RESUMEN
Non-alcoholic fatty liver is the most common liver disease worldwide. Here, we show that the mitochondrial protein mitofusin 2 (Mfn2) protects against liver disease. Reduced Mfn2 expression was detected in liver biopsies from patients with non-alcoholic steatohepatitis (NASH). Moreover, reduced Mfn2 levels were detected in mouse models of steatosis or NASH, and its re-expression in a NASH mouse model ameliorated the disease. Liver-specific ablation of Mfn2 in mice provoked inflammation, triglyceride accumulation, fibrosis, and liver cancer. We demonstrate that Mfn2 binds phosphatidylserine (PS) and can specifically extract PS into membrane domains, favoring PS transfer to mitochondria and mitochondrial phosphatidylethanolamine (PE) synthesis. Consequently, hepatic Mfn2 deficiency reduces PS transfer and phospholipid synthesis, leading to endoplasmic reticulum (ER) stress and the development of a NASH-like phenotype and liver cancer. Ablation of Mfn2 in liver reveals that disruption of ER-mitochondrial PS transfer is a new mechanism involved in the development of liver disease.
Asunto(s)
GTP Fosfohidrolasas/metabolismo , Proteínas Mitocondriales/metabolismo , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Fosfatidilserinas/metabolismo , Animales , Modelos Animales de Enfermedad , Retículo Endoplásmico/metabolismo , Estrés del Retículo Endoplásmico/fisiología , Hepatocitos/metabolismo , Hepatocitos/patología , Humanos , Inflamación/metabolismo , Hígado/patología , Hepatopatías/etiología , Hepatopatías/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Mitocondrias/metabolismo , Cultivo Primario de Células , Transporte de Proteínas/fisiología , Transducción de Señal , Triglicéridos/metabolismoRESUMEN
Mitochondrial dysfunction and accumulation of damaged mitochondria are considered major contributors to aging. However, the molecular mechanisms responsible for these mitochondrial alterations remain unknown. Here, we demonstrate that mitofusin 2 (Mfn2) plays a key role in the control of muscle mitochondrial damage. We show that aging is characterized by a progressive reduction in Mfn2 in mouse skeletal muscle and that skeletal muscle Mfn2 ablation in mice generates a gene signature linked to aging. Furthermore, analysis of muscle Mfn2-deficient mice revealed that aging-induced Mfn2 decrease underlies the age-related alterations in metabolic homeostasis and sarcopenia. Mfn2 deficiency reduced autophagy and impaired mitochondrial quality, which contributed to an exacerbated age-related mitochondrial dysfunction. Interestingly, aging-induced Mfn2 deficiency triggers a ROS-dependent adaptive signaling pathway through induction of HIF1α transcription factor and BNIP3. This pathway compensates for the loss of mitochondrial autophagy and minimizes mitochondrial damage. Our findings reveal that Mfn2 repression in muscle during aging is a determinant for the inhibition of mitophagy and accumulation of damaged mitochondria and triggers the induction of a mitochondrial quality control pathway.
Asunto(s)
Envejecimiento , Autofagia , GTP Fosfohidrolasas/metabolismo , Mitofagia , Músculo Esquelético/patología , Sarcopenia/patología , Animales , Ratones , Ratones NoqueadosRESUMEN
Mitochondria are dynamic subcellular organelles that convert nutrient intermediates into readily available energy equivalents. Optimal mitochondrial function is ensured by a highly evolved quality control system, coordinated by protein machinery that regulates a process of continual fusion and fission. In this work, we provide in vivo evidence that the ATP-independent metalloprotease OMA1 plays an essential role in the proteolytic inactivation of the dynamin-related GTPase OPA1 (optic atrophy 1). We also show that OMA1 deficiency causes a profound perturbation of the mitochondrial fusion-fission equilibrium that has important implications for metabolic homeostasis. Thus, ablation of OMA1 in mice results in marked transcriptional changes in genes of lipid and glucose metabolic pathways and substantial alterations in circulating blood parameters. Additionally, Oma1-mutant mice exhibit an increase in body weight due to increased adipose mass, hepatic steatosis, decreased energy expenditure and impaired thermogenenesis. These alterations are especially significant under metabolic stress conditions, indicating that an intact OMA1-OPA1 system is essential for developing the appropriate adaptive response to different metabolic stressors such as a high-fat diet or cold-shock. This study provides the first description of an unexpected role in energy metabolism for the metalloprotease OMA1 and reinforces the importance of mitochondrial quality control for normal metabolic function.
