HIF1A and Hyperglycemia: Temporary hypoxia is needed for angiogenesis as increased expression of HIF-1α dimerizes and activates hypoxia response elements causing increased expression of VEGF, but the presence of hyperglycemia affects the stability and activation of HIF-1α and attenuates angiogenesis through suppression of PDGF, VEGF, and TGF-β [26].