Association of an ACSL1 gene variant with polyunsaturated fatty acids in bovine skeletal muscle

Regulation of Milk Fat Synthesis: Key Genes and Microbial Functions

Milk is rich in a variety of essential nutrients, including fats, proteins, and trace elements that are important for human health. In particular, milk fat has an alleviating effect on diseases such as heart disease and diabetes. Fatty acids, the basic units of milk fat, play an important role in many biological reactions in the body, including the involvement of glycerophospholipids and sphingolipids in the formation of cell membranes. However, milk fat synthesis is a complex biological process involving multiple organs and tissues, and how to improve milk fat of dairy cows has been a hot research issue in the industry. There exists a close relationship between milk fat synthesis, genes, and microbial functions, as a result of the organic integration between the different tissues of the cow's organism and the external environment. This review paper aims (1) to highlight the synthesis and regulation of milk fat by the first and second genomes (gastrointestinal microbial genome) and (2) to discuss the effects of ruminal microorganisms and host metabolites on milk fat synthesis. Through exploring the interactions between the first and second genomes, and discovering the relationship between microbial and host metabolite in the milk fat synthesis pathway, it may become a new direction for future research on the mechanism of milk fat synthesis in dairy cows.

Proteome Analysis Related to Unsaturated Fatty Acid Synthesis by Interfering with Bovine Adipocyte ACSL1 Gene

Unsaturated fatty acids (UFAs) in beef play a vital role in promoting human health. Long-chain fatty acyl-CoA synthase 1 (ACSL1) is a crucial gene for UFA synthesis in bovine adipocytes. To investigate the protein expression profile during UFA synthesis, we performed a proteomic analysis of bovine adipocytes by RNA interference and non-interference with ACSL1 using label-free techniques. A total of 3558 proteins were identified in both the NC and si-treated groups, of which 1428 were differentially expressed proteins (DEPs; fold change ≥ 1.2 or ≤ 0.83 and p-value < 0.05). The enrichment analysis of the DEPs revealed signaling pathways related to UFA synthesis or metabolism, including cAMP, oxytocin, fatty acid degradation, glycerol metabolism, insulin, and the regulation of lipolysis in adipocytes (p-value < 0.05). Furthermore, based on the enrichment analysis of the DEPs, we screened 50 DEPs that potentially influence the synthesis of UFAs and constructed an interaction network. Moreover, by integrating our previously published transcriptome data, this study established a regulatory network involving differentially expressed long non-coding RNAs (DELs), highlighting 21 DEPs and 13 DELs as key genes involved in UFA synthesis. These findings present potential candidate genes for further investigation into the molecular mechanisms underlying UFA synthesis in bovines, thereby offering insights to enhance the quality of beef and contribute to consumer health in future studies.

Molecular and Cellular Mechanisms of Intramuscular Fat Development and Growth in Cattle

Intramuscular fat, also referred to as marbling fat, is the white fat deposited within skeletal muscle tissue. The content of intramuscular fat in the skeletal muscle, particularly the longissimus dorsi muscle, of cattle is a critical determinant of beef quality and value. In this review, we summarize the process of intramuscular fat development and growth, the factors that affect this process, and the molecular and epigenetic mechanisms that mediate this process in cattle. Compared to other species, cattle have a remarkable ability to accumulate intramuscular fat, partly attributed to the abundance of sources of fatty acids for synthesizing triglycerides. Compared to other adipose depots such as subcutaneous fat, intramuscular fat develops later and grows more slowly. The commitment and differentiation of adipose precursor cells into adipocytes as well as the maturation of adipocytes are crucial steps in intramuscular fat development and growth in cattle. Each of these steps is controlled by various factors, underscoring the complexity of the regulatory network governing adipogenesis in the skeletal muscle. These factors include genetics, epigenetics, nutrition (including maternal nutrition), rumen microbiome, vitamins, hormones, weaning age, slaughter age, slaughter weight, and stress. Many of these factors seem to affect intramuscular fat deposition through the transcriptional or epigenetic regulation of genes directly involved in the development and growth of intramuscular fat. A better understanding of the molecular and cellular mechanisms by which intramuscular fat develops and grows in cattle will help us develop more effective strategies to optimize intramuscular fat deposition in cattle, thereby maximizing the quality and value of beef meat.

Transcriptional Regulation Associated with Subcutaneous Adipogenesis in Porcine ACSL1 Gene

Long-chain acyl-CoA synthetase 1 (ACSL1) plays an important role in fatty acid metabolism and fat deposition. The transcription of the ACSL1 gene is regulated specifically among cells and physiological processes, and transcriptional regulation of ACSL1 in adipogenesis remains elusive. Here, we characterize transcription factors (TFs) associated with adipogenesis in the porcine ACSL1 gene. CCAAT-enhancer binding protein (C/EBP)α, a well-known adipogenic marker, was found to enhance the expression of the ACSL1 gene via binding two tandem motifs in the promoter. Further, we demonstrate that ACSL1 mediates C/EBPα effects on adipogenesis in preadipocytes cultured from subcutaneous fat tissue of pigs via gain- and loss-of-function analyses. The cAMP-response element binding protein, another TF involved in adipogenesis, was also identified in the regulation of ACSL1 gene expression. Additionally, single nucleotide polymorphisms (SNPs) were screened in the promoter of ACSL1 among four breeds including the Chinese indigenous Min, and Duroc, Berkshire, and Yorkshire pigs through sequencing of PCR products. Two tightly linked SNPs, -517G>T and -311T>G, were found exclusively in Min pigs. The haplotype mutation decreases promoter activity in PK-15 and ST cells, and in vivo the expression of ACSL1, illustrating a possible role in adipogenesis regulated by C/EBPα/ACSL1 axis. Additionally, a total of 24 alternative splicing transcripts were identified, indicating the complexity of alternative splicing in the ACSL1 gene. The results will contribute to further revealing the regulatory mechanisms of ACSL1 during adipogenesis and to the characterization of molecular markers for selection of fat deposition in pigs.

Global analysis of the association between pig muscle fatty acid composition and gene expression using RNA-Seq

Fatty acids (FAs) play an essential role as mediators of cell signaling and signal transduction, affecting metabolic homeostasis and determining meat quality in pigs. However, FAs are transformed by the action of several genes, such as those encoding desaturases and elongases of FAs in lipogenic tissues. The aim of the current work was to identify candidate genes, biological processes, and pathways involved in the modulation of intramuscular FA profile from longissimus dorsi muscle. FA profile by gas chromatography of methyl esters and gene expression by RNA-Seq were determined in 129 Iberian × Duroc backcrossed pigs. An association analysis between the muscle transcriptome and its FA profile was performed, followed by a concordance and functional analysis. Overall, a list of well-known (e.g., PLIN1, LEP, ELOVL6, SC5D, NCOA2, ACSL1, MDH1, LPL, LGALS12, TFRC, GOT1, and FBP1) and novel (e.g., TRARG1, TANK, ENSSSCG00000011196, and ENSSSCG00000038429) candidate genes was identified, either in association with specific or several FA traits. Likewise, several of these genes belong to biological processes and pathways linked to energy, lipid, and carbohydrate metabolism, which seem determinants in the modulation of FA compositions. This study can contribute to elucidate the complex relationship between gene expression and FA profile in pig muscle.

