Long-chain acyl-CoA synthetase 4 modulates prostaglandin E₂ release from human arterial smooth muscle cells

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.

Pharmacological effects of Pugionium cornutum (L.) Gaertn. extracts on gastrointestinal motility are partially mediated by quercetin

BACKGROUND

The majority of global population suffer from various functional gastrointestinal disorders. Pugionium cornutum (L.) Gaertn. (PCG) is used to relieve indigestive symptoms in traditional Chinese medicine. However, little is known about the effects of bioactive components from PCG extracts on gastrointestinal motility.

METHODS

Crude ethanol extract of PCG (EEP) was prepared from Pugionium cornutum (L.) Gaertn. Different solvents were used to prepare fine extracts from EEP, including water extract of PCG (WEP), petroleum ether extract of PCG (PEEP), dichloromethane extract of PCG (DEP) and ethyl acetate extract of PCG (EAEP). Smooth muscle cell model and colonic smooth muscle stripe model were used to test the bioactive effects and mechanisms of different PCG extracts on contraction and relaxation. Diverse chromatographic methods were used to identify bioactive substances from PCG extracts.

RESULTS

EEP was found to promote the relaxation of gastric smooth muscle cell and inhibit the contraction of colonic smooth muscle strip. Among the fractions of EEP, EAEP mainly mediated the relaxation effect by stimulating intracellular calcium influx. Further evidences revealed that EAEP was antagonistic to acetylcholine. In addition, COX and NO-GC-PKC pathways may be also involved in EAEP-mediated relaxation effect. Quercetin was identified as a bioactive compound from PCG extract for the relaxation effect.

CONCLUSION

Our research supports the notion that PCG extracts promote relaxation and inhibits contraction of gastrointestinal smooth muscle at least partially through the effect from quercetin.

Roles of microRNAs in carbohydrate and lipid metabolism disorders and their therapeutic potential

MicroRNAs (miRNAs) are small (∼21 nucleotides), endogenous, non-coding RNA molecules implicated in the post-transcriptional gene regulation performed through target mRNA cleavage or translational inhibition. In recent years, several investigations have demonstrated that miRNAs are involved in regulating both carbohydrate and lipid homeostasis in humans and other organisms. Moreover, it has been observed that the dysregulation of these metabolism-related miRNAs leads to the development of several metabolic disorders, such as type 2 diabetes, obesity, nonalcoholic fatty liver, insulin resistance, and hyperlipidemia. Hence, in this current review, with the aim to impulse the research arena of the micro-transcriptome implications in vital metabolic pathways as well as to highlight the remarkable potential of miRNAs as therapeutic targets for metabolic disorders in humans, we provide an overview of the regulatory roles of metabolism-associated miRNAs in humans and murine models.

Ferroptosis Is a Potential Novel Diagnostic and Therapeutic Target for Patients With Cardiomyopathy

Cardiomyocyte death is a fundamental progress in cardiomyopathy. However, the mechanism of triggering the death of myocardial cells remains unclear. Ferroptosis, which is the nonapoptotic, iron-dependent, and peroxidation-driven programmed cell death pathway, that is abundant and readily accessible, was not discovered until recently with a pharmacological approach. New researches have demonstrated the close relationship between ferroptosis and the development of many cardiovascular diseases, and several ferroptosis inhibitors, iron chelators, and small antioxidant molecules can relieve myocardial injury by blocking the ferroptosis pathways. Notably, ferroptosis is gradually being considered as an important cell death mechanism in the animal models with multiple cardiomyopathies. In this review, we will discuss the mechanism of ferroptosis and the important role of ferroptosis in cardiomyopathy with a special emphasis on the value of ferroptosis as a potential novel diagnostic and therapeutic target for patients suffering from cardiomyopathy in the future.

Ferroptosis as a novel therapeutic target for cardiovascular disease

Cell death is an important component of the pathophysiology of cardiovascular disease. An understanding of how cardiomyocytes die, and why regeneration of cells in the heart is limited, is a critical area of study. Ferroptosis is a form of regulated cell death that is characterized by iron overload, leading to accumulation of lethal levels of lipid hydroperoxides. The metabolism of iron, lipids, amino acids and glutathione tightly controls the initiation and execution of ferroptosis. Emerging evidence shows that ferroptosis is closely associated with the occurrence and progression of various diseases. In recent years, ferroptosis has been found to play critical roles in cardiomyopathy, myocardial infarction, ischemia/reperfusion injury, and heart failure. This article reviews the mechanisms by which ferroptosis is initiated and controlled and discusses ferroptosis as a novel therapeutic target for various cardiovascular diseases.

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.

Diet and Exercise Training Influence Skeletal Muscle Long-Chain acyl-CoA Synthetases

INTRODUCTION

Long-chain acyl-CoA synthetases (ACSL) are implicated as regulators of oxidation and storage of fatty acids within skeletal muscle; however, to what extent diet and exercise alter skeletal muscle ACSL remains poorly understood.

PURPOSE

This study aimed to determine the effects of diet and exercise training on skeletal muscle ACSL and to examine relationships between ACSL1 and ACSL6 and fat oxidation and fat storage, respectively.

METHODS

Male C57BL/6J mice consumed a 60% high-fat diet (HFD) for 12 wk to induce obesity compared with low-fat diet (LFD). At week 4, mice began aerobic exercise (EX-Tr) or remained sedentary (SED) for 8 wk. At week 12, the protein abundance of five known ACSL isoforms and mRNA expression for ACSL1 and ACSL6 were measured in gastrocnemius muscle, as was skeletal muscle lipid content. Fat oxidation was measured using metabolic cage indirect calorimetry at week 10.

RESULTS

Of the five known ACSL isoforms, four were detected at the protein level. HFD resulted in greater, yet nonsignificant, ACSL1 protein abundance (+18%, P = 0.13 vs LFD), greater ACSL6 (+107%, P < 0.01 vs LFD), and no difference in ACSL4 or ACSL5. Exercise training resulted in greater ACSL6 protein abundance in LFD mice (P = 0.05 LFD EX-Tr vs SED), whereas ACSL4 was lower after exercise training compared with sedentary, regardless of diet. Under fasted conditions, skeletal muscle ACSL1 protein abundance was not related to measures of whole-body fat oxidation. Conversely, skeletal muscle ACSL6 protein abundance was positively correlated with intramyocellular lipid content (P < 0.01, r = 0.22).

CONCLUSION

We present evidence that ACSL isoforms 1, 4, and 6 may undergo regulation by HFD and/or exercise training. We further conclude that increased skeletal muscle ACSL6 may facilitate increased intramyocellular fat storage during HFD-induced obesity.

