Dysregulation of intestinal immune response plays a critical role in the pathogenesis of Inflammatory Bowel Disease (IBD). Mastic’s anti-inflammatory properties are well established. Our aim was to investigate Mastic’s regulatory effect on IL-17A serum levels in IBD patients. Alterations of the faecal metabolome as a functional readout of microbial activity were explored. A randomized, double-blind, placebo-controlled, parallel-group design was applied for a total of 3 months in active and 6 months in inactive IBD patients. Serum IL-17A increased significantly in Mastic group (p = 0.006), and the mean change differed significantly between Mastic and placebo (p = 0.003) even after adjusting for age, sex and BMI (p = 0.001) in inactive patients.
In inactive UC patients IL-17A decreased significantly only in placebo (p = 0.033). No significant differences were detected in active disease. Faecal metabolomics indicated that intervention with Mastic influenced considerably the metabolic profile of IBD patients in remission exhibiting, in between others, increased levels of glycine and tryptophan. Glycine has been proposed to have a therapeutic effect against IBD, while tryptophan derivatives are involved in immunoregalutory mechanisms, such as the Th17 cells differentiation. Thus, it is quite possible that the immunoregulatory role of Mastic in quiescent IBD involves the regulation of Th17 cells function and differentiation.