bims-moremu 2023-07-09 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–07–09
25 papers selected by
Anna Vainshtein, Craft Science Inc.

CISD3 is required for Complex I function, mitochondrial integrity, and skeletal muscle maintenance.
The importance of serial sarcomere addition for muscle function and the impact of aging.
Zfp697 is an RNA-binding protein that regulates skeletal muscle inflammation and regeneration.
CDK4-E2F3 signals enhance oxidative skeletal muscle fiber numbers and function to affect myogenesis and metabolism.
Age and sex dependent effects of metabolic response to muscle contraction.
Deletion of Nmnat1 in Skeletal Muscle Leads to the Reduction of NAD+ Levels but Has No Impact on Skeletal Muscle Morphology and Fiber Types.
DNA-PKcs regulates myogenesis in an Akt-dependent manner independent of induced DNA damage.
A cellular and molecular spatial atlas of dystrophic muscle.
The time-course of cancer cachexia onset reveals biphasic transcriptional disruptions in female skeletal muscle distinct from males.
Zeb1 and Tle3 are trans-factors that differentially regulate the expression of myosin heavy chain-embryonic and skeletal muscle differentiation.
Net39 protects muscle nuclei from mechanical stress during the pathogenesis of Emery-Dreifuss muscular dystrophy.
Editorial: Systemic markers of muscle loss.
Myofiber directs macrophages IL-10-Vav1-Rac1 efferocytosis pathway in inflamed muscle following CTX myoinjury by activating the intrinsic TGF-β signaling.
Altered muscle niche contributes to myogenic deficit in the D2-mdx model of severe DMD.
Editorial: Cellular heterogeneity in physiological and pathological myogenesis.
The CEBPA-FGF21 regulatory network may participate in the T2DM-induced skeletal muscle atrophy by regulating the autophagy-lysosomal pathway.
MFGE8 inhibits insulin signaling through PTP1B.
Single-cell and spatial transcriptomics identify a macrophage population associated with skeletal muscle fibrosis.
Circadian transcriptome processing and analysis: a workflow for muscle stem cells.
17α-estradiol Alleviates High-Fat Diet-Induced Inflammatory and Metabolic Dysfunction in Skeletal Muscle of Male and Female Mice.
Promising AAV.U7snRNAs vectors targeting DMPK improve DM1 hallmarks in patient-derived cell lines.
Different mouse models of nemaline myopathy harboring Acta1 mutations display differing abnormalities related to mitochondrial biology.
Nur77 is involved in the regulation of obesity-related lower muscle mass by promoting Pten degradation.
Post-natal muscle growth and protein turnover: a narrative review of current understanding.
Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis.

bioRxiv. 2023 Jun 04. pii: 2023.06.03.543558. [Epub ahead of print]

CISD3 is required for Complex I function, mitochondrial integrity, and skeletal muscle maintenance.

Henri-Baptiste Marjault, Ola Karmi, Linda Rowland, Thi Thao Nguyen, DeAna Grant, Camila Manrique-Acevedo, Rachel Nechushtai, Ron Mittler.

Mitochondria play a central role in muscle metabolism and function. In skeletal muscles, a unique family of iron-sulfur proteins, termed CISD proteins, support mitochondrial function. The abundance of these proteins declines with aging leading to muscle degeneration. Although the function of the outer mitochondrial proteins CISD1 and CISD2 has been defined, the role of the inner mitochondrial protein CISD3, is currently unknown. Here we show that CISD3 deficiency in mice results in muscle atrophy that shares proteomic features with Duchenne Muscular Dystrophy. We further reveal that CISD3 deficiency impairs the function and structure of skeletal muscle mitochondria, and that CISD3 interacts with, and donates its clusters to, Complex I respiratory chain subunit NDUFV2. These findings reveal that CISD3 is important for supporting the biogenesis and function of Complex I, essential for muscle maintenance and function. Interventions that target CISD3 could therefore impact muscle degeneration syndromes, aging, and related conditions.

DOI: https://doi.org/10.1101/2023.06.03.543558
J Appl Physiol (1985). 2023 Jul 06.

The importance of serial sarcomere addition for muscle function and the impact of aging.

Avery Hinks, Thomas J Hawke, Martino V Franchi, Geoffrey A Power.

  During natural aging, skeletal muscle experiences impairments in mechanical performance due, in part, to changes in muscle architecture and size, notably with a loss of muscle cross-sectional area. Another important factor that has received less attention is the shortening of fascicle length, potentially reflective of a decrease in serial sarcomere number (SSN). Interventions that promote the growth of new serial sarcomeres, such as chronic stretching and eccentric-biased resistance training, have been suggested as potential ways to mitigate age-related impairments in muscle function. While current research suggests it is possible to stimulate serial sarcomerogenesis in muscle in old age, the magnitude of sarcomerogenesis may be less than in young muscle. This blunted effect may be partly due to age-related impairments in the pathways regulating mechanotransduction, muscle gene expression, and protein synthesis, as some have been implicated in SSN adaptation. The purpose of this review was to investigate the impact of aging on the ability for serial sarcomerogenesis, and elucidate the molecular pathways that may limit serial sarcomerogenesis in old age. Age-related changes in mTOR, IGF-1, myostatin, and serum response factor signalling, MuRFs, and satellite cells may hinder serial sarcomerogenesis. In addition, our current understanding of SSN in older humans is limited by assumptions based on ultrasound-derived fascicle length. Future research should explore the effects of age-related changes in the identified pathways on the ability to stimulate serial sarcomerogenesis, and better estimate SSN adaptations to gain a deeper understanding of the adaptability of muscle in old age.

Keywords:  Aging; Muscle; force-length relationship; force-velocity relationship; ultrasound

DOI:  https://doi.org/10.1152/japplphysiol.00205.2023
bioRxiv. 2023 Jun 13. pii: 2023.06.12.544338. [Epub ahead of print]

Zfp697 is an RNA-binding protein that regulates skeletal muscle inflammation and regeneration.

