics variations in a common space and simultaneously models the relationships among omics at the consistency representation and cross-omics correlation levels, overcoming the need for compromise between discrimination and correlation as with the existing integrative multi-omics methods. Because of the consistency representation learning incorporated into the objective function of PANDA, this method seeks a common discriminant space to minimize the differences in distributions among omics, can lead to a more robust latent representations than other methods, and is against the inconsistency of the different omics. We compared PANDA to 10 other state-of-the-art multi-omics data integration methods using both simulated and real-world multi-omics datasets and found that PANDA consistently outperformed them while providing meaningful discriminant latent representations. PANDA is implemented using both R and MATLAB, with codes available at https://github.com/WuLabMDA/PANDA.

Liver X Receptor-Inducible Host E3 Ligase IDOL Targets a Human Cytomegalovirus Reactivation Determinant

Liver X receptor (LXR) signaling broadly restricts virus replication; however, the mechanisms of restriction are poorly defined. Here, we demonstrate that the cellular E3 ligase LXR-inducible degrader of low-density lipoprotein receptor (IDOL) targets the human cytomegalovirus (HMCV) UL136p33 protein for turnover. UL136 encodes multiple proteins that differentially impact latency and reactivation. UL136p33 is a determinant of reactivation. UL136p33 is targeted for rapid turnover by the proteasome, and its stabilization by mutation of lysine residues to arginine results in a failure to quiet replication for latency. We show that IDOL targets UL136p33 for turnover but not the stabilized variant. IDOL is highly expressed in undifferentiated hematopoietic cells where HCMV establishes latency but is sharply downregulated upon differentiation, a stimulus for reactivation. We hypothesize that IDOL maintains low levels of UL136p33 for the establishment of latency. Consistent with this hypothesis, knockdown of IDOL impacts viral gene expression in wild-type (WT) HCMV infection but not in infection where UL136p33 has been stabilized. Furthermore, the induction of LXR signaling restricts WT HCMV reactivation from latency but does not affect the replication of a recombinant virus expressing a stabilized variant of UL136p33. This work establishes the UL136p33-IDOL interaction as a key regulator of the bistable switch between latency and reactivation. It further suggests a model whereby a key viral determinant of HCMV reactivation is regulated by a host E3 ligase and acts as a sensor at the tipping point between the decision to maintain the latent state or exit latency for reactivation. IMPORTANCE Herpesviruses establish lifelong latent infections, which pose an important risk for disease particularly in the immunocompromised. Our work is focused on the betaherpesvirus human cytomegalovirus (HCMV) that latently infects the majority of the population worldwide. Defining the mechanisms by which HCMV establishes latency or reactivates from latency is important for controlling viral disease. Here, we demonstrate that the cellular inducible degrader of low-density lipoprotein receptor (IDOL) targets a HCMV determinant of reactivation for degradation. The instability of this determinant is important for the establishment of latency. This work defines a pivotal virus-host interaction that allows HCMV to sense changes in host biology to navigate decisions to establish latency or to replicate.

Transcriptomic Context of RUNX3 Expression in Monocytes: A Cross-Sectional Analysis

The runt-related transcription factor 3 (RUNX3) regulates the differentiation of monocytes and their response to inflammation. However, the transcriptomic context of RUNX3 expression in blood monocytes remains poorly understood. We aim to learn about RUNX3 from its relationships within transcriptomes of bulk CD14+ cells in adults. This study used immunomagnetically sorted CD14+ cell gene expression microarray data from the Multi-Ethnic Study of Atherosclerosis (MESA, n = 1202, GSE56047) and the Correlated Expression and Disease Association Research (CEDAR, n = 281, E-MTAB-6667) cohorts. The data were preprocessed, subjected to RUNX3-focused correlation analyses and random forest modeling, followed by the gene ontology analysis. Immunity-focused differential ratio analysis with intermediary inference (DRAIMI) was used to integrate the data with protein-protein interaction network. Correlation analysis of RUNX3 expression revealed the strongest positive association for EVL (r_mean = 0.75, p_FDR-MESA = 5.37 × 10^-140, p_FDR-CEDAR = 5.52 × 10^-80), ARHGAP17 (r_mean = 0.74, p_FDR-MESA = 1.13 × 10^-169, p_FDR-CEDAR = 9.20 × 10^-59), DNMT1 (r_mean = 0.74, p_FDR-MESA = 1.10 × 10^-169, p_FDR-CEDAR = 1.67 × 10^-58), and CLEC16A (r_mean = 0.72, p_FDR-MESA = 3.51 × 10^-154, p_FDR-CEDAR = 2.27 × 10^-55), while the top negative correlates were C2ORF76 (r_mean = -0.57, p_FDR-MESA = 8.70 × 10^-94, p_FDR-CEDAR = 1.31 × 10^-25) and TBC1D7 (r_mean = -0.55, p_FDR-MESA = 1.36 × 10^-69, p_FDR-CEDAR = 7.81 × 10^-30). The RUNX3-associated transcriptome signature was involved in mRNA metabolism, signal transduction, and the organization of cytoskeleton, chromosomes, and chromatin, which may all accompany mitosis. Transcriptomic context of RUNX3 expression in monocytes hints at its relationship with cell growth, shape maintenance, and aspects of the immune response, including tyrosine kinases.

