Reg was induced in insulin producing pancreatic β-cells by inflammatory stimulation such as by interleukin-6 (IL-6)/glucocorticoids and IL-22166,173–175) and acted as an autocrine/paracrine growth factor for β-cell regeneration via a cell surface Reg receptor (see Figs. 16 and 17)165,167) to ameliorate experimental diabetes.154,156,169) Further the Reg gene is only expressed during islet regeneration,157,161) suggesting that the regeneration and proliferation of pancreatic β-cells for the increase of the cell mass were primarily regulated by the Reg gene expression. Here, REG1A is linked to diabetes mellitus.