RESUMO
Accumulating evidence indicates that the MDM2 oncoprotein promotes tumorigenesis beyond its canonical negative effects on the p53 tumor suppressor, but these p53-independent functions remain poorly understood. Here, we show that a fraction of endogenous MDM2 is actively imported in mitochondria to control respiration and mitochondrial dynamics independently of p53. Mitochondrial MDM2 represses the transcription of NADH-dehydrogenase 6 (MT-ND6) in vitro and in vivo, impinging on respiratory complex I activity and enhancing mitochondrial ROS production. Recruitment of MDM2 to mitochondria increases during oxidative stress and hypoxia. Accordingly, mice lacking MDM2 in skeletal muscles exhibit higher MT-ND6 levels, enhanced complex I activity, and increased muscular endurance in mild hypoxic conditions. Furthermore, increased mitochondrial MDM2 levels enhance the migratory and invasive properties of cancer cells. Collectively, these data uncover a previously unsuspected function of the MDM2 oncoprotein in mitochondria that play critical roles in skeletal muscle physiology and may contribute to tumor progression.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/patologia , Transformação Celular Neoplásica/patologia , Complexo I de Transporte de Elétrons/metabolismo , Regulação Neoplásica da Expressão Gênica , Mitocôndrias/patologia , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenocarcinoma/patologia , Animais , Carcinoma Pulmonar de Células não Pequenas/genética , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Movimento Celular , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Complexo I de Transporte de Elétrons/genética , Genoma Mitocondrial , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/metabolismo , Invasividade Neoplásica , Estresse Oxidativo , Proteínas Proto-Oncogênicas c-mdm2/genética , Transdução de Sinais , Transcrição Gênica , Células Tumorais Cultivadas , Proteína Supressora de Tumor p53/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Dystrophin deficiency alters the sarcolemma structure, leading to muscle dystrophy, muscle disuse, and ultimately death. Beyond limb muscle deficits, patients with Duchenne muscular dystrophy have numerous transit disorders. Many studies have highlighted the strong relationship between gut microbiota and skeletal muscle. The aims of this study were: i) to characterize the gut microbiota composition over time up to 1 year in dystrophin-deficient mdx mice, and ii) to analyze the intestine structure and function and expression of genes linked to bacterial-derived metabolites in ileum, blood, and skeletal muscles to study interorgan interactions. Mdx mice displayed a significant reduction in the overall number of different operational taxonomic units and their abundance (α-diversity). Mdx genotype predicted 20% of ß-diversity divergence, with a large taxonomic modification of Actinobacteria, Proteobacteria, Tenericutes, and Deferribacteres phyla and the included genera. Interestingly, mdx intestinal motility and gene expressions of tight junction and Ffar2 receptor were down-regulated in the ileum. Concomitantly, circulating inflammatory markers related to gut microbiota (tumor necrosis factor, IL-6, monocyte chemoattractant protein-1) and muscle inflammation Tlr4/Myd88 pathway (Toll-like receptor 4, which recognizes pathogen-associated molecular patterns) were up-regulated. Finally, in mdx mice, adiponectin was reduced in blood and its receptor modulated in muscles. This study highlights a specific gut microbiota composition and highlights interorgan interactions in mdx physiopathology with gut microbiota as the potential central metabolic organ.
