RESUMEN
PURPOSE: Phosphorous metabolite ratios in human myocardium were determined by a combination of acquisition weighted CSI and a SLOOP evaluation and the results were compared to corresponding SLOOP experiments using standard CSI. MATERIALS AND METHODS: 10 healthy subjects were examined at 1.5 T using both standard CSI and acquisition weighted CSI. Both experiments were performed with a similar acquisition time and the same spatial resolution. The PCr/ATP ratio was determined and the localization properties of both experiments were compared. RESULTS: The PCr/ATP ratio of 2.2±0.4 found for the experiment using acquisition weighted CSI was almost identical to the value of 2.0±0.4 for standard CSI. The sensitivity and the localization properties improved in all subjects using SLOOP evaluation of the acquisition weighted sampling in comparison to the standard CSI acquisition with an average of 3% and 18%, respectively. CONCLUSION: The employment of acquisition weighting allows for a further improvement of the (31)P SLOOP spectroscopy of the human heart.
Asunto(s)
Adenosina Trifosfato/metabolismo , Algoritmos , Espectroscopía de Resonancia Magnética/métodos , Imagen Molecular/métodos , Miocardio/metabolismo , Fosfocreatina/metabolismo , Adulto , Femenino , Humanos , Masculino , Valores de Referencia , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Plasticity of the cellular bioenergetic system is fundamental to every organ function, stress adaptation and disease tolerance. Here, remodelling of phosphotransfer and substrate utilization networks in response to chronic creatine kinase (CK) deficiency, a hallmark of cardiovascular disease, has been revealed in transgenic mouse models lacking either cytosolic M-CK (M-CK(-/-)) or both M-CK and sarcomeric mitochondrial CK (M-CK/ScCKmit(-/-)) isoforms. The dynamic metabolomic signatures of these adaptations have also been defined. Tracking perturbations in metabolic dynamics with (18)O and (13)C isotopes and (31)P NMR and mass spectrometry demonstrate that hearts lacking M-CK have lower phosphocreatine (PCr) turnover but increased glucose-6-phosphate (G-6-P) turnover, glucose utilization and inorganic phosphate compartmentation with normal ATP γ-phosphoryl dynamics. Hearts lacking both M-CK and sarcomeric mitochondrial CK have diminished PCr turnover, total phosphotransfer capacity and intracellular energetic communication but increased dynamics of ß-phosphoryls of ADP/ATP, G-6-P and γ-/ß-phosphoryls of GTP, indicating redistribution of flux through adenylate kinase (AK), glycolytic and guanine nucleotide phosphotransfer circuits. Higher glycolytic and mitochondrial capacities and increased glucose tolerance contributed to metabolic resilience of M-CK/ScCKmit(-/-) mice. Multivariate analysis revealed unique metabolomic signatures for M-CK(-/-) and M-CK/ScCKmit(-/-) hearts suggesting that rearrangements in phosphotransfer and substrate utilization networks provide compensation for genetic CK deficiency. This new information highlights the significance of integrated CK-, AK-, guanine nucleotide- and glycolytic enzyme-catalysed phosphotransfer networks in supporting the adaptivity and robustness of the cellular energetic system.
