Tissue expression profiles and transcriptional regulation of elongase of very long chain fatty acid 6 in bovine mammary epithelial cells

The fatty acid elongase ELOVL6 regulates bortezomib resistance in multiple myeloma

Resistance to the proteasome inhibitor bortezomib (BTZ) represents a major obstacle in the treatment of multiple myeloma (MM). The contribution of lipid metabolism in the resistance of MM cells to BTZ is mostly unknown. Here we report that levels of fatty acid elongase 6 (ELOVL6) were lower in MM cells from BTZ-nonresponsive vs BTZ-responsive patients and in cultured MM cells selected for BTZ resistance compared with parental counterparts. Accordingly, depletion of ELOVL6 in parental MM cells suppressed BTZ-induced endoplasmic reticulum (ER) stress and cytotoxicity, whereas restoration of ELOVL6 levels in BTZ-resistant MM cells sensitized them to BTZ in tissue culture settings and, as xenografts, in a plasmacytoma mouse model. Furthermore, for the first time, we identified changes in the BTZ-induced lipidome between parental and BTZ-resistant MM cell lines underlying a functional difference in their response to BTZ. We demonstrated that restoration of ELOVL6 levels in BTZ-resistant MM cells resensitized them to BTZ largely via upregulation of ELOVL6-dependent ceramide species, which was a prerequisite for BTZ-induced ER stress and cell death in these cells. Our data characterize ELOVL6 as a major clinically relevant regulator of MM cell resistance to BTZ, which can emerge from the impaired ability of these cells to alter ceramide composition in response to BTZ.

Elongase of very long chain fatty acids 6 (ELOVL6) promotes lipid synthesis in buffalo mammary epithelial cells

Recent studies have shown elongase of very-long-chain fatty acids 6 (ELOVL6) is a vital protein for endogenous synthesis of saturated and monounsaturated long-chain fatty acids in some mammals. Nevertheless, its role in lipid synthesis in buffalo mammary gland is still unclear. In this work, the full-length coding sequence (CDS) of ELOVL6 was cloned and identified from buffalo mammary gland. As a result, the CDS of this gene is 795 bp, which encodes a polypeptide of 264 amino acid residues. The buffalo ELOVL6 contains an ELO domain which belongs to the ELO superfamily. Among the 10 tissues of buffalo in peak lactation detected by RT-qPCR, the expression level of ELOVL6 was the highest in the brain, followed by the spleen, and then decreased in the mammary gland, muscle, kidney, heart, liver, rumen, intestine and lung. However, only the expression in the brain and spleen was statistically different from that in other tissues (p < 0.05). Compared with that of the dry-off period, the mRNA abundance of ELOVL6 in the mammary gland was significantly increased in peak lactation. The experiments based on lentivirus transfection in buffalo mammary epithelial cells (BuMECs) displayed that the overexpression of ELOVL6 markedly promoted the expression of INSIG1, INSIG2, SREBP, PPARG, FASN, GPAM, DGAT2 and APGAT6 genes, and the knockdown of ELOVL6 significantly decreased the mRNA abundance of INSIG2, SREBP, FASN, SCD, GPAM, APGAT6 and TIP47 genes. In addition, the increase or decrease of ELOVL6 expression level also caused the corresponding change of total triglyceride content in the BuMECs. The results here suggest that the ELOVL6 can catalyse the synthesis of long-chain fatty acids in the BuMECs, and it can indirectly affect the expression of genes related to milk fat synthesis through its catalytic products to promote the lipid biosynthesis of BuMECs.

Transcriptional regulation of adipogenic marker genes for the improvement of intramuscular fat in Qinchuan beef cattle

The intramuscular fat content plays a crucial role in meat quality traits. Increasing the degree of adipogenesis in beef cattle leads to an increase in the content of intramuscular fat. Adipogenesis a complex biochemical process which is under firm genetic control. Over the last three decades, the Qinchuan beef cattle have been extensively studied for the improvement of meat production and quality traits. In this study, we reviewed the literature regarding adipogenesis and intramuscular fat deposition. Then, we summarized the research conducted on the transcriptional regulation of key adipogenic marker genes, and also reviewed the roles of adipogenic marker genes in adipogenesis of Qinchuan beef cattle. This review will elaborate our understanding regarding transcriptional regulation which is a vital physiological process regulated by a cascade of transcription factors (TFs), key target marker genes, and regulatory proteins. This synergistic action of TFs and target genes ensures the accurate and diverse transmission of the genetic information for the accomplishment of central physiological processes. This information will provide an insight into the transcriptional regulation of the adipogenic marker genes and its role in bovine adipogenesis for the breed improvement programs especially for the trait of intramuscular fat deposition.

