Inhibits Muscle Atrophy Research Articles

Inhibitory effects of curcuminoids on dexamethasone-induced muscle atrophy in differentiation of C2C12 cells

BackgroundSarcopenia is a disease of progressive loss of muscle mass due to the imbalance of protein synthesis and proteolysis, and tends to emerge with ageing. Currently its treatment consists of non-drug therapies and drug therapies, but some medications can have various side effects. Therefore, it is important to search for effective herbal medicines that can modulate muscle mass. PurposeIn this study, we investigated the inhibition effects of Cu, De, Bis, CRE, CRE-SD, CRE-Bin, and CRE-Ter on dexamethasone-induced muscle atrophy in differentiation of C2C12 cells. MethodsC2C12 cells were cultured and treated with various concentrations of curcuminoids including, Cu, De, Bis, CRE, CRE-SD, CRE-Bin, and CRE-Ter. The inhibitory effects were studied using various methods, including MTT and LDH assays for cell viability and cell cytotoxicity, RT-qPCR for gene expression analysis, and Western blots for protein analysis. In this study, dexamethasone-treated C2C12 myotubes (Dex) are the positive drug control and used as in vitro models of muscle atrophy. ResultsThe results revealed that treating differentiated C2C12 cells with Cu, CRE, CRE-Bin, and CRE-Ter reduced Atrogin-1 and MuRF-1 expression, whereas CRE-SD reduced only MuRF-1 expression. The Western blot analysis results show that Cu, CRE, CRE-Bin, CRE-Ter, and CRE-SD upregulated the phosphorylation level of Akt, which is an important protein in the mTOR signaling pathway. ConclusionOur results show that Cu, CRE, CRE-Bin, CRE-SD, and CRE-Ter tend to inhibit muscle atrophy by decreasing expression of Atrogin-1 and MuRF-1 inhibiting protein degradation, and to upregulate Phospho-Akt to stimulate protein synthesis. These results provide corroborating evidence of therapeutic potential to treat sarcopenia patients.

Engineering of Highly Interconnected Inverse Opal Extracellular Matrix Scaffolds for Enhanced Cell Transplantation and Vascularization of Ischemic Tissue

The therapeutic effectiveness of cell transplantation in treatment of diseases and injuries is often limited by low cell retention, survivability, and engraftment. Extracellular matrix (ECM)-derived scaffolds are capable of controlling cell responses, thereby offering potential solutions to current challenges associated with cell therapy. However, it remains a technical challenge to produce ECM scaffolds with highly interconnected porous structure specifically required for cell transplantation. Here, we developed inverse opal porous extracellular matrix (ioECM) scaffolds through subcutaneous implantation of sacrificial templates assembled from polymer microspheres, followed by removal of the microsphere template and cellular content. Such highly interconnected porous ioECM scaffolds supported the anchorage, proliferation, viability, anti-apoptotic and paracrine activities of rat bone marrow mesenchymal stem cells (BMSCs), which further promoted endothelial cell migration, tube formation and proliferation. Upon transplantation into nude mouse critical limb ischemic model, ioECM promoted the engraftment of laden BMSCs, facilitated interconnected vascular network formation with accelerated recovery of blood perfusion and inhibited muscle atrophy and fibrosis. Our study demonstrates a unique strategy to engineer highly porous yet well-interconnected ECM scaffolds specifically for cell transplantation with marked improvement of survivability and vascularization, which offers an essential step toward the success of cell therapy and regenerative medicine.

Dioscorea nipponica extracts enhance recovery from skeletal muscle atrophy by suppressing NF-κB expression

Abstract Saponin derived from natural extracts can alleviate muscle atrophy. Dioscorea nipponica Makino (DNM) is commonly used in herbal medicine and contains various steroidal saponins, although its efficacy and mechanisms of action for treating muscle atrophy remain unknown. Here, differentiated myoblast cells treated with DNM showed increased MyoD and MyoG expression and effectively promoted muscle formation. DNM effectively inhibited muscle atrophy induced by tumor necrosis factor alpha (TNFα) monotherapy, and combination treatment with protodioscin and protogracillin (among the tested DNM constituents) showed a synergistic effect on differentiated myoblast cells. DNM and this combination repressed TNFα-induced increased MuRF1 and Atrogin1/MAFbx expression by inhibiting nuclear factor-kappa B (NF-κB) expression. DNM also effectively promoted the recovery of muscle formation in injured mice. Therefore, DNM and its multi-constituents can potentially be used as therapeutic agents for muscle-related diseases and represent prospective food supplements.

