We describe the anaerobic conversion of inositol stereoisomers to propionate and acetate by the abundant intestinal genus Anaerostipes. A inositol pathway was elucidated by nuclear magnetic resonance using [¹³C]-inositols, mass spectrometry and proteogenomic analyses in A. rhamnosivorans, identifying 3-oxoacid CoA transferase as a key enzyme involved in both 3-oxopropionyl-CoA and propionate formation. This pathway also allowed conversion of phytate-derived inositol into propionate as shown with [¹³C]-phytate in fecal samples amended with A. rhamnosivorans. Metabolic and (meta)genomic analyses explained the adaptation of Anaerostipes spp. to inositol-containing substrates and identified a propionate-production gene cluster to be inversely associated with metabolic biomarkers in (pre)diabetes cohorts. Co-administration of myo-inositol with live A. rhamnosivorans in western-diet fed mice reduced fasting-glucose levels comparing to heat-killed A. rhamnosivorans after 6-weeks treatment. Altogether, these data suggest a potential beneficial role for intestinal Anaerostipes spp. in promoting host health.

Summary: Intestinimonas is a newly described bacterial genus with representative strains present in the intestinal tract of human and other animals. Despite unique metabolic features including the production of butyrate from both sugars and amino acids, there is to date no data on their diversity, ecology, and physiology. Using a comprehensive phylogenetic approach, Intestinimomas was found to include at least three species that colonize primarily the human and mouse intestine. We focused on the most common and cultivable species of the genus, Intestinimonas butyriciproducens , and performed detailed genomic and physiological comparison of strains SRB521 ^T and AF211, isolated from the mouse and human gut respectively. The complete 3.3‐Mb genomic sequences of both strains were highly similar with 98.8% average nucleotide identity, testifying to their assignment to one single species. However, thorough analysis revealed significant genomic rearrangements, variations in phage‐derived sequences, and the presence of new CRISPR sequences in both strains. Moreover, strain AF211 appeared to be more efficient than strain SRB521 ^T in the conversion of the sugars arabinose and galactose. In conclusion, this study provides genomic and physiological insight into Intestinimonas butyriciproducens , a prevalent butyrate‐producing species, differentiating strains that originate from the mouse and human gut.

The human gut microbiome strongly influences host metabolism by fermenting dietary components into metabolites that signal to the host. Our previous work has shown that Intestinimonas butyriciproducens is a prevalent commensal bacterium with the unique ability to convert dietary fructoselysine to butyrate, a well-known signaling molecule with proven health benefits. Dietary fructoselysine is an abundant Amadori product formed in foods during thermal treatment and is part of foods rich in dietary advanced glycation end products which have been associated with cardiometabolic disease. It is therefore of interest to investigate the causal role of this bacterium and fructoselysine metabolism in metabolic disorders. We assessed associations of I. butyriciproducens with metabolic risk biomarkers at both strain and functional levels using a human cohort characterized by fecal metagenomic analysis. We observed that the level of the bacterial strain as well as fructoselysine fermentation genes were negatively associated with BMI, triglycerides, HbA1c, and fasting insulin levels. We also investigated the fructoselysine degradation capacity within the Intestinimonas genus using a culture-dependent approach and found that I. butyriciproducens is a key player in the butyrogenic fructoselysine metabolism in the gut. To investigate the function of I. butyriciproducens in host metabolism, we used the diet-induced obesity mouse model to mimic the human metabolic syndrome. Oral supplementation with I. butyriciproducens counteracted body weight gain, hyperglycemia, and adiposity. In addition, within the inguinal white adipose tissue, bacterial administration reduced inflammation and promoted pathways involved in browning and insulin signaling. The observed effects may be partly attributable to the formation of the short-chain fatty acids butyrate from dietary fructoselysine, as butyrate plasma and cecal levels were significantly increased by the bacterial strain, thereby contributing to the systemic effects of the bacterial treatment. I. butyriciproducens ameliorates host metabolism in the context of obesity and may therefore be a good candidate for new microbiota-therapeutic approaches to prevent or treat metabolic diseases.

