FGF19 and obesity due to melanocortin 4 receptor deficiency: In addition, AMP-activated protein kinase/sirtuin 1 (AMPK/SIRT1), fibroblast growth factor-19/21 (FGF19/21), Janus kinase/signal transducer and activator of transcription (JAK/STAT), and Notch signaling pathways implicated in obesity could also be investigated.