Comprehensive analysis of stearoyl-coenzyme A desaturase in prostate adenocarcinoma: insights into gene expression, immune microenvironment and tumor progression.

Prostate adenocarcinoma (PRAD) is a prevalent global malignancy which depends more on lipid metabolism for tumor progression compared to other cancer types. Although Stearoyl-coenzyme A desaturase (SCD) is documented to regulate lipid metabolism in multiple cancers, landscape analysis of its implications in PRAD are still missing at present. Here, we conducted an analysis of diverse cancer datasets revealing elevated SCD expression in the PRAD cohort at both mRNA and protein levels. Interestingly, the elevated expression was associated with SCD promoter hypermethylation and genetic alterations, notably the L134V mutation. Integration of comprehensive tumor immunological and genomic data revealed a robust positive correlation between SCD expression levels and the abundance of CD8+ T cells and macrophages. Further analyses identified significant associations between SCD expression and various immune markers in tumor microenvironment. Single-cell transcriptomic profiling unveiled differential SCD expression patterns across distinct cell types within the prostate tumor microenvironment. The Gene Ontology and Kyoto Encyclopedia of Genes and Genome analyses showed that SCD enriched pathways were primarily related to lipid biosynthesis, cholesterol biosynthesis, endoplasmic reticulum membrane functions, and various metabolic pathways. Gene Set Enrichment Analysis highlighted the involvement of elevated SCD expression in crucial cellular processes, including the cell cycle and biosynthesis of cofactors pathways. In functional studies, SCD overexpression promoted the proliferation, metastasis and invasion of prostate cancer cells, whereas downregulation inhibits these processes. This study provides comprehensive insights into the multifaceted roles of SCD in PRAD pathogenesis, underscoring its potential as both a therapeutic target and prognostic biomarker.

Combination of low glucose and SCD1 inhibition impairs cancer metabolic plasticity and growth in MCF-7 cancer cells: a comprehensive metabolomic and lipidomic analysis.

BACKGROUND: Cancer cells exhibit remarkable metabolic plasticity, enabling them to adapt to fluctuating nutrient conditions. This study investigates the impact of a combination of low glucose levels and inhibition of stearoyl-CoA desaturase 1 (SCD1) using A939572 on cancer metabolic plasticity and growth. METHODS: A comprehensive metabolomic and lipidomic analysis was conducted to unravel the intricate changes in cellular metabolites and lipids. MCF-7 cells were subjected to low glucose conditions, and SCD1 was inhibited using A939572. The resulting alterations in metabolic pathways and lipid profiles were explored to elucidate the synergistic effects on cancer cell physiology. RESULTS: The combination of low glucose and A939572-induced SCD1 inhibition significantly impaired cancer cell metabolic plasticity. Metabolomic analysis highlighted shifts in key glycolytic and amino acid pathways, indicating the cells' struggle to adapt to restricted glucose availability. Lipidomic profiling revealed alterations in lipid composition, implying disruptions in membrane integrity and signaling cascades. CONCLUSION: Our findings underscore the critical roles of glucose availability and SCD1 activity in sustaining cancer metabolic plasticity and growth. Simultaneously targeting these pathways emerges as a promising strategy to impede cancer progression. The comprehensive metabolomic and lipidomic analysis provides a detailed roadmap of molecular alterations induced by this combination treatment, that may help identify potential therapeutic targets.

Severity Ranking of Missense and Frameshift Genetic Variants in SCD1 by In Silico and In Vitro Functional Analysis.

