FiND
Research type
Research Study
Full title
A new non-invasive diagnostic method for detection of pathogenic mitochondrial DNA variants using faecal-derived DNA samples.
IRAS ID
295392
Contact name
Gráinne Gorman
Contact email
Sponsor organisation
The Newcastle upon Tyne Hospitals NHS Foundation Trust
Duration of Study in the UK
1 years, 0 months, 1 days
Research summary
Research Summary
As a group, mitochondrial diseases are one of the commonest inherited neurometabolic disorders, which are clinically heterogeneous and often associated with multisystem disorders. Pathogenic mitochondrial DNA (mtDNA) variants are the most common causative genetic defects in adult-related mitochondrial disease with an estimated point prevalence of more than 1 in 5000 and a carrier frequency of ∼1 in 400 for the most common pathogenic variant, m.3243A>G, in the MT-TL1 gene.
The understanding of genetics and advances in sequencing technologies has transformed the diagnosis of mitochondrial disease. However, several aspects of mitochondrial genetics complicate prediction of the risk of serious disease. These include mtDNA heteroplasmy (the mix of pathogenic (potentially disease causing) and wild-type (usual non-disease causing) mtDNA within a cell), threshold effect (the heteroplasmy level at which disease symptoms occur; this threshold varies with different pathogenic variants, from one tissue to another and between individuals), and mitochondrial genetic bottleneck - the term describing a process that can lead to offspring being born with a range of different mtDNA heteroplasmy levels.
Whilst skeletal muscle biopsy remains an important diagnostic tool in the investigation of patients with mitochondrial disease, it is expensive, invasive, often only performed at specialist centres and in the paediatric population often poses an additional risk for general anaesthesia. Similarly, less invasive blood and urine sampling form part of standard diagnostic mitochondrial disease pathways, but some mtDNA variants are lost from blood or segregate markedly across different tissues, resulting in a gross underestimation of heteroplasmy and consequently the risk of serious disease.
The aim of this study is to develop and validate the use of faecal tissue (stool) as a potential novel and non-invasive diagnostic tool for mitochondrial disease.Summary of Results
Why was the FiND Study needed?
Mitochondria are the ‘batteries’ of the cell that generate the energy we need. When these batteries are faulty, it can cause conditions known as mitochondrial diseases. There are many different causes of mitochondrial diseases, and people affected experience a range of symptoms.
All cells contain genetic material called DNA. Mitochondria also contain their own separate type of DNA called mitochondrial DNA (mtDNA). Some mitochondrial diseases happen because of errors in mtDNA.
A way to diagnose some mitochondrial diseases is to look for mtDNA containing these errors. We look at how much mtDNA with errors we find compared to how much ‘normal’ mtDNA there is. We call this the ‘mtDNA heteroplasmy’ level.
Currently to measure mtDNA heteroplasmy, we use samples of muscle or blood. This involves a muscle biopsy or blood sample and needs a visit to the hospital or clinic. It can also be painful or uncomfortable.
In this study we tested whether we could use faecal samples (poo) to diagnose mitochondrial disease.
We collected faecal samples from people we know have a certain type of mitochondrial disease. We then measured mtDNA heteroplasmy levels in these samples to check if they matched levels previously recorded from other samples (e.g. muscle or blood).
Who designed, led and funded the study?
This study was designed by doctors and scientists at the Wellcome Centre for Mitochondrial Research, Newcastle University and at The Newcastle upon Tyne Hospitals NHS Foundation Trust.
The Medical Research Council provided funding via their Confidence in Concept funding scheme.
Where and when did the study take place?
FiND took place between June 2022 and December 2023. People were able to take part in the study remotely from home and did not need to attend a study site for any visits.
Who took part and what was involved?
Adults and children with a confirmed diagnosis of mitochondrial disease were able to take part. Participants provided consent (online or on paper) and were then asked to provide a poo sample. This sample was returned to the study site in Newcastle in a special container by post.
A special kit and gloves for collecting the samples were provided to make collection easy, clean and safe.
Results from previous blood and other tests, were obtained from each participant’s hospital medical records.
Some participants also took part in a focus group discussion. They were asked what they thought about using faecal samples to diagnose mitochondrial disease.
How many people took part?
Forty-seven people returned samples and completed the study.
We were hoping to look at samples from between 30 and 50 people and so we met our recruitment target.
What were the results?
We have now completed all the work in the lab for this study. When we assessed our results to see how they compare to mtDNA heteroplasmy results from ‘usual’ samples such as blood or muscle, we found that, in most cases (38 out of the 47 samples), the heteroplasmy aligned well (within 10%) with heteroplasmy from at least one of the other tissues available.
Once our analyses are complete, we will publish a full report.
The feedback we obtained from the Focus Group was that faecal samples were felt to be an acceptable way of diagnosing mitochondrial disease.
All the participants in this study who returned their samples did so without any issues. The samples were able to be fully analysed on receipt in the lab.
Was the study useful?
We don’t know how useful the study will have been until we have completed analysing the results. However we hope that the study findings may help us develop new, less invasive way of diagnose mitochondrial disease in future.
Where can I find out more?
Further information is available from the Mitochondrial Research team at Newcastle University. The following website contains contact details and information about our research: https://www.newcastle-mitochondria.com/REC name
East of Scotland Research Ethics Service REC 1
REC reference
21/ES/0075
Date of REC Opinion
27 Jul 2021
REC opinion
Favourable Opinion