Search Results (670)

Background/Objectives: Malignant hyperthermia (MH) is a life-threatening pharmacogenetic disorder of skeletal muscle primarily associated with pathogenic variants in RYR1; however, a substantial proportion of MH-susceptible individuals lack identifiable variants in known genes. This study aimed to identify novel genetic contributors in Ca²⁺-induced Ca²⁺ release (CICR)-positive patients without RYR1 variants and to evaluate their functional relevance. Methods: Among 29 CICR-positive individuals without pathogenic variants identified by gene panel testing, five patients underwent whole-exome sequencing (WES). In one family, heterozygous variants in ANO5 (p.Arg547Gln) and ORAI3 (p.Arg287Cys) were identified. To evaluate their functional significance, intracellular Ca²⁺ dynamics were analyzed in primary myotubes derived from Case 165, an affected individual carrying both variants, and compared with those from CICR-negative controls and CICR-positive patients harboring RYR1 variants. Results: Myotubes derived from Case 165 demonstrated enhanced sensitivity to caffeine and 4-chloro-m-cresol, elevated resting intracellular Ca²⁺ levels, and greater Ca²⁺ reduction under Ca²⁺-free conditions compared with CICR-negative controls, resembling the phenotype observed in the RYR1 variant group. In contrast, dantrolene-induced Ca²⁺ reduction was significantly greater only in the RYR1 variant group. Conclusions: These findings suggest that ANO5 and ORAI3 variants may contribute to abnormal Ca²⁺ regulation in MH-susceptible individuals without RYR1 mutations and highlight the importance of combining genomic analysis with functional validation to identify novel genetic contributors to MH susceptibility. Full article

HS-1-associated protein X-1 (HAX-1) is a ubiquitously expressed, multifunctional protein that regulates Ca²⁺ homeostasis and cell survival in cardiac muscle. In addition to its well-established anti-apoptotic function, HAX-1 has recently been implicated in autophagy regulation. In the present study, we explored the molecular mechanisms underlying HAX-1-mediated autophagy modulation in cellular models, including cardiac-derived H9c2 myotubes. HAX-1 overexpression enhanced autophagic activity, as evidenced by decreased sequestosome-1 (p62), increased microtubule-associated protein light chain 3-II (LC3-II), enhanced LC3 puncta formation, and elevated autophagic flux. Conversely, HAX-1 knockdown attenuated autophagic activity. Mechanistically, co-immunoprecipitation assays showed that HAX-1 associates with both p62 and LC3. Bioinformatic analysis of the HAX-1 protein sequence identified two conserved LC3-interacting region (LIR) motifs within its N-terminal domain. Deletion of this LIR-containing region (HAX-1ΔLIR) reduced LC3 association, decreased autophagic activity, and impaired autophagy-dependent clearance of HAX-1 itself following autophagy induction, suggesting the importance of these motifs. At a cardiac-relevant level, HAX-1 promoted a chloroquine-sensitive reduction in protein levels of its known binding partner, phospholamban (PLN), a key regulator of sarcoplasmic reticulum (SR) Ca²⁺ cycling. These findings indicate a previously unrecognized LC3/LIR-dependent mechanism underlying HAX-1-mediated autophagy modulation and suggest a potential role for HAX-1 in SR protein proteostasis. Full article

Age-related skeletal muscle atrophy (sarcopenia) poses a major public health challenge, emphasizing the need for safe and effective interventions. Our previous studies demonstrated that C-C chemokine receptor type 5 (CCR5) is a key therapeutic target for skeletal muscle atrophy, as its activation by C-C motif chemokine ligand 11 (CCL11) promotes the dissociation and degradation of the structural protein α-actin, ultimately contributing to muscle loss. To identify potential CCR5 inhibitors, a database of 7860 natural alkaloids was constructed for pharmacophore-based virtual screening using the CCR5–Maraviroc crystal structure. Screening yielded 789 candidates, and subsequent batch molecular docking analysis identified Isoliensinine (ISO), a lotus seed alkaloid, as a potential CCR5 inhibitor with low binding energy (−10 kcal/mol) and stable hydrogen bonding interactions with Glu283 and Tyr251. Molecular dynamics simulations further confirmed the structural stability of the ISO–CCR5 complex. Molecular dynamics simulations further confirmed the structural stability of the ISO-CCR5 complex. In vitro, ISO dose-dependently inhibited CCL11-induced CCR5 activity (IC₅₀ = 1.314 μM) with low cytotoxicity in C2C12 myotubes, and markedly alleviated CCL11-induced myotube atrophy by suppressing CCR5 activation and the upregulation of the muscle atrophy–related markers MAFbx and MuRF1. These findings provide preliminary evidence for ISO as a potential CCR5-targeting candidate for further investigation in sarcopenia. Full article

