Enzymes Of Fatty Acid Synthesis Research Articles

Modulation of Medium-Chain Fatty Acid Synthesis in Synechococcus sp. PCC 7002 by Replacing FabH with a Chaetoceros Ketoacyl-ACP Synthase.

The isolation or engineering of algal cells synthesizing high levels of medium-chain fatty acids (MCFAs) is attractive to mitigate the high clouding point of longer chain fatty acids in algal based biodiesel. To develop a more informed understanding of MCFA synthesis in photosynthetic microorganisms, we isolated several algae from Great Salt Lake and screened this collection for MCFA accumulation to identify strains naturally accumulating high levels of MCFA. A diatom, Chaetoceros sp. GSL56, accumulated particularly high levels of C14 (up to 40%), with the majority of C14 fatty acids allocated in triacylglycerols. Using whole cell transcriptome sequencing and de novo assembly, putative genes encoding fatty acid synthesis enzymes were identified. Enzymes from this Chaetoceros sp. were expressed in the cyanobacterium Synechococcus sp. PCC 7002 to validate gene function and to determine whether eukaryotic enzymes putatively lacking bacterial evolutionary control mechanisms could be used to improve MCFA production in this promising production strain. Replacement of the Synechococcus 7002 native FabH with a Chaetoceros ketoacyl-ACP synthase III increased MCFA synthesis up to fivefold. The level of increase is dependent on promoter strength and culturing conditions.

Nutritional and Hormonal Regulation of Citrate and Carnitine/Acylcarnitine Transporters: Two Mitochondrial Carriers Involved in Fatty Acid Metabolism.

The transport of solutes across the inner mitochondrial membrane is catalyzed by a family of nuclear-encoded membrane-embedded proteins called mitochondrial carriers (MCs). The citrate carrier (CiC) and the carnitine/acylcarnitine transporter (CACT) are two members of the MCs family involved in fatty acid metabolism. By conveying acetyl-coenzyme A, in the form of citrate, from the mitochondria to the cytosol, CiC contributes to fatty acid and cholesterol synthesis; CACT allows fatty acid oxidation, transporting cytosolic fatty acids, in the form of acylcarnitines, into the mitochondrial matrix. Fatty acid synthesis and oxidation are inversely regulated so that when fatty acid synthesis is activated, the catabolism of fatty acids is turned-off. Malonyl-CoA, produced by acetyl-coenzyme A carboxylase, a key enzyme of cytosolic fatty acid synthesis, represents a regulator of both metabolic pathways. CiC and CACT activity and expression are regulated by different nutritional and hormonal conditions. Defects in the corresponding genes have been directly linked to various human diseases. This review will assess the current understanding of CiC and CACT regulation; underlining their roles in physio-pathological conditions. Emphasis will be placed on the molecular basis of the regulation of CiC and CACT associated with fatty acid metabolism.

SCD1 is associated with tumor promotion, late stage and poor survival in lung adenocarcinoma.

The discovery of Warburg effect opens a new era in anti-cancer therapy. Aerobic glycolysis is regarded as a hallmark of cancer cells and increasing literatures indicates that metabolic changes are critical for the maintenance and progression of cancer cells. Besides aerobic glycolysis, increased fatty acid synthesis is also required for the rapid growth of cancer cells, and is considered as one of the most typical metabolic symbols of cancer either. Thus, targeting fatty acid metabolism may provide a potential avenue for the diagnosis and therapeutic treatment of cancer. In this study, we have identified Sterol-CoA desaturase-1 (SCD1) which is the rate-limiting enzyme of unsaturated fatty acid synthesis, universally and highly expressed in lung adenocarcinoma and was required for the cell proliferation, migration and invasion. Both in vitro and in vivo studies demonstrated that high expression of SCD1 remarkably enhanced the ability of tumor formation and invasion, while knockdown of SCD1 significantly repressed tumorigenesis and induced cell apoptosis. Clinical association study suggested that high expression of SCD1 is more frequently observed in late stage patients and presents poor prognosis. Taken together, our results suggested that SCD1 is a potentially novel biomarker of lung adenocarcinoma, and targeting SCD1 may represent a new anti-cancer strategy.

