Biosynthesis Of Saturated Fatty Acids Research Articles

Molecular and physiological mechanisms of aging are distinct in the cardiac right and left ventricles

AbstractAging is the primary risk factor for heart disease, the leading global cause of death. Right ventricular (RV) function predicts survival in several age‐related clinical contexts, yet no therapies directly improve RV function, in large part due to a poor mechanistic understanding of RV aging and how it is distinct from the widely studied left ventricle (LV). To address this gap, we comprehensively quantified RV functional and morphological remodeling with age. We further aimed to identify molecular mechanisms of RV aging thus we performed RNAseq on RV and LV from male and female young (4 months) and aged (19–21 months) C57BL6 mice. Contrary to the concentric hypertrophic remodeling and diastolic dysfunction that occurs in the LV, the aging RV underwent eccentric remodeling with significant dilation and impaired systolic function. Transcriptomic data were also consistent with ventricle‐specific aging, with few genes (13%) similarly shared between ventricles with aging. KEGG analysis identified shared aging genes in inflammatory and immune cell pathways that were confirmed by flow cytometry that demonstrated higher percent of GR1+ myeloid cells in both ventricles. Unique RV aging genes enriched in the biosynthesis of saturated fatty acids, PPAR signaling, and butanoate metabolism, and we identified putative novel RV‐specific aging genes. Together, we suggest that the RV and LV are unique cardiac chambers that undergo distinct remodeling with age. These robust differences may explain why therapies designed from LV‐based studies fail to improve RV function and suggest that future efforts emphasizing ventricular differences may elucidate new therapies for healthy cardiac aging.

Application of synthetic biology strategies to promote biosynthesis of fatty acids and their derivatives.

Fatty acids and their derivatives are indispensable biomolecules in all organisms, and can be used as intermediates in the synthesis of pharmaceuticals, biofuels and pesticides, and thus their demand has increased dramatically in recent years. In addition to serving as structural components of cell membranes and metabolic energy, fatty acids and their derivatives can also be used as signal transduction and regulatory bioactive molecules to regulate cell functions. Biosynthesis of fatty acids and their derivatives through microbial catalysis provides green and alternative options to meet the goal. However, the low biosynthetic titer of fatty acids and their derivatives limits their industrial production and application. In this review, we first summarize the metabolic pathways and related enzymes of fatty acids and their derivatives biosynthesis. Then, the strategies and research progress of biosynthesis of fatty acids and derivatives through metabolic and enzyme engineering were reviewed. The biosynthesis of saturated fatty acids (medium chain fatty acids and long chain fatty acids), bioactive fatty acids (PUFAs, oxylipins, ether lipids), and their derivatives with microbial and enzymatic catalysis were respectively summarized. Finally, synthetic biology strategies to improve fatty acids and their derivatives production through enzyme rational design, carbon metabolism flux, cofactors balance, and metabolic pathways design were discussed. The review provides references and prospects for fatty acids and their derivatives biosynthesis and industrial production.

Salvianolic acid B and tanshinone IIA synergistically improve early diabetic nephropathy through regulating PI3K/Akt/NF-κB signaling pathway

Ethnopharmacological relevanceDiabetic nephropathy (DN) is one of the most common and serious complications of diabetes, which lacks effective treatment. Salviae Miltiorrhizae Radix Et Rhizoma is one of the key compatible traditional Chinese medicine in the prescription for the treatment of DN. Salvianolic acid B and tanshinone IIA are two monomer active components with high content and clear structure in Salvia miltiorrhiza, which can effectively improve early (DN), respectively. Aim of the studyTo evaluate the compatible effect of salvianolic acid B and tanshinone IIA on early DN rats and elucidate the mechanism. MethodsEarly DN rats were induced by streptozotocin combined with high glucose and high fat diet, and intervened by salvianolic acid B, tanshinone IIA and their combinations. The pathological sections of kidney, liver and biochemical indexes were analyzed. Network pharmacology method was used to predict the possible mechanism. The mechanisms were elucidated by metabolomics, Elisa, and Western blot. ResultsGiven our analysis, salvianolic acid B and tanshinone IIA can synergistically regulate 24 h UTP, Urea and Scr and improve kidney damage in early DN rats. The metabolic abnormalities of early DN rats were improved by regulating the biosynthesis of saturated fatty acids, glycerol phospholipid metabolism, steroid biosynthesis, alanine, and arachidonic acid. Salvianolic acid B combined with tanshinone IIA at a mass ratio of 13.4:1 can significantly reduce kidney inflammation, up-regulate p-PI3K/PI3K and p-Akt/Akt and down-regulate p-NF-κB/NF-κB, which better than the single-used group and can be reversed by PI3K inhibitor LY294002. ConclusionSalvianolic acid B and tanshinone IIA can synergistically improve glucose and lipid disorders, liver and kidney damage, and resist kidney inflammation in early DN rats, and the mechanism may be related to regulating PI3K/Akt/NF-κB signaling pathway.

