bims-moremu 2022-12-04 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2022‒12‒04
twenty-six papers selected by
Anna Vainshtein
Craft Science Inc.

Nicotinamide riboside kinases regulate skeletal muscle fiber-type specification and are rate-limiting for metabolic adaptations during regeneration.
Peroxisome proliferator-activated receptor γ coactivator 1-α overexpression improves angiogenic signalling potential of skeletal muscle-derived extracellular vesicles.
Regulation of muscle stem cell fate.
Nuclear corepressor SMRT acts as a strong regulator of both β-oxidation and suppressor of fibrosis in the differentiation process of mouse skeletal muscle cells.
Muscle-to-Brain Signaling Via Myokines and Myometabolites.
High Intensity Acute Aerobic Exercise Elicits Alterations in Circulating and Skeletal Muscle Tissue Expression of Neuroprotective Exerkines.
Loss of FoxOs in muscle increases strength and mitochondrial function during aging.
Extracellular vesicle-derived miRNAs improve stem cell-based therapeutic approaches in muscle wasting conditions.
Cultured Neonatal Murine Primary Myotubes as a Model to Study Muscle Atrophy.
Skeletal muscle Nox4 knockout prevents and Nox2 knockout blunts loss of maximal diaphragm force in mice with heart failure with reduced ejection fraction.
The mechanosensitive ion channel PIEZO1 promotes satellite cell function in muscle regeneration.
A post-middle-age crisis for CD47 and THBS1 that turns into a vicious cycle.
Inter-set stretch: A potential time-efficient strategy for enhancing skeletal muscle adaptations.
Loss of 4E-BPs Prevents the Hindlimb Immobilization-Induced Decrease in Protein Synthesis in Skeletal Muscle.
Sex based comparisons of muscle cellular adaptations after 10-weeks of progressive resistance training in middle-aged adults.
p62/Sqstm1 rescue in muscle retards the progression of steatohepatitis in p62/Sqstm1-null mice fed a high-fat diet.
What about hybrids? Supplemental methods for skeletal muscle fibre typing.
MicroRNA profiling of different exercise interventions for alleviating skeletal muscle atrophy in naturally aging rats.
Effects of an exogenous ketone ester using multi-omics in skeletal muscle of aging C57BL/6J male mice.
Genome Editing to Abrogate Muscle Atrophy.
Not young but still immature: a HIF-1α-mediated maturation checkpoint in regenerating muscle.
Low aerobic capacity in McArdle disease: a role for mitochondrial network impairment?
Loss-of-rescue of Ryr1I4895T-related pathology by the genetic inhibition of the ER stress response mediator CHOP.
Minimal adaptation of the molecular regulators of mitochondrial dynamics in response to unilateral limb immobilisation and retraining in middle-aged men.
Exon skipping caused by splicing mutation in TNNT1 nemaline myopathy.
Valosin-containing protein (VCP/p97) inhibition reduces viral clearance and induces toxicity associated with muscular damage.

Front Cell Dev Biol. 2022 ;10 1049653

Nicotinamide riboside kinases regulate skeletal muscle fiber-type specification and are rate-limiting for metabolic adaptations during regeneration.

Tanja Sonntag, Sara Ancel, Sonia Karaz, Paulina Cichosz, Guillaume Jacot, Maria Pilar Giner, José Luis Sanchez-Garcia, Alice Pannérec, Sofia Moco, Vincenzo Sorrentino, Carles Cantó, Jérôme N Feige.

  Nicotinamide riboside kinases (NRKs) control the conversion of dietary Nicotinamide Riboside (NR) to NAD+, but little is known about their contribution to endogenous NAD+ turnover and muscle plasticity during skeletal muscle growth and remodeling. Using NRK1/2 double KO (NRKdKO) mice, we investigated the influence of NRKs on NAD+ metabolism and muscle homeostasis, and on the response to neurogenic muscle atrophy and regeneration following muscle injury. Muscles from NRKdKO animals have altered nicotinamide (NAM) salvage and a decrease in mitochondrial content. In single myonuclei RNAseq of skeletal muscle, NRK2 mRNA expression is restricted to type IIx muscle fibers, and perturbed NAD+ turnover and mitochondrial metabolism shifts the fiber type composition of NRKdKO muscle to fast glycolytic IIB fibers. NRKdKO does not influence muscle atrophy during denervation but alters muscle repair after myofiber injury. During regeneration, muscle stem cells (MuSCs) from NRKdKO animals hyper-proliferate but fail to differentiate. NRKdKO also alters the recovery of NAD+ during muscle regeneration as well as mitochondrial adaptations and extracellular matrix remodeling required for tissue repair. These metabolic perturbations result in a transient delay of muscle regeneration which normalizes during myofiber maturation at late stages of regeneration via over-compensation of anabolic IGF1-Akt signaling. Altogether, we demonstrate that NAD+ synthesis controls mitochondrial metabolism and fiber type composition via NRK1/2 and is rate-limiting for myogenic commitment and mitochondrial maturation during skeletal muscle repair.

Keywords:  NAD+; NRK; fiber type; mitochondria; muscle regeneration; muscle stem cell (satellite cell); nicotinamide riboside; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2022.1049653
Exp Physiol. 2022 Dec 01.

Peroxisome proliferator-activated receptor γ coactivator 1-α overexpression improves angiogenic signalling potential of skeletal muscle-derived extracellular vesicles.

Chris K Kargl, Brian P Sullivan, Derek Middleton, Andrew York, Lundon C Burton, Jeffrey J Brault, Shihuan Kuang, Timothy P Gavin.

