Mammalian long-chain acyl-CoA synthetases

Severe riboflavin deficiency induces alterations in the hepatic proteome of starter Pekin ducks

Suboptimal vitamin B2 status is encountered globally. Riboflavin deficiency depresses growth and results in a fatty liver. The underlying mechanisms remain to be established and an overview of molecular alterations is lacking. We investigated hepatic proteome changes induced by riboflavin deficiency to explain its effects on growth and hepatic lipid metabolism. In all, 360 1-d-old Pekin ducks were divided into three groups of 120 birds each, with twelve replicates and ten birds per replicate. For 21 d, the ducks were fed ad libitum a control diet (CAL), a riboflavin-deficient diet (RD) or were pair-fed with the control diet to the mean daily intake of the RD group (CPF). When comparing RD with CAL and CPF, growth depression, liver enlargement, liver lipid accumulation and enhanced liver SFA (C6 : 0, C12 : 0, C16 : 0, C18 : 0) were observed. In RD, thirty-two proteins were enhanced and thirty-one diminished (>1·5-fold) compared with CAL and CPF. Selected proteins were confirmed by Western blotting. The diminished proteins are mainly involved in fatty acid β-oxidation and the mitochondrial electron transport chain (ETC), whereas the enhanced proteins are mainly involved in TAG and cholesterol biosynthesis. RD causes liver lipid accumulation and growth depression probably by impairing fatty acid β-oxidation and ETC. These findings contribute to our understanding of the mechanisms of liver lipid metabolic disorders due to RD.

Phosphatidylserine decarboxylase CT699, lysophospholipid acyltransferase CT775, and acyl-ACP synthase CT776 provide membrane lipid diversity to Chlamydia trachomatis

De novo lipid synthesis and scavenging of fatty acids (FA) are processes essential for the formation of the membrane of the human pathogen Chlamydia trachomatis (C.t.). Host FA are assimilated via esterification by the bacterial acyl-acyl carrier protein (ACP) synthase AasC but inhibitors of the host acyl-CoA synthetase enymes ACSL also impaired growth of C.t. in human cells. In E. coli, activity of AasC was sensitive to triacsin C and rosiglitazone G. The absence of a triacsin C-insensitive pathway and the increased inhibition by rosiglitazone G confirmed the sensitivity of the bacterial acyl-ACP synthase to these drugs in infected human cells. We found no evidence that the human ACSL enzymes are required for lipid formation by C.t. The broad substrate specificity of acyltransferase CT775 provides C.t. with the capacity to incorporate straight-chain and bacterial specific branched-chain fatty acids. CT775 accepts both acyl-ACP and acyl-CoA as acyl donors and, 1- or 2-acyl isomers of lysophosphoplipids as acyl acceptors. The enzyme responsible for remodeling of human phosphatidylserine to bacterial phosphatidylethanolamine was identified as CT699. These findings provide evidence that the pathogen has the ability to extend the lipid diversity of its membrane.

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.

Valnoctamide, which reduces rat brain arachidonic acid turnover, is a potential non-teratogenic valproate substitute to treat bipolar disorder

BACKGROUND

Valproic acid (VPA), used for treating bipolar disorder (BD), is teratogenic by inhibiting histone deacetylase. In unanaesthetized rats, chronic VPA, like other mood stabilizers, reduces arachidonic acid (AA) turnover in brain phospholipids, and inhibits AA activation to AA-CoA by recombinant acyl-CoA synthetase-4 (Acsl-4) in vitro. Valnoctamide (VCD), a non-teratogenic constitutional isomer of VPA amide, reported effective in BD, also inhibits recombinant Acsl-4 in vitro.

HYPOTHESIS

VCD like VPA will reduce brain AA turnover in unanaesthetized rats.

METHODS

A therapeutically relevant (50mg/kg i.p.) dose of VCD or vehicle was administered daily for 30 days to male rats. AA turnover and related parameters were determined using our kinetic model, following intravenous [1-¹⁴C]AA in unanaesthetized rats for 10min, and measuring labeled and unlabeled lipids in plasma and high-energy microwaved brain.

RESULTS

VCD, compared with vehicle, increased λ, the ratio of brain AA-CoA to unesterified plasma AA specific activities; and decreased turnover of AA in individual and total brain phospholipids.

CONCLUSIONS

VCD's ability like VPA to reduce rat brain AA turnover and inhibit recombinant Acsl-4, and its efficacy in BD, suggest that VCD be further considered as a non-teratogenic VPA substitute for treating BD.

Effects of dietary lipids on the hepatopancreas transcriptome of Chinese mitten crab (Eriocheir sinensis)

Fish oil supplies worldwide have declined sharply over the years. To reduce the use of fish oil in aquaculture, many studies have explored the effects of fish oil substitutions on aquatic animals. To illustrate the effects of dietary lipids on Chinese mitten crab and to improve the use of vegetable oils in the diet of the crabs, 60 male juvenile Chinese mitten crabs were fed one of five diets for 116 days: fish oil (FO), soybean oil (SO), linseed oil (LO), FO + SO (1:1, FSO), and FO + LO (1:1, FLO). Changes in the crab hepatopancreas transcriptome were analyzed using RNA sequencing. There were a total 55,167 unigenes obtained from the transcriptome, of which the expression of 3030 was significantly altered in the FLO vs. FO groups, but the expression of only 412 unigenes was altered in the FSO vs. FO groups. The diets significantly altered the expression of many enzymes involved in lipid metabolism, such as pancreatic lipase, long-chain acyl-CoA synthetases, carnitine palmitoyltransferase I, acetyl-CoA carboxylase, fatty acid synthase, and fatty acyl Δ9-desaturase. The dietary lipids also affected the Toll-like receptor and Janus activated kinase-signal transducers and activators of transcription signaling pathways. Our results indicate that substituting fish oil with vegetable oils in the diet of Chinese mitten crabs might decrease the digestion and absorption of dietary lipids, fatty acids biosynthesis, and immunologic viral defense, and increase β-oxidation by altering the expression of the relevant genes. Our results lay the foundation for further understanding of lipid nutrition in Chinese mitten crab.

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.

17β-estradiol-induced ACSL4 protein expression promotes an invasive phenotype in estrogen receptor positive mammary carcinoma cells

Long chain acyl-CoA synthase-4 (ACSL4) expression has been associated with an aggressive phenotype in breast carcinoma cells, whereas its role in ERα-positive breast cancer has not been studied. ACSL4 prefers 20-carbon polyunsaturated fatty acid (PUFA) substrates, and along with other ACSLs has been associated with cellular uptake of exogenous fatty acids. 17β-estradiol induces proliferation and invasive capacities in ERα+ve breast carcinoma that is associated with modifications of cellular lipid metabolism. In this study, treatment of steroid-starved ERα-positive MCF-7 and T47D mammary carcinoma cells with 17β-estradiol resulted in increased cellular uptake of the PUFA arachidonic acid (AA) and eicosapentaenoic acid (EPA), important building blocks for cellular membranes, and increased ACSL4 protein levels. There was no change in the expression of the ACSL1, ACSL3 and ACSL6 protein isotypes. Increased ACSL4 protein expression was not accompanied by changes in ACSL4 mRNA expression, but was associated with a significant increase in the protein half-life compared to untreated cells. ERα silencing reversed the impact of 17β-estradiol on ACSL4 protein levels and half-life. Silencing of ACSL4 eliminated the 17β-estradiol-induced increase in AA and EPA uptake, as well as the 17β-estradiol-induced cell migration, proliferation and invasion capacities. ASCL4 silencing also prevented the 17β-estradiol induced increases in p-Akt and p-GSK3β, and decrease in E-cadherin expression, important events in epithelial to mesenchymal transition. Taken together, these results demonstrate that ACSL4 is a target of 17β-estradiol-stimulated ERα and is required for the cellular uptake of exogenous PUFA and the manifestation of a more malignant phenotype in ERα+ve breast carcinoma cells.

