线粒体呼吸链复合物Ⅰ缺陷导致幼儿肝内胆汁淤积症

线粒体呼吸链复合物缺陷是导致儿童线粒体病的主要原因。本文就1例线粒体呼吸链复合物Ⅰ缺陷导致的幼儿胆汁淤积症患者的临床经过、生化特点、线粒体呼吸链复合物活性分析及基因突变进行回顾性研究。患儿,男,自1岁1个月起腹泻,体重下降,伴无力、进行性黄疸、肝损害。经多种检查、尿液有机酸分析及血液氨基酸、酯酰肉碱谱分析未见特异性改变。外周血白细胞线粒体呼吸链复合物Ⅰ活性降低,线粒体基因分析发现患儿及其母亲tRNA 5821G>A突变,证实患儿存在线粒体呼吸链复合物Ⅰ缺陷。患儿疾病进展迅速,治疗无效,于1岁5个月时夭折。复合物Ⅰ缺陷是线粒体呼吸链缺陷中最常见的类型,本研究首次诊断了1例线粒体呼吸链复合物Ⅰ缺陷所导致的中国儿童患者,其临床表现为胆汁淤积症。线粒体肝病是导致儿童代谢性肝病的主要原因之一,生化分析、线粒体呼吸链复合物活性测定及基因分析是病因诊断的关键。     

线粒体呼吸链复合物Ⅱ缺陷与疾病

本文就近年关于线粒体呼吸链复合物Ⅱ的结构、功能及其缺陷的临床表型、诊断、治疗及分子遗传学研究方面的进展进行文献综述。线粒体呼吸链复合物Ⅱ亦称琥珀酸泛醌氧化还原酶,是线粒体呼吸链的重要组分之一,对细胞的氧化磷酸化起着关键作用。呼吸链复合物Ⅱ与氧化性应激密切相关,是细胞内毒性物质以及异常代谢产物的敏感靶标。复合物Ⅱ缺陷导致的线粒体病临床表现多样,以神经肌肉进行性损害为主要表现,少数表现为心肌病、发作性呕吐、溶血尿毒综合征等。诊断有赖于线粒体呼吸链酶复合物活性测定和基因分析。患者受累组织的呼吸链复合物Ⅱ活性降低。已发现SDHA基因与编码复合物Ⅱ组装因子的SDHAF1基因的突变可导致复合物Ⅱ缺陷。目前线粒体呼吸链复合物Ⅱ缺陷的治疗主要是以改善线粒体功能为主。     

ND3基因10191T>C突变导致的线粒体呼吸链复合物Ⅰ缺陷

本文报道1例由于ND3基因突变导致线粒体呼吸链复合物 Ⅰ 缺陷的患儿。该患儿自6岁起出现眼睑下垂、无力、癫癎及运动倒退,呈进行性加重。血液乳酸、丙酮酸增高,脑MRI示双侧基底节对称性损害,符合Leigh综合征诊断。为明确病因,提取患儿和父母的外周血白细胞线粒体蛋白,进行氧化磷酸化酶复合物 Ⅰ～V活性测定,并提取DNA,分析编码线粒体呼吸链复合物 Ⅰ 的7个线粒体结构基因。结果显示患儿线粒体呼吸链复合物 Ⅰ 活性为33.1 nmol/min?毫克线粒体总蛋白（正常对照44.0±5.4 nmol/min?毫克线粒体总蛋白）,复合物 Ⅰ 与柠檬酸合酶活性比值为19.8%（正常对照48.1%±11.0%）,均降低。复合物 Ⅱ～V活性正常。患儿线粒体ND3基因10191T>C突变。其父母线粒体基因及呼吸链复合物酶活性正常。治疗后,现患者16岁,癫癎控制良好,双下肢痉挛性瘫痪,智力正常。通过外周血白细胞线粒体氧化磷酸化酶复合物活性测定及基因分析,本研究首次诊断了编码线粒体呼吸链复合物Ⅰ亚基的ND3基因10191T>C突变导致复合物Ⅰ缺陷,为Leigh综合征的发病原因提供依据。     

