PYGL and bronchopulmonary dysplasia: On the 14th day, the expression level of STAT4 was significantly lower in patients with BPD than in controls (median 0.882 vs. 1.364 ng/ml, p < 0.05), whereas PELI1 (p > 0.05) and PYGL (p > 0.05) were not significantly different at the two different time points (Figures 3A,B).