RESUMEN
Increasing mouse litter size [crowded litter (CL)] presumably imposes a transient nutrient stress during suckling and extends lifespan through unknown mechanisms. Chronic calorically restricted and rapamycin-treated mice have decreased DNA synthesis and mTOR complex 1 (mTORC1) signaling but maintained protein synthesis, suggesting maintenance of existing cellular structures. We hypothesized that CL would exhibit similar synthetic and signaling responses to other long-lived models and, by comparing synthesis of new protein to new DNA, that insight may be gained into the potential preservation of existing cellular structures in the CL model. Protein and DNA synthesis was assessed in gastroc complex, heart, and liver of 4- and 7-mo CL mice. We also examined mTORC1 signaling in 3- and 7-mo aged animals. Compared with controls, 4-mo CL had greater DNA synthesis in gastroc complex with no differences in protein synthesis or mTORC1 substrate phosphorylation across tissues. Seven-month CL had less DNA synthesis than controls in heart and greater protein synthesis and mTORC1 substrate phosphorylation across tissues. The increased new protein-to-new DNA synthesis ratio suggests that new proteins are synthesized more so in existing cells at 7 mo, differing from 4 mo, in CL vs. controls. We propose that, in CL, protein synthesis shifts from being directed toward new cells (4 mo) to maintenance of existing cellular structures (7 mo), independently of decreased mTORC1.
Asunto(s)
Envejecimiento , Tamaño de la Camada , Complejos Multiproteicos/metabolismo , Biosíntesis de Proteínas , Procesamiento Proteico-Postraduccional , Transducción de Señal , Serina-Treonina Quinasas TOR/metabolismo , Regulación hacia Arriba , Algoritmos , Animales , Animales Lactantes , Cruzamientos Genéticos , ADN/biosíntesis , Regulación hacia Abajo , Femenino , Corazón/crecimiento & desarrollo , Miembro Posterior , Hígado/crecimiento & desarrollo , Hígado/metabolismo , Longevidad , Diana Mecanicista del Complejo 1 de la Rapamicina , Ratones , Músculo Esquelético/crecimiento & desarrollo , Músculo Esquelético/metabolismo , Miocardio/metabolismo , FosforilaciónRESUMEN
Synaptotagmin is the major calcium sensor for fast synaptic transmission that requires the synchronous fusion of synaptic vesicles. Synaptotagmin contains two calcium-binding domains: C2A and C2B. Mutation of a positively charged residue (R233Q in rat) showed that Ca2+-dependent interactions between the C2A domain and membranes play a role in the electrostatic switch that initiates fusion. Surprisingly, aspartate-to-asparagine mutations in C2A that inhibit Ca2+ binding support efficient synaptic transmission, suggesting that Ca2+ binding by C2A is not required for triggering synchronous fusion. Based on a structural analysis, we generated a novel mutation of a single Ca2+-binding residue in C2A (D229E in Drosophila) that inhibited Ca2+ binding but maintained the negative charge of the pocket. This C2A aspartate-to-glutamate mutation resulted in â¼80% decrease in synchronous transmitter release and a decrease in the apparent Ca2+ affinity of release. Previous aspartate-to-asparagine mutations in C2A partially mimicked Ca2+ binding by decreasing the negative charge of the pocket. We now show that the major function of Ca2+ binding to C2A is to neutralize the negative charge of the pocket, thereby unleashing the fusion-stimulating activity of synaptotagmin. Our results demonstrate that Ca2+ binding by C2A is a critical component of the electrostatic switch that triggers synchronous fusion. Thus, Ca2+ binding by C2B is necessary and sufficient to regulate the precise timing required for coupling vesicle fusion to Ca2+ influx, but Ca2+ binding by both C2 domains is required to flip the electrostatic switch that triggers efficient synchronous synaptic transmission.
