miR-34a-5p Increases Hepatic Triglycerides and Total Cholesterol Levels by Regulating ACSL1 Protein Expression in Laying Hens

Transcriptomic Analysis Reveals the Effects of miR-122 Overexpression in the Liver of Qingyuan Partridge Chickens

The liver of chickens is essential for maintaining physiological activities and homeostasis. This study aims to investigate the specific function and molecular regulatory mechanism of microRNA-122 (miR-122), which is highly expressed in chicken liver. A lentivirus-mediated overexpression vector of miR-122 was constructed and used to infect 12-day-old female Qingyuan Partridge chickens. Transcriptome sequencing analysis was performed to identify differentially expressed genes in the liver. Overexpression of miR-122 resulted in 776 differentially expressed genes (DEGs). Enrichment analyses, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) revealed associations with lipid metabolism, cellular senescence, cell adhesion molecules, and the MAPK signaling pathway. Eight potential target genes of miR-122 (ARHGAP32, CTSD, LBH, PLEKHB2, SEC14L1, SLC2A1, SLC6A14, and SP8) were identified through miRNA target prediction platforms and literature integration. This study provides novel insights into the molecular regulatory mechanisms of miR-122 in chicken liver, highlighting its role in key biological processes and signaling pathways. These discoveries enhance our understanding of miR-122's impact on chicken liver function and offer valuable information for improving chicken production performance and health.

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.

LncRNA lncMGR regulates skeletal muscle development and regeneration by recruiting CDK9 and sponging miRNAs

Long non-coding RNAs (lncRNAs) play an essential role in vertebrate myogenesis and muscle diseases. However, the dynamic expression patterns, biological functions, and mechanisms of lncRNAs in skeletal muscle development and regeneration remain largely unknown. In this study, a novel lncRNA (named lncMGR) was differentially expressed during breast muscle development in fast- and slow-growing chickens. Functionally, lncMGR promoted myoblast differentiation, inhibited myoblast proliferation in vitro, and promoted myofiber hypertrophy and injury repair in vivo. Mechanistically, lncMGR increased the mRNA and protein expression of skeletal muscle myosin heavy chain 1 A (MYH1A) via both transcriptional and post-transcriptional regulation. Nuclear lncMGR recruited cyclin-dependent kinase 9 (CDK9) to the core transcriptional activation region of the MYH1A gene to activate MYH1A transcription. Cytoplasmic lncMGR served as a competitive endogenous RNA (ceRNA) to competitively absorb miR-2131-5p away from MYH1A and subsequently protected the MYH1A from miR-2131-5p-mediated degradation. Besides miR-2131-5p, cytoplasmic lncMGR could also sponge miR-143-3p to reconcile the antagonist between the miR-2131-5p/MYH1A-mediated inhibition effects and miR-143-3p-mediated promotion effects on myoblast proliferation, thereby inhibiting myoblast proliferation. Collectively, lncMGR could recruit CDK9 and sponge multiple miRNAs to regulate skeletal muscle development and regeneration, and could be a therapeutic target for muscle diseases.

LncHLEF promotes hepatic lipid synthesis through miR-2188-3p/GATA6 axis and encoding peptides and enhances intramuscular fat deposition via exosome

Long noncoding RNAs (lncRNAs) have emergingly been implicated in mammalian lipid metabolism. However, their biological functions and regulatory mechanisms underlying adipogenesis remain largely elusive in chicken. Here, we systematically characterized the genome-wide full-length lncRNAs in the livers of pre- and peak-laying hens, and identified a novel intergenic lncRNA, lncHLEF, an RNA macromolecule with a calculated molecular weight of 433 kDa. lncHLEF was primarily distributed in cytoplasm of chicken hepatocyte and significantly up-regulated in livers of peak-laying hens. Functionally, lncHLEF could promote hepatocyte lipid droplet formation, triglycerides and total cholesterol contents. Mechanistically, lncHLEF could not only serve as a competitive endogenous RNA to modulate miR-2188-3p/GATA6 axis, but also encode three small functional polypeptides that directly interact with ACLY protein to enable its stabilization. Importantly, adeno-associated virus-mediated liver-specific lncHLEF overexpression resulted in increased hepatic lipid synthesis and intramuscular fat (IMF) deposition, but did not alter abdominal fat (AbF) deposition. Furthermore, hepatocyte lncHLEF could be delivered into intramuscular and abdominal preadipocytes via hepatocyte-secreted exosome to enhance intramuscular preadipocytes differentiation without altering abdominal preadipocytes differentiation. In conclusion, this study revealed that the lncHLEF could promote hepatic lipid synthesis through two independent regulatory mechanisms, and could enhance IMF deposition via hepatocyte-adipocyte communications mediated by exosome.

