Current understanding of the connection between endometriosis and intestinal microbiocenosis: a literature review

Abstract

Endometriosis is a complex condition that affects at least 10% of women in their reproductive years worldwide. It is characterized by persistent pelvic pain, dysmenorrhea, impaired pelvic organ function, infertility, and psychological distress. Alarmingly, about 30% of patients experience a recurrence of the disease even after receiving full treatment. Given the urgent nature of this problem, extensive studies are regularly conducted to investigate the various factors that contribute to the development of endometriosis. One area of particular interest is the relationship between the condition and changes in the intestinal microflora. Research suggests that endometriosis is primarily associated with a decrease in the number of Lactobacillus bacteria and an increase in the presence of potentially harmful flora, including Enterobacteriaceae, Bifidobacterium, Parabacteroides, Proteobacteria, Actinobacteria, Cyanobacteria, Saccharibacteria, Fusobacteria etc. Furthermore, there is a focus on the ratio of Firmicutes to Bacteroidetes. Such dysbiosis leads to abnormal cytokine expression and immune cell dysfunction, ultimately resulting in chronic inflammation. A correlation has been found between changes in the intestinal microflora in endometriosis and an increase in the levels of TNF-α, NF-κB, and IL-8. Additionally, the condition has been linked to factors related to apoptosis (Fas and Bax), proliferation (epidermal growth factor), and angiogenesis (VEGF). Another significant aspect is the role of the intestinal microbiota in the breakdown of estrogen. Enzymes such as β-glucuronidase and β-glucosidase, secreted by the microbiota, contribute to the breakdown of estrogen and subsequently increase the levels of free estrogen in the bloodstream. This increase in free estrogen is believed to play a role in the development of endometriosis by promoting the proliferative activity of endometrial cells. It further confirms the significance of intestinal dysbiosis in the pathogenesis of the disease. However, despite these findings, additional research is still required to fully understand the mechanisms behind the development of endometriosis.