Transcriptional analysis of microRNAs related to unsaturated fatty acid synthesis by interfering bovine adipocyte ACSL1 gene

Long-chain fatty acyl-CoA synthase 1 (ACSL1) plays a vital role in the synthesis and metabolism of fatty acids. The proportion of highly unsaturated fatty acids in beef not only affects the flavor and improves the meat’s nutritional value. In this study, si-ACSL1 and NC-ACSL1 were transfected in bovine preadipocytes, respectively, collected cells were isolated on the fourth day of induction, and then RNA-Seq technology was used to screen miRNAs related to unsaturated fatty acid synthesis. A total of 1,075 miRNAs were characterized as differentially expressed miRNAs (DE-miRNAs), of which the expressions of 16 miRNAs were upregulated, and that of 12 were downregulated. Gene ontology analysis indicated that the target genes of DE-miRNAs were mainly involved in biological regulation and metabolic processes. Additionally, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis identified that the target genes of DE-miRNAs were mainly enriched in metabolic pathways, fatty acid metabolism, PI3K-Akt signaling pathway, glycerophospholipid metabolism, fatty acid elongation, and glucagon signaling pathway. Combined with the previous mRNA sequencing results, several key miRNA-mRNA targeting relationship pairs, i.e., novel-m0035-5p—ACSL1, novel-m0035-5p—ELOVL4, miR-9-X—ACSL1, bta-miR-677—ACSL1, miR-129-X—ELOVL4, and bta-miR-485—FADS2 were screened via the miRNA-mRNA interaction network. Thus, the results of this study provide a theoretical basis for further research on miRNA regulation of unsaturated fatty acid synthesis in bovine adipocytes.

Fortification of diets with omega-3 long-chain polyunsaturated fatty acids enhances feedlot performance, intramuscular fat content, fat melting point, and carcass characteristics of Tattykeel Australian White MARGRA lambs

Meat eating quality indices such as intramuscular fat content (IMF) and fat melting point (FMP) of the Longissimus thoracis et lumborum muscle and the feedlot performance, carcass traits, and commercial wholesale cuts of lot-fed Tattykeel Australian White (TAW) MARGRA lambs as a result of dietary fortification of the diet with omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) were evaluated. A total of 75 TAW MARGRA lambs at 6 months of age with an average liveweight of 30 ± 1.2 kg were used. The lambs were randomly allocated to the following three dietary treatments of 25 lambs each in a 47-day feeding trial using a completely randomized experimental design: (1) control diet of hay plus pellets without omega-3 oil, (2) hay plus commercial whole grain pellets (MSM) without omega-3 oil, and (3) hay plus pellets fortified with omega-3 oil. It was hypothesized that dietary supplementation with omega-3 fortified pellets will improve feedlot performance, meat-eating quality indices of IMF, FMP, and carcass characteristics. Lot-fed lambs on the MSM whole grain had the highest feed intake of 1.69 kg/day, followed by the control at 1.57 kg/day and the lowest in the omega-3 diet at 1.01 kg/day (p = 0.0001). However, the omega-3 diet had the highest average daily gain of 230 g/head/day (p = 0.0001), indicating the greatest feed efficiency since it had the best growth response with minimal feed intake. Post-slaughter evaluation of the Longissimus thoracis et lumborum muscle revealed significant treatment variations in IMF (p = 0.0001), FMP (p = 0.0001), pH (p = 0.0380), and wholesale French rack primal cut (p = 0.0001). Strong correlations (p < 0.05) between liveweight, temperature, pH, FMP, and IMF were observed. Similarly, significant correlations between carcass characteristics of total saleable meat yield, lean trim, fat trims, bones, and leg shank were evident (p < 0.05). However, there were no treatment differences in the final liveweight, GR fat depth, hot standard carcass weight, or dressing percentage. The findings indicate that feedlot performance, meat-eating quality traits such as IMF and FMP, and commercial wholesale French rack cuts can be further improved during feedlot finishing of TAW MARGRA lambs through dietary supplementation with omega-3 oils, and hence the tested hypothesis of improved meat quality attributes is partially confirmed.

Novel Insight Into the Role of ACSL1 Gene in Milk Production Traits in Buffalo

Understanding the genetic mechanisms underlying milk production traits contribute to improving the production potential of dairy animals. Long-chain acyl-CoA synthetase 1 (ACSL1) plays a key role in fatty acid metabolism and was highly expressed in the lactating mammary gland epithelial cells (MGECs). The objectives of the present study were to detect the polymorphisms within ACSL1 in Mediterranean buffalo, the genetic effects of these mutations on milk production traits, and understand the gene regulatory effects on MGECs. A total of twelve SNPs were identified by sequencing, including nine SNPs in the intronic region and three in the exonic region. Association analysis showed that nine SNPs were associated with one or more traits. Two haplotype blocks were identified, and among these haplotypes, the individuals carrying the H2H2 haplotype in block 1 and H5H1 in block 2 were superior to those of other haplotypes in milk production traits. Immunohistological staining of ACSL1 in buffalo mammary gland tissue indicated its expression and localization in MGECs. Knockdown of ACSL1 inhibited cell growth, diminished MGEC lipid synthesis and triglyceride secretion, and downregulated CCND1, PPARγ, and FABP3 expression. The overexpression of ACSL1 promoted cell growth, enhanced the triglyceride secretion, and upregulated CCND1, PPARγ, SREBP1, and FABP3. ACSL1 was also involved in milk protein regulation as indicated by the decreased or increased β-casein concentration and CSN3 expression in the knockdown or overexpression group, respectively. In summary, our present study depicted that ACSL1 mutations were associated with buffalo milk production performance. This may be related to its positive regulation roles on MGEC growth, milk fat, and milk protein synthesis. The current study showed the potential of the ACSL1 gene as a candidate for milk production traits and provides a new understanding of the physiological mechanisms underlying milk production regulation.

Interference With ACSL1 Gene in Bovine Adipocytes: Transcriptome Profiling of mRNA and lncRNA Related to Unsaturated Fatty Acid Synthesis

The enzyme long-chain acyl-CoA synthetase 1 (ACSL1) is essential for lipid metabolism. The ACSL1 gene controls unsaturated fatty acid (UFA) synthesis as well as the formation of lipid droplets in bovine adipocytes. Here, we used RNA-Seq to determine lncRNA and mRNA that regulate UFA synthesis in bovine adipocytes using RNA interference and non-interference with ACSL1. The corresponding target genes of differentially expressed (DE) lncRNAs and the DE mRNAs were found to be enriched in lipid and FA metabolism-related pathways, according to GO and KEGG analyses. The differentially expressed lncRNA- differentially expressed mRNA (DEL-DEM) interaction network indicated that some DELs, such as TCONS_00069661, TCONS_00040771, TCONS_ 00035606, TCONS_00048301, TCONS_001309018, and TCONS_00122946, were critical for UFA synthesis. These findings assist our understanding of the regulation of UFA synthesis by lncRNAs and mRNAs in bovine adipocytes.

