Mechanisms of muscle atrophy and hypertrophy: implications in health and disease

Role of AMBRA1 in mitophagy regulation: emerging evidence in aging-related diseases

Aging is a gradual and irreversible physiological process that significantly increases the risks of developing a variety of pathologies, including neurodegenerative, cardiovascular, metabolic, musculoskeletal, and immune system diseases. Mitochondria are the energy-producing organelles, and their proper functioning is crucial for overall cellular health. Over time, mitochondrial function declines causing an increased release of harmful reactive oxygen species (ROS) and DNA, which leads to oxidative stress, inflammation and cellular damage, common features associated with various age-related pathologies. The impairment of mitophagy, the selective removal of damaged or dysfunctional mitochondria by autophagy, is relevant to the development and progression of age-related diseases. The molecular mechanisms that regulates mitophagy levels in aging remain largely uncharacterized. AMBRA1 is an intrinsically disordered scaffold protein with a unique property of regulating the activity of both proliferation and autophagy core machineries. While the role of AMBRA1 during embryonic development and neoplastic transformation has been extensively investigated, its functions in post-mitotic cells of adult tissues have been limited due to the embryonic lethality caused by AMBRA1 deficiency. Recently, a key role of AMBRA1 in selectively regulating mitophagy in post-mitotic cells has emerged. Here we summarize and discuss these results with the aim of providing a comprehensive view of the mitochondrial roles of AMBRA1, and how defective activity of AMBRA1 has been functionally linked to mitophagy alterations observed in age-related degenerative disorders, including muscular dystrophy/sarcopenia, Parkinson diseases, Alzheimer diseases and age-related macular degeneration.Abbreviations: AD: Alzheimer disease; AMD: age-related macular degeneration; AMBRA1: autophagy and beclin 1 regulator 1; APOE4: apolipoprotein E4; ATAD3A: ATPase family AAA domain containing 3A; ATG: autophagy related; BCL2: BCL2 apoptosis regulator; BH3: BCL2-homology-3; BNIP3L/NIX: BCL2 interacting protein 3 like; CDK: cyclin dependent kinase; CHUK/IKKα: component of inhibitor of nuclear factor kappa B kinase complex; CRL2: CUL2-RING ubiquitin ligase; DDB1: damage specific DNA binding protein 1; ER: endoplasmic reticulum; FOXO: forkhead box O; FUNDC1: FUN14 domain containing 1; GBA/β-glucocerebrosidase: glucosylceramidase beta; HUWE1: HECT, UBA and WWE domain containing E3 ubiquitin protein ligase 1; IDR: intrinsically disordered region; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; MCL1: MCL1 apoptosis regulator, BCL2 family member; MFN2: mitofusin 2; MTOR: mechanistic target of rapamycin kinase; MSA: multiple system atrophy; MYC: MYC proto-oncogene, bHLH transcription factor; NUMA1: nuclear mitotic apparatus protein 1; OMM; mitochondria outer membrane; PD: Parkinson disease; PHB2: prohibitin 2; PINK1: PTEN induced kinase 1; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PTK2/FAK: protein tyrosine kinase 2; ROS: reactive oxygen species; RPE: retinal pigment epithelium; SAD: sporadic AD; SOCS3: suppressor of cytokine signaling 3; SRC, SRC proto-oncogene, non-receptor tyrosine kinase; STAT3: signal transducer and activator of transcription 3; STING1: stimulator of interferon response cGAMP interactor 1; SQSTM1/p62: sequestosome 1; TBK1: TANK binding kinase 1; TGFB/TGFβ: transforming growth factor beta; TOMM: translocase of outer mitochondrial membrane; TRAF6: TNF receptor associated factor 6; TRIM32: tripartite motif containing 32; ULK1: unc-51 like autophagy activating kinase 1.

LPS-related muscle loss is associated with the alteration of Bacteroidetes abundance, systemic inflammation, and mitochondrial morphology in a weaned piglet model

We previously demonstrated that lipopolysaccharide (LPS) injection-induced immune stress could impair muscle growth in weaned piglets, but the precise mechanisms behind this remain elusive. Here, we found that chronic immune stress induced by LPS resulted in a significant reduction of 36.86% in the total muscle mass of piglets at 5 d post-treatment compared with the control group. At 1 d, prior to muscle mass loss, multiple alterations were noted in response to LPS treatment. These included a reduction in the abundance of Bacteroidetes, an increase in serum concentrations of pro-inflammatory cytokines, compromised mitochondrial morphology, and an upregulation in the expression of dynamin-related protein 1 (Drp1), a critical protein involved in mitochondrial fission. We highlight a strong negative correlation between Bacteroidetes abundance and the levels of serum pro-inflammatory cytokines, corroborated by in vivo intervention strategies in the musculature of both pig and mouse models. Mechanistically, the effects of Bacteroidetes on inflammation and muscle mass loss may involve the signaling pathway of the tauro-β-muricholic acid-fibroblast growth factor 15. Furthermore, the induction of overexpression of inflammatory cytokines, achieved without LPS treatment through oral administration of recombinant human IL-6 (rhIL-6), led to increased levels of circulating cytokines, subsequently causing a decrease in muscle mass. Notably, pre-treatment with Mdivi-1, an inhibitor of Drp-1, markedly attenuated the LPS-induced elevation in reactive oxygen species levels and rescued the associated decline in muscle mass. Collectively, these data indicate that LPS-induced muscle mass loss was linked to the reduction of Bacteroidetes abundance, increased inflammation, and the disruption of mitochondrial morphology. These insights offer promising avenues for the identification of potential therapeutic targets aimed at mitigating muscle mass loss.

A molecular pathway for cancer cachexia-induced muscle atrophy revealed at single-nucleus resolution

Cancer cachexia is a prevalent and often fatal wasting condition that cannot be fully reversed with nutritional interventions. Muscle atrophy is a central component of the syndrome, but the mechanisms whereby cancer leads to skeletal muscle atrophy are not well understood. We performed single-nucleus multi-omics on skeletal muscles from a mouse model of cancer cachexia and profiled the molecular changes in cachexic muscle. Our results revealed the activation of a denervation-dependent gene program that upregulates the transcription factor myogenin. Further studies showed that a myogenin-myostatin pathway promotes muscle atrophy in response to cancer cachexia. Short hairpin RNA inhibition of myogenin or inhibition of myostatin through overexpression of its endogenous inhibitor follistatin prevented cancer cachexia-induced muscle atrophy in mice. Our findings uncover a molecular basis of muscle atrophy associated with cancer cachexia and highlight potential therapeutic targets for this disorder.

Combination of transcriptomics and proteomics for analyzing potential biomarker and molecular mechanism underlying skeletal muscle atrophy

BACKGROUND

The skeletal muscle atrophy is prevalently occurred in numerous chronic disease complications. Despite its important clinical significance, there are currently no therapeutic drugs, so new biomarkers and molecular mechanisms need to be discovered urgently.

METHODS

Transcriptome and proteome sequencing data were collected from normal and skeletal muscle atrophic mice. The differentially expressed genes (DEGs) and proteins (DEPs) were analyzed. Applying PPI analysis to obtain overlapping genes and proteins, which were next subjected to GO and KEGG enrichment analysis. Combined analysis of transcriptomics and proteomics was performed to get key genes that were simultaneously found in GO and KEGG enrichment results. Subsequently, RT-qPCR and immunofluorescence were constructed to verify the expression of screened key genes.

RESULTS

By combination of transcriptomics, proteomics and RT-qPCR results, we identified 14 key genes (Cav1, Col3a1, Dnaja1, Postn, Ptges3, Cd44, Clec3b, Igfbp6, Lamc1, Alb, Itga6, Mmp2, Timp2 and Cd9) that were markedly different in atrophic mice. Single-gene GSEA and immunofluorescence suggested Cd9 was probably the biomarker for skeletal muscle atrophy.

CONCLUSIONS

Our study hinted that Cd9 was potential biomarker and may interfere with skeletal muscle atrophy through process of aerobic respiration, oxidative phosphorylation, and metabolism of amino acids and fatty acids.

SIGNIFICANCE

The present study holds the subsequent significance: Frist, we investigated biomarkers for skeletal muscle atrophy using multi-omics approach. A total of 14 genes were markedly different in skeletal muscle atrophic mice. We finally found Cd9 is a potential biomarker for skeletal muscle atrophy. Our work presents novel biomarkers and potential regulatory mechanisms for the early detection and intervention of muscle atrophy.

Ameliorative Effects of Fermented Red Ginseng Extract on Muscle Atrophy in Dexamethasone-Induced C2C12 Cell And Hind Limb-Immobilized C57BL/6J Mice

Fermented red ginseng (FRG) enhances the bioactivity and bioavailability of ginsenosides, which possess various immunomodulatory, antiaging, anti-obesity, and antidiabetic properties. However, the effects of FRG extract on muscle atrophy and the underlying molecular mechanisms remain unclear. This study aimed to elucidate the effects of FRG extract on muscle atrophy using both in vitro and in vivo models. In vitro experiments used dexamethasone (DEX)-induced C2C12 myotubes to assess cell viability, myotube diameter, and fusion index. In vivo experiments were conducted on hind limb immobilization (HI)-induced mice to evaluate grip strength, muscle mass, and fiber cross-sectional area (CSA) of the gastrocnemius (GAS), quadriceps (QUA), and soleus (SOL) muscles. Molecular mechanisms were investigated through the analysis of key signaling pathways associated with muscle protein synthesis, energy metabolism, and protein degradation. FRG extract treatment enhanced viability of DEX-induced C2C12 myotubes and restored myotube diameter and fusion index. In HI-induced mice, FRG extract improved grip strength, increased muscle mass and CSA of GAS, QUA, and SOL muscles. Mechanistic studies revealed that FRG extract activated the insulin-like growth factor 1/protein kinase B (Akt)/mammalian target of rapamycin signaling pathway, promoted muscle energy metabolism via the sirtuin 1/peroxisome proliferator-activated receptor gamma-coactivator-1α pathway, and inhibited muscle protein degradation by suppressing the forkhead box O3a, muscle ring-finger 1, and F-box protein (Fbx32) signaling pathways. FRG extract shows promise for ameliorating muscle atrophy by modulating key molecular pathways associated with muscle protein synthesis, energy metabolism, and protein degradation, offering insights for future drug development.

