bims-moremu 2023-01-29 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023‒01‒29
25 papers selected by
Anna Vainshtein
Craft Science Inc.

Isolation of extracellular fluids reveals novel secreted bioactive proteins from muscle and fat tissues.
Effects of a 2-year exercise training on neuromuscular system health in older individuals with low muscle function.
Potential mechanisms involved in regulating muscle protein turnover after acute exercise: A brief review.
Caloric restriction delays age-related muscle atrophy by inhibiting 11β-HSD1 to promote the differentiation of muscle stem cells.
LSD1 defines the fiber type-selective responsiveness to environmental stress in skeletal muscle.
Protein therapy of skeletal muscle atrophy and mechanism by angiogenic factor AGGF1.
Early adaptive responses in the skeletal muscle of young mice with hereditary hemochromatosis.
Acute resistance exercise training does not augment mitochondrial remodelling in master athletes or untrained older adults.
MME+ fibro-adipogenic progenitors are the dominant adipogenic population during fatty infiltration in human skeletal muscle.
Regulation of the endocannabinoid system by endurance and resistance exercise in hypoxia in human skeletal muscle.
Mitochondrial creatine sensitivity is lost in the D2.mdx model of Duchenne muscular dystrophy and rescued by the mitochondrial-enhancing compound Olesoxime.
Neuregulin-1β increases glucose uptake and promotes GLUT4 translocation in palmitate-treated C2C12 myotubes by activating PI3K/AKT signaling pathway.
Mesenchymal stromal cells ameliorate diabetes-induced muscle atrophy through exosomes by enhancing AMPK/ULK1-mediated autophagy.
A reduction of skeletal muscle DHA content does not result in impaired whole-body glucose tolerance or skeletal muscle basal insulin signaling in healthy mice.
The role of exercise and hypoxia on glucose transport and regulation.
Metabolic reprogramming underlies cavefish muscular endurance despite loss of muscle mass and contractility.
Nuclear envelope transmembrane proteins involved in genome organization are misregulated in myotonic dystrophy type 1 muscle.
Gut-muscle crosstalk. A perspective on influence of microbes on muscle function.
Temporal static and dynamic imaging of skeletal muscle in vivo.
The early inhibition of the COX-2 pathway in viperid phospholipase A2-induced skeletal muscle myotoxicity accelerates the tissue regeneration.
Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations.
Combined prenatal to postnatal protein restriction augments protein quality control processes and proteolysis in the muscle of rat offspring.
Improving quantification of myotube width and nuclear/cytoplasmic ratio in myogenesis research.
Micro-dystrophin expression as a surrogate endpoint for Duchenne muscular dystrophy clinical trials.
Distinct effect of exercise modes on mood-related behavior in mice.

Cell Metab. 2023 Jan 14. pii: S1550-4131(22)00577-0. [Epub ahead of print]

Isolation of extracellular fluids reveals novel secreted bioactive proteins from muscle and fat tissues.

Melanie J Mittenbühler, Mark P Jedrychowski, Jonathan G Van Vranken, Hans-Georg Sprenger, Sarah Wilensky, Phillip A Dumesic, Yizhi Sun, Andrea Tartaglia, Dina Bogoslavski, Mu A, Haopeng Xiao, Katherine A Blackmore, Anita Reddy, Steven P Gygi, Edward T Chouchani, Bruce M Spiegelman.

  Proteins are secreted from cells to send information to neighboring cells or distant tissues. Because of the highly integrated nature of energy balance systems, there has been particular interest in myokines and adipokines. These are challenging to study through proteomics because serum or plasma contains highly abundant proteins that limit the detection of proteins with lower abundance. We show here that extracellular fluid (EF) from muscle and fat tissues of mice shows a different protein composition than either serum or tissues. Mass spectrometry analyses of EFs from mice with physiological perturbations, like exercise or cold exposure, allowed the quantification of many potentially novel myokines and adipokines. Using this approach, we identify prosaposin as a secreted product of muscle and fat. Prosaposin expression stimulates thermogenic gene expression and induces mitochondrial respiration in primary fat cells. These studies together illustrate the utility of EF isolation as a discovery tool for adipokines and myokines.

Keywords:  PGC1α; cold adaptation; exercise; extracellular fluid; prosaposin; proteomics; secreted proteins; secretome

DOI:  https://doi.org/10.1016/j.cmet.2022.12.014
J Cachexia Sarcopenia Muscle. 2023 Jan 28.

Effects of a 2-year exercise training on neuromuscular system health in older individuals with low muscle function.

Elena Monti, Sara Tagliaferri, Sandra Zampieri, Fabio Sarto, Giuseppe Sirago, Martino Vladimiro Franchi, Andrea Ticinesi, Yari Longobucco, Elisa Adorni, Fulvio Lauretani, Stephan Von Haehling, Emanuele Marzetti, Riccardo Calvani, Roberto Bernabei, Matteo Cesari, Marcello Maggio, Marco Vincenzo Narici.

  BACKGROUND: Ageing is accompanied by a progressive loss of skeletal muscle mass and strength, potentially determining the insurgence of sarcopenia. Evidence suggests that motoneuron and neuromuscular junction (NMJ) degeneration contribute to sarcopenia pathogenesis. Seeking for strategies able to slow down sarcopenia insurgence and progression, we investigated whether a 2-year mixed-model training involving aerobic, strength and balance exercises would be effective for improving or preserving motoneuronal health and NMJ stability, together with muscle mass, strength and functionality in an old, sarcopenic population.METHODS: Forty-five sarcopenic elderly (34 females; 11 males) with low dual-energy X-ray absorptiometry (DXA) lean mass and Short Physical Performance Battery (SPPB) score <9 were randomly assigned to either a control group [Healthy Aging Lifestyle Education (HALE), n = 21] or an intervention group [MultiComponent Intervention (MCI), n = 24]. MCI trained three times per week for 2 years with a mix of aerobic, strength and balance exercises matched with nutritional advice. Before and after the intervention, ultrasound scans of the vastus lateralis (VL), SPPB and a blood sample were obtained. VL architecture [pennation angle (PA) and fascicle length (Lf)] and cross-sectional area (CSA) were measured. As biomarkers of neuronal health and NMJ stability status, neurofilament light chain (NfL) and C-terminal agrin fragment (CAF) concentrations were measured in serum. Differences in ultrasound parameters, NfL and CAF concentration and physical performance between baseline and follow-up were tested with mixed ANOVA or Wilcoxon test. The relationship between changes in physical performance and NfL or CAF concentration was assessed through correlation analyses.
RESULTS: At follow-up, MCI showed preserved VL architecture (PA, Lf) despite a reduced CSA (-8.4%, P < 0.001), accompanied by maintained CAF concentration and ameliorated overall SPPB performance (P = 0.007). Conversely, HALE showed 12.7% decrease in muscle CSA (P < 0.001), together with 5.1% and 5.5% reduction in PA and Lf (P < 0.001 and P = 0.001, respectively), and a 6.2% increase in CAF (P = 0.009) but improved SPPB balance score (P = 0.007). NfL concentration did not change in either group. In the population, negative correlations between changes in CAF concentration and SPPB total score were found (P = 0.047), whereas no correlation between NfL and SPPB variations was observed.
CONCLUSIONS: The present findings suggest that our 2-year mixed aerobic, strength and balance training seemed effective for preventing the age and sarcopenia-related increases in CAF concentration, preserving NMJ stability as well as muscle structure (PA and Lf) and improving physical performance in sarcopenic older individuals.

