bims-moremu 2023-12-03 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–12–03
35 papers selected by
Anna Vainshtein, Craft Science Inc.

Loss of mitochondrial Ca2+ uptake protein 3 impairs skeletal muscle calcium handling and exercise capacity.
CARM1 drives mitophagy and autophagy flux during fasting-induced skeletal muscle atrophy.
Skeletal muscle-specific inducible AMPKα1/α2 knockout mice develop muscle weakness, glycogen depletion, and fibrosis that persists during disuse atrophy.
Muscle miRNAs are influenced by sex at baseline and in response to exercise.
Mouse skeletal muscle adaptations to different durations of treadmill exercise after the cessation of FOLFOX chemotherapy.
Soluble Factors Associated with Denervation-induced Skeletal Muscle Atrophy.
Targeted brain-specific tauopathy compromises peripheral skeletal muscle integrity and function.
Aged gastrocnemius muscle of mice positively responds to a late onset adapted physical training.
Filamin A cooperates with the androgen receptor in preventing skeletal muscle senescence.
Class IIa HDACs inhibit cell death pathways and protect muscle integrity in response to lipotoxicity.
Extracellular matrix: the critical contributor to skeletal muscle regeneration-a comprehensive review.
Genetic diversity modulates the physical and transcriptomic response of skeletal muscle to simulated microgravity in male mice.
Downhill running and caloric restriction attenuate insulin resistance associated skeletal muscle atrophy via the promotion of M2-like macrophages through TRIB3-AKT pathway.
The Effects of Antioxidants and Pulsed Magnetic Fields on Slow and Fast Skeletal Muscle Atrophy Induced by Streptozotocin: A Preclinical Study.
Enhancement of mitochondrial energy metabolism by melatonin promotes vascularized skeletal muscle regeneration in a volumetric muscle loss model.
Exercise and Ischemia-Activated Pathways in Limb Muscle Angiogenesis and Vascular Regeneration.
Lack of vitamin D signalling shifts skeletal muscles towards oxidative metabolism.
Camk2a suppresses denervated muscle atrophy by maintaining the Ca2+ homeostasis in muscle cells.
Remodelling of skeletal muscle myosin metabolic states in hibernating mammals.
Biomechanical Stimulation of Muscle Constructs Influences Phenotype of Bone Constructs by Modulating Myokine Secretion.
Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis.
Profiling of adenine-derived signaling molecules, cytokinins, in myotubes reveals fluctuations in response to lipopolysaccharide-induced cell stress.
Skeletal muscle-secreted DLPC orchestrates systemic energy homeostasis by enhancing adipose browning.
A human immune/muscle xenograft model of FSHD muscle pathology.
Human HDL subclasses modulate energy metabolism in skeletal muscle cells.
Early in vivo detection of denervation-induced atrophy by luminescence transient nanothermometry.
Spontaneous Alignment of Myotubes through Myogenic Progenitor Cell Migration.
GDF8 inhibition enhances musculoskeletal recovery and mitigates posttraumatic osteoarthritis following joint injury.
Interleukin 4 improved adipose-derived stem cells engraftment via interacting with fibro/adipogenic progenitors in dystrophic mice.
RBFOX2 regulated EYA3 isoforms partner with SIX4 or ZBTB1 to control transcription during myogenesis.
Diosmin Promotes Myogenesis via Activating the Akt/FOXO1 Pathway to Facilitate the Proliferation of C2C12 Myoblasts.
Titin-based force regulates cardiac myofilament structures mediating length-dependent activation.
All-trans retinoic acid and dexamethasone regulate phagocytosis-related gene expression and enhance dead cell uptake in C2C12 myoblast cells.
Editorial: Sarcopenia and frailty: the role of physical activity for better aging.
Exercise Regulates Myokines on Aging-related Diseases through Muscle-brain Crosstalk.

J Physiol. 2023 Nov 28.

Loss of mitochondrial Ca2+ uptake protein 3 impairs skeletal muscle calcium handling and exercise capacity.

Barbara Roman, Yusuf Mastoor, Yingfan Zhang, Dennis Gross, Danielle Springer, Chengyu Liu, Brian Glancy, Elizabeth Murphy.

  Mitochondrial calcium concentration ([Ca2+ ]m ) plays an essential role in bioenergetics, and loss of [Ca2+ ]m homeostasis can trigger diseases and cell death in numerous cell types. Ca2+ uptake into mitochondria occurs via the mitochondrial Ca2+ uniporter (MCU), which is regulated by three mitochondrial Ca2+ uptake (MICU) proteins localized in the intermembrane space, MICU1, 2, and 3. We generated a mouse model of systemic MICU3 ablation and examined its physiological role in skeletal muscle. We found that loss of MICU3 led to impaired exercise capacity. When the muscles were directly stimulated there was a decrease in time to fatigue. MICU3 ablation significantly increased the maximal force of the KO muscle and altered fibre type composition with an increase in the ratio of type IIb (low oxidative capacity) to type IIa (high oxidative capacity) fibres. Furthermore, MICU3-KO mitochondria have reduced uptake of Ca2+ and increased phosphorylation of pyruvate dehydrogenase, indicating that KO animals contain less Ca2+ in their mitochondria. Skeletal muscle from MICU3-KO mice exhibited lower net oxidation of NADH during electrically stimulated muscle contraction compared with wild-type. These data demonstrate that MICU3 plays a role in skeletal muscle physiology by setting the proper threshold for mitochondrial Ca2+ uptake, which is important for matching energy demand and supply in muscle. KEY POINTS: Mitochondrial calcium uptake is an important regulator of bioenergetics and cell death and is regulated by the mitochondrial calcium uniporter (MCU) and three calcium sensitive regulatory proteins (MICU1, 2 and 3). Loss of MICU3 leads to impaired exercise capacity and decreased time to skeletal muscle fatigue. Skeletal muscle from MICU3-KO mice exhibits a net oxidation of NADH during electrically stimulated muscle contractions, suggesting that MICU3 plays a role in skeletal muscle physiology by matching energy demand and supply.

Keywords:  MICU3; calcium uptake; skeletal muscle

DOI:  https://doi.org/10.1113/JP284894
Autophagy. 2023 Nov 29.

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

Derek W Stouth, Tiffany L vanLieshout, Andrew I Mikhail, Sean Y Ng, Rozhin Raziee, Brittany A Edgett, Goutham Vasam, Erin K Webb, Kevin S Gilotra, Matthew Markou, Hannah C Pineda, Brianna G Bettencourt-Mora, Haleema Noor, Zachary Moll, Megan E Bittner, Brendon J Gurd, Keir J Menzies, Vladimir Ljubicic.

  CARM1 (coactivator associated arginine methyltransferase 1) has recently emerged as a powerful regulator of skeletal muscle biology. However, the molecular mechanisms by which the methyltransferase remodels muscle remain to be fully understood. In this study, carm1 skeletal muscle-specific knockout (mKO) mice exhibited lower muscle mass with dysregulated macroautophagic/autophagic and atrophic signaling, including depressed AMP-activated protein kinase (AMPK) site-specific phosphorylation of ULK1 (unc-51 like autophagy activating kinase 1; Ser555) and FOXO3 (forkhead box O3; Ser588), as well as MTOR (mechanistic target of rapamycin kinase)-induced inhibition of ULK1 (Ser757), along with AKT/protein kinase B site-specific suppression of FOXO1 (Ser256) and FOXO3 (Ser253). In addition to lower mitophagy and autophagy flux in skeletal muscle, carm1 mKO led to increased mitochondrial PRKN/parkin accumulation, which suggests that CARM1 is required for basal mitochondrial turnover and autophagic clearance. carm1 deletion also elicited PPARGC1A (PPARG coactivator 1 alpha) activity and a slower, more oxidative muscle phenotype. As such, these carm1 mKO-evoked adaptations disrupted mitophagy and autophagy induction during food deprivation and collectively served to mitigate fasting-induced muscle atrophy. Furthermore, at the threshold of muscle atrophy during food deprivation experiments in humans, skeletal muscle CARM1 activity decreased similarly to our observations in mice, and was accompanied by site-specific activation of ULK1 (Ser757), highlighting the translational impact of the methyltransferase in human skeletal muscle. Taken together, our results indicate that CARM1 governs mitophagic, autophagic, and atrophic processes fundamental to the maintenance and remodeling of muscle mass. Targeting the enzyme may provide new therapeutic approaches for mitigating skeletal muscle atrophy.

