bims-moremu 2023-10-15 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–10–15
29 papers selected by
Anna Vainshtein, Craft Science Inc.

GADD45A is a mediator of mitochondrial loss, atrophy, and weakness in skeletal muscle.
Fn14 promotes myoblast fusion during regenerative myogenesis.
Physical exercise elicits UPRmt in the skeletal muscle: The role of c-Jun N-terminal kinase.
Interleukin-1β triggers muscle-derived extracellular superoxide dismutase expression and protects muscles from doxorubicin-induced atrophy.
Voluntary wheel running mitigates disease in an Orai1 gain-of-function mouse model of tubular aggregate myopathy.
Integrated single-cell multiome analysis reveals muscle fiber-type gene regulatory circuitry modulated by endurance exercise.
Adaptability to Eccentric Exercise Training is Diminished with Age in Female Mice.
ERRα fosters running endurance by driving myofiber aerobic transformation and fuel efficiency.
Pax7 haploinsufficiency impairs muscle stem cell function in Cre-recombinase mice and underscores the importance of appropriate controls.
Fiber Type Identification of Human Skeletal Muscle.
Postnatal skeletal muscle myogenesis governed by signal transduction networks: MAPKs and PI3K-Akt control multiple steps.
Maintenance of subsynaptic myonuclei number is not driven by neural input.
Characterization of differential distribution patterns between mitofusin isoforms and their interaction in developing skeletal muscles of rat.
Effect of Yeast-Derived Peptides on Skeletal Muscle Function and Exercise-Induced Fatigue in C2C12 Myotube Cells and ICR Mice.
Palmitate-induced insulin resistance causes actin filament stiffness and GLUT4 mis-sorting without altered Akt signaling.
Skeletal Muscle Extracellular Matrix Structure Under Applied Deformation Observed Using Second Harmonic Generation Microscopy.
Single-Nuclei RNA-Sequencing of the Gastrocnemius Muscle in Peripheral Artery Disease.
Non-canonical Ca2+- Akt signaling pathway mediates the antiproteolytic effects induced by oxytocin receptor stimulation in skeletal muscle.
Regeneration of neuromuscular synapses after acute and chronic denervation by inhibiting the gerozyme 15-prostaglandin dehydrogenase.
From amino-acid to disease: the effects of oxidation on actin-myosin interactions in muscle.
Kinin B1 receptor modulates glucose homeostasis and physical exercise capacity by altering adrenal catecholamine synthesis and secretion.
Effects of Moderate Exercise Training on Cancer-Induced Muscle Wasting.
SIRT1 induction in the skeletal muscle of male mice partially attenuates changes to whole-body metabolism in response to androgen deprivation.
Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?
Calorie restriction modulates the transcription of genes related to stress response and longevity in human muscle: The CALERIE study.
Exercise mitigates Age-related Metabolic Diseases by improving Mitochondrial Dysfunction.
Sedentary Behavior Impacts on the Epigenome and Transcriptome: Lessons from Muscle Inactivation in Drosophila Larvae.
AAV-mediated skeletal muscle specific irisin expression does not contribute to weight loss in mice.
Deep coverage and quantification of the bone proteome provides enhanced opportunities for new discoveries in skeletal biology and disease.

JCI Insight. 2023 Oct 10. pii: e171772. [Epub ahead of print]

GADD45A is a mediator of mitochondrial loss, atrophy, and weakness in skeletal muscle.

George R Marcotte, Matthew J Miller, Hawley E Kunz, Zachary C Ryan, Matthew D Strub, Patrick M Vanderboom, Carrie J Heppelmann, Sarah Chau, Zachary D Von Ruff, Sean P Kilroe, Andrew T McKeen, Jason M Dierdorff, Jennifer I Stern, Karl A Nath, Chad E Grueter, Vitor A Lira, Andrew R Judge, Blake B Rasmussen, K Sreekumaran Nair, Ian R Lanza, Scott M Ebert, Christopher M Adams.

  Aging and many illnesses and injuries impair skeletal muscle mass and function, but the molecular mechanisms are not well understood. To better understand the mechanisms, we generated and studied transgenic mice with skeletal muscle-specific expression of Growth Arrest and DNA Damage Inducible Alpha (GADD45A), a signaling protein whose expression in skeletal muscle rises during aging and a wide range of illnesses and injuries. We found that GADD45A induced several cellular changes that are characteristic of skeletal muscle atrophy, including a reduction in skeletal muscle mitochondria and oxidative capacity, selective atrophy of glycolytic muscle fibers, and paradoxical expression of oxidative myosin heavy chains despite mitochondrial loss. These cellular changes were at least partly mediated by MEKK4, a protein kinase that is directly activated by GADD45A. By inducing these changes, GADD45A decreased the mass of muscles that are enriched in glycolytic fibers, and it impaired strength, specific force, and endurance exercise capacity. Furthermore, as predicted by data from mouse models, we found that GADD45A expression in skeletal muscle was associated with muscle weakness in humans. Collectively, these findings identify GADD45A as a mediator of mitochondrial loss, atrophy, and weakness in mouse skeletal muscle and a potential target for muscle weakness in humans.

Keywords:  Metabolism; Mitochondria; Muscle Biology; Skeletal muscle

DOI:  https://doi.org/10.1172/jci.insight.171772
Life Sci Alliance. 2023 Dec;pii: e202302312. [Epub ahead of print]6(12):

Fn14 promotes myoblast fusion during regenerative myogenesis.

Meiricris Tomaz da Silva, Aniket S Joshi, Micah B Castillo, Tatiana E Koike, Anirban Roy, Preethi H Gunaratne, Ashok Kumar.

Skeletal muscle regeneration involves coordinated activation of an array of signaling pathways. Fibroblast growth factor-inducible 14 (Fn14) is a bona fide receptor for the TWEAK cytokine. Levels of Fn14 are increased in the skeletal muscle of mice after injury. However, the cell-autonomous role of Fn14 in muscle regeneration remains unknown. Here, we demonstrate that global deletion of the Fn14 receptor in mice attenuates muscle regeneration. Conditional ablation of Fn14 in myoblasts but not in differentiated myofibers of mice inhibits skeletal muscle regeneration. Fn14 promotes myoblast fusion without affecting the levels of myogenic regulatory factors in the regenerating muscle. Fn14 deletion in myoblasts hastens initial differentiation but impairs their fusion. The overexpression of Fn14 in myoblasts results in the formation of myotubes having an increased diameter after induction of differentiation. Ablation of Fn14 also reduces the levels of various components of canonical Wnt and calcium signaling both in vitro and in vivo. Forced activation of Wnt signaling rescues fusion defects in Fn14-deficient myoblast cultures. Collectively, our results demonstrate that Fn14-mediated signaling positively regulates myoblast fusion and skeletal muscle regeneration.

DOI: https://doi.org/10.26508/lsa.202302312
Mol Metab. 2023 Oct 10. pii: S2212-8778(23)00150-3. [Epub ahead of print] 101816

Physical exercise elicits UPRmt in the skeletal muscle: The role of c-Jun N-terminal kinase.

Rodrigo Stellzer Gaspar, Carlos Kiyoshi Katashima, Barbara Moreira Crisol, Fernanda Silva Carneiro, Igor Sampaio, Leonardo Dos Reis Silveira, Adelino Sanchez Ramos da Silva, Dennys Esper Cintra, José Rodrigo Pauli, Eduardo Rochete Ropelle.