Advances of Molecular Markers and Their Application for Body Variables and Carcass Traits in Qinchuan Cattle

This review considers the unique characteristics of Chinese cattle and intramuscular fat content (IMF) as factors influencing meat quality, including tenderness, flavor, and juiciness of meat. Due to its nutritional qualities, meat contributes to a healthy and balanced diet. The intramuscular fat content and eating quality of beef are influenced by many factors, which can generally be divided into on-farm and pre-slaughter factors (breed, sex of cattle, age at slaughter, housing system, diet, and pre-slaughter handling) and postmortem factors (post-slaughter processing, chilling temperature, and packaging). Meat quality traits can also be influenced by the individual genetic background of the animal. Worldwide, the function of genes and genetic polymorphisms that have potential effects on fattening of cattle and beef quality have been investigated. The use of DNA markers is recognized as a powerful and efficient approach to achieve genetic gain for desirable phenotypic characteristics, which is helpful for economic growth. The polymorphisms of the SIRT4, SIRT6, SIRT7, CRTC3, ABHD5, KLF6, H-FABP, and ELOVL6 genes for body and growth characteristics of cattle, and also for beef quality, are considered with the aim of highlighting the significance of beef intramuscular fat content, and that growth, body, and meat quality characteristics are polygenically regulated.

Dissecting the Components of Sindbis Virus from Arthropod and Vertebrate Hosts: Implications for Infectivity Differences

Sindbis virus (SINV) is an enveloped, single-stranded RNA virus, which is transmitted via mosquitos to a wide range of vertebrate hosts. SINV produced by vertebrate, baby hamster kidney (BHK) cells is more than an order of magnitude less infectious than SINV produced from mosquito (C6/36) cells. The cause of this difference is poorly understood. In this study, charge detection mass spectrometry was used to determine the masses of intact SINV particles isolated from BHK and C6/36 cells. The measured masses are substantially different: 52.88 MDa for BHK derived SINV and 50.69 MDa for C6/36 derived. Further analysis using several mass spectrometry-based methods and biophysical approaches indicates that BHK derived SINV has a substantially higher mass than C6/36 derived because in the lipid bilayer, there is a higher portion of lipids containing long chain fatty acids. The difference in lipid composition could influence the organization of the lipid bilayer. As a result, multiple stages of the viral lifecycle may be affected including assembly and budding, particle stability during transmission, and fusion events, all of which could contribute to the differences in infectivity.

Molecular Cloning, Characterization, and Nutritional Regulation of Elovl6 in Large Yellow Croaker (Larimichthys crocea)

Elongation of very long chain fatty acids protein 6 (Elovl6) is a key enzyme in fatty acid synthesis, which participates in converting palmitate (C16:0) to stearate (C18:0). Although studies of Elovl6 have been carried out in mammals, the nutritional regulation of elovl6 in fish remains poorly understood. In the present study, the cloning and nutritional regulation of elovl6 were determined in large yellow croaker. Sequence and phylogenetic analysis revealed that the full-length cDNA of elovl6 was 1360 bp, including an open reading frame of 810 bp encoding a putative protein of 269 amino acid that possesses the characteristic features of Elovl proteins. The transcript level of elovl6 was significantly increased in the liver of croaker fed the diets with soybean oil (enriched with 18: 2n-6, LA) or linseed oil (enriched with 18: 3n-3, ALA) than that in croaker fed the diet with fish oil (enriched with 20: 5n-3 and 22: 6n-3). Correspondingly, the elovl6 expression in croaker’s hepatocytes treated with ALA or LA was remarkably increased compared to the controls. Furthermore, the transcription factors including hepatocyte nuclear factor 1α (HNF1α), CCAAT-enhancer-binding protein β (CEBPβ), retinoid X receptor α (RXRα), and cAMP response element-binding protein 1 (CREB1) greatly enhanced promoter activity of elovl6 in large yellow croaker, and the expression of transcription factors is consistent with the changes of elovl6 expression in response to fatty acids in vivo and in vitro. In conclusion, this study revealed that elovl6 expression in large yellow croaker could be upregulated by dietary ALA or LA via the increased transcriptional expression of transcription factors including hnf1α, cebpβ, rxrα, and creb1.