Keywords:  Atrophy; autophagy; coactivator-associated arginine methyltransferase 1; fasting; mitophagy; skeletal muscle

DOI:  https://doi.org/10.1080/15548627.2023.2288528
Am J Physiol Endocrinol Metab. 2023 Nov 29.

Skeletal muscle-specific inducible AMPKα1/α2 knockout mice develop muscle weakness, glycogen depletion, and fibrosis that persists during disuse atrophy.

Jonathan J Petrocelli, Jingtong Liu, Elena M Yee, Patrick J Ferrara, Paul-Emile Bourrant, Naomi M M P de Hart, Sean M Tatum, William J Holland, Katsuhiko Funai, Micah J Drummond.

  The 5' adenosine monophosphate-activated protein kinase (AMPK) is an important skeletal muscle regulator implicated as a possible therapeutic target to ameliorate the local undesired deconditioning of disuse atrophy. However, the muscle-specific role of AMPK in regulating muscle function, fibrosis, and transcriptional reprogramming during physical disuse are unknown. The purpose of this study was to determine how the absence of both catalytic subunits of AMPK in skeletal muscle influence muscle force production, collagen deposition, and the transcriptional landscape. We generated skeletal muscle-specific tamoxifen inducible AMPKα1/α2 knock out (AMPKα-/-) mice that underwent 14 days of hindlimb unloading (HU) or remained ambulatory for 14 days (AMB). We found that AMPKα-/- during ambulatory conditions altered body weight and myofiber size, decreased muscle function, depleted glycogen stores and TBC1 domain family member 1 (TBC1D1) phosphorylation, increased collagen deposition, and altered transcriptional pathways. Primarily pathways related to cellular senescence, and mitochondrial biogenesis and function were influenced by the absence of AMPKα. The effects of AMPKα-/- persisted, but were not worsened, following hindlimb unloading. Together, we report that AMPKα is necessary to maintain skeletal muscle quality.

Keywords:  AMPK; collagen; hindlimb unloading; muscle fatigue; senescence

DOI:  https://doi.org/10.1152/ajpendo.00261.2023
BMC Biol. 2023 Nov 27. 21(1): 273

Muscle miRNAs are influenced by sex at baseline and in response to exercise.

Danielle Hiam, Shanie Landen, Macsue Jacques, Sarah Voisin, Séverine Lamon, Nir Eynon.

   BACKGROUND: Sex differences in microRNA (miRNA) expression profiles have been found across multiple tissues. Skeletal muscle is one of the most sex-biased tissues of the body. MiRNAs are necessary for development and have regulatory roles in determining skeletal muscle phenotype and have important roles in the response to exercise in muscle. Yet there is limited research into the role and regulation of miRNAs in the skeletal muscle at baseline and in response to exercise, a well-known modulator of miRNA expression. The aim of this study was to investigate the effect of sex on miRNA expression in the skeletal muscle at baseline and after an acute bout of high-intensity interval exercise. A total of 758 miRNAs were measured using Taqman®miRNA arrays in the skeletal muscle of 42 healthy participants from the Gene SMART study (23 males and 19 females of comparable fitness levels and aged 18-45 years), of which 308 were detected. MiRNAs that differed by sex at baseline and whose change in expression following high-intensity interval exercise differed between the sexes were identified using mixed linear models adjusted for BMI and Wpeak. We performed in silico analyses to identify the putative gene targets of the exercise-induced, sex-specific miRNAs and overrepresentation analyses to identify enriched biological pathways. We performed functional assays by overexpressing two sex-biased miRNAs in human primary muscle cells derived from male and female donors to understand their downstream effects on the transcriptome.
RESULTS: At baseline, 148 miRNAs were differentially expressed in the skeletal muscle between the sexes. Interaction analysis identified 111 miRNAs whose response to an acute bout of high-intensity interval exercise differed between the sexes. Sex-biased miRNA gene targets were enriched for muscle-related processes including proliferation and differentiation of muscle cells and numerous metabolic pathways, suggesting that miRNAs participate in programming sex differences in skeletal muscle function. Overexpression of sex-biased miRNA-30a and miRNA-30c resulted in profound changes in gene expression profiles that were specific to the sex of the cell donor in human primary skeletal muscle cells.
CONCLUSIONS: We uncovered sex differences in the expression levels of muscle miRNAs at baseline and in response to acute high-intensity interval exercise. These miRNAs target regulatory pathways essential to skeletal muscle development and metabolism. Our findings highlight that miRNAs play an important role in programming sex differences in the skeletal muscle phenotype.

Keywords:  Sex differences; Skeletal muscle; Transcriptome; miRNA

DOI:  https://doi.org/10.1186/s12915-023-01755-3
Front Physiol. 2023 ;14 1283674

Mouse skeletal muscle adaptations to different durations of treadmill exercise after the cessation of FOLFOX chemotherapy.

Jessica L Halle, Brittany R Counts, Quan Zhang, Kylie M James, Melissa J Puppa, Stephen E Alway, James A Carson.

  FOLFOX (5-fluorouracil, leucovorin, oxaliplatin) chemotherapy is a treatment for colorectal cancer that can induce persistent fatigue and metabolic dysfunction. Regular exercise after chemotherapy cessation is widely recommended for cancer patients and has been shown to improve fatigue resistance in mice. However, gaps remain in understanding whether the early systemic and skeletal muscle adaptations to regular exercise are altered by prior FOLFOX chemotherapy treatment. Furthermore, the effects of exercise duration on early metabolic and skeletal muscle transcriptional adaptations are not fully established. Purpose: Investigate the effects of prior FOLFOX chemotherapy treatment on the early adaptations to repeated short- or long-duration treadmill exercise, including the fasting regulation of circulating metabolic regulators, skeletal muscle COXIV activity and myokine/exerkine gene expression in male mice. Methods: Male C57BL6/J mice completed 4 cycles of FOLFOX or PBS and were allowed to recover for 4-weeks. Subsets of mice performed 14 sessions (6 d/wk, 18 m/min, 5% grade) of short- (10 min/d) or long-duration (55 min/d) treadmill exercise. Blood plasma and muscle tissues were collected 48-72 h after the last exercise bout for biochemical analyses. Results: Long-duration exercise increased fasting plasma osteocalcin, LIF, and IL-6 in healthy PBS mice, and these changes were ablated by prior FOLFOX treatment. Slow-oxidative soleus muscle COXIV activity increased in response to long-duration exercise in PBS mice, which was blocked by prior FOLFOX treatment. Fast-glycolytic plantaris muscle COXIV activity increased with short-duration exercise independent of FOLFOX administration. There was a main effect for long-duration exercise to increase fasting muscle IL-6 and COXIV mRNA expression independent of FOLFOX. FOLFOX administration reduced muscle IL-6, LIF, and BDNF mRNA expression irrespective of long-duration exercise. Interestingly, short-duration exercise suppressed the FOLXOX induction of muscle myostatin mRNA expression. Conclusion: FOLFOX attenuated early exercise adaptations related to fasting circulating osteocalcin, LIF, and IL-6. However, prior FOLFOX treatment did not alter the exercise adaptations of plantaris muscle COXIV activity and plasma adiponectin. An improved understanding of mechanisms underlying exercise adaptations after chemotherapy will provide the basis for successfully treating fatigue and metabolic dysfunction in cancer survivors.

Keywords:  COXIV; IL-6; LIF; cancer survivors; exerkines; myokines; myostatin

DOI:  https://doi.org/10.3389/fphys.2023.1283674
Curr Protein Pept Sci. 2023 Nov 24.

Soluble Factors Associated with Denervation-induced Skeletal Muscle Atrophy.

Marianny Portal, Claudio Cabello-Verrugio.

  Skeletal muscle tissue has the critical function of mechanical support protecting the body. In addition, its functions are strongly influenced by the balanced synthesis and degradation processes of structural and regulatory proteins. The inhibition of protein synthesis and/or the activation of catabolism generally determines a pathological state or condition called muscle atrophy, a reduction in muscle mass that results in partial or total loss of function. It has been established that many pathophysiological conditions can cause a decrease in muscle mass. Skeletal muscle innervation involves stable and functional neural interactions with muscles via neuromuscular junctions and is essential for maintaining normal muscle structure and function. Loss of motor innervation induces rapid skeletal muscle fiber degeneration with activation of atrophy-related signaling and subsequent disassembly of sarcomeres, altering normal muscle function. After denervation, an inflammation stage is characterized by the increased expression of pro-inflammatory cytokines that determine muscle atrophy. In this review, we highlighted the impact of some soluble factors on the development of muscle atrophy by denervation.