   OBJECTIVE: The mitochondrial unfolded protein response (UPRmt) is an adaptive cellular response to stress to ensure mitochondrial proteostasis and function. Here we explore the capacity of physical exercise to induce UPRmt in the skeletal muscle.
METHODS: Therefore, we combined mouse models of exercise (swimming and treadmill running), pharmacological intervention, and bioinformatics analyses.
RESULTS: Firstly, RNA sequencing and Western blotting analysis revealed that an acute aerobic session stimulated several mitostress-related genes and protein content in muscle, including the UPRmt markers. Conversely, using a large panel of isogenic strains of BXD mice, we identified that BXD73a and 73b strains displayed low levels of several UPRmt-related genes in the skeletal muscle, and this genotypic feature was accompanied by body weight gain, lower locomotor activity, and aerobic capacity. Finally, we identified that c-Jun N-terminal kinase (JNK) activation was critical in exercise-induced UPRmt in the skeletal muscle since pharmacological JNK pathway inhibition blunted exercise-induced UPRmt markers in mice muscle.
CONCLUSION: Our findings provide new insights into how exercise triggers mitostress signals toward the oxidative capacity in the skeletal muscle.

Keywords:  JNK; Mitochondria; Physical exercise; Skeletal muscle; UPR(mt)

DOI:  https://doi.org/10.1016/j.molmet.2023.101816
J Physiol. 2023 Oct 10.

Interleukin-1β triggers muscle-derived extracellular superoxide dismutase expression and protects muscles from doxorubicin-induced atrophy.

Mami Yamada, Mitsuharu Okutsu.

  Doxorubicin, a conventional chemotherapeutic agent prescribed for cancer, causes skeletal muscle atrophy and adversely affects mobility and strength. Given that doxorubicin-induced muscle atrophy is attributable primarily to oxidative stress, its effects could be mitigated by antioxidant-focused therapies; however, these protective therapeutic targets remain ambiguous. The aim of this study was to demonstrate that doxorubicin triggers severe muscle atrophy via upregulation of oxidative stress (4-hydroxynonenal and malondialdehyde) and atrogenes (atrogin-1/MAFbx and muscle RING finger-1) in association with decreased expression of the antioxidant enzyme extracellular superoxide dismutase (EcSOD), in cultured C2C12 myotubes and mouse skeletal muscle. Supplementation with EcSOD recombinant protein elevated EcSOD levels on the cellular membrane of cultured myotubes, consequently inhibiting doxorubicin-induced oxidative stress and myotube atrophy. Furthermore, doxorubicin treatment reduced interleukin-1β (IL-1β) mRNA expression in cultured myotubes and skeletal muscle, whereas transient IL-1β treatment increased EcSOD protein expression on the myotube membrane. Notably, transient IL-1β treatment of cultured myotubes and local administration in mouse skeletal muscle attenuated doxorubicin-induced muscle atrophy, which was associated with increased EcSOD expression. Collectively, these findings reveal that the regulation of skeletal muscle EcSOD via maintenance of IL-1β signalling is a potential therapeutic approach to counteract the muscle atrophy mediated by doxorubicin and oxidative stress. KEY POINTS: Doxorubicin, a commonly prescribed chemotherapeutic agent for patients with cancer, induces severe muscle atrophy owing to increased expression of oxidative stress; however, protective therapeutic targets are poorly understood. Doxorubicin induced muscle atrophy owing to increased expression of oxidative stress and atrogenes in association with decreased protein expression of extracellular superoxide dismutase (EcSOD) in cultured C2C12 myotubes and mouse skeletal muscle. Supplementation with EcSOD recombinant protein increased EcSOD levels on the cellular membrane of cultured myotubes, resulting in inhibition of doxorubicin-induced oxidative stress and myotube atrophy. Doxorubicin treatment decreased interleukin-1β (IL-1β) expression in cultured myotubes and skeletal muscle, whereas transient IL-1β treatment in vivo and in vitro increased EcSOD protein expression and attenuated doxorubicin-induced muscle atrophy. These findings reveal that regulation of skeletal muscle EcSOD via maintenance of IL-1β signalling is a possible therapeutic approach for muscle atrophy mediated by doxorubicin and oxidative stress.

Keywords:  cell culture; doxorubicin; extracellular superoxide dismutase; interleukin-1β; mouse skeletal muscle; muscle atrophy; oxidative stress

DOI:  https://doi.org/10.1113/JP285174
bioRxiv. 2023 Sep 29. pii: 2023.09.29.559036. [Epub ahead of print]

Voluntary wheel running mitigates disease in an Orai1 gain-of-function mouse model of tubular aggregate myopathy.

Thomas N O'Connor, Nan Zhao, Haley M Orciuoli, Alice Brasile, Laura Pietrangelo, Miao He, Linda Groom, Jennifer Leigh, Zahra Mahamed, Chen Liang, Sundeep Malik, Feliciano Protasi, Robert T Dirksen.

Tubular aggregate myopathy (TAM) is an inherited skeletal muscle disease associated with progressive muscle weakness, cramps, and myalgia. Tubular aggregates (TAs) are regular arrays of highly ordered and densely packed SR straight-tubes in muscle biopsies; the extensive presence of TAs represent a key histopathological hallmark of this disease in TAM patients. TAM is caused by gain-of-function mutations in proteins that coordinate store-operated Ca 2+ entry (SOCE): STIM1 Ca 2+ sensor proteins in the sarcoplasmic reticulum (SR) and Ca 2+ -permeable ORAI1 channels in the surface membrane. We have previously shown that voluntary wheel running (VWR) prevents formation of TAs in aging mice. Here, we assessed the therapeutic potential of endurance exercise (in the form of VWR) in mitigating the functional and structural alterations in a knock-in mouse model of TAM ( Orai1 G100S/+ or GS mice) based on a gain-of-function mutation in the ORAI1 pore. WT and GS mice were singly-housed for six months (from two to eight months of age) with either free-spinning or locked low profile wheels. Six months of VWR exercise significantly increased soleus peak tetanic specific force production, normalized FDB fiber Ca 2+ store content, and markedly reduced TAs in EDL muscle from GS mice. Six months of VWR exercise normalized the expression of mitochondrial proteins found to be altered in soleus muscle of sedentary GS mice in conjunction with a signature of increased protein translation and biosynthetic processes. Parallel proteomic analyses of EDL muscles from sedentary WT and GS mice revealed changes in a tight network of pathways involved in formation of supramolecular complexes, which were also normalized following six months of VWR. In summary, sustained voluntary endurance exercise improved slow twitch muscle function, reduced the presence of TAs in fast twitch muscle, and normalized the muscle proteome of GS mice consistent with protective adaptions in proteostasis, mitochondrial structure/function, and formation of supramolecular complexes.

DOI: https://doi.org/10.1101/2023.09.29.559036
bioRxiv. 2023 Oct 09. pii: 2023.09.26.558914. [Epub ahead of print]

Integrated single-cell multiome analysis reveals muscle fiber-type gene regulatory circuitry modulated by endurance exercise.

