Muscle RING-finger Protein-1 Research Articles

Tumor necrosis factor alpha regulates myogenesis to inhibit differentiation and promote proliferation in satellite cells

TNF-α and NF-κB signaling is involved in the wasting of skeletal muscle in various conditions, in addition to cancer cachexia. TNF-α and NF-κB signaling promotes the expression level of muscle RING finger protein 1, a ubiquitin ligase, causing muscle degradation. Several studies have indicated that of TNF-α and NF-κB signaling suppresses muscle differentiation by reducing the levels of MyoD protein. On the other hand, TNF-α and NF-κB is required for myoblast proliferation. Thus, the role of TNF-α and NF-κB signaling in the process of myogenesis and regeneration of skeletal muscle is not completely elucidated. Here, we reported that TNF-α reduced the width of single fibers of skeletal muscle in an organ culture model. TNF-α and p65 repressed the transactivation of MyoD and suppressed myoblast differentiation. In addition, TNF-α increased the number of satellite cells, and NF-κB signaling was promoted at the proliferation stage during skeletal muscle regeneration in vivo. TNF-α and NF-κB signaling regulate myogenesis to inhibit differentiation and promote proliferation in satellite cells.

Preliminary Observations on Skeletal Muscle Adaptation and Plasticity in Homer 2-/- Mice.

Homer represents a diversified family of scaffold and transduction proteins made up of several isoforms. Here, we present preliminary observations on skeletal muscle adaptation and plasticity in a transgenic model of Homer 2-/- mouse using a multifaceted approach entailing morphometry, quantitative RT-PCR (Reverse Transcription PCR), confocal immunofluorescence, and electrophysiology. Morphometry shows that Soleus muscle (SOL), at variance with Extensor digitorum longus muscle (EDL) and Flexor digitorum brevis muscle (FDB), displays sizable reduction of fibre cross-sectional area compared to the WT counterparts. In SOL of Homer 2-/- mice, quantitative RT-PCR indicated the upregulation of Atrogin-1 and Muscle ring finger protein 1 (MuRF1) genes, and confocal immunofluorescence showed the decrease of neuromuscular junction (NMJ) Homer content. Electrophysiological measurements of isolated FDB fibres from Homer 2-/- mice detected the exclusive presence of the adult ε-nAChR isoform excluding denervation. As for NMJ morphology, data were not conclusive, and further work is needed to ascertain whether the null Homer 2 phenotype induces any endplate remodelling. Within the context of adaptation and plasticity, the present data show that Homer 2 is a co-regulator of the normotrophic status in a muscle specific fashion.

Dulaglutide improves muscle function by attenuating inflammation through OPA-1-TLR-9 signaling in aged mice.

Dulaglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, is widely used to treat diabetes. However, its effects on muscle wasting due to aging are poorly understood. In the current study, we investigated the therapeutic potential and underlying mechanism of dulaglutide in muscle wasting in aged mice. Dulaglutide improved muscle mass and strength in aged mice. Histological analysis revealed that the cross-sectional area of the tibialis anterior (TA) in the dulaglutide-treated group was thicker than that in the vehicle group. Moreover, dulaglutide increased the shift toward middle and large-sized fibers in both young and aged mice compared to the vehicle. Dulaglutide increased myofiber type I and type IIa in young (18.5% and 8.2%) and aged (1.8% and 19.7%) mice, respectively, compared to the vehicle group. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis, decreased but increased by dulaglutide in aged mice. The expression of atrophic factors such as myostatin, atrogin-1, and muscle RING-finger protein-1 was decreased in aged mice, whereas that of the myogenic factor, MyoD, was increased in both young and aged mice following dulaglutide treatment. In aged mice, optic atrophy-1 (OPA-1) protein was decreased, whereas Toll-like receptor-9 (TLR-9) and its targeting inflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor-α [TNF-α]) were elevated in the TA and quadriceps (QD) muscles. In contrast, dulaglutide administration reversed this expression pattern, thereby significantly attenuating the expression of inflammatory cytokines in aged mice. These data suggest that dulaglutide may exert beneficial effects in the treatment of muscle wasting due to aging.

Impact of different frequencies of controlled breath and pressure-support levels during biphasic positive airway pressure ventilation on the lung and diaphragm in experimental mild acute respiratory distress syndrome.