Transcriptomics analysis of Daheng broilers reveals that PLIN2 regulates chicken preadipocyte proliferation, differentiation and apoptosis

BACKGROUND

Intramuscular fat content, an important meat quality trait, strongly affects flavor, juiciness, and tenderness. Sex hormones regulate lipid metabolism, and female hormones stimulate fat deposition, thereby making the female chickens always fatter than males. In this study, the effect of sex on IMF deposition was screened following transcriptomics in chickens.

METHODS AND RESULTS

Results confirmed significantly higher IMF content of 150-day female chickens as compared to the male chickens. The female chickens manifested higher serum TG, LDL-C, and VLDL, and significantly lower HDL-C contents than male chickens. Moreover, differential expression of genes involved in lipid metabolism were obtained in the muscle and liver between female and male chicken, which could partly interpret the possible reasons for the sex-mediated differences of IMF content. Cellular results revealed that inhibition of PLIN2 significantly inhibited chicken preadipocyte proliferation and induces apoptosis of preadipocytes, as well as promoted adipocyte differentiation.

CONCLUSIONS

According to our results, PLIN2 may be considered as a molecular marker for poultry meat quality and applying this gene in early breed selection.

Interference with ACSL1 gene in bovine adipocytes: Transcriptome profiling of circRNA related to unsaturated fatty acid production

Long-chain acyl-CoA synthetase 1 (ACSL1) is a member of the acyl-CoA synthetase family that plays a vital role in lipid metabolism. We have previously shown that the ACSL1 gene regulates the composition of unsaturated fatty acids (UFAs) in bovine skeletal muscle, which in turn regulates the fatty acid synthesis and the generation of lipid droplets. Here, we used RNA-Seq to screen circRNAs that regulated the expression of ACSL1 gene and other UFA synthesis-related genes by RNA interference and noninterference in bovine adipocytes. The results of KEGG pathway analysis showed that the parental genes of differentially expressed (DE)-circRNAs were primarily enriched in the adipocytokine signaling pathway. The prediction results showed that novel_circ_0004855, novel_circ_0001507, novel_circ_0001731, novel_circ_0005276, novel_circ_0002060, novel_circ_0005405 and novel_circ_0004254 regulated UFA synthesis-related genes by interacting with the related miRNAs. These results could help expand our knowledge of the molecular mechanisms of circRNAs in the regulation of UFA synthesis in bovine adipocytes.

Single nucleotide polymorphism scanning and expression analysis of ACSL1 from different duck breeds

Accumulating studies have indicated that the long-chain fatty acyl-CoA1 (ACSL1) gene is related to fat deposition and meat quality in mammals. However, few studies have investigated the relationship between ACSL1 and lipid deposition in ducks. To examine this, we assessed the physicochemical property, homologous alignment, and phylogenetic analyses of the ACSL1 amino acid sequence using bioinformatics tools. The analysis indicated that the ACSL1 amino acid sequence varies in animals, and the duck ACSL1 protein is most closely related to that of chicken. Two single nucleotide polymorphism (SNP) sites were identified at 1749 and 1905 bp of the coding region of ACSL1 by sequencing. Quantitative real-time PCR and western blotting were used to measure mRNA and protein levels in abdominal fat, breast muscle, and liver tissue of Pekin duck (BD) and Cherry Valley duck (CD). mRNA and protein expression were significantly higher in BD than in CD in abdominal fat and liver tissue (P < 0.05). In breast muscle, the mRNA level of ACSL1 was also significantly higher in BD than in CD (P < 0.05), and protein expression in BD tended to be higher than that of CD. These results suggest that ACSL1 may contribute to lipid deposition and meat quality in ducks.

Nutritional Enhancement of Health Beneficial Omega-3 Long-Chain Polyunsaturated Fatty Acids in the Muscle, Liver, Kidney, and Heart of Tattykeel Australian White MARGRA Lambs Fed Pellets Fortified with Omega-3 Oil in a Feedlot System

Simple Summary

The problem addressed in this research was the possibility of enhancing the nutritional value and health beneficial omega-3 long-chain fatty acid content of lamb and its edible components. The aims and objectives were to evaluate the omega-3 contents of muscle, liver, kidney, and heart of lot-fed Tattykeel Australian White lambs of the MARGRA brand, in response to dietary supplementation with or without omega-3 oil fortified pellets. The findings demonstrate that the inclusion of omega-3 oil in feedlot diets of lambs enhances the human health beneficial omega-3 long-chain polyunsaturated fatty acid profiles of edible muscle tissue and organs without compromising meat quality or shelf life. These results are valuable to society because of increased functionality, health benefits, micro-marbling, tender, mouth-melting taste, and high-end eating quality experience of MARGRA lamb tissues and organs.

Abstract

The aim of this research was to evaluate the nutritional enhancement of omega-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) composition of edible lamb Longissimus thoracis et lumborum muscle, heart, kidney, and liver in response to dietary supplementation of lot-fed lambs with or without omega-3 oil fortified pellets. The hypothesis tested was that fortifying feedlot pellets with omega-3 oil will enhance the human health beneficial n-3 LC-PUFA composition of edible lamb muscle tissue and organs. Seventy-five Tattykeel Australian White lambs exclusive to the MARGRA brand, with an average body weight of 30 kg at six months of age, were randomly assigned to the following three dietary treatments of 25 lambs each, and lot-fed as a cohort for 47 days in a completely randomized experimental design: (1) Control grain pellets without oil plus hay; (2) Omega-3 oil fortified grain pellets plus hay; and (3) Commercial whole grain pellets plus hay. All lambs had ad libitum access to the basal hay diet and water. Post-slaughter fatty acid composition of the Longissimus thoracis et lumborum muscle, liver, kidney, and heart were determined using thee gas chromatography–mass spectrophotometry technique. Results indicated significant variations (p < 0.05) in fatty acid profiles between tissues and organs. Omega-3 oil fortified pellets significantly (p < 0.05) increased ≥C20 n-3 LC-PUFA (C20:5n-3 eicosapentaenoate, EPA + C22:5n3 docosapentaenoate, DPA + C22:6n3 docosahexanoate DHA); C18:3n-3 alpha-linolenate, ALA; C18:2 conjugated linoleic acid, CLA; total monounsaturated fatty acids, MUFA; polyunsaturated fatty acids, PUFA contents; and reduced the ratio of omega-6 to omega-3 fatty acids in all lamb organs and tissues without impacting shelf-life. The findings demonstrate that the inclusion of omega-3 oil in feedlot diets of lambs enhances the human health beneficial omega-3 long-chain polyunsaturated fatty acid profiles of edible muscle tissue and organs without compromising meat quality.