Optogenetic induction of mechanical muscle stress identifies myosin regulatory ubiquitin ligase NHL-1 in C. elegans

Mechanical stress during muscle contraction is a constant threat to proteome integrity. However, there is a lack of experimental systems to identify critical proteostasis regulators under mechanical stress conditions. Here, we present the transgenic Caenorhabditis elegans model OptIMMuS (Optogenetic Induction of Mechanical Muscle Stress) to study changes in the proteostasis network associated with mechanical forces. Repeated blue light exposure of a muscle-expressed Chlamydomonas rheinhardii channelrhodopsin-2 variant results in sustained muscle contraction and mechanical stress. Using OptIMMuS, combined with proximity labeling and mass spectrometry, we identify regulators that cooperate with the myosin-directed chaperone UNC-45 in muscle proteostasis. One of these is the TRIM E3 ligase NHL-1, which interacts with UNC-45 and muscle myosin in genetic epistasis and co-immunoprecipitation experiments. We provide evidence that the ubiquitylation activity of NHL-1 regulates myosin levels and functionality under mechanical stress. In the future, OptIMMuS will help to identify muscle-specific proteostasis regulators of therapeutic relevance.

Research Progress on the Effect and Mechanism of Exercise Intervention on Sarcopenia Obesity

With the increasingly severe situation of obesity and population aging, there is growing concern about sarcopenia obesity (SO). SO refers to the coexistence of obesity and sarcopenia, which imposes a heavier burden on individuals and society compared to obesity or sarcopenia alone. Therefore, comprehending the pathogenesis of SO and implementing effective clinical interventions are vital for its prevention and treatment. This review uses a comprehensive literature search and analysis of PubMed, Web of Science, and CNKI databases, with search terms including "Sarcopenic obesity", "exercise", "cytokines", "inflammation", "mitochondrial quality control", and "microRNA", covering relevant studies published up to July 2024. The results indicate that the pathogenesis of SO is complex, involving mechanisms like age-related changes in body composition, hormonal alterations, inflammation, mitochondrial dysfunction, and genetic and epigenetic factors. Regarding exercise interventions for SO, aerobic exercise can reduce fat mass, resistance exercise can increase skeletal muscle mass and strength, and combined exercise can achieve both, making it the optimal intervention for SO. The potential mechanisms by which exercise may prevent and treat SO include regulating cytokine secretion, inhibiting inflammatory pathways, improving mitochondrial quality, and mediating microRNA expression. This review emphasizes the effectiveness of exercise interventions in mitigating sarcopenic obesity through comprehensive analysis of its multifactorial pathogenesis and the mechanistic insights into exercise's therapeutic effects. Understanding these mechanisms informs targeted therapeutic strategies aimed at alleviating the societal and individual burdens associated with SO.

Insights into the epitranscriptomic role of N6-methyladenosine on aging skeletal muscle

The modification of RNA through the N6-methyladenosine (m6A) has emerged as a growing area of research due to its regulatory role in gene expression and various biological processes regulating the expression of genes. m6A RNA methylation is a post-transcriptional modification that is dynamic and reversible and found in mRNA, tRNA, rRNA, and other non-coding RNA of most eukaryotic cells. It is executed by special proteins known as "writers," which initiate methylation; "erasers," which remove methylation; and "readers," which recognize it and regulate the expression of the gene. Modification by m6A regulates gene expression by affecting the splicing, translation, stability, and localization of mRNA. Aging causes molecular and cellular damage, which forms the basis of most age-related diseases. The decline in skeletal muscle mass and functionality because of aging leads to metabolic disorders and morbidities. The inability of aged muscles to regenerate and repair after injury poses a great challenge to the geriatric populace. This review seeks to explore the m6A epigenetic regulation in the myogenesis and regeneration processes in skeletal muscle as well as the progress made on the m6A epigenetic regulation of aging skeletal muscles.

Epigenetics of Skeletal Muscle Atrophy

Skeletal muscle atrophy, characterized by diminished muscle strength and mass, arises from various causes, including malnutrition, aging, nerve damage, and disease-related secondary atrophy. Aging markedly escalates the prevalence of sarcopenia. Concurrently, the incidence of muscle atrophy significantly rises among patients with chronic ailments such as heart failure, diabetes, and chronic obstructive pulmonary disease (COPD). Epigenetics plays a pivotal role in skeletal muscle atrophy. Aging elevates methylation levels in the promoter regions of specific genes within muscle tissues. This aberrant methylation is similarly observed in conditions like diabetes, neurological disorders, and cardiovascular diseases. This study aims to explore the relationship between epigenetics and skeletal muscle atrophy, thereby enhancing the understanding of its pathogenesis and uncovering novel therapeutic strategies.

Impact of Selected Glucagon-like Peptide-1 Receptor Agonists on Serum Lipids, Adipose Tissue, and Muscle Metabolism-A Narrative Review

Glucagon-like peptide-1 receptor agonists (GLP-1 RA) are novel antihyperglycemic agents. By acting through the central nervous system, they increase satiety and reduce food intake, thus lowering body weight. Furthermore, they increase the secretion of insulin while decreasing the production of glucagon. However, recent studies suggest a more complex metabolic impact through the interaction with various other tissues. In our present review, we aim to provide a summary of the effects of GLP-1 RA on serum lipids, adipose tissue, and muscle metabolism. It has been found that GLP-1 RA therapy is associated with decreased serum cholesterol levels. Epicardial adipose tissue thickness, hepatic lipid droplets, and visceral fat volume were reduced in obese patients with cardiovascular disease. GLP-1 RA therapy decreased the level of proinflammatory adipokines and reduced the expression of inflammatory genes. They have been found to reduce endoplasmic reticulum stress in adipocytes, leading to better adipocyte function and metabolism. Furthermore, GLP-1 RA therapy increased microvascular blood flow in muscle tissue, resulting in increased myocyte metabolism. They inhibited muscle atrophy and increased muscle mass and function. It was also observed that the levels of muscle-derived inflammatory cytokines decreased, and insulin sensitivity increased, resulting in improved metabolism. However, some clinical trials have been conducted on a very small number of patients, which limits the strength of these observations.

Diabetes-induced muscle wasting: molecular mechanisms and promising therapeutic targets

Diabetes has become a serious public health crisis, presenting significant challenges to individuals worldwide. As the largest organ in the human body, skeletal muscle is a significant target of this chronic disease, yet muscle wasting as a complication of diabetes is still not fully understood and effective treatment methods have yet to be developed. Here, we discuss the targets involved in inducing muscle wasting under diabetic conditions, both validated targets and emerging targets. Diabetes-induced skeletal muscle wasting is known to involve changes in various signaling molecules and pathways, such as protein degradation pathways, protein synthesis pathways, mitochondrial function, and oxidative stress inflammation. Recent studies have shown that some of these present potential as promising therapeutic targets, including the neuregulin 1/epidermal growth factor receptor family, advanced glycation end-products, irisin, ferroptosis, growth differentiation factor 15 and more. This study's investigation and discussion of such pathways and their potential applications provides a theoretical basis for the development of clinical treatments for diabetes-induced muscle wasting and a foundation for continued focus on this disease.

Therapeutic Potential of Quercetin as an Antioxidant for Bone-Muscle-Tendon Regeneration and Aging

Quercetin (QC), a naturally occurring bioflavonoid found in various fruits and vegetables, possesses many potential health benefits, primarily attributed to its robust antioxidant properties. The generation of oxidative stress in bone cells is a key modulator of their physiological behavior. Moreover, oxidative stress status influences the pathophysiology of mineralized tissues. Increasing scientific evidence demonstrates that manipulating the redox balance in bone cells might be an effective technique for developing bone disease therapies. The QC antioxidant abilities in skeletal muscle significantly enhance muscle regeneration and reduce muscle atrophy. In addition, QC has been shown to have protective effects against oxidative stress, inflammation, apoptosis, and matrix degradation in tendons, helping to maintain the structural integrity and functionality of tendons. Thus, the antioxidant properties of QC might be crucial for addressing age-related musculoskeletal disorders like osteoporosis, sarcopenia, and tendon-related inflammatory conditions. Understanding how QC influences redox signaling pathways involved in musculoskeletal disorders, including their effect on bone, muscle, and tendon differentiation, might provide insights into the diverse advantages of QC in promoting tissue regeneration and preventing cellular damage. Therefore, this study reviewed the intricate relationship among oxidative stress, inflammation, and tissue repair, affected by the antioxidative abilities of QC, in age-related musculoskeletal tissues to improve the overall health of bones, muscles, and tendons of the skeletal system. Also, reviewing the ongoing clinical trials of QC for musculoskeletal systems is encouraging. Given the positive effect of QC on musculoskeletal health, further scientific investigations and controlled human intervention studies are necessary to explore the therapeutic potential to its optimum strength.

