A new study led by Ohio State University researchers suggests a connection between air pollution and diabetes.

The study, published online today in the journal Circulation, reports that dirty air makes fat mice more likely to get diabetes and raises questions about how closely pollution and Type 2 diabetes are linked in humans.

The study found that air pollution exaggerates insulin resistance and fat inflammation in overfed mice exposed to either filtered air or dirty air for six months.

All the mice were fed a fast-food diet before the experiment to make them obese, said lead researcher Dr. Sanjay Rajagopalan, director of vascular medicine at Ohio State University Medical Center. The National Institutes of Health paid for the research.

The amount of soot in the air breathed by the mice in the pollution group was comparable to the air you'd breathe sitting behind an idling truck, he said.

"We found a very, very strong exaggeration of diabetes" in the pollution group, Rajagopalan said.

Much remains unanswered, but the explanation could lie inside the walls of blood vessels, where inflammation can occur. And inflammation has been linked to environmental factors, including pollution.

"This inflammation in the vessel wall, it's not unique to atherosclerosis. It's in fact the molecular underpinning of obesity and diabetes," he said.

"The mechanisms that lead to heart disease and metabolic diseases such as diabetes are in fact very similar."

Aruni Bhatnagar, a professor of medicine in the division of cardiology at the University of Louisville, said the study is thought-provoking and should prompt more research.

"The human story is quite complicated, and nothing like this has been done in humans," said Bhatnagar, who wrote an editorial to accompany the research.

But pollution has been linked to heart disease, and diabetes, obesity and heart disease have almost identical risk factors, making a connection seem plausible, he said.

"Almost everything that causes heart disease also causes diabetes. It is not altogether surprising that, given the exposure, there appears to be a link."

About 24 million Americans have diabetes.

Although the researchers caution that more study is needed, they say their work might add more weight to efforts to toughen clean-air standards.

"I think the evidence is surely coming to a point where these standards may need to be revised again," Rajagopalan said.

mcrane@dispatch.com

The explanation might lie in inflamed blood-vessel walls. To see more of The Columbus Dispatch, or to subscribe to the newspaper, go to http://www.columbusdispatch.com. Copyright (c) 2009, The Columbus Dispatch, Ohio Distributed by McClatchy-Tribune Information Services. For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA.