Fecal microbiota transplantation fails to impart the benefits of circadian-dependent intermittent fasting following ischemic stroke

Intermittent fasting (IF) is known to induce significant ischemic tolerance. Diet is a major proponent of gut microbiota, and gut microbial dysbiosis plays a role in post-stroke brain damage. Hence, we currently evaluated whether IF-mediated ischemic tolerance is mediated by gut microbiota. Additionally, circadian cycle is known to modulate post-ischemic outcomes, and thus we further evaluated if gut microbiota would be influenced by prophylactic IF during the inactive phase (fasting during daytime; IIF) or active phase (fasting during nighttime; AIF). The AIF, but not IIF, cohort showed a significantly decreased fecal Firmicutes/Bacteroidetes ratio compared with the ad libitum (AL) cohort. Moreover, the levels of gut microbiota-derived metabolites butyrate and propionate decreased in AL cohort following focal ischemia, whereas they increased in AIF cohort. However, fecal microbiota transplantation (FMT) from IIF or AIF cohort had no significant effects on post-ischemic motor and cognitive function recovery, anxiety-, and depression-like behaviors compared with FMT from AL cohort. Furthermore, FMT from IIF or AIF cohort did not influence the post-ischemic infarct volume, atrophy volume or white matter damage. Overall, the current findings indicate that the beneficial effects of IF after focal ischemia are not mediated by the gut microbiota.