Muscle Growth Research Articles

Unveils key proteins in Xinjiang goat muscle linked to post-mortem meat quality: A TMT-based proteomic analysis

An extensive proteomic analysis utilizing the tandem mass tag (TMT) method was conducted to investigate the changes in protein expression in the longissimus dorsi muscle of Xinjiang goats over various post-mortem intervals: immediately after death within 0 h, 12 h, 24 h and 48 h. The investigation carefully identified around 108 proteins that showed significant changes in expression during these intervals. Among these proteins, six were highlighted for their crucial roles in muscle growth and differentiation of muscle fibers post-mortem. These proteins, namely COL12A1, MRPL46, CTNNB1, MYH1, CAPZA1, and MYL9, have a direct effect on the meat's quality attributes, such as tenderness and color. Further discuss observed a progressive increase in the expression of proteins linked with oxidative metabolism (MSRB2, ENOX1, LOC102170282, GSTM1, and AOC3) as the post-mortem aging period extended, particularly between 24 h to 48 h. These proteins are instrumental in defining the color and flavor profiles of goat meat, underscoring the importance of precise processing and storage conditions to preserve meat quality during the critical aging phase. This enhanced understanding of protein expression dynamics offers significant implications for optimizing meat quality and provides a scientific basis for post-mortem handling practices in the goat meat industry.

Effects of thyroid hormones in skeletal muscle protein turnover.

Thyroid hormones (THs) are critical regulators of muscle metabolism in both healthy and unhealthy conditions. Acting concurrently as powerful anabolic and catabolic factors, THs are endowed with a vital role in muscle mass maintenance. As a result, thyroid dysfunctions are the leading cause of a wide range of muscle pathologies, globally identified as myopathies. Whether muscle wasting is a common feature in patients with hyperthyroidism and is mainly caused by THs-dependent stimulation of muscle proteolysis, also muscle growth is often associated with hyperthyroid conditions, linked to THs-dependent stimulation of muscle protein synthesis. Noteworthy, also hypothyroid status negatively impacts on muscle physiology, causing muscle weakness and fatigue. Most of these symptoms are due to altered balance between muscle protein synthesis andbreakdown. Thus, a comprehensive understanding of THs-dependent skeletal muscle protein turnover might facilitate the management of physical discomfort or weakness in conditions of thyroid disease. Herein, we describe the molecular mechanisms underlying the THs-dependent alteration of skeletal muscle structure and function associated with muscle atrophy and hypertrophy, thus providing new insights for targeted modulation of skeletal muscle dynamics.

Pleiotropic Gene HMGA2 Regulates Myoblast Proliferation and Affects Body Size of Sheep.

Uncovering genes associated with muscle growth and body size will benefit the molecular breeding of meat Hu sheep. HMGA2 has proven to be an important gene in mouse muscle growth and is associated with the body size of various species. However, its roles in sheep are still limited. Using sheep myoblast as a cell model, the overexpression of HMGA2 significantly promoted sheep myoblast proliferation, while interference with HMGA2 expression inhibited proliferation, indicated by qPCR, EdU, and CCK-8 assays. Furthermore, the dual-luciferase reporter system indicated that the region NC_056056.1: 154134300-154134882 (-618 to -1200 bp upstream of the HMGA2 transcription start site) was one of the habitats of the HMGA2 core promoter, given the observation that this fragment led to a ~3-fold increase in luciferase activity. Interestingly, SNP rs428001129 (NC_056056.1:g.154134315 C>A) was detected in this fragment by Sanger sequencing of the PCR product of pooled DNA from 458 crossbred sheep. This SNP was found to affect the promoter activity and was significantly associated with chest width at birth and two months old, as well as chest depth at two and six months old. The data obtained in this study demonstrated the phenotypic regulatory role of the HMGA2 gene in sheep production traits and the potential of rs428001129 in marker-assisted selection for sheep breeding in terms of chest width and chest depth.

