bims-moremu 2024-01-07 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024‒01‒07
28 papers selected by
Anna Vainshtein, Craft Science Inc.

Three-dimensional mapping of ultrasound-derived skeletal muscle shear wave velocity.
The YBX3 RNA-binding protein post-transcriptionally controls SLC1A5 mRNA in proliferating and differentiating skeletal muscle cells.
Alterations in neuromuscular junction morphology with ageing and endurance training modulate neuromuscular transmission and myofibre composition.
Acute exercise modulates Trim63 and Bmal1 in the skeletal muscle of IL-10 knockout mice.
The MuSK-BMP pathway maintains myofiber size in slow muscle through regulation of Akt-mTOR signaling.
Skeletal Muscle Satellite Cells Co-Opt the Tenogenic Gene Scleraxis to Instruct Regeneration.
3D Mitochondrial Structure in Aging Human Skeletal Muscle: Insights into MFN-2 Mediated Changes.
CHCHD4-TRIAP1 regulation of innate immune signaling mediates skeletal muscle adaptation to exercise.
Retention of stress susceptibility in the mdx mouse model of Duchenne muscular dystrophy after PGC-1α overexpression or ablation of IDO1 or CD38.
Mitochondrial-derived microprotein MOTS-c attenuates immobilization-induced skeletal muscle atrophy by suppressing lipid infiltration.
The neuronal nitric oxide synthase expression increases during satellite cell-derived primary myoblasts differentiation.
Cannabinoids improve mitochondrial function in skeletal muscle of exhaustive exercise training rats by inhibiting mitophagy through the Pink1/Parkin and Bnip3 pathways.
The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix.
Physiological determinants of mechanical efficiency during advanced ageing and disuse.
Extracellular vesicles from obese and diabetic mouse plasma alter C2C12 myotube glucose uptake and gene expression.
Loss of lysosomal acid lipase results in mitochondrial dysfunction and fiber switch in skeletal muscles of mice.
Population-scale skeletal muscle single-nucleus multi-omic profiling reveals extensive context specific genetic regulation.
Motor neuron activity enhances the proteomic stress caused by autophagy defects in the target muscle.
Proteomic analysis shows decreased type I fibers and ectopic fat accumulation in skeletal muscle from women with PCOS.
The ubiquitin-conjugating enzyme UBE2D/eff maintains a youthful proteome and ensures protein quality control during aging.
Combinatorial effects of ion channel mis-splicing as a cause of myopathy in myotonic dystrophy.
Moderate dietary restriction delays the onset of age-associated sarcopenia in Caenorhabditis elegans due to reduced myosin UNC-54 degradation.
Structural and functional interactions between the EF hand domain and S2-S3 loop in the type-1 ryanodine receptor ion channel.
Putrescine promotes MMP9-induced angiogenesis in skeletal muscle through hydrogen peroxide/METTL3 pathway.
Higher resistance training volume offsets muscle hypertrophy non-responsiveness in older individuals.
Verapamil mitigates chloride and calcium bi-channelopathy in a myotonic dystrophy mouse model.
Glucose restriction enhances oxidative fiber formation: A multi-omic signal network involving AMPK and CaMK2.
Editorial: Insights in molecular mechanisms of aging 2022.

Front Bioeng Biotechnol. 2023 ;11 1330301

Three-dimensional mapping of ultrasound-derived skeletal muscle shear wave velocity.

Tobias Götschi, Jess G Snedeker, Daniel P Fitze, Fabio Sarto, Jörg Spörri, Martino V Franchi.

  Introduction: The mechanical properties of skeletal muscle are indicative of its capacity to perform physical work, state of disease, or risk of injury. Ultrasound shear wave elastography conducts a quantitative analysis of a tissue's shear stiffness, but current implementations only provide two-dimensional measurements with limited spatial extent. We propose and assess a framework to overcome this inherent limitation by acquiring numerous and contiguous measurements while tracking the probe position to create a volumetric scan of the muscle. This volume reconstruction is then mapped into a parameterized representation in reference to geometric and anatomical properties of the muscle. Such an approach allows to quantify regional differences in muscle stiffness to be identified across the entire muscle volume assessed, which could be linked to functional implications. Methods: We performed shear wave elastography measurements on the vastus lateralis (VL) and the biceps femoris long head (BFlh) muscle of 16 healthy volunteers. We assessed test-retest reliability, explored the potential of the proposed framework in aggregating measurements of multiple subjects, and studied the acute effects of muscular contraction on the regional shear wave velocity post-measured at rest. Results: The proposed approach yielded moderate to good reliability (ICC between 0.578 and 0.801). Aggregation of multiple subject measurements revealed considerable but consistent regional variations in shear wave velocity. As a result of muscle contraction, the shear wave velocity was elevated in various regions of the muscle; showing pre-to-post regional differences for the radial assessement of VL and longitudinally for BFlh. Post-contraction shear wave velocity was associated with maximum eccentric hamstring strength produced during six Nordic hamstring exercise repetitions. Discussion and Conclusion: The presented approach provides reliable, spatially resolved representations of skeletal muscle shear wave velocity and is capable of detecting changes in three-dimensional shear wave velocity patterns, such as those induced by muscle contraction. The observed systematic inter-subject variations in shear wave velocity throughout skeletal muscle additionally underline the necessity of accurate spatial referencing of measurements. Short high-effort exercise bouts increase muscle shear wave velocity. Further studies should investigate the potential of shear wave elastography in predicting the muscle's capacity to perform work.

Keywords:  biomechanics; elasticity; muscle; shear wave elastography; stiffness; ultrasound

DOI:  https://doi.org/10.3389/fbioe.2023.1330301
J Biol Chem. 2023 Dec 28. pii: S0021-9258(23)02631-5. [Epub ahead of print] 105602

The YBX3 RNA-binding protein post-transcriptionally controls SLC1A5 mRNA in proliferating and differentiating skeletal muscle cells.

Silina Awad, William Skipper, William Vostrejs, Kendall Ozorowski, Kristen Min, Liva Pfuhler, Darshan Mehta, Amy Cooke.

  In humans, skeletal muscles comprise nearly 40% of total body mass, which is maintained throughout adulthood by a balance of muscle protein synthesis and breakdown. Cellular amino acid (AA) levels are critical for these processes, and mammalian cells contain transporter proteins that import AAs to maintain homeostasis. Until recently, the control of transporter regulation has largely been studied at the transcriptional and post-translational levels. However, here we report that the RNA-binding protein YBX3 is critical to sustain intracellular AAs in mouse skeletal muscle cells, which aligns with our recent findings in human cells. We find that YBX3 directly binds the SLC1A5 AA transporter messenger (m)RNA to post-transcriptionally control SLC1A5 expression during skeletal muscle cell differentiation. YBX3 regulation of SLC1A5 requires the 3' untranslated region (UTR). Additionally, intracellular AAs transported by SLC1A5, either directly or indirectly through coupling to other transporters, are specifically reduced when YBX3 is depleted. Further, we find that reduction of the YBX3 protein reduces proliferation and impairs differentiation in skeletal muscle cells, and that YBX3 and SLC1A5 protein expression increase substantially during skeletal muscle differentiation, independently of their respective mRNA levels. Taken together, our findings suggest that YBX3 regulates AA transport in skeletal muscle cells and that its expression is critical to maintain skeletal muscle cell proliferation and differentiation.