  NEW FINDINGS: What is the central question of this study? Skeletal muscle extracellular vesicles likely act as pro-angiogenic signalling factors: does overexpression of peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) alter skeletal muscle myotube extracellular vesicle release, contents and angiogenic potential? What is the main finding and its importance? Overexpression of PGC-1α results in secretion of extracellular vesicles that elevate measures of angiogenesis and protect against acute oxidative stress in vitro. Skeletal muscle with high levels of PGC-1α expression, commonly associated with exercise induced angiogenesis and high basal capillarization, may secrete extracellular vesicles that support capillary growth and maintenance.ABSTRACT: Skeletal muscle capillarization is proportional to muscle fibre mitochondrial content and oxidative capacity. Skeletal muscle cells secrete many factors that regulate neighbouring capillary endothelial cells (ECs), including extracellular vesicles (SkM-EVs). Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) regulates mitochondrial biogenesis and the oxidative phenotype in skeletal muscle. Skeletal muscle PGC-1α also regulates secretion of multiple angiogenic factors, but it is unknown whether PGC-1α regulates SkM-EV release, contents and angiogenic signalling potential. PGC-1α was overexpressed via adenovirus in primary human myotubes. EVs were collected from PGC-1α-overexpressing myotubes (PGC-EVs) as well as from green fluorescent protein-overexpressing myotubes (GFP-EVs), and from untreated myotubes. EV release and select mRNA contents were measured from EVs. Additionally, ECs were treated with EVs to measure angiogenic potential of EVs in normal conditions and following an oxidative stress challenge. PGC-1α overexpression did not impact EV release but did elevate EV content of mRNAs for several antioxidant proteins (nuclear factor erythroid 2-related factor 2, superoxide dismutase 2, glutathione peroxidase). PGC-EV treatment of cultured human umbilical vein endothelial cells (HUVECs) increased their proliferation (+36.6%), tube formation (length: +28.1%; number: +25.7%) and cellular viability (+52.9%), and reduced reactive oxygen species levels (-41%) compared to GFP-EVs. Additionally, PGC-EV treatment protected against tube formation impairments and induction of cellular senescence following acute oxidative stress. Overexpression of PGC-1α in human myotubes increases the angiogenic potential of SkM-EVs. These angiogenic benefits coincided with increased anti-oxidative capacity of recipient HUVECs. High PGC-1α expression in skeletal muscle may prompt the release of SkM-EVs that support vascular redox homeostasis and angiogenesis.

Keywords:  PGC-1α; angiogenesis; endothelial cells; extracellular vesicles; skeletal muscle

DOI:  https://doi.org/10.1113/EP090874
Cell Regen. 2022 Dec 02. 11(1): 40

Regulation of muscle stem cell fate.

Xin Fu, Cheng-le Zhuang, Ping Hu.

  Skeletal muscle plays a critical role in human health. Muscle stem cells (MuSCs) serve as the major cell type contributing to muscle regeneration by directly differentiating to mature muscle cells. MuSCs usually remain quiescent with occasionally self-renewal and are activated to enter cell cycle for proliferation followed by differentiation upon muscle injury or under pathological conditions. The quiescence maintenance, activation, proliferation, and differentiation of MuSCs are tightly regulated. The MuSC cell-intrinsic regulatory network and the microenvironments work coordinately to orchestrate the fate transition of MuSCs. The heterogeneity of MuSCs further complicates the regulation of MuSCs. This review briefly summarizes the current progress on the heterogeneity of MuSCs and the microenvironments, epigenetic, and transcription regulations of MuSCs.

Keywords:  Asymmetric division; Microenvironments; MuSC heterogeneity; Muscle stem cells; Skeletal muscle regeneration; Transcription regulation

DOI:  https://doi.org/10.1186/s13619-022-00142-7
PLoS One. 2022 ;17(12): e0277830

Nuclear corepressor SMRT acts as a strong regulator of both β-oxidation and suppressor of fibrosis in the differentiation process of mouse skeletal muscle cells.

Hiroaki Shimizu, Yasuhiro Horibata, Izuki Amano, Megan J Ritter, Mariko Domae, Hiromi Ando, Hiroyuki Sugimoto, Ronald N Cohen, Anthony N Hollenberg.

BACKGROUND: Silencing Mediator of Retinoid and Thyroid hormone receptors (SMRT; NCoR2) is a transcriptional corepressor (CoR) which has been recognized as an important player in the regulation of hepatic lipogenesis and in somatic development in mouse embryo. SMRT protein is also widely expressed in mouse connective tissues, for example adipocytes and muscle. We recently reported that mice with global deletion of SMRT develop significant obesity and muscle wasting which are independent from thyroid hormone (TH) signaling and thermogenesis. However, the tissue specific role of SMRT in skeletal muscle is still not clear.METHODS: To clarify role of SMRT in muscle differentiation, we made myogenic C2C12 clones which lack SMRT protein (C2C12-SKO) by using CRISPR-Cas9. Wild-type C2C12 (C2C12-WT) and C2C12-SKO cells were cultured in differentiation medium, and the resulting gene and protein profiles were compared between the two cell lines both before and after differentiation. We also analyzed muscle tissues which were dissected from whole body SMRT knockout (KO) mice and their controls.
RESULTS: We found significant up-regulation of muscle specific β-oxidation markers; Peroxisome proliferator-activated receptor δ (PPARδ) and PPARγ coactivator-1α (PGC-1α) in the C2C12-SKO cells, suggesting that the cells had a similar gene profile to what is found in exercised rodent skeletal muscle. On the other hand, confocal microscopic analysis showed the significant loss of myotubes in C2C12-SKO cells similar to the morphology found in immature myoblasts. Proteomics analysis also confirmed that the C2C12-SKO cells had higher expression of markers of fibrosis (ex. Collagen1A1; COL1A1 and Fibroblast growth factor-2; FGF-2), indicating the up-regulation of Transforming growth factor-β (TGF-β) receptor signaling. Consistent with this, treatment with a specific TGF-β receptor inhibitor ameliorated both the defects in myotube differentiation and fibrosis.
CONCLUSION: Taken together, we demonstrate that SMRT functions as a pivotal transcriptional mediator for both β-oxidation and the prevention for the fibrosis via TGF-β receptor signaling in the differentiation of C2C12 myoblasts. In contrast to the results from C2C12 cells, SMRT does not appear to play a role in adult skeletal muscle of whole body SMRT KO mice. Thus, SMRT plays a significant role in the differentiation of myoblasts.

DOI: https://doi.org/10.1371/journal.pone.0277830
Brain Plast. 2022 ;8(1): 43-63

Muscle-to-Brain Signaling Via Myokines and Myometabolites.

Mamta Rai, Fabio Demontis.

  Skeletal muscle health and function are important determinants of systemic metabolic homeostasis and organism-wide responses, including disease outcome. While it is well known that exercise protects the central nervous system (CNS) from aging and disease, only recently this has been found to depend on the endocrine capacity of skeletal muscle. Here, we review muscle-secreted growth factors and cytokines (myokines), metabolites (myometabolites), and other unconventional signals (e.g. bioactive lipid species, enzymes, and exosomes) that mediate muscle-brain and muscle-retina communication and neuroprotection in response to exercise and associated processes, such as the muscle unfolded protein response and metabolic stress. In addition to impacting proteostasis, neurogenesis, and cognitive functions, muscle-brain signaling influences complex brain-dependent behaviors, such as depression, sleeping patterns, and biosynthesis of neurotransmitters. Moreover, myokine signaling adapts feeding behavior to meet the energy demands of skeletal muscle. Contrary to protective myokines induced by exercise and associated signaling pathways, inactivity and muscle wasting may derange myokine expression and secretion and in turn compromise CNS function. We propose that tailoring muscle-to-CNS signaling by modulating myokines and myometabolites may combat age-related neurodegeneration and brain diseases that are influenced by systemic signals.

