GCG and diabetic retinopathy: GLP-1 (100 nM) or exendin-4 (10 nM) treatment inhibited TNF-α-induced expression of receptor for advanced glycation end products (RAGE), ICAM-1, and VCAM-1 in human retinal pigment epithelial cells [32], suggesting that GLP-1-based therapies might have beneficial effects on diabetic retinopathy.