BACKGROUND: A considerable proportion of the symptoms associated with excessive dietary intake can be attributed to systemic imbalances in lipid metabolism. The prominent toxicity of saturated fatty acids has been repeatedly demonstrated and sheds light on the protective role of stearoyl-CoA desaturase-1 (SCD1), the key enzyme for fatty acid desaturation. SCD1 protein expression is regulated at the levels of transcription, translation, and degradation. However, the modulating effect of the variability of the human genome must also be taken into account. Therefore, we aimed to ascertain whether natural missense or frameshift mutations in SCD1 (p.H125P, p.M224L, p.A333T, p.R253AfsTer7) could influence the expression, degradation, or function of the enzyme. METHODS: In silico and in vitro experiments were conducted to comprehensively evaluate the consequences associated with each genetic variation, with the objective of using the results to propose a risk or severity ranking of SCD1 variants. RESULTS: As anticipated, the p.R253AfsTer7 variant was identified as the most deleterious in structural, functional, and quantitative terms. The p.H125P variant also reduced the desaturation capacity of the enzyme in accordance with the predicted structural alterations and augmented degradation resulting from folding complications. This was aggravated by increased mRNA instability and accompanied by mild endoplasmic reticulum stress induction. The p.A333T protein exhibited an intermediate phenotype, whereas p.M224L showed no deleterious effects and even increased the amount of SCD1. CONCLUSIONS: In conclusion, the large-scale identification of genetic variations needs to be supplemented with comprehensive functional characterization of these variations to facilitate adequate personalized prevention and treatment of lipid metabolism-related conditions.

Utility of Arabidopsis KASII Promoter in Development of an Effective CRISPR/Cas9 System for Soybean Genome Editing and Its Application in Engineering of Soybean Seeds Producing Super-High Oleic and Low Saturated Oils.

This study reports the use of the Arabidopsis KASII promoter (AtKASII) to develop an efficient CRISPR/Cas9 system for soybean genome editing. When this promoter was paired with Arabidopsis U6 promoters to drive Cas9 and single guide RNA expression, respectively, simultaneous editing of the three fatty acid desaturase genes GmFAD2-1A, GmFAD2-1B, and GmFAD3A occurred in more than 60% of transgenic soybean lines at T2 generation, and all the triple mutants possessed desirable high-oleic traits. In sharp contrast, not a single line underwent simultaneous editing of the three target genes when AtKASII was replaced by the widely used AtEC1.2 promoter. Furthermore, our study showed that the stable and inheritable mutations in the high-oleic lines did not alter the overall contents of oil and protein or amino acid composition while increasing the oleic acid content up to 87.6% from approximately 23.8% for wild-type seeds, concomitant with 34.4- and 3.7-fold reductions in linoleic and linolenic acid, respectively. Collectively, this study demonstrates that the AtKASII promoter is highly promising for optimization of the CRISPR/Cas9 system for genome editing in soybean and possibly beyond.

Transcriptomic characterization of recombinant Clostridium beijerinckii NCIMB 8052 expressing methylglyoxal synthase and glyoxal reductase from Clostridium pasteurianum ATCC 6013.

Bioconversion of abundant lactose-replete whey permeate to value-added chemicals holds promise for valorization of this expanding food processing waste. Efficient conversion of whey permeate-borne lactose requires adroit microbial engineering to direct carbon to the desired chemical. An engineered strain of Clostridium beijerinckii NCIMB 8052 (C. beijerinckii_mgsA+mgR) that produces 87% more butanol on lactose than the control strain was assessed for global transcriptomic changes. The results revealed broadly contrasting gene expression patterns in C. beijerinckii_mgsA+mgR relative to the control strain. These were characterized by widespread decreases in the abundance of mRNAs of Fe-S proteins in C. beijerinckii_mgsA+mgR, coupled with increased differential expression of lactose uptake and catabolic genes, iron uptake genes, two-component signal transduction and motility genes, and genes involved in the biosynthesis of vitamins B5 and B12, aromatic amino acids (particularly tryptophan), arginine, and pyrimidines. Conversely, the mRNA patterns suggest that the L-aspartate-dependent de novo biosynthesis of NAD as well as biosynthesis of lysine and asparagine and metabolism of glycine and threonine were likely down-regulated. Furthermore, genes involved in cysteine and methionine biosynthesis and metabolism, including cysteine desulfurase-a central player in Fe-S cluster biosynthesis-equally showed reductions in mRNA abundance. Genes involved in biosynthesis of capsular polysaccharides and stress response also showed reduced mRNA abundance in C. beijerinckii_mgsA+mgR. The results suggest that remodeling of cellular and metabolic networks in C. beijerinckii_mgsA+mgR to counter anticipated effects of methylglyoxal production from heterologous expression of methylglyoxal synthase led to enhanced growth and butanol production in C. beijerinckii_mgsA+mgR. IMPORTANCE: Biological production of commodity chemicals from abundant waste streams such as whey permeate represents an opportunity for decarbonizing chemical production. Whey permeate remains a vastly underutilized feedstock for bioproduction purposes. Thus, enhanced understanding of the cellular and metabolic repertoires of lactose-mediated production of chemicals such as butanol promises to identify new targets that can be fine tuned in recombinant and native microbial strains to engender stronger coupling of whey permeate-borne lactose to value-added chemicals. Our results highlight new genetic targets for future engineering of C. beijerinckii for improved butanol production on lactose and ultimately in whey permeate.