Aliza B Rubenstein, Gregory R Smith, Zidong Zhang, Xi Chen, Toby L Chambers, Frederique Ruf-Zamojski, Natalia Mendelev, Wan Sze Cheng, Michel Zamojski, Mary Anne S Amper, Venugopalan D Nair, Andrew R Marderstein, Stephen B Montgomery, Olga G Troyanskaya, Elena Zaslavsky, Todd Trappe, Scott Trappe, Stuart C Sealfon.

Endurance exercise is an important health modifier. We studied cell-type specific adaptations of human skeletal muscle to acute endurance exercise using single-nucleus (sn) multiome sequencing in human vastus lateralis samples collected before and 3.5 hours after 40 min exercise at 70% VO2max in four subjects, as well as in matched time of day samples from two supine resting circadian controls. High quality same-cell RNA-seq and ATAC-seq data were obtained from 37,154 nuclei comprising 14 cell types. Among muscle fiber types, both shared and fiber-type specific regulatory programs were identified. Single-cell circuit analysis identified distinct adaptations in fast, slow and intermediate fibers as well as LUM-expressing FAP cells, involving a total of 328 transcription factors (TFs) acting at altered accessibility sites regulating 2,025 genes. These data and circuit mapping provide single-cell insight into the processes underlying tissue and metabolic remodeling responses to exercise.

DOI: https://doi.org/10.1101/2023.09.26.558914
J Appl Physiol (1985). 2023 Oct 12.

Adaptability to Eccentric Exercise Training is Diminished with Age in Female Mice.

Cory W Baumann, Colleen S Deane, Timothy Etheridge, Nathaniel J Szewczyk, Craig R G Willis, Dawn A Lowe.

  The ability of skeletal muscle to adapt to eccentric contractions has been suggested to be blunted in older muscle. If eccentric exercise is to be a safe and efficient training mode for older adults, preclinical studies need to establish if older muscle can effectively adapt and if not, determine the molecular signatures that are causing this impairment. The purpose of this study was to quantify the extent age impacts functional adaptations of muscle and identify genetic signatures associated with adaptation (or lack thereof). The anterior crural muscles of young (4 mo) and older (28 mo) female mice performed repeated bouts of eccentric contractions in vivo (50 contractions/wk for 5 wk) and isometric torque was measured across the initial and final bouts. Transcriptomics was completed by RNA-sequencing 1 wk following the 5th bout to identify common and differentially regulated genes. Young muscle exhibited a robust ability to adapt, increasing isometric torque 20-36%, while isometric torque of older muscle decreased up to 18%; adaptive potential was less in older muscle compared to young muscle (p≤0.047). Using differential gene expression, young and older muscles shared some common transcriptional changes in response to eccentric exercise training, whereas other transcripts appeared to be age dependent. That is, the ability to express particular genes after repeated bouts of eccentric contractions was not the same between ages. These molecular signatures may reveal, in part, why older muscles do not appear to be as adaptive to exercise training as young muscles.

Keywords:  repeated bout effect; resistance training; skeletal muscle; strength; transcriptomics

DOI:  https://doi.org/10.1152/japplphysiol.00428.2023
Mol Metab. 2023 Oct 05. pii: S2212-8778(23)00148-5. [Epub ahead of print] 101814

ERRα fosters running endurance by driving myofiber aerobic transformation and fuel efficiency.

Hui Xia, Charlotte Scholtes, Catherine R Dufour, Christina Guluzian, Vincent Giguère.

   OBJECTIVE: Estrogen related receptor α (ERRα) occupies a central node in the transcriptional control of energy metabolism, including in skeletal muscle, but whether modulation of its activity can directly contribute to extend endurance to exercise remains to be investigated. The goal of this study was to characterize the benefit of mice engineered to express a physiologically relevant activated form of ERRα on skeletal muscle exercise metabolism and performance.
METHODS: We recently shown that mutational inactivation of three regulated phosphosites in the amino terminal domain of the nuclear receptor ERRα impedes its degradation, leading to an accumulation of ERRα proteins and perturbation of metabolic homeostasis in ERRα3SA mutant mice. Herein, we used a multi-omics approach in combination with physical endurance tests to ascertain the consequences of expressing the constitutively active phospho-deficient ERRα3SA form on muscle exercise performance and energy metabolism.
RESULTS: Genetic heightening of ERRα activity enhanced exercise capacity, fatigue-resistance, and endurance. This phenotype resulted from extensive reprogramming of ERRα global DNA occupancy and transcriptome in muscle leading to an increase in oxidative fibers, mitochondrial biogenesis, fatty acid oxidation, and lactate homeostasis.
CONCLUSION: Our findings support the potential to enhance physical performance and exercise-induced health benefits by targeting molecular pathways regulating ERRα transcriptional activity.

Keywords:  Diabetes; Endurance exercise; Fuel metabolism; Lactate; Mitochondrial oxidative metabolism; Muscle function; Muscle wasting; Myofibers; Nuclear receptor

DOI:  https://doi.org/10.1016/j.molmet.2023.101814
Stem Cell Res Ther. 2023 Oct 13. 14(1): 294

Pax7 haploinsufficiency impairs muscle stem cell function in Cre-recombinase mice and underscores the importance of appropriate controls.

Despoina Mademtzoglou, Perla Geara, Philippos Mourikis, Frederic Relaix.

  Ever since its introduction as a genetic tool, the Cre-lox system has been widely used for molecular genetic studies in vivo in the context of health and disease, as it allows time- and cell-specific gene modifications. However, insertion of the Cre-recombinase cassette in the gene of interest can alter transcription, protein expression, or function, either directly, by modifying the landscape of the locus, or indirectly, due to the lack of genetic compensation or by indirect impairment of the non-targeted allele. This is sometimes the case when Cre-lox is used for muscle stem cell studies. Muscle stem cells are required for skeletal muscle growth, regeneration and to delay muscle disease progression, hence providing an attractive model for stem cell research. Since the transcription factor Pax7 is specifically expressed in all muscle stem cells, tamoxifen-inducible Cre cassettes (CreERT2) have been inserted into this locus by different groups to allow targeted gene recombination. Here we compare the two Pax7-CreERT2 mouse lines that are mainly used to evaluate muscle regeneration and development of pathological features upon deletion of specific factors or pathways. We applied diverse commonly used tamoxifen schemes of CreERT2 activation, and we analyzed muscle repair after cardiotoxin-induced injury. We show that consistently the Pax7-CreERT2 allele targeted into the Pax7 coding sequence (knock-in/knock-out allele) produces an inherent defect in regeneration, manifested as delayed post-injury repair and reduction in muscle stem cell numbers. In genetic ablation studies lacking proper controls, this inherent defect could be misinterpreted as being provoked by the deletion of the factor of interest. Instead, using an alternative Pax7-CreERT2 allele that maintains bi-allelic Pax7 expression or including appropriate controls can prevent misinterpretation of experimental data. The findings presented here can guide researchers establish appropriate experimental design for muscle stem cell genetic studies.

Keywords:  Cre-lox; Mouse molecular genetics; Muscle stem cells; Pax7; Satellite cells; Stem cell research

DOI:  https://doi.org/10.1186/s13287-023-03506-1
J Vis Exp. 2023 Sep 22.

Fiber Type Identification of Human Skeletal Muscle.

Heidy K Latchman, Stefan G Wette, Dion J Ellul, Robyn M Murphy, Noni T Frankenberg.

