New insights into the pathogenesis of Crohn's disease: are they relevant for therapeutic options?

During the last few years significant advances have been achieved in the understanding of the pathogenesis of inflammatory bowel disease (IBD). A genetic susceptibility to Crohn's disease has been proven by identification of variations as risk factor NOD2/CARD15. Functional data on NOD2/CARD15 and NF-kappaB activation indicate that an inflammatory reaction of the intestinal mucosa, as an immediate response of the innate immune system, may be necessary for the maintenance of gut homeostasis. Crohn's disease is now also discussed as an impaired and inadequate immune reaction and no longer only as a hyper-responsiveness of the mucosal immune system. Data on NOD2/CARD15 expression suggest that macrophages and epithelial cells could be the locus of the primary pathophysiological defect and that T-cell activation might just be a secondary effect inducing chronification of the inflammation, perhaps as backup mechanism to insufficient innate immunity. In addition to NOD2/CARD15 there are more "innate" pathways by which commensal and pathogenic bacteria can directly be hindered to invade the human body (such as interaction with Toll like receptors, TLRs and defensins). The "germ-concept" and the "genetic concept" of IBD pathophysiology are converging. However, more time is needed until these important insights in IBD pathogenesis will make their way into routine diagnostic procedures and treatment of patients with IBD

High altitude journeys, flights and hypoxia: any role for disease flares in IBD patients?

The importance of environmental factors in the pathogenesis including their disease-modifying potential are increasingly recognized in inflammatory bowel disease (IBD) patients, largely driven by the perception that the prevalence and incidence of IBD are on the rise within the last few years, especially in non-western countries. One of those factors is believed to be hypoxia. The role of hypoxia as a modifying or even causative factor in the genesis and maintenance of inflammation has been increasingly elucidated in recent years. Hypoxia is believed to be a main inducing factor of inflammation. This has been studied in different animal experiments as well as in humans exposed to hypoxia. In several studies - mainly in mice - animals exposed to short-term hypoxia accumulated inflammatory cells in multiple organs and showed elevated cytokines in the blood. Comparable studies were performed in humans, mainly in healthy mountaineers. Recently, we reported on the association between IBD flare-up episodes and antecedent journeys to high-altitude region and aircraft travels. According to these findings, we concluded that flights and stays at high altitudes of >2,000 mg are a risk factor for increased disease activity in IBD. To evaluate the potential influence of hypoxia on the course of IBD on a biomolecular level and to test the effects of hypoxia under standardized conditions, we initiated a prospective and controlled investigation in both healthy controls and IBD patients in stable remission. The study participants underwent a 3-hour exposure to hypoxic conditions simulating an altitude of 4,000 m above sea level in a hyperbaric pressure chamber and clinical parameters as well as blood and stool samples were collected at several time points. The first results of this study are expected in the near future

Crohn's disease: loss of tolerance or a disorder of autophagy?

Crohn's disease (CD) is characterized by a breakdown of the intestinal epithelial barrier function leading to an uncontrolled immune response to bacterial antigens. Available data demonstrate that appropriate response and early host defense against invading bacteria are crucial to maintain tolerance towards commensal bacteria. When the mechanisms of early removal of invading bacteria are disturbed, a loss of tolerance and a full-blown adaptive immune reaction, which is mounted against the usually harmless commensal flora, are induced. Dysfunction of autophagy caused by genetic variations within CD susceptibility genes, such as ATG16L1 and IRGM, results in defective handling of intracellular and invading bacteria and causes prolonged survival and defective clearance of those microbes. Dysfunction of ATG16L1 and IRGM has also been shown to cause aberrant Paneth cell function and uncontrolled secretion of proinflammatory cytokines finally resulting in increased susceptibility to bacterial infection and the onset of colitis. Interestingly, autophagy can also be regulated by other CD susceptibility genes, such as NOD2 (nucleotide oligomerization domain 2) or PTPN2 (protein tyrosine phosphatase nonreceptor type 2) and the presence of the CD-associated variations within these genes results in similar effects. Taken together, more and more evidence suggests a close functional correlation between loss of tolerance and defective autophagy in CD patients. Therefore, most likely, the onset of CD is triggered by both a loss of tolerance as well as a dysfunction of autophagy, which finally results in the onset of chronic intestinal inflammation

Lifestyle factors associated with inflammatory bowel disease: data from the Swiss IBD cohort study.