The Mechanism of Ferroptosis and Applications in Tumor Treatment

Iron-dependent ferroptosis is a new form of cell death in recent years, which is driven by lipid peroxidation. The lethal lipid accumulation caused by glutathione depletion or inactivation of glutathione peroxidase 4 (GPX4) is characteristic of the ferroptosis process. In recent years, with the in-depth study of ferroptosis, various types of diseases have been reported to be related to ferroptosis. In other words, ferroptosis, which has attracted widespread attention in the fields of biochemistry, oncology, and especially materials science, can undoubtedly provide a new way for patients. This review introduces the relevant mechanisms of ferroptosis, the relationship between ferroptosis and various cancers, as well as the application of ferroptosis in tumor treatment. We also sorted out the genes and drugs that regulate ferroptosis. Moreover, small molecule compound-induced ferroptosis has a strong inhibitory effect on tumor growth in a drug-resistant environment, which can enhance the sensitivity of chemotherapeutic drugs, suggesting that ferroptosis is very important in the treatment of tumor drug resistance, but the details are still unclear. How to use ferroptosis to fight cancer, and how to prevent drug-resistant tumor cells have become the focus and direction of research. At the end of the article, some existing problems related to ferroptosis are summarized for future research.

The Drosophila melanogaster as Genetic Model System to Dissect the Mechanisms of Disease that Lead to Neurodegeneration in Adrenoleukodystrophy

Drosophila melanogaster is the most successful genetic model organism to study different human disease with a recent increased popularity to study neurological disorders. Drosophila melanogaster has a complex yet well-defined brain with defined anatomical regions with specific functions. The neuronal network in the adult brain has a structural organization highly similar to human neurons, but in a brain that is much more amenable for complex analyses. The availability of sophisticated genetic tools to study neurons permits to examine neuronal functions at the single cell level in the whole brain by confocal imaging, which does not require sections. Thus, Drosophila has been used to successfully study many neurological disorders such as Parkinson's disease and has been recently adopted to understand the complex networks leading to neurological disorders with metabolic origins such as Leigh disease and X-linked adrenoleukodystrophy (X-ALD).In this review, we will describe the genetic tools available to study neuronal structures and functions and also illustrate some limitations of the system. Finally, we will report the experimental efforts that in the past 10 years have established Drosophila melanogaster as an excellent model organism to study neurodegenerative disorders focusing on X-ALD.

TNF-α induces acyl-CoA synthetase 3 to promote lipid droplet formation in human endothelial cells

Chronic inflammation contributes to cardiovascular disease. Increased levels of the inflammatory cytokine, TNF-α, are often present in conditions associated with cardiovascular disease risk, and TNF-α induces a number of pro-atherogenic effects in macrovascular endothelial cells, including expression of adhesion molecules and chemokines, and lipoprotein uptake and transcytosis to the subendothelial tissue. However, little is known about the roles of acyl-CoA synthetases (ACSLs), enzymes that esterify free fatty acids into their acyl-CoA derivatives, or about the effects of TNF-α on ACSLs in endothelial cells. Therefore, we investigated the effects of TNF-α on ACSLs and downstream lipids in cultured human coronary artery endothelial cells and human umbilical vein endothelial cells. We demonstrated that TNF-α induces ACSL1, ACSL3, and ACSL5, but not ACSL4, in both cell types. TNF-α also increased oleoyl-CoA levels, consistent with the increased ACSL3 expression. RNA-sequencing demonstrated that knockdown of ACSL3 had no marked effects on the TNF-α transcriptome. Instead, ACSL3 was required for TNF-α-induced lipid droplet formation in cells exposed to oleic acid. These results demonstrate that increased acyl-CoA synthesis as a result of ACSL3 induction is part of the TNF-α response in human macrovascular endothelial cells.

Sirt1 regulates the expression of critical metabolic genes in chicken hepatocytes

Context Studies in mammals show that SIRT1 plays an important role in many biological processes including liver metabolism through histone and non-histone deacetylation. Little is known about the function of Sirt1 in the chicken. Aims The current study investigated the expression pattern of Sirt1 mRNA in the chicken and its functions in the chicken liver. Methods In this work, we used real-time quantitative polymerase chain reaction to quantify the expression levels of Sirt1 mRNA in major chicken organs and tissue types, siRNA to knock down Sirt1 expression in primary chicken hepatocytes, RNA sequencing to identify gene-expression changes induced by Sirt1 knockdown, and analysed the function of the differentially expressed genes (DEGs) through gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes ontology analysis. Key results In total, 86 DEGs were found between Sirt1 knockdown and control chicken hepatocytes, of which 63 genes were downregulated and 23 genes were upregulated by Sirt1 knockdown. The Kyoto Encyclopedia of Genes and Genomes analysis showed that 24 DEGs were involved in metabolism. Seven DEGs were involved in carbohydrate and lipid metabolism. Conclusions The present study showed that Sirt1 regulates the expression of genes involved in carbohydrate and lipid metabolism and many other biological processes in the chicken liver. Implications The results of the present study imply that Sirt1 has various functions in the chicken liver and that Sirt1 plays a potentially important role in hepatic carbohydrate and lipid metabolism in the chicken.

The Emerging Roles of Ferroptosis in Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is a clinical syndrome that encompasses all forms of cognitive deficits caused by cerebrovascular disease, from mild cognitive impairment to dementia. Vascular dementia, the second most common type of dementia after Alzheimer’s disease (AD), accounts for approximately 20% of dementia patients. Ferroptosis is a recently defined iron-dependent form of cell death, which is distinct from apoptosis, necrosis, autophagy, and other forms of cell death. Emerging evidence suggests that ferroptosis has significant implications in neurological diseases such as stroke, traumatic brain injury, and AD. Additionally, ferroptosis inhibition has an obvious neuroprotective effect and ameliorates cognitive impairment in various animal models. Here, we summarize the underlying mechanisms of ferroptosis and review the close relationship between ferroptosis and VCI.

Long-chain acyl-CoA synthetase 4 participates in the formation of highly unsaturated fatty acid-containing phospholipids in murine macrophages

Long-chain acyl-coenzyme A synthetases (ACSLs) are a family of enzymes that convert free long-chain fatty acids into their acyl-coenzyme A (CoA) forms. ACSL4, belonging to the ACSL family, shows a preferential use of arachidonic acid (AA) as its substrate and plays a role in the remodeling of AA-containing phospholipids by incorporating free AA. However, little is known about the roles of ACSL4 in inflammatory responses. Here, we assessed the roles of ACSL4 on the effector functions of bone marrow-derived macrophages (BMDMs) obtained from mice lacking ACSL4. Liquid chromatography-tandem mass spectrometry analysis revealed that various highly unsaturated fatty acid (HUFA)-derived fatty acyl-CoA species were markedly decreased in the BMDMs obtained from ACSL4-deficient mice compared with those in the BMDMs obtained from wild-type mice. BMDMs from ACSL4-deficient mice also showed a reduced incorporation of HUFA into phosphatidylcholines. The stimulation of BMDMs with lipopolysaccharide (LPS) elicited the release of prostaglandins (PGs), such as PGE₂, PGD₂ and PGF_2α, and the production of these mediators was significantly enhanced by ACSL4 deficiency. In contrast, neither the LPS-induced release of cytokines, such as IL-6 and IL-10, nor the endocytosis of zymosan or dextran was affected by ACSL4 deficiency. These results suggest that ACSL4 has a crucial role in the maintenance of HUFA composition of certain phospholipid species and in the incorporation of free AA into the phospholipids in LPS-stimulated macrophages. ACSL4 dysfunction may facilitate inflammatory responses by an enhanced eicosanoid storm.

