Acyl-CoA synthetase 1 is required for oleate and linoleate mediated inhibition of cholesterol efflux through ATP-binding cassette transporter A1 in macrophages

The Octadecanoids: Synthesis and Bioactivity of 18-Carbon Oxygenated Fatty Acids in Mammals, Bacteria, and Fungi

The octadecanoids are a broad class of lipids consisting of the oxygenated products of 18-carbon fatty acids. Originally referring to production of the phytohormone jasmonic acid, the octadecanoid pathway has been expanded to include products of all 18-carbon fatty acids. Octadecanoids are formed biosynthetically in mammals via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) activity, as well as nonenzymatically by photo- and autoxidation mechanisms. While octadecanoids are well-known mediators in plants, their role in the regulation of mammalian biological processes has been generally neglected. However, there have been significant advancements in recognizing the importance of these compounds in mammals and their involvement in the mediation of inflammation, nociception, and cell proliferation, as well as in immuno- and tissue modulation, coagulation processes, hormone regulation, and skin barrier formation. More recently, the gut microbiome has been shown to be a significant source of octadecanoid biosynthesis, providing additional biosynthetic routes including hydratase activity (e.g., CLA-HY, FA-HY1, FA-HY2). In this review, we summarize the current field of octadecanoids, propose standardized nomenclature, provide details of octadecanoid preparation and measurement, summarize the phase-I metabolic pathway of octadecanoid formation in mammals, bacteria, and fungi, and describe their biological activity in relation to mammalian pathophysiology as well as their potential use as biomarkers of health and disease.

Type I IFN induces long-chain acyl-CoA synthetase 1 to generate a phosphatidic acid reservoir for lipotoxic saturated fatty acids

Long-chain acyl-CoA synthetase 1 (ACSL1) catalyzes the conversion of long-chain fatty acids to acyl-CoAs. ACSL1 is required for β-oxidation in tissues that rely on fatty acids as fuel, but no consensus exists on why ACSL1 is induced by inflammatory mediators in immune cells. We used a comprehensive and unbiased approach to investigate the role of ACSL1 induction by interferon type I (IFN-I) in myeloid cells in vitro and in a mouse model of IFN-I overproduction. Our results show that IFN-I induces ACSL1 in macrophages via its interferon-α/β receptor, and consequently that expression of ACSL1 is increased in myeloid cells from individuals with systemic lupus erythematosus (SLE), an autoimmune condition characterized by increased IFN production. Taking advantage of a myeloid cell-targeted ACSL1-deficient mouse model and a series of lipidomics, proteomics, metabolomics and functional analyses, we show that IFN-I leverages induction of ACSL1 to increase accumulation of fully saturated phosphatidic acid species in macrophages. Conversely, ACSL1 induction is not needed for IFN-I's ability to induce the prototypical IFN-stimulated protein signature or to suppress proliferation or macrophage metabolism. Loss of ACSL1 in IFN-I stimulated myeloid cells enhances apoptosis and secondary necrosis in vitro, especially in the presence of increased saturated fatty acid load, and in a mouse model of atherosclerosis associated with IFN overproduction, resulting in larger lesion necrotic cores. We propose that ACSL1 induction is a mechanism used by IFN-I to increase phosphatidic acid saturation while protecting the cells from saturated fatty acid-induced cell death.

Up-regulation of long non-coding RNA H19 ameliorates renal tubulointerstitial fibrosis by reducing lipid deposition and inflammatory response through regulation of the microRNA-130a-3p/long-chain acyl-CoA synthetase 1 axis

Long non-coding RNA (lncRNA) H19 is an extensively studied lncRNA that is related to numerous pathological changes. Our previous findings have documented that serum lncRNA H19 levels are decreased in patients with chronic kidney disorder and lncRNA H19 reduction is closely correlated with renal tubulointerstitial fibrosis, an essential step in developing end-stage kidney disease. Nonetheless, the precise function and mechanism of lncRNA H19 in renal tubulointerstitial fibrosis are not fully comprehended. The present work utilized a mouse model of unilateral ureteral obstruction (UUO) and transforming growth factor-β1 (TGF-β1)-stimulated HK-2 cells to investigate the possible role and mechanism of lncRNA H19 in renal tubulointerstitial fibrosis were investigated. Levels of lncRNA H19 decreased in kidneys of mice with UUO and HK-2 cells stimulated with TGF-β1. Up-regulation of lncRNA H19 in mouse kidneys remarkably relieved kidney injury, fibrosis and inflammation triggered by UUO. Moreover, the increase of lncRNA H19 in HK-2 cells reduced epithelial-to-mesenchymal transition (EMT) induced by TGF-β1. Notably, up-regulation of lncRNA H19 reduced lipid accumulation and triacylglycerol content in kidneys of mice with UUO and TGF-β1-stimulated HK-2 cells, accompanied by the up-regulation of long-chain acyl-CoA synthetase 1 (ACSL1). lncRNA H19 was identified as a sponge of microRNA-130a-3p, through which lncRNA H19 modulates the expression of ACSL1. The overexpression of microRNA-130a-3p reversed the lncRNA H19-induced increases in the expression of ACSL1. The suppressive effects of lncRNA H19 overexpression on the EMT, inflammation and lipid accumulation in HK-2 cells were diminished by ACSL1 silencing or microRNA-130a-3p overexpression. Overall, the findings showed that lncRNA H19 ameliorated renal tubulointerstitial fibrosis by reducing lipid deposition via modulation of the microRNA-130a-3p/ACSL1 axis.

Targeting ACSLs to modulate ferroptosis and cancer immunity

Five acyl-CoA synthetase long-chain family members (ACSLs) are responsible for catalyzing diverse long-chain fatty acids (LCFAs) into LCFA-acyl-coenzyme A (CoA) for their subsequent metabolism, including fatty acid oxidation (FAO), lipid synthesis, and protein acylation. In this review, we focus on ACSLs and their LCFA substrates and introduce their involvement in regulation of cancer proliferation, metastasis, and therapeutic resistance. Along with the recognition of the decisive role of ACSL4 in ferroptosis - an immunogenic cell death (ICD) initiated by lipid peroxidation - we review the functions of ACSLs on regulating ferroptosis sensitivity. Last, we discuss the current understanding of ACSL on the antitumor immune response. We emphasize the necessity to explore the functions of immune cells expressing ACSLs for developing novel strategies to augment immunotherapy by targeting ACSL.

