Intramuscular preadipocytes impede differentiation and promote lipid deposition of muscle satellite cells in chickens

Mature adipocytes inhibit differentiation of myogenic cells but stimulate proliferation of fibro-adipogenic precursors derived from trout muscle in vitro

Interactions between tissues and cell types, mediated by cytokines or direct cell-cell exchanges, regulate growth. To determine whether mature adipocytes influence the in vitro growth of trout mononucleated muscle cells, we developed an indirect coculture system, and showed that adipocytes (5 × 106 cells/well) derived from perivisceral adipose tissue increased the proliferation (BrdU-positive cells) of the mononucleated muscle cells (26% vs. 39%; p < 0.001) while inhibiting myogenic differentiation (myosin+) (25% vs. 15%; p < 0.001). Similar effects were obtained with subcutaneous adipose tissue-derived adipocytes, although requiring more adipocytes (3 × 107 cells/well vs. 5 × 106 cells/well). Conditioned media recapitulated these effects, stimulating proliferation (31% vs. 39%; p < 0.001) and inhibiting myogenic differentiation (32 vs. 23%; p < 0.001). Adipocytes began to reduce differentiation after 24 h, whereas proliferation stimulation was observed after 48 h. While adipocytes did not change pax7+ and myoD1/2+ percentages, they reduced myogenin+ cells showing inhibition from early differentiation stage. Finally, adipocytes increased BrdU+ cells in the Pdgfrα+ population but not in the myoD+ one. Collectively, our results demonstrate that trout adipocytes promote fibro-adipocyte precursor proliferation while inhibiting myogenic cells differentiation in vitro, suggesting the key role of adipose tissue in regulating fish muscle growth.

RNA sequencing identifies key genes involved in intramuscular fat deposition in chickens at different developmental stages

BACKGROUND

Intramuscular fat (IMF) is an important factor in meat quality, and triglyceride (TG) and Phospholipids (PLIP), as the main components of IMF, are of great significance to the improvement of meat quality.

RESULTS

In this study, we used 30 RNA sequences generated from the transcriptome of chicken breast muscle tissues at different developmental stages to construct a gene expression matrix to map RNA sequence reads to the chicken genome and identify the transcript of origin. We used weighted gene co-expression network analysis (WGCNA) and identified 27 co-expression modules, 10 of which were related to TG and PLIP. We identified 150 highly-connected hub genes related to TG and PLIP, respectively, which were found to be mainly enriched in the adipocytokine signaling pathway, MAPK signaling pathway, mTOR signaling pathway, FoxO signaling pathway, and TGF-beta signaling pathway. Additionally, using the BioMart database, we identified 134 and 145 candidate genes related to fat development in the TG-related module and PLIP-related module, respectively. Among them, RPS6KB1, BRCA1, CDK1, RPS3, PPARGC1A, ACSL1, NDUFAB1, NDUFA9, ATP5B and PRKAG2 were identified as candidate genes related to fat development and highly-connected hub genes in the module, suggesting that these ten genes may be important candidate genes affecting IMF deposition.

CONCLUSIONS

RPS6KB1, BRCA1, CDK1, RPS3, PPARGC1A, ACSL1, NDUFAB1, NDUFA9, ATP5B and PRKAG2 may be important candidate genes affecting IMF deposition. The purpose of this study was to identify the co-expressed gene modules related to chicken IMF deposition using WGCNA and determine key genes related to IMF deposition, so as to lay a foundation for further research on the molecular regulation mechanism underlying chicken fat deposition.

Genomic Insights into Molecular Regulation Mechanisms of Intramuscular Fat Deposition in Chicken

Intramuscular fat (IMF) plays an important role in the tenderness, water-holding capacity, and flavor of chicken meat, which directly affect meat quality. In recent years, regulatory mechanisms underlying IMF deposition and the development of effective molecular markers have been hot topics in poultry genetic breeding. Therefore, this review focuses on the current understanding of regulatory mechanisms underlying IMF deposition in chickens, which were identified by multiple genomic approaches, including genome-wide association studies, whole transcriptome sequencing, proteome sequencing, single-cell RNA sequencing (scRNA-seq), high-throughput chromosome conformation capture (HiC), DNA methylation sequencing, and m6A methylation sequencing. This review comprehensively and systematically describes genetic and epigenetic factors associated with IMF deposition, which provides a fundamental resource for biomarkers of IMF deposition and provides promising applications for genetic improvement of meat quality in chicken.