Asunto(s)
Proteínas de Unión al Calcio/antagonistas & inhibidores , Proteínas de Unión al Calcio/fisiología , Calcio/metabolismo , Electricidad Estática , Transmisión Sináptica/fisiología , Sinaptotagminas/fisiología , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Proteínas de Unión al Calcio/metabolismo , Drosophila melanogaster , Femenino , Humanos , Masculino , Ratones , Datos de Secuencia Molecular , Inhibición Neural/fisiología , Unión Proteica/fisiología , Estructura Terciaria de Proteína/fisiología , Ratas , Sinaptotagminas/deficiencia , Sinaptotagminas/genética , TermodinámicaRESUMEN
The vesicle protein synaptotagmin I is the Ca(2+) sensor that triggers fast, synchronous release of neurotransmitter. Specifically, Ca(2+) binding by the C(2)B domain of synaptotagmin is required at intact synapses, yet the mechanism whereby Ca(2+) binding results in vesicle fusion remains controversial. Ca(2+)-dependent interactions between synaptotagmin and SNARE (soluble N-ethylmaleimide-sensitive fusion protein attachment receptor) complexes and/or anionic membranes are possible effector interactions. However, no effector-interaction mutations to date impact synaptic transmission as severely as mutation of the C(2)B Ca(2+)-binding motif, suggesting that these interactions are facilitatory rather than essential. Here we use Drosophila to show the functional role of a highly conserved, hydrophobic residue located at the tip of each of the two Ca(2+)-binding pockets of synaptotagmin. Mutation of this residue in the C(2)A domain (F286) resulted in a â¼50% decrease in evoked transmitter release at an intact synapse, again indicative of a facilitatory role. Mutation of this hydrophobic residue in the C(2)B domain (I420), on the other hand, blocked all locomotion, was embryonic lethal even in syt I heterozygotes, and resulted in less evoked transmitter release than that in syt(null) mutants, which is more severe than the phenotype of C(2)B Ca(2+)-binding mutants. Thus, mutation of a single, C(2)B hydrophobic residue required for Ca(2+)-dependent penetration of anionic membranes results in the most severe disruption of synaptotagmin function in vivo to date. Our results provide direct support for the hypothesis that plasma membrane penetration, specifically by the C(2)B domain of synaptotagmin, is the critical effector interaction for coupling Ca(2+) binding with vesicle fusion.
Asunto(s)
Calcio/metabolismo , Fusión de Membrana/fisiología , Vesículas Sinápticas/fisiología , Sinaptotagminas/metabolismo , Factores de Edad , Análisis de Varianza , Animales , Animales Modificados Genéticamente , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Drosophila , Proteínas de Drosophila/genética , Electrofisiología , Embrión no Mamífero , Potenciales Postsinápticos Excitadores/genética , Fraccionamiento de Campo-Flujo/métodos , Técnicas In Vitro , Fusión de Membrana/genética , Mutagénesis Sitio-Dirigida/métodos , Proteínas del Tejido Nervioso/metabolismo , Unión Neuromuscular/fisiología , Estructura Terciaria de Proteína/genética , Ratas , Proteínas SNARE/genética , Proteínas SNARE/metabolismo , Alineación de Secuencia , Análisis Espectral , Sinaptotagminas/química , Sinaptotagminas/genéticaRESUMEN
Importance: Detailed analysis of infection rates paired with behavioral and employee-reported risk factors is vital to understanding how transmission of SARS-CoV-2 infection may be exacerbated or mitigated in the workplace. Institutions of higher education are heterogeneous work units that supported continued in-person employment during the COVID-19 pandemic, providing a test site for occupational health evaluation. Objective: To evaluate the association between self-reported protective behaviors and prevalence of SARS-CoV-2 infection among essential in-person employees during the first 6 months of the COVID-19 pandemic in the US. Design, Setting, and Participants: This cross-sectional study was conducted from July 13 to September 2, 2020, at an institution of higher education in Fort Collins, Colorado. Employees 18 years or older without symptoms of COVID-19 who identified as essential in-person workers during the first 6 months of the pandemic were included. Participants completed a survey, and blood and nasal swab samples were collected to assess active SARS-CoV-2 infection via quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and past infection by serologic testing. Exposure: Self-reported practice of protective behaviors against COVID-19 according to public health guidelines provided to employees. Main Outcomes and Measures: Prevalence of current SARS-CoV-2 infection detected by qRT-PCR or previous SARS-CoV-2 infection detected by an IgG SARS-CoV-2 testing platform. The frequency of protective behavior practices and essential workers' concerns regarding contracting COVID-19 and exposing others were measured based on survey responses. Results: Among 508 participants (305 [60.0%] women, 451 [88.8%] non-Hispanic White individuals; mean [SD] age, 41.1 [12.5] years), there were no qRT-PCR positive test results, and only 2 participants (0.4%) had seroreactive IgG antibodies. Handwashing and mask wearing were reported frequently both at work (480 [94.7%] and 496 [97.8%] participants, respectively) and outside work (465 [91.5%] and 481 [94.7%] participants, respectively). Social distancing was reported less frequently at work (403 [79.5%]) than outside work (465 [91.5%]) (P < .001). Participants were more highly motivated to avoid exposures because of concern about spreading the infection to others (419 [83.0%]) than for personal protection (319 [63.2%]) (P < .001). Conclusions and Relevance: In this cross-sectional study of essential workers at an institution of higher education, when employees reported compliance with public health practices both at and outside work, they were able to operate safely in their work environment during the COVID-19 pandemic.