Weighted gene co-expression network analysis identified hub genes critical to fatty acid composition in Gushi chicken breast muscle

BACKGROUND

The composition and content of fatty acids in the breast muscle are important factors influencing meat quality. In this study, we investigated the fatty acid composition and content in the breast muscle of Gushi chickens at different developmental stages (14 weeks, 22 weeks, and 30 weeks). Additionally, we utilized transcriptomic data from the same tissue and employed WGCNA and module identification methods to identify key genes associated with the fatty acid composition in Gushi chicken breast muscle and elucidate their regulatory networks.

RESULTS

Among them, six modules (blue, brown, green, light yellow, purple, and red modules) showed significant correlations with fatty acid content and metabolic characteristics. Enrichment analysis revealed that these modules were involved in multiple signaling pathways related to fatty acid metabolism, including fatty acid metabolism, PPAR signaling pathway, and fatty acid biosynthesis. Through analysis of key genes, we identified 136 genes significantly associated with fatty acid phenotypic traits. Protein-protein interaction network analysis revealed that nine of these genes were closely related to fatty acid metabolism. Additionally, through correlation analysis of transcriptome data, we identified 51 key ceRNA regulatory networks, including six central genes, 7 miRNAs, and 28 lncRNAs.

CONCLUSION

This study successfully identified key genes closely associated with the fatty acid composition in Gushi chicken breast muscle, as well as their post-transcriptional regulatory networks. These findings provide new insights into the molecular regulatory mechanisms underlying the flavor characteristics of chicken meat and the composition of fatty acids in the breast 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.

The miR-216/miR-217 Cluster Regulates Lipid Metabolism in Laying Hens With Fatty Liver Syndrome via PPAR/SREBP Signaling Pathway

Fatty liver syndrome (FLS), a common metabolic disease in laying hens, caused by excessive hepatic fat deposition is a bottleneck in the poultry industry. However, no specific therapeutic methods have been developed. Evidence suggests that microRNAs (miRNAs) are essential for liver lipid metabolism and homeostasis, providing strong evidence for targeting miRNAs as a potential treatment option for liver diseases. However, the roles of miRNAs in the pathogenesis of FLS remain unclear. In present study, RNA-sequencing was performed to discern the expression patterns of miRNAs in normal and fatty livers of laying hens. In total, 12 dysregulated miRNAs (2 down-regulated and 10 up-regulated) were detected between the normal and fatty livers. Functional enrichment analysis showed the potential impacts of the dysregulated miRNAs on lipid metabolism. Notably, miR-216a/b and miR-217-5p, which belong to the miR-216/miR-217 cluster, were up-regulated in the sera and livers of FLS chickens, as well as free fatty acid (FFA)-induced LMH cells. Oil-red O staining revealed that up-regulation of the miR-216/miR-217 cluster induced lipid accumulation in FFA-induced LMH cells. Furthermore, the dual luciferase gene reporter assay and RT-qPCR analysis demonstrated that 3-hydroxyacyl-CoA dehydratase 2, F-box protein 8, and transmembrane 9 superfamily member 3 (TM9SF3) were directly targeted by miR-216a/b and miR-217-5p, respectively, and suppressed in the fatty livers of laying hens. Moreover, overexpression of the miR-216/miR-217 cluster or reduction in TM9SF3 levels led to activation of the proliferator-activated receptor/sterol regulatory-element binding protein (PPAR/SREBP) pathway. Overall, these results demonstrate that the miR-216/miR-217 cluster regulates lipid metabolism in laying hens with FLS, which should prove helpful in the development of new interventional strategies.

Associations of the T329S Polymorphism in Flavin-Containing Monooxygenase 3 With Atherosclerosis and Fatty Liver Syndrome in 90-Week-Old Hens

