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Composition of cecal bile acids in ex-germfree mice inoculated with human intestinal bacteria
1Laboratory of Veterinary Public Health, Graduate School of Agriculture and Life Science, The University of Tokyo, Bunkyo, Japan.
Abstract:
Germfree (GF) mice were orally inoculated with human fecal suspension or various components of human fecal microbiota. Three weeks after the inoculation, cecal bile acid composition of these mice was examined. More than 80% of total bile acids was deconjugated in the cecal contents of ex-GF mice associated with human fecal dilutions of 10(-2) or 10(-6), or anaerobic growth from a dilution of 10(-6). In these ex-GF mice, deoxycholic acid accounted for about 20% of total bile acids. In the cecal contents of ex-GF mice associated only with clostridia, unconjugated bile acids made up less than 40% of total bile acids, about half of those in other ex-GF groups. However, the percentage of deoxycholic acid in these mice was the same as that in the other groups. These results indicate that dominant anaerobic bacterial combination is efficient for deconjugation of primary bile acids, and that clostridia in the human feces may play an important role in 7alpha-dehydroxylation of unconjugated primary bile acids in the intestine.
Insights
Introducing gut microbiota to germfree mice altered bile acid composition. Specific anaerobic bacteria, including Clostridia, efficiently deconjugated bile acids and produced deoxycholic acid in the mouse intestine.
Area of Science:
- Microbiology
- Gastroenterology
- Metabolomics
Background:
- Gut microbiota plays a crucial role in host metabolism, including bile acid transformation.
- Germfree (GF) animal models are essential for dissecting the specific contributions of the microbiota.
Purpose of the Study:
- To investigate the impact of human fecal microbiota colonization on cecal bile acid composition in germfree mice.
- To identify key bacterial groups responsible for bile acid deconjugation and 7alpha-dehydroxylation.
Main Methods:
- Oral inoculation of germfree mice with human fecal suspensions or specific bacterial components.
- Analysis of cecal bile acid composition three weeks post-inoculation using chromatographic techniques.
- Quantification of total and individual bile acids, including deconjugated forms.
Main Results:
- Colonization with human fecal dilutions (10(-2), 10(-6)) or anaerobic growth from 10(-6) dilution resulted in >80% deconjugated bile acids.
- Deoxycholic acid constituted approximately 20% of total bile acids in these mice.
- Mice colonized solely with Clostridia showed <40% deconjugated bile acids, but similar deoxycholic acid percentages.
Conclusions:
- Dominant anaerobic bacterial communities are highly efficient in deconjugating primary bile acids.
- Clostridia appear to play a significant role in the 7alpha-dehydroxylation of unconjugated primary bile acids within the intestine.