Mitochondrial oxygen use in blood, muscle, and skin of people with long COVID

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

Researchers will test whether mitochondria use oxygen differently in blood cells, muscle, and skin of people with long COVID compared with people who fully recovered after COVID-19.

Quick facts

• Study type: Observational
• Enrollment: 54 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Universitair Ziekenhuis Brussel (Academic / other)
• Locations: 1 site (Jette, Brussels Capital)
• Trial ID: NCT07134673 on ClinicalTrials.gov

What this trial studies

This observational study will compare mitochondrial oxygen consumption between adults with long COVID (symptoms ≥6 months) and convalescent individuals who fully recovered, using three measurement techniques applied to peripheral blood mononuclear cells, skeletal muscle, and skin. Participants will complete surveys, wear an activity tracker for seven days, undergo non-invasive functional tests across two visits about a week apart, and provide a blood sample. The protocol also examines how well the three techniques agree in quantifying oxygen use across the three tissues. Results will look for consistent differences that could indicate mitochondrial dysfunction in long COVID.

Who should consider this trial

Good fit: Ideal candidates are adults (≥18) with a confirmed past SARS-CoV-2 infection who meet the WHO definition of long COVID with symptoms for at least six months and a Post-COVID-19 Functional Status grade 2–4 (pre-infection grade 0).

Not a fit: People with pre-existing chronic diseases that affect functional status, those taking metabolism-altering drugs, individuals with high alcohol intake, or those with skin conditions aggravated by sunlight or who cannot understand Dutch, French, or English may not be eligible or likely to directly benefit.

Why it matters

Potential benefit: If successful, the study could identify measurable mitochondrial changes that help diagnose long COVID or guide future targeted treatments.

How similar studies have performed: Small prior studies and research in related conditions like ME/CFS have suggested mitochondrial abnormalities, but findings are limited and inconsistent, so this specific multi-tissue comparison is partly supported but remains novel.

Eligibility criteria

Individuals with long COVID:

Inclusion criteria:

* 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.

Exclusion criteria:

* 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.

Convalescent individuals

Inclusion criteria:

* History of confirmed or documented SARS-CoV-2 infection.
* 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).

Exclusion criteria:

* 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.

Where this trial is running

Jette, Brussels Capital

• Laarbeeklaan 101 — Jette, Brussels Capital, Belgium (Recruiting)

Study contacts

• Principal investigator: Elisabeth De Waele, MD. PhD. — Vitality Research Group, Metabolism and Nutrition, Vrije Universiteit Brussel (VUB), Clinical Nutrition Department, Universitair Ziekenhuis Brussel (UZ Brussel)
• Study coordinator: Berenice G. Jimenez Garcia, Master of Science

Conditions Long COVID; Post-COVID-19 Condition; mitochondrial dysfunction