DPP-4 inhibits angiogenesis by suppressing FGF-2/EGR-1/VEGF-A signaling.

<p>(A) Known peptide sequences of the NH2-terminal of mature FGF-2 in mice, rats, and humans (upper panel). Lower panel indicates peptide sequences of the NH2-terminal of mature FGF-2 after incubation with DPP-4 (analyzed by LC-MS/MS). (B, C) Quantitative PCR for <i>Egr1</i> and <i>Vegfa</i> in neonatal rat ventricular myocytes (NRVMs) incubated with PBS, recombinant FGF-2 (FGF-2)(50 ng/ml, 2 hr), or DPP-4 (0.1 μg/ml, 2 hr) in Fig 4B (n = 4,4,4), and with FGF-2 (50 ng/ml, 8 hr) or DPP-4 (0.1 μg/ml, 8 hr) in Fig 4C(n = 4,4,4)). As for experiments in Fig 4B and C, FGF-2 was pre-incubated with DPP-4 in tube for totally 8 hours at 37°C before administration to cells in the FGF-2+DPP-4 group. (D) Tube formation by human umbilical vein endothelial cells (HUVECs) incubated with PBS or recombinant FGF-2 (FGF-2) (35 ng/ml for 12 hr), either with DPP-4 (0.1 μg/ml for 12 hr) or without DPP-4 (Con). Right panel indicates quantification of tube length for experiments shown in the left panel (n = 3,3,3). (E) Quantitative PCR for <i>Egr1</i> and <i>Vegfa</i> expression in neonatal rat ventricular myocytes (NRVMs) after introduction of control si-RNA (si-Con) or si-Egr1 (n = 4,4). (F) Scheme showing a summary of the present findings. Metabolic stress increases circulating DPP-4, which suppresses FGF-2/EGR-1/VEGF-A signaling in cardiac tissue, leading to capillary rarefaction and cardiac dysfunction. In addition to blocking DPP-4, linagliptin, a DPP-4 inhibitor (DPP-4i), increased citrulline and creatine levels in cardiac tissue, which may also have contributed to suppressing pathologic changes in the obese failing heart. Whether there is a link between altered metabolic profile and angiogenic response remains to be determined. Data were analyzed by the 2-tailed Student’s t-test (E), or 2-way ANOVA followed by Tukey’s multiple comparison test (B, C, D). *P<0.05, **P<0.01. All values represent the mean ± s.e.m. NS = not significant.