Phospholipid oxidation products in ferroptotic myocardial cell death

Cell death is an important component of the pathophysiology of any disease. Myocardial disease is no exception. Understanding how and why cells die, particularly in the heart where cardiomyocyte regeneration is limited at best, becomes a critical area of study. Ferroptosis is a recently described form of nonapoptotic cell death. It is an iron-mediated form of cell death that occurs because of accumulation of lipid peroxidation products. Reactive oxygen species and iron-mediated phospholipid peroxidation is a hallmark of ferroptosis. To date, ferroptosis has been shown to be involved in cell death associated with Alzheimer’s disease, Huntington’s disease, cancer, Parkinson’s disease, and kidney degradation. Myocardial reperfusion injury is characterized by iron deposition as well as reactive oxygen species production. These conditions, therefore, favor the induction of ferroptosis. Currently there is no available treatment for reperfusion injury, which accounts for up to 50% of the final infarct size. This review will summarize the evidence that ferroptosis can induce cardiomyocyte death following reperfusion injury and the potential for this knowledge to open new therapeutic approaches for myocardial ischemia-reperfusion injury.

Non-coding RNAs derailed: The many influences on the fatty acid reprogramming of cancer

Non-coding RNAs (NcRNAs), a family of functional RNA molecules that cannot translate into proteins but control specific gene expression programs, have been shown to be implicated in various biological processes, including fatty acid metabolism. Fast-growing tumor cells rewire their fatty acid metabolic circuitry in order to meet the needs of energy storage, membrane proliferation, and the generation of signaling molecules, which is achieved by regulating a variety of key enzymes along with related signaling pathways in fatty acid metabolism. This review presents an update of our knowledge about the regulatory network of ncRNAs-specifically, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs)-in this metabolic shift and discusses the possibility of ncRNA-based therapeutics being applied to the restoration of cancer-related fatty acid metabolism.

Analysis on the Substrate Specificity of Recombinant Human Acyl-CoA Synthetase ACSL4 Variants

Acyl-CoA synthetase long-chain family members (ACSLs) are a family of enzymes that convert long-chain free fatty acids into their acyl-CoAs. ACSL4 is an ACSL isozyme with a strong preference for arachidonic acid (AA) and has been hypothesized to modulate the metabolic fates of AA. There are two ACSL4 splice variants: ACSL4V1, which is the more abundant transcript, and ACSL4V2, which is believed to be restricted to the brain. In the present study, we expressed recombinant human ACSL4V1 and V2 in Spodoptera frugiperda 9 (Sf9) cells using the baculovirus expression system and then partially purified both variants by cobalt affinity column chromatography. We then established a novel ACSL assay system with LC-MS/MS, which is highly sensitive and applicable to various kinds of fatty acids, and used it to investigate the substrate specificity of recombinant human ACSL4V1 and V2. The results showed that both ACSL4 variants preferred various kinds of highly unsaturated fatty acids (HUFAs), including docosahexaenoic acid (DHA), adrenic acid (docosatetraenoic acid) and eicosapentaenoic acid (EPA), as well as AA as a substrate. Moreover, our kinetic studies revealed that the two variants had similar relative affinities for AA, EPA and DHA but different reaction rates for each HUFA. These results confirmed the importance of both of ACSL4 variants in the maintenance of membrane phospholipids bearing HUFAs. Structural analysis of these variants might reveal the molecular mechanism by which they maintain membrane phospholipids bearing HUFAs.

Liver-specific knockdown of long-chain acyl-CoA synthetase 4 reveals its key role in VLDL-TG metabolism and phospholipid synthesis in mice fed a high-fat diet

Long-chain acyl-CoA synthetase 4 (ACSL4) has a unique substrate specificity for arachidonic acid. Hepatic ACSL4 is coregulated with the phospholipid (PL)-remodeling enzyme lysophosphatidylcholine (LPC) acyltransferase 3 by peroxisome proliferator-activated receptor δ to modulate the plasma triglyceride (TG) metabolism. In this study, we investigated the acute effects of hepatic ACSL4 deficiency on lipid metabolism in adult mice fed a high-fat diet (HFD). Adenovirus-mediated expression of a mouse ACSL4 shRNA (Ad-shAcsl4) in the liver of HFD-fed mice led to a 43% reduction of hepatic arachidonoyl-CoA synthetase activity and a 53% decrease in ACSL4 protein levels compared with mice receiving control adenovirus (Ad-shLacZ). Attenuated ACSL4 expression resulted in a substantial decrease in circulating VLDL-TG levels without affecting plasma cholesterol. Lipidomics profiling revealed that knocking down ACSL4 altered liver PL compositions, with the greatest impact on accumulation of abundant LPC species (LPC 16:0 and LPC 18:0) and lysophosphatidylethanolamine (LPE) species (LPE 16:0 and LPE 18:0). In addition, fasting glucose and insulin levels were higher in Ad-shAcsl4-transduced mice versus control (Ad-shLacZ). Glucose tolerance testing further indicated an insulin-resistant phenotype upon knockdown of ACSL4. These results provide the first in vivo evidence that ACSL4 plays a role in plasma TG and glucose metabolism and hepatic PL synthesis of hyperlipidemic mice.

Biphasic Dynamics of Macrophage Immunometabolism during Mycobacterium tuberculosis Infection

Macrophages are the primary targets of Mycobacterium tuberculosis infection; the early events of macrophage interaction with M. tuberculosis define subsequent progression and outcome of infection. M. tuberculosis can alter the innate immunity of macrophages, resulting in suboptimal Th1 immunity, which contributes to the survival, persistence, and eventual dissemination of the pathogen.

Macrophages are the primary targets of Mycobacterium tuberculosis infection; the early events of macrophage interaction with M. tuberculosis define subsequent progression and outcome of infection. M. tuberculosis can alter the innate immunity of macrophages, resulting in suboptimal Th1 immunity, which contributes to the survival, persistence, and eventual dissemination of the pathogen. Recent advances in immunometabolism illuminate the intimate link between the metabolic states of immune cells and their specific functions. In this review, we describe the little-studied biphasic metabolic dynamics of the macrophage response during progression of infection by M. tuberculosis and discuss their relevance to macrophage immunity and M. tuberculosis pathogenicity. The early phase of macrophage infection, which is marked by M1 polarization, is accompanied by a metabolic switch from mitochondrial oxidative phosphorylation to hypoxia-inducible factor 1 alpha (HIF-1α)-mediated aerobic glycolysis (also known as the Warburg effect in cancer cells), as well as by an upregulation of pathways involving oxidative and antioxidative defense responses, arginine metabolism, and synthesis of bioactive lipids. These early metabolic changes are followed by a late adaptation/resolution phase in which macrophages transition from glycolysis to mitochondrial oxidative metabolism, with a consequent dampening of macrophage proinflammatory and antimicrobial responses. Importantly, the identification of upregulated metabolic pathways and/or metabolic regulatory mechanisms with immunomodulatory functions during M1 polarization has revealed novel mechanisms of M. tuberculosis pathogenicity. These advances can lead to the development of novel host-directed therapies to facilitate bacterial clearance in tuberculosis by targeting the metabolic state of immune cells.

