bims-musmir 2024-09-01 papers

bims-musmir

Biomed News

on microRNAs in muscle

Issue of 2024‒09‒01
eighteen papers selected by
Katarzyna Agnieszka Goljanek-Whysall, University of Galway

Betaine delays age-related muscle loss by mitigating Mss51-induced impairment in mitochondrial respiration via Yin Yang1.
Dysregulation of muscle cholesterol transport in amyotrophic lateral sclerosis.
Loss of mitochondria long-chain fatty acid oxidation impairs skeletal muscle contractility by disrupting myofibril structure and calcium homeostasis.
Severe trauma leads to sustained muscle loss, induced frailty, and distinct temporal changes in myokine and chemokine profiles of older patients.
The Impact of Sciatic Nerve Injury on Extracellular Matrix of Lower Limb Muscle and Thoracolumbar Fascia: An Observational Study.
Mitohormesis during advanced stages of Duchenne muscular dystrophy reveals a redox-sensitive creatine pathway that can be enhanced by the mitochondrial-targeting peptide SBT-20.
Inducible deletion of endothelial cell Efnb2 delays capillary regeneration and attenuates myofibre reinnervation following myotoxin injury in mice.
Semen Strychni Pulveratum and Vomicine Alleviate Neuroinflammation in Amyotrophic Lateral Sclerosis through cGAS-STING-TBK1 Pathway.
Single-Nucleus RNA Sequencing Unravels Early Mechanisms of Human Becker Muscular Dystrophy.
Exercise-induced Nrf2 activation increases antioxidant defenses in skeletal muscles.
CaV1.1 voltage-sensing domain III exclusively controls skeletal muscle excitation-contraction coupling.
Increased Homer Activity and NMJ Localization in the Vestibular Lesion het-/- Mouse soleus Muscle.
Astrocyte-Neuron Interactions Contributing to Amyotrophic Lateral Sclerosis Progression.
Does AMPK bind glycogen in skeletal muscle or is the relationship correlative?
Risk Factors Associated With Perioperative Skeletal Muscle Loss in Patients With Colorectal Cancer.
Spatiotemporal transcriptomic mapping of regenerative inflammation in skeletal muscle reveals a dynamic multilayered tissue architecture.
miR-29 is an important driver of aging-related phenotypes.
Long-term survival of participants in a phase II randomized trial of RNS60 in amyotrophic lateral sclerosis.

J Cachexia Sarcopenia Muscle. 2024 Aug 26.

Betaine delays age-related muscle loss by mitigating Mss51-induced impairment in mitochondrial respiration via Yin Yang1.

Si Chen, Tongtong He, Jiedong Chen, Dongsheng Wen, Chen Wang, Wenge Huang, Zhijun Yang, Mengtao Yang, Mengchu Li, Siyu Huang, Zihui Huang, Huilian Zhu.

  BACKGROUND: Mitochondrial dysfunction is one of the hallmarks of aging and a leading contributor to sarcopenia. Nutrients are essential for improving mitochondrial function and skeletal muscle health during the aging process. Betaine is a nutrient with potential muscle-preserving properties. However, whether and how betaine could regulate the mitochondria function in aging muscle are poorly understood. We aimed to explore the molecular target and underlying mechanism of betaine in attenuating the age-related mitochondrial dysfunction in skeletal muscle.METHODS: Young mice (YOU, 2 months), old mice (OLD, 15 months), and old mice with betaine treatment (BET, 15 months) were fed for 12 weeks. The effects of betaine on muscle mass, strength, function, and subcellular structure of muscle fibres were assessed. RNA sequencing (RNA-seq) was conducted to identify the molecular target of betaine. The impacts of betaine on mitochondrial-related molecules, superoxide accumulation, and oxidative respiration were examined using western blotting (WB), immunofluorescence (IF) and seahorse assay. The underlying mechanism of betaine regulation on the molecular target to maintain mitochondrial function was investigated by luciferase reporter assay, chromatin immunoprecipitation and electrophoretic mobility shift assay. Adenoassociated virus transfection, succinate dehydrogenase staining (SDH), and energy expenditure assessment were performed on 20-month-old mice for validating the mechanism in vivo.
RESULTS: Betaine intervention demonstrated anti-aging effects on the muscle mass (P = 0.017), strength (P = 0.010), and running distance (P = 0.013). Mitochondrial-related markers (ATP5a, Sdha, and Uqcrc2) were 1.1- to 1.5-fold higher in BET than OLD (all P ≤ 0.036) with less wasted mitochondrial vacuoles accumulating in sarcomere. Bioinformatic analysis from RNA-seq displayed pathways related to mitochondrial respiration activity was higher enriched in BET group (NES = -0.87, FDR = 0.10). The quantitative real time PCR (qRT-PCR) revealed betaine significantly reduced the expression of a novel mitochondrial regulator, Mss51 (-24.9%, P = 0.002). In C2C12 cells, betaine restored the Mss51-mediated suppression in mitochondrial respiration proteins (all P ≤ 0.041), attenuated oxygen consumption impairment, and superoxide accumulation (by 20.7%, P = 0.001). Mechanically, betaine attenuated aging-induced repression in Yy1 mRNA expression (BET vs. OLD: 2.06 vs. 1.02, P = 0.009). Yy1 transcriptionally suppressed Mss51 mRNA expression both in vitro and in vivo. This contributed to the preservation of mitochondrial respiration, improvement for energy expenditure (P = 0.008), and delay of muscle loss during aging process.
CONCLUSIONS: Altogether, betaine transcriptionally represses Mss51 via Yy1, improving age-related mitochondrial respiration in skeletal muscle. These findings suggest betaine holds promise as a dietary supplement to delay skeletal muscle degeneration and improve age-related mitochondrial diseases.