Superoxide is an Intrinsic Signaling Molecule Triggering Muscle Hypertrophy

Aims: Redox signaling plays a key role in skeletal muscle remodeling induced by exercise and prolonged inactivity, but it is unclear which oxidant triggers myofiber hypertrophy due to the lack of strategies to precisely regulate individual oxidants in vivo. In this study, we used tetrathiomolybdate (TM) to dissociate the link between superoxide (O2•-) and hydrogen peroxide and thereby to specifically explore the role of O2•- in muscle hypertrophy in C2C12 cells and mice. Results: TM can linearly regulate intracellular O2•- levels by inhibition of superoxide dismutase 1 (SOD1). A 70% increase in O2•- levels in C2C12 myoblast cells and mice is necessary and sufficient for triggering hypertrophy of differentiated myotubes and can enhance exercise performance by more than 50% in mice. SOD1 knockout blocks TM-induced O2•- increments and thereby prevents hypertrophy, whereas SOD1 restoration rescues all these effects. Scavenging O2•- with antioxidants abolishes TM-induced hypertrophy and the enhancement of exercise performance, whereas the restoration of O2•- levels with a O2•- generator promotes muscle hypertrophy independent of SOD1 activity. Innovation and Conclusion: These findings suggest that O2•- is an endogenous initiator of myofiber hypertrophy and that TM may be used to treat muscle wasting diseases. Our work not only suggests a novel druggable mechanism to increase muscle mass but also provides a tool for precisely regulating O2•- levels in vivo.

The "Sunshine Vitamin" and Its Antioxidant Benefits for Enhancing Muscle Function

Pathological states marked by oxidative stress and systemic inflammation frequently compromise the functional capacity of muscular cells. This progressive decline in muscle mass and tone can significantly hamper the patient's motor abilities, impeding even the most basic physical tasks. Muscle dysfunction can lead to metabolic disorders and severe muscle wasting, which, in turn, can potentially progress to sarcopenia. The functionality of skeletal muscle is profoundly influenced by factors such as environmental, nutritional, physical, and genetic components. A well-balanced diet, rich in proteins and vitamins, alongside an active lifestyle, plays a crucial role in fortifying tissues and mitigating general weakness and pathological conditions. Vitamin D, exerting antioxidant effects, is essential for skeletal muscle. Epidemiological evidence underscores a global prevalence of vitamin D deficiency, which induces oxidative harm, mitochondrial dysfunction, reduced adenosine triphosphate production, and impaired muscle function. This review explores the intricate molecular mechanisms through which vitamin D modulates oxidative stress and its consequent effects on muscle function. The aim is to evaluate if vitamin D supplementation in conditions involving oxidative stress and inflammation could prevent decline and promote or maintain muscle function effectively.

Resveratrol and Vitamin D: Eclectic Molecules Promoting Mitochondrial Health in Sarcopenia

Sarcopenia refers to the progressive loss and atrophy of skeletal muscle function, often associated with aging or secondary to conditions involving systemic inflammation, oxidative stress, and mitochondrial dysfunction. Recent evidence indicates that skeletal muscle function is not only influenced by physical, environmental, and genetic factors but is also significantly impacted by nutritional deficiencies. Natural compounds with antioxidant properties, such as resveratrol and vitamin D, have shown promise in preventing mitochondrial dysfunction in skeletal muscle cells. These antioxidants can slow down muscle atrophy by regulating mitochondrial functions and neuromuscular junctions. This review provides an overview of the molecular mechanisms leading to skeletal muscle atrophy and summarizes recent advances in using resveratrol and vitamin D supplementation for its prevention and treatment. Understanding these molecular mechanisms and implementing combined interventions can optimize treatment outcomes, ensure muscle function recovery, and improve the quality of life for patients.

Epigenetic control of skeletal muscle atrophy

Skeletal muscular atrophy is a complex disease involving a large number of gene expression regulatory networks and various biological processes. Despite extensive research on this topic, its underlying mechanisms remain elusive, and effective therapeutic approaches are yet to be established. Recent studies have shown that epigenetics play an important role in regulating skeletal muscle atrophy, influencing the expression of numerous genes associated with this condition through the addition or removal of certain chemical modifications at the molecular level. This review article comprehensively summarizes the different types of modifications to DNA, histones, RNA, and their known regulators. We also discuss how epigenetic modifications change during the process of skeletal muscle atrophy, the molecular mechanisms by which epigenetic regulatory proteins control skeletal muscle atrophy, and assess their translational potential. The role of epigenetics on muscle stem cells is also highlighted. In addition, we propose that alternative splicing interacts with epigenetic mechanisms to regulate skeletal muscle mass, offering a novel perspective that enhances our understanding of epigenetic inheritance's role and the regulatory network governing skeletal muscle atrophy. Collectively, advancements in the understanding of epigenetic mechanisms provide invaluable insights into the study of skeletal muscle atrophy. Moreover, this knowledge paves the way for identifying new avenues for the development of more effective therapeutic strategies and pharmaceutical interventions.

Skeletal Muscle Proteome Modifications following Antibiotic-Induced Microbial Disturbances in Cancer Cachexia

Cancer cachexia is an involuntary loss of body weight, mostly of skeletal muscle. Previous research favors the existence of a microbiota-muscle crosstalk, so the aim of the study was to evaluate the impact of microbiota alterations induced by antibiotics on skeletal muscle proteins expression. Skeletal muscle proteome changes were investigated in control (CT) or C26 cachectic mice (C26) with or without antibiotic treatment (CT-ATB or C26-ATB, n = 8 per group). Muscle protein extracts were divided into a sarcoplasmic and myofibrillar fraction and then underwent label-free liquid chromatography separation, mass spectrometry analysis, Mascot protein identification, and METASCAPE platform data analysis. In C26 mice, the atrogen mafbx expression was 353% higher than CT mice and 42.3% higher than C26-ATB mice. No effect on the muscle protein synthesis was observed. Proteomic analyses revealed a strong effect of antibiotics on skeletal muscle proteome outside of cachexia, with adaptative processes involved in protein folding, growth, energy metabolism, and muscle contraction. In C26-ATB mice, proteome adaptations observed in CT-ATB mice were blunted. Differentially expressed proteins were involved in other processes like glucose metabolism, oxidative stress response, and proteolysis. This study confirms the existence of a microbiota-muscle axis, with a muscle response after antibiotics that varies depending on whether cachexia is present.

Malnutrition management in children with chronic kidney disease

Chronic kidney disease (CKD) encompasses diverse conditions such as congenital anomalies, glomerulonephritis, and hereditary nephropathies, necessitating individualized nutritional interventions. Early detection is pivotal due to the heightened risk of adverse outcomes, including compromised growth and increased healthcare costs. The nutritional assessment in pediatric CKD employs a comprehensive, multidisciplinary approach, considering disease-specific factors, growth metrics, and dietary habits. The prevalence of malnutrition, as identified through diverse tools and guidelines, underscores the necessity for regular and vigilant monitoring. Nutritional management strategies seek equilibrium in calorie intake, protein requirements, and electrolyte considerations. Maintaining a well-balanced nutritional intake is crucial for preventing systemic complications and preserving the remaining kidney function. The nuanced landscape of enteral nutrition, inclusive of gastrostomy placement, warrants consideration in scenarios requiring prolonged support, with an emphasis on minimizing risks for optimized outcomes. In conclusion, the ongoing challenge of managing nutrition in pediatric CKD necessitates continuous assessment and adaptation. This review underscores the significance of tailored dietary approaches, not only to foster growth and prevent complications but also to enhance the overall quality of life for children grappling with CKD.

Fermented Yak-Kong using Bifidobacterium animalis derived from Korean infant intestine effectively relieves muscle atrophy in an aging mouse model

Yak-Kong (YK) is a small black soybean widely cultivated in Korea. It is considered to have excellent health functionality, as it has been reported to have better antioxidant efficacy than conventional black or yellow soybeans. Since YK has been described as good for the muscle health of the elderly in old oriental medicine books, this study sought to investigate the effect of fermented YK with Bifidobacterium animalis subsp. lactis LDTM 8102 (FYK) on muscle atrophy. In C2C12 mouse myoblasts, FYK elevated the expression of MyoD, total MHC, phosphorylated AKT, and PGC1α. In addition, two kinds of in vivo studies were conducted using both an induced and normal aging mouse model. The behavioral test results showed that in the induced aging mouse model, FYK intake alleviated age-related muscle weakness and loss of exercise performance. In addition, FYK alleviated muscle mass decrease and improved the expression of biomarkers including total MHC, myf6, phosphorylated AKT, PGC1α, and Tfam, which are related to myoblast differentiation, muscle protein synthesis, and mitochondrial generation in the muscle. In the normal aging model, FYK consumption did not increase muscle mass, but did upregulate the expression levels of biomarkers related to myoblast differentiation, muscle hypertrophy, and muscle function. Furthermore, it mitigated age-related declines in skeletal muscle force production and functional limitation by enhancing exercise performance and grip strength. Taken together, the results suggest that FYK has the potential to be a new functional food material that can alleviate the loss of muscle mass and strength caused by aging and prevent sarcopenia.

