Mitochondrial membrane potential and ATP production in primary disorders of ATP synthase

Studies of fibroblasts with primary defects in mitochondrial ATP synthase (ATPase) due to heteroplasmic mtDNA mutations in the ATP6 gene, affecting protonophoric function or synthesis of subunit a, show that at high mutation loads, mitochondrial membrane potential DeltaPsi(m) at state 4 is normal, but ADP-induced discharge of DeltaPsi(m) is impaired and ATP synthesis at state 3-ADP is decreased. Increased DeltaPsi(m) and low ATP synthesis is also found when the ATPase content is diminished by altered biogenesis of the enzyme complex. Irrespective of the different pathogenic mechanisms, elevated DeltaPsi(m) in primary ATPase disorders could increase mitochondrial production of reactive oxygen species and decrease energy provision.

[Corneal ulceration complicating surgical correction of ptosis in patient with Kearns-Sayre syndrome--a case report]

The aim is to report a rare complication of surgical ptosis correction in a patient with Kearns Sayre syndrome and the therapeutic possibilities of its treatment.

METHODS

Exposure corneal ulceration caused by lagophtalmos developed gradually in a 30-year-old woman after an upper eyelid ptosis surgery of the right eye performed at another eye clinic. During an examination a limited movement of both eyes and retinal pigmentary changes (salt-pepper-like appearance) were diagnosed. A suspicion of the Kearns Sayre syndrome was expressed according to the clinical picture, the diagnosis was confirmed by molecular analyses in muscle biopsy, which revealed 5.2 kb deletion of mitochondrial DNA.

RESULTS

Corneal ulceration was treated by partial external tarsorrhaphy and frequent instillation of lubricants. The upper eyelid ptosis of the left eye was treated with a spectacle with ptosis support.

CONCLUSION

During the correction of upper eyelid ptosis in patients with progressive external ophtalmoplegia it is necessary to be aware of the risk of surgical exposure keratopathy and corneal ulceration due to the atony of musculus orbicularis oculi muscle and only slightly expressed Bell's phenomenon.

Mitochondrial encephalocardio-myopathy with early neonatal onset due to TMEM70 mutation

OBJECTIVE

Mitochondrial disturbances of energygenerating systems in childhood are a heterogeneous group of disorders. The aim of this multi-site survey was to characterise the natural course of a novel mitochondrial disease with ATP synthase deficiency and mutation in the TMEM70 gene.

METHODS

Retrospective clinical data and metabolic profiles were collected and evaluated in 25 patients (14 boys, 11 girls) from seven European countries with a c.317-2A-->G mutation in the TMEM70 gene.

RESULTS

Severe muscular hypotonia (in 92% of newborns), apnoic spells (92%), hypertrophic cardiomyopathy (HCMP; 76%) and profound lactic acidosis (lactate 5-36 mmol/l; 92%) with hyperammonaemia (100-520 micromol/l; 86%) were present from birth. Ten patients died within the first 6 weeks of life. Most patients surviving the neonatal period had persisting muscular hypotonia and developed psychomotor delay. HCMP was non-progressive and even disappeared in some children. Hypospadia was present in 54% of the boys and cryptorchidism in 67%. Increased excretion of lactate and 3-methylglutaconic acid (3-MGC) was observed in all patients. In four surviving patients, life-threatening hyperammonaemia occurred during childhood, triggered by acute gastroenteritis and prolonged fasting.

CONCLUSIONS

ATP synthase deficiency with mutation in TMEM70 should be considered in the diagnosis and management of critically ill neonates with early neonatal onset of muscular hypotonia, HCMP and hypospadias in boys accompanied by lactic acidosis, hyperammonaemia and 3-MGC-uria. However, phenotype severity may vary significantly. The disease occurs frequently in the Roma population and molecular-genetic analysis of the TMEM70 gene is sufficient for diagnosis without need of muscle biopsy in affected children.