Lipid Synthesis Is a Metabolic Liability of Non-Small Cell Lung Cancer.

The renaissance in the study of cancer metabolism has refocused efforts to identify and target metabolic dependencies of tumors as an approach for cancer therapy. One of the unique metabolic requirements that cancer cells possess to sustain their biosynthetic growth demands is altered fatty acid metabolism, in particular the synthesis of de novo fatty acids that are required as cellular building blocks to support cell division. Enhanced fatty acid synthesis that is observed in many tumor types has been postulated to open a therapeutic window for cancer therapy and, correspondingly, efforts to pharmacologically inhibit key enzymes of fatty acid synthesis are being pursued. However, despite these efforts, whether inhibition of fatty acid synthesis stunts tumor growth in vivo has been poorly understood. In this review, we focus on the recent evidence that pharmacologic inhibition of acetyl-CoA carboxylase, the enzyme that regulates the rate-limiting step of de novo fatty acid synthesis, exposes a metabolic liability of non-small cell lung cancer and represses tumor growth in preclinical models.

Abstract B06: TSC2 loss induces aberrant choline lysoglycerophospholipid metabolism

Abstract Tuberous Sclerosis Complex (TSC) is an autosomal dominant disease characterized by multi-organ proliferation of TSC2-deficient cells with aberrant activation of the mechanistic/mammalian Target of Rapamycin Complex 1 (mTORC1), a master regulator of cell growth and metabolism. Up to 80% of women with TSC develop lymphangioleiomyomatosis (LAM), which consists of diffuse proliferation of TSC2-deficient smooth muscle-like cells with progressive cystic destruction of the lung. LAM can also occur as a sporadic disorder of women. A downstream effector of mTORC1, the Sterol Regulatory Element-Binding Protein (SREBP), regulates the transcription of de novo fatty acid synthesis enzymes in TSC2-deficient cells. The impact of loss of the TSC proteins on the lipidome and how complex lipid species are affected by rapamycin and its analogs are unknown. Here, we report the first systematic study of the TSC lipidome, revealing unexpected findings. Using mass spectrometry, we profiled 131 complex lipid species discovered elevated levels (p<0.05) of 4 lysophosphatidylcholine (LPC) species (C16:0, C18:0, C18:1, C20:4) in the plasma of LAM patients compared with healthy control women. LPC are a class of bioactive lipids generated by phospholipase A (PLA) activity. To investigate whether these lipids are generated in a TSC2-dependent manner, we profiled in vitro pre-clinical models of TSC/LAM and found significant LPC accumulation in TSC2-deficient cells relative to TSC2-expressing control cells. These lysoglycerophospholipid changes occurred alongside changes in other phospholipid, including the LPC precursors phosphatidylcholines (PC) and sphingolipids, and neutral lipid species, including triacylglycerols and cholesterol esters. To determine whether TSC2-deficient cells generate LPC using de novo synthesized PC, TSC2-deficient and TSC2-expressing cells were labeled with deuterated choline (choline chloride 1,1,2,2-d4) for 6 hours, and lipids isolated to measure choline incorporation into two saturated LPC (C16:0 and C18:0) and two parent PC (C32:0 and C34:0) species. Incorporation of deuterated choline into PC and LPC was greater than 2 fold higher in TSC2-deficient cells compared to TSC2-expressing controls (p<0.05). Surprisingly, treatment with rapamycin, the mTOR catalytic inhibitor Torin1, or downregulation of the mTORC1-regulated lipogenic transcription factor SREBP (Sterol Regulatory Element-Binding Protein) did not suppress LPC in TSC2-deficient cells, while they suppressed other phospholipid species. Finally, pharmacologic and genetic approaches revealed that inhibition of distinct isoforms of PLA2 may decrease the proliferation of TSC2-deficient but not TSC2-expressing cells. Collectively, these results demonstrate for the first time that TSC2-deficient cells have enhanced choline phospholipid metabolism, revealing a novel function of the TSC proteins in choline lysoglycerophospholipid metabolism, with implications for disease pathogenesis and targeted therapeutic strategies. Citation Format: Carmen Priolo, Stéphane J. H. Ricoult, Damir Khabibullin, Harilaos Filippakis, Jane Yu, Brendan Manning, Clary Clish, Elizabeth P. Henske. TSC2 loss induces aberrant choline lysoglycerophospholipid metabolism. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B06.

