Ferric reducing ability of plasma and assessment of selected plasma antioxidants in adults with celiac disease.

Introduction: Oxidative stress with an excessive free radical production and a reduction in the activity of protective antioxidants is considered as one of the mechanisms responsible for gluten toxicity. However, its role in celiac disease (CD) is unclear.

Objectives: Evaluation of plasma nonenzymatic antioxidant capacity in patients with CD (both untreated patients and those receiving gluten-free diet [GFD]) by measuring the ferric reducing ability of plasma (FRAP) as well as assessing selected plasma antioxidants.

Patients And Methods: The study included 169 adult patients: 48 patients with untreated active CD, 72 patients with CD on a GFD, and 49 healthy controls. In each group, we measured the serum levels of selected antioxidants (uric acid, bilirubin, albumin, and vitamin E) and used the FRAP assay to assess the total antioxidant capacity (TAC) of plasma. In each patient, serological and histopathological activity of CD was also evaluated.

Results: There were no significant differences in the TAC of plasma measured with the FRAP assay between the study groups. Patients with CD had higher uric acid levels compared with controls (p <0.001), while bilirubin levels were lower in patients with active disease than in controls (p <0.05). Serum vitamin E levels were lower in all patients with CD compared with controls (p <0.01).

Conclusions: The FRAP assay is not the method of choice for assessing the TAC of plasma in patients with CD. Owing to high serum uric acid levels, the FRAP assay results in these patients may be overestimated despite the reduced levels of other plasma antioxidants.