This study aimed to evaluate the effects of the spontaneous genetic mutation T329S in flavin-containing monooxygenase 3 (FMO3) on atherosclerosis (AS), fatty liver syndrome (FLS), and adiposity in 90-week-old layers. At 90 weeks of age, 27 FMO3 genotyped Rhode Island White chickens (consisting of nine AA hens, nine AT hens, and nine TT hens) with normal laying performance were selected. The AS lesions, incidence of FLS, fat deposition, metabolic characteristics, and production performance of these egg-layers with different FMO3 genotypes were assessed. The T329S mutation in TT hens reduced the AS lesions (P < 0.01) and altered the plasma metabolic indices more than it did in the AA and AT hens. Furthermore, it reduced the incidence of FLS, hepatic triglyceride deposition (P < 0.05), liver indices (P < 0.05), and fat deposition (P < 0.05) in the subcutis and abdomen of TT hens compared to those of AA and AT hens. Moreover, as an effect of T329S, TT hens laid a higher than average number of eggs and maintained a higher egg-laying rate from 68 to 90 weeks than AA and AT hens. Our study confirmed that the T329S mutation in FMO3 could reduce the development of AS lesions, the incidence of FLS, and fat deposition, which are associated with changes in plasma and hepatic metabolic indices and improvements in the laying performance of older layers. Our results may provide a new strategy for using the T329S mutation to improve the health status and production performance of layers during the late laying period.

Expression of Oocyte Vitellogenesis Receptor Was Regulated by C/EBPα in Developing Follicle of Wanxi White Goose

Yolk precursor was synthesized under regulation of hormone secretion, while the mechanism of its incorporation into follicle is still unknown. The reproductive hormones, oocyte vitellogenesis receptor (OVR) expression at pre-, early-, peak- and ceased-laying period, and localization of Wanxi White goose were determined in this study. The results showed that the concentration of LH was lowest in serum at peak laying period compared to the other periods (p < 0.01). Moreover, the concentration of E2 was highest (p < 0.01) in serum at early laying period than that of other periods. Moreover, the gene expression level of OVR was highest at ceased laying period compared to other periods (p = 0.014) and was higher in developing follicles than other follicles (p < 0.01). The OVR was distributed in the granular cell layer and decreased with the maturation of follicles. Five transcription factors were predicted in the promoter of OVR, then were screened and verified by overexpression in granulosa cells. C/EBPα and MF3 significantly stimulated the expression of OVR. The combined overexpression of C/EBPα and OVR significantly stimulated the transportation of lipid from culture medium to cytoplasm. In conclusion, C/EBPα is the key transcription factor promoting OVR expression in goose follicle granulosa cells.

Emerging Roles of Non-Coding RNAs in the Feed Efficiency of Livestock Species

A global population of already more than seven billion people has led to an increased demand for food and water, and especially the demand for meat. Moreover, the cost of feed used in animal production has also increased dramatically, which requires animal breeders to find alternatives to reduce feed consumption. Understanding the biology underlying feed efficiency (FE) allows for a better selection of feed-efficient animals. Non-coding RNAs (ncRNAs), especially micro RNAs (miRNAs) and long non-coding RNAs (lncRNAs), play important roles in the regulation of bio-logical processes and disease development. The functions of ncRNAs in the biology of FE have emerged as they participate in the regulation of many genes and pathways related to the major FE indicators, such as residual feed intake and feed conversion ratio. This review provides the state of the art studies related to the ncRNAs associated with FE in livestock species. The contribution of ncRNAs to FE in the liver, muscle, and adipose tissues were summarized. The research gap of the function of ncRNAs in key processes for improved FE, such as the nutrition, heat stress, and gut–brain axis, was examined. Finally, the potential uses of ncRNAs for the improvement of FE were discussed.

MiR-218-5p Affects Subcutaneous Adipogenesis by Targeting ACSL1, A Novel Candidate for Pig Fat Deposition

As a centre enzyme in fatty acid activation, acyl-CoA synthetase long-chain family member 1 (ACSL1) plays an important role in body lipid homeostasis. However, the functions of ACSL1 in the subcutaneous adipogenesis of pigs are largely unknown. In the present study, we found that the expression of ACSL1 significantly increased during the process of porcine preadipocyte differentiation. Moreover, silencing of ACSL1 in preadipocytes decreased levels of triglyceride and adipogenic-related markers, including FABP4, APOE, and FASN (p < 0.01), and simultaneously increased levels of lipolytic-related markers, such as ATGL and HSL (p < 0.05). Conversely, overexpression of ACSL1 in preadipocytes increased levels of triglyceride and FABP4, APOE, and FASN (p < 0.01), and reduced levels of ATGL and HSL (p < 0.05). Luciferase reporter assays revealed that ACSL1 is a target of miR-218-5p, which can reduce the mRNA and protein levels of ACSL1 by directly binding the 3′ untranslated region of ACSL1. Furthermore, miR-218-5p has an inhibition role in porcine preadipocyte differentiation by suppressing ACSL1 expression. Taken together, these data provide insights into the mechanism of the miR-218-5p/ACSL1 axis in regulating subcutaneous fat deposition of pigs.

A Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Molecular Mechanisms Adapting to the Physiological Changes From Pre-laying to Peak-Laying Stage in Liver of Hens (Gallus gallus)

Along with sexual maturity, the liver undergoes numerous metabolic processes to adapt the physiological changes associated with egg-laying in hens. However, mechanisms regulating the processes were unclear. In this study, comparative hepatic proteome and acetyl-proteome between pre- and peak-laying hens were performed. The results showed that the upregulated proteins were mainly related to lipid and protein biosynthesis, while the downregulated proteins were mainly involved in pyruvate metabolism and were capable of inhibiting gluconeogenesis and lactate synthesis in peak-laying hens compared with that in pre-laying hens. With unchanged expression level, the significant acetylated proteins were largely functioned on activation of polyunsaturated fatty acid oxidation in peroxisome, while the significant deacetylated proteins were principally used to elevate medium and short fatty acid oxidation in mitochondria and oxidative phosphorylation. Most of the proteins which involved in gluconeogenesis, lipid transport, and detoxification were influenced by both protein expression and acetylation. Taken overall, a novel mechanism wherein an alternate source of acetyl coenzyme A was produced by activation of FA oxidation and pyruvate metabolism to meet the increased energy demand and lipid synthesis in liver of laying hens was uncovered. This study provides new insights into molecular mechanism of adaptation to physiological changes in liver of laying hens.

MicroRNA-mRNA Regulatory Networking Fine-Tunes Polyunsaturated Fatty Acid Synthesis and Metabolism in the Inner Mongolia Cashmere Goat

Fatty acid composition is an important aspect of meat quality in ruminants. Improving the beneficial fatty acid level in cashmere goat meat is important to its economic value. To investigate microRNAs (miRNAs) and mRNAs that regulate or coregulate polyunsaturated fatty acid (PUFA) synthesis and metabolism in the Inner Mongolia cashmere goat, we used longissimus dorsi muscle (WLM) and biceps femoris muscle (WBM) for transcript-level sequencing. RT-qPCR was used to evaluate the expression of mRNAs and miRNAs associated with PUFA synthesis and metabolism. The total PUFA content in the WBM was significantly higher than that in the WLM (P < 0.05). Our study is the first to systematically report miRNAs in cashmere goat meat. At the mRNA level, 20,375 genes were identified. ACSL1, CD36 and TECRL were at the center of a gene regulatory network and contributed significantly to the accumulation and metabolic regulation of fatty acids. At the miRNA level, 426 known miRNAs and 30 novel miRNAs were identified. KEGG analysis revealed that the miRNA target genes were involved mainly in the PPAR signaling pathway. The mRNA-miRNA coregulation analysis showed that ACSL1 was negatively targeted by nine miRNAs: chi-miR-10a-5p, chi-miR-10b-5p, chi-miR-130b-5p, chi-miR-15a-5p_R-1, chi-miR-15b-5p, chi-miR-16a-5p, chi-miR-16b-5p, chi-miR-181c-5p_R+1, and chi-miR-26b-5p. Finally, we speculated that the simultaneous silencing of ACSL1 by one or more of these nine miRNAs through PPAR signaling led to low ACSL1 expression in the WLM and, ultimately to high PUFA content in the WBM. Our study helps elucidate the metabolic regulation of fatty acids in Inner Mongolia cashmere goats.

Molecular Regulation of Lipogenesis, Adipogenesis and Fat Deposition in Chicken

In the poultry industry, excessive fat deposition is considered an undesirable factor, affecting feed efficiency, meat production cost, meat quality, and consumer’s health. Efforts to reduce fat deposition in economically important animals, such as chicken, can be made through different strategies; including genetic selection, feeding strategies, housing, and environmental strategies, as well as hormone supplementation. Recent investigations at the molecular level have revealed the significant role of the transcriptional and post-transcriptional regulatory networks and their interaction on modulating fat metabolism in chickens. At the transcriptional level, different transcription factors are known to regulate the expression of lipogenic and adipogenic genes through various signaling pathways, affecting chicken fat metabolism. Alternatively, at the post-transcriptional level, the regulatory mechanism of microRNAs (miRNAs) on lipid metabolism and deposition has added a promising dimension to understand the structural and functional regulatory mechanism of lipid metabolism in chicken. Therefore, this review focuses on the progress made in unraveling the molecular function of genes, transcription factors, and more notably significant miRNAs responsible for regulating adipogenesis, lipogenesis, and fat deposition in chicken. Moreover, a better understanding of the molecular regulation of lipid metabolism will give researchers novel insights to use functional molecular markers, such as miRNAs, for selection against excessive fat deposition to improve chicken production efficiency and meat quality.