Acyl-CoA Synthetase Long-Chain Isoenzymes in Kidney Diseases: Mechanistic Insights and Therapeutic Implications

Long-chain acyl-CoA synthetases (ACSLs) are pivotal enzymes in fatty acid metabolism, essential for maintaining cellular homeostasis and energy production. Recent research has uncovered their significant involvement in the pathophysiology of various kidney diseases, including acute kidney injury (AKI), chronic kidney disease (CKD), diabetic kidney disease (DKD), and renal cell carcinoma (RCC). While ACSL1, ACSL3, ACSL4, and ACSL5 have been extensively studied for their roles in processes such as ferroptosis, lipid peroxidation, renal fibrosis, epithelial-mesenchymal transition, and tumor progression, the role of ACSL6 in kidney diseases remain largely unexplored. Notably, these isoenzymes exhibit distinct functions in different kidney diseases. Therefore, to provide a comprehensive understanding of their involvement, this review highlights the molecular pathways influenced by ACSLs and their roles in modulating cell death, inflammation, and fibrosis during kidney disease progression. By examining these mechanisms in detail, this review underscores the potential of ACSLs as biomarkers and therapeutic targets, advocating for further research to elucidate the precise roles of individual ACSL isoenzymes in kidney disease progression. Understanding these mechanisms opens new avenues for developing targeted interventions and improving therapeutic outcomes for patients with kidney diseases.

Lipid droplets provide metabolic flexibility for cancer progression

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation of LDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Platelet-Derived Microvesicles Mediate Cardiomyocyte Ferroptosis by Transferring ACSL1 During Acute Myocardial Infarction

Acute myocardial infarction (AMI) is one of the critical health conditions often caused by the rupture of unstable coronary artery plaque, triggering a series of events, such as platelet activation, thrombus formation, coronary artery blockage, lasted severe ischemia, and hypoxia in cardiomyocytes, and culminating in cell death. Platelet-derived microvesicles (PMVs) act as intermediates for cellular communication. Nevertheless, the role of PMVs in myocardial infarction remains unclear. Initially, AMI-related messenger ribose nucleic acid (mRNA) and micro RNA (miRNA) datasets from the Gene Expression Omnibus (GEO) database were analyzed, specifically focusing on the expressed genes associated with Ferroptosis. Further, a miRNA-mRNA regulatory network specific to AMI was constructed. Then, the effect of PMVs on cardiomyocyte survival was further confirmed through in vitro experiments. High ACSL1 expression was observed in the platelets of AMI patients. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that ACSL1, located in the mitochondria, played a key role in the PPAR signaling pathway. The elevated ACSL1 expression in a co-culture model of PMVs and AC16 cardiomyocytes significantly increased the AC16 cell Ferroptosis. Further, we validated that the platelet ACSL1 expression could be regulated by hsa-miR-449a. Together, these findings suggested that platelet ACSL1 could trigger myocardial cell death via PMV transport. In addition, this research provided a theoretical framework for attenuating myocardial cell Ferroptosis in patients with acute myocardial infarction.

Pien Tze Huang regulates phosphorylation of metabolic enzymes in mice of hepatocellular carcinoma

The Chinese medicine formula Pien Tze Huang (PZH) has been applied to the treatment of various diseases, the reported anti-tumor mechanisms included regulation of inflammation-associated cytokine secretion and cancer growth pathways. However, the potential influence of PZH on tumor metabolism remains unclear. This study aimed to investigate the global effect of PZH on hepatocellular carcinoma (HCC) compared with the anti-tumor agent sorafenib based on tandem mass tag (TMT) label proteomic and phosphoproteomic analysis in addition to parallel reaction monitoring (PRM) verification. It was observed that PZH could inhibit tumor weight by 59-69% in different concentrations. TMT proteomic studies indicated that fructose/mannose metabolism and glucagon signaling pathway in PZH group, and arachidonic acid metabolism and PPAR signaling pathway in sorafenib group, were significantly enriched, while glycolysis/gluconeogenesis pathway was found to be enriched remarkably both in PZH and sorafenib groups in TMT phosphoproteomic study. PRM verification further indicated that both PZH and sorafenib could down-regulate phosphorylations of the glycolytic enzymes phosphofructokinases 1, fructose-bisphosphate Aldolase A, phosphoglycerate mutase 2 and lactate dehydrogenase A chain, while phosphorylations of long chain fatty acid CoA ligase in fatty acid activation and acetyl-coenzyme A synthetase in glycolysis were significantly inhibited by PZH and sorafenib, respectively. This study proposed that PZH shared a similar anti-tumor mechanism of metabolic regulation to sorafenib, but differed in the regulation of some metabolic nodes. This is the first time to uncover the relationship between the anti-tumor effect of PZH and metabolic related enzymes, which distinguished from the known mechanisms of PZH. These data provided the potential molecular basis for PZH acting as a therapeutic drug for HCC, and offered cues of manipulation on Warburg effect under the treatment of PZH.

An update on the therapeutic implications of long-chain acyl-coenzyme A synthetases in nervous system diseases

Long-chain acyl-coenzyme A synthetases (ACSLs) are a family of CoA synthetases that activate fatty acid (FA) with chain lengths of 12-20 carbon atoms by forming the acyl-AMP derivative in an isozyme-specific manner. This family mainly includes five members (ACSL1, ACSL3, ACSL4, ACSL5, and ACSL6), which are thought to have specific and different functions in FA metabolism and oxidative stress of mammals. Accumulating evidence shows that the dysfunction of ACSLs is likely to affect cell proliferation and lead to metabolic diseases in multiple organs and systems through different signaling pathways and molecular mechanisms. Hence, a central theme of this review is to emphasize the therapeutic implications of ACSLs in nervous system disorders.