Lipid dynamics of 'Fenjiao' bananas (Musa ABB Pisang Awak) during post-ripening based on lipidomics analysis

Changes in cellular lipid homeostasis during ripening of ‘Fenjiao’ bananas (Musa ABB Pisang Awak) significantly affected its storage tolerance, and an in-depth understanding of the changes in cellular lipids during fruit ripening could provide more information and basic data for post-harvest quality regulation of 'Fenjiao' bananas. In this study, a comprehensive metabolomics approach was employed to annotate and characterize a total of 184 lipids, which encompassed glycerides, glycero-phospholipids, sphingolipids, and sterols. In the pulp of 'Fenjiao' bananas at three different stages of ripening (color-transferring, yellow-ripening, and over-ripening), of which glycerides and glycerophospho-lipids were the most predominant lipid constituents in the pulp of ‘Fenjiao’ bananas, with the percentages of the species accounting for 60.33% and 30.43%, respectively. During the post-ripening process of ‘Fenjiao’ bananas, the percentage of glycerides in the pulp exhibited a decreasing trend followed by an increasing trend. In contrast, the trend of glycerophospholipids was opposite to that of glycerides, showing an increasing trend followed by a decreasing trend. The tria-cylglycerol (TAG) content will increase significantly during the senescence stage of the 'Fenjiao' bananas, whereas the levels of diglycerides (DAG), Phosphatidylinositol (PI), Pho-sphatidylcholine (PC), and Phosphatidylethanolamine (PE) will gradually decrease. Through analysis of the differential lipid metabolites, it was discovered that these lipids were primarily enriched in the glycerolipid metabolism, glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids, saturated fatty acid biosynthesis, and phosphatidylinositol signaling pathway. This study is the first to describe and analyze the lipid dynamics during the post-ripening process of 'Fenjiao' bananas, providing valuable insights into its cellular lipid metabolism during this stage.

Biosynthesis and Significance of Fatty Acids, Glycerophospholipids, and Triacylglycerol in the Processes of Glioblastoma Tumorigenesis

One area of glioblastoma research is the metabolism of tumor cells and detecting differences between tumor and healthy brain tissue metabolism. Here, we review differences in fatty acid metabolism, with a particular focus on the biosynthesis of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) by fatty acid synthase (FASN), elongases, and desaturases. We also describe the significance of individual fatty acids in glioblastoma tumorigenesis, as well as the importance of glycerophospholipid and triacylglycerol synthesis in this process. Specifically, we show the significance and function of various isoforms of glycerol-3-phosphate acyltransferases (GPAT), 1-acylglycerol-3-phosphate O-acyltransferases (AGPAT), lipins, as well as enzymes involved in the synthesis of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and cardiolipin (CL). This review also highlights the involvement of diacylglycerol O-acyltransferase (DGAT) in triacylglycerol biosynthesis. Due to significant gaps in knowledge, the GEPIA database was utilized to demonstrate the significance of individual enzymes in glioblastoma tumorigenesis. Finally, we also describe the significance of lipid droplets in glioblastoma and the impact of fatty acid synthesis, particularly docosahexaenoic acid (DHA), on cell membrane fluidity and signal transduction from the epidermal growth factor receptor (EGFR).