Possible Mechanisms Linking Obesity, Steroidogenesis, and Skeletal Muscle Dysfunction

Increasing evidence suggests that skeletal muscles may play a role in the pathogenesis of obesity and associated conditions due to their impact on insulin resistance and systemic inflammation. Skeletal muscles, as well as adipose tissue, are largely recognized as endocrine organs, producing biologically active substances, such as myokines and adipokines. They may have either beneficial or harmful effects on the organism and its functions, acting through the endocrine, paracrine, and autocrine pathways. Moreover, the collocation of adipose tissue and skeletal muscles, i.e., the amount of intramuscular, intermuscular, and visceral adipose depots, may be of major importance for metabolic health. Traditionally, the generalized and progressive loss of skeletal muscle mass and strength or physical function, named sarcopenia, has been thought to be associated with age. That is why most recently published papers are focused on the investigation of the effect of obesity on skeletal muscle function in older adults. However, accumulated data indicate that sarcopenia may arise in individuals with obesity at any age, so it seems important to clarify the possible mechanisms linking obesity and skeletal muscle dysfunction regardless of age. Since steroids, namely, glucocorticoids (GCs) and sex steroids, have a major impact on the amount and function of both adipose tissue and skeletal muscles, and are involved in the pathogenesis of obesity, in this review, we will also discuss the role of steroids in the interaction of these two metabolically active tissues in the course of obesity.

Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Hepatic Lipid Metabolism in Layer Hens with Fatty Liver Hemorrhagic Syndrome

The feeding of high-energy and low-protein diets often induces fatty liver hemorrhagic syndrome (FLHS) in laying hens. However, the mechanism of hepatic fat accumulation in hens with FLHS remains uncertain. In this research, a comprehensive hepatic proteome and acetyl-proteome analysis was performed in both normal and FLHS-affected hens. The results indicated that the upregulated proteins were primarily associated with fat digestion and absorption, the biosynthesis of unsaturated fatty acids, and glycerophospholipid metabolism, while the downregulated proteins were mainly related to bile secretion and amino acid metabolism. Furthermore, the significant acetylated proteins were largely involved in ribosome and fatty acid degradation, and the PPAR signaling pathway, while the significant deacetylated proteins were related to valine, leucine, and isoleucine degradation in laying hens with FLHS. Overall, these results demonstrate that acetylation inhibits hepatic fatty acid oxidation and transport in hens with FLHS, and mainly exerts its effects by affecting protein activity rather than expression. This study provides new nutritional regulation options to alleviate FLHS in laying hens.

Towards a More Realistic In Vitro Meat: The Cross Talk between Adipose and Muscle Cells

According to statistics and future predictions, meat consumption will increase in the coming years. Considering both the environmental impact of intensive livestock farming and the importance of protecting animal welfare, the necessity of finding alternative strategies to satisfy the growing meat demand is compelling. Biotechnologies are responding to this demand by developing new strategies for producing meat in vitro. The manufacturing of cultured meat has faced criticism concerning, above all, the practical issues of culturing together different cell types typical of meat that are partly responsible for meat’s organoleptic characteristics. Indeed, the existence of a cross talk between adipose and muscle cells has critical effects on the outcome of the co-culture, leading to a general inhibition of myogenesis in favor of adipogenic differentiation. This review aims to clarify the main mechanisms and the key molecules involved in this cross talk and provide an overview of the most recent and successful meat culture 3D strategies for overcoming this challenge, focusing on the approaches based on farm-animal-derived cells.

Recent advances in the crosstalk between adipose, muscle and bone tissues in fish

Control of tissue metabolism and growth involves interactions between organs, tissues, and cell types, mediated by cytokines or direct communication through cellular exchanges. Indeed, over the past decades, many peptides produced by adipose tissue, skeletal muscle and bone named adipokines, myokines and osteokines respectively, have been identified in mammals playing key roles in organ/tissue development and function. Some of them are released into the circulation acting as classical hormones, but they can also act locally showing autocrine/paracrine effects. In recent years, some of these cytokines have been identified in fish models of biomedical or agronomic interest. In this review, we will present their state of the art focusing on local actions and inter-tissue effects. Adipokines reported in fish adipocytes include adiponectin and leptin among others. We will focus on their structure characteristics, gene expression, receptors, and effects, in the adipose tissue itself, mainly regulating cell differentiation and metabolism, but in muscle and bone as target tissues too. Moreover, lipid metabolites, named lipokines, can also act as signaling molecules regulating metabolic homeostasis. Regarding myokines, the best documented in fish are myostatin and the insulin-like growth factors. This review summarizes their characteristics at a molecular level, and describes both, autocrine effects and interactions with adipose tissue and bone. Nonetheless, our understanding of the functions and mechanisms of action of many of these cytokines is still largely incomplete in fish, especially concerning osteokines (i.e., osteocalcin), whose potential cross talking roles remain to be elucidated. Furthermore, by using selective breeding or genetic tools, the formation of a specific tissue can be altered, highlighting the consequences on other tissues, and allowing the identification of communication signals. The specific effects of identified cytokines validated through in vitro models or in vivo trials will be described. Moreover, future scientific fronts (i.e., exosomes) and tools (i.e., co-cultures, organoids) for a better understanding of inter-organ crosstalk in fish will also be presented. As a final consideration, further identification of molecules involved in inter-tissue communication will open new avenues of knowledge in the control of fish homeostasis, as well as possible strategies to be applied in aquaculture or biomedicine.