We hypothesized that a decrease in frequency of controlled breaths during biphasic positive airway pressure (BIVENT), associated with an increase in spontaneous breaths, whether pressure support (PSV)-assisted or not, would mitigate lung and diaphragm damage in mild experimental acute respiratory distress syndrome (ARDS). Wistar rats received Escherichia coli lipopolysaccharide intratracheally. After 24 hours, animals were randomly assigned to: 1) BIVENT-100+PSV0%: airway pressure (Phigh) adjusted to VT = 6 mL/kg and frequency of controlled breaths (f) = 100 bpm; 2) BIVENT-50+PSV0%: Phigh adjusted to VT = 6 mL/kg and f = 50 bpm; 3) BIVENT-50+PSV50% (PSV set to half the Phigh reference value, i.e., PSV50%); or 4) BIVENT-50+PSV100% (PSV equal to Phigh reference value, i.e., PSV100%). Positive end-expiratory pressure (Plow) was equal to 5 cmH2O. Nonventilated animals were used for lung and diaphragm histology and molecular biology analysis. BIVENT-50+PSV0%, compared to BIVENT-100+PSV0%, reduced the diffuse alveolar damage (DAD) score, the expression of amphiregulin (marker of alveolar stretch) and muscle atrophy F-box (marker of diaphragm atrophy). In BIVENT-50 groups, the increase in PSV (BIVENT-50+PSV50% versus BIVENT-50+PSV100%) yielded better lung mechanics and less alveolar collapse, interstitial edema, cumulative DAD score, as well as gene expressions associated with lung inflammation, epithelial and endothelial cell damage in lung tissue, and muscle ring finger protein 1 (marker of muscle proteolysis) in diaphragm. Transpulmonary peak pressure (Ppeak,L) and pressure-time product per minute (PTPmin) at Phigh were associated with lung damage, while increased spontaneous breathing at Plow did not promote lung injury. In the ARDS model used herein, during BIVENT, the level of PSV and the phase of the respiratory cycle in which the inspiratory effort occurs affected lung and diaphragm damage. Partitioning of inspiratory effort and transpulmonary pressure in spontaneous breaths at Plow and Phigh is required to minimize VILI.

Sarcopenia, Ectopic Fat Infiltration Into the Lumbar Paravertebral Muscles, and Lumbo-Pelvic Deformity in Older Adults Undergoing Lumbar Surgery.

A retrospective analysis of a prospective, non-randomized cohort dataset. To cross-sectionally examine the prevalence of sarcopenia and the association between spine-pelvic deformity and skeletal muscle volume loss and ectopic fat infiltration into lumbar paravertebral muscles (PVMs) in patients who underwent lumbar surgery. Muscle quality deterioration has been considered the main pathology of sarcopenia, reducing muscle strength directly. The qualitative deterioration as well as volume loss in PVM, which contributes significantly to core body extension, might cause aging-related spine deformity. In total, 184 patients were included. Sarcopenia was diagnosed at baseline, and all patients underwent whole-body X-ray. The amount of fat in lumbar PVM was evaluated with the Goutallier classification in magnetic resonance imaging findings. The expression of adipogenesis- and atrophy-promoting factors in PVM was evaluated with quantitative polymerase chain reaction. In total, 36.1% of adults aged ≥60 years were diagnosed with sarcopenia. The values of skeletal muscle indexes of the limb and trunk were inversely correlated with the sagittal vertical axis, pelvic tilt (PT), and pelvic incidence minus lumbar lordosis (PI-LL) values. The PT and PI-LL were greater, PVM area was smaller, and Goutallier grade was greater in sarcopenic adults than in non-sarcopenic older adults. Additionally, the PVM area correlated with the LL value, and Goutallier's grade correlated with the PT and PI-LL values. Moreover, the amount of ectopic fat in PVMs inversely correlated with skeletal muscle indexes. The expression levels of atrophy gene-1 and muscle ring-finger protein-1 did not differ between the groups and did not correlate with the PVM area. In contrast, the expression of Pparg and Cebpa was upregulated in sarcopenic older adults, where it correlated with Goutallier's grade. The volume loss of skeletal muscle, including lumbar PVM, and ectopic fat infiltration into the PVM, may cause the lumbo-pelvic deformity.Level of Evidence: 3.

Exogenous insulin-like growth factor 1 attenuates cisplatin-induced muscle atrophy in mice.

