Introduction:G protein coupled receptor (GPR) 39 is an orphan receptor differentially expressed in variety of tissues. Endothelial cells (ECs) are responsible for tissue repair and to maintain vascular homeostasis, whose dysfunction increases the risk of cardiovascular morbidity in diabetic patients. However, whether GPR39 plays a role in regulating EC function is not known. We hypothesize that the mitochondrial function in endothelial cells can be preserved by deleting GPR 39, thus protecting endothelial function in hyperglycemia.Methods and Results:Healthy human aortic endothelial cells (H-HAECs) and diabetic human aortic endothelial cells (D-HAECs) were cultured in vitro. studies in vitrohave shown reduced migration potential (modified Boyden Chamber assay) and tube formation capacity in H-HAECs transfected with adenovirus carrying human GPR39, using transfection of adenovirus carrying egfpas control (n=5-6, p<0.05). Conversely, knocking down GPR39 by siRNA in D-HAECs improved cell migration (n=5, p<0.05). Primary cultured mouse aortic ECs from global GPR39 knockout (GPR39null) mice have shown lower levels of superoxide anions (MitoSOX) and better maintained mitochondrial membrane potential (TMRM/MitoTracker ratio) than that in MAECs from control (GPR39WT) litters in high glucose treatment (25mM, 72 hours). GPR39nulland GPR39WTmice were rendered hyperglycemic by low-dose streptozotocin (STZ) injections. After 3 months, these animals received hind limb ischemia by left femoral artery ligation. We observed a poor blood flow recovery measured by Laser Doppler imaging and high gangrene rate (60.0%) in STZ-GPR39WTmice (n=13, p<0.05 vs. Control-GPR39WT) whereas there was better blood flow and lower gangrene rate (33.3%) in STZ-GPR39nullmice (n=10, p<0.05 vs. STZ-GPR39WT).Conclusions:Based on our results, we believe that deletion of GPR39 protects the mitochondrial function in ECs and maintains vascular homeostasis under high glucose conditions. Thus, the endothelial cell health can be regulated by controlling the levels of GPR39 expression. GPR39 represents a potential therapeutic target in preventing vascular complications in diabetic patients.