Effects of different iron replacement methods to gut microbiome of IBD and non IBD patients

Objective Iron deficiency is a common complication inpatients with IBD and oral iron therapy is suggested toexacerbate IBD symptoms. We performed an open labelledclinical trial to compare the effects of per oral(PO) versus intravenous (IV) iron replacement therapy(IRT).Design The study population included patients withCrohn's disease (CD; N=31), UC (N=22) and controlsubjects with iron deficiency (non-inflamed, NI=19).After randomisation, participants received iron sulfate(PO) or iron sucrose (IV) over 3 months. Clinicalparameters, faecal bacterial communities andmetabolomes were assessed before and afterintervention.Results Both PO and IV treatments ameliorated irondeficiency, but higher ferritin levels were observed withIV. Changes in disease activity were independent of irontreatment types. Faecal samples in IBD werecharacterised by marked interindividual differences, lowerphylotype richness and proportions of Clostridiales.Metabolite analysis also showed separation of both UCand CD from control anaemic participants. Major shiftsin bacterial diversity occurred in approximately half of allparticipants after IRT, but patients with CD were mostsusceptible. Despite individual-specific changes inphylotypes due to IRT, PO treatment was associated withdecreased abundances of operational taxonomic unitsassigned to the species Faecalibacterium prausnitzii,Ruminococcus bromii, Dorea sp. and Collinsellaaerofaciens. Clear IV-specific and PO-specific fingerprintswere evident at the level of metabolomes, with changesaffecting cholesterol-derived host substrates.Conclusions Shifts in gut bacterial diversity andcomposition associated with iron treatment arepronounced in IBD participants. Despite similar clinicaloutcome, oral administration differentially affectsbacterial phylotypes and faecal metabolites comparedwith IV therapy.