Two studies being presented at the American Thoracic Society's 2008 International Conference in Toronto on May 21 provide insights into lung disease and lung function in young adults. One links low levels of a protein called adiponectin in fat cells to an increase in asthma risk in young women. A second finds that high levels of a protein called ICAM-1 is associated with lower lung function.
The data from both studies comes from the National Heart, Lung, and Blood Institute's CARDIA (Coronary Artery Risk Development in Young Adults) observational cohort, which recently completed 20 years of health assessment in more than 5,000 young adults. Participants were healthy 18 to 30 year-olds when the study began in 1985 and 1986. The goal of the research has been to look for risk factors for cardiovascular and lung disease as participants age.
Low Levels of Protein in Fat Cells May Increase Asthma Risk in Women
Low levels of adiponectin, a protein produced by fat cells, are associated with an increased risk of asthma in women, according to one CARDIA study.
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 to 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 percent 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, M.D., M.P.H., associate professor in the Division of Pulmonary and Critical Care Medicine at the University of New Mexico Health Sciences Center School of Medicine in Albuquerque. "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 hyperreactivity, 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.
The talk is entitled: "Adipokine-Asthma association: Does Lung "Talk" to Adipose Tissue?"
High Protein Levels May Signal Lower Lung Function
A second study based on CARDIA data finds that higher levels of proteins called ICAM-1 (intracellular adhesion molecule) are associated with lower lung function.
ICAM-1 exists in the cells called 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, Ph.D., Mayo Professor of Public Health at the University of Minnesota in Minneapolis. "We've known that people with lower lung function have more cardiovascular disease and cardiovascular deaths than those with better lung function, and that these two things are somehow related, but the relationship between the lungs and blood vessels has been puzzling. For instance, air pollution, although it is breathed in through the lungs, has been shown to cause more heart disease than lung disease."
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.
The talk is etitled: "Association of Circulating Adhesion Molecules with Lung Function: Results from the CARDIA Study"
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