RESUMO
Iron homeostasis is essential for mitochondrial function, and iron deficiency has been associated with skeletal muscle weakness and decreased exercise capacity in patients with different chronic disorders. We hypothesized that iron deficiency-induced loss of skeletal muscle mitochondria is caused by increased mitochondrial clearance. To study this, C2C12 myotubes were subjected to the iron chelator deferiprone. Mitochondrial parameters and key constituents of mitophagy pathways were studied in presence or absence of pharmacological autophagy inhibition or knockdown of mitophagy-related proteins. Furthermore, it was explored if mitochondria were present in extracellular vesicles (EV). Iron chelation resulted in an increase in BCL2/Adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3) and BNIP3-like gene and protein levels, and the appearance of mitochondria encapsulated by lysosome-like vesicular structures in myotubes. Moreover, mitochondria were secreted via EV. These changes were associated with cellular mitochondrial impairments. These impairments were unaltered by autophagy inhibition, knockdown of mitophagy-related proteins BNIP3 and BNIP3L, or knockdown of their upstream regulator hypoxia-inducible factor 1 alpha. In conclusion, mitophagy is not essential for development of iron deficiency-induced reductions in mitochondrial proteins or respiratory capacity. The secretion of mitochondria-containing EV could present an additional pathway via which mitochondria can be cleared from iron chelation-exposed myotubes.
Assuntos
Deficiências de Ferro , Mitocôndrias Musculares/patologia , Mitocôndrias/patologia , Proteínas Mitocondriais/metabolismo , Mitofagia , Músculo Esquelético/patologia , Vesículas Secretórias/metabolismo , Animais , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Mitocôndrias/metabolismo , Mitocôndrias Musculares/metabolismo , Proteínas Mitocondriais/genética , Músculo Esquelético/metabolismo , Espécies Reativas de OxigênioRESUMO
Previous research has shown that a perinatal obesogenic, high-fat diet (HFD) is able to exacerbate ozone-induced adverse effects on lung function, injury, and inflammation in offspring, and it has been suggested that mitochondrial dysfunction is implicated herein. The aim of this study was to investigate whether a perinatal obesogenic HFD affects ozone-induced changes in offspring pulmonary oxidant status and the molecular control of mitochondrial function. For this purpose, female Long-Evans rats were fed a control diet or HFD before and during gestation, and during lactation, after which the offspring were acutely exposed to filtered air or ozone at a young-adult age (forty days). Directly following this exposure, the offspring lungs were examined for markers related to oxidative stress; oxidative phosphorylation; and mitochondrial fusion, fission, biogenesis, and mitophagy. Acute ozone exposure significantly increased pulmonary oxidant status and upregulated the molecular machinery that controls receptor-mediated mitophagy. In female offspring, a perinatal HFD exacerbated these responses, whereas in male offspring, responses were similar for both diet groups. The expression of the genes and proteins involved in oxidative phosphorylation and mitochondrial biogenesis, fusion, and fission was not affected by ozone exposure or perinatal HFD. These findings suggest that a perinatal HFD influences ozone-induced responses on pulmonary oxidant status and the molecular control of mitophagy in female rat offspring.
Assuntos
Dieta Hiperlipídica/efeitos adversos , Pulmão/patologia , Mitocôndrias/patologia , Mitofagia , Oxidantes/metabolismo , Ozônio/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal/patologia , Animais , Animais Recém-Nascidos , Feminino , Perfilação da Expressão Gênica , Pulmão/metabolismo , Masculino , Fenômenos Fisiológicos da Nutrição Materna , Mitocôndrias/metabolismo , Fosforilação Oxidativa , Estresse Oxidativo , Gravidez , Efeitos Tardios da Exposição Pré-Natal/etiologia , Ratos , Ratos Long-EvansRESUMO
Disturbances in mitochondrial structure and function in lung epithelial cells have been implicated in the pathogenesis of various lung diseases, including chronic obstructive pulmonary disease (COPD). Such disturbances affect not only cellular energy metabolism but also alter a range of indispensable cellular homeostatic functions in which mitochondria are known to be involved. These range from cellular differentiation, cell death pathways, and cellular remodeling to physical barrier function and innate immunity, all of which are known to be impacted by exposure to cigarette smoke and have been linked to COPD pathogenesis. Next to their well-established role as the first physical frontline against external insults, lung epithelial cells are immunologically active. Malfunctioning epithelial cells with defective mitochondria are unable to maintain homeostasis and respond adequately to further stress or injury, which may ultimately shape the phenotype of lung diseases. In this review, we provide a comprehensive overview of the impact of cigarette smoke on the development of mitochondrial dysfunction in the lung epithelium and highlight the consequences for cell function, innate immune responses, epithelial remodeling, and epithelial barrier function in COPD. We also discuss the applicability and potential therapeutic value of recently proposed strategies for the restoration of mitochondrial function in the treatment of COPD.