Genome-Wide Association Study for Fatty Acid Composition in American Angus Cattle

Livestock is an important commodity playing a major role in the global economy. Red meat plays an important role in human life, as it is a good source of animal protein and energy. The fatty acid content of beef has been shown to impact the eating experience and nutritional value of beef. Therefore, this study aimed to identify genomic regions which can account for genetic variation in meat fatty acid content. Genotypes imputed to the Illumina BovineHD 770K BeadChip were used in this study. Thirty-six 1-Mb genomic regions with a posterior probability of inclusion (PPI) greater than 0.90 were identified to be associated with variation in the content of at least one fatty acid. The genomic regions (1Mb) which were associated with more than one fatty acid trait with high genetic variance and harbored good candidate genes were on Chromosome (Chr) 6 (fatty acid binding protein 2), Chr 19 (thyroid hormone receptor alpha, fatty acid synthase), Chr 26 (stearoyl-CoA desaturase), and Chr 29 (thyroid hormone responsive, fatty acid desaturase 2, and fatty acid desaturase 3). Further studies are required to identify the causal variants within the identified genomic regions. Findings from the present study will help to increase understanding of the variation in fatty acid content of beef and help to enhance selection for beef with improved fatty acid composition.

Polymorphisms of the ACSL1 Gene Influence Milk Production Traits and Somatic Cell Score in Chinese Holstein Cows

Simple Summary

Milk production traits of cows are important economic indicators of the livestock industry. Many dairy farms strive to improve the quality of their milk. Long-chain acyl-CoA synthetase 1 (ACSL1) is a gene related to lipid metabolism. It is widely found in various organisms and can affect fat content and protein content in milk. Single nucleotide polymorphisms (SNP) refers to the polymorphism of DNA sequence caused by a single nucleotide variation at the gene level, which plays a vital function in the genetic study of milk production traits in dairy cows. Our study identified six SNPs of the ACSL1 gene in Chinese Holstein cows, which were related to milk yield, milk fat content, milk protein content and somatic cell score (SCS) to some extent. In summary, the pleiotropic effects of bovine ACSL1 for milk production traits were found in this paper, which will provide a reference for Chinese Holstein cow breeding selection and high economic benefits.

Abstract

Improving the quality of milk is a challenge for zootechnicians and dairy farms across the globe. Long-chain acyl-CoA synthetase 1 (ACSL1) is a significant member of the long-chain acyl-CoA synthetase gene family. It is widely found in various organisms and influences the lactation performance of cows, including fat percentage, milk protein percentage etc. Our study was aimed to investigate the genetic effects of single nucleotide polymorphisms (SNPs) in ACSL1 on milk production traits. Twenty Chinese Holstein cows were randomly selected to extract DNA from their blood samples for PCR amplification and sequencing to identify SNPs of the bovine ACSL1 gene, and six SNPs (5’UTR-g.20523C>G, g.35446C>T, g.35651G>A, g.35827C>T, g.35941G>A and g.51472C>T) were discovered. Then, Holstein cow genotyping (n = 992) was performed by Sequenom MassARRAY based on former SNP information. Associations between SNPs and milk production traits and somatic cell score (SCS) were analyzed by the least-squares method. The results showed that SNP g.35827C>T was in high linkage disequilibrium with g.35941G>A. Significant associations were found between SNPs and test-day milk yield (TDMY), fat content (FC), protein content (PC) and SCS (p < 0.05). Among these SNPs, SNP 5’UTR-g.20523C>G showed an extremely significant effect on PC and SCS (p < 0.01). The SNP g.35446C>T showed a statistically significant effect on FC, PC, and SCS (p < 0.01), and also TDMY (p < 0.05). The SNP g.35651G>A had a statistically significant effect on PC (p < 0.01). The SNP g.35827C>T showed a highly significant effect on TDMY, FC, and SCS (p < 0.01) and significantly influenced PC (p < 0.05). Lastly, SNP g.51472C>T was significantly associated with TDMY, FC, and SCS (p < 0.05). In summary, the pleiotropic effects of bovine ACSL1 for milk production traits were found in this paper, but further investigation will be required on the intrinsic correlation to provide a theoretical basis for the research on molecular genetics of milk quality traits of Holstein cows.

Effects of overexpression of ACSL1 gene on the synthesis of unsaturated fatty acids in adipocytes of bovine

There exists a positive correlation between the unsaturated fatty acids (UFA) content in the bovine species and their taste and nutritional significance. Long-chain acyl-CoA synthetase 1 (ACSL1) is known to be involved in lipid synthesis as well as fatty acid transport and degradation. This gene has been identified as the key candidate gene for regulating lipid composition in the bovine skeletal muscle; however, its mechanism of action in regulating UFA synthesis in bovine adipocytes is unclear. In this study, we used a recombinant adenovirus vector (Ad-ACSL1) to overexpress the ACSL1 gene using Ad-NC (recombinant adenovirus of green fluorescent protein) as the control. Quantitative real-time PCR (qRT-PCR) was done to examine the gene expression associated with the synthesis of UFA, followed by the analysis of the fatty acid composition. Oil red O staining was done to examine the aggregation of lipid droplets. We found that ACSL1 overexpression was associated with an upregulated expression of PPARγ, FABP3, ACLY, SCD1, and FASN, and downregulated expression of CPT1A. Additionally, ACSL1 overexpression resulted in elevated saturated fatty acid content, especially C16:0 and C18:0, than the control group (Ad-NC cells) (p < 0.05). Furthermore, the overexpression of ACSL1 enhanced the proportion of eicosapentaenoic acid (EPA), decreased the proportion of C22:4, and significantly upregulated polyunsaturated fatty acid (PUFA) content. These results were supported by oil red O staining, which revealed an increase in the lipid droplets in bovine adipocytes after the overexpression of the ACSL1 gene. Thus, the results of this study indicated that ACSL1 positively regulated PUFA synthesis in bovine adipocytes.

Comparative Transcriptome Analyses of Longissimus thoracis Between Pig Breeds Differing in Muscle Characteristics

The two breeds, Mashen (MS; a northern China breed) and Large White (LW; a western lean breed) pigs, show important phenotypic differences in growth, adaptability, intramuscular fat (IMF) content, and energy metabolism since early developmental stage. The main aim of this study was the evaluation of longissimus thoracis muscle transcriptome profile of both genetic types to identify genes, pathways responsible for their differentiated phenotype. Longissimus thoracis of MS and LW pigs were sampled at 0 day (early stage), 90 days (middle stage), and 180 days (later stage) after birth. A total of 3,487 differentially expressed genes (DEGs) were identified at the three time points. Sample clustering analysis revealed the slower growth rate of MS than LW pigs. Gene expression pattern analysis revealed that multicellular organism growth genes (GHSR, EZR, FOXS1, DRD2, SH3PXD2B, CSF1, and TSHR) were involved in the fast growth rate of LW pigs at early stage. Furthermore, DEGs (ACACA, ACSF3, OXSM, CBR4, and HSD17B8) functionally related to fatty acid synthesis revealed that IMF accumulation occurred around 90 and up to 180 days. These DEGs provided valuable resource to study the phenotypic difference in longissimus thoracis muscle between MS and LW pigs.