Keywords:  3’ untranslated region (UTR); C2C12 myoblasts; RNA-binding protein; SLC1A5; SLC3A2; SLC7A5; YBX3; amino acid transport

DOI:  https://doi.org/10.1016/j.jbc.2023.105602
J Physiol. 2024 Jan 03.

Alterations in neuromuscular junction morphology with ageing and endurance training modulate neuromuscular transmission and myofibre composition.

Tatsuhiro Yamaguchi, Karina Kouzaki, Kazushige Sasaki, Koichi Nakazato.

  Both ageing and exercise training affect the neuromuscular junction (NMJ) structure. Morphological alterations in the NMJ have been considered to influence neuromuscular transmission and myofibre properties, but the direct link between the morphology and function has yet to be established. We measured the neuromuscular transmission, myofibre composition and NMJ structure of 5-month-old (young) and 24-month-old untrained (aged control) and trained (aged trained) mice. Aged trained mice were subjected to 2 months of endurance training before the measurement. Neuromuscular transmission was evaluated in vivo as the ratio of ankle plantar flexion torque evoked by the sciatic nerve stimulation to that by direct muscle stimulation. The torque ratio was significantly lower in aged mice than in young and aged trained mice at high-frequency stimulations, showing a significant positive correlation with voluntary grip strength. The degree of pre- to post-synaptic overlap of the NMJ was also significantly lower in aged mice and positively correlated with the torque ratio. We also found that the proportion of fast-twitch fibres in the soleus muscle decreased with age, and that age-related denervation occurred preferentially in fast-twitch fibres. Age-related denervation and a shift in myofibre composition were partially prevented by endurance training. These results suggest that age-related deterioration of the NMJ structure impairs neuromuscular transmission and alters myofibre composition, but these alterations can be prevented by structural amelioration of NMJ with endurance training. Our findings highlight the importance of the NMJ as a major determinant of age-related deterioration of skeletal muscles and the clinical significance of endurance training as a countermeasure. KEY POINTS: The neuromuscular junction (NMJ) plays an essential role in neuromuscular transmission and the maintenance of myofibre properties. We show that neuromuscular transmission is impaired with ageing but recovered by endurance training, which contributes to alterations in voluntary strength. Neuromuscular transmission is associated with the degree of pre- to post-synaptic overlap of the NMJ. Age-related denervation of fast-twitch fibres and a shift in myofibre composition toward a slower phenotype are partially prevented by endurance training. Our study provides substantial evidence that age-related and exercise-induced alterations in neuromuscular transmission and myofibre properties are associated with morphological changes in the NMJ.

Keywords:  age; denervation; exercise; motor unit; muscle strength; skeletal muscle

DOI:  https://doi.org/10.1113/JP285143
Cytokine. 2023 Dec 29. pii: S1043-4666(23)00362-9. [Epub ahead of print]175 156484

Acute exercise modulates Trim63 and Bmal1 in the skeletal muscle of IL-10 knockout mice.

Gustavo Eduardo da Mata, Rafael Bricola, Danielle Naves Ribeiro, Fernando M Simabuco, José R Pauli, Ellen C de Freitas, Eduardo R Ropelle, Adelino S R da Silva, Ana P Pinto.

  The anti-inflammatory role of physical exercise is mediated by interleukin 10 (IL-10), and their release is possibly upregulated in response to IL-6. Previous studies demonstrated that mice lacking IL-6 (IL-6 KO mice) exhibited diminished exercise tolerance, and reduced strength. Rev-erbα, a transcriptional suppressor involved in circadian rhythm, has been discovered to inhibit the expression of genes linked to bodily functions, encompassing inflammation and metabolism. It also plays a significant role in skeletal muscle and exercise performance capacity. Given the potential association between Rev-erbα and the immune system and the fact that both pathways are modulated following acute aerobic exercise, we examined the physical performance of IL-10 KO mice and analyzed the modulation of the atrophy and Rev-erbα pathways in the muscle of wild type (WT) and IL-10 KO mice following one session of acute exercise. For each phenotype, WT and IL-10 KO were divided into two subgroups (Control and Exercise). The acute exercise session started at 6 m/min, followed by 3 m/min increments every 3 min until animal exhaustion. Two hours after the end of the exercise protocol, the gastrocnemius muscle was removed and prepared for the reverse transcription-quantitative polymerase chain reaction (RT-q-PCR) and immunoblotting technique. In summary, compared to WT, the IL-10 KO animals showed lower body weight and grip strength in the baseline. The IL-10 control group presented a lower protein content of BMAL1. After the exercise protocol, the IL-10 KO group had higher mRNA levels of Trim63 (atrophy signaling pathway) and lower mRNA levels of Clock and Bmal1 (Rev-erbα signaling pathway). This is the first study showing the relationship between Rev-erbα and atrophy in IL-10 KO mice. Also, we accessed a public database that analyzed the gastrocnemius of MuRF KO mice submitted to two processes of muscle atrophy, a denervation surgery and dexamethasone (Dexa) injections. Independently of knockout, the denervation demonstrated lower Nr1d1 levels. In conclusion, IL-10 seems to be a determinant in the Rev-erbα pathway and atrophy after acute exercise, with no modulation in the baseline state.

Keywords:  Atrophy; Immunology; Molecular pathways; Nr1d1; Strength

DOI:  https://doi.org/10.1016/j.cyto.2023.156484
Skelet Muscle. 2024 Jan 03. 14(1): 1

The MuSK-BMP pathway maintains myofiber size in slow muscle through regulation of Akt-mTOR signaling.

Diego Jaime, Lauren A Fish, Laura A Madigan, Chengjie Xi, Giorgia Piccoli, Madison D Ewing, Bert Blaauw, Justin R Fallon.

  Myofiber size regulation is critical in health, disease, and aging. MuSK (muscle-specific kinase) is a BMP (bone morphogenetic protein) co-receptor that promotes and shapes BMP signaling. MuSK is expressed at all neuromuscular junctions and is also present extrasynaptically in the mouse soleus, whose predominantly oxidative fiber composition is akin to that of human muscle. To investigate the role of the MuSK-BMP pathway in vivo, we generated mice lacking the BMP-binding MuSK Ig3 domain. These ∆Ig3-MuSK mice are viable and fertile with innervation levels comparable to wild type. In 3-month-old mice, myofibers are smaller in the slow soleus, but not in the fast tibialis anterior (TA). Transcriptomic analysis revealed soleus-selective decreases in RNA metabolism and protein synthesis pathways as well as dysregulation of IGF1-Akt-mTOR pathway components. Biochemical analysis showed that Akt-mTOR signaling is reduced in soleus but not TA. We propose that the MuSK-BMP pathway acts extrasynaptically to maintain myofiber size in slow muscle by promoting protein synthetic pathways including IGF1-Akt-mTOR signaling. These results reveal a novel mechanism for regulating myofiber size in slow muscle and introduce the MuSK-BMP pathway as a target for promoting muscle growth and combatting atrophy.

Keywords:  Atrophy; BMP; Cachexia; IGF1; MuSK; Muscle fiber types; Slow muscle; mTOR

DOI:  https://doi.org/10.1186/s13395-023-00329-9
bioRxiv. 2023 Dec 11. pii: 2023.12.10.570982. [Epub ahead of print]

Skeletal Muscle Satellite Cells Co-Opt the Tenogenic Gene Scleraxis to Instruct Regeneration.

