Engineering erucic acid biosynthesis in camelina (Camelina sativa) via FAE1 gene cloning and antisense technology.

Oil seeds now make up the world's second-largest food source after cereals. In recent years, the medicinal- oil plant Camelina sativa has attracted much attention for its high levels of unsaturated fatty acids and low levels of saturated fatty acids as well as its resistance to abiotic stresses. Improvement of oil quality is considered an important trait in this plant. Erucic acid is one of the fatty acids affecting the quality of camelina oil. Altering the fatty acid composition in camelina oil through genetic manipulation requires the identification, isolation, and cloning of genes involved in fatty acid biosynthesis. The Fatty Acid Elongase 1 (FAE1) gene encodes the enzyme ß-ketoacyl CoA synthase (KCS), a crucial enzyme in the biosynthesis of erucic acid. In this study, the isolation and cloning of the FAE1 gene from Camelina sativa were conducted to construct an antisense structure. The molecular homology modeling of DFAE1 proteins using the SWISS-MODEL server on ExPASy led to the generation of the 3D structures of FAE1 and DFAE1 proteins. The GMQE values of 0.44 for FAE1 and 0.08 for DFAE1 suggest high accuracy in the structural estimation of these genes. The fragments were isolated from the DNA source of the genomic Soheil cultivar with an erucic acid content of about 3% (in matured seeds) using PCR. After cloning the FAE1 gene into the Bluescript II SK+ vector and sequencing, the resulting fragments were utilized to construct the antisense structure in the pBI121 plant expression vector. The approved antisense structure was introduced into the Camelina plant using the Agrobacterium-mediated method, with optimization of tissue culture and gene transfer conditions. This approach holds potential to advance our knowledge of fat biosynthesis, leading to potential improvements in oil quality in Camelina sativa.

miR-218-5p promotes hepatic lipogenesis through targeting Elovl5 in non-alcoholic fatty liver disease.

Investigating and identifying pathogenic molecules of non-alcoholic fatty liver disease (NAFLD) has become imperative, which would serve as effective targets in the future. We established high-fat diet (HFD)-induced NAFLD model in mice and palmitic acid (PA)-induced model in mouse AML12 cells. The level of miR-218-5p was examined by qRT-PCR, and Elovl5 was identified as the potential target gene of miR-218-5p. The binding relationship between miR-218-5p and Elovl5 was validated by double luciferase reporter gene assay, and inhibition/overexpression of miR-218-5p in vitro. The functional mechanisms of miR-218-5p/Elovl5 in regulating lipogenesis in NAFLD were investigated in vivo and in vitro through gain- and loss-of-function studies. MiR-218-5p was significantly increased, and Elovl5 was decreased in model group. According to the double luciferase reporter and gene interference experiments in AML12 cells, Elovl5 was a target gene of miR-218-5p and its expression was regulated by miR-218-5p. The SREBP1-mediated lipogenesis signaling pathway regulated by Elovl5 was upregulated in model group. Moreover, silencing of miR-218-5p significantly upregulated Elovl5 expression, and suppressed SREBP1 signaling pathway in PA-induced AML-12 cells. Correspondingly, the cell injury, elevated TC, TG contents and lipid droplet accumulation were ameliorated. Furthermore, the effect of miR-218-5p on lipogenesis in vitro and in vivo was obstructed by si-Elovl5, implicating that miR-218-5p promotes lipogenesis by targeting ELOVL5 in NAFLD. miR-218-5p could promote fatty acid synthesis by targeting Elovl5, thereby accelerating the development of NAFLD, which is one of the key pathogenic mechanisms of NAFLD and provides a new molecular target for the management of NAFLD.

Alleviation effects of dexmedetomidine on myocardial ischemia/reperfusion injury through fatty acid metabolism pathway via Elovl6.

