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1.
Anesth Analg ; 131(5): 1373-1379, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-33079858

RESUMO

BACKGROUND: Postpartum hemorrhage is a leading cause of maternal mortality. Antifibrinolytic therapy has the potential to influence outcomes in postpartum hemorrhage, but the incidence of elevated fibrinolytic activity in postpartum hemorrhage is unknown. METHODS: We retrospectively reviewed thromboelastography (TEG) results obtained for postpartum hemorrhage from 118 deliveries at The University of Chicago. TEG results were obtained as part of our postpartum hemorrhage protocol when blood loss exceeded 500 mL after vaginal delivery or 1000 mL after cesarean delivery. Our primary outcome was the incidence of elevated fibrinolytic activity, which we predefined as clot lysis ≥3% at 30 minutes (Ly30) on kaolin TEG. Platelet-mediated clot retraction can also lead to an elevated Ly30 on kaolin TEG. Therefore, to distinguish between fibrinolysis and clot retraction, we evaluated clot lysis using functional fibrinogen TEG, which contains a platelet inhibitor. We considered a kaolin TEG Ly30 ≥3% in conjunction with a nonzero functional fibrinogen TEG Ly30 suggestive of elevated fibrinolytic activity. We also recorded quantitative blood loss, primary etiology of hemorrhage, standard laboratory measurements of coagulation, and demographic and obstetric characteristics of the study population. RESULTS: The median kaolin TEG Ly30 was 0.2% (interquartile range: 0%-0.8%). Fifteen of 118 women (12.7%; 95% confidence interval, 7.9%-19.9%) had kaolin TEG Ly30 values ≥3%. Of 15 patients with elevated Ly30 values, functional fibrinogen TEG Ly30 was available for 13, of which none demonstrated detectable clot lysis. CONCLUSIONS: Our observation that none of the patients in our sample with kaolin TEG Ly30 values ≥3% had a nonzero functional fibrinogen TEG Ly30 value suggests that the observed elevations in kaolin TEG Ly30 may have been secondary to platelet-mediated clot retraction as opposed to fibrinolysis. Platelet-mediated clot retraction should be distinguished from fibrinolysis when assayed using viscoelastic techniques in postpartum hemorrhage. Further research is necessary to determine the optimal methods to assess fibrinolytic activity in postpartum hemorrhage.


Assuntos
Fibrinólise , Hemorragia Pós-Parto/sangue , Hemorragia Pós-Parto/epidemiologia , Tromboelastografia/métodos , Adulto , Testes de Coagulação Sanguínea , Viscosidade Sanguínea , Retração do Coágulo , Parto Obstétrico , Técnicas de Imagem por Elasticidade , Feminino , Humanos , Incidência , Inibidores da Agregação de Plaquetas/farmacologia , Gravidez , Estudos Retrospectivos , Resultado do Tratamento , Adulto Jovem
2.
Curr Opin Anaesthesiol ; 33(6): 793-799, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33002958

RESUMO

PURPOSE OF REVIEW: Recognition of the increasing maternal mortality rate in the United States has been accompanied by intense efforts to improve maternal safety. This article reviews recent advances in maternal safety, highlighting those of particular relevance to anesthesiologists. RECENT FINDINGS: Cardiovascular and other chronic medical conditions contribute to an increasing number of maternal deaths. Anesthetic complications associated with general anesthesia are decreasing, but complications associated with neuraxial techniques persist. Obstetric early warning systems are evolving and hold promise in identifying women at risk for adverse intrapartum events. Postpartum hemorrhage rates are rising, and rigorous evaluation of existing protocols may reveal unrecognized deficiencies. Development of regionalized centers for high-risk maternity care is a promising strategy to match women at risk for adverse events with appropriate resources. Opioids are a growing threat to maternal safety. There is growing evidence for racial inequities and health disparities in maternal morbidity and mortality. SUMMARY: Anesthesiologists play an essential role in ensuring maternal safety. While continued intrapartum vigilance is appropriate, addressing the full spectrum of contributors to maternal mortality, including those with larger roles beyond the immediate peripartum time period, will be essential to ongoing efforts to improve maternal safety.


