(‘Metformin’ [MeSH] OR metformin) AND (‘Diabetes Mellitus, Type 2’ [Mesh] OR ‘type two diabet*’ OR ‘insulin resistan*’) AND (‘Vitamin B 12 Deficiency’ [Mesh] OR ‘vitamin B12 deficien*’ OR ‘cobalamin deficien*’ OR ‘megaloblastic anemi*’ OR ‘megaloblastic anaemi*’). The gene discussed is INS; the disease is diabetes mellitus.