Arylhydrocarbon receptor-dependent mIndy (Slc13a5) induction as possible contributor to benzo[a]pyrene-induced lipid accumulation in hepatocytes.

Non-alcoholic fatty liver disease is a growing problem in industrialized and developing countries. Hepatic lipid accumulation is the result of an imbalance between fatty acid uptake, fatty acid de novo synthesis, β-oxidation and secretion of triglyceride-rich lipoproteins from the hepatocyte. A central regulator of hepatic lipid metabolism is cytosolic citrate that can either be derived from the mitochondrium or be taken up from the blood via the plasma membrane sodium citrate transporter NaCT, the product of the mammalian INDY gene (SLC13A5). mINDY ablation protects against diet-induced steatosis whereas mINDY expression is increased in patients with hepatic steatosis. Diet-induced hepatic steatosis is also enhanced by activation of the arylhyrocarbon receptor (AhR) both in humans and animal models. Therefore, the hypothesis was tested whether the mINDY gene might be a target of the AhR. In accordance with such a hypothesis, the AhR activator benzo[a]pyrene induced the mINDY expression in primary cultures of rat hepatocytes in an AhR-dependent manner. This induction resulted in an increased citrate uptake and citrate incorporation into lipids which probably was further enhanced by the benzo[a]pyrene-dependent induction of key enzymes of fatty acid synthesis. A potential AhR binding site was identified in the mINDY promoter that appears to be conserved in the human promoter. Elimination or mutation of this site largely abolished the activation of the mINDY promoter by benzo[a]pyrene. This study thus identified the mINDY as an AhR target gene. AhR-dependent induction of the mINDY gene might contribute to the development of hepatic steatosis.

Identification of Inhibitors of Fatty Acid Synthesis Enzymes in Mycobacterium Smegmatis

Antibiotic-resistant strains of Mycobacterium tuberculosis have rendered some of the current treatments for tuberculosis ineffective, creating a need for new treatments. Today, the most efficient way to find new drugs to treat tuberculosis and other diseases is to use virtual screening to quickly consider millions of potential drug candidates and filter out all but the ones most likely to inhibit the disease. These top hits can then be tested in a traditional wet lab to determine their potential effectiveness. Using supercomputers, we screened over 4 million potential drug molecules against each of two enzymes that are critical to the survival of Mycobacterium tuberculosis. During this process, we determined the top candidate molecules to test in the wet lab.

Discovery of natural alkaloid bouchardatine as a novel inhibitor of adipogenesis/lipogenesis in 3T3-L1 adipocytes

Bouchardatine (1), a naturally occurring β-indoloquinazoline alkaloid, was synthesized. For the first time, the lipid-lowering effect and mechanism of 1 was investigated in 3T3-L1 adipocytes. Our study showed that 1 could significantly reduce lipid accumulation without cytotoxicity and mainly inhibited early differentiation of adipocyte through proliferation inhibition and cell cycle arrested in dose-dependent manner. Furthermore, the inhibition of early differentiation was reflected by down-regulation of key regulators of adipogenesis/lipogenesis, including CCAAT enhancer binding proteins (C/EBPβ, C/EBPδ, C/EBPα), peroxisome proliferator-activated receptors γ (PPARγ) and sterol-regulatory element binding protein-1c (SREBP-1c), in both of mRNA and protein levels. Subsequently decreasing the protein levels of acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), and stearyl coenzyme A desaturated enzyme 1 (SCD-1), the rate-limited metabolic enzymes of fatty acid synthesis, were also observed. Further studies revealed that 1 persistently activated adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) during differentiation, suggesting that the AMPK may be an upstream mechanism for the effect of 1 on adipogenesis and lipogenesis. Our data suggest that 1 can be a candidate for the development of new therapeutic drugs against obesity and related metabolic disorders.

