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1.
Artigo em Inglês | MEDLINE | ID: mdl-32216614

RESUMO

Traditionally, the evaluation of cardiac function has focused on systolic function, however, there is a growing appreciation for the contribution of diastolic function to overall cardiac health. Given the emerging interest in evaluating diastolic function in all models of heart failure, there is a need for sensitivity, accuracy, and precision in the hemodynamic assessment of diastolic function. Hemodynamics measures cardiac pressures in vivo - offering a direct assessment of diastolic function. In this review, we summarize the underlying principles of diastolic function, dividing diastole into two phases: (1) relaxation and (2) filling. We identify parameters used to comprehensively evaluate diastolic function by hemodynamics, clarify how each parameter is obtained, and give consideration to the advantages and limitations associated with each measure. We provide a summary of the sensitivity of each diastolic parameter to loading conditions. Further, we discuss differences that can occur in the accuracy of diastolic and systolic indices when generated by automated software compared to custom software analysis, and the magnitude each parameter is influenced during inspiration with healthy breathing and a mild breathing load, commonly expected in heart failure. Finally, we identify key variables to control (e.g., body temperature, anesthetic, sampling rate) when collecting hemodynamic data. This review provides fundamental knowledge for users to succeed in troubleshooting and guidelines for evaluating diastolic function by hemodynamics in experimental models of heart failure.

2.
J Physiol ; 598(4): 683-697, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31845331

RESUMO

KEY POINTS: Although the role of TBC1D1 within the heart remains unknown, expression of TBC1D1 increases in the left ventricle following an acute infarction, suggesting a biological importance within this tissue. We investigated the mechanistic role of TBC1D1 within the heart, aiming to establish the consequences of attenuating TBC1D1 signalling in the development of diabetic cardiomyopathy, as well as to determine potential sex differences. TBC1D1 ablation increased plasma membrane fatty acid binding protein content and myocardial palmitate oxidation. Following high-fat feeding, TBC1D1 ablation dramatically increased fibrosis and induced end-diastolic dysfunction in both male and female rats in the absence of changes in mitochondrial bioenergetics. Altogether, independent of sex, ablating TBC1D1 predisposes the left ventricle to pathological remodelling following high-fat feeding, and suggests TBC1D1 protects against diabetic cardiomyopathy. ABSTRACT: TBC1D1, a Rab-GTPase activating protein, is involved in the regulation of glucose handling and substrate metabolism within skeletal muscle, and is essential for maintaining pancreatic ß-cell mass and insulin secretion. However, the function of TBC1D1 within the heart is largely unknown. Therefore, we examined the role of TBC1D1 in the left ventricle and the functional consequence of ablating TBC1D1 on the susceptibility to high-fat diet-induced abnormalities. Since mutations within TBC1D1 (R125W) display stronger associations with clinical parameters in women, we further examined possible sex differences in the predisposition to diabetic cardiomyopathy. In control-fed animals, TBC1D1 ablation did not alter insulin-stimulated glucose uptake, or echocardiogram parameters, but increased accumulation of a plasma membrane fatty acid transporter and the capacity for palmitate oxidation. When challenged with an 8 week high-fat diet, TBC1D1 knockout rats displayed a four-fold increase in fibrosis compared to wild-type animals, and this was associated with diastolic dysfunction, suggesting a predisposition to diet-induced cardiomyopathy. Interestingly, high-fat feeding only induced cardiac hypertrophy in male TBC1D1 knockout animals, implicating a possible sex difference. Mitochondrial respiratory capacity and substrate sensitivity to pyruvate and ADP were not altered by diet or TBC1D1 ablation, nor were markers of oxidative stress, or indices of overt heart failure. Altogether, independent of sex, ablation of TBC1D1 not only increased the susceptibility to high-fat diet-induced diastolic dysfunction and left ventricular fibrosis, independent of sex, but also predisposed male animals to the development of cardiac hypertrophy. These data suggest that TBC1D1 may exert cardioprotective effects in the development of diabetic cardiomyopathy.

3.
J Cachexia Sarcopenia Muscle ; 10(3): 643-661, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30938481

RESUMO

BACKGROUND: Muscle wasting and weakness in Duchenne muscular dystrophy (DMD) causes severe locomotor limitations and early death due in part to respiratory muscle failure. Given that current clinical practice focuses on treating secondary complications in this genetic disease, there is a clear need to identify additional contributions in the aetiology of this myopathy for knowledge-guided therapy development. Here, we address the unresolved question of whether the complex impairments observed in DMD are linked to elevated mitochondrial H2 O2 emission in conjunction with impaired oxidative phosphorylation. This study performed a systematic evaluation of the nature and degree of mitochondrial-derived H2 O2 emission and mitochondrial oxidative dysfunction in a mouse model of DMD by designing in vitro bioenergetic assessments that attempt to mimic in vivo conditions known to be critical for the regulation of mitochondrial bioenergetics. METHODS: Mitochondrial bioenergetics were compared with functional and histopathological indices of myopathy early in DMD (4 weeks) in D2.B10-DMDmdx /2J mice (D2.mdx)-a model that demonstrates severe muscle weakness. Adenosine diphosphate's (ADP's) central effect of attenuating H2 O2 emission while stimulating respiration was compared under two models of mitochondrial-cytoplasmic phosphate exchange (creatine independent and dependent) in muscles that stained positive for membrane damage (diaphragm, quadriceps, and white gastrocnemius). RESULTS: Pathway-specific analyses revealed that Complex I-supported maximal H2 O2 emission was elevated concurrent with a reduced ability of ADP to attenuate emission during respiration in all three muscles (mH2 O2 : +17 to +197% in D2.mdx vs. wild type). This was associated with an impaired ability of ADP to stimulate respiration at sub-maximal and maximal kinetics (-17 to -72% in D2.mdx vs. wild type), as well as a loss of creatine-dependent mitochondrial phosphate shuttling in diaphragm and quadriceps. These changes largely occurred independent of mitochondrial density or abundance of respiratory chain complexes, except for quadriceps. This muscle was also the only one exhibiting decreased calcium retention capacity, which indicates increased sensitivity to calcium-induced permeability transition pore opening. Increased H2 O2 emission was accompanied by a compensatory increase in total glutathione, while oxidative stress markers were unchanged. Mitochondrial bioenergetic dysfunctions were associated with induction of mitochondrial-linked caspase 9, necrosis, and markers of atrophy in some muscles as well as reduced hindlimb torque and reduced respiratory muscle function. CONCLUSIONS: These results provide evidence that Complex I dysfunction and loss of central respiratory control by ADP and creatine cause elevated oxidant generation during impaired oxidative phosphorylation. These dysfunctions may contribute to early stage disease pathophysiology and support the growing notion that mitochondria are a potential therapeutic target in this disease.