Comparing genomic signatures of domestication in two Atlantic salmon (Salmo salar L.) populations with different geographical origins

Selective breeding and genetic improvement have left detectable signatures on the genomes of domestic species. The elucidation of such signatures is fundamental for detecting genomic regions of biological relevance to domestication and improving management practices. In aquaculture, domestication was carried out independently in different locations worldwide, which provides opportunities to study the parallel effects of domestication on the genome of individuals that have been selected for similar traits. In this study, we aimed to detect potential genomic signatures of domestication in two independent pairs of wild/domesticated Atlantic salmon populations of Canadian and Scottish origins, respectively. Putative genomic regions under divergent selection were investigated using a 200K SNP array by combining three different statistical methods based either on allele frequencies (LFMM, Bayescan) or haplotype differentiation (Rsb). We identified 337 and 270 SNPs potentially under divergent selection in wild and hatchery populations of Canadian and Scottish origins, respectively. We observed little overlap between results obtained from different statistical methods, highlighting the need to test complementary approaches for detecting a broad range of genomic footprints of selection. The vast majority of the outliers detected were population-specific but we found four candidate genes that were shared between the populations. We propose that these candidate genes may play a role in the parallel process of domestication. Overall, our results suggest that genetic drift may have override the effect of artificial selection and/or point toward a different genetic basis underlying the expression of similar traits in different domesticated strains. Finally, it is likely that domestication may predominantly target polygenic traits (e.g., growth) such that its genomic impact might be more difficult to detect with methods assuming selective sweeps.

Oncogenic H-Ras Expression Induces Fatty Acid Profile Changes in Human Fibroblasts and Extracellular Vesicles

Extracellular vesicles (EVs) are lipid bilayer surrounded particles that are considered an additional way to transmit signals outside the cell. Lipids have not only a structural role in the organization of EVs membrane bilayer, but they also represent a source of lipid mediators that may act on target cells. Senescent cells are characterized by a permanent arrest of cell proliferation, but they are still metabolically active and influence nearby tissue secreting specific signaling mediators, including those carried by EVs. Notably, cellular senescence is associated with increased EVs release. Here, we used gas chromatography coupled to mass spectrometry to investigate the total fatty acid content of EVs released by fibroblasts undergoing H-RasV12-induced senescence and their parental cells. We find that H-RasV12 fibroblasts show increased level of monounsaturated and decreased level of saturated fatty acids, as compared to control cells. These changes are associated with transcriptional up-regulation of specific fatty acid-metabolizing enzymes. The EVs released by both controls and senescent fibroblasts show a higher level of saturated and polyunsaturated species, as compared to parental cells. Considering that fibroblasts undergoing H-RasV12-induced senescence release a higher number of EVs, these findings indicate that senescent cells release via EVs a higher amount of fatty acids, and in particular of polyunsaturated and saturated fatty acids, as compared to control cells.

Roles of Long-chain Acyl Coenzyme A Synthetase in Absorption and Transport of Fatty Acid

Long-chain acyl coenzyme A synthetase (ACSL) is a member of the synthetase family encoded by a multigene family; it plays an important role in the absorption and transport of fatty acid. Here we review the roles of ACSL in the regulating absorption and transport of fatty acid, as well as the connection between ACSL and some metabolic diseases.

Nitro-fatty acid formation and metabolism

Nitro-fatty acids (NO₂-FA) are pleiotropic modulators of redox signaling pathways. Their effects on inflammatory signaling have been studied in great detail in cell, animal and clinical models primarily using exogenously administered nitro-oleic acid. While we know a considerable amount regarding NO₂-FA signaling, endogenous formation and metabolism is relatively unexplored. This review will cover what is currently known regarding the proposed mechanisms of NO₂-FA formation, dietary modulation of endogenous NO₂-FA levels, pathways of NO₂-FA metabolism and the detection of NO₂-FA and corresponding metabolites.

Correlations between gene expression highlight a different activation of ACE/TLR4/PTGS2 signaling in symptomatic and asymptomatic plaques in atherosclerotic patients

Inflammation has a key role and translates the effects of many known risk factors for the disease in atherosclerotic vulnerable plaques. Aiming to look into the elements that induce the development of either a vulnerable or stable atherosclerotic plaque, and considering that inflammation has a central role in the progression of lesions, we analyzed the expression of genes involved in the ACE/TLR4/PTGS2 signaling in carotid plaques of symptomatic and asymptomatic patients. Patients with internal carotid artery stenosis undergoing carotid endarterectomy at Verona University Hospital were included in this study. A total of 71 patients was considered for gene expression analysis (29 atherothrombotic stroke patients and 42 asymptomatic patients). Total RNA was extracted from the excised plaques and expression of PTGS2, ACE, TLR4, PTGER4, PTGER3, EPRAP and ACSL4 genes was analyzed by real-time PCR. The correlation between the pair of genes was studied by Spearman coefficient. From the analyzed genes, we did not observe any individual difference in gene expression but the network of co-expressed genes suggests a different activation of pathways in the two groups of plaques.

Mineralocorticoid receptor antagonism reverses diabetes-related coronary vasodilator dysfunction: A unique vascular transcriptomic signature

Coronary microvascular dysfunction predicts and may be a proximate cause of cardiac dysfunction and mortality in diabetes; however, few effective treatments exist for these conditions. We recently demonstrated that mineralocorticoid receptor (MR) antagonism reversed cardiovascular dysfunction in early-stage obesity/insulin resistance. The mechanisms underlying this benefit of MR antagonism and its relevance in the setting of long-term obesity complications like diabetes; however, remain unclear. Thus, the present study evaluated the impact of MR antagonism on diabetes-related coronary dysfunction and defines the MR-dependent vascular transcriptome in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat recapitulating later stages of human diabetes. OLETF rats were treated with spironolactone (Sp) and compared to untreated OLETF and lean Long-Evans Tokushima Otsuka rats. Sp treatment attenuated diabetes-associated adipose and cardiac inflammation/fibrosis and improved coronary endothelium-dependent vasodilation but did not alter enhanced coronary vasoconstriction, blood pressure, or metabolic parameters in OLETF rats. Further mechanistic studies using RNA deep sequencing of OLETF rat aortas revealed 157 differentially expressed genes following Sp including upregulation of genes involved in the molecular regulation of nitric oxide bioavailability (Hsp90ab1, Ahsa1, Ahsa2) as well as novel changes in α_1D adrenergic receptors (Adra1d), cyclooxygenase-2 (Ptgs2), and modulatory factors of these pathways (Ackr3, Acsl4). Further, Ingenuity Pathway Analysis predicted inhibition of upstream inflammatory regulators by Sp and inhibition of 'migration of endothelial cells', 'differentiation of smooth muscle', and 'angiogenesis' biological functions by Sp in diabetes. Thus, this study is the first to define the MR-dependent vascular transcriptome underlying treatment of diabetes-related coronary microvascular dysfunction by Sp.