Angiotensin (1-7) Decreases Myostatin-Induced NF-κB Signaling and Skeletal Muscle Atrophy.

Myostatin is a myokine that regulates muscle function and mass, producing muscle atrophy. Myostatin induces the degradation of myofibrillar proteins, such as myosin heavy chain or troponin. The main pathway that mediates protein degradation during muscle atrophy is the ubiquitin proteasome system, by increasing the expression of atrogin-1 and MuRF-1. In addition, myostatin activates the NF-κB signaling pathway. Renin–angiotensin system (RAS) also regulates muscle mass. Angiotensin (1-7) (Ang-(1-7)) has anti-atrophic properties in skeletal muscle. In this paper, we evaluated the effect of Ang-(1-7) on muscle atrophy and signaling induced by myostatin. The results show that Ang-(1-7) prevented the decrease of the myotube diameter and myofibrillar protein levels induced by myostatin. Ang-(1-7) also abolished the increase of myostatin-induced reactive oxygen species production, atrogin-1, MuRF-1, and TNF-α gene expressions and NF-κB signaling activation. Ang-(1-7) inhibited the activity mediated by myostatin through Mas receptor, as is demonstrated by the loss of all Ang-(1-7)-induced effects when the Mas receptor antagonist A779 was used. Our results show that the effects of Ang-(1-7) on the myostatin-dependent muscle atrophy and signaling are blocked by MK-2206, an inhibitor of Akt/PKB. Together, these data indicate that Ang-(1-7) inhibited muscle atrophy and signaling induced by myostatin through a mechanism dependent on Mas receptor and Akt/PKB.

Myoferlin Regulates Wnt/β-Catenin Signaling-Mediated Skeletal Muscle Development by Stabilizing Dishevelled-2 Against Autophagy.

Myoferlin (MyoF), which is a calcium/phospholipid-binding protein expressed in cardiac and muscle tissues, belongs to the ferlin family. While MyoF promotes myoblast differentiation, the underlying mechanisms remain poorly understood. Here, we found that MyoF not only promotes C2C12 myoblast differentiation, but also inhibits muscle atrophy and autophagy. In the present study, we found that myoblasts fail to develop into mature myotubes due to defective differentiation in the absence of MyoF. Meanwhile, MyoF regulates the expression of atrophy-related genes (Atrogin-1 and MuRF1) to rescue muscle atrophy. Furthermore, MyoF interacts with Dishevelled-2 (Dvl-2) to activate canonical Wnt signaling. MyoF facilitates Dvl-2 ubiquitination resistance by reducing LC3-labeled Dvl-2 levels and antagonizing the autophagy system. In conclusion, we found that MyoF plays an important role in myoblast differentiation during skeletal muscle atrophy. At the molecular level, MyoF protects Dvl-2 against autophagy-mediated degradation, thus promoting activation of the Wnt/β-catenin signaling pathway. Together, our findings suggest that MyoF, through stabilizing Dvl-2 and preventing autophagy, regulates Wnt/β-catenin signaling-mediated skeletal muscle development.

Red Bean Extract Inhibits Immobilization-Induced Muscle Atrophy in C57BL/6N Mice.

