15 patients with refractory celiac disease (RCD) and 15 patients with CD responsive to the GFD between the ages of 21 and 60 will be enrolled. The aim of the research will be: 1) to characterize the intestinal, blood and duodenal microbiota, then to evaluate both the taxonomy of the identified bacteria and their relative abundance 2) to analyse the profile of miRNAs from biopsy and fibroblasts isolated in the first duodenal portion, highlighting any basal deregulation and, for fibroblasts, after treatment with the 33-mer immunogenic peptide 3) quantify and know the composition of the fecal microbiota in celiac patients with persistent symptoms and in refractory celiac patients before (T0) and after (T28) treatment with a low-FODMAP diet. The aim of the study is to observe a diversification of the microbiota pattern of refractory patients vs. normoresponsive celiac patients and to observe a deregulation in the expression of miRNAs, both basally on biopsies and after treatment with the immunogenic peptide in primary fibroblast cultures.

Celiac disease (CD) is a chronic, autoimmune, multisystemic disorder caused by ingestion of gluten contained in wheat. A chronic gluten-free diet (GFD) is the only therapy for CD, however a small subgroup of patients is refractory to a GFD, in fact the pathology does not regress even with a strict diet. The microbiota plays a fundamental role in the CD, in fact, especially intestinal homeostasis requires balanced interactions between the microbiota, food antigens and the host. It is widely recognized that intestinal microbiota plays a role in the initiation and progression of intestinal inflammation in numerous chronic conditions, but recent studies have shown that even the blood microbiota plays a fundamental role in autoimmune diseases. Also microRNAs (miRNAs), RNA sequences of 20-22 non-coding nucleotides that post-transcriptionally regulate gene expression, are molecules of interest in many common diseases and therefore also in CD. Fermentable, Oligo-, Di-, Mono-saccharides And Polyol (FODMAP) are short-chain carbohydrates with poor absorption in the small intestine which increases gas production and intestinal osmolarity, which can trigger gastrointestinal symptoms in sensitive individuals. A diet low in FODMAPs is a new dietary option for the treatment of persistent gastrointestinal symptoms in celiac patients. Evaluating the effect of this type of diet on intestinal microbiota changes and miRNA expression in celiac patients with persistent gastroenterological symptoms and in patients with refractory celiac disease represents an opportunity to understand how this dietary modification could contribute to the development of this disease.

15 patients with refractory celiac disease (RCD) and 15 patients with CD responsive to the GFD between the ages of 21 and 60 will be enrolled. The aim of the research will be: 1) to characterize the intestinal, blood and duodenal microbiota, then to evaluate both the taxonomy of the identified bacteria and their relative abundance 2) to analyse the profile of miRNAs from biopsy and fibroblasts isolated in the first duodenal portion, highlighting any basal deregulation and, for fibroblasts, after treatment with the 33-mer immunogenic peptide 3) quantify and know the composition of the fecal microbiota in celiac patients with persistent symptoms and in refractory celiac patients before (T0) and after (T28) treatment with a low-FODMAP diet. The aim of the study is to observe a diversification of the microbiota pattern of refractory patients vs. normoresponsive celiac patients and to observe a deregulation in the expression of miRNAs, both basally on biopsies and after treatment with the immunogenic peptide in primary fibroblast cultures.

Inclusion Criteria:

• patients on a proper gluten-free diet (assessing adherence to the gluten-free diet using the Celiac Dietary Adherence Test (CDAT)
• celiac subjects diagnosed through a positive serological test of anti-endomysium antibodies (EMA) and tissue transglutaminase antibodies (TTG) evaluated through a histological abnormality in duodenal biopsies in accordance with Marsh's modified classification
• refractory celiac disease (CD)

Exclusion Criteria:

• Women who are pregnant or breastfeeding
• Subjects who follow special diets: vegetarianism, veganism
• Subjects with psychiatric disorders, diabetes mellitus, autoimmune systemic diseases, previous anaphylactic episodes, systemic disorders
• individual intolerance to disaccharides evaluated through the expired hydrogen test (lactose and fructose)