Yun Bai, Tyler Harvey, Minjie Hu, Colin Bilyou, Chen-Ming Fan.

Skeletal muscles connect bones and tendons for locomotion and posture. Understanding the regenerative processes of muscle, bone and tendon is of importance to basic research and clinical applications. Despite their interconnections, distinct transcription factors have been reported to orchestrate each tissue's developmental and regenerative processes. Here we show that Scx expression is not detectable in adult muscle stem cells (also known as satellite cells, SCs) during quiescence. Scx expression begins in activated SCs and continues throughout regenerative myogenesis after injury. By SC-specific Scx gene inactivation (ScxcKO), we show that Scx function is required for SC expansion/renewal and robust new myofiber formation after injury. We combined single-cell RNA-sequencing and CUT&RUN to identify direct Scx target genes during muscle regeneration. These target genes help explain the muscle regeneration defects of ScxcKO, and are not overlapping with Scx -target genes identified in tendon development. Together with a recent finding of a subpopulation of Scx -expressing connective tissue fibroblasts with myogenic potential during early embryogenesis, we propose that regenerative and developmental myogenesis co-opt the Scx gene via different mechanisms.

DOI: https://doi.org/10.1101/2023.12.10.570982
bioRxiv. 2023 Dec 14. pii: 2023.11.13.566502. [Epub ahead of print]

3D Mitochondrial Structure in Aging Human Skeletal Muscle: Insights into MFN-2 Mediated Changes.

Estevão Scudese, Zer Vue, Prassana Katti, Andrea Marshall, Larry Vang, Edgar Garza López, Kit Neikirk, Dominique Stephens, Duane D Hall, Rahmati Rostami, Jian-Qiang Shao, Margaret Mungai, Salma T AshShareef, Innes Hicsasmaz, Sasha Manus, Celestine Wanjalla, Aaron Whiteside, Clintoria Williams, Steven M Damo, Jennifer A Gaddy, Annet Kirabo, Brian Glancy, Estélio Henrique Martin Dantas, André Kinder, Fabiana Scartoni, Matheus Baffi, Melanie R McReynolds, Mark A Phillips, Anthonya Cooper, Sandra A Murray, Vernat Exil, Bret C Mobley, Antentor Hinton.

Sarcopenia is an age-related loss of skeletal muscle, characterized by loss of mass, strength, endurance, and oxidative capacity during aging. Notably, bioenergetics and protein turnover studies have shown that mitochondria mediate this decline in function. Although mitochondrial aging is associated with decreased mitochondrial capacity, the three-dimensional (3D) mitochondrial structure associated with morphological changes in skeletal muscle during aging still requires further elucidation. Although exercise has been the only therapy to mitigate sarcopenia, the mechanisms that govern these changes remain unclear. We hypothesized that aging causes structural remodeling of mitochondrial 3D architecture representative of dysfunction, and this effect is mitigated by exercise. We used serial block-face scanning electron microscopy to image human skeletal tissue samples, followed by manual contour tracing using Amira software for 3D reconstruction and subsequent analysis of mitochondria. We then applied a rigorous in vitro and in vivo exercise regimen during aging. We found that mitochondria became less complex with age. Specifically, mitochondria lost surface area, complexity, and perimeter, indicating age-related declines in ATP synthesis and interaction capacity. Concomitantly, muscle area, exercise capacity, and mitochondrial dynamic proteins showed age-related losses. Exercise stimulation restored mitofusin 2 (MFN2), which we show is required for mitochondrial structure. Furthermore, we show that this pathway is evolutionarily conserved with Marf, the MFN2 ortholog in Drosophila , as Marf knockdown alters mitochondrial morphology and leads to the downregulation of genes regulating mitochondrial processes. Our results define age-related structural changes in mitochondria and further suggest that exercise may mitigate age-related structural decline through modulation of mitofusins.

DOI: https://doi.org/10.1101/2023.11.13.566502
Cell Rep. 2023 Dec 28. pii: S2211-1247(23)01637-6. [Epub ahead of print]43(1): 113626

CHCHD4-TRIAP1 regulation of innate immune signaling mediates skeletal muscle adaptation to exercise.

Jin Ma, Ping-Yuan Wang, Jie Zhuang, Annie Y Son, Alexander K Karius, Abu Mohammad Syed, Masahiro Nishi, Zhichao Wu, Mateus P Mori, Young-Chae Kim, Paul M Hwang.

  Exercise training can stimulate the formation of fatty-acid-oxidizing slow-twitch skeletal muscle fibers, which are inversely correlated with obesity, but the molecular mechanism underlying this transformation requires further elucidation. Here, we report that the downregulation of the mitochondrial disulfide relay carrier CHCHD4 by exercise training decreases the import of TP53-regulated inhibitor of apoptosis 1 (TRIAP1) into mitochondria, which can reduce cardiolipin levels and promote VDAC oligomerization in skeletal muscle. VDAC oligomerization, known to facilitate mtDNA release, can activate cGAS-STING/NFKB innate immune signaling and downregulate MyoD in skeletal muscle, thereby promoting the formation of oxidative slow-twitch fibers. In mice, CHCHD4 haploinsufficiency is sufficient to activate this pathway, leading to increased oxidative muscle fibers and decreased fat accumulation with aging. The identification of a specific mediator regulating muscle fiber transformation provides an opportunity to understand further the molecular underpinnings of complex metabolic conditions such as obesity and could have therapeutic implications.

Keywords:  CHCHD4; CP: Immunology; MyoD; TRIAP1; VDAC; cardiolipin; exercise adaptation; innate immune signaling; mitochondria; mtDNA; skeletal muscle

DOI:  https://doi.org/10.1016/j.celrep.2023.113626
Hum Mol Genet. 2024 Jan 05. pii: ddad206. [Epub ahead of print]

Retention of stress susceptibility in the mdx mouse model of Duchenne muscular dystrophy after PGC-1α overexpression or ablation of IDO1 or CD38.

Erynn E Johnson, W Michael Southern, Baird Doud, Brandon Steiger, Maria Razzoli, Alessandro Bartolomucci, James M Ervasti.

  Duchenne muscular dystrophy (DMD) is a lethal degenerative muscle wasting disease caused by the loss of the structural protein dystrophin with secondary pathological manifestations including metabolic dysfunction, mood and behavioral disorders. In the mildly affected mdx mouse model of DMD, brief scruff stress causes inactivity, while more severe subordination stress results in lethality. Here, we investigated the kynurenine pathway of tryptophan degradation and the nicotinamide adenine dinucleotide (NAD+) metabolic pathway in mdx mice and their involvement as possible mediators of mdx stress-related pathology. We identified downregulation of the kynurenic acid shunt, a neuroprotective branch of the kynurenine pathway, in mdx skeletal muscle associated with attenuated peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) transcriptional regulatory activity. Restoring the kynurenic acid shunt by skeletal muscle-specific PGC-1α overexpression in mdx mice did not prevent scruff -induced inactivity, nor did abrogating extrahepatic kynurenine pathway activity by genetic deletion of the pathway rate-limiting enzyme, indoleamine oxygenase 1. We further show that reduced NAD+ production in mdx skeletal muscle after subordination stress exposure corresponded with elevated levels of NAD+ catabolites produced by ectoenzyme cluster of differentiation 38 (CD38) that have been implicated in lethal mdx response to pharmacological β-adrenergic receptor agonism. However, genetic CD38 ablation did not prevent mdx scruff-induced inactivity. Our data do not support a direct contribution by the kynurenine pathway or CD38 metabolic dysfunction to the exaggerated stress response of mdx mice.

