Treatment Of Mitochondrial Diseases Research Articles

Stimulating Mitochondrial Biogenesis with Deoxyribonucleosides Increases Functional Capacity in ECHS1-Deficient Cells.

The lack of effective treatments for mitochondrial disease has seen the development of new approaches, including those that stimulate mitochondrial biogenesis to boost ATP production. Here, we examined the effects of deoxyribonucleosides (dNs) on mitochondrial biogenesis and function in Short chain enoyl-CoA hydratase 1 (ECHS1) ‘knockout’ (KO) cells, which exhibit combined defects in both oxidative phosphorylation (OXPHOS) and mitochondrial fatty acid β-oxidation (FAO). DNs treatment increased mitochondrial DNA (mtDNA) copy number and the expression of mtDNA-encoded transcripts in both CONTROL (CON) and ECHS1 KO cells. DNs treatment also altered global nuclear gene expression, with key gene sets including ‘respiratory electron transport’ and ‘formation of ATP by chemiosmotic coupling’ increased in both CON and ECHS1 KO cells. Genes involved in OXPHOS complex I biogenesis were also upregulated in both CON and ECHS1 KO cells following dNs treatment, with a corresponding increase in the steady-state levels of holocomplex I in ECHS1 KO cells. Steady-state levels of OXPHOS complex V, and the CIII2/CIV and CI/CIII2/CIV supercomplexes, were also increased by dNs treatment in ECHS1 KO cells. Importantly, treatment with dNs increased both basal and maximal mitochondrial oxygen consumption in ECHS1 KO cells when metabolizing either glucose or the fatty acid palmitoyl-L-carnitine. These findings highlight the ability of dNs to improve overall mitochondrial respiratory function, via the stimulation mitochondrial biogenesis, in the face of combined defects in OXPHOS and FAO due to ECHS1 deficiency.

Direct evidence of CRISPR-Cas9-mediated mitochondrial genome editing

Pathogenic mitochondrial DNA (mtDNA) mutations can cause a variety of human diseases. The recent development of genome-editing technologies to manipulate mtDNA, such as mitochondria-targeted DNA nucleases and base editors, offer a promising way for curing mitochondrial diseases caused by mtDNA mutations. The CRISPR-Cas9 system is a widely used tool for genome editing; however, its application in mtDNA editing is still under debate. In this study, we developed a mito-Cas9 system by adding the mitochondria-targeted sequences and 3′ untranslated region of nuclear-encoded mitochondrial genes upstream and downstream of the Cas9 gene, respectively. We confirmed that the mito-Cas9 system was transported into mitochondria and enabled knockin of exogenous single-stranded DNA oligonucleotides (ssODNs) into mtDNA based on proteinase and DNase protection assays. Successful knockin of exogenous ssODNs into mtDNA was further validated using polymerase chain reaction-free third-generation sequencing technology. We also demonstrated that RS-1, an agonist of RAD51, significantly increased knockin efficiency of the mito-Cas9 system. Collectively, we provide direct evidence that mtDNA can be edited using the CRISPR-Cas9 system. The mito-Cas9 system could be optimized as a promising approach for the treatment of mitochondrial diseases caused by pathogenic mtDNA mutations, especially those with homoplasmic mtDNA mutations.

Acipimox in Mitochondrial Myopathy (AIMM): study protocol for a randomised, double-blinded, placebo-controlled, adaptive design trial of the efficacy of acipimox in adult patients with mitochondrial myopathy