Keywords:  Skeletal muscle; aging; brain; central nervous system; feeding behavior; myokine; myometabolite; neurodegeneration; retina; stress signaling

DOI:  https://doi.org/10.3233/BPL-210133
Brain Plast. 2022 ;8(1): 5-18

High Intensity Acute Aerobic Exercise Elicits Alterations in Circulating and Skeletal Muscle Tissue Expression of Neuroprotective Exerkines.

Corey E Mazo, Edwin R Miranda, James Shadiow, Michael Vesia, Jacob M Haus.

  Background: Cathepsin B (CTSB) and brain derived neurotrophic factor (BDNF) are increased with aerobic exercise (AE) and skeletal muscle has been identified as a potential source of secretion. However, the intensity of AE and the potential for skeletal muscle contributions to circulating CTSB and BDNF have not been fully studied in humans.Objective: Determine the effects of AE intensity on circulating and skeletal muscle CTSB and BDNF expression profiles.
Methods: Young healthy subjects (n = 16) completed treadmill-based AE consisting of VO2max and calorie-matched acute AE sessions at 40%, 65% and 80% VO2max. Fasting serum was obtained before and 30-minutes after each bout of exercise. Skeletal muscle biopsies (vastus lateralis) were taken before, 30-minutes and 3-hours after the 80% bout. Circulating CTSB and BDNF were assayed in serum. CTSB protein, BDNF protein and mRNA expression were measured in skeletal muscle tissue.
Results: Serum CTSB increased by 20±7% (p = 0.02) and 30±18% (p = 0.04) after 80% and VO2max AE bouts, respectively. Serum BDNF showed a small non-significant increase (6±3%; p = 0.09) after VO2max. In skeletal muscle tissue, proCTSB increased 3 h-post AE (87±26%; p < 0.01) with no change in CTSB gene expression. Mature BDNF protein decreased (31±35%; p = 0.03) while mRNA expression increased (131±41%; p < 0.01) 3 h-post AE. Skeletal muscle fiber typing revealed that type IIa and IIx fibers display greater BDNF expression compared to type I (p = 0.02 and p < 0.01, respectively).
Conclusions: High intensity AE elicits greater increases in circulating CTSB compared with lower intensities. Skeletal muscle protein and gene expression corroborate the potential role of skeletal muscle in generating and releasing neuroprotective exerkines into the circulation.NEW AND NOTEWORTHY: 1) CTSB is enriched in the circulation in an aerobic exercise intensity dependent manner. 2) Skeletal muscle tissue expresses both message and protein of CTSB and BDNF. 3) BDNF is highly expressed in glycolytic skeletal muscle fibers.

Keywords:  Human; brain derived neurotrophic factor; cathepsin B

DOI:  https://doi.org/10.3233/BPL-220137
J Cachexia Sarcopenia Muscle. 2022 Nov 28.

Loss of FoxOs in muscle increases strength and mitochondrial function during aging.

Christie M Penniman, Gourav Bhardwaj, Colette J Nowers, Chandler U Brown, Taylor L Junck, Cierra K Boyer, Jayashree Jena, Jordan D Fuqua, Vitor A Lira, Brian T O'Neill.

  BACKGROUND: Muscle mitochondrial decline is associated with aging-related muscle weakness and insulin resistance. FoxO transcription factors are targets of insulin action and deletion of FoxOs improves mitochondrial function in diabetes. However, disruptions in proteostasis and autophagy are hallmarks of aging and the effect of chronic inhibition of FoxOs in aged muscle is unknown. This study investigated the role of FoxOs in regulating muscle strength and mitochondrial function with age.METHODS: We measured muscle strength, cross-sectional area, muscle fibre-type, markers of protein synthesis/degradation, central nuclei, glucose/insulin tolerance, and mitochondrial bioenergetics in 4.5-month (Young) and 22-24-month-old (Aged) muscle-specific FoxO1/3/4 triple KO (TKO) and littermate control (Ctrl) mice.
RESULTS: Lean mass was increased in Aged TKO compared with both Aged Ctrl and younger groups by 26-33% (P < 0.01). Muscle strength, measured by max force of tibialis anterior (TA) contraction, was 20% lower in Aged Ctrl compared with Young Ctrls (P < 0.01) but was not decreased in Aged TKOs. Increased muscle strength in Young and Aged TKO was associated with 18-48% increased muscle weights compared with Ctrls (P < 0.01). Muscle cross-sectional analysis of TA, soleus, and plantaris revealed increases in fibre size distribution and a 2.5-10-fold increase in central nuclei in Young and Aged TKO mice, without histologic signs of muscle damage. Age-dependent increases in Gadd45a and Ube4a expression as well accumulation of K48 polyubiquitinated proteins were observed in quad and TA but were prevented by FoxO deletion. Young and Aged TKO muscle showed minimal changes in autophagy flux and no accumulation of autophagosomes compared with Ctrl groups. Increased strength in Young and Aged TKO was associated with a 10-20% increase in muscle mitochondrial respiration using glutamate/malate/succinate compared with controls (P < 0.05). OXPHOS subunit expression and complex I activity were decreased 16-34% in Aged Ctrl compared with Young Ctrl but were prevented in Aged TKO. Both Aged Ctrl and Aged TKO showed impaired glucose tolerance by 33% compared to young groups (P < 0.05) indicating improved strength and mitochondrial respiration are not due to improved glycemia.
CONCLUSIONS: FoxO deletion increases muscle strength even during aging. Deletion of FoxOs maintains muscle strength in part by mild suppression of atrophic pathways, including inhibition of Gadd45a and Ube4a expression, without accumulation of autophagosomes in muscle. Deletion of FoxOs also improved mitochondrial function by maintenance of OXPHOS in both young and aged TKO.

Keywords:  Aging; FoxO; Glucose tolerance; Insulin resistance; Mitochondrial function; Muscle hypertrophy

DOI:  https://doi.org/10.1002/jcsm.13124
Front Immunol. 2022 ;13 977617

Extracellular vesicle-derived miRNAs improve stem cell-based therapeutic approaches in muscle wasting conditions.