Genome-wide analysis of the acyl-coenzyme A synthetase family and their association with the formation of goat milk flavour

Goat milk is rich in fat and protein, thus, has high nutritional values and benefits human health. However, goaty flavour is a major concern that interferes with consumer acceptability of goat milk and the 4-alkyl-branched-chain fatty acids (vBCFAs) are the major substances relevant to the goaty flavour in goat milk. Previous research reported that the acyl-coenzyme A synthetases (ACSs) play a key role in the activation of fatty acids, which is a prerequisite for fatty acids entering anabolic and catabolic processes and highly involved in the regulation of vBCFAs metabolism. Although ACS genes have been identified in humans and mice, they have not been systematically characterized in goats. In this research, we performed genome-wide characterization of the ACS genes in goats, identifying that a total of 25 ACS genes (without ACSM2A) were obtained in the Capra hircus and each ACS protein contained the conserved AMP-binding domain. Phylogenetic analysis showed that out of the 25 genes, 21 belonged to the ACSS, ACSM, ACSL, ACSVL, and ACSBG subfamilies. However, AACS, AASDH, ACSF, and ACSF3 genes were not classified in the common evolutionary branch and belonged to the ACS superfamily. The genes in the same clade had similar conserved structures, motifs and protein domains. The expression analysis showed that the majority of ACS genes were expressed in multi tissues. The comparative analysis of expression patterns in non-lactation and lactation mammary glands of goat, sheep and cow indicated that ACSS2 and ACSF3 genes may participate in the formation mechanisms of goaty flavour in goat milk. In conclusion, current research provides important genomic resources and expression information for ACSs in goats, which will support further research on investigating the formation mechanisms of the goaty flavour in goat milk.

Macrophage polarization by potential nutraceutical compounds: A strategic approach to counteract inflammation in atherosclerosis

Chronic inflammation represents a main event in the onset and progression of atherosclerosis and is closely associated with oxidative stress in a sort of vicious circle that amplifies and sustains all stages of the disease. Key players of atherosclerosis are monocytes/macrophages. According to their pro- or anti-inflammatory phenotype and biological functions, lesional macrophages can release various mediators and enzymes, which in turn contribute to plaque progression and destabilization or, alternatively, lead to its resolution. Among the factors connected to atherosclerotic disease, lipid species carried by low density lipoproteins and pro-oxidant stimuli strongly promote inflammatory events in the vasculature, also by modulating the macrophage phenotyping. Therapies specifically aimed to balance macrophage inflammatory state are increasingly considered as powerful tools to counteract plaque formation and destabilization. In this connection, several molecules of natural origin have been recognized to be active mediators of diverse metabolic and signaling pathways regulating lipid homeostasis, redox state, and inflammation; they are, thus, considered as promising candidates to modulate macrophage responsiveness to pro-atherogenic stimuli. The current knowledge of the capability of nutraceuticals to target macrophage polarization and to counteract atherosclerotic lesion progression, based mainly on in vitro investigation, is summarized in the present review.

Adoptive transfer of metabolically reprogrammed macrophages for atherosclerosis treatment in diabetic ApoE−/- mice

Atherosclerosis is characterized by inflammation in the arterial wall, which is known to be exacerbated by diabetes. Therapeutic repression of inflammation is a promising strategy for treating atherosclerosis. In this study, we showed that diabetes aggravated atherosclerosis in apolipoproteinE knockout (ApoE^−/-) mice, in which increased expression of long-chain acyl-CoA synthetase 1 (Acsl1) in macrophages played an important role. Knockdown of Acsl1 in macrophages (Mφ^shAcsl1) reprogrammed macrophages to an anti-inflammatory phenotype, especially under hyperglycemic conditions. Injection of Mφ^shAcsl1 reprogrammed macrophages into streptozotocin (STZ)-induced diabetic ApoE^−/- mice (ApoE^−/-+ STZ) alleviated inflammation locally in the plaque, liver and spleen. Consistent with the reduction in inflammation, plaques became smaller and more stable after the adoptive transfer of reprogrammed macrophages. Taken together, our findings indicate that increased Acsl1 expression in macrophages play a key role in aggravated atherosclerosis of diabetic mice, possibly by promoting inflammation. Adoptive transfer of Acsl1 silenced macrophages may serve as a potential therapeutic strategy for atherosclerosis.

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Increased Acsl1 in macrophages is responsible for the exacerbated inflammation in diabetes

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Mφ^shAcsl1 is characterized as anti-inflammatory phenotype

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Adoptive transfer of Mφ^shAcsl1 alleviates atherosclerosis in diabetic ApoE^−/- mice

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Mφ^shAcsl1 inhibits both local and systemic inflammation in vivo

Macrophage-Mediated Immune Responses: From Fatty Acids to Oxylipins

Macrophages have diverse functions in the pathogenesis, resolution, and repair of inflammatory processes. Elegant studies have elucidated the metabolomic and transcriptomic profiles of activated macrophages. However, the versatility of macrophage responses in inflammation is likely due, at least in part, to their ability to rearrange their repertoire of bioactive lipids, including fatty acids and oxylipins. This review will describe the fatty acids and oxylipins generated by macrophages and their role in type 1 and type 2 immune responses. We will highlight lipidomic studies that have shaped the current understanding of the role of lipids in macrophage polarization.

Lipid nutrition: "In silico" studies and undeveloped experiments

This review examines lipids and lipid-binding sites on proteins in relation to cardiovascular disease. Lipid nutrition involves food energy from ingested fatty acids plus fatty acids formed from excess ingested carbohydrate and protein. Non-esterified fatty acids (NEFA) and lipoproteins have many detailed attributes not evident in their names. Recognizing attributes of lipid-protein interactions decreases unexpected outcomes. Details of double bond position and configuration interacting with protein binding sites have unexpected consequences in acyltransferase and cell replication events. Highly unsaturated fatty acids (HUFA) have n-3 and n-6 motifs with documented differences in intensity of destabilizing positive feedback loops amplifying pathophysiology. However, actions of NEFA have been neglected relative to cholesterol, which is co-produced from excess food. Native low-density lipoproteins (LDL) bind to a high-affinity cell surface receptor which poorly recognizes biologically modified LDLs. NEFA increase negative charge of LDL and decrease its processing by "normal" receptors while increasing processing by "scavenger" receptors. A positive feedback loop in the recruitment of monocytes and macrophages amplifies chronic inflammatory pathophysiology. Computer tools combine multiple components in lipid nutrition and predict balance of energy and n-3:n-6 HUFA. The tools help design and execute precise clinical nutrition monitoring that either supports or disproves expectations.