Keywords:  Betaine; Mitochondrial dysfunction; Mss51; Muscle loss; Transcription factor; Yin yang1 (Yy1)

DOI:  https://doi.org/10.1002/jcsm.13558
Brain. 2024 Aug 28. pii: awae270. [Epub ahead of print]

Dysregulation of muscle cholesterol transport in amyotrophic lateral sclerosis.

PULSE study group

  Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting motor neurons, with a typical lifespan of 3-5 years. Altered metabolism is a key feature of ALS that strongly influences prognosis, with an increase in whole-body energy expenditure and changes in skeletal muscle metabolism, including greater reliance on fat oxidation. Dyslipidemia has been described in ALS as part of the metabolic dysregulation, but its role in the pathophysiology of the disease remains controversial. Among the lipids, cholesterol is of particular interest as a vital component of cell membranes, playing a key role in signal transduction and mitochondrial function in muscle. The aim of this study was to investigate whether motor dysfunction in ALS might be associated with dysregulation of muscle cholesterol metabolism. We determined cholesterol content and analyzed the expression of key determinants of the cholesterol metabolism pathway in muscle biopsies from thirteen ALS patients and ten asymptomatic ALS-mutation gene carriers compared to sixteen controls. Using human control primary myotubes, we further investigated the potential contribution of cholesterol dyshomeostasis to reliance on mitochondrial fatty acid. We found that cholesterol accumulates in the skeletal muscle of ALS patients and that cholesterol overload significantly correlates with disease severity evaluated by the Revised ALS Functional Rating Scale. These defects are associated with overexpression of the genes of the lysosomal cholesterol transporters Niemann-Pick type C1 (NPC1) and 2 (NPC2), which are required for cholesterol transfer from late endosomes/lysosomes to cellular membranes. Most notably, a significant increase in NPC2 mRNA levels could be detected in muscle samples from asymptomatic ALS-mutation carriers, long before disease onset. We found that filipin-stained unesterified cholesterol accumulated in the lysosomal compartment in ALS muscle samples, suggesting dysfunction of the NPC1/2 system. Accordingly, we report here that experimental NPC1 inhibition or lysosomal pH alteration in human primary myotubes was sufficient to induce the overexpression of NPC1 and NPC2 mRNA. Finally, acute NPC1 inhibition in human control myotubes induced a shift towards a preferential use of fatty acids, thus reproducing the metabolic defect characteristic of ALS muscle. We conclude that cholesterol homeostasis is dysregulated in ALS muscle from the presymptomatic stage. Targeting NPC1/2 dysfunction may be a new therapeutic strategy for ALS to restore muscle energy metabolism and slow motor symptom progression.

Keywords:  disease progression; metabolism; presymptomatic stage

DOI:  https://doi.org/10.1093/brain/awae270
Mol Metab. 2024 Aug 27. pii: S2212-8778(24)00146-7. [Epub ahead of print] 102015

Loss of mitochondria long-chain fatty acid oxidation impairs skeletal muscle contractility by disrupting myofibril structure and calcium homeostasis.

Andrea S Pereyra, Regina F Fernandez, Adam Amorese, Jasmine N Castro, Chien-Te Lin, Espen E Spangenburg, Jessica M Ellis.

  Abnormal lipid metabolism in mammalian tissues can be highly deleterious, leading to organ failure. Carnitine Palmitoyltransferase 2 (CPT2) deficiency is an inherited metabolic disorder affecting the liver, heart, and skeletal muscle due to impaired mitochondrial oxidation of long-chain fatty acids (mLCFAO) for energy production. However, the basis of tissue damage in mLCFAO disorders is not fully understood. Mice lacking CPT2 in skeletal muscle (Cpt2Sk-/-) were generated to investigate the nexus between mFAO deficiency and myopathy. Compared to controls, ex-vivo contractile force was reduced by 70% in Cpt2Sk-/- oxidative soleus muscle despite the preserved capacity to couple ATP synthesis to mitochondrial respiration on alternative substrates to long-chain fatty acids. Increased mitochondrial biogenesis, lipid accumulation, and the downregulation of 80% of dystrophin-related and contraction-related proteins severely compromised the structure and function of Cpt2Sk-/- soleus. CPT2 deficiency affected oxidative muscles more than glycolytic ones. Exposing isolated sarcoplasmic reticulum to long-chain acylcarnitines (LCACs) inhibited calcium uptake. In agreement, Cpt2Sk-/- soleus had decreased calcium uptake and significant accumulation of palmitoyl-carnitine, suggesting that LCACs and calcium dyshomeostasis are linked in skeletal muscle. Our data demonstrate that loss of CPT2 and mLCFAO compromise muscle structure and function due to excessive mitochondrial biogenesis, downregulation of the contractile proteome, and disruption of calcium homeostasis.

Keywords:  CPT2; Calcium; Fatty acid oxidation; Muscle contraction; Palmitoyl-carnitine

DOI:  https://doi.org/10.1016/j.molmet.2024.102015
Surgery. 2024 Aug 22. pii: S0039-6060(24)00550-6. [Epub ahead of print]

Severe trauma leads to sustained muscle loss, induced frailty, and distinct temporal changes in myokine and chemokine profiles of older patients.

Valerie E Polcz, Evan L Barrios, Michael C Cox, Ivanna Rocha, Muxuan Liang, Russell B Hawkins, Dijoia Darden, Ricardo Ungaro, Marvin Dirain, Robert Mankowski, Alicia M Mohr, Frederick A Moore, Lyle L Moldawer, Philip A Efron, Scott C Brakenridge, Tyler J Loftus.

