bims-moremu 2022-10-09 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2022–10–09
35 papers selected by
Anna Vainshtein, Craft Science Inc.

Role of macrophages during skeletal muscle regeneration and hypertrophy-Implications for immunomodulatory strategies.
Phytoecdysteroids Accelerate Recovery of Skeletal Muscle Function Following in vivo Eccentric Contraction-Induced Injury in Adult and Old Mice.
Muscle fibro-adipogenic progenitors from a single-cell perspective: Focus on their "virtual" secretome.
Effects of different modes of exercise on skeletal muscle mass and function and IGF-1 signaling during early aging in mice.
Roles of super enhancers and enhancer RNAs in skeletal muscle development and disease.
miR21 deletion in osteocytes has direct and indirect effects on skeletal muscle in a sex-dimorphic manner in mice.
Defining the Specific Skeletal Muscle Adaptations Responsible for Exercise Training Improvements in Heart Failure With Preserved Ejection Fraction.
Muscle injury induces a transient senescence-like state that is required for myofiber growth during muscle regeneration.
Geometric basis of action potential of skeletal muscle cells and neurons.
Deletion of skeletal muscle Akt1/2 causes osteosarcopenia and reduces lifespan in mice.
Resistance training prevents damage to the mitochondrial function of the skeletal muscle of rats exposed to secondary cigarette smoke.
Single-cell dissection of the obesity-exercise axis in adipose-muscle tissues implies a critical role for mesenchymal stem cells.
Heavy-load exercise in older adults activates vasculogenesis and has a stronger impact on muscle gene expression than in young adults.
RNA-seq transcriptomic analysis of 4-octyl itaconate repressing myogenic differentiation.
Gut microbiota as a promising therapeutic target for age-related sarcopenia.
Effect of caffeine on mitochondrial biogenesis in the skeletal muscle - A narrative review.
Long noncoding RNA lncMREF promotes myogenic differentiation and muscle regeneration by interacting with the Smarca5/p300 complex.
Lamin A precursor localizes to the Z-disc of sarcomeres in the heart and is dynamically regulated in muscle cell differentiation.
DUX4 expression activates JNK and p38 MAP kinases in myoblasts.
Impact of Different Training Modalities on Molecular Alterations in Skeletal Muscle of Patients With Heart Failure With Preserved Ejection Fraction: A Substudy of the OptimEx Trial.
Inter-organellar and systemic responses to impaired mitochondrial matrix protein import in skeletal muscle.
Association of lithocholic acid with skeletal muscle hypertrophy through TGR5-IGF-1 and skeletal muscle mass in cultured mouse myotubes, chronic liver disease rats and humans.
Different responses of skeletal muscles to femoral artery ligation-induced ischemia identified in BABL/c and C57BL/6 mice.
Klotho: An Emerging Factor With Ergogenic Potential.
Motor units alterations with muscle disuse: what is new?
Mice with R2509C-RYR1 mutation exhibit dysfunctional Ca2+ dynamics in primary skeletal myocytes.
Assessment of PABPN1 nuclear inclusions on a large cohort of patients and in a human xenograft model of oculopharyngeal muscular dystrophy.
Muscle O2 diffusion capacity by NIRS: a new approach in the air.
Proteomic analysis of skeletal muscle in Chinese hamsters with type 2 diabetes mellitus reveals that OPLAH downregulation affects insulin resistance and impaired glucose uptake.
Metastatic or xenograft colorectal cancer induce divergent anabolic deficits and pro-inflammatory effectors of muscle wasting in a tumor-type dependent manner.
LP07 and LLC pre-clinical models of lung cancer induce divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting.
Targeted transcript analysis in muscles from patients with genetically diverse congenital myopathies.
Extracellular vesicles secreted from mouse muscle cells improve delayed bone repair in diabetic mice.
Mechanisms and significance of tissue-specific MICU regulation of the mitochondrial calcium uniporter complex.
A first-in-human phase I/IIa gene transfer clinical trial for Duchenne muscular dystrophy using rAAVrh74.MCK.GALGT2.

Physiol Rep. 2022 Oct;10(19): e15480

Role of macrophages during skeletal muscle regeneration and hypertrophy-Implications for immunomodulatory strategies.

Clara Bernard, Aliki Zavoriti, Quentin Pucelle, Bénédicte Chazaud, Julien Gondin.

Skeletal muscle is a plastic tissue that regenerates ad integrum after injury and adapts to raise mechanical loading/contractile activity by increasing its mass and/or myofiber size, a phenomenon commonly refers to as skeletal muscle hypertrophy. Both muscle regeneration and hypertrophy rely on the interactions between muscle stem cells and their neighborhood, which include inflammatory cells, and particularly macrophages. This review first summarizes the role of macrophages in muscle regeneration in various animal models of injury and in response to exercise-induced muscle damage in humans. Then, the potential contribution of macrophages to skeletal muscle hypertrophy is discussed on the basis of both animal and human experiments. We also present a brief comparative analysis of the role of macrophages during muscle regeneration versus hypertrophy. Finally, we summarize the current knowledge on the impact of different immunomodulatory strategies, such as heat therapy, cooling, massage, nonsteroidal anti-inflammatory drugs and resolvins, on skeletal muscle regeneration and their potential impact on muscle hypertrophy.

DOI: https://doi.org/10.14814/phy2.15480
Front Rehabil Sci. 2021 ;2 757789

Phytoecdysteroids Accelerate Recovery of Skeletal Muscle Function Following in vivo Eccentric Contraction-Induced Injury in Adult and Old Mice.

Kevin A Zwetsloot, R Andrew Shanely, Joshua S Godwin, Charles F Hodgman.

  Background: Eccentric muscle contractions are commonly used in exercise regimens, as well as in rehabilitation as a treatment against muscle atrophy and weakness. If repeated multiple times, eccentric contractions may result in skeletal muscle injury and loss of function. Skeletal muscle possesses the remarkable ability to repair and regenerate after an injury or damage; however, this ability is impaired with aging. Phytoecdysteroids are natural plant steroids that possess medicinal, pharmacological, and biological properties, with no adverse side effects in mammals. Previous research has demonstrated that administration of phytoecdysteroids, such as 20-hydroxyecdysone (20E), leads to an increase in protein synthesis signaling and skeletal muscle strength. Methods: To investigate whether 20E enhances skeletal muscle recovery from eccentric contraction-induced damage, adult (7-8 mo) and old (26-27 mo) mice were subjected to injurious eccentric contractions (EC), followed by 20E or placebo (PLA) supplementation for 7 days. Contractile function via torque-frequency relationships (TF) was measured three times in each mouse: pre- and post-EC, as well as after the 7-day recovery period. Mice were anesthetized with isoflurane and then electrically-stimulated isometric contractions were performed to obtain in vivo muscle function of the anterior crural muscle group before injury (pre), followed by 150 EC, and then again post-injury (post). Following recovery from anesthesia, mice received either 20E (50 mg•kg-1 BW) or PLA by oral gavage. Mice were gavaged daily for 6 days and on day 7, the TF relationship was reassessed (7-day). Results: EC resulted in significant reductions of muscle function post-injury, regardless of age or treatment condition (p < 0.001). 20E supplementation completely recovered muscle function after 7 days in both adult and old mice (pre vs. 7-day; p > 0.05), while PLA muscle function remained reduced (pre vs. 7-day; p < 0.01). In addition, histological markers of muscle damage appear lower in damaged muscle from 20E-treated mice after the 7-day recovery period, compared to PLA. Conclusions: Taken together, these findings demonstrate that 20E fully recovers skeletal muscle function in both adult and old mice just 7 days after eccentric contraction-induced damage. However, the underlying mechanics by which 20E contributes to the accelerated recovery from muscle damage warrant further investigation.

Keywords:  20-hydroxyecdysone (20E); exercise; muscle aging; muscle damage; muscle injury; muscle regeneration

DOI:  https://doi.org/10.3389/fresc.2021.757789
Front Cell Dev Biol. 2022 ;10 952041

Muscle fibro-adipogenic progenitors from a single-cell perspective: Focus on their "virtual" secretome.

Elisa Negroni, Maria Kondili, Laura Muraine, Mona Bensalah, Gillian Sandra Butler-Browne, Vincent Mouly, Anne Bigot, Capucine Trollet.