Macrophage Responses to Environmental Stimuli During Homeostasis and Disease

Work over the last 40 years has described macrophages as a heterogeneous population that serve as the frontline surveyors of tissue immunity. As a class, macrophages are found in almost every tissue in the body and as distinct populations within discrete microenvironments in any given tissue. During homeostasis, macrophages protect these tissues by clearing invading foreign bodies and/or mounting immune responses. In addition to varying identities regulated by transcriptional programs shaped by their respective environments, macrophage metabolism serves as an additional regulator to temper responses to extracellular stimuli. The area of research known as "immunometabolism" has been established within the last decade, owing to an increase in studies focusing on the crosstalk between altered metabolism and the regulation of cellular immune processes. From this research, macrophages have emerged as a prime focus of immunometabolic studies, although macrophage metabolism and their immune responses have been studied for centuries. During disease, the metabolic profile of the tissue and/or systemic regulators, such as endocrine factors, become increasingly dysregulated. Owing to these changes, macrophage responses can become skewed to promote further pathophysiologic changes. For instance, during diabetes, obesity, and atherosclerosis, macrophages favor a proinflammatory phenotype; whereas in the tumor microenvironment, macrophages elicit an anti-inflammatory response to enhance tumor growth. Herein we have described how macrophages respond to extracellular cues including inflammatory stimuli, nutrient availability, and endocrine factors that occur during and further promote disease progression.

Effects of overexpression of ACSL1 gene on the synthesis of unsaturated fatty acids in adipocytes of bovine

There exists a positive correlation between the unsaturated fatty acids (UFA) content in the bovine species and their taste and nutritional significance. Long-chain acyl-CoA synthetase 1 (ACSL1) is known to be involved in lipid synthesis as well as fatty acid transport and degradation. This gene has been identified as the key candidate gene for regulating lipid composition in the bovine skeletal muscle; however, its mechanism of action in regulating UFA synthesis in bovine adipocytes is unclear. In this study, we used a recombinant adenovirus vector (Ad-ACSL1) to overexpress the ACSL1 gene using Ad-NC (recombinant adenovirus of green fluorescent protein) as the control. Quantitative real-time PCR (qRT-PCR) was done to examine the gene expression associated with the synthesis of UFA, followed by the analysis of the fatty acid composition. Oil red O staining was done to examine the aggregation of lipid droplets. We found that ACSL1 overexpression was associated with an upregulated expression of PPARγ, FABP3, ACLY, SCD1, and FASN, and downregulated expression of CPT1A. Additionally, ACSL1 overexpression resulted in elevated saturated fatty acid content, especially C16:0 and C18:0, than the control group (Ad-NC cells) (p < 0.05). Furthermore, the overexpression of ACSL1 enhanced the proportion of eicosapentaenoic acid (EPA), decreased the proportion of C22:4, and significantly upregulated polyunsaturated fatty acid (PUFA) content. These results were supported by oil red O staining, which revealed an increase in the lipid droplets in bovine adipocytes after the overexpression of the ACSL1 gene. Thus, the results of this study indicated that ACSL1 positively regulated PUFA synthesis in bovine adipocytes.

Analysis of Low Molecular Weight Substances and Related Processes Influencing Cellular Cholesterol Efflux

Cholesterol efflux is the key process protecting the vascular system from the development of atherosclerotic lesions. Various extracellular and intracellular events affect the ability of the cell to efflux excess cholesterol. To explore the possible pathways and processes that promote or inhibit cholesterol efflux, we applied a combined cheminformatic and bioinformatic approach. We performed a comprehensive analysis of published data on the various substances influencing cholesterol efflux and found 153 low molecular weight substances that are included in the Chemical Entities of Biological Interest (ChEBI) database. Pathway enrichment was performed for substances identified within the Reactome database, and 45 substances were selected in 93 significant pathways. The most common pathways included the energy-dependent processes related to active cholesterol transport from the cell, lipoprotein metabolism and lipid transport, and signaling pathways. The activators and inhibitors of cholesterol efflux were non-uniformly distributed among the different pathways: the substances influencing ‘biological oxidations’ activate cholesterol efflux and the substances influencing ‘Signaling by GPCR and PTK6’ inhibit efflux. This analysis may be used in the search and design of efflux effectors for therapies targeting structural and functional high-density lipoprotein deficiency.

Monocytes and Macrophages as Protagonists in Vascular Complications of Diabetes

With the increasing prevalence of diabetes worldwide, vascular complications of diabetes are also on the rise. Diabetes results in an increased risk of macrovascular complications, with atherosclerotic cardiovascular disease (CVD) being the leading cause of death in adults with diabetes. The exact mechanisms for how diabetes promotes CVD risk are still unclear, although it is evident that monocytes and macrophages are key players in all stages of atherosclerosis both in the absence and presence of diabetes, and that phenotypes of these cells are altered by the diabetic environment. Evidence suggests that at least five pro-atherogenic mechanisms involving monocytes and macrophages contribute to the accelerated atherosclerotic lesion progression and hampered lesion regression associated with diabetes. These changes include (1) increased monocyte recruitment to lesions; (2) increased inflammatory activation; (3) altered macrophage lipid accumulation and metabolism; (4) increased macrophage cell death; and (5) reduced efferocytosis. Monocyte and macrophage phenotypes and mechanisms have been revealed mostly by different animal models of diabetes. The roles of specific changes in monocytes and macrophages in humans with diabetes remain largely unknown. There is an ongoing debate on whether the changes in monocytes and macrophages are caused by altered glucose levels, insulin deficiency or insulin resistance, lipid abnormalities, or combinations of these factors. Current research in humans and mouse models suggests that reduced clearance of triglyceride-rich lipoproteins and their remnants is one important mechanism whereby diabetes adversely affects macrophages and promotes atherosclerosis and CVD risk. Although monocytes and macrophages readily respond to the diabetic environment and can be seen as protagonists in diabetes-accelerated atherosclerosis, they are likely not instigators of the increased CVD risk.

Long-Chain Acyl-CoA Synthetase 1 Role in Sepsis and Immunity: Perspectives From a Parallel Review of Public Transcriptome Datasets and of the Literature

A potential role for the long-chain acyl-CoA synthetase family member 1 (ACSL1) in the immunobiology of sepsis was explored during a hands-on training workshop. Participants first assessed the robustness of the potential gap in biomedical knowledge identified via an initial screen of public transcriptome data and of the literature associated with ACSL1. Increase in ACSL1 transcript abundance during sepsis was confirmed in several independent datasets. Querying the ACSL1 literature also confirmed the absence of reports associating ACSL1 with sepsis. Inferences drawn from both the literature (via indirect associations) and public transcriptome data (via correlation) point to the likely participation of ACSL1 and ACSL4, another family member, in inflammasome activation in neutrophils during sepsis. Furthermore, available clinical data indicate that levels of ACSL1 and ACSL4 induction was significantly higher in fatal cases of sepsis. This denotes potential translational relevance and is consistent with involvement in pathways driving potentially deleterious systemic inflammation. Finally, while ACSL1 expression was induced in blood in vitro by a wide range of pathogen-derived factors as well as TNF, induction of ACSL4 appeared restricted to flagellated bacteria and pathogen-derived TLR5 agonists and IFNG. Taken together, this joint review of public literature and omics data records points to two members of the acyl-CoA synthetase family potentially playing a role in inflammasome activation in neutrophils. Translational relevance of these observations in the context of sepsis and other inflammatory conditions remain to be investigated.