Assuntos
Células Epiteliais/fisiologia , Pulmão/fisiopatologia , Mitocôndrias/fisiologia , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Animais , Células Epiteliais/efeitos dos fármacos , Humanos , Pulmão/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mucosa Respiratória/efeitos dos fármacos , Mucosa Respiratória/fisiopatologia , Fumar/efeitos adversos , Nicotiana/efeitos adversosRESUMO
BACKGROUND: Both mitophagy, a selective mechanism for clearance of mitochondria, and mitochondrial biogenesis are key processes determining mitochondrial content and oxidative capacity of the musculature. Abnormalities in these processes could therefore contribute to deterioration of peripheral muscle oxidative capacity as observed in e.g. chronic obstructive pulmonary disease. Although it has been suggested that inflammatory mediators can modulate both mitophagy and mitochondrial biogenesis, it is unknown whether acute pulmonary inflammation affects these processes in oxidative and glycolytic skeletal muscle in vivo. Therefore, we hypothesised that molecular signalling patterns of mitochondrial breakdown and biogenesis temporally shift towards increased breakdown and decreased biogenesis in the skeletal muscle of mice exposed to one single bolus of IT-LPS, as a model for acute lung injury and pulmonary inflammation. METHODS: We investigated multiple important constituents and molecular regulators of mitochondrial breakdown, biogenesis, dynamics, and mitochondrial content in skeletal muscle over time in a murine (FVB/N background) model of acute pulmonary- and systemic inflammation induced by a single bolus of intra-tracheally (IT)-instilled lipopolysaccharide (LPS). Moreover, we compared the expression of these constituents between gastrocnemius and soleus muscle. RESULTS: Both in soleus and gastrocnemius muscle, IT-LPS instillation resulted in molecular patterns indicative of activation of mitophagy. This coincided with modulation of mRNA transcript abundance of genes involved in mitochondrial fusion and fission as well as an initial decrease and subsequent recovery of transcript levels of key proteins involved in the molecular regulation of mitochondrial biogenesis. Moreover, no solid differences in markers for mitochondrial content were found. CONCLUSIONS: These data suggest that one bolus of IT-LPS results in a temporal modulation of mitochondrial clearance and biogenesis in both oxidative and glycolytic skeletal muscle, which is insufficient to result in a reduction of mitochondrial content.