Analysis of ATP-citrate lyase and malic enzyme mutants of Yarrowia lipolytica points out the importance of mannitol metabolism in fatty acid synthesis

The role of the two key enzymes of fatty acid (FA) synthesis, ATP-citrate lyase (Acl) and malic enzyme (Mae), was analyzed in the oleaginous yeast Yarrowia lipolytica. In most oleaginous yeasts, Acl and Mae are proposed to provide, respectively, acetyl-CoA and NADPH for FA synthesis. Acl was mainly studied at the biochemical level but no strain depleted for this enzyme was analyzed in oleaginous microorganisms. On the other hand the role of Mae in FA synthesis in Y. lipolytica remains unclear since it was proposed to be a mitochondrial NAD(H)-dependent enzyme and not a cytosolic NADP(H)-dependent enzyme. In this study, we analyzed for the first time strains inactivated for corresponding genes. Inactivation of ACL1 decreases FA synthesis by 60 to 80%, confirming its essential role in FA synthesis in Y. lipolytica. Conversely, inactivation of MAE1 has no effects on FA synthesis, except in a FA overaccumulating strain where it improves FA synthesis by 35%. This result definitively excludes Mae as a major key enzyme for FA synthesis in Y. lipolytica. During the analysis of both mutants, we observed a negative correlation between FA and mannitol level. As mannitol and FA pathways may compete for carbon storage, we inactivated YlSDR, encoding a mannitol dehydrogenase converting fructose and NADPH into mannitol and NADP+. The FA content of the resulting mutant was improved by 60% during growth on fructose, demonstrating that mannitol metabolism may modulate FA synthesis in Y. lipolytica.

Dibenzoylmethane exerts metabolic activity through regulation of AMP-activated protein kinase (AMPK)-mediated glucose uptake and adipogenesis pathways.

Dibenzoylmethane (DBM) has been shown to exert a variety of beneficial effects on human health. However, the mechanism of action is poorly understood. In this study, DBM increased phosphorylation of AMP-activated protein kinase (AMPK) and stimulated glucose uptake in a skeletal muscle cell line. Both knockdown of AMPK with siRNA and inhibition with AMPK inhibitor blocked DBM-induced glucose uptake. DBM increased the concentration of intracellular calcium and glucose uptake due to DBM was abolished by STO-609 (a calcium/calmodulin-dependent protein kinase inhibitor). DBM stimulated phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), which was blocked by pretreatment with compound C, an AMPK inhibitor. The expression of glucose transporter type 4 (GLUT4) was increased by DBM. The translocation of GLUT4 to the plasma membrane was also increased by DBM in AMPK dependently. In addition, DBM suppressed weight gain and prevented fat accumulation in the liver and abdomen in mice fed a high-fat diet. In pre-adipocyte cells, DBM decreased the activity of acetyl-CoA carboxylase (ACC), the rate-limiting enzyme of fatty acid synthesis. Expression of the adipogenic gene, fatty acid synthase (FAS), was suppressed by DBM in an AMPK-dependent manner. These results showed that the beneficial metabolic effects of DBM might be due to regulation of glucose uptake via AMPK in skeletal muscle and inhibition of adipogenesis in pre-adipocytes.

Effects of High Hydrostatic Pressure Extract of Korean Fresh Ginseng on Hepatic Lipid Accumulation and AMPK Activation in HepG2 Cells

Ginseng is widely used as a medicinal herb and has demonstrated effects against liver diseases. The aim of this study is to investigate the hypolipidemic effects of the high hydrostatic pressure extract of Korean fresh ginseng (HEG) on hepatic lipid accumulation in HepG2 cells. The intracellular triglyceride and cholesterol contents were determined using enzymatic colorimetric methods. The mRNA levels of fatty acid synthase (FAS) and 3-hydroxy-3-methyl-glutaryl CoA reductase (HMGCR) were assayed by quantitative real-time PCR. The activity of AMP-activated protein kinase (AMPK) was measured with an AMPK kinase assay kit. HEG significantly reduced hepatic triglyceride and cholesterol contents in HepG2 cells. Furthermore, HEG suppressed the expression of FAS, a key enzyme in fatty acid synthesis, and HMGCR, a rate-limiting enzyme in hepatic cholesterol synthesis. Additionally, HEG increased the activity of AMPK, a major regulator of lipid metabolism. These results suggest that HEG reduces hepatic lipid accumulation with inhibition of FAS and HMGCR expression and stimulation of AMPK activity in HepG2 cells. Consequently, HEG may be beneficial as a functional food ingredient to improve various hepatic diseases by reducing hepatic lipid accumulation.

