bims-moremu 2024-08-04 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024‒08‒04
28 papers selected by
Anna Vainshtein, Craft Science Inc.

The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.
Methylglyoxal reduces resistance exercise-induced protein synthesis and anabolic signaling in rat tibialis anterior muscle.
New insights into the cellular and molecular mechanisms of skeletal muscle fatigue: The Marion J. Siegman Award Lectureships.
Counterpoint to: The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.
Exploring NADPH oxidases 2 and 4 in cardiac and skeletal muscle adaptations - a cross-tissue comparison‡.
Serotonin reuptake inhibitors improve muscle stem cell function and muscle regeneration in male mice.
The role of interleukin-10 in mitigating endoplasmic reticulum stress in aged mice through exercise.
Response to: Counterpoint to: The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.
The central role of magnesium in skeletal muscle: from myogenesis to performance.
The Risks and Rewards of the Synergist Ablation Model in Skeletal Muscle Biology Research: Editorial Focus.
Suppression of gp130 attenuated insulin-mediated signaling and glucose uptake in skeletal muscle cells.
Protocol for characterizing non-genetic heterogeneity and expression dynamics of surface proteins in mouse muscle stem cells using flow cytometry.
Mitochondria can substitute for parvalbumin to lower cytosolic calcium levels in the murine fast skeletal muscle.
Inhibition of the ubiquitin-proteasome system reduces the abundance of pyruvate dehydrogenase kinase 1 in cultured myotubes.
DNA methylation of Ad4BP/SF-1 suppresses Cyp11a1 and StAR transcripts in C2C12 myoblasts.
Sporadic inclusion body myositis-derived myotube culture revealed muscle cell-autonomous expression profiles.
Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy.
Gene body DNA hydroxymethylation restricts the magnitude of transcriptional changes during aging.
Leg Cycling Efficiency is Unaltered in Healthy Aging Regardless of Sex, or Training Status.
Structural switch in acetylcholine receptors in developing muscle.
Histone β-hydroxybutyrylation is critical in reversal of sarcopenia.
Studying the impact of geometrical and cellular cues on myogenesis with a skeletal muscle-on-chip.
Greater molecular potential for glucose metabolism in adipose tissue and skeletal muscle of women compared with men.
Age-related differences in the loss and recovery of serial sarcomere number following disuse atrophy in rats.
Exploring protein relative relations in skeletal muscle proteomic analysis for insights into insulin resistance and type 2 diabetes.
Diagnosing sarcopenia with semi-automated skeletal muscle computed tomography cutoff values and the association of these muscle metrics with long-term physical exercise.
l-Carnitine relieves cachexia-related skeletal muscle fibrosis by inducing deltex E3 ubiquitin ligase 3L to negatively regulate the Runx2/COL1A1 axis.
Multiorgan biological age shows that no organ system is an island.

Am J Physiol Cell Physiol. 2024 Jul 29.

The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.

Benjamin I Burke, Ahmed Ismaeel, John J McCarthy.

  Skeletal muscle exhibits remarkable plasticity to adapt to stimuli such as mechanical loading. The mechanisms that regulate skeletal muscle hypertrophy due to mechanical overload have been thoroughly studied. Remarkably, our understanding of many of the molecular and cellular mechanisms that regulate hypertrophic growth were first identified using the rodent synergist ablation (SA) model and subsequently corroborated in human resistance exercise training studies. To demonstrate the utility of the SA model, we briefly summarize the hypertrophic mechanisms identified using the model and the following translation of these mechanism to human skeletal muscle hypertrophy induced by resistance exercise training.

Keywords:  mTOR signaling; microRNAs; protein synthesis; ribosome biogenesis; satellite cell fusion

DOI:  https://doi.org/10.1152/ajpcell.00362.2024
J Muscle Res Cell Motil. 2024 Jul 31.

Methylglyoxal reduces resistance exercise-induced protein synthesis and anabolic signaling in rat tibialis anterior muscle.

Masayuki Tanaka, Miho Kanazashi, Hiroyo Kondo, Hidemi Fujino.

  Resistance exercise provides significant benefits to skeletal muscle, including hypertrophy and metabolic enhancements, supporting overall health and disease management. However, skeletal muscle responsiveness to resistance exercise is significantly reduced in conditions such as aging and diabetes. Recent reports suggest that glycation stress contributes to muscle atrophy and impaired exercise-induced muscle adaptation; however, its role in the muscle response to resistance exercise remains unclear. Therefore, in this study, we investigated whether methylglyoxal (MGO), a key factor in glycation stress, affects the acute responsiveness of skeletal muscles to resistance exercise, focusing on protein synthesis and the key signaling molecules. This study included 12 8-week-old male Sprague-Dawley rats divided into two groups: one received 0.5% MGO-supplemented drinking water (MGO group) and the other received regular water (control group). After 10 weeks, the left tibialis anterior muscle of each rat was subjected to electrical stimulation (ES) to mimic resistance exercise, with the right muscle serving as a non-stimulated control. Muscle protein-synthesis rates were evaluated with SUnSET, and phosphorylation levels of key signaling molecules (p70S6K and S6rp) were quantified using western blotting. In the control group, stimulated muscles exhibited significantly increased muscle protein synthesis and phosphorylation levels of p70S6K and S6rp. In the MGO group, these increases were attenuated, indicating that MGO treatment suppresses the adaptive response to resistance exercise. MGO diminishes the skeletal muscle's adaptive response to ES-simulated resistance exercise, affecting both muscle protein synthesis and key signaling molecules. The potential influence of glycation stress on the effectiveness of resistance exercise or ES emphasizes the need for individualized interventions in conditions of elevated glycation stress, such as diabetes and aging.

Keywords:  Anabolic resistance; Methylglyoxal; Protein synthesis; Resistance training; Skeletal muscle

DOI:  https://doi.org/10.1007/s10974-024-09680-w
Am J Physiol Cell Physiol. 2024 Jul 29.