Assuntos
Analgesia Obstétrica/tendências , Anestesia Obstétrica/tendências , Anestesiologistas/psicologia , Parto Obstétrico/tendências , Mortalidade Materna/tendências , Hemorragia Pós-Parto/prevenção & controle , Analgesia Obstétrica/efeitos adversos , Analgesia Obstétrica/métodos , Anestesia Obstétrica/efeitos adversos , Anestesia Obstétrica/métodos , Parto Obstétrico/efeitos adversos , Parto Obstétrico/métodos , Feminino , Humanos , Serviços de Saúde Materna/normas , Erros Médicos/prevenção & controle , Gravidez , Complicações na Gravidez , Estados Unidos
4.
Circ Res ; 127(3): e94-e106, 2020 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-32290757

RESUMO

RATIONALE: The heartbeat is organized by the cardiac conduction system (CCS), a specialized network of cardiomyocytes. Patterning of the CCS into atrial node versus ventricular conduction system (VCS) components with distinct physiology is essential for the normal heartbeat. Distinct node versus VCS physiology has been recognized for more than a century, but the molecular basis of this regional patterning is not well understood. OBJECTIVE: To study the genetic and genomic mechanisms underlying node versus VCS distinction and investigate rhythm consequences of failed VCS patterning. METHODS AND RESULTS: Using mouse genetics, we found that the balance between T-box transcriptional activator, Tbx5, and T-box transcriptional repressor, Tbx3, determined the molecular and functional output of VCS myocytes. Adult VCS-specific removal of Tbx5 or overexpression of Tbx3 re-patterned the fast VCS into slow, nodal-like cells based on molecular and functional criteria. In these cases, gene expression profiling showed diminished expression of genes required for VCS-specific fast conduction but maintenance of expression of genes required for nodal slow conduction physiology. Action potentials of Tbx5-deficient VCS myocytes adopted nodal-specific characteristics, including increased action potential duration and cellular automaticity. Removal of Tbx5 in vivo precipitated inappropriate depolarizations in the atrioventricular (His)-bundle associated with lethal ventricular arrhythmias. TBX5 bound and directly activated cis-regulatory elements at fast conduction channel genes required for fast physiological characteristics of the VCS action potential, defining the identity of the adult VCS. CONCLUSIONS: The CCS is patterned entirely as a slow, nodal ground state, with a T-box dependent, physiologically dominant, fast conduction network driven specifically in the VCS. Disruption of the fast VCS gene regulatory network allowed nodal physiology to emerge, providing a plausible molecular mechanism for some lethal ventricular arrhythmias.

