Gut Bacteria Less Diverse in PCOS; Could Probiotics Be a Therapy?

Nancy A Melville

January 24, 2018

Women with polycystic ovary syndrome (PCOS) have significantly less diversity in their gut microbiomes compared with healthy women, and these reductions are associated with hyperandrogenism, a new study shows.

The results were published online January 23 in the Journal of Clinical Endocrinology & Metabolism.

"Our findings suggest testosterone and other androgen hormones may help shape the gut microbiome," says senior author Varykina G Thackray, PhD, of the University of California San Diego School of Medicine, La Jolla, in a press statement issued by the Endocrine Society.

"These changes may influence the development of PCOS and the impact it has on a women's quality of life."

Metabolic conditions including obesity and diabetes have been shown to be associated with reductions in the diversity of gut bacteria, and the latter is now acknowledged to play a key role in human health. With these metabolic conditions highly prevalent in women with PCOS, researchers sought to evaluate gut microbiota diversity in women with the syndrome.

"In terms of the gut microbiome, it is possible that decreased bacterial diversity results in changes in gut function that could exacerbate diseases including PCOS, though much work remains to be done to understand how changes in the gut microbiome influence host physiology," they say.

Nevertheless, future studies to determine whether specific gut bacterial species play a causative role in PCOS will "be important in determining whether probiotics are a treatment option for PCOS," they note.

Hirsutism and Testosterone Linked to Less Diversity in Gut Microbiome

For their study, researchers analyzed fecal swabs from 73 women diagnosed with PCOS recruited at the Poznan University of Medical Sciences in Poland and compared them with swabs from 48 healthy women and 42 women who had polycystic ovarian morphology (PCOM) but lacked other diagnostic criteria of PCOS.

The results showed significantly lower alpha diversity, which describes overall species richness, among women with PCOS compared with healthy women in terms of abundance (P = .04) and phylogenetic diversity (P = .02).

Alpha diversity was also lower in women with PCOM compared with healthy women, however, the levels were not significantly reduced.

The women with PCOM nevertheless showed an "intermediate phenotype" of gut microbiome alpha diversity, "suggesting that further studies are warranted to determine whether the gut microbiome of women with PCOM is significantly altered compared to healthy women," the authors say.

Total testosterone and hirsutism were meanwhile each negatively associated with alpha diversity, while hyperandrogenism strongly correlated not only with alpha, but with beta diversity (P = .0009). The latter relates to changes in the composition of the microbial community, as opposed to changes in overall species richness (alpha diversity).

Do Treatments for PCOS Alter the Gut Microbiome?  

The authors note that their findings are consistent with other research published in the past year. In one study, published in PLOS One (2017;12;e0168390), evaluation of stool samples of 24 patients with PCOS and 19 healthy controls also showed lower gut microbiome diversity and an altered phylogenetic profile in women with PCOS.

Another study, published in Frontiers of Microbiology (2017;8:324), evaluated the overall composition of gut microbiota in women with PCOS and interestingly showed an altered gut microbial pattern in nonobese women with PCOS, as well as obese women with PCOS, compared with nonobese healthy controls.

Speaking about their current study, researchers note that body mass index (BMI) and insulin resistance were not found to correlate with changes in alpha or beta diversity of gut bacteria, although they note a possible limitation could be that the average BMI of women in their trial was relatively low, at about 24 kg/m2.

"Further sampling of the gut microbiome of obese women with or without PCOS could address whether obesity and insulin resistance influence the gut microbiome in women with PCOS."

And if hyperandrogenism drives the microbial composition of the gut, "it would be interesting to determine if treatment of PCOS with androgen antagonists or oral contraceptives results in recovery of the gut microbiome and improvement of the PCOS metabolic phenotype," they note.

Overall, "our findings suggest that androgens may be an important factor in shaping the gut microbiome, and that changes in the gut microbiome may influence the development and pathology of PCOS."

However, "given the variation in the human gut microbiome, large clinical cohorts will likely be needed to address these questions," including the issue of whether probiotics play a role in treatment, they conclude.

The study was funded by the National Institute of Child Health and Human Development through a cooperative agreement as part of the National Centers for Translational Research in Reproduction and Infertility. The authors have reported no relevant financial relationships.

J Clin Endocrinol Metab. Published online January 23, 2018. Full article

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