New Strategies to Promote Macrophage Cholesterol Efflux

The capacity of macrophages to dispose of cholesterol deposited in the atherosclerotic plaque depends on their ability to activate cholesterol efflux pathways. To develop athero-protective therapies aimed at promoting macrophage cholesterol efflux, cholesterol metabolism in THP-1 monocyte-derived macrophages has been extensively studied, but the intrinsic sensitivity of monocytes and the lack of a standardized procedure to differentiate THP-1 monocytes into macrophages have made it difficult to utilize THP-1 macrophages in the same or similar degree of differentiation across studies. The variability has resulted in lack of understanding of how the differentiation affects cholesterol metabolism, and here we review and investigate the effects of THP-1 differentiation on cholesterol efflux. The degree of THP-1 differentiation was inversely associated with ATP binding cassette A1 (ABCA1) transporter-mediated cholesterol efflux. The differentiation-associated decrease in ABCA1-mediated cholesterol efflux occurred despite an increase in ABCA1 expression. In contrast, DSC1 expression decreased during the differentiation. DSC1 is a negative regulator of the ABCA1-mediated efflux pathway and a DSC1-targeting agent, docetaxel showed high potency and efficacy in promoting ABCA1-mediated cholesterol efflux in THP-1 macrophages. These data suggest that pharmacological targeting of DSC1 may be more effective than increasing ABCA1 expression in promoting macrophage cholesterol efflux. In summary, the comparison of THP-1 macrophage subtypes in varying degrees of differentiation provided new insights into cholesterol metabolism in macrophages and allowed us to identify a viable target DSC1 for the promotion of cholesterol efflux in differentiated macrophages. Docetaxel and other pharmacological strategies targeting DSC1 may hold significant potential for reducing atherogenic cholesterol deposition.

The Pathogenic Role of Foam Cells in Atherogenesis: Do They Represent Novel Therapeutic Targets?

BACKGROUND

Foam cells, mainly derived from monocytes-macrophages, contain lipid droplets essentially composed of cholesterol in their cytoplasm. They infiltrate the intima of arteries, contributing to the formation of atherosclerotic plaques.

PATHOGENESIS

Foam cells damage the arterial cell wall via the release of proinflammatory cytokines, free radicals, and matrix metalloproteinases, enhancing the plaque size up to its rupture.

THERAPY

A correct dietary regimen seems to be the most appropriate therapeutic approach to minimize obesity, which is associated with the formation of foam cells. At the same time, different types of antioxidants have been evaluated to arrest the formation of foam cells, even if the results are still contradictory. In any case, a combination of antioxidants seems to be more efficient in the prevention of atherosclerosis.

Preparation of LDL , Oxidation , Methods of Detection, and Applications in Atherosclerosis Research

The concept of lipid peroxidation has been known for a long time. It is now well established that LDL plays a major role in atherosclerosis. Oxidized low-density lipoprotein (Ox-LDL) has been studied for over 35 years. Numerous pro- and anti-atherogenic properties have been attributed to Ox-LDL. Component composition of Ox-LDL is complex due to the influence of various factors, including the source, method of preparation, storage and use. Hence, it is very difficult to clearly define and characterize Ox-LDL. It contains unoxidized and oxidized fatty acid derivatives both in the ester and free forms, their decomposition products, cholesterol and its oxidized products, proteins with oxidized amino acids and cross-links, polypeptides with varying extents of covalent modification with lipid oxidation products and many others. The measurement of lipid oxidation has been a great boon, not only to the understanding of the process but also in providing numerous serendipitous discoveries and methodologies. In this chapter, we outline the methodologies for the preparation and testing of various lipoproteins for oxidation studies.