New insights into the cellular and molecular mechanisms of skeletal muscle fatigue: The Marion J. Siegman Award Lectureships.

Edward P Debold, Håkan Westerblad.

  Skeletal muscle fibers need to have mechanisms to decrease energy consumption during intense physical exercise to avoid devastatingly low ATP levels, with the formation of rigor cross-bridges and defective ion pumping. These protective mechanisms inevitably lead to declining contractile function in response to intense exercise, characterizing fatigue. Through our work we have gained insights into cellular and molecular mechanisms underlying the decline in contractile function during acute fatigue. Key mechanistic insights have been gained from studies performed on intact and skinned single muscle fibers, and more recently from studies performed and single myosin molecules. Studies on intact single fibers revealed several mechanisms of impaired sarcoplasmic reticulum (SR) Ca2+ release and experiments on single myosin molecules provide direct evidence of how putative agents of fatigue impact myosin's ability to generate force and motion. We conclude that changes in metabolites due to an increased dependency on anaerobic metabolism (e.g. accumulation of inorganic phosphate ions and H+) act to directly and indirectly (i.e. via decreased Ca2+ activation) inhibit myosin's force and motion generating capacity. These insights into the acute mechanisms of fatigue may help improve endurance training strategies and reveal potential targets for therapies to attenuate fatigue in chronic diseases.

Keywords:  actin; calcium sensitivity; muscle fatigue; myosin; phosphate

DOI:  https://doi.org/10.1152/ajpcell.00213.2024
Am J Physiol Cell Physiol. 2024 Jul 29.

Counterpoint to: The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.

Michael D Roberts, Troy A Hornberger, Stuart M Phillips.



Keywords:  skeletal muscle; synergist ablation

DOI:  https://doi.org/10.1152/ajpcell.00405.2024
Free Radic Biol Med. 2024 Jul 26. pii: S0891-5849(24)00581-1. [Epub ahead of print]

Exploring NADPH oxidases 2 and 4 in cardiac and skeletal muscle adaptations - a cross-tissue comparison‡.

Roberto Meneses-Valdés, Samantha Gallero, Carlos Henriquez-Olguín, Thomas E Jensen.

  Striated muscle cells, encompassing cardiac myocytes and skeletal muscle fibers, are fundamental to athletic performance, facilitating blood circulation and coordinated movement through contraction. Despite their distinct functional roles, these muscle types exhibit similarities in cytoarchitecture, protein expression, and excitation-contraction coupling. Both muscle types also undergo molecular remodeling in energy metabolism and cell size in response to acute and repeated exercise stimuli to enhance exercise performance. Reactive oxygen species (ROS) produced by NADPH oxidase (NOX) isoforms 2 and 4 have emerged as signaling molecules that regulate exercise adaptations. This review systematically compares NOX2 and NOX4 expression, regulation, and roles in cardiac and skeletal muscle responses across exercise modalities. We highlight the many gaps in our knowledge and opportunities to let future skeletal muscle research into NOX-dependent mechanisms be inspired by cardiac muscle studies and vice versa. Understanding these processes could enhance the development of exercise routines to optimize human performance and health strategies that capitalize on the advantages of physical activity.

Keywords:  Cardiac muscle; Exercise; Hypertrophy; Metabolism; Redox; Skeletal muscle

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.07.035
Nat Commun. 2024 Jul 31. 15(1): 6457

Serotonin reuptake inhibitors improve muscle stem cell function and muscle regeneration in male mice.

Mylène Fefeu, Michael Blatzer, Anita Kneppers, David Briand, Pierre Rocheteau, Alexandre Haroche, David Hardy, Mélanie Juchet-Martin, Anne Danckaert, François Coudoré, Abdulkarim Tutakhail, Corinne Huchet, Aude Lafoux, Rémi Mounier, Olivier Mir, Raphaël Gaillard, Fabrice Chrétien.

Serotonin reuptake inhibitor antidepressants such as fluoxetine are widely used to treat mood disorders. The mechanisms of action include an increase in extracellular level of serotonin, neurogenesis, and growth of vessels in the brain. We investigated whether fluoxetine could have broader peripheral regenerative properties. Following prolonged administration of fluoxetine in male mice, we showed that fluoxetine increases the number of muscle stem cells and muscle angiogenesis, associated with positive changes in skeletal muscle function. Fluoxetine also improved skeletal muscle regeneration after single and multiples injuries with an increased muscle stem cells pool and vessel density associated with reduced fibrotic lesions and inflammation. Mice devoid of peripheral serotonin treated with fluoxetine did not exhibit beneficial effects during muscle regeneration. Specifically, pharmacological, and genetic inactivation of the 5-HT1B subtype serotonin receptor also abolished the enhanced regenerative process induced by fluoxetine. We highlight here a regenerative property of serotonin on skeletal muscle.

DOI: https://doi.org/10.1038/s41467-024-50220-4
Am J Physiol Endocrinol Metab. 2024 Jul 31.

The role of interleukin-10 in mitigating endoplasmic reticulum stress in aged mice through exercise.

Bruno Brieda Marafon, Ana Paula Pinto, Ivo Vieira de Sousa Neto, Caroline Mantovani da Luz, José Rodrigo Pauli, Dennys Esper Cintra, Eduardo Rochete Ropelle, Fernando Moreira Simabuco, Leandro Pereira de Moura, Ellen Cristini de Freitas, Donato Americo Rivas, Adelino Sanchez Ramos da Silva.