线粒体呼吸链复合物Ⅱ缺陷所致Leigh综合征

线粒体呼吸链复合物Ⅱ缺陷是较为少见的氧化磷酸化障碍性疾病。本文对1例单纯线粒体呼吸链复合物Ⅱ缺陷所致Leigh综合征患儿的诊疗进行回顾性分析。患儿,男,10个月,8个月时出现发热,热退后出现进行性全身无力、运动发育倒退和吞咽困难。血乳酸、丙酮酸增高,脑MRI显示双侧基底节对称性损害。对患儿进行了外周血白细胞线粒体氧化磷酸化酶复合物I-V活性测定和线粒体基因突变位点筛查分析。线粒体呼吸链复合物Ⅱ活性为21.9 nmol/min?mg线粒体总蛋白（正常对照47.3±5.3 nmol/min?mg线粒体总蛋白）,柠檬酸合酶活性为22.1%（正常对照50.9%±10.7%）,均显著降低。线粒体基因分析未发现异常。患儿确诊为线粒体呼吸链复合物Ⅱ缺陷所致Leigh综合征。经治疗患儿运动功能明显恢复。目前患儿22个月,病情稳定。     

TMEM70基因新型复合杂合突变致线粒体呼吸链酶复合物V缺乏症1例报告

<正>线粒体呼吸链酶复合物V也称为三磷酸腺苷（ATP）合酶,是位于线粒体内膜上的大蛋白复合体,是提供线粒体能量的关键酶,在氧化磷酸化过程中催化ATP的合成。ATP合酶需要多种基因参与编码,包括ATP5E、ATP5F1A、ATPAF2、ATP5F1D、TMEM70等基因,ATP合酶相关基因缺陷会导致线粒体能量代谢异常,引起多系统异常,患儿常表现为生长发育迟缓、肌张力减退、代谢性酸中毒、血氨升高等,肥厚性心肌病也是该疾病相对特征性的表现。本文报告1例TMEM70基因突变致ATP合酶缺乏症患儿,     

线粒体呼吸链复合物Ⅲ缺陷五例的临床特点与生化分析

目的 对5例线粒体呼吸链复合物Ⅲ缺陷患儿进行临床特点和生化分析.方法 对5例患儿(男3例,女2例)临床特点进行归纳总结,并抽取患儿静脉血,分取白细胞线粒体蛋白,采用分光光度测定法检测线粒体呼吸链复合物Ⅰ～Ⅴ活性.结果 (1)5例分别于1个月～15岁时来院就诊.其中3例临床表型符合Leigh综合征,主要表现为智力运动发育落后,运动倒退.l例表现为肝损害,胆汁淤积症.l例表现为进行性肌无力.(2)线粒体呼吸链复合物Ⅰ+Ⅲ活性为3.0～14.2 nmoL/(min·mg线粒体总蛋白),200名正常对照为84.4±28.5 nmol/( min·mg线粒体总蛋白),患儿酶活性降低至正常对照的10.4％～49.3％;复合物Ⅰ+Ⅲ与柠檬酸合酶活性比值为3.5％～22.9％,显著低于正常对照[(66.1±l4.7)％],复合物Ⅰ、Ⅱ、Ⅳ和Ⅴ活性正常,符合单纯线粒体呼吸链复合物Ⅲ缺陷诊断.结论 线粒体呼吸链复合物Ⅲ缺陷病临床表现复杂多样,累及多个系统;复合物Ⅰ+Ⅲ活性以及与柠檬酸合酶活性比值均低于正常对照,而所有患儿复合物Ⅰ、Ⅱ、Ⅳ和Ⅴ活性均未发现异常.     

儿童线粒体脑病的临床和分子遗传学特点及其预后

目的探讨儿童线粒体脑病临床及分子遗传学特点和预后。方法对中国人民解放军总医院儿科2008—2013年收治的儿童线粒体脑病11例患儿临床表现、一般实验室检查、肌肉病理及线粒体基因点检测结果进行分析并随访。结果患儿发病年龄6个月~12岁,病程2个月~3年,其中线粒体脑肌病伴乳酸酸中毒和卒中样发作(MELAS)型6例,其他呼吸链酶缺陷引起的线粒体疾病5例。主要表现为抽搐、呕吐、头痛、智力低下、偏瘫等;10例患儿有乳酸升高,其中7例伴丙酮酸升高;6例脑电图示背景慢波增多;头颅磁共振显示受累部位依次为:双侧基底节2例、颞顶枕叶3例、脑内多发病变2例、额顶枕叶1例、顶枕1例、丘脑中脑1例;其中3例行磁共振血管成像(MRA)检查,2例正常,1例左大脑中后动脉分支较对侧少;磁共振波谱分析(MRS)乳酸高峰者3例。2例患儿行骨骼肌病理检查,1例接受骨骼肌病理检查显示异常线粒体堆积。线粒体呼吸链复合物(I~V)缺陷结果复合物Ⅳ缺陷2例,Ⅴ缺陷1例,联合复合物缺陷Ⅰ+Ⅲ缺陷2例。5例白细胞线粒体DNA发现不同位点突变,分别为T8993G、T8993C突变、A3243G突变和11777突变。结论儿童线粒体脑病临床表现多样,实验室检查、头颅影像、基因突变及呼吸链酶学检查有助于早期诊断和治疗,该病预后不佳。     