Proteomic signature of muscle fibre hyperplasia in response to faba bean intake in grass carp

Fish muscle growth is important for the rapidly developing global aquaculture industry, particularly with respect to production and quality. Changes in muscle fibre size are accomplished by altering the balance between protein synthesis and proteolysis. However, our understanding regarding the effects of different protein sources on fish muscle proteins is still limited. Here we report on the proteomic profile of muscle fibre hyperplasia in grass carp fed only with whole faba bean. From the results, a total of 99 significantly changed proteins after muscle hyperplasia increase were identified (p < 0.05, ratio <0.5 or >2). Protein–protein interaction analysis demonstrated the presence of a network containing 56 differentially expressed proteins, and muscle fibre hyperplasia was closely related to a protein–protein network of 12 muscle component proteins. Muscle fibre hyperplasia was also accompanied by decreased abundance in the fatty acid degradation and calcium signalling pathways. In addition, metabolism via the pentose phosphate pathway decreased in grass carp after ingestion of faba bean, leading to haemolysis. These findings could provide a reference for the prevention and treatment of human glucose-6-phosphate dehydrogenase deficiency (“favism”).

Phytosphingosine degradation pathway includes fatty acid α-oxidation reactions in the endoplasmic reticulum

Although normal fatty acids (FAs) are degraded via β-oxidation, unusual FAs such as 2-hydroxy (2-OH) FAs and 3-methyl-branched FAs are degraded via α-oxidation. Phytosphingosine (PHS) is one of the long-chain bases (the sphingolipid components) and exists in specific tissues, including the epidermis and small intestine in mammals. In the degradation pathway, PHS is converted to 2-OH palmitic acid and then to pentadecanoic acid (C15:0-COOH) via FA α-oxidation. However, the detailed reactions and genes involved in the α-oxidation reactions of the PHS degradation pathway have yet to be determined. In the present study, we reveal the entire PHS degradation pathway: PHS is converted to C15:0-COOH via six reactions [phosphorylation, cleavage, oxidation, CoA addition, cleavage (C1 removal), and oxidation], in which the last three reactions correspond to the α-oxidation. The aldehyde dehydrogenase ALDH3A2 catalyzes both the first and second oxidation reactions (fatty aldehydes to FAs). In Aldh3a2-deficient cells, the unmetabolized fatty aldehydes are reduced to fatty alcohols and are incorporated into ether-linked glycerolipids. We also identify HACL2 (2-hydroxyacyl-CoA lyase 2) [previous name, ILVBL; ilvB (bacterial acetolactate synthase)-like] as the major 2-OH acyl-CoA lyase involved in the cleavage (C1 removal) reaction in the FA α-oxidation of the PHS degradation pathway. HACL2 is localized in the endoplasmic reticulum. Thus, in addition to the already-known FA α-oxidation in the peroxisomes, we have revealed the existence of FA α-oxidation in the endoplasmic reticulum in mammals.

Ceramide Is Metabolized to Acylceramide and Stored in Lipid Droplets

In an approach aimed at defining interacting partners of ceramide synthases (CerSs), we found that fatty acyl-CoA synthase ACSL5 interacts with all CerSs. We demonstrate that ACSL5-generated FA-CoA was utilized with de novo ceramide for the generation of acylceramides, poorly studied ceramide metabolites. Functionally, inhibition of ceramide channeling to acylceramide enhanced accumulation of de novo ceramide and resulted in augmentation of ceramide-mediated apoptosis. Mechanistically, we show that acylceramide generation is catalyzed by diacylglycerol acyltransferase 2 (DGAT2) on lipid droplets. In summary, this study identifies a metabolic pathway of acylceramide generation and its sequestration in LDs in cells and in livers of mice on a high-fat diet. The study also implicates this pathway in ceramide-mediated apoptosis, and has implications in co-regulation of triglyceride and sphingolipid metabolisms.

Analysis of large versus small dogs reveals three genes on the canine X chromosome associated with body weight, muscling and back fat thickness

Domestic dog breeds display significant diversity in both body mass and skeletal size, resulting from intensive selective pressure during the formation and maintenance of modern breeds. While previous studies focused on the identification of alleles that contribute to small skeletal size, little is known about the underlying genetics controlling large size. We first performed a genome-wide association study (GWAS) using the Illumina Canine HD 170,000 single nucleotide polymorphism (SNP) array which compared 165 large-breed dogs from 19 breeds (defined as having a Standard Breed Weight (SBW) >41 kg [90 lb]) to 690 dogs from 69 small breeds (SBW ≤41 kg). We identified two loci on the canine X chromosome that were strongly associated with large body size at 82-84 megabases (Mb) and 101-104 Mb. Analyses of whole genome sequencing (WGS) data from 163 dogs revealed two indels in the Insulin Receptor Substrate 4 (IRS4) gene at 82.2 Mb and two additional mutations, one SNP and one deletion of a single codon, in Immunoglobulin Superfamily member 1 gene (IGSF1) at 102.3 Mb. IRS4 and IGSF1 are members of the GH/IGF1 and thyroid pathways whose roles include determination of body size. We also found one highly associated SNP in the 5'UTR of Acyl-CoA Synthetase Long-chain family member 4 (ACSL4) at 82.9 Mb, a gene which controls the traits of muscling and back fat thickness. We show by analysis of sequencing data from 26 wolves and 959 dogs representing 102 domestic dog breeds that skeletal size and body mass in large dog breeds are strongly associated with variants within IRS4, ACSL4 and IGSF1.

Characterization of Acyl-CoA synthetase isoforms in pancreatic beta cells: Gene silencing shows participation of ACSL3 and ACSL4 in insulin secretion

Long-chain acyl-CoA synthetases (ACSLs) convert fatty acids to fatty acyl-CoAs to regulate various physiologic processes. We characterized the ACSL isoforms in a cell line of homogeneous rat beta cells (INS-1 832/13 cells) and human pancreatic islets. ACSL4 and ACSL3 proteins were present in the beta cells and human and rat pancreatic islets and concentrated in insulin secretory granules and less in mitochondria and negligible in other intracellular organelles. ACSL1 and ACSL6 proteins were not seen in INS-1 832/13 cells or pancreatic islets. ACSL5 protein was seen only in INS-1 832/13 cells. With shRNA-mediated gene silencing we developed stable ACSL knockdown cell lines from INS-1 832/13 cells. Glucose-stimulated insulin release was inhibited ∼50% with ACSL4 and ACSL3 knockdown and unaffected in cell lines with knockdown of ACSL5, ACLS6 and ACSL1. Lentivirus shRNA-mediated gene silencing of ACSL4 and ACSL3 in human pancreatic islets inhibited glucose-stimulated insulin release. ACSL4 and ACSL3 knockdown cells showed inhibition of ACSL enzyme activity more with arachidonate than with palmitate as a substrate, consistent with their preference for unsaturated fatty acids as substrates. ACSL4 knockdown changed the patterns of fatty acids in phosphatidylserines and phosphatidylethanolamines. The results show the involvement of ACLS4 and ACLS3 in insulin secretion.

