An accumulation of histamine and mast cells is found in IBD and gastrointestinal food allergy. Histamine may exert a broad range of proinflammatory and immuno-regulatory effects, particularly if this amine isn't degraded enzymatically within short time.
In this study the enzyme activity of diamine oxidase (DAO), one of the main histamine catabolizing enzymes, was investigated in patients with food allergy and ulcerative colitis, idiopathic ulcerative colitis and Crohn's Disease. The enzyme activity was determined in the homogenate of the biopsy using 14C-putrescine (substrate) during 60 minutes. The 14C labelled organic end product (1-pyrrolin) was extracted in the organic phase and then measured by liquid scintillation counting.
DAO activities (cpm/h/mg ww) showed a physiological value of 61.6±44 in control persons (n=67 biopsies) Patients with food allergy and ulcerative colitis (n=31) had significantly reduced DAO levels (40.7±46, p=0.001) similarly to chronic idiopathic ulcerative colitis (38.4±39, p=0.001, n=40). Although reduced, DAO levels in Crohn's Disease did not reach statistical significane (45.6±32,p<0.07, n=47). Interestingly, corresponding to the decrease of DAO activity, increased tissue histamine levels were observed in patients with food allergy and ulcerative colitis and in idiopathic ulcerative colitis (both p<0.01), but not in Crohn's Disease.
This analysis of the DAO activity demonstrates that the oxidative capacity of gut mucosa to rapidly degrade histamine, is impaired in food allergy and IBD, suggesting that histamine may further enhance mucosal inflammation. Th2 dominated disease as food allergy and ulcerative colitis are found to be at a higher risk to loose DAO from epithelial cells during inflammation and to exhibit more elevated tissue histamine levels than Crohn's Disease. The reduced activity of DAO also suggests to use histamine-poor or -free diets and antihistamines during acute phases of mucosal inflammation.
