Medical Research: What is the background for this study? What are the main findings?
Dr. Marco: Probiotics encompass certain strains of bacteria and yeast that when administered alive and in sufficient amounts can confer specific health benefits. Probiotics are increasingly added to foods, beverages, and intestinal supplements for delivery to the digestive tract. (Fermented) dairy products are currently the most popular food carriers for probiotic strains in clinical studies and commercial products. Although microorganisms generally respond quickly and adapt to their surrounding environments (e.g. in foods), the importance of the carrier format on probiotic function in vivo has yet to be systematically and mechanistically investigated. To address this need, we performed a couple studies in rodents to (i) examine whether probiotic Lactobacillus casei produces different proteins during low temperature (refrigeration) incubation in milk and (ii) measure whether incubation in milk is required for L. casei protection against inflammation. We found by shot-gun proteomics that L. casei does adapt for growth and survival in milk by producing a variety of (extra)cellular proteins, even at low-temperatures used to store dairy products prior to consumption. Such exposure of L. casei to milk was also essential for reducing the severity of disease in a mouse model of Ulcerative Colitis (UC), an inflammatory bowel disease characterized by continuous inflammation in the large intestine. Consuming milk alone also provided some protection against weight loss and intestinal inflammation in the Ulcerative Colitis mouse model but was not as effective as L. casei and milk in combination. Lastly, the importance of dairy for L. casei in preventing Ulcerative Colitis was confirmed by our findings that L. casei mutants lacking the capacity to synthesize proteins which are selectively produced during low-temperature incubation in milk were also impaired in preventing inflammatory responses in the intestine.
Medical Research: What should clinicians and patients take away from your report?
Dr. Marco: Probiotics are unlikely to be equally efficacious in all carrier formats. The carrier matrix should be able to support high numbers of living probiotic cells, and as our studies suggest, also maintain probiotic survival through the digestive tract. Specifically, we found that the levels at which Lactobacillus casei survived in the intestine were directly related to disease prevention. Although more research is needed to determine the best carrier formats for different probiotic species, (fermented) dairy products seem to be a good choice for delivery of probiotic L. casei, and might be more efficacious when consumed in those types of products than in other foods or in nutritional supplements.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Marco: Presently, only one (underpowered) human study has been performed to evaluate delivery format on probiotic efficacy. Therefore, more placebo-controlled, cross-over design human studies comparing different delivery formats on probiotic-mediated health benefits should be performed. Secondly, the mechanisms by which probiotics function should be more thoroughly investigated. By identifying the specific effector compounds (such as proteins and metabolites) produced by probiotics that alter host immune and epithelial cell response pathways in the intestine to result in localized and systemic health benefits, it will be possible to design carrier matrices that optimize the production of probiotic effectors and delivery of those effectors to the appropriate sites in the digestive tract.
Attenuation of colitis by Lactobacillus casei BL23 is dependent on the dairy delivery matrixApplied Environmental Microbiology
doi: 10.1128/AEM.01360-15 Available online on July 10, 2015
DOI: 10.1021/acs.jproteome.5b00387 Available online on July 7, 2015
Maria L Marco, PhD (2015). Dairy Products May Enhance Efficacy of Probiotics