Assuntos
Distrofina , Microbioma Gastrointestinal , Distrofia Muscular de Duchenne , Animais , Humanos , Camundongos , Distrofina/deficiência , Distrofina/genética , Camundongos Endogâmicos mdx , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patologiaRESUMO
The objective of the present study was to determine the effects of dry immersion, an innovative ground-based human model of simulated microgravity and extreme physical inactivity, on iron homeostasis and distribution. Twenty young healthy men were recruited and submitted to 5 days of dry immersion (DI). Fasting blood samples and MRI were performed before and after DI exposure to assess iron status, as well as hematological responses. DI increased spleen iron concentrations (SIC), whereas hepatic iron store (HIC) was not affected. Spleen iron sequestration could be due to the concomitant increase in serum hepcidin levels (P < .001). Increased serum unconjugated bilirubin, as well as the rise of serum myoglobin levels support that DI may promote hemolysis and myolysis. These phenomena could contribute to the concomitant increase of serum iron and transferrin saturation levels (P < .001). As HIC remained unchanged, increased serum hepcidin levels could be due both to higher transferrin saturation level, and to low-grade pro-inflammatory as suggested by the significant rise of serum ferritin and haptoglobin levels after DI (P = .003 and P = .003, respectively). These observations highlight the need for better assessment of iron metabolism in bedridden patients, and an optimization of the diet currently proposed to astronauts.
Assuntos
Ferro/metabolismo , Simulação de Ausência de Peso/efeitos adversos , Adulto , Repouso em Cama/efeitos adversos , Bilirrubina/sangue , Ferritinas/sangue , Hepcidinas/sangue , Humanos , Imersão , Fígado/metabolismo , Masculino , Mioglobina/sangue , Baço/metabolismo , Transferrina/análise , Simulação de Ausência de Peso/métodosRESUMO
NEW FINDINGS: What is the central question of this study? Could skeletal muscle be involved in microgravity-induced iron misdistribution by modulating expression of hepcidin, the master regulator of iron metabolism? What is the main finding and its importance? We demonstrate, in rats, that hepcidin upregulation is not a transient adaptation associated with early exposure to microgravity and that intermittent reloading does not limit microgravity-induced iron misdistribution despite having a beneficial effect on soleus muscle wasting. ABSTRACT: In humans, exposure to microgravity during spaceflight causes muscle atrophy, changes in iron storage and a reduction in iron availability. We previously observed that during 7 days of simulated microgravity in rats, hepcidin plays a key role in iron misdistribution, and we suggested that a crosstalk between skeletal muscle and liver could regulate hepcidin synthesis in this context. In the present study in rats, we investigated the medium-term effects of simulated microgravity on iron metabolism. We also tested whether intermittent reloading (IR) to target skeletal muscle atrophy limits iron misdistribution efficiently. For this purpose, Wistar rats underwent 14 days of hindlimb unloading (HU) combined or not combined with daily IR. At the end of this period, the serum iron concentration and transferrin saturation were significantly reduced, whereas hepatic hepcidin mRNA was upregulated. However, the main signalling pathways involved in hepcidin synthesis in the liver (BMP-small mothers against decapentaplegic (SMAD), interleukin-6-STAT3 and ERK1/2) were unaffected. Unlike what was observed after 7 days of HU, the iron concentration in the spleen, liver and skeletal muscle was comparable between control animals and those that underwent HU or HU plus IR for 14 days. Despite its beneficial effect on soleus muscle atrophy and slow-to-fast myosin heavy chain distribution, IR did not significantly prevent a reduction in iron availability and hepcidin upregulation. Altogether, these results highlight that iron availability is durably reduced during longer exposure to simulated microgravity and that the related hepcidin upregulation is not a transient adaptation to these conditions. The results also suggest that skeletal muscle does not necessarily play a key role in the iron misdistribution that occurs during simulated microgravity.
