In summary, our work reveals a new mechanism of β cell dysfunction and insulin resistance in the development of T2D, suggesting that rs3819316 C > T mutation in Reg1cp can be added to the growing list of genes implicated in the risk of developing T2D and screening the Reg1cp+/mut or Reg1cpmut/mut individuals might be beneficial to early clinical diagnosis of T2D. The gene discussed is REG1CP; the disease is type 2 diabetes mellitus.