5.
Anesth Analg ; 131(3): 830-839, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-31567326

RESUMO

BACKGROUND: Functional capacity assessment plays a core role in the preoperative evaluation. The Duke Activity Status Index (DASI) and the 6-minute walk test (6MWT) are 2 methods that have demonstrated the ability to evaluate functional capacity and predict perioperative outcomes. Smartphones offer a novel method to facilitate functional capacity assessment as they can easily administer a survey and accelerometers can track patient activity during a 6MWT. We developed a smartphone application to administer a 6MWT and DASI survey and performed a pilot study to evaluate the accuracy of a smartphone-based functional capacity tool in our Anesthesia and Perioperative Medicine Clinic. METHODS: Using the Apple ResearchKit software platform, we developed an application that administers a DASI survey and 6MWT on an iOS smartphone. The DASI was presented to the patient 1 question on the screen at a time and the application calculated the DASI score and estimated peak oxygen uptake (VO2). The 6MWT used the CMPedometer class from Apple's core motion facility to retrieve accelerometer data collected from the device's motion coprocessor to estimate steps walked. Smartphone estimated steps were compared to a research-grade pedometer using the intraclass correlation coefficient (ICC). Distance walked was directly measured during the 6MWT and we performed a multivariable linear regression with biometric variables to create a distance estimation algorithm to estimate distance walked from the number of steps recorded by the application. RESULTS: Seventy-eight patients were enrolled in the study and completed the protocol. Steps measured by the smartphone application as compared to the pedometer demonstrated moderate agreement with an ICC (95% CI) of 0.87 (0.79-0.92; P = .0001). The variables in the distance estimation algorithm included (ß coefficient [slope], 95% CI) steps walked (0.43, 0.29-0.57; P < .001), stride length (0.38, 0.22-0.53; P < .001), age in years (-1.90, -3.06 to -0.75; P = .002), and body mass index (-2.59, -5.13 to -0.06; P = .045). The overall model fit was R = 0.72, which indicates a moderate level of goodness of fit and explains 72% of the variation of distance walked during a 6MWT. CONCLUSIONS: Our pilot study demonstrated that a smartphone-based functional capacity assessment is feasible using the DASI and 6MWT. The DASI was easily completed by patients and the application clearly presented the results of the DASI to providers. Our application measured steps walked during a 6MWT moderately well in a preoperative patient population; however, future studies are needed to improve the smartphone application's step-counting accuracy and distance estimation algorithm.


Assuntos
Actigrafia/instrumentação , Aptidão Cardiorrespiratória , Monitores de Aptidão Física , Aplicativos Móveis , Cuidados Pré-Operatórios/instrumentação , Smartphone , Inquéritos e Questionários , Telemedicina/instrumentação , Teste de Caminhada/instrumentação , Idoso , Tolerância ao Exercício , Feminino , Nível de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Valor Preditivo dos Testes , Estudos Prospectivos , Reprodutibilidade dos Testes
7.
Anesth Analg ; 129(6): 1621-1626, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31743183

RESUMO

BACKGROUND: Many cases of maternal mortality and morbidity are preventable. A delayed response to clinical warning signs contributes to preventability. Therefore, the National Partnership for Maternal Safety devised maternal early warning criteria (MEWC), composed of abnormal vital signs that trigger bedside evaluation by a provider with the capacity to escalate care. The relationship of the MEWC to maternal morbidity has not been studied. We evaluated the correlation between the MEWC and maternal morbidity. METHODS: We retrospectively reviewed the first 400 deliveries at the University of Chicago in 2016. We analyzed the electronic medical record to determine whether vital signs triggered the MEWC during the admission to labor and delivery and whether patients experienced morbidity during their delivery hospitalization. The association between MEWC and morbidity was tested using χ analysis. We calculated the sensitivity, specificity, and positive and negative predictive values of the MEWC. RESULTS: Two hundred eighty-one (70%) of 400 patients triggered the MEWC at least once, and 198 (50%) of 400 patients had multiple or recurrent triggers. Ninety-nine (25%) of 400 patients experienced morbidity. The most common causes of morbidity were hemorrhage, suspected infection, and preeclampsia with severe features. The relative risk of maternal morbidity with at least a single trigger was 13.55 (95% confidence interval [CI], 4.38-41.91) and with recurrent or multiple triggers was 5.29 (95% CI, 3.22-8.71). The sensitivity of the MEWC in predicting morbidity was 0.97 (95% CI, 0.92-0.99) and the specificity was 0.39 (95% CI, 0.33-0.44) when patients with at least a single trigger were included. When including only patients with multiple or recurrent triggers, the sensitivity was 0.84 (95% CI, 0.75-0.90) and the specificity was 0.62 (95% CI, 0.56-0.67). The positive predictive value of the MEWC in our population was 0.34 (95% CI, 0.29-0.40), and the negative predictive value was 0.97 (95% CI, 0.93-0.99). When considering only patients with multiple or recurrent triggers, the positive predictive value was 0.42 (95% CI, 0.38-0.46) and the negative predictive value was 0.92 (95% CI, 0.88-0.95). CONCLUSIONS: The MEWC are associated with maternal morbidity. As a screening tool, they appropriately prioritize sensitivity and have an excellent negative predictive value. The criteria demonstrate low specificity, which is slightly improved by considering only patients with recurrent or multiple triggers. Additional efforts to improve the specificity of MEWC, with a focus on identifying sustained or recurrent patterns of abnormal vital signs, may be necessary before their widespread implementation.