Asunto(s)
Forma MB de la Creatina-Quinasa/deficiencia , Forma Mitocondrial de la Creatina-Quinasa/deficiencia , Músculo Esquelético/metabolismo , Miocardio/metabolismo , Adenilato Quinasa/metabolismo , Animales , Forma MB de la Creatina-Quinasa/genética , Forma MB de la Creatina-Quinasa/metabolismo , Forma Mitocondrial de la Creatina-Quinasa/genética , Forma Mitocondrial de la Creatina-Quinasa/metabolismo , Glucosa/metabolismo , Prueba de Tolerancia a la Glucosa , Glucólisis , Nucleótidos de Guanina/metabolismo , Metabolómica , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias Cardíacas/metabolismoRESUMEN
To evaluate multivoxel (31)P-MR spectroscopy (MRS) for assessment of energy metabolism in patients with myocardial infarction (MI) in correlation to left ventricular (LV) wall thickness and the outcome of revascularization. Thirty patients with subacute anterior myocardial infarction and planned revascularization were enrolled. 3D-chemical shift imaging was applied to determine PCr/ATP ratios in two areas: infarcted/anterior and noninfarcted/septal myocardium. MRI was used to evaluate LV function and wall thickness, and was repeated 6 months after revascularization to assess myocardial viability. Fifteen volunteers were controls. Fifteen patients showed normalization of wall motion abnormalities after revascularization (Group 1; viable), 15 not (Group 2; non-viable). Regarding infarcted/anterior myocardium, Group 2 had lower PCr/ATP ratios (0.81 +/- 0.60 vs 1.17 +/- 0.25), and PCr/ATP ratios were reduced in both groups compared to controls (1.45 +/- 0.29). Regarding noninfarcted/septal myocardium, again Group 2 had lower ratios (0.93 +/- 0.53 vs 1.31 +/- 0.38); however, compared to controls (1.51 +/- 0.32) a reduction of PCr/ATP ratios was only found in Group 2. For both myocardial regions, no correlations between PCr/ATP ratios and LV wall thickness were detected. The more severe energetic alteration in irreversibly damaged myocardium is not an effect of differences of wall thinning. Additional alterations of noninfarcted, adjacent myocardium can be detected.
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Imagen por Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética/métodos , Infarto del Miocardio/patología , Miocardio/patología , Adulto , Anciano , Estudios de Casos y Controles , Electrocardiografía , Metabolismo Energético , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Masculino , Persona de Mediana Edad , Infarto del Miocardio/terapia , Miocardio/metabolismo , Isótopos de Fósforo , Estadísticas no Paramétricas , Remodelación VentricularRESUMEN
The aim of this study was to apply (31)P magnetic resonance spectroscopy (MRS) using spatial localization with optimal point spread function (SLOOP) to investigate possible age and gender dependencies of the energy metabolite concentrations in the human heart. Thirty healthy volunteers (18 males and 12 females, 21-67 years old, mean = 40.7 years) were examined with the use of (31)P-MRS on a 1.5 T scanner. Intra- and interobserver variability measures (determined in eight of the volunteers) were both 3.8% for phosphocreatine (PCr), and 4.7% and 8.3%, respectively, for adenosine triphosphate (ATP). High-energy phosphate (HEP) concentrations in mmol/kg wet weight were 9.7 +/- 2.4 (age < 40 years, N = 16) and 7.7 +/- 2.5 (age >or= 40 years, N = 14) for PCr, and 5.1 +/- 1.0 (age < 40 years) and 4.1 +/- 0.8 (age >or= 40 years) for ATP, respectively. Separated by gender, PCr concentrations of 9.2 +/- 2.4 (men, N = 18) and 8.0 +/- 2.8 (women, N = 12) and ATP concentrations of 4.9 +/- 1.0 (men) and 4.2 +/- 0.9 (women) were measured. A significant decrease of PCr and ATP was found for volunteers older than 40 years (P < 0.05), but the differences in metabolic concentrations between both sexes were not significant. In conclusion, age has a minor but still significant impact on cardiac energy metabolism, and no significant gender differences were detected.