Muscle atrophy, which is characterized by a decrease in muscle mass, function, and protein content, can be caused by aging, disease, and physical inactivity. Red bean or Adzuki bean (Vigna angularis) has been consumed as an edible legume. Red bean possesses various functional properties, such as antidiabetes, antiaging, anti-inflammatory, anticancer, and hepatoprotective activities. However, little is known about its potential inhibitory effect on muscle atrophy. In this study, we investigated the inhibitory effect of red bean extract (RBE) on muscle atrophy in an immobilized hindlimb muscle of C57BL/6J mice. RBE dose-dependently increased grip strength, exercise endurance, muscle weight, and myofiber area. At the molecular level, RBE significantly reduced the mRNA expression of proteolysis-related genes, such as muscle ring finger and muscle atrophy F-box by preventing the translocation of Forkhead box 3. RBE also activated the phosphatidylinositol 3 kinase/Akt pathway, subsequently stimulating the mammalian target of rapamycin/70-kDa ribosomal protein S6 kinase/eukaryotic initiation factor 4E binding protein 1 pathway involved in protein synthesis. Overall, red bean could be used as a functional food ingredient or therapeutic agent to inhibit muscle atrophy.

Effect of Oral Branched-Chain Amino Acids and Glutamine Supplementation on Skeletal Muscle Atrophy After Total Gastrectomy in Rat Model

BackgroundSarcopenia is closely related to short-term outcomes of surgery and long-term prognosis. After gastrectomy, a decrease in muscle strength occurs because of insufficient nutrient intake and disturbed digestive function. Branched-chain amino acids (BCAAs) and glutamine (Gln) play vital roles in the signaling pathways regulating protein synthesis and protein degradation. In this study, we investigated the effects of BCAA and Gln supplementation alone or in combination on skeletal muscle atrophy after total gastrectomy in a rat model. MethodsMale Wistar rats were divided into five groups: (1) sham operation (n = 8); (2) total gastrectomized rats (TG [control group], n = 16); (3) TG with BCAA (TG-B, n = 16); (4) TG with Gln (TG-G, n = 16); and (5) TG with BCAA and Gln (TG-BG, n = 16). In all groups, body weight, muscle weight, and marker for muscle metabolism were examined. ResultsWeight gain was significantly greater in the TG-BG group (130.5%) than in the TG group (108.1%) at 15 wk (P < 0.05). The gastrocnemius muscle weight was significantly higher for TG-BG (2.84 g) than for TG (2.44 g) at 15 wk (P < 0.05). Western blotting indicated that atrogin-1 and MuRF1 levels were lower in the TG-BG group than in the TG group but were not suppressed in the TG-B or TG-G group. ConclusionsIn a rodent sarcopenia model induced by TG, the administration of BCAA in combination with Gln more effectively inhibited muscle atrophy than the administration of BCAA or Gln alone.

Transcutaneous carbon dioxide application inhibits muscle atrophy after fracture in rats

BackgroundMuscle atrophy causes difficulty in resuming daily activities after a fracture. Because transcutaneous carbon dioxide (CO2) application has previously upregulated oxygen pressure in the local tissue, thereby demonstrating its potential in preventing muscle atrophy, here we investigated effects of CO2 application on muscle atrophy after femoral shaft fracture. MethodsThirty fracture model rats were produced and randomly divided into a no treatment (control group) and treatment (CO2 group) groups. After treatment, the soleus muscle was dissected at post-fracture days 0, 14, and 21. Evaluations were performed by measuring muscle weight and performing histological examination and gene expression analysis. ResultsMuscle weight was significantly higher in the CO2 group than in the control group. Histological analysis revealed that the muscle fiber cross-sectional area was reduced in both groups. Nevertheless, the extent of atrophy was lesser in the CO2 group. Muscle fibers in the control group tended to change into fast muscle fibers. Vascular staining revealed that more capillary vessels surrounded the muscle fibers in the CO2 group than in the control group. Messenger RNA (mRNA) analysis revealed that the CO2 group had a significantly enhanced expression of genes that were related to muscle synthesis. ConclusionTranscutaneous CO2 application may be a novel therapeutic strategy for preventing skeletal muscle atrophy after fracture.

