Skeletal Muscle Growth Research Articles

352 Supplementing bovine satellite cells with anabolic hormones and/or zinc at differentiation impacts abundance of mRNA involved in growth, mineral transport, and oxidative stress

Abstract Zinc (Zn) is the most utilized metal in biological processes and supports growth through critical roles in protein turnover. The Zn requirements of skeletal muscle may be augmented when growth promoting technologies, such as anabolic hormones are being utilized. Both anabolic hormones and Zn affect protein synthesis and degradation in skeletal muscle. However, the molecular mechanisms through which Zn may interact with anabolic hormones to support skeletal muscle growth remains unknown. The objective of this study was to determine whether trenbolone acetate (TBA), estradiol (E2) and Zn interact to promote differentiation of bovine satellite cell (BSC) cultures by assessing abundance of mRNA involved in growth, mineral transport, differentiation, protein turnover and oxidative stress. To do this, primary BSC cultures were isolated from three different steers and grown to 80% confluency and induced to differentiate in 3% horse serum, at which time a factorial design was employed to assess the impact of Zn (0, 10, 20 or 40 μM) as ZnCl2 and/or the impact of hormone (10 nM TBA,10 nM E2, 10 nM TBA and 10 nM E2). Zinc concentrations represent physiologically relevant plasma Zn concentrations. Total mRNA was isolated from the treated cultures at 4 h, 12 h and 24 h post-treatment. Assays utilizing cultures from each steer were run in duplicate (n = 6). The mRNA abundance of 45 genes were examined and analyzed using the PROC MIXED procedure of SAS with time as a repeated measure to evaluate the fixed effects of hormone, mineral, time, and all interactions. No effects (P ≥ 0.19) of hormone x mineral x time, hormone x time, hormone x mineral or hormone were noted. A mineral x time effect (P ≤ 0.04) was noted for the igf1r, slc39a7, mapk1, mmp2, and G6pd. A mineral effect was found for hormone receptors (ir, ar, esr1, esr2, and gper; P ≤ 0.03), mRNA involved in mineral transport (slc30a10, slc30a7, sod1, sod2, slc2a4, and slc39a8; P ≤ 0.009), and genes related to skeletal muscle differentiation (pax7, myf5, myf6, spry1, myog, mef2a, and myod; P ≤ 0.02) and protein turnover (akt1, fox01, fox04, mstn,fbox32, fox03, mtor, trim63, and CKM; P ≤ 0.03). These differences are generally driven by abundance being increased (P ≤ 0.05) in cultures treated with 40 or 20 μM Zn compared with cultures receiving 0 or 10 μM Zn. These results indicate that while Zn and hormone do not appear to interact to influence gene expression of differentiating primary BSC cultures at the time points measured, increased concentrations of Zn appear to increase mRNA abundance of hormone receptors, mineral transporters, and genes involved in skeletal muscle differentiation and protein turnover.

Crosstalk among canonical Wnt and Hippo pathway members in skeletal muscle and at the neuromuscular junction.

Skeletal muscles are essential for locomotion, posture, and metabolic regulation. To understand physiological processes, exercise adaptation, and muscle-related disorders, it is critical to understand the molecular pathways that underlie skeletal muscle function. The process of muscle contraction, orchestrated by a complex interplay of molecular events, is at the core of skeletal muscle function. Muscle contraction is initiated by an action potential and neuromuscular transmission requiring a neuromuscular junction. Within muscle fibers, calcium ions play a critical role in mediating the interaction between actin and myosin filaments that generate force. Regulation of calcium release from the sarcoplasmic reticulum plays a key role in excitation-contraction coupling. The development and growth of skeletal muscle are regulated by a network of molecular pathways collectively known as myogenesis. Myogenic regulators coordinate the differentiation of myoblasts into mature muscle fibers. Signaling pathways regulate muscle protein synthesis and hypertrophy in response to mechanical stimuli and nutrient availability. Several muscle-related diseases, including congenital myasthenic disorders, sarcopenia, muscular dystrophies, and metabolic myopathies, are underpinned by dysregulated molecular pathways in skeletal muscle. Therapeutic interventions aimed at preserving muscle mass and function, enhancing regeneration, and improving metabolic health hold promise by targeting specific molecular pathways. Other molecular signaling pathways in skeletal muscle include the canonical Wnt signaling pathway, a critical regulator of myogenesis, muscle regeneration, and metabolic function, and the Hippo signaling pathway. In recent years, more details have been uncovered about the role of these two pathways during myogenesis and in developing and adult skeletal muscle fibers, and at the neuromuscular junction. In fact, research in the last few years now suggests that these two signaling pathways are interconnected and that they jointly control physiological and pathophysiological processes in muscle fibers. In this review, we will summarize and discuss the data on these two pathways, focusing on their concerted action next to their contribution to skeletal muscle biology. However, an in-depth discussion of the non-canonical Wnt pathway, the fibro/adipogenic precursors, or the mechanosensory aspects of these pathways is not the focus of this review.