Asunto(s)
Adenosina Trifosfato/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Miocardio/metabolismo , Fosfatos/metabolismo , Fosfocreatina/metabolismo , Adulto , Factores de Edad , Anciano , Metabolismo Energético , Femenino , Humanos , Masculino , Persona de Mediana Edad , Isótopos de Fósforo , Factores Sexuales , Estadísticas no ParamétricasRESUMEN
A decrease in the supply of ATP from the creatine kinase (CK) system is thought to contribute to the evolution of heart failure. However, previous studies on mice with a combined knockout of the mitochondrial and cytosolic CK (CK(-/-)) have not revealed overt left ventricular dysfunction. The aim of this study was to employ novel MRI techniques to measure maximal myocardial velocity (V(max)) and myocardial perfusion and thus determine whether abnormalities in the myocardial phenotype existed in CK(-/-) mice, both at baseline and 4 wk after myocardial infarction (MI). As a result, myocardial hypertrophy was seen in all CK(-/-) mice, but ejection fraction (EF) remained normal. V(max), however, was significantly reduced in the CK(-/-) mice [wild-type, 2.32 +/- 0.09 vs. CK(-/-), 1.43 +/- 0.16 cm/s, P < 0.05; and wild-type MI, 1.53 +/- 0.11 vs. CK(-/-) MI, 1.26 +/- 0.11 cm/s, P = not significant (NS), P < 0.05 vs. baseline]. Myocardial perfusion was also lower in the CK(-/-) mice (wild-type, 6.68 +/- 0.27 vs. CK(-/-), 4.12 +/- 0.63 ml/g.min, P < 0.05; and wild-type MI, 3.97 +/- 0.65 vs. CK(-/-) MI, 3.71 +/- 0.57 ml/g.min, P = NS, P < 0.05 vs. baseline), paralleled by a significantly reduced capillary density (histology). In conclusion, myocardial function in transgenic mice may appear normal when only gross indexes of performance such as EF are assessed. However, the use of a combination of novel MRI techniques to measure myocardial perfusion and mechanics allowed the abnormalities in the CK(-/-) phenotype to be detected. The myocardium in CK-deficient mice is characterized by reduced perfusion and reduced maximal contraction velocity, suggesting that the myocardial hypertrophy seen in these mice cannot fully compensate for the absence of the CK system.
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Circulación Coronaria/genética , Circulación Coronaria/fisiología , Creatina Quinasa/deficiencia , Creatina Quinasa/genética , Contracción Miocárdica/genética , Contracción Miocárdica/fisiología , Miocitos Cardíacos/patología , Animales , Capilares/patología , Electrocardiografía , Femenino , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía de Contraste de Fase , Fenotipo , Marcadores de Spin , Remodelación VentricularRESUMEN
An impaired high-energy phosphate metabolism might play a critical role in the pathogenesis of right ventricular (RV) failure due to chronic pulmonary arterial hypertension (PAH). 31P-NMR spectroscopy is well established for measurements of high-energy phosphate metabolites in various left ventricular heart diseases, however, mainly for technical and sensitivity reasons, its successful transfer for measurements in the RV is currently missing. In the present study, the usefulness of this non-invasive approach is not only shown in RV failure due to PAH but also tested during subsequent therapy.
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Antihipertensivos/uso terapéutico , Hipertensión Pulmonar/tratamiento farmacológico , Hipertensión Pulmonar/fisiopatología , Sulfonamidas/uso terapéutico , Disfunción Ventricular Derecha/tratamiento farmacológico , Disfunción Ventricular Derecha/fisiopatología , Función Ventricular Derecha/efectos de los fármacos , Bosentán , Humanos , Hipertensión Pulmonar/complicaciones , Hipertensión Pulmonar/diagnóstico , Hipertensión Pulmonar/metabolismo , Espectroscopía de Resonancia Magnética , Masculino , Persona de Mediana Edad , Fosfatos/metabolismo , Presión Esfenoidal Pulmonar/efectos de los fármacos , Volumen Sistólico/efectos de los fármacos , Disfunción Ventricular Derecha/diagnóstico , Disfunción Ventricular Derecha/etiología , Disfunción Ventricular Derecha/metabolismoRESUMEN
Decreases in total creatine kinase (CK) activity and creatine [Cr] combine to limit the capacity of the failing heart to rapidly re-synthesize ATP (energy reserve). If the loss in energy reserve could be reversed, cardiac contractile reserve may be improved. Here we test whether these changes are reversible during recovery from heart failure. Left ventricular (LV) contractile function was measured in chronically instrumented conscious dogs with heart failure (CHF) induced by cardiac pacing for 3-4 weeks, and after recovery from heart failure (Recovery) (unpaced) for 5-6 weeks. LV contractile function and contractile reserve were depressed in CHF but returned to control in Recovery. CK capacity fell by 55% in CHF due to decreases in [Cr] (-39%) and CK activity (-25%), but was fully restored in Recovery. CK-B isozyme activity, protein (Western) and mRNA levels (real time PCR), respectively, were higher by 2-, 5.4- and 11-fold in CHF and higher by 3-, 2- and 2-fold in Recovery. CK-MM activity was decreased (-30%) in CHF but returned to normal levels during Recovery; CK-M protein was 30% lower in both CHF and Recovery even though there were no changes in mRNA levels. A similar pattern was found for mitochondrial CK (sMtCK). Deceases in CK activity and [Cr] in CHF are reversible. Decreases in CK-MM and sMtCK activities, but not the increases in CK-BB and CK-MB, also reversed. Neither the changes in protein nor mRNA levels for CK-B and CK-M correlated to their activities, suggesting that CK is under complex post-transcriptional regulation.