Expression profiles and polymorphic identification of the ACSL1 gene and their association with body size traits in Dezhou donkeys

Finding out the genetic mechanism of growth and development traits and the development of related molecular markers can help improve the breeding of livestock. The long-chain acyl coenzyme A synthase 1 (ACSL1) gene plays a major role in lipid synthesis and fatty acid catabolism. However, there are few studies on the ACSL1 gene polymorphism of Dezhou donkeys. This study analyzed the expression level of the ACSL1 gene in different tissues of young and adult Dezhou donkeys, as well as association analysis of four gene polymorphic loci in 450 individuals. The results showed that expression levels of the ACSL1 gene are higher in heart, liver, spleen, lung, renal, gastric and muscle tissues of adult donkeys than in those of young donkeys. In the association analysis between genotype and body size traits, the wild genotype DD at the ACSL1-1 locus in female and male donkeys was greater than the mutant genotype II (P<0.05); genotype II of ACSL1-2 was significantly higher than that of DD in withers height, body length, rump width and body weight of male donkeys (P<0.05); and ACSL1-3 showed a tendency for the wild genotype II to be greater than the mutant genotype DD in female and male donkeys (P<0.05). In addition, among the five haplotype combinations constructed, Hap3Hap3 (II-II-DD-DD) and Hap6Hap6 (DD-II-II-II) haplotype combinations were superior to other haplotype combinations in growth traits, which also indicated that the results of haplotype combination association analysis and genotype association analysis tended to be the same. In conclusion, the results of this study indicate that the polymorphic loci of the ACSL1 gene can be used as candidate molecular markers for the growth and development of Dezhou donkeys, and provide a theoretical reference for the breeding of Dezhou donkeys.

Evolution, expression profile, and regulatory characteristics of ACSL gene family in chicken (Gallus gallus)

Long chain acyl-CoA synthetases (ACSLs), which drive the conversion of long chain fatty acid into acyl-CoA, an ingredient of lipid synthesis, have been well-acknowledged to exert an indispensable role in many metabolic processes in mammals, especially lipid metabolism. However, in chicken, the evolutionary characteristics, expression profiles and regulatory mechanisms of ACSL gene family are rarely understood. Here, we analyzed the genomic synteny, gene structure, evolutionary event and functional domains of the ACSL gene family members using bioinformatics methods. The spatiotemporal expression profiles of ACSL gene family, and their regulatory mechanism were investigated via bioinformatics analysis incorporated with in vivo and in vitro estrogen-treated experiments. Our results indicated that ACSL2 gene was indeed evolutionarily lost in the genome of chicken. Chicken ACSLs shared an AMP-binding functional domain, as well as highly conversed ATP/AMP and FACS signature motifs, and were clustered into two clades, ACSL1/5/6 and ACSL3/4, based on high sequence similarity, similar gene features and conversed motifs. Chicken ACSLs showed differential tissue expression distributions, wherein the significantly decreased expression level of ACSL1 and the significantly increased expression level of ACSL5 were found, respectively, the expression levels of the other ACSL members remained unchanged in the liver of peak-laying hens versus pre-laying hens. Moreover, the transcription activity of ACSL1, ACSL3 and ACSL4 was silenced and ACSL6 was activated by estrogen, but no response to ACSL5. In conclusion, though having highly conversed functional domains, chicken ACSL gene family is organized into two separate groups, ACSL1/5/6 and ACSL3/4, and exhibits varying expression profiles and estrogen effects. These results not only pave the way for better understanding the specific functions of ACSL genes in avian lipid metabolism, but also provide a valuable evidence for gene family characteristics.

Fatty Acid Profile of Muscles from Crossbred Angus-Simmental, Wagyu-Simmental, and Chinese Simmental Cattles

This study assessed breed differences in fatty acid composition and meat quality of Longissimus thoracis et lumborum (LTL) and semitendinosus (SE) of Angus× Chinese Simmental (AS), Wagyu×Chinese Simmental (WS), and Chinese Simmental (CS). CS (n=9), AS (n=9) and WS (n=9) were randomly selected from a herd of 80 bulls which were fed and managed under similar conditions. Fatty acid profile and meat quality parameters were analyzed in duplicate. Significant breed difference was observed in fatty acid and meat quality profiles. AS exhibited significantly (p<0.05) lower C16:0 and higher C18:1n9c compared with CS. AS breed also had a tendency (p<0.10) to lower total saturated fatty acid (SFA), improve C18:3n3 and total unsaturated fatty acid (UFA) compared with CS. Crossbreed of AS and WS had significantly (p<0.05) improved the lightness, redness, and yellowness of muscles, and lowered cooking loss, pressing loss, and shear force compared with CS. These results indicated that fatty acid composition and meat quality generally differed among breeds, although the differences were not always similar in different tissues. Fatty acid composition, meat color, water holding capacity, and tenderness favored AS over CS. Thus, Angus cattle might be used to improve fatty acid and meat quality profiles of CS, and AS might contain better nutritive value, organoleptic properties, and flavor, and could be potentially developed as an ideal commercial crossbreed.

Identification and Annotation of Potential Function of Regulatory Antisense Long Non-Coding RNAs Related to Feed Efficiency in Bos taurus Bulls

Long non-coding RNAs (lncRNAs) can influence transcriptional and translational processes in mammalian cells and are associated with various developmental, physiological and phenotypic conditions. However, they remain poorly understood and annotated in livestock species. We combined phenotypic, metabolomics and liver transcriptomic data of bulls divergent for residual feed intake (RFI) and fat accretion. Based on a project-specific transcriptome annotation for the bovine reference genome ARS-UCD.1.2 and multiple-tissue total RNA sequencing data, we predicted 3590 loci to be lncRNAs. To identify lncRNAs with potential regulatory influence on phenotype and gene expression, we applied the regulatory impact factor algorithm on a functionally prioritized set of loci (n = 4666). Applying the algorithm of partial correlation and information theory, significant and independent pairwise correlations were calculated and co-expression networks were established, including plasma metabolites correlated with lncRNAs. The network hub lncRNAs were assessed for potential cis-actions and subjected to biological pathway enrichment analyses. Our results reveal a prevalence of antisense lncRNAs positively correlated with adjacent protein-coding genes and suggest their participation in mitochondrial function, acute phase response signalling, TCA-cycle, fatty acid β-oxidation and presumably gluconeogenesis. These antisense lncRNAs indicate a stabilizing function for their cis-correlated genes and a putative regulatory role in gene expression.

Effects of Long-Chain Fatty Acyl-CoA Synthetase 1 on Diglyceride Synthesis and Arachidonic Acid Metabolism in Sheep Adipocytes

Long-chain fatty acyl-CoA synthetase (ACSLs) is an essential enzyme for the synthesis of fatty acyl-CoA. ACSL1 plays a key role in the synthesis of triglycerides, phospholipids, and cholesterol esters.