BACKGROUND Various environmental risk factors have been associated with the pathogenesis of inflammatory bowel disease. In this study we aimed to identify lifestyle factors that affect the onset of Crohn's disease and ulcerative colitis. METHODS 2294 patients from the Swiss IBD Cohort Study received a questionnaire regarding physical activity, nutritional habits and status of weight. In addition, a control group was formed comprising patients' childhood friends, who grew up in a similar environment. RESULTS Overall, 1111 questionnaires were returned (response rate: 48.4%). Significantly more patients with inflammatory bowel disease reported no regular practice of sport during childhood and beginning of adulthood compared to the control group (p = 0.0001). No association between intake of refined sugar and onset of inflammatory bowel disease was observed. More patients with Crohn's disease compared to ulcerative colitis and controls suffered from overweight during childhood (12.8% vs. 7.7% and 9.7%, respectively; p = 0.027). CONCLUSIONS Our study underlines the relevance of environmental factors in the development of inflammatory bowel disease. Our results imply a protective effect of physical activity regarding the onset of inflammatory bowel disease

Lifestyle factors associated with inflammatory bowel disease: data from the Swiss IBD cohort study

BACKGROUND: Various environmental risk factors have been associated with the pathogenesis of inflammatory bowel disease. In this study we aimed to identify lifestyle factors that affect the onset of Crohn's disease and ulcerative colitis. METHODS: 2294 patients from the Swiss IBD Cohort Study received a questionnaire regarding physical activity, nutritional habits and status of weight. In addition, a control group was formed comprising patients' childhood friends, who grew up in a similar environment. RESULTS: Overall, 1111 questionnaires were returned (response rate: 48.4%). Significantly more patients with inflammatory bowel disease reported no regular practice of sport during childhood and beginning of adulthood compared to the control group (p = 0.0001). No association between intake of refined sugar and onset of inflammatory bowel disease was observed. More patients with Crohn's disease compared to ulcerative colitis and controls suffered from overweight during childhood (12.8% vs. 7.7% and 9.7%, respectively; p = 0.027). CONCLUSIONS: Our study underlines the relevance of environmental factors in the development of inflammatory bowel disease. Our results imply a protective effect of physical activity regarding the onset of inflammatory bowel disease

Effect of distance to specialist care for the diagnosis and disease outcome of inflammatory bowel disease in the Swiss inflammatory bowel disease cohort study

Background: Inflammatory bowel disease (IBD) needs early interventions and an individual specialist-patient relationship. Distance from a tertiary IBD center might affect patient's disease course and outcome. We investigated whether the patient-to-specialist distance has an impact on the disease course using the well-defined patient collective of the Swiss Inflammatory Bowel Disease Cohort Study (SIBDCS). Methods: Patient's home address at diagnosis (postal zip code) was extracted from the SIBDCS database. Distance between each zip code and the nearest located IBD specialist center was calculated and classified into the following three sections based on proximity: 35 km (group 3). Results: Our study included in total 408 IBD patients [234 Crohn's disease (CD), 154 ulcerative colitis (UC), 20 IBD unclassified (IBDU)]. Median age was lowest in group 2 at diagnosis (G1: 28 years; G2: 21 years, G3: 26 years, p < 0.01). The diagnostic delay did not differ between groups. CD patients in group 1 were treated more often with anti-tumor necrosis factor (TNF) agents (72% versus 56%, p = 0.04) and 5-aminosalicylates (44% versus 28%, p = 0.04) than in group 3. UC/IBDU patients in group 1 were treated more often with corticosteroids than patients in group 3 (83% versus 58%, p < 0.01). The occurrence of IBD-related surgeries did not differ between groups. Conclusions: Patient-to-specialist distance might affect drug treatment. However, disease course and the need for IBD-related surgery does not seem to be associated with a longer distance to specialist care in Switzerland

Temperature-triggered in situ forming lipid mesophase gel for local treatment of ulcerative colitis

Ulcerative colitis is a chronic inflammatory bowel disease that strongly affects patient quality of life. Side effects of current therapies necessitate new treatment strategies that maximise the drug concentration at the site of inflammation, while minimizing systemic exposure. Capitalizing on the biocompatible and biodegradable structure of lipid mesophases, we present a temperature-triggered in situ forming lipid gel for topical treatment of colitis. We show that the gel is versatile and can host and release drugs of different polarities, including tofacitinib and tacrolimus, in a sustained manner. Further, we demonstrate its adherence to the colonic wall for at least 6 h, thus preventing leakage and improving drug bioavailability. Importantly, we find that loading known colitis treatment drugs into the temperature-triggered gel improves animal health in two mouse models of acute colitis. Overall, our temperature-triggered gel may prove beneficial in ameliorating colitis and decreasing adverse effects associated with systemic application of immunosuppressive treatments