Asunto(s)
Creatina Quinasa/análisis , Creatina/análisis , Insuficiencia Cardíaca/enzimología , Insuficiencia Cardíaca/metabolismo , Animales , Western Blotting , Estimulación Cardíaca Artificial , Cardiotónicos/farmacología , Creatina/metabolismo , Creatina Quinasa/genética , Creatina Quinasa/metabolismo , Forma BB de la Creatina-Quinasa , Forma MM de la Creatina-Quinasa , Dobutamina/farmacología , Perros , Relación Dosis-Respuesta a Droga , Gliceraldehído-3-Fosfato Deshidrogenasas/análisis , Gliceraldehído-3-Fosfato Deshidrogenasas/metabolismo , Insuficiencia Cardíaca/etiología , Isoenzimas/análisis , Isoenzimas/genética , Isoenzimas/metabolismo , ARN Mensajero/análisis , ARN Mensajero/metabolismo , Distribución Aleatoria , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de TiempoRESUMEN
OBJECTIVE: Creatine kinase (CK) is responsible for the transport of high-energy phosphates in excitable tissue and is of central importance in myocardial energy homeostasis. Significant changes in myocardial energetics have been reported in mice lacking the various CK isoenzymes. Our hypothesis was that ablation of CK isoenzymes leads to cardiac hypertrophy, impaired function, and aggravation of left ventricular remodeling post-myocardial infarction. METHODS: CK-deficient mice (CK KO) were examined by cardiac magnetic resonance imaging (MRI) to determine left ventricular volumes, ejection fraction, and mass: ten wild-type (WT), 6 mitochondrial CK KO (Mito-CK-/-), 10 cytosolic CK KO (M-CK-/-), and 10 mice with combined KO (M/Mito-CK-/-). RESULTS: While ejection fraction was similar in all groups, there was significant LV dilatation with a approximately 30% increase in LV end-diastolic volumes in Mito-CK-/- and in M/Mito-CK-/-. Compared to WT, there was a striking 73% and 64% increase of LV mass in Mito-CK-/- and in M/Mito-CK-/- mice, respectively, but no significant increase of LV mass (+33%; p=n.s.) in M-CK-/-. Furthermore, significant re-expression of beta-MHC, a marker of myocardial hypertrophy, was found in all CK-deficient hearts. LV remodeling was investigated by MRI in hearts of 7 WT and 10 M/Mito-CK-/- mice 4 weeks postmyocardial infarction (MI). Four weeks post-LAD ligation (MI size approximately 32%), WT and M/Mito-CK-/- showed a similar degree of cardiac dysfunction, dilatation, and hypertrophy. CONCLUSION: Mito-CK-/- and M/Mito-CK-/- mice show significant LV dilatation and marked LV hypertrophy, but LV remodeling post-MI is not aggravated. CK ablation leads to substantial adaptational changes in heart.