BackgroundMitochondrial disease is a heterogenous group of rare, complex neurometabolic disorders. Despite their individual rarity, collectively mitochondrial diseases represent the most common cause of inherited metabolic disorders in the UK; they affect 1 in every 4300 individuals, up to 15,000 adults (and a similar number of children) in the UK. Mitochondrial disease manifests multisystem and isolated organ involvement, commonly affecting those tissues with high energy demands, such as skeletal muscle. Myopathy manifesting as fatigue, muscle weakness and exercise intolerance is common and debilitating in patients with mitochondrial disease. Currently, there are no effective licensed treatments and consequently, there is an urgent clinical need to find an effective drug therapy.AimTo investigate the efficacy of 12-week treatment with acipimox on the adenosine triphosphate (ATP) content of skeletal muscle in patients with mitochondrial disease and myopathy.MethodsAIMM is a single-centre, double blind, placebo-controlled, adaptive designed trial, evaluating the efficacy of 12 weeks’ administration of acipimox on skeletal muscle ATP content in patients with mitochondrial myopathy. Eligible patients will receive the trial investigational medicinal product (IMP), either acipimox or matched placebo. Participants will also be prescribed low dose aspirin as a non-investigational medical product (nIMP) in order to protect the blinding of the treatment assignment.Eighty to 120 participants will be recruited as required, with an interim analysis for sample size re-estimation and futility assessment being undertaken once the primary outcome for 50 participants has been obtained. Randomisation will be on a 1:1 basis, stratified by Fatigue Impact Scale (FIS) (dichotomised as < 40, ≥ 40). Participants will take part in the trial for up to 20 weeks, from screening visits through to follow-up at 16 weeks post randomisation.The primary outcome of change in ATP content in skeletal muscle and secondary outcomes relating to quality of life, perceived fatigue, disease burden, limb function, balance and walking, skeletal muscle analysis and symptom-limited cardiopulmonary fitness (optional) will be assessed between baseline and 12 weeks.DiscussionThe AIMM trial will investigate the effect of acipimox on modulating muscle ATP content and whether it can be repurposed as a new treatment for mitochondrial disease with myopathy.Trial registrationEudraCT2018-002721-29. Registered on 24 December 2018,ISRCTN 12895613. Registered on 03 January 2019, https://www.isrctn.com/search?q=aimm

Mitochondria – expanding the role of the powerhouse

In this issue of The Biochemist, we are bringing you articles that cover all the things that you didn’t know about mitochondria.We all know the definition of mitochondria as ‘the powerhouse of the cell’. When I first learnt about mitochondria, I was amazed and in awe of learning how chemistry and life connect. I was thrilled to dedicate a whole issue of The Biochemist on the topic of mitochondria and I was amazed again when I read the submissions – the knowledge we have about mitochondria has expanded way beyond that high school definition. Take the article from the Picard Lab, which explores how they are investigating the way in which mitochondria might influence mental and physiological functions: pushing the boundaries of how we understand individual elements within biology and how they can contribute to the system they exist within – beyond a singular function.This issue explores not only the wide-ranging role of mitochondria but also the many ways in which researchers can investigate and think about the role of mitochondria to better understand their function.It’s clear that in biology, individual components cannot be looked at in isolation. In visualizing and considering mitochondria and biological systems, it can be incredibly useful to work with artists and designers to shift the thinking and push research questions into new directions. I was incredibly excited by the article on the collaborative project from the Royal Society of Edinburgh and the Biochemical Society, and subsequent work which has led to the creation of a global collective–a network of researchers, biologists, artists and designers–to reframe how we think about mitochondria. One aspect of this work involved looking to the future of the study of mitochondria and this creative approach might aid researchers in making those next leaps in understanding these important organelle.I was also pleased to read about the advancements in mitochondrial DNA engineering techniques which are supporting the possibility of treatments for mitochondrial diseases. This area has not been as quick to advance due to the incompatibility of techniques developed for nuclear DNA but now some breakthroughs give hope in this area.In this edition of The Biochemist, you can also find a news section which features important updates on how the publications from the Biochemical Society are moving towards an open scholarship model and the steps that have been taken over the past few years to achieve that.The Biochemist magazine is, of course, free and available for all to read. The best way to support the publication if you enjoy reading articles is to share via social media and email.

Fixing the powerhouse: genetic engineering of mitochondrial DNA

Mitochondria are complex factories that provide our cells with most of the energy we need to survive and perform daily tasks. They comprise their own small genome, mitochondrial DNA (mtDNA), which contains genes for parts of the energy-producing machinery. Mutations in mtDNA can lead to mitochondrial diseases, which are a devastating group of heterogenous inheritable diseases that can develop at any stage of life. Despite rapid developments in genome engineering for nuclear DNA, the incompatibility of certain techniques in mitochondria has meant that the field of mitochondrial genome modification has been impeded for many years. However, recent advances in mtDNA engineering techniques, such as programmable nucleases and base editors, will allow for a deeper understanding of the processes taking place in mitochondria and improve the prospects of developing treatments for mitochondrial diseases.

Progress on the Physiological Function of Mitochondrial DNA and Its Specific Detection and Therapy.