Jorge C Correia, Paulo R Jannig, Maya L Gosztyla, Igor Cervenka, Serge Ducommun, Stine M Præstholm, Kyle Dumont, Zhengye Liu, Qishan Liang, Daniel Edsgärd, Olof Emanuelsson, Paul Gregorevic, Håkan Westerblad, Tomas Venckunas, Marius Brazaitis, Sigitas Kamandulis, Johanna T Lanner, Gene W Yeo, Jorge L Ruas.

Muscular atrophy is a mortality risk factor that happens with disuse, chronic disease, and aging. Recovery from atrophy requires changes in several cell types including muscle fibers, and satellite and immune cells. Here we show that Zfp697/ZNF697 is a damage-induced regulator of muscle regeneration, during which its expression is transiently elevated. Conversely, sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Myofiber-specific Zfp697 ablation hinders the inflammatory and regenerative response to muscle injury, compromising functional recovery. We uncover Zfp697 as an essential interferon gamma mediator in muscle cells, interacting primarily with ncRNAs such as the pro-regenerative miR-206. In sum, we identify Zfp697 as an integrator of cell-cell communication necessary for tissue regeneration.
One Sentence Summary: Zfp697 is necessary for interferon gamma signaling and muscle regeneration.

DOI: https://doi.org/10.1101/2023.06.12.544338
J Clin Invest. 2023 07 03. pii: e162479. [Epub ahead of print]133(13):

CDK4-E2F3 signals enhance oxidative skeletal muscle fiber numbers and function to affect myogenesis and metabolism.

Young Jae Bahn, Hariom Yadav, Paolo Piaggi, Brent S Abel, Oksana Gavrilova, Danielle A Springer, Ioannis Papazoglou, Patricia M Zerfas, Monica C Skarulis, Alexandra C McPherron, Sushil G Rane.

  Understanding how skeletal muscle fiber proportions are regulated is vital to understanding muscle function. Oxidative and glycolytic skeletal muscle fibers differ in their contractile ability, mitochondrial activity, and metabolic properties. Fiber-type proportions vary in normal physiology and disease states, although the underlying mechanisms are unclear. In human skeletal muscle, we observed that markers of oxidative fibers and mitochondria correlated positively with expression levels of PPARGC1A and CDK4 and negatively with expression levels of CDKN2A, a locus significantly associated with type 2 diabetes. Mice expressing a constitutively active Cdk4 that cannot bind its inhibitor p16INK4a, a product of the CDKN2A locus, were protected from obesity and diabetes. Their muscles exhibited increased oxidative fibers, improved mitochondrial properties, and enhanced glucose uptake. In contrast, loss of Cdk4 or skeletal muscle-specific deletion of Cdk4's target, E2F3, depleted oxidative myofibers, deteriorated mitochondrial function, and reduced exercise capacity, while increasing diabetes susceptibility. E2F3 activated the mitochondrial sensor PPARGC1A in a Cdk4-dependent manner. CDK4, E2F3, and PPARGC1A levels correlated positively with exercise and fitness and negatively with adiposity, insulin resistance, and lipid accumulation in human and rodent muscle. All together, these findings provide mechanistic insight into regulation of skeletal muscle fiber-specification that is of relevance to metabolic and muscular diseases.

Keywords:  Metabolism; Mitochondria; Muscle Biology; Skeletal muscle

DOI:  https://doi.org/10.1172/JCI162479
bioRxiv. 2023 Jun 01. pii: 2023.05.30.542769. [Epub ahead of print]

Age and sex dependent effects of metabolic response to muscle contraction.

Matthew D Campbell, Danijel Djukovic, Daniel Raftery, David Marcinek.

Sarcopenia, the age-related loss of muscle mass and function, contributes to decreased quality of life in the elderly and increased healthcare costs. Decreased skeletal muscle mass, specific force, increased overall fatty depositions in the skeletal muscle, frailty and depressed energy maintenance are all associated with increased oxidative stress and the decline in mitochondrial function with age. We hypothesized that elevated mitochondrial stress with age alters the capacity of mitochondria to utilize different substrates following muscle contraction. To test this hypothesis, we designed two in vivo muscle-stimulation protocols to simulate high-intensity intervals (HII) or low intensity steady-state (LISS) exercise to characterize the effect of age and sex on mitochondrial substrate utilization in skeletal muscle following muscle contraction. Following HII stimulation, mitochondria from young skeletal muscle increased fatty acid oxidation compared to non-stimulated control muscle; however, mitochondria from aged muscle decreased fatty acid oxidation. In contrast, following LISS, mitochondrial from young skeletal muscle decreased fatty acid oxidation, whereas aged mitochondria increased fatty acid oxidation. We also found that HII can inhibit mitochondrial oxidation of glutamate in both stimulated and non-stimulated aged muscle, suggesting HII initiates circulation of an exerkine capable of altering whole-body metabolism. Analyses of the muscle metabolome indicates that changes in metabolic pathways induced by HII and LISS contractions in young muscle are absent in aged muscle. Treatment with elamipretide, a mitochondrially targeted peptide, restored glutamate oxidation and metabolic pathway changes following HII suggesting rescuing redox status and improving mitochondrial function in aged muscle enhances the metabolic response to muscle contraction.

DOI: https://doi.org/10.1101/2023.05.30.542769
J Nutr Sci Vitaminol (Tokyo). 2023 ;69(3): 184-189

Deletion of Nmnat1 in Skeletal Muscle Leads to the Reduction of NAD+ Levels but Has No Impact on Skeletal Muscle Morphology and Fiber Types.

Mariam Karim, Tooba Iqbal, Allah Nawaz, Keisuke Yaku, Takashi Nakagawa.