Transcriptome analysis reveals the molecular regulatory network of muscle development and meat quality in Sunit lamb supplemented with dietary probiotic

Supplementing animal feed with probiotic additives can promote muscle production and improve meat quality. The study aimed to explore the effects of dietary probiotics supplementation on the performance, meat quality and muscle transcriptome profile in Sunit lamb. Overall, feeding probiotics significantly increased the body length, LT area, pH24h and intramuscular fat (IMF) content, but decreased cooking loss and meat shear force compared to the control group (P < .05). A total of 651 differentially expressed genes (DEGs) were found in probiotic supplemented lambs. Pathway analysis revealed that DEGs were involved in multiple pathways related to muscle development and fat deposition, such as the ECM-receptor interactions, the MAPK signaling pathway and the FoxO signaling pathway. Therefore, dietary probiotic supplementation can improve muscle development and final meat quality in Sunit lambs by altering gene expression profiles associated with key pathways, providing unique insights into the molecular mechanisms by which dietary probiotics regulate muscle development in the lamb industry.

Apolipoprotein H: a novel regulator of fat accumulation in duck myoblasts

Apolipoprotein H (APOH) primarily engages in fat metabolism and inflammatory disease response. This study aimed to investigate the effects of APOH on fat synthesis in duck myoblasts (CS2s) by APOH overexpression and knockdown. CS2s overexpressing APOH showed enhanced triglyceride (TG) and cholesterol (CHOL) contents and elevated the mRNA and protein expression of AKT serine/threonine kinase 1 (AKT1), ELOVL fatty acid elongase 6 (ELOVL6), and acetyl-CoA carboxylase 1 (ACC1) while reducing the expression of protein kinase AMP-activated catalytic subunit alpha 1 (AMPK), peroxisome proliferator activated receptor gamma (PPARG), acyl-CoA synthetase long chain family member 1 (ACSL1), and lipoprotein lipase (LPL). The results showed that knockdown of APOH in CS2s reduced the content of TG and CHOL, reduced the expression of ACC1, ELOVL6, and AKT1, and increased the gene and protein expression of PPARG, LPL, ACSL1, and AMPK. Our results showed that APOH affected lipid deposition in myoblasts by inhibiting fatty acid beta-oxidation and promoting fatty acid biosynthesis by regulating the expression of the AKT/AMPK pathway. This study provides the necessary basic information for the role of APOH in fat accumulation in duck myoblasts for the first time and enables researchers to study the genes related to fat deposition in meat ducks in a new direction.

Integrating genomics and transcriptomics to identify candidate genes for subcutaneous fat deposition in beef cattle

Fat deposition is a complex economic trait regulated by polygenic genetic basis and environmental factors. Therefore, integrating multi-omics data to uncover its internal regulatory mechanism has attracted extensive attention. Here, we performed genomics and transcriptomics analysis to detect candidates affecting subcutaneous fat (SCF) deposition in beef cattle. The association of 770K SNPs with the backfat thickness captured nine significant SNPs within or near 11 genes. Additionally, 13 overlapping genes regarding fat deposition were determined via the analysis of differentially expressed genes and weighted gene co-expression network analysis (WGCNA). We then calculated the correlations of these genes with BFT and constructed their interaction network. Finally, seven biomarkers including ACACA, SCD, FASN, ACOX1, ELOVL5, HACD2, and HSD17B12 were screened. Notably, ACACA, identified by the integration of genomics and transcriptomics, was more likely to exert profound effects on SCF deposition. These findings provided novel insights into the regulation mechanism underlying bovine fat accumulation.

Comprehensive Transcriptome Sequencing Analysis of Hirudinaria manillensis in Different Growth Periods

Medical leeches are widely been used in biochemical and clinical medical studies, helping to restore blood circulation to grafted or severely injured tissue. Mostly, adult leeches are being used in the traditional pharmacopeia, but the gene expression profiling of leeches in different growth periods is not well-reported. So, in this study, we used transcriptome analysis to analyze the comparative gene expression patterns of Hirudinaria manillensis (H. manillensis) in different growth periods, including larval, young, and adult stages. We constructed 24 cDNA libraries from H. manillensis larval, young, and adult stages, and about 54,639,118 sequences were generated, 18,106 mRNA transcripts of which 958 novel mRNAs and 491 lncRNAs were also assembled as well. Furthermore, the results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the differentially upregulated genes from the larval to adult stages were enriched in pathways such as cilium, myofibril, contractile fiber, cytoskeleton proteins, dilated cardiomyopathy, adrenergic signaling in cardiomyocytes, etc. Moreover, in the adult stages, a significant increase in the expression of the Hirudin-HM (HIRM2) genes was detected. In addition, our comparative transcriptome profiling data from different growth stages of H. manillensis also identified a large number of DEGs and DElncRNAs which were tentatively found to be associated with the growth of H. manillensis; as it grew, the muscle-related gene expression increased, while the lipid metabolism and need for stimulation and nutrition-related genes decreased. Similarly, the higher expression of HIRM2 might attribute to the high expression of protein disulfide isomerase gene family (PDI) family genes in adulthood, which provides an important clue that why adult leeches rather than young leeches are widely used in clinical therapeutics and traditional Chinese medicine.