Assuntos
Hepcidinas/metabolismo , Elevação dos Membros Posteriores/fisiologia , Membro Posterior/metabolismo , Ferro/metabolismo , Músculo Esquelético/metabolismo , Animais , Masculino , Atrofia Muscular/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Ratos Wistar , Regulação para CimaRESUMO
Gut microbiota is involved in the development of several chronic diseases, including diabetes, obesity, and cancer, through its interactions with the host organs. It has been suggested that the cross talk between gut microbiota and skeletal muscle plays a role in different pathological conditions, such as intestinal chronic inflammation and cachexia. However, it remains unclear whether gut microbiota directly influences skeletal muscle function. In this work, we studied the impact of gut microbiota modulation on mice skeletal muscle function and investigated the underlying mechanisms. We determined the consequences of gut microbiota depletion after treatment with a mixture of a broad spectrum of antibiotics for 21 days and after 10 days of natural reseeding. We found that, in gut microbiota-depleted mice, running endurance was decreased, as well as the extensor digitorum longus muscle fatigue index in an ex vivo contractile test. Importantly, the muscle endurance capacity was efficiently normalized by natural reseeding. These endurance changes were not related to variation in muscle mass, fiber typology, or mitochondrial function. However, several pertinent glucose metabolism markers, such as ileum gene expression of short fatty acid chain and glucose transporters G protein-coupled receptor 41 and sodium-glucose cotransporter 1 and muscle glycogen level, paralleled the muscle endurance changes observed after treatment with antibiotics for 21 days and reseeding. Because glycogen is a key energetic substrate for prolonged exercise, modulating its muscle availability via gut microbiota represents one potent mechanism that can contribute to the gut microbiota-skeletal muscle axis. Taken together, our results strongly support the hypothesis that gut bacteria are required for host optimal skeletal muscle function.
Assuntos
Metabolismo Energético/fisiologia , Microbioma Gastrointestinal/fisiologia , Glucose/metabolismo , Músculo Esquelético/fisiologia , Animais , Antibacterianos/farmacologia , Disbiose/induzido quimicamente , Disbiose/metabolismo , Disbiose/microbiologia , Disbiose/fisiopatologia , Metabolismo Energético/efeitos dos fármacos , Microbioma Gastrointestinal/efeitos dos fármacos , Glicogênio/metabolismo , Homeostase/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Contração Muscular/efeitos dos fármacos , Contração Muscular/fisiologia , Músculo Esquelético/efeitos dos fármacosRESUMO
Myostatin (Mstn) inactivation or inhibition is considered as a promising treatment for various muscle-wasting disorders because it promotes muscle growth. However, myostatin-deficient hypertrophic muscles show strong fatigability associated with abnormal mitochondria and lipid metabolism. Here, we investigated whether endurance training could improve lipid metabolism and mitochondrial membrane lipid composition in mice where the Mstn gene was genetically ablated (Mstn-/- mice). In Mstn-/- mice, 4 weeks of daily running exercise sessions (65-70% of the maximal aerobic speed for 1 h) improved significantly aerobic performance, particularly the endurance capacity (up to +280% compared with untrained Mstn-/- mice), to levels comparable to those of trained wild type (WT) littermates. The expression of oxidative and lipid metabolism markers also was increased, as indicated by the upregulation of the Cpt1, Ppar-δ and Fasn genes. Moreover, endurance training also increased, but far less than WT, citrate synthase level and mitochondrial protein content. Interestingly endurance training normalized the cardiolipin fraction in the mitochondrial membrane of Mstn-/- muscle compared with WT. These results suggest that the combination of myostatin inhibition and endurance training could increase the muscle mass while preserving the physical performance with specific effects on cardiolipin and lipid-related pathways.