IMB0901 inhibits muscle atrophy induced by cancer cachexia through MSTN signaling pathway

BackgroundCancer cachexia as a metabolic syndrome can lead to at least 25% of cancer deaths. The inhibition of muscle atrophy is a main strategy to treat cancer cachexia. In this process, myostatin (MSTN) can exert a dual effect on protein metabolism, including inhibition of protein biosynthesis and enhancement of protein degradation. In this study, we will test the effect on muscle atrophy induced by cancer cachexia of IMB0901, a MSTN inhibitor.MethodsTwo high-throughput screening models against MSTN were developed. By screening, IMB0901, 2-((1-(3,4-dichlorophenyl)-1H-pyrazolo [3,4-d] pyrimidin-4-yl) amino) butan-1-ol, was picked out from the compound library. The in vitro cell model and the C26 animal model of muscle atrophy induced by cancer cachexia were used to determine the pharmacological activity of IMB0901. Whether IMB0901 could inhibit the aggravating effect of doxorubicin on muscle wasting was examined in vitro and in vivo.ResultsIMB0901 inhibited the MSTN promoter activity, the MSTN signaling pathway, and the MSTN positive feedback regulation. In atrophied C2C12 myotubes, IMB0901 had a potent efficiency of decreasing MSTN expression and modulating MSTN signaling pathway which was activated by C26-conditioned medium (CM). In C2C12 myotubes, the expressions of three common myotube markers, myosin heavy chain (MyHC), myogenic differentiation 1 (MyoD), and myogenin (MyoG), were downregulated by CM, which could be efficiently reversed by IMB0901 via reduction of ubiquitin-mediated proteolysis and enhancement of AKT/mTOR-mediated protein synthesis. In the C26 animal model, IMB0901 mitigated the weight loss of body, quadricep and liver, and protected the quadriceps cell morphology. Furthermore, IMB0901 decreased the expression of two E3 ligases Atrogin-1 and MuRF-1 in the quadriceps in vivo. At the cellular level, IMB0901 had no influence on anti-tumor effect of three chemotherapeutic agents (cisplatin, doxorubicin, and gemcitabine) and lowered doxorubicin-induced upregulation of MSTN in C2C12 myotubes. IMB0901 did not affect the inhibitory effect of doxorubicin on C26 tumor and delayed the weight loss of muscle and adipose tissue caused by C26 tumor and doxorubicin.ConclusionsIMB0901 inhibits muscle atrophy induced by cancer cachexia by suppressing ubiquitin-mediated proteolysis and promoting protein synthesis. These findings collectively suggest that IMB0901 is a promising leading compound for the management of muscle atrophy induced by cancer cachexia.

Regulation of muscle atrophy-related genes by the opposing transcriptional activities of ZEB1/CtBP and FOXO3.

Multiple physiopathological and clinical conditions trigger skeletal muscle atrophy through the induction of a group of proteins (atrogenes) that includes components of the ubiquitin–proteasome and autophagy-lysosomal systems. Atrogenes are induced by FOXO transcription factors, but their regulation is still not fully understood. Here, we showed that the transcription factor ZEB1, best known for promoting tumor progression, inhibits muscle atrophy and atrogene expression by antagonizing FOXO3-mediated induction of atrogenes. Compared to wild-type counterparts, hindlimb immobilization in Zeb1-deficient mice resulted in enhanced muscle atrophy and higher expression of a number of atrogenes, including Atrogin-1/Fbxo32, MuRF1/Trim63, Ctsl, 4ebp1, Gabarapl1, Psma1 and Nrf2. Likewise, in the C2C12 myogenic cell model, ZEB1 knockdown augmented both myotube diameter reduction and atrogene upregulation in response to nutrient deprivation. Mechanistically, ZEB1 directly represses in vitro and in vivo Fbxo32 and Trim63 promoter transcription in a stage-dependent manner and in a reverse pattern with MYOD1. ZEB1 bound to the Fbxo32 promoter in undifferentiated myoblasts and atrophic myotubes, but not in non-atrophic myotubes, where it is displaced by MYOD1. ZEB1 repressed both promoters through CtBP-mediated inhibition of FOXO3 transcriptional activity. These results set ZEB1 as a new target in therapeutic approaches to clinical conditions causing muscle mass loss.