The new isolated Archaea strain improved grain yield, metabolism and quality of wheat plants under Co stress conditions

Heavy metal (e.g. cobalt) pollution causes a serious of environmental and agricultural problems. On the other hand, plant growth-promoting microorganisms enhance plant growth and mitigate heavy metal stress. Herein, we isolated and identified the unclassified species strain NARS9, belong to Haloferax,. Cobalt (Co, 200 mg/kg soil) stress mitigating impact of the identified on wheat grains yield, primary and secondary metabolism and grain quality was investigated. Co alone significantly induced Co accumulation in wheat grain (260%), and consequently reduced wheat yield (130%) and quality. Haloferax NARS9 alone significantly enhanced grain chemicals composition (i.e., total sugars (89%) and organic acids (e.g., oxalic and isobutyric acids), essential amino acids (e.g., threonine, lysine, and histidine) and unsaturated fatty acids (e.g. eicosenoic, erucic and tetracosenoic acids). Interestingly, Co stress induced wheat grain yield, reduction were significantly mitigated by Haloferax NARS9 treatment by 26% compared to Co stress alone. Under Co stress, Haloferax NARS9 significantly increased sugar metabolism including sucrose and starch levels and their metabolic enzymes (i.e. invertases, sucrose synthase, starch synthase). This in turn increased organic acid (e.g. oxalic (70%) and malic acids (60%)) and amino acids. levels and biosynthetic enzymes, e.g. glutamine synthetase and threonine synthase. Increased sugars levels by Haloferax NARS9 under Co treatment also provided a route for the biosynthesis of saturated fatty acids, particularly palmitic and stearic acids. Furthermore, Haloferax NARS9 treatment supported the wheat nutritive value through increasing minerals (Ca, Fe, Mn, Zn) and antioxidants i.e., polyphenol, flavonoids, ASC and GSH and total polyamines by 50%, 110%, 400%, 30%, and 90% respectively). These in parallel with the increase in the activity of (phenylalanine ammonia-lyase (110%) in phenolic metabolism). Overall, this study demonstrates the potentiality of Haloferax NARS9 in harnessing carbon and nitrogen metabolism differentially in wheat plants to cope with Co toxicity. Our results also suggested that the use of Haloferax NARS9 in agricultural fields can improve growth and nutritional value of wheat grains.

Effect of astragaloside IV and salvianolic acid B on antioxidant stress and vascular endothelial protection in the treatment of atherosclerosis based on metabonomics.

Vascular endothelial cells and oxidation reduction system play an important role in the pathogenesis of atherosclerosis (AS). If these conditions are disordered, it will inevitably lead to plaque formation and even rupture. Astragaloside IV (AsIV) and salvianolic acid B (Sal B) are the main active ingredients of Astragalus membranaceus and Salvia miltiorrhiza, respectively, and found to ameliorate vascular endothelial dysfunction and protect against oxidative stress in recent studies. However, it is still unknown if the combination of AsIV and Sal B (AsIV + Sal B) can inhibit the development of plaque through amplifying the protective effect of vascular endothelial cells and anti-oxidative stress effect. To clarify the role of AsIV + Sal B in AS, we observed the efficacy of each group (Control, Model, AsIV, Sal B, and AsIV + Sal B) by biomolecular assays, such as observing the pathological morphology of the aorta by oil red O staining, evaluating the level of oxidative stress and endothelial cells in the serum by the Elisa test, and analyzing the changes of all small molecule metabolites in liver tissue by UPLC-QTOF-MS. Results showed that AsIV, Sal B and AsIV + Sal B decreased the deposition of lipid in the arterial wall, so as to exert the effect of anti-oxidant stress and vascular endothelial protection, where the inhibitory effect of AsIV + Sal B was the most obvious. Metabonomics analysis showed that Sal B regulated the metabolic pathways of arginine and proline. AsIV regulated glycerol metabolism and saturated fatty acid biosynthesis metabolism. AsIV + Sal B is mainly related to the regulation of the citrate cycle (TCA cycle), alanine, aspartic acid, and glutamate metabolism, cysteine, and methionine metabolism. Succinic acid and methionine are synergistic metabolites that exert an enhancing effect when AsIV and Sal B were used in combination. In conclusion, we demonstrated that AsIV acompanied with Sal B can be successfully used for anti-oxidative stress and vascular endothelial protection of AS, and succinic acid and methionine are the synergistic metabolites.

Zinc Finger Protein LipR Represses Docosahexaenoic Acid and Lipid Biosynthesis in Schizochytrium sp.

