Mapping of Fatty Aldehydes in the Diabetic Rat Brain Using On-Tissue Chemical Derivatization and Air-Flow-Assisted Desorption Electrospray Ionization-Mass Spectrometry Imaging

Exploring new frontiers in type 1 diabetes through advanced mass-spectrometry-based molecular measurements

Type 1 diabetes (T1D) is a devastating autoimmune disease for which advanced mass spectrometry (MS) methods are increasingly used to identify new biomarkers and better understand underlying mechanisms. For example, integration of MS analysis and machine learning has identified multimolecular biomarker panels. In mechanistic studies, MS has contributed to the discovery of neoepitopes, and pathways involved in disease development and identifying therapeutic targets. However, challenges remain in understanding the role of tissue microenvironments, spatial heterogeneity, and environmental factors in disease pathogenesis. Recent advancements in MS, such as ultra-fast ion-mobility separations, and single-cell and spatial omics, can play a central role in addressing these challenges. Here, we review recent advancements in MS-based molecular measurements and their role in understanding T1D.

Efficacy of Astragalus membranaceus-Carthamus tinctorius in cerebral ischemia/reperfusion injury: Insights from metabolomics and mass spectrometry imaging

BACKGROUND

The combination of Astragalus membranaceus and Carthamus tinctorius (AC) exhibits significant therapeutic effects in cerebral ischemia/reperfusion injury (CIRI). Understanding the metabolic characteristics of brain microregions and disturbances in tissues and systemic circulation is crucial for elucidating the mechanisms of CIRI and the therapeutic benefits of AC. However, in situ metabolic regulation of the complex brain structure has not been adequately studied, and the therapeutic mechanism of AC requires immediate clarification.

PURPOSE

The present study aimed to unveil the specific metabolic reprogramming of CIRI at systemic and microregional levels, identify key metabolic pathways and metabolites, and elucidate the therapeutic mechanisms of AC.

METHODS

Air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI), a newly developed technique, was used to investigate metabolites in brain microregions. Hematoxylin-eosin, Nissl, and immunofluorescence staining were performed to visualize the microscopic changes associated with spatial metabolism. A comprehensive metabolomics study was conducted on serum, brain tissue, and microregions, along with neurological assessments, cerebral infarction measurements, and Evans blue experiments, to assess the systemic and local metabolic effects of AC treatment for CIRI.

RESULTS

AC significantly reduced neurological damage, minimized infarct size, and repaired blood-brain barrier damage in CIRI rats. AFADESI-MSI demonstrated that the metabolic imbalance caused by CIRI primarily occurs in the cerebral cortex, hippocampus, caudate putamen, thalamus, cerebellar cortex, and fiber tract regions. Significant changes in 16 metabolites were observed in these regions, corresponding to neuron damage, glial cell activation, and neural repair. 20 metabolites from serum and 4 from brain tissue varied significantly with the sham group. Comprehensive metabolomics analysis indicated a close relationship among serum, tissue, and microregional metabolism. CIRI-induced systemic and localized metabolic disorders involve 14 metabolic pathways. AC conferred therapeutic benefits in CIRI by reversing various metabolic imbalances.

CONCLUSION

AFADESI-MSI efficiently visualized brain microregion metabolism. Comprehensive metabolomics analysis revealed detailed insights into the specific metabolic reprogramming in CIRI and the therapeutic impacts of AC. AC demonstrated significant clinical potential as an adjunct therapy to existing CIRI treatments.

On-tissue chemical derivatization-enhanced spatially resolved lipidomics reveals abnormal metabolism in type 2 diabetic rat brain

Neurologic disorders are often accompanied by alterations in lipids and oxylipins in the brain. However, the complexity of the lipidome in the brain and its changes during brain damage caused by diabetes remain poorly understood. Herein, we developed an enhanced spatially resolved lipidomics approach with the assistance of on-tissue chemical derivatization to study lipid metabolism in the rat brain. This method enabled the spatially resolved analysis of 560 lipids and oxylipins in 19 brain microregions in coronal and sagittal sections and remarkably improved the coverage of lipidome detection. We applied this method to lipidomic studies of the diabetic rat brain and found that lipid dysregulation followed a microregion-specific pattern. Carnitines and glycerolipids were mainly elevated in the corpus callosum (midbrain) and pineal gland regions, respectively. In addition, most oxylipins, including fatty aldehydes and oxo fatty acids, were significantly upregulated in nine brain microregions. We produced a spatially resolved analysis of lipids and oxylipins, providing a novel analytical tool for brain metabolism research.

Mobilized Electrospray Device for On-Tissue Chemical Derivatization in MALDI-MS Imaging

Applying solutions of a matrix or derivatization agent via microdroplets is a common sample preparation technique for matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) experiments. Mobilized nebulizer sprayers are commonly used to create a homogeneous matrix or reagent layer across large surfaces. Electrospray devices have also been used to produce microdroplets for the same purpose but are rarely used for large tissues due to their immobility. Herein, we present a movable electrospray device that can be used for large tissue sample preparation through a simple modification to an automatic commercial nebulizer device. As demonstrated for on-tissue chemical derivatization (OTCD) with Girard's reagent T using a mimetic tissue model, the sprayer has the additional benefit of being able to investigate reaction acceleration in OTCD when comparing electrostatically charged spray to electrostatically neutral spray. Finally, MALDI-MSI of fatty aldehydes is successfully demonstrated in rat brain tissues using this device for both OTCD and matrix application.