4.
J Physiol ; 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30674086

RESUMO

KEY POINTS: Ninety-eight per cent of patients with Duchenne muscular dystrophy (DMD) develop cardiomyopathy, with 40% developing heart failure. While increased propensity for mitochondrial induction of cell death has been observed in left ventricle, it remains unknown whether this is linked to impaired mitochondrial respiratory control and elevated H2 O2 emission prior to the onset of cardiomyopathy. Classic mouse models of DMD demonstrate hyper-regeneration in skeletal muscle which may mask mitochondrial abnormalities. Using a model with less regenerative capacity that is more akin to DMD patients, we observed elevated left ventricular mitochondrial H2 O2 and impaired oxidative phosphorylation in the absence of cardiac remodelling or overt cardiac dysfunction at 4 weeks. These impairments were associated with dysfunctions at complex I, governance by ADP and creatine-dependent phosphate shuttling, which results in a less efficient response to energy demands. Mitochondria may be a therapeutic target for the treatment of cardiomyopathy in DMD. ABSTRACT: In Duchenne muscular dystrophy (DMD), mitochondrial dysfunction is predicted as a response to numerous cellular stressors, yet the contribution of mitochondria to the onset of cardiomyopathy remains unknown. To resolve this uncertainty, we designed in vitro assessments of mitochondrial bioenergetics to model mitochondrial control parameters that influence cardiac function. Both left ventricular mitochondrial responsiveness to the central bioenergetic controller ADP and the ability of creatine to facilitate mitochondrial-cytoplasmic phosphate shuttling were assessed. These measurements were performed in D2.B10-DMDmdx /2J mice - a model that demonstrates skeletal muscle atrophy and weakness due to limited regenerative capacities and cardiomyopathy more akin to people with DMD than classic models. At 4 weeks of age, there was no evidence of cardiac remodelling or cardiac dysfunction despite impairments in ADP-stimulated respiration and ADP attenuation of H2 O2 emission. These impairments were seen at both submaximal and maximal ADP concentrations despite no reductions in mitochondrial content markers. The ability of creatine to enhance ADP's control of mitochondrial bioenergetics was also impaired, suggesting an impairment in mitochondrial creatine kinase-dependent phosphate shuttling. Susceptibly to permeability transition pore opening and the subsequent activation of cell death pathways remained unchanged. Mitochondrial H2 O2 emission was elevated despite no change in markers of irreversible oxidative damage, suggesting alternative redox signalling mechanisms should be explored. These findings demonstrate that selective mitochondrial dysfunction precedes the onset of overt cardiomyopathy in D2.mdx mice, suggesting that improving mitochondrial bioenergetics by restoring ADP, creatine-dependent phosphate shuttling and complex I should be considered for treating DMD patients.

5.
Can J Physiol Pharmacol ; 96(11): 1060-1068, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30102865

RESUMO

During physiological stress (e.g., exercise, hypoxia), blood flow is shunted to specific anatomical regions to protect critical organs; yet, splenic blood flow in these circumstances remains to be investigated. Despite being classically viewed as a non-critical organ, recent experimental and epidemiological evidence suggests the spleen plays a significant role in cardiovascular pathophysiology. We hypothesized that splenic blood flow is prioritized in the development of heart failure (i.e., chronic state of reduced cardiac output). Five-week-old male Wistar rats were randomized for either myocardial infarction (MI; n = 58) or sham (n = 56) surgery. At 2, 5, and 9 weeks post-surgery, Doppler ultrasound measurements of the splenic, left renal, left common carotid, and left femoral arteries were performed. Cardiac function was assessed at all time points using echocardiography and at 9 weeks post-surgery using invasive hemodynamic analysis. Splenic and cerebral blood flow was preferentially maintained at 9 weeks post-MI, whereas blood flow to the lower limb and kidney were reduced. Spleen size increased by 5 weeks post-MI and remained elevated. Splenic blood flow was maintained in conditions of decreased cardiac output, when other tissues showed decreased blood flow. The maintenance of blood flow in the face of decreased cardiac output indicates that splenic function is being prioritized during heart failure.