The heterotrophic marine microalgae Schizochytrium sp. is an important industrial producer of docosahexaenoic acid (DHA). Increased production of DHA and lipids in Schizochytrium sp. has been achieved by standard fermentation optimization and metabolic engineering methods; however, regulatory mechanisms for DHA and lipid biosynthesis remain unknown. In this study, the C2H2 zinc finger protein LipR was identified in Schizochytrium sp. ATCC 20888 by transcriptional analysis. Deletion of the lipR gene significantly (P < 0.001) increased production of total lipids and DHA by 33% and 48%, respectively. LipR repressed DHA and lipid production by directly inhibiting transcription of polyunsaturated fatty acid (PUFA) and fatty acid synthase (FAS) genes (pfa1, pfa2, pfa3, and fas). Specific binding of LipR to 9-bp recognition sequence 5'-(C/A)(A/G)CCATCTT-3' in upstream regions of target genes was demonstrated by electrophoretic mobility shift assays (EMSAs) and DNase I footprinting assays. Expression of several key genes (acc, acl, ampD, fabD, mae, zwf, and dga1) related to levels of precursors and NADPH, and to triacylglycerol storage rate, were also directly repressed by LipR. Our findings, taken together, indicate that the evolutionarily unique regulator LipR is an essential repressor of DHA and saturated fatty acid biosynthesis in Schizochytrium sp. IMPORTANCE Regulatory mechanisms for DHA and saturated fatty acid biosynthesis in the heterotrophic marine microalgae Schizochytrium sp. are unclear. We demonstrate here that deletion of the gene (lipR) encoding the C2H2 zinc finger protein LipR promotes DHA and saturated fatty acid production in this genus. LipR acts as a key repressor of such production by binding to 9-bp consensus sequence 5'-(C/A)(A/G)CCATCTT-3' in the upstream regions of polyunsaturated fatty acid and fatty acid synthase genes (pfa1, pfa2, pfa3, and fas), and genes related to levels of precursors and NADPH (acc, acl, ampD, fabD, mae, and zwf), and to triacylglycerol storage rate (dga1). This is the first demonstration that a regulator inhibits synthesis of DHA and lipids in Schizochytrium sp. by directly controlling transcription of PUFA synthase and fas genes. Manipulation of the lipR gene provides a potential strategy for enhancing accumulation of polyunsaturated fatty acids and lipids in thraustochytrids.

Identification dehydratase domains from Schizochytrium sp. and Shewanella sp. and distinct functions in biosynthesis of fatty acids.

Polyunsaturated fatty acid (PUFA) synthase is a special and effective enzyme for PUFA synthesis, and dehydratase (DH) domain played a crucial role in it. In this work, we compared four different DH domains from different strains (Schizochytrium sp. HX-308 and Shewanella sp. BR-2) and different gene clusters. First bioinformatics analysis showed that DH1, 2 and DH3 were similar to FabA and PKS-DH, respectively, and all of them got a hot-dog structure. Second, four DH domains were expressed in Escherichia coli that increased biomass. Especially, Schi-DH1,2 presented the highest dry cell weight of 2.3g/L which was 1.62 times of that of control. Fatty acids profile analysis showed that DH1,2 could enhance the percentage of unsaturated fatty acids, especially DH1,2 from Schizochytrium sp., while DH3 benefited for the saturated fatty acid biosynthesis. Furthermore, five kinds of fatty acids were added to the medium to study the substrate preferences. Results revealed that DH1,2 domain preferred to acting on C16:0, while DH3 domain trended acting on C14:0 and C15:0, which illustrated DH from different clusters do have specific substrate preference. Besides, DH expression could save the cell growth inhibition by mid-chain fatty acids. This study provided more information about the catalysis mechanism of polyunsaturated fatty acid synthase and might promote the modification study based on this enzyme.

Clostridium cellulovorans Proteomic Responses to Butanol Stress.