Keywords:  C-terminal agrin fragment (CAF); elderly; exercise intervention; neurofilament light chain (NfL); sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13173
Front Physiol. 2022 ;13 1106425

Potential mechanisms involved in regulating muscle protein turnover after acute exercise: A brief review.

Guy Hajj-Boutros, Antony D Karelis, Marina Cefis, José A Morais, Juliette Casgrain, Gilles Gouspillou, Vita Sonjak.

  It is well established that resistance training increases muscle mass. Indeed, there is evidence to suggest that a single session of resistance training is associated with an increase in muscle protein synthesis in young adults. However, the fundamental mechanisms that are involved in regulating muscle protein turnover rates after an acute bout of physical exercise are unclear. Therefore, this review will briefly focus on summarizing the potential mechanisms behind the growth of skeletal muscle after physical exercise. We also present mechanistic differences that may exist between young and older individuals during muscle protein synthesis and breakdown after physical exercise. Pathways leading to the activation of AKT/mTOR signals after resistance exercise and the activation of AMPK signaling pathway following a HIIT (High intensity interval training) are discussed.

Keywords:  high intensity interval training (HIIT); mechanical stress; muscle protein breakdown; muscle protein synthesis; resistance training

DOI:  https://doi.org/10.3389/fphys.2022.1106425
Front Med (Lausanne). 2022 ;9 1027055

Caloric restriction delays age-related muscle atrophy by inhibiting 11β-HSD1 to promote the differentiation of muscle stem cells.

Shan Lv, Qianjin Shen, Hengzhen Li, Qun Chen, Wenqing Xie, Yusheng Li, Xiaodong Wang, Guoxian Ding.

  Introduction: Calorie restriction (CR) is an important direction for the delay of sarcopenia in elderly individuals. However, the specific mechanisms of CR against aging are still unclear.Methods: In this study, we used a CR model of elderly mice with muscle-specific 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) knockout mice and 11β-HSD1 overexpression mice to confirm that CR can delay muscle aging by inhibiting 11β-HSD1 which can transform inactive GC(cortisone) into active GC(cortisol). The ability of self-proliferation and differentiation into muscle fibers of these mouse muscle stem cells (MuSCs) was observed in vitro. Additionally, the mitochondrial function and mitochondrial ATP production capacity of MuSCs were measured by mitochondrial oxygen consumption.
Results: It was found that the 11β-HSD1 expression level was increased in age-related muscle atrophy. Overexpression of 11β-HSD1 led to muscle atrophy in young mice, and 11β-HSD1 knockout rescued age-related muscle atrophy. Moreover, CR in aged mice reduced the local effective concentration of glucocorticoid (GC) through 11β-HSD1, thereby promoting the mitochondrial function and differentiation ability of MuSCs.
Conclusions: Together, our findings highlight promising sarcopenia protection with 40% CR in older ages. Furthermore, we speculated that targeting an 11β-HSD1-dependent metabolic pathway may represent a novel strategy for developing therapeutics against age-related muscle atrophy.

Keywords:  11β-HSD1; caloric restriction (CR); mitochondrial function; muscle atrophy; muscle stem cells (MuSCs)

DOI:  https://doi.org/10.3389/fmed.2022.1027055
Elife. 2023 Jan 25. pii: e84618. [Epub ahead of print]12

LSD1 defines the fiber type-selective responsiveness to environmental stress in skeletal muscle.

Hirotaka Araki, Shinjiro Hino, Kotaro Anan, Kanji Kuribayashi, Kan Etoh, Daiki Seko, Ryuta Takase, Kensaku Kohrogi, Yuko Hino, Yusuke Ono, Eiichi Araki, Mitsuyoshi Nakao.

  Skeletal muscle exhibits remarkable plasticity in response to environmental cues, with stress-dependent effects on the fast-twitch and slow-twitch fibers. Although stress-induced gene expression underlies environmental adaptation, it is unclear how transcriptional and epigenetic factors regulate fiber type-specific responses in the muscle. Here, we show that flavin-dependent lysine-specific demethylase-1 (LSD1) differentially controls responses to glucocorticoid and exercise in postnatal skeletal muscle. Using skeletal muscle-specific LSD1-knockout mice and in vitro approaches, we found that LSD1 loss exacerbated glucocorticoid-induced atrophy in the fast fiber-dominant muscles, with reduced nuclear retention of Foxk1, an anti-autophagic transcription factor. Furthermore, LSD1 depletion enhanced endurance exercise-induced hypertrophy in the slow fiber-dominant muscles, by induced expression of ERRγ, a transcription factor that promotes oxidative metabolism genes. Thus, LSD1 serves as an 'epigenetic barrier' that optimizes fiber type-specific responses and muscle mass under the stress conditions. Our results uncover that LSD1 modulators provide emerging therapeutic and preventive strategies against stress-induced myopathies such as sarcopenia, cachexia, and disuse atrophy.

Keywords:  LSD1; cell biology; chromosomes; gene expression; mouse; muscle atrophy; muscle hypertrophy; transcriptional regulation

DOI:  https://doi.org/10.7554/eLife.84618
J Cachexia Sarcopenia Muscle. 2023 Jan 25.

Protein therapy of skeletal muscle atrophy and mechanism by angiogenic factor AGGF1.

Zuhan He, Qixue Song, Yubing Yu, Feng Liu, Jinyan Zhao, Waikeong Un, Xingwen Da, Chengqi Xu, Yufeng Yao, Qing K Wang.

