As dysregulation of leptin signaling is tightly associated with human obesity and diabetes (10), our discovery of a dual action of TET3 (5hmC modification and recruitment of chromatin-modifiers) in the regulation of Agrp/AGRP expression in both human and mouse cells offers new opportunities for the future development of therapeutic interventions for metabolic disorders and related psychiatric conditions. This evidence concerns the gene TET3 and obesity due to melanocortin 4 receptor deficiency.