Keywords:  Muscular atrophy; cytokines; denervation; muscle fiber degeneration; pro-inflammatory cytokines.; protein synthesis; soluble factors

DOI:  https://doi.org/10.2174/0113892037189827231018092036
bioRxiv. 2023 Nov 17. pii: 2023.11.17.567586. [Epub ahead of print]

Targeted brain-specific tauopathy compromises peripheral skeletal muscle integrity and function.

Bryan Alava, Gabriela Hery, Silvana Sidhom, Stefan Prokop, Karyn Esser, Jose Abisambra.

Tauopathies are neurodegenerative disorders in which the pathological intracellular aggregation of the protein tau causes cognitive deficits. Additionally, clinical studies report muscle weakness in populations with tauopathy. However, whether neuronal pathological tau species confer muscle weakness, and whether skeletal muscle maintains contractile capacity in primary tauopathy remains unknown. Here, we identified skeletal muscle abnormalities in a mouse model of primary tauopathy, expressing human mutant P301L-tau using adeno-associated virus serotype 8 (AAV8). AAV8-P301L mice showed grip strength deficits, hyperactivity, and abnormal histological features of skeletal muscle. Additionally, spatially resolved gene expression of muscle cross sections were altered in AAV8-P301L myofibers. Transcriptional changes showed alterations of genes encoding sarcomeric proteins, proposing a weakness phenotype. Strikingly, specific force of the soleus muscle was blunted in AAV8-P301L tau male mice. Our findings suggest tauopathy has peripheral consequences in skeletal muscle that contribute to weakness in tauopathy.

DOI: https://doi.org/10.1101/2023.11.17.567586
Front Cell Dev Biol. 2023 ;11 1273309

Aged gastrocnemius muscle of mice positively responds to a late onset adapted physical training.

Barbara Cisterna, Francesco Demetrio Lofaro, Maria Assunta Lacavalla, Federico Boschi, Manuela Malatesta, Daniela Quaglino, Carlo Zancanaro, Federica Boraldi.

  Introduction: A regular physical training is known to contribute to preserve muscle mass and strength, maintaining structure and function of neural and vascular compartments and preventing muscle insulin resistance and inflammation. However, physical activity is progressively reduced during aging causing mobility limitations and poor quality of life. Although physical exercise for rehabilitation purposes (e.g., after fractures or cardiovascular events) or simply aiming to counteract the development of sarcopenia is frequently advised by physicians, nevertheless few data are available on the targets and the global effects on the muscle organ of adapted exercise especially if started at old age. Methods: To contribute answering this question for medical translational purposes, the proteomic profile of the gastrocnemius muscle was analyzed in 24-month-old mice undergoing adapted physical training on a treadmill for 12 weeks or kept under a sedentary lifestyle condition. Proteomic data were implemented by morphological and morphometrical ultrastructural evaluations. Results and Discussion: Data demonstrate that muscles can respond to adapted physical training started at old age, positively modulating their morphology and the proteomic profile fostering protective and saving mechanisms either involving the extracellular compartment as well as muscle cell components and pathways (i.e., mitochondrial processes, cytoplasmic translation pathways, chaperone-dependent protein refolding, regulation of skeletal muscle contraction). Therefore, this study provides important insights on the targets of adapted physical training, which can be regarded as suitable benchmarks for future in vivo studies further exploring the effects of this type of physical activity by functional/metabolic approaches.

Keywords:  ageing; electron microscopy; matrix; physical training; proteomics; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2023.1273309
Cell Death Discov. 2023 Dec 02. 9(1): 437

Filamin A cooperates with the androgen receptor in preventing skeletal muscle senescence.

Marzia Di Donato, Antimo Moretti, Carmela Sorrentino, Giuseppe Toro, Giulia Gentile, Giovanni Iolascon, Gabriella Castoria, Antimo Migliaccio.

Aging induces a slow and progressive decrease in muscle mass and function, causing sarcopenia. Androgens control muscle trophism and exert important anabolic functions through the binding to the androgen receptor. Therefore, analysis of the androgen receptor-mediated actions in skeletal muscle might provide new hints for a better understanding of sarcopenia pathogenesis. In this study, we report that expression of the androgen receptor in skeletal muscle biopsies from 20 subjects is higher in young, as compared with old subjects. Co-immunoprecipitation experiments reveal that the androgen receptor is complexed with filamin A mainly in young, that in old subjects. Therefore, we have in depth analyzed the role of such complex using C2C12 myoblasts that express a significant amount of the androgen receptor. In these cells, hormone stimulation rapidly triggers the assembly of the androgen receptor/filamin A complex. Such complex prevents the senescence induced by oxidative stress in C2C12 cells, as disruption of the androgen receptor/filamin A complex by Rh-2025u stapled peptide re-establishes the senescent phenotype in C2C12 cells. Simultaneously, androgen stimulation of C2C12 cells rapidly triggers the activation of various signaling effectors, including Rac1, focal adhesion kinase, and mitogen-activated kinases. Androgen receptor blockade by bicalutamide or perturbation of androgen receptor/filamin A complex by Rh-2025u stapled peptide both reverse the hormone activation of signaling effectors. These findings further reinforce the role of the androgen receptor and its extranuclear partners in the rapid hormone signaling that controls the functions of C2C12 cells. Further investigations are needed to promote clinical interventions that might ameliorate muscle cell function as well the clinical outcome of age-related frailty.

DOI: https://doi.org/10.1038/s41420-023-01737-y
Cell Death Dis. 2023 Dec 01. 14(12): 787

Class IIa HDACs inhibit cell death pathways and protect muscle integrity in response to lipotoxicity.

Sheree D Martin, Timothy Connor, Andrew Sanigorski, Kevin A McEwen, Darren C Henstridge, Brunda Nijagal, David De Souza, Dedreia L Tull, Peter J Meikle, Greg M Kowalski, Clinton R Bruce, Paul Gregorevic, Mark A Febbraio, Fiona M Collier, Ken R Walder, Sean L McGee.

Lipotoxicity, the accumulation of lipids in non-adipose tissues, alters the metabolic transcriptome and mitochondrial metabolism in skeletal muscle. The mechanisms involved remain poorly understood. Here we show that lipotoxicity increased histone deacetylase 4 (HDAC4) and histone deacetylase 5 (HDAC5), which reduced the expression of metabolic genes and oxidative metabolism in skeletal muscle, resulting in increased non-oxidative glucose metabolism. This metabolic reprogramming was also associated with impaired apoptosis and ferroptosis responses, and preserved muscle cell viability in response to lipotoxicity. Mechanistically, increased HDAC4 and 5 decreased acetylation of p53 at K120, a modification required for transcriptional activation of apoptosis. Redox drivers of ferroptosis derived from oxidative metabolism were also reduced. The relevance of this pathway was demonstrated by overexpression of loss-of-function HDAC4 and HDAC5 mutants in skeletal muscle of obese db/db mice, which enhanced oxidative metabolic capacity, increased apoptosis and ferroptosis and reduced muscle mass. This study identifies HDAC4 and HDAC5 as repressors of skeletal muscle oxidative metabolism, which is linked to inhibition of cell death pathways and preservation of muscle integrity in response to lipotoxicity.

DOI: https://doi.org/10.1038/s41419-023-06319-5
Inflamm Regen. 2023 Nov 27. 43(1): 58

Extracellular matrix: the critical contributor to skeletal muscle regeneration-a comprehensive review.

Khurshid Ahmad, Sibhghatulla Shaikh, Hee Jin Chun, Shahid Ali, Jeong Ho Lim, Syed Sayeed Ahmad, Eun Ju Lee, Inho Choi.

  The regenerative ability of skeletal muscle (SM) in response to damage, injury, or disease is a highly intricate process that involves the coordinated activities of multiple cell types and biomolecular factors. Of these, extracellular matrix (ECM) is considered a fundamental component of SM regenerative ability. This review briefly discusses SM myogenesis and regeneration, the roles played by muscle satellite cells (MSCs), other cells, and ECM components, and the effects of their dysregulations on these processes. In addition, we review the various types of ECM scaffolds and biomaterials used for SM regeneration, their applications, recent advances in ECM scaffold research, and their impacts on tissue engineering and SM regeneration, especially in the context of severe muscle injury, which frequently results in substantial muscle loss and impaired regenerative capacity. This review was undertaken to provide a comprehensive overview of SM myogenesis and regeneration, the stem cells used for muscle regeneration, the significance of ECM in SM regeneration, and to enhance understanding of the essential role of the ECM scaffold during SM regeneration.