INTRODUCTION: Sarcopenia is a known risk factor for adverse outcomes across multiple disease states, including severe trauma. Factors such as age, hyperinflammation, prolonged immobilization, and critical illness may not only exacerbate progression of this disease but may also contribute to the development of induced sarcopenia, or sarcopenia secondary to hospitalization. This study seeks to (1) determine the effects of severe traumatic injury on changes in skeletal muscle mass in older adults; (2) test whether changes in skeletal muscle mass are associated with clinical frailty, physical performance, and health-related quality of life; and (3) examine trauma-induced frailty and temporal changes in myokine and chemokine profiles.METHODS: A prospective, longitudinal cohort study of 47 critically ill, older (≥45 years) adults presenting after severe blunt trauma was conducted. Repeated measures of computed tomography-based skeletal muscle index, frailty, and quality of life were obtained in addition to selected plasma biomarkers over 6 months.
RESULTS: Severe trauma was associated with significant losses in skeletal muscle mass and increased incidence of sarcopenia from 36% at baseline to 60% at 6 months. Severe trauma also was associated with a transient worsening of induced frailty and reduced quality of life irrespective of sarcopenia status, which returned to baseline by 6 months after injury. Admission biomarker levels were not associated with skeletal muscle index at the time points studied but demonstrated distinct temporal changes across our entire cohort.
CONCLUSIONS: Severe blunt trauma in older adults is associated with increased incidence of induced sarcopenia and reversible induced frailty. Despite muscle wasting, functional decline is transient, with a return to baseline by 6 months, suggesting a need for holistic definitions of sarcopenia and further investigation into long-term functional outcomes in this population.

DOI: https://doi.org/10.1016/j.surg.2024.07.031
Int J Mol Sci. 2024 Aug 16. pii: 8945. [Epub ahead of print]25(16):

The Impact of Sciatic Nerve Injury on Extracellular Matrix of Lower Limb Muscle and Thoracolumbar Fascia: An Observational Study.

Xiaoxiao Zhao, Caterina Fede, Lucia Petrelli, Carmelo Pirri, Elena Stocco, Chenglei Fan, Andrea Porzionato, Cesare Tiengo, Raffaele De Caro, Stefano Masiero, Carla Stecco.

  Peripheral nerve injury (PNI) is a complex clinical challenge resulting in functional disability. Neurological recovery does not always ensure functional recovery, as extracellular matrix (ECM) alterations affect muscle function. This study evaluates hyaluronan (HA) and collagen concentration in the gastrocnemius muscle and thoracolumbar fascia (TLF) in unilateral lower limb PNI rats to explore systemic ECM alterations following PNI and their impacts on functional recovery. Eighteen 8-week-old male Sprague-Dawley rats were divided into experimental (n = 12 left sciatic nerve injury) and control (n = 6) groups. After six weeks, motor function was evaluated. Muscle and TLF samples were analysed for HA and collagen distribution and concentrations. SFI and gait analysis confirmed a functional deficit in PNI rats 6 weeks after surgery. HA concentration in both sides of the muscles decreased by approximately one-third; both sides showed significantly higher collagen concentration than healthy rats (12.74 ± 4.83 µg/g), with the left (32.92 ± 11.34 µg/g) significantly higher than the right (20.15 ± 7.03 µg/g). PNI rats also showed significantly lower HA (left: 66.95 ± 20.08 µg/g; right: 112.66 ± 30.53 µg/g) and higher collagen (left: 115.89 ± 28.18 µg/g; right: 90.43 ± 20.83 µg/g) concentrations in both TLF samples compared to healthy rats (HA: 167.18 ± 31.13 µg/g; collagen: 47.51 ± 7.82 µg/g), with the left TLF more affected. Unilateral lower limb PNI induced HA reduction and collagen accumulation in both the lower limb muscles and the TLF, potentially exacerbating motor function impairment and increasing the risk of low back dysfunctions.

Keywords:  collagen; extracellular matrix; hyaluronan; intramuscular connective tissue; peripheral nerve injury; thoracolumbar fascia

DOI:  https://doi.org/10.3390/ijms25168945
Redox Biol. 2024 Aug 20. pii: S2213-2317(24)00297-0. [Epub ahead of print]76 103319

Mitohormesis during advanced stages of Duchenne muscular dystrophy reveals a redox-sensitive creatine pathway that can be enhanced by the mitochondrial-targeting peptide SBT-20.

Meghan C Hughes, Sofhia V Ramos, Aditya N Brahmbhatt, Patrick C Turnbull, Nazari N Polidovitch, Madison C Garibotti, Uwe Schlattner, Thomas J Hawke, Jeremy A Simpson, Peter H Backx, Christopher Gr Perry.

