Bidirectional relationships between the gut microbiome and sexual traits

The human gut microbiota is known to be shaped by a variety of environmental factors (diet, drugs, geography, and sanitation) and host intrinsic factors (age and sexual development). The differences in gut microbiota between sexes are minimal before adulthood and late adulthood, and marked during adulthood. For instance, consistent higher relative abundances of Akkermansia and Ruminococcus have been observed in adult women compared with men and most studies have found higher relative abundances of Prevotella and Fusobacterium (linked to a diet rich in animal proteins) in adult men compared with women. The gut microbiota taxonomy and functionality present in women is more similar to men once reached the menopause. In fact, specific taxa have been associated with the levels of different sexual hormones and their precursors in blood. The gut microbiota composition and circulating testosterone levels are also tightly linked to the extent that microbial signatures can predict its levels in blood. At the same time, the gut microbiota participates in the metabolism of sexual hormones, with some bacteria being able to metabolize gonadal steroid hormones (one example is 3b-hydroxysteroid dehydrogenase, a testosterone degrading enzyme). In summary, the relationships between the gut microbiome and sexual traits are bidirectional. In addition, other phenotypes and cultural gender-related factors could drive sex-related differences. It is important to note that other members of the microbiome (Archaea, viruses, and fungi) have been largely unexplored in relation to this sexual dimorphism. More research is needed on this topic.

Automated summary

The composition of the human gut microbiota is influenced by environmental and host factors, including diet, drugs, geography, sanitation, age, and sexual development. The impact of gender on the gut microbiota is minimal before and after adulthood, but significant during adulthood. Adult women have higher abundances of certain bacteria in their gut microbiota compared to men, while adult men have higher abundances of other bacteria, particularly associated with a diet rich in animal proteins. The gut microbiota of women becomes more similar to men after menopause. The gut microbiota is also linked to the levels of sexual hormones and their precursors in blood, and can participate in the metabolism of these hormones.