Progression of total training volume in resistance training studies and its application to skeletal muscle growth.

Progressive overload describes the gradual increase of stress placed on the body during exercise training, and is often quantified (i.e. in resistance training studies) through increases in total training volume (i.e. sets × repetitions × load) from the first to final week of the exercise training intervention. Within the literature, it has become increasingly common for authors to discuss skeletal muscle growth adaptations in the context of increases in total training volume (i.e. the magnitude progression in total training volume). The present manuscript discusses a physiological rationale for progressive overload and then explains why, in our opinion, quantifying the progression of total training volume within research investigations tells very little about muscle growth adaptations to resistance training. Our opinion is based on the following research findings: (1) a noncausal connection between increases in total training volume (i.e. progressively overloading the resistance exercise stimulus) and increases in skeletal muscle size; (2) similar changes in total training volume may not always produce similar increases in muscle size; and (3) the ability to exercise more and consequently amass larger increases in total training volume may not inherently produce more skeletal muscle growth. The methodology of quantifying changes in total training volume may therefore provide a means through which researchers can mathematically determine the total amount of external 'work' performed within a resistance training study. It may not, however, always explain muscle growth adaptations.

Metabolic benefits afforded by estradiol and testosterone in both sexes: clinical considerations.

Testosterone (T) and 17β-estradiol (E2) are produced in male and female humans and are potent metabolic regulators in both sexes. When E2 and T production stops or decreases during aging, metabolic dysfunction develops and promotes degenerative metabolic and vascular disease. Here, we discuss the shared benefits afforded by E2 and T for metabolic function human females and males. In females, E2 is central to bone and vascular health, subcutaneous adipose tissue distribution, skeletal muscle insulin sensitivity, antiinflammatory immune function, and mitochondrial health. However, T also plays a role in female skeletal, vascular, and metabolic health. In males, T's conversion to E2 is fundamental to bone and vascular health, as well as prevention of excess visceral adiposity and the promotion of insulin sensitivity via activation of the estrogen receptors. However, T and its metabolite dihydrotestosterone also prevent excess visceral adiposity and promote skeletal muscle growth and insulin sensitivity via activation of the androgen receptor. In conclusion, T and E2 are produced in both sexes at sex-specific concentrations and provide similar and potent metabolic benefits. Optimizing levels of both hormones may be beneficial to protect patients from cardiometabolic disease and frailty during aging, which requires further study.

Functional study of the ST6GAL2 gene regulating skeletal muscle growth and development

ST6GAL2, a member of the sialoglycosyltransferase family, primarily localizes within the cellular Golgi apparatus. However, the role of the ST6GAL2 gene in skeletal muscle growth and development remains elusive. In this study, the impact of the ST6GAL2 gene on the proliferation, differentiation, and apoptosis of primary chicken myoblasts at the cellular level was investigated. Quantitative fluorescent PCR was used to measure the expression levels of genes. Subsequently, using gene knockout mice, we assessed its effects on skeletal muscle growth and development in vivo. Our findings reveal that the ST6GAL2 gene promotes the expression of cell cycle and proliferation-related genes, including CCNB2 and PCNA, and apoptosis-related genes, such as Fas and Caspase-9. At the individual level, double knockout of ST6GAL2 inhibited the formation of both fast and slow muscle fibers in the quadriceps, extensor digitorum longus, and tibial anterior muscle, while promoting their formation in the gastrocnemius and soleus. These results collectively demonstrate that the ST6GAL2 gene facilitates the proliferation, apoptosis, and fusion processes of primary chicken myoblasts. Additionally, it promotes the enlargement of cross-sectional muscle fiber areas and regulates the formation of fast and slow muscle fibers at the individual level, albeit inhibiting muscle fusion. This study provides valuable insights into the role of the ST6GAL2 gene in promoting proliferation of skeletal muscle.