  Mitochondrial creatine kinase (mtCK) regulates the "fast" export of phosphocreatine to support cytoplasmic phosphorylation of ADP to ATP which is more rapid than direct ATP export. Such "creatine-dependent" phosphate shuttling is attenuated in several muscles, including the heart, of the D2.mdx mouse model of Duchenne muscular dystrophy at only 4 weeks of age. However, the degree to which creatine-dependent and -independent systems of phosphate shuttling progressively worsen or potentially adapt in a hormetic manner throughout disease progression remains unknown. Here, we performed a series of proof-of-principle investigations designed to determine how phosphate shuttling pathways worsen or adapt in later disease stages in D2.mdx (12 months of age). We also determined whether changes in creatine-dependent phosphate shuttling are linked to alterations in mtCK thiol redox state. In permeabilized muscle fibres prepared from cardiac left ventricles, we found that 12-month-old male D2.mdx mice have reduced creatine-dependent pyruvate oxidation and elevated complex I-supported H2O2 emission (mH2O2). Surprisingly, creatine-independent ADP-stimulated respiration was increased and mH2O2 was lowered suggesting that impairments in the faster mtCK-mediated phosphocreatine export system resulted in compensation of the alternative slower pathway of ATP export. The apparent impairments in mtCK-dependent bioenergetics occurred independent of mtCK protein content but were related to greater thiol oxidation of mtCK and a more oxidized cellular environment (lower GSH:GSSG). Next, we performed a proof-of-principle study to determine whether creatine-dependent bioenergetics could be enhanced through chronic administration of the mitochondrial-targeting, ROS-lowering tetrapeptide, SBT-20. We found that 12 weeks of daily treatment with SBT-20 (from day 4-∼12 weeks of age) increased respiration and lowered mH2O2 only in the presence of creatine in D2.mdx mice without affecting calcium-induced mitochondrial permeability transition activity. In summary, creatine-dependent mitochondrial bioenergetics are attenuated in older D2.mdx mice in relation to mtCK thiol oxidation that seem to be countered by increased creatine-independent phosphate shuttling as a unique form of mitohormesis. Separate results demonstrate that creatine-dependent bioenergetics can also be enhanced with a ROS-lowering mitochondrial-targeting peptide. These results demonstrate a specific relationship between redox stress and mitochondrial hormetic reprogramming during dystrophin deficiency with proof-of-principle evidence that creatine-dependent bioenergetics could be modified with mitochondrial-targeting small peptide therapeutics.

Keywords:  Antioxidant; Creatine; Mitochondria; Muscle; Respiration; Small molecule therapy

DOI:  https://doi.org/10.1016/j.redox.2024.103319
J Physiol. 2024 Aug 28.

Inducible deletion of endothelial cell Efnb2 delays capillary regeneration and attenuates myofibre reinnervation following myotoxin injury in mice.

Aaron B Morton, Nicole L Jacobsen, Alexandra R Diller, Jacob A Kendra, Shadi Golpasandi, D D W Cornelison, Steven S Segal.

  Acute injury of skeletal muscle disrupts myofibres, microvessels and motor innervation. Myofibre regeneration is well characterized, however its relationship with the regeneration of microvessels and motor nerves is undefined. Endothelial cell (EC) ephrin-B2 (Efnb2) is required for angiogenesis during embryonic development and promotes neurovascular regeneration in the adult. We hypothesized that, following acute injury to skeletal muscle, loss of EC Efnb2 would impair microvascular regeneration and the recovery of neuromuscular junction (NMJ) integrity. Mice (aged 3-6 months) were bred for EC-specific conditional knockout (CKO) of Efnb2 following tamoxifen injection with non-injected CKO mice as controls (CON). The gluteus maximus, tibialis anterior or extensor digitorum longus muscle was then injured with local injection of BaCl2. Intravascular staining with wheat germ agglutinin revealed diminished capillary area in the gluteus maximus of CKO vs. CON at 5 days post-injury (dpi); both recovered to uninjured (0 dpi) level by 10 dpi. At 0 dpi, tibialis anterior isometric force of CKO was less than CON. At 10 dpi, isometric force was reduced by half in both groups. During intermittent contractions (75 Hz, 330 ms s-1, 120 s), isometric force fell during indirect (sciatic nerve) stimulation whereas force was maintained during direct (electrical field) stimulation of myofibres. Neuromuscular transmission failure correlated with perturbed presynaptic (terminal Schwann cells) and postsynaptic (nicotinic acetylcholine receptors) NMJ morphology in CKO. Resident satellite cell number on extensor digitorum longus myofibres did not differ between groups. Following acute injury of skeletal muscle, loss of Efnb2 in ECs delays capillary regeneration and attenuates recovery of NMJ structure and function. KEY POINTS: The relationship between microvascular regeneration and motor nerve regeneration following skeletal muscle injury is undefined. Expression of Efnb2 in endothelial cells (ECs) is essential to vascular development and promotes neurovascular regeneration in the adult. To test the hypothesis that EfnB2 in ECs is required for microvascular regeneration and myofibre reinnervation, we induced conditional knockout of Efnb2 in ECs of mice. Acute injury was then induced by BaCl2 injection into gluteus maximus, tibialis anterior or extensor digitorum longus (EDL) muscle. Capillary regeneration was reduced at 5 days post-injury (dpi) in gluteus maximus of conditional knockout vs. controls; at 10 dpi, neither differed from uninjured. Nerve stimulation revealed neuromuscular transmission failure in tibialis anterior with perturbed neuromuscular junction structure. Resident satellite cell number on EDL myofibres did not differ between groups. Conditional knockout of EC Efnb2 delays capillary regeneration and attenuates recovery of neuromuscular junction structure and function.

Keywords:  Schwann cells; angiogenesis; ephrin‐B2; microcirculation; neuromuscular junction; neuromuscular transmission failure

DOI:  https://doi.org/10.1113/JP285402
J Ethnopharmacol. 2024 Aug 26. pii: S0378-8741(24)01040-7. [Epub ahead of print] 118741

Semen Strychni Pulveratum and Vomicine Alleviate Neuroinflammation in Amyotrophic Lateral Sclerosis through cGAS-STING-TBK1 Pathway.

Yingshi Zhan, Jingyan Huang, Xiaohui Tang, Baoxin Du, Biying Yang.

