The central leptin gene therapy has also been effective to insulin-deficient diabetes in obesity animal models such as ob/ob mise, diet-induced obese mice, and insulin-deficient type 1 diabetes mice (Kojima et al., 2009), and in patients with inactivating mutations in the leptin gene (Farooqi et al., 1999). Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.