  Skeletal muscle is a highly plastic tissue composed of a number of heterogeneous cell populations that, by interacting and communicating with each other, participate to the muscle homeostasis, and orchestrate regeneration and repair in healthy and diseased conditions. Although muscle regeneration relies on the activity of muscle stem cells (MuSCs), many other cellular players such as inflammatory, vascular and tissue-resident mesenchymal cells participate and communicate with MuSCs to sustain the regenerative process. Among them, Fibro-Adipogenic Progenitors (FAPs), a muscle interstitial stromal population, are crucial actors during muscle homeostasis and regeneration, interacting with MuSCs and other cellular players and dynamically producing and remodelling the extra-cellular matrix. Recent emerging single-cell omics technologies have resulted in the dissection of the heterogeneity of each cell populations within skeletal muscle. In this perspective we have reviewed the recent single-cell omics studies with a specific focus on FAPs in mouse and human muscle. More precisely, using the OutCyte prediction tool, we analysed the "virtual" secretome of FAPs, in resting and regenerating conditions, to highlight the potential of RNAseq data for the study of cellular communication.

Keywords:  FAPs; cell-cell communication; extracellular matrix; in silico; scRNAseq; secretome; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2022.952041
J Exp Biol. 2022 Oct 07. pii: jeb.244650. [Epub ahead of print]

Effects of different modes of exercise on skeletal muscle mass and function and IGF-1 signaling during early aging in mice.

Bowen Li, Lili Feng, Xiaonan Wu, Mengxin Cai, JaneJie Yu, Zhenjun Tian.

  Skeletal muscle mass and function tend to decline with increasing age. Insulin-like growth factor 1 (IGF-1) plays a key role in promoting skeletal muscle growth. Exercise improves skeletal muscle mass and function via activating the IGF-1 signaling. The aim of this study was to investigate whether different types of exercise could promote muscle hypertrophy, exercise and metabolic capacities, and activate IGF-1 signaling in early aging mice. 12-month-old male C57/BL6 mice were randomly divided into five groups: control group (CON), aerobic exercise group (AE), resistance exercise group (RE), whole-body vibration group (WBV) and electrical stimulation group (ES). Muscle weight, myofiber size, levels of IGF-1 signaling, oxidative stress, protein synthesis and degradation, and apoptosis in gastrocnemius muscle were detected. C2C12 cells were used to explore the mechanism. In this study, we confirmed that four modes of exercise increased skeletal muscle mass, exercise capacity, indicators of metabolism and protein synthesis, and inhibited oxidative stress and apoptosis via activating the IGF-1 pathway. The most effective intervention was RE. We found that WBV promoted muscle hypertrophy better than AE. Furthermore, in vitro experiment, the importance of IGF-1 / IGF-1R-PI3K / Akt signaling for maintaining skeletal muscle mass was further confirmed. AE, RE, WBV and ES increase skeletal muscle mass, exercise capacities, protein synthesis and metabolic enzyme activities, inhibit protein degradation and apoptosis in mice undergoing early aging via activating IGF-1 signaling. Among them, WBV has been shown to be significantly effective and has a similar effect of conventional exercise in promoting muscle hypertrophy.

Keywords:  Early aging; Exercise; Insulin-like growth factor-1; Skeletal muscle

DOI:  https://doi.org/10.1242/jeb.244650
Cell Cycle. 2022 Oct 02. 1-11

Roles of super enhancers and enhancer RNAs in skeletal muscle development and disease.

Si Lei, Cheng Li, Yanling She, Shanyao Zhou, Huacai Shi, Rui Chen.

  Skeletal muscle development is a multistep biological process regulated by a variety of myogenic regulatory factors, including MyoG, MyoD, Myf5, and Myf6 (also known as MRF4), as well as members of the FoxO subfamily. Differentiation and regeneration during skeletal muscle myogenesis contribute to the physiological function of muscles. Super enhancers (SEs) and enhancer RNAs (eRNAs) are involved in the regulation of development and diseases. Few studies have identified the roles of SEs and eRNAs in muscle development and pathophysiology. To develop approaches to enhance skeletal muscle mass and function, a more comprehensive understanding of the key processes underlying muscular diseases is needed. In this review, we summarize the roles of SEs and eRNAs in muscle development and disease through affecting of DNA methylation, FoxO subfamily, RAS-MEK signaling, chromatin modifications and accessibility, MyoD and cis regulating target genes. The summary could inform strategies to increase muscle mass and treat muscle-related diseases.

Keywords:  Development; differentiation; enhancer RNAs; skeletal muscle; super enhancers

DOI:  https://doi.org/10.1080/15384101.2022.2129240
Biol Sex Differ. 2022 Oct 01. 13(1): 56

miR21 deletion in osteocytes has direct and indirect effects on skeletal muscle in a sex-dimorphic manner in mice.

Alyson L Essex, Padmini Deosthale, Joshua R Huot, Hannah M Davis, Nicholas Momeni, Andrea Bonetto, Lilian I Plotkin.

BACKGROUND: Osteocytic microRNA21 (miR21) removal alters cytokine production and bone mass by modulating osteoclast and osteoblast differentiation and activity. Removing osteocytic miR21 increases osteoclast/osteoblast numbers and bone mass in male mice, whereas it decreases osteoclasts/osteoblasts without affecting bone mass in female mice. On the other hand, it leads to sex-independent increases in bone mechanical properties. Because changes in bone remodeling and strength affect skeletal muscle through bone-muscle crosstalk, we investigated whether osteocytic miR21 deletion influences skeletal muscle.
METHODS: miR21fl/fl mice and 8kbDMP1-Cre mice were mated to obtain miR21-deficient mice primarily in the osteocyte (OtmiR21Δ) and littermate controls (miR21fl/fl). Four-month-old male and female mice were analyzed. Body composition was examined by DXA/Piximus and gene expression was assessed by qPCR. Ex vivo cultures of long bones devoid of bone-marrow cells from male and female 4-month-old were maintained for 48 h. Conditioned media were collected and used for the C2C12 assays. Two-way ANOVA analyses were performed to determine the contributions of genotype and sex and their interaction to the effects of miR21 deficiency.
RESULTS: Lean body mass was increased only in female OtmiR21Δ mice, although miR21 levels in soleus muscle were similar in miR21fl/fl (0.05 ± 0.02) and OtmiR21Δ (0.09 ± 0.04) mice. Female, but not male, OtmiR21Δ mice exhibited increased soleus (42%) and gastrocnemius (21%) muscle weight compared to miR21fl/fl littermates. However, muscle strength and gastrocnemius muscle fiber cross-sectional area were unaltered for either sex. Kinase phosphorylation (phospho/total protein ratio) in soleus muscle, measured as a surrogate for kinase activity by means of multiplex analysis, was also selectively changed depending on the mouse sex. Thus, female OtmiR21Δ mice had higher T185/Y187-ERK1/2 but lower S473-Akt phosphorylation than miR21fl/fl controls, while male OtmiR21Δ mice had higher S473-Akt phosphorylation, suggesting sex-dimorphic shifts in anabolic vs. catabolic signaling. Consistently, levels of FOXO3 and MuRF-1, known to be regulated by Akt, were only increased in male OtmiR21Δ mice. Atrogin-1 mRNA levels were upregulated in female OtmiR21Δ mice, suggesting a potential shift in protein regulation. Sex-specific effects were also found by exposing myotube cultures to conditioned media from 48-h-cultured marrow-flushed bones. Thus 5-day differentiated C2C12 myotubes treated with conditioned media of female OtmiR21Δ mice exhibit 12% higher average diameter compared to cells exposed to miR21fl/fl bone conditioned media. Yet, conditioned media from male bones had no effect on myotube size.
CONCLUSIONS: We present a novel aspect of bone-muscle crosstalk in which osteocyte-derived miR21 influences skeletal muscle size, but not strength, in female but not male mice; whereas, intracellular signaling alterations resulting from loss of miR21 seem to alter protein dynamics in a sex-dimorphic fashion.

DOI: https://doi.org/10.1186/s13293-022-00465-9
Circ Heart Fail. 2022 Oct 06. 101161CIRCHEARTFAILURE122010003

Defining the Specific Skeletal Muscle Adaptations Responsible for Exercise Training Improvements in Heart Failure With Preserved Ejection Fraction.

Wesley J Tucker, Dalane W Kitzman.



Keywords:  Editorials; cardiorespiratory fitness; exercise training; heart failure, preserved ejection fraction; high-intensity interval training; mitochondria; muscular atrophy

DOI:  https://doi.org/10.1161/CIRCHEARTFAILURE.122.010003
FASEB J. 2022 Nov;36(11): e22587

Muscle injury induces a transient senescence-like state that is required for myofiber growth during muscle regeneration.

