Navegando por Palavras-chave "Mitochondrial myopathy"
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- ItemAcesso aberto (Open Access)Avaliação das cinéticas do consumo de oxigênio e da reoxigenação muscular esquelética na recuperação do exercício de alta intensidade em pacientes com miopatia mitocondrial: implicações sobre os mecanismos de intolerância ao exercício(Universidade Federal de São Paulo (UNIFESP), 2011-03-31) Bravo, Daniela Manzoli [UNIFESP]; Nery, Luiz Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Background: Mitochondrial Myopathy patients (MM) and Progressive External Ophthalmoplegia (PEO) present with respiratory chain dysfunction and inability to increase muscle oxygen extraction and aerobic ATP synthesis, leading to exercise intolerance and slower O2 kinetics. When oxygen extraction is impaired, in an attempt to maintain muscle oxygen uptake, these patients could increase oxygen delivery, thus exhibiting a hyperkinetic cardiovascular and ventilatory response. On the other hand, some evidence of oxygen delivery impairment was found in MM patients, such as a decrease in muscle blood flow in the forearm and a greater capacity for ATP production after oxygen supplementation. Recovery O2 kinetics provides information on tissue oxygen debt repayment and oxygen blood store replenishment after exercise. To our knowledge, recovery O2 kinetics has never been evaluated in MM patients, as well as its integration with the non-invasive cardiovascular and muscle reoxygenation responses. Objective: to contrast oxygen delivery and utilization dynamics on exercise recovery of MM patients and to identify the main pathophysiologic mechanisms of exercise intolerance in these subjects. Methods: Were evaluated in 12 MM patients and 12 healthy controls, the recovery kinetics of: (i) O2 (ii) deoxyhemoglobin variation ([HHb], measured by near-infrared spectroscopy - NIRS) in vastus lateralis, (iii) cardiac output (CO) by transthoracic bioimpedance, after a high-intensity constant work rate test (70% of maximal workload in a previous incremental test) to the limit of tolerance in a cycle ergometer. Results: We detected slower kinetics for [HHb] ([HHb] = 43.7 ± 21.2 vs. 27.5 ± 6.7) and for O2 ( O2 = 58.1 ± 25.1 vs. 38.8 ± 7.6) in MM patients compared to controls, respectively. Additionally, these responses were associated with a faster recovery CO kinetics in relation to O2 kinetics in MM patients compared to controls (T½DC*1,44 / O2 = 1,3 ± 0,4 vs. 1,7 ± 0,6). Conclusion: Patients with MM and PEO present with a higher oxygen debt and slower reoxygenation kinetics in the recovery of a high-intensity exercise test. Those responses were associated with a faster CO recovery in relation to O2 kinetics, indicating a microvascular oxygen transport deficit, besides the characteristic mitochondrial impairment observed in these patients.
- ItemAcesso aberto (Open Access)Effect of L-carnitine on exercise performance in patients with mitochondrial myopathy(Associação Brasileira de Divulgação Científica, 2015-01-01) Gimenes, Ana Cristina Oliveira [UNIFESP]; Bravo, Daniela Manzoli [UNIFESP]; Nápolis, Lara Maris [UNIFESP]; Mello, Marco Tulio de [UNIFESP]; Oliveira, Acary Souza Bulle [UNIFESP]; Neder, Jose Alberto [UNIFESP]; Nery, Luiz Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Exercise intolerance due to impaired oxidative metabolism is a prominent symptom in patients with mitochondrial myopathy (MM), but it is still uncertain whether L-carnitine supplementation is beneficial for patients with MM. The aim of our study was to investigate the effects of L-carnitine on exercise performance in MM. Twelve MM subjects (mean age±SD=35.4±10.8 years) with chronic progressive external ophthalmoplegia (CPEO) were first compared to 10 healthy controls (mean age±SD=29±7.8 years) before they were randomly assigned to receive L-carnitine supplementation (3 g/daily) or placebo in a double-blind crossover design. Clinical status, body composition, respiratory function tests, peripheral muscle strength (isokinetic and isometric torque) and cardiopulmonary exercise tests (incremental to peak exercise and at 70% of maximal), constant work rate (CWR) exercise test, to the limit of tolerance [Tlim]) were assessed after 2 months of L-carnitine/placebo administration. Patients with MM presented with lower mean height, total body weight, fat-free mass, and peripheral muscle strength compared to controls in the pre-test evaluation. After L-carnitine supplementation, the patients with MM significantly improved their Tlim (14±1.9 vs 11±1.4 min) and oxygen consumption ( V ˙ O 2 ) at CWR exercise, both at isotime (1151±115 vs 1049±104 mL/min) and at Tlim (1223±114 vs 1060±108 mL/min). These results indicate that L-carnitine supplementation may improve aerobic capacity and exercise tolerance during high-intensity CWRs in MM patients with CPEO.
