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Background Duchenne muscular dystrophy (DMD) is an X-linked lethal genetic disorder for which there is no effective treatment. Previous studies have shown that stem cell transplantation into mdx mice can promote muscle regeneration and improve muscle function, however, the specific molecular mechanisms remain unclear. DMD suffers varying degrees of hypoxic damage during disease progression. This study aimed to investigate whether induced pluripotent stem cells (iPSCs) have protective effects against hypoxia-induced skeletal muscle injury. Results In this study, we co-cultured iPSCs with C2C12 myoblasts using a Transwell nested system and placed them in a DG250 anaerobic workstation for oxygen deprivation for 24 h. We found that iPSCs reduced the levels of lactate dehydrogenase and reactive oxygen species and downregulated the mRNA and protein levels of BAX/BCL2 and LC3II/ LC3I in hypoxia-induced C2C12 myoblasts. Meanwhile, iPSCs decreased the mRNA and protein levels of atrogin-1 and MuRF-1 and increased myotube width. Furthermore, iPSCs downregulated the phosphorylation of AMPKA and ULK1 in C2C12 myotubes exposed to hypoxic damage. Conclusions Our study showed that iPSCs enhanced the resistance of C2C12 myoblasts to hypoxia and inhibited apoptosis and autophagy in the presence of oxidative stress. Further, iPSCs improved hypoxia-induced autophagy and atrophy of C2C12 myotubes through the AMPK/ULK1 pathway. This study may provide a new theoretical basis for the treatment of muscular dystrophy in stem cells.
ABSTRACT
BACKGROUND: The regulation of mitochondrial energy metabolism by adenylate activated protein kinase (AMPK) is an important cause of fat accumulation in obese and type 2 diabetic patients. Chronic inflammation will further induce skeletal muscle atrophy. Aerobic exercise can increase the activity of AMPK and regulate energy metabolism, but the mechanism of aerobic exercise in improving skeletal muscle atrophy in type 2 diabetes by increasing AMPK is unclear. OBJECTIVE: To explore the effect of aerobic exercise on skeletal muscle atrophy in type 2 diabetic rats and the role of AMPK. METHODS: The model of type 2 diabetic rats was established by high fat feeding and streptozotocin injection, and the rats were divided into four groups: control group (n=6), exercise group (n=9), diabetic control group (n=8) and diabetic exercise group (n=12). The control group and the diabetic control group were kept for 4 weeks, and the exercise group and the diabetic exercise group were given aerobic exercise intervention for 4 weeks. After 4 weeks of aerobic exercise (running speed 16 m/min, 60 min/d, 5 days/week), the muscle atrophy of soleus was observed by immunohistochemical staining. The expression levels of AMPK, PGC-1 α, MAFbx and MuRF1 were detected by western blot assay. The study protocol was approved by the Ethical Committee of School of Sport Science, Beijing Sport University in China on June 25, 2016, with approval No. 2016014. RESULTS AND CONCLUSION: Blood glucose of type 2 diabetes rats was significantly increased, and body weight and insulin levels of type 2 diabetes rats were significantly decreased (P < 0.01). The mean cross sectional area of soleus fiber in the diabetic group was significantly lower than that in the control group (P < 0.01), and the cross sectional area of soleus muscle fiber in the diabetic exercise group was significantly higher than that in the diabetic group (P < 0.01). The expression levels of AMPK and PGC-1 α in the soleus muscle of diabetic rats were significantly lower than those in the control group, and the expression levels of MAFbx and MuRF1 were significantly higher than those in the control group (P < 0.01). The expression levels of AMPK, MAFbx and MuRF1 in the diabetic exercise group were significantly higher than those in the diabetic group (P < 0.01). These results suggest that aerobic exercise can improve mitochondrial function, inhibit the expression of MAFbx and MuRF1, improve skeletal muscle atrophy and restore the metabolic balance of type 2 diabetes mellitus to some extent by activating AMPK/PGC-1α signaling pathway.
