Is the assay of disaccharidase activity in small bowel mucosal biopsy relevant for clinical gastroenterologists?

Biomarkers of small intestinal mucosal damage induced by chemotherapy: an emerging role for the 13C sucrose breath test

Gastrointestinal mucosal toxicity is extremely common following cytotoxic therapies. The alimentary mucosa is particularly susceptible to injury and dysfunction, leading to many debilitating complications. Despite much research, there is currently no single noninvasive biomarker to detect gut injury. Several biomarkers have been investigated in the context of gastrointestinal diseases, which may prove useful in the oncology arena. Identification of a biomarker that is easy to obtain and measure and that accurately identifies mucosal damage would allow for improved patient diagnosis of toxicities and for personalized treatment regimens. In this review, we highlight the effectiveness of urine and breath tests as potential clinically effective biomarkers, with significant focus placed on the emerging role of the carbon-13 sucrose breath test (13C SBT). The 13C SBT provides a simple, noninvasive, and integrated measure of gut function. The 13C SBT also has the potential to monitor gut function in the setting of cytotoxic therapy-induced mucositis, or in the assessment of the efficacy of antimucositis agents.

Lactose intolerance in active Crohn's disease: clinical value of duodenal lactase analysis

BACKGROUND

Patients with active Crohn's disease (CD) often report having abdominal symptoms after ingestion of milk products, but the pathomechanism for lactose malabsorption seems to be complex.

GOALS

To investigate the prevalence of clinical milk intolerance and to objectify symptoms with hydrogen (H 2 ) breath testing, analysis of lactase protein, and enzyme activity in the duodenal mucosa in patients with CD and in healthy controls.

STUDY

In 49 patients with CD and 24 controls, H 2 breath testing was performed. All individuals underwent endoscopy of the upper gastrointestinal tract, in which multiple pinch samples were taken from the distal duodenum. Lactase activity was measured using the method of Dahlquist. The lactase protein expression was analyzed by gel electrophoresis using the monoclonal antibody mlac 10 and by immunochemistry using the monoclonal antibody mlac 4.

RESULTS

Prevalence of milk intolerance in healthy controls was 16.6% versus 46.9% in patients with CD, with a high frequency (83.3%) in patients with active disease (CD activity index >150). Milk intolerance was correlated to the duration of inflammatory bowel disease ( p = 0.023) but not to the location or previous bowel resection. Hydrogen breath testing had a moderate sensitivity in detecting lactose maldigestion (70.4%) and a high specificity (95.6%). Duodenal lactase levels were also correlated to disease activity, whereas correlations to clinical symptoms remained poor. Patients with milk intolerance had a significantly reduced bone density at the lumbar spine (z-score, -1.33 +/- 0.92 vs. -0.19 +/- 0.95 [mean +/- SD]; p = 0.002)

CONCLUSIONS

Milk intolerance is a frequent problem in active CD, which can be objectified accurately by H 2 lactose breath testing. Decreased lactase levels in the duodenal mucosa may be found during an acute flare but are not the predominant cause of milk intolerance in CD.

Gastroduodenal permeability in Crohn's disease

BACKGROUND

Gastric permeability was prospectively investigated by determination of sucrose excretion in 100 patients with Crohn's disease. Results were compared with histological findings and the lactulose-mannitol ratio as a measure of intestinal permeability.

METHODS

All subjects underwent oesophagogastroduodenoscopy with biopsies of all investigated parts. Thirty-two Helicobacter pylori-positive patients were excluded from further analyses.

RESULTS

Gastroduodenal permeability was significantly higher in patients with Crohn's disease than in control subjects (P < 0.00001). Sucrose excretion alone did not predict microscopic inflammation of the upper gastrointestinal tract. Increased gastroduodenal permeability with a concomitant rise in intestinal permeability predicted histological upper gastrointestinal involvement of Crohn's disease with a likelihood of 86%. The negative predictive value was 43%.

CONCLUSION

In parallel with findings in the small intestine, gastroduodenal permeability is increased in a high proportion of patients with Crohn's disease. In patients with an increased lactulose-mannitol ratio, elevated sucrose excretion is highly predictive of histological gastroduodenal involvement.

A retrospective assessment of the clinical value of jejunal disaccharidase analysis

BACKGROUND

The measurement of jejunal disaccharidases is used by several gastroenterologists when investigating suspected small-bowel disease. The clinical value of this analysis is assessed.

METHOD

The histology and disaccharidase results in 1585 jejunal biopsy specimens were reviewed retrospectively.

RESULTS

Disaccharidase and histology results concurred in most cases (72%). However, disaccharidases were an insensitive indicator of small-bowel disease: low levels were found in only 65% of coeliac patients with villous atrophy, 15% of patients with giardiasis, and 6% of patients with villous atrophy associated with non-coeliac histology. Low disaccharidase levels were sometimes found in patients with normal histology (1.6%) and when biopsy specimens were unwittingly taken from non-jejunal sites (1.4%). Isolated low lactase activities were found in 3.2%. Usually this finding was not clinically relevant because patients had no symptoms of lactose intolerance (38%), had another diagnosis that responded to appropriate treatment (8%), or had no response to a low-lactose diet (14%). In 16 patients sucrase activities were markedly low, and this investigation proved central to the diagnosis of sucrase-alpha-dextrinase deficiency, which was subsequently confirmed in 9.

CONCLUSION

Jejunal disaccharidases are clinically useful only in the diagnosis of sucrase-alpha-dextrinase deficiency. We recommend that their measurement be reserved for the investigation of patients suspected of having this condition.

Lactose intolerance in a calf

Lactose intolerance was identified as the cause of bovine neonatal diarrhea. Glucose and xylose oral absorptions were normal whereas lactose absorption was reduced relative to normal calves. Lactase deficiency is common in people but rarely reported in animals. The treatment of whole milk with lactase alleviated the diarrhea.