Asunto(s)
COVID-19 , Pandemias , Salud Pública , SARS-CoV-2 , Conducta Social , Universidades , Lugar de Trabajo , Adulto , COVID-19/sangre , COVID-19/prevención & control , COVID-19/transmisión , COVID-19/virología , Prueba de COVID-19 , Colorado , Control de Enfermedades Transmisibles , Estudios Transversales , Femenino , Guías como Asunto , Humanos , Inmunoglobulina G/sangre , Masculino , Persona de Mediana Edad , Salud Laboral , Reacción en Cadena de la Polimerasa , SARS-CoV-2/crecimiento & desarrollo , SARS-CoV-2/inmunología , AutoinformeRESUMEN
Sedentary obesity is associated with increased risk of many cardio-metabolic diseases, including type 2 diabetes. Weight loss is therefore a desirable goal for sedentary adults with obesity. Weight loss is also a well-documented side effect of sodium glucose co-transporter 2 (SGLT2) inhibition, a pharmaceutical strategy for diabetes treatment. We hypothesized that, compared with placebo, SGLT2 inhibition as an adjunct to out-patient dietary counselling for weight loss would lead to more favorable modification of body mass and composition, and greater improvement in glucose regulation and lipid profile. Using a randomized, double-blind, repeated measures parallel design, 50 sedentary men and women (body mass index: 33.4 ± 4.7 kg/m2; mean ± SD) were assigned to 12 weeks of dietary counselling, supplemented with daily ingestion of either a placebo or SGLT2 inhibitor (dapagliflozin: up to 10 mg/day). Dietary counselling favorably modified body mass, body fat, glucose regulation, and fasting concentrations of triglyceride and very low-density lipoprotein cholesterol (main effects of counselling: p < 0.05); SGLT2 inhibition did not influence any of these adaptations (counselling × medication interactions: p > 0.05). However, SGLT2 inhibition when combined with dietary counselling led to greater loss of fat-free mass (counselling × medication interaction: p = 0.047) and attenuated the rise in high-density lipoprotein cholesterol (counselling × medication interaction: p = 0.028). In light of these data and the health implications of decreased fat-free mass, we recommend careful consideration before implementing SGLT2 inhibition as an adjunct to dietary counselling for weight loss in sedentary adults with obesity.
Asunto(s)
Compuestos de Bencidrilo/administración & dosificación , Dieta Reductora , Consejo Dirigido , Glucósidos/administración & dosificación , Obesidad/terapia , Sobrepeso/terapia , Inhibidores del Cotransportador de Sodio-Glucosa 2/administración & dosificación , Programas de Reducción de Peso , Adolescente , Adulto , Anciano , Distribución de la Grasa Corporal , Índice de Masa Corporal , Método Doble Ciego , Femenino , Glucosa/metabolismo , Humanos , Lipoproteínas VLDL/metabolismo , Masculino , Persona de Mediana Edad , Obesidad/metabolismo , Sobrepeso/metabolismo , Resultado del Tratamiento , Triglicéridos/metabolismo , Adulto JovenRESUMEN
The synaptic vesicle protein, synaptotagmin I, is a multifunctional protein required for several steps in the synaptic vesicle cycle. It is primarily composed of two calcium-binding domains, C(2)A and C(2)B. Within each of these domains, a polylysine motif has been identified that is proposed to mediate specific functions within the synaptic vesicle cycle. While the C(2)B polylysine motif plays an important role in synaptic transmission in vivo, the C(2)A polylysine motif has not previously been analyzed at an intact synapse. Here, we show that mutation of the C(2)A polylysine motif increases the frequency of spontaneous transmitter release in vivo. The increased frequency is not a developmental consequence of disrupted synaptic transmission, as evoked transmitter release is unimpaired in the mutants. Our results demonstrate that synaptotagmin I plays a direct role in regulating spontaneous transmitter release, indicative of an active role in synaptic vesicle stabilization mediated by the C(2)A polylysine motif.
