Our gut bacteria may hold the answers to this mysterious disease that affects millions
As widespread as it may be, very little is known about myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). According to the Centers for Disease Control and Prevention, an estimated 2.5 million Americans have the chronic condition, and many cases appear to occur in women after infection. That aside, however, the researchers were embarrassed to explain the key questions: Why do symptoms vary so much between people with the condition? Is there a foolproof way to diagnose? And what causes ME/CFS?
These questions are of particular concern to the public these days thanks to the COVID-19 pandemic. Long-term COVID patients are currently struggling to get serious treatment for their symptoms, and many people with ME/CFS have recognized the similarities between their conditions and have helped organize and advocate for concerted research into both conditions.
Two new studies, both published in the journal Cell Host & Microbe on February 8th, now give us some answers by relating ME/CFS to the inner workings of the human body. The new research links the condition to an underlying disorder in a person’s gut microbiome — the bacteria and other microorganisms that live in harmony and conflict with the cells in the gastrointestinal tract.
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Research into the gut microbiome has begun over the past decade to explain both the causes and effects of all types of diseases, from diseases affecting the gastrointestinal tract to neurodegenerative diseases. It’s not far-fetched to look at the role of the microbiome in a condition like ME/CFS, which can cause gastrointestinal and neurological symptoms.
Given the growing body of research, the first study, while interesting, wasn’t that groundbreaking. A team led by Columbia University researchers analyzed stool samples from 106 people with ME/CFS and 91 healthy individuals. They found that ME/CFS patients had lower levels of a certain type of bacteria Faecalibacterium prausnitzii than those without the condition. Additionally, levels of these bacteria were associated with fatigue, with lower levels being associated with more severe symptoms.
However, the second study, led by researchers at the Jackson Laboratory, was far more intriguing. The team analyzed blood and stool samples from 149 ME/CFS patients and 79 healthy people. Unlike the other study, the researchers chose to classify the sick patients as either short- or long-term ME/CFS based on whether they were diagnosed within the past four years or more than 10 years ago. Julia Oh, a genomics medicine researcher at the Jackson Laboratory who led the study, told The Daily Beast in an email that ME/CFS can look very different to different people and the researchers wanted to see how the chronic disease presented people had something to do with its duration.
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What they found was startling. Originally, ME/CFS was associated with transient disturbances in the gut microbiome. Over time, the microbiome recovered, but other health and metabolic issues persisted. The researchers found that these problems were reflected in both the people’s blood counts and their symptoms. Long-term patients had higher cholesterol levels and were more likely to report fibromyalgia, constipation, and trouble sleeping; On the other hand, people with a recent ME/CFS diagnosis were more likely to report loss of appetite, which the researchers say is consistent with gastrointestinal disorders.
Both studies are correlative, meaning that these microbiome changes may not cause ME/CFS symptoms, but may actually be a consequence of the chronic disease.
Still, Oh and her team have a theory about how all the pieces fit together. First, a person with ME/CFS can lose beneficial bacteria and other microbes. Then their out-of-balance microbiome can have “cumulative and long-term effects where damage can be caused by an initial trigger, leading to cascading events,” Oh said. Even when the initial disorder is restored, a person’s metabolism can be permanently altered. Now that more and more evidence suggests links to the gut microbiome, researchers can investigate whether giving prebiotics or probiotics to people with ME/CFS could help relieve symptoms and reverse metabolic changes.
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Because there are no approved laboratory tests to diagnose ME/CFS, Oh hopes her team’s method will help in future diagnosis of the disease because it was very accurate in distinguishing between patients and controls in the study. Still, she added, future research needs to compare the microbiomes and metabolites of ME/CFS patients to those with similar conditions, such as fibromyalgia.
Understanding ME/CFS, in turn, will shed light on other poorly understood chronic diseases – both by identifying common disease-causing pathways and by demonstrating the benefits of separating patient populations into short- and long-term cohorts.
“The approaches taken here could be followed over a long COVID hiatus” to help scientists and patients find answers they desperately want, Oh said.
Read more at The Daily Beast.
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