Search

Objective: Sarcopenia manifests as a chronic, low-level inflammation along with multiple inflammatory cells infiltration. Interleukin (IL)-25 can regulate the function of macrophages. However, the specific role and mechanisms through which IL-25 functions in sarcopenia are still not fully understood and require further investigation., Methods: Aged mice were utilized as sarcopenia models and examined the expression of inflammatory factors. To investigate the effects of IL-25 on sarcopenia, the model mice received IL-25 treatment and underwent in vivo adoptive transfer of IL-25-induced macrophages. Meanwhile, RAW264.7 cells, bone marrow-derived macrophages, satellite cells and C2C12 cells were used in vitro. Shh insufficiency was induced through intramuscular administration of SHH-shRNA adenoviruses. Then, various assays including scratch wound, cell counting kit-8 and Transwell assays, as well as histological staining and molecular biological methods, were conducted., Results: Aged mice exhibited an accelerated decline in muscle strength and mass, along with an increased muscle lipid droplets and macrophage infiltration, and decreased IL-25 levels compared to the young group. IL-25 therapy and the transfer of IL-25-preconditioned macrophages could improve these conditions by promoting M2 macrophage polarization in vivo as well as in vitro. M2 macrophage conditioned medium enhanced satellite cell proliferation and migration, as well as the vitality, migration, and differentiation of C2C12 cells in vitro. Furthermore, IL-25 enhanced Shh expression in macrophages in vitro, and activated the Shh signaling pathway in muscle tissue of aged mice, which could be suppressed by either the inhibitor cyclopamine or Shh knockdown. Mechanistic studies showed that Shh insufficiency suppressed the activation of Akt/mTOR signaling pathway in muscle tissue of aged mice., Conclusion: IL-25 promotes the secretion of Shh by M2 macrophages and activates the Shh/Akt/mTOR signaling pathway, which improves symptoms and function in sarcopenia mice. This suggests that IL-25 has potential as a therapeutic agent for treating sarcopenia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Obesity-induced muscle atrophy leads to physical impairment and metabolic dysfunction, which are risky for older adults. The activity of pyruvate dehydrogenase (PDH), a critical regulator of glucose metabolism, is reduced in obesity. Additionally, PDH activator dichloroacetate (DCA) improves metabolic dysfunction. However, the effects of PDH activation on skeletal muscles in obesity remain unclear. Thus, this study aimed to evaluate the effects of PDH activation by DCA treatment on obesity-induced muscle atrophy in vitro and in vivo and elucidate the possible underlying mechanisms. Results showed that PDH activation by DCA treatment ameliorated muscle loss, decreased the cross-sectional area, and reduced grip strength in C57BL/6 mice fed a high-fat diet (HFD). Elevation of muscle atrophic factors atrogin-1 and muscle RING-finger protein-1 (MuRF-1) and autophagy factors LC3BII and p62 were abrogated by DCA treatment in palmitate-treated C2C12 myotubes and in the skeletal muscles of HFD-fed mice. Moreover, p-Akt, p-FoxO1, and p-FoxO3 protein levels were reduced and p-NF-κB p65 and p-p38 MAPK protein levels were elevated in palmitate-treated C2C12 myotubes, which were restored by DCA treatment. However, the protective effects of DCA treatment against myotube atrophy were reversed by treatment with Akt inhibitor MK2206. Taken together, our study demonstrated that PDH activation by DCA treatment can alleviate obesity-induced muscle atrophy. It may serve as a basis for developing novel strategies to prevent obesity-associated muscle loss., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biallelic pathogenic variants in INPP5K have been associated with a rare congenital muscular dystrophy that presents with muscle weakness, short stature, intellectual disability, and early-onset cataracts. A characteristic pattern of muscle involvement has been identified on muscle MRI in a small case series, including involvement of the vasti, anterior tibialis, and peronei with relative sparing of the rectus femoris, sartorius, and gracilis muscles. This case describes a patient who initially presented in infancy with hypotonia, motor delays, and short stature. She was eventually diagnosed at almost 3 years with INPP5K -related muscular dystrophy after extensive workup that included multiple subspecialist evaluations, genetic testing for non-neuromuscular disorders, and a muscle biopsy. Muscle ultrasound (MUS) was performed at the end of this diagnostic journey, which demonstrated characteristic features that supported the diagnosis, including notable involvement of the vasti muscles with sparing of the rectus femoris. This case highlights how MUS can be a useful tool in the evaluation of children for neuromuscular disorders. MUS can help refine the differential and guide further steps in evaluation when performed early in the diagnostic process and may help clarify interpretation of genetic testing results when performed later.

Objectives: To investigate the therapeutic effect and mechanism of Danggui Buxue Tang in the treatment of biceps longus tendon lesions, and to preliminarily explore the relevant factors affecting this injury., Methods: Using network pharmacology analysis methods, the potential mechanism of Danggui Buxue Tang in treating key lesions of the long head of the biceps brachii muscle was studied., Results: Model analysis revealed 44 protein-protein interactions associated with long head binding. The distribution of 19 strongly correlated targets is Pharmaper>SEA>Stitch>Swiss. Further discovery revealed 17 immune system and inflammation related KEGG pathways with P values less than 0.01. The TNF and sphingolipid signaling pathways are associated with inflammation, while the MAPK signaling pathway is associated with immunity. Finally, it was found that the FoxO and HIF-1 signaling pathways are directly associated with long head restraint injury in the biceps brachii muscle., Conclusion: Danggui Buxue Tang inhibits related pathways, regulates the immune system, reduces inflammation, and alleviates disease progression. Danggui Buxue Tang can be an effective choice for treating combined lesions of the long head of the biceps brachii muscle., Competing Interests: The authors have no conflict of interest.

Background/aim: Postoperative changes in body composition, especially loss of muscle mass, often occur in gastrointestinal cancer patients. Few studies have reported perioperative changes in the body composition of patients with colorectal cancer. Therefore, this study aimed at clarifying changes in body composition during the perioperative period and identifying risk factors for skeletal muscle mass loss in patients with colorectal cancer., Patients and Methods: This prospective observational study included 148 patients who underwent robot- or laparoscopic-assisted surgery for colorectal cancer., Results: The rate of change in body composition at discharge was -6.25% for body fat, with a higher rate of decrease than that for skeletal muscle mass (-3.30%; p=0.0006) and body water mass (-2.66%; p=0.0001). Similarly, even at one month postoperatively, body fat mass (-8.05%) was reduced at a greater rate than skeletal muscle mass (-2.02% p=0.0001) and body water mass (-1.33% p=0.0001).The site-specific percent change in limb skeletal and trunk muscle mass at discharge was the greatest in the lower extremities at -5.37%, but one month after surgery, the upper extremities had the greatest change at -4.44%. The Prognostic Nutritional Index (PNI) influenced skeletal muscle mass loss at discharge [odds ratio (OR)=2.6; 95% confidence interval (CI)=1.30-5.58], while diabetes (OR=4.1; 95%CI=1.40-12.43) and ileostomy (OR=6.7; 95%CI=1.45-31.11) influenced skeletal muscle loss one month postoperatively., Conclusion: Preoperative and postoperative nutritional guidance/intervention and body part-specific rehabilitation should be provided to prevent skeletal muscle mass loss in patients with low PNI, diabetes, and those undergoing ileostomy., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Abstract: X-linked myopathy with excessive autophagy is a rare disorder caused by a mutation in the vacuolar ATPase assembly factor gene which causes slowly progressive early onset proximal weakness and loss of ambulation by the age of 50-70 years. Electrodiagnostic (EDx) testing usually shows widespread complex repetitive and myotonic discharges, even in muscles unaffected clinically. We report a 65-year-old man who presented with progressive proximal weakness since his teenage years. Extensive workup over 30 years revealed inconclusive EDx and muscle histopathology findings. The diagnosis was finally made with genetic testing. Subsequent neuromuscular ultrasound was more informative of disease severity than repeat EDx and directed a muscle biopsy that showed an autophagic vacuolar myopathy and the novel identification of vacuoles in capillary endothelial cells. Although genetic testing is required for confirmation, in milder cases of X-linked myopathy with excessive autophagy, neuromuscular ultrasound may aid in diagnosis even when EDx findings are inconclusive., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