Lipidomics analysis of monocytes from patients with acute myocardial infarction reveals lactosylceramide as a new player in monocyte migration

Monocyte recruitment after vascular injury and their migration through the vessel wall represent crucial events in the initiation, progression, and destabilization of atherosclerotic plaque. Circulating monocytes are exposed to stimuli that alter their physiological state, and among them, lipids play a key role. Several studies investigated the mechanisms by which lipids affect monocyte functions promoting coronary atherosclerotic plaque initiation, but information on the relationship between lipid composition and function of monocyte is scant. We aimed at studying the migration of circulating monocytes isolated from patients with acute myocardial infarction (AMI) at hospital presentation and investigating its correlation with cellular lipid profile. The migration of monocytes was tested using both fetal bovine serum (FBS) and autologous serum as chemoattractant stimuli. Monocyte lipid profile was evaluated through an untargeted lipidomics approach, using a liquid chromatography/time-of-flight mass spectrometry platform. We observed that AMI patients' monocytes showed a significant increase in FBS and autologous serum-mediated migration compared to controls. Moreover, a different monocyte lipidomic profile between the two study groups was detected. In particular, AMI patients' monocytes showed an altered composition in ceramides, with an increase in lactosylceramide and in phospholipids (ie, phosphatidylethanolamine and lisophosphatidylethanolamine). Of note, a positive correlation between lactosylceramide levels and monocyte migration was observed. Furthermore, the lactosylceramide synthase inhibition significantly reduced FBS-induced monocyte migration. Our results highlight the influence of lactosylceramide on the monocyte migration capacity, pointing out a new possible mechanism of lipids in the onset of atherothrombosis and, hence, in AMI.

Molecular Mechanisms of Lipid Metabolism Disorders in Infectious Exacerbations of Chronic Obstructive Pulmonary Disease

Exacerbations largely determine the character of the progression and prognosis of chronic obstructive pulmonary disease (COPD). Exacerbations are connected with changes in the microbiological landscape in the bronchi due to a violation of their immune homeostasis. Many metabolic and immune processes involved in COPD progression are associated with bacterial colonization of the bronchi. The objective of this review is the analysis of the molecular mechanisms of lipid metabolism and immune response disorders in the lungs in COPD exacerbations. The complex role of lipid metabolism disorders in the pathogenesis of some infections is only beginning to be understood, however, there are already fewer and fewer doubts even now about its significance both in the pathogenesis of infectious exacerbations of COPD and in general in the progression of the disease. It is shown that the lipid rafts of the plasma membranes of cells are involved in many processes related to the detection of pathogens, signal transduction, the penetration of pathogens into the cell. Smoking disrupts the normally proceeded processes of lipid metabolism in the lungs, which is a part of the COPD pathogenesis.

Lipid droplet: A functionally active organelle in monocyte to macrophage differentiation and its inflammatory properties

Lipid droplets (LDs) perform several important functions like inflammatory responses, membrane trafficking, acts as secondary messengers, etc. rather than simply working as an energy reservoir. LDs have been implicated as a controlling factor in the progression of atherosclerosis followed by foam cell formation that derives from macrophages during the differentiation process. However, the role of LDs in monocyte differentiation or its further immunological function is still an area that mandates in-depth investigation. We report that LD dynamics is important for differentiation of monocytes and is absolutely required for sustained and prolonged functional activity of differentiated macrophages. In THP-1 cell line model system, we elucidated that increase in total LD content in monocyte by external lipid supplements, can induce monocyte differentiation independent of classical stimuli, PMA. Differential expression of PLIN2 and ATGL during the event, together with abrogation of de novo lipogenesis further confirmed the fact. Besides, an increase in LD content by free fatty acid supplement was able to exert a synergistic effect with PMA on differentiation and phagocytic activity compared to when they are used alone. Additionally, we have shown Rab5a to play a vital role in LDs biosynthesis/maturation in monocytes and thereby directly affecting differentiation of monocytes into macrophages via AKT pathway. Thus our study reveals the multi-faceted function of LDs during the process of monocyte to macrophage differentiation and thereby helping to maintain the functional activity.

Plasminogen-induced foam cell formation by macrophages occurs through a histone 2B (H2B)-PAR1 pathway and requires integrity of clathrin-coated pits

OBJECTIVE

Plasminogen/plasmin is a serine protease system primarily responsible for degrading fibrin within blood clots. Plasminogen mediates its functions by interacting with plasminogen receptors on the cell surface. H2B, one such plasminogen receptor, is found on the surface of several cell types including macrophages. Both basic and clinical studies support the role of plasminogen in the process of foam cell formation (FCF), a hallmark of atherosclerosis. Growing evidence also implicates serine protease-activated receptors (PARs) in atherosclerosis. These receptors are also found on macrophages, and plasmin is capable of activating PAR1 and PAR4. The goal of this study was to determine the extent of H2B's contribution to plasminogen-mediated FCF by macrophages and if PARs are involved in this process.