Macrophage fatty acid metabolism and atherosclerosis: The rise of PUFAs

Among the pathways involved in the regulation of macrophage functions, the metabolism of unsaturated fatty acids is central. Indeed, unsaturated fatty acids act as precursors of bioactive molecules such as prostaglandins, leukotrienes, resolvins and related compounds. As components of phospholipids, they have a pivotal role in cell biology by regulating membrane fluidity and membrane-associated cellular processes. Finally, polyunsaturated fatty acids (PUFAs) are also endowed with ligand properties for numerous membrane or nuclear receptors. Although myeloid cells are dependent on the metabolic context for the uptake of essential FAs, recent studies showed that these cells autonomously handle the synthesis of n-3 and n-6 long chain PUFAs such as arachidonic acid and eicosapentaenoic acid. Moreover, targeting PUFA metabolism in macrophages influences pathological processes, including atherosclerosis, by modulating macrophage functions. Omics evidence also supports a role for macrophage PUFA metabolism in the development of cardiometabolic diseases in humans. Currently, there is a renewed interest in the role of n-3/n-6 PUFAs and their oxygenated derivatives in the onset of atherosclerosis and plaque rupture. Purified n-3 FA supplementation appears as a potential strategy in the treatment and prevention of cardiovascular diseases. In this context, the ability of immune cells to handle and to synthesize very long chain PUFA must absolutely be integrated and better understood.

Targeting Long Chain Acyl-CoA Synthetases for Cancer Therapy

The deregulation of cancer cell metabolic networks is now recognized as one of the hallmarks of cancer. Abnormal lipid synthesis and extracellular lipid uptake are advantageous modifications fueling the needs of uncontrolled cancer cell proliferation. Fatty acids are placed at the crossroads of anabolic and catabolic pathways, as they are implicated in the synthesis of phospholipids and triacylglycerols, or they can undergo β-oxidation. Key players to these decisions are the long-chain acyl-CoA synthetases, which are enzymes that catalyze the activation of long-chain fatty acids of 12-22 carbons. Importantly, the long-chain acyl-CoA synthetases are deregulated in many types of tumors, providing a rationale for anti-tumor therapeutic opportunities. The purpose of this review is to summarize the last up-to-date findings regarding their role in cancer, and to discuss the related emerging tumor targeting opportunities.

Intracellular and Plasma Membrane Events in Cholesterol Transport and Homeostasis

Cholesterol transport between intracellular compartments proceeds by both energy- and non-energy-dependent processes. Energy-dependent vesicular traffic partly contributes to cholesterol flux between endoplasmic reticulum, plasma membrane, and endocytic vesicles. Membrane contact sites and lipid transfer proteins are involved in nonvesicular lipid traffic. Only “active" cholesterol molecules outside of cholesterol-rich regions and partially exposed in water phase are able to fast transfer. The dissociation of partially exposed cholesterol molecules in water determines the rate of passive aqueous diffusion of cholesterol out of plasma membrane. ATP hydrolysis with concomitant conformational transition is required to cholesterol efflux by ABCA1 and ABCG1 transporters. Besides, scavenger receptor SR-B1 is involved also in cholesterol efflux by facilitated diffusion via hydrophobic tunnel within the molecule. Direct interaction of ABCA1 with apolipoprotein A-I (apoA-I) or apoA-I binding to high capacity binding sites in plasma membrane is important in cholesterol escape to free apoA-I. ABCG1-mediated efflux to fully lipidated apoA-I within high density lipoprotein particle proceeds more likely through the increase of “active” cholesterol level. Putative cholesterol-binding linear motifs within the structure of all three proteins ABCA1, ABCG1, and SR-B1 are suggested to contribute to the binding and transfer of cholesterol molecules from cytoplasmic to outer leaflets of lipid bilayer. Together, plasma membrane events and intracellular cholesterol metabolism and traffic determine the capacity of the cell for cholesterol efflux.

Identification of differentially expressed miRNAs in the fatty liver of Landes goose (Anser anser)

Unlike mammals, in palmipedes de novo lipogenesis from diet takes place mostly in the liver. The French Landes Goose is famous for its high capacity and susceptibility to fatty liver production. While miRNAs play a critical role in the posttranscriptional regulation of gene expression, miRNAs that are involved in the regulation of goose hepatic steatosis have yet to be elucidated. Using high-throughput sequencing, we analyzed miRNAs expression profile of Landes goose liver after overfeeding for 21 days. Aan-miR-122-5p was the most frequently sequenced known miRNA, but it was unchanged after overfeeding. Compared with normal liver, we identified that 16 conserved miRNAs were up-regulated while the other 9 conserved miRNAs were down-regulated in fatty livers. Many of their predicted target genes played key roles in metabolic pathways leading to the development of hepatic steatosis in the goose by KEGG pathways analysis. ACSL1 and ELOVL6 were critical genes in hepatic lipid metabolism and had opposite expression patterns with aan-miR-203a and aan-miR-125b-5p, respectively. And we validated that aan-miR-203a and aan-miR-125b-5p might involve in the regulation of hepatic lipid metabolism by targeting ACSL1 and ELOVL6, respectively. These results add to our current understanding of the regulation network in goose lipid metabolism.

High expression of long chain acyl-coenzyme A synthetase 1 in peripheral blood may be a molecular marker for assessing the risk of acute myocardial infarction

The current study aimed to investigate whether the increased expression of long chain acyl-coenzymeA synthetase 1 (ACSL1) in peripheral blood leukocytes (PBL) may be a molecular marker for the genetic evaluation of acute myocardial infarction (AMI). The mechanism of action of ACSL1 in the pathogenesis of AMI was also investigated. A total of 75 patients with AMI and 70 individuals without coronary heart disease were selected to participate in the present study. The demographic and clinical information of the enrolled subjects was recorded. Reverse transcription quantitative polymerase chain reaction and western blot analysis were applied to measure the expression of ACSL1 at the mRNA and protein levels. It was demonstrated that the expression of ACSL1 mRNA and protein in PBL was increased in patients with AMI compared with controls. Logistic regression analysis indicated that ACSL1 expression in PBL was an independent risk factor of AMI. There was a significant positive association between the level of ACSL1 expression and the degree of atherosclerosis in the coronary artery. Furthermore, patients with AMI exhibited an increased risk of atherosclerosis due to increased fasting blood glucose, total cholesterol, triglyceride and lipoprotein levels and decreased high-density lipoprotein levels, compared with controls. Therefore, the current study demonstrated that ACSL1 expression was increased in the PBLs of patients with AMI. The elevated expression of ACSL1 acts an independent risk factor of AMI and may act as a potential biomarker when determining the risk of AMI.