  Nicotinamide adenine dinucleotide (NAD+) is a coenzyme that mediates many redox reactions in energy metabolism. NAD+ is also a substrate for ADP-ribosylation and deacetylation by poly (ADP-ribose) polymerase and sirtuin, respectively. Nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1) is a NAD+ biosynthesizing enzyme found in the nucleus. Recent research has shown that the maintaining NAD+ levels is critical for sustaining muscle functions both in physiological and pathological conditions. However, the role of Nmnat1 in skeletal muscle remains unexplored. In this study, we generated skeletal muscle-specific Nmnat1 knockout (M-Nmnat1 KO) mice and investigated its role in skeletal muscle. We found that NAD+ levels were significantly lower in the skeletal muscle of M-Nmnat1 KO mice than in control mice. M-Nmnat1 KO mice, in contrast, had similar body weight and normal muscle histology. Furthermore, the distribution of muscle fiber size and gene expressions of muscle fiber type gene expression were comparable in M-Nmnat1 KO and control mice. Finally, we investigated the role of Nmnat1 in muscle regeneration using cardiotoxin-induced muscle injury model, but muscle regeneration appeared almost normal in M-Nmnat1 KO mice. These findings imply that Nmnat1 has a redundancy in the pathophysiology of skeletal muscle.

Keywords:  NAD+; Nmnat1; fiber type; muscle injury; skeletal muscle

DOI:  https://doi.org/10.3177/jnsv.69.184
Cell Death Differ. 2023 Jul 03.

DNA-PKcs regulates myogenesis in an Akt-dependent manner independent of induced DNA damage.

Haser Hasan Sutcu, Benjamin Montagne, Miria Ricchetti.

Skeletal muscle regeneration relies on muscle stem (satellite) cells. We previously demonstrated that satellite cells efficiently and accurately repair radiation-induced DNA double-strand breaks (DSBs) via the DNA-dependent kinase DNA-PKcs. We show here that DNA-PKcs affects myogenesis independently of its role in DSB repair. Consequently, this process does not require the accumulation of DSBs and it is also independent of caspase-induced DNA damage. We report that in myogenic cells DNA-PKcs is essential for the expression of the differentiation factor Myogenin in an Akt2-dependent manner. DNA-PKcs interacts with the p300-containing complex that activates Myogenin transcription. We show also that SCID mice that are deficient in DNA-PKcs, and are used for transplantation and muscle regeneration studies, display altered myofiber composition and delayed myogenesis upon injury. These defects are exacerbated after repeated injury/regeneration events resulting in reduced muscle size. We thus identify a novel, caspase-independent, regulation of myogenic differentiation, and define a differentiation phase that does not involve the DNA damage/repair process.

DOI: https://doi.org/10.1038/s41418-023-01177-2
Proc Natl Acad Sci U S A. 2023 Jul 18. 120(29): e2221249120

A cellular and molecular spatial atlas of dystrophic muscle.

Michael J Stec, Qi Su, Christina Adler, Lance Zhang, David R Golann, Naveen P Khan, Lampros Panagis, S Armando Villalta, Min Ni, Yi Wei, Johnathon R Walls, Andrew J Murphy, George D Yancopoulos, Gurinder S Atwal, Sandra Kleiner, Gabor Halasz, Mark W Sleeman.

  Asynchronous skeletal muscle degeneration/regeneration is a hallmark feature of Duchenne muscular dystrophy (DMD); however, traditional -omics technologies that lack spatial context make it difficult to study the biological mechanisms of how asynchronous regeneration contributes to disease progression. Here, using the severely dystrophic D2-mdx mouse model, we generated a high-resolution cellular and molecular spatial atlas of dystrophic muscle by integrating spatial transcriptomics and single-cell RNAseq datasets. Unbiased clustering revealed nonuniform distribution of unique cell populations throughout D2-mdx muscle that were associated with multiple regenerative timepoints, demonstrating that this model faithfully recapitulates the asynchronous regeneration observed in human DMD muscle. By probing spatiotemporal gene expression signatures, we found that propagation of inflammatory and fibrotic signals from locally damaged areas contributes to widespread pathology and that querying expression signatures within discrete microenvironments can identify targetable pathways for DMD therapy. Overall, this spatial atlas of dystrophic muscle provides a valuable resource for studying DMD disease biology and therapeutic target discovery.

Keywords:  Duchenne muscular dystrophy; asynchronous regeneration; skeletal muscle; spatial transcriptomics

DOI:  https://doi.org/10.1073/pnas.2221249120
BMC Genomics. 2023 Jul 04. 24(1): 374

The time-course of cancer cachexia onset reveals biphasic transcriptional disruptions in female skeletal muscle distinct from males.

Francielly Morena da Silva, Seongkyun Lim, Ana Regina Cabrera, Eleanor R Schrems, Ronald G Jones, Megan E Rosa-Caldwell, Tyrone A Washington, Kevin A Murach, Nicholas P Greene.

   BACKGROUND: Cancer-cachexia (CC) is a debilitating condition affecting up to 80% of cancer patients and contributing to 40% of cancer-related deaths. While evidence suggests biological sex differences in the development of CC, assessments of the female transcriptome in CC are lacking, and direct comparisons between sexes are scarce. This study aimed to define the time course of Lewis lung carcinoma (LLC)-induced CC in females using transcriptomics, while directly comparing biological sex differences.
RESULTS: We found the global gene expression of the gastrocnemius muscle of female mice revealed biphasic transcriptomic alterations, with one at 1 week following tumor allograft and another during the later stages of cachexia development. The early phase was associated with the upregulation of extracellular-matrix pathways, while the later phase was characterized by the downregulation of oxidative phosphorylation, electron transport chain, and TCA cycle. When DEGs were compared to a known list of mitochondrial genes (MitoCarta), ~ 47% of these genes were differently expressed in females exhibiting global cachexia, suggesting transcriptional changes to mitochondrial gene expression happens concomitantly to functional impairments previously published. In contrast, the JAK-STAT pathway was upregulated in both the early and late stages of CC. Additionally, we observed a consistent downregulation of Type-II Interferon signaling genes in females, which was associated with protection in skeletal muscle atrophy despite systemic cachexia. Upregulation of Interferon signaling was noted in the gastrocnemius muscle of cachectic and atrophic male mice. Comparison of female tumor-bearing mice with males revealed ~ 70% of DEGs were distinct between sexes in cachectic animals, demonstrating dimorphic mechanisms of CC.
CONCLUSION: Our findings suggest biphasic disruptions in the transcriptome of female LLC tumor-bearing mice: an early phase associated with ECM remodeling and a late phase, accompanied by the onset of systemic cachexia, affecting overall muscle energy metabolism. Notably, ~ 2/3 of DEGs in CC are biologically sex-specific, providing evidence of dimorphic mechanisms of cachexia between sexes. Downregulation of Type-II Interferon signaling genes appears specific to CC development in females, suggesting a new biological sex-specific marker of CC not reliant on the loss of muscle mass, that might represent a protective mechanism against muscle loss in CC in female mice.

