Effects of linagliptin on AGE-exposed HUVECs. HUVECs were treated with 100 μg/ml AGE-BSA or non-glycated BSA in the presence or absence of 10 nM or 0.5 μM linagliptin for 4 hr. (A) Cells were incubated with DHE. Upper panel shows typical microphotographs of the cells. Lower panel shows quantitative data of ROS generation evaluated by fluorescent intensity. N = 50 per group. (B-D) Total RNAs were transcribed and amplified by real-time PCR. Data were normalized by the intensity of β-actin (B) or 18S mRNA-derived signals (C and D) and then related to the value obtained with non-glycated BSA. (B) N = 15 per group. (B) N = 15 per group. (C and D) N = 9 per group. * and **, p < 0.05 and p < 0.01 compared to the value with AGEs alone, respectively.