[Clinical, biochemical and molecular characteristics in 11 Czech children with tyrosinemia type I]

BACKGROUND

Hereditary tyrosinemia type 1 (HT1) is a rare autosomal recessive inborn error of metabolism caused by deficiency of fumarylacetoacetate hydrolase. HT1 manifests with severe liver and kidney impairment and associates with an increased risk of liver cancer development. The aim of our study is to present a detailed clinical picture and results of biochemical and molecular genetic analyses in 11 Czech patients with HT1 diagnosed in our clinic within 1982-2006.

METHODS AND RESULTS

In 9 patients the disease manifested between 1.5-7 months of age with refusal to eat, failure to thrive and vomiting. In 4 children HT1 progressed to acute liver failure. One clinically healthy boy was diagnosed because of affected sister. In one boy with liver cirrhosis the diagnosis was delayed until the age of 5.5 years. In all children the biochemical investigation showed elevated liver enzymes, alpha1-fetoprotein and hypophosphatemic rickets. Metabolic investigation revealed increased plasma tyrosine level, urinary excretion of succinylacetone and in 8 measured patients also increased urinary delta-aminolevulinic acid concentration. Three patients born before 1988 died due to liver cancer development (two of them) or liver failure. The average age of our 8 living patients is 10.7 +/- 8.3 years. Mutation analysis of FAH gene confirmed the HT1 in these patients and three novel mutations were found in FAH gene: c.579C>A, c.680G>T and c.1210G>A. Clinical status in six patients is favourable on strict low protein diet combined with Orfadin therapy. However, in two children despite of the maximal available therapy lasting 2 and 10 years resp., the disease progressed towards liver cancer development and necessity of liver transplantation.

CONCLUSIONS

Early diagnostics of HT1 as a part of extended newborn screening is the only possibility to further improve the prognosis of the patients. Moreover, available molecular-genetic analysis of the FAH gene enables prenatal diagnostics in affected families.

Ultrastructural Changes of Mitochondria in the Cultivated Skin Fibroblasts of Patients with Point Mutations in Mitochondrial DNA

Mitochondrial disorders represent a heterogeneous group of multisystem diseases with extreme variability in clinical phenotype. The diagnosis of mitochondrial disorders relies heavily on extensive biochemical and molecular analyses combined with morphological studies including electron microscopy. Although muscle is the tissue of choice for electron microscopic studies, the authors investigated cultivated human skin fibroblasts (HSF) harboring 3 different pathologic mtDNA mutations: 3243A > G, 8344A > G, 8993T > G. They addressed to the possibility of whether mtDNA mutations influence mitochondrial morphology in HSF and if ultrastructural changes of mitochondria may be used for differential diagnostics of mitochondrial disorders caused by mtDNA mutations. Ultrastructural analysis of patients' HSF revealed a heterogeneous mixture of mainly abnormal, partially swelling mitochondria with unusual and sparse cristae. The most characteristic cristal abnormalities were heterogeneity in size and shapes or their absence. Typical filamentous and branched mitochondria with numerous cristae as appeared in control HSF were almost not observed. In all lines of cultured HSF with various mtDNA mutations, similar ultrastructural abnormalities and severely changed mitochondrial interior were found, although no alterations in function and amount of OXPHOS were detected by routinely used biochemical methods in two lines of cultured HSF. This highlights the importance of morphological analysis, even in cultured fibroblasts, in diagnostics of mitochondrial disorders.

TMEM70 mutations cause isolated ATP synthase deficiency and neonatal mitochondrial encephalocardiomyopathy

We carried out whole-genome homozygosity mapping, gene expression analysis and DNA sequencing in individuals with isolated mitochondrial ATP synthase deficiency and identified disease-causing mutations in TMEM70. Complementation of the cell lines of these individuals with wild-type TMEM70 restored biogenesis and metabolic function of the enzyme complex. Our results show that TMEM70 is involved in mitochondrial ATP synthase biogenesis in higher eukaryotes.

