Desorption Electrospray Ionization (DESI) Mass Spectrometric Imaging of Spatially Regulated In Vivo Metabolic Rates

Weber State University

Desorption electrospray ionization (DESI) is an ambient ionization technique used for mass spectrometric imaging of biological samples. When coupled with isotopic ratio measurements of deuterium-labeled tissues, DESI provides a means of measuring metabolic rates on a spatially resolved basis. In vivo metabolic rates are desired to better understand diseases such as Alzheimer’s, Parkinson’s, and Huntington’s and to study the impact of space travel on muscle tissue growth and wasting. Although DESI has been used to image lipids and metabolites of a variety of tissues and other imaging techniques, such as NIMS, have been used to study kinetic turnover rates, DESI has not yet been used to study in vivo metabolic rates using deuterium labeled tissue. This paper describes how we optimized our DESI source for imaging of biological tissue, how we developed a MATLAB graphical user interface (GUI) to process and interpret the large mass spectral data files, and how we conducted our initial mouse brain study for proof-of-concept. Our initial mouse brain study involved labeling mice with deuterium enriched water, preparing tissue slices for DESI analysis, imaging the tissue slices using DESI coupled with a Bruker mass spectrometer, analyzing the mass spectral data using our custom-designed image_inspector program, and creating incorporation curves to measure in vivo metabolic rates.