Of mice and humans through the looking glass: "reflections" on epigenetics of lipid metabolism

Over the past decade, epigenetics has emerged as a new layer of regulation of gene expression. Several investigations demonstrated that nutrition and lifestyle regulate lipid metabolism by influencing epigenomic remodeling. Studies on animal models highlighted the role of epigenome modifiers in specific metabolic contexts and established clear links between dysregulation of epigenetic mechanisms and metabolic dysfunction. The relevance of findings in animal models has been translated to humans, as epigenome-wide association studies (EWAS) deeply investigated the relationship between lifestyle and epigenetics in human populations. In this review, we will provide an outlook of recent studies addressing the link between epigenetics and lipid metabolism, by comparing results obtained in animal models and in human subjects.

Detection of Placental Proteomes at Different Uterine Positions in Large White and Meishan Gilts on Gestational Day 90

Within-litter uniformity in pigs is a major factor affecting piglet survival and growth performance. We know that Meishan (MS) gilts have higher piglet survival rate than Large White (LW) gilts because their foetal weight is less varied. To understand the molecular basis for placental nutritional transport during the late stages of gestation in LW and MS, we employed the isobaric tags for relative and absolute quantification (iTRAQ) method to investigate alterations in the placental proteomes of LW and MS gilts on gestational day 90. Investigation of foetal weight at different uterine positions revealed that the foetal and placental weights as well as the foetal concentration of glucose were significantly higher in LW gilts positioned towards the utero-tubal junction than in those positioned toward the cervix; however, no such differences were observed in MS gilts, and MS gilts had a greater uniformity in foetal weight on day 90 of gestation. Comparisons of the proteomes between placentas positioned toward the cervix and those positioned toward the utero-tubal junction identified 38 differentially expressed proteins in the two breeds. These proteins play a central role in nutrient transport and metabolism, as well as in transcriptional and translational regulation. Of particular interest is the finding that the placentas of LW gilts showed 14 differential expression of proteins mainly related to lipid transport and energy metabolism (including solute carrier family 27, mitochondrial trifunctional protein, and NADH dehydrogenase [ubiquinone] flavoprotein 2), but only 2 proteins in MS gilts. In contrast, the differentially expressed proteins in MS gilts were primarily involved in transcriptional and translational regulation (such as ribosome-sec61 and 40S ribosomal protein S23), with a few related to glucose and coenzyme transport and metabolism (including glucose transport protein and ferrochelatase). Our results revealed that placental lipid and energy metabolism might play a crucial role in the regulation of foetal weight, based on uterine position in two distinct pig breeds. These findings provide a deeper understanding of placental efficiency that can be utilized to provide a new method to enhance the efficiency of livestock production.

Identification of Hepatic Lysophosphatidylcholine Acyltransferase 3 as a Novel Target Gene Regulated by Peroxisome Proliferator-activated Receptor δ

Peroxisome proliferator-activated receptor δ (PPARδ) regulates many genes involved in lipid metabolism. Hepatic lysophosphatidylcholine acyltransferase 3 (LPCAT3) has critical functions in triglycerides transport and endoplasmic reticulum stress response due to its unique ability to catalyze the incorporation of polyunsaturated fatty acids into phospholipids. Previous studies identified liver X receptor as the transcription factor controlling LPCAT3 expression in mouse liver tissue. Here we show that the hepatic LPCAT3 gene is transcriptionally regulated by PPARδ. Adenovirus-mediated knockdown of PPARδ in cultured hepatic cells and liver tissue reduced LPCAT3 mRNA levels, and exogenous overexpression of PPARδ increased LPCAT3 mRNA expression. Activation of PPARδ in HepG2, Huh7, and Hepa 1-6 cells with its specific agonists increased LPCAT3 mRNA levels in all three hepatic cell lines. Through conducting sequence analysis, LPCAT3 promoter assays, and direct DNA binding assays, we have mapped the functional PPAR-responsive element to a proximal region from -135 to -123 of the LPCAT3 promoter that plays an essential role in mediating PPARδ-induced transactivation of the LPCAT3 gene. Finally, we have provided in vivo evidence showing that activation of PPARδ by agonist L165041 in mice increased hepatic LPCAT3 mRNA abundance and LPCAT enzymatic activity, which is associated with increased incorporations of arachidonate into liver phosphatidylcholine and phosphatidylethanolamine. Furthermore, transient liver-specific knockdown of LPCAT3 in mice affected PPARδ-mediated activation of several hepatic genes involving in FA metabolism. Altogether, our new findings identify LPCAT3 as a direct PPARδ target gene and suggest a novel function of PPARδ in regulation of phospholipid metabolism through LPCAT3.

Molecular cloning and nutrient regulation analysis of long chain acyl-CoA synthetase 1 gene in grass carp, Ctenopharyngodon idella L

Long chain acyl-CoA synthetase 1 (ACSL1), a key regulatory enzyme of fatty acid metabolism, catalyzes the conversion of long-chain fatty acids to acyl-coenzyme A. The full-length cDNAs of ACSL1a and ACSL1b were cloned from the liver of a grass carp. Both cDNAs contained a 2094bp open reading frame encoding 697 amino acids. Amino acid sequence alignment showed that ACSL1a shared 73.5% sequence identity with ACSL1b. Each of the two ACSL1s proteins had a transmembrane domain, a P-loop domain, and L-, A-, and G-motifs, which were relatively conserved in comparison to other vertebrates. Relative expression profile of ACSL1 mRNAs in different tissues indicated that ACSL1a is highly expressed in heart, mesenteric adipose, and brain tissues, whereas ACSL1b is highly expressed in heart, white muscle, foregut, and liver tissues. Nutrient regulation research showed that the expression levels of ACSL1a and ACSL1b were significantly down-regulated when 3, 6, and 9% fish oil were added in diet of grass carp as compared to the control group. However, no significant difference in the levels of ACSL1 mRNA was observed between the experimental groups. This study demonstrated the relationship between ACSL1a and ACSL1b genes in grass carp and laid a foundation for further research on ACSL family members in other species.

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.