核基因突变导致儿童线粒体病的分子遗传学进展

<正>线粒体病是由线粒体基因或核基因突变引起线粒体代谢酶功能缺陷,导致ATP合成障碍、能量产生不足所引起的一组多系统性疾病。基因诊断是目前诊断线粒体病的金标准~([1~3])。线粒体蛋白组包含约1 500种蛋白质,线粒体基因仅编码其中的13种,大部分由核基因编码,其突变引起的线粒体病占75%~95%~([4,5])。核基因突变可分为10种类型:呼吸链复合物亚基及组装因子突变,维持线粒体基     

病毒感染所致的心肌线粒体损伤

心肌线粒体是心肌细胞的能量供应站、Ca2 浓度调节器、细胞死亡执行者。病毒感染过程中病毒直接损害、免疫损害、氧自由基损伤使心肌线粒体的结构和功能发生改变，进而引起线粒体的钙超载、呼吸链功能障碍、凋亡、DNA损伤，最终使ATP合成受阻，心肌能量供应不足；膜离子运输系统紊乱，心肌异常电位产生；凋亡调控系统激活，心肌细胞发生凋亡。     

脓毒症与线粒体呼吸链酶复合物Ⅴ研究进展

脓毒症是一种复杂的病理生理功能紊乱性疾病,是由病原微生物感染机体导致的全身性炎性反应,是ICU重症患者的主要死因之一.脓毒症患者发病过程中存在线粒体功能失调以及氧化磷酸化功能受损.线粒体呼吸链酶复合物Ⅴ是线粒体氧化磷酸化的关键酶,在脓毒症前期主要促进ATP合成且酶活性降低;在脓毒症后期即局部缺血的条件下,主要发挥水解功能且活性上调.该文就脓毒症患者复合物Ⅴ活性变化、变化机制以及治疗的研究进展进行阐述.     

Clinical presentations and laboratory investigations in respiratory chain deficiency

Respiratory chain deficiencies have long been regarded as neuromuscular diseases. In fact, oxidative phosphorylation, i.e., ATP synthesis by the respiratory chain not only occurs in the neuromuscular system, indeed, a number of nonneuromuscular organs and tissues are dependent upon mitochondrial energy supply. For this reason, a respiratory chain deficiency can theoretically give rise to any symptom, in any organ or tissue, at any age with any mode of inheritance, due to the twofold genetic origin of respiratory enzymes (nuclear DNA and mitochondrial DNA).     

Analysis of the mitochondrial encoded subunits of complex I in 20 patients with a complex I deficiency

NADH-ubiquinone oxidoreductase or complex I deficiency is a frequently diagnosed enzyme defect of the oxidative phosphorylation (OXPHOS) system in humans. However, in many patients, with complex I deficiency and clinical symptoms suggestive of mitochondrial disease, often no genetic defect can be found after investigation of the most common mitochondrial DNA (mtDNA) mutations. In this study, 20 patients were selected with a biochemically documented complex I defect and no common mtDNA mutation. We used the Denaturing Gradient Gel Electrophoresis (DGGE) method with primers encompassing all mitochondrial encoded fragments, to search in a systematic manner for mutations in the mitochondrial genome of complex I. In our group of patients, we were able to detect a total of 96 nucleotide changes. We were not able to find any disease causing mutation in the mitochondrial encoded subunits of complex I. These results suggested that the complex I deficiency in this group of patients is most probably caused by a defect in one of the nuclear encoded structural genes of complex I, or in one of the genes involved in proper assembly of the enzyme.     

Intractable secretory diarrhea in a Japanese boy with mitochondrial respiratory chain complex I deficiency

The etiology of secretory diarrhea in early life is often unclear. We report a Japanese boy who survived until 3 years of age, despite intractable diarrhea commencing soon after birth. The fecal sodium content was strikingly high (109 mmol/L [normal range, 27–35 mmol/L]) and the osmotic gap was decreased (15 mOsm/kg), consistent with the findings of congenital sodium diarrhea. We examined the mitochondrial respiratory chain function by blue native polyacrylamide gel electrophoresis (BN-PAGE) in-gel enzyme staining, BN-PAGE western blotting, respiratory chain enzyme activity assay, and immunohistochemistry. Liver respiratory chain complex (Co) I activity was undetectable, while other respiratory chain complex activities were increased (Co II, 138%; Co III, 153%; Co IV, 126% versus respective control activities). Liver BN-PAGE in-gel enzyme staining and western blotting showed an extremely weak complex I band, while immunohistochemistry showed extremely weak staining for the 30-kDa subunit of complex I, but normal staining for the 70-kDa subunit of complex II. The patient was, therefore, diagnosed with complex I deficiency. The overall complex I activity of the jejunum was substantially decreased (63% of the control activity). The immunohistochemistry displayed apparently decreased staining of the 30-kDa complex I subunit, together with a slightly enhanced staining of the 70-kDa complex II subunit in intestinal epithelial cells. These data imply that intestinal epithelial cells are also complex I-deficient in this patient. Complex I deficiency is a novel cause of secretory diarrhea and may act via disrupting the supply of adenosine triphosphate (ATP) needed for the maintenance of ion gradients across membranes.     

