bims-moremu 2023-01-08 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–01–08
twenty-one papers selected by
Anna Vainshtein, Craft Science Inc.

SMN promotes mitochondrial metabolic maturation during myogenesis by regulating the MYOD-miRNA axis.
Myonuclear alterations associated with exercise are independent of age in humans.
The molecular athlete: exercise physiology from mechanisms to medals.
Two weeks of high-intensity interval training increases skeletal muscle mitochondrial respiration via complex-specific remodeling in sedentary humans.
Mitochondrial response to inactivity-induced muscle disuse and exercise training.
NRF2 and its targets in skeletal muscle repair and regeneration.
Ablation of NLRP3 inflammasome attenuates muscle atrophy via inhibiting pyroptosis, proteolysis and apoptosis following denervation.
Exercise preserves physical fitness during aging through AMPK and mitochondrial dynamics.
Mitochondria transplant therapy improves regeneration and restoration of injured skeletal muscle.
Linc-RAM is a metabolic regulator maintaining whole-body energy homeostasis in mice.
lncRNA UCA1 inhibits mitochondrial dysfunction of skeletal muscle in type 2 diabetes mellitus by sequestering miR-143-3p to release FGF21.
Adipose tissue is a source of regenerative cells that augment the repair of skeletal muscle after injury.
15 N-labelled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production.
Ageing Skeletal Muscle: The Ubiquitous Muscle Stem Cell.
Tissue-specific effects of exercise as NAD+ -boosting strategy: current knowledge and future perspectives.
Editorial: Untangling energy metabolism in skeletal muscle: From physiology to pharmacology.
Lactate metabolism is essential in early-onset mitochondrial myopathy.
Is dexamethasone-induced muscle atrophy an alternative model for naturally aged sarcopenia model?
Diverse effector and regulatory functions of fibro/adipogenic progenitors during skeletal muscle fibrosis in muscular dystrophy.
Protocol to assess arteriovenous differences across the liver and hindlimb muscles in mice following treadmill exercise.
Hallmarks of aging: An expanding universe.

Life Sci Alliance. 2023 Mar;pii: e202201457. [Epub ahead of print]6(3):

SMN promotes mitochondrial metabolic maturation during myogenesis by regulating the MYOD-miRNA axis.

Akihiro Ikenaka, Yohko Kitagawa, Michiko Yoshida, Chuang-Yu Lin, Akira Niwa, Tatsutoshi Nakahata, Megumu K Saito.

Spinal muscular atrophy (SMA) is a congenital neuromuscular disease caused by the mutation or deletion of the survival motor neuron 1 (SMN1) gene. Although the primary cause of progressive muscle atrophy in SMA has classically been considered the degeneration of motor neurons, recent studies have indicated a skeletal muscle-specific pathological phenotype such as impaired mitochondrial function and enhanced cell death. Here, we found that the down-regulation of SMN causes mitochondrial dysfunction and subsequent cell death in in vitro models of skeletal myogenesis with both a murine C2C12 cell line and human induced pluripotent stem cells. During myogenesis, SMN binds to the upstream genomic regions of MYOD1 and microRNA (miR)-1 and miR-206. Accordingly, the loss of SMN down-regulates these miRs, whereas supplementation of the miRs recovers the mitochondrial function, cell survival, and myotube formation of SMN-deficient C2C12, indicating the SMN-miR axis is essential for myogenic metabolic maturation. In addition, the introduction of the miRs into ex vivo muscle stem cells derived from Δ7-SMA mice caused myotube formation and muscle contraction. In conclusion, our data revealed novel transcriptional roles of SMN during myogenesis, providing an alternative muscle-oriented therapeutic strategy for SMA patients.

DOI: https://doi.org/10.26508/lsa.202201457
J Physiol. 2023 Jan 04.

Myonuclear alterations associated with exercise are independent of age in humans.

E Battey, J A Ross, A Hoang, D G S Wilson, Y Han, Y Levy, R D Pollock, M Kalakoutis, J N Pugh, G L Close, G M Ellison-Hughes, N R Lazarus, T Iskratsch, S D R Harridge, J Ochala, M J Stroud.

