A recent study (Am J Gastroenterol dii:10.1038/ajg.2014.355) from Helsinki examined 177 patients with celiac disease. Their goal was to investigate whether altered intestinal microbiota may be associated with persisting gastrointestinal symptoms in celiac patients who had been following a strict gluten-free diet (GFD) for at least 3 years.
After administering a questionnaire (Gastrointestinal Symptom Rating Scale or GSRS) to those with negative celiac antibodies and normal small bowel mucosa (n=164), the researchers identified the 18 subjects with the highest total score (persistent symptom group) and compared them to the 18 subjects with the lowest total score. Three duodenal biopsies during endoscopy had been frozen and were subsequently analyzed for their microbial DNA. In each group, one microbial profile was unsuccessful.
Key findings:
- In the persistent symptom group, there was lower relative abundance of Bacteroidetes (15% vs. 25%, P=0.01), lower Firmicutes (33% vs 46%, P=0.05) and higher relative abundance of Proteobacteria (40% vs 21%, P=0.04).
- The “microbial richness,” measured as a number of detected genera or operational taxonomic units (OTUs), was reduced in patients with persistent symptoms. On average, patients with persistent symptoms had 32 genera and 72 OTUs per sample; in contrast, those without symptoms, on average had 37 genera and 106 OTUs.
Some of the strengths of this study include the normal villous architecture for all of the patients; this helps exclude refractory celiac disease as an etiology for the persistent symptoms. In the discussion, the authors note that the “intestinal microbiota composition in healthy adults is relatively stable and can tolerate normal stress in the intestine caused by, e.g. daily changes in diet.” The speculate that long-term untreated celiac disease “may disrupt a stable intestinal microbiota community that, in some patients, could then reform in a dysbiotic state.”
The limitations of this study include the difficulty of excluding small intestinal bacterial overgrowth which could be related and the difficulty of excluding coexisting irritable bowel syndrome. Like most studies regarding the micro biome, this study cannot “show causality or distinguish the effects of different bacteria to the persistent symptoms.”
Bottomline: Treated celiac patients with persistent symptoms have a different duodenal microbiome compared to treated celiac patients whose symptoms resolved with a gluten-free diet.
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