English: "Six epigenetic clocks applied to independent test data from four rat tissue type (columns): blood, liver, heart, and hypothalamus. A–D Rat pan-tissue clock. E Rat blood clock applied to blood. F Rat liver clock applied to liver. G Rat blood clock applied to heart. H Rat brain clock applied to hypothalamus. I–L Human-rat clock measure of absolute age. M–P Human-rat clock measure of relative age defined as age/maximum species lifespan. Each bar plot reports the mean value and one standard error. p values result from analysis of variance. Student’s T test p values result from a two-group comparison of old controls (left bar) versus old, treated samples (right bar), i.e., the young controls were omitted"