Dexmedetomidine (Dex) is widely used in the sedation in intensive care units and as an anesthetic adjunct. Considering the anti-inflammatory and antioxidant properties of Dex, we applied in vivo rat model as well as in vitro cardiomyocyte models (embryonic rat cardiomyocytes H9c2 cells and neonatal rat cardiomyocytes, NRCMs) to evaluate the effects of Dex against myocardial ischemia reperfusion (I/R) injury. Transcriptomic sequencing for gene expression in heart tissues from control rats and Dex-treated rats identified that genes related to fatty acid metabolism were significantly regulated by Dex. Among these genes, the elongation of long-chain fatty acids (ELOVL) family member 6 (Elovl6) was most increased upon Dex-treatment. By comparing the effects of Dex on both wild type and Elovl6-knockdown H9c2 cells and NRCMs under oxygen-glucose deprivation/reoxygenation (OGD/R) challenge, we found that Elovl6 knockdown attenuated the protection efficiency of Dex, which was supported by the cytotoxicity endpoints (cell viability and lactate dehydrogenase release) and apoptosis as well as key gene expressions. These results indicate that Dex exhibited the protective function against myocardial I/R injury via fatty acid metabolism pathways and Elovl6 plays a key role in the process, which was further confirmed using palmitate exposure in both cells, as well as in an in vivo rat model. Overall, this study systematically evaluates the protective effects of Dex on the myocardial I/R injury and provides better understanding on the fatty acid metabolism underlying the beneficial effects of Dex.

Identifying MSMO1, ELOVL6, AACS, and CERS2 related to lipid metabolism as biomarkers of Parkinson's disease.

The mechanisms underlying lipid metabolic disorders in Parkinson's diseases (PD) remain unclear. Weighted Gene Co-Expression Network Analysis (WGCNA) was conducted to identify PD-related modular genes and differentially expressed genes (DEGs). Lipid metabolism-related genes (LMRGs) were extracted from Molecular Signatures Database. Candidate genes were assessed with overlapping modular genes, DEGs, and LMRGs for the purpose of building protein-protein interaction (PPI) networks. Then, biomarkers were generated by machine learning and Backpropagation Neural Network development according to candidate genes. Biomarker-based enrichment and network modulation analyses were executed to investigate related signaling pathways. Following dimensionality reduction clustering and annotation, scRNA-seq was submitted to cellular interactions and trajectory analysis to analyze regulatory mechanisms of critical cells. Finally, qRT-PCR was conducted to confirm the expression of biomarkers in PD patients. Four biomarkers (MSMO1, ELOVL6, AACS, and CERS2) were obtained and highly predictive after analysis mentioned above. Then, OPC, Oli, and Neu cells were the primary expression sites for biomarkers according to scRNA-seq studies. Finally, we confirmed mRNA of MSMO1, ELOVL6 and AACS were downregulated in PD patients comparing with control, while CERS2 was upregulated. In conclusion, MSMO1, ELOVL6, AACS, and CERS2 related to LMRGs could be new biomarkers for diagnosing and treating PD.

A fatty acid elongase complex regulates cell membrane integrity and septin-dependent host infection by the rice blast fungus.

Very-long-chain fatty acids (VLCFAs) regulate biophysical properties of cell membranes to determine growth and development of eukaryotes, such as the pathogenesis of the rice blast fungus Magnaporthe oryzae. The fatty acid elongase Elo1 regulates pathogenesis of M. oryzae by modulating VLCFA biosynthesis. However, it remains unknown whether and how Elo1 associates with other factors to regulate VLCFA biosynthesis in fungal pathogens. Here, we identified Ifa38, Phs1 and Tsc13 as interacting proteins of Elo1 by proximity labelling in M. oryzae. Elo1 associated with Ifa38, Phs1 and Tsc13 on the endoplasmic reticulum (ER) membrane to control VLCFA biosynthesis. Targeted gene deletion mutants Δifa38, Δphs1 and Δtsc13 were all similarly impaired as Δelo1 in vegetative growth, conidial morphology, stress responses in ER, cell wall and membrane. These deletion mutants also displayed severe damage in cell membrane integrity and failed to organize the septin ring that is essential for penetration peg formation and pathogenicity. Our study demonstrates that M. oryzae employs a fatty acid elongase complex to regulate VLCFAs for maintaining or remodelling cell membrane structure, which is important for septin-mediated host penetration.