Asunto(s)
GTP Fosfohidrolasas/metabolismo , Metaloendopeptidasas/deficiencia , Metaloproteasas/deficiencia , Proteínas Mitocondriales/deficiencia , Obesidad/metabolismo , Termogénesis/fisiología , Adipocitos Marrones/metabolismo , Animales , Glucemia/análisis , Dieta Alta en Grasa , Embrión de Mamíferos , Fibroblastos/metabolismo , Metabolismo de los Lípidos , Metaloendopeptidasas/genética , Metaloproteasas/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias/fisiología , Proteínas Mitocondriales/genéticaRESUMEN
PURPOSE OF REVIEW: The review summarizes our current knowledge of the role of signal transducer and activator of transcription 3 (STAT3) signaling in skeletal muscle regeneration and the maintenance of muscle mass. RECENT FINDINGS: STAT3 signaling plays a pivotal role in regulating the function of multiple cell types in skeletal muscle. This includes muscle stem cells, myofibers, and macrophages. It regulates muscle stem cell function by antagonizing self-renewal. STAT3 also functions in myofibers to regulate skeletal muscle mass. This is highly relevant under pathological conditions where STAT3 activation promotes protein degradation and muscle atrophy. Transient pharmacological inhibition of STAT3 partially prevents muscle wasting. However, the mechanisms responsible for the improvement of muscle condition are not currently well understood. This is because of the complexity of the system, as STAT3 has a critical role in regulating the function of several cell types residing in skeletal muscle. SUMMARY: Muscle wasting is associated with several human diseases such as muscle dystrophies or cancer cachexia. However, currently there are no effective treatments for this condition, and there is a critical need to identify new potential targets for the development of efficient therapeutic approaches.
Asunto(s)
Células Madre Adultas/metabolismo , Autorrenovación de las Células , Modelos Biológicos , Desarrollo de Músculos , Músculo Esquelético/metabolismo , Factor de Transcripción STAT3/metabolismo , Adulto , Células Madre Adultas/citología , Células Madre Adultas/efectos de los fármacos , Células Madre Adultas/patología , Animales , Diferenciación Celular , Proliferación Celular , Autorrenovación de las Células/efectos de los fármacos , Humanos , Macrófagos/citología , Macrófagos/inmunología , Macrófagos/metabolismo , Macrófagos/patología , Terapia Molecular Dirigida , Desarrollo de Músculos/efectos de los fármacos , Músculo Esquelético/citología , Músculo Esquelético/crecimiento & desarrollo , Músculo Esquelético/patología , Trastornos Musculares Atróficos/tratamiento farmacológico , Trastornos Musculares Atróficos/inmunología , Trastornos Musculares Atróficos/metabolismo , Trastornos Musculares Atróficos/patología , Factor de Transcripción STAT3/antagonistas & inhibidores , Síndrome Debilitante/tratamiento farmacológico , Síndrome Debilitante/inmunología , Síndrome Debilitante/metabolismo , Síndrome Debilitante/patologíaRESUMEN
Diabetes mellitus--whether driven by insulin deficiency or insulin resistance--causes major alterations in muscle metabolism. These alterations have an impact on nutrient handling, including the metabolism of glucose, lipids, and amino acids, and also on muscle mass and strength. However, the ways in which the distinct forms of diabetes affect muscle mass differ greatly. The most common forms of diabetes mellitus are type 1 and type 2. Thus, whereas type 1 diabetic subjects without insulin treatment display a dramatic loss of muscle, most type 2 diabetic subjects show no changes or even an increase in muscle mass. However, the most commonly used rodent models of type 2 diabetes are characterized by muscle atrophy and do not mimic the features of the disease in humans in terms of muscle mass. In this review, we analyze the processes that are differentially regulated under these forms of diabetes and propose regulatory mechanisms to explain them.