Combination of butanol-hyperproducing and hypertolerant phenotypes is essential for developing microbial strains suitable for industrial production of bio-butanol, one of the most promising liquid biofuels. Clostridium cellulovorans is among the microbial strains with the highest potential for direct production of n-butanol from lignocellulosic wastes, a process that would significantly reduce the cost of bio-butanol. However, butanol exhibits higher toxicity compared to ethanol and C. cellulovorans tolerance to this solvent is low. In the present investigation, comparative gel-free proteomics was used to study the response of C. cellulovorans to butanol challenge and understand the tolerance mechanisms activated in this condition. Sequential Window Acquisition of all Theoretical fragment ion spectra Mass Spectrometry (SWATH-MS) analysis allowed identification and quantification of differentially expressed soluble proteins. The study data are available via ProteomeXchange with the identifier PXD024183. The most important response concerned modulation of protein biosynthesis, folding and degradation. Coherent with previous studies on other bacteria, several heat shock proteins (HSPs), involved in protein quality control, were up-regulated such as the chaperones GroES (Cpn10), Hsp90, and DnaJ. Globally, our data indicate that protein biosynthesis is reduced, likely not to overload HSPs. Several additional metabolic adaptations were triggered by butanol exposure such as the up-regulation of V- and F-type ATPases (involved in ATP synthesis/generation of proton motive force), enzymes involved in amino acid (e.g., arginine, lysine, methionine, and branched chain amino acids) biosynthesis and proteins involved in cell envelope re-arrangement (e.g., the products of Clocel_4136, Clocel_4137, Clocel_4144, Clocel_4162 and Clocel_4352, involved in the biosynthesis of saturated fatty acids) and a redistribution of carbon flux through fermentative pathways (acetate and formate yields were increased and decreased, respectively). Based on these experimental findings, several potential gene targets for metabolic engineering strategies aimed at improving butanol tolerance in C. cellulovorans are suggested. This includes overexpression of HSPs (e.g., GroES, Hsp90, DnaJ, ClpC), RNA chaperone Hfq, V- and F-type ATPases and a number of genes whose function in C. cellulovorans is currently unknown.

Abstract 1004: Defining stearoyl-CoA desaturase 1 as a molecular therapeutic target against cholangiocarcinoma

Abstract Cancer cells increase lipid metabolism by up-regulation lipogenic enzymes such as stearoyl-CoA desaturase 1 (SCD1). It is the rate-limiting enzyme in the de novo synthesis of fatty acids (FAs), catalyzing the conversion and biosynthesis of saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs). We developed SSI-4, a novel highly specific SCD1 inhibitor. The anti-tumor activity ofSSI-4 was examined against different cholangiocarcinoma (CCA) models that included human and mouseCCA cell lines, CCA patient-derived xenografts (PDX) NOD SCID gamma (NSG) mouse models, and CCA PDX derived organoids. Using cell proliferation assay, we examined twelve CCA cell lines and 4 were very sensitive to SSI-4 (1-40 nM IC50). The remaining CCA cell lines showed moderate to no sensitivity to SSI-4. Studies at the protein level have shown that SCD1 is present in both sensitive and non-sensitive cells. Thus, SCD1 must be present in sensitive cells but is not predictive of response to an SCD1 inhibitor. In an effort to identify biomarkers predicting response to therapy, we performed assays, such as lipid, lactate, or energy phenotype which identified elevated lactate and unsaturated fatty acid levels as well as a glycolytic energy phenotype. In vivo, CCA PDX models have demonstrated that SSI-4strongly inhibited tumor growth. Immunohistochemical analysis of CCA tumors revealed elevated glycolytic genes in sensitive cells and thus, a potential predictive biomarker. We are currently pursuing a better understanding of the relationship between glycolysis and fatty acid synthesis/metabolism. We are also testing novel combination therapy of SSI-4 with the standard of care and other drugs to develop novel treatments for CCA. Using CCA PDX derived organoids showed synergistic antitumor activity of SSI-4in combination with cancer standard of care drugs such as gemcitabine and cisplatin. Collectively, we expect to develop a biomarker-driven selection of CCA patients sensitive to SCD1 inhibitors and novel SSI-4 combination therapy leading to improved patient survival. Citation Format: Justyna J. Gleba, Laura A. Marlow, Erin E. Miller, James L. Miller, Aylin Alasonyalilar-Demirer, Yi Guo, Kabir Mody, Lewis R. Roberts, Steven R. Alberts, Mark J. Truty, Tushar C. Patel, John A. Copland. Defining stearoyl-CoA desaturase 1 as a molecular therapeutic target against cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1004.