APPROACH AND RESULTS

Treating macrophages with plasminogen increases their oxidized low-density lipoprotein uptake and plasminogen-mediated foam cell formation (Plg-FCF) significantly. The magnitude of Plg-FCF correlates with cell-surface expression of the H2B level. H2B blockade or downregulation reduces Plg-FCF, whereas its overexpression or high endogenous levels increases Plg-FCF. Modulating PAR1 level in mouse macrophages affects Plg-FCF. Activation/overexpression of PAR1 increases and its blockade/knockdown reduces this response. Confocal imaging indicates that both H2B and PAR1 colocalize with clathrin coated pits on the surface of macrophages, and reducing expression of clathrin or interfering with the clathrin-coated pits integrity reduces Plg-FCF.

CONCLUSION

Our data indicate that the magnitude of Plg-FCF by macrophages is proportional to the H2B levels and demonstrate for the first time that PAR1 is involved in this process and that the integrity of clathrin-coated pits is required for the full effect of Plg-induced FCF.

Simulation of hemo- and biochemical toxicities associated with chronic inhalation exposure to 2,2-Dichlorovinyl dimethyl phosphate (DDVP) in Wistar rat

DDVP is a commonly used pesticide in Nigeria and those involved with DDVP manufacturing, packaging or utilizing facilities seldom use PPE to limit pesticide exposure. The study aim was to determine the impact of chronic exposure to DDVP by monitoring hematological and biochemical changes in Wistar rats. Male rats (n = 60; 150-180 g) were exposed to graded DDVP concentrations (0%, 20 %, 40 %, 60 %, 80 % and 100 %) via inhalation route for 60 days. Body weights were initially measured and then at 20-day intervals. Blood samples were collected for hematology and serum biochemistry on day 61. Results showed significant (p < 0.05) polycythemia, neutrophilia, thrombocytosis, hepatic and renal derangement in rats exposed to DDVP. Also, albumin, AST, ALP, creatinine, blood urea nitrogen, bilirubin levels and dyslipidemia significantly increased. Cholinergic signs and stunted growth were observed in higher concentrations. Study emphasized hazards of DDVP mishandling and risks of non-compliance with PPE use by workers in-contact with DDVP, as well as misuse/abuse in animals.

Amorphous silica nanoparticles accelerated atherosclerotic lesion progression in ApoE-/- mice through endoplasmic reticulum stress-mediated CD36 up-regulation in macrophage

Background

The biosafety concern of silica nanoparticles (SiNPs) is rapidly expanding alongside with its mass production and extensive applications. The cardiovascular effects of SiNPs exposure have been gradually confirmed, however, the interaction between SiNPs exposure and atherosclerosis, and the underlying mechanisms still remain unknown. Thereby, this study aimed to explore the effects of SiNPs on the progression of atherosclerosis, and to investigate related mechanisms.

Results

We firstly investigated the in vivo effects of SiNPs exposure on atherosclerosis via intratracheal instillation of ApoE^−/− mice fed a Western diet. Ultrasound microscopy showed a significant increase of pulse wave velocity (PWV) compared to the control group, and the histopathological investigation reflected a greater plaque burden in the aortic root of SiNPs-exposed ApoE^−/− mice. Compared to the control group, the serum levels of total triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) were elevated after SiNPs exposure. Moreover, intensified macrophage infiltration and endoplasmic reticulum (ER) stress was occurred in plaques after SiNPs exposure, as evidenced by the upregulated CD68 and CHOP expressions. Further in vitro, SiNPs was confirmed to activate ER stress and induce lipid accumulation in mouse macrophage, RAW264.7. Mechanistic analyses showed that 4-PBA (a classic ER stress inhibitor) pretreatment greatly alleviated SiNPs-induced macrophage lipid accumulation, and reversed the elevated CD36 expression induced by SiNPs.

Conclusions

Our results firstly revealed the acceleratory effect of SiNPs on the progression of atherosclerosis in ApoE^−/− mice, which was related to lipid accumulation caused by ER stress-mediated upregulation of CD36 expression in macrophage.

Graphical abstract

Peripheral leukocyte counts vary with lipid levels, age and sex in subjects from the healthy population

BACKGROUND AND AIMS

Disorders in blood lipid metabolism and leukocyte-mediated inflammation are considered the main mechanisms of the pathogenesis of atherosclerosis. This study aims to show whether and how peripheral leukocyte counts are associated with serum lipid levels.