Fatty acid activation in thermogenic adipose tissue

Channeling carbohydrates and fatty acids to thermogenic tissues, including brown and beige adipocytes, have garnered interest as an approach for the management of obesity-related metabolic disorders. Mitochondrial fatty acid oxidation (β-oxidation) is crucial for the maintenance of thermogenesis. Upon cellular fatty acid uptake or following lipolysis from triglycerides (TG), fatty acids are esterified to coenzyme A (CoA) to form active acyl-CoA molecules. This enzymatic reaction is essential for their utilization in β-oxidation and thermogenesis. The activation and deactivation of fatty acids are regulated by two sets of enzymes called acyl-CoA synthetases (ACS) and acyl-CoA thioesterases (ACOT), respectively. The expression levels of ACS and ACOT family members in thermogenic tissues will determine the substrate availability for β-oxidation, and consequently the thermogenic capacity. Although the role of the majority of ACS and ACOT family members in thermogenesis remains unclear, recent proceedings link the enzymatic activities of ACS and ACOT family members to metabolic disorders and thermogenesis. Elucidating the contributions of specific ACS and ACOT family members to trafficking of fatty acids towards thermogenesis may reveal novel targets for modulating thermogenic capacity and treating metabolic disorders.

Fatty acid metabolism in breast cancer subtypes

Dysregulation of fatty acid metabolism is recognized as a component of malignant transformation in many different cancers, including breast; yet the potential for targeting this pathway for prevention and/or treatment of cancer remains unrealized. Evidence indicates that proteins involved in both synthesis and oxidation of fatty acids play a pivotal role in the proliferation, migration and invasion of breast cancer cells. The following essay summarizes data implicating specific fatty acid metabolic enzymes in the genesis and progression of breast cancer, and further categorizes the relevance of specific metabolic pathways to individual intrinsic molecular subtypes of breast cancer. Based on mRNA expression data, the less aggressive luminal subtypes appear to rely on a balance between de novo fatty acid synthesis and oxidation as sources for both biomass and energy requirements, while basal-like, receptor negative subtypes overexpress genes involved in the utilization of exogenous fatty acids. With these differences in mind, treatments may need to be tailored to individual subtypes.

A role for long-chain acyl-CoA synthetase-4 (ACSL4) in diet-induced phospholipid remodeling and obesity-associated adipocyte dysfunction

Objective

Regulation of fatty acid (FA) metabolism is central to adipocyte dysfunction during diet-induced obesity (DIO). Long-chain acyl-CoA synthetase-4 (ACSL4) has been hypothesized to modulate the metabolic fates of polyunsaturated FA (PUFA), including arachidonic acid (AA), but the in vivo actions of ACSL4 are unknown. The purpose of our studies was to determine the in vivo role of adipocyte ACSL4 in regulating obesity-associated adipocyte dysfunction.

Methods

We developed a novel mouse model with adipocyte-specific ablation of ACSL4 (Ad-KO) using loxP Cre recombinase technology. Metabolic phenotyping of Ad-KO mice relative to their floxed littermates (ACSL4^floxed) was performed, including body weight and body composition over time; insulin and glucose tolerance tests; and energy expenditure, activity, and food intake in metabolic cages. Adipocytes were isolated for ex vivo adipocyte oxygen consumption by Clark electrode and lipidomics analysis. In vitro adipocyte analysis including oxygen consumption by Seahorse and real-time PCR analysis were performed to confirm our in vivo findings.

Results

Ad-KO mice were protected against DIO, adipocyte death, and metabolic dysfunction. Adipocytes from Ad-KO mice fed high-fat diet (HFD) had reduced incorporation of AA into phospholipids (PL), free AA, and levels of the AA lipid peroxidation product 4-hydroxynonenal (4-HNE). Additionally, adipocytes from Ad-KO mice fed HFD had reduced p53 activation and increased adipocyte oxygen consumption (OCR), which we demonstrated are direct effects of 4-HNE on adipocytes in vitro.

Conclusion

These studies are the first to elucidate ACSL4's in vivo actions to regulate the incorporation of AA into PL and downstream effects on DIO-associated adipocyte dysfunction. By reducing the incorporation of AA into PL and free fatty acid pools in adipocytes, Ad-KO mice were significantly protected against HFD-induced increases in adipose and liver fat accumulation, adipocyte death, gonadal white adipose tissue (gWAT) inflammation, and insulin resistance (IR). Additionally, deficiency of adipocyte ACSL4 expression in mice fed a HFD resulted in increased gWAT adipocyte OCR and whole body energy expenditure (EE).

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ACSL4 expression is upregulated in murine white adipocytes during diet-induced obesity.

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Mice with adipocyte-specific ablation of ACSL4 (Ad-KO) are protected against diet-induced obesity, adipocyte death and metabolic dysfunction.

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Lipidomics profiling of isolated adipocytes from Ad-KO mice fed a high-fat diet (HFD) had reduced arachidonic acid (AA) in phospholipids.

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Adipocytes from Ad-KO mice fed HFD had reduced free AA and levels of the AA lipid peroxidation product 4-hydroxynonenal (4-HNE).

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Adipocytes from Ad-KO mice fed HFD had reduced p53 activation and increased adipocyte oxygen consumption (OCR).

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P53 activation and inhibited adipocyte OCR are direct effects of 4-HNE on adipocytes in vitro.

Baicalin inhibits PDGF-BB-induced hepatic stellate cell proliferation, apoptosis, invasion, migration and activation via the miR-3595/ACSL4 axis

Hepatic fibrosis is a physiological response to liver injury that includes a range of cell types. The pathogenesis of hepatic fibrosis currently focuses on hepatic stellate cell (HSC) activation into muscle fiber cells and fibroblasts. Baicalin is a flavone glycoside. It is the glucuronide of baicalein, which is extracted from the dried roots of Scutellaria baicalensis Georgi. Previous work focused on the anti-viral, -inflammatory and -tumor properties of baicalin. However, the potential anti-fibrotic effects and mechanisms of baicalin are not known. The present study demonstrated that baicalin influenced the activation, proliferation, apoptosis, invasion and migration of platelet-derived growth factor-BB-induced activated HSC-T6 cells in a dose-dependent manner. To investigate the anti-fibrotic effect of baicalin, a one-color micro (mi)RNA array and reverse transcription-quantitative polymerase chain reaction analyses were used. Results demonstrated that baicalin increased the expression of the miRNA, miR-3595. In addition, the inhibition of miR-3595 substantially reversed the anti-fibrotic effect of baicalin. The present data also suggested that miR-3595 negatively regulates the long-chain-fatty-acid-CoA ligase 4 (ACSL4). Furthermore, ACSL4 acted in a baicalin-dependent manner to exhibit anti-fibrotic effects. Taken together, it was concluded that baicalin induces miR-3595 expression that modulates the expression levels of ACSL4. To the best of our knowledge, the present study is the first to demonstrate that baicalin induces overexpression of human miR-3595, and subsequently decreases the expression of ACSL4, resulting in an anti-fibrotic effect.