The technique described here can be used to identify specific myosin heavy chain (MHC) isoforms in segments of individual muscle fibers using dot blotting, hereafter referred to as Myosin heavy chain detection by Dot Blotting for IDentification of muscle fiber type (MyDoBID). This protocol describes the process of freeze-drying human skeletal muscle and isolating segments of single muscle fibers. Using MyDoBID, type I and II fibers are classified with MHCI- and IIa-specific antibodies, respectively. Classified fibers are then combined into fiber type-specific samples for each biopsy. The total protein in each sample is determined by Sodium Dodecyl-Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and UV-activated gel technology. The fiber type of samples is validated using western blotting. The importance of performing protein loading normalization to enhance target protein detection across multiple western blots is also described. The benefits of consolidating classified fibers into fiber type-specific samples compared to single-fiber western blots, include sample versatility, increased sample throughput, shorter time investment, and cost-saving measures, all while retaining valuable fiber type-specific information that is frequently overlooked using homogenized muscle samples. The purpose of the protocol is to achieve accurate and efficient identification of type I and type II fibers isolated from freeze-dried human skeletal muscle samples. These individual fibers are subsequently combined to create type I and type II fiber type-specific samples. Furthermore, the protocol is extended to include the identification of type IIx fibers, using Actin as a marker for fibers that were negative for MHCI and MHCIIa, which are confirmed as IIx fibers by western blotting. Each fiber type-specific sample is then used to quantify the expression of various target proteins using western blotting techniques.

DOI: https://doi.org/10.3791/65750
Biochem Biophys Res Commun. 2023 Sep 27. pii: S0006-291X(23)01084-7. [Epub ahead of print]682 223-243

Postnatal skeletal muscle myogenesis governed by signal transduction networks: MAPKs and PI3K-Akt control multiple steps.

Takeshi Endo.

  Skeletal muscle myogenesis represents one of the most intensively and extensively examined systems of cell differentiation, tissue formation, and regeneration. Muscle regeneration provides an in vivo model system of postnatal myogenesis. It comprises multiple steps including muscle stem cell (or satellite cell) quiescence, activation, migration, myogenic determination, myoblast proliferation, myocyte differentiation, myofiber maturation, and hypertrophy. A variety of extracellular signaling and subsequent intracellular signal transduction pathways or networks govern the individual steps of postnatal myogenesis. Among them, MAPK pathways (the ERK, JNK, p38 MAPK, and ERK5 pathways) and PI3K-Akt signaling regulate multiple steps of myogenesis. Ca2+, cytokine, and Wnt signaling also participate in several myogenesis steps. These signaling pathways often control cell cycle regulatory proteins or the muscle-specific MyoD family and the MEF2 family of transcription factors. This article comprehensively reviews molecular mechanisms of the individual steps of postnatal skeletal muscle myogenesis by focusing on signal transduction pathways or networks. Nevertheless, no or only a partial signaling molecules or pathways have been identified in some responses during myogenesis. The elucidation of these unidentified signaling molecules and pathways leads to an extensive understanding of the molecular mechanisms of myogenesis.

Keywords:  MAPK pathways; Muscle regeneration; MyoD family; PI3K–Akt signaling; Signal transduction; Skeletal muscle myogenesis

DOI:  https://doi.org/10.1016/j.bbrc.2023.09.048
Front Physiol. 2023 ;14 1266950

Maintenance of subsynaptic myonuclei number is not driven by neural input.

Lloyd P Ruiz, Peter C Macpherson, Susan V Brooks.

  The development and maintenance of neuromuscular junctions (NMJ) are supported by a specialized population of myonuclei that are referred to as the subsynaptic myonuclei (SSM). The relationship between the number of SSM and the integrity of the NMJ as well as the impact of a loss of innervation on SSM remain unclear. This study aimed to clarify these associations by simultaneously analyzing SSM counts and NMJ innervation status in three distinct mouse models of acute and chronic NMJ disruption. SSM were identified using fluorescent immunohistochemistry for Nesprin1 expression, which is highly enriched in SSM, along with anatomical location beneath the muscle fiber motor endplate. Acute denervation, induced by surgical nerve transection, did not affect SSM number after 7 days. Additionally, no significant changes in SSM number were observed during normal aging or in mice with chronic oxidative stress (Sod1 -/-). Both aging WT mice and Sod1 -/- mice accumulated degenerating and denervated NMJ in skeletal muscle, but there was no correlation between innervation status of a given NMJ and SSM number in aged or Sod1 -/- mice. These findings challenge the notion that a loss of SSM is a primary driver of NMJ degradation and leave open questions of the mechanisms that regulate SSM number as well as the physiological significance of the precise SSM number. Further investigations are required to define other properties of the SSM, such as transcriptional profiles and structural integrity, to better understand their role in NMJ maintenance.

Keywords:  aging; innervation; muscle; myonuclei; neuromuscular junction; subsynaptic

DOI:  https://doi.org/10.3389/fphys.2023.1266950
J Cell Biochem. 2023 Oct 10.

Characterization of differential distribution patterns between mitofusin isoforms and their interaction in developing skeletal muscles of rat.

Unmod Senapati, Sunil Pani, Subhasmita Rout, Bijayashree Sahu, Punyadhara Pani, Gourabamani Swalsingh, Benudhara Pati, Naresh C Bal.

  Skeletal muscle during postnatal development undergoes several structural and biochemical modifications. It is proposed that these changes are closely intertwined with the increase in load-bearing capacity of the muscle (i.e., myofibrils) and molecular machinery to support the energy demand (i.e., mitochondria). Concomitant establishment of the sarcoplasmic reticulum (SR) and mitochondrial network seems to be a major developmental adjustment of skeletal muscle leading to adult phenotype. Here, we have studied oxidativeness, vascularization, and the changes in mitofusins (Mfn) 1-Mfn 2 expression and interaction in the due course of muscle development. Toward this, we used a series of histochemical techniques to compare neonatal and adult limb muscles (Gastrocnemius and Quadriceps) of Wistar rat (Rattus norvegicus). Additionally, we probed the proximity between Mfn 1 and Mfn 2 using a highly sensitive antibody-based proximity ligation assay indicating the change in mitochondrial fusion pattern or mitochondria-SR interaction. The results show that neonatal fibers bear a uniform distribution of mitochondria while a differential pattern of distribution is seen in adults. The distribution of the blood vessels is also quite distinct in adult muscles with a well-formed capillary network but in neonates, only central blood vessels are seen. Interestingly, our Mfn 1-Mfn 2 interaction data show that this interaction is uniformly distributed throughout the neonatal fibers, while it becomes peripherally localized in fibers of adult muscles. This peripheralization of Mfn 1-Mfn 2 interaction must be an important event of muscle development and might be critical to cater to the metabolic needs of adult muscle.

Keywords:  development; mitochondria; mitofusins; neonate; protein-protein interaction; skeletal muscle

DOI:  https://doi.org/10.1002/jcb.30489
J Agric Food Chem. 2023 Oct 08.

Effect of Yeast-Derived Peptides on Skeletal Muscle Function and Exercise-Induced Fatigue in C2C12 Myotube Cells and ICR Mice.

Jiaming Cai, Lujuan Xing, Wangang Zhang, Jian Zhang, Lei Zhou, Zixu Wang.