  While unfolded protein response (UPR) is essential for cellular protection, its prolonged activation may induce apoptosis, compromising cellular longevity. The aging process increases the endoplasmic reticulum (ER) stress in skeletal muscle. However, whether combined exercise can prevent age-induced ER stress in skeletal muscle remains unknown. Evidence suggests that ER stress may increase inflammation by counteracting the positive effects of interleukin-10 (IL-10), while its administration in cells inhibits ER stress and apoptosis. This study verified the effects of aging and combined exercise on physical performance, ER stress markers, and inflammation in the quadriceps of mice. Moreover, we verified the effects of IL-10 on ER stress markers. C57BL/6 mice were distributed into young (Y, 6-month-old), old sedentary (OS, sedentary, 24-month-old), and old trained group (OT, submitted to short-term combined exercise, 24-month-old). To clarify the role of IL-10 in UPR pathways, knockout mice lacking IL-10 were used. The OS mice presented worse physical performance and higher ER stress-related proteins, such as CHOP and p-eIF2α/eIF2α. The exercise protocol increased muscle strength and IL-10 protein levels in OT while inducing the downregulation of CHOP protein levels compared to OS. Furthermore, mice lacking IL-10 increased BiP, CHOP, and p-eIF2α/eIF2α protein levels, indicating this cytokine can regulate the ER stress response in skeletal muscle. Bioinformatics analysis showed that endurance and resistance training downregulated DDIT3 and XBP1 gene expression in the vastus lateralis of older people, reinforcing our findings. Thus, combined exercise is a potential therapeutic intervention for promoting adjustments in ER stress markers in aged skeletal muscle.

Keywords:  IL-10; Organelle stress; Physical activity; Protein folding; Senescence

DOI:  https://doi.org/10.1152/ajpendo.00204.2024
Am J Physiol Cell Physiol. 2024 Jul 29.

Response to: Counterpoint to: The Utility of the Rodent Synergist Ablation Model in Identifying Molecular and Cellular Mechanisms of Skeletal Muscle Hypertrophy.

Benjamin I Burke, Ahmed Ismaeel, Ferdinand von Walden, Kevin A Murach, John J McCarthy.



Keywords:  hypertrophy; muscle; resistance training; synergist ablation

DOI:  https://doi.org/10.1152/ajpcell.00418.2024
Magnes Res. 2024 Jul 01. 37(1): 1-11

The central role of magnesium in skeletal muscle: from myogenesis to performance.

Sara Castiglioni, Andrzej Mazur, Jeanette A Maier.

  A physiological concentration of magnesium (Mg) is essential for optimal skeletal muscle function. Indeed, Mg plays a crucial role during the differentiation process (myogenesis), in muscle fiber composition, muscle contraction and performance. This narrative review describes in detail the relevance of Mg in skeletal muscle, highlighting the importance of adequate Mg intake to ensure optimal skeletal muscle cell function and performance in individuals of all ages.

Keywords:  magnesium; muscle contraction; muscle fibers; muscle performance.; myogenesis; skeletal muscle

DOI:  https://doi.org/10.1684/mrh.2024.0526
Am J Physiol Cell Physiol. 2024 Jul 29.

The Risks and Rewards of the Synergist Ablation Model in Skeletal Muscle Biology Research: Editorial Focus.

Anika L Syroid, Thomas J Hawke.



Keywords:  editorial

DOI:  https://doi.org/10.1152/ajpcell.00504.2024
Sci Rep. 2024 Jul 30. 14(1): 17496

Suppression of gp130 attenuated insulin-mediated signaling and glucose uptake in skeletal muscle cells.

Koji Sato.

  The aim of the present study was to investigate the effects of Oncostatin M receptor (OSMR) subunit gp130 knockdown on insulin-stimulated glucose metabolism-related signaling pathways and glucose uptake in skeletal muscle cells. siRNA-mediated gp130 knockdown was conducted in C2C12 muscle cells, and insulin was added and incubated for 1 h. The cells were cultivated to analyze the mRNA levels of gp130, phosphorylation of STAT3, and glucose metabolism-regulated signaling pathways, and OSM levels in the culture medium were analyzed. The phosphorylation of STAT 3 was significantly decreased in gp130-/- cell. The insulin stimulation was significantly increased in both gp130-/- and gp130+/+ and the phosphorylation of IRS-1 Ser 1101 was significantly decreased in gp130-/-. PI3-kinase activity and Akt Thr 308 phosphorylation were significantly decreased in gp130-/-. The insulin-stimulated increase in glucose uptake rate was significantly attenuated in gp130-/-. In the culture medium, OSM levels were significantly lower in gp130+/+compared to gp130-/- cell. In conclusion, the knockdown of gp130 caused a decrease in STAT 3 phosphorylation and resulted in the attenuation of insulin-mediated glucose metabolism signaling in skeletal muscle cells. Thus, an excessive increase in extracellular OSM may induce blunted insulin action in skeletal muscle cells.

Keywords:  Glucose metabolism; Insulin action; Oncostatin M; Skeletal muscle

DOI:  https://doi.org/10.1038/s41598-024-68613-2
STAR Protoc. 2024 Jul 27. pii: S2666-1667(24)00381-2. [Epub ahead of print]5(3): 103216

Protocol for characterizing non-genetic heterogeneity and expression dynamics of surface proteins in mouse muscle stem cells using flow cytometry.

Laura Pisapia, Vincenzo Mercadante, Gennaro Andolfi, Gabriella Minchiotti, Ombretta Guardiola.

  Here, we present a protocol for investigating the non-genetic heterogeneity of membrane proteins expression within murine muscle stem cell (MuSC) population isolated from injured skeletal muscles. We describe a protocol that employs flow cytometry technology to detect variations in membrane CRIPTO protein levels and ensure measurements standardization. We detail steps for muscle digestion, bulk muscle cell staining, and phenotypic analysis. This approach allows for the identification of MuSC fractions with distinct phenotypic and functional properties. For complete details on the use and execution of this protocol, please refer to Guardiola et al.1.

Keywords:  Cell Biology; Cell isolation; Flow Cytometry; Stem Cells

DOI:  https://doi.org/10.1016/j.xpro.2024.103216
Acta Physiol (Oxf). 2024 Jul 30. e14208

Mitochondria can substitute for parvalbumin to lower cytosolic calcium levels in the murine fast skeletal muscle.