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene that abolish dystrophin expression. Prime editing enables precise genome modification without generating double-strand DNA breaks or requiring donor DNA templates. We established an in vitro prime editing workflow to generate and subsequently correct the mdx5cv mutation in mouse C2C12 myoblasts. Following optimization of engineered prime editing guide RNAs (epegRNAs) and PAM-flexible prime editors, wild-type cells were edited, clonally isolated, and genotyped. Mutation correction was then evaluated using optimized epegRNA designs. Two rounds of prime editing introduced the mdx5cv mutation into approximately 20% of alleles in C2C12 cells creating the mdx5cv C2C12 cell line. Clonal isolation yielded five homozygous mutant clones among 59 expanded colonies. Optimization studies identified an epegRNA containing a 16 nucleotide reverse transcription template and a 10 nucleotide primer binding site (RTT16/PBS10) as the most efficient design. Correction of the pathogenic allele reached approximately 26%, whereas longer PBS lengths reduced editing efficiency. In silico off-target analysis using Cas-OFFinder identified no candidate genomic loci with fewer than three mismatches for the spacer sequences used in either mutation generation or correction, suggesting a favorable predicted specificity profile. Corrected mdx5cv C2C12 myoblasts retained their capacity to differentiate into multinucleated myotubes. Representative Western blot analysis detected dystrophin protein expression in differentiated corrected mdx5cv myotubes, consistent with successful correction of the pathogenic mutation. These findings establish a robust prime editing platform for both the generation and correction of the mdx5cv mutation and provide proof of concept that precise correction of the pathogenic mutation is associated with restoration of dystrophin expression following myogenic differentiation. Full article

Background/Objectives: In obese skeletal muscle, impaired insulin signalling and persistent low-grade inflammation frequently arise together, jointly driving metabolic dysfunction; yet a single intracellular node capable of simultaneously correcting both defects has not been identified. Curcumol is the principal active sesquiterpene of the traditional Chinese herb Curcuma zedoaria (Christm.) Rosc. We therefore sought to determine whether curcumol modulates obesity-driven insulin resistance and inflammatory activation in skeletal muscle, and to delineate the responsible molecular pathway. Methods: The study combined in vivo and in vitro experiments with network pharmacology, molecular docking, pharmacological inhibition, and cellular thermal shift assay (CETSA). In vivo experiments used mice rendered obese by prolonged high-fat diet (HFD) feeding; in vitro, insulin resistance was modelled in C2C12 myotubes via palmitate challenge. Network pharmacology implicated SRC as a principal candidate target, and molecular docking assigned SRC kinase the highest binding affinity for curcumol. Selective blockade of SRC (PP2) and PI3K (LY294002) was used to delineate the signalling hierarchy. Results: Network pharmacology and molecular docking identified SRC kinase as the highest-ranked candidate target of curcumol. In both HFD-induced obese mice and palmitate-challenged C2C12 myotubes, curcumol restored SRC phosphorylation and activated the downstream PI3K/AKT axis, concurrently improving insulin sensitivity and attenuating NF-kB-driven inflammatory responses. Selective PI3K inhibition abolished all functional benefits of curcumol without altering SRC phosphorylation, whereas SRC blockade with PP2 prevented both PI3K/AKT activation and the downstream recovery of insulin sensitivity and inflammatory suppression, placing SRC upstream of PI3K/AKT in the signalling order. Direct binding of curcumol to SRC protein was confirmed by a cellular thermal shift assay. Conclusions: Curcumol directly engages SRC kinase and, through subsequent PI3K/AKT axis activation, concurrently rescues skeletal muscle insulin sensitivity and suppresses metabolic inflammation. These findings provide mechanistic justification for developing curcumol as a candidate dietary bioactive compound toward preventing and treating obesity-related metabolic disturbances. Full article

