Endocrine Abstracts

Metformin is a biguanide class agent widely used as a first-line treatment for type 2 diabetes, however the detailed mode of action and exact pharmacodynamics has not been clarified. Moreover there is no studies in humans displaying the effect of metformin on DNA methylation. We therefore performed a clinical study involving twelve healthy nondiabetic individuals who were subjected to the 1 week of metformin (2×850 mg/day) treatment. Peripheral blood for DNA isolation was drawn at three time points during metformin treatment: i) right before metformin treatment, ii) 10 hours after the first metformin dose and iii) after a week-long metformin administration. DNA methylation was estimated using genome-wide Illumina Infinium HumanMethylation450 BeadChip (Illumina), which allows interrogation of 485 512 CpG dinucleotides. Analysis global methylation data displayed predominance of demethylated CpGs over the methylated as the result of metformin treatment. In order to identify differentially methylated gene promoter regions we filtered all CpGs located in 2000 pb proximity of the transcription start site and having median methylation change across all samples larger than 3% with Bonferroni corrected P values. This stringent approach resulted total in 35 genes with differentially methylated CpG regions near the promoters. Five genes, considered most likely biologically relevant to have impact in diabetes were those involved in processing of energy molecules, differentiation and formation of adipocytes and exhibiting GTF-ase activities. Eighteen regions included genes with known specific functions that are not directly linkable to influencing diabetic phenotype. Finally 12 genes where either pseudogenes or had unknown function. In conclusion this is the first study that shows influence of metformin in altering DNA methylation in humans and identified markers may prove to be valuable biomarkers for the understanding of the molecular basis of metformin action and may lead to the identification of new drug targets.