A selected population study reveals the biochemical mechanism of intramuscular fat deposition in chicken meat

BACKGROUND

Increasing intramuscular fat (IMF) is an important strategy to improve meat quality, but the regulation mechanism of IMF deposition needs to be systematically clarified.

RESULTS

A total of 520 chickens from a selected line with improved IMF content and a control line were used to investigate the biochemical mechanism of IMF deposition in chickens. The results showed that the increased IMF would improve the flavor and tenderness quality of chicken meat. IMF content was mainly determined both by measuring triglyceride (TG) and phospholipid (PLIP) in muscle tissue, but only TG content was found to be decisive for IMF deposition. Furthermore, the increase in major fatty acid (FA) components in IMF is mainly derived from TGs (including C16:0, C16:1, C18:1n9c, and C18:2n6c, etc.), and the inhibition of certain very-long-chain FAs would help to IMF/TG deposition.

CONCLUSIONS

Our study elucidated the underlying biochemical mechanism of IMF deposition in chicken: Prevalent accumulation of long-chain FAs and inhibitions of medium-chain FAs and very long chain FA would jointly result in the increase of TGs with the FA biosynthesis and cellular uptake ways. Our findings will guide the production of high-quality chicken meat.

The effect of the PLIN1 gene on the metabolism and mitochondria of porcine skeletal muscle satellite cells

BACKGROUND

Perilipin 1 (PLIN1) is a lipid droplet scaffolding protein that plays a regulatory role in fat decomposition and mitochondrial function.

OBJECTIVE

In this study, the effects of PLIN1 gene knockout (PLIN1-KO) and PLIN1 gene overexpression (PLIN1-EX) on cell metabolism and mitochondrial function in porcine skeletal muscle satellite cells were assessed.

METHODS

Porcine skeletal muscle satellite cells were used as the control group (NC). The expression of mitochondrial function-related proteins was detected by western blot. Apoptosis, cell cycle, mitochondrial function-related indices, mitochondrial structure, and morphology were measured by flow cytometry.

RESULTS

Our results demonstrated that stable expression of the PLIN1 gene in skeletal muscle satellite cells is critical to maintaining cell metabolism and mitochondrial function. After knockout and overexpression of the PLIN1 gene, the anti-apoptotic ability of cells was enhanced, and the metabolic activity of the cells was accelerated, but at the cost of mitochondrial structural damage, reduction in the number of mitochondria, and decreased mitochondrial function.

CONCLUSION

This study explored the effect of the PLIN1 gene on the mitochondria and metabolism of porcine skeletal muscle satellite cells and provided a theoretical basis for the subsequent study of the effects of PLIN1 on muscle tissue development and meat quality.

Differentially Expressed lncRNAs Related to the Development of Abdominal Fat in Gushi Chickens and Their Interaction Regulatory Network

Chickens are one of the most important sources of meat worldwide, and the growth status of abdominal fat is closely related to production efficiency. Long noncoding RNAs (lncRNAs) play an important role in lipid metabolism and deposition regulation. However, research on the expression profile of lncRNAs related to the development of abdominal fat in chickens after hatching and their interaction regulatory networks is still lacking. To characterize the lncRNA expression profile during the development of chicken abdominal fat, abdominal adipose tissues from 6-, 14-, 22-, and 30-week-old Chinese Gushi chickens were herein used to construct 12 cDNA libraries, and a total of 3,827 new lncRNAs and 5,466 previously annotated lncRNAs were revealed. At the same time, based on the comparative analysis of five combinations, 276 differentially expressed lncRNAs (DE-lncRNAs) were screened. Functional enrichment analysis showed that the predicted target genes of these DE-lncRNAs were significantly enriched in pathways related to the posttranscriptional regulation of gene expression, negative regulation of cell proliferation, cell adhesion and other biological processes, glycosphingolipid biosynthesis, PPAR signaling, fatty acid degradation, fatty acid synthesis and others. In addition, association analysis of the lncRNA transcriptome profile was performed, and DE-lncRNA-related lncRNA-mRNA, lncRNA-miRNA and lncRNA-miRNA-mRNA interaction regulatory networks were constructed. The results showed that DE-lncRNA formed a complex network with PPAR pathway components, including PPARD, ACOX1, ADIPOQ, CPT1A, FABP5, ASBG2, LPL, PLIN2 and related miRNAs, including mir-200b-3p, mir-130b-3p, mir-215-5p, mir-122-5p, mir-223 and mir-125b-5p, and played an important regulatory role in biological processes such as lipid metabolism, adipocyte proliferation and differentiation. This study described the dynamic expression profile of lncRNAs in the abdominal fat of Gushi chickens for the first time and constructed the DE-lncRNA interaction regulatory network. The results expand the number of known lncRNAs in chicken abdominal fat and provide valuable resources for further elucidating the posttranscriptional regulatory mechanism of chicken abdominal fat development or deposition.