Mitochondrial DNA (mtDNA) is the genetic information of mitochondrion, and its structure is circular double-stranded. Despite the diminutive size of the mitochondrial genome, mtDNA mutations are an important cause of mitochondrial diseases which are characterized by defects in oxidative phosphorylation (OXPHOS). Mitochondrial diseases are involved in multiple systems, particularly in the organs that are highly dependent on aerobic metabolism. The diagnosis of mitochondrial disease is more complicated since mtDNA mutations can cause various clinical symptoms. To realize more accurate diagnosis and treatment of mitochondrial diseases, the detection of mtDNA and the design of drugs acting on it are extremely important. Over the past few years, many probes and therapeutic drugs targeting mtDNA have been developed, making significant contributions to fundamental research including elucidation of the mechanisms of mitochondrial diseases at the genetic level. In this review, we summarize the structure, function, and detection approaches for mtDNA. The most current topics in this field, such as mechanistic exploration and treatment of mtDNA mutation-related disorders, are also reviewed. Specific attention is given to discussing the design and development of these probes and drugs for mtDNA. We hope that this review will provide readers with a comprehensive understanding of the importance of mtDNA, and promote the development of effective molecules for theragnosis of mtDNA mutation-related diseases.

Endocrine Manifestations and New Developments in Mitochondrial Disease.

Mitochondrial diseases are a group of common inherited diseases causing disruption of oxidative phosphorylation. Some patients with mitochondrial disease have endocrine manifestations, with diabetes mellitus being predominant but also include hypogonadism, hypoadrenalism, and hypoparathyroidism. There have been major developments in mitochondrial disease over the past decade that have major implications for all patients. The collection of large cohorts of patients has better defined the phenotype of mitochondrial diseases and the majority of patients with endocrine abnormalities have involvement of several other systems. This means that patients with mitochondrial disease and endocrine manifestations need specialist follow-up because some of the other manifestations, such as stroke-like episodes and cardiomyopathy, are potentially life threatening. Also, the development and follow-up of large cohorts of patients means that there are clinical guidelines for the management of patients with mitochondrial disease. There is also considerable research activity to identify novel therapies for the treatment of mitochondrial disease. The revolution in genetics, with the introduction of next-generation sequencing, has made genetic testing more available and establishing a precise genetic diagnosis is important because it will affect the risk for involvement for different organ systems. Establishing a genetic diagnosis is also crucial because important reproductive options have been developed that will prevent the transmission of mitochondrial disease because of mitochondrial DNA variants to the next generation.

Preparation and characterization of a polyclonal antibody against PTEN-Long.

Phosphatase and tensin homolog-long (PTEN-L) is a translational isoform of PTEN, which exists in both intracellular and extracellular locations. Previous studies demonstrated that PTEN-L could inhibit oncogenesis due to its lipid phosphatase activity. However, recent studies found that PTEN-L could promote the proliferation of some types of cancer cells. Moreover, as a protein phosphatase, PTEN-L can suppress mitophagy by counteracting PTEN-induced putative kinase protein 1 (PINK1)-Parkin-mediated ubiquitin phosphorylation, namely, PTEN-L is critical for exploring the mitophagy progression and the treatment of mitochondrial diseases. Accounting for the critical functions of PTEN-L, its antibody can be used for the treatment or prognosis of tumors and mitochondrial diseases. Currently, the commercial antibody of PTEN-L is not available. In our study, the recombinant PTEN-L protein was expressed in Escherichia coli BL21 and used as an antigen to immunize Japan's big-eared white rabbit for the preparation of polyclonal antibody. The PTEN-L protein can be captured by PTEN-L antibody specifically and effectively. Taken together, a PTEN_L antibody is a valuable tool for further exploring the function of PTEN-L in oncogenesis and mitochondrial diseases, and it would be a new choice for the prognosis or treatment of cancer and mitochondrial diseases.

