Study reveals the potential of gut bacteria-derived metabolites, such as 4-hydroxyindole, to revolutionize endometriosis diagnosis and treatment, paving the way for microbiota-based therapies.
Study: Identification of distinct stool metabolites in women with endometriosis for non-invasive diagnosis and potential for microbiota-based therapies. Image Credit: Kateryna Kon / Shutterstock
In a recent study published in the journal Med, researchers in the United States identified a distinct stool metabolite signature and explored potential non-invasive diagnostic methods by combining gut microbiome and metabolomic signatures in fecal samples from women with endometriosis.
Background
Endometriosis is a leading cause of infertility in women. In endometriosis, the endometrium extends beyond the uterus into the peritoneal space. These ectopic endometriotic lesions give rise to pelvic pain and inflammation. These symptoms increase the disease burden, worsened by delayed diagnosis.
Current diagnostic methods like exploratory laparoscopy are invasive and less accessible for routine screening. The clinical management of endometriosis remains a challenge, with no known cure. Despite surgical removal of the ectopic endometrium, symptoms often recur in up to 75% of cases.
The gut microbiome is a primary factor that shapes the peritoneal region. Human gut bacteria convert nutrients into active metabolites that regulate inflammation.
According to the "leaky gut" hypothesis, microbial imbalance in the gut enhances inflammatory processes in the endometriotic lesions and promotes their growth. Studies have reported altered gut microbial profiles in women with endometriosis.
Metronidazole antibiotic treatment can prevent the progression of endometriosis in animal models. Research also indicates that short-chain fatty acids (SCFA) produced by gut microbes protect against endometriosis. However, these findings pertain to murine models. Further research is warranted to enable clinical translation to human subjects.
About the study
In the present study, researchers investigated microbiome-metabolome features that distinguish women with and without endometriosis. They determined the influence of gut bacteria-derived metabolites on endometriosis development.
Researchers collected fecal samples from 18 female endometriosis patients and 31 controls. The samples underwent 16S bacterial sequencing to determine the microbiome signature of endometriosis. Unbiased metabolomics evaluated the condition’s metabolomic characteristics.
The team conducted functional studies for selected microbiome-derived metabolites in vitro using patient-derived cells. Liquid chromatography-mass spectrometry (LC-MS) confirmed the metabolite levels.
The researchers used mice xenotransplanted with immortalized human endometriotic cells expressing luciferase for in vivo analysis. They evaluated the impact of gut metabolites on the initiation, development, and progression of endometriotic lesions in the mice. To induce endometriosis, endometrial fragments were injected into the peritoneal space of recipient mice. Subsequently, they administered metabolites orally daily over two weeks.
Ki-67 expression indicated cell proliferation in the endometriotic lesions. F4/80 macrophage staining and flow cytometric assessment of peritoneal lavage assessed immune infiltration.
A reduction in the intensity of bioluminescent signals up to four weeks after metabolite treatment indicated lesion regression.
Nuclear factor kappa B (NF-κB), interleukin-6 (IL-6), arginase-1 (Arg1), insulin-like growth factor-1 (IGF-1), and transforming growth factor beta (TGF-β) gene expression indicated the extent of inflammation.
Alpha diversity, measured by the Simpson index, and beta diversity, assessed by UniFrac distance, revealed differences in bacterial composition between groups. Taxonomic comparisons revealed differences in bacterial abundance. Quantitative polymerase chain reaction (PCR) confirmed the bacterial counts. Partial least squares discriminant analysis (PLS-DA) and variable importance in the projection (VIP) scorings identified metabolites distinct in endometriosis patients.
Results
The researchers identified a unique bacteria-derived metabolite signature associated with endometriosis. The participants’ fecal metabolite profile showed altered purine metabolism, which correlated strongly with inflammatory bowel disease (IBD), a comorbidity often found in women with endometriosis.
The team detected altered gut bacteria-derived metabolites that could enable non-invasive diagnosis of endometriosis. One such metabolite is 4-hydroxyindole (4HI). Endometriosis patients had reduced 4HI levels in their fecal samples. 4HI treatment suppressed endometriosis-related pain and inflammation in murine models. Moreover, it prevented the development and progression of endometriotic lesions and promoted their regression. The metabolite reduced lesion mass, volume, epithelial thickness, cell viability, proliferation, immune infiltration, and the number of endometrial glands.
Researchers identified several biomarkers that may enable non-invasive diagnosis of endometriosis. These included not only 2’-deoxyadenosine, linoleic acid, and N-formyl-L-methionine, but also cytosine, adenosine, and adenine.
The team also identified reduced alpha diversity and significantly deviated beta diversity in the gut microbiomes of endometriosis patients. Endometriosis patients showed reduced abundances of Dorea, Faecalibacterium, Ruminococcus, Roseburia, and Alistipes.
In contrast, the counts of Bacteroides, Streptococcus, Actinomyces, Erysipelatoclostridium, Tyzzerella, and Lacticaseibacillus increased. There were strong correlations of 4HI with bacterial organisms like Faecalibacterium, Dorea, and Lachnospiraceae among endometriosis patients.
The study findings reveal a distinct fecal metabolite profile of endometriosis patients, which could enable the development of a noninvasive diagnostic method for the condition.
Future studies could investigate the therapeutic potential of the gut microbiome-derived metabolite 4HI in endometriosis. 4HI is abundant in the healthy gut, and restoring its levels in endometriosis patients may improve the condition and lower the disease burden. This discovery paves the way for microbiota-based therapies and innovative diagnostic tools.