Intestinal Fatty Acid Binding Protein And D-lactate For Diagnosis Of Ischemic Bowel Disease

Ischemic bowel disease is a severe intestinal emergency with high mortality due to insufficient blood supply of the small intestine and(or) colon. It can be divided into acute mesenteric ischemia(AMI), chronic mesenteric ischemia(CMI), and ischemic colitis(CI). It can be precipitated by a number of pathophysiological processes such as arterial embolism, arterial and venous thrombosis, aortic dissection, intestinal obstruction due to adhesive diseases after previous operations, hypovolemia, andhypotension. Clinical diagnosis of intestinal ischemia remains difficult, because of the nonspecific clinical signs in the early phase. Especially, in high-risk patients clinical history taking and physical examination is hampered because of sedation and analgesia. In addition, the lack of appropriate diagnostic tests further hampers correct diagnosis.A delay in diagnosis can lead to irreversible full-thickness necrosis of the bowel(gastrointestinal motility disorders, intestinal digestion and absorption dysfunction, intestinal barrier dysfunction), and thus can lead to intestinal flora translocation and endotoxemia, intestinal release of inflammatory mediators, amplifying inflammatory cascade, systemic inflammatory response syndrome, damage Liver, lung, kidney and other distant organs, and ultimately can lead to multiple organ dysfunction syndrome and multiple organ failure. Rapid and accurate diagnosis is essential to improve the prognosis and quality of life of patients with ischemic bowel disease. Even when the latest high-technology diagnostic devices, such as angiography, multidetector computed tomography (CT)and ultrasund, are used, these diseases are sometimes overlooked. It remains difficult, even for experienced physicians, to identify patients at risk of bowel necrosis among patients presenting with acute abdomen. Therefore, it is important to improve early diagnosis of ischemic bowel disease.Organ-specific biomarkers are widely used for the diagnosis of various diseases by blood analysis [alanine aminotransferase for hepatic injury, creatine phosphokinase (CPK) for myocardial infarction, and amylase for pancreatitis], because they are easily measurable and are useful for identifying patients who really need further examination. However, to date, no specific blood marker is available for the detection of injury to the bowel.Intestinal fatty acid-binding protein (I-FABP) is abundant in intestinal epithelial villus. I-FABP value is very low in peripheral blood in normal, but when subjected to hypoxia, ischemia and reperfusion damage, releasing I-FABP through the capillaries and the capillary Lymphatics into the blood circulation, which can be detected in the peripheral blood. I-FABP can be characterized as follows:(1)a soluble protein in the cytoplasm, (2) high tissue specificity, (3) abundance in the tissue, and(4) small molecular weight and easy to be detected. That mentioned above make it potentially suitable as a blood marker for the diagnosis of ischemic bowel disease.When intestinal ischemia occur, a great amount of D-LAC produced by local bacteria through the destroied intestinal biological barrier into the peripheral blood, lead to inreaseing of the blood levels of D-LAC. The mechanisms including: intestinal ischemia damaged the mucosal barrier directly, D-LAC produced by local bacteria due to intestinal ischemia, release of inflammatory factors of body, resulting in increased permeability of intestinal mucosa. Therefore, plasma D-LAC can be used as reaction intestinal ischemic injury markers. However, all intestinal ischemia caused by hypoxia, and the factors that lead to increased intestinal permeability will lead to the levels of plasma D-LAC higher, such as severe trauma, shock, intestinal ischemia, and severe type of intestinal Obstruction.ObjectiveThis study aims at improving diagnosis of ischemic bowel disease, in animal experiments and clinical trials, by measuring plasma I-FABP and D-LAC levels, base on I-FABP the sensitivity of the intestinal mucosal injury, and the D-LAC specificity for intestinal ischemia. 