association between the synonymous variant organic cation transporter 3 (oct3)-1233g>a and the glycemic response following metformin therapy in patients with type 2 diabetes

objective(s): organic cation transporter 3 (oct3) as a high-capacity transporter contribute to the metabolism of metformin. the present study was conducted to determine the genotype frequencies of the variant oct3-1233g>a (rs2292334) in patients with newly diagnosed type 2 diabetes (t2d) and its relationship with response to metformin. materials and methods: this study included 150 patients with t2d who were classified into two groups following three months of metformin therapy: responders (by more than 1% reduction in hba1c from baseline) and nonresponders (less than 1% reduction in hba1c from baseline). pcr-based restriction fragment length polymorphism (rflp) served to genotype oct3-564g>a variant. results: the parameters such as hba1c (p<0.001) and bmi (p<0.001) in both patients with ga + aa genotype and gg genotype decreased significantly following 3 months of metformin therapy compared with baseline. the mean reduction in hba1c levels following 3 months was higher in patients with the a allele (0.77% reduction from baseline) than in those with the homozygous g allele (0.54% reduction from baseline). also, in ga + aa genotypes compared with gg genotypes, the mean reduction in hba1c values from baseline was 0.34% for responders and 0.14% for non-responders. conclusion: considering the roles of genetic variations in the function of metformin transporters, the effect of variations such as 1233g>a in the oct3, which is a high-capacity transporter widely expressed in various tissues cannot be ignored. comparing the allele frequencies of oct3-1233g>a variant in our study and different ethnic populations confirm that the variant is a highly polymorphic variant.