Keywords:  Biomaterials; ECM scaffold; Extracellular matrix; Muscle loss; Regeneration; Skeletal muscle

DOI:  https://doi.org/10.1186/s41232-023-00308-z
NPJ Microgravity. 2023 Dec 01. 9(1): 86

Genetic diversity modulates the physical and transcriptomic response of skeletal muscle to simulated microgravity in male mice.

Yasmina Zeineddine, Michael A Friedman, Evan G Buettmann, Lovell B Abraham, Gabriel A Hoppock, Henry J Donahue.

Developments in long-term space exploration necessitate advancements in countermeasures against microgravity-induced skeletal muscle loss. Astronaut data shows considerable variation in muscle loss in response to microgravity. Previous experiments suggest that genetic background influences the skeletal muscle response to unloading, but no in-depth analysis of genetic expression has been performed. Here, we placed eight, male, inbred founder strains of the diversity outbred mice (129S1/SvImJ, A/J, C57BL/6J, CAST/EiJ, NOD/ShiLtJ, NZO/HILtJ, PWK/PhJ, and WSB/EiJ) in simulated microgravity (SM) via hindlimb unloading for three weeks. Body weight, muscle morphology, muscle strength, protein synthesis marker expression, and RNA expression were collected. A/J and CAST/EiJ mice were most susceptible to SM-induced muscle loss, whereas NOD/ShiLtJ mice were the most protected. In response to SM, A/J and CAST/EiJ mice experienced reductions in body weight, muscle mass, muscle volume, and muscle cross-sectional area. A/J mice had the highest number of differentially expressed genes (68) and associated gene ontologies (328). Downregulation of immunological gene ontologies and genes encoding anabolic immune factors suggest that immune dysregulation contributes to the response of A/J mice to SM. Several muscle properties showed significant interactions between SM and mouse strain and a high degree of heritability. These data imply that genetic background plays a role in the degree of muscle loss in SM and that more individualized programs should be developed for astronauts to protect their skeletal muscles against microgravity on long-term missions.

DOI: https://doi.org/10.1038/s41526-023-00334-8
Free Radic Biol Med. 2023 Nov 28. pii: S0891-5849(23)01124-3. [Epub ahead of print]

Downhill running and caloric restriction attenuate insulin resistance associated skeletal muscle atrophy via the promotion of M2-like macrophages through TRIB3-AKT pathway.

Wei Luo, Yue Zhou, Qiang Tang, Yuhang Wang, Yansong Liu, Lei Ai.

   BACKGROUD: Downhill running has recently become a promising exercise modality for metabolic syndrome, but the effect and precise mechanism of downhill running training on insulin resistance (IR) induced skeletal muscle atrophy remains unclear. The current study aimed to explore the benefits of downhill running training accompanied by a low-fat diet on skeletal muscle atrophy in IR mice and its possible mechanisms.
METHODS: For in vivo study, high-fat diet (HFD) -induced IR mice were submitted to the downhill running training or/and caloric restriction for 8 weeks. In vitro study was performed using co-cultured RAW264.7 macrophages and C2C12 myoblasts model. Glucose tolerance test (GTT), insulin tolerance test (ITT), immunofluorescence staining, western blot analysis, hematoxylin and eosin (H&E) staining, enzyme-linked immunosorbent assay (ELISA), Cell counting kit-8 (CCK-8) assays and glucose uptake assays were employed to explore the benefits and possible mechanisms of downhill running training accompanied by a low-fat diet on IR mice.
RESULTS: Our data revealed that HFD induces IR, which leading to skeletal muscle atrophy. Downhill running accompanied by caloric restriction mitigated HFD-induced IR and improve skeletal muscle atrophy. Further study suggested that descended TRIB3 mediated the favorable impact of downhill running on IR induced skeletal muscle atrophy by suppressing M1-like macrophages and promoting M2-like macrophages. Macrophages-specific knockdown of TRIB3 exerted similar effects on the macrophage polarization and IR related myogenesis to downhill running training accompanied by caloric restriction. In contrast, macrophages-specific overexpression of TRIB3 descended phosphorylation of AKT, further activated M1-like macrophages and aggravated IR related inhibition of myogenesis.
CONCLUSIONS: This finding demonstrated the beneficial effects of downhill running training and caloric restriction on IR related skeletal muscle atrophy by promoting M2-like macrophages through TRIB3-AKT pathway.

Keywords:  Downhill running; Insulin resistance; Macrophage polarization; Skeletal muscle atrophy; TRIB3-AKT pathway

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.11.023
J Diabetes Res. 2023 ;2023 6657869

The Effects of Antioxidants and Pulsed Magnetic Fields on Slow and Fast Skeletal Muscle Atrophy Induced by Streptozotocin: A Preclinical Study.

Bora Tastekin, Aykut Pelit, Tugce Sapmaz, Alper Celenk, Muhammed Majeed, Lakshmi Mundkur, Kalyanam Nagabhushanam.

Results: Our findings suggest that antioxidants and PMF may alleviate impaired protein synthesis and degradation pathways in skeletal muscle atrophy. PTS showed a positive effect on the anabolic pathway, while RSV and PMF demonstrated potential for ameliorating the catabolic pathway. Notably, the combination therapy of antioxidants and PMF exhibited a stronger ameliorative effect on skeletal muscle atrophy than either intervention alone.
Conclusion: The present results highlight the benefits of employing a multimodal approach, involving both antioxidant and PMF therapy, for the management of muscle-wasting conditions. These treatments may have potential therapeutic implications for skeletal muscle atrophy.

DOI: https://doi.org/10.1155/2023/6657869
Free Radic Biol Med. 2023 Nov 25. pii: S0891-5849(23)01122-X. [Epub ahead of print]210 146-157

Enhancement of mitochondrial energy metabolism by melatonin promotes vascularized skeletal muscle regeneration in a volumetric muscle loss model.

Xiaoyang Ge, Chengyue Wang, Guanyu Yang, Dimulati Maimaiti, Mingzhuang Hou, Hao Liu, Huilin Yang, Xi Chen, Yong Xu, Fan He.

  Volumetric muscle loss (VML) is a condition that results in the extensive loss of 20 % or more of skeletal muscle due to trauma or tumor ablation, leading to severe functional impairment and permanent disability. The current surgical interventions have limited functional regeneration of skeletal muscle due to the compromised self-repair mechanism. Melatonin has been reported to protect skeletal muscle from exercise-induced oxidative damage and holds great potential to treat muscle diseases. In this study, we hypothesize that melatonin can enhance myoblast differentiation and promote effective recovery of skeletal muscle following VML. In vitro administration of melatonin resulted in a significant enhancement of myogenesis in C2C12 myoblast cells, as evidenced by the up-regulation of myogenic marker genes in a dose-dependent manner. Further experiments revealed that silent information of regulator type 3 (SIRT3) played a critical role in the melatonin-enhanced myoblast differentiation through enhancement of mitochondrial energy metabolism and activation of mitochondrial antioxidant enzymes such as superoxide dismutase 2 (SOD2). Silencing of Sirt3 completely abrogated the protective effect of melatonin on the mitochondrial function of myoblasts, evidenced by the increased reactive oxygen species, decreased adenosine triphosphate production, and down-regulated myoblast-specific marker gene expression. In order to attain a protracted and consistent release, liposome-encapsuled melatonin was integrated into gelatin methacryloyl hydrogel (GelMA-Lipo@MT). The implantation of GelMA-Lipo@MT into a tibialis anterior muscle defect in a VML model effectively stimulated the formation of myofibers and new blood vessels in situ, while concurrently inhibiting fibrotic collagen deposition. The findings of this study indicate that the incorporation of melatonin with GelMA hydrogel has facilitated the de novo vascularized skeletal muscle regeneration by augmenting mitochondrial energy metabolism. This represents a promising approach for the development of skeletal muscle tissue engineering, which could be utilized for the treatment of VML and other severe muscle injuries.

Keywords:  C2C12; Melatonin; Mitochondrial energy metabolism; SIRT3; Skeletal muscle; Volumetric muscle loss

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.11.021
Methodist Debakey Cardiovasc J. 2023 ;19(5): 58-68

Exercise and Ischemia-Activated Pathways in Limb Muscle Angiogenesis and Vascular Regeneration.

Vihang A Narkar.