Circulating myostatin as a biomarker of muscle mass and strength in individuals with cancer or obesity

BACKGROUND & AIMS

Our study aims to determine whether myostatin (MSTN) is associated with muscle mass and strength in individuals with cancer or obesity, as well as with cancer cachexia (CC) or sarcopenic obesity (SO).

METHODS

The ACTICA study included individuals with CC (n = 70) or without CC (NC, n = 73). The MYDIASECRET study included individuals with obesity evaluated before (T0) and 3 months (T3) after bariatric surgery (n = 62). Body composition was assessed using bioelectrical impedance analysis (BIA). Skeletal muscle mass (SMM) and appendicular SMM (ASMM) were calculated from Janssen's and Sergi's equations, respectively, and expressed as indexes (SMMI and ASMMI). Handgrip strength (HGS) was assessed using a Jamar hand-held dynamometer. MSTN plasma levels were measured using ELISA. Spearman's coefficient was used to correlate MSTN with muscle mass and strength. Receiver operating characteristic (ROC) curve analysis was performed to identify an optimal MSTN cutoff level for the prediction of CC or SO.

RESULTS

In the ACTICA study, muscle mass and strength were lower in CC individuals than in NC individuals (SMMI: 8.0 kg/m2vs 9.0 kg/m2, p = 0.004; ASMMI: 6.2 kg/m2vs 7.2 kg/m2, p < 0.001; HGS: 28 kg vs 38 kg, p < 0.001). MSTN was also lower in CC individuals than in NC individuals (1434 pg/mL vs 2149 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN (SMMI: R = 0.500, p < 0.001; ASMMI: R = 0.479, p < 0.001; HGS: R = 0.495, p < 0.001). ROC curve analysis showed a MSTN cutoff level of 1548 pg/mL (AUC 0.684, sensitivity 57%, specificity 75%, p < 0.001) for the prediction of CC. In the MYDIASECRET study, muscle mass and strength were reduced at T3 (SMMI: -8%, p < 0.001; ASMMI: -12%, p < 0.001; HGS: -6%, p = 0.005). MSTN was also reduced at T3 (1773 pg/mL vs 2582 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN at T0 and T3 (SMMI-T0: R = 0.388, p = 0.002; SMMI-T3: R = 0.435, p < 0.001; HGS-T0: R = 0.337, p = 0.007; HGS-T3: R = 0.313, p = 0.013). ROC curve analysis showed a MSTN cutoff level of 4225 pg/mL (AUC 0.835, sensitivity 98%, specificity 100%, p = 0.014) for the prediction of SO at T3.

CONCLUSIONS

MSTN is positively correlated with muscle mass and strength in individuals with cancer or obesity, suggesting its potential use as a biomarker of muscle mass and strength. The ROC curve analysis suggests the potential use of MSTN as a screening tool for CC and SO.

mTORC1 and BMP-Smad1/5 regulation of serum-stimulated myotube hypertrophy: a role for autophagy

Protein synthesis regulation is critical for skeletal muscle hypertrophy, yet other established cellular processes are necessary for growth-related cellular remodeling. Autophagy has a well-acknowledged role in muscle quality control, but evidence for its role in myofiber hypertrophy remains equivocal. Both mammalian target of rapamycin complex I (mTORC1) and bone morphogenetic protein (BMP)-Smad1/5 (Sma and Mad proteins from Caenorhabditis elegans and Drosophila, respectively) signaling are reported regulators of myofiber hypertrophy; however, gaps remain in our understanding of how this regulation is integrated with growth processes and autophagy regulation. Therefore, we investigated the mTORC1 and Smad1/5 regulation of protein synthesis and autophagy flux during serum-stimulated myotube growth. Chronic serum stimulation experiments were performed on day 5 differentiated C2C12 myotubes incubated in differentiation medium [2% horse serum (HS)] or growth medium [5% fetal bovine serum (FBS)] for 48 h. Rapamycin or LDN193189 was dosed for 48 h to inhibit mTORC1 and BMP-Smad1/5 signaling, respectively. Acute serum stimulation was examined in day 7 differentiated myotubes. Protein synthesis was measured by puromycin incorporation. Bafilomycin A1 and immunoblotting for LC3B were used to assess autophagy flux. Chronic serum stimulation increased myotube diameter 22%, total protein 21%, total RNA 100%, and Smad1/5 phosphorylation 404% and suppressed autophagy flux. Rapamycin, but not LDN193189, blocked serum-induced myotube hypertrophy and the increase in total RNA. Acute serum stimulation increased protein synthesis 111%, Smad1/5 phosphorylation 559%, and rpS6 phosphorylation 117% and suppressed autophagy flux. Rapamycin increased autophagy flux during acute serum stimulation. These results provide evidence for mTORC1, but not BMP-Smad1/5, signaling being required for serum-induced myotube hypertrophy and autophagy flux by measuring LC3BII/I expression. Further investigation is warranted to examine the role of autophagy flux in myotube hypertrophy.NEW & NOTEWORTHY The present study demonstrates that myotube hypertrophy caused by chronic serum stimulation requires mammalian target of rapamycin complex 1 (mTORC1) signaling but not bone morphogenetic protein (BMP)-Smad1/5 signaling. The suppression of autophagy flux was associated with serum-induced myotube hypertrophy and mTORC1 regulation of autophagy flux by measuring LC3BII/I expression. Rapamycin is widely investigated for beneficial effects in aging skeletal muscle and sarcopenia; our results provide evidence that rapamycin can regulate autophagy-related signaling during myotube growth, which could benefit skeletal muscle functional and metabolic health.

Skeletal muscle: molecular structure, myogenesis, biological functions, and diseases

Skeletal muscle is an important motor organ with multinucleated myofibers as its smallest cellular units. Myofibers are formed after undergoing cell differentiation, cell-cell fusion, myonuclei migration, and myofibril crosslinking among other processes and undergo morphological and functional changes or lesions after being stimulated by internal or external factors. The above processes are collectively referred to as myogenesis. After myofibers mature, the function and behavior of skeletal muscle are closely related to the voluntary movement of the body. In this review, we systematically and comprehensively discuss the physiological and pathological processes associated with skeletal muscles from five perspectives: molecule basis, myogenesis, biological function, adaptive changes, and myopathy. In the molecular structure and myogenesis sections, we gave a brief overview, focusing on skeletal muscle-specific fusogens and nuclei-related behaviors including cell-cell fusion and myonuclei localization. Subsequently, we discussed the three biological functions of skeletal muscle (muscle contraction, thermogenesis, and myokines secretion) and its response to stimulation (atrophy, hypertrophy, and regeneration), and finally settled on myopathy. In general, the integration of these contents provides a holistic perspective, which helps to further elucidate the structure, characteristics, and functions of skeletal muscle.

Unravelling the complexity of the mitochondrial Ca2+ uniporter: regulation, tissue specificity, and physiological implications

Calcium (Ca2+) signalling acts a pleiotropic message within the cell that is decoded by the mitochondria through a sophisticated ion channel known as the Mitochondrial Ca2+ Uniporter (MCU) complex. Under physiological conditions, mitochondrial Ca2+ signalling is crucial for coordinating cell activation with energy production. Conversely, in pathological scenarios, it can determine the fine balance between cell survival and death. Over the last decade, significant progress has been made in understanding the molecular bases of mitochondrial Ca2+ signalling. This began with the elucidation of the MCU channel components and extended to the elucidation of the mechanisms that regulate its activity. Additionally, increasing evidence suggests molecular mechanisms allowing tissue-specific modulation of the MCU complex, tailoring channel activity to the specific needs of different tissues or cell types. This review aims to explore the latest evidence elucidating the regulation of the MCU complex, the molecular factors controlling the tissue-specific properties of the channel, and the physiological and pathological implications of mitochondrial Ca2+ signalling in different tissues.

Identifying the potential therapeutic effects of miR‑6516 on muscle disuse atrophy

Muscle atrophy is a debilitating condition with various causes; while aging is one of these causes, reduced engagement in routine muscle‑strengthening activities also markedly contributes to muscle loss. Although extensive research has been conducted on microRNAs (miRNAs/miRs) and their associations with muscle atrophy, the roles played by miRNA precursors remain underexplored. The present study detected the upregulation of the miR‑206 precursor in cell‑free (cf)RNA from the plasma of patients at risk of sarcopenia, and in cfRNAs from the muscles of mice subjected to muscle atrophy. Additionally, a decline in the levels of the miR‑6516 precursor was observed in mice with muscle atrophy. The administration of mimic‑miR‑6516 to mice immobilized due to injury inhibited muscle atrophy by targeting and inhibiting cyclin‑dependent kinase inhibitor 1b (Cdkn1b). Based on these results, the miR‑206 precursor appears to be a potential biomarker of muscle atrophy, whereas miR‑6516 shows promise as a therapeutic target to alleviate muscle deterioration in patients with muscle disuse and atrophy.

Enhanced protective effect of whey protein fermented with Lacticaseibacillus rhamnosus IM36 on dexamethasone-induced myotube atrophy

This study investigated the preventive potential of whey protein fermented with Lacticaseibacillus rhamnosus IM36 (FWP) against muscle atrophy induced by dexamethasone (DEX). FWP exhibited enhanced antioxidant activities compared with those of unfermented whey protein, effectively suppressing DEX-induced reactive oxygen species production. FWP was treated before the administration of 100 μM DEX on C2C12 myotubes and compared to unfermented whey (WP). DEX significantly inhibited myotube viability and muscle protein synthesis and enhanced degradation. FWP exhibited a dose-dependent attenuation of cell viability loss compared with that of WP. Additionally, FWP stimulated the formation of myotubes and muscle protein synthesis by upregulating myogenesis and insulin-like growth factor-1 expression. Furthermore, FWP significantly attenuated forkhead box protein O3a-mediated ubiquitin ligases and autophagy of lysosomes activated by DEX, inhibiting pathways that lead to muscle protein breakdown. These findings suggest that FWP enhances antioxidant activity and prevented DEX-induced muscle atrophy by regulating muscle protein homeostasis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01640-x.

