Risk factors in inflammatory bowel disease

Etiopathogenesis of pediatric Crohn's disease. Biologic pathways based on interactions between genetic and environmental factors

The incidence and prevalence of Crohn's disease (CD) among children in developed countries is extremely high. Although, dietary factors have long been implicated, to date no single causative element has been identified. Risks or benefits for CD from dietary elements would depend on their appropriate metabolism within the gut by xenobiotic metabolising enzymes (XME). The metabolising capacity among individuals differs and is determined by the level and/or activity of the specific XME. As the latter is the function of the DNA variants that code them, we propose that certain individuals exposed to dietary elements are likely to be more or less susceptible for CD. We highlight this hypothesis by describing gene-environment interaction (GxE) mechanisms that could determine susceptibility for CD. We suggest that investigating these mechanisms will be paramount for the appropriate identification of susceptible populations, such that preventive and/or therapeutic interventions could be adequately targeted.

Inflammatory bowel disease and environmental influences

Some environmental factors have been established firmly as influences on the development of IBD, such as smoking and appendectomy. Other behaviors, such as oral contraceptive use and sugar intake, have been suggested as risk factors, but he data conflict sharply. The importance of other behaviors, such as breast-feeding, is even murkier with sharply divergent data. Some issues studied may not be factors in themselves but rather markers for other unidentified influences. The conflicting evidence in many of these studies may be clarified as specific genes are identified and the interplay between these environmental factors and genetic subtypes is investigated.

Appendectomy, tonsillectomy, and risk of inflammatory bowel disease: case-controlled study in Crete

PURPOSE

Appendectomy has been suggested as a possible protective factor in ulcerative colitis and as a risk factor in Crohn's disease. Tonsillectomy has also been associated with Crohn's disease. We performed a case-controlled study to investigate these associations in a homogeneous Greek population.

METHODS

One hundred thirty-four consecutive cases of ulcerative colitis and 76 cases of Crohn's disease were included in the study. For each inflammatory bowel disease patient and a corresponding healthy control subject, matched for gender, age, and educational level, a standard record on various risk factors was completed by interview. The association between disease status and risk factors was assessed by Pearson's chi-squared test and the independent contribution of each risk factor was analyzed by means of logistic regression analysis.

RESULTS

Appendectomy had been performed in 11 (8.2 percent) patients with ulcerative colitis, in 18 (13.4 percent) of their matched healthy control cases, in 19 (25.0 percent) patients with Crohn's disease, and in 10 (13.2 percent) of their matched healthy control cases. Odds ratio for development of ulcerative colitis after appendectomy was 0.6 (95 percent confidence interval, 0.26-1.27). Odds ratio for Crohn's disease was 2.2 (95 percent confidence interval, 0.94-5.12). Odds ratio for development of ulcerative colitis or Crohn's disease after tonsillectomy was 0.95 (95 percent confidence interval, 0.49-1.82) and 3.29 (95 percent confidence interval, 1.29-8.37), respectively. The logistic regression analysis showed that appendectomy and tonsillectomy have no independent association with the risk of developing ulcerative colitis, whereas in Crohn's disease both appendectomy and tonsillectomy have positive associations. Well-established risk factors, such as family history and smoking status, were also verified in this study.

CONCLUSIONS

This case-control study, using multivariate logistic regression analysis, showed a less pronounced association between ulcerative colitis and appendectomy than previous reports. Our data also support the conclusion that tonsillectomy is a risk factor for developing Crohn's disease.

Effect of N-3 polyunsaturated fatty acid supplemented diet on neutrophil-mediated ileal permeability and neutrophil function in the rat

RATIONALE AND OBJECTIVE

Fish oil, rich in n-3 polyunsaturated fatty acids, can alter leukotriene production and hence neutrophil function, factors which may be important in the inflammation of Crohn's disease (CD). Therefore we studied the effect of dietary PUFA on neutrophil mediated ileal inflammation and neutrophil function in the rat.

METHODS

Animals were ad libitum-fed pellet diets containing 9.5% fish oil (menhaden oil, rich in n-3 PUFA) with 0.5% safflower oil, 10% safflower oil (rich in n-6 PUFA) or standard chow (6% fat) for 50 days prior to the study. Weight and circulating leukocyte and total neutrophil counts were identical in all three groups. Neutrophil mediated ileal inflammation induced by formyl-methionyl-leucyl-phenylalanine (fMLP) perfusion was evaluated by measuring macromolecular uptake of radiolabelled dextran (MW 70,000) and changes in mucosal neutrophil infiltration.

RESULTS

The fish oil diet group showed no difference in fMLP-induced permeability changes relative to the Chow Control group. However, the Safflower Oil supplemented diet group had a reduced permeability response (p < 0.01). Mirroring the permeability changes, there was diminished mucosal neutrophil infiltration in the Safflower Oil group following ileal perfusion with fMLP (< .005). Chemotaxis and chemiluminescence, two important neutrophil functions, were also significantly suppressed in the Safflower Oil animals (p < 0.05).

CONCLUSIONS

The failure of a n-3 PUFA enriched diet to diminish the ileal inflammatory response to a bacterial peptide and suppress neutrophil function in the rat suggests such therapy would not be expected to be highly successful in CD. However, it requires confirmation in man, especially under the more complicated inflammatory conditions found in CD. On the other hand, the decreased neutrophil mediated responses with a high linoleic acid (n-6 PUFA) diet warrant further investigation.