Cellular and Molecular Mechanisms of Diabetic Atherosclerosis: Herbal Medicines as a Potential Therapeutic Approach

An increasing number of patients diagnosed with diabetes mellitus eventually develop severe coronary atherosclerosis disease. Both type 1 and type 2 diabetes mellitus increase the risk of cardiovascular disease associated with atherosclerosis. The cellular and molecular mechanisms affecting the incidence of diabetic atherosclerosis are still unclear, as are appropriate strategies for the prevention and treatment of diabetic atherosclerosis. In this review, we discuss progress in the study of herbs as potential therapeutic agents for diabetic atherosclerosis.

Association of long-chain acyl-coenzyme A synthetase 5 expression in human breast cancer by estrogen receptor status and its clinical significance

The lipid metabolic enzymes are considered candidate therapeutic targets for breast cancer. Long-chain acyl-coenzyme A (CoA) synthase (ACSL) is one of lipid metabolic enzymes and converts free-fatty acid to fatty acid-CoA. Five ACSL isoforms including ACSL1, ACSL3, ACSL4, ACSL5 and ACSL6 are identified in human. High ACSL4 expression has been observed in aggressive breast cancer phenotype. However, the role of other isoforms is still little-known. We therefore, analyzed the expression of ACSL isoforms in each subtype of breast cancer within METABRIC dataset and cancer cell line encyclopedia dataset. The expression levels of ACSL1, ACSL4 and ACSL5 in estrogen receptor (ER)-negative group were higher than that in ER-positive group. Similar expression pattern was detected among breast cancer cell lines MCF-7 (ER-positive) and MDA-MB-231 (ER-negative). Treatment of ACSL inhibitor triacsin C which inhibited enzyme activity of ACSL 1, 3, 4 and 5 suppressed cell growth of MCF-7 and MDA-MB-231. Our results further showed that high ACSL5 expression was associated with good prognosis in patients with both ER-positive and ER-negative breast cancer through KM plotter analysis. These results suggest that ACSL1, ACSL4 and ACSL5 expression is regulated by ER signaling pathways and ACSL5 is a potential novel biomarker for predicting prognosis of breast cancer patients.

HBXIP up-regulates ACSL1 through activating transcriptional factor Sp1 in breast cancer

The oncoprotein hepatitis B X-interacting protein (HBXIP) results in the dysregulation of lipid metabolism to enhance the development of breast cancer. Acyl-CoA synthetase long-chain family member 1 (ACSL1) is required for thioesterification of long-chain fatty acids into their acyl-CoA derivatives. In this study, we present a hypothesis that HBXIP might be involved in the regulation of ACSL1 in breast cancer. Interestingly, we found that the overexpression of HBXIP was able to up-regulate ACSL1 at the levels of mRNA and protein in a dose-dependent manner in breast cancer cells. Conversely, silencing of HBXIP led to the opposite results. Mechanistically, HBXIP as a coactivator interacted with transcriptional factor Sp1 through binding to the promoter of ACSL1 by ChIP assays analysis, leading to the transcription of ACSL1 in breast cancer cells. Immunohistochemistry staining revealed that the positive rate of ACSL1 was 71.4% (35/49) in clinical breast cancer tissues, HBXIP 79.6% (39/49), in which the positive rate of ACSL1 was 76.9% (30/39) in the HBXIP-positive specimens. But, few positive rate of ACSL1 10% (1/10) was observed in normal breast tissues. The mRNA levels of ACSL1 were significantly higher in clinical breast cancer tissues than those in their corresponding peritumor tissues. The mRNA levels of ACSL1 were positively associated with those of HBXIP in clinical breast cancer tissues. Thus, we conclude that the oncoprotein HBXIP is able to up-regulate ACSL1 through activating the transcriptional factor Sp1 in breast cancer.

Fatty acid metabolism in macrophages: a target in cardio-metabolic diseases

PURPOSE OF REVIEW

Recent studies have highlighted that macrophages dynamically and autonomously handle all the facets of fatty acid (FA) metabolism including FA oxidation and FA synthesis as well as the synthesis of monounsaturated FAs and long chain n-3 and n-6 polyunsaturated FAs.

RECENT FINDINGS

Macrophage M2 polarization is associated with an increase of FA oxidation. However, whether increased FA oxidation simply correlates with or is required for M2 polarization needs to be further evaluated. Macrophage M1 polarization is associated with the activation of FA synthesis, which directly contributes to the inflammatory response and affects cholesterol homeostasis and neutral lipid accumulation. Finally, recent evidences suggest that macrophages are able to autonomously produce signaling monounsaturated FAs, such as palmitoleic acid (C16 : 1 n-7), and long chain n-3 and n-6 polyunsaturated FAs, such as arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. This pathway is regulated by liver X receptors and has significant consequences on inflammation and on the FA composition of atheroma plaques.

SUMMARY

These studies shed new light on the tight relationship between FA metabolism, macrophage polarization, and M1/M2 macrophage functions. These processes may have major consequences for atherosclerosis pathogenesis as well as other metabolic disorders.