TIA1/SQSTM1 myopathy is one of the few digenic myopathies. We describe four new French adult male patients carrying the TIA1 p.Asn357Ser and SQSTM1 p.Pro392Leu variant and review the literature to include 20 additional cases to define the spectrum of the disease. These twenty-four patients (75% males) had late-onset (52,6 ± 10,1 years), mainly asymmetric, distal ankle and hand finger extension weakness (75%), mild CK elevation (82.4%) and myopathic EMG. Two of the four French patients had sensorimotor axonal polyneuropathy and an additional one had neurogenic changes in muscle biopsy. Muscle biopsy showed rimmed vacuoles (44.4%), myofibrillar disorganization (16.7%) or both (38.9%), with P62/TDP43 aggregates. The TIA1 p.Asn357Ser variant was present in all patients and the SQSTM1 p.Pro392Leu was the most frequent (71%) of the four reported SQSTM1 variants. We reviewed the distal myopathy gene panels of Pitié-Salpêtrière's hospital cohort finding a prevalence of 11/414=2.7% of the TIA1 p.Asn357Ser variant, with two patients having an alternative diagnosis (TTN and MYH7) with atypical phenotypes, resembling some of the features seen in TIA1/SQSTM1 myopathy. Overall, TIA1/SQSTM1 myopathy has a homogenous phenotype reinforcing the pathogenicity of its digenic variants. We confirm an increased burden of the TIA1 p.Asn357Ser variant in distal myopathy patients which could act as a genetic modifier., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

This study investigated the anti-sarcopenic effect of fermented Tenebrio molitor larvae (mealworms) extract (FME) in both dexamethasone (DEX)-treated C2C12 cells and mice. FME (100 µg/mL) increased the diameter of myotubes and inhibited the gene and protein expression of atrogin-1 compared to DEX- or non-fermented mealworms extract (ME)-treated C2C12 cells. Male C57BL/6N mice were divided into five groups: Normal Control (NC), DEX (10 mg/kg, intraperitoneal), and three groups of DEX+FME (100, 200, or 500 mg FME/kg/day, oral) for two weeks. FME at doses of 200 and 500 mg/kg effectively improved grip strength when compared to the DEX group. Histological analysis of the quadriceps muscle showed a larger muscle fiber size in the DEX+FME groups compared to DEX group. FME (200 and 500 mg/kg) significantly increased cross-sectional area of the muscle fiber compared to DEX group. FME (500 mg/kg) significantly decreased the ubiquitin, atrogin-1 and MuRF-1 protein levels, and increased levels of MHC and MyoG in DEX-treated mice. The puromycin labeling assay revealed that FME increased protein synthesis in DEX-induced muscle atrophy. The FME treatment demonstrated significant upregulation in phosphorylation levels, including mTOR, FoxO3α, Akt, and PI3K compared to DEX group. In conclusion, FME inhibited the increase in proteins associated with muscle atrophy, including, atrogin-1 and MuRF-1, by regulating the PI3K-Akt-FoxO3α pathway. FME improved the PI3K-Akt-mTOR signaling pathway, which was reduced by DEX. This study suggests that FME has the potential for use in sarcopenia therapy, possibly serving as a natural agent that counteracts the negative effects of DEX on muscle tissue., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Limb-girdle muscular dystrophy recessive 27 is associated with biallelic variants in JAG2, encoding the JAG2 notch ligand. Twenty-four affected individuals from multiple families have been described in two reports. We present two Australian families with three novel JAG2 missense variants: (c.1021G>T, p.(Gly341Cys)) homozygous in two siblings of Pakistani origin, and compound heterozygous variants (c.703T>C, p.(Trp235Arg); c.2350C>T, p.(Arg784Cys)) in a proband of European ancestry. Patients presented with childhood-onset limb-girdle-like myopathy with difficulty or inability walking. MRI revealed widespread torso and limb muscle involvement. Muscle pathology showed myopathic changes with fatty infiltration. Muscle RNA sequencing revealed significant downregulation of myogenesis genes PAX7, MYF5, and MEGF10 similar to previous JAG2-related muscular dystrophy cases or Jag2-knockdown cells. In absence of functional assays to characterise JAG2 variants, clinical, MRI and transcriptomic profiling collectively may help discern JAG2-related muscular dystrophy, diagnosis of which is essential for patients and families given the severity of disease and reoccurrence risk., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024. Published by Elsevier B.V.)

Roberts et al. have provided an insightful counterpoint to our review article on the utility of the synergist ablation model. The purpose of this review is to provide some further dialogue regarding the strengths and weaknesses of the synergist ablation model. Specifically, we highlight that the robustness of the model overshadows surgical limitations. We also compare the transcriptomic responses to synergist ablation in mice and resistance exercise in humans to identify common pathways. We conclude that "cell growth is cell growth" and that the mechanisms available to cells to accumulate biomass and increase in size are similar across cell types and independent of the rate of growth.

Most firearm related homicides involve the deceased being forensically examined within a day or two, however, there are times when bodies have been examined and the fired components removed several days or weeks after death, when the body is in an active or advanced state of decomposition. In these cases, ballistic investigation has been found to be complicated due to the damage to the bullets, however the extent of this is not yet known. To date, there have been no studies investigating the effect of human decomposition and the subsequent analysis of bullets lodged in the body in an Australian context. Herein, seven fired copper jacketed bullets were manually inserted into three specific tissue types; lungs, abdomen and leg muscle (twenty-one bullets in total), of human donors in both cool and warm conditions at the Australian Facility for Taphonomic Experimental Research (AFTER). Bullets were removed every three days for a period of twenty-one days, and each bullet underwent manual microscopic examinations by firearms examiners across Australia. Results have indicated that the bullets corrode quickly in warm conditions, compared to bullets exposed to decomposition in cooler conditions. The results of this study will inform investigators and pathologists of the need to remove and examine fired bullets from decomposed bodies as soon as possible, especially in warm conditions to provide firearms examiners with the best opportunity to link fired bullets to a common source., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In this issue, Burke et al. discuss the utility of the rodent synergist ablation (SA) model for examining mechanisms associated with skeletal muscle hypertrophy. In this invited perspective, we aim to complement their original perspective by discussing limitations to the model along with alternative mechanical overload models that have strengths and limitations.

Skeletal muscle exhibits remarkable plasticity to adapt to stimuli such as mechanical loading. The mechanisms that regulate skeletal muscle hypertrophy due to mechanical overload have been thoroughly studied. Remarkably, our understanding of many of the molecular and cellular mechanisms that regulate hypertrophic growth were first identified using the rodent synergist ablation (SA) model and subsequently corroborated in human resistance exercise training studies. To demonstrate the utility of the SA model, we briefly summarize the hypertrophic mechanisms identified using the model and the following translation of these mechanism to human skeletal muscle hypertrophy induced by resistance exercise training.