   KEY POINTS: The nucleus plays an active role in translating forces into biochemical signals Myonuclear aberrations in a group of muscular dystrophies called laminopathies suggest that the shape and mechanical properties of myonuclei are important for maintaining muscle function. Here, we present striking differences in myonuclear shape and mechanics associated with exercise, in both young and old humans. Myonuclei from trained individuals were more spherical, less deformable, and contained a thicker nuclear lamina than untrained individuals. We conclude that exercise is associated with age-independent myonuclear remodelling, which may help to maintain muscle function throughout the lifespan.
ABSTRACT: Age-related decline in skeletal muscle structure and function can be mitigated by regular exercise. However, the precise mechanisms that govern this are not fully understood. The nucleus plays an active role in translating forces into biochemical signals (mechanotransduction), with nuclear lamina protein Lamin A regulating nuclear shape, nuclear mechanics, and ultimately gene expression. Defective Lamin A expression causes muscle pathologies and premature ageing syndromes, but the roles of nuclear structure and function in physiological ageing and in exercise adaptations remain obscure. Here, we isolated single muscle fibres and carried out detailed morphological and functional analyses on myonuclei from young and older exercise-trained individuals. Strikingly, myonuclei from trained individuals were more spherical, less deformable, and contained a thicker nuclear lamina than untrained individuals. Complementary to this, exercise resulted in increased levels of Lamin A and increased myonuclear stiffness in mice. We conclude that exercise is associated with myonuclear remodelling, independently of age, which may contribute to the preservative effects of exercise on muscle function throughout the lifespan. Abstract figure legend Structural and mechanical properties of myonuclei in trained young and aged individuals. In skeletal muscle fibres from trained individuals, myonuclei are more spherical, have greater Lamin A and are stiffer compared to untrained counterparts. This may protect nuclei from damage when subjected to contractile forces during exercise, and permit effective transduction of these forces to regulate gene expression and signalling pathways (mechanotransduction). In skeletal muscle from untrained older individuals, myonuclei are more elongated, nuclear lamina levels are lower, and myonuclei are more deformable. This may increase susceptibility to myonuclear damage and defective mechanotransduction, contributing to declines in muscle mass and function. This article is protected by copyright. All rights reserved.

Keywords:  ageing; exercise; nuclear lamina; nuclear shape; nuclei

DOI:  https://doi.org/10.1113/JP284128
Physiol Rev. 2023 Jan 05.

The molecular athlete: exercise physiology from mechanisms to medals.

Regula Furrer, John A Hawley, Christoph Handschin.

  Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength, to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial and error" approach with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and inter-individual differences in exercise capacity and performance, with special considerations given to the ageing athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise, and how such adaptations translate from "molecules to medals".

Keywords:  athlete; endurance training; exercise; resistance training; skeletal muscle

DOI:  https://doi.org/10.1152/physrev.00017.2022
J Appl Physiol (1985). 2023 Jan 05.

Two weeks of high-intensity interval training increases skeletal muscle mitochondrial respiration via complex-specific remodeling in sedentary humans.

Philip M Batterson, Erin M McGowan, Harrison D Stierwalt, Sarah E Ehrlicher, Sean A Newsom, Matthew M Robinson.

  Aerobic training remodels the quantity and quality (function per unit) of skeletal muscle mitochondria to promote substrate oxidation, however, there remain key gaps in understanding the underlying mechanisms during initial training adaptations. We used short-term high-intensity interval training (HIIT) to determine changes to mitochondrial respiration and regulatory pathways that occur early in remodeling. Fifteen normal-weight sedentary adults started seven sessions of HIIT over fourteen days and fourteen participants completed the intervention. We collected vastus lateralis biopsies before and 48-hours after HIIT to determine mitochondrial respiration, RNA sequencing, and western blotting for proteins of mitochondrial respiration and degradation via autophagy. HIIT increased respiration per mitochondrial protein for lipid (+23% P=0.020), complex I (+18%, P=0.0015), complex I+II (+14%, P<0.0001) and complex II (+24% P<0.0001). Transcripts that increased with HIIT identified several gene sets of mitochondrial respiration, particularly for complex I, while transcripts that decreased identified pathways of DNA and chromatin remodeling. HIIT lowered protein abundance of autophagy markers for p62 (-19%, P=0.012) and LC3 II/I (-20%, P=0.004) in whole-tissue lysates but not isolated mitochondria. Meal tolerance testing revealed HIIT increased the change in whole-body respiratory exchange ratio and lowered cumulative plasma insulin concentrations. Gene transcripts and respiratory function indicate remodeling of mitochondria within 2 weeks of HIIT. Overall changes are consistent with increased protein quality driving rapid improvements in substrate oxidation.

Keywords:  HIIT; exercise; mitochondrial respiration; skeletal muscle

DOI:  https://doi.org/10.1152/japplphysiol.00467.2022
Eur J Appl Physiol. 2023 Jan 06.

Mitochondrial response to inactivity-induced muscle disuse and exercise training.

Nicolas J Pillon.

DOI: https://doi.org/10.1007/s00421-022-05120-0
Antioxid Redox Signal. 2023 Jan 03.

NRF2 and its targets in skeletal muscle repair and regeneration.

Agnieszka Loboda, Jozef Dulak.