Mitochondria-Associated Membranes As Networking Platforms and Regulators of Cancer Cell Fate

The tight cross talk between two essential organelles of the cell, the endoplasmic reticulum (ER) and mitochondria, is spatially and functionally regulated by specific microdomains known as the mitochondria-associated membranes (MAMs). MAMs are hot spots of Ca2+ transfer between the ER and mitochondria, and emerging data indicate their vital role in the regulation of fundamental physiological processes, chief among them mitochondria bioenergetics, proteostasis, cell death, and autophagy. Moreover, and perhaps not surprisingly, it has become clear that signaling events regulated at the ER-mitochondria intersection regulate key processes in oncogenesis and in the response of cancer cells to therapeutics. ER-mitochondria appositions have been shown to dynamically recruit oncogenes and tumor suppressors, modulating their activity and protein complex formation, adapt the bioenergetic demand of cancer cells and to regulate cell death pathways and redox signaling in cancer cells. In this review, we discuss some emerging players of the ER-mitochondria contact sites in mammalian cells, the key processes they regulate and recent evidence highlighting the role of MAMs in shaping cell-autonomous and non-autonomous signals that regulate cancer growth.

Regulation of lipids is central to replicative senescence

Cellular replicative senescence, a state of permanent cell-cycle arrest, has been linked to organismal aging, tissue repair and tumorigenesis. In this study, we comparatively investigated the global lipid profiles and mRNA content of proliferating and senescent-state BJ fibroblasts. We found that both expression levels of lipid-regulating genes and the abundance of specific lipid families, are actively regulated. We further found that 19 specific polyunsaturated triacylglycerol species constituted the most prominent changes in lipid composition during replicative senescence. Based on the transcriptome analysis, we propose that the activation of CD36-mediated fatty acid uptake and diversion to glycerolipid biosynthesis could be responsible for the accumulation of triacylglycerols during replicative senescence. This, in turn, could be a cellular mechanism to prevent lipotoxicity under increased oxidative stress conditions observed in this process. Our results indicate that regulation of specific lipid species has a central role during replicative senescence.

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.

Human MicroRNA-548p Decreases Hepatic Apolipoprotein B Secretion and Lipid Synthesis

OBJECTIVE

MicroRNAs (miRs) play important regulatory roles in lipid metabolism. Apolipoprotein B (ApoB), as the only essential scaffolding protein in the assembly of very-low-density lipoproteins, is a target to treat hyperlipidemia and atherosclerosis. We aimed to find out miRs that reduce apoB expression.

APPROACH AND RESULTS

Bioinformatic analyses predicted that hsa-miR-548p can interact with apoB mRNA. MiR-548p or control miR was transfected in human and mouse liver cells to test its role in regulating apoB secretion and mRNA expression levels. Site-directed mutagenesis was used to identify the interacting site of miR-548p in human apoB 3'-untranslated region. Fatty acid oxidation and lipid syntheses were examined in miR-548p overexpressing cells to investigate its function in lipid metabolism. We observed that miR-548p significantly reduces apoB secretion from human hepatoma cells and primary hepatocytes. Mechanistic studies showed that miR-548p interacts with the 3'-untranslated region of human apoB mRNA to enhance post-transcriptional degradation. Bioinformatic algorithms suggested 2 potential binding sites of miR-548p on human apoB mRNA. Site-directed mutagenesis studies revealed that miR-548p targets site I involving both seed and supplementary sequences. MiR-548p had no effect on fatty acid oxidation but significantly decreased lipid synthesis in human hepatoma cells by reducing HMGCR (3-hydroxy-3-methylglutaryl-coenzyme A reductase) and ACSL4 (Acyl-CoA synthetase long-chain family member 4) enzymes involved in cholesterol and fatty acid synthesis. In summary, miR-548p reduces lipoprotein production and lipid synthesis by reducing expression of different genes in human liver cells.

CONCLUSIONS

These studies suggest that miR-548p regulates apoB secretion by targeting mRNA. It is likely that it could be useful in treating atherosclerosis, hyperlipidemia, and hepatosteatosis.

Oxidized arachidonic and adrenic PEs navigate cells to ferroptosis

Enigmatic lipid peroxidation products have been claimed as the proximate executioners of ferroptosis-a specialized death program triggered by insufficiency of glutathione peroxidase 4 (GPX4). Using quantitative redox lipidomics, reverse genetics, bioinformatics and systems biology, we discovered that ferroptosis involves a highly organized oxygenation center, wherein oxidation in endoplasmic-reticulum-associated compartments occurs on only one class of phospholipids (phosphatidylethanolamines (PEs)) and is specific toward two fatty acyls-arachidonoyl (AA) and adrenoyl (AdA). Suppression of AA or AdA esterification into PE by genetic or pharmacological inhibition of acyl-CoA synthase 4 (ACSL4) acts as a specific antiferroptotic rescue pathway. Lipoxygenase (LOX) generates doubly and triply-oxygenated (15-hydroperoxy)-diacylated PE species, which act as death signals, and tocopherols and tocotrienols (vitamin E) suppress LOX and protect against ferroptosis, suggesting a homeostatic physiological role for vitamin E. This oxidative PE death pathway may also represent a target for drug discovery.

Nitro-fatty acid pharmacokinetics in the adipose tissue compartment

Electrophilic nitro-FAs (NO₂-FAs) promote adaptive and anti-inflammatory cell signaling responses as a result of an electrophilic character that supports posttranslational protein modifications. A unique pharmacokinetic profile is expected for NO₂-FAs because of an ability to undergo reversible reactions including Michael addition with cysteine-containing proteins and esterification into complex lipids. Herein, we report via quantitative whole-body autoradiography analysis of rats gavaged with radiolabeled 10-nitro-[¹⁴C]oleic acid, preferential accumulation in adipose tissue over 2 weeks. To better define the metabolism and incorporation of NO₂-FAs and their metabolites in adipose tissue lipids, adipocyte cultures were supplemented with 10-nitro-oleic acid (10-NO₂-OA), nitro-stearic acid, nitro-conjugated linoleic acid, and nitro-linolenic acid. Then, quantitative HPLC-MS/MS analysis was performed on adipocyte neutral and polar lipid fractions, both before and after acid hydrolysis of esterified FAs. NO₂-FAs preferentially incorporated in monoacyl- and diacylglycerides, while reduced metabolites were highly enriched in triacylglycerides. This differential distribution profile was confirmed in vivo in the adipose tissue of NO₂-OA-treated mice. This pattern of NO₂-FA deposition lends new insight into the unique pharmacokinetics and pharmacologic actions that could be expected for this chemically-reactive class of endogenous signaling mediators and synthetic drug candidates.