BackgroundA reduction in the skeletal muscle mass worsens the prognosis of patients with various cancers. Our previous studies indicated that cisplatin administration to mice caused muscle atrophy. This is a concern for human patients receiving cisplatin. The insulin‐like growth factor 1 (IGF‐1)/phosphoinositide 3‐kinase (PI3K)/Akt pathway stimulates the rate of protein synthesis in skeletal muscle. Thus, IGF‐I can be a central therapeutic target for preventing the loss of skeletal muscle mass in muscle atrophy, although it remains unclear whether pharmacological activation of the IGF‐1/PI3K/Akt pathway attenuates muscle atrophy induced by cisplatin. In this study, we examined whether exogenous recombinant human IGF‐1 attenuated cisplatin‐induced muscle atrophy.MethodsMale C57BL/6J mice (8–9 weeks old) were injected with cisplatin or saline for four consecutive days. On Day 5, quadriceps muscles were isolated. Mecasermin (recombinant human IGF‐1) or the vehicle control was subcutaneously administered 30 min prior to cisplatin administration. A dietary restriction group achieving weight loss equivalent to that caused by cisplatin administration was used as a second control. C2C12 myotubes were treated with cisplatin with/without recombinant mouse IGF‐1. The skeletal muscle protein synthesis/degradation pathway was analysed by histological and biochemical methods.ResultsCisplatin reduced protein level of IGF‐1 by about 85% compared with the vehicle group and also reduced IGF‐1/PI3K/Akt signalling in skeletal muscle. Under this condition, the protein levels of muscle ring finger protein 1 (MuRF1) and atrophy gene 1 (atrogin‐1) were increased in quadriceps muscles (MuRF1; 3.0 ± 0.1 folds, atrogin‐1; 3.0 ± 0.3 folds, P < 0.001, respectively). The administration of a combination of cisplatin and IGF‐1 significantly suppressed the cisplatin‐induced downregulation of IGF‐1/PI3K/Akt signalling and upregulation of MuRF1 and atrogin‐1 (up to 1.6 ± 0.3 and 1.5 ± 0.4 folds, P < 0.001, respectively), resulting in diminished muscular atrophy. IGF‐1 showed similar effects in cisplatin‐treated C2C12 myotubes, as well as the quadriceps muscle in mice.ConclusionsThe downregulation of IGF‐1 expression in skeletal muscle might be one of the factors playing an important role in the development of cisplatin‐induced muscular atrophy. Compensating for this downregulation with exogenous IGF‐1 suggests that it could be a therapeutic target for limiting the loss of skeletal muscle mass in cisplatin‐induced muscle atrophy.

High glucose induces apoptosis, glycogen accumulation and suppresses protein synthesis in muscle cells of olive flounder Paralichthys olivaceus.

The effect and the mechanism of high glucose on fish muscle cells are not fully understood. In the present study, muscle cells of olive flounder (Paralichthys olivaceus) were treated with high glucose (33 mM) in vitro. Cells were incubated in three kinds of medium containing 5 mM glucose, 5 mM glucose and 28 mM mannitol (as an isotonic contrast) or 33 mM glucose named the Control group, the Mannitol group and the high glucose (HG) group, respectively. Results showed that high glucose increased the ADP:ATP ratio and the reactive oxygen species (ROS) level, decreased mitochondrial membrane potential (MMP), induced the release of cytochrome C (CytC) and cell apoptosis. High glucose also led to cell glycogen accumulation by increasing the glucose uptake ability and affecting the mRNA expressions of glycogen synthase and glycogen phosphorylase. Meanwhile, it activated AMP-activated protein kinase (AMPK), inhibited the activity of mammalian target of rapamycin (mTOR) signalling pathway and the expressions of myogenic regulatory factors (MRF). The expressions of myostatin-1 (mstn-1) and E3 ubiquitin ligases including muscle RING-finger protein 1 (murf-1) and muscle atrophy F-box protein (mafbx) were also increased by the high glucose treatment. No difference was found between the Mannitol group and the Control group. These results demonstrate that high glucose has the effects of inducing apoptosis, increasing glycogen accumulation and inhibiting protein synthesis on muscle cells of olive flounder. The mitochondria-mediated apoptotic signalling pathway, AMPK and mTOR pathways participated in these biological effects.