The key role of myostatin b in somatic growth in fishes derived from distant hybridization

The basic mechanism of heterosis has not been systematically and completely characterized. In previous studies, we obtained three economically important fishes that exhibit rapid growth, WR (WCC ♀ × RCC ♂), WR-II (WR ♀ × WCC ♂), and WR-III (WR-II ♀ × 4nAU ♂), through distant hybridization. However, the mechanism underlying this rapid growth remains unclear. In this study, we found that WR, WR-II, and WR-III showed muscle hypertrophy and higher muscle protein and fat contents compared with their parent species (RCC and WCC). Candidate genes responsible for this rapid growth were then obtained through an analysis of 12 muscle transcriptomes. Notably, the mRNA level of mstnb (myostatin b), which is a negative regulator of myogenesis, was significantly reduced in WR, WR-II, and WR-III compared with the parent species. To verify the function of mstnb, a mstnb-deficient mutant RCC line was generated using the CRISPR-Cas9 technique. The average body weight of mstnb-deficient RCC at 12 months of age was significantly increased by 29.57% compared with that in wild-type siblings. Moreover, the area and number of muscle fibers were significantly increased in mstnb-deficient RCC, indicating hypertrophy and hyperplasia. Furthermore, the muscle protein and fat contents were significantly increased in mstnb-deficient RCC. The molecular regulatory mechanism of mstnb was then revealed by transcription profiling, which showed that genes related to myogenesis (myod, myog, and myf5), protein synthesis (PI3K-AKT-mTOR), and lipogenesis (pparγ and fabp3) were highly activated in hybrid fishes and mstnb-deficient RCC. This study revealed that low expression or deficiency of mstnb regulates somatic growth by promoting myogenesis, protein synthesis, and lipogenesis in hybrid fishes and mstnb-deficient RCC, which provides evidence for the molecular mechanism of heterosis via distant hybridization.

The role of TGF-β signaling in muscle atrophy, sarcopenia and cancer cachexia

Skeletal muscle, comprising a significant proportion (40 to 50 percent) of total body weight in humans, plays a critical role in maintaining normal physiological conditions. Muscle atrophy occurs when the rate of protein degradation exceeds protein synthesis. Sarcopenia refers to age-related muscle atrophy, while cachexia represents a more complex form of muscle wasting associated with various diseases such as cancer, heart failure, and AIDS. Recent research has highlighted the involvement of signaling pathways, including IGF1-Akt-mTOR, MuRF1-MAFbx, and FOXO, in regulating the delicate balance between muscle protein synthesis and breakdown. Myostatin, a member of the TGF-β superfamily, negatively regulates muscle growth and promotes muscle atrophy by activating Smad2 and Smad3. It also interacts with other signaling pathways in cachexia and sarcopenia. Inhibition of myostatin has emerged as a promising therapeutic approach for sarcopenia and cachexia. Additionally, other TGF-β family members, such as TGF-β1, activin A, and GDF11, have been implicated in the regulation of skeletal muscle mass. Furthermore, myostatin cooperates with these family members to impair muscle differentiation and contribute to muscle loss. This review provides an overview of the significance of myostatin and other TGF-β signaling pathway members in muscular dystrophy, sarcopenia, and cachexia. It also discusses potential novel therapeutic strategies targeting myostatin and TGF-β signaling for the treatment of muscle atrophy.

Korean Mint (Agastache rugosa) Extract and Its Bioactive Compound Tilianin Alleviate Muscle Atrophy via the PI3K/Akt/FoxO3 Pathway in C2C12 Myotubes

Skeletal muscle atrophy, which is characterized by diminished muscle mass, strength, and function, is caused by malnutrition, physical inactivity, aging, and diseases. Korean mint (Agastache rugosa Kuntze) possesses various biological functions, including anti-inflammatory, antioxidant, anticancer, and antiosteoporosis activities. Moreover, it contains tilianin, which is a glycosylated flavone that exerts antioxidant, anti-inflammatory, antidiabetic, and neuroprotective activities. However, no studies have analyzed the inhibitory activity of A. rugosa extract (ARE) and tilianin on muscle atrophy. Thus, the present study investigated the potential of ARE and tilianin on muscle atrophy and their underlying mechanisms of action in C2C12 myotubes treated with tumor necrosis factor-α (TNF-α). The results showed that ARE and tilianin promoted the phosphatidylinositol 3-kinase/protein kinase B pathway, thereby activating mammalian target of rapamycin (a protein anabolism-related factor) and its downstream factors. Moreover, ARE and tilianin inhibited the mRNA expression of muscle RING-finger protein-1 and atrogin-1 (protein catabolism-related factors) by blocking Forkhead box class O3 translocation. ARE and tilianin also mitigated inflammatory responses by downregulating nuclear factor-kappa B expression levels, thereby diminishing the expression levels of inflammatory cytokines, including TNF-α and interleukin-6. Additionally, ARE and tilianin enhanced the expression levels of antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase. Overall, these results suggest that ARE and tilianin are potential functional ingredients for preventing or improving muscle atrophy.

Respiratory SARS-CoV-2 Infection Causes Skeletal Muscle Atrophy and Long-Lasting Energy Metabolism Suppression

Muscle fatigue represents the most prevalent symptom of long-term COVID, with elusive pathogenic mechanisms. We performed a longitudinal study to characterize histopathological and transcriptional changes in skeletal muscle in a hamster model of respiratory SARS-CoV-2 infection and compared them with influenza A virus (IAV) and mock infections. Histopathological and bulk RNA sequencing analyses of leg muscles derived from infected animals at days 3, 30, and 60 post-infection showed no direct viral invasion but myofiber atrophy in the SARS-CoV-2 group, which was accompanied by persistent downregulation of the genes related to myofibers, ribosomal proteins, fatty acid β-oxidation, tricarboxylic acid cycle, and mitochondrial oxidative phosphorylation complexes. While both SARS-CoV-2 and IAV infections induced acute and transient type I and II interferon responses in muscle, only the SARS-CoV-2 infection upregulated TNF-α/NF-κB but not IL-6 signaling in muscle. Treatment of C2C12 myotubes, a skeletal muscle cell line, with combined IFN-γ and TNF-α but not with IFN-γ or TNF-α alone markedly impaired mitochondrial function. We conclude that a respiratory SARS-CoV-2 infection can cause myofiber atrophy and persistent energy metabolism suppression without direct viral invasion. The effects may be induced by the combined systemic interferon and TNF-α responses at the acute phase and may contribute to post-COVID-19 persistent muscle fatigue.

Epsti1 Regulates the Inflammatory Stage of Early Muscle Regeneration through STAT1-VCP Interaction

During muscle regeneration, interferon-gamma (IFN-γ) coordinates inflammatory responses critical for activation of quiescent muscle stem cells upon injury via the Janus kinase (JAK) - signal transducer and activator of transcription 1 (STAT1) pathway. Dysregulation of JAK-STAT1 signaling results in impaired muscle regeneration, leading to muscle dysfunction or muscle atrophy. Until now, the underlying molecular mechanism of how JAK-STAT1 signaling resolves during muscle regeneration remains largely elusive. Here, we demonstrate that epithelial-stromal interaction 1 (Epsti1), an interferon response gene, has a crucial role in regulating the IFN-γ-JAK-STAT1 signaling at early stage of muscle regeneration. Epsti1-deficient mice exhibit impaired muscle regeneration with elevated inflammation response. In addition, Epsti1-deficient myoblasts display aberrant interferon responses. Epsti1 interacts with valosin-containing protein (VCP) and mediates the proteasomal degradation of IFN-γ-activated STAT1, likely contributing to dampening STAT1-mediated inflammation. In line with the notion, mice lacking Epsti1 exhibit exacerbated muscle atrophy accompanied by increased inflammatory response in cancer cachexia model. Our study suggests a crucial function of Epsti1 in the resolution of IFN-γ-JAK-STAT1 signaling through interaction with VCP which provides insights into the unexplored mechanism of crosstalk between inflammatory response and muscle regeneration.

Quadriceps recovery and pain relief in knee osteoarthritis rats by cog polydioxanone filament insertion

Quadriceps muscles play a pivotal role in knee osteoarthritis (OA) progression and symptom manifestation, particularly pain. This research investigates the therapeutic effectiveness of muscle enhancement and support therapy (MEST), a recently developed device intended for intramuscular insertion of cog polydioxanone filaments, in quadriceps restoration to alleviate OA pain. Knee OA was induced in Sprague Dawley rats via monoiodoacetate injections. MEST or sham treatment was performed in OA or Naive rat quadriceps. Pain was assessed using paw withdrawal threshold and weight bearing. Quadriceps injury and recovery via MEST were evaluated using biomarkers, tissue morphology, muscle mass, contractile force and hindlimb torque. Satellite cell and macrophage activation, along with their activators, were also assessed. Data were compared at 1- and 3-weeks post-MEST treatment (M-W1 and M-W3). MEST treatment in OA rats caused muscle injury, indicated by elevated serum aspartate transferase and creatinine kinase levels, and local β-actin changes at M-W1. This injury triggered pro-inflammatory macrophage and satellite cell activation, accompanied by heightened interleukin-6 and insulin-like growth factor-1 levels. However, by M-W3, these processes gradually shifted toward inflammation resolution and muscle restoration. This was seen in anti-inflammatory macrophage phenotypes, sustained satellite cell activation and injury markers regressing to baseline. Quadriceps recovery in mass and strength from atrophy correlated with substantial OA pain reduction at M-W3. This study suggests that MEST-induced minor muscle injury triggers macrophage and satellite cell activation, leading to recovery of atrophied quadriceps and pain relief in OA rats.