SIGNIFICANCE: Skeletal muscles have a robust regenerative capacity in response to acute and chronic injuries. Muscle repair and redox homeostasis are intimately linked: increased generation of reactive oxygen species leads to cellular dysfunction and contributes to muscle wasting and progression of muscle diseases. In exemplary muscle disease, Duchenne muscular dystrophy (DMD), caused by mutations in the DMD gene that encodes the muscle structural protein dystrophin, the regeneration machinery is severely compromised, while oxidative stress contributes to the progression of the disease. The nuclear factor erythroid 2-related factor 2 (NRF2) and its target genes, including heme oxygenase-1 (HO-1), provide protective mechanisms against oxidative insults.
RECENT ADVANCES: Relevant advances have been evolving in recent years in understanding the mechanisms by which NRF2 regulates processes that contribute to effective muscle regeneration. To this end, pathways related to muscle satellite cell differentiation, oxidative stress, mitochondrial metabolism, inflammation, fibrosis, and angiogenesis have been studied. The regulatory role of NRF2 in skeletal muscle ferroptosis has been also suggested. Animal studies have shown that NRF2 pathway activation can stop or reverse skeletal muscle pathology, especially when endogenous stress defence mechanisms are imbalanced.
CRITICAL ISSUES: Despite the growing recognition of NRF2 as a factor that regulates various aspects of muscle regeneration, the mechanistic impact on muscle pathology in various models of muscle injury remains imprecise.
FUTURE DIRECTIONS: Further studies are necessary to fully uncover the role of NRF2 in muscle regeneration, both in physiological and pathological conditions, and to investigate the possibilities for development of new therapeutic modalities.

DOI: https://doi.org/10.1089/ars.2022.0208
Theranostics. 2023 ;13(1): 374-390

Ablation of NLRP3 inflammasome attenuates muscle atrophy via inhibiting pyroptosis, proteolysis and apoptosis following denervation.

Zongqi You, Xinying Huang, Yaoxian Xiang, Junxi Dai, Lei Xu, Junjian Jiang, Jianguang Xu.

  Rationale: The inflammasome has been widely reported to be involved in various myopathies, but little is known about its role in denervated muscle. Here, we explored the role of NLRP3 inflammasome activation in experimental models of denervation in vitro and in vivo. Methods: Employing muscular NLRP3 specific knock-out (NLRP3 cKO) mice, we evaluated the effects of the NLRP3 inflammasome on muscle atrophy in vivo in muscle-specific NLRP3 conditional knockout (cKO) mice subjected to sciatic nerve transection and in vitro in cells incubated with NLRP3 inflammasome activator (NIA). To evaluate the underlying mechanisms, samples were collected at different time points for RNA-sequencing (RNA-seq), and the interacting molecules were comprehensively analysed. Results : In the experimental model, NLRP3 inflammasome activation after denervation led to pyroptosis and upregulation of MuRF1 and Atrogin-1 expression, facilitating ubiquitin-proteasome system (UPS) activation, which was responsible for muscle proteolysis. Conversely, genetic knockout of NLRP3 in muscle inhibited pyroptosis-associated protein expression and significantly ameliorated muscle atrophy. Furthermore, cotreatment with shRNA-NLRP3 markedly attenuated NIA-induced C2C12 myotube pyroptosis and atrophy. Intriguingly, inhibition of NLRP3 inflammasome activation significantly suppressed apoptosis. Conclusions: These in vivo and in vitro findings demonstrate that during denervation, the NLRP3 inflammasome is activated and stimulates muscle atrophy via pyroptosis, proteolysis and apoptosis, suggesting that it may contribute to the pathogenesis of neuromuscular diseases.

Keywords:  NLRP3 inflammasome; apoptosis; denervation; muscle atrophy; proteolysis; pyroptosis

DOI:  https://doi.org/10.7150/thno.74831
Proc Natl Acad Sci U S A. 2023 Jan 10. 120(2): e2204750120

Exercise preserves physical fitness during aging through AMPK and mitochondrial dynamics.

Juliane Cruz Campos, Luiz Henrique Marchesi Bozi, Barbara Krum, Luiz Roberto Grassmann Bechara, Nikolas Dresch Ferreira, Gabriel Santos Arini, Rudá Prestes Albuquerque, Annika Traa, Takafumi Ogawa, Alexander M van der Bliek, Afshin Beheshti, Edward T Chouchani, Jeremy M Van Raamsdonk, T Keith Blackwell, Julio Cesar Batista Ferreira.

  Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size, and function. Here we have investigated the role of mitochondrial dynamics during exercise in the model organism Caenorhabditis elegans. We show that in body-wall muscle, a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and physical fitness decline that occur with aging. Maintenance of proper mitochondrial dynamics is essential for physical fitness, its enhancement by exercise training, and exercise-induced remodeling of the proteome. Surprisingly, among the long-lived genotypes we analyzed (isp-1,nuo-6, daf-2, eat-2, and CA-AAK-2), constitutive activation of AMP-activated protein kinase (AMPK) uniquely preserves physical fitness during aging, a benefit that is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for physical fitness to be enhanced by exercise, with our findings together suggesting that exercise may enhance muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining physical fitness and exercise responsiveness during aging and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging.