Mitochondrial Transplantation as a Novel Therapeutic Strategy for Mitochondrial Diseases

Mitochondria are the major source of intercellular bioenergy in the form of ATP. They are necessary for cell survival and play many essential roles such as maintaining calcium homeostasis, body temperature, regulation of metabolism and apoptosis. Mitochondrial dysfunction has been observed in variety of diseases such as cardiovascular disease, aging, type 2 diabetes, cancer and degenerative brain disease. In other words, the interpretation and regulation of mitochondrial signals has the potential to be applied as a treatment for various diseases caused by mitochondrial disorders. In recent years, mitochondrial transplantation has increasingly been a topic of interest as an innovative strategy for the treatment of mitochondrial diseases by augmentation and replacement of mitochondria. In this review, we focus on diseases that are associated with mitochondrial dysfunction and highlight studies related to the rescue of tissue-specific mitochondrial disorders. We firmly believe that mitochondrial transplantation is an optimistic therapeutic approach in finding a potentially valuable treatment for a variety of mitochondrial diseases.

The Redox Modulating Sonlicromanol Active Metabolite KH176m and the Antioxidant MPG Protect Against Short-Duration Cardiac Ischemia-Reperfusion Injury

PurposeSonlicromanol is a phase IIB clinical stage compound developed for treatment of mitochondrial diseases. Its active component, KH176m, functions as an antioxidant, directly scavenging reactive oxygen species (ROS), and redox activator, boosting the peroxiredoxin-thioredoxin system. Here, we examined KH176m’s potential to protect against acute cardiac ischemia-reperfusion injury (IRI), compare it with the classic antioxidant N-(2-mercaptopropionyl)-glycine (MPG), and determine whether protection depends on duration (severity) of ischemia.MethodsIsolated C56Bl/6N mouse hearts were Langendorff-perfused and subjected to short (20 min) or long (30 min) ischemia, followed by reperfusion. During perfusion, hearts were treated with saline, 10 μM KH176m, or 1 mM MPG. Cardiac function, cell death (necrosis), and mitochondrial damage (cytochrome c (CytC) release) were evaluated. In additional series, the effect of KH176m treatment on the irreversible oxidative stress marker 4-hydroxy-2-nonenal (4-HNE), formed during ischemia only, was determined at 30-min reperfusion.ResultsDuring baseline conditions, both drugs reduced cardiac performance, with opposing effects on vascular resistance (increased with KH176m, decreased with MPG). For short ischemia, KH176m robustly reduced all cell death parameters: LDH release (0.2 ± 0.2 vs 0.8 ± 0.5 U/min/GWW), infarct size (15 ± 8 vs 31 ± 20%), and CytC release (168.0 ± 151.9 vs 790.8 ± 453.6 ng/min/GWW). Protection by KH176m was associated with decreased cardiac 4-HNE. MPG only reduced CytC release. Following long ischemia, IRI was doubled, and KH176m and MPG now only reduced LDH release. The reduced protection against long ischemia was associated with the inability to reduce cardiac 4-HNE.ConclusionProtection against cardiac IRI by the antioxidant KH176m is critically dependent on duration of ischemia. The data suggest that with longer ischemia, the capacity of KH176m to reduce cardiac oxidative stress is rate-limiting, irreversible ischemic oxidative damage maximally accumulates, and antioxidant protection is strongly diminished.

Mitochondria Donation by Mesenchymal Stem Cells: Current Understanding and Mitochondria Transplantation Strategies.

The phenomenon of mitochondria donation is found in various tissues of humans and animals and is attracting increasing attention. To date, numerous studies have described the transfer of mitochondria from stem cells to injured cells, leading to increased ATP production, restoration of mitochondria function, and rescue of recipient cells from apoptosis. Mitochondria transplantation is considered as a novel therapeutic approach for the treatment of mitochondrial diseases and mitochondrial function deficiency. Mitochondrial dysfunction affects cells with high energy needs such as neural, skeletal muscle, heart, and liver cells and plays a crucial role in type 2 diabetes, as well as Parkinson’s, Alzheimer’s diseases, ischemia, stroke, cancer, and age-related disorders. In this review, we summarize recent findings in the field of mitochondria donation and mechanism of mitochondria transfer between cells. We review the existing clinical trials and discuss advantages and disadvantages of mitochondrial transplantation strategies based on the injection of stem cells, isolated functional mitochondria, or EVs containing mitochondria.

Mitochondrial Medicine: Genetic Underpinnings and Disease Modeling Using Induced Pluripotent Stem Cell Technology.