Assuntos
Lesão Pulmonar Aguda/metabolismo , Inflamação/metabolismo , Mitocôndrias Musculares/metabolismo , Dinâmica Mitocondrial/genética , Mitofagia/fisiologia , Músculo Esquelético/metabolismo , Biogênese de Organelas , Lesão Pulmonar Aguda/induzido quimicamente , Lesão Pulmonar Aguda/fisiopatologia , Animais , Inflamação/fisiopatologia , Lipopolissacarídeos/efeitos adversos , Camundongos , Músculo Esquelético/fisiopatologia , Doença Pulmonar Obstrutiva Crônica/metabolismo , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Transdução de SinaisRESUMO
Acute viral myocarditis (VM), characterised by leukocyte infiltration and dysfunction of the heart, is an important cause of sudden cardiac death in young adults. Unfortunately, to date, the pathological mechanisms underlying cardiac failure in VM remain incompletely understood. In the current study, we investigated if acute VM leads to cardiac metabolic rewiring and if this process is driven by local inflammation. Transcriptomic analysis of cardiac biopsies from myocarditis patients and a mouse model of VM revealed prominent reductions in the expression of a multitude of genes involved in mitochondrial oxidative energy metabolism. In mice, this coincided with reductions in high-energy phosphate and NAD levels, as determined by Imaging Mass Spectrometry, as well as marked decreases in the activity, protein abundance and mRNA levels of various enzymes and key regulators of cardiac oxidative metabolism. Indicative of fulminant cardiac inflammation, NF-κB signalling and inflammatory cytokine expression were potently induced in the heart during human and mouse VM. In cultured cardiomyocytes, cytokine-mediated NF-κB activation impaired cardiomyocyte oxidative gene expression, likely by interfering with the PGC-1 (peroxisome proliferator-activated receptor (PPAR)-γ co-activator) signalling network, the key regulatory pathway controlling cardiomyocyte oxidative metabolism. In conclusion, we provide evidence that acute VM is associated with extensive cardiac metabolic remodelling and our data support a mechanism whereby cytokines secreted primarily from infiltrating leukocytes activate NF-κB signalling in cardiomyocytes thereby inhibiting the transcriptional activity of the PGC-1 network and consequently modulating myocardial energy metabolism.
Assuntos
Infecções por Coxsackievirus/metabolismo , Enterovirus Humano B , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Proteínas Musculares/metabolismo , Miocardite/metabolismo , NF-kappa B/metabolismo , Doença Aguda , Animais , Infecções por Coxsackievirus/patologia , Modelos Animais de Doenças , Feminino , Humanos , Masculino , Camundongos , Miocardite/patologia , Miocardite/virologia , PPAR gama/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Abnormal mitochondria have been observed in bronchial- and alveolar epithelial cells of patients with chronic obstructive pulmonary disease (COPD). However, it is unknown if alterations in the molecular pathways regulating mitochondrial turnover (mitochondrial biogenesis vs mitophagy) are involved. Therefore, in this study, the abundance of key molecules controlling mitochondrial turnover were assessed in peripheral lung tissue from non-COPD patients (n = 6) and COPD patients (n = 11; GOLDII n = 4/11; GOLDIV n = 7/11) and in both undifferentiated and differentiated human primary bronchial epithelial cells (PBEC) from non-COPD patients and COPD patients (n = 4-7 patients/group). We observed significantly decreased transcript levels of key molecules controlling mitochondrial biogenesis (PPARGC1B, PPRC1, PPARD) in peripheral lung tissue from severe COPD patients. Interestingly, mRNA levels of the transcription factor TFAM (mitochondrial biogenesis) and BNIP3L (mitophagy) were increased in these patients. In general, these alterations were not recapitulated in undifferentiated and differentiated PBECs with the exception of decreased PPARGC1B expression in both PBEC models. Although these findings provide valuable insight in these pathways in bronchial epithelial cells and peripheral lung tissue of COPD patients, whether or not these alterations contribute to COPD pathogenesis, underlie changes in mitochondrial function or may represent compensatory mechanisms remains to be established.
Assuntos
Pulmão , Doença Pulmonar Obstrutiva Crônica , Humanos , Pulmão/patologia , Doença Pulmonar Obstrutiva Crônica/patologia , Renovação Mitocondrial , Mitocôndrias/metabolismo , Células Epiteliais/metabolismo , Proteínas de Ligação a RNA/metabolismoRESUMO
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy. METHODS: Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors. RESULTS: Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors. CONCLUSIONS: In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.
