Diabetic cardiomyopathy, structurally characterized by cardiomyocyte hypertrophy and increased extracellular matrix (ECM) protein deposition, eventually leads to heart failure. We investigated the role of transcriptional co-activator p300 and its interaction with myocyte enhancer factor 2 (MEF2) in diabetes-induced cardiomyocyte hypertrophy. Methods: Neonatal rat cardiomyocytes, were exposed to variable level of glucose. Cardiomyocytes were analyzed with respect to their size. mRNA expression of p300, MEF2A, MEF2C, atrial natriuretic polypeptide (ANP), brain natriuretic polypeptide (BNP), angiotensinogen (ANG), cAMP-responsive element binding protein (CREB)-binding protein (CBP) and protein analysis of MEF2 were done with or without p300 blockade. We investigated the hearts of STZ-induced diabetic rats and compared them to age- and sex-matched controls after one and four months of follow-up with or without treatment with p300 blocker curcumin. Results: Cardiomyocytes, exposed to 25mM glucose for 48hours, showed cellular hypertrophy and augmented mRNA expression of ANP, BNP and ANG, molecular markers of cardiac hypertrophy. Glucose caused a duration dependent increase of mRNA and protein expression in MEF2A and MEF2C and transcriptional co-activator p300. Curcumin, a p300 blocker, and p300 siRNA prevented these abnormalities. Similarly, ANP, BNP and ANG mRNA expression was significantly higher in the hearts of diabetic rats compared to the controls, in association with increased p300, MEF2A and MEF2C expression. Treatment with p300 blocker curcumin prevented diabetes-induced upregulation of these transcripts. Conclusions: Data from these studies demonstrate a novel glucose-induced epigenetic mechanism regulating gene expression and cardiomyocyte hypertrophy in diabetes.