Laura Yedigaryan, Ester Martínez-Sarrà, Giorgia Giacomazzi, Nefele Giarratana, Bernard K van der Veer, Alessio Rotini, Silvia Querceto, Hanne Grosemans, Álvaro Cortés-Calabuig, Sara Salucci, Michela Battistelli, Elisabetta Falcieri, Rik Gijsbers, Mattia Quattrocelli, Kian Peng Koh, Liesbeth De Waele, Gunnar M Buyse, Rita Derua, Maurilio Sampaolesi.

  Skeletal muscle holds an intrinsic capability of growth and regeneration both in physiological conditions and in case of injury. Chronic muscle illnesses, generally caused by genetic and acquired factors, lead to deconditioning of the skeletal muscle structure and function, and are associated with a significant loss in muscle mass. At the same time, progressive muscle wasting is a hallmark of aging. Given the paracrine properties of myogenic stem cells, extracellular vesicle-derived signals have been studied for their potential implication in both the pathogenesis of degenerative neuromuscular diseases and as a possible therapeutic target. In this study, we screened the content of extracellular vesicles from animal models of muscle hypertrophy and muscle wasting associated with chronic disease and aging. Analysis of the transcriptome, protein cargo, and microRNAs (miRNAs) allowed us to identify a hypertrophic miRNA signature amenable for targeting muscle wasting, consisting of miR-1 and miR-208a. We tested this signature among others in vitro on mesoangioblasts (MABs), vessel-associated adult stem cells, and we observed an increase in the efficiency of myogenic differentiation. Furthermore, injections of miRNA-treated MABs in aged mice resulted in an improvement in skeletal muscle features, such as muscle weight, strength, cross-sectional area, and fibrosis compared to controls. Overall, we provide evidence that the extracellular vesicle-derived miRNA signature we identified enhances the myogenic potential of myogenic stem cells.

Keywords:  aging; extracellular vesicle; hypertrophy; miRNA; muscular dystrophy; skeletal muscle

DOI:  https://doi.org/10.3389/fimmu.2022.977617
Curr Protoc. 2022 Nov;2(11): e616

Cultured Neonatal Murine Primary Myotubes as a Model to Study Muscle Atrophy.

Ankit Kumar Tamta, Bhoomika Shivanaiah, Sunayana Ningaraju, Arathi Bangalore Prabhashankar, Nagalingam Ravi Sundaresan.

  Besides genetic disorders, skeletal muscle atrophy mainly occurs as a consequence of underlying conditions such as prolonged inactivity, aging, and metabolic diseases, ultimately contributing to the risk of disability. Disturbances in cellular and molecular mechanisms involved in proteolysis and protein synthesis underpin muscle fiber shrinkage and decreased muscle fiber diameter. Stress-induced primary myotube culture is an established model for studying muscle atrophy. An in vitro model is an essential criterion in establishing preliminary data in a cell-autonomous manner that can later be validated using in vivo models. Here, we describe protocols for the isolation, culture, and differentiation of primary murine myotubes and the induction of myotube atrophy using dexamethasone, a synthetic corticosteroid. We further elaborate the procedure to validate degenerative parameters, such as assessing muscle fiber diameter, expression of muscle atrophy genes, and protein synthesis status under dexamethasone treatment. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Isolation and culture of primary myoblasts from rat or mouse pups Support Protocol 1: Preparation of coated tissue culture ware Support Protocol 2: Subculture of myoblasts Basic Protocol 2: Induction and assessment of myotube atrophy.

Keywords:  dexamethasone; murine; muscle atrophy; primary myotubes; stress

DOI:  https://doi.org/10.1002/cpz1.616
Free Radic Biol Med. 2022 Nov 24. pii: S0891-5849(22)00988-1. [Epub ahead of print]194 23-32

Skeletal muscle Nox4 knockout prevents and Nox2 knockout blunts loss of maximal diaphragm force in mice with heart failure with reduced ejection fraction.

Ravi A Kumar, Dongwoo Hahn, Rachel C Kelley, Derek R Muscato, Alex Shamoun, Nuria Curbelo-Bermudez, W Greyson Butler, Svetlana Yegorova, Terence E Ryan, Leonardo F Ferreira.

  Patients with heart failure with reduced ejection fraction (HFrEF) experience diaphragm weakness that contributes to the primary disease symptoms of fatigue, dyspnea, and exercise intolerance. Weakness in the diaphragm is related to excessive production of reactive oxygen species (ROS), but the exact source of ROS remains unknown. NAD(P)H Oxidases (Nox), particularly the Nox2 and 4 isoforms, are important sources of ROS within skeletal muscle that contribute to optimal cell function. There are reports of increased Nox activity in the diaphragm of patients and animal models of HFrEF, implicating these complexes as possible sources of diaphragm dysfunction in HFrEF. To investigate the role of these proteins on diaphragm weakness in HFrEF, we generated inducible skeletal muscle specific knockouts of Nox2 or Nox4 using the Cre-Lox system and assessed diaphragm function in a mouse model of HFrEF induced by myocardial infarction. Diaphragm maximal specific force measured in vitro was depressed by ∼20% with HFrEF. Skeletal muscle knockout of Nox4 provided full protection against the loss of maximal force (p < 0.01), while the knockout of Nox2 provided partial protection (7% depression, p < 0.01). Knockout of Nox2 from skeletal myofibers improved survival from 50 to 80% following myocardial infarction (p = 0.026). Our findings show an important role for skeletal muscle NAD(P)H Oxidases contributing to loss of diaphragm maximal force in HFrEF, along with systemic pathophysiological responses following myocardial infarction.

Keywords:  Diaphragm; HFrEF; Heart failure; Muscle; NADPH Oxidases; Weakness

DOI:  https://doi.org/10.1016/j.freeradbiomed.2022.11.025
Life Sci Alliance. 2023 Feb;pii: e202201783. [Epub ahead of print]6(2):

The mechanosensitive ion channel PIEZO1 promotes satellite cell function in muscle regeneration.

Kotaro Hirano, Masaki Tsuchiya, Akifumi Shiomi, Seiji Takabayashi, Miki Suzuki, Yudai Ishikawa, Yuya Kawano, Yutaka Takabayashi, Kaori Nishikawa, Kohjiro Nagao, Eiji Umemoto, Yasuo Kitajima, Yusuke Ono, Keiko Nonomura, Hirofumi Shintaku, Yasuo Mori, Masato Umeda, Yuji Hara.