Lorenzo Marcucci, Leonardo Nogara, Marta Canato, Elena Germinario, Anna Raffaello, Michela Carraro, Paolo Bernardi, Laura Pietrangelo, Simona Boncompagni, Feliciano Protasi, Nazareno Paolocci, Carlo Reggiani.

  AIM: Parvalbumin (PV) is a primary calcium buffer in mouse fast skeletal muscle fibers. Previous work showed that PV ablation has a limited impact on cytosolic Ca2+ ([Ca2+]cyto) transients and contractile response, while it enhances mitochondrial density and mitochondrial matrix-free calcium concentration ([Ca2+]mito). Here, we aimed to quantitatively test the hypothesis that mitochondria act to compensate for PV deficiency.METHODS: We determined the free Ca2+ redistribution during a 2 s 60 Hz tetanic stimulation in the sarcoplasmic reticulum, cytosol, and mitochondria. Via a reaction-diffusion Ca2+ model, we quantitatively evaluated mitochondrial uptake and storage capacity requirements to compensate for PV lack and analyzed possible extracellular export.
RESULTS: [Ca2+]mito during tetanic stimulation is greater in knock-out (KO) (1362 ± 392 nM) than in wild-type (WT) (855 ± 392 nM), p < 0.05. Under the assumption of a non-linear intramitochondrial buffering, the model predicts an accumulation of 725 μmoles/Lfiber (buffering ratio 1:11 000) in KO, much higher than in WT (137 μmoles/Lfiber, ratio 1:4500). The required transport rate via mitochondrial calcium uniporter (MCU) reaches 3 mM/s, compatible with available literature. TEM images of calcium entry units and Mn2+ quenching showed a greater capacity of store-operated calcium entry in KO compared to WT. However, levels of [Ca2+]cyto during tetanic stimulation were not modulated to variations of extracellular calcium.
CONCLUSIONS: The model-based analysis of experimentally determined calcium distribution during tetanic stimulation showed that mitochondria can act as a buffer to compensate for the lack of PV. This result contributes to a better understanding of mitochondria's role in modulating [Ca2+]cyto in skeletal muscle fibers.

Keywords:  calcium; mitochondria; mouse skeletal muscle fibers; parvalbumin; reaction–diffusion model

DOI:  https://doi.org/10.1111/apha.14208
J Muscle Res Cell Motil. 2024 Jul 31.

Inhibition of the ubiquitin-proteasome system reduces the abundance of pyruvate dehydrogenase kinase 1 in cultured myotubes.

Blaž Kociper, Nives Škorja Milić, Ivana Ogrizek, Katarina Miš, Sergej Pirkmajer.

  Pyruvate dehydrogenase kinase (PDK), which phosphorylates the pyruvate dehydrogenase complex, regulates glucose metabolism in skeletal muscle. PDK1, an isozyme whose expression is controlled by hypoxia-inducible factor-1α (HIF-1α), is thought to play a role in muscle adaptation to hypoxia. While transcriptional upregulation of PDK1 by HIF-1α is well characterised, mechanisms controlling proteolysis of PDK1 in skeletal muscle have not been thoroughly investigated. Proteasome inhibitor MG132 paradoxically reduced the abundance of PDK1 in human cancer cells and rat L6 myotubes, suggesting that MG132 might direct PDK1 towards autophagic degradation. The objectives of our current study were to determine (1) whether MG132 suppresses PDK1 levels in primary human myotubes, (2) whether chloroquine, an inhibitor of autophagy, prevents MG132-induced suppression of PDK1 in L6 myotubes, and (3) whether PYR-41, an inhibitor of ubiquitination, suppresses PDK1 in L6 myotubes. Using qPCR and/or immunoblotting, we found that despite markedly upregulating HIF-1α protein, MG132 did not alter the PDK1 expression in cultured primary human myotubes, while it suppressed both PDK1 mRNA and protein in L6 myotubes. The PDK1 levels in L6 myotubes were suppressed also during co-treatment with chloroquine and MG132. PYR-41 markedly increased the abundance of HIF-1α in primary human and L6 myotubes, while reducing the abundance of PDK1. In L6 myotubes treated with PYR-41, chloroquine increased the abundance of the epidermal growth factor receptor, but did not prevent the suppression of PDK1. Collectively, our results suggest that cultured myotubes degrade PDK1 via a pathway that cannot be inhibited by MG132, PYR-41, and/or chloroquine.

Keywords:  Chloroquine; Hypoxia-inducible factor-1α (HIF-1α); MG132; Myotubes; PYR-41; Pyruvate dehydrogenase kinase 1 (PDK1)

DOI:  https://doi.org/10.1007/s10974-024-09679-3
Mol Cell Endocrinol. 2024 Jul 31. pii: S0303-7207(24)00192-8. [Epub ahead of print] 112336

DNA methylation of Ad4BP/SF-1 suppresses Cyp11a1 and StAR transcripts in C2C12 myoblasts.

Jumpei Fujiki, Maeda Naoyuki, Kosuke Yamaguchi, Yuya Ohtsuki, Hidetomo Iwano.

  Steroidogenesis occurs locally in peripheral tissues and via adrenal and gonadal glands' biosynthesis. The C2C12 mouse myoblast cell line and rat skeletal muscles harbor a local steroidogenesis pathway for glucocorticoids, and corticosterone is biosynthesized from skeletal muscle cells. However, Cyp11a1 and StAR protein expressions are not observed in C2C12 cells or rat muscular tissues. In this context, this study investigated the relationship between DNA methylation and key steroidogenic genes. Bioinformatics analysis of methylated DNA immune precipitation showed that C2C12 myoblasts and myotubes did not have remarkable DNA methylated regions in the gene-body of Cyp11a1. However, a highly methylated region in the CpG island was detected in the intronic enhancer of Ad4BP/SF-1, known as the transcriptional factor for steroidogenic genes. After C2C12 myoblasts treatment with 5-aza-2-deoxycytidine, the gene expressions of Ad4BP/SF-1, Cyp11a1, and StAR were significantly time- and concentration-dependent upregulated. To clarify the contribution of Ad4BP/SF-1 on Cyp11a1 and StAR transcripts, we silenced Ad4BP/SF-1 during the 5-aza-2-deoxycytidine treatment in C2C12 myoblasts, resulting in significant suppression of both Cyp11a1 and StAR. Additionally, pregnenolone levels in the supernatants of C2C12 cells were enhanced by 5-aza-2-deoxycytidine treatment, whereas pregnenolone production by C2C12 myoblasts was significantly suppressed by Ad4BP/SF-1 knockdown. These results indicate that DNA methylation of Ad4BP/SF-1 might be involved in the downregulation of steroidogenic genes, such as Cyp11a1 and StAR in C2C12 myoblasts.

