F. prausnitzii : a biomarker of chronic fatigue syndrome

Chronic fatigue syndrome, also known as myalgic encephalomyelitis (ME/CFS), is characterized by symptoms such as exhaustion, post-exertional malaise, memory problems, pain, gastrointestinal disturbances, immune abnormalities, and sleep disorders. Even though it affects between 0.4% and 2.5% of the world’s population, mainly adult women aged between 20 and 40 years, this debilitating chronic disease remains poorly understood. However, scientists are studying the role of gut-brain communications ¹ in the disease and in particular the involvement of the gut microbiota. By focusing on changes in the microbiota, two recent studies published in the journal Cell Host & Microbe ^2,3 have sought to better understand the disease and identify potential biomarkers.

The potential role of butyrate-producing bacteria

In the first study, metagenomic and metabolomic analyses were performed on fecal samples collected from 106 patients and 91 healthy controls living in 5 US states. The study highlights a major gut dysbiosis in CFS patients, with differences between the two groups in terms of gut microbiome diversity, abundance, functional biological pathways, and interactions. Specifically, Faecalibacterium prausnitzii and Eubacterium rectale, two beneficial butyrate-producing bacteria, were depleted in those suffering from chronic fatigue. Further analyses confirmed a lower synthesis of bacterial butyrate in the CFS patients. Moreover, the more F. prausnitzii was depleted, the more severe the fatigue.

Short-term patients vs. long-term patients

The second study, also US-based, included 149 patients and 79 healthy controls, and further distinguished two groups among the patients: 75 patients who had been ill for less than 4 years and 74 patients who had been ill for more than 10 years. Here again, the researchers found a major gut dysbiosis, especially in the short-term patients, with depleted levels of F. prausnitzii. The gut microbiota composition of the long-term patients was closer to that of the healthy controls (with some notable differences in terms of low abundance species and heterogeneity), suggesting a return to relative homeostasis.

On the other hand, these long-term patients presented more severe clinical symptoms and a more greatly altered metabolism than the other patients, including at immune system level. The researchers thus suggest that chronic fatigue may begin with a loss of beneficial bacteria, particularly those that produce butyrate, which then leads to metabolic changes in the host. In some individuals, these modifications may lead to irreversible metabolic and phenotypic changes and thus to an altered state of health over the long term.