Single Nucleotide Polymorphisms of Porcine lncMGPF Regulate Meat Production Traits by Affecting RNA Stability

lncMGPF is a novel positive regulator of myogenic differentiation, muscle growth and regeneration in mouse, pig, and human. But whether natural mutations within lncMGPF gene regulate animal meat production traits is unclear. In this study, ten single nucleotide polymorphisms (SNPs) of pig lncMGPF (plncMGPF) gene were identified among commercial pig breeds and Chinese local pig breeds. These SNPs are highly linked and constructed into multiple haplotypes, and haplotype ATTCATGTTC (H1) mainly exists in commercial pig breeds while haplotype GCCTGCACCT (H3) is more frequent in Chinese local pig breeds. Association analysis indicated that all SNPs are significantly associated with the backfat thickness and loin muscle area (P < 0.05), respectively, and homologous H1 individuals have higher loin muscle area and lower backfat thickness than H3 pigs. Bioinformatics and functional analysis showed that haplotype H1 has a longer half-life and more stable RNA secondary structure than haplotype H3. plncMGPF haplotype H1 has stronger effects on pig primary myogenic progenitor cells differentiation and muscle growth than haplotype H3. Further experiments showed that two SNPs (rs81403974 and rs325492834) function together to confer plncMGPF stability and function. Our observation suggested that the SNPs in lncMGPF can change the RNA stabilities and lncMGPF function, thereby affecting the porcine meat production traits.

Transcriptional Insights into Key Genes and Pathways Underlying Muscovy Duck Subcutaneous Fat Deposition at Different Developmental Stages

Simple Summary

Subcutaneous fat is an important factor affecting the meat quality and feed conversion rate of waterfowl. The current study compared the transcriptome data of Muscovy duck subcutaneous fat among three developmental stages, aiming at exploring the key regulatory genes for subcutaneous fat deposition. The results generated abundant candidate genes and pathways involving in subcutaneous fat deposition in Muscovy duck. This study provides an important reference for revealing the developmental mechanisms of subcutaneous fat in duck.

Abstract

Subcutaneous fat is a crucial trait for waterfowl, largely associated with meat quality and feed conversion rate. In this study, RNA-seq was used to identify differentially expressed genes of subcutaneous adipose tissue among three developmental stages (12, 35, and 66 weeks) in Muscovy duck. A total of 138 and 129 differentially expressed genes (DEGs) were identified between 35 and 12 weeks (wk), and 66 and 35 wk, respectively. Compared with 12 wk, subcutaneous fat tissue at 35 wk upregulated several genes related to cholesterol biosynthesis and fatty acid biosynthesis, including HSD17B7 and MSMO1, while it downregulated fatty acid beta-oxidation related genes, including ACOX1 and ACSL1. Notably, most of the DEGs (92.2%) were downregulated in 66 wk compared with 35 wk, consistent with the slower metabolism of aging duck. Protein network interaction and function analyses revealed GC, AHSG, FGG, and FGA were the key genes for duck subcutaneous fat from adult to old age. Additionally, the PPAR signaling pathway, commonly enriched between the two comparisons, might be the key pathway contributing to subcutaneous fat metabolism among differential developmental stages in Muscovy duck. These results provide several candidate genes and pathways potentially involved in duck subcutaneous fat deposition, expanding our understanding of the molecular mechanisms underlying subcutaneous fat deposition during development.

MYOD1 inhibits avian adipocyte differentiation via miRNA-206/KLF4 axis

BACKGROUND

A considerable number of muscle development-related genes were differentially expressed in the early stage of avian adipocyte differentiation. However, the functions of them in adipocyte differentiation remain largely known. In this study, the myoblast determination protein 1 (MYOD1) was selected as a representative of muscle development. We investigated its expression, function, and regulation in avian adipocyte differentiation.

RESULTS

The expression of MYOD1 decreased significantly in the early stage of avian adipocyte differentiation. CRISPR/Cas9-mediated deletion of MYOD1 induced adipocyte differentiation, whereas over-expression of MYOD1 inhibited adipogenesis. The mRNA-seq data showed that MYOD1 could perturb the lipid biosynthetic process during differentiation. Our results showed that MYOD1 directly up-regulates the miR-206 expression by binding the upstream 1200 bp region of miR-206. Then, over-expression of miR-206 can inhibit the adipogenesis. Furthermore, MYOD1 affected the expression of endogenous miR-206 and its target gene Kruppel-like factor 4 (KLF4), which is an important activator of adipogenesis. Accordingly, the inhibition of miR-206 or over-expression of KLF4 could counteract the inhibitory effect of MYOD1 on adipocyte differentiation.

CONCLUSIONS

Our results establish that MYOD1 inhibits adipocyte differentiation by up-regulating miR-206 to suppress the KLF4 expression. These findings identify a novel function of MYOD1 in adipocyte differentiation, suggesting a potential role in body-fat distribution regulation.