  BACKGROUND: Skeletal muscle atrophy is a common condition without a pharmacologic therapy. AGGF1 encodes an angiogenic factor that regulates cell differentiation, proliferation, migration, apoptosis, autophagy and endoplasmic reticulum stress, promotes vasculogenesis and angiogenesis and successfully treats cardiovascular diseases. Here, we report the important role of AGGF1 in the pathogenesis of skeletal muscle atrophy and attenuation of muscle atrophy by AGGF1.METHODS: In vivo studies were carried out in impaired leg muscles from patients with lumbar disc herniation, two mouse models for skeletal muscle atrophy (denervation and cancer cachexia) and heterozygous Aggf1+/- mice. Mouse muscle atrophy phenotypes were characterized by body weight and myotube cross-sectional areas (CSA) using H&E staining and immunostaining for dystrophin. Molecular mechanistic studies include co-immunoprecipitation (Co-IP), western blotting, quantitative real-time PCR analysis and immunostaining analysis.
RESULTS: Heterozygous Aggf1+/- mice showed exacerbated phenotypes of reduced muscle mass, myotube CSA, MyHC (myosin heavy chain) and α-actin, increased inflammation (macrophage infiltration), apoptosis and fibrosis after denervation and cachexia. Intramuscular and intraperitoneal injection of recombinant AGGF1 protein attenuates atrophy phenotypes in mice with denervation (gastrocnemius weight 81.3 ± 5.7 mg vs. 67.3 ± 5.1 mg for AGGF1 vs. buffer; P < 0.05) and cachexia (133.7 ± 4.7 vs. 124.3 ± 3.2; P < 0.05). AGGF1 expression undergoes remodelling and is up-regulated in gastrocnemius and soleus muscles from atrophy mice and impaired leg muscles from patients with lumbar disc herniation by 50-60% (P < 0.01). Mechanistically, AGGF1 interacts with TWEAK (tumour necrosis factor-like weak inducer of apoptosis), which reduces interaction between TWEAK and its receptor Fn14 (fibroblast growth factor-inducing protein 14). This leads to inhibition of Fn14-induced NF-kappa B (NF-κB) p65 phosphorylation, which reduces expression of muscle-specific E3 ubiquitin ligase MuRF1 (muscle RING finger 1), resulting in increased MyHC and α-actin and partial reversal of atrophy phenotypes. Autophagy is reduced in Aggf1+/- mice due to inhibition of JNK (c-Jun N-terminal kinase) activation in denervated and cachectic muscles, and AGGF1 treatment enhances autophagy in two atrophy models by activating JNK. In impaired leg muscles of patients with lumbar disc herniation, MuRF1 is up-regulated and MyHC and α-actin are down-regulated; these effects are reversed by AGGF1 by 50% (P < 0.01).
CONCLUSIONS: These results indicate that AGGF1 is a novel regulator for the pathogenesis of skeletal muscle atrophy and attenuates skeletal muscle atrophy by promoting autophagy and inhibiting MuRF1 expression through a molecular signalling pathway of AGGF1-TWEAK/Fn14-NF-κB. More importantly, the results indicate that AGGF1 protein therapy may be a novel approach to treat patients with skeletal muscle atrophy.

Keywords:  AGGF1; Fn14; NF-κB; TWEAK; cancer cachexia; skeletal muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13179
Mol Biol Rep. 2023 Jan 26.

Early adaptive responses in the skeletal muscle of young mice with hereditary hemochromatosis.

Varun V Dhorajia, Jonghan Kim, Yuho Kim.

  BACKGROUND: Hereditary hemochromatosis (HH) is characterized by iron overload that can cause multiple organ dysfunction primarily due to uncontrolled iron-mediated oxidative stress. Although HH leads to muscular weakness, disorder, and fatigue, the mechanism by which HH affects skeletal muscle physiology is largely unknown.METHODS: Using Hfe knockout mice (6-7 months old), a well-defined mouse model of HH, we examined iron status in the skeletal muscle, as well as other organs. As mitochondria are key organelle for muscular function, this study also explored how molecular markers for mitochondrial function and related systems are regulated in the HH skeletal muscle using western blots.
RESULTS: Although iron overload was evident at the systemic level, only mild iron overload was observed in the skeletal muscle of HH. Of note, mitochondrial electron transport chain complex I was upregulated in the HH skeletal muscle, which was accompanied by enhanced autophagy. However, these molecular changes were not associated with oxidative stress, suggesting altered mitochondrial metabolism in the muscle in response to iron overload.
CONCLUSIONS: These early adaptive responses may be important for supporting mitochondrial health before fully developing skeletal muscle dysfunction in HH. More studies are needed to determine the role of autophagy in the HH-related muscle mitochondrial dysfunction.

Keywords:  Autophagy; Hereditary hemochromatosis; Iron overload; Mitochondria; Muscle disorder

DOI:  https://doi.org/10.1007/s11033-023-08264-0
Front Physiol. 2022 ;13 1097988

Acute resistance exercise training does not augment mitochondrial remodelling in master athletes or untrained older adults.

Ryan Neil Marshall, James McKendry, Benoit Smeuninx, Alex Peter Seabright, Paul T Morgan, Carolyn Greig, Leigh Breen.

  Background: Ageing is associated with alterations to skeletal muscle oxidative metabolism that may be influenced by physical activity status, although the mechanisms underlying these changes have not been unraveled. Similarly, the effect of resistance exercise training (RET) on skeletal muscle mitochondrial regulation is unclear. Methods: Seven endurance-trained masters athletes ([MA], 74 ± 3 years) and seven untrained older adults ([OC]. 69 ± 6 years) completed a single session of knee extension RET (6 x 12 repetitions, 75% 1-RM, 120-s intra-set recovery). Vastus lateralis muscle biopsies were collected pre-RET, 1 h post-RET, and 48h post-RET. Skeletal muscle biopsies were analyzed for citrate synthase (CS) enzyme activity, mitochondrial content, and markers of mitochondrial quality control via immunoblotting. Results: Pre-RET CS activity and protein content were ∼45% (p < .001) and ∼74% greater in MA compared with OC (p = .006). There was a significant reduction (∼18%) in CS activity 48 h post-RET (p < .05) in OC, but not MA. Pre-RET abundance of individual and combined mitochondrial electron transport chain (ETC) complexes I-V were significantly greater in MA compared with OC, as were markers of mitochondrial fission and fusion dynamics (p-DRP-1Ser616, p-MFFSer146, OPA-1 & FIS-1, p < .05 for all). Moreover, MA displayed greater expression of p-AMPKThr172, PGC1α, TFAM, and SIRT-3 (p < .05 for all). Notably, RET did not alter the expression of any marker of mitochondrial content, biogenesis, or quality control in both OC and MA. Conclusion: The present data suggest that long-term aerobic exercise training supports superior skeletal muscle mitochondrial density and protein content into later life, which may be regulated by greater mitochondrial quality control mechanisms and supported via superior fission-fusion dynamics. However, a single session of RET is unable to induce mitochondrial remodelling in the acute (1h post-RET) and delayed (48 h post-RET) recovery period in OC and MA.

Keywords:  ageing; healthy ageing; mitochondria; resistance exercise; skeletal muscle

DOI:  https://doi.org/10.3389/fphys.2022.1097988
Commun Biol. 2023 Jan 27. 6(1): 111

MME+ fibro-adipogenic progenitors are the dominant adipogenic population during fatty infiltration in human skeletal muscle.