Keywords:  C. elegans; aging; exercise; mitochondrial fission; mitochondrial fusion

DOI:  https://doi.org/10.1073/pnas.2204750120
J Cachexia Sarcopenia Muscle. 2023 Jan 05.

Mitochondria transplant therapy improves regeneration and restoration of injured skeletal muscle.

Stephen E Alway, Hector G Paez, Christopher R Pitzer, Peter J Ferrandi, Mohammad Moshahid Khan, Junaith S Mohamed, James A Carson, Michael R Deschenes.

   BACKGROUND: Injection of exogenous mitochondria has been shown to improve the ischaemia-damaged myocardium, but the effect of mitochondrial transplant therapy (MTT) to restore skeletal muscle mass and function has not been tested following neuromuscular injury. Therefore, we tested the hypothesis that MTT would improve the restoration of muscle function after injury.
METHODS: BaCl2 was injected into the gastrocnemius muscle of one limb of 8-12-week-old C57BL/6 mice to induce damage without injury to the resident stem cells. The contralateral gastrocnemius muscle was injected with phosphate-buffered saline (PBS) and served as the non-injured intra-animal control. Mitochondria were isolated from donor mice. Donor mitochondria were suspended in PBS or PBS without mitochondria (sham treatment) and injected into the tail vein of BaCl2 injured mice 24 h after the initial injury. Muscle repair was examined 7, 14 and 21 days after injury.
RESULTS: MTT did not increase systemic inflammation in mice. Muscle mass 7 days following injury was 21.9 ± 2.1% and 17.4 ± 1.9% lower (P < 0.05) in injured as compared with non-injured intra-animal control muscles in phosphate-buffered saline (PBS)- and MTT-treated animals, respectively. Maximal plantar flexor muscle force was significantly lower in injured as compared with uninjured muscles of PBS-treated (-43.4 ± 4.2%, P < 0.05) and MTT-treated mice (-47.7 ± 7.3%, P < 0.05), but the reduction in force was not different between the experimental groups. The percentage of collagen and other non-contractile tissue in histological muscle cross sections, was significantly greater in injured muscles of PBS-treated mice (33.2 ± 0.2%) compared with MTT-treated mice (26.5 ± 0.2%) 7 days after injury. Muscle wet weight and maximal muscle force from injured MTT-treated mice had recovered to control levels by 14 days after the injury. However, muscle mass and force had not improved in PBS-treated animals by 14 days after injury. The non-contractile composition of the gastrocnemius muscle tissue cross sections was not different between control, repaired PBS-treated and repaired MTT-treated mice 14 days after injury. By 21 days following injury, PBS-treated mice had fully restored gastrocnemius muscle mass of the injured muscle to that of the uninjured muscle, although maximal plantar flexion force was still 19.4 ± 3.7% (P < 0.05) lower in injured/repaired gastrocnemius as compared with uninjured intra-animal control muscles.
CONCLUSIONS: Our results suggest that systemic mitochondria delivery can enhance the rate of muscle regeneration and restoration of muscle function following injury.

Keywords:  Mitochondria; Muscle fibre types; Muscle force; Muscle injury; Regeneration

DOI:  https://doi.org/10.1002/jcsm.13153
Acta Biochim Biophys Sin (Shanghai). 2022 Nov 25. 54(11): 1684-1693

Linc-RAM is a metabolic regulator maintaining whole-body energy homeostasis in mice.

Qianying Zhang, Lili Zhai, Qian Chen, Yixia Zhao, Ruiting Wang, Hu Li, Tian Gao, Meihong Chen, Dahai Zhu, Yong Zhang.

  Long noncoding RNAs (lncRNAs) are known to have profound functions in regulating cell fate specification, cell differentiation, organogenesis, and disease, but their physiological roles in controlling cellular metabolism and whole-body metabolic homeostasis are less well understood. We previously identified a skeletal muscle-specific long intergenic noncoding RNA (linc-RNA) activator of myogenesis, Linc-RAM, which enhances muscle cell differentiation during development and regeneration. Here, we report that Linc-RAM exerts a physiological function in regulating skeletal muscle metabolism and the basal metabolic rate to maintain whole-body metabolic homeostasis. We first demonstrate that Linc-RAM is preferentially expressed in type-II enriched glycolytic myofibers, in which its level is more than 60-fold higher compared to that in differentiated myotubes. Consistently, genetic deletion of the Linc-RAM gene in mice increases the expression levels of genes encoding oxidative fiber versions of myosin heavy chains and decreases those of genes encoding rate-limiting enzymes for glycolytic metabolism. Physiologically, Linc-RAM-knockout mice exhibit a higher basal metabolic rate, elevated insulin sensitivity and reduced fat deposition compared to their wild-type littermates. Together, our findings indicate that Linc-RAM is a metabolic regulator of skeletal muscle metabolism and may represent a potential pharmaceutical target for preventing and/or treating metabolic diseases, including obesity.