BACKGROUND

In the current study, triglyceride content did not increase after overexpression of the ACSL1 gene.

METHODS

RNA-seq and lipid metabolome profiling were performed to determine why triglyceride levels did not change with ACSL1 overexpression.

RESULTS

Fatty acyl-CoA produced by ACSL1 was determined to be involved in the diglyceride synthesis pathway, and diglyceride content significantly increased when ACSL1 was overexpressed. Moreover, the arachidonic acid (AA) content in sheep adipocytes significantly increased, and the level of cyclooxygenase 2 (COX2) expression, the downstream metabolic gene, was significantly downregulated. Knocking down the ACSL1 gene was associated with an increase in COX2 mRNA expression, as well as an increase in prostaglandin content, which is the downstream metabolite of AA.

CONCLUSIONS

The overexpression of the ACSL1 gene promotes the production of AA via downregulation of COX2 gene expression.

Biological Network Approach for the Identification of Regulatory Long Non-Coding RNAs Associated With Metabolic Efficiency in Cattle

Background: Genomic regions associated with divergent livestock feed efficiency have been found predominantly outside protein coding sequences. Long non-coding RNAs (lncRNA) can modulate chromatin accessibility, gene expression and act as important metabolic regulators in mammals. By integrating phenotypic, transcriptomic, and metabolomic data with quantitative trait locus data in prioritizing co-expression network analyses, we aimed to identify and functionally characterize lncRNAs with a potential key regulatory role in metabolic efficiency in cattle. Materials and Methods: Crossbred animals (n = 48) of a Charolais x Holstein F₂-population were allocated to groups of high or low metabolic efficiency based on residual feed intake in bulls, energy corrected milk in cows and intramuscular fat content in both genders. Tissue samples from jejunum, liver, skeletal muscle and rumen were subjected to global transcriptomic analysis via stranded total RNA sequencing (RNAseq) and blood plasma samples were used for profiling of 640 metabolites. To identify lncRNAs within the indicated tissues, a project-specific transcriptome annotation was established. Subsequently, novel transcripts were categorized for potential lncRNA status, yielding a total of 7,646 predicted lncRNA transcripts belonging to 3,287 loci. A regulatory impact factor approach highlighted 92, 55, 35, and 73 lncRNAs in jejunum, liver, muscle, and rumen, respectively. Their ensuing high regulatory impact factor scores indicated a potential regulatory key function in a gene set comprising loci displaying differential expression, tissue specificity and loci overlapping with quantitative trait locus regions for residual feed intake or milk production. These were subjected to a partial correlation and information theory analysis with the prioritized gene set. Results and Conclusions: Independent, significant and group-specific correlations (|r| > 0.8) were used to build a network for the high and the low metabolic efficiency group resulting in 1,522 and 1,732 nodes, respectively. Eight lncRNAs displayed a particularly high connectivity (>100 nodes). Metabolites and genes from the partial correlation and information theory networks, which each correlated significantly with the respective lncRNA, were included in an enrichment analysis indicating distinct affected pathways for the eight lncRNAs. LncRNAs associated with metabolic efficiency were classified to be functionally involved in hepatic amino acid metabolism and protein synthesis and in calcium signaling and neuronal nitric oxide synthase signaling in skeletal muscle cells.

Analysis of gene co-expression networks and function modules at different developmental stages of chicken breast muscle

The development of poultry muscle fibers after hatching is closely related to meat quality and production efficiency. It is necessary to identify functional modules (groups of functionally related genes) related to muscle development at different developmental stages, and to investigate their relationships based on the weighted gene co-expression network analysis (WGCNA) methods. Accordingly, we investigated the co-expression associations between genes related to chicken breast muscle at four different developmental stages (between 2 and 14 weeks of age), and systematically analyzed the network topology in Jinmao Hua chicken. As a result, 2341 differentially expressed genes were identified and subjected to co-expression analysis. Four modules were identified to be related to a particular growth stage for the development of breast muscle. A series of genes with the highest connectivity were identified in the pink (2 weeks), yellow (6 weeks), green (10 weeks) and black modules (14 weeks), respectively, and visualized by Cytoscape. These hub genes (FGF, MAPKAPK5, NRG1, SCD, ACSL1, PPAR etc.) were mainly enriched in 15 pathways, such as MAPK signaling pathway, NRG/ErbB signaling pathway, and insulin signaling pathway. They shared biological functions related to development of breast muscle and adipogenesis. This is the first study of gene network with different stages of muscle development in Jinmao Hua chicken to observe co-expression patterns. It may contribute to the underlied molecular mechanisms of chicken breast muscle development.

Longissimus dorsi muscle transcriptomic analysis of Yunling and Chinese simmental cattle differing in intramuscular fat content and fatty acid composition

Intramuscular fat (IMF) content and fatty acid (FA) composition vary significantly across beef cattle breeds, which play an important role in taste and nutritional value. However, the molecular mechanisms underlying these phenotypic differences remain unknown. The present study compared meat quality traits between Yunling cattle and Chinese Simmental cattle. Yunling cattle showed a lower IMF content and proportion of monounsaturated fatty acids (MUFA), as well as higher proportions of saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), and short-chain fatty acids (sc-FA) in the longissimus dorsi (LD) muscle than Chinese Simmental cattle. To further identify the candidate genes and pathways responsible for these phenotypic differences, the transcriptome of LD muscle from the two breeds were measured using RNA-seq. A total of 1347 differentially expressed genes were identified. The major metabolic pathways that were differentially modulated were lipolysis and glycometabolism. Yunling cattle showed a higher expression of lipolysis genes (ALDH9A1, ACSL5, ACADM, ACAT2, ACOT2) and a lower expression of genes related to glycometabolism (PGM1, GALM, PGM1, GPI, LDHA). This research identified candidate genes and pathways for IMF content and FA composition in the LD muscle of beef cattle, which may facilitate the design of new selection strategies to improve meat quality.

Distinct correlations between lipogenic gene expression and fatty acid composition of subcutaneous fat among cattle breeds

BACKGROUND

The fatty acid (FA) composition of adipose tissue influences the nutritional quality of meat products. The unsaturation level of FAs is determined by fatty acid desaturases such as stearoyl-CoA desaturases (SCDs), which are under control of the transcription factor sterol regulatory element-binding protein (SREBP). Differences in SCD genotype may thus confer variations in lipid metabolism and FA content among cattle breeds. This study investigated correlations between FA composition and lipogenic gene expression levels in the subcutaneous adipose tissue of beef cattle breeds of different gender from the Basque region of northern Spain. Pirenaica is the most important beef cattle breed in northern Spain, while Salers cattle and Holstein-Friesian cull cows are also an integral part of the regional beef supply.