Gillian Fitzgerald, Guillermo Turiel, Tatiane Gorski, Inés Soro-Arnaiz, Jing Zhang, Nicola C Casartelli, Evi Masschelein, Nicola A Maffiuletti, Reto Sutter, Michael Leunig, Jean Farup, Katrien De Bock.

Fatty infiltration, the ectopic deposition of adipose tissue within skeletal muscle, is mediated via the adipogenic differentiation of fibro-adipogenic progenitors (FAPs). We used single-nuclei and single-cell RNA sequencing to characterize FAP heterogeneity in patients with fatty infiltration. We identified an MME+ FAP subpopulation which, based on ex vivo characterization as well as transplantation experiments, exhibits high adipogenic potential. MME+ FAPs are characterized by low activity of WNT, known to control adipogenic commitment, and are refractory to the inhibitory role of WNT activators. Using preclinical models for muscle damage versus fatty infiltration, we show that many MME+ FAPs undergo apoptosis during muscle regeneration and differentiate into adipocytes under pathological conditions, leading to a reduction in their abundance. Finally, we utilized the varying fat infiltration levels in human hip muscles and found less MME+ FAPs in fatty infiltrated human muscle. Altogether, we have identified the dominant adipogenic FAP subpopulation in skeletal muscle.

DOI: https://doi.org/10.1038/s42003-023-04504-y
J Appl Physiol (1985). 2023 Jan 26.

Regulation of the endocannabinoid system by endurance and resistance exercise in hypoxia in human skeletal muscle.

Sophie van Doorslaer de Ten Ryen, Sebastiaan Dalle, Romano Terrasi, Katrien Koppo, Giulio G Muccioli, Louise Deldicque.

  Exercise modulates the circulating levels of the endocannabinoids ligands N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) and possibly the levels of their receptors and downstream signaling in skeletal muscle. The aim of the present study was to investigate the regulation of the endocannabinoid system by several exercise paradigms in human skeletal muscle. A second aim was to compare endocannabinoid regulation in healthy and prediabetic people in response to an acute endurance exercise. Blood and muscle samples were taken before and after resistance and endurance exercise in normoxia and hypoxia to measure plasma endocannabinoid levels as well as muscle protein expression of CB1, CB2 and downstream signaling. We found that: 1) an acute resistance exercise session decreased plasma 2-AG and N-palmitoylethanolamine (PEA) levels in normoxia; 2) 4 weeks resistance training decreased plasma AEA, PEA and N-oleoylethanolamine (OEA) levels in both normoxia and hypoxia; 3) an acute moderate intensity endurance exercise increased plasma OEA levels in the healthy and prediabetic groups in normoxia and hypoxia while plasma 2-AG levels increased in the healthy group and AEA in the prediabetic group only in normoxia. The expression of the cannabinoid receptors was only marginally regulated by acute exercise, hypoxia and prediabetes and downstream signaling did not follow the changes detected in the endocannabinoid ligands. Altogether, our results suggest that resistance and endurance exercise regulate the levels of the endocannabinoid ligands and CB1 expression in opposite ways. The physiological impact of the changes observed in the endocannabinoid ligands in human skeletal muscle after exercise needs further investigation.

Keywords:  endocannabinoid; exercise; hypoxia

DOI:  https://doi.org/10.1152/japplphysiol.00645.2022
Am J Physiol Cell Physiol. 2023 Jan 23.

Mitochondrial creatine sensitivity is lost in the D2.mdx model of Duchenne muscular dystrophy and rescued by the mitochondrial-enhancing compound Olesoxime.

Catherine A Bellissimo, Luca J Delfinis, Meghan C Hughes, Patrick C Turnbull, Shivam Gandhi, Sara N DiBenedetto, Fasih A Rahman, Peyman Tadi, Christina A Amaral, Ali Dehghani, James Cobley, Joe Quadrilatero, Uwe Schlattner, Christopher G R Perry.

  Duchenne muscular dystrophy (DMD) is associated with distinct mitochondrial stress responses. Here, we aimed to determine whether the prospective mitochondrial-enhancing compound Olesoxime prevents early-stage mitochondrial stress in limb and respiratory muscle from D2.mdx mice using a proof-of-concept short-term regimen spanning 10-28 days of age. As mitochondrial-cytoplasmic energy transfer occurs via ATP- or phosphocreatine-dependent phosphate shuttling, we assessed bioenergetics with or without creatine in vitro. We observed that disruptions in Complex I-supported respiration and H2O2 emission in D2.mdx quadriceps and diaphragm were amplified by creatine demonstrating mitochondrial creatine insensitivity manifests ubiquitously and early in this model. Olesoxime selectively rescued or maintained creatine sensitivity in both muscles, independent of the abundance of respiration-related mitochondrial proteins or mitochondrial creatine kinase cysteine oxidation in quadriceps. Mitochondrial calcium retention capacity and glutathione were altered in a muscle-specific manner in D2.mdx but were generally unchanged by Olesoxime. Treatment reduced serum creatine kinase (muscle damage) and preserved cage hang-time, microCT-based volumes of lean compartments including whole body, hindlimb and bone, recovery of diaphragm force after fatigue, and cross-sectional area of diaphragm type IIX fibre, but reduced type I fibres in quadriceps. Grip strength, voluntary wheel-running and fibrosis were unaltered by Olesoxime. In summary, locomotor and respiratory muscle mitochondrial creatine sensitivities are lost during early stages in D2.mdx mice but are preserved by short-term treatment with Olesoxime in association with specific indices of muscle quality suggesting early myopathy in this model is at least partially attributed to mitochondrial stress.

Keywords:  Muscle; Neuromuscular disease; Oxidative phosphorylation; Permeability transition pore; Reactive oxygen species

DOI:  https://doi.org/10.1152/ajpcell.00377.2022
Front Pharmacol. 2022 ;13 1066279

Neuregulin-1β increases glucose uptake and promotes GLUT4 translocation in palmitate-treated C2C12 myotubes by activating PI3K/AKT signaling pathway.

Meirong Yu, Shuang Wu, Chao Gong, Lianhua Chen.