Skeletal muscle wasting is a clinically proven pathology associated with Japanese encephalitis virus (JEV) infection; however, underlying factors that govern skeletal muscle damage are yet to be explored. The current study aims to investigate the pathobiology of skeletal muscle damage using a mouse model of JEV infection. Our study reveals a significant increment in viral copy number in skeletal muscle post-JEV infection, which is associated with enhanced skeletal muscle cell death. Molecular and biochemical analysis confirms NOX2-dependent generation of reactive oxygen species, leading to autophagy flux inhibition and cell apoptosis. Along with this, an alteration in mitochondrial dynamics (change in fusion and fission process) and a decrease in the total number of mitochondria copies were found during JEV disease progression. The study represents the initial evidence of skeletal muscle damage caused by JEV and provides insights into potential avenues for therapeutic advancement., (© 2024 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Autophagy is essential for the adaptive response to exercise and physiological skeletal muscle functionality. However, the mechanisms leading to the activation of macroautophagy and chaperone-mediated autophagy in human skeletal muscle in response to high-intensity exercise remain elusive. Our findings demonstrate that macroautophagy and chaperone-mediated autophagy are stimulated by high-intensity exercise in normoxia (P I O 2 : 143 mmHg) and severe acute hypoxia (P I O 2 : 73 mmHg) in healthy humans. High-intensity exercise induces macroautophagy initiation through AMPKα phosphorylation, which phosphorylates and activates ULK1. ULK1 phosphorylates BECN1 at Ser 15 , eliciting the dissociation of BECN1-BCL2 crucial for phagophore formation. Besides, high-intensity exercise elevates the LC3B-II:LC3B-I ratio, reduces total SQSTM1/p62 levels, and induces p-Ser 349 SQSTM1/p62 phosphorylation, suggesting heightened autophagosome degradation. PHAF1/MYTHO, a novel macroautophagy biomarker, is highly upregulated in response to high-intensity exercise. The latter is accompanied by elevated LAMP2A expression, indicating chaperone-mediated autophagy activation regardless of post-exercise HSPA8/HSC70 downregulation. Despite increased glycolytic metabolism, severe acute hypoxia does not exacerbate the autophagy signaling response. Signaling changes revert within 1 min of recovery with free circulation, while the application of immediate post-exercise ischemia impedes recovery. Our study concludes that macroautophagy and chaperone-mediated autophagy pathways are strongly activated by high-intensity exercise, regardless of PO 2 , and that oxygenation is necessary to revert these signals to pre-exercise values. PHAF1/MYTHO emerges as a pivotal exercise-responsive autophagy marker positively associated with the LC3B-II:LC3B-I ratio., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Cancer cachexia, the unintentional loss of lean mass, contributes to functional dependency, poor treatment outcomes, and decreased survival. Although its pathogenicity is multifactorial, metabolic dysfunction remains a hallmark of cachexia. However, significant knowledge gaps exist in understanding the role of skeletal muscle lipid metabolism and dynamics in this condition. We examined skeletal muscle metabolic dysfunction, intramyocellular lipid droplet (LD) content, LD morphology and subcellular distribution, and LD-mitochondrial interactions using the Lewis lung carcinoma (LLC) murine model of cachexia. C57/BL6 male mice ( n = 20) were implanted with LLC cells (10 6 ) in the right flank or underwent PBS sham injections. Skeletal muscle was excised for transmission electron microscopy (TEM; soleus), oil red O/lipid staining [tibialis anterior (TA)], and protein (gastrocnemius). LLC mice had a greater number (232%; P = 0.006) and size (130%; P = 0.023) of intramyocellular LDs further supported by increased oil-red O positive (87%; P = 0.0109) and "very high" oil-red O positive (178%; P = 0.0002) fibers compared with controls and this was inversely correlated with fiber size ( R 2 = 0.5294; P < 0.0001). Morphological analyses of LDs show increased elongation and complexity [aspect ratio: intermyofibrillar (IMF) = 9%, P = 0.046) with decreases in circularity [circularity: subsarcolemmal (SS) = 6%, P = 0.042] or roundness (roundness: whole = 10%, P = 0.033; IMF = 8%, P = 0.038) as well as decreased LD-mitochondria touch (-15%; P = 0.006), contact length (-38%; P = 0.036), and relative contact (86%; P = 0.004). Furthermore, dysregulation in lipid metabolism (adiponectin, CPT1b) and LD-associated proteins, perilipin-2 and perilipin-5, in cachectic muscle ( P < 0.05) were observed. Collectively, we provide evidence that skeletal muscle myosteatosis, altered LD morphology, and decreased LD-mitochondrial interactions occur in a preclinical model of cancer cachexia. NEW & NOTEWORTHY We sought to advance our understanding of skeletal muscle lipid metabolism and dynamics in cancer cachexia. Cachexia increased the number and size of intramyocellular lipid droplets (LDs). Furthermore, decreases in LD-mitochondrial touch, contact length, and relative contact along with increased LD shape complexity with decreases in circularity and roundness. Dysregulation in lipid metabolism and LD-associated proteins was also documented. Collectively, we show that myosteatosis, altered LD morphology, and decreased LD-mitochondrial interactions occur in cancer cachexia.

Background: Fibromyalgia (FM) is a complex syndrome with somatic symptoms connected to the operational state of muscles. Although radiotherapy is a cornerstone in cancer treatment, it is implicated in the aggravation of FM. Lately, formulation of medicines in nano-forms become of great prominence due to their prospective applications in medicine. So, this study aimed to assess possible therapeutic benefits of formulating pregabalin in a nono-form (N-PG) for managing FM during exposure to gamma radiation., Methods: Gamma rays administered in fractionated doses (2 Gy/day) to male rats after one hour of s.c. injection of reserpine (1 mL/kg per day) to induce FM, then treated with single daily dose of (30 mg/kg, p.o.) PG or N-PG for ten successive days. Rats were subjected to behavioral tests, then sacrificed to obtain serum and gastrocnemius muscles., Results: N-PG significantly antagonized reserpine-induced FM as proved by; the immobility and performance times in forced swim and rotarod performance tests, respectively were restored near to the normal time, serum IL-8 and MCP-1 chemokines were nearby the normal levels, mitigated oxidative stress through increasing total thiol, Sirt3, CAT enzyme and decreasing COX-1, inhibition of inflammation via IL-1β and MIF significant reduction, it possessed anti-apoptotic effect verified by decreasing PARP-1 and increasing Bcl-X L , gastrocnemius muscles had minimal fibrosis levels as seen after Masson trichrome staining. Histopathological results were coincidence with biochemical inspection., Conclusion: This study identifies N-PG as a novel drug that could be of a value in the management of FM particularly in cancer patients undergoing radiotherapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Ribosomal DNA (rDNA) copies exist across multiple chromosomes, and interindividual variation in copy number is speculated to influence the hypertrophic response to resistance training. Thus, we examined if rDNA copy number was associated with resistance training-induced skeletal muscle hypertrophy. Participants ( n = 53 male, 21 ± 1 yr old; n = 29 female, 21 ± 2 yr old) performed 10-12 wk of full-body resistance training. Hypertrophy outcomes were determined, as was relative rDNA copy number from preintervention vastus lateralis (VL) biopsies. Pre- and postintervention VL biopsy total RNA was assayed in all participants, and mRNA/rRNA markers of ribosome content and biogenesis were also assayed in the 29 female participants before training, 24 h following training bout 1 , and in the basal state after 10 wk of training. Across all participants, no significant associations were evident between relative rDNA copy number and training-induced changes in whole body lean mass ( r = -0.034, P = 0.764), vastus lateralis thickness ( r = 0.093, P = 0.408), mean myofiber cross-sectional area ( r = -0.128, P = 0.259), or changes in muscle RNA concentrations ( r = 0.026, P = 0.818), and these trends were similar when examining each gender. However, all Pol-I regulon mRNAs as well as 45S pre-rRNA, 28S rRNA, and 18S rRNA increased 24 h following the first training bout in female participants. Follow-up studies using LHCN-M2 myotubes demonstrated that a reduction in relative rDNA copy number induced by bisphenol A did not significantly affect insulin-like-growth factor-induced myotube hypertrophy. These findings suggest that relative rDNA copy number is not associated with myofiber hypertrophy. NEW & NOTEWORTHY We examined ribosomal DNA (rDNA) copy numbers in men and women who resistance trained for 10-12 wk and found no significant associations with skeletal muscle hypertrophy outcomes. These data, along with in vitro data in immortalized human myotubes whereby rDNA copy number was reduced, provide strong evidence that relative rDNA copy number is not associated with anabolism.

Background: The interleukin-17 (IL-17) signaling pathway is intricately linked with immunity and inflammation; however, the association between the IL-17 signaling pathway and skeletal muscle inflammation remains poorly understood. The study aims to investigate the role of the IL-17 signaling pathway in skeletal muscle inflammation and to evaluate the therapeutic potential of anti-IL-17 antibodies in reducing muscle inflammation., Methods: A skeletal muscle inflammation model was induced by cardiotoxin (CTX) injection in C57BL6/J mice. Following treatment with an anti-IL-17 antibody, we conducted a comprehensive analysis integrating single-cell RNA sequencing (scRNA-seq), bioinformatics, enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and Western blot techniques to elucidate underlying mechanisms., Results: scRNA-seq analysis revealed a significant increase in neutrophil numbers and activity in inflamed skeletal muscle compared to other cell types, including macrophages, T cells, B cells, endothelial cells, fast muscle cells, fibroblasts, and skeletal muscle satellite cells. The top 30 differentially expressed genes within neutrophils, along with 55 chemokines, were predominantly enriched in the IL-17 signaling pathway. Moreover, the IL-17 signaling pathway exhibited heightened expression in inflamed skeletal muscle, particularly within neutrophils. Treatment with anti-IL-17 antibody resulted in the suppression of IL-17 signaling pathway expression, accompanied by reduced levels of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, as well as decreased numbers and activity of Ly6g + /Mpo + neutrophils compared to CTX-induced skeletal muscle inflammation., Conclusion: Our findings suggest that the IL-17 signaling pathway plays a crucial role in promoting inflammation within skeletal muscle. Targeting this pathway may hold promise as a therapeutic strategy for ameliorating the inflammatory micro-environment and reducing cytokine production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

