bims-symami Biomed News
on Symptom management in mitochondrial disease
Issue of 2023–05–07
nine papers selected by
The Lily Foundation



  1. Exp Mol Med. 2023 May 01.
      Mitochondria are of fundamental importance in programmed cell death, cellular metabolism, and intracellular calcium concentration modulation, and inheritable mitochondrial disorders via mitochondrial DNA (mtDNA) mutation cause several diseases in various organs and systems. Nevertheless, mtDNA editing, which plays an essential role in the treatment of mitochondrial disorders, still faces several challenges. Recently, programmable editing tools for mtDNA base editing, such as cytosine base editors derived from DddA (DdCBEs), transcription activator-like effector (TALE)-linked deaminase (TALED), and zinc finger deaminase (ZFD), have emerged with considerable potential for correcting pathogenic mtDNA variants. In this review, we depict recent advances in the field, including structural biology and repair mechanisms, and discuss the prospects of using base editing tools on mtDNA to broaden insight into their medical applicability for treating mitochondrial diseases.
    DOI:  https://doi.org/10.1038/s12276-023-00973-7
  2. Medicine (Baltimore). 2023 May 05. 102(18): e33725
       RATIONALE: Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is the most common subtype of mitochondrial encephalopathy. In the past, it was believed that most hereditary white matter lesions were lysosome storage disorders or peroxisome diseases. However, in recent years, white matter lesions have been increasingly regarded as a common feature of patients with mitochondrial diseases. In addition to stroke-like lesions, about half of the patients with MELAS reported white matter lesions in the brain.
    PATIENT CONCERNS: Herein, we provide a case of A 48-year-old female who presented with episodic loss of consciousness with twitching of extremities. Previous medical history revealed 10 years of history of epilepsy, 10 years of history of diabetes, a history of hearing loss, and unknown etiology. Ancillary findings included brain magnetic fluid-attenuated inversion recovery showed symmetrical lesions in the bilateral parietal lobe with high signal intensity at the edge, and high signal intensity in the bilateral occipital lobe, paraventricular white matter, corona radiata, and the center of semiovale.
    DIAGNOSES: Mitochondrial deoxyribonucleic acid gene sequencing returned A3243G point mutation and it supports the diagnosis of intracranial hypertension.
    INTERVENTIONS: Considered the diagnosis of symptomatic epilepsy, the patient was treated with mechanical ventilation, midazolam, and levetiracetam, and the limb twitching symptoms were controlled. The patient was comatose, chronically bedridden, with gastrointestinal dysfunction, and was treated prophylactically with antibiotics against infection, parenteral nutrition, and other supportive measures. B vitamins, vitamin C, vitamin E, coenzyme Q10, and idebenone were given, and mechanical ventilation and midazolam were stopped after 8 days. He was discharged from the hospital on 30 days and continued symptomatic treatment with B-vitamins, vitamin C, vitamin E, coenzyme Q10, and idebenone, and antiepileptic treatment with levetiracetam, with outpatient follow-up.
    OUTCOMES: No further seizures were recorded and the patient recovered well.
    LESSONS: MELAS syndrome without stroke-like episodes of diffuse posterior cerebral white matter lesions is rare in clinical practice, and the possibility of MELAS syndrome should be considered in symmetric posterior cerebral white matter lesions.
    DOI:  https://doi.org/10.1097/MD.0000000000033725
  3. Eur Heart J Case Rep. 2023 Apr;7(4): ytad132
       Background: Mitochondrial diseases represent an important potential cause of cardiomyopathy and should be considered in patients presenting with multisystem manifestations. Timely diagnosis of a mitochondrial disorder is needed as it can have reproductive implications for the offspring of the proband.
    Case Summary: We describe a case of undifferentiated rising and persistent troponin elevation in a 70-year-old female with only mild heart failure symptoms and signs. An eventual diagnosis of a mitochondrial cytopathy was made after genetic testing, striated muscle, and endomyocardial biopsy. Multidisciplinary involvement was vital in securing the ultimate diagnosis and is a key lesson from this case. On follow up, with institution of heart failure therapy including cardiac resynchronisation device therapy there was improvement in exercise tolerance and symptoms.