  ETHNOPHARMACOLOGICAL RELEVANCE: Amyotrophic lateral sclerosis (ALS) is a fetal neuromuscular disorder characterized by the gradual deterioration of motor neurons. Semen Strychni pulveratum (SSP), a processed version of Semen Strychni (SS) powder, is widely used to treat ALS in China. Vomicine is one of the most primary components of SS. However, their pharmacological effects and mechanisms for ALS remain elusive.AIM OF THE STUDY: This study aimed to evaluate the neuroprotective and anti-neuroinflammatory effects of SSP and vomicine, as well as to explore their protective roles in ALS and the underlying mechanisms.
MATERIALS AND METHODS: In vivo, 8-week-old hSOD1-WT mice and hSOD1-G93A mice were orally administered different concentrations of SSP (SSP-L = 5.46 mg/ml, SSP-M = 10.92 mg/ml or SSP-H = 16.38 mg/ml) once every other day for 8 weeks. A series of experiments, including body weight measurement, footprint tests, Hematoxylin & Eosin staining, and Nissl staining, were performed to evaluate the preventive effect of SSP. Immunofluorescence staining, western blotting, and RT-qPCR were subsequently performed to evaluate activation of the cGAS-STING-TBK1 pathway in the spinal cord. In vitro, hSOD1G93A NSC-34 cells were treated with vomicine to further explore the pharmacological mechanism of vomicine in the treatment of ALS via the cGAS-STING-TBK1 pathway.
RESULTS: SSP improved motor function, body weight loss, gastrocnemius muscle atrophy, and motor neuron loss in the spine and cortex of hSOD1-G93A mice. Furthermore, the cGAS-STING-TBK1 pathway was activated in the spinal cord of hSOD1-G93A mice, with activation predominantly observed in neurons and microglia. However, the levels of cGAS, STING, and pTBK1 proteins and cGAS, IRF3, IL-6, and IL-1β mRNA were reversed following intervention with SSP. Vomicine not only downregulated the levels of cGAS, TBK1, IL-6 and IFN-β mRNA, but also the levels of cGAS and STING protein in hSOD1G93A NSC-34 cells.
CONCLUSION: This study demonstrated that SSP and vomicine exert neuroprotective and anti-neuroinflammatory effects in the treatment of ALS. SSP and vomicine may reduce neuroinflammation by regulating the cGAS-STING-TBK1 pathway, and could thereby play a role in ALS treatment.

Keywords:  Amyotrophic Lateral Sclerosis; Neuroinflammation; Semen Strychni Pulveratum; Vomicine; cGAS-STING-TBK1 Pathway

DOI:  https://doi.org/10.1016/j.jep.2024.118741
Ann Neurol. 2024 Aug 27.

Single-Nucleus RNA Sequencing Unravels Early Mechanisms of Human Becker Muscular Dystrophy.

Zhihao Xie, Chang Liu, Chengyue Sun, Yilin Liu, Jieru Peng, Lingchao Meng, Jianwen Deng, Zhaoxia Wang, Chunxia Yang, Yun Yuan, Zhiying Xie.

OBJECTIVE: The transcriptional heterogeneity at a single-nucleus level in human Becker muscular dystrophy (BMD) dystrophic muscle has not been explored. Here, we aimed to understand the transcriptional heterogeneity associated with myonuclei, as well as other mononucleated cell types that underly BMD pathogenesis by performing single-nucleus RNA sequencing.METHODS: We profiled single-nucleus transcriptional profiles of skeletal muscle samples from 7 BMD patients and 3 normal controls.
RESULTS: A total of 17,216 nuclei (12,879 from BMD patients and 4,337 from controls) were classified into 13 known cell types, including 9 myogenic lineages and 4 non-myogenic lineages, and 1 unclassified nuclear type according to their cell identities. Among them, type IIx myonuclei were the first to degenerate in response to dystrophin reduction. Differential expression analysis revealed that the fibro-adipogenic progenitors (FAPs) population had the largest transcriptional changes among all cell types. Sub-clustering analysis identified a significantly compositional increase in the activated FAPs (aFAPs) subpopulation in BMD muscles. Pseudotime analysis, regulon inference, and deconvolution analysis of bulk RNA-sequencing data derived from 29 BMD patients revealed that the aFAPs subpopulation, a distinctive and previously unrecognized mononuclear subtype, was profibrogenic and expanded in BMD patients. Muscle quantitative real-time polymerase chain reaction and immunofluorescence analysis confirmed that the mRNA and protein levels of the aFAPs markers including LUM, DCN, and COL1A1 in BMD patients were significantly higher than those in controls, respectively.
INTERPRETATION: Our results provide insights into the transcriptional diversity of human BMD muscle at a single-nucleus resolution and new potential targets for anti-fibrosis therapies in BMD. ANN NEUROL 2024.

DOI: https://doi.org/10.1002/ana.27070
Free Radic Biol Med. 2024 Aug 22. pii: S0891-5849(24)00590-2. [Epub ahead of print]

Exercise-induced Nrf2 activation increases antioxidant defenses in skeletal muscles.

Scott K Powers, Ronette Lategan-Potgieter, Erica Goldstein.

