Biomarkers Of Mitochondrial Disease Research Articles

Apomorphine rescues reactive oxygen species-induced apoptosis of fibroblasts with mitochondrial disease

Mitochondrial disease is a genetic disorder in which individuals suffer from energy insufficiency. The various clinical phenotypes of mitochondrial disease include Leigh syndrome (LS), myopathy encephalopathy lactic acidosis and stroke-like episodes (MELAS). Thus far, no curative treatment is available, and effective treatment options are eagerly awaited. We examined the cell protective effect of an existing commercially available chemical library on fibroblasts from four patients with LS and MELAS and identified apomorphine as a potential therapeutic drug for mitochondrial disease. We conducted a cell viability assay under oxidative stress induced by L-butionine (S, R)-sulfoximine (BSO), a glutathione synthesis inhibitor. Among the chemicals of library, 4 compounds (apomorphine, olanzapine, phenothiazine and ethopropazine) rescued cells from death induced by oxidative stress much more effectively than idebenone, which was used as a positive control. The EC50 value showed that apomorphine was the most effective compound. Apomorphine also significantly improved all of the assessed oxygen consumption rate values by the extracellular flux analyzer for fibroblasts from LS patients with complex I deficiency. In addition, the elevation of the Growth Differentiation Factor-15 (GDF-15), a biomarker of mitochondrial disease, was significantly reduced by apomorphine. Among 441 apomorphine-responsive genes identified by the microarray, apomorphine induced the expression of genes that inhibit the mammalian target of rapamycin (mTOR) activity and inflammatory responses, suggesting that apomorphine induced cell survival via a new potential pathway. In conclusion, apomorphine rescued fibroblasts from cell death under oxidative stress and improved the mitochondrial respiratory activity and appears to be potentially useful for treating mitochondrial disease.

Fibroblast growth factor 21 as a biomarker for long-term complications in organic acidemias

BackgroundThere is increasing evidence that long-term complications in organic acidemias are caused by impaired mitochondrial metabolism. Currently, there is no specific biomarker to monitor mitochondrial dysfunction in organic acidemias. Serum fibroblast growth factor 21 (FGF-21) is a biomarker for mitochondrial disease and could be a candidate to monitor mitochondrial function in the deleterious course of disease.MethodsData of 17 patients with classical organic acidemias (11 propionic acidemia (PA), four methylmalonic acidemia (MMA) and two isovaleric acidemia (IVA) patients) were included. The clinical course was evaluated; metabolic decompensations and long-term complications were correlated with plasma FGF-21 levels. Cardiomyopathy, prolonged QT interval, renal failure, and optic neuropathy were defined as long-term complications.ResultsPatients ages ranged from 16 months up to 32 years. Serious long-term complications occurred in eight patients (five PA and three MMA patients). In MMA and PA patients plasma FGF-21 levels during stable metabolic periods were significantly higher in patients with long-term complications (Mdn = 2556.0 pg/ml) compared to patients without (Mdn = 287.0 pg/ml). A median plasma FGF-21 level above 1500 pg/ml during a stable metabolic period, measured before the occurrence of long-term complications, had a positive predictive value of 0.83 and a negative predictive value of 1.00 on long-term complications in MMA and PA patients.ConclusionThis study demonstrates the potential role of FGF-21 as a biomarker for long-term complications in classical organic acidemias, attributed to mitochondrial dysfunction.

Lipidomic profiling of plasma samples from patients with mitochondrial disease

Mitochondrial disease (MD) is a rare mitochondrial respiratory chain disorder with a high mortality and extremely challenging to treat. Although genomic, transcriptomic, and proteomic analyses have been performed to investigate the pathogenesis of MD, the role of metabolomics in MD, particularly of lipidomics remains unclear. This study was undertaken to identify potential lipid biomarkers of MD. An untargeted lipidomic approach was used to compare the plasma lipid metabolites in 20 MD patients and 20 controls through Liquid Chromatography coupled to Mass Spectrometry. Volcano plot analysis was performed to identify the different metabolites. Receiver operating characteristic (ROC) curves were constructed and the area under the ROC curves (AUC) was calculated to determine the potentially sensitive and specific biomarkers. A total of 41 lipids were significantly different in MD patients and controls. ROC curve analysis showed the top 5 AUC values of lipids (phosphatidylinositols 38:6, lysoPC 20:0, 19:0, 18:0, 17:0) are more than 0.99. Multivariate ROC curve based exploratory analysis showed the AUC of combination of top 5 lipids is 1, indicating they may be potentially sensitive and specific biomarkers for MD. We propose combination of these lipid species may be more valuable in predicting the development and progression of MD, and this will have important implications for the diagnosis and treatment of MD.

Mitochondrial A3243G mutation results in corneal endothelial polymegathism.