  Exercise has a profound effect on cardiovascular disease, particularly through vascular remodeling and regeneration. Peripheral artery disease (PAD) is one such cardiovascular condition that benefits from regular exercise or rehabilitative physical therapy in terms of slowing the progression of disease and delaying amputations. Various rodent pre-clinical studies using models of PAD and exercise have shed light on molecular pathways of vascular regeneration. Here, I review key exercise-activated signaling pathways (nuclear receptors, kinases, and hypoxia inducible factors) in the skeletal muscle that drive paracrine regenerative angiogenesis. The rationale for highlighting the skeletal muscle is that it is the largest organ recruited during exercise. During exercise, skeletal muscle releases several myokines, including angiogenic factors and cytokines that drive tissue vascular regeneration via activation of endothelial cells, as well as by recruiting immune and endothelial progenitor cells. Some of these core exercise-activated pathways can be extrapolated to vascular regeneration in other organs. I also highlight future areas of exercise research (including metabolomics, single cell transcriptomics, and extracellular vesicle biology) to advance our understanding of how exercise induces vascular regeneration at the molecular level, and propose the idea of "exercise-mimicking" therapeutics for vascular recovery.

Keywords:  angiogenesis; exercise; limb ischemia; peripheral artery disease

DOI:  https://doi.org/10.14797/mdcvj.1304
J Cachexia Sarcopenia Muscle. 2023 Dec 02.

Lack of vitamin D signalling shifts skeletal muscles towards oxidative metabolism.

Anamica Das, Neha Jawla, Vaidehee Meena, Suchitra D Gopinath, Gopalakrishnan Aneeshkumar Arimbasseri.

   BACKGROUND: Mice lacking vitamin D receptor (VDR) exhibit a glycogen storage disorder, disrupting carbohydrate utilization in muscle. Here, we asked if the defective carbohydrate metabolism alters the fat utilization by the skeletal muscles of vdr-/- mice.
METHODS: To check the effect of high-fat-containing diets on muscle mass and metabolism of vdr-/- mice, we subjected them to two different milk fat-based diets (milk fat diet with 60% of energy from milk fat and milk-based diet [MBD] with 37% of energy from milk fat) and lard-based high-fat diet (HFD) containing 60% of energy from lard fat. Skeletal muscles and pancreas from these mice were analysed using RNA sequencing, quantitative reverse transcription polymerase chain reaction and western blot to understand the changes in signalling and metabolic pathways. Microscopic analyses of cryosections stained with haematoxylin and eosin, BODIPY, succinate dehydrogenase and periodic acid-Schiff reagent were performed to understand changes in morphology and metabolism of muscle fibres and pancreatic islets.
RESULTS: Transcriptomic analyses showed that the skeletal muscles of vdr-/- mice exhibit upregulation of the fatty acid oxidation pathways, suggesting a shift towards increased lipid utilization even in a carbohydrate-enriched regular chow diet (chow). Two different milk fat-enriched diets restored body weight (12.01 ± 0.33 g in chow vs. 17.99 ± 0.62 g in MBD) and muscle weights (38.58 ± 3.84 mg in chow vs. 110.72 ± 1.96 mg in MBD for gastrocnemius [GAS]) of vdr-/- mice. Muscle ATP levels (0.56 ± 0.18 μmol in chow vs. 1.48 ± 0.08 μmol in MBD) and protein synthesis (0.25 ± 0.04 A.U. in chow vs. 2.02 ± 0.06 A.U. in MBD) were upregulated by MBD. However, despite increasing muscle energy levels, HFD failed to restore the muscle mass and cross-sectional area to that of wild-type (WT) mice (104.95 ± 2.6 mg for WT mice on chow vs. 77.26 ± 1.7 mg for vdr-/- mice on HFD for GAS). Moreover, HFD disrupted glucose homeostasis in vdr-/- mice, while MBD restored it. We further analysed insulin response and pancreatic insulin levels of these mice to show that HFD led to reduced insulin levels in pancreatic beta cells of vdr-/- mice (mean intensity of 1.5 × 10-8 for WT mice on chow vs. 4.3 × 10-9 for vdr-/- mice on HFD). At the same time, MBD restored glucose-stimulated pancreatic insulin response (mean intensity of 9.2 × 10-9 ).
CONCLUSIONS: Skeletal muscles of vdr-/- mice are predisposed to utilize fatty acids as their primary energy source to circumvent their defective carbohydrate utilization. Thus, HFDs could restore energy levels in the skeletal muscles of vdr-/- mice. This study reveals that when mice are subjected to a lard-based HFD, VDR signalling is essential for maintaining insulin levels in pancreatic islets. Our data show a critical role of VDR in muscle metabolic flexibility and pancreatic insulin response.

Keywords:  VDR; energy metabolism; glucose homeostasis; insulin; milk fat diet; skeletal muscle; vitamin D

DOI:  https://doi.org/10.1002/jcsm.13378
Cell Mol Biol (Noisy-le-grand). 2023 Nov 15. 69(11): 25-29

Camk2a suppresses denervated muscle atrophy by maintaining the Ca2+ homeostasis in muscle cells.

Yanan Zhang, Mingjie Xia, Tianyu Zhao, Qinyang Zhang, Rulin Li, Lei Yang.

Denervated muscle atrophy is a severe neurological complication that significantly impacts patients' quality of life. Currently, there is a lack of effective treatment methods. This study aims to investigate the molecular mechanisms associated with denervated muscle atrophy and explore potential therapeutic targets. In this study, we assessed the severity of denervated muscle atrophy by measuring the wet-weight ratio of the calf muscles. We conducted Western blot and immunofluorescence experiments to observe the morphology and cross-sectional area of muscle fibers following sciatic nerve transection. Simultaneously, we evaluated the expression of Camk2a in muscle tissue and measured changes in Ca2+ using the BCA method. Additionally, we performed HE and Sirius Red staining on denervated muscle tissue to observe the cross-sectional area of muscle fibers and collagen deposition in response to Camk2a overexpression. In our study, We observed a significant decrease in the wet weight ratio of the muscles, myosin, and muscle fiber cross-sectional area with the prolonged duration of sciatic nerve transection. Subsequently, we observed varying degrees of elevation in Ca2+ levels in denervated muscle tissue, while Camk2a, which regulates Ca2+ signal transduction, significantly decreased in denervated muscle tissue. Overexpression of Camk2a reduced the accumulation of Ca2+ in muscle tissue, resulting in higher muscle wet weight ratios, larger muscle fiber cross-sectional areas, and a significant reduction in collagen deposition in muscle tissue. In conclusion, our study provides the first evidence that Camk2a can alleviate calcium overload in muscle cells and ameliorate denervated muscle atrophy. Our findings suggest that Camk2a may serve as a crucial regulatory target in denervated muscle atrophy.

DOI: https://doi.org/10.14715/cmb/2023.69.11.4
bioRxiv. 2023 Nov 16. pii: 2023.11.14.566992. [Epub ahead of print]

Remodelling of skeletal muscle myosin metabolic states in hibernating mammals.

Christopher T A Lewis, Elise G Melhedegaard, Marija M Ognjanovic, Mathilde S Olsen, Jenni Laitila, Robert A E Seaborne, Magnus Nørregaard Grønset, Chengxin Zhang, Hiroyuki Iwamoto, Anthony L Hessel, Michel N Kuehn, Carla Merino, Nuria Amigó, Ole Fröbert, Sylvain Giroud, James F Staples, Anna V Goropashnaya, Vadim B Fedorov, Brian M Barnes, Øivind Tøien, Kelly L Drew, Ryan J Sprenger, Julien Ochala.

Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus . We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus , changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20°C). Upon repeating loaded Mant-ATP chase experiments at 8°C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus , which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.

DOI: https://doi.org/10.1101/2023.11.14.566992
JBMR Plus. 2023 Nov;7(11): e10804

Biomechanical Stimulation of Muscle Constructs Influences Phenotype of Bone Constructs by Modulating Myokine Secretion.

Harshini Suresh Kumar, Edwina N Barnett, John L Fowlkes, Evangelia Kalaitzoglou, Ramkumar T Annamalai.

