Direct profiling and identification of peptide expression differences in the pancreas of control and ob/ob mice by imaging mass spectrometry

Imaging mass spectrometry (IMS) technology utilizes MALDI MS to map molecules of interest in thin tissue sections. In this study, we have evaluated the potential of MALDI IMS to study peptide expression patterns in the mouse pancreas under normal and pathological conditions, and to in situ identify peptides of interest using MS/MS. Different regions of the pancreas of both control and ob/ob mice were imaged, resulting in peptide-specific profiles. The distribution of ions of m/z 3120 and 3439 displayed a striking resemblance with Langerhans islet's histology and, following MS/MS fragmentation and database searching were identified as C-peptide of insulin and glicentin-related polypeptide, respectively. In addition, a significant increase of the 3120 peak intensity in the obese mice was observed. This study underscores the potential of MALDI IMS to study the contribution of peptides to pancreas pathology.