Diamine Oxidase As A Marker For Early Diagnosis Of Superior Mesenteric Arterial Occlusion

Back ground and objectiveSuperior mesenteric arterial occlusion (SMA-O) is a rare but very serious emergency for gastrointestinal surgery.This grave disease is characterized by sharp advance,intestinal necrosis and toxic within a short term.Despite deeply understanding of SMA-O,but the mortality rate is as high as 60%-80%.The prognosis depends on early diagnosis and treatment without delay.So, to save the threaten lives, the early detection of SMA-O is very important.Superior mesenteric arterial occlusion frequently presents a diagnostic dilemma to gastrointestinal surgeon since the clinical symptoms and signs are nonspecific,and the biochemical markers of laboratory test are low specific.Detection of serum enzymes has been payed a close attention for its non-invasive, rapid and diverse methods.Diamine oxidase (DAO) is a constitutive enzyme with high activity in the small-intestinal mucosal cells. Because it is released into the blood after intestinal mucosal injury, elevated serum DAO activity indicates damage to intestinal mucosal cells and the intestinal barrier. In this study, we detected the activity of serum DAO in a rat superior mesenteric arterial occlusion (SMA-O) model and verified the relationship between DAO activity and the extent of intestinal mucosal injury. We aimed to find a more sensitive and non-invasive marker of intestinal mucosal injury that would provide evidence for early diagnosis and surgical treatment of SMA-O.MethodSeventy mature male Sprague-Dawley rats were used in the study. These were divided into 7 groups of 10 rats each: 10-min, 15-min, 30-min, 45-min, 60-min, and 90-min superior mesenteric arterial occlusion (SMA-O) groups, and a sham group. Blood samples were taken at the indicated time points for measuring serum DAO activity. Simultaneously, the small-intestinal segments were assessed histologically and graded according to Chiu's score. Resu1t1)Alterations in the activity of serum DAO after intestinal ischemia: Compared with the activity of serum DAO in the sham group, the activity in I15 group increased significantly (41.47±5.4 versus 24.02±2.17 U/L, p < 0.01; Table 3-2) and peaked at 45 min (55.15±8.18 U/L), but decreased quickly thereafter. The activity of serum DAO at 90 min was much lower than that at 45 min (42.13±5.92 versus 55.15±8.18 U/L, p < 0.05).2)Correlation between superior mesenteric arterial occlusion duration and extent of intestinal mucosal injury: Intestinal mucosal injury aggravated with time, and thus the scores increased. The results of linear correlation analysis showed that ischemia duration and intestinal mucosal injury score were significantly positively correlated (r = 0.909, p < 0.01; Figure 3-1).3)Correlation between intestinal mucosal injury and DAO activity in rat serum: Compared with the DAO activity in the sham group, the activity increased significantly when the injury was scored as grade 2 (42.51±6.51 versus 25.95±6.43 U/L, p < 0.01; Table 3-3). DAO activity increased in a time-dependent manner according to the extent of intestinal injury and peaked at grade 4 (p < 0.05, compared with grade 2). However, DAO activity decreased in the grade 5 group, in which the DAO activity was significantly lower than that in the grade 4 group (42.08±7.61 versus 51.56±7.73 U/L, p < 0.05).4)Curve estimation of intestinal mucosal injury score and serum DAO activity: The best curve estimation for serum DAO activity according to Chiu's score was achieved with the cubic model. In the cubic equation y = a + bx + cx~2 + dx~3, y stands for DAO activity, x stands for Chiu's score, and a, b, c, and d are constants calculated using the SPSS software for each of the variables. Therefore, we used the following equations: y = 25.366 + 0.126x + 5.882x~2 - 1.051 x~3, r~2 = 0.985, p < 0.01 (Figure 3-4).5)The diagnostic effectiveness of DAO activity for early SMA-O:The bilateral upper bound of the 95% activity of serum DAO in the I10 group is 29.81u/L.Taking DAO=29.81u/L as a early diagnostic standard for superior mesenteric arterial occlusion,the sensitivity, accuracy and specificity were 94.34%(50/53),95.71%(67/70),100%(17/17) respectively (Table 3-5). ConclusionThe level of serum diamine oxidase correlates with intestinal mucosa damage in a curvilinear manner. DAO activity increases significantly and immediately with superior mesenteric arterial occlusion, and this change occurs before irreversible damage to the intestinal epithelium. This indicates that DAO activity can be used as a marker for early diagnosis of superior mesenteric arterial occlusion. However, further study is needed before clinical application in the diagnosis of superior mesenteric arterial occlusion diseases.