Fibromyalgia and microflora

The composition of the intestinal microbiome has changed with fibromyalgia

Ekaterina Rusakova, N+1

Doctors have found that the composition of the intestinal microbiome changes in women suffering from fibromyalgia, according to an article published in the journal Pain (Minerbi et al., Altered microbiome composition in individuals with fibromyalgia). Scientists cannot yet say whether this change is only a marker of the disease, or whether microorganisms affect its occurrence and development. But they, at least, have found a potential method for diagnosing fibromyalgia, since there is no single way to diagnose it today.

Fibromyalgia is a chronic symmetrical musculoskeletal pain that is not accompanied by inflammation or damage to internal organs. Other symptoms of the disease are sleep and memory disorders, it can be accompanied by depression, chronic fatigue syndrome, migraines. It is estimated that 2-8 percent of the world's population suffers from fibromyalgia, the vast majority of them are women. There is no single test to diagnose the disease; I usually diagnose it by the combination of symptoms and the absence of other possible causes of pain. The causes of the disease are unknown, although sometimes it begins after an injury, surgery or severe psychological stress. Possible causes are hypersensitivity to pain, genetic factors preceding the onset of the disease sleep disorders.

In recent years, it has become clear that the intestinal microbiome affects the occurrence and development of a number of diseases, including cardiovascular, mental, neurological, oncological. As recent studies have shown, the intestinal microbiome can influence the occurrence of visceral (i.e. related to internal organs) and chemotherapy-induced neuropathic pain. Scientists from the McGill University Health Center of Canada, led by Amir Minerbi, suggested that the intestinal microbiome may also play a role in the occurrence of fibromyalgia – which means that its composition will change.

To test this assumption, doctors invited 156 volunteers for the study. In the experimental group there were 77 patients of the Health Center 30-60 years old suffering from fibromyalgia, in the control group there were 79 people. 11 of them were mothers, daughters or sisters of patients who were invited as genetic control; the other group included 28 family members of patients of both sexes aged 30-70 years, as control of the environment of patients. The third group consisted of 48 healthy women aged 30-60 years. Fecal samples were taken from all participants of the experiment and the composition of the intestinal microbiome was determined by sequencing bacterial genomes and subsequent metagenomic phylogenetic analysis and analysis of the 16S RNA gene, which allow us to identify groups of bacteria in the mixture.

It turned out that in women suffering from fibromyalgia, the composition of the intestinal microbiome really changed. 19 groups of bacteria were found in their intestines in greater or lesser numbers than in women from the control group (p<0.05). The number of Clostridium scindens, bacteria that are associated with the suppression of the growth of pathogenic Clostridioides difficile and Parabacteroides merdae, microorganisms that help break down plant polysaccharides, has changed the most. There were more of them in women suffering from fibromyalgia. And the bacteria Prevotella copri and Bacteroides uniformis, which are often found in patients with rheumatoid arthritis, on the contrary, have become fewer.

The types of bacteria that were found in greater numbers in fibromyalgia sufferers (left) and healthy women (right). Figure from the article by Minerbi et al.

Also, the number of microorganisms involved in the metabolism of butyric and propionic acids has changed in the patients. Butyric acid is produced in the intestine and affects intestinal homeostasis, produces antimicrobial substances (as well as propionic acid) and stimulates the immune system. The authors of the article analyzed the concentration of salts of both acids in blood plasma and found that in women suffering from fibromyalgia, the amount of butyric acid became greater compared to the control group (p=0.005), and the amount of propionic acid was less (p=0.006).

However, according to the researchers, fibromyalgia will now be easier to diagnose. "We sorted a large amount of data and identified 19 species [of bacteria], the number of which in people with fibromyalgia either decreased or increased," says one of the co–authors of the study Emmanuel Gonzalez (Emmanuel Gonzalez) from McGill University. "Using only machine learning, our computer was able to diagnose fibromyalgia with 87 percent accuracy only based on the composition of the microbiome. When we can back up the first results with a large number of studies, I hope we will be able to increase the accuracy of diagnosis..."

It is not yet known how the intestinal microbiome affects (and whether it affects at all) chronic pain in fibromyalgia. But recently it turned out that changing its composition affects tolerance to painkillers, in particular to opioids. Researchers have shown in mice that lactic acid and bifidobacteria increase addiction to morphine.

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