Mitochondrial medicine is an exciting and rapidly evolving field. While the mitochondrial genome is small and differs from the nuclear genome in that it is circular and free of histones, it has been implicated in neurodegenerative diseases, type 2 diabetes, aging and cardiovascular disorders. Currently, there is a lack of efficient treatments for mitochondrial diseases. This has promoted the need for developing an appropriate platform to investigate and target the mitochondrial genome. However, developing these therapeutics requires a model system that enables rapid and effective studying of potential candidate therapeutics. In the past decade, induced pluripotent stem cells (iPSCs) have become a promising technology for applications in basic science and clinical trials, and have the potential to be transformative for mitochondrial drug development. Engineered iPSC-derived cardiomyocytes (iPSC-CM) offer a unique tool to model mitochondrial disorders. Additionally, these cellular models enable the discovery and testing of novel therapeutics and their impact on pathogenic mtDNA variants and dysfunctional mitochondria. Herein, we review recent advances in iPSC-CM models focused on mitochondrial dysfunction often causing cardiovascular diseases. The importance of mitochondrial disease systems biology coupled with genetically encoded NAD+/NADH sensors is addressed toward developing an in vitro translational approach to establish effective therapies.

Therapeutical Management and Drug Safety in Mitochondrial Diseases-Update 2020.

Mitochondrial diseases (MDs) are a group of genetic disorders that may manifest with vast clinical heterogeneity in childhood or adulthood. These diseases are characterized by dysfunctional mitochondria and oxidative phosphorylation deficiency. Patients are usually treated with supportive and symptomatic therapies due to the absence of a specific disease-modifying therapy. Management of patients with MDs is based on different therapeutical strategies, particularly the early treatment of organ-specific complications and the avoidance of catabolic stressors or toxic medication. In this review, we discuss the therapeutic management of MDs, supported by a revision of the literature, and provide an overview of the drugs that should be either avoided or carefully used both for the specific treatment of MDs and for the management of comorbidities these subjects may manifest. We finally discuss the latest therapies approved for the management of MDs and some ongoing clinical trials.

Therapeutic Approaches to Treat Mitochondrial Diseases: "One-Size-Fits-All" and "Precision Medicine" Strategies.

Primary mitochondrial diseases (PMD) refer to a group of severe, often inherited genetic conditions due to mutations in the mitochondrial genome or in the nuclear genes encoding for proteins involved in oxidative phosphorylation (OXPHOS). The mutations hamper the last step of aerobic metabolism, affecting the primary source of cellular ATP synthesis. Mitochondrial diseases are characterized by extremely heterogeneous symptoms, ranging from organ-specific to multisystemic dysfunction with different clinical courses. The limited information of the natural history, the limitations of currently available preclinical models, coupled with the large variability of phenotypical presentations of PMD patients, have strongly penalized the development of effective therapies. However, new therapeutic strategies have been emerging, often with promising preclinical and clinical results. Here we review the state of the art on experimental treatments for mitochondrial diseases, presenting “one-size-fits-all” approaches and precision medicine strategies. Finally, we propose novel perspective therapeutic plans, either based on preclinical studies or currently used for other genetic or metabolic diseases that could be transferred to PMD.

AMP-independent activator of AMPK for treatment of mitochondrial disorders.

Mitochondrial diseases are a clinically heterogenous group of disorders caused by respiratory chain dysfunction and associated with progressive, multi-systemic phenotype. There is no effective treatment or cure, and no FDA-approved drug for treating mitochondrial disease. To identify and characterize potential therapeutic compounds, we developed an in vitro screening assay and identified a group of direct AMP-activated protein kinase (AMPK) activators originally developed for the treatment of diabetes and metabolic syndrome. Unlike previously investigated AMPK agonists such as AICAR, these compounds allosterically activate AMPK in an AMP-independent manner, thereby increasing specificity and decreasing pleiotropic effects. The direct AMPK activator PT1 significantly improved mitochondrial function in assays of cellular respiration, energy status, and cellular redox. PT1 also protected against retinal degeneration in a mouse model of photoreceptor degeneration associated with mitochondrial dysfunction and oxidative stress, further supporting the therapeutic potential of AMP-independent AMPK agonists in the treatment of mitochondrial disease.

Treatment for mitochondrial diseases.