  Insulin resistance (IR) is a feature of type 2 diabetes (T2DM) accompanied by reduced glucose uptake and glucose transporter 4 (GLUT4) translocation by skeletal muscle. Neuregulin-1β (NRG-1β) is essential for myogenesis and the regulation of skeletal muscle metabolism. Neuregulin-1β increases insulin sensitivity, promotes glucose uptake and glucose translocation in normal skeletal muscle. Here, we explored whether Neuregulin-1β increased glucose uptake and GLUT4 translocation in palmitate (PA)-treated C2C12 myotubes. After C2C12 myoblasts differentiated into myotubes, we used palmitate to induce cellular insulin resistance. Cells were incubated with or without Neuregulin-1β and glucose uptake was determined using the 2-NBDG assay. The expression level of glucose transporter 4 (GLUT4) was measured via immunofluorescence and Western blotting. MK2206, an inhibitor of AKT, was employed to reveal the important role played by AKT signaling in PA-treated C2C12 myotubes. We then established an animal model with T2DM and evaluated the effects of Neuregulin-1β on body weight and the blood glucose level. The GLUT4 level in the gastrocnemius of T2DM mice was also measured. NRG-1β not only increased glucose uptake by PA-treated myotubes but also promoted GLUT4 translocation to the plasma membrane. The effect of NRG-1β on PA-treated C2C12 myotubes was associated with AKT activation. In T2DM mice, Neuregulin-1β not only improved diabetes-induced weight loss and diabetes-induced hyperglycemia, but also promoted GLUT4 translocation in the gastrocnemius. In summary, Neuregulin-1β increased glucose uptake and promoted translocation of GLUT4 to the plasma membrane in PA-treated C2C12 myotubes by activating the PI3K/AKT signaling pathway.

Keywords:  C2C12 myotubes; GLUT4 translocation; Neuregulin-1β; PI3K/AKT; glucose uptake

DOI:  https://doi.org/10.3389/fphar.2022.1066279
J Cachexia Sarcopenia Muscle. 2023 Jan 27.

Mesenchymal stromal cells ameliorate diabetes-induced muscle atrophy through exosomes by enhancing AMPK/ULK1-mediated autophagy.

Jia Song, Jidong Liu, Chen Cui, Huiqing Hu, Nan Zang, Mengmeng Yang, Jingwen Yang, Ying Zou, Jinquan Li, Lingshu Wang, Qin He, Xinghong Guo, Ruxing Zhao, Fei Yan, Fuqiang Liu, Xinguo Hou, Zheng Sun, Li Chen.

  BACKGROUND: Diabetes and obesity are associated with muscle atrophy that reduces life quality and lacks effective treatment. Mesenchymal stromal cell (MSC)-based therapy can ameliorate high fat-diet (HFD) and immobilization (IM)-induced muscle atrophy in mice. However, the effect of MSCs on muscle atrophy in type 2 diabetes mellitus (T2DM) and the potential mechanism is unclear. Here, we evaluated the efficacy and explored molecular mechanisms of human umbilical cord MSCs (hucMSCs) and hucMSC-derived exosomes (MSC-EXO) on diabetes- and obesity-induced muscle atrophy.METHODS: Diabetic db/db mice, mice fed with high-fat diet (HFD), mice with hindlimb immobilization (IM), and C2C12 myotubes were used to explore the effect of hucMSCs or MSC-EXO in alleviating muscle atrophy. Grip strength test and treadmill running were used to measure skeletal muscle strength and performance. Body composition, muscle weight, and muscle fibre cross-sectional area (CSA) was used to evaluate muscle mass. RNA-seq analysis of tibialis anterior (TA) muscle and Western blot analysis of muscle atrophy signalling, including MuRF1 and Atrogin 1, were performed to investigate the underlying mechanisms.
RESULTS: hucMSCs increased grip strength (P = 0.0256 in db/db mice, P = 0.012 in HFD mice, P = 0.0097 in IM mice), running endurance (P = 0.0154 in HFD mice, P = 0.0006 in IM mice), and muscle mass (P = 0.0004 in db/db mice, P = 0.0076 in HFD mice, P = 0.0144 in IM mice) in all models tested, with elevated CSA of muscle fibres (P < 0.0001 in db/db mice and HFD mice, P = 0.0088 in IM mice) and reduced Atrogin1 (P = 0.0459 in db/db mice, P = 0.0088 in HFD mice, P = 0.0016 in IM mice) and MuRF1 expression (P = 0.0004 in db/db mice, P = 0.0077 in HFD mice, P = 0.0451 in IM mice). MSC-EXO replicated all these hucMSC-mediated changes (P = 0.0103 for grip strength, P = 0.013 for muscle mass, P < 0.0001 for CSA of muscle fibres, P = 0.0171 for Atrogin1 expression, and P = 0.006 for MuRF1 expression). RNA-seq revealed that hucMSCs activated the AMPK/ULK1 signalling and enhanced autophagy. Knockdown of AMPK or inhibition of autophagy with 3-methyladenine (3-MA) diminished the beneficial anti-atrophy effects of hucMSCs or MSC-EXO.
CONCLUSIONS: Our results suggest that human umbilical cord mesenchymal stromal cells mitigate diabetes- and obesity-induced muscle atrophy via enhancing AMPK/ULK1-mediated autophagy through exosomes, with implications of applying hucMSCs or hucMSC-derived exosomes to treat muscle atrophy.

Keywords:  AMPK/ULK1; Autophagy; Exosome; Muscle atrophy; hucMSCs

DOI:  https://doi.org/10.1002/jcsm.13177
Am J Physiol Endocrinol Metab. 2023 Jan 25.

A reduction of skeletal muscle DHA content does not result in impaired whole-body glucose tolerance or skeletal muscle basal insulin signaling in healthy mice.

Joshua M Budd, Barbora Hucik, Chenwuan Wang, Alexa King, Ousseynou Sarr, Manabu T Nakamura, Ewa Harasim-Symbor, Adrian Chabowski, David J Dyck, David M Mutch.

  Delta-6 desaturase (D6D), encoded by the Fads2 gene, catalyzes the first step in the conversion of alpha-linolenic acid to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ablation of D6D in whole-body Fads2-/- knockout (KO) mice results in an inability to endogenously produce EPA and DHA. Evidence supports a beneficial role for EPA and DHA on insulin-stimulated glucose disposal in skeletal muscle in the context of a metabolic challenge; however, it is unknown how low EPA and DHA levels impact skeletal muscle fatty acid composition and insulin signaling in a healthy context. The objective of this study was to examine the impact of ablating the endogenous production of EPA and DHA on skeletal muscle fatty acid composition, whole-body glucose and insulin tolerance, and a key marker of skeletal muscle insulin signaling (pAkt). Male C57BL/6J wild-type (WT), Fads2+/- heterozygous and KO mice were fed a low-fat diet (16% kcal from fat) modified to contain either 7% w/w lard or 7% w/w flaxseed for 24 weeks. No differences in total phospholipid (PL), triacylglycerol, or reactive lipid content were observed between genotypes. As expected, KO mice on both diets had significantly less DHA content in skeletal muscle PL. Despite this, KOmice did not have significantly different glucose or insulin tolerance compared to WT mice on either diet. Basal pAktSer473 was not significantly different between the genotypes within each diet. Ultimately, this study shows for the first time that the reduction of DHA in skeletal muscle is not necessarily detrimental to glucose homeostasis in otherwise healthy animals.

