bims-moremu 2024-07-28 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024–07–28
34 papers selected by
Anna Vainshtein, Craft Science Inc.

Molecular aspects of the exercise response and training adaptation in skeletal muscle.
Methylome-proteome integration after late-life voluntary exercise training reveals regulation and target information for improved skeletal muscle health.
Loss of Calpain 3 dysregulates store-operated calcium entry and its exercise response in mice.
Muscle cell-derived Ccl8 is a negative regulator of skeletal muscle regeneration.
We need to talk-how muscle stem cells communicate.
RBP4 promotes denervation-induced muscle atrophy through STRA6-dependent pathway.
Mitigating skeletal muscle wasting in unloading and augmenting subsequent recovery.
Loss of Tob1 promotes muscle regeneration through muscle stem cell expansion.
Restoring Skeletal Muscle Health through Exercise in Breast Cancer Patients and after Receiving Chemotherapy.
Mustn1 in Skeletal Muscle: A Novel Regulator?
Cardiomyopathy in Duchenne Muscular Dystrophy and the Potential for Mitochondrial Therapeutics to Improve Treatment Response.
The emerging roles of necroptosis in skeletal muscle health and disease.
The Role of Branched Chain Ketoacid Dehydrogenase Kinase (BCKDK) in Skeletal Muscle Biology and Pathogenesis.
The Multiple Roles of Lactate in the Skeletal Muscle.
Mitochondria as Nutritional Targets to Maintain Muscle Health and Physical Function During Ageing.
IL-33 Facilitates Fibro-Adipogenic Progenitors to Establish the Pro-Regenerative Niche after Muscle Injury.
AAV-NRIP gene therapy ameliorates motor neuron degeneration and muscle atrophy in ALS model mice.
Resveratrol and Vitamin D: Eclectic Molecules Promoting Mitochondrial Health in Sarcopenia.
P38α MAPK Coordinates Mitochondrial Adaptation to Caloric Surplus in Skeletal Muscle.
The Double-Edged Sword of ROS in Muscle Wasting and COPD: Insights from Aging-Related Sarcopenia.
Systemic delivery of full-length dystrophin in Duchenne muscular dystrophy mice.
Sympathetic Activation Promotes Sodium Glucose Co-Transporter-1 Protein Expression in Rodent Skeletal Muscle.
Identification of Genomic Predictors of Muscle Fiber Size.
Ammonia transporter RhBG initiates downstream signaling and functional responses by activating NFκB.
Molecular mechanisms of cancer cachexia. Role of exercise training.
Recent Advances in Pre-Clinical Development of Adiponectin Receptor Agonist Therapies for Duchenne Muscular Dystrophy.
Dystrophin deficiency impairs cell junction formation during embryonic myogenesis from pluripotent stem cells.
Intramuscular administration of fractalkine modulates mitochondrial properties and promotes fast glycolytic phenotype.
Skeletal muscle-on-a-chip in microgravity as a platform for regeneration modeling and drug screening.
Eccentric contraction increases hydrogen peroxide levels and alters gene expression through Nox2 in skeletal muscle of male mice.
T-Allele Carriers of Mono Carboxylate Transporter One Gene Polymorphism rs1049434 Demonstrate Altered Substrate Metabolization during Exhaustive Exercise.
Dapagliflozin improves skeletal muscle insulin sensitivity through SIRT1 activation induced by nutrient deprivation state.
Single cell RNA sequencing of human FAPs reveals different functional stages in Duchenne muscular dystrophy.
Magnetic-field-driven targeting of exosomes modulates immune and metabolic changes in dystrophic muscle.

Free Radic Biol Med. 2024 Jul 24. pii: S0891-5849(24)00572-0. [Epub ahead of print]

Molecular aspects of the exercise response and training adaptation in skeletal muscle.

Regula Furrer, Christoph Handschin.

  Skeletal muscle plasticity enables an enormous potential to adapt to various internal and external stimuli and perturbations. Most notably, changes in contractile activity evoke a massive remodeling of biochemical, metabolic and force-generating properties. In recent years, a large number of signals, sensors, regulators and effectors have been implicated in these adaptive processes. Nevertheless, our understanding of the molecular underpinnings of training adaptation remains rudimentary. Specifically, the mechanisms that underlie signal integration, output coordination, functional redundancy and other complex traits of muscle adaptation are unknown. In fact, it is even unclear how stimulus-dependent specification is brought about in endurance or resistance exercise. In this review, we will provide an overview on the events that describe the acute perturbations in single endurance and resistance exercise bouts. Furthermore, we will provide insights into the molecular principles of long-term training adaptation. Finally, current gaps in knowledge will be identified, and strategies for a multi-omic and -cellular analyses of the molecular mechanisms of skeletal muscle plasticity that are engaged in individual, acute exercise bouts and chronic training adaptation discussed.

Keywords:  athletic performance; exercise; skeletal muscle; training adaptation; transcriptional regulation

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.07.026
J Physiol. 2024 Jul 26.

Methylome-proteome integration after late-life voluntary exercise training reveals regulation and target information for improved skeletal muscle health.

Toby L Chambers, Andrea Dimet-Wiley, Alexander R Keeble, Amin Haghani, Wen-Juo Lo, Gyumin Kang, Robert Brooke, Steve Horvath, Christopher S Fry, Stanley J Watowich, Yuan Wen, Kevin A Murach.

  Exercise is a potent stimulus for combatting skeletal muscle ageing. To study the effects of exercise on muscle in a preclinical setting, we developed a combined endurance-resistance training stimulus for mice called progressive weighted wheel running (PoWeR). PoWeR improves molecular, biochemical, cellular and functional characteristics of skeletal muscle and promotes aspects of partial epigenetic reprogramming when performed late in life (22-24 months of age). In this investigation, we leveraged pan-mammalian DNA methylome arrays and tandem mass-spectrometry proteomics in skeletal muscle to provide detailed information on late-life PoWeR adaptations in female mice relative to age-matched sedentary controls (n = 7-10 per group). Differential CpG methylation at conserved promoter sites was related to transcriptional regulation genes as well as Nr4a3, Hes1 and Hox genes after PoWeR. Using a holistic method of -omics integration called binding and expression target analysis (BETA), methylome changes were associated with upregulated proteins related to global and mitochondrial translation after PoWeR (P = 0.03). Specifically, BETA implicated methylation control of ribosomal, mitoribosomal, and mitochondrial complex I protein abundance after training. DNA methylation may also influence LACTB, MIB1 and UBR4 protein induction with exercise - all are mechanistically linked to muscle health. Computational cistrome analysis predicted several transcription factors including MYC as regulators of the exercise trained methylome-proteome landscape, corroborating prior late-life PoWeR transcriptome data. Correlating the proteome to muscle mass and fatigue resistance revealed positive relationships with VPS13A and NPL levels, respectively. Our findings expose differential epigenetic and proteomic adaptations associated with translational regulation after PoWeR that could influence skeletal muscle mass and function in aged mice. KEY POINTS: Late-life combined endurance-resistance exercise training from 22-24 months of age in mice is shown to improve molecular, biochemical, cellular and in vivo functional characteristics of skeletal muscle and promote aspects of partial epigenetic reprogramming and epigenetic age mitigation. Integration of DNA CpG 36k methylation arrays using conserved sites (which also contain methylation ageing clock sites) with exploratory proteomics in skeletal muscle extends our prior work and reveals coordinated and widespread regulation of ribosomal, translation initiation, mitochondrial ribosomal (mitoribosomal) and complex I proteins after combined voluntary exercise training in a sizeable cohort of female mice (n = 7-10 per group and analysis). Multi-omics integration predicted epigenetic regulation of serine β-lactamase-like protein (LACTB - linked to tumour resistance in muscle), mind bomb 1 (MIB1 - linked to satellite cell and type 2 fibre maintenance) and ubiquitin protein ligase E3 component N-recognin 4 (UBR4 - linked to muscle protein quality control) after training. Computational cistrome analysis identified MYC as a regulator of the late-life training proteome, in agreement with prior transcriptional analyses. Vacuolar protein sorting 13 homolog A (VPS13A) was positively correlated to muscle mass, and the glycoprotein/glycolipid associated sialylation enzyme N-acetylneuraminate pyruvate lyase (NPL) was associated to in vivo muscle fatigue resistance.

