ObjectivePrevious studies have presented conflicting results on Western diets and the risk of inflammatory bowel disease (IBD). This study aimed to evaluate the role of a pre‐illness Western dietary pattern in the development of IBD.MethodsThe Western dietary pattern was defined as that met at least two of the following, either a high intake of refined grains, red and processed meat, animal protein, animal fats or high‐fat dairy products, or with a low consumption of fruit and vegetables. Four medical databases (PubMed, EMBASE, the Cochrane Library and the China National Knowledge Infrastructure) were searched to identify all relevant references. Risk estimate and corresponding 95% confidence interval (CI) were pooled using a random‐effects model.ResultsNine studies (seven case‐control studies and two prospective cohorts) were included, with a total of 1491 IBD cases and 53 089 controls. A Western dietary pattern was associated with a risk of all IBD (relative risk [RR] 1.92, 95% CI 1.37‐2.68) and separately with Crohn's disease (CD) (RR 1.72, 95% CI 1.01‐2.93) and ulcerative colitis (UC) (RR 2.15, 95% CI 1.38‐3.34). Subgroup analysis by region showed that a Western dietary pattern was associated with the risk of CD and UC for studies performed in Europe (RR 2.25, 95% CI 1.44‐3.50 for CD; RR 2.65, 95% CI 1.61‐4.36 for UC). The pooled RR was 2.26 (95% CI 1.42‐3.59) in the pediatric CD subgroup.ConclusionThis meta‐analysis indicates that a pre‐illness Western dietary pattern may increase the risk of developing CD and UC.

Polymorphisms of MDR1 are associated with patient's GC response and a predisposition to CD in Chinese population. Further studies are needed to elucidate the role of MDR1 polymorphisms in IBD and that as genetic markers for GC response.

Background:The Montreal classification defines L4 Crohn’s disease (CD) as any disease location proximal to the terminal ileum, which anatomically includes L4-esophagogastroduodenal (EGD), L4-jejunal, and L4-proximal ileal involvement. L4-jejunal disease was established to be associated with poor prognosis. However, the outcome of patients with L4-proximal ileal disease or L4-EGD remains to be clarified. Our study aimed to investigate whether the outcome differs among CD patients with L4-EGD, L4-jejunal, and L4-proximal ileal disease.Methods:In our retrospective cohort study, 483 patients with confirmed CD were included. The primary outcome was intestinal surgery. Demographic features and outcomes were compared among L4-EGD, L4-jejunal, and L4-proximal ileal disease.Results:Thirty-nine (8.1%) patients had isolated L4 disease, whereas 146 patients had L4 as well as concomitant L1, L2, or L3 disease. During a median follow up of 5.8 years, L4 patients were more likely to have intestinal surgeries compared to non-L4 patients (31% versus 16%, p < 0.001). The percentage of L4-jejunal patients who underwent surgery was higher than that of L4-proximal ileal (66% versus 28%, p < 0.001), and both of these subtypes of L4 were at higher risk for intestinal resection compared to L4-EGD patients (66% and 28% versus 9%, respectively, p < 0.001 and p < 0.05). On multi-variable analysis, L4-jejunal (HR 3.08; 95% CI 1.30–7.31) and L4-proximal ileal disease (HR 1.83; 95% CI 1.07–3.15) were independent predictors for intestinal resection.Conclusions:L4 disease had worse prognosis compared to non-L4 disease. Within L4 disease, phenotype of L4-jejunal and L4-proximal ileal disease indicated higher risk for intestinal surgery. It might be justified to further characterize the L4 phenotype of the Montreal classification into three specific subgroups including L4-EGD, L4-jejunal, and L4-proximal ileal disease, similar to the Paris classification of pediatric patients.

The PI3K/Akt/mTOR signaling pathway was activated in CD. The activation of the PI3K/Akt/mTOR pathway caused by PTEN downregulation may be involved in the pathogenesis of CD.

Higher 6-TGN levels are independently associated with a reduced rate of endoscopically active disease and a higher rate of mucosal healing in CD patients. Prospective studies of adequate sample size are required to confirm these findings.