Selenium promotes broiler myoblast proliferation through the ROS/PTEN/PI3K/AKT signaling axis

Selenium (Se), an indispensable trace element in broiler chickens, is closely associated with the growth and development of skeletal muscles. However, the role of Se in the proliferation of broiler myoblasts and its specific biological mechanisms have not been elucidated. In the present study, an in vitro growth model of broiler pectoral myoblasts cultured with Se (Na2SeO3) for 24 h was established. Using light microscopy, Cell Counting Kit-8 (CCK-8) assay, and flow cytometry, we found that compared to the control (Con) group, Se supplemental level obviously promoted myoblast proliferation and prevented cell cycle arrest from the G1 phase to the S + G2 phase. Through intracellular reactive oxygen species (ROS) generation detection, western blotting, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR), the study showed that the reduced ROS production caused by Se supplementation significantly decreased PTEN expression and activated the PI3K/AKT signaling pathway in myoblasts, thereby promoting the P53/P21/CyclinD1-regulated cell cycle progression, as well as the expression of proliferation-related myogenic regulatory factors (MRF). Our findings support the potential of Se to maintain the proliferative capacity of chicken myoblasts and emphasize the importance of Se intake in regulating skeletal muscle growth and development in poultry.

Anabolic deficits and divergent unfolded protein response underlie skeletal and cardiac muscle growth impairments in the Yoshida hepatoma tumor model of cancer cachexia.

Cancer cachexia manifests as whole body wasting, however, the precise mechanisms governing the alterations in skeletal muscle and cardiac anabolism have yet to be fully elucidated. In this study, we explored changes in anabolic processes in both skeletal and cardiac muscles in the Yoshida AH-130 ascites hepatoma model of cancer cachexia. AH-130 tumor-bearing rats experienced significant losses in body weight, skeletal muscle, and heart mass. Skeletal and cardiac muscle loss was associated with decreased ribosomal (r)RNA, and hypophosphorylation of the eukaryotic factor 4E binding protein 1. Endoplasmic reticulum stress was evident by higher activating transcription factor mRNA in skeletal muscle and growth arrest and DNA damage-inducible protein (GADD)34 mRNA in both skeletal and cardiac muscles. Tumors provoked an increase in tissue expression of interferon-γ in the heart, while an increase in interleukin-1β mRNA was apparent in both skeletal and cardiac muscles. We conclude that compromised skeletal muscle and heart mass in the Yoshida AH-130 ascites hepatoma model involves a marked reduction translational capacity and efficiency. Furthermore, our observations suggest that endoplasmic reticulum stress and tissue production of pro-inflammatory factors may play a role in the development of skeletal and cardiac muscle wasting.

Effect of breed and dietary composition on the miRNA profile of beef steers divergent for feed efficiency

Identifying and breeding cattle that are more feed efficient is of great benefit to beef production. Additionally, it is crucial that genes contributing to feed efficiency are robust across varying management settings including dietary source as well as being relevant across contrasting breeds of cattle. The aim of this study was to determine miRNAs that are contributing to the expression of residual feed intake (RFI) across two breeds and dietary sources. miRNA profiling was undertaken in Longissimus dorsi tissue of Charolais and Holstein–Friesian steers divergent for RFI phenotype following two contrasting consecutive diets (high-forage and high-concentrate). Ten miRNA were identified as differentially expressed (adj. P < 0.1) across the breed and diet contrasts examined. Of particular interest was the differential expression of miR-2419-5p and miR-2415-3p, both of which were up-regulated in the Low-RFI Charolais steers across each dietary phase. Pathway analysis of target mRNA genes of differentially expressed miRNA revealed enrichment (P < 0.05) for pathways including metabolic related pathways, insulin receptor signalling, adipogenesis as well as pathways related to skeletal muscle growth. These results provide insight into the skeletal muscle miRNAome of beef cattle and their potential molecular regulatory mechanisms relating to feed efficiency in beef cattle.

