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Clinical relevance of the serum dipeptidyl peptidase IV (DPP IV/CD26) activity in patients with inflammatory bowel diseases

The aim of this study was to evaluate the clinical relevance of the changes in serum dipeptidyl peptidase IV (DPP IV/CD26) activity in adult patients with inflammatory bowel diseases (Crohn's disease, CD and ulcerative colitis, UC). We hypothesized that changes in DPP IV serum activity could relate to the disease activity. Furthermore, we wanted to estimate if the serum DPP IV activity could be a potential distinguishing marker between Crohn's disease and ulcerative colitis. The dipeptidyl peptidase IV (DPP IV/CD26) is an abundant, widely distributed serine protease that is able to cleave the N-terminal dipeptides from polypeptides. The cleavage by DPP IV can result in activation, inactivation or even significant change in the activity of physiological peptides. This membrane-bound glycoprotein is a unique multifunctional protein, acting as a receptor, binding and proteolitic molecule, also expressed on the surface of various cell types, including epithelial and endothelial cells and lymphocytes. DPP IV is also present in a soluble form in the serum (1, 2). The study was performed on 62 patients, 38 with CD (age 42, 71 ± 14, 37 ; 19 males, 19 females), and 24 with UC (age 45, 58 ± 17, 61 ; 13 males, 11 females). The diagnosis of CD or UC were established on the basis of clinical history, laboratory, endoscopic and histological data. The CD activity was evaluated using the Crohn´s Disease Activity Index (CDAI), while the UC activity was evaluated by the Truelove and Witts' (TW) classification. The control group included 65 healthy donors (age 41, 60 ± 12, 14 ; 32 males, 33 females). The serum dipeptidyl peptidase IV (DPP IV/CD26 ; EC 3.4.14.5) activity has been measured spectrofotometrically at 405 nm by detection of free 4-nitroaniline in an assay mixture using Gly-Pro p-nitroanilide as the substrate, according to the protocol of Kreisel W. et al. (3). Enzyme activities were expressed as international unit per liter of serum (U/L). Both serum DPP IV activities in patients with CD (36, 83 ± 9, 74 U/L) and UC (33, 87 ± 10, 69 U/L) were statistically significantly decreased compared with the levels in healthy controls (48, 37 ± 8, 94 U/L), (p<0, 001). Values correlated inversely with the disease severity for both diseases. No statistically significant difference in the serum DPP IV activity in patients with CD and UC was found. The results of this study sustained the statement that the serum DPP IV is involved in the pathophysiology of IBD. The obtained results confirm a functional compartmentalization of DPP IV, which can be interpreted as an adaptive systemic immune response to a local inflammatory reaction. As no statistically significant difference in the serum DPP IV activity was found between CD and UC, this indicates that the serum DPP IV activity could not be a good marker for the differential diagnosis between those two diseases. However, the serum DPP IV activity appears to be useful as an available, non-invasive marker in the diagnosis of the disease activity. 1. M. D. Gorrell, V. Gysbers, and G. W. McCaughan, Scand J Immunol 54 (2001) 249-264. 2. E. Boonacker and C. J. F. Van Noorden, European Journal of Cell Biology 82 (2003) 53 - 73. 3. W. Kreisel, R. Heussner, B. Volk, R. Büchsel, W. Reutter, and W. Gerok, FEBS Lett 147 (1982) 85-88.

dipeptidyl peptidase IV (DPP IV/CD26) ; serum activity ; inflammatory bowel diseases ; Crohn's disease ; ulcerative colitis

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