The Dark Side of Alcohol: Implications for Muscle Growth, mTOR Pathway, and Athletic Recovery

Introduction and Objective: Alcohol is a prevalent substance in many cultures, often associated with socializing, relaxation, and even post-exercise rituals. Despite its widespread use, the effects of alcohol on muscle recovery and hypertrophy are not well understood by the general public. Emerging research suggests that alcohol may have negative health effects on these factors. Understanding the interaction between alcohol consumption and resistance training is crucial for athletes and individuals aiming to optimize their fitness outcomes. The main aim of this article is to show clinicians, patients and, above all, athletes, the negative effects of alcohol on training and leading a healthy lifestyle. Review and Methods: Review and summary of studies and meta-analysis of studies available in open-source format on Google Scholar, Web of Science and PubMed. Abbreviated Description of the State of Knowledge: Resistance training is a proven method for increasing muscle mass and strength through the process of hypertrophy, where muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB). The mechanistic/mammalian target of rapamycin (mTOR) signaling pathway plays a key role in regulating MPS and hypertrophy. Summary: Alcohol has been shown to impair muscle protein synthesis, primarily through its negative effects on the mTOR signaling pathway, which is crucial for muscle growth. Additionally, alcohol disrupts sleep quality, further hindering recovery and performance.

The physical demands and physiological responses to CrossFit®: a scoping review with evidence gap map and meta-correlation

BackgroundCrossFit® combines different types of activities (weightlifting, gymnastics, and cardiovascular training) that challenge aerobic and anaerobic pathways. Over the last few years, the scientific interest in CrossFit® has increased considerably. However, there have been no published reviews characterizing the physical demands and physiological responses to CrossFit®. The present study synthesizes current evidence on the physical demands and physiological responses to CrossFit®.MethodsThe search was performed in three electronic databases (PubMed, Scopus, and Web of Science). Manuscripts related to the physical and physiological performance of adult CrossFit® participants written in English, Portuguese, and Spanish were retrieved for the analysis.ResultsIn addition, a meta-correlation was conducted to examine the predictors of CrossFit® performance. A total of 68 papers were included in the review. Physical and physiological markers differed between the different workouts analyzed. In addition, 48 to 72 h are needed to recover from a CrossFit® challenge. Specific tests that involve CrossFit® movements were more related to CrossFit® performance than non-specific.ConclusionAlthough the characterization of CrossFit® is dependent on the workout examined, the benefits of muscle hypertrophy are aligned with the recent findings of concurrent training. The characterization of CrossFit® entire sessions and appropriate recovery strategies should be considered in future studies to help coaches manipulate and adjust the training load.

Engineered myovascular tissues for studies of endothelial/satellite cell interactions

In native skeletal muscle, capillaries reside in close proximity to muscle stem cells (satellite cells, SCs) and regulate SC numbers and quiescence through partially understood mechanisms that are difficult to study in vivo. This challenge could be addressed by the development of a 3-dimensional (3D) in vitro model of vascularized skeletal muscle harboring both a pool of quiescent SCs and a robust network of capillaries. Still, studying interactions between SCs and endothelial cells (ECs) within a tissue-engineered muscle environment has been hampered by the incompatibility of commercially available EC media with skeletal muscle differentiation. In this study, we first optimized co-culture media and cellular ratios to generate highly functional vascularized human skeletal muscle tissues (“myovascular bundles”) with contractile properties (∼10 mN/mm2) equaling those of avascular, muscle-only tissues (“myobundles”). Within one week of muscle differentiation, ECs in these tissues formed a dense network of capillaries that co-aligned with muscle fibers and underwent initial lumenization. Incorporating vasculature within myobundles increased the total SC number by 82%, with SC density and quiescent signature being increased proximal (≤20μm) to EC networks. In vivo, at two weeks post-implantation into dorsal window chambers in nude mice, vascularized myobundles exhibited improved calcium handling compared to avascular implants. In summary, we engineered highly functional myovascular tissues that enable studies of the roles of EC-SC crosstalk in human muscle development, physiology, and disease. Statement of significanceIn native skeletal muscle, intricate relationships between vascular cells and muscle stem cells (“satellite cells”) play critical roles in muscle growth and regeneration. Current methods for in vitro engineering of contractile skeletal muscle do not recreate capillary networks present in vivo. Our study for the first time generates in vitro robustly vascularized, highly functional engineered human skeletal muscle tissues. Within these tissues, satellite cells are more abundant and, similar to in vivo, they are more dense and less proliferative proximal to endothelial cells. Upon implantation in mice, vascularized engineered muscles show improved calcium handling compared to muscle-only implants. We expect that this versatile in vitro system will enable studies of muscle-vasculature crosstalk in human development and disease.

Sulforaphane Promotes Proliferation of Porcine Granulosa Cells via the H3K27ac-Mediated GDF8-ALK5-ERK Pathway.

