SDSU researcher examines link between gut bacteria and metabolic disease

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SDSU researcher examines link between gut bacteria and metabolic disease

by Adriana Millar, Staff Writer

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A new study conducted by a San Diego State professor suggests a link between gut bacteria and metabolic disorders, which often occur with polycystic ovary syndrome (PCOS).

Gut bacteria are microbes that influence immune responses in the body, among other functions, and metabolic disorders are abnormal chemical reactions in the body.

Lead researcher and biology professor Scott Kelley collaborated with UC San Diego researcher Varykina Thackary in a study published in multidisciplinary journal PLOS ONE in January.

Previous studies have found links between gut bacteria and metabolic disorders like obesity and diabetes, which are also common symptoms of PCOS, Kelley said.

“So we thought well, let’s look at this syndrome, because this is a major complaint with women with PCOS,” Kelley said.

PCOS is a hormonal disorder that affects about 10 percent of women globally, according to SDSU NewsCenter.

Women with PCOS commonly have increased levels of testosterone, menstrual cycle irregularity and cysts on the ovaries, which lead to high rates of infertility.

“In the public’s mind it’s something you can potentially have when you’re infertile, but what we’re interested as well is what are the other risks that are associated with this disorder,” Thackary said. “There’s actually a pretty high risk for disruption of your metabolism, which then leads to increased risk of diabetes and heart disease, and some other diseases as well.”

The study used a mouse model developed by Thackary, who is part of UCSD’s Department of Reproductive Medicine.

Half of the mice in the study were given the drug letrozole, which inhibits the the conversion of testosterone to estrogen, Kelley said. The other half were given a placebo.

“(Letrozole) inhibits this enzyme that does the conversion, and (the mice) get almost all the symptoms of PCOS,” Kelley said. “It seems like an excellent model of human PCOS.”

The study found that mice with letrozole had much higher rates of obesity and blood glucose levels.

The study also found that mice with the placebo had much higher diversity in gut bacteria than the letrozole group.

“After one week you see huge changes in the gut microbiome,” Kelley said. “Microbiome is all the microbes in a biome, in this case the gut.”

Thackary said the study demonstrates that there is an association between the mouse model of PCOS and altered gut microbiome.

“So if the mice have this PCOS syndrome, they have a different microbiome than control mice,” Thackary said.

Although the study found a strong correlation between gut bacteria and the symptoms of PCOS, the next step is discovering whether the gut bacteria is causative, Kelley said.

“It’s kind of like the chicken and the egg question: Does the change in the microbiome happen because of what PCOS has done to the body, or is it possible that the change in the microbiome has caused some of the symptoms of PCOS that we observed?” Thackary said.

Kelley and his collaborators are currently working to see if the gut bacteria is causative.

“So we have a lot of evidence that it’s looking like the microbes could play a role, but how do you prove that?” he said.

“So the next thing we’re going to do is just change the microbes, and not the drug.”

Kelley said the current data suggest it is transferable if microbes are changed.

“We have a lot more data to collect and have to some analysis, but it’s looking really good actually,” he said.

Thackary said the team hopes to be able to treat metabolic disorders in the future. Right now there is no cure for PCOS.

“If we can figure out what in the microbiome is responsible for the effect, then potentially we could figure out how to treat it or prevent this effect basically,” she said.

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