Assuntos
Deleção de Genes , Metabolismo dos Lipídeos , Miostatina/genética , Animais , Lipidômica , Masculino , Camundongos , Camundongos Knockout , Miostatina/metabolismo , Condicionamento Físico Animal , Resistência Física , CorridaRESUMO
BACKGROUND: Skeletal muscle atrophy is a common feature of numerous chronic pathologies and is correlated with patient mortality. The REDD1 protein is currently recognized as a negative regulator of muscle mass through inhibition of the Akt/mTORC1 signaling pathway. REDD1 expression is notably induced following glucocorticoid secretion, which is a component of energy stress responses. RESULTS: Unexpectedly, we show here that REDD1 instead limits muscle loss during energetic stresses such as hypoxia and fasting by reducing glycogen depletion and AMPK activation. Indeed, we demonstrate that REDD1 is required to decrease O2 and ATP consumption in skeletal muscle via reduction of the extent of mitochondrial-associated endoplasmic reticulum membranes (MAMs), a central hub connecting energy production by mitochondria and anabolic processes. In fact, REDD1 inhibits ATP-demanding processes such as glycogen storage and protein synthesis through disruption of the Akt/Hexokinase II and PRAS40/mTORC1 signaling pathways in MAMs. Our results uncover a new REDD1-dependent mechanism coupling mitochondrial respiration and anabolic processes during hypoxia, fasting, and exercise. CONCLUSIONS: Therefore, REDD1 is a crucial negative regulator of energy expenditure that is necessary for muscle adaptation during energetic stresses. This present study could shed new light on the role of REDD1 in several pathologies associated with energetic metabolism alteration, such as cancer, diabetes, and Parkinson's disease.
Assuntos
Metabolismo Energético/genética , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Estresse Fisiológico/genética , Fatores de Transcrição/fisiologia , Adaptação Fisiológica/genética , Animais , Hipóxia Celular , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Camundongos , Atrofia Muscular/genética , Transdução de Sinais , Fatores de Transcrição/genéticaRESUMO
Myostatin (Mstn) deficiency leads to skeletal muscle overgrowth and Mstn inhibition is considered as a promising treatment for muscle-wasting disorders. Mstn gene deletion in mice also causes metabolic changes with decreased mitochondria content, disturbance in mitochondrial respiratory function and increased muscle fatigability. However the impact of MSTN deficiency on these metabolic changes is not fully elucidated. Here, we hypothesized that lack of MSTN will alter skeletal muscle membrane lipid composition in relation with pronounced alterations in muscle function and metabolism. Indeed, phospholipids and in particular cardiolipin mostly present in the inner mitochondrial membrane, play a crucial role in mitochondria function and oxidative phosphorylation process. We observed that Mstn KO muscle had reduced fat membrane transporter levels (FAT/CD36, FABP3, FATP1 and FATP4) associated with decreased lipid oxidative pathway (citrate synthase and ß-HAD activities) and impaired lipogenesis (decreased triglyceride and free fatty acid content), indicating a role of mstn in muscle lipid metabolism. We further analyzed phospholipid classes and fatty acid composition by chromatographic methods in muscle and mitochondrial membranes. Mstn KO mice showed increased levels of saturated and polyunsaturated fatty acids at the expense of monounsaturated fatty acids. We also demonstrated, in this phenotype, a reduction in cardiolipin proportion in mitochondrial membrane versus the proportion of others phospholipids, in relation with a decrease in the expression of phosphatidylglycerolphosphate synthase and cardiolipin synthase, enzymes involved in cardiolipin synthesis. These data illustrate the importance of lipids as a link by which MSTN deficiency can impact mitochondrial bioenergetics in skeletal muscle.