Keywords:  Duchenne muscular dystrophy; NAD+; kynurenine; skeletal muscle; stress physiology

DOI:  https://doi.org/10.1093/hmg/ddad206
Am J Physiol Endocrinol Metab. 2024 Jan 03.

Mitochondrial-derived microprotein MOTS-c attenuates immobilization-induced skeletal muscle atrophy by suppressing lipid infiltration.

Hiroshi Kumagai, Su-Jeong Kim, Brendan Miller, Toshiharu Natsume, Junxiang Wan, Michi Emma Kumagai, Ricardo Ramirez Ii, Shin Hyung Lee, Ayaka Sato, Hemal H Mehta, Kelvin Yen, Pinchas Cohen.

  MOTS-c, a mitochondrial microprotein, has been described as a novel regulator of glucose and lipid metabolism. In addition to its role as a metabolic regulator, MOTS-c prevents skeletal muscle atrophy in high-fat-fed mice. Here, we examined the preventive effect of MOTS-c on skeletal muscle mass using an immobilization-induced muscle atrophy model and explored its underlying mechanisms. Male C57BL/6J mice (10-week-old) were randomly assigned to one of the three experimental groups: non-immobilization control group (sterilized water injection), immobilization control group (sterilized water injection), and immobilization and MOTS-c treated group (15 mg/kg/day MOTS-c injection). We used casting tape for the immobilization experiment. After eight days of the experimental period, skeletal muscle samples were collected and used for the Western blotting, RNA sequencing, lipid, and collagen assays. Immobilization reduced ~15% of muscle mass, while MOTS-c treatment attenuated muscle loss with only a 5% reduction. MOTS-c treatment also normalized phospho-AKT, phospho-FOXO1, and phospho-FOXO3a expression levels, and reduced circulating inflammatory cytokines, such as interleukin-1b (IL-1β), interleukin-6 (IL-6), chemokine C-X-C motif ligand 1 (CXCL1), and monocyte chemoattractant protein 1 (MCP-1), in immobilized mice. An unbiased RNA sequencing and its downstream analyses demonstrated that MOTS-c modified adipogenic-modulating gene expression within the peroxisome proliferator-activated receptors (PPARs) pathway. Supporting this observation, muscle fatty acid levels were lower in the MOTS-c treated group than in the casted-controls. These results suggest that MOTS-c treatment inhibits skeletal muscle lipid infiltration by regulating adipogenesis-related genes and prevents immobilization-induced muscle atrophy.

Keywords:  MOTS-c; Mitochondrial microprotein; immobilization; muscle atrophy; myosteatosis

DOI:  https://doi.org/10.1152/ajpendo.00285.2023
Cell Mol Biol (Noisy-le-grand). 2023 Dec 10. 69(13): 128-133

The neuronal nitric oxide synthase expression increases during satellite cell-derived primary myoblasts differentiation.

Masaki Kusano, Kazuya Sakai, Yuki Tomiga, Ai Ito, Shihoko Nakashima, Yoshinari Uehara, Kentaro Kawanaka, Yasuo Kitajima, Yasuki Higaki.

The neuronal nitric oxide synthase (nNOS; encoded by NOS1)-derived nitric oxide (NO) plays an important role in maintaining skeletal muscle mass. In adult skeletal muscle, nNOS localizes to the cell membrane, cytosol, and nucleus, and regulates muscle hypertrophy and atrophy in various subcellular fractions. However, its role in muscle stem cells (also known as muscle satellite cells), which provide myonuclei for postnatal muscle growth, maintenance, and regeneration, remains unclear. The present study aimed to determine nNOS expression in muscle satellite cell-derived primary myoblasts during differentiation and its DNA methylation levels, an epigenetic modification that controls gene expression. Undifferentiated and differentiated satellite cell-derived primary myoblasts were found to express nNOS. Immunohistochemical analysis revealed that nNOS colocalized with Pax7 (satellite cell marker) only in the undifferentiated myoblasts. Furthermore, nNOS immunoreactivity spread to the cytosol of Pax7-negative differentiated myotube-like cells. The level of Nos1µ mRNA, the main isoform of skeletal muscle nNOS, was increased in differentiated satellite cell-derived primary myoblasts compared to that in the undifferentiated cells. However, Nos1 methylation levels remained unchanged during differentiation. These findings suggest that nNOS induction and the appropriate transition of its subcellular localization may contribute to muscle differentiation.

DOI: https://doi.org/10.14715/cmb/2023.69.13.20
Chem Biol Interact. 2024 Jan 03. pii: S0009-2797(24)00001-2. [Epub ahead of print] 110855

Cannabinoids improve mitochondrial function in skeletal muscle of exhaustive exercise training rats by inhibiting mitophagy through the Pink1/Parkin and Bnip3 pathways.

Juncheng Si, Lili Sun, Ying Qin, Lina Peng, Yongshan Gong, Chun Gao, Wenhui Shen, Mengqi Li.

  Cannabidiol (CBD) is a pure natural phytocannabinoid derived from cannabis that has anti-inflammatory, antiapoptotic and antioxidative stress abilities. In recent years, an increasing number of studies have reported the regulatory effect of CBD on skeletal muscle injury induced by exercise, but its mechanism is still unclear. Mitochondria are the main organelles responsible for the energy supply within eukaryotic cells, and their function has been closely linked to cellular health. Moderate exercise improves mitochondrial function, but the excessive exercise has a negative impact on mitochondria. Therefore, we speculate that CBD may promote exercise induced skeletal muscle cell damage by improving mitochondrial function. In this study, by establishing an animal model of exhaustive exercise training in rats, the effects of CBD on the protective effect of CBD on skeletal muscle mitochondrial structure and function was elaborated, and the possible molecular mechanism was discussed based on transcriptomics. Our results indicate that skeletal muscle mitochondrial structure and function were improved after CBD intervention. GO and KEGG pathway enrichment analysis showed that exhaustive exercise training induced mitochondrial dysfunction in skeletal muscle is associated with excessive autophagy/mitophagy, the signaling pathways involved in FOXO3 and GABARAPL1 may play important roles. After CBD intervention, the protein expression of Pink1, Parkin and Bnip3 was down-regulated, indicating that CBD may improve the mitochondrial function by inhibiting mitophagy through the Pink1/Parkin and Bnip3 pathway.

Keywords:  Cannabinoid; Exhaustive exercise; Mitophagy; Skeletal muscle; Transcriptome

DOI:  https://doi.org/10.1016/j.cbi.2024.110855
JCI Insight. 2024 Jan 04. pii: e173246. [Epub ahead of print]

The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix.

Joseph G O'Brien, Alexander B Willis, Ashlee M Long, Jason M Kwon, GaHyun Lee, Frank W Li, Patrick Gt Page, Andy H Vo, Michele Hadhazy, Melissa J Spencer, Rachelle H Crosbie, Alexis R Demonbreun, Elizabeth M McNally.