Hypoxia-responsive micelles deprive cofactor of stearoyl-CoA desaturase-1 and sensitize ferroptotic ovarian cancer therapy.

Ferroptosis has been recognized as a promising therapeutic strategy for cancer due to its unique mechanism of action. However, the upregulation of stearoyl-CoA desaturase 1 (SCD1) in ovarian cancer leads to resistance to ferroptotic therapy. Zinc ion (Zn2+) serves as the cofactor of SCD1. It was hypothesized that selective deprivation of Zn2+ from SCD1 could sensitize ferroptotic ovarian cancer therapy. Here, we report a hypoxia-responsive polymer micelle for enhanced ferroptosis of ovarian cancer cells. A SCD1 inhibitor, PluriSIn 1 (Plu), and a ferroptosis inducer, Auranofin (Aur), were co-encapsulated in nitroimidazole-bearing micelles. Under the hypoxic tumor microenvironment, the conversion of nitroimidazole to aminoimidazole triggered the cargo release and induced the depletion of antioxidant molecules (e.g., glutathione, thioredoxin, and NADPH). Meanwhile, because of the strong coordination between aminoimidazole and Zn2+ compared to that of histidine and Zn2+, such conversion can deprive the metal cofactor of SCD1, hence sensitizing the action of Plu and Aur. The proof-of-concept was demonstrated in cell and animal models with minimal systemic toxicity. The current work integrates ferroptosis induction with SCD1 inhibition in a hypoxia-responsive vehicle, offering a promising strategy for addressing the ferroptosis resistance and opening novel avenues for managing the difficult-to-treat ovarian cancer.

Fads2 knockout mice reveal that ALA prevention of hepatic steatosis is dependent on delta-6 desaturase activity.

The production of the omega-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from alpha-linolenic acid (ALA) relies on the delta-6 desaturase (D6D) enzyme encoded by the Fads2 gene. While EPA and DHA reduce hepatic triacylglycerol (TAG) storage and regulate lipogenesis, the independent impact of ALA is less understood. To address this gap in knowledge, hepatic fatty acid metabolism was investigated in male wildtype (WT) and Fads2 knockout (KO) mice fed diets (16% kcal from fat) containing either lard (no n-3 LCPUFA), flaxseed oil (ALA rich), or menhaden oil (EPA/DHA rich) for 21 weeks. Fat content and composition, as well as markers of lipogenesis, glyceroneogenesis, and TAG synthesis, were analyzed using histology, gas chromatography, and reverse transcription quantitative PCR (RT-qPCR). Mice fed the menhaden diet had significantly lower hepatic TAG compared to both lard- and flax-fed mice, concomitant with changes in n-3 and n-6 LCPUFA in both TAG and phospholipid (PL) fractions (all p < 0.05). Flax-fed WT mice had lower liver TAG content compared to their KO counterparts. Menhaden-fed mice had significantly lower expression of key lipogenic (Scd1, Srebp-1c, Fasn, Fads1, Fads2), glyceroneogenic (Pck1), and TAG synthesis (Agpat3) genes compared to lard, with flax-fed mice showing some intermediate effects. Gene expression effects were independent of D6D activity, since no differences were detected between WT and KO mice fed the same diet. This study demonstrates that EPA/DHA and not ALA itself is critical for the prevention of hepatic steatosis.