Assuntos
Débito Cardíaco , Insuficiência Cardíaca/fisiopatologia , Infarto do Miocárdio/fisiopatologia , Fluxo Sanguíneo Regional , Baço/irrigação sanguínea , Animais , Modelos Animais de Doenças , Progressão da Doença , Ecocardiografia , Coração/diagnóstico por imagem , Coração/fisiopatologia , Humanos , Masculino , Infarto do Miocárdio/etiologia , Tamanho do Órgão , Ratos , Ratos Wistar , Baço/diagnóstico por imagem , Baço/fisiopatologia , Ultrassonografia Doppler
6.
Front Physiol ; 9: 472, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29867532

RESUMO

A growing proportion of heart failure (HF) patients present with impairments in both ventricles. Experimental pressure-overload (i.e., transverse aortic constriction, TAC) induces left ventricle (LV) hypertrophy and failure, as well as right ventricle (RV) dysfunction. However, little is known about the coordinated progression of biventricular dysfunction that occurs in TAC. Here we investigated the time course of systolic and diastolic function in both the LV and RV concurrently to improve our understanding of the chronology of events in TAC. Hemodynamic, histological, and morphometric assessments were obtained from the LV and RV at 2, 4, 9, and 18 weeks post-surgery. Results: Systolic pressures peaked in both ventricles at 4 weeks, thereafter steadily declining in the LV, while remaining elevated in the RV. The LV and RV followed different structural and functional timelines, suggesting the patterns in one ventricle are independent from the opposing ventricle. RV hypertrophy/fibrosis and pulmonary arterial remodeling confirmed a progressive right-sided pathology. We further identified both compensation and decompensation in the LV with persistent concentric hypertrophy in both phases. Finally, diastolic impairments in both ventricles manifested as an intricate progression of multiple parameters that were not in agreement until overt systolic failure was evident. Conclusion: We establish pulmonary hypertension was secondary to LV dysfunction, confirming TAC is a model of type II pulmonary hypertension. This study also challenges some common assumptions in experimental HF (e.g., the relationship between fibrosis and filling pressure) while addressing a knowledge gap with respect to temporality of RV remodeling in pressure-overload.

7.
J Physiol ; 596(15): 3391-3410, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29604069

RESUMO

KEY POINTS: In the present study, we provide evidence for divergent physiological responses to moderate compared to severe hypoxia, addressing an important knowledge gap related to severity, duration and after-effects of hypoxia encountered in cardiopulmonary situations. The physiological responses to moderate and severe hypoxia were not proportional, linear or concurrent with the time-of-day. Hypoxia elicited severity-dependent physiological responses that either persisted or fluctuated throughout normoxic recovery. The physiological basis for these distinct cardiovascular responses implicates a shift in the sympathovagal set point and probably not molecular changes at the artery resulting from hypoxic stress. ABSTRACT: Hypoxia is both a consequence and cause of many acute and chronic diseases. Severe hypoxia causes hypertension with cardiovascular sequelae; however, the rare studies using moderate severities of hypoxia indicate that it can be beneficial, suggesting that hypoxia may not always be detrimental. Comparisons between studies are difficult because of the varied classifications of hypoxic severities, methods of delivery and use of anaesthetics. Thus, to investigate the long-term effects of moderate hypoxia on cardiovascular health, radiotelemetry was used to obtain in vivo physiological measurements in unanaesthetized mice during 24 h of either moderate (FIO2=0.15) or severe (FIO2=0.09) hypoxia, followed by 72 h of normoxic recovery. Systolic blood pressure was decreased during recovery following moderate hypoxia but increased following severe hypoxia. Moderate and severe hypoxia increased haeme oxygenase-1 expression during recovery, suggesting parity in hypoxic stress at the level of the artery. Severe but not moderate hypoxia increased the low/high frequency ratio of heart rate variability 72 h post-hypoxia, indicating a shift in sympathovagal balance. Moderate hypoxia dampened the amplitude of circadian rhythm, whereas severe disrupted rhythm during the entire insult, with perturbations persisting throughout normoxic recovery. Thus, hypoxic severity differentially regulates circadian blood pressure.


Assuntos
Hipóxia/fisiopatologia , Animais , Pressão Sanguínea , Frequência Cardíaca , Masculino , Camundongos Endogâmicos C57BL
8.
J Med Internet Res ; 20(4): e111, 2018 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-29695375

