To further reveal how the inhibitory effect of metformin treatment on IL-1β secretion (mature IL-1β) modulates the development of psoriasis, we focused on IL-1β-inducible pro-inflammatory cytokines, chemokines and antibiotic peptides including IL-36γ, CXCL1, CXCL2, CCL20, S100A7, S100A8 and S100A9, which are closely related to the development of psoriasis34–39. Here, CCL20 is linked to psoriasis.