A novel transgenic mouse model of lysosomal storage disorder

Knockout technology has proven useful for delineating functional roles of specific genes. Here we describe and provide an explanation for striking pathology that occurs in a subset of genetically engineered mice expressing a rat Ca_Vβ2a transgene under control of the cardiac α-myosin heavy chain promoter. Lesions were limited to mice homozygous for transgene and independent of native Cacnb2 genomic copy number. Gross findings included an atrophied pancreas; decreased adipose tissue; thickened, orange intestines; and enlarged liver, spleen, and abdominal lymph nodes. Immune cell infiltration and cell engulfment by macrophages were associated with loss of pancreatic acinar cells. Foamy macrophages diffusely infiltrated the small intestine's lamina propria, while similar macrophage aggregates packed liver and splenic red pulp sinusoids. Periodic acid-Schiff-positive, diastase-resistant, iron-negative, Oil Red O-positive, and autofluorescent cytoplasm was indicative of a lipid storage disorder. Electron microscopic analysis revealed liver sinusoids distended by clusters of macrophages containing intracellular myelin "swirls" and hepatocytes with enlarged lysosomes. Additionally, build up of cholesterol, cholesterol esters, and triglycerides, along with changes in liver metabolic enzyme levels, were consistent with a lipid processing defect. Because of this complex pathology, we examined the transgene insertion site. Multiple transgene copies inserted into chromosome 19; at this same site, an approximate 180,000 base pair deletion occurred, ablating cholesterol 25-hydroxylase and partially deleting lysosomal acid lipase and CD95 Loss of gene function can account for the altered lipid processing, along with hypertrophy of the immune system, which define this phenotype, and serendipitously provides a novel mouse model of lysosomal storage disorder.

Lipid metabolism in Rhodnius prolixus: Lessons from the genome

The kissing bug Rhodnius prolixus is both an important vector of Chagas' disease and an interesting model for investigation into the field of physiology, including lipid metabolism. The publication of this insect genome will bring a huge amount of new molecular biology data to be used in future experiments. Although this work represents a promising scenario, a preliminary analysis of the sequence data is necessary to identify and annotate the genes involved in lipid metabolism. Here, we used bioinformatics tools and gene expression analysis to explore genes from different genes families and pathways, including genes for fat breakdown, as lipases and phospholipases, and enzymes from β-oxidation, fatty acid metabolism, and acyl-CoA and glycerolipid synthesis. The R. prolixus genome encodes 31 putative lipase genes, including 21 neutral lipases and 5 acid lipases. The expression profiles of some of these genes were analyzed. We were able to identify nine phospholipase A2 genes. A variety of gene families that participate in fatty acid synthesis and modification were studied, including fatty acid synthase, elongase, desaturase and reductase. Concerning the synthesis of glycerolipids, we found a second isoform of glycerol-3-phosphate acyltransferase that was ubiquitously expressed throughout the organs. Finally, all genes involved in fatty acid β-oxidation were identified, but not a long-chain acyl-CoA dehydrogenase. These results provide fundamental data to be used in future research on insect lipid metabolism and its possible relevance to Chagas' disease transmission.

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.

On the cellular metabolism of the click chemistry probe 19-alkyne arachidonic acid

Alkyne and azide analogs of natural compounds that can be coupled to sensitive tags by click chemistry are powerful tools to study biological processes. Arachidonic acid (AA) is a FA precursor to biologically active compounds. 19-Alkyne-AA (AA-alk) is a sensitive clickable AA analog; however, its use as a surrogate to study AA metabolism requires further evaluation. In this study, AA-alk metabolism was compared with that of AA in human cells. Jurkat cell uptake of AA was 2-fold greater than that of AA-alk, but significantly more AA-Alk was elongated to 22:4. AA and AA-alk incorporation into and remodeling between phospholipid (PL) classes was identical indicating equivalent CoA-independent AA-PL remodeling. Platelets stimulated in the pre-sence of AA-alk synthesized significantly less 12-lipoxygenase (12-LOX) and cyclooxygenase products than in the presence of AA. Ionophore-stimulated neutrophils produced significantly more 5-LOX products in the presence of AA-alk than AA. Neutrophils stimulated with only exogenous AA-alk produced significantly less 5-LOX products compared with AA, and leukotriene B₄ (LTB₄₎-alk was 12-fold less potent at stimulating neutrophil migration than LTB₄, collectively indicative of weaker leukotriene B₄ receptor 1 agonist activity of LTB₄-alk. Overall, these results suggest that the use of AA-alk as a surrogate for the study of AA metabolism should be carried out with caution.

Acyl-CoA synthetase long-chain 5 genotype is associated with body composition changes in response to lifestyle interventions in postmenopausal women with overweight and obesity: a genetic association study on cohorts Montréal-Ottawa New Emerging Team, and Complications Associated with Obesity

BACKGROUND

Genetic studies on Acyl-CoA Synthetase Long-Chain 5 (ACSL5) demonstrate an association between rs2419621 genotype and rate of weight loss in women with obesity in response to caloric restriction. Our objectives were to (1) confirm results in two different populations of women with overweight and obesity (2) study rs2419621's influence on body composition parameters of women with overweight and obesity following lifestyle interventions.

METHODS

rs2419621 genotype was determined in women with overweight and obesity who participated in the Montréal-Ottawa New Emerging Team (MONET n = 137) and Complications Associated with Obesity (CAO n = 37) studies. Genotyping was done using TaqMan MGB probe-based assay. Multiple linear regression analyses were used to test for associations.

RESULTS

When studying women with overweight and obesity, rs2419621 [T] allele carriers had a significantly greater decrease in visceral fat, absolute and percent fat mass and a greater increase in percent lean mass in response to lifestyle intervention in comparison to non-carriers. Studying only individuals with obesity showed similar results with rs2419621 [T] allele carriers also displaying a significantly greater decrease in body mass index following the lifestyle intervention in comparison to non-carriers.

CONCLUSION

Women with overweight and obesity carrying the ACSL5 rs2419621 [T] allele are more responsive to lifestyle interventions in comparison to non-carriers. Conducting such genetic association studies can aid in individualized treatments/interventions catered towards an individual's genotype.

Fatty Acid Oxidation Mediated by Acyl-CoA Synthetase Long Chain 3 Is Required for Mutant KRAS Lung Tumorigenesis

KRAS is one of the most commonly mutated oncogenes in human cancer. Mutant KRAS aberrantly regulates metabolic networks. However, the contribution of cellular metabolism to mutant KRAS tumorigenesis is not completely understood. We report that mutant KRAS regulates intracellular fatty acid metabolism through Acyl-coenzyme A (CoA) synthetase long-chain family member 3 (ACSL3), which converts fatty acids into fatty Acyl-CoA esters, the substrates for lipid synthesis and β-oxidation. ACSL3 suppression is associated with depletion of cellular ATP and causes the death of lung cancer cells. Furthermore, mutant KRAS promotes the cellular uptake, retention, accumulation, and β-oxidation of fatty acids in lung cancer cells in an ACSL3-dependent manner. Finally, ACSL3 is essential for mutant KRAS lung cancer tumorigenesis in vivo and is highly expressed in human lung cancer. Our data demonstrate that mutant KRAS reprograms lipid homeostasis, establishing a metabolic requirement that could be exploited for therapeutic gain.