  In our previous study, the antioxidant peptides (XHY69AP, AP-D, YPLP, and AGPL) were obtained from potential probiotic yeast (Yamadazyma triangularis XHY69), which was selected by our lab from dry-cured ham. This work aimed to explore the effects of yeast-derived peptides on skeletal muscle function and muscle fatigue. Results showed that yeast-derived peptides up-regulated slow-twitch fiber expression and down-regulated fast-twitch fiber expression in C2C12 cells (p < 0.05). The peptides improved mitochondrial membrane potential, adenosine triphosphate generation, and expression of cytochrome-relative genes, thus promoting mitochondrial function. Among these peptides, YPLP up-regulated the relative gene expression of the AMP-activated protein kinase (AMPK) pathway and activated AMPK by phosphorylation. Moreover, YPLP could prolong treadmill time, increase muscle and liver glycogen contents, reduce lactic acid and urea nitrogen contents, and alleviate muscle tissue injury in ICR exercise mice. These results demonstrate that yeast-derived peptides could change the muscle fiber composition, improve muscle function, and relieve muscle fatigue.

Keywords:  AMPK; antifatigue; mitochondria; muscle fiber; yeast-derived peptides

DOI:  https://doi.org/10.1021/acs.jafc.3c02281
J Cell Sci. 2023 Oct 10. pii: jcs.261300. [Epub ahead of print]

Palmitate-induced insulin resistance causes actin filament stiffness and GLUT4 mis-sorting without altered Akt signaling.

Victoria L Tokarz, Sivakami Mylvaganam, Amira Klip.

  Skeletal muscle insulin resistance, a major contributor to Type 2 Diabetes, is linked to the consumption of saturated fats. This insulin resistance arises from failure of insulin-induced translocation of glucose transporter type 4 (GLUT4) to the plasma membrane to facilitate glucose uptake into muscle. The mechanisms of defective GLUT4 translocation are poorly understood, limiting development of insulin-sensitizing therapies targeting muscle glucose uptake. While many studies identify early insulin signaling defects and suggest they are responsible for insulin resistance, their cause-effect has been debated. Here, we find that the saturated fat palmitate (PA) causes insulin resistance of GLUT4 translocation in skeletal muscle myoblasts and myotubes without impairing signaling to Akt or AS160. Instead, PA altered two basal-state events: a) the intracellular localization of GLUT4 and its sorting towards a perinuclear storage compartment, and b) actin filament stiffness that prevents Rac1-dependent actin remodeling. These defects were triggered by distinct mechanisms, respectively protein palmitoylation and endoplasmic reticulum (ER) stress. Our findings highlight that saturated fats elicit muscle cell-autonomous dysregulation of the basal-state machinery required for GLUT4 translocation that 'primes' cells for insulin resistance.

Keywords:  Actin cytoskeleton; GLUT4; Insulin resistance; Palmitate

DOI:  https://doi.org/10.1242/jcs.261300
Acta Biomater. 2023 Oct 05. pii: S1742-7061(23)00593-7. [Epub ahead of print]

Skeletal Muscle Extracellular Matrix Structure Under Applied Deformation Observed Using Second Harmonic Generation Microscopy.

Niamh Hennessy, Ciaran Simms.

  The mechanical and structural properties of passive skeletal muscle are important for musculoskeletal models in impact biomechanics, rehabilitation engineering and surgical simulation. Passive properties of skeletal muscle depend strongly on the architecture of the extracellular matrix (ECM), but the structure of ECM and its realignment under applied deformation remain poorly understood. We apply second harmonic generation (SHG) microscopy to study muscle ECM in intact muscle samples both under deformation and in the undeformed state. A method for regional relocation was developed, so that the same ECM segment could be viewed before and after applying deformations. Skeletal muscle ECM was viewed at multiple scales and in three states: undeformed, under compression and under tension. Results show that second harmonic generation microscopy provides substantial detail of skeletal muscle ECM over a wide range of length scales, especially the perimysium structure. We present images of individual portions of skeletal muscle ECM both undeformed and subjected to tensile/compressive deformation. We also present data showing the response of the perimysium to a partial thickness cut applied to a section under tensile deformation. STATEMENT OF SIGNIFICANCE: : Second Harmonic Generation (SHG) microscopy is an imaging technique which takes advantage of a non-linear and coherent frequency doubling optical effect that is present in a small number of biological molecules, primarily collagen Type I, II and myosin. Collagen I is the most abundant collagen type in skeletal muscle, making SHG a promising option for visualisation of the skeletal muscle extracellular matrix (ECM). SHG microscopy does not require fixing or staining. This short communication presents the application of SHG microscopy to skeletal muscle ECM to improve our understanding of how collagen fibres reorganise under applied tensile and compression, including microscopic observations of collagen fibre reorganisation for intact samples by using a method to re-identify specific regions in repeated deformation tests.

Keywords:  Extracellular Matrix; Perimysium; Second Harmonic Generation; Skeletal Muscle; Tension-Compression

DOI:  https://doi.org/10.1016/j.actbio.2023.09.047
Circ Res. 2023 Oct 12.

Single-Nuclei RNA-Sequencing of the Gastrocnemius Muscle in Peripheral Artery Disease.

Caroline Pass, Victoria Palzkill, Jianna Tan, Kyoungrae Kim, Trace Thome, Qingping Yang, Brian Fazzone, Scott T Robinson, Kerri A O'Malley, Feng Yue, Salvatore T Scali, Scott A Berceli, Terence E Ryan.

   BACKGROUND: Lower extremity peripheral artery disease (PAD) is a growing epidemic with limited effective treatment options. Here, we provide a single-nuclei atlas of PAD limb muscle to facilitate a better understanding of the composition of cells and transcriptional differences that comprise the diseased limb muscle.
METHODS: We obtained gastrocnemius muscle specimens from 20 patients with PAD and 12 non-PAD controls. Nuclei were isolated and single-nuclei RNA-sequencing was performed. The composition of nuclei was characterized by iterative clustering via principal component analysis, differential expression analysis, and the use of known marker genes. Bioinformatics analysis was performed to determine differences in gene expression between PAD and non-PAD nuclei, as well as subsequent analysis of intercellular signaling networks. Additional histological analyses of muscle specimens accompany the single-nuclei RNA-sequencing atlas.
RESULTS: Single-nuclei RNA-sequencing analysis indicated a fiber type shift with patients with PAD having fewer type I (slow/oxidative) and more type II (fast/glycolytic) myonuclei compared with non-PAD, which was confirmed using immunostaining of muscle specimens. Myonuclei from PAD displayed global upregulation of genes involved in stress response, autophagy, hypoxia, and atrophy. Subclustering of myonuclei also identified populations that were unique to PAD muscle characterized by metabolic dysregulation. PAD muscles also displayed unique transcriptional profiles and increased diversity of transcriptomes in muscle stem cells, regenerating myonuclei, and fibro-adipogenic progenitor cells. Analysis of intercellular communication networks revealed fibro-adipogenic progenitors as a major signaling hub in PAD muscle, as well as deficiencies in angiogenic and bone morphogenetic protein signaling which may contribute to poor limb function in PAD.
CONCLUSIONS: This reference single-nuclei RNA-sequencing atlas provides a comprehensive analysis of the cell composition, transcriptional signature, and intercellular communication pathways that are altered in the PAD condition.

