METRNL, a secreted protein homologous to Meteorin, shows high levels of expression in white adipose tissue and barrier tissues.? Low expression of METRNL is observed in the adult mouse brain and it is expressed in restricted sites of the brain during development.? Based on its expression and distinct functions, METRNL is also called Cometin, Subfatin, and Interleukin 39.? METRNL?is induced following exercise or cold exposure that promotes energy expenditure.? It stimulates energy expenditure associated with the browning of the white fat adipose tissues and improves glucose tolerance.? METRNL?stimulates an eosinophil-dependent increase in IL-4 expression and promotes alternative activation of adipose tissue macrophages.? METRNL?is also involved in neural development.? Jorgensen et al first described METRNL? protein and demonstrated its function as a neurotrophic factor similar to Meteorin.? METRNL?was shown to be a latent process gene involved in neurite extension.? BioLegend in-house testing shows METRNL?can induce C6 glioma cell adhesion and also enhance neurite outgrowth from cultured mouse cortical neurons.??