Keywords:  Androgen; Cholesterol; Cyp17a1; Estrogen; Glucocorticoid; Mitochondrion; Sulfate–sulfatase pathway

DOI:  https://doi.org/10.1016/j.mce.2024.112336
PLoS One. 2024 ;19(8): e0306021

Sporadic inclusion body myositis-derived myotube culture revealed muscle cell-autonomous expression profiles.

Naoki Suzuki, Makoto Kanzaki, Masashi Koide, Rumiko Izumi, Ryo Fujita, Tadahisa Takahashi, Kazumi Ogawa, Yutaka Yabe, Masahiro Tsuchiya, Masako Suzuki, Ryuhei Harada, Akiyuki Ohno, Hiroya Ono, Naoko Nakamura, Kensuke Ikeda, Hitoshi Warita, Shion Osana, Yoshitsugu Oikawa, Takafumi Toyohara, Takaaki Abe, Muliang Rui, Satoru Ebihara, Ryoichi Nagatomi, Yoshihiro Hagiwara, Masashi Aoki.

Sporadic inclusion body myositis (sIBM) is a muscle disease in older people and is characterized by inflammatory cell invasion into intact muscle fibers and rimmed vacuoles. The pathomechanism of sIBM is not fully elucidated yet, and controversy exists as to whether sIBM is a primary autoimmune disease or a degenerative muscle disease with secondary inflammation. Previously, we established a method of collecting CD56-positive myoblasts from human skeletal muscle biopsy samples. We hypothesized that the myoblasts derived from these patients are useful to see the cell-autonomous pathomechanism of sIBM. With these resources, myoblasts were differentiated into myotubes, and the expression profiles of cell-autonomous pathology of sIBM were analyzed. Myoblasts from three sIBM cases and six controls were differentiated into myotubes. In the RNA-sequencing analysis of these "myotube" samples, 104 differentially expressed genes (DEGs) were found to be significantly upregulated by more than twofold in sIBM, and 13 DEGs were downregulated by less than twofold. For muscle biopsy samples, a comparative analysis was conducted to determine the extent to which "biopsy" and "myotube" samples differed. Fifty-three DEGs were extracted of which 32 (60%) had opposite directions of expression change (e.g., increased in biopsy vs decreased in myotube). Apolipoprotein E (apoE) and transmembrane protein 8C (TMEM8C or MYMK) were commonly upregulated in muscle biopsies and myotubes from sIBM. ApoE and myogenin protein levels were upregulated in sIBM. Given that enrichment analysis also captured changes in muscle contraction and development, the triggering of muscle atrophy signaling and abnormal muscle differentiation via MYMK or myogenin may be involved in the pathogenesis of sIBM. The presence of DEGs in sIBM suggests that the myotubes formed from sIBM-derived myoblasts revealed the existence of muscle cell-autonomous degeneration in sIBM. The catalog of DEGs will be an important resource for future studies on the pathogenesis of sIBM focusing on primary muscle degeneration.

DOI: https://doi.org/10.1371/journal.pone.0306021
Cytoskeleton (Hoboken). 2024 Aug 01.

Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy.

Subarna Dutta, T Muraganadan, Madavan Vasudevan.

  Most of the single point mutations of the LMNA gene are associated with distinct muscular dystrophies, marked by heterogenous phenotypes but primarily the loss and symmetric weakness of skeletal muscle tissue. The molecular mechanism and phenotype-genotype relationships in these muscular dystrophies are poorly understood. An effort has been here to delineating the adaptation of mechanical inputs into biological response by mutant cells of lamin A associated muscular dystrophy. In this study, we implement engineered smooth and pattern surfaces of particular young modulus to mimic muscle physiological range. Using fluorescence and atomic force microscopy, we present distinct architecture of the actin filament along with abnormally distorted cell and nuclear shape in mutants, which showed a tendency to deviate from wild type cells. Topographic features of pattern surface antagonize the binding of the cell with it. Correspondingly, from the analysis of genome wide expression data in wild type and mutant cells, we report differential expression of the gene products of the structural components of cell adhesion as well as LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes. This study also reveals mis expressed downstream signaling processes in mutant cells, which could potentially lead to onset of the disease upon the application of engineered materials to substitute the role of conventional cues in instilling cellular behaviors in muscular dystrophies. Collectively, these data support the notion that lamin A is essential for proper cellular mechanotransduction from extracellular environment to the genome and impairment of the muscle cell differentiation in the pathogenic mechanism for lamin A associated muscular dystrophy.

Keywords:  confocal imaging; lamins; mechanotransduction; muscular dystrophy; nuclear morphometry

DOI:  https://doi.org/10.1002/cm.21895
Nat Commun. 2024 Jul 28. 15(1): 6357

Gene body DNA hydroxymethylation restricts the magnitude of transcriptional changes during aging.

James R Occean, Na Yang, Yan Sun, Marshall S Dawkins, Rachel Munk, Cedric Belair, Showkat Dar, Carlos Anerillas, Lin Wang, Changyou Shi, Christopher Dunn, Michel Bernier, Nathan L Price, Julie S Kim, Chang-Yi Cui, Jinshui Fan, Moitrayee Bhattacharyya, Supriyo De, Manolis Maragkakis, Rafael de Cabo, Simone Sidoli, Payel Sen.