Keywords:  ischemia; lower extremity; peripheral arterial disease; peripheral vascular diseases; transcriptome

DOI:  https://doi.org/10.1161/CIRCRESAHA.123.323161
Biochem Pharmacol. 2023 Oct 11. pii: S0006-2952(23)00441-0. [Epub ahead of print] 115850

Non-canonical Ca2+- Akt signaling pathway mediates the antiproteolytic effects induced by oxytocin receptor stimulation in skeletal muscle.

Tatiane de Oliveira Santos, João da Cruz-Filho, Daniely Messias Costa, Raquel Prado da Silva, Hevely Catharine Dos Anjos-Santos, José Ronaldo Dos Santos, Luís Carlos Reis, Ísis do Carmo Kettelhut, Luiz Carlos Navegantes, Enilton Aparecido Camargo, Sandra Lauton-Santos, Daniel Badauê-Passos, André de Souza Mecawi, Danilo Lustrino.

  Although it has been previously demonstrated that oxytocin (OXT) receptor stimulation can control skeletal muscle mass in vivo, the intracellular mechanisms that mediate this effect are still poorly understood. Thus, rat oxidative skeletal muscles were isolated and incubated with OXT or WAY-267,464, a non-peptide selective OXT receptor (OXTR) agonist, in the presence or absence of atosiban (ATB), an OXTR antagonist, and overall proteolysis was evaluated. The results indicated that both OXT and WAY-267,464 suppressed muscle proteolysis, and this effect was blocked by the addition of ATB. Furthermore, the WAY-induced anti-catabolic action on protein metabolism did not involve the coupling between OXTR and Gαi since it was insensitive to pertussis toxin (PTX). The decrease in overall proteolysis induced by WAY was probably due to the inhibition of the autophagic/lysosomal system, as estimated by the decrease in LC3 (an autophagic/lysosomal marker), and was accompanied by an increase in the content of Ca2+-dependent protein kinase (PKC)-phosphorylated substrates, pSer473-Akt, and pSer256-FoxO1. Most of these effects were blocked by the inhibition of inositol triphosphate receptors (IP3R), which mediate Ca2+ release from the sarcoplasmic reticulum to the cytoplasm, and triciribine, an Akt inhibitor. Taken together, these findings indicate that the stimulation of OXTR directly induces skeletal muscle protein-sparing effects through a Gαq/IP3R/Ca2+-dependent pathway and crosstalk with Akt/FoxO1 signaling, which consequently decreases the expression of genes related to atrophy, such as LC3, as well as muscle proteolysis.

Keywords:  Akt/FoxO/LC3; Oxytocin; Oxytocin receptor; Proteolysis; Skeletal muscle

DOI:  https://doi.org/10.1016/j.bcp.2023.115850
Sci Transl Med. 2023 Oct 11. 15(717): eadg1485

Regeneration of neuromuscular synapses after acute and chronic denervation by inhibiting the gerozyme 15-prostaglandin dehydrogenase.

Mohsen A Bakooshli, Yu Xin Wang, Elena Monti, Shiqi Su, Peggy Kraft, Minas Nalbandian, Ludmila Alexandrova, Joshua R Wheeler, Hannes Vogel, Helen M Blau.

To date, there are no approved treatments for the diminished strength and paralysis that result from the loss of peripheral nerve function due to trauma, heritable neuromuscular diseases, or aging. Here, we showed that denervation resulting from transection of the sciatic nerve triggered a marked increase in the prostaglandin-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in skeletal muscle in mice, providing evidence that injury drives early expression of this aging-associated enzyme or gerozyme. Treating mice with a small-molecule inhibitor of 15-PGDH promoted regeneration of motor axons and formation of neuromuscular synapses leading to an acceleration in recovery of force after an acute nerve crush injury. In aged mice with chronic denervation of muscles, treatment with the 15-PGDH inhibitor increased motor neuron viability and restored neuromuscular junctions and function. These presynaptic changes synergized with previously reported muscle tissue remodeling to result in a marked increase in the strength of aged muscles. We further found that 15-PGDH aggregates defined the target fibers that are histopathologic hallmarks of human neurogenic myopathies, suggesting that the gerozyme may be involved in their etiology. Our data suggest that inhibition of 15-PGDH may constitute a therapeutic strategy to physiologically boost prostaglandin E2, restore neuromuscular connectivity, and promote recovery of strength after acute or chronic denervation due to injury, disease, or aging.

DOI: https://doi.org/10.1126/scitranslmed.adg1485
J Muscle Res Cell Motil. 2023 Oct 08.

From amino-acid to disease: the effects of oxidation on actin-myosin interactions in muscle.

Daren Elkrief, Oleg Matusovsky, Yu-Shu Cheng, Dilson E Rassier.

  Actin-myosin interactions form the basis of the force-producing contraction cycle within the sarcomere, serving as the primary mechanism for muscle contraction. Post-translational modifications, such as oxidation, have a considerable impact on the mechanics of these interactions. Considering their widespread occurrence, the explicit contributions of these modifications to muscle function remain an active field of research. In this review, we aim to provide a comprehensive overview of the basic mechanics of the actin-myosin complex and elucidate the extent to which oxidation influences the contractile cycle and various mechanical characteristics of this complex at the single-molecule, myofibrillar and whole-muscle levels. We place particular focus on amino acids shown to be vulnerable to oxidation in actin, myosin, and some of their binding partners. Additionally, we highlight the differences between in vitro environments, where oxidation is controlled and limited to actin and myosin and myofibrillar or whole muscle environments, to foster a better understanding of oxidative modification in muscle. Thus, this review seeks to encompass a broad range of studies, aiming to lay out the multi layered effects of oxidation in in vitro and in vivo environments, with brief mention of clinical muscular disorders associated with oxidative stress.

Keywords:  Actin-myosin interaction; Force generation; Muscle aging and disease; Myofibrillar weakness; Oxidation; Skeletal and cardiac muscle

DOI:  https://doi.org/10.1007/s10974-023-09658-0
Mol Cell Endocrinol. 2023 Oct 10. pii: S0303-7207(23)00236-8. [Epub ahead of print] 112085

Kinin B1 receptor modulates glucose homeostasis and physical exercise capacity by altering adrenal catecholamine synthesis and secretion.

Marcos Fernandes Gregnani, Alexandre Budu, Rogério Oliveira Batista, Fábio Henrique Ornellas, Gabriel Rufino Estrela, Adriano Cleis Arruda, Leandro Ceotto Freitas Lima, Jean Lucas Kremer, Lys Angela Favaroni Mendes, Dulce Elena Casarini, Claudimara Ferini Pacicco Lotfi, Lila Missae Oyama, Michael Bader, Ronaldo Carvalho Araújo.