Keywords:  Biological sex dimorphism; Cancer cachexia; Lewis lung carcinoma; Mitocarta; RNA-sequencing; Type-II interferon

DOI:  https://doi.org/10.1186/s12864-023-09462-7
FASEB J. 2023 Aug;37(8): e23074

Zeb1 and Tle3 are trans-factors that differentially regulate the expression of myosin heavy chain-embryonic and skeletal muscle differentiation.

Pankaj Kumar, Aatifa Zehra, Masum Saini, Sam J Mathew.

  Myosin heavy chain-embryonic encoded by the Myh3 gene is a skeletal muscle-specific contractile protein expressed during mammalian development and regeneration, essential for proper myogenic differentiation and function. It is likely that multiple trans-factors are involved in this precise temporal regulation of Myh3 expression. We identify a 4230 bp promoter-enhancer region that drives Myh3 transcription in vitro during C2C12 myogenic differentiation and in vivo during muscle regeneration, including sequences both upstream and downstream of the Myh3 TATA-box that are necessary for complete Myh3 promoter activity. Using C2C12 mouse myogenic cells, we find that Zinc-finger E-box binding homeobox 1 (Zeb1) and Transducin-like Enhancer of Split 3 (Tle3) proteins are crucial trans-factors that interact and differentially regulate Myh3 expression. Loss of Zeb1 function results in earlier expression of myogenic differentiation genes and accelerated differentiation, whereas Tle3 depletion leads to reduced expression of myogenic differentiation genes and impaired differentiation. Tle3 knockdown resulted in downregulation of Zeb1, which could be mediated by increased expression of miR-200c, a microRNA that binds to Zeb1 transcript and degrades it. Tle3 functions upstream of Zeb1 in regulating myogenic differentiation since double knockdown of Zeb1 and Tle3 resulted in effects seen upon Tle3 depletion. We identify a novel E-box in the Myh3 distal promoter-enhancer region, where Zeb1 binds to repress Myh3 expression. In addition to regulation of myogenic differentiation at the transcriptional level, we uncover post-transcriptional regulation by Tle3 to regulate MyoG expression, mediated by the mRNA stabilizing Human antigen R (HuR) protein. Thus, Tle3 and Zeb1 are essential trans-factors that differentially regulate Myh3 expression and C2C12 cell myogenic differentiation in vitro.

Keywords:  C2C12 cells; Tle3; Zeb1; mouse; myogenin; myosin heavy chain-embryonic; regeneration; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202201698RR
J Clin Invest. 2023 07 03. pii: e163333. [Epub ahead of print]133(13):

Net39 protects muscle nuclei from mechanical stress during the pathogenesis of Emery-Dreifuss muscular dystrophy.

Yichi Zhang, Andres Ramirez-Martinez, Kenian Chen, John R McAnally, Chunyu Cai, Mateusz Z Durbacz, Francesco Chemello, Zhaoning Wang, Lin Xu, Rhonda Bassel-Duby, Ning Liu, Eric N Olson.

  Mutations in genes encoding nuclear envelope proteins lead to diseases known as nuclear envelopathies, characterized by skeletal muscle and heart abnormalities, such as Emery-Dreifuss muscular dystrophy (EDMD). The tissue-specific role of the nuclear envelope in the etiology of these diseases has not been extensively explored. We previously showed that global deletion of the muscle-specific nuclear envelope protein NET39 in mice leads to neonatal lethality due to skeletal muscle dysfunction. To study the potential role of the Net39 gene in adulthood, we generated a muscle-specific conditional knockout (cKO) of Net39 in mice. cKO mice recapitulated key skeletal muscle features of EDMD, including muscle wasting, impaired muscle contractility, abnormal myonuclear morphology, and DNA damage. The loss of Net39 rendered myoblasts hypersensitive to mechanical stretch, resulting in stretch-induced DNA damage. Net39 was downregulated in a mouse model of congenital myopathy, and restoration of Net39 expression through AAV gene delivery extended life span and ameliorated muscle abnormalities. These findings establish NET39 as a direct contributor to the pathogenesis of EDMD that acts by protecting against mechanical stress and DNA damage.

Keywords:  DNA repair; Gene therapy; Muscle Biology

DOI:  https://doi.org/10.1172/JCI163333
Front Nutr. 2023 ;10 1210976

Editorial: Systemic markers of muscle loss.

Amanda Soares Santos, Brandon M Roberts, Gabriela Salim de Castro.



Keywords:  aging; cachexia; muscle loss; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.3389/fnut.2023.1210976
Cell Commun Signal. 2023 Jul 04. 21(1): 168

Myofiber directs macrophages IL-10-Vav1-Rac1 efferocytosis pathway in inflamed muscle following CTX myoinjury by activating the intrinsic TGF-β signaling.

Zhaohong Liao, Haiqiang Lan, Xiaoting Jian, Jingwen Huang, Han Wang, Jijie Hu, Hua Liao.

