Long COVIDMitoLoCoNCT07134673
Mitochondrial Function in Peripheral Blood Mononuclear Cells, Muscle, and Skin of Long COVID Patients
An observational study of Long COVID and Post-COVID-19 Condition, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
Trial summary
Mitochondria are structures inside cells that are responsible for producing energy from nutrients through a series of steps, using oxygen. To have an idea of how well the mitochondria can produce energy, we can measure how much oxygen they use. The goal of this study is to: 1. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Long COVID, Post-COVID-19 Condition
- How many people
- 54 participants
- Where
- 1 siteBelgium
- Study dates
- 21 Jan 2026to Jul 2026
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Study population: Study participants will be recruited in the Universitair Ziekenhuis Brussel, from the general population in Belgium through traditional and social media, as well as in the vicinity of the study site through leaflets and posters.
Who may be able to join
- Long COVID diagnosis, based on the WHO definition;
- Presence of long COVID symptoms for a minimum of 6 months.
- History of confirmed or documented SARS-CoV-2 infection.
- Adult (≥18 years of age).
- Post-COVID-19 Functional Status Scale grade 2-4, while they had a grade 0 before the SARS-CoV-2 infection.
- History of confirmed or documented SARS-CoV-2 infection.
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- Complete recovery after the SARS-CoV-2 infection, no history of long COVID based on the WHO definition;
- Post-COVID-19 Functional Status Scale [2] grade 0 both before the infection and currently.
- Adult (≥18 years of age).
Who cannot join
- Pre-existing chronic diseases potentially affecting the functional status scale.
- Treatment with metabolism altering drugs.
- > 10 standard units of alcohol (10 grams of alcohol/glass) per week.
- Unable to understand oral and written instructions in Dutch, French or English.
- Allergies to medical adhesive bandages.
- Porphyria and other skin conditions aggravated by sunlight.
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- Convalescent individuals
- Pre-existing chronic non-communicable diseases (e.g. hypertension, chronic respiratory diseases, diabetes).
- Treatment with metabolism altering drugs.
- > 10 standard units of alcohol (10 grams of alcohol/glass) per week.
- Unable to understand oral and written instructions in Dutch, French or English.
- Allergies to medical adhesive bandages.
- Porphyria and other skin conditions aggravated by sunlight.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Berenice G. Jimenez Garcia, Master of Science contact
Belgium1 site, 1 recruiting
- Recruiting
Laarbeeklaan 101
Jette, Brussels Capital, 1090
Berenice G. Jimenez Garcia, MSc., +3224749624, berenice.gabriela.jimenez.garcia@vub.be
About this study
Official title: Mitochondrial Oxygen Consumption and Substrate Utilisation In Vitro in Peripheral Blood Mononuclear Cells, and In Vivo on Muscle and Skin in Long COVID Patients and Convalescent Individuals: A Case-Control and Diagnostic Accuracy Study
Mitochondria are structures inside cells that are responsible for producing energy from nutrients through a series of steps, using oxygen. To have an idea of how well the mitochondria can produce energy, we can measure how much oxygen they use. The goal of this study is to:
- To compare the oxygen use between people with long COVID and people who completely recovered after COVID-19, using three techniques that measure the oxygen use in blood cells, on the skin and in the muscle
- To test how similar these three techniques are in measuring the oxygen used in the three different tissues
Read more
Participants will:
- Complete surveys,
- Wear an activity tracker (7 days),
- Undergo several non-invasive tests, and
- Donate a blood sample The study will take place in UZ Brussel hospital and will take 2 study visits, approximately 7 days apart.
- Conditions
- Long COVID, Post-COVID-19 Condition
- Keywords
- mitochondrial dysfunction
- Medical subject headings
- Post-Acute COVID-19 Syndrome, Mitochondrial Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| Individuals with long COVID | History of a confirmed or documented SARS-CoV-2 infection and long COVID according to the World Health Organisation's clinical case definition | |
| Convalescent individuals | History of a confirmed or documented SARS-CoV-2 infection, complete recovery after the SARS-CoV-2 infection, no history of long COVID according to the World Health Organisation's clinical case definition |
What is being measured
The primary outcome is the main question the study is designed to answer.
