Figure 3. Fed-state serum metabolome and enriched pathways impacted by aging. Serum samples from 3-, 12-, 18- and 28 months old (3M, 12M, 18M and 28M) mice at the fed state were analyzed (n=4, 5, 4 and 4, respectively). (A) PCA analysis shows the grouped discriminations of the different age groups. 12M and 18M groups clustered together on the PC1 axis. (B) Mummichog pathway analysis plot, using peaks-to-pathway analysis module in MetaboAnalyst 4.0. The color and size of each circle corresponds to its p-value and enrichment factor, respectively. The enrichment factor of a pathway is calculated as the ratio between the number of significant pathway hits and the expected number of compound hits within the pathway . The corresponding pathways are listed in Table 1.