Effect of Genetic Variants in MATE1 and OCT3 on the Pharmacodynamics of Metformin in African Americans

To investigate the potential association of polymorphic genetic variants MATE1 and OCT3 with altered response to metformin, a genotype to phenotype strategy is employed. Specifically, the investigators will evaluate this hypothesis in African-Americans, a population which has a high incidence of type 2 diabetes and which has high variant allele frequencies (44.5% for MATE1-66T\>C and 11.3% in OCT3-81G\>delGA) relative to other ethic groups. To assess the effects of these variants on metformin response, the investigators will measure metformin renal clearance (pharmacokinetics of metformin), and plasma glucose and insulin levels (pharmacodynamic response) in healthy and diabetic patients who carry either the reference or variant alleles.