Association of Serum FGL2 Levels with Asthma Severity and Airway Remodeling

This study evaluated the relationship between serum fibrinogen-like protein 2 (FGL2) levels, asthma severity, lung function impairment, Th2-driven inflammation, and airway remodeling.

A comparative analysis was performed on 129 patients with asthma and 120 age- and sex-matched healthy controls. Demographic characteristics, pulmonary function indices, and serum biomarkers were assessed, and correlation analyses were conducted to examine the associations between FGL2 expression and clinical parameters.

Serum FGL2 levels were significantly elevated in patients with asthma, particularly during exacerbation. FGL2 showed moderate negative correlations with forced expiratory volume in 1 second (FEV1; r = -0.333, p < 0.001) and FEV1/FVC (r = -0.321, p < 0.001) and a moderate-to-strong negative correlation with peak expiratory flow (r = -0.481, p < 0.001). Weak-to-moderate positive correlations were observed with total IgE (r = 0.255), eosinophil count (r = 0.403), and fractional exhaled nitric oxide (FeNO; r = 0.387) (all p < 0.01). Serum FGL2 levels were moderately positively correlated with Th2 cytokines, including interleukin (IL)-4 (r = 0.421), IL-5 (r = 0.277), and IL-13 (r = 0.472) (all p ≤ 0.001). Associations with airway remodeling markers were weak for matrix metalloproteinase (MMP)-2 and MMP-9, moderate for transforming growth factor-β1 (r = 0.393), and moderate to strong for hyaluronan (r = 0.481, p < 0.001). FGL2 demonstrated a good discriminatory ability for asthma, with high specificity and moderate sensitivity.

Elevated serum FGL2 levels correlate with asthma severity, Th2-mediated inflammation, and airway remodeling markers, supporting its potential as a complementary biomarker.