Nicotinamide Riboside Vitamin B3 Mitigated C26 Adenocarcinoma–Induced Cancer Cachexia

Nicotinamide riboside (NR), vitamin B3, is a substrate for nicotinamide adenine dinucleotide (NAD+)–consuming enzymes and is a coenzyme for hydride-transfer enzymes, including adenosine diphosphate (ADP)–ribose transferases, poly (ADP-ribose) polymerases, cADP-ribose synthases, and sirtuins, which play a central role in the aging process, neurodegenerative processes, and myopathy. Since cancer cachexia is a disease condition presenting with weight loss, skeletal muscle atrophy, and loss of adipose tissue in patients with advanced cancer, we hypothesized that NR intake could ameliorate sarcopenia. In this study, we investigated whether preemptive administration of NR ameliorated C26 adenocarcinoma–induced cancer cachexia and explored anti-cachexic mechanisms focused on the changes in muscle atrophy, cachexic inflammation, and catabolic catastrophe. Dietary intake of the NR-containing pellet diet significantly attenuated cancer cachexia in a mouse model. Starting with significant inhibition of cachexic factors, tumor necrosis factor alpha, and interleukin-6, NR significantly inhibited muscle-specific ubiquitin-proteasome ligases, such as atrogin-1, muscle RING-finger protein-1 (MuRF-1), mitofusin-2, and peroxisome proliferator–activated receptor gamma coactivator-1-alpha (PCG-1α). Significant inhibition of epididymal fat lipolysis was noted with significant inhibition of adipose triglyceride lipase (ATGL) gene. Furthermore, NR administration significantly increased the levels of crucial enzymes involved in the biosynthesis of NAD+ and nicotinamide phosphoribosyl transferase and significantly inhibited the NAD+-sensitive deacetylase sirtuin 1 (SIRT1). Preemptive intake of NR in patients vulnerable to cachexia can be a preemptive option to ameliorate cancer cachexia.

Role and mechanism underlying FoxO6 inskeletal muscle invitro and invivo.

Skeletal muscle atrophy is a common feature of patients suffering with chronic infection and other systemic diseases, including acquired immunodeficiency syndrome, chronic kidney disease and cancer. Therefore, understanding the molecular basis of muscle loss is of importance. The majority of members of the forkhead box O (FoxO) family can induce skeletal muscle atrophy; however, the effect of FoxO6 on skeletal muscle is not completely understood. The present study investigated the role of FoxO6 invitro and invivo. Compared with the small interfering RNA (si)‑negative control (NC) group, C2C12 cell proliferation (Cell Counting Kit‑8 assay), myotube differentiation and myotube production were significantly decreased by FoxO6 knockdown, which was different from the known functions of other FoxO members. The immunofluorescence assay results demonstrated that si‑FoxO6 clearly downregulated the expression levels of myosin heavy chain (MyHC) in C2C12 myotubes compared with si‑NC. The western blotting results indicated that compared with the si‑NC group, FoxO6 knockdown induced C2C12 myotube atrophy by notably downregulating myoblast determination protein1 (MyoD), mTOR and MyHC expression levels, and by markedly upregulating ubiquitin ligase (atrogin1) and muscle RING‑finger protein‑1 (MURF1) expression levels. Similarly, in an invitro model of TNF‑α‑induced myotube atrophy, the western blotting results indicated that FoxO6 expression levels were decreased, whereas atrogin1, MURF1, FoxO1 and FoxO3a expression levels were increased compared with the control group. Therefore, the results indicated that, unlike FoxO1 or FoxO3a, FoxO6 maintained C2C12 myotubes and protected against atrophy. Consistent with the invitro data, similar results were observed invivo. Collectively, the results of the present study suggested that FoxO6 served a critical role in muscle cell metabolism invitro and invivo, and might serve as a promising therapeutic target for ameliorating skeletal muscle atrophy.

Drinking Off(s) the Clock: Chronic Alcohol Suppresses Skeletal Muscle Molecular Clock