Assuntos
Ácidos Graxos/metabolismo , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Miostatina/deficiência , 3-Hidroxiacil-CoA Desidrogenases/genética , 3-Hidroxiacil-CoA Desidrogenases/metabolismo , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Citrato (si)-Sintase/genética , Citrato (si)-Sintase/metabolismo , Ácidos Graxos/genética , Masculino , Camundongos , Camundongos Knockout , Mitocôndrias Musculares/genética , Mitocôndrias Musculares/patologia , Músculo Esquelético/patologia , OxirreduçãoRESUMO
Duchenne muscular dystrophy (DMD) is characterized by myofiber death from apoptosis or necrosis, leading in many patients to fatal respiratory muscle weakness. Among other pathological features, DMD muscles show severely deranged metabolic gene regulation and mitochondrial dysfunction. Defective mitochondria not only cause energetic deficiency, but also play roles in promoting myofiber atrophy and injury via opening of the mitochondrial permeability transition pore. Autophagy is a bulk degradative mechanism that serves to augment energy production and eliminate defective mitochondria (mitophagy). We hypothesized that pharmacological activation of AMP-activated protein kinase (AMPK), a master metabolic sensor in cells and on-switch for the autophagy-mitophagy pathway, would be beneficial in the mdx mouse model of DMD. Treatment of mdx mice for 4 weeks with an established AMPK agonist, AICAR (5-aminoimidazole-4-carboxamide-1-ß-d-ribofuranoside), potently triggered autophagy in the mdx diaphragm without inducing muscle fiber atrophy. In AICAR-treated mdx mice, the exaggerated sensitivity of mdx diaphragm mitochondria to calcium-induced permeability transition pore opening was restored to normal levels. There were associated improvements in mdx diaphragm histopathology and in maximal force-generating capacity, which were not linked to increased mitochondrial biogenesis or up-regulated utrophin expression. These findings suggest that agonists of AMPK and other inducers of the autophagy-mitophagy pathway can help to promote the elimination of defective mitochondria and may thus serve as useful therapeutic agents in DMD.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Autofagia , Diafragma/enzimologia , Diafragma/patologia , Distrofia Muscular Animal/enzimologia , Distrofia Muscular Animal/patologia , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Animais , Diafragma/fisiopatologia , Diafragma/ultraestrutura , Metabolismo Energético/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Técnicas In Vitro , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Poro de Transição de Permeabilidade Mitocondrial , Complexos Multiproteicos , Contração Muscular/efeitos dos fármacos , Distrofia Muscular Animal/fisiopatologia , Oxirredução/efeitos dos fármacos , Proteínas/metabolismo , Ribonucleotídeos/farmacologia , Transdução de Sinais/efeitos dos fármacos , Serina-Treonina Quinases TORRESUMO
Loss of myostatin (mstn) function leads to a decrease in mitochondrial content, a reduced expression of cytochrome c oxidase, and a lower citrate synthase activity in skeletal muscle. These data suggest functional or ultrastructural mitochondrial abnormalities that can impact on muscle endurance characteristics in such phenotype. To address this issue, we investigated subsarcolemmal and intermyofibrillar (IMF) mitochondrial activities, skeletal muscle redox homeostasis, and muscle fiber endurance quality in mstn-deficient mice [mstn knockout (KO)]. We report that lack of mstn induced a decrease in the coupling of IMF mitochondria respiration, with significantly higher basal oxygen consumption. No lysis of mitochondrial cristae or excessive swelling were observed in mstn KO mice compared with wild-type (WT) mice. Concerning redox status, mstn KO gastrocnemius exhibited a significant decrease in lipid peroxidation levels (-56%; P < 0.01 vs. WT) together with a significant upregulation of the antioxidant glutathione system. In contrast, superoxide dismutase and catalase activities were altered in mstn KO, gastrocnemius and soleus with a reduction of up to 80% compared with WT animals. The force production observed after contractile endurance test was significantly lower in extensor digitorum longus and soleus muscles of mstn KO mice compared with the controls (17 ± 3 and 36 ± 5% vs. 28 ± 4 and 56 ± 5%, respectively, P < 0.05). Together, these findings indicate that, besides an increased skeletal muscle mass, genetic mstn inhibition has differential effects on redox homeostasis and mitochondrial function that would have functional consequences on muscle response to endurance exercise.