OR-019 VEGF-B inhibits skeletal muscle apoptosis after exercise in Chronic heart failure rats

Objective To investigate the effects of vascular endothelial growth factor B in aerobic exercise mediated chronic heart failure rats cardiac function improvement and skeletal muscle remodeling.&#x0D; Methods We employed transverse abdominal aortic constriction (TAC) inducing CHF in Sprague Dawley rats. Controls were sham-operated animals. At 4 weeks after surgery, rats were randomized to 4 weeks of aerobic exercise (CHF+E) or to untrained groups (CHF). After 8 weeks, all rats went echocardiography test. After which, rats were sacrificed and samples were collected. Muscular cytokine VEGFB and its receptor NRP1 expression were analyzed. Expression of apoptosis and muscle atrophy markers were assessed in cardiac muscle、gastrocnemius.&#x0D; Results TAC rats developed CHF (preserved LV ejection fraction, hypertrophy of myocardial cells, decreased FS, increased LVAW d and LVID s). Exercise ameliorate CHF rat cardiac function. TAC rat skeletal muscle developed irregular muscle fiber distribution.The two atrophy-related ubiquitin ligases atrogin-1 and MuRF1, as well as genes involved in apoptosis and autophagy were upregulated in muscles in CHF rats. Exercise inhibited muscle atrophy and skeletal muscle apoptosis.VEGFB and its receptor NRPI decreased significantly in CHF muscle. Exercise promoted VEGFB and NRP1 expression in cardiac tissue, gastrocnemius.&#x0D; Conclusions Exercise ameliorates CHF rat cardiac function. VEGFB inhibits cardiac muscle and gastrocnemius apoptosis in CHF rats.

Exogenous Delta-Like 1 Homolog (DLK1)-Fc Treatment Attenuates Muscle Atrophy in Both Dexamethasone and High-Fat Diet–Induced Obesity Mice Models

Skeletal muscle degeneration is accelerated in elderly patients with diabetes and the imbalance between muscle growth and wasting can lead to metabolic dysfunction. DLK1 is a member of the EGF-like family and essential for skeletal muscle development and regeneration. To identify whether exogenous DLK1 treatment can prevent muscle wasting, we assessed muscle mass as well as muscle differentiation and atrophy markers in two different models: dexamethasone and high fat diet (HFD)-induced obesity mice models (n=7-8 per each group). In the dexamethasone model, mice were divided into (1) control, (2) dexamethasone treatment (1mg/Kg, 2 weeks), and (3) DLK1 (0.8mg/Kg, 2 weeks) and dexamethasone treatment groups. In the HFD model, mice were divided into (1) control, (2) HFD (60% calories from fat, 8 weeks), and (3) HFD with DLK1 treatment (0.8mg/Kg, 8 weeks) groups. The expressions of genes related to muscle differentiation and atrophy were determined using RT-PCR. We observed that dexamethasone reduced muscle mass and markedly increased atrophy makers including atrogin-1 and murf-1. DLK1 treatment attenuated these degenerative changes. Furthermore, the level of myostatin, which inhibits muscle cell growth, was reduced in DLK1 treatment group compared to dexamethasone group. Additionally, compared to HFD group, DLK1 inhibited muscle atrophy by increasing the differentiation marker: myoD, and decreasing the atrophy markers: mysotatin, atrogin-1, and murf-1. Taken together, these results suggest that DLK1 attenuates both dexamethasone and HFD-induced muscle atrophy in mice by suppressing the downstream signaling of myostatin/atrogin-1/murf-1 pathway. The increased expression of myoD indicates that DLK1 treatment can also improve the quality of muscle formation. Our study implies that DLK1 could be a promising candidate in the treatment of aging or diabetes-related sarcopenia, characterized by muscle atrophy and dysfunction. Disclosure J. Lee: None. M. Lee: None. H. Jung: None. J. Lee: None. Y. Cho: None. J. Bae: None. Y. Lee: None. B. Lee: None. E. Kang: None. B. Cha: None.