Assuntos
Trabalho de Parto/fisiologia , Mortalidade Materna/tendências , Guias de Prática Clínica como Assunto/normas , Sinais Vitais/fisiologia , Adulto , Bases de Dados Factuais/tendências , Feminino , Humanos , Morbidade/tendências , Gravidez , Estudos Retrospectivos , Adulto Jovem
8.
J Clin Invest ; 124(4): 1844-52, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24642470

RESUMO

Variants in SCN10A, which encodes a voltage-gated sodium channel, are associated with alterations of cardiac conduction parameters and the cardiac rhythm disorder Brugada syndrome; however, it is unclear how SCN10A variants promote dysfunctional cardiac conduction. Here we showed by high-resolution 4C-seq analysis of the Scn10a-Scn5a locus in murine heart tissue that a cardiac enhancer located in Scn10a, encompassing SCN10A functional variant rs6801957, interacts with the promoter of Scn5a, a sodium channel-encoding gene that is critical for cardiac conduction. We observed that SCN5A transcript levels were several orders of magnitude higher than SCN10A transcript levels in both adult human and mouse heart tissue. Analysis of BAC transgenic mouse strains harboring an engineered deletion of the enhancer within Scn10a revealed that the enhancer was essential for Scn5a expression in cardiac tissue. Furthermore, the common SCN10A variant rs6801957 modulated Scn5a expression in the heart. In humans, the SCN10A variant rs6801957, which correlated with slowed conduction, was associated with reduced SCN5A expression. These observations establish a genomic mechanism for how a common genetic variation at SCN10A influences cardiac physiology and predisposes to arrhythmia.


Assuntos
Variação Genética , Miocárdio/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Canal de Sódio Disparado por Voltagem NAV1.8/genética , Adulto , Animais , Arritmias Cardíacas/etiologia , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatologia , Elementos Facilitadores Genéticos , Feminino , Regulação da Expressão Gênica , Coração/embriologia , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Canal de Sódio Disparado por Voltagem NAV1.5/fisiologia , Canal de Sódio Disparado por Voltagem NAV1.8/fisiologia , Polimorfismo de Nucleotídeo Único , Gravidez , Regiões Promotoras Genéticas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
9.
J Clin Invest ; 122(7): 2509-18, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22728936

RESUMO

Cardiac conduction system (CCS) disease, which results in disrupted conduction and impaired cardiac rhythm, is common with significant morbidity and mortality. Current treatment options are limited, and rational efforts to develop cell-based and regenerative therapies require knowledge of the molecular networks that establish and maintain CCS function. Recent genome-wide association studies (GWAS) have identified numerous loci associated with adult human CCS function, including TBX5 and SCN5A. We hypothesized that TBX5, a critical developmental transcription factor, regulates transcriptional networks required for mature CCS function. We found that deletion of Tbx5 from the mature murine ventricular conduction system (VCS), including the AV bundle and bundle branches, resulted in severe VCS functional consequences, including loss of fast conduction, arrhythmias, and sudden death. Ventricular contractile function and the VCS fate map remained unchanged in VCS-specific Tbx5 knockouts. However, key mediators of fast conduction, including Nav1.5, which is encoded by Scn5a, and connexin 40 (Cx40), demonstrated Tbx5-dependent expression in the VCS. We identified a TBX5-responsive enhancer downstream of Scn5a sufficient to drive VCS expression in vivo, dependent on canonical T-box binding sites. Our results establish a direct molecular link between Tbx5 and Scn5a and elucidate a hierarchy between human GWAS loci that affects function of the mature VCS, establishing a paradigm for understanding the molecular pathology of CCS disease.


