In several animal models of obesity and diabetes, including db/db mice, diet-induced obesity mice and lethal yellow agouti mice, peripheral administration of BDNF has been shown to prevent or ameliorate the diabetic and obese phenotypes (Nakagawa et al., 2003; Yamanaka et al., 2008). The gene discussed is BDNF; the disease is obesity due to melanocortin 4 receptor deficiency.