Description:Metformin, a biguanide molecule, which is used as first line therapy for type 2 diabetes. In this study, we would like to investigate the inhibition of an enzyme called diamine oxidase (DAO) (also known as ABP1), by metformin. Based on our preliminary in vitro study using diamine oxidase enzyme, we saw increased level of putrescine with increasing metformin concentrations (see reference PMID: 26335661). This proposed in vivo study was to determine whether metformin could increase putrescine levels and other metabolites in mice. Aminoguanidine, a known inhibitor of DAO, in this study as positive control, following similar study design described in this paper (PMID: 8912017).