The complex polymicrobial composition of human gut microbiota plays a key role in health and disease. Lachnospiraceae belong to the core of gut microbiota, colonizing the intestinal lumen from birth and increasing, in terms of species richness and their relative abundances during the host’s life. Although, members of Lachnospiraceae are among the main producers of short-chain fatty acids, different taxa of Lachnospiraceae are also associated with different intra- and extraintestinal diseases. Their impact on the host physiology is often inconsistent across different studies. Here, we discuss changes in Lachnospiraceae abundances according to health and disease. With the aim of harnessing Lachnospiraceae to promote human health, we also analyze how nutrients from the host diet can influence their growth and how their metabolites can, in turn, influence host physiology.

https://www.mdpi.com/2076-2607/8/4/573/pdf

The Controversial Role of Human Gut Lachnospiraceae.

The environment, diet, microbiota and body’s metabolism shape complex biological processes in health and disease. However, our understanding of the molecular pathways involved in these processes is still limited. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that integrates environmental, dietary, microbial and metabolic cues to control complex transcriptional programmes in a ligand-specific, cell-type-specific and context-specific manner. In this Review, we summarize our current knowledge of AHR and the transcriptional programmes it controls in the immune system. Finally, we discuss the role of AHR in autoimmune and neoplastic diseases of the central nervous system, with a special focus on the gut immune system, the gut–brain axis and the therapeutic potential of targeting AHR in neurological disorders. By sensing environmental, dietary, microbial and metabolic cues, the ligand-activated transcription factor aryl hydrocarbon receptor controls complex transcriptional programmes that are relevant to autoimmune, neoplastic, metabolic and degenerative diseases.

The aryl hydrocarbon receptor: an environmental sensor integrating immune responses in health and disease.

Low-grade inflammation is the hallmark of metabolic disorders such as obesity, type 2 diabetes and nonalcoholic fatty liver disease. Emerging evidence indicates that these disorders are characterized by alterations in the intestinal microbiota composition and its metabolites, which translocate from the gut across a disrupted intestinal barrier to affect various metabolic organs, such as the liver and adipose tissue, thereby contributing to metabolic inflammation. Here, we discuss some of the recently identified mechanisms that showcase the role of the intestinal microbiota and barrier dysfunction in metabolic inflammation. We propose a concept by which the gut microbiota fuels metabolic inflammation and dysregulation. Here, the authors describe how metabolic disorders, such as type 2 diabetes and nonalcoholic fatty liver disease, are driven by alterations in the composition of the intestinal microbiota and its metabolites, which translocate from the gut across a disrupted intestinal barrier and contribute to metabolic inflammation.

The intestinal microbiota fuelling metabolic inflammation

Metabolic disorders represent a growing worldwide health challenge due to their dramatically increasing prevalence. The gut microbiota is a crucial actor that can interact with the host by the production of a diverse reservoir of metabolites, from exogenous dietary substrates or endogenous host compounds. Metabolic disorders are associated with alterations in the composition and function of the gut microbiota. Specific classes of microbiota-derived metabolites, notably bile acids, short-chain fatty acids, branched-chain amino acids, trimethylamine N-oxide, tryptophan and indole derivatives, have been implicated in the pathogenesis of metabolic disorders. This review aims to define the key classes of microbiota-derived metabolites that are altered in metabolic diseases and their role in pathogenesis. They represent potential biomarkers for early diagnosis and prognosis as well as promising targets for the development of novel therapeutic tools for metabolic disorders.

https://gut.bmj.com/content/gutjnl/70/6/1174.full.pdf

Gut microbiota-derived metabolites as central regulators in metabolic disorders.

Qualified presumption of safety (QPS) was developed to provide a generic safety evaluation for biological agents to support EFSA's Scientific Panels. The taxonomic identity, body of knowledge, safety concerns and antimicrobial resistance are assessed. Safety concerns identified for a taxonomic unit (TU) are where possible to be confirmed at strain or product level, reflected by 'qualifications'. No new information was found that would change the previously recommended QPS TUs and their qualifications. The list of microorganisms notified to EFSA was updated with 54 biological agents, received between April and September 2019; 23 already had QPS status, 14 were excluded from the QPS exercise (7 filamentous fungi, 6 Escherichia coli, Sphingomonas paucimobilis which was already evaluated). Seventeen, corresponding to 16 TUs, were evaluated for possible QPS status, fourteen of these for the first time, and Protaminobacter rubrum, evaluated previously, was excluded because it is not a valid species. Eight TUs are recommended for QPS status. Lactobacillus parafarraginis and Zygosaccharomyces rouxii are recommended to be included in the QPS list. Parageobacillus thermoglucosidasius and Paenibacillus illinoisensis can be recommended for the QPS list with the qualification 'for production purposes only' and absence of toxigenic potential. Bacillus velezensis can be recommended for the QPS list with the qualification 'absence of toxigenic potential and the absence of aminoglycoside production ability'. Cupriavidus necator, Aurantiochytrium limacinum and Tetraselmis chuii can be recommended for the QPS list with the qualification 'production purposes only'. Pantoea ananatis is not recommended for the QPS list due to lack of body of knowledge in relation to its pathogenicity potential for plants. Corynebacterium stationis, Hamamotoa singularis, Rhodococcus aetherivorans and Rhodococcus ruber cannot be recommended for the QPS list due to lack of body of knowledge. Kodamaea ohmeri cannot be recommended for the QPS list due to safety concerns.

https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2020.5965

Update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA 13: suitability of taxonomic units notified to EFSA until September 2020.

Impaired Aryl Hydrocarbon Receptor Ligand Production by the Gut Microbiota Is a Key Factor in Metabolic Syndrome.

Host-microbe balance maintains intestinal homeostasis and strongly influences inflammatory conditions such as inflammatory bowel diseases (IBD) Here we focused on bacteria-fungi interactions and their implications on intestinal inflammation, a poorly understood area Dextran sodium sulfate (DSS)-induced colitis was assessed in mice treated with vancomycin (targeting gram-positive bacteria) or colistin (targeting Enterobacteriaceae) and supplemented with either Saccharomyces boulardii CNCM I-745 or Candida albicans Inflammation severity as well as bacterial and fungal microbiota compositions was monitored While S boulardii improved DSS-induced colitis and C albicans worsened it in untreated settings, antibiotic treatment strongly modified DSS susceptibility and effects of fungi on colitis Vancomycin-treated mice were fully protected from colitis, while colistin-treated mice retained colitis phenotype but were not affected anymore by administration of fungi Antibacterial treatments not only influenced bacterial populations but also had indirect effects on fungal microbiota Correlations between bacterial and fungal relative abundance were dramatically decreased in colistin-treated mice compared to vancomycin-treated and control mice, suggesting that colistin-sensitive bacteria are involved in interactions with fungi Restoration of the Enterobacteriaceae population by administrating colistin-resistant Escherichia coli reestablished both beneficial effects of S boulardii and pathogenic effects of C albicans on colitis severity This effect was at least partly mediated by an improved gut colonization by fungi Fungal colonization of the gut is affected by the Enterobacteriaceae population, indirectly modifying effects of mycobiome on the host This finding provides new insights into the role of inter-kingdom functional interactions in intestinal physiopathology and potentially in IBD

/pdf/enterobacteriaceae-are-essential-for-the-modulation-of-2u97q4ubjq.pdf

Jérémy Glodt

Papers

Impaired Aryl Hydrocarbon Receptor Ligand Production by the Gut Microbiota Is a Key Factor in Metabolic Syndrome.

Enterobacteriaceae are essential for the modulation of colitis severity by fungi