Asunto(s)
Diabetes Mellitus/patología , Animales , Autofagia , Complicaciones de la Diabetes/metabolismo , Complicaciones de la Diabetes/patología , Diabetes Mellitus/metabolismo , Modelos Animales de Enfermedad , Humanos , Insulina/metabolismo , Ratones , Modelos Biológicos , Atrofia Muscular/complicaciones , Atrofia Muscular/metabolismo , Proteínas/metabolismo , RatasRESUMEN
PURPOSE OF REVIEW: The main aim of this review is to summarize current knowledge of tumor protein p53-inducible nuclear protein 2 (TP53INP2) function and its role in skeletal muscle proteostasis. RECENT FINDINGS: Autophagy is directly involved in the regulation of skeletal muscle mass. Thus, excessive autophagy is associated with several diseases that cause muscle wasting, and it promotes the loss of muscle protein. Furthermore, compromised autophagy also leads to muscle atrophy. In this regard, TP53INP2 activates autophagy in skeletal muscle, thus causing a reduction in muscle mass. Moreover, TP53INP2 gain of function enhances muscle wasting in a highly catabolic context such as in streptozotocin-induced diabetes. However, TP53INP2 is naturally repressed in human insulin resistance and in murine models of diabetes. These observations suggest that TP53INP2 repression would reduce muscle atrophy under conditions that favor protein loss in skeletal muscle. SUMMARY: To date, there is no effective treatment for muscle wasting. Thus, the identification of new putative pharmacological targets to effectively treat this devastating condition is crucial. Given current knowledge about the role of TP53INP2 in skeletal muscle, this protein may be an optimal candidate to target for the prevention of muscle wasting.
Asunto(s)
Autofagia , Proteínas Musculares/metabolismo , Músculo Esquelético , Atrofia Muscular/metabolismo , Enfermedades Musculares/metabolismo , Proteínas Nucleares/metabolismo , Síndrome Debilitante/metabolismo , Animales , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Transducción de SeñalRESUMEN
Mitochondria are dynamic organelles that play a key role in energy conversion. Optimal mitochondrial function is ensured by a quality-control system tightly coupled to fusion and fission. In this connection, mitofusin 2 (Mfn2) participates in mitochondrial fusion and undergoes repression in muscle from obese or type 2 diabetic patients. Here, we provide in vivo evidence that Mfn2 plays an essential role in metabolic homeostasis. Liver-specific ablation of Mfn2 in mice led to numerous metabolic abnormalities, characterized by glucose intolerance and enhanced hepatic gluconeogenesis. Mfn2 deficiency impaired insulin signaling in liver and muscle. Furthermore, Mfn2 deficiency was associated with endoplasmic reticulum stress, enhanced hydrogen peroxide concentration, altered reactive oxygen species handling, and active JNK. Chemical chaperones or the antioxidant N-acetylcysteine ameliorated glucose tolerance and insulin signaling in liver-specific Mfn2 KO mice. This study provides an important description of a unique unexpected role of Mfn2 coordinating mitochondria and endoplasmic reticulum function, leading to modulation of insulin signaling and glucose homeostasis in vivo.
Asunto(s)
Retículo Endoplásmico/fisiología , GTP Fosfohidrolasas/fisiología , Glucosa/metabolismo , Homeostasis , Insulina/metabolismo , Mitocondrias/fisiología , Transducción de Señal , Animales , Resistencia a la Insulina , Hígado/metabolismo , Ratones , Ratones Noqueados , Músculo Esquelético/metabolismoRESUMEN
Sarcopenia is a major contributor to disability in older adults, and thus, it is key to elucidate the mechanisms underlying its development. Increasing evidence suggests that impaired macroautophagy/autophagy contributes to the development of sarcopenia. However, the mechanisms leading to reduced autophagy during aging remain largely unexplored, and whether autophagy activation protects from sarcopenia has not been fully addressed. Here we show that the autophagy regulator TP53INP2/TRP53INP2 is decreased during aging in mouse and human skeletal muscle. Importantly, chronic activation of autophagy by muscle-specific overexpression of TRP53INP2 prevents sarcopenia and the decline of muscle function in mice. Acute re-expression of TRP53INP2 in aged mice also improves muscle atrophy, enhances mitophagy, and reduces ROS production. In humans, high levels of TP53INP2 in muscle are associated with increased muscle strength and healthy aging. Our findings highlight the relevance of an active muscle autophagy in the maintenance of muscle mass and prevention of sarcopenia.Abbreviation: ATG7: autophagy related 7; BMI: body mass index; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; ROS: reactive oxygen species; TP53INP2: tumor protein p53 inducible nuclear protein 2; WT: wild type.
