Introduction: There is a complex epidemiologic relationship between type two diabetes mellitus (DM) and heart failure (HF), and it is unclear whether the biochemical basis of HF differs in patients with and without DM.Hypothesis: Proteomic profiling of myocardial tissue from patients with and without DM will identify unique signatures of diabetic HF.Methods: Using the Olink aptamer-based platform, we performed proteomic profiling of 552 proteins on 37 myocardial tissue samples: 9 controls, 10 with HF, 7 with DM, and 11 with HF+DM. One-way ANOVA was first used to identify proteins that differed across the four groups. Associated proteins were then tested for differences between HF+DM and each other group independently; we retained proteins with the same direction of effect for each comparison. Each analysis was controlled for false discovery rate (q<0.1).Results: We identified 12 proteins that differed significantly between HF+DM and all three other groups. Among these, six proteins were significant after FDR adjusted ANOVA and had the same direction of effect. These included 5’-NT (q=5.35E-07), a regulator of intracellular energy utilization, and carboxypeptidase A2, a metalloprotease that cleaves peptides during digestion (q=0.0003). Expression of myocardial leptin receptors (q=0.001), complement factor H related protein (q=0.003), and carbonic anhydrase (q=0.006) were also upregulated in diabetic HF, and have previously been linked to myocyte hypertrophy. Markers of endothelial dysfunction - ESM-1 (q=5.62E-06) and VEGFR-3 (q=0.024) - were also increased in HF+DM myocardium as compared to other groups (Figure 1).Conclusions: Proteomic profiling of HF, DM, and HF+DM myocardial tissue suggest alterations in intracellular energy substrate utilization as well as increased expression of tissue biomarkers previously associated with ventricular hypertrophy and myocardial remodeling.