Assuntos
Tolerância ao Exercício , Mitocôndrias Musculares/metabolismo , Contração Muscular , Miofibrilas/metabolismo , Miostatina/metabolismo , Estresse Oxidativo , Animais , Biomarcadores/metabolismo , Citrato (si)-Sintase/metabolismo , Técnicas In Vitro , Peroxidação de Lipídeos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Mitocôndrias Musculares/ultraestrutura , Desenvolvimento Muscular , Músculo Esquelético/enzimologia , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Miofibrilas/ultraestrutura , Miostatina/genética , Oxirredução , Fosforilação OxidativaRESUMO
RATIONALE: Diaphragmatic function is a major determinant of the ability to successfully wean patients from mechanical ventilation (MV). Paradoxically, MV itself results in a rapid loss of diaphragmatic strength in animals. However, very little is known about the time course or mechanistic basis for such a phenomenon in humans. OBJECTIVES: To determine in a prospective fashion the time course for development of diaphragmatic weakness during MV; and the relationship between MV duration and diaphragmatic injury or atrophy, and the status of candidate cellular pathways implicated in these phenomena. METHODS: Airway occlusion pressure (TwPtr) generated by the diaphragm during phrenic nerve stimulation was measured in short-term (0.5 h; n = 6) and long-term (>5 d; n = 6) MV groups. Diaphragmatic biopsies obtained during thoracic surgery (MV for 2-3 h; n = 10) and from brain-dead organ donors (MV for 24-249 h; n = 15) were analyzed for ultrastructural injury, atrophy, and expression of proteolysis-related proteins (ubiquitin, nuclear factor-κB, and calpains). MEASUREMENTS AND MAIN RESULTS: TwPtr decreased progressively during MV, with a mean reduction of 32 ± 6% after 6 days. Longer periods of MV were associated with significantly greater ultrastructural fiber injury (26.2 ± 4.8 vs. 4.7 ± 0.6% area), decreased cross-sectional area of muscle fibers (1,904 ± 220 vs. 3,100 ± 329 µm²), an increase of ubiquitinated proteins (+19%), higher expression of p65 nuclear factor-κB (+77%), and greater levels of the calcium-activated proteases calpain-1, -2, and -3 (+104%, +432%, and +266%, respectively) in the diaphragm. CONCLUSIONS: Diaphragmatic weakness, injury, and atrophy occur rapidly in critically ill patients during MV, and are significantly correlated with the duration of ventilator support.
Assuntos
Diafragma/lesões , Debilidade Muscular/etiologia , Respiração Artificial/efeitos adversos , Adulto , Calpaína/análise , Diafragma/química , Diafragma/patologia , Diafragma/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Debilidade Muscular/patologia , Debilidade Muscular/fisiopatologia , Atrofia Muscular/etiologia , Atrofia Muscular/patologia , Atrofia Muscular/fisiopatologia , Fatores de Tempo , Fator de Transcrição RelA/análise , Proteínas Ubiquitinadas/análise , Adulto JovemRESUMO
The human gut microbiota is currently the focus of converging interest in many diseases and sports performance. This review presents gut microbiota as a real "orchestra conductor" in the host's physio(patho)logy due to its implications in many aspects of health and disease. Reciprocally, gut microbiota composition and activity are influenced by many different factors, such as diet and physical activity. Literature data have shown that macro- and micro-nutrients influence gut microbiota composition. Cumulative data indicate that gut bacteria are sensitive to modulation by physical activity, as shown by studies using training and hypoactivity models. Sports performance studies have also presented interesting and promising results. Therefore, gut microbiota could be considered a "pivotal" organ for health and sports performance, leading to a new concept: the nutrition-microbiota-physical activity triad. The next challenge for the scientific and medical communities is to test this concept in clinical studies. The long-term aim is to find the best combination of the three elements of this triad to optimize treatments, delay disease onset, or enhance sports performance. The many possibilities offered by biotic supplementation and training modalities open different avenues for future research.
