Visualization and quantification of cerebral metabolic fluxes of glucose in awake mice

Abstract

Biotransformation of glucose in organs includes multiple pathways, while quantitative evaluation of percentages of its utilization for individual pathways and their spatial heterogeneity in vivo remain unknown. Imaging MS (IMS) and metabolomics combined with a focused microwave irradiation for rapidly fixing tissue metabolism allowed us to quantify and visualize metabolic fluxes of glucose-derived metabolites in the mouse brain in vivo. At 15 min after the intraperitoneal injection of (13) C6 -labeled glucose, the mouse brain was exposed to focused microwave irradiation, which can stop brain metabolism within 1 s. Quantification of metabolic intermediates containing (13) C atoms revealed that a majority of the (13) C6 -glucose was diverted into syntheses of glutamate, lactate, and uridine diphosphate (UDP)-glucose. IMS showed that regions rich in glutaminergic neurons exhibited a large signal of (13) C2 -labeled glutamate. On the other hand, the midbrain region was enriched with an intensive (13) C6 -labeled UDP-glucose signal, suggesting an active glycogen synthesis. Collectively, application of the current method makes it possible to examine the fluxes of glucose metabolism in a region-specific manner.

Rewiring of embryonic glucose metabolism via suppression of PFK-1 and aldolase during mouse chorioallantoic branching

“…We investigated the distribution of lactate within E9.5 embryos using matrix-assisted laser desorption/ ionization-imaging mass spectrometry (MALDI-IMS), a useful method for visualizing the spatial distribution of individual biomolecules at a spatial resolution of ∼30 µm pitch on intact tissues (Bailey et al, 2015;Hamilton et al, 2015;Sugiura et al, 2014). Fresh frozen embryos were sectioned and analyzed by MALDI-IMS.…”

Effective Sample Preparations in Imaging Mass Spectrometry

“…Comparison of labile metabolites distributions using di erent sampling methods. 14) e FMW-treatment successfully suppressed these changes and resulted in high quality distribution images. (FMW; focused microwave irradiation, ISF; in-situ freezing, and PEF; posteuthanized freezing method)…”

“…Quantitatively, the ATP concentration in the PEF treated tissue was dramatically decreased by 1/10 compared to that for FMW treated tissue. 14) TISSUE THICKNESS e thickness of tissue slices can be an important factor. Comparison of labile metabolites distributions using di erent sampling methods.…”

Development of an Imaging Mass Spectrometry Technique for Visualizing Localized Cellular Signaling Mediators in Tissues

“…In one study, Sugiura et al, 26) we demonstrated that FMW treatment is an essential process for investigation of glucoseoriginated metabolic pathways in vivo using MS both for imaging and quanti cation.…”

“…In particular, we have developed several key techniques, including (i) a sample preparation procedure that eliminates the common e ect of postmortem (PM) degradation of labile metabolites, 26) and (ii) on-tissue derivatization of metabolites that could enhance the analyte ionization e ciency. 27) ese techniques have enabled visualization of diverse metabolite species, including not only abundant phospholipids [28][29][30] but also metabolites present in trace amounts such as minor amino acids, 31) nucleotides, 32,33) neurotransmitters, [34][35][36] and bioactive lipids, 37) in various tissues of diseased model animals (as summarized in Fig.…”