Circadian rhythms generated both centrally in the suprachiasmatic nucleus (SCN) and peripherally at the tissue level assist in the maintenance of physiological homeostasis, while circadian disruption is a characteristic of several diseases. The intrinsic skeletal muscle core clock has emerged as a key feature of metabolic control and influences several aspects of muscle physiology including contractile strength and mitochondrial content. Alcoholic muscle disease or myopathy is characterized by skeletal muscle weakness and myofiber atrophy resulting from the prolonged consumption of alcohol. Despite alcoholic myopathy being more prevalent than alcoholic liver disease, the entirety of mechanisms leading to its onset remains unknown. Alcohol disrupts normal cyclic expression of several core clock genes within the brain and liver, and we previously reported that acute alcohol intoxication disrupts the skeletal muscle core clock. Thus, the goal of this work was to determine whether the chronic consumption of alcohol dysregulates the skeletal muscle core molecular clock and clock-controlled genes (CCGs) in concert with alcoholic myopathy. Methods: C57BL/6Hsd female mice (12wks old) were pair fed a control liquid diet (CON) or an isocaloric ethanol (EtOH) containing liquid diet of increasing concentration (up to 32% kcal EtOH) for 7 weeks. Gastrocnemius muscles were collected from CON (n=4) and EtOH (n=3-4) mice every 4-hours for 24-hours. RNA was isolated, cDNA synthesized, and RT-PCR was performed. Results: Body weight and fat mass between groups was similar at sacrifice while liver mass was increased by alcohol. Lean mass assessed by MRI tended to be decreased by alcohol (p=0.06). Chronic alcohol consumption disrupted genes of the core clock including suppressing the rhythmic peak in expression of brain muscle ARNT like-1 (Bmal1), period (Per) 1 and 2, and cryptochrome 2 (Cry2). Genes involved in the regulation of Bmal1 also exhibited lower rhythmic peaks including Rev-erb (NR1D1) and myoblast determination protein 1 (MyoD), with significant reductions apparent at several of the 4-hour time points. The CCG D-box binding PAR BZIP transcription factor (DBP) was also suppressed at the end of the light phase and beginning of the dark active phase (ZT8 and ZT12). Skeletal muscle atrophy related genes forkhead box O1 (Foxo1), regulated in development and DNA damage response 1 (Redd1) and muscle RING-finger protein 1 (Murf1) were also altered by alcohol at the start of the dark (active) cycle. These data contrasted our previously described acute model in which subtle rhythmic shifts and large changes in the expression of several genes were observed specifically when blood alcohol levels (~4-12hr) were elevated. Therefore, there is a differential response of the skeletal muscle to acute and chronic alcohol consumption with prolonged intake leading to a lower amplitude of change over the 24-hour cycle of several core clock related genes. Future work will focus on determining the contribution of these disruptions to metabolic and functional perturbations characteristic of chronic alcoholic myopathy and the impact of these disruptions on the development of alcoholic myopathy.

Differentiation-promoting and Protective Effects of the Fractions of Various Ginseng Species in C2C12 Cells

Background: The effects of Panax ginseng C. A. Meyer in protecting and promoting the differentiation of muscle cells have been reported. However, the influences of various ginseng species and various fractions were not investigated.<BR>Methods and Results: In this study, these effects on muscle cells were confirmed using butanol and water fractions of various ginseng species. The fractions of P. ginseng were confirmed to have a cytoprotective effect on C2C12 cells. The myogenin expression level was significantly higher by 1.5 times or more, in the P. ginseng fraction groups than in the other groups, confirming that the P. ginseng fractions promoted cell differentiation. Both fractions of P. ginseng significantly reduced the rate of production of reactive oxygen species when compared with that of the control group. In the mechanism study, P. ginseng fractions tended to decrease muscle RING-finger protein-1 (MuRF-1), AMP-activated protein kinase (AMPK), forkhead box O3α (Foxo3α), and the expression of the BCL2-associated agonist of cell death (BAD). In particular, AMPK was significantly reduced in the P. ginseng water fraction group when compared to that in the butanol fraction and control groups.<BR>Conclusions: The results of this study confirmed that P. ginseng has superior cell differentiation-promoting and protective effects on muscle cells when compared with the effects of Panax quinquefolium and Panax notoginseng.

Morin attenuates dexamethasone-mediated oxidative stress and atrophy in mouse C2C12 skeletal myotubes

Glucocorticoids are the drugs most commonly used to manage inflammatory diseases. However, they are prone to inducing muscle atrophy by increasing muscle proteolysis and decreasing protein synthesis. Various studies have demonstrated that antioxidants can mitigate glucocorticoid-induced skeletal muscle atrophy. Here, we investigated the effect of a potent antioxidative natural flavonoid, morin, on the muscle atrophy and oxidative stress induced by dexamethasone (Dex) using mouse C2C12 skeletal myotubes. Dex (10 μM) enhanced the production of reactive oxygen species (ROS) in C2C12 myotubes via glucocorticoid receptor. Moreover, Dex administration reduced the diameter and expression levels of the myosin heavy chain protein in C2C12 myotubes, together with the upregulation of muscle atrophy-associated ubiquitin ligases, such as muscle atrophy F-box protein 1/atrogin-1, muscle ring finger protein-1, and casitas B-lineage lymphoma proto-oncogene-b. Dex also significantly decreased phosphorylated Foxo3a and increased total Foxo3a expression. Interestingly, Dex-induced ROS accumulation and Foxo3a expression were inhibited by morin (10 μM) pretreatment. Morin also prevented the Dex-induced reduction of myotube thickness, together with muscle protein degradation and suppression of the upregulation of atrophy-associated ubiquitin ligases. In conclusion, our results suggest that morin effectively prevents glucocorticoid-induced muscle atrophy by reducing oxidative stress.