Elongation capacity of polyunsaturated fatty acids in the annelid Platynereis dumerilii.

Elongation of very long-chain fatty acid (Elovl) proteins plays pivotal functions in the biosynthesis of the physiologically essential long-chain polyunsaturated fatty acids (LC-PUFA). Polychaetes have important roles in marine ecosystems, contributing not only to nutrient recycling but also exhibiting a distinctive capacity for biosynthesizing LC-PUFA. To expand our understanding of the LC-PUFA biosynthesis in polychaetes, this study conducted a thorough molecular and functional characterization of Elovl occurring in the model organism Platynereis dumerilii. We identify six Elovl in the genome of P. dumerilii. The sequence and phylogenetic analyses established that four Elovl, identified as Elovl2/5, Elovl4 (two genes) and Elovl1/7, have putative functions in LC-PUFA biosynthesis. Functional characterization confirmed the roles of these elongases in LC-PUFA biosynthesis, demonstrating that P. dumerilii possesses a varied and functionally diverse complement of Elovl that, along with the enzymatic specificities of previously characterized desaturases, enables P. dumerilii to perform all the reactions required for the biosynthesis of the LC-PUFA. Importantly, we uncovered that one of the two Elovl4-encoding genes is remarkably long in comparison with any other animals' Elovl, which contains a C terminal KH domain unique among Elovl. The distinctive expression pattern of this protein in photoreceptors strongly suggests a central role in vision.

Expansion of omega-3 polyunsaturated fatty acid metabolism of the oleaginous diatom Fistulifera solaris by genetic engineering.

Omega-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) are widely used as additives in fish feed in the aquaculture sector. To date, the supply of omega-3 PUFAs have heavily depended upon fish oil production. As the need for omega-3 PUFAs supply for the growing population increases, a more sustainable approach is required to keep up with the demand. The oleaginous diatom Fistulifera solaris is known to synthesize EPA with the highest level among autotrophically cultured microalgae, however, this species does not accumulate significant amounts of DHA, which, in some cases, is required in aquaculture rather than EPA. This is likely due to the lack of expression of essential enzymes namely Δ5 elongase (Δ5ELO) and Δ4 desaturase. In this study, we identified endogenous Δ5ELO genes in F. solaris and introduced recombinant expression cassettes harboring Δ5ELO into F. solaris through bacterial conjugation. As a result, it managed to induce the synthesis of docosapentaenoic acid (DPA; C22:5n-3), a direct precursor of DHA. This study paves the way for expanding our understanding of the omega-3 PUFAs pathway using endogenous genes in the oleaginous diatom.

Fish oil replacement with different vegetable oils in Onychostoma macrolepis: Effects on fatty acid metabolism based on whole-body fatty acid balance method and genes expression.

To evaluate the fatty acid (FA) metabolism status and possibility as a DHA source of farmed Onychostoma macrolepis, a total of 168 fish (2.03 ± 0.23 g) were fed four diets supplemented with fish oil (FO), linseed oil (LO), soybean oil (SO), and a mixture of LO and SO oil (MO), respectively, for 70 days. Body FA compositions were modified reflecting dietary FAs. Comparing liver and intestine fatty acids with fish fed four diets, the content of ARA in fish fed SO was significantly higher than others (P < 0.05), but showed no difference in muscle. The tissue FA profile showed that the FO-fed group successfully deposited DHA, while the LO-fed group converted ALA to DHA effectively, as well as the liver and intestine EPA was notably highest in the FO group, whereas no difference between the FO and LO group in the muscle. The FA results showed that the DHA contents in the muscle of Onychostoma macrolepis are at a medium-high level compared with several other fish species with the highest aquaculture yield. Correspondingly, in the fish fed diet with LO, SO, and MO, the genes of most FA biosynthesis, transportation, and transcriptional regulation factors were increased in the liver and muscle, but no significant difference was observed in the gene expression of Elovl4b, FATP1, and FABP10 in the muscle. In addition, the enzyme activity involved in PUFA metabolism was higher in fish fed vegetable oil-based diets, corroborating the results of the gene expression. Increased in vivo elongase and desaturase (Δ5, Δ6, and Δ9) activities were recorded in fish fed fish oil-devoid diets, which resulted in the appearance of products associated with elongase and desaturase activities in fish. Besides, as the specific n-3 PUFA synthesis substrate, the dietary supplementation of ALA not only retains most of the nutrition value but also ensures the muscular texture, such as fiber diameter and density. It is concluded that farmed O. macrolepis owns strong n-3 LC-PUFA biosynthetic capacity and high DHA contents so it can be a good DHA source for the population.