Asunto(s)
Autofagia , Músculo Esquelético , Sarcopenia , Sarcopenia/patología , Sarcopenia/metabolismo , Autofagia/fisiología , Animales , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Ratones , Envejecimiento Saludable/fisiología , Envejecimiento Saludable/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Mitofagia/fisiología , Masculino , Ratones Endogámicos C57BL , Proteínas NuclearesRESUMEN
Mitofusin 2 (Mfn2), a protein that participates in mitochondrial fusion, is required to maintain normal mitochondrial metabolism in skeletal muscle and liver. Given that muscle Mfn2 is repressed in obese or type 2 diabetic subjects, this protein may have a potential pathophysiological role in these conditions. To evaluate whether the metabolic effects of Mfn2 can be dissociated from its function in mitochondrial dynamics, we studied a form of human Mfn2, lacking the two transmembrane domains and the COOH-terminal coiled coil (ΔMfn2). This form localized in mitochondria but did not alter mitochondrial morphology in cells or in skeletal muscle fibers. The expression of ΔMfn2 in mouse skeletal muscle stimulated glucose oxidation and enhanced respiratory control ratio, which occurred in the absence of changes in mitochondrial mass. ΔMfn2 did not stimulate mitochondrial respiration in Mfn2-deficient muscle cells. The expression of ΔMfn2 in mouse liver or in hepatoma cells stimulated gluconeogenesis. In addition, ΔMfn2 activated basal and maximal respiration both in muscle and liver cells. In all, we show that a form of Mfn2 lacking mitochondrial fusion activity stimulates mitochondrial function and enhances glucose metabolism in muscle and liver tissues. This study suggests that Mfn2 regulates metabolism independently of changes in mitochondrial morphology.
Asunto(s)
GTP Fosfohidrolasas/fisiología , Hígado/enzimología , Mitocondrias Hepáticas/fisiología , Mitocondrias Musculares/fisiología , Dinámicas Mitocondriales , Proteínas Mitocondriales/fisiología , Músculo Esquelético/enzimología , Animales , Células Cultivadas , GTP Fosfohidrolasas/química , Expresión Génica , Células HEK293 , Hepatocitos/enzimología , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mitocondrias Hepáticas/enzimología , Mitocondrias Musculares/enzimología , Proteínas Mitocondriales/química , Isoformas de Proteínas/química , Isoformas de Proteínas/fisiología , Estructura Terciaria de Proteína , RatasRESUMEN
Brown adipose tissue (BAT) thermogenesis affects energy balance, and thereby it has the potential to induce weight loss and to prevent obesity. Here, we document a macroautophagic/autophagic-dependent mechanism of peroxisome proliferator-activated receptor gamma (PPARG) activity regulation that induces brown adipose differentiation and thermogenesis and that is mediated by TP53INP2. Disruption of TP53INP2-dependent autophagy reduced brown adipogenesis in cultured cells. In vivo specific-tp53inp2 ablation in brown precursor cells or in adult mice decreased the expression of thermogenic and mature adipocyte genes in BAT. As a result, TP53INP2-deficient mice had reduced UCP1 content in BAT and impaired maximal thermogenic capacity, leading to lipid accumulation and to positive energy balance. Mechanistically, TP53INP2 stimulates PPARG activity and adipogenesis in brown adipose cells by promoting the autophagic degradation of NCOR1, a PPARG co-repressor. Moreover, the modulation of TP53INP2 expression in BAT and in human brown adipocytes suggests that this protein increases PPARG activity during metabolic activation of brown fat. In all, we have identified a novel molecular explanation for the contribution of autophagy to BAT energy metabolism that could facilitate the design of therapeutic strategies against obesity and its metabolic complications.