ACSL4 promotes prostate cancer growth, invasion and hormonal resistance

Increases in fatty acid metabolism have been demonstrated to promote the growth and survival of a variety of cancers, including prostate cancer (PCa). Here, we examine the expression and function of the fatty acid activating enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), in PCa. Ectopic expression of ACSL4 in ACSL4-negative PCa cells increases proliferation, migration and invasion, while ablation of ACSL4 in PCa cells expressing endogenous ACSL4 reduces cell proliferation, migration and invasion. The cell proliferative effects were observed both in vitro, as well as in vivo. Immunohistochemical analysis of human PCa tissue samples indicated ACSL4 expression is increased in malignant cells compared with adjacent benign epithelial cells, and particularly increased in castration-resistant PCa (CRPC) when compared with hormone naive PCa. In cell lines co-expressing both ACSL4 and AR, proliferation was independent of exogenous androgens, suggesting that ACSL4 expression may lead to CRPC. In support for this hypothesis, ectopic ACSL4 expression induced resistance to treatment with Casodex, via decrease in apoptosis. Our studies further indicate that ACSL4 upregulates distinct pathway proteins including p-AKT, LSD1 and β-catenin. These results suggest ACSL4 could serve as a biomarker and potential therapeutic target for CRPC.

Acsl, the Drosophila ortholog of intellectual-disability-related ACSL4, inhibits synaptic growth by altered lipids

Nervous system development and function are tightly regulated by metabolic processes, including the metabolism of lipids such as fatty acids. Mutations in long-chain acyl-CoA synthetase 4 (ACSL4) are associated with non-syndromic intellectual disabilities. We previously reported that Acsl, the Drosophila ortholog of mammalian ACSL3 and ACSL4, inhibits neuromuscular synapse growth by suppressing bone morphogenetic protein (BMP) signaling. Here, we report that Acsl regulates the composition of fatty acids and membrane lipids, which in turn affects neuromuscular junction (NMJ) synapse development. Acsl mutant brains had a decreased abundance of C16:1 fatty acyls; restoration of Acsl expression abrogated NMJ overgrowth and the increase in BMP signaling. A lipidomic analysis revealed that Acsl suppressed the levels of three lipid raft components in the brain, including mannosyl glucosylceramide (MacCer), phosphoethanolamine ceramide and ergosterol. The MacCer level was elevated in Acsl mutant NMJs and, along with sterol, promoted NMJ overgrowth, but was not associated with the increase in BMP signaling in the mutants. These findings suggest that Acsl inhibits NMJ growth by stimulating C16:1 fatty acyl production and concomitantly suppressing raft-associated lipid levels.

Measurement of Long-Chain Fatty Acyl-CoA Synthetase Activity

Long-chain fatty acyl-CoA synthetases (ACS) are a family of essential enzymes of lipid metabolism, activating fatty acids by thioesterification with coenzyme A. Fatty acyl-CoA molecules are then readily utilized for the biosynthesis of storage and membrane lipids, or for the generation of energy by ß-oxidation. Acyl-CoAs also function as transcriptional activators, allosteric inhibitors, or precursors for inflammatory mediators. Recent work suggests that ACS enzymes may drive cellular fatty acid uptake by metabolic trapping, and may also regulate the channeling of fatty acids towards specific metabolic pathways. The implication of ACS enzymes in widespread lipid associated diseases like type 2 diabetes has rekindled interest in this protein family. Here, we describe in detail how to measure long-chain fatty acyl-CoA synthetase activity by a straightforward radiometric assay. Cell lysates are incubated with ATP, coenzyme A, Mg(2+), and radiolabeled fatty acid bound to BSA. Differential phase partitioning of fatty acids and acyl-CoAs is exploited to quantify the amount of generated acyl-CoA by scintillation counting. The high sensitivity of this assay also allows the analysis of small samples like patient biopsies.

Characterization of the promoter region of the bovine long-chain acyl-CoA synthetase 1 gene: Roles of E2F1, Sp1, KLF15, and E2F4

The nutritional value and eating qualities of beef are enhanced when the unsaturated fatty acid content of fat is increased. Long-chain acyl-CoA synthetase 1 (ACSL1) plays key roles in fatty acid transport and degradation, as well as lipid synthesis. It has been identified as a plausible functional and positional candidate gene for manipulations of fatty acid composition in bovine skeletal muscle. In the present study, we determined that bovine ACSL1was highly expressed in subcutaneous adipose tissue and longissimus thoracis. To elucidate the molecular mechanisms involved in bovine ACSL1 regulation, we cloned and characterized the promoter region of ACSL1. Applying 5′-rapid amplification of cDNA end analysis (RACE), we identified multiple transcriptional start sites (TSSs) in its promoter region. Using a series of 5′ deletion promoter plasmids in luciferase reporter assays, we found that the proximal minimal promoter of ACSL1 was located within the region −325/−141 relative to the TSS and it was also located in the predicted CpG island. Mutational analysis and electrophoretic mobility shift assays demonstrated that E2F1, Sp1, KLF15 and E2F4 binding to the promoter region drives ACSL1 transcription. Together these interactions integrate and frame a key functional role for ACSL1 in mediating the lipid composition of beef.

Generation and esterification of electrophilic fatty acid nitroalkenes in triacylglycerides

Electrophilic fatty acid nitroalkenes (NO(2)-FA) are products of nitric oxide and nitrite-mediated unsaturated fatty acid nitration. These electrophilic products induce pleiotropic signaling actions that modulate metabolic and inflammatory responses in cell and animal models. The metabolism of NO(2)-FA includes reduction of the vinyl nitro moiety by prostaglandin reductase-1, mitochondrial β-oxidation, and Michael addition with low molecular weight nucleophilic amino acids. Complex lipid reactions of fatty acid nitroalkenes are not well defined. Herein we report the detection and characterization of NO(2)-FA-containing triacylglycerides (NO(2)-FA-TAG) via mass spectrometry-based methods. In this regard, unsaturated fatty acids of dietary triacylglycerides are targets for nitration reactions during gastric acidification, where NO(2)-FA-TAG can be detected in rat plasma after oral administration of nitro-oleic acid (NO(2)-OA). Furthermore, the characterization and profiling of these species, including the generation of beta oxidation and dehydrogenation products, could be detected in NO(2)-OA-supplemented adipocytes. These data revealed that NO(2)-FA-TAG, formed by either the direct nitration of esterified unsaturated fatty acids or the incorporation of nitrated free fatty acids into triacylglycerides, contribute to the systemic distribution of these reactive electrophilic mediators and may serve as a depot for subsequent mobilization by lipases to in turn impact adipocyte homeostasis and tissue signaling events.

