Spatially resolved characterization of tissue metabolic compartments in fasted and high-fat diet livers

Abstract

Cells adapt their metabolism to physiological stimuli, and metabolic heterogeneity exists between cell types, within tissues, and subcellular compartments. The liver plays an essential role in maintaining whole-body metabolic homeostasis and is structurally defined by metabolic zones. These zones are well-understood on the transcriptomic level, but have not been comprehensively characterized on the metabolomic level. Mass spectrometry imaging (MSI) can be used to map hundreds of metabolites directly from a tissue section, offering an important advance to investigate metabolic heterogeneity in tissues compared to extraction-based metabolomics methods that analyze tissue metabolite profiles in bulk. We established a workflow for the preparation of tissue specimens for matrix-assisted laser desorption/ionization (MALDI) MSI that can be implemented to achieve broad coverage of central carbon, nucleotide, and lipid metabolism pathways. Herein, we used this approach to visualize the effect of nutrient stress and excess on liver metabolism. Our data revealed a highly organized metabolic tissue compartmentalization in livers, which becomes disrupted under high fat diet. Fasting caused changes in the abundance of several metabolites, including increased levels of fatty acids and TCA intermediates while fatty livers had higher levels of purine and pentose phosphate-related metabolites, which generate reducing equivalents to counteract oxidative stress. This spatially conserved approach allowed the visualization of liver metabolic compartmentalization at 30 μm pixel resolution and can be applied more broadly to yield new insights into metabolic heterogeneity in vivo.

Identification of the metabolic state of surviving cardiomyocytes in the human infarcted heart by spatial single-cell transcriptomics

“…ScMetabolism analysis suggests that surviving CMs exhibit upregulated purine and pyrimidine metabolism, which may be beneficial in protecting ischemic CM from glucose starvation in the ischemic environment. In addition, the increased activity of pyrimidine and purine metabolism implies an increased demand for nucleotides, which is a typical feature of proliferating cells, and for DNA repair and biosynthesis owing to oxidative stress-induced DNA damage [35,36] .…”

Spatial metabolomics and its application in the liver

“…In addition, a recent study using MSI has shown hepatocyte heterogeneity in terms of amino acid and lipid composition 69 . Also, using MSI, liver metabolome was shown to change with fasting in a localized pattern, including increased levels of fatty acids and tricarboxylic acid cycle intermediates 70 …”

“…• HFD associated with oxidative stress, PPP, and purine metabolism 2022 Stopka et al [70] Abbreviations: (Au)LDI-MS, gold-laser desorption/ionization mass spectrometry; Au-CBS-LDI MS, sodium-doped gold-assisted laser desorption ionization mass spectrometry; B model, hepatocyte fatty acid content within the liver microenvironment was specific to proximity to the vasculature under nonfasting conditions. Specifically, fatty acid docosahexaenoic and arachidonic acid were spatially distributed, with docosahexaenoic closer to the blood vessels opposing to the arachidonic acid location.…”

“…This technique revealed new perspectives of looking at spatial liver zonation to better understand how liver cells cope with different nutrient supplies and how it modulates liver disease. [70] The alleviation effect of the Asian herb Eurycoma longifolia on HFD-fed mice resulted in weight loss with beneficial effects for the treatment of NAFLD, namely enhanced decomposition and inhibition of accumulation of lipids. [141] Using DESI, HFD mice treated with E. longifolia showed an altered metabolic profile, mainly affecting the levels of amino acids, organic acids, phospholipids, and glycerolipids.…”

“…Spatial liver metabolomics was recently used in another study to achieve broad coverage of central carbon, nucleotide, and lipid metabolism pathways 70 . A workflow was implemented to prepare tissue specimens for MALDI-MSI.…”