Muscle satellite cells (MuSCs), myogenic stem cells in skeletal muscles, play an essential role in muscle regeneration. After skeletal muscle injury, quiescent MuSCs are activated to enter the cell cycle and proliferate, thereby initiating regeneration; however, the mechanisms that ensure successful MuSC division, including chromosome segregation, remain unclear. Here, we show that PIEZO1, a calcium ion (Ca2+)-permeable cation channel activated by membrane tension, mediates spontaneous Ca2+ influx to control the regenerative function of MuSCs. Our genetic engineering approach in mice revealed that PIEZO1 is functionally expressed in MuSCs and that Piezo1 deletion in these cells delays myofibre regeneration after injury. These results are, at least in part, due to a mitotic defect in MuSCs. Mechanistically, this phenotype is caused by impaired PIEZO1-Rho signalling during myogenesis. Thus, we provide the first concrete evidence that PIEZO1, a bona fide mechanosensitive ion channel, promotes proliferation and regenerative functions of MuSCs through precise control of cell division.

DOI: https://doi.org/10.26508/lsa.202201783
Cell Stem Cell. 2022 Dec 01. pii: S1934-5909(22)00450-7. [Epub ahead of print]29(12): 1613-1615

A post-middle-age crisis for CD47 and THBS1 that turns into a vicious cycle.

Pier Lorenzo Puri.

In this issue of Cell Stem Cell, Porpiglia et al.1 report on alterations in CD47 and THBS1 expression and function in aged muscle stem cells that disrupt their regeneration capacity. Targeting THBS1-CD47 cross-signaling is sufficient to reverse sarcopenia and restore muscle mass and function in aged mice.

DOI: https://doi.org/10.1016/j.stem.2022.11.003
Front Sports Act Living. 2022 ;4 1035190

Inter-set stretch: A potential time-efficient strategy for enhancing skeletal muscle adaptations.

Brad J Schoenfeld, Henning Wackerhage, Eduardo De Souza.

  Time is considered a primary barrier to exercise adherence. Therefore, developing time-efficient resistance training (RT) strategies that optimize muscular adaptations is of primary interest to practitioners. A novel approach to the problem involves combining intensive stretch protocols with RT. Conceivably, integrating stretch into the inter-set period may provide an added stimulus for muscle growth without increasing session duration. Mechanistically, stretch can regulate anabolic signaling via both active and passive force sensors. Emerging evidence indicates that both lengthening contractions against a high load as well as passive stretch can acutely activate anabolic intracellular signaling pathways involved in muscle hypertrophy. Although longitudinal research investigating the effects of stretching between RT sets is limited, some evidence suggests it may in fact enhance hypertrophic adaptations. Accordingly, the purpose of this paper is threefold: (1) to review how the active force of a muscle contraction and the force of a passive stretched are sensed; (2) to present evidence for the effectiveness of RT with inter-set stretch for muscle hypertrophy (3) to provide practical recommendations for application of inter-set stretch in program design as well as directions for future research.

Keywords:  contraction; force sensors; hypertrophy; lengthening; mechanical tension

DOI:  https://doi.org/10.3389/fspor.2022.1035190
J Appl Physiol (1985). 2022 Dec 01.

Loss of 4E-BPs Prevents the Hindlimb Immobilization-Induced Decrease in Protein Synthesis in Skeletal Muscle.

Gregory N Kincheloe, Paul A Roberson, Allyson L Toro, Bruce A Stanley, Anne E Stanley, Leonard S Jefferson, Michael D Dennis, Scot R Kimball.

  The present study was designed to test the hypothesis that upregulating protein synthesis attenuates the loss of muscle mass in a model of disuse atrophy. The studies compared the effect of unilateral hindlimb immobilization in wild-type (WT) mice and double-knockout (DKO) mice lacking the translational regulators 4E-BP1 and 4E-BP2. Immobilization-induced downregulation of protein synthesis occurred in both groups of mice, but protein synthesis was higher in gastrocnemius muscle from the immobilized hindlimb of fasted DKO compared to WT mice. Surprisingly, although protein synthesis was partially elevated in DKO compared to WT mice, atrophy occurred to the same extent in both groups of animals. This may be partially due to impaired leucine-induced stimulation of protein synthesis in DKO compared to WT mice due to down-regulated eukaryotic initiation factor eIF4E expression in muscle of DKO compared to WT mice. Expression of the E3 ubiquitin ligases MAFbx and MuRF-1 mRNAs and total protein ubiquitylation were upregulated in the immobilized compared with the non-immobilized hindlimb of both WT and DKO mice, with little difference in the magnitude of the upregulation between genotypes. Analysis of newly synthesized proteins revealed a downregulation of several glycolytic enzymes in the gastrocnemius of DKO mice compared to WT mice, as well as in the immobilized compared to the non-immobilized hindlimb. Overall, the results suggest that the elevated rate of protein synthesis during hindlimb immobilization in fasted DKO mice is insufficient to prevent disuse-induced muscle atrophy, probably due to induction of compensatory mechanisms including downregulation of eIF4E expression.

Keywords:  4E-BP1; Disuse Muscle Atrophy; eIF4E; mTORC1

DOI:  https://doi.org/10.1152/japplphysiol.00563.2022
J Appl Physiol (1985). 2022 Dec 01.

Sex based comparisons of muscle cellular adaptations after 10-weeks of progressive resistance training in middle-aged adults.

Emileigh R Binet, Colleen F McKenna, Amadeo F Salvador, Isabel G Martinez, Rafael A Alamilla, Nicolas Collao, Giana Bodnariuc, Naiman A Khan, Scott A Paluska, Nicholas A Burd, Michael De Lisio.

  Resistance training combined with adequate protein intake supports skeletal muscle strength and hypertrophy. These adaptations are supported by the action of muscle stem cells (MuSCs) which are regulated, in part, by fibro-adipogenic progenitors (FAPs) and circulating factors delivered through capillaries. It is unclear if middle-aged males and females have similar adaptations to resistance training at the cellular level. To address this gap, 27 (13 males, 14 females) middle-aged (40-64 years) adults participated in 10-weeks of whole-body resistance training with dietary counselling. Muscle biopsies were collected from the vastus lateralis pre- and post-training. Type II fibre cross-sectional area increased similarly with training in both sexes (P = 0.014). MuSC content was not altered with training; however, training increased PDGFRα+/CD90+ FAP content (P < 0.0001) and reduced PDGFRα+/CD90- FAP content (P = 0.044), independent of sex. The number of CD31+ capillaries per fibre also increased similarly in both sexes (p<0.05). These results suggest that muscle fibre hypertrophy, stem/progenitor cell, and capillary adaptations are similar between middle-aged males and females in response to whole-body resistance training.

