TIE1 and Hyperglycemia: It is interesting that the serum and vitreous TTR levels in DR patients should be associated with DR progression [15], and in vitro, TTR has been proved to prevent the progression of DR [14], and repress angiogenesis by the Tie signaling pathway in hyperglycemia [16] or promote the apoptosis of hRECs by the GRP78-dependent pathway [17].