Keywords:  Linc-RAM; basal metabolic rate; long noncoding RNA; metabolic homeostasis; muscle fiber type

DOI:  https://doi.org/10.3724/abbs.2022170
Cell Tissue Res. 2023 Jan 05.

lncRNA UCA1 inhibits mitochondrial dysfunction of skeletal muscle in type 2 diabetes mellitus by sequestering miR-143-3p to release FGF21.

Sha Huang, Kai Wu, Bingfa Li, Yuan Liu.

  Increasing evidence suggests that insulin resistance in type 2 diabetes mellitus (T2DM) is associated with mitochondrial dysfunction in skeletal muscle, while the underlying molecular mechanisms remain elusive. This study aims to construct a ceRNA regulatory network that is involved in mitochondrial dysfunction of skeletal muscle in T2DM. Based on GEO database analysis, differentially expressed lncRNA and mRNA profiles were identified in skeletal muscle tissues of T2DM. Next, LASSO regression analysis was conducted to predict the key lncRNAs related to T2DM, which was validated by receiver operating characteristic (ROC) analysis. Moreover, the miRNAs related to skeletal muscle in T2DM were identified by WGCNA, followed by construction of gene-gene interaction network and GO and KEGG enrichment analyses. It was found that 12 lncRNAs and 6 miRNAs were related to skeletal muscle in T2DM. Moreover, the lncRNA-miRNA-mRNA ceRNA network involving UCA1, miR-143-3p, and FGF21 was constructed. UCA1, and FGF21 were downregulated, while miR-143-3p was upregulated in skeletal muscle cells (SkMCs) exposed to palmitic acid. Additionally, ectopic expression experiments were performed in SkMCs to confirm the effects of UCA1/miR-143-3p/FGF21 on mitochondrial dysfunction by determining mitochondrial ROS, oxygen consumption rate (OCR), membrane potential, and ATP level. Overexpression of miR-143-3p increased ROS accumulation and reduced the OCR, fluorescence ratio of JC-1, and ATP level, which were reversed by upregulation of UCA1 or FGF21. Collectively, lncRNA UCA1 inhibited mitochondrial dysfunction of skeletal muscle in T2DM by sequestering miR-143-3p away from FGF21, therefore providing a potential therapeutic target for alleviating mitochondrial dysfunction of skeletal muscle in T2DM.

Keywords:  FGF21; Mitochondrial dysfunction; Skeletal muscle; Type 2 diabetes mellitus; ceRNA regulatory network; lncRNA UCA1; miR-143-3p

DOI:  https://doi.org/10.1007/s00441-022-03733-7
Nat Commun. 2023 Jan 05. 14(1): 80

Adipose tissue is a source of regenerative cells that augment the repair of skeletal muscle after injury.

Quentin Sastourné-Arrey, Maxime Mathieu, Xavier Contreras, Sylvie Monferran, Virginie Bourlier, Marta Gil-Ortega, Enda Murphy, Claire Laurens, Audrey Varin, Christophe Guissard, Corinne Barreau, Mireille André, Noémie Juin, Marie Marquès, Benoit Chaput, Cédric Moro, Donal O'Gorman, Louis Casteilla, Amandine Girousse, Coralie Sengenès.

Fibro-adipogenic progenitors (FAPs) play a crucial role in skeletal muscle regeneration, as they generate a favorable niche that allows satellite cells to perform efficient muscle regeneration. After muscle injury, FAP content increases rapidly within the injured muscle, the origin of which has been attributed to their proliferation within the muscle itself. However, recent single-cell RNAseq approaches have revealed phenotype and functional heterogeneity in FAPs, raising the question of how this differentiation of regenerative subtypes occurs. Here we report that FAP-like cells residing in subcutaneous adipose tissue (ScAT), the adipose stromal cells (ASCs), are rapidly released from ScAT in response to muscle injury. Additionally, we find that released ASCs infiltrate the damaged muscle, via a platelet-dependent mechanism and thus contribute to the FAP heterogeneity. Moreover, we show that either blocking ASCs infiltration or removing ASCs tissue source impair muscle regeneration. Collectively, our data reveal that ScAT is an unsuspected physiological reservoir of regenerative cells that support skeletal muscle regeneration, underlining a beneficial relationship between muscle and fat.