Identification of Novel Genetic Determinants of Erythrocyte Membrane Fatty Acid Composition among Greenlanders

Fatty acids (FAs) are involved in cellular processes important for normal body function, and perturbation of FA balance has been linked to metabolic disturbances, including type 2 diabetes. An individual’s level of FAs is affected by diet, lifestyle, and genetic variation. We aimed to improve the understanding of the mechanisms and pathways involved in regulation of FA tissue levels, by identifying genetic loci associated with inter-individual differences in erythrocyte membrane FA levels. We assessed the levels of 22 FAs in the phospholipid fraction of erythrocyte membranes from 2,626 Greenlanders in relation to single nucleotide polymorphisms genotyped on the MetaboChip or imputed. We identified six independent association signals. Novel loci were identified on chromosomes 5 and 11 showing strongest association with oleic acid (rs76430747 in ACSL6, beta (SE): -0.386% (0.034), p = 1.8x10^-28) and docosahexaenoic acid (rs6035106 in DTD1, 0.137% (0.025), p = 6.4x10^-8), respectively. For a missense variant (rs80356779) in CPT1A, we identified a number of novel FA associations, the strongest with 11-eicosenoic acid (0.473% (0.035), p = 2.6x10^-38), and for variants in FADS2 (rs174570), LPCAT3 (rs2110073), and CERS4 (rs11881630) we replicated known FA associations. Moreover, we observed metabolic implications of the ACSL6 (rs76430747) and CPT1A (rs80356779) variants, which both were associated with altered HbA1c (0.051% (0.013), p = 5.6x10^-6 and -0.034% (0.016), p = 3.1x10^-4, respectively). The latter variant was also associated with reduced insulin resistance (HOMA-IR, -0.193 (0.050), p = 3.8x10^-6), as well as measures of smaller body size, including weight (-2.676 kg (0.523), p = 2.4x10^-7), lean mass (-1.200 kg (0.271), p = 1.7x10^-6), height (-0.966 cm (0.230), p = 2.0x10^-5), and BMI (-0.638 kg/m² (0.181), p = 2.8x10^-4). In conclusion, we have identified novel genetic determinants of FA composition in phospholipids in erythrocyte membranes, and have shown examples of links between genetic variants associated with altered FA membrane levels and changes in metabolic traits.

Disruption of fatty-acid balance has in several previous studies been linked to human health conditions, including the metabolic syndrome, type 2 diabetes, and insulin resistance. Composition of fatty acids in lipid membranes is influenced, not only by diet and lifestyle, but also by genetic variation. By identifying genes linked to changes in the level of specific fatty acids, it may be possible to identify biological mechanisms and pathways central to regulation of fatty-acid composition in lipid membranes. We therefore aimed at finding such genes by studying Greenlanders. We identified six genomic regions harboring variants, which were associated with the level of at least one of 22 assessed erythrocyte membrane fatty acids, including two novel regions not previously linked to fatty acid levels. Moreover, we showed that two of the identified variants were associated with altered levels of glycosylated hemoglobin, and one of these variants was associated with reduced insulin resistance and decreased measures of body size. These results contribute to our understanding of fatty acid metabolism, and support a link between fatty acid balance and metabolic health.

Mechanisms of ferroptosis

Ferroptosis is a non-apoptotic form of cell death that can be triggered by small molecules or conditions that inhibit glutathione biosynthesis or the glutathione-dependent antioxidant enzyme glutathione peroxidase 4 (GPX4). This lethal process is defined by the iron-dependent accumulation of lipid reactive oxygen species and depletion of plasma membrane polyunsaturated fatty acids. Cancer cells with high level RAS-RAF-MEK pathway activity or p53 expression may be sensitized to this process. Conversely, a number of small molecule inhibitors of ferroptosis have been identified, including ferrostatin-1 and liproxstatin-1, which can block pathological cell death events in brain, kidney and other tissues. Recent work has identified a number of genes required for ferroptosis, including those involved in lipid and amino acid metabolism. Outstanding questions include the relationship between ferroptosis and other forms of cell death, and whether activation or inhibition of ferroptosis can be exploited to achieve desirable therapeutic ends.

Bisphenol S alters embryonic viability, development, gallbladder size, and messenger RNA expression in chicken embryos exposed via egg injection

Amid concerns about the toxicological effects and environmental prevalence of bisphenol A (BPA), efforts to find suitable, safer replacement alternatives are essential. Bisphenol S (BPS) is a potential chemical substitute for BPA; however, few studies are available confirming that it has a more desirable ecotoxicological profile. In the present study, BPS was injected into the air cell of unincubated, fertilized chicken embryos at 6 concentrations ranging from 0 μg/g to 207 μg/g egg to determine effects on pipping success, development, hepatic messenger ribonucleic acid (mRNA) expression, thyroid hormone levels, and circulating bile acid concentrations. Concentrations of BPS increased in a dose-dependent manner in whole-embryo homogenates, and exposure to the highest dose, 207 μg/g, resulted in decreased pipping success (estimated median lethal dose  = 279 μg/g; 95% confidence interval = 161-486 μg/g). Exposure to BPS also reduced growth metrics including embryo mass and tarsus length, whereas the most pronounced phenotypic effect was the concentration-dependent, significant increase in gallbladder size at concentrations ≥52.8 μg/g. These adverse phenotypic outcomes were associated with the modulation of gene targets from a chicken ToxChip polymerase chain reaction array, which are involved with xenobiotic metabolism, lipid homeostasis, bile acid synthesis, and the thyroid hormone pathway. Expression levels of 2 estrogen-responsive genes, apolipoprotein II and vitellogenin, were too low at the sampling time point assessed (i.e., pipping embryos) to quantify changes, and no effects were observed on circulating free thyroxine or bile acid concentrations. The present study provides novel, whole-animal toxicological data for a BPA replacement alternative that is not well characterized. Environ Toxicol Chem 2016;35:1541-1549. © 2015 SETAC.

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.

Purification, gene cloning, and characterization of γ-butyrobetainyl CoA synthetase from Agrobacterium sp. 525a

The report is the first of purification, overproduction, and characterization of a unique γ-butyrobetainyl CoA synthetase from soil-isolated Agrobacterium sp. 525a. The primary structure of the enzyme shares 70-95% identity with those of ATP-dependent microbial acyl-CoA synthetases of the Rhizobiaceae family. As distinctive characteristics of the enzyme of this study, ADP was released in the catalytic reaction process, whereas many acyl CoA synthetases are annotated as an AMP-forming enzyme. The apparent Km values for γ-butyrobetaine, CoA, and ATP were, respectively, 0.69, 0.02, and 0.24 mM.

Very-long-chain fatty acid sphingomyelin in nuclear lipid microdomains of hepatocytes and hepatoma cells: can the exchange from C24:0 to C16:0 affect signal proteins and vitamin D receptor?

Lipid microdomains localized in the inner nuclear membrane are considered platforms for active chromatin anchoring. Stimuli such as surgery, vitamin D, or glucocorticoid drugs influence their gene expression, DNA duplication, and RNA synthesis. In this study, we used ultrafast liquid chromatography-tandem mass spectrometry to identify sphingomyelin (SM) species coupled with immunoblot analysis to comprehensively map differences in nuclear lipid microdomains (NLMs) purified from hepatocytes and hepatoma cells. We showed that NLMs lost saturated very-long-chain fatty acid (FA; C24:0) SM in cancer cells and became enriched in long-chain FA (C16:0) SM. We also found that signaling proteins, such as STAT3, Raf1, and PKCζ, were increased and vitamin D receptor was reduced in cancer cells. Because recent researches showed a shift in sphingolipid composition from C24:0 to C16:0 in relation to cell life, we performed a comparative analysis of properties among C16:0 SM, C24:0 SM, and cholesterol. Our results led us to hypothesize that the enrichment of C16:0 SM could determine enhanced dynamic properties of NLMs in cancer cells with an increased shuttling of protein signaling molecules.