    Discussion: For discussion is the investigation of undifferentiated cardiomyopathies and consideration of mitochondrial disorders as an important diagnosis to exclude prior to diagnosis as an idiopathic cardiomyopathy.
    Keywords:  Cardiovascular magnetic resonance imaging; Case report; Mitochondrial cytopathy; Troponin
    DOI:  https://doi.org/10.1093/ehjcr/ytad132
  4. Mutagenesis. 2023 May 05. pii: gead010. [Epub ahead of print]
      Mitochondrial DNA mutation and toxicity have been linked to several inherited and acquired diseases; however, these are challenging to diagnose and characterise due to clinical and genetic heterogeneity. This review investigates current techniques for the analysis of mitochondrial perturbations, and novel, emerging endpoints for routine application within the clinical setting. Particular focus is given to the biochemistry of the mitochondria influencing each endpoint and the relation of these to toxicity. Current approaches such as the use of metabolic markers (e.g., lactate production), and muscle biopsies to measure mitochondrial proteins were found to lack specificity. Newly emerging identified endpoints were: fibroblast growth factor-21, glucose uptake, mitochondrial membrane potential, mitochondrial morphology, mtDNA heteroplasmy, and mutation of mtDNA and nuclear DNA. Owed to the advancement in genetic analysis techniques, it is suggested by this review that genotypic endpoints of mtDNA mutation and heteroplasmy show particular promise as indicators of mitochondrial disease. It is, however, acknowledged that any single endpoint in isolation offers limited information; therefore, it is recommended that analysis of several endpoints simultaneously will offer the greatest benefit in terms of disease diagnosis and study. It is hoped that this review further highlights the need for advancement in understanding mitochondrial disease.
    DOI:  https://doi.org/10.1093/mutage/gead010
  5. Neurol India. 2023 Mar-Apr;71(2):71(2): 323-325
      Mitochondrial neurogastrointestinal encephalopathy (MNGIE) is an autosomal recessive disease associated with the mutation of the TYMP gene. MNGIE causes gastrointestinal and neurological symptoms, and the gastrointestinal symptoms are usually notable, which may lead to misdiagnosis. However, we herein report a 29-year-old female who presented with prominent neurological symptoms, while her gastrointestinal symptoms were mild. Brain MRI revealed prominent diffused leukoencephalopathy and peripheral neuropathy was confirmed by the nerve conduction velocity test. Biochemical tests showed elevated plasma thymidine, deoxyuridine, and lactate levels. Molecular genetic testing demonstrated a novel homozygous TYMP c. 447 dupG mutation and the patient's mother was heterozygous for the mutation but had no clinical features. MNGIE was diagnosed based on the results. Unlike other patients who had notable gastrointestinal symptoms, this patient presented with more prominent neurological symptoms than gastrointestinal symptoms, which might have been caused by the novel mutation in the TYMP gene.
    Keywords:  Frameshift mutation; MNGIE; TYMP; neurological symptoms; novel mutation
    DOI:  https://doi.org/10.4103/0028-3886.375429
  6. J Med Ethics. 2023 May 02. pii: jme-2022-108659. [Epub ahead of print]
      Mitochondrial replacement techniques (MRTs) are a new group of biotechnologies that aim to aid women whose eggs have disease-causing deleteriously mutated mitochondria to have genetically related healthy children. These techniques have also been used to aid women with poor oocyte quality and poor embryonic development, to have genetically related children. Remarkably, MRTs create humans with DNA from three sources: nuclear DNA from the intending mother and father, and mitochondrial DNA from the egg donor. In a recent publication Françoise Baylis argued that MRTs are detrimental for genealogical research via mitochondrial DNA because they would obscure the lines of individual descent. In this paper, I argue that MRTs do not obscure genealogical research, but rather that MRT-conceived children can have two mitochondrial lineages. I argue for this position by showing that MRTs are reproductive in nature and, thus, they create genealogy.