The mitochondrial DNA point mutation A3243G leads to a spectrum of syndromes ranging from MIDD to MELAS. Ocular manifestations include pattern macular dystrophy and concentric perifoveal atrophy. Given the high metabolic demand of corneal endothelial cells, we performed specular biomicroscopy analysis in patients harboring the mitochondrial DNA point mutation A3243G to assess for the associated presence of corneal endothelial abnormalities. We present a case series with participants from two institutions. Patients diagnosed with macular dystrophy associated with MIDD or MELAS, and the mitochondrial DNA point mutation A3243G were recruited. Exclusion criteria included a prior diagnosis, or a positive family history, of endothelial corneal dystrophy. Slit-lamp corneal examination and specular biomicroscopy were performed. Corneal endothelial cell count, cell size and polymegathism, and central corneal thickness were assessed. Patients diagnosed with MIDD or MELAS based on clinical history and examination were genetically tested for the mitochondrial DNA point mutation A3243G using pyrosequencing. Five patients (two male and three female participants) from five different families, and with different ethnic backgrounds, met the inclusion criteria. Their ages ranged from 41 to 60years. Corneal endothelial changes observed using slit-lamp examination were primarily mild to rare guttata. Specular biomicroscopy displayed mainly polymegathism associated with guttata. The average endothelial cell count was 2358±456 cells per mm2, the average endothelial cell size was 442±103μm2 and the average central corneal thickness (CCT) was 551±33μm. These values were similar to that of the average population. The average coefficient of variation (COV), an index of heterogeneity in cell size, was 42.0 ± 4.1%. When compared to the average population, the average COV was significantly higher than predicted for the patients' age. None of the patients had signs of corneal edema. One patient had a pre-Descemet's opacity. In patients with the mitochondrial DNA point mutation A3243G, corneal endothelial polymegathism is present. This is mainly associated with mild guttata. The findings of corneal endothelial cell polymegathism may be a biomarker of mitochondrial disease, specifically in patients with the mitochondrial DNA A3243G mutation.

Use of FGF-21 as a Biomarker of Mitochondrial Disease in Clinical Practice.

Recent work has suggested that fibroblast growth factor-21 (FGF-21) is a useful biomarker of mitochondrial disease (MD). We routinely measured FGF-21 levels on patients who were investigated at our centre for MD and evaluated its diagnostic performance based on detailed genetic and other laboratory findings. Patients’ FGF-21 results were assessed by the use of age-adjusted z-scores based on normalised FGF-21 values from a healthy population. One hundred and fifty five patients were investigated. One hundred and four of these patients had molecular evidence for MD, 27 were deemed to have disorders other than MD (non-MD), and 24 had possible MD. Patients with defects in mitochondrial DNA (mtDNA) maintenance (n = 32) and mtDNA rearrangements (n = 17) had the highest median FGF-21 among the MD group. Other MD patients harbouring mtDNA point mutations (n = 40) or mutations in other autosomal genes (n = 7) and those with partially characterised MD had lower FGF-21 levels. The area under the receiver operating characteristic curve for distinguishing MD from non-MD patients was 0.69. No correlation between FGF-21 and creatinine, creatine kinase, or cardio-skeletal myopathy score was found. FGF-21 was significantly associated with plasma lactate and ocular myopathy. Although FGF-21 was found to have a low sensitivity for detecting MD, at a z-score of 2.8, its specificity was above 90%. We suggest that a high serum concentration of FGF-21 would be clinically useful in MD, especially in adult patients with chronic progressive external ophthalmoplegia, and may enable bypassing muscle biopsy and directly opting for genetic analysis. Availability of its assay has thus modified our diagnostic pathway.

Metabolic profiling of mitochondrial disease at rest and with exercise

The mitochondrial respiratory chain disorders represent a large collection of individually rare syndromes. Their phenotypic heterogeneity, combined with the large number of causal genetic and environmental factors, makes their diagnosis and management challenging. While characterisation of the mitochondrial proteome, in combination with next generation sequencing is transforming their molecular diagnosis, we still lack facile biomarkers and useful therapies. In this talk, I will present our lab's recent efforts applying metabolomics technology to study the cellular and human biochemical response to mitochondrial dysfunction. The results provide new insights into the metabolic ripples that ensue in response to mitochondrial respiratory chain dysfunction to give rise to diverse pathology observed in these disorders. We are combining this cell-based work with studies of patients with mitochondrial disease at rest and with exercise. Our work has implications for discovering new biomarkers of mitochondrial disease, as well as for nominating new therapeutic strategies for these challenging disorders. The mitochondrial respiratory chain disorders represent a large collection of individually rare syndromes. Their phenotypic heterogeneity, combined with the large number of causal genetic and environmental factors, makes their diagnosis and management challenging. While characterisation of the mitochondrial proteome, in combination with next generation sequencing is transforming their molecular diagnosis, we still lack facile biomarkers and useful therapies. In this talk, I will present our lab's recent efforts applying metabolomics technology to study the cellular and human biochemical response to mitochondrial dysfunction. The results provide new insights into the metabolic ripples that ensue in response to mitochondrial respiratory chain dysfunction to give rise to diverse pathology observed in these disorders. We are combining this cell-based work with studies of patients with mitochondrial disease at rest and with exercise. Our work has implications for discovering new biomarkers of mitochondrial disease, as well as for nominating new therapeutic strategies for these challenging disorders.