Keywords:  Fads2; delta-6-desaturase; fatty acids; glucose tolerance test; n-3 PUFA

DOI:  https://doi.org/10.1152/ajpendo.00308.2022
Eur J Appl Physiol. 2023 Jan 23.

The role of exercise and hypoxia on glucose transport and regulation.

J Soo, A Raman, N G Lawler, P S R Goods, L Deldicque, O Girard, T J Fairchild.

  Muscle glucose transport activity increases with an acute bout of exercise, a process that is accomplished by the translocation of glucose transporters to the plasma membrane. This process remains intact in the skeletal muscle of individuals with insulin resistance and type 2 diabetes mellitus (T2DM). Exercise training is, therefore, an important cornerstone in the management of individuals with T2DM. However, the acute systemic glucose responses to carbohydrate ingestion are often augmented during the early recovery period from exercise, despite increased glucose uptake into skeletal muscle. Accordingly, the first aim of this review is to summarize the knowledge associated with insulin action and glucose uptake in skeletal muscle and apply these to explain the disparate responses between systemic and localized glucose responses post-exercise. Herein, the importance of muscle glycogen depletion and the key glucoregulatory hormones will be discussed. Glucose uptake can also be stimulated independently by hypoxia; therefore, hypoxic training presents as an emerging method for enhancing the effects of exercise on glucose regulation. Thus, the second aim of this review is to discuss the potential for systemic hypoxia to enhance the effects of exercise on glucose regulation.

Keywords:  Exercise; Glucose; Glucose metabolism; Hypoxia; Insulin resistance

DOI:  https://doi.org/10.1007/s00421-023-05135-1
Proc Natl Acad Sci U S A. 2023 Jan 31. 120(5): e2204427120

Metabolic reprogramming underlies cavefish muscular endurance despite loss of muscle mass and contractility.

Luke Olsen, Michaella Levy, J Kyle Medley, Huzaifa Hassan, Brandon Miller, Richard Alexander, Emma Wilcock, Kexi Yi, Laurence Florens, Kyle Weaver, Sean A McKinney, Robert Peuß, Jenna Persons, Alexander Kenzior, Ernesto Maldonado, Kym Delventhal, Andrew Gluesenkamp, Edward Mager, David Coughlin, Nicolas Rohner.

  Physical inactivity is a scourge to human health, promoting metabolic disease and muscle wasting. Interestingly, multiple ecological niches have relaxed investment into physical activity, providing an evolutionary perspective into the effect of adaptive physical inactivity on tissue homeostasis. One such example, the Mexican cavefish Astyanax mexicanus, has lost moderate-to-vigorous activity following cave colonization, reaching basal swim speeds ~3.7-fold slower than their river-dwelling counterpart. This change in behavior is accompanied by a marked shift in body composition, decreasing total muscle mass and increasing fat mass. This shift persisted at the single muscle fiber level via increased lipid and sugar accumulation at the expense of myofibrillar volume. Transcriptomic analysis of laboratory-reared and wild-caught cavefish indicated that this shift is driven by increased expression of pparγ-the master regulator of adipogenesis-with a simultaneous decrease in fast myosin heavy chain expression. Ex vivo and in vivo analysis confirmed that these investment strategies come with a functional trade-off, decreasing cavefish muscle fiber shortening velocity, time to maximal force, and ultimately maximal swimming speed. Despite this, cavefish displayed a striking degree of muscular endurance, reaching maximal swim speeds ~3.5-fold faster than their basal swim speeds. Multi-omic analysis suggested metabolic reprogramming, specifically phosphorylation of Pgm1-Threonine 19, as a key component enhancing cavefish glycogen metabolism and sustained muscle contraction. Collectively, we reveal broad skeletal muscle changes following cave colonization, displaying an adaptive skeletal muscle phenotype reminiscent to mammalian disuse and high-fat models while simultaneously maintaining a unique capacity for sustained muscle contraction via enhanced glycogen metabolism.

Keywords:  evolutionary physiology; physical activity; skeletal muscle metabolism

DOI:  https://doi.org/10.1073/pnas.2204427120
Front Cell Dev Biol. 2022 ;10 1007331

Nuclear envelope transmembrane proteins involved in genome organization are misregulated in myotonic dystrophy type 1 muscle.

Vanessa Todorow, Stefan Hintze, Benedikt Schoser, Peter Meinke.

  Myotonic dystrophy type 1 is a multisystemic disorder with predominant muscle and neurological involvement. Despite a well described pathomechanism, which is primarily a global missplicing due to sequestration of RNA-binding proteins, there are still many unsolved questions. One such question is the disease etiology in the different affected tissues. We observed alterations at the nuclear envelope in primary muscle cell cultures before. This led us to reanalyze a published RNA-sequencing dataset of DM1 and control muscle biopsies regarding the misregulation of NE proteins. We could identify several muscle NE protein encoding genes to be misregulated depending on the severity of the muscle phenotype. Among these misregulated genes were NE transmembrane proteins (NETs) involved in nuclear-cytoskeletal coupling as well as genome organization. For selected genes, we could confirm that observed gene-misregulation led to protein expression changes. Furthermore, we investigated if genes known to be under expression-regulation by genome organization NETs were also misregulated in DM1 biopsies, which revealed that misregulation of two NETs alone is likely responsible for differential expression of about 10% of all genes being differentially expressed in DM1. Notably, the majority of NETs identified here to be misregulated in DM1 muscle are mutated in Emery-Dreifuss muscular dystrophy or clinical similar muscular dystrophies, suggesting a broader similarity on the molecular level for muscular dystrophies than anticipated. This shows not only the importance of muscle NETs in muscle health and disease, but also highlights the importance of the NE in DM1 disease progression.

Keywords:  genome organization; muscle biopsy; myotonic dystrophy type 1; nuclear envelope; nuclear envelope transmembrane proteins

DOI:  https://doi.org/10.3389/fcell.2022.1007331
Front Med (Lausanne). 2022 ;9 1065365

Gut-muscle crosstalk. A perspective on influence of microbes on muscle function.

Weixuan Chew, Yen Peng Lim, Wee Shiong Lim, Edward S Chambers, Gary Frost, Sunny Hei Wong, Yusuf Ali.

