Subgrouping Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Linking the Powerhouses of Cells to the Autonomic Nervous System (MITAP)

November 4, 2026 updated by: Jente Van Campenhout, Vrije Universiteit Brussel

Mitochondrial Dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Are Autonomic Phenotypes Necessary to Clear Conflicting Results?

The goal of this study is to investigate whether mitochondrial dysfunction is present in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) by subgrouping them into autonomic phenotypes. The main questions it aims to answer are:

  • When patients with ME/CFS are exposed to situations stressing the mitochondria and autonomic nervous system, is the response of their mitochondria and autonomic nervous system dependent on to which autonomic profile the patients belong?
  • Is the presence of mitochondrial dysfunction dependent on to which autonomic profile a patient with ME/CFS belongs? Researchers will compare healthy control subjects because very little is known about the link between mitochondria and the autonomic nervous system. It is therefore important that this is also investigated in healthy control subjects to gain a better understanding of which biological changes are normal and which changes may be involved in the symptoms of patients with ME/CFS.

Participants will:

  • Undergo an exercise test (to stress the mitochondria) and an orthostatic test (to stress the autonomic nervous system)
  • Fill in questionnaires
  • Undergo blood collection

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

ME/CFS is a debilitating disease with unknown pathophysiology. Mitochondrial dysfunction has been proposed as a potential pathophysiological mechanism because the mitochondria are important for energy metabolism. Moreover, patients with mitochondrial diseases experience similar symptoms as patients with ME/CFS, including fatigue, pain and autonomic symptoms. However, literature reports conflicting results regarding mitochondrial dysfunction in patients with ME/CFS. As ME/CFS patients present with a broad range of symptoms, subgrouping them might provide new insights.

Next to mitochondrial dysfunction, the involvement of the autonomic nervous system (ANS) has been proposed as it can be linked to common symptoms such as autonomic symptoms, post-exertional malaise (PEM) and cognitive impairments. Recently, ME/CFS patients were subgrouped into autonomic phenotypes. The presence of autonomic symptoms in patients with mitochondrial diseases highlights that there is a link between the mitochondria and ANS. Although the nature of this link remains unclear, a recent animal study showed that activation of adrenergic receptors - the binding sites of catecholamines (i.e. messengers of the ANS) - increased the production of reactive oxidative species, which are in turn known to influence autonomic function, damage the mitochondria, and regulate mitochondrial DNA methyltransferase (DNMT) expression. Mitochondrial DNMTs are responsible for mtDNA methylation (mtDNAm), which directly affects mitochondrial gene expression and could thus have a major impact on mitochondrial function. Interestingly, Buyn et al. reported that heart rate variability, an important marker to subgroup patients with ME/CFS into autonomic phenotypes, was associated with mtDNAm in a study investigating air pollution in 48 healthy males.

This raises the question whether mitochondrial dysfunction in patients with ME/CFS depends on to which autonomic phenotype they belong and whether this relation can be explained by mtDNAm, which is influenced by reactive oxygen species production upon adrenergic receptor activation. Consequently, this relation may lead to autonomic phenotype-dependent mitochondrial dysfunction. Hence, this project entails a cross-over study designed to clear the conflicting results regarding mitochondrial dysfunction in patients with ME/CFS by subgrouping them into autonomic phenotypes.

The investigators will perform an experimental cross-over study, in which the autonomic phenotypes will be validated and linked to additional biological information (i.e., mitochondrial (dys)function and mitochondrial DNA methylation). Study participants will visit the hospital twice with two weeks in between the visits. During each visit, autonomic, clinical and biological outcomes will be assessed before and after the experimental procedure, which include a single bout of submaximal exercise (Aerobic Power Index) to create a high-energy demand situation and stress the mitochondria, and an orthostatic test (Active Standing test) to stress the autonomic nervous system (ANS). The order of these experimental procedures is defined by randomly dividing all participants into two groups. Additionally, this project will assess the presence and severity of post-exertional malaise (PEM) 24h and 7 days after the experimental procedure via online assessments allowing the investigators to determine whether autonomic phenotype and mitochondrial function can predict PEM severity.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
105

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Belgium
      • Jette, Belgium, 1090
        • Universitair Ziekenhuis Brussel - Vrije Universiteit Brussel

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years to 70 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Between the ages of 18 and 70
  • Speak Dutch
  • ME/CFS syndrome (confirmed by a medical diagnosis)
  • Healthy individuals wishing to participate must be currently pain-free and healthy (i.e., participants must not be ill during the period of study participation)

Exclusion Criteria:

  • Pregnant women or women who were pregnant in the past year
  • Persons with a chronic illness such as a rheumatological, endocrine, neurological or psychiatric condition
  • Persons with a history of cancer or heart disease
  • Persons taking medications that affect the autonomic nervous system such as beta blockers

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Healthy controls

Study participants will visit the hospital twice with two weeks in between the visits. During each visit, autonomic, clinical and biological outcomes will be assessed before and after the experimental procedure, which include a single bout of submaximal exercise (Aerobic Power Index) to create a high-energy demand situation and stress the mitochondria, and an orthostatic test (Active Standing test) to stress the autonomic nervous system (ANS). The order of these experimental procedures is defined by randomly dividing all participants into two groups. Additionally, this project will assess the presence and severity of post-exertional malaise (PEM) 24h and 7 days after the experimental procedure via online assessments allowing us to determine whether autonomic phenotype and mitochondrial function can predict PEM severity.
Other: Exercise test

The Aerobic Power Index (API) will be used to create a high-energy demand situation and stress the mitochondria. Briefly, cycling starts at a constant rate of 70 cycles/min and workload of 25 Watt/min, increasing 25 Watt/min until the patient reaches 75% of the age-predicted maximal heart rate.

