Maryland, USA: As many as 2.5 million Americans live with myalgic encephalomyelitis/chronic fatigue syndrome, or ME/CFS for short. It’s a serious disease that can often arise after an infection, leaving people profoundly ill for decades with pain, cognitive difficulties, severe fatigue, and other debilitating symptoms.
Because ME/CFS has many possible causes, it doesn’t affect everybody in the same way. That’s made studying the disease especially challenging. But NIH is now supporting specialized research centers on ME/CFS in the hope that greater collaboration among scientists will cut through the biological complexity and reveal answers for people with ME/CFS and their families.
So, I’m pleased to share some progress on this research front from two NIH-funded ME/CFS Collaborative Research Centers. The findings, published in two papers from the latest issue of the journal Cell Host & Microbe, add further evidence connecting ME/CFS to distinctive disruptions in the trillions of microbes that naturally live in our gastrointestinal tracts, called the gut microbiome [1,2].
Right now, the evidence establishes an association, not direct causation, meaning more work is needed to nail down this lead. But it’s a solid lead, suggesting that imbalances in certain bacterial species inhabiting the gut could be used as measurable biomarkers to aid in the accurate and timely diagnosis of ME/CFS. It also points to a possible therapeutic target to explore.
The first paper comes from Julia Oh and her colleagues at The Jackson Laboratory, Farmington, CT, and the second publication was led by Brent L. Williams and colleagues at Columbia University, New York. While the causes of ME/CFS remain unknown, the teams recognized the disease involves many underlying factors, including changes in metabolism, immunity, and the nervous system.
Earlier studies also had pointed to a role for the gut microbiome in ME/CFS, although those studies were limited in their size and ability to tease out precise microbial differences. Given the intimate connections between the microbiome and immune system, the teams behind these new studies set out to look even deeper into the microbiome in larger numbers of people with and without ME/CFS.
At the Jackson Laboratory, Oh, Derya Unutmaz, and colleagues joined forces with other ME/CFS experts to study microbiome abnormalities in different phases of ME/CFS. They matched clinical data (the medical history) with fecal and blood samples (the biological history) from 149 people with ME/CFS, including 74 who had been diagnosed within the previous four years and another 75 who had been diagnosed more than a decade ago. They also enlisted 79 people to serve as healthy volunteers.
Their in-depth microbial analyses showed that the more short-term ME/CFS group had less microbial diversity in their guts than the other two groups. This suggested a disruption, or imbalance, in a previously stable gut microbiome early in the disease. Interestingly, those who had been diagnosed longer with ME/CFS had apparently re-established a stable gut microbiome that was comparable to the healthy volunteers.
Oh’s team also examined detailed clinical and lifestyle data from the participants. Combining this information with genetic and metabolic data, they found that they could accurately classify and differentiate ME/CFS from healthy controls. Through this classification approach, they discovered that individuals with long-term ME/CFS had a more balanced microbiome but showed more severe clinical symptoms and progressive metabolic irregularities compared to the other two groups.
In the second study, Williams, Columbia’s W. Ian Lipkin, and their collaborators also analyzed the genetic makeup of gut bacteria in fecal samples from a geographically diverse group of 106 people with ME/CFS and another 91 healthy volunteers. Their extensive genomic analyses revealed key differences in microbiome diversity, abundance, metabolism, and the interactions among various dominant species of gut bacteria.
Of particular note, Williams team found that people with ME/CFS had abnormally low levels of several bacterial species, including Faecalibacterium prausnitzii (F. prausnitzii) and Eubacterium rectale. Both bacteria ferment non-digestible dietary fiber in the GI tract to produce a nutrient called butyrate. Intriguingly, Oh’s team also uncovered changes in several butyrate-producing microbial species, including F. prausnitzii.
Further detailed analyses in the Williams lab confirmed that the observed reduction in these bacteria was associated with reduced butyrate production in people with ME/CFS. That’s of special interest because butyrate serves as a primary energy source for cells that line the gut. Butyrate provides those cells with up to 70 percent of the energy they need, while supporting gut immunity.
Butyrate and other metabolites detected in the blood are important for regulating immune, metabolic, and endocrine functions throughout the body. That includes the amino acid tryptophan. The Oh team also found all ME/CFS participants had a reduction in gut microbes associated with breaking down tryptophan.
While butyrate-producing bacteria were found in smaller numbers, other microbes with links to autoimmune and inflammatory bowel diseases were increased. Williams’ group also reported an abundance of F. prausnitzii was inversely associated with fatigue severity in ME/CFS, further suggesting a possible link between changes in these gut bacteria and disease symptoms.
It is exciting to see this more-collaborative approach to ME/CFS research starting to cut through the biological complexity of this disease. More data and fresh leads will be coming in the months and years ahead. It is my sincere hope that they bring us closer to our ultimate goal: to help the millions of people with ME/CFS recover and reclaim their lives from this terrible disease.
I should also mention later this year on December 12-13, NIH will host a research conference on ME/CFS. The conference will be held in-person at NIH, Bethesda, MD, and virtually. It also will highlight recent research advances in the field. The NIH will post information about the conference in the months ahead. Be sure to check back, if you’d like to attend.
by Lawrence Tabak, D.D.S., Ph.D