METHODS

This is a cross-sectional study of 175,079 subjects from the healthy population.

RESULTS

Age and sex are two key factors dictating the relationship between peripheral leukocyte counts and serum lipid levels. The log-transformed level of triglycerides (LnTG) was positively associated with all leukocyte counts in males except monocyte count in younger subjects. LnTG was positively associated with total leukocyte count in females regardless of age, and it was positively associated with lymphocyte and monocyte counts and neutrophil count only in elderly and young women, respectively. Total cholesterol levels were positively associated with total leukocyte, neutrophil and lymphocyte counts only in young males and with lymphocyte counts only in elderly women. LDL-C was negatively associated with monocyte count in males regardless of age; by contrast, it was positively associated with total leukocyte and lymphocyte counts in females regardless of age range and neutrophil and LnEosinophil counts only in young women. HDL-C was negatively associated with total leukocyte, lymphocyte and monocyte counts in both young men and young women; was negatively associated with monocyte count in elderly men and women; and was negatively associated with LnEosinophil count only in older men.

CONCLUSIONS

Peripheral leukocyte counts are extensively associated with serum lipid levels, with patterns differing by sex, age, lipid and leukocyte subset.

Regulation of Macrophage Foam Cell Formation During Nitrogen Mustard (NM)-Induced Pulmonary Fibrosis by Lung Lipids

Nitrogen mustard (NM) is a vesicant known to target the lung, causing acute injury which progresses to fibrosis. Evidence suggests that activated macrophages contribute to the pathologic response to NM. In these studies, we analyzed the role of lung lipids generated following NM exposure on macrophage activation and phenotype. Treatment of rats with NM (0.125 mg/kg, i.t.) resulted in a time-related increase in enlarged vacuolated macrophages in the lung. At 28 days postexposure, macrophages stained positively for Oil Red O, a marker of neutral lipids. This was correlated with an accumulation of oxidized phospholipids in lung macrophages and epithelial cells and increases in bronchoalveolar lavage fluid (BAL) phospholipids and cholesterol. RNA-sequencing and immunohistochemical analysis revealed that lipid handling pathways under the control of the transcription factors liver-X receptor (LXR), farnesoid-X receptor (FXR), peroxisome proliferator-activated receptor (PPAR)-ɣ, and sterol regulatory element-binding protein (SREBP) were significantly altered following NM exposure. Whereas at 1-3 days post NM, FXR and the downstream oxidized low-density lipoprotein receptor, Cd36, were increased, Lxr and the lipid efflux transporters, Abca1 and Abcg1, were reduced. Treatment of naïve lung macrophages with phospholipid and cholesterol enriched large aggregate fractions of BAL prepared 3 days after NM exposure resulted in upregulation of Nos2 and Ptgs2, markers of proinflammatory activation, whereas large aggregate fractions prepared 28 days post NM upregulated expression of the anti-inflammatory markers, Il10, Cd163, and Cx3cr1, and induced the formation of lipid-laden foamy macrophages. These data suggest that NM-induced alterations in lipid handling and metabolism drive macrophage foam cell formation, potentially contributing to the development of pulmonary fibrosis.

Progression of Multifaceted Immune Cells in Atherosclerotic Development

Atherosclerosis is a major cause of morbidity and mortality due to cardiovascular diseases, such as coronary artery disease, stroke, and peripheral vascular disease, that are associated with thrombosis-induced organ infarction. In Westernized countries, the high prevalence of obesity-induced insulin resistance is predicted to be a major factor leading to atherosclerotic vascular disease. Both genetic and environmental factors interfere with immune responses in atherosclerosis development with chronic and non-resolving states. The most known autoimmune disease therapy is cytokine-targeted therapy, which targets tumor necrosis factor-α and interleukin (IL)-17 antagonists. Recently, a clinical trial with the anti-IL-1β antibody (canakinumab) had shown that the anti-inflammatory effects in canakinumab-treated subjects play a critical role in reducing cardiovascular disease prevalence. Recent emerging data have suggested effective therapeutics involving anti-obesity and anti-diabetic agents, as well as statin and anti-platelet drugs, for atherothrombosis prevention. It is well-known that specialized immune differentiation and activation completely depends on metabolic reprogramming mediated by mitochondrial dynamics in distinct immune cells. Therefore, there is a strong mechanistic link between metabolism and immune function mediated by mitochondrial function. In this review, we describe that cellular metabolism in immune cells is strongly interconnected with systemic metabolism in terms of diverse phenotypes and activation.

