FGF21 and obesity due to melanocortin 4 receptor deficiency: Several recently discovered batokines, such as FGF21, NRG4, BMP8b, CXCL14, or adiponectin have been shown to exert a protective role against obesity by enhancing beiging of WAT, lipolysis, sympathetic innervation, or polarization of M2 macrophages (Ahmad et al., 2021).