Follicle development, a crucial process in reproductive biology, hinges upon the dynamic proliferation of granulosa cells (GCs). Growth differentiation factor-8 (GDF8) is well-known as myostatin for inhibiting skeletal muscle growth, and it also exists in ovarian GCs and follicle fluid. However, the relationship between GCs proliferation and GDF8 remains elusive. Sulforaphane (SFN) is a potent bioactive compound, which in our study has been demonstrated to induce the expression of GDF8 in GCs. Meanwhile, we discover a novel role of SFN in promoting the proliferation of porcine GCs. Specifically, SFN enhances GCs proliferation by accelerating the progression of the cell cycle through the G1 phase to the S phase. By performing gene expression profiling, we showed that the promoting proliferative effects of SFN are highly correlated with the TGF-β signaling pathways and cell cycle. Among the ligand factors of TGF-β signaling, we identify GDF8 as a critical downstream effector of SFN, which acts through ALK5 to mediate SFN-induced proliferation and G1/S transition. In addition, we identify a noncanonical downstream pathway by which GDF8 induces the activation of MAPK/ERK to facilitate the cell cycle progression in GCs. Moreover, we reveal that the expression of GDF8 is regulated by SFN through epigenetic modifications of H3K27 acetylation. These findings not only provide mechanistic insights into the regulation of GCs proliferation but also establish a previously unrecognized role of GDF8 in follicle development, which have significant implications for developing strategies to improve female fertility.

Unravelling the impact of epigenetic mechanisms on offspring growth, production, reproduction and disease susceptibility.

Epigenetic mechanisms, such as DNA methylation, histone modifications and non-coding RNA molecules, play a critical role in gene expression and regulation in livestock species, influencing development, reproduction and disease resistance. DNA methylation patterns silence gene expression by blocking transcription factor binding, while histone modifications alter chromatin structure and affect DNA accessibility. Livestock-specific histone modifications contribute to gene expression and genome stability. Non-coding RNAs, including miRNAs, piRNAs, siRNAs, snoRNAs, lncRNAs and circRNAs, regulate gene expression post-transcriptionally. Transgenerational epigenetic inheritance occurs in livestock, with environmental factors impacting epigenetic modifications and phenotypic traits across generations. Epigenetic regulation revealed significant effect on gene expression profiling that can be exploited for various targeted traits like muscle hypertrophy, puberty onset, growth, metabolism, disease resistance and milk production in livestock and poultry breeds. Epigenetic regulation of imprinted genes affects cattle growth and metabolism while epigenetic modifications play a role in disease resistance and mastitis in dairy cattle, as well as milk protein gene regulation during lactation. Nutri-epigenomics research also reveals the influence of maternal nutrition on offspring's epigenetic regulation of metabolic homeostasis in cattle, sheep, goat and poultry. Integrating cyto-genomics approaches enhances understanding of epigenetic mechanisms in livestock breeding, providing insights into chromosomal structure, rearrangements and their impact on gene regulation and phenotypic traits. This review presents potential research areas to enhance production potential and deepen our understanding of epigenetic changes in livestock, offering opportunities for genetic improvement, reproductive management, disease control and milk production in diverse livestock species.

Circular RNA expression in turkey skeletal muscle satellite cells is significantly altered by thermal challenge.

Understanding the genetic mechanisms behind muscle growth and development is crucial for improving the efficiency of animal protein production. Recent poultry studies have identified genes related to muscle development and explored how environmental stressors, such as temperature extremes, affect protein production and meat quality. Non-coding RNAs, including circular RNAs (circRNAs), play crucial roles in modulating gene expression and regulating the translation of mRNAs into proteins. This study examined circRNA expression in turkey skeletal muscle stem cells under thermal stress. The objectives were to identify and quantify circRNAs, assess circRNA abundance following RNAse R depletion, identify differentially expressed circRNAs (DECs), and predict potential microRNA (miRNA) targets for DECs and their associated genes. Cultured cells from two genetic lines (Nicholas commercial turkey and The Ohio State Random Bred Control 2) under three thermal treatments: cold (33°C), control (38°C), and hot (43°C) were compared at both the proliferation and differentiation stages. CircRNA prediction and differential expression and splicing analyses were conducted using the CIRIquant pipeline for both the untreated and RNase R depletion treated libraries. Predicted interactions between DECs and miRNAs, as well as the potential impact of circRNA secondary structure on these interactions, were investigated. A total of 11,125 circRNAs were predicted within the treatment groups, between both untreated and RNase R treated libraries. Differential expression analyses indicated that circRNA expression was significantly altered by thermal treatments and the genetic background of the stem cells. A total of 140 DECs were identified across the treatment comparisons. In general, more DECs within temperature treatment comparisons were identified in the proliferation stage and more DECs within genetic line comparisons were identified in the differentiation stage. This study highlights the significant impact of environmental stressors on non-coding RNAs and their role in gene regulation. Elucidating the role of non-coding RNAs in gene regulation can help further our understanding of muscle development and poultry production, underscoring the broader implications of this research for enhancing animal protein production efficiency.

