Expression of Microbiota, Toll-like Receptors, and Their Regulators in the Small Intestinal Mucosa in Celiac Disease

Objectives: Less than one-tenth of the carriers of the risk genes HLA-DQ2 or HLA-DQ8 develop celiac disease, suggesting that other genetic and environmental factors are important in the pathogenesis. The role of gut microbiota has been addressed previously with inconsistent findings. Our aim was to evaluate microbiota, its receptors (Toll-like receptors [TLRs]), and regulators of the TLRs in the small intestinal mucosa in celiac disease. Methods: Microbiota was analyzed by quantitative polymerase chain reaction (total bacteria and 10 bacterial group- and species-specific primers) and gene expression of interleukin-8 (IL-8), TLR2, TLR3, TLR4, TLR5, TLR9, and regulators of TLRs, Toll-interacting protein (TOLLIP), and single immunoglobulin IL-1R-related molecule, by relative quantitative reverse transcription-polymerase chain reaction in 10 children with celiac disease (untreated celiacs), 9 children with normal small intestinal mucosa (controls), and 6 adults with celiac disease with normal small intestinal mucosa after following a gluten-free diet (treated celiacs). Results: Small intestinal microbiota was comparable among controls, untreated celiacs, and treated celiacs. Expression of IL-8 mRNA, a marker of intestinal inflammation, was significantly increased in untreated celiacs as compared with treated celiacs (P = 0.002) and controls (P = 0.001). Expression of TLR-2 mRNA was significantly decreased in untreated (P = 0.001) and treated (P = 0.03) celiacs, whereas expression of TLR-9 mRNA was increased in untreated celiacs (P = 0.001) as compared with controls. Expression of TOLLIP mRNA was downregulated in untreated celiacs as compared with controls (P = 0.02). Conclusions: Altered gene expression of TLR2, TLR9, and TOLLIP in small intestinal biopsies in celiac disease suggests that microbiota-associated factors may be important in the development of the disease.