MTNR1B and type 2 diabetes mellitus: To exclude the effects of OATP1B1 and CYP2C8 genetic polymorphisms on the response to repaglinide, 95 patients with different MTNR1B genotypes, but the same OATP1B1 521TT and CYP2C8*3 139Arg genotypes, were randomly selected from the 300 T2DM patients.