Gut Microbiota–Derived Short-Chain Fatty Acids Promote Poststroke Recovery in Aged Mice

Abstract

Rationale: The elderly experience profound systemic responses after stroke, which contribute to higher mortality and more severe long-term disability. Recent studies have revealed that stroke outcomes can be influenced by the composition of gut microbiome. However, the potential benefits of manipulating the gut microbiome after injury is unknown. Objective: To determine if restoring youthful gut microbiota after stroke aids in recovery in aged subjects, we altered the gut microbiome through young fecal transplant gavage (young FTG) in aged mice after experimental stroke. Further, the effect of direct enrichment of selective bacteria producing short-chain fatty acids (SCFAs) was tested as a more targeted and refined microbiome therapy. Methods and Results: Aged male mice (18-20 months) were subjected to ischemic stroke by middle cerebral artery occlusion (MCAO). We performed FTG three days after MCAO using young donor biome (2-3 months) or aged biome (18-20 months). At day 14 after stroke, aged stroke mice receiving young FTG had less behavioral impairment, and reduced brain and gut inflammation. Based on data from microbial sequencing and metabolomics analysis demonstrating that young fecal transplants contained much higher SCFA levels and related bacterial strains, we selected four SCFA-producers (Bifidobacterium longum, Clostridium symbiosum, Faecalibacterium prausnitzii and Lactobacillus fermentum) for transplantation. These SCFA-producers alleviated post-stroke neurological deficits and inflammation, and elevated gut, brain and plasma SCFA concentrations in aged stroke mice. Conclusions: This is the first study suggesting that the poor stroke recovery in aged mice can be reversed via "post-stroke bacteriotherapy" following the replenishment of youthful gut microbiome via modulation of immunologic, microbial and metabolomic profiles in the host.

Potential caveats of putative microglia-specific markers for assessment of age-related cerebrovascular neuroinflammation

“…A previously published brain single-cell suspension protocol was used [14,40]. In brief, mice were euthanized by avertin injection.…”

“…Brain immune cell isolation was performed by optimized enzymatic digested followed by Percoll gradient protocol [14,41]. For ex vivo studies, LPS (at 100 ng/mL concentration, from Escherichia coli O111:B4, purified by phenol extraction, Millipore Sigma) was added to RPMI (containing 10% heat-inactivated fetal bovine serum, Sigma Aldrich, Cat: 12106C, ≤ 10 EU/mL endotoxin) and incubated at the sterile cell-culture environment at 37°C for 12 h. The brain tissue was harvested after cardiac perfusion with PBS to eliminate the blood from the brain tissue.…”

“…(n = 4/gp, a one-way ANOVA with Sidak's multiple comparisons test, *p < 0.05, **p < 0.01, ***p < 0.001) performed by optimized enzymatic digestion followed by Percoll gradient protocol (Fig. 4a) [14,41]. After the Percoll gradient step for myelin removal, the post-Percoll brain cells from the same brain hemispheres were incubated with or without LPS for 3 h prior to surface marker staining and analysis by flow cytometry (Fig.…”

Modulation of the Gut Microbiota of type 2 Diabetic Mice by Sodium Butyrate Attenuates Ischemic Stroke Injury

“…In recent years, tremendous progress has been made in identifying the bidirectional interactions that occur between the gut and the brain, namely, the gut-brain axis. A series of provocative studies have suggested a prominent role for the gut microbiota in ischemic stroke [22][23][24]. Thus, we aimed to seek answers from the gut.…”

“…Spychala et al [23] showed that transplantation of the gut microbiota from young mice improves stroke outcome in aged mice, suggesting that targeting microbiota composition might exert bene cial effects in those with a high risk of stroke. A recent study demonstrated that fecal transplants from young mice contain much higher levels of SCFAs and related bacterial strains, which promote poststroke recovery [24].…”