Assuntos
Desempenho Atlético , Microbioma Gastrointestinal , Microbiota , Exercício Físico , Humanos , Estado NutricionalRESUMO
Myostatin deficiency leads to extensive skeletal muscle hypertrophy, but its consequence on post-mortem muscle proteolysis is unknown. Here, we compared muscle myofibrillar protein degradation, and autophagy, ubiquitin-proteasome and Ca2+-dependent proteolysis relative to the energetic and redox status in wild-type (WT) and myostatin knock-out mice (KO) during early post-mortem storage. KO muscles showed higher degradation of myofibrillar proteins in the first 24 h after death, associated with preserved antioxidant status, compared with WT muscles. Analysis of key autophagy and ubiquitin-proteasome system markers indicated that these two pathways were not upregulated in post-mortem muscle (both genotypes), but basal autophagic flux and ATP content were lower in KO muscles. Proteasome and caspase activities were not different between WT and KO mice. Conversely, calpain activity was higher in KO muscles, concomitantly with higher troponin T and desmin degradation. Altogether, these results suggest that calpains but not the autophagy, proteasome and caspase systems, explain the difference in post-mortem muscle protein proteolysis between both genotypes.
Assuntos
Calpaína , Miostatina , Animais , Calpaína/genética , Calpaína/metabolismo , Inativação Gênica , Camundongos , Músculo Esquelético/metabolismo , Miostatina/genética , ProteóliseRESUMO
Gut microbiota, a major contributor to human health, is influenced by physical activity and diet, and displays a functional cross-talk with skeletal muscle. Conversely, few data are available on the impact of hypoactivity, although sedentary lifestyles are widespread and associated with negative health and socio-economic impacts. The study aim was to determine the effect of Dry Immersion (DI), a severe hypoactivity model, on the human gut microbiota composition. Stool samples were collected from 14 healthy men before and after 5 days of DI to determine the gut microbiota taxonomic profiles by 16S metagenomic sequencing in strictly controlled dietary conditions. The α and ß diversities indices were unchanged. However, the operational taxonomic units associated with the Clostridiales order and the Lachnospiraceae family, belonging to the Firmicutes phylum, were significantly increased after DI. Propionate, a short-chain fatty acid metabolized by skeletal muscle, was significantly reduced in post-DI stool samples. The finding that intestine bacteria are sensitive to hypoactivity raises questions about their impact and role in chronic sedentary lifestyles.
Assuntos
Microbioma Gastrointestinal/fisiologia , Descanso/fisiologia , Comportamento Sedentário , Adulto , Fezes/química , Fezes/microbiologia , Voluntários Saudáveis , Humanos , Imersão/fisiopatologia , Masculino , Propionatos/metabolismo , Simulação de Ausência de PesoRESUMO
Myostatin (mstn) blockade, resulting in muscle hypertrophy, is a promising therapy to counteract age-related muscle loss. However, oxidative and mitochondrial deficit observed in young mice with myostatin inhibition could be detrimental with aging. The aim of this study was (a) to bring original data on metabolic and mitochondrial consequences of mstn inhibition in old mice, and (b) to examine whether 4-weeks of AICAR treatment, a pharmacological compound known to upregulate oxidative metabolism, may be useful to improve exercise capacity and mitochondrial deficit of 20-months mstn KO versus wild-type (WT) mice. Our results show that despite the enlarged muscle mass, the oxidative and mitochondrial deficit associated with reduced endurance running capacity is maintained in old mstn KO mice but not worsened by aging. Importantly, AICAR treatment induced a significant beneficial effect on running limit time only in old mstn KO mice, with a marked increase in PGC-1α expression and slight beneficial effects on mitochondrial function. We showed that AICAR effects were autophagy-independent. This study underlines the relevance of aged muscle remodelling by complementary approaches that impact both muscle mass and function, and suggest that mstn inhibition and aerobic metabolism activators should be co-developed for delaying age-related deficits in skeletal muscle.