Laura V Young, Griffen Wakelin, Alasdair W R Cameron, Stevan A Springer, Joel P Ross, Grant Wolters, J Patrick Murphy, Michel G Arsenault, Sean Ng, Nicolás Collao, Michael De Lisio, Vladimir Ljubicic, Adam P W Johnston.

  Cellular senescence is the irreversible arrest of normally dividing cells and is driven by the cell cycle inhibitors Cdkn2a, Cdkn1a, and Trp53. Senescent cells are implicated in chronic diseases and tissue repair through their increased secretion of pro-inflammatory factors known as the senescence-associated secretory phenotype (SASP). Here, we use spatial transcriptomics and single-cell RNA sequencing (scRNAseq) to demonstrate that cells displaying senescent characteristics are "transiently" present within regenerating skeletal muscle and within the muscles of D2-mdx mice, a model of Muscular Dystrophy. Following injury, multiple cell types including macrophages and fibrog-adipogenic progenitors (FAPs) upregulate senescent features such as senescence pathway genes, SASP factors, and senescence-associated beta-gal (SA-β-gal) activity. Importantly, when these cells were removed with ABT-263, a senolytic compound, satellite cells are reduced, and muscle fibers were impaired in growth and myonuclear accretion. These results highlight that an "acute" senescent phenotype facilitates regeneration similar to skin and neonatal myocardium.

Keywords:  muscle; regeneration; senescence; single-cell RNA sequencing

DOI:  https://doi.org/10.1096/fj.202200289RR
Open Life Sci. 2022 ;17(1): 1191-1199

Geometric basis of action potential of skeletal muscle cells and neurons.

Qing Li.

  Although we know something about single-cell neuromuscular junctions, it is still unclear how multiple skeletal muscle cells coordinate to complete intricate spatial curve movement. Here, we hypothesize that skeletal muscle cell populations with action potentials are aligned according to curved manifolds in space (a curved shape in space). When a specific motor nerve impulse is transmitted, the skeletal muscle also moves according to the corresponding shape (manifolds). The action potential of motor nerve fibers has the characteristics of a time curve manifold, and this time-manifold curve of motor nerve fibers comes from the visual cortex in which spatial geometric manifolds are formed within the synaptic connection of neurons. This spatial geometric manifold of the synaptic connection of neurons originates from spatial geometric manifolds outside nature that are transmitted to the brain through the cone cells and ganglion cells of the retina. The essence of life is that life is an object that can move autonomously, and the essence of life's autonomous movement is the movement of proteins. Theoretically, because of the infinite diversity of geometric manifold shapes in nature, the arrangement and combination of 20 amino acids should have infinite diversity, and the geometric manifold formed by the protein three-dimensional spatial structure should also have infinite diversity.

Keywords:  action potential; skeletal muscle cells; space curved manifolds; synaptic connection of neurons; time curved manifolds

DOI:  https://doi.org/10.1515/biol-2022-0488
Nat Commun. 2022 Oct 05. 13(1): 5655

Deletion of skeletal muscle Akt1/2 causes osteosarcopenia and reduces lifespan in mice.

Takayoshi Sasako, Toshihiro Umehara, Kotaro Soeda, Kazuma Kaneko, Miho Suzuki, Naoki Kobayashi, Yukiko Okazaki, Miwa Tamura-Nakano, Tomoki Chiba, Domenico Accili, C Ronald Kahn, Tetsuo Noda, Hiroshi Asahara, Toshimasa Yamauchi, Takashi Kadowaki, Kohjiro Ueki.

Aging is considered to be accelerated by insulin signaling in lower organisms, but it remained unclear whether this could hold true for mammals. Here we show that mice with skeletal muscle-specific double knockout of Akt1/2, key downstream molecules of insulin signaling, serve as a model of premature sarcopenia with insulin resistance. The knockout mice exhibit a progressive reduction in skeletal muscle mass, impairment of motor function and systemic insulin sensitivity. They also show osteopenia, and reduced lifespan largely due to death from debilitation on normal chow and death from tumor on high-fat diet. These phenotypes are almost reversed by additional knocking out of Foxo1/4, but only partially by additional knocking out of Tsc2 to activate the mTOR pathway. Overall, our data suggest that, unlike in lower organisms, suppression of Akt activity in skeletal muscle of mammals associated with insulin resistance and aging could accelerate osteosarcopenia and consequently reduce lifespan.

DOI: https://doi.org/10.1038/s41467-022-33008-2
Life Sci. 2022 Sep 29. pii: S0024-3205(22)00717-2. [Epub ahead of print]309 121017

Resistance training prevents damage to the mitochondrial function of the skeletal muscle of rats exposed to secondary cigarette smoke.

Ana Caroline Rippi Moreno, André Olean-Oliveira, Tiago Olean-Oliveira, Maria Tereza Nunes, Marcos F S Teixeira, Patricia Monteiro Seraphim.

   AIM: To analyze the consumption of oxygen and to quantify the mitochondrial respiratory chain proteins (OXPHOS) in the gastrocnemius muscle of rats exposed to cigarette smoke and/or RT practitioners.
MAIN METHODS: Wistar rats were divided into groups: Control (C), Smoker (S), Exercise (E) and Exercise Smoker (ES). Groups F and ES were exposed to the smoke of 4 cigarettes for 30 min, 2× a day, 5× a week, for 16 weeks. Groups E and ES performed four climbs with progressive load, 1× per day, 5× per week, for 16 weeks. The gastrocnemius muscle was collected for analysis of OXPHOS content and oxygen consumption. Groups S (vs. C) and ES (vs. C and E) showed lower body weight gain when observing the evolution curve.
KEY FINDINGS: The S rats showed a reduction in the NDUFB8 proteins of complex 1, SDHB of complex 2, MTC01 of complex 4 and ATP5A of complex 5 (ATP Synthase) compared to Group C. Additionally, S rats also showed increased consumption of O2 in Basal, Leak, Complex I and I/II combined measures compared to the other groups, suggesting that the activity of the mitochondria of these animals increased in terms of coupling and uncoupling parameters.
SIGNIFICANCE: Our data suggest that exposure to cigarette smoke for 16 weeks is capable of causing impairment of mitochondrial function with reduced expression of respiratory chain proteins in skeletal muscle. However, the RT was effective in preventing impairment of mitochondrial function in the skeletal muscle of rats exposed to secondary cigarette smoke.

Keywords:  Mitochondria; Resistive exercise; Respiratory chain; Skeletal muscle; Smoking

DOI:  https://doi.org/10.1016/j.lfs.2022.121017
Cell Metab. 2022 Oct 04. pii: S1550-4131(22)00394-1. [Epub ahead of print]34(10): 1578-1593.e6

Single-cell dissection of the obesity-exercise axis in adipose-muscle tissues implies a critical role for mesenchymal stem cells.

Jiekun Yang, Maria Vamvini, Pasquale Nigro, Li-Lun Ho, Kyriakitsa Galani, Marcus Alvarez, Yosuke Tanigawa, Ashley Renfro, Nicholas P Carbone, Markku Laakso, Leandro Z Agudelo, Päivi Pajukanta, Michael F Hirshman, Roeland J W Middelbeek, Kevin Grove, Laurie J Goodyear, Manolis Kellis.

  Exercise training is critical for the prevention and treatment of obesity, but its underlying mechanisms remain incompletely understood given the challenge of profiling heterogeneous effects across multiple tissues and cell types. Here, we address this challenge and opposing effects of exercise and high-fat diet (HFD)-induced obesity at single-cell resolution in subcutaneous and visceral white adipose tissue and skeletal muscle in mice with diet and exercise training interventions. We identify a prominent role of mesenchymal stem cells (MSCs) in obesity and exercise-induced tissue adaptation. Among the pathways regulated by exercise and HFD in MSCs across the three tissues, extracellular matrix remodeling and circadian rhythm are the most prominent. Inferred cell-cell interactions implicate within- and multi-tissue crosstalk centered around MSCs. Overall, our work reveals the intricacies and diversity of multi-tissue molecular responses to exercise and obesity and uncovers a previously underappreciated role of MSCs in tissue-specific and multi-tissue beneficial effects of exercise.

Keywords:  circadian rhythm pathway; exercise; extracellular matrix remodeling; mesenchymal stem cell; multi-tissue crosstalk; obesity; single-cell atlas; skeletal muscle; white adipose tissue; within-tissue crosstalk

DOI:  https://doi.org/10.1016/j.cmet.2022.09.004
Eur Rev Aging Phys Act. 2022 Oct 01. 19(1): 23

Heavy-load exercise in older adults activates vasculogenesis and has a stronger impact on muscle gene expression than in young adults.