Other Names:
  • Aerobic Power Index
Other: Active standing test

The ANS will be stressed via an Active Standing (AS) test, an ecological valid orthostatic test. Subjects will start in a supine position followed by standing up within five seconds, these instructions will be explained to the subjects prior to the start of the AS test. After standing up, the subjects need to maintain an upright posture quietly for seven minutes, afterwards the patients will be returned to the supine position.

Other Names:
  • orthostatic test
Experimental: ME/CFS patients

Study participants will visit the hospital twice with two weeks in between the visits. During each visit, autonomic, clinical and biological outcomes will be assessed before and after the experimental procedure, which include a single bout of submaximal exercise (Aerobic Power Index) to create a high-energy demand situation and stress the mitochondria, and an orthostatic test (Active Standing test) to stress the autonomic nervous system (ANS). The order of these experimental procedures is defined by randomly dividing all participants into two groups. Additionally, this project will assess the presence and severity of post-exertional malaise (PEM) 24h and 7 days after the experimental procedure via online assessments allowing us to determine whether autonomic phenotype and mitochondrial function can predict PEM severity.
Other: Exercise test

The Aerobic Power Index (API) will be used to create a high-energy demand situation and stress the mitochondria. Briefly, cycling starts at a constant rate of 70 cycles/min and workload of 25 Watt/min, increasing 25 Watt/min until the patient reaches 75% of the age-predicted maximal heart rate.

Other Names:
  • Aerobic Power Index
Other: Active standing test

The ANS will be stressed via an Active Standing (AS) test, an ecological valid orthostatic test. Subjects will start in a supine position followed by standing up within five seconds, these instructions will be explained to the subjects prior to the start of the AS test. After standing up, the subjects need to maintain an upright posture quietly for seven minutes, afterwards the patients will be returned to the supine position.

Other Names:
  • orthostatic test

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Mitochondrial function will be investigated in patients with ME/CFS compaired to healthy controls at baseline and after a physical exercise test.
Time Frame: Blood collection immediatly before procedure and after

The primary objective is to examine the difference in mitochondrial function between 75 ME/CFS patients and 30 healthy controls. Mitochondrial function will be determined in isolated peripheral blood mononuclear cells (PBMCs). Following the manufacturer's instructions, the Seahorse XF Cell Mito Stress Test Kit (Agilent) will be used to determine the oxygen consumption rate (OCR).
Blood collection immediatly before procedure and after
Autonomic nervous system (ANS) function will be explored in patients with ME/CFS and healthy controls at baseline and after an orthostatic test.
Time Frame: During intervention (approximately 45 mins) in hospital

The investigators will explore autonomc nervous system (ANS) function, enabling clinical stratification of 75 patients with ME/CFS. During the othostatic test or active standing test, the ANS will be monitored with the SOMNOTouch NIBP device, providing a non-invasive continuous blood pressure monitoring.
During intervention (approximately 45 mins) in hospital
Autonomic nervous system (ANS) function will be explored in patients with ME/CFS and healthy controls at baseline and after an orthostatic test.
Time Frame: During intervention (approximately 45 mins) in hospital

The investigators will explore autonomc nervous system (ANS) function, enabling clinical stratification of 75 patients with ME/CFS. During the othostatic test or active standing test, the ANS will be monitored with the SOMNOTouch NIBP device, providing a non-invasive continuous heart rate monitoring.
During intervention (approximately 45 mins) in hospital
Autonomic nervous system (ANS) function will be explored in patients with ME/CFS and healthy controls at baseline and after an orthostatic test.
Time Frame: During intervention (approximately 45 mins) in hospital

The investigators will explore autonomc nervous system (ANS) function, enabling clinical stratification of 75 patients with ME/CFS. During the othostatic test or active standing test, the ANS will be monitored with the SOMNOTouch NIBP device, providing a non-invasive continuous arterial stiffness measurement.
During intervention (approximately 45 mins) in hospital

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Prediction of severity of post-exertional malaise in patients with ME/CFS.
Time Frame: 24hours after both study visits

Prediction of the severity of early- (24h) post-exertional malaise (PEM) in 75 patients with ME/CFS via online assessments including the Chronic Fatigue Syndrome Symptom List.
24hours after both study visits
Prediction of severity of post-exertional malaise in patients with ME/CFS.
Time Frame: 7 days after both study visits

Prediction of the severity of late-onset (7 days) PEM in 75 patients with ME/CFS via online assessments including the Quality of Life Scale (quality of life, health and other areas of life, min score = not at all, max score=absolutely), Fatigue Severity Scale (min score 0=strongly disagree, max score 6=strongly agree), International Physical Activity Questionnaire and Chronic Fatigue Syndrome Symptom List.
7 days after both study visits

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Vrije Universiteit Brussel

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
October 21, 2024

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
November 30, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
July 18, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 4, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 9, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 9, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 4, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • EC-2023-391

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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