Keywords:  Muscle stem cells; aging; exercise; fibro-adipogenic progenitors; satellite cells

DOI:  https://doi.org/10.1152/japplphysiol.00274.2022
Front Physiol. 2022 ;13 993995

p62/Sqstm1 rescue in muscle retards the progression of steatohepatitis in p62/Sqstm1-null mice fed a high-fat diet.

Ikuru Miura, Kosuke Okada, Akiko Ishii, Eiji Warabi, Takahisa Watahiki, Keii To, Hitoshi Shimano, Shunichi Ariizumi, Junichi Shoda.

  Introduction: Obesity is a risk factor for many diseases because it leads to a reduction in skeletal muscle mass and promotes insulin resistance. p62/Sqstm1-knockout mice are a model of metabolic syndrome; show obesity, insulin resistance, and non-alcoholic fatty liver (NAFL); and develop non-alcoholic steatohepatitis (NASH) in response to the feeding of a high-fat diet (HFD). These phenotypes suggest that muscle p62 may prevent obesity-induced muscle dysfunction. In the present study, we aimed to determine the effects of muscle p62 on skeletal muscle mass, muscle strength, insulin resistance, and NASH pathology. Methods: We generated muscle-specific p62 gene rescue mice (p62-mRes), which express p62 only in muscle and were derived from p62-knock out mice (p62 KIKI ) using the cre/loxp system. p62 KIKI and p62-mRes mice were fed an HFD for 20 weeks and their phenotypes were compared. Results: HFD-feeding caused severe obesity in both p62 KIKI and p62-mRes mice, but there was no effect of muscle p62 on body mass. Limb skeletal muscle mass, grip strength, and the cross-sectional area of muscle fibers were higher in p62-mRes mice than in p62 KIKI . The glucose tolerance and insulin sensitivity of the p62-mRes mice were also superior. The protein expression of mechanistic target of rapamycin, which promotes muscle protein synthesis, and GLUT4, a glucose transporter in skeletal muscle, were higher in the p62-mRes mice. p62 KIKI mice developed severe NASH when fed an HFD, but the progression of NASH was retarded by p62 gene rescue in muscle, and the expression of Tgf-β1, which encodes a factor that promotes hepatic fibrosis, was reduced. Conclusion: Rescue of muscle-specific p62 in the whole-body p62 knock-out mice ameliorates the insulin resistance and retards the progression of NASH caused by systemic p62 ablation.

Keywords:  insulin resistance; non-alcoholic steatohepatitis; obesity; p62/SQSTM1; skeletal muscle

DOI:  https://doi.org/10.3389/fphys.2022.993995
J Physiol. 2022 Nov 30.

What about hybrids? Supplemental methods for skeletal muscle fibre typing.

Omar B El-Kurd, Patrick Bialy, Maty Kirkes.



Keywords:  hybrid muscle fibre; myosin heavy chain; skeletal muscle fibre

DOI:  https://doi.org/10.1113/JP284038
J Cachexia Sarcopenia Muscle. 2022 Dec 01.

MicroRNA profiling of different exercise interventions for alleviating skeletal muscle atrophy in naturally aging rats.

Jiling Liang, Hu Zhang, Zhengzhong Zeng, Jun Lv, Jielun Huang, Xiaowen Wu, Minghui Wang, Jiahao Xu, Jingjing Fan, Ning Chen.

  BACKGROUND: Exercise is an affordable and practical strategy to alleviate several detrimental outcomes from the aging process, including sarcopenia. The elucidation of molecular mechanisms to alleviate sarcopenia is one of the most important steps towards understanding human aging. Although microRNAs (miRNAs) regulate muscle growth, regeneration and aging, the potential role of exercise-mediated miRNAs during the prevention and rehabilitation of skeletal muscle atrophy upon exercise interventions remains unclear.METHODS: A miRNA profile by miRNA sequencing for gastrocnemius muscle of a 24-month-old aged male rat model mimicking the naturally aging process was established through screening the differentially expressed miRNAs (DEMs) for alleviating aging-induced skeletal muscle atrophy upon optimal exercise intervention. The screened miRNAs and hub genes, as well as biomarkers with the most significantly enriched pathways, were validated by quantitative real-time polymerase chain reaction and western blotting.
RESULTS: The sarcopenia index (SI) value and cross-sectional area (CSA) of rats from the old control (OC) group significantly decreased when compared with the youth control (YC) group (P < 0.001, P < 0.01), whereas an increased SI value and an enlarged CSA of rats from the old-aerobic exercise (OE), old-resistance exercise (OR) and old-mixed exercise (OM) groups were determined (P < 0.01, P < 0.001, P < 0.05; P < 0.01, P < 0.01, P < 0.05). Our results demonstrate that 764 known miRNAs, 201 novel miRNAs and 505 miRNA-mRNA interaction networks were identified to be related to aging-induced muscular atrophy. Among them, 13 miRNAs were differentially expressed (P < 0.05 and log2 |fold change| > 1) between the YC group and the OC group. Compared with the OC group, 7, 2 and 11 miRNAs were differentially expressed in the OE, OR and OM groups after exercise interventions, respectively. Meanwhile, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the identified DEMs were primarily related to apoptosis, autophagy and the NF-κB/MuRF1 signalling pathways (P < 0.05). Meanwhile, four DEMs (miR-7a-1-3p, miR-135a-5p, miR-151-5p and miR-196b-5p), six hub genes (Ar, Igf1, Hif1a, Bdnf, Fak and Nras) and several biomarkers (LC3, Beclin1, p62, Bax, Bcl-2 and NF-κB/MuRF1) with the most significantly enriched pathways were confirmed, which may play a key role in muscular atrophy during the aging process.
CONCLUSIONS: These findings are closely correlated with the progression of sarcopenia and could act as potential biomarkers for the diagnosis and interventional monitoring of aging-induced skeletal muscle atrophy.

Keywords:  exercise intervention; miRNA sequencing; microRNA; sarcopenia; skeletal muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13137
Front Nutr. 2022 ;9 1041026

Effects of an exogenous ketone ester using multi-omics in skeletal muscle of aging C57BL/6J male mice.

Brandon M Roberts, Sarah E Deemer, Daniel L Smith, James A Mobley, Nicolas Musi, Eric P Plaisance.