Asunto(s)
Cardiomiopatía Dilatada/genética , Creatina Quinasa/genética , Hipertrofia Ventricular Izquierda/genética , Isoenzimas/genética , Miocardio/enzimología , Animales , Cardiomiopatía Dilatada/patología , Citosol/enzimología , Femenino , Hipertrofia Ventricular Izquierda/patología , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Noqueados , Mitocondrias Cardíacas/enzimología , Miocardio/patologíaRESUMEN
PURPOSE: To determine whether the recently applied technique of acquisition-weighted 31P-MR spectroscopy (AW-MRS) allows for the detection of depressed energy metabolism in patients with inferior wall myocardial infarctions. MATERIALS AND METHODS: Eight patients with subacute myocardial infarction and wall motion abnormalities restricted to the inferior wall were examined with a 1.5-T MR scanner. Global and regional left ventricular (LV) function was assessed by cine MRI, and the size and extent of myocardial infarction was assessed by late enhancement (LE). MRS was performed with an AW three-dimensional chemical shift imaging sequence. Phosphocreatine/ATP ratios were determined with the postprocessing model AMARES for four voxels positioned in the anterior, lateral, inferior, and septal parts of the LV. RESULTS: The LV ejection fraction (EF) was reduced to 37.5%+/-9.0%. Seven of eight patients had transmural LE in the inferior wall, and one patient showed subendocardial enhancement in the inferior-lateral parts. Phosphocreatine/ATP ratios of the inferior wall were significantly reduced (P <0.05) compared to all other parts of the LV (1.03 +/- 0.39 (inferior), 1.67 +/- 0.81 (lateral), 1.73 +/- 0.29 (anterior), and 1.49 +/- 0.31 (septal)). The ratios in five of seven patients with transmural enhancement were <1.00 in the inferior wall. CONCLUSION: Acquisition weighting allows for the detection of inferior wall infarctions in patients. Transmural signal enhancement is associated with significant depression of phosphocreatine/ATP ratios.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Infarto del Miocardio/diagnóstico , Miocardio/patología , Adenosina Trifosfato/metabolismo , Adulto , Anciano , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/metabolismo , Miocardio/metabolismo , Fosfocreatina/metabolismo , Isótopos de Fósforo , Valores de Referencia , Estadísticas no ParamétricasRESUMEN
The creatine kinase (CK) system is involved in the rapid transport of high-energy phosphates from the mitochondria to the sites of maximal energy requirements such as myofibrils and sarcolemmal ion pumps. Hearts of mice with a combined knockout of cytosolic M-CK and mitochondrial CK (M/Mito-CK(-/-)) show unchanged basal left ventricular (LV) performance but reduced myocardial high-energy phosphate concentrations. Moreover, skeletal muscle from M/Mito-CK(-/-) mice demonstrates altered Ca2+ homeostasis. Our hypothesis was that in CK-deficient hearts, a cardiac phenotype can be unmasked during acute stress conditions and that susceptibility to ischemia-reperfusion injury is increased because of altered Ca2+ homeostasis. We simultaneously studied LV performance and myocardial Ca2+ metabolism in isolated, perfused hearts of M/Mito-CK(-/-) (n = 6) and wild-type (WT, n = 8) mice during baseline, 20 min of no-flow ischemia, and recovery. Whereas LV performance was not different during baseline conditions, LV contracture during ischemia developed significantly earlier (408 +/- 72 vs. 678 +/- 54 s) and to a greater extent (50 +/- 2 vs. 36 +/- 3 mmHg) in M/Mito-CK(-/-) mice. During reperfusion, recovery of diastolic function was impaired (LV end-diastolic pressure: 22 +/- 3 vs. 10 +/- 2 mmHg), whereas recovery of systolic performance was delayed, in M/Mito-CK(-/-) mice. In parallel, Ca2+ transients were similar during baseline conditions; however, M/Mito-CK(-/-) mice showed a greater increase in diastolic Ca2+ concentration ([Ca2+]) during ischemia (237 +/- 54% vs. 167 +/- 25% of basal [Ca2+]) compared with WT mice. In conclusion, CK-deficient hearts show an increased susceptibility of LV performance and Ca2+ homeostasis to ischemic injury, associated with a blunted postischemic recovery. This demonstrates a key function of an intact CK system for maintenance of Ca2+ homeostasis and LV mechanics under metabolic stress conditions.