RESUMO

BACKGROUND: Clinical guidelines recommend monitoring of blood pressure at home using an automatic blood pressure device for the management of hypertension. Devices are not often calibrated against direct blood pressure measures, leaving health care providers and patients with less reliable information than is possible with current technology. Rigorous assessments of medical devices are necessary for establishing clinical utility. OBJECTIVE: The purpose of our study was 2-fold: (1) to assess the validity and perform iterative calibration of indirect blood pressure measurements by a noninvasive wrist cuff blood pressure device in direct comparison with simultaneously recorded peripheral and central intra-arterial blood pressure measurements and (2) to assess the validity of the measurements thereafter of the noninvasive wrist cuff blood pressure device in comparison with measurements by a noninvasive upper arm blood pressure device to the Canadian hypertension guidelines. METHODS: The cloud-based blood pressure algorithms for an oscillometric wrist cuff device were iteratively calibrated to direct pressure measures in 20 consented patient participants. We then assessed measurement validity of the device, using Bland-Altman analysis during routine cardiovascular catheterization. RESULTS: The precalibrated absolute mean difference between direct intra-arterial to wrist cuff pressure measurements were 10.8 (SD 9.7) for systolic and 16.1 (SD 6.3) for diastolic. The postcalibrated absolute mean difference was 7.2 (SD 5.1) for systolic and 4.3 (SD 3.3) for diastolic pressures. This is an improvement in accuracy of 33% systolic and 73% diastolic with a 48% reduction in the variability for both measures. Furthermore, the wrist cuff device demonstrated similar sensitivity in measuring high blood pressure compared with the direct intra-arterial method. The device, when calibrated to direct aortic pressures, demonstrated the potential to reduce a treatment gap in high blood pressure measurements. CONCLUSIONS: The systolic pressure measurements of the wrist cuff have been iteratively calibrated using gold standard central (ascending aortic) pressure. This improves the accuracy of the indirect measures and potentially reduces the treatment gap. Devices that undergo auscultatory (indirect) calibration for licensing can be greatly improved by additional iterative calibration via intra-arterial (direct) measures of blood pressure. Further clinical trials with repeated use of the device over time are needed to assess the reliability of the device in accordance with current and evolving guidelines for informed decision making in the management of hypertension. TRIAL REGISTRATION: ClinicalTrials.gov NCT03015363; https://clinicaltrials.gov/ct2/show/NCT03015363 (Archived by WebCite at http://www.webcitation.org/6xPZgseYS).


Assuntos
Determinação da Pressão Arterial/instrumentação , Monitores de Pressão Arterial/normas , Pressão Sanguínea/fisiologia , Hipertensão/diagnóstico , Punho/irrigação sanguínea , Adulto , Idoso , Calibragem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes
9.
Am J Physiol Regul Integr Comp Physiol ; 315(2): R191-R204, 2018 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-29513565

RESUMO

Supplementation with dietary inorganic nitrate ([Formula: see text]) is increasingly recognized to confer cardioprotective effects in both healthy and clinical populations. While the mechanism(s) remains ambiguous, in skeletal muscle oral consumption of NaNO3 has been shown to improve mitochondrial efficiency. Whether NaNO3 has similar effects on mitochondria within the heart is unknown. Therefore, we comprehensively investigated the effect of NaNO3 supplementation on in vivo left ventricular (LV) function and mitochondrial bioenergetics. Healthy male Sprague-Dawley rats were supplemented with NaNO3 (1 g/l) in their drinking water for 7 days. Echocardiography and invasive hemodynamics were used to assess LV morphology and function. Blood pressure (BP) was measured by tail-cuff and invasive hemodynamics. Mitochondrial bioenergetics were measured in LV isolated mitochondria and permeabilized muscle fibers by high-resolution respirometry and fluorometry. Nitrate decreased ( P < 0.05) BP, LV end-diastolic pressure, and maximal LV pressure. Rates of LV relaxation (when normalized to mean arterial pressure) tended ( P = 0.13) to be higher with nitrate supplementation. However, nitrate did not alter LV mitochondrial respiration, coupling efficiency, or oxygen affinity in isolated mitochondria or permeabilized muscle fibers. In contrast, nitrate increased ( P < 0.05) the propensity for mitochondrial H2O2 emission in the absence of changes in cellular redox state and decreased the sensitivity of mitochondria to ADP (apparent Km). These results add to the therapeutic potential of nitrate supplementation in cardiovascular diseases and suggest that nitrate may confer these beneficial effects via mitochondrial redox signaling.


Assuntos
Suplementos Nutricionais , Metabolismo Energético/efeitos dos fármacos , Peróxido de Hidrogênio/metabolismo , Mitocôndrias Cardíacas/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Nitratos/farmacologia , Difosfato de Adenosina/metabolismo , Animais , Pressão Sanguínea/efeitos dos fármacos , Masculino , Mitocôndrias Cardíacas/metabolismo , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Oxirredução , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Função Ventricular Esquerda/efeitos dos fármacos , Pressão Ventricular/efeitos dos fármacos
10.
Am J Physiol Regul Integr Comp Physiol ; 314(4): R611-R622, 2018 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-29351418

RESUMO

Moderate anemia is associated with increased mortality and morbidity, including acute kidney injury (AKI), in surgical patients. A red blood cell (RBC)-specific antibody model was utilized to determine whether moderate subacute anemia could result in tissue hypoxia as a potential mechanism of injury. Cardiovascular and hypoxic cellular responses were measured in transgenic mice capable of expressing hypoxia-inducible factor-1α (HIF-1α)/luciferase activity in vivo. Antibody-mediated anemia was associated with mild intravascular hemolysis (6 h) and splenic RBC sequestration ( day 4), resulting in a nadir hemoglobin concentration of 89 ± 13 g/l on day 4. At this time point, renal tissue oxygen tension (PtO2) was decreased in anemic mice relative to controls (13.1 ± 4.3 vs. 20.8 ± 3.7 mmHg, P < 0.001). Renal tissue hypoxia was associated with an increase in HIF/luciferase expression in vivo ( P = 0.04) and a 20-fold relative increase in renal erythropoietin mRNA transcription ( P < 0.001) but no increase in renal blood flow ( P = 0.67). By contrast, brain PtO2 was maintained in anemic mice relative to controls (22.7 ± 5.2 vs. 23.4 ± 9.8 mmHg, P = 0.59) in part because of an increase in internal carotid artery blood flow (80%, P < 0.001) and preserved cerebrovascular reactivity. Despite these adaptive changes, an increase in brain HIF-dependent mRNA levels was observed (erythropoietin: P < 0.001; heme oxygenase-1: P = 0.01), providing evidence for subtle cerebral tissue hypoxia in anemic mice. These data demonstrate that moderate subacute anemia causes significant renal tissue hypoxia, whereas adaptive cerebrovascular responses limit the degree of cerebral tissue hypoxia. Further studies are required to assess whether hypoxia is a mechanism for acute kidney injury associated with anemia.