Ligands and Regulatory Modes of Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Avians.

Nutrient and gene interaction is an important aspect of poultry metabolism that determines performance capacity. New technological tools in biochemistry and biotechnology make it possible to explore the molecular base of phenotypic characteristics of poultry production. Fats act as energy deposits in the poultry body and are an essential constituent of animal cell membranes. From a functional standpoint, it has been suggested that ingested lipids change liver fatty acid synthesis and other lipogenic enzymes by regulating mRNA synthesis. Nuclear hormone receptors are ligand-activated transcription factors that control several genes involved in lipid metabolism. The peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of transcription factors. Three separate PPAR genes have been identified; they are known as α, δ, and γ. The most important metabolic effect of PPARγ in chicken is its task in adipogenesis. Reviewing the ligands of chicken PPARγ gene can be useful to a better understanding of PPARγ regulatory functions.

Effects of epigallocatechin gallate on lipid metabolism and its underlying molecular mechanism in broiler chickens.

The objective of this study was to investigate the effects of epigallocatechin gallate (EGCG) on fat metabolism and to establish the molecular mechanism of these effects in broilers. Seventy-two 28-day-old male Ross 308 broiler chickens were divided into three groups with different levels of EGCG supplementation for 4weeks: normal control (NC) group, L-EGCG (a low-level supplement of EGCG, 40mg/kg body weight daily) and H-EGCG (a high-level supplement of EGCG, 80mg/kg body weight daily). After 4weeks of oral administration, EGCG significantly reduced the level of abdominal fat deposition in broilers. The serum triglycerides and low-density lipoprotein cholesterol of chickens in H-EGCG group were also significantly decreased compared with the NC group, and the high-density lipoprotein cholesterol was notably increased at the same time. Moreover, the vital role of the liver and abdominal adipose tissue in lipid metabolism of poultry animals was examined through gene expression and enzyme activities related to fat anabolism and catabolism in these organs. Our data show that EGCG supplementation for 2weeks significantly downregulated the expression of fatty acid synthesis and fat deposition-related genes, and upregulated the expression of genes involved in fatty acid β-oxidation and lipolysis genes. Simultaneously, the activities of hepatic fatty acid synthesis enzymes (fatty acid synthase and acetyl CoA carboxylase) were significantly decreased, and the activity of carnitine palmitoyl transferase-1 was notably elevated. The results suggest that EGCG could alleviate fat deposition in broilers through inhibiting fat anabolism and stimulating lipid catabolism in broilers.

Propionic acid and butyric acid inhibit lipolysis and de novo lipogenesis and increase insulin-stimulated glucose uptake in primary rat adipocytes

Fermentation of dietary fibers by colonic microbiota generates short-chain fatty acids (SCFAs), e.g., propionic acid and butyric acid, which have been described to have “anti-obesity properties” by ameliorating fasting glycaemia, body weight and insulin tolerance in animal models. In the present study, we therefore investigate if propionic acid and butyric acid have effects on lipolysis, de novo lipogenesis and glucose uptake in primary rat adipocytes. We show that both propionic acid and butyric acid inhibit isoproterenol- and adenosine deaminase-stimulated lipolysis as well as isoproterenol-stimulated lipolysis in the presence of a phosphodiesterase (PDE3) inhibitor. In addition, we show that propionic acid and butyric acid inhibit basal and insulin-stimulated de novo lipogenesis, which is associated with increased phosphorylation and thus inhibition of acetyl CoA carboxylase, a rate-limiting enzyme in fatty acid synthesis. Furthermore, we show that propionic acid and butyric acid increase insulin-stimulated glucose uptake. To conclude, our study shows that SCFAs have effects on fat storage and mobilization as well as glucose uptake in rat primary adipocytes. Thus, the SCFAs might contribute to healthier adipocytes and subsequently also to improved energy metabolism with for example less circulating free fatty acids, which is beneficial in the context of obesity and type 2 diabetes.