Asunto(s)
Tejido Adiposo Pardo , PPAR gamma , Ratones , Humanos , Animales , Tejido Adiposo Pardo/metabolismo , PPAR gamma/metabolismo , Autofagia , Obesidad/metabolismo , Termogénesis/genética , Proteínas Nucleares/metabolismo , Co-Represor 1 de Receptor Nuclear/metabolismoRESUMEN
Studies on microbial communities, and their associated organic biomarkers, that are found thriving in the aphotic euxinic waters in modern stratified ecosystems are scarce compared to those undertaken in euxinic photic zones. The Dziani Dzaha (Mayotte, Indian Ocean) is a tropical, saline, alkaline crater lake that has recently been presented as a modern analog of Proterozoic Oceans due to its thalassohaline classification (having water of marine origin) and specific biogeochemical characteristics. Continuous intense photosynthetic production and microbial mineralization keep most of the water column permanently aphotic and anoxic preventing the development of a euxinic (sulfidic and anoxic) photic zone despite a high sulfide/sulfate ratio and the presence of permanent or seasonal haloclines. In this study, the molecular composition of the organic matter in Lake Dziani Dzaha was investigated and compared to the microbial diversity evaluated through 16S rRNA gene amplicon sequencing, over two contrasting seasons (rainy vs. dry) that influence water column stratification. Depth profiles of organic biomarker concentrations (chlorophyll-a and lipid biomarkers) and bacterial and archaeal OTU abundances appeared to be strongly dependent on the presence of aphotic haloclines and euxinia. OTU abundances revealed the importance of specific haloalkaliphilic bacterial and archaeal assemblages in phytoplanktonic biomass recycling and the biogeochemical functioning of the lake, suggesting new haloalkaline non-phototrophic anaerobic microbial precursors for some of the lipid biomarkers. Uncultured Firmicutes from the family Syntrophomonadaceae (Clostridiales), and Bacteroidetes from the ML635J-40 aquatic group, emerged as abundant chemotrophic bacterial members in the anoxic or euxinic waters and were probably responsible for the production of short-chain n-alkenes, wax esters, diplopterol, and tetrahymanol. Halocline-dependent euxinia also had a strong impact on the archaeal community which was dominated by Woesearchaeota in the sulfide-free waters. In the euxinic waters, methanogenic Euryarchaeota from the Methanomicrobia, Thermoplasmata, and WSA2 classes dominated and were likely at the origin of common hydrocarbon biomarkers of methanogens (phytane, pentamethyl-eicosenes, and partially hydrogenated squalene).
Asunto(s)
Lagos , Microbiota , Archaea , Biomarcadores , Lagos/química , Filogenia , ARN Ribosómico 16S/genéticaRESUMEN
Metabolic reprogramming is an active regulator of stem cell fate choices, and successful stem cell differentiation in different compartments requires the induction of oxidative phosphorylation. However, the mechanisms that promote mitochondrial respiration during stem cell differentiation are poorly understood. Here we demonstrate that Stat3 promotes muscle stem cell myogenic lineage progression by stimulating mitochondrial respiration in mice. We identify Fam3a, a cytokine-like protein, as a major Stat3 downstream effector in muscle stem cells. We demonstrate that Fam3a is required for muscle stem cell commitment and skeletal muscle development. We show that myogenic cells secrete Fam3a, and exposure of Stat3-ablated muscle stem cells to recombinant Fam3a in vitro and in vivo rescues their defects in mitochondrial respiration and myogenic commitment. Together, these findings indicate that Fam3a is a Stat3-regulated secreted factor that promotes muscle stem cell oxidative metabolism and differentiation, and suggests that Fam3a is a potential tool to modulate cell fate choices.
Asunto(s)
Diferenciación Celular , Citocinas/fisiología , Desarrollo de Músculos/fisiología , Mioblastos/fisiología , Factor de Transcripción STAT3/fisiología , Células Madre/fisiología , Animales , Animales Recién Nacidos , Linaje de la Célula/fisiología , Células Cultivadas , Embrión de Mamíferos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias/metabolismo , Músculo Estriado/citología , Músculo Estriado/crecimiento & desarrollo , Fosforilación Oxidativa , Transducción de Señal/fisiologíaRESUMEN
Cancer cachexia is a multifactorial syndrome characterized by anorexia, weight loss and muscle wasting that impairs patients' quality of life and survival. Aim of this work was to evaluate the impact of either autophagy inhibition (knocking down beclin-1) or promotion (overexpressing TP53INP2/DOR) on cancer-induced muscle wasting. In C26 tumor-bearing mice, stress-induced autophagy inhibition was unable to rescue the loss of muscle mass and worsened muscle morphology. Treating C26-bearing mice with formoterol, a selective ß2-agonist, muscle sparing was paralleled by reduced static autophagy markers, although the flux was maintained. Conversely, the stimulation of muscle autophagy exacerbated muscle atrophy in tumor-bearing mice. TP53INP2 further promoted atrogene expression and suppressed mitochondrial dynamics-related genes. Excessive autophagy might impair mitochondrial function through mitophagy. Consistently, tumor-induced mitochondrial dysfunction was detected by reduced ex vivo muscle fiber respiration. Overall, the results evoke a central role for muscle autophagy in cancer-induced muscle wasting.
