Heart failure with preserved ejection fraction (HFpEF) which results from diastolic dysfunction is a growing epidemiologic problem. However, the pathophysiology of this disease is poorly understood. Our goal is to investigate whether microvessel disease may promote HFpEF. To do so we have used Leptin receptor deficient (Leprdb/db) female mice as a model of HFpEF and performed a transcriptomic analysis via RNA sequencing of the cardiac vascular fraction of both these mice and their control Leprdb/+littermates. In Leprdb/db female mice, end diastolic pressure (EDP) signing diastolic dysfunction is significantly increased from 3 month of age. It is correlated with a cardiac and cardiomayocyte hypertrophy, vascular leakage, endothelial cell activation and leucocyte infiltration. As expected, the RNA sequencing analysis confirmed endothelial dysfunction. Besides, it also revealed a strong increase in several mast cell markers. We confirmed, via histology, an accumulation of mast cells in the heart of Leprdb/db mice. Importantly, it was associated with increased levels of circulating IgE. Leprdb/db mice were then treated or not with Cromolyn sodium, an inhibitor of mast cell degranulation. After a month treatment, EDP was significantly reduced in Leprdb/db mice demonstrating the critical role of mast cell in the development of diastolic dysfunction in diabetic obese mice.