Epsilon Open Archive

Abstract

Lactobacillus reuteri is one of the most clinically studied probiotic bacteria. It has e.g. been shown to reduce the incidence and alleviate infantile colic and acute diarrhoea in children aged 3-60 months. The mechanisms of action behind the clinical effects are not fully understood, but two possibilities are inhibition of increased intestinal permeability (leaky gut) and alleviation of pain perception through inhibition of one of the key receptors (TRPV1) involved in visceral pain. The most studied strain of L. reuteri is DSM 17938, which has demonstrated good effects in clinical studies.

To study whether DSM 17938 and other strains could produce bioactive metabolites with a possible inhibitory effect against leaky gut syndrome, different varieties of barley flour were used as growth substrate. Growth and metabolic activity were analysed for different L. reuteri-barley flour combinations, through an overview of the metabolic profile and more targeted chemical analyses. Catabolites of tryptophan previously shown to be bioactive compounds (e.g. AhR-ligands) were detected. Supernatants from L. reuteri-barley flour combinations with high and low concentrations of these catabolites were evaluated for possible protective effect against increased permeability in an intestinal epithelial cell model. Only a minor protective effect was seen for a few supernatants and no correlations were found between content of AhR-ligands and effect on leakage.

In further attempts to improve the clinical effect of L. reuteri, experiments were performed to enhance certain functional properties through the use of experimental evolution. DSM 17938 has been shown to have flaws in certain properties that might contribute to the probiotic efficacy, e.g. freeze-thaw tolerance, bile tolerance and binding to intestinal mucus. Through experimental evolution, these properties were improved for DSM 17938 and, although genetic differences were only seen in two variants compared with the wild type, differences in protein expression were seen for all new variants.

Evaluation of the new variants in cell culture models showed that they had similar effects to wild-type DSM 17938 on inhibition of TRPV1, although in vitro tests using intestinal epithelial cells revealed that some of the variants had lost their inhibitory effect against increased permeability. Overall, however, the variants retained most of the properties seen in vitro for wild-type DSM 17938