Figure 1.

NRG4 is brown adipocyte adipokine that promotes neurite outgrowth. Neuregulin 4 (Nrg4) is more highly expressed in brown adipocytes compared to white adipocytes. Upon cold exposure, norepinephrine (NE) is secreted and activates brown fat as well as initiating the “browning” of white fat resulting in upregulated Nrg4 mRNA. NRG4 is secreted by brown adipocytes and can signal to neurons to promote neurite outgrowth. Thus, NRG4 is a brown/brown-in-white (BRITE) adipokine that has a potential role in enhancing sympathetic innervation of adipose tissues needed to activate thermogenic functions.