DOI: https://doi.org/10.1038/s41467-022-35524-7
Acta Physiol (Oxf). 2023 Jan 06. e13924

15 N-labelled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production.

Stefan Kadach, Ji Won Park, Zdravko Stoyanov, Matthew I Black, Anni Vanhatalo, Mark Burnley, Peter J Walter, Hongyi Cai, Alan N Schechter, Barbora Piknova, Andrew M Jones.

   AIM: Dietary nitrate (NO3 - ) supplementation increases nitric oxide bioavailability and can enhance exercise performance. We investigated the distribution and metabolic fate of ingested NO3 - at rest and during exercise with a focus on skeletal muscle.
METHODS: In a randomised, crossover study, ten healthy volunteers consumed 12.8 mmol 15 N-labelled potassium nitrate (K15 NO3 ; NIT) or potassium chloride placebo (PLA). Muscle biopsies were taken at baseline, at 1-h and 3-h post-supplement ingestion, and immediately following the completion of 60 maximal intermittent contractions of the knee extensors. Muscle, plasma, saliva and urine samples were analysed using chemiluminescence to determine absolute [NO3 - ] and [NO2 - ], and by mass spectrometry to determine the proportion of NO3 - and NO2 - that was 15 N-labelled.
RESULTS: Neither muscle [NO3 - ] nor [NO2 - ] were altered by PLA. Following NIT, muscle [NO3 - ] (but not [NO2 - ]) was elevated at 1-h (from ~35 to 147 nmol.g-1 , P<0.001) and 3-h, with almost all of the increase being 15 N-labelled. There was a significant reduction in 15 N-labelled muscle [NO3 - ] from pre- to post-exercise. Relative to PLA, mean muscle torque production was ~7% greater during the first 18 contractions following NIT. This improvement in torque was correlated with the pre-exercise 15 N-labelled muscle [NO3 - ] and the magnitude of decline in 15 N-labelled muscle [NO3 - ] during exercise (r=0.66 and r=0.62, respectively; P<0.01).
CONCLUSION: This study shows, for the first time, that skeletal muscle rapidly takes up dietary NO3 - , the elevated muscle [NO3 - ] following NO3 - ingestion declines during exercise, and muscle NO3 - dynamics are associated with enhanced torque production during maximal intermittent muscle contractions.

Keywords:  contraction; exercise; metabolism; nitric oxide; nitrite; performance

DOI:  https://doi.org/10.1111/apha.13924
Subcell Biochem. 2023 ;102 365-377

Ageing Skeletal Muscle: The Ubiquitous Muscle Stem Cell.

Claire E Stewart.

  In 1999, in a review by Beardsley, the potential of adult stem cells, in repair and regeneration was heralded (Beardsley Sci Am 281:30-31, 1999). Since then, the field of regenerative medicine has grown exponentially, with the capability of restoring or regenerating the function of damaged, diseased or aged human tissues being an underpinning motivation. If successful, stem cell therapies offer the potential to treat, for example degenerative diseases. In the subsequent 20 years, extensive progress has been made in the arena of adult stem cells (for a recent review see (Zakrzewski et al. Stem Cell Res Ther 10:68, 2019)). Prior to the growth of the adult stem cell research arena, much focus had been placed on the potential of embryonic stem cells (ESCs). The first research revealing the potential of these cells was published in 1981, when scientists reported the ability of cultured stem cells from murine embryos, to not only self-renew, but to also become all cells of the three germ layers of the developing embryo (Evans and Kaufman Nature 292:154-156, 1981), (Martin Proc Natl Acad Sci U S A 78:7634-7638, 1981). It took almost 20 years, following these discoveries, for this technology to translate to human ESCs, using donated human embryos. In 1998, Thomson et al. reported the creation of the first human embryonic cell line (Thomson et al. Science 282:1145-1147, 1998). However, research utilising human ESCs was hampered by ethical and religious constraints and indeed in 2001 George W. Bush restricted US research funding to human ESCs, which had already been banked. The contentious nature of this arena perhaps facilitated the use of and the research potential for adult stem cells. It is beyond the scope of this review to focus on ESCs, although their potential for enhancing our understanding of human development is huge (for a recent review see (Cyranoski Nature 555:428-430, 2018)). Rather, although ESCs and their epigenetic regulation will be introduced for background understanding, the focus will be on stem cells more generally, the role of epigenetics in stem cell fate, skeletal muscle, skeletal muscle stem cells, the impact of ageing on muscle wasting and the mechanisms underpinning loss, with a focus on epigenetic adaptation.

Keywords:  Ageing; Epigenetics; Muscle; Myoblast; Sarcopenia; Stem cell

DOI:  https://doi.org/10.1007/978-3-031-21410-3_14
Acta Physiol (Oxf). 2023 Jan 04. e13921

Tissue-specific effects of exercise as NAD+ -boosting strategy: current knowledge and future perspectives.

David Walzik, Wiebke Jonas, Niklas Joisten, Sergen Belen, Rob C I Wüst, Gilles Guillemin, Philipp Zimmer.