  The Murphy Roths Large (MRL) mouse strain has "super-healing" properties that enhance recovery from injury. In mice, the DBA/2J strain intensifies many aspects of muscular dystrophy so we evaluated the ability of the MRL strain to suppress muscular dystrophy in the Sgcg null mouse model of limb girdle muscular dystrophy. A comparative analysis of Sgcg null mice in the DBA/2J versus MRL strains showed greater myofiber regeneration with reduced structural degradation of muscle in the MRL strain. Transcriptomic profiling of dystrophic muscle indicated strain-dependent expression of the extracellular matrix (ECM) and TGF-β signaling genes. To investigate the MRL ECM, cellular components were removed from dystrophic muscle sections to generate decellularized myoscaffolds. Decellularized myoscaffolds from dystrophic mice in the protective MRL strain had significantly less deposition of collagen and matrix-bound TGF-β1 and TGF-β3 throughout the matrix. Dystrophic myoscaffolds from the MRL background, but not the DBA/2J background, were enriched in myokines like IGF-1 and IL-6. C2C12 myoblasts seeded onto decellularized matrices from Sgcg-/- MRL and Sgcg-/- DBA/2J muscles showed the MRL background induced greater myoblast differentiation compared to dystrophic DBA/2J myoscaffolds. Thus, the MRL background imparts its effect through a highly regenerative ECM, which is active even in muscular dystrophy.

Keywords:  Extracellular matrix; Fibrosis; Muscle Biology; Stem cells

DOI:  https://doi.org/10.1172/jci.insight.173246
J Physiol. 2024 Jan 02.

Physiological determinants of mechanical efficiency during advanced ageing and disuse.

Massimo Venturelli, Garrett R Morgan, Cantor Tarperi, Jia Zhao, Fabio Naro, Carlo Reggiani, Anthony J Donato, Russell S Richardson, Federico Schena.

  This study aimed to determine which physiological factors impact net efficiency (ηnet) in oldest-old individuals at different stages of skeletal muscle disuse. To this aim, we examined ηnet, central haemodynamics, peripheral circulation, and peripheral factors (skeletal muscle fibre type, capillarization and concentration of mitochondrial DNA [mtDNA]). Twelve young (YG; 25 ± 2 years), 12 oldest-old mobile (OM; 87 ± 3 years), and 12 oldest-old immobile (OI; 88 ± 4 years) subjects performed dynamic knee extensor (KE) and elbow flexors (EF) exercise. Pulmonary oxygen uptake, photoplethysmography, Doppler ultrasound and muscle biopsies of the vastus lateralis and biceps brachii were used to assess central and peripheral adaptations to advanced ageing and disuse. Compared to the YG (12.1 ± 2.4%), the ηnet of lower-limb muscle was higher in the OM (17.6 ± 3.5%, P < 0.001), and lower in the OI (8.9 ± 1.9%, P < 0.001). These changes in ηnet during KE were coupled with significant peripheral adaptations, revealing strong correlations between ηnet and the proportion of type I muscle fibres (r = 0.82), as well as [mtDNA] (r = 0.77). No differences in ηnet were evident in the upper-limb muscles between YG, OM and OI. In view of the differences in limb-specific activity across the lifespan, these findings suggest that ηnet is reduced by skeletal muscle inactivity and not by chronological age, per se. Likewise, this study revealed that the age-related changes in ηnet are not a consequence of central or peripheral haemodynamic adaptations, but are likely a product of peripheral changes related to skeletal muscle fibre type and mitochondrial density. KEY POINTS: Although the effects of ageing and muscle disuse deeply impact the cardiovascular and skeletal muscle function, the combination of these factors on the mechanical efficiency are still a matter of debate. By measuring both upper- and lower-limb muscle function, which experience differing levels of disuse, we examined the influence of central and peripheral haemodynamics, and skeletal muscle factors linked to mechanical efficiency. Across the ages and degree of disuse, upper-limb muscles exhibited a preserved work economy. In the legs the oldest-old without mobility limitations exhibited an augmented mechanical efficiency, which was reduced in those with an impairment in ambulation. These changes in mechanical efficiency were associated with the proportion of type I muscle fibres. Recognition that the mechanical efficiency is not simply age-dependent, but the consequence of inactivity and subsequent skeletal muscle changes, highlights the importance of maintaining physical activity across the lifespan.

Keywords:  fibre type; mechanical efficiency; mitochondrial content; oldest-old

DOI:  https://doi.org/10.1113/JP285639
Physiol Rep. 2024 Jan;12(1): e15898

Extracellular vesicles from obese and diabetic mouse plasma alter C2C12 myotube glucose uptake and gene expression.

Christopher R Pitzer, Hector G Paez, Peter J Ferrandi, Junaith S Mohamed, Stephen E Alway.

  Recent studies have indicated a role for circulating extracellular vesicles (EVs) in the pathogenesis of multiple diseases. However, most in vitro studies have used variable and arbitrary doses of EVs rather than interpreting EVs as an existing component of standard skeletal muscle cell culture media. The current study provides an initial investigation into the effects of circulating EVs on the metabolic phenotype of C2C12 myotubes by replacing EVs from fetal bovine serum with circulating EVs from control mice or mice with obesity and type 2 diabetes (OT2D). We report that EVs associated with OT2D decrease 2-NBDG uptake (a proxy measure of glucose uptake) in the insulin-stimulated state compared to controls. OT2D associated EV treatment also significantly decreased myosin heavy chain type 1 (MHCI) mRNA abundance in myotubes but had no effect on mRNA expression of any other myosin heavy chain isoforms. OT2D-associated circulating EVs also significantly increased lipid accumulation within myotubes without altering the expression of a selection of genes important for lipid entry, synthesis, or catabolism. The data indicate that, in a severely diabetic state, circulating EVs may contribute to insulin resistance and alter gene expression in myotubes in a manner consistent with the skeletal muscle phenotype observed in OT2D.

Keywords:  extracellular vesicles; metabolism; muscle; obesity; type 2 diabetes

DOI:  https://doi.org/10.14814/phy2.15898
Mol Metab. 2023 Dec 30. pii: S2212-8778(23)00203-X. [Epub ahead of print]79 101869

Loss of lysosomal acid lipase results in mitochondrial dysfunction and fiber switch in skeletal muscles of mice.

Alena Akhmetshina, Valentina Bianco, Ivan Bradić, Melanie Korbelius, Anita Pirchheim, Katharina B Kuentzel, Thomas O Eichmann, Helga Hinteregger, Dagmar Kolb, Hansjoerg Habisch, Laura Liesinger, Tobias Madl, Wolfgang Sattler, Branislav Radović, Simon Sedej, Ruth Birner-Gruenberger, Nemanja Vujić, Dagmar Kratky.

  OBJECTIVE: Lysosomal acid lipase (LAL) is the only enzyme known to hydrolyze cholesteryl esters (CE) and triacylglycerols in lysosomes at an acidic pH. Despite the importance of lysosomal hydrolysis in skeletal muscle (SM), research in this area is limited. We hypothesized that LAL may play an important role in SM development, function, and metabolism as a result of lipid and/or carbohydrate metabolism disruptions.RESULTS: Mice with systemic LAL deficiency (Lal-/-) had markedly lower SM mass, cross-sectional area, and Feret diameter despite unchanged proteolysis or protein synthesis markers in all SM examined. In addition, Lal-/- SM showed increased total cholesterol and CE concentrations, especially during fasting and maturation. Regardless of increased glucose uptake, expression of the slow oxidative fiber marker MYH7 was markedly increased in Lal-/-SM, indicating a fiber switch from glycolytic, fast-twitch fibers to oxidative, slow-twitch fibers. Proteomic analysis of the oxidative and glycolytic parts of the SM confirmed the transition between fast- and slow-twitch fibers, consistent with the decreased Lal-/- muscle size due to the "fiber paradox". Decreased oxidative capacity and ATP concentration were associated with reduced mitochondrial function of Lal-/- SM, particularly affecting oxidative phosphorylation, despite unchanged structure and number of mitochondria. Impairment in muscle function was reflected by increased exhaustion in the treadmill peak effort test in vivo.
CONCLUSION: We conclude that whole-body loss of LAL is associated with a profound remodeling of the muscular phenotype, manifested by fiber type switch and a decline in muscle mass, most likely due to dysfunctional mitochondria and impaired energy metabolism, at least in mice.

