Increase in nitric oxide urinary products during gluten challenge in children with coeliac disease

Background: Coeliac disease is a gluten-sensitive enteropathy where pro-inflammatory cytokines and excess nitric oxide (NO) production can contribute to mucosal damage. NO urinary products are elevated in coeliac children on a gluten diet, but it is not known how rapidly this increase develops after gluten exposure. Methods: Oral gluten challenge was performed in 25 children whose families kept a daily record of gluten intake and symptoms. Blood was analysed monthly for antigliadin (AGA) and endomysium antibodies (EMA). Urine was analysed every second week for NO products, i.e. the sum of nitrite and nitrate was measured with a colorimetric method. We performed a third biopsy when clinical symptoms indicated a relapse. Median age at the post-challenge biopsy was 3.8 (2.7-8.8) years. Results: Signs of morphological or serological relapse were seen in all children. Mean daily gluten intake was 0.10 (range 0.02-0.26) g/kg bodyweight. Median NO level was doubled and significantly higher after 4 weeks of challenge but not after 2 weeks. EMA, but not AGA levels, correlated positively with NO. Intraepithelial lymphocyte count was significantly higher in the, post-challenge biopsy, but did not correlate with the NO levels. Conclusions: NO products in urine increased during gluten challenge. EMA levels reflected severity of mucosal damage, and NO products reflected the inflammatory response, which was doubled after 4 weeks of challenge. The NO analysis is simple and non-traumatic for the child. It can be performed repeatedly during investigation of children with suspected coeliac disease.