• BMB Reports
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• v.28 no.3
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• pp.191-196
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• 1995

The role of polyamines in skeletal myoblast differentiation was investigated using the polyamine metabolic inhibitor methylglyoxal bis(guanylhydrazone)(MGBG). Concentrations of intracellular free spermidine and spermine increased 2 to 2.5-fold at the onset of myoblast fusion. The systhesis of actin, and creatine kinase activity both dramatically increased during myotube formation. However, MGBG at a concentration of 0.5 mM not only abolished the increase of intracellular free polyamines, but also reduced cell fusion to almost half the level of untreated cells, without noticeable morphological alteration. The production of actin, and creatine kinase activity were almost completely abolished by MGBG. The inhibition of myoblast fusion by MGBG was partially recovered with 0.1 mM of spermidine or spermine added externally. Results indicate that polyamines are necessary for normal myoblast differentiation. Since the first indication of myoblast differentiation is alignment of muscle cells and membrane fusion of adjacent cells, and since polyamine depletion completely inhibited the synthesis of actin, which might be associted with membranes, polyamine might be involved in myoblast differentiation through membrane reorganization events.

• Molecules and Cells
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• v.21 no.2
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• pp.294-301
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• 2006

We have previously reported that phosphorylation of eukaryotic elongation factor 2 (eEF2) is related to the differentiation of chick embryonic muscle cells in culture. In the present study, we found that eEF2 phosphorylation declined shortly after induction of differentiation of L6 myoblasts, when the cells prepare for terminal differentiation by withdrawing from the cell cycle. This decrease in phosphorylation was prevented by inhibitors of phosphoinositide 3-kinase (PI3-kinase) that strongly inhibit myoblast differentiation. We hypothesized that PI3-kinase plays an important role in myoblast differentiation by regulating eEF2 phosphorylation in the early stages of differentiation. To test this hypothesis, myoblasts were synchronized at in $G_2/M$ and cultured in fresh differentiation medium (DM) or growth medium (GM). In DM the released cells accumulated in $G_0$/$G_1$ while in GM they progressed to S phase. In addition, cyclin D1 was more rapidly degraded in DM than in GM, and eEF2 phosphorylation decreased more. Inhibitors of PI3-kinase increased eEF2 phosphorylation, but PI3-kinase became more activated when eEF2 phosphorylation declined. These results suggest that the regulation of L6 myoblast differentiation by PI3-kinase is related to eEF2 phosphorylation.

• Molecules and Cells
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• v.38 no.4
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• pp.362-372
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• 2015

Setdb1, an H3-K9 specific histone methyltransferase, is associated with transcriptional silencing of euchromatic genes through chromatin modification. Functions of Setdb1 during development have been extensively studied in embryonic and mesenchymal stem cells as well as neurogenic progenitor cells. But the role of Sedtdb1 in myogenic differentiation remains unknown. In this study, we report that Setdb1 is required for myogenic potential of C2C12 myoblast cells through maintaining the expressions of MyoD and muscle-specific genes. We find that reduced Setdb1 expression in C2C12 myoblast cells severely delayed differentiation of C2C12 myoblast cells, whereas exogenous Setdb1 expression had little effect on. Gene expression profiling analysis using oligonucleotide microarray and RNA-Seq technologies demonstrated that depletion of Setdb1 results in downregulation of MyoD as well as the components of muscle fiber in proliferating C2C12 cells. In addition, exogenous expression of MyoD reversed transcriptional repression of MyoD promoter-driven luciferase reporter by Setdb1 shRNA and rescued myogenic differentiation of C2C12 myoblast cells depleted of endogenous Setdb1. Taken together, these results provide new insights into how levels of key myogenic regulators are maintained prior to induction of differentiation.