  Following the discovery that exercise increases the production of reactive oxygen species in contracting skeletal muscles, evidence quickly emerged that endurance exercise training increases the abundance of key antioxidant enzymes in the trained muscles. Since these early observations, knowledge about the impact that regular exercise has on skeletal muscle antioxidant capacity has increased significantly. Importantly, in recent years, our understanding of the cell signaling pathways responsible for this exercise-induced increase in antioxidant enzymes has expanded exponentially. Therefore, the goals of this review are: 1) summarize our knowledge about the influence that exercise training has on the abundance of key antioxidant enzymes in skeletal muscles; and 2) to provide a state-of-the-art review of the nuclear factor erythroid 2-related factor (Nrf2) signaling pathway that is responsible for many of the exercise-induced changes in muscle antioxidant capacity. We begin with a discussion of the sources of reactive oxygen species in contracting muscles and then examine the exercise-induced changes in the antioxidant enzymes that eliminate both superoxide radicals and hydrogen peroxide in muscle fibers. We conclude with a discussion of the advances in our understanding of the exercise-induced control of the Nrf2 signaling pathway that is responsible for the expression of numerous antioxidant proteins. In hopes of stimulating future research, we also identify gaps in our knowledge about the signaling pathways responsible for the exercise-induced increases in muscle antioxidant enzymes.

Keywords:  cell signaling; endurance exercise; oxidative stress; reactive oxygen species

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.07.041
Nat Commun. 2024 Aug 28. 15(1): 7440

CaV1.1 voltage-sensing domain III exclusively controls skeletal muscle excitation-contraction coupling.

Simone Pelizzari, Martin C Heiss, Monica L Fernández-Quintero, Yousra El Ghaleb, Klaus R Liedl, Petronel Tuluc, Marta Campiglio, Bernhard E Flucher.

Skeletal muscle contractions are initiated by action potentials, which are sensed by the voltage-gated calcium channel (CaV1.1) and are conformationally coupled to calcium release from intracellular stores. Notably, CaV1.1 contains four separate voltage-sensing domains (VSDs), which activate channel gating and excitation-contraction (EC-) coupling at different voltages and with distinct kinetics. Here we show that a single VSD of CaV1.1 controls skeletal muscle EC-coupling. Whereas mutations in VSDs I, II and IV affect the current properties but not EC-coupling, only mutations in VSD III alter the voltage-dependence of depolarization-induced calcium release. Molecular dynamics simulations reveal comprehensive, non-canonical state transitions of VSD III in response to membrane depolarization. Identifying the voltage sensor that activates EC-coupling and detecting its unique conformational changes opens the door to unraveling the downstream events linking VSD III motion to the opening of the calcium release channel, and thus resolving the signal transduction mechanism of skeletal muscle EC-coupling.

DOI: https://doi.org/10.1038/s41467-024-51809-5
Int J Mol Sci. 2024 Aug 06. pii: 8577. [Epub ahead of print]25(16):

Increased Homer Activity and NMJ Localization in the Vestibular Lesion het-/- Mouse soleus Muscle.

Gabor Trautmann, Katharina Block, Martina Gutsmann, Stéphane Besnard, Sandra Furlan, Pierre Denise, Pompeo Volpe, Dieter Blottner, Michele Salanova.

  We investigated the shuttling of Homer protein isoforms identified in soluble (cytosolic) vs. insoluble (membrane-cytoskeletal) fraction and Homer protein-protein interaction/activation in the deep postural calf soleus (SOL) and non-postural gastrocnemius (GAS) muscles of het-/- mice, i.e., mice with an autosomal recessive variant responsible for a vestibular disorder, in order to further elucidate a) the underlying mechanisms of disrupted vestibular system-derived modulation on skeletal muscle, and b) molecular signaling at respective neuromuscular synapses. Heterozygote mice muscles served as the control (CTR). An increase in Homer cross-linking capacity was present in the SOL muscle of het-/- mice as a compensatory mechanism for the altered vestibule system function. Indeed, in both fractions, different Homer immunoreactive bands were detectable, as were Homer monomers (~43-48 kDa), Homer dimers (~100 kDa), and several other Homer multimer bands (>150 kDA). The het-/- GAS particulate fraction showed no Homer dimers vs. SOL. The het-/- SOL soluble fraction showed a twofold increase (+117%, p ≤ 0.0004) in Homer dimers and multimers. Homer monomers were completely absent from the SOL independent of the animals studied, suggesting muscle-specific changes in Homer monomer vs. dimer expression in the postural SOL vs. the non-postural GAS muscles. A morphological assessment showed an increase (+14%, p ≤ 0.0001) in slow/type-I myofiber cross-sectional area in the SOL of het-/- vs. CTR mice. Homer subcellular immuno-localization at the neuromuscular junction (NMJ) showed an altered expression in the SOL of het-/-mice, whereas only not-significant changes were found for all Homer isoforms, as judged by RT-qPCR analysis. Thus, muscle-specific changes, myofiber properties, and neuromuscular signaling mechanisms share causal relationships, as highlighted by the variable subcellular Homer isoform expression at the instable NMJs of vestibular lesioned het-/- mice.

Keywords:  Homer; NMJ; vestibular lesion

DOI:  https://doi.org/10.3390/ijms25168577
Adv Neurobiol. 2024 ;39 285-318

Astrocyte-Neuron Interactions Contributing to Amyotrophic Lateral Sclerosis Progression.

Brigid K Jensen.