Neuromuscular impairments of cerebral palsy: contributions to gait abnormalities and implications for treatment.

Identification of neuromuscular impairments in cerebral palsy (CP) is essential to providing effective treatment. However, clinical recognition of neuromuscular impairments in CP and their contribution to gait abnormalities is limited, resulting in suboptimal treatment outcomes. While CP is the most common childhood movement disorder, clinical evaluations often do not accurately identify and delineate the primary neuromuscular and secondary musculoskeletal impairments or their specific impact on mobility. Here we discuss the primary neuromuscular impairments of CP that arise from early brain injury and the progressive secondary musculoskeletal impairments, with a focus on spastic CP, the most common form of CP. Spastic CP is characterized by four primary interrelated neuromuscular impairments: 1. muscle weakness, 2. short muscle-tendon units due to slow muscle growth relative to skeletal growth, 3. muscle spasticity characterized by increased sensitivity to stretch, and 4. impaired selective motor control including flexor and extensor muscle synergies. Specific gait events are affected by the four primary neuromuscular impairments of spastic CP and their delineation can improve evaluation to guide targeted treatment, prevent deformities and improve mobility. Emerging information on neural correlates of neuromuscular impairments in CP provides the clinician with a more complete context with which to evaluate and develop effective treatment plans. Specifically, addressing the primary neuromuscular impairments and reducing secondary musculoskeletal impairments are important treatment goals. This perspective on neuromuscular mechanisms underlying gait abnormalities in spastic CP aims to inform clinical evaluation of CP, focus treatment more strategically, and guide research priorities to provide targeted treatments for CP.

Regional morphological adaptations of vastus lateralis muscle in response to different progressive resistance training programs: A randomised controlled trial.

Resistance training often increases muscle size, a phenomenon known as muscle hypertrophy. These morphological adaptations were typically documented to occur in a non-uniform pattern. Investigating the specific morphological adaptations to different training programs was of interest. This study aimed to investigate two resistance training programs, a high-intensity program (HI) and a combined high-intensity with low-intensity blood flow restriction program (MIX), on morphological adaptations of vastus lateralis muscle in healthy young men. Eighteen active participants were recruited and randomly assigned to the HI (n = 10) or MIX (n = 8) groups, undergoing different 6-week resistance training programs. The training volume set was equated and progressively increased from three sets in weeks 1 and 2 to six sets, and eight sets in weeks 3-4 and 5-6, respectively. Three specific regions of vastus lateralis were assessed by magnetic resonance imaging (MRI) and ultrasound imaging (US) during pre-and post-intervention. Statistical analysis revealed statistically significant increases in muscle area at the proximal (HI: Δ12%, MIX: Δ9.2%), middle (HI: Δ8.7%, MIX: Δ9.0%), and distal (HI: Δ14%, MIX: Δ13%) regions. Additionally, both HI and MIX groups showed statistically significant increases in the sum of muscle thickness post-intervention (HI: Δ12%, MIX: Δ19%) and in the sum of fascia thickness post-intervention (HI: Δ27%, MIX: Δ54%). Despite the MIX group training with higher volume load, no statistical differences were observed between groups for any week. These findings suggested that both HI and MIX programs effectively induced increases in muscle area and sums of muscle and fascia thickness in healthy young men, allowing practitioners to choose either program based on individual preferences and constraints.

Analysis of potential TAK1/Map3k7 phosphorylation targets in hypertrophy and cachexia models of skeletal muscle.

