Researcher receives grant to study how changes in gut bacteria could lead to obesity-related disorders

Andrew Gewirtz, a professor in the Institute for Biomedical Sciences at Georgia State University, has received a four-year, $1.8-million federal grant to study how changes in intestinal bacteria could lead to obesity and metabolic syndrome.

The United States is facing an epidemic of obesity-related disorders, including high blood pressure, high blood sugar, insulin resistance, hyperlipidemia (too many fats in the blood) and hepatic steatosis (a buildup of fat in the liver), which are collectively referred to as metabolic syndrome. Metabolic syndrome increases a person's risk of heart disease, diabetes and stroke.

Gewirtz is examining the role of gut microbiota, the diverse bacteria that normally inhabit the intestinal tract, in these diseases. Previous studies show if healthy bacteria aren't maintained in the intestine, the imbalance can result in metabolic syndrome. The grant is funded by the National Institute of Diabetes and Digestive Kidney Diseases of the National Institutes of Health.

"The overall goal of the project is to understand how alterations in bacteria in the intestine can promote low-grade inflammation and metabolic diseases, including obesity," Gewirtz said. "Additionally, we're going to be looking at how changes in diet can protect against obesity, especially how dietary fiber can alter gut bacteria in a beneficial way."

Of the project's three aims, the first is to test whether previous findings from mice studies apply to human metabolic syndrome. Gewirtz will investigate the extent to which metabolic syndrome is linked to alterations in gut microbiota that drive low-grade inflammation. The second aim is to understand how an altered microbiota actually promotes inflammation and how to protect the liver against low-grade inflammation and non-alcoholic fatty liver disease. The third aim is to examine how dietary fiber can affect the microbiota and protect against obesity. The second and third aims will be tested in mice.

"We're comparing different types of fiber," Gewirtz said. "In simple terms, you could think of fiber as being insoluble, simply just passing through and providing bulk, or fiber that can be metabolized by bacteria, which is called soluble or fermentable fiber. Our preliminary results indicate that these have very different types of effects."

Both soluble and insoluble fiber are sold in stores, and they're either found naturally in foods or added in, he said.

"Hopefully in the end we'll have a better understanding of what type should be consumed, for fibers that are naturally in foods or as supplements," Gewirtz said.