  Diabetes is a chronic metabolic disorder that can lead to diabetic myopathy and bone diseases. The etiology of musculoskeletal complications in such metabolic disorders and the interplay between the muscular and osseous systems are not well understood. Exercise training promises to prevent diabetic myopathy and bone disease and offer protection. Although the muscle-bone interaction is largely biomechanical, the muscle secretome has significant implications for bone biology. Uncoupling effects of biophysical and biochemical stimuli on the adaptive response of bone during exercise training may offer therapeutic targets for diabetic bone disease. Here, we have developed an in vitro model to elucidate the effects of mechanical strain on myokine secretion and its impact on bone metabolism decoupled from physical stimuli. We developed bone constructs using cross-linked gelatin, which facilitated osteogenic differentiation of osteoprogenitor cells. Then muscle constructs were made from fibrin, which enabled myoblast differentiation and myotube formation. We investigated the myokine expression by muscle constructs under strain regimens replicating endurance (END) and high-intensity interval training (HIIT) in hyperglycemic conditions. In monocultures, both regimens induced higher expression of Il15 and Igf1, whereas END supported more myoblast differentiation and myotube maturation than HIIT. When co-cultured with bone constructs, HIIT regimen increased Glut4 expression in muscle constructs more than END, supporting higher glucose uptake. Likewise, the muscle constructs under the HIIT regimen promoted a healthier and more matured bone phenotype than END. Under static conditions, myostatin (Mstn) expression was significantly downregulated in muscle constructs co-cultured with bone constructs compared with monocultures. Together, our in vitro co-culture system allowed orthogonal manipulation of mechanical strain on muscle constructs while facilitating bone-muscle biochemical cross-talk. Such systems can provide an individualized microenvironment that allows decoupled biomechanical manipulation, help identify molecular targets, and develop engineered therapies for metabolic bone disease. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Keywords:  BONE; DIABETES; EXERCISE; GELATIN; MICROGELS; MUSCLE; MYOSTATIN

DOI:  https://doi.org/10.1002/jbm4.10804
J Physiol. 2023 Nov 27.

Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis.

Renjia Zhong, Michael T Rua, Lan Wei-LaPierre.

  Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.

Keywords:  ALS; mitochondria calcium; motor neuron; skeletal muscle; therapeutic target

DOI:  https://doi.org/10.1113/JP284143
Physiol Rep. 2023 Dec;11(23): e15870

Profiling of adenine-derived signaling molecules, cytokinins, in myotubes reveals fluctuations in response to lipopolysaccharide-induced cell stress.

Stephanie W Tobin, Dev Seneviratne, Lorna Phan, Mark Seegobin, Alexander L Rico, Beth Westby, Anna Kisiala, Sanela Martic, Craig R Brunetti, R J Neil Emery.

  Cytokinins (CTKs) are a diverse collection of evolutionarily conserved adenine-derived signaling molecules classically studied as phytohormones; however, their roles and production have been less studied in mammalian systems. Skeletal muscles are sensitive to cellular cues such as inflammation and in response, alter their secretome to regulate the muscle stem cell and myofiber niche. Using cultured C2C12 muscle cells, we profiled CTK levels to understand (1) whether CTKs are part of the muscle secretome and (2) whether CTKs are responsive to cellular stress. To induce cellular stress, C2C12 myotubes were treated with lipopolysaccharides (LPS) for 24 h and then media and cell fractions were collected for ultra high-performance liquid chromatography tandem mass spectrometry with electrospray ionization (UHPLC-(ESI+)-HRMS/MS) for metabolomics and CTK profiling. Across LPS-treated and control cells, 11 CTKs were detected in the extracellular space while 6 were detected intracellularly. We found that muscle cells are enriched in isopentenyladenine (iP) species (from free base, riboside to nucleotide forms), and that extracellular levels are increased after LPS treatment. Our study establishes that muscle cells express various forms of CTKs, and that CTK levels are responsive to LPS-induced cell stress, suggesting a role for CTKs in intra- and extracellular signaling of mammalian cells.

Keywords:  cytokinin; muscle; myokine

DOI:  https://doi.org/10.14814/phy2.15870
Nat Commun. 2023 Nov 30. 14(1): 7916

Skeletal muscle-secreted DLPC orchestrates systemic energy homeostasis by enhancing adipose browning.

Xiaodi Hu, Mingwei Sun, Qian Chen, Yixia Zhao, Na Liang, Siyuan Wang, Pengbin Yin, Yuanping Yang, Sin Man Lam, Qianying Zhang, Alimujiang Tudiyusufu, Yingying Gu, Xin Wan, Meihong Chen, Hu Li, Xiaofei Zhang, Guanghou Shui, Suneng Fu, Licheng Zhang, Peifu Tang, Catherine C L Wong, Yong Zhang, Dahai Zhu.

MyoD is a skeletal muscle-specifically expressed transcription factor and plays a critical role in regulating myogenesis during muscle development and regeneration. However, whether myofibers-expressed MyoD exerts its metabolic function in regulating whole body energy homeostasis in vivo remains largely unknown. Here, we report that genetic deletion of Myod in male mice enhances the oxidative metabolism of muscle and, intriguingly, renders the male mice resistant to high fat diet-induced obesity. By performing lipidomic analysis in muscle-conditioned medium and serum, we identify 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) as a muscle-released lipid that is responsible for MyoD-orchestrated body energy homeostasis in male Myod KO mice. Functionally, the administration of DLPC significantly ameliorates HFD-induced obesity in male mice. Mechanistically, DLPC is found to induce white adipose browning via lipid peroxidation-mediated p38 signaling in male mice. Collectively, our findings not only uncover a novel function of MyoD in controlling systemic energy homeostasis through the muscle-derived lipokine DLPC but also suggest that the DLPC might have clinical potential for treating obesity in humans.

DOI: https://doi.org/10.1038/s41467-023-43402-z
bioRxiv. 2023 Nov 17. pii: 2023.11.17.567590. [Epub ahead of print]

A human immune/muscle xenograft model of FSHD muscle pathology.

Katelyn Daman, Jing Yan, Lisa M Burzenski, Jamie Kady, Leonard D Shultz, Michael A Brehm, Charles P Emerson.

Background: Facioscapulohumeral muscular dystrophy (FSHD) disease progression is associated with muscle inflammation, although its role in FSHD muscle pathology is unknown.
Methods: We have developed a novel humanized mouse strain, NSG-SGM3-W41, that supports the co- engraftment of human hematopoietic stem cells (HSCs) and muscle myoblasts as an experimental model to investigate the role of innate immunity in FSHD muscle pathology.
Results: The NSG-SGM3-W41 mouse supports the selective expansion of human innate immune cell lineages following engraftment of human HSCs and the co-engraftment and differentiation of patient-derived FSHD or control muscle myoblasts. Immunohistological and NanoString RNA expression assays establish that muscle xenografts from three FSHD subjects were immunogenic compared to those from unaffected first-degree relatives. FSHD muscle xenografts preferentially accumulated human macrophages and B cells and expressed early complement genes of the classical and alternative pathways including complement factor C3 protein, which is a mediator of early complement function through opsonization to mark damaged cells for macrophage engulfment. FSHD muscle xenografts also underwent immune donor dependent muscle turnover as assayed by human spectrin β1 immunostaining of muscle fibers and by NanoString RNA expression assays of muscle differentiation genes.
Conclusions: The NSG-SGM3-W41 mouse provides an experimental model to investigate the role of innate immunity and complement in FSHD muscle pathology and to develop FSHD therapeutics targeting DUX4 and the innate immunity inflammatory responses.

DOI: https://doi.org/10.1101/2023.11.17.567590
J Lipid Res. 2023 Nov 24. pii: S0022-2275(23)00154-2. [Epub ahead of print] 100481

Human HDL subclasses modulate energy metabolism in skeletal muscle cells.

Jenny Lund, Emilia Lähteenmäki, Tiia Eklund, Hege G Bakke, G Hege Thoresen, Eija Pirinen, Matti Jauhiainen, Arild C Rustan, Maarit Lehti.

  In addition to its anti-atherogenic role, HDL reportedly modulates energy metabolism at the whole-body level. HDL functionality is associated with its structure and composition, and functional activities can differ between HDL subclasses. Therefore, we studied if HDL2 and HDL3, the two major HDL subclasses, are able to modulate energy metabolism of skeletal muscle cells. Differentiated mouse and primary human skeletal muscle myotubes were used to investigate the influences of human HDL2 and HDL3 on glucose and fatty uptake and oxidation. HDL-induced changes in lipid distribution and mRNA expression of genes related to energy substrate metabolism, mitochondrial function and HDL receptors were studied with human myotubes. Additionally, we examined the effects of apoA-I and discoidal, reconstituted HDL particles (d-rHDLs) on substrate metabolism. In mouse myotubes, HDL subclasses strongly enhanced glycolysis upon high and low glucose concentrations. HDL3 caused a minor increase in ATP-linked respiration upon glucose conditioning but HDL2 improved complex I mediated mitochondrial respiration upon fatty acid treatment. In human myotubes, glucose metabolism was attenuated but fatty acid uptake and oxidation were markedly increased by both HDL subclasses, which also increased mRNA expression of genes related to fatty acid metabolism and HDL receptors. Finally, both HDL subclasses induced incorporation of oleic acid into different lipid classes. These results, demonstrating that HDL subclasses enhance fatty acid oxidation in human myotubes but improve anaerobic metabolism in mouse myotubes, support the role of HDL as a circulating modulator of energy metabolism. Exact mechanisms and components of HDL causing the change, require further investigation.

