LEP and obesity due to melanocortin 4 receptor deficiency: However, when the experiment was realized without VEGF and bFGF, human leptin stimulated HUVEC proliferation in a dose-dependent manner, and a significant increasing effect was observed at concentrations reflecting obesity conditions and pharmacological concentrations at 96 h (+21 and +75% at 100 and 1 000 ng/mL respectively, p<0.05) compared to leptin-free controls (Fig. 2B).