TGFβ-activated kinase-1 (TAK1) is phosphorylated during both muscle growth and muscle wasting. To understand how this can lead to such opposite effects, we first performed multiplex kinase array of mouse embryonic stem cells with and without stimulation of TAK1 to determine its potential downstream targets. The phosphorylation of these targets was then compared in three different models: hypertrophic longissimus muscle of Texel sheep, tibialis anterior muscle of mice with cancer-induced cachexia and C2C12-derived myofibers, with and without blockade of TAK1 phosphorylation. In both Texel sheep and in cancer-induced cachexia, phosphorylation of both TAK1 and p38 was increased. Whereas p90RSK was increased in Texel sheep but not cachexia and the phosphorylation of HSP27 and total Jnk were increased in cachexia but not Texel. To understand this further, we examined the expression of these proteins in C2C12 cells as they differentiated into myotubes, with and without blockade of TAK1 phosphorylation. In C2C12 cells, decreased phosphorylation of TAK1 leads to reduced phosphorylation of p38, JNK, and HSP27 after 16 h and muscle fiber hypertrophy after 3 days. However, continuous blockade of this pathway leads to muscle fiber failure, suggesting that the timing of TAK1 activation controls the expression of context-dependent targets.

One Copy Number Variation within the Angiopoietin-1 Gene Is Associated with Leizhou Black Goat Meat Quality.

The ANGPT1 gene plays a crucial role in the regulation of angiogenesis and muscle growth, with previous studies identifying copy number variations (CNVs) within this gene among Leizhou black goats. In this study, we investigated three ANGPT1 CNVs in 417 individuals of LZBG using quantitative PCR (qPCR), examining the impact of different CNV types on the ANGPT1 gene expression and their associations with growth and meat quality traits. Notably, the ANGPT1 CNV-1 (ARS1_chr14:24950001-24953600) overlaps with protein-coding regions and conserved domains; its gain-of-copies genotype (copies ≥ 3) was significantly correlated with ANGPT1 mRNA expression in muscle tissue (p < 0.01). Furthermore, the gain-of-copies genotype of CNV-1 demonstrated significant correlations with various phenotypic traits, including carcass weight, body weight, shear stress, chest circumference, and cross-sectional area of longissimus dorsi muscle. These findings indicate that the CNV-1 gain-of-copies genotype in the ANGPT1 gene may serve as a valuable marker for selecting Leizhou black goats exhibiting enhanced growth and muscular development characteristics, thereby holding potential applications in targeted breeding programs aimed at improving meat quality.

Treatment outcome and associated factors of infantile hypertrophic pyloric stenosis at eastern Ethiopia public hospitals

BackgroundInfantile hypertrophic pyloric stenosis (IHPS) is a condition whose etiology is not clear, but it is characterized by progressive hypertrophy of the circular muscles of the pylorus with consequent obstruction of the gastric outflow, mostly in neonates and infants under the age of one year.ObjectivesTo assess the treatment outcome and associated factors of infantile pyloric sphincter stenosis among paediatric patients admitted to HFCSUH and JUSHYRH.MethodologyA retrospective patient record review with 78 participants was studied consecutively using a structured questionnaire. The data was processed and analyzed using Epi Info 7 and SPSS version 24. Descriptive analysis was done, and then associated factors to the outcome were assessed using logistic regression analysis. The association’s significance was determined using an odds ratio with a 95% confidence interval and a P-value less than 0.05. The study period was from November 1st to 30th, 2022.ResultsThe magnitude of unfavorable IHPS was 17.1% with a 95% confidence interval of 16.7–23.9%. Hypokalemia (AOR = 2.3, CI = 3.015–19.54), severe dehydration (AOR = 30.9, CI = 2.89–31.75), and delayed presentation (AOR = 7.37, CI = 2.761–12.08) were independent predictors.ConclusionsThe study found a highly unfavorable treatment outcome with delayed presentation; dehydration and electrolyte disturbance were the main predictors of poor outcome. It is recommended to increase community awareness about non-bilious vomiting in infants and ensure high suspicion among healthcare providers. Moreover, following guidelines to correct fluid and electrolyte disturbances and managing these patients in the pediatric ICU postoperatively.

