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Review
. 2013 Jan 1;4(1):29-35.
doi: 10.3945/an.112.003061.

Microbial biotransformations of bile acids as detected by electrospray mass spectrometry

Lee R Hagey  1 , Matthew D Krasowski
Affiliations
Review

Microbial biotransformations of bile acids as detected by electrospray mass spectrometry

Lee R Hagey et al. Adv Nutr. .

Abstract

Many current experiments investigating the effects of diet, dietary supplements, and pre- and probiotics on the intestinal environments do not take into consideration the potential for using bile salts as markers of environmental change. Intestinal bacteria in vertebrates can metabolize bile acids into a number of different structures, with deamidation, hydroxyl group oxidation, and hydroxyl group elimination. Fecal bile acids are readily available to sample and contain a considerable structural complexity that directly relates to intestinal morphology, bile acid residence time in the intestine, and the species of microbial forms in the intestinal tract. Here we offer a classification scheme that can serve as an initial guide to interpret the different bile acid patterns expressed in vertebrate feces.

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Conflict of interest statement

Author disclosures: L. R. Hagey and M. D. Krasowski: no conflicts of interest.

Figures

Figure 1
Figure 1
Structures of cholesterol, the C27 precursor compound of bile salts; taurocholic acid, a trihydroxy C24 bile acid; cholic acid, a deconjugated trihydroxy C24 bile acid; and deoxycholic acid, a deconjugated and dehydroxylated C24 bile acid.
Figure 2
Figure 2
NanoESI-MS profile of Zebra danio (Zebrafish, Danio rerio) feces. It shows a type Ic pattern in which C27 bile alcohol sulfates excreted in feces are identical to those excreted in bile. Peak identification: m/z 499, sulfate-conjugated trihydroxy C27 bile alcohol; m/z 515, sulfate-conjugated tetrahydroxy C27 bile alcohol; m/z 531, sulfate-conjugated pentahydroxy C27 bile alcohol; m/z 547, sulfate-conjugated hexahydroxy C27 bile alcohol.
Figure 3
Figure 3
NanoESI-MS profile of Snowy owl (Bubo scandiacus) feces. It shows a type IIb pattern in which bile salts are partly deconjugated with dehydroxylation. Peak identification: m/z 375, deconjugated monohydroxy C24 bile acid; m/z 387, deconjugated dihydroxy C24 bile acid with a loss of 4 protons; m/z 389, deconjugated dihydroxy C24 bile acid with a loss of 2 protons; m/z 391, deconjugated dihydroxy C24 bile acid; m/z 401, deconjugated trihydroxy C24 bile acid with a loss of 6 protons; m/z 403, deconjugated trihydroxy C24 bile acid with a loss of 4 protons; m/z 405, deconjugated trihydroxy C24 bile acid with a loss of 2 protons; m/z 407, deconjugated trihydroxy C24 bile acid; m/z 494, taurine-conjugated dihydroxy C24 bile acid with a loss of 4 protons; m/z 496, taurine-conjugated dihydroxy C24 bile acid with a loss of 2 protons; m/z 498, taurine-conjugated dihydroxy C24 bile acid; m/z 510, taurine-conjugated trihydroxy C24 bile acid with a loss of 4 protons; m/z 512, taurine-conjugated trihydroxy C24 bile acid with a loss of 2 protons; m/z 514, taurine-conjugated trihydroxy C24 bile acid.
Figure 4
Figure 4
NanoESI-MS profile of human (Homo sapiens) feces. It shows a type IIIb pattern in which the bile salts are completely deconjugated with partial dehydroxylation. Peak identification: m/z 373, deconjugated monohydroxy C24 bile acid with a loss of 2 protons; m/z 375, deconjugated monohydroxy C24 bile acid; m/z 389, deconjugated dihydroxy C24 bile acid with a loss of 2 protons; m/z 391, deconjugated dihydroxy C24 bile acid; m/z 407, deconjugated trihydroxy C24 bile acid; m/z dihydroxy C24 bile acid conjugated with sulfate.
Figure 5
Figure 5
NanoESI-MS profile of domestic mouse (Mus musculus) feces. It shows a type V pattern in which the bile acids are enriched (compared with bile) in sulfate conjugation. Peak identification: m/z 375, deconjugated monohydroxy C24 bile acid; m/z 387, deconjugated dihydroxy C24 bile acid with a loss of 4 protons; m/z 389, deconjugated dihydroxy C24 bile acid with a loss of 2 protons; m/z 391 deconjugated dihydroxy C24 bile acid; m/z 403, deconjugated trihydroxy C24 bile acid with a loss of 4 protons; m/z 405, deconjugated trihydroxy C24 bile acid with a loss of 2 protons; m/z 407, deconjugated trihydroxy C24 bile acid; m/z 471, sulfate-conjugated dihydroxy C24 bile acid; m/z 485, sulfate-conjugated trihydroxy C24 bile acid with a loss of 2 protons; m/z 487, sulfate-conjugated trihydroxy C24 bile acid; m/z 514, taurine-conjugated trihydroxy C24 bile acid.
Figure 6
Figure 6
NanoESI-MS profile of probiotic (inulin)-fed domestic mouse. The change in intestinal flora and retention time in this mouse has greatly altered (enriched) the proportion of deconjugated sulfated bile acids compared with the normal domestic mouse. Peak identification: m/z 389, deconjugated dihydroxy C24 bile acid with a loss of 2 protons; m/z 391, deconjugated dihydroxy C24 bile acid; m/z 405, deconjugated trihydroxy bile acid with a loss of 2 protons; m/z 407, deconjugated trihydroxy C24 bile acid; m/z 423 deconjugated tetrahydroxy C24 bile acid; m/z 471, sulfate-conjugated dihydroxy C24 bile acid; m/z 487 sulfate-conjugated trihydroxy C24 bile acid; m/z 509, the sodium salt of a sulfate-conjugated trihydroxy C24 bile acid.
Figure 7
Figure 7
NanoESI-MS profile of IL-10 knockout domestic mouse feces. Intestinal cell–mediated bile acid conjugation is markedly decreased. Peak identification: m/z 391, deconjugated dihydroxy C24 bile acid; m/z 405, deconjugated trihydroxy C24 bile acid with a loss of 2 protons; m/z 407, deconjugated trihydroxy C24 bile acid; m/z 487, sulfate-conjugated, deamidated trihydroxy C24 bile acid; m/z 509, the sodium salt of a sulfate-conjugated deamidated trihydroxy C24 bile acid.
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