Long-chain acyl-CoA synthetase 2 knockdown leads to decreased fatty acid oxidation in fat body and reduced reproductive capacity in the insect Rhodnius prolixus

Long-chain acyl-CoA esters are important intermediates in lipid metabolism and are synthesized from fatty acids by long-chain acyl-CoA synthetases (ACSL). The hematophagous insect Rhodnius prolixus, a vector of Chagas' disease, produces glycerolipids in the midgut after a blood meal, which are stored as triacylglycerol in the fat body and eggs. We identified twenty acyl-CoA synthetase genes in R. prolixus, two encoding ACSL isoforms (RhoprAcsl1 and RhoprAcsl2). RhoprAcsl1 transcripts increased in posterior midgut on the second day after feeding, and RhoprAcsl2 was highly transcribed on the tenth day. Both enzymes were expressed in Escherichia coli. Recombinant RhoprACSL1 and RhoprACSL2 had broad pH optima (7.5-9.5 and 6.5-9.5, respectively), were inhibited by triacsin C, and were rosiglitazone-insensitive. Both showed similar apparent Km for palmitic and oleic acid (2-6 μM), but different Km for arachidonic acid (0.5 and 6 μM for RhoprACSL1-Flag and RhoprACSL2-Flag, respectively). The knockdown of RhoprAcsl1 did not result in noticeable phenotypes. However, RhoprACSL2 deficient insects exhibited a 2.5-fold increase in triacylglycerol content in the fat body, and 90% decrease in fatty acid β-oxidation. RhoprAcsl2 knockdown also resulted in 20% increase in lifespan, delayed digestion, 30% reduced oviposition, and 50% reduction in egg hatching. Laid eggs and hatched nymphs showed remarkable alterations in morphology. In summary, R. prolixus ACSL isoforms have distinct roles on lipid metabolism. Although RhoprACSL1 functions remain unclear, we propose that RhoprACSL2 is the main contributor for the formation of the intracellular acyl-CoA pool channeled for β-oxidation in the fat body, and is also required for normal reproduction.

High incorporation of long-chain fatty acids contributes to the efficient production of acylated ghrelin in ghrelin-producing cells

The mechanisms for supplying octanoic acid for ghrelin acylation in X/A-like cells are incompletely understood. We found that long-chain fatty acids were incorporated at a higher rate in the ghrelin-producing cell line MGN3-1 than in MIN6 cells, in part due to higher expression level of long-chain fatty acyl-CoA synthetase family member 1 (Acsl1). Inhibition of ACSLs by triacsin C profoundly suppressed acylated ghrelin production. These results suggest that high incorporation of long-chain fatty acids into the ghrelin-producing cells plays a role in the supply of octanoic acid for ghrelin acylation.

Use of a Novel Double-Crested Cormorant ToxChip PCR Array and the EROD Assay to Determine Effects of Environmental Contaminants in Primary Hepatocytes

In vitro screening tools and 'omics methods are increasingly being incorporated into toxicity studies to determine mechanistic effects of chemicals and mixtures. To date, the majority of these studies have been conducted with well-characterized laboratory animal models. In the present study, well-established methods developed for chicken embryonic hepatocyte (CEH) studies were extended to a wild avian species, the double-crested cormorant (DCCO; Phalacrocorax auritus), in order to compare the effects of several environmental contaminants on cytotoxicity, ethoxyresorufin O-deethylase (EROD) activity, and mRNA expression. Five organic flame retardants and one plasticizer decreased cormorant hepatocyte viability in a similar manner to that observed in previous studies with CEH. EROD activity was induced in a concentration-dependent manner following exposure to two dioxin-like chemicals and the calculated EC50 values were concordant with domestic avian species from similar species sensitivity categories. Transcriptomic effects were determined using a novel DCCO PCR array, which was designed, constructed and validated in our laboratory based on a commercially available chicken PCR array. The DCCO array has 27 target genes covering a wide range of toxicity pathways. Gene profiles were variable among the 10 chemicals screened; however, good directional concordance was observed with regard to results previously obtained in CEH. Overall, the application of well-established methods (i.e., CEH and chicken PCR array) to the double-crested cormorant demonstrated the portability of the techniques to an indicator species of ecological relevance.

Predicting delayed kidney graft function with gene expression in preimplantation biopsies and first-day posttransplant blood

The purpose of this study was to investigate possible markers for predicting delayed graft function (DGF). To this end we analyzed, in pre-implantation biopsies (PIB) and in first-day post-Tx peripheral blood mononuclear cells (PBMC), the expression of five genes (ACSL4, CUBN, DEFB1, FABP3, GK) through real-time TaqMan PCR assays. These genes were selected from a large scale gene expression study in PIB. DEFB1, FABP3 and GK expression levels in PIB were lower in cases with DGF and, in a multivariate analysis which included these genes and clinical variables, only FABP3 expression remained independently associated with DGF. FABP3 expression lower than -1.32 units of relative expression conferred an odds ratio for DGF of 41.1. Compared to the PBMC of recipients without DGF, recipients with prolonged DGF (pDGF) had lower ACSL4 and higher DEFB1 expression levels. In a multivariate analysis, including PBMC gene expression levels of ACSL4, DEFB1 and TLR4 (data from a previous study with the same patients) and clinical variables, only TLR4 remained independently associated with pDGF. In summary, this study revealed FABP3 expression in PIB as a marker for DGF and disclosed new genes possibly involved in the pathogenesis of DGF.

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.

SREBP2 Activation Induces Hepatic Long-chain Acyl-CoA Synthetase 1 (ACSL1) Expression in Vivo and in Vitro through a Sterol Regulatory Element (SRE) Motif of the ACSL1 C-promoter

Long-chain acyl-CoA synthetase 1 (ACSL1) plays a key role in fatty acid metabolism. To identify novel transcriptional modulators of ACSL1, we examined ACSL1 expression in liver tissues of hamsters fed a normal diet, a high fat diet, or a high cholesterol and high fat diet (HCHFD). Feeding hamsters HCHFD markedly reduced hepatic Acsl1 mRNA and protein levels as well as acyl-CoA synthetase activity. Decreases in Acsl1 expression strongly correlated with reductions in hepatic Srebp2 mRNA level and mature Srebp2 protein abundance. Conversely, administration of rosuvastatin (RSV) to hamsters increased hepatic Acsl1 expression. These new findings were reproduced in mice treated with RSV or fed the HCHFD. Furthermore, the RSV induction of acyl-CoA activity in mouse liver resulted in increases in plasma and hepatic cholesterol ester concentrations and reductions in free cholesterol amounts. Investigations on different ACSL1 transcript variants in HepG2 cells revealed that the mRNA expression of C-ACSL1 was specifically regulated by the sterol regulatory element (SRE)-binding protein (SREBP) pathway, and RSV treatment increased the C-ACSL1 abundance from a minor mRNA species to an abundant transcript. We analyzed 5'-flanking sequence of exon 1C of the human ACSL1 gene and identified one putative SRE site. By performing a promoter activity assay and DNA binding assays, we firmly demonstrated the key role of this SRE motif in SREBP2-mediated activation of C-ACSL1 gene transcription. Finally, we demonstrated that knockdown of endogenous SREBP2 in HepG2 cells lowered ACSL1 mRNA and protein levels. Altogether, this work discovered an unprecedented link between ACSL1 and SREBP2 via the specific regulation of the C-ACSL1 transcript.