Lactobacillus-derived protoporphyrin IX and SCFAs regulate the fiber size via glucose metabolism in the skeletal muscle of chickens

The gut microbiota contributes to skeletal muscle energy metabolism and is an indirect factor affecting meat quality. However, the role of specific gut microbes in energy metabolism and fiber size of skeletal muscle in chickens remains largely unknown. In this study, we first performed cecal microbiota transplantation from Chinese indigenous Jingyuan chickens (JY) to Arbor Acres chickens (AA), to determine the effects of microbiota on skeletal muscle fiber and energy metabolism. Then, we used metagenomics, gas chromatography, and metabolomics analysis to identify functional microbes. Finally, we validated the role of these functional microbes in regulating the fiber size via glucose metabolism in the skeletal muscle of chickens through feeding experiments. The results showed that the skeletal muscle characteristics of AA after microbiota transplantation tended to be consistent with that of JY, as the fiber diameter was significantly increased, and glucose metabolism level was significantly enhanced in the pectoralis muscle. L. plantarum, L. ingluviei, L. salivarius, and their mixture could increase the production of the microbial metabolites protoporphyrin IX and short-chain fatty acids, therefore increasing the expression levels of genes related to the oxidative fiber type (MyHC SM and MyHC FRM), mitochondrial function (Tfam and CoxVa), and glucose metabolism (PFK, PK, PDH, IDH, and SDH), thereby increasing the fiber diameter and density. These three Lactobacillus species could be promising probiotics to improve the meat quality of chicken.IMPORTANCEThis study revealed that the L. plantarum, L. ingluviei, and L. salivarius could enhance the production of protoporphyrin IX and short-chain fatty acids in the cecum of chickens, improving glucose metabolism, and finally cause the increase in fiber diameter and density of skeletal muscle. These three microbes could be potential probiotic candidates to regulate glucose metabolism in skeletal muscle to improve the meat quality of chicken in broiler production.

Lost in translation: challenges of current pharmacotherapy for sarcopenia

A healthy lifespan relies on independent living, in which active skeletal muscle is a critical element. The cost of not recognizing and acting earlier on unhealthy or aging muscle could be detrimental, since muscular weakness is inversely associated with all-cause mortality. Sarcopenia is characterized by a decline in skeletal muscle mass and strength and is associated with aging. Exercise is the only effective therapy to delay sarcopenia development and improve muscle health in older adults. Although numerous interventions have been proposed to reduce sarcopenia, none has yet succeeded in clinical trials. This review evaluates the biological gap between recent clinical trials targeting sarcopenia and the preclinical studies on which they are based, and suggests an alternative approach to bridge the discrepancy.

Mechanisms Underlying the Rarity of Skeletal Muscle Cancers

Skeletal muscle (SKM), despite comprising ~40% of body mass, rarely manifests cancer. This review explores the mechanisms that help to explain this rarity, including unique SKM architecture and function, which prohibits the development of new cancer as well as negates potential metastasis to SKM. SKM also presents a unique immune environment that may magnify the anti-tumorigenic effect. Moreover, the SKM microenvironment manifests characteristics such as decreased extracellular matrix stiffness and altered lactic acid, pH, and oxygen levels that may interfere with tumor development. SKM also secretes anti-tumorigenic myokines and other molecules. Collectively, these mechanisms help account for the rarity of SKM cancer.

Whole-genome SNP allele frequency differences between Tibetan and Large white pigs reveal genes associated with skeletal muscle growth

BACKGROUND

The skeletal muscle growth rate and body size of Tibetan pigs (TIB) are lower than Large white pigs (LW). However, the underlying genetic basis attributing to these differences remains uncertain. To address this knowledge gap, the present study employed whole-genome sequencing of TIB (slow growth) and LW (fast growth) individuals, and integrated with existing NCBI sequencing datasets of TIB and LW individuals, enabling the identification of a comprehensive set of genetic variations for each breed. The specific and predominant SNPs in the TIB and LW populations were detected by using a cutoff value of 0.50 for SNP allele frequency and absolute allele frequency differences (△AF) between the TIB and LW populations.

RESULTS

A total of 21,767,938 SNPs were retrieved from 44 TIB and 29 LW genomes. The analysis detected 2,893,106 (13.29%) and 813,310 (3.74%) specific and predominant SNPs in the TIB and LW populations, and annotated to 24,560 genes. Further GO analysis revealed 291 genes involved in biological processes related to striated and/or skeletal muscle differentiation, proliferation, hypertrophy, regulation of striated muscle cell differentiation and proliferation, and myoblast differentiation and fusion. These 291 genes included crucial regulators of muscle cell determination, proliferation, differentiation, and hypertrophy, such as members of the Myogenic regulatory factors (MRF) (MYOD, MYF5, MYOG, MYF6) and Myocyte enhancer factor 2 (MEF2) (MEF2A, MEF2C, MEF2D) families, as well as muscle growth inhibitors (MSTN, ACVR1, and SMAD1); KEGG pathway analysis revealed 106 and 20 genes were found in muscle growth related positive and negative regulatory signaling pathways. Notably, genes critical for protein synthesis, such as MTOR, IGF1, IGF1R, IRS1, INSR, and RPS6KA6, were implicated in these pathways.

CONCLUSION

This study employed an effective methodology to rigorously identify the potential genes associated with skeletal muscle development. A substantial number of SNPs and genes that potentially play roles in the divergence observed in skeletal muscle growth between the TIB and LW breeds were identified. These findings offer valuable insights into the genetic underpinnings of skeletal muscle development and present opportunities for enhancing meat production through pig breeding.

Bioreactor development for skeletal muscle hypertrophy and atrophy by manipulating uniaxial cyclic strain: proof of concept

Skeletal muscles overcome terrestrial, gravitational loading by producing tensile forces that produce movement through joint rotation. Conversely, the microgravity of spaceflight reduces tensile loads in working skeletal muscles, causing an adaptive muscle atrophy. Unfortunately, the design of stable, physiological bioreactors to model skeletal muscle tensile loading during spaceflight experiments remains challenging. Here, we tested a bioreactor that uses initiation and cessation of cyclic, tensile strain to induce hypertrophy and atrophy, respectively, in murine lineage (C2C12) skeletal muscle myotubes. Uniaxial cyclic stretch of myotubes was conducted using a StrexCell® (STB-1400) stepper motor system (0.75 Hz, 12% strain, 60 min day^-1). Myotube groups were assigned as follows: (a) quiescent over 2- or (b) 5-day (no stretch), (c) experienced 2-days (2dHY) or (d) 5-days (5dHY) of cyclic stretch, or (e) 2-days of cyclic stretch followed by a 3-day cessation of stretch (3dAT). Using ß-sarcoglycan as a sarcolemmal marker, mean myotube diameter increased significantly following 2dAT (51%) and 5dAT (94%) vs. matched controls. The hypertrophic, anabolic markers talin and Akt phosphorylation (Thr308) were elevated with 2dHY but not in 3dAT myotubes. Inflammatory, catabolic markers IL-1ß, IL6, and NF-kappaB p65 subunit were significantly higher in the 3dAT group vs. all other groups. The ratio of phosphorylated FoxO3a/total FoxO3a was significantly lower in 3dAT than in the 2dHY group, consistent with elevated catabolic signaling during unloading. In summary, we demonstrated proof-of-concept for a spaceflight research bioreactor, using uniaxial cyclic stretch to produce myotube hypertrophy with increased tensile loading, and myotube atrophy with subsequent cessation of stretch.

Unlocking the Nexus of Sirtuins: A Comprehensive Review of Their Role in Skeletal Muscle Metabolism, Development, and Disorders

The sirtuins constitute a group of histone deacetylases reliant on NAD+ for their activity that have gained recognition for their critical roles as regulators of numerous biological processes. These enzymes have various functions in skeletal muscle biology, including development, metabolism, and the body's response to disease. This comprehensive review seeks to clarify sirtuins' complex role in skeletal muscle metabolism, including glucose uptake, fatty acid oxidation, mitochondrial dynamics, autophagy regulation, and exercise adaptations. It also examines their critical roles in developing skeletal muscle, including myogenesis, the determination of muscle fiber type, regeneration, and hypertrophic responses. Moreover, it sheds light on the therapeutic potential of sirtuins by examining their impact on a range of skeletal muscle disorders. By integrating findings from various studies, this review outlines the context of sirtuin-mediated regulation in skeletal muscle, highlighting their importance and possible consequences for health and disease.