SCAP/SREBP pathway is required for the full steroidogenic response to cyclic AMP

Luteinizing hormone (LH) stimulates steroidogenesis largely through a surge in cyclic AMP (cAMP). Steroidogenic rates are also critically dependent on the availability of cholesterol at mitochondrial sites of synthesis. This cholesterol is provided by cellular uptake of lipoproteins, mobilization of intracellular lipid, and de novo synthesis. Whether and how these pathways are coordinated by cAMP are poorly understood. Recent phosphoproteomic analyses of cAMP-dependent phosphorylation sites in MA10 Leydig cells suggested that cAMP regulates multiple steps in these processes, including activation of the SCAP/SREBP pathway. SCAP [sterol-regulatory element-binding protein (SREBP) cleavage-activating protein] acts as a cholesterol sensor responsible for regulating intracellular cholesterol balance. Its role in cAMP-mediated control of steroidogenesis has not been explored. We used two CRISPR (clustered regularly interspaced short palindromic repeat)-Cas9 (CRISPR associated protein 9) knockout approaches to test the role of SCAP in steroidogenesis. Our results demonstrate that SCAP is required for progesterone production induced by concurrent inhibition of the cAMP phosphodiesterases PDE4 and PDE8. These inhibitors increased SCAP phosphorylation, SREBP2 activation, and subsequent expression of cholesterol biosynthetic genes, whereas SCAP deficiency largely prevented these effects. Reexpression of SCAP in SCAP-deficient cells restored SREBP2 protein expression and partially restored steroidogenic responses, confirming the requirement of SCAP-SREBP2 in steroidogenesis. Inhibitors of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase and isoprenylation attenuated, whereas exogenously provided cholesterol augmented, PDE inhibitor-induced steroidogenesis, suggesting that the cholesterol substrate needed for steroidogenesis is provided by both de novo synthesis and isoprenylation-dependent mechanisms. Overall, these results demonstrate a novel role for LH/cAMP in SCAP/SREBP activation and subsequent regulation of steroidogenesis.

Systematic Analysis of Gene Expression Alterations and Clinical Outcomes for Long-Chain Acyl-Coenzyme A Synthetase Family in Cancer

Dysregulated lipid metabolism contributes to cancer progression. Our previous study indicates that long-chain fatty acyl-Co A synthetase (ACSL) 3 is essential for lipid upregulation induced by endoplasmic reticulum stress. In this report, we aimed to identify the role of ACSL family in cancer with systematic analysis and in vitro experiment. We explored the ACSL expression using Oncomine database to determine the gene alteration during carcinogenesis and identified the association between ACSL expression and the survival of cancer patient using PrognoScan database. ACSL1 may play a potential oncogenic role in colorectal and breast cancer and play a potential tumor suppressor role in lung cancer. Co-expression analysis revealed that ACSL1 was coexpressed with MYBPH, PTPRE, PFKFB3, SOCS3 in colon cancer and with LRRFIP1, TSC22D1 in lung cancer. In accordance with PrognoScan analysis, downregulation of ACSL1 in colon and breast cancer cell line inhibited proliferation, migration, and anchorage-independent growth. In contrast, increase of oncogenic property was observed in lung cancer cell line by attenuating ACSL1. High ACSL3 expression predicted a better prognosis in ovarian cancer; in contrast, high ACSL3 predicted a worse prognosis in melanoma. ACSL3 was coexpressed with SNUPN, TRIP13, and SEMA5A in melanoma. High expression of ACSL4 predicted a worse prognosis in colorectal cancer, but predicted better prognosis in breast, brain and lung cancer. ACSL4 was coexpressed with SERPIN2, HNRNPCL1, ITIH2, PROCR, LRRFIP1. High expression of ACSL5 predicted good prognosis in breast, ovarian, and lung cancers. ACSL5 was coexpressed with TMEM140, TAPBPL, BIRC3, PTPRE, and SERPINB1. Low ACSL6 predicted a worse prognosis in acute myeloid leukemia. ACSL6 was coexpressed with SOX6 and DARC. Altogether, different members of ACSLs are implicated in diverse types of cancer development. ACSL-coexpressed molecules may be used to further investigate the role of ACSL family in individual type of cancers.

Genetic association of long-chain acyl-CoA synthetase 1 variants with fasting glucose, diabetes, and subclinical atherosclerosis

Long-chain acyl-CoA synthetase 1 (ACSL1) converts free fatty acids into acyl-CoAs. Mouse studies have revealed that ACSL1 channels acyl-CoAs to β-oxidation, thereby reducing glucose utilization, and is required for diabetes-accelerated atherosclerosis. The role of ACSL1 in humans is unknown. We therefore examined common variants in the human ACSL1 locus by genetic association studies for fasting glucose, diabetes status, and preclinical atherosclerosis by using the MAGIC and DIAGRAM consortia; followed by analyses in participants from the Multi-Ethnic Study of Atherosclerosis, the Penn-T2D consortium, and a meta-analysis of subclinical atherosclerosis in African Americans; and finally, expression quantitative trait locus analysis and identification of DNase I hypersensitive sites (DHS). The results show that three SNPs in ACSL1 (rs7681334, rs735949, and rs4862423) are associated with fasting glucose or diabetes status in these large (>200,000 subjects) data sets. Furthermore, rs4862423 is associated with subclinical atherosclerosis and coincides with a DHS highly accessible in human heart. SNP rs735949 is in strong linkage disequilibrium with rs745805, significantly associated with ACSL1 levels in skin, suggesting tissue-specific regulatory mechanisms. This study provides evidence in humans of ACSL1 SNPs associated with fasting glucose, diabetes, and subclinical atherosclerosis and suggests links among these traits and acyl-CoA synthesis.

Metabolic-epigenetic crosstalk in macrophage activation

Epigenetic enzymes are emerging as crucial controllers of macrophages, innate immune cells that determine the outcome of many inflammatory diseases. Recent studies demonstrate that the activity of particular chromatin-modifying enzymes is regulated by the availability of specific metabolites like acetyl-coenzyme A, S-adenosylmethionine, α-ketoglutarate, nicotinamide adenine dinucleotide and polyamines. In this way chromatin-modifying enzymes could sense the macrophage's metabolic status and translate this into gene expression and phenotypic changes. Importantly, distinct macrophage activation subsets display particular metabolic pathways. IFNγ/lipopolysaccharide-activated macrophages (MIFNγ/LPS or M1) display high glycolysis, which directly drives their inflammatory phenotype. In contrast, oxidative mitochondrial metabolism and enhanced polyamine production are hallmarks and requirements for IL-4-induced macrophage activation (MIL-4 or M2). Here we report how epigenetics could serve as a bridge between altered macrophage metabolism, macrophage activation and disease.