Mitochondrial diseases are predominantly caused by mutations of mitochondrial or nuclear DNA, resulting in multisystem defects. Current treatments are largely supportive, and the disorders progress relentlessly. Nutritional supplements, pharmacological agents and physical therapies have been used in different clinical trials, but the efficacy of these interventions need to be further evaluated. Several recent reviews discussed some of the interventions but ignored bias in those trials. This review was conducted to discover new studies and grade the original studies for potential bias with revised Cochrane Collaboration guidelines. We focused on seven published studies and three unpublished studies; eight of these studies showed improvement in outcome measurements. In particular, two of the interventions have been tested in studies with strict design, which we believe deserve further clinical trials with a large sample. Additionally, allotopic expression of the ND4 subunit seemed to be an effective new treatment for patients with Leber hereditary optic neuropathy.

Retraction "Advances in drug therapy for mitochondrial diseases".

[This retracts the article DOI: 10.21037/atm.2019.10.113.].

Discovery of 6-Phenylhexanamide Derivatives as Potent Stereoselective Mitofusin Activators for the Treatment of Mitochondrial Diseases.

Mutations in the mitochondrial fusion protein mitofusin (MFN) 2 cause the chronic neurodegenerative condition Charcot-Marie-Tooth disease type 2A (CMT2A), for which there is currently no treatment. Small-molecule activators of MFN1 and MFN2 enhance mitochondrial fusion and offer promise as therapy for this condition, but prototype compounds have poor pharmacokinetic properties. Herein, we describe a rational design of a series of 6-phenylhexanamide derivatives whose pharmacokinetic optimization yielded a 4-hydroxycyclohexyl analogue, 13, with the potency, selectivity, and oral bioavailability of a preclinical candidate. Studies of 13 cis- and trans-4-hydroxycyclohexyl isostereomers unexpectedly revealed functionality and protein engagement exclusively for the trans form, 13B. Preclinical absorption, distribution, metabolism, and excretion (ADME) and in vivo target engagement studies of 13B support further development of 6-phenylhexanamide derivatives as therapeutic agents for human CMT2A.

Pioglitazone and Deoxyribonucleoside Combination Treatment Increases Mitochondrial Respiratory Capacity in m.3243A>G MELAS Cybrid Cells.

The lack of effective treatments for mitochondrial disease has seen the development of new approaches, including those that aim to stimulate mitochondrial biogenesis to boost ATP generation above a critical disease threshold. Here, we examine the effects of the peroxisome proliferator-activated receptor γ (PPARγ) activator pioglitazone (PioG), in combination with deoxyribonucleosides (dNs), on mitochondrial biogenesis in cybrid cells containing >90% of the m.3243A>G mutation associated with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). PioG + dNs combination treatment increased mtDNA copy number and mitochondrial mass in both control (CON) and m.3243A>G (MUT) cybrids, with no adverse effects on cell proliferation. PioG + dNs also increased mtDNA-encoded transcripts in CON cybrids, but had the opposite effect in MUT cybrids, reducing the already elevated transcript levels. Steady-state levels of mature oxidative phosphorylation (OXPHOS) protein complexes were increased by PioG + dNs treatment in CON cybrids, but were unchanged in MUT cybrids. However, treatment was able to significantly increase maximal mitochondrial oxygen consumption rates and cell respiratory control ratios in both CON and MUT cybrids. Overall, these findings highlight the ability of PioG + dNs to improve mitochondrial respiratory function in cybrid cells containing the m.3243A>G MELAS mutation, as well as their potential for development into novel therapies to treat mitochondrial disease.

Pathogenic Mitochondria DNA Mutations: Current Detection Tools and Interventions

Mitochondria are best known for their role in energy production, and they are the only mammalian organelles that contain their own genomes. The mitochondrial genome mutation rate is reported to be 10–17 times higher compared to nuclear genomes as a result of oxidative damage caused by reactive oxygen species during oxidative phosphorylation. Pathogenic mitochondrial DNA mutations result in mitochondrial DNA disorders, which are among the most common inherited human diseases. Interventions of mitochondrial DNA disorders involve either the transfer of viable isolated mitochondria to recipient cells or genetically modifying the mitochondrial genome to improve therapeutic outcome. This review outlines the common mitochondrial DNA disorders and the key advances in the past decade necessary to improve the current knowledge on mitochondrial disease intervention. Although it is now 31 years since the first description of patients with pathogenic mitochondrial DNA was reported, the treatment for mitochondrial disease is often inadequate and mostly palliative. Advancements in diagnostic technology improved the molecular diagnosis of previously unresolved cases, and they provide new insight into the pathogenesis and genetic changes in mitochondrial DNA diseases.