Muscle growth differences in Lijiang pigs revealed by ATAC-seq multi-omics.

As one of the largest tissues in the animal body, skeletal muscle plays a pivotal role in the production and quality of pork. Consequently, it is of paramount importance to investigate the growth and developmental processes of skeletal muscle. Lijiang pigs, which naturally have two subtypes, fast-growing and slow-growing, provide an ideal model for such studies by eliminating breed-related influences. In this study, we selected three fast-growing and three slow-growing 6-month-old Lijiang pigs as subjects. We utilized assay for transposase-accessible chromatin with sequencing (ATAC-seq) combined with genomics, RNA sequencing, and proteomics to screen for differentially expressed genes and transcription factors linked to increased longissimus dorsi muscle volume in Lijiang pigs. We identified 126 genes through ATAC-seq, including PPARA, TNRC6B, NEDD1, and FKBP5, that exhibited differential expression patterns during muscle growth. Additionally, we identified 59 transcription factors, including Foxh1, JunB, Mef2 family members (Mef2a/b/c/d), NeuroD1, and TEAD4. By examining open chromatin regions (OCRs) with significant genetic differentiation, genes such as SAV1, CACNA1H, PRKCG, and FGFR4 were found. Integrating ATAC-seq with transcriptomics and transcriptomics with proteomics, we identified differences in open chromatin regions, transcription, and protein levels of FKBP5 and SCARB2 genes in fast-growing and slow-growing Lijiang pigs. Utilizing multi-omics analysis with R packages, we jointed ATAC-seq, transcriptome, and proteome datasets, identifying enriched pathways related to glycogen metabolism and skeletal muscle cell differentiation. We pinpointed genes such as MYF6 and HABP2 that exhibit strong correlations across these diverse data types. This study provides a multi-faceted understanding of the molecular mechanisms that lead to differences in pig muscle fiber growth.

The Regulatory Role of Myomaker in the Muscle Growth of the Chinese Perch (Siniperca chuatsi).

The fusion of myoblasts is a crucial stage in the growth and development of skeletal muscle. Myomaker is an important myoblast fusion factor that plays a crucial role in regulating myoblast fusion. However, the function of Myomaker in economic fish during posthatching has been poorly studied. In this study, we found that the expression of Myomaker in the fast muscle of Chinese perch (Siniperca chuatsi) was higher than that in other tissues. To determine the function of Myomaker in fast muscle, Myomaker-siRNA was used to knockdown Myomaker in Chinese perch and the effect on muscle growth was determined. The results showed that the growth of Chinese perch was significantly decreased in the Myomaker-siRNA group. Furthermore, both the diameter of muscle fibers and the number of nuclei in single muscle fibers were significantly reduced in the Myomaker-siRNA group, whereas there was no significant difference in the number of BrdU-positive cells (proliferating cells) between the control and the Myomaker-siRNA groups. Together, these findings indicate that Myomaker may regulate growth of fast muscle in Chinese perch juveniles by promoting myoblast fusion rather than proliferation.

