Dysbiosis of the intestinal microbiota has been implicated in insulin resistance, although evidence regarding causality in humans is scarce. We performed a phase I/II dose-finding and safety study on the effect of oral intake of the anaerobic butyrogenic strain Anaerobutyricum soehngenii on glucose metabolism in 24 subjects with metabolic syndrome. We found that treatment with A. soehngenii was safe and observed a significant correlation between the measured fecal abundance of administered A. soehngenii and improvement in peripheral insulin sensitivity after 4 weeks of treatment. This was accompanied by an altered microbiota composition and a change in bile acid metabolism. Finally, we show that metabolic response upon administration of A. soehngenii (defined as improved insulin sensitivity 4 weeks after A. soehngenii intake) is dependent on microbiota composition at baseline. These data in humans are promising, but additional studies are needed to reproduce our findings and to investigate long-term effects, as well as other modes of delivery.

The importance of the commensal microbiota to human health and well-being has become increasingly evident over the past decades. From a therapeutic perspective, the popularity of fecal microbiota transplantation (FMT) to restore a disrupted microbiota and amend imbalances has increased. To date, most clinical experience with FMT originates from the treatment of recurrent or refractory Clostridioides difficile infections (rCDI), with resolution rates up to 90%. In addition to CDI, a role for the intestinal microbiome has been implicated in several disorders. FMT has been tested in several randomized controlled trials for the treatment of inflammatory bowel disease, irritable bowel disease and constipation with mixed results. FMT has also been explored for extra-gastrointestinal disorders such as metabolic syndrome, hepatic encephalopathy and graft-versus-host disease. With the exception of recurrent CDI, FMT is currently used in experimental settings only and should not yet be offered as standard care. In addition, it is critical to further standardize and optimize procedures for FMT preparation. This includes determination of active components of FMT to develop (personalized) approaches to treat disease.

There is significant interest in altering the course of cardiometabolic disease development via gut microbiomes. Nevertheless, the highly abundant phage members of the complex gut ecosystem -which impact gut bacteria- remain understudied. Here, we show gut virome changes associated with metabolic syndrome (MetS), a highly prevalent clinical condition preceding cardiometabolic disease, in 196 participants by combined sequencing of bulk whole genome and virus like particle communities. MetS gut viromes exhibit decreased richness and diversity. They are enriched in phages infecting Streptococcaceae and Bacteroidaceae and depleted in those infecting Bifidobacteriaceae. Differential abundance analysis identifies eighteen viral clusters (VCs) as significantly associated with either MetS or healthy viromes. Among these are a MetS-associated Roseburia VC that is related to healthy control-associated Faecalibacterium and Oscillibacter VCs. Further analysis of these VCs revealed the Candidatus Heliusviridae, a highly widespread gut phage lineage found in 90+% of participants. The identification of the temperate Ca. Heliusviridae provides a starting point to studies of phage effects on gut bacteria and the role that this plays in MetS.

ObjectiveAlthough gut dysbiosis is increasingly recognised as a pathophysiological component of metabolic syndrome (MetS), the role and mode of action of specific gut microbes in metabolic health remain elusive. Previously, we identified the commensal butyrogenic Anaerobutyricum soehngenii to be associated with improved insulin sensitivity in subjects with MetS. In this proof-of-concept study, we investigated the potential therapeutic effects of A. soehngenii L2-7 on systemic metabolic responses and duodenal transcriptome profiles in individuals with MetS.DesignIn this randomised double-blind placebo-controlled cross-over study, 12 male subjects with MetS received duodenal infusions of A. soehngenii/ placebo and underwent duodenal biopsies, mixed meal tests (6 hours postinfusion) and 24-hour continuous glucose monitoring.ResultsA. soehngenii treatment provoked a markedly increased postprandial excursion of the insulinotropic hormone glucagon-like peptide 1 (GLP-1) and an elevation of plasma secondary bile acids, which were positively associated with GLP-1 levels. Moreover, A. soehngenii treatment robustly shaped the duodenal expression of 73 genes, with the highest fold induction in the expression of regenerating islet-protein 1B (REG1B)-encoding gene. Strikingly, duodenal REG1B expression positively correlated with GLP-1 levels and negatively correlated with peripheral glucose variability, which was significantly diminished in the 24 hours following A. soehngenii intake. Mechanistically, Reg1B expression is induced upon sensing butyrate or bacterial peptidoglycan. Importantly, A. soehngenii duodenal administration was safe and well tolerated.ConclusionsA single dose of A. soehngenii improves peripheral glycaemic control within 24 hours; it specifically stimulates intestinal GLP-1 production and REG1B expression. Further studies are needed to delineate the specific pathways involved in REG1B induction and function in insulin sensitivity.Trial registration numberNTR-NL6630.