20(s)‑ginseonside‑Rg3 modulation of AMPK/FoxO3 signaling to attenuate mitochondrial dysfunction in a dexamethasone‑injured C2C12 myotube‑based model of skeletal atrophy invitro.

Muscle atrophy, a side effect from administration of the anti-inflammatory medication dexamethasone (DEX), is preventable by concomitant administration of the major monomeric constituent of Panax ginseng C.A. Meyer, 20(S)-ginsenoside Rg3 (S-Rg3). Putative S-Rg3-associated prevention of DEX-induced muscle atrophy may involve S-Rg3 mitigation of DEX-induced mitochondrial dysfunction. In the present study, MTT assays revealed enhanced cell viability following S-Rg3 treatment of DEX-injured C2C12 myotubes. Subsequent PCR and western blotting results demonstrated S-Rg3-induced reduction of expression of muscle atrophy F-box protein (atrogin-1) and muscle RING-finger protein-1, proteins previously linked to muscle atrophy. Additionally, S-Rg3 treatment of DEX-injured myotubes led to aggregation of Rg3 monomers in cells and dose-dependent increases in cellular mitochondrial basal respiratory oxygen consumption rate and intracellular ATP levels compared with their levels in untreated DEX-injured myotubes. In addition, S-Rg3 treatment significantly reversed DEX-induced reductions of expression of key mitochondrial respiratory electron transport chain subunits of protein complexes II, III and V in DEX-injured myotube cells. Furthermore, S-Rg3 alleviation of mitochondrial dysfunction associated with DEX-induced injury of C2C12 myotubes was linked to S-Rg3-associated decreases in both forkhead box O3 (FoxO3) protein expression and phosphorylation of AMP-activated protein kinase (AMPK). Collectively, these results implicate S-Rg3 modulation of signaling within the AMPK-FoxO3 pathway as a putative mechanism underlying S-Rg3 alleviation of DEX-induced muscle atrophy.

Juzentaihoto Suppresses Muscle Atrophy and Decreased Motor Function in SAMP8 Mice.

Sarcopenia is a disease whose symptoms include decreased muscle mass and weakened muscle strength with age. In sarcopenia, decreased production of insulin-like growth factor-1 (IGF-1) increases ubiquitin ligases, such as Atrogin1 and Muscle RING-Finger Protein-1 (MuRF1), by activating forkhead box O (FOXO), and inflammatory cytokines and oxidative stress increase the expression of ubiquitin ligases by activating the transcription factor nuclear factor-kappa B (NF-κB). In addition, increased levels of ubiquitin ligases cause skeletal muscle atrophy. Conversely, sirtuin 1 (Sirt1) is known to regulate the expression of ubiquitin ligases by suppressing the activities of NF-κB and FOXO. In this study, we evaluated the effect that juzentaihoto hot water extract (JTT) has on skeletal muscle atrophy and motor function by administering it to senescence-accelerated mouse prone-8 (SAMP8). The group treated with JTT displayed larger gastrocnemius muscle (GA) and extensor digitorum longus (EDL) weights, larger GA muscle fiber cross-sectional areas, and motor function decline during rota-rod tests. JTT also increased IGF-1 serum levels, as well as mRNA Sirt1 levels in GA. Serum levels of tumor necrosis factor-α, interleukin-6, and mRNA levels of Atrogin1 and MuRF1 in GA were reduced by JTT. The muscle fiber cross-sectional area of GA was correlated with the mRNA levels of Sirt1 in GA. The results of this study suggested that JTT administration suppresses skeletal muscle atrophy and motor function decline in SAMP8 mice. This effect may be associated with the increased expression levels of Sirt1 and IGF-1 by JTT.

Effects of Rehmannia glutinosa polysaccharides on bone tissue structure and skeletal muscle atrophy in rats with disuse

