Gut Microbial Dysbiosis is Correlated with Stroke Severity Markers in Aged Rats Following Stroke

Background: An imbalanced gut microbial community, or dysbiosis, has been shown to occur following stroke. It is possible that this dysbiosis negatively impacts stroke recovery and rehabilitation. Species level resolution measurements of the gut microbiome following stroke are needed to develop and test precision interventions such as probiotic or fecal microbiota transplant therapies that target the gut microbiome following stroke. Previous studies have used 16S rRNA amplicon sequencing in young male mice to obtain broad profiling of the gut microbiome at the genus level following stroke, but further investigations will be needed with whole genome shotgun sequencing in aged rats of both sexes to obtain species level resolution in a model which will better translate to the demographics of human stroke patients.Results: 39 aged male and female rats underwent middle cerebral artery occlusion. Fecal samples were collected before stroke and three days post stroke to measure gut microbiome. Machine learning was used to identify the top ranked bacteria which were changed following stroke. MRI imaging was used to obtain infarct and edema size and cerebral blood flow (CBF). ELISA was used to obtain inflammatory markers. Dysbiosis was demonstrated by an increase in pathogenic bacteria such as Butyricimonas virosa (15.52 fold change, p<0.0001), Bacteroides vulgatus (7.36 fold change, p<0.0001), and Escherichia coli (47.67 fold change, p<0.0001). These bacteria were positively associated with infarct and edema size and with the inflammatory markers Ccl19, Ccl24, IL17a, IL3, and complement C5; they were negatively correlated with CBF. Conversely, beneficial bacteria such as Ruminococcus flavefaciens (0.14 fold change, p<0.0001), Akkermansia muciniphila (0.78 fold change, p<0.0001), and Lactobacillus murinus (0.40 fold change, p<0.0001) were decreased following stroke and associated with all the previous parameters in the opposite direction of the pathogenic species. There were not significant microbiome differences between the sexes.Conclusion: The species level resolution measurements found here can be used as a foundation to develop and test precision interventions targeting the gut microbiome following stroke. Probiotics that include Ruminococcus flavefaciens, Akkermansia muciniphila, and Lactobacillus murinus should be developed to target the deficit following stroke to measure the impact on stroke severity.

n-6 High Fat Diet Induces Gut Microbiome Dysbiosis and Colonic Inflammation

Background: Concerns are emerging that a high-fat diet rich in n-6 PUFA (n-6HFD) may alter gut microbiome and increase the risk of intestinal disorders. Research is needed to model the relationships between consumption of an n-6HFD starting at weaning and development of gut dysbiosis and colonic inflammation in adulthood. We used a C57BL/6J mouse model to compare the effects of exposure to a typical American Western diet (WD) providing 58.4%, 27.8%, and 13.7% energy (%E) from carbohydrates, fat, and protein, respectively, with those of an isocaloric and isoproteic soybean oil-rich n-6HFD providing 50%E and 35.9%E from total fat and carbohydrates, respectively on gut inflammation and microbiome profile. Methods: At weaning, male offspring were assigned to either the WD or n-6HFD through 10–16 weeks of age. The WD included fat exclusively from palm oil whereas the n-6HFD contained fat exclusively from soybean oil. We recorded changes in body weight, cyclooxygenase-2 (COX-2) expression, colon histopathology, and gut microbiome profile. Results: Compared to the WD, the n-6HFD increased plasma levels of n-6 fatty acids; colonic expression of COX-2; and the number of colonic inflammatory and hyperplastic lesions. At 16 weeks of age, the n-6HFD caused a marked reduction in the gut presence of Firmicutes, Clostridia, and Lachnospiraceae, and induced growth of Bacteroidetes and Deferribacteraceae. At the species level, the n-6HFD sustains the gut growth of proinflammatory Mucispirillum schaedleri and Lactobacillus murinus. Conclusions: An n-6HFD consumed from weaning to adulthood induces a shift in gut bacterial profile associated with colonic inflammation.

Lactobacillus Murinus Alleviates Intestinal Ischemia/Reperfusion Injury Through Promoting the Release of Interleukin-10 From M2 Macrophages via Toll-like Receptor 2 Signaling

BackgroundIntestinal ischemia/reperfusion (I/R) injury has high morbidity and mortality. Gut microbiota is one of the potential key factors affecting intestinal I/R injury. Different populations exhibit different sensitivities to intestinal I/R injury, but whether this is related to differences in gut microbiota is unclear. Here, to elucidate the interaction between the gut microbiome and intestinal I/R injury, we conducted 16S rRNA gene sequencing and fecal microbiota transplantation experiment in an I/R mouse model. Toll-like receptor 2 (TLR2)-deficient mice, interleukin-10 (IL-10)-deficient mice as well as the transwell co-culture system of small intestine organoids and macrophages were used to explore the potential mechanism of bacteria attenuating intestinal I/R injury.ResultsThe intestinal I/R-sensitive (Sen) and resistant (Res) mice were first defined according to different survival outcomes of mice suffering from intestinal I/R. Fecal microbiota composition and diversity prior to intestinal ischemia were different between in Sen and Res mice. The relative abundance of Lactobacillus murinus (L. murinus) at the species level was higher in Res mice than in Sen mice, and the fold change was the largest. Clinically, the abundance of L. murinus in preoperative feces of patients undergoing cardiopulmonary bypass surgery was closely related to the degree of intestinal I/R injury after surgery. Treatment with L. murinus significantly prevented from intestinal I/R-induced intestinal injury and improved the survival of mice, which depends on the participation of macrophages. Further, in vivo and vitro experiments indicated that L. murinus promoted the release of IL-10 from M2 macrophages via activating TLR2 signaling to alleviate intestinal I/R injury. ConclusionGut microbiome is involved in the postoperative outcome of intestinal I/R. L. murinus promotes the release of IL-10 from M2 macrophages through TLR2 signaling to alleviate intestinal I/R injury, revealing a novel mechanism of intestinal I/R injury and new therapeutic strategy for clinical practice.