Asunto(s)
Caquexia/complicaciones , Mitocondrias/patología , Atrofia Muscular/complicaciones , Neoplasias/complicaciones , Síndrome Debilitante/complicaciones , Animales , Autofagia , Caquexia/patología , Línea Celular Tumoral , Femenino , Humanos , Masculino , Ratones Endogámicos C57BL , Músculo Esquelético/patología , Atrofia Muscular/patología , Neoplasias/patología , Síndrome Debilitante/patologíaRESUMEN
Fibro-adipogenic progenitors (FAPs) are typically activated in response to muscle injury, and establish functional interactions with inflammatory and muscle stem cells (MuSCs) to promote muscle repair. We found that denervation causes progressive accumulation of FAPs, without concomitant infiltration of macrophages and MuSC-mediated regeneration. Denervation-activated FAPs exhibited persistent STAT3 activation and secreted elevated levels of IL-6, which promoted muscle atrophy and fibrosis. FAPs with aberrant activation of STAT3-IL-6 signalling were also found in mouse models of spinal cord injury, spinal muscular atrophy, amyotrophic lateral sclerosis (ALS) and in muscles of ALS patients. Inactivation of STAT3-IL-6 signalling in FAPs effectively countered muscle atrophy and fibrosis in mouse models of acute denervation and ALS (SODG93A mice). Activation of pathogenic FAPs following loss of integrity of neuromuscular junctions further illustrates the functional versatility of FAPs in response to homeostatic perturbations and suggests their potential contribution to the pathogenesis of neuromuscular diseases.
Asunto(s)
Adipogénesis , Esclerosis Amiotrófica Lateral/metabolismo , Desnervación/métodos , Interleucina-6/metabolismo , Atrofia Muscular Espinal/metabolismo , Atrofia Muscular/metabolismo , Mioblastos Esqueléticos/metabolismo , Músculo Cuádriceps/metabolismo , Factor de Transcripción STAT3/metabolismo , Transducción de Señal , Traumatismos de la Médula Espinal/metabolismo , Adipogénesis/efectos de los fármacos , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Esclerosis Amiotrófica Lateral/prevención & control , Animales , Cardiotoxinas , Línea Celular , Técnicas de Cocultivo , Modelos Animales de Enfermedad , Fibrosis , Humanos , Interleucina-6/antagonistas & inhibidores , Interleucina-6/genética , Masculino , Ratones Endogámicos C57BL , Ratones Transgénicos , Atrofia Muscular/genética , Atrofia Muscular/patología , Atrofia Muscular/prevención & control , Atrofia Muscular Espinal/genética , Atrofia Muscular Espinal/patología , Atrofia Muscular Espinal/prevención & control , Mutación , Mioblastos Esqueléticos/efectos de los fármacos , Mioblastos Esqueléticos/patología , Fármacos Neuromusculares/farmacología , Músculo Cuádriceps/efectos de los fármacos , Músculo Cuádriceps/inervación , Músculo Cuádriceps/patología , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Transcripción STAT3/genética , Nervio Ciático/cirugía , Traumatismos de la Médula Espinal/genética , Traumatismos de la Médula Espinal/patología , Traumatismos de la Médula Espinal/prevención & control , Superóxido Dismutasa-1/genéticaRESUMEN
Muscle stem cells (MuSCs) exhibit distinct behavior during successive phases of developmental myogenesis. However, how their transition to adulthood is regulated is poorly understood. Here, we show that fetal MuSCs resist progenitor specification and exhibit altered division dynamics, intrinsic features that are progressively lost postnatally. After transplantation, fetal MuSCs expand more efficiently and contribute to muscle repair. Conversely, niche colonization efficiency increases in adulthood, indicating a balance between muscle growth and stem cell pool repopulation. Gene expression profiling identified several extracellular matrix (ECM) molecules preferentially expressed in fetal MuSCs, including tenascin-C, fibronectin, and collagen VI. Loss-of-function experiments confirmed their essential and stage-specific role in regulating MuSC function. Finally, fetal-derived paracrine factors were able to enhance adult MuSC regenerative potential. Together, these findings demonstrate that MuSCs change the way in which they remodel their microenvironment to direct stem cell behavior and support the unique demands of muscle development or repair.
