COPD-T2DM is considered a syndrome that can share risk factors (such as smoking) [17], genes (such as β2-adrenergic receptor gene, ADRB2) [18], proteins (such as Nod-like receptor containing a pyrin domain 3, NLRP3) [19, 20] and pathways (such as systemic inflammation and oxidative stress) [21–23]. Here, ADRB2 is linked to type 2 diabetes mellitus.