Kaare M Gautvik, Ole K Olstad, Ulrika Raue, Vigdis T Gautvik, Karl J Kvernevik, Tor P Utheim, Solveig Ravnum, Camilla Kirkegaard, Håvard Wiig, Garan Jones, Luke C Pilling, Scott Trappe, Truls Raastad, Sjur Reppe.

   BACKGROUND: A striking effect of old age is the involuntary loss of muscle mass and strength leading to sarcopenia and reduced physiological functions. However, effects of heavy-load exercise in older adults on diseases and functions as predicted by changes in muscle gene expression have been inadequately studied.
METHODS: Thigh muscle global transcriptional activity (transcriptome) was analyzed in cohorts of older and younger adults before and after 12-13 weeks heavy-load strength exercise using Affymetrix microarrays. Three age groups, similarly trained, were compared: younger adults (age 24 ± 4 years), older adults of average age 70 years (Oslo cohort) and above 80 years (old BSU cohort). To increase statistical strength, one of the older cohorts was used for validation. Ingenuity Pathway analysis (IPA) was used to identify predicted biological effects of a gene set that changed expression after exercise, and Principal Component Analysis (PCA) was used to visualize differences in muscle gene expressen between cohorts and individual participants as well as overall changes upon exercise.
RESULTS: Younger adults, showed few transcriptome changes, but a marked, significant impact was observed in persons of average age 70 years and even more so in persons above 80 years. The 249 transcripts positively or negatively altered in both cohorts of older adults (q-value < 0.1) were submitted to gene set enrichment analysis using IPA. The transcripts predicted increase in several aspects of "vascularization and muscle contractions", whereas functions associated with negative health effects were reduced, e.g., "Glucose metabolism disorder" and "Disorder of blood pressure". Several genes that changed expression after intervention were confirmed at the genome level by containing single nucleotide variants associated with handgrip strength and muscle expression levels, e.g., CYP4B1 (p = 9.2E-20), NOTCH4 (p = 9.7E-8), and FZD4 (p = 5.3E-7). PCA of the 249 genes indicated a differential pattern of muscle gene expression in young and elderly. However, after exercise the expression patterns in both young and old BSU cohorts were changed in the same direction for the vast majority of participants.
CONCLUSIONS: The positive impact of heavy-load strength training on the transcriptome increased markedly with age. The identified molecular changes translate to improved vascularization and muscular strength, suggesting highly beneficial health effects for older adults.

Keywords:  Exercise; Muscle; Muscle biopsies; Older adults; Transcriptome

DOI:  https://doi.org/10.1186/s11556-022-00304-1
Arch Biochem Biophys. 2022 Sep 29. pii: S0003-9861(22)00305-8. [Epub ahead of print] 109420

RNA-seq transcriptomic analysis of 4-octyl itaconate repressing myogenic differentiation.

Lili Wang, Zheng Chen, Yu Feng, Rongrong Wang, Xiaohui Bai, Weihua Liu, Dawei Wang.

   BACKGROUND: The 4-octyl itaconate (OI) is a type of cell-permeable itaconate derivative. Studies have shown that with an anti-fibrotic effect in systemic sclerosis, the OI also affects osteoclast differentiation. The aim of this study was to explore the molecular mechanisms underlying the effects of OI on myoblast differentiation by RNA-seq analysis.
METHODS: Myoblast proliferation, differentiation, and muscle regulatory factors were examined in C2C12 myoblasts treated with OI of various concentrations (2.5, 10, 25, 50, and 100 μmol/L). Cells were treated with the PI3K-Akt activator IGF-1 to explore the role of the PI3K-Akt pathway in OI inhibition of myogenic differentiation. The regulatory mechanisms of OI in myogenesis were further investigated by RNA-seq and subsequent gene ontology (GO), kyoto encyclopedia of genes and genomes (KEGG) and, gene set enrichment analysis (GSEA).
RESULTS: OI of various concentrations did not show any effect during cell proliferation. During differentiation, OI inhibited the expressions of the marker of mature myotubes myosin heavy chain (MHC) and myogenin in a dose-dependent manner. OI inhibited muscle differentiation by affecting MyoD-regulated activity through inhibition of AKT1 phosphorylation. The results of the KEGG enrichment analysis and GSEA showed that OI affected multiple metabolic pathways during myogenic differentiation, including PI3K-Akt signaling, calcium signaling, and PPAR signaling.
CONCLUSIONS: Our study broadens the understanding of the OI inhibition of myogenic differentiation. OI plays its functions by targeting multiple molecules and pathways, providing novel insights into the understanding of the overall effect of OI.

Keywords:  -Akt1; 4-Octyl itaconate; MyoD; Myogenesis; Regeneration; p

DOI:  https://doi.org/10.1016/j.abb.2022.109420
Ageing Res Rev. 2022 Sep 28. pii: S1568-1637(22)00181-7. [Epub ahead of print]81 101739

Gut microbiota as a promising therapeutic target for age-related sarcopenia.

Ting Zhang, Jin-Ke Cheng, Yao-Min Hu.

  Sarcopenia is characterized by a progressive loss of skeletal muscle mass and function with aging. Recently, sarcopenia has been shown to be closely related with gut microbiota. Strategies such as probiotics and fecal microbiota transplantation have shown potential to ameliorate the muscle loss. This review will focus on the age-related sarcopenia, in particular on the relationship between gut microbiota and age-related sarcopenia, how gut microbiota is engaged in sarcopenia, and the potential role of gut microbiota in the treatment of age-related sarcopenia.

Keywords:  Aging; Gut microbiota; Microbiota; Probiotics; Sarcopenia; Skeletal muscle

DOI:  https://doi.org/10.1016/j.arr.2022.101739
Clin Nutr ESPEN. 2022 Oct;pii: S2405-4577(22)00464-8. [Epub ahead of print]51 1-6

Effect of caffeine on mitochondrial biogenesis in the skeletal muscle - A narrative review.

André K Yamada, Gustavo D Pimentel, Craig Pickering, André V Cordeiro, Vagner R R Silva.

  Caffeine is one of the most widely used substances as recreational drug for performance-enhancement in sport, underpinned by a strong evidence base. Although the effects of caffeine are widely investigated within the scope of performance physiology, the molecular effects of caffeine within skeletal muscle remain unclear. Evidence from in vitro and in vivo models suggest that caffeine regulates the glucose metabolism in the skeletal muscle. Moreover, caffeine seems to stimulate CaMKII, PPARδ/β, AMPK and PGC1α, classical markers of exercise-adaptations, including mitochondrial biogenesis and mitochondrial content. This review summarizes evidence to suggest caffeine-effects within skeletal muscle fibers, focusing on the putative role of caffeine on mitochondrial biogenesis to explore whether caffeine supplementation might be a strategy to enhance mitochondrial biogenesis.

Keywords:  Caffeine; Exercise; Mitochondria; Skeletal muscle

DOI:  https://doi.org/10.1016/j.clnesp.2022.09.001
Nucleic Acids Res. 2022 Oct 06. pii: gkac854. [Epub ahead of print]

Long noncoding RNA lncMREF promotes myogenic differentiation and muscle regeneration by interacting with the Smarca5/p300 complex.

Wei Lv, Wei Jiang, Hongmei Luo, Qian Tong, Xiaoyu Niu, Xiao Liu, Yang Miao, Jingnan Wang, Yiwen Guo, Jianan Li, Xizhen Zhan, Yunqing Hou, Yaxin Peng, Jian Wang, Shuhong Zhao, Zaiyan Xu, Bo Zuo.

Long noncoding RNAs (lncRNAs) play important roles in the spatial and temporal regulation of muscle development and regeneration. Nevertheless, the determination of their biological functions and mechanisms underlying muscle regeneration remains challenging. Here, we identified a lncRNA named lncMREF (lncRNA muscle regeneration enhancement factor) as a conserved positive regulator of muscle regeneration among mice, pigs and humans. Functional studies demonstrated that lncMREF, which is mainly expressed in differentiated muscle satellite cells, promotes myogenic differentiation and muscle regeneration. Mechanistically, lncMREF interacts with Smarca5 to promote chromatin accessibility when muscle satellite cells are activated and start to differentiate, thereby facilitating genomic binding of p300/CBP/H3K27ac to upregulate the expression of myogenic regulators, such as MyoD and cell differentiation. Our results unravel a novel temporal-specific epigenetic regulation during muscle regeneration and reveal that lncMREF/Smarca5-mediated epigenetic programming is responsible for muscle cell differentiation, which provides new insights into the regulatory mechanism of muscle regeneration.