Patterns of perinatal polyunsaturated fatty acid status and associated dietary or candidate-genetic factors.

Perinatal exposure to omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) can be characterized through biomarkers in maternal or cord blood or breast milk. Objectives were to describe perinatal PUFA status combining multiple biofluids and to investigate how it was influenced by dietary intake during pregnancy and maternal FADS and ELOVL gene polymorphisms. This study involved 1,901 mother-child pairs from the EDEN cohort, with PUFA levels measured in maternal and cord erythrocytes, and colostrum. Maternal dietary PUFA intake during the last trimester was derived from a food frequency questionnaire. Twelve single-nucleotide polymorphisms in FADS and ELOVL genes were genotyped from maternal DNA. Principal component analysis incorporating PUFA levels from the three biofluids identified patterns of perinatal PUFA status. Spearman's correlations explored associations between patterns and PUFA dietary intake, and linear regression models examined pattern associations with FADS or ELOVL haplotypes. Five patterns were retained: "High omega-3 LC-PUFAs, low omega-6 LC-PUFAs"; "Omega-6 LC-PUFAs"; "Colostrum LC-PUFAs"; "Omega-6 precursor (LA) and DGLA"; "Omega-6 precursor and colostrum ALA". Maternal omega-3 LC-PUFA intakes were correlated with "High omega-3 LC-PUFAs, low omega-6 LC-PUFAs" (r(DHA) = 0.33) and "Omega-6 LC-PUFAs" (r(DHA) = -0.19) patterns. Strong associations were found between FADS haplotypes and PUFA patterns except for "High omega-3 LC-PUFAs, low omega-6 LC-PUFAs". Lack of genetic association with the "High omega-3 LC-PUFAs, low omega-6 LC-PUFAs" pattern, highly correlated with maternal omega-3 LC-PUFA intake, emphasizes the importance of adequate omega-3 LC-PUFA intake during pregnancy and lactation. This study offers a more comprehensive assessment of perinatal PUFA status and its determinants.

Silencing the fatty acid elongase gene elovl6 induces reprogramming of nutrient metabolism in male Oreochromis niloticus.

Elongation of very long-chain fatty acids protein 6 (ELOVL6) plays a pivotal role in the synthesis of endogenous fatty acids, influencing energy balance and metabolic diseases. The primary objective of this study was to discover the molecular attributes and regulatory roles of ELOVL6 in male Nile tilapia, Oreochromis niloticus. The full-length cDNA of elovl6 was cloned from male Nile tilapia, and was determined to be 2255-bp long, including a 5'-untranslated region of 193 bp, a 3'-untranslated region of 1252 bp, and an open reading frame of 810 bp encoding 269 amino acids. The putative protein had typical features of ELOVL proteins. The transcript levels of elovl6 differed among various tissues and among fish fed with different dietary lipid sources. Knockdown of elovl6 in Nile tilapia using antisense RNA technology resulted in significant alterations in hepatic morphology, long-chain fatty acid synthesis, and fatty acid oxidation, and led to increased fat deposition in the liver and disrupted glucose/lipid metabolism. A comparative transcriptomic analysis (elovl6 knockdown vs. the negative control) identified 5877 differentially expressed genes with significant involvement in key signaling pathways including the peroxisome proliferator-activated receptor signaling pathway, fatty acid degradation, glycolysis/gluconeogenesis, and the insulin signaling pathway, all of which are crucial for lipid and glucose metabolism. qRT-PCR analyses verified the transcript levels of 13 differentially expressed genes within these pathways. Our findings indicate that elovl6 knockdown in male tilapia impedes oleic acid synthesis, culminating in aberrant nutrient metabolism.

