PLCB4 and chronic obstructive pulmonary disease: Eleven hub genes (DTL, TTK, FPR3, CDK1, HJURP, GINS2, IGF2R, NDUFAB1, NDUFS8, PLCB4, and SCD) and some vital pathways linked to regular exercise training were discovered: chemokine receptor biding, tricarboxylic acid (TCA) cycle, fatty acid metabolism, and oxidative phosphorylation, which were known to be associated with the pathophysiology of COPD [3, 45, 45].