Basal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress test analysis of the peripheral blood mononuclear cells (PBMCs)
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Tissue Saturation Index (TSI)
Near-infrared spectroscopy
Measured: Second study visit (approximately 7 days after the first study visit)
Mitochondrial oxygen tension (mitoPO2) (mmHg/s)
Cellular Oxygen Metabolism monitoring
Measured: Second study visit (approximately 7 days after the first study visit)
Mitochondrial oxygen consumption (mitoVO2)
Cellular Oxygen Metabolism monitoring
Measured: Second study visit (minimally 7 days after the first study visit)
Secondary outcomes (16)
Proportion of participants meeting the criteria for PEM
De Paul Symptom Questionnaire - Post-exertional malaise (DSQ-PEM)
Measured: Second study visit (minimally 7 days after the first study visit)
General fatigue
Multidimensional Fatigue Inventory (MFI-20)
Measured: Second study visit (approximately 7 days after the first study visit)
Physical fatigue
Multidimensional Fatigue Inventory (MFI-20)
Measured: Second study visit (approximately 7 days after the first study visit)
Mental fatigue
Multidimensional Fatigue Inventory (MFI-20)
Measured: Second study visit (approximately 7 days after the first study visit)
Reduced activities
Multidimensional Fatigue Inventory (MFI-20)
Measured: Second study visit (approximately 7 days after the first study visit)
Reduced motivation
Multidimensional Fatigue Inventory (MFI-20)
Measured: Second study visit (approximately 7 days after the first study visit)
Severity and impact of fatigue on daily life
The Fatigue Severity Scale (FSS) contains nine statements that rate the severity of the fatigue symptoms. The statements are rated from 1 to 7, with a low value indicating strong disagreement with the statement and a high value indicating strong agreement with the statement. The total score is the sum of the individual scores, with a higher score indicating a greater impact of fatigue on daily life.
Measured: Second study visit (approximately 7 days after the first study visit)
Symptom burden (θ)
Item Response Theory (IRT) will be applied to estimate a latent trait representing symptom burden, using Section 2.6 of the WHO Post-COVID-19 Case Report Form. Symptoms will be coded as binary variables (1 = symptom present, 0 = symptom absent). IRT modeling will be used to derive a latent trait estimate (θ) for each individual, reflecting the overall severity or burden of symptoms.
Measured: First study visit
Resting Energy Expenditure (kcal/kg body weight/day)
Indirect calorimetry will be used to measure the Resting Energy Expenditure (kcal/day). This value will be divided by the body weight (kg) on that same day.
Measured: Second study visit (approximately 7 days after the first study visit)
Basal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor Etomoxir is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Basal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor UK5099 is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Basal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor BPTES is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress Test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor Etomoxir is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress Test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor UK5099 is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Seahorse XF Substrate Oxidation Stress Test analysis of the peripheral blood mononuclear cells (PBMCs) after substrate pathway inhibitor BPTES is used
Measured: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Respiratory Quotient
Indirect calorimetry
Measured: Second study visit (approximately 7 days after the first study visit)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 Aug 2025
- Study start21 Jan 2026
- Primary completionJul 2026 (estimated)
- Study completionJul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Long COVIDStudies of the same condition, open and under way.
- More trials run by Universitair Ziekenhuis BrusselThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case-control
- Time perspective
- Prospective
- Enrolment
- 54 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Universitair Ziekenhuis Brussel
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Elisabeth De Waele, Universitair Ziekenhuis Brussel
- Investigators
- Elisabeth De Waele, MD. PhD., Principal investigator, Vitality Research Group, Metabolism and Nutrition, Vrije Universiteit Brussel (VUB), Clinical Nutrition Department, Universitair Ziekenhuis Brussel (UZ Brussel)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07134673
- Sponsor's protocol ID
- EC-2025-071
- Other IDs
- G075423N
- Acronym
- MitoLoCo
- Status last verified
- Aug 2025
- First submitted
- 25 Jun 2025
- Last updated
- 22 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: Based on the guidelines and regulations of the Vrije Universiteit Brussel, the IPD will be shared. Plan is yet to be determined.
Study at a glance
From the registry record, last updated by the sponsor on 22 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Mitochondrial Oxygen Consumption and Substrate Utilisation In Vitro in Peripheral Blood Mononuclear Cells, and In Vivo on Muscle and Skin in Long COVID Patients and Convalescent Individuals: A Case-Control and Diagnostic Accuracy Study
- ClinicalTrials.gov ID
- NCT07134673
- Acronym / sponsor ID
- MitoLoCo / EC-2025-071
- Conditions
- Long COVID, Post-COVID-19 Condition
- Keywords
- mitochondrial dysfunction
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 54 participants (estimated)
- Lead sponsor
- Universitair Ziekenhuis BrusselUniversity, hospital or other
- Study start
- 21 Jan 2026 (actual)
- Primary completion
- Jul 2026 (estimated)
- Study completion
- Jul 2026 (estimated)
- First posted
- 21 Aug 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Mitochondria are structures inside cells that are responsible for producing energy from nutrients through a series of steps, using oxygen. To have an idea of how well the mitochondria can produce energy, we can measure how much oxygen they use. The goal of this study is to:
- To compare the oxygen use between people with long COVID and people who completely recovered after COVID-19, using three techniques that measure the oxygen use in blood cells, on the skin and in the muscle
- To test how similar these three techniques are in measuring the oxygen used in the three different tissues
Participants will:
- Complete surveys,
- Wear an activity tracker (7 days),
- Undergo several non-invasive tests, and
- Donate a blood sample The study will take place in UZ Brussel hospital and will take 2 study visits, approximately 7 days apart.
