PURPOSE OF THE STUDY.
To evaluate the underlying mechanisms in obesity-associated asthma in children.
One hundred twenty children 7 to 11 years of age were enrolled and assigned to 4 different groups: (1) obese asthmatic children, (2) atopic nonobese asthmatic children, (3) obese nonasthmatic children, and (4) nonobese, nonasthmatic children.
All children performed pulmonary function testing, and anthropometric data were obtained. Asthma severity was classified based on daytime and nighttime symptoms, exercise limitation, and albuterol use (parental report). Blood was obtained for serum cytokines, T-cell responses to mitogen and allergen, and phenotyping.
Serum interleukin (IL)-4 and IL-13 levels were higher among nonobese asthmatic children, consistent with a T-helper (Th)2 phenotype of atopic asthma. In contrast, obese asthmatic children had lower levels of IL-13 and higher levels of tumor necrosis factor-α and IL-6, consistent with a Th1 phenotype. Obese asthmatic children had higher Th1 response to phorbol 12-myristate 13-acetate and tetanus and lower Th2 responses to phorbol 12-myristate 13-acetate and dust mite allergen compared to nonobese asthmatic children. The Th pattern did not differ between obese asthmatic children and obese nonasthmatic children. Spirometric data were within the normal range in all 4 study groups. However, the forced expiratory volume in 1 second/forced vital capacity ratio was lower in obese asthmatic children compared with the other asthmatic children.
Obese asthmatic children exhibited a Th1 polarization in contrast to the Th2 polarization seen in atopic childhood asthma. The Th1 response did not differ between obese asthmatic children and obese nonasthmatic children. This suggests that obese asthmatic children exhibit a systemic Th1 polarization that may be modulated more by obesity and less by their asthma.
Obesity-associated asthma has been proposed as a distinct entity, and this is one of the first studies to try to characterize the underlying mechanism and compare them to atopic asthma in children. Given the obesity epidemic facing our children, understanding these differences can be helpful in treating this population. Given the fact that the inflammation seems to be influenced more by the obesity itself, addressing the obesity may be a major therapeutic intervention to treat obese asthmatic patients.
- Copyright © 2012 by the American Academy of Pediatrics