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Rationale DIUTHAME (desorption ionization using through‐hole alumina membrane), a recently developed matrix‐free ionization‐assisting substrate, was examined for reproducibility in terms of mass accuracy and intensity using standard lipid and mouse brain sections. The impregnation property of DIUTHAME significantly improved the reproducibility of mass accuracy and intensity compared with 2,5‐dihydroxybenzoic acid (DHB). Methods Frozen tissue sections were mounted on indium tin oxide‐coated glass slides. DIUTHAME and DHB were applied to individual sections. Subsequently, a solution of a phosphatidylcholine standard, PC(18:2/18:2), was poured onto the DIUTHAME and matrix. Finally, the samples were subjected to laser desorption ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry. The reproducibility was tested by calculating the mean ± standard deviation values of mass errors and intensities of individual ion species. Results Analysis of the PC(18:2/18:2) standard showed significantly (p < 0.01) lower mass error for DIUTHAME‐MS than for MALDI‐MS. Endogenous PC(36:4) analysis in mouse brain section also showed significantly (p < 0.05) lower mass errors for DIUTHAME‐MS. Furthermore, we investigated the mass error of some abundant lipid ions in brain sections and observed similar results. DIUTHAME‐MS displayed lower signal intensity in standard PC analysis. Interestingly, it offered higher signal intensities for all the endogenous lipid ions. Lower fluctuations of both mass accuracies and signal intensities were observed in DIUTHAME‐MS. Conclusions Our results demonstrated that DIUTHAME‐MS offers higher reproducibility for mass accuracies and intensities than MALDI‐MS in both standard lipid and mouse brain tissue analyses. It can potentially be used instead of conventional MALDI‐MS and mass spectrometry imaging analyses to achieve highly reproducible data for mass accuracy and intensity.

Background: Maintaining bioenergetic homeostasis provides a means to reduce the risk of cardiovascular events during chronological aging. Nicotinamide adenine dinucleotide (NAD + ) acts as a signaling molecule, and its levels were used to govern several biological pathways, for example, promoting angiogenesis by SIRT1 (sirtuin 1)-mediated inhibition of Notch signaling to rejuvenate capillary density of old-aged mice. NAD + modulation shows promise in the vascular remodeling of endothelial cells. However, NAD + distribution in atherosclerotic regions remains uncharacterized. Omega-3 polyunsaturated fatty acids consumption, such as docosahexaenoic acid and eicosapentaenoic acid, might increase the abundance of cofactors in blood vessels due to omega-3 polyunsaturated fatty acids metabolism. Methods: Apolipoprotein E-deficient ( ApoE −/− ) mice were fed a Western diet, and the omega-3 polyunsaturated fatty acids-treated groups were supplemented with docosahexaenoic acid (1%, w/w) or eicosapentaenoic acid (1%, w/w) for 3 weeks. Desorption electrospray ionization mass spectrometry imaging was exploited to detect exogenous and endogenous NAD + imaging. Results: NAD + , NADH, NADP + , NADPH, FAD + , FADH, and nicotinic acid adenine dinucleotide of the aortic arches were detected higher in the omega-3 polyunsaturated fatty acids-treated mice than the nontreated control. Comparing the distribution in the outer and inner layers of the arterial walls, only NADPH was detected slightly higher in the outer part in eicosapentaenoic acid-treated mice. Conclusions: Supplementation of adding docosahexaenoic acid or eicosapentaenoic acid to the Western diet led to a higher NAD + , FAD + , and their metabolites in the aortic arch. Considering the pleiotropic roles of NAD + in biology, this result serves as a beneficial therapeutic strategy in the animal model counter to pathological conditions.

Glycans are diverse structured biomolecules that play crucial roles in various biological processes. Glycosylation, an enzymatic system through which various glycans are bound to proteins and lipids, is the most common and functionally crucial post-translational modification process. It is known to be associated with brain development, signal transduction, molecular trafficking, neurodegenerative disorders, psychopathologies, and brain cancers. Glycans in glycoproteins and glycolipids expressed in brain cells are involved in neuronal development, biological processes, and central nervous system maintenance. The composition and expression of glycans are known to change during those physiological processes. Therefore, imaging of glycans and the glycoconjugates in the brain regions has become a “hot” topic nowadays. Imaging techniques using lectins, antibodies, and chemical reporters are traditionally used for glycan detection. However, those techniques offer limited glycome detection. Mass spectrometry imaging (MSI) is an evolving field that combines mass spectrometry with histology allowing spatial and label-free visualization of molecules in the brain. In the last decades, several studies have employed MSI for glycome imaging in brain tissues. The current state of MSI uses on-tissue enzymatic digestion or chemical reaction to facilitate successful glycome imaging. Here, we reviewed the available literature that applied MSI techniques for glycome visualization and characterization in the brain. We also described the general methodologies for glycome MSI and discussed its potential use in the three-dimensional MSI in the brain.

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