Crucial amino acids identified in Δ12 fatty acid desaturases related to linoleic acid production in Perilla frutescens.

Perilla oil from the medicinal crop Perilla frutescens possess a wide range of biological activities and is generally used as an edible oil in many countries. The molecular basis for its formation is of particular relevance to perilla and its breeders. Here in the present study, four PfFAD2 genes were identified in different perilla cultivars, PF40 and PF70, with distinct oil content levels, respectively. Their function was characterized in engineered yeast strain, and among them, PfFAD2-1PF40, PfFAD2-1PF70 had no LA biosynthesis ability, while PfFAD2-2PF40 in cultivar with high oil content levels possessed higher catalytic activity than PfFAD2-2PF70. Key amino acid residues responsible for the enhanced catalytic activity of PfFAD2-2PF40 was identified as residue R221 through sequence alignment, molecular docking, and site-directed mutation studies. Moreover, another four amino acid residues influencing PfFAD2 catalytic activity were discovered through random mutation analysis. This study lays a theoretical foundation for the genetic improvement of high-oil-content perilla cultivars and the biosynthesis of LA and its derivatives.

Small molecule inhibitors of fungal Δ(9) fatty acid desaturase as antifungal agents against Candida auris.

Candida auris has emerged as a significant healthcare-associated pathogen due to its multidrug-resistant nature. Ongoing constraints in the discovery and provision of new antifungals create an urgent imperative to design effective remedies to this pressing global blight. Herein, we screened a chemical library and identified aryl-carbohydrazide analogs with potent activity against both C. auris and the most prevalent human fungal pathogen, C. albicans. SPB00525 [N'-(2,6-dichlorophenyl)-5-nitro-furan-2-carbohydrazide] exhibited potent activity against different strains that were resistant to standard antifungals. Using drug-induced haploinsufficient profiling, transcriptomics and metabolomic analysis, we uncovered that Ole1, a Δ(9) fatty acid desaturase, is the likely target of SPB00525. An analog of the latter, HTS06170 [N'-(2,6-dichlorophenyl)-4-methyl-1,2,3-thiadiazole-5-carbohydrazide], had a superior antifungal activity against both C. auris and C. albicans. Both SPB00525 and HTS06170 act as antivirulence agents and inhibited the invasive hyphal growth and biofilm formation of C. albicans. SPB00525 and HTS06170 attenuated fungal damage to human enterocytes and ameliorate the survival of Galleria mellonella larvae used as systemic candidiasis model. These data suggest that inhibiting fungal Δ(9) fatty acid desaturase activity represents a potential therapeutic approach for treating fungal infection caused by the superbug C. auris and the most prevalent human fungal pathogen, C. albicans.

Lipid-Mediated Mechanisms of Thermal Adaptation and Thermoregulatory Behavior in Animals.

Temperature affects a variety of cellular processes because the molecular motion of cellular constituents and the rate of biochemical reactions are sensitive to temperature changes. Thus, the adaptation to temperature is necessary to maintain cellular functions during temperature fluctuation, particularly in poikilothermic organisms. For a wide range of organisms, cellular lipid molecules play a pivotal role during thermal adaptation. Temperature changes affect the physicochemical properties of lipid molecules, resulting in the alteration of cell membrane-related functions and energy metabolism. Since the chemical structures of lipid molecules determine their physicochemical properties and cellular functions, cellular lipids, particularly fatty acid-containing lipid molecules, are remodeled as a thermal adaptation response to compensate for the effects of temperature change. In this chapter, we first introduce the structure and biosynthetic pathway of fatty acid-containing lipid molecules, such as phospholipid and triacylglycerol, followed by a description of the cellular lipid-mediated mechanisms of thermal adaptation and thermoregulatory behavior in animals.