Development of a human mitochondrial oligonucleotide microarray (h-MitoArray) and gene expression analysis of fibroblast cell lines from 13 patients with isolated F1Fo ATP synthase deficiency

Background

To strengthen research and differential diagnostics of mitochondrial disorders, we constructed and validated an oligonucleotide microarray (h-MitoArray) allowing expression analysis of 1632 human genes involved in mitochondrial biology, cell cycle regulation, signal transduction and apoptosis. Using h-MitoArray we analyzed gene expression profiles in 9 control and 13 fibroblast cell lines from patients with F₁F_o ATP synthase deficiency consisting of 2 patients with mt9205ΔTA microdeletion and a genetically heterogeneous group of 11 patients with not yet characterized nuclear defects. Analysing gene expression profiles, we attempted to classify patients into expected defect specific subgroups, and subsequently reveal group specific compensatory changes, identify potential phenotype causing pathways and define candidate disease causing genes.

Results

Molecular studies, in combination with unsupervised clustering methods, defined three subgroups of patient cell lines – M group with mtDNA mutation and N1 and N2 groups with nuclear defect. Comparison of expression profiles and functional annotation, gene enrichment and pathway analyses of differentially expressed genes revealed in the M group a transcription profile suggestive of synchronized suppression of mitochondrial biogenesis and G1/S arrest. The N1 group showed elevated expression of complex I and reduced expression of complexes III, V, and V-type ATP synthase subunit genes, reduced expression of genes involved in phosphorylation dependent signaling along MAPK, Jak-STAT, JNK, and p38 MAP kinase pathways, signs of activated apoptosis and oxidative stress resembling phenotype of premature senescent fibroblasts. No specific functionally meaningful changes, except of signs of activated apoptosis, were detected in the N2 group. Evaluation of individual gene expression profiles confirmed already known ATP6/ATP8 defect in patients from the M group and indicated several candidate disease causing genes for nuclear defects.

Conclusion

Our analysis showed that deficiency in the ATP synthase protein complex amount is generally accompanied by only minor changes in expression of ATP synthase related genes. It also suggested that the site (mtDNA vs nuclear DNA) and the severity (ATP synthase content) of the underlying defect have diverse effects on cellular gene expression phenotypes, which warrants further investigation of cell cycle regulatory and signal transduction pathways in other OXPHOS disorders and related pharmacological models.

[Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE)]

BACKGROUND

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a disorder with autosomal recessive inheritance caused by mutations in the gene encoding thymidine phosphorylase (TP). TP deficiency results in imbalance of mitochondrial pool of nucleotides leading secondary to multiple deletions and depletion of mitochondrial DNA (mtDNA) and impairment of oxidative phosphorylation system. The disease is clinically characterized by gastrointestinal dysmotility with symptoms of pseudo-obstruction, severe failure to thrive, ptosis, leukoencephalopathy, peripheral neuropathy and myopathy. We present results of the clinical, histochemical, biochemical and molecular analyses of the first Czech patient with MNGIE syndrome.

METHODS AND RESULTS

Man, 33-years old with twenty-year history of failure to thrive (height 168 cm, weight 34 kg) and progressive gastrointestinal dysmotility, external ophthalmoplegia, leucoencephalopathy and peripheral neuropathy was recommended to metabolic center. Histochemical analyses in muscle biopsy showed the presence of "ragged red fibers" with focal decrease of cytochrome c oxidase activity, but spectrophotometric analyses in isolated muscle mitochondria revealed normal activities of all respiratory chain complexes. Metabolic investigation revealed markedly increased plasma level of thymidine (6.6 micromol/l, controls <0.05 micromol/l) and deoxyuridine (15 micromol/l, controls <0.05 micromol/l). The activity of TP in isolated lymphocytes was low (0.02 micromol/hour/mg protein, reference range 0.78 +/- 0.18). Molecular analyses in muscle biopsy revealed multiple mtDNA deletions and homozygous mutation 1419G>A (Gly145Arg) was found in gene for TP. Both parents are heterozygotes.

CONCLUSIONS

MNGIE has to be considered in patients presenting with a combination of gastrointestinal and neurological symptoms. Plasma level of thymidine may serve as the best method for laboratory screening of MNGIE, but molecular analyses are necessary for genetic counselling and prenatal diagnosis in affected families.