We describe two anti-3‑hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) antibody-positive patients with treatment-responsive ophthalmoparesis. Patient 1 was a 53-year-old male with progressive proximal limb weakness, dysphagia, ptosis, and diplopia over 6 weeks and creatine kinase (CK) of 3,512 units/L. Patient 2 was a 55-year-old female with progressive proximal weakness, dysarthria, ptosis, diplopia, and dyspnea over 2 weeks with CK of 31,998 units/L. Both patients had normal thyroid studies and repetitive nerve stimulation, myopathic electromyography with fibrillation potentials, magnetic resonance imaging demonstrating abnormal enhancement of extraocular muscles, muscle biopsy showing necrotic myofibers, and positive anti-HMGCR antibodies. Patient 1 also had weakly positive anti-PM/Scl antibodies. Immunomodulatory therapies led to resolution of oculobulbar weakness and normalization of CK levels in both patients, while limb weakness resolved completely in patient 1 and partially in patient 2. These cases expand the phenotypic spectrum of anti-HMGCR antibody-associated myopathies to include subacute ophthalmoparesis with limb-girdle weakness and markedly elevated CK., Competing Interests: Declaration of competing interest The authors, as designated in the list below declare no financial interests relevant to the work submitted. Authors: Brendan Putko, MD, Fellow, Neuromuscular Medicine, Mayo Clinic, Rochester, MN Alan Pestronk, MD, Professor, Neurology, Washington University in St. Louis, St. Louis, MO Gregory van Stavern, MD, Robert C. Drews Professor, Ophthalmology and Visual Sciences, Washington University in St. Louis, St. Lois, MO Cecile Phan, MD, Associate Clinical Professor, Neurology, University of Alberta, Edmonton, AB Grayson Beecher, MD, Assistant Professor, Neurology, University of Alberta, Edmonton, AB Teerin Liewluck, MD, Professor, Neurology, Mayo Clinic, Rochester, MN, (Copyright © 2024. Published by Elsevier B.V.)

Background: Skeletal muscle ischaemia-reperfusion injury (IRI) is a prevalent condition encountered in clinical practice, characterised by muscular dystrophy. Owing to limited treatment options and poor prognosis, it can lead to movement impairments, tissue damage, and disability. This study aimed to determine and verify the influence of transient receptor potential canonical 6 (TRPC6) on skeletal muscle IRI, and to explore the role of TRPC6 in the occurrence of skeletal muscle IRI and the signal transduction pathways activated by TRPC6 to provide novel insights for the treatment and intervention of skeletal muscle IRI., Methods: In vivo ischaemia/reperfusion (I/R) and in vitro hypoxia/reoxygenation (H/R) models were established, and data were comprehensively analysed at histopathological, cellular, and molecular levels, along with the evaluation of the exercise capacity in mice., Results: By comparing TRPC6 knockout mice with wild-type mice, we found that TRPC6 knockout of TRPC6 could reduced skeletal muscle injury after I/R or H/R, of skeletal muscle, so as therebyto restoringe some exercise capacity inof mice. TRPC6 knockdown can reduced Ca 2+ overload in cells, therebyo reducinge apoptosis. In additionAdditionally, we also found that TRPC6 functionsis not only a key ion channel involved in skeletal muscle I/R injury, but also can affects Ca 2+ levels and then phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signalling pathway. by knocking downTherefore, knockdown of TRPC6, so as to alleviated the injury inducedcaused by skeletal muscle I/R or and H/R., Conclusions: These findingsdata indicate that the presence of TRPC6 exacerbatescan aggravate the injury of skeletal muscle injury after I/Rischemia/reperfusion, leading towhich not only causes Ca 2+ overload and apoptosis., Additionally, it impairsbut also reduces the self- repair ability of cells by inhibiting the expression of the PI3K/Akt/mTOR signalling pathway. ETo exploringe the function and role of TRPC6 in skeletal muscle maycan presentprovide a novelew approachidea for the treatment of skeletal muscle ischemia/reperfusion injury., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Shou-Tian Li reports financial support was provided by The National Natural Science Foundation of China. Shou-Tian Li reports financial support was provided by The Science and Technology Foundation of Guizhou Province. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disease caused by the degeneration of the α-motor neurons in the anterior horn of the spinal cord. SMA is clinically characterized by progressive and symmetrical muscle weakness and muscle atrophy and ends up with systemic multisystem abnormalities. Quantitative MRI (qMRI) has the advantages of non-invasiveness, objective sensitivity, and high reproducibility, and has important clinical value in evaluating the severity of neuromuscular diseases and monitoring the efficacy of treatment. This article summarizes the clinical use of muscular MRI and magnetic resonance neurography in assessing the progress of SMA., (Copyright © 2024 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Due to an unexpected activation of different zinc (Zn) transporters in a recent prospective clinical study, we have revisited the role of Zn homeostasis and the activation of matrix metalloproteinases (MMPs) in skeletal muscle exposed to the intensive care unit (ICU) condition (immobilization and mechanical ventilation). ICU patients exposed to 12 days ICU condition were followed longitudinally with six repeated muscle biopsies while they showed a progressive preferential myosin loss, i.e., the hallmark of Critical Illness Myopathy (CIM), in parallel with the activation of Zn-transporters. In this study, we have revisited the expression of Zn-transporters and the activation of MMPs in clinical as well as in experimental studies using an established ICU model. MMPs are a group Zn-dependent endopeptidases which do not only target and cleave extracellular proteins but also intracellular proteins including multiple sarcomeric proteins. MMP-9 is of specific interest since the hallmark of CIM, the preferential myosin loss, has also been reported in dilated cardiomyopathy and coupled to MMP-9 activation. Transcriptional activation of Zn-transporters was observed in both clinical and experimental studies as well as the activation of MMPs, in particular MMP-9, in various limb and respiratory muscles in response to long-term exposure to the ICU condition. The activation of Zn-transporters was paralleled by increased Zn levels in skeletal muscle which in turn showed a negative linear correlation with the preferential myosin loss associated with CIM, offering a potential intervention strategy. Thus, activation of Zn-transporters, increased intramuscular Zn levels, and activation of the Zn-dependent MMPs are forwarded as a probable mechanism involved in CIM pathophysiology. These effects were confirmed in different rat strains subjected to a model of CIM and exacerbated by old age. This is of specific interest since old age and muscle wasting are the two factors most strongly associated with ICU mortality., Competing Interests: Declaration of competing interest We declare no conflict of interest., (Copyright © 2024. Published by Elsevier Inc.)

Variability in disease onset and progression is a hallmark of amyotrophic lateral sclerosis (ALS), both in sporadic and genetic forms. Recently, we found that SOD1-G93A transgenic mice expressing the same amount of mutant SOD1 but with different genetic backgrounds, C57BL/6JOlaHsd and 129S2/SvHsd, show slow and rapid muscle wasting and disease progression, respectively. Here, we investigated the different molecular mechanisms underlying muscle atrophy. Although both strains showed similar denervation-induced degradation of muscle proteins, only the rapidly progressing mice exhibited early and sustained STAT3 activation that preceded atrophy in gastrocnemius muscle. We therefore investigated the therapeutic potential of sunitinib, a tyrosine kinase inhibitor known to inhibit STAT3 and prevent cancer-induced muscle wasting. Although sunitinib treatment reduced STAT3 activation in the gastrocnemius muscle and lumbar spinal cord, it did not preserve spinal motor neurons, improve neuromuscular impairment, muscle atrophy and disease progression in the rapidly progressing SOD1-G93A mice. Thus, the effect of sunitinib is not equally positive in different diseases associated with muscle wasting. Moreover, given the complex role of STAT3 in the peripheral and central compartments of the neuromuscular system, the present study suggests that its broad inhibition may lead to opposing effects, ultimately preventing a potential positive therapeutic action in ALS., Competing Interests: Declaration of competing interest The authors declare no competing interest., (Copyright © 2024. Published by Elsevier Inc.)

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease that results in the loss of motor neurons and severe skeletal muscle atrophy. The etiology of ALS is linked to skeletal muscle, which can activate a retrograde signaling cascade that destroys motor neurons. This is why satellite cells and mitochondria play a crucial role in the health and performance of skeletal muscles. This review presents current knowledge on the involvement of mitochondrial dysfunction, skeletal muscle atrophy, muscle satellite cells, and neuromuscular junction (NMJ) in ALS. It also discusses current therapeutic strategies, including exercise, drugs, stem cells, gene therapy, and the prospective use of mitochondrial transplantation as a viable therapeutic strategy., (© 2024. The Author(s).)

