Fig. 3: SA pathway metabolite levels anti-correlate with lipid droplet levels during aging.

a The SA-BNA pathway, including metabolite names, genes, and sources of crosstalk (purple dashed arrows) between the aromatic amino acid synthesis and BNA pathways. b–i Ratios of metabolites from glycolysis, the shikimate and aromatic amino acid pathways, and the BNA pathway are plotted black, red, or blue, respectively. b Middle-aged Control (WT, AB18-07) and BNA2-OE cells were analyzed by global metabolomics (see Methods). Measurements of specific metabolites (arbitrary units) detected from n = 3 independent experiments were normalized to cell counts within each experiment. The normalized measurements from BNA2-OE cells were divided by the normalized measurements from Control (WT) cells for each experiment, and these ratios were then averaged and plotted as a ratio of metabolite levels in BNA2-OE versus control cells ± SEM (see Supplementary Fig. 4 and source data). c–i Cells as indicated were analyzed by targeted metabolomics (see Methods and source data). Measurements of specific metabolites detected in the shikimate (red symbols) or BNA (blue symbols) pathways in Control (WT, AB18-07, dots), BNA2-OE (squares), BNA2-OE aro1 (triangles), and BNA2-OE bna6 (diamonds) cells were normalized to cell counts, averaged from n = 4 independent experiments and reported as arbitrary units ± SEM. #Below limit of detection. Paired t-test (two-tailed): p ≤ 0.05 indicated in figure panels; ****p ≤ 0.0001; p > 0.05 indicated as ns (not significant). j Model for the mechanism by which BNA2-OE suppresses the accumulation of lipid droplets during aging and extends lifespan. Aged Control (WT) cells accumulate lipid droplets during normal aging. BNA2 overexpression (BNA2-OE) decreases lipid-droplet accumulation by pulling some substrates away from lipid droplets through the shikimate and aromatic amino acid (SA) pathways toward the BNA pathway. A deletion in ARO1 prevents BNA2-OE from pulling flux through the SA pathway and from suppressing lipid-droplet accumulation during aging, whereas lifespan extension by BNA2-OE correlates with increasing the branch point metabolite xanthurenate. Source data for (b–i) are provided as a Source data file.