Assuntos
Inibidores Enzimáticos/uso terapêutico , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Indóis/uso terapêutico , Maleimidas/uso terapêutico , Músculo Esquelético/patologia , Atrofia Muscular/patologia , Atrofia Muscular/prevenção & controle , Doença Pulmonar Obstrutiva Crônica/prevenção & controle , Animais , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Modelos Animais de Doenças , Inibidores Enzimáticos/farmacologia , Glucocorticoides/farmacologia , Quinase 3 da Glicogênio Sintase/efeitos dos fármacos , Cobaias , Indóis/farmacologia , Lipopolissacarídeos/efeitos adversos , Masculino , Maleimidas/farmacologia , Desenvolvimento Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Doença Pulmonar Obstrutiva Crônica/induzido quimicamente , Doença Pulmonar Obstrutiva Crônica/patologia , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
Chronic obstructive pulmonary disease (COPD) is a devastating lung disease for which cigarette smoking is the main risk factor. Acetaldehyde, acrolein, and formaldehyde are short-chain aldehydes known to be formed during pyrolysis and combustion of tobacco and have been linked to respiratory toxicity. Mitochondrial dysfunction is suggested to be mechanistically and causally involved in the pathogenesis of smoking-associated lung diseases such as COPD. Cigarette smoke (CS) has been shown to impair the molecular regulation of mitochondrial metabolism and content in epithelial cells of the airways and lungs. Although it is unknown which specific chemicals present in CS are responsible for this, it has been suggested that aldehydes may be involved. Therefore, it has been proposed by the World Health Organization to regulate aldehydes in commercially-available cigarettes. In this review, we comprehensively describe and discuss the impact of acetaldehyde, acrolein, and formaldehyde on mitochondrial function and content and the molecular pathways controlling this (biogenesis versus mitophagy) in epithelial cells of the airways and lungs. In addition, potential therapeutic applications targeting (aldehyde-induced) mitochondrial dysfunction, as well as regulatory implications, and the necessary required future studies to provide scientific support for this regulation, have been covered in this review.
Assuntos
Fumar Cigarros , Doença Pulmonar Obstrutiva Crônica , Nicotiana/efeitos adversos , Aldeídos/metabolismo , Acroleína/toxicidade , Acroleína/metabolismo , Fumar Cigarros/efeitos adversos , Pulmão/patologia , Doença Pulmonar Obstrutiva Crônica/patologia , Células Epiteliais/metabolismo , Formaldeído , Acetaldeído/toxicidade , Acetaldeído/metabolismo , Mitocôndrias/metabolismoRESUMO
Mitochondrial functionality is crucial for the execution of physiologic functions of metabolically active cells in the respiratory tract including airway epithelial cells (AECs). Cigarette smoke is known to impair mitochondrial function in AECs. However, the potential contribution of mitochondrial dysfunction in AECs to airway infection and airway epithelial barrier dysfunction is unknown. In this study, we used an in vitro model based on AECs exposed to cigarette smoke extract (CSE) followed by an infection with Streptococcus pneumoniae (Sp). The levels of oxidative stress as an indicator of mitochondrial stress were quantified upon CSE and Sp treatment. In addition, expression of proteins associated with mitophagy, mitochondrial content, and biogenesis as well as mitochondrial fission and fusion was quantified. Transcriptional AEC profiling was performed to identify the potential changes in innate immune pathways and correlate them with indices of mitochondrial function. We observed that CSE exposure substantially altered mitochondrial function in AECs by suppressing mitochondrial complex protein levels, reducing mitochondrial membrane potential and increasing mitochondrial stress and mitophagy. Moreover, CSE-induced mitochondrial dysfunction correlated with reduced enrichment of genes involved in apical junctions and innate immune responses to Sp, particularly type I interferon responses. Together, our results demonstrated that CSE-induced mitochondrial dysfunction may contribute to impaired innate immune responses to Sp.