DOI: https://doi.org/10.1093/nar/gkac854
Philos Trans R Soc Lond B Biol Sci. 2022 Nov 21. 377(1864): 20210490

Lamin A precursor localizes to the Z-disc of sarcomeres in the heart and is dynamically regulated in muscle cell differentiation.

Daniel Brayson, Catherine M Shanahan.

  The lamin A precursor, prelamin A, requires extensive processing to yield mature lamin A and effect its primary function as a structural filament of the nucleoskeleton. When processing is perturbed, nuclear accumulation of prelamin A is toxic and causes laminopathic diseases such as Hutchinson-Gilford progeria syndrome and cardiomyopathy. However, the physiological role of prelamin A is largely unknown and we sought to identify novel insights about this. Using rodent heart tissue, primary cells and the C2C12 model of myofibrillogenesis, we investigated the expression and localization patterns of prelamin A in heart and skeletal muscle cells. We found that endogenous prelamin A was detectable in mouse heart localized to the sarcomere in both adult mouse heart and isolated neonatal rat cardiomyocytes. We investigated the regulation of prelamin A in C2C12 myofibrillogenesis and found it was dynamically regulated and organized into striations upon myofibril formation, colocalizing with the Z-disc protein α-actinin. These data provide evidence that prelamin A is a component of the sarcomere, underpinning a physiological purpose for unprocessed prelamin A. This article is part of the theme issue 'The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease'.

Keywords:  heart; lamin A; muscle; prelamin A; sarcomere

DOI:  https://doi.org/10.1098/rstb.2021.0490
Dis Model Mech. 2022 Oct 05. pii: dmm.049516. [Epub ahead of print]

DUX4 expression activates JNK and p38 MAP kinases in myoblasts.

Christopher M Brennan, Abby S Hill, Michael St Andre, Xianfeng Li, Vijaya Madeti, Susanne Breitkopf, Seth Garren, Liang Xue, Tamara Gilbert, Angela Hadjipanayis, Mara Monetti, Charles P Emerson, Robert Moccia, Jane Owens, Nicolas Christoforou.

  Facioscapulohumoral muscular dystrophy (FSHD) is caused by misexpression of the DUX4 transcription factor in skeletal muscle that results in transcriptional alterations, abnormal phenotypes, and cell death. To gain insight into the kinetics of DUX4-induced stresses, we activated DUX4 expression in myoblasts and performed longitudinal RNA sequencing paired with proteomics and phosphoproteomics. This analysis revealed changes in cellular physiology including DNA damage and altered mRNA splicing. Phosphoproteomic analysis uncovered widespread changes in protein phosphorylation rapidly following DUX4 induction indicating that alterations in kinase signaling may play a role in DUX4-mediated stress and cell death. Indeed, we demonstrate that two stress-responsive MAP kinase pathways, JNK and p38, are activated in response to DUX4 expression. Inhibition of each of these pathways ameliorated DUX4-mediated cell death in myoblasts. These findings uncover JNK as a novel pathway involved in DUX4-mediated cell death as well as provide additional insights into the role of the p38 pathway, a clinical target for the treatment of FSHD.

Keywords:  MAP kinase signaling; Muscular dystrophy; Phosphoproteomics

DOI:  https://doi.org/10.1242/dmm.049516
Circ Heart Fail. 2022 Oct 06. 101161CIRCHEARTFAILURE121009124

Impact of Different Training Modalities on Molecular Alterations in Skeletal Muscle of Patients With Heart Failure With Preserved Ejection Fraction: A Substudy of the OptimEx Trial.

Ephraim B Winzer, Antje Augstein, Antje Schauer, Stephan Mueller, Tina Fischer-Schaepmann, Keita Goto, Jennifer Hommel, Emeline M van Craenenbroeck, Ulrik Wisløff, Burkert Pieske, Martin Halle, Axel Linke, Volker Adams.

   BACKGROUND: Exercise intolerance is a cardinal feature of heart failure with preserved ejection fraction and so far exercise training (ET) is the most effective treatment. Since the improvement in exercise capacity is only weakly associated with changes in diastolic function other mechanisms, like changes in the skeletal muscle, contribute to improvement in peak oxygen consumption. The aim of the present study was to analyze molecular changes in skeletal muscle of patients with heart failure with preserved ejection fraction performing different ET modalities.
METHODS: Skeletal muscle biopsies were taken at study begin and after 3 and 12 months from patients with heart failure with preserved ejection fraction randomized either into a control group (guideline based advice for ET), a high-intensity interval training group (HIIT) or a moderate continuous training group. The first 3 months of ET were supervised in-hospital followed by 9 months home-based ET. Protein and mRNA expression of atrophy-related proteins, enzyme activities of enzymes linked to energy metabolism and satellite cells (SCs) were quantified.
RESULTS: Exercise capacity improved 3 months after moderate continuous exercise training and HIIT. This beneficial effect was lost after 12 months. HIIT mainly improved markers of energy metabolism and the amount and function of SC, with minor changes in markers for muscle atrophy. Only slight changes were observed after moderate continuous exercise training. The molecular changes were no longer detectable after 12 months.
CONCLUSIONS: Despite similar improvements in exercise capacity by HIIT and moderate continuous exercise training after 3 months, only HIIT altered proteins related to energy metabolism and amount/function of SC. These effects were lost after switching from in-hospital to at-home-based ET.
REGISTRATION: URL: https://www.
CLINICALTRIALS: gov; Unique identifier: NCT02078947.

Keywords:  atrophy; energy metabolism; exercise training; satellite cells; skeletal muscle

DOI:  https://doi.org/10.1161/CIRCHEARTFAILURE.121.009124
Commun Biol. 2022 Oct 05. 5(1): 1060

Inter-organellar and systemic responses to impaired mitochondrial matrix protein import in skeletal muscle.

Nirajan Neupane, Jayasimman Rajendran, Jouni Kvist, Sandra Harjuhaahto, Bowen Hu, Veijo Kinnunen, Yang Yang, Anni I Nieminen, Henna Tyynismaa.

Effective protein import from cytosol is critical for mitochondrial functions and metabolic regulation. We describe here the mammalian muscle-specific and systemic consequences to disrupted mitochondrial matrix protein import by targeted deletion of the mitochondrial HSP70 co-chaperone GRPEL1. Muscle-specific loss of GRPEL1 caused rapid muscle atrophy, accompanied by shut down of oxidative phosphorylation and mitochondrial fatty acid oxidation, and excessive triggering of proteotoxic stress responses. Transcriptome analysis identified new responders to mitochondrial protein import toxicity, such as the neurological disease-linked intermembrane space protein CHCHD10. Besides communication with ER and nucleus, we identified crosstalk of distressed mitochondria with peroxisomes, in particular the induction of peroxisomal Acyl-CoA oxidase 2 (ACOX2), which we propose as an ATF4-regulated peroxisomal marker of integrated stress response. Metabolic profiling indicated fatty acid enrichment in muscle, a shift in TCA cycle intermediates in serum and muscle, and dysregulated bile acids. Our results demonstrate the fundamental importance of GRPEL1 and provide a robust model for detecting mammalian inter-organellar and systemic responses to impaired mitochondrial matrix protein import and folding.

DOI: https://doi.org/10.1038/s42003-022-04034-z
Elife. 2022 Oct 07. pii: e80638. [Epub ahead of print]11

Association of lithocholic acid with skeletal muscle hypertrophy through TGR5-IGF-1 and skeletal muscle mass in cultured mouse myotubes, chronic liver disease rats and humans.

Yasuyuki Tamai, Akiko Eguchi, Ryuta Shigefuku, Hiroshi Kitamura, Mina Tempaku, Ryosuke Sugimoto, Yoshinao Kobayashi, Motoh Iwasa, Yoshiyuki Takei, Hayato Nakagawa.