• The Korea Journal of Herbology
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• v.34 no.2
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• pp.59-66
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• 2019

Objectives : Decrease in muscle mass and loss of muscle function due to aging are associated with various diseases. As interest in healthy aging increases, efforts to prevent and treat muscle hypoxia as an illness are increasing. Considering the physical limitations, a pharmacologic approach to the treatment of myopenia is needed. Methods : Terminalia chebula Rets has a wide range of pharmacological effects and is used as a medicinal product in traditional medicine. However, the drug effect on the treatment of muscle disorders has not been revealed. The purpose of this study was to evaluate the value of water extract of Terminalia chebula (WETC) as a therapeutic agent to relieve symptoms of muscle hypoxia. Results : WETC showed strong radical scavenging ability. In addition, WETC increased cell activity of myoblast, and we observed that WETC induces myoblast differentiation by immunoblot analysis using differentiation protein markers as well as cell morphology of myoblast. Based on these results, we examined the effect of chebulic acid, chebulagic acid, gallic acid, geraniin, and punicalagin on cell activity and differentiation of myoblasts. Gallic acid significantly increased cell activity of myoblast, and it was found to be an effective substance which not only induces myoblast differentiation but also promotes proliferation. Conclusions : We suggest that the WETC with antioxidant effect and its indicator gallic acid on cell activity, proliferation and differentiation of myoblast can be studied and developed as a food and medicine for prevention and treatment of various muscle diseases.

• The Korean Journal of Zoology
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• v.32 no.2
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• pp.163-175
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• 1989

Transferrin (Tf) has been known to exert profound effect on the myoblast differentiation in uirto. Therefore, the changes in the amount and affinity of the Tf receptor would accompany the myoblast differentiation. To investigate this possibility, we exarnined the afteration pattern in the level of the Tf receptor during the myoblast fusion. The level of Tf receptor was assayed by measuring the bound 125 I-Tf onto the surface of cultured myoblasts, and it was known that the level of Tf receptor reached the maximum at about 12 hr before the initi ation of the myoblast fusion and decreased as the differentiation proceeded, and that the affinity of Tf receptor to Tf was also decreased. In addition, various inhibitiors of the myoblast fusion also influenced the level of the Tf receptor. Accroding to these results, it is postulated that the level of Tf receptor is highly regulated during the myoblast differentiation.

• Molecules and Cells
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• v.40 no.9
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• pp.667-676
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• 2017

Abnormal differentiation of muscle is closely associated with aging (sarcopenia) and diseases such as cancer and type II diabetes. Thus, understanding the mechanisms that regulate muscle differentiation will be useful in the treatment and prevention of these conditions. Protein lysine acetylation and methylation are major post-translational modification mechanisms that regulate key cellular processes. In this study, to elucidate the relationship between myogenic differentiation and protein lysine acetylation/methylation, we performed a PCR array of enzymes related to protein lysine acetylation/methylation during C2C12 myoblast differentiation. Our results indicated that the expression pattern of HDAC11 was substantially increased during myoblast differentiation. Furthermore, ectopic expression of HDAC11 completely inhibited myoblast differentiation, concomitant with reduced expression of key myogenic transcription factors. However, the catalytically inactive mutant of HDAC11 (H142/143A) did not impede myoblast differentiation. In addition, wild-type HDAC11, but not the inactive HDAC11 mutant, suppressed MyoD-induced promoter activities of MEF2C and MYOG (Myogenin), and reduced histone acetylation near the E-boxes, the MyoD binding site, of the MEF2C and MYOG promoters. Collectively, our results indicate that HDAC11 would suppress myoblast differentiation via regulation of MyoD-dependent transcription. These findings suggest that HDAC11 is a novel critical target for controlling myoblast differentiation.

• Journal of Life Science
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• v.12 no.1
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• pp.55-60
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• 2002

The differentiation of skeletal muscle precursor cells in culture is marked by the transcriptional activation of muscle-specific genes and the morphological differentiation of myoblast into multinucleate myotube. In this study, we examined the effect of TSA (Trichostatin A) on WF-kB DNA binding activity and muscle cell fusion in the process of myogenesis. Under TSA treatment, C2C12 myoblast could not fuse to myotube and its NF-kB DNA binding activity was also blocked. To investigate whether these phenomenons were affected by TSA in direct or not, differentiation media (DM) used to differentiate cells without TSA was concentrated and added to C2C12 myoblast with TSA simultaneously. C2C12 myoblast was fused to myotube and NF-kB DNA binding activity was recovered. These results suggest that TSA affects on the differentiation of myoblast, perhaps through several factors, by inhibiting myoblst fusion and blocking NF-kB DNA binding activity.