  Our gastrointestinal system functions to digest and absorb ingested food, but it is also home to trillions of microbes that change across time, nutrition, lifestyle, and disease conditions. Largely commensals, these microbes are gaining prominence with regards to how they collectively affect the function of important metabolic organs, from the adipose tissues to the endocrine pancreas to the skeletal muscle. Muscle, as the biggest utilizer of ingested glucose and an important reservoir of body proteins, is intricately linked with homeostasis, and with important anabolic and catabolic functions, respectively. Herein, we provide a brief overview of how gut microbiota may influence muscle health and how various microbes may in turn be altered during certain muscle disease states. Specifically, we discuss recent experimental and clinical evidence in support for a role of gut-muscle crosstalk and include suggested underpinning molecular mechanisms that facilitate this crosstalk in health and diseased conditions. We end with a brief perspective on how exercise and pharmacological interventions may interface with the gut-muscle axis to improve muscle mass and function.

Keywords:  cytokines; gut microbes; metabolites; muscle function; sarcopenia

DOI:  https://doi.org/10.3389/fmed.2022.1065365
Exp Cell Res. 2023 Jan 21. pii: S0014-4827(23)00031-9. [Epub ahead of print] 113484

Temporal static and dynamic imaging of skeletal muscle in vivo.

Brendan Evano, Liza Sarde, Shahragim Tajbakhsh.

  A major challenge in the study of living systems is understanding how tissues and organs are established, maintained during homeostasis, reconstituted following injury or deteriorated during disease. Most of the studies that interrogate in vivo cell biological properties of cell populations within tissues are obtained through static imaging approaches. However, in vertebrates, little is known about which, when, and how extracellular and intracellular signals are dynamically integrated to regulate cell behaviour and fates due to technical challenges. Intravital imaging of cellular dynamics in mammalian models has exposed surprising properties that have been missed by conventional static imaging approaches. Here we highlight some selected examples of intravital imaging in mouse intestinal stem cells, hematopoietic stem cells, hair follicle stem cells, and neural stem cells in the brain, each of which have distinct features from an anatomical and niche architecture perspective. Intravital imaging of mouse skeletal muscles is comparatively less advanced due to several technical constraints that will be discussed, yet this approach holds great promise as a complementary investigative method to validate findings obtained by static imaging, as well as a method for discovery.

Keywords:  Intravital imaging; Live imaging; Muscle stem cell; Regeneration; Skeletal muscle

DOI:  https://doi.org/10.1016/j.yexcr.2023.113484
Toxicol Appl Pharmacol. 2023 Jan 23. pii: S0041-008X(23)00022-4. [Epub ahead of print] 116384

The early inhibition of the COX-2 pathway in viperid phospholipase A2-induced skeletal muscle myotoxicity accelerates the tissue regeneration.

Ana Carolina Siqueira Zuntini, Marcio Vinícius Damico, Cristiane Damas Gil, Rosely Oliveira Godinho, Enio Setsuo Arakaki Pacini, Consuelo Latorre Fortes-Dias, Vanessa Moreira.

  The administration of non-steroidal anti-inflammatory drugs in the treatment of injury and muscle regeneration is still contradictory in effectiveness, especially regarding the timing of their administration. This can interfere with the production of prostaglandins originating from inflammatory isoform cyclooxygenase-2 (COX-2), which is essential to modulate tissue regeneration. The phospholipases A2 (PLA2) from viperid venoms cause myotoxicity, therefore constituting a tool for the study of supportive therapies to improve skeletal muscle regeneration. This study investigated the effect of early administration of lumiracoxib (selective inhibitor of COX-2) on the degeneration and regeneration stages of skeletal muscle after injury induced by a myotoxic PLA2. After 30 min and 48 h of intramuscular injection of PLA2, mice received lumiracoxib orally and histological, functional, and transcriptional parameters of muscle were evaluated from 6 h to 21 days. Inhibition of COX-2 in the early periods of PLA2-induced muscle degeneration reduced leukocyte influx, edema, and tissue damage. After the second administration of lumiracoxib, in regenerative stage, muscle showed increase in number of basophilic fibers, reduction in fibrosis content and advanced recovery of functionality characterized by the presence of fast type II fibers. The expression of Pax7 and myogenin were increased, indicating a great capacity for storing satellite cells and advanced mature state of tissue. Our data reveals a distinct role of COX-2-derived products during muscle degeneration and regeneration, in which early administration of lumiracoxib was a therapeutic strategy to modulate the effects of prostaglandins, providing a breakthrough in muscle tissue regeneration induced by a myotoxic PLA2.

Keywords:  Cyclooxygenase-2; Myotoxicity; Phospholipase A(2); Selective COX-2 inhibitor; Tissue repair

DOI:  https://doi.org/10.1016/j.taap.2023.116384
J Strength Cond Res. 2023 Feb 01. 37(2): 494-536

Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations.

James L Nuzzo.

ABSTRACT: Nuzzo, JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res 37(2): 494-536, 2023-Biological sex and its relation with exercise participation and sports performance continue to be discussed. Here, the purpose was to inform such discussions by summarizing the literature on sex differences in numerous strength training-related variables and outcomes-muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training. Male subjects become notably stronger than female subjects around age 15 years. In adults, sex differences in strength are more pronounced in upper-body than lower-body muscles and in concentric than eccentric contractions. Greater male than female strength is not because of higher voluntary activation but to greater muscle mass and type II fiber areas. Men participate in strength training more frequently than women. Men are motivated more by challenge, competition, social recognition, and a desire to increase muscle size and strength. Men also have greater preference for competitive, high-intensity, and upper-body exercise. Women are motivated more by improved attractiveness, muscle "toning," and body mass management. Women have greater preference for supervised and lower-body exercise. Intrasexual competition, mate selection, and the drive for muscularity are likely fundamental causes of exercise behaviors in men and women. Men and women increase muscle size and strength after weeks of strength training, but women experience greater relative strength improvements depending on age and muscle group. Men exhibit higher strength training injury rates. No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.

DOI: https://doi.org/10.1519/JSC.0000000000004329
J Nutr Biochem. 2023 Jan 18. pii: S0955-2863(23)00007-4. [Epub ahead of print] 109273

Combined prenatal to postnatal protein restriction augments protein quality control processes and proteolysis in the muscle of rat offspring.

Pandarinath Savitikadi, Ramesh Gogulothu, Ayesha Ismail, G Bhanuprakash Reddy, V Sudhakar Reddy.

