Abstract
The human gastro-intestinal tract hosts a complex and diverse microbial community, whose collective genetic coding capacity vastly exceeds that of the human genome. As a consequence, the gut microbiota produces metabolites from a large range of molecules that host's enzymes are not able to convert. Among these molecules, two main classes of steroids, cholesterol and bile acids, denote two different examples of bacterial metabolism in the gut. Therefore, cholesterol is mainly converted into coprostanol, a non absorbable sterol which is excreted in the feces. Moreover, this conversion occurs in a part of the human population only. Conversely, the primary bile acids (cholic and chenodeoxycholic acids) are converted to over twenty different secondary bile acid metabolites by the gut microbiota. The main bile salt conversions, which appear in the gut of the whole human population, include deconjugation, oxidation and epimerization of hydroxyl groups at C3, C7 and C12, 7-dehydroxylation, esterification and desulfatation. If the metabolisms of cholesterol and bile acids by the gut microbiota are known for decades, their consequences on human health and disease are poorly understood and only start to be considered.
Highlights
If fetuses are sterile in uteri, bacteria from the mother and the surrounding environment colonise the infant’s gut rapidly after birth
The mechanism of cholesterol reduction by Eubacterium coprostanoligenes was deciphered, showing that isomerization of the 5-6 double bond to a 4-5 double bond occurred via a mechanism involving the transfer of C-4 H to the C-6 position during the cholesterol-to-coprostanol conversion [16]
bile salt hydrolases (BSHs) genes have been detected in the main bacterial genera of the gut microbiota [32] and the enzyme has been purified from Bacteroides fragilis, B. vulgatus, Clostridium perfringens, Listeria monocytogenes and several species of Lactobacillus and Bifidobacterium
Summary
If fetuses are sterile in uteri, bacteria from the mother and the surrounding environment colonise the infant’s gut rapidly after birth This microbiota changes during the first years of life, under the control of different factors including the effects of the microbiota itself, developmental changes in the gut Pathogens 2014, 3 environment, the host genotype, and transition to an adult diet [1]. Adult humans are colonized by microbes from nine divisions (deep evolutionary lineages) of Bacteria and at least one division of Archaea. This represents only a small fraction of the more than 70 bacterial and 13 archaeal divisions known in the biosphere. The microbial metabolism in the gut of two classes of steroids is described: Cholesterol originating from the diet or synthesized de novo in the liver and other tissues; Bile acids synthesized from cholesterol in the liver and excreted via the biliary tract
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