  Our group has shown in several papers that kinin B1 receptor (B1R) is involved in metabolic adaptations, mediating glucose homeostasis and interfering in leptin and insulin signaling. Since catecholamines are involved with metabolism management, we sought to evaluate B1R role in catecholamine synthesis/secretion. Using B1R global knockout mice, we observed increased basal epinephrine content, accompanied by decreased hepatic glycogen content and increased glucosuria. When these mice were challenged with maximal intensity exercise, they showed decreased epinephrine and norepinephrine response, accompanied by disturbed glycemic responses to effort and poor performance. This phenotype was related to alterations in adrenal catecholamine synthesis: increased basal epinephrine concentration and reduced norepinephrine content in response to exercise, as well decreased gene expression and protein content of tyrosine hydroxylase and decreased gene expression of dopamine beta hydroxylase and kinin B2 receptor. We conclude that the global absence of B1R impairs catecholamine synthesis, interfering with glucose metabolism at rest and during maximal exercise.

Keywords:  Catecholamines; Glucose homeostasis; Kinin receptors; Physical exercise

DOI:  https://doi.org/10.1016/j.mce.2023.112085
Healthcare (Basel). 2023 Sep 29. pii: 2652. [Epub ahead of print]11(19):

Effects of Moderate Exercise Training on Cancer-Induced Muscle Wasting.

Ana Cristina Corrêa Figueira, Ana Pereira, Luís Leitão, Rita Ferreira, Paula A Oliveira, José Alberto Duarte.

   BACKGROUND: Muscle wasting is a common phenomenon in oncology and seems to be attenuated by exercise training. The aim of this study is to determine the degree of aggressiveness of cancer-induced muscle wasting in two different phenotypic muscles. It will also determine whether exercise training can attenuate this muscle dysfunction.
METHODS: Fifty Sprague Dawley rats were randomly assigned to four experimental groups: two breast cancer model groups (sedentary and exercise) and two control groups (sedentary and exercise). Breast cancer was induced by 1-methyl-1-nitrosoureia (MNU). After 35 weeks of endurance training, animals were sacrificed, and gastrocnemius and soleus muscles harvested for morphometric analysis.
RESULTS: In sedentary tumor-bearing animals, a significant reduction in cross-sectional area was found in both muscles (p < 0.05). Interstitial fibrosis was significantly higher in the gastrocnemius muscle of the sedentary tumor-bearing animals (p < 0.05), but not in the soleus muscle. In the gastrocnemius of sedentary tumor-bearing animals, a shift from large to small fibers was observed. This cancer-related muscle dysfunction was prevented by long-term exercise training.
CONCLUSIONS: In sedentary animals with tumors, the gastrocnemius muscle showed a very pronounced reduction in cross-sectional area and a marked degree of interstitial fibrosis. There was no difference in collagen deposition between tumor groups, and the soleus muscle showed a less pronounced but significant reduction in cross-sectional area. These contrasting results confirm that cancer-induced muscle wasting can affect specific types of fibers and specific muscles, namely fast glycolytic muscles, and that exercise training can be used to improve it.

Keywords:  breast tumor; cancer-induced muscle wasting; exercise training; gastrocnemius; soleus

DOI:  https://doi.org/10.3390/healthcare11192652
Biochem Biophys Res Commun. 2023 Oct 03. pii: S0006-291X(23)01145-2. [Epub ahead of print]682 124-131

SIRT1 induction in the skeletal muscle of male mice partially attenuates changes to whole-body metabolism in response to androgen deprivation.

Grant R Laskin, Jennifer L Steiner, Claire E Berryman, Bradley S Gordon.

  In males, androgens regulate whole body metabolism. The components in androgen target organs contributing to whole-body metabolic function remain ill defined. Sirtuin1 (SIRT1) protein levels are lower in the limb muscle of male mice subjected to androgen deprivation. Because SIRT1 can influence whole-body metabolism, the purpose was to assess whether muscle specific SIRT1 induction attenuated changes to whole-body metabolism in response to androgen deprivation. Physically mature male mice containing an inducible muscle specific SIRT1 transgene (SIRT1) were subjected to a sham or castration surgery and compared to sham and castrated male mice where the SIRT1 transgene was not induced (WT). The respiratory exchange ratio (RER), energy expenditure, and carbohydrate and fat oxidation rates were determined using metabolic cages. Castration lowered RER in WT mice and the lower RER coincided with lower energy expenditure, lower carbohydrate oxidation rates, and higher fat oxidation rates. SIRT1 induction attenuated the castration-induced changes to RER and fat oxidation rates. Changes to energy expenditure and glucose oxidation rates were not affected by SIRT1. Decreases in muscle SIRT1 protein in males may partially contribute to the dysregulation of whole-body metabolism in response to androgen deprivation.

Keywords:  Amino acid oxidation; Fat oxidation; Glucose oxidation; Hypogonadism; Testosterone

DOI:  https://doi.org/10.1016/j.bbrc.2023.10.005
Biochimie. 2023 Oct 10. pii: S0300-9084(23)00256-0. [Epub ahead of print]

Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?

Charlotte Claeyssen, Nathan Bulangalire, Bruno Bastide, Onnik Agbulut, Caroline Cieniewski-Bernard.

  Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.

Keywords:  Desmin; Intermediate filaments; O-GlcNAcylation; Phosphorylation; Striated muscles; αB-Crystallin

DOI:  https://doi.org/10.1016/j.biochi.2023.10.002
Aging Cell. 2023 Oct 12. e13963

Calorie restriction modulates the transcription of genes related to stress response and longevity in human muscle: The CALERIE study.

Jayanta Kumar Das, Nirad Banskota, Julián Candia, Michael E Griswold, Melissa Orenduff, Rafael de Cabo, David L Corcoran, Sai Krupa Das, Supriyo De, Kim Marie Huffman, Virginia B Kraus, William E Kraus, Corby K Martin, Susan B Racette, Leanne M Redman, Birgit Schilling, Daniel W Belsky, Luigi Ferrucci.

  The lifespan extension induced by 40% caloric restriction (CR) in rodents is accompanied by postponement of disease, preservation of function, and increased stress resistance. Whether CR elicits the same physiological and molecular responses in humans remains mostly unexplored. In the CALERIE study, 12% CR for 2 years in healthy humans induced minor losses of muscle mass (leg lean mass) without changes of muscle strength, but mechanisms for muscle quality preservation remained unclear. We performed high-depth RNA-Seq (387-618 million paired reads) on human vastus lateralis muscle biopsies collected from the CALERIE participants at baseline, 12- and 24-month follow-up from the 90 CALERIE participants randomized to CR and "ad libitum" control. Using linear mixed effect model, we identified protein-coding genes and splicing variants whose expression was significantly changed in the CR group compared to controls, including genes related to proteostasis, circadian rhythm regulation, DNA repair, mitochondrial biogenesis, mRNA processing/splicing, FOXO3 metabolism, apoptosis, and inflammation. Changes in some of these biological pathways mediated part of the positive effect of CR on muscle quality. Differentially expressed splicing variants were associated with change in pathways shown to be affected by CR in model organisms. Two years of sustained CR in humans positively affected skeletal muscle quality, and impacted gene expression and splicing profiles of biological pathways affected by CR in model organisms, suggesting that attainable levels of CR in a lifestyle intervention can benefit muscle health in humans.

Keywords:  FOXO; calorie restriction; heat shock response; inflammation; mitochondrial biogenesis; skeletal muscle; splicing

DOI:  https://doi.org/10.1111/acel.13963
Ageing Res Rev. 2023 Oct 11. pii: S1568-1637(23)00246-5. [Epub ahead of print] 102087

Exercise mitigates Age-related Metabolic Diseases by improving Mitochondrial Dysfunction.