Effects and Molecular Mechanism of Single-Nucleotide Polymorphisms of MEG3 on Porcine Skeletal Muscle Development

Maternally expressed gene 3 (MEG3) is a long non-coding RNA that is a crucial regulator of skeletal muscle development. Some single-nucleotide polymorphism (SNP) mutants in MEG3 had strong associations with meat quality traits. Nevertheless, the function and mechanism of MEG3 mutants on porcine skeletal muscle development have not yet been well-demonstrated. In this study, eight SNPs were identified in MEG3 of fat- and lean-type pig breeds. Four of these SNPs (g.3087C > T, g.3108C > T, g.3398C > T, and g.3971A > C) were significantly associated with meat quality and consisted of the CCCA haplotype for fat-type pigs and the TTCC haplotype for lean-type pigs. Quantitative real-time PCR results showed that the expression of MEG3-TTCC was higher than that of MEG3-CCCA in transcription level (P < 0.01). The stability assay showed that the lncRNA stability of MEG3-TTCC was lower than that of MEG3-CCCA (P < 0.05). Furthermore, the results of qRT-PCR, Western blot, and Cell Counting Kit-8 assays demonstrated that the overexpression of MEG3-TTCC more significantly inhibited the proliferation of porcine skeletal muscle satellite cells (SCs) than that of MEG3-CCCA (P < 0.05). Moreover, the overexpression of MEG3-TTCC more significantly promoted the differentiation of SCs than that of MEG3-CCCA (P < 0.05). The Western blot assay suggested that the overexpression of MEG3-TTCC and MEG3-CCCA inhibited the proliferation of SCs by inhibiting PI3K/AKT and MAPK/ERK1/2 signaling pathways. The overexpression of the two haplotypes also promoted the differentiation of SCs by activating the JAK2/STAT3 signaling pathway in different degrees. These data are valuable for further studies on understanding the crucial role of lncRNAs in skeletal muscle development.

Intermittent pressure imitating rolling manipulation ameliorates injury in skeletal muscle cells through oxidative stress and lipid metabolism signalling pathways

BACKGROUND

Traditional Chinese medicine manipulation (TCMM) is often used to treat human skeletal muscle injury, but its mechanism remains unclear due to difficulty standardizing and quantifying manipulation parameters.

METHODS

Here, dexamethasone sodium phosphate (DSP) was utilized to induce human skeletal muscle cell (HSkMC) impairments. Cells in a three-dimensional environment were divided into the control normal group (CNG), control injured group (CIG) and rolling manipulation group (RMG). The RMG was exposed to intermittent pressure imitating rolling manipulation (IPIRM) of TCMM via the FX‑5000™ compression system. Skeletal muscle damage was assessed via the cell proliferation rate, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and creatine kinase (CK) activity. Isobaric tagging for relative and absolute protein quantification (iTRAQ) and bioinformatic analysis were used to evaluate differentially expressed proteins (DEPs).

RESULTS

Higher-pressure IPIRM ameliorated the skeletal muscle cell injury induced by 1.2 mM DSP. Thirteen common DEPs after IPIRM were selected. Key biological processes, molecular functions, cellular components, and pathways were identified as mechanisms underlying the protective effect of TCMM against skeletal muscle damage. Some processes (response to oxidative stress, response to wounding, response to stress and lipid metabolism signalling pathways) were related to skeletal muscle cell injury. Western blotting for 4 DEPs confirmed the reliability of iTRAQ.

CONCLUSIONS

Higher-pressure IPIRM downregulated the CD36, Hsp27 and FABP4 proteins in oxidative stress and lipid metabolism pathways, alleviating excessive oxidative stress and lipid metabolism disorder in injured HSkMCs. The techniques used in this study might provide novel insights into the mechanism of TCMM.

Positive selection signatures in Anqing six-end-white pig population based on reduced-representation genome sequencing data

Anqing six-end-white (AQ) pig performs well on resistance to coarse fodder and disease, reproduction and meat quality, offering high potential for exploitation. Environmental conditions and strict selections from local farmers have cultivated the AQ pig to be an outstanding and unique local pig breed. Thus we aim to detect genetic positive selection signatures within the AQ pig population to explore underlying genetic mechanisms. A relative extended haplotype homozygosity (REHH) test was performed in the population of 79 AQ pigs to seek evidence demonstrating that selective actions have left an imprint on the whole genome. In total, 430 500 REHH tests were performed on 53 067 core regions with average REHH tests of 8.11, average lengths of 11.50 kb and an overall length of 610.38 Mb which accounted for 26.94% of the whole genome. Finally, a total of 1819 core haplotypes (P < 0.01) and 586 candidate genes were obtained. These genes were mainly related to meat quality (MYOG, SNX19), resistance to disease (CRISPLD2, CD14) and reproduction traits (ERBB2, NRP2). A panel of genes within the 30 top significant REHH tests was mainly categorized to traits of meat quality and disease resistance. Among 13 KEGG pathways, MAPK, GnRH and Oxytocin signaling pathways, associated with the biological processes of crucial economic traits, were noteworthy. The excellent characteristics of the AQ pig benefited from the combination of natural and human factors. We provide a sketch map that shows the distribution of selection footprints on the whole genome of AQ pig and found potential genes for future studies.