Background/Objectives: Sarcopenia involves a gradual decline in skeletal muscle mass that may occur during aging or in association with chronic pathological conditions. It markedly reduces muscle strength and mobility, thereby impairing quality of life. Because sarcopenia’s severity directly correlates with frailty, it represents an important predictor of prognosis and disease risk. Current preventive and therapeutic strategies rely mainly on physical activity, which is not feasible for all patients. This study investigated the biological effects of two independently prepared Tuber borchii (T. borchii) extracts in an in vitro model of sarcopenic stress. Methods: The activity of T. borchii extracts was investigated in a cell-based model of sarcopenia, following previous observations that these preparations influence proliferation-related pathways, including ERK1/2 phosphorylation. Specifically, differentiated myotubes were exposed to D-galactose to reproduce atrophy-associated cellular changes, and the impact of T. borchii extracts on protein synthesis, turnover, and cell morphology was assessed. Results: T. borchii extracts enhanced protein synthesis and turnover in myotubes. Furthermore, the treatment significantly reduced the expression of key galactose-induced sarcopenia and atrophy markers, such as MuRF1. Morphological analysis confirmed this protective effect, showing that treated myotubes maintained greater thickness and exhibited a larger cross-sectional area despite exposure to the sarcopenic stimulus. Conclusions: These results indicate that T. borchii extracts can attenuate selected cellular alterations associated with muscle aging. Future identification of the most active components may support their development as nutraceutical supplements. Full article

Molecule Interacting with CasL 1 (MICAL1) is a flavoprotein monooxygenase that promotes filamentous actin (F-actin) depolymerization. Transcriptomic studies have linked MICAL1 downregulation to skeletal muscle atrophy and muscular dystrophy, yet its functional contribution to myogenesis remains unexplored. We found that MICAL1 protein increased progressively during myogenic differentiation of C2C12 cells, reaching a maximum on day 5 in parallel with myosin heavy chain (MyHC). siRNA-mediated MICAL1 silencing produced an ~1.7-fold accumulation of F-actin, while total β-actin protein remained unchanged, indicating a shift in the G-/F-actin equilibrium toward polymerization rather than altered actin expression. The accumulated F-actin reduced YAP1 phosphorylation, promoted its nuclear translocation, and increased the expression of the YAP1 target gene CTGF. MICAL1 depletion also enhanced myoblast proliferation: EdU incorporation and cell viability increased, and PCNA, CCNB1, and CCND1 protein expression was upregulated, while the cell cycle distribution shifted toward the G2/M phase, with a reciprocal loss in G0/G1. Concurrently, MICAL1 knockdown suppressed MyoD, Myogenin, and MyHC throughout differentiation and severely impaired myotube formation, with reductions in the fusion index, myotube area, and length. We conclude that MICAL1 is required for the proliferation-to-differentiation switch in myoblasts and that its activity restrains F-actin-driven YAP1 signaling to permit timely myogenic commitment. MICAL1 may therefore represent a candidate for further investigation in muscle-wasting diseases. Full article