Aims: To identify and highlight pertinent US features that could serve as imaging biomarkers to describe different patient phenotypes, within Great Trochanteric Pain Syndrome (GTPS) clinical diagnosis., Materials and Methods: Using ultrasound we evaluated eighty-eight clinically diagnosed patients with GTPS, for tendon matrix changes and calcium deposits in the gluteus medius (superoposterior and lateral aspects) and in the gluteus minimus. Peritrochanteric examination included fascia lata, trochanteric bursa, cortical irregularities and the presence of enthesophytes. The association of pathological changes with pain and functionality was evaluated using multivariate regression models., Results: Out of the 88 patients, 86 examinations (97.7%) detected gluteus medius tendinopathy, and 54 patients (61.4%) had gluteus minimus tendinopathy in addition. Calcium deposits were present in 97.7% of patients, associated with tenderness (p = 0.009), and most often located in the gluteus medius rather than in the gluteus minimus (p = 0.014); calcifications were associated with tendon thickness (p = 0.042), hypoechogenicity (p = 0.005) and the presence of partial tears (p = 0.030). Bursa swelling occurred in 36 patients (40.9%); multivariate regression models predicted less pain in patients with bursa distension (p = 0.008) and dysfunction in patients with gluteal muscle atrophy (p = 0.001) and loss of fibrillar pattern in the gluteus medius (p = 0.002)., Conclusion: GTPS involves both degenerative calcifying gluteal tendinopathy and alterations in the peritrochanteric space associated with physical function and pain. The severity of GTPS can be assessed using ultrasound imaging biomarkers., (© 2023. Società Italiana di Ultrasonologia in Medicina e Biologia (SIUMB).)

Purpose: Human skeletal muscle has the profound ability to hypertrophy in response to resistance training (RT). However, this has a high energy and protein cost and is presumably mainly restricted to recruited muscles. It remains largely unknown what happens with nonrecruited muscles during RT. This study investigated the volume changes of 17 recruited and 13 nonrecruited muscles during a 10-wk single-joint RT program targeting upper arm and upper leg musculature., Methods: Muscle volume changes were measured by manual or automatic 3D segmentation in 21 RT novices. Subjects ate ad libitum during the study and energy and protein intake were assessed by self-reported diaries., Results: Posttraining, all recruited muscles increased in volume (range: +2.2% to +17.7%, P < 0.05), whereas the nonrecruited adductor magnus (mean: -1.5% ± 3.1%, P = 0.038) and soleus (-2.4% ± 2.3%, P = 0.0004) decreased in volume. Net muscle growth ( r = 0.453, P = 0.045) and changes in adductor magnus volume ( r = 0.450, P = 0.047) were positively associated with protein intake. Changes in total nonrecruited muscle volume ( r = 0.469, P = 0.037), adductor magnus ( r = 0.640, P = 0.002), adductor longus ( r = 0.465, P = 0.039), and soleus muscle volume ( r = 0.481, P = 0.032) were positively related to energy intake. When subjects were divided into a HIGH or LOW energy intake group, overall nonrecruited muscle volume (-1.7% ± 2.0%), adductor longus (-5.6% ± 3.7%), adductor magnus (-2.8% ± 2.4%), and soleus volume (-3.7% ± 1.8%) decreased significantly ( P < 0.05) in the LOW but not the HIGH group., Conclusions: To our knowledge, this is the first study documenting that some nonrecruited muscles significantly atrophy during a period of RT. Our data therefore suggest muscle mass reallocation, that is, that hypertrophy in recruited muscles takes place at the expense of atrophy in nonrecruited muscles, especially when energy and protein availability are limited., (Copyright © 2024 by the American College of Sports Medicine.)

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., (© 2024. Science China Press.)

Skeletal muscles serve both in movement and as endocrine organs. Myokines secreted by skeletal muscles activate biological functions within muscles and throughout the body via autocrine, paracrine, and/or endocrine pathways. Skeletal muscle atrophy can influence myokine expression and secretion, while myokines can impact the structure and function of skeletal muscles. Regulating the expression and secretion of myokines through the pharmacological approach is a strategy for alleviating skeletal muscle atrophy. Natural products possess complex structures and chemical properties. Previous studies have demonstrated that various natural products exert beneficial effects on skeletal muscle atrophy. This article reviewed the regulatory effects of natural products on myokines and summarized the research progress on skeletal muscle atrophy associated with myokine regulation. The focus is on how small-molecule natural products affect the regulation of interleukin 6 (IL-6), irisin, myostatin, IGF-1, and FGF-21 expression. We contend that the development of small-molecule natural products targeting the regulation of myokines holds promise in combating skeletal muscle atrophy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The cell membrane protein, dystroglycan, plays a crucial role in connecting the cytoskeleton of a variety of mammalian cells to the extracellular matrix. The α-subunit of dystroglycan (αDG) is characterized by a high level of glycosylation, including a unique O-mannosyl matriglycan. This specific glycosylation is essential for binding of αDG to extracellular matrix ligands effectively. A subset of muscular dystrophies, called dystroglycanopathies, are associated with aberrant, dysfunctional glycosylation of αDG. This defect prevents myocytes from attaching to the basal membrane, leading to contraction-induced injury. Here, we describe a novel Western blot (WB) assay for determining levels of αDG glycosylation in skeletal muscle tissue. The assay described involves extracting proteins from fine needle tibialis anterior (TA) biopsies and separation using SDS-PAGE followed by WB. Glycosylated and core αDG are then detected in a multiplexed format using fluorescent antibodies. A practical application of this assay is demonstrated with samples from normal donors and patients diagnosed with LGMD2I/R9. Quantitative analysis of the WB, which employed the use of a normal TA derived calibration curve, revealed significantly reduced levels of αDG in patient biopsies relative to unaffected TA. Importantly, the assay was able to distinguish between the L276I homozygous patients and a more severe form of clinical disease observed with other FKRP variants. Data demonstrating the accuracy and reliability of the assay are also presented, which further supports the potential utility of this novel assay to monitor changes in ⍺DG of TA muscle biopsies in the evaluation of potential therapeutics., (© 2024. ML Bio Solutions Inc., a BridgeBio Pharma, Inc. Company.)

Skeletal muscle atrophy and dysfunction commonly accompany cardiovascular diseases such as peripheral arterial disease and may be partially attributable to systemic inflammation. We sought to determine whether acute systemic inflammation in a model of hindlimb ischaemia (HLI) could affect skeletal muscle macrophage infiltration, fibre size, or capillarization, independent of the ischaemia. Eight-week-old C57BL/6 male mice underwent either Sham or HLI surgery, and were killed 1, 3, or 7 days post-surgery. Circulating inflammatory cytokine concentrations were measured, as well as immune cell infiltration and morphology of skeletal muscle from both limbs of HLI and Sham mice. In HLI compared with Sham mice at day 1, plasma interleukin-1β levels were 216% higher (0.48 ± 0.10 vs. 0.15 ± 0.01 pg/μL, P = 0.005) and decreased by day 3. This was followed by increased macrophage presence in muscle from both ischaemic and non-ischaemic limbs of HLI mice by day 7 (7.3- and 2.3-fold greater than Sham, respectively, P < 0.0001). In HLI mice, muscle from the ischaemic limb had 21% lower fibre cross-sectional area than the non-ischaemic limb (724 ± 28 vs. 916 ± 46 μm 2 , P = 0.01), but the non-ischaemic limb of HLI mice was no different from Sham. This shows that HLI induces acute systemic inflammation accompanied by immune infiltration in both ischaemic and remote skeletal muscle; however, this did not induce skeletal muscle atrophy in remote muscle within the 7-day time course of this study. This effect of local skeletal muscle ischaemia on the inflammatory status of remote skeletal muscle may signal a priming of muscle for subsequent atrophy over a longer time course. HIGHLIGHTS: What is the central question of this study? Does hindlimb ischaemia-induced inflammation cause acute immune, inflammatory and morphological alterations in remote non-ischaemic skeletal muscle? What is the main finding and its importance? Hindlimb ischaemia induced systemic inflammation with subsequent neutrophil and macrophage infiltration in both ischaemic and non-ischaemic skeletal muscle; however, morphological changes did not occur in non-ischaemic muscle within 7 days. These immune alterations may have functional implications that take longer than 7 days to manifest, and subsequent or prolonged systemic inflammation and immune infiltration of muscle could lead to morphological changes and functional decline., (© 2024 The Author(s). Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Limited information exists regarding abductor muscle quality variation across its length and which locations are most representative of overall muscle quality. This is exacerbated by time-intensive processes for manual muscle segmentation, which limits feasibility of large cohort analyses. The purpose of this study was to develop an automated and localized analysis pipeline that accurately estimates hip abductor muscle quality and size in individuals with mild-to-moderate hip osteoarthritis (OA) and identifies regions of each muscle which provide best estimates of overall muscle quality. Forty-four participants (age 52.7 ± 16.1 years, BMI 23.7 ± 3.4 kg/m 2 , 14 males) with and without mild-to-moderate radiographic hip OA were recruited for this study. Unilateral hip magnetic resonance (MR) images were acquired on a 3.0 T MR scanner and included axial T 1 -weighted fast spin echo and 3D axial Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation (IDEAL-IQ) spoiled gradient-recalled echo (SPGR) with multi-peak fat spectrum modeling and single T 2 * correction. A three dimensional (3D) V-Net convolutional neural network was trained to automatically segment the gluteus medius (GMED), gluteus minimus (GMIN), and tensor fascia lata (TFL) on axial IDEAL-IQ. Agreement between manual and automatic segmentation and associations between axial fat fraction (FF) estimated from IDEAL-IQ and overall muscle FF were evaluated. Dice scores for automatic segmentation were 0.94, 0.87, and 0.91 for GMED, GMIN, and TFL, respectively. GMED, GMIN, and TFL volumetric and FF measures were strongly correlated (r: 0.92-0.99) between automatic and manual segmentations, where all values fell within the 95% limits of agreement of [-9.79 cm 3 , 17.43 cm 3 ] and [-1.99%, 2.89%], respectively. Axial FF was significantly associated with overall FF with the strongest correlations at 50%, 50%, and 65% the length of the GMED, GMIN, and TFL muscles, respectively (r: 0.93-0.97). An automated and localized analysis can provide efficient and accurate estimates of hip abductor muscle quality and size across muscle length. Specific regions of the muscle may be used to estimate overall muscle quality in an abbreviated evaluation of muscle quality., Competing Interests: Declaration of competing interest None., (Copyright © 2023. Published by Elsevier Inc.)

