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What Mice — And Their Gut Bacteria — Teach Us About Lupus

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Right now, gut bacteria are having their moment in the media spotlight; they’re being discussed everywhere from the The New York Times to probiotic yogurt commercials.

And it’s with good reason.

Dr. Michele Kosiewicz is a researcher in the University of Louisville’s Department of Microbiology and Immunology. She said medical professionals recognize the natural bacteria in our guts, known also as our flora or microbiota, have a lot of different functions.

“For example, there are a number of different vitamins that we actually get through the metabolism of different chemicals in the gut — vitamin K, B-12, all the Bs,” Kosiewicz said.

She continues: “The bacteria in the gut are responsible for the breakdown of non-digestible fibers — we can’t do that ourselves, so we need them. They synthesize some of the building blocks for proteins and all the different molecules, and they can even metabolize lipids.”

But perhaps most interestingly in the context of Kosiewicz’s research, these natural bacteria also impact how the body’s immune system responds — so when our gut bacteria are out of balance, it can impact how our bodies deal with disease or certain autoimmune disorders.

Knowing this, she became interested in seeing if male and female mice that are genetically programmed to develop lupus actually have different gut bacteria — especially since lupus is an autoimmune condition that predominantly affects women. (Men only comprise 4 to 18 percent of those diagnosed with the disease).

In Kosiewicz’ lab at U of L, they found that the gut bacteria of young male and female mice are very similar.

But once the mice age, they observed changes in the male’s microbiota — so she decided to transplant some of the gut bacteria from the male mice into the female mice.

“And we markedly increased survival,” she said. “We were able to dramatically decrease disease.”

This is a big deal because it means there is something in the male mouse microbiota that serves as some kind of protectant against lupus.

There are a lot factors that could explain why the male mouse microbiota is different — potentially including elevated levels of testosterone; figuring that out is a next step in their research.

Kosiewicz’s team has also now identified about 90 compounds produced by gut microbes that differ in males and females, which could have implications for human lupus treatment.

“That’s why we are really interested in the chemical product that the bacteria are making, because that is certainly something that could certainly be developed into a therapeutic of sorts,” Kosiewicz said.