Both rapid hyperplasia and hypertrophy promoted skeletal muscle growth in mandarin fish Siniperca chuatsi, compared to big-eye mandarin fish Siniperca kneri

As important cultured fishes in China, mandarin fish, Siniperca chuatsi and big-eye mandarin fish, Siniperca kneri share similar external morphology and genomes, but have significant differences in growth rates. In this study, we used 6 mph (month post hatching) mandarin fish and big-eye mandarin fish to compare differences in skeletal muscle growth over a one-month period, and use transcriptomes to explore the reasons for the growth differences. The results showed that the different value in number of muscle fibers (2.72 times), density (2.56 times), area (1.95 times) and diameter (2.73 times) of mandarin fish are significantly higher than that of big-eye mandarin fish (P<0.05). Hypertrophy (Contribution rate: 97.9%) is the dominant factor in big-eye mandarin fish, and both hypertrophy and hyperplasia (Contribution rate: 2.1%) were significantly different from mandarin fish (P<0.05). Transcriptome results showed that differential genes were enriched in proliferation of satellite cells, protein synthesis and degradation. Further analysis of the transcriptome results showed that the number of Pax7-positive cells per unit area of mandarin fish was 2.3 fold higher that of big-eye mandarin fish (P<0.05). Myod, pax3, pax7, and myf5 mRNA expression of mandarin fish were significantly higher than those of big-eye mandarin fish(P<0.05). In muscle fiber fusion, mef2, myog, and myomaker mRNA expression of mandarin fish were significantly higher than that of big-eye mandarin fish (P < 0.05). In protein deposits, the results showed that the muscle fiber area of mandarin fish was 2.85 times larger than that of big-eye mandarin fish by comparing the muscle fiber area with the same number of nuclei. Polr2a, mtorc1, 4e-bp1, s6, e1, murf, foxo3, atg5, beclin, and atg14 mRNA expression of mandarin fish were significantly higher than that of big-eye mandarin fish (P < 0.05), while eef2, eif2α, gcn2, eif2b, capn and cast of mandarin fish was significantly lower than that of big-eye mandarin fish (P < 0.05). This work verified that the skeletal muscle growth rate of mandarin fish is faster than that of big-eye mandarin fish. The greater number and higher activity of satellite cells of mandarin fish increased hyperplasia efficiency, and the faster fusion rate and protein precipitation rate increased hypertrophy efficiency. Both hyperplasia and hypertrophy contribute to faster skeletal muscle growth of mandarin fish than that of big-eye mandarin fish.

Abstract Mo122: Investigating the Role of the Lysine Methyltransferase SMYD1 in Striated Muscle Motor Domain Folding

Properly coordinated folding and assembly of myosin into the sarcomere thick filament is critical for cardiac and skeletal muscle development, function, growth, and maintenance. The motor domain of myosin heavy chain (MHC) requires muscle-specific chaperones for proper folding, making it currently impossible to fold in non-muscle cells. Previous studies found that HSP90 and UNC45B are necessary, but not sufficient, for folding the motor domain, indicating other factors are involved. Defining the minimal set of factors for motor domain folding would allow for development of an improved expression system and accelerate the study of myosin mutations and myosin-targeted drug development. We hypothesize that the muscle-specific lysine methyltransferase SMYD1 contributes to MHC folding and stability. We found SMYD1 associates with UNC45B, HSP90, and MHC in the adult human heart. To study motor domain folding we generated a human MYH7 motor domain fused to GFP (MD::GFP). Transfection into COS-7 cells resulted in unfolded aggregates while adenoviral infection of C 2 C 12 myotubes leads to folded and functional MD::GFP. Interestingly, the folded MD::GFP contains lysine trimethylation, which may arise from the methyltransferase activity of SMYD1. When COS-7 cells were co-transfected with UNC45B and SMYD1, we observed increased total protein levels of non-functional MD::GFP without affecting RNA levels as assessed by RT-qPCR. This effect was not observed when MD::GFP was co-transfected with UNC45B or SMYD1 alone and is dependent on HSP90. We found that UNC45B and SMYD1 stabilized MD::GFP as determined by cycloheximide chase assays. We also found SMYD1 associates with MD::GFP, suggesting this stabilizing effect is due to a direct interaction. Interestingly, a catalytically inactive SMYD1 also increased MD::GFP protein levels in COS-7 cells, consistent with our observation that no significant changes in global protein methylation were observed in the presence of WT SMYD1. Our data suggests that SMYD1 stabilizes the motor domain of striated muscle myosin in conjunction with UNC45B and HSP90, in a manner that is independent of its methyltransferase activity. However, UNC45B and SMYD1 are insufficient for motor domain folding in a non-muscle cell line, suggesting that additional folding factors or proper stoichiometric ratios of chaperones/co-chaperones may be required.