   BACKGROUND: To explore the role of skeletal muscle specific TGF-β signaling on macrophages efferocytosis in inflamed muscle caused by Cardiotoxin (CTX) injection.
METHODS: CTX myoinjury was manipulated in TGF-βr2flox/flox (control) mice or transgenic mice with TGF-β receptor 2 (TGF-βr2) being specifically deleted in skeletal muscle (SM TGF-βr2-/-). Gene levels of TGF-β signal molecules, special inflammatory mediators in damaged muscle or in cultured and differentiated myogenic precursor cells (MPC-myotubes) were monitored by transcriptome microarray or qRT-PCR. TGF-β pathway molecules, myokines and embryonic myosin heavy chain in regenerating myofibers, the phenotype and efferocytosis of macrophages were evaluated by immunofluorescence, immunoblotting, Luminex, or FACS analysis. In vitro apoptotic cells were prepared by UV-irradiation.
RESULTS: In control mice, TGF-β-Smad2/3 signaling were significantly up-regulated in regenerating centronuclear myofibers after CTX-myoinjury. More severe muscle inflammation was caused by the deficiency of muscle TGF-β signaling, with the increased number of M1, but the decreased number of M2 macrophages. Notably, the deficiency of TGF-β signaling in myofibers dramatically affected on the ability of macrophages to conduct efferocytosis, marked by the decreased number of Annexin-V-F4/80+Tunel+ macrophages in inflamed muscle, and the impaired uptake of macrophages to PKH67+ apoptotic cells transferred into damaged muscle. Further, our study suggested that, the intrinsic TGF-β signaling directed IL-10-Vav1-Rac1 efferocytosis signaling in muscle macrophages.
CONCLUSIONS: Our data demonstrate that muscle inflammation can be suppressed potentially by activating the intrinsic TGF-β signaling in myofibers to promote IL-10 dependent-macrophages efferocytosis. Video Abstract.

Keywords:  IL-10; Macrophages efferocytosis; Myoinjury; TGF-β signaling

DOI:  https://doi.org/10.1186/s12964-023-01163-8
Cell Death Discov. 2023 Jul 04. 9(1): 224

Altered muscle niche contributes to myogenic deficit in the D2-mdx model of severe DMD.

Davi A G Mázala, Ravi Hindupur, Young Jae Moon, Fatima Shaikh, Iteoluwakishi H Gamu, Dhruv Alladi, Georgiana Panci, Michèle Weiss-Gayet, Bénédicte Chazaud, Terence A Partridge, James S Novak, Jyoti K Jaiswal.

Lack of dystrophin expression is the underlying genetic basis for Duchenne muscular dystrophy (DMD). However, disease severity varies between patients, based on specific genetic modifiers. D2-mdx is a model for severe DMD that exhibits exacerbated muscle degeneration and failure to regenerate even in the juvenile stage of the disease. We show that poor regeneration of juvenile D2-mdx muscles is associated with an enhanced inflammatory response to muscle damage that fails to resolve efficiently and supports the excessive accumulation of fibroadipogenic progenitors (FAPs), leading to increased fibrosis. Unexpectedly, the extent of damage and degeneration in juvenile D2-mdx muscle is significantly reduced in adults, and is associated with the restoration of the inflammatory and FAP responses to muscle injury. These improvements enhance regenerative myogenesis in the adult D2-mdx muscle, reaching levels comparable to the milder B10-mdx model of DMD. Ex vivo co-culture of healthy satellite cells (SCs) with juvenile D2-mdx FAPs reduces their fusion efficacy. Wild-type juvenile D2 mice also manifest regenerative myogenic deficit and glucocorticoid treatment improves their muscle regeneration. Our findings indicate that aberrant stromal cell responses contribute to poor regenerative myogenesis and greater muscle degeneration in juvenile D2-mdx muscles and reversal of this reduces pathology in adult D2-mdx muscle, identifying these responses as a potential therapeutic target for the treatment of DMD.

DOI: https://doi.org/10.1038/s41420-023-01503-0
Front Cell Dev Biol. 2023 ;11 1235520

Editorial: Cellular heterogeneity in physiological and pathological myogenesis.

Monica Dentice, Stefano Biressi, Lorenzo Giordani, Ombretta Guardiola.



Keywords:  heterogeneity; muscle aging; muscle disease; muscle regeneration; muscle stem cells

DOI:  https://doi.org/10.3389/fcell.2023.1235520
Acta Diabetol. 2023 Jul 01.

The CEBPA-FGF21 regulatory network may participate in the T2DM-induced skeletal muscle atrophy by regulating the autophagy-lysosomal pathway.

Kai Wu, Sha Huang, Fan Zheng, Yuan Liu.

   AIMS: Recent years have witnessed an increasing research interest in the roles of transcription factor (TF)-gene regulatory network in type 2 diabetes mellitus (T2DM). Thus, we sought to characterize the mechanistic insights based on the TF-gene regulatory network in skeletal muscle atrophy in T2DM.
METHODS: Differentially expressed TFs (DETFs) and mRNAs (DEmRNAs) were obtained in T2DM-related gene expression profiles (GSE12643, GSE55650, GSE166502, and GSE29221), followed by WGCNA, and GO and KEGG enrichment analyses. Next, the iRegulon plug-in unit of Cytoscape software was used to construct a TF-mRNA regulatory network. Besides, RT-qPCR and ChIP-seq were utilized to measure the expression of CEBPA and FGF21 in the skeletal muscle tissues or cells of T2DM rat models. At last, the effect of overexpression of FGF21 on the autophagy-lysosomal pathway was examined in skeletal muscle cells of T2DM rats.
RESULTS: Totally, 12 DETFs and 102 DEmRNAs were found in the skeletal muscle tissues of T2DM samples. The DEmRNAs were mainly enriched in the autophagy-lysosomal pathway. CEBPA affected the skeletal muscle atrophy in T2DM by regulating 5 target genes via the autophagy-lysosomal pathway. CEBPA could target FGF21. In addition, the expression of CEBPA was elevated, while the expression of FGF21 was diminished in the skeletal muscle tissues or cells of T2DM rats. The CEBPA-FGF21 regulatory network promoted skeletal muscle atrophy in T2DM by activating the autophagy-lysosomal pathway.
CONCLUSION: The CEBPA-FGF21 regulatory network may participate in the T2DM-induced skeletal muscle atrophy by regulating the autophagy-lysosomal pathway. Thus, our study provides interesting targets for prevention of skeletal muscle atrophy in T2DM.