Asunto(s)
Calcio/metabolismo , Creatina Quinasa/deficiencia , Homeostasis , Isquemia Miocárdica/etiología , Daño por Reperfusión Miocárdica/etiología , Miocardio/enzimología , Animales , Susceptibilidad a Enfermedades , Corazón/fisiopatología , Membranas Intracelulares/metabolismo , Ratones , Ratones Noqueados , Isquemia Miocárdica/fisiopatología , Daño por Reperfusión Miocárdica/fisiopatologíaRESUMEN
To study the mechanisms by which missense mutations in alpha-tropomyosin cause familial hypertrophic cardiomyopathy, we generated transgenic rats overexpressing alpha-tropomyosin with one of two disease-causing mutations, Asp(175)Asn or Glu(180)Gly, and analyzed phenotypic changes at molecular, morphological, and physiological levels. The transgenic proteins were stably integrated into the sarcomere, as shown by immunohistochemistry using a human-specific anti-alpha-tropomyosin antibody, ARG1. In transgenic rats with either alpha-tropomyosin mutation, molecular markers of cardiac hypertrophy were induced. Ca(2+) sensitivity of cardiac skinned-fiber preparations from animals with mutation Asp(175)Asn, but not Glu(180)Gly, was decreased. Furthermore, elevated frequency and amplitude of spontaneous Ca(2+) waves were detected only in cardiomyocytes from animals with mutation Asp(175)Asn, suggesting an increase in intracellular Ca(2+) concentration compensating for the reduced Ca(2+) sensitivity of isometric force generation. Accordingly, in Langendorff-perfused heart preparations, myocardial contraction and relaxation were accelerated in animals with mutation Asp(175)Asn. The results allow us to propose a hypothesis of the pathogenetic changes caused by alpha-tropomyosin mutation Asp(175)Asn in familial hypertrophic cardiomyopathy on the basis of changes in Ca(2+) handling as a sensitive mechanism to compensate for alterations in sarcomeric structure.
Asunto(s)
Cardiomiopatía Hipertrófica Familiar/fisiopatología , Corazón/fisiopatología , Mutación Missense , Tropomiosina/genética , Animales , Animales Modificados Genéticamente , Asparagina , Ácido Aspártico , Biomarcadores/análisis , Calcio/metabolismo , Calcio/farmacología , Cardiomiopatía Hipertrófica Familiar/genética , Cardiomiopatía Hipertrófica Familiar/metabolismo , Expresión Génica , Ácido Glutámico , Glicina , Ventrículos Cardíacos , Humanos , Inmunohistoquímica , Técnicas In Vitro , Fibras Musculares Esqueléticas/efectos de los fármacos , Contracción Miocárdica , Miocitos Cardíacos/metabolismo , Ratas , Sarcómeros/metabolismo , Transgenes , Tropomiosina/metabolismoRESUMEN
As mitoxantrone is a recently approved immunosuppressant for managing multiple sclerosis, the number of patients treated with this effective but potentially cardiotoxic anthracenedione derivative will increase substantially. To detect subclinical mitoxantrone-induced cardiotoxicity, sensitive non-invasive diagnostic tools are required. Assuming that changes in myocardial high-energy phosphate metabolism and alterations in left ventricular (LV) diastolic performance might be early markers of mitoxantrone-induced cardiotoxicity we examined fifteen MS patients treated with mitoxantrone up to 100 mg/m2 compared with 15 matched control MS patients. 31P-magnetic resonance (MR) spectroscopy was employed to measure myocardial high-energy phosphate metabolism, MR imaging for morphometric evaluation of changes in LV geometry. Indices of diastolic performance were assessed by Doppler echocardiography. In this exploratory study, phosphocreatine/ATP ratios were comparable between mitoxantrone-treated and control patients (1.48 +/- 0.23 and 1.43 +/- 0.41). LV mass, LV end-diastolic and systolic volumes, wall motion score, EF and cardiac output did not differ between both groups. All parameters of diastolic performance (E/A-ratio, isovolumic relaxation time, and E-wave deceleration time) were not different and within normal limits.In conclusion, using advanced diagnostic methodology, including functional, morphometric, and biochemical measurements no cardiotoxic effect of mitoxantrone up to a cumulative dose range of 100 mg/m2 could be detected.
