Evaluation of intestinal brush border enzyme function

Sepsis, septic shock and concomitant multiorgan failure are major causes of morbidity and mortality on intensive care units. Sepsis affects millions of people each year and its frequency is increasing. During SIRS and septic shock the role of the gut seems to be uncertain. Besides digestion the gastrointestinal tract represents the largest immunological organ of the body. As it serves as an intestinal barrier which allows the symbiotic relationship between man and enteric bacteria increased gut permeability during critical illness is accused to promote sepsis. Furthermore gut-derived substances can cause lung damage as well as promote systemic inflammation. However, SIRS and septic shock also have a direct influence on the gastrointestinal mucosa. Recently, in vivo animal studies demonstrated a decreased microvascular blood flow in the gut mucosa and a disturbed intestinal epithelial cell cycle. The role of the gut mucosa and especially of brush border enzymes to maintain the gut barrier has recently been elucidated by Goldberg et al. In a rat model they could show that the brush border enzyme intestinal alkaline phosphatase has the ability to detoxify lipopolysaccharides and prevent bacterial invasion across the gut mucosal barrier. However, influence of SIRS and septic shock on brush-border enzymes in man, which seem to be involved in the gut mucosal defence has never been investigated. Therefore, the aim of our study is to assess the influence of SIRS and septic shock on brush border enzyme function in man and to evaluate the morphology of the brush border as well as the location and appearance of several brush border enzymes. Design: open monocentric pilot study Aim of the study: Evaluation of intestinal brush border morphology and distribution of brush border enzymes as well as mRNA and function of maltase, sucrase and intestinal alkaline phosphatase in patients with SIRS and septic shock compared to control patients assessing histology and using enzyme assays. Study approach: Control patients will be recruited from the outpatient ward referred to the endoscopy of the department of gastroenterology and hepatology for upper GI-endoscopy because of epigastric pain or reflux symptoms. Three additional duodenal biopsies will be taken during the routine gastroscopy after given informed consent. Critically ill patients will only be enrolled in the study in the case of clinical indication for upper GI- endoscopy within 72 h after fulfilling the inclusion criteria. Duodenal biopsies are taken during routine gastroscopy, too. Biopsies are only taken in patients without continuous anticoagulant therapy and when platelets are > 50 G/l and prothrombin time is > 50% for safety reasons. Half of the biopsies will be assessed histologically. The other part will be taken for assessing of brush border enzyme function and RNA.

Sepsis is the inflammation of the whole body caused by an infection. Sepsis, septic shock (sepsis plus circulatory failure) and concomitant failure of organs are major causes of morbidity and mortality in intensive care units. Sepsis affects millions of people each year and its frequency has been increasing. During sepsis the role of the gut seems to be uncertain. It is hypothesized that the source of the whole-body infection are bacteria from the gut. According to this theory bacteria would migrate from inside the gut through the intestinal wall into the blood stream of a patient. Via the blood stream bacteria could spread to the whole body. Therefore, it is of utmost importance to investigate the role of the intestine and especially of the intestinal wall in patients with sepsis. In a rat model researchers have shown that the enzyme Intestinal Alkaline Phosphatase (IAP) - which is located at the inner side of the intestinal wall (brush border membrane) - is an important factor to hinder the migration of bacteria from the gut to the blood stream. Therefore, in the current project we investigated if the protein IAP may also be a factor in the migration of bacteria in human patients during sepsis. We investigated this by taking biopsies (tissue samples) from the intestine using a gastroscope in patients with septic shock, SIRS (whole-body inflammation not caused by bacteria), and in healthy individuals. In these tissue samples we determined the activity of the enzyme IAP and compared the IAP activity between these three groups. Altogether we evaluated 19 healthy individuals, 7 patients with SIRS, and 13 with septic shock (interim analysis). We found that the activity of the protein IAP was 2678 IU/L in healthy individuals, 2744 IU/L in patients with SIRS and 1479 IU/L in patients with septic shock (all median values). Figure 1: The activity of the enzyme intestinal alkaline phosphatase (IAP) was determined in patients with septic shock, SIRS, and in healthy individuals (controls). No statistically significant differences were found between these three groups in the interim analysis. The activity of the brush border enzyme IAP was not statistically different between healthy individuals, patients with SIRS, and septic shock in the interim analysis. Influence of the enzyme IAP in the migration of bacteria from the gut into the bloodstream in patients with sepsis cannot be estimated at the moment.