Biochemical parameters to assess choroid plexus dysfunction in Kearns-Sayre syndrome patients

Laboratory testing for mitochondrial diseases: biomarkers for diagnosis and follow-up

The currently available biomarkers generally lack the specificity and sensitivity needed for the diagnosis and follow-up of patients with mitochondrial diseases (MDs). In this group of rare genetic disorders (mutations in approximately 350 genes associated with MDs), all clinical presentations, ages of disease onset and inheritance types are possible. Blood, urine, and cerebrospinal fluid surrogates are well-established biomarkers that are used in clinical practice to assess MD. One of the main challenges is validating specific and sensitive biomarkers for the diagnosis of disease and prediction of disease progression. Profiling of lactate, amino acids, organic acids, and acylcarnitine species is routinely conducted to assess MD patients. New biomarkers, including some proteins and circulating cell-free mitochondrial DNA, with increased diagnostic specificity have been identified in the last decade and have been proposed as potentially useful in the assessment of clinical outcomes. Despite these advances, even these new biomarkers are not sufficiently specific and sensitive to assess MD progression, and new biomarkers that indicate MD progression are urgently needed to monitor the success of novel therapeutic strategies. In this report, we review the mitochondrial biomarkers that are currently analyzed in clinical laboratories, new biomarkers, an overview of the most common laboratory diagnostic techniques, and future directions regarding targeted versus untargeted metabolomic and genomic approaches in the clinical laboratory setting. Brief descriptions of the current methodologies are also provided.

Cerebrospinal fluid monoamines, pterins, and folate in patients with mitochondrial diseases: systematic review and hospital experience

Mitochondrial diseases are a group of genetic disorders leading to the dysfunction of mitochondrial energy metabolism pathways. We aimed to assess the clinical phenotype and the biochemical cerebrospinal fluid (CSF) biogenic amine profiles of patients with different diagnoses of genetic mitochondrial diseases. We recruited 29 patients with genetically confirmed mitochondrial diseases harboring mutations in either nuclear or mitochondrial DNA (mtDNA) genes. Signs and symptoms of impaired neurotransmission and neuroradiological data were recorded. CSF monoamines, pterins, and 5-methyltetrahydrofolate (5MTHF) concentrations were analyzed using high-performance liquid chromatography with electrochemical and fluorescence detection procedures. The mtDNA mutations were studied by Sanger sequencing, Southern blot, and real-time PCR, and nuclear DNA was assessed either by Sanger or next-generation sequencing. Five out of 29 cases showed predominant dopaminergic signs not attributable to basal ganglia involvement, harboring mutations in different nuclear genes. A chi-square test showed a statistically significant association between high homovanillic acid (HVA) values and low CSF 5-MTHF values (chi-square = 10.916; p = 0.001). Seven out of the eight patients with high CSF HVA values showed cerebral folate deficiency. Five of them harbored mtDNA deletions associated with Kearns-Sayre syndrome (KSS), one had a mitochondrial point mutation at the mtDNA ATPase6 gene, and one had a POLG mutation. In conclusion, dopamine deficiency clinical signs were present in some patients with mitochondrial diseases with different genetic backgrounds. High CSF HVA values, together with a severe cerebral folate deficiency, were observed in KSS patients and in other mtDNA mutation syndromes.

Follow-up of folinic acid supplementation for patients with cerebral folate deficiency and Kearns-Sayre syndrome

Background

Kearns-Sayre syndrome (KSS) is a mitochondrial DNA deletion syndrome that presents with profound cerebral folate deficiency and other features. Preliminary data support the notion that folinic acid therapy might be useful in the treatment of KSS patients. Our aim was to assess the clinical and neuroimaging outcomes of KSS patients receiving folinic acid therapy.

Methods

Patients: We recruited eight patients with diagnoses of KSS. Four cases were treated at 12 de Octubre Hospital, and the other two cases were treated at Sant Joan de Déu Hospital. Two patients refused to participate in the treatment protocol.