  Exogenous ketone ester supplementation provides a means to increase circulating ketone concentrations without the dietary challenges imposed by ketogenic diets. Our group has shown that oral R,S-1,3, butanediol diacetoacetate (BD-AcAc2) consumption results in body weight loss or maintenance with moderate increases in circulating ketones. We have previously shown a diet consisting of 25% BD-AcAc2 can maintain lean body mass (LBM) and induce fat mass (FM) loss in young, healthy male mice, but the underlying mechanisms are still unknown. Therefore, the purpose of this study was to determine if a diet consisting of 25% BD-AcAc2 (ketone ester, KE) would alter body composition, transcriptional regulation, the proteome, and the lipidome of skeletal muscle in aged mice. We hypothesized that the KE group would remain weight stable with improvements in body composition compared to controls, resulting in a healthy aging phenotype. Male C57BL/6J mice (n = 16) were purchased from Jackson Laboratories at 72 weeks of age. After 1 week of acclimation, mice were weighed and randomly assigned to one of two groups (n = 8 per group): control (CON) or KE. A significant group by time interaction was observed for body weight (P < 0.001), with KE fed mice weighing significantly less than CON. FM increased over time in the control group but was unchanged in the KE group. Furthermore, LBM was not different between CON and KE mice despite KE mice weighing less than CON mice. Transcriptional analysis of skeletal muscle identified 6 genes that were significantly higher and 21 genes that were significantly lower in the KE group compared to CON. Lipidomic analysis of skeletal muscle identified no differences between groups for any lipid species, except for fatty acyl chains in triacylglycerol which was 46% lower in the KE group. Proteomics analysis identified 44 proteins that were different between groups, of which 11 were lower and 33 were higher in the KE group compared to CON. In conclusion, 72-week-old male mice consuming the exogenous KE, BD-AcAc2, had lower age-related gains in body weight and FM compared to CON mice. Furthermore, transcriptional and proteomics data suggest a signature in skeletal muscle of KE-treated mice consistent with markers of improved skeletal muscle regeneration, improved electron transport chain utilization, and increased insulin sensitivity.

Keywords:  ketone ester; lipidomics; nutrition; proteomics; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.3389/fnut.2022.1041026
Adv Exp Med Biol. 2023 ;1396 157-176

Genome Editing to Abrogate Muscle Atrophy.

Tingting Yang, Priyanka Gokulnath, Xinxiu Meng, Guoping Li, Junjie Xiao.

  Muscle atrophy is a multifactor syndrome, which not only decreases the patients' quality of life significantly but also increases the morbidity and mortality of patients with chronic diseases. At present, no effective clinical treatments for muscle atrophy except for exercise are available. The emerging field of genome editing is gaining momentum as it has shown great advantage in the treatment of various diseases, including muscle atrophy. In our current review, we systematically evaluate the etiology and related signaling pathways of muscle atrophy and discuss the application of genome editing in the treatment of muscle atrophy.

Keywords:  Genome editing; Muscle atrophy; Treatment

DOI:  https://doi.org/10.1007/978-981-19-5642-3_11
J Clin Invest. 2022 Dec 01. pii: e165322. [Epub ahead of print]132(23):

Not young but still immature: a HIF-1α-mediated maturation checkpoint in regenerating muscle.

Rahagir Salekeen, Michael Kyba.

Muscle fibers express particular isoforms of contractile proteins, depending on the fiber's function and the organism's developmental stage. In the adult, after a muscle injury, newly generated fibers transition through embryonic and neonatal myosins, prior to selecting their distinctive adult myosin isoform. In this issue of the JCI, Wang et al. discover a checkpoint that regulates the neonatal-to-adult myosin isoform transition. They found that HIF-1α regulated this checkpoint, with elevated HIF-1α levels blocking progression, while HIF-1α knockout accelerated the transition. They further related these findings to centronuclear myopathy, a disease in which HIF-1α is similarly elevated and neonatal myosin expression is maintained. These findings highlight a maturation checkpoint that impacts the skeletal muscle regeneration following ischemic injury, providing a pharmacologically accessible pathway in injury and diseases such as centronuclear myopathy.

DOI: https://doi.org/10.1172/JCI165322
Mol Metab. 2022 Nov 28. pii: S2212-8778(22)00217-4. [Epub ahead of print] 101648

Low aerobic capacity in McArdle disease: a role for mitochondrial network impairment?

M Villarreal-Salazar, A Santalla, A Real-Martínez, G Nogales-Gadea, P L Valenzuela, C Fiuza-Luces, A L Andreu, J C Rodríguez-Aguilera, M A Martín, J Arenas, J Vissing, A Lucia, T O Krag, T Pinós.

  BACKGROUND: McArdle disease is caused by myophosphorylase deficiency and results in complete inability for muscle glycogen breakdown. A hallmark of this condition is muscle oxidation impairment (e.g., low peak oxygen uptake (VO2peak)), a phenomenon traditionally attributed to reduced glycolytic flux and Krebs cycle anaplerosis. Here we hypothesized an additional role for muscle mitochondrial network alterations associated with massive intracellular glycogen accumulation.METHODS: We analyzed in depth mitochondrial characteristics--content, biogenesis, ultrastructure--and network integrity in skeletal-muscle from McArdle/control mice and two patients. We also determined VO2peak in patients (both sexes, N=145) and healthy controls (N=133).
RESULTS: Besides corroborating very poor VO2peak values in patients and impairment in muscle glycolytic flux, we found that, in McArdle muscle: (a) damaged fibers are likely those with a higher mitochondrial and glycogen content, which show major disruption of the three main cytoskeleton components--actin microfilaments, microtubules and intermediate filaments--thereby contributing to mitochondrial network disruption in skeletal muscle fibers; (b) there was an altered subcellular localization of mitochondrial fission/fusion proteins and of the sarcoplasmic reticulum protein calsequestrin--with subsequent alteration in mitochondrial dynamics/function; impairment in mitochondrial content/biogenesis; and (c) several OXPHOS-related complex proteins/activities were also affected.
CONCLUSIONS: In McArdle disease, severe muscle oxidative capacity impairment could also be explained by a disruption of the mitochondrial network, at least in those fibers with a higher capacity for glycogen accumulation. Our findings might pave the way for future research addressing the potential involvement of mitochondrial network alterations in the pathophysiology of other glycogenoses.

Keywords:  McArdle disease; aerobic capacity; cytoskeleton and mitochondrial network; glycogen; skeletal muscle

DOI:  https://doi.org/10.1016/j.molmet.2022.101648
Sci Rep. 2022 Nov 30. 12(1): 20632

Loss-of-rescue of Ryr1I4895T-related pathology by the genetic inhibition of the ER stress response mediator CHOP.

Serena Germani, Alessia Celeste Marchetti, Andrea Guidarelli, Orazio Cantoni, Vincenzo Sorrentino, Ester Zito.

