Figure 5.

(A) Relative infarct volume 30 days after stroke in young and aged mice with either a young microbiota (biome) or aged biome. Regardless of the biome received, aged mice (N = 10) had significantly smaller levels of cerebral atrophy after stroke compared to young mice (N = 10; p = 0.004 Kruskal‐Wallis ANOVA on ranks). *p < 0.05 compared to corresponding species in the young. (B, left side of panels) Fecal propionate and acetate compositions were significantly less in aged mice when compared to young at baseline p < 0.001 for each SCFA, n = 8/group, left side of the upper and lower panels). (B, right side of panels) Changes in acetate and propionate after fecal transplant gavage but immediately before MCAO (time 0) and several time points over 28 days post‐MCAO. As with the naïve mice, both acetate and propionate were decreased in mice with aged microbiomes. For acetate in both the young and aged mice (B, top panel), there was a significant main effect of microbiome (young or aged, p < 0.001; N = 8/group), a significant effect of time after MCAO (p = 0.018), and a significant interaction between time after MCAO and microbiome (p = 0.005). Similarly, propionate showed a significant main effect of the microbiome for both young and aged mice (p < 0.001; N = 8/group) and a significant interaction between microbiome and time (p = 0.012). *p ≤ 0.01 compared to corresponding group with an aged microbiome (Holm‐Sidak post‐hoc test). ANOVA = analysis of variance; MCAO = middle cerebral artery occlusion; SCFA = short‐chain fatty acid.