    Keywords:  fertilization in vitro; gene transfer techniques; genetic engineering; genetic therapy; in vitro techniques
    DOI:  https://doi.org/10.1136/jme-2022-108659
  7. Eur Heart J Case Rep. 2023 Apr;7(4): ytad183
       Background: Mitochondrial cardiomyopathy (MCM) is an alteration in cardiac structure and function caused by gene mutations or deletions affecting components of the mitochondrial respiratory chain. We report a case of MCM presenting as cardiogenic shock, ultimately requiring left ventricular assist device (LVAD) placement.
    Case summary: A 35-year-old woman with chronic weakness and non-ischaemic cardiomyopathy, on home dobutamine, was referred to our institution for heart transplantation evaluation. She was admitted to the hospital for suspected cardiogenic shock after laboratory tests revealed a lactate level of 5.4 mmol/L (ref: 0.5-2.2 mmol/L). Her hospital course was complicated by persistently undulating lactate levels (0.2-8.6 mmol/L) that increased with exertion and did not correlate with mixed venous oxygen saturation measurements obtained from a pulmonary artery catheter. Electrodiagnostic testing demonstrated a proximal appendicular and axial myopathy. A left deltoid muscle biopsy was performed that demonstrated evidence of a mitochondrial disease on light and electron microscopy. Muscle genetic testing revealed two large-scale mitochondrial deoxyribonucleic acid sequence deletions, confirming the diagnosis of MCM. She subsequently underwent LVAD placement, which was complicated by significant right ventricular failure requiring early mechanical support. She was ultimately discharged home with chronic inotropic support.
    Discussion: Mitochondrial cardiomyopathy in adults is a diagnostic and therapeutic challenge. Prompt diagnosis should be made in patients with unknown causes of heart failure via skeletal muscle histopathology guided by electrodiagnostic studies, and targeted genetic testing in affected tissue. Outcomes in adult MCM patients who receive an LVAD are unknown and warrant further investigation.
    Keywords:  Advanced heart failure; Case report; Mechanical circulatory support device; Mitochondrial DNA disease; Mitochondrial cardiomyopathy
    DOI:  https://doi.org/10.1093/ehjcr/ytad183
  8. BMC Genomics. 2023 May 02. 24(1): 229
       BACKGROUND: Mitochondrial genome sequences have become critical to the study of biodiversity. Genome skimming and other short-read based methods are the most common approaches, but they are not well-suited to scale up to multiplexing hundreds of samples. Here, we report on a new approach to sequence hundreds to thousands of complete mitochondrial genomes in parallel using long-amplicon sequencing. We amplified the mitochondrial genome of 677 specimens in two partially overlapping amplicons and implemented an asymmetric PCR-based indexing approach to multiplex 1,159 long amplicons together on a single PacBio SMRT Sequel II cell. We also tested this method on Oxford Nanopore Technologies (ONT) MinION R9.4 to assess if this method could be applied to other long-read technologies. We implemented several optimizations that make this method significantly more efficient than alternative mitochondrial genome sequencing methods.
    RESULTS: With the PacBio sequencing data we recovered at least one of the two fragments for 96% of samples (~ 80-90%) with mean coverage ~ 1,500x. The ONT data recovered less than 50% of input fragments likely due to low throughput and the design of the Barcoded Universal Primers which were optimized for PacBio sequencing. We compared a single mitochondrial gene alignment to half and full mitochondrial genomes and found, as expected, increased tree support with longer alignments, though whole mitochondrial genomes were not significantly better than half mitochondrial genomes.
    CONCLUSIONS: This method can effectively capture thousands of long amplicons in a single run and be used to build more robust phylogenies quickly and effectively. We provide several recommendations for future users depending on the evolutionary scale of their system. A natural extension of this method is to collect multi-locus datasets consisting of mitochondrial genomes and several long nuclear loci at once.
    Keywords:  DNA barcoding; Long read sequencing; LongAmp; MinION; Plasmid; Third generation sequencing; mtDNA
    DOI:  https://doi.org/10.1186/s12864-023-09277-6