Led by one of the current authors (JRP), it was an international effort that aimed to address the lack of cardiovascular data in the area of metformin use in type 1 diabetes by conducting a double-blind, placebo-controlled trial to test whether 3 years of metformin treatment (1000 mg twice daily) added to titrated insulin therapy (towards target HbA1c, 7.0% [53.0 mmol/mol]) reduces progression of atherosclerosis in adults aged 40 years or older with confirmed type 1 diabetes and three or more cardiovascular risk factors [8, 9]. This evidence concerns the gene INS and type 1 diabetes mellitus.