  Nicotinamide adenine dinucleotide (NAD+ ) is an evolutionarily highly conserved coenzyme with multi-faceted cell functions, including energy metabolism, molecular signaling processes, epigenetic regulation, and DNA repair. Since the discovery that lower NAD+ levels are a shared characteristic of various diseases and ageing per se, several NAD+ -boosting strategies have emerged. Other than pharmacological and nutritional approaches, exercise is thought to restore NAD+ homeostasis through metabolic adaption to chronically recurring states of increased energy demand. In this review we discuss the impact of acute exercise and exercise training on tissue-specific NAD+ metabolism of rodents and humans to highlight the potential value as NAD+ -boosting strategy. By interconnecting results from different investigations, we aim to draw attention to tissue-specific alterations in NAD+ metabolism and the associated implications for whole-body NAD+ homeostasis. Acute exercise led to profound alterations of intracellular NAD+ metabolism in various investigations, with the magnitude and direction of changes being strongly dependent on the applied exercise modality, cell type, and investigated animal model or human population. Exercise training elevated NAD+ levels and NAD+ metabolism enzymes in various tissues. Based on these results, we discuss molecular mechanisms that might connect acute exercise-induced disruptions of NAD+ /NADH homeostasis to chronic exercise adaptions in NAD+ metabolism. Taking this hypothesis-driven approach, we hope to inspire future research on the molecular mechanisms of exercise as NAD+ -modifying lifestyle intervention, thereby elucidating the potential therapeutic value in NAD+ -related pathologies.

Keywords:  NAD+; NADH; Nicotinamide adenine dinucleotide; exercise; health; metabolism

DOI:  https://doi.org/10.1111/apha.13921
Front Physiol. 2022 ;13 1113860

Editorial: Untangling energy metabolism in skeletal muscle: From physiology to pharmacology.

Sergej Pirkmajer, Pablo M Garcia-Roves, Arild C Rustan, Alexander V Chibalin.



Keywords:  AMPK; angiotensin-converting enzyme (ACE); double-stranded RNA-activated protein kinase; energy metabolism; metformin; myosin; obesity; skeletal muscle

DOI:  https://doi.org/10.3389/fphys.2022.1113860
Sci Adv. 2023 Jan 04. 9(1): eadd3216

Lactate metabolism is essential in early-onset mitochondrial myopathy.

Zhenkang Chen, Bogdan Bordieanu, Rushendhiran Kesavan, Nicholas P Lesner, Siva Sai Krishna Venigalla, Spencer D Shelton, Ralph J DeBerardinis, Prashant Mishra.

Myopathies secondary to mitochondrial electron transport chain (ETC) dysfunction can result in devastating disease. While the consequences of ETC defects have been extensively studied in culture, little in vivo data are available. Using a mouse model of severe, early-onset mitochondrial myopathy, we characterized the proteomic, transcriptomic, and metabolic characteristics of disease progression. Unexpectedly, ETC dysfunction in muscle results in reduced expression of glycolytic enzymes in our animal model and patient muscle biopsies. The decrease in glycolysis was mediated by loss of constitutive Hif1α signaling, down-regulation of the purine nucleotide cycle enzyme AMPD1, and activation of AMPK. In vivo isotope tracing experiments indicated that myopathic muscle relies on lactate import to supply central carbon metabolites. Inhibition of lactate import reduced steady-state levels of tricarboxylic acid cycle intermediates and compromised the life span of myopathic mice. These data indicate an unexpected mode of metabolic reprogramming in severe mitochondrial myopathy that regulates disease progression.

DOI: https://doi.org/10.1126/sciadv.add3216
J Orthop Translat. 2023 Mar;39 12-20

Is dexamethasone-induced muscle atrophy an alternative model for naturally aged sarcopenia model?

Belle Yu-Hsuan Wang, Allen Wei-Ting Hsiao, Nicodemus Wong, Yi-Fan Chen, Chien-Wei Lee, Wayne Yuk Wai Lee.

