Fig. 5

Heatmap of hierarchical clustering analysis of differential metabolites for 25 weeks (n = 3 biological replicates, each measured 3 times) old RPE cells versus 4 (n = 3 biological replicates, each measured 3 times), 12 (n = 3 biological replicates, each measured 3 times), and 17 (n = 3 biological replicates, each measured 3 times) weeks old cells, A in positive ion mode and B in negative ion mode (see Additional file 4 for individual data values). Significantly different compounds were found through Kruskal–Wallis test with Benjamini–Hochberg correction and only the ones with adjusted p value < 0.001 and fold-change > 16 were plotted. Data was averaged among replicates. Relevant clusters of metabolites are highlighted