Dandan Jia, Zhenjun Tian, Ru Wang.

  The benefits of regular physical activity are related to delaying and reversing the onset of ageing and age-related disorders, including cardiomyopathy, neurodegenerative diseases, cancer, obesity, diabetes, and fatty liver diseases. However, the molecular mechanisms of the benefits of exercise or physical activity on ageing and age-related disorders remain poorly understood. Mitochondrial dysfunction is implicated in the pathogenesis of ageing and age-related metabolic diseases. Mitochondrial health is an important mediator of cellular function. Therefore, exercise alleviates metabolic diseases in individuals with advancing ageing and age-related diseases by the remarkable promotion of mitochondrial biogenesis and function. Exerkines are identified as signaling moieties released in response to exercise. Exerkines released by exercise have potential roles in improving mitochondrial dysfunction in response to age-related disorders. This review comprehensive summarizes the benefits of exercise in metabolic diseases, linking mitochondrial dysfunction to the onset of age-related diseases. Using relevant examples utilizing this approach, the possibility of designing therapeutic interventions based on these molecular mechanisms is addressed.

Keywords:  age-related diseases; ageing; exerkines; mitochondrial dysfunction

DOI:  https://doi.org/10.1016/j.arr.2023.102087
Cells. 2023 Sep 22. pii: 2333. [Epub ahead of print]12(19):

Sedentary Behavior Impacts on the Epigenome and Transcriptome: Lessons from Muscle Inactivation in Drosophila Larvae.

Avivit Brener, Dana Lorber, Adriana Reuveny, Hila Toledano, Lilach Porat-Kuperstein, Yael Lebenthal, Eviatar Weizman, Tsviya Olender, Talila Volk.

  The biological mechanisms linking sedentary lifestyles and metabolic derangements are incompletely understood. In this study, temporal muscle inactivation in Drosophila larvae carrying a temperature-sensitive mutation in the shibire (shi1) gene was induced to mimic sedentary behavior during early life and study its transcriptional outcome. Our findings indicated a significant change in the epigenetic profile, as well as the genomic profile, of RNA Pol II binding in the inactive muscles relative to control, within a relatively short time period. Whole-genome analysis of RNA-Pol II binding to DNA by muscle-specific targeted DamID (TaDa) protocol revealed that muscle inactivity altered Pol II binding in 121 out of 2010 genes (6%), with a three-fold enrichment of genes coding for lncRNAs. The suppressed protein-coding genes included genes associated with longevity, DNA repair, muscle function, and ubiquitin-dependent proteostasis. Moreover, inducing muscle inactivation exerted a multi-level impact upon chromatin modifications, triggering an altered epigenetic balance of active versus inactive marks. The downregulated genes in the inactive muscles included genes essential for muscle structure and function, carbohydrate metabolism, longevity, and others. Given the multiple analogous genes in Drosophila for many human genes, extrapolating our findings to humans may hold promise for establishing a molecular link between sedentary behavior and metabolic diseases.

Keywords:  Drosophila larvae; aging; epigenetics; lncRNA; proteostasis; sarcopenia; ubiquitination

DOI:  https://doi.org/10.3390/cells12192333
Biochem Biophys Res Commun. 2023 Oct 04. pii: S0006-291X(23)01141-5. [Epub ahead of print]682 111-117

AAV-mediated skeletal muscle specific irisin expression does not contribute to weight loss in mice.

Bernadette B Bagon, Junhyeong Lee, Merc Emil Matienzo, Sangyi Lim, Jae-Il Park, Sohi Kang, Keon Kim, Chang-Min Lee, Changjong Moon, Dong-Il Kim, Min-Jung Park.

  Obesity, a chronic disease, significantly increases the risk of various diseases, including diabetes, cardiovascular diseases, and cancers. Exercise is crucial for weight management not only through energy expenditure by muscle activity but also through stimulating the secretion of myokines, which affect various tissues. Irisin, derived from the proteolytic processing of fibronectin type III domain-containing protein 5 (Fndc5), is a well-studied myokine with beneficial effects on metabolism. This study explored the feasibility of adeno-associated virus (AAV)-mediated Fndc5 gene therapy to treat obesity in a mouse model using the AAV-DIO system to express Fndc5 specifically in skeletal muscle, and investigated its anti-obesity effect. Although Fndc5 was specifically expressed in the muscle, no significant impact on body weight under normal chow or high-fat diets was observed, and no change in thermogenic gene expression in inguinal white adipose tissue was detected. Notably, Fndc5 transduction did affect bone metabolism, consistent with previous reports. These findings suggest that AAV-mediated Fndc5 gene therapy may not be an efficient strategy for obesity, contrary to our expectations. Further research is needed to elucidate the complex mechanisms involved in irisin's role in obesity and related disorders.

Keywords:  AAV-DIO; Gene therapy; Myokine; Obesity; Skeletal muscle; fndc5

DOI:  https://doi.org/10.1016/j.bbrc.2023.10.004
PLoS One. 2023 ;18(10): e0292268

Deep coverage and quantification of the bone proteome provides enhanced opportunities for new discoveries in skeletal biology and disease.

Jacob P Rose, Charles A Schurman, Christina D King, Joanna Bons, Sandip K Patel, Jordan B Burton, Amy O'Broin, Tamara Alliston, Birgit Schilling.

Dysregulation of cell signaling in chondrocytes and in bone cells, such as osteocytes, osteoblasts, osteoclasts, and an elevated burden of senescent cells in cartilage and bone, are implicated in osteoarthritis (OA). Mass spectrometric analyses provides a crucial molecular tool-kit to understand complex signaling relationships in age-related diseases, such as OA. Here we introduce a novel mass spectrometric workflow to promote proteomic studies of bone. This workflow uses highly specialized steps, including extensive overnight demineralization, pulverization, and incubation for 72 h in 6 M guanidine hydrochloride and EDTA, followed by proteolytic digestion. Analysis on a high-resolution Orbitrap Eclipse and Orbitrap Exploris 480 mass spectrometer using Data-Independent Acquisition (DIA) provides deep coverage of the bone proteome, and preserves post-translational modifications, such as hydroxyproline. A spectral library-free quantification strategy, directDIA, identified and quantified over 2,000 protein groups (with ≥ 2 unique peptides) from calcium-rich bone matrices. Key components identified were proteins of the extracellular matrix (ECM), bone-specific proteins (e.g., secreted protein acidic and cysteine rich, SPARC, and bone sialoprotein 2, IBSP), and signaling proteins (e.g., transforming growth factor beta-2, TGFB2), and lysyl oxidase homolog 2 (LOXL2), an important protein in collagen crosslinking. Post-translational modifications (PTMs) were identified without the need for specific enrichment. This includes collagen hydroxyproline modifications, chemical modifications for collagen self-assembly and network formation. Multiple senescence factors were identified, such as complement component 3 (C3) protein of the complement system and many matrix metalloproteinases, that might be monitored during age-related bone disease progression. Our innovative workflow yields in-depth protein coverage and quantification strategies to discover underlying biological mechanisms of bone aging and to provide tools to monitor therapeutic interventions. These novel tools to monitor the bone proteome open novel horizons to investigate bone-specific diseases, many of which are age-related.

DOI: https://doi.org/10.1371/journal.pone.0292268