Keywords:  BETA; DNA methylation; ageing; mitoribosome; proteomics

DOI:  https://doi.org/10.1113/JP286681
FASEB J. 2024 Jul 31. 38(14): e23825

Loss of Calpain 3 dysregulates store-operated calcium entry and its exercise response in mice.

Katelyn R Villani, Renjia Zhong, C Spencer Henley-Beasley, Giorgia Rastelli, Erin Harris, Simona Boncompagni, Elisabeth R Barton, Lan Wei-LaPierre.

  Limb-Girdle Muscular Dystrophy R1/2A (LGMD R1/2A) is caused by mutations in the CAPN3 gene encoding Calpain 3, a skeletal-muscle specific, Ca2+-dependent protease. Localization of Calpain 3 within the triad suggests it contributes to Ca2+ homeostasis. Through live-cell Ca2+ measurements, muscle mechanics, immunofluorescence, and electron microscopy (EM) in Capn3 deficient (C3KO) and wild-type (WT) mice, we determined whether loss of Calpain 3 altered Store-Operated Calcium Entry (SOCE) activity. Direct Ca2+ influx measurements revealed loss of Capn3 elicits elevated resting SOCE and increased resting cytosolic Ca2+, supported by high incidence of calcium entry units (CEUs) observed by EM. C3KO and WT mice were subjected to a single bout of treadmill running to elicit SOCE. Within 1HR post-treadmill running, C3KO mice exhibited diminished force production in extensor digitorum longus muscles and a greater decay of Ca2+ transients in flexor digitorum brevis muscle fibers during repetitive stimulation. Striking evidence for impaired exercise-induced SOCE activation in C3KO mice included poor colocalization of key SOCE proteins, stromal-interacting molecule 1 (STIM1) and ORAI1, combined with disappearance of CEUs in C3KO muscles. These results demonstrate that Calpain 3 is a key regulator of SOCE in skeletal muscle and identify SOCE dysregulation as a contributing factor to LGMD R1/2A pathology.

Keywords:  Limb Girdle Muscular Dystrophy R1/2A; ORAI1; STIM1; calcium homeostasis; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202400697R
FASEB J. 2024 Jul 31. 38(14): e23841

Muscle cell-derived Ccl8 is a negative regulator of skeletal muscle regeneration.

A Boss-Kennedy, D Kim, P Barai, C Maldonado, A Reyes-Ordoñez, J Chen.

  Skeletal muscles undergo robust regeneration upon injury, and infiltrating immune cells play a major role in not only clearing damaged tissues but also regulating the myogenic process through secreted cytokines. Chemokine C-C motif ligand 8 (Ccl8), along with Ccl2 and Ccl7, has been reported to mediate inflammatory responses to suppress muscle regeneration. Ccl8 is also expressed by muscle cells, but a role of the muscle cell-derived Ccl8 in myogenesis has not been reported. In this study, we found that knockdown of Ccl8, but not Ccl2 or Ccl7, led to increased differentiation of C2C12 myoblasts. Analysis of existing single-cell transcriptomic datasets revealed that both immune cells and muscle stem cells (MuSCs) in regenerating muscles express Ccl8, with the expression by MuSCs at a much lower level, and that the temporal patterns of Ccl8 expression were different in MuSCs and macrophages. To probe a function of muscle cell-derived Ccl8 in vivo, we utilized a mouse system in which Cas9 was expressed in Pax7+ myogenic progenitor cells (MPCs) and Ccl8 gene editing was induced by AAV9-delivered sgRNA. Depletion of Ccl8 in Pax7+ MPCs resulted in accelerated muscle regeneration after barium chloride-induced injury in both young and middle-aged mice, and intramuscular administration of a recombinant Ccl8 reversed the phenotype. Accelerated regeneration was also observed when Ccl8 was depleted in Myf5+ or MyoD+ MPCs by similar approaches. Our results suggest that muscle cell-derived Ccl8 plays a unique role in regulating the initiation of myogenic differentiation during injury-induced muscle regeneration.

Keywords:  Ccl8; myogenic progenitor cell; myokine; satellite cell; skeletal muscle regeneration

DOI:  https://doi.org/10.1096/fj.202400184R
Front Cell Dev Biol. 2024 ;12 1378548

We need to talk-how muscle stem cells communicate.

Karolina Majchrzak, Erik Hentschel, Katja Hönzke, Christiane Geithe, Julia von Maltzahn.

  Skeletal muscle is one of the tissues with the highest ability to regenerate, a finely controlled process which is critically depending on muscle stem cells. Muscle stem cell functionality depends on intrinsic signaling pathways and interaction with their immediate niche. Upon injury quiescent muscle stem cells get activated, proliferate and fuse to form new myofibers, a process involving the interaction of multiple cell types in regenerating skeletal muscle. Receptors in muscle stem cells receive the respective signals through direct cell-cell interaction, signaling via secreted factors or cell-matrix interactions thereby regulating responses of muscle stem cells to external stimuli. Here, we discuss how muscle stem cells interact with their immediate niche focusing on how this controls their quiescence, activation and self-renewal and how these processes are altered in age and disease.

Keywords:  aging; muscle stem cell; niche; receptor; regeneration; rhabdomyosarcoma; satellite cell; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2024.1378548
J Cachexia Sarcopenia Muscle. 2024 Jun 21.

RBP4 promotes denervation-induced muscle atrophy through STRA6-dependent pathway.

Kang-Zhen Zhang, Jia-Wen Li, Jin-Shui Xu, Zheng-Kai Shen, Yu-Shuang Lin, Can Zhao, Xiang Lu, Yun-Feng Rui, Wei Gao.

   BACKGROUNDS: Fat infiltration of skeletal muscle has been recognized as a common feature of many degenerative muscle disorders. Retinol binding protein 4 (RBP4) is an adipokine that has been demonstrated to be correlated with the presence and severity of sarcopenia in the elderly. However, the exact role and the underlying mechanism of RBP4 in muscle atrophy remains unclear.
METHODS: Denervation-induced muscle atrophy model was constructed in wild-type and RBP4 knockout mice. To modify the expression of RBP4, mice were received intramuscular injection of retinol-free RBP4 (apo-RBP4), retinol-bound RBP4 (holo-RBP4) or oral gavage of RBP4 inhibitor A1120. Holo-RBP4-stimulated C2C12 myotubes were treated with siRNAs or specific inhibitors targeting signalling receptor and transporter of retinol 6 (STRA6)/Janus kinase 2 (JAK2)/Signal transducer and activator of transcription 3 (STAT3) pathway. Fat accumulation, myofibre cross-sectional area, myotube diameter and the expression of muscle atrophy markers and myogenesis markers were analysed.
RESULTS: The expression levels of RBP4 in skeletal muscles were significantly up-regulated more than 2-fold from 7 days and sustained for 28 days after denervation. Immunofluorescence analysis indicated that increased RBP4 was localized in the infiltrated fatty region in denervated skeletal muscles. Knockout of RBP4 alleviated denervation-induced fatty infiltration and muscle atrophy together with decreased expression of atrophy marker Atrogin-1 and MuRF1 as well as increased expression of myogenesis regulators MyoD and MyoG. By contrast, injection of retinol-bound holo-RBP4 aggregated denervation-induced ectopic fat accumulation and muscle atrophy. Consistently, holo-RBP4 stimulation also had a dose-dependent effect on the reduction of C2C12 myotube diameter and myofibre cross-sectional area, as well as on the increase of Atrogin-1and MuRF1 expression and decrease of MyoD and MyoG expression. Mechanistically, holo-RBP4 treatment increased the expression of its membrane receptor STRA6 (>3-fold) and promoted the phosphorylation of downstream JAK2 and STAT3. Inhibition of STRA6/JAK2/STAT3 pathway either by specific siRNAs or inhibitors could decrease the expression of Atrogin-1 and MuRF1 (>50%) and decrease the expression of MyoD and MyoG (>3-fold) in holo-RBP4-treated C2C12 myotube. RBP4 specific pharmacological antagonist A1120 significantly inhibited the activation of STRA6/JAK2/STAT3 pathway, ameliorated ectopic fat infiltration and protected against denervation-induced muscle atrophy (30% increased myofibre cross-sectional area) in mice.
CONCLUSIONS: In conclusion, our data reveal that RBP4 promotes fat infiltration and muscle atrophy through a STRA6-dependent and JAK2/STAT3 pathway-mediated mechanism in denervated skeletal muscle. Our results suggest that lowering RBP4 levels might serve as a promising therapeutic approach for prevention and treatment of muscle atrophy.

