STUDY ON THE FUNCTIONALITY OF TWO DIFFERENT LACTOBACILLUS RHAMNOSUS STRAINS IN A MURINE MODEL

Park S., Ji Y., Choi S., Holzapfel W.
Handong Global University, South Korea

Introduction:
With widening interest in the use of probiotics and beneficial bacteria, requirements and expectations are increasing for deeper and better understanding on particular modes of action in support of appropriate use. Even though lactic acid bacteria (LAB), a major group of probiotic strains, are considered generally as safe and beneficial, mechanisms basic to positive impacts on various health conditions are still ambiguous. Vagueness in these issues may open debatable questions on the definition of a beneficial feature. Investigations to clarify the underlying basis for beneficial effects of LAB have pointed to key metabolites or/and components of specific strains. In our study, we focused on two different Lactobacillus rhamnosus strains and their strain-specific effect on lowering cholesterol level and on comparison of their complete genome sequences to trace potential mechanisms of the specific beneficial effect. We used Lb. rhamnosus GG as a “standard” and strain BFE5264, isolated from Maasai fermented milk. Their cholesterol-lowering effect was monitored in a murine model receiving a high-cholesterol diet. As people of the Maasai tribe in Kenya are well known for their excellent health conditions and low cholesterol levels although the fermented milk, containing around 3.4-4.0 % (W/V) of animal fat, serves as their primary food. We therefore expected BFE5264 strain to have a special influence on lipid metabolism

Methods:
Lb. rhamnosus strains BFE5264 and GG were administered to C57BL6 male mice receiving an atherogenic (high-cholesterol) diet. Blood and hepatic cholesterol levels were analysed after nine weeks. Lovastatin, inhibitor of HMG-CoA reductase, was used as control to compare the impact of LAB strains on cholesterol metabolism in the murine model. To assess the influence of two different strains on intestinal environment, composition of gut microbiota and short-chain fatty acids from mice faecal samples were analysed. Complete genome sequencing of Lb. rhamnosus BFE5264 opened the scope for comparison with the genome of the LGG strain, and of possible candidate gene(s), responsible for strain-specific effects.

Results:
Even belonging to the same species, Lb. rhamnosus, these two strains showed differences in lipid metabolism and effects on gut microbiota. Comparison of whole genome of the two strains opened understanding of some key differences between these strains.

Discussion:
It is generally agreed that probiotic functions are strain specific. Insights into intra-species diversity are opened by comparing full genome sequences of phenotypically different strains of a species. Advantages of this approach are obvious, thereby providing a solid scientific basis for differences in key functions thus also giving added valuable to functional claims in support of commercial applications. In this study, we have shown the strain-specific functionality of BFE5264 strain and identified several possible genes as potential targets of a cholesterol-lowering treatment. Improved understanding of underlying mechanisms may enforce future research on selected functional characteristics, and towards deepening insight into LAB interactions in complex ecosystem such as the GIT. This may also open new possibilities for developing and validating of in vitro models.

Keywords: Lactobacillus rhamnosus, Probiotics, Cholesterol-lowering, Gene comparison, Fermented milk, Strain-specific effect

Citation:
Park S., et al. (2016). Study on the functionality of two defferent Lactobacillus Rhamnosus strains in a murine model. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 57.). IPC2016

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