Asunto(s)
Calcio/metabolismo , Polilisina/genética , Vesículas Sinápticas/metabolismo , Sinaptotagmina I/metabolismo , Secuencia de Aminoácidos , Animales , Sitios de Unión/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/ultraestructura , Electrofisiología , Potenciales Postsinápticos Excitadores , Immunoblotting , Microscopía Electrónica , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido , Transmisión Sináptica , Vesículas Sinápticas/fisiología , Sinaptotagmina I/química , Sinaptotagmina I/genéticaRESUMEN
CONTEXT: The combination of two beneficial antidiabetes interventions, regular exercise and pharmaceuticals, is intuitively appealing. However, metformin, the most commonly prescribed diabetes medication, attenuates the favorable physiological adaptations to exercise; in turn, exercise may impede the action of metformin. OBJECTIVE: We sought to determine the influence of an alternative diabetes treatment, sodium glucose cotransporter 2 (SGLT2) inhibition, on the response to endurance exercise training. DESIGN, PARTICIPANTS, AND INTERVENTION: In a randomized, double-blind, repeated measures parallel design, 30 sedentary overweight and obese men and women were assigned to 12 weeks of supervised endurance exercise training, with daily ingestion of either a placebo or SGLT2 inhibitor (dapagliflozin: ≤10 mg/day). OUTCOME MEASUREMENTS AND RESULTS: Endurance exercise training favorably modified body mass, body composition (dual-energy x-ray absorptiometry), peak oxygen uptake (graded exercise with indirect calorimetry), responses to standardized submaximal exercise (indirect calorimetry, heart rate, and blood lactate), and skeletal muscle (vastus lateralis) citrate synthase activity (main effects of exercise training, all P < 0.05); SGLT2 inhibition did not influence any of these physiological adaptations (exercise training × treatment interaction, all P > 0.05). However, after endurance exercise training, fasting blood glucose was greater with SGLT2 inhibition, and increased insulin sensitivity (oral glucose tolerance test/Matsuda index) was abrogated with SGLT2 inhibition (exercise training × treatment interaction, P < 0.01). CONCLUSION: The efficacy of combining two beneficial antidiabetes interventions, regular endurance exercise and SGLT2 inhibition, was not supported. SGLT2 inhibition blunted endurance exercise training-induced improvements in insulin sensitivity, independent of effects on aerobic fitness or body composition.
Asunto(s)
Adaptación Fisiológica/efectos de los fármacos , Diabetes Mellitus Tipo 2/terapia , Entrenamiento Aeróbico/métodos , Terapia por Ejercicio/métodos , Inhibidores del Cotransportador de Sodio-Glucosa 2/efectos adversos , Adolescente , Adulto , Compuestos de Bencidrilo/efectos adversos , Glucemia/análisis , Glucemia/efectos de los fármacos , Glucemia/fisiología , Terapia Combinada/efectos adversos , Terapia Combinada/métodos , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/metabolismo , Método Doble Ciego , Femenino , Glucósidos/efectos adversos , Humanos , Insulina/sangre , Insulina/metabolismo , Resistencia a la Insulina/fisiología , Masculino , Persona de Mediana Edad , Resistencia Física/efectos de los fármacos , Resistencia Física/fisiología , Conducta Sedentaria , Transportador 2 de Sodio-Glucosa/metabolismo , Resultado del Tratamiento , Adulto JovenRESUMEN
Metformin and exercise independently improve insulin sensitivity and decrease the risk of diabetes. Metformin was also recently proposed as a potential therapy to slow aging. However, recent evidence indicates that adding metformin to exercise antagonizes the exercise-induced improvement in insulin sensitivity and cardiorespiratory fitness. The purpose of this study was to test the hypothesis that metformin diminishes the improvement in insulin sensitivity and cardiorespiratory fitness after aerobic exercise training (AET) by inhibiting skeletal muscle mitochondrial respiration and protein synthesis in older adults (62 ± 1 years). In a double-blinded fashion, participants were randomized to placebo (n = 26) or metformin (n = 27) treatment during 12 weeks of AET. Independent of treatment, AET decreased fat mass, HbA1c, fasting plasma insulin, 24-hr ambulant mean glucose, and glycemic variability. However, metformin attenuated the increase in whole-body insulin sensitivity and VO2 max after AET. In the metformin group, there was no overall change in whole-body insulin sensitivity after AET due to positive and negative responders. Metformin also abrogated the exercise-mediated increase in skeletal muscle mitochondrial respiration. The change in whole-body insulin sensitivity was correlated to the change in mitochondrial respiration. Mitochondrial protein synthesis rates assessed during AET were not different between treatments. The influence of metformin on AET-induced improvements in physiological function was highly variable and associated with the effect of metformin on the mitochondria. These data suggest that prior to prescribing metformin to slow aging, additional studies are needed to understand the mechanisms that elicit positive and negative responses to metformin with and without exercise.