Assuntos
Regulação da Expressão Gênica , Sistema de Condução Cardíaco/fisiopatologia , Canais de Sódio/metabolismo , Proteínas com Domínio T/fisiologia , Animais , Arritmias Cardíacas/diagnóstico por imagem , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatologia , Sítios de Ligação , Conexinas/genética , Conexinas/metabolismo , Eletrocardiografia , Elementos Facilitadores Genéticos , Técnicas de Inativação de Genes , Sistema de Condução Cardíaco/metabolismo , Sistema de Condução Cardíaco/patologia , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Camundongos , Camundongos Transgênicos , Contração Miocárdica , Canal de Sódio Disparado por Voltagem NAV1.5 , Canais de Sódio/genética , Proteínas com Domínio T/genética , Proteínas com Domínio T/metabolismo , Ultrassonografia
10.
Birth Defects Res A Clin Mol Teratol ; 91(6): 578-85, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21538814

RESUMO

Proper function of an organized Cardiac Conduction System (CCS) is vital to the survival of metazoans ranging from fly to man. The routine use of non-invasive electrocardiogram measures in the diagnosis and monitoring of cardiovascular health has established a trove of reliable CCS functional data in both normal and diseased cardiac states. Recent combination of echocardiogram (ECG) data with genome-wide association studies has identified genomic regions implicated in ECG variability which impact CCS function. In this study, we review the substantial recent progress in this area, highlighting the identification of novel loci, confirming the importance of previously implicated loci in CCS function, and exploring potential links between genes with important roles in developmental processes and variation in function of the CCS.


Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Sistema de Condução Cardíaco/crescimento & desenvolvimento , Sistema de Condução Cardíaco/metabolismo , Animais , Eletrocardiografia , Estudo de Associação Genômica Ampla , Cardiopatias/fisiopatologia , Humanos
11.
Genesis ; 49(11): 878-84, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21504046

RESUMO

Inducible Cre recombination is a powerful technology that allows for spatial and temporal modulation of gene expression in vivo. Diseases of the cardiac conduction system (CCS) pose a significant clinical burden but are not currently well understood at the molecular level. To enable inducible recombination in the murine CCS, we created a minK:CreERT(2) bacterial artificial chromosome (BAC) transgenic mouse line. Cre activity is present after tamoxifen administration in the atrioventricular (AV) node, AV bundle, and bundle branches of adult transgenic mice. We anticipate that by enabling inducible recombination specifically in the AV node, bundle, and bundle branches, minK:CreERT(2) BAC transgenic mice will prove useful in advancing our understanding of CCS disease and function.


Assuntos
Nó Atrioventricular/efeitos dos fármacos , Cromossomos Artificiais Bacterianos/metabolismo , Integrases/metabolismo , Camundongos Transgênicos/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana/metabolismo , Recombinação Genética , Animais , Nó Atrioventricular/enzimologia , Fascículo Atrioventricular/efeitos dos fármacos , Fascículo Atrioventricular/enzimologia , Cromossomos Artificiais Bacterianos/genética , Embrião de Mamíferos/efeitos dos fármacos , Embrião de Mamíferos/enzimologia , Escherichia coli/genética , Escherichia coli/metabolismo , Genes Reporter , Coração/efeitos dos fármacos , Coração/embriologia , Integrases/genética , Camundongos , Camundongos Transgênicos/embriologia , Camundongos Transgênicos/metabolismo , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Coloração e Rotulagem , Tamoxifeno/administração & dosagem , Tamoxifeno/farmacologia
12.
Mol Cell Biol ; 26(22): 8217-27, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16966378

