In the case of carnosine, homocarnosine and anserine metabolism, the plasma levels of CNDP1 were significantly higher (p < 0.001), whereas those of carnosine dipeptidase 2 (CNDP2) were lower (p < 0.001) in the DKD group than in the T2DM and control groups. The gene discussed is CNDP2; the disease is type 2 diabetes mellitus.