Keywords:  Autophagy-lysosomal pathway; CEBPA; FGF21; Skeletal muscle atrophy; Transcription factor; Type 2 diabetes mellitus

DOI:  https://doi.org/10.1007/s00592-023-02131-x
bioRxiv. 2023 Jun 01. pii: 2023.05.30.542928. [Epub ahead of print]

MFGE8 inhibits insulin signaling through PTP1B.

Ritwik Datta, Michael J Podolsky, Christopher D Yang, Diana L Alba, Sukhmani Singh, Suneil Koliwad, Carlos O Lizama, Kamran Atabai.

The role of integrins in regulating insulin signaling is incompletely understood. We have previously shown that binding of the integrin ligand milk fat globule epidermal growth factor like 8 (MFGE8) to the αvβ5 integrin promotes termination of insulin receptor signaling in mice. Upon ligation of MFGE8, β5 complexes with the insulin receptor beta (IRβ) in skeletal muscle resulting in dephosphorylation of IRβ and reduction of insulin-stimulated glucose uptake. Here we investigate the mechanism by which the interaction between β5 and IRβ impacts IRβ phosphorylation status. We show that β5 blockade inhibits and MFGE8 promotes PTP1B binding to and dephosphorylation of IRβ resulting in reduced or increased insulin-stimulated myotube glucose uptake respectively. The β5-PTP1B complex is recruited by MFGE8 to IRβ leading to termination of canonical insulin signaling. β5 blockade enhances insulin-stimulated glucose uptake in wild type but not Ptp1b KO mice indicating that PTP1B functions downstream of MFGE8 in modulating insulin receptor signaling. Furthermore, in a human cohort, we report serum MFGE8 levels correlate with indices of insulin resistance. These data provide mechanistic insights into the role of MFGE8 and β5 in regulating insulin signaling.

DOI: https://doi.org/10.1101/2023.05.30.542928
Sci Adv. 2023 Jul 07. 9(27): eadd9984

Single-cell and spatial transcriptomics identify a macrophage population associated with skeletal muscle fibrosis.

Gerald Coulis, Diego Jaime, Christian Guerrero-Juarez, Jenna M Kastenschmidt, Philip K Farahat, Quy Nguyen, Nicholas Pervolarakis, Katherine McLinden, Lauren Thurlow, Saba Movahedi, Brandon S Hughes, Jorge Duarte, Andrew Sorn, Elizabeth Montoya, Izza Mozaffar, Morgan Dragan, Shivashankar Othy, Trupti Joshi, Chetan P Hans, Virginia Kimonis, Adam L MacLean, Qing Nie, Lindsay M Wallace, Scott Q Harper, Tahseen Mozaffar, Marshall W Hogarth, Surajit Bhattacharya, Jyoti K Jaiswal, David R Golann, Qi Su, Kai Kessenbrock, Michael Stec, Melissa J Spencer, Jesse R Zamudio, S Armando Villalta.

Macrophages are essential for skeletal muscle homeostasis, but how their dysregulation contributes to the development of fibrosis in muscle disease remains unclear. Here, we used single-cell transcriptomics to determine the molecular attributes of dystrophic and healthy muscle macrophages. We identified six clusters and unexpectedly found that none corresponded to traditional definitions of M1 or M2 macrophages. Rather, the predominant macrophage signature in dystrophic muscle was characterized by high expression of fibrotic factors, galectin-3 (gal-3) and osteopontin (Spp1). Spatial transcriptomics, computational inferences of intercellular communication, and in vitro assays indicated that macrophage-derived Spp1 regulates stromal progenitor differentiation. Gal-3+ macrophages were chronically activated in dystrophic muscle, and adoptive transfer assays showed that the gal-3+ phenotype was the dominant molecular program induced within the dystrophic milieu. Gal-3+ macrophages were also elevated in multiple human myopathies. These studies advance our understanding of macrophages in muscular dystrophy by defining their transcriptional programs and reveal Spp1 as a major regulator of macrophage and stromal progenitor interactions.

DOI: https://doi.org/10.1126/sciadv.add9984
FEBS Open Bio. 2023 07;13(7): 1228-1237

Circadian transcriptome processing and analysis: a workflow for muscle stem cells.

Valentina Sica, Oleg Deryagin, Jacob G Smith, Pura Muñoz-Canoves.

  Circadian rhythms coordinate biological processes with Earth's 24-h daily light/dark cycle. In the last years, efforts in the field of chronobiology have sought to understand the ways in which the circadian clock controls transcription across tissues and cells. This has been supported by the development of different bioinformatic approaches that allow the identification of 24-h oscillating transcripts. This workflow aims to describe how to isolate muscle stem cells for RNA sequencing analysis from a typical circadian experiment and introduces bioinformatic tools suitable for the analysis of circadian transcriptomes.

Keywords:  bioinformatics; circadian rhythms; muscle stem cells; satellite cells

DOI:  https://doi.org/10.1002/2211-5463.13629
bioRxiv. 2023 Jun 15. pii: 2023.05.30.542870. [Epub ahead of print]

17α-estradiol Alleviates High-Fat Diet-Induced Inflammatory and Metabolic Dysfunction in Skeletal Muscle of Male and Female Mice.