Genome-wide association study of blood lipids in Indians confirms universality of established variants

Lipids foster energy production and their altered levels have been coupled with metabolic ailments. Indians feature high prevalence of metabolic diseases, yet uncharacterized for genes regulating lipid homeostasis. We performed first GWAS for quantitative lipids (total cholesterol, LDL, HDL, and triglycerides) exclusively in 5271 Indians. Further to corroborate our genetic findings, we investigated DNA methylation marks in peripheral blood in Indians at the identified loci (N = 233) and retrieved gene regulatory features from public domains. Recurrent GWAS loci-CELSR2, CETP, LPL, ZNF259, and BUD13 cropped up as lead signals in Indians, reflecting their universal applicability. Besides established variants, we found certain unreported variants at sub-genome-wide level-QKI, REEP3, TMCC2, FAM129C, FAM241B, and LOC100506207. These variants though failed to attain GWAS significance in Indians, but largely turned out to be active CpG sites in human subcutaneous adipose tissue and showed robust association to two or more lipid traits. Of which, QKI variants showed significant association to all four lipid traits and their designated region was observed to be a key gene regulatory segment denoting active transcription particularly in human subcutaneous adipose tissue. Both established and novel loci were observed to be significantly associated with altered DNA methylation in Indians for specific CpGs that resided in key regulatory elements. Further, gene-based association analysis pinpointed novel GWAS loci-LINC01340 and IQCJ-SCHIP1 for TC; IFT27, IFT88, and LINC02141 for HDL; and TEX26 for TG. Present study ascertains universality of selected known genes and also identifies certain novel loci for lipids in Indians by integrating data from various levels of gene regulation.

Gender Dictates the Relationship between Serum Lipids and Leukocyte Counts in the National Health and Nutrition Examination Survey 1999⁻2004

Dyslipidemias and leukocytosis are associated with cardiovascular disease and immune disorders. Mechanistic studies have shown lipoprotein metabolism to play a significant role in the regulation of atherosclerosis development and leukocyte activation, whereas lipid-lowering treatments have been shown to exert beneficial anti-inflammatory and immunomodulatory effects in clinical trials. However, the relationship between clinical markers of lipid metabolism and leukocyte counts has not been extensively evaluated at the population level. We aimed to determine whether clinical blood lipid measures are associated with leukocyte counts in the general U.S. population represented in the National Health and Nutrition Examination Survey (NHANES) 1999–2004, and whether differences exist between men and women (n = 5647). We observed a strong positive linear trend between serum triglycerides vs. blood lymphocyte and basophil counts in both men and women, whereas a positive trend between monocytes vs. triglycerides and lymphocytes vs. total cholesterol and LDL-cholesterol (LDL-C) was only detected in women. Conversely, HDL-C was inversely associated with a greater number of leukocyte subsets in men, whereas inverse trends between HDL-C vs. lymphocytes were observed in both men and women. In multiple regression models, a 10% increase in total cholesterol, LDL-C, and triglycerides was associated with a predicted 1.6%, 0.6%, and 1.4% increase in blood lymphocyte counts in women, respectively, whereas no relationship was observed in men. In both men and women, a 10% increase in triglycerides was additionally associated with higher lymphocyte, neutrophil, and basophil counts, whereas 10% increases in HDL-cholesterol were associated with significantly lower lymphocyte, neutrophil, eosinophil, and basophil counts in men, in addition to lower lymphocyte and monocyte counts in women. These findings suggest that clinical lipid markers may be used to predict blood leukocyte distributions, and that a gender-specific relationship exists between distinct classes of serum lipids and immune cell subsets.

ALDH2 deficiency inhibits Ox-LDL induced foam cell formation via suppressing CD36 expression

Foam cell formation plays an important role in the initiation and progression of atherosclerosis. Aldehyde dehydrogenase 2 (ALDH2), a key enzyme for aldehyde metabolism, is associated with coronary artery disease and affects atherosclerotic plaque vulnerability. However, the role of ALDH2 in foam cell formation remains unclear. Using peritoneal macrophages from ALDH2-deficient and control mice, we found that ALDH2 deficiency suppressed foam cell formation induced by oxidized low-density lipoproteins (ox-LDL) but not acetylated low-density lipoproteins (ac-LDL) ex vivo. After incubation with ox-LDL, ALDH2-deficient macrophages expressed lower levels of CD36 but the expression of other lipid metabolism-related proteins including SRA, LOX-1, ABCA-1, ABCG-1 and ACAT-1 was not changed in ALDH2^-/- macrophages. Using CD36 inhibitor, we confirmed that CD36 contributes to the effect of ALDH2 on foam cell formation. PPARγ was downregulated in ox-LDL treated ALDH2^-/- macrophages. 4-HNE was increased by ALDH2 deficiency and high concentration of 4-HNE suppressed the expression of PPARγ. These data suggest that ALDH2 plays an important role in foam cell formation via 4-HNE/PPARγ/CD36 pathway.