Saturated fatty acids regulate retinoic acid signalling and suppress tumorigenesis by targeting fatty acid-binding protein 5

Long chain fatty acids (LCFA) serve as energy sources, components of cell membranes, and precursors for signalling molecules. Here we show that these biological compounds also regulate gene expression and that they do so by controlling the transcriptional activities of the retinoic acid (RA)-activated nuclear receptors RAR and PPARβ/δ. The data indicate that these activities of LCFA are mediated by FABP5 which delivers ligands from the cytosol to nuclear PPARβ/δ. Both saturated and unsaturated LCFA (SLCFA, ULCFA) bind to FABP5, thereby displacing RA and diverting it to RAR. However, while SLCFA inhibit, ULCFA activate the FABP5/PPARβ/δ pathway. We show further that, by concomitantly promoting activation of RAR and inhibiting the activation of PPARβ/δ, SLCFA suppress the oncogenic properties of FABP5-expressing carcinoma cells in cultured cells and in vivo. The observations suggest that compounds that inhibit FABP5 may constitute a new class of drugs for therapy of certain types of cancer.

Differential Gene Expression and Protein Localization of Cryptosporidium parvum Fatty Acyl-CoA Synthetase Isoforms

Cryptosporidium parvum is unable to synthesize fatty acids de novo, but possesses three long-chain fatty acyl-CoA synthetase (CpACS) isoforms for activating fatty acids. We have recently shown that these enzymes could be targeted to kill the parasite in vitro and in vivo. Here, we demonstrated that the CpACS genes were differentially expressed during the parasite life cycle, and their proteins were localized to different subcellular structures by immunofluorescence and immuno-electron microscopies. Among them, CpACS1 displayed as an apical protein in sporozoites and merozoites, but no or little presence during the intracellular merogony until the release of merozoites, suggesting that CpACS1 probably functioned mainly during the parasite invasion and/or early stage of intracellular development. Both CpACS2 and CpACS3 proteins were present in all parasite life cycle stages, in which CpACS2 was present in the parasite and the parasitophorous vacuole membranes (PVM), whereas CpACS3 was mainly present in the parasite plasma membranes with little presence in the PVM. These observations suggest that CpACS2 and CpACS3 may participate in scavenging and transport of fatty acids across the PVM and the parasite cytoplasmic membranes, respectively.

MicroRNA-34a Promotes Hepatic Stellate Cell Activation via Targeting ACSL1

BACKGROUND

The incidence of liver fibrosis remains high due to the lack of effective therapies. Our previous work found that microRNA (miR)-34a expression was increased, while acy1-CoA synthetase long-chain family member1 (ACSL1) was decreased, in a dimethylnitrosamine (DNS)-induced hepatic fibrosis rat model. We hypothesized that miR-34a may play a role in the process of hepatic fibrosis by targeting ACSL1.

MATERIAL AND METHODS

From days 2 to 14, cultured primary hepatic stellate cells (HSCs) underwent cell morphology, immunocytochemical staining, and quantitative reverse transcription PCR (RT-qPCR) for alpha smooth muscle actin (a-SMA), desmin, rno-miR-34a, and ACSL1 expression. Wild-type and mutant luciferase reporter plasmids were constructed according to the predicted miR-34a binding site on the 3'-untranslated region (UTR) of the ACSL1 mRNA and then transfected into HEK293 cells. rno-miR-34a was silenced in HSCs to confirm that rno-miR-34a negatively regulates ACSL1 expression. mRNA and protein expression of α-SMA, type I collagen, and desmin were assayed in miR-34a-silenced HSCs.

RESULTS

HSCs were deemed quiescent during the first 3 days and activated after 10 days. rno-miR-34a expression increased, and ACSL1 expression decreased, from day 2 to 7 to 14. rno-miR-34a was shown to specifically bind to the 3'-UTR of ACSL1. miR-34a-silenced HSCs showed higher ACSL1and lower α-SMA, type I collagen, and desmin expression than that of matching negative controls and non-transfected cells.

CONCLUSIONS

miR-34a appears to play an important role in the process of liver fibrosis by targeting ACSL1 and may show promise as a therapeutic molecular target for hepatic fibrosis.

Giardia fatty acyl-CoA synthetases as potential drug targets

Giardiasis caused by Giardia intestinalis (syn. G. lamblia, G. duodenalis) is one of the leading causes of diarrheal parasitic diseases worldwide. Although limited drugs to treat giardiasis are available, there are concerns regarding toxicity in some patients and the emerging drug resistance. By data-mining genome sequences, we observed that G. intestinalis is incapable of synthesizing fatty acids (FA) de novo. However, this parasite has five long-chain fatty acyl-CoA synthetases (GiACS1 to GiACS5) to activate FA scavenged from the host. ACS is an essential enzyme because FA need to be activated to form acyl-CoA thioesters before they can enter subsequent metabolism. In the present study, we performed experiments to explore whether some GiACS enzymes could serve as drug targets in Giardia. Based on the high-throughput datasets and protein modeling analyses, we initially studied the GiACS1 and GiACS2, because genes encoding these two enzymes were found to be more consistently expressed in varied parasite life cycle stages and when interacting with host cells based on previously reported transcriptome data. These two proteins were cloned and expressed as recombinant proteins. Biochemical analysis revealed that both had apparent substrate preference toward palmitic acid (C16:0) and myristic acid (C14:0), and allosteric or Michaelis–Menten kinetics on palmitic acid or ATP. The ACS inhibitor triacsin C inhibited the activity of both enzymes (IC₅₀ = 1.56 μM, K_i = 0.18 μM for GiACS1, and IC₅₀ = 2.28 μM, K_i = 0.23 μM for GiACS2, respectively) and the growth of G. intestinalis in vitro (IC₅₀ = 0.8 μM). As expected from giardial evolutionary characteristics, both GiACSs displayed differences in overall folding structure as compared with their human counterparts. These observations support the notion that some of the GiACS enzymes may be explored as drug targets in this parasite.

Human Haploid Cell Genetics Reveals Roles for Lipid Metabolism Genes in Nonapoptotic Cell Death

Little is known about the regulation of nonapoptotic cell death. Using massive insertional mutagenesis of haploid KBM7 cells we identified nine genes involved in small-molecule-induced nonapoptotic cell death, including mediators of fatty acid metabolism (ACSL4) and lipid remodeling (LPCAT3) in ferroptosis. One novel compound, CIL56, triggered cell death dependent upon the rate-limiting de novo lipid synthetic enzyme ACC1. These results provide insight into the genetic regulation of cell death and highlight the central role of lipid metabolism in nonapoptotic cell death.

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.

Involvement of acyl-CoA synthetase genes in n-alkane assimilation and fatty acid utilization in yeast Yarrowia lipolytica

Here, we investigated the roles of YAL1 (FAA1) and FAT1 encoding acyl-CoA synthetases (ACSs) and three additional orthologs of ACS genes FAT2-FAT4 of the yeast Yarrowia lipolytica in the assimilation or utilization of n-alkanes and fatty acids. ACS deletion mutants were generated to characterize their function. The FAT1 deletion mutant exhibited decreased growth on n-alkanes of 10-18 carbons, whereas the FAA1 mutant showed growth reduction on n-alkane of 16 carbons. However, FAT2-FAT4 deletion mutants did not show any growth defects, suggesting that FAT1 and FAA1 are involved in the activation of fatty acids produced during the metabolism of n-alkanes. In contrast, deletions of FAA1 and FAT1-FAT4 conferred no defect in growth on fatty acids. The wild-type strain grew in the presence of cerulenin, an inhibitor of fatty acid synthesis, by utilizing exogenously added fatty acid or fatty acid derived from n-alkane when oleic acid or n-alkane of 18 carbons was supplemented. However, the FAA1 deletion mutant did not grow, indicating a critical role for FAA1 in the utilization of fatty acids. Fluorescent microscopic observation and biochemical analyses suggested that Fat1p is present in the peroxisome and Faa1p is localized in the cytosol and to membranes.