Assuntos
Lesão Renal Aguda/sangue , Anemia/sangue , Anticorpos Monoclonais , Encéfalo/irrigação sanguínea , Eritrócitos/metabolismo , Hipóxia Encefálica/sangue , Rim/irrigação sanguínea , Oxigênio/sangue , Lesão Renal Aguda/imunologia , Lesão Renal Aguda/patologia , Lesão Renal Aguda/fisiopatologia , Anemia/imunologia , Anemia/patologia , Anemia/fisiopatologia , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Circulação Cerebrovascular , Modelos Animais de Doenças , Eritrócitos/imunologia , Eritrócitos/patologia , Eritropoetina/genética , Eritropoetina/metabolismo , /imunologia , Hemólise , Hipóxia Encefálica/imunologia , Hipóxia Encefálica/patologia , Hipóxia Encefálica/fisiopatologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Rim/metabolismo , Rim/patologia , Masculino , Camundongos Transgênicos , Circulação Renal , Índice de Gravidade de Doença , Baço/metabolismo , Baço/patologia , Regulação para Cima
11.
Nat Commun ; 8: 15518, 2017 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-28548091

RESUMO

Noonan syndrome (NS) is caused by mutations in RAS/ERK pathway genes, and is characterized by craniofacial, growth, cognitive and cardiac defects. NS patients with kinase-activating RAF1 alleles typically develop pathological left ventricular hypertrophy (LVH), which is reproduced in Raf1L613V/+ knock-in mice. Here, using inducible Raf1L613V expression, we show that LVH results from the interplay of cardiac cell types. Cardiomyocyte Raf1L613V enhances Ca2+ sensitivity and cardiac contractility without causing hypertrophy. Raf1L613V expression in cardiomyocytes or activated fibroblasts exacerbates pressure overload-evoked fibrosis. Endothelial/endocardial (EC) Raf1L613V causes cardiac hypertrophy without affecting contractility. Co-culture and neutralizing antibody experiments reveal a cytokine (TNF/IL6) hierarchy in Raf1L613V-expressing ECs that drives cardiomyocyte hypertrophy in vitro. Furthermore, postnatal TNF inhibition normalizes the increased wall thickness and cardiomyocyte hypertrophy in vivo. We conclude that NS-cardiomyopathy involves cardiomyocytes, ECs and fibroblasts, TNF/IL6 signalling components represent potential therapeutic targets, and abnormal EC signalling might contribute to other forms of LVH.


Assuntos
Citocinas/metabolismo , Hipertrofia Ventricular Esquerda/patologia , Interleucina-6/metabolismo , Miócitos Cardíacos/patologia , Síndrome de Noonan/patologia , Proteínas Proto-Oncogênicas c-raf/genética , Fator de Necrose Tumoral alfa/metabolismo , Alelos , Animais , Técnicas de Cocultura , Modelos Animais de Doenças , Fibroblastos/metabolismo , Fibrose , Técnicas de Introdução de Genes , Humanos , Hipertrofia Ventricular Esquerda/genética , Sistema de Sinalização das MAP Quinases/genética , Masculino , Camundongos , Camundongos Transgênicos , Mutação , Miocárdio/citologia , Miocárdio/patologia , Miócitos Cardíacos/metabolismo , Síndrome de Noonan/tratamento farmacológico , Síndrome de Noonan/genética , Cultura Primária de Células , Proteínas Proto-Oncogênicas c-raf/metabolismo , Fator de Necrose Tumoral alfa/antagonistas & inibidores
12.
J Am Soc Echocardiogr ; 30(6): 612-623.e1, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28528655

RESUMO

BACKGROUND: Echocardiography is a valuable noninvasive technique to estimate cardiac output (CO) from the left ventricle (LV) not only in clinical practice but also in small-animal experiments. CO is used to grade cardiac function and is especially important when investigating cardiac injury (e.g., myocardial infarction [MI]). Critically, MI deforms the LV, invalidating the assumptions fundamental to calculating of cardiac volumes directly from the LV. Thus, the purpose of this study was to determine if Doppler-derived blood flow through the pulmonary trunk (pulmonary flow [PF]) was an improved method over conventional LV-dependent echocardiography to accurately determine CO after MI. METHODS: Variations in CO were induced either by transverse aortic constriction or MI. Echocardiography was performed in healthy (n = 27), transverse aortic constriction (n = 25), and MI (n = 41) mice. CO calculated from PF (pulsed-wave Doppler) was internally compared with CO calculated from left ventricular images using M-mode (Teichholz formula) and the single-plane ellipsoid two-dimensional (2D) formula and externally compared with the gold standard, flow probe CO. RESULTS: In healthy mice, all three echocardiographic methods (M-mode, 2D, and PF) correlated well with flow probe-derived CO. In MI mice, only PF CO values correlated well with flow probe values. Bland-Altman analysis confirmed that PF was improved over M-mode and 2D echocardiography. Inter- and intrauser variability of PF CO was reduced, and both inter- and intraclass correlation coefficients were improved compared with either M-mode or 2D CO calculations. CONCLUSIONS: PF CO calculated from pulsed-wave Doppler through the pulmonary trunk was an improved method of estimating CO over LV-dependent formulas after MI.


