In T2DM patients, three methylation sites (PBX/Knotted 1 Homeobox 2 (PKNOX2), WD and Tetratricopeptide Repeats 1 (WDTC1), and MHC Class I Polypeptide-Related Sequence B (MICB)) have been linked to the effects of metformin on HbA1c levels [82]. Here, PKNOX2 is linked to type 2 diabetes mellitus.