For example, leptin could induce vasodilation to modulate blood pressure homeostasis (Fruhbeck, 1999; Lembo et al., 2000); however, obesity-induced hyperleptinemia resulted in an increase of endothelin-1, which then leads to vasoconstriction (Quehenberger et al., 2002). This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.