Fatty Acids and Their Lipogenic Enzymes in Anorexia Nervosa Clinical Subtypes.

Disordered eating behavior differs between the restricting subtype (AN-R) and the binging and purging subtype (AN-BP) of anorexia nervosa (AN). Yet, little is known about how these differences impact fatty acid (FA) dysregulation in AN. To address this question, we analyzed 26 FAs and 7 FA lipogenic enzymes (4 desaturases and 3 elongases) in 96 women: 25 AN-R, 25 AN-BP, and 46 healthy control women. Our goal was to assess subtype-specific patterns. Lauric acid was significantly higher in AN-BP than in AN-R at the fasting timepoint (p = 0.038) and displayed significantly different postprandial changes 2 h after eating. AN-R displayed significantly higher levels of n-3 alpha-linolenic acid, stearidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid, and n-6 linoleic acid and gamma-linolenic acid compared to controls. AN-BP showed elevated EPA and saturated lauric acid compared to controls. Higher EPA was associated with elevated anxiety in AN-R (p = 0.035) but was linked to lower anxiety in AN-BP (p = 0.043). These findings suggest distinct disordered eating behaviors in AN subtypes contribute to lipid dysregulation and eating disorder comorbidities. A personalized dietary intervention may improve lipid dysregulation and enhance treatment effectiveness for AN.

Low expression of ELOVL6 may be involved in fat loss in white adipose tissue of cancer-associated cachexia.

BACKGROUND: Cancer-associated cachexia (CAC) arises from malignant tumors and leads to a debilitating wasting syndrome. In the pathophysiology of CAC, the depletion of fat plays an important role. The mechanisms of CAC-induced fat loss include the enhancement of lipolysis, inhibition of lipogenesis, and browning of white adipose tissue (WAT). However, few lipid-metabolic enzymes have been reported to be involved in CAC. This study hypothesized that ELOVL6, a critical enzyme for the elongation of fatty acids, may be involved in fat loss in CAC. METHODS: Transcriptome sequencing technology was used to identify CAC-related genes in the WAT of a CAC rodent model. Then, the expression level of ELOVL6 and the fatty acid composition were analyzed in a large clinical sample. Elovl6 was knocked down by siRNA in 3T3-L1 mouse preadipocytes to compare with wild-type 3T3-L1 cells treated with tumor cell conditioned medium. RESULTS: In the WAT of patients with CAC, a significant decrease in the expression of ELOVL6 was found, which was linearly correlated with the extent of body mass reduction. Gas chromatographic analysis revealed an increase in palmitic acid (C16:0) and a decrease in linoleic acid (C18:2n-6) in these tissue samples. After treatment with tumor cell-conditioned medium, 3T3-L1 mouse preadipocytes showed a decrease in Elovl6 expression, and Elovl6-knockdown cells exhibited a reduction in preadipocyte differentiation and lipogenesis. Similarly, the knockdown of Elovl6 in 3T3-L1 cells resulted in a significant increase in palmitic acid (C16:0) and a marked decrease in oleic acid (C18:1n-9) content. CONCLUSION: Overall, the expression of ELOVL6 was decreased in the WAT of CAC patients. Decreased expression of ELOVL6 might induce fat loss in CAC patients by potentially altering the fatty acid composition of adipocytes. These findings suggest that ELOVL6 may be used as a valuable biomarker for the early diagnosis of CAC and may hold promise as a target for future therapies.

A complete biosynthetic pathway of the long-chain polyunsaturated fatty acids in an amphidromous fish, ayu sweetfish Plecoglossus altivelis (Stomiati; Osmeriformes).

