Nesfatin-1 is a recently discovered feeding inhibitory peptide encoded in the precursor protein, nucleobindin 2 (pronesfatin). Previous studies have shown pronesfatin expression in the brain, stomach and pancreas. However, the identity of cells that express nesfatin in the pancreas remain unknown. The objective of this study was to determine which cells in the pancreas of mice and rats express pronesfatin immunoreactivity. We found pronesfatin immunopositive cells exclusively in the pancreatic islets of both CD1 mice and Fischer 344 rats. Our novel results indicate that the insulin producing beta cells colocalize pronesfatin in the islets of both mice and rats. No colocalization Of glucagon and pronesfatin Was found in mice, while some glucagon positive cells were positive for pronesfatin in rat islets. The abundant presence of pronesfatin immunoreactivity and its colocalization with insulin suggests a potential role for pronesfatin-derived peptides in islet biology and glucose homeostasis in rodents. (C) 2009 Elsevier Inc. All Fights reserved.