Characterization of the proteome of cytoplasmic lipid droplets in mouse enterocytes after a dietary fat challenge

Dietary fat absorption by the small intestine is a multistep process that regulates the uptake and delivery of essential nutrients and energy. One step of this process is the temporary storage of dietary fat in cytoplasmic lipid droplets (CLDs). The storage and mobilization of dietary fat is thought to be regulated by proteins that associate with the CLD; however, mechanistic details of this process are currently unknown. In this study we analyzed the proteome of CLDs isolated from enterocytes harvested from the small intestine of mice following a dietary fat challenge. In this analysis we identified 181 proteins associated with the CLD fraction, of which 37 are associated with known lipid related metabolic pathways. We confirmed the localization of several of these proteins on or around the CLD through confocal and electron microscopy, including perilipin 3, apolipoprotein A-IV, and acyl-CoA synthetase long-chain family member 5. The identification of the enterocyte CLD proteome provides new insight into potential regulators of CLD metabolism and the process of dietary fat absorption.

Identification of genes associated with resilience/vulnerability to sleep deprivation and starvation in Drosophila

BACKGROUND AND STUDY OBJECTIVES

Flies mutant for the canonical clock protein cycle (cyc(01)) exhibit a sleep rebound that is ∼10 times larger than wild-type flies and die after only 10 h of sleep deprivation. Surprisingly, when starved, cyc(01) mutants can remain awake for 28 h without demonstrating negative outcomes. Thus, we hypothesized that identifying transcripts that are differentially regulated between waking induced by sleep deprivation and waking induced by starvation would identify genes that underlie the deleterious effects of sleep deprivation and/or protect flies from the negative consequences of waking.

DESIGN

We used partial complementary DNA microarrays to identify transcripts that are differentially expressed between cyc(01) mutants that had been sleep deprived or starved for 7 h. We then used genetics to determine whether disrupting genes involved in lipid metabolism would exhibit alterations in their response to sleep deprivation.

SETTING

Laboratory.

PATIENTS OR PARTICIPANTS

Drosophila melanogaster.

INTERVENTIONS

Sleep deprivation and starvation.

MEASUREMENTS AND RESULTS

We identified 84 genes with transcript levels that were differentially modulated by 7 h of sleep deprivation and starvation in cyc(01) mutants and were confirmed in independent samples using quantitative polymerase chain reaction. Several of these genes were predicted to be lipid metabolism genes, including bubblegum, cueball, and CG4500, which based on our data we have renamed heimdall (hll). Using lipidomics we confirmed that knockdown of hll using RNA interference significantly decreased lipid stores. Importantly, genetically modifying bubblegum, cueball, or hll resulted in sleep rebound alterations following sleep deprivation compared to genetic background controls.

CONCLUSIONS

We have identified a set of genes that may confer resilience/vulnerability to sleep deprivation and demonstrate that genes involved in lipid metabolism modulate sleep homeostasis.

ACSL1 Is Associated With Fetal Programming of Insulin Sensitivity and Cellular Lipid Content

Individuals who are born small for gestational age (SGA) have a risk to develop various metabolic diseases during their life course. The biological memory of the prenatal state of growth restricted individuals may be reflected in epigenetic alterations in stem cell populations. Mesenchymal stem cells (MSCs) from the Wharton's jelly of umbilical cord tissue are multipotent, and we generated primary umbilical cord MSC isolates from SGA and normal neonates, which were subsequently differentiated into adipocytes. We established chromatin state maps for histone marks H3K27 acetylation and H3K27 trimethylation and tested whether enrichment of these marks was associated with gene expression changes. After validating gene expression levels for 10 significant chromatin immunoprecipitation sequencing candidate genes, we selected acyl-coenzyme A synthetase 1 (ACSL1) for further investigations due to its key roles in lipid metabolism. The ACSL1 gene was found to be highly associated with histone acetylation in adipocytes differentiated from MSCs with SGA background. In SGA-derived adipocytes, the ACSL1 expression level was also found to be associated with increased lipid loading as well as higher insulin sensitivity. ACSL1 depletion led to changes in expression of candidate genes such as proinflammatory chemokines and down-regulated both, the amount of cellular lipids and glucose uptake. Increased ACSL1, as well as modulated downstream candidate gene expression, may reflect the obese state, as detected in mice fed a high-fat diet. In summary, we believe that ACSL1 is a programmable mediator of insulin sensitivity and cellular lipid content and adipocytes differentiated from Wharton's jelly MSCs recapitulate important physiological characteristics of SGA individuals.

Significantly Different Covalent Binding of Oxidative Metabolites, Acyl Glucuronides, and S-Acyl CoA Conjugates Formed from Xenobiotic Carboxylic Acids in Human Liver Microsomes

Xenobiotic carboxylic acids may be metabolized to oxidative metabolites, acyl glucuronides, and/or S-acyl-CoA thioesters (CoA conjugates) in vitro, e.g., in hepatocytes, and in vivo. These metabolites can potentially be reactive species and bind covalently to tissue proteins and are generally considered to mediate adverse drug reactions in humans. Acyl glucuronide metabolites have been the focus of reactive metabolite research for decades, whereas drug-CoA conjugates, which have been shown to be up to 40-70 times more reactive, have been given much less attention. In an attempt to dissect the contribution of different pathways to covalent binding, we utilized human liver microsomes supplemented with NADPH, uridine 5'-diphosphoglucuronic acid (UDPGA), or CoA to evaluate the reactivity of each metabolite separately. Seven carboxylic acid drugs were included in this study. While ibuprofen and tolmetin are still on the market, ibufenac, fenclozic acid, tienilic acid, suprofen, and zomepirac were stopped before their launch or withdrawn. The reactivities of the CoA conjugates of ibuprofen, ibufenac, fenclozic acid, and tolmetin were higher compared to those of their corresponding oxidative metabolites and acyl glucuronides, as measured by the level of covalent binding to human liver microsomal proteins. The highest covalent binding was observed for ibuprofenyl-CoA and ibufenacyl-CoA, to levels of 1000 and 8600 pmol drug eq/mg protein, respectively. In contrast and in agreement with the proposed P450-mediated toxicity for these drug molecules, the reactivities of oxidative metabolites of suprofen and tienilic acid were higher compared to the reactivities of their conjugated metabolites, with NADPH-dependent covalent binding of 250 pmol drug eq/mg protein for both drugs. The seven drugs all formed UDPGA-dependent acyl glucuronides, but none of these resulted in covalent binding. This study shows that, unlike studies with hepatocytes or in vivo, human liver microsomes provide an opportunity to investigate the reactivity of individual metabolites.

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.