The growing global demand for ethical, resource-efficient protein sources has renewed serious interest in cultured meat as a viable alternative to conventional livestock production. Two revolutionary biotechnological systems, induced pluripotent stem cell (iPSC) reprogramming and CRISPR-Cas9-mediated genome editing, when combined, offer unparalleled accuracy and scalability for the biofabrication of avian flesh. In this review, we present a comprehensive pipeline that involves the ectopic expression of Yamanaka factors (Oct4, Sox2, Klf4, and c-Myc) to reprogram primary somatic cells derived from Gallus gallus into induced pluripotent stem cells (iPSCs). This process is subsequently followed by targeted genome editing to enhance myogenic potential, growth efficiency, nutritional composition, and disease resistance. iPSCs are cultivated in a xeno-free bioreactor following genome editing, and subsequently directed to develop into myoblasts and mature myotubes. Three-dimensional tissue biofabrication is realized by combining biomaterial scaffolds and perfusion bioreactor systems, structuring an authentic muscle tissue matrix. These engineering platforms enable precise control over microenvironmental parameters, including oxygenation and nutrient perfusion. The resulting biofabricated poultry product is compositionally optimized, free of antibiotic residues, and exhibits a significantly reduced environmental footprint than poultry that is grown in the traditional way. This all-in-one solution solves important problems in food security, animal welfare, land use efficiency, and greenhouse gas emissions while also setting up a scalable biomanufacturing framework for making proteins for the next generation. Full article

The development of reusable and biocompatible biomaterial-based culture substrates is increasingly relevant for improving sustainability in biomedical research workflows. In this study, polyethylene terephthalate glycol-modified (PETG) was evaluated as a potential alternative to conventional polystyrene (PS) for in vitro cell culture applications. PETG substrates were fabricated through laser cutting and tested for their ability to support cell adhesion, viability, proliferation, and lineage-specific differentiation across multiple human cell models, including calvarial mesenchymal stromal cells (CMSCs), bone marrow-derived mesenchymal stromal cells (hBM-MSCs), dermal fibroblasts, LHCN-M2 myoblasts, and SH-SY5Y neuroblastoma cells. Morphological and immunofluorescence analyses demonstrated that PETG supported cell attachment and focal adhesion formation, comparable to standard PS surfaces. Cell viability and proliferation assays confirmed metabolic activity and growth over time. Furthermore, PETG substrates supported osteogenic, adipogenic, myogenic, and neuronal differentiation, as demonstrated by histological staining, myotube formation, neurite outgrowth, and lineage-specific gene expression analyses. Finally, PETG maintained CMSC morphology and metabolic activity after repeated recovery, ethanol/UV treatment, and gelatin re-coating, with comparable results between new substrates and those reused for up to three cycles. These findings support PETG as a biocompatible culture substrate with preliminary short-term reuse potential and possible sustainability benefits for laboratory workflows. Full article

β-hydroxy-β-methylbutyrate (HMB), a bioactive metabolite of leucine, is widely recognized for its anabolic and anti-catabolic effects in skeletal muscle. However, the molecular mechanisms underlying these effects, particularly in relation to circadian regulation, remain incompletely understood. Here, we investigated the impact of HMB on dexamethasone-induced muscle atrophy in C2C12 myotubes, with a focus on anabolic signaling and circadian clock regulation. C2C12 myotubes were treated with HMB or HMB after dexamethasone-induced atrophy. HMB treatment significantly improved cell viability, surface area and fiber diameter by reducing expression of CBL-B, MuRF1 and Atrogin1, key mediators of muscle proteolysis, and increasing myogenin expression compared with atrophic conditions. While HMB did not activate AKT or mTOR, it robustly increased phosphorylation of P70S6K and S6 through a phospholipase D (PLD)-dependent mechanism. HMB restored disrupted circadian clock gene expression induced by dexamethasone, including normalization of expression patterns. HMB also enhanced circadian rhythmic amplitude and advanced phase timing, indicating improved clock robustness. These findings identify circadian regulation as a novel target of HMB action and demonstrate that HMB preserves muscle homeostasis through coordinated modulation of anabolic signaling and intrinsic circadian machinery. This study provides mechanistic insight into how HMB protects against muscle atrophy and highlights circadian regulation as an important contributor to skeletal muscle health. Full article

