Considering impaired cardiac contractility as a major cause of diabetic cardiomyopathy (Malhotra and Sanghi, 1997; Boudina and Abel, 2007), our results provide a novel role of MMP9 in diabetic hearts and a novel therapeutic approach for ameliorating contractile dysfunction of diabetic hearts by suppressing MMP9. The gene discussed is MMP9; the disease is diabetic cardiomyopathy.