Assuntos
Fumar Cigarros , Streptococcus pneumoniae , Brônquios/metabolismo , Células Epiteliais/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Streptococcus pneumoniae/metabolismo , Nicotiana/efeitos adversos , Nicotiana/metabolismoRESUMO
Exposure to cigarette smoke (CS) is the primary risk factor for developing chronic obstructive pulmonary disease. The impact of CS exposure on the molecular mechanisms involved in mitochondrial quality control in airway epithelial cells is incompletely understood. Undifferentiated or differentiated primary bronchial epithelial cells were acutely/chronically exposed to whole CS (WCS) or CS extract (CSE) in submerged or air-liquid interface conditions. Abundance of key regulators controlling mitochondrial biogenesis, mitophagy and mitochondrial dynamics was assessed. Acute exposure to WCS or CSE increased the abundance of components of autophagy and receptor-mediated mitophagy in all models. Although mitochondrial content and dynamics appeared to be unaltered in response to CS, changes in both the molecular control of mitochondrial biogenesis and a shift toward an increased glycolytic metabolism were observed in particular in differentiated cultures. These alterations persisted, at least in part, after chronic exposure to WCS during differentiation and upon subsequent discontinuation of WCS exposure. In conclusion, smoke exposure alters the regulation of mitochondrial metabolism in airway epithelial cells, but observed alterations may differ between various culture models used. This article has an associated First Person interview with the joint first authors of the paper.
Assuntos
Fumar Cigarros , Doença Pulmonar Obstrutiva Crônica , Brônquios , Células Epiteliais , Humanos , Mitocôndrias , Mitofagia , Doença Pulmonar Obstrutiva Crônica/etiologia , Nicotiana/efeitos adversosRESUMO
Chronic obstructive pulmonary disease (COPD) is a devastating lung disease primarily caused by exposure to cigarette smoke (CS). During the pyrolysis and combustion of tobacco, reactive aldehydes such as acetaldehyde, acrolein, and formaldehyde are formed, which are known to be involved in respiratory toxicity. Although CS-induced mitochondrial dysfunction has been implicated in the pathophysiology of COPD, the role of aldehydes therein is incompletely understood. To investigate this, we used a physiologically relevant in vitro exposure model of differentiated human primary bronchial epithelial cells (PBEC) exposed to CS (one cigarette) or a mixture of acetaldehyde, acrolein, and formaldehyde (at relevant concentrations of one cigarette) or air, in a continuous flow system using a puff-like exposure protocol. Exposure of PBEC to CS resulted in elevated IL-8 cytokine and mRNA levels, increased abundance of constituents associated with autophagy, decreased protein levels of molecules associated with the mitophagy machinery, and alterations in the abundance of regulators of mitochondrial biogenesis. Furthermore, decreased transcript levels of basal epithelial cell marker KRT5 were reported after CS exposure. Only parts of these changes were replicated in PBEC upon exposure to a combination of acetaldehyde, acrolein, and formaldehyde. More specifically, aldehydes decreased MAP1LC3A mRNA (autophagy) and BNIP3 protein (mitophagy) and increased ESRRA protein (mitochondrial biogenesis). These data suggest that other compounds in addition to aldehydes in CS contribute to CS-induced dysregulation of constituents controlling mitochondrial content and function in airway epithelial cells.
Assuntos
Aldeídos , Doença Pulmonar Obstrutiva Crônica , Humanos , Aldeídos/metabolismo , Acroleína/toxicidade , Acroleína/metabolismo , Células Epiteliais/metabolismo , Mitocôndrias/metabolismo , Doença Pulmonar Obstrutiva Crônica/metabolismo , Acetaldeído/toxicidade , Acetaldeído/metabolismo , Nicotiana , Formaldeído , RNA Mensageiro/metabolismo , FumarRESUMO
BACKGROUND: Physical inactivity contributes to muscle wasting and reductions in mitochondrial oxidative phenotype (OXPHEN), reducing physical performance and quality of life during aging and in chronic disease. Previously, it was shown that inactivation of glycogen synthase kinase (GSK)-3ß stimulates muscle protein accretion, myogenesis, and mitochondrial biogenesis. Additionally, GSK-3ß is inactivated during recovery of disuse-induced muscle atrophy. AIM: Therefore, we hypothesize that GSK-3 inhibition is required for reloading-induced recovery of skeletal muscle mass and OXPHEN. METHODS: Wild-type (WT) and whole-body constitutively active (C.A.) Ser21/9 GSK-3α/ß knock-in mice were subjected to a 14-day hind-limb suspension/14-day reloading protocol. Soleus muscle mass, fiber cross-sectional area (CSA), OXPHEN (abundance of sub-units of oxidative phosphorylation (OXPHOS) complexes and fiber-type composition), as well as expression levels of their main regulators (respectively protein synthesis/degradation, myogenesis and peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) signaling) were monitored. RESULTS: Subtle but consistent differences suggesting suppression of protein turnover signaling and decreased expression of several OXPHOS sub-units and PGC-1α signaling constituents were observed at baseline in C.A. GSK-3 versus WT mice. Although soleus mass recovery during reloading occurred more rapidly in C.A. GSK-3 mice, this was not accompanied by a parallel increased CSA. The OXPHEN response to reloading was not distinct between C.A. GSK-3 and WT mice. No consistent or significant differences in reloading-induced changes in the regulatory steps of protein turnover, myogenesis or muscle OXPHEN were observed in C.A. GSK-3 compared to WT muscle. CONCLUSION: This study indicates that GSK-3 inactivation is dispensable for reloading-induced recovery of muscle mass and OXPHEN.