Study design
- Observational model
- Case-control
- Time perspective
- Prospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Individuals with long COVID | – | –History of a confirmed or documented SARS-CoV-2 infection and long COVID according to the World Health Organisation's clinical case definition |
| Convalescent individuals | – | –History of a confirmed or documented SARS-CoV-2 infection, complete recovery after the SARS-CoV-2 infection, no history of long COVID according to the World Health Organisation's clinical case definition |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
- Study population
- Study participants will be recruited in the Universitair Ziekenhuis Brussel, from the general population in Belgium through traditional and social media, as well as in the vicinity of the study site through leaflets and posters.
Key inclusion criteria (9 listed)
- Long COVID diagnosis, based on the WHO definition;
- Presence of long COVID symptoms for a minimum of 6 months.
- History of confirmed or documented SARS-CoV-2 infection.
- Adult (≥18 years of age).
- Post-COVID-19 Functional Status Scale grade 2-4, while they had a grade 0 before the SARS-CoV-2 infection.
Key exclusion criteria (13 listed)
- Pre-existing chronic diseases potentially affecting the functional status scale.
- Treatment with metabolism altering drugs.
- > 10 standard units of alcohol (10 grams of alcohol/glass) per week.
- Unable to understand oral and written instructions in Dutch, French or English.
- Allergies to medical adhesive bandages.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Basal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Seahorse XF Substrate Oxidation Stress test analysis of the peripheral blood mononuclear cells (PBMCs)
Tissue Saturation Index (TSI)
Time frame: Second study visit (approximately 7 days after the first study visit)
Near-infrared spectroscopy
Mitochondrial oxygen tension (mitoPO2) (mmHg/s)
Time frame: Second study visit (approximately 7 days after the first study visit)
Cellular Oxygen Metabolism monitoring
Mitochondrial oxygen consumption (mitoVO2)
Time frame: Second study visit (minimally 7 days after the first study visit)
Cellular Oxygen Metabolism monitoring
16 secondary outcomes
Proportion of participants meeting the criteria for PEM
Time frame: Second study visit (minimally 7 days after the first study visit)
General fatigue
Time frame: Second study visit (approximately 7 days after the first study visit)
Physical fatigue
Time frame: Second study visit (approximately 7 days after the first study visit)
Mental fatigue
Time frame: Second study visit (approximately 7 days after the first study visit)
Reduced activities
Time frame: Second study visit (approximately 7 days after the first study visit)
Reduced motivation
Time frame: Second study visit (approximately 7 days after the first study visit)
Severity and impact of fatigue on daily life
Time frame: Second study visit (approximately 7 days after the first study visit)
Symptom burden (θ)
Time frame: First study visit
Resting Energy Expenditure (kcal/kg body weight/day)
Time frame: Second study visit (approximately 7 days after the first study visit)
Basal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Basal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Basal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Maximal Oxygen Consumption rate (pmol O2/min)
Time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)
Respiratory Quotient
Time frame: Second study visit (approximately 7 days after the first study visit)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 22 Apr 2026.
- Individual participant dataSharing planned: Undecided. Based on the guidelines and regulations of the Vrije Universiteit Brussel, the IPD will be shared. Plan is yet to be determined.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Berenice G. Jimenez Garcia, Master of Science contact
Elisabeth De Waele, MD. PhD. principal investigator
Vitality Research Group, Metabolism and Nutrition, Vrije Universiteit Brussel (VUB), Clinical Nutrition Department, Universitair Ziekenhuis Brussel (UZ Brussel)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Long COVID and Post-COVID-19 Condition, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 9 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 22 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Berenice G. Jimenez Garcia, Master of Science (+3224749624, berenice.gabriela.jimenez.garcia@vub.be), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Basal Oxygen Consumption rate (pmol O2/min) (time frame: Blood sample is taken during the second study visit (approximately 7 days after the first study visit) and the PBMCs are cryopreserved until analysis (after all participants have been recruited, estimated to be within 1 year of the start of the study)). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 22 Apr 2026.