Direct visualization of de novo lipogenesis in single living cells.

Increased de novo lipogenesis is being increasingly recognized as a hallmark of cancer. Despite recent advances in fluorescence microscopy, autoradiography and mass spectrometry, direct observation of de novo lipogenesis in living systems remains to be challenging. Here, by coupling stimulated Raman scattering (SRS) microscopy with isotope labeled glucose, we were able to trace the dynamic metabolism of glucose in single living cells with high spatial-temporal resolution. As the first direct visualization, we observed that glucose was largely utilized for lipid synthesis in pancreatic cancer cells, which occurs at a much lower rate in immortalized normal pancreatic epithelial cells. By inhibition of glycolysis and fatty acid synthase (FAS), the key enzyme for fatty acid synthesis, we confirmed the deuterium labeled lipids in cancer cells were from de novo lipid synthesis. Interestingly, we also found that prostate cancer cells exhibit relatively lower level of de novo lipogenesis, but higher fatty acid uptake compared to pancreatic cancer cells. Together, our results demonstrate a valuable tool to study dynamic lipid metabolism in cancer and other disorders.

Fatty acid synthesis enzyme clans.

Ketoacyl reductases (KRs), hydroxyacyl dehydratases (HDs), and enoyl reductases (ERs) are part of the fatty acid/polyketide synthesis cycle. They are known as acyl dehydrogenases, enoyl hydratases, and hydroxyacyl dehydrogenases, respectively, when catalyzing their reverse reactions. Earlier, we classified these enzymes into four KR, eight HD, and five ER families by statistical criteria. Members of all four KR families and three ER families have Rossmann folds, while five HD family members have HotDog folds. This suggests that those proteins with the same folds in different families may be distantly related, and therefore in clans, even though their amino acid sequences may not be homologous. We have now defined two clans containing three of the four KR families and two of the eight HD families, using manual and statistical tests. One of the ER families is related to the KR clan.

HIF prolyl 4-hydroxylase-2 inhibition improves glucose and lipid metabolism and protects against obesity and metabolic dysfunction.

Obesity is a major public health problem, predisposing subjects to metabolic syndrome, type 2 diabetes, and cardiovascular diseases. Specific prolyl 4-hydroxylases (P4Hs) regulate the stability of the hypoxia-inducible factor (HIF), a potent governor of metabolism, with isoenzyme 2 being the main regulator. We investigated whether HIF-P4H-2 inhibition could be used to treat obesity and its consequences. Hif-p4h-2-deficient mice, whether fed normal chow or a high-fat diet, had less adipose tissue, smaller adipocytes, and less adipose tissue inflammation than their littermates. They also had improved glucose tolerance and insulin sensitivity. Furthermore, the mRNA levels of the HIF-1 targets glucose transporters, glycolytic enzymes, and pyruvate dehydrogenase kinase-1 were increased in their tissues, whereas acetyl-CoA concentration was decreased. The hepatic mRNA level of the HIF-2 target insulin receptor substrate-2 was higher, whereas that of two key enzymes of fatty acid synthesis was lower. Serum cholesterol levels and de novo lipid synthesis were decreased, and the mice were protected against hepatic steatosis. Oral administration of an HIF-P4H inhibitor, FG-4497, to wild-type mice with metabolic dysfunction phenocopied these beneficial effects. HIF-P4H-2 inhibition may be a novel therapy that not only protects against the development of obesity and its consequences but also reverses these conditions.

Overexpression of the soybean transcription factor GmDof4 significantly enhances the lipid content of Chlorella ellipsoidea.