   Background: Hepatic sarcopenia is one of many complications associated with chronic liver disease (CLD) and has a high mortality rate; however, the liver-muscle axis is not fully understood. Therefore, few effective treatments exist for hepatic sarcopenia, the best of which being branched-chain amino acid (BCAA) supplementation to help increase muscle mass. Our aim was to investigate the molecular mechanism(s) of hepatic sarcopenia focused on bile acid (BA) composition.
Methods: The correlation between serum BA levels and psoas muscle mass index (PMI) was examined in 73 CLD patients. Gastrocnemius muscle phenotype and serum BA levels were assessed in CLD rats treated with BCAA. Mouse skeletal muscle cells (C2C12) were incubated with lithocholic acid (LCA), G-protein-coupled receptor 5 (TGR5) agonist or TGR5 antagonist to assess skeletal muscle hypertrophy.
Results: In human CLD, serum LCA levels were the sole factor positively correlated with PMI and were significantly decreased in both the low muscle mass group and the deceased group. Serum LCA levels were also shown to predict patient survival. Gastrocnemius muscle weight significantly increased in CLD rats treated with BCAA via suppression of protein degradation pathways, coupled with a significant increase in serum LCA levels. LCA treated C2C12 hypertrophy occurred in a concentration-dependent manner linked with TGR5-Akt pathways based upon inhibition results via a TGR5 antagonist.
Conclusions: Our results indicate LCA-mediated skeletal muscle hypertrophy via activation of TGR5-IGF1-Akt signaling pathways. In addition, serum LCA levels were associated with skeletal muscle mass in cirrhotic rats, as well as CLD patients, and predicted overall patient survival.
Funding: This research was supported by JSPS KAKENHI Grant Number 22K08011 and 21H02892, and AMED under Grant Number JP21fk0210090 and JP22fk0210115. Maintaining cirrhotic rats were partially supported by Otsuka Pharmaceutical Company.

Keywords:  bile acids; cell biology; chronic liver diseases; human; lithocholic acid; liver-muscle axis; low muscle mass; medicine; rat; skeletal muscle

DOI:  https://doi.org/10.7554/eLife.80638
Front Physiol. 2022 ;13 1014744

Different responses of skeletal muscles to femoral artery ligation-induced ischemia identified in BABL/c and C57BL/6 mice.

Huiyin Tu, Junliang Qian, Dongze Zhang, Aaron N Barksdale, Michael C Wadman, Iraklis I Pipinos, Yu-Long Li.

  Peripheral arterial disease (PAD) is a common circulatory problem in lower extremities, and the murine ischemic model is used to reproduce human PAD. To compare strain differences of skeletal muscle responses to ischemia, the left femoral artery was blocked by ligation to reduce blood flow to the limb of BALB/c and C57BL/6 mice. After 6 weeks of the femoral artery ligation, the functional and morphological changes of the gastrocnemius muscle were evaluated. BALB/c mice displayed serious muscular dystrophy, including smaller myofibers (524.3 ± 66 µM2), accumulation of adipose-liked tissue (17.8 ± 0.9%), and fibrosis (6.0 ± 0.5%), compared to C57BL/6 mice (1,328.3 ± 76.3 µM2, 0.27 ± 0.09%, and 1.56 ± 0.06%, respectively; p < 0.05). About neuromuscular junctions (NMJs) in the gastrocnemius muscle, 6 weeks of the femoral artery ligation induced more damage in BALB/c mice than that in C57BL/6 mice, demonstrated by the fragment number of nicotinic acetylcholine receptor (nAChR) clusters (8.8 ± 1.3 in BALB/c vs. 2.5 ± 0.7 in C57BL/6 mice, p < 0.05) and amplitude of sciatic nerve stimulated-endplate potentials (EPPs) (9.29 ± 1.34 mV in BALB/c vs. 20.28 ± 1.42 mV in C57BL/6 mice, p < 0.05). More importantly, 6 weeks of the femoral artery ligation significantly weakened sciatic nerve-stimulated skeletal muscle contraction in BALB/c mice, whereas it didn't alter the skeletal muscle contraction in C57BL/6 mice. These results suggest that the femoral artery ligation in BALB/c mice is a useful animal model to develop new therapeutic approaches to improve limb structure and function in PAD, although the mechanisms about strain differences of skeletal muscle responses to ischemia are unclear.

Keywords:  animal model; femoral artery ligation; injury; ischemia; limb; neuromuscular junction; peripheral arterial disease; skeletal muscle

DOI:  https://doi.org/10.3389/fphys.2022.1014744
Front Rehabil Sci. 2021 ;2 807123

Klotho: An Emerging Factor With Ergogenic Potential.

Eliott Arroyo, Ashley D Troutman, Ranjani N Moorthi, Keith G Avin, Andrew R Coggan, Kenneth Lim.

  Sarcopenia and impaired cardiorespiratory fitness are commonly observed in older individuals and patients with chronic kidney disease (CKD). Declines in skeletal muscle function and aerobic capacity can progress into impaired physical function and inability to perform activities of daily living. Physical function is highly associated with important clinical outcomes such as hospitalization, functional independence, quality of life, and mortality. While lifestyle modifications such as exercise and dietary interventions have been shown to prevent and reverse declines in physical function, the utility of these treatment strategies is limited by poor widespread adoption and adherence due to a wide variety of both perceived and actual barriers to exercise. Therefore, identifying novel treatment targets to manage physical function decline is critically important. Klotho, a remarkable protein with powerful anti-aging properties has recently been investigated for its role in musculoskeletal health and physical function. Klotho is involved in several key processes that regulate skeletal muscle function, such as muscle regeneration, mitochondrial biogenesis, endothelial function, oxidative stress, and inflammation. This is particularly important for older adults and patients with CKD, which are known states of Klotho deficiency. Emerging data support the existence of Klotho-related benefits to exercise and for potential Klotho-based therapeutic interventions for the treatment of sarcopenia and its progression to physical disability. However, significant gaps in our understanding of Klotho must first be overcome before we can consider its potential ergogenic benefits. These advances will be critical to establish the optimal approach to future Klotho-based interventional trials and to determine if Klotho can regulate physical dysfunction.

Keywords:  Klotho; chronic kidney disease (CKD); physical function; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.3389/fresc.2021.807123
J Physiol. 2022 Oct 06.

Motor units alterations with muscle disuse: what is new?

Fabio Sarto, Giacomo Valli, Elena Monti.



Keywords:  firing rate; immobilisation; intramuscular electromyography; neuromuscular junction; physical inactivity; unloading

DOI:  https://doi.org/10.1113/JP283868
J Gen Physiol. 2022 Nov 07. pii: e202213136. [Epub ahead of print]154(11):

Mice with R2509C-RYR1 mutation exhibit dysfunctional Ca2+ dynamics in primary skeletal myocytes.

Yoshitaka Tsuboi, Kotaro Oyama, Fuyu Kobirumaki-Shimozawa, Takashi Murayama, Nagomi Kurebayashi, Toshiaki Tachibana, Yoshinobu Manome, Emi Kikuchi, Satoru Noguchi, Takayoshi Inoue, Yukiko U Inoue, Ichizo Nishino, Shuichi Mori, Ryosuke Ishida, Hiroyuki Kagechika, Madoka Suzuki, Norio Fukuda, Toshiko Yamazawa.

Type 1 ryanodine receptor (RYR1) is a Ca2+ release channel in the sarcoplasmic reticulum (SR) of the skeletal muscle and plays a critical role in excitation-contraction coupling. Mutations in RYR1 cause severe muscle diseases, such as malignant hyperthermia, a disorder of Ca2+-induced Ca2+ release (CICR) through RYR1 from the SR. We recently reported that volatile anesthetics induce malignant hyperthermia (MH)-like episodes through enhanced CICR in heterozygous R2509C-RYR1 mice. However, the characterization of Ca2+ dynamics has yet to be investigated in skeletal muscle cells from homozygous mice because these animals die in utero. In the present study, we generated primary cultured skeletal myocytes from R2509C-RYR1 mice. No differences in cellular morphology were detected between wild type (WT) and mutant myocytes. Spontaneous Ca2+ transients and cellular contractions occurred in WT and heterozygous myocytes, but not in homozygous myocytes. Electron microscopic observation revealed that the sarcomere length was shortened to ∼1.7 µm in homozygous myocytes, as compared to ∼2.2 and ∼2.3 µm in WT and heterozygous myocytes, respectively. Consistently, the resting intracellular Ca2+ concentration was higher in homozygous myocytes than in WT or heterozygous myocytes, which may be coupled with a reduced Ca2+ concentration in the SR. Finally, using infrared laser-based microheating, we found that heterozygous myocytes showed larger heat-induced Ca2+ transients than WT myocytes. Our findings suggest that the R2509C mutation in RYR1 causes dysfunctional Ca2+ dynamics in a mutant-gene dose-dependent manner in the skeletal muscles, in turn provoking MH-like episodes and embryonic lethality in heterozygous and homozygous mice, respectively.

DOI: https://doi.org/10.1085/jgp.202213136
Acta Neuropathol. 2022 Oct 05.

Assessment of PABPN1 nuclear inclusions on a large cohort of patients and in a human xenograft model of oculopharyngeal muscular dystrophy.

