A breakthrough study has revealed commercially available probiotic bacteria exert significant influence over gene expression and cellular metabolic functions in human small intestine.
Researchers looked at the effects of a milk drink containing the probiotic strains Lactobacillus acidophilus Lafti-L10, L. casei CRL-431, and L. rhamnosus GG and compared these with a placebo drink. They found the probiotic drink affected the expression of hundreds of genes involved in regulating basal metabolism of cells lining the intestine. Some of the effects are considered to be clinically significant and may lead to targeted therapeutic use of specific probiotic strains.
The study was conducted by researchers from NIZO Food Research, Maastricht University, UMC St Radboud and Wageningen UR, led by Professor Michiel Kleerebezem, whose previous work has pushed the boundaries of probiotic knowledge. The study is published in the Proceedings of the National Academy of Sciences (PNAS).
According to Prof Kleerebezem, the latest study reveals "Probiotics cause a local reaction in the mucosa of the small intestines." What's more "These effects are similar to the effects of components that the pharmaceutical industry applies to medicines, but less strong."
Some of the changes seen when the probiotic drink was administered resembled the effects of medicines that positively influence the immune system and those that are used for lowering blood pressure.
During the study the treatment group were given the milk drink containing the probiotic bacteria while a control group were given a placebo milk drink containing no probiotics bacteria. Six hours after participants had consumed these drinks, the researchers took biopsies (tissue samples) from the upper part of the small intestine (duodenum) and analysed the activity of a large number of genes.
Prof Kleerebezem and colleagues report that this analysis revealed "...hundreds of differentially expressed genes that participate in (the regulation of) basal mucosal pathways, some with clinical relevance."
"This shows that investigating the effect of specific bacterial strains in cross-over trials using human volunteers may yield clinically relevant results", they added.
"The results from this study may also contribute to the identification of the bacterial molecules that are involved in co-regulating human mucosal function. We consider that probiotics research might eventually deliver therapeutic interventions that correct mild deviations from normal intestinal metabolism and may contribute to maintenance of intestinal health under conditions of mild stress, such as physical exercise."
This study opens the way for further study investigating the possibility of probiotic treatments that are tailored to an individual's unique genetics and gut flora composition, which in theory would greatly improve the effectiveness of such treatment. Prof Kleerebezem draws direct comparisons to the emerging field of nutrigenomics which looks at how specific nutrients have different effects on the body based on the genetic makeup of each person.
"This study could, therefore, be among the first steps to investigate the interplay between microbiota, probiotic, or other nutritional supplements and human genetics," the researchers say.
In conclusion, the work of Prof Kleerebezem and colleagues highlights the complexity of the human gut flora and its interactions with the tissues of the small intestine and even the genes that regulate their metabolism. The knowledge obtained however, also point the way to a future where probiotic therapy is tailored to the individual rather than being somewhat hit and miss.
Source: van Baarlen P Troost F van der Meer C Hooiveld G Boekschoten M Brummer RJM Kleerebezem M (2010) Human mucosal in vivo transcriptome responses to three lactobacilli indicate how probiotics may modulate human cellular pathways Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1000079107
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