Effects of miR-125b-5p on Preadipocyte Proliferation and Differentiation in Chicken

Our previous studies have shown that miR-125b-5p was highly expressed and significantly upregulated during abdominal fat deposition in chickens. However, the role of miR-125b in the regulation of adipogenesis is not clear in chickens. Therefore, we evaluated the effects of miR-125b-5p on preadipocyte proliferation and differentiation and the interaction between miR-125b-5p and the acyl-CoA synthetase bubblegum family member 2 (ACSBG2) gene in adipogenesis in chicken abdominal adipose tissue. Here, transfection tests of miR-125b-5p mimic/inhibitor were performed in preadipocytes, and the effects of miR-125b-5p on preadipocytes proliferation and differentiation were analyzed. The target site of miR-125b-5p in the 3'UTR (untranslated region) of ACSBG2 were verified by a luciferase reporter assay. Our results showed that miR-125b-5p overexpression inhibited proliferation and reduced the number of cells in S phase and G2/M phase in preadipocytes; conversely, miR-125b-5p inhibition promoted the proliferation and increased the number of cells in S phase and G2/M phase. In adipocytes after induction, miR-125b-5p overexpression led to a notable increase in the accumulation of lipid droplets as well as in the concentration of triglycerides, while miR-125b-5p inhibition had the opposite effect. Furthermore, miR-125b-5p could directly bind to the 3'UTR of ACSBG2, and its overexpression could significantly repress the mRNA and protein expression of ACSBG2. These results indicate that miR-125b-5p can inhibit preadipocyte proliferation and can promote preadipocyte differentiation to affect adipogenesis in chicken abdominal adipose tissues, at least partially by downregulating ACSBG2.

Global DNA methylation pattern involved in the modulation of differentiation potential of adipogenic and myogenic precursors in skeletal muscle of pigs

Background

Skeletal muscle is a complex and heterogeneous tissue accounting for approximately 40% of body weight. Excessive ectopic lipid accumulation in the muscle fascicle would undermine the integrity of skeletal muscle in humans but endow muscle with marbling-related characteristics in farm animals. Therefore, the balance of myogenesis and adipogenesis is of great significance for skeletal muscle homeostasis. Significant DNA methylation occurs during myogenesis and adipogenesis; however, DNA methylation pattern of myogenic and adipogenic precursors derived from skeletal muscle remains unknown yet.

Methods

In this study, reduced representation bisulfite sequencing was performed to analyze genome-wide DNA methylation of adipogenic and myogenic precursors derived from the skeletal muscle of neonatal pigs. Integrated analysis of DNA methylation and transcription profiles was further conducted. Based on the results of pathway enrichment analysis, myogenic precursors were transfected with CACNA2D2-overexpression plasmids to explore the function of CACNA2D2 in myogenic differentiation.

Results

As a result, 11,361 differentially methylated regions mainly located in intergenic region and introns were identified. Furthermore, 153 genes with different DNA methylation and gene expression level between adipogenic and myogenic precursors were characterized. Subsequently, pathway enrichment analysis revealed that DNA methylation programing was involved in the regulation of adipogenic and myogenic differentiation potential through mediating the crosstalk among pathways including focal adhesion, regulation of actin cytoskeleton, MAPK signaling pathway, and calcium signaling pathway. In particular, we characterized a new role of CACNA2D2 in inhibiting myogenic differentiation by suppressing JNK/MAPK signaling pathway.

Conclusions

This study depicted a comprehensive landmark of DNA methylome of skeletal muscle-derived myogenic and adipogenic precursors, highlighted the critical role of CACNA2D2 in regulating myogenic differentiation, and illustrated the possible regulatory ways of DNA methylation on cell fate commitment and skeletal muscle homeostasis.

Supplementary information

The online version contains supplementary material available at 10.1186/s13287-020-02053-3.

RNA-Seq Analysis Reveals Hub Genes Involved in Chicken Intramuscular Fat and Abdominal Fat Deposition During Development

Fat traits are important in the chicken industry where there is a desire for high intramuscular fat (IMF) and low abdominal fat. However, there is limited knowledge on the relationship between the dynamic status of gene expression and the body fat deposition in chicken. Transcriptome data were obtained from breast muscle and abdominal fat of female chickens from nine developmental stages (from embryonic day 12 to hatched day 180). In total, 8,545 genes in breast muscle and 6,824 genes in abdominal fat were identified as developmentally dynamic genes. Weighted correlation network analysis was used to identify gene modules and the hub genes. Twenty-one hub genes were identified, e.g., ENSGALG00000041996, which represents a candidate for high IMF, and CREB3L1, which relates to low abdominal fat weight. The transcript factor L3MBTL1 and the transcript factor cofactors TNIP1, HAT1, and BEND6 related to both high breast muscle IMF and low abdominal fat weight. Our results provide a resource of developmental transcriptome profiles in chicken breast muscle and abdominal fat. The candidate genes can be used in the selection for increased IMF content and/or a decrease in abdominal fat weight which would contribute to the improvement of these traits.