Fanny Roth, Jamila Dhiab, Alexis Boulinguiez, Hadidja-Rose Mouigni, Saskia Lassche, Elisa Negroni, Laura Muraine, Alix Marhic, Alison Oliver, Jeanne Lainé, Andrée Rouche, Erin K O'Ferrall, Baziel van Engelen, Coen Ottenheijm, Hagar Greif, Sergiu Blumen, Jean Lacau St Guily, Sophie Perie, Gillian Butler-Browne, Vincent Mouly, Capucine Trollet.

  Oculopharyngeal muscular dystrophy (OPMD) is a rare muscle disease characterized by an onset of weakness in the pharyngeal and eyelid muscles. The disease is caused by the extension of a polyalanine tract in the Poly(A) Binding Protein Nuclear 1 (PABPN1) protein leading to the formation of intranuclear inclusions or aggregates in the muscle of OPMD patients. Despite numerous studies stressing the deleterious role of nuclear inclusions in cellular and animal OPMD models, their exact contribution to human disease is still unclear. In this study, we used a large and unique collection of human muscle biopsy samples to perform an in-depth analysis of PABPN1 aggregates in relation to age, genotype and muscle status with the final aim to improve our understanding of OPMD physiopathology. Here we demonstrate that age and genotype influence PABPN1 aggregates: the percentage of myonuclei containing PABPN1 aggregates increases with age and the chaperone HSP70 co-localize more frequently with PABPN1 aggregates with a larger polyalanine tract. In addition to the previously described PRMT1 and HSP70 co-factors, we identified new components of PABPN1 aggregates including GRP78/BiP, RPL24 and p62. We also observed that myonuclei containing aggregates are larger than myonuclei without. When comparing two muscles from the same patient, a similar amount of aggregates is observed in different muscles, except for the pharyngeal muscle where fewer aggregates are observed. This could be due to the peculiar nature of this muscle which has a low level of PAPBN1 and contains regenerating fibers. To confirm the fate of PABPN1 aggregates in a regenerating muscle, we generated a xenograft model by transplanting human OPMD muscle biopsy samples into the hindlimb of an immunodeficient mouse. Xenografts from subjects with OPMD displayed regeneration of human myofibers and PABPN1 aggregates were rapidly present-although to a lower extent-after muscle fiber regeneration. Our data obtained on human OPMD samples add support to the dual non-exclusive models in OPMD combining toxic PABPN1 intranuclear inclusions together with PABPN1 loss of function which altogether result in this late-onset and muscle selective disease.

Keywords:  Human biopsies; Inclusions; Loss of function; Nuclear aggregates; OPMD; PABPN1; Xenograft

DOI:  https://doi.org/10.1007/s00401-022-02503-7
J Physiol. 2022 Oct 07.

Muscle O2 diffusion capacity by NIRS: a new approach in the air.

Giorgio Manferdelli, Antoine Raberin, Grégoire P Millet.



Keywords:  NIRS; hypoxia; oxygen diffusion capacity; skeletal muscle

DOI:  https://doi.org/10.1113/JP283882
Free Radic Biol Med. 2022 Oct 01. pii: S0891-5849(22)00619-0. [Epub ahead of print]

Proteomic analysis of skeletal muscle in Chinese hamsters with type 2 diabetes mellitus reveals that OPLAH downregulation affects insulin resistance and impaired glucose uptake.

Zeya Shi, Yitong Huo, Jianan Hou, Ruihu Zhang, Jianqin Wu, Wentao Wang, Jingjing Yu, Hailong Wang, Yu Liu, Guohua Song, Zhenwen Chen, Zhaoyang Chen.

  Type 2 diabetes mellitus (T2DM) is a metabolic disease controlled by a combination of genetic and environmental factors. The Chinese hamster, as a novel animal model of spontaneous T2DM with high phenotypic similarity to human disease, is of great value in identifying potential therapeutic targets for T2DM. Here, we used tandem mass tag (TMT) quantitative proteomics based on liquid chromatography-tandem mass spectrometry to assess the skeletal muscles of a Chinese hamster diabetes model. We identified 38 differentially abundant proteins, of which 14 were upregulated and 24 were downregulated. Further analysis of the differentially abundant proteins revealed that five of them (OPLAH, GST, EPHX1, SIRT5, ALDH1L1) were associated with oxidative stress; these were validated at the protein and mRNA levels, and the results were consistent with the proteomic analysis results. In addition, we evaluated the role of OPLAH in the pathogenesis of T2DM in human skeletal muscle cells (HSKMCs) by silencing it. The knockdown of OPLAH caused an increase in reactive oxygen species content, decreased the GSH content, inhibited the PI3K/Akt/GLUT4 signaling pathway, and reduced glucose uptake. We propose that OPLAH downregulation plays a role in insulin resistance and glucose uptake disorders in HSKMCs possibly via oxidative stress, making it a new therapeutic target for T2DM.

Keywords:  Chinese hamster; OPLAH; Proteomics; Skeletal muscle; Type 2 diabetes mellitus

DOI:  https://doi.org/10.1016/j.freeradbiomed.2022.09.029
J Appl Physiol (1985). 2022 Oct 06.

Metastatic or xenograft colorectal cancer induce divergent anabolic deficits and pro-inflammatory effectors of muscle wasting in a tumor-type dependent manner.

Hyo-Gun Kim, Joshua R Huot, Fabrizio Pin, Daniel J Belcher, Andrea Bonetto, Gustavo A Nader.

  We investigated the impact of tumor burden on muscle wasting in metastatic (m) and xenograft (x) models of colorectal cancer (CRC). Male Nod SCID gamma and CD2F1 mice were injected subcutaneously or intrasplenically with HCT116 or C26 tumor cells, respectively. CRC tumors resulted in significant muscle wasting regardless of tumor type or model, although muscle loss was exacerbated in mHCT116 hosts. The mHCT116 model decreased ribosomal (r)RNA content and rDNA transcription, while the mC26 tumor showed no loss of rRNA and the upregulation of rDNA transcription. The xHCT116 model reduced mTOR, RPS6, and 4E-BP1 phosphorylation, while the mHCT116 model had a similar effect on RPS6 and 4E-BP1without altering mTOR phosphorylation. The C26 models caused a reduction in 4E-BP1 phosphorylation independent of mTOR. Muscle interleukin (IL) -6 mRNA was elevated in all models except xHCT116, and the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) mRNA was induced only in the mC26 model. IL-1β mRNA increased in all groups with greater expression in metastatic relative to the xenograft model regardless of tumor types. Our findings indicate that HCT116 tumor burden results in more drastic muscle wasting and anabolic deficits, while C26 tumor burden causes similar muscle wasting but exhibits a divergent pro-inflammatory phenotype. These results highlight potentially important divergence in the pathogenesis of muscle wasting among pre-clinical models of CRC, and demonstrate that tumor burden plays a role in determining anabolic deficits and the expression of pro-inflammatory effectors of muscle wasting in a tumor type-dependent manner.

Keywords:  cachexia; colorectal cancer; inflammation; muscle wasting; ribosomal RNA

DOI:  https://doi.org/10.1152/japplphysiol.00247.2022
J Appl Physiol (1985). 2022 Oct 06.

LP07 and LLC pre-clinical models of lung cancer induce divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting.

Daniel J Belcher, Maria Guitart, Brian Hain, Hyo-Gun Kim, David Waning, Esther Barreiro, Gustavo A Nader.

  Pre-clinical models have been instrumental to elucidate the mechanisms underlying muscle wasting in lung cancer (LC). We investigated anabolic deficits and the expression of pro-inflammatory effectors of muscle wasting in the LP07 and Lewis lung carcinoma (LLC) tumor models. Tumor growth resulted in significant weakness in LP07 but not in LLC mice despite similar reductions in gastrocnemius muscle mass in both models. The LP07 tumors caused a reduction in ribosomal (r)RNA and a decrease in rRNA gene (rDNA) transcription elongation, while no changes in ribosomal capacity were evident in LLC tumor bearing mice. Expression of RNA Polymerase I (Pol I) elongation-associated subunits Polr2f, PAF53, and Znrd1 mRNAs was significantly elevated in the LP07 model, while Pol I elongation-related factors FACT and Spt4/5 mRNAs were elevated in the LLC mice. Reductions in RPS6 and 4E-BP1 phosphorylation were similar in both models but was independent of mTOR phosphorylation in LP07 mice. Muscle inflammation was also tumor-specific, IL-6 and TNF-α mRNA increased with LLC tumors, but upregulation of NLRP3 mRNA was independent of tumor type. In summary, while both models caused muscle wasting, only the LP07 model displayed muscle weakness with reductions in ribosomal capacity. Intracellular signaling diverged at the mTOR level with similar reductions in RPS6 and 4E-BP1 phosphorylation regardless of tumor type. The increase in pro-inflammatory factors was more pronounced in the LLC model. Our results demonstrate novel divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting in the LP07 and LLC pre-clinical models of lung cancer.