PSI-3 Effects of a Retinoid X Receptor agonist on primary ovine satellite cells

Abstract Sheep producers are typically paid based on body weight, so understanding the mechanisms of postnatal skeletal muscle growth is vital. Satellite cells are responsible for the capacity for postnatal skeletal muscle growth. Satellite cells proliferate and then differentiate into myoblasts before fusing with existing myotubes. The retinoid X receptor (RXR) is a transcription factor that enhances myogenic differentiation 1 (MyoD) expression, which increases differentiation and fusion of myoblasts in sheep. LG 100268 is an RXR agonist, which activates the RXR. The objective of this project is to measure the effect of LG 100268 on primary ovine satellite cell (OSC) proliferation and protein synthesis rates. Primary OSC were isolated from the hind legs of 9-mo old commercial hair sheep wethers (n = 3). For proliferation, cultures were grown to approximately 70% confluency, followed by treatment with 5% fetal bovine serum (FBS) or 300 nM of LG 100268 in 5% FBS. For protein synthesis, cultures were grown to approximately 80% confluency, at which point cultures were induced to differentiate and treated 48-h later with serum free media (SFM) or 300 nM LG 100268 in SFM. Proliferation rates were measured at 24-h post-treatment, and protein synthesis rates were measured at 6-h post-treatment. Treatment with 300 nM LG 100268 increased (P = 0.004) OSC proliferation rates compared with control cultures. Preliminary protein synthesis results suggest that LG 100268 does not alter (P = 0.22) protein synthesis rates of fused OSC. However, more research is warranted to clarify the role of the RXR in sheep skeletal muscle growth.

PSII-18 Prematurity alters nutrient signaling and protein synthesis in skeletal muscle of neonatal piglets

Abstract Extrauterine growth restriction is common in infants born preterm, and negatively affects lean mass accretion and health. Prematurity has been shown to inhibit the feeding-induced stimulation of protein synthesis in skeletal muscle. We hypothesized that nutrient signaling, activation of the mechanistic target of rapamycin complex 1 (mTORC1), and protein synthesis in the muscle are limited in preterm infants which negatively impacts muscle growth. The objective of this study was to examine how prematurity influences the mechanisms involved in insulin- and amino acid-induced signaling and protein synthesis in skeletal muscle of piglets delivered either 9 d preterm (104 d, n = 25) or at term (112 d, n = 26) by cesarean section. After resuscitation, they were surgically implanted with jugular vein and carotid artery catheters and placed in individual incubators. They were randomly allotted to one of three treatments within each preterm and term birth groups: euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps on 4 d after birth. After the clamp procedure, the piglets were euthanized to collect longissimus dorsi muscle for estimating in vivo fractional protein synthesis rates and the abundance and activation of components related to insulin and amino acid signaling. Data were analyzed using the MIXED procedure of SAS. The leucine sensor, Sestrin1 bound to GATOR2 (P &amp;lt; 0.05) was reduced in response to AA whereas the abundance of the mTOR-RagA and mTOR-RagC complexes increased (P &amp;lt; 0.05). The phosphorylation of Akt was increased (P &amp;lt; 0.05) in response to INS and the phosphorylation of mTORC1 and protein synthesis increased (P &amp;lt; 0.05) in response to both AA and INS. Prematurity did not affect the protein abundances of the AA transporters for glutamine (SLC38A2), leucine (SLC7A5), and arginine (SLC38A9). However, prematurity reduced (P &amp;lt; 0.05) the abundances of the leucine sensors SAR1B, the Sestrin1-GATOR complex, the AA sensor, RAB1A, and the threonine sensor, TARS2 (P &amp;lt; 0.05). The abundances of the glutamine sensor, ARF1, the arginine sensor, CASTOR, and the methionine-SAMTOR GATOR complex were similar. Prematurity reduced (P &amp;lt; 0.05) the abundance of the mTOR-RagA and mTOR-RagC complexes, the phosphorylation of mTORC1 and muscle protein synthesis (P &amp;lt; 0.05). In conclusion, prematurity negatively affects protein synthesis in skeletal muscle of neonatal preterm piglets by blunting anabolic pathways responsible for nutrient-sensing and mTORC1 activation. The reduced anabolic response likely contributes to reduced lean growth and extrauterine growth restriction following preterm birth.