RYR1 is the gene encoding the ryanodine receptor 1, a calcium release channel of the endo/sarcoplasmic reticulum. I4898T in RYR1 is one of the most common mutations that give rise to central core disease (CCD), with a variable phenotype ranging from mild to severe myopathy to lethal early-onset core-rod myopathy. Mice with the corresponding I4895T mutation in Ryr1 present mild myopathy when the mutation is heterozygous while I4895T homozygous is perinatal-lethal. Here we show that skeletal muscles of I4895T homozygous mice at birth present signs of stress of the endoplasmic reticulum (ER stress) and of the related unfolded protein response (UPR) with increased levels of the maladaptive mediators CHOP and ERO1. To gain information on the role of CHOP in the pathogenesis of RYR1I4895T-related myopathy, we generated compound Ryr1I4895T, Chop knock-out (-/-) mice. However, the genetic deletion of Chop, although it attenuates ER stress in the skeletal muscle of the newborns, does not rescue any phenotypic or functional features of Ryr1I4895T in mice: neither the perinatal-lethal phenotype nor the inability of Ryr1I4895T to respond to its agonist caffeine, but protects from ER stress-induced apoptosis. These findings suggest that genetic deletion of the ER stress response mediator CHOP is not sufficient to counteract the pathological Ryr1I4895T phenotype.

DOI: https://doi.org/10.1038/s41598-022-25198-y
Eur J Appl Physiol. 2022 Nov 30.

Minimal adaptation of the molecular regulators of mitochondrial dynamics in response to unilateral limb immobilisation and retraining in middle-aged men.

Chantal A Pileggi, Christopher P Hedges, Randall F D'Souza, Brenan R Durainayagam, Nina Zeng, Vandre C Figueiredo, Anthony J R Hickey, Cameron J Mitchell, David Cameron-Smith.

  PURPOSE: Mitochondrial dynamics are regulated by the differing molecular pathways variously governing biogenesis, fission, fusion, and mitophagy. Adaptations in mitochondrial morphology are central in driving the improvements in mitochondrial bioenergetics following exercise training. However, there is a limited understanding of mitochondrial dynamics in response to inactivity.METHODS: Skeletal muscle biopsies were obtained from middle-aged males (n = 24, 49.4 ± 3.2 years) who underwent sequential 14-day interventions of unilateral leg immobilisation, ambulatory recovery, and resistance training. We quantified vastus lateralis gene and protein expression of key proteins involved in mitochondrial biogenesis, fusion, fission, and turnover in at baseline and following each intervention.
RESULTS: PGC1α mRNA decreased 40% following the immobilisation period, and was accompanied by a 56% reduction in MTFP1 mRNA, a factor involved in mitochondrial fission. Subtle mRNA decreases were also observed in TFAM (17%), DRP1 (15%), with contrasting increases in BNIP3L and PRKN following immobilisation. These changes in gene expression were not accompanied by changes in respective protein expression. Instead, we observed subtle decreases in NRF1 and MFN1 protein expression. Ambulatory recovery restored mRNA and protein expression to pre-intervention levels of all altered components, except for BNIP3L. Resistance training restored BNIP3L mRNA to pre-intervention levels, and further increased mRNA expression of OPA-1, MFN2, MTFP1, and PINK1 past baseline levels.
CONCLUSION: In healthy middle-aged males, 2 weeks of immobilisation did not induce dramatic differences in markers of mitochondria fission and autophagy. Restoration of ambulatory physical activity following the immobilisation period restored altered gene expression patterns to pre-intervention levels, with little evidence of further adaptation to resistance exercise training.

Keywords:  Fissions; Fusion; Immobilisation; Mitochondria; Mitophagy; Muscle

DOI:  https://doi.org/10.1007/s00421-022-05107-x
J Hum Genet. 2022 Nov 29.

Exon skipping caused by splicing mutation in TNNT1 nemaline myopathy.

Guangyu Wang, Dandan Zhao, Chuanzhu Yan, Pengfei Lin.

The TNNT1 gene encoding the slow skeletal muscle TnT has been identified as a causative gene for nemaline myopathy. TNNT1 nemaline myopathy is mainly characterized by neonatal-onset muscle weakness, pectus carinatum and respiratory insufficiency. Herein, we report on a Chinese girl with TNNT1 nemaline myopathy with mild clinical phenotypes without thoracic deformities or decreased respiratory function. Muscle biopsy showed moderate to marked type 1 fiber atrophy and nemaline rods. Next-generation sequencing identified the compound heterozygous c. 587dupA (p. D196Efs*41) and c. 387+5G>A mutations in the TNNT1 gene according to the transcript NM_003283.4. RNA sequencing revealed complete exon 9 skipping caused by the c. 387+5G>A mutation. Through quantitative PCR, we found that both the truncation c. 587dupA (p. D196Efs*41) and the splicing c. 387+5G>A mutations triggered nonsense-mediated mRNA decay (NMD). Western blotting showed the residual amount of the truncated TNNT1 protein by deletion of exon 9, which may ameliorate the disease to some extent.

DOI: https://doi.org/10.1038/s10038-022-01096-z
Cell Death Dis. 2022 Dec 01. 13(12): 1015

Valosin-containing protein (VCP/p97) inhibition reduces viral clearance and induces toxicity associated with muscular damage.

Marta Del Rio Oliva, Michael Basler.

Valosin-containing protein (VCP)/p97 has emerged as a central regulator of the ubiquitin-proteasome system by connecting ubiquitylation and degradation. The development of CB-5083, an ATPase D2-domain-selective and orally bioavailable inhibitor of VCP/p97, allows targeting of the ubiquitin-proteasome system in human diseases. In this study, we evaluated the effect of CB-5083 on the immune response in mice by using the lymphocytic choriomeningitis virus (LCMV) as an infection model. We demonstrate that LCMV infection increased the susceptibility to CB-5083 treatment in a CD8-independent manner. Administration of CB-5083 to mice reduced the cytotoxic T cell response and impaired viral clearance. Compared to uninfected cells, CB-5083 treatment enhanced the unfolded protein response in LCMV-infected cells. Administration of CB-5083 during the expansion of CD8+ T cells led to strong toxicity in mice within hours, which resulted in enhanced IL-6 levels in the serum and accumulation of poly-ubiquitinated proteins. Furthermore, we linked the observed toxicity to the specific formation of aggregates in the skeletal muscle tissue and the upregulation of both lactate dehydrogenase and creatine kinase in the serum.

DOI: https://doi.org/10.1038/s41419-022-05461-w