Asunto(s)
Adaptación Fisiológica , Ejercicio Físico , Metformina/farmacología , Mitocondrias/metabolismo , Anciano , Glucemia/metabolismo , Capacidad Cardiovascular , Respiración de la Célula/efectos de los fármacos , Femenino , Humanos , Resistencia a la Insulina , Masculino , Persona de Mediana Edad , Mitocondrias/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Biosíntesis de Proteínas/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Homeostasis del Telómero/efectos de los fármacosRESUMEN
Maintaining proteostasis is a key mechanism for preserving cell function. Exercise-stimulated proteostasis is regulated, in part, by redox-sensitive signaling. Several studies suggest that supplementation with exogenous antioxidants blunts exercise-induced cellular adaptations, although this conclusion lacks consensus. Our group uses a fundamentally different approach to maintain redox balance by treatment with bioactive phytochemicals to activate the transcription factor nuclear factor (erythroid-derived 2)-like 2 and downstream endogenous antioxidant pathways. We hypothesized that vitamin C (VitC) would interfere with redox-sensitive proteostatic mechanisms in skeletal muscle, whereas phytochemical treatment would permit proteostatic maintenance. We measured protein and DNA synthesis in skeletal muscle from high-volume voluntary wheel-running rats. Whereas phytochemical treatment permitted mitochondrial and other proteostatic adaptations to exercise, VitC treatment did not. During an in vitro oxidative challenge, phytochemical treatment helped maintain proteostasis, including the mitochondrial fraction while VitC did not. Our findings support the conclusion that VitC can blunt some of the beneficial adaptations to exercise. We propose that regulation of endogenous antioxidants represents a novel approach to maintain redox balance while still permitting redox-sensitive proteostatic adaptations. NEW & NOTEWORTHY Whether vitamin C blocks aerobic exercise adaptions lacks consensus, perhaps because of approaches that only assess markers of mitochondrial biogenesis. By directly measuring mitochondrial biogenesis, we demonstrate that vitamin C blunts exercise-induced adaptations. Furthermore, we show that treatment with Protandim, a purported nuclear factor (erythroid-derived 2)-like 2 activator that upregulates endogenous antioxidants, permits mitochondrial biogenesis. We confirm that vitamin C blunts aerobic exercise adaptions, whereas Protandim does not, suggesting targeting the endogenous antioxidant network facilitates adaptations to exercise.
Asunto(s)
Adaptación Fisiológica/efectos de los fármacos , Ácido Ascórbico/farmacología , Medicamentos Herbarios Chinos/farmacología , Músculo Esquelético/efectos de los fármacos , Condicionamiento Físico Animal/fisiología , Animales , Antioxidantes/metabolismo , Suplementos Dietéticos , Masculino , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Músculo Esquelético/metabolismo , Biogénesis de Organelos , Oxidación-Reducción/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Transducción de Señal/efectos de los fármacosRESUMEN
In older adults, chronic oxidative and inflammatory stresses are associated with an impaired increase in skeletal muscle protein synthesis after acute anabolic stimuli. Conjugated linoleic acid (CLA) and Protandim have been shown to activate nuclear factor erythroid-derived 2-like 2 (Nrf2), a transcription factor for the antioxidant response element and anti-inflammatory pathways. This study tested the hypothesis that compared to a placebo control (CON), CLA and Protandim would increase skeletal muscle subcellular protein (myofibrillar, mitochondrial, cytoplasmic) and DNA synthesis in older adults after 6 weeks of milk protein feeding. CLA decreased oxidative stress and skeletal muscle oxidative damage with a trend to increase messenger RNA (mRNA) expression of a Nrf2 target, NAD(P)H dehydrogenase quinone 1 (NQO1). However, CLA did not influence other Nrf2 targets (heme oxygenase-1 (HO-1), glutathione peroxidase 1 (Gpx1)) or protein or DNA synthesis. Conversely, Protandim increased HO-1 protein content but not the mRNA expression of downstream Nrf2 targets, oxidative stress, or skeletal muscle oxidative damage. Rates of myofibrillar protein synthesis were maintained despite lower mitochondrial and cytoplasmic protein syntheses after Protandim versus CON. Similarly, DNA synthesis was non-significantly lower after Protandim compared to CON. After Protandim, the ratio of protein to DNA synthesis tended to be greater in the myofibrillar fraction and maintained in the mitochondrial and cytoplasmic fractions, emphasizing the importance of measuring both protein and DNA synthesis to gain insight into proteostasis. Overall, these data suggest that Protandim may enhance proteostatic mechanisms of skeletal muscle contractile proteins after 6 weeks of milk protein feeding in older adults.
