To investigate the impact of the combination of the diabetic environment and the Hif1a-deficient sympathetic nervous system on the adult heart, we induced diabetes by low doses of STZ treatment, which reduces beta cell mass in the pancreas, and utilized a conditional Hif1a deletion mediated by Isl1Cre (Hif1aCKO), which results in altered cardiac sympathetic innervation and formation of sympathetic ganglia [42] (Schematics of experimental study design in Fig. 1A). The gene discussed is HIF1A; the disease is diabetes mellitus.