The human intestinal tract harbors diverse and complex microbial communities that have a vast metabolic capacity including the breakdown of complex carbohydrates into short chain fatty acids, acetate, propionate, and butyrate. As butyrate is beneficial for gut health there is much attention on butyrogenic bacteria and their role in the colonic anaerobic food chain. However, our understanding how production of butyrate by gut microorganisms is controlled by interactions between different species and environmental nutrient availability is very limited. To address this, we set up experimental in vitro co-culture systems to study the metabolic interactions of Anaerostipes rhamnosivorans, a butyrate producer with each of its partners; Blautia hydrogenotrophica, an acetogen; Methanobrevibacter smithii, a methanogen and Bacteroides thetaiotaomicron, a versatile degrader of plant cell wall pectins; through corresponding specific cross-feeding. In all co-cultures, A. rhamnosivorans was able to benefit from its partner for enhanced butyrate formation compared to monocultures. Interspecies transfer of hydrogen or formate from A. rhamnosivorans to the acetogen B. hydrogenotrophica and in turn of acetate from the acetogen to the butyrogen were essential for butyrate formation. A. rhamnosivorans grown on glucose supported growth of M. smithii via interspecies formate/hydrogen transfer enhancing butyrate formation. In the co-culture with pectin, lactate was released by B. thetaiotaomicron which was concomitantly used by A. rhamnosivorans for the production of butyrate. Our findings indicate enhanced butyrate formation through microbe-microbe interactions between A. rhamnosivorans and an acetogen, a methanogen or a pectin-degrader. Such microbial interactions enhancing butyrate formation may be beneficial for colonic health.

Dietary intake of phytate has various reported health benefits. Previous work showed that the gut microbiota can convert phytate to short-chain fatty acids (SCFAs), but the microbial species and metabolic pathway are unclear. Here we identified Mitsuokella jalaludinii as an efficient phytate degrader, which works synergistically with Anaerostipes rhamnosivorans to produce the SCFA propionate. Analysis of published human gut taxonomic profiles revealed that Mitsuokella spp., in particular M. jalaludinii, are prevalent in human gut microbiomes. NMR spectroscopy using ¹³C-isotope labelling, metabolomic and transcriptomic analyses identified a complete phytate degradation pathway in M. jalaludinii, including production of the intermediate Ins(2)P/myo-inositol. The major end product, 3-hydroxypropionate, was converted into propionate via a synergistic interaction with Anaerostipes rhamnosivorans both in vitro and in mice. Upon [¹³C₆]phytate administration, various ¹³C-labelled components were detected in mouse caecum in contrast with the absence of [¹³C₆] InsPs or [¹³C₆]myo-inositol in plasma. Caco-2 cells incubated with co-culture supernatants exhibited improved intestinal barrier integrity. These results suggest that the microbiome plays a major role in the metabolism of this phytochemical and that its fermentation to propionate by M. jalaludinii and A. rhamnosivorans may contribute to phytate-driven health benefits.

Anaerobutyricum soehngenii (previously Eubacterium hallii) is a butyrate-producing next-generation beneficial microbe generally recognized as safe. Several short-term intervention trials by A. soehngenii L2-7 have shown improvement of insulin sensitivity in prediabetic subjects and type 2 diabetes patients. To determine the long-term cardiometabolic benefits and safety, we performed a 3-month double-blind, randomized placebo-controlled intervention in 98 prediabetic insulin-resistant adults in Europe and U.S. with daily administration of encapsulated cells of A. soehngenii CH-106, a tetracycline-sensitive isogenic derivative of strain L2-7. Compared to placebo, A. soehngenii-treated subjects showed significantly reduced glycemic variability (1% reduction in the coefficient of variation; p = 0.01) and improved glycemic control (6% reduction in the overall net glycemic action-1; p < 0.05), including reduced serum glycated hemoglobin (HbA1c) levels when including the 4-week washout period (1 mmol/mol reduction; p < 0.05). Moreover, diastolic blood pressure was significantly reduced in all A. soehngenii-treated subjects (3 mm Hg; p < 0.05). The study product was well-tolerated and had no effect on the global intestinal microbiota composition, including alpha and beta-diversity, besides an increased abundance of A. soehngenii in the treatment group, indicative of compliance. The U.S. participants, compared to those in Europe, responded best, notably in the oral glucose tolerance tests (15% improvement in the area-under-the curve of plasma glucose levels; p = 0.039) or coefficient of variation (reduction of 3.1%; p < 0.05). This potentially relates to a more severe prediabetic state in U.S. subjects, associated with significantly reduced (1.5-3.5-fold) relative abundance of Bifidobacterium, Coprococcus, Ruminococcus spp. and two-fold increased relative abundance of Lachnoclostridium spp. In conclusion, daily oral supplementation with A. soehngenii was safe and improved various markers of glycemic control, reduced HbA1c levels and diastolic blood pressure, indicating a novel microbiome-based approach to improve cardio-metabolic health in adults at risk for developing type 2 diabetes.Clinical trial reg. no. NCT04529473, clinicaltrials.govSocial media summary 120 characters: Anaerobutyricum soehngenii supplementation improves #cardio-metabolic health in subjects at risk for type 2 #diabetes.