Studies Provide Insights Into Lung Disease and Lung Function in Young Adults

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Title: Studies Provide Insights Into Lung Disease and Lung Function in Young Adults
URL: http://www.pslgroup.com/dg/221BCA.htm
Doctor's Guide
May 22, 2008

TORONTO -- May 22, 2008 -- Two studies being presented at the 2008 International Conference of the American Thoracic Society (ATS) in Toronto on May 21 provided insights into lung disease and lung function in young adults. One linked low levels of a protein called adiponectin in fat cells to an increase in asthma risk in young women. A second found that high levels of a protein called ICAM-1 are associated with lower lung function.

The data from both presentations came from the Coronary Artery Risk Development in Young Adults (CARDIA) observational trial, which recently completed 20 years of health assessment in more than 5,000 young adults at the National Heart, Lung, and Blood Institute, Bethesda, Maryland. Participants were healthy 18- to 30-year-olds when the study began in 1985 and 1986. The goal of the research was to look for risk factors for cardiovascular and lung disease as participants age.

Low levels of adiponectin, a protein produced by fat cells, were associated with an increased risk of asthma in women, according to one CARDIA study presented at ATS 2008.

Although adiponectin is produced in fat cells, obesity may trigger an inflammatory response to it and its production is diminished in obese people. Levels of adiponectin increase with weight loss. To determine the effect of adiponectin on asthma, researchers divided 2,890 men and women from the CARDIA study into thirds according to the amount of adiponectin their fat cells produced.

Women with the lowest amount of adiponectin, who also tended to be more obese, had almost double the risk of developing asthma, compared with women who had the most adiponectin in their blood. This was true regardless of the women's weight. The effect was most evident in the premenopausal women, who represented 90% of the 1,603 women included in the study. The researchers did not see a similar relationship between adiponectin levels and asthma in men.

"Our finding that adiponectin may have a protective effect on asthma in women may open up doors to new ways of treating asthma," said lead researcher Akshay Sood, MD, MPH, Associate Professor, Division of Pulmonary and Critical Care Medicine, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, New Mexico. "The findings have particular relevance for obese women, since they are more likely to have low blood adiponectin concentrations."

While human studies of adiponectin and asthma are still in the early stages, studies of mice indicate that this protein plays a role in airway inflammation and airway hyper-reactivity, or "twitchiness," both of which are factors in asthma.

"Because of the increase in asthma prevalence, as well as obesity, there should be a lot of interest in continuing to study the effect of products of fat cells on asthma," Dr. Sood said.

A second study based on CARDIA data found that higher levels of a protein called intracellular adhesion molecule 1 (ICAM-1) are associated with lower lung function.

ICAM-1 exists in endothelial cells that line the arteries and helps initiate the immune system's inflammatory response to "invaders" such as cholesterol deposits.

"Circulating ICAM-1 is a measure of dysfunction of the endothelial cells, which are the intimal lining of arteries and are in capillaries," said study co-author David Jacobs, PhD, Mayo Professor of Public Health, University of Minnesota, Minneapolis, Minnesota.

The study included 2,455 participants from CARDIA. Their levels of ICAM-1 during year 15 of the study were compared with their lung function in year 20. "We found a fairly substantial decline in lung function in people with the highest levels of ICAM, compared with people with lower levels, regardless of their weight," Dr. Jacobs said. "It suggests that lung function and endothelial health are related in some way. I think of endothelial dysfunction, oxidative stress, and inflammation as evil triplets, feeding on each other."

More research is needed to better understand the relationship between the lungs and blood vessels, in order to help preserve better lung function throughout a person's life, he said.

SOURCE: American Thoracic Society

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