- ItemAcesso aberto (Open Access)Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise(Associação Brasileira de Divulgação Científica, 2011-04-01) Gimenes, Ana Cristina Oliveira [UNIFESP]; Neder, Jose Alberto [UNIFESP]; Dal Corso, Simone [UNIFESP]; Nogueira, Cristiano Rabelo [UNIFESP]; Nápolis, Lara Maris [UNIFESP]; Mello, Marco Tulio de [UNIFESP]; Oliveira, Acary Souza Bulle [UNIFESP]; Nery, Luiz Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ) of oxygen consumption (
O2) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the O2 on-exercise mean response time (MRT) and the gas exchange threshold (GET). The ΔO2/ΔWR slope was calculated up to GET (S1), above GET (S2) and over the entire linear portion of the response (S T). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak O2 and muscle performance were lower in patients than controls (P < 0.05). Patients had significantly lower ΔO2/ΔWR than controls, especially the S2 component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min-1·W-1, respectively; P < 0.001). There were significant relationships between ΔO2/ΔWR (S T) and muscle endurance, MRT-O2, GET and peak O2 in MM patients (P < 0.05). In fact, all patients with ΔO2/ΔWR below 8 mL·min-1·W-1 had severely reduced peak O2 values (<60% predicted). Moreover, patients with higher cardiopulmonary stresses during exercise (e.g., higher Δ ventilation/carbon dioxide output and Δ heart rate/ΔO2) had lower ΔO2/ΔWR (P < 0.05). In conclusion, a readily available, effort-independent index of aerobic dysfunction during dynamic exercise (ΔO2/ΔWR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress. - ItemSomente MetadadadosSkeletal muscle reoxygenation after high-intensity exercise in mitochondrial myopathy(Springer, 2012-05-01) Bravo, Daniela M. [UNIFESP]; Gimenes, Ana Cristina [UNIFESP]; Nascimento, Rubia B. [UNIFESP]; Ferreira, Eloara V. M. [UNIFESP]; Siqueira, Ana Cristina B. [UNIFESP]; Meda, Ethiane D. S. [UNIFESP]; Neder, J. Alberto [UNIFESP]; Nery, Luiz Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)This study addressed whether O-2 delivery during recovery from high-intensity, supra-gas exchange threshold exercise would be matched to O-2 utilization at the microvascular level in patients with mitochondrial myopathy (MM). Off-exercise kinetics of (1) pulmonary O-2 uptake (V) over dotO(2p)); (2) an index of fractional O-2 extraction by near-infrared spectroscopy (Delta[deoxy-Hb + Mb]) in the vastus lateralis and (3) cardiac output (Q'(T)) by impedance cardiography were assessed in 12 patients with biopsy-proven MM (chronic progressive external ophthalmoplegia) and 12 age-and gender-matched controls. Kinetics of (V) over dotO(2p) were significantly slower in patients than controls (tau = 53.8 +/- 16.5 vs. 38.8 +/- 7.6 s, respectively; p < 0.05). Q'(T)0, however, declined at similar rates (s = 64.7 +/- 18.8 vs. 73.0 +/- 21.6 s; p > 0.05) being typically slower than (V) over dotO(2p) in both groups. Importantly, Delta[deoxy-Hb + Mb] dynamics (MRT) were equal to, or faster than, tau(V) over dotO(2p) in patients and controls, respectively. in fact, there were no between-group differences in tau(V) over dotO(2p)/MRTD[deoxy-Hb + Mb] (1.1 +/- 0.4 vs. 1.0 +/- 0.2, p > 0.05) thereby indicating similar rates of microvascular O-2 delivery. These data indicate that the slower rate of recovery of muscle metabolism after highintensity exercise is not related to impaired microvascular O-2 delivery in patients with MM. This phenomenon, therefore, seems to reflect the intra-myocyte abnormalities that characterize this patient population.