Figure 1

Changes of polar metabolites during BAT-aging. (a) Venn diagram representing metabolites from BAT samples that were collected from animals aged 2.5, 5, 10, 15, 21, and 25 months (n = 3/ age-group). All metabolites were detected by LC–MS and GC–MS metabolomic analysis. 368 compounds were detected (light grey) and grouped into non-polar lipid species (227 candidates; light blue) and polar metabolites (141 candidates; light red). For each group, clusters of metabolites with significant correlation to aging across the age-groups were identified, corresponding to 48 non-polar lipid species (dark blue) and 20 polar metabolites (dark red). (b) Heatmap representing concentrations of the 20 individual polar metabolites that were significantly correlated to BAT-aging in the individual animals from each age group. (c) Pathway enrichment analysis for the 20 polar metabolites with significant age-related correlation using MetaboAnalyst software. Grey line indicates formal threshold of significant enrichment. (d) Summary of all pathways identified from the enriched polar metabolites, including pathways with significant enrichment (bold; p < 0.05), after grouping into three functionally related sub-clusters, i.e. (1) nutrient/ energy metabolism, (2) nucleotide metabolism, and (3) vitamin metabolism.