Low-temperature effects on docosahexaenoic acid biosynthesis in Schizochytrium sp. TIO01 and its proposed underlying mechanism

BackgroundSchizochytrium species are known for their abundant production of docosahexaenoic acid (DHA). Low temperatures can promote the biosynthesis of polyunsaturated fatty acids (PUFAs) in many species. This study investigates low-temperature effects on DHA biosynthesis in Schizochytrium sp. TIO01 and its underlying mechanism.ResultsThe Schizochytrium fatty acid biosynthesis pathway was evaluated based on de novo genome assembly (contig N50 = 2.86 Mb) and iTRAQ-based protein identification. Our findings revealed that desaturases, involved in DHA synthesis via the fatty acid synthase (FAS) pathway, were completely absent. The polyketide synthase (PKS) pathway and the FAS pathway are, respectively, responsible for DHA and saturated fatty acid synthesis in Schizochytrium. Analysis of fatty acid composition profiles indicates that low temperature has a significant impact on the production of DHA in Schizochytrium, increasing the DHA content from 43 to 65% of total fatty acids. However, the expression levels of PKS pathway genes were not significantly regulated as the DHA content increased. Further, gene expression analysis showed that pathways related to the production of substrates (acetyl-CoA and NADPH) for fatty acid synthesis (the branched-chain amino acid degradation pathway and the pentose phosphate pathway) and genes related to saturated fatty acid biosynthesis (the FAS pathway genes and malic enzyme) were, respectively, upregulated and downregulated. These results indicate that low temperatures increase the DHA content by likely promoting the entry of relatively large amounts of substrates into the PKS pathway.ConclusionsIn this study, we provide genomic, proteomic, and transcriptomic evidence for the fatty acid synthesis pathway in Schizochytrium and propose a mechanism by which low temperatures promote the accumulation of DHA in Schizochytrium. The high-quality and nearly complete genome sequence of Schizochytrium provides a valuable reference for investigating the regulation of polyunsaturated fatty acid biosynthesis and the evolutionary characteristics of Thraustochytriidae species.

Human Fatty Acid Synthase: A Computational Study of the Transfer of the Acyl Moieties from MAT to the ACP Domain

AbstractHuman Fatty Acid Synthase (hFAS) is a multidomain enzyme responsible for the biosynthesis of saturated fatty acids, which are crucial for numerous biological processes. During the biosynthetic reaction, hFAS incorporates acetyl and malonyl moieties through the action of its malonyl‐acetyl transferase (MAT) domain. These precursor molecules are transferred from CoA to the acyl‐carrier protein (ACP) domain by a two‐stage ping‐pong catalytic mechanism. The first stage, during which the acyl moieties are relocated from CoA to the MAT domain, has been elucidated in a previous work of ours. In this study, we employ QM/MM calculations at the DLPNO‐CCSD(T)/CBS:AMBER level of theory to understand the catalytic machinery behind the transfer of the acyl moieties from MAT to the ACP domain. The results show that the acyl transfer to the ACP's phosphopantetheine (PNS) occurs in two sequential events: Step 3) asynchronous concerted reaction that combines the deprotonation of the PNS's thiol group and the nucleophilic attack on the acyl‐Ser581 ester carbon; Step 4) tetrahedral intermediate breakdown and regeneration of the catalytic Ser581/His683 dyad. The energy barriers of these two steps are inferior to those reported for the first catalytic stage, suggesting that the rate‐limiting step of the MAT mechanism lies on Stage 1, particularly on the concerted nucleophilic attack that starts the reaction. The oxyanion hole, formed by the backbone amines of Met499 and Leu582, was reported to transiently stabilize the tetrahedral intermediate and to play a favorable catalytic effect on the overall MAT reaction, particularly through the reduction of the energetic span. The knowledge gathered in this work complements previous experimental and theoretical studies and instigates further investigations that explore the therapeutic potential of hFAS.

Aldose reductase inhibitor protects mice from alcoholic steatosis by repressing saturated fatty acid biosynthesis

Alcoholic liver injury results in morbidity and mortality worldwide, but there are currently no effective and safe therapeutics. Previously we demonstrated that aldose reductase (AR) inhibitor ameliorated alcoholic hepatic steatosis. To clarify the mechanism whereby AR inhibitor improves alcoholic hepatic steatosis, herein we investigated the effect of AR inhibitor on hepatic metabolism in mice fed a Lieber-DeCarli liquid diet with 5% ethanol. Nontargeted metabolomics showed carbohydrates and lipids were characteristic categories in ethanol diet-fed mice with or without AR inhibitor treatment, whereas AR inhibitor mainly affected carbohydrates and peptides. Ethanol-induced galactose metabolism and fatty acid biosynthesis are important for the induction of hepatic steatosis, while AR inhibitor impaired galactose metabolism without perturbing fatty acid biosynthesis. In parallel with successful treatment of steatosis, AR inhibitor suppressed ethanol-activated galactose metabolism and saturated fatty acid biosynthesis. Sorbitol in galactose metabolism and stearic acid in saturated fatty acid biosynthesis were potential biomarkers responsible for ethanol or ethanol plus AR inhibitor treatment. In vitro analysis confirmed that exogenous addition of sorbitol augmented ethanol-induced steatosis and stearic acid. These findings not only reveal metabolic patterns associated with disease and treatment, but also shed light on functional biomarkers contribute to AR inhibition therapy.