Metabolomic fingerprint of coronary blood in STEMI patients depends on the ischemic time and inflammatory state

In this study we investigated whether the metabolomic analysis could identify a specific fingerprint of coronary blood collected during primary PCI in STEMI patients. Fifteen samples was subjected to metabolomic analysis. Subsequently, the study population was divided into two groups according to the peripheral blood neutrophil-to-lymphocyte ratio (NLR), a marker of the systemic inflammatory response. Regression analysis was then applied separately to the two NLR groups. A partial least square (PLS) regression identified the most significant involved metabolites and the PLS-class analysis revealed a significant correlation between the metabolic profile and the total ischemic time only in patients with an NLR > 5.77.

Foam cell formation: A new target for fighting atherosclerosis and cardiovascular disease

During atherosclerosis, the gradual accumulation of lipids into the subendothelial space of damaged arteries results in several lipid modification processes followed by macrophage uptake in the arterial wall. The way in which these modified lipoproteins are dealt with determines the likelihood of cholesterol accumulation within the monocyte-derived macrophage and thus its transformation into the foam cell that makes up the characteristic fatty streak observed in the early stages of atherosclerosis. The unique expression of chemokine receptors and cellular adhesion molecules expressed on the cell surface of monocytes points to a particular extravasation route that they can take to gain entry into atherosclerotic site, in order to undergo differentiation into the phagocytic macrophage. Indeed several GWAS and animal studies have identified key genes and proteins required for monocyte recruitment as well cholesterol handling involving lipid uptake, cholesterol esterification and cholesterol efflux. A re-examination of the previously accepted paradigm of macrophage foam cell origin has been called into question by recent studies demonstrating shared expression of scavenger receptors, cholesterol transporters and pro-inflammatory cytokine release by alternative cell types present in the neointima, namely; endothelial cells, vascular smooth muscle cells and stem/progenitor cells. Thus, therapeutic targets aimed at a more heterogeneous foam cell population with shared functions, such as enhanced protease activity, and signalling pathways, mediated by non-coding RNA molecules, may provide greater therapeutic outcome in patients. Finally, studies targeting each aspect of foam cell formation and death using both genetic knock down and pharmacological inhibition have provided researchers with a clearer understanding of the cellular processes at play, as well as helped researchers to identify key molecular targets, which may hold significant therapeutic potential in the future.

Common Pathogenesis of Acne Vulgaris and Atherosclerosis

Foam cells are lipid-loaded macrophages and neutrophils that are generated from a massive uptake of oxidized lipid. Foam cells are a pathological hallmark of atherosclerosis, and have also been found in acne lesions. The same pathological changes determine the common pathogenesis. According to the pathological function of foam cells in these lesions, we put forward a viewpoint on the pathogenesis of acne and atherosclerotic plaques.

Label-free leukocyte sorting and impedance-based profiling for diabetes testing

Circulating leukocytes comprise of approximately 1% of all blood cells and efficient enrichment of these cells from whole blood is critical for understanding cellular heterogeneity and biological significance in health and diseases. In this work, we report a novel microfluidic strategy for rapid (< 1 h) label-free leukocyte sorting and impedance-based profiling to determine cell activation in type 2 diabetes mellitus (T2DM) using whole blood. Leukocytes were first size-fractionated into different subtypes (neutrophils, monocytes, lymphocytes) using an inertial spiral sorter prior to single-cell impedance measurement in a microfluidic device with coplanar electrode design. Significant changes in membrane dielectric properties (size and opacity) were detected between healthy and activated leukocytes (TNF-α/LPS stimulated), during monocyte differentiation and among different monocyte subsets (classical, intermediate, non-classical). As proof-of-concept for diabetes testing, neutrophil/monocyte dielectric properties in T2DM subjects (n = 8) were quantified which were associated with cardiovascular risk factors including lipid levels, C-reactive protein (CRP) and vascular functions (LnRHI) (P < 0.05) were observed. Overall, these results clearly showed that T2DM subjects have pro-inflammatory leukocyte phenotypes and suggest leukocyte impedance signature as a novel surrogate biomarker for inflammation.