Keywords:  Energy metabolism; LAL; LAL deficiency; Lal-deficient mouse; Muscle proteomics

DOI:  https://doi.org/10.1016/j.molmet.2023.101869
bioRxiv. 2023 Dec 15. pii: 2023.12.15.571696. [Epub ahead of print]

Population-scale skeletal muscle single-nucleus multi-omic profiling reveals extensive context specific genetic regulation.

Arushi Varshney, Nandini Manickam, Peter Orchard, Adelaide Tovar, Zhenhao Zhang, Fan Feng, Michael R Erdos, Narisu Narisu, Christa Ventresca, Kirsten Nishino, Vivek Rai, Heather M Stringham, Anne U Jackson, Tricia Tamsen, Chao Gao, Mao Yang, Olivia I Koues, Joshua D Welch, Charles F Burant, L Keoki Williams, Chris Jenkinson, Ralph A DeFronzo, Luke Norton, Jouko Saramies, Timo A Lakka, Markku Laakso, Jaakko Tuomilehto, Karen L Mohlke, Jacob O Kitzman, Heikki A Koistinen, Jie Liu, Michael Boehnke, Francis S Collins, Laura J Scott, Stephen C J Parker.

Skeletal muscle, the largest human organ by weight, is relevant to several polygenic metabolic traits and diseases including type 2 diabetes (T2D). Identifying genetic mechanisms underlying these traits requires pinpointing the relevant cell types, regulatory elements, target genes, and causal variants. Here, we used genetic multiplexing to generate population-scale single nucleus (sn) chromatin accessibility (snATAC-seq) and transcriptome (snRNA-seq) maps across 287 frozen human skeletal muscle biopsies representing 456,880 nuclei. We identified 13 cell types that collectively represented 983,155 ATAC summits. We integrated genetic variation to discover 6,866 expression quantitative trait loci (eQTL) and 100,928 chromatin accessibility QTL (caQTL) (5% FDR) across the five most abundant cell types, cataloging caQTL peaks that atlas-level snATAC maps often miss. We identified 1,973 eGenes colocalized with caQTL and used mediation analyses to construct causal directional maps for chromatin accessibility and gene expression. 3,378 genome-wide association study (GWAS) signals across 43 relevant traits colocalized with sn-e/caQTL, 52% in a cell-specific manner. 77% of GWAS signals colocalized with caQTL and not eQTL, highlighting the critical importance of population-scale chromatin profiling for GWAS functional studies. GWAS-caQTL colocalization showed distinct cell-specific regulatory paradigms. For example, a C2CD4A/B T2D GWAS signal colocalized with caQTL in muscle fibers and multiple chromatin loop models nominated VPS13C , a glucose uptake gene. Sequence of the caQTL peak overlapping caSNP rs7163757 showed allelic regulatory activity differences in a human myocyte cell line massively parallel reporter assay. These results illuminate the genetic regulatory architecture of human skeletal muscle at high-resolution epigenomic, transcriptomic, and cell state scales and serve as a template for population-scale multiomic mapping in complex tissues and traits.

DOI: https://doi.org/10.1101/2023.12.15.571696
PLoS One. 2024 ;19(1): e0291477

Motor neuron activity enhances the proteomic stress caused by autophagy defects in the target muscle.

Saurabh Srivastav, Kevin van der Graaf, Prisha C Jonnalagadda, Maanvi Thawani, James A McNew, Michael Stern.

Several lines of evidence demonstrate that increased neuronal excitability can enhance proteomic stress. For example, epilepsy can enhance the proteomic stress caused by the expression of certain aggregation-prone proteins implicated in neurodegeneration. However, unanswered questions remain concerning the mechanisms by which increased neuronal excitability accomplishes this enhancement. Here we test whether increasing neuronal excitability at a particular identified glutamatergic synapse, the Drosophila larval neuromuscular junction, can enhance the proteomic stress caused by mutations in the ER fusion/GTPase gene atlastin (atl). It was previously shown that larval muscle from the atl2 null mutant is defective in autophagy and accumulates protein aggregates containing ubiquitin (poly-UB aggregates). To determine if increased neuronal excitability might enhance the increased proteomic stress caused by atl2, we activated the TrpA1-encoded excitability channel within neurons. We found that TrpA1 activation had no effect on poly-UB aggregate accumulation in wildtype muscle, but significantly increased poly-UB aggregate number in atl2 muscle. Previous work has shown that atl loss from either neuron or muscle increases muscle poly-UB aggregate number. We found that neuronal TrpA1 activation enhanced poly-UB aggregate number when atl was removed from muscle, but not from neuron. Neuronal TrpA1 activation enhanced other phenotypes conferred by muscle atl loss, such as decreased pupal size and decreased viability. Taken together, these results indicate that the proteomic stress caused by muscle atl loss is enhanced by increasing neuronal excitability.

DOI: https://doi.org/10.1371/journal.pone.0291477
Elife. 2024 Jan 05. pii: RP87592. [Epub ahead of print]12

Proteomic analysis shows decreased type I fibers and ectopic fat accumulation in skeletal muscle from women with PCOS.

Elisabet Stener-Victorin, Gustaw Eriksson, Man Mohan Shrestha, Valentina Rodriguez Paris, Haojiang Lu, Jasmine Banks, Manisha Samad, Charlène Perian, Baptiste Jude, Viktor Engman, Roberto Boi, Emma Nilsson, Charlotte Ling, Jenny Nyström, Ingrid Wernstedt Asterholm, Nigel Turner, Johanna Lanner, Anna Benrick.

  Background: Polycystic ovary syndrome's (PCOS) main feature is hyperandrogenism, which is linked to a higher risk of metabolic disorders. Gene expression analyses in adipose tissue and skeletal muscle reveal dysregulated metabolic pathways in women with PCOS, but these differences do not necessarily lead to changes in protein levels and biological function.Methods: To advance our understanding of the molecular alterations in PCOS, we performed global proteomic and phosphorylation site analysis using tandem mass spectrometry, and analyzed gene expression and methylation. Adipose tissue and skeletal muscle were collected at baseline from 10 women with and without PCOS, and in women with PCOS after 5 weeks of treatment with electrical stimulation.
Results: Perilipin-1, a protein that typically coats the surface of lipid droplets in adipocytes, was increased whereas proteins involved in muscle contraction and type I muscle fiber function were downregulated in PCOS muscle. Proteins in the thick and thin filaments had many altered phosphorylation sites, indicating differences in protein activity and function. A mouse model was used to corroborate that androgen exposure leads to a shift in muscle fiber type in controls but not in skeletal muscle-specific androgen receptor knockout mice. The upregulated proteins in muscle post treatment were enriched in pathways involved in extracellular matrix organization and wound healing, which may reflect a protective adaptation to repeated contractions and tissue damage due to needling. A similar, albeit less pronounced, upregulation in extracellular matrix organization pathways was also seen in adipose tissue.
Conclusions: Our results suggest that hyperandrogenic women with PCOS have higher levels of extra-myocellular lipids and fewer oxidative insulin-sensitive type I muscle fibers. These could be key factors leading to insulin resistance in PCOS muscle while electric stimulation-induced tissue remodeling may be protective.
Funding: Swedish Research Council (2020-02485, 2022-00550, 2020-01463), Novo Nordisk Foundation (NNF22OC0072904), and IngaBritt and Arne Lundberg Foundation. Clinical trial number NTC01457209.