Biosynthetic mechanisms of omega-3 polyunsaturated fatty acids in microalgae.

Marine microalgae are the primary producers of ω3 polyunsaturated fatty acids (PUFAs), such as octadecapentaenoic acid (OPA, 18:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) for food chains. However, the biosynthetic mechanisms of these PUFAs in the algae remain elusive. To study how these fatty acids are synthesized in microalgae, a series of radiolabeled precursors were used to trace the biosynthetic process of PUFAs in Emiliania huxleyi. Feeding the alga with 14C-labeled acetic acid in a time course showed that OPA was solely found in glycoglycerolipids such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) synthesized plastidically by sequential desaturations while DHA was exclusively found in phospholipids synthesized extraplastidically. Feeding the alga with 14C-labeled α-linolenic acid (ALA), linoleic acid (LA), and oleic acid (OA) showed that DHA was synthesized extraplastidically from fed ALA and LA, but not from OA, implying that the aerobic pathway of DHA biosynthesis is incomplete with missing a Δ12 desaturation step. The in vitro enzymatic assays with 14C-labeled malonyl-CoA showed that DHA was synthesized from acetic acid by a PUFA synthase. These results provide the first and conclusive biochemistry evidence that OPA is synthesized by a plastidic aerobic pathway through sequential desaturations with the last step of Δ3 desaturation, while DHA is synthesized by an extraplastidic anaerobic pathway catalyzed by a PUFA synthase in the microalga.

Delta-6 desaturase FADS2 is a tumor-promoting factor in cholangiocarcinoma.

Cholangiocarcinoma is a fatal disease with limited therapeutic options. We screened genes required for cholangiocarcinoma tumorigenicity and identified FADS2, a delta-6 desaturase. FADS2 depletion reduced in vivo tumorigenicity and cell proliferation. In clinical samples, FADS2 was expressed in cancer cells but not in stromal cells. FADS2 inhibition also reduced the migration and sphere-forming ability of cells and increased apoptotic cell death and ferroptosis markers. Lipidome assay revealed that triglyceride and cholesterol ester levels were decreased in FADS2-knockdown cells. The oxygen consumption ratio was also decreased in FADS2-depleted cells. These data indicate that FADS2 depletion causes a reduction in lipid levels, resulting in decrease of energy production and attenuation of cancer cell malignancy.

Stearoyl-CoA desaturase 1 is targeted by EBV-encoded miR-BART20-5p and regulates cell autophagy, proliferation, and migration in EBV-associated gastric cancer.

Epstein-Barr virus (EBV) is the first human oncogenic virus known to express microRNAs (miRNAs), which are closely associated with the development of various tumors, including nasopharyngeal and gastric cancers. Stearoyl-CoA Desaturase 1 (SCD1) is a key enzyme in fatty acid synthesis, highly expressed in numerous tumors, promoting tumor growth and metastasis, making it a potential therapeutic target. In this study, we found that SCD1 expression in EBV-associated gastric cancer (EBVaGC) was significantly lower than in EBV-negative gastric cancer (EBVnGC) at both cellular and tissue levels. In addition, EBV-miR-BART20-5p targets the 3'-UTR of SCD1, downregulating its expression. Moreover, overexpression of SCD1 in EBVaGC cells promoted cell migration and proliferation while inhibiting autophagy. These results suggest that EBV-encoded miRNA-BART20-5p may contribute to EBVaGC progression by targeting SCD1.

Dissection of the synthesis of polyunsaturated fatty acids in nematodes and Collembola of the soil fauna.