The influence of isoflavone for denervation-induced muscle atrophy.

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with a high level (20%) of isoflavone inhibits muscle atrophy after short-term denervation (at 4days) in mice. The present study was designed to elucidate whether the dietary isoflavone aglycone (AglyMax) at a 0.6% prevents denervation-mediated muscle atrophy, based on the modulation of atrogin-1- or apoptosis-dependent signaling. Mice were fed either a normal diet or 0.6% AglyMax diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, amount of atrogin-1 and cleaved caspase-3 proteins, and the percentages of apoptotic nuclei were examined in the gastrocnemius muscle at 14days after denervation. The 0.6% AglyMax diet significantly attenuated denervation-induced decreases in fiber atrophy but not the muscle wet weight. In addition, dietary isoflavone suppressed the denervation-induced apoptosis in spite of there being no significant changes in the amount of cleaved caspase-3 protein. In contrast, the 0.6% AglyMax diet did not significantly modulate the protein expression of atrogin-1 in the denervated muscle of mice. The isoflavone aglycone (AglyMax) at a 0.6% significantly would modulate muscle atrophy after denervation in mice, probably due to the decrease in apoptosis-dependent signaling.

Pyrrolidine Dithiocarbamate (PDTC) Attenuates Cancer Cachexia by Affecting Muscle Atrophy and Fat Lipolysis.

Cancer cachexia is a kind of whole body metabolic disorder syndrome accompanied with severe wasting of muscle and adipose tissue. NF-κB signaling plays an important role during skeletal muscle atrophy and fat lipolysis. As an inhibitor of NF-κB signaling, Pyrrolidine dithiocarbamate (PDTC) was reported to relieve cancer cachexia; however, its mechanism remains largely unknown. In our study, we showed that PDTC attenuated cancer cachexia symptom in C26 tumor bearing mice models in vivo without influencing tumor volume. What’s more, PDTC inhibited muscle atrophy and lipolysis in cells models in vitro induced by TNFα and C26 tumor medium. PDTC suppressed atrophy of myotubes differentiated from C2C12 by reducing MyoD and upregulating MuRF1, and preserving the expression of perilipin as well as blocking the activation of HSL in 3T3-L1 mature adipocytes. Meaningfully, we observed that PDTC also inhibited p38 MAPK signaling besides the NF-κB signaling in cancer cachexia in vitro models. In addition, PDTC also influenced the protein synthesis of skeletal muscle by activating AKT signaling and regulated fat energy metabolism by inhibiting AMPK signaling. Therefore, PDTC primarily influenced different pathways in different tissues. The study not only established a simple and reliable screening drugs model of cancer cachexia in vitro but also provided new theoretical basis for future treatment of cancer cachexia.

Muscle-protective effects of Schisandrae Fructus extracts in old mice after chronic forced exercise