The biosynthetic capability of the long-chain polyunsaturated fatty acids (LC-PUFA) in teleosts are highly diversified due to evolutionary events such as gene loss and subsequent neo- and/or sub-functionalisation of enzymes encoded by existing genes. In the present study, we have comprehensively characterised genes potentially involved in LC-PUFA biosynthesis, namely one front-end desaturase (fads2) and eight fatty acid elongases (elovl1a, elovl1b, elovl4a, elovl4b, elovl5, elovl7, elovl8a and elovl8b) from an amphidromous teleost, Ayu sweetfish, Plecoglossus altivelis. Functional analysis confirmed Fads2 with Δ6, Δ5 and Δ8 desaturase activities towards multiple PUFA substrates and several Elovl enzymes exhibited elongation capacities towards C18-20 or C18-22 PUFA substrates. Consequently, P. altivelis possesses a complete enzymatic capability to synthesise physiologically important LC-PUFA including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) from their C18 precursors. Interestingly, the loss of elovl2 gene in P. altivelis was corroborated by genomic and phylogenetic analyses. However, this constraint would possibly be overcome by the function of alternative Elovl enzymes, such as Elovl1b, which has not hitherto been functionally characterised in teleosts. The present study contributes novel insights into LC-PUFA biosynthesis in the relatively understudied teleost group, Osmeriformes (Stomiati), thereby enhancing our understanding of the complement of LC-PUFA biosynthetic genes within teleosts.

Sex-dependent differences in tissue and blood n-3 PUFA levels following ALA or ALA + DHA feeding of liver-specific Elovl2-KO and control mice.

Docosahexaenoic acid (DHA, 22:6n-3) must be consumed from the diet or synthesized from polyunsaturated fatty acid (PUFA) precursors, such as α-linolenic acid (ALA, 18:3n-3). Elongase 2 (encoded by Elovl2 gene) catalyzes two elongation reactions in the PUFA biosynthesis pathway and may be important in regulating the observed sex differences in n-3 PUFA levels. Our aim was to determine how targeted knockout of liver Elovl2 affects tissue and blood n-3 PUFA levels in male and female C57BL/6J mice. Twenty-eight-day old male and female liver Elovl2-KO and control mice were placed onto one of two dietary protocols for a total of 8 weeks (4-8 mice per genotype, per diet, per sex): 1) an 8-week 2 % ALA in total fat diet or 2) a 4-week 2 % ALA diet followed by a 4-week 2 % ALA + 2 % DHA diet. Following this 8-week feeding period, 12-week-old mice were sacrificed and serum, red blood cells (RBC), liver, heart and brain were collected and fatty acid levels measured. Significant interaction effects (p < 0.05, sex x genotype) for serum, RBC, liver and heart DHA levels were identified. In serum and liver, DHA levels were significantly different (p < 0.01) between all groups with male controls > female controls > female KO > male KO in serum and female controls > male controls > female KO > male KO in liver. In RBCs and the heart, female controls = male controls > female KO > male KO (p < 0.001). The addition of DHA to diet removed the interaction effects on DHA levels in the serum, liver and heart, yielding a significant sex effect in serum, liver (female > male, p < 0.01) and brain (male > female, p < 0.05) and genotype effect in serum and heart (control > KO, p < 0.05). Ablation of liver Elovl2 results in significantly lower blood and tissue DHA in a sex-dependent manner, suggesting a role for Elovl2 on sex differences in n-3 PUFA levels.

Daily Consumption of α-Linolenic Acid Increases Conversion Efficiency to Eicosapentaenoic Acid in Mice.

To maintain a beneficial concentration of eicosapentaenoic acid (EPA), the efficient conversion of its precursor, α-linolenic acid (α-LA), is important. Here, we studied the conversion of α-LA to EPA using ICR and C57BL/6 mice. A single dose of perilla oil rich-in α-LA or free α-LA had not been converted to EPA 18 h following administration. The α-LA was absorbed into the circulation, and its concentration peaked 6 h after administration, after which it rapidly decreased. In contrast, EPA administration was followed by an increase in circulating EPA concentration, but this did not decrease between 6 and 18 h, indicating that the clearance of EPA is slower than that of α-LA. After ≥1 week perilla oil intake, the circulating EPA concentration was >20 times higher than that of the control group which consumed olive oil, indicating that daily consumption, but not a single dose, of α-LA-rich oil might help preserve the physiologic EPA concentration. The consumption of high concentrations of perilla oil for 4 weeks also increased the hepatic expression of Elovl5, which is involved in fatty acid elongation; however, further studies are needed to characterize the relationship between the expression of this gene and the conversion of α-LA to EPA.