Cynops orientalis, a member of the Salamandridae family, can regenerate severely injured limbs throughout its lifespan. The molecular mechanisms regulating limb regeneration in C. orientalis remain largely unknown. SERCA1 (sarcoplasmic/endoplasmic reticulum calcium ATPase 1) is a major sarco/endoplasmic reticulum calcium pump in skeletal muscle, and our previous transcriptomic sequencing results showed increased SERCA1 mRNA expression during the early stages of newt limb regeneration. In the present study, we investigated the role and regulatory mechanism of SERCA1 during newt limb regeneration by using a limb-amputation model, shRNA-mediated knockdown, Thapsigargin-mediated SERCA1 inhibition, miRNAomics analysis, dual-luciferase reporter assays and Agomir therapy. Knockdown of SERCA1 expression or suppression of SERCA1 activity impaired skeletal muscle cell dedifferentiation, disrupted AEC and blastema formation, reduced cell proliferation, and significantly delayed limb regeneration compared with control animals. Through miRNAomics analysis and in vitro dual-luciferase reporter assays, we identified miR-20487-5p as a negative regulator of SERCA1 expression in C. orientalis. In vivo treatment with miR-20487-5p Agomir down-regulated SERCA1 expression resulted in limb-regenerative defects. Mechanistically, shRNA-SERCA1 or miR-20487-5p Agomir treatment reduced ERK phosphorylation in regenerating limb tissue, suggesting an association between the miR-20487-5p/SERCA1 axis and MAPK/ERK activation. Taken together, our study supports the significant role of the miR-20487-5p/SERCA1/MAPK/ERK axis in early newt limb regeneration. This study expands the current understanding of molecular mechanisms initiating newt limb regeneration. Full article

Piscirickettsia salmonis is one of the most significant pathogens affecting salmon farming. Besides liver, head kidney and spleen, skeletal muscle has shown transcriptional immune responses to these bacteria, but the contribution of non-coding RNAs remains poorly understood. This study investigates the role of long non-coding RNAs (lncRNAs) in the immune response of rainbow trout skeletal muscle and primary myotube cultures infected with P. salmonis. Using RNA-seq data from both in vivo and in vitro muscle under control and infected conditions, the analysis identified 4263 candidate lncRNAs through a stringent bioinformatics pipeline. These lncRNAs were mostly classified as exonic and intergenic, showing distinct genomic distributions and structural differences depending on the source. Expression analyses revealed that cell type had a stronger effect on lncRNA profiles than infection status. From 764 differentially expressed lncRNAs, 191 were uniquely associated with infected and 180 with control conditions, mainly unannotated. Functional predictions based on co-expression and proximity to coding genes suggest that lncRNAs are primarily involved in downregulation of structural-cellular maintenance under control conditions, whereas during infection, they are related to immunity, signaling, and apoptosis. Overall, the findings indicate that lncRNAs exhibit origin-specific regulatory roles and are modulated by P. salmonis infection, highlighting their potential importance in fish immune responses. Full article

Sarcopenia is characterized by progressive loss of skeletal muscle mass and function and is a major contributor to frailty, disability, and mortality in older adults. Store-operated calcium entry (SOCE) is a crucial regulator of skeletal muscle calcium homeostasis, and impaired SOCE has been linked to age-related muscle weakness. Here, we identify the synaptophysin family member synaptophysin-like protein 2, also known as mitsugumin 29 (MG29; encoded by the human gene SYPL2 and the mouse ortholog Mg29), as a key organizer of triad membrane cholesterol and lipid signaling required for normal SOCE during aging. Using Mg29^−/− mice as a model of accelerated sarcopenia, together with RNA interference against Mg29 in adult muscle and primary myotubes, we quantified changes in muscle morphology, contractile function, SOCE activity, and targeted lipidomic profiles. Reduced MG29 expression led to decreased muscle fiber cross-sectional area, reduced specific force, blunted SOCE, and marked alterations in membrane cholesterol content and fatty acid-derived lipid mediators. Cholesterol depletion by methyl-β-cyclodextrin in wild-type myotubes produced SOCE defects similar to those observed in aged wild-type and young Mg29^−/− muscles, indicating that MG29-dependent maintenance of membrane cholesterol is required for normal SOCE. Acute Mg29 knockdown also altered myogenic differentiation, the expression of calcium-handling and stress-response genes, and the release and consumption of specific polyunsaturated fatty acid-derived lipid mediators. Together, these findings identify MG29 as a critical regulator of SOCE and lipid signaling in skeletal muscle and suggest that its age-related decline contributes to sarcopenia by disrupting triad membrane organization and excitation–contraction coupling. Full article