  Amyotrophic lateral sclerosis (ALS) is a complex disease impacting motor neurons of the brain, brainstem, and spinal cord. Disease etiology is quite heterogeneous with over 40 genes causing the disease and a vast ~90% of patients having no prior family history. Astrocytes are major contributors to ALS, particularly through involvement in accelerating disease progression. Through study of genetic forms of disease including SOD1, TDP43, FUS, C9orf72, VCP, TBK1, and more recently patient-derived cells from sporadic individuals, many biological mechanisms have been identified to cause intrinsic or glial-mediated neurotoxicity to motor neurons. Overall, many of the normally supportive and beneficial roles that astrocytes contribute to neuronal health and survival instead switch to become deleterious and neurotoxic. While the exact pathways may differ based on disease-origin, altered astrocyte-neuron communication is a common feature of ALS. Within this chapter, distinct genetic forms are examined in detail, along with what is known from sporadic patient-derived cells. Overall, this chapter highlights the interplay between astrocytes and neurons in this complex disease and describes the key features underlying: astrocyte-mediated motor neuron toxicity, excitotoxicity, oxidative/nitrosative stress, protein dyshomeostasis, metabolic imbalance, inflammation, trophic factor withdrawal, blood-brain/blood-spinal cord barrier involvement, disease spreading, and the extracellular matrix/cell adhesion/TGF-β signaling pathways.

Keywords:  Amyotrophic lateral sclerosis (ALS); Excitotoxicity; Inflammation; Metabolic imbalance; Trophic factors

DOI:  https://doi.org/10.1007/978-3-031-64839-7_12
Essays Biochem. 2024 Aug 28. pii: EBC20240006. [Epub ahead of print]

Does AMPK bind glycogen in skeletal muscle or is the relationship correlative?

Barnaby P Frankish, Robyn M Murphy.

  Since its discovery over five decades ago, an emphasis on better understanding the structure and functional role of AMPK has been prevalent. In that time, the role of AMPK as a heterotrimeric enzyme that senses the energy state of various cell types has been established. Skeletal muscle is a dynamic, plastic tissue that adapts to both functional and metabolic demands of the human body, such as muscle contraction or exercise. With a deliberate focus on AMPK in skeletal muscle, this review places a physiological lens to the association of AMPK and glycogen that has been established biochemically. It discusses that, to date, no in vivo association of AMPK with glycogen has been shown and this is not altered with interventions, either by physiological or biochemical utilisation of glycogen in skeletal muscle. The reason for this is likely due to the persistent phosphorylation of Thr148 in the β-subunit of AMPK which prevents AMPK from binding to carbohydrate domains. This review presents the correlative data that suggests AMPK senses glycogen utilisation through a direct interaction with glycogen, the biochemical data showing that AMPK can bind carbohydrate in vitro, and highlights that in a physiological setting of rodent skeletal muscle, AMPK does not directly bind to glycogen.

Keywords:  AMPK; glycogen; skeletal muscle

DOI:  https://doi.org/10.1042/EBC20240006
Anticancer Res. 2024 Sep;44(9): 4019-4029

Risk Factors Associated With Perioperative Skeletal Muscle Loss in Patients With Colorectal Cancer.

Hajime Kayano, Nana Mamuro, Yutaro Kamei, Takashi Ogimi, Hiroshi Miyakita, Yasuhiro Kanatani, Masaki Mori, Kenichi Okada, Kazuo Koyanagi, Seiichiro Yamamoto.

  BACKGROUND/AIM: Postoperative changes in body composition, especially loss of muscle mass, often occur in gastrointestinal cancer patients. Few studies have reported perioperative changes in the body composition of patients with colorectal cancer. Therefore, this study aimed at clarifying changes in body composition during the perioperative period and identifying risk factors for skeletal muscle mass loss in patients with colorectal cancer.PATIENTS AND METHODS: This prospective observational study included 148 patients who underwent robot- or laparoscopic-assisted surgery for colorectal cancer.
RESULTS: The rate of change in body composition at discharge was -6.25% for body fat, with a higher rate of decrease than that for skeletal muscle mass (-3.30%; p=0.0006) and body water mass (-2.66%; p=0.0001). Similarly, even at one month postoperatively, body fat mass (-8.05%) was reduced at a greater rate than skeletal muscle mass (-2.02% p=0.0001) and body water mass (-1.33% p=0.0001).The site-specific percent change in limb skeletal and trunk muscle mass at discharge was the greatest in the lower extremities at -5.37%, but one month after surgery, the upper extremities had the greatest change at -4.44%. The Prognostic Nutritional Index (PNI) influenced skeletal muscle mass loss at discharge [odds ratio (OR)=2.6; 95% confidence interval (CI)=1.30-5.58], while diabetes (OR=4.1; 95%CI=1.40-12.43) and ileostomy (OR=6.7; 95%CI=1.45-31.11) influenced skeletal muscle loss one month postoperatively.
CONCLUSION: Preoperative and postoperative nutritional guidance/intervention and body part-specific rehabilitation should be provided to prevent skeletal muscle mass loss in patients with low PNI, diabetes, and those undergoing ileostomy.

Keywords:  Colon cancer; adjuvant chemotherapy; body composition; perioperative period; skeletal muscle loss

DOI:  https://doi.org/10.21873/anticanres.17231
J Clin Invest. 2024 Aug 27. pii: e173858. [Epub ahead of print]

Spatiotemporal transcriptomic mapping of regenerative inflammation in skeletal muscle reveals a dynamic multilayered tissue architecture.

Andreas Patsalos, Laszlo Halasz, Darby Oleksak, Xiaoyan Wei, Gergely Nagy, Petros Tzerpos, Thomas Conrad, David W Hammers, H Lee Sweeney, Laszlo Nagy.

