Seasonal changes in the metabolomic profile of white adipose tissue in hibernating thirteen-lined ground squirrels

Hypothesis: Hibernator white adipose tissue will exhibit season-dependent remodeling of metabolic pathways. Methods: Thirteen-lined ground squirrels were captured near Lincoln, Nebraska, and housed in University of Nebraska-Lincoln veterinary facilities. Seasonal adjustments in environmental chamber lighting and air temperature were used to induce hibernation, and tissues were taken at different timepoints throughout the seasonal activity-torpor cycle. Polar compounds were extracted from white adipose tissue (N=47 across five groups) and analyzed by hydrophilic interaction liquid chromatography-mass spectrometry (HILIC-MS) in both positive and negative ion modes. Spectra were aligned, and peaks detected and identified using MS2 libraries search (mzCloud, MoNA, in-house) with Compound Discoverer (Thermo). Normalized and QC corrected feature intensities were processed using MetaboAnalyst 5.0 for statistical analysis and pathway enrichment. Results: We identified 185 compounds and 85 compounds from positive and negative HILIC-MS, respectively, including 15 compounds identified in both ion modes. Unsupervised clustering using principal component analysis revealed discrete clusters representing the different seasonal timepoints throughout hibernation. One-way analysis of variance and feature intensity heatmaps revealed metabolites that varied in abundance between active and torpid timepoints. Pathway analysis compared against the KEGG database demonstrated enrichment of amino acid metabolism and aminoacyl-tRNA biosynthesis pathways among our identified compounds. Carnitine derivatives and ketones were among molecules found to be elevated during torpor-associated timepoints relative to the active state. Summary and Conclusion: We report here the polar metabolomic profile of ground squirrel white adipose tissue at different points throughout the seasonal hibernation cycle. We identified 255 compounds and showed seasonal differences in white adipose metabolites indicating a shift of hibernator metabolism associated with torpor. Our findings indicate it is possible that white adipose directly produces ketones, rather than solely relying on hepatic ketogenesis. As our results represent steady-state measurements of metabolite abundance, further work is currently underway to identify whether hibernator adipose tissue can directly synthesize these compounds and contribute to the elevated plasma ketone concentrations during torpor observed in previous work. Funding: University of Nebraska This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.