Although population‐level evidence confirms that both miR‐21 and SMAD7 are closely associated with T1DM and T2DM, whether SMAD7 expression is affected by miR‐21 in the long‐term, and the exact role of miR‐21 and SMAD7 in myocardial fibrosis and heart failure in patients with T1DM needs more evidence in the future prospective clinic studies. Here, SMAD7 is linked to type 2 diabetes mellitus.