DNA hydroxymethylation (5hmC), the most abundant oxidative derivative of DNA methylation, is typically enriched at enhancers and gene bodies of transcriptionally active and tissue-specific genes. Although aberrant genomic 5hmC has been implicated in age-related diseases, its functional role in aging remains unknown. Here, using mouse liver and cerebellum as model organs, we show that 5hmC accumulates in gene bodies associated with tissue-specific function and restricts the magnitude of gene expression changes with age. Mechanistically, 5hmC decreases the binding of splicing associated factors and correlates with age-related alternative splicing events. We found that various age-related contexts, such as prolonged quiescence and senescence, drive the accumulation of 5hmC with age. We provide evidence that this age-related transcriptionally restrictive function is conserved in mouse and human tissues. Our findings reveal that 5hmC regulates tissue-specific function and may play a role in longevity.

DOI: https://doi.org/10.1038/s41467-024-50725-y
J Appl Physiol (1985). 2024 Aug 01.

Leg Cycling Efficiency is Unaltered in Healthy Aging Regardless of Sex, or Training Status.

Justin J Duong, Robert G Leija, Adam D Osmond, Jose A Arevalo, George A Brooks.

  Muscular efficiency during exercise has been used to interrogate aspects of human muscle energetics, including mitochondrial coupling and biomechanical efficiencies. Typically, assessments of muscular efficiency have involved graded exercises. Results of previous studies have been interpreted to indicate a decline in exercise efficiency with aging owing to decreased mitochondrial function. However, discrepancies in variables such as exercise stage duration, cycling cadence, and treadmill walking mechanics may have affected interpretations of results. Furthermore, recent data from our lab examining the ATP to oxygen ratio (P:O) in mitochondrial preparations isolated from NIA mouse skeletal muscle showed no change with aging. Thus, we hypothesized that Delta Efficiency (∆€) during steady-rate cycling exercise would not be altered in older healthy subjects compared to young counterparts regardless of biological sex or training status. Young (21-35 years) and older (60-80 years) men (n=21) and women (n=20) underwent continual, progressive leg cycle ergometer tests pedaling at 60 RPM for 3 stages (35, 60, 85 W) lasting 4 minutes. ∆€ was calculated as: (∆ Work Accomplished/∆ Energy Expended). Overall, cycling efficiencies were not significantly different in older compared to young subjects. Similarly, trained subjects did not exhibit significantly different exercise efficiency compared to untrained. Moreover, there were no differences between men and women. Hence, our results obtained on healthy young and older subjects are interpreted to mean that previous reports of decreased efficiency in older individuals were attributable to metabolic or biomechanical comorbidities, not aging per se.

Keywords:  Aging; excitation-contraction coupling; human metabolism; muscle mechanical efficiency; oxidative phosphorylation efficiency

DOI:  https://doi.org/10.1152/japplphysiol.00393.2024
Nature. 2024 Jul 31.

Structural switch in acetylcholine receptors in developing muscle.

Huanhuan Li, Jinfeng Teng, Ryan E Hibbs.

During development, motor neurons originating in the brainstem and spinal cord form elaborate synapses with skeletal muscle fibres1. These neurons release acetylcholine (ACh), which binds to nicotinic ACh receptors (AChRs) on the muscle, initiating contraction. Two types of AChR are present in developing muscle cells, and their differential expression serves as a hallmark of neuromuscular synapse maturation2-4. The structural principles underlying the switch from fetal to adult muscle receptors are unknown. Here, we present high-resolution structures of both fetal and adult muscle nicotinic AChRs, isolated from bovine skeletal muscle in developmental transition. These structures, obtained in the absence and presence of ACh, provide a structural context for understanding how fetal versus adult receptor isoforms are tuned for synapse development versus the all-or-none signalling required for high-fidelity skeletal muscle contraction. We find that ACh affinity differences are driven by binding site access, channel conductance is tuned by widespread surface electrostatics and open duration changes result from intrasubunit interactions and structural flexibility. The structures further reveal pathogenic mechanisms underlying congenital myasthenic syndromes.

DOI: https://doi.org/10.1038/s41586-024-07774-6
Aging Cell. 2024 Jul 30. e14284

Histone β-hydroxybutyrylation is critical in reversal of sarcopenia.

Qiquan Wang, Xinqiang Lan, Hao Ke, Siman Xu, Chunping Huang, Jiali Wang, Xiang Wang, Tiane Huang, Xia Wu, Mengxin Chen, Yingqi Guo, Lin Zeng, Xiao-Li Tian, Yang Xiang.

  Sarcopenia, a leading cause for global disability and mortality, is an age-related muscular disorder, characterized by accelerated muscle mass loss and functional decline. It is known that caloric restriction (CR), ketogenic diet or endurance exercise lessen sarcopenia and elevate circulating β-hydroxybutyrate (β-HB) levels. Whether the elevated β-HB is essential to the reversal of sarcopenia, however, remains unclear. Here we show in both Caenorhabditis elegans and mouse models that an increase of β-HB reverse myofiber atrophy and improves motor functions at advanced ages. β-HB-induced histone lysine β-hydroxybutyrylation (Kbhb) is indispensable for the reversal of sarcopenia. Histone Kbhb enhances transcription of genes associated with mitochondrial pathways, including oxidative phosphorylation, ATP metabolic process and aerobic respiration. This ultimately leads to improve mitochondrial integrity and enhance mitochondrial respiration. The histone Kbhb are validated in mouse model with CR. Thus, we demonstrate that β-HB induces histone Kbhb, increases mitochondrial function, and reverses sarcopenia.

Keywords:  mitochondria; sarcopenia; skeletal muscle; β‐hydroxybutyrate; β‐hydroxybutyrylation

DOI:  https://doi.org/10.1111/acel.14284
Lab Chip. 2024 Jul 29.

Studying the impact of geometrical and cellular cues on myogenesis with a skeletal muscle-on-chip.