Whole-transcriptome sequencing revealed the ceRNA regulatory network during the proliferation and differentiation of goose myoblast

The Shitou goose, the largest meat-type goose breed, is an ideal model for offering insights into enhancing meat production efficiency through understanding its genetic regulation of muscle development. Here, through whole-transcriptomic analysis of embryonic leg muscles, we identified 847 differentially expressed genes (DEG), 244 differentially expressed lncRNAs (DEL), 37 differentially expressed circRNAs (DEC), and 84 differentially expressed miRNAs (DEM). Gene ontology (GO) analysis highlighted the significant enrichment of differentially expressed RNAs in muscle structure development, actin filament-based processes, and the actin cytoskeleton pathway. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified pathways associated with the FoxO signaling pathway, AMPK signaling pathway, Wnt signaling pathway and calcium signaling pathway. Furthermore, we utilized Miranda, TargetScan, and miRDB to identify regulatory networks that involve interactions between lncRNA-mRNA, circRNA-mRNA, miRNA-mRNA, lncRNA-miRNA-mRNA, and circRNA-miRNA-mRNA, which regulated the growth and development of skeletal muscle. Notably, differentially expressed genes within the ceRNA network were most significantly enriched in the regulation of actin cytoskeletal organization. Additionally, a lncRNA/circRNA-miRNA-mRNA ceRNA network related to muscle growth and development was constructed based on protein-protein interaction (PPI) analysis and hub genes selection using Cytoscape. This further elucidated the regulatory roles of noncoding RNAs (ncRNA) in the formation of muscle fibers in Shitou goose. In summary, this study provides a valuable transcriptional regulatory network for goose muscle development laying the groundwork for further exploration of the molecular regulatory mechanisms underlying the excellent meat production performance of Shitou goose.

Activin Signaling Pathway Specialization During Embryonic and Skeletal Muscle Development in Rainbow Trout (Oncorhynchus mykiss).

Activin signaling is essential for proper embryonic, skeletal muscle, and reproductive development. Duplication of the pathway in teleost fish has enabled diversification of gene function across the pathway but how gene duplication influences the function of activin signaling in non-mammalian species is poorly understood. Full characterization of activin receptor signaling pathway expression was performed across embryonic development and during early skeletal muscle growth in rainbow trout (RBT, Oncorhynchus mykiss). Rainbow trout are a model salmonid species that have undergone two additional rounds of whole genome duplication. A small number of genes were expressed early in development and most genes increased expression throughout development. There was limited expression of activin Ab in RBT embryos despite these genes exhibiting significantly elevated expression in post-hatch skeletal muscle. CRISPR editing of the activin Aa1 ohnolog and subsequent production of meiotic gynogenetic offspring revealed that biallelic disruption of activin Aa1 did not result in developmental defects, as occurs with knockout of activin A in mammals. The majority of gynogenetic offspring exhibited homozygous activin Aa1 genotypes (wild type, in-frame, or frameshift) derived from the mosaic founder female. The research identifies mechanisms of specialization among the duplicated activin ohnologs across embryonic development and during periods of high muscle growth in larval and juvenile fish. The knowledge gained provides insights into potential viable gene-targeting approaches for engineering the activin receptor signaling pathway and establishes the feasibility of employing meiotic gynogenesis as a tool for producing homozygous F1 genome-edited fish for species with long-generation times, such as salmonids.

Myostatin's marvels: From muscle regulator to diverse implications in health and disease.

Myostatin, a member of the transforming growth factor-β superfamily, is a pivotal regulator of skeletal muscle growth in mammals. Its discovery has sparked significant interest due to its multifaceted roles in various physiological processes and its potential therapeutic implications. This review explores the diverse functions of myostatin in skeletal muscle development, maintenanceand pathology. We delve into its regulatory mechanisms, including its interaction with other signalling pathways and its modulation by various factors such as microRNAs and mechanical loading. Furthermore, we discuss the therapeutic strategies aimed at targeting myostatin for the treatment of muscle-related disorders, including cachexia, muscular dystrophyand heart failure. Additionally, we examine the impact of myostatin deficiency on craniofacial morphology and bone development, shedding light on its broader implications beyond muscle biology. Through a comprehensive analysis of the literature, this review underscores the importance of further research into myostatin's intricate roles and therapeutic potential in human health and disease.