Asunto(s)
Matriz Extracelular/metabolismo , Regulación del Desarrollo de la Expresión Génica , Desarrollo de Músculos/genética , Músculo Esquelético/metabolismo , Mioblastos Esqueléticos/metabolismo , Animales , Colágeno Tipo VI/genética , Colágeno Tipo VI/metabolismo , Embrión de Mamíferos , Feto , Fibronectinas/genética , Fibronectinas/metabolismo , Genes Reporteros , Luciferasas/genética , Luciferasas/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Transgénicos , Músculo Esquelético/citología , Músculo Esquelético/crecimiento & desarrollo , Mioblastos Esqueléticos/citología , Mioblastos Esqueléticos/trasplante , Transducción de Señal , Trasplante de Células Madre , Tenascina/genética , Tenascina/metabolismo , Cicatrización de Heridas/fisiologíaRESUMEN
We have investigated the differential mitochondrial oxidative stress between males and females to understand the molecular mechanisms enabling females to live longer than males. Mitochondria are a major source of free radicals in cells. Those from female rats generate half the amount of peroxides than those of males. This does not occur in ovariectomized animals. Estrogen replacement therapy prevents the effect of ovariectomy. Mitochondria from females have higher levels of reduced glutathione than those from males. Those from ovariectomized rats have similar levels to males, and estrogen therapy prevents the fall in glutathione levels that occurs in ovariectomized animals. Oxidative damage to mitochondrial DNA in males is 4-fold higher than that in females. This is due to higher expression and activities of Mn-superoxide dismutase and of glutathione peroxidase in females, which behave as double transgenics overexpressing superoxide dismutase and glutathione peroxidase, conferring protection against free-radical-mediated damage in aging. Moreover, 16S rRNA expression, which decreases significantly with aging, is four times higher in mitochondria from females than in those from males of the same chronological age. The facts reported here provide molecular evidence to explain the different life span in males and females.
Asunto(s)
Antioxidantes/metabolismo , Regulación Enzimológica de la Expresión Génica , Glutatión Peroxidasa/genética , Mitocondrias Hepáticas/enzimología , Estrés Oxidativo , Superóxido Dismutasa/genética , Animales , Cartilla de ADN/química , ADN Mitocondrial/metabolismo , Estrógenos/farmacología , Femenino , Glutatión/metabolismo , Glutatión Peroxidasa/metabolismo , Masculino , Ovariectomía , Oxidación-Reducción , Estrés Oxidativo/efectos de los fármacos , Oxígeno/metabolismo , Peróxidos/metabolismo , ARN/metabolismo , ARN Ribosómico 16S/genética , ARN Ribosómico 16S/metabolismo , Ratas , Ratas Wistar , Especies Reactivas de Oxígeno/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Superóxido Dismutasa/metabolismoRESUMEN
Mitochondria are essential to cellular aging, and free radical production by mitochondria is increased with aging. The rate of oxidant production by mitochondria correlates inversely with maximal life span of species. In many species, females live longer than males. We report that mitochondrial oxidant production by females is significantly lower than that of males. However, mitochondria from ovariectomized females have a similar oxidant production as those of males. Thus, gender difference in life span can be explained, at least in part, by different oxidant generation by mitochondria. Administration of antioxidants, such as vitamins C and E, or a Ginkgo biloba extract, protects against age-associated oxidative damage to mitochondrial DNA, oxidation of glutathione, and other signs of oxidative damage to mitochondria.
