Inflammatory bowel disease (IBD) is a complex multifactorial disorder in which external and environmental factors have a large influence on its onset and development, especially in genetically susceptible individuals. Crohn’s disease (CD), one of the two types of IBD, is characterized by transmural inflammation, which is most frequently located in the region of the terminal ileum. Oxidative stress, caused by an overabundance of reactive oxygen species, is present locally and systemically in patients with CD and appears to be associated with the well-described imbalanced immune response and dysbiosis in the disease. Oxidative stress could also underlie some of the environmental risk factors proposed for CD. Although the exact etiopathology of CD remains unknown, the key role of oxidative stress in the pathogenesis of CD is extensively recognized. Epigenetics can provide a link between environmental factors and genetics, and numerous epigenetic changes associated with certain environmental risk factors, microbiota, and inflammation are reported in CD. Further attention needs to be focused on whether these epigenetic changes also have a primary role in the pathogenesis of CD, along with oxidative stress.

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory condition of the gastrointestinal tract; it is a heterogeneous and multifactorial disorder resulting from a complex interplay between genetic variation, intestinal microbiota, the host immune system and environmental factors such as diet, drugs, breastfeeding and smoking. The interactions between dietary nutrients and intestinal immunity are complex. There is a compelling argument for environmental factors such as diet playing a role in the cause and course of IBD, given that three important factors in the pathogenesis of IBD can be modulated and controlled by diet: intestinal microbiota, the immune system and epithelial barrier function. The aim of this review is to summarize the epidemiological findings regarding diet and to focus on the effects that nutrients exert on the intestinal mucosa–microbiota–permeability interaction. The nature of these interactions in IBD is influenced by alterations in the nutritional metabolism of the gut microbiota and host cells that can influence the outcome of nutritional intervention. A better understanding of diet–host–microbiota interactions is essential for unravelling the complex molecular basis of epigenetic, genetic and environmental interactions underlying IBD pathogenesis as well as for offering new therapeutic approaches for the treatment of IBD.

Background/Objectives: Crohn’s disease (CD) is a chronic immune-mediated disorder with heterogeneous response to biologic therapies. Ustekinumab (UST), an anti-IL-12/23 monoclonal antibody, is effective in CD, but predictive biomarkers of treatment response remain lacking. This study aimed to investigate cytokine dynamics during UST induction and to evaluate their association with clinical and biochemical outcomes in an observational cohort of CD patients. Methods: We prospectively recruited 31 adult patients with moderate-to-severe active CD initiating UST therapy at a tertiary referral center. Peripheral blood and stool samples were collected at baseline and weeks 4, 8, and 16. UST trough concentrations, C-reactive protein (CRP), fecal calprotectin (FC), hemoglobin, albumin, and 13 serum cytokines (including IL-1β, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-17, IL-23, TNF-α, and OSM) were analyzed. Response was defined as a ≥70% reduction in FC at week 16, or, alternatively, CRP < 5 mg/L or a Harvey–Bradshaw Index < 3. Results: Eighteen patients (58%) achieved response at week 16. Responders showed significant reductions in FC, CRP, and disease activity, while non-responders exhibited limited biochemical improvement. Overall, UST induction was associated with a global decrease in proinflammatory cytokines, particularly TNF-α and IL-1β. Responders displayed distinct cytokine patterns, with higher IL-13 levels at week 8 and lower IL-8 concentrations at week 16 compared with non-responders. UST trough levels tended to be higher in responders, and inverse correlations were observed between drug concentrations and several cytokines, including IL-6, IL-8, IL-13, and IL-23. Conclusions: UST induction leads to measurable immunological changes in CD, with differential cytokine dynamics distinguishing responders from non-responders. These findings support the potential of cytokine signatures, in combination with therapeutic drug monitoring, as pharmacodynamic biomarkers to optimize personalized treatment strategies in CD.

Inflammatory bowel disease leads to debilitating gastrointestinal symptoms and reduced quality of life, resulting in a significant burden on healthcare utilization and costs. Despite substantial advancements in diagnosis and treatment, there may still be considerable delays in diagnosing some patients. To reduce disease progression before the full disease spectrum appears and improve prognostic outcomes, several strategies have concentrated on early intervention and prevention. Recent evidence shows that initial immune response changes and endoscopic lesions may exist for years before diagnosis, implying the existence of a preclinical phase of inflammatory bowel disease comparable to findings in other immune-mediated disorders. In this review, we highlight the most relevant findings regarding preclinical inflammatory bowel disease and the prospective role of novel omics techniques in this field.