Yukihiro Akita

L-arginine improves the symptoms of strokelike episodes in MELAS.

Based on the hypothesis that mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) are caused by impaired vasodilation in an intracerebral artery, the authors evaluated the effects of administering l-arginine, a nitric oxide precursor. Patients were administered l-arginine intravenously at the acute phase or orally at the interictal phase. l-Arginine infusions significantly improved all strokelike symptoms, suggesting that oral administration within 30 minutes of a stroke significantly decreased frequency and severity of strokelike episodes.

Endothelial dysfunction in MELAS improved by l-arginine supplementation

The authors evaluated endothelial function in patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke) by flow-mediated vasodilation (FMD) and found a significant decrease vs controls. Two years of supplementation with oral l-arginine, a nitric oxide precursor, significantly improved endothelial function to control levels and was harmonized with the normalized plasma levels of l-arginine in patients. l-Arginine therapy improved endothelial dysfunction and showed promise in treating strokelike episodes in MELAS.

Heterogeneous presentation in A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene.

AIMS To clarify the phenotype–genotype relation associated with the A3243G mitochondrial DNA mutation. METHODS Five unrelated probands harbouring the A3243G mutation but presenting different clinical phenotype were analysed. Probands include Leigh syndrome (LS3243), mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS3243), progressive external ophthalmoplegia (PEO3243), and mitochondrial diabetes mellitus (MDM3243). Extensive clinical, histological, biochemical, and molecular genetic studies were performed on five families. RESULTS All patients showed ragged red fibres (RRF), and focal cytochrome c oxidase (COX) deficiency except for the patient with MDM3243. The mutation load was highest in the proband with LS3243 (>90%), who also presented the highest proportion of RRF (68%) and COX negative fibres (10%), and severe complex I plus IV deficiency. These proportions were lower in the probands with PEO3243 and with MDM3243. CONCLUSION The most severe clinical phenotype, LS3243, was associated with the highest proportion of the A3243G mutation as well as the most prominent histological and biochemical abnormalities.

Fatal hypertrophic cardiomyopathy associated with an A8296G mutation in the mitochondrial tRNALys gene

We describe an 8‐day‐old baby girl presenting a fatal infantile form of hypertrophic obstructive cardiomyopathy, associated with an A8296G mutation in the mitochondrial tRNALys gene. She was born from a healthy unrelated couple, and was the first infant of dizygotic twins. Soon after birth, she was noted to have tachypnea and generalized hypotonia. She had high levels of lactate and pyruvate, and was diagnosed as having hypertrophic cardiomyopathy using echocardiography. She died by cardiac failure. Mitochondrial DNA analysis was performed by sequencing after PCR‐subcloning methods, and the percentage of mutation was measured using PCR‐RFLP methods. In various tissues obtained at autopsy, analysis showed a heteroplasmic population of A8296G mutation in the mitochondrial tRNALys gene in all the tissues examined. Maternal inheritance was demonstrated in the family members. Our data demonstrated that an A8296G mutation in the mitochondrial tRNALys gene showed clinical heterogeneity from a milder form previously reported as mitochondrial diabetes mellitus, to a more severe form as hypertrophic obstructive cardiomyopathy, according to the spatial distribution of this mutation. Hum Mutat 15:382, 2000.

Inappropriate intracranial hemodynamics in the natural course of MELAS

The abnormalities of intracranial hemodynamics associated with strokelike episodes in MELAS are variable depend on the time phase from the onset of strokelike episodes and on the progression of the dementia state. To clarify the regional cerebral blood flows (rCBF) in the natural course of MELAS is very important to understand the pathogenic mechanism of this disorder, either cytopathy, angiopathy or both. We analyzed the serial studies of brain statistical parametric mapping (SPM) 99 single photon emission computed tomography (SPECT) in 5 MELAS patients in maximum 10 years interval, who fulfilled the clinical, pathological and genetic criteria of MELAS, and have an A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene. SPM is a proven and effective method for the voxel-by-voxel analysis of functional images which show the advantage in its promise of fully automated neurophysiological imaging analysis throughout the whole brain using various statistical analyses. SPECT acquisition was initiated and was reconstructed by iterative algorithm and were processed and analyzed with SPM 99 for Windows software. Statistics were displayed as Z scores (threshold: P < 0.01). The inappropriate intracranial hemodynamics was found not only at the acute but at the interictal phase, and was getting worse as the disease progress. Hypoperfusion in the posterior cingulate cortex was always observed (corrected P < 0.01) in MELAS patients, which is the typical finding reported in Alzheimers disease. The inappropriate intracranial hemodynamics is a common feature and may be related with mitochondrial angiopathy in the natural course of MELAS.