Asunto(s)
Medicamentos Herbarios Chinos/uso terapéutico , Ácidos Linoleicos Conjugados/uso terapéutico , Proteínas de la Leche/uso terapéutico , Proteínas Musculares/metabolismo , Músculo Esquelético/metabolismo , Factor 2 Relacionado con NF-E2/metabolismo , Anciano , Método Doble Ciego , Femenino , Hemo-Oxigenasa 1/metabolismo , Humanos , Masculino , Persona de Mediana Edad , NAD(P)H Deshidrogenasa (Quinona)/metabolismo , Estrés Oxidativo/efectos de los fármacos , ARN Mensajero/metabolismoRESUMEN
Maintaining proteostasis is thought to be a key factor in slowed aging. In several growth-restricted models of long-life, we have shown evidence of increased proteostatic mechanisms, suggesting that proteostasis may be a shared characteristic of slowed aging. The Snell dwarf mouse is generated through the mutation of the Pit-1 locus causing reductions in multiple hormonal growth factors and mTORC1 signaling. Snell dwarfs are one of the longest lived rodent models of slowed aging. We hypothesized that proteostatic mechanisms would be increased in Snell compared to control (Con) as in other models of slowed aging. Using D2O, we simultaneously assessed protein synthesis in multiple subcellular fractions along with DNA synthesis in skeletal muscle, heart, and liver over 2 weeks in both sexes. We also assessed mTORC1-substrate phosphorylation. Skeletal muscle protein synthesis was decreased in all protein fractions of Snell compared to Con, varied by fraction in heart, and was not different between groups in liver. DNA synthesis was lower in Snell skeletal muscle and heart but not in liver when compared to Con. The new protein to new DNA synthesis ratio was increased threefold in Snell skeletal muscle and heart compared to Con. Snell mTORC1-substrate phosphorylation was decreased only in heart and liver. No effect of sex was seen in this study. Together with our previous investigations in long-lived models, we provide evidence further supporting proteostasis as a shared characteristic of slowed aging and show that increased proteostatic mechanisms may not necessarily require a decrease in mTORC1.
Asunto(s)
Envejecimiento , Replicación del ADN/fisiología , Longevidad/fisiología , Complejos Multiproteicos/metabolismo , Músculo Esquelético/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Animales , Femenino , Hígado/metabolismo , Masculino , Diana Mecanicista del Complejo 1 de la Rapamicina , Ratones , Biosíntesis de Proteínas/fisiología , Transducción de Señal/genética , Factores de Transcripción/genéticaRESUMEN
Canis lupus familiaris, the domesticated dog, is capable of extreme endurance performance. The ability to perform sustained aerobic exercise is dependent on a well-developed mitochondrial reticulum. In this study we examined the cumulative muscle protein and DNA synthesis in groups of athletic dogs at the onset of an exercise training program and following a strenuous exercise training program. We hypothesized that both at the onset and during an exercise training program there would be greater mitochondrial protein synthesis rates compared with sedentary control with no difference in mixed or cytoplasmic protein synthesis rates. Protein synthetic rates of three protein fractions and DNA synthesis were determined over 1 wk using (2)H2O in competitive Alaskan Huskies and Labrador Retrievers trained for explosive device detection. Both groups of dogs had very high rates of skeletal muscle protein synthesis in the sedentary state [Alaskan Huskies: Mixed = 2.28 ± 0.12, cytoplasmic (Cyto) = 2.91 ± 0.10, and mitochondrial (Mito) = 2.62 ± 0.07; Labrador Retrievers: Mixed = 3.88 ± 0.37, Cyto = 3.85 ± 0.06, and Mito = 2.92 ± 0.20%/day]. Mitochondrial (Mito) protein synthesis rates did not increase at the onset of an exercise training program. Exercise-trained dogs maintained Mito protein synthesis during exercise training when mixed (Mixed) and cytosolic (Cyto) fractions decreased, and this coincided with a decrease in p-RpS6 but also a decrease in p-ACC signaling. Contrary to our hypothesis, canines did not have large increases in mitochondrial protein synthesis at the onset or during an exercise training program. However, dogs have a high rate of protein synthesis compared with humans that perhaps does not necessitate an extra increase in protein synthesis at the onset of aerobic exercise training.
