Effects of peripheral administration of a Neuromedin U receptor 2-selective agonist on food intake and body weight in obese mice

Background: Neuromedin U (NMU) is a neuropeptide with various physiological functions, including regulation of smooth-muscle contraction, blood pressure, stress responses and feeding behaviors. NMU activates two distinct receptors, NMUR1 and NMUR2, which are predominantly expressed in peripheral tissues and the central nervous system (CNS), respectively. It is reported that the NMU signaling system regulates food intake (FI) and body weight (BW) via NMUR2, suggesting that an NMUR2 agonist exhibiting anorectic effects would be a potential therapy for obesity. Methods: Antiobesity effects of NMUR2 activation were assessed using a recently developed, novel NMUR2-selective agonist, NMU-7005 (a polyethylene glycolated octapeptide). Here we assessed cumulative FI and BW loss after peripheral administration of NMU-7005 in NMUR2 knockout and diet-induced obese mice. To gain mechanistic insights, we performed immunohistochemical analysis of c-Fos-like protein expression in the brain. Results: We found that NMU-7005 was a NMUR2-selective agonist with little activity toward NMUR1. The anorectic effect of NMU-7005 was completely abrogated in NMUR2 knockout mice. Repeated subcutaneous administration of NMU-7005 showed a potent antiobesity effect with FI inhibition ( P