  Tissue regeneration is orchestrated by macrophages that clear damaged cells and promote regenerative inflammation. How macrophages spatially adapt and diversify their functions to support the architectural requirements of actively regenerating tissue remains unknown. In this study, we reconstructed the dynamic trajectories of myeloid cells isolated from acutely injured and early-stage dystrophic muscles. We identified divergent subsets of monocytes/macrophages and dendritic cells (DCs) and validated markers (e.g., GPNMB) and transcriptional regulators associated with defined functional states. In dystrophic muscle, specialized repair-associated subsets exhibited distinct macrophage diversity and reduced DC heterogeneity. Integrating spatial transcriptomics analyses with immunofluorescence uncovered the ordered distribution of subpopulations and multilayered regenerative inflammation zones (RIZs) where distinct macrophage subsets are organized in functional zones around damaged myofibers supporting all phases of regeneration. Importantly, intermittent glucocorticoid treatment disrupted the RIZs. Our findings suggest that macrophage subtypes mediated the development of the highly ordered architecture of regenerative tissues, unveiling the principles of the structured yet dynamic nature of regenerative inflammation supporting effective tissue repair.

Keywords:  Expression profiling; Inflammation; Macrophages; Skeletal muscle

DOI:  https://doi.org/10.1172/JCI173858
Commun Biol. 2024 Aug 27. 7(1): 1055

miR-29 is an important driver of aging-related phenotypes.

Vijay Swahari, Ayumi Nakamura, Emilie Hollville, Yu-Han Hung, Matt Kanke, C Lisa Kurtz, Xurde M Caravia, David Roiz-Valle, Shenghui He, Janakiraman Krishnamurthy, Sahil Kapoor, Varun Prasad, Cornelius Flowers, Matt Beck, Jeanette Baran-Gale, Norman Sharpless, Carlos López-Otín, Praveen Sethupathy, Mohanish Deshmukh.

Aging is a consequence of complex molecular changes, but whether a single microRNA (miRNA) can drive aging remains unclear. A miRNA known to be upregulated during both normal and premature aging is miR-29. We find miR-29 to also be among the top miRNAs predicted to drive aging-related gene expression changes. We show that partial loss of miR-29 extends the lifespan of Zmpste24-/- mice, an established model of progeria, indicating that miR-29 is functionally important in this accelerated aging model. To examine whether miR-29 alone is sufficient to promote aging-related phenotypes, we generated mice in which miR-29 can be conditionally overexpressed (miR-29TG). miR-29 overexpression is sufficient to drive many aging-related phenotypes and led to early lethality. Transcriptomic analysis of both young miR-29TG and old WT mice reveals shared downregulation of genes associated with extracellular matrix organization and fatty acid metabolism, and shared upregulation of genes in pathways linked to inflammation. These results highlight the functional importance of miR-29 in controlling a gene expression program that drives aging-related phenotypes.

DOI: https://doi.org/10.1038/s42003-024-06735-z
Brain Behav Immun. 2024 Aug 28. pii: S0889-1591(24)00566-X. [Epub ahead of print]122 456-462

Long-term survival of participants in a phase II randomized trial of RNS60 in amyotrophic lateral sclerosis.

RNS60-ALS Study Group

  BACKGROUND: Positive effects of RNS60 on respiratory and bulbar function were observed in a phase 2 randomized, placebo-controlled trial in people with amyotrophic lateral sclerosis (ALS).OBJECTIVE: to investigate the long-term survival of trial participants and its association with respiratory status and biomarkers of neurodegeneration and inflammation.
STUDY DESIGN AND SETTINGS: A randomized, double blind, phase 2 clinical trial was conducted. Trial participants were enrolled at 22 Italian Expert ALS Centres from May 2017 to January 2020. Vital status of all participants was ascertained thirty-three months after the trial's last patient last visit (LPLV). Participants were patients with Amyotrophic Lateral Sclerosis, classified as slow or fast progressors based on forced vital capacity (FVC) slope during trial treatment. Demographic, clinical, and biomarker levels and their association with survival were also evaluated.
RESULTS: Mean duration of follow-up was 2.8 years. Long-term median survival was six months longer in the RNS60 group (p = 0.0519). Baseline FVC, and rates of FVC decline during the first 4 weeks of trial participation, were balanced between the active and placebo treatment arms. After 6 months of randomized, placebo-controlled treatment, FVC decline was significantly slower in the RNS60 group compared to the placebo group. Rates of FVC progression during the treatment were strongly associated with long-term survival (median survival: 3.7 years in slow FVC progressors; 1.6 years in fast FVC progressors). The effect of RNS60 in prolonging long-term survival was higher in participants with low neurofilament light chain (NfL) (median survival: >4 years in low NfL - RNS60 group; 3.3 years in low NfL - placebo group; 1.9 years in high NfL - RNS60 group; 1.8 years in high NfL - placebo group) and Monocyte Chemoattractant Protein-1 (MCP-1) (median survival: 3.7 years in low MCP-1 - RNS60 group; 2.3 years in low MCP-1 - placebo group; 2.8 years in high MCP-1 - RNS60 group; 2.6 years in high MCP-1 - placebo group) levels at baseline.
CONCLUSIONS AND RELEVANCE: In this post-hoc analysis, long term survival was longer in participants randomized to RNS60 compared with those randomized to placebo and was correlated with slower FVC progression rates, suggesting that longer survival may be mediated by the drug's effect on respiratory function. In these post-hoc analyses, the beneficial effect of RNS60 on survival was most pronounced in participants with low NfL and MCP-1 levels at study entry, suggesting that this could be a subgroup to target in future studies investigating the effects of RNS60 on survival.
TRIAL REGISTRATION: Study preregistered on 13/Jan/2017 in EUDRA-CT (2016-002382-62). The study was also registered at ClinicalTrials.gov number NCT03456882.

Keywords:  Amyotrophic lateral sclerosis; Clinical trial; Forced vital capacity; Survival

DOI:  https://doi.org/10.1016/j.bbi.2024.08.044