The cytokine interleukin-38 (IL-38), a recently discovered member of the IL-1 family, has been shown to regulate inflammation and improve hepatic endoplasmic reticulum stress and lipid metabolism in individuals with obesity. However, its impact on insulin signaling in skeletal muscle cells and the underlying mechanisms remain unclear. In vitro obesity models were established using palmitate treatment, and Western blot analysis was performed to assess target proteins. Commercial kits were used to measure glucose uptake in cultured myocytes. Our study showed that IL-38 treatment alleviated the impairment of insulin signaling, including IRS-1 and Akt phosphorylation, and increased glucose uptake in palmitate-treated C2C12 myocytes. Increased levels of STAT3-mediated signaling and oxidative stress were observed in these cells following palmitate treatment, and these effects were reversed by IL-38 treatment. In addition, IL-38 treatment upregulated the expression of PPARδ, SIRT1 and antioxidants. Knockdown of PPARδ or SIRT1 using appropriate siRNAs abrogated the effects of IL-38 on insulin signaling, oxidative stress, and the STAT3-dependent pathway. These results suggest that IL-38 alleviates insulin resistance by inhibiting STAT3-mediated signaling and oxidative stress in skeletal muscle cells through PPARδ/SIRT1. This study provides fundamental evidence to support the potential use of IL-38 as a safe therapeutic agent for the treatment of insulin resistance and type 2 diabetes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Transport protein particle (TRAPP) is a multiprotein complex that functions in localising proteins to the Golgi compartment. The TRAPPC11 subunit has been implicated in diseases affecting muscle, brain, eye and to some extent liver. We present three patients who are compound heterozygotes for a missense variant and a structural variant in the TRAPPC11 gene. TRAPPC11 structural variants have not yet been described in association with a disease. In order to reveal the estimated genesis of identified structural variants, we performed sequencing of individual breakpoint junctions and analysed the extent of homology and the presence of repetitive elements in and around the breakpoints., Methods: Biochemical methods including isoelectric focusing on serum transferrin and apolipoprotein C-III, as well as mitochondrial respiratory chain complex activity measurements, were used. Muscle biopsy samples underwent histochemical analysis. Next-generation sequencing was employed for identifying sequence variants associated with neuromuscular disorders, and Sanger sequencing was used to confirm findings., Results: We suppose that non-homologous end joining is a possible mechanism of deletion origin in two patients and non-allelic homologous recombination in one patient. Analyses of mitochondrial function performed in patients' skeletal muscles revealed an imbalance of mitochondrial metabolism, which worsens with age and disease progression., Conclusion: Our results contribute to further knowledge in the field of neuromuscular diseases and mutational mechanisms. This knowledge is important for understanding the molecular nature of human diseases and allows us to improve strategies for identifying disease-causing mutations., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Muscle quality index (MQI) is a novel indicator reflecting the quality of skeletal muscles. The association between MQI and the development of advanced fibrosis in patients with nonalcoholic fatty liver disease (NAFLD) is unknown. We investigated the association of low MQI with advanced fibrosis among adults with NAFLD using a nationally representative sample of the US population. Adults with NAFLD who participated in the National Health and Nutrition Examination Survey (NHANES) 2011-2014 were included. Sex-specific standard was used to define low and extremely low MQI. Univariate and multivariate logistic regressions were used to assess the association between MQI level and advanced fibrosis. In the study, 3758 participants with NAFLD were included. The prevalence of low and extremely low MQI was 11.7% (95% CI 10.4-13.0%) and 2.2% (95% CI 1.6-2.8%), respectively. Among these participants, 96 were assessed to have advanced fibrosis. Individuals with low [(odds ratio (OR) 2.45, 95% confidence interval (CI) 1.22-4.91)] and extremely low MQI (OR 10.48, 95% CI 3.20-34.27) were associated with advanced fibrosis in multivariable analysis. A linear trend relationship was also observed between MQI level and the risk of advanced fibrosis (P trend  = 0.001). Subgroup and sensitivity analyses yielded similar results to the main analyses. Decreased MQI is highly prevalent, and is associated with an increased risk of advanced fibrosis in adult US population with NAFLD., (© 2024. The Author(s).)

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., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Chitinase-3 like-protein-1 (CHI3L1) is a member of the mammalian chitinase-like proteins and elevated serum CHI3L1 level has been proved to be associated with poor prognosis in hepatocellular carcinoma (HCC). This study aimed to investigate the relationship between serum CHI3L1 levels and body composition parameters in patients with HCC after liver transplantation (LT)., Methods: This retrospective study enrolled 200 patients after LT for HCC. Blood samples were collected and serum concentrations of CHI3L1 were measured by enzyme-linked immunosorbent assay. Computer tomography (CT) were used to estimate skeletal muscle and adipose tissue mass. Spearman's rank correlation test was performed to assess associations between serum CHI3L1 levels and these body composition parameters. A Cox proportional-hazards regression model was performed to identify independent prognostic factors. Overall survival (OS) and recurrence-free survival (RFS) curves were constructed using the Kaplan-Meier method and compared by the log-rank test., Results: Total 71 patients (35.5%) were diagnosed with myosteatosis according to skeletal muscle radiation attenuation (SMRA). The 5-year OS rates were 66.9% in non-myosteatosis group, significantly higher than 49.5% in myosteatosis group (p = 0.025), while the RFS of myosteatosis group (5-year RFS: 52.6%) or non-myosteatosis group (5-year RFS: 42.0%) shown no significant difference (p = 0.068). The serum CHI3L1 level were significantly negative correlated with SMRA (r = -0.3, p < 0.001). Interestingly, in patients with myosteatosis, Kaplan-Meier analysis revealed that elevated serum CHI3L1 levels were associated with worse OS (p < 0.001) and RFS (p = 0.047). However, in patients without myosteatosis, Kaplan-Meier analysis found elevated serum CHI3L1 levels were not associated with OS (p = 0.070) or RFS (p = 0.104)., Conclusions: Elevated CHI3L1 was negatively correlated with SMRA, and predicted poorer prognosis in Chinese population after LT for HCC, especially in those patients with concomitant myosteatosis. Monitoring serum CHI3L1 can predict prognosis and effectively guide individual nutrition intervention., (© 2024. The Author(s).)