Polarographic evaluation of mitochondrial enzymes activity in isolated mitochondria and in permeabilized human muscle cells with inherited mitochondrial defects

Inherited disturbances of the mitochondrial energy generating system represent a heterogeneous group of disorders associated with a broad spectrum of metabolic abnormalities and clinical symptoms. We used the polarographic and spectrophotometric method for detection of mitochondrial disorders, because these two techniques provide a different insight into mitochondrial function. In six patients suspected of mitochondrial disease we found defects of complex I (two patients), complex III (one patient), complex IV (two patients) and a combination of defect of complex III and IV (one patient). Citrate synthase activity, used as the reference enzyme, was not changed. A comparison of the two methods showed several differences in evaluation of mitochondrial enzymes activity due to the fact that both methods used different conditions for enzyme activity measurements. In contrast to oxygen consumption measurements, where the function of the whole-integrated respiratory chain is characterized, spectrophotometric measurements characterize activities of isolated complexes in disintegrated membranes. However, it may be concluded from our experiments that both methods provide useful and complementary data about mitochondrial energetic functions. Whereas spectrophotometric data are suitable for evaluation of maximal enzyme activities of mitochondrial enzyme complexes, polarographic data provide better information about enzyme activities in cells with mitochondrial defects under in situ conditions.

[Variation in manifestations of heteroplasmic mtDNA mutation 8993 T>G in two families]

BACKGROUND

The most frequent manifestations of heteroplasmic mitochondrial DNA (mtDNA) mutation 8993 T > G are Leigh syndrome or NARP syndrome (Neurogenic Muscle Weakness, Ataxia, and Retinitis Pigmentosa). The authors describe heterogeneity of clinical symptoms and results of biochemical and molecular analyses in seven severely clinically affected children from two unrelated families with heteroplasmic mtDNA mutation 8993 T > G.

METHODS AND RESULTS

Seven clinically affected children from two unrelated families were born in term after an uneventful pregnancy. The failure to thrive, psychomotor retardation, hypotonic or spastic quadruparesis, hypertrophic cardiomyopathy, hepatopathy and hyperlactacidaemia developed after birth. Five children died in the first year of life during acute respiratory infection, one girl died at the age of 3 months with sudden death syndrome, only one boy with spastic quadruparesis and severe psychomotor retardation survived to the age of 8 years. Molecular analyses in all investigated children and their clinically non-affected mothers revealed the presence of heteroplasmic mtDNA mutation 8993 T > G. Mutated copies of mtDNA molecules in maternal tissues were in the range of 15-22%. The mutation load in all analysed children's tissues was higher than 90%.

CONCLUSIONS

A broad spectrum of clinical symptoms may be observed in families with heteroplasmic mtDNA mutations 8993 T > G. Affected children with a mutation load higher than 90% usually do not survive after infancy. In both investigated families, a profound increase in the levels of heteroplasmy of mtDNA mutation 8993 T > G was observed in two subsequent generations.

[Disorders of mitochondrial energy metabolism in patients with the Kearns-Sayre syndrome]

BACKGROUND

Kearns-Sayre syndrome is a multisystem disorder caused by rearrangements of mitochondrial genome including various deletions and/or duplications. The aim of the study is to analyse the impact of mitochondrial DNA (mtDNA) deletions on the mitochondrial energetic metabolism in five patients with Kearns-Sayre syndrome.

METHODS AND RESULTS

The course of the disease is progressive in all patients. All of them have bilateral ptosis and external opthalmoplegia, four have retinitis pigmentosa, three have progressive muscle weakness and three have pacemaker because of complete A-V heart block. One patient underwent renal transplantation at the age of 12 because of a chronic renal failure. Southern blot analysis in muscle tissue revealed large scale heteroplasmic mtDNA deletions (3-7.4 kb) in all patients, the number of mutated copies of mtDNA ranged from 50 to 70%. Spectrophotometric measurements of respiratory chain complexes activities in muscle tissue revealed various combinations of defects of complex III, IV and I + III activities in all patients. Nevertheless, the lactic acidosis was permanently present only in one patient. Ragged-red fibers were found in two patients.