1.The relevance of the serum I-FABP level, D-LAC levels, ischemic time and intestinal tissue injury in animal model.2.The diference of the serum I-FABP level, D-LAC level in patients with ischemic bowel disease and without ischemic bowel disease and health.3.The cut-off value of the serum I-FABP level and D-LAC level, and both diagnosic specificity and sensitivity.4.The diagnosic specificity and sensitivity of optimization model combined serum I-FABP and D-LAC.Method1.Build the model of Rat mesenteric artery ischemia, randomized groups according to ischemic time, comparing the serum I-FABP and D-LAC level in hoth teams by ELISA, assessment of I-FABP value in damaged intestinal mucosa by immunohistochemistry.2.Collected serum samples of acute abdominal pain patients. Two groups, including ischemic bowel group (ICBD) and non-ischemic bowel disease group (NICBD), were compared of serum I-FABP and D-LAC level by ELISA, The cutoff level of serum I-FABP and D-LAC level for the diagnosis of ischemic bowel disease was determined by receiver operating characteristic (ROC) analysis on the basis of the data for enrolled patients.3.According to the cut-off value, verify the diagnostic utility of serum I-FABP and D-LAC in the diagnosis of ischemic bowel disease, analysis of diagnostic sensitivity and specificity base on a mathematical optimization model.Results1.The serum I-FABP was significantly increased from ischemic 30min, peaked at 90min, and then extend the ischemic time with the reduction in the level.2.The serum D-LAC was significantly increased from ischemic 60min, and then extend the ischemic time with the increasing in the level.3.ICBD group of patients with serum I-FABP and D-LAC median levels were significantly higher than the control group and patients with other diagnoses (p<0.05), NICBD levels of serum I-FABP levels were significantly higher than the control group (p<0.05), while NICBD levels of serum D-LAC median level of healthy controls no significant difference (p>0.05);4.The serum of I-FABP and D-LAC levels in the patients with acute mesenteric ischemia were significantly higher than that of ischemic colitis and focal colon ischemia patients (p<0.05); the serum I-FABP levels in focal ischemia patients and in mechanical bowel obstruction patients were not significantly difference (p>0.05), but the serum D-LAC levels was higher than that in patients with mechanical intestinal obstruction (p<0.05);5.The serum I-FABP levels of patients with small bowel ischemia were significantly higher than that of colorectal ischemia group (p<0.05), while no significant difference in both of the serum D-LAC levels (p>0.05), The serum I-FABP levels of patients with small bowel desease were significantly higher than that of colorectal desease group (p<0.05). The serum D-LAC levels of patients with colorectal ischemia were significantly higher than that of small desease group (p<0.05). No significant difference in both of the serum I-FABP levels (p>0.05).6.The cut-off value of I-FABP was 86.21ng/ml, and of D-LAC was 34.28ug/ml. sensitivity of 76.2%, specificity of 74.8%, positive predictive value of 32.1%,96.3% negative predictive value, positive likelihood value of 3.05, negative likelihood value of 0.24 for I-FABP. Sensitivity of 66.7%, specificity of 81.9%, positive predictive value of 51.3%, negative predictive value of 68.6%, positive likelihood value of 2.62, negative likelihood was 0.31, for D-LAC. The likelihood of I-FABP and D-LAC were significantly higher than the diagnostic LDH, CK, CRP and WBC.7.Verification of ischemic bowel disease in patients, critical value of serum I-FABP with a sensitivity of 100%, specificity 70%, the critical value of serum D-LAC with a sensitivity of 50%, and a specificity of 100%.8.Compared optimization model for the diagnosis of ischemic bowel disease, with a sensitivity of 100%, specificity of 100%.Conclusion 1.The serum I-FABP levels in intestinal ischemia peak at 90min, within 90min of intestinal ischemia was significantly associated with tissue injury.2.The serum D-LAC was significantly increased from ischemic 60min, after 60min of intestinal ischemia was significantly associated with tissue injury.3.Healthy human serum I-FABP concentration was 8.33±6.25ng/ml, serum D-LAC concentration of 5.47±3.64ug/ml, The serum I-FABP and D-LAC levels in patients with ischemic bowel disease was significantly higher than healthy people.4.The cut-off value of I-FABP was 86.21ng/ml, and D-LAC was 34.28ug/ml. Can not determine the diagnosis of ischemic bowel disease by I-FABP and D-LAC positive results. patients with I-FABP-negative results (NPV 96.3%) can determine the possibility of the development of intestinal ischemia was 3.7%.5.I-FABP and D-LAC, with high diagnostic likelihood, have high differential diagnosis value.6.By Compared optimization model, could increase the sensitivity and specificity for the diagnosis of ischemic bowel disease.