Keywords:  HDL subclasses; cellular respiration; fatty acid/transport; glucose; glycolysis; lipoproteins/metabolism; lipoproteins/receptors; mitochondria; oxidative phosphorylation; skeletal muscle myotubes; substrate oxidation

DOI:  https://doi.org/10.1016/j.jlr.2023.100481
J Biophotonics. 2023 Nov 27. e202300249

Early in vivo detection of denervation-induced atrophy by luminescence transient nanothermometry.

José Lifante, Álvaro Moreno-Rupérez, Erving Ximendes, Riccardo Marin, Teresa Priego, Asunción López-Calderón, Ana Isabel Martín, María Paz Nieto-Bona, Elena Nebot, Ginés Lifante-Pedrola, Daniel Jaque, Luis Monge, Nuria Fernández, Miriam Granado.

  Denervation induces skeletal muscle atrophy due to the loss of control and feedback with the nervous system. Unfortunately, muscle atrophy only becomes evident days after the denervation event when it could be irreversible. Alternative diagnosis tools for early detection of denervation-induced muscle atrophy are, thus, required. In this work we demonstrate how the combination of transient thermometry, a technique already used for early diagnosis of tumors, and infrared emitting nanothermometers makes possible the in vivo detection of the onset of muscle atrophy at short (< 1 day) times after a denervation event. The physiological reasons behind these experimental results have been explored by performing three dimensional numerical simulations based on the Pennes' bioheat equation. It is concluded that the alterations in muscle thermal dynamics at the onset of muscle atrophy are consequence of the skin perfusion increment caused by the alteration of peripheral nervous autonomous system. This work demonstrates the potential of infrared luminescence thermometry for early detection of diseases of the nervous system opening the venue towards the development of new diagnosis tools. This article is protected by copyright. All rights reserved.

Keywords:  denervation; infrared emitting nanoparticles; luminescent nanothermometers; muscle atrophy; transient thermometry

DOI:  https://doi.org/10.1002/jbio.202300249
Tissue Eng Part A. 2023 Nov 29.

Spontaneous Alignment of Myotubes through Myogenic Progenitor Cell Migration.

Lauren Mehanna, Adrianna R Osborne, Charlotte A Peterson, Brad J Berron.

In large volume muscle injuries, widespread damage to muscle fibers and the surrounding connective tissue prevents myogenic progenitor cells (MPCs) from initiating repair. There is a clinical need to rapidly fabricate large muscle tissue constructs for integration at the site of large volume muscle injuries. Most strategies for myotube alignment require microfabricated structures or prolonged orientation times. We utilize the MPC's natural propensity to close gaps across an injury site to guide alignment on collagen I. When MPCs are exposed to an open boundary free of cells, they migrate unidirectionally into the cell-free region and align perpendicular to the original boundary direction. We study the utility of this phenomenon with biotin - streptavidin adhesion to position the cells on the substrate, and then demonstrate the robustness of this strategy with unmodified cells, creating a promising tool for MPC patterning without interrupting their natural function. We pre-position MPCs in straight-line patterns separated with small gaps. This temporary positioning initiates the migratory nature of the MPCs to align and form myotubes across the gaps, similar to how they migrate and align with a single open boundary. There is a directional component to the MPC migration perpendicular (90°) to the original biotin-streptavidin surface patterns. The expression of myosin heavy chain, the motor protein of muscle thick filaments, is confirmed through immunocytochemistry (ICC) in myotubes generated from MPCs in our patterning process, acting as a marker of skeletal muscle differentiation. The rapid and highly specific binding of biotin-streptavidin allows for quick formation of temporary patterns, with MPC alignment based on natural regenerative behavior rather than complex fabrication techniques.

DOI: https://doi.org/10.1089/ten.TEA.2023.0177
Sci Adv. 2023 Dec;9(48): eadi9134

GDF8 inhibition enhances musculoskeletal recovery and mitigates posttraumatic osteoarthritis following joint injury.

Camille R Brightwell, Christine M Latham, Alexander R Keeble, Nicholas T Thomas, Allison M Owen, Kelsey A Reeves, Douglas E Long, Matthew Patrick, Sara Gonzalez-Velez, Varag Abed, Ramkumar T Annamalai, Cale Jacobs, Caitlin E Conley, Gregory S Hawk, Austin V Stone, Jean L Fry, Katherine L Thompson, Darren L Johnson, Brian Noehren, Christopher S Fry.

Musculoskeletal disorders contribute substantially to worldwide disability. Anterior cruciate ligament (ACL) tears result in unresolved muscle weakness and posttraumatic osteoarthritis (PTOA). Growth differentiation factor 8 (GDF8) has been implicated in the pathogenesis of musculoskeletal degeneration following ACL injury. We investigated GDF8 levels in ACL-injured human skeletal muscle and serum and tested a humanized monoclonal GDF8 antibody against a placebo in a mouse model of PTOA (surgically induced ACL tear). In patients, muscle GDF8 was predictive of atrophy, weakness, and periarticular bone loss 6 months following surgical ACL reconstruction. In mice, GDF8 antibody administration substantially mitigated muscle atrophy, weakness, and fibrosis. GDF8 antibody treatment rescued the skeletal muscle and articular cartilage transcriptomic response to ACL injury and attenuated PTOA severity and deficits in periarticular bone microarchitecture. Furthermore, GDF8 genetic deletion neutralized musculoskeletal deficits in response to ACL injury. Our findings support an opportunity for rapid targeting of GDF8 to enhance functional musculoskeletal recovery and mitigate the severity of PTOA after injury.

DOI: https://doi.org/10.1126/sciadv.adi9134
Cell Mol Life Sci. 2023 Nov 27. 80(12): 375

Interleukin 4 improved adipose-derived stem cells engraftment via interacting with fibro/adipogenic progenitors in dystrophic mice.

Huan Li, Jinfu Lin, Liang Wang, Ruojie He, Jing Li, Menglong Chen, Weixi Zhang, Cheng Zhang.

  Adipose-derived stem cells (ADSC) therapy shows promise as an effective treatment for dystrophinopathy. Fibro-/adipogenic progenitors (FAPs) play an essential role in the myogenesis of muscle satellite cells and contribute to muscle fibrosis and adipocyte infiltration. The interleukin 4 (IL-4) pathway acts as a switch that regulates the functions of FAPs. The interaction between FAPs and engrafted cells remains unclear. In this study, we used a co-culture system to investigate possible crosstalk between the FAPs of dystrophic mice and ADSC overexpressing IL4 (IL4-ADSC) and control ADSC. Systemic transplantation of IL4-ADSC and control ADSC in dystrophic mice was conducted for 16 weeks, after which motor function and molecular improvements were evaluated. Overexpression of IL4 in ADSC significantly promoted myogenesis in vitro, increasing the expression of Pax7, Myogenin, and MyHC. Co-culture indicated that although myoblasts derived from control ADSC promoted adipogenic and fibrogenic differentiation of FAPs, FAPs did not significantly affect myogenesis of ADSC-derived myoblasts. However, overexpression of IL4 in ADSC inhibited their myotube-dependent promotion of FAPs differentiation on the one hand and promoted FAPs to enhance myogenesis on the other. Dystrophic mice administered with IL4-ADSC-derived myoblasts displayed significantly better motor ability, more engrafted cells showing dystrophin expression, and less muscle fibrosis, intramuscular adipocytes, and macrophage infiltration than mice administered control-ADSC-derived myoblasts. In conclusion, IL4 activation enhanced the therapeutic potential of ADSC transplantation in dystrophic mice, possibly by improving the myogenesis of IL4-ADSC and altering the crosstalk between engrafted stem cells and resident FAPs.

Keywords:  Adipose-derived stem cells; Dystrophinopathy; Fibro-/adipogenic progenitors; IL4; Muscle fibrosis

DOI:  https://doi.org/10.1007/s00018-023-05020-2
iScience. 2023 Nov 17. 26(11): 108258

RBFOX2 regulated EYA3 isoforms partner with SIX4 or ZBTB1 to control transcription during myogenesis.

Hannah J Wiedner, R Eric Blue, Matheus Sadovsky, C Allie Mills, Xander H T Wehrens, Laura E Herring, Jimena Giudice.

