A lung-irritating protein made by fat cells may be the missing link between obesity and asthma, say Australian researchers.

Obesity makes it about three times more likely a person will have asthma. And when obese people with asthma lose weight, their asthma gets better, says Michael Rolph, PhD, one of the researchers on the study.

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Why the improvement?

The answer may be a protein made by fat cells, suggests a research team led by Rolph, of the Garvan Institute of Medical Research, in Sydney, Australia.

The protein, called aP2, helps fat cells store fat molecules. Rolph, Bennett O.V. Shum, and colleagues now show it inflames cells lining the surface of the lung’s airways.

"We were really surprised to find aP2 in the lung," Shum said in a news release. "We then looked at what would happen when we removed the aP2 gene in mouse models [of asthma]. Mice without aP2 are protected from asthma attacks."

And it's not just asthma. The fat-cell protein may play a role in other lung diseases as well. That makes aP2 a target for new drugs.

"Blocking aP2 function is a novel approach for asthma treatment and other inflammatory lung diseases," Shum said.

The findings appear in the August issue of the Journal of Clinical Investigation.

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SOURCES: Shum, B.O.V. Journal of Clinical Investigation, August 2006; advance online edition. News release, Research Australia.