CARM1 drives mitophagy and autophagy flux during fasting-induced skeletal muscle atrophy

CARM1 (coactivator associated arginine methyltransferase 1) has recently emerged as a powerful regulator of skeletal muscle biology. However, the molecular mechanisms by which the methyltransferase remodels muscle remain to be fully understood. In this study, carm1 skeletal muscle-specific knockout (mKO) mice exhibited lower muscle mass with dysregulated macroautophagic/autophagic and atrophic signaling, including depressed AMP-activated protein kinase (AMPK) site-specific phosphorylation of ULK1 (unc-51 like autophagy activating kinase 1; Ser555) and FOXO3 (forkhead box O3; Ser588), as well as MTOR (mechanistic target of rapamycin kinase)-induced inhibition of ULK1 (Ser757), along with AKT/protein kinase B site-specific suppression of FOXO1 (Ser256) and FOXO3 (Ser253). In addition to lower mitophagy and autophagy flux in skeletal muscle, carm1 mKO led to increased mitochondrial PRKN/parkin accumulation, which suggests that CARM1 is required for basal mitochondrial turnover and autophagic clearance. carm1 deletion also elicited PPARGC1A (PPARG coactivator 1 alpha) activity and a slower, more oxidative muscle phenotype. As such, these carm1 mKO-evoked adaptations disrupted mitophagy and autophagy induction during food deprivation and collectively served to mitigate fasting-induced muscle atrophy. Furthermore, at the threshold of muscle atrophy during food deprivation experiments in humans, skeletal muscle CARM1 activity decreased similarly to our observations in mice, and was accompanied by site-specific activation of ULK1 (Ser757), highlighting the translational impact of the methyltransferase in human skeletal muscle. Taken together, our results indicate that CARM1 governs mitophagic, autophagic, and atrophic processes fundamental to the maintenance and remodeling of muscle mass. Targeting the enzyme may provide new therapeutic approaches for mitigating skeletal muscle atrophy.Abbreviation: ADMA: asymmetric dimethylarginine; AKT/protein kinase B: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ATG: autophagy related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; CARM1: coactivator associated arginine methyltransferase 1; Col: colchicine; CSA: cross-sectional area; CTNS: cystinosin, lysosomal cystine transporter; EDL: extensor digitorum longus; FBXO32/MAFbx: F-box protein 32; FOXO: forkhead box O; GAST: gastrocnemius; H2O2: hydrogen peroxide; IMF: intermyofibrillar; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; mKO: skeletal muscle-specific knockout; MMA: monomethylarginine; MTOR: mechanistic target of rapamycin kinase; MYH: myosin heavy chain; NFE2L2/NRF2: NFE2 like bZIP transcription factor 2; OXPHOS: oxidative phosphorylation; PABPC1/PABP1: poly(A) binding protein cytoplasmic 1; PPARGC1A/PGC-1α: PPARG coactivator 1 alpha; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase; PRMT: protein arginine methyltransferase; Sal: saline; SDMA: symmetric dimethylarginine; SIRT1: sirtuin 1; SKP2: S-phase kinase associated protein 2; SMARCC1/BAF155: SWI/SNF related, matrix associated, actin dependent regulator of chromatin subfamily c member 1; SOL: soleus; SQSTM1/p62: sequestosome 1; SS: subsarcolemmal; TA: tibialis anterior; TFAM: transcription factor A, mitochondrial; TFEB: transcription factor EB; TOMM20: translocase of outer mitochondrial membrane 20; TRIM63/MuRF1: tripartite motif containing 63; ULK1: unc-51 like autophagy activating kinase 1; VPS11: VPS11 core subunit of CORVET and HOPS complexes; WT: wild-type.

Cancer anorexia-cachexia syndrome is characterized by more than one inflammatory pathway

BACKGROUND

The interdependence of cytokines and appetite-modifying hormones implicated in cancer anorexia-cachexia syndrome (CACS) remains unclear. This study aimed to regroup these cytokines and hormones into distinct inflammatory (or non-inflammatory) pathways and determine whether these pathways can classify patients with CACS phenotypes.

METHODS

Clinical characteristics of 133 patients [61.7% male; mean age = 63.4 (SD: 13.1) years] with advanced cancer prior to oncology treatments were documented, including weight loss history. Patients completed the Functional Assessment of Anorexia-Cachexia Therapy (FAACT) questionnaire and Timed Up and Go test and had their sex-standardized skeletal muscle index (z-SMI) and fat mass index (z-FMI) derived using computed tomography scans. Their plasma levels of cytokines and appetite-modifying hormones were also determined. Date of death was recorded. Exploratory factor analysis (EFA) was used to regroup 15 cytokines and hormone into distinct inflammatory pathways (factors). For each patient, regression factor scores (RFS), which tell how strongly the patient associates with each factor, were derived. Two-step cluster analysis on the RFS was used to classify patients into groups. CACS phenotypes were correlated with RFS and compared between groups. Groups' survival was estimated using Kaplan-Meier analysis.

RESULTS

Patients had low z-SMI (mean = -3.78 cm2/m2; SD: 8.88) and z-FMI (mean = 0.08 kg2/m2; SD: 56.25), and 62 (46.6%) had cachexia. EFA identified three factors: (F-1) IFN-γ, IL-1β, Il-4, IL-6, IL-10, IL-12, TGFβ1 (positive contribution), and IL-18 (negative); (F-2) IL-8, IL-18, MCP-1, TGFβ1, TNF-α (positive), and ghrelin (negative); and (F-3) TRAIL and leptin (positive), and TGFβ1 and adiponectin (negative). RFS-1 was associated with cachexia (P = 0.002); RFS-2, with higher CRP (P < 0.0001) and decreased physical function (P = 0.01); and RFS-3 with better appetite (P = 0.04), lower CRP (P = 0.002), higher z-SMI (P = 0.04) and z-FMI (P < 0.0001), and less cachexia characteristics (all P < 0.001). Four patient groups were identified with specific RFS clusters aligning with the CACS continuum from no cachexia to pre-cachexia, cachexia, and terminal cachexia. Compared to the other two groups, groups 1 and 2 had higher plasma levels of IL-18 and TRAIL. Group 1 also had lower inflammatory cytokines, adiponectin, and CRP compared to the other three groups. Group 3 had inflammatory cytokine levels similar to group 2, except for TNF-α and leptin which were lower. Group 4 had very high inflammatory cytokines, adiponectin, and CRP compared to the other 3 groups (all P < 0.0001). Groups 3 and 4 had worse cachexia characteristics (P < 0.05) and shorter survival (log rank: P = 0.0009) than the other two groups.

CONCLUSIONS

This exploratory study identified three distinct pathways of inflammation, or lack thereof, characterizing different CACS phenotypes.

Clinical outcomes of multidimensional association of type 2 diabetes mellitus, COVID-19 and sarcopenia: an algorithm and scoping systematic evaluation

BACKGROUND

The aim of this study was to provide a scoping and comprehensive review for the clinical outcomes from the cross-link of Type 2 diabetes mellitus (T2DM), COVID-19, and sarcopenia.

METHODS

By using PRISMA guidelines and searching through different databases that could provide findings of evidence on the association of T2DM, COVID-19, and sarcopenia.

RESULTS

Thirty-three studies reported a relationship between sarcopenia with T2DM, twenty-one studies reported the prognosis COVID-19 in patients with T2DM, ten studies reported the prognosis of COVID-19 in patients with sarcopenia, five studies discussed the outcomes of sarcopenia in patients with COVID-19, and one study reported sarcopenia outcomes in the presence of T2DM and COVID-19.

CONCLUSION

There is an obvious multidimensional relationship between T2DM, COVID-19 and sarcopenia which can cause prejudicial effects, poor prognosis, prolonged hospitalisation, lowered quality of life and a higher mortality rate during the current COVID-19 pandemic.

Thbs1 regulates skeletal muscle mass in a TGFβ-Smad2/3-ATF4-dependent manner

Loss of muscle mass is a feature of chronic illness and aging. Here, we report that skeletal muscle-specific thrombospondin-1 transgenic mice (Thbs1 Tg) have profound muscle atrophy with age-dependent decreases in exercise capacity and premature lethality. Mechanistically, Thbs1 activates transforming growth factor β (TGFβ)-Smad2/3 signaling, which also induces activating transcription factor 4 (ATF4) expression that together modulates the autophagy-lysosomal pathway (ALP) and ubiquitin-proteasome system (UPS) to facilitate muscle atrophy. Indeed, myofiber-specific inhibition of TGFβ-receptor signaling represses the induction of ATF4, normalizes ALP and UPS, and partially restores muscle mass in Thbs1 Tg mice. Similarly, myofiber-specific deletion of Smad2 and Smad3 or the Atf4 gene antagonizes Thbs1-induced muscle atrophy. More importantly, Thbs1-/- mice show significantly reduced levels of denervation- and caloric restriction-mediated muscle atrophy, along with blunted TGFβ-Smad3-ATF4 signaling. Thus, Thbs1-mediated TGFβ-Smad3-ATF4 signaling in skeletal muscle regulates tissue rarefaction, suggesting a target for atrophy-based muscle diseases and sarcopenia with aging.

Association between the systemic immune-inflammation index and sarcopenia: a systematic review and meta-analysis

BACKGROUND

Sarcopenia is associated with increased morbidity and mortality. The systemic immune-inflammation index (SII) has been correlated to a variety of disorders. The present study conducted a systematic review and meta-analysis to investigate the relationship between SII and sarcopenia.

METHODS

A literature search was performed in Web of Science, PubMed, Embase, Cochrane Library, CINAHL, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, Wanfang Database, and VIP Chinese Science and Technology Database, from inception to March 2024. Then, the literature quality was assessed. After the heterogeneity test, a random effects or fixed effects model was applied to establish the forest plot, and investigate the relationship between SII and sarcopenia. Then, the sensitivity analysis and publication bias were examined.

RESULTS

Nine articles, which included 18,634 adults, were analyzed. Sarcopenic adults had higher SII levels, when compared to non-sarcopenic adults (standardized mean difference [SMD] = 0.66, 95% confidence interval [CI] = 0.22 - 0.19, p = 0.003). The high SII level was associated to the increased risk of sarcopenia (odds ratio = 1.52, 95% CI = 1.09-2.13, p = 0.01). In addition, the subgroup analysis revealed that the SII levels were higher in the sarcopenic group, when compared to the non-sarcopenic group, in elderly adults, as well as in adults with or without gastrointestinal disorders. The analysis was robust with a low risk of publication bias.

CONCLUSIONS

SII is closely associated to sarcopenia. Sarcopenic adults had elevated SII levels. The high SII level increased the risk of sarcopenia. Large scale multi-center prospective studies are required to validate these study findings.

AMPK as a mediator of tissue preservation: time for a shift in dogma?

Ground-breaking discoveries have established 5'-AMP-activated protein kinase (AMPK) as a central sensor of metabolic stress in cells and tissues. AMPK is activated through cellular starvation, exercise and drugs by either directly or indirectly affecting the intracellular AMP (or ADP) to ATP ratio. In turn, AMPK regulates multiple processes of cell metabolism, such as the maintenance of cellular ATP levels, via the regulation of fatty acid oxidation, glucose uptake, glycolysis, autophagy, mitochondrial biogenesis and degradation, and insulin sensitivity. Moreover, AMPK inhibits anabolic processes, such as lipogenesis and protein synthesis. These findings support the notion that AMPK is a crucial regulator of cell catabolism. However, studies have revealed that AMPK's role in cell homeostasis might not be as unidirectional as originally thought. This Review explores emerging evidence for AMPK as a promoter of cell survival and an enhancer of anabolic capacity in skeletal muscle and adipose tissue during catabolic crises. We discuss AMPK-activating interventions for tissue preservation during tissue wasting in cancer-associated cachexia and explore the clinical potential of AMPK activation in wasting conditions. Overall, we provide arguments that call for a shift in the current dogma of AMPK as a mere regulator of cell catabolism, concluding that AMPK has an unexpected role in tissue preservation.

LncRNA 4930581F22Rik promotes myogenic differentiation by regulating the ERK/MAPK signaling pathway

The skeletal muscle is the largest organ in mammals and is the primary motor function organ of the body. Our previous research has shown that long non-coding RNAs (lncRNAs) are significant in the epigenetic control of skeletal muscle development. Here, we observed progressive upregulation of lncRNA 4930581F22Rik expression during skeletal muscle differentiation. Knockdown of lncRNA 4930581F22Rik hindered skeletal muscle differentiation and resulted in the inhibition of the myogenic markers MyHC and MEF2C. Furthermore, we found that lncRNA 4930581F22Rik regulates myogenesis via the ERK/MAPK signaling pathway, and this effect could be attenuated by the ERK-specific inhibitor PD0325901. Additionally, in vivo mice injury model results revealed that lncRNA 4930581F22Rik is involved in skeletal muscle regeneration. These results establish a theoretical basis for understanding the contribution of lncRNAs in skeletal muscle development and regeneration.

Microbiota-derived 3-phenylpropionic acid promotes myotube hypertrophy by Foxo3/NAD+ signaling pathway

BACKGROUND

Gut microbiota and their metabolites play a regulatory role in skeletal muscle growth and development, which be known as gut-muscle axis. 3-phenylpropionic acid (3-PPA), a metabolite produced by colonic microorganisms from phenylalanine in the gut, presents in large quantities in the blood circulation. But few study revealed its function in skeletal muscle development.

RESULTS

Here, we demonstrated the beneficial effects of 3-PPA on muscle mass increase and myotubes hypertrophy both in vivo and vitro. Further, we discovered the 3-PPA effectively inhibited protein degradation and promoted protein acetylation in C2C12 and chick embryo primary skeletal muscle myotubes. Mechanistically, we supported that 3-PPA reduced NAD+ synthesis and subsequently suppressed tricarboxylic acid cycle and the mRNA expression of SIRT1/3, thus promoting the acetylation of total protein and Foxo3. Moreover, 3-PPA may inhibit Foxo3 activity by directly binding.

CONCLUSIONS

This study firstly revealed the effect of 3-PPA on skeletal muscle growth and development, and newly discovered the interaction between 3-PPA and Foxo3/NAD+ which mechanically promote myotubes hypertrophy. These results expand new understanding for the regulation of gut microbiota metabolites on skeletal muscle growth and development.

Considerations for cultivated crustacean meat: potential cell sources, potential differentiation and immortalization strategies, and lessons from crustacean and other animal models

Cultivated crustacean meat (CCM) is a means to create highly valued shrimp, lobster, and crab products directly from stem cells, thus removing the need to farm or fish live animals. Conventional crustacean enterprises face increasing pressures in managing overfishing, pollution, and the warming climate, so CCM may provide a way to ensure sufficient supply as global demand for these products grows. To support the development of CCM, this review briefly details crustacean cell culture work to date, before addressing what is presently known about crustacean muscle development, particularly the molecular mechanisms involved, and how this might relate to recent work on cultivated meat production in vertebrate species. Recognizing the current lack of cell lines available to establish CCM cultures, we also consider primary stem cell sources that can be obtained non-lethally including tissues from limbs which are readily released and regrown, and putative stem cells in circulating hemolymph. Molecular approaches to inducing myogenic differentiation and immortalization of putative stem cells are also reviewed. Finally, we assess the current status of tools available to CCM researchers, particularly antibodies, and propose avenues to address existing shortfalls in order to see the field progress.

Skeletal Muscle Injury in Chronic Kidney Disease-From Histologic Changes to Molecular Mechanisms and to Novel Therapies

Chronic kidney disease (CKD) is associated with significant reductions in lean body mass and in the mass of various tissues, including skeletal muscle, which causes fatigue and contributes to high mortality rates. In CKD, the cellular protein turnover is imbalanced, with protein degradation outweighing protein synthesis, leading to a loss of protein and cell mass, which impairs tissue function. As CKD itself, skeletal muscle wasting, or sarcopenia, can have various origins and causes, and both CKD and sarcopenia share common risk factors, such as diabetes, obesity, and age. While these pathologies together with reduced physical performance and malnutrition contribute to muscle loss, they cannot explain all features of CKD-associated sarcopenia. Metabolic acidosis, systemic inflammation, insulin resistance and the accumulation of uremic toxins have been identified as additional factors that occur in CKD and that can contribute to sarcopenia. Here, we discuss the elevation of systemic phosphate levels, also called hyperphosphatemia, and the imbalance in the endocrine regulators of phosphate metabolism as another CKD-associated pathology that can directly and indirectly harm skeletal muscle tissue. To identify causes, affected cell types, and the mechanisms of sarcopenia and thereby novel targets for therapeutic interventions, it is important to first characterize the precise pathologic changes on molecular, cellular, and histologic levels, and to do so in CKD patients as well as in animal models of CKD, which we describe here in detail. We also discuss the currently known pathomechanisms and therapeutic approaches of CKD-associated sarcopenia, as well as the effects of hyperphosphatemia and the novel drug targets it could provide to protect skeletal muscle in CKD.

Systemic LPS Administration Stimulates the Activation of Non-Neuronal Cells in an Experimental Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by deficiency of the survival motor neuron (SMN) protein. Although SMA is a genetic disease, environmental factors contribute to disease progression. Common pathogen components such as lipopolysaccharides (LPS) are considered significant contributors to inflammation and have been associated with muscle atrophy, which is considered a hallmark of SMA. In this study, we used the SMNΔ7 experimental mouse model of SMA to scrutinize the effect of systemic LPS administration, a strong pro-inflammatory stimulus, on disease outcome. Systemic LPS administration promoted a reduction in SMN expression levels in CNS, peripheral lymphoid organs, and skeletal muscles. Moreover, peripheral tissues were more vulnerable to LPS-induced damage compared to CNS tissues. Furthermore, systemic LPS administration resulted in a profound increase in microglia and astrocytes with reactive phenotypes in the CNS of SMNΔ7 mice. In conclusion, we hereby show for the first time that systemic LPS administration, although it may not precipitate alterations in terms of deficits of motor functions in a mouse model of SMA, it may, however, lead to a reduction in the SMN protein expression levels in the skeletal muscles and the CNS, thus promoting synapse damage and glial cells' reactive phenotype.

Brain-muscle communication prevents muscle aging by maintaining daily physiology

A molecular clock network is crucial for daily physiology and maintaining organismal health. We examined the interactions and importance of intratissue clock networks in muscle tissue maintenance. In arrhythmic mice showing premature aging, we created a basic clock module involving a central and a peripheral (muscle) clock. Reconstituting the brain-muscle clock network is sufficient to preserve fundamental daily homeostatic functions and prevent premature muscle aging. However, achieving whole muscle physiology requires contributions from other peripheral clocks. Mechanistically, the muscle peripheral clock acts as a gatekeeper, selectively suppressing detrimental signals from the central clock while integrating important muscle homeostatic functions. Our research reveals the interplay between the central and peripheral clocks in daily muscle function and underscores the impact of eating patterns on these interactions.