Objective: Anthocyanins (AC) have been shown to elicit anti-inflammatory and antioxidant effects in several animal models of colitis. Furthermore, AC lowered biochemical disease activity in our double-blind randomized trial in patients with ulcerative colitis. Here, we report on the changes in the faecal microbiome composition in the patient upon AC exposure in this trial. Methods: Ulcerative colitis patients received a 3g daily dose of an AC-rich bilberry extract (ACRE) for eight weeks. We determined the microbiome composition in longitudinal stool samples from 24 patients and quantified the degree of change over time. We also correlated the relative abundances of individual microbial taxa at different time points to faecal concentration measurements of calprotectin. Results: Microbiome compositions did not change over time as a result of the intervention, both in terms of alpha and beta diversity. Before the intervention, Haemophilus parainfluenzae was positively correlated with faecal calprotectin concentrations, and this correlation persisted in placebo-treated subjects throughout the study. In contrast, the correlation between H. parainfluenzae and the concentration of faecal calprotectin vanished in ACRE-treated subjects, while the relative abundance of H. parainfluenzaae did not change. Conclusion: Our results suggest that ACRE treatment mitigates the contribution of H. parainfluenzae to inflammation. Further research is warranted to better comprehend the role of microbial composition in response to medical therapy including AC-rich extract in ulcerative colitis patients.

MD reports traveling fees from Takeda, FALK, Abbvie as well as consulting fees from Takeda. LB reports fees for consulting-advisory board from Abbvie, MSD, Vifor, Falk, Esocap, Calypso, Ferring, Pfizer, Shire, Takeda, Janssen, Ewopharma. GR declares consulting fees from Abbvie, Augurix, BMS, Boehringer, Calypso, Celgene, FALK, Ferring, Fisher, Genentech, Gilead, Janssen, MSD, Novartis, Pfizer, Phadia, Roche, UCB, Takeda, Tillots, Vifor, Vital Solutions and Zeller as well as speaker's honoraria from Astra Zeneca, Abbvie, FALK, Janssen, MSD, Pfizer, Phadia, Takeda, Tillots, UCB, Vifor and Zeller, and grants support from Abbvie, Ardeypharm, Augurix, Calypso, FALK, Flamentera, MSD, Novartis, Pfizer, Roche, Takeda, Tillots, UCB, and Zeller. GEL is an employee and shareholder of PharmaBiome. All other authors declare no conflicts of interest

NCT04000139

This study was funded by the Swiss National Science Foundation (SNF) to GR [Grant No. 33IC30_166844] and the Litwin Foundation (New Hyde Park, NY)

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Swiss ethics committee approval approval number: BASEC2017-00156, Date of authorisation by the ethics committee 14.02.2019 Authorisation initially for Canton Zurich (University Hospital, Prof. Rogler) and then extension of the approval to the rest participating centers (Basel, Bern, Geneva, Lausanne, St. Gallen)

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All data produced in the present study are available upon reasonable request to the authors