Background: Neutral Lipid Storage Disease with Myopathy (NLSDM) is a rare lipid metabolism disorder caused by PNPLA2 gene mutations. Clinical manifestations are heterogeneous, and diagnosis is often delayed, usually gaining patients' attention due to the increased risk of cardiomyopathy., Case Presentation: We herein report a 36-year-old Asian male presenting with progressive limb weakness, muscle atrophy of limbs and trunk, dysarthria, and heart failure. Electromyography indicated myogenic changes, and muscle biopsy results revealed characteristics of lipid storage myopathy. Genetic analysis of PNPLA2 revealed two heterozygous mutations: c.757 + 1G > T (chr11-823588, splice-5) on intron 6 and c.919delG (chr11-823854, p.A307Pfs*13) on exon 7. The patient improved limb strength, and dysarthria disappeared after the Medium Chain Fatty Acids diet., Conclusions: In conclusion, we report for the first time that the two heterozygous mutations PNPLA2 c.919delG and c.757 + 1G > T together induced NLSDM, which was confirmed by muscle biopsy., (© 2024. The Author(s).)

Reduced skeletal muscle mass and oxidative capacity coexist in patients with pulmonary emphysema and are independently associated with higher mortality. If reduced cellular respiration contributes to muscle atrophy in that setting remains unknown. Using a mouse with genetically induced pulmonary emphysema that recapitulates muscle dysfunction, we found that reduced activity of succinate dehydrogenase (SDH) is a hallmark of its myopathic changes. We generated an inducible, muscle-specific SDH knockout mouse that demonstrates lower mitochondrial oxygen consumption, myofiber contractility, and exercise endurance. Respirometry analyses show that in vitro complex I respiration is unaffected by loss of SDH subunit C in muscle mitochondria, which is consistent with the pulmonary emphysema animal data. SDH knockout initially causes succinate accumulation associated with a down-regulated transcriptome but modest proteome effects. Muscle mass, myofiber type composition, and overall body mass constituents remain unaltered in the transgenic mice. Thus, while SDH regulates myofiber respiration in experimental pulmonary emphysema, it does not control muscle mass or other body constituents.

Purpose: To evaluate for correlation between MRI paraspinous muscle (PSM) enhancement and clinical measures of cirrhosis severity (CMCS) utilizing established imaging biomarkers of sarcopenia as comparison., Materials and Methods: Retrospective evaluation of 224 patients (mean age 59.6± 9.7 years, 135 males and 89 females) with liver cirrhosis who underwent contrast-enhanced MRI between August 2021 and August 2022 was performed. Assessed variables included: body mass index (BMI), varices and ascites present on imaging (VPI and API), albumin, total bilirubin (Tbili), international normalized ratio (INR), creatinine, MELD score, as well as history of paracentesis (PH), spontaneous bacterial peritonitis, and variceal bleed (VBH). These variables were compared to PSM skeletal muscle index (SMI), PSM signal fat fractions (sFF), and PSM contrast enhancement fraction (CEFR) calculated on arterial (CEFR-ART), portal venous (CEFR-PV), and delayed (CEFR-DEL) phases collected on MRI., Results: Patients with MELD>17, PH, and VPI had lower PSM CEFR-ART (0.06vs. 0.11, p = 0.01; 0.07vs. 0.11, p = 0.01; and 0.09vs. 0.13, p = 0.03, respectively). PSM CEFR-ART correlated negatively with MELD. Patients with MELD>17 and PH had lower PSM CEFR-PV (0.16vs. 0.23, p = 0.02; 0.18 vs. 0.23, p = 0.01, respectively). PSM CEFR-PV correlated positively with albumin and negatively with Tbili, INR, and MELD. PSM CEFR-DEL correlated negatively with Tbili and MELD. Patients with API, PH, and VBH had lower PSM SMI (4.68vs. 5.59, p<0.001; 4.37vs. 5.48, p<0.001; 4.78vs. 5.35, p = 0.04, respectively). PSM SMI correlated negatively with Tbili and positively with BMI. PSM sFF correlated positively with BMI, PSM CEFR-PV, and PSM CEFR-DEL., Conclusion: PSM CEFR is significantly reduced on MRI in patients with clinical manifestations of severe liver cirrhosis. Further investigation into PSM CEFR's usefulness as an imaging biomarker for evaluating liver disease severity is warranted., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 du Pisanie et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Facioscapulohumeral muscular dystrophy (FSHD) is an inherited myopathy, characterized by progressive and asymmetric muscle atrophy, primarily affecting muscles of the face, shoulder girdle, and upper arms before affecting muscles of the lower extremities with age and greater disease severity. FSHD is a disabling condition, and patients may also present with various extramuscular symptoms. FSHD is caused by the aberrant expression of double homeobox 4 ( DUX4 ) in skeletal muscle, arising from compromised epigenetic repression of the D4Z4 array. DUX4 encodes the DUX4 protein, a transcription factor that activates myotoxic gene programs to produce the FSHD pathology. Therefore, sequence-specific oligonucleotides aimed at reducing DUX4 levels in patients is a compelling therapeutic approach, and one that has received considerable research interest over the last decade. This review aims to describe the current preclinical landscape of oligonucleotide therapies for FSHD. This includes outlining the mechanism of action of each therapy and summarizing the preclinical results obtained regarding their efficacy in cellular and/or murine disease models. The scope of this review is limited to oligonucleotide-based therapies that inhibit the DUX4 gene, mRNA, or protein in a way that does not involve gene editing.

Nephropathic cystinosis is an orphan autosomal recessive lysosomal storage disease characterized by a deficiency of cystinosin, a cystine transporter protein, leading to tissue damage, primarily in the kidney and cornea. With the introduction of cystine-depleting therapy with cysteamine and the possibility to survive to adulthood, new challenges of skeletal complications are a concern, with sparse data available regarding bone development. The aim of the current study was to gain more information on bone density and geometry in these patients. Fifty-one patients (29 males, 22 females) with genetically proven nephropathic cystinosis were clinically evaluated with a medical history, physical examination, grip strength measurements, and biochemical and imaging studies. Bone mineral density, bone geometry, and muscle cross sectional area were measured, and muscle was evaluated. Results were compared with age- and gender-specific reference data. Z-scores for height (mean [M] = -1.75, standard deviation [SD] = 1.43), weight (M = -1.67, SD = 1.29), and BMI (M = -0.98, SD = 1.29) were lower than reference data. Medullary cross-sectional area (CSA) and cortical density z-scores were not compromised (M = 0.12, SD = 1.56 and M = -0.25, SD = 1.63, respectively), but cortical CSA z-scores and Strength-Strain Index (SSI) were reduced (M = -2.16, SD = 1.08, M = -2.07, SD = 1.08). Muscular deficits were reflected by reduced z-scores for muscle CSA (M = -2.43, SD = 1.27) and grip strength (M = -3.01, SD = 1.10), along with jump force (34% lower than reference value). Multiple regression analyses indicated an association of muscle mass with medullary CSA and SSI, but not with cortical CSA. While bone density parameters were normal, bone geometry was altered, resulting in a thinner cortex with possible impact on bone strength. Muscle weakness be partially responsible for altered bone geometry and could provide a potential treatment target., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society for Bone and Mineral Research. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