Keywords:  PCOS; adipose tissue; genetics; genomics; human; medicine; methylation; mouse; proteomics; skeletal muscle; transcriptomics

DOI:  https://doi.org/10.7554/eLife.87592
bioRxiv. 2023 Dec 13. pii: 2023.12.12.571303. [Epub ahead of print]

The ubiquitin-conjugating enzyme UBE2D/eff maintains a youthful proteome and ensures protein quality control during aging.

Liam C Hunt, Kudzai Nyamkondiwa, Anna Stephan, Jianqin Jiao, Kanisha Kavdia, Vishwajeeth Pagala, Junmin Peng, Fabio Demontis.

Ubiquitin-conjugating enzymes (E2s) are key for regulating protein function and turnover via ubiquitination but it remains undetermined which E2s maintain proteostasis during aging. Here, we find that E2s have diverse roles in handling a model aggregation-prone protein (huntingtin-polyQ) in the Drosophila retina: while some E2s mediate aggregate assembly, UBE2D/effete (eff) and other E2s are required for huntingtin-polyQ degradation. UBE2D/eff is key for proteostasis also in skeletal muscle: eff protein levels decline with aging, and muscle-specific eff knockdown causes an accelerated buildup in insoluble poly-ubiquitinated proteins (which progressively accumulate with aging) and shortens lifespan. Transgenic expression of human UBE2D2, homologous to eff, partially rescues the lifespan and proteostasis deficits caused by muscle-specific eff RNAi by re-establishing the physiological levels of eff RNAi -regulated proteins. Interestingly, UBE2D/eff knockdown in young age reproduces many of the proteomic changes that normally occur in old muscles, suggesting that the decrease in UBE2D/eff protein levels that occurs with aging contributes to reshaping the composition of the muscle proteome. Altogether, these findings indicate that UBE2D/eff is a key E2 ubiquitin-conjugating enzyme for maintaining a youthful proteome and for ensuring protein quality control during aging.

DOI: https://doi.org/10.1101/2023.12.12.571303
J Clin Invest. 2024 Jan 02. pii: e176089. [Epub ahead of print]134(1):

Combinatorial effects of ion channel mis-splicing as a cause of myopathy in myotonic dystrophy.

Larissa Nitschke, Thomas A Cooper.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder caused by an unstable expanded CTG repeat located in the 3'-UTR of the DM1 protein kinase (DMPK) gene. The pathogenic mechanism results in misregulated alternative splicing of hundreds of genes, creating the dilemma of establishing which genes contribute to the mechanism of DM1 skeletal muscle pathology. In this issue of the JCI, Cisco and colleagues systematically tested the combinatorial effects of DM1-relevant mis-splicing patterns in vivo and identified the synergistic effects of mis-spliced calcium and chloride channels as a major contributor to DM1 skeletal muscle impairment. The authors further demonstrated the therapeutic potential for calcium channel modulation to block the synergistic effects and rescue myopathy.

DOI: https://doi.org/10.1172/JCI176089
Mech Ageing Dev. 2023 Dec 30. pii: S0047-6374(23)00126-4. [Epub ahead of print] 111900

Moderate dietary restriction delays the onset of age-associated sarcopenia in Caenorhabditis elegans due to reduced myosin UNC-54 degradation.

Sobha Tumbapo, Adam Strudwick, Jana J Stastna, Simon C Harvey, Marieke J Bloemink.

  Sarcopenia, a gradual decrease in skeletal muscle mass and strength, is a major component of frailty in the elderly, with age, (lack of) exercise and diet found to be the major risk factors. The nematode Caenorhabditis elegans is an important model of sarcopenia. Although many studies describe loss of muscle function in ageing C. elegans, surprisingly few report on the loss of muscle mass. Here, in order to quantify loss of muscle mass under various dietary restriction (DR) conditions, we used an internal GFP standard to determine levels of the major body wall muscle myosin (UNC-54) in transgenic unc-54::gfp worms over their lifespan. Myosin density linearly increased during the first week of adulthood and there was no significant effect of DR. In contrast, an exponential decrease in myosin density was seen during the second week of adulthood, with reduced rates of myosin loss for mild and medium DR compared to control. UNC-54 turnover rates, previously determined using pulse-labelling methods, correspond well with the t1/2 value found here for UNC-54-GFP using fluorescence (control t1/2 = 12.0 days), independently validating our approach. These data indicate that sarcopenia is delayed in worms under mild and medium DR due to a reduced rate of myosin UNC-54 degradation, thereby maintaining protein homeostasis.

Keywords:  Aging; C. elegans; healthspan; myosin UNC-54; sarcopenia

DOI:  https://doi.org/10.1016/j.mad.2023.111900
J Biol Chem. 2023 Dec 28. pii: S0021-9258(23)02635-2. [Epub ahead of print] 105606

Structural and functional interactions between the EF hand domain and S2-S3 loop in the type-1 ryanodine receptor ion channel.

Venkat R Chirasani, Millar Elferdink, MacKenzie Kral, Jordan S Carter, Savannah Heitmann, Gerhard Meissner, Naohiro Yamaguchi.

  Previous cryo-electron micrographs suggested that the skeletal muscle Ca2+ release channel, RyR1, is regulated by intricate interactions between the EF hand Ca2+ binding domain and the cytosolic loop (S2-S3 loop). However, the precise molecular details of these interactions and functional consequences of the interactions remain elusive. Here, we employed molecular dynamics simulations to explore the specific amino acid pairs involved in hydrogen bond interactions within the EF hand - S2-S3 loop interface. Our simulations unveiled two key interactions: (1) K4101 (EF hand) with D4730 (S2-S3 loop) and (2) E4075, Q4078, and D4079 (EF hand) with R4736 (S2-S3 loop). To probe the functional significance of these interactions, we constructed mutant RyR1 cDNAs and expressed them in HEK293 cells for [3H]ryanodine binding assays. Our results demonstrated that mutations in the EF hand, specifically K4101E and K4101M, resulted in reduced affinities for Ca2+/Mg2+-dependent inhibitions. Interestingly, the K4101E mutation increased the affinity for Ca2+-dependent activation. Conversely, mutations in the S2-S3 loop, D4730K and D4730N, did not significantly change the affinities for Ca2+/Mg2+-dependent inhibitions. Our previous finding that skeletal disease-associated RyR1 mutations, R4736Q and R4736W, impaired Ca2+-dependent inhibition, is consistent with the current results. In silico mutagenesis analysis aligned with our functional data, indicating altered hydrogen bonding patterns upon mutations. Taken together, our findings emphasize the critical role of the EF hand-S2-S3 loop interaction in Ca2+/Mg2+-dependent inhibition of RyR1 and provide insights into potential therapeutic strategies targeting this domain interaction for the treatment of skeletal myopathies.