Asunto(s)
Mitoxantrona/toxicidad , Mitoxantrona/uso terapéutico , Esclerosis Múltiple/tratamiento farmacológico , Esclerosis Múltiple/metabolismo , Función Ventricular Izquierda/efectos de los fármacos , Adolescente , Adulto , Estudios de Casos y Controles , Ecocardiografía Doppler/métodos , Femenino , Corazón/diagnóstico por imagen , Corazón/efectos de los fármacos , Corazón/fisiología , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/diagnóstico por imagen , Proyectos Piloto , Radiografía , Estudios Retrospectivos , Estadísticas no Paramétricas , Función Ventricular Izquierda/fisiologíaRESUMEN
The beta-adrenergic receptor system not only plays a central role in modulating heart rate and left-ventricular (LV) contractility, but is also involved in the development of heart failure. We have, recently, shown that heart-specific overexpression of the beta(1)-adrenergic receptor in transgenic mice (TG) initially leads to increased contractility, followed by LV hypertrophy and heart failure. Since one feature for all forms of heart failure are characteristic changes in myocardial energy metabolism, we asked whether alterations in energetics are detectable in these mice before signs of LV impairment are present. Myocardial energetics ((31)P NMR spectroscopy) and LV performance were measured simultaneously in isolated perfused hearts at different workloads. LV performance as well as contractile reserve was identical for hearts of 4-month-old TG and wild-type mice. The ratio of phosphocreatine to ATP (1.16 +/- 0.05 vs. 1.46 +/- 0.10) and total creatine content (17.6 +/- 1.2 vs. 22.6 +/- 0.9 mmol/l) were significantly reduced in TG. Furthermore, there was a significant decrease in creatine transporter content (-43%), mitochondrial (-44%) and total creatine kinase (CK) activity (-21%) as well as citrate synthase activity (-25%), indicating impaired oxidative energy generation in TG. In conclusion, these findings of alterations in the CK system, creatine metabolism and mitochondrial proteins in TG hearts prior to the development of LV dysfunction provide further evidence that changes in myocardial energetics play a central role in the deterioration of cardiac function after chronic beta-adrenergic stimulation.
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Creatina Quinasa/metabolismo , Isoenzimas/metabolismo , Contracción Miocárdica/fisiología , Miocardio/enzimología , Receptores Adrenérgicos beta 1/genética , Animales , Calcio/metabolismo , Forma MB de la Creatina-Quinasa , Espectroscopía de Resonancia Magnética , Ratones , Miocardio/metabolismo , Fosfatos/metabolismo , Receptores Adrenérgicos beta 1/metabolismoRESUMEN
Fabry disease is an X-linked lysosomal storage disorder that results from a deficiency of the enzyme alpha-galactosidase A (alpha-Gal A). The lack of alpha-Gal A causes an intracellular accumulation of glycosphingolipids, mainly globotriaosyceramide (GL3). Affected organs include, among others, the vascular endothelium, heart, brain, and kidneys, leading to end-stage renal disease (ESRD). Since Fabry disease cannot be cured at present, clinical management is symptomatic. Enzyme replacement therapy (ERT) with recombinant alpha-Gal A has been introduced as a new therapeutic option for the treatment of Fabry patients. Short-term (one year) clinical studies have positively correlated ERT with improvement of clinical symptoms and microvascular endothelial cell clearance. Treatment outcome concerning severe organ manifestations such as proteinuria and renal function impairment, left ventricular hypertrophy, and heart failure in the long run has yet to be shown. In our studies we used sensitive and noninvasive techniques such as ultrasound-based strain rate imaging and magnetic resonance imaging (MRI), combined with MR-spectroscopy (MR-S), for the quantification of functional abnormalities at an early stage of the disease and during long-term follow-up. Future issues should determine the appropriate timing to start therapy and how children and heterozygous females should be managed. Given the diagnostic and therapeutic potential today, it is of importance to identify patients at an early stage and to start therapeutic intervention before progression of organ damage is inevitable.