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ADN/biosíntesis , Perros/fisiología , Proteínas Musculares/biosíntesis , Músculo Esquelético/fisiología , Condicionamiento Físico Animal/métodos , Resistencia Física/fisiología , Adaptación Fisiológica/fisiología , Aerobiosis/fisiología , Animales , Perros/clasificación , Femenino , Masculino , Mitocondrias Musculares/fisiología , Proteínas Mitocondriales/biosíntesis , Especificidad de la EspecieRESUMEN
Studying long-lived animals provides novel insight into shared characteristics of aging and represents a unique model to elucidate approaches to prevent chronic disease. Oxidant stress underlies many chronic diseases and resistance to stress is a potential mechanism governing slowed aging. The transcription factor nuclear factor (erythroid-derived 2)-like 2 is the "master regulator" of cellular antioxidant defenses. Nrf2 is upregulated by some longevity promoting interventions and may play a role in regulating species longevity. However, Nrf2 expression and activity in long-lived models have not been well described. Here, we review evidence for altered Nrf2 signaling in a variety of slowed aging models that accomplish lifespan extension via pharmacological, nutritional, evolutionary, genetic, and presumably epigenetic means.
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Envejecimiento , Longevidad , Modelos Biológicos , Factor 2 Relacionado con NF-E2/metabolismo , Animales , Restricción Calórica , Miocardio/metabolismo , NAD(P)H Deshidrogenasa (Quinona)/metabolismo , Transducción de Señal , Superóxido Dismutasa/metabolismoRESUMEN
The Alaskan Husky has been specifically bred for endurance performance and is capable of extreme endurance performance. We examined sled dogs in the trained state at the beginning of the race season and after a 1,600-km race (Iditarod). Our hypothesis was that lipids would be the predominant substrate during submaximal exercise in long-distance racing sled dogs, and a 1,600-km race would increase the reliance on lipids during an exercise bout at the same absolute exercise intensity. The experiments were completed over three testing periods, which were completed in January of two different years before participation in a 1,600-km race, or in March shortly after completion of a 1,600-km race. After determination of H(13)CO3 (-) recovery, the dogs were tested with primed continuous infusions of [1,1,2,3,3-(2)H]glycerol, [3-(13)C]lactate, or [6,6-(2)H2]glucose. During exercise, respiratory exchange ratio was significantly higher in raced (0.92 ± 0.01) compared with nonraced (0.87 ± 0.01) dogs. During exercise, glucose rate of appearance was potentially sustained by a large glycerol rate of disappearance with an increase in lactate rates of oxidation after a 1,600-km race. Therefore, contrary to our hypothesis, the sled dogs were dependent on carbohydrate energy sources, a reliance that increased further after participation in a 1,600-km race.
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Metabolismo de los Hidratos de Carbono/fisiología , Carrera/fisiología , Algoritmos , Umbral Anaerobio/fisiología , Animales , Bicarbonatos/metabolismo , Perros , Femenino , Glucosa/metabolismo , Glicerol/metabolismo , Cinética , Ácido Láctico/metabolismo , Metabolismo de los Lípidos/fisiología , Masculino , Oxidación-Reducción , Condicionamiento Físico Animal , Resistencia Física/fisiologíaRESUMEN
In hypoxia, endurance exercise performance is diminished; pharmacotherapy may abrogate this performance deficit. Based on positive outcomes in preclinical trials, we hypothesized that oral administration of methazolamide, a carbonic anhydrase inhibitor, aminophylline, a nonselective adenosine receptor antagonist and phosphodiesterase inhibitor, and/or methazolamide combined with aminophylline would attenuate hypoxia-mediated decrements in endurance exercise performance in humans. Fifteen healthy males (26 ± 5 years, body-mass index: 24.9 ± 1.6 kg/m(2); mean ± SD) were randomly assigned to one of four treatments: placebo (n = 9), methazolamide (250 mg; n = 10), aminophylline (400 mg; n = 9), or methazolamide (250 mg) with aminophylline (400 mg; n = 8). On two separate occasions, the first in normoxia (FIO2 = 0.21) and the second in hypoxia (FIO2 = 0.15), participants sat for 4.5 hours before completing a standardized exercise bout (30 minutes, stationary cycling, 100 W), followed by a 12.5-km time trial. The magnitude of time trial performance decrement in hypoxia versus normoxia did not differ between placebo (+3.0 ± 2.7 minutes), methazolamide (+1.4 ± 1.7 minutes), and aminophylline (+1.8 ± 1.2 minutes), all with p > 0.09; however, the performance decrement in hypoxia versus normoxia with methazolamide combined with aminophylline was less than placebo (+0.6 ± 1.5 minutes; p = 0.01). This improvement may have been partially mediated by increased SpO2 in hypoxia with methazolamide combined with aminophylline compared with placebo (73% ± 3% vs. 79% ± 6%; p < 0.02). In conclusion, coadministration of methazolamide and aminophylline may promote endurance exercise performance during a sojourn at high altitude.