RESUMO

LKB1 is a tumor suppressor that may also be fundamental to cell metabolism, since LKB1 phosphorylates and activates the energy sensing enzyme AMPK. We generated muscle-specific LKB1 knockout (MLKB1KO) mice, and surprisingly, found that a lack of LKB1 in skeletal muscle enhanced insulin sensitivity, as evidenced by decreased fasting glucose and insulin concentrations, improved glucose tolerance, increased muscle glucose uptake in vivo, and increased glucose utilization during a hyperinsulinemic-euglycemic clamp. MLKB1KO mice had increased insulin-stimulated Akt phosphorylation and a > 80% decrease in muscle expression of TRB3, a recently identified Akt inhibitor. Akt/TRB3 binding was present in skeletal muscle, and overexpression of TRB3 in C2C12 myoblasts significantly reduced Akt phosphorylation. These results demonstrate that skeletal muscle LKB1 is a negative regulator of insulin sensitivity and glucose homeostasis. LKB1-mediated TRB3 expression provides a novel link between LKB1 and Akt, critical kinases involved in both tumor genesis and cell metabolism.


Assuntos
Proteínas de Ciclo Celular/metabolismo , Glucose/farmacocinética , Resistência à Insulina , Músculo Esquelético/metabolismo , Proteínas Serina-Treonina Quinases/fisiologia , Proteínas Quinases Ativadas por AMP , Animais , Linhagem Celular , Cruzamentos Genéticos , Feminino , Homeostase , Masculino , Camundongos , Camundongos Knockout , Complexos Multienzimáticos/metabolismo , PPAR alfa/metabolismo , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Transativadores/metabolismo , Fatores de Transcrição
13.
Diabetes ; 55(7): 2067-76, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16804077

RESUMO

Insulin and contraction increase GLUT4 translocation in skeletal muscle via distinct signaling mechanisms. Akt substrate of 160 kDa (AS160) mediates insulin-stimulated GLUT4 translocation in L6 myotubes, presumably through activation of Akt. Using in vivo, in vitro, and in situ methods, insulin, contraction, and the AMP-activated protein kinase (AMPK) activator AICAR all increased AS160 phosphorylation in mouse skeletal muscle. Insulin-stimulated AS160 phosphorylation was fully blunted by wortmannin in vitro and in Akt2 knockout (KO) mice in vivo. In contrast, contraction-stimulated AS160 phosphorylation was only partially decreased by wortmannin and unaffected in Akt2 KO mice, suggesting additional regulatory mechanisms. To determine if AMPK mediates AS160 signaling, we used AMPK alpha2-inactive (alpha2i) transgenic mice. AICAR-stimulated AS160 phosphorylation was fully inhibited, whereas contraction-stimulated AS160 phosphorylation was partially reduced in the AMPK alpha2i transgenic mice. Combined AMPK alpha2 and Akt inhibition by wortmannin treatment of AMPK alpha2 transgenic mice did not fully ablate contraction-stimulated AS160 phosphorylation. Maximal insulin, together with either AICAR or contraction, increased AS160 phosphorylation in an additive manner. In conclusion, AS160 may be a point of convergence linking insulin, contraction, and AICAR signaling. While Akt and AMPK alpha2 activities are essential for AS160 phosphorylation by insulin and AICAR, respectively, neither kinase is indispensable for the entire effects of contraction on AS160 phosphorylation.