Keywords:  RBP4; STRA6; denervation; fat infiltration; skeletal muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13518
J Physiol. 2024 Jul 19.

Mitigating skeletal muscle wasting in unloading and augmenting subsequent recovery.

J Max Michel, Zachary Hettinger, Fabrisia Ambrosio, Brendan Egan, Michael D Roberts, Arny A Ferrando, Zachary A Graham, Marcas M Bamman.

  Skeletal muscle wasting is the hallmark pathophysiological adaptation to unloading or disuse that demonstrates the dependency on frequent mechanical stimulation (e.g. muscle activation and subsequent loading) for homeostasis of normally load-bearing muscles. In the absence of mitigation strategies, no mammalian organism is resistant to muscle atrophy driven by unloading. Given the profound impact of unloading-induced muscle wasting on physical capacity, metabolic health and immune function; mitigation strategies during unloading and/or augmentation approaches during recovery have broad healthcare implications in settings of bed-bound hospitalization, cast immobilization and spaceflight. This topical review aims to: (1) provide a succinct, state-of-the-field summary of seminal and recent findings regarding the mechanisms of unloading-induced skeletal muscle wasting; (2) discuss unsuccessful vs. promising mitigation and recovery augmentation strategies; and (3) identify knowledge gaps ripe for future research. We focus on the rapid muscle atrophy driven by relatively short-term mechanical unloading/disuse, which is in many ways mechanistically distinct from both hypermetabolic muscle wasting and denervation-induced muscle atrophy. By restricting this discussion to mechanical unloading during which all components of the nervous system remain intact (e.g. without denervation models), mechanical loading requiring motor and sensory neural circuits in muscle remain viable targets for both mitigation and recovery augmentation. We emphasize findings in humans with comparative discussions of studies in rodents which enable elaboration of key mechanisms. We also discuss what is currently known about the effects of age and sex as biological factors, and both are highlighted as knowledge gaps and novel future directions due to limited research.

Keywords:  atrophy; muscle; recovery; resistance training; unloading; wasting

DOI:  https://doi.org/10.1113/JP284301
J Cell Sci. 2024 Jul 22. pii: jcs.261886. [Epub ahead of print]

Loss of Tob1 promotes muscle regeneration through muscle stem cell expansion.

Yasuo Kitajima, Kiyoshi Yoshioka, Yoko Mikumo, Shun Ohki, Kazumitsu Maehara, Yasuyuki Ohkawa, Yusuke Ono.

  Muscle stem cells (MuSCs) play an indispensable role in postnatal muscle growth and hypertrophy in adult. MuSCs also retain a highly regenerative capacity and are therefore considered a promising stem cell source for regenerative therapy of muscle diseases. In this study, we identify tumor-suppressor protein Tob1 as a Pax7-target gene that negatively controls the population expansion of MuSCs. Tob1 protein is undetectable in the quiescent state but is upregulated during activation in MuSCs. Tob1 ablation in mice accelerates MuSC population expansion and boosts muscle regeneration. Moreover, inactivation of Tob1 in MuSCs ameliorates the efficiency of MuSC transplantation in a murine muscular dystrophy model. Collectively, selective targeting of Tob1 may be a therapeutic option for the treatment of muscular diseases, including muscular dystrophy and age-related sarcopenia.

Keywords:  Muscle Stem Cells; Muscle regeneration; Satellite cells; Tob1

DOI:  https://doi.org/10.1242/jcs.261886
Int J Mol Sci. 2024 Jul 09. pii: 7533. [Epub ahead of print]25(14):

Restoring Skeletal Muscle Health through Exercise in Breast Cancer Patients and after Receiving Chemotherapy.

Inês Aires, José Alberto Duarte, Rui Vitorino, Daniel Moreira-Gonçalves, Paula Oliveira, Rita Ferreira.

  Breast cancer (BC) stands out as the most commonly type of cancer diagnosed in women worldwide, and chemotherapy, a key component of treatment, exacerbates cancer-induced skeletal muscle wasting, contributing to adverse health outcomes. Notably, the impact of chemotherapy on skeletal muscle seems to surpass that of the cancer itself, with inflammation identified as a common trigger for muscle wasting in both contexts. In skeletal muscle, pro-inflammatory cytokines modulate pathways crucial for the delicate balance between protein synthesis and breakdown, as well as satellite cell activation and myonuclear accretion. Physical exercise consistently emerges as a crucial therapeutic strategy to counteract cancer and chemotherapy-induced muscle wasting, ultimately enhancing patients' quality of life. However, a "one size fits all" approach does not apply to the prescription of exercise for BC patients, with factors such as age, menopause and comorbidities influencing the response to exercise. Hence, tailored exercise regimens, considering factors such as duration, frequency, intensity, and type, are essential to maximize efficacy in mitigating muscle wasting and improving disease outcomes. Despite the well-established anti-inflammatory role of aerobic exercise, resistance exercise proves equally or more beneficial in terms of mass and strength gain, as well as enhancing quality of life. This review comprehensively explores the molecular pathways affected by distinct exercise regimens in the skeletal muscle of cancer patients during chemotherapy, providing critical insights for precise exercise implementation to prevent skeletal muscle wasting.

Keywords:  aerobic exercise; mammary tumorigenesis; metabolic remodeling; muscle wasting; physical activity; resistance training

DOI:  https://doi.org/10.3390/ijms25147533
Genes (Basel). 2024 Jun 23. pii: 829. [Epub ahead of print]15(7):

Mustn1 in Skeletal Muscle: A Novel Regulator?

Charles J Kim, Michael Hadjiargyrou.

  Skeletal muscle is a complex organ essential for locomotion, posture, and metabolic health. This review explores our current knowledge of Mustn1, particularly in the development and function of skeletal muscle. Mustn1 expression originates from Pax7-positive satellite cells in skeletal muscle, peaks during around the third postnatal month, and is crucial for muscle fiber differentiation, fusion, growth, and regeneration. Clinically, Mustn1 expression is potentially linked to muscle-wasting conditions such as muscular dystrophies. Studies have illustrated that Mustn1 responds dynamically to injury and exercise. Notably, ablation of Mustn1 in skeletal muscle affects a broad spectrum of physiological aspects, including glucose metabolism, grip strength, gait, peak contractile strength, and myofiber composition. This review summarizes our current knowledge of Mustn1's role in skeletal muscle and proposes future research directions, with a goal of elucidating the molecular function of this regulatory gene.

Keywords:  Mustn1; development; knockout; mouse; repair; skeletal muscle

DOI:  https://doi.org/10.3390/genes15070829
Cells. 2024 Jul 09. pii: 1168. [Epub ahead of print]13(14):

Cardiomyopathy in Duchenne Muscular Dystrophy and the Potential for Mitochondrial Therapeutics to Improve Treatment Response.

Shivam Gandhi, H Lee Sweeney, Cora C Hart, Renzhi Han, Christopher G R Perry.

  Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease caused by mutations to the dystrophin gene, resulting in deficiency of dystrophin protein, loss of myofiber integrity in skeletal and cardiac muscle, and eventual cell death and replacement with fibrotic tissue. Pathologic cardiac manifestations occur in nearly every DMD patient, with the development of cardiomyopathy-the leading cause of death-inevitable by adulthood. As early cardiac abnormalities are difficult to detect, timely diagnosis and appropriate treatment modalities remain a challenge. There is no cure for DMD; treatment is aimed at delaying disease progression and alleviating symptoms. A comprehensive understanding of the pathophysiological mechanisms is crucial to the development of targeted treatments. While established hypotheses of underlying mechanisms include sarcolemmal weakening, upregulation of pro-inflammatory cytokines, and perturbed ion homeostasis, mitochondrial dysfunction is thought to be a potential key contributor. Several experimental compounds targeting the skeletal muscle pathology of DMD are in development, but the effects of such agents on cardiac function remain unclear. The synergistic integration of small molecule- and gene-target-based drugs with metabolic-, immune-, or ion balance-enhancing compounds into a combinatorial therapy offers potential for treating dystrophin deficiency-induced cardiomyopathy, making it crucial to understand the underlying mechanisms driving the disorder.