ABSTRACTPurposeTo study effects of Rehmannia glutinosa polysaccharides (RGP) on bone tissue structure and skeletal muscle atrophy in rats with disuse.MethodsA rat model of disuse osteoporosis combined with muscle atrophy was established by removing the bilateral ovaries of rats and fixing their hind limbs for a long time. Forty SD rats were administered intragastrically for 12 weeks. The bone histomorphometry parameters and the level of oxidative stress were measured. In addition, the changes of muscle atrophy F-box (MAFbx), muscle RING-finger protein-1 (MuRF1), forkhead box O1 (FOXO1) mRNA expression in skeletal muscle of rats were observed.ResultsRGP significantly increased the percentage of fluorescence perimeter and bone mineralization deposition rate of the second lumbar vertebrae of rats. It also significantly increased the wet weight ratio and muscle fiber cross-sectional area of the gastrocnemius muscle of rats. At the same time, RGP significantly increased the levels of super oxide dismutase (SOD) and catalase (CAT) in the skeletal muscle of rats, and reduced the content of malondialdehyde (MDA). Rehmannia glutinosa polysaccharides also significantly reduced the expression levels of FOXO1, MAFbx and MuRF1 mRNA in rat skeletal muscle.ConclusionsRGP could improve the bone structure of osteoporotic rats. It could also improve muscle that atrophy may be related to the inhibition of FOXO1-mediated ubiquitin-proteasome pathway.

Effects of neuromuscular electrical stimulation on pulmonary alveola and cytokines in chronic obstructive pulmonary disease (COPD) and skeletal muscle atrophy model mice.

[Purpose] It has been reported that exercise affects skeletal muscle in the chronic obstructive pulmonary disease (COPD) disease model. In this study, we examined the effects of neuromuscular electrical stimulation (NMES) in skeletal muscle on alveoli and cytokines. [Materials and Methods] We used twenty wild-type mice, randomly divided into three groups: Group A: Control (non-COPD, non-amyotrophia, non-NMES), Group B: COPD, amyotrophia with NMES and Group C: COPD, amyotrophia without NMES. Among those, a group of mice with ages from 12 to 14 weeks were used to create a chronic obstructive pulmonary disease (COPD) model, a group of mice with ages from 15 to 16 weeks was used to create a disuse syndrome by hind limb suspension, and a group of mice with ages from 17 to 28 weeks (12 weeks) were used to implement NMES. In this study, we used the real-time PCR method to assess the mRNA expression levels. We also conducted morphological analysis, assessed macrophage expression level by staining (general staining and immunostaining), and employed spirometry. [Results] Our study results showed significant decreases in Interleukin-6 (IL-6) levels in the lungs and muscle RING-finger protein-1 (MuRF1) in the muscles. Moreover, the pulmonary stromal macrophage marker (F4/80) and the protease marker (MMP12) showed significantly decreased expression, while no change was observed in the morphological of the alveolar spaces (mean linear intercept). [Conclusion] On the basis of these findings, our study reveals that NMES affects cytokines and macrophages in COPD skeletal muscle atrophy.

Expression of titin-linked putative mechanosensing proteins in skeletal muscle after power resistance exercise in resistance-trained men.

Little is known about the molecular responses to power resistance exercise that lead to skeletal muscle remodeling and enhanced athletic performance. We assessed the expression of titin-linked putative mechanosensing proteins implicated in muscle remodeling: muscle ankyrin repeat proteins (Ankrd 1, Ankrd 2, and Ankrd 23), muscle-LIM proteins (MLPs), muscle RING-finger protein-1 (MuRF-1), and associated myogenic proteins (MyoD1, myogenin, and myostatin) in skeletal muscle in response to power resistance exercise with or without a postexercise meal, in fed, resistance-trained men. A muscle sample was obtained from the vastus lateralis of seven healthy men on separate days, 3 h after 90 min of rest (Rest) or power resistance exercise with (Ex + Meal) or without (Ex) a postexercise meal to quantify mRNA and protein levels. The levels of phosphorylated HSP27 (pHSP27-Ser15) and cytoskeletal proteins in muscle and creatine kinase activity in serum were also assessed. The exercise increased (P ≤ 0.05) pHSP27-Ser15 (∼6-fold) and creatine kinase (∼50%), whereas cytoskeletal protein levels were unchanged (P > 0.05). Ankrd 1 (∼15-fold) and MLP (∼2-fold) mRNA increased, whereas Ankrd 2, Ankrd 23, MuRF-1, MyoD1, and myostatin mRNA were unchanged. Ankrd 1 (∼3-fold, Ex) and MLPb (∼20-fold, Ex + Meal) protein increased, but MLPa, Ankrd 2, Ankrd 23, and the myogenic proteins were unchanged. The postexercise meal did not affect the responses observed. Power resistance exercise, as performed in practice, induced subtle early responses in the expression of MLP and Ankrd 1 yet had little effect on the other proteins investigated. These findings suggest possible roles for MLP and Ankrd 1 in the remodeling of skeletal muscle in individuals who regularly perform this type of exercise.NEW & NOTEWORTHY This is the first study to assess the early changes in the expression of titin-linked putative mechanosensing proteins and associated myogenic regulatory factors in skeletal muscle after power resistance exercise in fed, resistance-trained men. We report that power resistance exercise induces subtle early responses in the expression of Ankrd 1 and MLP, suggesting these proteins play a role in the remodeling of skeletal muscle in individuals who regularly perform this type of exercise.