BackgroundThe lipid content of microalgae is regarded as an important indicator for biodiesel. Many attempts have been made to increase the lipid content of microalgae through biochemical and genetic engineering. Significant lipid accumulation in microalgae has been achieved using biochemical engineering, such as nitrogen starvation, but the cell growth was severely limited. However, enrichment of lipid content in microalgae by genetic engineering is anticipated. In this study, GmDof4 from soybean (Glycine max), a transcription factor affecting the lipid content in Arabidopsis, was transferred into Chlorella ellipsoidea. We then investigated the molecular mechanism underlying the enhancement of the lipid content of transformed C. ellipsoidea.ResultsWe constructed a plant expression vector, pGmDof4, and transformed GmDof4 into C. ellipsoidea by electroporation. The resulting expression of GmDof4 significantly enhanced the lipid content by 46.4 to 52.9%, but did not affect the growth rate of the host cells under mixotrophic culture conditions. Transcriptome profiles indicated that 1,076 transcripts were differentially regulated: of these, 754 genes were significantly upregulated and 322 genes were significantly downregulated in the transgenic strains under mixotrophic culture conditions. There are 22 significantly regulated genes (|log2 ratio| >1) involved in lipid and fatty acid metabolism. Quantitative real-time PCR and an enzyme activity assay revealed that GmDof4 significantly up-regulated the gene expression and enzyme activity of acetyl-coenzyme A carboxylase, a key enzyme for fatty acid synthesis, in transgenic C. ellipsoidea cells.ConclusionsThe hetero-expression of a transcription factor GmDof4 gene from soybean can significantly increase the lipid content but not affect the growth rate of C. ellipsoidea under mixotrophic culture conditions. The increase in lipid content could be attributed to the large number of genes with regulated expression. In particular, the acetyl-coenzyme A carboxylase gene expression and enzyme activity were significantly upregulated in the transgenic cells. Our research provides a new way to increase the lipid content of microalgae by introducing a specific transcription factor to microalgae strains that can be used for the biofuel and food industries.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-014-0128-4) contains supplementary material, which is available to authorized users.

Role of maternal tissue in the synthesis of polyunsaturated fatty acids in response to a lipid-deficient diet during pregnancy and lactation in rats

During pregnancy and lactation, metabolic adaptations involve changes in expression of desaturases and elongases (Elovl2 and Elovl5) in the mammary gland and liver for the synthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) such as arachidonic acid (AA) required for fetal and postnatal growth. Adipose tissue is a pool of LC-PUFAs. The response of adipose tissue for the synthesis of these fatty acids in a lipid-deficient diet of dams is unknown. The aim of this study was to explore the role of maternal tissue in the synthesis of LC-PUFAs in rats fed a low-lipid diet during pregnancy and lactation. Fatty acid composition (indicative of enzymatic activity) and gene expression of encoding enzymes for fatty acid synthesis were measured in liver, mammary gland and adipose tissue in rats fed a low-lipid diet. Gene expression of desaturases, elongases, fatty acid synthase (Fasn) and their regulator Srebf-1c was increased in the mammary gland, liver and adipose tissue of rats fed a low-lipid diet compared with rats from the adequate-lipid diet group throughout pregnancy and lactation. Genes with the highest (P<0.05) expression in the mammary gland, liver and adipose tissue were Elovl5 (1333%), Fads2 (490%) and Fasn (6608%), respectively, in a low-lipid diet than in adequate-lipid diet. The percentage of AA in the mammary gland was similar between the low-lipid diet and adequate-lipid diet groups during the second stage of pregnancy and during lactation. The percentage of monounsaturated and saturated fatty acids was significantly (P<0.05) increased throughout pregnancy and lactation in all tissues in rats fed a low-lipid diet than in rats fed an adequate-lipid diet. Results suggest that maternal metabolic adaptations used to compensate for lipid-deficient diet during pregnancy and lactation include increased expression of genes involved in LC-PUFAs synthesis in a stage- and tissue-specific manner and elevated lipogenic activity (saturated and monounsaturated fatty acid synthesis) of maternal tissues including adipose tissue.

Editorial (Thematic Issue: Current Status and Perspective on Drug Targets in Tubercle Bacilli and Drug Design of Antituberculous Agents Based on Structure-Activity Relationship)

Editorial (Thematic Issue: Current Status and Perspective on Drug Targets in Tubercle Bacilli and Drug Design of Antituberculous Agents Based on Structure-Activity Relationship)