  Alternative splicing is a prevalent gene-regulatory mechanism, with over 95% of multi-exon human genes estimated to be alternatively spliced. Here, we describe a tissue-specific, developmentally regulated, highly conserved, and disease-associated alternative splicing event in exon 7 of the eyes absent homolog 3 (Eya3) gene. We discovered that EYA3 expression is vital to the proliferation and differentiation of myoblasts. Genome-wide transcriptomic analysis and mass spectrometry-based proteomic studies identified SIX homeobox 4 (SIX4) and zinc finger and BTB-domain containing 1 (ZBTB1), as major transcription factors that interact with EYA3 to dictate gene expression. EYA3 isoforms differentially regulate transcription, indicating that splicing aids in temporal control of gene expression during muscle cell differentiation. Finally, we identified RNA-binding fox-1 homolog 2 (RBFOX2) as the main regulator of EYA3 splicing. Together, our findings illustrate the interplay between alternative splicing and transcription during myogenesis.

Keywords:  Molecular biology; Omics; Physiology

DOI:  https://doi.org/10.1016/j.isci.2023.108258
J Agric Food Chem. 2023 Nov 29.

Diosmin Promotes Myogenesis via Activating the Akt/FOXO1 Pathway to Facilitate the Proliferation of C2C12 Myoblasts.

Dingding Zhang, Xuan Zhang, Zhaojun Liu, Xiangfei Ma, Hongmin Li, Ming Shen, Jie Chen, Honglin Liu.

  Our previous study with artificial intelligence (AI)-assisted screening found that diosmin, a natural flavonoid extracted from citrus, may affect myoblast proliferation and differentiation. At present, few studies have been conducted regarding the biological function of diosmin in muscle cells. Here, using molecular biological techniques, we found that diosmin elevated the proliferation ability of C2C12 myoblasts via activating the Akt/FOXO1 pathway to promote FOXO1 nuclear export, thus repressing p27 protein expression, increasing CDK2, CDK4, and cyclin D1 and cyclin E1 protein expression and accelerating cell cycle transformation, which contributed to myogenesis. Moreover, diosmin suppressed differentiation of C2C12 myoblasts by delaying the terminal exit of the cell cycle in early differentiated myoblasts and inhibiting autophagic flux in mature myotubes. Furthermore, diosmin promoted myogenesis by activating the Akt/FOXO1 pathway to facilitate myoblast proliferation, which had a positive biological effect on the repair of muscle injury. This study revealed the effect and mechanism of diosmin on skeletal muscle cells and simultaneously provided a new candidate drug for the treatment of myopathy.

Keywords:  Akt/FOXO1 pathway; diosmin; muscle injury repair; myoblast differentiation; myoblast proliferation

DOI:  https://doi.org/10.1021/acs.jafc.3c04828
bioRxiv. 2023 Nov 13. pii: 2023.11.09.566413. [Epub ahead of print]

Titin-based force regulates cardiac myofilament structures mediating length-dependent activation.

Anthony L Hessel, Michel N Kuehn, Nichlas M Engels, Devin L Nissen, Johanna K Freundt, Weikang Ma, Thomas C Irving, Wolfgang A Linke.

The Frank-Starling law states that the heart's stroke volume increases with greater preload due to increased venous return, allowing the heart to adapt to varying circulatory demands. Molecularly, increasing preload increases sarcomere length (SL), which alters sarcomere structures that are correlated to increased calcium sensitivity upon activation. The titin protein, spanning the half-sarcomere, acts as a spring in the I-band, applying a SL-dependent force suggested to pull against and alter myofilaments in a way that supports the Frank-Starling effect. To evaluate this, we employed the titin cleavage (TC) model, where a tobacco-etch virus protease recognition site is inserted into distal I-band titin and allows for rapid, specific cleavage of titin in an otherwise-healthy sarcomere. Here, we evaluated the atomic-level structures of amyopathic cardiac myofilaments following 50% titin cleavage under passive stretch conditions using small-angle X-ray diffraction, which measures these structures under near-physiological (functional) conditions. We report that titin-based forces in permeabilized papillary muscle regulate both thick and thin myofilament structures clearly supporting titin's role in the Frank-Starling mechanism.

DOI: https://doi.org/10.1101/2023.11.09.566413
Sci Rep. 2023 Nov 28. 13(1): 21001

All-trans retinoic acid and dexamethasone regulate phagocytosis-related gene expression and enhance dead cell uptake in C2C12 myoblast cells.

Maysaa Adil Ali, Éva Garabuczi, Nastaran Tarban, Zsolt Sarang.

Extensive mechanical stress frequently causes micro-traumas in skeletal muscle, followed by a regeneration period. The effective removal of dead myofibers is a prerequisite for proper regeneration, and several cell types, including professional phagocytes, were reported to be active in this process. Myoblasts express several molecules of the phagocytic machinery, such as BAI1, stabilin-2, and TAM (Tyro3, Axl, Mertk) tyrosine kinase receptors, but these molecules were reported to serve primarily cell fusion and survival, and their role in the phagocytosis was not investigated. Therefore, we aimed to investigate the in vitro phagocytic capacity of the C2C12 mouse myoblast cell line. RNA sequencing data were analyzed to determine the level and changes of phagocytosis-related gene expression during the differentiation process of C2C12 cells. To study the phagocytic capacity of myoblasts and the effect of dexamethasone, all-trans retinoic acid, hemin, and TAM kinase inhibitor treatments on phagocytosis, C2C12 cells were fed dead thymocytes, and their phagocytic capacity was determined by flow cytometry. The effect of dexamethasone and all-trans retinoic acid on phagocytosis-related gene expression was determined by quantitative PCR. Both undifferentiated and differentiated cells engulfed dead cells being the undifferentiated cells more effective. In line with this, we observed that the expression of several phagocytosis-related genes was downregulated during the differentiation process. The phagocytosis could be increased by dexamethasone and all-trans retinoic acid and decreased by hemin and TAM kinase inhibitor treatments. Our results indicate that myoblasts not only express phagocytic machinery genes but are capable of efficient dead cell clearance as well, and this is regulated similarly, as reported in professional phagocytes.

DOI: https://doi.org/10.1038/s41598-023-48492-9
Front Public Health. 2023 ;11 1303223

Editorial: Sarcopenia and frailty: the role of physical activity for better aging.

Ricardo Aurélio Carvalho Sampaio, Priscila Yukari Sewo Sampaio, Luciane Portas Capelo, Marco Carlos Uchida, Hidenori Arai.



Keywords:  aging; body composition; disability; muscle strength; physical function; public health

DOI:  https://doi.org/10.3389/fpubh.2023.1303223
Gerontology. 2023 Nov 24.

Exercise Regulates Myokines on Aging-related Diseases through Muscle-brain Crosstalk.

Bingqing Wang, Jiling Liang, Chen Lu, Aming Lu, Cenyi Wang.

BACKGROUND: The related functions of skeletal muscle and brain decrease significantly with age, and muscle-brain-related diseases are primarily associated with each other. Exercise can promote the secretion of myokines in skeletal muscle, showing a beneficial effect on the function of both, reflecting muscle-brain crosstalk. However, the key mechanism of action of exercise-regulated myokines in muscle-brain diseases remains unclear.
METHODS: Web of Science, PubMed, EBSCO, OVID, and China National Knowledge Infrastructure were searched from July 2022 to February 2023 using "myokine," "myokines," "exercise," "training," "physical activity," "aging," "brain" and "crosstalk" as keywords.
RESULTS: Twenty-four experimental studies were selected from 2,941 studies involving seven common myokines. The exercises studied included aerobic exercise, resistance exercise, combined aerobic and resistance exercise, high-intensity interval training (HIIT), and high-intensity circuit training (HICT). Eighteen of the studies mentioned brain-derived neurotrophic factor (BDNF), four mentioned insulin-like growth factor 1 (IGF-1), three mentioned cathepsin B (CATB), and four mentioned irisin. There were four with vascular endothelial growth factor (VEGF), five with interleukin 6 (IL-6), and three with fibroblast growth factor 21 (FGF-21). There are multiple studies involving multiple myokines at the same time.
CONCLUSIONS: Type, duration, intensity, and frequency of exercise may affect the expression of myokines in muscle-brain crosstalk. Both low- to moderate-intensity aerobic exercise three times a week for 12 weeks or more and resistance exercise two or three times a week with low or moderate-intensity for 12 weeks have a strong effect on the expression of myokines. However, there are few studies on the effects of combined aerobic and resistance exercise, HIIT, and HICT on myokines, and more empirical studies are required in the future.

DOI: https://doi.org/10.1159/000535339