Matthew P Bubak, Shivani N Mann, Agnieszka K Borowik, Atul Pranay, Albert Batushansky, Samim Ali Mondal, Stephen M Diodge, Arik Davidyan, Marcelina M Szczygiel, Fredrick R Peelor, Sandra Rigsby, Matle Broomfield, Charles I Lacy, Heather C Rice, Michael B Stout, Benjamin F Miller.

Skeletal muscle has a central role in maintaining metabolic homeostasis. 17α-estradiol (17α-E2), a naturally-occurring non-feminizing diastereomer of 17β-estradiol that demonstrates efficacy for improving metabolic outcomes in male, but not female, mice. Despite several lines of evidence showing that 17α-E2 treatment improves metabolic parameters in middle-aged obese and old male mice through effects in brain, liver, and white adipose tissue little is known about how 17α-E2 alters skeletal muscle metabolism, and what role this may play in mitigating metabolic declines. Therefore, this study aimed to determine if 17α-E2 treatment improves metabolic outcomes in skeletal muscle from obese male and female mice following chronic high fat diet (HFD) administration. We hypothesized that male, but not female, mice, would benefit from 17α-E2 treatment during HFD. To test this hypothesis, we used a multi-omics approach to determine changes in lipotoxic lipid intermediates, metabolites, and proteins related to metabolic homeostasis. In male mice, we show that 17α-E2 alleviates HFD-induced metabolic detriments of skeletal muscle by reducing the accumulation of diacylglycerol (DAGs) and ceramides, inflammatory cytokine levels, and reduced the abundance of most of the proteins related to lipolysis and beta-oxidation. In contrast to males, 17α-E2 treatment in female mice had little effect on the DAGs and ceramides content, muscle inflammatory cytokine levels, or changes to the relative abundance of proteins involved in beta-oxidation. These data support to the growing evidence that 17α-E2 treatment could be beneficial for overall metabolic health in male mammals.

DOI: https://doi.org/10.1101/2023.05.30.542870
Front Cell Dev Biol. 2023 ;11 1181040

Promising AAV.U7snRNAs vectors targeting DMPK improve DM1 hallmarks in patient-derived cell lines.

Camila F Almeida, Florence Robriquet, Tatyana A Vetter, Nianyuan Huang, Reid Neinast, Lumariz Hernandez-Rosario, Dhanarajan Rajakumar, W David Arnold, Kim L McBride, Kevin M Flanigan, Robert B Weiss, Nicolas Wein.

  Myotonic dystrophy type 1 (DM1) is the most common form of muscular dystrophy in adults and affects mainly the skeletal muscle, heart, and brain. DM1 is caused by a CTG repeat expansion in the 3'UTR region of the DMPK gene that sequesters muscleblind-like proteins, blocking their splicing activity and forming nuclear RNA foci. Consequently, many genes have their splicing reversed to a fetal pattern. There is no treatment for DM1, but several approaches have been explored, including antisense oligonucleotides (ASOs) aiming to knock down DMPK expression or bind to the CTGs expansion. ASOs were shown to reduce RNA foci and restore the splicing pattern. However, ASOs have several limitations and although being safe treated DM1 patients did not demonstrate improvement in a human clinical trial. AAV-based gene therapies have the potential to overcome such limitations, providing longer and more stable expression of antisense sequences. In the present study, we designed different antisense sequences targeting exons 5 or 8 of DMPK and the CTG repeat tract aiming to knock down DMPK expression or promote steric hindrance, respectively. The antisense sequences were inserted in U7snRNAs, which were then vectorized in AAV8 particles. Patient-derived myoblasts treated with AAV8. U7snRNAs showed a significant reduction in the number of RNA foci and re-localization of muscle-blind protein. RNA-seq analysis revealed a global splicing correction in different patient-cell lines, without alteration in DMPK expression.

Keywords:  U7snRNA; aav; gene therapy; myotonic dystrophy; spliceopathy

DOI:  https://doi.org/10.3389/fcell.2023.1181040
Am J Pathol. 2023 Jul 05. pii: S0002-9440(23)00239-0. [Epub ahead of print]

Different mouse models of nemaline myopathy harboring Acta1 mutations display differing abnormalities related to mitochondrial biology.

Jennifer A Tinklenberg, Rebecca A Slick, Jessica Sutton, Liwen Zhang, Hui Meng, Margaret J Beatka, Mark Vanden Avond, Mariah J Prom, Emily Ott, Federica Montanaro, James Heisner, Rafael Toro, Edna C Hardeman, Aron M Geurts, David Stowe, R Blake Hill, Michael W Lawlor.

ACTA1 encodes skeletal muscle-specific α-actin, which polymerizes to form the thin filament of the sarcomere. Mutations in ACTA1 are responsible for roughly 30% of nemaline myopathy (NM) cases. Previous studies of weakness in NM have focused on muscle structure and contractility, but genetic issues alone do not explain the phenotypic heterogeneity observed in NM patients or mouse models. To identify additional biological processes related to NM phenotypic severity, proteomic analysis was performed using muscle protein isolates from wild type (WT) mice in comparison to moderately affected KI.Acta1H40Y and the minimally affected TgACTA1D286G NM mouse models. This analysis revealed abnormalities in mitochondrial function and stress-related pathways in both mouse models, supporting an in-depth assessment of mitochondrial biology. Interestingly, evaluating each model in comparison to its WT counterpart identified different degrees of mitochondrial abnormality that correlated well with the phenotypic severity of the mouse model. Muscle histology, mitochondrial respiration, electron transport chain function, and mitochondrial membrane potential (ΔΨm) were all normal or minimally affected in the TgACTA1D286G mouse model. In contrast, the more severely affected KI.Acta1H40Y mice displayed significant abnormalities in relation to muscle histology, mitochondrial respirometry, ATP, ADP, and phosphate content, and ΔΨm. These findings suggest that abnormal energy metabolism is related to symptomatic severity in NM and may constitute a contributor to phenotypic variability and a novel treatment target.