Metabolic profiling of mitochondrial disease at rest and with exercise

The mitochondrial respiratory chain disorders represent a large collection of individually rare syndromes. Their phenotypic heterogeneity, combined with the large number of causal genetic and environmental factors, makes their diagnosis and management challenging. While characterisation of the mitochondrial proteome, in combination with next generation sequencing is transforming their molecular diagnosis, we still lack facile biomarkers and useful therapies. In this talk, I will present our lab's recent efforts applying metabolomics technology to study the cellular and human biochemical response to mitochondrial dysfunction. The results provide new insights into the metabolic ripples that ensue in response to mitochondrial respiratory chain dysfunction to give rise to diverse pathology observed in these disorders. We are combining this cell-based work with studies of patients with mitochondrial disease at rest and with exercise. Our work has implications for discovering new biomarkers of mitochondrial disease, as well as for nominating new therapeutic strategies for these challenging disorders.

Fibroblast growth factor 21 is a sensitive biomarker of mitochondrial disease

To prospectively determine the reliability and validity of serum fibroblast growth factor 21 (FGF-21) as a biomarker for mitochondrial disease in a cross-sectional cohort of adults with mitochondrial disease from a specialist primary care and tertiary referral clinic. We recruited 140 subjects, including 54 adults with mitochondrial disease, 20 patients with nonmitochondrial neuromuscular disease, and 66 control subjects, between November 2011 and October 2012. We compared serum FGF-21 concentrations to classical biomarkers, serum creatine kinase, lactate, pyruvate, and lactate to pyruvate ratio, to determine its validity and reliability as a biomarker of mitochondrial disease. We determined the sensitivity, odds ratio (OR), and overall reliability of FGF-21 as a marker of mitochondrial disease using statistical analyses. Median serum FGF-21 concentrations were significantly elevated in patients with mitochondrial disease and differed significantly between all experimental groups. FGF-21 showed a markedly higher diagnostic OR (45.7 [95% confidence interval = 12.6-166.5], p < 0.0001) when compared to other biomarkers and was the best predictor of disease according to sensitivity and receiver operating characteristic curve analysis. After multivariate logistic regression analysis controlling for potential confounders, FGF-21 was the only measured parameter capable of predicting mitochondrial disease. This prospective study establishes serum FGF-21 levels as a sensitive biomarker of mitochondrial disease and demonstrates that they are the best predictor of this disorder when compared to serum levels of classical indicators: creatine kinase, lactate, pyruvate, and the lactate to pyruvate ratio.

New treatments for mitochondrial disease-no time to drop our standards.

Mitochondrial dysfunction is a common cause of inherited multisystem disease that often involves the nervous system. Despite major advances in our understanding of the pathophysiology of mitochondrial diseases, clinical management of these conditions remains largely supportive. Using a systematic approach, we identified 1,039 publications on treatments for mitochondrial diseases, only 35 of which included observations on more than five patients. Reports of a positive outcome on the basis of a biomarker of unproven clinical significance were more common in nonrandomized and nonblinded studies, suggesting a publication bias toward positive but poorly executed studies. Although trial design is improving, there is a critical need to develop new biomarkers of mitochondrial disease. In this Perspectives article, we make recommendations for the design of future treatment trials in mitochondrial diseases. Patients and physicians should no longer rely on potentially biased data, with the associated costs and risks.

Biomarkers of Abnormal Energy Metabolism in Children with Autism Spectrum Disorder

Biomarkers of mitochondrial disease were studies in 133 consecutive autism spectrum disorder patients to determine the prevalence of abnormalities in biomarkers of mitochondrial disease. Biomarkers included traditional biomarkers of mitochondrial disease (lactate, alanine), fatty-acid oxidation defects (acyl-carnitine panel) and recently described novel biomarkers of detecting mitochondrial dysfunction in individuals with autism spectrum disorder (alanine-to-lysine ratio, creatine kinase, aspartate transaminase). Biomarkers were collected in the morning fasting state. Abnormal biomarker values were verified by repeat testing. For those with abnormal acyl-carnitine panels, secondary disorders of fatty acid metabolism were ruled out. Abnormalities in lactate, alanine-to-lysine ratio and acyl-carnitine panels occurred in over 30% of children on initial testing. Among the patients with abnormal biomarkers who had repeated testing, abnormalities were confirmed about half of the time except for alanine which was only confirmed 20% of the time. Elevation in alanine-to-lysine ratio was associated with epilepsy and elevation in multiple acyl-carnitines was associated with regression. In order to confirm the significance of certain biomarkers, a wide variety of mitochondrial biomarker values were compared between specific subgroups of children with abnormal biomarkers and matched children without any abnormalities in biomarkers. Lactate, alanine-to-lysine ratio and acyl-carnitine panel groups demonstrated abnormalities in multiple mitochondrial biomarkers, confirming the validity of these biomarkers of mitochondrial dysfunction. This study demonstrates that multiple biomarkers of mitochondrial dysfunction are elevated in a significant portion of children with autism spectrum disorder and lend support to the notion that disorders of energy production may affect a significant subset of children with autism.