A recent study has found that the primary controller medications for asthma, glucocorticoids, are 40% less effective in overweight or obese patients than they are in individuals of normal weight. The researchers also identified a possible mechanism for the resistance, recognizing a possible target for future therapeutic medications.

“This study identifies what could be a significant issue for the 20 million Americans with asthma; specifically, the main controller medication might be less effective if you are overweight or obese,” says lead researcher E. Rand Sutherland MD, MPH.

In order to understand why glucocorticoids are less effective in overweight and obese patients, the researchers measured the response of cells in the blood and lungs to the steroid dexamethasone. Forty-five nonsmoking adults, 33 of which had asthma, participated in the study.

When the dexamethasone was applied to cultures of the participants blood cells, the steroids did not increase the level of a molecule known as MKP-1 (MAP kinase phosphatase-1) as effectively in overweight and obese participants as it did in participants of normal weight. MKP-1 is normally increased when steroids interfere with inflammatory signaling pathways.

“Steroids were clearly less effective in overweight and obese asthma patients. Previous studies have suggested a link between weight and response to steroids in patients, and this study suggests a potential mechanism by which this occurs,” says Sutherland. “It also suggests that future research should be directed specifically to understanding how asthma medications work in overweight and obese asthmatics.”

The study will be published in the October 1 issue of the American Journal of Respiratory and Critical Care Medicine.