BDNF and obesity due to melanocortin 4 receptor deficiency: Obesity in mice with BDNF deficiency is associated with hyperglycemia and impaired glucose tolerance (Kernie et al., 2000; Rios et al., 2001; Liao et al., 2012), and this glucose phenotype is at least in part attributable to the direct action of BDNF on glucose homeostasis.