Gut bacteria imbalance ‘linked to chronic fatigue syndrome'
Patients recently diagnosed with chronic fatigue syndrome have reduced levels of certain types of gut bacteria that support digestive health, research suggests.
Scientists in the US have also found that patients living with the condition, also known as myalgic encephalomyelitis (ME/CFS), for 10 years or longer have differences in blood metabolites – substances made or used when the body breaks down food – compared to those without the disease.
The researchers said their work, published in two separate papers in the journal Cell Host & Microbe, only shows a “correlation, not causation, between these microbiome changes and ME/CFS”.
Julia Oh, an associate professor at the Jackson Laboratory in the US and senior author of one of the two papers, said: “These findings are the prelude to many other mechanistic experiments that we hope to do to understand more about ME/CFS and its underlying causes.”
ME/CFS is usually a long-term condition with a wide range of symptoms, the most common one being extreme tiredness.
This condition can affect anyone, including children, but is more common in women, and tends to develop between the sufferer’s mid-20s and mid-40s.
It is estimated there are more than 250,000 people in England and Wales with ME/CFS.
While there is currently no cure for the disease, there are treatments that may help manage the condition.
For the study, the researchers used a technique known as shotgun metagenomics sequencing, which allowed them to sample all the genes in all the organisms found in a complex environment, such as the gut microbiome.
The scientists focused on 74 patients with “short-term” ME/CFS – diagnosed in the previous four years, and 75 “long-term” patients – with symptoms for more than 10 years.
The researchers analysed their stool and blood samples and compared these to the samples taken from 79 healthy volunteers.
Among patients who were recently diagnosed with the disease, the researchers found reduced levels of bacteria in the gut that produce butyrate – a key nutrient aiding digestive health.
Butyrate also is the main energy source for colon cells and has other health benefits, such as supporting the immune system.
In contrast, the researchers found that those with long-term disease had gut bacteria that had re-established and were more similar to the healthy controls.
But those participants had accumulated a number of changes in the metabolites in their blood plasma, including many of those related to the immune system, they added.
Patients with long-term ME/CFS were also found to have differences in levels of certain types of immune cells compared with the healthy controls.
The experts said further research is needed to provide direct evidence that gut bacteria influence chronic symptom presentation.
Commenting on the study, Professor Chris Ponting, principal investigator at the MRC Human Genetics Unit, Institute of Genetics and Cancer and Investigator on the DecodeME project, University of Edinburgh, said: “The two microbiome studies are large in scale and ambition, seeking to link changes in gut bacteria to the terrible symptoms experienced by millions of people with ME/CFS worldwide.
“As the authors themselves note, they’re unable to tell whether any bacterial changes cause, or else are downstream consequences of, ME/CFS.
“This crucial question deserves future experiments that perturb these bacteria in predictable and long-lasting ways.”