KDR and Hyperglycemia: It is of particular interest that vascular endothelial growth factor receptor-2 (VEGFR-2) was downregulated under hyperglycemia in a dose-dependent manner (−1.95-fold, p = 3.23E−04) for 16.5 mmol/L and (−3.0-fold, p = 5.3E−06) for 25 mmol/L and not improved by metformin treatment (Additional file 1: Table S3).