However, this result does not completely address the role of VMH BDNF in the control of energy homeostasis, because the obesity phenotype in this mutant was very subtle in comparison to mutant mice where the Bdnf gene was deleted in many brain regions or where TrkB was systemically down-regulated (Rios et al., 2001; Xu et al., 2003). The gene discussed is BDNF; the disease is obesity due to melanocortin 4 receptor deficiency.