ABSTRACT
This study had as objective to analyze the acute eff ects of resistance exercise (RE) on the mRNA levels of the following genes (MyoD, myogenin, IGF-1, atrogin-1, MuRF-1, and myostatin) in rheumatoid arthritis (experimental arthritis). Therefore, 26 females rats were randomly allocated into four groups, control (CT, n=7), exercise (Ex, n=6), rheumatoid arthritis (RA, n=6) and RA with exercise (RAEx, n=7). Met-BSA was injected into the tibiotarsal joint in the RA and RAEx groups. After 15 days from injection, the animals were submitted to an acute bout of RE and six hours post protocol the animals were euthanized. We evaluated the joint thickness, infl ammation score, cross-sectional area (CSA) of gastrocnemius muscle fi bers and mRNA expression of the IGF-1, MyoD, myogenin, myostatin, MuRF-1, atrogin-1 and GAPDH. It was observed that the joint thickness and score strongly increased in arthritic rats (p <0.001) while the CSA decreased (p ≤ 0.05). Increased mRNA levels of IGF-1 (2.0 fold), myostatin (4.5 fold), atrogin-1 (2.5 fold), MyoD (3.7-fold) and myogenin (5 fold) were observed in muscle of arthritic rats. The mRNA expression of myostatin, atrogin-1, MyoD and myogenin decreased in the RAEx group. In this way, we can conclude that experimental arthritis-increased gene expressions in muscle atrophy myostatin, atrogin-1, MyoD and myogenin) are restored back to control as a response to acute RE....(AU)
O presente estudo teve como objetivo analisar o efeito agudo do Exercício com pesos sobre os níves de mRNA de genes envolvidos no anabolismo ou catabolismo muscular em um modelo experimental de Artrite Reumatóide. Para tanto, 26 ratas fêmeas foram randomicamente alocadas em quatro grupos, controle (CT, n=7), Exercício (Ex, n=6), Artrite Reumatóide (AR, n=6) e Artrite Reumatóide com exercício (AREx, n=7). Uma substância contendo Albumina bovina metilada foi injetada na articulação tíbio-tarsal nos grupos AR e AREx para indução da Artrite Reumatóide. Após 15 dias da injeção, os animais foram submetidos a um estímulo agudo de treinamento com pesos e 6 horas após o exercício os animais foram eutanasiados. Nós avaliamos a espessura da articulação, escore de infl amação, a área de secção transversa (AST) das fi bras do músculo Gastrocnêmio e a mRNA de IGF-1, MyoD, Myogenina (genes envolvidos no anabolismo muscular), e MuRF-1, atrogina-1 (genes envolvidos no catabolismo muscular), além do gene controle , GAPDH. Foi observado que a espessura articular e o escore de infl amação aumentaram fortemente nas ratas induzidas a Artrite Reumatóide (p <0,001), enquanto a AST reduziu (p ≤ 0,05). Um aumento nos níveis de mRNA de IGF-1 (2,0 vezes), miostatina (4,5 vezes), atrogina-1 (2,5 vezes), MyoD (3,7 vezes) e miogenina (5 vezes) foi observado no músculo das ratas induzidas a Artrite Reumatóide. mRNA de miostatina, atrogina-1, MyoD e miogenina reduziu no grupo RAEx. Desta forma, podemos concluir, que o modelo experimental de Artrite Reumatóide induziu um aumento da expressão de genes durante a atrofi a muscular (myostatin, atrogin-1, MyoD and myogenin) e que estas alterações foram reguladas pelo Exercício com peso....(AU)
Subject(s)
Animals , Rats , Cachexia , MyoD Protein , Myogenin , Myostatin , Physical Education and TrainingABSTRACT
ObjectiveTo study the effect of berberine on diabetes or insulin resistance accompanied with reduction of skeletal moscle and wasting in db/db mice.Methods db/db mouse-a model of diabetes/insulin-resistance was studied,with the wild type mouse as control.After being treated with berberine ( 5 mg · kg-1 · d-1 ) for 3 weeks,the muscle size of tibia anterior (TA) of the animals was measured after staining with laminine/Hyosin Heavy chain-Slow using immunochemistry,then observed under fluorescent microscope and calculated with software.The rate of [ 14 C ] -Phenalanine incorporation into the uuscle was measured to analyze the protein synthesis,and the [ 3 H ] -Tyrosine released into the medium was determined in order to analyze protein degradation.The mRNA expressions of muscle atrophy Fbox-1 ( Atrogin-1 ) and muscle ring finger-1 ( MuRF-1 ) were measured by Northern blot.Results With berberine treatment,blood glucose and fat levels were lowered [ ( 18.55 ± 3.79 vs 26.32 ± 4.02 ) mmol/L,P＜0.01 ; ( 2.75 ± 0.30 vs 3.77 ± 0.52 ) g,P＜0.05 ],but tibia anterior muscle weight/length ratio and cross-section area were decreased,rates of protein synthesis in isolated muscles of db/db mice were decreased by 18％ -22％,and the rates of degradation were significantly raised by 24％ -26％ after berberine treatment.There also was increased the transcription and translation of Atrogin-1 and MuRF-1,accompanied with decreased eukaryotic initiation factor 3 subunit (eIF3-f)protein level simultaneously. ConclusionBerberine improves hyperglycemia and insulin resistance by down-regulating blood sugar and body fat,but it causes reduced protein synthesis and minimally enhanced protein degradation.The mechanism might be related to berberine-induced up-regulating Atrogin-1 、MurF-1 and down-regulating eIF3-f.
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[Objective]Skeletal Muscle atrophy is induced in response to unloading by Hindlimb Suspension (HS). Numerous studies have been performed to prevent Skeletal Muscle atrophy. However, the molecular mechanisms underlying Electro-acupuncture (EA) on skeletal muscle have not been identified, and the effect of EA to prevent skeletal muscle atrophy is unknown. Therefore, we aimed to determine the effect of EA and Chishin (where the needles are kept in muscle for thirty minutes) on skeletal muscle atrophy in an animal experiment.<BR>[Methods]Twenty mice (8 week, C57BL6) were randomly grouped into 4 groups;Normal group (N group), Hindlimb Suspension Group (HS group), HS +Chishin group (Chishin group), and HS +EA 1Hz group (1Hz group) (n = 5/group, respectively). Acupuncture interventions were conducted on the gastrocnemius of the Chishin and 1Hz groups. We measured the muscle mass, the cross sectional area, the percentage of Antrogin-1 and MuRF1 (Atrophy related E3ubiquitin ligases) expressions of the soleus 0f each mouse at 2 weeks after acupuncture interventions.<BR>[Result]The weight and Cross sectional area of the soleus of the 1Hz group were significantly greater than the HS group (P<0.01, P<0.01, respectively). On the contrary, the percentage of Atrogin-1 and MuRF1 expressions of the 1Hz group was significantly less than the HS groups (P<0.01, P<0.05, respectively).<BR>[Conclusion]These results suggest that EA and Chishin may influence the activity of Atrogin-1 &MuRF1 expression.