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Master's Dissertation
DOI
Document
Author
Full name
Marjory Irineu Bená
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2018
Supervisor
Committee
Sobreira, Claudia Ferreira da Rosa (President)
Tengan, Celia Harumi
Fazan, Valeria Paula Sassoli
Felipe, Joaquim Cezar
Title in Portuguese
Avaliação quantitativa da função mitocondrial no músculo esquelético em pacientes com distrofia muscular de cinturas
Keywords in Portuguese
Cadeia respiratória
Coenzima Q10
Disfunção mitocondrial
Distrofia muscular de cinturas
Abstract in Portuguese
As distrofias musculares de cinturas (DMC) representam um grupo heterogêneo de desordens hereditárias e degenerativas da musculatura esquelética, com evolução progressiva, caracterizadas principalmente pelo acometimento predominante das cinturas escapular e/ou pélvica. São classificadas de acordo com o padrão de herança e o gene envolvido, podendo ser autossômicas dominantes ou autossômicas recessivas. Embora as disfunções mitocondriais tenham sido pouco descritas nas DMC, alguns estudos apresentaram evidências morfológicas e bioquímicas de alterações secundárias na cadeia respiratória mitocondrial. As razões envolvidas em tais disfunções na DMC permanecem pouco compreendidas. Portanto, é imprescindível uma caracterização detalhada da disfunção mitocondrial nos pacientes com DMC para uma melhor compreensão dos processos fisiopatológicos envolvidos na doença. Os objetivos do estudo foram: quantificar a CoQ10 em fragmentos do músculo esquelético de pacientes com DMC; quantificar a atividade enzimática de cada complexo da cadeia respiratória isoladamente; quantificar a atividade dos complexos II+III em conjunto como avaliação indireta da CoQ10; verificar a relação entre a área relativa de fibras musculares no fragmento de biópsia e o grau de disfunção mitocondrial nesses fragmentos; correlacionar a função mitocondrial com parâmetros clínicos de pacientes com DMC. Participaram do estudo 21 pacientes com DMC e 9 controles saudáveis. Os parâmetros clínicos incluídos foram idade no momento da biópsia, idade de início dos sintomas e tempo de evolução da doença. A análise do metabolismo mitocondrial foi realizada por: quantificação da coenzima Q10 nos fragmentos de biópsia muscular e quantificação da atividade dos complexos enzimáticos mitocondriais I, II, III, II+III e IV da cadeia respiratória e da enzima da matriz mitocondrial citrato sintase. Foram correlacionados os parâmetros clínicos, a proporção de fibras na biópsia muscular e os resultados das análises bioquímicas para a caracterização da função mitocondrial. A média dos pacientes com DMC em relação à idade no momento da biópsia, início dos sintomas e tempo de evolução da doença foi de 28,9 anos (DP ±11,7), 16,7 anos (DP ±10,3) e 12,1 anos (DP ±10,9), respectivamente. O grupo controle apresentou média de idade no momento da biópsia de 29,6 anos (DP ±10,3). A dosagem média de CoQ10 nos fragmentos de biópsia de pacientes com DMC foi de 17,9 µg/g de tecido (DP ±9,2) e nos fragmentos dos controles foi de 29,5 µg/g de tecido (DP ±4,4). Não foi observada alteração das atividades isoladas dos complexos enzimáticos da cadeia respiratória. Houve deficiência da atividade do conjunto de complexos II+III nos pacientes com DMC. A média da área ocupada por fibras musculares nos pacientes com DMC foi de 58,5% (DP ±26,1%) e nos controles foi de 76,35% (DP ±1,9%). Observou-se correlação moderada entre a quantidade de CoQ10 e a área relativa de fibras musculares (r= 0,57 e p= 0,007). Não houve correlação da CoQ10 com os parâmetros clínicos. No presente estudo, concluímos que existe uma deficiência secundária de CoQ10 em pacientes com DMC, sendo um achado importante para melhor entendimento do acometimento mitocondrial nessa doença e uma abordagem terapêutica mais eficaz.
Title in English
Quantitative assessment of mitochondrial function in skeletal muscle of patients with limb-girdle muscular dystrophy
Keywords in English
Coenzyme CoQ10
Limb-Girdle Muscular Dystrophy
Mitochondrial dysfunction
Respiratory chain
Abstract in English
The limb-girdle muscular dystrophy (LGMD) is a group of inherited and degenerative disorders of the skeletal muscle, with a progressive clinical course and predominant involvement of the scapular and/or pelvic girdles. They are classified according to the pattern of inheritance (autosomal dominant or autosomal recessive) and the gene involved. Mitochondrial dysfunction has been reported in the LGMD, some studies have described morphological and biochemical evidences of secondary mitochondrial respiratory chain alterations in patients with LGMD. The reasons involved in such dysfunctions in the LGMD remain poorly understood. Therefore, a detailed characterization of the mitochondrial dysfunction in patients with LGMD allows a better understanding of the pathophysiological processes involved in the disease. Therefore, a detailed characterization of mitochondrial dysfunction in patients with LGMD is essential for a better understanding of the pathophysiological processes involved in the disease. The purposes of the study were: to quantify CoQ10 in fragments of muscle biopsy of patients with LGMD; quantify the enzymatic activity of each respiratory chain complex isolated; quantify the activity of the II + III complexes together as an indirect measure of CoQ10; to verify the relation between the relative area of muscular fibers in the fragment of biopsy and the degree of mitochondrial dysfunction in these fragments; correlate mitochondrial function with clinical parameters of patients with LGMD. Twenty-one patients with LGMD and nine healthy controls participated in the study. The clinical parameters included were age at the time of biopsy, age of onset of symptoms and time of disease progression. The analysis of mitochondrial metabolism was performed by: quantification of CoQ10 in the muscle biopsy fragments and quantification of the activity of the mitochondrial enzyme complexes I, II, III, II + III and IV of the respiratory chain and the enzyme of the mitochondrial matrix citrate synthase. We analyzed the correlation of the clinical parameters, the proportion of fibers in the muscle biopsy and the results of the biochemical analyzes for the characterization of the mitochondrial function. For the LGMD groups, the mean age at the time of biopsy, onset of symptoms and disease duration was 28.9 years (SD ± 11.7), 16.7 years (SD ± 10.3) and 12.1 years (SD ± 10.9), respectively. The control group presented a mean age at the time of biopsy of 29.6 years (SD ± 10.3). The mean CoQ10 dosage in the biopsy specimens of patients with LGMD was 17.9 ?g / g tissue (SD ± 9.2) and in the fragments of the controls was 29.5 ?g / g tissue (SD ± 4, 4). No alterations were observed in the isolated activities of the enzymatic complexes of the respiratory chain. There was a deficiency of the activity of complexes II + III in patients with LGMD. The mean area occupied by muscle fibers in patients with LGMD was 58.5% (SD ± 26.1%) and in controls it was 76.35% (SD ± 1.9%). A moderate correlation was observed between the amount of CoQ10 and the relative area of muscle fibers (r = 0.57 and p = 0.007). There was no correlation of CoQ10 with clinical parameters. In the present study, we conclude that there is a secondary deficiency of CoQ10 in patients with LGMD, which has important implications in the understanding of mitochondrial involvement in this group of diseases and the development of a more effective therapeutic approach.
 
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Publishing Date
2019-06-11
 
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