Centennial Review: Metabolic microRNA - shifting gears in the regulation of metabolic pathways in poultry

Over 20 yr ago, a small noncoding class of RNA termed microRNA (miRNA) that was able to recognize sequences in mRNAs and inhibit their translation was discovered in Caenorhabditis elegans. In the intervening years, miRNA have been discovered in most eukaryotes and are now known to regulate the majority of protein-coding genes. It has been discovered that disruption of miRNA function often leads to the development of pathological conditions. One physiological system under extensive miRNA-mediated regulation is metabolism. Metabolism is one of the most dynamic of biological networks within multiple organs, including the liver, muscle, and adipose tissue, working in concert to respond to ever-changing nutritional cues and energy demands. Therefore, it is not surprising that miRNA regulate virtually all aspects of eukaryotic metabolism and have been linked to metabolic disorders, such as obesity, fatty liver diseases, and diabetes, just to name a few. Chickens, and birds in general, face their own unique metabolic challenges, particularly after hatching, when their metabolism must completely transform from using lipid-rich yolk to carbohydrate-rich feed as fuel in a very short period of time. Furthermore, commercial poultry breeds have undergone extensive selection over the last century for more desirable production traits, which has resulted in numerous metabolic consequences. Here, we review the current knowledge of miRNA-mediated regulation of metabolic development and function in chickens.

Evolution, Expression Profile, Regulatory Mechanism, and Functional Verification of EBP-Like Gene in Cholesterol Biosynthetic Process in Chickens (Gallus Gallus)

The emopamil binding protein (EBP) is an important enzyme participating in the final steps of cholesterol biosynthesis in mammals. A predictive gene EBP-like, which encodes the protein with a high identity to human EBP, was found in chicken genome. No regulatory mechanisms and biological functions of EBP-like have been characterized in chickens. In the present study, the coding sequence of EBP-like was cloned, the phylogenetic trees of EBP/EBP-like were constructed and the genomic synteny of EBP-like was analyzed. The regulatory mechanism of EBP-like were explored with in vivo and in vitro experiments. The biological functions of EBP-like in liver cholesterol biosynthetic were examined by using gain- or loss-of-function strategies. The results showed that chicken EBP-like gene was originated from a common ancestral with Japanese quail EBP gene, and was relatively conservative with EBP gene among different species. The EBP-like gene was highly expressed in liver, its expression level was significantly increased in peak-laying stage, and was upregulated by estrogen. Inhibition of the EBP-like mRNA expression could restrain the expressions of EBP-like downstream genes (SC5D, DHCR24, and DHCR7) in the cholesterol synthetic pathway, therefore downregulate the liver intracellular T-CHO level. In conclusion, as substitute of EBP gene in chickens, EBP-like plays a vital role in the process of chicken liver cholesterol synthesis. This research provides a basis for revealing the molecular regulatory mechanism of cholesterol synthesis in birds, contributes insights into the improvement of the growth and development, laying performance and egg quality in poultry.

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.

Estrogen Abolishes the Repression Role of gga-miR-221-5p Targeting ELOVL6 and SQLE to Promote Lipid Synthesis in Chicken Liver

Few studies have been conducted regarding the biological function and regulation role of gga-miR-221-5p in the liver. We compared the conservation of miR-221-5p among species and investigated the expression pattern of gga-miR-221-5p, validating the direct target genes of gga-miR-221-5p by dual luciferase reporter assay, the biological function of gga-miR-221-5p in the liver was studied by gga-miR-221-5p overexpression and inhibition. Furthermore, we explored the regulation of gga-miR-221-5p and its target genes by treatment with estrogen and estrogen antagonists in vivo and in vitro. The results showed that miR-221-5p was highly conserved among species, expressed in all tested tissues and significantly downregulated in peak-laying hen liver compared to pre-laying hen liver. Gga-miR-221-5p could directly target the expression of elongase of very long chain fatty acids 6 (ELOVL6) and squalene epoxidase (SQLE) genes to affect triglyceride and total cholesterol content in the liver. 17β-estradiol could significantly inhibit the expression of gga-miR-221-5p but promote the expression of ELOVL6 and SQLE genes. In conclusion, the highly conservative gga-miR-221-5p could directly target ELOVL6 and SQLE mRNAs to affect the level of intracellular triglyceride and total cholesterol. Meanwhile, 17β-estradiol could repress the expression of gga-miR-221-5p but increase the expression of ELOVL6 and SQLE, therefore promoting the synthesis of intracellular triglyceride and cholesterol levels in the liver of egg-laying chicken.