Dataset Information

Metabolism of Oxo-Bile Acids and Characterization of Recombinant 12?-Hydroxysteroid Dehydrogenases from Bile Acid 7?-Dehydroxylating Human Gut Bacteria.

ABSTRACT: Bile acids are important cholesterol-derived nutrient signaling hormones, synthesized in the liver, that act as detergents to solubilize dietary lipids. Bile acid 7?-dehydroxylating gut bacteria generate the toxic bile acids deoxycholic acid and lithocholic acid from host bile acids. The ability of these bacteria to remove the 7-hydroxyl group is partially dependent on 7?-hydroxysteroid dehydrogenase (HSDH) activity, which reduces 7-oxo-bile acids generated by other gut bacteria. 3?-HSDH has an important enzymatic activity in the bile acid 7?-dehydroxylation pathway. 12?-HSDH activity has been reported for the low-activity bile acid 7?-dehydroxylating bacterium Clostridium leptum; however, this activity has not been reported for high-activity bile acid 7?-dehydroxylating bacteria, such as Clostridium scindens, Clostridium hylemonae, and Clostridium hiranonis Here, we demonstrate that these strains express bile acid 12?-HSDH. The recombinant enzymes were characterized from each species and shown to preferentially reduce 12-oxolithocholic acid to deoxycholic acid, with low activity against 12-oxochenodeoxycholic acid and reduced activity when bile acids were conjugated to taurine or glycine. Phylogenetic analysis suggests that 12?-HSDH is widespread among Firmicutes, Actinobacteria in the Coriobacteriaceae family, and human gut ArchaeaIMPORTANCE 12?-HSDH activity has been established in the medically important bile acid 7?-dehydroxylating bacteria C. scindens, C. hiranonis, and C. hylemonae Experiments with recombinant 12?-HSDHs from these strains are consistent with culture-based experiments that show a robust preference for 12-oxolithocholic acid over 12-oxochenodeoxycholic acid. Phylogenetic analysis identified novel members of the gut microbiome encoding 12?-HSDH. Future reengineering of 12?-HSDH enzymes to preferentially oxidize cholic acid may provide a means to industrially produce the therapeutic bile acid ursodeoxycholic acid. In addition, a cholic acid-specific 12?-HSDH expressed in the gut may be useful for the reduction in deoxycholic acid concentration, a bile acid implicated in cancers of the gastrointestinal (GI) tract.

SUBMITTER: Doden H

PROVIDER: S-EPMC5930368 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Publications

Metabolism of Oxo-Bile Acids and Characterization of Recombinant 12α-Hydroxysteroid Dehydrogenases from Bile Acid 7α-Dehydroxylating Human Gut Bacteria.

Doden Heidi H Sallam Lina A LA Devendran Saravanan S Ly Lindsey L Doden Greta G Daniel Steven L SL Alves João M P JMP Ridlon Jason M JM

Applied and environmental microbiology 20180501 10

Bile acids are important cholesterol-derived nutrient signaling hormones, synthesized in the liver, that act as detergents to solubilize dietary lipids. Bile acid 7α-dehydroxylating gut bacteria generate the toxic bile acids deoxycholic acid and lithocholic acid from host bile acids. The ability of these bacteria to remove the 7-hydroxyl group is partially dependent on 7α-hydroxysteroid dehydrogenase (HSDH) activity, which reduces 7-oxo-bile acids generated by other gut bacteria. 3α-HSDH has an ...[more]

PMID: 29549099

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Project description:The formation of secondary bile acids by gut microbes is a current topic of considerable biomedical interest. However, a detailed understanding of the biology of anaerobic bacteria in the genus Clostridium that are capable of generating secondary bile acids is lacking. We therefore sought to determine the transcriptional responses of two prominent secondary bile acid producing bacteria, Clostridium hylemonae and Clostridium hiranonis to bile salts (in vitro) and the cecal environment of gnotobiotic mice. The genomes of C. hylemonae DSM 15053 and C. hiranonis DSM 13275 were closed, and found to encode 3,647 genes (3,584 protein-coding) and 2,363 predicted genes (of which 2,239 are protein-coding), respectively, and 1,035 orthologs were shared between C. hylemonae and C. hiranonis. RNA-Seq analysis was performed in growth medium alone, and in the presence of cholic acid (CA) and deoxycholic acid (DCA). Growth with CA resulted in differential expression (>0.58 log2FC; FDR < 0.05) of 197 genes in C. hiranonis and 118 genes in C. hylemonae. The bile acid-inducible operons (bai) from each organism were highly upregulated in the presence of CA but not DCA. We then colonized germ-free mice with human gut bacterial isolates capable of metabolizing taurine-conjugated bile acids. This consortium included bile salt hydrolase-expressing Bacteroides uniformis ATCC 8492, Bacteroides vulgatus ATCC 8482, Parabacteroides distasonis DSM 20701, as well as taurine-respiring Bilophila wadsworthia DSM 11045, and deoxycholic/lithocholic acid generating Clostridium hylemonae DSM 15053 and Clostridium hiranonis DSM 13275. Butyrate and iso-bile acid-forming Blautia producta ATCC 27340 was also included. The Bacteroidetes made up 84.71% of 16S rDNA cecal reads, B. wadsworthia, constituted 14.7%, and the clostridia made up <.75% of 16S rDNA cecal reads. Bile acid metabolomics of the cecum, serum, and liver indicate that the synthetic community were capable of functional bile salt deconjugation, oxidation/isomerization, and 7α-dehydroxylation of bile acids. Cecal metatranscriptome analysis revealed expression of genes involved in metabolism of taurine-conjugated bile acids. The in vivo transcriptomes of C. hylemonae and C. hiranonis suggest fermentation of simple sugars and utilization of amino acids glycine and proline as electron acceptors. Genes predicted to be involved in trimethylamine (TMA) formation were also expressed.

Dataset Information

Metabolism of Oxo-Bile Acids and Characterization of Recombinant 12?-Hydroxysteroid Dehydrogenases from Bile Acid 7?-Dehydroxylating Human Gut Bacteria.

Publications

Metabolism of Oxo-Bile Acids and Characterization of Recombinant 12α-Hydroxysteroid Dehydrogenases from Bile Acid 7α-Dehydroxylating Human Gut Bacteria.

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