DOI: https://doi.org/10.1016/j.ajpath.2023.06.008
FASEB J. 2023 08;37(8): e23083

Nur77 is involved in the regulation of obesity-related lower muscle mass by promoting Pten degradation.

Feng Chen, Yang Yu, Huanlian Tian, Guojing Ma, Ruze Ma, Tingting Tian, Difei Wang.

  Obesity may impair muscle function and is sometimes associated with lower muscle mass. However, the internal regulatory mechanism is still unclear. Nur77 has been reported to improve obesity phenotype by regulating glucose and lipid metabolism and inhibiting the production of inflammatory factors and reactive oxygen species. Concurrently, Nur77 also plays an important role in muscle differentiation and development. We aimed to investigate the role of Nur77 in obesity-related lower muscle mass. Our in vivo and in vitro experiments illustrated that the reduction of obesity-related Nur77 accelerated the occurrence of lower muscle mass by interfering with the signaling pathways involved in the regulation of myoprotein synthesis and degradation. We further demonstrated that Nur77 activates the PI3K/Akt pathway by promoting Pten degradation, which enhances the phosphorylation of the Akt/mTOR/p70S6K pathway and inhibits the expression of skeletal muscle-specific E3 ligases (MAFbx/MuRF1). Nur77 induces Pten degradation by increasing the transcription of its specific E3 ligase Syvn1. Our study confirms that Nur77 is a key factor in ameliorating obesity-related lower muscle mass, providing a new therapeutic target and theoretical basis for the treatment of obesity-related lower muscle mass.

Keywords:  Nur77; Pten; muscle mass; myoprotein synthesis and degradation; obesity

DOI:  https://doi.org/10.1096/fj.202201983RR
Nutr Res Rev. 2023 Jul 03. 1-82

Post-natal muscle growth and protein turnover: a narrative review of current understanding.

D Joe Millward.

  A model explaining the dietary-protein driven post-natal skeletal muscle growth and protein turnover in the rat is updated, and the mechanisms involved described in this narrative review. Dietary protein controls both length and muscle growth which are interrelated through mechanotransduction mechanisms with muscle growth induced by both stretching subsequent to bone length growth and from internal work against gravity. This induces satellite cell activation, myogenesis and remodeling of the extracellular matrix, establishing a growth capacity for myofibre length and cross-sectional area. Protein deposition within this capacity is enabled by adequate dietary protein and other key nutrients. After briefly reviewing the experimental animal origins of the growth model, key concepts and processes important for growth are reviewed. These include the growth in number and size of the myonuclear domain, satellite cell activity during post-natal development and the autocrine/paracrine action of IGF-1. Regulatory and signalling pathways reviewed include developmental mechanotransduction; signalling through the insulin/IGF-1-PI3K-Akt and the Ras-MAPK pathways in the myofibre and during mechanotransduction of satellite cells. Likely pathways activated by maximal-intensity muscle contractions are highlighted and the regulation of the capacity for protein synthesis in terms of ribosome assembly and the translational regulation of 5-TOPmRNA classes by mTORC1 and LARP1 are discussed. Evidence for and potential mechanisms by which volume limitation of muscle growth can occur which would limit protein deposition within the myofibre is reviewed. An understanding of how muscle growth is achieved allows better nutritional management of its growth in health and disease.

Keywords:  IGF-1; Modelling muscle growth; mechanotransduction; myonuclear domain; protein synthesis; satellite cells; signalling pathways

DOI:  https://doi.org/10.1017/S0954422423000124
Br J Sports Med. 2023 Jul 06. pii: bjsports-2023-106807. [Epub ahead of print]

Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis.

Brad S Currier, Jonathan C Mcleod, Laura Banfield, Joseph Beyene, Nicky J Welton, Alysha C D'Souza, Joshua A J Keogh, Lydia Lin, Giulia Coletta, Antony Yang, Lauren Colenso-Semple, Kyle J Lau, Alexandria Verboom, Stuart M Phillips.

   OBJECTIVE: To determine how distinct combinations of resistance training prescription (RTx) variables (load, sets and frequency) affect muscle strength and hypertrophy.
DATA SOURCES: MEDLINE, Embase, Emcare, SPORTDiscus, CINAHL, and Web of Science were searched until February 2022.
ELIGIBILITY CRITERIA: Randomised trials that included healthy adults, compared at least 2 predefined conditions (non-exercise control (CTRL) and 12 RTx, differentiated by load, sets and/or weekly frequency), and reported muscle strength and/or hypertrophy were included.
ANALYSES: Systematic review and Bayesian network meta-analysis methodology was used to compare RTxs and CTRL. Surface under the cumulative ranking curve values were used to rank conditions. Confidence was assessed with threshold analysis.
RESULTS: The strength network included 178 studies (n=5097; women=45%). The hypertrophy network included 119 studies (n=3364; women=47%). All RTxs were superior to CTRL for muscle strength and hypertrophy. Higher-load (>80% of single repetition maximum) prescriptions maximised strength gains, and all prescriptions comparably promoted muscle hypertrophy. While the calculated effects of many prescriptions were similar, higher-load, multiset, thrice-weekly training (standardised mean difference (95% credible interval); 1.60 (1.38 to 1.82) vs CTRL) was the highest-ranked RTx for strength, and higher-load, multiset, twice-weekly training (0.66 (0.47 to 0.85) vs CTRL) was the highest-ranked RTx for hypertrophy. Threshold analysis demonstrated these results were extremely robust.
CONCLUSION: All RTx promoted strength and hypertrophy compared with no exercise. The highest-ranked prescriptions for strength involved higher loads, whereas the highest-ranked prescriptions for hypertrophy included multiple sets.
PROSPERO REGISTRATION NUMBER: CRD42021259663 and CRD42021258902.

Keywords:  aging; muscle; muscle, skeletal; weight lifting

DOI:  https://doi.org/10.1136/bjsports-2023-106807