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 outco...

https://www.ahajournals.org/doi/pdf/10.1161/CIRCRESAHA.119.316448?download=true

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

Mounting evidence suggests that the gut microbiome impacts brain development and function. Gut-brain connections may be mediated by an assortment of microbial molecules that are produced in the gastrointestinal tract, which can subsequently permeate many organs, including sometimes the brain. Studies in animal models have identified molecular cues propagated from intestinal bacteria to the brain that can affect neurological function and/or neurodevelopmental and neurodegenerative conditions. Herein, we describe bacterial metabolites with known or suspected neuromodulatory activity, define mechanisms of signalling pathways from the gut microbiota to the brain and discuss direct effects that gut bacterial molecules are likely exerting on specific brain cells. Many discoveries are recent, and the findings described in this Perspective are largely novel and yet to be extensively validated. However, expanding research into the dynamic molecular communications between gut microorganisms and the CNS continues to uncover critical and previously unappreciated clues in understanding the pathophysiology of behavioural, psychiatric and neurodegenerative diseases.

Gut microbial molecules in behavioural and neurodegenerative conditions.

Microbiota-derived acetate enables the metabolic fitness of the brain innate immune system during health and disease

Background The intestinal microbiota and its metabolites have been reported to play an important role in stroke. Gut microbiota-originating short-chain fatty acids (SCFAs) modulate brain functions directly or indirectly through immune, endocrine, vagal, and other humoral pathways. However, relatively few investigations have evaluated the gut microbiome and SCFAs spectrum or their potential associations with stroke outcomes in acute ischemic stroke (AIS) patients with different stroke severities. Methods We used 16S rRNA gene sequencing and gas chromatography to compare the fecal microbial composition and SCFA spectrum between AIS patients (n = 140) and healthy controls (n = 92). Their associations with 90-day poor functional outcomes were evaluated by logistic regression models. Results We found that the intestinal microbiota distinguished AIS patients from healthy controls. A lack of SCFAs-producing bacteria and a low fecal SCFAs level defined dysbiosis in AIS patients, especially those with increased stroke severity. The SCFAs levels were negatively correlated with stroke severity and prognosis. Reduced SCFAs levels, especially acetate, were associated with an increased risk of 90-day poor functional outcomes even after adjustments. Conclusions Dysbiosis of SCFAs-producing bacteria and SCFAs in AIS patients increased the subsequent risk for poor functional outcomes, indicating that SCFAs could be potential prognostic markers and therapeutic targets for stroke.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jpen.1861

Dysbiosis of Gut Microbiota and Short-Chain Fatty Acids in Acute Ischemic Stroke and the Subsequent Risk for Poor Functional Outcomes

Multiple sclerosis (MS), an autoimmune disease of the central nervous system, generally starts as the relapsing remitting form (RRMS), but often shifts into secondary progressive MS (SPMS). SPMS represents a more advanced stage of MS, characterized by accumulating disabilities and refractoriness to medications. The aim of this study was to clarify the microbial and functional differences in gut microbiomes of the different stages of MS. Here, we compared gut microbiomes of patients with RRMS, SPMS, and two closely related disorders with healthy controls (HCs) by 16S rRNA gene and whole metagenomic sequencing data from fecal samples and by fecal metabolites. Each patient group had a number of species having significant changes in abundance in comparison with HCs, including short-chain fatty acid (SCFA)-producing bacteria reduced in MS. Changes in some species had close association with clinical severity of the patients. A marked reduction in butyrate and propionate biosynthesis and corresponding metabolic changes were confirmed in RRMS compared with HCs. Although bacterial composition analysis showed limited differences between the patient groups, metagenomic functional data disclosed an increase in microbial genes involved in DNA mismatch repair in SPMS as compared to RRMS. Together with an increased ratio of cysteine persulfide to cysteine in SPMS revealed by sulfur metabolomics, we postulate that excessive DNA oxidation could take place in the gut of SPMS. Thus, gut ecological and functional microenvironments were significantly altered in the different stages of MS. In particular, reduced SCFA biosynthesis in RRMS and elevated oxidative level in SPMS were characteristic.

https://www.pnas.org/content/pnas/117/36/22402.full.pdf

Riccardo Troisi

Papers

Propionic Acid Shapes the Multiple Sclerosis Disease Course by an Immunomodulatory Mechanism