Modeling of Human Fatty Acid Synthase and in Silico Docking of Acyl Carrier Protein Domain and Its Partner Catalytic Domains.

Human fatty acid synthase (hFAS) is a megasynthase whose main function is de novo biosynthesis of saturated fatty acids. Interest has been drawn to this enzyme beyond its physiological role due to the association between high levels of hFAS and clinical conditions such as obesity, diabetes, and cancer. Thus, it has become an undeniably attractive pharmacological target. Until now, no crystal structure of the complete hFAS is available, hindering attempts to fully understand this protein. Using homology modeling, we built a model of the entire megasynthase, encompassing all of its domains, including the acyl carrier protein (ACP) and thioesterase (TE) mobile domains absent in the crystal structure of mammalian fatty acid synthase (FAS). On a second stage, we used data-driven protein-protein docking between the substrate shuttling domain ACP and every catalytic domain in the protein. We also propose sets of amino acids at the interface of each domain that we believe are important to favor the interaction between ACP and each domain of hFAS. After inspection, we validated each complex between ACP and MAT/KS/KR/DH/ER domains through classical molecular dynamics simulations and RMSd analysis. Additionally, we mapped the interactions between the residues at the active site of each catalytic domain and its intermediaries. In every docking, we ensured that the distance between catalytic residues and the intermediaries was maintained. Until now, there was not a complete 3D model of this megasynthase. This study is the first to present a homology model for the whole hFAS, including its two mobile domains and possible poses of ACP throughout the cycle of fatty acid biosynthesis, thus mapping obligatory checkpoints in its trajectory. Hence, we believe that these structural insights will allow for future studies of the catalytic mechanism of the overall hFAS.

A chemical approach to manipulate the algal growth, lipid content and high-value alpha-linolenic acid for biodiesel production

Microalgal cultivation systems for energy production are not yet economically viable due to the low yield of lipids and biomass. In this study, we propose a chemical approach, using exogenous bioactive molecules for improving algal growth, lipid content and the production of high-value alpha-linolenic acid (ALA), using Chlorella protothecoides as a model. Based on our findings, among the cytokinin and auxin classes, Kinetin increased the biosynthesis of ALA by 26.5% at 1ppm concentration, and indole-3-butyric acid at 2ppm improved the biomass and lipid productivity up to 29.15±2.02gm−2day−1, and 6.69±0.56gm−2day−1, respectively. Methyl jasmonate as a stress-related phytohormone also showed a positive stimulatory effect on growth of C. protothecoides, and the biomass productivity was increased up to 25.26±1.48gm−2day−1 at the concentration of 5ppm (lipid content: 219.66±13.20mgg−1dw; lipid productivity: 5.61±0.25gm−2day−1; ALA: 0.81±0.16gm−2day−1). A difference in the composition of fatty acids, due to the type and concentrations of stress-related phytohormones was observed, and under the influence of stress-related phytohormones, the biosynthesis of saturated fatty acids increased, and polyunsaturated fatty acids decreased in C. protothecoides. Butylated hydroxyanisole, at a concentration of 0.05ppm, increased the ALA content by 60.5%. Our study shows that the proposed bioactive molecules could increase the biomass productivity of C. protothecoides at a lower cost compared to the use of acetate as a carbon source.