Assuntos
Envelhecimento , Aminoimidazol Carboxamida/análogos & derivados , Hipoglicemiantes/farmacologia , Músculo Esquelético/metabolismo , Miostatina/deficiência , Condicionamento Físico Animal , Ribonucleotídeos/farmacologia , Aminoimidazol Carboxamida/farmacologia , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Autofagia , Proteína Beclina-1 , Antígenos CD36/metabolismo , Transportador de Glucose Tipo 4/metabolismo , Hipertrofia , Masculino , Camundongos Knockout , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/patologia , Miostatina/genética , Tamanho do Órgão , Consumo de Oxigênio , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Resistência Física , Proteínas de Ligação a RNA/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Clenbuterol, a ß2-agonist, induces skeletal muscle hypertrophy and a shift from slow-oxidative to fast-glycolytic muscle fiber type profile. However, the cellular mechanisms of the effects of chronic clenbuterol administration on skeletal muscle are not completely understood. As the intracellular Ca2+ concentration must be finely regulated in many cellular processes, the aim of this study was to investigate the effects of chronic clenbuterol treatment on force, fatigue, intracellular calcium (Ca2+) homeostasis and Ca2+-dependent proteolysis in fast-twitch skeletal muscles (the extensor digitorum longus, EDL, muscle), as they are more sensitive to clenbuterol-induced hypertrophy. Male Wistar rats were chronically treated with 4 mg.kg-1 clenbuterol or saline vehicle (controls) for 21 days. Confocal microscopy was used to evaluate sarcoplasmic reticulum Ca2+ load, Ca2+-transient amplitude and Ca2+ spark properties. EDL muscles from clenbuterol-treated animals displayed hypertrophy, a shift from slow to fast fiber type profile and increased absolute force, while the relative force remained unchanged and resistance to fatigue decreased compared to control muscles from rats treated with saline vehicle. Compared to control animals, clenbuterol treatment decreased Ca2+-transient amplitude, Ca2+ spark amplitude and frequency and the sarcoplasmic reticulum Ca2+ load was markedly reduced. Conversely, calpain activity was increased by clenbuterol chronic treatment. These results indicate that chronic treatment with clenbuterol impairs Ca2+ homeostasis and this could contribute to the remodeling and functional impairment of fast-twitch skeletal muscle.
Assuntos
Agonistas Adrenérgicos beta/administração & dosagem , Cálcio/metabolismo , Clembuterol/administração & dosagem , Homeostase/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Animais , Sinalização do Cálcio , Calpaína/metabolismo , Masculino , Fibras Musculares de Contração Rápida/efeitos dos fármacos , Fibras Musculares de Contração Rápida/fisiologia , Músculo Esquelético/citologia , Fenótipo , Ratos , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/metabolismoRESUMO
In previous studies, we characterized a new hormonal pathway involving a mitochondrial T3 receptor (p43) acting as a mitochondrial transcription factor. In in vitro and in vivo studies, we have shown that p43 increases mitochondrial transcription and mitochondrial biogenesis. In addition, p43 overexpression in skeletal muscle stimulates mitochondrial respiration and induces a shift in metabolic and contractile features of muscle fibers which became more oxidative.Here we have studied the influence of p43 overexpression in skeletal muscle of mice during aging. We report that p43 overexpression initially increased mitochondrial mass. However, after the early rise in mitochondrial DNA occurring at 2 months of age in transgenic mice, we observed a progressive decrease of mitochondrial DNA content which became 2-fold lower at 23 months of age relatively to control animals. Moreover, p43 overexpression induced an oxidative stress characterized by a strong increase of lipid peroxidation and protein oxidation in quadriceps muscle, although antioxidant enzyme activities (catalase and superoxide dismutase) were stimulated. In addition, muscle atrophy became detectable at 6 months of age, probably through a stimulation of the ubiquitin proteasome pathway via two muscle-specific ubiquitin ligases E3, Atrogin-1/MAFbx and MuRF1.Taken together, these results demonstrate that a prolonged stimulation of mitochondrial activity induces muscle atrophy. In addition, these data underline the importance of a tight control of p43 expression and suggest that a deregulation of the direct T3 mitochondrial pathway could be one of the parameters involved in the occurrence of sarcopenia.