It is becoming increasingly clear that not only unicellular, photoautotrophic eukaryotes, plants, and fungi, but also invertebrates are capable of synthesizing ω3 long-chain polyunsaturated fatty acids (LC-PUFA) de novo. However, the distribution of this anabolic capacity among different invertebrate groups and its implementation at the gene and protein level are often still unknown. This study investigated the PUFA pathways in common soil fauna, i.e. two nematode and two Collembola species. Of these, one species each (Panagrellus redivivus, Folsomia candida) was assumed to produce ω3 LC-PUFA de novo, while the others (Acrobeloides bodenheimeri, Isotoma caerulea) were supposed to be unable to do so. A highly labeled oleic acid (99 % 13C) was supplemented and the isotopic signal was used to trace its metabolic path. All species followed the main pathway of lipid biosynthesis. However, in A. bodenheimeri this terminated at arachidonic acid (ω6 PUFA), whereas the other three species continued the pathway to eicosapentaenoic acid (ω3 PUFA), including I. caerulea. For the nematode P. redivivus the identification and functional characterization of four new fatty acid desaturase (FAD) genes was performed. These genes encode the FAD activities Δ9, Δ6, and Δ5, respectively. Additionally, the Δ12 desaturase was analyzed, yet the observed activity of an ω3 FAD could not be attributed to a coding gene. In the Collembola F. candida, 11 potential first desaturases (Δ9) and 13 front-end desaturases (Δ6 or Δ5 FADs) have been found. Further sequence analysis indicates the presence of omega FADs, specifically Δ12, which are likely derived from Δ9 FADs.

Discovery of Novel (5-Mercapto-4-phenyl-4H-1,2,4-triazol-3-yl)methyl Phenyl Carbamate as a Potent Phytoene Desaturase Inhibitor through Scaffold Hopping and Linker Modification.

Phytoene desaturase (PDS) is a key rate-limiting enzyme in the carotenoid biosynthesis pathway. Although commercial PDS inhibitors have been developed for decades, it remains necessary to develop novel PDS inhibitors with higher bioactivity. In this work, we used the scaffold hopping and linker modification approaches to design and synthesize a series of compounds (7a-7o, 8a-8l, and 14a-14d). The postemergence application assay demonstrated that 8e and 7e separately showed the best herbicidal activity at 750 g a.i./ha and lower doses (187.5 g, 375g a.i./ha) without no significant toxicity to maize and wheat. The surface plasmon resonance revealed strong binding affinity between 7e and Synechococcus PDS (SynPDS). The HPLC analysis confirmed that 8e at 750 g a.i./ha caused significant phytoene accumulation in Arabidopsis seedlings. This work demonstrates the efficacy of structure-guided optimization through scaffold hopping and linker modification to design potent PDS inhibitors with enhanced bioactivity and crop safety.

Stigmasterol: An Enigmatic Plant Stress Sterol with Versatile Functions.

Sterols play important structural and regulatory roles in numerous intracellular processes. Unlike animals, plants contain a distinctive and diverse variety of sterols. Recently, information has emerged showing that stigmasterol is a "stress sterol". Stigmasterol is synthesized via the mevalonate biosynthesis pathway and has structural similarity to ß-sitosterol but differs in the presence of a trans-oriented double bond in the side chain. In plants, the accumulation of stigmasterol has been observed in response to various stresses. However, the precise ways that stigmasterol is involved in the stress responses of plants remain unclear. This comprehensive review provides an update on the biology of stigmasterol, particularly the physicochemical properties of this ethylsterol, its biosynthesis, and its occurrence in higher plants and extremophilic organisms, e.g., mosses and lichens. Special emphasis is given to the evolutionary aspects of stigmasterol biosynthesis, particularly the variations in the gene structure of C22-sterol desaturase, which catalyzes the formation of stigmasterol from ß-sitosterol, in a diversity of evolutionarily distant organisms. The roles of stigmasterol in the tolerance of plants to hostile environments and the prospects for its biomedical applications are also discussed. Taken together, the available data suggest that stigmasterol plays important roles in plant metabolism, although in some aspects, it remains an enigmatic compound.