Cytomegalovirus disease in inflammatory bowel disease: epidemiology and disease characteristics in a large single-centre experience

BACKGROUND Patients with inflammatory bowel disease (IBD) show an increased risk of developing cytomegalovirus (CMV) disease because of immunosuppressive medication and malnutrition. Here, we aimed to investigate the prevalence and clinical characteristics of CMV disease in our cohort of IBD patients. PATIENTS AND METHODS We carried out a retrospective analysis of 1023 IBD patients treated at our IBD clinic at the University Hospital Zurich between 2007 and 2014. CMV disease was defined as a positive immunohistochemistry for CMV and 14 patients were identified. RESULTS The prevalence of CMV disease in our IBD cohort was 1.37%. Twelve patients had ulcerative colitis and two had Crohn's disease with colonic involvement. All patients who developed CMV disease received immunosuppressive medication or, as in one case, had HIV infection. The most used immunosuppressive medications were steroids and azathioprine. The most common therapeutic strategy was the consecutive use of ganciclovir and valganciclovir. Ten patients recovered and two were treatment refractory; among these, one required colectomy and two had a relapse. CONCLUSION CMV disease may influence the clinical course of IBD. There is probably an association between CMV disease and IBD-specific medication. Risk factors, epidemiology and therapeutic strategy need to be further investigated

Bone health in patients with inflammatory bowel disease.

Patients with inflammatory bowel disease (IBD) are prone to reduced bone mineral density and elevated overall fracture risk. Osteopenia affects up to 40% of patients with IBD (high regional variability). Besides disease activity, IBD specialists must consider possible side effects of medication and the presence of associated diseases and extraintestinal manifestations. Osteopenia and osteoporosis remain frequent problems in patients with IBD and are often underestimated because of widely differing screening and treatment practices. Malnutrition, chronic intestinal inflammation and corticosteroid intake are the major pathophysiological factors contributing to osteoporosis. Patients with IBD are screened for osteoporosis using dual-energy X-ray absorptiometry (DXA), which is recommended for all patients with a prolonged disease course of more than three months, with repeated corticosteroid administration, aged >40 years with a high FRAX risk score or aged <40 years with multiple risk factors. From a therapeutic perspective, besides good disease control, vitamin D supplementation and glucocorticoid sparing, several specific osteological options are available: bisphosphonates, receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors (denosumab), parathyroid hormone (PTH) analogues and selective estrogen receptor modulators. This review provides an overview of the pathophysiology, diagnosis, prevention and treatment of IBD-associated bone loss

Glycoprotein (GP)96 is essential for maintaining intestinal epithelial architecture by supporting its self-renewal capacity

BACKGROUND & AIMS Glycoprotein (GP)96 is an endoplasmic reticulum (ER)-resident master chaperone for cell surface receptors including the Wnt co-receptors LRP5/6. Intestinal epithelial cells (IEC)-specific deletion of Gp96 is embryonically lethal. However, the role of GP96 in adult intestinal tissue and especially within the intestinal stem cell (ISC) niche has not been studied so far. Here, we investigated how GP96-loss interferes with intestinal homeostasis by compromising viability, proliferation and differentiation of IEC. METHODS Tamoxifen was used to induce Cre-mediated deletion of Gp96 in GP96-Villin$^{creERT2}$ mice and intestinal organoids. With H&E- and immunofluorescence staining we assessed alterations in intestinal morphology and the presence and localization of IEC-types. Real-time PCR and Western blot analysis were performed to explore the molecular mechanisms underlying the severe phenotype of Gp96 KO mice and organoids. RESULTS IEC-specific deletion of Gp96 in adult mice resulted in a rapid degeneration of the stem cell niche, followed by a complete eradication of the epithelial layer and death within few days. These effects were due to severe defects in ISC renewal and premature ISC differentiation, which resulted from defective Wnt and Notch signaling. Furthermore, depletion of GP96 led to massive induction of ER stress. While effects on ISC renewal and adequate differentiation were partly reversed upon activation of Wnt/Notch signaling, viability could not be restored, indicating that reduced viability was mediated by other mechanisms. CONCLUSIONS Our work demonstrates that GP96 plays a fundamental role in regulating ISC fate and epithelial regeneration and is therefore indispensable for maintaining intestinal epithelial homeostasis