Background: Cancer-associated cachexia (CAC) can affect up to 80% of patients with late-stage cancer and is characterized by depletion of skeletal muscle mass with or without loss of fat tissue. No effective treatments are currently available, and reversing CAC requires understanding the intracellular processes of muscle atrophy and its cancer-related extracellular triggers. In this study, we aimed to disentangle tumor- and host-driven mechanisms in CAC muscle wasting. Methods: In skeletal muscle tissue obtained from control non-tumor-bearing mice and cachectic mice resulting from orthotopically implanted 344P lung adenocarcinoma cells, transcriptomic analyses were performed to identify muscle wasting-associated processes. To explore whether these reflected direct tumor-induced effects, 344P tumor-conditioned medium (tCM) was applied to in vitro cultured C2C12 skeletal muscle cells to investigate the impact on muscle proteolysis, myogenesis and mitochondrial function. Results: RNAseq data revealed increased proteolysis along with decreased myogenesis-related processes, and prominent downregulation of genes encoding mitochondrial OXPHOS complexes, in cachectic mouse muscle. Exposure of cultured skeletal muscle cells to tCM reduced mitochondrial respiration and induced changes in mitochondrial mass and mitochondrial DNA copy number. tCM did not induce myotube atrophy, or activation of proteolysis-related signaling, in fully differentiated myotubes. In contrast, tCM reversibly inhibited myoblast–myotube fusion, and reduced myogenic and muscle-specific gene expression in differentiating myoblasts. Application of CCCP to simulate muscle mitochondrial dysfunction reproduced the myogenesis-impairing phenotype caused by tCM. Conclusions: Our results show that factors present in the cachexia-inducing lung tumor secretome directly impair myogenesis and muscle mitochondrial function, whereas activation of muscle catabolic processes requires host-dependent mechanisms. Full article

Background/Objectives: Rumex obtusifolius L. (Polygonaceae) has been traditionally used to treat various disorders, including hepatic and gastrointestinal diseases. However, the phytochemical constituents of its roots and their potential protective effects against skeletal muscle atrophy remain poorly understood. This study aimed to isolate and characterize bioactive constituents from R. obtusifolius roots and evaluate their protective effects against dexamethasone (DEX)-induced muscle atrophy in C2C12 myotubes. Methods: LC–MS-guided phytochemical investigation of the ethanol extract of R. obtusifolius roots, followed by successive column chromatography and HPLC purification, resulted in the isolation of four naphthalene-type glycosides. Their structures were elucidated using 1D and 2D NMR spectroscopy, HR-ESIMS, and chemical transformation. The protective effects of compounds 1 and 4 against dexamethasone (DEX)-induced muscle atrophy were evaluated by assessing myotube morphology, myogenic and atrophy-related protein expression, and PI3K/Akt/mTOR signaling. Results: A new naphthalene malonylglucoside, nepodin-8-O-β-D-(6′-O-malonyl)-glucopyranoside (1), together with three known glycosides (2–4), was identified. Among the isolated compounds, compound 1 significantly attenuated DEX-induced muscle atrophy in a concentration-dependent manner by increasing myotube diameter and improving myotube morphology. It restored the expression of the myogenic markers MyoD and myogenin while suppressing the atrophy-related proteins MuRF1 and MAFBX. Furthermore, compound 1 reversed DEX-induced suppression of the PI3K/Akt/mTOR signaling pathway, indicating recovery of anabolic signaling. Conclusions: This study reports a new naphthalene malonylglucoside (1) from R. obtusifolius roots and demonstrates that compound 1 protects against DEX-induced skeletal muscle atrophy through restoration of myogenic differentiation and activation of the PI3K/Akt/mTOR pathway. These findings suggest that compound 1 is a promising natural lead compound for the development of therapeutics targeting muscle wasting disorders. Full article