Ethnopharmacological relevanceSchisandrae Fructus (SF), the dried fruit of Schisandra chinensis (Turcz.) Baill., is a well-known traditional herb used in Asia for enhancing physical work capacity as well as providing anti-stress and anti-inflammatory effects. Extracts of SF (SFe) have also been reported to increase skeletal muscle mass and inhibit muscle atrophy. Aim of the studyWe examined whether SFe had muscle-protective effects in old mice after chronic forced exercises, and, if so, relevant mechanisms. Materials and methodsTen-month-old aged male mice were divided into six groups. One group received no forced swimming after oral administration of distilled water (Intact); the other groups received forced swimming after administration of distilled water (SW), oxymetholone (OXY), or SFe at 500, 250 and 125mg/kg (SFe500, SFe250, and SFe125, respectively). Forced swimming was conducted for 2min at 30min after oral administration; the treatment was repeated for 28 days. Muscle thickness, weight, lean proportion, and strength were examined. The sampled muscles were subjected to histopathological and biochemical analyses. Plasma was examined by biochemical analyses. ResultsThe thicknesses of the calf muscle and the sampled gastrocnemius and soleus, protein proportion and muscle strength increased significantly in the SW group versus Intact, and they were further increased in the SFe and OXY groups versus SW. The forced swimming in the SW group upregulated mRNA expression related to protein synthesis (Akt1, PI3K) and muscle growth (A1R, TRPV4), while it downregulated mRNAs related to protein degradation (atrogin-1, MuRF1) and muscle growth inhibitor (myostatin, SIRT1). The detected upregulation and downregulation were enhanced in the SFe groups. In addition, the SFe administration inhibited lipid peroxidation and reactive oxygen species, and accelerated activities of endogenous anti-oxidants and anti-oxidant enzymes. Plasma biochemistry showed decreases in creatine, creatine kinase and LDH in the SFe groups versus SW, suggesting muscle-protective effects of SFe. In the SFe groups versus SW, histopathological analyses revealed an increase in myofibre diameter, and immunohistochemistry showed increases in myofibres immunoreactive for ATPase and decreases in myofibres for apoptosis markers (caspase-3, PARP) and oxidative stress markers (NT, 4HNE, iNOS). ConclusionsOral administration of SFe, especially SFe500, enhanced exercise-induced adaptive muscle strengthening in aged mice after forced swimming through anti-apoptotic and anti-oxidant effects, mediated via modulation of gene expression related to muscle synthesis or degradation. These results suggest that SFe may be helpful in improvement various muscle disorders as an adjuvant therapy to exercise-based remedies.

Korean mistletoe (Viscum album coloratum) extract regulates gene expression related to muscle atrophy and muscle hypertrophy

BackgroundKorean mistletoe (Viscum album coloratum) is a semi-parasitic plant that grows on various trees and has a diverse range of effects on biological functions, being implicated in having anti-tumor, immunostimulatory, anti-diabetic, and anti-obesity properties. Recently, we also reported that Korean mistletoe extract (KME) improves endurance exercise in mice, suggesting its beneficial roles in enhancing the capacity of skeletal muscle.MethodsWe examined the expression pattern of several genes concerned with muscle physiology in C2C12 myotubes cells to identify whether KME inhibits muscle atrophy or promotes muscle hypertrophy. We also investigated these effects of KME in denervated mice model.ResultsInterestingly, KME induced the mRNA expression of SREBP-1c, PGC-1α, and GLUT4, known positive regulators of muscle hypertrophy, in C2C12 cells. On the contrary, KME reduced the expression of Atrogin-1, which is directly involved in the induction of muscle atrophy. In animal models, KME mitigated the decrease of muscle weight in denervated mice. The expression of Atrogin-1 was also diminished in those mice. Moreover, KME enhanced the grip strength and muscle weight in long-term feeding mice.ConclusionsOur results suggest that KME has beneficial effects on muscle atrophy and muscle hypertrophy.

Chinese Herbal Medicine Baoyuan Jiedu Decoction Inhibited Muscle Atrophy of Cancer Cachexia through Atrogin-l and MuRF-1.

The aim of this study is to investigate the mechanisms of Chinese herbal medicine called “Baoyuan Jiedu” (BYJD for short) decoction, improving life quality and preventing muscle atrophy of cancer cachexia model mice. We showed that the effect of BYJD decoction increased body weights of mice and reduced tumor volume and tumor mass. Furthermore, BYJD decoction increased the gastrocnemii mass and the transverse diameter of muscle fiber morphology. Moreover, BYJD reduced the expression of Atrogin-1 and MuRF-1 protein. Collectively, our results show that BYJD decoction improves the life quality of cancer cachexia mice and prevents muscle atrophy by downregulating expression of Atrogin-1 and MuRF-1.

History, Mechanisms and Clinical Value of Fibrillation Analyses in Muscle Denervation and Reinnervation by Single Fiber Electromyography and Dynamic Echomyography.