Abnormal saturated fatty acids and sphingolipids metabolism in asthma.

Recent advances in fatty acid analysis have highlighted the links between lipid disruption and disease development. Lipid abnormalities are well-established risk factors for many of the most common chronic illnesses, and their involvement in asthma is also becoming clear. Here, we review research demonstrating the role of abnormal lipid metabolism in asthma, with a focus on saturated fatty acids and sphingolipids. High levels of palmitic acid, the most abundant saturated fatty acid in the human body, have been found in the airways of asthmatic patients with obesity, and were shown to worsen eosinophilic airway inflammation in asthma model mice on a high-fat diet. Aside from being a building block of longer-chain fatty acids, palmitic acid is also the starting point for de novo synthesis of ceramides, a class of sphingolipids. We outline the three main pathways for the synthesis of ceramides, which have been linked to the severity of asthma and act as precursors for the dynamic lipid mediator sphingosine 1-phosphate (S1P). S1P signaling is involved in allergen-induced eosinophilic inflammation, airway hyperresponsiveness, and immune-cell trafficking. A recent study of mice with mutations for the elongation of very long-chain fatty acid family member 6 (Elovl6), an enzyme that elongates fatty acid chains, has highlighted the potential role of palmitic acid composition, and thus lipid balance, in the pathophysiology of allergic airway inflammation. Elovl6 may be a potential therapeutic target in severe asthma.

Mouse serum albumin induces neuronal apoptosis and tauopathies.

The elderly frequently present impaired blood-brain barrier which is closely associated with various neurodegenerative diseases. However, how the albumin, the most abundant protein in the plasma, leaking through the disrupted BBB, contributes to the neuropathology remains poorly understood. We here demonstrated that mouse serum albumin-activated microglia induced astrocytes to A1 phenotype to remarkably increase levels of Elovl1, an astrocytic synthase for very long-chain saturated fatty acids, significantly promoting VLSFAs secretion and causing neuronal lippoapoptosis through endoplasmic reticulum stress response pathway. Moreover, MSA-activated microglia triggered remarkable tau phosphorylation at multiple sites through NLRP3 inflammasome pathway. Intracerebroventricular injection of MSA into the brains of C57BL/6J mice to a similar concentration as in patient brains induced neuronal apoptosis, neuroinflammation, increased tau phosphorylation, and decreased the spatial learning and memory abilities, while Elovl1 knockdown significantly prevented the deleterious effect of MSA. Overall, our study here revealed that MSA induced tau phosphorylation and neuron apoptosis based on MSA-activated microglia and astrocytes, respectively, showing the critical roles of MSA in initiating the occurrence of tauopathies and cognitive decline, and providing potential therapeutic targets for MSA-induced neuropathology in multiple neurodegenerative disorders.

ELOVL6 promotes the progression of head and neck squamous cell carcinoma via activating WNT/ß-catenin pathway.