Homologous Delta-12 Fatty Acid Desaturase (FAD2) Genes Affect Gene Expression and Linoleic Acid Levels in Lentinula edodes under Heat Stress.

Delta-12 fatty acid desaturases (FAD2s) actively regulate stress responses and cell differentiation in living organisms. In this study, six homologous FAD2 genes were identified based on the genome sequence of Lentinula edodes. Then, the six FAD2 protein sequences were analyzed using bioinformatics tools, including ExPASy ProtParam, SignalP, TMHMM, and TargetP. These analyses were performed to predict the physical and chemical properties, signal peptides, and transmembrane and conserved domains of these proteins. The polypeptide sequences were aligned, and a maximum likelihood phylogenetic tree was constructed using MEGA 7.0 software to elucidate the phylogenetic relationships between homologous FAD2 sequences. The results demonstrated that the FAD2 proteins contained three conserved histidine-rich regions (HXXXH, HXXHH, and HXXHH), which included eight histidine residues. The linoleic acid content and FAD2 enzyme activity were further analyzed, and the levels in the mutagenic heat-tolerant strain 18N44 were lower than those in the wild-type strain 18. Interestingly, the expression levels of the FAD2-2 and FAD2-3 genes under heat stress in strain 18N44 were lower than those in strain 18. These findings indicated that FAD2-2 and FAD2-3 may play major roles in the synthesis of linoleic acid during heat stress.

Molecular cloning and functional analysis of a plastidial ω3 desaturase from Emiliania huxleyi.

Emiliania huxleyi is a marine microalga playing a significant ecological and biogeochemical role in oceans. It can produce several polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA, 22:6-4,7,10,13,16,19) and octadecapentaenoic acid (OPA, 18:5-3,6,9,12,15), providing a primary source for nutritionally important ω3 PUFAs in the marine food chain. However, the biosynthesis of these PUFAs in this organism is not well understood. In this study, a full length plastidial ω3 desaturase cDNA (EhN3) was cloned from this alga. Heterologous expression of EhN3 with and without the chloroplast targeting peptide (cTP) in cyanobacterium Synechococcus elongatus showed that it possessed high desaturation activity toward C18-ω6 PUFAs, linoleic acid (LA, 18:2-9,12), γ-linolenic acid (GLA, 18:3-6,9,12), and C20-ω6 PUFAs, dihomo-γ-linolenic acid (DGLA, 20:3-8,11,14) and arachidonic acid (ARA, 20:4-5,8,11,14) that were exogenously supplied. Desaturation efficiency could reach almost 100% in a time course. On the other hand, when expressed in Saccharomyces cerevisiae, EhN3 with and without cTP did not exhibit any activity. Lipid analysis of Synechococcus transformants expressing EhN3 showed that it utilized galactolipids as substrates. Transcriptional expression analysis revealed that the expression of the gene increased while the growth temperature decreased, which was correlated with the increased production of ω3-PUFAs, particularly OPA. This is the first report of a plastidial ω3 desaturase from microalgae that can effectively introduce an ω3 double bond into both C18-ω6 and C20-ω6 PUFAs. EhN3 might also be one of the key enzymes involved in the biosynthesis of OPA in E. huxleyi through the plastidial aerobic pathway.

The Candida albicans quorum-sensing molecule farnesol alters sphingolipid metabolism in human monocyte-derived dendritic cells.