This work reviews history, current clinical relevance and future of fibrillation, a functional marker of skeletal muscle denervated fibers. Fibrillations, i.e., spontaneous contraction, in denervated muscle were first described during the nineteenth century. It is known that alterations in membrane potential are responsible for the phenomenon and that they are related to changes in electrophysiological factors, cellular metabolism, cell turnover and gene expression. They are known to inhibit muscle atrophy to some degree and are used to diagnose neural injury and reinnervation that are occurring in patients. Electromyography (EMG) is useful in determining progress, prognosis and efficacy of therapeutic interventions and their eventual change. For patients with peripheral nerve injury, and thus without the option of volitional contractions, electrical muscle stimulation may be helpful in preserving the contractility and extensibility of denervated muscle tissue and in retarding/counteracting muscle atrophy. It is obvious from the paucity of recent literature that research in this area has declined over the years. This is likely a consequence of the decrease in funding available for research and the fact that the fibrillations do not appear to cause serious health issues. Nonetheless, further exploration of them as diagnostic tools in long-term denervation is merited, in particular if Single Fiber EMG (SFEMG) is combined with Dynamic Echomyography (DyEM), an Ultra Sound muscle approach we recently designed and developed to explore denervated and reinnervating muscles.

History, mechanisms and clinical value of fibrillation analyses in muscle denervation and reinnervation by Single Fiber Electromyography and Dynamic Echomyography

This work reviews history, current clinical relevance and future of fibrillation, a functional marker of skeletal muscle denervated fibers. Fibrillations, i.e., spontaneous contraction, in denervated muscle were first described during the nineteenth century. It is known that alterations in membrane potential are responsible for the phenomenon and that they are related to changes in electrophysiological factors, cellular metabolism, cell turnover and gene expression. They are known to inhibit muscle atrophy to some degree and are used to diagnose neural injury and reinnervation that are occurring in patients. Electromyography (EMG) is useful in determining progress, prognosis and efficacy of therapeutic interventions and their eventual change. For patients with peripheral nerve injury, and thus without the option of volitional contractions, electrical muscle stimulation may be helpful in preserving the contractility and extensibility of denervated muscle tissue and in retarding/counteracting muscle atrophy. It is obvious from the paucity of recent literature that research in this area has declined over the years. This is likely a consequence of the decrease in funding available for research and the fact that the fibrillations do not appear to cause serious health issues. Nonetheless, further exploration of them as diagnostic tools in long-term denervation is merited, in particular if Single Fiber EMG (SFEMG) is combined with Dynamic Echomyography (DyEM), an Ultra Sound muscle approach we recently designed and developed to explore denervated and reinnervating muscles.

SIRT1 Protein, by Blocking the Activities of Transcription Factors FoxO1 and FoxO3, Inhibits Muscle Atrophy and Promotes Muscle Growth

In several cell types, the protein deacetylase SIRT1 regulates the activities of FoxO transcription factors whose activation is critical in muscle atrophy. However, the possible effects of SIRT1 on the activity of FoxOs in skeletal muscle and on the regulation of muscle size have not been investigated. Here, we show that after food deprivation, SIRT1 levels fall dramatically in type II skeletal muscles (tibialis anterior), which show marked atrophy, unlike in the liver (where SIRT1 rises) or heart or the soleus, a type I muscle (where SIRT1 is unchanged). Maintenance of high SIRT1 levels by electroporation in mouse muscle inhibits markedly the muscle wasting induced by fasting as well as by denervation, and these protective effects require its deacetylase activity. SIRT1 overexpression reduces muscle wasting by blocking the activation of FoxO1 and 3. It thus prevents the induction of key atrogenes, including the muscle-specific ubiquitin ligases, atrogin1 and MuRF1, and multiple autophagy (Atg) genes and the increase in overall proteolysis. In normal muscle, SIRT1 overexpression by electroporation causes rapid fiber hypertrophy without, surprisingly, activation of the PI3K-AKT signaling pathway. Thus, SIRT1 activation favors postnatal muscle growth, and its fall appears to be critical for atrophy during fasting. Consequently, SIRT1 activation represents an attractive possible pharmacological approach to prevent muscle wasting and cachexia.