Role of miRNAs and lncRNAs in dexamethasone-induced myotube atrophy in vitro.

Skeletal muscle atrophy is a well-known adverse effect of long-term glucocorticoid (GC) therapy. MicroRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs) are important regulators in a number of physiological and pathological processes. However, the role of miRNAs and lncRNAs in the regulation of GC-treated muscle atrophy remains poorly understood. In the current study, muscular atrophy was induced and the results indicated that C2C12 myotubes were thinner than normal, while the expression of muscle ring finger protein 1 and Atrogin-1 was increased. The expression of nine miRNAs and seven lncRNAs associated with proliferation and differentiation were analyzed in a dexamethasone (DEX)-induced muscle atrophy cell model. In addition, the mRNA expression of the downstream targets of lncRNAs that were differentially expressed between DEX-treated and control cells were determined. The results indicated that the expression of miR-133a, miR-133b, miR-206 and five lncRNAs (increased Atrolnc-1, Dum, MAR1, linc-MD1 and decreased Myolinc) were significantly different between the DEX and the control group. Furthermore, the relative mRNA expression of Wnt5a and MyoD was significantly different between the two groups. The results of the current study indicated that some important miRNAs and lncRNAs are associated with DEX-induced muscle atrophy and have the potential to be further developed as a diagnostic tool for this condition.

Camphene Attenuates Skeletal Muscle Atrophy by Regulating Oxidative Stress and Lipid Metabolism in Rats.

Sarcopenia- or cachexia-related muscle atrophy is due to imbalanced energy metabolism and oxidative stress-induced muscle dysfunction. Monoterpenes play biological and pharmacological reactive oxygen species (ROS) scavenging roles. Hence, we explored the effects of camphene, a bicyclic monoterpene, on skeletal muscle atrophy in vitro and in vivo. We treated L6 myoblast cells with camphene and then examined the ROS-related oxidative stress using Mito TrackerTM Red FM and anti-8-oxoguanine antibody staining. To investigate lipid metabolism, we performed real-time polymerase chain reactions, holotomographic microscopy, and respiratory gas analysis. Rat muscle atrophy in in vivo models was observed using 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography and immunocytochemistry. Camphene reversed the aberrant cell size and muscle morphology of L6 myoblasts under starvation and in in vivo models. Camphene also attenuated E3 ubiquitin ligase muscle RING-finger protein-1, mitochondrial fission, and 8-oxoguanine nuclear expression in starved myotubes and hydrogen peroxide (H2O2)-treated cells. Moreover, camphene significantly regulated lipid metabolism in H2O2-treated cells and in vivo models. These findings suggest that camphene may potentially affect skeletal muscle atrophy by regulating oxidative stress and lipid metabolism.

Linalool Prevents Cisplatin Induced Muscle Atrophy by Regulating IGF-1/Akt/FoxO Pathway.

Skeletal muscle atrophy is an important feature of cancer cachexia, which can be induced by chemotherapy, and affects the survival and quality of life of cancer patients seriously. No specific drugs for cancer cachexia have been applied in clinical practice. This study explored the therapeutic effect of linalool (LIN) on cisplatin (DDP) induced skeletal muscle atrophy. In vivo, LIN can improve skeletal muscle weight loss, anorexia, muscle strength decline and other cachexia symptoms caused by cisplatin treatment in a Lewis lung cancer tumor bearing mouse model, and cause no adverse effects on the anti-tumour effect. LIN treatment decreased the expression of muscle RING-finger protein-1 (MuRF1) and Atrogin1(MAFbx) in muscle, and the activation of insulin-like growth factor-1 (IGF-1)/protein kinase B (Akt)/forkhead box O (FoxO) pathway was observed. In vitro, LIN alleviated DDP induced C2C12 myotube atrophy, and IGF-1 receptor inhibitor Picropodophyllin (PIC), which had no adverse effect on C2C12 myotube cells, could reverse the protective effect of LIN. These results indicate that LIN down-regulates the expression of Atrogin1 and MuRF1 through the IGF-1/Akt/FoxO pathway, alleviating DDP-induced muscle atrophy and improving cachexia symptoms. LIN has the potential to be developed as a drug against cancer cachexia.