Aryl hydrocarbon receptor nuclear translocator (ARNT), also known as hypoxia-inducible factor-1 beta (HIF-1β), is a transcription factor that functions as a master regulator of glucose homeostasis. We have previously demonstrated that ARNT expression is highest in the heart, where it is required for maintaining normal cardiac metabolism and cardiac function. Diabetes is associated with a loss of ARNT, although the specific role of ARNT in the diabetic heart is still unknown. Diabetes is also characterized by endothelial dysfunction. Thus, investigating the role of endothelial ARNT in diabetic cardiovascular disease could lead to new therapies for treatment or prevention.