Keywords:  cachexia; inflammation; lung cancer; muscle wasting; ribosomal RNA

DOI:  https://doi.org/10.1152/japplphysiol.00246.2022
Brain Commun. 2022 ;4(5): fcac224

Targeted transcript analysis in muscles from patients with genetically diverse congenital myopathies.

Christoph Bachmann, Martina Franchini, Luuk R Van den Bersselaar, Nick Kruijt, Nicol C Voermans, Karlijn Bouman, Erik-Jan Kamsteeg, Karl Christian Knop, Lucia Ruggiero, Lucio Santoro, Yoram Nevo, Jo Wilmshurst, John Vissing, Michael Sinnreich, Daniele Zorzato, Francesco Muntoni, Heinz Jungbluth, Francesco Zorzato, Susan Treves.

  Congenital myopathies are a group of early onset muscle diseases of variable severity often with characteristic muscle biopsy findings and involvement of specific muscle types. The clinical diagnosis of patients typically relies on histopathological findings and is confirmed by genetic analysis. The most commonly mutated genes encode proteins involved in skeletal muscle excitation-contraction coupling, calcium regulation, sarcomeric proteins and thin-thick filament interaction. However, mutations in genes encoding proteins involved in other physiological functions (for example mutations in SELENON and MTM1, which encode for ubiquitously expressed proteins of low tissue specificity) have also been identified. This intriguing observation indicates that the presence of a genetic mutation impacts the expression of other genes whose product is important for skeletal muscle function. The aim of the present investigation was to verify if there are common changes in transcript and microRNA expression in muscles from patients with genetically heterogeneous congenital myopathies, focusing on genes encoding proteins involved in excitation-contraction coupling and calcium homeostasis, sarcomeric proteins, transcription factors and epigenetic enzymes. Our results identify RYR1, ATPB2B and miRNA-22 as common transcripts whose expression is decreased in muscles from congenital myopathy patients. The resulting protein deficiency may contribute to the muscle weakness observed in these patients. This study also provides information regarding potential biomarkers for monitoring disease progression and response to pharmacological treatments in patients with congenital myopathies.

Keywords:  congenital myopathies; expression; muscle biopsies; mutations; transcripts miRNAs

DOI:  https://doi.org/10.1093/braincomms/fcac224
Endocr J. 2022 Oct 05.

Extracellular vesicles secreted from mouse muscle cells improve delayed bone repair in diabetic mice.

Yoshimasa Takafuji, Naoyuki Kawao, Takashi Ohira, Yuya Mizukami, Kiyotaka Okada, Jun-Ichiro Jo, Yasuhiko Tabata, Hiroshi Kaji.

  Humoral factors that are secreted from skeletal muscles can regulate bone metabolism and contribute to muscle-bone relationships. Although extracellular vesicles (EVs) play important roles in physiological and pathophysiological processes, the roles of EVs that are secreted from skeletal muscles in bone repair have remained unclear. In the present study, we investigated the effects of the local administration of muscle cell-derived EVs on bone repair in control and streptozotocin-treated diabetic female mice. Muscle cell-derived EVs (Myo-EVs) were isolated from the conditioned medium from mouse muscle C2C12 cells by ultracentrifugation, after which Myo-EVs and gelatin hydrogel sheets were transplanted on femoral bone defect sites. The local administration of Myo-EVs significantly improved delayed bone repair that was induced by the diabetic state in mice 9 days after surgery. Moreover, this administration significantly enhanced the ratio of bone volume to tissue volume at the damaged sites 9 days after surgery in the control mice. Moreover, the local administration of Myo-EVs significantly blunted the number of Osterix-positive cells that were suppressed by the diabetic state at the damage sites after bone injury in mice. Additionally, Myo-EVs significantly blunted the mRNA levels of Osterix and alkaline phosphatase (ALP), and ALP activity was suppressed by advanced glycation end product 3 in ST2 cells that were treated with bone morphogenetic protein-2. In conclusion, we have shown for the first time that the local administration of Myo-EVs improves delayed bone repair that is induced by the diabetic state through an enhancement of osteoblastic differentiation in female mice.

Keywords:  Bone repair; Diabetes; Extracellular vesicles; Gelatin hydrogel; Muscle-bone interaction

DOI:  https://doi.org/10.1507/endocrj.EJ22-0340
Mol Cell. 2022 Oct 06. pii: S1097-2765(22)00895-4. [Epub ahead of print]82(19): 3661-3676.e8

Mechanisms and significance of tissue-specific MICU regulation of the mitochondrial calcium uniporter complex.

Chen-Wei Tsai, Madison X Rodriguez, Anna M Van Keuren, Charles B Phillips, Hannah M Shushunov, Jessica E Lee, Anastacia M Garcia, Amrut V Ambardekar, Joseph C Cleveland, Julie A Reisz, Catherine Proenza, Kathryn C Chatfield, Ming-Feng Tsai.

  Mitochondrial Ca2+ uptake, mediated by the mitochondrial Ca2+ uniporter, regulates oxidative phosphorylation, apoptosis, and intracellular Ca2+ signaling. Previous studies suggest that non-neuronal uniporters are exclusively regulated by a MICU1-MICU2 heterodimer. Here, we show that skeletal-muscle and kidney uniporters also complex with a MICU1-MICU1 homodimer and that human/mouse cardiac uniporters are largely devoid of MICUs. Cells employ protein-importation machineries to fine-tune the relative abundance of MICU1 homo- and heterodimers and utilize a conserved MICU intersubunit disulfide to protect properly assembled dimers from proteolysis by YME1L1. Using the MICU1 homodimer or removing MICU1 allows mitochondria to more readily take up Ca2+ so that cells can produce more ATP in response to intracellular Ca2+ transients. However, the trade-off is elevated ROS, impaired basal metabolism, and higher susceptibility to death. These results provide mechanistic insights into how tissues can manipulate mitochondrial Ca2+ uptake properties to support their unique physiological functions.

Keywords:  calcium channels; cardiac pathophysiology; cellular metabolism; intracellular calcium signaling; membrane-transport mechanisms; mitochondrial physiology; mitochondrial proteases; organellar channels; protein complexes

DOI:  https://doi.org/10.1016/j.molcel.2022.09.006
Mol Ther Methods Clin Dev. 2022 Dec 08. 27 47-60

A first-in-human phase I/IIa gene transfer clinical trial for Duchenne muscular dystrophy using rAAVrh74.MCK.GALGT2.

Kevin M Flanigan, Tatyana A Vetter, Tabatha R Simmons, Megan Iammarino, Emma C Frair, Federica Rinaldi, Louis G Chicoine, Johan Harris, John P Cheatham, Sharon L Cheatham, Brian Boe, Megan A Waldrop, Deborah A Zygmunt, Davin Packer, Paul T Martin.

  In a phase 1/2, open-label dose escalation trial, we delivered rAAVrh74.MCK.GALGT2 (also B4GALNT2) bilaterally to the legs of two boys with Duchenne muscular dystrophy using intravascular limb infusion. Subject 1 (age 8.9 years at dosing) received 2.5 × 1013 vector genome (vg)/kg per leg (5 × 1013 vg/kg total) and subject 2 (age 6.9 years at dosing) received 5 × 1013 vg/kg per leg (1 × 1014 vg/kg total). No serious adverse events were observed. Muscle biopsy evaluated 3 or 4 months post treatment versus baseline showed evidence of GALGT2 gene expression and GALGT2-induced muscle cell glycosylation. Functionally, subject 1 showed a decline in 6-min walk test (6MWT) distance; an increase in time to run 100 m, and a decline in North Star Ambulatory Assessment (NSAA) score until ambulation was lost at 24 months. Subject 2, treated at a younger age and at a higher dose, demonstrated an improvement over 24 months in NSAA score (from 20 to 23 points), an increase in 6MWT distance (from 405 to 478 m), and only a minimal increase in 100 m time (45.6-48.4 s). These data suggest preliminary safety at a dose of 1 × 1014 vg/kg and functional stabilization in one patient.

Keywords:  AAV; B4GALNT; Duchenne muscular dystrophy; GALGT2; gene therapy

DOI:  https://doi.org/10.1016/j.omtm.2022.08.009