M-L Nguyen, N Demri, B Lapin, F Di Federico, G Gropplero, F Cayrac, K Hennig, Edgar R Gomes, C Wilhelm, W Roman, S Descroix.

In the skeletal muscle tissue, cells are organized following an anisotropic architecture, which is both required during myogenesis when muscle precursor cells fuse to generate myotubes and for its contractile function. To build an in vitro skeletal muscle tissue, it is therefore essential to develop methods to organize cells in an anisotropic fashion, which can be particularly challenging, especially in 3D. In this study, we present a versatile muscle-on-chip system with adjustable collagen hollow tubes that can be seeded with muscle precursor cells. The collagen acts both as a tube-shaped hollow mold and as an extracellular matrix scaffold that can house other cell types for co-culture. We found that the diameter of the channel affects the organization of the muscle cells and that proper myogenesis was obtained at a diameter of 75 μm. In these conditions, muscle precursor cells fused into long myotubes aligned along these collagen channels, resulting in a fascicle-like structure. These myotubes exhibited actin striations and upregulation of multiple myogenic genes, reflecting their maturation. Moreover, we showed that our chip allowed muscle tissue culture and maturation over a month, with the possibility of fibroblast co-culture embedding in the collagen matrix.

DOI: https://doi.org/10.1039/d4lc00417e
FASEB J. 2024 Aug 15. 38(15): e23845

Greater molecular potential for glucose metabolism in adipose tissue and skeletal muscle of women compared with men.

Trine S Nicolaisen, Kim A Sjøberg, Christian S Carl, Erik A Richter, Bente Kiens, Andreas M Fritzen, Anne-Marie Lundsgaard.

  Women typically have less muscle mass and more fat mass than men, while at the same time possessing similar or even greater whole-body insulin sensitivity. Our study aimed to investigate the molecular factors in primarily adipose tissue, but also in skeletal muscle, contributing to this sex difference. In healthy, moderately active premenopausal women and men with normal weight (28 ± 5 and 23 ± 3 years old; BMI 22.2 ± 1.9 and 23.7 ± 1.7) and in healthy, recreationally active women and men with overweight (32.2 ± 6 and 31.0 ± 5 years old; BMI 29.8 ± 4.3 & 30.9 ± 3.7) matched at age, BMI, and fitness level, we assessed insulin sensitivity and glucose tolerance with a hyperinsulinemic-euglycemic clamp or oral glucose tolerance test and studied subcutaneous adipose tissue and skeletal muscle samples with western blotting. Additionally, we traced glucose-stimulated glucose disposal in adipose tissues of female and male C57BL/6J littermate mice aged 16 weeks and measured glucose metabolic proteins. Our findings revealed greater protein expression related to glucose disposal in the subcutaneous adipose tissue (AKT2, insulin receptor, glucose transport 4) and skeletal muscle (hexokinase II, pyruvate dehydrogenase) in women compared to matched men with normal weight and with overweight. This increased protein capacity for glucose uptake extended to white adipose tissues of mice accompanied with ~2-fold greater glucose uptake compared to male mice. Furthermore, even in the obese state, women displayed better glucose tolerance than matched men, despite having 46% body fat and 20 kg less lean mass. In conclusion, our findings suggest that the superior potential for glucose disposal in female subcutaneous adipose tissue and skeletal muscle, driven by greater expression of various glucose metabolic proteins, compensates for their lower muscle mass. This likely explains women's superior glucose tolerance and tissue insulin sensitivity compared to men.

Keywords:  adipocytes; adiponectin; gender; glucose metabolism; insulin action; obesity; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202302377R
Skelet Muscle. 2024 Aug 02. 14(1): 18

Age-related differences in the loss and recovery of serial sarcomere number following disuse atrophy in rats.

Avery Hinks, Geoffrey A Power.

  BACKGROUND: Older adults exhibit a slower recovery of muscle mass following disuse atrophy than young adults. At a smaller scale, muscle fibre cross-sectional area (i.e., sarcomeres in parallel) exhibits this same pattern. Less is known, however, about age-related differences in the recovery of muscle fibre length, driven by increases in serial sarcomere number (SSN), following disuse. The purpose of this study was to investigate age-related differences in SSN adaptations and muscle mechanical function during and following muscle immobilization. We hypothesized that older adult rats would experience a similar magnitude of SSN loss during immobilization, however, take longer to recover SSN than young following cast removal, which would limit the recovery of muscle mechanical function.METHODS: We casted the plantar flexors of young (8 months) and old (32 months) male rats in a shortened position for 2 weeks, and assessed recovery during 4 weeks of voluntary ambulation. Following sacrifice, legs were fixed in formalin for measurement of soleus SSN and physiological cross-sectional area (PCSA) with the un-casted soleus acting as a control. Ultrasonographic measurements of pennation angle (PA) and muscle thickness (MT) were conducted weekly. In-vivo active and passive torque-angle relationships were constructed pre-cast, post-cast, and following 4 weeks of recovery.
RESULTS: From pre- to post-cast, young and older adult rats experienced similar decreases in SSN (-20%, P < 0.001), muscle wet weight (-25%, P < 0.001), MT (-30%), PA (-15%, P < 0.001), and maximum isometric torque (-40%, P < 0.001), but there was a greater increase in passive torque in older (+ 180%, P < 0.001) compared to young adult rats (+ 68%, P = 0.006). Following cast removal, young exhibited quicker recovery of SSN and MT than old, but SSN recovered sooner than PA and MT in both young and old. PCSA nearly recovered and active torque fully recovered in young adult rats, whereas in older adult rats these remained unrecovered at ∼ 75%.
CONCLUSIONS: This study showed that older adult rats retain a better ability to recover longitudinal compared to parallel muscle morphology following cast removal, making SSN a highly adaptable target for improving muscle function in elderly populations early on during rehabilitation.

Keywords:  Fascicle length; Force-length relationship; Muscle architecture; Muscle thickness; Pennation angle; Sarcomere length

DOI:  https://doi.org/10.1186/s13395-024-00351-5
Sci Rep. 2024 Jul 31. 14(1): 17631

Exploring protein relative relations in skeletal muscle proteomic analysis for insights into insulin resistance and type 2 diabetes.