CONCLUSIONS

Although the diagnostic of Kearns-Sayre syndrome is based on clinical features, molecular analysis of mtDNA is necessary to confirm the diagnosis. The prognosis of the disease is unfavourable and co-operation between the patient and various specialists is necessary for the treatment, which is currently only symptomatic.

[Treatment of infertility in nonobstructive azoospermia using the TESE method (testicular sperm extraction)--clinical results]

Sperm was found in 56.6% of TESE cycles in 27 men with non-obstructive azoospermia. Using testicular sperm, 30% oocytes were fertilized. Embryos were transferred in 11 cycles. Twins were delivered in the 34th week of pregnancy. Two further pregnancies are ongoing. The pregnancy rate was 27% per ET. Testicular biopsy in all azoospermic men is recommended in special IVF centers not only for histological examination but also for ICSI procedure with testicular sperm which could be provided at the same time.

[Treatment of infertility in non-obstructive azoospermia using the TESE (testicular sperm extraction) method--clinical study]

Testicular sperm extraction (TESE) was performed in 27 men in 30 cycles. All men were examined for genetics, serum hormonal status, biochemical status of semen samples. All men were examined by an urologist. No prognostic evaluation able to provide information about the prognosis of TESE procedure was found. Even a high FSH level, testicular hypotrophy or previous histological examination cannot exclude any patient from testicular biopsy.

Infertility treatment of men with non-obstructive azoospermia

Male infertility can be treated by several methods with varying degree of success. We present evidence that "open" testicular biopsy is favorable for men suffering from non-obstructive azoospermia (NOA). Moreover, any NOA patient may be subjected to this treatment even though his past histopathological examinations suggest that it is likely no sperm will be found in the testicular tissue. Thus, we recommend the testicular sperm extraction (TESE) procedure for NOA patients.

[The current role of intracytoplasmic single sperm injection (ICSI) in assisted reproduction]

Intracytoplasmic sperm injection (ICSI) plays a unique role in the treatment of male infertility. ICSI results are not influenced by either sperm number, motility or sperm morphology. In our group we studied 90 cycles in which conventional IVF and ICSI were performed on sibling oocytes in couples with borderline semen analysis (more than 50,000 sperm/oocyte). A higher number of A quality embryos was found in the ICSI oocyte group (40%/32%). In 38% of IVF cycles no embryos were found, whereas with ICSI the absence decreased to only 12%. In only 4% of the cycles, the IVF method was more successful than that of ICSI treatment. In only 7% of our combined group there were no embryos for transfer. The positive influence of ICSI on our centre results -32% pregnancy rate/ET and an 18% baby take home rate--are discussed. In our retrospective study, ICSI is more successful than IVF alone and a combination of IVF and ICSI achieves the best results in the borderline sperm analysis group. An increased use of the ICSI technique in assisted reproduction can be expected in future.

Analysis of pharmacotherapy of hypertension in out-patients

In the present pilot study an attempt was made to evaluate the usefulness of results obtained about the treatment of patients suffering from high blood pressure for a pharmacoepidemiological study of the therapeutic value of antihypertensive agents. Data from 90 hypertensive patients were used in the present retrospective-prospective study. These patients all attended an out-patient clinic located in one of the East-Bohemian districts that are participating in the MONICA programme. Instead of the analysis of the population data, regular blood pressure measurements, plasma glucose levels, and total cholesterol concentrations were measured and analysed. The consumption of various antihypertensive drugs in this study was similar to that found in larger studies performed in other health districts of the Czech Republic. Diuretics were the drugs most frequently prescribed for hypertensive patients. General practitioners rarely prescribed calcium channel blockers and angiotensin-converting enzyme inhibitors in 1990 and 1991. The metabolic effects of antihypertensive drugs, mostly diuretics, were not significantly evident. The most frequent occurrence of non-compensated blood pressure was recorded for the treatments with Trimecryton and methyldopa. However, the validity of these findings should be tested in a larger group of hypertensic patients.