Neuropeptide B (NPB) regulates food intake, body weight and energy homeostasis by interacting with NPBW1/NPBW2 in humans and NPBW1 in rodents. NPB and NPBW1 are widely expressed in the central nervous system and peripheral tissues including pancreatic islets. Although previous studies have demonstrated a prominent role for NPB and NPBW1 in controlling glucose and energy homeostasis, it remains unknown as to whether NPB modulates pancreatic βâcell functions. Therefore, the aim of the present study was to investigate the effects of NPB on insulin expression and secretion in vitro. Furthermore, the role of NPB in the modulation of INSâ1E cell growth, viability and death was examined. Gene expression was assessed by reverse transcriptionâquantitative PCR. Cell proliferation and viability were determined by BrdU or MTT tests, respectively. Apoptotic cell death was evaluated by relative quantification histoneâcomplexed DNA fragments (monoâand oligonucleosomes). Insulin secretion was studied using an ELISA test. Protein phosphorylation was assessed by western blot analysis. NPB and NPBW1 mRNA was expressed in INSâ1E cells and rat pancreatic islets. In INSâ1E cells, NPB enhanced insulin 1 mRNA expression via an ERK1/2âdependent mechanism. Furthermore, NPB stimulated insulin secretion from INSâ1E cells and rat pancreatic islets. By contrast, NPB failed to affect INSâ1E cell growth or death. We conclude that NPB may regulate insulin secretion and expression in INSâ1E cells and insulin secretion in rat pancreatic islets.