RESULTS

Pirenaica heifers showed higher monounsaturated FA (MUFA) and conjugated linoleic acid (CLA) contents in subcutaneous adipose tissue than other breeds (P < 0.001). Alternatively, Salers bulls produced the highest oleic acid content, followed by Pirenaica heifers (P < 0.001). There was substantial variability in SCD gene expression among breeds, consistent with these differences in MUFA and CLA content. Correlations between SCD1 expression and most FA desaturation indexes (DIs) were positive in Salers (P < 0.05) and Pirenaica bulls, while, in general, SCD5 expression showed few significant correlations with DIs. There was a significant linear correlation between SCD1 and SRBEP1 in all breeds, suggesting strong regulation of SCD1 expression by SRBEP1. Pirenaica heifers showed a stronger correlation between SCD1 and SREBP1 than Pirenaica bulls. We also observed a opposite relationship between SCD1 and SCD5 expression levels and opposite associations of isoform expression levels with the ∆9 desaturation indexes.

CONCLUSIONS

These results suggest that the relationships between FA composition and lipogenic gene expression are influenced by breed and sex. The opposite relationship between SCD isoforms suggests a compensatory regulation of total SCD activity, while opposite relationships between SCD isoforms and desaturation indexes, specially 9c-14:1 DI, previously reported as an indicator of SCD activity, may reflect distinct activities of SCD1 and SCD5 in regulation of FA content. These findings may be useful for beef/dairy breeding and feeding programs to supply nutritionally favorable products.

Systematic Profiling of Short Tandem Repeats in the Cattle Genome

Short tandem repeats (STRs), or microsatellites, are genetic variants with repetitive 2–6 base pair motifs in many mammalian genomes. Using high-throughput sequencing and experimental validations, we systematically profiled STRs in five Holsteins. We identified a total of 60,106 microsatellites and generated the first high-resolution STR map, representing a substantial pool of polymorphism in dairy cattle. We observed significant STRs overlap with functional genes and quantitative trait loci (QTL). We performed evolutionary and population genetic analyses using over 20,000 common dinucleotide STRs. Besides corroborating the well-established positive correlation between allele size and variance in allele size, these analyses also identified dozens of outlier STRs based on two anomalous relationships that counter expected characteristics of neutral evolution. And one STR locus overlaps with a significant region of a summary statistic designed to detect STR-related selection. Additionally, our results showed that only 57.1% of STRs located within SNP-based linkage disequilibrium (LD) blocks whereas the other 42.9% were out of blocks. Therefore, a substantial number of STRs are not tagged by SNPs in the cattle genome, likely due to STR's distinct mutation mechanism and elevated polymorphism. This study provides the foundation for future STR-based studies of cattle genome evolution and selection.

Identification of differentially expressed genes in longissimus dorsi muscle between Wei and Yorkshire pigs using RNA sequencing

Intramuscular fat (IMF) content is an important trait closely related to meat quality, which is highly variable among pig breeds from diverse genetic backgrounds. High-throughput sequencing has become a powerful technique for analyzing the whole transcription profiles of organisms. In order to elucidate the molecular mechanism underlying porcine meat quality, we adopted RNA sequencing to detect transcriptome in the longissimus dorsi muscle of Wei pigs (a Chinese indigenous breed) and Yorkshire pigs (a Western lean-type breed) with different IMF content. For the Wei and Yorkshire pig libraries, over 57 and 64 million clean reads were generated by transcriptome sequencing, respectively. A total of 717 differentially expressed genes (DEGs) were identified in our study (false discovery rate < 0.05 and fold change > 2), with 323 up-regulated and 394 down-regulated genes in Wei pigs compared with Yorkshire pigs. Gene Ontology analysis showed that DEGs significantly related to skeletal muscle cell differentiation, phospholipid catabolic process, and extracellular matrix structural constituent. Pathway analysis revealed that DEGs were involved in fatty acid metabolism, steroid biosynthesis, glycerophospholipid metabolism, and protein digestion and absorption. Quantitative real time PCR confirmed the differential expression of 11 selected DEGs in both pig breeds. The results provide useful information to investigate the transcriptional profiling in skeletal muscle of different pig breeds with divergent phenotypes, and several DEGs can be taken as functional candidate genes related to lipid metabolism (ACSL1, FABP3, UCP3 and PDK4) and skeletal muscle development (ASB2, MSTN, ANKRD1 and ANKRD2).

Comparative analysis on genome-wide DNA methylation in longissimus dorsi muscle between Small Tailed Han and Dorper×Small Tailed Han crossbred sheep

Objective

The objective of this study was to compare the DNA methylation profile in the longissimus dorsi muscle between Small Tailed Han and Dorper×Small Tailed Han crossbred sheep which were known to exhibit significant difference in meat-production.

Methods

Six samples (three in each group) were subjected to the methylated DNA immunoprecipitation sequencing (MeDIP-seq) and subsequent bioinformatics analyses to detect differentially methylated regions (DMRs) between the two groups.

Results

23.08 Gb clean data from six samples were generated and 808 DMRs were identified in gene body or their neighboring up/downstream regions. Compared with Small Tailed Han sheep, we observed a tendency toward a global loss of DNA methylation in these DMRs in the crossbred group. Gene ontology enrichment analysis found several gene sets which were hypo-methylated in gene-body region, including nucleoside binding, motor activity, phospholipid binding and cell junction. Numerous genes were found to be differentially methylated between the two groups with several genes significantly differentially methylated, including transforming growth factor beta 3 (TGFB3), acyl-CoA synthetase long chain family member 1 (ACSL1), ryanodine receptor 1 (RYR1), acyl-CoA oxidase 2 (ACOX2), peroxisome proliferator activated receptor-gamma2 (PPARG2), netrin 1 (NTN1), ras and rab interactor 2 (RIN2), microtubule associated protein RP/EB family member 1 (MAPRE1), ADAM metallopeptidase with thrombospondin type 1 motif 2 (ADAMTS2), myomesin 1 (MYOM1), zinc finger, DHHC type containing 13 (ZDHHC13), and SH3 and PX domains 2B (SH3PXD2B). The real-time quantitative polymerase chain reaction validation showed that the 12 genes are differentially expressed between the two groups.

Conclusion

In the current study, a tendency to a global loss of DNA methylation in these DMRs in the crossbred group was found. Twelve genes, TGFB3, ACSL1, RYR1, ACOX2, PPARG2, NTN1, RIN2, MAPRE1, ADAMTS2, MYOM1, ZDHHC13, and SH3PXD2B, were found to be differentially methylated between the two groups by gene ontology enrichment analysis. There are differences in the expression of 12 genes, of which ACSL1, RIN2, and ADAMTS2 have a negative correlation with methylation levels and the data suggest that DNA methylation levels in DMRs of the 3 genes may have an influence on the expression. These results will serve as a valuable resource for DNA methylation investigations on screening candidate genes which might be related to meat production in sheep.

