CYP2C9 and type 2 diabetes mellitus: T2DM patients (n = 60) with different MTNR1B rs10830963 but the same SLCO1B1 521TT and CYP2C9*1 genotypes were randomly selected to participate in our study to avoid the potential impacts of SLCO1B1 and CYP2C9 genetic polymorphisms.