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MICROBIOTA-DERIVED ACETATE ENABLES THE METABOLIC FITNESS OF THE CNS INNATE IMMUNE SYSTEM DURING HEALTH AND DISEASE

ABSTRACT: As tissue macrophages of the central nervous system (CNS) microglia constitute the pivotal immune cells of this organ. Microglial features are strongly dependent on environmental cues such as commensal microbiota. Gut bacteria are known to continuously modulate microglia maturation and function by the production of short-chain fatty acids (SCFA). However, the precise mechanism of this crosstalk is unknown. Here we determined that the immature phenotype of microglia from germ-free (GF) mice is epigenetically imprinted by H3K4me3 and H3K9ac on metabolic genes associated with substantial functional alterations including increased mitochondrial mass and specific respiratory chain dysfunctions. We identified acetate as the essential microbiome-derived SCFA driving microglia maturation and regulating the homeostatic metabolic state, and further showed that it is able to modulate microglial phagocytosis and disease progression during neurodegeneration. These findings indicate that acetate is an essential bacteria-derived molecule driving metabolic pathways and functions of microglia during health and perturbation.

ORGANISM(S): Mus musculus

PROVIDER: GSE184881 | GEO | 2021/11/01

REPOSITORIES: GEO

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Project description:Background: Acetate, propionate, and butyrate are the main short-chain fatty acids (SCFA) produced in the colon as a result of microbial fermentation of dietary fibers. An increasing amount of evidence suggests that these SCFA have major health benefits. The composition of the microbiota is altered by dietary fat, and this is believed to impact SCFA production. Currently it is unknown whether host gene expression responses to SCFA are modulated by fat content of the diet. The aim of this study was to compare the changes in colonic gene expression profiles after acetate, propionate and butyrate infusions between a low fat and high fat diet. Methods: Male C57BL/6J mice were fed semi-synthetic low fat (10 energy%) or high fat (45 E%) diets starting 2 weeks before the SCFA treatment period. During treatment, mice received a rectal infusion of either an acetate, propionate, butyrate, or a saline (control) solution for 6 consecutive days, after which colon was subjected to gene expression profiling. Unsupervised visualization of the dataset was performed using Independent Principal Component Analysis. For each SCFA, similarities of its effects on a low fat and a high fat diet were assessed using Rank-Rank Hypergeometric Overlap. In addition, differentially expressed genes were identified, and gene set enrichment analysis was performed to determine functional implications of the regulated genes. Results: Taking into account the complete dataset, we observed that more variation in gene expression profiles was explained by fat content of the diet than by SCFA treatment. Gene expression responses to acetate and butyrate were similar on the low fat versus high fat diet, but were opposite for propionate. Functionally the expression changes reflected differential modulation of several metabolic processes; genes involved in oxidative phosphorylation, lipid catabolism, lipoprotein metabolism and cholesterol transport were suppressed by acetate and butyrate treatment, whereas propionate treatment resulted in changes in fatty acid and sterol biosynthesis, and in amino acid and carbohydrate metabolism. Conclusions: We demonstrated that dietary fat content impacts the colonic gene expression response to propionate, and to a lesser extent to acetate and butyrate. The study demonstrates that knowledge on diet composition is essential when studying effects of SCFAs on metabolism.

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MICROBIOTA-DERIVED ACETATE ENABLES THE METABOLIC FITNESS OF THE CNS INNATE IMMUNE SYSTEM DURING HEALTH AND DISEASE

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