• BMB Reports
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• v.49 no.6
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• pp.303-304
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• 2016

Myoblast fusion is important for skeletal muscle formation. Even though the knowledge of myoblast fusion mechanism has accumulated over the years, the initial signal of fusion is yet to be elucidated. Our study reveals the novel function of a phosphatidylserine (PS) receptor, stabilin-2 (Stab2), in the modulation of myoblast fusion, through the recognition of PS exposed on myoblasts. During differentiation of myoblasts, Stab2 expression is higher than other PS receptors and is controlled by calcineurin/NFAT signaling on myoblasts. The forced expression of Stab2 results in an increase in myoblast fusion; genetic ablation of Stab2 in mice causes a reduction in muscle size, as a result of impaired myoblast fusion. After muscle injury, muscle regeneration is impaired in Stab2-deficient mice, resulting in small myofibers with fewer nuclei, which is due to reduction of fusion rather than defection of myoblast differentiation. The fusion-promoting role of Stab2 is dependent on its PS-binding motif, and the blocking of PS-Stab2 binding impairs cell-cell fusion on myoblasts. Given our previous finding that Stab2 recognizes PS exposed on apoptotic cells for sensing as an "eat-me" signal, we propose that PS-Stab2 binding is required for sensing of a "fuse-me" signal as the initial signal of myoblast fusion.

• The Korea Journal of Herbology
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• v.35 no.3
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• pp.25-32
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• 2020

Objectives : At present, aging-related degenerative muscle diseases are considered a serious problem. However, the effects on muscles regarding the efficacy of blueberry have not been studied. In this study, we tried to find out the correlation between blueberry and muscle. Methods : 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay was performed to confirm the antioxidant efficacy of blueberry hydrothermal extract. To determine the effect of blueberry hydrothermal extracts (BHE) on myoblast activity, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay was performed. To confirm the effect of blueberry hydrothermal extracts on the differentiation of myoblast into myotubes, protein expression levels of myosin heavy chain 3 (Myh3) and paired box 3/7 (pax3/7) were confirmed by immunoblot analysis. In addition, immunofluorescence microscopy was performed to confirm the effect on myotube formation of blueberry hydrothermal extracts. Results : Antioxidative efficacy and low toxicity were confirmed through ABTS assay and MTS assay of blueberry extract for myoblasts. As a result of immunoblot analysis and immunofluorescence analysis, the decrease in myogenic marker Pax3/7 was not confirmed, but myotubes The specific expression inhibitory activity of the forming protein Myh3 was confirmed. Through this, it was confirmed that the blueberry extract has a negative activity against myoblast differentiation. Conclusion : This experiment confirmed that blueberry hydrothermal extract has excellent antioxidant efficacy and negative results in inhibiting the differentiation and proliferation of myoblast. This requires deep study of certain ingredients and requires reassessment of the dietary intake of blueberries.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.158-158
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• 2015

Myoblast are myogenic precursors that proliferate, activate, and differentiate on muscle injury to sustain the regenerative capacity of skeletal muscle; The neuronal isoform of nitric oxide synthase (nNOS, termed also NOS-I) is expressed in normal adult skeletal muscle, suggesting important functions for Nitric oxide (NO) in muscle biology1,2,3. However, the expression and subcellular localization of NO in muscle development and myoblast differentiation are largely unknown. In this study, we examined effects of the nitric oxide generated by a microwave plasma torch, on proliferation/differentiation of rat myoblastic L6 cells. Experimental data pertaining to nitric oxide production are presented in terms of the oxygen input in units of cubic centimetres per minute. The various levels of nitric oxide are observed depending on the flow rate of nitrogen gas, the ratio of oxygen gas, and the microwave power4. In order to evaluate the potential of nitric oxide as an activator of cell differentiation, we applied nitric oxide generated from the microwave plasma torch to L6 skeletal muscles. Differentiation of L6 cells into myotubes was significantly enhanced the differentiation after nitric oxide treatment. Nitric oxide treatment also increase the expression of myogenesis marker proteins and mRNA level, such as myogenin and myosin heavy chain (MHC), as well as cyclic guanosine monophosphate (cGMP), However during the myotube differentiation we found that NO activate oxidative stress signaling erks expression. Therefore, these results establish a role of NO and cGMP in regulating myoblast differentiation and elucidate their mechanism of action, providing a direct link with oxidative stress signalling, which is a key player in myogenesis. Based on these findings, nitric oxide generated by plasma can be used as a possible activator of cell differentiation and tissue regeneration.