Vitamin D3 supplementation decreases a unique circulating monocyte cholesterol pool in patients with type 2 diabetes

Cross-sectional studies indicate consistent associations between low 25(OH)D concentration and increased risk of cardiovascular disease (CVD), but results of randomized control trials (RCTs) are mixed. However, the majority of the RCTs do not focus on type 2 diabetics, potentially obscuring the effects of vitamin D in this population. In vitro 1,25(OH)₂D₃ downregulates macrophage cholesterol deposition, but the in vivo effects are unknown. To explore potential mechanisms of the effects of vitamin D on CVD risk in patients with type 2 diabetes, we isolated monocytes in a subset of 26 patients from our RCT of diabetics with baseline serum 25(OH)D <25ng/mL randomized to vitamin D₃ 4000 IU/day or placebo for 4 months. Upon enrollment, the mean 25(OH)D level was 17ng/mL, which increased to 36ng/mL after vitamin D and remained unchanged in the placebo group. Before randomization, groups demonstrated similar mean hemoglobin A1c and plasma lipids levels, none of which was significantly altered by vitamin D supplementation. Moreover, assessment of oxidized LDL uptake in monocytes cultured in the patient's own serum before vs. after treatment resulted in >50% reduction in the vitamin D group with no change in the placebo group. This was mediated through suppression of endoplasmic reticulum stress and scavenger receptor CD36 protein expression. The reduction in monocyte cholesterol uptake was reflected in a 19% decrease in total monocyte cholesterol content. Interestingly, cross-sectional analysis of circulating monocytes from vitamin D-deficient vs. sufficient diabetic patients revealed 8-fold higher cholesteryl ester content, confirming the capacity of these monocytes to uptake and carry cholesterol in the circulation. This study identifies a unique circulating cholesterol pool within monocytes that is modulated by vitamin D and has the potential to contribute to CVD in type 2 diabetes.

Quantification of sterol-specific response in human macrophages using automated imaged-based analysis

BACKGROUND

The transformation of normal macrophage cells into lipid-laden foam cells is an important step in the progression of atherosclerosis. One major contributor to foam cell formation in vivo is the intracellular accumulation of cholesterol.

METHODS

Here, we report the effects of various combinations of low-density lipoprotein, sterols, lipids and other factors on human macrophages, using an automated image analysis program to quantitatively compare single cell properties, such as cell size and lipid content, in different conditions.

RESULTS

We observed that the addition of cholesterol caused an increase in average cell lipid content across a range of conditions. All of the sterol-lipid mixtures examined were capable of inducing increases in average cell lipid content, with variations in the distribution of the response, in cytotoxicity and in how the sterol-lipid combination interacted with other activating factors. For example, cholesterol and lipopolysaccharide acted synergistically to increase cell lipid content while also increasing cell survival compared with the addition of lipopolysaccharide alone. Additionally, ergosterol and cholesteryl hemisuccinate caused similar increases in lipid content but also exhibited considerably greater cytotoxicity than cholesterol.

CONCLUSIONS

The use of automated image analysis enables us to assess not only changes in average cell size and content, but also to rapidly and automatically compare population distributions based on simple fluorescence images. Our observations add to increasing understanding of the complex and multifactorial nature of foam-cell formation and provide a novel approach to assessing the heterogeneity of macrophage response to a variety of factors.

Sortilin: A novel regulator in lipid metabolism and atherogenesis

Several lines of evidence have shown that SORT1 gene within 1p13.3 locus is an important modulator of the low-density lipoprotein-cholesterol (LDL-C) level and atherosclerosis risk. Here, we summarize the effects of SORT1, which codes for sortilin, on lipid metabolism and development of atherosclerosis and explore the mechanisms underlying sortilin effects on lipid metabolism especially in hepatocytes and macrophages. Recent epidemiological evidence demonstrated that sortilin has been implicated as the causative factor and regulates lipid metabolism in vivo. Hepatic sortilin overexpression leads to both increased and decreased LDL-C levels by several different mechanisms, suggesting the complex roles of sortilin in hepatic lipid metabolism. Macrophage sortilin causes internalization of LDL and probably a reduction in cholesterol efflux, resulting in the intracellular accumulation of excessive lipids. In addition, sortilin deficiency in an atherosclerotic mouse model results in decreased aortic atherosclerotic lesion. Sortilin involves in lipid metabolism, promotes the development of atherosclerosis, and possibly becomes a potential therapeutic target for atherosclerosis treatment.