This study was to explore the role of ELOVL6 in the development of head and neck squamous cell carcinoma (HNSCC). Considering its previously identified oncogenic role in hepatocellular carcinoma. ELOVL6 gene expression, clinicopathological analysis, enrichment analysis, and immune infiltration analysis were based on the data from Gene Expression Omnibus and The Cancer Genome Atlas, with additional bioinformatics analyses performed. Human HNSCC tissue microarray and cell lines were used. The expression of ELOVL6 in HNSCC was detected by quantitative polymerase chain reaction, immunohistochemistry assay, and western blot analysis. The proliferation ability of HNSCC cells, invasion, and apoptosis were evaluated using cell counting kit-8 method, Transwell assay, and flow cytometry, respectively. Based on the data derived from the cancer databases and our HNSCC cell and tissue studies, we found that ELOVL6 was overexpressed in HNSCC. Moreover, ELOVL6 expression level had a positive correlation with clinicopathology of HNSCC. Gene set enrichment analysis showed that ELOVL6 affected the occurrence of HNSCC through WNT signaling pathway. Functional experiments demonstrated that ELOVL6 knockdown inhibited the proliferation and invasion of HNSCC cells while promoting apoptosis. Additionally, compound 3f, an agonist of WNT/ß-catenin signaling pathway, enhances the effect of ELOVL6 on the progression of HNSCC cells. ELOVL6 is upregulated in HNSCC and promotes the development of HNSCC cells by inducing WNT/ß-catenin signaling pathway. ELOVL6 stands a potential target for the treatment of HNSCC and a prognosis indicator of human HNSCC.

Diversity in fatty acid elongation enzymes: The FabB long-chain ß-ketoacyl-ACP synthase I initiates fatty acid synthesis in Pseudomonas putida F1.

The condensation of acetyl-CoA with malonyl-acyl carrier protein (ACP) by ß-ketoacyl-ACP synthase III (KAS III, FabH) and decarboxylation of malonyl-ACP by malonyl-ACP decarboxylase are the two pathways that initiate bacterial fatty acid synthesis (FAS) in Escherichia coli. In addition to these two routes, we report that Pseudomonas putida F1 ß-ketoacyl-ACP synthase I (FabB), in addition to playing a key role in fatty acid elongation, also initiates FAS in vivo. We report that although two P. putida F1 fabH genes (PpfabH1 and PpfabH2) both encode functional KAS III enzymes, neither is essential for growth. PpFabH1 is a canonical KAS III similar to E. coli FabH whereas PpFabH2 catalyzes condensation of malonyl-ACP with short- and medium-chain length acyl-CoAs. Since these two KAS III enzymes are not essential for FAS in P. putida F1, we sought the P. putida initiation enzyme and unexpectedly found that it was FabB, the elongation enzyme of the oxygen-independent unsaturated fatty acid pathway. P. putida FabB decarboxylates malonyl-ACP and condenses the acetyl-ACP product with malonyl-ACP for initiation of FAS. These data show that P. putida FabB, unlike the paradigm E. coli FabB, can catalyze the initiation reaction in FAS.

Catalytic mechanism of trans-2-enoyl-CoA reductases in the fatty acid elongation cycle and its cooperative action with fatty acid elongases.

The fatty acid (FA) elongation cycle produces very-long-chain FAs with ≥C21, which have unique physiological functions. Trans-2-enoyl-CoA reductases (yeast, Tsc13; mammals, TECR) catalyze the reduction reactions in the fourth step of the FA elongation cycle and in the sphingosine degradation pathway. However, their catalytic residues and coordinated action in the FA elongation cycle complex are unknown. To reveal these, we generated and analyzed Ala-substituted mutants of 15 residues of Tsc13. An in vitro FA elongation assay showed that nine of these mutants were less active than WT protein, with E91A and Y256A being the least active. Growth complementation analysis, measurement of ceramide levels, and deuterium-sphingosine labeling revealed that the function of the E91A mutant was substantially impaired in vivo. In addition, we found that the activity of FA elongases, which catalyze the first step of the FA elongation cycle, were reduced in the absence of Tsc13. Similar results were observed in Tsc13 E91A-expressing cells, which is attributable to reduced interaction between the Tsc13 E91A mutant and the FA elongases Elo2/Elo3. Finally, we found that E94A and Y248A mutants of human TECR, which correspond to E91A and Y256A mutants of Tsc13, showed reduced and almost no activity, respectively. Based on these results and the predicted three-dimensional structure of Tsc13, we speculate that Tyr256/Tyr248 of Tsc13/TECR is the catalytic residue that supplies a proton to trans-2-enoyl-CoAs. Our findings provide a clue concerning the catalytic mechanism of Tsc13/TECR and the coordinated action in the FA elongation cycle complex.