Background The increasing interest to perform and investigate the efficacy of fecal microbiota transplantation (FMT) has generated an urge for feasible donor screening. We report our experience with stool donor recruitment, screening, follow-up, and associated costs in the context of clinical FMT trials. Methods Potential stool donors, aged between 18−65 years, underwent a stepwise screening process starting with an extensive questionnaire followed by feces and blood investigations. When eligible, donors were rescreened for MDROs and SARS-CoV-2 every 60-days, and full rescreening every 4−6 months. The costs to find and retain a stool donor were calculated. Results From January 2018 to August 2021, 393 potential donors underwent prescreening, of which 202 (51.4%) did not proceed primarily due to loss to follow-up, medication use, or logistic reasons (e.g. COVID-19 measures). 191 potential donors filled in the questionnaire, of which 43 (22.5%) were excluded. The remaining 148 candidates underwent parasitology screening: 91 (61.5%) were excluded, mostly due to Dientamoeba fragilis and/or high amounts of Blastocystis spp. After additional feces investigations 18/57 (31.6%) potential donors were excluded (mainly for presence of Helicobacter Pylori and ESBL-producing organisms). One donor failed serum testing. Overall, 38 out of 393 (10%) potential donors were enrolled. The median participation time of active stool donors was 13 months. To recruit 38 stool donors, €64.112 was spent. Conclusion Recruitment of stool donors for FMT is challenging. In our Dutch cohort, failed eligibility of potential donors was often caused by the presence of the protozoa Dientamoeba fragilis and Blastocystis spp.. The exclusion of potential donors that carry these protozoa, especially Blastocystis spp., is questionable and deserves reconsideration. High-quality donor screening is associated with substantial costs.

The commensal gut microbiota is important for human health and well-being whereas deviations of the gut microbiota have been associated with a multitude of diseases. Restoration of a balanced and diverse microbiota by fecal microbiota transplantation (FMT) has emerged as a potential treatment strategy and promising tool to study causality of the microbiota in disease pathogenesis. However, FMT comes with logistical challenges and potential safety risks, such as the transfer of pathogenic microorganisms, undesired phenotypes or an increased risk of developing disease later in life. Therefore, a more controlled, personalized mixture of cultured beneficial microbes might prove a better alternative. Most of these beneficial microbes will be endogenous commensals to the host without a long history of safe and beneficial use and are therefore commonly referred to as next-generation probiotics (NGP) or live biotherapeutic products (LBP). Following a previous FMT study within our group, the commensal butyrate producer Anaerobutyricum spp. (previously named Eubacterium hallii) was found to be associated with improved insulin-sensitivity in subjects with the metabolic syndrome. After the preclinical testing with Anaerobutyricum soehngenii in mice models was completed, the strain was produced under controlled conditions and several clinical studies evaluating its safety and efficacy in humans were performed. Here, we describe and reflect on the development of A. soehngenii for clinical use, providing practical guidance for the development and testing of NGPs and reflecting on the current regulatory framework.

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Objective: The microbiota-derived short chain fatty acid (SCFA) butyrate has been shown to modulate blood pressure (BP) in rodent studies, while in humans, plasma butyrate levels have been associated with BP. Nonetheless the net effect of butyrate on hypertension in humans remains uncovered. In this study, we aimed to determine the effect of oral butyrate on BP in hypertensive patients. Design and method: We performed a double-blind randomized placebo-controlled trial including 23 patients with grade I hypertension. Antihypertensive medication was discontinued for the duration of the study with a wash-out period of four weeks before starting the intervention. Participants received either oral sodium butyrate capsules 4 g per day or placebo capsules with an equivalent amount of sodium chloride for four weeks. The primary outcome was daytime 24-hours systolic BP. We also collected data on short-term heart rate variability (HRV) using finger photoplethysmography, and extracellular water percentage using body impedance analyses. We measured plasma renin, aldosterone, and fecal SCFA levels. Gut microbiota composition was determined using 16S rRNA sequencing. Differences between groups over time were assessed using linear mixed models (group*time interaction). Results: Study participants had a mean age of 59.0 ± 3.7 years, 56.5% female and an average baseline office systolic BP of 143.5 ± 14.6 mmHg and diastolic BP of 93.0 ± 8.3 mmHg. Daytime 24-hours systolic and diastolic BP significantly increased over the intervention period in the butyrate compared to the -placebo group, with an effect size of 9.65 (95%CI 3.88 - 17.15) mmHg in daytime 24-hours systolic BP and 5.08 (95%CI 1.89 - 8.76) mmHg in diastolic BP in the linear mixed model. Heart rate and extracellular water percentage changes were not significantly different between the groups. There was a trend towards increasing HRV in the butyrate group (group*time p = 0.078), but no significant changes in renin and aldosterone levels, nor in fecal SCFA levels. Butyrate did not impact gut microbiota composition substantially. Conclusions: Four weeks of oral butyrate treatment increased daytime systolic and diastolic BP in hypertensive subjects. Our findings implicate that not all SCFA have beneficial effects on human cardiovascular health which warrants caution in future prebiotic and butyrate intervention studies.