Keywords:  Duchenne muscular dystrophy; antioxidants; bioenergetics; calcium balance; cardiomyopathy; elamipretide; gene therapy; inflammation; ion dysregulation; metabolism; mitochondria; reactive oxygen species; sarcolemmal tearing; skeletal muscle; therapy

DOI:  https://doi.org/10.3390/cells13141168
Pflugers Arch. 2024 Jul 22.

The emerging roles of necroptosis in skeletal muscle health and disease.

Rizwan Qaisar.

  Necroptosis is a regulated form of cell death with implications in various physiological and pathological processes in multiple tissues. However, the relevant findings from post-mitotic tissues, such as skeletal muscle, are scarce. This review summarizes the potential contributions of necroptosis to skeletal muscle health and diseases. It first discusses the physiological roles of necroptosis in muscle regeneration and development. It then summarizes the contributions of necroptosis to the pathogenesis of multiple muscle diseases, including muscular dystrophies, inflammatory myopathies, cachexia, and neuromuscular disorders. Lastly, it unravels the gaps in our understanding and therapeutic challenges of inhibiting necroptosis as a potential intervention for muscle diseases. Specifically, the findings from the transgenic animal models and the use of pharmacological inhibitors of necroptosis are discussed with relevance to improving the structure and/or function of skeletal muscle in various diseases. Recent developments from experimental animal models and clinical data are presented to discuss the roles of necroptosis in skeletal muscle health and diseases.

Keywords:  Muscle atrophy; Necroptosis; Skeletal muscle

DOI:  https://doi.org/10.1007/s00424-024-02994-1
Int J Mol Sci. 2024 Jul 11. pii: 7601. [Epub ahead of print]25(14):

The Role of Branched Chain Ketoacid Dehydrogenase Kinase (BCKDK) in Skeletal Muscle Biology and Pathogenesis.

Joshua Fernicola, Sagar Vyavahare, Sonu Kumar Gupta, Aditya Kalwaghe, Kate Kosmac, Adam Davis, Matthew Nicholson, Carlos M Isales, Rahul Shinde, Sadanand Fulzele.

  Muscle wasting can be caused by nutrition deficiency and inefficient metabolism of amino acids, including Branched Chain Amino Acids (BCAAs). Branched Chain Amino Acids are a major contributor to the metabolic needs of healthy muscle and account for over a tenth of lean muscle mass. Branched chain alpha-ketoacid dehydrogenase (BCKD) is the rate limiting enzyme of BCAA metabolism. Inhibition of BCKD is achieved through a reversible phosphorylation event by Branched Chain a-ketoacid dehydrogenase kinase (BCKDK). Our study set out to determine the importance of BCKDK in the maintenance of skeletal muscle. We used the Gene Expression Omnibus Database to understand the role of BCKDK in skeletal muscle pathogenesis, including aging, muscular disease, and interrupted muscle metabolism. We found BCKDK expression levels were consistently decreased in pathologic conditions. These results were most consistent when exploring muscular disease followed by aging. Based on our findings, we hypothesize that decreased BCKDK expression alters BCAA catabolism and impacts loss of normal muscle integrity and function. Further research could offer valuable insights into potential therapeutic strategies for addressing muscle-related disorders.

Keywords:  BCKDK; muscle pathogenesis; skeletal muscle

DOI:  https://doi.org/10.3390/ijms25147601
Cells. 2024 Jul 10. pii: 1177. [Epub ahead of print]13(14):

The Multiple Roles of Lactate in the Skeletal Muscle.

Bianca Bartoloni, Michele Mannelli, Tania Gamberi, Tania Fiaschi.

  Believed for a long time to be merely a waste product of cell metabolism, lactate is now considered a molecule with several roles, having metabolic and signalling functions together with a new, recently discovered role as an epigenetic modulator. Lactate produced by the skeletal muscle during physical exercise is conducted to the liver, which uses the metabolite as a gluconeogenic precursor, thus generating the well-known "Cori cycle". Moreover, the presence of lactate in the mitochondria associated with the lactate oxidation complex has become increasingly clear over the years. The signalling role of lactate occurs through binding with the GPR81 receptor, which triggers the typical signalling cascade of the G-protein-coupled receptors. Recently, it has been demonstrated that lactate regulates chromatin state and gene transcription by binding to histones. This review aims to describe the different roles of lactate in skeletal muscle, in both healthy and pathological conditions, and to highlight how lactate can influence muscle regeneration by acting directly on satellite cells.

Keywords:  GPR81 receptor; lactate; muscle renewal

DOI:  https://doi.org/10.3390/cells13141177
Sports Med. 2024 Jul 26.

Mitochondria as Nutritional Targets to Maintain Muscle Health and Physical Function During Ageing.

Sophie C Broome, Jamie Whitfield, Leonidas G Karagounis, John A Hawley.

The age-related loss of skeletal muscle mass and physical function leads to a loss of independence and an increased reliance on health-care. Mitochondria are crucial in the aetiology of sarcopenia and have been identified as key targets for interventions that can attenuate declines in physical capacity. Exercise training is a primary intervention that reduces many of the deleterious effects of ageing in skeletal muscle quality and function. However, habitual levels of physical activity decline with age, making it necessary to implement adjunct treatments to maintain skeletal muscle mitochondrial health and physical function. This review provides an overview of the effects of ageing and exercise training on human skeletal muscle mitochondria and considers several supplements that have plausible mechanistic underpinning to improve physical function in ageing through their interactions with mitochondria. Several supplements, including MitoQ, urolithin A, omega-3 polyunsaturated fatty acids (n3-PUFAs), and a combination of glycine and N-acetylcysteine (GlyNAC) can improve physical function in older individuals through a variety of inter-dependent mechanisms including increases in mitochondrial biogenesis and energetics, decreases in mitochondrial reactive oxygen species emission and oxidative damage, and improvements in mitochondrial quality control. While there is evidence that some nicotinamide adenine dinucleotide precursors can improve physical function in older individuals, such an outcome seems unrelated to and independent of changes in skeletal muscle mitochondrial function. Future research should investigate the safety and efficacy of compounds that can improve skeletal muscle health in preclinical models through mechanisms involving mitochondria, such as mitochondrial-derived peptides and mitochondrial uncouplers, with a view to extending the human health-span.

DOI: https://doi.org/10.1007/s40279-024-02072-7
Adv Sci (Weinh). 2024 Jul 22. e2405299

IL-33 Facilitates Fibro-Adipogenic Progenitors to Establish the Pro-Regenerative Niche after Muscle Injury.

Congcong Zhang, Guoqi Li, Fan Zhang, Yanhong Zhang, Shiyao Hong, Shijuan Gao, Yan Liu, Jie Du, Yulin Li.

  During the process of muscle regeneration post-injury in adults, muscle stem cells (MuSCs) function is facilitated by neighboring cells within the pro-regenerative niche. However, the precise mechanism triggering the initiation of signaling in the pro-regenerative niche remains unknown. Using single-cell RNA sequencing, 14 different muscle cells are comprehensively mapped during the initial stage following injury. Among these, macrophages and fibro-adipogenic progenitor cells (FAPs) exhibit the most pronounced intercellular communication with other cells. In the FAP subclusters, the study identifies an activated FAP phenotype that secretes chemokines, such as CXCL1, CXCL5, CCL2, and CCL7, to recruit macrophages after injury. Il1rl1, encoding the protein of the interleukin-33 (IL-33) receptor, is identified as a highly expressed signature surface marker of the FAP phenotype. Following muscle injury, autocrine IL-33, an alarmin, has been observed to activate quiescent FAPs toward this inflammatory phenotype through the IL1RL1-MAPK/NF-κB signaling pathway. Il1rl1 deficiency results in decreased chemokine expression and recruitment of macrophages, accompanied by impaired muscle regeneration. These findings elucidate a novel mechanism involving the IL-33/IL1RL1 signaling pathway in promoting the activation of FAPs and facilitating muscle regeneration, which can aid the development of therapeutic strategies for muscle-related disorders and injuries.

Keywords:  IL‐33; fibro‐adipogenic progenitors; inflammation; muscle regeneration

DOI:  https://doi.org/10.1002/advs.202405299
Skelet Muscle. 2024 Jul 24. 14(1): 17

AAV-NRIP gene therapy ameliorates motor neuron degeneration and muscle atrophy in ALS model mice.