Assuntos
Velocidade do Fluxo Sanguíneo , Débito Cardíaco , Ecocardiografia Doppler/métodos , Testes de Função Cardíaca/métodos , Infarto do Miocárdio/diagnóstico , Infarto do Miocárdio/fisiopatologia , Circulação Pulmonar , Animais , Interpretação de Imagem Assistida por Computador/métodos , Masculino , Camundongos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
13.
Sci Transl Med ; 9(390)2017 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-28515334

RESUMO

Diaphragmatic weakness is a feature of heart failure (HF) associated with dyspnea and exertional fatigue. Most studies have focused on advanced stages of HF, leaving the cause unresolved. The long-standing theory is that pulmonary edema imposes a mechanical stress, resulting in diaphragmatic remodeling, but stable HF patients rarely exhibit pulmonary edema. We investigated how diaphragmatic weakness develops in two mouse models of pressure overload-induced HF. As in HF patients, both models had increased eupneic respiratory pressures and ventilatory drive. Despite the absence of pulmonary edema, diaphragmatic strength progressively declined during pressure overload; this decline correlated with a reduction in diaphragm cross-sectional area and preceded evidence of muscle weakness. We uncovered a functional codependence between angiotensin II and ß-adrenergic (ß-ADR) signaling, which increased ventilatory drive. Chronic overdrive was associated with increased PERK (double-stranded RNA-activated protein kinase R-like ER kinase) expression and phosphorylation of EIF2α (eukaryotic translation initiation factor 2α), which inhibits protein synthesis. Inhibition of ß-ADR signaling after application of pressure overload normalized diaphragm strength, Perk expression, EIF2α phosphorylation, and diaphragmatic cross-sectional area. Only drugs that were able to penetrate the blood-brain barrier were effective in treating ventilatory overdrive and preventing diaphragmatic atrophy. These data provide insight into why similar drugs have different benefits on mortality and symptomatology, despite comparable cardiovascular effects.


Assuntos
Insuficiência Cardíaca/terapia , Debilidade Muscular/fisiopatologia , Angiotensina II/metabolismo , Animais , Barreira Hematoencefálica/metabolismo , Diafragma/metabolismo , Diafragma/fisiologia , Fator de Iniciação 2 em Eucariotos/metabolismo , Insuficiência Cardíaca/fisiopatologia , Pulmão/metabolismo , Masculino , Camundongos , Debilidade Muscular/metabolismo , Fosforilação/fisiologia , Respiração , Transdução de Sinais/fisiologia
14.
Appl Physiol Nutr Metab ; 42(6): 647-655, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28177704

RESUMO

Tre-2/USP6, BUB2, cdc16 domain family, member 1 (TBC1D1), a Rab-GTPase activating protein, is a paralogue of AS160, and has been implicated in the canonical insulin-signaling cascade in peripheral tissues. More recently, TBC1D1 was identified in rat and human pancreatic islets; however, the islet function of TBC1D1 remains not fully understood. We examined the role of TBC1D1 in glucose homeostasis and insulin secretion utilizing a rat knockout (KO) model. Chow-fed TBC1D1 KO rats had improved insulin action but impaired glucose-tolerance tests (GTT) and a lower insulin response during an intraperitoneal GTT compared with wild-type (WT) rats. The in vivo data suggest there may be an islet defect. Glucose-stimulated insulin secretion was higher in isolated KO rat islets compared with WT animals, suggesting TBC1D1 is a negative regulator of insulin secretion. Moreover, KO rats displayed reduced ß-cell mass, which likely accounts for the impaired whole-body glucose homeostasis. This ß-cell mass reduction was associated with increased active caspase 3, and unaltered Ki67 or urocortin 3, suggesting the induction of apoptosis rather than decreased proliferation or dedifferentiation may account for the decline in islet mass. A similar phenotype was observed in TBC1D1 heterozygous animals, highlighting the sensitivity of the pancreas to subtle reductions in TBC1D1 protein. An 8-week pair-fed high-fat diet did not further alter ß-cell mass or apoptosis in KO rats, suggesting that dietary lipids per se, do not lead to a further impairment in glucose homeostasis. The present study establishes a fundamental role for TBC1D1 in maintaining in vivo ß-cell mass.


Assuntos
Glicemia/metabolismo , Proteínas Ativadoras de GTPase/metabolismo , Homeostase , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Proteínas/metabolismo , Animais , Apoptose , Caspase 3/genética , Caspase 3/metabolismo , Hormônio Liberador da Corticotropina/genética , Hormônio Liberador da Corticotropina/metabolismo , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Feminino , Intolerância à Glucose/genética , Transportador de Glucose Tipo 4/genética , Transportador de Glucose Tipo 4/metabolismo , Insulina/sangue , Insulina/metabolismo , Resistência à Insulina , Secreção de Insulina , Antígeno Ki-67/genética , Antígeno Ki-67/metabolismo , Masculino , Proteínas/genética , Ratos , Transdução de Sinais , Urocortinas/genética , Urocortinas/metabolismo
16.
J Am Soc Nephrol ; 27(8): 2422-35, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-26802179

