Markers of Oxidative Stress in Inflammatory Bowel Diseases: Risk Factors and Implications for a Dietetic Approach

Overview

Inflammatory bowel disease (IBD), including Crohn's disease (CD), Ulcerative Colitis (UC) and IBD-unclassified (IBD-U) is a chronic inflammatory intestinal disorders that affect both children and adults. Patients with IBD can present with severe gastrointestinal symptoms, require frequent hospitalizations, expensive medical treatments and can develop invalidating complications requiring surgery. The incidence of IBD is increasing worldwide. The pathogenesis is multifactorial with immunological, environmental and genetic factors contributing to the disease. There is evidence that oxidative stress (OS) imbalance is involved in IBD onset and evolution, although the exact contribution to the pathogenes is unclear. An antioxidant dietetic approach is promising as an adjunctive treatment of IBD. The main aims of this project are to characterize the OS imbalance in IBD in relation to disease's features and to genetic factors and to evaluate the efficacy of an antioxidant dietetic treatment

IBD is a complex disorder that is thought to be the result of an aberrant immune response to commensal bacteria in a genetically susceptible host. The chronic inflammation along the gastrointestinal tract that characterizes IBD results from an imbalance of effector lymphocytes and pro-inflammatory cytokines. Some of the cytokines, as well as the triggered leukocytes and activated macrophages, can produce large amounts of reactive oxygen species (ROS) thus predisposing to oxidative stress disturbances. Many of the clinical and pathophysiological features of IBD, particularly tissue injury (mucosal erosions) and fibrosis have been associated to redox imbalance due to continuous ROS production and a net decrease of antioxidant molecules. Although uncontrolled oxidative stress is destructive in inflammatory conditions, the body's antioxidant defenses can counteract the effects caused by excess of ROS. Antioxidants are protective molecules/compounds toward pro-oxidant molecules. They can be endogenous or/and come from the diet. Endogenous compounds include intracellular enzymatic antioxidants such as superoxide dismutases (SODs), glutathione peroxidase (GPX), and catalase (CAT), intracellular nonenzymatic antioxidant such as glutathione (GSH) and extracellular antioxidants such as vitamins (Vit. A-C-E-B group). GSH is considered the major non-protein low molecular weight defender against oxidative (or redox) stress and the most important cellular thiol buffer. Moreover it acts as cofactor for the antioxidant enzymes GPxs and GST. GSH has been used as a biomarker for inflammation and several studies showed reduced levels of GSH in inflammatory conditions. Experimental colitis models showed decreased GSH levels that can be restored to a normal level by antioxidants supplementation. Also antioxidant enzymes as SODs, CAT and GPxs were found dysregulated in IBD condition. The differences in the regulation of expression of SOD, CAT and GPxs may not only reflect their importance in physiology, but may be also insufficient in removal of ROS under inflammatory conditions such as IBD. Recently an association between SOD1, CAT and GSHPX1 polymorphisms and the risk of inflammatory bowel disease in the Polish population has been described. Kosaka et al. found a correlation between age of onset and severity of IBD with polymorphisms in SOD2 manganese superoxide dismutase and NAD(P)H quinone oxidoreductase. In this respect, IBD disease can be regarded as multifactorial disease. There are several lines of evidence to suggest that diet is a key player in the onset, perpetuation and management of IBD. The most important evidence linking diet to IBD comes from exclusive enteral nutrition (EEN) that is the primary induction treatment of active paediatric Crohn Disease (CD). Epidemiological evidence associates certain dietary nutrients and components to the increased risk of IBD. There is emerging evidence that some diets, including the Specific Carbohydrate Diet (SCD) and the CD Exclusion Diet (CDED) could treat or prevent subsequent disease flare. Data previously presented induce to the hypothesis that an antioxidant dietetic approach, could have a role in the treatment of IBD. Dietary antioxidants may include ascorbic acid, vitamin E, glutathione, methionine, carotenoids, polyphenolic compounds, selenium and vitamin A. Clinical experience evaluating antioxidant dietetic approach in IBD patients is limited to few studies, mostly investigating the effects of single antioxidants in small number of patients. So far pediatric data regarding the oxidative status in children with IBD have rarely been reported. Collecting data in IBD children and comparing these with adults data, particularly in subjects at diagnosis, would give the unique opportunity to evaluate the role of oxidative stress in IBD pathogenesis. OxIBDiet working hypothesis is that oxidative stress imbalance is a key feature of IBD and the persistence of such imbalance is likely to contribute to the development of complications and more broadly to the evolution of the disease. A comparison between oxidative stress imbalance in children and adults with IBD and controls will address the question whether the stress imbalance is a consequence or a primary event in the inflammatory burden of IBD. Addressing these pathways and targeting the oxidative damage can have potential implications in IBD monitoring and treatment. This study has been granted by the Italian Ministry of Health (grant RF 2018-12366976)