Research Progress on the Regulating Factors of Muscle Fiber Heterogeneity in Livestock: A Review.

The type of muscle fiber plays a crucial role in the growth, development, and dynamic plasticity of animals' skeletal muscle. Additionally, it is a primary determinant of the quality of both fresh and processed meat. Therefore, understanding the regulatory factors that contribute to muscle fibers' heterogeneity is of paramount importance. Recent advances in sequencing and omics technologies have enabled comprehensive cross-verification of research on the factors affecting the types of muscle fiber across multiple levels, including the genome, transcriptome, proteome, and metabolome. These advancements have facilitated deeper exploration into the related biological questions. This review focused on the impact of individual characteristics, feeding patterns, and genetic regulation on the proportion and interconversion of different muscle fibers. The findings indicated that individual characteristics and feeding patterns significantly influence the type of muscle fiber, which can effectively enhance the type and distribution of muscle fibers in livestock. Furthermore, non-coding RNA, genes and signaling pathways between complicated regulatory mechanisms and interactions have a certain degree of impact on muscle fibers' heterogeneity. This, in turn, changes muscle fiber profile in living animals through genetic selection or environmental factors, and has the potential to modulate the quality of fresh meat. Collectively, we briefly reviewed the structure of skeletal muscle tissue and then attempted to review the inevitable connection between the quality of fresh meat and the type of muscle fiber, with particular attention to potential events involved in regulating muscle fibers' heterogeneity.

Ankrd1 inhibits the FAK/Rho-GTPase/F-actin pathway by downregulating ITGA6 transcriptional to regulate myoblast functions.

Skeletal muscle constitutes the largest percentage of tissue in the animal body and plays a pivotal role in the development of normal life activities in the organism. However, the regulation mechanism of skeletal muscle growth and development remains largely unclear. This study investigated the effects of Ankrd1 on the proliferation and differentiation of C2C12 myoblasts. Here, we identified Ankrd1 as a potential regulator of muscle cell development, and found that Ankrd1 knockdown resulted in the proliferation ability decrease but the differentiation level increase of C2C12 cells. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyzes as well as RNA-seq results showed that Ankrd1 knockdown activated focal adhesion kinase (FAK)/F-actin signal pathway with most genes significantly enriched in this pathway upregulated. The integrin subunit Itga6 promoter activity is increased when Ankrd1 knockdown, as demonstrated by a dual-luciferase reporter assay. This study revealed the molecular mechanism by which Ankrd1 knockdown enhanced FAK phosphorylation activity through the alteration of integrin subunit levels, thus activating FAK/Rho-GTPase/F-actin signal pathway, eventually promoting myoblast differentiation. Our data suggested that Ankrd1 might serve as a potential regulator of muscle cell development. Our findings provide new insights into skeletal muscle growth and development and valuable references for further study of human muscle-related diseases.

Insulin-like growth factor-1 infusion in preterm piglets does not affect growth parameters of skeletal muscle or tendon tissue.