Fatty acid-related modulations of membrane fluidity in cells: detection and implications

Metabolic homeostasis of fatty acids is complex and well-regulated in all organisms. The biosynthesis of saturated fatty acids (SFA) in mammals provides substrates for β-oxidation and ATP production. Monounsaturated fatty acids (MUFA) are products of desaturases that introduce a methylene group in cis geometry in SFA. Polyunsaturated fatty acids (n-6 and n-3 PUFA) are products of elongation and desaturation of the essential linoleic acid and α-linolenic acid, respectively. The liver processes dietary fatty acids and exports them in lipoproteins for distribution and storage in peripheral tissues. The three types of fatty acids are integrated in membrane phospholipids and determine their biophysical properties and functions. This study was aimed at investigating effects of fatty acids on membrane biophysical properties under varying nutritional and pathological conditions, by integrating lipidomic analysis of membrane phospholipids with functional two-photon microscopy (fTPM) of cellular membranes. This approach was applied to two case studies: first, pancreatic beta-cells, to investigate hormetic and detrimental effects of lipids. Second, red blood cells extracted from a genetic mouse model defective in lipoproteins, to understand the role of lipids in hepatic diseases and metabolic syndrome and their effect on circulating cells.

Seed Oil Content and Fatty Acid Composition from Different Populations of Calotropis procera (Aiton) W. T. Aiton (Apocynaceae)

AbstractCalotropis procera is a soft‐wooded, evergreen, perennial shrub species which grows in a variety of environments including dry habitats such as the Brazilian semi‐arid region. This study aimed to evaluate the variation in the oil content and fatty acid composition of C. procera seeds from four climatically different locations in the state of Pernambuco in the northeast of Brazil. The seed oil content of C. procera ranged from 19.7 to 24.0 %. Five main fatty acids were identified, with a predominance of unsaturated linoleic and oleic acids (approximately 70 %). Our results suggesting that environmental conditions influenced the seed oil biosynthesis of C. procera, because the localities with high temperature and low precipitation had increased oil content and total biosynthesis of saturated fatty acids. Multivariate analysis showed high similarity among three localities which share certain physiographic characteristics and climatic conditions such as temperature and precipitation values. The oil profile of C. procera presents interesting features that highlight its potential as a future alternative for the biodiesel market, especially in semi‐arid regions.

Inhibition of StearoylCoA Desaturase-1 Inactivates Acetyl-CoA Carboxylase and Impairs Proliferation in Cancer Cells: Role of AMPK

Cancer cells activate the biosynthesis of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in order to sustain an increasing demand for phospholipids with appropriate acyl composition during cell replication. We have previously shown that a stable knockdown of stearoyl-CoA desaturase 1 (SCD1), the main Δ9-desaturase that converts SFA into MUFA, in cancer cells decreases the rate of lipogenesis, reduces proliferation and in vitro invasiveness, and dramatically impairs tumor formation and growth. Here we report that pharmacological inhibition of SCD1 with a novel small molecule in cancer cells promoted the activation of AMP-activated kinase (AMPK) and the subsequent reduction of acetylCoA carboxylase activity, with a concomitant inhibition of glucose-mediated lipogenesis. The pharmacological inhibition of AMPK further decreased proliferation of SCD1-depleted cells, whereas AMPK activation restored proliferation to control levels. Addition of supraphysiological concentrations of glucose or pyruvate, the end product of glycolysis, did not reverse the low proliferation rate of SCD1-ablated cancer cells. Our data suggest that cancer cells require active SCD1 to control the rate of glucose-mediated lipogenesis, and that when SCD1 activity is impaired cells downregulate SFA synthesis via AMPK-mediated inactivation of acetyl-CoA carboxylase, thus preventing the harmful effects of SFA accumulation.

Regulation of fatty acid metabolism in bacteria

In Escherichia coli, the main player in transcription regulation of fatty acid metabolism is the FadR protein, which is involved in negative regulation of fatty acid degradation and in positive and negative regulation of the cellular processes related to it, as well as in positive regulation of the biosynthesis of unsaturated fatty acids in a concerted manner with negative regulation of FabR. On the other hand, Bacillus subtilis possesses two global transcriptional regulators, FadR (YsiA) and FapR. B. subtilis FadR represses fatty acid degradation, whereas FapR represses almost all the processes in the biosynthesis of saturated fatty acids and phospholipids. Furthermore, Streptococcus pneumoniae FabT represses the genes of fatty acid biosynthesis that are clustered in its genome. Long-chain acyl-CoAs appear to be metabolic signals for fatty acid degradation by bacteria in general, and antagonize the FadR protein from either E. coli or B. subtilis. However, malonyl-CoA is a metabolic signal for fatty acid and phospholipid biosynthesis by Gram-positive low-GC bacteria, and it antagonizes FapR. These would be the primary aspects for understanding the elaborate and complex regulation of fatty acid metabolism in bacteria to maintain membrane lipid homeostasis.