   Background: Primary sarcopenia is usually known as age-related skeletal muscle loss; however, other factors like endocrine, lifestyle and inflammation can also cause muscle loss, known as secondary sarcopenia. Although many studies have used different sarcopenia animal models for exploring the underlying mechanism and therapeutic approaches for sarcopenia, limited study has provided evidence of the relevance of these animal models. This study aims to investigate the similarity and difference in muscle qualities between primary and secondary sarcopenia mice models, using naturally aged mice and dexamethasone-induced mice.
Methods: 21-month-old mice were used as naturally aged primary sarcopenia mice and 3-month-old mice received daily intraperitoneal injection of dexamethasone (20 mg/ kg body weight) for 10 days were used as secondary sarcopenia model. This study provided measurements for muscle mass and functions, including Dual-energy X-ray absorptiometry (DXA) scanning, handgrip strength test and treadmill running to exhaustion test. Besides, muscle contraction, muscle fibre type measurements and gene expression were also performed to provide additional information on muscle qualities.
Results: The results suggest two sarcopenia animal models shared a comparable decrease in forelimb lean mass, muscle fibre size, grip strength and muscle contraction ability. Besides, the upregulation of protein degradation genes was also observed in two sarcopenia animal models. However, only primary sarcopenia mice were identified with an early stage of mtDNA deletion.
Conclusion: Collectively, this study evaluated that the dexamethasone-induced mouse model could be served as an alternative model for primary sarcopenia, according to the comparable muscle mass and functional changes. However, whether dexamethasone-induced mice can be used as an animal model when studying the molecular mechanisms of sarcopenia needs to be carefully evaluated.
The translational potential of this article: The purpose of sarcopenia research is to investigate appropriate treatments for reversing the loss of skeletal muscle mass and functions. Using animal models for the preclinical study could predict the safety and efficacy of the treatments. This study compared the typical age-related sarcopenia mice model and dexamethasone-induced secondary sarcopenia mice to provide evidence of the pathological and functional changes in the mice models.

Keywords:  Animal model; Dexamethasone; Sarcopenia; Skeletal muscle function; Skeletal muscle mass

DOI:  https://doi.org/10.1016/j.jot.2022.11.005
iScience. 2023 Jan 20. 26(1): 105775

Diverse effector and regulatory functions of fibro/adipogenic progenitors during skeletal muscle fibrosis in muscular dystrophy.

Xingyu Wang, Jianming Chen, Sachiko T Homma, Yinhang Wang, Gregory R Smith, Frederique Ruf-Zamojski, Stuart C Sealfon, Lan Zhou.

  Fibrosis is a prominent pathological feature of skeletal muscle in Duchenne muscular dystrophy (DMD). The commonly used disease mouse model, mdx 5cv , displays progressive fibrosis in the diaphragm but not limb muscles. We use single-cell RNA sequencing to determine the cellular expression of the genes involved in extracellular matrix (ECM) production and degradation in the mdx 5cv diaphragm and quadriceps. We find that fibro/adipogenic progenitors (FAPs) are not only the primary source of ECM but also the predominant cells that express important ECM regulatory genes, including Ccn2, Ltbp4, Mmp2, Mmp14, Timp1, Timp2, and Loxs. The effector and regulatory functions are exerted by diverse FAP clusters which are different between diaphragm and quadriceps, indicating their activation by different tissue microenvironments. FAPs are more abundant in diaphragm than in quadriceps. Our findings suggest that the development of anti-fibrotic therapy for DMD should target not only the ECM production but also the pro-fibrogenic regulatory functions of FAPs.

Keywords:  Genetics; Musculoskeletal medicine

DOI:  https://doi.org/10.1016/j.isci.2022.105775
STAR Protoc. 2023 Jan 03. pii: S2666-1667(22)00865-6. [Epub ahead of print]4(1): 101985

Protocol to assess arteriovenous differences across the liver and hindlimb muscles in mice following treadmill exercise.

Stephen P Ashcroft, Sara L Jepsen, Amy M Ehrlich, Jonas T Treebak, Jens J Holst, Juleen R Zierath.

  The tissue-specific release and uptake of metabolites in response to exercise is incompletely understood. Here, we detail a protocol to assess arteriovenous differences across the liver and hindlimb muscles in response to treadmill exercise in mice. We describe steps for the treadmill running of mice and the region-specific sampling of blood from the liver and hindlimb. This procedure is particularly relevant for the study of tissue-specific metabolism in response to exercise. For complete details on the use and execution of this protocol, please refer to Sato et al. (2022).1.

Keywords:  Behavior; Health Sciences; Metabolism; Model Organisms

DOI:  https://doi.org/10.1016/j.xpro.2022.101985
Cell. 2022 Dec 26. pii: S0092-8674(22)01377-0. [Epub ahead of print]

Hallmarks of aging: An expanding universe.

Carlos López-Otín, Maria A Blasco, Linda Partridge, Manuel Serrano, Guido Kroemer.

Aging is driven by hallmarks fulfilling the following three premises: (1) their age-associated manifestation, (2) the acceleration of aging by experimentally accentuating them, and (3) the opportunity to decelerate, stop, or reverse aging by therapeutic interventions on them. We propose the following twelve hallmarks of aging: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, disabled macroautophagy, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, chronic inflammation, and dysbiosis. These hallmarks are interconnected among each other, as well as to the recently proposed hallmarks of health, which include organizational features of spatial compartmentalization, maintenance of homeostasis, and adequate responses to stress.

DOI: https://doi.org/10.1016/j.cell.2022.11.001