204 Changes in DNA methylation 5 days after exposure to acute heat stress in beef cattle skeletal muscle

Abstract The objective of this study was to investigate the effects of acute heat stress on the skeletal muscle epigenome using reduced representation bisulfite sequencing (RRBS). March-born crossbred (5/8 Red Angus, 3/8 Simmental) steers (n = 14; average body weight = 308.7 kg) were exposed to heat stress (HS) conditions of 35°C + 35% relative humidity (Temperature Humidity Index = 81) for 12h/d for 2 d (48 h). Longissimus dorsi samples were collected via biopsy and flash-frozen in liquid nitrogen immediately following the HS period at 48 h and from the contralateral longissimus dorsi 5 d later. DNA was isolated and underwent RRBS using 150 bp paired-end reads at an achieved average depth of 15.3 million reads/sample. Reads were trimmed and mapped to a bisulfite-converted bovine genome (ARSUCD1.2). Methylation calls were extracted and used to identify differentially methylated regions (DMRs) with methylkit in R comparing samples collected 5 d post-HS to those taken immediately post-48 h of HS. Differentially methylated regions (1,000 bp) had q &amp;lt; 0.05 and at least a 15% difference in methylation. There were 1,015 DMRs in genes. Hypomethylated DMRs 5 d post-HS included IGF1R, IGF2, IGF2BP1, IGFBP4, IGF2R, IKBKB, and IL34. Hypermethylated DMRs 5 d post-HS included FGF5, FGFR1, and FGFR3. There were 81 DMRs in putative promoter regions (2000 bp 5’ of a gene). MYLK2, SIGIRR, and 25 other genes had hypomethylated promoter regions. Genes that contained DMRs were used as input for DAVID to explore KEGG pathways. Enriched pathways (P &amp;lt; 0.1) included multiple hormone pathways, MAPK, PI3K-Akt, HIF-1, and VEGF. Hypomethylation of IGF-related genes and hypermethylation of FGF-related genes suggests impaired growth capacity post-HS, as does the enrichment of MAPK and PI3K-Akt pathways. Hypomethylation of SIGIRR’s promoter region, IL34 and IKBKB, indicates enhanced anti-inflammatory activity given their known regulation of inflammatory cytokine production. This, coupled with enrichment of the HIF-1 and VEGF pathways, suggests regulatory dampening of HS-induced oxidative stress. These findings reveal key regulatory changes in muscle growth, inflammatory response, and oxidative stress activity for cattle recovering from acute HS. Previous cattle skeletal muscle RNA studies predicted that HS altered metabolism, inflammation, and oxidative stress pathways, similar to the methylation results of this study. Overall, evidence suggests growth dysregulation, which may help explain observed HS-induced poor growth due to HS, as well as subsequent anti-inflammatory activity during recovery from HS.

170 Understanding how zinc and manganese interact with the hormones found in anabolic implants to alter growth of bovine satellite cells

Abstract It has been well established in both in vitro and in vivo models that the hormones found in anabolic implants [estradiol (E2) and trenbolone acetate (TBA)] positively impact skeletal muscle growth. Previous research has demonstrated that treating primary bovine satellite cells (BSC) with E2 or TBA results in increases in proliferation and protein synthesis and decreases in protein degradation, leading to enhanced skeletal muscle growth. This improved skeletal muscle growth occurs through partially defined pathways, but many unknowns remain. More recently, research has emerged demonstrating that strategic supplementation of specific trace minerals (TM) may further augment the positive effects of E2 and TBA on skeletal muscle growth. There are many ways through which the complex signaling pathways induced by the hormones found in anabolic implants may interact with TM to further enhance skeletal muscle growth. Zinc (Zn) and manganese (Mn) are two of the TM that we have recently investigated. Zinc is the most utilized metal in biological processes and supports animal growth through critical roles in the functions of IGF-1, GH, and DNA synthesis. Manganese is an essential TM providing catalytic activity to enzymes involved in protein glycosylation, nitrogen metabolism, and antioxidant capacity. However, additional research is needed to determine if hormones and TM interact to impact growth of skeletal muscle, specifically. As such, the goal of recent research that has been conducted by our group is to utilize an in vitro primary BSC model to determine whether hormones and TM interact to alter differentiation and protein synthesis. Preliminary research from our group assesses the impacts of varying, physiological concentrations of Zn or Mn on differentiation and protein synthesis of primary BSC cultures that have also been treated with or without the hormones found in anabolic implants. These preliminary findings demonstrate that while there seems to be no interaction between Zn and hormones in differentiating BSC, supplemental Zn on the higher end of physiologically relevant concentrations has a positive effect on signaling pathways involved in growth, protein turnover, skeletal muscle differentiation, and mineral transporters. However, it appears that Zn and Mn each interact with hormones to positively augment protein synthesis in primary BSC cultures. A deeper understanding of the relationship these TM and others may have with hormones will allow for more strategic supplementation practices that can potentially improve skeletal muscle growth.