Asunto(s)
Enfermedad de Fabry/diagnóstico , Enfermedad de Fabry/terapia , HumanosRESUMEN
One major function of the creatine kinase system is to maintain energy demand of myofibrillar contraction processes. Loss of the CK-system led to adaptations in skeletal muscle. To analyze the impact on myocardial function contractile parameters and intracellular calcium metabolism of transgenic mice lacking mitochondrial CK (ScCKmit(-/-)) alone or both mitochondrial and cytoplasmic ScCK (CK(-/-)) were investigated compared to wild type at various workload conditions using isolated intact muscle fibers. Force development at baseline conditions, force-frequency relationship (60-600/min), and rapid frequency switch (60-600/min) were unaltered in myocardium of transgenic mice compared to wild type. Intracellular calcium metabolism revealed unchanged amplitude of the intracellular calcium transients (ICT), refilling of the sarcoplasmic reticulum (calcium reuptake, post-rest behavior) in the ScCKmit(-/-) and CK(-/-) mice. The results demonstrate the effectiveness of myocardial energy-recruiting compensatory mechanisms at baseline as well as under stress conditions in CK depleted myocardium of transgenic mice.
Asunto(s)
Calcio/metabolismo , Creatina Quinasa/genética , Isoenzimas/genética , Contracción Miocárdica , Miocardio/metabolismo , Adaptación Fisiológica , Animales , Forma MB de la Creatina-Quinasa , Forma Mitocondrial de la Creatina-Quinasa , Técnicas de Cultivo , Estimulación Eléctrica , Contracción Isométrica , Cinética , Ratones , Ratones Noqueados , Ratones Transgénicos , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/fisiología , Relajación MuscularRESUMEN
The individual functional significance of the various creatine kinase (CK) isoenzymes for myocardial energy homeostasis is poorly understood. Whereas transgenic hearts lacking the M subunit of CK (M-CK) show unaltered cardiac energetics and left ventricular (LV) performance, deletion of M-CK in combination with loss of sarcomeric mitochondrial CK (ScCKmit) leads to significant alterations in myocardial high-energy phosphate metabolites. To address the question as to whether this alteration is due to a decrease in total CK activity below a critical threshold or due to the specific loss of ScCKmit, we studied isolated perfused hearts with selective loss of ScCKmit (ScCKmit(-/-), remaining total CK activity approximately 70%) using (31)P NMR spectroscopy at two different workloads. LV performance in ScCKmit(-/-) hearts (n = 11) was similar compared with wild-type hearts (n = 9). Phosphocreatine/ATP, however, was significantly reduced in ScCKmit(-/-) compared with wild-type hearts (1.02 +/- 0.05 vs. 1.54 +/- 0.07, P < 0.05). In parallel, free [ADP] was higher (144 +/- 11 vs. 67 +/- 7 microM, P < 0.01) and free energy release for ATP hydrolysis (DeltaG(ATP)) was lower (-55.8 +/- 0.5 vs. -58.5 +/- 0.5 kJ/mol, P < 0.01) in ScCKmit(-/-) compared with wild-type hearts. These results demonstrate that M- and B-CK containing isoenzymes are unable to fully substitute for the loss of ScCKmit. We conclude that ScCKmit, in contrast to M-CK, is critically necessary to maintain normal high-energy phosphate metabolite levels in the heart.