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). This evidence concerns the gene NTRK2 and obesity due to melanocortin 4 receptor deficiency.