Hsin-Hsiung Chen, Hsin-Tung Yeo, Yun-Hsin Huang, Li-Kai Tsai, Hsing-Jung Lai, Yeou-Ping Tsao, Show-Li Chen.

   BACKGROUND: Amyotrophic lateral sclerosis (ALS) is characterized by progressive motor neuron (MN) degeneration, leading to neuromuscular junction (NMJ) dismantling and severe muscle atrophy. The nuclear receptor interaction protein (NRIP) functions as a multifunctional protein. It directly interacts with calmodulin or α-actinin 2, serving as a calcium sensor for muscle contraction and maintaining sarcomere integrity. Additionally, NRIP binds with the acetylcholine receptor (AChR) for NMJ stabilization. Loss of NRIP in muscles results in progressive motor neuron degeneration with abnormal NMJ architecture, resembling ALS phenotypes. Therefore, we hypothesize that NRIP could be a therapeutic factor for ALS.
METHODS: We used SOD1 G93A mice, expressing human SOD1 with the ALS-linked G93A mutation, as an ALS model. An adeno-associated virus vector encoding the human NRIP gene (AAV-NRIP) was generated and injected into the muscles of SOD1 G93A mice at 60 days of age, before disease onset. Pathological and behavioral changes were measured to evaluate the therapeutic effects of AAV-NRIP on the disease progression of SOD1 G93A mice.
RESULTS: SOD1 G93A mice exhibited lower NRIP expression than wild-type mice in both the spinal cord and skeletal muscle tissues. Forced NRIP expression through AAV-NRIP intramuscular injection was observed in skeletal muscles and retrogradely transduced into the spinal cord. AAV-NRIP gene therapy enhanced movement distance and rearing frequencies in SOD1 G93A mice. Moreover, AAV-NRIP increased myofiber size and slow myosin expression, ameliorated NMJ degeneration and axon terminal denervation at NMJ, and increased the number of α-motor neurons (α-MNs) and compound muscle action potential (CMAP) in SOD1 G93A mice.
CONCLUSIONS: AAV-NRIP gene therapy ameliorates muscle atrophy, motor neuron degeneration, and axon terminal denervation at NMJ, leading to increased NMJ transmission and improved motor functions in SOD1 G93A mice. Collectively, AAV-NRIP could be a potential therapeutic drug for ALS.

Keywords:  AAV; ALS; Gene therapy; Motor neuron; Muscle; NRIP; Neuromuscular junction; SOD1 G93A

DOI:  https://doi.org/10.1186/s13395-024-00349-z
Int J Mol Sci. 2024 Jul 09. pii: 7503. [Epub ahead of print]25(14):

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

Cristina Russo, Maria Stella Valle, Floriana D'Angeli, Sofia Surdo, Lucia Malaguarnera.

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

Keywords:  mitochondria; muscle dysfunction; muscle homeostasis; oxidative stress; resveratrol; vitamin D

DOI:  https://doi.org/10.3390/ijms25147503
Int J Mol Sci. 2024 Jul 16. pii: 7789. [Epub ahead of print]25(14):

P38α MAPK Coordinates Mitochondrial Adaptation to Caloric Surplus in Skeletal Muscle.

Liron Waingerten-Kedem, Sharon Aviram, Achinoam Blau, Tony Hayek, Eyal Bengal.

  Excessive calorie intake leads to mitochondrial overload and triggers metabolic inflexibility and insulin resistance. In this study, we examined how attenuated p38α activity affects glucose and fat metabolism in the skeletal muscles of mice on a high-fat diet (HFD). Mice exhibiting diminished p38α activity (referred to as p38αAF) gained more weight and displayed elevated serum insulin levels, as well as a compromised response in the insulin tolerance test, compared to the control mice. Additionally, their skeletal muscle tissue manifested impaired insulin signaling, leading to resistance in insulin-mediated glucose uptake. Examination of muscle metabolites in p38αAF mice revealed lower levels of glycolytic intermediates and decreased levels of acyl-carnitine metabolites, suggesting reduced glycolysis and β-oxidation compared to the controls. Additionally, muscles of p38αAF mice exhibited severe abnormalities in their mitochondria. Analysis of myotubes derived from p38αAF mice revealed reduced mitochondrial respiratory capacity relative to the myotubes of the control mice. Furthermore, these myotubes showed decreased expression of Acetyl CoA Carboxylase 2 (ACC2), leading to increased fatty acid oxidation and diminished inhibitory phosphorylation of pyruvate dehydrogenase (PDH), which resulted in elevated mitochondrial pyruvate oxidation. The expected consequence of reduced mitochondrial respiratory function and uncontrolled nutrient oxidation observed in p38αAF myotubes mitochondrial overload and metabolic inflexibility. This scenario explains the increased likelihood of insulin resistance development in the muscles of p38αAF mice compared to the control mice on a high-fat diet. In summary, within skeletal muscles, p38α assumes a crucial role in orchestrating the mitochondrial adaptation to caloric surplus by promoting mitochondrial biogenesis and regulating the selective oxidation of nutrients, thereby preventing mitochondrial overload, metabolic inflexibility, and insulin resistance.

Keywords:  high-fat diet; insulin resistance; metabolomics; mitochondrial metabolism; p38α MAPK; skeletal muscle

DOI:  https://doi.org/10.3390/ijms25147789
Antioxidants (Basel). 2024 Jul 22. pii: 882. [Epub ahead of print]13(7):

The Double-Edged Sword of ROS in Muscle Wasting and COPD: Insights from Aging-Related Sarcopenia.

S M H Chan, S Selemidis, R Vlahos.

  An elevation in reactive oxygen species (ROS) is widely accepted to be a key mechanism that drives chronic obstructive pulmonary disease (COPD) and its major co-morbidity, skeletal muscle wasting. However, it will be perhaps a surprise to many that an elevation in ROS in skeletal muscle is also a critical process for normal skeletal muscle function and in the adaptations to physical exercise. The key message here is that ROS are not solely detrimental. This duality of ROS suggests that the mere use of a broad-acting antioxidant is destined to fail in alleviating skeletal muscle wasting in COPD because it will also be influencing critical physiological ROS-dependent processes. Here, we take a close look at this duality of ROS in skeletal muscle physiology and pathophysiology pertaining to COPD and will aim to gain critical insights from other skeletal muscle wasting conditions due to aging such as sarcopenia.

Keywords:  COPD comorbidities; antioxidants; inflammaging; microRNAs; oxidative stress

DOI:  https://doi.org/10.3390/antiox13070882
Nat Commun. 2024 Jul 21. 15(1): 6141

Systemic delivery of full-length dystrophin in Duchenne muscular dystrophy mice.

Yuan Zhou, Chen Zhang, Weidong Xiao, Roland W Herzog, Renzhi Han.

Current gene therapy for Duchenne muscular dystrophy (DMD) utilizes adeno-associated virus (AAV) to deliver micro-dystrophin (µDys), which does not provide full protection for striated muscles as it lacks many important functional domains of full-length (FL) dystrophin. Here we develop a triple vector system to deliver FL-dystrophin into skeletal and cardiac muscles. We split FL-dystrophin into three fragments linked to two orthogonal pairs of split intein, allowing efficient assembly of FL-dystrophin. The three fragments packaged in myotropic AAV (MyoAAV4A) restore FL-dystrophin expression in both skeletal and cardiac muscles in male mdx4cv mice. Dystrophin-glycoprotein complex components are also restored at the sarcolemma of dystrophic muscles. MyoAAV4A-delivered FL-dystrophin significantly improves muscle histopathology, contractility, and overall strength comparable to µDys, but unlike µDys, it also restores defective cavin 4 localization and associated signaling in mdx4cv heart. Therefore, our data support the feasibility of a mutation-independent FL-dystrophin gene therapy for DMD, warranting further clinical development.

DOI: https://doi.org/10.1038/s41467-024-50569-6
Biomedicines. 2024 Jul 01. pii: 1456. [Epub ahead of print]12(7):

Sympathetic Activation Promotes Sodium Glucose Co-Transporter-1 Protein Expression in Rodent Skeletal Muscle.

Jennifer R Matthews, Lakshini Y Herat, Markus P Schlaich, Vance B Matthews.