Asunto(s)
Envejecimiento/fisiología , Apoptosis/fisiología , Mitocondrias/metabolismo , Estrés Oxidativo , Animales , Femenino , Masculino , Mitocondrias/patología , Ratas , Especies Reactivas de Oxígeno/metabolismo , Caracteres SexualesRESUMEN
The progressive loss of muscle regenerative capacity with age or disease results in part from a decline in the number and function of satellite cells, the direct cellular contributors to muscle repair. However, little is known about the molecular effectors underlying satellite cell impairment and depletion. Elevated levels of inflammatory cytokines, including interleukin-6 (IL-6), are associated with both age-related and muscle-wasting conditions. The levels of STAT3, a downstream effector of IL-6, are also elevated with muscle wasting, and STAT3 has been implicated in the regulation of self-renewal and stem cell fate in several tissues. Here we show that IL-6-activated Stat3 signaling regulates satellite cell behavior, promoting myogenic lineage progression through myogenic differentiation 1 (Myod1) regulation. Conditional ablation of Stat3 in Pax7-expressing satellite cells resulted in their increased expansion during regeneration, but compromised myogenic differentiation prevented the contribution of these cells to regenerating myofibers. In contrast, transient Stat3 inhibition promoted satellite cell expansion and enhanced tissue repair in both aged and dystrophic muscle. The effects of STAT3 inhibition on cell fate and proliferation were conserved in human myoblasts. The results of this study indicate that pharmacological manipulation of STAT3 activity can be used to counteract the functional exhaustion of satellite cells in pathological conditions, thereby maintaining the endogenous regenerative response and ameliorating muscle-wasting diseases.
Asunto(s)
Factor de Transcripción STAT3/fisiología , Células Satélite del Músculo Esquelético/fisiología , Envejecimiento/genética , Envejecimiento/patología , Envejecimiento/fisiología , Animales , Proliferación Celular , Células Cultivadas , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos mdx , Ratones Noqueados , Desarrollo de Músculos/fisiología , Proteína MioD/genética , Proteína MioD/metabolismo , Factor de Transcripción PAX7/metabolismo , Regeneración/fisiología , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Transcripción STAT3/genética , Células Satélite del Músculo Esquelético/citología , Transducción de SeñalRESUMEN
FATP1 mediates skeletal muscle cell fatty acid import, yet its intracellular localization and metabolic control role are not completely defined. Here, we examine FATP1 localization and metabolic effects of its overexpression in mouse skeletal muscle. The FATP1 protein was detected in mitochondrial and plasma membrane fractions, obtained by differential centrifugation, of mouse gastrocnemius muscle. FATP1 was most abundant in purified mitochondria, and in the outer membrane and soluble intermembrane, but not in the inner membrane plus matrix, enriched subfractions of purified mitochondria. Immunogold electron microscopy localized FATP1-GFP in mitochondria of transfected C2C12 myotubes. FATP1 was overexpressed in gastrocnemius mouse muscle, by adenovirus-mediated delivery of the gene into hindlimb muscles of newborn mice, fed after weaning a chow or high-fat diet. Compared to GFP delivery, FATP1 did not alter body weight, serum fed glucose, insulin and triglyceride levels, and whole-body glucose tolerance, in either diet. However, fatty acid levels were lower and ß-hydroxybutyrate levels were higher in FATP1- than GFP-mice, irrespective of diet. Moreover, intramuscular triglyceride content was lower in FATP1- versus GFP-mice regardless of diet, and ß-hydroxybutyrate content was unchanged in high-fat-fed mice. Electroporation-mediated FATP1 overexpression enhanced palmitate oxidation to CO2, but not to acid-soluble intermediate metabolites, while CO2 production from ß-hydroxybutyrate was inhibited and that from glucose unchanged, in isolated mouse gastrocnemius strips. In summary, FATP1 was localized in mitochondria, in the outer membrane and intermembrane parts, of mouse skeletal muscle, what may be crucial for its metabolic effects. Overexpressed FATP1 enhanced disposal of both systemic fatty acids and intramuscular triglycerides. Consistently, it did not contribute to the high-fat diet-induced metabolic dysregulation. However, FATP1 lead to hyperketonemia, likely secondary to the sparing of ketone body oxidation by the enhanced oxidation of fatty acids.