  Several human epidemiological and animal studies suggest that a maternal low-protein (MLP) diet affects skeletal muscle (SM) health in the offspring. However, effect of combined prenatal to postnatal protein restriction (chronic PR) and prenatal to perinatal PR with postnatal rehabilitation (maternal protein restriction; MPR) on protein quality control (PQC) processes and proteolysis in the offspring remains poorly understood. The current study explored the impact of chronic PR and MPR on SM protein degradation rates, chaperones, unfolded protein response (UPR), ubiquitin-proteasome system (UPS), autophagy, and apoptosis, in the adult offspring. Wistar rats were randomly assigned to a normal protein (NP; 20% casein), or low-protein (LP; 8% casein) isocaloric diets from 7 weeks prior to breeding through weaning. Offspring born to NP dams received the same diet (NP offspring) while a group of LP offspring remained on LP diet and another group was rehabilitated with NP diet (LPR offspring) from weaning for 16 weeks. LP offspring displayed lower body weight, lean mass, and myofiber cross-sectional area than NP. Furthermore, LP offspring demonstrated increased total protein degradation, urinary 3-methyl histidine, ER stress, autophagy, UPS components, proteasomal activity, muscle atrophy markers, and apoptosis-related proteins than NP. However, MPR showed little or no effect on muscle proteolysis, UPR, UPS, autophagy, apoptosis, and muscle atrophy in LPR offspring. These results indicate that exposure to chronic PR diets induces muscle atrophy and accelerates SM proteolysis via augmenting PQC processes in the offspring, while MPR shows little or no effect.

Keywords:  maternal low-protein; muscle atrophy; protein quality control; proteolysis; skeletal muscle; ubiquitin-proteasome system

DOI:  https://doi.org/10.1016/j.jnutbio.2023.109273
Comput Methods Programs Biomed. 2023 Jan 13. pii: S0169-2607(23)00021-4. [Epub ahead of print]230 107354

Improving quantification of myotube width and nuclear/cytoplasmic ratio in myogenesis research.

Arnon Dias Jurberg, Geyse Gomes, Marianna Reis Seixas, Claudia Mermelstein, Manoel Luis Costa.

  BACKGROUND AND OBJECTIVE: The culture of skeletal muscle cells is particularly relevant to basic biomedical research and translational medicine. The incubation of dissociated cells under controlled conditions has helped to dissect several molecular mechanisms associated with muscle cell differentiation, in addition to contributing for the evaluation of drug effects and prospective cell therapies for patients with degenerative muscle pathologies. The formation of mature multinucleated myotubes is a stepwise process involving well defined events of cell proliferation, commitment, migration, and fusion easily identified through optical microscopy methods including immunofluorescence and live cell imaging. The characterization of each step is usually based on muscle cell morphology and nuclei number, as well as the presence and intracellular location of specific cell markers. However, manual quantification of these parameters in large datasets of images is work-intensive and prone to researcher's subjectivity, mostly because of the extremely elongated cell shape of large myotubes and because myotubes are multinucleated.METHODS: Here we provide two semi-automated ImageJ macros aimed to measure the width of myotubes and the nuclear/cytoplasmic localization of molecules in fluorescence images. The width measuring macro automatically determines the best angle, perpendicular to most cells, to draw a profile plot and identify and measure individual myotubes. The nuclear/cytoplasmic ratio macro compares the intensity values along lines, drawn by the user, over cytoplasm and nucleus.
RESULTS: We show that the macro measurements are more consistent than manual measurements by comparing with our own results and with the literature.
CONCLUSIONS: By relying on semi-automated muscle specific ImageJ macros, we seek to improve measurement accuracy and to alleviate the laborious routine of counting and measuring muscle cell features.

Keywords:  Cell culture; Fluorescence image quantification; ImageJ macro; Myogenesis

DOI:  https://doi.org/10.1016/j.cmpb.2023.107354
Hum Gene Ther. 2023 Jan 24.

Micro-dystrophin expression as a surrogate endpoint for Duchenne muscular dystrophy clinical trials.

Jeffrey Chamberlain, Melissa Robb, Serge Braun, Kristy Brown, Olivier Danos, Annie Ganot, Pedro Gonzalez-Alegre, Nina Hunter, Craig McDonald, Carl Morris, Mark Tobolowsky, Kathryn Wagner, Olivia Ziolkowski, Dongsheng Duan.

Duchenne muscular dystrophy (DMD) is a serious, rare genetic disease, affecting primarily boys. It is caused by mutations in the DMD gene and is characterized by progressive muscle degeneration that results in loss of function and early death due to respiratory and/or cardiac failure. Although limited treatment options are available, some for only small subsets of the patient population, DMD remains a disease with large unmet medical needs. The adeno-associated virus (AAV) vector is the leading gene delivery system for addressing genetic neuromuscular diseases. Since the gene encoding the full-length dystrophin protein exceeds the packaging capacity of a single AAV vector, gene replacement therapy based on AAV-delivery of shortened yet functional micro-dystrophin genes has emerged as a promising treatment. This paper seeks to explain the rationale for use of the accelerated approval pathway to advance AAV micro-dystrophin gene therapy for DMD. Specifically, we provide support for the use of micro-dystrophin expression as a surrogate endpoint that could be used in clinical trials to support accelerated approval.

DOI: https://doi.org/10.1089/hum.2022.190
Biochem Biophys Res Commun. 2023 Jan 20. pii: S0006-291X(23)00078-5. [Epub ahead of print]646 36-43

Distinct effect of exercise modes on mood-related behavior in mice.

Ki Hoon Yuk, Sun Min Lee, Woo Ri Bae, Jae Yeon Park, Song Won Woo, Parkyong Song, In Cheol Jeong, Ji-Seok Kim, Hyo Youl Moon.

  Exercise can afford several benefits to combat mood disorders in both rodents and humans. Engagement in various physical activities upregulates levels of neurotrophic factors in several brain regions and improves mental health. However, the type of exercise that regulates mood and the underlying mechanisms in the brain remain elusive. Herein, we performed two distinct types of exercise and RNA sequencing analyses to investigate the effect of exercise on mood-related behaviors and explain the distinct patterns of gene expression. Specifically, resistance exercise exhibited reduced immobility time in the forced swim test when compared with both no exercise and treadmill exercise (in the aerobic training [AT] group). Interestingly, anxiety-like behaviors in the open field and nest-building tests were ameliorated in the AT group when compared with those in the control group; however, this was not observed in the RT group. To elucidate the mechanism underlying these different behavioral changes caused by distinct exercise types, we examined the shift in the gene expression pattern in the hippocampus, a brain region that plays a critical role in regulating mood. We discovered that 38 and 40 genes were altered in the AT and RT groups, respectively, compared with the control group. Both exercises regulated 16 common genes. Compared with the control group, mitogen-activated protein kinase (MAPK) was enriched in the AT group and phosphatidylinositol-3-kinase (PI3K)/AKT and neurotrophin signaling pathways were enriched in the RT group, as determined by bioinformatics pathway analysis. PCR results revealed that Cebpβ expression was increased in AT group, and Dcx expression was upregulated in both groups. Our findings indicate that different exercise types may exert substantially distinct effects on mood-like behaviors. Accordingly, appropriate types of exercise can be undertaken based on the mood disorder to be regulated.

Keywords:  Aerobic exercise; Anxiety; Depression; Neurogenesis; Resistance exercise; The type of exercise

DOI:  https://doi.org/10.1016/j.bbrc.2023.01.047