Methods: Clinical, biochemical and neuroimaging data (magnetic resonance imaging or computed tomography scan) were collected in baseline conditions and at different time points after the initiation of therapy. Cerebrospinal fluid 5-methyltetrahydrofolate levels were analysed with HPLC and fluorescence detection. Large-scale mitochondrial DNA deletions were analysed by Southern blot.

Treatment protocol: The follow-up periods ranged from one to eight years. Cases 1–4 received oral folinic acid at a dose of 1 mg/kg/day, and cases 6 and 8 received 3 mg/kg/day.

Results

No adverse effects of folinic acid treatment were observed. Cerebral 5-methyltetrahydrofolate deficiencies were observed in all cases in the baseline conditions. Moreover, all three patients who accepted lumbar puncture after folinic acid therapy exhibited complete recoveries of their decreased basal cerebrospinal fluid 5-methyltetrahydrofolate levels to normal values. Two cases neurologically improved after folinic therapy. Disease worsened in the other patients.

Post-treatment neuroimaging was performed for the 6 cases that received folinic acid therapy. One patient exhibited improvements in white matter abnormalities. The remaining patients displayed progressions in subcortical cerebral white matter, the cerebellum and cerebral atrophy.

Conclusions

Four patients exhibited clinical and radiological progression of the disease following folinic acid treatment. Only one patient who was treated in an early stage of the disease exhibited both neurological and radiological improvements following elevated doses of folinic acid, and an additional patient experienced neurological improvement. Early treatment with high-dose folinic acid therapy seems to be advisable for the treatment of KSS.

Trial registration

EudracT2007-00-6748-23

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-014-0217-2) contains supplementary material, which is available to authorized users.

Diagnosis and management of mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society

PURPOSE

The purpose of this statement is to review the literature regarding mitochondrial disease and to provide recommendations for optimal diagnosis and treatment. This statement is intended for physicians who are engaged in diagnosing and treating these patients.

METHODS

The Writing Group members were appointed by the Mitochondrial Medicine Society. The panel included members with expertise in several different areas. The panel members utilized a comprehensive review of the literature, surveys, and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve.

RESULTS

Consensus-based recommendations are provided for the diagnosis and treatment of mitochondrial disease.

CONCLUSION

The Delphi process enabled the formation of consensus-based recommendations. We hope that these recommendations will help standardize the evaluation, diagnosis, and care of patients with suspected or demonstrated mitochondrial disease.

Clonally expanded mitochondrial DNA deletions within the choroid plexus in multiple sclerosis

Mitochondrial DNA deletions (∆-mtDNA) have been implicated in the pathogenesis of Alzheimer's disease (AD), multiple sclerosis (MS) and Parkinson's disease (PD), as well as ageing. Clonal expansion of ∆-mtDNA is the process by which a mutant mtDNA molecule increases to high levels within a single cell containing both wild-type and mutant mtDNA. Unlike in AD and PD, the diffuse inflammatory process in MS involves the choroid plexus, and mitochondria are exposed to reactive oxygen and nitrogen species over a prolonged period. We determined the extent of respiratory enzyme deficiency and ∆-mtDNA at a single cell level within choroid plexus epithelial cells in MS as well as in AD, PD and controls. The respiratory enzyme-deficient (lacking complex IV and with intact complex II activity) cells were more prevalent within the choroid plexus in AD, MS and PD compared with controls. The main catalytic subunit of complex IV (subunit-I of cytochrome c oxidase) was lacking in significantly more respiratory enzyme-deficient cells in MS compared with AD, PD and controls. The single cell analysis showed a fourfold increase in the percentage of respiratory enzyme-deficient choroid plexus epithelial cells harbouring clonally expanded ∆-mtDNA in MS. Our findings establish clonal expansion of ∆-mtDNA as a feature relatively more prominent within the choroid plexus epithelium in MS than AD, PD or controls. We propose clonal expansion of ∆-mtDNA as a molecular link between inflammation and part of a delayed cellular energy failure in MS.