Assuntos
Aminoimidazol Carboxamida/análogos & derivados , Proteínas Ativadoras de GTPase/metabolismo , Insulina/farmacologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Ribonucleotídeos/farmacologia , Transdução de Sinais/fisiologia , Adenilato Quinase/metabolismo , Aminoimidazol Carboxamida/farmacologia , Animais , Feminino , Proteínas Ativadoras de GTPase/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Cinética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Contração Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Fosforilação , Transporte Proteico
14.
Am J Physiol Endocrinol Metab ; 291(5): E1031-7, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16803855

RESUMO

The serine/threonine kinase Akt/PKB plays diverse roles in cells, and genetic studies have indicated distinct roles for the three Akt isoforms expressed in mammalian cells and tissues. Akt2 is a key signaling intermediate for insulin-stimulated glucose uptake and glycogen synthesis in skeletal muscle. Akt2 has also been shown to be activated by exercise and muscle contraction in both rodents and humans. In this study, we used Akt2 knockout mice to explore the role of Akt2 in exercise-stimulated glucose uptake and glycogen synthesis as well as intracellular signaling pathways that regulate glycogen metabolism in skeletal muscle. We found that Akt2 deficiency does not affect basal or exercise-stimulated glucose uptake or intracellular glycogen content in the soleus muscle. In addition, lack of Akt2 did not result in alterations in basal Akt Thr(308) or basal and contraction-stimulated glycogen synthase kinase-3beta (GSK-3beta) Ser(9) phosphorylation, glycogen synthase phosphorylation, or glycogen synthase activity. In contrast, in situ contraction failed to elicit normal increases in Akt T-loop Thr(308) phosphorylation and GSK-3alpha Ser(21) phosphorylation in tibialis anterior muscles from Akt2-deficient animals. Our data establish a key role for Akt2 in the regulation of GSK-3alpha Ser(21) phosphorylation with contraction and add genetic evidence to support the separation of the intracellular pathways regulated by insulin and exercise that converge on glucose uptake and glycogen synthesis in skeletal muscle.


Assuntos
Glicemia/metabolismo , Contração Muscular/fisiologia , Músculo Esquelético/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/fisiologia , Animais , Glicogênio/biossíntese , Quinase 3 da Glicogênio Sintase/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Músculo Esquelético/citologia , Fosforilação , Esforço Físico/fisiologia , Proteínas Proto-Oncogênicas c-akt/genética , Serina/metabolismo
15.
Biochem Biophys Res Commun ; 319(2): 419-25, 2004 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-15178423

RESUMO

Activation of Akt and deactivation of GSK3 are critical signals regulating a number of cellular processes in multiple systems. Whether physical exercise alters Akt and GSK3 activity in human skeletal muscle is controversial. beta-Catenin, a GSK3 substrate and important Wnt signaling protein that alters gene transcription, has not been investigated in human skeletal muscle. In the present study, eight healthy human subjects performed 30min of cycling exercise at 75% of maximum workload (submaximal) followed by 6 bouts of 60s at 125% maximum workload (maximal). Biopsies of vastus lateralis muscle were taken at rest (basal), and within 15s following cessation of the submaximal and maximal exercise bouts. Exercise at both submaximal and maximal intensities significantly increased Akt activity (40% and 110%, respectively). Increases in Akt activity were accompanied by increases in Akt Thr(308) and Ser(473) phosphorylation, decreased GSK3alpha activity ( approximately 30% at both intensities), and increased phosphorylation of GSK3alpha Ser(21). Exercise at both intensities also decreased beta-catenin Ser(33/37)Thr(41) phosphorylation (50-60% at both intensities). These results demonstrate that Akt, GSK3, and beta-catenin signaling are regulated by exercise in human skeletal muscle, and as such identify them as possible molecular mediators of exercise's effect on metabolic and transcriptional processes in skeletal muscle.


Assuntos
Exercício Físico , Quinases da Glicogênio Sintase/metabolismo , Músculo Esquelético/enzimologia , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Adulto , Glicemia/análise , Proteínas do Citoesqueleto/metabolismo , Feminino , Glicogênio/metabolismo , Humanos , Insulina/sangue , Ácido Láctico/sangue , Masculino , Fosforilação , Proteínas Proto-Oncogênicas c-akt , Transdução de Sinais , Transativadores/metabolismo , beta Catenina
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