Metabolic Disruption in Long COVID: How Mitochondria, Lactate, and Oxygen Balance May Drive Persistent Fatigue

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This paper addresses:  

Lactate, Capnia, and Fat Oxidation as Therapeutic Axes for SARS-CoV-2 Spike Protein-Induced Sequelae https://www.thieme-connect.de/products/ejournals/abstract/10.1055/a-2794-9646

Interpretation:

Post-acute COVID-19 syndrome, commonly known as Long COVID, has drawn increasing attention due to persistent symptoms that continue long after infection. Similar symptoms have also been reported in some individuals after COVID-19 vaccination. A growing body of research suggests that many of these cases involve disturbances in the body’s energy metabolism—specifically how cells produce and use energy.

One theory proposes that the body’s energy system becomes disrupted at the cellular level. Mitochondria, the power producers of cells, may not function efficiently in some affected individuals. When mitochondria are impaired, the body struggles to generate energy normally. Studies also suggest that the body burns less fat for steady energy and instead relies more on carbohydrates, while lactate accumulates earlier during activity. As a result, even mild exertion can push the body into a state similar to intense exercise, causing severe fatigue and worsening symptoms after activity.

These symptoms often appear as a characteristic triad: post-exertional malaise (PEM), persistent fatigue, and cognitive impairment known as “brain fog.” People with PEM experience a worsening of symptoms after physical or mental activity that would normally be manageable, sometimes lasting for hours or days.

Researchers believe mitochondrial dysfunction may play a central role. Laboratory studies have shown that the SARS-CoV-2 spike protein can disrupt mitochondrial function in cell cultures, providing a possible explanation for how the virus might interfere with the body’s energy system. If mitochondria cannot efficiently produce cellular energy, fatigue and cognitive problems may result.

Physiological studies also show that many patients have a significantly reduced lactate threshold—the point at which lactate builds up faster than the body can clear it. While this usually occurs during moderate to intense exercise in healthy individuals, some post-COVID patients reach this threshold during very light activity. Muscle biopsies and metabolic studies also indicate damaged mitochondria and reduced fat oxidation, forcing the body to rely more on carbohydrates for energy.

Another factor researchers are investigating is the balance between carbon dioxide (CO₂) and oxygen in the blood. Carbon dioxide helps regulate how oxygen is released from hemoglobin to tissues through a mechanism called the Bohr effect. If CO₂ levels become too low—such as through chronic over-breathing—oxygen may not be delivered efficiently to muscles and the brain, potentially worsening fatigue and energy deficits.

Based on these findings, researchers have proposed several possible therapeutic strategies. These include increasing the lactate threshold, improving tissue oxygenation by restoring a healthy CO₂–oxygen balance, and enhancing the body’s ability to burn fat for energy.

To describe this metabolic pattern, scientists sometimes use comparisons from exercise science. The body may behave as if it has too many fast-twitch muscle characteristics, relying heavily on carbohydrate metabolism rather than fat oxidation. Others compare the condition to a high-altitude state, where oxygen delivery is limited. Some researchers also describe it as the opposite of “fat adaptation,” a process seen in endurance athletes who efficiently burn fat for long-lasting energy.

Although research is still evolving, this metabolic perspective provides a potential framework for understanding the fatigue, cognitive problems, and exercise intolerance seen in Long COVID. Further studies on mitochondrial function, metabolism, and oxygen delivery may help clarify the underlying mechanisms and guide future treatments.

Connection: The Bohr effect is closely related to the Haldane effect.

© 2000-2030 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right. Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9

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