Combined deficiencies of the pyruvate dehydrogenase complex and enzymes of the respiratory chain in mitochondrial myopathies

In six patients with mitochondrial (encephalo-) myopathy investigations of skeletal muscle revealed a defect of pyruvate dehydrogenase complex (PDHC) in combination with one or more respiratory chain complex deficiencies. A combination of defects of this kind has not been reported previously. Five of the six patients presented within the 1st year of life and had a severe clinical course. Intrafamilial variability of the clinical course in dizygotic twins both suffering from a cytochrome c oxidase deficiency and one of them also from a PDHC deficiency suggests an additional effect of PDHC deficiency on the clinical symptoms. Immunoblot studies of PDHC in five of the patients revealed no abnormalities in their subunit pattern, rendering a defect of mitochondrial protein import or assembly unlikely. The finding of a combined PDHC and respiratory chain deficiency has implications for the diagnostic approach, for therapy and genetic counselling. The exact pathogenetic mechanism of this combination of defects remains to be elucidated.     

Mitochondrial dysfunction in skeletal muscle of children with cardiomyopathy

OBJECTIVES: This study sought to examine skeletal muscle of children with cardiomyopathy (CM) for changes in mitochondrial enzyme activities and in mitochondrial DNA (mtDNA). BACKGROUND: Heart mitochondrial enzymatic activity defects have been often found in dilated and hypertrophic CM. The defects primarily involve the activities of the electron transport system and oxidative phosphorylation pathway including respiratory complexes I, III, IV, and V. METHODS: Skeletal muscle biopsies of 8 children with CM were examined for specific mitochondrial enzyme activities, mtDNA copy number and the presence of pathogenic mutations and deletions in mtDNA. RESULTS: A marked deficiency in specific mitochondrial enzyme activities was found in 6 of 8 patients in skeletal muscle as well as in 2 of 3 hearts of those in whom cardiac tissue was available. Specific activity defects were found in complex I (2 cases), complex III (5 cases), complex IV (3 cases), and complex V (4 cases). Complex II and citrate synthase activities were unaffected. None of the previously reported pathogenic mutations associated with CM were detected, nor was there any evidence of mtDNA depletion. The incidence of defective respiratory complex activities in skeletal muscle was similar to the incidence of defective complex activities previously reported in cardiac tissue. CONCLUSIONS: Mitochondrial analysis of skeletal muscle is warranted in the overall clinical evaluation of children with CM, and particularly before consideration for cardiac transplantation.     

Clinical Presentations of Mitochondrial Cardiomyopathies

To determine the clinical manifestations and interfamilial variability of patients diagnosed with a mitochondrial cardiomyopathy, we reviewed the charts of 14 patients with cardiomyopathy out of 59 patients with mitochondrial disorders who attended the mitochondrial disease clinic at Wolfson Medical Center from 1996 to 2001. All patients underwent a metabolic evaluation including blood lactate, pyruvate, carnitine, and amino acids and urine organic acids. Respiratory chain enzymes were assessed in 10 patients. The mitochondrial DNA (mtDNA) was assessed for mutations.The age at presentation ranged between 6 months and 24 years. Six of the patients died, 5 from heart failure. The cardiomyopathy was hypertrophic in 10 and dilated in 4. Conduction and rhythm abnormalities were present in 6. Eleven patients had family members with mitochondrial disorders. All the patients had additional involvement of one or more systems. Seven patients exhibited a deficiency of a respiratory chain enzyme in the muscle. The MELAS mtDNA point mutation (3243) was found in one patient. Blood lactic acid levels were increased in 5. Brain MRI abnormalities were observed in 4.Conclusions Mitochondrial dysfunction frequently affects the heart and may cause both hypertrophic and dilated cardiomyopathy. The cardiomyopathy is usually a part of a multisystem involvement and may rarely be isolated. The course may be stable for many years, but rapid deterioration may occur. Understanding the biochemical and genetic features of these diseases will enable us to comprehend the clinical heterogeneity of these disorders.