Abstract Body: Heart failure occurs at twice the rate in diabetic patients as compared to normal patients, and reduced NAD levels are associated with diabetic cardiomyopathy. Sterile Alpha and Tir Motif Containing 1 (SARM1) is an intracellular NAD hydrolase. We hypothesized that SARM1 promotes NAD decline and diabetic cardiomyopathy. We subjected wild type (WT) and global SARM1 knockout mice to chronic diabetic stress induced by streptozotocin injections. We showed that 16-week diabetic stress promoted progressive decline in systolic and diastolic function, and in NAD levels, which were ameliorated by SARM1 deficiency despite similar plasma glucose and lipid levels. Gene Module Network Analysis of cardiac transcriptomics identified upregulation of genes in fatty acid and glucose metabolic processes, and suppression of genes in mitochondrial processes in diabetic WT hearts. SARM1 deficiency reversed upregulated fatty acid metabolic genes but had no impact on glucose metabolic and mitochondrial gene expressions in diabetic hearts. By transmission electron microscopy and Oil Red O staining, we observed increases in lipid droplet sizes and lipid accumulation in diabetic WT hearts, which were suppressed by SARM1 deficiency. SARM1 deficiency did not reverse mitochondrial gene expression, but it mitigated the reduction in ADP-driven respiration, mitochondrial fragmentation, and abnormal cristae structure in diabetic WT hearts. Diabetic WT hearts had increased phospho-PDH and PDK4 levels as well as activated HIF signaling, exhibiting an increase in expression of HIF-1a target genes (55 genes) , many of which were related to lipid storage. SARM1 deficiency suppressed expression of HIF1-a target genes (53 genes) , and reduced phospho-PDH and PDK4 levels. These data suggest that SARM1 regulates pseudohypoxic HIF-dependent signaling in diabetic hearts. In summary, our current data support the hypothesis that SARM1 regulates HIF-dependent transcription events, particularly those influencing lipid metabolism of diabetic hearts. However, SARM1 promotes mitochondrial dysfunction in diabetic hearts independent of transcription of mitochondrial genes. Further studies will continue to elucidate the role of SARM1 in diabetic cardiomyopathy, and its potential as a novel therapeutic target.