Researchers who studied a mouse model of polycystic ovary syndrome (PCOS) find that changes in gut bacteria are closely linked to obesity and signs of type 2 diabetes.
PCOS can affect a woman’s ability to produce eggs and is associated with insulin resistance, which is characteristic in type 2 diabetes. Women with PCOS therefore have a higher risk of developing type 2 diabetes.
Weight gain can also be a contributing factor to PCOS, and studies in recent years have found that people with obesity or type 2 diabetes tend to have different bacteria in their guts compared to healthy people.
This new study, conducted by researchers at San Diego State University (SDSU) and the University of California, aimed to investigate if women with PCOS have similar changes in gut bacteria.
Lead author Scott Kelly, a biologist at SDSU, and colleagues experimented on mouse models of PCOS which was induced by the drug letrozole. Letrozole blocks the conversion of testosterone into estrogen and results in a condition called hyperandrogenism, which develops in roughly 80 per cent of women with PCOS.
One group of mice received letrozole and a second group were given placebo. Both groups ate the same diet. After five weeks, the letrozole group had gained significantly more weight than the control group and had higher blood glucose levels, which is linked with insulin resistance.
The researchers then collected fecal pellets from the mice and analysed bacterial DNA to observe any changes in gut bacteria. The pellets of the letrozole group had a lower number of different bacterial species.
Kelley said: “At first, things started out the same in the letrozole and control groups. But rapidly, the gut bacterial communities as a whole diverged. In fact, the letrozole mice just stayed the same over the course of the study. The diversity of the gut bacteria didn’t go up with age, whereas the control mice got more and more diverse over time.”

The findings suggest that gut bacteria changes can affect development of PCOS independently of diet, and that controlling the gut microbiome could help treat metabolic disorders associated with PCOS.
However, the researchers stressed that they cannot be sure if the mice that gained weight in the letrozole group did so because of bacterial changes, or if weight gain was the cause of the changes.
“The good part about this study is that we can increase our understanding not only of women’s health but also our biology in general and how we might control the gut microbiomen,” Kelley concluded.
The study is published in the journal PLOS ONE.

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