RESUMO

Podocytes are specialized epithelial cells of the kidney blood filtration barrier that contribute to permselectivity via a series of interdigitating actin-rich foot processes. Positioned between adjacent projections is a unique cell junction known as the slit diaphragm, which is physically connected to the actin cytoskeleton via the transmembrane protein nephrin. Evidence indicates that tyrosine phosphorylation of the intracellular tail of nephrin initiates signaling events, including recruitment of cytoplasmic adaptor proteins Nck1 and Nck2 that regulate actin cytoskeletal dynamics. Nephrin tyrosine phosphorylation is altered in human and experimental renal diseases characterized by pathologic foot process remodeling, prompting the hypothesis that phosphonephrin signaling directly influences podocyte morphology. To explore this possibility, we generated and analyzed knockin mice with mutations that disrupt nephrin tyrosine phosphorylation and Nck1/2 binding (nephrin(Y3F/Y3F) mice). Homozygous nephrin(Y3F/Y3F) mice developed progressive proteinuria accompanied by structural changes in the filtration barrier, including podocyte foot process effacement, irregular thickening of the glomerular basement membrane, and dilated capillary loops, with a similar but later onset phenotype in heterozygous animals. Furthermore, compared with wild-type mice, nephrin(Y3F/Y3F) mice displayed delayed recovery in podocyte injury models. Profiling of nephrin tyrosine phosphorylation dynamics in wild-type mice subjected to podocyte injury indicated site-specific differences in phosphorylation at baseline, injury, and recovery, which correlated with loss of nephrin-Nck1/2 association during foot process effacement. Our results define an essential requirement for nephrin tyrosine phosphorylation in stabilizing podocyte morphology and suggest a model in which dynamic changes in phosphotyrosine-based signaling confer plasticity to the podocyte actin cytoskeleton.


Assuntos
Podócitos/fisiologia , Podócitos/ultraestrutura , Tirosina/metabolismo , Animais , Feminino , Masculino , Proteínas de Membrana , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Transdução de Sinais
17.
Am J Physiol Heart Circ Physiol ; 310(5): H572-86, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26702144

RESUMO

Dyspnea and reduced exercise capacity, caused, in part, by respiratory muscle dysfunction, are common symptoms in patients with heart failure (HF). However, the etiology of diaphragmatic dysfunction has not been identified. To investigate the effects of HF on diaphragmatic function, models of HF were surgically induced in CD-1 mice by transverse aortic constriction (TAC) and acute myocardial infarction (AMI), respectively. Assessment of myocardial function, isolated diaphragmatic strip function, myofilament force-pCa relationship, and phosphorylation status of myofilament proteins was performed at either 2 or 18 wk postsurgery. Echocardiography and invasive hemodynamics revealed development of HF by 18 wk postsurgery in both models. In vitro diaphragmatic force production was preserved in all groups while morphometric analysis revealed diaphragmatic atrophy and fibrosis in 18 wk TAC and AMI groups. Isometric force-pCa measurements of myofilament preparations revealed reduced Ca(2+) sensitivity of force generation and force generation at half-maximum and maximum Ca(2+) activation in 18 wk TAC. The rate of force redevelopment (ktr) was reduced in all HF groups at high levels of Ca(2+) activation. Finally, there were significant changes in the myofilament phosphorylation status of the 18 wk TAC group. This includes a decrease in the phosphorylation of troponin T, desmin, myosin light chain (MLC) 1, and MLC 2 as well as a shift in myosin isoforms. These results indicate that there are multiple changes in diaphragmatic myofilament function, which are specific to the type and stage of HF and occur before overt impairment of in vitro force production.


Assuntos
Diafragma/metabolismo , Dispneia/metabolismo , Insuficiência Cardíaca/metabolismo , Contração Isométrica , Proteínas Musculares/metabolismo , Força Muscular , Miofibrilas/metabolismo , Animais , Sinalização do Cálcio , Diafragma/fisiopatologia , Modelos Animais de Doenças , Progressão da Doença , Dispneia/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Técnicas In Vitro , Masculino , Camundongos , Infarto do Miocárdio/metabolismo , Infarto do Miocárdio/fisiopatologia , Fosforilação , Fatores de Tempo , Remodelação Ventricular
18.
J Appl Physiol (1985) ; 119(11): 1347-54, 2015 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-26472868

RESUMO

The purpose of this investigation was to determine whether exercise-induced increases in adipose tissue interleukin 6 (IL-6) signaling occurred as part of a larger proinflammatory response to exercise and whether the induction of IL-6 signaling with acute exercise was altered in trained mice in parallel with changes in the IL-6 receptor complex. Sedentary and trained C57BL/6J mice were challenged with an acute bout of exercise. Adipose tissue and plasma were collected immediately and 4 h afterward and analyzed for changes in indices of IL-6 signaling, circulating IL-6, markers of adipose tissue inflammation, and expression/content of IL-6 receptor and glycoprotein 130 (gp130). In untrained mice, IL-6 mRNA increased immediately after exercise, and increases in indices of IL-6 signaling were increased 4 h after exercise in epididymal, but not inguinal adipose tissue. This occurred independent of increases in plasma IL-6 and alterations in markers of inflammation. When compared with untrained mice, in trained mice, acute exercise induced the expression of gp130 and IL-6 receptor alpha (IL-6Rα), and training increased the protein content of these. Acute exercise induced the expression, and training increased the protein content, of glycoprotein 130 and IL-6Rα and was associated with a more rapid increase in markers of IL-6 signaling in epididymal adipose tissue from trained compared with untrained mice. The ability of exogenous IL-6 to increase phosphorylation of STAT3 was similar between groups. Our findings demonstrate that acute exercise increases IL-6 signaling in a depot-dependent manner, likely through an autocrine/paracrine mechanism. This response is initiated more rapidly after exercise in trained mice, potentially as a result of increases in IL-6Rα and gp130.