  The hyperactivation of the sympathetic nervous system (SNS) is linked to obesity, hypertension, and type 2 diabetes, which are characterized by elevated norepinephrine (NE) levels. Previous research has shown increased sodium-dependent glucose cotransporter 1 (SGLT1) protein levels in kidneys of hypertensive rodents, prompting investigation into the expression of SGLT1 in various tissues, such as skeletal muscle. This study aimed to assess (i) whether skeletal muscle cells and tissue express SGLT1 and SGLT2 proteins; (ii) if NE increases SGLT1 levels in skeletal muscle cells, and (iii) whether the skeletal muscle of neurogenically hypertensive mice exhibits increased SGLT1 expression. We found that (i) skeletal muscle cells and tissue are a novel source of the SGLT2 protein and that (ii) NE significantly elevated SGLT1 levels in skeletal muscle cells. As SGLT2 inhibition (SGLT2i) with Empagliflozin increased SGLT1 levels, in vivo studies with the dual inhibitor SGLT1/2i, Sotagliflozin were warranted. The treatment of neurogenically hypertensive mice using Sotagliflozin significantly reduced blood pressure. Our findings suggest that SNS activity upregulates the therapeutic target, SGLT1, in skeletal muscle, potentially worsening cardiometabolic control. As clinical trial data suggest cardiorenal benefits from SGLT2i, future studies should aim to utilize SGLT1i by itself, which may offer a therapeutic strategy for conditions with heightened SNS activity, such as hypertension, diabetes, and obesity.

Keywords:  blood pressure; diabetes; glucose; hypertension; sglt1; sglt2; skeletal muscle; sodium

DOI:  https://doi.org/10.3390/biomedicines12071456
Cells. 2024 Jul 18. pii: 1212. [Epub ahead of print]13(14):

Identification of Genomic Predictors of Muscle Fiber Size.

João Paulo L F Guilherme, Ekaterina A Semenova, Naoki Kikuchi, Hiroki Homma, Ayumu Kozuma, Mika Saito, Hirofumi Zempo, Shingo Matsumoto, Naoyuki Kobatake, Koichi Nakazato, Takanobu Okamoto, George John, Rinat A Yusupov, Andrey K Larin, Nikolay A Kulemin, Ilnaz M Gazizov, Edward V Generozov, Ildus I Ahmetov.

  The greater muscle fiber cross-sectional area (CSA) is associated with greater skeletal muscle mass and strength, whereas muscle fiber atrophy is considered a major feature of sarcopenia. Muscle fiber size is a polygenic trait influenced by both environmental and genetic factors. However, the genetic variants underlying inter-individual differences in muscle fiber size remain largely unknown. The aim of our study was to determine whether 1535 genetic variants previously identified in a genome-wide association study of appendicular lean mass are associated with the CSA of fast-twitch muscle fibers (which better predict muscle strength) in the m. vastus lateralis of 148 physically active individuals (19 power-trained and 28 endurance-trained females, age 28.0 ± 1.1; 28 power-trained and 73 endurance-trained males, age 31.1 ± 0.8). Fifty-seven single-nucleotide polymorphisms (SNPs) were identified as having an association with muscle fiber size (p < 0.05). Of these 57 SNPs, 31 variants were also associated with handgrip strength in the UK Biobank cohort (n = 359,729). Furthermore, using East Asian and East European athletic (n = 731) and non-athletic (n = 515) cohorts, we identified 16 SNPs associated with athlete statuses (sprinter, wrestler, strength, and speed-strength athlete) and weightlifting performance. All SNPs had the same direction of association, i.e., the lean mass-increasing allele was positively associated with the CSA of muscle fibers, handgrip strength, weightlifting performance, and power athlete status. In conclusion, we identified 57 genetic variants associated with both appendicular lean mass and fast-twitch muscle fiber size of m. vastus lateralis that may, in part, contribute to a greater predisposition to power sports.

Keywords:  athletes; athletic status; genetic diversity; genetic predisposition; genotype; human genetics; muscle hypertrophy; muscle strength; myofibers; sports

DOI:  https://doi.org/10.3390/cells13141212
Proc Natl Acad Sci U S A. 2024 Jul 30. 121(31): e2314760121

Ammonia transporter RhBG initiates downstream signaling and functional responses by activating NFκB.

Saurabh Mishra, Nicole Welch, Shashi Shekhar Singh, Khuraijam Dhanachandra Singh, Annette Bellar, Avinash Kumar, Lars N Deutz, Maxmillian D Hanlon, Sashi Kant, Sumitava Dastidar, Hailee Patel, Vandana Agrawal, Amy H Attaway, Ryan Musich, George R Stark, Francesco Saverio Tedesco, George A Truskey, I David Weiner, Sadashiva S Karnik, Srinivasan Dasarathy.

  Transceptors, solute transporters that facilitate intracellular entry of molecules and also initiate intracellular signaling events, have been primarily studied in lower-order species. Ammonia, a cytotoxic endogenous metabolite, is converted to urea in hepatocytes for urinary excretion in mammals. During hyperammonemia, when hepatic metabolism is impaired, nonureagenic ammonia disposal occurs primarily in skeletal muscle. Increased ammonia uptake in skeletal muscle is mediated by a membrane-bound, 12 transmembrane domain solute transporter, Rhesus blood group-associated B glycoprotein (RhBG). We show that in addition to its transport function, RhBG interacts with myeloid differentiation primary response-88 (MyD88) to initiate an intracellular signaling cascade that culminates in activation of NFκB. We also show that ammonia-induced MyD88 signaling is independent of the canonical toll-like receptor-initiated mechanism of MyD88-dependent NFκB activation. In silico, in vitro, and in situ experiments show that the conserved cytosolic J-domain of the RhBG protein interacts with the Toll-interleukin-1 receptor (TIR) domain of MyD88. In skeletal muscle from human patients, human-induced pluripotent stem cell-derived myotubes, and myobundles show an interaction of RhBG-MyD88 during hyperammonemia. Using complementary experimental and multiomics analyses in murine myotubes and mice with muscle-specific RhBG or MyD88 deletion, we show that the RhBG-MyD88 interaction is essential for the activation of NFkB but not ammonia transport. Our studies show a paradigm of substrate-dependent regulation of transceptor function with the potential for modulation of cellular responses in mammalian systems by decoupling transport and signaling functions of transceptors.

Keywords:  NFkB; hyperammonemia; skeletal muscle; solute transporter; transceptor

DOI:  https://doi.org/10.1073/pnas.2314760121
Mol Aspects Med. 2024 Jul 25. pii: S0098-2997(24)00052-9. [Epub ahead of print]99 101293

Molecular mechanisms of cancer cachexia. Role of exercise training.

Eva Tamayo-Torres, Amanda Garrido, Rafael de Cabo, Julián Carretero, María Carmen Gómez-Cabrera.

  Cancer-associated cachexia represents a multifactorial syndrome mainly characterized by muscle mass loss, which causes both a decrease in quality of life and anti-cancer therapy failure, among other consequences. The definition and diagnostic criteria of cachexia have changed and improved over time, including three different stages (pre-cachexia, cachexia, and refractory cachexia) and objective diagnostic markers. This metabolic wasting syndrome is characterized by a negative protein balance, and anti-cancer drugs like chemotherapy or immunotherapy exacerbate it through relatively unknown mechanisms. Due to its complexity, cachexia management involves a multidisciplinary strategy including not only nutritional and pharmacological interventions. Physical exercise has been proposed as a strategy to counteract the effects of cachexia on skeletal muscle, as it influences the mechanisms involved in the disease such as protein turnover, inflammation, oxidative stress, and mitochondrial dysfunction. This review will summarize the experimental and clinical evidence of the impact of physical exercise on cancer-associated cachexia.

Keywords:  Cachexia; Cancer; Cancer patients; Experimental models; Molecular mechanisms; Physical exercise

DOI:  https://doi.org/10.1016/j.mam.2024.101293
Biomedicines. 2024 Jun 25. pii: 1407. [Epub ahead of print]12(7):

Recent Advances in Pre-Clinical Development of Adiponectin Receptor Agonist Therapies for Duchenne Muscular Dystrophy.

Shivam Gandhi, Gary Sweeney, Christopher G R Perry.