In previous studies, we have demonstrated that stress response-induced high glucocorticoid levels could be the underlying cause of traumatic heterotopic ossification (HO), and we have developed a glucocorticoid-induced ectopic mineralization (EM) mouse model by systemic administration of a high dose of dexamethasone (DEX) to animals with muscle injury induced by cardiotoxin injection. In this model, dystrophic calcification (DC) developed into HO in a cell autonomous manner. However, it is not clear how DC is formed after DEX treatment. Therefore, in this study, we aimed to explore how glucocorticoids initiate muscle EM at a cellular and molecular level. We showed that DEX treatment inhibited inflammatory cell infiltration into injured muscle but inflammatory cytokine production in the muscle was significantly increased, suggesting that other non-inflammatory muscle cell types may regulate the inflammatory response and the muscle repair process. Accompanying this phenotype, transforming growth factor β1 (TGF-β1) expression in fibro-adipogenic progenitors (FAPs) was greatly downregulated. Since TGF-β1 is a strong immune suppressor and FAP's regulatory role has a large impact on muscle repair, we hypothesized that downregulation of TGF-β1 in FAPs after DEX treatment resulted in this hyperinflammatory state and subsequent failed muscle repair and EM formation. To test our hypothesis, we utilized a transgenic mouse model to specifically knockout Tgfb1 gene in PDGFRα-positive FAPs to investigate if the transgenic mice could recapitulate the phenotype that was induced by DEX treatment. Our results showed that the transgenic mice completely phenocopied this hyperinflammatory state and spontaneously developed EM following muscle injury. On the contrary, therapeutics that enhanced TGF-β1 signaling in FAPs inhibited the inflammatory response and attenuated muscle EM. In summary, these results indicate that FAPs-derived TGF-β1 is a key molecule in regulating muscle inflammatory response and subsequent EM, and that glucocorticoids exert their effect via downregulating TGF-β1 in FAPs., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society for Bone and Mineral Research. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Nuclear lamins, a type V intermediate filament, are crucial components of the nuclear envelope's inner layer, maintaining nuclear integrity and mediating interactions between the nucleus and cytoplasm. Research on human iPSC-derived cells and animal models has demonstrated the importance of lamins in cardiac and skeletal muscle development and function. Mutations in lamins result in laminopathies, a group of diseases including muscular dystrophies, Hutchison-Gilford progeria syndrome, and cardiomyopathies with conduction defects. These conditions have been linked to disrupted autophagy, mTOR, Nrf2-Keap, and proteostasis signaling pathways, indicating complex interactions between the nucleus and cytoplasm. Despite progress in understanding these pathways, many questions remain about the mechanisms driving lamin-induced pathologies, leading to limited therapeutic options. This review examines the current literature on dysregulated pathways in cardiac and skeletal muscle laminopathies and explores potential therapeutic strategies for these conditions.

Skeletal muscle atrophy is a morbidity and mortality risk factor that happens with disuse, chronic disease, and aging. The tissue remodeling that happens during recovery from atrophy or injury involves changes in different cell types such as muscle fibers, and satellite and immune cells. Here, we show that the previously uncharacterized gene and protein Zfp697 is a damage-induced regulator of muscle remodeling. Zfp697/ZNF697 expression is transiently elevated during recovery from muscle atrophy or injury in mice and humans. Sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Notably, although Zfp697 is expressed in several cell types in skeletal muscle, myofiber-specific Zfp697 genetic ablation in mice is sufficient to hinder the inflammatory and regenerative response to muscle injury, compromising functional recovery. We show that Zfp697 is an essential mediator of the interferon gamma response in muscle cells and that it functions primarily as an RNA-interacting protein, with a very high number of miRNA targets. This work identifies Zfp697 as an integrator of cell-cell communication necessary for tissue remodeling and regeneration., Competing Interests: Competing interests statement:G.W.Y. is an Scientific Advisory Board (SAB) member of Jumpcode Genomics and a co-founder, member of the Board of Directors, on the SAB, equity holder, and paid consultant for Locanabio and Eclipse BioInnovations. G.W.Y. is a distinguished visiting professor at the National University of Singapore. G.W.Y.’s interests have been reviewed and approved by the University of California, San Diego in accordance with its conflict-of-interest policies.

Chikungunya (CHIKV) and Mayaro (MAYV) viruses are arthritogenic alphaviruses that promote an incapacitating and long-lasting inflammatory muscle-articular disease. Despite studies pointing out the importance of skeletal muscle (SkM) in viral pathogenesis, the long-term consequences on its physiology and the mechanism of persistence of symptoms are still poorly understood. Combining molecular, morphological, nuclear magnetic resonance imaging, and histological analysis, we conduct a temporal investigation of CHIKV and MAYV replication in a wild-type mice model, focusing on the impact on SkM composition, structure, and repair in the acute and late phases of infection. We found that viral replication and induced inflammation promote a rapid loss of muscle mass and reduction in fiber cross-sectional area by upregulation of muscle-specific E3 ubiquitin ligases MuRF1 and Atrogin-1 expression, both key regulators of SkM fibers atrophy. Despite a reduction in inflammation and clearance of infectious viral particles, SkM atrophy persists until 30 days post-infection. The genomic CHIKV and MAYV RNAs were still detected in SkM in the late phase, along with the upregulation of chemokines and anti-inflammatory cytokine expression. In agreement with the involvement of inflammatory mediators on induced atrophy, the neutralization of TNF and a reduction in oxidative stress using monomethyl fumarate, an agonist of Nrf2, decreases atrogen expression and atrophic fibers while increasing weight gain in treated mice. These data indicate that arthritogenic alphavirus infection could chronically impact body SkM composition and also harm repair machinery, contributing to a better understanding of mechanisms of arthritogenic alphavirus pathogenesis and with a description of potentially new targets of therapeutic intervention.

There remains a critical need to define molecular pathways underlying sarcopenia to identify putative therapeutic targets. Research in the mechanisms of aging and sarcopenia relies heavily on preclinical rodent models. In this issue of the JCI, Kerr et al. implemented a clinically-relevant sarcopenia classification system of aged C57BL/6J mice, capturing sarcopenia prevalence across both sexes. The authors performed detailed physiological, molecular, and energetic analyses and demonstrated that mitochondrial biogenesis, oxidative capacity, and AMPK-autophagy signaling decreased as sarcopenia progressed in male mice. Sarcopenia was less prevalent in female mice with fewer alterations compared with the male-affected processes. The findings highlight factors beyond age as necessary for classifying the sarcopenic phenotype in rodent models, reveal sexual dimorphism across the trajectory of age-related declines in muscle mass and function in a commonly used rodent model, and provide insight into sex-dependent molecular alterations associated with sarcopenia progression.

Background: Dysferlin-deficient limb-girdle muscular dystrophy type 2B (Dysf) mice are notorious for their mild phenotype. Raising plasma total cholesterol (CHOL) via apolipoprotein E (ApoE) knockout (KO) drastically exacerbates muscle wasting in Dysf mice. However, dysferlinopathic patients have abnormally reduced plasma high-density lipoprotein cholesterol (HDL-C) levels. The current study aimed to determine whether HDL-C lowering can exacerbate the mild phenotype of dysferlin-null mice., Methods: Human cholesteryl ester transfer protein (CETP), a plasma lipid transfer protein not found in mice that reduces HDL-C, and/or its optimal adapter protein human apolipoprotein B (ApoB), were overexpressed in Dysf mice. Mice received a 2% cholesterol diet from 2 months of age and characterized through ambulatory and hanging functional tests, plasma analyses, and muscle histology., Results: CETP/ApoB expression in Dysf mice caused reduced HDL-C (54.5%) and elevated ratio of CHOL/HDL-C (181.3%) compared to control Dysf mice in plasma, but without raising CHOL. Compared to the severe muscle pathology found in high CHOL Dysf/ApoE double knockout mice, Dysf/CETP/ApoB mice did not show significant changes in ambulation, hanging capacity, increases in damaged area, collagen deposition, or decreases in cross-sectional area and healthy myofibre coverage., Conclusions: CETP/ApoB over-expression in Dysf mice decreases HDL-C without increasing CHOL or exacerbating muscle pathology. High CHOL or nonHDL-C caused by ApoE KO, rather than low HDL-C, likely lead to rodent muscular dystrophy phenotype humanization., (© 2024. The Author(s).)

Fibrosis is a complex pathological process that can lead to the permanent loss of biological function, with P2ry2 playing a crucial role in this process. Long non-coding RNAs (lncRNAs) have been reported to play an critically important role in the fibrotic process. However, it remains unclear whether lncRNAs can regulate fibrosis through P2ry2. In this study, we detected the expression of the long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (lnc-MALAT1). We investigated the expression patterns of lnc-MALAT1 and P2ry2 in denervated skeletal muscle, a classical model of fibrosis. Additionally, we utilized a TGF-β-mediated fibrosis model in NIH/3T3 cells to examine the effects of lnc-MALAT1 and P2ry2 on fibroblast activation and the underlying regulatory mechanisms in vitro. Our results demonstrated that the expression levels of lnc-MALAT1 and P2ry2 were consistently elevated in denervated skeletal muscle, correlating with the degree of fibrosis. In vitro experiments confirmed the regulatory effect of lnc-MALAT1 on P2ry2. Furthermore, we identified miR-335-3p as a potential key molecule in the regulatory relationship of lnc-MALAT1/P2ry2. Dual luciferase reporter assays and AGO2-RIP verified the molecular sponging effect of lnc-MALAT1 on miR-335-3p. Additionally, we validated the regulation of the lnc-MALAT1/miR-335-3p/P2ry2 axis through experimental approaches. In conclusion, our study identified a crucial role of lnc-MALAT1/miR-335-3p/P2ry2 axis in fibroblast activation, providing a promising treatment option against the fibrosis., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)