280 AntagomiR-22-3p Injection alters miRNA expression and muscle fiber type of intrauterine growth restricted lambs

Abstract microRNAs (miRNA) are small non-coding RNAs that modulate muscle satellite cell proliferation. Previous research identified miR-22-3p as differentially expressed during ovine muscle development and in vitro experiments showed that antagomir-22-3p treatment enhanced satellite cell proliferation. The objective of this study was to test in vivo vascular injection of antagomir-22-3p in lateral saphenous vein on miRNA and HDAC family mRNA expression in intrauterine growth restricted lambs. Pregnant ewes (n = 18) with twins were either fed at 100% of NRC (CON) or nutrient restricted (60% NRC; NR) from gestational d 85 to parturition. On d 12 of age, NR lambs (n = 8) were randomly selected and given a systemic injection of antagomir-22-3p in the lateral saphenous vein of the right leg (MIR-NR). CON lambs (n = 8) were also randomly selected and given a sham injection of PBS in the lateral saphenous vein of the right leg (SHAM-CON). Antagomir-22-3p was reconstituted in phosphate buffered saline (PBS). Injections were given for 3 consecutive days and lambs harvested 24 d later. Blood samples were collected from each lamb weekly to monitor miR-22-3p expression. Lambs were slaughtered 24 d after the first injection and muscle mass measured. Muscle samples were removed for miR-22-3p and mRNA expression of potential targets. Cell-free circulating RNA was isolated from blood samples and miR-22-3p expression examined over time. Cell-free circulating miR-22-3p expression was downregulated (P &amp;lt; 0.05) for MIR-NR compared with SHAM-CON on d 14 after injection. On d 21 after injection, miR-22-3p expression in plasma tended (P = 0.08) to be down-regulated in MIR-NR compared with SHAM-CON. Lamb body weight and muscle weights at harvest were similar between MIR-NR and SHAM-CON treatments. In heart and semimembranosus (SM) muscles, expression of miR-22-3p was down-regulated (P &amp;lt; 0.05) in MIR-NR compared with SHAM-CON. In the gastrocnemius and semitendinosus muscle, miR-22-3p expression was unchanged (P &amp;gt; 0.05). The number of type I and IIa muscle fibers were greater (P &amp;lt; 0.05) for MIR-NR than SHAM-CON. Muscle fiber area of Type I, IIa or IIx fibers did not differ (P &amp;gt; 0.05) by treatment. The number of type IIx fibers did not differ (P &amp;gt; 0.05) between treatments. MIR-NR treatment appears to shift muscle fibers towards more oxidative metabolism and down-regulate HDAC-1, 3, and 11 and SIRT6 in SM. The systemic injection of antagomir-22-3P down-regulated miR-22-3p expression in circulation and in muscle tissues, which altered expression of HDAC/SIRT genes involved in muscle fiber type conversion and hypertrophy.

Functional Role of Extracellular Vesicles in Skeletal Muscle Physiology and Sarcopenia: The Importance of Physical Exercise and Nutrition.

Extracellular vesicles (EVs) play a key role in intercellular communication by transferring miRNAs and other macromolecules between cells. Understanding how diet and exercise modulate the release and content of skeletal muscle (SM)-derived EVs could lead to novel therapeutic strategies to prevent age-related muscle decline and other chronic diseases, such as sarcopenia. This review aims to provide an overview of the role of EVs in muscle function and to explore how nutritional and physical interventions can optimise their release and function. A literature review of studies examining the impact of exercise and nutritional interventions on MS-derived EVs was conducted. Major scientific databases, including PubMed, Scopus and Web of Science, were searched using keywords such as 'extracellular vesicles', 'muscle', 'exercise', 'nutrition' and 'sarcopenia'. The selected studies included randomised controlled trials (RCTs), clinical trials and cohort studies. Data from these studies were synthesised to identify key findings related to the release of EVs, their composition and their potential role as therapeutic targets. Dietary patterns, specific foods and supplements were found to significantly modulate EV release and composition, affecting muscle health and metabolism. Exercise-induced changes in EV content were observed after both acute and chronic interventions, with a marked impact on miRNAs and proteins related to muscle growth and inflammation. Nutritional interventions, such as the Mediterranean diet and omega-3 fatty acids, have also shown the ability to alter EV profiles, suggesting their potential to improve cardiovascular health and reduce inflammation. EVs are emerging as critical mediators of the beneficial effects of diet and exercise on muscle health. Both exercise and nutritional interventions can modulate the release and content of MS-derived EVs, offering promising avenues for the development of novel therapeutic strategies targeting sarcopenia and other muscle diseases. Future research should focus on large-scale RCT studies with standardised methodologies to better understand the role of EVs as biomarkers and therapeutic targets.