The mitochondrial DNA C3303T mutation can cause cardiomyopathy and/or skeletal myopathy

OBJECTIVE Several mutations in mitochondrial DNA have been associated with infantile cardiomyopathy, including a C3303T mutation in the mitochondrial transfer RNA(Leu(UUR)) gene. Although this mutation satisfied generally accepted criteria for pathogenicity, its causative role remained to be confirmed in more families. Our objective was to establish the frequency of the C3303T mutation and to define its clinical presentation. STUDY DESIGN Families with cardiomyopathy and maternal inheritance were studied by polymerase chain reaction/restriction fragment length polymorphism analysis looking for the C3303T mutation. RESULTS We found the C3303T mutation in 8 patients from 4 unrelated families. In one, the clinical presentation was infantile cardiomyopathy; in the second family, proximal limb and neck weakness dominated the clinical picture for the first 10 years of life, when cardiac dysfunction became apparent; in the third family, 2 individuals presented with isolated skeletal myopathy and 2 others with skeletal myopathy and cardiomyopathy; in the fourth family, one patient had fatal infantile cardiomyopathy and the other had a combination of skeletal myopathy and cardiomyopathy. CONCLUSIONS Our findings confirm the pathogenicity of the C3303T mutation and suggest that this mutation may not be rare. The C3303T mutation should be considered in the differential diagnosis of skeletal myopathies and cardiomyopathy, especially when onset is in infancy.

Single-fiber analysis of mitochondrial A3243G mutation in four different phenotypes

Abstract Five unrelated patients harboring the A3243G mutation in the mitochondrial DNA (mtDNA) but presenting with different clinical phenotype were studied for their percentage of mutation at the single muscle fiber levels. One patient had a clinically and pathologically defined Leigh syndrome (LS), two showed mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), another showed progressive external ophthalmoplegia (PEO), and the other showed mitochondrial diabetes mellitus (MDM). The mutation load was greater in the muscle from the patient with LS (92%), who showed more than 80% even in the non-ragged red fibers (RRF) and also presented the highest proportion of RRF. The patients with MELAS had lower mutation levels as well as a lower proportion of RRF, and these two parameters were even lower in the PEO and MDM patients. These results were consistent with the concept that differences in the mutation load and in the somatic distribution of the mutation among different cells and tissues are responsible for the differences in phenotypical expression of the disease.

Increased mitochondrial processing intermediates associated with three tRNALeu(UUR) gene mutations

Accumulation of RNA 19 has been associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes. We analyzed total RNA in muscle specimens from six patients who had one of three pathogenetic point mutations in the mitochondrial tRNA(Leu(UUR)) gene, including A3243G, T3271C, and T3303C. Mitochondrial processing intermediates were identified and quantitated by Northern blotting. The percentage of DNA with the mutation also was determined in each patient. The intermediate (RNA 19) was significantly increased in all patients. The proportion of mutation-carrying RNA in processing intermediates was always higher than in the DNA fraction, suggesting that these mutations may have dominant-negative effects on mitochondrial RNA processing events at the tRNA(Leu(UUR)) gene boundary.

Effect of l-arginine on synaptosomal mitochondrial function

OBJECTIVE Specific aim of this study is to elucidate the direct effects of L-arginine on the synaptosomal neurotransmission related to the mitochondrial respiratory function. METHODS Using isolated endbrains from wild-type mice (ICR), crude synaptosome was analyzed for their concentration of gamma-aminobutyric acid (GABA) and glutamate (Glu) with/without addition of L-arginine. We analyzed the contents of releasing amino acids evoked by high potassium condition and uptake of them in three separated fractions (cytosol, vesicles, and intact mitochondria). The oxygen consumption was also measured by oxygen electrode. RESULTS The entire uptakes of GABA and Glu were inhibited by rotenone (about 30 nmol/mg protein) with dose-dependent manner and showed a plateau at about 70% of total uptake. L-arginine inhibited the uptake of Glu logarithmically, however it showed no change in uptake of GABA. The contents of GABA and Glu in synaptosome were decreased in the presence of L-arginine. L-arginine enhanced the respiration of state II by succinate on synaptosomal respiration, although the respiration of synaptosomal mitochondrial fraction and the respiratory chains enzyme activities were almost unaffected by L-arginine. In the presence of rotenone, L-arginine decreased the uptake of Glu without changing the uptake of GABA, increased the releasing of GABA, and may modulate the excitability of neuronal state on the cytosol, cytomembrane, and/or organelles except for mitochondria. CONCLUSIONS L-arginine may modulate excitation by neurotransmitters at nerve endings, in relation to potentiated respiratory metabolism of succinate in synaptosomes. Such effects might contribute to alleviation of stroke-like symptoms in MELAS.

Prediction of acute encephalopathy with biphasic seizures and late reduced diffusion in patients with febrile status epilepticus

INTRODUCTION Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common subtype of acute encephalopathy among children in Japan. The pathogenesis of AESD is mostly delayed cerebral edema caused by excitotoxic injury. It is difficult to discriminate AESD and complex febrile seizure in the early phase. Many cases have neurologic sequelae because early intervention is difficult. METHODS To establish an early diagnostic method, we assessed 213 hospitalized cases of febrile status epilepticus (FSE) between January 2004 and August 2014. We categorized FSE cases into an AESD group and a non-AESD group and compared their clinical courses, laboratory data and cranial computed tomography (CT) findings. RESULTS Of 213 hospitalized FSE cases, 19 (9%) were AESD. Univariate analysis showed that the AESD group took a significantly longer time to wake after FSE, had a higher degree of respiratory acidemia, and higher levels of serum AST, ALT, LD, hyperglycemia and hyperammonemia than the non-AESD group. We developed a scoring model that predicts AESD based on multivariate analysis. Using cut-off points of 4 and more with this scoring model, we could identify the AESD cases with 93% sensitivity and 91% specificity. These scores also had a positive correlation with prognosis. DISCUSSION Our scoring model enables early diagnosis of AESD. Patients with high scores should be observed carefully and early intervention should be considered.