The Effect of VSL#3 Probiotic Preparation on the Bile Acid Metabolism in Patients With Inflammatory Bowel Disease

VSL#3 (Original De Simone formulation, further abbreviated as VSL#3), a potent probiotic preparation, has been tested as an adjuvant therapy in inflammatory bowel diseases (IBD), chronic unspecific inflammatory disorders of the gastrointestinal tract (the most frequent forms of IBD are Crohn's disease (CD) and ulcerative colitis (UC)). VSL#3 has been shown to improve symptoms of IBD both in animal models and in humans-the most impressive results have been observed in preventing of pouchitis in UC patients. Several possible mechanisms of its action have been suggested, including change in gut microbial diversity, immunomodulatory function (upregulation of interleukine-10), etc., however, the list is probably far from complete.

Bile acids (BA) play an important role in the gastrointestinal tract - besides facilitating fat (and protein) digestion and resorption, they act as general antimicrobial agents within the small intestine (maintaining the small intestine more or less microbe-free), colonic microflora modifiers, intestinal innate immunity regulators, and importantly as signalling molecules on the liver-intestine/intestine-liver axis. Under pathological conditions (such as BA malabsorption) BA can worsen the IBD symptoms (namely diarrhoea), by irritating colonic mucosa or by inducing colonic secretion of electrolytes.

The study hypothesis is that the beneficial effect of VSL#3 might be partially explained by alteration of BA metabolism. There exists a complex crosstalk between gut microflora and BA: BA affect microbial growth, whereas BA structure is modified by bacteria (deconjugation, 7 α dehydroxylation). Several observations might support this hypothesis: VSL#3 ameliorates symptoms of radiation or chemotherapy induced diarrhoea, as well as diarrhoea of critically ill patients - conditions, that can be caused by BA malabsorption. Similarly, oxalate absorption (closely related to BA malabsorption) has been shown to be lowered by VSL#3. The main question to be addressed in the proposed study is, therefore, whether VSL#3 administration can somehow change metabolism of bile acids (BA).

Additionally, urinary metabolite levels are strongly influenced by differences in the intestinal microbiota, since both gut bacterial metabolism, and shared metabolism by the host and bacterial species ('co-metabolism'), generate specific metabolic products. Such metabolites may therefore be used as markers of microbial metabolic activity, reflecting systemic, functional differences. This application of urinary metabolic profiling avoids the technical difficulties, and methodological differences, found in molecular studies of the intestinal microbiota in IBD, which have contributed to often discrepant findings. Specific urinary metabolites related to gut microbial metabolism differ between CD patients, UC patients, and controls. The emerging technique of urinary NMR-based metabolic profiling with multivariate analysis was able to distinguish these cohorts. This study should address the question, whether VSL#3 administration changes the nuclear magnetic resonance-based urinary metabolomic profile.