Anna Czajkowska, Marcin Czajkowski, Lukasz Szczerbinski, Krzysztof Jurczuk, Daniel Reska, Wojciech Kwedlo, Marek Kretowski, Piotr Zabielski, Adam Kretowski.

The escalating prevalence of insulin resistance (IR) and type 2 diabetes mellitus (T2D) underscores the urgent need for improved early detection techniques and effective treatment strategies. In this context, our study presents a proteomic analysis of post-exercise skeletal muscle biopsies from individuals across a spectrum of glucose metabolism states: normal, prediabetes, and T2D. This enabled the identification of significant protein relationships indicative of each specific glycemic condition. Our investigation primarily leveraged the machine learning approach, employing the white-box algorithm relative evolutionary hierarchical analysis (REHA), to explore the impact of regulated, mixed mode exercise on skeletal muscle proteome in subjects with diverse glycemic status. This method aimed to advance the diagnosis of IR and T2D and elucidate the molecular pathways involved in its development and the response to exercise. Additionally, we used proteomics-specific statistical analysis to provide a comparative perspective, highlighting the nuanced differences identified by REHA. Validation of the REHA model with a comparable external dataset further demonstrated its efficacy in distinguishing between diverse proteomic profiles. Key metrics such as accuracy and the area under the ROC curve confirmed REHA's capability to uncover novel molecular pathways and significant protein interactions, offering fresh insights into the effects of exercise on IR and T2D pathophysiology of skeletal muscle. The visualizations not only underscored significant proteins and their interactions but also showcased decision trees that effectively differentiate between various glycemic states, thereby enhancing our understanding of the biomolecular landscape of T2D.

DOI: https://doi.org/10.1038/s41598-024-68568-4
Res Diagn Interv Imaging. 2023 Jun;6 100026

Diagnosing sarcopenia with semi-automated skeletal muscle computed tomography cutoff values and the association of these muscle metrics with long-term physical exercise.

Robert Janiszewski, Nathan Law, Ryan Walters, Tami DenOtter.

DOI: https://doi.org/10.1016/j.redii.2023.100026
J Cachexia Sarcopenia Muscle. 2024 Aug 02.

l-Carnitine relieves cachexia-related skeletal muscle fibrosis by inducing deltex E3 ubiquitin ligase 3L to negatively regulate the Runx2/COL1A1 axis.

Zongliang Lu, Li Wang, Zhenyu Huo, Na Li, Ning Tong, Feifei Chong, Jie Liu, Yaowen Zhang, Hongxia Xu.

  BACKGROUND: Cancer cachexia-induced skeletal muscle fibrosis (SMF) impairs muscle regeneration, alters the muscle structure and function, reduces the efficacy of anticancer drugs, diminishes the patient's quality of life and shortens overall survival. RUNX family transcription factor 2 (Runx2), a transcription factor, and collagen type I alpha 1 chain (COL1A1), the principal constituent of SMF, have been linked previously, with Runx2 shown to directly modulate COL1A1 mRNA levels. l-Carnitine, a marker of cancer cachexia, can alleviate fibrosis in liver and kidney models; however, its role in cancer cachexia-associated fibrosis and the involvement of Runx2 in the process remain unexplored.METHODS: Female C57 mice (48 weeks old) were inoculated subcutaneously with MC38 cells to establish a cancer cachexia model. A 5 mg/kg dose of l-carnitine or an equivalent volume of water was administered for 14 days via oral gavage, followed by assessments of muscle function (grip strength) and fibrosis. To elucidate the interplay between the deltex E3 ubiquitin ligase 3L(DTX3L)/Runx2/COL1A1 axis and fibrosis in transforming growth factor beta 1-stimulated NIH/3T3 cells, a suite of molecular techniques, including quantitative real-time PCR, western blot analysis, co-immunoprecipitation, molecular docking, immunofluorescence and Duolink assays, were used. The relevance of the DTX3L/Runx2/COL1A1 axis in the gastrocnemius was also explored in the in vivo model.
RESULTS: l-Carnitine supplementation reduced cancer cachexia-induced declines in grip strength (>88.2%, P < 0.05) and the collagen fibre area within the gastrocnemius (>57.9%, P < 0.05). At the 5 mg/kg dose, l-carnitine also suppressed COL1A1 and alpha-smooth muscle actin (α-SMA) protein expression, which are markers of SMF and myofibroblasts. Analyses of the TRRUST database indicated that Runx2 regulates both COL1A1 and COL1A2. In vitro, l-carnitine diminished Runx2 protein levels and promoted its ubiquitination. Overexpression of Runx2 abolished the effects of l-carnitine on COL1A1 and α-SMA. Co-immunoprecipitation, molecular docking, immunofluorescence and Duolink assays confirmed an interaction between DTX3L and Runx2, with l-carnitine enhancing this interaction to promote Runx2 ubiquitination. l-Carnitine supplementation restored DTX3L levels to those observed under non-cachectic conditions, both in vitro and in vivo. Knockdown of DTX3L abolished the effects of l-carnitine on Runx2, COL1A1 and α-SMA in vitro. The expression of DTX3L was negatively correlated with the levels of Runx2 and COL1A1 in untreated NIH/3T3 cells.
CONCLUSIONS: This study revealed a previously unrecognized link between Runx2 and DTX3L in SMF and demonstrated that l-carnitine exerted a significant therapeutic impact on cancer cachexia-associated SMF, potentially through the upregulation of DTX3L.

Keywords:   l‐carnitine; DTX3L; Runx2; cancer cachexia; skeletal muscle fibrosis

DOI:  https://doi.org/10.1002/jcsm.13544
Nat Aging. 2024 Aug 02.

Multiorgan biological age shows that no organ system is an island.

DOI: https://doi.org/10.1038/s43587-024-00690-4