Transcriptional regulation of bovine elongation of very long chain fatty acids protein 6 in lipid metabolism and adipocyte proliferation

The elongation of very long chain fatty acids protein 6 (ELOVL6) gene encodes a key enzyme that plays a role in lipogenesis through the catalytic elongation of both saturated and monounsaturated fatty acids. Previous studies have described the high expression of bovine ELOVL6 in adipose tissues. However, transcriptional regulation and the functional role of ELOVL6 in lipid metabolism and adipocyte proliferation remain unexplored. Here, a 1.5 kb fragment of the 5'-untranslated region promoter region of ELOVL6 was amplified from the genomic DNA of Qinchuan cattle and sequenced. The core promoter region was identified through unidirectional 5'-end deletion of the promoter plasmid vector. In silico analysis predicted important transcription factors that were then validated through site-directed mutation and small interfering RNA interference with an electrophoretic mobility shift assay. We found that the binding of KLF6 and PU.1 transcription factors occurred in the region -168/+69. Both perform a vital regulatory function in the transcription of bovine ELOVL6. Overexpression of ELOVL6 significantly upregulated the expression of peroxisome proliferator activated receptor γ (PPARγ), but inhibited the expression of fatty acid-binding protein 4 (FABP4), while silencing of ELOVL6 negatively regulated the messenger RNA expression level of PPARγ, FABP4, ACSL, and FATP1. In addition, ELOVL6 promotes adipocyte proliferation by regulating the cell-cycle genes' expression. Taken together, these findings provide useful information about the transcriptional regulation and functional mechanisms of bovine ELOVL6 in lipid metabolism and adipocyte proliferation in Qinchuan cattle.

Genome wide association study identifies SNPs associated with fatty acid composition in Chinese Wagyu cattle

Background

Fatty acids are important traits that affect meat quality and nutritive values in beef cattle. Detection of genetic variants for fatty acid composition can help to elucidate the genetic mechanism underpinning these traits and promote the improvement of fatty acid profiles. In this study, we performed a genome-wide association study (GWAS) on fatty acid composition using high-density single nucleotide polymorphism (SNP) arrays in Chinese Wagyu cattle.

Results

In total, we detected 15 and 8 significant genome-wide SNPs for individual fatty acids and fatty acid groups in Chinese Wagyu cattle, respectively. Also, we identified nine candidate genes based on 100 kb regions around associated SNPs. Four SNPs significantly associated with C14:1 cis-9 were embedded with stearoyl-CoA desaturase (SCD), while three SNPs in total were identified for C22:6 n-3 within Phospholipid scramblase family member 5 (PLSCR5), Cytoplasmic linker associated protein 1 (CLASP1), and Chymosin (CYM). Notably, we found the top candidate SNP within SCD can explain ~ 7.37% of phenotypic variance for C14:1 cis-9. Moreover, we detected several blocks with high LD in the 100 kb region around SCD. In addition, we found three significant SNPs within a 100 kb region showing pleiotropic effects related to multiple FA groups (PUFA, n-6, and PUFA/SFA), which contains BAI1 associated protein 2 like 2 (BAIAP2L2), MAF bZIP transcription factor F (MAFF), and transmembrane protein 184B (TMEM184B).

Conclusions

Our study identified several significant SNPs and candidate genes for individual fatty acids and fatty acid groups in Chinese Wagyu cattle, and these findings will further assist the design of breeding programs for meat quality in cattle.

The elongation of very long-chain fatty acid 6 gene product catalyses elongation of n-13 : 0 and n-15 : 0 odd-chain SFA in human cells

Normal odd-chain SFA (OCSFA), particularly tridecanoic acid (n-13 : 0), pentadecanoic acid (n-15 : 0) and heptadecanoic acid (n-17 : 0), are normal components of dairy products, beef and seafood. The ratio of n-15 : 0:n-17 : 0 in ruminant foods (dairy products and beef) is 2:1, while in seafood and human tissues it is 1:2, and their appearance in plasma is often used as a marker for ruminant fat intake. Human elongases encoded by elongation of very long-chain fatty acid (ELOVL)1, ELOVL3, ELOVL6 and ELOVL7 catalyse biosynthesis of the dominant even-chain SFA; however, there are no reports of elongase function on OCSFA. ELOVL transfected MCF7 cells were treated with n-13 : 0, n-15 : 0 or n-17 : 0 (80 µm) and products analysed. ELOVL6 catalysed elongation of n-13 : 0→n-15 : 0 and n-15 : 0→n-17 : 0; and ELOVL7 had modest activity toward n-15 : 0 (n-15 : 0→n-17 : 0). No elongation activity was detected for n-17 : 0→n-19 : 0. Our data expand ELOVL specificity to OCSFA, providing the first molecular evidence demonstrating ELOVL6 as the major elongase acting on OCSFA n-13 : 0 and n-15 : 0 fatty acids. Studies of food intake relying on OCSFA as a biomarker should consider endogenous human metabolism when relying on OCSFA ratios to indicate specific food intake.