Anti-inflammatory effects of enteral diet components on Crohn's disease-affected tissues in vitro.

Background: The mechanism of action of elemental diet in Crohn's disease treatment, is unknown. Alteration of bacterial flora, low antigenicity, low fat content and improvement of nutritional status are postulated to play a role in the anti-inflammatory effect of elemental diet.
Aim: To determine whether elemental diet or its modifications has a direct anti-inflammatory effect on colonic tissue biopsies in vitro.
Patients and Methods: Colonic or ileal biopsies from 39 patients with inflammatory bowel disease and control patients were incubated for 24 hours with enteral diets in which nitrogen sources were amino acids as in elemental diet, casein or whey. Tissues were incubated with elemental diet, casein or whey, at dilutions of 1:5, 1:10 or 1:20 in Waymouth's complete medium; a medium control was also included. Tissue viability was assessed by bromodeoxyuridine uptake. Interleukin-1beta, interleukin-1 receptor antagonist and interleukin-10 concentrations in supernatants were measured by immunoassay (enzyme-linked immunosorbent assay).
Results: Incubation of tissues from Crohn's disease with elemental diet resulted in an increase in the ratio of interleukin-1 receptor antagonist/interleukin-1beta vs control statistically significant at 1:10 (89.6+/-17 vs 45.7+/-9. 1, p<0.05). Incubation of Crohn's tissue with casein resulted in a significant increase of interleukin-1 receptor antagonist/interleukin-1beta ratio at dilutions 1:20, 1:10 and 1:5 (101.8+/-22.0, p=0.05, 142.8+/-24.6, p<0.05; 109.7+/-25.0, p=0.05). In ulcerative colitis tissue and non-inflamed non-inflammatory bowel disease control tissue, no significant increase in interleukin 1 receptor antagonist/interleukin-1beta ratio was seen after incubation with elemental diet, casein and whey.
Conclusion: Elemental diet incubation increases anti-inflammatory:proinflammatory cytokine ratio in Crohn's disease and this anti-inflammatory effect is not specifically due to amino acid composition, as diets containing casein have similar anti-inflammatory effects.