Prematurity has physical consequences, such as lower birth weight, decreased muscle mass and increased risk of adult-onset metabolic disease. Insulin-like growth factor 1 (IGF-1) has therapeutic potential to improve the growth and quality of muscle and tendon in premature births, and thus attenuate some of these sequalae. We investigated the effect of IGF-1 on extensor carpi radialis muscle and biceps brachii tendon of preterm piglets. The preterm group consisted of 19-day-old preterm (10 days early) piglets, treated with either IGF-1 or vehicle. Term controls consisted of groups of 9-day-old piglets (D9) and 19-day-old piglets (D19). Muscle samples were analysed by immunofluorescence to determine the cross-sectional area (CSA) of muscle fibres, fibre type composition, satellite cell content and central nuclei-containing fibres in the muscle. Tendon samples were analysed for CSA, collagen content and maturation, and vascularization. Gene expression of the tendon was measured by RT-qPCR. Across all endpoints, we found no significant effect of IGF-1 treatment on preterm piglets. Preterm piglets had smaller muscle fibre CSA compared to D9 and D19 control group. Satellite cell content was similar across all groups. For tendon, we found an effect of age on tendon CSA, and mRNA levels of COL1A1, tenomodulin and scleraxis. Immunoreactivity for elastin and CD31, and several markers of tendon maturation, were increased in D9 compared to the preterm piglets. Collagen content was similar across groups. IGF-1 treatment of preterm-born piglets does not influence the growth and maturation of skeletal muscle and tendon.

Expression and secretion of SPARC, FGF-21 and DCN in bovine muscle cells: Effects of age and differentiation.

Skeletal muscle growth is an economically important trait in the cattle industry. Secreted muscle-derived proteins, referred to as myokines, have important roles in regulating the growth, metabolism, and health of skeletal muscle in human and biomedical research models. Accumulating evidence supports the importance of myokines in skeletal muscle and whole-body health, though little is known about the potential presence and functional significance of these proteins in cattle. This study evaluates and confirms that secreted proteins acidic and rich in cysteine (SPARC), fibroblast growth factor 21 (FGF-21), myostatin (MSTN), and decorin (DCN) are expressed and SPARC, FGF-21, and DCN are secreted by primary bovine satellite cells from 3- (BSC3; n = 3) and 11- (BSC11; n = 3) month -old commercial angus steers. Cells were cultured and collected at zero, 12, 24, and 48 hours to characterize temporal expression and secretion from undifferentiated and differentiated cells. The expression of SPARC was higher in the undifferentiated (p = 0.04) and differentiated (p = 0.07) BSC11 than BSC3. The same was observed with protein secretion from undifferentiated (p <0.0001) BSC11 compared to BSC3. Protein secretion of FGF-21 was higher in undifferentiated BSC11 (p < 0.0001) vs. BSC3. DCN expression was higher in differentiated BSC11 (p = 0.006) vs. BSC3. Comparing undifferentiated vs. differentiated BSC, MSTN expression was higher in differentiated BSC3 (p ≤ 0.001) for 0, 12, and 24 hours and in BSC11 (p ≤ 0.03) for 0, 12, 24, and 48 hours. There is also a change over time for SPARC expression (p ≤ 0.03) in undifferentiated and differentiated BSC and protein secretion (p < 0.0001) in undifferentiated BSC, as well as FGF-21 expression (p = 0.007) in differentiated BSC. This study confirms SPARC, FGF-21, and DCN are secreted, and SPARC, FGF-21, MSTN, and DCN are expressed in primary bovine muscle cells with age and temporal differences.

Skeletal muscle feature of different populations in large yellow croaker (Larimichthys crocea): from an epigenetic point of view.

Fish skeletal muscle is composed of well-defined fiber types. In order to identify potential candidate genes affecting muscle growth and development under epigenetic regulation. Bisulfite sequencing was utilized to analyze and compare the muscle DNA methylation profiles of Larimichthys crocea inhabiting different environments. The results revealed that DNA methylation in L. crocea was predominantly CG methylation, with 2,396 differentially methylated regions (DMRs) identified through comparisons among different populations. The largest difference in methylation was observed between the ZhouShan and JinMen wild populations, suggesting that L. crocea may have undergone selection and domestication. Additionally, GO and KEGG enrichment analysis of differentially methylated genes (DMGs) revealed 626 enriched GO functional categories, including various muscle-related genes such as myh10, myf5, myf6, ndufv1, klhl31, map3k4, syn2b, sostdc1a, bag4, and hsp90ab. However, significant enrichment in KEGG pathways was observed only in the JinMen and XiangShan populations of L. crocea. Therefore, this study provides a theoretical foundation for a better understanding of the epigenetic regulation of skeletal muscle growth and development in L. crocea under different environmental conditions.