DPP4 and diabetes mellitus: Some illustrative examples are shown in Fig. 3, including the effect of chronic obstructive pulmonary disease (COPD) on GART expression (Fig. 3a), the effect of diabetes on LRRK2 expression (Fig. 3b), and the effect of smoking on ADK, CD55, DPP4 and MET expression (Fig. 3c–f).