Establishment of a Method for Direct Analysis of the Mouse Brain Metabolome Using the DPiMS-8060

Significance of the Topic

Metabolome analysis enables comprehensive profiling of endogenous compounds such as amino acids, organic acids, fatty acids, and sugars and has become essential in life science research.
Direct ionization techniques like probe electrospray ionization (PESI) minimize sample preparation, reduce analysis time, and allow high-throughput studies of complex tissues such as the brain.

Objectives and Overview of the Study

This study aimed to establish a rapid, pretreatment-free method for direct analysis of the mouse brain metabolome using the newly developed DPiMS-8060 mass spectrometer combining PESI with tandem mass spectrometry.
Key goals included validation of metabolite detection, discrimination between drug-treated and control groups, and assessment of local metabolic distributions in distinct brain regions.

Methodology and Instrumentation

Standard solutions of 25 metabolites (amino acids, organic acids, sugars) were prepared in 50% ethanol and analyzed by PESI-MS/MS using selected multiple reaction monitoring (MRM) transitions.
Mass spectrometer parameters, including collision energy, were optimized for each compound.
Rapid analysis was performed in 0.2 minutes per sample without chromatographic separation.

Used Instrumentation

• DPiMS-8060 probe electrospray ionization tandem mass spectrometer (Shimadzu)
• PESI ultrafine sampling probe (tip diameter ~700 nm)

Main Results and Discussion

• Detection of 25 metabolites directly from mouse brain samples within 0.2 min per run.
• PLS-DA clearly separated metabolomic profiles of drug-treated (AM-2201) and control mice, identifying glutamic acid and succinic acid as key discriminators.
• Spatial analysis of frontal cortex and hippocampus revealed distinct local metabolite distributions despite similar matrix effects, demonstrating the probe's nanoscale sampling capability.

Benefits and Practical Applications of the Method

• Elimination of complex and time-consuming pretreatment steps.
• High throughput and rapid turnaround suitable for large-scale studies.
• Minimal invasiveness due to ultrafine probe enabling localized metabolite mapping.

Future Trends and Potential Applications

• Integration with imaging techniques for in situ metabolic mapping at the cellular level.
• Expansion to other tissues and organisms for rapid metabolomic screening.
• Potential use in clinical diagnostics, pharmacodynamics, and toxicology studies requiring spatially resolved metabolite data.

Conclusion

The PESI-MS/MS approach on the DPiMS-8060 offers a powerful platform for rapid, sensitive, and pretreatment-free metabolome analysis of brain tissue, with added capability for local distribution studies using an ultrafine sampling probe.

Reference

Hayashi Y; Zaitsu K; Murata T et al. Analytica Chimica Acta 2017, 983, 160–165.