One year of gluten free diet impacts gut function and microbiome in celiac disease

BACKGROUND & AIMS Currently, the main treatment option for coeliac disease (CD) is a gluten free diet (GFD). This observational cohort study investigated the impact of CD and 1 year of GFD on gut function and microbiome. METHODS 36 newly diagnosed patients and 36 healthy volunteers (HV) were studied at baseline and at 12 months follow up. Small bowel water content (SBWC), whole gut transit time (WGTT) and colon volumes were measured by MRI. Stool samples DNA was subjected to shotgun metagenomic sequencing. Species level abundances and gene functions, including carbohydrate active enzymes (CAZymes) were determined. RESULTS SBWC was significantly higher in people with CD 157±15 mL versus HVs 100±12 mL (p=0.003). WGTT was delayed in people with CD 68±8 hours versus HVs 41±5 hours (p=0.002). The differences reduced after 12 months of GFD but not significantly. Wellbeing in the CD group significantly improved after GFD but did not recover to control values. CD faecal microbiota showed high abundance of proteolytic gene functions, associated with Escherichia coli, Enterobacter and Peptostreptococcus . GFD significantly reduced Bifidobacteria and increased Blautia wexerelae . Microbiome composition correlated positively with WGTT, colonic volume and Akkermansia municphilia but negatively with B.wexerelae . Following GFD the reduction in WGTT and colonic volume significantly associated with increased abundance of B.wexerelae . There were also significant alterations in CAZyme profiles, specifically starch and arabinoxylan degrading families. CONCLUSIONS CD impacted gut function and microbiota. GFD ameliorated but did not reverse these effects, significantly reducing Bifidobacteria associated with reduced intake of resistant starch and arabinoxylan from wheat. ### Competing Interest Statement The authors have declared no competing interest.