Candida albicans, an opportunistic fungal pathogen, produces the quorum-sensing molecule farnesol, which we have shown alters the transcriptional response and phenotype of human monocyte-derived dendritic cells (DCs), including their cytokine secretion and ability to prime T cells. This is partially dependent on the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ), which has numerous ligands, including the sphingolipid metabolite sphingosine 1-phosphate. Sphingolipids are a vital component of membranes that affect membrane protein arrangement and phagocytosis of C. albicans by DCs. Thus, we quantified sphingolipid metabolites in monocytes differentiating into DCs by High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Farnesol increased the activity of serine palmitoyltransferase, leading to increased levels of 3-keto-dihydrosphingosine, dihydrosphingosine, and dihydrosphingosine 1-phosphate and inhibited dihydroceramide desaturase by inducing oxidative stress, leading to increased levels of dihydroceramide and dihydrosphingomyelin species and reduced ceramide levels. Accumulation of dihydroceramides can inhibit mitochondrial function; accordingly, farnesol reduced mitochondrial respiration. Dihydroceramide desaturase inhibition increases lipid droplet formation, which we observed in farnesol-treated cells, coupled with an increase in intracellular triacylglycerol species. Furthermore, inhibition of dihydroceramide desaturase with either farnesol or specific inhibitors impaired the ability of DCs to prime interferon-γ-producing T cells. The effect of farnesol on sphingolipid metabolism, triacylglycerol synthesis, and mitochondrial respiration was not dependent on PPAR-γ. In summary, our data reveal novel effects of farnesol on sphingolipid metabolism, neutral lipid synthesis, and mitochondrial function in DCs that affect their instruction of T cell cytokine secretion, indicating that C. albicans can manipulate host cell metabolism via farnesol secretion.IMPORTANCECandida albicans is a common commensal yeast, but it is also an opportunistic pathogen which is one of the leading causes of potentially lethal hospital-acquired infections. There is growing evidence that its overgrowth in the gut can influence diseases as diverse as alcohol-associated liver disease and COVID-19. Previously, we found that its quorum-sensing molecule, farnesol, alters the phenotype of dendritic cells differentiating from monocytes, impairing their ability to drive protective T cell responses. Here, we demonstrate that farnesol alters the metabolism of sphingolipids, important structural components of the membrane that also act as signaling molecules. In monocytes differentiating to dendritic cells, farnesol inhibited dihydroceramide desaturase, resulting in the accumulation of dihydroceramides and a reduction in ceramide levels. Farnesol impaired mitochondrial respiration, known to occur with an accumulation of dihydroceramides, and induced the accumulation of triacylglycerol and oil bodies. Inhibition of dihydroceramide desaturase resulted in the impaired ability of DCs to induce interferon-γ production by T cells. Thus, farnesol production by C. albicans could manipulate the function of dendritic cells by altering the sphingolipidome.

Functional Impact of the FADS1 rs174546 Single Nucleotide Polymorphism on Serum Lipid Levels: Insights from Molecular Mechanisms and Therapeutic Perspectives in Korean Population.

SCOPE: Single nucleotide polymorphisms (SNP) in the fatty acid desaturase 1 (FADS1) gene is suggested as risk factor of metabolic diseases in genome-wide association studies (GWAS). This study hypothesized that FADS1_rs174546T associates with serum triglycerides (TG) in Korean Genome and Epidemiology Study (KoGES). In addition, functional study of SNP genotypes in cultured cells is performed. METHODS AND RESULTS: FADS1_rs174546T is associated with high level of serum TG (effect size of variant: 6.48 ± 1.84 mg dL-1) in Korean individuals (normotriglyceridemia, n = 5128; hypertriglyceridemia, n = 3714). Functional study in cells with FADS1_rs174546T, shows reduced transcriptional activity, when compared with rs174546C. MiR-6728-3p, which is predicted to bind with rs174546T, decreases transcriptional activity of rs174546T but not in rs174546C, and it is reversed by miR-6728-3p inhibitor. Formononetin is selected as binding molecule to 3'-UTR of FADS1 and increases luciferase activity in both rs174546 (C/T). Moreover, formononetin compensates for the reduced luciferase activity by rs174546T and miR-6728-3p. Formononetin also increases endogenous FADS1 expression and long-chain polyunsaturated fatty acid (LC-PUFA) ratio. CONCLUSION: FADS1_rs174546T is a crucial risk factor for hypertriglyceridemia in the Koreans potentially through the interaction with miR-6728-3p. Formononetin can be a potent dietary intervention to prevent and improve hypertriglyceridemia in both rs174546 (C/T) populations.