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Aminofilina/administración & dosificación , Ejercicio Físico/fisiología , Hipoxia/tratamiento farmacológico , Metazolamida/administración & dosificación , Resistencia Física/efectos de los fármacos , Adulto , Altitud , Quimioterapia Combinada , Prueba de Esfuerzo/efectos de los fármacos , Voluntarios Sanos , Humanos , Hipoxia/fisiopatología , Masculino , Adulto JovenRESUMEN
Chronic inhibition of the protein synthesis regulator mTORC1 through rapamycin extends life span in mice, with longer extension in females than in males. Whether rapamycin treatment inhibits protein synthesis or whether it does so differently between sexes has not been examined. UM-HET3 mice were fed a control or rapamycin-supplemented (Rap) diet for 12 weeks. Protein synthesis in mixed, cytosolic (cyto), and mitochondrial (mito) fractions and DNA synthesis and mTORC1 signaling were determined in skeletal muscle, heart, and liver. In both sexes, mito protein synthesis was maintained in skeletal muscle from Rap despite decreases in mixed and cyto fractions, DNA synthesis, and rpS6 phosphorylation. In the heart, no change in protein synthesis occurred despite the decreased DNA synthesis. In the heart and liver, Rap males were more sensitive to mTORC1 inhibition than Rap females. In conclusion, we show changes in protein synthesis and mTORC1 signaling that differ by sex and tissue.
Asunto(s)
Mitocondrias , Recambio Mitocondrial/efectos de los fármacos , Complejos Multiproteicos/metabolismo , Biosíntesis de Proteínas , Transducción de Señal , Sirolimus , Serina-Treonina Quinasas TOR/metabolismo , Animales , Antibióticos Antineoplásicos/metabolismo , Antibióticos Antineoplásicos/farmacología , Óxido de Deuterio/farmacología , Dieta/métodos , Femenino , Longevidad/efectos de los fármacos , Longevidad/genética , Masculino , Diana Mecanicista del Complejo 1 de la Rapamicina , Ratones , Mitocondrias/efectos de los fármacos , Mitocondrias/genética , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Fosforilación/efectos de los fármacos , Fosforilación/genética , Biosíntesis de Proteínas/efectos de los fármacos , Biosíntesis de Proteínas/genética , Proteína S6 Ribosómica/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Sirolimus/metabolismo , Sirolimus/farmacologíaRESUMEN
The soy-derived phytoestrogen genistein (GEN) has received attention for its potential benefits on the cardiovascular system by providing direct protection to cardiomyocytes against pathophysiological stresses. Here, we employed a proteomic approach to study the concentration-dependent effects of GEN treatments on cardiomyocytes. Cultured HL-1 cardiomyocytes were treated with low (1µM) and high (50µM) concentrations of GEN. Proteins were pre-fractionated by sequential hydrophilic/hydrophobic extraction and both protein fractions from each treatment group were separated by 2D gel electrophoresis (2DE). Overall, approximately 2,700 spots were visualized on the 2D gels. Thirty-nine and 99 spots changed in volume relative to controls (p<0.05) following the low- and high-concentration GEN treatments, respectively. From these spots, 25 and 62 protein species were identified by ESI-MS/MS and Mascot database searching, respectively. Identified proteins were further categorized according to their functions and possible links to cardioprotection were discussed. MetaCore gene ontology analysis suggested that 1µM GEN significantly impacted the anti-apoptosis process, and that both the low and high concentrations of GEN influenced the glucose catabolic process and regulation of ATPase activity. This proteomics study provides the first global insight into the molecular events triggered by GEN treatment in cardiomyocytes.