The DPP4 inhibitor sitagliptin can ameliorate airway remodeling in mice with chronic asthma by reducing the production of IL-13, inflammatory cells, and fibrotic factors such as TGF-β.[40] Therefore, it is speculated that our finding of the relationship between serum DPP4 and FEV1/FVC may be associated with the impact of DPP4 on airway remodeling, subsequently influencing lung ventilatory function. The gene discussed is TGFB1; the disease is chronic asthma.