Expression of selected genes related to energy mobilisation and insulin resistance in dairy cows

The physiological and metabolic adaptation characterising the transition period in the dairy cows is developed by a complex modulation of different metabolic pathways as well as the expression of selected tissue-specific gene. The aim of this study was to evaluate the age effect on expression of selected genes in adipose, hepatic and muscle tissues in dairy cows during their transition period using the quantitative real-time PCR. Twenty-two pluriparous dairy cows were divided into three groups in relation to age: Group A (38 ± 2 months); Group B (52 ± 2 months) and Group C (80 ± 8 months). Lower levels of peroxisome proliferator-activated receptor gamma and higher levels of adiponectin were found in adipose tissue in Group C than Groups A and B (P < 0.05). Higher levels of solute carrier family 2/facilitated glucose transporter member 4 were found in muscle in Group C than Group A (P < 0.001) and Group B (P < 0.05). The present study showed in dairy cows that the expression of selected genes associated with mobilisation of energy and with insulin resistance are influenced by age demonstrating and highlighting the importance of a genomics approach to assess the metabolic status of dairy cows during the transition period.

Consumer Acceptability of Intramuscular Fat

Fat in meat greatly improves eating quality, yet many consumers avoid visible fat, mainly because of health concerns. Generations of consumers, especially in the English-speaking world, have been convinced by health authorities that animal fat, particularly saturated or solid fat, should be reduced or avoided to maintain a healthy diet. Decades of negative messages regarding animal fats has resulted in general avoidance of fatty cuts of meat. Paradoxically, low fat or lean meat tends to have poor eating quality and flavor and low consumer acceptability. The failure of low-fat high-carbohydrate diets to curb "globesity" has prompted many experts to re-evaluate of the place of fat in human diets, including animal fat. Attitudes towards fat vary dramatically between and within cultures. Previous generations of humans sought out fatty cuts of meat for their superior sensory properties. Many consumers in East and Southeast Asia have traditionally valued more fatty meat cuts. As nutritional messages around dietary fat change, there is evidence that attitudes towards animal fat are changing and many consumers are rediscovering and embracing fattier cuts of meat, including marbled beef. The present work provides a short overview of the unique sensory characteristics of marbled beef and changing consumer preferences for fat in meat in general.

Characterization of the promoter region of the bovine long-chain acyl-CoA synthetase 1 gene: Roles of E2F1, Sp1, KLF15, and E2F4

The nutritional value and eating qualities of beef are enhanced when the unsaturated fatty acid content of fat is increased. Long-chain acyl-CoA synthetase 1 (ACSL1) plays key roles in fatty acid transport and degradation, as well as lipid synthesis. It has been identified as a plausible functional and positional candidate gene for manipulations of fatty acid composition in bovine skeletal muscle. In the present study, we determined that bovine ACSL1was highly expressed in subcutaneous adipose tissue and longissimus thoracis. To elucidate the molecular mechanisms involved in bovine ACSL1 regulation, we cloned and characterized the promoter region of ACSL1. Applying 5′-rapid amplification of cDNA end analysis (RACE), we identified multiple transcriptional start sites (TSSs) in its promoter region. Using a series of 5′ deletion promoter plasmids in luciferase reporter assays, we found that the proximal minimal promoter of ACSL1 was located within the region −325/−141 relative to the TSS and it was also located in the predicted CpG island. Mutational analysis and electrophoretic mobility shift assays demonstrated that E2F1, Sp1, KLF15 and E2F4 binding to the promoter region drives ACSL1 transcription. Together these interactions integrate and frame a key functional role for ACSL1 in mediating the lipid composition of beef.

Genome-wide association and prediction of direct genomic breeding values for composition of fatty acids in Angus beef cattle

BACKGROUND

As consumers continue to request food products that have health advantages, it will be important for the livestock industry to supply a product that meet these demands. One such nutrient is fatty acids, which have been implicated as playing a role in cardiovascular disease. Therefore, the objective of this study was to determine the extent to which molecular markers could account for variation in fatty acid composition of skeletal muscle and identify genomic regions that harbor genetic variation.

RESULTS

Subsets of markers on the Illumina 54K bovine SNPchip were able to account for up to 57% of the variance observed in fatty acid composition. In addition, these markers could be used to calculate a direct genomic breeding values (DGV) for a given fatty acids with an accuracy (measured as simple correlations between DGV and phenotype) ranging from -0.06 to 0.57. Furthermore, 57 1-Mb regions were identified that were associated with at least one fatty acid with a posterior probability of inclusion greater than 0.90. 1-Mb regions on BTA19, BTA26 and BTA29, which harbored fatty acid synthase, Sterol-CoA desaturase and thyroid hormone responsive candidate genes, respectively, explained a high percentage of genetic variance in more than one fatty acid. It was also observed that the correlation between DGV for different fatty acids at a given 1-Mb window ranged from almost 1 to -1.

CONCLUSIONS

Further investigations are needed to identify the causal variants harbored within the identified 1-Mb windows. For the first time, Angus breeders have a tool whereby they could select for altered fatty acid composition. Furthermore, these reported results could improve our understanding of the biology of fatty acid metabolism and deposition.

Expression of genes controlling fat deposition in two genetically diverse beef cattle breeds fed high or low silage diets

Background

Both genetic background and finishing system can alter fat deposition, thus indicating their influence on adipogenic and lipogenic factors. However, the molecular mechanisms underlying fat deposition and fatty acid composition in beef cattle are not fully understood. This study aimed to assess the effect of breed and dietary silage level on the expression patterns of key genes controlling lipid metabolism in subcutaneous adipose tissue (SAT) and longissimus lumborum (LL) muscle of cattle. To that purpose, forty bulls from two genetically diverse Portuguese bovine breeds with distinct maturity rates, Alentejana and Barrosã, were selected and fed either low (30% maize silage/70% concentrate) or high silage (70% maize silage/30% concentrate) diets.

Results

The results suggested that enhanced deposition of fatty acids in the SAT from Barrosã bulls, when compared to Alentejana, could be due to higher expression levels of lipogenesis (SCD and LPL) and β-oxidation (CRAT) related genes. Our results also indicated that SREBF1 expression in the SAT is increased by feeding the low silage diet. Together, these results point out to a higher lipid turnover in the SAT of Barrosã bulls when compared to Alentejana. In turn, lipid deposition in the LL muscle is related to the expression of adipogenic (PPARG and FABP4) and lipogenic (ACACA and SCD) genes. The positive correlation between ACACA expression levels and total lipids, as well trans fatty acids, points to ACACA as a major player in intramuscular deposition in ruminants. Moreover, results reinforce the role of FABP4 in intramuscular fat development and the SAT as the major site for lipid metabolism in ruminants.

Conclusions

Overall, the results showed that SAT and LL muscle fatty acid composition are mostly dependent on the genetic background. In addition, dietary silage level impacted on muscle lipid metabolism to a greater extent than on that of SAT, as evaluated by gene expression levels of adipogenic and lipogenic factors. Moreover, the response to diet composition evaluated through mRNA levels and fatty acid composition showed interesting differences between Alentejana and Barrosã bulls. These findings provide evidence that the genetic background should be taken into account while devising diet-based strategies to manipulate fatty acid composition of beef cattle tissues.