A PEGylated analog of short-length neuromedin U with potent anorectic and anti-obesity effects

Publication date: Available online 21 February 2017
Source:Bioorganic & Medicinal Chemistry
Author(s): Hiroshi Inooka, Kotaro Sakamoto, Tokuyuki Shinohara, Yasushi Masuda, Michiko Terada, Satoshi Kumano, Kotaro Yokoyama, Jiro Noguchi, Naoki Nishizawa, Hidenori Kamiguchi, Hisashi Fujita, Taiji Asami, Shiro Takekawa, Tetsuya Ohtaki
Neuromedin U (NMU) is a neuropeptide known to regulate food intake and energy homeostasis that is widely distributed in the gastrointestinal tract, hypothalamus, and pituitary. A short form of NMU, porcine NMU-8 has potent agonist activity for the receptors NMUR1 and NMUR2; however, its short half-life precludes its effective use in vivo. To address this limitation, we designed and synthesized NMU-8 analogs modified by polyethyleneglycol (PEG) with a molecular weight of 30 kDa (PEG30k) via a variety of linkers (i.e., ω-amino- and ω-imino-carboxylic acid linker). Integrated evaluation of NMUR1 and NMUR2 binding affinities in vitro and anorectic activity in mice revealed that the introduction of a linker with a rigid ring group, e.g., 2-(piperazin-1-yl)acetic acid (PipAc), yielded a highly potent anorectic peptide, PEG30k-PipAc-NMU-8 (14), possessing improved receptor binding affinity. Subsequent optimization of the molecular weight of the PEG moiety led to the discovery of a PEG20k conjugate (15), which exhibited significant anti-obesity effect upon once-daily subcutaneous administration in diet-induced obese mice with 10% and 22% body weight loss at doses of 10 and 30 nmol/kg, respectively. In addition, 15 reduced the weights of the liver and adipose tissue in a dose-dependent manner and improved the plasma biochemical parameters, e.g., insulin, glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, and total cholesterol. Thus, our results suggest that 15, which showed potent and long-lasting biological profiles in vivo, represents a candidate peptide for investigating the central and peripheral actions of NMU and its potential for clinical use.

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