Assuntos
Glicogênio Sintase Quinase 3 beta/genética , Desenvolvimento Muscular/genética , Atrofia Muscular/tratamento farmacológico , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/genética , Animais , Quinase 3 da Glicogênio Sintase/genética , Glicogênio Sintase Quinase 3 beta/antagonistas & inibidores , Elevação dos Membros Posteriores , Humanos , Camundongos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Proteínas Musculares/genética , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Atrofia Muscular/genética , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Fosforilação Oxidativa/efeitos dos fármacos , Fenótipo , Qualidade de Vida , Transdução de Sinais/efeitos dos fármacos , Fatores de Transcrição/genéticaRESUMO
Systemic inflammation is a recognized hallmark of chronic obstructive pulmonary disease pathogenesis. Although the origin and mechanisms responsible for the persistent chronic inflammatory process remain to be elucidated, it is recognized that it plays an important role in skeletal muscle pathology as observed in chronic obstructive pulmonary disease and several other chronic inflammatory disorders. This article describes state-of-the-art knowledge and novel insights in the role of inflammatory processes on several aspects of inflammation-related skeletal muscle pathology and offers new insights in therapeutic perspectives.
Assuntos
Inflamação/complicações , Músculo Esquelético/fisiopatologia , Doenças Musculares/etiologia , Doença Pulmonar Obstrutiva Crônica/complicações , Apoptose , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Atrofia Muscular/etiologia , Atrofia Muscular/metabolismo , Atrofia Muscular/fisiopatologia , Doenças Musculares/patologia , Doenças Musculares/fisiopatologia , Estresse Oxidativo , Doença Pulmonar Obstrutiva Crônica/fisiopatologiaRESUMO
SCOPE: The capacity of skeletal muscle to contribute to glucose homeostasis depends on muscular insulin sensitivity. The expression of glucose transporter (GLUT)-4 is increased during myoblast differentiation, a process essential in maintenance of adult muscle. Therefore, processes that affect muscle differentiation may influence insulin dependent glucose homeostasis. Conjugated linoleic acids, and in particular trans-10, cis-12 CLA (t10, c12-CLA), are potent inducers of NF-kB in cultured skeletal myotubes, and NF-kB activation inhibits muscle differentiation. The aims of this study were to evaluate whether CLAs inhibit myogenic differentiation and lower GLUT4 mRNA expression and to address the involvement of NF-kB activation in potential effects of CLA on these processes. METHODS AND RESULTS: Incubation of C2C12 cells with t10, c12-CLA blocked the formation of myotubes, which was accompanied by reduced expression of the muscle specific genes creatine kinase, myogenin, myosin heavy chain perinatal and myosin heavy chain IIB, as well as decreased GLUT4 mRNA levels. However, genetic blockade of NF-kB was not sufficient to restore reduced myosin heavy chain protein expression following t10, c12-CLA treatment. Surprisingly, in contrast to myotubes, t10, c12-CLA was not able to activate NF-kB transcriptional activity in myoblasts. CONCLUSION: In conclusion, t10, c12-CLA inhibits myogenic differentiation and GLUT4 expression, independently from NF-kB activation.