Assuntos
Tecido Adiposo/fisiopatologia , Inflamação/fisiopatologia , Interleucina-6 , Condicionamento Físico Animal , Esforço Físico , Transdução de Sinais , Tecido Adiposo/metabolismo , Animais , Receptor gp130 de Citocina/metabolismo , Epididimo/metabolismo , Ácidos Graxos não Esterificados/sangue , Interleucina-6/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Receptores de Interleucina-6 , Fator de Transcrição STAT3/metabolismo , Comportamento Sedentário
19.
Am J Physiol Regul Integr Comp Physiol ; 309(7): R780-7, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26246509

RESUMO

The obesity epidemic is considered one of the most serious public health problems of the modern world. Physical therapy is the most accessible form of treatment; however, compliance is a major obstacle due to exercise intolerance and dyspnea. Respiratory muscle atrophy is a cause of dyspnea, yet little is known of obesity-induced respiratory muscle dysfunction. Our objective was to investigate whether obesity-induced skeletal muscle wasting occurs in the diaphragm, the main skeletal muscle involved in inspiration, using the Zucker diabetic fatty (ZDF) rat. After 14 wk, ZDF rats developed obesity, hyperglycemia, and insulin resistance, compared with lean controls. Hemodynamic analysis revealed ZDF rats have impaired cardiac relaxation (P = 0.001) with elevated end-diastolic pressure (P = 0.006), indicative of diastolic dysfunction. Assessment of diaphragm function revealed weakness (P = 0.0296) in the absence of intrinsic muscle impairment in ZDF rats. Diaphragm morphology revealed increased fibrosis (P < 0.0001), atrophy (P < 0.0001), and reduced myosin heavy-chain content (P < 0.001), compared with lean controls. These changes are accompanied by activation of the myostatin signaling pathway with increased serum myostatin (P = 0.017), increased gene expression (P = 0.030) in the diaphragm and retroperitoneal adipose (P = 0.033), and increased SMAD2 phosphorylation in the diaphragm (P = 0.048). Here, we have confirmed the presence of respiratory muscle atrophy and weakness in an obese, diabetic model. We have also identified a pathological role for myostatin signaling in obesity, with systemic contributions from the adipose tissue, a nonskeletal muscle source. These findings have significant implications for future treatment strategies of exercise intolerance in an obese, diabetic population.


Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Debilidade Muscular/fisiopatologia , Músculos Respiratórios/fisiopatologia , Animais , Diabetes Mellitus Experimental/complicações , Hemodinâmica , Resistência à Insulina , Masculino , Debilidade Muscular/patologia , Miostatina/metabolismo , Obesidade/fisiopatologia , Ratos , Ratos Zucker , Músculos Respiratórios/patologia , Transdução de Sinais , Proteína Smad2/genética , Proteína Smad2/metabolismo , Regulação para Cima
20.
Med Sci Sports Exerc ; 47(10): 2034-42, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25785928

RESUMO

INTRODUCTION: Adipose tissue insulin action is impaired in obesity and is associated with inflammation, macrophage infiltration, and polarization toward a proinflammatory phenotype. Acute exercise can reduce markers of adipose inflammation, including interleukin (IL) 6, in parallel with improvements in insulin action; however, others have provided evidence that IL-6 has anti-inflammatory properties. PURPOSE: This study aimed to examine the relation between IL-6 signaling, macrophage infiltration, and polarization and insulin action in inguinal fat after acute exercise in obese, insulin-resistant mice. METHODS: Male C57BL/6 mice were fed a low-fat diet (10% kcal lard) or a high-fat diet (HFD, 60% kcal lard) for 7 wk and then underwent an acute bout of exercise (2-h treadmill running: 15 m·min, 5% incline). RESULTS: The HFD resulted in increased body mass, glucose intolerance, and attenuated insulin-induced AKT Thr308 phosphorylation in inguinal fat. This was accompanied by increases in indices of macrophage infiltration (F4/80, CD68, and monocyte chemoattractant protein-1 expression) and polarization toward an M1 phenotype (increased expression of CD11c, CD11c/galactose-type C-type lectin 1, and inducible nitric oxide synthase). Immunofluorescence imaging demonstrated increased F4/80- and CD11c-positive cells with the HFD. Two hours after exercise, the insulin-induced activation of AKT Th308 phosphorylation was recovered in HFD mice. This was accompanied by an upregulation of IL-6 and IL-10 signaling, as demonstrated by increased expression of IL-6, IL-10, and SOCS3 as well as STAT3 phosphorylation. Furthermore, acute exercise resulted in a shift toward reduction in M1 polarization indicated by a decrease in the ratio of CD11c to galactose-type C-type lectin 1 mRNA as well as a decline in F4/80- and CD11c-positive cells. CONCLUSIONS: The results suggest a link between exercise-induced increases in IL-6, reductions in indices of M1 macrophages, and increased IL-10, a reputed anti-inflammatory cytokine with insulin-sensitizing properties.


Assuntos
Tecido Adiposo/metabolismo , Insulina/metabolismo , Interleucina-6/metabolismo , Condicionamento Físico Animal/fisiologia , Animais , Índice de Massa Corporal , Dieta com Restrição de Gorduras , Dieta Hiperlipídica , Resistência à Insulina , Interleucina-10/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Macrófagos/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Obesos , Corrida/fisiologia
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