Asthma is a chronic inflammatory disease, in which the airway progressively undergoes structural changes collectively termed as airway remodeling. Severe refractory bronchospasm elicits mechanical stress of bronchial wall and it is responsible for airway inflammation and remodeling. In this study, we planned to examine the relationship between asthmatic lung functions and the serum folliculin level. Folliculin is released from bronchial epithelial cells in response to compressive stress, mimicking bronchospasm.
Materials and Methods
Folliculin levels in serum were measured by ELISA in asthma patients (n=405) who visited the asthma center in a tertiary referral hospital from May 2005 to December 2014, and healthy controls (n=94) who visited the Health Examination Center in the same hospital. Folliculin levels were compared in two groups and we investigated if the level of folliculin is correlated with lung function and other clinical variables within the group of asthma. Patients whose folliculin level over 148pg/ml were defined as “high follicullin group” and we sought to find out clinical characteristics of the ‘high folliculin’ phenotype.
The serum concentrations of folliculin were significantly higher in asthmatics (148.92± 240.71 vs 73.57± 78.34 pg/ml, p < 0.001) than in healthy controls. We found negative correlation between serum folliculin level and post bronchodilator FEV1 (R=-0.228, p = 0.00) and post bronchodilator FEV1/FVC (R=-0.155, p = 0.00). The high-folliculin group was older at onset of asthma (65.01±88.08 vs 97.12±121.88 months, P= 0.007), had heavier history of smoking (7.90 vs 13.08 pack-years, p= 0.011), presented more frequent exacerbations (0.36/3months vs 0.57/3months, p=0.041), and showed lower FEV1 % predicted (73.63 vs 66.65, p=0.00).
The results demonstrate that serum folliculin concentration is higher in asthmatics and is associated with lower lung function. Thus, follucilin can be a novel biomarker for asthma.