  Duchenne muscular dystrophy (DMD) is caused by genetic mutations in the cytoskeletal-sarcolemmal anchor protein dystrophin. Repeated cycles of sarcolemmal tearing and repair lead to a variety of secondary cellular and physiological stressors that are thought to contribute to weakness, atrophy, and fibrosis. Collectively, these stressors can contribute to a pro-inflammatory milieu in locomotor, cardiac, and respiratory muscles. Given the many unwanted side effects that accompany current anti-inflammatory steroid-based approaches for treating DMD (e.g., glucocorticoids), there is a need to develop new therapies that address inflammation and other cellular dysfunctions. Adiponectin receptor (AdipoR) agonists, which stimulate AdipoR1 and R2 isoforms on various cell types, have emerged as therapeutic candidates for DMD due to their anti-inflammatory, anti-fibrotic, and pro-myogenic properties in pre-clinical human and rodent DMD models. Although these molecules represent a new direction for therapeutic intervention, the mechanisms through which they elicit their beneficial effects are not yet fully understood, and DMD-specific data is limited. The overarching goal of this review is to investigate how adiponectin signaling may ameliorate pathology associated with dystrophin deficiency through inflammatory-dependent and -independent mechanisms and to determine if current data supports their future progression to clinical trials.

Keywords:  Duchenne muscular dystrophy; adiponectin; cardiomyopathy; inflammation; skeletal muscle

DOI:  https://doi.org/10.3390/biomedicines12071407
iScience. 2024 Jul 19. 27(7): 110242

Dystrophin deficiency impairs cell junction formation during embryonic myogenesis from pluripotent stem cells.

Elise Mozin, Emmanuelle Massouridès, Virginie Mournetas, Clémence Lièvre, Audrey Bourdon, Dana L Jackson, Jonathan S Packer, Juyoung Seong, Cole Trapnell, Caroline Le Guiner, Oumeya Adjali, Christian Pinset, David L Mack, Jean-Baptiste Dupont.

  Mutations in the DMD gene lead to Duchenne muscular dystrophy (DMD), a severe neuromuscular disorder affecting young boys as they acquire motor functions. DMD is typically diagnosed at 2-4 years of age, but the absence of dystrophin has negative impacts on skeletal muscles before overt symptoms appear in patients, which poses a serious challenge in current standards of care. Here, we investigated the consequences of dystrophin deficiency during skeletal muscle development. We used single-cell transcriptome profiling to characterize the myogenic trajectory of human pluripotent stem cells and showed that DMD cells bifurcate to an alternative branch when they reach the somite stage. Dystrophin deficiency was linked to marked dysregulations of cell junction proteins involved in the cell state transitions characteristic of embryonic somitogenesis. Altogether, this work demonstrates that in vitro, dystrophin deficiency has deleterious effects on cell-cell communication during myogenic development, which should be considered in future therapeutic strategies for DMD.

Keywords:  biochemistry; biological sciences; cell biology; developmental biology; natural sciences; stem cells research

DOI:  https://doi.org/10.1016/j.isci.2024.110242
Biofactors. 2024 Jul 25.

Intramuscular administration of fractalkine modulates mitochondrial properties and promotes fast glycolytic phenotype.

Gourabamani Swalsingh, Punyadhara Pani, Unmod Senapati, Bijayashree Sahu, Sunil Pani, Benudhara Pati, Subhasmita Rout, Naresh C Bal.

  A newly categorized myokine called fractalkine (CX3CL1) has been associated with divergent conditions such as obesity, tissue inflammation, and exercise. CX3CL1 works through specific membrane-bound receptors (CX3CR1) found in various tissues including skeletal muscles. Studies indicate CX3CL1 induces muscles to uptake energy substrates thereby improving glucose utilization and countering diabetes. Here, we tested if the administration of purified CX3CL1 directly into mice skeletal muscles affects its histoarchitecture, mitochondrial activity, and expression of metabolic proteins. We analyzed four muscles: two upper-limb (quadriceps, hamstrings) and two lower-limb (tibialis anterior, gastrocnemius), contralateral leg muscles were taken as controls. The effects of CX3CL1 treatment on histoarchitecture, mitochondrial activity, and expression of metabolic proteins in muscles were characterized. We used histochemical staining succinate dehydrogenase (SDH)/cytochrome c oxidase (COX), myosin ATPase, alkaline phosphatase (ALP) to evaluate the mitochondrial activity, fiber types, and vascularization in the muscles, respectively. Western blotting was used to evaluate the expression of proteins associated with mitochondrial metabolism (OXPHOS), glycolysis, and vascularization. Overall, this study indicates CX3CL1 primarily modulates mitochondrial metabolism and shifts substrate preference toward glucose in the skeletal muscle. Evidence also supports that CX3CL1 stimulates the relative composition of fast fiber types, influencing selection of energy substrates in the skeletal muscle.

Keywords:  CX3CL1; OXPHOS; fiber types; mitochondria; myokine; skeletal muscle; vascularization

DOI:  https://doi.org/10.1002/biof.2092
Stem Cell Reports. 2024 Jul 06. pii: S2213-6711(24)00190-5. [Epub ahead of print]

Skeletal muscle-on-a-chip in microgravity as a platform for regeneration modeling and drug screening.

Soochi Kim, Bugra Ayan, Mahdis Shayan, Thomas A Rando, Ngan F Huang.

  Microgravity has been shown to lead to both muscle atrophy and impaired muscle regeneration. The purpose was to study the efficacy of microgravity to model impaired muscle regeneration in an engineered muscle platform and then to demonstrate the feasibility of performing drug screening in this model. Engineered human muscle was launched to the International Space Station National Laboratory, where the effect of microgravity exposure for 7 days was examined by transcriptomics and proteomics approaches. Gene set enrichment analysis of engineered muscle cultured in microgravity, compared to normal gravity conditions, highlighted a metabolic shift toward lipid and fatty acid metabolism, along with increased apoptotic gene expression. The addition of pro-regenerative drugs, insulin-like growth factor-1 (IGF-1) and a 15-hydroxyprostaglandin dehydrogenase inhibitor (15-PGDH-i), partially inhibited the effects of microgravity. In summary, microgravity mimics aspects of impaired myogenesis, and the addition of these drugs could partially inhibit the effects induced by microgravity.

Keywords:  aging; atrophy; microgravity; regeneration; skeletal muscle; tissue engineering; transcriptomics

DOI:  https://doi.org/10.1016/j.stemcr.2024.06.010
J Appl Physiol (1985). 2024 Jul 25.

Eccentric contraction increases hydrogen peroxide levels and alters gene expression through Nox2 in skeletal muscle of male mice.

Ryotaro Kano, Tatsuya Kusano, Reo Takeda, Hideki Shirakawa, David C Poole, Yutaka Kano, Daisuke Hoshino.

  Hydrogen peroxide (H2O2) is one of the key signaling factors regulating skeletal muscle adaptation to muscle contractions. Eccentric (ECC) and concentric (CONC) contractions drive different muscle adaptations with ECC resulting in greater changes. The present investigation tested the hypothesis that ECC produces higher cytosolic and mitochondrial H2O2 concentrations [H2O2] and alters gene expression more than CONC. Cytosolic and mitochondrial H2O2-sensitive fluorescent proteins, HyPer7 and MLS-HyPer7, were expressed in the anterior tibialis muscle of C57BL6J male mice. Before and for 60 min after either CONC or ECC (100 Hz, 50 contractions), [H2O2]cyto and [H2O2]mito were measured by in vivo fluorescence microscopy. RNA sequencing was performed in control (non-contracted), CONC and ECC muscles to identify genes impacted by the contractions. [H2O2]cyto immediately after ECC was greater than after CONC (CONC: + 6%, ECC: + 11% vs rest, p < 0.05) and remained higher for at least 60 min into recovery. In contrast, the elevation of [H2O2]mito was independent of the contraction modes (Time; p < 0.0042, contraction mode; p = 0.4965). The impact of ECC on [H2O2]cyto were abolished by NADPH oxidase 2 (Nox2) inhibition (GSK2795039). Differentially expressed genes were not present after CONC or ECC+GSK but were found after ECC and were enriched for vascular development and apoptosis-related genes, among others. In conclusion, in mouse anterior tibialis ECC, but not CONC, evoke a pronounced cytosolic H2O2 response, caused by Nox2, that is mechanistically linked to gene expression modifications.