Inhibition of long-chain acyl-CoA synthetase 4 facilitates production of 5, 11-dihydroxyeicosatetraenoic acid via the cyclooxygenase-2 pathway

Long chain acyl-CoA synthetases (ACSLs) are a family of enzymes that convert free long chain fatty acids into their acyl-CoA forms. Among ACSL enzymes, ACSL4 prefers arachidonic acid (AA) as a substrate and plays an important role in re-esterification of free AA. We previously reported that the suppression of ACSL4 activity by treatment with an ACSL inhibitor or a small interfering RNA markedly enhanced interleukin-1β (IL-1β)-dependent prostaglandin (PG) biosynthesis in rat fibroblastic 3Y1 cells. We show here that in addition to these prostanoids, cytokine-dependent production of 5,11-dihydroxyeicosatetraenoic acid (5,11-diHETE), a cyclooxygenase product of 5-hydroxyeicosatetraenoic acid (5-HETE), was enhanced by the inhibition of ACSL4 activity. Treatment of several types of cells with an ACSL inhibitor, triacsin C, markedly enhanced IL-1β-dependent production of 5,11-diHETE. siRNA-mediated knockdown of ACSL4 also enhanced IL-1β-dependent production of 5,11-diHETE from 3Y1 cells. The production of 5,11-diHETE was significantly decreased by a cyclooxygenase (COX)-2 selective inhibitor, NS-398, but not by a 5-lipoxygenase activating protein (FLAP) inhibitor, MK-886. The inhibition of ACSL enzymes significantly facilitated release of not only 5-HETE but also 8-HETE, 9-HETE, 11-HETE, 12-HETE, and 15-HETE, independently of IL-1β stimulation. In vitro analysis showed that a recombinant COX-2 enzyme more effectively metabolized 5(S)-HETE to 5-11-diHETE compared to COX-1 enzyme. From these results, we proposed the following mechanism of 5,11-diHETE biosynthesis in these cells: 1) inhibition of ACSL4 causes accumulation of free AA; 2) the accumulated AA is nonspecifically converted into various HETEs; and 3) among these HETEs, 5-HETE is metabolized into 5,11-diHETE by cytokine-induced COX-2.

Lipid droplets in activated mast cells - a significant source of triglyceride-derived arachidonic acid for eicosanoid production

Mast cells are potent effectors of immune reactions and key players in various inflammatory diseases such as atherosclerosis, asthma, and rheumatoid arthritis. The cellular defense response of mast cells represents a unique and powerful system, where external signals can trigger cell activation resulting in a stimulus-specific and highly coordinated release of a plethora of bioactive mediators. The arsenal of mediators encompasses preformed molecules stored in cytoplasmic secretory granules, as well as newly synthesized proteinaceous and lipid mediators. The release of mediators occurs in strict chronological order and requires proper coordination between the endomembrane system and various enzymatic machineries. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoid biosynthesis. Recent studies have revealed that not only phospholipids in mast cell membranes, but also triglycerides in mast cell lipid droplets are a substrate source for eicosanoid formation. The present review summarizes current knowledge about mast cell lipid droplet biology, and discusses expansions and challenges of traditional mechanistic models for eicosanoid production.

Polyunsaturated fatty acid-phospholipid remodeling and inflammation

PURPOSE OF REVIEW

To highlight some of the recent advances related to the control of polyunsaturated fatty acid (PUFA) incorporation and remodeling in membrane glycerophospholipids in inflammatory cells.

RECENT FINDINGS

Several enzymes have recently been identified that are associated with the control of PUFA incorporation and remodeling into membrane phospholipids and their release. The functional roles of the different enzyme isotypes in the control of PUFA availability for lipid mediator biosynthesis and cell signaling are only now being established. The expression of specific acyl-CoA synthetase, lysophospholipid acyltransferase and phospholipase A2 isotypes has recently been shown to have an impact on membrane PUFA content, on the production of lipid mediators and on inflammation.

SUMMARY

A better understanding of the complex processes associated with the control PUFA remodeling in membrane phospholipids may lead to the discovery of new therapeutic targets for the treatment of inflammatory diseases.

Long-chain acyl-CoA synthetase in fatty acid metabolism involved in liver and other diseases: An update

Long-chain acyl-CoA synthetase (ACSL) family members include five different ACSL isoforms, each encoded by a separate gene and have multiple spliced variants. ACSLs on endoplasmic reticulum and mitochondrial outer membrance catalyze fatty acids with chain lengths from 12 to 20 carbon atoms to form acyl-CoAs, which are lipid metabolic intermediates and involved in fatty acid metabolism, membrane modifications and various physiological processes. Gain- or loss-of-function studies have shown that the expression of individual ACSL isoforms can alter the distribution and amount of intracellular fatty acids. Changes in the types and amounts of fatty acids, in turn, can alter the expression of intracellular ACSLs. ACSL family members affect not only the proliferation of normal cells, but the proliferation of malignant tumor cells. They also regulate cell apoptosis through different signaling pathways and molecular mechanisms. ACSL members have individual functions in fatty acid metabolism in different types of cells depending on substrate preferences, subcellular location and tissue specificity, thus contributing to liver diseases and metabolic diseases, such as fatty liver disease, obesity, atherosclerosis and diabetes. They are also linked to neurological disorders and other diseases. However, the mechanisms are unclear. This review addresses new findings in the classification and properties of ACSLs and the fatty acid metabolism-associated effects of ACSLs in diseases.

Metabolomics and diabetes: analytical and computational approaches

Diabetes is characterized by altered metabolism of key molecules and regulatory pathways. The phenotypic expression of diabetes and associated complications encompasses complex interactions between genetic, environmental, and tissue-specific factors that require an integrated understanding of perturbations in the network of genes, proteins, and metabolites. Metabolomics attempts to systematically identify and quantitate small molecule metabolites from biological systems. The recent rapid development of a variety of analytical platforms based on mass spectrometry and nuclear magnetic resonance have enabled identification of complex metabolic phenotypes. Continued development of bioinformatics and analytical strategies has facilitated the discovery of causal links in understanding the pathophysiology of diabetes and its complications. Here, we summarize the metabolomics workflow, including analytical, statistical, and computational tools, highlight recent applications of metabolomics in diabetes research, and discuss the challenges in the field.

PPARδ activation induces hepatic long-chain acyl-CoA synthetase 4 expression in vivo and in vitro

The arachidonic acid preferred long-chain acyl-CoA synthetase 4 (ACSL4) is a key enzyme for fatty acid metabolism in various metabolic tissues. In this study, we utilized hamsters fed a normal chow diet, a high-fat diet or a high cholesterol and high fat diet (HCHFD) as animal models to explore novel transcriptional regulatory mechanisms for ACSL4 expression under hyperlipidemic conditions. Through cloning hamster ACSL4 homolog and tissue profiling ACSL4 mRNA and protein expressions we observed a selective upregulation of ACSL4 in testis and liver of HCHFD fed animals. Examination of transcriptional activators of the ACSL family revealed an increased hepatic expression of PPARδ but not PPARα in HCHFD fed hamsters. To explore a role of PPARδ in dietary cholesterol-mediated upregulation of ACSL4, we administered a PPARδ specific agonist L165041 to normolipidemic and dyslipidemic hamsters. We observed significant increases of hepatic ACSL4 mRNA and protein levels in all L165041-treated hamsters as compared to control animals. The induction of ACSL4 expression by L165041 in liver tissue in vivo was recapitulated in human primary hepatocytes and hepatocytes isolated from hamster and mouse. Moreover, employing the approach of adenovirus-mediated gene knockdown, we showed that depletion of PPARδ in hamster hepatocytes specifically reduced ACSL4 expression. Finally, utilizing HepG2 as a model system, we demonstrate that PPARδ activation leads to increased ACSL4 promoter activity, mRNA and protein expression, and consequently higher arachidonoyl-CoA synthetase activity. Taken together, we have discovered a novel PPARδ-mediated regulatory mechanism for ACSL4 expression in liver tissue and cultured hepatic cells.