During their visit of consultation on the follow-up to the type 2 diabetes, les patients will be selected on the basis of active metformin treatment at a dose greater than or equal to 1400 mg/day. Patients will have to achieve a 10 ml blood sample. The blood will be processed by Ficoll gradient centrifugation to remove the red cells and isolate circulating leukocytes: this stage will be conducted in the CERITD. Analysis on circulating leukocytes and in particular the quantification of expressions of isoforms A and B of the INSR1 by quantitative RT - PCR gene will be conducted in the laboratory of the Professor Marc Peschanski (unit INSERM 861 I - STEM of Evry).

After inclusion in the study to J0, metformin treatment will be interrupted between J1 and J30, replaced by Januvia 100 mg/day dose, then resumed at J31.

After inclusion in the study to J0, metformin treatment will be interrupted between J1 and J30, replaced by Januvia 100 mg/day dose, then resumed at J31.

comparison of the A isoform (without inclusion of exon 11) and B isoform (with inclusion of exon 11) ratio of the receptor in insulin, during the first period (without metformin) and the second period (with metformin)