Keywords:  Cytosolic; Eccentric contraction; Mitochondria; Reactive oxygen species (ROS); transcriptomics

DOI:  https://doi.org/10.1152/japplphysiol.00335.2024
Genes (Basel). 2024 Jul 14. pii: 918. [Epub ahead of print]15(7):

T-Allele Carriers of Mono Carboxylate Transporter One Gene Polymorphism rs1049434 Demonstrate Altered Substrate Metabolization during Exhaustive Exercise.

Benedikt Gasser, Alain Dössegger, Marie-Noëlle Giraud, Martin Flück.

   BACKGROUND: Polymorphism rs1049434 characterizes the nonsynonymous exchange of adenosine (A) by thymidine (T) in the gene for monocarboxylate transporter 1 (MCT1). We tested whether T-allele carriers of rs1049434 demonstrate increased accumulation of markers of metabolic strain.
METHODS: Physically active, healthy, young male subjects (n = 22) conducted a power-matched one-legged cycling exercise to exhaustion. Metabolic substrates in capillary blood, selected metabolic compounds, and indices for the slow oxidative phenotype of vastus lateralis muscle were quantified in samples collected before and after exercise. The genotypes of the rs1049434 polymorphism were determined with polymerase chain reactions.
RESULTS: One-legged exercise affected the concentration of muscle metabolites entering the tricarboxylic acid cycle, such as acetyl-co-enzyme A (+448%) and acetyl-L-carnitine (+548%), muscle glycogen (-59%), and adenosine monophosphate (-39%), 30 min post-exercise. Exercise-related variability in the muscular concentration of glycogen, long-chain acyl co-enzyme As and a triglyceride, nicotinamide adenine dinucleotide (NADH), and adenosine monophosphate (AMP) interacted with rs1049434. T-allele carriers demonstrated a 39% lesser reduction in glycogen after exercise than non-carriers when NADH increased only in the non-carriers. Muscle lactate concentration was 150% higher, blood triacyl-glyceride concentration was 53% lower, and slow fiber percentage was 20% lower in T-allele carriers.
DISCUSSION: The observations suggest a higher anaerobic glycolytic strain during exhaustive exercise and a lowered lipid handling in T-allele non-carriers.

Keywords:  aerobic; exercise; fatigue; genotype; ketone; lactate; mass spectroscopy; metabolism; muscle fiber; skeletal muscle; slow

DOI:  https://doi.org/10.3390/genes15070918
Sci Rep. 2024 Jul 23. 14(1): 16878

Dapagliflozin improves skeletal muscle insulin sensitivity through SIRT1 activation induced by nutrient deprivation state.

Qi Gao, Yingying Jiang, Zhenqiang Song, Huizhu Ren, Yan Kong, Cong Wang, Miaoyan Zheng, Chunyan Shan, Yanhui Yang.

  Lipid peroxidation and mitochondrial damage impair insulin sensitivity in skeletal muscle. Sirtuin-1 (SIRT1) protects mitochondria and activates under energy restriction. Dapagliflozin (Dapa) is an antihyperglycaemic agent that belongs to the sodium-glucose cotransporter-2 (SGLT2) inhibitors. Evidence shows that Dapa can induce nutrient deprivation effects, providing additional metabolic benefits. This study investigates whether Dapa can trigger nutrient deprivation to activate SIRT1 and enhance insulin sensitivity in skeletal muscle. We treated diet-induced obese (DIO) mice with Dapa and measured metabolic parameters, lipid accumulation, oxidative stress, mitochondrial function, and glucose utilization in skeletal muscle. β-hydroxybutyric acid (β-HB) was intervened in C2C12 myotubes. The role of SIRT1 was verified by RNA interference. We found that Dapa treatment induced nutrient deprivation state and reduced lipid deposition and oxidative stress, improved mitochondrial function and glucose tolerance in skeletal muscle. The same positive effects were observed after β-HB intervening for C2C12 myotubes, and the promoting effects on glucose utilization were diminished by SIRT1 RNA interference. Thus, Dapa promotes a nutrient deprivation state and enhances skeletal muscle insulin sensitivity via SIRT1 activation. In this study, we identified a novel hypoglycemic mechanism of Dapa and the potential mechanistic targets.

Keywords:  Insulin resistance; Nutrient deprivation state; SGLT2 inhibitor; SIRT1; Skeletal muscle

DOI:  https://doi.org/10.1038/s41598-024-67755-7
Front Cell Dev Biol. 2024 ;12 1399319

Single cell RNA sequencing of human FAPs reveals different functional stages in Duchenne muscular dystrophy.

Esther Fernández-Simón, Patricia Piñol-Jurado, Rasya Gokul-Nath, Adrienne Unsworth, Jorge Alonso-Pérez, Marianela Schiava, Andres Nascimento, Giorgio Tasca, Rachel Queen, Dan Cox, Xavier Suarez-Calvet, Jordi Díaz-Manera.

  Background: Duchenne muscular dystrophy is a genetic disease produced by mutations in the dystrophin gene characterized by early onset muscle weakness leading to severe and irreversible disability. Muscle degeneration involves a complex interplay between multiple cell lineages spatially located within areas of damage, termed the degenerative niche, including inflammatory cells, satellite cells (SCs) and fibro-adipogenic precursor cells (FAPs). FAPs are mesenchymal stem cell which have a pivotal role in muscle homeostasis as they can either promote muscle regeneration or contribute to muscle degeneration by expanding fibrotic and fatty tissue. Although it has been described that FAPs could have a different behavior in DMD patients than in healthy controls, the molecular pathways regulating their function as well as their gene expression profile are unknown. Methods: We used single-cell RNA sequencing (scRNAseq) with 10X Genomics and Illumina technology to elucidate the differences in the transcriptional profile of isolated FAPs from healthy and DMD patients. Results: Gene signatures in FAPs from both groups revealed transcriptional differences. Seurat analysis categorized cell clusters as proliferative FAPs, regulatory FAPs, inflammatory FAPs, and myofibroblasts. Differentially expressed genes (DEGs) between healthy and DMD FAPs included upregulated genes CHI3L1, EFEMP1, MFAP5, and TGFBR2 in DMD. Functional analysis highlighted distinctions in system development, wound healing, and cytoskeletal organization in control FAPs, while extracellular organization, degradation, and collagen degradation were upregulated in DMD FAPs. Validation of DEGs in additional samples (n = 9) using qPCR reinforced the specific impact of pathological settings on FAP heterogeneity, reflecting their distinct contribution to fibro or fatty degeneration in vivo. Conclusion: Using the single-cell RNA seq from human samples provide new opportunities to study cellular coordination to further understand the regulation of muscle homeostasis and degeneration that occurs in muscular dystrophies.

Keywords:  adipogenesis; fibro-adipogenic progenitor cells; fibrosis; muscle dystrophies; single cell RNA sequencing

DOI:  https://doi.org/10.3389/fcell.2024.1399319
Nat Nanotechnol. 2024 Jul 22.

Magnetic-field-driven targeting of exosomes modulates immune and metabolic changes in dystrophic muscle.

Chiara Villa, Valeria Secchi, Mirco Macchi, Luana Tripodi, Elena Trombetta, Desiree Zambroni, Francesco Padelli, Michele Mauri, Monica Molinaro, Rebecca Oddone, Andrea Farini, Antonella De Palma, Laura Varela Pinzon, Federica Santarelli, Roberto Simonutti, PierLuigi Mauri, Laura Porretti, Marcello Campione, Domenico Aquino, Angelo Monguzzi, Yvan Torrente.

Exosomes are promising therapeutics for tissue repair and regeneration to induce and guide appropriate immune responses in dystrophic pathologies. However, manipulating exosomes to control their biodistribution and targeting them in vivo to achieve adequate therapeutic benefits still poses a major challenge. Here we overcome this limitation by developing an externally controlled delivery system for primed annexin A1 myo-exosomes (Exomyo). Effective nanocarriers are realized by immobilizing the Exomyo onto ferromagnetic nanotubes to achieve controlled delivery and localization of Exomyo to skeletal muscles by systemic injection using an external magnetic field. Quantitative muscle-level analyses revealed that macrophages dominate the uptake of Exomyo from these ferromagnetic nanotubes in vivo to synergistically promote beneficial muscle responses in a murine animal model of Duchenne muscular dystrophy. Our findings provide insights into the development of exosome-based therapies for muscle diseases and, in general, highlight the formulation of effective functional nanocarriers aimed at optimizing exosome biodistribution.

DOI: https://doi.org/10.1038/s41565-024-01725-y