Regulation of HDL genes: transcriptional, posttranscriptional, and posttranslational

HDL regulation is exerted at multiple levels including regulation at the level of transcription initiation by transcription factors and signal transduction cascades; regulation at the posttranscriptional level by microRNAs and other noncoding RNAs which bind to the coding or noncoding regions of HDL genes regulating mRNA stability and translation; as well as regulation at the posttranslational level by protein modifications, intracellular trafficking, and degradation. The above mechanisms have drastic effects on several HDL-mediated processes including HDL biogenesis, remodeling, cholesterol efflux and uptake, as well as atheroprotective functions on the cells of the arterial wall. The emphasis is on mechanisms that operate in physiologically relevant tissues such as the liver (which accounts for 80% of the total HDL-C levels in the plasma), the macrophages, the adrenals, and the endothelium. Transcription factors that have a significant impact on HDL regulation such as hormone nuclear receptors and hepatocyte nuclear factors are extensively discussed both in terms of gene promoter recognition and regulation but also in terms of their impact on plasma HDL levels as was revealed by knockout studies. Understanding the different modes of regulation of this complex lipoprotein may provide useful insights for the development of novel HDL-raising therapies that could be used to fight against atherosclerosis which is the underlying cause of coronary heart disease.

Acyl-CoA metabolism and partitioning

Long-chain fatty acyl-coenzyme As (CoAs) are critical regulatory molecules and metabolic intermediates. The initial step in their synthesis is the activation of fatty acids by one of 13 long-chain acyl-CoA synthetase isoforms. These isoforms are regulated independently and have different tissue expression patterns and subcellular locations. Their acyl-CoA products regulate metabolic enzymes and signaling pathways, become oxidized to provide cellular energy, and are incorporated into acylated proteins and complex lipids such as triacylglycerol, phospholipids, and cholesterol esters. Their differing metabolic fates are determined by a network of proteins that channel the acyl-CoAs toward or away from specific metabolic pathways and serve as the basis for partitioning. This review evaluates the evidence for acyl-CoA partitioning by reviewing experimental data on proteins that are believed to contribute to acyl-CoA channeling, the metabolic consequences of loss of these proteins, and the potential role of maladaptive acyl-CoA partitioning in the pathogenesis of metabolic disease and carcinogenesis.

Integrated analysis of transcript-level regulation of metabolism reveals disease-relevant nodes of the human metabolic network

Metabolic diseases and comorbidities represent an ever-growing epidemic where multiple cell types impact tissue homeostasis. Here, the link between the metabolic and gene regulatory networks was studied through experimental and computational analysis. Integrating gene regulation data with a human metabolic network prompted the establishment of an open-sourced web portal, IDARE (Integrated Data Nodes of Regulation), for visualizing various gene-related data in context of metabolic pathways. Motivated by increasing availability of deep sequencing studies, we obtained ChIP-seq data from widely studied human umbilical vein endothelial cells. Interestingly, we found that association of metabolic genes with multiple transcription factors (TFs) enriched disease-associated genes. To demonstrate further extensions enabled by examining these networks together, constraint-based modeling was applied to data from human preadipocyte differentiation. In parallel, data on gene expression, genome-wide ChIP-seq profiles for peroxisome proliferator-activated receptor (PPAR) γ, CCAAT/enhancer binding protein (CEBP) α, liver X receptor (LXR) and H3K4me3 and microRNA target identification for miR-27a, miR-29a and miR-222 were collected. Disease-relevant key nodes, including mitochondrial glycerol-3-phosphate acyltransferase (GPAM), were exposed from metabolic pathways predicted to change activity by focusing on association with multiple regulators. In both cell types, our analysis reveals the convergence of microRNAs and TFs within the branched chain amino acid (BCAA) metabolic pathway, possibly providing an explanation for its downregulation in obese and diabetic conditions.

Monocyte gene expression and coronary artery disease

PURPOSE OF REVIEW

Despite current therapy, coronary artery disease (CAD) remains the major cause of morbidity and mortality worldwide. CAD is the consequence of a complex array of deranged metabolic processes including the immune system. In this context, monocytes and macrophages are indisputable players. Thus, monocyte gene expression analysis could be a powerful tool to provide new insights in the pathophysiology of CAD and improve identification of individuals at risk. We discuss current literature assessing monocyte gene expression and its association with CAD.

RECENT FINDINGS

Monocyte surface markers CD14 ⁺⁺and CD16⁺ have been established as biomarkers for increased cardiovascular disease risk in a large number of studies. More in-depth gene expression analysis identified several interesting genes, such as ABCA1, CD36 and MSR1 with an increased expression in circulating monocytes from patients with CAD. The results for CD36 were replicated in one other study. For ABCA1 and MSR1 conflicting data are published.

SUMMARY

Recent findings indicate that genetic differences exist in circulating monocytes of patients suffering from CAD, giving us more insights into the underlying mechanisms. However, larger studies are required to prove that monocytes' expression signature could serve as a marker for diagnostic purposes in the future.

Inflammation and diabetes-accelerated atherosclerosis: myeloid cell mediators

Monocytes and macrophages respond to and govern inflammation by producing a plethora of inflammatory modulators, including cytokines, chemokines, and arachidonic acid (C20:4)-derived lipid mediators. One of the most prevalent inflammatory diseases is cardiovascular disease, caused by atherosclerosis, and accelerated by diabetes. Recent research has demonstrated that monocytes/macrophages from diabetic mice and humans with type 1 diabetes show upregulation of the enzyme, acyl-CoA synthetase 1 (ACSL1), which promotes C20:4 metabolism, and that ACSL1 inhibition selectively protects these cells from the inflammatory and proatherosclerotic effects of diabetes, in mice. Increased understanding of the role of ACSL1 and other culprits in monocytes/macrophages in inflammation and diabetes-accelerated atherosclerosis offers hope for new treatment strategies to combat diabetic vascular disease.

Diabetes promotes an inflammatory macrophage phenotype and atherosclerosis through acyl-CoA synthetase 1

The mechanisms that promote an inflammatory environment and accelerated atherosclerosis in diabetes are poorly understood. We show that macrophages isolated from two different mouse models of type 1 diabetes exhibit an inflammatory phenotype. This inflammatory phenotype associates with increased expression of long-chain acyl-CoA synthetase 1 (ACSL1), an enzyme that catalyzes the thioesterification of fatty acids. Monocytes from humans and mice with type 1 diabetes also exhibit increased ACSL1. Furthermore, myeloid-selective deletion of ACSL1 protects monocytes and macrophages from the inflammatory effects of diabetes. Strikingly, myeloid-selective deletion of ACSL1 also prevents accelerated atherosclerosis in diabetic mice without affecting lesions in nondiabetic mice. Our observations indicate that ACSL1 plays a critical role by promoting the inflammatory phenotype of macrophages associated with type 1 diabetes; they also raise the possibilities that diabetic atherosclerosis has an etiology that is, at least in part, distinct from the etiology of nondiabetic vascular disease and that this difference is because of increased monocyte and macrophage ACSL1 expression.