Keywords:  Ca(2+)-dependent regulation; hydrogen bonding; mutation analysis; ryanodine receptor; skeletal muscle disorders

DOI:  https://doi.org/10.1016/j.jbc.2023.105606
Free Radic Biol Med. 2023 Dec 28. pii: S0891-5849(23)01203-0. [Epub ahead of print]

Putrescine promotes MMP9-induced angiogenesis in skeletal muscle through hydrogen peroxide/METTL3 pathway.

Chengjun Hu, Fengjie Ji, Renlong Lv, Hanlin Zhou, Guanyu Hou, Tieshan Xu.

  Blood vessels play a crucial role in the development of skeletal muscle, ensuring the supply of nutrients and oxygen. Putrescine, an essential polyamine for eukaryotic cells, has an unclear impact on skeletal muscle angiogenesis. In this study, we observed lower vessel density and reduced putrescine level in the muscle of low-birth-weight piglet models, and identified a positive correlation between putrescine content and muscle vessel density. Furthermore, putrescine was found to promote angiogenesis in skeletal muscle both in vitro and in vivo by targeting matrix metalloproteinase 9 (MMP9). On a mechanistic level, putrescine augmented the expression of methyltransferase like 3 (METTL3) by attenuating hydrogen peroxide production, thereby increasing the level of N6-methyladenosine (m6A)-modified MMP9 mRNA. This m6A-modified MMP9 mRNA was subsequently recognized and bound by the YTH N6-methyladenosine RNA binding protein 1 (YTHDF1), enhancing the stability of MMP9 mRNA and its protein expression, consequently accelerating angiogenesis in skeletal muscle. In summary, our findings suggest that putrescine enhances MMP9-mediated angiogenesis in skeletal muscle via the hydrogen peroxide/METTL3 pathway.

Keywords:  Hydrogen peroxide; METTL3; MMP9; Putrescine; Skeletal muscle angiogenesis

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.12.041
J Appl Physiol (1985). 2024 Jan 04.

Higher resistance training volume offsets muscle hypertrophy non-responsiveness in older individuals.

Manoel E Lixandrão, Marcas Bamman, Felipe C Vechin, Miguel S Conceição, Guilherme Telles, Igor Longobardi, Felipe Damas, Kaleen M Lavin, Devin J Drummer, Jeremy S McAdam, Cory M Dungan, Alice E Leitão, Luiz A Riani Costa, André Y Aihara, Cleiton A Libardi, Bruno Gualano, Hamilton Roschel.

  The magnitude of muscle hypertrophy in response to resistance training (RT) is highly variable between individuals (response heterogeneity). Manipulations in RT variables may modulate RT-related response heterogeneity; yet, this remains to be determined. Using a within-subject unilateral design, we aimed to investigate the effects of RT volume manipulation on whole-muscle hypertrophy (quadriceps muscle cross-sectional area [qCSA]) among non-responders and responders to a low RT dose (single-set). We also investigated the effects of RT volume manipulation on muscle strength in these responsiveness groups. Eighty-five older individuals (41M/44F, age=68±4 y; BMI=26.4±3.7 kg/m2) had one leg randomly allocated to a single (1)-set and the contralateral leg allocated to 4 sets of unilateral knee-extension RT at 8-15 repetition maximum (RM) for 10-wk 2d/wk. Pre- and post-intervention, participants underwent magnetic resonance imaging (MRI) and unilateral knee-extension 1-RM strength testing. MRI typical error (2xTE=3.27%) was used to classify individuals according to responsiveness patterns. N=51 were classified as non-responders (≤2xTE) and N=34 as responders (>2xTE) based on pre- to post-intervention change qCSA following the single-set RT protocol. Non-responders to single-set training showed a dose-response, with significant time*set interactions for qCSA and 1-RM strength, indicating greater gains in response to the higher volume prescription (time*set: P<0.05 for both outcomes). Responders improved qCSA (time: P<0.001), with a tendency towards higher benefit from the 4 sets RT protocol (time*set: P=0.08); on the other hand, 1-RM increased similarly irrespectively of RT volume prescription (time*set: P>0.05). Our findings support the use of higher RT volume to mitigate non-responsiveness among older adults.

Keywords:  Aging; Muscle mass; Muscle strength; Resistance exercise; Sets

DOI:  https://doi.org/10.1152/japplphysiol.00670.2023
J Clin Invest. 2024 Jan 02. pii: e173576. [Epub ahead of print]134(1):

Verapamil mitigates chloride and calcium bi-channelopathy in a myotonic dystrophy mouse model.

Lily A Cisco, Matthew T Sipple, Katherine M Edwards, Charles A Thornton, John D Lueck.

  Myotonic dystrophy type 1 (DM1) involves misregulated alternative splicing for specific genes. We used exon or nucleotide deletion to mimic altered splicing of genes central to muscle excitation-contraction coupling in mice. Mice with forced skipping of exon 29 in the CaV1.1 calcium channel combined with loss of ClC-1 chloride channel function displayed markedly reduced lifespan, whereas other combinations of splicing mimics did not affect survival. The Ca2+/Cl- bi-channelopathy mice exhibited myotonia, weakness, and impairment of mobility and respiration. Chronic administration of the calcium channel blocker verapamil rescued survival and improved force generation, myotonia, and respiratory function. These results suggest that Ca2+/Cl- bi-channelopathy contributes to muscle impairment in DM1 and is potentially mitigated by common clinically available calcium channel blockers.

Keywords:  Calcium channels; Chloride channels; Muscle; Muscle Biology; Therapeutics

DOI:  https://doi.org/10.1172/JCI173576
iScience. 2024 Jan 19. 27(1): 108590

Glucose restriction enhances oxidative fiber formation: A multi-omic signal network involving AMPK and CaMK2.

Kaiyi Zhang, Ning Xie, Huaqiong Ye, Jiakun Miao, Boce Xia, Yu Yang, Huanqi Peng, Shuang Xu, Tianwen Wu, Cong Tao, Jinxue Ruan, Yanfang Wang, Shulin Yang.

  Skeletal muscle is a highly plastic organ that adapts to different metabolic states or functional demands. This study explored the impact of permanent glucose restriction (GR) on skeletal muscle composition and metabolism. Using Glut4m mice with defective glucose transporter 4, we conducted multi-omics analyses at different ages and after low-intensity treadmill training. The oxidative fibers were significantly increased in Glut4m muscles. Mechanistically, GR activated AMPK pathway, promoting mitochondrial function and beneficial myokine expression, and facilitated slow fiber formation via CaMK2 pathway. Phosphorylation-activated Perm1 may synergize AMPK and CaMK2 signaling. Besides, MAPK and CDK kinases were also implicated in skeletal muscle protein phosphorylation during GR response. This study provides a comprehensive signaling network demonstrating how GR influences muscle fiber types and metabolic patterns. These insights offer valuable data for understanding oxidative fiber formation mechanisms and identifying clinical targets for metabolic diseases.

Keywords:  Comp; Genomics; Metabolomics; Omics; Proteomics

DOI:  https://doi.org/10.1016/j.isci.2023.108590
Front Aging. 2023 ;4 1339786

Editorial: Insights in molecular mechanisms of aging 2022.

Marco Brotto, Consuelo Borrás.



Keywords:  aging; bone; regenerative medicine; senescence; skeletal muscle

DOI:  https://doi.org/10.3389/fragi.2023.1339786