Serum Nitrate Levels in Ulcerative Colitis and Crohn's Disease

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Abstract
Background: Nitric oxide is an important mediator in inflammatory and autoimmune-mediated tissue destruction and may be of pathophysiologic importance in inflammatory bowel disease. We studied whether serum levels of nitrate, the stable end-product of nitric oxide, are increased in active Crohn's disease or ulcerative colitis, in comparison with quiescent disease and healthy controls. The setting was the gastroenterology unit of the Free University Hospital, Amsterdam. Methods: In 146 patients—75 with ulcerative colitis and 71 with Crohn's disease—and 33 controls serum nitrate was measured by the Griess reaction after enzymatic conversion of nitrate to nitrite with nitrate reductase. Results: Median serum nitrate concentrations did not differ statistically significantly between ulcerative colitis (median, 34.2 μmol/l; range, 15.6–229.4 μmol/l), Crohn's disease (median 32.3 μmol/l; range 13.2–143.2 μmol/l), and healthy controls (median, 28.7 μmol/l; range, 13.0–108.4 μmol/l). However, when active ulcerative colitis patients (median, 44 μmol/l; range, 29.1–229.4 μmol/l were compared with inactive ulcerative colitis patients (median, 31.2 μmol/l; range, 15.6–59.7 μmol/l). a significant difference in nitrate concentration was found (p < 0.0001). A significant positive correlation was found between Serum nitrate levels in ulcerative colitis and erythrocyte sedimentation rate (ESR) (r = 0.30, p = 0.01), leucocyte count (r = 0.27, p = 0.02), and thrombocyte count (r = 0.24, p = 0.04). Comparing active Crohn's disease patients (median, 37.5 μmol/l; range, 13.2–143.2 μmol/l) with inactive Crohn's disease patients (median, 31.3 μmol/l; range, 14.5–92.3 μmol/l) also showed a significant difference in serum nitrate concentration (p < 0.009). Serum nitrate levels correlated with the ESR (r = 0.26, p = 0.028) and serum albumin (r = -0.38, p = 0.004) as well. Conclusion: Nitric oxide production is increased in both active ulcerative colitis and Crohn's disease and may be implicated in the pathogenesis of inflammatory bowel disease.