Molecular signatures of muscle growth and composition deciphered by the meta-analysis of age-related public transcriptomics data

The lean-to-fat ratio is a major issue in the beef meat industry from both carcass and meat production perspectives. This industrial perspective has motivated meat physiologists to use transcriptomics technologies to decipher mechanisms behind fat deposition within muscle during the time course of muscle growth. However, synthetic biological information from this volume of data remains to be produced to identify mechanisms found in various breeds and rearing practices. We conducted a meta-analysis on 10 transcriptomic data sets stored in public databases, from the longissimus thoracis of five different bovine breeds divergent by age. We updated gene identifiers on the last version of the bovine genome (UCD1.2), and the 715 genes common to the 10 studies were subjected to the meta-analysis. Of the 238 genes differentially expressed (DEG), we identified a transcriptional signature of the dynamic regulation of glycolytic and oxidative metabolisms that agrees with a known shift between those two pathways from the animal puberty. We proposed some master genes of the myogenesis, namely MYOG and MAPK14, as probable regulators of the glycolytic and oxidative metabolisms. We also identified overexpressed genes related to lipid metabolism (APOE, LDLR, MXRA8, and HSP90AA1) that may contribute to the expected enhanced marbling as age increases. Lastly, we proposed a transcriptional signature related to the induction (YBX1) or repression (MAPK14, YWAH, ERBB2) of the commitment of myogenic progenitors into the adipogenic lineage. The relationships between the abundance of the identified mRNA and marbling values remain to be analyzed in a marbling biomarkers discovery perspectives.

Effects of atmospheric ammonia on the production performance, serum biochemical indices, and liver RNA-seq data of laying ducks

1. Ammonia is a toxic gas and an air pollutant of great concern. The effects of ammonia-induced damage in ducks are rarely reported. 2. A total of 176 laying ducks were randomly allocated to one of two groups with four replicates and were exposed to ammonia at 5 ± 5 ppm (low ammonia, LA) or 75 ± 5 ppm (high ammonia, HA), respectively, for 30 days. 3. The results showed that atmospheric ammonia exposure significantly decreased body weight and laying performance (P < 0.05). It significantly changed serum biochemical indices by increasing alanine aminotransferase and aspartate aminotransferase (P < 0.05), and decreasing superoxide dismutase activity (P < 0.05). Haematoxylin and eosin staining of hepatocytes revealed severe fatty degeneration. Results of RNA-seq analyses revealed that eight genes were significantly up-regulated in the HA group, which were involved in catalytic activity, single-organism metabolic processes, oxidation-reduction processes, and carbohydrate metabolic processes. 4. These results indicated that atmospheric ammonia exposure reduced production performance, affected serum biochemical indices, and led to severe fatty degeneration in the liver of laying ducks. Differentially expressed genes in liver indicated that there were effects of ammonia exposure on the metabolism and detoxification capabilities in ducks.

Transcriptome for the breast muscle of Jinghai yellow chicken at early growth stages

Background

The meat quality of yellow feathered broilers is better than the quality of its production. Growth traits are important in the broiler industry. The exploration of regulation mechanisms for the skeletal muscle would help to increase the growth performance of chickens. At present, some progress has been made by researchers, but the molecular mechanisms of the skeletal muscle still remain unclear and need to be improved.

Methods

In this study, the breast muscles of fast- and slow-growing female Jinghai yellow chickens (F4F, F8F, F4S, F8S) and slow-growing male Jinghai yellow chickens (M4S, M8S) aged four and eight weeks were selected for transcriptome sequencing (RNA-seq). All analyses of differentially expressed genes (DEGs) and functional enrichment were performed. Finally, we selected nine DEGs to verify the accuracy of the sequencing by qPCR.

Results

The differential gene expression analysis resulted in 364, 219 and 111 DEGs (adjusted P-value ≤ 0.05) for the three comparison groups, F8FvsF4F, F8SvsF4S, and M8SvsM4S, respectively. Three common DEGs (ADAMTS20, ARHGAP19, and Novel00254) were found, and they were all highly expressed at four weeks of age. In addition, some other genes related to growth and development, such as ANXA1, COL1A1, MYH15, TGFB3 and ACTC1, were obtained. The most common DEGs (n = 58) were found between the two comparison groups F8FvsF4F and F8SvsF4S, and they might play important roles in the growth of female chickens. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway also showed some significant enrichment pathways, for instance, extracellular matrix (ECM)-receptor interaction, focal adhesion, cell cycle, and DNA replication. The two pathways that were significantly enriched in the F8FvsF4F group were all contained in that of F8SvsF4S. The same two pathways were ECM–receptor interaction and focal adhesion, and they had great influence on the growth of chickens. However, many differences existed between male and female chickens in regards to common DEGs and KEGG pathways. The results would help to reveal the regulation mechanism of the growth and development of chickens and serve as a guideline to propose an experimental design on gene function with the DEGs and pathways.